Methods of removing particles from over semiconductor substrates
Some embodiments include methods of removing particles from over surfaces of semiconductor substrates. Liquid may be flowed across the surfaces and the particles. While the liquid is flowing, electrophoresis and/or electroosmosis may be utilized to enhance transport of the particles from the surfaces and into the liquid. In some embodiments, temperature, pH and/or ionic strength within the liquid may be altered to assist in the removal of the particles from over the surfaces of the substrates.
1. A method of removing particles from a surface of a semiconductor substrate, the method comprising:
placing the semiconductor substrate within a bath providing liquid flowing parallel to a primary surface of the substrate;
while the semiconductor substrate is within the bath, exposing the primary surface to continuously varying ionic strength cycles, wherein the continuously varying ionic strength cycles comprise a plurality of cycles that each comprise an increase and decrease in ionic strength of said liquid; and
while the primary surface is exposed to the continuously varying ionic strength cycles, imparting an electric field across the primary surface, wherein the electric field and continuously varying ionic strength cycles enhance transport of particles from the primary surface into the liquid.
2. The method of claim 1 wherein the ionic strength of the liquid experiences at least a twofold change during at least one of the cycles.
3. The method of claim 1 wherein the electric field induces electrophoresis to cause forces on the particles, with such forces being primarily perpendicular to the primary surface of the substrate.
4. The method of claim 1 wherein the ionic strength cycles over a range of orders of magnitude.
5. The method of claim 1 wherein at least one of the cycles lasts at least three seconds.