RF power control device for RF plasma applications
First Claim
1. A VHF generator for delivering rf power to a plasma, comprising,a) a variable rf signal generator including a power amplifier connected to a directional coupler;
- b) the directional coupler having one output connected to a matching network wherein power is delivered to plasma in a processing chamber;
c) at least one output of the directional coupler disposed to sample a forward power signal of the rf signal generator and at least one output of the directional coupler disposed to sample a reflected power signal of the rf signal generator;
d) each of the sampled forward and reflected signals is connected to mixers for mixing with an intermediate frequency of an oscillator;
e) the mixed forward and reflected signals are passed through low pass filters;
f) the filtered forward and reflected signals are connected to amplifiers and detectors; and
g) the detected forward and reflected signals are fed back to a power control circuit wherein the power delivered to the plasma is monitored without interference from spurious frequency signals generated by the plasma.
1 Assignment
0 Petitions
Accused Products
Abstract
There is provided by this invention an improved rf power control device for plasma applications for optimization of the feedback control voltage in the presence of harmonic and non-harmonic spurious frequencies. In this system, an oscillator and mixer, similar to those normally used in radio receiver applications are placed at the sampled output of the solid state rf signal source used for plasma ignition. The sampled output is mixed to a low frequency and filtered to remove the spurious frequencies that is created in the non-linear plasma. In this way, the feedback power control essentially ignores the spurious frequencies. In this application, the oscillator and mixer do not interfere with other desirable system characteristics and effectively isolate the feedback control voltage from changes in plasma spurious content. This allows rf power to be delivered to the plasma with greater accuracy than would otherwise be possible with conventional power control device and methods.
26 Citations
25 Claims
-
1. A VHF generator for delivering rf power to a plasma, comprising,
a) a variable rf signal generator including a power amplifier connected to a directional coupler; -
b) the directional coupler having one output connected to a matching network wherein power is delivered to plasma in a processing chamber; c) at least one output of the directional coupler disposed to sample a forward power signal of the rf signal generator and at least one output of the directional coupler disposed to sample a reflected power signal of the rf signal generator; d) each of the sampled forward and reflected signals is connected to mixers for mixing with an intermediate frequency of an oscillator; e) the mixed forward and reflected signals are passed through low pass filters; f) the filtered forward and reflected signals are connected to amplifiers and detectors; and g) the detected forward and reflected signals are fed back to a power control circuit wherein the power delivered to the plasma is monitored without interference from spurious frequency signals generated by the plasma. - View Dependent Claims (2, 3, 4)
-
-
5. A VHF generator for delivering rf power to a plasma, comprising,
a) an rf signal generator including a power amplifier connected to a directional coupler; -
b) the directional coupler having one output connected to a matching network wherein power is delivered to plasma in a processing chamber; c) at least one output of the directional coupler disposed to sample a forward power signal of the rf signal generator and at least one output of the directional coupler disposed to sample a reflected power signal of the rf signal generator; d) each of the sampled forward and reflected signals is connected to a first mixer; e) a first oscillator connected to a second mixer for mixing a sampled output of the variable rf signal generator with a first intermediate frequency; f) the output of the second mixer is connected to a first band pass filter and then connected to a third mixer for mixing with a second intermediate frequency of a second oscillator; g) the output of the third mixer is connected to a second band pass filter and connected to the first mixer; h) the mixed forward and reflected signals are passed through low pass filters; i) the filtered forward and reflected signals are connected to amplifiers and detectors; and j) the detected forward and reflected signals are fed back to a power control circuit wherein the power delivered to the plasma is monitored without interference from spurious frequency signals generated by the plasma. - View Dependent Claims (6, 7, 8)
-
-
9. An apparatus for delivering RF power to a plasma, comprising:
-
a. an RF power source that delivers power to a plasma in a processing chamber; and b. an output sampler disposed between the RF power source and the plasma, the output sampler disposed to sample at least one output characteristic of the RF power source and thereby generate at least one output signal;
wherein the output signal is mixed with an oscillator frequency to generate a mixed signal, the mixed signal processed to generate a filtered mixed signal, and the filtered mixed signal fed back to a control circuit for controlling the RF power source. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17)
-
-
18. A method of delivering RF power to a plasma, comprising,
a. providing an RF power source that delivers power to a plasma in a processing chamber; -
b. providing an output sampler between the RF power source and the plasma; c. sampling at least one output characteristic of the RF power source using the output sampler, thereby generating at least one output signal; d. mixing the output signal with an oscillator frequency to generate a mixed signal; e. processing the mixed signal to generate a filtered mixed signal; and f. using the filtered mixed signal to control the RF power source. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25)
-
Specification