Dr. Sunit S. Dixit Profile

Dr. Sunit S. Dixit

Retired

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Publications (10)

Proceedings Article | 12 June 2003 Paper

TMAH soak process optimization with DNQ positive resist for lift-off applications

Salem Mullen, Medhat Toukhy, Ping-Hung Lu, Sunit Dixit, Paul Sellers

Proceedings Volume 5039, (2003) https://doi.org/10.1117/12.485198

KEYWORDS: Photoresist processing, Standards development, Semiconducting wafers, Floods, Photoresist developing, Metals, Scanning electron microscopy, Photoresist materials, Coating, Metrology

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Proceedings Article | 23 June 2000 Paper

Optimization of bottom antireflective coating materials for dual damascene process

Shuji Ding, Wen-Bing Kang, Hatsuyuki Tanaka, Sunit Dixit, Ronald Eakin, Jianhui Shan, Eleazar Gonzalez, Ying Liu, Dinesh Khanna

Proceedings Volume 3999, (2000) https://doi.org/10.1117/12.388377

KEYWORDS: Polymers, Etching, Deep ultraviolet, Semiconducting wafers, Coating, Fourier transforms, Lithography, Thin film coatings, Bottom antireflective coatings, Silicon

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Proceedings Article | 23 June 2000 Paper

Lithographic performance enhancement using top antireflective coating compositions made from water-soluble polymers

Sunit Dixit, M. Rahman

Proceedings Volume 3999, (2000) https://doi.org/10.1117/12.388257

KEYWORDS: Antireflective coatings, Coating, Lithography, Polymers, Reflectivity, Bottom antireflective coatings, Thin films, Scanning electron microscopy, Optical lithography, Thin film devices

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Proceedings Article | 2 June 2000 Paper

Application of top-down CD-SEM metrology in measuring and correlating profile with CD data in resist films with various thickness and sidewall profiles

Sunit Dixit, Amir Azordegan, Ying Liu

Proceedings Volume 3998, (2000) https://doi.org/10.1117/12.386446

KEYWORDS: Critical dimension metrology, Scanning electron microscopy, Semiconducting wafers, Metrology, Photoresist materials, Lithography, Inspection, Image processing, Etching, Signal processing

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To have a more complete and clear picture for resist characterization, a second metric is needed to supplement the traditional linewidth data. A fast and non-destructive metrology system is desired to provide resist profile information. Electron scan and SEM image correlation capability will provide this second metric to effectively select the correct and precise process window. Monitoring for high electron line scan correlation values allows one to maintain a sharp sidewall profile of photoresist while supporting high aspect ratios. This is ideal for magneto- resistive (MR) and inductive thin film recording head coil plating and many other mission-critical applications. An automated top-down CD-SEM technique, capable of acquiring and analyzing electron waveform profiles of resist lines in addition to the traditional linewidth values is reported here. These measurements were made using a KLA-Tencor 8100 CD SEM, taking advantage of its new Pattern Quality Confirmation (pQC) feature. Process engineer using pQC can correlate signal intensity and images against stored templates, and then output the correlation scores. The technique has been applied to silicon wafers coated with various AZ^R photoresists, such as AZ^R 3300, AZ^R7200, AZ^R7500, and AZ^R7900, with thickness of 1 - 3 microns. Wafers were exposed using a Nikon I line stepper and then developed by AZ^R 300 metal ion free developer. Focus-Exposure dose-array fields were measured to investigate their profiles transformation as well as CD through and beyond their exposure latitude. Correlation scores were derived using aspect ratio of film thickness vs. CD size in each resist family. The study was extended by inspecting 'image correlation' values of high aspect ratio Contact Holes. Possibility of automating determination of open versus closed Contact Holes printed in these photoresists is also discussed. The goal of this study is to optimize determination of acceptable process window, by utilizing line and image correlation to compliment CD data.

Proceedings Article | 14 June 1999 Paper

Application of top-down CD-SEM metrology in measuring wafers with resist film thickness of 24 um with various sidewall profiles

Sunit Dixit, Ying Liu, Amir Azordegan

Proceedings Volume 3677, (1999) https://doi.org/10.1117/12.350784

KEYWORDS: Scanning electron microscopy, Metrology, Photoresist materials, Critical dimension metrology, Semiconducting wafers, Nondestructive evaluation, Thin films, Head, Plating, Electron microscopes

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An automated top-down CD-SEM technique, complimenting the existing high angle tilt SEM method has been developed for measuring features printed at a film thickness of 24 microns. Measurements of resist linewidth versus exposure dose were made using a KLA 8100 top-down CD-SEM. The advantage of this CD-SEM is the automated collection of a large statistical pool of data and the ability to determine the linewidth independently of operator, accurately and consistently. The technique has been applied to AZ P4000 and AZ 9000 photoresist thick films through and beyond their exposure latitude. Maintaining a sharp sidewall profile of photoresist while supporting high aspect ratios is ideal for magneto-resistive and inductive thin film recording head coil plating and many other mission-critical applications. Also a fast and non-destructive thin film recording head coil plating and many other mission-critical applications. Also a fast and non-destructive metrology technique is desired and preferred to support future more costly and larger substrates. Results are reported for 10 and 6 micron reticle linesizes, respectively, at a film thickness of 24 microns using the AZ P4620 and AZ 9262 positive photoresist over bare silicon wafers. Wafers were exposed using an Ultratech Ultrastep Stepper model 1500 system and then developed by AZ 400 K inorganic developer. Exposure dose- array fields were measured first on the top-down KLA CD-SEM and then coated and re-measured on a Hitachi scanning electron microscope with 60 degrees-tilt capability. The importance of knowledge of resist profile and choosing the proper metrology tool is discussed. Linewidth values were compared with result from the standard tilt microscope reading method. Agreement to within 10 percent is noted for profiles corresponding to most exposure doses. Profiles for higher, over-exposed fields resemble a 'coke bottle' and linewidth for bottom of resist is inferred by extrapolation based on the prior correlation found between the two SEMs. The AZ 9262 resist line features showed a smaller 'coke bottle' profile at higher doses than AZ P4620 line features. Further work is planned for other positive resists with non- traditional profiles on unconventional substrates.

Proceedings Article | 11 June 1999 Paper

Process and performance optimization of bottom antireflective coatings: II

Shuji Ding, John Sagan, Jianhui Shan, Eleazar Gonzalez, Sunit Dixit, Ying Liu, Dinesh Khanna

Proceedings Volume 3678, (1999) https://doi.org/10.1117/12.350152

KEYWORDS: Coating, Electroluminescence, Bottom antireflective coatings, Particles, Semiconducting wafers, Edge roughness, Liquids, Photoresist materials, Chemical analysis, Scanning electron microscopy

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Proceedings Article | 29 June 1998 Paper

Process and performance optimization of bottom antireflective coatings

Shuji Ding, Ping-Hung Lu, Jianhui Shan, Eleazar Gonzalez, Salem Mehtsun, Sunit Dixit, Dinesh Khanna

Proceedings Volume 3333, (1998) https://doi.org/10.1117/12.312480

KEYWORDS: Coating, Photoresist materials, Semiconducting wafers, Lithography, Bottom antireflective coatings, Silicon, Refractive index, Reflectivity, Antireflective coatings, Silicon films

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Proceedings Article | 29 June 1998 Paper

Novel novolak block copolymers for advanced i-line resists

Stan Wanat, M. Rahman, Sunit Dixit, Ping-Hung Lu, Douglas McKenzie, Michelle Cook

Proceedings Volume 3333, (1998) https://doi.org/10.1117/12.312451

KEYWORDS: Polymers, Resistance, Solids, Lithography, Absorption, Picture Archiving and Communication System, Chromatography, Optics manufacturing, Electroluminescence, Lutetium

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Proceedings Article | 7 July 1997 Paper

Use of highly absorptive azo dyes in photoresist coatings

Ping-Hung Lu, Shuji Ding, T. Hannigan, D. Eberly, Elaine Kokinda, Sunit Dixit, Salem Mehtsun, Anthony Corso, Dinesh Khanna

Proceedings Volume 3049, (1997) https://doi.org/10.1117/12.275880

KEYWORDS: Reflectivity, Photoresist materials, Lithography, Aluminum, Dysprosium, Thin film coatings, Absorbance, Semiconducting wafers, Chromophores, Critical dimension metrology

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Proceedings Article | 1 June 1992 Paper

Photoresist formulation optimization through the use of statistical design of experimentation

Ken Bell, Nadine Acuna, Sunit Dixit, Richard Lazarus, George Talor

Proceedings Volume 1672, (1992) https://doi.org/10.1117/12.59770

KEYWORDS: Lithography, Photoresist materials, Thermal modeling, Statistical analysis, Optimization (mathematics), Solids, Scanning electron microscopy, Data modeling, Photoresist processing, Photoresist developing

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This paper describes the use of statistical design experimentation to improve the photoresist performance properties of Dynachem's Nova 2070. A full factorial design was employed to investigate the effects of changes in the weight percent of both the minor resin and sensitizer in the total solids and of changes in the major resin's molecular weight on the after-hardbake wall profiles. The effect of the formulation changes on lithographic properties such as process latitude and resolution has also been measured. Scanning electron micrographs (SEMs) were generated to measure wall profile, thermal, and lithographic properties. A SEM measurement technique was then developed to quantify resist thermal stability. From these measurements models were generated to show the effects of the various formulation changes and to make predictions with respect to optimum formulations. Graphs of profile tendencies as a function of formulation changes and hardbake temperature and response surfaces generated from the various models are presented to help illustrate the optimization trends. With respect to lithographic performance, the experimental and model data indicate that the optimum resist formulation within the tested experimental matrix has the following make-up: high major resin molecular weight, low minor resin content, and high sensitizer content. With respect to thermal stability, the data suggests that the optimum resist formulation is the following: high major resin molecular weight, high minor resin content, and low to medium sensitizer content. The lithographic property optimum formula was retested to optimize its performance as a function of process changes according to a quadratic statistical design. Comparative process latitude graphs contrasting the optimum formula to alternative formulas under their respective optimized process conditions are also presented. These studies are collectively analyzed to indicate the direction that future resist formulation changes could be made to further optimize resist performance.

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