Submicronic etching of borophosphosilicate glass using NF 3 and NF 3/He radio frequency glow discharge

Abstract

The etching of borophosphosilicate glass (BPSG) in NF 3 and NF 3/He radio frequency (RF) glow discharge has been characterized. The etch rates, BPSG/resist selectivity and etch profile have been investigated along with the reactor geometry, namely the inter electrode distance, by which the process can be optimized. The results shows that the etch rates of BPSG are 650 nm/min at RF power of 500 W, pressure of 0.3×10 2 Pa and 60 sccm flow rate of NF 3 gas. The selective etching BPSG/resist has also been examined and was significantly enhanced from a value of 1.2 to 2 under 16% of Helium injection into NF 3 discharge at high pressure of 0.9×10 2 Pa. The increase of inter electrode distance of the reactor improves the selectivity value but reduces the BPSG etch rate. The BPSG etch profile became isotrope for inter electrode distance value of 5×10 −2 m and higher. The best value of the selectivity was obtained for an inter electrode distance of 15×10 −2 m. For completeness of the process anisotropic etching was achieved, the obtained tapered sidewall was characterized as having an angle of 38° with the normal surface.