Three-dimensional top-down metrology: a viable alternative to AFM or cross-section?

Abstract

Automated critical dimension (CD) metrology has long been known to have certain limitations. As a top down imaging technique, retrograde profiles, resist thickness loss and other process issues are difficult to detect with the standard production CD SEMs used throughout the industry. Tilting capability has recently added much needed degrees of freedom to CD SEMs, potentially opening the door to three dimensional metrology. Various methodologies can be used to interpret tilt image information. This paper investigates one particular technique used to extract three dimensional information. Using cross section and/or atomic force microscopy (AFM), one can evaluate the potential benefits and validity of CD SEM tilt capability. Sidewall angle, film thickness and possibly other parameters could possibly become standard calculations the top down CD SEM could perform on a routine basis.Data is reported comparing 3D information generated from top down CD SEM to AFM. Potentially, a couple of different approaches to evaluating 3D information will be compared. Lastly, recommendations for future applications will be discussed.

Final CD control through slope/sidewall angle correlation with stepper defocus and electrical parametric

“…[5] Several advantages of profile reconstruction using the technology have been reported. [6,7] In this paper, we demonstrate sidewall angle impact in etch bias. It is clearly shown that in order to control final CD, both resist linewidth and sidewall angles have to be monitored and controlled.…”