Plasma non-uniformity detection

Abstract

A method of detecting non-uniformity of a plasma in a radio frequency plasma processing system, the method comprising: generating a plasma within a reaction chamber of the radio frequency plasma processing system; and detecting electrical signals from the plasma in a frequency range from a frequency of radio frequency power sustaining the plasma to a multiple of about ten times the frequency with a plurality of sensors disposed at azimuthal angles with respect to a chamber symmetry axis of the radio frequency plasma processing system. The method further comprises comparing waveforms of the electrical signals picked up from the plasma by the plurality of sensors; and determining when plasma non-uniformity occurs based on comparing electrical properties of the plasma detected by each of the plurality of sensors.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to U.S. Provisional Application No. 62 / 959,644, filed January 10, 2020, and U.S. Non-Provisional Patent Application No. 17 / 145,202, filed January 8, 2021, the contents of which are incorporated herein by reference. Background Technology

[0003] Radio frequency (RF) plasma-enhanced processing is widely used in semiconductor manufacturing for etching different types of films, depositing thin films at low to medium processing temperatures, and performing surface treatments and cleaning. This process utilizes plasma, a partially ionized gas, to generate neutral species and ions from precursors within the reaction chamber, providing energy for ion bombardment and / or performing other actions. Controlling plasma density during this process is challenging, and plasma inhomogeneity within the reaction chamber affects wafer processing uniformity and the yield of integrated circuits or other devices being fabricated.

[0004] Non-uniform plasma density within the reaction chamber can lead to uneven etch rates or inhomogeneities across the substrate. In some systems, the uniformity of plasma density within the reaction chamber is monitored using probes. These probes can rely on the coating being exposed to the plasma environment and can use active electronics to infer the plasma density. Such systems 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 the use of complex analyses to infer non-uniformity. Neither of these techniques is sensitive or fast enough to effectively address non-uniformity issues, and they can be more expensive to implement. Attached Figure Description

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

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

[0007] Figure 2 This 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 electrodes.

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

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

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

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

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

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

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

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

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

[0017] Figure 12 This is a schematic side 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 This is a schematic partial cross-sectional view of a dielectric wall of an RF plasma processing system according to an embodiment of the present disclosure, wherein a sensor is mounted on the dielectric surface near an inductively coupled antenna. Detailed Implementation

[0019] Illustrative examples of the subjects required below will now be disclosed. For clarity, not all features of an actual implementation are described in this specification. It is understood that in the development of any such actual implementation, many implementation-specific decisions can be made to achieve the developer's specific objectives, such as complying with system-related and business-related constraints, which will vary from implementation to implementation. Furthermore, it is understood that such development work, even if complex and time-consuming, is routine work for those skilled in the art who have the benefit of this disclosure.

[0020] Furthermore, as used herein, the article “a” is intended to have its common meaning in the patent field, namely “one or more”. Here, the term “about” 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 otherwise expressly specified. Furthermore, the term “substantially” as used herein, for example, means a quantity ranging from approximately 51% to approximately 100%, such as most, almost all, or all, or approximately 51%. Moreover, the examples here are for illustrative purposes only and are presented for discussion purposes rather than in a limiting manner.

[0021] Turn Figure 1 This diagram illustrates a 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 device, and a base 135. The plasma power supply device may be, for example, a spray head 130 or an equivalent power supply element such as an electrode. As used herein, a plasma power supply device may refer to any device that introduces power to generate plasma and may include, for example, a spray head 130 and / or other types of electrodes and antennas, etc.

[0022] The RF plasma processing system 100 may include one or more RF generators 105, 110 that supply power to a reaction chamber 140 via 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 a spray head 130 or sidewall, to electrodes outside the spray head 130, or to an inductive antenna (not shown) that electromagnetically supplies power to the plasma. Thereafter, the power flows from the plasma to ground and / or to a base 135 and / or to a second impedance matching network 120. Generally, the first impedance matching network 115 compensates for variations in the load impedance within the reaction chamber 140 by adjusting reactive components within the first impedance matching network 115, such as variable capacitors, so that the combined impedance of the spray head 130 and the first impedance matching network 115 is equal to the output impedance of the first RF generator 105, for example, 50 ohms. Furthermore, the reflected power can be modified by adjusting the frequency within a range of approximately plus or minus ten percent of the RF power. The term "approximately" used here acknowledges that in practice, some imprecision relative to the range or value may occur, yet satisfactory results can still be obtained. This imprecision may be due to, for example, loss, degradation, or drift in calibration during operation. However, in these cases, the range or value expressed is a nominal target for the operating conditions at the time of use.

[0023] 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 that 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 that of the first RF generator 105. Typically, the frequencies of the first and second RF generators 105 and 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 and 110 can also have their frequencies adjusted to modify the reflected power.

[0024] Impedance matching networks 115, 120 are designed to adjust their internal reactive components to match the load impedance to the source impedance. Generally, low reflected power is considered positive; however, embodiments of this disclosure ensure that the delivered power in reaction chamber 140 and the power reflected back toward the first and second RF generators 105, 110 are maintained, and even when reflected power is relatively high, the associated impedance matching networks 115, 120 can monitor the forward and reflected power entering and leaving reaction chamber 140 and adjust adjustable reactive components, such as vacuum variable capacitors, using a motor drive system. In some embodiments, electronically controlled capacitors, such as pin diodes of electronic variable capacitors, can be used. Impedance matching networks 115, 120 may include circuitry to measure the phase and magnitude of signals to determine the levels of forward and reflected power from the intended load. Therefore, embodiments of this disclosure can be effective even when reflected power is high. If a significant amount of reflected power is present at a dominant frequency, the capacitors vary until the reflected power is minimized, for example, less than about 5 watts and / or less than about one percent, or in some embodiments, less than 1 watt, during that period. Normally, harmonic frequency signals, including reflected power at harmonic frequencies, are not measured. Furthermore, the frequency can be adjusted within approximately 10% of the RF power, which can modify the reflected power.

[0025] Despite the numerous advantages of RF plasma processing systems 100, they have historically faced the challenge of maintaining plasma density control throughout the multi-step processing. For example, a design tolerance of one percent non-uniformity relative to the nominal density range remains a challenge. As feature sizes shrink to below approximately 3 nm and layer thicknesses to less than or greater than 10 nm, achieving optimal integrated circuit (IC) yields on each wafer requires progressively tighter control over plasma and neutral material uniformity to levels of 1% or even less. Non-uniform plasma density within the reaction chamber, or an average density deviating from the desired range, can be caused by slow changes in the reaction chamber, alterations to the RF circuitry, or rapid growth (on the order of milliseconds) of parasitic or secondary plasmas, which, due to non-uniform etch rates, can lead to non-uniformity of nanoscale features across the entire processed wafer.

[0026] Because even a difference of one percent in etch rate across the entire wafer can cause yield problems in advanced technologies, and because a significant amount of time is typically spent completing wafer processing to see yield losses, it is necessary to detect non-uniform plasma density or plasma density deviations from the desired range in a timely and accurate manner within a timeframe that may be less than approximately one millisecond, in order to avoid irreversible deviations from the desired feature profile on the wafer.

[0027] Those skilled in the art will understand that electromagnetic (EM) surface waves can propagate on the surface within an RF-powered plasma in reaction chamber 140. These surface waves will have considerable energy at both the fundamental RF drive frequency and the RF harmonics. The average power and power distribution of the harmonics are sensitive functions of plasma density and inhomogeneity. Hereinafter, the harmonic profile is defined as the spectrum of the surface wave whose frequencies are integer multiples of the fundamental drive frequency of the RF plasma in reaction chamber 140. For example, if 2 MHz of RF drive power is supplied to reaction chamber 140, the injected power will generate a surface wave at that frequency, which propagates along the interface between the plasma and the inner surface of reaction chamber 140. The reflected power can be modified by adjusting the frequency by approximately adding or subtracting ten percent of the RF power. Harmonic surface waves at integer multiples of the frequency can also be generated. For example, a 2 MHz electromagnetic wave can generate surface waves of 4, 6, or 8 MHz. Both odd and even harmonics (2nd, 3rd, 4th, 5th, etc.) can occur, but in some examples, odd harmonics may predominate.

[0028] Various aspects of this disclosure can provide sensor locations on and around the reaction chamber 140 and its components, allowing for the detection and analysis of RF surface waves to locate 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 on or near the surface of the electrodes, the base of the base, the chamber wall, or the strip, and a conductive line that transmits the signal from the pickup to a connector or cable. The current sensor may include a conductive element that may include one or more loops or partial loops or linear conductors, wherein one end of the conductive element is at a reference potential, which may be local electrical ground.

[0029] Multiple sensors, such as two or more, can be positioned on a chamber component, as will be discussed in detail below. These sensors are at different angles about the chamber's axis of symmetry and are used to measure the surface voltage or current associated with this surface wave. Here, the angle measured about the axis of symmetry, taken 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.

[0030] 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 surfaces of electrodes, such as base 135 and / or spray head 130. Sensors can also be mounted on the base of electrodes inside or outside a vacuum environment. Sensors can be mounted inside the chamber on one or more metal wall surfaces of the reaction chamber 140, as well as on inner or outer wall regions containing dielectric material, or on an antenna that can be used to inductively supply 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 strips that connect the first or second impedance matching networks 115, 120 to electrodes, antennas, or other components such as base 135 and / or spray head 130 that transmit power to the plasma within the reaction chamber 140. Sensors can also be connected to electrical ground. Thus, sensors can pick up signals from different parts of the RF plasma processing system 100 as they propagate on their respective component surfaces.

[0031] At the electrode-plasma interface, for example at Figure 1 Within the sheath 125, the spectrum of RF harmonics is generated, and the waves propagate in all directions; therefore, the amplitude and phase of all wave components will vary with the 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 wall that may be adjacent to the plasma. The amplitude and phase of these 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 the harmonic surface waves propagating on the surface of the electrode base facing the impedance matching networks 115, 120, on the surface 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 allow determination of which part of the total EM wave field at each frequency is azimuthally symmetric and which part is asymmetric.

[0032] In the case of induced plasma, signals from the plasma, such as the fundamental and harmonic frequencies, can propagate back to the antenna and then to the impedance matching network feeding the antenna. The frequency and phase distributions of both the fundamental and harmonic RF waves can be monitored on microsecond scales or even faster using sensors mounted on these surfaces, and can be compared with specified ranges and phase relationships as indicators of plasma asymmetry or changes in plasma density or conductivity. Signals from such sensors can be transmitted to a detector via cable or other means, which analyzes the frequency components of the signal to generate the amplitude and phase values ​​of each frequency component at each sensor location.

[0033] In some implementations, the amplitude and phase of the detected RF harmonic components can be rapidly determined by circuitry (detectors) in a signal analysis compartment, which may be a separate metal box or chassis, or may be within, connected to, or part of an impedance matching network 115, 120. This amplitude and phase can be used to determine the plasma state, including radial distribution and asymmetry, by applying algorithms and plasma inhomogeneity calibration. The signal from the sensor can be subjected to Fourier analysis by dedicated circuitry (detectors) fast enough to perform near-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 periods might take less than 50 microseconds to process via Fourier analysis, and for a pulsed plasma where each element of the pulse occurs at 5 kHz, this allows for updates to the plasma state at a rate of 10 kHz.

[0034] The results of dedicated Fourier analyses of the fundamental and harmonic frequencies can be stored on separate storage media, which can be read and / or written 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 the asymmetry parameters of each of the fundamental and harmonic frequencies. The asymmetry parameters can be compared with values ​​previously stored on separate (or different) storage media, using algorithms (also stored on separate or different storage media) to quickly identify “plasma fault” conditions. The analysis processor can then transmit appropriate commands to the first and second RF generators 105, 110, and in some embodiments, not just two RF generators, and, when appropriate, to the impedance matching network associated with these generators, such as continuing processing under the current conditions or making necessary changes to the processing conditions. In some embodiments, three, four, or more RF generators may be used. Then, the first and second RF generators 105, 110 can continue, stop, or change the power supplied, modify the reflected power by changing the frequency by approximately 10 percent of the RF power, or respond in some other suitable manner—for example, by entering a reduced power mode or a pulse mode, or by commanding certain corrective actions, such as alarm triggering, power interruption, etc., to avoid inappropriate wafer handling in the event of a plasma failure or other unacceptable circumstances.

[0035] The sensor used to detect and characterize surface waves (electric and magnetic fields) can be located on the peripheral surface (exposed or dielectrically covered) of the base 135 outside the wafer-covered area in some embodiments. For example, if the reaction chamber 140 is to process a circular wafer with a radius of 150 mm, the sensor mounted on the base can be located at a radius greater than 150 mm from the wafer center, in some cases where the wafer center may be located below the annular peripheral dielectric used to control edge effects. The sensor can be attached to or alternatively located on the surface or periphery of the spray head 130 facing the wafer, or on the surface of the base of the base 135 or the base of the spray head 130, whether these locations are inside or outside the evacuated processing environment. The sensor 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 processed plasma.

[0036] Using sensors outside the evacuated processing environment, such as at the base of the connection base and one or more of the impedance matching networks 115, 120, the base of the base 135, and / or the strip or bus of the spray head 130, may eliminate the need to transmit signals via vacuum feedthroughs or mounting transmission cables within the evacuated volume of the reaction chamber 140. Sensors in such locations can monitor the fundamental and harmonic EM waves substantially continuously. This allows the RF plasma processing system 100 to continuously provide plasma density uniformity and determine, within a very short time, whether a fault condition has occurred or whether appropriate wafer or substrate processing should continue.

[0037] In some example embodiments, this disclosure may provide apparatus and methods for detecting plasma deviation from a desired “processing window” within an RF plasma processing system 100. The RF plasma processing system 100 may include a reaction chamber 140, which may include a spray head 130 for injecting reactive gases into the reaction chamber 140 and may also include a wafer support base 135. However, in other embodiments, the spray head 130 may not inject gas into the reaction chamber 140. In some embodiments, the spray head 130 may be mounted with its center near an approximate axis of symmetry of the reaction chamber 140 and equipped with a plurality of sensors positioned at selected azimuth angles around the axis of symmetry. Additionally or alternatively, such sensors may be positioned on a wafer-facing surface in a peripheral region of the spray head 130 to detect and measure propagating EM surface waves as the wafer is processed.

[0038] Furthermore, in some embodiments, multiple sensors may be mounted on the outer surface of the wafer support base 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 plasma or covered by a dielectric or a dielectric and metal cap. Alternatively, the sensors may be located on the periphery of the base of the base 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 base to detect surface electromagnetic waves propagating toward or away from the wafer support area of ​​the base and on the surface of the base. In some embodiments, the sensors may be mounted close to the wafer plane (e.g., less than 10 cm).

[0039] Alternatively, the sensor may be mounted on a portion of the base 135, which is made of metal or other conductive material, and located outside the evacuated area of ​​the reaction chamber 140 under atmospheric conditions. The sensor located outside the evacuated area may be mounted on a region of the base 135 whose radius relative to the axis of symmetry of the base is at least 50% of the maximum radius of the base 135, and may even exceed 75% of the maximum radius of the base 135. Such a sensor may be positioned close—in some embodiments, within a few centimeters of the vacuum seal supporting the base 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 may 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 the sensor according to embodiments of this disclosure will be discussed in detail below.

[0040] Turn Figure 2 This diagram 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. Each of the two components of the electrodes, namely, base 235 and spray head 230 or equivalent other power supply elements, can use separate RF generators 205 or 210 and impedance matching networks 215 and 220. Alternatively, the electrodes can have multiple generators and matching networks feeding them. Arrow 245 along the surface of base 235 indicates the radial direction in which RF current and power flow inward from the bottom (biased) RF generator 210, which is electrically connected to base 235 via impedance matching network 220. The resulting electric field facilitates the formation of plasma (not shown) between the electrodes and a radial outward countercurrent of current and power, indicated by arrow 250, which flows along the lower surface of spray head 235 or other power supply elements and ultimately to a selective grounding circuit in the impedance matching network 215 of spray head 230 or other power supply elements.

[0041] In some embodiments, the reaction chamber 240, having RF power from the first and second RF generators 205, 210 and impedance matching networks 215, 220, may include sensors 255 on the periphery of a base 235, the periphery of which may be covered by a dielectric 260. A communication line 265 may transmit signals from each sensor 255 to a Fourier analysis circuit (not shown), which calculates the amplitude and phase of both the fundamental and harmonic frequencies of the surface waves picked up by each sensor 255. In some embodiments, each sensor 255 may be approximately equidistant from the axis of symmetry of the base.

[0042] In some implementations, Fourier analysis circuits can calculate the magnitude and phase of the fundamental and higher harmonics of a periodic electromagnetic surface waveform. The resulting series of magnitudes is called the Fourier series, and their phases are derived from the relationship between functions in the time domain and functions in the frequency domain.

[0043] Furthermore, some embodiments of the disclosed matching network 220 may include a signal analysis compartment 275 or an appendage of the matching network 220 that is separate from and RF-isolated from the RF power processing and impedance matching circuitry systems or components of the matching network 220. The signal analysis compartment 275 may include one or more Fourier analysis circuits (detectors) for analyzing sensor signals and generating digital amplitude and phase of the RF fundamental and harmonic frequencies. The signal analysis compartment 275 may also include a high-speed digital logic or computational processor for analyzing the relative magnitude and phase of the signals at harmonic frequencies and deriving quantitative parameters characterizing the relative magnitude and relative phase of the axisymmetric and non-axisymmetric harmonic components at each frequency. Furthermore, in some embodiments, the disclosed matching network 220 may be connected via a very fast network to the controller (not shown) of the second RF generator 210 and the reaction chamber 240 or RF plasma processing system 200 where the sensor 255 is located. In some embodiments, the disclosed enhanced impedance matching network 220 may be able to send commands to the first RF generator 205 and communicate its calculated parameters to the processing chamber controller and / or tool control system.

[0044] Furthermore, another first RF generator 205 and impedance matching network 215 may also be electrically coupled to another electrode, which may be the spray head 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.

[0045] Similarly, impedance matching network 215 monitors reflected power from the electrodes and processing chamber 240, and can be adjusted if significant reflected power is present from the electrodes. In some embodiments, the second RF generator 210 may be a 400 kHz RF generator, a 2 MHz RF generator, or a 13.56 MHz RF generator or others, while the first RF generator 205 may operate at a slightly higher frequency. In some embodiments, the first RF generator 205 may operate at frequencies greater than 25 MHz, such as 60 MHz, 100 MHz, or higher.

[0046] In one embodiment, the primary function of the first RF generator 205 may be to power the reaction chamber 240 to generate plasma between the spray head 230 or another power source such as the electrodes and the base 235, to both generate reactive chemicals such as fluorine, chlorine and combinations thereof, and to accelerate and bombard the wafers deployed on the base 235 with ions from the generated plasma.

[0047] A set of sensors 280 deployed on the upper electrode surface, i.e., the spray head 230, facing the lower electrode, i.e., the base 235, can have a bandwidth approximately 10 times greater than the frequency of the highest-frequency RF generator connected to that electrode. In some embodiments, each of them can have an impedance greater than approximately 100 ohms, and in some embodiments greater than 500 ohms. The sensors 280 can be voltage or current sensors, or both capabilities can be combined in a single package—for example, where a current sensor can include one or more segments of wire that can be covered by an electrostatic shield.

[0048] In some embodiments, sensor 280 has an electrical connection to a Fourier analysis circuit in the signal analysis compartment 285 of impedance matching network 215. The Fourier analysis circuit can output the amplitude and phase of different frequency components from each sensor 280 and compare them with other sensors 280 and / or with a reference level stored in memory. In some embodiments, the analysis of the signal may include pattern recognition of amplitude or phase or both, or processing using artificial intelligence (AI) algorithms that can use neural network learning algorithms or conventional digital algorithms for the signal from sensor 280.

[0049] The signal processing, which involves the Fourier analysis circuit identifying the fundamental and harmonic components, including both amplitude and phase, can be completed in less than approximately 10 microseconds, and in a preferred embodiment, 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 high computational power and very high-speed (<1 ns cycle time) circuitry using 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.

[0050] In some embodiments, software programs for calculating parameters from signal amplitude and phase, and further logical algorithms for determining the impact of acceptable plasma condition deviations on processing uniformity, may reside on a removable “plug-in” component containing data storage and connected to the signal processing compartment. The software or logic calculates the degree to which the RF electromagnetic surface wave spectrum deviates from the nominal characteristic or appropriate operating conditions. Based on this, a processor associated with the controller can “decide” on corrective action or terminate processing within approximately milliseconds before the wafer is erroneously processed. In some embodiments, the expected effect of the deviation on processing uniformity or other properties can be quantitatively assessed within approximately 500 microseconds after occurrence, so that remedial action can be initiated within milliseconds. Furthermore, actions can be taken to minimize or eliminate damage to the wafer or substrate being processed in reaction chamber 240 at this time, thereby avoiding yield losses for that wafer or substrate.

[0051] In some embodiments, the evaluations and / or decisions made in the signal analysis compartment 285 of the impedance matching network 215 can be performed by a very fast computing or analysis system using algorithms residing in the plug-in storage unit and / or detachable data processing unit. In still other embodiments, the evaluation decisions made in the signal analysis compartment 285 can be performed using an analog or neural network type processor. This decision can be further implemented using a decision algorithm, which can reside in the detachable storage unit or processing unit. Commands for corrective action can then be rapidly transmitted from compartment 275 of the impedance matching network 215 to the RF generator 205 via a high-speed data line, which can temporarily interrupt, alter, or terminate the power or RF frequency of the plasma. This ensures that plant management can promptly take or plan corrective actions for the processing chamber 240 and the RF plasma processing system 200.

[0052] Figure 2A set of sensors 290 is also shown, which are configured on the outer surface of the base 295 of the spray head 230, outside the vacuum region within the reaction chamber 240 under atmospheric conditions. In some embodiments, an additional sensor 296 may be mounted on the base 297 of the pedestal and connected via a high-speed signal cable to the signal processing compartment 275 of the disclosed impedance matching network 220, as with the sensor 290. The sensor 296 being located outside the vacuum environment of the reaction chamber 240 significantly reduces cost and facilitates integration into information and processing networks because it eliminates the need for vacuum feeding.

[0053] Sensor 255 can be deployed in some configurations to sense voltage and / or current on the surface of base 235 and can be covered and protected from plasma by dielectric cover 260. Sensors of this type and location, close to the wafer and / or substrate, may have a sensitivity advantage in detecting certain EM surface wave modes that indicate plasma asymmetry—a significant type of plasma inhomogeneity. These indoor sensors 255 can use communication lines passing through the vacuum wall via feedthroughs or, in some embodiments, wireless communication links operating optically or at lower frequencies.

[0054] Generally, the phase and amplitude patterns of EM surface waves at each frequency on the surfaces of the spray head 230 and base 235 can be determined by analyzing signals from any group of voltage, current, phase, or combined sensors 255, 280, 290, and 296. Generally, EM surface waves at a given frequency generate voltage and current signals that are phase-dependent with signals at other frequencies. The magnitude of the voltage at each frequency and at each point is the sum of the voltages of all waves at that frequency from all points on the electrode surface. For axisymmetric electrode surfaces, where power is symmetrically fed and the plasma is axisymmetric, the axisymmetric surface wave pattern will be generated by the superposition of waves from all parts of the electrode and other surfaces in the reaction chamber 240. Generally, a perfectly symmetrical plasma in a symmetrical chamber with symmetrical electrodes centered on the axis of symmetry of the chamber will primarily have a circular line of symmetry with equal phase and amplitude centered on the center of base 235.

[0055] Turn Figure 3A cross-sectional view of a dual-plate electrode assembly according to an embodiment of the present disclosure is shown. This assembly has a wide-bandwidth sensor that provides a voltage signal via an electrical connector having low shunt capacitance to the surrounding area of ​​the electrode and to electrical ground. In some embodiments, an electrode, such as a spray head 330, may include two conductive plates 331, 332 configured to be approximately parallel, center-aligned, and having a shape substantially the same as the substrate or wafer. The surface of the first plate 331 remote from the second plate 332 may be exposed to a vacuum environment and plasma. The first plate 331 is separated from the second plate 332 by a distance equal to the length of the dielectric support 333. The first plate 331 may have an embedded sensor 334, the puck or pickup of which is a conductive material, and the surface of the sensor 334 is approximately coplanar with the surface of the first plate 331 remote from the second plate 332.

[0056] In some embodiments, sensor 334 may be mounted in a first plate 331 and 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 may be less than 5, and in some embodiments, for inorganic materials, such as quartz-based aerogels, the dielectric constant may be less than 2. Sensor 334 may have a high bandwidth extending from 100 kHz to at least 10 times the highest drive frequency connected to the chamber, and may be able to sense surface voltage, surface current, or both, the highest drive frequency of which may be up to or above 300 MHz. The sensitivity of sensor 334 may vary by less than 30% in some embodiments 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 the inner conductor 338 of a vacuum electrical signal feedthrough 339, the base 341 of which is mounted in an electrically grounded second plate 215. In some embodiments, leads from each sensor may be directly connected to a circuit board located in a similar position to 332, which has a ground plane and detector circuitry, one for each sensor, to determine the amplitude and phase of each frequency component.

[0057] The inner conductor 338 of the feedthrough 339 may 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 less than 2 pf in some embodiments)—so that the total shunt capacitance from the sensor 334 plus the lead 337 plus the feedthrough 339 to ground should be less than 5 pf and less than 3 pf in some embodiments. In some embodiments, the output from the base 341 mounted to the grounded second plate 332 may be connected to an attenuator (not shown). In some embodiments, the attenuator may include a resistor with a resistance greater than approximately 100 ohms. A shunt resistor may be present in parallel with the resistor 404 to ground 405. The resistance of the shunt resistor may be, for example, 50 ohms, or alternatively may be equal to the impedance of the cable connecting the attenuator to the communication network or the controller of the plasma chamber. The detector, instead of the connector shown, is located at... 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 located in the compartment of the matching network.

[0058] Each sensor 334 can measure the voltage or current amplitude of a combined electromagnetic surface wave mode, having the fundamental and harmonic frequencies of all RF generators powering the plasma as components. The fundamental and harmonic frequency range extends from approximately 10 kHz to up to approximately 500 MHz or more. In other embodiments, the sensor can measure the voltage at the fundamental and harmonic frequencies in the range of approximately 100 kHz to approximately 1 GHz.

[0059] 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. The voltage sensor 401 may be mounted in electrodes, such as in a base 400. In some embodiments, the sensor 401 may be connected to electrical ground 406 via a resistor. The tip or locator of the sensor 401 may have a lead 402 surrounded by a dielectric 403 (optionally air or vacuum). In some embodiments, the lead 402 from the sensor 401 may be connected to electrical ground 406 via an attenuator, such as one or more resistors 404 and a shunt resistor 405, which in some embodiments may be approximately 50 ohms. Such a resistor 404 may be non-inductive and may have a resistance in the range of approximately 100 ohms to approximately 100,000 ohms. In some embodiments, the resistance may be between approximately 500 ohms and approximately 10,000 ohms. Resistor 405 may also be non-inductive.

[0060] Furthermore, the dielectric 403 should generally be nonmagnetic and have a low loss tangent, less than about 0.01 in some embodiments or less than about 0.001 in others. The shunt capacitance between the tip of sensor 401 and the lead 402 leading to the ground electrode should be less than about 5 pF, or less than about 2 pF in some embodiments, so that the reactance between sensor 401 and the electrode of base 400 should be greater than about 100 ohms at 300 MHz. The purpose of such a low shunt capacitance is to reduce the load of sensor 401 on surface waves, minimizing its absorption of wave energy and allowing the wave to propagate as if sensor 401 were not present. Under such conditions, the detected surface potential will not differ significantly from the surface potential on the electrode without such sensor 401.

[0061] Turn Figure 5 A schematic side view of a base with associated RF and control components according to an embodiment of the present disclosure is shown. The base 501 power supply circuitry 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; in some embodiments, the compartments may be in or attached to the impedance matching network 506. A high-speed line 513 of the data network carries information from the impedance matching network 506 to one or more controllers 514 of the reaction chamber, generator, or tooling or plant (not shown). Sensors 502, 503 are mounted on or near the base 504 of the base 501; the sensors may be inside or outside the vacuum region of the reaction chamber.

[0062] In some embodiments, a signal analysis, such as a fault detection compartment 510, may be 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 sensors 502 and 503 via cables 511 and 12. The signal analysis compartment 510 then transmits the signals from each sensor 502 and 503 to internal circuitry, which may be referred to as a detector and may include electronic components such as transistors and passive components. In an alternative embodiment where the amplitude and phase of each frequency component are directly found 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.

[0063] Each detector (not shown) in compartment 510 can perform RF spectrum analysis on signals from a single sensor 502, 503 or from a set of sensors that can be analyzed in parallel. This analysis may include averaging the signals from the set 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 harmonic frequencies, there may be outputs of amplitude and phase from each detector. The outputs from each detector for each harmonic signal can then be input to an analog-to-digital converter to generate digitized values ​​of both amplitude and phase for each measured harmonic.

[0064] These digital amplitude and phase values ​​for each frequency component and each sensor can be input to a high-speed digital processor in a signal analysis compartment associated with a disclosed impedance matching network with virtually no delay, e.g., <10 microseconds. The digital processor can analyze both the fundamental and each harmonic amplitude and phase information from the sensors, determining the relative magnitudes of different surface wave modes for both the fundamental and harmonics, including axisymmetric and non-axisymmetric modes. Different non-axisymmetric modes may exist for each frequency component, one or more of which may be indicators of plasma inhomogeneity.

[0065] In some embodiments, such non-axisymmetric modes can be rapidly identified by an algorithm residing on the plug-in. A reference database relating the magnitude of the non-axisymmetric mode to the percentage of plasma inhomogeneity can also reside on the plug-in or a detachable processor. The digital processor can also calculate the rate of change of wave mode amplitude and the acceleration of one or more wave mode amplitudes to determine the likelihood of failure in the near future. One measure of the magnitude of a non-axisymmetric mode at a given frequency could be the difference between the phases of surface waves at that given frequency at different sensor locations, symmetrically located within an axisymmetric chamber at radial distances from the center of the circular electrode. Alternatively, a second indicator of the non-axisymmetric mode could be the difference between the amplitudes of surface waves at a given frequency at different sensor locations, symmetrically located within an axisymmetric chamber at radial distances from the center of the circular electrode.

[0066] A matching network 506 with an isolation compartment 510 containing a multi-channel detector system (not shown) can simultaneously perform Fourier analysis, digitize, and record the voltage amplitude and phase of EM waves propagating at various locations on the base 501. Due to inherent noise, each determined voltage amplitude and phase can be averaged over short time intervals as needed, and averaging can be performed on a group of sensors 502, 503 to determine relative magnitude or time averages over a relatively large number of pulses.

[0067] Spray heads, bases, or other power supply components such as electrodes equipped with sensor arrays or groups can be used as test systems to generate data to characterize and record the relationship between the spectral and spatial patterns of EM wave modes and various non-uniformities of plasma density during RF processing. In some embodiments, this data can be analyzed offline by engineers to characterize and classify plasma behavior and store it in a database, which can be stored in a plug-in storage device that can be connected to a matching network compartment or other controller or monitoring system.

[0068] The relationship between the amplitude and phase pattern characteristics of non-axisymmetric and axisymmetric EM modes, as well as processing and plasma inhomogeneities or deviations from appropriate conditions, can be stored in a plug-in of a disclosed signal analysis compartment connected to a matching network. In embodiments where the RF plasma processing system may be used as a production tool, plasma and processing inhomogeneities can thus be rapidly detected during operation in the monitoring chamber. For example, as... Figure 2 The configuration shown Figure 4 The disclosed type of sensor shown can be mounted on, for example... Figure 1 The RF plasma system shown.

[0069] To determine whether the processed 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, in part, based on the magnitude of the non-axisymmetric EM modes of each of a pre-specified set of harmonics at some electrodes or antennas. In some embodiments, the processor can then compare these parameters to a reference range in a database. Such a reference database can reside on a plug-in connected to the signal analysis compartment, which may be located within or associated with the impedance matching network.

[0070] The database can store parameters characterizing various plasma conditions to help determine whether and how severe a plasma deviation from an acceptable "processing window" has occurred. In some embodiments, the analysis may include comparing the phase of each harmonic from each sensor or a group of sensors at a given distance from the electrode center. Such a phase difference between a sensor or a group of sensors with respect to any azimuth angle may be a measure of the asymmetry in the generation and / or propagation of that harmonic mode, and thus a measure of plasma asymmetry and inhomogeneity. In some embodiments, the analysis may include calculating the difference in amplitude between a sensor or a group of sensors at a given distance from the axis of symmetry. Such amplitude variation between a sensor or a group of adjacent sensors within an azimuth angle range may also be a measure of the asymmetry in the generation and / or propagation of that harmonic mode, and thus a measure of plasma asymmetry and inhomogeneity.

[0071] A quantitative measure of the asymmetry of each harmonic in a set of harmonics, i.e., a parameter, can then be stored in the plug-in unit and transmitted to the room and tool controller via a data network. Furthermore, the trend and acceleration of the parameter can be calculated and compared with 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 that can be stored on the plug-in can be executed in a processor residing in the compartment to determine a process for remedial or preventative action. This action can then be rapidly transmitted to the RF generator and / or the room and / or tool controller.

[0072] In some embodiments, all these databases of parameters, algorithms, standards, and specifications for comparing parameters, rates of change of parameters, and accelerations of parameters may reside on a data storage device or a removable processor connected to a port, which may be an input / output port of a signal analysis compartment. Analysis of surface wave patterns based on signals from sensors and the resulting parameters is performed rapidly by the processor, such that any fault declaration and remedial action commands can be transmitted via network to the RF generator and reported to the room or system controller within five milliseconds or less after the event. In some embodiments, a fault condition and specified remedial action commands can be transmitted to the generator within one millisecond.

[0073] In some embodiments, many types of plasma deviations from the desired plasma homogeneity can be detected quickly enough that the tooling or chamber controller can take steps to correct the plasma fault condition before the wafer or substrate is mishandled. In some cases, the specified remedial action might be a brief change in the RF power format, such as continuous wave (CW) or pulse, or a complete power shutdown for a short period, or stopping the current wafer processing and saving it for later processing or discarding it, or shutting down the reaction chamber for maintenance. Therefore, adjusting the frequency within approximately ten percent of the RF power can thereby modify the reflected power.

[0074] In some embodiments, upon detection of a plasma fault condition, the disclosed signal analysis compartment associated with the matching network can command appropriate corrective actions to be performed by the RF generator and / or, in some embodiments, by the matching network. For example, the RF processing generator can initiate a termination process in response to a signal measured by sensors on the spray head and / or base to end wafer processing. In specific embodiments, the frequency can be adjusted, i.e., increased or decreased in the range of approximately one-thousandth to ten percent. Alternatively, power interruption of the RF plasma processing deposition system, e.g., the establishment of pulsed power, can be used to stop or pulse the plasma, thereby stopping or significantly reducing secondary plasma. In some cases, after a very brief interruption, a specified remedial action may be provided, and processing can then continue. In some implementations, the remedial action can be determined based on yield data or other wafer diagnostics via, for example, machine learning and / or programmed remedial procedures.

[0075] Turn Figure 6 A top view is shown illustrating the propagation of an axisymmetric surface wave across a base according to an embodiment of the present disclosure, wherein the plasma in the reaction chamber is axisymmetric. Figure 6 In the diagram, circle 601 represents the curves of constant phase and amplitude of the fundamental and harmonic frequency components of the axisymmetric surface wave mode. The circle is concentric with the electrode. These modes are highly dominant when both the electrode and the plasma are axisymmetric and coaxial in the chamber. The propagation vector 602 of the surface wave at any frequency will be radial. The wave will propagate towards and away from the center, and as it propagates, it will inject power into the plasma.

[0076] Turn Figure 7 A top view is shown illustrating the propagation of a transverse electromagnetic surface wave across electrodes according to an embodiment of the present disclosure. Figure 7In the model, lines 701-704 of constant phase and equal amplitude for a specific individual non-axisymmetric mode are approximately straight and parallel, whether at the fundamental frequency or its harmonics. Such surface waves can be detected by sensors deployed on the base or spray head of the RF plasma deposition system. This mode can be referred to as "lateral," meaning the direction of propagation, as seen in propagation vectors 705-707, spans the electrode surface from one side to the other or from the central plane to the left and right sides. Other non-axisymmetric modes may also exist, where the constant-phase line may be a curve whose center of curvature is displaced from the electrode center. Detector readings at each frequency can be decomposed into a sum of axisymmetric modes and (typically a small number) non-axisymmetric modes, which reflect the dominant non-uniformity of the plasma. Typically, this decomposition allows for the identification of a lateral mode component and / or a dominant "off-center" or displaced radial mode, either of which is characteristic of the plasma non-uniformity configuration. The association of the plasma non-uniformity configuration with specific non-axisymmetric modes is completed prior to production processing as part of building a database, which may reside on the plug-in unit or elsewhere.

[0077] Turn Figure 8 The image shows a top view of an exemplary azimuth sensor deployment in a reaction chamber according to an embodiment of the present disclosure. In this embodiment, a plurality of sensors 800 may be deployed at azimuth angles around one or more components of the reaction chamber and / or on the reaction chamber itself. As briefly discussed above, the plurality of sensors 800, which may be four in this embodiment, may be positioned at different angles about the chamber axis of symmetry 805 on some chamber components, such as spray heads and / or bases, for measuring surface voltage or current associated with surface waves. In this case, they are spaced at 90-degree intervals, but in some embodiments they may be spaced at regular azimuth angles.

[0078] Sensor 800 may include a passive sensor 800 that picks up changing electric or magnetic fields. Sensor 800 may be deployed at different azimuth angles relative to the chamber axis of symmetry 805 for detecting EM waves with different types of propagation modes. Sensor 800 may be deployed at equidistant locations around the chamber axis of symmetry 805 and / or components within the reaction chamber or around the reaction chamber itself. Similarly, sensors 800 may be deployed diametrically opposite each other such that the spacing between sensors 800 and the axis of symmetry can be approximately the same. For example, the distance between sensors 800-1 and 800-2 and the distance between 800-3 and 800-4 are approximately the same. Similarly, each sensor 800 is located at the same distance from the chamber axis of symmetry 805. Examples of the spacing and location of the sensors 800 will be discussed in more detail below.

[0079] As shown in the figure, sensors 800 are deployed at diameter-opposite positions. For example, sensors 800-1 and 800-3 are diameter-opposite, while sensors 800-2 and 800-4 are diameter-opposite. Therefore, sensors 800 can detect waveform differences on different sides of the reaction chamber and / or its components for non-axisymmetric plasmas, and provide notification, as explained above, when waveform differences occur, so that remedial or proactive actions can be taken. For example, if sensors 800-1 and 800-4 sense and report waveform differences from their diameter-opposite positions, such differences can provide an indication of harmonic out-of-phase or different amplitudes, which may therefore indicate the presence of plasma inhomogeneity and asymmetry. This waveform difference occurs when there is a difference in the relative phase or amplitude of one or more harmonics in the signals picked up by the opposite sensors between the diameter-opposite detectors.

[0080] In some embodiments, four sensors 800 can be used, such as Figure 8 As shown in the diagram. However, in other embodiments, different numbers of sensors 800 can be used, such as six, eight, twelve, fourteen, sixteen, eighteen, twenty, or more sensors 800. In some embodiments, the azimuth angles between sensors may not be equal; however, the same characteristics of non-azimuth-symmetric plasma modes can be observed through the sensors. In some embodiments, having six to twelve sensors 800 may be advantageous. The more sensors 800 there are, the more data can be collected, thereby providing enhanced noise discrimination capabilities and sensitivity to non-uniformity detection. However, by increasing the number of sensors 800, data processing may slow down, resulting in slower remedial and preventative actions. Those skilled in the art will understand that balancing the number of sensors 800 with the desired level of data granularity allows for optimization of RF plasma processing. Therefore, increasing the number of sensors 800 may be beneficial as computing power and the speed at which data can be processed increase. In some embodiments, specific sensors 800 may be selectively turned off and on, thereby allowing the controller to access certain desired data. For example, in a system with eight sensors, four of them can be selected and turned off, thereby reducing the amount of data generated. In other embodiments, additional sensors can be added or removed during operation, thereby changing the amount of data generated.

[0081] Sensor 800 may also include various types of sensors, including circular and other geometries. In some 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 insulating layer or coating to protect sensor 800 from the plasma or reactive substances in the reaction chamber, and may also include other optional coatings and layers, such as a Faraday shield for a current sensor, an aluminum coating, etc.

[0082] Turn Figure 9 The diagram shows a side cross-sectional view of a sensor mounted at an azimuth angle 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 spray head 930 through the base 935. In other embodiments, the axis of symmetry 905 may extend longitudinally from the center of another electrode, such as an antenna. Multiple sensors 900 may be deployed at azimuth angles at various locations around and inside the reaction chamber 940, and around or associated with specific components such as the spray head 930 and / or the base 935. Figure 9 This is a cross-section, illustrating only two sensors 900 at each location. However, more sensors 900 can be used during RF plasma monitoring processes, as discussed in [the relevant section]. Figure 8 It was discussed in detail.

[0083] In some embodiments, sensor 900-1 may be deployed around the edge or periphery of spray head 930. In such embodiments, sensor 900-1 may be deployed at least partially or completely embedded within spray head 900-1, and the outer surface of sensor 900-1 may be coated with an insulating layer to protect sensor 900-1 from the environment within reaction chamber 940. In such embodiments, two or more sensors 900-1 may be deployed at an azimuth angle around the edge of spray head 930, and preferably four or more sensors, thereby allowing the detection of non-uniformity and asymmetry in RF plasma processing.

[0084] In other embodiments, sensor 900-2 may 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 may be partially or completely embedded in base 935 and may or may not include an insulating layer deployed on its outer surface. Furthermore, in some embodiments, a dielectric protective portion covering them may be provided. In addition to sensor 900-2 deployed around base 935 within the vacuum, other sensors 900-3 and 900-4 may be deployed outside the vacuum of reaction chamber 940 and around base 935. Such sensors 900-3 and 900-4 may be deployed along base 935 and / or its base portion on a metallic surface. Sensor 900 may also be deployed on or associated with other support structures of base 935.

[0085] In other embodiments, sensor 900-5 may be deployed and / or otherwise integrated into the sidewall of reaction chamber 940. In such embodiments, where the wall is dielectric, sensor 900-5 may be deployed on the outer chamber wall 915 outside reaction chamber 940, or may be integrated into the sidewall such that sensor 900-5 is within the vacuum of reaction chamber 940. For metallic walls, the sensors should expose their pickups on the inner surface of the wall to sense the EM field inside the chamber. Other sensors 900-6 may be deployed in observation ports 920, which are positioned along the outer chamber wall 915. In such embodiments, the sensors 900-6 in the observation ports may be located outside the vacuum of reaction chamber 940 or inside reaction chamber 940.

[0086] In yet another embodiment, sensor 900-7 may be deployed in a dielectric material located, for example, around spray head 930, while in other embodiments, sensor 900-7 may be deployed in a dielectric material located around base 935. Although the specific location of sensor 900 has been discussed herein, sensor 900 may be located in and around reaction chamber 940 at various other locations. For example, sensor 900 may be deployed inside or outside a dielectric wall near an antenna or other component. Sensor 900 may further be located in various other locations inside the metal wall of reaction chamber 940.

[0087] In some embodiments, combinations of sensors 900-1 through 900-7 can be used for more accurate monitoring of the RF plasma process. For example, sensor 900-1 around the edge of the spray head 930 can be combined with sensor 900-2 around the edge of the base 935. Similarly, a combination of sensors 900-5 outside the reaction chamber 940 can be combined with sensors 900-1 / 900-2 located inside the reaction chamber 940. In still other embodiments, combinations of three, four, five, six, seven, or more of the sensor 900 positions can be used to further optimize the monitoring of the RF plasma process.

[0088] Turn Figure 10 The diagram 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 sensors 1000 deployed in azimuth angles around a bottom electrode are shown; in this example, the bottom electrode is a base 1035. (This is related to the above regarding...) Figure 9 The sensor discussed is similar to the 1000. Figure 10 The illustration shows sensors 1000 deployed in various locations. Sensor 1000-1 is deployed around the outer edge of the base 1035. Sensor azimuth position 1000-2 is deployed around the interior of the reaction chamber 1040, while sensor azimuth position 1000-3 is deployed around the periphery of the reaction chamber 1040 adjacent to the observation port.

[0089] In this embodiment, 12 sensors 1000 are illustrated at each location; however, in other embodiments, other numbers of sensors 1000 may be used, including fewer and more. Furthermore, in addition to the explicitly illustrated sensor 1000 locations, other sensor 1000 locations may be used to further enhance the RF plasma processing.

[0090] Turn Figure 11 The diagram illustrates a schematic cross-sectional side view of a reaction chamber according to an embodiment of the present disclosure. In this embodiment, a sensor 1100 is illustrated deployed around the antenna of an inductively coupled plasma source 1105. Therefore, the sensor 1100 can sense RF current or voltage from a plasma source located within the reaction chamber 1140.

[0091] Turn Figure 12 This diagram 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 base 1235. The base 1235 includes a sensor 1240 deployed along the upper outer edge of the base 1235. As described above, the sensor 1240 may be deployed on the upper outer edge, embedded within the base 1235, or may be alternately deployed around the outer edge of the vacuum interior or exterior of the reaction chamber.

[0092] The RF plasma processing system 1200 also includes a circuit system 1245 connected to the sensor 1240 via a communication line 1250. When the sensor 1240 receives sensing data from the RF plasma processing system 1200, the data can be sent to the circuit system 1245 for processing. Because the circuit system 1245 is relatively close to the sensor 1240, the time spent transferring sensing data between the two can be reduced. Therefore, initial calculations of the electrical properties sensed by the sensor 1240 can be performed more quickly, and then the initial calculations can be transferred to other components 1255 of the RF plasma processing system 1200. Other components 1255 may include, for example, an RF generator, an impedance matching network, a fault detection compartment, an operation controller for the reaction chamber, an operation controller for the tool, a plug-in device, a signal analysis compartment, or one or more other components connected to the RF plasma processing system 1200.

[0093] Then, components 1200, 1255, or others (not shown) can adjust various aspects of the RF plasma processing system 1200 to correct faults detected by sensor 1240 and at least partially processed within circuitry 1245. Circuitry 1245 may be located within a base 1235 outside the vacuum of the reaction chamber in an isolated structure to protect circuitry 1245 from conditions within the reaction chamber. In other embodiments, circuitry 1245 may be located in the base of base 1235 or in other areas adjacent to base 1235.

[0094] along with Figure 12 The illustration shows a cross-sectional view of the components of the RF plasma processing system 1200. Those skilled in the art will understand that the circuitry 1245 can be deployed around the base 1235 at different azimuth angles at approximately the same radius. Therefore, individual circuitry 1245 can be used for each sensor 1240, or the sensors 1240 can be connected to a centralized circuitry 1245 located at one or more selected locations around and / or within the base 1235.

[0095] Turn Figure 13 A partial cross-sectional view of an inductively coupled RF plasma processing system according to an embodiment of the present disclosure is shown. It shows that a sensor 1340 is configured to approach the inductive antenna 1330 and can be mounted externally or internally to a dielectric wall (not shown) adjacent to the antenna.

[0096] In some embodiments, the method of this application can provide a means of detecting non-uniformity of plasma in an RF plasma processing system. The method may include generating plasma within the reaction chamber of the RF plasma processing system and detecting electrical signals from the plasma in a frequency range from the frequency of the RF power sustaining the plasma to multiples of approximately ten times that frequency using multiple sensors, said multiple sensors being deployed in an azimuth about the chamber's axis of symmetry of the RF plasma processing system. The electrical signals may include at least one of voltage and current generated by electromagnetic surface waves.

[0097] In operation, the method may further include comparing the waveforms of electrical signals picked up from the plasma by a plurality of sensors, and determining when plasma inhomogeneity occurs based on a comparison of the electrical properties of the plasma detected by each of the plurality of sensors. In some embodiments, the comparison may further include comparing the amplitudes of at least one radio frequency harmonic picked up by at least two different sensors. In a specific embodiment, the comparison may further include comparing the phases of at least one radio frequency harmonic picked up by at least two sensors, the at least two sensors being separated by an azimuth angle of at least 90 degrees about the chamber axis of symmetry. In still other embodiments, determining that plasma inhomogeneity has occurred may further include determining the azimuth angle change of the electrical signals picked up from the plasma by the plurality of sensors, the azimuth angle change increasing over time over a period of time greater than 10 microseconds.

[0098] Determining that plasma inhomogeneity has occurred may further include using Fourier analysis of electrical signals picked up from the plasma by multiple sensors at different azimuth angles and comparing the variance of at least one of the amplitudes and phases of one or more frequency components of the multiple sensors with reference values ​​in a plasma control database. Determining that plasma inhomogeneity has occurred may further include detecting an increase in azimuth variation of the electrical signals picked up from the plasma by the multiple sensors over a period of at least 100 microseconds and / or may further include calculating the plasma inhomogeneity based on the azimuth variance of the amplitude and phase of at least one harmonic of the frequency of the radio frequency power sustaining the plasma. Aspects of this disclosure may further include inhomogeneity having a variation in plasma density as a function of the azimuth angle about the chamber's axis of symmetry.

[0099] In operation, aspects of this disclosure may further include a method for detecting non-uniformity of plasma in a radio frequency plasma processing system. This method may include generating plasma within the radio frequency plasma processing system. The method may also include detecting electrical signals from the plasma at multiple frequencies, the multiple frequencies being integer multiples of at least one radio frequency excitation frequency, the multiple broadband radio frequency sensors being deployed azimuthally about the chamber symmetry axis of the radio frequency plasma processing system. Some embodiments may then include determining plasma asymmetry based on azimuthal changes in at least one of the multiple detected frequency components of the detected electrical signals.

[0100] The foregoing description, for purposes of explanation, has used specific terminology to provide a thorough understanding of this disclosure. However, it will be clear to those skilled in the art that specific details of practicing the systems and methods described herein are not required. The above description of specific examples is for illustrative and descriptive purposes. They are not intended to be exhaustive or to limit this disclosure to the precise forms described. It will be apparent that many modifications and variations are possible in light of the foregoing teachings. These examples are shown and described in order to best explain the principles and practical application of this disclosure, thereby enabling others skilled in the art to best utilize this disclosure and the various examples, and to modify them in various ways to suit a particular intended use. The scope of this disclosure is defined by the appended claims and their equivalents.

Claims

1. A method for detecting non-uniformity in a radio frequency plasma processing system, the method comprising: generating a plasma within a reaction chamber of the radio frequency plasma processing system; detecting electrical signals from the plasma in a frequency range from a frequency of a radio frequency power sustaining the plasma to a multiple of ten times the frequency with a plurality of sensors, the plurality of sensors disposed on a surface of at least one of one or more plasma powered devices within the reaction chamber and at azimuthal angles with respect to a chamber symmetry axis of the reaction chamber; comparing waveforms of the electrical signals picked up by the plurality of sensors from the plasma; and determining when a plasma non-uniformity has occurred based on the comparison of the waveforms of the electrical signals detected by each of the plurality of sensors.

2. The method of claim 1, wherein, The comparison further comprises comparing amplitudes of at least one radio frequency harmonic picked up by at least two different sensors.

3. The method of claim 1, wherein, The comparison further comprises comparing phases of at least one radio frequency harmonic picked up by at least two sensors separated by at least 90 degrees in azimuthal angle with respect to the chamber symmetry axis.

4. The method of claim 1, wherein, The non-uniformity comprises a variation in plasma density as a function of azimuthal angle with respect to the chamber symmetry axis.

5. The method of claim 1, wherein, Determining that a plasma non-uniformity has occurred further comprises determining an azimuthal variation of the electrical signals picked up by the plurality of sensors from the plasma over a time period greater than 10 microseconds that increases over time.

6. The method of claim 1, wherein, The electrical signals are at least one of a voltage and a current generated by an electromagnetic surface wave.

7. The method of claim 1, wherein, Determining that a plasma non-uniformity has occurred further comprises Fourier analyzing the electrical signals picked up by the plurality of sensors at different azimuthal angles from the plasma and comparing at least one of amplitudes and phases of one or more frequency components of the plurality of sensors to reference values in a plasma control database.

8. The method of claim 1, wherein, Determining that a plasma non-uniformity has occurred further comprises finding an azimuthal variation of the electrical signals picked up by the plurality of sensors that increases over a time period of at least 100 microseconds.

9. The method of claim 1, wherein, Determining that a plasma non-uniformity has occurred further comprises calculating a plasma non-uniformity from azimuthal variances of amplitudes and phases of at least one harmonic of a frequency of a radio frequency power sustaining the plasma. Determining that a plasma non-uniformity has occurred further comprises calculating a plasma non-uniformity from azimuthal variances of amplitudes and phases of at least one harmonic of a frequency of a radio frequency power sustaining the plasma.

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