Surface chemistry study of gallium arsenide wafers during chemically amplified resist patterning and resist studies with fluorescence.

摘要

Adhesion failure has been experienced when using a negative chemically amplified resist, Shipley SAL 605, on GaAs wafer surfaces. The results of ESCA analysis show a 10 A oxide layer on the original surface. A contact angle of 50 degrees was obtained on this surface. In order to get adequate adhesion, the work of adhesion has to be larger than 5 dyne/cm, which corresponds to contact angles larger than 60 degrees. Hydrochloric acid treatment can effectively remove the native oxide layer and form an As-rich, hydrophobic surface. This treatment produced a surface with a contact angle of 64 degrees. Using this surface treatment, we were able to produce 1 cm long 0.15 micron wide lines in 0.5 micron thick resist on GaAs.; A near-field fluorescence imaging technique was explored with collaboration from Yale University for the determination of acid distribution in a negative resist, SAL 605. Both fluorescence and shear-force images were obtained on 0.215 micron features. This work demonstrated that near-field optical microscopy combined with fluorescence measurements can provide adequate spatial resolution necessary for imaging sub-quarter micron features and may be used for acid diffusion measurements.; An on-wafer spectrofluorometric imaging technique was developed to evaluate the relative efficiency of various photoacid generators. This technique involves adding a small amount of pH-sensitive fluorescent material, Cl-NERF, into resists and measuring the fluorescent response as a function of exposure doses for each resist. Three compounds were evaluated with this technique and compared to Shipley SAL 605. The advantages of this technique are that it is fast, convenient, and robust.; A confocal fluorescence imaging technique for acid diffusion determination was developed and used to measure the acid diffusion in a positive resist, Shipley UV-III. The fluorescence measurement results showed the acid diffusion occurred in the resist, and an upper limit of the diffusion coefficient obtained was 3 x 10-15 cm2/s. This technique directly probes the acid distribution in a latent image without the convolution with other effects from subsequent processes.