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Process A&C
Focus
Post Exposure Bake
 

Process Window Studies

Weir PW & LithoWorks PW

 
Analysis of Focus - SPIE (2002) Discusses the use of Phase Grating Metrology (PGM) reticles and Phase Shift (PSFM)  patterns to analyze lithographic scanner performance.
Study of the influence of substrate topography on the focusing performance of advanced lithography scanners - SPIE 5040-47 (2003) Weir PSFM software is used to model and analyze focus variations encountered in lithography. Special etched structures in the wafer illustrate the ability of the PSFM/PGM reticle and Weir to measure small focus steps.
Critical evaluation of focus analysis methods - SPIE 5377 (2004)

Line-end-shortening (LES), ASML FOCAL, PSFM and PGM focus analysis techniques are analyzed and compared in performance.

Scanner lens-slit and reticle-scan signatures are derived by each and compared against Zernike coefficients for the same lens. Scanner induced systematic distortions of these signatures are shown and modeled as a function of wafer location and reticle scan direction.

Flight of the Scanner Slit (MLW 2004)

The PSFM reticle is used to analyze the flight-path of the reticle stage during exposure. The stage is show to pitch, roll, bank and tilt similar to an airfoil in flight. Analyses show a sensitivity of focus errors to the scan direction and residual acceleration at the start/stop of scan.

NOTE:

PSFM/PGM focus reticles are marketed by Benchmark Technologies Inc.

FOCAL is a registered trademark of ASM Lithography, Inc.

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