Control of water bow in multiple stations
A system for controlling of wafer bow in plasma processing stations is described. The system includes a circuit that provides a low frequency RF signal and another circuit that provides a high frequency RF signal. The system includes an output circuit and the stations. The output circuit combines the low frequency RF signal and the high frequency RF signal to generate a plurality of combined RF signals for the stations. Amount of low frequency power delivered to one of the stations depends on wafer bow, such as non-flatness of a wafer. A bowed wafer decreases low frequency power delivered to the station in a multi-station chamber with a common RF source. A shunt inductor is coupled in parallel to each of the stations to increase an amount of current to the station with a bowed wafer. Hence, station power becomes less sensitive to wafer bow to minimize wafer bowing.
1. A power distributor for delivering power to a plurality of plasma processing stations, comprising:
a low frequency circuit coupled to a low frequency impedance matching network and configured to provide a plurality of low frequency radio frequency (RF) signals, wherein the low frequency circuit includes a plurality of high frequency blocking circuits, wherein each of the plurality of high frequency blocking circuits includes an inductor coupled in parallel with a capacitor;
a high frequency circuit coupled to a high frequency impedance matching network and configured to provide a plurality of high frequency RF signals, wherein the high frequency circuit is coupled to the low frequency circuit;
an output circuit coupled to the high frequency circuit and the plurality of plasma processing stations, wherein the output circuit is configured to combine the plurality of low frequency RF signals and the plurality of high frequency RF signals to provide a plurality of combined RF signals to the plurality of plasma processing stations; and
a plurality of shunt inductors, wherein each of the plurality of shunt inductors is coupled to a ground connection at one end and to a corresponding one of the plurality of high frequency blocking circuits at an opposite end to control an amount of current to a corresponding one of the plurality of plasma processing stations, wherein each of the plurality of shunt inductors is coupled in parallel to a corresponding one of a plurality of capacitors.
2. The power distributor of claim 1 , wherein one of the plurality of shunt inductors is coupled between an input of the low frequency circuit and an end of a coaxial cable that couples an output of the output circuit to the corresponding one of the plurality of plasma processing stations.
3. The power distributor of claim 1 , wherein one of the plurality of shunt inductors is coupled via one of the plurality of high frequency blocking circuits and a switch to a balancing inductor of the output circuit.
4. The power distributor of claim 3 , wherein the corresponding one of the plurality of capacitors is coupled to the ground connection at one end and to the corresponding one of the plurality of high frequency blocking circuits at an opposite end.
5. The power distributor of claim 1 , wherein each of the plurality of shunt inductors is a variable inductor or a fixed inductor.
6. A power distributor, for delivering power to a plurality of plasma processing stations, comprising:
a low frequency circuit coupled to a low frequency impedance matching network and configured to provide a plurality of low frequency radio frequency (RF) signals, wherein the low frequency circuit includes a plurality of direct current (DC) blocking capacitors;
a high frequency circuit coupled to a high frequency impedance matching network and configured to provide a plurality of high frequency RF signals, wherein the high frequency circuit is coupled to the low frequency circuit;
an output circuit coupled to the high frequency circuit and the plurality of plasma processing stations, wherein the output circuit is configured to combine the plurality of low frequency RF signals and the plurality of high frequency RF signals to provide a plurality of combined RF signals to the plurality of plasma processing stations; and
a plurality of shunt inductors, wherein each of the plurality of shunt inductors is coupled at a point between an input of the low frequency circuit and a corresponding one of the plurality of DC blocking capacitors of the low frequency circuit to control an amount of current to a corresponding one of the plurality of plasma processing stations.
7. The power distributor of claim 6 , wherein each of the plurality of shunt inductors is a variable inductor or a fixed inductor.
8. The power distributor of claim 6 , wherein one of the plurality of shunt inductors is coupled between an input of the low frequency circuit and an end of a coaxial cable that couples an output of the output circuit to the corresponding one of the plurality of plasma processing stations.
9. A power distributor for delivering power to a plurality of plasma processing stations, comprising:
a low frequency circuit coupled to a low frequency impedance matching network and configured to provide a plurality of low frequency radio frequency (RF) signals, wherein the low frequency circuit includes a plurality of direct current (DC) blocking capacitors and a plurality of inductors;
a high frequency circuit coupled to a high frequency impedance matching network and configured to provide a plurality of high frequency RF signals, wherein the high frequency circuit is coupled to the low frequency circuit;
an output circuit coupled to the high frequency circuit and the plurality of plasma processing stations, wherein the output circuit is configured to combine the plurality of low frequency RF signals and the plurality of high frequency RF signals to provide a plurality of combined RF signals to the plurality of plasma processing stations; and
a plurality of shunt inductors, wherein each of the plurality of shunt inductors is coupled at a point between a corresponding one of the plurality of DC blocking capacitors of the low frequency circuit and a corresponding one of the plurality of inductors of the low frequency circuit to control an amount of current to a corresponding one of the plurality of plasma processing stations.
10. The power distributor of claim 9 , wherein one of the plurality of shunt inductors is coupled between an input of the low frequency circuit and an end of a coaxial cable that couples an output of the output circuit to the corresponding one of the plurality of plasma processing stations.
11. The power distributor of claim 9 , wherein each of the plurality of shunt inductors is a variable inductor or a fixed inductor.
12. A system for delivering power to a plurality of plasma processing stations, comprising:
a first radio frequency (RF) generator configured to generate a first RF signal having a first frequency;
a second RF generator configured to generate a second RF signal having a second frequency;
a first matching network coupled to the first RF generator to receive the first RF signal, wherein the first matching network is configured to output a first modified RF signal upon receiving the first RF signal from the first RF generator;
a second matching network coupled to the second RF generator to receive the second RF signal, wherein the second matching network is configured to output a second modified RF signal upon receiving the second RF signal from the second RF generator;
a power distributor coupled to an output of the first matching network and an output of the second matching network, wherein the power distributor is configured to combine the first modified RF signal and the second modified RF signal to provide a plurality of combined RF signals to the plurality of plasma processing stations, wherein the power distributor has multiple outputs coupled to the plurality of plasma processing stations, wherein the power distributor includes:
a low frequency circuit coupled to the first matching network and configured to receive the first modified RF signal to provide a plurality of low frequency RF signals, wherein the low frequency circuit includes a plurality of high frequency blocking circuits, wherein each of the plurality of high frequency blocking circuits includes an inductor coupled in parallel with a capacitor;
a high frequency circuit coupled to the second matching network and to the low frequency circuit and configured to receive the second modified RF signal to provide a plurality of high frequency RF signals; and
an output circuit coupled to the high frequency circuit and the plurality of plasma processing stations, wherein the output circuit is configured to combine the plurality of low frequency RF signals and the plurality of high frequency RF signals to provide the plurality of combined RF signals to the plurality of plasma processing stations; and
a plurality of shunt inductors, wherein each of the plurality of shunt inductors is coupled to a ground connection at one end and to a corresponding one of the plurality of high frequency blocking circuits at an opposite end to control an amount of current to a corresponding one of the plurality of plasma processing stations, wherein each of the plurality of shunt inductors is coupled in parallel to a corresponding one of a plurality of capacitors.
13. The system of claim 12 , wherein one of the plurality of shunt inductors is coupled between an input of the low frequency circuit and an end of a coaxial cable that couples an output of the output circuit to the corresponding one of the plurality of plasma processing stations.
14. The system of claim 12 , wherein one of the plurality of shunt inductors is coupled via one of the plurality of high frequency blocking circuits and a switch to a balancing inductor of the output circuit.
15. The system of claim 14 , wherein the corresponding one of the plurality of capacitors is coupled to the ground connection at one end and to the corresponding one of the plurality of high frequency blocking circuits at an opposite end.
16. The system of claim 12 , wherein each of the plurality of shunt inductors is a variable inductor or a fixed inductor.