FRINGE STABILIZATION AND DEPTH MONITORING DURING THE HOLOGRAPHIC PHOTOELECTROCHEMICAL ETCHING OF N-INP(100) SUBSTRATES

The holographic photoelectrochemical etching of n-InP (100) samples in aqueous 1 M HCl was monitored optically using the synchronous detecti on of two wave mixing from the interfering beams. This signal was empl oyed to operate a negative feedback system which stabilizes the projec ted interference pattern. The use of the stabilization system permits the recording of high spatial frequency gratings (<0.5 mu m), though t heir depth is limited to the value at which the self-diffracted signal passes through zero, It was shown that in the range where scalar theo ry may be applied, optical monitoring can be used to determine the abs olute depth and the rate of relief development. Using this method the influence of sample orientation on the etching rate was studied, and s ome aspects of the etching process are discussed. (C) 1996 American Va cuum Society.