Jm. Qiao et al., Development of self-aligned contact technology for 0.18 mu m static randomaccess memory devices, J VAC SCI B, 17(5), 1999, pp. 2373-2377
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].