Dynamic frequency tuning for microwave power amplifiers

Abstract

In some aspects, the embodiments described herein relate to a method for tuning the frequency of microwave power delivered to a cavity, the method comprising exciting plasma in the cavity. Embodiments may further include scanning the frequencies from a first frequency to a second frequency, wherein a setpoint frequency within the range of the first to the second frequencies has the lowest reflected power. In embodiments, the method further includes setting the frequency of the microwave power delivered to the cavity as the setpoint frequency. The method may further include changing the setpoint frequency when a measured value of the reflected power exceeds a threshold.

Description

[0001] Interactive reference for related applications

[0002] This application claims priority to U.S. Patent Application No. 18 / 624,990, filed April 2, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This embodiment relates to the field of semiconductor manufacturing, and more specifically to a process for frequency tuning of a microwave power amplifier for use in plasma processing operations. Background Technology

[0004] In plasma handling equipment, a power delivery path is provided to deliver power (e.g., radio frequency (RF) power or microwave power) to the chamber. This power delivery path may include a power supply coupled to a power amplifier, coaxial cables, impedance matching, and an antenna. Ideally, the power delivery path is tuned to minimize reflected power returning to the power delivery path. This can be achieved by matching the impedance of the power delivery path to the impedance of the load (e.g., the plasma within the chamber). Reducing reflected power is beneficial because reflected power can damage the power delivery path and reduce its efficiency. For example, high levels of reflected power can negatively affect and / or damage power amplifiers, coaxial interconnects, etc. Summary of the Invention

[0005] In some aspects, the embodiments described herein relate to a method for tuning the frequency of microwave power delivered to a cavity, the method comprising exciting a plasma in the cavity. Embodiments may further include scanning the frequency from a first frequency to a second frequency, wherein a setpoint frequency within the range from the first frequency to the second frequency has the lowest reflected power. In embodiments, the method further includes setting the frequency of the microwave power delivered to the cavity to the setpoint frequency. The method may further include changing the setpoint frequency when a measured value of the reflected power exceeds a threshold.

[0006] In some aspects, the technology described herein relates to an apparatus comprising a microwave power amplifier, wherein the microwave power amplifier includes a sweep generator. In one embodiment, an impedance match is coupled to the microwave power amplifier, and an antenna is coupled to the impedance match. In another embodiment, the apparatus may further include a controller communicatively coupled to the microwave power amplifier and configured to control the sweep generator.

[0007] In some aspects, the technology described herein relates to a method for frequency tuning of a multi-channel power amplifier system, the method comprising scanning a plurality of power amplifiers by means of a frequency range from a first frequency to a second frequency. The method may further comprise setting each of the plurality of power amplifiers to a setpoint frequency that provides the lowest reflected power, and automatically tuning each of the plurality of power amplifiers during process formulation. In embodiments, automatic tuning comprises changing the setpoint frequency for each of the plurality of power amplifiers. Attached Figure Description

[0008] Figure 1A This is a cross-sectional view of a semiconductor processing tool for generating microwave plasma using multiple dielectric resonator antennas (DRAs) according to an embodiment.

[0009] Figure 1B This is a plan view of a DRA array above a dielectric plate for use in a microwave plasma semiconductor processing tool, according to an embodiment.

[0010] Figure 2 This is a schematic diagram of a microwave power transfer system for a semiconductor processing tool used to generate microwave plasma, according to an embodiment.

[0011] Figure 3 This is a schematic diagram of a microwave power delivery system having multiple power delivery channels according to an embodiment, wherein each channel includes a sweep generator coupled to a controller.

[0012] Figure 4 This is a flowchart of a process for tuning the frequency of a power amplifier in a microwave power delivery channel to minimize reflected power, according to an embodiment.

[0013] Figure 5 This is a flowchart of a process for automatically tuning the frequency after a frequency sweep, according to an embodiment.

[0014] Figure 6 It is a graph showing the frequency change over time during the microwave power transfer tuning process during the process formulation, according to the embodiment.

[0015] Figure 7A This is a diagram illustrating the process of tuning a microwave frequency during a recipe with multiple pulses, according to an embodiment.

[0016] Figure 7B It is a diagram of a process for tuning microwave frequencies during a recipe with multiple pulses, according to an embodiment, wherein each pulse includes two different airflows.

[0017] Figure 7CThis is a diagram illustrating the process of tuning microwave frequencies during a formulation with a single continuous airflow, according to an embodiment.

[0018] Figure 8 This is a block diagram of an exemplary computer system according to an embodiment, which can be used in conjunction with processing tools. Detailed Implementation

[0019] The embodiments described herein include apparatus and processes for tuning the frequency of a microwave power amplifier to reduce reflected power. Several specific details are set forth in the following description to provide a thorough understanding of the embodiments. These embodiments may be practiced by those skilled in the art without such specific details. In other instances, well-known aspects have not been described in detail to avoid unnecessarily obscuring the embodiments. Furthermore, it should be understood that the various embodiments shown in the accompanying drawings are exemplary representations and are not necessarily drawn to scale.

[0020] This document describes various embodiments or aspects of the present disclosure. In some embodiments, these embodiments are practiced separately. However, the embodiments are not limited to those practiced in isolation. For example, two or more different embodiments may be combined to be practiced as a single device, process, structure, etc. In some cases, all of the various embodiments may be combined together. In other cases, a portion of a first embodiment may be combined with portions of one or more different embodiments. For example, a portion of a first embodiment may be combined with a portion of a second embodiment, or a portion of a first embodiment may be combined with portions of a second and a third embodiment.

[0021] The embodiments described and discussed herein in conjunction with the accompanying drawings are provided for the purpose of explaining some of the principles in the basic principles of this disclosure. However, the scope of this disclosure covers all related, potential, and / or possible embodiments, even if they differ from the idealized and / or exemplary examples presented. This disclosure even covers the incorporation and / or utilization of modern, future, and / or unknown components, devices, systems, etc., as alternatives to functionally equivalent, similar, and / or analogous components, devices, systems, etc., used in the embodiments described and / or discussed herein for purposes of explanation, demonstration, and example.

[0022] The increasing importance of microwave plasma sources in semiconductor processing environments has been observed. This is likely at least in part due to the improved plasma performance provided when using microwave power supplies. Compared to conventional radio frequency (RF)-based plasmas (e.g., capacitively coupled plasma (CCP), inductively coupled plasma (ICP), etc.), microwave plasmas provide a higher free radical flux to the substrate. That is, the plasma density of microwave plasmas can be higher. Simultaneously, the ion energy at the substrate surface from microwave plasmas is lower than that from typical RF-based plasmas. More specifically, the ion energy is typically well below the general damage threshold of approximately 30 eV.

[0023] Previous attempts to provide microwave power relied on magnetron solutions. The use of magnetrons resulted in bulky and difficult-to-control systems. Magnetron solutions for implementing impedance matching are particularly problematic when multi-channel microwave plasma tools are required. Standard impedance matching solutions for magnetron-based architectures use fixed frequencies and short-circuit tuners (e.g., containing a single or multiple short wires). A short-circuit tuner is a mechanically movable short wire that can short-circuit a section of the transmission line along the main signal line. Variable impedance can be provided by changing the short wire's location and / or geometry. Therefore, the short wire and its associated actuator occupy a relatively large space. This additional space is not particularly problematic when using a single microwave power delivery channel. However, when using multi-channel solutions, each channel requires a dedicated short wire (or group of short wires) and associated actuators. This can significantly increase the overall size of the tool and also increase the complexity of short wire control. Therefore, solutions using multiple short-wire tuners quickly become impractical.

[0024] Therefore, solid-state solutions have been recommended for microwave power supplies. Solid-state solutions offer enhanced control while also reducing the form factor of the power delivery system. The benefit of a reduced form factor is that multiple microwave channels can be used for a single processing tool. Solid-state power amplifiers allow for variable frequency operation instead of fixed frequency. Impedance matching can also be optimized by controlling various parameters of each microwave channel to minimize or eliminate reflected power in the system.

[0025] However, existing tuning capabilities remain limited, even with solid-state solutions. In particular, existing power amplifier tuning is slow and performed one-by-one. For example, tuning the frequency of each power amplifier can take up to three minutes. For multi-channel tools, such as those described herein, this can require more than an hour of tuning before the tool can be used to process the substrate. Because tuning is a time-consuming process, multi-operation process formulations (e.g., different gases flowing into the chamber during a single formulation) are also difficult to optimize. Using variable impedance matching may offer some benefits, but including and controlling multiple variable impedance matches (e.g., one variable impedance match per power delivery channel) is difficult to manage in high-volume manufacturing tools.

[0026] Therefore, the embodiments disclosed herein include microwave plasma tools comprising a multi-channel microwave power delivery system, wherein each of the power amplifiers includes a frequency tuning component. In an embodiment, the frequency tuning component may include a sweep generator that allows for rapid sweeping across a frequency range. During a frequency scan, the frequency with the lowest reflected power is set as a setpoint frequency. Subsequently, an automatic tuning process is used to monitor the setpoint frequency to maintain low reflected power throughout the process formulation.

[0027] Frequency sweeping can be performed rapidly (e.g., within less than 100 ms). Therefore, multiple frequency sweeps can be performed throughout the process formulation to maintain low reflected power even when conditions inside the chamber change (e.g., due to different gas flows). Furthermore, frequency sweeping can be performed in parallel on each microwave power transfer channel in the microwave power transfer channel.

[0028] Therefore, frequency tuning processes that previously took over an hour can now be performed directly during the process recipe itself. This allows for a significant increase in tool uptime following planned maintenance (PM) and / or changes to the microwave power delivery path and / or hardware changes throughout the tool. The embodiments disclosed herein also allow for an extended operating window for a given tool to enable the implementation of different process recipes without requiring substantial downtime to tune each individual recipe. Furthermore, a single microwave plasma tool can be used for different types of processes, such as plasma-enhanced atomic layer deposition (PEALD), plasma-enhanced chemical vapor deposition (PECVD), annealing, plasma cleaning, and / or plasma treatment.

[0029] Examples of multi-channel microwave plasma tools Figure 1A As shown. Now refer to Figure 1AA cross-sectional view of a semiconductor processing tool 100 is illustrated according to an embodiment. The semiconductor processing tool 100 may be a tool for processing a substrate 101 using plasma 105 generated by using microwave power. In embodiments, the tool 100 may be a plasma deposition tool (e.g., microwave PECVD, microwave PEALD, etc.), a microwave plasma etching tool, a microwave plasma processing tool, and / or other similar tools. The substrate 101 may be any substrate suitable for fabricating semiconductor structures. For example, the substrate 101 may be a silicon wafer or any other semiconductor wafer. The substrate 101 may contain any suitable shape factor, such as a 300 mm diameter, a 400 mm diameter, or a similar diameter. In embodiments, the substrate 101 may be supported on a base 108. The base may include clamping means for securing the substrate 101 during processing. The clamping means may include an electrostatic chuck (ESC) or a similar device.

[0030] In an embodiment, tool 100 may include chamber 107. Chamber 107 may be adapted to support a vacuum environment within chamber 107. This vacuum environment may be at a pressure suitable for plasma 105 formation. That is, a “vacuum environment” does not necessarily mean a perfect vacuum environment is required. For example, chamber 107 may support a rough vacuum (e.g., pressures up to approximately 800 Torr). Nevertheless, chamber 107 may also support a higher vacuum environment (i.e., a lower pressure). A low-pressure environment can be provided by using an exhaust device, a vacuum pump, and / or similar devices (not shown for simplicity). Chamber 107 may also include a slit valve (not shown) for allowing substrate 101 to enter and exit chamber 107.

[0031] In some embodiments, tool 100 may include a cover assembly 110. Cover assembly 110 may include a dielectric plate 112 disposed opposite base 108. The dielectric material of dielectric plate 112 may include ceramic in some embodiments. Dielectric plate 112 may include paths, channels, holes, and / or similar arrangements (not shown) for dispersing gas into chamber 107. In some cases, dielectric plate 112 may be referred to as a shower head. In some embodiments, a plurality of dielectric resonator antennas (DRAs) 115 may be distributed on the top surface of dielectric plate 112. Each DRA 115 may each include a disk 116 and a pin 117 inserted into a hole in the top surface of disk 116.

[0032] In one embodiment, disk 116 is a dielectric material, such as ceramic. Disk 116 may be the same dielectric material as dielectric plate 112. However, in other embodiments, disk 116 and dielectric plate 112 may be made of different materials. In one embodiment, disk 116 is a cylindrical object. However, other axisymmetric shapes may also be used in some embodiments. The size and material of disk 116 may be selected to set the desired resonant frequency in order to couple microwave power into plasma 105.

[0033] In one embodiment, pin 117 is a conductive pin (e.g., copper). Pin 117 may be inserted into a hole in disk 116 to a desired depth. The depth of insertion into disk 116 can be controlled to provide the desired response. In another embodiment, the opposite end of pin 117 is coupled to the rest of the microwave power supply system (described in more detail below). For example, pin 117 may be impedance matched.

[0034] In the illustrated embodiment, DRA 115 is depicted as a bare dielectric material disk 116 with conductive pins 117. However, it should be understood that DRA 115 may include a housing surrounding a portion (or all) of DRA 115. For example, a conductive housing may be provided around DRA 115. This conductive housing may be grounded in some embodiments. In embodiments, the housing may contain aluminum, etc.

[0035] Now for reference Figure 1B A plan view of the cover assembly 110 is shown according to an embodiment. In this embodiment, the cover assembly 110 may be related to the above-described... Figure 1A The cover assembly 110 is similar. For example, the cover assembly 110 may include a dielectric plate 112. Figure 1B The dielectric plate 112 is illustrated as circular. However, in other embodiments, the dielectric plate 112 can have any shape. In some embodiments, the dielectric plate 112 may comprise a ceramic material.

[0036] In one implementation, multiple DRAs 115 may be distributed on the dielectric plate 112. These DRAs 115 may be related to those described above. Figure 1A The DRA 115s are similar. For example, each DRA 115 may include a disc and a pin. A housing may also surround the disc and pin of each DRA 115. In the illustrated embodiment, twenty-five DRA 115s are distributed on the dielectric plate 112. However, it should be understood that in other embodiments, the cover assembly 110 may include one or more DRA 115s. In a particular embodiment, nineteen DRA 115s are provided on the dielectric plate 112.

[0037] In implementations, the layout of the plurality of DRA 115s can include any suitable pattern. In a particular implementation, the DRA 115s may be provided in a symmetrical pattern around the dielectric plate 112. Implementations may also include a series of rings of DRA 115s that are generally concentric with each other, such as... Figure 1B As shown. Other packaging configurations can also be used to provide a denser DRA 115 layout.

[0038] Using multiple DRAs 115 allows for better control of the processing environment within chamber 107. That is, plasma 105 can be controlled with greater spatial variation. This allows different plasma parameters to be applied, for example, to the center and edges of substrate 101. Variable control in this manner can result in improved overall processing uniformity.

[0039] Now for reference Figure 2 A schematic diagram of a microwave power delivery system 220 is shown according to an embodiment. In this embodiment, the microwave power delivery system 220 may be coupled to a plasma processing tool similar to the tool 100 described in more detail herein. The microwave power delivery system 220 may be a solid-state microwave power delivery system 220. That is, microwaves can be generated without the use of a magnetron or the like. Therefore, a plurality of microwave power delivery channels 230 may be included within a reasonable form factor. Figure 2 Microwave power delivery channels 230A to 230N are provided as examples. The number of microwave power delivery channels 230 can be equal to the number of DRAs required by the tool. For example, there may be one or more microwave power delivery channels 230, ten or more microwave power delivery channels 230, or twenty or more microwave power delivery channels 230. In a particular embodiment, there may be nineteen microwave power delivery channels 230.

[0040] In some implementations, the microwave power delivery system 220 may include a power supply 222. A single power supply 222 may supply power to each of the microwave power delivery channels 230. For example, a coaxial cable 223 may electrically couple the power supply 222 to multiple microwave channels 230. In some implementations, the power supply 222 may be an AC / DC power supply. More specifically, the power supply 222 may be a solid-state microwave power supply 222. Although in Figure 2 The diagram shows a single power source 222, but it should be understood that in other embodiments, two or more power sources 222 may be used in the power delivery system 220.

[0041] In one embodiment, the microwave power delivery channel 230 may each include multiple components that acquire microwave power and deliver it to a plasma processing tool. In another embodiment, the microwave power delivery channel 230 may include a microwave power amplifier 231, such as a solid-state microwave power amplifier. The microwave power amplifier may be electrically coupled to an impedance matching 235 via a coaxial cable 224. In some embodiments, the impedance matching 235 may be a conical impedance matching (CIT). In another embodiment, the impedance matching 235 is electrically coupled to a DRA 215. The DRA 215 may resemble any DRA described in more detail herein. For example, the DRA 215 may include a disk 216 and a pin 217. The pin 217 may be coupled to the impedance matching 235 via soldering, a connector, or the like. The DRA 215 may be used to couple microwave power to a gas (not shown) within the chamber to initiate and / or sustain plasma within the chamber.

[0042] Impedance matching 235 can be used to match the impedance of DRA 215 to the characteristic impedance of coaxial cable 224. This is done to reduce (or eliminate) reflected power in the system at a given frequency. For example, at an operating frequency of approximately 2,450 MHz, the impedance of coaxial cable 224 might be approximately 50 ohms.

[0043] As described above, high levels of reflected power can damage the microwave power delivery system 220. Processing may be paused when high reflected power is detected. This could occur midway through the process formulation, and the substrate being processed may not receive proper handling. The substrate may need to be scrapped or reworked. Therefore, yield and production volume are negatively impacted. Alternatively, if the tool fails to stop in time, reflected power may damage the microwave power amplifier 231 or other components. This increases the ownership cost of the tool because parts need to be replaced more frequently. Replacement of parts also results in tool downtime, which can increase ownership costs and reduce production volume.

[0044] To reduce reflected power, the embodiments disclosed herein include a microwave power delivery path that enables dynamic frequency tuning. Specifically, frequency sweeping is performed to find frequencies within a range exhibiting the lowest reflected power. After finding the ideal frequency to minimize reflected power, the device continues to monitor the reflected power and adjust the frequency of the microwave power to maintain a low reflected power level. Figure 3 A microwave power delivery system 320 capable of providing such dynamic tuning is shown.

[0045] Now for reference Figure 3A schematic diagram of a microwave power delivery system 320 is shown according to an embodiment. In this embodiment, the microwave power delivery system 320 may include a plurality of microwave power delivery channels 330A to 330N. The number of microwave power delivery channels 330 may match the number of antennas (e.g., DRA 315) required by a microwave plasma tool (not shown).

[0046] In one embodiment, each microwave power delivery channel 330 may include a microwave power amplifier 331, which is coupled to an impedance match 335 via a coaxial cable 324. In another embodiment, the impedance match 335 may be a fixed match, such as a CIT. In yet another embodiment, the impedance match 335 is electrically coupled to a DRA 315. The DRA 315 may resemble any DRA described in more detail herein. For example, the DRA 315 may include a disk 316 and a pin 317. The pin 317 may be coupled to the impedance match 335 via soldering, a connector, or the like. The DRA 315 may be used to couple microwave power to a gas (not shown) within a cavity to initiate and / or sustain plasma within the cavity.

[0047] To enable dynamic frequency tuning, power amplifier 331 may include sweep generator 332. Sweep generator 332 may be a component suitable for generating a frequency sweep across a range from a first frequency to a second frequency. In some embodiments, the first frequency may be 2,400 MHz and the second frequency may be 2,500 MHz. However, different ranges may be used in some embodiments. In some embodiments, the first frequency may refer to a start frequency and the second frequency may refer to a stop frequency. However, the frequency sweep may also include a frequency range exceeding the range defined by the first and second frequencies. The frequency sweep generated by sweep generator 332 may be completed within a short duration. For example, in some embodiments, the duration of the frequency sweep may be as long as 100 ms. The sweep speed of the frequency sweep may be between 0.5 MHz per millisecond and 5 MHz per millisecond. However, faster or slower frequency sweeps may be used in some embodiments.

[0048] The sweep generator 332 can be used as part of the initial fast sweep process of dynamic tuning operation, as will be described in more detail herein. The sweep generator 332 (or another suitable frequency modulation component) can enable autotuning operation during dynamic tuning operation. In the autotuning section, the sweep generator may modulate the frequency between 0.1 MHz per millisecond and 1.0 MHz per millisecond. These small variations can be used to see if reflected power can be reduced during the execution of the process recipe. For example, changes in load (e.g., plasma) or other chamber conditions may cause changes in impedance. This could result in an increase in reflected power if autotuning is not implemented. A more detailed description of the autotuning application will be provided herein.

[0049] In this implementation, power amplifier 331 may be coupled to controller 340. More specifically, sweep generator 332 of power amplifier 331 may be coupled to controller 340. Controller 340 may include any suitable computer, server, or other computing device. Controller 340 may receive feedback from the microwave power transfer system related to reflected power. For example, a sensor (not shown) for measuring the reflected power along each microwave power transfer channel in microwave power transfer channel 330 may provide controller 340 with a measurement of the reflected power. Controller 340 uses this feedback to control sweep generator 332 to perform frequency sweeping and / or autotuning processes to minimize reflected power.

[0050] In an implementation, controller 340 may be coupled to each of the microwave power delivery channels 330A through 330N. This allows for simultaneous (also known as parallel) frequency tuning control of all microwave power delivery channels 330 in the microwave power delivery system 320. This provides significant time savings compared to existing solutions that tune individual channels sequentially. Due to rapid frequency sweeps (e.g., less than 100 milliseconds) and continuous autotuning after the frequency sweep, frequency tuning across the entire microwave power delivery system 320 can be performed at the start of the process recipe (and throughout the entire process recipe). As mentioned above, this is a significant benefit compared to existing solutions that require tuning before the process recipe is executed. This also allows for more accurate tuning of multiple process recipes that may contain different processing conditions in a single recipe (e.g., reducing reflected power). Therefore, the operational range of microwave plasma processing tools is extended to support a wider range of applications and / or recipes.

[0051] Now for reference Figure 4According to an embodiment, a process 450 for tuning a microwave power transfer system to reduce reflected power during operation is illustrated. In an embodiment, process 450 may begin with operation 451. In an embodiment, operation 451 may include exciting plasma in a chamber. This chamber may be a chamber of a microwave plasma processing tool, such as tool 100 described in more detail herein. In an embodiment, plasma excitation may take between approximately 1.0 ms and approximately 100 ms. During plasma excitation, the frequency of the microwave power may be substantially stable. The excitation frequency may be a default frequency. For example, in some embodiments, the excitation frequency may be 2,450 MHz. The excitation frequency may also be set to a frequency determined in previous iterations of the process recipe. For example, information from previous frequency tuning operations may be used to begin subsequent processes.

[0052] In one embodiment, process 450 can proceed to operation 452, which includes scanning the frequency of microwave power delivered to the chamber from a first frequency scan to a second frequency scan. In another embodiment, the frequency scan can be implemented using a sweep generator or the like. In yet another embodiment, the frequency sweep can be a linear sweep, a stepped sweep, a nonlinear sweep, etc. In some embodiments, the frequency sweep may sometimes be referred to as a "chirp." The first and second frequencies can be the expected minimum and maximum frequencies for operation suitable for a particular process formulation. For example, the first frequency might be 2,400 MHz, and the second frequency might be 2,500 MHz. However, in some embodiments, different first and second frequencies may also be used (e.g., frequencies with a larger range, a smaller range, or similarly sized ranges with different endpoints).

[0053] In implementations, frequency scanning may include scan rates up to approximately 5.0 MHz per millisecond. For example, in some implementations, scan rates between 0.5 MHz and 5.0 MHz per millisecond may be used. In implementations, the duration of frequency scanning may be up to approximately 100 ms. More generally, the duration of frequency scanning may be similar to the duration of plasma excitation. The duration of frequency scanning may also be less than 5%, less than 2%, or less than 1% of the duration of pulses in the process formulation.

[0054] In an implementation, a setpoint frequency within the range of a first frequency to a second frequency may have the lowest reflected power. That is, in a frequency scanning device, the reflected power of each frequency in the power is measured (e.g., by a sensor) to determine which frequency provides the best reflected power performance (i.e., the lowest reflected power).

[0055] In one implementation, process 450 then proceeds to operation 453, which may include setting the frequency of the microwave power delivered to the chamber to a setpoint frequency. Setting the frequency to the setpoint frequency initiates the process with ideal reflected power performance.

[0056] In an implementation, process 450 may proceed to operation 454, which includes tuning the frequency of microwave power delivered to the cavity by changing (e.g., increasing or decreasing) the setpoint frequency while simultaneously monitoring the level of reflected power. Operation 454 may sometimes be referred to as autotuning. In an implementation, the setpoint frequency may be changed at periodic intervals and / or when the reflected power exceeds a predetermined threshold. The rate at which the frequency can be changed during operation 454 can be as high as approximately 2 MHz per millisecond. For example, the frequency change may be implemented at a rate between 0.1 MHz per millisecond and 1.0 MHz per millisecond.

[0057] Now for reference Figure 5 A more detailed process flow diagram for implementing automatic tuning 550 is illustrated. In an embodiment, process 550 may begin with operation 551, which includes providing microwave power to the chamber along a power delivery path. The power delivery path may be similar to the microwave power delivery channel described in more detail herein. In an embodiment, the microwave power is at a first frequency. In an embodiment, the first frequency may be a setpoint frequency determined during a frequency sweep similar to operation 452 described in more detail above.

[0058] In one implementation, process 550 may proceed to operation 552, which includes monitoring the level of reflected power along the power transfer path. In another implementation, a sensor may be integrated into the power transfer path to provide a measurement of the reflected power.

[0059] In one implementation, process 550 may proceed to operation 553, which includes changing the first frequency to a second frequency when the level of reflected power exceeds a threshold. For example, the threshold might be a percentage of a previously measured level of reflected power. In some implementations, the threshold level might include an increase in reflected power greater than 1%, greater than 3%, or greater than 5%. That is, when reflected power increases, autotuning operation might initiate a feedback loop to reduce reflected power.

[0060] In implementation, the reflected power may change for a variety of reasons. For example, the reflected power may increase when the conditions within the chamber (e.g., plasma properties) change. This can occur when the process formulation changes, the flow rate of the gas entering the chamber changes, the power level changes, or there is wear on chamber components. Therefore, autotuning allows for flexibility in implementing plasma processing formulations with non-uniform process conditions.

[0061] In implementation, operations 552 and 553 can be repeated any number of times during the duration of the process formulation. For example, operations 552 and 553 may be repeated multiple times during a single pulse of gas flow into the chamber. The dynamic variation of frequency during the single pulse provides performance improvement to the processing tool by maintaining low reflected power along the power delivery path. As can be understood, subsequent iterations of operation 553 can be viewed as repeating a series of steps to change the plasma excitation frequency, to sweep the frequency, and to automatically tune the frequency during each process formulation cycle.

[0062] In implementation, processes 450 and 550 can operate in conjunction with each other. For example, process 550 can be considered a more detailed explanation of operation 454 within process 450. Processes 450 and 550 can be implemented within a single process recipe. Processes 450 and 550 can be performed once, or they can be repeated an arbitrary number of times. Examples of different implementations of processes 450 and 550 are provided. Figure 6 and Figures 7A to 7C Illustration.

[0063] Now for reference Figure 6 According to an embodiment, Figure 660 illustrates the frequency of microwave power delivered to the chamber as a function of time. In this embodiment, the first duration 661 comprises a fixed frequency (e.g., approximately 2,450 MHz) when the plasma is struck in the chamber. The first duration 661 may correspond to operation 451 in process 450. In this embodiment, the first duration 661 may be as long as approximately 100 ms.

[0064] Subsequently, the second duration 662 illustrates a frequency sweep similar to operation 452 in process 450. In Figure 660, the frequency sweep is shown as linear. However, other sweep modes (such as those described above) may also be used during the second duration 662. In one embodiment, the sweep during the second duration 662 begins with a constant input frequency from the first duration 661. However, in other embodiments, the starting frequency of the frequency sweep can be any suitable frequency (e.g., 2,400 MHz).

[0065] As described above, the frequency sweep in the second duration 662 can be used to set the setpoint frequency during the third duration 663. In an embodiment, the third duration 663 can be considered an auto-tuning region. As shown, tuning operations 664 (e.g., increasing and / or decreasing the frequency) can be implemented to maintain low reflection power throughout the process formulation.

[0066] Now for reference Figure 7A According to an embodiment, Figure 770 illustrates the frequency tuning process in the process formulation. Figure 7AIn this context, the Y-axis is arbitrary. That is, the Y-position of each line is not associated with any value, but rather used to more clearly illustrate the distinctions between different operations in the frequency tuning process. Figure 7A In this process formulation, the process formulation may include repeating cycles (i.e., pulses) of substantially the same application of gas and / or process conditions within the plasma chamber. For example, the three pulses 771 to 773 may be substantially similar to each other in some embodiments. In embodiments, pulses 771 to 773 may be separated by gaps 778. These gaps 778 may be purge cycles, rest cycles, etc.

[0067] In an implementation, each pulse 771 to 773 may begin with a plasma excitation region 774. Following the plasma excitation region 774, a frequency sweep region 775 is performed. The frequency sweep region 775 may resemble operation 452 in process 450. The frequency sweep region 775 can be used to determine a setpoint frequency, which is subsequently used during an auto-tuning region 776. The auto-tuning region 776 may resemble operation 454 of process 450 or process 550. As shown, the duration of the auto-tuning region 776 may be longer than the duration of the plasma excitation region 774 and / or the frequency sweep region 775.

[0068] Now for reference Figure 7B According to an embodiment, a graph 770 illustrates the frequency tuning process in the process formulation. Figure 7B In this context, the Y-axis is arbitrary. That is, the Y-position of each line is not related to any value, and the Y-position is used to more clearly illustrate the interruptions between different operations in the frequency tuning process. Figure 7B In this process formulation, the process formulation may include repeated cycles (i.e., pulses) of substantially the same application of gas and / or process conditions within the plasma chamber. For example, the three pulses 771 to 773 may be substantially similar to each other in some embodiments. In embodiments, pulses 771 to 773 may be separated by gaps 778. These gaps 778 may be purge cycles, rest cycles, etc.

[0069] In an implementation, each of pulses 771 to 773 may include a first duration and a second duration (e.g., 771A and 771B, 772A and 772B, and 773A and 773B). A portion of each pulse may correspond to a first chamber condition, and a portion B of each pulse may correspond to a second chamber condition. For example, the first chamber condition may be a first gas flow rate and / or composition, while the second chamber condition may be a second gas flow rate and / or composition. In one implementation, the first gas composition may be an inert gas flow, and the second gas composition may be a process gas composition. Other implementations may include two different process gas compositions. Furthermore, although each pulse is illustrated as having two durations (A and B), it should be understood that any number of durations can be used in each pulse (for any number of different chamber conditions). Additionally, although each of pulses 771 to 773 is illustrated as substantially similar to each other, two or more pulses in pulses 771 to 773 may be different from each other.

[0070] In one implementation, the first duration (A) of each pulse 771 to 773 may begin with a plasma excitation region 774. Following the plasma excitation region 774, a first frequency sweep region 775A is implemented. The first frequency sweep region 775A may be similar to operation 452 in process 450. The first frequency sweep region 775A can be used to determine a first setpoint frequency, which is subsequently used during a first auto-tuning region 776A. The first auto-tuning region 776A may be similar to operation 454 of process 450 or process 550.

[0071] A second frequency sweep region 775B is implemented as the second duration (B) of each pulse 771 to 773 changes. The second frequency sweep region 775B may be similar to the first frequency sweep region 775A. However, implementations may also include differences between the first frequency sweep region 775A and the second frequency sweep region 775B (e.g., different sweep rates, different ranges, etc.). The second frequency sweep region 775B can be used to determine a second setpoint frequency, which is subsequently used during a second auto-tuning region 776B. The second auto-tuning region 776B may be similar to the first auto-tuning region 776A. However, implementations may also include differences between the first frequency auto-tuning region 776A and the second auto-tuning region 776B (e.g., different thresholds, etc.).

[0072] Now for reference Figure 7C A diagram 770 illustrating the frequency tuning process in the process formulation is provided according to an embodiment. Figure 7CIn this model, the Y-axis is arbitrary. That is, the Y-position of each line is independent of any value, and the Y-position is used to more clearly illustrate the interruptions between different operations in the frequency tuning process. Figure 7C In this context, the process formulation may include a single continuous process. For example, the process may be a PECVD process, a plasma treatment process, a plasma cleaning process, etc. That is, in some embodiments, a single process 777 with substantially constant chamber conditions (without any pulses) may be used.

[0073] In one implementation, process 777 may begin with plasma excitation region 774. Following plasma excitation region 774, a frequency sweep region 775 is performed. Frequency sweep region 775 may resemble operation 452 in process 450. Frequency sweep region 775 can be used to determine a setpoint frequency, which is subsequently used during autotuning region 776. Autotuning region 776 may resemble operation 454 in process 450 or process 550. As shown, the duration of autotuning region 776 may be longer than the duration of plasma excitation region 774 and / or frequency sweep region 775. Autotuning region 776 may continue until the end of process 777.

[0074] Now for reference Figure 8 A block diagram of an exemplary computer system 800 of a processing tool is illustrated according to an embodiment. In this embodiment, the computer system 800 is coupled to and controls the processing within the processing tool. The computer system 800 may be connected (e.g., networked) to other machines in a local area network (LAN), an internal network, an external network, or the Internet. The computer system 800 may operate as a server or client machine in a client-server network environment, or act as a peer machine in a peer-to-peer (or distributed) network environment. The computer system 800 may be a personal computer (PC), a tablet PC, a set-top box (STB), a personal digital assistant (PDA), a mobile phone, a network facility, a server, a network router, a switch, or a bridge, or any machine capable of executing a set of instructions (sequentially or otherwise) specifying the actions to be taken by that machine. Furthermore, although only a single machine is shown for the computer system 800, the term "machine" should also be understood to include a collection of any machines (e.g., computers) that individually or collectively execute a set (or more sets) of instructions to perform any or more of the methodologies described herein.

[0075] Computer system 800 may include computer program product or software 822 having a non-transitory machine-readable medium on which instructions are stored, which can be used to program computer system 800 (or other electronic device) to perform processes according to an embodiment. Machine-readable medium includes any mechanism for storing or transmitting information in a machine-readable (e.g., computer-readable) form. For example, machine-readable (e.g., computer-readable) media include machine-readable (e.g., computer-readable) storage media (e.g., read-only memory (“ROM”), random access memory (“RAM”), disk storage media, optical disk storage media, flash memory devices, etc.), machine-readable (e.g., computer-readable) transmission media (electrical, optical, acoustic, or other forms of propagated signals (e.g., infrared signals, digital signals, etc.)), and so on.

[0076] In one embodiment, the computer system 800 includes a system processor 802, main memory 804 (e.g., read-only memory (ROM), flash memory, dynamic random access memory (DRAM), such as synchronous DRAM (SDRAM) or Rambus DRAM (RDRAM), etc.), static memory 806 (e.g., flash memory, static random access memory (SRAM), etc.) and auxiliary memory 818 (e.g., a data storage device), which communicate with each other via a bus 830.

[0077] System processor 802 represents one or more general-purpose processing devices, such as microsystem processors, central processing units, etc. More specifically, the system processor may be a Complex Instruction Set Computing (CISC) microsystem processor, a Reduced Instruction Set Computing (RISC) microsystem processor, a Very Long Instruction Word (VLIW) microsystem processor, a system processor implementing other instruction sets, or a system processor implementing a combination of instruction sets. System processor 802 may also be one or more special-purpose processing devices, such as application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), digital signal system processors (DSPs), network system processors, etc. System processor 802 is configured to execute processing logic 826 to perform the operations described herein.

[0078] The computer system 800 may further include a system network interface device 808 for communicating with other devices or machines. The computer system 800 may also include an image display unit 810 (e.g., a liquid crystal display (LCD), a light-emitting diode display (LED), or a cathode ray tube (CRT)), an alphanumeric input device 812 (e.g., a keyboard), a cursor control device 814 (e.g., a mouse), and a signal generation device 816 (e.g., a speaker).

[0079] Auxiliary memory 818 may include machine-accessible storage medium 831 (or more specifically, computer-readable storage medium) on which one or more instruction sets (e.g., software 822) are stored, embodying any or more of the methods or functions described herein. Software 822 may also reside wholly or at least partially in main memory 804 and / or system processor 802 during execution by computer system 800, which also constitute machine-readable storage media. Software 822 may further be transmitted or received via network 861 through system network interface device 808. In embodiments, network interface device 808 may operate using RF coupling, optical coupling, acoustic coupling, or inductive coupling.

[0080] Although machine-accessible storage medium 831 is shown as a single medium in the exemplary embodiment, the term "machine-readable storage medium" should be understood to include a single medium or multiple media (e.g., a centralized or distributed database, and / or associated caches and servers) that store one or more instruction sets. The term "machine-readable storage medium" should also be understood to include any medium capable of storing or encoding instruction sets for execution by a machine, and enabling the machine to perform any one or more methodologies. Therefore, "machine-readable storage medium" should be understood to include, but is not limited to, solid-state memory, optical media, and magnetic media.

[0081] Specific exemplary embodiments have been described in the foregoing specification. It is obvious that various modifications can be made to these embodiments without departing from the scope of the following claims. Therefore, the specification and drawings should be considered illustrative rather than restrictive.

Claims

1. A method for tuning the frequency of microwave power delivered to a cavity, the method comprising: Plasma is excited in the chamber; The frequencies are scanned from a first frequency to a second frequency, wherein a set point frequency within the range of the first frequency to the second frequency has the lowest reflection power; The frequency of the microwave power delivered to the cavity is set to the setpoint frequency; and The setpoint frequency is changed when the measured value of the reflected power exceeds the threshold.

2. The method of claim 1, wherein the threshold includes an increase of 5% or more in the reflected power.

3. The method of claim 1, wherein the first frequency is 2,400 MHz and the second frequency is 2,500 MHz.

4. The method of claim 1, wherein the duration of scanning the frequency is up to 100 ms.

5. The method of claim 1, wherein the frequency change rate during scanning the frequency is up to 5 MHz per millisecond.

6. The method of claim 1, wherein exciting the plasma, scanning the frequency, setting the setpoint frequency, and changing the setpoint frequency all occur within a single pulse of the processing formulation performed within the chamber.

7. The method of claim 6, wherein the single pulse further comprises: The frequency of the microwave power transmitted to the cavity is scanned a second time from the first frequency to the second frequency, wherein the second set point frequency in the range of the first frequency to the second frequency has the lowest reflected power; The frequency of the microwave power delivered to the cavity is set to the second setpoint frequency; and When the measured value of the reflected power exceeds the second threshold, the second setpoint frequency is changed.

8. The method of claim 7, wherein the single pulse comprises: The first gas component is introduced into the chamber for a first duration; as well as After the first duration, a second gas component is introduced into the chamber for a second duration, wherein the second scan of the frequency occurs during the second duration.

9. The method of claim 1, further comprising: Simultaneously, multiple frequencies of the microwave power delivered to the cavity along multiple power delivery paths are tuned.

10. The method of claim 9, wherein the tuning of the plurality of frequencies of the microwave power transmitted to the cavity along the plurality of power delivery paths is controlled by a controller communicatively coupled to a plurality of power amplifiers along each of the plurality of power delivery paths.

11. An apparatus, the apparatus comprising: A microwave power amplifier, wherein the microwave power amplifier includes a sweep generator; Impedance matching, wherein the impedance matching is coupled to the microwave power amplifier; Antenna, the antenna being coupled to the impedance matching; as well as A controller, which is communicatively coupled to the microwave power amplifier and configured to control the sweep generator.

12. The device of claim 11, wherein the impedance matching is fixed impedance matching.

13. The device of claim 11, wherein the antenna is a dielectric resonator antenna (DRA).

14. The device of claim 11, wherein the controller is communicatively coupled to a plurality of microwave power amplifiers, each of the plurality of microwave power amplifiers being impedance matched and coupled to an antenna.

15. The device of claim 14, wherein the plurality of microwave power amplifiers comprises ten or more power amplifiers.

16. A method for frequency tuning of a multi-channel power amplifier system, the method comprising: Multiple power amplifiers are scanned across a frequency range from a first frequency to a second frequency. Each of the plurality of power amplifiers is set to a setpoint frequency that provides the lowest reflected power; as well as During the process formulation, each of the plurality of power amplifiers is automatically tuned, wherein the automatic tuning includes changing the setpoint frequency for each of the plurality of power amplifiers.

17. The method of claim 16, wherein two or more of the setpoint frequencies are different from each other.

18. The method of claim 16, wherein the method is performed for each pulse of the process formulation.

19. The method of claim 16, wherein the plurality of power amplifiers comprises ten or more power amplifiers.

20. The method of claim 16, wherein the process formulation is a plasma-enhanced chemical vapor deposition (PECVD) process, a plasma-enhanced atomic layer deposition (PEALD) process, a plasma cleaning process, or a plasma treatment process.

Images