V trench dry etch

A method of etching a patterned substrate, the method comprising:

• placing the patterned substrate in a substrate processing region of a substrate processing chamber, wherein the patterned substrate comprises a flat silicon facet disposed between two adjacent silicon-containing portions, wherein the flat silicon facet is covered with a native oxide;
• flowing a first halogen-containing precursor into the substrate processing region while forming a local plasma in the substrate processing region to remove the native oxide and initiate a trench in the flat silicon facet to form a remaining silicon portion, wherein the first halogen-containing precursor comprises one or more of fluorine, chlorine and bromine;
• flowing a second halogen-containing precursor into a remote plasma region while forming a remote plasma having a remote plasma power in the remote plasma region to produce plasma effluents, wherein the second halogen-containing precursor comprises one or both of chlorine and bromine;
• flowing the plasma effluents into the substrate processing region through through-holes in a showerhead;
• and
• selectively etching the remaining silicon portion to form two opposing silicon facets which form a substantially V-shaped trench, wherein the patterned substrate is not exposed to external atmosphere between placing the patterned substrate into the substrate processing region and selectively etching the remaining silicon portion;
• wherein any local plasma power applied to the substrate processing region during the selectively etching operation is less than 15% of the remote plasma power and wherein the substrate processing region and the remote plasma region are each devoid of fluorine during the selectively etching operation.

A method of etching a patterned substrate, the method comprising:

• placing the patterned substrate in a substrate processing region of a substrate processing chamber, wherein the patterned substrate comprises a silicon portion disposed between two adjacent masking portions;
• flowing a halogen-containing precursor into the substrate processing region while forming a local plasma in the substrate processing region to initiate a trench in the silicon portion to form a remaining silicon portion;
• flowing molecular chlorine or molecular bromine into a remote plasma region while forming a remote plasma in the remote plasma region to produce plasma effluents;
• flowing the plasma effluents into the substrate processing region through through-holes in a showerhead;
• and
• selectively etching the remaining silicon portion to form a “V”-shaped trench in the remaining silicon portion.