High aspect ratio trench filling using two-step subatmospheric chemical vapor deposited borophosphosilicate glass for < 0.18 mu m device application

As a premetal dielectric, borophosphosilicate glass (BPSG) has been widely used for device planarization. in order to meet the stringent gap filling r equirements as the device evolves toward smaller feature sizes, the current BPSG deposition process using ozone/tetraethoxysilane chemistry was fully characterized to explore its extendibility for achieving high aspect ratio gap filling. Based on the characterization results, a two-layer film deposi tion process was developed to accommodate the gap filling capability as wel l as the system throughput. Without stretching the thermal budget, the curr ent process is able to achieve void-free gap filling at a >6:1 aspect ratio , 0.06 mu m width, even with reentrant profile. Other film properties, incl uding film stress, moisture absorption, dopant profile and flow, were also studied extensively. Postdeposition film reflow can be performed using eith er conventional furnace or rapid thermal annealing, the reflowed profile de pends on annealing temperature as well as ambient gases. A low thermal budg et can be maintained using a steam anneal. (C) 1999 The Electrochemical Soc iety. S0013-4651(98)07-103-1. All rights reserved.