Superior PSZ-SOD Gap-Fill Process Integration Using Ultra-Low Dispensation Amount in STI for 28 nm NAND Flash Memory and beyond

Abstract

The gap-fill performance and process of perhydropolysilazane-based inorganic spin-on dielectric (PSZ-SOD) film in shallow trench isolation (STI) with the ultra-low dispensation amount of PSZ-SOD solution have been investigated in this study. A PSZ-SOD film process includes liner deposition, PSZ-SOD coating, and furnace curing. For liner deposition, hydrophilic property is required to improve the contact angle and gap-fill capability of PSZ-SOD coating. Prior to PSZ-SOD coating, the additional treatment on liner surface is beneficial for the fluidity of PSZ-SOD solution. The superior film thickness uniformity and gap-fill performance of PSZ-SOD film are achieved due to the improved fluidity of PSZ-SOD solution. Following that up, the low dispensation rate of PSZ-SOD solution leads to more PSZ-SOD filling in the trenches. After PSZ-SOD coating, high thermal curing process efficiently promotes PSZ-SOD film conversion into silicon oxide. Adequate conversion from PSZ-SOD into silicon oxide further increases the etching resistance inside the trenches. Integrating the above sequence of optimized factors, void-free gap-fill and well-controlled STI recess uniformity are achieved even when the PSZ-SOD solution dispensation volume is reduced 3 to 6 times compared with conventional condition for the 28 nm node NAND flash and beyond.