A novel dopant selective etching technique, which uses pulsed anodizing voltages applied to silicon samples immersed in KOH:H/sub 2/O solutions, has been developed. The use of pulsed anodization causes passivation of p-type silicon while n-type silicon continues to etch, making it possible to selectively etch-stop on p-type material. These results are consistent with a process which is rate-limiting by holes in the semiconductor. To demonstrate this technique, a 12 mu m-thick p-type membrane was formed. This method differs from the conventional p-n junction etch-stop in that a diode is not required to accomplish selective anodization and etch-stop. In this way, the performance of the etch-stop does not depend on the presence or quality of the diode.<>

Results from an investigation of the electrochemical etching of silicon in KOH:H/sub 2/O and CsOH:H/sub 2/O solutions are presented. Current versus voltage (I-V) scans were performed on both n- and p-type silicon as a function of etchant concentration (20-60% by weight KOH and 25-70% by weight CsOH) and temperature (25-80 degrees C). Voltage scans were swept from potentials cathodic of the open-circuit potential (OCP) to potentials anodic of the passivation potential. The purpose of the I-V scans was to investigate systematically how varying etchant concentration and temperature affected the passivation potential and final passivation current density of n- and p-type silicon. The results of the I-V scans are used to help investigate conditions for optimizing the performance of three-electrode electrochemical etch stop on n/sup +/-p junction samples. A model is presented to describe the effect of reverse diode leakage on etch-stop performance which uses the previously measured electrochemical etching parameters. Experimental measurements of the etch stop are used to confirm the model.<>