Impedance transformation in radio frequency assisted plasma generation

Abstract

An apparatus for providing a signal to an apparatus may include one or more RF signal generators, and an electrically small transmission line coupling the signal from the one or more RF signal generators to a manufacturing chamber. The apparatus may also include a reactive circuit to convert the impedance of the electrically small transmission line from a region of relatively high impedance sensitivity to a region of relatively low impedance sensitivity.

Description

This application is a divisional application of the patent application with application number 202080083903.4, application date December 2, 2020, and invention title "Impedance Transformation in Radio Frequency Assisted Plasma Generation". Incorporated by reference

[0001] The PCT application form is submitted simultaneously with this specification as part of this application. Each application for which this application claims the benefit or priority as identified in the PCT application form submitted simultaneously is incorporated herein by reference in its entirety and for all purposes. Background Art

[0002] The descriptions of the background and context included herein are provided only for the purpose of presenting the context of the disclosure as a whole. Many of the presented achievements of the inventors, and simply because such achievements are described in the background art section or presented elsewhere herein as context does not mean that such achievements are considered prior art.

[0003] The fabrication of semiconductor wafers for forming integrated circuits may include many different processing steps. In certain processing steps that may occur after various materials are deposited on the semiconductor wafer, the materials may be etched away so that additional materials such as metals can be deposited. Such deposition may involve the formation of conductive traces, transistor gates, vias, circuit elements, and the like. However, at least in some cases, semiconductor manufacturing processes, such as those involving plasma-based etching, plasma-enhanced atomic layer deposition, or other processes, uncontrollable process variations may lead to lower yields, costs, re-design of semiconductor layouts and masks, and so on. In some cases, such uncontrollable process variations may be caused in response to changes in the energy coupled to the fabrication chamber for forming the plasma. Thus, techniques for increasing control over plasma-based wafer etching and / or plasma-enhanced atomic layer deposition or other manufacturing processes remain an active area of research. Summary of the Invention

[0004] In one aspect, there is provided an apparatus for providing a signal to a device, wherein the apparatus includes: one or more radio frequency (RF) signal generators; one or more electrical small transmission lines for coupling the signals from the one or more RF signal generators to a fabrication chamber; and a reactance circuit for transforming the impedance of each of the electrical small transmission lines from a region having a first impedance sensitivity to a region having a second impedance sensitivity.

[0005] In some aspects, the reactance circuit includes at least series reactance. In some aspects, the reactance circuit includes at least shunt susceptance. In some aspects, the reactance circuit includes at least series reactance and shunt susceptance. In some aspects, the region with relatively high impedance sensitivity corresponds to a region in the impedance space, and the real part of the impedance corresponds to a value greater than about 100 ohms. In some aspects, the region with relatively low impedance sensitivity corresponds to a region in the impedance space, and wherein the real part of the impedance corresponds to a value less than about 100 ohms. In some aspects, the reactance circuit for transforming the impedance avoids the possibility of the resonant transmission line at any frequency less than the frequency of the signal from one or more of the RF signal generators. In some aspects, the electrically small transmission line corresponds to a transmission line that transforms the impedance from the region of relatively high impedance sensitivity to the region of relatively low impedance sensitivity at a frequency less than the frequency of the signal generated by the RF signal generator in the medium of the transmission line without traversing the transmission line resonance. In some aspects, the resistive loss of the electrically small transmission line combined with the loss of the reactance circuit corresponds to less than about 20%. In some aspects, the resistive loss of the electrically small transmission line corresponds to less than 10%.

[0006] In another aspect, a device is provided, wherein the device includes: an electrically small transmission line for coupling a signal from one or more of the RF signal generators to a manufacturing chamber; and a reactance circuit for converting the impedance of the electrically small transmission line from a region of relatively high impedance sensitivity to a region of relatively low impedance sensitivity, the reactance circuit for moving an impedance control point in a direction opposite to the direction of movement through the length of the transmission line.

[0007] In some aspects, the electrically small transmission line corresponds to a transmission line that moves the impedance control point from the region of relatively high impedance sensitivity to the region of relatively low impedance sensitivity at a frequency less than the frequency of the signal generated by the RF signal generator in the medium of the transmission line without traversing the transmission line resonance. In some aspects, the reactance circuit includes series capacitive reactance. In some aspects, the reactance circuit includes at least shunt inductive susceptance. In some aspects, the reactance circuit includes series capacitive reactance and shunt inductive susceptance. In some aspects, the resistive loss of the electrically small transmission line combined with the loss of the reactance circuit corresponds to less than about 20%. In some aspects, the resistive loss of the electrically small transmission line corresponds to less than 10%.

[0008] In another aspect, there is provided an integrated circuit fabrication chamber, which includes: a plurality of integrated circuit fabrication stations; one or more input ports for coupling a radio frequency (RF) signal to at least one of the plurality of integrated circuit fabrication stations; electrical small transmission lines for coupling signals from one or more of RF signal generators to the fabrication chamber; and a reactance circuit for transforming the impedance of the electrical small transmission lines from a region of relatively high impedance sensitivity to a region of relatively low impedance sensitivity.

[0009] In some aspects, the region of relatively high impedance sensitivity corresponds to a region in the impedance space, and wherein the real part of the impedance corresponds to a value greater than about 100 ohms. In some aspects, the region of relatively low impedance sensitivity corresponds to a region in the impedance space, where the real part of the impedance corresponds to a value less than about 100 ohms. In some aspects, the region having the first impedance sensitivity corresponds to the region having low impedance sensitivity, and the region having the second impedance sensitivity corresponds to the region having high impedance sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 A substrate processing apparatus for depositing a film on a semiconductor substrate using any number of processes is shown.

[0011] Figure 2 is a block diagram showing various components of a system for performing a semiconductor manufacturing process according to an embodiment.

[0012] Figure 3 Shows a power-versus-time curve of radio frequency (RF) power of a station coupled to a multi-station integrated circuit fabrication chamber according to an embodiment.

[0013] Figure 4 is a diagram showing an RF matching unit coupled to a load (Z L ) through transmission lines of different lengths according to an embodiment, and a corresponding impedance diagram in the impedance space.

[0014] Figure 5A and 5B depicts the impedance sensitivity at the control points of an RF matching unit in response to transmission lines of different lengths according to an embodiment.

[0015] Figure 6A and 6B is a schematic diagram showing the use of electrical small transmission lines and reactance elements according to an embodiment, the electrical small transmission lines and reactance elements being arranged to transform the impedance of a control point from a relatively high impedance sensitivity region of the impedance space to a relatively low impedance sensitivity region of the impedance space.

[0016] Figure 7It is a circuit diagram of a transmission line model according to an embodiment. Detailed Description

[0017] In certain embodiments or implementations, impedance transformation in radio frequency (RF)-assisted plasma generation can be used in various semiconductor manufacturing processes, such as plasma-based wafer fabrication. The impedance transformation can enable the ability to more easily control the RF power delivered to a station of the processing chamber in a manner that allows dynamic adjustment of varying loads presented by one or more stations of a multi-station processing chamber. Such dynamic adjustment provides a real-time ability to match the load impedance presented by the in-chamber plasma to the source impedance of one or more RF power generators, even if such loads may experience significant increases and decreases during the course of a manufacturing process. Accordingly, the RF power delivered to each station can be increased while the RF power reflected from the RF power generator can be reduced.

[0018] Certain embodiments or implementations can be used in a variety of wafer fabrication processes, such as various plasma-enhanced atomic layer deposition (ALD) processes, various plasma-enhanced chemical vapor deposition (CVD) processes, or can be used on-the-fly during a single deposition process. In certain implementations, the RF power matching network utilizes a simplified circuit topology to accommodate load variations at any signal frequency, such as intermediate frequencies (e.g., frequencies between 300 kHz and 3 MHz), high frequencies (e.g., frequencies between 3 MHz and 30 MHz), and very high frequencies (e.g., frequencies between 30 MHz and 300 MHz). However, in other implementations, the RF power matching network can operate at any signal frequency, such as at relatively low frequencies, e.g., frequencies between 50 kHz and 300 kHz, and at higher signal frequencies, e.g., frequencies above 300 MHz.

[0019] It should be noted that while the specific embodiments described herein may show and / or describe electrical small transmission lines and reactance elements for use with 4 stations of a processing chamber, in other embodiments, a lesser number of stations of the processing chamber may be used, such as 1 station, 2 stations, or 3 stations. In other embodiments, the electrical small transmission lines and reactance elements can be used with a greater number of stations of the processing chamber, such as with 5 stations, 6 stations, 7 stations, 8 stations, 10 stations, 12 stations, or any other number of stations of the processing chamber.

[0020] The fabrication of semiconductor devices generally involves depositing one or more thin films on a planar or non-planar substrate in an integrated manufacturing process. In some aspects of the integrated process, it may be useful to deposit a thin film that conforms to the substrate topography. One type of reaction that is useful in certain cases involves chemical vapor deposition (CVD). In a typical CVD process, gaseous reactants are introduced into a station of a reaction chamber simultaneously and undergo a gas-phase reaction. The reaction products are deposited on the substrate surface. The reaction can be driven by a plasma, in which case the process can be referred to as a plasma-enhanced chemical vapor deposition (PECVD) reaction. As used herein, unless otherwise indicated, the term CVD is intended to include PECVD. CVD processes have certain disadvantages that make them less suitable in certain cases. For example, mass transport limitations in CVD gas-phase reactions can result in a "loaf-shaped" deposition effect, which presents a thicker deposition at the top surface (e.g., the top surface of a gate stack), and a thinner deposition at a recessed surface (e.g., the bottom corner of a gate stack). Additionally, since some die will have regions of different device densities, mass transport effects across the substrate surface can result in thickness variations within the die and within the wafer. These thickness variations can lead to over-etching in some regions and under-etching in other regions, which reduces device performance and die yield. Another issue associated with CVD processing is that they generally cannot form a conformal film in high aspect ratio features. As device dimensions continue to shrink, this problem may become increasingly severe.

[0021] In another example, some other deposition processes involve multiple film deposition cycles, where each one results in a "discrete" film thickness. For example, in atomic layer deposition (ALD), any technique for placing thin film layers and for repeating sequential events can be considered to involve multiple deposition cycles. As device and feature sizes continue to shrink in the semiconductor industry, and also as three-dimensional device structures become more common in integrated circuit (IC) design, the ability to deposit thin conformal films (material films having a uniform thickness relative to the topography of the underlying structure, even if non-planar) becomes even more important. ALD is a film-forming technique well-suited for conformal film deposition due to the fact that a single cycle of ALD deposits a single thin material layer, the thickness of which is limited by the amount of one or more film precursor reactants that can adsorb on the substrate surface prior to their own film-forming chemical reaction (i.e., form an adsorption-limited layer). Then, multiple "ALD cycles" can be used to build up a film of the desired thickness, and since each layer is thin and conformal, the resulting film is substantially conformal to the shape of the underlying device structure. In certain embodiments, each ALD cycle includes the following steps:

[0022] Exposing the substrate surface to a first precursor.

[0023] Purge the reaction chamber in which the substrate is located.

[0024] Activate the reaction on the substrate surface, typically using plasma and / or a second precursor.

[0025] Purge the reaction chamber in which the substrate is located.

[0026] The duration of an ALD cycle can typically be less than 25 seconds, or less than 10 seconds, or less than 5 seconds. One (or more) plasma exposure steps of an ALD cycle can have a short duration, such as 1 second or less.

[0027] Figure 1 A substrate processing apparatus is shown that deposits a film on a semiconductor substrate using any number of processes. Figure 1 The apparatus 100 uses a single processing station 102 of a processing chamber, which has a single substrate holder 108 (e.g., a pedestal) in its internal volume, and this internal volume can be maintained under vacuum by a vacuum pump 118. A gas delivery system 101 and a showerhead 106 are also fluidly connected to the processing chamber for delivering (e.g.) film precursors, carrier gases, and / or purge gases, and / or processing gases, second reactants, etc. In Figure 1 Equipment for generating plasma in the processing chamber is also shown. Figure 1 The apparatus schematically depicted in can be adapted to perform plasma-enhanced CVD in particular.

[0028] For simplicity, the processing apparatus 100 is depicted as an independent processing station (102) of a processing chamber, which is used to maintain a low-pressure environment. However, it should be understood that multiple processing stations can be included in a common processing tool environment as described herein (e.g., within a common reaction chamber). For example, Figure 2 An implementation of a multi-station processing tool is depicted, which will be discussed in further detail below. Additionally, it should be understood that in some implementations, one or more hardware parameters of the processing apparatus 100 (including those discussed in detail herein) can be programmatically adjusted by one or more system controllers.

[0029] The station 102 of the processing chamber is in fluid communication with the gas delivery system 101 for delivering process gases (which can include liquids and / or gases) to the distribution showerhead 106. The gas delivery system 101 includes a mixing vessel 104 for mixing and / or conditioning the process gases delivered to the showerhead 106. One or more mixing vessel inlet valves 120 can control the introduction of process gases into the mixing vessel 104.

[0030] Some reactants can be stored in liquid form before vaporization and subsequent delivery to the processing station 102 of the processing chamber. Figure 1Implementation solutions include a vaporization point 103, which is used to vaporize the liquid reactants to be supplied to the mixing vessel 104. In some implementation solutions, the vaporization point 103 can be a heated liquid injection module. In some other implementation solutions, the vaporization point 103 can be a heated vaporizer. In still other implementation solutions, the vaporization point 103 can be eliminated from the processing station. In some implementation solutions, a liquid flow controller (LFC) upstream of the vaporization point 103 can provide for controlling the mass flow rate of the liquid to be vaporized and transported to the processing station 102.

[0031] The showerhead 106 distributes process gas and / or reactants (e.g., film precursors) toward the substrate 112 at the processing station, and its flow rate is controlled by more than one valve (e.g., valves 120, 120A, 105) upstream of the showerhead. In Figure 1 the illustrated implementation solution, the substrate 112 is positioned below the showerhead 106 and is shown placed on the pedestal 108. The showerhead 106 can have any suitable shape and can have any suitable number and arrangement of ports for distributing the processing gas to the substrate 112. In some implementation solutions having two or more stations, the gas delivery system 101 includes valves or other flow control structures upstream of the showerhead, which can independently control the flow of the process gas and / or reactants to each station, such that the gas can flow to one station and not to another. Additionally, the gas delivery system 101 can be configured to independently control the process gas and / or reactants delivered to each station in a multi-station device, such that the gas compositions provided to different stations are different; for example, at the same time, the partial pressures of the gas components can vary between multiple stations.

[0032] The volume 107 is positioned below the showerhead 106. In some implementation solutions, 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 the processing pressure, reactant concentration, etc. within the volume 107.

[0033] In Figure 1 this case, the showerhead 106 and the pedestal 108 are electrically coupled to the radio frequency power supply 114 and the matching network 116 to power the plasma generator. In some implementation solutions, the plasma energy (e.g., via a system controller having appropriate machine-readable instructions and / or control logic) can be controlled by controlling more than one of the processing station pressure, gas concentration, RF power source, etc. For example, the radio frequency power supply 114 and the matching network 116 can operate at any suitable power to form a plasma having a desired radical species composition. Similarly, the radio frequency power supply 114 can provide RF power at any suitable frequency or group of frequencies and power.

[0034] In some implementations, appropriate hardware and / or appropriate machine-readable instructions in a system controller are utilized to control plasma ignition and maintenance conditions, and the system controller can provide control instructions via a series of input / output control (IOC) instructions. In one example, instructions for setting the plasma for plasma ignition or maintenance are provided in the form of a plasma activation recipe that processes the recipe. In certain cases, the process recipes can be arranged sequentially such that all instructions for the process are executed concurrently with the process. In some implementations, instructions for setting one or more plasma parameters can be included in the recipe prior to the plasma process. For example, a first recipe can include instructions for setting the flow rates of an inert gas (e.g., helium) and / or a reactive gas, instructions for setting the plasma generator to a power set point, and a time delay instruction for the first recipe. A second subsequent recipe can include instructions for enabling the plasma generator and a time delay instruction for the second recipe. A third recipe can include instructions for disabling the plasma generator and a time delay instruction for the third recipe. It should be understood that within the scope of the present disclosure, these recipes can be further subdivided and / or repeated in any suitable manner.

[0035] In some deposition processes, the plasma excitation duration is about several seconds or longer. In certain implementations described herein, much shorter plasma excitations can be applied during the processing cycle. These can be on the order of less than 50 milliseconds, with 25 milliseconds being a specific example.

[0036] For simplicity, in Figure 1 the processing apparatus 100 is depicted as a stand-alone station (102) for a processing chamber that maintains a low-pressure environment. However, it can be understood that multiple processing stations can be included in a multi-station processing tool environment, such as Figure 2 shown, which depicts a schematic view of an embodiment of a multi-station processing tool.

[0037] The processing apparatus 200 employs an integrated circuit fabrication chamber 263 that includes a plurality of fabrication processing stations, each of which can be used to perform a processing operation on a substrate held in a wafer holder (e.g., Figure 1 the pedestal 108) at a particular processing station. In Figure 2 the embodiment, the integrated circuit fabrication chamber 263 is shown as having four processing stations 251, 252, 253, and 254, and 4 cables 266 that provide RF power to each of the four processing stations through an input port 267. Other similar multi-station processing apparatuses can have more or fewer processing stations depending on the implementation and, for example, the desired degree of parallel wafer processing, size / space limitations, cost limitations, etc. Figure 2Also shown is a substrate transfer robot 275, which can operate under the control of a system controller 290 and is configured to move a substrate from a wafer cassette (not shown in Figure 2 ), enter the integrated circuit manufacturing chamber 263 from the load port 180, and reach one of the processing stations 251, 252, 253, and 254.

[0038] Figure 2 An embodiment of a system controller 290 for controlling the processing conditions and hardware states of the processing apparatus 200 is also depicted. The system controller 290 may include one or more memory devices, one or more mass storage devices, and one or more processors. The one or more processors may include a central processing unit, analog and / or digital input / output connectors, a stepper motor controller board, and the like. In some embodiments, the system controller 290 controls all activities of the processing tool 200. The system controller 290 executes system control software stored in the mass storage device, which may be loaded into the memory device and executed on the hardware processor of the system controller. The software executed by the processor of the system controller 290 may include instructions for controlling timing, gas mixtures, manufacturing chamber and / or station pressures, manufacturing chamber and / or station temperatures, wafer temperatures, substrate pedestals, chucks, and / or susceptor positions, the number of cycles performed on one or more substrates, and other parameters of a particular process performed by the processing tool 200. These programmed processes may include various types of processes, including but not limited to: processes related to determining the amount of deposition on the surface inside the chamber, processes including multiple cycles related to the deposition of a film on a substrate, and processes related to the clean room. The system control software executable by one or more processors of the system controller 290 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 required to perform various tool processes.

[0039] In some embodiments, the software for execution by the processor of the system controller 290 may include input / output control (IOC) sequence instructions for controlling the above various parameters. For example, each stage of the deposition of a substrate and the deposition cycle may include one or more instructions executed by the system controller 290. Instructions for setting the processing conditions of the ALD / CFD deposition processing stage may be included in the corresponding ALD / CFD deposition recipe stage. In some embodiments, the recipe stages may be arranged sequentially such that all instructions for a processing stage are executed simultaneously with that processing stage.

[0040] In some embodiments, other computer software and / or programs stored on the mass storage device of the system controller 290 and / or on a memory device accessible to the system controller 290 may be employed. Examples of programs or program segments for this purpose include a substrate positioning program, a process gas control program, a pressure control program, a heater control program, and a plasma control program. The substrate positioning program may include program code for a processing tool component that loads a substrate onto the pedestal 108 of ( Figure 2 and) controls the spacing between the substrate and other components of the processing apparatus 200. The positioning program may include instructions for appropriately moving the substrate into and out of the reaction chamber as needed to deposit a film on the substrate and clean the chamber.

[0041] The process gas control program may include program code for controlling the gas composition and flow rate and optionally for flowing gas into one or more processing stations prior to deposition to stabilize the pressure in the processing stations. In some embodiments, the process gas control program includes instructions for introducing gas during film formation on a substrate in the reaction chamber. This may include introducing gas for one or more substrates in a batch of substrates for different numbers of cycles. The pressure control program may include program code for controlling the pressure in the processing stations by adjusting, for example, a throttle valve in the exhaust system of the processing station, the gas flow rate into the processing station, etc. The pressure control program may include instructions for maintaining the same pressure during deposition for different numbers of cycles on one or more substrates during batch processing.

[0042] The heater control program may include program code for controlling the current flowing to the heating unit 110 for heating the substrate of ( Figure 1 and). Alternatively, the heater control program may control the delivery of a heat transfer gas (e.g., helium) to the substrate.

[0043] In some embodiments, there may be a user interface associated with the system controller 290. The user interface may include a display screen, a graphical software display of the apparatus and / or processing conditions, and user input devices such as a pointing device, a keyboard, a touch screen, a microphone, etc.

[0044] In some embodiments, the parameters adjusted by the system controller 290 may relate to processing conditions. Non-limiting examples include process gas composition and flow rate, temperature, pressure, plasma conditions, etc. These parameters may be provided to the user in the form of a recipe, which the user may input using the user interface. The recipe for a batch of substrates may include a compensated cycle count for one or more substrates within the batch to account for thickness trends during processing of the batch.

[0045] Signals for monitoring the process can be provided through analog and / or digital input connections of system controller 290 from various process tool sensors. Signals for controlling the process can be output through analog and / or digital input connections of process tool 200. Non-limiting examples of process tool sensors that can be monitored include mass flow controllers, pressure sensors (such as pressure gauges), thermocouples, and the like. Sensors can also be included that are used to monitor and determine the buildup on one or more surfaces inside the chamber and / or the thickness of a material layer on a substrate within the chamber. Appropriately programmed feedback and control algorithms can be used with data from these sensors to maintain process conditions.

[0046] System controller 290 can provide program instructions for implementing the deposition process described above. The program instructions can control various process parameters, such as DC power level, pressure, temperature, number of cycles for the substrate, amount of buildup on at least one surface inside the chamber, and the like. The instructions can control the parameters to operate the in-situ deposition of the film stack according to the various embodiments described herein.

[0047] For example, the system controller can include control logic for performing the techniques described herein, such as (a) determining the amount of deposited material currently accumulated on at least one internal region inside the deposition chamber, applying the determined amount of deposited material or a parameter derived therefrom to the relationship between (i) the number of ALD cycles required to achieve a target deposition thickness and (ii) a variable representative of the amount of accumulated deposited material to obtain a compensated number of ALD cycles for producing the target deposition thickness given the current amount of deposited material accumulated on the internal region inside the deposition chamber, and performing the compensated number of ALD cycles on one or more substrates in the batch of substrates. The system can also include control logic for determining that the accumulated amount in the chamber has reached an accumulation limit and stopping the processing of the batch of substrates in response to that determination, and for causing cleaning inside the chamber.

[0048] In addition to the foregoing determined functions and / or operations performed by Figure 2 system controller 290, the controller can additionally control and / or manage the operation of RF subsystem 295, which can generate RF power and transmit it via RF input port 267 to integrated circuit manufacturing chamber 263. As further described herein, such operations can involve, for example, determining upper and lower thresholds for the RF power to be delivered to integrated circuit manufacturing chamber 263; determining the actual (e.g., real-time) level of RF power delivered to integrated circuit manufacturing chamber 263, RF power activation / deactivation times, RF power on / off durations, operating frequencies, and the like.

[0049] In certain embodiments, the integrated circuit fabrication chamber 263 may include input ports in addition to the input port 267 ( Figure 2 additional input ports not shown in). Thus, the integrated circuit fabrication chamber 263 may utilize eight RF input ports. In certain embodiments, the processing stations 251-254 of the integrated circuit fabrication chamber 165 may each utilize first and second input ports, where the first input port may transmit a signal having a first frequency and the second input port may transmit a signal having a second frequency. The use of dual frequencies may result in improved plasma characteristics, which may lead to deposition rates within certain limits and / or more easily controlled deposition rates. Dual frequencies may result in other desirable outcomes, different from those described herein. In some embodiments, frequencies between about 300 kHz and about 300 MHz may be utilized.

[0050] In Figure 2 , the RF power from the RF signal source 276 may be distributed among four output channels, which may be coupled to a corresponding one of the input ports 267 of the integrated circuit fabrication chamber 263. In at least certain embodiments, it may be useful to divide the RF power from the RF signal source 276 into relatively equal parts (e.g., differing by about +1%). Thus, in an example, if the RF signal source 276 provides an output power of 1000 W, then approximately 250 W (+1%) is transmitted to each input port 267 of the fabrication chamber 263.

[0051] Figure 3 shows a power-versus-time curve of the RF power coupled to a station of a multi-station integrated circuit fabrication chamber. In Figure 3 , the vertical axis represents the power delivered, which corresponds to the total power delivered to the fabrication chamber by an RF distribution unit such as ( Figure 2 the) single-input RF distribution unit 289. As indicated by the fluctuating curve of the total input power, the power delivered to the single-input RF distribution unit may vary significantly, e.g., it may include variations of up to 100 W, 150 W, or 200 W. Although Figure 3 depicts the total power input and the power input curves for the first and second processing stations (Sta1 and Sta2), in other embodiments, power may be coupled to more stations of a multi-station fabrication chamber, such as 3 stations, 4 stations, 5 stations, etc.

[0052] Power fluctuations may occur in the power delivered to a single-input RF distribution unit in response to different RF loads corresponding to individual stations in a multi-station integrated circuit fabrication chamber 263. For example, during a transition within a station in fabrication chamber 263, such as during a gas purge used in an atomic layer deposition process, the RF load impedance presented by an individual station (e.g., one of stations 251, 252, 253, 254) may increase. In some cases, during the purge portion of an atomic layer deposition cycle, when a precursor gas is purged or withdrawn from a processing station, the load impedance presented by a particular station can increase significantly. This increase in load impedance can be used to reduce the power coupled to the processing station. Conversely, during a portion of the atomic layer distribution cycle, when a certain volume of precursor gas is injected into the fabrication chamber, the input impedance presented by a particular station in the multi-station fabrication chamber can decrease significantly.

[0053] As Figure 3 shown, the RF power coupled to Station 1 (Sta1) is combined with the RF power coupled to Station 2 (Sta2) to form a total input power. Thus, although not shown in Figure 3 it can be understood that if the total power input increases, the power coupled to each station in the multi-station fabrication chamber can increase proportionally. Additionally, as the total power input decreases, the power coupled to each station in the multi-station fabrication chamber may decrease proportionally. However, it can also be understood that when the total power input to the multi-station fabrication chamber decreases while the power coupled to a particular station (e.g., Sta 1) increases, the power coupled to one or more other stations (e.g., Sta 2) decreases to maintain a substantially constant total power input.

[0054] In Figure 3 an example that can be related to a multi-station fabrication chamber having two processing stations (Sta 1 and Sta 2), if the total power input remains stable, such as at a level of 100% of a nominal value, the power coupled to an individual station in the multi-station fabrication chamber can remain at a value close to, for example, approximately 50% of the nominal value. However, also as Figure 3 shown, sometimes, the RF power coupled to a particular station (e.g., Sta1) may increase, perhaps increase for a short period of time, in response to, for example, a reduction in load impedance caused by converting a gaseous precursor into an ionized plasma material. In response to the increase in RF power at Sta 1, the RF power coupled to Sta2 can decrease by an amount corresponding to that increase over a similar short time period so that the sum equals the total power input. However, as Figure 3 shown, the total power input to the fabrication chamber may occasionally decrease, which may occur due to a mismatch between the output impedance of the RF power generator and the input impedance of the fabrication chamber. In this case, when the total power input decreases and the power of an individual station (e.g., Sta 1) increases, the power coupled to a different station (e.g., Sta2) may approachFigure 3 The lower threshold shown.

[0055] In certain embodiments, it may be undesirable for the power coupled to a single station to approach or reach a particular lower threshold. In some cases, in response to the power flow to a station in a multi-station fabrication chamber dropping below a lower threshold, that station may represent a high impedance load. As a result, the power coupled to other stations in the multi-station fabrication chamber may increase, which may undesirably increase the plasma density in other fabrication stations. In some cases, such an increase in power consumption at a station in a multi-station integrated circuit fabrication chamber may result in an arc discharge or other abnormal plasma event. In some cases, a power coupling below a threshold level may additionally result in an imbalance in the deposition rate occurring within the multi-station fabrication chamber. Thus, for example, if the power coupled to a station is below the lower threshold of Sta 2, it may be necessary to extend the fabrication process of Sta 2. Such an extension may include additional cycles, such as atomic layer deposition cycles, or may involve other additional processing and / or metrology to determine whether such a power reduction has a negative impact on the quality of the fabricated wafers.

[0056] Thus, to reduce the incidence of power flow dropping below a lower threshold, it may be useful to ensure that the RF power coupled from an RF power generator (e.g., RF signal source 276) remains at a consistent and relatively high level. Thus, an output port, such as Figure 2 the output port of a single-input RF distribution unit 289, may include a matching unit ( Figure 2 not shown in ) that can operate without user input to insert reactance components (e.g., series capacitors, series inductors, parallel capacitors, parallel inductors) into the input signal path starting from the RF signal source 276. In some cases, the single-input RF distribution unit 289 may utilize one or more computer processors, which are coupled to one or more memory circuits to allow execution of a set of computer-implemented instructions (e.g., algorithms) that can be used to dynamically insert reactance components into the signal path starting from the RF signal source 276.

[0057] Figure 4 is a diagram showing an RF matching unit coupled to a load impedance (Z L ) through a first or second length of transmission line according to an embodiment, and a corresponding impedance diagram in a representative impedance space.

[0058] In Figure 4 , schematic diagram 401 shows the RF signal source 276 being indicated as providing an input to the single-input RF distribution unit 289. As mentioned previously herein, the single-input RF distribution unit 289 may utilize reactance components (e.g., series capacitors, series inductors, parallel capacitors, parallel inductors), which in Figure 4In the figure, it is represented by Cser and Cshu. The values of the reactive components Cser and Cshu can be controlled by a computer, so as to dynamically adjust according to the change of the load presented by a single station in the multi-station integrated circuit manufacturing chamber 263. The load impedance presented by a single station in the manufacturing chamber 263 is Figure 4 represented as Z L . Although not shown in Figure 4 , the additional load impedance is presented by other stations in the manufacturing chamber 263 (e.g., Sta 1, Sta 2, Sta 3, etc.). In a specific embodiment, the single-station load Z L can correspond to a load with a relatively small real part and a relatively large imaginary part. In a specific example of Figure 4 , the impedance measured in the Z L plane can be characterized as having a real impedance value between about 1 - 10 ohms and an imaginary impedance value between about 10 - 40 ohms.

[0059] In a specific embodiment, an electrical short cable 266, such as a coaxial cable between about 35 inches and about 45 inches, can be used to couple the single-input RF distribution unit 289 to the input port of a station in the multi-station integrated circuit manufacturing chamber. Therefore, in an example of Figure 4 , transforming the load impedance presented by Z L in the representative impedance space 402 from the Z L plane to the control point at the output port of the single-input RF distribution unit 289 corresponds to rotating the Z L plane through approximately a portion of the wavelength in the transmission medium (such as a coaxial cable). In this case, the transmission medium can correspond to a 50-ohm coaxial cable. Therefore, rotating the load through a portion of the wavelength at the signal frequency (relative to the center point of the representative impedance space 402) transforms the load into an impedance value corresponding to an impedance having a real part between about 25 - 50 ohms and a reactive component between about 100 - 200 ohms. The representative impedance space 402 shows that point (1) is rotated through path (2), and path (2) corresponds to approximately a portion of a wavelength to reach point (3).

[0060] It can be understood that Figure 4 the representative impedance space 402 includes a region with relatively low impedance sensitivity (corresponding to the interval of the representative impedance space where the real and imaginary parts of the impedance are less than about 100 ohms). The representative impedance space 402 can additionally include a region with relatively high impedance sensitivity (corresponding to the interval of the impedance space where the real and imaginary parts of the impedance are greater than about 100 ohms). Therefore, it can be understood that rotating the load impedance Z L in the plane through a portion of the wavelength has the effect of transforming the impedance Z LThe effect of transitioning from a region of low impedance sensitivity (e.g., corresponding to a region of relatively low real and imaginary impedance (e.g., a ratio of reactance to resistance < 2.5)) to a region of high impedance sensitivity (e.g., corresponding to a region of relatively high real and imaginary impedance (e.g., a ratio of reactance to resistance > 2.5)). However, as further discussed with respect to Figure 5A it may, in some cases, be difficult to determine the exact values of the reactive components (e.g., Figure 4 Cser and Cshu) of, for example, in order to obtain a susceptance or inductance that provides a conjugate match or other type of match for delivering maximum power flow and minimum reflected power to the load impedance Z L

[0061] Figure 5A and 5B depicts the impedance sensitivity at the control points of an RF matching unit in response to different lengths of transmission lines according to an embodiment. As Figure 5A shown, it may be problematic to determine the real and imaginary parts necessary to achieve a match (e.g., conjugate match), which can result in a low reflection coefficient if the load impedance is in a high impedance sensitivity region. Thus, transforming the impedance, for example, by an electrical short transmission line (at frequencies between 10 and 100 MHz), can result in an undesirably high standard deviation of the impedance introduced by resistive and reactive circuit elements. Thus, the effort to match such a load may require multiple iterations as resistive and reactive elements are inserted into the matching network, tested to determine the effect of inserting such elements on the reflection coefficient (or voltage standing wave ratio), and then adjusted and re-measured in an effort to reduce the reflection coefficient below a threshold. Such impedance transformation is shown in Figure 4 a representative impedance space 402 where the load impedance ZL at point (1) is in a region of low impedance sensitivity. Rotating the load impedance Z L from point (1) through path (2) in the representative impedance space results in the load impedance Z

[0062] being transformed to point (3) within a region of high impedance sensitivity. Figure 4 However, referring again to L a RF cable (266) having a greater electrical length at frequencies between approximately 10 MHz and approximately 100 MHz can be used to transform the load impedance Z Figure 4 from a first region of low impedance sensitivity to a second region of low impedance sensitivity in the representative impedance space 403 of​Figure 4 For example (lower right portion), a 15-foot coaxial cable transmission line represents slightly more than one-half wavelength. It can also be understood that this rotation through path (4) avoids attempting to provide conjugate matching in regions of high impedance sensitivity.

[0063] Figure 5B illustrates the uncertainty in the real and imaginary impedances corresponding to the point (5) indicated in the representative impedance space 403 ( Figure 4 ). As Figure 5B shown, the uncertainty around point (5) corresponds to a relatively low standard deviation in the impedance introduced by the reactive element to provide conjugate matching. Thus, matching such a load may only require a single measurement of the reflection coefficient, followed by insertion of appropriate resistive and / or reactive circuit elements to drive the measured reflection coefficient below a threshold value.

[0064] However, it should be noted that in addition to the regions of low impedance sensitivity and high impedance sensitivity, Figure 4 the representative impedance spaces 402 and 403 can include resonance and anti-resonance intervals. For example, referring to impedance space 403, the transformation of the load impedance (Z L ) from point (1) to point (5) via an electrically long (e.g., between about 10 feet and about 20 feet) coaxial cable corresponds to the cross-resonance and anti-resonance points of the impedance space. For example, the transformation of the load impedance Z L from point (1) through path (4) on the representative impedance space 403 is shown as the intersection point (6), which can correspond to a point of theoretically infinite impedance. In this case, the voltage present on the transmission line (e.g., coaxial cable) may increase to relatively high values while the current decreases to relatively low values. Such high voltage values occurring in the transmission line in response to traversing the anti-resonance point (6) may cause dielectric breakdown of the coaxial cable and / or lead to other undesirable consequences.

[0065] It should be noted that in a particular embodiment, the impedance transformation can occur from a region with a first impedance sensitivity to a region with a second impedance sensitivity.

[0066] Path (4) shown on the representative impedance space 403 also crosses or passes through point (7), which can represent a point of theoretically zero (0) impedance. At this point, the voltage present on the transmission line (e.g., coaxial cable) may decrease to very low or negligible values while the current increases to very high values. Such high current values may cause the coaxial cable to overheat, which may damage the coaxial cable and / or the RF signal source 276.

[0067] In addition, in addition to traversing the resonance (e.g., high current / low voltage) points and anti-resonance (e.g., high voltage / low current) points, using a longer cable (e.g., a 15-foot cable) may result in other adverse consequences, such as increased resistance loss. In addition, using a longer cable may cause cable routing problems, where the excess cable length must be coiled, stored, or otherwise accounted for to avoid interfering with other equipment associated with the fabrication chamber. For example, the coiling of such excess cable length may produce parasitic effects, where adjacent portions of the coiled cable affect each other, which may result in an increase in capacitance and, in turn, affect the characteristic impedance (Z0) of the cable.

[0068] Therefore, for the reasons described above, it may be necessary to use an electrically small transmission line (e.g., a coaxial cable from about 10 inches to 50 inches) rather than an electrically longer transmission line (e.g., a coaxial cable from about 10 feet to 20 feet). In this document, the term "electrically small" refers to a transmission line that transfers impedance from a region of relatively high impedance sensitivity to a region of relatively low impedance sensitivity without traversing the transmission line resonance or transmission line anti-resonance at frequencies smaller than the frequency of the signal generated by the RF signal generator in the medium of the transmission line. Thus, as an example, a 40-inch transmission line that transmits a signal between 1 MHz and 50 MHz can be classified as electrically small because transferring the load impedance Z L from point (1) in the representative impedance space to point (3) does not traverse the anti-resonance point (6). On the other hand, a 15-foot transmission line that transmits a signal between about 1 MHz and 50 MHz can be classified as not electrically small because transferring the load impedance Z L from point (1) in the representative impedance space to point (5) traverses the anti-resonance point (6).

[0069] Figure 6A and 6B is a schematic diagram showing the use of an electrically small transmission line and reactive components according to an embodiment, the electrically small transmission line and reactive components being arranged to transfer the impedance of a control point from a region of relatively high impedance sensitivity in the impedance space to a region of relatively low impedance sensitivity in the impedance space.

[0070] As Figure 6A shown, an electrically long (e.g., 15-foot) cable is used to transfer the load impedance (ZL), which represents the load presented by the processing station of the multi-station integrated circuit fabrication chamber 263. As previously referenced Figure 4 and 5A discussed with 5B, the load impedance (Z L) can be transformed from a first point in the region of low impedance sensitivity to a second point in the region of low impedance sensitivity. This control can be achieved at the single-input RF distribution unit 289 through a computer-controlled matching network (e.g., by executing an appropriate algorithm). However, as also mentioned previously, using an electrically long (e.g., 15-inch) cable or other transmission lines that allow traversing resonant or anti-resonant points of the representative impedance space may have adverse consequences such as increased resistive losses, parasitic capacitance variations, cable routing / storage issues, and so on.

[0071] Therefore, to avoid the above-mentioned drawbacks, an electrically small cable can be utilized along with an appropriate reactive circuit to transform the load impedance from the plane corresponding to the input port of the station of a multi-station fabrication chamber to the desired control point. A particular implementation can overcome the drawbacks of using an electrically small cable, such as transforming the load impedance from a region of low impedance sensitivity to a region of high impedance sensitivity. Thus, in Figure 6B , the load impedance (Z L ) is shown as being transformed from point (1) to point (2A). As described previously in this document, this transformation corresponds to a transformation of the impedance from a region of low impedance sensitivity to a region of high impedance sensitivity. However, by inserting a lumped-element shunt inductor (e.g., Figure 6B 's L1), the impedance at the control point of a single RF distribution unit moves in the representative impedance space along the path created by inserting L1. Thus, it can be understood that this transformation of the impedance of the control point may be desirable because it helps avoid the need for matching in the high impedance sensitivity portion of the impedance space. By using a lumped-element series reactance, such as inserting C1 in the circuit, as Figure 6B shows, an additional transformation of the load impedance from a high impedance sensitivity range to a low impedance sensitivity range can be achieved. It can be understood that the insertion of this reactance causes the movement of the control point, such as from Figure 6B 's point (3A) to point (4) in the impedance space.

[0072] Thus, in certain embodiments, an electrically small transmission line can be utilized to couple the RF distribution unit to the input port and thus to the stations of a multi-station fabrication chamber. The use of such an electrically small transmission line can avoid various drawbacks, such as attempting to provide conjugate matching in regions of high impedance sensitivity. Such an electrically small transmission line can be used in combination with the insertion of circuit elements that introduce capacitive reactance or susceptance. The use of such circuit elements helps to transform the impedance from a region of high impedance sensitivity back to a region of low impedance sensitivity. Additionally, the use of such an electrically small transmission line, along with appropriate inductive / capacitive circuit elements that can be coupled as series or shunt devices, can provide relatively low resistive losses, reduce capacitive coupling, such as capacitive coupling between adjacent segments of a long and perhaps coiled transmission line, and avoid cable routing issues. In certain embodiments, by using an electrically small transmission line (e.g., a 10-inch to 50-inch coaxial cable), the resistive losses of the transmission line can be minimized, e.g., below 5%, below 10%, or below 15%. Additionally, although the insertion of various circuit elements such as shunt inductors and series capacitors may result in resistive losses, the combined losses, including the transmission line losses and the losses from the various circuit elements, can be kept below a nominal level, e.g., below about 20%.

[0073] While Figure 6B the examples utilize the insertion of a shunt inductor to provide susceptance and a series capacitor to provide capacitive reactance, in other embodiments, different circuit topologies can be used. Thus, depending on the specific impedance transformation requirements, other embodiments can include various combinations of capacitive elements, inductive elements, resistive elements, transmission line lengths, etc.

[0074] Figure 7 is a circuit diagram of a transmission line model according to one embodiment.

[0075] In Figure 7 a series inductor (L) and a parallel capacitor (C) are shown. Figure 7 The lumped elements of Figure 6B are contrasted with Figure 6B where a series capacitor (C1) and a parallel inductor (L1) are used. Thus, Figure 6B the lumped circuit elements of Figure 7 represent the relative (or opposite) model of the standard transmission line model of

[0076] In the foregoing detailed description, numerous specific details were set forth to provide a thorough understanding of the presented embodiments or implementations. The disclosed embodiments or implementations may be practiced without some or all of these specific details. In other instances, well-known process operations have not been described in detail so as not to unnecessarily obscure the disclosed embodiments or implementations. Although the disclosed embodiments or implementations are described in connection with specific embodiments or implementations, it should be understood that such description is not intended to limit the disclosed embodiments or implementations.

[0077] For purposes of describing the disclosed aspects, the foregoing detailed description is directed to certain embodiments or implementations. However, the teachings herein may be applied and implemented in a variety of different ways. In the foregoing detailed description, reference is made to the accompanying drawings. Although the disclosed embodiments or implementations have been described in sufficient detail to enable those skilled in the art to practice these embodiments or implementations, it should be understood that these examples are not limiting; other embodiments or implementations may be used and changes may be made to the disclosed embodiments or implementations without departing from the spirit and scope of the invention. Additionally, it should be understood that, unless otherwise indicated, the conjunctive "or" is intended to be inclusive in this context; for example, the phrase "A, B, or C" is intended to include the possibilities: "A", "B", "C", "A and B", "B and C", "A and C", and "A, B, and C".

[0078] In this application, the terms "semiconductor wafer", "wafer", "substrate", "wafer substrate", and "partially fabricated integrated circuit" are used interchangeably. Those skilled in the art will understand that the term "partially fabricated integrated circuit" can refer to a silicon wafer during any stage of the many stages of integrated circuit fabrication thereon. Wafers or substrates used in the semiconductor device industry typically include diameters of 200 mm, or 300 mm, or 450 mm. The foregoing detailed description assumes that the embodiments or implementations are practiced on a wafer or in connection with processes associated with the formation or manufacture of a wafer. However, the claimed subject matter is not limited thereto. Workpieces can have various shapes, sizes, and materials. In addition to semiconductor wafers, other workpieces that can utilize the claimed subject matter can include various articles, such as printed circuit boards, or the manufacture of printed circuit boards, and the like.

[0079] Unless the context of the present disclosure clearly requires otherwise, throughout the specification and claims, the words "comprise," "comprising," and the like shall be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is, the meaning of "including, but not limited to." Words using the singular or plural number generally also include the plural or singular respectively. When the word "or" is used in reference to a list of more than two items, that word covers all of the following interpretations of the word: any one of the items in the list, all of the items in the list, and any combination of the items in the list. The term "implementation" refers to implementations of the technologies and methods described herein, as well as physical objects embodying such structures and / or combinations of the technologies and / or methods described herein.

Claims

1. A device for providing a signal to a device, comprising: One or more electrical small transmission lines for coupling signals from one or more RF signal generators to a manufacturing chamber; And A reactance circuit for transforming the impedance of each of the one or more electrical small transmission lines from a region having a first impedance sensitivity to a region having a second impedance sensitivity.

2. The apparatus according to claim 1, wherein, The reactance circuit includes at least a series reactance.

3. The device according to claim 1, wherein The reactance circuit includes at least a shunt susceptance.

4. The device according to claim 1, wherein The reactance circuit includes at least a series reactance and a shunt susceptance.

5. The device according to claim 1, wherein The region having the first impedance sensitivity corresponds to a region of relatively high impedance sensitivity in impedance space, and wherein the real part of the impedance corresponds to a value greater than about 100 ohms.

6. The apparatus according to claim 1, wherein, The region having the second impedance sensitivity corresponds to a region of relatively low impedance sensitivity in impedance space, and wherein the real part of the impedance corresponds to a value less than about 100 ohms.

7. The device according to claim 1, wherein the reactance circuit for transforming the impedance avoids the possibility of the resonant transmission line at any frequency less than the frequency of the signal from one or more of the RF signal generators.

8. The device according to claim 1, wherein the electrical small transmission line in the one or more electrical small transmission lines corresponds to a transmission line that transforms the impedance from the relatively high impedance sensitivity region to the relatively low impedance sensitivity region without traversing the transmission line resonance at a frequency less than the frequency of the signal generated by the RF signal generator in the medium of the transmission line among the one or more RF signal generators.

9. The device according to claim 1, wherein the resistive loss of the electrical small transmission line combined with the loss of the reactance circuit corresponds to less than about 20%.

10. The device according to claim 1, wherein, The resistive loss of the electrical small transmission line corresponds to less than 10%.

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