Patent Application
20230031768
Radio frequency (“RF”) plasma-enhanced processing is extensively used in semiconductor manufacturing to etch different types of films, deposit thin films at low to intermediate processing temperatures, and perform surface treatment and cleaning. One characteristic of such processes is the employment of a plasma, i.e., a partially ionized gas, that is used to generate neutral species and ions from precursors inside a reaction chamber, provide energy for ion bombardment, and/or perform other actions. Radio frequency plasma-enhanced processing is performed by what are known as radio frequency processing devices.
Radio frequency plasma processing devices may include a radio frequency power generator that transmits a signal to a plasma reaction chamber. A radio frequency matching device, which may have a variable impedance, may be located between the radio frequency power generator and the plasma reaction chamber. The radio frequency matching device may be controlled, or otherwise tuned by varying the impedance of the radio frequency matching device. Tuning the radio frequency matching device reduces reflected power from the plasma reaction chamber and/or the radio frequency matching device, which may increase power that is transferred from the radio frequency power generator to the plasma reaction chamber and into the plasma process.
Tuning may be performed, in part, via variable capacitors which may have their capacitance adjusted by a motor. The goal of the adjustment is to provide the proper settings so that the combination of capacitors on different parts of a tuning network perform tuning so that power is efficiently transferred from input to the plasma chamber. In this context, efficiency relates to minimizing reflections and properly converting the impedance of the reaction chamber so that, viewing from the input, the forward power sees the proper impedance (e.g., 50 Ohms). Typical tuning algorithms utilize a fixed gain when calculating an adjustment for the variable capacitors.
The present disclosure is best understood from the following detailed description when read with the accompanying Figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.
Illustrative examples of the subject matter claimed below will now be disclosed. In the interest of clarity, not all features of an actual implementation are described for every example in this specification. It will be appreciated that in the development of any such actual implementation, numerous implementation-specific decisions may be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort, even if complex and time-consuming, would be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.
Further, as used herein, the article “a” is intended to have its ordinary meaning in the patent arts, namely “one or more.” Herein, the term “about” when applied to a value generally means within the tolerance range of the equipment used to produce the value, or in some examples, means plus or minus 10%, or plus or minus 5%, or plus or minus 1%, unless otherwise expressly specified. Further, herein the term “substantially” as used herein means a majority, or almost all, or all, or an amount with a range of about 51% to about 100%, for example. Moreover, examples herein are intended to be illustrative only and are presented for discussion purposes and not by way of limitation.
Embodiments of the present disclosure may provide systems and methods for tuning and otherwise controlling matching networks in radio frequency plasma processing devices. During operation, a radio frequency power generator may be energized to form a plasma within a reaction chamber. The plasma may be produced after a source gas is injected into the reaction chamber and power is supplied within the reaction chamber by the radio frequency power generator.
Under certain conditions, the power that is supplied to the reaction chamber may be reflected back from the reaction chamber. One cause of the reflected power may be a mismatch in the characteristic impedance of the system and the load formed by the plasma within the reaction chamber. To help prevent reflected power, an impedance matching network may be disposed between the radio frequency power generator and the reaction chamber. Such impedance matching networks may include a number of variable capacitors or other impedance elements. The variable capacitors may be tuned so that the complex load impedance within the reaction chamber matches the impedance of the radio frequency power generator.
While multiple methods of controlling or otherwise tuning impedance matching networks have been used, such methods may not reliably and efficiently result in impedance matching. Matching networks may include stepper motors, which have a specific number of steps that are a function unique to a particular stepper motor. During operation, a capacitor may be driven by a motor that has a range between zero and one hundred percent. Embodiments of the present disclosure may provide for the adjustment of a capacitor position based, at least in part, on “variable gain algorithm” where the gain value used in adjustment calculations comes from a pre-defined table or from a calculation based on currently and/or recently measured values. The calculations may or may not utilize values from the above-mentioned pre-defined table (i.e., gain values may be based on calculations alone). In some cases, the adjustments will have a greater magnitude when current conditions are further away from their target values and smaller magnitude when measurements are near target.
Embodiments of the present disclosure may provide systems and methods for the operation of matching networks using a variable gain algorithm to minimize, or at least address, the currently experienced problems identified above. For example, addressing the above issues may include adjusting a property of one or more capacitors within the matching network. In some embodiments, changes to impedance may be made in non-linear fashion. In some cases, a different gain values may be used for a high region of operation versus a low region of operation (See
Some capacitors may have two or more different regions of operation (e.g., regions that are stable for the uses disclosed herein). For example, a capacitor may have a region A and a region B that are both designated as regions of operation for that capacitor. If a fixed gain is used, adjustments may be stable in region A but too slow for region B. If you increase the fixed gain value, oscillations may occur in region A with stability for region B. Accordingly, it may be desirable to utilize variable gain values that are altered for the different regions of operation for distinct capacitors. Having optimized and variable gain values for both region A and region B (that are different from each other) may eliminate oscillations or slow-tuning. The non-linear nature of capacitors is outlined in table 1 below. Note that Table 1 is merely a single example used for illustration purposes, different capacitors will have different values than the those shown.
For some (if not most) systems it may be difficult to have the response of the control system be critically damped in all regions of operation with a fixed gain. The response of the control system may be over-damped and under-damped in different regions with a fixed gain. By varying the gain based on region of operation, the same system can be critically damped in all regions of operation.
Additionally, in some cases, the variable gain amount may be based on two related factors such as frequency and duty cycle settings from the radio frequency power generator. Accordingly, for a given frequency the amount of gain may be different based on different duty cycle values (See
Turning to
One or more of the first and second radio frequency power generators 105, 110 may deliver power to a reaction chamber 140 through one or more impedance matching networks 115, 120. In this example, radio frequency power flows from the first radio frequency power generator 105 through the first impedance matching network 115 to showerhead 130 into plasma in reaction chamber 140, to an electrode (not shown) other than showerhead 130, or to an inductive antenna (also not shown) that electromagnetically provides power to the plasma. The power flows from the plasma to ground and/or to pedestal 135 and/or to second impedance matching network 120. Generally, first impedance matching network 115 compensates for variations in a load impedance inside reaction chamber 140 so the combined impedance of showerhead 130 and first impedance matching network 115 is equal to the optimal load impedance of the first radio frequency power generator 105 by adjusting the reactive components (not separately shown), e.g., variable capacitors, within first impedance matching network 115.
In certain examples, first radio frequency generator 105 may provide power at a RF frequency between about 350 KHz and 162 MHz, while second radio frequency power generator 110 connected to pedestal 135 may supply power at a radio frequency lower than that of first radio frequency power generator 105. However, in certain implementations, second radio frequency power generator 110 may not supply power at a radio frequency lower than that of first radio frequency power generator 105. Typically, the frequencies of first and second radio frequency power generators 105, 110 are such that first radio frequency power generator 105 is at a radio frequency that is not an integer multiple, nor an integer fraction, of the frequency of second radio frequency power generator 110.
Impedance matching networks 115, 120 are designed to adjust their internal reactive elements such that the load impedance matches the source impedance. In other examples of the plasma processing system 100, different numbers of radio frequency power generators 105/110 may be used, as well as different numbers of impedance matching networks 115/120. Impedance matching networks 115/120 may include a number of internal components, such as inductors and variable capacitors that will be discussed in greater detail below.
Turning to
First variable capacitor 220 is connected to a second capacitor 225, which is connected to a ground 230. First variable capacitor 220 and second capacitor 225 are also connected to a third variable capacitor 235. Third variable capacitor 235 may include a capacitor with a capacitance range of approximately 10-2000 pF. Third variable capacitor 235 is also connected to an inductor 240, which further connects to splitter branch 210. Third variable capacitor 235 may be used for adjusting the phase and/or magnitude for impedance matching network 200 that includes splitter branch 210 (inner branch to outer branch).
Splitter branch 210 receives radio frequency power from matching branch 205, which splits the received radio frequency power between a fourth variable capacitor 245 and a fifth variable capacitor 250. Fourth variable capacitor 245 and fifth variable capacitor 250 control the current split ratio of splitter branch 210. Fourth variable capacitor 245 may have a capacitance range of approximately 10-2000 pF while fifth variable capacitor 250 may have a capacitance range of approximately 10-2000 pF.
Fifth variable capacitor 250 is connected to an inner coil 255 (e.g., as mentioned above, an inductive antenna that electromagnetically provides power to the plasma). Between fifth variable capacitor 250 and inner coil 255 on the inner branch section of splitter branch 210, one or more sensors 260 may be disposed. Sensor 260 may be used to measure, for example, voltage between fifth variable capacitor 250 and ground 275. Similarly, fourth variable capacitor 245 is connected to an outer coil 265 on the outer branch section of splitter branch 210. Between fourth variable capacitor 245 and outer coil 265, one or more sensors 270 may be disposed. Sensors 270 may be used to measure, for example, voltage between fourth variable capacitor 245 and ground 290.
Inner coil 255 may further be connected to a ground 275 and outer coil 265 may be connected to circuitry that includes a sensor 280 and a sixth capacitor 285. Sensor 280 may be used to measure, for example, voltage between outer coil 265 and ground 290. Inner coil 255 and outer coil 265 may be located outside of the circuitry of the matching network 200, as indicated by offset box 295.
As discussed above, the impedance matching network 200 in
The impedance matching network 200, which in one embodiment may be employed as a current split ratio matching network, may be controlled using a programmable logic controller, such as the computing device 825, shown in
In other embodiments, the circuitry of matching network 200 may include fewer or additional components and the orientation of the circuitry may differ. For example, fewer or greater numbers of variable capacitors, inductors, sensors, and the like may be present. Additionally, in certain embodiments, a different orientation of coils, antennas, and the like may be used to provide tuned radio frequency power to a reaction chamber, such as the reaction chamber 140 shown in
Turning to
Reaction chamber 310 may include various components that allow for the processing of a manufacturing operation, such as those associated with the semiconductor industries. Reaction chamber 310 may include one or more sensors (not shown) for measuring certain properties occurring within reaction chamber 310. Reaction chamber 310 may also include a pedestal (also not shown) on which substrates to be manufactured may be placed during operation. Reaction chamber 310 may also include or otherwise be connected to coils (not individually shown), such as those discussed above, as well as showerheads, etc.
Radio frequency plasma processing device 300 may also include a matching network 315. Matching network 315 may be located between radio frequency power generator 305 and reaction chamber 310. Matching network 315 may include variable capacitors (not shown), as well as other components to balance impedance between radio frequency power generator 305 and reaction chamber 310, as discussed in greater detail above. For example, to transform the impedance of reaction chamber 310 to the “ideal” load impedance of the radio frequency power generator 305. During operation, the matching network may be tuned, e.g., by adjusting capacitor positions, in order to provide the matching impedances. The adjustments may be determined, in part, using a variable gain algorithm as described herein.
During operation, as power is supplied from radio frequency power generator 305 to a plasma (not shown) within reaction chamber 310, a condition may occur, such as power may be reflected from reaction chamber 310. Such reflected power may result in undesirable conditions that result in inefficient processing, damage to a substrate, damage to components of radio frequency plasma processing device 300, and the like. To resolve the condition and improve operability of radio frequency plasma processing device 300, a tuning module 337 includes programmable logic controller 335 that may provide commands to matching network 315 to adjust a capacitor position, thereby providing matching impedances to minimize reflected power. Programmable logic controller 335 may be connected to storage device 340 to store these commands or data obtained during operation.
During operation, programmable logic controller 335 may identify a capacitor within matching network 315. For example, if the impedance matching network 315 is implemented in the manner shown in
Adjustments to variable capacitors may be made in different ways. In one example, adjustments are made by changing the capacitance of the capacitor using a stepper motor associated with the capacitor. In some cases, a zero step value may represent the point of minimum capacitance within a capacitor's usable range. That same capacitor may have a maximum step value (e.g., 1000 steps) the represents the point of maximum capacitance within the capacitor's usable range. During operation, the capacitance of the capacitor may be varied by changing the step value to a number between zero and 1000, for example.
To assist in a variable gain algorithm implementation, like that of the present disclosure, different amounts of adjustments may be impacted by a gain value that is either calculated or determined from a pre-defined table. Examples of calculations and gain value tables are discussed below. These calculations or tables may be stored in programmable logic (e.g., for use by programmable logic controller 335) or in a database (e.g., database on storage device 340), which may be used during operation to adjust operation of matching network 315. As such, the impedance for a particular capacitor position may be determined during operation of matching network 315. Using the measured impedance for each position of the capacitors for matching network 315, a table is constructed reflecting variable gain adjustments to apply to one or more of the capacitors, thereby optimizing the tuning conditions for a plasma processing device.
Turning to
Techniques disclosed herein may control speed with which a variable capacitor is adjusted based on a match region of operation, and whether the capacitor is trying to increase or decrease capacitance to achieve the target match region of operation. Speed gains are scheduled in table 500 based on match region of operation (
As explained throughout this disclosure, using a variable gain may have improvements over previously implemented fixed gain adjustments. For example, a traditional motor speed adjustment may be determined by a calculation as shown here:
Polarity×Gain×SpeedtoSignal×Error_Signal≤Speed Limit
where: Polarity indicates direction of capacitor movement; Gain is traditionally a fixed value; Speed_to_Signal is typically a fixed value; and Error_signal indicates a distance from a match target region.
Using a variable gain adjustment, the above Gain value is not fixed. The Gain value may be obtained from an equation and/or from a table. The equation may or may not utilize pre-defined values from a table.
Further, one example equation to determine control of a variable capacitor speed based on a match region of operation (Region for short) is shown here:
Gain=Scalar*eRegion*Exponent
Another example equation for dynamic averaging (as discussed above) for use with a variable gain adjustment is shown here:
ErrorFilt(n)=alpha×ErrorRaw(n)+[1+alpha]×ErrorFilt(n−1), 0<alpha<1
where: alpha is decreased as you approach match target region.
Note this is an example of a recursive equation where a filtered value (ErrorFilt current) is utilized to determine a next filtered value (ErrorFilt next) based on an unfiltered adjustment value (ErrorRaw). Dynamic averaging may be implemented using a rolling average within a fixed window or with a dynamic window based on a distance from the target match region of operation.
Turning to
Turning to
During operation, method 700 may further include determining a match region of operation (block 715), the match region of operation for a given capacitor indicates which gain values may be used, because, as explained above, it may be desirable to have different gain values to allow for critical damping within different regions of operation for a capacitor. Also, as explained above for
During operation, method 700, may further include determining a gain value (block 720) to use for adjustment of one or more capacitors within the match network. As mentioned above, typical matching networks utilize a fixed gain value, whereas the matching network described herein utilizes a variable gain feature. The gain value for disclosed embodiments may utilize a gain value obtained from one or more pre-defined tables where lookup is based on current (or recent) operational characteristics of the matching network. In other examples, the gain value may be derived from a calculation based on current attributes (e.g., measurements) of the matching network. In some cases, a combination of lookup and calculation may be utilized.
During operation, method 700 may further include determining capacitor adjustments based on the variable gain value determined previously (block 725). The adjustments may be made to effect the best available tuning parameters for the matching network. As mentioned above, a properly tuned matching network optimizes power delivered to the plasma chamber in operation.
During operation, method 700 may further include providing the adjustment information (block 730) to a capacitor to adjust that capacitor to a specific impedance based on the measured values. When the range of capacitor positions are known for a specific capacitor within a matching network, the capacitor positions may be tuned in order to provide an optimized capacitor position for a particular operation. Finally, during operation, method 700 may repeat (block 735 loop to block 715) itself throughout a plasma generation operation.
Turning now to
Referring now to
Each of the one or more CPUs 905 may be a single-core processor (not independently illustrated) or a multi-core processor (not independently illustrated). Multi-core processors typically include a plurality of processor cores (not shown) disposed on the same physical die (not shown) or a plurality of processor cores (not shown) disposed on multiple die (not shown) that are collectively disposed within the same mechanical package (not shown). Computer processing device 900 may include one or more core logic devices such as, for example, host bridge 910 and input/output (“IO”) bridge 915.
CPU 905 may include an interface 908 to host bridge 910, an interface 918 to system memory 920, and an interface 923 to one or more IO devices, such as, for example, graphics processing unit (“GFX”) 925. GFX 925 may include one or more graphics processor cores (not independently shown) and an interface 928 to display 930. In certain embodiments, CPU 905 may integrate the functionality of GFX 925 and interface directly (not shown) with display 930. Host bridge 910 may include an interface 908 to CPU 905, an interface 913 to IO bridge 915, for embodiments where CPU 905 does not include interface 918 to system memory 920, an interface 916 to system memory 920, and for embodiments where CPU 905 does not include integrated GFX 925 or interface 923 to GFX 925, an interface 921 to GFX 925.
One of ordinary skill in the art will recognize that CPU 905 and host bridge 910 may be integrated, in whole or in part, to reduce chip count, motherboard footprint, thermal design power, and power consumption. IO bridge 915 may include an interface 913 to host bridge 910, one or more interfaces 933 to one or more IO expansion devices 935, an interface 938 to keyboard 940, an interface 943 to mouse 945, an interface 948 to one or more local storage devices 950, and an interface 953 to one or more network interface devices 955.
Each local storage device 950 may be a solid-state memory device, a solid-state memory device array, a hard disk drive, a hard disk drive array, or any other non-transitory computer readable medium. Each network interface device 955 may provide one or more network interfaces including, for example, Ethernet, Fibre Channel, WiMAX, Wi-Fi, Bluetooth, EtherCAT, Device Net, Mod Bus, RS-232, or any other network protocol suitable to facilitate networked communications. Computer processing device 900 may include one or more network-attached storage devices 960 in addition to, or instead of, one or more local storage devices 950. Network-attached storage device 960 may be a solid-state memory device, a solid-state memory device array, a hard disk drive, a hard disk drive array, or any other non-transitory computer readable medium. Network-attached storage device 960 may or may not be collocated with computer processing device 900 and may be accessible to computer processing device 900 via one or more network interfaces provided by one or more network interface devices 955.
One of ordinary skill in the art will recognize that computer processing device 900 may include one or more application specific integrated circuits (“ASICs”) that are configured to perform a certain function, such as, for example, hashing (not shown), in a more efficient manner. The one or more ASICs may interface directly with an interface of CPU 905, host bridge 910, or IO bridge 915. Alternatively, an application-specific computing device (not shown), sometimes referred to as mining systems, may be reduced to only those components necessary to perform the desired function, such as hashing via one or more hashing ASICs, to reduce chip count, motherboard footprint, thermal design power, and power consumption. As such, one of ordinary skill in the art will recognize that the one or more CPUs 905, host bridge 910, IO bridge 915, or ASICs or various sub-sets, super-sets, or combinations of functions or features thereof, may be integrated, in whole or in part, or distributed among various devices in a way that may vary based on an application, design, or form factor in accordance with one or more example embodiments. As such, the description of computer processing device 900 is merely exemplary and not intended to limit the type, kind, or configuration of components that constitute a computing device suitable for performing computing operations, including, but not limited to, hashing functions. Additionally, one of ordinary skill in the art will recognize that computer device 900, an application specific computing device (not shown), or combination thereof, may be disposed in a standalone, desktop, server, or rack mountable form factor.
One of ordinary skill in the art will recognize that computer processing device 900 may be a cloud-based server, a server, a workstation, a desktop, a laptop, a netbook, a tablet, a smartphone, a mobile device, and/or any other type of computing device in accordance with one or more example embodiments.
In certain embodiments, advantages of the present disclosure may provide for computer executable instructions for adjustment of capacitor positions associated with matching networks in radio frequency plasma processing devices.
In certain embodiments, advantages of the present disclosure may provide improved adjustment settings for tuning of capacitors associated with matching networks in radio frequency plasma processing devices.
In certain embodiments, advantages of the present disclosure may provide a method for storing variable gain table information for plasma processing conditions, which may assist in properly controlling different capacitor trajectories when attempting to match the rapidly changing conditions that may be present during operation of a plasma chamber.
The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the disclosure. However, it will be apparent to one skilled in the art that the specific details are not required to practice the systems and methods described herein. The foregoing descriptions of specific examples are presented for purposes of illustration and description. They are not intended to be exhaustive of or to limit this disclosure to the precise forms described. Obviously, many modifications and variations are possible in view of the above teachings. The examples are shown and described in order to best explain the principles of this disclosure and practical applications, to thereby enable others skilled in the art to best utilize this disclosure and various examples with various modifications as are suited to the particular use contemplated. It is intended that the scope of this disclosure be defined by the claims and their equivalents below.
