Plasma non-uniformity detection

Abstract

To provide a method for detecting plasma non-uniformity in a radio frequency plasma processing system includes generating plasma in a reaction chamber of the radio frequency plasma processing system and detecting electrical signals from the plasma in a frequency range from the frequency of the radio frequency power sustaining the plasma to approximately 10 times the frequency with a plurality of sensors arranged azimuthally about an axis of symmetry of the chamber of the radio frequency plasma processing system.SOLUTION: A method further includes comparing waveforms of electrical signals obtained from plasma by multiple sensors and determining when plasma non-uniformity occurs on the basis of comparison of the electrical characteristics of the plasma detected by each of the multiple sensors.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims the benefit of U.S. Provisional Application No. 62959 - 644, filed Jan. 10, 2020, and U.S. Non - Provisional Patent Application No. 17 - 145 - 202, filed Jan. 8, 2021, the contents of which are hereby incorporated by reference.

Summary of the Invention

Problems to be Solved by the Invention

[0002] High - frequency (RF) plasma processes are widely used in semiconductor manufacturing for etching various types of films, depositing thin films at low to intermediate processing temperatures, and performing surface treatment and cleaning. A characteristic of such processes is the use of a plasma, i.e., a partially ionized gas that is used to generate neutral species and ions from precursors in a reaction chamber, supply the energy of ion bombardment, and / or perform other operations. Controlling the plasma density during such processes is challenging, and the non - uniformity of the plasma in the reaction chamber affects the uniformity and yield of wafer processing of the integrated circuits or other devices being manufactured.

Means for Solving the Problems

[0003] Non-uniform plasma density in the reaction chamber can cause non-uniform etching rates or specific characteristics across the substrate. In certain systems, monitoring the uniformity of plasma density in the reaction chamber is performed using a probe. Such a probe may be exposed to a plasma environment that depends on the coating and may use active electronics to infer the plasma density. Such systems may take several milliseconds or more to respond to changes in the plasma. Emission spectroscopy may also be used to determine the profile of plasma density in the reaction chamber, but such systems require multiple lines of sight through the plasma and may use complex analysis to infer non-uniformity. None of these techniques have sufficient sensitivity and speed to effectively solve the problem of non-uniformity, and furthermore, they may be costly to implement.

Brief Description of the Drawings

[0004] The present disclosure is best understood from the following detailed description when read in conjunction with the accompanying drawings. It is emphasized that the various features are not drawn to scale in accordance with standard practice in the art. In fact, the dimensions of the various features can be arbitrarily increased or decreased to clarify the discussion.

[0005] [Fig. 1] FIG. 1 is a schematic side view of an RF plasma processing system according to an embodiment of the present disclosure.

[0006] [Fig. 2] FIG. 2 is a schematic side view of a plasma chamber having high bandwidth sensors attached at various positions of an electrode according to an embodiment of the present disclosure.

[0007] [Fig. 3] FIG. 3 is a cross-sectional view of a dual plate electrode assembly having a sensor that supplies a voltage signal via an electrical connector having a low shunt capacitance to electrical ground according to an embodiment of the present disclosure.

[0008] [Fig. 4]Cross-sectional view of a pedestal in which a high-bandwidth voltage sensor according to an embodiment of the present disclosure is embedded.

[0009] [Fig. 5] Schematic side view of a pedestal according to an embodiment of the present disclosure.

[0010] [Fig. 6] Top view showing the propagation of an axisymmetric surface wave across a pedestal in which the plasma in the reaction chamber according to an embodiment of the present disclosure is axisymmetric.

[0011] [Fig. 7] Top view of the propagation of a transverse electromagnetic surface wave across an electrode according to an embodiment of the present disclosure.

[0012] [Fig. 8] Horizontal cross-sectional view of a sensor attached azimuthally (centered on the chamber symmetry axis) to a reaction chamber according to an embodiment of the present disclosure.

[0013] [Fig. 9] Vertical cross-sectional view of a sensor attached azimuthally to the electrodes, electrode base, upper dielectric plate, viewing window, and dielectric walls of a reaction chamber according to an embodiment of the present disclosure.

[0014] [Fig. 10] Vertical cross-sectional view of a capacitively coupled plasma reaction chamber having several sensor array positions according to an embodiment of the present disclosure.

[0015] [Fig. 11] Vertical cross-sectional view of a model-induced plasma reaction chamber according to an embodiment of the present disclosure.

[0016] [Fig. 12] Schematic side partial cross-sectional view of an RF plasma processing system having several possible sensor positions according to an embodiment of the present disclosure.

[0017] [Fig. 13] A schematic partial cross-sectional view including a dielectric wall of an RF plasma processing system in which a sensor is attached to a dielectric surface proximate to an inductively coupled antenna according to an embodiment of the present disclosure.

DETAILED DESCRIPTION

[0018] Exemplary embodiments of the subject matter claimed below are disclosed. To clarify, not all features of an actual implementation are described herein. It is understood that in the development of any such actual implementation, numerous implementation-specific decisions may be made to achieve the developer's specific goals, such as compliance with system-related and business-related constraints that vary from one implementation to another. Further, it is understood that such development efforts, even if complex and time-consuming, are routine for those of ordinary skill in the art who would benefit from the present disclosure.

[0019] Further, as used herein, the article “a” is intended to have its ordinary meaning in the patent arts, i.e., “one or more.” Here, the term “about” when applied to a value generally means within the tolerance of the device used to generate the value and, in some instances, means ±10%, ±5%, or ±1% unless specifically specified otherwise. Further, here, the term “substantially” means an amount having a range, for example, of more than half, almost all, all, or from about 51% to about 100%. Further, the examples herein are intended only to be illustrative and are presented for discussion purposes and not for limitation.

[0020] Turning to FIG. 1, a side schematic view of an RF plasma processing system 100 according to an embodiment of the present disclosure is shown. 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 such as a showerhead 130 or an equivalent power supply element such as an electrode, and a pedestal 135. As used herein, the plasma power supply device may refer to any device that introduces power to generate plasma, and may include, for example, the showerhead 130 and / or other types of electrodes as well as antennas and the like.

[0021] The RF plasma processing system 100 may have one or more RF generators 105, 110 that supply power to the reaction chamber 140 via one or more impedance matching networks 115, 120. The RF power flows from the first RF generator 105 through the impedance matching network 115 to the plasma in the reaction chamber 140, flows to the showerhead 130 or the sidewalls, flows to electrodes other than the showerhead 130, or flows to an induction antenna (not shown) that electromagnetically supplies power to the plasma. Thereafter, the power flows from the plasma to ground and / or the pedestal 135 and / or the 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 a variable capacitor, so that the coupling impedance between the showerhead 130 and the first impedance matching network 115 equals the output impedance of the first RF generator 105, e.g., 50 Ω. Additionally, the reflected wave power can be corrected by adjusting the frequency within a range of approximately ±10% of the RF power. As used herein, the term "about" acknowledges that satisfactory results can be obtained even though some inaccuracy with respect to a range or value is actually experienced. Such inaccuracies can be due, for example, to calibration losses or degradation or drift during operation. However, in these situations, the stated range or value is a nominal target value for the operating conditions during use.

[0022] In certain examples, the first RF generator 105 may supply power at an RF frequency between about 400 KHz and 150 MHz, while the second RF generator 110 connected to the pedestal 135 may supply power at an RF frequency lower than the frequency of the first RF generator 105. However, in certain implementations, the second RF generator 110 may not supply power at an RF frequency lower than the frequency of the first RF generator 105. Typically, the frequencies of the first RF generator 105 and the second RF generator 110 are such that the first RF generator 105 is at an RF frequency that is neither an integer multiple nor an integer fraction of the frequency of the second RF generator 110. One or more of the first RF generator 105 and the second RF generator 110 may adjust the frequency to modify the reflected wave power.

[0023] The impedance matching networks 115, 120 are designed to adjust their internal reactive elements so that the load impedance matches the power supply impedance. Generally, low reflected wave power is considered positive, but embodiments of the present disclosure ensure that the supplied power is maintained within the reaction chamber 140, that the power is reflected towards the first RF generator 105 and the second RF generator 110, and that even when the reflected wave power is relatively high, the associated impedance matching networks 115, 120 monitor the forward wave power to the reaction chamber 140 and the reflected wave power from the reaction chamber 140 and can adjust variable reactor elements, such as vacuum variable capacitors, by using a motor drive system. In certain embodiments, an electronically controlled capacitor, such as a PIN diode for an electronically variable capacitor, may be used. The impedance matching networks 115, 120 may include circuitry for measuring the phase and magnitude of signals to determine the levels of forward and reflected wave power from the intended load. Thus, embodiments of the present disclosure can be effective even when there is a large amount of reflected wave power. If there is a significant amount of reflected wave power at the primary frequency, the capacitor varies until the reflected wave power is minimized, e.g., to less than about 5 W and / or less than about 1% over a period, or in certain embodiments, to less than 1 W. Generally, harmonic frequency signals, including reflected wave power at harmonic frequencies, are not measured. Additionally, the frequency may be adjusted within a range of about ±10% of the RF power, whereby the reflected wave power may be corrected.

[0024] The RF plasma processing system 100 has many advantages, but historically, it has been a challenge to maintain control of plasma density through a multi-step process. Design tolerances with a density range of the same order as the nominal value, e.g., on the order of 1% non-uniformity, remain a challenge. Also, to achieve an optimal integrated circuit (IC) yield per wafer with miniaturization of about 3 nm or less and thick film formation of about 10 nm or less, it is necessary to strictly control the uniformity of plasma and neutral species to the 1% level or even lower. A non-uniform plasma density or an average density deviating from the desired value beyond the desired range within the reaction chamber is caused by slow changes within the chamber, changes in the RF circuit, or rapid growth (on the order of less than 1 millisecond) of parasitic or secondary plasmas, which can thereby result in non-uniformity of nano-scale features across the entire processed wafer due to non-uniformity of the etching rate.

[0025] Even a 1% difference in etching rate across the entire wafer can potentially cause yield problems in state-of-the-art technologies and often requires a significant amount of time to complete wafer processing to see yield losses. Therefore, to avoid irreversible deviations on the wafer from the desired feature profile, there is a need to quickly and accurately detect non-uniform plasma density or plasma density deviating from the desired range within the reaction chamber at a time period that may need to be less than about 1 millisecond.

[0026] One skilled in the art understands that electromagnetic (EM) surface waves may propagate along the surfaces within the RF power plasma in the reaction chamber 140. These surface waves have energy that can be evaluated at both the fundamental RF drive frequency and RF harmonics. The average power and power distribution of the harmonics are factors that affect plasma density and non-uniformity. Here, the harmonic profile is defined as the spectrum of surface waves having frequencies that are integer multiples of the fundamental drive frequency of the RF plasma-based reaction chamber 140. For example, when 2 MHz of RF drive power is provided to the reaction chamber 140, the injected power generates surface waves at that frequency that propagate along the interface between the plasma and the surface of the inner reaction chamber 140. By adjusting the frequency by about ±10% of the RF power, the reflected wave power can be corrected. Harmonic surface waves at integer multiple frequencies may also be generated. For example, a 2 MHz electromagnetic wave may generate surface waves at 4 MHz, 6 MHz, or 8 MHz. Odd and even harmonics (second, third, fourth, fifth, etc.) may appear, and in some examples, the odd harmonics may be dominant.

[0027] Aspects of the present disclosure may provide sensor locations for the reaction chamber 140 and its components that enable detecting and analyzing RF surface waves to determine the amplitude and phase of the fundamental and harmonic waves at a plurality of points within or adjacent to the reaction chamber 140. The waves may be detected by sensing the RF voltage or RF current at the fundamental and harmonic frequencies on the surface of the chamber components. In some embodiments, the sensor for the voltage has a pickup configured on or proximate to the surface of an electrode, pedestal base, chamber wall, or strap, and a conductive wire that transmits a signal from the pickup to a connector or cable. The current sensor may have a conductive element that includes one or more loops or partial loops or linear conductors, and one end of the conductive element may be at a reference potential that may be a local electrical ground.

[0028] A plurality of sensors, for example, two or more sensors, may be arranged at different angles about the symmetry axis of the chamber on specific chamber components described in detail below to measure the surface voltage or current associated with such surface waves. Here, the measured angle about the symmetry axis from a reference point of the chamber is defined as the azimuth angle. In some embodiments, such sensors may be arranged at substantially the same distance from the symmetry axis of the chamber.

[0029] The sensors may be attached at various locations on or with respect to the reaction chamber and / or its components. For example, the sensors may be attached to the surface of an electrode such as pedestal 135 and / or showerhead 130. The sensors may be attached to the pedestal of any electrode either inside or outside the vacuum. The sensors may be attached to the inside or outside of one or more metal walls and wall regions containing dielectric material of the reaction chamber 140 within the chamber, or to an antenna that may be used to inductively power the plasma. The sensors may be placed on or in proximity to a passive antenna that may be used to detect electromagnetic waves in proximity to the plasma boundary, or on or in proximity to a plurality of conductive buses or straps that connect the first impedance matching network 115 or the second impedance matching network 120 to an electrode such as pedestal 135 and / or showerhead 130, an antenna, or other components that transmit power to the plasma within the reaction chamber 140. The sensors may be connected to electrical ground. Thereby, the sensors can acquire signals as the signals propagate from various components of the RF plasma processing system 100 at the respective component surfaces.

[0030] The spectrum of RF harmonics is generated at the electrode-plasma interface, e.g., sheath 125 in FIG. 1, and the waves propagate in all directions such that both the amplitude and phase of all wave components vary with the position of the electrode or susceptor. Such waves 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 such waves vary in response to changes in the plasma, e.g., plasma density and non-uniformity, and the response time is on the order of a few microseconds or less. Further, the frequency distribution and phase distribution of the RF harmonic surface waves propagating at the electrode-plasma interface determine the frequency and phase distribution of the harmonic surface waves propagating on the electrode-based surface towards 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 positions enable the determination of the azimuthally symmetric and asymmetric parts of the total EM wave field for each frequency.

[0031] In the case of an inductive plasma, signals from the plasma, e.g., fundamental and harmonic waves, may propagate back to the antenna and then to the impedance matching network that powers the antenna. The frequency and phase distribution of the fundamental and harmonic RF waves may be monitored on a microsecond or faster time scale using sensors attached to such a surface and compared in terms of specified ranges and phase relationships as an indicator of plasma asymmetry or changes in plasma density or conductivity. To generate the amplitude and phase values of each frequency component at each sensor position, the signals from such sensors may be transmitted via a cable or the like to a detector that analyzes the frequency components of the signal.

[0032] In a particular implementation, the amplitude and phase of the detected RF harmonic components may be determined rapidly by a circuit (detector) within the signal analysis section, which may be a separate metal box or chassis, or may be within or connected to impedance matching networks 115, 120. Such amplitude and phase may be used to determine a state including the radial distribution and asymmetry of the plasma by applying algorithms and plasma non-uniformity calibration. Signals from the sensor may be Fourier analyzed by a dedicated circuit (detector) at a rate sufficient to perform a virtually continuous spectral analysis, updated as frequently as possible, and may result in a high-speed data stream. For example, for a 13.56 MHz plasma output, it takes less than 50 microseconds to process 512 cycles by Fourier analysis, and for a pulsed plasma when each element of the pulse is generated at 5 KHz, the state of the plasma can be updated at a rate of 10 KHz.

[0033] The results of the dedicated Fourier analysis of the fundamental wave and harmonics may be stored in another storage medium that can be read and / or written by an analysis processor associated with the signal analysis section. Either the stored results or the real-time signal may be sent to a high-speed calculation processor to determine the asymmetry parameter for each of the fundamental wave and harmonics. In order to very quickly recognize the "plasma defect" state, the asymmetry parameter may be compared with a value pre-stored in another storage medium (or a different storage medium) using an algorithm (which may also be stored in another storage medium or a different storage medium). Subsequently, the analysis processor may send appropriate commands, for example, to the first RF generator 105 and the second RF generator 110, more than two RF generators in a particular implementation, and the impedance matching network associated with these generators when appropriate, to continue the process under the current conditions or to make the necessary changes in the process conditions. In a particular implementation, three, four or more RF generators may be used. The first RF generator 105 and the second RF generator 110 may then continue, stop, change the supplied power, change the frequency of the RF power by about ±10% to correct the reflected wave power, or any other appropriate method - for example, respond to a transition to a reduced power mode or a pulse mode, or perform specific corrective actions to avoid improper wafer processing during a plasma failure or other unacceptable situation, such as commands for an alarm trigger, power cut-off, etc.

[0034] The location of the sensor for detecting surface waves (electric and magnetic fields) and characterizing the surface waves may, in some embodiments, be the peripheral surface of the pedestal 135 (bare or covered by a dielectric) outside the area covered by the wafer. For example, when the reaction chamber 140 processes a circular wafer with a radius of 150 mm, the pedestal mount sensor may be placed at a radius greater than 150 mm from the center of the wafer, which may, in some cases, be under the annular peripheral dielectric for controlling the edge effect. The sensor may be additionally or alternatively placed on the surface or periphery of the showerhead 130 facing the wafer or on the base of the pedestal 135 or on the surface of the base of the showerhead 130, regardless of whether these locations are within or outside the vacuum process environment. The sensor may be placed in various other locations described in detail below and may be monitored continuously or periodically to provide process plasma uniformity.

[0035] Using sensors outside the vacuum process environment, such as one or more of the impedance matching networks 115, 120, sensors on the base of the pedestal 135 and / or straps or buses connecting the base to the showerhead 130, may obviate the need to transmit signals through vacuum feedthroughs or transmission cables within the vacuum vessel of the reaction chamber 140. Sensors in such locations may monitor the fundamental and harmonic EM waves substantially continuously. This may enable 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.

[0036] In certain exemplary embodiments, the present disclosure can provide an apparatus and method for detecting deviations of plasma from the required "process window" within an RF plasma processing system 100. The RF plasma processing system 100 may include a reaction chamber 140, which may include a showerhead 130 for injecting a reaction gas into the reaction chamber 140, and the reaction chamber 140 may include a wafer support pedestal 135. However, in other implementations, the showerhead 130 may not inject gas into the reaction chamber 140. In some embodiments, the showerhead 130 may be provided with a plurality of sensors having their centers mounted near the approximate axis of symmetry of the reaction chamber 140 and arranged in a selected orientation about the axis of symmetry. Additionally or alternatively, such sensors may be disposed on the surface facing the wafer in the peripheral region of the showerhead 130 for detecting and measuring EM surface waves propagating while the wafer is being processed.

[0037] Further, in some embodiments, there may be a plurality of sensors mounted on the outer surface of the wafer support pedestal 135 outside the region occupied by the wafer for detecting both the amplitude and phase of the RF harmonic and fundamental surface waves. Such sensors may be exposed to the plasma or may be covered by a dielectric cover or a dielectric and metal cover. Additionally or alternatively, the sensors may be located at the periphery of the pedestal 135 base, inside or outside the vacuum chamber, and / or below the plane defined by the wafer. In some embodiments, the sensors may be disposed on the pedestal base for detecting surface electromagnetic waves propagating towards or away from the wafer support region of the pedestal and surface electromagnetic waves propagating along the surface of the pedestal base. In certain embodiments, the sensors may be mounted near the wafer plane (e.g., less than 10 cm).

[0038] Alternatively, the sensor may be attached to a portion of the pedestal 135 that is made of metal or other conductive material and is located outside the vacuum region of the reaction chamber 140 under atmospheric conditions. The sensor located outside the vacuum region may be attached to the region of the pedestal 135 at a radius that is at least 50% of the maximum radius of the pedestal 135 or exceeds 75% of the maximum radius of the pedestal 135 from the pedestal symmetry axis. Such a sensor may be positioned near, within a few centimeters in some embodiments, a vacuum seal for the support pedestal 135, e.g., an O-ring. In some embodiments, the total radial and axial propagation distance from the edge of the wafer to the sensor may be less than about 25 cm, or less than about 15 cm, or about 10 cm in some embodiments. The specific location and orientation of the sensor according to embodiments of the present disclosure will be discussed in detail below.

[0039] Turning to FIG. 2, a schematic side view of a plasma chamber having high impedance sensors attached at various positions of the electrodes in accordance with an embodiment of the present disclosure is shown. Each of the two components that function as electrodes, namely, the pedestal 235 and the showerhead 230 or other equivalent power supply element, may use separate RF generators 205 or 210 and impedance matching networks 215 and 220. Alternatively, the electrodes may have a plurality of generators and matching networks that supply power thereto. The arrow 245 along the surface of the pedestal 235 indicates the inner radial direction of the flow of RF current and power from the lower (bias) RF generator 210 electrically connected to the pedestal 235 via the impedance matching network 220. The generated electric field contributes to the formation of a plasma (not shown) between the electrodes and to the external radial backflow of current and power indicated by the arrow 250 along the lower surface of the showerhead 235 or other power element, and ultimately contributes to the selective ground circuit of the impedance matching network 215 for the showerhead 230 or other power element.

[0040] In certain embodiments, the reaction chamber 240 having RF power from the first RF generator 205, the second RF generator 210, and the impedance matching networks 215, 220 may have sensors 255 at the periphery of a pedestal 235 that may be covered by a dielectric 260. The communication line 265 may transmit signals from each of the sensors 255, which may be substantially equidistant from the pedestal symmetry axis in some embodiments, to a Fourier analysis circuit (not shown) that calculates the amplitudes and phases of both the fundamental frequency surface wave and the harmonic frequency surface wave acquired by each sensor 255.

[0041] In some implementations, the Fourier analysis circuit may calculate the magnitudes and phases of the fundamental and higher order harmonics of the periodic electromagnetic surface waveform. The resulting magnitudes and their phases, known as a series of Fourier series, result from the relationship between a function in the time domain and a function in the frequency domain.

[0042] Furthermore, some embodiments of the disclosed matching network 220 may have a signal analysis section 275 or appendage of the matching network 220 that is separated from the RF power processing and impedance matching circuits or components of the matching network 220 and is decoupled from the RF. The signal analysis section 275 may have (one or more) Fourier analysis circuits (detectors) for analyzing sensor signals and providing the digital amplitude and phase of the RF fundamental and harmonics. The signal analysis section 275 may analyze the relative magnitude and phase of the signals at the harmonic frequencies and derive quantitative parameters that characterize the relative magnitude and relative phase of the axisymmetric and non-axisymmetric harmonic components at each frequency. Further, in some embodiments, the disclosed matching network 220 may be connected via a very high speed network not only to the second RF generator 210 but also to a controller (not shown) for the reaction chamber 240 or the RF plasma processing system 200 in which the sensor 255 is disposed. In some embodiments, the disclosed enhanced impedance matching network 220 may be capable of transmitting commands to the first RF generator 205 and transmitting the calculated parameters to the process chamber controller and / or the tool control system.

[0043] Furthermore, another first RF generator 205 and an impedance matching network 215 may be electrically coupled to another electrode that may be the showerhead 230 of the reaction chamber 240. In one embodiment, the first RF generator 205 may operate at a frequency different from that of the second RF generator 210, and that frequency may not be an integer multiple of the frequency of the second RF generator 210.

[0044] Similarly, the impedance matching network 215 may monitor the reflected wave power from the electrodes and the processing chamber 240 and make adjustments if there is significant reflected wave power from the electrodes. In some embodiments, the second RF generator 210 may be a 400KHz RF generator, a 2MHz RF generator, a 13.56MHz RF generator, etc., while the first RF generator 205 may operate at a somewhat higher frequency. In some embodiments, the first RF generator 205 may operate at a frequency greater than 25MHz, such as 60MHz, 100MHz or higher.

[0045] In one embodiment, the main function of the first RF generator 205 is to generate reactive species such as fluorine, chlorine and their compositions and accelerate the ions from the generated plasma to collide with the wafer placed on the pedestal 235. This may be achieved by powering the reaction chamber 240 to generate plasma between another power source such as the showerhead 230 or the electrode and the pedestal 235.

[0046] A set of sensors 280 having a bandwidth greater than about 10 times the frequency of the highest frequency RF generator connected to the electrode may be disposed on the lower electrode surface, i.e., the upper electrode facing the pedestal 235, i.e., the showerhead 230. In some embodiments, each of these may have an impedance greater than about 100Ω, and in some embodiments, an impedance greater than 500Ω. The sensor 280 may be a voltage sensor or a current sensor, or may combine both capabilities in a single package. For example, the current sensor may have one or more segments of wire that may be covered by an electrostatic shield.

[0047] In some embodiments, sensor 280 has an electrical connection to the Fourier analysis circuit in the signal analysis section 285 of impedance matching network 215. The Fourier analysis circuit may output the amplitudes and phases of different frequency components from each of sensors 280 and compare the amplitudes and phases of the frequency components of other sensors 280 and / or with a reference level stored in memory. The analysis of signals in some embodiments may include artificial intelligence (AI) that employs a learning algorithm that may use pattern recognition of amplitude or phase or both, or a neural network, or a conventional digital algorithm process of the signals from sensors 280.

[0048] Signal processing by a Fourier analysis circuit to find fundamental wave component signals and harmonic component signals of both amplitude and phase may be performed in less than about 10 microseconds for each of the sensor signals and, in a preferred embodiment, in less than 1 microsecond. The separate signal analysis section 285 of impedance matching network 215 may incorporate at least one computing or logic processor having substantial computing power by a very high speed (<1 ns cycle time) circuit employing very high speed logic ICs. In some embodiments, the processor of signal analysis section 285 is programmable such that a dedicated algorithm or analysis software of a computing “platform” provided by the provider or user of processing chamber 240 to impedance matching network 215 can be provided or implemented.

[0049] In some embodiments, the software program for calculating parameters from signal amplitude and phase and the separate logic algorithm for determining the impact on process uniformity of deviations from acceptable plasma conditions may reside in a removable "plugin" component having data storage and connected to the signal processing section. This software or logic calculates the degree of deviation of the RF electromagnetic surface wave spectrum from the nominal operating conditions or characteristics of the appropriate operating conditions. Based on this, the processor associated with the controller can "decide" on a corrective action or end of the process within about 1 millisecond before the wafer is mishandled. In some embodiments, a quantitative determination regarding the expected impact of the deviation on process uniformity or other characteristics may be made within about 500 microseconds from occurrence so that the corrective action can be initiated within 1 millisecond. Further, measures may be taken to avoid loss of wafer or substrate yield in order to minimize or eliminate damage to the wafer or substrate being processed in the reaction chamber 240 at that time.

[0050] In some embodiments, the evaluation and / or determination performed in the signal analysis section 285 of the impedance matching network 215 may be performed by an ultra-high-speed computing or analysis system using algorithms residing in a plugin storage and / or removable data processing device. In yet another embodiment, the evaluation determination performed in the signal analysis section 285 may be performed using an analog or neural net type processor. Such determination may further use a decision algorithm that may reside in a removable storage device or processing device. Thereafter, an instruction for a corrective action may be promptly transmitted from section 275 of the impedance matching network 215 to the RF generator 205 via a high-speed data line to temporarily interrupt, change, or terminate the power or RF frequency to the plasma. This ensures that the factory manager can promptly take or plan for a corrective action for the processing chamber 240 and the RF plasma processing system 200.

[0051] Also, FIG. 2 shows a set of sensors 290, which are configured on the outer surface of the pedestal 295 of the showerhead 230 outside the vacuum region within the reaction chamber 240 under atmospheric conditions. In some embodiments, additional sensors 296 may be attached to the pedestal base 297 and connected to the disclosed signal processing section 275 of the impedance matching network 220 with a high-speed signal cable in the same manner as the sensors 290. The sensors 296 located outside the vacuum environment of the reaction chamber 240 are significantly less expensive as they do not require a vacuum feed and are not difficult to integrate into the information and processing network.

[0052] The sensor 255 may be arranged in several configurations to detect the voltage and / or current on the surface of the pedestal 235, and may be covered by the dielectric cover 260 and protected from the plasma. Sensors of this type and location are close to the wafer and / or substrate, and thus can have an advantage in sensitivity when detecting specific modes of EM surface waves that exhibit plasma asymmetry, which is an important type of plasma non-uniformity. These in-chamber sensors 255 may use a communication line passing through the vacuum wall via a feedthrough or a wireless communication link operating at optical frequencies or low frequencies in some embodiments.

[0053] In general, the phase and amplitude patterns of the EM surface waves at each frequency on the surfaces of the showerhead 230 and the pedestal 235 may be determined by analyzing the signals from any of the 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 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 from all the waves at that frequency generated from all the points on the entire electrode surface. In the case of an axially symmetric electrode surface where power is supplied symmetrically and the plasma is axially symmetric, the axially symmetric surface wave mode results from the superposition of waves from all parts of the electrode and other surfaces of the reaction chamber 240. Generally, a completely symmetric plasma in a symmetric chamber with a symmetric electrode centered on the axis of symmetry of the chamber mainly has symmetric lines of equal phase and amplitude in the form of a circle centered on the center of the pedestal 235.

[0054] Turning to FIG. 3, a cross-sectional view of a dual-plate electrode assembly having a broadband sensor that supplies a voltage signal to the periphery of the electrode and to electrical ground via an electrical connector having a low shunt capacitance according to an embodiment of the present disclosure is shown. In some embodiments, an electrode, such as showerhead 330, may have two conductive plates 331, 332 that are centered and configured substantially parallel to each other and have a shape substantially the same as the substrate or wafer. The surface of the first plate 331 facing away from the second plate 332 may be exposed to a vacuum environment and plasma. The first plate 331 is spaced apart from the second plate 332 by a distance that is the length of the dielectric standoff support 333. The first plate 331 may have an embedded sensor 334 whose pack or pickup is a conductive material and whose surface is on a plane substantially the same as the surface of the first plate 331 facing away from the second plate 332.

[0055] In some embodiments, sensor 334 may be attached to a first plate 331 surrounded by a dielectric 336 having a low dielectric constant, such as quartz or other suitable material. In some embodiments, dielectric 336 may have a dielectric constant of less than 5, and in some embodiments, the dielectric constant may be less than 2 for an inorganic material such as a silica-based aerogel. Sensor 334 may have a high bandwidth extending from 100 KHz to at least 10 times the highest drive frequency connected to the chamber, the high bandwidth may be 300 MHz or more, and it may be possible to detect surface voltage, surface current, or both. The sensitivity of sensor 334 in some embodiments may vary by less than 30% over the frequency range of the harmonics of the main fundamental RF frequency used in the reaction chamber. In some embodiments, at least one lead wire 337 from each sensor is connected to an inner conductor 338 of a vacuum electrical signal feedthrough 339 having a base 341 attached to an electrically grounded second plate 215. In some embodiments, the lead wires from each sensor may be directly connected to a circuit board in a similar position to 332 having one detection circuit for each ground plane and each sensor to determine the amplitude and phase for each frequency component.

[0056] The internal conductor 338 of the feedthrough 339 is attached to the base 341 of the feedthrough 339 mounted on the grounded second plate 332 such that the total shunt capacitance from the sensor 334 + lead 337 + feedthrough 339 to ground is less than 5 pf and in some embodiments less than 3 pf, and may have a small shunt capacitance, for example, 5 picofarads (pf, less than 2 pf in some embodiments). In some embodiments, the output from the base 341 mounted on the grounded second plate 332 may be connected to an attenuator (not shown). In some embodiments, the attenuator may have an electrical resistor with a resistance value greater than about 100 Ω. A shunt resistor to ground 405 may be present in parallel with the electrical resistor 404. The resistance of the shunt resistor may be, for example, 50 Ω, or alternatively, may be equal to the impedance of the cable connecting the attenuator to the controller of the communication network or plasma chamber. When a detector is placed instead of the connector as shown in FIG. 3, the signal output from the detector, which is the voltage or current amplitude and phase at each frequency of the sensor, may be transmitted to an analysis processor in a section of the matching network.

[0057] Each sensor 334 may measure the voltage or current amplitude of the coupled electromagnetic surface wave mode having the fundamental frequency and harmonic frequencies of all RF generators supplying power to the plasma. The range of the fundamental frequency and harmonic frequencies is from about 10 KHz to about 500 MHz or more of the same order. In other embodiments, the sensor may measure the voltage at fundamental and harmonic frequencies in the range from about 100 KHz to about 1 GHz.

[0058] FIG. 4 is a cross-sectional view of a pedestal in which a broadband voltage sensor according to an embodiment of the present disclosure is embedded. The voltage sensor 401 may be attached to an electrode such as the pedestal 400. In some embodiments, the sensor 401 may be connected to an electrical ground 406 via a resistor. The tip or pack of the sensor 401 may have a lead wire 402 surrounded by a dielectric 403 (which may optionally be air or vacuum). In some embodiments, the lead wire 402 from the sensor 401 may pass through an attenuator such as a resistor(s) 404 having a shunt resistor 405 that is in some embodiments about 50 Ω and may be connected to the electrical ground 406. Such a resistor 404 may be non-inductive and may have a resistance in the range between about 100 Ω and about 100,000 Ω. In some embodiments, the resistance may be between about 500 Ω and about 10,000 Ω. The resistor 405 may be non-inductive.

[0059] Furthermore, the dielectric 403 is generally non-magnetic and has a low loss tangent that is less than about 0.01 in some embodiments or less than about 0.001 in other embodiments. The shunt capacitance between the tip of the sensor 401 and the lead wire 402 to the ground electrode is less than about 5 pf, or in some embodiments less than about 2 pf, such that the reactance between the sensor 401 and the electrode of the pedestal 400 is greater than about 100 Ω at 300 MHz. The purpose of such a low shunt capacitance is to minimize the absorption of wave energy and reduce the loading of surface waves by the sensor 401 such that the wave propagates as it would in the absence of the sensor 401. Under such conditions, the detected surface potential does not differ significantly from the potential at the electrode without such a sensor 401.

[0060] Turning to FIG. 5, a schematic side view of a pedestal having associated RF and control components according to an embodiment of the present disclosure is shown. The power supply circuit of pedestal 501 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 a section that may be within or attached to impedance matching network 506 in some embodiments. The high-speed line 513 of the data network captures information from the impedance matching network 506 to the (one or more) controllers 514 of the reaction chamber or generator or to a tool or factory (not shown). Sensors 502, 503 are mounted on or near base 504 of pedestal 501, which may be inside or outside the vacuum region of the reaction chamber.

[0061] In some embodiments, there may be a signal analysis section associated with impedance matching network 506, such as a fault detection section 510. The signal analysis section 510 may be electrically and / or RF-isolated from specific components such as the vacuum capacitors and high-voltage electronics of the impedance matching network 506. The signal analysis section 510 receives signals from sensors 502, 503 via cables 511, 112. The signal analysis section 510 directs the signals to an internal circuit that may include electronic components such as transistors and passive components, also referred to as detectors, from each sensor 502, 503. In an alternative embodiment where the amplitude and phase are found directly adjacent to the sensor for each frequency component, the signals arriving at the signal analysis section may be the amplitude and phase for each frequency component rather than the raw signals.

[0062] Each detector (not shown) within the partition 510 may perform RF spectral analysis of signals from one sensor 502, 503 or from a group of sensors analyzed in parallel. The analysis may include temporally averaging the signals of the group of sensors or the signals of one or more sensors 502, 503 for noise reduction. In some embodiments, there may be outputs from each detector for the signals acquired by each sensor 502, 503, for example, the amplitude and phase for each frequency component of the fundamental wave and harmonics. The outputs from each detector may be input to an analog-to-digital converter for each harmonic signal to produce digitized values for both the measured amplitude and phase of each harmonic.

[0063] These digital amplitude and phase values for each frequency component and each sensor may be input to a high-speed digital processor in a signal analysis section associated with the disclosed impedance matching network with little delay, for example, in less than 10 microseconds. The digital processor may analyze information on both the amplitude and phase of the fundamental wave and each harmonic from the sensor and determine the relative magnitudes of various surface wave modes including axisymmetric and non-axisymmetric modes for both the fundamental wave and harmonics. There may be various non-axisymmetric modes for each frequency component, and one or more of them may be indicators of plasma non-uniformity.

[0064] In some embodiments, such non-axisymmetric modes may be quickly identified by an algorithm present in the plug-in. A reference database correlating the size of the non-axisymmetric mode with the plasma non-uniformity % may also be present in this plug-in or a removable processor. The digital processor may calculate the rate of change of the amplitude of the wave mode and the rate of increase of the amplitude of one or more wave modes to determine the likelihood of a near-future malfunction. One indicator of the size of the non-axisymmetric mode at a given frequency may be the phase difference of the surface wave at a given frequency at various sensor positions having the same radial distance from the center of the circular electrode symmetrically disposed in the axisymmetric chamber. Alternatively, a second indicator of the non-axisymmetric mode may be the difference between the amplitudes of the surface wave at a given frequency at various sensor positions having the same radial distance from the center of the circular electrode symmetrically disposed in the axisymmetric chamber.

[0065] The coherent network 506 having an insulating compartment 510 including a multi-channel detector system (not shown) can perform simultaneous Fourier analysis, digitization, and recording of the voltage amplitude and phase of the EM waves propagating at various positions of the pedestal 501. Due to the inherent noise, each of the determined voltage amplitudes and phases may be averaged over a short time interval, if necessary, averaged over the group of sensors 502, 503 to make a determination of the relative magnitude or averaged temporally over a relatively large number of pulses.

[0066] Other power supply elements such as a showerhead, pedestal, or electrode equipped with a group or array of sensors may be used as a test system to generate data characterizing and recording the relationship between the spectrum and spatial pattern of the EM wave modes during the RF process and the various non-uniformities of the plasma density. In some embodiments, these data may be analyzed offline by an engineer to characterize and classify the behavior of the plasma and stored in a database that may be placed in a plug-in storage device that may be connected to the coherent network compartment or other controller or monitoring system.

[0067] The relationship between the amplitude and phase pattern characteristics of non-axisymmetric EM modes and axisymmetric EM modes and the non-uniformity of the process and plasma or deviations from proper conditions may be stored in a plugin that connects to the disclosed signal analysis section of the matching network. In an implementation where the RF plasma processing system may be used as a production tool, plasma and process non-uniformities may be quickly detected when the operation of the chamber is being monitored thereby. For example, a sensor of the disclosed type shown in FIG. 4 configured as shown in FIG. 2 may be incorporated into the RF plasma system as shown in FIG. 1.

[0068] To determine whether the process plasma may have experienced a plasma fault condition, the analysis processor of the signal analysis section associated with the impedance matching network may calculate a parameter based in part on the magnitude of the non-axisymmetric EM mode for each of a predefined series of harmonics of the drive frequency of several electrodes or antennas. The processor in some embodiments may compare these parameters to a reference range in a database. Such a reference database may be present in a plugin connected to the signal analysis section which may be a section of the impedance matching network or a section associated therewith.

[0069] The database may store parameters characterizing various plasma conditions to help determine how severe a deviation of the plasma from an acceptable "process window" is. In some embodiments, the analysis may include a comparison of the phases of each harmonic from all sensors or a group thereof at a given distance from the center of the electrode. Such a change in phase for a sensor or group of sensors for any orientation may be a measure of the asymmetry of the generation and / or propagation of that harmonic mode and, thus, may be a measure of the asymmetry and non-uniformity of the plasma. In some embodiments, the analysis may include calculating the difference in amplitude between sensors or groups of sensors at a given distance from the axis of symmetry. Such a change in amplitude for adjacent sensors or groups of sensors over a range of orientations may be a measure of the asymmetry of the generation and / or propagation of that harmonic mode and, thus, may be a measure of the asymmetry and non-uniformity of the plasma.

[0070] A quantitative measure of asymmetry, a parameter, for each of a set of harmonics may be stored in a plug-in unit and transmitted to the chamber and tool controller via a data network. Further, trends and rates of increase in the parameters may be calculated as part of a process for determining whether a fault condition occurs and compared to reference values and criteria in the database. In some embodiments, when such a fault condition occurs, algorithms and criteria that may be stored in the plug-in may be executed in a processor present in the section to determine a course of corrective or preventive action. Such actions may be transmitted quickly to the RF generator and / or the chamber and / or the tool controller.

[0071] In some embodiments, all such databases of parameters, algorithms, criteria, and specifications for comparing parameters, rates of change of parameters, and rates of increase of parameters may be in a data storage device or removable processor that may be connected to ports that may be input / output ports of the signal analysis section. Analysis of surface wave modes based on signals from sensors and the parameters obtained therefrom may be performed very quickly by a processor, and any fault declarations and improvement measure commands may be sent to the RF generator and reported to the controller for the chamber or system via the network within 5 milliseconds from generation. In some embodiments, the fault condition and the specified improvement measure command may be sent to the generator within 1 millisecond.

[0072] In some embodiments, deviations of many types of plasmas from the desired plasma uniformity may be detected quickly enough so that the tool or chamber controller can take measures to correct the plasma fault condition before the wafer or substrate is mishandled. In some situations, the specified improvement measure may be in the form of RF power, for example, the continuous wave (CW) or the pulse is changed in a short time or the power is completely turned off in a short time, or the processing of the current wafer is stopped and the wafer is saved for later processing or disposal, or the reaction chamber may be powered off for maintenance. Therefore, the reflected wave power may be changed by adjusting the frequency within a range of about ±10% of the RF power.

[0073] In certain embodiments, upon detection of a plasma fault condition, the disclosed signal analysis section related to the matching network may command appropriate corrective actions to be performed by the RF generator and / or in some embodiments by the matching network. For example, the RF process generator may initiate an end process to terminate the processing of the wafer in response to signals measured by sensors of the showerhead and / or pedestal. In a specific embodiment, the frequency may be adjusted within a range from about one tenth to 10%, i.e., it may be increased or decreased. Alternatively, the power, e.g., the pulse power mechanism, may be interrupted by the RF plasma processing deposition system to stop or pulse the plasma such that the secondary plasma stops or significantly decreases. In some embodiments, after a very short interruption, the specified remedial action may provide that the process can then continue. In certain embodiments, the remedial action may be determined, for example, through machine learning based on yield data or other wafer diagnostics and / or a programmed remedial program.

[0074] Turning to FIG. 6, there is shown a top view of the propagation of an axisymmetric surface wave across the entire pedestal where the plasma in the reaction chamber according to an embodiment of the present disclosure is axisymmetric. In FIG. 6, circle 601 is a curve with constant phase and amplitude for the fundamental frequency component and harmonic frequency components of the axisymmetric surface wave mode. The circle is concentric with the electrode. These modes are very dominant when the chamber, the electrode, and the plasma are all axisymmetric and coaxial. The propagation vector 602 of the surface wave at any frequency is radial. The wave propagates towards the center and away from the center, and as the wave propagates, such a wave injects power into the plasma.

[0075] Turning to FIG. 7, there is shown a top view of the lateral electromagnetic surface wave propagation across the electrodes according to an embodiment of the present disclosure. In FIG. 7, lines 701, 704 of constant phase and equal amplitude for a particular single non-axisymmetric mode are substantially straight and parallel regardless of the fundamental frequency or its harmonics. Such surface waves may be detected by sensors disposed on the pedestal or showerhead of an RF plasma deposition apparatus. This mode may be referred to as "lateral" in that, as seen by propagation vectors 705, 707, the propagation direction is from one side to the other across the entire electrode surface or both from the central plane to the left and right sides. There may also be other non-axisymmetric modes in which the lines of constant phase are curves having a center of curvature displaced from the center of the electrode. The measured values of the detectors at each frequency can be decomposed into a sum of the axisymmetric mode and the (often few) non-axisymmetric modes that reflect the main inhomogeneities of the plasma. Typically, the decomposition enables the identification of lateral mode components and / or one main "off-center" or displaced radial mode, either of which is characteristic of the configuration of the plasma inhomogeneities. The correlation between the configuration of the plasma inhomogeneities and the particular non-axisymmetric modes is performed prior to the production process as part of the construction of a database that may exist in a plug-in unit or elsewhere.

[0076] Turning to FIG. 8, there is shown a top view of one exemplary azimuth sensor arrangement for a reaction chamber according to an embodiment of the present disclosure. In this embodiment, a plurality of sensors 800 may be azimuthally disposed around one or more components of the reaction chamber and / or on the reaction chamber itself. As briefly described above, in this embodiment, a plurality of sensors 800, which may be four, may be disposed at various angles about the chamber symmetry axis 805 on particular chamber components such as the showerhead and / or pedestal to measure the surface voltage or current associated with the surface wave. In this case, the intervals are 90 degrees, although in some embodiments, the intervals may be irregular in azimuth.

[0077] The sensor 800 may include a passive sensor 800 that acquires a changing electric potential or magnetic field. The sensor 800 may be arranged in various orientations to detect EM waves having various types of propagation modes with respect to the chamber symmetry axis 805. The sensor 800 may be arranged at equidistant positions around the chamber symmetry axis 805 and / or components of the reaction chamber or the reaction chamber itself. Similarly, the sensors 800 may be arranged diametrically opposite to each other such that the distance between the sensor 800 and the symmetry axis is substantially the same. For example, the distance between sensors 800-1 and 800-2 is substantially the same as the distance between 800-3 and 800-4. Similarly, each sensor 800 is arranged at the same distance from the chamber symmetry axis 805. Examples of the spacing and position of the sensors 800 are discussed in more detail below.

[0078] As shown, the sensors 800 are arranged at diametrically opposed positions. For example, sensor 800-1 is diametrically opposed to sensor 800-3, while sensor 800-2 is diametrically opposed to sensor 800-4. The sensors 800 may find differences in waveforms on different sides of the reaction chamber and / or its components for non-axisymmetric plasmas, and as described above, provide a notification so that corrective or preventive measures can be taken when such waveform differences occur. For example, if sensors 800-1 and 800-4 detect and report a waveform difference from diametrically opposed positions, such a difference provides an indication that the harmonics are out of phase or have different amplitudes, thereby indicating the presence of plasma non-uniformity and asymmetry. Such waveform differences occur when there is a difference in the relative phase or amplitude of one or more harmonics of the signals acquired by detectors diametrically opposed.

[0079] In certain embodiments, as shown in FIG. 8, four sensors 800 may be used. However, in other embodiments, a different number of sensors 800, such as 6, 8, 12, 14, 16, 18, 20 or more sensors 800, may be used. In some embodiments, the azimuth angles between the sensors may not be equal, and nevertheless, the same characteristics of the non-azimuth symmetric plasma mode can be observed by the sensors. In certain embodiments, it may be beneficial to have a number of sensors 800 between 6 and 12. As the number of sensors 800 increases, more data can be collected, thereby enhancing the discrimination ability against noise and the sensitivity for the recognition of non-uniformity. However, increasing the number of sensors 800 may slow down data processing, and thereby, improvements and preventive measures may occur even more slowly. Those skilled in the art will understand that it is possible to optimize the RF plasma process by balancing the number of sensors 800 and the desired level of data granularity. Therefore, it is beneficial to increase the number of sensors 800 as the computing power increases and the speed at which data can be processed increases. In certain embodiments, specific sensors 800 may be selectively turned off and on, thereby enabling the controller to access specific desired data. For example, in a system having a number of 8 sensors, four of the sensors may be selected and turned off, thereby reducing the amount of data generated. In other embodiments, additional sensors may be added or removed from operation, thereby changing the amount of data generated.

[0080] The sensor 800 may include various types of sensors, both circular and other geometric shapes. In certain embodiments, the sensor 800 may be circular with an area between about 0.1 cm 2 and about 10 cm 2 The sensor 800 may further include a surface insulator layer or coating for protecting the sensor 800 from the plasma or reactive species in the reaction chamber, and may include any other coatings and layers such as a Faraday shield for a current sensor, an aluminum coating, etc.

[0081] Turning to FIG. 9, a vertical cross-sectional view of a sensor azimuthally attached to a reaction chamber according to an embodiment of the present disclosure is shown. In this embodiment, the reaction chamber 940 has a symmetry axis 905 that extends longitudinally from the center of the showerhead 930 through the pedestal 935. In other embodiments, the symmetry axis 905 may extend longitudinally from the center of another electrode, such as an antenna. A plurality of sensors 900 may be arranged azimuthally around and within the reaction chamber 940 and around or in relation to certain components such as the showerhead 930 and / or the pedestal 935 at various positions. Since FIG. 9 is a cross-section, only two sensors 900 are shown for each location, but as discussed in detail with respect to FIG. 8, more sensors 900 may be used during the implementation of the RF plasma monitoring process.

[0082] In certain embodiments, the sensor 900-1 may be arranged around the edge or periphery of the showerhead 930. In such an embodiment, the sensor 900-1 may be arranged 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, thereby protecting the sensor 900-1 from the environment within the reaction chamber 940. In such embodiments, two or more sensors 900-1 may be arranged azimuthally around the edge of the showerhead 930, preferably four or more sensors, thereby enabling the detection of non-uniformities and asymmetries in the RF plasma treatment.

[0083] In other embodiments, sensor 900-2 may be disposed along the edge of pedestal 935 within the vacuum of reaction chamber 940. As described above with respect to sensor 900-1, sensor 900-2 may be partially or fully embedded in pedestal 935, and sensor 900-2 may or may not include an insulating layer disposed on its outer surface. Further, in some embodiments, sensor 900-2 may have a dielectric protection portion that covers sensor 900-2. In addition to sensor 900-2 disposed around pedestal 935 within the vacuum, other sensors 900-3 and 900-4 may be disposed around pedestal 935 outside the vacuum of reaction chamber 940. Such sensors 900-3 and 900-4 may be disposed on a metal surface along pedestal 935 and / or its base portion. Sensor 900 may be disposed on pedestal 935 or other support structure associated therewith.

[0084] In yet another embodiment, sensor 900-5 may be disposed on the sidewall of reaction chamber 940 and / or incorporated in other ways. In such embodiments where the wall is dielectric, sensor 900-5 may be disposed on chamber outer wall 915 outside reaction chamber 940 or incorporated into the sidewall such that sensor 900-5 is within the vacuum of reaction chamber 940. In the case of a metal wall, the sensor needs to expose a pickup on the inner surface of the wall so that the EM field inside the chamber can be detected. Other sensors 900-6 may be disposed in viewing window 920 disposed along outer chamber wall 915. In such embodiments, the viewing window sensor 900-6 may be located outside the vacuum of reaction chamber 940 or inside reaction chamber 940.

[0085] In yet another embodiment, the sensor 900-7 may be disposed, for example, in a dielectric located around the showerhead 930, while in other embodiments, the sensor 900-7 may be disposed in a dielectric located around the pedestal 935. Although specific locations of the sensor 900 are discussed herein, the sensor 900 may be disposed at various other locations within and around the reaction chamber 940. For example, the sensor 900 may be disposed inside or outside a dielectric wall near an antenna or other component. The sensor 900 may be disposed at various other locations inside the metal wall of the reaction chamber 940.

[0086] In certain embodiments, a combination of sensors 900-1 through 900-7 may be used to more accurately monitor the RF plasma process. For example, the sensor 900-1 around the edge of the showerhead 930 may be combined with the sensor 900-2 around the edge of the pedestal 935. Similarly, a combination of sensors 900-5 outside the reaction chamber 940 may be combined with sensors 900-1 / 900-2 located within the reaction chamber 940. In yet another embodiment, combinations of 3, 4, 5, 6, 7 or more variations of the positions of the sensors 900 may be used to further optimize the monitoring of the RF plasma process.

[0087] Turning to FIG. 10, a vertical cross-section of a model reaction chamber according to an embodiment of the present disclosure is shown. In this embodiment, exemplary positions of sensors 1000 arranged at a plurality of azimuth angles around a lower electrode, which is the pedestal 1035 in this example, are shown. Similar to the sensor 1000 described above with respect to FIG. 9, FIG. 10 shows sensors 1000 arranged at various positions. The sensor 1000-1 is arranged around the outer edge of the pedestal 1035. The sensor azimuth position shown as 1000-2 is arranged around the inside of the reaction chamber 1040, and the sensor azimuth position 1000-3 is arranged around the outside of the reaction chamber 1040 adjacent to the viewing window.

[0088] In this embodiment, twelve sensors 1000 are shown at each position, but in other embodiments, fewer or more sensors 1000 may be used. Also, in addition to the positions of the sensors 1000 shown explicitly, positions of other sensors 1000 may also be used to further enhance the RF plasma processing.

[0089] Turning to FIG. 11, a vertical schematic cross-sectional view of a reaction chamber according to an embodiment of the present disclosure is shown. In this embodiment, the sensor 1100 is shown to be disposed around the antenna of the inductively coupled plasma source 1105. Accordingly, the sensor 1100 can detect the RF current or voltage from the plasma source disposed within the reaction chamber 1140.

[0090] Turning to FIG. 12, a partial cross-section of an RF plasma processing system according to an embodiment of the present disclosure is shown. In this embodiment, the RF plasma processing system 1200 has a pedestal 1235. The pedestal 1235 has sensors 1240 disposed along the upper outer edge of the pedestal 1235. As described above, the sensors 1240 may be disposed on the upper outer edge, may be embedded within the pedestal 1235, or may be alternately disposed around the outer edge either inside or outside the vacuum of the reaction chamber.

[0091] The RF plasma processing system 1200 also has a circuit 1245 connected to the sensors 1240 via a communication line 1250. When the sensors 1240 receive the detected data from the RF plasma processing system 1200, the data may be transmitted to the circuit 1245 for processing. Since the circuit 1245 is relatively close to the sensors 1240, the time required to transfer the detected data therebetween can be reduced. Accordingly, the initial calculations regarding the electrical characteristics detected by the sensors 1240 may be performed more quickly and then transferred to other components 1255 of the RF plasma processing system 1200. The other components 1255 may have, for example, an RF generator, an impedance matching network, a fault detection section, an operation controller for the reaction chamber, an operation controller for the tool, a plug-in device, a signal analysis section, or other components (s) connected to the RF plasma processing system 1200.

[0092] Either the component 1200, 1255 or other components not shown can be detected by the sensor 1240 and the side of the RF plasma processing system 1200 can be adjusted to correct the faults that are at least partially processed within the circuit 1245. The circuit 1245 may be arranged in a pedestal 1235 outside the vacuum of the reaction chamber in a separated structure to protect the circuit 1245 from the state within the reaction chamber. In other embodiments, the circuit 1245 may be arranged in the base of the pedestal 1235 or other regions adjacent to the pedestal 1235.

[0093] Since FIG. 12 shows a cross-section of the components of the RF plasma processing system 1200, those skilled in the art will understand that the circuit 1245 may be arranged at substantially the same radius at various azimuth angles around the pedestal 1235. Therefore, the independent circuit 1245 may be available for each sensor 1240, or the sensor 1240 may be connected to a centralized circuit 1245 arranged at one or more selected positions around and / or inside the pedestal 1235.

[0094] Turning to FIG. 13, a partial cross-sectional view of an inductively coupled RF plasma processing system according to an embodiment of the present disclosure is shown. The sensor 1340 is shown configured to be close to the inductive antenna 1330 and may be attached to the outside or inside of a dielectric wall (not shown) adjacent to the antenna.

[0095] In certain embodiments, the method of the present application can provide detection of plasma non-uniformity in an RF plasma processing system. The method may include generating plasma in a reaction chamber of a high-frequency plasma processing system and detecting an electrical signal from the plasma in a frequency range from the frequency of the high-frequency power maintaining the plasma to about 10 times that frequency with a plurality of sensors arranged at azimuth angles centered on the chamber symmetry axis of the high-frequency plasma processing system. The electrical signal may have at least one of a voltage and a current generated by an electromagnetic surface wave.

[0096] In operation, the method may further include comparing waveforms of electrical signals acquired from a plasma by a plurality of sensors and determining when plasma non-uniformity has occurred based on a comparison of electrical characteristics of the plasma detected by each of the plurality of sensors. In a particular implementation, comparing may include comparing the amplitudes of at least one radio frequency harmonic picked up by at least two different sensors. In a particular implementation, comparing may include comparing the phases of at least one high frequency harmonic acquired by at least two sensors separated by an azimuth angle of at least 90 degrees about a chamber symmetry axis. In yet another embodiment, it may include determining azimuthal variations of signals from a plurality of sensors that increase over time over a period longer than 10 microseconds.

[0097] Determining may further include performing Fourier analysis on signals from a plurality of sensors at different azimuth angles and comparing at least one change in the amplitude and phase of one or more frequency components for the plurality of sensors to reference values in a plasma control database. Determining that non-uniformity has occurred may be in finding an increase over a time period of at least 100 microseconds, and / or determining may include calculating plasma non-uniformity from azimuthal variations in the amplitude and phase of at least one harmonic of the frequency of the high frequency power maintaining the plasma. An aspect of the present disclosure may further include non-uniformity having variations in plasma density as a function of azimuth about a chamber symmetry axis.

[0098] In operation, aspects of the present disclosure may include a method for detecting plasma non-uniformity in a high-frequency plasma processing system. The method may include generating plasma within a high-frequency plasma processing system. The method may further include using a plurality of broadband high-frequency sensors disposed at azimuthal angles about the chamber symmetry axis of the high-frequency plasma processing system to detect electrical signals from the plasma at a plurality of frequencies that are integer multiples of at least one high-frequency excitation frequency. Certain implementations may include determining plasma asymmetry based on detection of at least one azimuthal variation of a plurality of detected frequency components of the electrical signals.

[0099] In the foregoing description, for purposes of explanation, specific nomenclature has been used to provide a thorough understanding of the present disclosure. However, it will be apparent to those skilled in the art that specific details are not required in order to practice the systems and methods described herein. The foregoing description of specific embodiments is presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the present disclosure to the precise forms described. Obviously, many modifications and variations are possible in light of the above teachings. The examples are shown and described in order to best explain the principles of the present disclosure and the practical applications, to thereby enable others skilled in the art to best utilize the present disclosure and various examples with various modifications as are suited to the particular use contemplated. It is intended that the scope of the present disclosure be defined by the following claims and their equivalents. The invention disclosed in this specification includes the following. [Aspect 1] A system for detecting changes in plasma in a high-frequency plasma processing system, comprising: a reaction chamber having a chamber symmetry axis; one or more plasma power supply devices for supplying high-frequency power to the plasma in the reaction chamber; a plurality of broadband high-frequency sensors arranged at azimuth angles centered on the chamber symmetry axis for detecting electromagnetic signals related to the plasma in the reaction chamber; at least one detector which is a Fourier transform processor connected to at least one of the plurality of broadband high-frequency sensors; a calculation processor connected to the at least one detector; A system comprising. [Aspect 2] The system according to Aspect 1, wherein the plurality of broadband high-frequency sensors are arranged at azimuth angles with three or more intervals centered on the chamber symmetry axis and substantially equidistant from the high-frequency plasma power supply device relative to the chamber symmetry axis. [Aspect 3] The system according to Aspect 1, further comprising one or more high-frequency generators connected to the calculation processor, wherein at least one of the high-frequency generators is adjustable in response to receiving a signal from the calculation processor. [Aspect 4] The system according to Aspect 1, further comprising at least one high-frequency detector configured to supply a digital output to a port connected to at least one of the plurality of broadband high-frequency sensors and also connected to the calculation processor. [Aspect 5] The system according to Aspect 4, wherein the at least one detector is connected to a removable storage medium. [Aspect 6] The system according to Aspect 5, wherein the storage medium includes at least one of instructions, algorithms, and data for generating an output that is the eccentricity of at least one frequency component of the electromagnetic wave. [Aspect 7] A method for detecting plasma non-uniformity in a high-frequency plasma processing system, comprising: generating plasma in a reaction chamber of the high-frequency plasma processing system; detecting electrical signals from the plasma in a frequency range from the frequency of the high-frequency power for maintaining the plasma to about 10 times that frequency with a plurality of sensors arranged at azimuth angles centered on the chamber symmetry axis of the high-frequency plasma processing system; Comparing waveforms of electrical signals acquired from the plasma by the plurality of sensors; Based on a comparison of the electrical characteristics of the plasma detected by each of the plurality of sensors, determining when plasma non-uniformity has occurred; A method comprising the steps of. [Aspect 8] The method according to aspect 7, wherein the comparing comprises comparing the amplitudes of at least one high-frequency harmonic acquired by at least two mutually different sensors. [Aspect 9] The method according to aspect 7, wherein the comparing comprises comparing the phases of at least one high-frequency harmonic acquired by at least two sensors separated by an azimuth angle of at least 90 degrees about the chamber symmetry axis. [Aspect 10] The method according to aspect 7, wherein the non-uniformity comprises a variation in plasma density as a function of azimuth about the chamber symmetry axis. [Aspect 11] The method according to aspect 7, wherein the determining comprises determining an azimuthal variation of signals from the plurality of sensors that increases temporally over a period longer than 10 microseconds. [Aspect 12] The method according to aspect 7, wherein the electrical signal is at least one of a voltage and a current generated by an electromagnetic surface wave. [Aspect 13] The method according to aspect 7, wherein the determining comprises performing a Fourier analysis on signals from the plurality of sensors at different azimuth angles and comparing at least one change in the amplitude and phase of one or more frequency components of the plurality of sensors with a reference value in a plasma control database. [Aspect 14] The method according to aspect 13, wherein determining that non-uniformity has occurred comprises finding an increase over a time period of at least 100 microseconds. [Aspect 15] The method according to aspect 7, wherein the determining comprises calculating plasma non-uniformity from azimuthal changes in the amplitude and phase of at least one harmonic of the frequency of the high-frequency power maintaining the plasma. [Aspect 16] A method for detecting plasma non-uniformity in a high-frequency plasma processing system, comprising: Generating plasma within the high-frequency plasma processing system; Detecting electrical signals from the plasma at a plurality of frequencies that are integer multiples of at least one high-frequency excitation frequency, using a plurality of broadband high-frequency sensors arranged at azimuth angles about the chamber symmetry axis of the high-frequency plasma processing system; Determining the asymmetry of the plasma based on the detection of the azimuthal variation of at least one of the detected frequency components of the electrical signal; A method comprising the above. [Aspect 17] The method according to aspect 16, wherein the determining is performed in about 10 milliseconds or less. [Aspect 18] The method according to aspect 16, wherein the plurality of broadband high-frequency sensors comprise at least four sensors, and at least one sensor is present in each quadrant of the azimuth angle centered on the chamber symmetry axis. [Aspect 19] The method according to aspect 16, wherein the plurality of broadband high-frequency sensors are arranged around the plasma power supply device. [Aspect 20] The method according to aspect 16, wherein the plurality of broadband high-frequency sensors are arranged azimuthally at substantially equal distances from the chamber symmetry axis at substantially equal intervals of the angle centered on the chamber symmetry axis.

Claims

Claim 1 A method for detecting non-uniformity of plasma in a high-frequency plasma processing system, comprising: generating plasma in the high-frequency plasma processing system; detecting electrical signals from the plasma at a plurality of frequencies that are integer multiples of at least one high-frequency excitation frequency, using a plurality of broadband high-frequency sensors arranged at azimuthal angles centered on the chamber symmetry axis of the high-frequency plasma processing system; determining the asymmetry of the plasma based on detection of at least one azimuthal variation of the plurality of detected frequency components of the electrical signals; and a method comprising the steps of: Claim 2 The method according to claim 1, wherein the determining is performed in about 10 milliseconds or less. Claim 3 The method according to claim 1, wherein the plurality of broadband high-frequency sensors comprises at least four sensors, and at least one sensor is present in each quadrant of the azimuthal angle centered on the chamber symmetry axis. Claim 4 The method according to claim 1, wherein the plurality of broadband high-frequency sensors are arranged around the plasma feeding device. Claim 5 The method according to claim 1, wherein the plurality of broadband high-frequency sensors are arranged at azimuthal angles at substantially equal intervals from the chamber symmetry axis and at substantially equal distances from the chamber symmetry axis at substantially equal intervals of the angle centered on the chamber symmetry axis.

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