Direct patterning of silicon by photoelectrochemical etching

A method for integrating optical elements on a silicon wafer, the method comprising steps of:

• selecting a single-crystal silicon wafer;
• placing said silicon wafer in an optically transmissive container or a container including an optically-transmissive window;
• modulating intensity of an exposure light by projecting said exposure light through a patterned mask onto at least a portion of said silicon wafer;
• electrochemically etching said silicon wafer in an HF-containing solution wherein an etch rate corresponds to said intensity of exposure light;
• and
• exposing said silicon wafer to a chemical dissolution solution to remove porous material from a pattern in the silicon wafer that correlates with the patterned mask.

A method for patterning a silicon substrate, the method comprising steps of:

• immersing a silicon substrate in an etchant solution;
• creating an etching current density on a surface of the silicon substrate while simultaneously projecting at least one optical pattern onto at least a portion of the surface of the silicon substrate;
• separating the silicon substrate from the etchant solution;
• and
• exposing the surface of the silicon substrate to a chemical dissolution solution to remove a porous layer and leave a three-dimensional pattern corresponding to the optical pattern.