Etch suppression with germanium
Methods of selectively etching silicon relative to silicon germanium are described. The methods include a remote plasma etch using plasma effluents formed from a fluorine-containing precursor and a hydrogen-containing precursor. Plasma effluents from the remote plasma are flowed into a substrate processing region where the plasma effluents react with the silicon. The plasmas effluents react with exposed surfaces and selectively remove silicon while very slowly removing other exposed materials. The methods are useful for removing Si (1-X) Ge X faster than Si (1-Y) Ge Y , for X<Y. In some embodiments, the silicon germanium etch selectivity results partly from the presence of an ion suppression element positioned between the remote plasma and the substrate processing region.
1. A method of etching silicon, the method comprising:
flowing a fluorine-containing precursor and an hydrogen-containing precursor into a remote plasma region fluidly coupled to a substrate processing region via through-holes in a showerhead;
forming a remote plasma in the remote plasma region to produce plasma effluents from the fluorine-containing precursor and the hydrogen-containing precursor; and
etching the silicon from a substrate disposed within the substrate processing region by flowing the plasma effluents into the substrate processing region through the through-holes in the showerhead, wherein the substrate is a patterned substrate which further comprises an exposed region of silicon germanium and the silicon is etched faster than the exposed region of silicon germanium.
2. The method of claim 1 wherein a flow rate of the hydrogen-containing precursor is greater than twice the flow rate of the fluorine-containing precursor.
3. The method of claim 1 wherein an atomic percentage of germanium in the silicon germanium is between about 28% and 70%.
4. The method of claim 1 wherein a temperature of the substrate is greater than or about 100° C. and less than or about 220° C. during the etching operation.