Category Archives: Metrology

by Bob Haavind, Editorial Director, Solid State Technology

Feb. 26, 2008 – While 193nm immersion lithography has taken the industry to 45nm it will get progressively tougher to move below that. Lithographers will struggle with shrinking margins, more metrology and process control, along with extensive computation, plus double exposure for critical layers which multiplies their problems.

The SPIE Advanced Lithography Conference in San Jose, CA, is exploring this road ahead. Below 40nm, lithography becomes much more sensitive to stepper variation, and computational optimization will be required, according to Martin van den Brink, EVP, ASML, in a plenary talk. Lithography uniformity becomes critical, and metrology will be very difficult, especially with double exposure.

“Stepper controls are not well used today,” he said. It is possible to adjust dose point-by-point across the wafer, he suggested, but only with a tremendous amount of computation. Angle-resolved scatterometry feedback loops in production with a DoseMapper recipe might provide optimization. There also must be increased feedback from manufacturing to design, van den Brink added.

While EUVL continues on track for 22nm, he believes that memory makers will make strong use of double-patterning before going to EUV. Overlay and CD control using application-specific scanner tuning with fast, integrated metrology feedback will help make this possible, according to van den Brink. The process will also require pattern-split software.

D. Mark Duncan, president/CEO of Micron, agreed in his plenary talk that double patterning will be needed for future memory cells, but as the shrink continues, he foresees accelerating patterning costs. Going to 3D will forestall the move below 32nm for a time, he suggested.

Pushing NA higher for immersion lithography using new lens materials and a higher index-of-refraction fluid, could help reduce the challenge. But this will not be an option for 22nm, pointed out Toshikaya Umatata, GM of development headquarters for Nikon Precision, in a presentation a day earlier.

“High index does not match with the Roadmap,” he stated. Instead, at 22nm, EUVL will be the only candidate for general patterning, he added.

Micron’s Duncan did an analysis that supported this view. “I am confident that EUV is at the end of the Roadmap,” he stated. He sees EUV as the route to lowering rising patterning costs in the 2010-2012 timeframe. Duncan pointed out that chipmakers have to make massive bets on new factories, spending $3B on a new fab, much more than for an auto assembly plant, for example. Only an offshore rig, at $1.5-$2B, comes close. Yet, Duncan showed that the incremental gain in dollars/die would be shrinking significantly over the next few nodes.

ASML’s van den Brink took note of this investment concern in discussing the push toward higher productivity exposure tools. An analysis shows that acceleration is much more critical than scan speed, he explained. Right now, he said, an immersion tool can move at 600mm/sec, but to boost productivity further, the goal is to push that beyond 1m/sec, with lower defects and even tighter metrology overlay capability, moving from 4nm down to 2nm. Current 193nm immersion tools reach an NA of 1.35 without new lens materials and higher-index fluids, which is scalable down to 38nm, he said. Then double patterning, and eventually EUVL, will be needed.

While some experimental EUV tools are in operation, the technology will not be suited for volume production until an entire infrastructure is in place, pointed out Ben Eynon, associate director of SEMATECH’s lithography division in Albany, NY (assigned from Samsung). He reviewed the EUV infrastructure status at a pre-conference session organized by KLA-Tencor.

A major concern is an X-ray source that can deliver sufficient power to the wafer to meet reasonable throughput goals. Current sources can deliver 6W to an intermediate focus point, but 180W will be needed. “We need two orders of magnitude improvement, and that is a big challenge,” he said.

One source candidate is a discharge-produced plasma (DPP), but this involves a heavy heat load and does not scale well. More promising, according to Eynon, is a laser-produced plasma (LPP), using droplets of tin. The burst power needs to be focused, but the scalability is promising, he said.

EUVL will also require a resist that provides high resolution, allows adequate throughput, and minimizes line-edge roughness (LER). Right now, candidate resists that meet one requirement fail at the others, so improved materials will be needed to meet all three together.

Reflective reticles are essentially mirrors that must be flawless, Eynon explained. Any flaw on the glass substrate is greatly amplified after depositing 80 alternate layers of silicon and molybdenum over a 10hr period — any pit or particle would build up, making the reticle useless. Methods are being developed to remove any particles over 4nm high, and each layer may be smoothed out as deposition proceeds to minimize potential flaws. The eventual target is about 1 defect every 5 blanks or so, Eynon said.

For production, an EUV aerial imaging tool will be needed, he said, but the market will be so small that SEMATECH will need to help in the development.

“EUV still looks more cost-effective than double exposure, if we can develop it in a reasonable time,” Eynon explained. “That’s why we’re still pushing.” — B.H.

Feb. 26, 2008 – Carl Zeiss and SEMATECH say they have completed final design for a next-generation photomask registration and overlay metrology system, dubbed “Prove,” that will enable production of advanced photomasks “with substantially improved image placement accuracy,” eyeing in particular the tighter placement control required for double-patterning technology.

The new system ascertains the accuracy of mask pattern alignment, and registration for 32nm half-pitch and beyond photomasks, they say in a statement. The metrology technology also forms part of the critical infrastructure of EUV. SEMATECH indicated the work has led to completion of design for quantifying image placement errors as small as 2.4nm. The tool itself is expected to be in production in 2009, targeting primarily mask manufacturers.

A key component of the system, the companies indicated, is a diffraction-limited, high-resolution imaging optics operating at 193nm corresponding to at-wavelength metrology for the majority of current and futures photomask applications. They also point to a “reasonable working distance” that allows through-pellicle measurements. Two illumination paths offer measurements both in transmission and reflection (e.g. for EUV), providing flexible illumination for maximum contrast imaging. The photomask resides on an ultra-precision stage, being the only movable part in the imaging path.

“Future lithographic scaling places a high reliance on very tight overlay control of the various device levels, and the photomask is a key component of the overlay error budget,” stated Michael Lercel, SEMATECH director of lithography and chairman of the ITRS Litho Working Group. “This new system will get us past several previously ‘no known solution’ challenges.”

February 25, 2008 — Steinmeyer Inc. has released its new high precision micro manipulator stage, MT 130-50-DC, geared toward nanotechnology, metrology, biomedical, and robotics applications.

Manufactured from high strength anodized aluminum, the standard table offers travel of 50 mm with positioning accuracy of 10 µm (micrometer), straightness/flatness runout of +/- 1µm and repeatability of +/- 1µm. With a sleek low profile design, it has a square footprint of 130 mm x 130 mm, height of 43 mm and weighs only 1.8 kg, the company announced in a news release.

Features include reloaded cross roller bearings, precision ground ball screw, limit switches, and integrated dc motor with rotary encoder. This product can be provided as a XY stage and can also be configured as a XYZ system-model MP 130-50-DC as a further enhancement. Motors, encoders and cabling are all hidden inside the table’s body.

Motor, limit switch and encoder interface are via SUB-D connectors located in a single area. This stage is suited for semiconductor metrology, biomedical, miniature robotics, and laser industry applications, the company says.

Feb. 21, 2008 – The latest move in metrology industry consolidation has occurred with KLA-Tencor’s proposed “friendly” acquisition of Belgium firm ICOS Vision Systems in a proposed €316.9M (US $465.8M) cash transaction.

The €36.50/share ($53.75) offer represented a 35% premium to ICOS’ three-month average closing price. KLA-Tencor also said will offer to purchase ICOS shares underlying all outstanding 2002 employee stock options and 2007 employee warrants.

The deal, anticipated to close sometime in 2Q08, requires approval from 85% of ICOS’ shareholders. Also, a clause indicated by both companies notes the bid must not be subject to review by government/jurisdictional antitrust authorities “beyond the initial phase of review.”

In a statement, KLA-Tencor CEO Rick Wallace noted “exceptional synergy” in markets and technologies, “with additional opportunities for both growth and diversification” — ICOS provides “a significant presence” in semiconductor packaging inspection, and inroads into growth sectors such as LED lighting and solar.

For ICOS, the proposed combination “would significantly increase our growth potential and provide remarkable resources for advanced technical development of our existing products and technologies,” stated president/CEO Anton De Proft.

Under the membership agreement, Rudolph and SEMATECH will jointly establish an International Process Characterization (IPC) program, aimed at the development of process, analysis, and characterization technology to address critical challenges in nanoelectronics research.

(February 21, 2008) — MEPTEC, the MicroElectronics Packaging and Test Engineering Council, has finalized the program for its 4th Annual Thermal Management symposium titled “The Heat Is On: Thermal Technology Solutions for Advanced Products.” This one-day technical event will be held on February 28, 2008, at the Wyndham Hotel, San Jose, CA.

Feb. 20, 2008 – Rudolph Technologies and SEMATECH are establishing an international process characterization program to develop process, analysis, and characterization technology targeting 32nm and beyond semiconductor manufacturing. Work will be headquartered at the U. of Albany’s College of Nanoscale Science and Engineering (CNSE). Rudolph says it is the first semiconductor equipment supplier to join SEMATECH’s metrology program at Albany.

The deal involves working with members of SEMATECH and subsidiary ISMI to accelerate development and application of measurement methods for advanced semiconductor technologies, particularly integrated metrology, inspection and yield enhancement software, under the goals of overcoming challenges of increased process complexity, shrinking sizes of systematic and extraneous defects, and harder-to-discern actionable information gleaned from raw data.

Initially the IPC program will addresses a range of issues, including the metrology of thin films and metal gate stacks; wafer front/back/edge macrodefect inspection; inspection and metrology for through-silicon vias (TSV) and 3D IC; immersion lithography process characterization; process modeling and optimization for yield enhancement; and automatic defect classification (ADC). Also, the program aims to establish benchmarks for cost-effective solutions by including cost-of-ownership criteria in all projects.

“The integration of advanced hardware and intelligent analytical software will be the key to meeting these challenges,” said Rudolph COO Alex Oscilowski, in a statement. “We’re looking forward to contributing our experience, front-end to back-end throughout the manufacturing process, and our broad expertise in metrology, inspection and data analysis technologies, to this important joint effort.”

Michael Polcari, president/CEO of SEMATECH, added that “ultimately, we believe the IPC program can serve as both a foundation and a model for expanded programs in this critical area of metrology and process characterization.”

The $7.5 million, three-year program, which is funded jointly by SRC and New York State, begins this month, with the UAlbany NanoCollege serving as home for the New York Center for Advanced Interconnect Science and Technology (NY CAIST). In addition to CNSE, universities contributing to the research results will be Columbia University, Cornell University, Lehigh University, Massachusetts Institute of Technology (MIT), Penn State, Rensselaer Polytechnic Institute (RPI), Stanford, SUNY Binghamton, University of Florida, University of Maryland, University of North Texas, University of Texas at Arlington, and the University of Texas at Austin.

(February 21, 2008) Flanders, NJ and Albany, NY — Rudolph Technologies Inc. and SEMATECH, have announced that Rudolph has become the first semiconductor equipment supplier company to join SEMATECH’s Metrology Program headquartered at the College of Nanoscale Science and Engineering (CNSE) of the University at Albany.

Metris Acquires X-Tek Group


February 15, 2008

(February 15, 2008) Leuven, Belgium — The X-Tek Group, specialists in microfocus and CT X-ray systems, signed an agreement with Metris for the sale of 100% of the X-Tek stock at the end of 2007. The acquisition will enable Metris to expand X-Tek’s CT capabilities into various applications within the metrology industry.

January 28, 2008 — Veeco Instruments Inc., has introduced its new InSight 3D Automated Atomic Force Microscope (AFM) Platform.

According to the company, the new platform is “the only metrology system available with the accuracy and precision required for non-destructive, high resolution three-dimensional measurements of critical 45nm and 32nm semiconductor features, with the speed to qualify as a true fab tool.”

Veeco’s InSight 3DAFM was designed specifically to address Critical Dimension (CD), depth and chemical mechanical planarization (CMP) metrology in a production environment, the company said.

Jan. 10, 2008 – Coming off a year in which it significantly changed its focus and carved out multiple businesses, Nanometrics is starting the new year where it left off.

The move, a response increasing softness in semiconductor capital equipment demand, will reduce the company’s global workforce by about 7%, affecting each of its worldwide locations. Restructuring charges of about $600K will be recorded in 1Q08, but cost savings will be “fully realized ” by 2Q08, according to president/CEO Tim Stultz. “While this was a difficult decision for us to make, it came about as a result of our stated strategy to run our business with reduced sensitivity to revenue level,” he said in a statement.

Stultz added that the company still holds a positive longer-term outlook about the metrology sector, and that the company is well-positioned in its markets and will remain “committed to investing in R&D.”

Nanometrics has had a busy past year, after acquiring two metrology firms in the summer of 2006 (Soluris and Accent Optical Technologies). In March of 2007 its CEO left the company, followed by the CFO and April. In the fall it sold off its Yosemite CD-SEM and DiVA product lines, consolidated its overlay metrology production in Korea (and closed the Soluris site in Concord, MA), sold an idle FPD-related facility in Japan and a machine/plating shop in the US, and appointed former Imago top exec Stultz as its new CEO.