<title>Developed photoresist metrology using scatterometry</title>

Abstract

Scatterometry is shown to be a viable alternative to current methods of post-developed line shape metrology. Five wafers with focus-exposure matrices of line-space grating patterns in chemically amplified resist were generated. The gratings were illuminated with a He-Ne laser and, utilizing only the specular reflected order measured as a function of incident angle, we were able to predict linewidth and top and bottom rounded features. The scatterometry results were verified with those obtained from scanning electron microscopy (SEM). A set of wafers having a SRAM device pattern was analyzed. These wafers contain columns of devices, each having received an incremental exposure dose. We present exposure predictions based on data taken with the dome scatterometer, a novel device which measures all diffraction orders simultaneously by projecting them onto a diffuse hemispherical `dome.' A statistical calibration routine was used to train on the diffraction patterns from die locations with known exposure values.