Sector-based distribution of plasma-based wafer processing systems

Abstract

A radio frequency plasma processing system comprises: a reaction chamber; an electrode having an electrode symmetry axis, the electrode being disposed in the reaction chamber; and a plurality of plates, each plate having a conductive layer, disposed in the reaction chamber around a perimeter of the electrode at a gap from a surface of the electrode at an azimuth angle relative to the electrode symmetry axis, each plate of the plurality of plates being connected to an electrical ground via a variable reactance circuit.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Application No. 62 / 959,636, filed on January 10, 2020, and U.S. Non-Provisional Patent Application No. 17 / 145,221, filed on January 8, 2021, the contents of which are incorporated herein by reference. Background Art

[0003] Radio frequency (RF) plasma-enhanced processing is widely used in semiconductor manufacturing to etch various types of films, deposit thin films at low to moderate process temperatures, and perform surface treatment and cleaning. This process utilizes a plasma, a partially ionized gas, to generate neutral species and ions from precursors within a reaction chamber, provide energy for ion bombardment, and / or perform other actions. During this process, controlling the plasma density presents challenges, and plasma non-uniformity within the reaction chamber impacts wafer processing uniformity and the yield of the integrated circuits or other devices being fabricated.

[0004] Non-uniform plasma density within the reaction chamber can result in non-uniform etch rates or certain characteristics across the substrate. In some systems, a probe is used to monitor the uniformity of the plasma density within the reaction chamber. Such a probe may rely on a coating that is exposed to the plasma environment and may use active electronics to infer the plasma density. Such a system may take milliseconds or longer to respond to changes in the plasma. Emission spectroscopy can also be used to determine the plasma density profile within the reaction chamber, but such systems may require multiple lines of sight through the plasma and use complex analysis to infer non-uniformity. These techniques are not sensitive or fast enough to effectively address non-uniformity issues and may be more expensive to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] When with Figure 1 The present disclosure can be best understood from the following detailed description when read together. It should be emphasized that, in accordance with standard industry practice, various features are not drawn to scale. In fact, the dimensions of various features may be arbitrarily increased or decreased for clarity of discussion.

[0006] Figure 1 is a side view schematic diagram of an RF plasma processing system according to an embodiment of the present disclosure.

[0007] Figure 2 is a schematic side view of a plasma chamber according to an embodiment of the present disclosure, wherein high bandwidth sensors are mounted at various locations on the electrode.

[0008] Figure 3is a cross-sectional view of a dual-plate electrode assembly having a sensor providing a voltage signal through an electrical connector having a low shunt capacitance to electrical ground according to an embodiment of the present disclosure.

[0009] Figure 4 is a cross-sectional view of a base with an embedded high-bandwidth voltage sensor according to an embodiment of the present disclosure.

[0010] Figure 5 is a schematic side view of a base according to an embodiment of the present disclosure.

[0011] Figure 6 is a top view of an axisymmetric surface wave propagating across a susceptor according to an embodiment of the present disclosure, wherein the plasma in the reaction chamber is axisymmetric.

[0012] Figure 7 is a top view of transverse electromagnetic surface wave propagation across electrodes according to an embodiment of the present disclosure.

[0013] Figure 8 is a top cross-sectional view of a sensor mounted azimuthally (about the chamber axis of symmetry) on a reaction chamber according to an embodiment of the present disclosure.

[0014] Figure 9 is a side cross-sectional view of an azimuthally mounted sensor on an electrode, electrode base, top dielectric plate, viewing port, and dielectric wall of a reaction chamber according to an embodiment of the present disclosure.

[0015] Figure 10 is a side cross-sectional view of a capacitively coupled plasma reactor chamber with some sensor array locations according to an embodiment of the present disclosure.

[0016] Figure 11 is a side cross-sectional view of a model inductive plasma reactor chamber according to an embodiment of the present disclosure.

[0017] Figure 12 is a schematic side partial cross-sectional view of an RF plasma processing system with some possible sensor locations according to an embodiment of the present disclosure.

[0018] Figure 13 is a schematic partial cross-sectional view of a dielectric wall comprising an RF plasma processing system with a sensor mounted on the dielectric surface proximate to an inductively coupled antenna according to an embodiment of the present disclosure.

[0019] Figure 14 is a side view in schematic form of an RF plasma processing system according to an embodiment of the present disclosure.

[0020] Figure 15 is a top view of a schematic diagram of an RF plasma processing system according to an embodiment of the present disclosure.

[0021] Figure 16 is a side view of a schematic diagram of an RF plasma processing system according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0022] Illustrative examples of the subject matter claimed below will now be disclosed. For the sake of clarity, not all features of an actual implementation are described in this specification. It will be appreciated that in the development of any such actual implementation, many implementation-specific decisions may be made to achieve the developer's particular goals, such as complying with system-related and business-related constraints, which will vary from implementation to implementation. Moreover, it will be appreciated that such development work, even if complex and time-consuming, would be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

[0023] Furthermore, as used herein, the articles "a" and "an" are intended to have their ordinary meaning in the patent art, i.e., "one or more." Here, the term "approximately," when applied to a value, generally means within the tolerance range of the equipment used to produce that value, or in some examples, means plus or minus 10%, or plus or minus 5%, or plus or minus 1%, unless expressly specified otherwise. Furthermore, the term "substantially," as used herein, means, for example, a majority, or nearly all, or all, or an amount in the range of about 51% to about 100%. Furthermore, the examples herein are for illustrative purposes only and are presented for discussion purposes only and not by way of limitation.

[0024] Steering Figure 1 , shows a schematic side view of an RF plasma processing system 100 according to an embodiment of the present disclosure. The RF plasma processing system 100 includes a first RF generator 105 and a second RF generator 110, a first impedance matching network 115, a second impedance matching network 120, a sheath 125, a plasma power supply, such as a showerhead 130 or an equivalent power supply element such as an electrode, and a pedestal 135. As used herein, a plasma power supply may refer to any device that introduces power to generate a plasma and may include, for example, the showerhead 130 and / or other types of electrodes and antennas.

[0025] The RF plasma processing system 100 can include one or more RF generators 105, 110 that deliver power to a reaction chamber 140 through one or more impedance matching networks 115, 120. RF power flows from the first RF generator 105 through the impedance matching network 115 into the plasma in the reaction chamber 140 to the showerhead 130 or sidewalls, to electrodes external to the showerhead 130, or to an inductive antenna (not shown) that electromagnetically provides power to the plasma. Thereafter, the power flows from the plasma to ground and / or to the pedestal 135 and / or to the second impedance matching network 120. Generally, the first impedance matching network 115 compensates for variations in load impedance within the reaction chamber 140 by adjusting reactive components, such as variable capacitors, within the first impedance matching network 115 so that the combined impedance of the showerhead 130 and the first impedance matching network 115 equals the output impedance of the first RF generator 105, e.g., 50 ohms. Furthermore, adjusting the frequency within a range of approximately plus or minus ten percent of the RF power can modify the reflected power. The term "approximately" is used herein to acknowledge that, in practice, some imprecision with respect to the range or value may occur while still obtaining satisfactory results. Such imprecision may result from, for example, loss or degradation of calibration or drift during operation. However, in these cases, the range or value expressed is a nominal target for the operating conditions at the time of use.

[0026] In some examples, the first RF generator 105 can provide power at an RF frequency between approximately 400 KHz and 150 MHz, while the second RF generator 110 connected to the base 135 can supply power at an RF frequency lower than the RF frequency of the first RF generator 105. However, in some embodiments, the second RF generator 110 may not supply power at an RF frequency lower than the RF frequency of the first RF generator 105. Typically, the frequencies of the first and second RF generators 105, 110 are such that the RF frequency of the first RF generator 105 is neither an integer multiple nor an integer fraction of the frequency of the second RF generator 110. One or more of the first and second RF generators 105, 110 can also adjust frequency to modify the reflected power.

[0027] Impedance matching networks 115, 120 are designed to adjust their internal reactive components to match the load impedance to the source impedance. While low reflected power is generally considered desirable, embodiments of the present disclosure ensure that both delivered power and reflected power back toward first and second RF generators 105, 110 are maintained within reaction chamber 140. Even when reflected power is relatively high, the associated impedance matching networks 115, 120 monitor the forward and reflected power entering and exiting reaction chamber 140 and, using a motor drive system, make adjustments to adjustable reactive components, such as vacuum variable capacitors. In certain embodiments, electronically controlled capacitors, such as diodes in the lead of electronic variable capacitors, may be used. Impedance matching networks 115, 120 may include circuitry that measures the phase and magnitude of the signals to determine the levels of forward and reflected power from the expected load. Thus, embodiments of the present disclosure can be effective even when reflected power levels are high. If significant reflected power is present at a key frequency, the capacitors are varied until the reflected power is minimized, for example, to less than approximately 5 watts and / or less than approximately one percent, or in certain embodiments, less than 1 watt, over a period of time. Typically, harmonic frequency signals, including reflected power at harmonic frequencies, are not measured. Additionally, the frequency can be adjusted within a range of approximately plus or minus ten percent of the RF power, which can modify the reflected power.

[0028] Despite the numerous advantages of RF plasma processing systems 100, they have historically faced challenges in maintaining plasma density control throughout the multi-step process. For example, design tolerances on the order of one percent non-uniformity, relative to a nominal density range of the same magnitude, remain a challenge. As feature sizes shrink to below approximately 3 nm and layer thicknesses less than or equal to 10 nm, achieving optimal integrated circuit (IC) yields on each wafer requires increasingly tighter control of plasma and neutral species uniformity, reaching levels of 1% or even less. Non-uniform plasma density within the reaction chamber, or deviations from the desired average density beyond a desired range, can be caused by slow changes in the reaction chamber, changes in the RF circuitry, or rapid growth (on the order of sub-milliseconds) of parasitic or secondary plasmas, which can result in non-uniformity of nanoscale features across the entire processed wafer due to non-uniform etch rates.

[0029] Because even a one percent difference in etch rate across a wafer can cause yield issues for advanced technologies, and because it often takes a significant amount of time to complete wafer processing before yield loss is seen, timely and accurate detection of non-uniform plasma density or plasma density that deviates from a desired range within a reaction chamber is needed within a time period that may require less than about 1 millisecond to avoid irreversible deviations from desired feature profiles on the wafer.

[0030] Those skilled in the art will appreciate that electromagnetic (EM) surface waves can propagate on surfaces within the RF-powered plasma in reaction chamber 140. These surface waves will have significant energy at both the fundamental RF drive frequency and RF harmonics. The average power and power distribution of the harmonics are sensitive functions of plasma density and non-uniformity. Herein, a harmonic profile is defined as the spectrum of surface waves whose frequencies are integer multiples of the fundamental drive frequency of reaction chamber 140, which is based on the RF plasma. For example, if a 2 MHz RF drive power is provided to reaction chamber 140, the injected power will generate surface waves at this frequency, which propagate along the interface between the plasma and the interior surface of reaction chamber 140. By adjusting the frequency by approximately 10 percent of the RF power, the reflected power can be modified. Harmonic surface waves at integer multiple frequencies can also be generated. For example, a 2 MHz electromagnetic wave can generate surface waves at 4, 6, or 8 MHz. Both odd and even harmonics (2nd, 3rd, 4th, 5th, etc.) may be present, but in some examples, odd harmonics may predominate.

[0031] Various aspects of the present disclosure can provide sensor locations on and around the reaction chamber 140 and its components that can allow for the detection and analysis of RF surface waves to find the amplitude and phase of the fundamental and harmonic frequencies at multiple points within or near the reaction chamber 140. These waves can be detected by sensing RF voltage or RF current at the fundamental and harmonic frequencies on the surface of the chamber components. In some embodiments, the voltage sensor will include a pickup disposed at or near the surface of an electrode, pedestal base, chamber wall, or strap, and a conductive line that conveys the signal from the pickup to a connector or cable. The current sensor can include a conductive element that can include one or more loops or partial loops or linear conductors, wherein one end of the conductive element is at a reference potential, which can be a local electrical ground.

[0032] Multiple sensors, for example, two or more, can be positioned on a chamber component, as discussed in detail below, at different angles relative to the chamber's axis of symmetry to measure the surface voltage or current associated with such surface waves. Here, the angle measured relative to the chamber's axis of symmetry, starting from a reference point of the chamber, is defined as the azimuth angle. In some embodiments, such sensors can be positioned at approximately the same distance from the chamber's axis of symmetry.

[0033] Sensors can be mounted at various locations on or around the reaction chamber and / or its components. For example, sensors can be mounted on the surface of an electrode, such as the surface of the pedestal 135 and / or the showerhead 130. Sensors can also be mounted on the base of an electrode within or outside the vacuum environment. Sensors can be mounted internally on one or more metallic wall surfaces of the reaction chamber 140, inner or outer wall regions containing dielectric material, or on antennas that can be used to inductively deliver power to the plasma. Sensors can also be placed on passive antennas that can be used to sense EM waves near the plasma boundary, or on or near multiple conductive buses or straps that connect the first or second impedance matching networks 115, 120 to electrodes, such as the pedestal 135 and / or showerhead 130, antennas, or other components that deliver power to the plasma within the reaction chamber 140. Sensors can also be connected to an electrical ground. Thus, sensors can pick up signals from different parts of the RF plasma processing system 100 as they propagate on the surfaces of their respective components.

[0034] At the electrode-plasma interface, e.g. Figure 1 A spectrum of RF harmonics is generated within the sheath 125, and the waves propagate in all directions, so the amplitude and phase of all wave components will vary with position on the electrode or support base. Such waves also propagate along the inner surface of the metal wall adjacent to the plasma and through any dielectric walls that may be adjacent to the plasma. The amplitude and phase of such waves change in response to changes in the plasma, for example, changes in plasma density and inhomogeneity, with response times on the order of microseconds or less. Furthermore, the frequency and phase distribution of the RF harmonic surface waves propagating at the electrode-plasma interface determines the frequency and phase distribution of harmonic surface waves propagating on the surface of the electrode base facing the impedance matching network 115, 120, on surfaces connected to the electrode or plasma-wall interface, or on the wall. The amplitude and phase of the fundamental and harmonic signals at different sensor locations allows determination of which portion of the total EM wave field at each frequency is azimuthally symmetric and which portion is asymmetric.

[0035] In the case of an inductive plasma, signals from the plasma, such as the fundamental and harmonics, can propagate back to the antenna and then to the impedance matching network that feeds the antenna. The frequency and phase distribution of both the fundamental and harmonic RF waves can be monitored on microsecond timescales or faster using sensors mounted on these surfaces and compared to specified ranges and phase relationships as indicators of plasma asymmetry or changes in plasma density or conductivity. The signals from such sensors can be transmitted via cables or other means to a detector, which analyzes the component frequencies of the signal to produce amplitude and phase values ​​for each frequency component at each sensor location.

[0036] In certain embodiments, the amplitude and phase of the detected RF harmonic components can be rapidly determined by circuitry (detectors) in a signal analysis compartment, which can be a separate metal box or chassis, or can be within, connected to, or part of the impedance matching network 115, 120. This amplitude and phase can be used to determine the state of the plasma, including radial distribution and asymmetry, by applying algorithms and plasma non-uniformity calibration. The signals from the sensors can be Fourier analyzed by dedicated circuitry (detectors) that is fast enough to perform nearly continuous spectral analysis, updating as frequently as possible and generating a high-speed data stream. For example, for a plasma power of 13.56 MHz, 512 time bins can take less than 50 microseconds to process through Fourier analysis, and for a pulsed plasma when each element of the pulse occurs at 5 kHz, this allows the plasma state to be updated at a rate of 10 kHz.

[0037] The results of the dedicated Fourier analysis of the fundamental and harmonics can be stored on a separate storage medium that can be read and / or written to by an analysis processor associated with the signal analysis compartment. The stored results or real-time signals can be routed to a high-speed computing processor to determine asymmetry parameters for each of the fundamental and harmonics. The asymmetry parameters can be compared to values ​​previously stored on a separate storage medium (or on a different storage medium) using an algorithm (also stored on a separate storage medium or on a different storage medium) to quickly identify a "plasma fault" condition. The analysis processor can then transmit appropriate commands to the first and second RF generators 105, 110, and in some embodiments, more than just two RF generators, and, when appropriate, to the impedance matching networks associated with these generators, e.g., to continue processing under the current conditions or to make necessary changes to the processing conditions. In some embodiments, three, four, or more RF generators can be used. The first and second RF generators 105, 110 may then continue, stop, change the power provided, vary the frequency by adding or subtracting approximately ten percent of the RF power to modify the reflected power, or respond in some other suitable manner—for example, by entering a reduced power mode or pulse mode, or commanding some corrective action, such as alarm triggering, power interruption, etc., to avoid improper wafer processing in the event of a plasma malfunction or other unacceptable condition.

[0038] The location of the sensors for detecting (electric and magnetic fields of) and characterizing surface waves can be, in some embodiments, on the peripheral surface of the pedestal 135 (exposed or covered by a dielectric) outside the area covered by the wafer. For example, if the reaction chamber 140 is to process a circular wafer with a radius of 150 mm, the sensors mounted on the pedestal can be located at a radius greater than 150 mm from the center of the wafer, which in some cases may be located below the annular peripheral dielectric used to control edge effects. The sensors can be located in addition or alternatively on the surface or periphery of the showerhead 130 facing the wafer, or on the base of the pedestal 135 or the surface of the base of the showerhead 130, whether these locations are within or outside the evacuated processing environment. The sensors can also be located in various other locations, which will be discussed in detail below, and can be monitored continuously or periodically to provide uniformity of the processing plasma.

[0039] Using sensors outside the evacuated processing environment, such as in a ribbon or bus connecting the base to one or more of the impedance matching networks 115, 120, the base of the pedestal 135, and / or the showerhead 130, may eliminate the need to pass signals through vacuum feedthroughs or install transmission cables within the evacuated volume of the reaction chamber 140. Sensors in such locations can monitor fundamental and harmonic EM waves substantially continuously. This allows the RF plasma processing system 100 to continuously provide uniformity in plasma density and determine in a very short time whether a fault condition has occurred or whether to continue with proper wafer or substrate processing.

[0040] In certain example embodiments, the present disclosure may provide an apparatus and method for detecting deviations of a plasma within an RF plasma processing system 100 from a desired "processing window." The RF plasma processing system 100 may include a reaction chamber 140 that may include a showerhead 130 for injecting a reactant gas into the reaction chamber 140 and may also include a wafer support pedestal 135. However, in other embodiments, the showerhead 130 may not inject a gas into the reaction chamber 140. In some embodiments, the showerhead 130 may be mounted with its center proximate an approximate axis of symmetry of the reaction chamber 140 and equipped with a plurality of sensors positioned at selected azimuth angles about the axis of symmetry. Additionally or alternatively, such sensors may be positioned on a wafer-facing surface in a peripheral region of the showerhead 130 to detect and measure propagating EM surface waves as the wafer is processed.

[0041] In addition, in some embodiments, there may be a plurality of sensors mounted on the outer surface of the wafer support pedestal 135, outside the area occupied by the wafer, for detecting both the amplitude and phase of RF harmonics and fundamental surface waves. Such sensors may be exposed to the plasma, or may be covered by a dielectric or a dielectric and a metal cover. In addition or alternatively, the sensors may be located on the periphery of the base of the pedestal 135, within or outside the evacuated volume and / or below the plane defined by the wafer. In some embodiments, the sensors may be positioned on the base of the pedestal to detect surface electromagnetic waves propagating toward or away from the wafer support area of ​​the pedestal and on the surface of the pedestal base. In certain embodiments, the sensors may be mounted close to the plane of the wafer (e.g., less than 10 cm).

[0042] Alternatively, the sensor can be mounted on a portion of pedestal 135 that is metal or other conductive material and located outside the evacuated region of reaction chamber 140 under atmospheric conditions. A sensor located outside the evacuated region can be mounted on an area of ​​pedestal 135 that has a radius from the pedestal's axis of symmetry that is at least 50% of the maximum pedestal 135 radius, or even greater than 75% of the maximum pedestal 135 radius. Such a sensor can be positioned close to—in some embodiments, within a few centimeters of—a vacuum seal supporting pedestal 135, such as an O-ring. In some embodiments, the sum of the radial and axial propagation distances from the wafer edge to the sensor can be less than about 25 cm, or in some embodiments, less than about 15 cm, or even about 10 cm. The specific location and orientation of sensors according to embodiments of the present disclosure are discussed in detail below.

[0043] Steering Figure 2 , shows a schematic side view of a plasma chamber with high impedance sensors mounted at various locations on the electrodes according to an embodiment of the present disclosure. Separate RF generators 205 or 210 and impedance matching networks 215 and 220 can be used for each of the two components of the electrode, namely, the base 235 and the showerhead 230 or other equivalent powered element. Alternatively, the electrode can have multiple generators and matching networks feeding it. Arrows 245 along the surface of the base 235 indicate the radial direction of RF current and power flow inward from the bottom (bias) RF generator 210, which is electrically connected to the base 235 via the impedance matching network 220. The resulting electric field facilitates the formation of a plasma (not shown) between the electrodes and the radially outward counterflow of current and power, indicated by arrows 250, along the lower surface of the showerhead 235 or other powered element and ultimately to the selective ground circuit in the impedance matching network 215 of the showerhead 230 or other powered element.

[0044] In some embodiments, the reaction chamber 240, which has RF power from the first and second RF generators 205, 210 and the impedance matching networks 215, 220, can include sensors 255 on the periphery of the pedestal 235, which can be covered by the dielectric 260. Communication lines 265 can transmit signals from each sensor 255 to a Fourier analysis circuit (not shown) that calculates the amplitude and phase of both the fundamental frequency and harmonic frequency surface waves picked up by each sensor 255. In some embodiments, each sensor 255 can be approximately equidistant from the pedestal axis of symmetry.

[0045] In some embodiments, a Fourier analysis circuit can calculate the magnitude and phase of the fundamental and higher-order harmonics of a periodic electromagnetic surface waveform. The resulting series of magnitudes, called the Fourier series, and its phase are derived from the relationship between a function in the time domain and a function in the frequency domain.

[0046] Furthermore, some embodiments of the disclosed matching network 220 may include a signal analysis compartment 275 or an appendage thereof that is separate and RF-isolated from the RF power processing and impedance matching circuitry or components of the matching network 220. The signal analysis compartment 275 may include one or more Fourier analysis circuits (detectors) for analyzing the sensor signal and generating digital amplitudes and phases of the RF fundamental and harmonics. The signal analysis compartment 275 may also include high-speed digital logic or computational processors for analyzing the relative magnitudes and phases of the signals at the harmonic frequencies and deriving quantitative parameters characterizing the relative magnitudes and relative phases of the axisymmetric and non-axisymmetric harmonic components at each frequency. Furthermore, in some embodiments, the disclosed matching network 220 may be connected to the second RF generator 210 and the controller (not shown) of the reaction chamber 240 or RF plasma processing system 200 where the sensor 255 is located via a very fast network. In some embodiments, the disclosed enhanced impedance matching network 220 may be capable of sending commands to the first RF generator 205 and communicating its calculated parameters to the chamber controller and / or tool control system.

[0047] In addition, another first RF generator 205 and an impedance matching network 215 may also be electrically coupled to another electrode, which may be a showerhead 230 in the reaction chamber 240. In one embodiment, the first RF generator 205 may operate at a different frequency than the second RF generator 210, and its frequency may not be an integer multiple of the frequency of the second RF generator 210.

[0048] Similarly, the impedance matching network 215 monitors the reflected power from the electrodes and the processing chamber 240 and can make adjustments if there is significant reflected power from the electrodes. In some embodiments, the second RF generator 210 can be a 400 KHz RF generator, a 2 MHz RF generator, or a 13.56 MHz RF generator, or other, while the first RF generator 205 can operate at a slightly higher frequency. In some embodiments, the first RF generator 205 can operate at a frequency greater than 25 MHz, such as 60 MHz, 100 MHz, or higher.

[0049] In one embodiment, the primary function of the first RF generator 205 may be to power the reaction chamber 240 to generate a plasma between the showerhead 230 or another power source such as an electrode and the pedestal 235 to both generate reactive chemicals such as fluorine, chlorine, and combinations thereof, and to accelerate ions from the generated plasma and impact a wafer disposed on the pedestal 235.

[0050] A set of sensors 280, deployed on the surface of the upper electrode, i.e., showerhead 230, facing the lower electrode, i.e., pedestal 235, can have a bandwidth greater than about 10 times the frequency of the highest-frequency RF generator connected to that electrode. In some embodiments, each of them can have an impedance greater than about 100 ohms, and in some embodiments, greater than 500 ohms. Sensors 280 can be voltage or current sensors, or can combine both capabilities in a single package—for example, where a current sensor can include one or more lengths of wire that can be covered by an electrostatic shield.

[0051] In some embodiments, the sensors 280 are electrically connected to a Fourier analysis circuit in the signal analysis compartment 285 of the impedance matching network 215. The Fourier analysis circuit can output the amplitude and phase of the different frequency components from each sensor 280 and compare them with other sensors 280 and / or with reference levels stored in memory. In some embodiments, the analysis of the signal can include pattern recognition of the amplitude or phase or both or employ artificial intelligence (AI) that can use a learning algorithm such as a neural network or traditional digital algorithm processing of the signal from the sensor 280.

[0052] The signal processing by the Fourier analysis circuit to find the fundamental and harmonic component signals, including both amplitude and phase, can be completed in less than approximately 10 microseconds, and in a preferred embodiment, can be completed in 1 microsecond or less for each sensor signal. The isolated signal analysis compartment 285 of the impedance matching network 215 can contain at least one computational or logic processor with substantial computational power, with very high speed (<1 ns cycle time) circuitry employing very high speed logic ICs. In some embodiments, the processor in the signal analysis compartment 285 is programmable so that the supplier or user of the processing chamber 240 can provide or implement proprietary algorithms or analysis software on the computational "platform" provided in the impedance matching network 215.

[0053] In some embodiments, a software program for calculating parameters from signal amplitude and phase, and further logic algorithms for determining the effect of deviations from acceptable plasma conditions on process uniformity, may reside on a removable "plug-in" component that contains data storage and is connected to the signal processing compartment. The software or logic calculates the extent to which the RF electromagnetic surface wave spectrum has deviated from the nominal characteristic or appropriate operating conditions. Based on this, a processor associated with the controller can "decide" corrective action or terminate processing within approximately milliseconds before the wafer is processed incorrectly. In some embodiments, a quantitative determination of the expected effect of the deviation on process uniformity or other properties can be made within approximately 500 microseconds of occurrence so that remedial action can be initiated within milliseconds. In addition, such action can be taken so that damage to the wafer or substrate being processed in the reaction chamber 240 at that time is minimal or no, thereby avoiding yield loss of the wafer or substrate.

[0054] The evaluations and / or decisions made in the signal analysis compartment 285 of the impedance matching network 215 can, in some embodiments, be performed by a very fast computing or analysis system using algorithms residing in the plug-in storage and / or removable data processing device. In still other embodiments, the evaluations and decisions made in the signal analysis compartment 285 can be performed using an analog or neural network-type processor. Such decisions can further utilize a decision-making algorithm, which can reside in the removable storage or processing device. Corrective action commands can then be rapidly transmitted from the compartment 275 of the impedance matching network 215 to the RF generator 205 via a high-speed data line, which can temporarily interrupt, change, or terminate the power or RF frequency to the plasma. This ensures that factory management can promptly take or plan corrective actions for the process chamber 240 and the RF plasma processing system 200.

[0055] Figure 2Also shown are a set of sensors 290, which are arranged on the outer surface of the base 295 of the showerhead 230, outside the vacuum region within the reaction chamber 240 under atmospheric conditions. In some embodiments, additional sensors 296 can be mounted on the base 297 of the pedestal and connected to the signal processing compartment 275 of the disclosed impedance matching network 220 via high-speed signal cables, similar to the sensors 290. The location of the sensors 296 outside the vacuum environment of the reaction chamber 240 significantly reduces cost and makes integration into information and processing networks easier because no vacuum feed is required.

[0056] In some configurations, sensors 255 can be deployed to sense voltage and / or current on the surface of pedestal 235 and can be covered and protected from the plasma by dielectric cover 260. Sensors of this type and location are close to the wafer and / or substrate and therefore may have a sensitivity advantage in detecting certain EM surface wave modes that indicate plasma asymmetry—an important type of plasma non-uniformity. These in-chamber sensors 255 can use communication lines that pass through the vacuum wall via feedthroughs or, in some embodiments, wireless communication links that operate optically or at lower frequencies.

[0057] In general, the phase and amplitude patterns of each frequency of EM surface waves on the surfaces of showerhead 230 and pedestal 235 can be determined by analyzing the signals from any set of voltage, current, phase, or combination sensors 255, 280, 290, and 296. In general, EM surface waves at a given frequency produce voltage and current signals that have a phase relationship with signals at other frequencies. The magnitude of the voltage at each frequency and each point is the sum of the voltages of all waves of that frequency from all points on the electrode surface. For an axisymmetric electrode surface, where power is fed symmetrically and the plasma is axisymmetric, an axisymmetric surface wave pattern will result from the superposition of waves from all portions of the electrode and other surfaces in reaction chamber 240. In general, a perfectly symmetrical plasma in a symmetrical chamber with symmetrical electrodes centered about the chamber's axis of symmetry will primarily have a circular symmetry line of equal phase and amplitude centered about the center of pedestal 235.

[0058] Steering Figure 3, shows a cross-sectional view of a dual-plate electrode assembly according to an embodiment of the present disclosure having a wide bandwidth sensor that provides a voltage signal through an electrical connector having a low shunt capacitance to the surrounding area of ​​the electrode and to electrical ground. In some embodiments, an electrode such as a showerhead 330 may include two conductive plates 331, 332 that are configured to be approximately parallel, center-aligned, and have approximately the same shape as a substrate or wafer. The surface of the first plate 331 remote from the second plate 332 may be exposed to a vacuum environment and a plasma. The first plate 331 is separated from the second plate 332 by a distance that is the length of a dielectric support 333. The first plate 331 may have an embedded sensor 334 whose puck or pickup is a conductive material and whose surface is approximately coplanar with the surface of the first plate 331 remote from the second plate 332.

[0059] In some embodiments, sensors 334 can be mounted in first plate 331, surrounded by a dielectric 336 having a low dielectric constant, such as quartz or some other suitable material. In some embodiments, the dielectric constant of dielectric 336 can be less than 5, and in some embodiments, for inorganic materials such as quartz-based aerogels, the dielectric constant can be less than 2. Sensors 334 can have a high bandwidth extending from 100 kHz to at least 10 times the highest drive frequency connected to the chamber, which can be up to or above 300 MHz, and can be capable of sensing surface voltage, surface current, or both. The sensitivity of sensors 334 can, in some embodiments, vary by less than 30% within the harmonic frequency range of the primary fundamental RF frequency used in the reaction chamber. In some embodiments, at least one lead 337 from each sensor is connected to an inner conductor 338 of a vacuum electrical signal feedthrough 339, the base 341 of which is mounted in the electrically grounded second plate 215. In some embodiments, the leads from each sensor can be connected directly to a circuit board located in a similar location as 332, with a ground plane and detector circuits, one for each sensor, to determine the amplitude and phase of each frequency component.

[0060] The inner conductor 338 of the feedthrough 339 can have a small shunt capacitance to the base 341 of the feedthrough 339 mounted in the grounded second plate 332 - for example, less than 5 picofarads (pf), and in some embodiments less than 2 pf, so that the total shunt capacitance from the sensor 334 plus the leads 337 plus the feedthrough 339 to ground should be less than 5 pf and in some embodiments less than 3 pf. In some embodiments, the output from the base 341 mounted to the grounded second plate 332 can be connected to an attenuator (not shown). In some embodiments, the attenuator can include a resistor having a resistance greater than about 100 ohms. There can be a shunt resistor to ground 405 in parallel with the resistor 404. The resistance of the shunt resistor can be, for example, 50 ohms, or alternatively can be equal to the impedance of the cable connecting the attenuator to a communications network or a controller of the plasma chamber. The attenuator is located at the detector rather than the connector as shown. Figure 3 In this case, the signal output from the detector, as the amplitude and phase of the voltage or current at each frequency of the sensor, can be transmitted to an analysis processor that can be in the compartment of the matching network.

[0061] Each sensor 334 can measure the voltage or current amplitude of a combined electromagnetic surface wave mode having as components the fundamental and harmonic frequencies of all RF generators providing power to the plasma. The fundamental and harmonic frequencies range from about 10 kHz up to about 500 MHz or more. In other embodiments, the sensors can measure voltage at fundamental and harmonic frequencies ranging from about 100 kHz to about 1 GHz.

[0062] Figure 4 A cross-sectional view of a base with an embedded broadband voltage sensor according to an embodiment of the present disclosure is shown. Voltage sensor 401 can be mounted into an electrode, such as base 400. In some embodiments, sensor 401 can be connected to electrical ground 406 via a resistor. The tip or positioner of sensor 401 can have a lead 402 surrounded by a dielectric 403 (which can optionally be air or vacuum). In some embodiments, lead 402 from sensor 401 can pass through an attenuator, such as (one or more) resistors 404 and a shunt resistor 405, which in some embodiments can be approximately 50 ohms and can also be connected to electrical ground 406. Such resistor 404 can be non-inductive and can have a resistance in the range of between approximately 100 ohms and approximately 100,000 ohms. In some embodiments, the resistance can be between approximately 500 ohms and approximately 10,000 ohms. Resistor 405 can also be non-inductive.

[0063] In addition, dielectric 403 should be generally non-magnetic and have a low loss tangent, less than about 0.01 in some embodiments or less than about 0.001 in other embodiments. The shunt capacitance between the tip of sensor 401 and lead 402 to the ground electrode should be less than about 5 pf, or in some embodiments less than about 2 pf, so that the reactance between sensor 401 and the base 400 electrode should be greater than about 100 ohms at 300 MHz. The purpose of such a low shunt capacitance is to reduce the loading of the surface wave by sensor 401, so that it absorbs the wave energy to a minimum and allows the wave to propagate as it would without sensor 401. Under such conditions, the detected surface potential will not be significantly different from the surface potential on the electrode without such sensor 401.

[0064] Steering Figure 5 , shows a schematic side view of a pedestal with associated RF and control components according to an embodiment of the present disclosure. The pedestal 501 power feed circuit includes an RF power generator 405 and an impedance matching network 506. High-speed signal lines, such as cables 511, 512, carry signals from sensors 502, 503 to compartments, which in some embodiments may be in or attached to the impedance matching network 506. High-speed lines 513 of a data network carry information from the impedance matching network 506 to (one or more) controllers 514 of a reaction chamber, or generator, or tool or factory (not shown). Sensors 502, 503 are mounted on or near the base 504 of the pedestal 501. The sensors may be inside or outside the vacuum region of the reaction chamber.

[0065] In some embodiments, there may be a signal analysis, such as a fault detection compartment 510, associated with the impedance matching network 506. The signal analysis compartment 510 may be electrically and / or RF-isolated from certain components of the impedance matching network 506, such as vacuum capacitors and high-voltage electronics. The signal analysis compartment 510 receives signals from the sensors 502, 503 via cables 511, 12. The signal analysis compartment 510 then passes the signal from each sensor 502, 503 to internal circuitry, which may be referred to as a detector and may include electronic components such as transistors and passive components. In alternative embodiments where the amplitude and phase of each frequency component are found directly near the sensor, the signal entering the signal analysis compartment may be the amplitude and phase of each frequency component, rather than the original signal.

[0066] Each detector (not shown) in compartment 510 can perform RF spectrum analysis on the signal from one sensor 502, 503 or from a group of sensors that can be analyzed in parallel. This analysis can include averaging the signals from a group of sensors or one or more sensors 502, 503 over a period of time to reduce noise. In some embodiments, for each frequency component of the signal obtained by each sensor 502, 503, such as the fundamental and harmonics, there can be an amplitude and phase output from each detector. The output from each detector for each harmonic signal can then be input to an analog-to-digital converter to produce digitized values ​​of both the amplitude and phase of each measured harmonic.

[0067] These digital amplitude and phase values ​​for each frequency component and each sensor can be input into a high-speed digital processor in a signal analysis compartment associated with the disclosed impedance matching network with virtually no latency, for example, <10 microseconds. The digital processor can analyze both the amplitude and phase information of the fundamental wave and each harmonic from the sensor, and determine the relative magnitudes of different surface wave modes, including axisymmetric and non-axisymmetric modes, for both the fundamental and harmonics. Different non-axisymmetric modes may exist for each frequency component, one or more of which may be an indicator of plasma inhomogeneity.

[0068] In some embodiments, such non-axisymmetric modes can be quickly identified by an algorithm resident on the plug-in. A reference database correlating the magnitude of non-axisymmetric modes to the percentage of plasma non-uniformity can also reside on the plug-in or a removable processor. The digital processor can also calculate the rate of change of the wave mode amplitude and the acceleration of one or more wave mode amplitudes to determine the likelihood of a failure in the near future. One measure of the magnitude of a non-axisymmetric mode at a given frequency can be the difference between the phases of the surface waves of the given frequency at different sensor locations that are the same radial distance from the center of the circular electrode and are symmetrically located in the axisymmetric chamber. Alternatively, a second indicator of a non-axisymmetric mode can be the difference between the amplitudes of the surface waves of the given frequency at different sensor locations that are the same radial distance from the center of the circular electrode and are symmetrically located in the axisymmetric chamber.

[0069] Matching network 506, with an isolated compartment 510 containing a multi-channel detector system (not shown), can simultaneously Fourier analyze, digitize, and record the voltage amplitude and phase of the propagating EM wave at various locations on pedestal 501. Due to inherent noise, each determined voltage amplitude and phase can be averaged over a brief time interval as needed, and can be averaged across a group of sensors 502, 503 to determine relative magnitude or time averages over a relatively large number of pulses.

[0070] A showerhead, pedestal, or other powered element such as an electrode equipped with a sensor array or array can be used as a test system to generate data to characterize and document the relationship between the spectrum and spatial pattern of EM wave modes and various non-uniformities in plasma density during RF processing. In some embodiments, this data can be analyzed offline by engineers to characterize and categorize plasma behavior and placed into a database that can be stored in a plug-in storage device that can be connected to a matching network compartment or other controller or monitoring system.

[0071] The relationship between the amplitude and phase pattern characteristics of the non-axisymmetric EM mode and the axisymmetric EM mode and process and plasma non-uniformities or deviations from proper conditions can be stored in a plug-in of the disclosed signal analysis compartment connected to the matching network. In embodiments where the RF plasma processing system may be used as a production tool, plasma non-uniformities and process can thereby be quickly detected while monitoring the operation of the chamber. For example, Figure 2 The configuration shown in Figure 4 A sensor of the type disclosed in the disclosure may be added to a Figure 1 The RF plasma system shown in FIG.

[0072] To determine whether a process plasma may have experienced a plasma fault condition, an analysis processor in a signal analysis compartment associated with an impedance matching network can calculate parameters based in part on the magnitude of a non-axisymmetric EM mode at each of a pre-specified set of harmonics of a drive frequency on some electrodes or antennas. In some embodiments, the processor can then compare these parameters to reference ranges in a database. Such a reference database can reside on a card connected to the signal analysis compartment, which can be a compartment located in or associated with the impedance matching network.

[0073] The database can store parameters that characterize various plasma conditions to help determine whether a situation in which the plasma deviates from an acceptable "processing window" has occurred and how severe the situation is. In some embodiments, the analysis can include comparing the phase of each harmonic from each sensor or group thereof at a given distance from the center of the electrode. The difference in such phase for a sensor or a group of sensors about any azimuth angle can be a measure of the asymmetry of the generation and / or propagation of the harmonic mode, and therefore a measure of plasma asymmetry and non-uniformity. In some embodiments, the analysis can include calculating the difference in amplitude for a sensor or a group of sensors at a given distance from the axis of symmetry. The variation in such amplitude for a sensor or a group of adjacent sensors over a range of azimuth angles can also be a measure of the asymmetry of the generation and / or propagation of the harmonic mode, and therefore a measure of plasma asymmetry and non-uniformity.

[0074] A quantitative measure of the asymmetry of each harmonic in a set of harmonics, i.e., a parameter, can be stored in the plug-in unit and transmitted to the chamber and tool controllers via a data network. Furthermore, trends and accelerations of the parameters can be calculated and compared to reference values ​​and standards in a database as part of a process to determine whether a fault condition has occurred. In some embodiments, when such a fault condition occurs, algorithms and standards, which may be stored on the plug-in, can be executed in a processor residing in the compartment to determine a course of remedial or preventative action. This action can then be rapidly transmitted to the RF generator and / or chamber and / or tool controllers.

[0075] In some embodiments, all of these databases of parameters, algorithms, standards, and specifications for comparing parameters, parameter rates of change, and parameter accelerations can reside on a data storage device or a removable processor that can be connected to a port that can be an input / output port of the signal analysis compartment. The analysis of the surface wave patterns of the signals from the sensors and the parameters derived therefrom is performed rapidly by the processor such that any fault declaration and remedial action commands can be transmitted to the RF generator via the network and reported to the room or system controller within five milliseconds or less of occurrence. In some embodiments, a fault condition and specified remedial action command can be transmitted to the generator within one millisecond.

[0076] In some embodiments, many types of plasma deviations from desired plasma uniformity can be detected quickly enough so that the tool or chamber controller can take action to correct the plasma fault condition before wafers or substrates are improperly processed. In some cases, the prescribed remedial action may be to temporarily change the RF power format, such as continuous wave (CW) or pulsed, or to completely shut down the power for a short period of time, or to stop processing the current wafer and save the wafer for later processing or discard the wafer, or to shut down the reaction chamber for maintenance. Thus, adjusting the frequency within a range of approximately plus or minus a percentage of the RF power can thereby modify the reflected power.

[0077] In certain embodiments, upon detection of a plasma fault condition, a disclosed signal analysis compartment associated with the matching network can command appropriate corrective action to be performed by the RF generator and / or, in some embodiments, by the matching network. For example, the RF processing generator can initiate termination of processing in response to a signal measured by a sensor on the showerhead and / or pedestal to end processing of the wafer. In specific embodiments, the frequency can be adjusted, i.e., increased or decreased, within a range of approximately one to ten percent. Alternatively, power can be interrupted by the RF plasma processing deposition system, e.g., by establishing pulsed power, to stop or pulse the plasma, thereby stopping or significantly reducing the secondary plasma. In some cases, after a very brief interruption, a specified remedial action may be provided and processing can then continue. In certain embodiments, the remedial action can be determined based on yield data or other wafer diagnostics, e.g., by machine learning and / or a programmed remedial program.

[0078] Steering Figure 6 , shows a top view of an axisymmetric surface wave propagating across a susceptor according to an embodiment of the present disclosure, wherein the plasma in the reaction chamber is axisymmetric. Figure 6 In the figure, circle 601 is a graph of constant phase and amplitude for the fundamental and harmonic frequency components of an axisymmetric surface wave mode. The circle is concentric with the electrode. These modes are highly dominant when the electrode and plasma are both axisymmetric and coaxial in the chamber. The propagation vector 602 of a surface wave at any frequency will be radial. The waves will propagate toward and away from the center, and as they propagate, they will inject power into the plasma.

[0079] Steering Figure 7 , showing a top view of transverse electromagnetic surface wave propagation across electrodes according to an embodiment of the present disclosure. Figure 7In Figure 1, the lines of constant phase and equal amplitude 701-704 of a particular single non-axisymmetric mode are approximately straight and parallel, both at the fundamental frequency and its harmonics. Such surface waves can be detected by sensors deployed on the pedestal or showerhead of an RF plasma deposition system. This mode can be referred to as "transverse," meaning that the propagation direction, as seen by propagation vectors 705-707, spans the electrode surface from side to side or from the central plane to the left and right sides. Other non-axisymmetric modes may exist, where the lines of constant phase may be curved, with the center of curvature displaced from the electrode center. The detector reading at each frequency can be decomposed into the sum of the axisymmetric mode and (usually a small number of) non-axisymmetric modes, which reflect the primary inhomogeneities of the plasma. Typically, this decomposition allows the identification of transverse mode components and / or a primary "off-center" or displaced radial mode, either of which is characteristic of the plasma inhomogeneity profile. The association of the plasma inhomogeneity profile with the specific non-axisymmetric mode is performed prior to production processing as part of building a database, which can reside on the plug-in unit or elsewhere.

[0080] Steering Figure 8 , shows a top view of an exemplary azimuth sensor deployment for a reaction chamber according to an embodiment of the present disclosure. In this embodiment, a plurality of sensors 800 can be deployed azimuthally around one or more components of the reaction chamber and / or on the reaction chamber itself. As briefly discussed above, a plurality of sensors 800, which in this embodiment can be four, can be positioned at various angles about the chamber axis of symmetry 805 on certain chamber components, such as the showerhead and / or susceptor, to measure surface voltages or currents associated with surface waves. In this case, they are spaced 90 degrees apart, but in some embodiments, they can be spaced azimuthally at regular intervals.

[0081] Sensors 800 may include passive sensors 800 that pick up changing electric potentials or magnetic fields. Sensors 800 may be deployed at different azimuth angles relative to the chamber axis of symmetry 805 to detect EM waves having different propagation modes. Sensors 800 may be deployed at equidistant locations around the chamber axis of symmetry 805 and / or components within the reaction chamber or the reaction chamber itself. Similarly, sensors 800 may be deployed diametrically opposite one another so that the spacing between sensors 800 and the axis of symmetry may be approximately the same. For example, the distance between sensors 800-1 and 800-2 is approximately the same as the distance between sensors 800-3 and 800-4. Similarly, each sensor 800 is located at the same distance from the chamber axis of symmetry 805. Examples of spacing and positioning of sensors 800 are discussed in more detail below.

[0082] As shown, sensors 800 are deployed at diametrically opposed locations. For example, sensor 800-1 is diametrically opposed to sensor 800-3, while sensor 800-2 is diametrically opposed to sensor 800-4. Thus, sensor 800 can detect waveform differences on different sides of a reaction chamber and / or its components for non-axisymmetric plasmas and, when waveform differences occur, provide notification, as explained above, so that remedial or proactive action can be taken. For example, if sensor 800-1 and sensor 800-4 sense and report differences in waveform from their diametrically opposed locations, such differences can provide an indication that the harmonics are out of phase or have different amplitudes, which may therefore indicate the presence of plasma non-uniformity and asymmetry. Such differences in waveform occur when there is a difference in the relative phase or amplitude of one or more harmonics in the signal picked up by the opposing sensors between the diametrically opposed detectors.

[0083] In some embodiments, four sensors 800 may be used, such as Figure 8 , as shown in . However, in other embodiments, a different number of sensors 800 may be used, such as six, eight, twelve, fourteen, sixteen, eighteen, twenty, or more sensors 800. In some embodiments, the azimuthal angles between the sensors may not be equal; nonetheless, the same characteristics of non-azimuthally symmetric plasma modes can be observed by the sensors. In certain embodiments, having six to twelve sensors 800 may be beneficial. A greater number of sensors 800 allows for more data to be collected, providing enhanced noise discrimination and sensitivity in identifying non-uniformities. However, increasing the number of sensors 800 may slow data processing, resulting in slower remedial and preventative actions. Those skilled in the art will appreciate that balancing the number of sensors 800 with the desired level of data granularity can allow for optimization of RF plasma processing. Therefore, as computing power increases and the speed at which data can be processed increases, increasing the number of sensors 800 may be beneficial. In certain embodiments, specific sensors 800 can be selectively turned off and on to allow the controller to access certain desired data. For example, in a system with eight sensors, four of the sensors can be selected and turned off, thereby reducing the amount of data generated. In other embodiments, additional sensors can be added or removed from operation, thereby changing the amount of data generated.

[0084] Sensor 800 may also include various types of sensors, including circular and other geometric shapes. In certain embodiments, sensor 800 may be circular with an area between approximately 0.1 square centimeters and approximately 10 square centimeters. Sensor 800 may further include a surface insulator layer or coating to protect sensor 800 from the plasma or reactants in the reaction chamber, and may also include other optional coatings and layers, such as a Faraday shield for the current sensor, an aluminum coating, and the like.

[0085] Steering Figure 9 , shows a side cross-sectional view of an azimuthally mounted sensor on a reaction chamber according to an embodiment of the present disclosure. In this embodiment, the reaction chamber 940 has an axis of symmetry 905 that extends longitudinally from the center of the showerhead 930 through the base 935. In other embodiments, the axis of symmetry 05 can extend longitudinally from the center of another electrode such as an antenna. Multiple sensors 900 can be deployed in azimuth at various locations around and within the reaction chamber 940 and around or associated with specific components such as the showerhead 930 and / or the base 935. Due to Figure 9 is a cross-section showing only two sensors 900 at each location, however, more sensors 900 may be used during implementation of the RF plasma monitoring process, as described with respect to FIG. Figure 8 Discussed in detail.

[0086] In certain embodiments, the sensor 900-1 may be deployed around the edge or periphery of the showerhead 930. In such an embodiment, the sensor 900-1 may be at least partially or completely embedded within the showerhead 900-1, and the outer surface of the sensor 900-1 may be coated with an insulating layer to protect the sensor 900-1 from the environment within the reaction chamber 940. In such an embodiment, two or more sensors 900-1 may be deployed azimuthally around the edge of the showerhead 930, and preferably four or more sensors, to allow for detection of non-uniformities and asymmetries in RF plasma processing.

[0087] In other embodiments, sensor 900-2 can be deployed along the edge of base 935 within the vacuum of reaction chamber 940. As explained above with respect to sensor 900-1, sensor 900-2 can be partially or completely embedded in base 935 and may or may not include an insulating layer deployed on its outer surface. In addition, in some embodiments, there can be a dielectric protection portion covering them. In addition to sensor 900-2 deployed around base 935 inside the vacuum, other sensors 900-3 and 900-4 can be deployed outside the vacuum of reaction chamber 940 and around base 935. Such sensors 900-3 and 900-4 can be deployed along base 935 and / or its base portion on a metal surface. Sensor 900 can also be deployed on other supporting structures of base 935 or associated with base 935.

[0088] In other embodiments, sensor 900-5 can be deployed and / or otherwise built into the sidewalls of reaction chamber 940. In such embodiments, where the walls are dielectric, sensor 900-5 can be deployed outside reaction chamber 940 on outer chamber wall 915, or can be built into the sidewall so that sensor 900-5 is within the vacuum of reaction chamber 940. For metallic walls, the sensors should have their pickups exposed to the inner surface of the wall so that they can sense the EM field on the interior of the chamber. Other sensors 900-6 can be deployed in viewing ports 920 that are located along outer chamber wall 915. In such embodiments, sensor 900-6 in the viewing port can be located outside the vacuum of reaction chamber 940 or within reaction chamber 940.

[0089] In yet other embodiments, sensor 900-7 can be disposed in a dielectric located, for example, around showerhead 930, while in other embodiments, sensor 900-7 can be disposed in a dielectric located around base 935. While specific locations for sensor 900 are discussed herein, sensor 900 can be located at various other locations in and around reaction chamber 940. For example, sensor 900 can be disposed inside or outside a dielectric wall near an antenna or other component. Sensor 900 can further be located at various other locations within the metal wall of reaction chamber 940.

[0090] In certain embodiments, to more accurately monitor the RF plasma process, a combination of sensors 900-1 through 900-7 may be used. For example, sensor 900-1 located around the edge of showerhead 930 may be combined with sensor 900-2 located around the edge of pedestal 935. Similarly, a combination of sensors 900-5 located outside of reaction chamber 940 may be combined with sensors 900-1 and 900-2 located within reaction chamber 940. In still other embodiments, combinations of three, four, five, six, seven, or more variations of sensor 900 locations may be used to further optimize monitoring of the RF plasma process.

[0091] Steering Figure 10 , shows a side cross-sectional view of a model reactor chamber according to an embodiment of the present disclosure. In this embodiment, exemplary locations of a plurality of azimuthally deployed sensors 1000 are shown around a bottom electrode, which in this example is a base 1035. Figure 9 The sensor 1000 discussed is similar, Figure 10 Sensors 1000 are shown deployed in various positions. Sensor 1000-1 is deployed around the outer edge of base 1035. Sensor azimuth position indicated as 1000-2 is deployed around the interior of reaction chamber 1040, while sensor azimuth position 1000-3 is deployed around the periphery of reaction chamber 1040 adjacent to the viewing port.

[0092] In this embodiment, twelve sensors 1000 are shown at each location, however, in other embodiments, other numbers of sensors 1000, including fewer and greater numbers, may be used. Additionally, in addition to the sensor 1000 locations specifically shown, other sensor 1000 locations may be used to further enhance RF plasma processing.

[0093] Steering Figure 11 , shows a side schematic cross-sectional view of a reaction chamber according to an embodiment of the present disclosure. In this embodiment, the sensor 1100 is shown disposed around the antenna of the inductively coupled plasma source 1105. Thus, the sensor 1100 can sense the RF current or voltage from the plasma source located within the reaction chamber 1140.

[0094] Steering Figure 12 , shows a partial cross-sectional view of an RF plasma processing system according to an embodiment of the present disclosure. In this embodiment, the RF plasma processing system 1200 includes a pedestal 1235. The pedestal 1235 includes a sensor 1240 disposed along an upper outer edge of the pedestal 1235. As described above, the sensor 1240 can be disposed on the upper outer edge, embedded within the pedestal 1235, or alternatively can be disposed around the outer edge of the reaction chamber, either inside or outside the vacuum.

[0095] The RF plasma processing system 1200 also includes circuitry 1245 connected to the sensor 1240 via a communication line 1250. When the sensor 1240 receives sensed data from the RF plasma processing system 1200, the data can be sent to the circuitry 1245 for processing. Because the circuitry 1245 is relatively close to the sensor 1240, the time spent transferring sensed data between the two can be reduced. As a result, the initial calculation of the electrical property sensed by the sensor 1240 can be performed more quickly and then transferred to other components 1255 of the RF plasma processing system 1200. The other components 1255 can include, for example, an RF generator, an impedance matching network, a fault detection compartment, operating controls for a reaction chamber, operating controls for a tool, a plug-in device, a signal analysis compartment, or one or more other components connected to the RF plasma processing system 1200.

[0096] Then, 1200, 1255, or other components not shown can adjust various aspects of the RF plasma processing system 1200 to correct the fault detected by the sensor 1240 and handled at least in part within the circuit system 1245. The circuit system 1245 can be located within the pedestal 1235 outside the vacuum of the reaction chamber in an isolated configuration to protect the circuit system 1245 from conditions within the reaction chamber. In other embodiments, the circuit system 1245 can be located in the base of the pedestal 1235 or in other areas proximate to the pedestal 1235.

[0097] along with Figure 12 While a cross-sectional view of components of the RF plasma processing system 1200 is shown, one skilled in the art will appreciate that the circuitry 1245 can be deployed at approximately the same radius at different azimuth angles around the pedestal 1235. Thus, a separate circuitry 1245 can be used for each sensor 1240, or the sensors 1240 can be connected to a centralized circuitry 1245 located in one or more selected locations around and / or within the pedestal 1235.

[0098] Steering Figure 13 , shows a partial cross-sectional view of an inductively coupled RF plasma processing system according to an embodiment of the present disclosure. The sensor 1340 is shown configured to be in proximity to the sensing antenna 1330 and can be mounted externally or internally to a dielectric wall (not shown) adjacent to the antenna.

[0099] Steering Figure 14 and Figure 15, respectively, show a side schematic view and a top schematic view of an RF plasma processing system according to an embodiment of the present disclosure. In this embodiment, the RF plasma processing system 1400 includes an electrode 1405 on which a wafer 1403 can be placed during processing. A plurality of plates 1410 can be disposed around the electrode 1405. In certain embodiments, the plates 1410 can be disposed outside of a dielectric ring. The plates 1410 can be formed of metal and each include a conductive layer. The plates 1410 can be placed on or embedded in a dielectric material 1409, such as a ceramic. The plates 1410 can be disposed within a reaction chamber (not shown) at an azimuth angle relative to the susceptor / electrode symmetry axis A. As shown, the plates 1410 can be positioned around the perimeter of the susceptor 1410 at a gap 1407 from the electrode 1405. The gap can be, for example, approximately 10 mm. The plates 1410 can be connected to an electrical ground 1415 via a variable impedance circuit 1420. The variable impedance circuit 1420 may include one or more capacitors 1425 , such as variable capacitors, and / or inductors 1430 .

[0100] An automatic controller (not shown) can be connected to the variable impedance circuit 1420 to vary the variable impedance of at least one plate 1410, thereby providing a specified shunt impedance between each plate 1410 and the electrical ground 1415. Each plate 1410 can cover an angular range of between approximately 10 degrees and approximately 120 degrees around the electrode 1405. In some embodiments, the angular range is individual for each plate 1410, while in other aspects, the angular range can vary between each individual plate 1410. In some embodiments, a dielectric material 1409 is disposed in a gap between one or more plates 1410 and the electrode 1405 and / or the electrode surface.

[0101] In certain embodiments, the inner radius of the plate 1410 can be larger than the outermost radius of the wafer or substrate mounted on the electrode 1405, but can be smaller than the outer radius of the electrode 1405. In still other embodiments, at least a portion of each of the one or more plates 1410 can be disposed at a radius that is larger than the outer radius of the electrode 1405. In such embodiments, the plates 1410 can bend to conform to the shape or circumference of the electrode 1405 to form a constant gap from the outer edge of the electrode 1405.

[0102] Steering Figure 16, which shows a side schematic diagram of an RF plasma processing system according to embodiments of the present disclosure, in certain aspects, at least a portion of each plate 1510 can be disposed in a plane parallel to the plasma-facing plane of the surface of electrode 1505. Plate 1510 can include a capacitance per unit area to electrode 1505 of between about 0.1 pF and about 100 pF. The maximum capacitance of capacitor 1525 can be less than the capacitance from the surface of electrode 1505 to the plate 1510 to which capacitor 1525 is connected.

[0103] In this embodiment, the RF processing system 1500 includes an electrode 1505 around which or on top of which one or more plates 1510 may be disposed. The plates may be placed on or embedded in a dielectric material 1509. In this regard, a variable resistance circuit 1520 having a capacitor 1525 and / or an inductor 1530 may be connected to ground, as described above with respect to Figure 14 and Figure 15 As described. Accordingly, Figure 16 The RF processing system 1500 can be used with Figure 14 and Figure 15 The RF processing system 1400 operates in the same manner.

[0104] The foregoing description, for the purpose of explanation, uses specific terms to provide a thorough understanding of the present disclosure. However, it will be clear to those skilled in the art that the specific details of the systems and methods described herein are not required to practice. The above descriptions of specific examples are for illustration and description purposes. They are not intended to be exhaustive or to limit the present disclosure to the precise form described. Obviously, many modifications and variations are possible in light of the above teachings. These examples are shown and described in order to best explain the principles and practical applications of the present disclosure, thereby enabling others skilled in the art to best utilize the present disclosure and the various examples and to make various modifications thereto to suit the specific purposes contemplated. The scope of the present disclosure is defined by the appended claims and their equivalents.

Claims

1. A radio frequency plasma processing system comprising: a reaction chamber receiving radio frequency power for exciting the plasma; an electrode, supplying power to the plasma and disposed in the reaction chamber; a plurality of sensors disposed within the reaction chamber and positioned adjacent to and spaced about a perimeter of the electrode, each sensor connected to a respective variable impedance circuit and configured to detect a parameter within the plasma; as well as An impedance matching network is adapted to vary each variable impedance circuit based on analysis of sensor signals received from the plurality of sensors to provide a specified shunt impedance between each sensor and electrical ground.

2. The system according to claim 1, wherein: Each sensor covers an angular range between 10 and 120 degrees.

3. The system according to claim 1, wherein: Each sensor includes a plate and a dielectric material disposed in a gap between the sensor and the surface of the electrode.

4. The system according to claim 2, wherein: The angular range is equal for each plate.

5. The system according to claim 3, wherein: The gap is less than 10 mm.

6. The system according to claim 1, wherein: At least a portion of each sensor is bent to conform to the shape of the peripheral edge of the electrode to form a constant gap with the peripheral edge of the electrode.

7. The system according to claim 1, wherein: Each variable impedance circuit includes a variable capacitor connected in series with a fixed inductor.

8. The system according to claim 1, wherein: Each variable impedance circuit includes a variable capacitor.

9. The system according to claim 1, wherein: A dielectric member covers at least one of the plurality of sensors.

10. The system according to claim 1, wherein: At least a portion of each sensor is disposed parallel to the plasma-facing surface of the electrode.

11. The system according to claim 7, wherein: At least one sensor has a capacitance per unit area of ​​the electrode between 0.1 picofarads and 100 picofarads.

12. The system according to claim 7, wherein: The maximum capacitance of the variable capacitor is smaller than the capacitance from the surface of the electrode to the sensor to which the variable capacitor is connected.

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