Sensor for radical measurement

Abstract

The sensor device comprises a quartz crystal microbalance (QCM) and a coating on at least a part of the surface of the QCM, the coating selectively reacts with radicals of the target gas and does not react with stable molecules of the target gas. The QCM is configured such that the resonance frequency of the QCM changes in response to the reaction between the radicals of the target gas and the coating, and the change in the resonance frequency of the QCM correlates with the amount of radicals of the target gas that have reacted with the coating.

Description

Technical Field

[0001]

[0001] This specification relates to gas measurement, and particularly to the measurement of radicals and / or ions in a gas stream.

Background Art

[0002]

[0002] In many processes such as those for forming semiconductors, photovoltaic cells, displays, etc., one or more gases are used for layer deposition, layer etching, substrate cleaning, etc. In some processes, plasma is formed and used during deposition, etching, cleaning, etc. Conventionally, a flow sensor such as a mass flow controller has been used to detect the amount of gas being flowed. However, current sensors cannot measure specific sub-species of gas such as only the amount of radicals in the gas or only the amount of ions in the gas.

[0003]

[0003] In semiconductor processing, radical species are often used in various processing steps within a chamber. For example, radical species such as atomic fluorine can be used in etching and chamber cleaning processes. Radical species can be formed by various processes. One process for generating radical species is to use plasma. For example, a fluorine-containing gas is flowed into a chamber and the compound is decomposed into fluorine elements by plasma. Radical species are highly chemically reactive.

[0004]

[0004] Process control of radical species is difficult. In particular, it is currently impossible to effectively measure the radical species concentration within a processing chamber. This is partly due to the high reactivity of radical species. Radical species react whenever they come into contact with any surface and other compounds. Even if the surface does not react with the radical species, it functions as a place for radicals to recombine with each other, and there is a possibility that the radical species are converted into other unwanted compounds. Thus, existing mass spectrometry measurement tools cannot measure the concentration of radical species. Without the ability to quantitatively measure the radical species concentration in existing semiconductor manufacturing tools, effective process control such as closed-loop control is impossible.

Summary of the Invention

[0005]

[0005] The following is a simplified summary of the present disclosure to provide a basic understanding of some aspects of the present disclosure. This summary is not an extensive overview of the present disclosure. It is not intended to identify fundamental or important elements of the present disclosure, nor to delineate any scope of particular implementations of the present disclosure or any scope of the claims. Its sole purpose is to present some concepts of the present disclosure in a simplified form as a prelude to the more detailed description that follows.

[0006]

[0006] In one aspect of the present disclosure, a sensor device includes a quartz crystal microbalance (QCM) and a coating on at least a portion of the surface of the QCM. The coating selectively reacts with radicals of a target gas and does not react with stable molecules of the target gas. The QCM is configured such that the resonance frequency of the QCM changes in response to the reaction between the radicals of the target gas and the coating, and the change in the resonance frequency of the QCM correlates with the amount of radicals of the target gas that have reacted with the coating.

[0007]

[0007] In one aspect of the present disclosure, a manufacturing system includes a plasma source that generates plasma, a process chamber connected to the plasma source via one or more delivery lines, and a sensor device connected to at least one of the plasma source, the process chamber, or the one or more delivery lines. The sensor device includes a quartz crystal microbalance (QCM) that includes a coating that selectively reacts with radicals of a target gas and does not react with stable molecules of the target gas to measure the amount of radicals of the target gas.

[0008]

[0008] In one aspect of the present disclosure, the method includes receiving a gas stream including one or more gases, the one or more gases including a first plurality of stable molecules of a target gas and a second plurality of radicals of the target gas. The method further includes measuring the second plurality of radicals of the target gas without measuring the first plurality of stable molecules of the target gas, using a quartz crystal microbalance (QCM) including a coating on at least one surface that reacts with the second plurality of radicals of the target gas but not with the first plurality of stable molecules of the target gas.

[0009]

[0009] The present disclosure is shown by way of example and not limitation in the figures of the accompanying drawings.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2A

Figure 2B

Figure 2C

Figure 2D

Figure 2E

Figure 2F

Figure 2G

Figure 2H

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0011]

[0021] Embodiments of the present disclosure relate to a new type of sensor capable of detecting specific species of molecules and / or atoms such as radicals and / or ions of a specific gas. Conventional gas sensors (for example, those of mass flow controllers, etc.) measure the total amount of gas and cannot distinguish specific species of gas molecules and / or atoms. For example, a mass flow controller can measure the total gas flow rate, but cannot measure the amount of any specific type of gas or the amount of a specific molecular species of a specific type of gas. In the embodiments described herein, a sensor device capable of detecting the amount and / or concentration of a specific molecular species of a specific gas is provided. For example, the sensor device described in the embodiments herein can be designed to measure the amount of fluorine radicals, or the amount of hydrogen radicals, or the amount of nitrogen radicals, which could not be detected by the sensor device without using expensive optical devices such as spectroscopic measuring instruments heretofore.

[0012]

[0022] Embodiments include a sensor device that employs a special coating on the surface of a piezoelectric material that vibrates at a measurable resonance frequency. This coating functions as a filter that excludes all molecules other than the radicals of the target gas species. An example of a piezoelectric material that can be used in this way is quartz. For example, embodiments include a quartz crystal microbalance (QCM) with such a special coating applied to one surface of the QCM. The special coating is designed for specific applications and reacts only with selected molecular gas species used in those specific applications. Examples of applications for which the sensor device can be designed include etching processes, plasma deposition processes (e.g., plasma atomic layer deposition), and the like. The coating on the piezoelectric material changes in mass based on the reaction of the coating to the selected molecular gas species (e.g., radicals of a specific molecule). The change in mass of the coating causes a change in the resonance frequency at which the piezoelectric material vibrates. This change in resonance frequency can be measured and used to determine the amount of molecular species that reacted with the coating. Thus, the sensor device can directly measure specific molecular species of a specific gas (e.g., fluorine radicals, hydrogen radicals, etc.). Such direct measurement of radicals enables closed-loop control of the plasma source.

[0013]

[0023] As an example, in a fluorine-based etching process, the etching rate can have a strong correlation with the concentration of fluorine radicals. However, since the concentration of fluorine radicals has not been directly detectable until now, engineers have been inferring the concentration of fluorine radicals based on other known values such as known plasma output, known gas flow rate, etc. By using the sensor device described herein, the amount of fluorine radicals flowing can be directly measured, and this measured value can be used to finely control the amount of radicals output from a plasma source such as a remote plasma source (RPS).

[0014]

[0024] Without the ability to quantitatively measure the concentration of radical species, closed-loop control of the processing environment is impossible. Closed-loop control refers to using a quantitative measurement as a feedback signal to a controller to change the processing conditions in an ongoing process. For example, in the case of measuring radical species, the concentration of the radical species can be measured and the measured value can be compared with a set value. If the measured value is lower than the set value, the processing parameters can be changed to increase the generation rate and output concentration of the radical species, or if the measured value is higher than the set value, the processing parameters can be changed to decrease the concentration of the radical species. Thus, in embodiments, a more stable and reproducible process can be executed. Accordingly, the embodiments disclosed herein include a radical sensor including a piezoelectric oscillator (e.g., a QCM) having a surface coated with a film that reacts with the target radical species of the target gas or molecule but does not react with the stable molecules of the gas or molecule, or the radical or stable species of other gases or molecules flowing with the target gas or molecule. The radical sensor enables closed-loop control of the plasma source.

[0015]

[0025] FIG. 1 is a cross-sectional view of a manufacturing system 100 that executes a plasma-based process in an embodiment. The manufacturing system can include a processing chamber 101 coupled to a plasma source 158 via one or more gas delivery lines 133. The processing chamber 101 can be, for example, a plasma etching reactor, a deposition chamber, etc. The processing chamber can be suitable for an etching process, a deposition process, a chamber cleaning process, a plasma treatment process, or any other type of process typical of semiconductor manufacturing equipment. In embodiments, one or more substrates (e.g., wafers) 144 can be disposed within the processing chamber 101. In embodiments, the processing chamber 101 can be maintained at a pressure suitable for the target process. In certain embodiments, the pressure can be from less than about 1 Torr to about 200 Torr.

[0016]

[0026] The processing chamber 101 and / or the plasma source 158 may be connected to a controller 188 that can control the processing of the plasma source 158 and / or the processing chamber 101 (e.g., by controlling set points, loading strategies, etc.). A radical sensor 135 may be connected to the gas delivery line(s) 133 to detect the concentration of radicals in the gas or plasma delivered by the plasma source 158.

[0017]

[0027] In an embodiment, the manufacturing system 100 may include a radical sensor 135 fluidly coupled to the processing chamber 101 and / or the gas delivery line(s) 133. For example, a valve may be provided along the tube between the processing chamber 101 and the radical sensor 135. In an embodiment, the valve is of a type that does not obstruct the line of sight between the processing chamber 101 and the radical sensor 135. For example, the valve may be an isolation gate valve. The isolation gate valve can enable a binary operating state. That is, the valve can be opened (i.e., 1) or closed (i.e., 0). When the valve is open, the line of sight is not blocked. Alternatively, another type of valve such as a needle valve can be used.

[0018]

[0028] In an embodiment, the radical sensor 135 includes a piezoelectric substrate within a holder. By passing an alternating current through the piezoelectric substrate, the piezoelectric substrate is vibrated at its resonant frequency. One or more surfaces of the piezoelectric substrate are coated with a film that reacts with a narrow range of molecular species. In particular, the film is composed of a material that reacts with the target molecular species of a specific target gas from among the gases used in the process. In one embodiment, the radical sensor includes a QCM having at least one coated surface coated with a film that selectively reacts with radicals of a specific gas. The radical sensor 135 will be described in further detail below with reference to a series of figures.

[0019]

[0029] In an embodiment, the plasma source 158 is a remote plasma source (RPS) that generates plasma at a remote location and delivers the externally generated plasma to the processing chamber 101. Alternatively, the processing chamber 101 may include an integrated plasma source (not shown) capable of generating plasma within the processing chamber. In either case, the radical sensor 135 may be disposed within or connected to the processing chamber 101, rather than being disposed within or connected to the gas delivery line 133 in the embodiment.

[0020]

[0030] The processing chamber 101 includes a substrate support assembly 150 according to some embodiments. The substrate support assembly 150 includes a pack 166 (which may include, for example, an electrostatic chuck (ESC)). The pack 166 may perform a chucking operation such as a vacuum chuck, an electrostatic chuck, etc. The substrate support assembly 150 may further include a base plate, a cooling plate, and / or an insulator plate (not shown).

[0021]

[0031] The processing chamber 100 includes a chamber body 102 and a lid 104 that surround an internal region 106. The chamber body 102 may be manufactured from aluminum, stainless steel, or other suitable materials. The chamber body 102 typically includes a side wall 108 and a bottom 110. For example, an outer liner 116 may be disposed adjacent to the side wall 108 to protect the chamber body 102. The outer liner 116 may be manufactured and / or coated with a plasma or halogen-containing gas resistant material. The outer liner 116 may be manufactured from aluminum oxide or coated with aluminum oxide. The outer liner 116 may be manufactured from yttria, yttrium alloy, their oxides, etc., or coated with them.

[0022]

[0032] An exhaust port 126 that can couple the internal region 106 to a pump system 128 may be defined in the chamber body 102. The pump system 128 may include one or more pumps, valves, lines, manifolds, tanks, etc. used for exhausting and pressure regulating the internal region 106.

[0023]

[0033] The lid 104 may be supported on the side wall 108 of the chamber body 102. The lid 104 may be openable to allow access to the internal region 106. When the lid 104 is closed, it can provide a sealing portion of the processing chamber 100. The plasma source 158 is coupled to the processing chamber 100 and can supply gases and / or plasmas such as process, cleaning, backing, flushing, etc. to the internal region 106 through the gas distribution assembly 130. The gas distribution assembly 130 may be integrated with the lid 104.

[0024]

[0034] Examples of process gases that can be used in the processing chamber 100 include halogen-containing gases such as F2, C2F6, SF6, SiCl4, HBr, NF3, CF4, CHF3, CH2F3, Cl2, and SiF4. Other reactive gases include O2 or N2O. Non-reactive gases such as N2, He, Ar, etc. can be used as flushing gases or carrier gases. The gas distribution assembly 130 (e.g., a showerhead) may include a plurality of apertures 132 on the downstream surface of the gas distribution assembly 130. The apertures 132 can direct the gas flow towards the surface of the substrate 144. In some embodiments, the gas distribution assembly may include a nozzle (not shown) extending through the holding portion of the lid 104. A sealing portion may occur between the nozzle and the lid 104. The gas distribution assembly 130 may be manufactured and / or coated with a ceramic material such as silicon carbide, yttrium oxide, etc. to provide resistance to the processing conditions of the processing chamber 100.

[0025]

[0035] The substrate support assembly 150 is disposed in the internal region 106 of the processing chamber 100 below the gas distribution assembly 130. The substrate support assembly 150 holds the substrate 144 during processing. An inner liner (not shown) may be coated on the periphery of the substrate support assembly 148. The inner liner 118 may share characteristics (such as manufacturing materials, functions, etc.) with the outer liner 116.

[0026]

[0036] The substrate support assembly 150 may include a support pedestal 152, an insulator plate, a base plate, a cooling plate, and a pack 166. The pack 166 may include electrodes 136 for providing one or more functions. The electrodes 136 may include chucking electrodes (for example, for fixing the substrate 144 to the upper surface of the pack 166), heating electrodes, RF electrodes for plasma control, etc.

[0027]

[0037] A protective ring 146 may be disposed on the outer periphery of the pack 166 and on a part of the pack 166. The pack 166 may be coated with a protective layer (not shown). The protective layer 136 may be a ceramic such as Y2O3 (yttria or yttrium oxide), Y4Al2O9 (YAM), Al2O3 (alumina), Y3Al5O 12 (YAG), YAlO3 (YAP), quartz, SiC (silicon carbide), Si3N4 (silicon nitride), sialon, AlN (aluminum nitride), AlON (aluminum oxynitride), TiO2 (titania), ZrO2 (zirconia), TiC (titanium carbide), ZrC (zirconium carbide), TiN (titanium nitride), TiCN (titanium carbonitride), Y2O3-stabilized ZrO2 (YSZ), etc. The protective layer may be a ceramic composite such as YAG dispersed in an alumina matrix, a yttria-zirconia solid solution, a silicon carbide-silicon nitride solid solution, etc. The protective layer may be sapphire or MgAlON.

[0028]

[0038] The pack 166 may further include a plurality of gas passages such as grooves, mesas, and other features that may be formed on the upper surface of the pack 166. The gas passages may be fluidly coupled to the gas source 105. The gas from the gas source 105 can be used as a heat transfer gas or a backside gas and can be used for controlling one or more lift pins of the pack 166. A plurality of gas sources can be used (not shown). The gas passages can provide a gas flow path for a backside gas such as He through holes drilled in the pack 166. The backside gas can be supplied into the gas passages at a controlled pressure to promote heat transfer between the pack 166 and the substrate 144.

[0029]

[0039] The pack 166 may include one or more clamp electrodes. The clamp electrodes can be controlled by the chucking power supply 182. The clamp electrodes may further be coupled to one or more RF power supplies through a matching circuit for maintaining a plasma formed from a process gas and / or other gases in the processing chamber 100. The RF power supply may be capable of generating an RF signal having a frequency from about 50 kilohertz (kHz) to about 3 gigahertz (GHz) and a maximum power of about 10,000 watts. The heating electrodes of the pack 166 may be coupled to the heater power supply 178.

[0030]

[0040] The controller 188 can control one or more parameters and / or setpoints of the plasma source 158 and / or the processing chamber 101. The system controller 188 can be and / or can include a computing device such as a personal computer, a server computer, a programmable logic controller (PLC), a microcontroller, etc. The system controller 188 can include one or more processing devices, which can be a general-purpose processing device such as a microprocessor, a central processing unit, etc. More specifically, the processing device can be a complex instruction set computing (CISC) microprocessor, a reduced instruction set computing (RISC) microprocessor, a very long instruction word (VLIW) microprocessor, or a processor implementing another instruction set, or a processor implementing a combination of instruction sets. The processing device can also be one or more special-purpose processing devices such as an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a digital signal processor (DSP), a network processor, etc. The system controller 188 can include a data storage device (e.g., one or more disk drives and / or solid-state drives), main memory, static memory, a network interface, and / or other components. The system controller 188 can execute instructions for performing any one or more of the methodologies and / or embodiments described herein. The instructions can be stored in a computer-readable storage medium that can include main memory, static memory, secondary storage, and / or the processing device (while the instructions are being executed). In an embodiment, the execution of instructions by the system controller 188 causes the system controller to execute the method of FIG. 4. For example, the system controller 188 can receive measurements from the radical sensor 135 indicating the concentration of a particular species of radicals in the received or generated plasma, and in response to the measured radical concentration, adjust one or more characteristics or settings of the plasma source 158 (e.g., plasma output, etc.). The system controller 188 can also be configured to enable input and display of data, operation commands, etc. by a human operator.

[0031]

[0041] Figures 2A to 2D are diagrams showing embodiments of a sensor for detecting radicals of a target gas species according to embodiments of the present disclosure. Figure 2A is a cross-sectional side view of a radical sensor according to some embodiments. Figure 2B is a rear view of the radical sensor of Figure 2A according to some embodiments. Figure 2C is a front view of the radical sensor of Figure 2A according to some embodiments.

[0032]

[0042] In an embodiment, the radical sensor includes a QCM sensor base. A single piece of solid material of any shape can usually vibrate at a specific resonance frequency. A typical result of increasing the mass of the vibrating unit is a decrease in the resonance frequency of the solid material. This is the basic principle of QCM.

[0033]

[0043] The QCM sensor base may include a thin plate crystal oscillator that vibrates in a thickness-shear mode because it is highly sensitive to mass changes on the crystal. Due to the piezoelectric characteristics of the crystal oscillator, it is possible to vibrate the crystal oscillator and measure its resonance frequency by simple electrical means. In an embodiment, the crystal oscillator is accurately cut at an angle with respect to its crystal axis. In an embodiment, the crystal oscillator is an AT-cut crystal oscillator.

[0034]

[0044] As shown in FIGS. 2A to 2C, the radical sensor 200 includes a crystal oscillator base 215 that can have a flat surface and a convex surface. The flat surface may be the front surface, and the convex surface may be the back surface. The flat surface may be covered by a front electrode 230. The convex surface may be covered by a back electrode including a back electrode edge 225 connected to a back electrode center 220 via one or more electrode bridges 227. With this configuration, it becomes possible to apply an alternating current to the electrodes and / or read from the electrodes without impairing the ability of the crystal 215 to vibrate freely. The sensing surface of the QCM may be a central region of the front surface (e.g., the central region of the front electrode 230). In an embodiment, the sensing surface of the QCM is coated with a film 235 that is sensitive to the reaction with a specific molecular species of the target gas species. The composition of the film 235 may depend on the application for which the radical sensor 200 is used.

[0035]

[0045] In some embodiments, the film 235 is composed of a material that reacts with the radical molecular species of the target gas but does not react with the stable molecular species of the target gas. For example, the material can react with fluorine radicals but cannot react with fluorine-containing stable molecules (e.g., F2, C2F6, SF6, NF3, CF4, CHF3, CH2F3, etc.). Also, this material may not react with other molecules that may be contained in the gas stream (whether these other molecules are radicals or stable molecular species). For example, this material may be able to react with fluorine radicals but may not react with carbon radicals, nitrogen radicals, hydrogen radicals, etc. Alternatively, this material may be able to react only with hydrogen radicals, or only with carbon radicals, or only with some other radical.

[0036]

[0046] In one embodiment where the radical sensor is tuned to detect fluorine radicals, the membrane or coating 235 comprises silicon dioxide (SiO2), tungsten, or tungsten oxide (e.g., tungsten(III) oxide or W2O3) and / or an organic material (such as photoresist). In one embodiment where the radical sensor is tuned to detect fluorine radicals, the membrane or coating 235 comprises a transition metal that reacts selectively with fluorine radicals. In one embodiment where the radical sensor is tuned to detect hydrogen radicals, the membrane or coating 235 comprises a polymer of carbon and hydrogen. An example of a polymer that can be used is polymethyl methacrylate (PMMA). In one embodiment where the radical sensor is tuned to detect nitrogen radicals, the membrane or coating 235 comprises a fluorinated polymer. In embodiments, the target radical reacts with the membrane 235 to form a gas that consumes a portion of the membrane 235. By consuming a portion of the membrane 235, the number of molecules of the membrane 235 decreases, and thus the overall mass of the membrane decreases. This decrease in mass can be detected by the QCM sensor on which the membrane 235 is formed.

[0037]

[0047] In some embodiments, the reaction of the target radical species with the membrane 235 produces a solid byproduct. The solid byproduct adheres to the membrane 235 and thus increases the mass of the membrane 235. This increase in mass can be detected by the QCM sensor on which the membrane 235 is formed.

[0038]

[0048] In some embodiments, the reaction between the target radical species and the film 235 is an absorption process in which the film 235 absorbs the target radical species. The absorption of the radical species increases the mass of the film 235. Once the film 235 is saturated with the target radical species and / or between process runs, a purging or cleaning process can be performed to desorb the radical species from the film 235. As an example, a PMMA coated QCM can be used to detect fluorine radicals. The PMMA can absorb fluorine radicals, and the change in mass of the film caused by the absorption of fluorine radicals can be detected by a change in the resonant frequency of the QCM. The fluorine radicals can then be desorbed by flowing another gas, such as argon, across the radical sensor 200.

[0039]

[0049] In one embodiment, membrane 235 has a thickness of about 1 to 100 microns. In one embodiment, membrane 235 has a thickness of about 30 to 40 microns. Other thicknesses can also be used for membrane 235, such as 10, 20, 30, 40, 50, 60, 70, 80, or 90 microns.

[0040]

[0050] The QCM sensor base, including the quartz crystal 215 and the electrodes 220, 225, 230, measures the areal mass density (mass per unit area) of material that uniformly covers the sensitive area on the sensing quartz crystal. For large loads on the quartz crystal 215, the accuracy depends on knowledge of the shear mode acoustic impedance value of the deposited material. Larger crystals do not necessarily have higher sensitivity. The QCM is not a metrology device since it does not require gravity. The QCM can be used in space with zero gravity. In an embodiment, the thickness measurement t f is the density of the membrane, ρ f By using t f ρ f The thickness can be derived from the areal mass density value, which is equal to . Entering an incorrect density value will result in an incorrect thickness measurement. In an embodiment, the areal mass density measurement is absolute. In an embodiment, no calibration is required for a properly designed QCM. Temperature changes, stress, gas absorption and desorption, surface reactions, etc. can all give erroneous signals.

[0041]

[0051] The QCM can measure the mass on the sensing surface of the QCM according to the formula TIFF2025520024000002.tif15170, and in the above formula, m / A is the mass per unit area, ρ is the density of the material on the sensing surface of the QCM, t is the thickness, n is a constant (≥0), and in the case of linear dependence, n is equal to 1. In an embodiment, the sensitivity of the QCM can be reduced to a better value of 1×10 -9 g / cm 2 or better. For a material with a density ρ = 2.7 g / cm 3 , such as the thickness of Al, the sensitivity of this QCM corresponds to 0.1 Å of Al. The change in thickness represented by the mass per unit area, or areal mass density, is more appropriate in terms of the elementary particle size.

[0042]

[0052] The piezoelectric resonator can be represented by a simple equivalent circuit for electrical analysis, as shown in FIG. 2E. The mechanical behavior of a crystal resonator (e.g., QCM) can be represented by the illustrated electrical equivalent model. This is the so-called Butterworth–Van Dyke (BVD) electrical model of the crystal resonator. In the motional arm (upper branch) of the BVD model, it is composed of three components that determine the series resonance frequency of the crystal vibration plate. R a corresponds to the energy dissipation due to the mechanical coupling between the crystal resonator and its holder. In the case of QCM applications, when a mass load is applied to the crystal resonator surface, R a also increases. L a corresponds to the mass that is displaced during vibration. In the case of QCM applications, the total mass includes the mass of the crystal resonator, electrodes, and deposited thin film materials. C a corresponds to the stored energy of the oscillator related to the elastic properties of the crystal, electrodes, and deposited materials. The parasitic capacitance C0 represents the sum of the capacitances of the crystal resonator electrodes, holder, and connecting cables.

[0043]

[0053] FIG. 2D is a cross-sectional side view of the radical sensor of FIG. 2A with a charged grid or grid added, according to some embodiments. The radical sensor 200 shown in FIGS. 2A-2C in the embodiments measures all radicals regardless of charge. In some embodiments, it may be advantageous to measure only neutral radicals or only radicals having a specific charge. To measure only the neutral radicals of a particular molecular species, a charged grid or grid 252 can be placed in front of the front surface of the radical sensor 200. The charged grid or grid 252 can include a stack of meshes (e.g., wire meshes) having a specific charge. In one embodiment, as shown, the first grid or mesh may be positively charged, the second grid or mesh may be grounded, and the third grid or mesh may be negatively charged. The positively charged mesh or grid can repel positively charged molecules or ions, and the negatively charged mesh or grid can repel negatively charged molecules or ions. As a result, the molecules reaching the membrane 235 can be only neutral molecules. Of the neutral molecules reaching the membrane 235, only the radicals of a particular gas species can actually react with the membrane 235.

[0044]

[0054] In one embodiment, a pair of radical sensors can be used to measure the amount of positively and / or negatively charged radicals. The first radical sensor may include a charged grid or lattice, and the second radical sensor may not include a charged grid or lattice. All radicals of the target gas species can be detected by the second radical sensor, and only neutral radicals of the target gas species can be detected by the first radical sensor. Thereafter, the difference between the measured values of the two radical sensors can be calculated to determine the amount of radicals attributable to charged radicals among the radicals detected by the second radical sensor. The grid can be modified to filter only positively charged molecules / ions or to filter only negatively charged molecules. Thus, by combining two or more radical sensors, each having a different grid configuration (e.g., one without any grid), the amount of positively charged radicals can be detected, the amount of negatively charged radicals can be detected, and / or the amount of neutral radicals can be detected.

[0045]

[0055] FIG. 2F is an enlarged view showing an example of a radical sensor included in a sensor holder. As shown, the cover compresses a crystal oscillator (e.g., having the form shown in FIGS. 2A - 2D and having a coating that reacts only with specific radical species on the sensing surface) against a spring contact. The aperture exposes the sensing surface including the coating. Many other differently configured sensor holders, such as those shown in FIGS. 2G and 2H, can also be used.

[0046]

[0056] FIG. 3 is a flow diagram of one embodiment of a method 300 for manufacturing a radical sensor. In block 305 of method 300, a coating is formed on the sensing surface of a QCM or other piezoelectric substrate. The coating can be composed of a material that selectively reacts with radicals of the target gas species, but does not react with stable molecules of a specific gas species, nor with stable molecules or radicals of other gas species used with the target gas species. The sensing surface can be coated by first placing a hard mask or a soft mask on the surface of the QCM or other piezoelectric substrate. Thereafter, the exposed regions of the surface of the QCM or other piezoelectric substrate can be coated and the mask can be removed. Alternatively, a coating can be formed over the entire surface and then a portion of the coating can be selectively removed (e.g., by forming a hard mask or a soft mask over the portion of the coating not to be removed, then etching the exposed portion of the coating, and finally removing the mask). In block 310, the radical sensor is then placed within a sensor holder, such as any of the sensor holders described above.

[0047]

[0057] FIG. 4 is a flowchart of an embodiment of a method 400 for controlling a plasma source using a radical sensor. In block 405 of method 400, a manufacturing system flows plasma using a first plasma source setting. The plasma can be generated by a remote plasma source (e.g., a plasma source external to the process chamber) or a local plasma source (e.g., a plasma source internal to the process chamber). In block 410, a radical sensor (e.g., as described above herein) is used to detect the concentration / amount of radicals in the plasma. Radicals of the target gas species can react with a coating on the radical sensor, changing the mass on the sensing surface of the radical sensor. The density and / or mass of the coating may be known, and the change in the mass of the coating can be detected based on a change in the resonance frequency of the vibrating piezoelectric material (e.g., QCM) of the radical sensor. This change in mass, along with knowledge of the mass of the material constituting the coating, can be used to determine the number of radicals that reacted with the coating and thus the concentration and / or amount of radicals in the gas flow.

[0048]

[0058] In block 415, processing logic compares the detected concentration / amount of radicals of the target gas species with the target concentration / amount of radicals of the plasma. In block 420, the processing logic determines whether the detected concentration / amount of radicals of the target gas species differs from the target concentration / amount by a threshold amount or more (e.g., when the difference between the target concentration and the detected concentration is greater than or equal to a difference threshold). If the difference exceeds the difference threshold, the method proceeds to block 425 and adjusts one or more settings of the plasma source. For example, the plasma output can be increased to increase the amount of radicals contained in the plasma, or the plasma power can be decreased to decrease the amount of radicals contained in the plasma. If the difference is less than the difference threshold, the method can end.

[0049]

[0059] Unless otherwise specified, the terms "first," "second," "third," "fourth," etc. used in this specification are used as labels for distinguishing different elements and may not have a sequential meaning based on their numerical designations.

[0050]

[0060] The embodiments described in this specification also relate to an apparatus for performing the methods described in this specification. This apparatus may include a general-purpose system that is specially constructed or selectively configured to perform the methods described in this specification.

[0051]

[0061] The terms "above," "below," "between," "disposed on," "supported by," and "on" as used in this specification refer to the relative position of one material layer or component with respect to another layer or component. For example, one layer disposed above, over, or below another layer may be in direct contact with the other layer or may have one or more intervening layers. Further, one layer disposed between two layers may be in direct contact with the two layers or may have one or more intervening layers. Similarly, unless otherwise specified, one feature disposed between two features may be in direct contact with the adjacent features or may have one or more intervening layers.

[0052]

[0062] The above description is illustrative and not restrictive. Although the present disclosure has been described with reference to specific exemplary embodiments and implementations, it will be recognized that the present disclosure is not limited to the described embodiments and implementations. The scope of the present disclosure should be determined with reference to the following claims, along with the full scope of equivalents to which the claims are entitled.

Claims

1. A sensor device comprising: A quartz crystal microbalance (QCM); A coating on at least a part of the surface of the QCM, the coating selectively reacting with radicals of a target gas but not with stable molecules of the target gas; And is provided with The QCM is configured such that the resonance frequency of the QCM changes in response to the reaction between the radicals of the target gas and the coating, and the change in the resonance frequency of the QCM correlates with the amount of the radicals of the target gas that have reacted with the coating. A sensor device.

2. The sensor device according to claim 1, wherein the coating contains a material that reacts with radicals of the target gas to form gaseous by-products and reduces the thickness of the coating.

3. The sensor device according to claim 2, wherein the target gas contains hydrogen and the material contains a polymer of carbon and hydrogen.

4. The sensor device according to claim 3, wherein the material contains polymethyl methacrylate (PMMA).

5. The target gas contains fluorine, and the material contains silicon dioxide (SiO ２ ), tungsten, or an oxide of tungsten. The sensor device according to claim 2.

6. The material is tungsten(III) oxide (W ２ O ３ ), the sensor device according to claim 5.

7. The sensor device according to claim 2, wherein the target gas contains nitrogen and the material contains a fluoropolymer.

8. The sensor device according to claim 1, wherein the coating contains a material that reacts with radicals of the target gas to form solid by-products and increases the thickness of the coating.

9. The sensor device according to claim 1, wherein the coating contains a material that absorbs radicals of the target gas and increases the mass of the coating.

10. The sensor device according to claim 9, wherein in response to the application of a second gas to the sensor device, the radicals of the target gas desorb from the material.

11. The sensor device according to claim 1, wherein the target gas is a constituent of a gas stream containing a plurality of gases, and the coating does not react with radicals of any gas other than the radicals of the target gas among the plurality of gases.

12. The sensor device according to claim 1, wherein the coating has a thickness of 1 to 100 microns.

13. The sensor device according to claim 1, wherein the surface of the QCM including the coating corresponds to the front electrode of the QCM.

14. A charged grid on the coating The sensor device according to claim 1, further comprising a charged grid for repelling ions of the target gas, so that only neutral radicals of the target gas reach the coating.

15. A manufacturing system, comprising: A plasma source for generating plasma; A process chamber connected to the plasma source via one or more delivery lines; A sensor device connected to at least one of the plasma source, the process chamber, or the one or more delivery lines, the sensor device including a quartz crystal microbalance (QCM) including a coating that selectively reacts with radicals of a target gas and does not react with stable molecules of the target gas for measuring the amount of radicals of the target gas A manufacturing system comprising the same.

16. The manufacturing system according to claim 15, wherein the QCM is configured such that a resonance frequency of the QCM changes in response to a reaction between radicals of the target gas and the coating, and the change in the resonance frequency of the QCM correlates with the amount of radicals of the target gas that have reacted with the coating.

17. A controller connected to the sensor device and the plasma source, the controller adjusting one or more parameters of the plasma source in response to the amount of radicals of the target gas detected by the sensor device. The manufacturing system according to claim 15, further comprising the same.

18. The manufacturing system according to claim 17, wherein the controller increases plasma output in response to a determination that the amount of radicals of the target gas is less than a target threshold.

19. A method, comprising: Receiving a gas stream including one or more gases, the one or more gases including a first plurality of stable molecules of a target gas and a second plurality of radicals of the target gas; Measuring the second plurality of radicals of the target gas without measuring the first plurality of stable molecules of the target gas using a quartz crystal microbalance (QCM) including a coating on at least one surface that reacts with the second plurality of radicals of the target gas but does not react with the first plurality of stable molecules of the target gas A method including the same.

20. The one or more gases include plasma output by a remote plasma source, adjusting one or more parameters of the remote plasma source to adjust the concentration of radicals of the target gas in response to measurement of a second plurality of radicals of the target gas The method according to claim 19, further comprising.

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