Air-turbulence-compensated interferometer for IC manufacturing

Steven A. Lis

doi:10.1117/12.209314

26 May 1995 Air-turbulence-compensated interferometer for IC manufacturing

Steven A. Lis

Proceedings Volume 2440, Optical/Laser Microlithography VIII; (1995) https://doi.org/10.1117/12.209314
Event: SPIE's 1995 Symposium on Microlithography, 1995, Santa Clara, CA, United States

Abstract

SPARTA has developed a novel dual wavelength interferometer which is directly aimed at stepper stage control and general IC metrology. It utilizes an existing HeNe based dual frequency interferometric system and couples it directly to a second system which provides the real time air turbulence compensation. The optical design provides for colinear optical beam paths for the two systems over the measurement path. Compensated position measurements are provided at a rate of 30 Hz which is sufficient to permit high throughput stage positioning for all modern steppers. Stage position accuracy is determined to 4 nm 3(sigma) and stage precision (which is a two pass operation) can be 5.6 nm 3(sigma) . Future improvements in performance can be expected since the present design is not near fundamental limits. The interferometric system design has a form factor compatible with existing stepper systems. Testing of this system has been carried out in a laboratory environment under a variety of conditions, including those which would simulate a clean room environment. Test results are used in detail and conclusions will be presented which define the impact this system can have on stepper overlay performance and IC metrology. Because the interferometer is the basic ruler upon which much of the stepper metrology, setup, and operation is based, an improvement in performance of this system provides numerous benefits in the areas of stage precision, alignment, lens metrology, and reticle qualification and fabrication. Furthermore, the elimination of air turbulence as a stepper design concern can permit improvements in stepper performance and throughput with fewer engineering compromises.

Citation Download Citation

Steven A. Lis "Air-turbulence-compensated interferometer for IC manufacturing", Proc. SPIE 2440, Optical/Laser Microlithography VIII, (26 May 1995); https://doi.org/10.1117/12.209314

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