Analysis of nanoparticles is often challenging especially when they are embedded in a matrix. Hence, we have used laser-assisted atom probe tomography (APT) to analyze the Au nanoclusters synthesized in situ using ion-beam implantation in a single crystal MgO matrix. APT analysis along with scanning transmission electron microscopy and energy dispersive spectroscopy (STEM-EDX) indicated that the nanoparticles have an average size ∼ 8–12 nm. While it is difficult to analyze the composition of individual nanoparticles using STEM, APT analysis can give three-dimensional compositions of the same. It was shown that the maximum Au concentration in the nanoparticles increases with increasing particle size, with a maximum Au concentration of up to 50%.

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

We report recent advances in tool and process hardening of a first of its kind 300 mm wafer-to-wafer (WtW) preprocessing, aligning, and bonding integrated tool. We have demonstrated sub-500 nm post-bond alignment accuracies for 300 mm WtW face-to-face (FtF) Cu-Cu thermocompression bonds, WtW FtF Si-Si fusion bonds, and WtW FtF oxideoxide fusion bonds. All process of record (POR) recipes that were developed had undetectable voids based on scanning acoustic microscope (C-SAM) measurements on representative bonded Cu, oxide, and Si blanket wafers. Optimized bonded patterned wafer splits in the Cu-Cu WtW thermocompression bonding step have shown alignment accuracies down to ∼190 nm, the highest accuracy to date. Using an infrared-enabled, high speed focused ion beam (FIB) system (with XeF 2 ) with a CAD overlay function to assist in selective sample preparation, we have verified that the bonding interfaces at the via chain structures with 1–5 μm diameter vias show no interfacial voids. Also, there is evidence of Cu interdiffusion, as supported by transmission electron microscopy (TEM) and electron backscattering diffraction (EBSD) data.

Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 – August 5, 2010.

Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009

Samples of red and black gloss from Greek Attic pottery of the late sixth to fifth centuries bc were examined using scanning electron microscopy (SEM and FIB/STEM). The focus of the study was the chemical and microstructural characterization of the red gloss that was first produced during this period. Two groupings of red gloss were revealed. One red was found to be compositionally similar to the black glosses (labelled ‘LCM coral red’). The other red showed more significant chemical differences, such as higher calcium and magnesium, in comparison to the black (labelled ‘HCM coral red’). The existence of two chemically distinct reds—otherwise identical in colour and texture—suggests that there was more than one source of clay available to the Attic potters for producing red .

Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008

Scanning transmission electron microscopy with scanning electron microscopes (SEM-STEM) has become increasing used in both SEM and dual-beam focused ion beam (FIB)SEM systems. This paper describes modeling undertaken to simulate the contrast seen in such images. Such modeling provides the ability to help understand and optimize imaging conditions and also support improved sample preparation techniques.

Recent developments in aberration-corrected transmission electron microscopy have drawn much attention from the semiconductor characterization community. Two new developments in transmission electron microscopy, image aberration correctors and probe aberration correctors, are discussed in term of their applications in characterizing gate oxide dielectrics for the IC industry.

Alternating aperture phase shift masks (AAPSM) continue to offer high contrast imaging for 65nm half-pitch using conventional 193mn illumination. The transition to high NA lithography systems including immersion lithography, and the ever-decreasing feature sizes have made the topography of the photomask a significant issue in the final resist image. Therefore, the influence of the alternating phase shift depth, the trench profile, and the critical dimension control through variable feature width must be considered and understood for optimized wafer imaging.This paper will examine the impact on imaging based on three photomasks, each employing different quartz etch chernistries. The three methods used to define the well structures include two all dry and a partial wet etch approach. As the photomask features continue to decrease, slight changes in the quartz etched trench profile and depth can severely affect the wafer prints, as the effective 180 degree phase shift for imaging is not achieved [ I]. In this work we correlate the imaging performance through pitch to a systematic evaluation of the photomask topography using complementary photomask metrology techniques.The actual depth and profile of the structures is obtained on a FEI Stylus nano-profilometer (SNP-XT) and from destructive cross sections. The CD linearity is measured on a top-down reticle CD SEM (KLA 8100XR). Based on photomask metrology data, rigorous electro-magnetic field (EMF) simulations of the various topographic profiles are performed. As a first printing performance estimate the photomasks are evaluated on a Zeiss AIMSfab193. Comparisons between the different evaluations will be made against wafer prints, obtained on an ASML PAS5500/1 100 ArF scanner working with a 0.75NA projection lens.This study will lead to an understanding of the impact of possible limitations of the current quartz etching processes on the imaging performance of alternating phase-shift masks for 65nm half-pitch.

The demands on photomask pattern transfer become tighter with every advancing technology node. Transferring patterns with feature sizes below 200nm threaten to limit lithography capabilities and prohibit the extension of current 248nm and 193nm lithography techniques. One demand that jeopardizes the current technology is the degradation of line resolution at the smaller features sizes. Transferring patterns smaller than the lithography wavelength can distort the image at the wafer. One of the resolution enhancement techniques (RET) for improving this performance and extending the lifetime of current lithography methodology is chromeless phase lithography (CPL).In this work chromeless phase lithography masks have been etched using the Tetrarm 11 Photomask Etch System. Process development of the CPL etch process is discussed with emphasis on etch depth uniformity and CD profile. Effects of varying process parameters on etch performance are discussed for a typical low load patterned mask showing excellent etch uniformity range and reactive ion etch (RIE) lag. The requirements for uniformity range and RIE lag performance (both typically < 1%) require Z-depth precision on the order of the 0.25nm provided by the SNP. Non destructive CD profiling capability of the SNP is used to show the vertical sidewall etch performance. The ability to eliminate microtrenching while maintaining excellent phase range and RIE lag is demonstrated. The capability of the TetraTM 11 Photomask etch system to undercut the chrome hard mask during quartz etch is also demonstrated.

While the National Institute of Standards and Technology (NIST) has critical dimension calibration standards for photomasks, the US agency has not yet developed a standard for phase measurements. To fill this void, a NIST-traceable phase-shift standard of varying wavelengths has been designed, fabricated, and tested.

In order to meet stringent mask CD uniformity requirements, mask makers require a high precision CD metrology tool. According to the 2003 revision of the International Technology Roadmap for Semiconductors, there are no known solutions for sub-nanometer CD precision requirements. Furthermore, ITRS lists non-destructive, production worthy mask level microscopy for CD measurement for 3D structures as one of the five difficult challenges for 2009 and beyond. This paper focuses on the recent development successes of a scanning force based microscopy platform (Stylus NanoProfilometry, SNP). Innovative scanning strategies are discussed that enable high throughput, sub nanometer CD precision on advanced mask structures. Advancements in tip technology are also highlighted with metrology data presented on re-entrant alternating aperture phase shift mask features.

A NIST traceable phase(1) shift standard has been designed, fabricated, and tested on three phase shift measurement tools using different wavelengths. By using the fundamentals of NIST traceable step height, quartz index, and the understanding of the illumination optics of the Lasertec phase metrology tool, a phase standard has been created which can be used to calibrate Lasertec phase metrology tools. The pattern that is used is compatible with the recommended best practices for calibrating and measuring step heights and phase on the Lasertec tools. The mask is made with multiple depths. The three mask depths allow for the mask to be calibrated to three NIST traceable depth heights. This was done using the FEI SNP XT depth metrology tool. Since the mask format is mask based (6x250 Cr on quartz), it can be easily used on mask manufacturing metrology systems. The depths are targeted at the 180-degree phase shift for 157nm, 193nm, and 248nm lithography. The mask can be used to set targets and check the linearity of the phase metrology tools. The patterns are compatible with AFM and Profilometer depth metrology tools as well as multiple Lasertec spot sizes and shearing distances. The quartz depths are fabricated using a wet quartz etch process. The wet etch minimizes the quartz roughness and removes that error source from the metrology. The pattern is also arrayed so that multiple sites can be used to confirm the metrology and the prime measurement site could be changed if there was a suspicion of pattern damage or contamination.

Etec Systems, the Mask Business Group of Applied Materials, is in a unique position within the mask making industry - Etec has the opportunity to integrate individual parts of the overall mask manufacturing process to provide a more complete solution. Here we present the integration of the DUV ALTA(R) laser 14 pattern generator and the Tetra(TM) photomask etch system with advanced CAR resist processes. Dry etch process effects of flow, overetch, and oxygen content (in a Cl-2/O-2/He plasma) are discussed for the baseline POR resist in terms of etch rate, selectivity, etch bias, CD uniformity and micro-loading; the optimized etch process space was then implemented for advanced CAR resists. Iso-dense bias, football pattern loading and other pattern transfer results influencing mask manufactureability are also presented. Within the synthesis and optimization of the pattern generation system, process, and dry etch sub 13 nm range process uniformity has been achieved. The integrated ALTA / Tetra / Advanced-CAR solution set is characterized on both Etec test patterns and customer demonstrations.

The ALTA 4300 system has been used to successfully write many advanced design layers previously only feasible with 50kV vector shaped beam tools. In order to further enlarge the application space of this high productivity an aerial image enhancement technique has been developed to deliver mask patterns that more closely match pattern data for corners and jogs. This image enhancement is done in real time in the ALTA system’s rasterizer by modifying the gray level mapping of pixels near the corner vertexes. SEM measurements of corner rounding with standard rasterization and the enhanced rasterization show an improvement of corner rounding radius from ~205 to ~132 nm. A direct comparison of SEM micrographs show no qualitative difference between vector scan mask features and those written with aerial image enhancement. This convincingly demonstrates that the ALTA 4300 system with the new image enhancement can write many layers requiring vector scan corner acuity.

As mask specifications continually tighten with the ever- present progression of Moore's law, mask manufacturing specifications have become increasingly difficult to achieve. Global process optimization from coast to etch is critical for achieving the required mask performance. As an Applied Materials company, Etec is in a unique position within the maskmaking industry to introduce mask manufacturing solutions that are optimized across a number of process steps. Working with the Applied Materials photomask etch team, Etec's laser mask-patterning group characterized and implemented an integrated process recipe for the deep UV, raster-scan, continuous-wave, laser mask- patterning ALTA 4000 system and the Applied Materials Tetra Photomask Etch System.

Endpoint measurement sensitivity requirements in photomask can make or break an etch. The exposed chronic on today's photomask can vary between 0.25% and approximately 50%. Although excessive overetch does not deleteriously impact the underlying quartz, accurate endpoint detection is essential for preserving the critical dimension (CD) and CD uniformity across the mask.In order to provide a strong endpoint solution for photomask etch. a systematic investigation of etches with varying chrome loads was conducted. Passive monitoring of the optical emission spectra does not impact or interfere with the etch process. Also this method does not need specified endpoint sites on the mask as interferometric methods and provides an integrated endpoint signal over the whole mask area independent of the chronic clearing pattern.Two strong candidate wavelengths for calling endpoint in chrome etch were identified. However, optical emission spectroscopy endpoint detection has two drawbacks, which have historically limited its applicibility. Firstly, the exposed area may be too low and/or secondly, the etch rate may be too slow for detection. Both of these concerns have been addressed in this paper by varying the exposed area on the photomasks from 0.25% to 99%. Endpoint was easily detected even for the slowest possible etch rate (99% chrome load) and for low exposed area (0.25% chronic load).

Shrinking design rules, optical proximity correction and advanced phase shifting techniques require new methods of photomask manufacturing. The Applied Materials Centura photomask etch chamber leverages Applied Materials' extensive etch experience to provide an innovative dry etch solution to the mask dry etch challenges for < 0.13 micrometers device generations. Repeatable, consistent, stable etch performance is critical for advanced mask manufacturing. An extended chamber matching and repeatability study for chrome etch found that stable chrome and photoresist etch rates (and therefore selectivities) are produced on the Applied Materials Centura photomask etch chamber. The etch responses are consistent mask to mask as well as chamber to chamber. Prior to the extended study, pumping efficiencies, RF source and bias calibrations and optical emission spectral responses were compared. Since the study was performed at several different sites, the metrology tools were calibrated using masks specifically designed for this purpose. The marathon testing illustrates the stable etch performance over time.

This paper discusses methods used for photoresist selection and etch processing for laser mask patterning tool characterization. A major requirement of a deep ultraviolet (DUV) resist is that is has a storage capability of more than 90 days. This means the material does not have to be coated on demand to deliver exceptional lithographic performance. Process difficulties in the development and implementation of an advanced DUV maskmaking solution and how they are being addressed is also described. The purpose of this paper is to provide a look at the resist, develop, and etch processes being developed at Etec Systems, Inc. for DUV maskmaking applications. Key topics are etch characterization and resist process optimization at 257nm associated with the migration to DUV from i-line manufacturing environments and turning from wafer to mask patterning applications. The paper also shows results of work being done to assess alternative resist chemistries in an attempt to maintain a precoated mask blank option for mask shop use. The paper points out issues to be considered when moving from diazoquinone (DNQ) chemistry to chemically amplified resists (CAR) processing in a mask manufacturing environment.