Anisotropic gap etch

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

• ion implanting the patterned substrate, wherein ion implanting the patterned substrate comprises ion implanting an exposed bottom portion of a gap in a silicon oxide layer on the patterned substrate, wherein the exposed bottom portion and an exposed sidewall portion of the gap each comprise silicon oxide;
• placing the patterned substrate in a substrate processing region of a substrate processing chamber;
• flowing a fluorine-containing precursor into a remote plasma region fluidly coupled to the substrate processing region by way of a showerhead while forming a remote plasma in the remote plasma region to produce plasma effluents;
• flowing a hydrogen-and-oxygen-containing precursor into the substrate processing region without first passing the hydrogen-and-oxygen-containing precursor through the remote plasma region, wherein the hydrogen-and-oxygen-containing precursor comprises an O—H bond;
• combining the plasma effluents with the hydrogen-and-oxygen-containing precursor in the substrate processing region;
• and
• anisotropically etching the patterned substrate such that the exposed sidewall portion of the gap and the exposed bottom portion of silicon oxide etch at different etch rates from one another.

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

• forming a gap in a material layer on the patterned substrate, wherein forming the gap forms an exposed undoped bottom portion of the gap and an exposed undoped sidewall portion of the gap having the same material composition upon formation;
• ion implanting the patterned substrate, wherein ion implanting the patterned substrate comprises ion implanting the exposed undoped bottom portion of the gap to form an exposed doped bottom portion of the gap;
• and
• anisotropically etching the patterned substrate such that the exposed undoped sidewall portion and the exposed doped bottom portion etch at different etch rates from one another.