Article

Metrology sensors for advanced resists

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Abstract

We have initiated an effort to develop metrology tools that isolate the effect of each process step. Light scattered from diffracting structures is analyzed to determine characteristics of the structure. The technique is rapid, non-destructive, and extremely sensitive to variations in the samples that were examined. Through our technical collaboration with Texas Instruments Inc. we obtained wafers coated with surface imaging resists and exposed under varying focus and exposure conditions. We present results that utilize scatterometry to monitor the exposure step to determine defocus and exposure variations in the latent image. We also report using scatterometry to monitor the post-exposure bake (PEB) process for chemically amplified resists. Wafer-to-wafer variations in resist and underlying film thicknesses result in CD variations for constant exposure. The PEB time can be adjusted for each wafer to account for some of the parameter variations. We present experimental data supporting the concept of a scatterometer PEB monitor.

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Thesis
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