A method for deep etching in dielectric films for 3D-chip and photonics applications

Abstract

In this paper, RIE of thick undoped silicate glass (USG) films for various applications is described. Though moderate etch rates (∼0.4 μm/min) were achieved for USG film, process development was quite challenging due to stringent requirements of deep USG etching (>6 μm) and vertical profile. Alternatively, etch process with higher etch rate (1.0 μm/min) was also evaluated for profile angle and results were found not comparable to low etch rate process. However, low etch rate process was found to have tool limitations and an alternate method called ‘discrete etching’ was proposed and successfully verified. Promising results were obtained with etch depth (6 μm) and vertical profile (∼89.50°) in USG as well as SiON films. Based on the results discrete etching method was found to have provided advantage of unlimited capability for deep etching.