RF Current Measurement in Semiconductor Processing Tools

Abstract

SOLUTION: To provide a method for plasma-assisted semiconductor processing at multiple stations within a processing chamber, which includes a) providing a substrate to each of a plurality of stations, b) supplying RF power to the plurality of stations thereby generating a plasma within the stations, in which the RF power is adjusted to reduce station-to-station variability, c) adjusting the frequency of the RF power, in which the adjustment of the frequency includes i) measuring the current in the plasma, ii) changing the frequency of the RF power according to the current measured in i), and iii) adjusting the frequency of the RF power, and d) performing a semiconductor processing operation on the substrate at each station.SELECTED DRAWING: Figure 5

Description

[Background technology]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to and the benefit of U.S. patent application Ser. No. 62 / 634,725, filed Feb. 23, 2018, entitled "RF CURRENT MEASUREMENT IN SEMICONDUCTOR PROCESSING TOOL," which is incorporated herein by reference in its entirety for all purposes.

[0002] Semiconductor device fabrication involves the processing of semiconductor wafers in semiconductor processing reactors. Typical processing involves the deposition and removal (i.e., etching) of materials from the wafer. In industrial-scale manufacturing, each wafer contains many copies of the specific semiconductor device being fabricated, and many wafers are required to achieve the required quantity of devices. The industrial feasibility of semiconductor processing operations depends heavily on the within-wafer uniformity and wafer-to-wafer reproducibility of processing conditions. Therefore, efforts are made to ensure that each portion of a given wafer, and each wafer being processed, is exposed to the same processing conditions. Variations in processing conditions can cause variations in deposition and etch rates that result in unacceptable variations in the overall process and product. Summary of the Invention

[0003] One or more computer systems may be configured to perform particular operations or functions by having software, firmware, hardware, or a combination thereof installed on the system that, when in operation, causes the system to perform the operations. One or more computer programs may be configured to perform particular operations or functions by comprising instructions that, when executed by a data processing device, cause the device to perform the operations.

[0004] One general aspect includes a method for performing plasma-assisted semiconductor processing at multiple stations within a processing chamber, the method comprising: a) providing a substrate at each of the multiple stations; b) supplying RF power to the multiple stations, thereby generating a plasma in the stations, the RF power being supplied according to RF power parameters adjusted to reduce station-to-station variation; c) adjusting a frequency of the RF power, the adjusting the frequency including: i) measuring a current of the plasma; ii) determining a change in the frequency of the RF power according to the current measured in i); and iii) adjusting the frequency of the RF power; and d) performing a semiconductor processing operation on the substrate at each station. Another embodiment of this aspect includes a corresponding computer system, apparatus, and computer program stored on one or more computer storage devices, each configured to perform the operations of the method.

[0005] Embodiments may include one or more of the following features. In the method, the semiconductor processing operation is one of deposition, etching, stripping, or thin film removal. In the method, i) comprises: a) measuring a voltage across an inductive element in a current sensor, the inductive element being electrically parallel to a capacitive element in the current sensor, the inductive element being electrically in series with a plasma current directed to the processing chamber to generate and sustain the plasma; and b) converting the measured voltage across the inductive element to a plasma current based in part on applying a linear proportionality factor dependent on the plasma RF power frequency. In the method, a measured voltage (V) across an inductive element (L) at the plasma RF power frequency (f) is converted to a plasma current (I) based in part on I=V / 2πfL, where the linear proportionality factor is expressed as 1 / 2πfL. In the method, the capacitive element and the inductive element are integrated on a printed circuit board. In the method, the capacitive element has a capacitance value of about 0.017 pf or less. In the method, the inductive element has an inductance value of about 610 nh or less. In the method, the linear proportionality coefficient is determined in part by the impedance z of the dielectric element at the RF power frequency of the plasma. In the method, the linear proportionality coefficient is determined in part by the resonant frequency ω of the current sensor. resIn the method, the linear proportionality factor is determined in part by determining the resonant frequency ω res and determining an impedance z of the current sensor over a frequency range including (a) and (b). In the method, the linear proportionality factor is determined in part by determining an inductance value l of the inductive element and a capacitance value c of the capacitive element. In the method, the RF power frequency is an RF frequency of approximately 56 MHz. In the method, the RF power frequency is changed to an adjusted RF power frequency, and further, i) is repeated with the current sensor at the adjusted RF power frequency using a second linear proportionality factor. In the method, the capacitive element has a capacitance value c=Ea / d, where E is the dielectric constant, a is the area of ​​the capacitive element, and d is the distance between the electrodes of the capacitive element.

[0006] One general aspect includes an apparatus for plasma-assisted semiconductor deposition, comprising a plurality of processing stations, each processing station including at least one wafer support and configured to receive at least one substrate, the plurality of processing stations within a chamber, a power supply configured to supply RF power to the chamber to generate and maintain a plasma, a current sensor configured to measure a plasma current, an RF frequency adjuster configured to adjust the RF power frequency, one or more RF power adjusters configured to adjust the RF power supplied to the plurality of processing stations to reduce station-to-station variations, and one or more controllers, wherein the one or more controllers, the power supply, the current sensor, the RF frequency adjuster, and the RF power adjuster are communicatively coupled, and the controller is configured to adjust the RF power frequency. and adjusting the RF power frequency includes: a) measuring a voltage across an inductive element in a current sensor, the inductive element being electrically parallel to a capacitive element in the current sensor, the inductive element being electrically in series with a plasma current directed to the chamber to generate and sustain the plasma; and b) converting the measured voltage across the inductive element to a plasma current based in part on applying a linear proportionality factor that depends on the RF power frequency of the plasma; i) determining the plasma current using the current sensor; ii) determining a change in the frequency of the RF power according to the current measured in i); iii) adjusting the frequency of the RF power via an RF frequency adjuster; and iv) instructing one or more RF power adjusters to adjust the RF power supplied to each station to reduce station-to-station variations when performing semiconductor processing operations at each processing station. Another embodiment of this aspect includes a corresponding computer system, apparatus, and computer program stored on one or more computer storage devices, each configured to perform the operations of the method.

[0007] Embodiments may include one or more of the following features. In the apparatus, the semiconductor processing operation is one of deposition, etching, stripping, or thin film removal. In the apparatus, a measured voltage (V) across a dielectric element (L) at the RF power frequency (f) of the plasma is converted to a current (I) in the plasma based in part on I=V / 2πfL, with a linear proportionality factor expressed as 1 / 2πfL. In the apparatus, the capacitive element and the inductive element are integrated on a printed circuit board. In the apparatus, the capacitive element has a capacitance value c=Ea / d, where E is the dielectric constant, a is the area of ​​the capacitive element, and d is the distance between the electrodes of the capacitive element. In the apparatus, the capacitive element has a capacitance value of about 0.017 pf or less. In the apparatus, the inductive element has an inductance value of about 610 nh or less. In the apparatus, the linear proportionality factor is determined in part by an impedance z of the current sensor at the RF power frequency of the plasma. In the device, the linear proportionality factor is determined in part by the resonant frequency ω of the current sensor. res In the device, the linear proportionality factor is determined, in part, by determining the resonant frequency ω res In the device, the linear proportionality factor is determined, in part, by determining the inductance value l of the inductive element and the capacitance value c of the capacitive element.

[0008] One general aspect includes a method for performing plasma-assisted semiconductor processing in a processing chamber, the method comprising: a) measuring a voltage across an inductive element in a current sensor, the inductive element being electrically parallel to a capacitive element in the current sensor, the inductive element being electrically in series with a plasma current directed to the processing chamber to generate and sustain the plasma; and b) converting the measured voltage across the inductive element to a current of the plasma based in part on applying a linear proportionality factor that is dependent on an RF power frequency of the plasma for performing semiconductor processing operations on substrates at a station in the processing chamber. Further embodiments of this aspect include corresponding computer systems, apparatus, and computer programs stored on one or more computer storage devices, each configured to perform the operations of the method.

[0009] Embodiments may include one or more of the following features. In the method, the semiconductor processing operation is one of deposition, etching, stripping, or thin film removal. In the method, a measured voltage (V) across a dielectric element (L) at a plasma RF power frequency (f) is converted to a plasma current (I) based in part on I=V / 2πfL, where the linear proportionality coefficient is expressed as 1 / 2πfL. In the method, the capacitive element has a capacitance value of about 0.017 pf or less, and the inductive element has an inductance value of about 610 nh or less. In the method, the capacitive element and the inductive element are integrated on a printed circuit board, and further, the capacitive element has a capacitance value c=Ea / d, where E is the dielectric constant, a is the area of ​​the capacitive element, and d is the distance between electrodes of the capacitive element. In the method, the linear proportionality coefficient is determined in part by an impedance z of the dielectric element at the plasma RF power frequency. In the method, the linear proportionality coefficient is determined in part by a resonant frequency ω of the current sensor. res In the method, the linear proportionality factor is determined in part by determining the resonant frequency ω resa) is determined by determining an impedance z of the current sensor over a frequency range including a second linear proportionality factor. In the method, the linear proportionality factor is determined in part by determining an inductance value l of the inductive element and a capacitance value c of the capacitive element. In the method, the RF power frequency is an RF frequency of about 13.56 MHz. In the method, the RF power frequency is changed to an adjusted RF power frequency, and further, b) is repeated with the current sensor at the adjusted RF power frequency using a second linear proportionality factor.

[0010] One general aspect includes an apparatus for plasma-assisted semiconductor processing in a processing chamber, the apparatus comprising: a processing station in the processing chamber, the processing station having at least one wafer support configured to receive at least one substrate; a power supply configured to supply RF power to the processing chamber to generate and maintain a plasma; a current sensor configured to measure a plasma current; and one or more controllers, wherein the one or more controllers, the power supply, and the current sensor are communicatively connected, and the controller is configured to: a) measure a voltage across an inductive element in the current sensor, the inductive element being electrically parallel to a capacitive element in the current sensor, and the inductive element being electrically in series with a plasma current directed toward the processing chamber to generate and maintain the plasma; and b) convert the measured voltage across the inductive element to a current of the plasma based in part on applying a linear proportionality coefficient that is dependent on a plasma RF power frequency for performing a semiconductor processing operation on a substrate at the station in the processing chamber.

[0011] Embodiments may include one or more of the following features. In the apparatus, the semiconductor processing operation is one of deposition, etching, stripping, or thin film removal. In the apparatus, a measured voltage (V) across a dielectric element (L) at a plasma RF power frequency (f) is converted to a plasma current (I) based in part on I=V / 2πfL, where the linear proportionality coefficient is expressed as 1 / 2πfL. In the apparatus, the capacitive element has a capacitance value of about 0.017 pf or less, and the inductive element has an inductance value of about 610 nh or less. In the apparatus, the capacitive element and the inductive element are integrated on a printed circuit board, and further, the capacitive element has a capacitance value c=Ea / d, where E is the dielectric constant, a is the area of ​​the capacitive element, and d is the distance between electrodes of the capacitive element. In the apparatus, the linear proportionality coefficient is determined in part by an impedance z of the dielectric element at the plasma RF power frequency. In the apparatus, the linear proportionality coefficient is determined in part by a resonant frequency ω of the current sensor. res In the device, the linear proportionality factor is determined, in part, by determining the resonant frequency ω res a) is determined by determining an impedance z of the current sensor over a frequency range including a second linear proportionality factor. In the apparatus, the linear proportionality factor is determined in part by determining an inductance value l of the inductive element and a capacitance value c of the capacitive element. In the apparatus, the RF power frequency is an RF frequency of about 13.56 MHz. In the apparatus, the RF power frequency is changed to an adjusted RF power frequency, and further, b) is repeated with the current sensor at the adjusted RF power frequency using a second linear proportionality factor. [Brief explanation of the drawings]

[0012] [Figure 1] 1 illustrates a substrate processing apparatus for depositing a film on a semiconductor substrate.

[0013] [Figure 2] FIG. 1 illustrates an example of a multi-station substrate processing apparatus that may utilize plasma balancing hardware.

[0014] [Figure 3] 1 is a schematic diagram showing various components of an example multi-station plasma reactor with multiple stations sharing an RF power source using RF frequency tuning.

[0015] [Figure 4A] 1 is a process flow diagram for a multi-station deposition process utilizing RF frequency adjustment and RF power parameter adjustment.

[0016] [Figure 4B] 1 is a process flow diagram for a multi-station deposition process utilizing RF frequency modulation.

[0017] [Figure 5] FIG. 1 illustrates an example of an in-line current sensor.

[0018] [Figure 6] FIG. 1 illustrates a printed circuit board (PCB) embodiment of an in-line current sensor.

[0019] [Figure 7] FIG. 10 illustrates an example of a flowchart for converting a measured voltage to a measured current.

[0020] [Figure 8] FIG. 10 illustrates an example of a linear proportional relationship between measured voltage and measured current for a particular frequency.

[0021] [Figure 9] FIG. 10 illustrates an example of a flow chart for calibrating and operating an in-line current sensor.

[0022] [Figure 10] FIG. 10 illustrates an example of a flow chart for calibrating and operating an in-line current sensor. DETAILED DESCRIPTION OF THE INVENTION

[0023] In the following detailed description, numerous specific examples are set forth. However, it will be apparent to those skilled in the art that the techniques and apparatus disclosed herein may be practiced without these specific details or may be practiced using alternative elements or processes. Additionally, well-known processes, procedures, and / or components have not been described in detail to avoid unnecessarily obscuring aspects of the present disclosure.

[0024] Accurate measurement of RF current is one of the main requirements for control and troubleshooting setup of semiconductor manufacturing tools. Techniques developed to measure RF current include, but are not limited to, Pearson probes and Rogowski coils. In such techniques, flux generated from the current is used to induce a current in a secondary coil. This induced current generates a voltage in the secondary coil that is proportional to the current in the primary flow path. Disadvantages of such techniques include, for example, narrow bandwidth.

[0025] An apparatus and method are provided for controlling RF power used in multi-cycle deposition in semiconductor tools with multiple processing stations that share an RF power source, where the RF power frequency and the power applied to each individual station that shares the RF power are controlled.

[0026] FIG. 1 illustrates a substrate processing apparatus for depositing a film on a semiconductor substrate. The apparatus 100 of FIG. 1 includes a single process chamber 102 with a single substrate holder 108 within an interior space that can be maintained at a vacuum by a vacuum pump 118. A gas delivery system 101 and a showerhead 106 are also fluidly connected to the chamber for the delivery of (for example) film precursors, carrier and / or purge gases and / or process gases, secondary reactants, etc. Apparatus for generating plasma within the process chamber is also illustrated in FIG. 1. The apparatus illustrated schematically in FIG. 1 provides basic equipment for performing film deposition operations, such as chemical vapor deposition (CVD) or ALD, on semiconductor substrates.

[0027] For simplicity, the processing apparatus 100 is illustrated as a stand-alone processing station having a processing chamber body 102 for maintaining a low-pressure environment. However, as described herein, it is understood that multiple processing stations may be included in a common processing tool environment (e.g., within a common reaction chamber). For example, FIG. 2 illustrates one embodiment of a multi-station processing tool. Furthermore, it is understood that in some embodiments, one or more hardware parameters of the processing apparatus 100 (such as those detailed above) may be programmably adjusted by one or more system controllers.

[0028] The processing station 100 is in fluid communication with a reactant delivery system 101 for supplying process gases to a delivery 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.

[0029] Some reactants may be contained in liquid form prior to vaporization and subsequent delivery to the processing chamber 102. The embodiment of FIG. 1 includes a vaporization point 103 for vaporizing the liquid reactants delivered to the mixing vessel 104. In some embodiments, the vaporization point 103 may be a heated liquid injection module. In some other embodiments, the vaporization point 103 may be a heated vaporizer. In yet other embodiments, the vaporization point 103 may be excluded from the processing station.

[0030] In some embodiments, a liquid flow controller (LFC) may be provided upstream of the vaporization point 103 to control the mass flow rate of the liquid for vaporization and delivery to the processing chamber 102 .

[0031] The showerhead 106 delivers process gases and / or reactants (e.g., film precursors) to the substrate 112 in the processing station, the flow of which is controlled by one or more valves (e.g., valves 120, 120A, 105) upstream of the showerhead. In the embodiment shown in Figure 1, the substrate 112 is positioned below the showerhead 106 and is shown on a pedestal 108. The showerhead 106 may have any suitable shape and may have any suitable number and arrangement of ports for delivering process gases to the substrate 112.

[0032] A volume 107 is disposed below the showerhead 106. In some embodiments, the pedestal 108 may 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 may be lowered and / or raised during portions of the deposition process to adjust the process pressure, reactant concentration, etc. within the volume 107.

[0033] 1 , the showerhead 106 and pedestal 108 are electrically connected to an RF power source 114 and a matching network 116 to power the plasma. In some embodiments, the plasma energy may be controlled (e.g., using a system controller having appropriate machine-readable instructions) by controlling one or more of the process station pressure, gas concentration, RF source power, RF source frequency, and plasma power pulse timing. For example, the RF power source 114 and the matching network 116 may be operated at any suitable power to form a plasma having a desired composition of radical species. Similarly, the RF power source 114 may supply RF power at any suitable frequency.

[0034] In some embodiments, the plasma may be monitored in-situ by one or more plasma monitors. In one scenario, plasma power may be monitored by one or more capacitance, voltage, and / or current sensors (e.g., load sensors such as VI probes). Examples of such sensors include the MKS VI-Probe-4100 and 350. Such sensors may measure capacitance, voltage, current, and phase difference. In certain embodiments, the sensors may be electrically connected to the RF power source and may be located at or near the showerhead. In such embodiments, the impedance seen by the RF power source may represent the impedance of the plasma. In another scenario, plasma density and / or process gas concentration may be measured by one or more optical emission spectroscopy (OES) sensors. In some embodiments, one or more plasma parameters may be programmably adjusted based on measurements from such in-situ plasma monitors. For example, load sensors may be used in a feedback loop to provide programmable control of plasma power. It will be appreciated that in some embodiments, other monitors may be used to monitor the plasma and other process characteristics. Such monitors may include, but are not limited to, infrared (IR) monitors, audio monitors, and pressure transducers.

[0035] In some embodiments, the plasma may be controlled by 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 examples, process recipes may be sequenced sequentially, such that all instructions for a process are executed simultaneously with that process. In some embodiments, instructions for setting one or more plasma parameters may be included in a recipe prior to a plasma process. For example, a first recipe may include instructions for setting a flow rate of an inert gas (e.g., helium) and / or a reactive gas, instructions for setting a plasma generator to a power setpoint, and a time delay instruction for the first recipe. A subsequent second recipe may include instructions for enabling the plasma generator and a time delay instruction for the second recipe. A third recipe may include instructions for disabling the plasma generator and a time delay instruction for the third recipe. It will be appreciated that these recipes may be further divided and / or repeated in any suitable manner within the scope of the present disclosure.

[0036] In some deposition processes, plasma strikes last for durations on the order of several seconds or more. In certain embodiments described herein, much shorter plasma strikes may be applied during a process cycle. These may be on the order of less than 50 milliseconds (25 milliseconds in a specific example). Such short RF plasma strikes require rapid stabilization and tuning of the plasma. To achieve rapid stabilization and tuning of the plasma, the plasma generator may be configured through a two-operation tuning process including a coarse tuning element and a fine tuning element. In the coarse tuning element, impedance matching may be preset to a specific impedance. The coarse tuning element may be preset so that the magnitude of the impedance is, for example, 50 ohms. In certain embodiments, the coarse tuning element may be limited to adjustments that affect the magnitude of the impedance. In the fine tuning element, the RF frequency may be allowed to float from a baseline frequency to attempt to match the phase to a target value (such as a phase value of zero). Conventionally, high-frequency plasma is generated at an RF frequency of approximately 13.56 MHz. In various embodiments disclosed herein, the frequency may be allowed to float to a value different from this nominal value in order to match the phase to a target value. In certain embodiments, the fine-tuning element may be limited to adjustments that affect the phase of the impedance. By allowing the frequency to float while keeping the impedance match fixed at a predetermined impedance, the plasma can be stabilized much more quickly. Rapid stabilization of the plasma can be beneficial for very short plasma strikes, such as those associated with ALD or atomic layer etching (ALE) cycles.

[0037] The first 1-2 milliseconds of a typical deposition cycle involves ignition of the plasma. After ignition, fine adjustments of the RF frequency are performed to align the plasma phase to the target value.

[0038] As described above, one or more processing stations may be included in a multi-station substrate processing tool. FIG. 2 illustrates an example of a multi-station substrate processing apparatus that may utilize plasma equilibration hardware. Various efficiencies, both in terms of equipment cost and operating costs, may be achieved by utilizing a multi-station processing apparatus such as that illustrated in FIG. 2 . For example, a single vacuum pump may be used to evacuate all four processing stations, thereby creating a single high-vacuum environment for all four processing stations. In some embodiments, each processing station may have its own dedicated showerhead for gas delivery, but may share the same gas delivery system. Similarly, certain elements of the plasma generation apparatus may be shared between processing stations (e.g., power supplies), while in some embodiments, certain aspects may be specific to a processing station (e.g., if a showerhead is used to apply a plasma-generating potential). Again, it should be understood that more or less processing stations per processing chamber can be used to achieve greater or lesser degrees of such efficiency, such as 2, 3, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16 or more processing stations per reaction chamber.

[0039] The substrate processing apparatus 200 of Figure 2 utilizes a single substrate processing chamber 214 that includes multiple substrate processing stations, each of which may be used to perform a processing operation on a substrate held by a wafer holder at that processing station. In this particular embodiment, the multi-station substrate processing apparatus 200 has four processing stations 201, 202, 203, and 204 as shown. Other similar multi-station processing apparatuses may have more or fewer processing stations depending on the embodiment and, for example, the desired level of parallel wafer processing, size / space constraints, cost constraints, etc. Also shown in Figure 2 is a substrate handler robot 226 and a controller 250.

[0040] As shown in FIG. 2, the multi-station processing tool 200 has a substrate loading port 220 and a robot 226 configured to move substrates from a cassette loaded through a pod 228, through the atmospheric port 220, into the processing chamber 214, and onto one of four processing stations 201, 202, 203, or 204.

[0041] The processing chamber 214 shown in FIG. 2 provides four processing stations 201, 202, 203, and 204. RF power is generated by an RF power system 213 and delivered to each of the stations 201-204. The RF power system may include one or more RF power sources (e.g., a high-frequency (HFRF) source and a low-frequency (LFRF) source), an impedance matching module, and a filter. In certain embodiments, the power source may be limited to only high-frequency or low-frequency sources. Unless otherwise specified, the deposition process described uses only high-frequency power. The RF power system's delivery system is symmetrical with respect to the reactor and has a high impedance. As a result of this symmetry and impedance, the amount of power delivered to each station is approximately equal. Small differences in RF power (on the order of 5-15%) can result from tolerances in delivery system components, station alignment, temperature differences, and processing conditions.

[0042] Small differences in RF power due to reasons including, but not limited to, imprecise adjustment of variable capacitors in the impedance matching module or imprecise measurement of current from the RF power source can cause wafer-to-wafer non-uniformity in various film properties (e.g., 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 individual stations and dynamically respond to changing station conditions can reduce wafer-to-wafer non-uniformity. It should be noted that the present methods and apparatus are not limited to multi-station reactors, and the methods and apparatus disclosed herein apply to other RF power systems in which multiple processing regions share an RF power source.

[0043] 2 also shows one embodiment of a substrate transfer apparatus 290 for transferring substrates between processing stations 201, 202, 203, and 204 within processing chamber 214. It is understood that any suitable substrate transfer apparatus may be used. Non-limiting examples include a wafer carousel and a wafer handler robot.

[0044] 2 also shows one embodiment of a system controller 250 used to control the processing 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 and / or special-purpose computers, one or more analog and / or digital input / output connections, one or more stepper motor controller boards, etc.

[0045] In some embodiments, the system controller 250 controls some or all of the operation of the processing tool 200, including the operation of the individual processing stations. The system controller 250 may execute machine-readable system control instructions 258 on the processor 252, which in some embodiments are loaded from the mass storage device 254 to the memory device 256. The system control instructions 258 may comprise instructions for controlling the timing; the mixture of gas and liquid reactants; the chamber and / or station pressure; the chamber and / or station temperature; the wafer temperature; the target power level; the RF power level; the RF exposure time; the position of the substrate pedestal, chuck, and / or susceptor; and other parameters of particular processes performed by the processing tool 200. These processes may include various types of processes, such as, but not limited to, processes related to the deposition of films on substrates. The system control instructions 258 may be configured in any suitable manner. For example, various processing tool component subroutines or control objects may be written to control the operation of the processing tool components. The system control instructions 258 may be coded in any suitable computer-readable programming language. In some embodiments, the system control instructions 258 are implemented in software, while in other embodiments the instructions may be implemented in hardware (e.g., hard-coded as logic in an ASIC (application-specific integrated circuit)), and in other embodiments, as a combination of software and hardware.

[0046] In some embodiments, the system control software 258 may include input / output control (IOC) sequence instructions for controlling the various parameters described above. For example, each step of one or more deposition processes may include one or more instructions for execution 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, as may instructions for a capping film deposition. In some embodiments, the recipes may be sequenced sequentially, such that all instructions for a process are executed simultaneously for that process.

[0047] Other computer-readable instructions and / or programs stored on the mass storage device 254 and / or memory device 256 associated with the system controller 250 may also be used in some embodiments. Examples of programs or program sections include a substrate positioning program, a process gas control program, a pressure control program, a heater control program, and a plasma control program.

[0048] In some embodiments, there may be a user interface associated with the system controller 250. The user interface may include a display screen (graphical software display of equipment and / or process conditions) and user input devices such as a pointing device, keyboard, touch screen, microphone, etc.

[0049] In some embodiments, the parameters adjusted by the system controller 250 may relate to process conditions. Non-limiting examples include process gas composition and flow rate, temperature, pressure, plasma conditions (such as RF bias power level, frequency, and exposure time), etc. These parameters may be provided to the user in the form of a recipe and may be entered using a user interface.

[0050] Signals for monitoring the process may be provided by analog and / or digital input connections of the system controller 250 from various process tool sensors. Signals for controlling the process may be output at analog and digital output connections of the process tool 200. Non-limiting examples of process tool sensors that may be monitored include mass flow controllers (MFCs), pressure sensors (such as pressure gauges), thermocouples, load sensors, OES sensors, etc. Appropriately programmed feedback and control algorithms may be used with data from these sensors to maintain process conditions.

[0051] The system controller 250 may provide machine-readable instructions for performing a 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, phase, capacitance, impedance, phase, load power, etc.), frequency adjustment parameters, pressure, temperature, etc. The instructions may control parameters such as, but not limited to, controlling variable capacitance in an impedance matching module or controlling a current source based on measurements of power delivered to the plasma from an RF power source to perform in-situ deposition of a film stack according to various embodiments described herein.

[0052] The system controller typically includes one or more memory devices and one or more processors configured to execute machine-readable instructions to cause the apparatus to perform operations according to the processes described 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.

[0053] Various other configurations for multi-cycle deposition processes and multi-station semiconductor processing equipment are described in U.S. Provisional Patent Application No. 61 / 994,025, filed May 15, 2014, and incorporated herein by reference.

[0054] FIG. 3 is a schematic diagram illustrating various components of an example multi-station plasma reactor with multiple stations sharing an RF power source using RF frequency regulation. As shown, RF power source 301 (which may be a high-frequency RF power source) is supplied to multiple stations 351 via a power distribution network 321. The HFRF may have a frequency of about 2 to 60 MHz, or about 13.56 MHz. In another embodiment, a low-frequency RF power source may be used in addition to or instead of the high-frequency RF power source. The low-frequency RF power source may have a frequency of about 100 kHz to about 1 MHz, or about 400 kHz. Some commercially available RF power sources have the ability to regulate the frequency of the RF power. Examples of such RF power sources include the Advanced Engineer Paramout series, the MKS SurePower series, the Comdel CB, CLX, and CDX series, and the Huettinger TruPlasma series.

[0055] Power from the RF power source 301 may be routed through an impedance matching system, which may include a fixed matching module 303. In certain embodiments including both high-frequency and low-frequency RF power sources, a high-pass filter and / or a low-pass filter may also be present. Additionally, in certain embodiments, power from the RF power source may be routed through an automatic matching module. In embodiments including a low-frequency RF power source, whether in addition to or instead of a high-frequency RF power source, the low-frequency power may be routed through either fixed or automatic matching. In certain embodiments, an automatic matching module may be used to match the RF power frequency to the set impedance of the plasma load. In other embodiments, a fixed matching module may be used that does not automatically match the RF power frequency to the set impedance of the plasma load.

[0056] In the embodiment shown in FIG. 3 , the RF power source 301 is connected to a power distribution network 321. The power distribution network 321 can supply RF power generated by the RF power source 301 to each of the multiple stations 351. The power distribution network 321 is connected to an RF adjuster 323 for each of the multiple stations 351. For each of the multiple stations 351, the RF adjuster 323 is connected to a power parameter sensor 333 in front of the showerhead 353. The power parameter sensor 333 can be any type of sensor previously disclosed, such as a voltage, power, capacitance, impedance, phase, load power, or OES sensor. The RF power source 301 can receive commands from the RF controller 343 to vary the frequency of the RF power distributed to the station. The command can be a frequency adjustment according to the voltage, current, capacitance, impedance, phase, or load power detected by one or more of the power parameter sensors 333. In another embodiment, an additional sensor can measure a final phase representative of the phase of the plasma at all of the stations 351. RF controller 343 may then vary the frequency of the RF power supplied to the stations according to the final phase measured by the additional sensor. In particular embodiments, RF controller 343 may include instructions (e.g., code) for varying the frequency of the RF power so that the phase of the impedance is at or near zero. In the embodiment shown in FIG. 3, RF controller 343 may vary the frequency of the RF power from RF power source 301 upstream of each station.

[0057] The RF adjuster 323 is controlled by an RF controller 343. The RF controller 343 may vary the RF power at each station 351 by an amount determined based on measurements from the sensor 333. In a particular embodiment, the RF adjuster 323 may be a variable capacitor. The RF controller 343 may control a stepper motor (not shown) that can vary the capacitance of the variable capacitor. Other methods for varying the capacitance may also be used. For example, the RF adjuster 323 may be a bank of capacitors with individual switches. The RF power may be controlled by activating (turning on) multiple capacitors having specified values. For example, the capacitors may be selected to add shunt capacitance of 1 pF, 2 pF, 4 pF, 8 pF, and 16 pF to the station. In this example, all combinations of active (on) and inactive (off) capacitors cover a range of 0 pF to 31 pF with 1 pF resolution. By selecting which capacitors to activate, the controller can vary the RF power to the station. This digital control can be faster than using a stepper motor to control a variable capacitor, especially if a wide range of capacitances needs to be covered. Depending on the available space and the amount of control required, one skilled in the art can design an RF adjuster that uses one or more capacitors to vary the RF power by a specific amount.

[0058] In another embodiment, the RF adjuster 323 may be a variable coil inductor. The RF controller 343 may control the variable coil inductor to affect the RF power supplied to the station. In certain embodiments, the RF adjuster is not limited to a capacitor and an inductor. In certain embodiments, other RF adjusters 323 may utilize different mechanisms for varying the RF adjuster power, such as a resonant circuit or a resistive circuit.

[0059] The sensor 333 measures at least one RF power parameter. The measured RF power parameter may be voltage, current, capacitance, impedance, phase, or load power. Commercially available probes may be used to measure the RF power parameter and provide the measurement to the RF controller 343. Non-RF parameters may also be measured and used as source signals for the RF controller 343. For example, optical emissions from station plasma or substrate temperature sensors can measure station characteristics and provide them to the adjuster controller 343. Optical emission systems may be installed near each station to collect light emitted by the station plasma. Substrate temperature sensors may use remote infrared detection systems integrated below the substrate. The sensor 333 may measure multiple RF power parameters, or multiple sensors may be used to measure multiple RF power parameters in certain embodiments.

[0060] In some embodiments, the RF adjuster may be set to a fixed value or range of values ​​throughout a multi-step process (such as a multi-cycle ALD process), and in such embodiments, little or no real-time sensing of one or more RF power parameters and adjustment of the station-to-station delivery of RF power is required.

[0061] In some embodiments, the RF adjuster 323 is used to automatically match the generator impedance of the RF power supply 301 and the load impedance of the plasma. For example, the RF adjuster 323 may include two variable capacitors. The first variable capacitor may be a series (tuning) capacitor, and the second variable capacitor may be a shunt (load) capacitor. The two variable capacitors may be adjusted to match the load impedance of the plasma to the generator impedance of the RF power supply 301 (e.g., 50 ohms) to minimize reflections and maximize power transfer.

[0062] In certain embodiments, the current flowing through RF adjuster 323 can indicate whether an impedance match is present or absent. For example, a current measurement indicating a maximum or minimum current indicates that the generator impedance and the load impedance are not matched. In various embodiments, RF controller 343 communicates with sensor 333 to obtain a measurement of the current flowing through RF adjuster 323, and RF controller 343 communicates with RF adjuster 323 to, for example, control a variable capacitor in RF adjuster 323 to vary the current from the maximum or minimum current.

[0063] The current sensors disclosed herein are not limited to being in sensor 333, nor are they limited to measuring current in RF adjuster 323. It should be understood that the current sensors disclosed herein may be used to measure current in various components within the multi-station plasma reactors described herein, and may also be used to measure current in other semiconductor devices.

[0064] In various embodiments, the sensor 333 can measure the current using various techniques. Examples of current measurement techniques include Pearson probes, Rogowski coils, etc. In such techniques, the flux generated from the current in the primary flow path is used to induce a current in a secondary coil. This induced current generates a voltage in the secondary coil that is proportional to the current in the primary flow path. In some scenarios, such techniques for current measurement are expensive, have narrow bandwidth, and exhibit high variability.

[0065] In certain embodiments, the sensor 333 is a wideband current sensor that measures in-line current of components within the multi-station plasma reactor. In some embodiments, the sensor 333 comprises at least an inductor and a capacitor. By way of non-limiting example, the inductor may be low value and may serve as the primary flow path for current, and the capacitor may be a low value capacitor (e.g., <1 pF) that may provide a high impedance circuit across which the voltage can be measured.

[0066] An example of a method for operating an embodiment of a sensor 333 configured to provide current sensing over a wide frequency bandwidth is illustrated with reference to the sensor 500 embodiment of FIG. 5 and the flowchart of FIG. 7. As shown in FIG. 5, a capacitor C is connected in parallel with an inductor L to form a parallel LC circuit. The illustrated embodiment of sensor 500 may be provided in series to measure current in components including, but not limited to, an RF adjuster 323, an RF power source 301, a power distribution network 321, a fixed matching module 303, or a plasma. In the diagrammatic example of FIG. 5, the sensor 500 measures the current flowing from the RF power source 501 to the plasma 511. When the sensor 500 is inserted in series with the location where the current is to be measured, a voltage V proportional to the current in the sensor 500 develops across the inductor L, and the voltage V is measured (step 705). The voltage across the inductor is linearly proportional to the current across the sensor 500 based on a frequency-dependent proportionality factor determined (step 710) for a particular operating frequency of, for example, the RF adjuster 323, the RF power supply 301, the power distribution network 321, the fixed matching module 303, or the plasma. Applying the frequency-dependent proportionality factor to the measured voltage V yields the measured current (step 715).

[0067] 8 provides an example of a frequency-dependent proportionality factor for converting a measured voltage to a measured current. As an example, a measured voltage of about 5 V can be converted to a measured current of about 6 A, and a measured voltage of about 10 V can be converted to a measured current of about 12 A, thereby corresponding to a proportionality factor of about 1.2. It should be appreciated that sensor 500 can be used to measure currents at different frequencies by changing the proportionality factor used to convert the measured voltage of inductor L to a current value without requiring hardware changes within sensor 500 or replacement of sensor 500.

[0068] The sensor 500 may include an interface for connecting to a voltage measurement device 521 for measuring the voltage at the terminals of the inductor L. The voltage measurement device may be implemented in any one of a variety of architectures known to those skilled in the art. In some embodiments, the voltage measurement may be performed with an oscilloscope. In various embodiments, a voltage divider and / or peak detection circuit is used to facilitate the measurement of the voltage in conjunction with devices such as data acquisition, input / output controllers, etc. The voltage measurement device may be integrated with the sensor 500 or may interface with the sensor 500 through an input / output port.

[0069] An example PCB layout of sensor 333 configured to provide current sensing over a wide frequency bandwidth is shown as sensor 600 in FIG. 6 . In some embodiments, the PCB current sensing board requires no additional active or passive components, making sensor 600 simple and cost-effective to manufacture. Sensor 600 includes an inductive element 605. In various embodiments, inductive element 605 provides a very low value of inductance and serves as the primary flow path (through line) for current. The inductance of the line depends on the line's length and width size (e.g., PCB board size). Sensor 600 also includes a capacitive element 610. Capacitive element 610 can be calculated and / or measured using the formula C=εA / d, where ε is the dielectric constant of the board material, A is the area of ​​the patch, and d is the board thickness. It should be understood that the backside of the board (not shown) has similar parallel patches that serve as electrodes for capacitive element 610. In various embodiments, the capacitive element provides a very low capacitance, creating a very high impedance circuit across which the voltage is measured. As shown in the example of FIG. 6 , a front plate connection 615 and a back plate connection 620 electrically connect the capacitor plates in capacitive element 610 to a through line with inductive element 605. In a specific embodiment, sensor 600 includes one or more fine tuning capacitors (one of which is identified as fine tuning capacitor 625), as indicated by four dotted patches of various sizes. For a sample embodiment of a 7 cm x 7 cm PCB current sensing board, the inventors observed an inductance of approximately 610 nH and a capacitance of approximately 0.017 pF. The sample PCB current sensing board provided approximately 18 V at 100 W, increasing to approximately 53 V at 3 kW. It should be understood that smaller boards can reduce inductance, capacitance, and measurement voltage. Furthermore, it should be understood that the same sensor board can be used to measure voltage and current, and that the phase difference can be accurate if the same node points are used.

[0070] In some embodiments, a frequency-dependent proportionality coefficient, which indicates a linear relationship between the measured voltage and current of inductor L in sensor 333, can be determined based on calibration measurements. For example, sensor 333 can be connected to a current source, inductor L can be connected to a voltmeter, and the current source can be configured to perform a ramp of the current magnitude (e.g., from 0 amps to 12 amps) at a particular frequency. The resulting relationship between voltage and current magnitude can be used to derive the proportionality coefficient for a particular frequency. The ramp of the current magnitude can be performed at different frequencies to obtain different proportionality coefficients for different frequencies.

[0071] In certain embodiments, sensor 333 may be utilized to determine current I using estimated inductance L and / or capacitance C values ​​based on theoretical calculations or manufacturing specifications. In various embodiments, sensor 333 may provide high accuracy without calibrated measurements of inductance or capacitance values. For example, if the actual capacitor value is 100% higher than the estimated capacitor value (e.g., 1 pF to 2 pF), the error in the measured current may be <0.0073%. Furthermore, if the actual capacitor value is 50% lower than the estimated capacitor value (e.g., 1 pF to 0.5 pF), the error in the measured current may be <0.0037%.

[0072] In various embodiments, the sensor 333 may be operated using inductance and capacitance values ​​based on calibration measurements, as shown in the example flow of Figure 9. For example, the calibration measurements for the sensor 333 may include a resonant frequency measurement (step 905). For example, one terminal of a parallel LC circuit, including an inductor L and a capacitor C, may be connected to a variable frequency generator, and the second terminal of the parallel LC circuit may be connected, for example, to electrical ground. The sensor 333 may measure a resonant frequency ω at the terminals of the capacitor C and the inductor L. res, may include an interface for connecting to a resonance meter for detecting the resonance frequency ω of the parallel LC circuit in sensor 333. The resonance meter may be integral with sensor 333 or may interface with sensor 333 through an input / output port. The resonance meter may be implemented in any one of a variety of architectures known to those skilled in the art. For example, at the resonance frequency, a minimum current flows through sensor 333, and the resonance meter may include an ammeter that measures the current through sensor 333. Continuing with this example, in a frequency scan performed by sweeping the output of a variable frequency generator over a range of frequencies, a plot of the current minimum versus frequency may indicate the resonance frequency ω of the parallel LC circuit in sensor 333. res The resonant frequency of a parallel LC circuit is a characteristic of the values ​​of L and C, and is related to the angular frequency ω res = 1 / sqrt(LC) or Hertz frequency = 1 / (2πsqrt()). For example, increasing the inductance L or capacitance C in a parallel LC circuit decreases the resonant frequency.

[0073] In some embodiments, measurements of impedance Z versus frequency curves may also be obtained (step 910), either as part of the frequency sweep to determine the resonant frequency or separately. In particular embodiments, impedance measurements are derived from voltage and current measurements, where impedance is the ratio V / I. Impedance, voltage, and / or current measurement devices may be implemented in any one of a variety of architectures known to those skilled in the art. The relationship of impedance Z versus frequency is Z=V / I=|(jωL) / (1−ω 2 LC)|

[0074] In a broad range of embodiments, calibration measurements that can be used to determine the resonant frequency and the relationship of impedance Z versus frequency ω are used to determine two known values ​​(i.e., ω ) that can be used to derive two unknown values ​​(i.e., L and C). res (or f res ) and Z) (step 915). Specifically, res = 1 / sqrt(LC) and Z = V / I = |(jωL) / (1-ω2 LC)| is the frequency ω-dependent expression L=(Z / ω)(1-(ω 2 / ω res 2 )) and C=1 / (ω res 2 The calibration-based determination of L and C is then utilized during operation of the sensor 333 for in-line current sensing to determine a frequency-dependent linear proportionality coefficient (step 920), such as by determining the impedance Z at a particular operating frequency ω=2πf. As non-limiting examples, equations including, but not limited to, I=C(dV / dt) or C=I / (dV / dt) allow for the derivation of the current I for a particular value of capacitance C and the rate of change of the measured capacitor voltage.

[0075] In various embodiments, the sensor 333 can be operated as shown in the example flow of Figure 10. The calibration measurements described above can be used to determine the resonant frequency (step 1005). For example, the capacitance element 610 in an embodiment of the sensor 333 can be calculated and / or measured using the formula C = εA / d, where ε is the dielectric constant of the board material, A is the area of ​​the patch, and d is the thickness of the PCB board (step 1010). The inductance L can be determined from the known C and the known resonant frequency, where ω res =1 / sqrt(LC) or f res = 1 / (2πsqrt(LC)) (step 1015). The voltage across the dielectric element is measured (step 1020). The impedance Z of the dielectric element L L Z L =jωL, the measured voltage V of the inductive element L can be converted to a measured current I (step 1025), where I=V / 2πfL, f represents the particular operating frequency, and ω=2πf.

[0076] In some embodiments, the parallel LC circuit in the sensor 333 may be characterized based on a Q factor. The Q factor represents the bandwidth selectivity of the parallel LC circuit and is proportional to the ratio C / L. For example, a higher inductance L and / or a lower capacitance C results in a lower Q factor, corresponding to a wider bandwidth for the sensor 333.

[0077] In some embodiments, the parallel LC circuit within the sensor 333 provides wideband current sensing capability for a bandwidth that includes potential noise signals. In certain embodiments, the bandwidth characteristics of the sensor 333 can be adjusted to reject potential noise signals by techniques including, but not limited to, varying the Q factor or shifting the center frequency. In various embodiments, a filter may be coupled to the sensor 333 to filter out potential noise signals. The filter may be implemented using any one of a variety of architectures known to those skilled 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 embodiments, the filter passes frequency signals in the range of 2 to 60 MHz (such as, but not limited to, 13.56 MHz). In certain embodiments, the filter passes frequency signals in the range of 100 kHz to approximately 1 MHz (such as, but not limited to, 400 kHz).

[0078] The inductors and capacitors in the sensor 333 may each be implemented using any one of a variety of architectures known to those skilled in the art. It should be understood that the term capacitor (or inductor) as used herein includes a single capacitor (or inductor) element or an equivalent capacitor (or inductor) corresponding to multiple capacitor (or inductor) elements. In certain embodiments, the capacitor is a variable capacitor and / or the inductor is a variable inductor. For example, the variable capacitor and / or variable inductor may be adjusted to change the frequency characteristics of the sensor 333 as a built-in fine-tuning mechanism. As a non-limiting example, the RF power supply controller 343 may control a stepper motor that can change the capacitance / inductance of the variable capacitor / inductor, or the RF controller 343 may control a bank of capacitors / inductors with individual switches.

[0079] It should be appreciated that embodiments of the sensor 333 for measuring RF current can be accurate, inexpensive, have a wide bandwidth, be easily manufactured (e.g., in a PCB package), and include a simple calibration procedure. In various embodiments, the sensor 333 can include a built-in fine-tuning mechanism so that the voltage across the capacitor is linearly proportional to the current. As detailed above, the proportionality coefficient varies with frequency, and the sensor 333 can be used at any frequency by varying the proportionality coefficient.

[0080] In certain embodiments, sensor 333 comprises an inductor, a capacitor, an interface for series connection with components in a multi-station plasma reactor, and an interface for connection to a voltage measurement device, where the inductor and capacitor are arranged in parallel, the inductor value is configured so that the inductor is the primary flow path for current through sensor 333, and the capacitor value is configured so that the capacitor creates a high impedance across the interface for the voltage measurement device. In various embodiments, sensor 333 is calibrated using a method that determines a resonant frequency, determines an impedance vs. frequency relationship, and determines inductance and capacitance values ​​of corresponding inductors and capacitors in sensor 333 based on the resonant frequency and the impedance vs. frequency relationship.

[0081] Each station 351 includes a showerhead 353 operating in conjunction with a grounded pedestal 357. The power and frequency provided are sufficient to generate a plasma from the process gases, for example, in the range of approximately 50-6,000 W per station. The power level may vary depending on the embodiment. RF power is connected to the station processing region through the showerhead 353 and generates or sustains a plasma when RF power is applied. The plasma deposits material on the substrate by various mechanisms. For example, the plasma causes the process gases to decompose and react on the substrate surface. In the illustrated embodiment, the RF current is grounded at the pedestal 357, which is connected to ground 331. In certain other embodiments, the RF current may be grounded at another location within the chamber, such as the showerhead.

[0082] The semiconductor tools described above may be used for plasma equilibration, which can be particularly advantageous in multi-cycle deposition processes with short cycle periods, such as ALD and atomic layer etching (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. Pat. No. 7,416,989, entitled "ADSORPTION BASED MATERIAL REMOVAL PROCESS," U.S. Pat. No. 7,977,249, entitled "METHODS OF REMOVING SILICON NITRIDE AND OTHER MATERIALS DURING FABRICATION OF CONTACTS," U.S. Pat. No. 8,187,486, entitled "MODULATING ETCH SELECTIVITY AND ETCH RATE OF SILICON NITRIDE THIN FILMS," U.S. Pat. No. 7,981,763, entitled "ATOMIC LAYER REMOVAL FOR HIGH ASPECT RATIO GAPFILL," and U.S. Pat. No. 8,058,179, entitled "ATOMIC LAYER REMOVAL PROCESS WITH HIGHER ETCH AMOUNT."

[0083] The plasma activation step of a multi-step deposition process having a short cycle period can be short. The duration of the plasma activation step can be about 150 milliseconds or less (e.g., about 50 milliseconds). Because of the short duration, controlling the consistency of the plasma has an impact on process uniformity. Plasma equilibration can be used to control the consistency of the plasma.

[0084] 4A is a process flow diagram for a multi-station deposition process utilizing RF frequency tuning and RF power parameter adjustment. The process described in FIG. 4A is applicable to various steps in a deposition process, such as step 3 of the ALD cycle described above. Although the process is discussed in the context of a deposition procedure, elements of the process may be applied to any plasma-assisted semiconductor process.

[0085] A substrate is provided in operation 401. The substrate may be provided to one or more stations of a multi-station tool. The substrate may be provided by loading the substrate into the station, or the substrate may already be in the station from a previous operation (e.g., from a previous cycle).

[0086] After the substrate is provided, gas flow is established in operation 403, and the pressure is stabilized at a set point. In operation 405, RF power generation begins. The RF power may be HFRF, LFRF, or both HFRF and LFRF. Before operation 405, the impedance between the electrode (typically a showerhead) and the substrate may be very high, similar to an open-circuit impedance. In operation 405, RF power may be generated and applied to ignite a plasma. The RF power may be applied so that the magnitude of the impedance is fixed to a specific resistance value (e.g., a resistance value of 50 ohms). 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 embodiments, the frequency of the RF power generated in operation 405 may not conform to a fixed frequency. In such embodiments, the frequency in operation 405 may be changed in various ways, such as using an algorithm, user input, or feedback from a previous operation of the deposition process. In certain embodiments, operation 405 may last for a limited period of time, such as a period of less than 5 milliseconds.

[0087] After the plasma is properly ignited, the process may proceed to operation 407. Full power is applied from operation 407 onward. Operations 407-419 are repeated for the remainder of the deposition process. Thus, if the process of FIG. 4A is used in step 3 of an ALD cycle, operations 407-419 are repeated until the end of step 3. In operation 407, the impedance of the plasma may be measured. During the process described in FIG. 4A, chemical reactions and changes in environmental conditions within the process station may lead to changes in the impedance of the plasma. The impedance may be measured by any sensor typically used to measure the impedance of a plasma. The measured impedance may be the impedance seen by the source of RF power. The impedance seen by the source of RF power may be measured by a sensor described elsewhere in this disclosure. For example, a load sensor conductively connected to the source of RF power may measure the impedance seen by the source of RF power.

[0088] In operation 408, the frequency of the RF power may be adjusted according to the impedance measured in step 407. Particular embodiments of the semiconductor processing tool may include a controller and associated instructions for matching the RF power frequency to the detected impedance. The instructions may be based on a plot, according to a formula, or according to other methods for calculating the required RF power frequency. For example, the RF power frequency may be adjusted so that the phase of the impedance is as close to a zero value as possible. As the impedance changes during semiconductor processing, the RF power frequency may be adjusted accordingly in operation 408. In particular embodiments, the impedance may be measured as an average of the impedance at each station. Another embodiment may include the ability to measure the impedance at each individual station. As described above, operations 407 and 408 are performed continuously until the end of the deposition processing step due to possible changes in impedance.

[0089] In operation 409, an RF power parameter may be measured at each station to determine station-to-station variations. The RF power parameter may be measured after plasma is generated in the station and reflects the operating impedance in each station. This parameter may be voltage, current, capacitance, impedance, phase, load power, power delivered to the station, or any combination thereof.

[0090] The measured RF power parameters may be compared to a set point for each station in operation 411. In certain embodiments of RF power balancing, the set point may be the same for every cycle of the deposition process. In other embodiments, the set point may vary between cycles of the deposition process. For example, the set point may be an average of the measured power delivered to each station. In yet other embodiments, the set point may be different for each station. This comparison may be performed by a local controller, a central controller for the RF adjusters, or a system control for the entire tool.

[0091] The total RF power delivered to all stations sharing a common RF source depends on the power setpoints at the RF generators, the impedance of the plasma load, and the impedance of the RF network. RF adjusters primarily affect the power distribution between stations. The adjuster's effect on the total power is usually secondary. In certain cases, depending on the type of RF adjuster used, reducing RF power at one station may increase RF power at other stations. In those cases, the controller may determine adjustments that take into account the RF power interactions between stations, or it may simply repeat the adjustments multiple times until measurements are within threshold limits for the setpoints.

[0092] In certain cases, absolute RF power levels are desired. In this case, RF power is measured at each station and two adjustments can be made. For example, first, the total power at the generator output is changed to match the sum of the station setpoints. Second, the station RF adjusters are adjusted to divide the power according to the setpoints. The order of adjustments (total power vs. division) can also be reversed. The procedure is repeated until the power division is within threshold limits for the setpoints.

[0093] In operation 413, the measured RF power parameter distribution may be compared to a setpoint. If the difference is greater than a threshold, an adjuster change at each station may be determined in operation 415. The required adjuster change may vary from station to station. Some stations may not require any adjuster change, while other stations may require an adjuster change. The adjuster change may be determined by the RF controller or another controller. Note that the parameter or RF characteristic being adjusted may be different from the measured RF power parameter. In one example, RF power may be measured and capacitance or impedance may be adjusted.

[0094] The necessary adjuster changes may be applied to adjust the station RF characteristics in operation 417. In particular embodiments, the station impedance may be adjusted by the adjuster change amount in operation 417. The impedance and station RF power parameters may then be measured again starting from operation 407, and the cycle of adjusting the RF power frequency and power parameters may continue until the deposition process is complete.

[0095] If the power parameters measured in operation 411 and compared in operation 413 are within the acceptable range, the semiconductor processing continues at operation 419. Processing may then continue starting at operation 407 until the deposition process is complete. While the description of certain embodiments in this disclosure is made in the context of a deposition process, it should be understood that other semiconductor processing operations, in addition to or instead of deposition, including, but not limited to, etching, stripping, or thin film removal from a substrate, are contemplated for the disclosed current measurement techniques. Furthermore, it should be understood that the disclosed current measurement techniques facilitate providing uniform and / or repeatable processing conditions (e.g., RF power, etc.) at multiple semiconductor processing stations for semiconductor processing operations (e.g., deposition, etching, stripping, cleaning, etc.), thereby improving semiconductor manufacturing yields.

[0096] In various embodiments, 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 another embodiment, operations 407-408 may be performed in parallel with operations 409-419. In yet another embodiment, measurement operations 407 and 409 may be performed before adjustment and adjustment operations 408 and 411-419.

[0097] In the context of power balancing, continuous RF power control during processing may be required for at least two reasons. One possibility is to follow an intentional RF power curve. The set point may change over time during the processing sequence. RF adjusters may be used to maintain a particular power distribution when the set point changes. Another possibility is that station RF power may have a tendency to fluctuate during processing and therefore needs to be adjusted based on dynamic feedback.

[0098] In certain embodiments, a semiconductor processing operation may include multiple different deposition processes within a single multi-station reactor. The multiple different deposition processes may deposit different materials, particularly material layers such as a barrier layer or nucleation layer in contact with the underlying substrate, a bulk layer on top of the nucleation layer, and a capping layer on top of the bulk layer. These individual layers may have relatively similar (or different) compositions. In some cases, the different deposition processes may use different process gases. When a semiconductor processing operation includes multiple different deposition processes, different recipes are typically used for the different deposition processes. In such cases, different RF power parameter set points for the individual stations may be used for the different recipes. In certain embodiments, the set point differences lead to differences between initial adjuster settings for the different recipes. Such initial adjuster settings may be included in or be part of the recipe for the deposition process. The different recipes for the different deposition processes may reflect differences in the initial adjuster settings for the different processes. In such cases, the initial adjuster settings for the separate processes may be determined through prior simulation or testing. In certain examples, the RF power frequency initially generated and delivered to the stations may be at different station-by-station power settings for individual recipes. In such examples, the RF adjusters may be further adjusted during the deposition process in accordance with the techniques described herein. In certain embodiments, the initial adjuster positions may be calculated adjuster positions that result in the least amount of RF adjuster adjustment when the deposition process is run over multiple cycles.

[0099] Figure 4B is a process flow diagram for a multi-station deposition process utilizing RF frequency adjustment. Figure 4B is similar to Figure 4A, except that Figure 4A describes a process utilizing both RF frequency adjustment and RF power parameter adjustment during the deposition process, whereas Figure 4B describes a process utilizing only RF frequency adjustment during the deposition process.

[0100] The process flow diagram of FIG. 4B may be used for a deposition process that utilizes RF frequency adjustments. A particular example may use the process shown in process 4B for individual deposition processes in a semiconductor processing operation that includes multiple different deposition processes. The multiple different deposition processes may deposit different materials, as described herein. In another embodiment, only a single deposition process is used. In either case, the RF power adjustments between stations may be fixed and set prior to the deposition process. Typically, the process does not utilize feedback of RF power parameters to determine appropriate RF power adjustments during deposition.

[0101] In process flowchart 420 of Figure 4B, operations 421 and 423 are similar to operations 401 and 403, respectively, of Figure 4A. In operation 425 of Figure 4B, RF adjustments for the multiple stations are determined. The RF adjustments for the multiple stations are determined prior to generating RF power and processing substrates. The RF adjustments may be determined from historical data, calculations, or through trial and error.

[0102] After the RF adjustment is performed in operation 425, processing may proceed to operation 427. Operations 427, 429, and 431 are similar to operations 405, 407, and 408, respectively, of FIG. 4A. In operation 433, the current cycle is processed for each station, and the process is repeated for a desired number of cycles. During each of the desired number of cycles, operations 427, 429, and 431 are repeated such that the RF power frequency is continuously adjusted according to the requirements of the measured impedance. The RF power frequency may be adjusted according to techniques described elsewhere in this disclosure.

[0103] It should be understood that in some embodiments, capacitance and / or current are measured instead of or in addition to the impedance measurements mentioned in Figures 4A and 4B, such as with embodiments of sensor 333 described herein. Furthermore, it should be understood that in some embodiments, the frequency of the RF power is adjusted based on the measured capacitance and / or current instead of or in addition to the measured impedances mentioned in Figures 4A and 4B, such as with embodiments of sensor 333 described herein.

[0104] Various other configurations and apparatus for power balancing for multi-station semiconductor processing equipment are described in U.S. Pat. No. 8,282,983, issued Oct. 9, 2012, which is incorporated herein by reference in its entirety.

Claims

1. 1. An apparatus for performing plasma-assisted semiconductor processing in a processing chamber, comprising: a current sensor, the current sensor having an inductive element and a capacitive element in parallel with the inductive element; one or more controllers communicatively connected to the current sensors, measuring a voltage across the inductive element in the current sensor; one or more controllers configured to determine a current of a plasma in the processing chamber by transforming the measured voltage across the inductive element based on a linear proportionality factor; An apparatus comprising:

2. 10. The apparatus of claim 1, The one or more controllers are further configured to adjust respective radio frequency (RF) power frequencies supplied to one or more processing stations of the processing chamber based on the determined plasma current.

3. 3. The apparatus of claim 2, The adjusting of the respective RF power frequencies comprises: determining a change to an RF power frequency according to the determined plasma current; and adjusting the RF power frequency based on the change to the determined RF current frequency; An apparatus comprising:

4. 4. The apparatus of claim 3, The apparatus further comprises a plurality of processing stations within the processing chamber; The apparatus, wherein the adjusting the RF power frequency comprises adjusting a respective RF power frequency at each of one or more of the plurality of processing stations.

5. 5. The apparatus of claim 4, The apparatus, wherein the adjustment of the RF power frequency is performed at a processing station of the plurality of processing stations when a difference between a set point and the RF power frequency exceeds a threshold.

6. 5. The apparatus of claim 4, The apparatus, wherein the one or more controllers are further configured to adjust a radio frequency (RF) power parameter based on a difference between the RF power frequency exceeding a threshold and a set point.

7. 7. The apparatus of claim 6, The apparatus, wherein the RF power parameters comprise voltage, current, capacitance, impedance, phase, load power, power supplied to one or more of the plurality of processing stations, or a combination thereof.

8. 5. The apparatus of claim 4, The one or more controllers are further configured to perform semiconductor processing operations on substrates at the one or more of the plurality of processing stations.

9. 10. The apparatus of claim 1, The one or more controllers are further configured to adjust radio frequency (RF) power characteristics based on a difference between an RF power parameter and a set point above a threshold, the RF power characteristics comprising an impedance associated with the current sensor or a capacitance of the capacitive element within the current sensor.

10. 1. An apparatus for performing plasma-assisted semiconductor processing in a processing chamber, comprising: a plurality of processing stations within the processing chamber; a current sensor, the current sensor having an inductive element and a capacitive element in parallel with the inductive element; one or more controllers communicatively connected to the plurality of processing stations and the current sensor; measuring a voltage across the inductive element in the current sensor; one or more controllers configured to determine a plasma current in one or more of the plurality of processing stations, the determining including converting the measured voltage to the plasma current based on a linear proportionality factor; An apparatus comprising:

11. 11. The apparatus of claim 10, further comprising: a power source configured to provide radio frequency (RF) power to each of the plurality of processing stations; an RF frequency adjuster configured to adjust an RF power frequency for each of the plurality of processing stations; The apparatus, wherein each of the plurality of processing stations is configured to generate a plasma based on the RF power.

12. 11. The apparatus of claim 10, The one or more controllers may further: determining a change to an RF power frequency of each of the one or more of the plurality of processing stations according to the determined plasma current in the one or more of the plurality of processing stations; an apparatus configured to adjust the respective RF power frequencies of one or more of the plurality of processing stations based on the changes to the determined respective RF power frequencies.

13. 13. The apparatus of claim 12, The apparatus, wherein the adjustment of the respective RF power frequency is performed when a difference between a set point and the RF power frequency exceeds a threshold.

14. 11. The apparatus of claim 10, The one or more controllers may further: determining a change to the RF power frequency of each of the one or more of the plurality of processing stations according to the impedance associated with the current sensor; an apparatus configured to adjust the respective RF power frequencies of one or more of the plurality of processing stations based on the determined respective RF power frequencies.

15. 11. The apparatus of claim 10, The one or more controllers are further configured to perform semiconductor processing operations on substrates at the one or more of the plurality of processing stations.

16. 1. A method for performing plasma-assisted semiconductor processing at multiple stations in a processing chamber, comprising: measuring a voltage across an inductive element in a current sensor having an inductive element and a capacitive element in parallel with the inductive element; 11. The method of claim 10, further comprising: determining a current of a plasma at one or more of the plurality of processing stations, the determining including converting the measured voltage to a current of the plasma based on a linear proportionality coefficient.

17. 17. The method of claim 16, further comprising: adjusting a respective radio frequency (RF) power frequency supplied to the one or more of the plurality of processing stations based on the determined plasma current.

18. 18. The method of claim 17, further comprising: comparing RF power parameters to setpoints for each of the one or more of the plurality of stations, the RF power parameters comprising voltage, current, capacitance, impedance, phase, load power, power delivered to one or more of the plurality of processing stations, or combinations thereof; adjusting one or more RF power characteristics of the plurality of processing stations based on a difference between the RF power parameter and the set point exceeding a threshold, the RF power characteristics comprising an impedance associated with the current sensor or a capacitance of the capacitive element within the current sensor.

19. 17. The method of claim 16, further comprising: performing a semiconductor processing operation on a substrate at said one or more of said plurality of processing stations.

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