Resolution and Sensitivity of a Resist with and without Hexamethyldisilazane Determined Using Profilometry

We evaluated the resolution and sensitivity of a resist with and without hexamethyldisilazane (HMDS), which improves resist adhesion to substrates, by using profilometry. HMDS was spin-coated onto a Si wafer by using a spin coater. The resist with HMDS was always thicker than that without HMDS for the same exposure dose. The resist pattern profile (resolution) with HMDS was better than that without HMDS. We found that UV absorbance of the resist with HMDS was greater than without HMDS. The resist was mixed with HMDS, and the phenolic hydroxyl groups of the resist were silylated by HMDS. The light through the resist was absorbed in the mixed layer. Also, the mixed layer weakened the reflected light from the Si substrate. We demonstrated that the mixed layer generated by resist with HMDS works as an antireflection coating for the resist.