Electrical and Computer Engineering ETDs

Publication Date

5-1993

Abstract

The smallest device geometries, the critical dimensions (CDs), diminish with each generation of microelectronics. This puts more demands on the lithography process to repeatably produce these small dimensions within their 10% tolerance. I believe that individual optimization of the lithography steps will be necessary to meet the stringent demands of smaller CDs. This is possible through analysis of the latent image (the exposed, undeveloped pattern in the resist). In this work, a metrology technique is discussed for the determination of optimum lithography parameters through an interrogation of the latent image. This technique involves illuminating a latent image grating with a laser and measuring the power in the diffracted orders. The power of the orders diffracted from the grating is shown to be directly related to the photoactive compound (PAC) concentration profile, and consequently, to the profile of the developed resist. Analysis of the power in the diffracted orders is made possible through modeling. The model uses lithography simulation software in conjunction with rigorous coupled wave diffraction analysis. The lithography simulator provides a PAC concentration profile for given wafer compositions and lithography conditions. Diffraction analysis is then performed on this PAC profile to determine the power of each diffracted order. Experiments have been conducted with both positive and negative resists. A variety of substrates have been investigated. Using the latent image analysis technique, we have been able to determine the optimum stepper focus for all of these samples.

Document Type

Thesis

Language

English

Degree Name

Electrical Engineering

Level of Degree

Masters

Department Name

Electrical and Computer Engineering

First Committee Member (Chair)

Steve Brueck

Second Committee Member

Unknown

Third Committee Member

Unknown

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