《1991 NH4OH-based etchants for silicon》.pdf

Sensors and Actuators A, 25-27 (1991) l-7 NH,OH-based Etants for Silicon Micromachiuing: Influence of Additives and Stability of Passivation Layers U SCHNAKENBERG, W BENECKE, B LJHEL, S ULLERICH and P LANGE Fraunhofer-lnstltut fur Mlkrostrukturtechmk, Ddlenburger Strosse 53, D-loo0 Berlin 33 (F R G) Abstract etchants whzh can be apphed wlthm IC fab- ncatlon lines Solutions based on ammomum Solutions based on ammomum hydroxide hydroxide-water (AHW) nuxtures fulfil tht and water were investigated for amsotroplc requirements for on rmcromachmmg bet- etchmg of monocrystalhne con In 2 65 M ter than commonly used etchants Very NH3 solutions at 80 “C, the addition of H202 pronusmg results dealing wth the nature of m a concentration between 0 65 x 10m2M pure AHW etchants for threedlmenslonal and 1 84 x low2M increases the silicon etch structurmg of monocrystalhne slhcon have rate m the (100) direction to 75 pm/h, which been published recently [2], but only a few 1sa factor of about 2 5 higher compared to prelmunary results about the etchmg be- pure etchants In addmon, when the pH havlour of passlvatlon layers were included value was adjusted above 11 3, slhcon etching An extended dlscusslon of the stability of proceeds m H,O,-doped solutions Hrlthout passlvatlon layers formed under vanous formation of pyramidal-shaped hillocks The preparation techniques follows m tis mvestl- influence of the pH value and H,O, concen- gatlon On the other hand, slhcon etchmg m tration