Compensating for parameter differences caused by matching circuits in multi-feed systems

Abstract

In one embodiment, the present disclosure relates to a system for providing energy to a plasma chamber having a plurality of power signal inputs. The power supply transmits an output signal to the matching circuit. Each matching circuit provides a different matching position. The memory stores, for each matching position of each matching circuit and for each output signal, parameter difference data of a parameter (e.g., power or phase) of the output signal at the output of the matching circuit. For each matching circuit and its respective output signal, the control circuit causes the power supply to change the parameter based on the parameter difference data, the change of the parameter preventing or reducing an expected difference between an expected value of the parameter and an actual value of the parameter.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to systems and methods for providing energy to a plasma chamber having multiple power signal inputs. BACKGROUND

[0002] Multi-feed plasma chambers for semiconductor processing applications benefit from accurate, repeatable, and uniform power delivery. However, such power delivery can be affected by unintended power loss and phase shift caused by impedance matching circuits used for impedance matching between a power source and the plasma chamber. SUMMARY

[0003] In one aspect, the present disclosure can relate to a system comprising: a power source transmitting output signals via power source outputs; a matching circuit coupled to the power source outputs, each matching circuit: configured to receive a single corresponding output signal of the output signals; comprising at least one variable network element, each variable network element having different configurations providing different matching positions; and configured to be coupled to a plasma chamber; a memory configured to store, for each matching position of each matching circuit and for each output signal, parameter difference data of a parameter of the output signal; wherein the parameter relates to power or phase of the output signal at an output of the matching circuit or at an input of the plasma chamber; and wherein the parameter difference data relates to an expected difference between a desired value of the parameter and an actual value of the parameter; and a control circuit configured to cause, for each matching circuit and its corresponding output signal, the power source to change the parameter of the output signal based on the parameter difference data of the matching position corresponding to a current matching position of the matching circuit, the change of the parameter of the output signal intended to prevent or reduce the expected difference between the desired value of the parameter and the actual value of the parameter.

[0004] In another aspect, a method of providing energy to a plasma chamber having multiple power signal inputs is disclosed, the method comprising: transmitting output signals to matching circuits such that each matching circuit receives a single corresponding output signal of the output signals; wherein each matching circuit comprises at least one variable network element, each variable network element having different configurations providing different matching positions, and each matching circuit is coupled to the plasma chamber; for each matching position of each matching circuit, and for each output signal, storing parameter difference data of a parameter of the output signal; wherein the parameter relates to a power or a phase of the output signal at an output of the matching circuit or at an input of the plasma chamber; and wherein the parameter difference data relates to an expected difference between a desired value of the parameter and an actual value of the parameter; and for each matching circuit and its corresponding output signal, causing the power supply to change the parameter of the output signal during system operation based on the parameter difference data of the matching position corresponding to a current matching position of the matching circuit, the change of the parameter of the output signal being intended to prevent or reduce the expected difference between the desired value of the parameter and the actual value of the parameter.

[0005] In another aspect, a system comprises: matching circuits configured to be coupled to a power supply, each matching circuit: configured to receive a corresponding output signal from the power supply; comprising at least one variable network element, each variable network element having different configurations providing different matching positions; and configured to be coupled to a plasma chamber; a memory configured to store, for each matching position of each matching circuit and for each output signal, parameter difference data of a parameter of the output signal; wherein the parameter relates to a power or a phase of the output signal at an output of the matching circuit or at an input of the plasma chamber; and wherein the parameter difference data is a value based on a difference between a desired value of the parameter and an actual value of the parameter; and a control circuit configured to, for each matching circuit and its corresponding output signal, cause the power supply to change the parameter of the output signal based on the parameter difference data of the matching position corresponding to a current matching position of the matching circuit, the change of the parameter of the output signal being intended to prevent or reduce an expected difference between the desired value of the parameter and the actual value of the parameter.

[0006] While the disclosed invention is applicable to semiconductor manufacturing systems, the invention is not limited thereto. BRIEF DESCRIPTION OF DRAWINGS

[0007] The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein:

[0008] Figure 1 is a schematic diagram of a system for manufacturing semiconductors according to one embodiment.

[0009] Figure 2 is a block diagram of a power supply according to one embodiment.

[0010] Figure 3is a matching circuit according to an embodiment.

[0011] Figure 4 is an electronic variable capacitor according to an embodiment.

[0012] Figure 5 is a schematic diagram of a first microstrip-based variable network element according to an embodiment.

[0013] Figure 6 is a schematic diagram of a second microstrip-based variable network element according to an embodiment.

[0014] Figure 7 is a flowchart of a method for providing energy to a plasma chamber having multiple power signal inputs according to an embodiment.

[0015] The accompanying drawings are not intended to limit the scope of the application, but rather to describe one or more embodiments thereof. DETAILED DESCRIPTION

[0016] The following description of preferred embodiments is merely exemplary in nature and is in no way intended to limit the scope of the present application(s) or the application(s) thereof. Descriptions of illustrative embodiments are intended to be read in connection with the drawings, which are to be considered part of the entire written description. The discussion herein describes and illustrates some possible non-limiting combinations of features that can exist alone or in other combinations of features. In addition, the term "or" as used herein, shall only be interpreted as a logical operator in terms of the greater than 50 percent probability and there is never intended to be a 50 / 50 division. In addition, the phrase "based on" as used herein shall not be construed as strictly a "based only on" but rather "based at least in part on." Further, the term "each" when used to refer to each of a plurality of items, does not require that every such item in the entire system or apparatus be addressed, but can instead simply refer to each of one or more such items recited in the system.

[0017] Ranges used throughout are used as shorthand for describing each and every value included in the range. Any value within the range can be selected as the terminus of the range. In addition, all references cited herein are hereby incorporated by reference in their entirety. In the event of a conflict in a definition in the present disclosure and that of a cited reference, the present disclosure takes precedent.

[0018] In the following description of drawings and descriptions of blocks or circuits, those skilled in the art will recognize that not all of the peripheral components or circuits are shown or described in the drawings or descriptions. For example, common components such as memory devices and power supplies can not be discussed herein as those of ordinary skill in the art will readily understand their role. In addition, the terms "coupled" and "operably coupled" can refer to a direct or indirect coupling of two components of a circuit.

[0019] Note that like or similar components or features can be described with like or similar reference numerals across different embodiments or figures. This does not presuppose that the components or features identified by a particular reference numeral are identical across every embodiment or figure, but rather that the components or features are generally similar or analogous.

[0020] Features of the present application can be implemented in software, hardware, firmware, or a combination thereof. The computer programs described herein are not limited to any particular embodiment and can be implemented in an operating system, application program, foreground or background process, driver, or any combination thereof. The computer programs can be executed on a single computer or server processor or multiple computers or server processors.

[0021] The processors described herein can be any central processing unit (CPU), microprocessor, microcontroller, computing or programmable device, or circuit configured to execute computer program instructions (e.g., code). The various processors can be embodied in any suitable type of computer and / or server hardware (e.g., desktop, laptop, notebook, tablet, cellular phone, etc.) and can include all of the usual ancillary components necessary to form a functional data processing device, including but not limited to a bus, software and data storage devices (such as volatile and non-volatile memory), input / output devices, graphical user interfaces (GUIs), removable data storage devices, and wired and / or wireless communication interface devices (including Wi-Fi, Bluetooth, LAN, etc.). As used herein, the term “processor” can refer to one or more processors.

[0022] The computer-executable instructions or programs (e.g., software or code) and data described herein can be programmed into and tangibly embodied in non-transitory computer- readable media that are accessible to and retrievable by the respective processors as described herein, which configure and direct the processors to perform the desired functions and processes by executing the instructions encoded in the media. A device embodying a programmable processor configured with such non-transitory computer-executable instructions or programs can be referred to as a “programmable device” or “device,” and multiple programmable devices in communication with one another can be referred to as a “programmable system.” It should be noted that the non-transitory “computer-readable media” as described herein can include, but is not limited to, any suitable volatile or non-volatile memory, including random access memory (RAM) and its various types, read-only memory (ROM) and its various types, USB flash memory, and magnetic or optical data storage devices (e.g., internal / external hard disks, floppy disks, magnetic tape, CD-ROMs, DVD-ROMs, optical disks, ZIP™ drives, Blu-ray disks, etc.), which can be written to and / or read by a processor operably connected to the media.

[0023] In certain embodiments, the present application can be embodied in the form of computer- implemented processes and apparatuses, such as processor-based data processing and communication systems or computer systems for practicing those processes. The present application can also be embodied in the form of software or computer program code embodied in a non-transitory computer-readable storage medium, which when loaded into and executed by a data processing and communication system or a computer system, configures the processor to create a specific logic circuit configured to implement the processes.

[0024] Semiconductor processing system

[0025] Referring now to the drawings, Figure 1 is a schematic diagram of a system 53 for manufacturing a semiconductor according to one embodiment, the system 53 including a system 54 for providing energy to a plasma chamber 19 having a plurality of power signal inputs. The system 54 includes a power supply 47. The illustrated power supply 47 transmits power signals S1-S6 to the plasma chamber 19 via power supply outputs 12.

[0026] Figure 2 is a block diagram of a power supply 47 according to one embodiment. The illustrated power supply 47 includes a frequency source 42 for providing an initial signal that is fed to an adjuster circuit 44. The adjuster circuit is configured to adjust the phase and / or amplitude of the initial signal. One or more amplifiers 14 can amplify the adjusted signal. Other possible components, such as filters, are not shown. The output signals S1-S6 of the power supply 47 are provided to the plasma chamber by conductors 17A (which can or can not include coaxial cables), for example coaxial connectors. It should be noted that the present application is not limited to the illustrated power supply 47. For example, the adjuster circuit 44 can be separate from the power supply 47, or can be a single circuit. In other embodiments, the power supply 47 can include multiple discrete power supplies. Figure 1

[0027] Returning to Figure 1 , the illustrated plasma chamber 19 includes a waveguide 91 that receives the power signals S1-S6. The illustrated waveguide 91 provides the signals S1-S6 to one or more dielectrics 92, which provide energy to one or more antennas 23 of the plasma chamber 19. The plasma chamber 19 includes a chuck 25 for holding a substrate. In processes known in the art, the first antennas 23 and the chuck 25 in combination with appropriate control systems (not shown) and plasma in the plasma chamber 19 enable deposition of material onto and / or etching of material from the substrate 27 to manufacture a semiconductor device. The manufactured semiconductor device can be a microprocessor, a memory chip, or other type of integrated circuit or device. The present application is not limited to the illustrated plasma chamber.

[0028] ​In this embodiment, the antenna 23 receives energy from the power supply 47, while the chuck 25 is ceramic and holds the substrate 27 and / or provides electrostatic (ESC) functionality. The one or more antennas 23 can be, for example, one or more slot antennas. The antennas can be made of various conductive materials, such as aluminum or copper.

[0029] Plasma processing involves energizing a gas mixture by imparting energy to the gas molecules through the introduction of RF energy into the gas mixture. The gas mixture is contained in a vacuum chamber (plasma chamber 19), and the RF energy is introduced into the plasma chamber 19 via the antenna 23. Thus, a plasma can be energized by coupling power from the power supply 47 into the plasma chamber 19 to perform deposition or etching. In certain plasma processes, the power supply 47 generates power at radio frequencies, and this power from the power supply 47 is transmitted through the cable 17A to the plasma chamber 19. In certain other plasma processes, a microwave frequency is used, such as 2.45 GHz, or 2-3 GHz, or at least 300 MHz, or at least 800 MHz. The present invention is not limited to one particular plasma process.

[0030] Commonly owned U.S. Patent No. 18 / 673,736 is incorporated by reference in its entirety. This application discloses systems and methods for distributing energy to one or more antennas of a plasma chamber having multiple power signal inputs using circular waveguides uniformly spaced in azimuthal angle about a center point. The signals provided to the inputs of the plasma chamber are phase adjusted in a manner that enables circular polarization and improved electric field uniformity. However, the present invention is not limited to such systems or methods.

[0031] The exemplified system 54 also includes a control circuit 45. The control circuit can receive inputs and provide instructions to components such as the power supply 47, the memory 42, and the matching circuit 17. Commonly owned U.S. Publication No. 2023 / 0215696 is incorporated by reference in its entirety. The functionality of the control circuit described therein can be similarly applied to the control circuit 45. The control circuit and the memory 42 will be described in further detail below in the discussion of compensating for parameter differences.

[0032] In the illustrated embodiment, control circuitry 45 includes a processor. The processor can be any type of suitably programmed processing device configured to execute computer program instructions (e.g., code), such as a computer or microprocessor. The processor can be embodied in any suitable type of computer and / or server hardware (e.g., desktop, laptop, notebook, tablet, cellular phone, etc.) and can include all common auxiliary components required to form a functional data processing device, including but not limited to buses, software and data memory (e.g., volatile and non-volatile memory), input / output devices, graphical user interfaces (GUIs), removable data memory, and wired and / or wireless communication interface devices (including Wi-Fi, Bluetooth, LAN, etc.). The processor in the illustrated embodiment is configured with specific algorithms to enable it to perform the functions described herein.

[0033] Matching circuit

[0034] System 54 also includes matching circuitry 11 coupled to power output 12, such that each matching circuitry 11 receives a single corresponding signal from the output signal. The impedance matching circuitry 11 helps maximize the amount of power transferred from power source 47 to plasma chamber 19 by matching the impedance at input 13 to the impedance of power source 47. Matching circuitry 11 may consist of a single module within a single housing designed for electrical connection to source 47 and plasma chamber 19. In other embodiments, components of matching circuitry 11 may be located in different housings, some components may be external to the housing, and / or some components may share the housing with components external to the matching circuitry.

[0035] As is known in the art, the plasma within plasma chamber 19 typically experiences certain fluctuations beyond operational control, resulting in a variable impedance presented by plasma chamber 19. Since the variable impedance of plasma chamber 19 cannot be fully controlled, an impedance matching circuit can be used to achieve impedance matching between plasma chamber 19 and source power 47.

[0036] Figure 3 A block diagram of an example matching circuit 11 is shown. The illustrated matching circuit 11 has an input 13 configured to be coupled to a power supply and an output 17 configured to be coupled to a plasma chamber. The matching circuit 11 or system 54 may include an input sensor 21 coupled between the impedance matching circuit 11 and the power supply 47. The matching circuit 11 or system 54 may also include an output sensor 49 coupled between the impedance matching circuit 11 and the plasma chamber 19, for example, enabling monitoring of the output from the impedance matching circuit and the plasma impedance presented by the plasma chamber 19. The matching circuit 11 may include its own control circuitry 46, or it may rely on external control circuitry, such as… Figure 1 The control circuit 45 shown.

[0037] Figure 3 The matching circuit 11 is a “pi” type matching circuit, utilizing two parallel electronic variable capacitors (EVCs) 31, 33 and a series inductor 35, although the application is not limited to a particular type of matching circuit. Commonly owned U.S. Publication No. 2023 / 0215696 discusses various potential matching networks, EVCs, and other variable elements, which is incorporated herein in its entirety by this reference.

[0038] Variable network elements

[0039] The EVCs 31, 33 are examples of variable network elements. As used herein, the term “variable network element” refers to any electrical component having different configurations that enable the matching circuit to provide different impedances, and thus enable the matching circuit to provide different matching positions for providing impedance matching.

[0040] In Figure 3 and Figure 4 , the variable network elements are EVCs 31, 33. As shown in Figure 4 , the illustrated EVC 31 includes a plurality of discrete capacitors 55 (one type of reactance element), each of which is switched into and out of the matching circuit 11 by a corresponding switch 61 to provide different capacitances (reactances). The switches 61 can be PIN or NIP diodes, MOSFETs, JFETs, or another type of switch. The switches 61 can be coupled to a switch driver circuit 39 for driving the switches on and off. The driver circuit 39 can receive instructions from the control circuit 45 or 46 instructing the EVC (or other variable network element) to assume a matching position that is best suited to providing impedance matching at a given point in time. The driver circuit 39 can also utilize chokes and filters.

[0041] However, the application is not limited to the use of EVCs or capacitors. In other embodiments, the variable network elements can include, for example, a plurality of discrete striplines or microstrips that are switched in and out to achieve different matching positions. In other embodiments, the discrete elements of the variable network elements can include other transmission lines or inductors.

[0042] Figure 5is a schematic diagram of a first microstrip-based variable network element 80 according to one embodiment. The first example variable network element 80 includes open-circuit microstrip stubs 82 that can be switched into and out of the circuit. The stubs 82 can have different lengths that provide different amounts of reactance. The first example element 80 has six stubs 82, but the invention is not limited to this. Each stub 82 includes a switch 83, which in this embodiment is a PIN diode 83, whose cathode is coupled (e.g., by a strap bond) to a center microstrip 81. An RF filter can be coupled between each diode 83 and the center microstrip 81. At node 84, each stub 82 is coupled to a driver circuit (not shown) that can forward or reverse bias the diode 83 to turn on or turn off the diode 83, and thus switch the corresponding stub 82 into or out of the circuit to enable the first variable network element 80 to provide varying total reactance. As described above, in other embodiments, the variable network element can change its reactance by other means.

[0043] Figure 6 is a schematic diagram of a second microstrip-based variable network element 90 according to one embodiment. The second example variable network element 90 includes open-circuit microstrip stubs 92 that can be switched into and out of the circuit. The stubs 92 can have different lengths that provide different amounts of reactance. The second example element 90 has twelve stubs 92, but the invention is not limited to this. Each stub 92 includes a switch 93, which in this embodiment is a PIN diode 93, whose cathode is coupled (e.g., by a strap bond) to a center microstrip 91. At node 94, each stub 92 is coupled to a driver circuit (not shown) that can forward or reverse bias the diode 93 to turn on or turn off the diode 93, and thus switch the corresponding stub 92 into or out of the circuit to enable the first variable network element 90 to provide varying total reactance. An RF filter can be coupled between each diode 93 and the center microstrip 91.

[0044] The center microstrip 91 includes a first section 96, a second section 97, and a fixed series element 98 connected in series between the first section 96 and the second section 97. The stubs 92 are arranged in a first group 99 of six stubs 92 each having its corresponding switch 93 coupled to the first section 96 of the center microstrip 91, and a second group 100 of six stubs 92 each having its corresponding switch 93 coupled to the second section 97 of the center microstrip 91. The stubs 92 can be arranged in pairs, one on either side of the center microstrip 91. This can help to minimize the required length of the center microstrip 91. Within each group 99, 100, a pair of stubs can be separated from an adjacent pair of stubs by a length of the center microstrip 91 sufficient to provide 180 degrees of phase separation between the adjacent pair of stubs, which allows the shunt reactance presented by each discrete stub to be effectively increased. However, the invention is not limited to this; the length of the center microstrip 91 separating adjacent pairs of stubs can be sufficient to provide 90 degrees or 45 degrees of phase separation.

[0045] The fixed series element 98 can be a transmission line having an impedance of 50 ohms, the length of which determines the separation between the two groups 99, 100 of stubs. This length can be chosen to provide a phase difference of 90 degrees between the input of the fixed series element 98 to which the first section is coupled and the output of the fixed series element 98 to which the second section is coupled. The fixed series element 98 can be a transmission line having an impedance of less than 50 ohms, which can provide increased bandwidth. This can be particularly useful in applications where the frequency of the signal input to the variable network element 90 can deviate from the expected value.

[0046] The second variable network element 90 can provide improved performance compared to the first variable network element 80. By providing two groups of stubs separated by a fixed series element, a larger region of impedance matching with an acceptable Q-factor at microwave frequencies can be provided compared to the first variable network element 80.

[0047] Compensating for parameter differences

[0048] Multi-feed electrode reactive plasma chambers for semiconductor processing applications, such as plasma chamber 19 in Figure 1 Benefit from accurate, repeatable, and uniform power delivery. These multi-feed systems can be employed when microwave energy is used for plasma excitation. Using multiple electrodes produces uniform plasma density across the wafer surface because the wafer can be larger than the wavelength at the microwave frequency. Uniform plasma density is directly related to uniform deposition across the wafer. Uniform deposition results in uniform dies on the wafer and higher yields.

[0049] As above with respect to Figure 1Discussion, a multi-feed system can employ multiple matching circuits. Each individual feed 12 can have its own matching circuit 11. Matching circuits are designed to change the impedance transformation from input to output. Power supplies in these applications are typically designed to deliver maximum power to a 50 ohm non-reactive load. But the plasma chamber impedance is rarely 50 ohms. The reactive portion of the chamber impedance can be inductive or capacitive, and the real portion of the chamber load impedance can be greater or less than 50 ohms. Therefore, a matching circuit is needed to achieve maximum power delivery. Furthermore, the chamber impedance can be different for each individual feed. Therefore, even though each matching circuit can be very similar, the impedance transformation for each feed can be different.

[0050] As discussed in commonly owned application U.S. Patent No. 18 / 673,736 (the entirety of which is incorporated by reference herein), a mode converter can be used to provide electromagnetic waves to a plasma chamber. The mode converter accepts a coaxial input and converts it to an electromagnetic waveguide launch. As the sinusoidal voltage of the feed varies, the resultant e-field in the chamber from all the various feeds will have constructive and destructive interference. Since a uniform field is desired to obtain a uniform plasma, the goal is to average the peaks and valleys of the distributed field.

[0051] Compensating for power loss

[0052] The absolute power of each individual feed into the plasma chamber directly affects the electric field (e-field) distribution in the chamber. Depending on the power and phase of each feed, the plasma e-field can be uniform, rotating, or non-uniform.

[0053] The matching circuit can be tuned for different impedance transformations. The matching circuit has variable losses depending on its location. For example, referring to Figure 4 Switching in each switch 61 (e.g., PIN diode) of the discrete components 55 at a given matching location can cause power loss. As a result, the more switches 61 switched in of the discrete components 55, the more loss the matching circuit will have, and different matching locations will have different power loss from the input to the output of the matching circuit. This loss can be measured on a network analyzer, and the loss can be stored (e.g., in a table) for each matching location. It is important to maintain the desired power output from each feed. Therefore, the power of the excitation source for each feed needs to be adjusted to compensate for the power loss through the RF power delivery system.

[0054] It is desirable to characterize the loss of each matching circuit at each possible matching position. This characterization can be done, for example, during production testing. The losses can be stored in memory. During operation, the amplitude of the power supply can be adjusted to compensate for the expected power loss. Since the exact position of each match is known at any time, the power loss can be looked up from the characterization table in memory. As a result, the relative power of the individual feeds into the chamber can still be maintained.

[0055] With reference to Figure 1 According to one embodiment, the memory 42 is configured to store, for each matching position of each matching circuit 11, and for each output signal S1-S6, parameter difference data for a parameter of the output signal. In this embodiment, the parameter is the power of the output signal. In other embodiments, the parameter can be a parameter related to the power or phase of the output signal at the output 17 of the matching circuit 11 or at the input 18 of the plasma chamber 19.

[0056] The parameter difference data can be any data related to or indicative of the expected difference between the expected value of the parameter and the actual value of the parameter. In this embodiment, it would be data related to the expected power and the actual power of a given feed at a given matching position, but the invention is not limited thereto. For example, the parameter difference data can be, for each matching position of each matching circuit, and for each output signal, the difference between the expected value of the parameter and the actual value of the parameter. The parameter difference data can also be, for each matching position of each matching circuit, and for each output signal, a value based on the difference between the expected value of the parameter and the actual value of the parameter. The parameter difference data can also be, for each matching position of each matching circuit, and for each output signal, related to a power setting or a phase setting of the power supply.

[0057] With reference again to Figure 1 The control circuit 45 is configured to determine, for each of the matching circuits 11 and the corresponding one of the output signals S1-S6, during operation of the system, the current matching position of the matching circuit 11. The control circuit 45 is further configured to cause, for each matching circuit and the corresponding one of the output signals, during operation of the system, the power supply to change the parameter of the output signal based on the parameter difference data for the matching position corresponding to the current matching position of the matching circuit. The change in the parameter of the output signal is intended to prevent or reduce the expected difference between the expected value of the parameter and the actual value of the parameter. For example, the change to the output signal by the control circuit can include the power supply increasing the power of the transmitted output signal to compensate for the power loss caused by the matching circuit.

[0058] Compensating for phase shift

[0059] The relative phase of each individual feed into the plasma chamber also directly affects the e-field distribution in the chamber. Depending on the phase of each feed, the plasma e-field can be uniform, rotating, or non-uniform.

[0060] As previously mentioned, the matching circuit can be tuned for different impedance transformations. As with power, the phase from the input to the output of the matching circuit will vary with the adjustment of the impedance transformation. It is important to maintain the desired phase shift between each field. For example, for the reasons discussed in commonly owned U.S. Patent No. 18 / 673,736, incorporated by reference herein, it is desirable to maintain a 60 degree desired phase difference between adjacent feeds in a six feed system. In other systems, the ideal phase shift can be different. To maintain the ideal phase shift, the phase of the excitation source for each feed needs to be adjusted to compensate for the phase shift through the RF power delivery system. Figure 1

[0061] It is desirable to measure the relative phase of each feed as close to the chamber as possible (e.g. the phase can be measured or calculated at the output of each matching circuit). The phase shift of each matching circuit can be characterized during production testing. The phase shift can be measured for each possible matching position. These phase shifts can be stored in memory. The phase shift of each individual amplifier can also be characterized. This can also be stored in memory for the controller for that system. During operation, the phase of the excitation source can be adjusted to compensate for these amplifiers and match the phase shift. Since the exact position of each match is known at any time, the phase shift can be looked up from the characterization table in memory. As a result, the relative phase of the individual feeds into the chamber can still be maintained.

[0062] Referring again to Figure 1 In this embodiment, the parameter relates to the phase of the first signal at the output 17 of the matching circuit 11 or at the input 18 of the plasma chamber 19. In addition, the change to the output signal S1 by the control circuit 45 includes the power supply 47 adjusting the phase of the transmitted output signal S1 to compensate for the phase shift caused by the matching circuit 11 and / or by the amplifier (if the amplifier is separate from the matching circuit 11). Note that in other embodiments, the parameter difference data can include data for both the power and the phase of the output signal S1 at the output 17 of the matching circuit 11 or at the input 18 of the plasma chamber 19.

[0063] Parameter matrix

[0064] ​In certain embodiments, for each matching circuit, parameter difference data can be determined based on parameter matrix data for the matching circuit. Each impedance matching circuit 11 coupled between the power supply 47 and the plasma chamber 19 can be characterized by one of several types of parameter matrices known to those skilled in the art, including two-port parameter matrices. S-parameter matrices and Z-parameter matrices are two examples of such parameter matrices. Other examples include, but are not limited to, Y-parameter matrices, G-parameter matrices, H-parameter matrices, T-parameter matrices, and ABCD-parameter matrices. Those skilled in the art will also recognize that these various parameter matrices can be mathematically converted from one to another for circuits such as matching networks.

[0065] As known in the art, S-parameter matrices are composed of components known as scattering parameters (or simply S-parameters). The S-parameter matrix for an impedance matching circuit has four S-parameters, S 11 , S 12 , S 21 , and S 22 , each of which represents a ratio of voltages at the input 13 and the output 17 of the matching circuit 11. All four S-parameters for an impedance matching circuit are predetermined and / or calculated such that the complete S-parameter matrix is known. The parameters for other types of parameter matrices can similarly be predetermined and / or calculated and incorporated into the parameter matrix. For example, a Z-parameter matrix for an impedance matching circuit has four Z-parameters, Z 11 , Z 12 , Z 21 , and Z 22 .

[0066] By compiling the parameter lookup table in this way, some of the overall time cost of the calculations occurs during the testing phase of the RF matching network, rather than during actual use of the RF matching network 11 with the plasma chamber 19. Furthermore, because locating a value in a lookup table can take less time than calculating that same value in real time, using a lookup table can help reduce the total time required to implement impedance matching. This time savings can help directly increase cost savings for the overall manufacturing process in a plasma deposition or etching process that can include hundreds or thousands of impedance matching adjustments throughout the process. The discussion of parameter matrices in commonly owned U.S. Publication No. 2023 / 0215696 is incorporated by reference in its entirety.

[0067] Alternatively, instead of S-plot data, predictions can be obtained using direct measurements, using hardware to measure phase shift. In these embodiments, parameter difference data is determined based on sensing an output value of a parameter at an output of a matching circuit and comparing the output value to an input value of the parameter at an input of the matching circuit. One approach is to measure the phase at the output of each matching circuit and compare it to the phase at the input of the same matching circuit. This phase shift can then be used to determine the amount of phase shift required at the source. Another approach is to measure the phase at the output of the matching circuit and compare it to the signal source. This will determine the total phase shift of each individual feed path. This information can then be used to determine the phase shift of each feed.

[0068] Control scheme

[0069] As described above, for each feed of a multi-feed system, there are multiple variables that need to be adjusted. Each path can have a directional coupler (or voltage, current, and phase sensors) in the amplifier. It can also have a phase sensor at the input and / or output of each match. Each match can have tens of thousands of positions. Each feed can have a 0-180 degree phase shift and amplitude control from 0 to full power.

[0070] Various methods can be used to tune this complex system. The goal is to reach the stable position as quickly as possible and stay there throughout the process. A first control method is to operate all channels of the multi-feed independently and simultaneously, and thus to change the parameters of each signal independently and simultaneously. In this case, power can be applied to the process chamber based on predetermined RF set points. Each match can be tuned individually to the ideal match position, each control loop cycle based on feedback from its V, I, and P (phase) sensors. When adjusting the match position, the relative phase and amplitude of each feed can be adjusted at each control loop cycle. For the reasons described above, the phase and amplitude will be adjusted. Naturally, since there is cross-talk between each individual feed, the sequential tuning of each channel can cause the previously tuned channels to be detuned again. Therefore, this process can be iterated in each control loop until the ideal conditions are reached. This process can take some time to reach the ideal match conditions, where the phase and amplitude of each channel are in the most ideal conditions.

[0071] It can be challenging to accurately measure V and I at microwave frequencies. In some embodiments, instead of measurements of V, I, and phase, the control loop cycle can be based on feedback from a gamma sensor, which provides a reflected parameter value and a phase value, such as a reflected power value and a phase value. More specifically, the reflected parameter value is a reflection coefficient value (sometimes referred to as a “gamma”), which represents the ratio of the amplitude of the reflected wave to the incident wave.

[0072] Another approach is to open only one pass of the multi-feed system at a time, strike the plasma and tune the match. Then, each of the other feeds can be opened at the same match position as the first feed. The phase can be set based on the phase and the desired phase shift between the passes of the uniform plasma recorded in memory. The pre-impingement impedance and the post-impingement impedance of the plasma can be very different, so using this approach will minimize the number of tuning steps for all feeds except the one that impinges the plasma. The other are tuned to the post-impingement impedance. According to this approach, the control circuit can change the parameter of one of the output signals while the other output signals are off, and subsequently turn the other output signals on and change the parameters of the other output signals.

[0073] Another approach is to assume that all the multi-feed paths are identical, and use sensor feedback from only one of the feeds, and then set the match position, amplitude and phase of all the other feeds. Then, once the system is close to the ideal conditions, sensor feedback from each individual feed can be used to fine tune each feed for optimal uniformity.

[0074] In another embodiment, the power difference data is derived from a machine learning algorithm that has been trained during operation from historical data of the parameter.

[0075] Method of providing energy to a plasma chamber having multiple power signal inputs

[0076] Finally, with reference to Figure 7 In another aspect, the invention can be understood as a method 70 of providing energy to a plasma chamber having multiple power signal inputs, the method comprising the following steps. In a first operation 71, output signals are transmitted to match circuits such that each of the match circuits receives a single corresponding one of the output signals. Each match circuit comprises at least one variable network element, each variable network element having different configurations that provide different match positions, and each match circuit is configured to be coupled to the plasma chamber. In operation 72, the method 70 stores, for each match position of each match circuit and for each output signal, parameter difference data of a parameter of the output signal. The parameter relates to a power or a phase of the output signal at an output of the match circuit or at an input of the plasma chamber. The parameter difference data relates to an expected difference between a desired value of the parameter and an actual value of the parameter. In operation 73, for each match circuit and the corresponding one of the output signals, the method 70 causes the power supply to change the parameter of the output signal during system operation based on the parameter difference data for the match position corresponding to the current match position of the match circuit. The change of the parameter of the output signal is intended to prevent or reduce the expected difference between the desired value of the parameter and the actual value of the parameter.

[0077] While the application has been described with respect to specific examples including presently preferred modes of carrying out the application, those skilled in the art will appreciate that there are numerous variations and permutations of the above described systems and techniques. It is to be understood that other embodiments can be utilized and structural and functional modifications can be made without departing from the scope of the present application. Thus, the spirit and scope of the application should be construed broadly as set forth in the appended claims.

Claims

1. A system comprising: The power supply transmits output signals through its output. Matching circuits, which are coupled to the power supply output, each matching circuit: Configured to receive a single corresponding output signal from the output signals; It includes at least one variable network element, each variable network element having a different configuration that provides different matching positions; and Configured to be coupled to the plasma chamber; A memory configured to store parameter difference data of the parameters of the output signal for each matching position of each matching circuit and for each output signal; The parameters are related to the power or phase of the output signal at the output of the matching circuit or the input of the plasma chamber; and The parameter difference data is related to the expected difference between the expected value and the actual value of the parameter; as well as The control circuit is configured such that, for each matching circuit and its corresponding output signal, the power supply changes the parameters of the output signal based on parameter difference data of the matching position corresponding to the current matching position of the matching circuit. The change in the parameters of the output signal is intended to prevent or reduce the expected difference between the expected value and the actual value of the parameters.

2. The system according to claim 1, wherein, For each matching position of each matching circuit, and for each output signal, the parameter difference data is the difference between the expected value of the parameter and the actual value of the parameter.

3. The system according to claim 1, wherein, For each matching position of each matching circuit, and for each output signal, the parameter difference data is based on the difference between the expected value and the actual value of the parameter.

4. The system according to claim 1, wherein, For each matching position of each matching circuit, and for each output signal, the parameter difference data is related to the power setting or phase setting of the power supply.

5. The system according to claim 1: in, The parameter is the power of the output signal; and The control circuit alters the output signal by increasing the power of the transmitted output signal to compensate for power loss caused by the matching circuit.

6. The system according to claim 1: in, The parameter is the phase of the output signal; and The control circuit's modification of the output signal includes adjusting the phase of the transmitted output signal by the power supply to compensate for the phase shift caused by the matching circuit.

7. The system according to claim 1, wherein, The parameter difference data includes power and phase data for the output signal at the output of the matching circuit or at the input of the plasma chamber.

8. The system according to claim 1, wherein, Each variable network element includes multiple discrete reactance elements that can be switched into and out of the matching circuit by corresponding switches to provide different reactances.

9. The system according to claim 8, wherein, The discrete reactive element includes a microstrip.

10. The system according to claim 9, wherein, Each matching circuit includes a central microstrip comprising a first segment, to which a first set of stubs are coupled; a second segment, to which a second set of stubs are coupled; and a fixed series element coupled between the first and second segments.

11. The system according to claim 10, wherein, The fixed series element is configured to provide a 90-degree phase difference between its input and its output.

12. The system according to claim 10, wherein, Adjacent stubs in each group are separated by a microstrip of a certain length configured to provide a 180-degree phase difference between adjacent stubs.

13. The system according to claim 1, wherein, The control circuit changes the parameter of only one of the output signals while turning off the other output signals, and then turns on the other output signals and changes their parameters.

14. The system according to claim 1, wherein, The parameter difference data is derived from a machine learning algorithm that has been trained on historical data of the parameters.

15. A method for supplying energy to a plasma chamber having multiple power signal inputs, the method comprising: The power supply is used to transmit the output signal to the matching circuit, so that each matching circuit receives a single corresponding output signal from the output signal; Each matching circuit includes at least one variable network element, and each variable network element has different configurations that provide different matching positions. Each matching circuit is coupled to the plasma chamber; For each matching position of each matching circuit, and for each output signal, store the parameter difference data of the output signal parameters; The parameters are related to the power or phase of the output signal at the output of the matching circuit or the input of the plasma chamber; and The parameter difference data is related to the expected difference between the expected value and the actual value of the parameter; as well as For each matching circuit and its corresponding output signal, the power supply changes the parameters of the output signal during system operation based on the parameter difference data of the matching position corresponding to the current matching position of the matching circuit. The change of the output signal parameters is intended to prevent or reduce the expected difference between the expected value and the actual value of the parameters.

16. The method according to claim 15, wherein, For each matching position of each matching circuit, and for each output signal, the parameter difference data is based on the difference between the expected value and the actual value of the parameter.

17. The method according to claim 15, wherein, For each matching position of each matching circuit, and for each output signal, the parameter difference data is related to the power setting or phase setting of the power supply.

18. A system comprising: Matching circuits, configured to be coupled to the power supply, each matching circuit: Configure it to receive the corresponding output signal from the power supply; It includes at least one variable network element, each variable network element having a different configuration that provides different matching positions; and Configured to be coupled to the plasma chamber; A memory configured to store parameter difference data of the parameters of the output signal for each matching position of each matching circuit and for each output signal; The parameters are related to the power or phase of the output signal at the output of the matching circuit or the input of the plasma chamber; and The parameter difference data is based on the difference between the expected value and the actual value of the parameter. as well as The control circuit is configured such that, for each matching circuit and its corresponding output signal, the power supply changes the parameters of the output signal based on parameter difference data of the matching position corresponding to the current matching position of the matching circuit. The change in the parameters of the output signal is intended to prevent or reduce the expected difference between the expected value and the actual value of the parameters.

19. The system according to claim 18: in, The parameter is the power of the output signal; and The control circuit alters the output signal by increasing the power of the transmitted output signal to compensate for power loss caused by the matching circuit.

20. The system according to claim 18: in, The parameter is the phase of the output signal; and The control circuit's modification of the output signal includes adjusting the phase of the transmitted output signal by the power supply to compensate for the phase shift caused by the matching circuit.

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