Surface smoothing of workpieces
Apparatus, systems, and methods for processing workpieces are provided. In one example implementation, a fluorine and oxygen plasma-based process can be used to smooth a roughened surface of a silicon and/or a silicon containing structure. The process can include generating species from a process gas using an inductive coupling element in a first chamber. The process can include introducing a fluorine containing gas and an oxygen containing gas with the species to create a mixture. The process can further include exposing the silicon and/or the silicon containing structure to the mixture such that the mixture at least partially etches a roughened portion to leave a smoother surface of the silicon and/or the silicon containing structure.
1. A method for processing a workpiece, the workpiece comprising a silicon containing layer, wherein a surface of the silicon containing layer comprises a roughened portion, the method comprising:
generating species from a process gas by generating a plasma using an inductive coupling element in a first chamber;
providing a fluorine-containing gas and an oxygen-containing gas into the species to generate a mixture;
exposing the surface of the silicon containing layer to the mixture such that the mixture at least partially etches the roughened portion to leave a smoother surface of the silicon containing layer,
wherein the workpiece is in a second chamber that is separated from the first chamber by a separation grid,
wherein the fluorine-containing gas and the oxygen-containing gas are introduced into the species generated by the plasma passing through the separation grid via a post-plasma gas injection source located between a first grid plate and a second grid plate of the separation grid, wherein each of the first grid plate and the second grid plate provide ion filtering, the fluorine-containing gas and the oxygen-containing gas being mixed with the species between the first grid plate and the second grid plate to generate the mixture for exposure to the workpiece.
2. The method of claim 1 , wherein the roughened portion comprises a concave area and a convex area, wherein the concave area is thicker than the convex area, wherein the mixture at least partially etches the concave area more than the convex area to leave the smoother surface of the silicon containing layer.
3. The method of claim 1 , wherein the mixture at least partially oxidizes and at least partially etches the roughened portion simultaneously to leave the smoother surface.
4. The method of claim 1 , wherein the process gas comprises an inert gas.
5. The method of claim 1 , wherein the silicon containing layer comprises crystalline silicon, polysilicon, or silicon germanium.
6. The method of claim 1 , wherein the fluorine-containing gas comprises tetrafluoromethane (CF 4 ), nitrogen trifluoride (NF 3 ), or a gas with a formula CF x H y , wherein x and y are positive integers.
7. The method of claim 1 , wherein the oxygen-containing gas comprises oxygen (O 2 ), water vapor (H 2 O), or nitrous oxide (NO 2 ).
8. The method of claim 1 , wherein an oxidation layer is formed on the smoother surface of the silicon containing layer.
9. The method of claim 8 , further comprising a wet process to at least partially remove the oxidation layer.
10. The method of claim 1 , wherein the smoother surface comprises a material with a formula SiO x F y C z , wherein x, y and z are positive integers.
11. The method of claim 10 , wherein the smoother surface is formed via a deposition process based at least in part on a reaction between the at least partially roughened portion and the mixture.