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

Abstract

Traditionally, lithography critical dimension (CD) measurements with stepper de-focus and deltas in sidewall angle do not correlate well with the ultimate product measurement, namely electrical performance. It is important in etch bias control, therefore, to control more than just the physical CD. It is at a minimum, important to show how the changes in sidewall angle control at lithography relate to etch biases. This is especially important as chip geometries shrink, and the size and shape of the sidewall becomes a larger portion of the line width geometry. This makes precise CD measurements coupled with slope angle measurements, in real time, important to process control in lithography so that ultimately the desired dimension is achieved at the post etch step, and therefore electrical performance can be gauged. We will present data taken from Focus/Exposure Matrices (FEMs) in the form of CD measurements, in-line sidewall angle reconstruction, and electrical measurements. We hope to correlate electrical performance to post develop CD and slope sidewall angle as measured without destructive cross sections.