Category Archives: Materials and Equipment

By James R. Dukart

A molecular diagnostic tool has been at the forefront of addressing the recent outbreak of E. coli detected in fresh spinach, which had resulted in nearly 200 cases of illness as of late September. The experience is motivating toolmakers to hone their abilities to prevent food safety problems in the future.

A government lab used a system manufactured by Sunnyvale, Calif.-based Cepheid to isolate the E. coli earlier this year. Using the system, researchers performed rapid molecular tests that pointed to a bag of spinach that sickened a New Mexico woman. While the technology provided a critical breakthrough in the case, Cepheid’s chief medical and technology officer, David Persing, says the goal must be to detect and intercept pathogens long before they enter the general food supply.

“We need to identify the source much earlier in the process, some way of testing foodstuffs coming out of a particular farm or on a lot-specific basis,” Persing says. “In this case, it may have been one truckload of spinach that was contaminated, and that single load knocked out so many others because we did not know exactly where it was.”

Persing envisions greater public awareness of food safety, perhaps including certification programs for bags of fresh produce. He likens it to the response to the anthrax scare at the post office. Cepheid works with Northrop Grumman and others to apply its technology at hundreds of U.S. Post Office branches throughout the country, and offers a range of sensors and diagnostic products aimed at testing for pathogens from anthrax to salmonella. Persing sees similar deployment of sensor technology for agricultural operations, food distribution centers and perhaps even grocery stores.

The company is not the only one pursuing the opportunity. Santa Clara, Calif.-based NanoSensors is licensing nanoporous silicon-based biosensor technology through Michigan State University and a university in Korea to develop food safety analysis systems. In addition to silicon-based filters, NanoSensors is also using carbon nanotube technology to detect and isolate biologically-based pathogens.


A government lab isolated E. coli from a bag of spinach that sickened a New Mexico woman by performing a rapid molecular diagnostic test with Cepheid’s SmartCycler instrument, shown here. Unlike traditional culture tests that take days to generate a result, molecular diagnostics quickly and accurately identify microorganisms by identifying specific segments of DNA. Photo courtesy of Cepheid
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“This is a market that is ripe for a solution,” says Joshua Moser, vice president and chief operating officer of NanoSensors. “Food safety may not be as sexy as testing for anthrax or liquid explosives in airports, but it’s a problem. We need to find a solution.”

Nano- or molecular-scaled devices operate at the same scale as the biological agents they target, he explained, allowing the technology to both detect and isolate targeted pathogens. Nanoprobes and filters can address viruses and bacteria at a level of specificity hard to get at with larger, more unwieldy technology, while at the same time promising faster, more accurate results than existing technology.

Another advantage to molecular detection, Persing adds, is that it works in ways contemporary culture-based technologies fall short. “The viability of the bacteria might go down over time,” he says. “It gets degraded, but that is where the molecular techniques really shine, since they can detect DNA whether alive or dead.”

Both Persing and Moser expect the movement of food-testing technology from research labs to the field to be expedited in light of recent events.

“We’re seeing a lot of attention paid to this now,” Moser says, “and not just because we are in California, which is such a large food producer.”

NanoSensors is working on a reusable testing kit – a disposable sensor that reports back to an external data acquisition unit – that can be used by people at all levels of the food distribution chain, from farmers to wholesalers to retail grocers. Moser refers to the product as a “razor/razorblade” model, where customers will buy and use disposable sensors on each specific lot of produce that is tested. He also sees government agencies pushing for stronger testing in the wake of the E. coli spinach outbreak.

“Situations like this cannot help but raise consciousness,” says Cepheid’s Persing. “The connection has already been proven by molecular testing. In addition to illness and loss of life, any significant outbreak of one of nature’s biothreats results in tremendous economic loss as well.”

3-D X-ray Inspection has Arrived BY DAVID BERNARD, Ph.D.,Dage Precision Industries

Advanced 3-D packages are replacing leadframe packages with the emergence of more subsystem integration, strengthened by advances in wafer-level technology. System designers prefer using completely tested subsystems and have encouraged the development of system-in-package (SiP) device integration. Board-level assembly requires surface mount technology, which means that packages need to interface with solder land pads or solder bumped pads. Multiple stacked-die packages, such as package-in-package (PiP) and package-on-package (PoP) (Figure 1) meet this demand for greater circuit density and improved electrical performance.

These complex 3-D package types are entering into mainstream production, and typically contain multiple stacked die with multi-level wire bonding, or wafer bumping, internal to the device.


Figure 1. Variations of advanced 3-D package technologies. (Courtesy of STATS ChipPAC)
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Package Complexity

3-D packages place a greater demand on any required X-ray inspection and provide unique challenges for package inspection and process qualification during the package, assembly, and test operation. Traditional analysis using 2-D X-ray imaging is often limited with these new package types since all layers within the device are seen at the same time. This can be analytically confusing with the multiple dies and multiple layers of wire bonds appearing to overlap each other in the image, as shown in Figure 2.

Computerized Tomography

Computerized tomography (CT) is an imaging method whereby computational geometric processing is used to generate a 3-D model of an object from a large series of individual 2-D X-ray images taken around a single axis of rotation. Since its invention in 1972, CT has aided medical diagnosticians around the world to predict, diagnose, and treat disease. This same technique is being applied to inspecting advanced 3-D packages, because of 2-D X-ray imaging systems’ limitations. Specifically, CT is increasingly being used to inspect for die-attach quality, and the quality and effectiveness of wire-bond integrity within complex 3-D packages. Until recently, the use of CT for semiconductor and 3-D package inspection has been hindered by its slow computer processing times, low resolution, and expense. While some CT systems have been used for semiconductor inspection, they typically have not delivered the analytical performance required for such critical, high-density applications. However, advancements in CT have improved imaging speed, increased resolution to allow complete analysis of detailed package features, and decreased the price. Therefore, computerized tomography is now an ideal inspection methodology for complex 3-D packages. The resulting 3-D model can be viewed with real-time manipulation so that interconnections normally obscured by other joints or components within the package can be diagnosed, assuring complete package inspection (Figure 3).


Figure 2. Complex 3-layer die and wire-bonded 3-D package.
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A CT model is developed computationally from a series of 2-D X-ray images taken as the sample, or semiconductor device, is rotated in an X-ray beam. The density variations within those images, and how their relative locations change as the sample rotates, are evaluated in a computer to reconstruct a 3-D model of the sample which can then be viewed and manipulated – providing analytical images, or slices, through any 2-D plane in the object CT model.

Imaging Requirements

The critical elements of producing a CT model for analysis include acquisition of the necessary 2-D X-ray images, computational reconstruction from those images into a CT model, and, finally, visualization and manipulation of the final 3-D model. A series of 2-D X-ray images are taken over a 360° rotation; taking a greater number of steps for each degree of rotation, and therefore a greater number of 2-D images, will provide a better CT model.


Figure 3. Two-layer stacked-die device.
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Image acquisition is the most time-consuming phase of the CT model production and is dependent upon the number of rotation steps used. For example, taking 720 X-ray images within a full rotation of the sample (2 images per degree of rotation) will take twice as long to complete as 360 images per rotation (1 image per degree). In addition, each 2-D X-ray image is produced from an average of a number of frames from the real-time image capture of the X-ray system. The number of frames averaged at each image step, and the time the X-ray system can acquire those frames, further governs the speed of the acquisition process. This can be particularly significant depending upon the type of image-capture device being used in the X-ray system. For example, taking an average of 32 frames per image (a reasonable trade-off between good final image quality and throughput speed), a digital image intensifier acquires 32 frames in 1.3 seconds as it operates at 25 frames per second (fps). In contrast, 32 frames at an acquisition rate typical for the alternative to a digital image intensifier, the flat-panel detector at 4 fps requires 8.0 seconds to complete. Therefore, a flat-panel detector will take 8.0 sec., or six times longer per step. Reducing the number of steps and/or reducing the frame average per step will speed up the acquisition process but will reduce the eventual reconstruction quality of the 3-D model.


Figure 4. CT image of 3D packaged device.
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Precision of the sample rotation during the image acquisition process is crucial for achieving good reconstructions at high resolution. Without this, the ability of the CT reconstruction algorithm is severely compromised because the math requires that density difference within each 2-D image be tracked precisely as the sample rotates. The increased availability of digital X-ray detectors in modern X-ray systems provides enhanced greyscale sensitivity in the 2-D X-ray images compared to earlier systems, which, in turn, provides a greater amount of subtle density-difference information that can be used during the reconstruction process.

For many CT systems, the CT volume reconstruction process is also a substantially time-consuming element. Vast ‘number crunching’ and computer processing time is needed to calculate the density variation of each pixel in each step image and work out how that density variation moves as the sample rotates. In this way the sample volume can be mapped out within a 3-D information matrix.

The resolution of the reconstructed 3-D matrix is generally defined in terms of volume pixels, or voxels. The more voxels, the more required processing, and the better the quality of the final 3-D model. Typically CT systems can have either 256 × 256 × 256 (2563) voxels, 512 × 512 × 512 (5123) voxels or 1024 × 1024 × 1024 (10243) voxels. It should be remembered that a 2563 voxel array contains 8× less information than a 5123 array and 64× less information than a 10243 array. For many CT systems substantial additional time is needed to produce the CT reconstruction because it is computationally hungry and is usually undertaken after completing image acquisition. With a single PC processor, necessary calculations are undertaken serially. If the model requires more voxels, there is a substantial and dramatic increase in the time required to achieve it. However, new CT systems are available that minimize the time required for the reconstruction process by feeding the acquired 2-D images into a dedicated reconstruction server as soon as they are produced. Such systems also have dedicated parallel processor boards to manipulate huge quantities of data as fast as possible. Therefore, these new systems have no real additional time penalty for the CT process when a 5123 voxel reconstruction model is required compared to a 2563 model. With a serial approach this would not be the case. In this manner, high-resolution CT models are available for viewing within moments of the image acquisition being completed. (Figure 4).

In addition to analysis of die-attach quality and wire-bond integrity within complex 3-D packages, many of these CT systems can also perform high-resolution 2-D inspection functions. Therefore, the user has a common inspection platform that has the flexibility to rapidly and easily convert their X-ray system from 3- to 2-D mode to satisfy manufacturing inspection needs. The latest X-ray tube advances means that 2- and 3-D analysis is possible with the greatest grey scale sensitivity and feature recognition down to as little as 250 nm (0.25 µm).

Inspection Capabilities and Model Visualization

The final, and vital, element of the CT process is the advanced processing software necessary to manipulate the reconstructed 3-D model and facilitate visualization of the necessary slices for the correct analytical view. This critical step allows the user to see the density contours within the sample CT model and change the viewed slice. The latest CT systems provide hardware accelerator graphics cards in the PC to specifically handle the manipulation and rendering of the CT model in real time. All of this can be viewed off-line of the image acquisition; allowing analysis of one model while the 2-D images of the next sample are being acquired. In this way individual slices can be viewed through any plane in the model to provide complete visualization of all stacked die, individual bumps, and multiple wire bonds within an advanced 3-D packaged device as shown in Figure 5.


Figure 5. Individual layers of stacked die device.
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The visualization software functions include image manipulation – rotate, pan, and zoom; clip to eliminate unwanted detail; volume rendering for creation of solid surfaces and maximum intensity, and to vary the opacity and color of volumes; slices – multiple cross-section at any orientation and the ability to vary the opacity and color of individual slices; illumination models – a single light source or two light sources with shadow computation for optimal 3-D perception; image save for saving 2-D images in JPG or TIF formats; creation of movie clips allowing a ‘flying trip’ through the model; and measurement functionality – for example when needing to inspect wire-bond loop heights.

Conclusion

Recent advancements in computerized tomography make it an ideal technique for inspection of advanced 3-D packaging because it allows complete viewing of interconnections within the package, which otherwise may be obscured by other joints when seen in 2-D X-ray inspection images. Fast CT volume reconstruction carried out at the same time as image acquisition allows complete package inspection, assuring die-attach quality, wire-bond integrity, and improved package performance.

DAVID BERNARD, Ph.D., product manager X-ray systems, may be contacted at Dage Precision Industries, Inc., 48065 Fremont Boulevard, Fremont, CA 94538; 510/683-3930; E-mail: [email protected].

(November 1, 2006) BOISE, ID &#151 Idaho Space Materials, Inc., developed a manufacturing process for single-walled carbon nanotubes (SWCNTs) that eliminates metal catalysts. The company believes this step will make removal of metal contaminants from SWCNTs an obsolete step, improving production efficiency on the relatively experimental material.

Oct. 31, 2006 — BOC Edwards, a supplier of technology, equipment and support services to the electronics and microelectronics industries, and Aviza Technology Inc., a supplier of semiconductor equipment and process technologies, announced that they have entered into a joint development agreement to develop Atomic Layer Deposition (ALD) technology for advanced semiconductor manufacturing.

The collaboration will utilize BOC Edwards’ expertise in chemical precursor formulation and Aviza’s advanced ALD hardware technology to optimize deposition processes for high-k materials and metals.

BOC Edwards’ new line of Flex-ALD precursors enables the deposition of very pure thin films and extends the range of ALD compatible compounds to include heavier elements not previously available. The company says the novel precursors can reduce the cost and improve the efficiency of ALD processes by increasing precursor utilization, providing stable and consistent delivery without decomposition or condensation, and increasing growth rates for higher throughput. The Flex-ALD precursors will be evaluated as part of the agreement with Aviza before full commercial release.

Aviza offers both single-wafer and batch ALD platforms for DRAM, flash and logic device application needs. The Celsior single wafer ALD system is specifically designed to meet high-volume manufacturing and research and development requirements. Celsior features an innovative chamber, which offers increased throughput, lower chemical consumption and an extended process window.

The Verano 5500 batch ALD system is designed to process load sizes up to 100 wafers. Enabled by Aviza’s patent pending Across-Flow technology, the Verano 5500 is intended to provide process flexibility and film composition control that achieves single wafer results in a batch environment.

(November 1, 2006) RUESCHLIKON, Switzerland &#151 In a new twist on the phrase “art imitates life,” researchers at IBM are developing an approach to cooling active packages based on a concept pulled from biology. “High thermal conductivity interface technology” involves structuring branched channels to function very similarly to the human circulatory system. Hierarchically organized to move large volumes of heat with minimal use of energy, the channels are built into a chip cap, where thermal interface material (TIM) is applied. The air-cooling technique, along with a similarly designed, closed-loop water method, is under development at the IBM Zurich Research Laboratory in Switzerland, where a biologists’ perspective permeates chip/package design.

October 26, 2006 – MEMC Electronic Materials Inc. said it has signed a deal to supply solar-grade solar wafers to Taiwan’s Gintech Energy Corp. over a 10-year period beginning in 2H07. With this deal, MEMC has agreements to supply solar wafers worth roughly $7-$9 billion in revenue over the next decade, noted MEMC CEO Nabeel Gareeb.

The supply agreement, structured on a “take or pay basis,” is expected to generate $2.5-$3.0 billion in revenues for MEMC. Gintech will also help fund expansion of MEMC’s manufacturing capacity, and provide eligibility for MEMC to purchase a 10% interest, as well as acquire rights to a 1.7 hectare parcel of land in the Hsinchu Science Park.

October 23, 2006 – Memory chipmakers’ conversion to copper damascene interconnect materials will drive 26% growth in demand for copper slurry for CMP, according to new data from market research firm The Information Network.

“We expect these manufacturers to start significantly increasing the use of copper interconnects in 2007,” stated president Robert Castellano, noting that NOR flash manufacturers have already started migrating, with NAND flash makers expected to start next year, and DRAM firms (except Micron Technology, which already has converted) migrating to copper in late 2007 or early 2008.

Copper slurry is expected to grow its share of the overall CMP slurry market to 45% in 2007 (of the total $800 million CMP market), up from 37% in the ~$700 million CMP market in 2006, the firm added. Leading the way: Cabot Microelectronics with a 32% share (2005), double that of its closest competitors Planar and Fujimi.

Flip chip interconnect will reportedly penetrate the market for wireless devices, logic, and other areas, due to favorable performance and form factor. The flip chip wafer-bumping market report segments data by product application, device type, package assembly, wafer count, and other criteria. Demand versus capacity, as well as geographical influences, provides forecasts for the market. The report lists contacts for service providers and suppliers.

(October 19, 2006) SAN JOSE, CA &#151 For the second month in a row, the North American-based manufacturers of semiconductor equipment posted equivalent amounts in bookings and billings, creating a September book-to-bill ratio of 1.00, according to SEMI’s monthly report.

by James Montgomery, News Editor

New figures from Gartner Inc. point to slightly lower-than-expected growth in semiconductor capital spending and equipment purchases, particularly for some backend segments, but the outlook for 2007 has improved somewhat as well.

The Stamford, CT-based firm now projects 2006 semiconductor capital spending will total $54.56 billion, representing 15.1% growth vs. the 16% growth Gartner forecasted in July. For 2007, the firm’s improved outlook calls for flat capital spending (0.1%), instead of a 3.3% decline, totaling $54.49 billion. The firm expects a rebound in 2008 (18.4%, less than July forecast’s 0.3%), followed by two years of contraction in 2009 (-5.1%) and 2010 (-2.0%), and a 14.2% rebound in 2011.

Comparing Gartner’s new capital expenditures forecast with its projections in July shows a few modifications. For semiconductor capital spending, the firm essentially has moved $800 million out of its estimates for 2006, and put an extra $1 billion into its 2007 numbers. “As we move into 2007, basically we’re looking potentially at factories being built, more than semiconductor equipment being purchased,” explained Dean Freeman, Gartner research VP, pointing mainly at Taiwanese memory firms PowerChip, ProMos, as well as Toshiba with its newest 100,000 wafer/month fab.

Freeman said that memory demand is still “really quite strong” right now, with a tight supply/demand balance swinging about 4%-8% either way, as companies “add supply at the same time as they’re pulling it out.” Memory spending is still relatively out of whack, with capex declining only to ~43% of sales next year, he said, but as huge amounts of capacity go in, by 2008-2009 that should drop to more normal levels of ~35%. “We see right now there’s fairly robust demand [for memory], because we see capacity coming online,” Freeman said. “But demand appears to be getting sucked up as it’s being built.”

Equipment spending is projected to stay strong at 23.5% in 2006, totaling $41.92 billion — but again, Gartner has pulled ~$600 million out of its total for the year, and tacked on ~$350 million to moderate a slowdown seen in 2007. Gartner’s new estimates show a -2.7% decline in equipment spending in 2007, vs. earlier projections of a -4.5% decline. A forecasted rebound in 2008 is seen to be a little weaker than previously thought (23.3% to $50.30 billion, vs. 24.5% growth forecasted in July), as is a downturn the following year in 2009 (-10.5% to $45.02 billion, instead of -9.5%).

Semiconductor capital equipment bookings have surged this year as chipmakers quickly add capacity, but there are a number of concerns, according to Klaus Rinnen, managing VP for Gartner’s semiconductor manufacturing and design research group, in a statement. He pointed to increasing chip inventories and a “strong potential for oversupply in both flash and DRAM if an increase in demand does not materialize,” as well as the continued gulf between steady growth in semiconductor revenues and the more volatile equipment spending growth. “Combined, these conditions create a scenario that could lead to a slight correction next year,” he said.

Gartner sees wafer fab equipment revenues rising 24.6% this year, thanks to high utilization rates (total in the low-90% range, and 97% for leading-edge capacity). However, these rates are expected to drop in 2007 (though still at around 90%) as new capacity comes online and customers absorb their shipments from 2006, resulting in slowing demand for additional capacity.

Equipment investments for backend operations seem to be more volatile in Gartner’s newer forecast, and Freeman explained that the packaging/assembly segment saw a buildup of package inventories in 1H06 resulting from environmental concerns (ROHS, lead-free, etc), but it appears that supplies have come back down.

From mid-2005 through 1Q06, the packaging and assembly equipment segment remained strong due to improving industry utilization rates, but PAE sales saw a significant decline starting in 2Q06, and end-user device demand will soften through the end of this year. Gartner called PAE tool demand “a bit murky at this point” as some semiconductor assembly and test services (SATS) suppliers take a more cautious, wait-and-see approach.

Demand for automatic test equipment (ATE) remains robust in 2006 (27.4% growth to $4.81 billion), fueled by demand for memory and system-in-package testers. But the ATE segment has also seen weakening orders in the latter half of 2006, although there are pockets of demand, with utilization rates for some segments still high, e.g. for LCD drivers. Like the other equipment segments, the ATE segment will also see a slight dip in 2007 (-1.7%), and will surge again in 2008 with nearly 30% growth. — J.M.

Oct. 16, 2006 — Scientists from Northwestern University have demonstrated a novel carbon nanotube-based nanoelectromechanical switch exhibiting bistability based on current tunneling. The device could help advance technological developments in memory chips and electronic sensing devices. The research was published online by the scientific journal Small.

“We believe the unique characteristics of this nano device will likely lead to many high-impact applications in the field of nanoelectronics and nanosensors,” said Horacio Espinosa, professor of mechanical engineering in the McCormick School of Engineering and Applied Science, in a prepared statement. Espinosa and Changhong Ke, a former graduate student of Espinosa’s, co-authored the paper.

“Although several carbon nanotube-based NEMS devices have been proposed, frankly, none of them has reached the level of commercial success,” said Espinosa. “There are many challenges associated with nanofabrication and reliability.”

The device is made of a free suspended multiwalled carbon nanotube interacting electrostatically with an underlying electrode. In the device circuit, there is a resistor in series with the nanotube, which plays an important role in the functioning of the device by adjusting the voltage drop between the nanotube and the underlying electrode.

Espinosa and Ke demonstrated the behaviors of the device by mounting individual carbon nanotubes to the tip of a tungsten probe using a nanomanipualtor inside a scanning electron microscope. Then the nanotube was actuated by applying a potential to an adjustable micron-size gap between the nanotube and an electrode. The motion of the nanotube was recorded by the electron microscope, and the current in the circuit was recorded by a source-measurement unit.

The research was supported by the Federal Aviation Administration and the National Science Foundation.