SiO_2 etching for optical device using pulse-modulated electron-beam-excited plasma

摘要

In the micro-machining process for fabricating optical devices, the fast atomic-beam etching (FABE) or the ion-beam etching (IBE) is used. However, the etch rates of these processes are typically around a few tens nm/min, so the higher etch-rate is strongly required to reduce the processing time. We investigated an etching process of a silicon-dioxide (SiO_2) using an electron-beam-excited plasma (EBEP) to realize a novel micro-machining process without any bias-power supply. The EBEP has an excellent potential for applying self-bias to the non-planar thick dielectric materials with the high-density electron beam. In the direct current (DC)-EBEP, the non-uniformity of etching and the thermal damage to photo-resist were observed. To overcome these problems, we have developed a pulse-modulated EBEP, and thus the non-uniformity of etching and the thermal damage were improved. Moreover, the maximum etch-rate of 450 nm/min was obtained and an anisotropy etching was realized. An optical fiber as a non-planar material was etched to demonstrate the application of this process. The clad area was etched for fabricating a core lens. We have found that the pulse-time-modulated EBEP has an excellent potential to realize micro-fabrications of optical fibers with the etch rate several times higher than that of the conventional FABE and IBE processes.