Patent ID: 6939472

Claim:
A method, comprising: loading a microstructure into an etch chamber, wherein the microstructure comprises a sacrificial material and one or more structural materials; providing a first discrete amount of spontaneous vapor phase etchant recipe during a first feeding cycle of a sequence of feeding cycles for removing the sacrificial material; pumping a portion of a gas out from the etching chamber, wherein the gas comprises a portion of the etchant recipe and a portion of an etching product; providing a second discrete amount of the etchant recipe after the first feeding cycle and during a second feeding cycle that follows the first feeding cycle of the sequence of feeding cycles for removing the sacrificial materials; and wherein another portion of the first amount of the etchant recipe is circulated in a circulation loop that passes through the etching chamber during the steps of pumping and providing the second discrete amount of the etchant recipe.