Plasma spreading apparatus and method of spreading plasma in process ovens
A device and method of spreading plasma which allows for plasma etching over a larger range of process chamber pressures. A plasma source, such as a linear inductive plasma source, may be choked to alter back pressure within the plasma source. The plasma may then be spread around a deflecting disc which spreads the plasma under a dome which then allows for very even plasma etch rates across the surface of a substrate. The apparatus may include a linear inductive plasma source above a plasma spreading portion which spreads plasma across a horizontally configured wafer or other substrate. The substrate support may include heating elements adapted to enhance the etching.
1. A method for plasma processing, said method comprising the steps of:
flowing process gas into a plasma source at a first end of said plasma source, wherein said plasma source is a linear-inductive plasma source with a cylindrical plasma chamber, said plasma source located above a substrate support;
constricting the flow of the plasma as it exits the plasma source through a central exit hole of a constricting disc, said constricting disc at a second end of said plasma source, a center of said central exit hole of a center of said constricting disc, said center of said constricting disc centrally located over a center of said substrate support; and
spreading the flow of the plasma after constricting the flow of the plasma, wherein the step of spreading the flow of the plasma comprises flowing the plasma around the outside circumference of a solid spreading disc located downstream from the central exit hole, said solid spreading disc coupled to said constricting disc, thereby distributing the plasma onto a substrate below the spreading.
2. The method of claim 1 wherein the step of flowing process gas into a plasma source comprises flowing the gas through a gas input showerhead at said first end of said plasma source.
3. The method of claim 2 wherein the step of constricting the flow of the plasma comprises flowing the gas through an annulus of a constricting disc, said annulus at the center of said constricting disc.
4. The method of claim 2 wherein the ratio of the diameter of the annulus in the constrictor plate to the interior diameter of the cylindrical plasma chamber is in the range of 1:8 to 1:3.
5. The method of claim 4 wherein the diameter of the spreading disc is larger than the diameter of the annulus in the constrictor plate.
6. The method of claim 1 wherein the step of constricting the flow of the plasma comprises flowing the gas through an annulus of a constricting disc, said annulus at the center of said constricting disc.
7. The method of claim 1 wherein the ratio of the diameter of the annulus in the constrictor plate to the interior diameter of the cylindrical plasma chamber is in the range of 1:8 to 1:3.
8. The method of claim 7 wherein the diameter of the spreading disc is larger than the diameter of the annulus in the constrictor plate.