New simplified positive-tone DESIRE process using liquid phase silylation in DUV lithography

摘要

A simplified positive tone process using liquid phase silylation in DUV lithography is presented in this paper. The diffusion enhanced silylated resist (DESIRE) process has been demonstrated as an attractive solution not only to improve resolution and process latitudes but also to cope with linewidth variations over highly reflective topography. Traditionally the silylation process has been carried out using hexamethlydisilazane (HMDS) although more lately alternative gaseous agents such as tetramethyldisilazane (TMDS) have begun to exhibit certain advantages. This technique requires stringent control of silylation track and dry development equipment. Several new resists (which consist of a novolac based resin with a photo- crosslinker) have been formulated for deep-UV, allowing silylation at room temperature. By using this photo-crosslinker, the PSB (pre-silylation bake) step can be removed. In this way the process can be even more simplified. Characterization of the silylation reaction and mechanism have been performed using thickness measurements, CO emission spectroscopy, Fourier transform infrared absorption (FTIR), and Rutherford backscattering spectroscopy (RBS). In order to explore the limits, this process has also been evaluated using phase shifting masks. The influence of partial coherence on the resolution and process latitudes has also been studied.