Comparison of optimised conditions for inductively coupled plasma-reactive ion etching of quartz substrates and its optical applications

A C₄F₈/He inductively coupled plasma-reactive ion etching (ICP-RIE) was studied to improve the etching conditions of quartz glass. The influences of C₄F₈ flow rate, He flow rate, chamber pressure, inductively coupled plasma (ICP) power, bias power and cooling temperature were investigated. A report is presented on an optimum etching condition for fabricating quartz-based optical components considering their application in diffractive optical element (DOE) devices. As per these etching results, the etched microstructure exhibited a depth of 44.2 μm and a vertical sidewall angle of 89° resulting from an ICP power of 3000 W, a bias power of 200 W, a chamber pressure of 2.5 mTorr and an etching time of 120 min in a mixture of C₄F₈ and He gases with 30 and 100 sccm flow rates, respectively. The successful fabrication of the DOE component by ICP-RIE is reported. This can be used to provide the uniform light intensity distribution for a DOE device.