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.
|
0. 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.
0. 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.
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.
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.
2. A vhf generator for delivering rf power to a plasma as recited in
3. A vhf generator for delivering rf power to a plasma as recited in
4. A vhf generator for delivering rf power to a plasma as recited in
6. A vhf generator for delivering rf power to a plasma as recited in
7. A vhf generator for delivering rf power to a plasma as recited in
8. A vhf generator for delivering rf power to a plasma as recited in
0. 10. The apparatus of claim 9 wherein the output sampler is a directional coupler.
0. 11. The apparatus of claim 9 wherein the output characteristic is one of forward or reflected power.
0. 12. The apparatus of claim 9, further comprising a matching network disposed between the output sampler and the plasma.
0. 13. The apparatus of claim 9 wherein the rf power source is a vhf generator.
0. 14. The apparatus of claim 9 wherein the rf power source is a variable frequency rf power source.
0. 15. The apparatus of claim 10, further comprising forward and reflected band pass filters disposed at the output of the directional coupler for removing harmonics and spurious low frequency signals.
0. 16. The apparatus of claim 15 wherein the filters are connected to detectors that monitor the power delivered to the plasma.
0. 17. The apparatus of claim 16 wherein the detectors are RMS detectors.
0. 19. The method of claim 18 wherein the output sampler is a directional coupler.
0. 20. The method of claim 18 wherein the output characteristic is one of forward or reflected power.
0. 21. The method of claim 18 wherein the rf power source is a vhf generator.
0. 22. The method of claim 18 wherein the rf power source is a variable frequency rf generator.
0. 23. The method of claim 19, further comprising providing forward and reflected band pass filters disposed at the output of the directional coupler for removing harmonics and spurious low frequency signals.
0. 24. The method of claim 23 wherein the filters are connected to detectors to monitor the power delivered to the plasma.
0. 25. The method of claim 24 wherein the detectors are RMS detectors.
|
1. Field of the Invention
This invention relates generally to plasma processing applications utilizing RF power and more particularly to RF power generators used in plasma processing applications having circuitry to improve power delivery characteristics.
2. Brief Description of the Prior Art
Heretofore, RF power generators used in plasma applications have relied on relatively simple diode peak detectors operating from the output of a directional coupler to monitor the power delivered to the plasma However, this method becomes unreliable in the presence of plasma induced spurious frequencies because the diode detectors cannot differentiate between the voltage of the generator output frequency and that of the plasma induced spurious frequencies. Synchronous detection methods have been used to eliminate the effect of spurious frequencies, however the cost and complexity of such a design is generally not acceptable for plasma generator applications. Other power detectors relying on thermal response have also been used. Bandpass filters of various types have been used to eliminate spurious frequencies. However, insertion losses in these filters are difficult to control, particularly when the offending frequency is very close to the generator output frequency.
It would be desirable if there were provided an RF generator that had improved power control stability by isolating the feedback control voltage from the plasma induced spurious frequencies.
Accordingly, it is an object of this invention to provide an improved RF power control method that is easily implemented to replace more expensive and complex designs currently used in the prior art.
It is a further object of this invention to replace the complex narrowband filters as used in prior art with a relatively simple low pass filter to remove the spurious signals.
It is yet another object of this invention to provide a means for using methods other than voltage detection of the generator output for monitoring its power.
It is yet another object of this invention to provide a means for improved matching network tuning in the presence of spurious frequencies.
There is provided by this invention an improved RF power control method for plasma applications that optimizes the feedback control voltage in the presence of harmonic and non-harmonic spurious caused by interaction between multiple generators acting on the non-linear plasma. In this system, an oscillator and mixer are placed at the sampled output of the solid state RF source used for plasma ignition. The sampled output is mixed to an intermediate frequency and filtered to remove the spurious frequencies that are 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 frequency content. This allows RF power to be delivered to the plasma with greater accuracy than would otherwise be possible with conventional power control methods
There is shown in
For this description, assume that the oscillator frequency is 162.2 MHz. A signal at the oscillator frequency is mixed (heterodyned) with the sensed forward and reflected power signals. This explanation describes only the forward power signal. The reflected power signal is treated in exactly the same way. The forward power signal has frequency components as follows,
PFwd=V(f0,2f0,3f0, . . . ,f0+f1,f0−f1,f0+2f1,f0−2f1, . . . )
where,
Thus the forward power signal may contain frequency components of 162 MHz, 324 MHz, 486 MHz, 648 MHz, 810 MHz, . . . etc.
When a signal with the above spectrum is mixed with the oscillator frequency at 162.2 MHz, the mixed products are generated according to the following trigonometric formula,
cos α cos β=½ cos(α−β)+½ cos(α+β)
Thus the mixed frequencies are at 200 kHz, 161.8 MHz, 164 MHz, 323.8 MHz, etc. This spectrum is then filtered through the low pass filters 30′,32′ that only allows the 200 KHz signal to pass through. Thus at the output of these filters there is a signal that has the same amplitude information as the sensed 162 MHz forward and reflected power signals. However, since it is filtered, it is insensitive to any other mixed frequencies, including harmonics of 162 MHz, 2 MHz sidebands, or any other chamber induced frequency that is sufficiently apart from the 162 MHz signal. The power detector may be designed for either fixed frequency or variable frequency generator operation.
The directional coupler forward and reflected power samples are band pass filtered to remove harmonics and low frequency spurious ahead of the mixers. It is understood that the output of the 162.2 MHz oscillator is filtered to reduce its harmonics. The outputs of the mixers are passed through 200 kHz filters. Other oscillator frequencies may be used to produce filter frequencies other than 200 kHz as long as the unwanted spurious frequencies appear outside the filter band pass. The filter output is amplified, detected, and used in the normal way for feedback power control of the generator.
Still another embodiment derives the oscillator frequency from the generator variable frequency source, thus allowing the heterodyne detector to track the variable output frequency of the generator. The block diagram of this embodiment is shown in
It will be further understood that, although the invention is described for a VHF application, it may be used at any frequency for the purpose of detecting and controlling generator output power. It will be still further understood that, although power control and metering is discussed as being internal to the generator, it may be accomplished by any number of means and be either internal or external to the generator as well as be controlled by a system CPU. It will be still further understood that detailed schematic diagrams have been eliminated for the purpose of clarity. It will be still further understood that the improved power detector may be used to accurately control power from any or all generators operating on the plasma.
The invention has been described in detail with particular reference to a preferred embodiment. It will be understood that variations and modifications in addition to those described can be effected within the spirit and scope of the invention. It will be further understood that changes, alterations, modifications, or substitutions can be made in the structure of the apparatus in accordance with the invention without departing from the spirit and scope of the invention.
Mavretic, Anton, Hauer, Frederick, Beizer, Theresa
Patent | Priority | Assignee | Title |
10026594, | Jan 10 2014 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | RF impedance matching network |
10026595, | Apr 20 2016 | AES GLOBAL HOLDINGS, PTE LTD | Apparatus for frequency tuning in a RF generator |
10217608, | Feb 18 2015 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | Switching circuit for RF currents |
10340879, | Feb 18 2015 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | Switching circuit |
10401221, | Apr 30 2012 | Agilent Technologies, Inc. | Optical emission system including dichroic beam combiner |
10431428, | Jan 10 2014 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | System for providing variable capacitance |
10455729, | Jan 10 2014 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | Enclosure cooling system |
10460912, | Jan 10 2014 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | RF impedance matching circuit and systems and methods incorporating same |
10483090, | Jul 10 2017 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | Restricted capacitor switching |
10707057, | Jan 10 2014 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | RF impedance matching circuit and systems and methods incorporating same |
10714314, | Jul 10 2017 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | Impedance matching network and method |
10720309, | Jul 10 2017 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | Impedance matching network and method |
10727029, | Jul 10 2017 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | Impedance matching using independent capacitance and frequency control |
10741364, | Jul 10 2017 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | Impedance matching network and method |
10984986, | Jun 29 2015 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | Impedance matching network and method |
11017983, | Feb 18 2015 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | RF power amplifier |
11081316, | Jun 29 2015 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | Impedance matching network and method |
11101110, | Jul 10 2017 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | Impedance matching network and method |
11114280, | Jul 10 2017 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | Impedance matching with multi-level power setpoint |
11150283, | Jun 29 2015 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | Amplitude and phase detection circuit |
11189466, | Jan 10 2014 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | High voltage switching circuit |
11195698, | Jan 10 2014 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | RF impedance matching circuit and systems and methods incorporating same |
11264210, | Jul 10 2017 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | Impedance matching network and method |
11289307, | Jul 10 2017 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | Impedance matching network and method |
11315758, | Jul 10 2017 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | Impedance matching using electronically variable capacitance and frequency considerations |
11335540, | Jun 29 2015 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | Impedance matching network and method |
11342160, | Jun 29 2015 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | Filter for impedance matching |
11342161, | Jun 29 2015 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | Switching circuit with voltage bias |
11393659, | Jul 10 2017 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | Impedance matching network and method |
11398370, | Jul 10 2017 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | Semiconductor manufacturing using artificial intelligence |
11476091, | Jul 10 2017 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | Impedance matching network for diagnosing plasma chamber |
11521831, | May 21 2019 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | Impedance matching network and method with reduced memory requirements |
11521833, | Jul 10 2017 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | Combined RF generator and RF solid-state matching network |
11538662, | May 21 2019 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | Impedance matching network and method with reduced memory requirements |
11557461, | Jul 10 2017 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | Impedance matching network |
11631570, | Feb 18 2015 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | Switching circuit |
11948775, | Jul 10 2017 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | Combined RF generator and RF solid-state matching network |
12119206, | Feb 18 2015 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | Switching circuit |
9170295, | Feb 28 2012 | NEW POWER PLASMA CO , LTD | Method and apparatus for detecting arc in plasma chamber |
9196459, | Jan 10 2014 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | RF impedance matching network |
9279722, | Apr 30 2012 | Agilent Technologies, Inc | Optical emission system including dichroic beam combiner |
9294100, | Dec 04 2012 | AES GLOBAL HOLDINGS, PTE LTD | Frequency tuning system and method for finding a global optimum |
9306533, | Feb 20 2015 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | RF impedance matching network |
9345122, | May 02 2014 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | Method for controlling an RF generator |
9496122, | Jan 10 2014 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | Electronically variable capacitor and RF matching network incorporating same |
9525412, | Feb 18 2015 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | Switching circuit |
9543122, | May 02 2014 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | Method for controlling an RF generator |
9584090, | Feb 20 2015 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | RF impedance matching network |
9591739, | May 02 2014 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | Multi-stage heterodyne control circuit |
9697991, | Jan 10 2014 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | RF impedance matching network |
9728378, | May 02 2014 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | Method for controlling an RF generator |
9729122, | Feb 18 2015 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | Switching circuit |
9748076, | Apr 20 2016 | Advanced Energy Industries, Inc | Apparatus for frequency tuning in a RF generator |
9752933, | Apr 30 2012 | Agilent Technologies, Inc. | Optical emission system including dichroic beam combiner |
9755641, | Jan 10 2014 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | High speed high voltage switching circuit |
9773644, | Dec 04 2012 | Advanced Energy Industries, Inc. | Power generator with frequency tuning for use with plasma loads |
9844127, | Jan 10 2014 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | High voltage switching circuit |
9865432, | Jan 10 2014 | RENO SUB-SYSTEMS, INC ; ASM America, Inc | RF impedance matching network |
Patent | Priority | Assignee | Title |
5175472, | Dec 30 1991 | XP POWER LLC | Power monitor of RF plasma |
5523955, | Mar 19 1992 | Advanced Energy Industries, Inc.; ADVANCED ENERGY INDUSTRIES, INC , A CORP OF CO | System for characterizing AC properties of a processing plasma |
5654679, | Jun 13 1996 | RF POWER PRODUCTS, INC | Apparatus for matching a variable load impedance with an RF power generator impedance |
5708250, | Mar 29 1996 | Lam Research Corporation | Voltage controller for electrostatic chuck of vacuum plasma processors |
5770922, | Jul 22 1996 | MKS Instruments, Inc | Baseband V-I probe |
5892198, | Mar 29 1996 | Lam Research Corporation | Method of and apparatus for electronically controlling r.f. energy supplied to a vacuum plasma processor and memory for same |
5939886, | Oct 24 1994 | Advanced Energy Industries, Inc | Plasma monitoring and control method and system |
6020794, | Feb 09 1998 | MKS Instruments, Inc | Ratiometric autotuning algorithm for RF plasma generator |
6472822, | Apr 28 2000 | Applied Materials, Inc. | Pulsed RF power delivery for plasma processing |
6535785, | Sep 17 1997 | Tokyo Electron Limited | System and method for monitoring and controlling gas plasma processes |
6608446, | Feb 25 2002 | BARCLAYS BANK PLC, AS COLLATERAL AGENT | Method and apparatus for radio frequency (RF) metrology |
6703080, | May 20 2002 | MKS Instruments, Inc | Method and apparatus for VHF plasma processing with load mismatch reliability and stability |
6768902, | Jul 29 1999 | ALPS Electric Co., Ltd. | Double frequency converter making possible shifting of the frequencies of first and second local oscillation signals by the same frequency |
6819052, | May 31 2002 | NAGANO JAPAN RADIO CO , LTD ; Tokyo Electron Limited | Coaxial type impedance matching device and impedance detecting method for plasma generation |
20040070347, | |||
20050057164, | |||
JP10041097, | |||
JP2001044873, | |||
JP2003017296, | |||
JP2003139804, | |||
JP5266990, |
Executed on | Assignor | Assignee | Conveyance | Frame | Reel | Doc |
Sep 11 2006 | Advanced Energy Industries, Inc. | (assignment on the face of the patent) | / | |||
Sep 13 2017 | Advanced Energy Industries, Inc | AES GLOBAL HOLDINGS, PTE LTD | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 043983 | /0615 |
Date | Maintenance Fee Events |
Feb 23 2012 | M1552: Payment of Maintenance Fee, 8th Year, Large Entity. |
Feb 17 2016 | M1553: Payment of Maintenance Fee, 12th Year, Large Entity. |
Date | Maintenance Schedule |
Nov 15 2014 | 4 years fee payment window open |
May 15 2015 | 6 months grace period start (w surcharge) |
Nov 15 2015 | patent expiry (for year 4) |
Nov 15 2017 | 2 years to revive unintentionally abandoned end. (for year 4) |
Nov 15 2018 | 8 years fee payment window open |
May 15 2019 | 6 months grace period start (w surcharge) |
Nov 15 2019 | patent expiry (for year 8) |
Nov 15 2021 | 2 years to revive unintentionally abandoned end. (for year 8) |
Nov 15 2022 | 12 years fee payment window open |
May 15 2023 | 6 months grace period start (w surcharge) |
Nov 15 2023 | patent expiry (for year 12) |
Nov 15 2025 | 2 years to revive unintentionally abandoned end. (for year 12) |