Advanced FTIR techniques for photoresist process characterization

Several applications of Fourier transform IR spectroscopy (FTIR) for the characterization of photoresist thin films are demonstrated. The applications are accurate resist thickness measurements, monitoring of solvent loss during the post-apply-bake, determination of the glass transition temperature, and deprotection reaction kinetics. Model based, spectral analysis is applied for the determination of photoresist thickness from mid-FTIR spectra and is shown to have linear correlation to measurements with UV-visible spectroscopic ellipsometry. Using this capability in conjunction with an external reflection accessory and rapid data acquisition hardware and software, measurements are performed on Shipley SPR-510L photoresist during the post apply bake step, deriving thickness and solvent loss information. The use of this approach is also explored for making glass transition measurements of an environmentally stable chemical amplification positive resist photoresist. Finally, in-situ PEB studies are illustrated for APEX-E photoresist. For off-line analysis, an in-sample compartment mapping accessories is applied to the characterization of multiple open frame exposure matrices on 200 mm double-side polished wafers.