Category Archives: Wafer Processing

Edwards and GlobalFoundries recognized by Singapore’s NationalÂ Environmental Agency

November 1, 2016

Edwards, one of the world’s largest manufacturers of integrated vacuum and abatement solutions, and GlobalFoundries Singapore, a full-service semiconductor design, development, fabrication and innovation company, were recognized by Singapore’s National Environment Agency in the Best Practices category at the 2016 Energy Efficiency National Partnership (EENP) Awards. The agency uses the awards to foster a culture of sustained energy efficiency improvement in industry and encourage companies to adopt a proactive approach towards energy management by identifying and sharing best practices for other companies to emulate.

The joint project between GlobalFoundries and Edwards involved a redesign of 35 abatement units to reduce liquefied petroleum gas (LPG) consumption. Thermal abatement units are used to break down process gases for safe disposal into the atmosphere. The two companies worked together to reduce gas consumption while maintaining destruction efficiency and total abatement capacity by designing and retrofitting smaller, more efficient chambers and nozzles along with a longer weir. The changes reduced annual LPG consumption by 31%, carbon emissions by 640 tons, and annual energy costs by $200,000 USD.

“Reducing energy use is an important priority for GlobalFoundries. We carefully studied our energy cost allocation and identified LPG as a major cost contributor. We also noted that different size combustion chambers on our abatement systems consume different amounts of LPG. We then worked with our strategic partner, Edwards, to reduce the LPG consumption,” states Gu Zhi Min, GM and VP of Fab Management for GlobalFoundries Singapore.

According to Kirel Tang, Applications Knowledge Management Director at Edwards Singapore, “This award is recognition of Edwards’ initiatives in the area of controlling emissions and promoting energy efficiency. It validates the focus and efforts that we have put in so far, and confirms that we are making real progress.”

Samsung Austin Semiconductor continues central Texas growth with more than $1B in investment

November 1, 2016

Samsung Austin Semiconductor LLC (SAS) announced plans to invest more than $1 billion by the first half of 2017. Investments in its facilities will enhance current System LSI production to meet the growing demands in the industry for advanced system-on-chip (SoC) products especially for mobile and other electronic devices.

“Samsung is a bellwether for Austin. As a company that the community and state partnered with to relocate here several years ago, they have far exceeded expectations,” said Mike Rollins, President, Austin Chamber of Commerce. “Samsung remains a shining example of what happens when we create a business friendly environment. The result is a win that enhances and sustains our community’s ability to create a broad range of new jobs and economic opportunities for Austinites and their families.”

According to an Impact Data Source Economic Impact Study, SAS added $3.6 billion into the regional economy of central Texas in 2015. During that same time, SAS supported 10,755 jobs in the area and $498 million in annual salaries. Since its establishment in 1997, Samsung has invested more than $16 billion for the expansion and maintenance of its Austin facility.

“I was glad to discuss this with Samsung when our trade delegation visited Korea, and I’m thrilled that this plan is coming to fruition,” said Austin Mayor Steve Adler. “Samsung is so often a source of good news in Austin whether it’s about jobs, education, workforce development, housing or helping the homeless. Samsung is a great partner for Austin’s present, and this announcement tells us that they’ll be an even bigger part of our future.”

“We are committed to Austin and our contributions to the community,” said Catherine Morse, General Counsel and Senior Director of Public Affairs at SAS. “This is our home, and we want to ensure our community is healthy and prospering. These investments will support this, while also ensuring our customers’ growing needs are met.”

Global semiconductor sales increase 11.5% in Q3

November 1, 2016

The Semiconductor Industry Association (SIA), representing U.S. leadership in semiconductor manufacturing, design, and research, today announced worldwide sales of semiconductors reached $88.3 billion for the third quarter of 2016, marking the industry’s highest-ever quarterly sales and an increase of 11.5 percent compared to the previous quarter. Sales for the month of September 2016 were $29.4 billion, an increase of 3.6 percent over the September 2015 total of $28.4 billion and 4.2 percent more than the previous month’s total of $28.2 billion. All monthly sales numbers are compiled by the World Semiconductor Trade Statistics (WSTS) organization and represent a three-month moving average.

“The global semiconductor market has rebounded markedly in recent months, with September showing the clearest evidence yet of resurgent sales,” said John Neuffer, president and CEO, Semiconductor Industry Association. “The industry posted its highest-ever quarterly sales total, with most regional markets and semiconductor product categories contributing to the gains. Indications are positive for increased sales in the coming months, but it remains to be seen whether the global market will surpass annual sales from last year.”

Regionally, month-to-month sales increased in September across all markets: China (5.4 percent), the Americas (4.6 percent), Asia Pacific/All Other (4.2 percent), Japan (2.3 percent), and Europe (1.6 percent). Compared to the same month last year, sales in September increased in China (12.0 percent), Japan (4.2 percent), and Asia Pacific/All Other (1.7 percent), but decreased in the Americas (-2.4 percent) and Europe (-4.0 percent).

“China stood out in September, leading all regional markets with growth of 5 percent month-to-month and 12 percent year-to-year,” Neuffer said. “Standouts among semiconductor product categories included NAND flash and microprocessors, both of which posted solid month-to-month growth in September.”

September 2016
Billions
Month-to-Month Sales
Market	Last Month	Current Month	% Change
Americas	5.43	5.68	4.6%
Europe	2.71	2.76	1.6%
Japan	2.74	2.80	2.3%
China	8.99	9.47	5.4%
Asia Pacific/All Other	8.37	8.73	4.2%
Total	28.24	29.43	4.2%

Year-to-Year Sales
Market	Last Year	Current Month	% Change
Americas	5.82	5.68	-2.4%
Europe	2.87	2.76	-4.0%
Japan	2.69	2.80	4.2%
China	8.45	9.47	12.0%
Asia Pacific/All Other	8.58	8.73	1.7%
Total	28.41	29.43	3.6%

Three-Month-Moving Average Sales
Market	Apr/May/Jun	Jul/Aug/Sept	% Change
Americas	4.94	5.68	15.0%
Europe	2.68	2.76	3.0%
Japan	2.53	2.80	10.8%
China	8.29	9.47	14.2%
Asia Pacific/All Other	7.97	8.73	9.5%
Total	26.41	29.43	11.5%

van der Pauw and Hall voltage measurements with a parameter analyzer

October 31, 2016

van der Pauw measurements with a parameter analyzer are examined followed by a look at Hall effects measurements.

BY MARY ANNE TUPTA, Keithley Instruments Product Line at Tektronix, Cleveland, OH

Semiconductor material research and device testing often involves determining the resistivity and Hall mobility of a sample. The resistivity of a particular semiconductor material primarily depends on the bulk doping used. In a device, the resistivity can affect the capacitance, the series resistance, and the threshold voltage, so it’s important to perform this measurement carefully and accurately.

The resistivity of the semiconductor material is often determined using a four-point probe or Kelvin technique where two of the probes are used to source current and the other two probes are used to measure voltage. Using four probes eliminates measurement errors due to probe resistance, spreading resistance under each probe, and contact resis- tance between each metal probe and the semiconductor material. Because a high impedance voltmeter draws little current, the voltage drops are very small.

One useful Kelvin technique for determining the resistivity of a semiconductor material is the van der Pauw (vdp) method using a parameter analyzer with high input impedance and accurate low current sourcing. This article first looks at van der Pauw measurements with a parameter analyzer followed by a look at Hall effects measurements.

van der Pauw resistivity measurements

The van der Pauw method involves applying a current and measuring voltage using four small contacts on the circumference of a flat, arbitrarily shaped sample of uniform thickness. This method is particularly useful for measuring very small samples because geometric spacing of the contacts is unimportant, meaning that effects due to a sample’s size are irrelevant.

Using this method, the resistivity is derived from a total of eight measurements that are made around the periphery of the sample using the configurations shown in FIGURE 1.

FIGURE 1. van der Pauw resistivity conventions.

Once all the voltage measurements are taken, two values of resistivity, ρA and ρB, are derived as follows:

where: ρA and ρB are volume resistivities in ohm-cm

t_s is the sample thickness in cm

V₁–V₈ represents the voltages measured by the voltmeter

I is the current through the sample in amperes

f_A and f_B are geometrical factors based on sample symmetry. They are related to the two resistance ratios Q_A and Q_B as shown in the following equations (f_A = f_B = 1 for perfect symmetry).

Q_A and Q_B are calculated using the measured voltages as follows:

Also, Q and f are related as follows:

A plot of this function is shown in FIGURE 2. The value of f can be found from this plot once Q has been calculated.

FIGURE 2. Plot of f vs. Q.

Once ρ_A and ρ_B are known, the average resistivity (ρ_AVG) can be determined as follows:

The electrical measurements for determining van der Pauw resistivity require a current source and a voltmeter. To automate measurements, it’s possible to use a programmable switch to switch the current source and the voltmeter to all sides of the sample. However, a parameter analyzer offers greater efficiency.

A parameter analyzer with four source measure units (SMU) and four preamps (for high resistance measurements) is well-suited for performing van der Pauw resis- tivity measurements, and enables measurements of resistances greater than 1012Ω. A key advantage is that each SMU instrument can be configured as a current source or as a voltmeter with no external switching required. This eliminates leakage and offsets errors caused by mechanical switches as well as the need for additional instruments and programming.

For high resistance materials, a current source that can output very small current with a high output impedance is necessary. A differential electrometer with high input impedance is required to minimize loading effects on the sample.

Each terminal of the sample is connected to one SMU instrument, so a parameter analyzer with four SMU instruments is required. A diagram of how the four SMUs are configured for each of the tests is shown in FIGURE 3. For each test, three of the SMU instruments are configured as a current bias and a voltmeter. One of the SMUs applies the test current and the other two SMUs are used as high impedance voltmeters with a test current of zero amps on a low current range (typically 1nA range). The fourth SMU instrument is set to common. The voltage difference is calculated between the two SMU instruments set up as high impedance voltmeters. This measurement setup is duplicated around the sample, with each of the four SMU instruments changing functions in each of the four tests. The test current and voltage differences between the terminals from the four tests are used to calculate resistivity.

FIGURE 3. SMU Instrument Configurations for van der Pauw Measurements.

For high resistance samples, it’s necessary to determine the settling time of the measurement. This is done by sourcing current into two terminals of the sample and measuring the voltage difference between the other two terminals. The settling time can be determined by graphing the voltage difference versus the time of the measurement. A timing graph of a very high resistance material is shown in FIGURE 4. Note that settling time needs to be determined every time for different materials; however, it’s not necessary for low resistance materials since they have a short settling time.

FIGURE 4. Voltage vs. time graph of a very high resistance sample.

Hall voltage measurements

Hall effect measurements are important to semiconductor material characterization because from the Hall voltage, the conductivity type, carrier density, and mobility can be derived. With an applied magnetic field, the Hall voltage can be measured using the configurations shown in FIGURE 5.

FIGURE 5. Hall voltage measurement configurations.

With a positive magnetic field, B, current is applied between terminals 1 and 3, and the voltage drop (V_2–4+) is measured between terminals 2 and 4. When the current is reversed, the voltage drop (V_4–2+) is measured. Next, current is applied between terminals 2 and 4, and the voltage drop (V_1–3+) between terminals 1 and 3 is measured. Then the current is reversed and the voltage (V_3–1+) is measured again.

Then the magnetic field, B, is reversed and the procedure is repeated again, measuring the four voltages: (V_2–4–), (V_4–2–), (V_1–3–), and (V_3–1–).

From the eight Hall voltage measurements, the average Hall coefficient can be calculated as follows:

where: R_HC and R_HD are Hall coefficients in cm³/C

t_s is the sample thickness in cm

V represents the voltages measured by the voltmeter

I is the current through the sample in amperes

B is the magnetic flux in Vs/cm² (1 Vs/cm² = 10⁸ gauss)

Once R_HC and R_HD have been calculated, the average Hall coefficient (R_HAVG) can be determined as follows:

From the resistivity (ρAVG) and the Hall coefficient (R_HAVG), the mobility (μH) can be calculated:

For successful resistivity measurements, potential sources of errors need to be considered. Here are the errors sources you are most likely to encounter.

Electrostatic Interference — Electrostatic interference occurs when an electrically charged object is brought near an uncharged object. Usually, the effects of the interference are not noticeable because the charge dissi- pates rapidly at low resistance levels. However, high resis- tance materials do not allow the charge to decay quickly and unstable measurements may result. The erroneous readings may be due to either DC or AC electrostatic fields.

To minimize the effects of these fields, an electrostatic shield can be built to enclose the sensitive circuitry. The shield should be made from a conductive material and connected to the low impedance (FORCE LO) terminal of the test instrument. The cabling in the circuit must also be shielded.

Leakage Current — For high resistance samples, leakage current may degrade measurements. The leakage current is due to the insulation resistance of the cables, probes, and test fixturing.

Leakage current may be minimized by using good quality insulators, by reducing humidity, and by using guarding.

A guard is a conductor connected to a low impedance point in the circuit that is nearly at the same potential as the high impedance lead being guarded. Using triax cabling and fixturing will ensure that the high impedance terminal of the sample is guarded. The guard connection will also reduce measurement time since the cable capacitance will no longer affect the time constant of the measurement.

Light — Currents generated by photoconductive effects can degrade measurements, especially on high resistance samples. To prevent this, the sample should be placed in a dark chamber.

Temperature — Thermoelectric voltages may also affect measurement accuracy. Temperature gradients may result if the sample temperature is not uniform. Thermoelectric voltages may also be generated from sample heating caused by the source current. Heating from the source current will more likely affect low resistance samples, because a higher test current is needed to make the voltage measure- ments easier. Temperature fluctuations in the laboratory environment may also affect measurements. Because semiconductors have a relatively large temperature coeffi- cient, temperature variations in the laboratory may need to be compensated for by using correction factors.

Carrier Injection — To prevent minority/majority carrier injection from influencing resistivity measurements, the voltage difference between the two voltage sensing terminals should be kept at less than 100mV, ideally 25mV, since the thermal voltage, kt/q, is approximately 26mV. The test current should be kept as low as possible without affecting the measurement precision.

Conclusion

The van der Pauw technique in conjunction with a parameter analyzer is a proven method for determining the resistivity of very small samples because geometric spacing of the contacts is unimportant. Hall effect measurements are important to semiconductor material characterization for determining conductivity type, carrier density, and mobility. Some parameter analyzers may include built-in configurable tests that include the necessary calculations.

For successful measurements, it’s important to consider potential sources of error including electronics interference, leakage current and environmental factor such as light and temperature. Resistivity can impact the characteristics of a device, serving as reminder of the importance of making accurate and repeatable measurements.

ON Semiconductor selects DSI to improve stock accuracy with Digital Supply Chain Platform

October 31, 2016

DSI announced today that ON Semiconductor has selected DSI’s Digital Supply Chain Platform (DSCP) to increase stock accuracy and improve worker productivity in its inventory processes across the global supply chain.

ON Semiconductor is a leading producer of semiconductors globally. The company chose the DSI DSCP for its unique ability to expand upon base ERP system functionality and work on- or offline through a certified, validated integration with its Oracle E-Business Suite (EBS) system. ON Semiconductor will deploy DSI’s mobile-first supply chain apps personalized by location and user, integrated with the company’s backend systems and business processes.

DSI will enable ON Semiconductor to manage parts used and product use-by dates in real time. The DSCP will automate the data capture process of moving materials while creating built-in measures that ensure the right chemicals are used on equipment. DSI’s automated validation of materials is expected to reduce costs associated with applying incorrect or expired materials.

Additionally, ON Semiconductor will gain efficiency and accuracy by filling gaps in functionality within its ERP system. The DSCP will enable ON Semiconductor’s employees to capture multiple pieces of data in a single scan and immediately update the backend system. The ability to extract multiple pieces of data in a different manner for each specific supplier will also help ON Semiconductor to speed the receiving process.

The speed with which the DSI platform scans, interprets and records the information will enable ON Semiconductor to have a single solution to improve efficiency across all its global operations, scanning 400% faster than the current solution. With this implementation, DSI will replace the company’s current solution, which was unable to perform at the required speed.

“The ability to perform whether online or disconnected was a key factor in selecting DSI,” said Fred Le Roy, Operations Manager, ON Semiconductor. “Having an app that continues to work offline protects the quality of our data and lets our personnel work efficiently in any environment.”

The speed and accuracy ON Semiconductor will be able to gain through the DSI platform will deliver benefits to production quality and efficiency as well as operational health and safety. The DSI solution enables mobile barcode scanners to work equally efficiently connected and disconnected. Switching seamlessly between both states ensures 100% data accuracy.

“Our customers choose DSI for a personalized user experience in enterprise-grade mobile apps that perform anywhere, on any device,” said Mark Goode, Chief Revenue Officer, DSI. “We look forward to working with ON Semiconductor to continue improving visibility and efficiency across its global supply chain with the Digital Supply Chain Platform.”

Reducing ESD in semiconductor fluoropolymer fluid handling systems while maintaining chemical purity

October 30, 2016

Fluoropolymer Electrostatic Discharge (ESD) tubing reduces electrostatic charge to levels below the ignition energy of flammable semiconductor chemicals and maintains chemical purity, ensuring safety and improving process yields.

BY MARK CAULFIELD, JOHN LEYS, JIM LINDER and BRETT REICHOW, Entegris, Billerica, MA

Semiconductor processes, such as photolithography and wet etch and clean, have become more metal sensitive at advanced process nodes. As a result, extracted metals from chemical delivery systems can cause critical wafer defects that negatively impact process yields. To counter this negative yield impact, fabs have converted many of their stainless steel fluid handling systems that had been traditionally selected for use with flammable solvents to fluoropolymer systems. The change to fluoropolymers resulted in reduced extracted metals in the process chemicals.

However, the increased use of fluoropolymer systems creates new concerns with ESD in components such as PFA tubing. Solvents used in the semiconductor industry have low-conductivity, which enables them to generate and hold electrical charge. When these solvents are transported in fluoropolymer systems there is a significantly greater risk of static charge generation and discharge due to the nonconductive nature of the fluoropolymer materials and the low conductivity properties of the solvents. ESD events generated in fluoropolymer systems that are transferring flammable solvents can create leak paths through the tubing and possible ignition of the surrounding, poten- tially flammable, solvent-rich environment. An example of an ESD-created leak path through PFA tubing is shown in FIGURE 1.

Factors influencing static charge accumulation

Low-conductivity fluid flowing in nonconductive tubing can cause charge separation at the fluid- tube wall boundary as shown in FIGURE 2. This separation of charge is similar to what happens when two materials move with respect to each other and transfer charge as shown in FIGURE 3. A charge is created as a result of the transfer of electrons and is similar to the charge that develops by walking across a carpet in dry conditions.

Tubing characteristics affecting charge generation

Table 1 lists the tubing characteristics that are factors for charge generation and accumulation. For each characteristic, the effect on the electric field strength is noted. As an example, as the inner diameter of the tube increases there is more surface area for charge generation, resulting in increased charge and electric field strength.

The overall mechanism of charge generation and accumulation in fluid handling systems is highly complex. A model for this charge generation and accumulation mechanism is described in Walmsley, H. L. (1996).[2] This model describes the factors influencing static charge generation and accumu- lation as a result of fluid flow in fluid handling systems.

Fluid properties and conditions affecting charge generation

Table 2 lists the fluid characteristics that affect charge generation and accumulation. National Fire Protection Association (NFPA®) 77 9.3.3.1 reads, “In grounded systems, the conductivity of the liquid phase has the most effect on the accumulation of charge in the liquid or on materials suspended in it.” [3]

Table 3 lists some low-conductivity chemistries used in the industry.

An example of a high-flow velocity ESD event in a non-solvent application

In the process of cleaning a newly installed PFA chemical line, dilute chemistry is introduced into the line followed by a nitrogen purge then ultrapure DI water. Before fully concentrated chemical can be introduced into the bulk delivery line, the water must be removed. To remove the final DI rinse water, high-purity dry nitrogen is forced through the lines at high velocities. The high-purity nitro-gen, along with the water droplets that cling to the inside diameter of the tube, can generate and hold significant static charge. These flow conditions can result in ESD events causing pinholes in tubing and fluid handling components. The same mechanism of charge generation and accumulation may also occur when processing with high-purity steam.

PFA systems for solvent chemical distribution could also go through a DI water flush and nitrogen purge sequence. However, it is far more common to perform only a nitrogen purge, which, when introduced, can cause an ESD event.

Potential effects of ESD on fluoropolymer fluid handling systems

Dielectric strength is the measure of a material’s insulating strength. NFPA 77 defines the dielectric strength as “the maximum electrical field the material can withstand without electrical breakdown”. [3]

Dielectric strength is usually specified in volts/mm of thickness. As wall thickness and dielectric strength increase the tubing becomes more resistant to electrical breakdown and discharge through the tubing wall.

Standard fluoropolymer tubing, such as PFA, is a very good insulator with high dielectric strength. PFA’s insulating properties make it difficult to ground and also contribute to charge generation and storage in tubing systems. There have been field instances where the generated charge was able to create a discharge path through the tubing wall and cause a leak. After the electrical discharge creates the first fluid leak path, it is likely that subsequent static generation will discharge through that same leak path at lower charge levels.

A spark from the outside of the tube to ground may ignite a solvent-laden environment
Two conditions that must be present to start a fire or explosion are an electrical discharge of sufficient energy and a flammable or combustible environment. A flammable solvent leak caused by discharge through the tubing wall or a discharge from the out- side of the tube to ground could cause an explosion.

The energy of a spark and its ability to ignite a flammable fluid or gas is directly related to the square of the voltage level of the discharge as shown in Equation 1. [3] As voltage increases, the energy available to cause ignition in a flammable environment increases.

W=1⁄2CV²

Where:

W = energy (joules)
C = capacitance (farads)
V = potential difference (volts)

To assess whether the electrical discharge energy is suffi- cient to cause ignition, the Minimum Ignition Energy (MIE) value of the fluid or vapor is considered. Table 4 lists MIE’s of commonly used semiconductor fluids ESD tubing: proposed solution for mitigating electrostatic discharge NFPA 77 lists several strategies for mitigating the amount of charge accumulation in electrically nonconductive pipes as a result of electrically nonconductive fluid flow. [4] Several of these are:

1. Reduce flow velocity
2. Reduce wall resistivity to less than 10^8ohm-m
3. Increase the breakdown strength of the pipe wall material by:
a. Increasing thickness
b. Changing material to one with higher break-down strength
4. Increase conductivity of fluids.(Unlike other industries this is rarely a possibility in the semiconductor process industry where any added particles, especially conductive, are not permitted.)
5. Incorporating an external grounded conductive layer on the piping

Entegris has chosen strategy #5 and has developed FluoroLine® tubing with static dissipative PFA stripes on the outside of the tubing that can be connected to ground (see FIGURE 4). Charge accumulation that develops on the outside of the tube as a result of fluid flow is redirected to external ground paths (FIGURE 5). This approach is consistent with the NFPA 77 observation that, “Carbon black can be added to some plastics or rubbers to increase conductivity.” [3] Carbon-filled plastics and rubber particles are sometimes sufficiently conductive to be grounded like metal objects.

The purpose of having coextruded, PFA carbon stripes only on the outer diameter is to preserve the cleanliness of the tubing’s pure PFA inner layer. Stripes were also used so the fluid can be seen inside the tubing.

Test assemblies were made to hold four-foot and 28-foot long samples of tubing that simulate how customers would use this tubing (FIGURE 6). The tube ends were attached to PFA fittings, the same fittings customers use, so that charge would not be discharged through the end connections.

To simulate a common flow condition used by customers during the commissioning of their systems, an alternating flow of non-conducting 18 Mohm Deionized (DI) water and Extreme Clean Dry Air (XCDA® purge gas) was used. Table 5 lists the flow ranges of XCDA and DI water along with the corresponding pressures at the tube inlet.

The 100% flow rate was the maximum flow through the tube that could be achieved with the test setup. Reduced flow rates were tested to determine the effect of flow rate on the level of charge generated.

A Monroe Electronics 257C-1, 20 KV to -20 KV electrostatic field meter was used to measure the charge level 1 cm from the outside of the tube (FIGURE 7). A resistivity meter was used to monitor the resistance of the DI water during the tests.

Note: Clean nitrogen and XCDA, because of their extreme cleanliness, are good insulators and thus possess the ability to create and hold large electrical potential.

Test procedure

• Tube was cut to length and installed in the fixtures with nonconductive PFA polymer fittings at each end. Tube samples, fittings and probe tips were wiped down with IPA after installation.
• DI water resistance was measured and monitored throughout the test.
• The electro static voltage field meter was placed with the probe at 1 cm distance from the tube OD.
• Alternating flows of DI water and XCDA were introduced to the tube and the field strength was measured at three different locations along the length of the tube. Each tube was subjected to this flow condition with and without a conductive ground strap connecting the tube to ground. In addition, the flow rate was reduced to 75%, 50% and 25% of the maximum flow rate to determine how the level of charge was affected.

Test conclusions

1. Grounding standard PFA tubing does not reduce the field voltage on the outside of the tube that is produced by flowing XCDA and DI water on the inside. Up to 20 KV field voltage was measured with the XCDA/DI water delivery system (Figure 8).
2. Grounding ESD PFA tubing and stainless steel does significantly reduce the field voltage on the outside of the tube that is produced by flowing XCDA and DI water flowing on the inside (FIGURE 8).
3. The field voltage developed along four- and 28-foot tube lengths does not vary significantly for PFA, ESD PFA and stainless steel.
4. With reduced flow rates,the maximum absolute field voltage was reduced for both grounded ESD PFA and PFA tubing (FIGURE 9).
5. No fluid leak paths were generated throughout this testing in either the PFA or ESD PFA tube.
6. The capacitance of a four-inch long PFA tube was measured to be 56 pF. Using this capacitance value and 20 KV levels of voltage measured by the field meter in this test, the energy of discharge is calculated as 11.2 mJ. This energy level exceeds the MIE of fluids listed in Table 4 and would be expected to cause fumes from these fluids to ignite.
Applying this same equation to grounded ESD tubing where a maximum of 1.5 KV field was measured along with 52 pF capacitance, the discharge energy was calcu- lated at 0.059 mJ and was below the threshold of ignition energy of the fluids listed in Table 4.

Conclusion

As semiconductor processes such as photolithography and wet etch and clean become more metal sensitive at advanced process nodes, fabs are converting to fluoropolymer fluid handling systems. The increased use of fluoropolymer systems creates new concerns with electrostatic discharge (ESD) in components such as PFA tubing.Electro static discharge increases the risks of leaks, flammability and potential explosions.

Solvents transported in fluoropolymer systems pose a significantly greater risk of static charge generation and discharge due to the nonconductive nature of the fluoropolymer materials and the frequent low-conductivity properties of the solvents. Understanding the factors that influence static charge generation and accumulation in a fluoropolymer fluid handling system, Entegris developed an effective solution that is proven to dissipate static charge accumulation on the exterior of the tubing. Entegris’ FluoroLine ESD tubing has external static dissipative PFA carbon stripes that redirect charge accumulation from the outside of the tube to external ground paths. This tubing maintains chemical purity, and when properly grounded, minimizes electrostatic discharge events, helping to increase process yields while ensuring safety.

References

1. Walmsley, H. L., “The Avoidance of Electrostatic Hazards in the Petroleum Industry,” p. 19 and p. 33.
2.Walmsley,H.L.(1996). “The electro static fields and potentials generated by the flow of liquid through plastic pipes,” Journal of Electrostatics, Volume 38, p. 249 – 266.
3. NFPA 77: 3.3:16, 6:9:1, 7.4.3.4, 779.3.3.1. National Fire Protection Association.
4. NFPA 77 (A.10.2) National Fire Protection Association.

Managing particle flows in process exhaust for safety and profitability

October 28, 2016

Solid particles in the abatement exhaust must be properly managed, and in some cases, substantially reduced from the gas stream before it is released into the environment.

BY CHRIS JONES, Edwards Vacuum, Ltd., Clevedon, U.K.

Many semiconductor manufacturing processes create solid particles in the process exhaust. Like other exhaust contaminants, these must be properly managed, and in many cases, removed from the stream before it is released into the environment. The permitted release levels vary for particles of different sizes and compositions, depending on their toxicity or potential to damage the environment. Regulations governing particle releases are evolving rapidly. However, the management of particulate flows in process exhaust is also important due to its potential impact on the process itself. Left unmanaged, particulate accumulations can result in shut downs for unplanned maintenance, excessive and premature wear and costly repairs, all of which directly affect the profitability of the manufacturing operation.

Solids may be formed in the exhaust stream of a semiconductor manufacturing process from a number of sources. One important source, though not the focus of this discussion, is the condensation of process gases in vacuum pump exhausts. If not controlled with a thermal management system (e.g. Smart TMS, Edwards) that maintains the pipe surfaces at a sufficiently high temperature, this condensation can quickly accumulate and force a halt to the manufacturing process. This article will discuss issues further downstream in the abatement process, where toxic volatile compounds are converted to more benign forms, some of which form solid particles that must then be removed from the exhaust gases. Many of these solids are oxides formed when gases, such as tungsten hexaflu- oride, silane, organo- and halo- silanes and others, are exposed to heat, air, and water. The particles are typically amorphous, i.e. non-crystalline. Many abatement processes use combustion to supply the heat needed to decompose toxic compounds and chemically convert them to a more harmless form. The particles thus formed have varying sizes and may be hydrophilic (formed from halosilanes), hydrophobic (formed from organsilanes) or mixed (mixed chlorides or silicon, aluminum and boron, for example), depending on the species combusted and the nature of the combustion process. Particle sizes can range from tens of nanometers to tens of microns. As shown in FIGURE 1, the size of the particles depends on, among other factors, the length of the combustion flame. Longer flames maintain the components at high temperature for a longer periods and result in the formation of larger particles.

FIGURE 1. A longer flame maintains the combusting components at higher temperature for a longer time and results in the formation of larger particles.

The behavior of particles once released into the environment varies depending on their sizes. Coarse particles, with diameters ranging from 2.5μm to 10μm, result largely from processes such as erosion, agriculture, or mining and include crustal dust, pollens, fungal spores, biological debris and sea salt. Because of their large size, these particles persist in the atmosphere for only a few hours or days. Fine particles, which range from 2.5μm to 0.1μm and include the particles of concern in semiconductor manufacturing exhaust, may be the direct result of a combustion processes or may also be formed by photochemical reactions between volatile organic compounds (VOC) and oxides in the presence of sunlight. Fine particles can stay suspended in ambient air for days to weeks. Ultrafine particles, less than 0.1μm, are generated by high temperature combustion or formed from the nucleation of atmospheric gases. Ultrafine particles are quickly removed from the atmosphere (minutes to hours) via diffusion to surfaces or coagulation, adsorption and condensing into fine particles.

Regulatory environment

Regulations governing the release of particles into the atmosphere are developing quickly worldwide as scientists expand their knowledge of the particles’ impacts on health and the environment. In addition to regulations governing emissions by particle size, there are specific regulations regarding especially harmful species, such as heavy metals, carcinogens and toxics. For example, the presence of an adsorbed species, like hydrofluoric acid (HF), on oxide particles increases the toxicity of the parent material.

In 2013 the United States Environmental Protection Agency specified an average daily limit of 150μg/m3 for coarse particles and 35μg/m³ for fine particles, and an average annual limit of 12μg/m3 for fine particles (down from 15μg/m3 in 2006). China, as of 2012, imposed limits based on both particle size and type, with permitted daily levels for coarse particles of 50μg/m³ and 150μg/m³ for type I and type II, respectively and 35μg/m³ and 75μg/m³, respectively for fine particles. China also limits annual averages for both sizes and types. The European Commission, the World Health Organization and the Australian National Environmental Council, among others, all specify their own limits. It is clearly incumbent on manufacturers to know and satisfy their local regulations. [1]

Health considerations

The health of employees in manufacturing facilities and people living near manufacturing operations is clearly a high priority for our industry. Epidemiological studies have provided plausible evidence that exposure to particulate material (PM) can impact health in a number of ways, including pulmonary and systemic inflammation, oxidative stress response, protein modification, stimulation of the autonomic nervous system, exaggerated allergic reactions, pro-coagulation activity, and suppression of immune response in the lungs.

Some studies have provided good news as well, specifically, that the amorphous silica particles produced during the abatement of gases used in semiconductor manufacturing have much less impact on lung function than the crystalline silica particles more often encountered in mining and building industries. These studies looked specifically at the effects of pure silica particles, an important caveat. Silica and other dusts that may have acids, such as HF, adsorbed on the particle surface constitute substantially greater health risks than the simple oxide. Other particulate oxides also represent serious health challenges. These include oxides of antimony, arsenic, barium, chromium, cobalt, nickel, phosphorus, tellurium and selenium.

Abatement performance

Just as condensed material deposited in the vacuum lines can shut down the production process, the accumulation of combustion-generated particulates can degrade the performance of the whole facility. In a typical point-of-use (POU) abatement system, after combustion the exhaust gases pass through a series of operations designed to remove particulates and other by-products. In the example shown in FIGURE 2 these include a water weir, quench tanks, a packed-bed scrubber and an atomized spray. Atomizing spray systems, in particular, have been shown to improve solids removal performance from 50 to 75 percent. Blockages can occur at the damper, in duct spurs leading from the abatement to the main duct, in the main duct, before or within the scrubber. In addition to blockages, failure to remove particulate at the primary abatement unit can also lead to environmental discharges and visible plumes at stacks. Any blockage will result in a process shutdown for system maintenance, lasting from a few hours to an entire day.

FIGURE 2. The accumulation of combustion generated particulates can degrade abatement system performance.

Mitigation options

A number of approaches exist for removing particulates downstream of the abatement system. One solution does not fit all and it is important to pick the one that best addresses the specific challenges. FIGURE 3 shows performance characteristics for various technologies. For example, highly toxic particles may require much higher removal rates than less harmful particles.

FIGURE 3. Performance characteristics for various particle removal technologies downstream of the abatement system. Courtesy: Waste-to-Energy Research and Technology Council (greyed out area not relevant to solids).

Edwards’ standard solution (FIGURE 4) for POU removal of fine particles is a wet electrostatic precipitator (WESP). A WESP uses electrostatic forces to remove particles. It requires power, water and pneumatics and can remove up to 95 percent of silica particles at flow rates of 1m³/ min, 85% at 2m³/min. WESP technology can be scaled to handle an entire facility. In one example, Edwards partnered in the installation of a large scale dual WESP integrated with a packed-bed wet scrubber and designed it to meet the specific challenges of arsenic abatement. The system ultimately demonstrated a 99 percent removal rate to meet the stringent requirements of the Chinese government for this highly toxic substance.

FIGURE 4. POU WESP uses electrostatic forces to remove particulates from the exhaust stream. It can remove up to 95 percent of silica particles at a flow rate of 1m³/min.

Alternative technologies that may be appropriate, but have not been evaluated for use in the management of waste gases from semiconductor manufacturing, are the Rotoclone family (from AAF International). POU units handle flow rates of 30m³/min, removing >97 percent of 1μm particles and >99.8 percent of 10μm particles. Duct-based Rotoclones with flow rates up to 1250m3/ min remove as much as 86 percent of 1μm particles and 99 percent of 10μm particles. Rotoclones require power, water, pneumatics and a drain.

More conventionally, a Venturi scrubber can be configured for various flow and removal rates. As a rule, smaller units controlling a low concentration waste stream will be much more expensive per unit of volumetric flow than larger units cleaning high pollutant-load flows. Venturi scrubbers can handle mists and flammable or explosive dusts. They have relatively low maintenance requirements, are simple in design and easy to install. Their collection efficiency can be varied. They can cool hot gases and neutralize corrosive gases. They are susceptible to corrosion and must be protected from freezing. Treated gases may require reheating to avoid a visible water plume. The collected particulate material may be contaminated and not recyclable, requiring expensive disposal of the waste sludge.

Filtration is another alternative for particle removal. It is normally restricted to the management of dry dusts at flow rates of 5 to 250m³/min. Removal rates higher than 99.9 percent are achievable. We have seen a limited number of large filter installations for the removal of hydrophobic silica solids at relative humidities as high as 80 percent. It is not clear how the presence of hydrophilic powder might impact the performance of these facilities.

In cases of highly toxic particles, high efficiency air particle (HEPA) filters can provide very high removal rates, higher than 99.999 percent. However, HEPA filters are appropriate only for very low contaminant concentrations. Edwards has been partnering with third-party suppliers regarding HEPA filtration for highly toxic dusts such as those generated during arsine management. These solutions are often used for highly toxic materials so they are often designed with bag-in-bag-out capability to eliminate potential exposure of maintenance personnel to the removed contaminants. Typically, these critical installations are also designed as dual systems with auto turnover to allow continuous operation of one system while the redundant system is serviced. HEPA technology can scale from POU to full facility.

Conclusion

All of these technologies are available now, but not all have been demonstrated in semicon- ductor manufacturing. Semiconductor manufacturers have long used POU WESPs and Venturi scrubbers and are very familiar with HEPA filtration systems, but primarily for particulate removal for air conditioning. Conventional filters are in operation on flat panel display exhausts (mainly on burner only dry abated CVD processes). Some of the technologies we have described, however, have not been proven in semiconductor applications, but are well developed and widely accepted in other industries. Rotoclone systems, for instance, are UL and CE certified, but have not been SEMI qualified. As semiconductor manufacturing processes continue to evolve, it will behove manufacturers to stay current on available technol- ogies and consider alternatives as performance and cost requirements dictate.

References

1. Review of the health impacts of emission sources, types and levels of particulate matter air pollution in ambient air in NSW; December, 2015; Produced for the NSW Environment Protection Authority and NSW Ministry of Health, Environmental Health Branch.

Power electronics powered by Picosun’s batch aluminum nitride

October 27, 2016

Picosun Oy, a supplier of advanced industrial ALD (Atomic Layer Deposition) technology, now provides its customers production-scale aluminum nitride batch process with superior film thickness uniformity and fast speed.

Aluminum nitride (AlN) is one of the key materials in semiconductor industries. Compatibility with III-V semiconductors makes it an excellent material for power electronics, and in mobile communications technology it is used in the production of several key components such as RF filters and microphones.

“We have achieved excellent results in our new AlN batch process, so we are very happy now to offer it to our industry customers for mass manufacturing applications. AlN is a very sought-after material amongst our microelectronics production customers,” says Dr. Erik Østreng, Applications and Services Director of Picosun.

High quality, but low cost microelectronics mass production is a prerequisite also for the rapidly expanding Internet-of-Things (IoT). Soon, the IoT will require trillions of sensors, actuators, transducers, energy harvesters and other, often independently operating electronic components. AlN thin films are important building blocks also in these devices.

In all semiconductor applications, the quality of the thin films, especially their uniformity and purity, is crucial. For the end product prices to stay competitive, the films must be manufactured fast and cost-efficiently in large batches.

“We at Picosun want to offer our customers comprehensive, turn-key ALD manufacturing solutions and the best and most agile customer care. A process, tailored, optimized and ramped-up for each customer’s individual needs is the core part of this solution”, continues Mr. Juhana Kostamo, Managing Director of Picosun.

Picosun’s production ALD systems are designed to fulfill the most stringent quality and reliability requirements of today’s semiconductor industry. With Picosun’s SEMI S2 compliant batch ALD tools equipped with fully automatic substrate handling in constant vacuum excellent AlN film thickness uniformities and conformality across the batch have been achieved.

Cadence CEO to be awarded Dr. Morris Chang Exemplary Leadership Award

October 27, 2016

The Global Semiconductor Alliance (GSA) announced the winner of the 2016 Dr. Morris Chang Exemplary Leadership Award: President and CEO of Cadence Design Systems, Inc. and Founder and Chairman of Walden International, Mr. Lip-Bu Tan. He will be presented with this achievement award during the GSA Awards Dinner Celebration on Thursday, December 8, 2016, at the Santa Clara Convention Center in Santa Clara, Calif.

“Lip-Bu Tan epitomizes what the Dr. Morris Chang Exemplary Leadership Award encompasses,” said Jodi Shelton, president of GSA. “We are honored to present this year’s award to someone who is a true global technology visionary that first helped pioneer the concept of venture capitalism worldwide and then lead Cadence Design Systems to the success, growth and strong customer focus that it enjoys today. Tan’s contribution to GSA and the entire semiconductor industry has and will continue to make a lasting impact.”

Established in 1999, the first GSA “Exemplary Leadership Award” was given to Dr. Morris Chang, chairman and chief executive officer of Taiwan Semiconductor Manufacturing Corporation (TSMC). Today, the Dr. Morris Chang Exemplary Leadership Award recognizes individuals for their exceptional contributions, exemplifying how their vision and global leadership have transformed and elevated the entire semiconductor industry.

“I am extremely honored and humbled to receive this award named after my close friend and role model Morris Chang, and which has been bestowed earlier on many amazing pioneers in our industry,” said Lip-Bu Tan. “I have learned so much from my peers in the global semiconductor industry and it has been my privilege to contribute in some way to their success through investments by Walden and collaboration by Cadence, leading to the delivery of some truly inspiring end products.”

Tan has served as President and CEO of Cadence Design Systems, Inc. since January 2009 and has been a member of the Cadence Board of Directors since February 2004. In 2015 and 2016, Cadence was named to FORTUNE’s list of the “100 Best Companies to Work For”. Tan founded Walden International in 1987 and currently serves as Chairman. Tan has been active in the venture capital industry for more than two decades. He specializes in cross border & early-stage technology investment. Prior to Walden International, he was Vice President at Chappell & Co. and held management positions at EDS Nuclear and ECHO Energy.

Tan is Co-Chairman of the Board of Directors of the Electronic System Design Alliance (ESD Alliance) and serves on the board of Global Semiconductor Association (GSA), as well as the boards of Ambarella Inc., Hewlett Packard Enterprise Co., and Semiconductor Manufacturing International Corp. He also serves on the Board of Trustees and the School of Engineering Dean’s Council at Carnegie Mellon University (CMU).

Tan holds an M.S. in Nuclear Engineering from Massachusetts Institute of Technology, an M.B.A. from the University of San Francisco, and a B.S. in Physics from Nanyang University in Singapore.

Each year the GSA recognizes companies that have demonstrated excellence through their vision, strategy, execution and future opportunity. The celebration honors the achievements of semiconductor companies in several categories ranging from outstanding leadership to financial accomplishments, as well as overall respect within the industry. The Awards Dinner Celebration will start at 5:00 p.m. with a networking reception, followed by dinner at 6:15 p.m. To make reservations to attend the Awards Dinner, visit the event website.

Qualcomm to acquire NXP

October 27, 2016

Qualcomm Incorporated (NASDAQ: QCOM) and NXP Semiconductors N.V. (NASDAQ: NXPI) today announced a definitive agreement, unanimously approved by the boards of directors of both companies, under which Qualcomm will acquire NXP. According to Qualcomm’s official press release, a subsidiary of Qualcomm will commence a tender offer to acquire all of the issued and outstanding common shares of NXP for $110.00 per share in cash, representing a total enterprise value of approximately $47 billion.

NXP is a developer of high-performance, mixed-signal semiconductor electronics, with products and solutions and leadership positions in automotive, broad-based microcontrollers, secure identification, network processing and RF power. As a semiconductor solutions supplier to the automotive industry, NXP also has leading positions in automotive infotainment, networking and safety systems, with solutions designed into 14 of the top 15 infotainment customers in 2016. NXP has a broad customer base, serving more than 25,000 customers through its direct sales channel and global network of distribution channel partners.

“With innovation and invention at our core, Qualcomm has played a critical role in driving the evolution of the mobile industry. The NXP acquisition accelerates our strategy to extend our leading mobile technology into robust new opportunities, where we will be well positioned to lead by delivering integrated semiconductor solutions at scale,” said Steve Mollenkopf, CEO of Qualcomm Incorporated. “By joining Qualcomm’s leading SoC capabilities and technology roadmap with NXP’s leading industry sales channels and positions in automotive, security and IoT, we will be even better positioned to empower customers and consumers to realize all the benefits of the intelligently connected world.”

The combined company is expected to have annual revenues of more than $30 billion, serviceable addressable markets of $138 billionin 2020 and leadership positions across mobile, automotive, IoT, security, RF and networking. The transaction has substantial strategic and financial benefits:

Complementary technology leadership in strategically important areas: The transaction combines leadership in general purpose and automotive grade processing, security, automotive safety sensors and RF; enabling more complete system solutions.
- Mobile: A leader in mobile SoCs, 3G/4G modems and security.
- Automotive: A leader in global automotive semiconductors, including ADAS, infotainment, safety systems, body and networking, powertrain and chassis, secure access, telematics and connectivity.
- IoT and Security: A leader in broad-based microcontrollers, secure identification, mobile transactions, payment cards and transit; strength in application processors and connectivity systems.
- Networking: A leader in network processors for wired and wireless communications and RF sub-segments, Wave-2 11ac/11ad, RF power and BTS systems.
Enhanced go-to-market capabilities to serve our customers: The combination of Qualcomm’s and NXP’s deep customer and ecosystem relationships and distribution channels enables the ability to deliver leading products and platforms at scale in mobile, automotive, IoT, industrial, security and networking.
Shared track record of innovation and commitment to operational discipline: Both companies have demonstrated a strong commitment to technology leadership and best-in-class product portfolios with focused investments in R&D. Qualcomm and NXP have both taken action to position themselves for profitable growth, while maintaining financial and operational discipline.
Substantial financial benefits: Qualcomm expects the transaction to be significantly accretive to non-GAAP EPS immediately upon close. Qualcomm expects to generate $500 million of annualized run-rate cost synergies within two years after the transaction closes. The transaction utilizes Qualcomm’s strong balance sheet and will be efficiently financed with offshore cash and new debt. The transaction structure allows tax efficient use of offshore cash flow and enables Qualcomm to reduce leverage rapidly.

Mollenkopf continued, “We have taken significant action to build a foundation for profitable growth and the acquisition of NXP is strongly aligned with our strategy. Our companies both have substantial expertise in delivering industry-leading solutions to our global customers, built upon a shared commitment to technology innovation, focused R&D investments and strong financial and operational discipline.”

“The combination of Qualcomm and NXP will bring together all technologies required to realize our vision of secure connections for the smarter world, combining advanced computing and ubiquitous connectivity with security and high performance mixed-signal solutions including microcontrollers. Jointly we will be able to provide more complete solutions which will allow us to further enhance our leadership positions, and expand the already strong partnerships with our broad customer base, especially in automotive, consumer and industrial IoT and device level security,” said Rick Clemmer, NXP Chief Executive Officer. “United in a common strategy, the complementary nature of our technologies and the scale of our portfolios will give us the ability to drive an accelerated level of innovation and value for the whole ecosystem. Such a strong fit will bring opportunities for our employees and customers, as well as provide immediate attractive value for our shareholders, in creating the semiconductor industry powerhouse.”

Sir Peter Bonfield, Chairman of NXP’s Board of Directors, said, “This is a major step in my ten years’ Chairmanship of NXP, and I am very pleased to see that the board of NXP has unanimously approved the proposed transaction and fully supports and recommends the offer for acceptance to NXP shareholders.”