Monitoring of radical particle concentration using mass spectrometry

Abstract

SUMMARY OF THE DISCLOSURE Provided are improved systems and methods for monitoring radical particle concentrations using mass spectrometry. A monitoring system detects and measures the quantity of radical particles in a gas. A test chamber is coupled to a flow channel that transmits a gas. The test chamber defines an aperture connecting the test chamber and the flow channel, the aperture allowing a subset of the gas to enter the test chamber from the flow channel. An ionizer is positioned within the test chamber and generates radical ions from the radical particles of the subset of the gas. A mass spectrometer measures the quantity of radical ions, thereby providing a measurement of the radical particles in the gas.

Description

Technical Field

[0001] Cross - reference to Related Applications This application claims the benefit of U.S. Provisional Patent Application No. 63 / 130257, filed on Dec. 23, 2020. The entire teachings of the above application are incorporated herein by reference.

Background Art

[0002] Remote plasma sources (RPS) are widely used for the generation of radical particles in semiconductor processing. Recently, radical particles have been widely applied in semiconductor device fabrication (especially at process nodes below 20 nm) due to their advantages of avoiding charging or sputtering damage in etching and deposition processes. When an RPS system is implemented in semiconductor processing, it can operate consistently under the same parameters, including gas flow rate, power, and pressure. However, even under common parameters, the performance in deposition rate, etching rate, and cleaning efficiency can vary significantly between operations due to changes in the concentration of radical particles. This change can occur following a maintenance cycle or during an extended operation cycle. As a result, the performance in semiconductor processing can become unpredictable.

Summary of the Invention

Means for Solving the Problems

[0003] An exemplary embodiment includes a system for monitoring radical particles, comprising a test chamber, an ionizer, and a mass spectrometer. The test chamber may be configured to couple with a flow channel adapted for gas transmission. The test chamber may define an aperture connecting the test chamber to the flow channel, which may be configured to allow a subset of the gas to enter the test chamber from the flow channel. The ionizer may be positioned within the test chamber and configured to generate radical ions from the radical particles of the gas subset. The mass spectrometer may be configured to measure the quantity of radical ions.

[0004] The mass spectrometer may be a residual gas analyzer (RGA). The test chamber can be configured to maintain its gas pressure lower than the gas pressure in the flow channel. The gas pressure in the test chamber may be less than 1e-2 Torr, while the gas pressure in the flow channel may be greater than 0.01 Torr. The ionizer can be positioned within 4 inches of the aperture. The ionizer can be configured to operate in a low-energy state to generate radical ions and minimize the generation of non-radical ions, the low-energy state being lower than the energy state associated with the generation of non-radical ions. The ionizer can be configured to operate in a number of low-energy states, each corresponding to a different radical particle. The ionizer can be configured to operate in a high-energy state to allow a reference signal to be obtained based on non-radical particles in a subset of the gas. The aperture may have a diameter of less than 1 millimeter. The aperture can allow the passage of a ratio of radical particles to non-radical particles exceeding 0.1% of the proportion present in the gas in the flow channel into the test chamber.

[0005] The projection of the test chamber may extend into the flow channel and encompass the volume of the test chamber, and the aperture may be positioned on the projection. The projection may be substantially conical in shape, and the aperture may be positioned at the tip of the cone. The ionizer may be positioned to generate radical ions within the volume defined by the cone. The cone may constitute the electrostatic element of the ionizer. An electrostatic lens may be configured to guide the radical ions as a beam toward the mass spectrometer.

[0006] The controller can be configured to control the operation of the radical particle source based on the quantity of radical ions measured by a mass spectrometer. This control may include controlling at least one of 1) the quantity of radical particles generated over a given time, and 2) the duration of time for which radical particles are generated. This control may also include controlling at least one of the power, gas flow, gas pressure, and temperature of the wet path of the flow channel of the radical source. This control may also include controlling the tooling process.

[0007] The stopper can be configured to selectively seal the aperture. The surface surrounding the aperture may be non-metallic and may exhibit lower reactivity and recombination coefficients to radical particles than a metal surface. Alternatively, the surface surrounding the aperture may be metallic and may exhibit low reactivity with radical particles. The flow channel may be a conduit extending from the radical source to the process chamber, a region downstream of the reaction zone in the process chamber, or a conduit downstream of the process chamber.

[0008] Further embodiments include a method for monitoring radical particles. A subset of gas can be introduced from the flow channel into the test chamber via an aperture connecting the test chamber and the flow channel. Radical ions can be generated from the radical particles of the gas subset via an ionizer. The quantity of radical ions can then be measured via a mass spectrometer.

[0009] The mass spectrometer may be a residual gas analyzer (RGA). The test chamber can be controlled to maintain its gas pressure lower than the gas pressure in the flow channel. The gas pressure in the test chamber may be less than 1e-2 Torr, while the gas pressure in the flow channel may exceed 0.01 Torr. The ionizer can be positioned within 4 inches of the aperture. The ionizer can operate in low-energy states to generate radical ions and minimize the generation of non-radical ions, the low-energy states being lower than the energy states associated with the generation of non-radical ions. The ionizer can operate in a number of low-energy states, each corresponding to a different radical particle. The ionizer can operate in high-energy states to allow a reference signal to be obtained based on non-radical particles in a subset of the gas. The aperture may have a diameter of less than 1 millimeter. The aperture can allow the passage of a ratio of radical particles to non-radical particles exceeding 0.1% of the proportion present in the gas in the flow channel into the test chamber.

[0010] The projection of the test chamber may extend into the flow channel and encompass the volume of the test chamber, and the aperture may be positioned at the projection. The projection may be substantially conical in shape, and the aperture may be positioned at the tip of the cone. Radical ions can be generated within the volume defined by the cone via an ionizer. The cone may be configured as the electrostatic element of the ionizer. Radical ions can be guided as a beam toward a mass spectrometer via an electrostatic lens.

[0011] The operation of the radical particle source can be controlled via a controller based on the quantity of radical ions measured by a mass spectrometer. This control may include controlling at least one of 1) the quantity of radical particles generated over a given time, and 2) the duration of time for which radical particles are generated. This control may also include controlling at least one of the power, gas flow, gas pressure, and temperature of the wet path of the flow channel of the radical source. This control may also include tool process control.

[0012] The aperture can be selectively sealed via a stopper. The surface surrounding the aperture may be non-metallic and may exhibit lower reactivity and recombination coefficients to radical particles than a metal surface. Alternatively, the surface surrounding the aperture may be metallic and may exhibit low reactivity with radical particles. The flow channel may be a conduit extending from the radical source to the process chamber, a region downstream of the reaction zone in the process chamber, or a conduit downstream of the process chamber.

[0013] The above explanation will become clearer from the following more specific description of exemplary embodiments, as shown in the attached drawings. In the attached drawings, similar reference letters throughout the different drawings refer to the same parts. The drawings are not necessarily to scale and the emphasis is on illustrating the embodiments. [Brief explanation of the drawing]

[0014] [Figure 1A] This is a diagram of a semiconductor processing system implementing a radical particle monitor in an exemplary embodiment. [Figure 1B] This is a diagram of a semiconductor processing system implementing a radical particle monitor in an exemplary embodiment. [Figure 1C] This is a diagram of a semiconductor processing system implementing a radical particle monitor in an exemplary embodiment. [Figure 1D] This is a diagram of a semiconductor processing system implementing a radical particle monitor in an exemplary embodiment. [Figure 1E]A diagram of a semiconductor processing system implementing a radical particle monitor in an exemplary embodiment. [Figure 1F] A diagram of a semiconductor processing system implementing a radical particle monitor in an exemplary embodiment. [Figure 2A] A diagram of a semiconductor processing system implementing a radical particle monitor in a further embodiment. [Figure 2B] A diagram of a semiconductor processing system implementing a radical particle monitor in a further embodiment. [Figure 2C] A diagram of a semiconductor processing system implementing a radical particle monitor in a further embodiment. [Figure 3A] A diagram of a subset of radical particle monitors in an exemplary embodiment. [Figure 3B] A diagram of a subset of radical particle monitors in an exemplary embodiment. [Figure 3C] A diagram of a subset of radical particle monitors in an exemplary embodiment. [Figure 3D] A diagram of a subset of radical particle monitors in an exemplary embodiment. [Figure 3E] A diagram of a subset of radical particle monitors in an exemplary embodiment. [Figure 3F] A diagram of a subset of radical particle monitors in an exemplary embodiment. [Figure 4A] A diagram of an inlet port that can be implemented with a radical particle monitor. [Figure 4B] A diagram of an inlet port that can be implemented with a radical particle monitor. [Figure 4C] A diagram of an inlet port that can be implemented with a radical particle monitor. [Figure 5A] A diagram of an inlet port configured to perform bias voltage or temperature control. [Figure 5B] A diagram of an inlet port configured to perform bias voltage or temperature control. [Figure 6A]An example configuration for implementing an aperture stopper is shown. [Figure 6B] An example configuration for implementing an aperture stopper is shown. [Figure 6C] An example configuration for implementing an aperture stopper is shown. [Figure 7] This is a diagram of a subset of radical particle monitors in a further configuration. [Figure 8] This is a flowchart of a process for monitoring the radical particle concentration in an exemplary embodiment. [Modes for carrying out the invention]

[0015] A description of exemplary embodiments follows below.

[0016] A residual gas analyzer (RGA) is a type of mass spectrometer typically designed for process control and contamination monitoring in vacuum systems. An RGA works by ionizing distinct components of a gas to produce various ions, which are then used to detect and determine the mass-to-charge ratio of those ions. A typical RGA is designed to detect stable chemical compounds. In contrast, radical particles typically react before reaching the particle sampler of the RGA. Therefore, such an RGA will fail to detect the presence of a significant number of radical particles due to excessive losses.

[0017] Previous RGAs employed various techniques for ion sampling, including polar bias, mid-axis potential, and anion capability. However, such RGAs do not provide a solution for radical detection in semiconductor process chambers (particularly for sampling radicals with short lifetimes and high recombination rates). Since the advent of mass spectrometry, various radical measurement methods have been developed, including infrared diode laser absorption spectroscopy, laser-induced spectroscopy, and cavity ring-down spectroscopy. More recently, atomic radicals have also been measured using compact vacuum ultraviolet absorption spectroscopy.

[0018] However, the above methods suffer from various drawbacks, including low sensitivity in detecting trace amounts of radicals, interference from other gas species, difficulty in achieving a stable baseline due to changes in process conditions, and the inability to quantify radicals in the system. Therefore, previous methods cannot accurately and reliably monitor radical concentrations. Consequently, semiconductor processes require real-time, precise, and accurate monitoring of radical concentrations in the process chamber. Such monitoring would be particularly advantageous for process control when applying radical-on-wafer processes at the advanced technology node.

[0019] Figure 1A depicts a semiconductor processing system 100 implementing a radical particle monitor 120 in an exemplary embodiment. The system 100 includes a process chamber 110 in which a semiconductor wafer 112 is processed, such as in an etching and / or deposition process. To facilitate this processing, a radical source 115, such as a remote plasma source (RPS), a capacitively coupled plasma source (CCP), or an inductively coupled plasma source (ICP), can release gas into the process chamber 110 through a supply channel 105, such as a straight, curved, or angled elbow. Depending on the desired process, the gas may have one of many different compositions of stable particles, radical particles, and ions (e.g., plasma gas). A throttle valve 190 can be selectively opened to pass the gas from the process chamber 110 to a foreline 192, which can then be discharged from the system 100 or collected for further use.

[0020] The radical particle monitor (RPM) 120 operates to monitor the presence of radical particles in a gas. The RPM 120 may include a test chamber 130, an ionizer 132, and a mass spectrometer 122. The test chamber 130 can be coupled to a gas flow channel, such as a supply channel 105, to receive a subset of the gas destined for the test chamber 130. The coupling point may be a straight, curved, or angled portion of the flow channel 105. The ionizer 132, positioned within the test chamber 130, may be configured to ionize radical particles in a subset of the gas to generate radical ions within the test chamber 130. The mass spectrometer 122 may be a residual gas analyzer (RGA) or equivalent system, and may include a mass spectrometer 124, a controller 126, and a pump 128. The mass spectrometer 124 can receive radical ions from the ionizer 132 and perform mass filtering and ion detection on the radical ions to measure the presence of radical ions. Next, the controller 126 can be further configured to process measurements from the mass spectrometer 124 to generate further results (such as a mass spectrum of the gas) and, based on the results, to control the operation of the radical source 115 or other parameters of the system 100. The pump 128 (e.g., vacuum or turbopump) can be operated to pump the gas from the mass spectrometer 124 and the test chamber 130 to maintain the chamber at an appropriate pressure (e.g., less than 1 e-2 torre) and to transfer the gas to the foreline 192 or another exhaust pipe.

[0021] In contrast to typical mass spectrometers (such as RGAs), the RPM 120 provides reliable measurement of radical particles in a gas. This capability is made possible by several features described herein, which can be implemented in various combinations, as provided below. Specifically, the test chamber 130 can be adapted to capture an optimal gas sample while minimizing the reaction of radical particles entering the test chamber 130. The ionizer 132 can also be configured to directly maximize the ionization of radical particles entering the test chamber 130. Various features of the test chamber 130, ionizer 132, and related elements are described below with reference to Figures 3A-F. Furthermore, the mass spectrometer 122 can operate in one or more low-energy states to ionize and measure radical particles without interference from non-radical particles, as described below. The RPM 120 can be further configured to provide multiple operating modes for detecting and measuring the presence of different radical particles and non-radical particles by operating in different energy states, for example, as described below.

[0022] Figures 1B–D show semiconductor processing systems 101–103 in further embodiments. Systems 101–105 can incorporate some or all of the features of system 100 described above, except that they can implement radical particle monitors and / or radical sources in different configurations. Figure 1B shows system 101 in which an RPM 120 is coupled to the wall of the process chamber 110 and configured to monitor the presence of radical particles in the process chamber. Figure 1C shows system 102 in which the RPM 120 is coupled to the wall of the foreline 192 above the throttle valve 190, and Figure 1D depicts system 103 in which the RPM 120 is coupled to the foreline 192 below the throttle valve 190.

[0023] When a predetermined gas is transmitted through systems 100-103, the gas sampled by the RPM 120 may vary depending on the location where the sample is collected. Specifically, the radical concentration is likely to decrease with distance from the radical source 115, and the concentrations of background gas and other particles may change after interaction with the wafer 112 and the inner surface that confines the gas. For these reasons, the RPM 120 can be calibrated based on the sampling location, and / or the measured values ​​of radical particles and other particles provided by the RPM 120 can be calculated based on the sampling location.

[0024] Figures 1E and 1F depict systems 104 and 105 in which the radical source 115 is positioned below the process chamber 110. In Figure 1E, the radical source 115 is positioned in the foreline 192 above the throttle valve 190, and in Figure 1F, the radical source 115 is positioned below the throttle valve 190. In such configurations, the radical source 115 can operate to release radical particles for cleaning the throttle valve 190 and / or the foreline 192 during maintenance cycles. To monitor the presence of radical particles (and optionally non-radical particles) in the gas, an RPM 120 can be coupled to the foreline 192 downstream of the radical source 115. Measurements captured by the RPM 120 can be used to determine the status and progress of the maintenance cycle, as well as to control the operation of the radical source 115 (gas flow and pressure, radical particle generation, temperature, and maintenance cycle length, etc.).

[0025] Figures 2A–C show semiconductor processing systems 200–202 in further embodiments. Systems 200–202 can incorporate some or all of the features of system 100 described above, except that they implement a radical particle source 116, such as a capacitively coupled plasma source (CCP) or an inductively coupled plasma source (ICP), instead of (or in addition to) the radical source 115 described above. The radical particle source 116 may occupy the upper volume of the process chamber 110 or be contained in a separate chamber adjacent to the process chamber 110. This configuration does not allow the use of a supply channel for sampling radical particles. Accordingly, the RPM 120 can instead be coupled to the wall of the process chamber 110, as shown in Figure 2A, and can be configured to monitor the presence of radical particles in the process chamber 110. Alternatively, the RPM 120 may be coupled to the wall of the foreline 192 above the throttle valve 190, as shown in Figure 2B, or to the foreline 192 below the throttle valve 190, as shown in Figure 2C.

[0026] Figure 3A shows a portion of the RPM 120 in more detail. Here, the test chamber 130 is shown to be in gas communication with the supply channel 105 via the aperture 140. Although the supply channel 105 is shown, the test chamber 130 can instead be coupled to a different flow chamber such as the process chamber 110 or the foreline 192, as shown in Figures 1B-F and 2A-C. The aperture 140 can be sized to allow the passage of an acceptable number of radical particles without causing a reaction, while maintaining a low gas pressure in the test chamber to facilitate particle detection. For example, if the mass spectrometer 124 is configured as an RGA, the test chamber 130 may need to maintain a pressure of less than 1e-2 tor, even though the supply channel maintains a pressure in the range of 0.01 to 10 tor. In such applications, the aperture 140 may have a diameter of less than 1 mm, and in one example, it may have a diameter of about 35 mm. The aperture 140 configured as described herein can allow a quantity of radical particles suitable for detection by the mass spectrometer 122 to pass into the test chamber 130 without excessive loss. This result can be expressed as the ratio of radical particles to non-radical particles present in the gas in the test chamber 130 compared to the proportion present in the gas in the supply channel 105. For example, the aperture 140 can allow a ratio of radical particles to non-radical particles exceeding 0.1% of the proportion present in the gas in the supply channel 105 to pass into the test chamber 130. In further embodiments, the proportion present in the test chamber 130 may be 1% or more greater than the proportion present in the supply channel 105 or another flow channel (such as the process chamber 110 or foreline 192 shown in Figures 1B-F) to which the test chamber 130 is coupled.

[0027] As radical particles are transported through the supply channel 105, radicals near the walls of the supply channel 105 frequently collide with the walls, resulting in a high recombination rate and potentially leading to the loss of radical particles. Consequently, the density of radical particles near the walls may be relatively low and may not represent the true number of radical particles delivered from the radical source 115. Therefore, sampling of radical particles near the walls of the supply channel 105 where the aperture is located on the wall may not have optimal efficiency for radical sampling, as described below.

[0028] In the conical sampler 150, the aperture 140 is positioned at the end of the sampler 150, and the sample point extends close to the center of the gas stream from the radical source 115, allowing the sampled species to experience fewer surface collisions. Such a sampling location may have a much higher radical density than the sampling location on the wall of the supply channel 105. Furthermore, the ionizer 132 can be positioned very close to the sampler 150 (e.g., within 4 inches, and in the shown example, within 0.5 inches) to increase detection sensitivity by intercepting a large portion of the visual cone of radicals spreading into the test chamber 130 after passing through the aperture 140. Also, the conical shape of the sampler 150 minimizes collisions with radical particles passing through the aperture 140 by giving particles a wider path at the entrance to the test chamber 130. Alternatively, the sampler 150 can form a projection defining one of a wide range of different shapes (such as hemispherical, cylindrical, prismatic, or elliptical or oval). In such an alternative configuration, the projection may extend into the supply channel 105 or another flow channel and encompass the volume of the test chamber 130, and the aperture 140 may be positioned at the end of the projection or on another surface. The sampler 150 may have a non-metallic surface made of glass, quartz, sapphire, SiO2, Al2O3 or another material that exhibits a low recombination rate (compared to a metal surface) with a predetermined set of radical particles to be measured (such as radical particles of H, N, O, OH, NHx, CHx, and NO). Alternatively, the sampler 150 may have a non-metallic surface made of glass, quartz, sapphire, SiO2, Al2O3, or another material that exhibits a low recombination rate (compared to a metal surface) with a predetermined set of radical particles to be measured (such as radical particles of F, Cl, NF x and CF x It may have a metallic surface made of aluminum or stainless steel, or aluminum nitride or aluminum oxide or another material, which exhibits a low reaction rate (compared to a non-metallic surface) with radical particles (such as those found in the material).

[0029] The above features, along with a high vacuum (e.g., 1e-5 Torr) within the test chamber 130, allow for a long mean free path for particles within the test chamber 130. Thus, most radical particles traveling through the aperture 140 reach the ionizer 132 before colliding with the wall or another particle, leading to an increase in the ionization rate of radicals. By extending the aperture 140 into the supply channel 105, allowing clearance for free radicals via the conical sampler 150, or positioning the ionizer 132 close to the aperture 140, a combination of some or all of the above features can enable the ionizer 132 to generate more radical ions from radical particles, thereby providing the mass spectrometer 124 with higher radical detection sensitivity.

[0030] Figures 3B–F show parts of the RPM 120 in further embodiments. Embodiments may include some or all of the features of the RPM 120 described above with reference to Figures 1A–3A, except that the interface between the supply channel 105 (or other flow channel) and the test chamber 130 is configured as described below. Figure 3B shows a configuration in which the test chamber 130 and the supply channel 105 share a common wall, and the aperture 141 is located in the common wall without any protrusions into the supply channel. The aperture 141 may be a prefabricated surface (e.g., a stainless steel gasket) having an orifice (e.g., welded) installed in a larger opening in the common wall. Alternatively, the aperture 141 may be a simple orifice drilled into the common wall.

[0031] Figures 3C and 3D show configurations having samplers 152 and 153 similar to sampler 150 in Figure 3A, including a conical shape, and apertures 142 at the ends of sampler 152. Furthermore, in contrast to Figure 3A, samplers 152 and 153 are partially (Figure 3C) or completely (Figure 3D) embedded in the wall of the supply channel 105. These configurations may be advantageous in applications where access to the supply channel 105 or other flow channels is restricted (meaning that components of the RPM 120 (e.g., ionizer 132 and / or mass spectrometer 122) must be positioned at a certain distance from the flow channels). However, these configurations may also have further advantages, such as reducing interference with the gas flow through the flow channels and positioning the apertures 142 closer to the ionizer 132 to increase the number of radical particles ionized in the test chamber 130.

[0032] Figure 3E shows a configuration identical to that of Figure 3A, except that the supply channel 106 has a T-shaped structure, which includes a single inlet and two or more outlets from the radical source 115, with one or both of the two or more outlets leading to the process chamber 110 such that the flow moves symmetrically away from the aperture 144. The test chamber 130 is positioned opposite the inlet of the supply channel 106 to form a cruciform arrangement, meaning that the aperture 144 of the sampler 154 is aligned axially with the gas flow path. As a result of this configuration, radical particles from the radical source 115 are likely to enter the test chamber 130 without causing prior wall collisions that could lead to particle reaction or recombination.

[0033] Figure 3F shows the sampling arrangement in a further configuration. Here, a sampling tube 160 is implemented instead of the sampler shown in Figures 3A and 3C-E. This configuration may be advantageous when some or all of the RPMs 120 must be positioned further away from the flow channel to be sampled. The sampling tube 160 may extend partially into the gas flow of the supply channel 105, as shown, and may extend over its distance in the conduit 165 before the opening into the test chamber 130. To facilitate the transport of radical particles along the internal volume of the sampling tube 160, the sampling tube 160 may be constructed of (or coated with) a material having a low reactivity or recombination rate with the radical particles to be measured. For example, the sampling tube 160 may have an inner surface of quartz or sapphire exhibiting a low recombination rate with N and H radical particles. Alternatively, the sampling tube 160 may have a surface made of aluminum, stainless steel, glass or equivalent material, and different surfaces may be optimal for minimizing the reaction of a given set of radical particles.

[0034] Figures 4A-C show prefabricated inflow ports 401-403 that can be implemented in the radical particle monitor. Ports 401-403 can be positioned between the flow channel and the test chamber to control the flow of a subset of the gas in the flow channel to the test chamber, as in the embodiments described above with reference to Figures 1A-3F. Port 401 includes a cylindrical plug 450, through which an aperture 440 passes. The aperture 440 can be sized and configured as other apertures described above, and may include one or more recesses on one or both sides of the plug 450, as shown, thereby allowing a larger flow of radical particles without causing a reaction. Port 402 includes a sampler 450, which defines a disk shape and has a conical shape toward its center, with an aperture 441 occupying the end of the conical shape. The sampler 441 can be configured equivalently to other samplers described above. Port 403 includes a sampling tube 460, which extends through a port (e.g., a cylindrical plug such as port 401) and terminates at aperture 442. The sampling tube 460 may include some or all of the features of the sampling tube 160 described above with reference to Figure 3F. Each of ports 401-403 may be made of any material suitable for gas transfer and vacuum applications, such as stainless steel, and may have one or more surfaces made of a material having a low recombination rate and reaction with target radical particles as described above.

[0035] Figures 5A and 5B show inlet ports 501 and 502 configured for bias voltage and temperature control features, respectively. In Figure 5A, inlet port 501 includes a sampler 551, which is conductive and coupled to the bias voltage. The bias voltage causes the sampler 551 to exhibit a charge that repels certain ions, thereby reducing the passage of those ions through aperture 541 and reducing ion interference in adjacent test chambers. The bias voltage can be positive or negative depending on the target ion. For example, a positive bias voltage can interfere with the measurement of nitrogen radical particles and nitrogen ions (N + ) may repel cations such as fluorine ions (F). Alternatively, a negative bias voltage may interfere with the measurement of fluorine radical particles. - It may repel anions such as ).

[0036] Moving to Figure 5B, the inlet port 502 includes a sampler 552 having one or more internal conduits, one or more of which are adapted to allow a flow of water or other liquid through the sampler 552, thereby cooling (or heating) the sampler 552 toward a target temperature. During RPM operation, radical recombination on the surface of the sampler 552 imparts heat to the sampler 552, raising its temperature and increasing the recombination rate with subsequent radical particles. By inducing a coolant through the sampler 552, the sampler 552 can be kept at a lower temperature, thereby reducing its recombination rate with radical particles. In further embodiments, the sampler can combine the bias voltage and temperature control features of samplers 551 and 552.

[0037] Figures 6A-C show exemplary configurations for implementing aperture stoppers. When the RPM is not operating as described above, it may be advantageous to protect the RPM by sealing the aperture between the flow channel and the test chamber, especially if the gas pressure or temperature in the flow channel is significantly elevated. Various mechanical means can be used to selectively seal the aperture. For example, as shown in Figure 6A, a mechanical throttle valve 670 can be positioned between the sampler 651 and the test chamber. When the throttle valve 670 is activated, a seal is formed between the sampler 651 and the test chamber, thereby preventing particles from entering the test chamber through the sampler. In Figure 6B, an automatic stopper 680 may be present in the embedded chamber on the opposite side of the flow channel from the sampler 652. When activated, the stopper 680 moves laterally to seal around the aperture 642, thereby blocking the flow channel from the test chamber on the opposite side of the sampler 652. Finally, Figure 6C shows an automatic stopper 680 located inside or adjacent to the test chamber. When activated, the stopper 681 moves toward the aperture 643 until a seal is formed with the sampler 653, thereby blocking the flow channel from the test chamber.

[0038] Figure 7 shows a portion of the RPM in a further embodiment. The RPM may include some or all applicable features of the embodiments described above with reference to Figures 1A-6C, and may include a test chamber 130 coupled to a sampler 750 to redirect a subset of gas from the supply channel 105 to the test chamber 130 via an aperture 740. In contrast to the above embodiments, the ionizer 732 is positioned near the sampler 750 and configured to ionize radical particles within the volume defined by the sampler 750, thereby generating a beam 790 of radical ions. To do this, the ionizer 732 may include an electron source 733 and a shield 734. The shield 734, shown in cross-section, covers two or more faces of the electron source 733 and may include a slit or orifice between the electron source 733 and the sampler 750 for guiding the beam of electrons from the electron source 733 through the volume of the sampler 750 to a region near the aperture 740.

[0039] The electron beam helps to ionize radical particles within the volume of the sampler 750, generating an ion beam 790, which is guided toward the RPM mass spectrometer 124 through another opening in the shield 734. In this configuration, the conical shape of the sampler 750 can act as an electrostatic element of the ionizer 732. The shield 734 may also cover other sides of the electron source 733 to deflect electrons away from the ion beam 790. The ion beam 790 extends toward the mass spectrometer 124 and is focused at the inlet of the mass spectrometer 124 by the electrostatic lens 770. The mass spectrometer 124 receives the radical ions from the ion beam 790 and can perform mass filtering and ion detection on the radical ions to measure the presence of the radical ions. Next, the controller 126 can be further configured to process measurements from the mass spectrometer 124 to generate further results (such as a gas mass spectrum), as described above with reference to Figure 1A, and to control the operation of the radical source or the tool process control parameters of the respective semiconductor processing system based on the results.

[0040] Figure 8 is a flow diagram of process 800 for monitoring the radical particle concentration. Process 800 can be carried out by any of the systems implementing RPM described above. Referring to the exemplary embodiments in Figures 1A and 3A, if the gas flows through a flow channel such as the supply channel 105, a subset of the gas can be guided into the test chamber 130 via the sampler 150 (805). Radical ions can be generated from the gas radical particles of the subset of gas in the test chamber 130 (810). To generate radical ions, the ionizer 132 can operate in a low-energy state, which is lower in energy than the energy state associated with the generation of non-radical ions of the same mass. The mass spectrometer 124 can receive the radical ions from the ion beam 790 and perform mass filtering and ion detection on the radical ions to measure the presence and quantity of radical ions (815). Different radical particles can be ionized in different energy states. For example, ionizer 132 can ionize N radicals at 24 eV, while fluorine radicals need to be ionized at a different energy state of 21 eV. Therefore, if it is desirable to measure the quantity of multiple different radicals in the gas, operations 810 and 815 can be repeated for each of the radical particles to be measured, and the energy level of ionizer 132 can be changed between each iteration. For example, RPM 120 can perform operations 810 and 815 to measure N radicals at 24 eV, then correct the energy level of the ionizer, and repeat operations 810 and 815 to measure H radicals at 16 eV. The process can then be repeated several more times in succession to measure the quantity of radical particles of N, O, OH, F, H, Cl, NHx, CHx, and NxOy. Thus, ionizer 132 can operate in a number of low-energy states, each of which corresponds to a different radical particle.

[0041] Next, the controller 126 can compare the measured radical quantity with its respective threshold or target value (815). If the target is met, monitoring can continue with the iteration of the process. Otherwise, the controller 126 can communicate with the radical source 115 and / or tool process control to correct its operation (820). For example, the controller 126 can control the operation of the radical source 115 or another radical particle source (e.g., radical particle source 116) by controlling the quantity of radical particles generated over a given time and / or the duration for which radical particles are generated. Furthermore, the controller 126 can send feedback to the radical source 115 or 116 to adjust one or more of the power, gas flow, gas pressure, and temperature of the wet path of the flow channel. The controller 126 can also send feedback to the process tool to adjust process parameters. Such adjustments, made in response to the measured number of radical particles, can improve the performance of the processing cycle by increasing the number of radical particles to an appropriate level, or by extending the processing cycle time to ensure that the wafer 112 receives sufficient exposure to radical particles. Following adjustment (820), process 800 can be repeated to provide continuous monitoring of radical particles in system 100.

[0042] In further embodiments, process 800 may include a “high-energy” mode for measuring the quantity of non-radical particles (e.g., background or reference gas). To perform the high-energy mode, the RPM 120 can adjust the energy state of the ionizer 132 to a higher energy state (such as 40 eV or 70 eV) and then operate a process equivalent to process 800 as described above. In doing so, the RPM 120 can measure the quantity of one or more non-radical particles constituting the gas being sampled. For example, the RPM 120 can first operate in a “low-energy state” of 15 eV to measure N radical particles. This energy level is too low to ionize a particular reference gas, such as argon, which has an ionization potential of 15.6 eV. Following this scan, the RPM 120 can then switch to a high-energy state of 40 eV to ionize argon particles and other reference gases. By appropriately adjusting the relative sensitivity mathematically, this signal can be used to normalize or calibrate the RPM response to the measured radical ion, thereby ensuring precise repeatability of the measurement.

[0043] While exemplary embodiments have been specifically shown and described, those skilled in the art will understand that various modifications of form and detail can be made without departing from the scope of embodiments covered by the appended claims. Furthermore, the present invention includes the following aspects. [Aspect 1] A system for monitoring radical particles, A test chamber configured to be coupled to a flow channel adapted for gas transmission, the test chamber defining an aperture connecting the test chamber and the flow channel, the aperture being configured such that a subset of the gas can enter the test chamber from the flow channel, An ionizer positioned within the test chamber, configured to generate radical ions from radical particles of a subset of the gas, A mass spectrometer configured to measure the quantity of the aforementioned radical ions A system that includes this. [Aspect 2] The system according to embodiment 1, wherein the mass spectrometer is a residual gas analyzer (RGA). [Aspect 3] The system according to embodiment 1, wherein the test chamber is configured to maintain its gas pressure lower than the gas pressure of the flow channel. [Aspect 4] The system according to embodiment 3, wherein the gas pressure in the test chamber is less than 1e-2 Torr, and the gas pressure in the flow channel is greater than 0.01 Torr. [Aspect 5] The system according to embodiment 1, wherein the ionizer is positioned within 4 inches of the aperture. [Aspect 6] The system according to Embodiment 1, wherein the ionizer is configured to operate in a low-energy state to generate the radical ions and minimize the generation of non-radical ions, the low-energy state being lower than the energy state associated with the generation of the non-radical ions. [Aspect 7] The system according to embodiment 1, wherein the ionizer is configured to operate in a number of low-energy states, each of which corresponds to a radical particle. [Aspect 8] The system according to embodiment 1, wherein the ionizer is configured to operate in a high-energy state so that a reference signal can be obtained based on non-radical particles of the subset of the gas. [Aspect 9] The system according to embodiment 1, wherein the aperture has a diameter of less than 1 millimeter. [Aspect 10] The system according to embodiment 1, wherein the aperture allows the passage of a ratio of radical particles to non-radical particles exceeding 0.1% of the proportion of the gas present in the flow channel into the test chamber. [Aspect 11] The system according to embodiment 1, further comprising a projection of the test chamber that extends into the flow channel and encompasses the volume of the test chamber, wherein the aperture is positioned on the projection. [Aspect 12] The system according to embodiment 11, wherein the projection is substantially conical in shape, and the aperture is positioned at the tip of the conical shape. [Aspect 13] The system according to embodiment 12, wherein the ionizer is positioned to generate radical ions within a volume defined by the conical shape. [Aspect 14] The system according to embodiment 13, wherein the conical shape is configured as an electrostatic element of the ionizer. [Aspect 15] The system according to embodiment 13, further comprising an electrostatic lens configured to guide the radical ions as a beam toward the mass spectrometer. [Aspect 16] The system according to embodiment 1, further comprising a controller configured to control the operation of the radical particle source based on the quantity of radical ions measured by the mass spectrometer. [Aspect 17] The system according to embodiment 16, wherein controlling the operation of the radical particle source includes controlling at least one of 1) the quantity of radical particles generated over a predetermined time and 2) the duration of time over which the radical particles are generated. [Aspect 18] The system according to embodiment 16, wherein controlling the operation of the radical particle source includes controlling at least one of the power, gas flow, gas pressure, and temperature of the wet path of the flow channel. [Aspect 19] The system according to embodiment 1, further comprising a stopper configured to selectively seal the aperture. [Aspect 20] The system according to embodiment 1, wherein the surface surrounding the aperture is non-metallic and exhibits lower reactivity and recombination coefficients for the radical particles than a metal surface. [Aspect 21] The system according to embodiment 1, wherein the surface surrounding the aperture is made of metal and exhibits low reactivity with the radical particles. [Aspect 22] The system according to embodiment 1, wherein the flow channel is a conduit extending from a radical source to a process chamber. [Aspect 23] The system according to embodiment 1, wherein the flow channel is a region downstream of the reaction zone of the process chamber. [Aspect 24] The system according to embodiment 1, wherein the flow channel is a pipeline downstream of the process chamber. [Aspect 25] A method for monitoring radical particles, A subset of the gas is guided from the flow channel to the test chamber via an aperture connecting the test chamber and the flow channel. The process involves generating radical ions from radical particles of the subset of the gas via an ionizer, The quantity of the radical ions is measured via a mass spectrometer. Methods that include... [Aspect 26] The method according to embodiment 25, wherein the mass spectrometer is a residual gas analyzer (RGA). [Aspect 27] The method according to embodiment 25, further comprising maintaining the gas pressure in the test chamber lower than the gas pressure in the flow channel. [Aspect 28] The method according to embodiment 27, wherein the gas pressure in the test chamber is less than 1e-2 Torr, and the gas pressure in the flow channel is greater than 0.01 Torr. [Aspect 29] The method according to embodiment 25, wherein the ionizer is positioned within 4 inches of the aperture. [Aspect 30] A method according to embodiment 25, further comprising operating the ionizer in a low-energy state to generate the radical ions and minimize the generation of non-radical ions, wherein the low-energy state is lower than the energy state associated with the generation of the non-radical ions. [Aspect 31] A method according to embodiment 25, further comprising operating the ionizer in a number of low-energy states, each of which corresponds to a radical particle. [Aspect 32] The method according to embodiment 25, further comprising operating the ionizer in a high-energy state so that a reference signal can be obtained based on non-radical particles of the subset of the gas. [Aspect 33] The method according to embodiment 25, wherein the aperture has a diameter of less than 1 millimeter. [Aspect 34] The method according to embodiment 25, wherein the aperture allows a ratio of radical particles to non-radical particles exceeding 0.1% of the proportion of the gas in the flow channel to pass through the test chamber. [Aspect 35] The method according to embodiment 25, wherein the projection of the test chamber extends into the flow channel and encompasses the volume of the test chamber, and the aperture is positioned on the projection. [Aspect 36] The method according to embodiment 35, wherein the protrusion is substantially conical in shape, and the aperture is positioned at the tip of the conical shape. [Aspect 37] The method according to embodiment 36, further comprising operating the ionizer to generate radical ions within a volume defined by the conical shape. [Aspect 38] The method according to embodiment 37, wherein the conical shape is configured as an electrostatic element of the ionizer. [Aspect 39] The method according to embodiment 37, further comprising guiding the radical ions as a beam toward the mass spectrometer via an electrostatic lens. [Aspect 40] The method according to embodiment 25, further comprising controlling the operation of the radical particle source based on the quantity of radical ions measured by the mass spectrometer. [Aspect 41] The method according to embodiment 40, wherein controlling the operation of the radical particle source includes controlling at least one of 1) the quantity of radical particles generated over a predetermined time and 2) the time length over which the radical particles are generated. [Aspect 42] The method according to embodiment 40, wherein controlling the operation of the radical particle source includes controlling at least one of the power, gas flow, gas pressure, and temperature of the wet path of the flow channel. [Aspect 43] The method according to embodiment 25, further comprising selectively sealing the aperture via a stopper. [Aspect 44] The method according to embodiment 25, wherein the surface surrounding the aperture is non-metallic and exhibits lower reactivity and recombination coefficients for the radical particles than a metal surface. [Aspect 45] The method according to embodiment 25, wherein the surface surrounding the aperture is made of metal and exhibits low reactivity with the radical particles. [Aspect 46] The method according to embodiment 25, wherein the flow channel is a conduit extending from a radical source to a process chamber. [Aspect 47] The method according to embodiment 25, wherein the flow channel is a region downstream of the reaction zone of the process chamber. [Aspect 48] The method according to embodiment 25, wherein the flow channel is a pipeline downstream of the process chamber.

Claims

1. A system for monitoring radical particles, A test chamber configured to be coupled to a flow channel adapted for gas transmission, the test chamber defining an aperture connecting the test chamber and the flow channel, the aperture being configured such that a subset of the gas can enter the test chamber from the flow channel, An ionizer positioned within the test chamber, configured to operate in a low-energy state and generate radical ions from radical particles of the subset of the gas, A mass spectrometer configured to measure the quantity of the aforementioned radical ions Includes, The ionizer is configured to operate in a high-energy state higher than the low-energy state, and the system is configured to acquire a reference signal based on the ionization of non-radical particles of the subset of the gas in the high-energy state, and the reference signal is used for normalizing or calibrating the monitoring of the radical particles.

2. The system according to claim 1, wherein the mass spectrometer is a residual gas analyzer (RGA).

3. The system according to claim 1, wherein the test chamber is configured to maintain its gas pressure lower than the gas pressure of the flow channel.

4. The system according to claim 3, wherein the gas pressure in the test chamber is less than 1e-2 Torr, and the gas pressure in the flow channel is greater than 0.01 Torr.

5. The system according to claim 1, wherein the ionizer is positioned within 4 inches of the aperture.

6. The system according to claim 1, wherein the ionizer is configured to operate in the low-energy state to generate the radical ions and minimize the generation of non-radical ions, the low-energy state being lower than the high-energy state associated with the generation of the non-radical ions.

7. The system according to claim 1, wherein the ionizer is configured to operate in a number of low-energy states, each of which corresponds to a radical particle.

8. The system according to claim 1, wherein the aperture has a diameter of less than 1 millimeter.

9. The system according to claim 1, wherein the aperture is an aperture that allows a gas to pass from the flow channel to the test chamber, and the ratio of radical particles to non-radical particles present in the gas in the flow channel is greater than 0.1% of the ratio of radical particles to non-radical particles present in the gas in the test chamber.

10. The system according to claim 1, further comprising a projection of the test chamber that extends into the flow channel and encompasses the volume of the test chamber, wherein the aperture is positioned on the projection.

11. The system according to claim 10, wherein the projection is substantially conical in shape, and the aperture is positioned at the tip of the conical shape.

12. The system according to claim 11, wherein the ionizer is positioned to generate radical ions within a volume defined by the conical shape.

13. The system according to claim 12, wherein the conical shape is configured as an electrostatic element of the ionizer.

14. The system according to claim 12, further comprising an electrostatic lens configured to guide the radical ions as a beam toward the mass spectrometer.

15. The system according to claim 1, further comprising a controller configured to control the operation of the radical particle source based on the quantity of radical ions measured by the mass spectrometer.

16. The system according to claim 15, wherein controlling the operation of the radical particle source includes controlling at least one of 1) the quantity of radical particles generated over a predetermined time and 2) the duration of time over which the radical particles are generated.

17. The system according to claim 15, wherein controlling the operation of the radical particle source includes controlling at least one of the power, gas flow, gas pressure, and temperature in the gas flow path of the flow channel.

18. The system according to claim 1, further comprising a stopper configured to selectively seal the aperture.

19. The system according to claim 1, wherein the surface surrounding the aperture is non-metallic and exhibits lower reactivity and recombination coefficients for the radical particles than a metal surface.

20. The system according to claim 1, wherein the surface surrounding the aperture is made of metal and exhibits low reactivity with the radical particles.

21. The system according to claim 1, wherein the flow channel is a conduit extending from a radical source to a process chamber.

22. The system according to claim 1, wherein the flow channel is a region downstream of the reaction zone of the process chamber.

23. The system according to claim 1, wherein the flow channel is a pipeline downstream of the process chamber.

24. A method for monitoring radical particles, A subset of the gas is guided from the flow channel to the test chamber via an aperture connecting the test chamber and the flow channel. The ionizer operates in a low-energy state to generate radical ions from the radical particles of the subset of the gas, The quantity of the radical ions is measured via a mass spectrometer. It includes, and further, A method comprising: operating the ionizer in a high-energy state higher than the low-energy state to obtain a reference signal based on the ionization of non-radical particles of the subset of the gas in the high-energy state; and normalizing or calibrating the monitoring of the radical particles using the reference signal.

25. The method according to claim 24, wherein the mass spectrometer is a residual gas analyzer (RGA).

26. The method according to claim 24, further comprising maintaining the gas pressure in the test chamber lower than the gas pressure in the flow channel.

27. The method according to claim 26, wherein the gas pressure in the test chamber is less than 1e-2 Torr, and the gas pressure in the flow channel is greater than 0.01 Torr.

28. The method according to claim 24, wherein the ionizer is positioned within 4 inches of the aperture.

29. The method according to claim 24, further comprising operating the ionizer in the low-energy state to generate the radical ions and minimize the generation of non-radical ions, wherein the low-energy state is lower than the high-energy state associated with the generation of the non-radical ions.

30. The method according to claim 24, further comprising operating the ionizer in a number of low-energy states, each of which corresponds to a radical particle.

31. The method according to claim 24, wherein the aperture has a diameter of less than 1 millimeter.

32. The method according to claim 24, wherein a gas is passed from the flow channel to the test chamber via the aperture, the ratio of radical particles to non-radical particles present in the gas in the flow channel is greater than 0.1% of the ratio of radical particles to non-radical particles present in the gas in the test chamber.

33. The method according to claim 24, wherein the projection of the test chamber extends into the flow channel and encompasses the volume of the test chamber, and the aperture is positioned on the projection.

34. The method according to claim 33, wherein the projection is substantially conical in shape, and the aperture is positioned at the tip of the conical shape.

35. The method according to claim 34, further comprising operating the ionizer to generate radical ions within a volume defined by the conical shape.

36. The method according to claim 35, wherein the conical shape is configured as an electrostatic element of the ionizer.

37. The method according to claim 35, further comprising guiding the radical ions as a beam toward the mass spectrometer via an electrostatic lens.

38. The method according to claim 24, further comprising controlling the operation of the radical particle source based on the quantity of radical ions measured by the mass spectrometer.

39. The method according to claim 38, wherein controlling the operation of the radical particle source includes controlling at least one of 1) the quantity of radical particles generated over a predetermined time and 2) the time length over which the radical particles are generated.

40. The method according to claim 38, wherein controlling the operation of the radical particle source includes controlling at least one of the power, gas flow, gas pressure, and temperature of the gas flow path of the flow channel.

41. The method according to claim 24, further comprising selectively sealing the aperture via a stopper.

42. The method according to claim 24, wherein the surface surrounding the aperture is non-metallic and exhibits lower reactivity and recombination coefficients for the radical particles than a metal surface.

43. The method according to claim 24, wherein the surface surrounding the aperture is made of metal and exhibits low reactivity with the radical particles.

44. The method according to claim 24, wherein the flow channel is a conduit extending from a radical source to a process chamber.

45. The method according to claim 24, wherein the flow channel is a region downstream of the reaction zone of the process chamber.

46. The method according to claim 24, wherein the flow channel is a pipeline downstream of the process chamber.

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