Cost effective radio frequency impedance matching networks

Abstract

The embodiments provided herein generally include apparatus and methods for rapid and inexpensive repair and replacement of RF sensors required for radio frequency (RF) power generation operations in plasma processing systems, and impedance matching equipment for generating plasma in a plasma chamber during semiconductor processing therein. Flexible communication between the equipment in the plasma processing system allows for the sharing of processing information and equipment settings for batch processing of multiple semiconductor wafers during the manufacturing process. Operating settings of the master plasma processing system can be used to control the operation of multiple slave processing systems. Furthermore, operating settings of the master plasma processing system can be recorded and reused to control multiple slave processing systems.

Description

Cost-effective RF impedance matching network Embodiments of the present disclosure generally relate to high power radio frequency (RF) power supplies and impedance matching networks suitable for generating plasma in semiconductor processing reactor chambers, and more particularly to cost-effective RF impedance matching networks and their associated subcomponents. In a plasma reactor chamber, an RF power source provides RF power to the plasma reactor chamber via an impedance matching network coupled between the RF power source and the plasma reactor chamber for generating plasma therein. The RF impedance of the plasma is a complex and highly variable function of many process parameters and conditions. The impedance matching network maximizes power transfer from the RF power source to the plasma in the reactor chamber. This is achieved when the output impedance of the impedance matching network is equal to the complex conjugate of the input impedance of the plasma in the reactor chamber. The impedance matching network converts the impedance of the plasma in the reactor chamber to the characteristic operating output impedance of the RF power source, e.g., 50 ohms, for optimal RF power transfer therefrom. An RF impedance matching network (RFIM) is a circuit placed between an RF power source and a plasma reactor to optimize RF power transfer efficiency. To optimize RF power transfer, it is important for the RFIM to be accurately tuned to the desired complex impedance at the desired frequency. This is crucial for providing reliable, efficient, and predictable plasma process results. To ensure operational accuracy, the RFIM relies on the accuracy of associated RF sensors, such as RF voltage, RF current, and RF power sensors, which are used to provide real-time plasma processing conditions, such as plasma chamber impedance and the RF power delivered to the plasma chamber during semiconductor manufacturing process operations. However, maintaining plasma chamber RF sensor operation and accuracy can be very time-consuming and labor-intensive, resulting in costly semiconductor process downtime. Thus, less costly and faster repair, calibration, and / or replacement of the RF sensor is required in order to maintain more operating time of the RF source and RF impedance matching network and thus increased plasma chamber processing utilization. Embodiments of the present disclosure include a radio frequency (RF) impedance matching unit adapted for coupling between an RF power generator and a plasma processing chamber. The RF impedance matching unit includes an RF tuning circuit having a first node adapted to couple to the RF power generator, a second node adapted to couple to the plasma processing chamber, and an adjustable tuning element adapted to convert an output resistance of the RF power generator into a plurality of impedances at the second node. The RF impedance matching unit further includes: a matching controller coupled to the adjustable tuning element of the RF tuning circuit, wherein the matching controller controls and monitors a position of the adjustable tuning element of the RF tuning circuit; and a communication interface coupled to the matching controller for receiving position information of the adjustable tuning element of the RF tuning circuit and transmitting the position information. Embodiments of the present disclosure include a system for controlling and monitoring a radio frequency (RF) power generator and an impedance matching unit for generating plasma in a plasma processing chamber. The RF power generator has an RF output and is coupled to a first communication interface for monitoring and controlling the RF power generator. An RF power measurement module is coupled to the output of the RF power generator and measures forward and reflected RF power at its output and calculates a standing wave ratio (SWR) based on the measured forward and reflected RF power. A second communication interface is coupled to the RF power measurement module to transmit the measured forward and reflected RF power and the calculated SWR. An RF tuning circuit has a first node coupled to the RF power measurement module and a plurality of adjustable tuning elements for converting the output impedance of the RF power generator to a plurality of impedances at a second node of the RF tuning circuit. A matching controller is coupled to the adjustable tuning elements of the RF tuning circuit, wherein the matching controller controls and monitors the position of the adjustable tuning elements of the RF tuning circuit. A third communication interface is coupled to the matching controller for receiving position information of an adjustable tuning element of the RF tuning circuit and transmitting the position information. An RF impedance measurement module is coupled between a second node of the RF tuning circuit and the plasma processing chamber and measures RF voltage, RF current, and frequency at the second node of the RF tuning circuit, determines an RF phase from the measured RF voltage and current, and calculates the RF impedance at the second node based on the measured RF voltage, RF current, RF phase, and frequency. A fourth communication interface is coupled to the RF impedance measurement module for transmitting the measured RF voltage, RF current, RF phase, frequency, and calculated impedance at the second node. A tool controller is adapted to control the RF power output of the RF power generator and to indicate process recipe tuning element settings to the matching controller when generating plasma. A fifth communication interface is coupled to the tool controller. At least two of the first communication interface, the second communication interface, the third communication interface, the fourth communication interface, and the fifth communication interface communicate with each other during operation to generate plasma in the plasma processing chamber. Embodiments of the present disclosure include a method for processing a plurality of semiconductor wafers in a group using a plurality of plasma processing systems by providing a master plasma processing system, the master plasma processing system comprising a master radio frequency (RF) power generator, a master impedance matching unit having a first node coupled to the master RF power generator and a second node adapted to be coupled to a master plasma processing chamber, the master impedance matching unit further comprising a master RF tuning circuit having an adjustable tuning element, and a communication interface coupled to the master RF power generator and the master impedance matching unit. Furthermore, a plurality of slave plasma processing systems are provided, each of the plurality of slave plasma processing systems comprising a slave RF power generator, a slave impedance matching unit having a first node coupled to the slave RF power generator and a second node adapted to be coupled to the slave plasma processing chamber, the slave impedance matching unit further comprising a slave RF tuning circuit having an adjustable tuning element, and a communication interface coupled to the slave RF power generator and the slave impedance matching unit. The method further provides for reading a master power setting of a master RF power generator during a master plasma processing operation and transferring the master power setting to each of the slave RF power generators, wherein each of the slave RF power generators operates at the master power setting during the slave plasma processing operation; and reading a master position setting of an adjustable tuning element of a master RF tuning circuit during the master plasma processing operation and transferring the master position setting to each of the slave impedance matching units, wherein each of the adjustable tuning elements of the slave impedance matching units operates at the same position setting of the adjustable tuning element of the master RF tuning circuit during the slave plasma processing operation. The method further provides for recording the master power setting and the master position setting of the adjustable tuning element before transferring the master power setting and the master position setting of the adjustable tuning element to the slave RF power generators and the slave impedance matching units. Embodiments of the present disclosure generally relate to apparatus and methods for rapid and inexpensive defect analysis, repair, and replacement of equipment used in the manufacture of semiconductor devices. More specifically, embodiments provided herein generally include apparatus and methods for rapid and inexpensive repair and replacement of radio frequency (RF) sensors required for RF power generation operations, as well as impedance matching equipment used to generate plasma in a plasma chamber during semiconductor processing therein. Embodiments of the present disclosure relate to input and output processing sensors, such as RF voltage and current, frequency, and RF power, that can be independent of an associated RF impedance matching unit in a plasma processing system and can be replaced after a failure or used for periodic recalibration without disturbing or disassembling other parts of the plasma processing system. The sensors can be inside or outside the RF impedance matching unit structure and have RF power and communication (for monitoring and control) connectors suitable for quick connection and disconnection. They can also be interchangeable and reusable for design and operational scalability. For example, sensor modules can be exchanged for periodic recalibration to ensure accuracy, resulting in reduced long-term operating and maintenance costs. Processing sensors can be configured as independent and autonomous modules with application-specific sensor interfaces, data processing, computation, and control functionality. Independent module communication using high-speed and secure protocols provides global communication between modules, tool controllers, and supervisory systems. Communication can be provided with industrial-quality software protocols such as, for example, but not limited to, Ethernet for Control Automation Technology (EtherCAT) or (ECAT). EtherCAT communication enables fast and easy module and system updates and maintenance in the field, as well as efficient testing and qualification during the manufacturing process of the manufacturing system. Sensor and controller module testing, qualification, and firmware / software updates can be completed remotely using File over Ethernet (FoE), which reduces maintenance, calibration, and logistics costs. Each EtherCAT communication interface can have a unique address and is suitable for transmitting sensor and control data to other EtherCAT communication interfaces, thereby making all processing information available to all modules in the system. RF impedance and RF power sensor information from independent RF impedance and power modules can be shared throughout the plasma processing system for diagnostic purposes and algorithm pre-learning. Modules providing sensor information can be reused for impedance matching unit design scalability. Sensor modules can be adapted for use with other impedance matching units and / or for operation at other RF frequencies and load impedances. Each sensor module can have a unique communication address and access its data, which can be used to record process data with all other plasma processing system modules, controllers, and manufacturing monitoring systems. In another embodiment of a plasma processing system comprising a plurality of plasma processing chambers, each chamber having a slave RF generator and a slave impedance matching unit, a set of process sensor modules can be used to control the operation of the slave RF generators and slave impedance matching units associated with the plurality of plasma processing chambers. In cases where the chambers and plasma processes are substantially identical, sensor information from only one processing chamber may be required, and the associated slave RF generator and impedance matching unit operations of the other processing chambers can be controlled by the lead or master processing chamber / sensor module information (process data). This synchronization between multiple in-line plasma processes can further be shared for diagnostic purposes and algorithm pre-learning. In some embodiments, sensor data from a plasma process can be used for learning purposes and recorded, after which the sensor can be disconnected and the recorded learning process data used in place of the sensor data. Process control settings (e.g., impedance matching element settings and RF power processing levels) can be stored in a tool controller and subsequently used by the tool controller for a plurality of different process recipes. Thus, a well-established and consistent manufacturing process can be executed without the need for sensor monitoring of the manufacturing process. This is particularly advantageous for the large number of chamber plasma processes that occur during a semiconductor device manufacturing day. The same process recipe need not be applied simultaneously to all plasma processing systems. Different plasma processing recipes can be distributed among the manufacturing plasma chamber systems, depending on the manufacturing requirements of different semiconductor products. Referring now to the drawings, the details of the exemplary embodiments are schematically illustrated. The same elements in the drawings will be represented by the same numerals, and similar elements will be represented by the same numerals with different lower case letter suffixes. Referring to FIG. 1 , a schematic block diagram of a semiconductor wafer plasma processing system is depicted according to a specific example embodiment of the present disclosure. The plasma processing system, generally designated by reference numeral 100 , may include a plasma chamber 102 for processing semiconductor wafers therein, an RF impedance matching unit 104 , an RF power generator 106 , a tool controller 108 , and a user interface 110 . The RF impedance matching unit 104 , the RF power generator 106 , the tool controller 108 , and the user interface 110 may communicate, control, and monitor the delivery of RF power to the plasma chamber during processing using protocols such as, but not limited to, Ethernet for Control Automation Technology (EtherCAT or ECAT), USB, serial RS-232, Ethernet, WiFi, and Bluetooth. For the purposes of this discussion, the primary means of communication, control, and monitoring will be EtherCAT. EtherCAT or "ECAT" is a high-performance, low-cost, easy-to-use industrial Ethernet technology with flexible topology. More information about EtherCat can be found on the EtherCat technology website at https: / / www.ethercat.org, which is incorporated herein by reference for all purposes. EtherCat uses the Ethernet packet form of communication but is significantly faster and more robust than conventional Ethernet systems and other similar communication protocols. It is particularly well-suited for industrial manufacturing processes that require high security and reliability while maintaining high data and control throughput in real time. The embodiments disclosed herein address flexibility, interchangeability, reliability, and rapid repair and replacement of defective modules. By making subsystems (e.g., equipment modules) interchangeable in the field without requiring specialized installation and calibration procedures, this allows for greater manufacturing uptime and lower overall system maintenance and manufacturing costs. Furthermore, standardization and interoperability between subsystems reduces equipment costs and enhances the ease of maintenance of such designed and deployed equipment. The impedance matching unit 104 may include an RF tuning circuit 112, a matching controller 114 for controlling the RF tuning circuit 112, a memory 116 coupled to the matching controller 114, a safety and operational interlock 118, an RF power measurement module 120 having an input coupled to the output of the RF power generator 106, an RF filter 122 coupled between the RF power measurement module 120 and the input of the RF tuning circuit 112, another RF filter 122a coupled to the output of the RF tuning circuit 112, an RF impedance measurement module 124, and a temperature sensor 126. The matching controller 114 may include a communication interface suitable for a communication protocol such as, for example, but not limited to, EtherCAT (ECAT) communication. The matching controller 114 may be an ECAT master or a slave, where the ECAT slave is used in an external control loop, with the tool controller 108 being the ECAT master. On the other hand, it is an ECAT master device for the internal control loop, wherein the RF tuning circuit 112, the variable capacitor in the RF sensor module 120 and / or 124 can be an ECAT slave device. All of the above modules can be monitored and controlled via EtherCat (ECAT) communication. A user interface 110 (e.g., a computer (laptop)) can communicate with the tool controller 108 (EtherCat master) using a USB to EtherCat adapter 128, or can be coupled to the tool controller 108 using RS-232, WiFi, or other standard communication protocols (not shown). This communication link allows the user interface 110 to access all sensor information and controls of the plasma processing system 100 via, for example, but not limited to, EtherCat communications coupled to each of its subsystems. RF power from the RF power generator 106 can be coupled to the RF power measurement module 120 via power delivery lines 130 (e.g., coaxial cable types LMR-600, TRU-500, and the like), and RF power from the impedance matching unit 104 can be coupled to the plasma chamber 102 RF coil (not shown) via power delivery lines 130a. It is contemplated and within the scope of the present disclosure that electrical conductors for delivering RF power between the module and the plasma chamber 102 may include, but are not limited to: (a) one or a combination of coaxial cables (such as a flexible coaxial cable connected in series with a rigid coaxial cable), (b) insulated high voltage corona resistant mounting wire, (c) bare wire, (d) metal rod, (e) electrical connector, or (f) any combination of the electrical conductors / cables of (a)-(e). 2 , a schematic block diagram of a semiconductor wafer plasma processing system with a field-replaceable external quick-connect sensor module is depicted in accordance with an exemplary embodiment of the present disclosure. The plasma processing system, generally designated by reference numeral 200, may include a plasma chamber 102 for processing semiconductor wafers therein, an RF impedance matching unit 204, an RF power generator 106, a tool controller 108, and a user interface 110. The RF impedance matching unit 204, the RF power generator 106, the tool controller 108, and the user interface 110 may communicate, be controlled, and monitored using protocols as described above with respect to the semiconductor wafer plasma processing system 100. The impedance matching unit 204 is substantially similar to the impedance matching unit 104 described above herein, except that at least one RF measurement module (e.g., RF impedance measurement module 224) is now located external to the housing of the impedance matching unit 204 and is coupled to the RF filter 122a using a quick-connect coaxial connector 232, such as, but not limited to, edgeless coaxial connectors manufactured by Myat, Inc., available at www.myat.com. Functionally, the plasma processing system 200 operates identically to the plasma processing system 100 shown in FIG. 1 , but with an external RF measurement module, such as RF impedance measurement module 224, that can be easily removed and replaced with a replacement module without disturbing any other components or having to disassemble the impedance matching unit 204 in the field. The only operations required to replace a defective RF impedance measurement module 224 in the field are to disconnect the coaxial cables 230a and 230b from the coaxial connectors 232a and 232 and the EtherCat communication cable, respectively, then replace the defective impedance measurement unit 204 with a working impedance measurement unit, reconnect the coaxial cables 230a and 230b back to the coaxial connectors 232a and 232, and reconnect the EtherCat communication / power cable (EtherCat-P). The impedance matching unit 204 can be configured for use with either an externally mounted RF measurement module and / or RF filter to facilitate field repair and / or replacement. The RF impedance measurement module 224 can be an ECAT slave device that communicates with the tool controller 108 or the matching controller 114. RF impedance and power determination Radio frequency (RF) impedance is determined by the RF voltage V(t), RF current I(t), phase angle θ, and frequency of the RF waveform. RF voltage and current sensors measure the RF voltage V(t) and RF current I(t) and determine the phase angle θ from them. Frequency is measured by a frequency detector. The phase angle is the lead or lag time between the RF voltage V(t) and RF current I(t) waveforms and is expressed in degrees θ. RF power P(t) is the product of voltage and current, or P(t) = V(t) * I(t). The corresponding RMS (root mean square) value after sensor detection is P = V * I * cos θ, where θ is the phase angle between the voltage and current waveforms. Using Ohm's law, Z(t) = V(t) / I(t), or Z can be expressed as Z = R + jX, where R = Z cosθ and jX = Z sinθ. jX = jωL - j / ωC, where ω = 2πf, f is the frequency, C is in farads, and L is in henries. R is the resistance in ohms and jX is the reactance in ohms, where +jX is the inductive reactance and -jX is the capacitive reactance. Power is frequency-independent, and impedance is frequency-dependent. Referring to FIG. 3 , a schematic block diagram of an RF impedance measurement module is depicted according to an exemplary embodiment of the present disclosure. The RF impedance measurement module 124 may include an RF current sensor 302, an RF voltage sensor 304, an RF frequency detector 306, an RF phase detector 308, a temperature sensor 310, a microcontroller 312 with memory 314 and digital signal processing (DSP) / fast Fourier transform (FFT) 316 capabilities, and an EtherCat communication interface 318. The RF impedance measurement module 124 may further include a quick-connect, flangeless coaxial connector 320 to facilitate removal and installation of the RF impedance measurement module 300, as well as EtherCat connectors 322 a and 322 b. The RF coaxial connectors 320 a and 320 b may be bidirectional, allowing one to function as an RF input and the other as an RF output. The EtherCat communication interface 318 may be adapted for EtherCat-P, which may provide DC power to the electronic components of the RF impedance measurement module 124 . RF current sensor 302 senses RF current I(t), and RF voltage sensor 304 senses RF voltage V(t). RF current I(t) and voltage V(t) are received via analog inputs to microcontroller 312 and can subsequently be converted to digital representations. Phase angle θ (the time difference between I(t) and V(t)) can be determined using phase detector 308 or after I(t) and V(t) have been converted to digital representations. Either way, phase angle θ can be converted to digital format by microcontroller 312. RF frequency detector 306 provides frequency information to microcontroller 312 in digital format, for example, from a time-based digital counter. Once the RF current, voltage, phase, and frequency are known, the impedance at RF coaxial connector 320 and the RF power entering the load (plasma processing chamber) can be calculated using the DSP / FFT 316 functionality of microcontroller 312, as described above. The memory 314 can be used to store the calculated real-time impedance and power, and can also be used to store calibration coefficients for the RF current and voltage sensors and frequency and phase detectors. In addition, the sensor, detector, impedance and power information can be presented in digital format from the microcontroller 312 to the EtherCat communication interface 318 for use (information and control) by the plasma processing system 100 and its other subsystems. RF forward and reverse power and voltage standing wave ratio By adjusting the impedance matching network to match the RF generator's output impedance (typically 50 ohms) to the complex load impedance of the plasma processing chamber, forward and reverse RF power measurements can be used to maximize the most efficient power transfer from the RF generator. Forward and reverse RF power sensors (detectors) can be used to obtain information to adjust the impedance matching network for maximum forward RF power acceptance from the RF generator and minimum reverse RF power returned to the RF generator. The forward and reverse power sensors can also be used to determine the standing wave ratio (SWR) along the transmission line from the RF generator's output to the matching network's input. Because the length of the transmission line (e.g., coaxial cable) between the RF generator and the impedance matching network is very short relative to the wavelength of the RF signal from the RF generator, the length of the transmission line can be neglected, and the SWR is then used as a measure of the matching quality of the impedance matching network to the RF generator. Because the output of the RF generator is at a fixed impedance (e.g., 50 ohms), the SWR is typically considered to be the maximum and minimum RF voltage along the transmission line (in this case, at the RF generator's output) and is referred to as the voltage standing wave ratio, or VSWR. The SWR can be determined by the effective forward and reflected voltages at the output of the RF generator, for the characteristic impedance for which the SWR detector has been designed. Since the power of the forward and reflected RF waves is proportional to the square of the voltage component attributable to each, the SWR can be expressed in terms of the forward and reflected power, where Pf is the forward power and Pr is the reflected power. As mentioned above, unlike RF impedance measurements, which are typically frequency-dependent, forward and reflected RF power measurements are based on a fixed, known impedance, such as 50 ohms. Therefore, SWR measurements are also frequency-independent. However, to be accurate, they must be measured at a known, fixed resistance. This is why power and SWR measurements are performed at the known, fixed resistance output of the RF generator and not on the complex impedance load side of an impedance matching network, where RF voltage, current, and frequency sensors must be used after determining the plasma process impedance. Referring to FIG. 4 , a schematic block diagram of an RF power measurement module is depicted according to an exemplary embodiment of the present disclosure. The RF power measurement module 120 may include a forward RF power sensor 402, a reflected RF power sensor 404, a temperature sensor 410, a microcontroller 412 with a memory 414, and an EtherCat communication interface 418. The RF power measurement module 120 may further include a quick-connect, flangeless coaxial connector 420 for easy removal and installation of the RF power measurement module 120, and EtherCat connectors 422a and 422b. The EtherCat communication interface 418 may be adapted for EtherCat-P, which provides DC power to the electronics of the RF power measurement module 120. The forward RF power sensor 402 senses the input RF power to the RF tuning unit 112, and the reflected RF power sensor 404 senses the RF power reflected back from the RF tuning unit 112. The SWR and reflected RF power can be used to verify the proper operation of the RF tuning unit 112 and / or assist in its matching operation (e.g., adjusting the RF tuning unit 112 for minimum SWR and / or reflected RF power). The forward and reflected RF power values ​​from the forward and reflected RF power sensors 402 and 404, respectively, are received via analog inputs to the microcontroller 412 and can then be converted to digital representations. As described above, the SWR at the RF output coaxial connector 420b can be calculated from the forward and reflected RF power values. The forward and reflected power, and SWR information, can be presented in digital format from the microcontroller 412 to the EtherCat communication interface 418 for use (information and control) by the pulp processing system 100 and its other subsystems (e.g., the matching controller 114). Impedance Matching Unit Control and Tuning Referring to Figures 5A, 5B, and 5C, schematic diagrams of RF tuning circuits are depicted according to specific example embodiments of the present disclosure. Figures 5A and 5B illustrate three variable capacitors VC1, VC2, and VC3, while Figure 5C illustrates two variable capacitors VC1 and VC3, for example, electrodynamic vacuum variable capacitors, in combination with inductors L1 (and L2) for RF tuning circuit 112. Variable capacitors VC1, VC2, and VC3 can have a capacitance range of, but not limited to, approximately 3 pF to approximately 5000 pF. L1 is an inductor and can have an inductance range of, but not limited to, approximately 0.01 μH to approximately 1000 μH. VC3 can be used to adjust a target frequency from approximately 100 kHz to approximately 250 MHz, and VC1 and VC2 can be used to tune to a target impedance. In some embodiments, particularly for complex loads at lower frequencies, the RF circuit schematic configuration shown in Figure 5B can be implemented. An additional inductor L2 may be added to adjust the RF tuning circuit 112 to a desired value. Inductor L2 may range from approximately 0.01 μH to approximately 1000 μH, but is not limited thereto. A low-pass Pi matching circuit is illustrated in Figures 5A and 5B. In some embodiments, the RF tuning circuit 112 may be an L-shaped circuit using only two electrically driven vacuum variable capacitors (e.g., VC1 and VC3), as shown in Figure 5C. The capacitance and / or inductance values ​​of the variable elements (e.g., VC1, VC2, VC3) may be controlled and monitored by position control and monitoring circuit 502 for each variable element (one shown). Additional capacitors and / or inductors may also be switched into the matching circuit (not shown) as needed. The motor position actuator of the position control and monitoring circuit 502 may also include a position sensor that indicates the mechanical position of the adjustable element, such as the amount of shaft rotation of a variable vacuum capacitor or the position count of a synchronized stepper motor (detecting maximum and minimum clockwise and counterclockwise shaft rotation) after the minimum and maximum rotational positions have been determined. The position values ​​can be correlated in a capacitance (or inductance)-position value table so that the capacitance and / or inductance values ​​can be monitored and set to a desired position based on the desired capacitance / inductance value. According to the teachings of the present disclosure, the tuning element position value can be used to monitor and pre-set the tuning element position. Referring to FIG. 6 , a schematic block diagram of a matching controller is depicted according to an exemplary embodiment of the present disclosure. The matching controller 114 can monitor and control the variable elements (e.g., variable capacitors VC1, VC2, and VC3) of the RF tuning circuit 112. The matching controller 114 can include a microcontroller 612, memory (volatile and / or non-volatile) 614, a stepper motor driver and position sensor 502 ( FIG. 5 ), and an EtherCat communication interface 618. Via EtherCat communication, the microcontroller 612 can receive plasma chamber impedance information from the associated RF impedance measurement module 124 or 224 and / or the RF power measurement module 120. Based on this impedance information, the microcontroller 612 can then control the position of the variable elements (e.g., variable capacitors VC1, VC2, and VC3) of the RF tuning circuit 112 to achieve impedance matching between the RF power generator 106 and the plasma chamber 102. When in slave mode (Figures 9 and 10), the microcontroller 612 can receive the positions of variable elements (e.g., variable capacitors VC1, VC2, and VC3) via EtherCat communication based on the substantially identical RF tuning circuit 112 of another plasma processing system 100 acting as a process master. This enables batch processing of identical semiconductor wafer workpieces using multiple substantially similar plasma processing systems slaved to the master plasma processing system (Figure 10). Alternatively, in high-volume and well-known plasma processes, the microcontroller 612 can receive the positions of variable elements (e.g., variable capacitors VC1, VC2, and VC3) via EtherCat communication based on a pre-recorded process recipe. The process recipe containing the positions of the variable elements can be stored in memory 614 to reduce EtherCat communication and microprocessor operation time. For autonomous plasma processes that do not require external input, this allows the process to utilize process data stored in memory 614 with stored locations during processing time. Referring to FIG. 7 , a schematic block diagram of a plasma processing chamber with two impedance matching units is depicted, according to a specific example embodiment of the present disclosure. Plasma processing chamber 702 includes an RF electrode 772 and a workpiece pedestal 774. RF electrode 772 is coupled to a first impedance matching unit 704, which receives RF power from an RF power generator 706. In one example, RF electrode 772 can be a showerhead for forming a capacitively coupled plasma in plasma processing chamber 702, or even a multi-turn coil for forming an inductively coupled plasma in plasma processing chamber 702. A second impedance matching unit 776 is coupled between workpiece pedestal 774 and RF power generator 778. A DC blocking capacitor 784 blocks high-voltage DC from high-voltage supply 780 and can also function as a high-pass filter. Optionally, an RF impedance measurement module similar to sensor module 224 ( FIG. 2 ) may be located at the output of the match 776 and / or between the base 774 and the second impedance match 776 . It is contemplated and within the scope of the present disclosure that one or more sensor modules may be shared between the two impedance match units 704 and 776 . A sensor module may be used only for learning purposes and subsequently removed. A sensor module may be used to form a virtual match set, for example, where data measured at the output of the impedance match unit 776 may be used to control the impedance match unit 704 . Sensor modules may also be added elsewhere, such as to roofs, underlayments, or siding (not shown), and may provide measurements that can be used to adjust any tuning element capacitors. The electrical characteristics of the plasma formed using the first impedance matching unit 704, RF power generator 706, second impedance matching unit 776, and RF power generator 778 can be monitored using sensor module 224, which is coupled to the node between the embedded electrode 770 and the second impedance matching unit 776 or the first impedance matching unit 704 and the RF electrode 772. Information from and control over these items can be processed in the tool controller 708, which communicate with each other via separate EtherCat communication lines. Impedance matching units 704 and 776 can be controlled by the tool controller 708 via communication over the EtherCat communication lines. Which sensor information is used to control which matching unit is simply a function of how the process is programmed, as all monitoring and control can be applied to all processing system components, such as sensors, matching unit component tuning, and RF power output. Referring to FIG. 8 , a schematic block diagram of a plasma processing chamber having an impedance matching unit controlled by a remote sensor is depicted, according to a specific example embodiment of the present disclosure. The plasma processing chamber system shown in FIG. 8 is similar to the plasma processing chamber system shown in FIG. 7 , except that the second impedance matching unit 776 and the RF power generator 778 have been removed, and a PV waveform generator 880 has been added. The PV waveform generator 880 can replace the RF bias generator 778 shown in FIG. The high voltage supply 780 and the PV waveform generator 880 can be coupled to the DC of the sensor 724 via an RF blocking filter 782 , which is coupled to a transmission line connected to the embedded electrode 770 . The outputs of the first impedance matching unit 704 and the RF power generator 706 , and / or the PV waveform generator 880 , can be controlled using signals provided from the sensor 724 and the tool controller 708 . Information from and control of these items may be processed in tool controllers 708 which communicate with each other via independent EtherCat communication links. Capacitor 884 blocks the high voltage DC from high voltage supply 780, which is coupled to ground, but allows an RF return path for sensor 724. Capacitor 884 can also function as a high-pass filter and / or RF return tuning. In some embodiments, first impedance matching unit 706 and RF generator 704 can be coupled to embedded electrode 770, and sensor 724 can be coupled to RF electrode 772. Capacitor 884 can alternatively be located between RF blocking filter 782 and sensor 724, rather than between sensor 724 and ground. It is contemplated and within the scope of the present disclosure that the RF sensing and tuning elements associated with the RF matching unit need not be located within the same housing, and that devices on the ECAT network can be adapted to form a virtual RF measurement group. Typically, RF voltage and current sensors may be located at both the input and output of the impedance matching unit, or only at the input (no output sensors). According to the teachings of the present disclosure, the sensors may be located external to the impedance matching unit housing and, via the tool controller, form a virtual group with any impedance matching unit on the plasma processing equipment. The input and output RF sensors do not need to be physically located within the impedance matching unit housing. For example, the RF input sensor may be located near the RF generators 778 and 708, and the output RF sensor may be located near the RF electrode 772 and / or the workpiece pedestal 774. The tool controller 708 may collect RF sensor data and tune the tuning elements within the same network. The matching controller 114 is optional. In some embodiments, the tool controller 108 may communicate directly with all sensors, tuning elements, and RF generators. In some other embodiments, the tool controller 108 can communicate with the shared sensor 224, RF generator, and matching controller, and the matching controller can communicate with the local tuning element and the local sensor modules 120 and / or 124. This is very easy to accomplish because all of these can access each other via EtherCat communication. Referring to FIG. 9 , a slave semiconductor wafer plasma processing system is depicted according to a specific example embodiment of the present disclosure. The slave plasma processing system, generally designated by reference numeral 900, may include a plasma chamber 102 for processing semiconductor wafers therein, an RF impedance matching unit 904, an RF power generator 106, and a tool controller 108. Impedance matching unit 904 is substantially similar to impedance matching units 104 and 204 described above, except that no local sensors are present. Instead, all operational control of the RF tuning unit 112 and the RF power generator originates from a remote control source. Optionally, tool controller 108 may be eliminated and a remote master tool controller 108, such as one of plasma processing systems 100 and 200 described above, may be used. In some embodiments, remote master tool controller 108 may directly control RF tuning unit 112, and matching controller 114 may not be required. If the slave plasma processing system 900 is physically (hardware-wise) substantially similar to the master plasma processing system 100 or 200 and uses the same process recipe, the positions of the variable elements (e.g., variable capacitors VC1, VC2, and VC3) can be sent directly to the slave matching controller 114 via EtherCat communication for direct setting of the tuning element positions of the RF tuning circuit 112 (replicating the master RF tuning circuit element positions). In some embodiments, the local sensor modules 120 and / or 124 are optionally located between the RF power generator 106 and the RF filter module 122. Enabling all modules to access and control read states provides application flexibility. Referring to FIG. 10 , a schematic block diagram of a multi-wafer plasma processing system having a master plasma processing subsystem and a plurality of slave plasma processing subsystems is depicted, according to a specific example embodiment of the present disclosure. This multi-chamber plasma processing system is an extension of the slave processing system illustrated in FIG. 9 and described above. For batch processing of identical semiconductor wafers using substantially identical plasma processing hardware (e.g., plasma chamber 192 , impedance matching unit 104 , and RF power generator 106 ), the same RF power and tuning component configuration can be used for each plasma processing subsystem. This embodiment is cost-effective for batch processing of multiple semiconductor wafers. The master plasma processing subsystem may include modules 102a, 104a, and 106a, each having an RF current sensor 302, an RF voltage sensor 304, an RF phase detector 308, a frequency detector 306, a forward RF power sensor 402, and a reflected RF power sensor 404, and operates substantially the same as plasma processing systems 100 and 200. The other slave plasma processing subsystems will simply emulate (copy) the RF power and tuning element settings of the master plasma processing subsystem. Optionally, all plasma processing subsystems can be slave systems, and pre-recorded process recipes can control the tuning element settings of the RF power generator 106 and the impedance matching unit 1004. Different pre-recorded process recipes can also be used with corresponding plasma chambers for batch processing of different semiconductor wafer products. The aforementioned processing options are easily implemented using EtherCat communication interconnectivity. The disclosure has been described in terms of one or more embodiments, and it should be understood that many equivalents, alternatives, variations, and modifications, besides those expressly stated, are possible and within the scope of the disclosure. 100: Plasma processing system 102: Plasma chamber 102a: Module 104: RF impedance matching unit 104a: Module 106: RF power generator 106a: Module 108: Tool controller 110: User interface 112: RF tuning circuit 114: Matching controller 116: Memory 118: Safety and operational interlocks 120: RF power measurement module 122: RF filter 122a: RF filter 124: RF impedance measurement module 126: Temperature sensor 128: EtherCat adapter 130: Power delivery Line 130a: Power delivery line 200: Plasma processing system 204: RF impedance matching unit 224: RF impedance measurement module 230a: Coaxial cable 230b: Coaxial cable 232: Coaxial connector 232a: Coaxial connector 300: RF impedance measurement module 302: RF current sensor 304: RF voltage sensor 306: RF frequency detector 308: RF phase detector 310: Temperature sensor 312: Microcontroller 314: Memory 316: Digital signal processing (DSP) / Fast Fourier Transform (FFT) 318: EtherCat communication interface 320a: RF coaxial connector 320b: RF coaxial connector 322a: EtherCat connector 322b: EtherCat connector 402: Forward RF power sensor 404: Reflected RF power sensor 410: Temperature sensor 412: Microcontroller 414: Memory 418: EtherCat communication interface 422a: EtherCat connector 422b: EtherCat connector 502: Position control and monitoring circuit 612: Microcontroller 614: Memory 618: EtherCat communication interface 702: Plasma processing Chamber 704: First Impedance Matching Unit 706: RF Power Generator 708: Tool Controller 724: Sensor 770: Embedded Electrode 772: RF Electrode 774: Workpiece Base 776: Second Impedance Matching Unit 778: RF Power Generator 780: High Voltage Supply 782: RF Blocking Filter 784: DC Blocking Capacitor 880: PV Waveform Generator 884: Capacitor 900: Slave Plasma Processing System 904: RF Impedance Matching Unit L1: Inductor L2: Inductor Pf: Forward Power Pr: Reflected Power RF: Radio Frequency VC1: Variable Capacitor VC2: Variable Capacitor VC3: Variable Capacitor θ: Phase Angle In order to better understand in detail the manner in which the above-described features of the present disclosure are employed, a more particular description of the present disclosure, briefly summarized herein, may be had by reference to embodiments, some of which are illustrated in the accompanying drawings. It will be noted, however, that the drawings illustrate only exemplary embodiments and are not to be considered limiting of its scope, as other equally effective embodiments may be admitted. FIG1 illustrates a schematic block diagram of a semiconductor wafer plasma processing system with a field-replaceable sensor module according to an exemplary embodiment of the present disclosure; FIG2 illustrates a schematic block diagram of a semiconductor wafer plasma processing system with a field-replaceable external quick-connect sensor module according to an exemplary embodiment of the present disclosure; FIG3 illustrates a schematic block diagram of an RF impedance measurement module according to a specific example embodiment of the present disclosure; FIG4 illustrates a schematic block diagram of an RF power measurement module according to a specific example embodiment of the present disclosure; 5A, 5B and 5C illustrate schematic diagrams of RF tuning circuits according to specific example embodiments of the present disclosure; FIG6 illustrates a schematic block diagram of a matching controller according to a specific example embodiment of the present disclosure; FIG. 7 is a schematic diagram of a plasma processing chamber having two impedance matching units according to an exemplary embodiment of the present disclosure. FIG. 8 is a schematic diagram of a plasma processing chamber having an impedance matching unit controlled by a remote sensor according to an exemplary embodiment of the present disclosure. FIG. 9 illustrates a schematic block diagram of a system for plasma processing a semiconductor wafer according to a specific example embodiment of the present disclosure; and FIG. 10 illustrates a schematic block diagram of a semiconductor wafer plasma processing system having a master plasma processing subsystem and a plurality of slave plasma processing subsystems according to an exemplary embodiment of the present disclosure. To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. Domestic deposit information (please note in the order of deposit organization, date, and number) None Foreign deposit information (please note in the order of deposit country, organization, date, and number) None 102: Plasma Chamber 106:RF Power Generator 108: Tool Controller 110: User Interface 112:RF tuning circuit 114:Matching controller 116: Memory 118: Safety and operation interlock 120:RF power measurement module 122:RF filter 122a:RF filter 126: Temperature sensor 128:EtherCat Adapter 130: Power delivery line 200:Plasma processing system 204:RF impedance matching unit 224:RF impedance measurement module 230a: coaxial cable 230b: coaxial cable 232: coaxial connector 232a: coaxial connector

Claims

1. A radio frequency (RF) impedance matching unit for coupling between an RF power generator and a plasma processing chamber, comprising: an RF tuning circuit having a first node adapted for coupling to the RF power generator, a second node adapted for coupling to the plasma processing chamber, and a plurality of adjustable tuning elements for converting an output resistance of the RF power generator into a plurality of impedances at the second node; a matching controller coupled to the adjustable tuning elements of the RF tuning circuit, wherein the matching controller controls and monitors a plurality of positions of the adjustable tuning elements of the RF tuning circuit; a first communication interface coupled to the matching controller for receiving and transmitting position information of the adjustable tuning elements of the RF tuning circuit; and an RF impedance measurement module coupled between the second node of the RF tuning circuit and the plasma processing chamber, the RF impedance measurement module comprising: a frequency detector having an input coupled to the second node; and an RF phase detector; A microcontroller has multiple inputs configured to receive signal information from multiple outputs of the frequency detector and the RF phase detector; and a second communication interface coupled to the microcontroller and adapted to communicate the measured frequency and RF phase.

2. The RF impedance matching unit as claimed in claim 1, wherein the RF impedance measurement module comprises: a sensor assembly including: an RF current sensor coupled between the second node and the plasma processing chamber; an RF voltage sensor having an input coupled to the second node; a frequency detector; and an RF phase detector coupled to a plurality of outputs of the RF voltage sensor and the RF current sensor; a microcontroller having a plurality of additional inputs configured to receive additional signal information from the outputs of the RF current sensor and the RF voltage sensor; and a second communication interface adapted to communicate the measured RF voltage and RF current.

3. The radio frequency impedance matching unit as claimed in claim 2, wherein the microcontroller calculates the RF impedance based on the measured RF voltage, RF current, frequency and RF phase, wherein the calculated RF impedance can be used for transmission by the second communication interface.

4. The RF impedance matching unit as described in claim 1, wherein the RF impedance measurement module and the RF impedance matching unit are integrated.

5. The RF impedance matching unit as claimed in claim 1, wherein the RF impedance measurement module is separate from the RF impedance matching unit and is adapted to couple between the RF impedance matching unit and the plasma processing chamber using a plurality of quick-connect coaxial RF connectors.

6. The RF impedance matching unit as described in claim 1 further includes an RF power measurement module coupled between the RF power generator and the first node of the RF tuning circuit.

7. The RF impedance matching unit as claimed in claim 6, wherein the RF power measurement module comprises: a forward RF power sensor; a reflected RF power sensor; an additional microcontroller having multiple inputs coupled to multiple outputs of the forward and reflected RF power sensors, and calculating a standing wave ratio (SWR) based on the measured forward and reflected RF power; and a third communication interface coupled to the additional microcontroller and adapted to communicate the measured forward and reflected RF power and the calculated SWR.

8. The radio frequency impedance matching unit as claimed in claim 7, wherein the first communication interface, the second communication interface and the third communication interface are adapted to communicate using an Ethernet communication protocol for control automation technology (EtherCaT).

9. The radio frequency impedance matching unit as described in claim 6, wherein the RF power measurement module and the radio frequency impedance matching unit are integrated.

10. The RF impedance matching unit as claimed in claim 6, wherein the RF power measurement module is separate from the RF impedance matching unit and is adapted to couple between the RF power generator and the RF impedance matching unit using a quick-connect coaxial RF connector.

11. The RF impedance matching unit as claimed in claim 1, wherein the matching controller comprises: an additional microcontroller communicating with the first communication interface and having multiple inputs and multiple outputs for monitoring the positions of multiple adjustable elements of a variable impedance network and controlling the adjustable elements of the variable impedance network; and a memory including information regarding a plurality of settings of one or more adjustable tuning elements stored therein, wherein the plurality of settings of one or more adjustable tuning elements are configured to match a selected impedance of the plurality of impedances at the second node with the output resistance of the RF power generator.

12. A plasma processing system for controlling and monitoring a radio frequency (RF) power generator and an impedance matching unit adapted to generate a plasma in a plasma processing chamber, the system comprising: the RF power generator having an RF power output and coupled to a first communication interface for monitoring and controlling the RF power output; An RF power measurement module is coupled to the output of the RF power generator and measures the forward and reflected RF power at the output of the RF power generator, and calculates the standing wave ratio (SWR) based on the measured forward and reflected RF power; a second communication interface is coupled to the RF power measurement module for transmitting the measured forward and reflected RF power and the calculated SWR; An RF tuning circuit includes a first node coupled to the RF power measurement module and a plurality of adjustable tuning elements for converting an output resistance of the RF power generator into a plurality of impedances at a second node of the RF tuning circuit; a matching controller coupled to the adjustable tuning elements of the RF tuning circuit, wherein the matching controller controls and monitors the position of the adjustable tuning elements of the RF tuning circuit; and a third communication interface coupled to the matching controller for receiving and transmitting position information of the adjustable tuning elements of the RF tuning circuit. An RF impedance measurement module is coupled between the second node of the RF tuning circuit and the plasma processing chamber, and measures the RF voltage, RF current, and frequency at the second node of the RF tuning circuit, determines the RF phase based on the measured RF voltage and RF current, and calculates the RF impedance at the second node based on the measured RF voltage, RF current, RF phase, and frequency; a fourth communication interface is coupled to the RF impedance measurement module for transmitting the measured RF voltage, RF current, RF phase, frequency, and calculated impedance at the second node; a tool controller is adapted to control the RF power output of the RF power generator during plasma generation; a fifth communication interface is coupled to the tool controller; wherein at least two of the first, second, third, fourth, and fifth communication interfaces communicate with each other during an operation in the plasma processing chamber to generate the plasma.

13. The plasma processing system of claim 12 further includes one or more slave radio frequency power generators and one or more slave impedance matching units, each having a communication interface and adapted to generate plasma in one or more additional plasma processing chambers, wherein a set of processing sensor modules controls the operation of the one or more slave radio frequency power generators and the one or more slave impedance matching units associated with the one or more additional plasma processing chambers.

14. The plasma processing system of claim 13, wherein the tool controller communicates with: a first communication interface, a second communication interface, a third communication interface, and a fourth communication interface associated with the RF power generator, the RF power measurement module, the matching controller, and the RF impedance measurement module, respectively; and the communication interfaces associated with the one or more slave RF power generators and the one or more slave impedance matching units; wherein the tool controller receives multiple operating configurations of the RF power generator and the impedance matching unit via the respective communication interfaces of the RF power generator and the impedance matching unit, and transmits the operating configurations to the one or more slave RF power generators and the one or more slave impedance matching units via the respective communication interfaces of the one or more slave RF power generators and the one or more slave impedance matching units.

15. The plasma processing system of claim 13, wherein the tool controller has a communication interface and communicates with: a first communication interface, a second communication interface, a third communication interface, and a fourth communication interface associated with the RF power generator, the RF power measurement module, the matching controller, and the RF impedance measurement module, respectively; and the communication interfaces associated with the one or more slave RF power generators and the one or more slave impedance matching units; wherein the tool controller receives multiple operating configurations of the RF power generator and the impedance matching unit via the respective communication interfaces of the RF power generator and the impedance matching unit during a semiconductor wafer manufacturing process, and transmits the received operating configurations to the one or more slave RF power generators and the one or more slave impedance matching units via the respective communication interfaces of the one or more slave RF power generators and the one or more slave impedance matching units.

16. The plasma processing system as claimed in claim 12, wherein the RF impedance measurement module and the RF tuning circuit are adapted for RF coupling and communication therebetween, and are in separate housings independent of each other.

17. The plasma processing system as claimed in claim 12, wherein the tool controller replaces the no longer needed operation of the matching controller and communicates directly with the RF power generator, the RF power measurement module, the RF tuning circuit, and the RF impedance measurement module.

18. The plasma processing system as described in claim 12, wherein: The RF power measurement module and the second communication interface are enclosed in a first housing; the RF impedance measurement module and the fourth communication interface are enclosed in a second housing; and the first housing and the second housing are independent of each other and are suitable for removal and replacement.

19. A method for processing a semiconductor wafer within a plurality of plasma processing systems, comprising the steps of: providing a master plasma processing system, comprising: a master radio frequency (RF) power generator; a master impedance matching unit having a first node coupled to the master RF power generator and a second node adapted for coupling to a master plasma processing chamber, the master impedance matching unit further comprising a master RF tuning circuit having a plurality of adjustable tuning elements; and a plurality of communication interfaces coupled to the master RF power generator and the master impedance matching unit; providing a plurality of slave plasma processing systems, each of the plurality of slave plasma processing systems comprising: a slave RF power generator; a slave impedance matching unit having a first node coupled to the slave RF power generator and a second node adapted for coupling to a slave plasma processing chamber, the slave impedance matching unit further comprising a slave RF tuning circuit having a plurality of adjustable tuning elements; and a plurality of communication interfaces coupled to the slave RF power generator and the slave impedance matching unit; During a primary plasma processing operation, the primary power settings of the primary RF power generator are read and transmitted to each of the secondary RF power generators, wherein each of the secondary RF power generators is configured to adjust its power settings based on the primary power settings during the secondary plasma processing operation; and during the primary plasma processing operation, a plurality of primary position settings of the adjustable tuning elements of the primary RF tuning circuit are read and transmitted to at least one of the secondary impedance matching units, wherein each of the adjustable tuning elements of the secondary impedance matching units is configured to adjust its adjustable tuning element based on the position settings of the adjustable tuning elements of the primary RF tuning circuit during the secondary plasma processing operation.

20. The method as described in claim 19 further comprises the step of: recording the main power settings and main position settings of the adjustable tuning elements before transmitting the main power settings and main position settings of the adjustable tuning elements to the slave RF power generators and the slave impedance matching units.

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