Optimization of optical properties of resist processes

Timothy A. Brunner

doi:10.1117/12.46410

1 June 1991 Optimization of optical properties of resist processes

Timothy A. Brunner

Proceedings Volume 1466, Advances in Resist Technology and Processing VIII; (1991) https://doi.org/10.1117/12.46410
Event: Microlithography, 1991, San Jose, CA, United States

Abstract

Thin film interference plays a dominant role in CD control of single layer photoresist processes, causing large changes in the effective exposure dose due to a tiny change in optical phase. Such interference effects are evident in the sinusoidal undulations of a plot of dose to clear versus resist thickness, the 'swing curve'. To quantify the interference swing, we define the swing ratio S as the ratio of the peak to valley change to the average value in the swing curve. S is a fundamental figure of merit for photoresist processes, since linewidth variations with small changes in resist thickness are proportional to S. A simple optical model of photoresist (as a Fabry-Perot etalon) leads to the following analytical expression for the swing ratio S: S approximately equals 4(root)R1R2 e-(alpha D) where R1 is the reflectivity of the resist/air interface, R2 is the reflectivity of the resist/substrate interface, and (alpha) is the resist absorption coefficient. Efforts to improve process control have lead to the invention of many cleaver resist processes including Top Surface Imaging (TSI), Anti-Reflection Coats (ARC), dyed resists, etc. Eq. 1 allows a classification of these processes according to which factor is modified. For example, TSI and dyed resist processed reduce S by increasing (alpha) . ARC processes reduce S as the square root of substrate reflectivity under the resist R2. Fundamental limits of the performance of thin absorbing ARC layers will be described. A novel approach, termed the Top Anti-Reflector (TAR) process, reduces the reflection at the top of the resist R1 and can be shown to dramatically improve process control over varying thicknesses of resist and thin film layers. The effects of multiple wavelength exposure and oblique rays from high NA optics are also briefly examined.

Citation Download Citation

Timothy A. Brunner "Optimization of optical properties of resist processes", Proc. SPIE 1466, Advances in Resist Technology and Processing VIII, (1 June 1991); https://doi.org/10.1117/12.46410

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available