Methods of removing particles from over semiconductor substrates
View Patent ↗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 over a surface of a semiconductor substrate, the method comprising:
flowing a liquid in parallel with and across a horizontal surface of the substrate and the particles, the liquid having thickness over the substrate, the substrate having an undulating topography and the particles being less than 100 nm in cross-sectional diameter, a first region of the thickness being near the substrate and comprising particles, a second region of the thickness being further from the substrate than the first region and having more flow than the first region;
while the liquid is flowing, imparting an electric field across at least a region of the surface from electrodes spaced apart from one another and configured to form an electric field across at least the first region of the substrate; and
inducing movement of the particles from the first region to the second region using the electric field, wherein
the electric field is provided for a duration;
the electric field is maintained with an alternating current for part of the duration; and
the electric field is maintained with a direct current for another part of the duration.
2. The method of claim 1 wherein, prior to the imparting the electric field, the first region comprises particles at a first concentration and the second region comprises particles at a second concentration, the first concentration being greater than the second, and upon imparting the electric field, the second concentration increases.
3. The method of claim 1 further comprising placing the semiconductor substrate within a bath of flowing liquid.
4. The method of claim 1 further comprising while flowing the liquid across the surface and the particles, exposing the semiconductor substrate surfaces to varying conditions which include one or more of continuously varying temperature, continuously varying ionic strength, and continuously varying pH.
5. The method of claim 4 wherein the electric field induces electrophoresis to cause forces on the particles, with such forces being primarily perpendicular to primary surfaces of the substrates.
6. The method of claim 4 further comprising removing at least a portion of the second region of liquid from the surface of the substrate.
7. The method of claim 1 wherein the substrate is rotated as the liquid is flowed and the electric field is imparted.
8. The method of claim 1 wherein the undulating topography defines valleys within the substrate, the method further comprising moving particles out of the valleys.