Plasma etching apparatus and method
A plasma etching apparatus for etching a semiconductor substrate comprises: a plasma chamber; a plasma generation device for sustaining a plasma within the plasma chamber; a substrate support disposed within the plasma chamber for supporting the semiconductor substrate, the substrate support comprising an electrically conductive structure; a power supply for providing an RF electrical signal having an RF power to the electrically conductive structure; and an annular dielectric ring structure comprising a backside surface, the backside surface comprising an electrically conductive coating; wherein the electrically conductive structure is spaced apart from and extends under the electrically conductive coating so that when RF power is provided to the electrically conductive structure the RF power couples to the electrically conductive coating. Associated methods are also disclosed.
1. A plasma etching apparatus for etching a semiconductor substrate, the plasma etching apparatus comprising:
a plasma chamber;
a plasma generation device for sustaining a plasma within the plasma chamber;
a substrate support disposed within the plasma chamber for supporting the semiconductor substrate, the substrate support comprising an electrically conductive structure;
a power supply for providing an RF electrical signal having an RF power to the electrically conductive structure; and
an annular dielectric ring structure comprising a backside surface, the backside surface comprising an electrically conductive coating, wherein the electrically conductive coating comprises a radially inner region and a radially outer region;
wherein the electrically conductive structure is entirely spaced apart from and extends under the inner region of the electrically conductive coating so that the RF power provided to the electrically conductive structure couples capacitively to the electrically conductive coating;
wherein the electrically conductive coating has an electrical potential that is electrically floating; and
wherein at least some of the electrically conductive coating is disposed above the semiconductor substrate such that the semiconductor substrate is disposed between the substrate support and the electrically conductive coating.
2. The apparatus according to claim 1 , wherein the annular dielectric ring structure comprises a wafer edge protection (WEP) structure.
3. The apparatus according to claim 2 , wherein the radially outer region is spaced apart from the electrically conductive structure by a smaller distance than the radially inner region because the outer region is disposed on the WEP structure.
4. The apparatus according to claim 1 , wherein the annular dielectric ring structure comprises a uniformity ring.
5. The apparatus according to claim 4 , further comprising a semiconductor substrate positioned on the substrate support, wherein the uniformity ring comprises an inner diameter that is larger than the diameter of the semiconductor substrate by a distance in the range of 1-5 mm.
6. The apparatus according to claim 1 , wherein the annular dielectric ring structure comprises a wafer edge protection (WEP) structure, wherein the annular dielectric ring structure comprises a uniformity ring, and wherein the uniformity ring is positioned on the WEP structure to form a stack of annular dielectric rings.
7. The apparatus according to claim 1 , wherein the annular dielectric ring structure is made from a ceramic material.
8. The apparatus according to claim 1 , wherein the electrically conductive coating is made from a metal or a metal alloy.
9. The apparatus according to claim 8 , wherein the metal is aluminium or titanium.
10. The apparatus according to claim 1 , wherein the electrically conductive coating has a non-zero thickness of less than about 50 μm.
11. The apparatus according to claim 1 , wherein the annular dielectric ring structure comprises a frontside surface facing away from the substrate support, the frontside surface comprising a radially inwardly facing inclined portion.
12. The apparatus according to claim 1 , wherein the electrically conductive structure comprises a conductive body and a conductive ring surrounding the conductive body.
13. The apparatus according to claim 1 , wherein the substrate support comprises an electrostatic chuck (ESC).
14. The apparatus according to claim 1 , wherein the RF electrical signal has a frequency of less than about 2 MHz.
15. The apparatus according to claim 1 , wherein the RF electrical signal has a frequency of about 13.56 MHz.
16. The apparatus according to claim 1 , wherein the RF electrical signal has a power in a range of 5-500 W.
17. The apparatus according to claim 1 , wherein the semiconductor substrate is a silicon wafer.
18. The apparatus according to claim 1 , wherein the plasma generation device is an inductively coupled plasma generation device.