|Publication number||USRE42917 E1|
|Application number||US 11/519,242|
|Publication date||Nov 15, 2011|
|Filing date||Sep 11, 2006|
|Priority date||Jul 15, 2003|
|Also published as||US6791274, WO2005010913A2, WO2005010913A3|
|Publication number||11519242, 519242, US RE42917 E1, US RE42917E1, US-E1-RE42917, USRE42917 E1, USRE42917E1|
|Inventors||Frederick Hauer, Theresa Beizer, Anton Mavretic|
|Original Assignee||Advanced Energy Industries, Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (21), Non-Patent Citations (5), Referenced by (9), Classifications (12), Legal Events (2)|
|External Links: USPTO, USPTO Assignment, Espacenet|
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, . . . )
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.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US5175472||Dec 30, 1991||Dec 29, 1992||Comdel, Inc.||Power monitor of RF plasma|
|US5523955 *||Mar 19, 1992||Jun 4, 1996||Advanced Energy Industries, Inc.||System for characterizing AC properties of a processing plasma|
|US5654679 *||Jun 13, 1996||Aug 5, 1997||Rf Power Products, Inc.||Apparatus for matching a variable load impedance with an RF power generator impedance|
|US5708250 *||Mar 29, 1996||Jan 13, 1998||Lam Resarch Corporation||Voltage controller for electrostatic chuck of vacuum plasma processors|
|US5770922||Jul 22, 1996||Jun 23, 1998||Eni Technologies, Inc.||Baseband V-I probe|
|US5892198||Mar 29, 1996||Apr 6, 1999||Lam Research Corporation||Method of and apparatus for electronically controlling r.f. energy supplied to a vacuum plasma processor and memory for same|
|US5939886 *||Nov 18, 1996||Aug 17, 1999||Advanced Energy Industries, Inc.||Plasma monitoring and control method and system|
|US6020794 *||Feb 9, 1998||Feb 1, 2000||Eni Technologies, Inc.||Ratiometric autotuning algorithm for RF plasma generator|
|US6472822 *||Apr 28, 2000||Oct 29, 2002||Applied Materials, Inc.||Pulsed RF power delivery for plasma processing|
|US6535785 *||Oct 31, 2001||Mar 18, 2003||Tokyo Electron Limited||System and method for monitoring and controlling gas plasma processes|
|US6608446 *||Feb 25, 2002||Aug 19, 2003||Eni Technology, Inc.||Method and apparatus for radio frequency (RF) metrology|
|US6703080 *||May 20, 2002||Mar 9, 2004||Eni Technology, Inc.||Method and apparatus for VHF plasma processing with load mismatch reliability and stability|
|US6768902||Jul 27, 2000||Jul 27, 2004||Alps Electric Co., Ltd.||Double frequency converter making possible shifting of the frequencies of first and second local oscillation signals by the same frequency|
|US6819052 *||May 20, 2003||Nov 16, 2004||Nagano Japan Radio Co., Ltd.||Coaxial type impedance matching device and impedance detecting method for plasma generation|
|US20040070347 *||Nov 21, 2001||Apr 15, 2004||Yasushi Nishida||Plasma generating apparatus using microwave|
|US20050057164 *||Sep 27, 2004||Mar 17, 2005||Toshiaki Kitamura||Coaxial type impedance matching device and impedance detecting method for plasma generation|
|JP2001044873A||Title not available|
|JP2003017296A||Title not available|
|JP2003139804A||Title not available|
|JPH1041097A||Title not available|
|JPH05266990A||Title not available|
|1||Japanese Patent Office, Third Party Observation, Jan. 7, 2011.|
|2||Japanese Patent Office, Third Party Observation, Jun. 11, 2010.|
|3||Shuichi Miyamoto; Japanese Office Action; Application No. 2006-520335; Dec. 16, 2009; Japanese Patent Office.|
|4||Shuichi Miyamoto; Japanese Office Action; Application No. 2006-520335; Jan. 18, 2011; Japanese Patent Office.|
|5||Shuichi Miyamoto; Japanese Office Action; Application No. 2006-520335; Jun. 9, 2010; Japanese Patent Office.|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US9170295 *||Feb 27, 2013||Oct 27, 2015||New Power Plasma Co., Ltd.||Method and apparatus for detecting arc in plasma chamber|
|US9196459||Mar 26, 2015||Nov 24, 2015||Reno Technologies, Inc.||RF impedance matching network|
|US9279722||Apr 30, 2012||Mar 8, 2016||Agilent Technologies, Inc.||Optical emission system including dichroic beam combiner|
|US9294100 *||Dec 2, 2013||Mar 22, 2016||Advanced Energy Industries, Inc.||Frequency tuning system and method for finding a global optimum|
|US9306533||Jun 9, 2015||Apr 5, 2016||Reno Technologies, Inc.||RF impedance matching network|
|US9345122 *||Apr 30, 2015||May 17, 2016||Reno Technologies, Inc.||Method for controlling an RF generator|
|US20130221847 *||Feb 27, 2013||Aug 29, 2013||New Power Plasma Co., Ltd.||Method and apparatus for detecting arc in plasma chamber|
|US20140155008 *||Dec 2, 2013||Jun 5, 2014||Advanced Energy Industries, Inc.||Frequency tuning system and method for finding a global optimum|
|US20150319837 *||Apr 30, 2015||Nov 5, 2015||Reno Technologies, Inc.||Method for controlling an rf generator|
|U.S. Classification||315/111.21, 315/111.51, 118/723.0MW, 333/17.3|
|International Classification||C23C16/00, H01J7/24, H01J37/32, H01P5/08|
|Cooperative Classification||H01J37/32082, H01J37/32174|
|European Classification||H01J37/32M8J, H01J37/32M8|
|Feb 23, 2012||FPAY||Fee payment|
Year of fee payment: 8
|Feb 17, 2016||FPAY||Fee payment|
Year of fee payment: 12