Capacitance measurement without breaking high power circuit

Abstract

A method and apparatus for plasma assisted semiconductor processing is provided. The method comprises: a) providing a substrate at each of the plurality of stations; b) allocating RF power comprising a first target frequency to a plurality of stations, thereby generating plasma within the stations, where the RF power is allocated according to RF power parameters configured to reduce variations between stations; c) tuning an impedance matching circuit for a first station included in the plurality of stations while distributing RF power to the first station by: i) measuring a capacitance of a capacitor in the impedance matching circuit without disconnecting the capacitor from the impedance matching circuit; and ii) adjusting the capacitance of the capacitor according to the capacitance and the RF power parameter measured in (i); and d) performing a semiconductor processing operation on the substrate at each station.

Description

This application is a divisional application of the invention patent application with application number 201980015041.9, application date February 22, 2019, applicant is Rum Research Company, and invention name is "Capacitance measurement of high-power circuits without disconnection". CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of USSN 62 / 634,730, filed February 23, 2018, entitled “CAPACITANCE MEASUREMENT WITHOUT DISCONNECTING FROM HIGH POWER CIRCUIT,” the entire contents of which are incorporated herein by reference for all purposes. Background Art

[0002] Semiconductor device manufacturing involves processing semiconductor wafers in semiconductor processing reactors. Typical processes include depositing and removing (i.e., etching) materials on the wafer. In commercial-scale manufacturing, each wafer contains many copies of the specific semiconductor device to be manufactured, and many wafers are required to achieve the required volume of the device. The commercial viability of semiconductor processing operations depends largely on the intra-wafer uniformity and wafer-to-wafer repeatability of process conditions. Therefore, efforts are made to ensure that every part of a given wafer and every wafer processed is exposed to the same processing conditions. Variations in processing conditions can lead to variations in deposition and etching rates, resulting in unacceptable variations in the overall process and product. Summary of the Invention

[0003] A system of one or more computers can be configured to perform specific operations or actions by installing software, firmware, hardware, or a combination thereof on the system that, when operated, causes the system to perform those actions. One or more computer programs can be configured to perform specific operations or actions by including instructions that, when executed by a data processing device, cause the device to perform those actions. One general aspect includes a method for plasma-assisted semiconductor processing in a plurality of stations in a processing chamber, the method comprising: a) providing a substrate at each of the plurality of stations; b) distributing RF power comprising a first target frequency to the plurality of stations to generate plasma within the stations, wherein the RF power is distributed according to RF power parameters configured to reduce station-to-station variation; c) tuning an impedance matching circuit for a first station included in the plurality of stations while distributing RF power to the first station by: i) measuring a capacitance of a capacitor in the impedance matching circuit without disconnecting the capacitor from the impedance matching circuit; and ii) adjusting the capacitance of the capacitor according to the capacitance measured in (i) and the RF power parameters; and d) performing a semiconductor processing operation on the substrate at each station. Other embodiments of this aspect include corresponding computer systems, apparatus, and computer programs recorded on one or more computer storage devices, each configured to perform the actions of the method.

[0004] Implementations may include one or more of the following features. The method, wherein the semiconductor processing operation is one of the following: depositing, etching, stripping, or cleaning a thin film. The method, wherein i) includes: aa) generating a first signal comprising a first frequency higher than the first target frequency in the allocated RF power; bb) filtering the signal at the capacitor, the signal at the capacitor being generated in response to at least the first signal and the allocated RF power; cc) measuring the filtered signal; and dd) converting the measured filtered signal into a measured capacitance value of the capacitor. The method, wherein the filtering includes a passband centered at a frequency greater than a tenth harmonic frequency of the first target frequency, and the filtering includes a stopband, the stopband including the first target frequency in the allocated RF power. The method, wherein the first target frequency in the allocated RF power is approximately 13.56 MHz, 27 MHz, 40 MHz, 60 MHz, or 100 MHz. The method, wherein the first target frequency in the allocated RF power is approximately 400 kHz. The method wherein: aa) includes generating an AC voltage (Vin) as the first signal using a fixed frequency oscillator configured at the first frequency (ω), the output of the fixed frequency oscillator being coupled to a resistor (R) in series with the capacitor; and dd) includes converting the measured filtered signal (Vout) to the measured capacitance value (c) based in part on the resistor (R), the first frequency (ω) and the AC voltage (Vin), wherein Vout / Vin=1 / (1+jωRC). The method includes: aa) generating an AC voltage (Vin) as the first signal using a variable frequency oscillator, the output of the variable frequency oscillator being coupled to an inductor (l) in series with the capacitor, the variable frequency oscillator being configured to sweep a frequency range including a resonant frequency (fo=ωo / 2π) of the capacitor and the inductor; cc) determining the resonant frequency using the measured filtered signal; and dd) converting the measured filtered signal into a measured capacitance value (c) based in part on the resonant frequency (fo=ωo / 2π) and the inductance (l), wherein fo=ωo / 2π=1 / 2πsqrt(lc).The method wherein: aa) comprises generating an AC voltage (Vin) as the first signal at the first frequency (ω) using an oscillator, the output of the oscillator being coupled to a first terminal of the capacitor through at least a first impedance (z1) and a second impedance (z2) each in series with the capacitor, the output of the oscillator being further coupled to a second terminal of the capacitor through at least a third impedance (z3) in series with the capacitor; cc) comprises measuring a current or voltage as the measured filtered signal at a node coupling the first impedance (z1), the second impedance (z2), and the third impedance (z3), wherein the measured filtered signal represents an imbalance between: a first impedance combination comprising the first impedance (z1) and the second impedance (z2) and a second impedance combination comprising the third impedance (z3) and the impedance (zC) of the capacitor. The method may further comprise: dd) comprises converting the measured filtered signal into a measured capacitance value (c) based in part on a ratio z1 / z2=z3 / zC, where zC=1 / jωc. The method wherein: aa) includes using an oscillator to generate an alternating voltage (Vin) as the first signal at the first frequency (ω), the output of the oscillator being coupled to a reference capacitor (cref) and connecting the reference capacitor in electrical parallel with the capacitor when the alternating voltage charges the reference capacitor to a reference voltage (vref); cc) includes measuring a voltage corresponding to the charge in the electrical parallel combination of the reference capacitor and the capacitor as the measured filtered signal at the first frequency (ω); and dd) includes converting the measured filtered signal to the measured capacitance value (c) based in part on c=cref(vref / Vout-1). The method wherein: aa) comprises generating an alternating current (Iin) as the first signal at the first terminal of the capacitor at the first frequency (ω) using a current source, the output of the current source being coupled to a voltage measurement interface for measuring a voltage (V); cc) comprises measuring a filtered current (I) corresponding to the current at the second terminal of the capacitor as the measured filtered signal; and dd) comprises converting the measured filtered signal into the measured capacitance value (c) based in part on the filtered current (I) and the rate of change (dv / dt) of the voltage measured at the voltage measurement interface, where i=c dv / dt.The method wherein: aa) includes generating a timer signal using a timer circuit, wherein a timer frequency (f) is configured using a first resistor (r1), a second resistor (r2), and the capacitance (c) of the capacitor; cc) includes measuring a count of timer pulses within a certain period of time as the measured filtered signal to determine the timer frequency (f); and dd) includes converting the measured filtered signal to the measured capacitance value (c) based in part on the determined timer frequency, wherein f=1 / (c×(r1+2×r2)×ln2). The method wherein an oscilloscope is used to measure the voltage drop across the capacitor at the first frequency (ω). The method wherein an inductance (l), capacitance (c), and resistance (R) meter (LCR meter) is used to measure the capacitance of the capacitor at the first frequency (ω), or a vector network analyzer is used to measure the impedance of the capacitor at the first frequency (ω).

[0005] Implementations of the described techniques may include hardware, methods or processes, or computer software on a computer-accessible medium. One general aspect includes an apparatus for plasma-assisted semiconductor processing, the apparatus comprising: a plurality of stations, wherein each of the stations comprises at least one wafer support and is configured to receive at least one substrate, and wherein the plurality of stations are within a processing chamber; a capacitance sensor; one or more controllers, wherein the one or more controllers are communicatively coupled to the capacitance sensor and configured to: a) provide a substrate at each of the plurality of stations; b) distribute RF power comprising a first target frequency to the plurality of stations to generate plasma within the stations, wherein the RF power is distributed according to an RF power parameter configured to reduce station-to-station variation; c) tune an impedance matching circuit for a first station included in the plurality of stations while distributing RF power to the first station by: i) measuring a capacitance of a capacitor in the impedance matching circuit using the capacitance sensor without disconnecting the capacitor from the impedance matching circuit; and ii) adjusting the capacitance of the capacitor based on the capacitance measured in (i) and the RF power parameter; and d) performing a semiconductor processing operation on the substrate at each station. Other embodiments of this aspect include corresponding computer systems, apparatus, and computer programs recorded on one or more computer storage devices, each configured to perform the actions of the method.

[0006] Implementations may include one or more of the following features. The apparatus, wherein the semiconductor processing operation is one of: depositing, etching, stripping, or cleaning a thin film. The apparatus, wherein i) includes: aa) generating a first signal comprising a first frequency higher than the first target frequency in the allocated RF power; bb) filtering the signal at the capacitor, the signal at the capacitor being generated in response to at least the first signal and the allocated RF power; cc) measuring the filtered signal; and dd) converting the measured filtered signal into a measured capacitance value of the capacitor. The apparatus, wherein the filtering includes a passband centered at a frequency greater than a tenth harmonic frequency of the first target frequency, and the filtering includes a stopband, the stopband including the first target frequency in the allocated RF power. The apparatus, wherein the first target frequency in the allocated RF power is approximately 13.56 MHz, 27 MHz, 40 MHz, 60 MHz, or 100 MHz. The apparatus, wherein the first target frequency in the allocated RF power is approximately 400 kHz. The device wherein: aa) includes generating an AC voltage (Vin) as the first signal using a fixed frequency oscillator configured at the first frequency (ω), the output of the fixed frequency oscillator being coupled to a resistor (R) in series with the capacitor; and dd) includes converting the measured filtered signal (Vout) to the measured capacitance value (c) based in part on the resistor (R), the first frequency (ω) and the AC voltage (Vin), wherein Vout / Vin=1 / (1+jωRC). The device wherein: aa) includes using a variable frequency oscillator to generate an AC voltage (Vin) as the first signal, the output of the variable frequency oscillator being coupled to an inductor (l) in series with the capacitor, the variable frequency oscillator being configured to sweep a frequency range including a resonant frequency (fo=ωo / 2π) of the capacitor and the inductor; cc) includes using the measured filtered signal to determine the resonant frequency; and dd) includes converting the measured filtered signal into the measured capacitance value (c) based in part on the resonant frequency (fo=ωo / 2π) and the inductance (l), wherein fo=ωo / 2π=1 / 2πsqrt(lc).The apparatus wherein: aa) comprises generating an AC voltage (Vin) as the first signal at the first frequency (ω) using an oscillator, the output of the oscillator being coupled to a first terminal of the capacitor via at least a first impedance (z1) and a second impedance (z2), each of which is in series with the capacitor, and the output of the oscillator being coupled to a second terminal of the capacitor via at least a third impedance (z3) in series with the capacitor; cc) comprises measuring a current or voltage as the measured filtered signal at a node coupling the first impedance (z1), the second impedance (z2), and the third impedance (z3), wherein the measured filtered signal represents an imbalance between: a first impedance combination comprising the first impedance (z1) and the second impedance (z2) and a second impedance combination comprising the third impedance (z3) and the impedance (zC) of the capacitor. The apparatus may further comprise: dd) comprises converting the measured filtered signal into a measured capacitance value (c) based in part on a ratio z1 / z2=z3 / zC, where zC=1 / jωc. The device wherein: aa) includes using an oscillator to generate an alternating voltage (Vin) as the first signal at the first frequency (ω), the output of the oscillator being coupled to a reference capacitor (cref) and connecting the reference capacitor in electrical parallel with the capacitor when the alternating voltage charges the reference capacitor to a reference voltage (vref); cc) includes measuring a voltage corresponding to the charge in the electrical parallel combination of the reference capacitor and the capacitor as the measured filtered signal at the first frequency (ω); and dd) includes converting the measured filtered signal into the measured capacitance value (c) based in part on c=cref(vref / Vout-1). The device wherein: aa) includes using a current source to generate an alternating current (Iin) as the first signal at the first terminal of the capacitor at the first frequency (ω), the output of the current source being coupled to a voltage measurement interface for measuring a voltage (V); cc) includes measuring a filtered current (I) corresponding to the current at the second terminal of the capacitor as the measured filtered signal; and dd) includes converting the measured filtered signal into the measured capacitance value (c) based in part on the filtered current (I) and the rate of change (dv / dt) of the voltage measured at the voltage measurement interface, where i=c dv / dt.The apparatus wherein: aa) includes generating a timer signal using a timer circuit, wherein a timer frequency (f) is configured using a first resistor (r1), a second resistor (r2), and the capacitance (c) of the capacitor; cc) includes measuring a count of timer pulses within a certain period of time as the measured filtered signal to determine the timer frequency (f); and dd) includes converting the measured filtered signal into the measured capacitance value (c) based in part on the determined timer frequency, wherein f=1 / (c×(r1+2×r2)×ln2). The apparatus wherein an oscilloscope is used to measure the voltage drop across the capacitor at the first frequency (ω). The apparatus wherein an inductance (l), capacitance (c), and resistance (R) meter (LCR meter) is used to measure the capacitance of the capacitor at the first frequency (ω), or a vector network analyzer is used to measure the impedance of the capacitor at the first frequency (ω).

[0007] Implementations of the described techniques may include hardware, methods or processes, or computer software on a computer-accessible medium. One general aspect includes an apparatus for measuring the capacitance of a capacitor without disconnecting the capacitor from a circuit for distributing RF power at a first target frequency, the apparatus comprising: a filter including a passband including a first frequency greater than a tenth harmonic of the first target frequency, the filter also having a stopband including the first target frequency; an oscillator for generating an AC voltage (Vin) at the first frequency (ω); a resistor (R), wherein an output of the oscillator is coupled to a first terminal of the resistor (R), and a second terminal of the resistor (R) is coupled to the filter electrically coupled in series with the capacitor; and a voltage measurement interface for measuring a filtered signal (Vout) at the second terminal of the resistor (R), wherein a measured capacitance value (c) of the capacitor is based in part on the resistor (R), the first frequency (ω), and the AC voltage (Vin), wherein Vout / Vin=1 / (1+jωRC). Other embodiments of this aspect include corresponding computer systems, apparatus, and computer programs recorded on one or more computer storage devices, each configured to perform the actions of the method.

[0008] Implementations may include one or more of the following features: The apparatus wherein the first target frequency in the allocated RF power is approximately 13.56 MHz, 27 MHz, 40 MHz, 60 MHz, or 100 MHz. The apparatus wherein the first target frequency in the allocated RF power is approximately 400 kHz.

[0009] Implementations of the described techniques may include hardware, a method or process, or computer software on a computer-accessible medium. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 A substrate processing apparatus for depositing a film on a semiconductor substrate is shown.

[0011] Figure 2 An exemplary multi-station substrate processing apparatus that may utilize plasma balancing hardware is shown.

[0012] Figure 3 is a schematic diagram illustrating various components in an exemplary multi-station plasma reactor having multiple stations that share an RF power source using impedance matching tuning.

[0013] Figure 4A FIG. 1 is a process flow diagram of a multi-station deposition process using impedance matching tuning and RF power parameter adjustment.

[0014] Figure 4B is a process flow diagram of a multi-station deposition process using impedance matching tuning.

[0015] Figure 5 An exemplary capacitance sensor using a voltage measurement method is shown.

[0016] Figure 6 An exemplary capacitive sensor using the resonant frequency method is shown.

[0017] Figure 7 An exemplary capacitance sensor using a Wheatstone bridge approach is shown.

[0018] Figure 8 An exemplary capacitive sensor using a charge-based approach is shown.

[0019] Figure 9 An exemplary capacitance sensor using the ramp rate method is shown.

[0020] Figure 10 An exemplary capacitive sensor using a timer-based approach is shown. DETAILED DESCRIPTION

[0021] In the detailed description that follows, a number of specific implementations are described. However, it will be apparent to those skilled in the art that the techniques and apparatus disclosed herein can be practiced without these specific details or by using alternative components or processes. In other cases, well-known processes, procedures, and components have not been described in detail to avoid unnecessarily obscuring aspects of the present disclosure.

[0022] Some semiconductor device manufacturing tools include two variable capacitors, such as a series capacitor (tuning) and a shunt capacitor (load), which match the load impedance to the generator impedance, for example, at a value of 50 ohms. Since one value for each capacitor results in the load impedance matching the generator impedance, it is very important to monitor the value of the capacitors. Existing techniques use, for example, stepper motors. Since stepper motors can have problems with sliding couplers, this technique can result in incorrect positions and therefore incorrect capacitor values, which can lead to scrapping of semiconductor wafers. In addition, conventional capacitance measurement methods require that the capacitor being measured be disconnected from the circuit, such as the high-power RF circuits involved in semiconductor manufacturing. A technique is needed to accurately measure capacitance for monitoring and control purposes without disconnecting the capacitor during use.

[0023] An apparatus and method for controlling RF power used in a multi-cycle deposition operation in a semiconductor tool having multiple processing stations sharing an RF power source is provided. The frequency of the RF power is controlled, as is the power applied to each station of the shared RF power source.

[0024] Figure 1 A substrate processing apparatus for depositing a film on a semiconductor substrate is shown. Figure 1 The apparatus 100 has a single process chamber 102 with a single substrate holder 108 within an interior volume, which substrate holder 108 may be maintained under vacuum by a vacuum pump 118. A gas delivery system 101 and a showerhead 106 are also fluidly coupled to the chamber for delivering, for example, film precursors, carrier and / or sweep gases and / or process gases, secondary reactants, and the like. Figure 1 Also shown is a facility for generating plasma within the processing chamber. Figure 1 The apparatus schematically illustrated in provides a basic facility for performing film deposition operations, such as chemical vapor deposition (CVD) or ALD, on semiconductor substrates.

[0025] For simplicity, the processing apparatus 100 is depicted as an independent processing station having a processing chamber body 102 for maintaining a low pressure environment. However, it should be understood that as described herein, multiple processing stations can be included in a common processing tool environment, for example, within a common reaction chamber. For example, Figure 2 Implementations of a multi-station processing tool are depicted.Furthermore, it should be understood that in some implementations, one or more hardware parameters of the processing device 100, including those discussed in detail above, may be programmatically adjusted by one or more system controllers.

[0026] The processing station 100 is in fluid communication with a reactant delivery system 101 for delivering process gases to a distribution showerhead 106. The reactant delivery system 101 includes a mixing vessel 104 for mixing and / or conditioning process gases for delivery to the showerhead 106. One or more mixing vessel inlet valves 120 can control the introduction of process gases into the mixing vessel 104.

[0027] Some reactants may be stored in liquid form prior to evaporation and subsequently delivered to the processing chamber 102 . Figure 1 Implementations include a vaporization point 103 for vaporizing liquid reactants to be supplied to a mixing vessel 104. In some implementations, the vaporization point 103 can be a heated liquid injection module. In some other implementations, the vaporization point 103 can be a heated vaporizer. In other implementations, the vaporization point 103 can be eliminated from the processing station.

[0028] In some implementations, a liquid flow controller (LFC) may be provided upstream of the vaporization point 103 to control the mass flow rate of the liquid that is vaporized and delivered to the process chamber 102 .

[0029] The showerhead 106 distributes process gases and / or reactants (e.g., film precursors) toward the substrate 112 at the processing station, with the flow rate controlled by one or more valves (e.g., valves 120, 120A, 105) upstream of the showerhead. Figure 1 In the illustrated implementation, the substrate 112 is positioned below the showerhead 106 and is shown resting on the pedestal 108. The showerhead 106 may have any suitable shape and may have any suitable number and arrangement of ports for distributing process gases to the substrate 112.

[0030] A volume 107 is located below the showerhead 106. In some implementations, the pedestal 108 can be raised or lowered to expose the substrate 112 to the volume 107 and / or to change the volume of the volume 107. Optionally, the pedestal 108 can be lowered and / or raised during portions of the deposition process to adjust process pressure, reactant concentrations, etc. within the volume 107.

[0031] exist Figure 1In the embodiment of the present invention, the showerhead 106 and the pedestal 108 are electrically connected to an RF power source 114 and a matching network 116 for powering the plasma. In some implementations, the plasma energy can be controlled by controlling one or more of the process station pressure, gas concentration, RF source power, RF source frequency, and / or plasma power pulse timing (e.g., via a system controller with appropriate machine-readable instructions). For example, the RF power source 114 and the matching network 116 can be operated at any suitable power to form a plasma having a desired radical species composition. Similarly, the RF power source 114 can provide RF power at any suitable frequency.

[0032] In some implementations, the plasma can be monitored in situ by one or more plasma monitors. In one case, the plasma power can be monitored by one or more capacitance, voltage, and / or current sensors (e.g., load cells such as VI probes). Examples of such sensors include the MKS VI-Probe-4100 and 350. Such sensors can measure capacitance, voltage, current, and phase difference. In certain implementations, the sensor can be electrically connected to the RF power source and can be located at or near the showerhead. In such an implementation, the impedance seen by the RF power source can represent the impedance of the plasma. In another case, the plasma density and / or process gas concentration can be measured by one or more optical emission spectroscopy (OES) sensors. In some implementations, one or more plasma parameters can be programmatically adjusted based on measurements from such in situ plasma monitors. For example, a load cell can be used in a feedback loop to provide programmatic control of the plasma power. It should be understood that in some implementations, other monitors can be used to monitor the plasma and other processing characteristics. Such monitors can include, but are not limited to, infrared (IR) monitors, acoustic monitors, and pressure sensors.

[0033] In some implementations, the plasma may be controlled via input / output control (IOC) sequencing instructions. In one example, instructions for setting plasma conditions for plasma activation may be included in a corresponding plasma activation recipe of a process recipe. In some cases, the process recipes may be arranged in sequence so that all instructions for a process are executed simultaneously with the process. In some implementations, instructions for setting one or more plasma parameters may be included in a recipe prior to plasma treatment. For example, a first recipe may include instructions for setting the flow rate of an inert gas (e.g., helium) and / or a reactant gas, instructions for setting a plasma generator to a power setting value, and a time delay instruction for the first recipe. A second subsequent recipe may include instructions for enabling a plasma generator and a time delay instruction for a second recipe. A third recipe may include instructions for disabling a plasma generator and a time delay instruction for a third recipe. It should be understood that within the scope of the present disclosure, these recipes may be further subdivided and / or iterated in any suitable manner.

[0034] In some deposition processes, plasma excitation lasts for a duration of several seconds or longer. In some implementations described herein, shorter plasma excitations may be applied during a process cycle. These excitations may be less than 50 milliseconds, with 25 milliseconds being a specific example. Such short RF plasma excitations require rapid stabilization and tuning of the plasma. To achieve rapid stabilization and tuning of the plasma, the plasma generator may be configured using a two-step tuning process comprising a coarse tuning component and a fine tuning component. In the coarse tuning component, impedance matching may be preset to a specific impedance. The coarse tuning component may be preset to cause the impedance magnitude to be, for example, 50 ohms. In some implementations, the coarse tuning component may be limited to adjustments affecting the impedance magnitude. In the fine tuning component, the RF frequency may be allowed to float relative to a baseline frequency in an attempt to match the phase to a target value (e.g., a zero phase value). Conventionally, high-frequency plasmas are generated at RF frequencies of approximately 13.56 MHz, 27 MHz, 40 MHz, 60 MHz, or 100 MHz. In various implementations disclosed herein, the frequency can be allowed to float to values different from the standard value in order to match the phase to the target value. In some implementations, the fine-tuning components can be limited to adjustments that affect the impedance phase. By allowing the frequency to float while fixing the impedance match to a predetermined impedance, the plasma can stabilize much faster. Very short plasma excitations (such as those associated with ALD or atomic layer etch (ALE) cycles) may benefit from rapid plasma stabilization.

[0035] The first 1-2 milliseconds of a typical deposition cycle involve ignition of the plasma. After the plasma is ignited, fine tuning of the RF frequency is then performed to match the plasma phase to the target value.

[0036] As described above, one or more processing stations may be included in a multi-station substrate processing tool. Figure 2 An exemplary multi-station substrate processing apparatus that can utilize plasma balancing hardware is shown. Figure 2 A multi-station processing apparatus such as the one shown can achieve various efficiencies. For example, a single vacuum pump can be used to create a single high vacuum environment for all four processing stations by evacuating waste process gases from all four processing stations. Depending on the implementation, each processing station can have its own dedicated showerhead for gas delivery, but can share the same gas delivery system. Similarly, certain elements of the plasma generator facility can be shared between processing stations (such as power supplies), but depending on the implementation, certain aspects may be specific to the processing station (for example, if showerheads are used to apply the potential for plasma generation). Once again, it should be understood that this efficiency can also be achieved to a greater or lesser extent by using a greater or lesser number of processing stations in each processing chamber (e.g., 2, 3, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16 processing stations per reaction chamber).

[0037] Figure 2 The substrate processing apparatus 200 of FIG. 1 employs a single substrate processing chamber 214 containing a plurality of substrate processing stations, each of which can be used to perform processing operations on a substrate held in a wafer holder at the processing station. In this particular implementation, a multi-station substrate processing apparatus 200 is shown having four processing stations 201, 202, 203, and 204. Other similar multi-station processing apparatuses may have more or fewer processing stations depending on the implementation and, for example, the desired level of parallel wafer processing, size / space constraints, cost constraints, etc. Figure 2 Also shown are a substrate handling robot 226 and a controller 250 .

[0038] like Figure 2 As shown, the multi-station processing tool 200 has a substrate loading port 220 and a robot 226 configured to move substrates from a cassette loaded via a wafer boat 228 through the atmospheric port 220 into the processing chamber 214 and onto one of the four stations 201 , 202 , 203 or 204 .

[0039] Figure 2The depicted process chamber 214 shown provides four processing stations 201, 202, 203 and 204. RF power is generated at an RF power system 213 and distributed to each of the stations 201-204. The RF power system may include one or more RF power sources, such as high frequency (HFRF) and low frequency (LFRF) sources, impedance matching modules and filters. In some implementations, the power source may be limited to high frequency or low frequency sources. Unless otherwise stated, it is assumed that the deposition process described uses only high frequency power. The distribution system of the RF power system is symmetrical about the reactor and has a high impedance. This symmetry and impedance result in approximately equal amounts of power being delivered to each station. Slight differences in RF power, between about 5% and 15%, may be due to tolerances in distribution system components, station alignment, temperature differences and process conditions.

[0040] Small differences in RF power due to various reasons (including but not limited to inaccurate tuning of variable capacitors in impedance matching modules or inaccurate current measurements from the RF power supply) can lead to wafer-to-wafer non-uniformity in various film properties, such as composition, thickness, density, amount of cross-linking, chemistry, reaction completion, stress, refractive index, dielectric constant, hardness, etch selectivity, stability, hermeticity, etc. The ability to fine-tune plasma power at a single station and dynamically respond to changes in station conditions can reduce wafer-to-wafer non-uniformity. Note that the present method and apparatus are not limited to multi-station reactors; the method and apparatus disclosed herein are applicable to other RF power systems in which multiple processing zones share an RF power source.

[0041] Figure 2 Also depicted is an implementation of a substrate transfer device 290 for transferring substrates between the processing stations 201, 202, 203, and 204 within the processing chamber 214. It should be understood that any suitable substrate transfer device may be employed. Non-limiting examples include wafer conveyor belts and wafer handling robots.

[0042] Figure 2 Also depicted is an implementation of a system controller 250 for controlling process conditions and hardware states of the processing tool 200 and its processing stations. The system controller 250 may include one or more memory devices 256, one or more mass storage devices 254, and one or more processors 252. The processor 252 may include one or more CPUs, ASICs, general-purpose computers and / or special-purpose computers, one or more analog and / or digital input / output connections, one or more stepper motor controller boards, and the like.

[0043] In some implementations, the system controller 250 controls some or all of the operations of the processing tool 200, including the operations of its various processing stations. The system controller 250 can execute machine-readable system control instructions 258 on the processor 252. In some implementations, the system control instructions 258 are loaded from the mass storage device 254 into the memory device 256. The system control instructions 258 may include instructions for controlling timing, gaseous and liquid reactant mixing, chamber and / or station pressure, chamber and / or station temperature, wafer temperature, target power level, RF power level, RF exposure time, substrate pedestal, chuck and / or base position, and other parameters of the specific processing performed by the processing tool 200. These processes may include various types of processes, including but not limited to processes related to depositing films on substrates. The system control instructions 258 can be configured in any suitable manner. For example, various processing tool component subroutines or control objects can be written to control the operations of the processing tool components. The system control instructions 258 can be encoded in any suitable computer-readable programming language. In some implementations, the system control instructions 258 are implemented in software, in other implementations the instructions may be implemented in hardware, for example, as logic hard-coded in an ASIC (application-specific integrated circuit), or in other implementations as a combination of software and hardware.

[0044] In some implementations, the system control software 258 may include input / output control (IOC) sequencing instructions for controlling the various parameters described above. For example, each step of one or more deposition processes may include one or more instructions executed by the system controller 250. For example, instructions for setting process conditions for a primary film deposition process may be included in a corresponding deposition recipe and also used for blanket film deposition. In some implementations, the recipes may be arranged sequentially so that all instructions for a process are executed concurrently with that process.

[0045] In some implementations, other computer-readable instructions and / or programs stored on the mass storage device 254 and / or the memory device 256 associated with the system controller 250 may be employed. Examples of programs or program portions include substrate positioning programs, process gas control programs, pressure control programs, heater control programs, and plasma control programs.

[0046] In some implementations, there may be a user interface associated with the system controller 250. The user interface may include a display screen, graphical software displays of apparatus and / or process conditions, and user input devices such as pointing devices, keyboards, touch screens, microphones, and the like.

[0047] In some implementations, the parameters regulated by the system controller 250 may relate to process conditions. Non-limiting examples include process gas composition and flow rate, temperature, pressure, plasma conditions (e.g., RF bias power level, frequency, and exposure time), etc. These parameters may be provided to the user in the form of a recipe that can be entered using a user interface.

[0048] Signals for monitoring the process can be provided from various process tool sensors via analog and / or digital input connections of the system controller 250. Signals for controlling the process can be output via analog and / or digital output connections of the process tool 200. Non-limiting examples of process tool sensors that can be monitored include mass flow controllers (MFCs), pressure sensors (e.g., manometers), thermocouples, load cells, OES sensors, etc. Appropriately programmed feedback and control algorithms can be used with the data from these sensors to maintain process conditions.

[0049] The system controller 250 may provide machine-readable instructions for implementing the deposition process. The instructions may control various process parameters, such as DC power levels, RF bias power levels, station-to-station variations, such as variations in RF power parameters (voltage, current, capacitance, impedance, phase, load power, etc.), frequency tuning parameters, pressure, temperature, etc. These instructions may control these parameters, for example, but not limited to, controlling a variable capacitor in an impedance matching module, or controlling a current source based on measuring the current delivered from the RF power source to the plasma, to perform in-situ deposition of a film stack according to various implementations described herein.

[0050] The system controller will typically include one or more memory devices and one or more processors configured to execute machine-readable instructions so that the apparatus will perform operations according to the processes disclosed herein. A machine-readable, non-transitory medium containing instructions for controlling operations according to the substrate doping processes disclosed herein may be coupled to the system controller.

[0051] Various other configurations for multi-cycle deposition processes and multi-station semiconductor processing apparatus are described in US Provisional Patent Application No. 61 / 994,025, filed May 15, 2014, and incorporated herein by reference.

[0052] Figure 3FIG2 is a schematic diagram illustrating various components of an exemplary multi-station plasma reactor having multiple stations that utilize RF frequency tuning to share an RF power source. As shown, an RF power source 301, which may be a high-frequency RF power source, is distributed to multiple stations 351 via a distribution network 321. The HFRF may have a target frequency of approximately 2-60 MHz, or approximately 13.56 MHz. In other implementations, a low-frequency RF power source may be used in addition to or in place of the high-frequency RF power source. The low-frequency RF power source may have a target frequency of approximately 100 kHz to approximately 1 MHz, or approximately 400 kHz. Certain commercially available RF power sources have the capability to tune the frequency of the RF power source. Examples of such RF power sources include Advanced Engineer's Paramount series, MKS's SurePower series, Comdel's CB, CLX, and CDX series, and Huettinger's TruPlasma series.

[0053] The power from the RF power source 301 can be delivered through an impedance matching system, which can include a fixed matching module 303. In some implementations that include both a high-frequency RF power source and a low-frequency RF power source, a high-pass filter and / or a low-pass filter can also be present. Additionally, in some implementations, the power from the RF power source can be delivered through an automatic matching module (e.g., an impedance matching circuit having one or more adjustable / variable / banked capacitors, etc.). In implementations that include a low-frequency RF power source (whether in addition to or in place of a high-frequency RF power source), the low-frequency power can be delivered through either a fixed match or an automatic match. In some implementations, an automatic matching module can be used to match the RF power source impedance to the load impedance of the plasma (e.g., 50 ohms). In other implementations, a fixed matching module can be used that does not automatically match the RF power source impedance to the impedance of the plasma load.

[0054] exist Figure 3In the illustrated implementation, the RF power source 301 is connected to a distribution network 321. The distribution network 321 can distribute the RF power generated by the RF power source 301 to each of a plurality of stations 351. In certain implementations, the RF power distributed to a particular station is in a range including, but not limited to, 1.5-10 kW. The distribution network 321 is connected to an RF regulator 323 for each of the plurality of stations 351. For each of the plurality of stations 351, the RF regulator 323 is connected to a power parameter sensor 333 before the showerhead 353. The power parameter sensor 333 can be any type of sensor previously disclosed, such as a voltage, current, capacitance, impedance, phase, load power, or OES sensor. The RF power source 301 can receive instructions from the RF controller 343 and change the frequency of the RF power distributed to each station. The instructions can be frequency adjustments based on the voltage, current, capacitance, impedance, phase, or load power detected by one or more power parameter sensors 333. In other implementations, additional sensors can measure a final phase representative of the phase of the plasma in all stations 351. The RF controller 343 can then change the frequency of the RF power allocated to the station based on the final phase measured by the additional sensor. In some implementations, the RF controller 343 can include instructions (e.g., code) to change the frequency of the RF power so that the phase of the impedance is zero or close to zero. Figure 3 In the illustrated implementation, the RF controller 343 may vary the frequency of the RF power from the RF power source 301 upstream of each station.

[0055] RF regulator 323 is controlled by RF controller 343. RF controller 343 can vary the RF power of each station by a determined amount based on measurements from sensor 333 at each station 351. In some implementations, RF regulator 323 can be a variable capacitor. RF controller 343 can control a stepper motor (not shown) that can vary the capacitance of the variable capacitor. Other methods of varying the capacitance can be used. For example, RF regulator 323 can also be a set of capacitors with individual switches. RF power can be controlled by activating (switching on) multiple capacitors with specified values. For example, capacitors can be selected to add 1pF, 2pF, 4pF, 8pF, and 16pF of parallel capacitance to a station. In this example, all combinations of active (on) and inactive (off) capacitors cover a range of 0pF to 31pF, with a resolution of 1pF. By selecting the capacitors to activate, the controller can vary the RF power delivered to the station. This digital control can be faster than using a stepper motor to control the variable capacitors, especially when a wide range of capacitance needs to be covered. Depending on the space available and the amount of control desired, one skilled in the art will be able to design an RF regulator using one or more capacitors to vary the RF power by a certain amount.

[0056] In other implementations, the RF modulator 323 may be a variable coil inductor. The RF controller 343 may control the variable coil inductor to affect the RF power delivered to the station. In some implementations, the RF modulator is not limited to capacitors and inductors. In some implementations, the other RF modulators 323 may utilize different mechanisms (e.g., a resonator circuit or a resistive circuit) to vary the RF power.

[0057] The sensor 333 measures at least one RF power parameter. The measured RF power parameter can be voltage, current, capacitance, impedance, phase, or load power. Commercially available probes can be used to measure the RF power parameters and provide the measurement results to the RF controller 343. Non-RF parameters can also be measured and used as source signals for the RF controller 343. For example, light emission from the station plasma or substrate temperature sensors can measure station characteristics and feed them to the regulator controller 343. A light emission system can be installed near each station to collect light emitted by the station plasma. The substrate temperature sensor can use a remote infrared detection system built under the substrate. The sensor 333 can also measure multiple RF power parameters, or in some implementations, multiple sensors can be used to measure multiple RF power parameters.

[0058] In some implementations, the RF regulator can be set to a fixed value or range of values in a multi-step process, such as a multi-cycle ALD process. In such implementations, little or no real-time sensing of RF power parameters and adjustment of RF power distribution between stations is required.

[0059] In some implementations, the RF regulator 323 is configured to automatically match the generator impedance of the RF power source 301 to the load impedance of the plasma. For example, the RF regulator 323 can include two variable capacitors. The first variable capacitor can be a series (tuning) capacitor, while the second variable capacitor can be a shunt (load) capacitor. The two variable capacitors can be adjusted so that the load impedance of the plasma matches the generator impedance of the RF power source 301 (e.g., 50 ohms).

[0060] In some implementations, each variable capacitor in the RF regulator 323 has a specific capacitance value that results in impedance matching. In various implementations, the RF controller 343 communicates with the sensor 333 to obtain a measurement of the capacitance value of the variable capacitor in the RF regulator 323, and the RF controller 343 communicates with the RF regulator 323 to control the variable capacitor in the RF regulator 323 to obtain the specific capacitance value that results in impedance matching.

[0061] In various implementations, the sensor 333 can use a variety of techniques to measure capacitance. Examples of capacitance measurement techniques include, but are not limited to, voltage measurement methods, resonant frequency methods, Wheatstone bridge methods, charge-based methods, ramp rate methods, timer methods, oscilloscope methods, LCR meter methods, or vector analyzer methods, as described in further detail below.

[0062] In one class of implementations, sensor 333 measures the capacitance of the variable capacitor in RF regulator 323 without disconnecting the variable capacitor from RF power source 301, such as by disconnecting it from distribution network 321 or fixed matching module 303. In some implementations, sensor 333 also measures the capacitance of the variable capacitor in RF regulator 323 when RF power source 301 is generating a high power RF output.

[0063] In various implementations, the sensor 333 includes a frequency generator, a filter, an interface for coupling to a capacitor included in a main circuit, and an interface for coupling to a device for measuring a parameter, the parameter including at least one of current, voltage, impedance, resonance, capacitance, charge, or pulse count, the filter having a passband including a first frequency signal generated by the frequency generator, and the filter also having a stopband including a second frequency signal generated in the main circuit (e.g., one or more target frequencies).

[0064] In some implementations, the sensor 333 includes at least a frequency generator, a resistor, and a filter. As an example, the frequency generator, the resistor, and the filter may be arranged in the sensor 333 so that the sensor 333 can perform capacitance measurement using a voltage measurement method.

[0065] An example of an implementation of a sensor 333 configured to measure the capacitance of a capacitor using a voltage measurement method without requiring the capacitor to be disconnected from the high power RF output is as follows: Figure 5 . As shown in the figure, the capacitor C to be measured is coupled to the main circuit represented by the dashed line, such as, but not limited to, the circuit in the RF power source 301, the distribution network 321, and / or the fixed matching module 303. The capacitor C is also coupled to the frequency generator Vin via a series resistor R and one or more filters F. The sensor 500 may include an interface for coupling to a voltage measurement device V to measure Vout, which is the voltage at the terminals of the capacitor C that pass through the filter. The voltage measurement device can be implemented using any of a variety of architectures known in the art. The voltage measurement device can be integrated with the sensor 500 or can be connected to the sensor 500 via an input / output port.

[0066] In certain implementations, frequency generator Vin in sensor 500 can correspond to a known frequency, for example, a frequency that is approximately 10 times greater than a frequency in the primary circuit, including, but not limited to, RF power source 301, network 321, and / or circuitry in fixed matching module 303. As an example, RF power source 301 can have a frequency of 13.56 MHz, and the frequency generator can have a frequency of 150 MHz. One or more filters F are configured to include frequencies generated by the frequency generator in a passband and frequencies generated by the primary circuit in a stopband. For example, the filter can be a VHF bandpass filter with a center frequency of 150 MHz to allow the output of the frequency generator to pass to capacitor C without significant attenuation, and the filter can have a roll-off characteristic that significantly attenuates frequencies of at least approximately 13.56 MHz. Continuing with this example, because the filter attenuates the 13.56 MHz frequency and other frequencies in the primary circuit, the alternating current (AC) voltage measured by the voltage measurement device across capacitor C is primarily determined based on the 150 MHz frequency generated by the frequency generator in sensor 500.

[0067] Based on the relationship between the AC voltage measured at Vout and the known or calculated AC voltage Vin of the frequency generator in the sensor 500, the capacitance of C can be determined without disconnecting the capacitor C from the main circuit. For example, the value of the AC voltage Vin of the frequency generator in the sensor 500 corresponds to the current flowing through the combined impedance of the known resistor R (e.g., based on manufacturing specifications, etc.) and the unknown capacitor C (represented by R+1 / jωC), where ω is the known operating frequency of the frequency generator in radians (or f is the known operating frequency of the frequency generator in Hertz, where fo=ωo / 2π). The AC voltage Vin is known or can be derived based on the configuration of the frequency generator. The measured AC voltage Vout corresponds to the current (filtered by one or more filters F) flowing through the impedance of the unknown capacitor C (represented by 1 / jωC). Using the known Vin and the measured Vout, the ratio Vout / Vin=1 / (1+jωRC) can be used to determine the unknown capacitance C using the known values of ω and R.

[0068] In some implementations, the sensor 333 includes at least a variable frequency generator, an inductor, and a filter. As an example, the variable frequency generator, the inductor, and the filter can be arranged in the sensor 333 to measure capacitance using a resonant frequency method.

[0069] exist Figure 6An example of an implementation of a sensor 333 for measuring capacitance using a resonant frequency method without disconnecting the capacitor from a high-power RF output is shown at sensor 600 in FIG. As shown, a capacitor C to be measured is coupled to a main circuit. Capacitor C is also coupled to a variable frequency generator Vin via a series inductor L and one or more filters F.

[0070] Sensor 600 may include an interface for coupling to a resonance meter for detecting the resonant frequency of capacitor C at its terminals passing through one or more filters F. The resonance meter may be implemented using any of a variety of architectures known in the art. For example, at the resonant frequency, the maximum current flows through capacitor C, and the resonance meter may be an ammeter that measures the current flowing in the circuit. Continuing with this example, in a frequency sweep performed by sweeping the output of a variable frequency generator over a frequency range, a peak value of the current versus frequency plot indicates the resonant frequency. The resonance meter may be integrated with sensor 600 or may be connected to sensor 600 via an input / output port.

[0071] As previously discussed with respect to the voltage measurement method, the variable frequency generator in sensor 600 can correspond to a known frequency band, for example, a frequency band greater than 10 times the frequency of the main circuit. Similar to the previously discussed method, one or more filters F are configured to include frequencies generated by the variable frequency generator in the passband and frequencies generated by the main circuit in the stopband. Consequently, the resonant frequency detected by the resonance meter on capacitor C is determined primarily based on the signal from the variable frequency generator in sensor 600.

[0072] Based on the relationship between the measured resonant frequency and the known value of the inductor L, the capacitance of C can be determined without disconnecting the capacitor C from the main circuit. For example, the resonant frequency of a series LC circuit corresponds to a situation where the inductive and capacitive reactances are equal in magnitude but 180 degrees out of phase and therefore cancel each other out. Resonance is represented by the equation fo = ωo / 2π = 1 / 2πsqrt(LC). The resonance meter can detect the Hertz frequency corresponding to the minimum impedance occurring at resonance and thus determine the value of fo. The unknown value of the capacitor C can then be calculated based on the measured fo and the known value of the inductor L (e.g., manufacturing specifications, inductance measurement results, etc.).

[0073] Although the previous examples were presented in the context of a voltage measurement method or a resonant frequency method, it should be understood that for other embodiments of capacitance measurement techniques (including but not limited to a Wheatstone bridge method, a charge-based method, a ramp rate method, a timer method, an oscilloscope method for measuring the voltage drop across a capacitor, an LCR meter method for directly measuring capacitance, or a vector analyzer method for directly measuring impedance and converting to a capacitance value), the capacitor being measured can be coupled to a frequency generator and filter similar to those described above so that the capacitance can be measured without disconnecting the capacitor being measured and / or stopping high power RF operations.

[0074] exist Figure 7 An example of an implementation of a sensor 333 for measuring capacitance using a Wheatstone bridge method without disconnecting the capacitor from the high power RF output is shown at sensor 700 in FIG. Figure 7 In FIG, one terminal of the capacitor is depicted as being connected to ground, but it will be appreciated that the ground connection may be at a node between the depicted impedance z2 and one or more filters F, for example.

[0075] The sensor 700 can measure capacitance by generating an AC voltage (Vin) at a frequency (ω) using an oscillator, wherein the output of the oscillator is coupled to a first terminal of the capacitor via at least a first impedance (z1) and a second impedance (z2) connected in series with the capacitor, respectively. The output of the oscillator is also coupled to a second terminal of the capacitor via at least a third impedance (z3) connected in series with the capacitor.

[0076] The sensor 700 measures a filtered current Aout (or a filtered voltage) at a node coupling the first impedance (z1), the second impedance (z2), and the third impedance (z3). The measured filtered signal represents the imbalance between the branches of the Wheatstone bridge. For example, Figure 7 The current Aout in represents the amount of imbalance between a first impedance combination comprising a first impedance (z1) and a second impedance (z2) and a second impedance combination comprising a third impedance (z3) and the impedance of the capacitor (zC). The amount of imbalance is measured and is proportional to the capacitance. For example, the operation of the sensor 700 involves converting the measured filtered signal to a measured capacitance value (C) based in part on the ratio z1 / z2=z3 / zC, where the impedance (zC) of a capacitor with capacitance (C) is represented by zC=1 / jωC. It should be understood that when the Wheatstone bridge is balanced, there is no current (Aout) in Figure 7 It will also be appreciated that one or more of the impedance elements depicted in the Wheatstone bridge may be a variable impedance.

[0077] exist Figure 8An example of an implementation of a sensor 333 for measuring capacitance using a charge-based method without disconnecting the capacitor from a high-power RF output is shown on sensor 800 in FIG. In an exemplary implementation, the charge-based method relies on a reference capacitor (CREF) being charged by a known voltage source (VREF) at a first frequency (ω). For example, CREF is first charged by VREF and then switched in parallel with the capacitor C being measured. In the case where the reference capacitor and the capacitor being measured have the same capacitance value, switching the reference capacitor in parallel with capacitor C causes the total charge in the reference capacitor to be evenly distributed between the reference capacitor and capacitor C (i.e., the total charge in the combined system of capacitors remains constant), resulting in the measured voltage Vout, filtered by one or more filters F, being half the voltage of VREF. Knowing the value of CREF and measuring the voltage across the combination of C and CREF (VOUT), the value of C can be determined based on C=CREF(VREF / VOUT-1). For example, continuing with the previous situation where the measured voltage is half the reference voltage, the ratio between capacitor C and reference capacitor CREF (VREF / VOUT-1) is 2-1=1, so the two capacitors have the same capacitance value, allowing the measured capacitance C to be deduced based on the known capacitance of reference capacitor CREF.

[0078] refer to Figure 8 , operating the sensor 800 includes generating an AC voltage (Vin) as a first signal at a first frequency (ω) using an oscillator, wherein the output of the oscillator is coupled to a reference capacitor (CREF). When the AC voltage charges the reference capacitor to a reference voltage (VREF), the reference capacitor is coupled to be electrically connected in parallel with the capacitor. The sensor 810 measures a voltage signal filtered by one or more filters F at the first frequency (ω), the voltage signal corresponding to the charge in the reference capacitor and the electrically parallel combination of the capacitor, and the sensor 800 or a processor portion coupled to the sensor 800 converts the measured filtered signal into a measured capacitance value (c) based on C=CREF(VREF / Vout-1). In some implementations, the node between the measurement node of Vout shown and the capacitor being measured may include at least a first capacitor C1 and a first inductor L1 ( Figure 8 (not shown), for example, parasitic elements that modify the measured voltage Vout, etc. The influence of L1 and C1 can be accounted for by, for example, calibration or adjustment.

[0079] exist Figure 9 An example of an implementation of a sensor 333 for measuring capacitance using a ramp rate method without requiring the capacitor to be disconnected from the high power RF output is shown at sensor 900 in FIG. In some implementations of the ramp rate method, the current and charge measurements are used to calculate the capacitance value. Figure 9 In an example of FIG. 1 , the ramp rate technique involves at least two source measure units (SMUs).

[0080] First SMU Figure 9 The SMU1 in Figure 1 forces a constant current at a first frequency (ω) into the device under test (DUT), such as the first terminal of a capacitor in an impedance matching circuit, and measures the voltage (V) and time (t) at the node at the output of SMU1, allowing the derivative of the rate of change of voltage, i.e., dV / dt, to be calculated. Simultaneously, the second SMU ( Figure 9 SMU2 in FIG1 is measuring the current (A) output from another node of the DUT (e.g., the second terminal of the capacitor being measured), which has been filtered by one or more filters F. The capacitance is then calculated using the equations I = C dV / dt or C = I / (dV / dt), which relate the measured current at SMU2 to the measured rate of change of voltage at SMU1.

[0081] exist Figure 10 An example of an implementation of a sensor 333 for measuring capacitance using a timer method without disconnecting the capacitor from the high power RF output is shown on sensor 1000 in FIG. In an exemplary implementation of the timer method, an analog timer circuit is used to generate a frequency that is inversely proportional to the capacitance to be measured, and then the pulses within a given period are counted, for example using a microcontroller, to calculate the frequency generated by the analog timer circuit. Based on the characteristics of the analog timer circuit, the generated frequency can be used to determine the capacitance C. For example, for a 555 timer circuit, the measured capacitor C and the frequency F (in Figure 10 The equation associated with the timer circuit (denoted as Fout in FIG) is F=1 / (C*(R1+2*R2)*ln2), where F is the frequency output of the timer circuit based on pulse counting, and R1 and R2 are as follows: Figure 10 Known resistor values are shown. It should be understood that timer circuits other than the 555 timer circuit may be used.

[0082] The frequency generator in sensor 333 can be implemented using any of a variety of architectures known in the art. In some implementations, the frequency generator corresponds to a frequency band of VHF (very high frequency). In some implementations, the frequency generator corresponds to a frequency that is typically greater than the 10th harmonic of the operating frequency of other circuits, including but not limited to main circuits such as automatic matching circuits. It should be understood that the frequency generator can be a fixed frequency or a variable frequency. It should be further understood that the frequency generator in sensor 333 can correspond to a frequency multiplier that is used to generate a frequency that is a multiple of a reference frequency signal used by other circuit systems, such as, but not limited to, RF power source 301.

[0083] The filter in sensor 333 can be implemented using any of a variety of architectures known in the art. It should be understood that the term filter as used herein includes a single filter element or an equivalent filter corresponding to multiple filter elements. In various implementations, the filter attenuates frequency signals in the range of 2-60 MHz (for example, but not limited to 13.56 MHz). In one class of implementations, the filter attenuates frequency signals in the range of 100 kHz to about 1 MHz (for example, but not limited to 400 kHz). In some implementations, the filter passes frequency signals in the VHF band. The filter can be a bandpass filter or a high-pass filter.

[0084] It should be understood that the frequency separation between the frequency generator and the main circuit frequency is based in part on the characteristics of the filter. For example, if the filter has a high Q value, the frequency generator can be configured to have a frequency less than the 10th harmonic of the main circuit frequency. As another example, if the filter has a low Q value, the frequency generator can be configured to have a frequency greater than the 10th harmonic of the main circuit frequency.

[0085] It should be noted that the capacitance sensors disclosed herein are not limited to use within sensor 333, nor are they limited to measuring capacitance for RF regulator 323. It should be understood that the capacitance sensors disclosed herein can be used to measure capacitance of various components in the multi-station plasma reactor described herein, and can also be used to measure capacitance in other devices.

[0086] Each station 351 includes a showerhead 353 that operates in conjunction with a grounded pedestal 357. The power and frequency provided are sufficient to generate a plasma from the process gas, for example, in the range of approximately 50-6,000 W per station. The power level may vary depending on the implementation. RF power is connected to the station processing region via the showerhead 353, and a plasma is generated or maintained when the RF power is applied. The plasma causes material to be deposited onto the substrate through a variety of mechanisms. For example, the plasma can cause the process gas to decompose and react on the substrate surface. In the illustrated implementation, the RF current is grounded at the pedestal 357, which is connected to the ground 331. In certain other implementations, the RF current can be grounded at a different location within the chamber, such as at the showerhead.

[0087] The previously described semiconductor tools can be used for plasma balancing. Plasma balancing can be particularly beneficial in multi-cycle deposition processes with short cycle durations, such as in ALD and atomic layer etch (ALE). Atomic layer etching methods are further discussed in the following U.S. patents, each of which is incorporated herein by reference in its entirety: U.S. Patent No. 7,416,989, entitled “ADSORPTION BASED MATERIAL REMOVAL PROCESS”; U.S. Patent No. 7,977,249, entitled “METHODS OF REMOVING SILICON NITRIDE AND OTHER MATERIALS DURING FABRICATION OF CONTACTS”; U.S. Patent No. 8,187,486, entitled “MODULATING ETCH SELECTIVITY AND ETCH RATE OF SILICON NITRIDE THIN FILMS”; U.S. Patent No. 7,981,763, entitled “ATOMIC LAYER REMOVAL FOR HIGH ASPECT RATIO GAPFILL”; and U.S. Patent No. 8,058,179, entitled “ATOMIC LAYER REMOVAL PROCESS WITH HIGHER ETCH AMOUNT”.

[0088] The plasma activation step of a multi-step deposition process with a short cycle duration can be brief. The duration of the plasma activation step can be about 150 milliseconds or less (e.g., about 50 milliseconds). Due to the short duration, control of the plasma concentration can affect process uniformity. Plasma balancing can be used to control the plasma concentration.

[0089] Figure 4A FIG. 1 is a process flow diagram of a multi-station deposition process using RF frequency tuning and RF power parameter adjustment. Figure 4A The process described in can be applied to various steps in a deposition process, such as step 3 of the ALD cycle described previously. Although the process is discussed in the context of a deposition process, elements of the process can be applied to any plasma-assisted semiconductor process.

[0090] In operation 401, a substrate is provided. The substrate may be provided to one or more stations in a multi-station tool. The substrate may be provided by loading the substrate on the station, or the substrate may already be in the station due to a previous operation (e.g., from a previous cycle).

[0091] After providing the substrate, in operation 403, a gas flow is established and the pressure is stabilized at a set value. Operation 405 begins generating RF power. The RF power can be HFRF, LFRF, or both HFRF and LFRF. Prior to operation 405, the impedance between the electrode (typically a showerhead) and the substrate may be very high, similar to the impedance of an open circuit. In operation 405, RF power may be generated and used to ignite the plasma. The RF power may be applied such that the magnitude of the impedance is fixed at a certain resistance (e.g., a 50 ohm resistor). The RF power may be applied at a fixed frequency. The fixed frequency may be a predetermined frequency of the RF power. In certain other implementations, the frequency of the RF power generated in operation 405 may not correspond to a fixed frequency. In such implementations, the frequency in operation 405 may be varied in various ways (e.g., through an algorithm, user input, feedback from previous operations of the deposition process, etc.). In certain implementations, operation 405 may last for a limited duration, e.g., a period of less than 5 milliseconds.

[0092] After the plasma has been properly ignited, the process may continue to operation 407. Full power may be delivered starting from operation 407. Operations 407-419 are repeated for the remaining duration of the deposition process step. Thus, if the plasma is used in step 3 of the ALD cycle, Figure 4A If the process is repeated, operations 407-419 are repeated until step 3 is completed. In operation 407, the capacitance of the variable capacitor in the impedance matching circuit can be measured. Figure 4A In the process described in, changes in chemical reactions and environmental conditions within the process station may cause changes in plasma impedance. Therefore, monitoring and adjusting the capacitance in the impedance matching circuit can help match the impedance of the plasma to the impedance of the RF power source (e.g., 50 ohms). The capacitance of the variable capacitor in the impedance matching circuit can be measured by a sensor as described elsewhere in this disclosure.

[0093] In operation 408, the impedance matching circuit can be tuned based on the capacitance measured in step 407. Certain implementations of semiconductor processing tools may include a controller and associated instructions to tune the impedance matching based on the detected capacitance. The instructions may be based on a graph, a formula, or other method of calculating the desired impedance matching. For example, in addition to or in lieu of RF power frequency tuning, the impedance matching can be tuned so that the phase of the impedance is as close to zero as possible. When the impedance changes during semiconductor processing, the impedance matching can be adjusted accordingly in operation 408. In certain implementations, the capacitance can be measured as an average of the capacitance at each station. Other implementations may include the ability to measure the capacitance at each individual station. As previously described, due to the possibility of impedance changes, operations 407 and 408 are performed continuously until the deposition process step is completed.

[0094] At operation 409, an RF power parameter may be measured at each station to determine variations between stations. The RF power parameter may be measured after plasma is generated in the station and reflects the dynamic impedance in each station. The parameter may be voltage, current, capacitance, impedance, phase, load power, power delivered to the station, or any combination thereof.

[0095] In operation 411, the RF power parameter measurements can be compared to the setpoints for each station. In some implementations of RF power balancing, the setpoints can be the same for each cycle of the deposition process. In other implementations, the setpoints can vary between cycles of the deposition process. For example, the setpoint can be the average of the measured powers delivered to each station. In other implementations, the setpoints can be different for each station. This comparison can be performed at a local controller, a central controller for the RF regulator, or at a system controller for the entire tool.

[0096] The total RF power delivered to all stations sharing a common RF source depends on the RF generator's power setting, the impedance of the plasma load, and the impedance of the RF network. The RF regulator primarily affects the power distribution between stations. The regulator's impact on total power is typically secondary. In some cases, depending on the type of RF regulator used, reducing RF power at one station can increase RF power at other stations. In these cases, the controller can determine adjustments based on the inter-station RF power interactions or simply repeat adjustments multiple times until the measured value is within a threshold margin of the setpoint.

[0097] In some cases, absolute RF power levels are required. In this case, the RF power can be measured at each station and then adjusted twice. For example, first, the total power at the generator output is changed to match the sum of the station's setpoints. Second, the station's RF regulators are tuned to distribute power according to the setpoints. The order of adjustments (total power versus distributed power) can be reversed. This process is repeated until the power distribution is within a threshold margin of the setpoints.

[0098] In operation 413, the measured RF power parameter profile can be compared to one or more set points. If the difference is above a threshold, a regulator change for each station can be determined at operation 415. The required regulator change can vary from station to station. Some stations may not require regulator changes at all, while other stations may require regulator changes. The regulator changes can be determined by the RF controller or another controller. Note that the parameter or RF characteristic to be adjusted may be different from the measured RF power parameter. In one example, the RF power can be measured and the capacitance or impedance matching can be adjusted.

[0099] The desired regulator changes may be applied to adjust the RF characteristics of the station in operation 417. In some implementations, the station impedance matching may be adjusted by the regulator change amount in operation 417. Then, starting from operation 407, the capacitance for impedance matching may be measured again, and the impedance matching adjustment cycle may continue until the deposition process has been completed.

[0100] If the power parameter measured in operation 411 and compared in operation 413 is within an acceptable range, semiconductor processing continues in operation 419. The process can then continue from operation 407 until the deposition process is completed. Although certain exemplary implementations of the present disclosure are described in the context of a deposition process, it should be understood that other semiconductor processing operations are contemplated for the disclosed capacitance measurement techniques in addition to or in lieu of deposition, including but not limited to etching, stripping, or cleaning thin films on a substrate. It should also be understood that the disclosed capacitance measurement techniques facilitate providing uniform and / or repeatable process conditions (e.g., RF power, etc.) for semiconductor processing operations (e.g., deposition, etching, stripping, cleaning, etc.) at multiple semiconductor processing stations, thereby improving the yield of semiconductor manufacturing.

[0101] In various implementations, the sequence of operations 407-419 may be arranged in a different order. For example, operation 409 (and possibly operations 409-419) may be performed before operation 407. In other implementations, operations 407-408 may be performed simultaneously with operations 409-419. In other implementations, measurement operations 407 and 409 may be performed before tuning and adjustment operations 408 and 411-419.

[0102] In the case of power balancing, continuous RF power control during processing may be necessary for at least two reasons. One possibility is to follow a deliberate RF power profile. During the processing sequence, the setpoint may change over time. RF regulators can be used to maintain a specific power allocation when the setpoint changes. Another possibility is that the station's RF power may drift during processing, requiring adjustment based on dynamic feedback.

[0103] In some implementations, a semiconductor processing operation may include multiple different deposition processes within a single multi-station reactor. These different deposition processes deposit different materials, particularly layers of material that contact an underlying substrate, such as a barrier or nucleation layer, a bulk layer atop the nucleation layer, a capping layer atop the bulk layer, and the like. These individual layers may have relatively similar (or different) compositions. In some cases, different deposition processes may utilize different process gases. When a semiconductor processing operation includes multiple different deposition processes, different recipes are typically used for the different deposition processes. In this case, different RF power parameter settings may be used for the different recipes at each station. In some implementations, these differences in settings result in differences in initial regulator settings for the different recipes. These initial regulator settings may be included in or part of the recipe for the deposition process. The different recipes for different deposition processes may reflect variations in the initial regulator settings for the different processes. In this case, the initial regulator settings for the individual processes may be determined based on previous simulation or test results. In some implementations, for a single recipe, the RF power frequency initially generated and assigned to the stations may be at different power settings for each station. In such an implementation, the RF regulator can be further adjusted during the deposition process according to the techniques described herein. In certain embodiments, the initial regulator position can be a regulator position that is calculated to result in a minimum amount of RF regulator tuning when the deposition process is performed over a plurality of cycles.

[0104] Figure 4B is a process flow diagram of a multi-station deposition process using impedance matching tuning. Figure 4B Similar to Figure 4A , however, despite Figure 4A A process utilizing both impedance matching tuning and RF power parameter adjustment during the deposition process is described, but Figure 4B A process is described that utilizes only impedance matching tuning during the deposition process.

[0105] Figure 4B The process flow diagram of FIG4B may be a process for a deposition process utilizing impedance matching tuning. Certain implementations may utilize the process shown in process 4B as a single deposition process for a semiconductor processing operation that includes multiple different deposition processes. As described herein, the multiple different deposition processes may deposit different materials. In other embodiments, only a single deposition process is used. In either embodiment, the RF power regulation between stations is fixed and can be set prior to the deposition process. Typically, the process does not utilize feedback of RF power parameters to determine appropriate RF power regulation during deposition.

[0106] exist Figure 4B In the process flow diagram 420, operations 421 and 423 are similar to Figure 4A Operations 401 and 403. Figure 4B In operation 425, RF adjustments for the plurality of stations are determined. RF adjustments for the plurality of stations are determined before generating RF power and processing the substrate. The RF adjustments may be determined by historical data, calculations, or trial and error.

[0107] After RF conditioning has been performed in operation 425, the process may proceed to operation 427. Operations 427, 429, and 431 are similar to Figure 4A Operations 405, 407, and 408 are performed. In operation 433, the current cycle is processed at each station and then the process is repeated for the desired number of cycles. During each of the desired number of cycles, operations 427, 429, and 431 are repeated so that the impedance match is continuously tuned according to the requirements of the measured impedance. The impedance match and / or the RF power frequency can be tuned according to the techniques described elsewhere in this disclosure.

[0108] Various other configurations and apparatus for power balancing of multi-station semiconductor processing apparatus are described in US Patent No. 8,282,983, issued October 9, 2012, which is incorporated herein by reference in its entirety for this purpose.

Claims

1. A method of performing plasma-assisted semiconductor processing in a plurality of stations in a processing chamber, the method comprising: For the first of multiple stops: measuring a first capacitance of a first capacitor in the impedance matching circuit without disconnecting the first capacitor from the impedance matching circuit; and The first capacitance of the first capacitor is adjusted based on at least the measured first capacitance.

2. The method of claim 1, wherein the plurality of stations in the processing chamber comprises a first station and at least a second station, the method further comprising providing a substrate to at least the first station and the second station.

3. The method of claim 2, further comprising distributing radio frequency (RF) power comprising a first target frequency to at least the first station and the second station to generate plasma in each of the first station and the second station. The method of claim 3 , wherein the first capacitance of the first capacitor is measured while distributing the RF power.

5. The method of claim 2 , further comprising performing a semiconductor processing operation on the substrate at each of the first station and the second station based on a radio frequency (RF) power parameter being within an acceptable range, the RF power parameter being configured to reduce variation between at least the first station and the second station.

6. The method of claim 5, wherein the semiconductor processing operation comprises depositing, etching, stripping, or cleaning a thin film.

7. The method of claim 5 , further comprising determining that the RF power parameter is within an acceptable range by: determining a difference between an RF power parameter and a set point associated with each of the first station and the second station; and It is determined that the difference does not exceed a threshold value.

8. The method of claim 3 , further comprising adjusting capacitance or impedance matching associated with at least one of the first station or the second station based on a difference between an RF power parameter and a set point associated with each of the first station and the second station exceeding a threshold.

9. The method of claim 1 , wherein for the second station among the plurality of stations: measuring a second capacitance of a second capacitor in the impedance matching circuit without disconnecting the second capacitor from the impedance matching circuit; and The second capacitance of the second capacitor is adjusted based on at least the measured second capacitance.

10. The method of claim 1 , wherein measuring the first capacitance of the first capacitor comprises: measuring a signal at the first capacitor; and The measured signal is converted into a capacitance value of the first capacitor.

11. The method of claim 1 , further comprising measuring the first capacitance of the first capacitor at the first frequency (ω) using an inductance (L), capacitance (C), and resistance (R) meter (LCR meter).

12. The method of claim 1, further comprising measuring the impedance of the first capacitor at the first frequency (ω) using a vector network analyzer.

13. An apparatus for plasma-assisted semiconductor processing, the apparatus comprising: a processing chamber comprising a first station and a second station, each of the first station and the second station being configured to receive at least one substrate; as well as One or more controllers, configured to: measuring a first capacitance of a first capacitor in the impedance matching circuit without disconnecting the first capacitor from the impedance matching circuit; and The first capacitance of the first capacitor is adjusted based on at least the measured first capacitance.

14. The device according to claim 13, wherein The one or more controllers are further configured to: for the second station: measuring a second capacitance of a second capacitor in the impedance matching circuit without disconnecting the second capacitor from the impedance matching circuit; and The second capacitance of the first capacitor is adjusted based on at least the measured second capacitance.

15. The device according to claim 13, wherein The one or more controllers are further configured to cause the first substrate to be provided to the first station and the second substrate to be provided to the second station.

16. The device according to claim 15, wherein The one or more controllers are further configured to cause distribution of radio frequency (RF) power comprising a first target frequency to at least the first station and the second station to generate a plasma in each of the first station and the second station.

17. The device according to claim 16, wherein A first capacitance of the first capacitor is measured while distributing RF power.

18. The device according to claim 15, wherein The one or more controllers are further configured to perform semiconductor processing operations on a first substrate at a first station and on a second substrate at a second station based on radio frequency (RF) power parameters being within an acceptable range, the RF power parameters being configured to reduce variations between at least the first station and the second station.

19. The device according to claim 18, wherein The semiconductor processing operations include depositing, etching, stripping or cleaning thin films.

20. The apparatus according to claim 18, wherein The one or more controllers are further configured to determine that the RF power parameter is within an acceptable range by: determining a difference between an RF power parameter and a set point associated with each of the first station and the second station; and It is determined that the difference does not exceed a threshold value.

21. The apparatus according to claim 15, wherein The one or more controllers are further configured to adjust capacitance or impedance matching associated with at least one of the first station or the second station based on a difference between a radio frequency (RF) power parameter and a set point associated with each of the first station and the second station exceeding a threshold.

22. The apparatus according to claim 13, wherein The measuring of the first capacitance of the first capacitor includes: measuring a signal at the first capacitor; and The measured signal is converted into a capacitance value of the first capacitor.

23. The apparatus according to claim 13, wherein The first capacitance of the first capacitor may be measured at a first frequency (ω) using an inductance (L), capacitance (C), and resistance (R) meter (LCR meter).

24. The apparatus according to claim 13, wherein The one or more controllers are further configured to obtain a measurement of the impedance of the first capacitor at the first frequency (ω) using a vector network analyzer.

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