A Hydrogen Plasma Treatment for Soft and Selective Silicon Nitride Etching

摘要

In this paper, the development of a soft and selective method to increase thernetching rate and control accurately the etched thickness of Si_3N_4 material isrnreported. This technique combines the low damage characteristics of wetrnetching with the anisotropy of plasma etching which is compatible with thernrequirements of many surface sensitive electronic devices such as MOSrntransistors. This consists on a local modification of the Si_3N_4 layer usingrnhydrogen-based plasma followed by wet chemical etching in buffered oxidernetch solution. The plasma conditions are optimized and a relatively high etchrnrate is demonstrated. FTIR analyses show clear evidence that the formationrnof N–H and Si–H species in the hydrogenated Si_3N_4 layer contributesrneffectively to the increase of the etching rate. Finally, a chemical etchingrnmodel is proposed to explain the higher etch rate of hydrogenated Si_3N_4.