Plasma processing is employed in fabrication of integrated circuits, masks for use in photolithographic processing of integrated circuits, plasma displays and solar technology, for example. In the fabrication of integrated circuits, a semiconductor wafer is processed in a plasma chamber. The process may be a reactive ion etch (RIE) process, a plasma enhanced chemical vapor deposition (PECVD) process or a plasma enhanced physical vapor deposition (PEPVD) process, for example. Recent technological advances in integrated circuits have reduced feature sizes to less than 32 nanometers. Further reductions will require more precise control over process parameters at the wafer surface, including plasma ion energy spectrum, plasma ion energy radial distribution (uniformity), plasma ion density and plasma ion density radial distribution (uniformity). In addition, better consistency in such parameters between reactors of identical design is required. Ion density is important in PEPVD processes, for example, because ion density at the wafer surface determines deposition rate and the competing etch rate. At the target surface, target consumption (sputtering) rate is affected by ion density at the target surface and ion energy at the target surface.
The ion density radial distribution and the ion energy radial distribution across the wafer surface can be controlled by impedance tuning of a sputtering frequency dependent power source. There is a need to set at least one tuning parameter for impedance control in a repeatable manner based on a measured process parameter.
A plasma reactor is provided for performing physical vapor deposition on a workpiece such as a semiconductor wafer. The reactor includes a chamber including a side wall and a ceiling, the side wall being coupled to an RF ground.
A workpiece support is provided within the chamber having a support surface facing the ceiling and a bias electrode underlying the support surface. A sputter target is provided at the ceiling with an RF source power supply of frequency fs coupled to the sputter target. An RF bias power supply of frequency fb is coupled to the bias electrode. A first multi-frequency impedance controller is coupled between RF ground and one of (a) the bias electrode, (b) the sputter target, the controller providing adjustable impedances at a first set of frequencies, the first set of frequencies including a first set of frequencies to be blocked and a first set of frequencies to be admitted. The first multi-frequency impedance controller includes a set of band pass filters connected in parallel and tuned to the first set of frequencies to be admitted, and a set of notch filters connected in series and tuned to the first set of frequencies to be blocked.
In one embodiment, the band pass filters comprise inductive and capacitive elements connected in series, while the notch filters comprise inductive and capacitive components connected in parallel. The capacitive elements of the band pass filter and of the notch filters are variable in accordance with one embodiment.
The reactor may further include a second multi-frequency impedance controller coupled between the bias electrode and RF ground and providing adjustable impedances at a second set of frequencies, the first set of frequencies comprising at least the source supply frequency fs. The first set of frequencies are selected from a set of frequencies that includes harmonics of fs, harmonics of fb, and intermodulation products of fs and fb, in one embodiment.
In accordance with a further aspect of the present invention, an automatic, motor-driven, variable capacitive tuner circuit for plasma processing apparatus is provided. The circuit can have a processor controlled feedback circuit is provided to tune and match ion energy on the wafer for a given setpoint (voltage, current, positional etc.), thereby allowing process results to be matched from chamber to chamber and resulting in improved wafer processing.
In accordance with another aspect of the present invention, a physical vapor deposition plasma reactor is provided, comprising a chamber including a side wall and a ceiling, said side wall being coupled to an RF ground, a workpiece support within the chamber having a support surface facing the ceiling and a bias electrode underlying the support surface, a sputter target at said ceiling, an RF source power supply of a first frequency coupled to said sputter target, and an RF bias power supply of a second frequency coupled to said bias electrode, a multi-frequency impedance controller coupled between RF ground and one of (a) the bias electrode, and providing at least a first adjustable impedance at a first set of frequencies, said multi-frequency impedance controller comprising a variable capacitor enabled to be placed in at least one of two states by a motor, the at least two states of the variable capacitor having different capacitances.
In accordance with yet another aspect of the present invention, the physical vapor deposition plasma reactor is provided, wherein the multi-frequency impedance controller further comprises an inductive element connected in series with the variable capacitor.
In accordance with yet another aspect of the present invention, the physical vapor deposition plasma reactor is provided, wherein the multi-frequency impedance controller further comprises a processor to control the motor of the variable capacitor.
In accordance with yet another aspect of the present invention, the physical vapor deposition plasma reactor is provided, wherein the multi-frequency impedance controller further comprises a current sensor to control the motor of the variable capacitor.
In accordance with yet another aspect of the present invention, the physical vapor deposition plasma reactor is provided, wherein the multi-frequency impedance controller further comprises a voltage sensor to control the motor of the variable capacitor.
In accordance with yet another aspect of the present invention, the physical vapor deposition plasma reactor is provided, wherein a state of the variable capacitor is associated with a process recipe in a process controller.
In accordance with yet another aspect of the present invention, the physical vapor deposition plasma reactor is provided, further comprising a housing for the variable capacitor.
In accordance with yet another aspect of the present invention, the physical vapor deposition plasma reactor is provided, wherein an output of the variable capacitor is connected to the housing.
In accordance with yet another aspect of the present invention, the physical vapor deposition plasma reactor is provided, wherein the housing is connected to ground.
In accordance with yet another aspect of the present invention, the physical vapor deposition plasma reactor is provided, wherein the process recipe is a common process recipe adjusted for a chamber-to-chamber variation.
In accordance with a further aspect of the present invention, a plasma reactor is provided, comprising a chamber including a side wall and a ceiling, said side wall being coupled to an RF ground, the chamber sustaining a plasma for material deposition, a workpiece support within the chamber having a support surface facing the ceiling and a bias electrode underlying the support surface, a source power applicator at said ceiling, an RF source power supply of a first frequency coupled to said source power applicator, and an RF bias power supply of a second frequency coupled to said bias electrode, a multi-frequency impedance controller coupled between RF ground and the bias electrode, and providing at least a first adjustable impedance at a first set of frequencies, said multi-frequency impedance controller comprising a variable capacitor enabled to be placed in at least one of two states by a motor, the at least two states of the variable capacitor having different capacitances.
In accordance with yet a further aspect of the present invention, a plasma reactor is provided, wherein the multi-frequency impedance controller further comprises an inductive element connected in series with the variable capacitor.
In accordance with yet a further aspect of the present invention, a plasma reactor is provided, wherein the multi-frequency impedance controller further comprises a processor to control the motor of the variable capacitor.
In accordance with yet a further aspect of the present invention, a plasma reactor is provided, wherein the multi-frequency impedance controller further comprises a current sensor to control the motor of the variable capacitor.
In accordance with yet a further aspect of the present invention, a plasma reactor is provided, wherein the multi-frequency impedance controller further comprises a voltage sensor to control the motor of the variable capacitor.
In accordance with yet a further aspect of the present invention, a plasma reactor is provided, wherein a state of the variable capacitor is associated with a process recipe in a process controller.
In accordance with yet a further aspect of the present invention, a plasma reactor is provided, further comprising a housing for the variable capacitor.
In accordance with yet a further aspect of the present invention, a plasma reactor is provided, wherein an output of the variable capacitor is connected to the housing.
In accordance with yet a further aspect of the present invention, a plasma reactor is provided, wherein the housing is connected to ground.
In accordance with yet a further aspect of the present invention, a plasma reactor is provided, wherein the process recipe is a common process recipe adjusted for a chamber-to-chamber variation.
So that the manner in which the exemplary embodiments of the present invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings. It is to be appreciated that certain well known processes are not discussed herein in order to not obscure the invention.
To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. It is to be noted, however, that the appended drawings illustrate only exemplary embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
In one embodiment, a first multi-frequency impedance controller is coupled between a sputter target of a PVD reactor and RF ground. Optionally, and in addition, a second multi-frequency impedance controller is coupled between the wafer susceptor or cathode and RF ground.
The first multi-frequency impedance controller (which is connected to the ceiling or sputter target) governs the ratio of the impedances to ground through the ceiling (sputter target) and the side wall. At low frequencies, this ratio affects the radial distribution of ion energy across the wafer. At very high frequencies, this ratio affects the radial distribution of ion density across the wafer.
The second multi-frequency impedance controller (which is connected to the cathode or wafer susceptor) governs the ratio of the impedances to ground through the cathode and the side wall. At low frequencies, this ratio affects the radial distribution of ion energy across the ceiling or sputter target. At very high frequencies, this ratio affects the radial distribution of ion density across ceiling or sputter target.
Each multi-frequency impedance controller governs the impedance to ground through the ceiling (in the case of the first controller) or through the cathode (in the case of the second controller) of different frequencies present in the plasma, including harmonics of the bias power frequency, harmonics of the source power frequency, inter-modulation products of the source and bias power frequencies and their harmonics, for example. The harmonics and intermodulation products may be selectively suppressed from the plasma by the multi-frequency impedance controller, in order to minimize inconsistencies in performance between reactors of the same design. It is our belief that some of these harmonics and intermodulation products are responsible for inconsistencies in reactor performance between reactors of identical design.
For very high frequencies, the first multi-frequency impedance controller's impedance to ground through the ceiling or target (with reference to the impedance through the grounded side wall) controls the radial distribution of ion density across the wafer surface is changed for fine adjustment. For low frequencies, the first multi-frequency impedance controller's impedance to ground through the ceiling or target (with reference to the impedance through the grounded side wall) controls the radial distribution of ion energy across the wafer surface is changed for fine adjustment.
For very high frequencies, the second multi-frequency impedance controller's impedance to ground through the wafer or cathode (with reference to the impedance through the grounded side wall) controls the radial distribution of ion density across the ceiling or sputter target. For low frequencies, the second multi-frequency impedance controller's impedance to ground through the wafer or cathode (with reference to the impedance through the grounded side wall) controls the radial distribution of ion energy across the sputter target or ceiling. The foregoing features provide a process control mechanism to regulate the reactor performance and uniformity.
In addition to governing distribution of ion energy and/or ion density across the wafer surface and across the ceiling (target) surface, the multi-frequency impedance controllers also govern the composite (total) ion density and ion energy at these surfaces through governance of impedance to ground at appropriate frequencies (e.g., low frequencies for ion energy and very high frequencies for ion density). Therefore, the controllers determine process rates at the wafer and target surfaces. Selected harmonics are tuned, depending upon the desired effect, either to promote their presence in the plasma or to suppress them. The tuning of the harmonics affects ion energies at wafer, thereby affecting process uniformity. In a PVD reactor, tuning of the ion energy affects step coverage, overhang geometry and physical film properties such as grain size, crystal orientation, film density, roughness and film composition. Each multiple frequency impedance controller can further be employed to enable or prevent deposition, etching or sputtering of the target or wafer or both, by appropriate adjustment of impedance to ground for selected frequencies, as will be described in detail in this specification. For example, in one mode, the target is sputtered while deposition is carried out on the wafer. In another mode, the wafer is etched while sputtering of the target is prevented, for example.
A planar conductive grid 116 may be encapsulated within the top insulating layer 112 to serve as an electrostatic clamping (ESC) electrode. A D.C. clamping voltage source 118 is connected to the ESC electrode 116. An RF plasma bias power generator 120 of a bias frequency fb may be coupled through an impedance match 122 to either the ESC electrode 116 or to the conductive base 114. The conductive base 114 may house certain utilities such as internal coolant channels (not shown), for example. If the bias impedance match 122 and bias generator 120 are connected to the ESC electrode 116 instead of the conductive base 114, then an optional capacitor 119 may be provided to isolate the impedance match 122 and RF bias generator 120 from the D.C. chucking power supply 118.
Process gas is introduced into the chamber 100 by suitable gas dispersing apparatus. For example, in the embodiment of
A PVD sputter target 140 is supported on the interior surface of the ceiling 104. A dielectric ring 105 insulates the ceiling 104 from the grounded side wall 102. The sputter target 140 is typically a material, such as a metal, to be deposited on the surface of the wafer 110. A high voltage D.C. power source 142 may be coupled to the target 140 to promote plasma sputtering. RF plasma source power may be applied to the target 140 from an RF plasma source power generator 144 of frequency fs through an impedance match 146. A capacitor 143 isolates the RF impedance match 146 from the D.C. power source 142. The target 140 functions as an electrode that capacitively couples RF source power to plasma in the chamber 100.
A first (or “target”) multi-frequency impedance controller 150 is connected between the target 140 and RF ground. Optionally, a second (or “bias”) multi-frequency impedance controller 170 is connected between the output of the bias match 122 (i.e., to either the conductive base 114 or to the grid electrode 116, depending upon which one is driven by the bias generator 120). A process controller 101 controls the two impedance controllers 150, 170. The process controller can respond to user instructions to increase or decrease the impedance to ground of a selected frequency through either of the first and second multi-frequency impedance controllers 150, 170.
Referring to
Referring still to
The notch filter array 172 and pass filter array 174 for the second multi-frequency impedance controller 170 may be implemented in a similar manner, as depicted in
The pass filter array 174 of
Precise control of RF ground return paths through each of the multi-frequency impedance controllers at selected frequencies is attained by the process controller 101 individually governing each of the variable capacitors 158, 164 of the first multi-frequency impedance controller 150 and each of the variable capacitors 178, 184 of the second multi-frequency impedance controller 170.
Referring now to
In this example, n=11. The resonant frequencies of the m notch filters 156-1 through 156-12 in the notch filter array 152 of the first multi-frequency impedance controller are also harmonics and intermodulation products of the source and bias power frequencies fs and fb may include the following frequencies: fs, 2fs, 3fs, fb, 2fb, 3fb, fs+fb, 2(fs+fb), 3(fs+fb), fs−fb, 2(fs−fb), 3(fs−fb). In this example, m=12. The notch filter 156-1 having the resonant frequency fs blocks the fundamental frequency of the source power generator 144 to prevent it from being shorted through the impedance controller 150.
Referring still to
As described above, each pass filter (162, 182) may include an optional switch (163, 183, respectively) to disable the pass filter in the event that its resonant frequency is to be blocked by a notch filter. For example, each pass filter 162 of
In one aspect of the method, ion density over wafer center is increased while decreasing ion density over wafer edge, by decreasing impedance to ground at fs through the bias multi-frequency impedance controller 170 relative to the impedance to ground at the source power frequency fs through the side wall (block 215 of
In another aspect, ion density is decreased over wafer center while increasing ion density over wafer edge by increasing impedance to ground at fs through the bias multi-frequency impedance controller 170 relative to the impedance to ground at fs through the side wall (block 220 of
In a further aspect, ion energy over wafer center is increased while decreasing ion energy over wafer edge by decreasing impedance to ground at the bias power frequency fb through the target multi-frequency impedance controller 150 relative to the impedance to ground at fb through the side wall (block 225 of
In a yet further aspect, ion energy over wafer center is decreased while increasing ion energy over wafer edge by increasing impedance to ground at fb through the target multi-frequency impedance controller 150 relative to the impedance to ground at fb through the side wall (block 230 of
In order to suppress at the target surface a particular frequency component corresponding to a certain harmonic or intermodulation product (block 330), the impedance to ground at that particular frequency through the target multi-frequency impedance controller 150 is increased (block 335). This may be accomplished by de-tuning (or disconnecting) the one pass filter in the pass filter array 154 most closely associated with that frequency (block 340). In addition the corresponding notch filter in the notch filter array 152 may be tuned more closely to the particular frequency (block 345). Optionally, and in addition, the impedance to ground at that same frequency through the pedestal multi-frequency impedance controller 170 is decreased, to divert those components to ground away from the target (block 350). This latter step may be accomplished by tuning the one pass filter of the pass filter array 174 to the particular frequency (block 355).
Some of the foregoing steps may be employed to promote a desired frequency component at either the wafer surface or at the target surface. The plasma current frequency component may be chosen to be one which promotes or increases a particular action of the plasma, such as sputtering or deposition or etching. For example, a chosen plasma current frequency component may be directed or diverted to the target for such a purpose. This direction or diversion may be accomplished by performing the step of block 325, in which a chosen plasma current frequency component is diverted to the target 140. The diversion may be more complete by additionally performing the step of block 315 to repulse the chosen frequency component from the wafer surface.
Another chosen plasma current frequency component may be diverted to the wafer surface for a similar or other purpose (increase etch rate, deposition rate or sputter rate at the wafer surface, for example). This diversion may be accomplished by performing the step of block 355, in which a chosen plasma current frequency component is diverted to the wafer surface. This diversion may more complete by additionally performing the step of block 345 to repulse the chosen frequency component from the target surface. As one example, the chosen frequency component may be a frequency (a fundamental or harmonic or intermodulation product) that promotes a particular plasma action, such as sputtering. If it is desired to sputter the wafer without sputtering the target, then that frequency component is diverted away from the target and to the wafer by raising the impedance at that frequency through the target impedance controller 150 while reducing the impedance at the same frequency through the bias impedance controller 170. Conversely, if it is desired to sputter the target without sputtering the wafer, then that frequency component is diverted away from the wafer and to the target by decreasing the impedance at that frequency through the target impedance controller 150 while increasing the impedance at the same frequency through the bias impedance controller 170. The desired plasma effect may be obtained with a particular set of plural frequency components. In such a case, the plural frequency components are controlled in the foregoing manner using plural notch and/or pass filters operated simultaneously in accordance with the foregoing.
The foregoing features may be implemented in a plasma reactor lacking a sputter target, e.g., a plasma reactor adapted for processes other than physical vapor deposition. In such a reactor, for example, the target 140 and DC source 142 of
In a further embodiment of the present invention tuning of the capacitive or inductive coupling of the substrate on the pedestal to the target is achieved by applying a variable capacitor that is put in a setting by a motor such as a stepping motor. It adjusts the substrate impedance, thereby adjusting the amount of bias that builds up on the substrate.
It has been shown above that the impedance of impedance controller 170 can be adjusted by variable capacitors 178 and/or 184 in impedance controller 170. It is desirable that reaction chambers of a specific common design for processing similar products or substrates can be put in an identical or close to identical operating condition. This can be achieved by having an operator or a processor or a combination of both provide a controller with identical or close to identical settings. These settings may include operational settings for a power source and the like. A common impedance setting in an impedance controller in one embodiment of a processing chamber is a common setting to achieve identical or close to identical operating conditions for at least two processing chambers. The impedance setting in a further embodiment relates to an impedance setting of a variable impedance between the pedestal and ground. In yet a further embodiment the impedance is made variable by a variable capacitor which can be operated to have one of several or a range of electronic capacitance.
Such variable capacitors are known, and may be obtained for instance from Comet North America's Office in San Jose, Calif.
Even if processing chambers are of the same designs there may be chamber to chamber variations, wherein individual parameter settings may vary to achieve identical or close to identical processing outcomes. A chamber may be provided with a specific (common) recipe for a desired outcome. A controller of the chamber may adjust at least one parameter in a standard recipe to adjust the required setting for a known variation to achieve the desired outcome.
In one embodiment the setting of the variable capacitor in a chamber may be determined to have a variation compared to a standard recipe to achieve a desired impedance adjustment for optimal ion energy or density distribution related to a desired processing outcome. In a further embodiment, the desired capacitance or capacitance setting may be programmed in a controller of the chamber. The variable capacitor can be set in a specific position for a desired capacitance. Based on a desired set-point a processor may control a motor, such as a stepper motor, to put the variable capacitor in a desired setting. A desired setpoint of the variable capacitor may be determined by a value of a voltage or a current at that setpoint. The processor is programmed to change the capacitance of the capacitor until the value of the voltage or current is achieved. The variable capacitor in that case is associated with a voltage or a current sensor that provides feedback to the processor and continues to adjust the capacitance of the variable capacitor until the desired value of the sensed voltage or current is achieved.
The above allows the setting of the variable capacitor for a desired common outcome for instance related to a specific recipe to be adjusted for chamber-to-chamber variation, while still achieving a desired outcome. It also allows a chamber to be provided with a menu driven automatic controller, wherein similar chambers are programmed and controlled to process and deliver identical or close to identical products, without having to manually adjust parameter settings when a certain menu option is selected. In one embodiment, one may have to go through a calibration step to determine to what extent a setting such as a variable capacitor setting has to be adjusted to achieve a predetermined outcome. Once, the calibration has taken place, one may program a process controller to put the variable capacitor in a required position. In a further embodiment, a position of the variable capacitor may be associated with a current or voltage as applied to achieve an optimal setting. A sensor collaborates with a processor to put the variable capacitor in a position that corresponds with the desired voltage or current value.
The above then achieves a tuning of an impedance of the chamber based on a desired and predefined outcome, taking into account chamber-to-chamber variation.
We will now turn to
The circuit allows the deposition of a metal or non-metal layer on a wafer/substrate. As will be discussed below, the variable capacitive tuning circuit can be automated for a given set point. The set point can be current, voltage or a percentage of the full scale of the capacitance of the variable capacitor. The set point can depend on the desired processing.
Referring to
A current through the variable capacitor 10 may be provided through an inductor 20 and may go through the sensor 18. The inductor 20 is optional. It may be provided to create a tuner circuit of the present invention with a certain band-pass characteristic. The sensor 18 is also optional and, if used, can be placed at points 27, 12 or 14 in the circuit.
The variable capacitor may be placed in a housing 29. The housing may be grounded via optional ground connection 31. The output 16 of the variable capacitor 10 may be connected through a connection 32 to the housing 29 and thus 16 has then the same potential as the housing. When the housing is grounded and connection 32 exists, then 16 also has the potential of ground.
In accordance with various aspects of the present invention, it is contemplated that other components can be provided in the circuit 1 of
The sensor circuit 18, if included, provides a feedback signal to the interface 22. The interface 22 provides the feedback signal to the processor 24. The processor 24 can be a dedicated electric circuit or it can also be a microprocessor or microcontroller based circuit. The interface 22 is optional. The interface 22 may provide a manual interface to set a position of the variable capacitor. The interface 22 may also provide a signal that reflects a capacitance setting of the variable capacitor. The interface 22 may be connected to the motor to provide a movable scale that provides a visual indication of the actual setting of the variable capacitor.
The processor 24 controls the motor controller 26 which controls the motor 28 in accordance with the mode control signal and the outputs of the sensors. The motor controller 26 causes the motor 28, which is preferably a stepper motor, to step through its positions to vary the capacitance of the variable capacitor 10 as a function of the mode control signal and of the outputs of the sensors. Accordingly, the variable capacitor can be put in a range of capacitance values, at least in a first capacitance and a second capacitance, which are different capacitances. Each capacitance of the variable capacitor in a range of capacitances corresponds to a state of the variable capacitor. A state of the variable capacitor corresponds with an impedance value at a certain frequency. In one embodiment, a variable capacitor is put in a first state to achieve an impedance at a first frequency.
A state of a variable capacitor 10 in one embodiment may be defined as a position of the interface 22, or as a position of the motor 28 or as a measured current or voltage by the sensor 18, or in any other phenomenon that defines a state of the variable capacitor. A state of the variable capacitor in a further embodiment is encoded in a process controller for a recipe of a desired outcome of a process run of the chamber. The state of the variable capacitor preferably being adjusted for chamber-to-chamber variations related to the desired outcome. Accordingly, when a process controller is initiated to run a pre-defined process in a chamber, a desired state of the variable capacitor is retrieved from a memory, that stores for instance a process recipe, and instructs the processor 24 to put variable capacitor 10 through for instance motor controller 26 to motor controller 28 in the desired position. It is to be understood that a desired position may depend on a variable factor such as a current or a voltage. During the chamber process the current may change. The processor 24 may enable the variable capacitor to follow variations in a current or a voltage during the process or to adjust to variations in a current or a voltage according to predefined control instructions.
In a further embodiment a state of the variable capacitor is related to a stage of a process in the chamber. A process controller may provide an instruction to change the state of the variable capacitor to a new state based on for instance a stage of the process.
The switch 64 selectively provides the power it receives on its input on one of its outputs, depending on the value of the signal on a control input 70. As illustrated in
The processor 24 decides what set point is desired and how to control the switch 64 based on an input on line 30 in
When the mode control input signal specifies a current control mode, the processor 24 causes the switch 64 to connect the current sensor 62 to the output of the variable capacitor 10 and controls the motor controller 26 based on the output of the current sensor 62 to maintain a constant current on the output of the variable capacitor 10.
When the mode control input signal specifies a setpoint mode, the processor 24 controls the motor controller based on a set point specified by the mode control input signal to cause the motor to vary the capacitance of the variable capacitor in accordance with the specified set point.
The processor 24 can also be a special purpose interface circuit. The main purpose of the interface circuit or processor 24 is to control the motor controller as a function of the mode control input, the voltage sensor output and the current sensor output, as just described. If the mode control input specifies a set point, then the motor controller 26 is controlled to generate the capacitance specified by the input. If the mode control input specifies a voltage mode, then the motor controller 26 controls the motor 28 in accordance with the output of the voltage sensor 62 to maintain a constant voltage at the capacitor 10. If the mode control input specifies a current mode, then the motor controller 26 controls the motor 28 to maintain a constant current at the capacitor 10.
As previously mentioned, the control circuit of
Any type of well known voltage sensor can be used in accordance with the various aspects of the present invention. Similarly, any type of well know current sensor can be used in accordance with the various aspects of the present invention. Both voltage sensors and current sensors are well known in the art.
A novel method of providing plasma processing such as physical vapor deposition or etching on a wafer supported on a pedestal is also provided. The method includes supporting a wafer on the pedestal, and supplying power to the pedestal in a frequency range based on the capacitance of the variable capacitor.
An input signal specifies an operational set point to a circuit that specifies the capacitance for the variable capacitor. The method can also include sensing a voltage or a current with a sensor and feeding the output of the sensor to a feedback circuit that controls the motor controller to place the variable capacitor in a desired position.
As shown above, the sensor can be a voltage sensor and the feedback circuit monitors the voltage at the output of the variable capacitor and controls the motor controller to maintain the voltage at the output of the variable capacitor as a constant value. The sensor can also be a current sensor and the feedback circuit monitors the current at the output of the variable capacitor and controls the motor controller to maintain the current at the output of the variable capacitor as a constant value.
While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/309,372 filed on Mar. 1, 2010, which is incorporated herein by reference in its entirety.
Number | Date | Country | |
---|---|---|---|
61309372 | Mar 2010 | US |