Development of self-aligned contact technology for 0.18 mu m static randomaccess memory devices

A self-aligned contact (SAC) technology is developed for the application of electrical contacts between the local interconnect and the silicon diffusi on regions for 0.18 mu m static random access memory cells. The key compone nts of this SAC technology include the deposition and gap fill of borophosp hosilicate glass (BPSG) films, a selective oxide etch process, and metal-pl ug contact formation by Ti/TiN-liner silicidation and W filling. The BPSG f ilm, deposited by plasma enhanced chemical vapor deposition, has exhibited an ability of filling 0.04 mu m spaces with an aspect ratio (AR) of about 1 0:1 after reflow at 800 degrees C. Reduction of the reflow temperature with out gap-fill deterioration by increasing the B incorporation in the BPSG fi lm is not feasible due to an increase of BPSG defects. The oxide SAC etch p erformance is modulated by an oxide-to-nitride etch selectivity which has s hown a strong dependence on the wafer temperature. The etch process window is improved by optimization of the process conditions including the wafer t emperature uniformity. A novel SAC etch process was demonstrated for an sim ilar to 0.2 mu m SAC opening. The electrical performance of a contact with an AR as high as 10:1 has met the design requirement, which has indicated s ufficient liner silicidation and an excellent W plug process. Investigation of the contact resistance dependence on the contact AR has shown a reducti on in contact resistance with increasing AR. All these findings are very in structive for our development projects. (C) 1999 American Vacuum Society. [ S0734-211X(99)04305-X].