Multi-channel microwave plasma impedance match tuning

Abstract

Embodiments disclosed herein may include a method for impedance match tuning. In an embodiment, the method includes setting a pin depth of a pin inserted into a hole in a dielectric resonator antenna (DRA) to adjust an input impedance of the DRA to match a load impedance of the DRA at a resonant frequency of the DRA. In an embodiment, the method further includes tuning a frequency of a microwave power amplifier that is electrically coupled to the microwave frequency to match the resonant frequency of the DRA. In an embodiment, the method further includes converting the load impedance of the DRA to a characteristic impedance of a coaxial transmission line with an impedance transformer, wherein the impedance transformer is electrically coupled between the microwave power amplifier and the DRA.

Description

[0001] MULTI-CHANNEL MICROWAVE PLASMA IMPEDANCE MATCH TUNING

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims priority to U.S. Patent Application No. 63 / 560,461, filed on March 1, 2024, the entire contents of which are hereby incorporated by reference herein.

[0004] FIELD

[0005] Embodiments relate to the field of semiconductor manufacturing and, in particular, to processes for tuning impedances in a multi-channel microwave plasma system.

[0006] DESCRIPTION OF RELATED ART

[0007] In some microwave plasma tools, an impedance match is provided between an antenna and a power amplifier in order to reduce reflected power in the system. Providing high quality matching significantly reduces the likelihood of damage to a microwave power amplifier, the fixed match, and the coaxial cables during operation of the microwave system. That is, when reflected power is too high, the reflected power is sent back to these components instead of being coupled into the plasma. The energy supplied by the reflected power can be sufficient to damage circuitry, cause arcing of various components, and / or otherwise harm such components.

[0008] When damage occurs to one or more of the components of the microwave power delivery system, the tool needs to be taken offline in order to diagnose and / or replace the damaged components. This can result in an increased cost of ownership for the microwave plasma tool, and throughput of substrates being processed in the fabrication facility is decreased. In some instances, damage to one or more of the components of the microwave power delivery system can require a processing recipe to be halted. This can result in misprocessed substrates that need to be scrapped or reworked. As such, device yield may also be impacted.

[0009] SUMMARY

[0010] Embodiments disclosed herein may include a method for impedance match tuning. In an embodiment, the method includes setting a pin depth of a pin inserted into a hole in a dielectric resonator antenna (DRA) to adjust an input impedance of the DRA to match a load impedance of the DRA at a resonant frequency of the DRA. In an embodiment, the method further includes tuning a frequency of a microwave power amplifier that is electrically coupled to the microwave frequency to match the resonant frequency of the DRA. In an embodiment, the method further includes converting the load impedance of the DRA to a characteristic impedance of a coaxial transmission line with an impedance transformer, wherein the impedance transformer is electrically coupled between the microwave power amplifier and the DRA.

[0011] Embodiments disclosed herein may also comprise a processing tool that includes a power supply, and a plurality of microwave lines coupled to the power supply. In an embodiment, each microwave line includes a microwave power amplifier, and an impedance match electrically coupled to the microwave power amplifier. The microwave line may also include a dielectric resonator antenna (DRA) coupled to the impedance transformer. In an embodiment the processing tool may also comprise a chamber, and a lid assembly to seal the chamber. In an embodiment, the plurality of DRAs are supported on the lid assembly, and the plurality of fixed matches are tuned to provide less than 10% reflected micro wave power along the microwave line.

[0012] Embodiments may also include a method for impedance match tuning that includes adjusting a load impedance of a plurality of pins with a first adjustment to match a load impedance of each of a plurality of the dielectric resonator antennas (DRAs) at a resonant frequency of each of the DRAs. In an embodiment, the first adjustment is done individually for each pin to DRA pair. The method may continue with refining the load impedance of the plurality of pins with a second adjustment. In an embodiment, the second adjustment is done in view of cross-talk between the plurality of DRAs. The method may continue with tuning a frequency of a plurality of microwave power amplifiers that are each electrically coupled to one of the plurality of pins in order to match the resonant frequency of the DRA. In an embodiment, the method may further include converting the load impedance for each of the plurality of DRAs to a characteristic impedance of a coaxial transmission line with one of a plurality of impedance transformers. In an embodiment, each of the plurality of impedance transformers is electrically coupled between different ones of the plurality of microwave power amplifiers and the plurality of DRAs.

[0013] BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1A is a cross-sectional illustration of a semiconductor processing tool for generating a micro wave plasma using a plurality of dielectric resonator antennas (DRAs), in accordance with an embodiment.

[0015] Figure IB is a plan view illustration of a DRA array over a dielectric plate for use in a microwave plasma semiconductor processing tool, in accordance with an embodiment. Figure 2 is a schematic illustrations of the microwave power delivery system of a semiconductor processing tool for generating a microwave plasma, in accordance with an embodiment.

[0016] Figure 3 A is a plot of the forward power over time of a microwave power delivery system, in accordance with an embodiment.

[0017] Figure 3B is a plot of the reflected power over time of a microwave power delivery system with a defective thermal break, in accordance with an embodiment.

[0018] Figure 4 is a cross-sectional illustration of a DRA with a pin that is inserted to a certain pin depth within a hole in a top surface of the dielectric puck, in accordance with an embodiment.

[0019] Figure 5A is a plot of the impedance of the input of the pin for three different pin depths, in accordance with an embodiment.

[0020] Figure 5B is a plot of the SI 1 parameter of the three different pin depths that shows the reflected power, in accordance with an embodiment.

[0021] Figure 6A is a plot of the Si l parameter during a frequency sweep of the vector network analyzer (VNA) used to match the resonant frequency of the DRA, in accordance with an embodiment.

[0022] Figure 6B is a plot of the R component and the X component of the impedance during the frequency sweep used to identify a resonant condition where the X-value is equal to 0 and the impedance matching R-value approximately matches the characteristic impedance of the coaxial transmission line, in accordance with an embodiment.

[0023] Figure 6C is a pair of plots of the reflected power (upper plot) during a frequency sweep (lower plot) of the microwave power amplifier over a frequency range, in accordance with an embodiment.

[0024] Figure 7 is a cross-sectional illustration of a conical impedance transformer that can be used for impedance matching in the microwave power delivery system, in accordance with an embodiment.

[0025] Figure 8 is a process flow diagram of a process for tuning the impedance of a microwave plasm processing tool, in accordance with an embodiment.

[0026] Figure 9 illustrates a block diagram of an exemplary computer system that may be used in conjunction with a processing tool, in accordance with an embodiment.

[0027] DETAILED DESCRIPTION

[0028] Embodiments described herein include apparatuses and processes for tuning impedances in a multi-channel microwave plasma system. In the following description, numerous specific details are set forth in order to provide a thorough understanding of embodiments. It will be apparent to one skilled in the art that embodiments may be practiced without these specific details. In other instances, well-known aspects are not described in detail in order to not unnecessarily obscure embodiments. Furthermore, it is to be understood that the various embodiments shown in the accompanying drawings are illustrative representations and are not necessarily drawn to scale. Various embodiments or aspects of the disclosure are described herein. In some implementations, the different embodiments are practiced separately. However, embodiments are not limited to embodiments being practiced in isolation. For example, two or more different embodiments can be combined together in order to be practiced as a single device, process, structure, or the like. The entirety of various embodiments can be combined together in some instances. In other instances, portions of a first embodiment can be combined with portions of one or more different embodiments. For example, a portion of a first embodiment can be combined with a portion of a second embodiment, or a portion of a first embodiment can be combined with a portion of a second embodiment and a portion of a third embodiment.

[0029] The embodiments illustrated and discussed in relation to the figures included herein are provided for the purpose of explaining some of the basic principles of the disclosure. However, the scope of this disclosure covers all related, potential, and / or possible, embodiments, even those differing from the idealized and / or illustrative examples presented. This disclosure covers even those embodiments which incorporate and / or utilize modern, future, and / or as of the time of this writing unknown, components, devices, systems, etc., as replacements for the functionally equivalent, analogous, and / or similar, components, devices, systems, etc., used in the embodiments illustrated and / or discussed herein for the purpose of explanation, illustration, and example.

[0030] Microwave plasma sources have seen a growth in importance in semiconductor processing environments. This can be due, at least in part, to the improved plasma performance that is provided when a microwave power source is used. Compared to traditional RF based plasmas (e.g., a capacitively coupled plasma (CCP), inductively coupled plasma (ICP), etc.), the flux of radicals provided to the substrate is higher for the microwave plasma. That is, a plasma density of the microwave plasma may be higher. At the same time, the ion energy at the substrate surface for a microwave plasma is lower than the ion energy at the substrate surface for a typical RF based plasma. More particularly, the ion energy is typically well below a general damage threshold of approximately 30eV.

[0031] Previous attempts to provide microwave power sources relied on magnetron solutions. The use of magnetrons results in bulky and hard to control systems. Magnetron solutions for implementing impedance matching are particularly problematic when a multi-channel microwave plasma tool is desired. A standard impedance matching solution for magnetron based architectures use a fixed frequency with a stub tuner (e.g., comprising a single stub or multiple stubs). Stub tuners are mechanically displaceable stubs that short-circuit a section of transmission line along the main signal line. By changing the positioning and / or geometry of the stubs, a variable impedance can be provided. Accordingly, the stubs and the associated actuators occupy a relatively large space. When a single microwave power delivery channel is used, this extra space is not particularly problematic. However, when multi-channel solutions are used, each channel needs a dedicated stub (or group of stubs) and the associated actuators. This can greatly increase the overall size of the tool, while also adding to the complexity of stub control. As such, it quickly becomes impractical to use multiple stub tuner solutions.

[0032] Accordingly, solid state solutions have been suggested for microwave power supplies. Solid state solutions provide enhanced control, while also shrinking the form factor of the power delivery system. One benefit of a reduced form factor is that a plurality of microwave channels can be used for a single processing tool. Instead of a fixed frequency, the solid state power amplifiers allow for variable frequency operation. Through control of various parameters of each microwave channel, the impedance matching can also be optimized to minimize or eliminate reflected power in the system. Such a multi-channel microwave plasma tool is shown in Figures 1A.

[0033] Referring now to Figure 1 A, a cross-sectional illustration of a semiconductor processing tool 100 is shown, in accordance with an embodiment. The semiconductor processing tool 100 may be a tool that processes a substrate 101 with plasma 105 that is generated through the use of microwave power. In an embodiment, the tool 100 may be a plasma deposition tool (e.g., a microwave plasma enhanced chemical vapor deposition (PECVD), a microwave plasma enhanced atomic layer deposition (PEALD), etc.), a microwave plasma etching tool, a micro wave plasma treatment tool, and / or the like. The substrate 101 may be any substrate suitable for fabricating semiconductor structures. For example, the substrate 101 may be a silicon wafer or any other semiconductor wafer. The substrate 101 may include any suitable form factor, such as a 300mm diameter, a 400mm diameter, or the like. In an embodiment, the substrate 101 may be supported on a pedestal 108. The pedestal may comprise a chucking device for securing the substrate 101 during processing. The chucking device may comprise an electrostatic chuck (ESC) or the like.

[0034] In an embodiment, the tool 100 may comprise a chamber 107. The chamber 107 may be suitable for supporting a vacuum environment within the chamber 107. The vacuum environment may be at a pressure suitable for the formation of the plasma 105. That is, a “vacuum environment” does not necessarily mean that a perfect vacuum environment is necessary. For example, the chamber 107 may support a rough vacuum (e.g., a pressure up to approximately 800Torr). Though, higher vacuum environments (i.e., lower pressures) may also be supported by the chamber 107. The low pressure environment may be provided through the use of an exhaust, a vacuum pump, and / or the like (not shown for simplicity). The chamber 107 may also include a slit valve (not shown) for passing the substrate 101 into and out of the chamber 107.

[0035] In an embodiment, the tool 100 may comprise a lid assembly 110. The lid assembly 110 may comprise a dielectric plate 112 that is provided opposite of the pedestal 108. The dielectric material of the dielectric plate 112 may comprise a ceramic in some embodiments. The dielectric plate 112 may comprise pathways, channels, holes, and / or the like (not shown) for distributing gasses into the chamber 107. In some instances, the dielectric plate 112 may be referred to as a showerhead. In an embodiment, a plurality of dielectric resonator antennas (DRAs) 115 may be distributed across the top surface of the dielectric plate 112. The DRAs 115 may each comprise a puck 1 16 and a pin 1 17 that is inserted into a hole into the top surface of the puck 116.

[0036] In an embodiment, the puck 116 is a dielectric material, such as a ceramic material or the like. The puck 116 may be the same dielectric material as the dielectric plate 112. Though, in other embodiments, the puck 116 and the dielectric plate 112 may be different materials. In an embodiment, the puck 116 is a cylindrical shaped object. Though, other axially symmetric shapes may also be used in some embodiments. The dimensions and material of the puck 116 may be chosen in order to set a desired resonant frequency for coupling microwave power into the plasma 105.

[0037] In an embodiment, the pin 117 is an electrically conductive pin (e.g., copper). The pin 117 may be inserted into the hole of the puck 116 to a desired depth. The depth into the puck 116 can be controlled in order to provide a desired response. In an embodiment, the opposite end of the pin 117 is coupled to a remainder of the microwave power supply system (which will be described in greater detail below). For example, the pin 117 may be coupled to a thermal break.

[0038] In the illustrated embodiment, the DR A 115 is shown as a bare dielectric material puck 116 with an electrically conductive pin 117. However, it is to be appreciated that the DRA 115 may comprise a housing that surrounds portions (or all of) the DRA 115. For example, an electrically conductive housing may be provided around the DRA 115. The electrically conductive housing may be grounded in some embodiments. In an embodiment, the housing may comprise aluminum or the like.

[0039] Referring now to Figure IB, a plan view illustration of a lid assembly 110 is shown, in accordance with an embodiment. In an embodiment, the lid assembly 110 may be similar to the lid assembly 110 described above with respect to Figure 1A. For example, the lid assembly 110 may comprise a dielectric plate 112. The dielectric plate 112 in Figure IB is shown as being circular. Though, in other embodiments, the dielectric plate 112 may have any shape. The dielectric plate 112 may comprise a ceramic material in some embodiments.

[0040] In an embodiment, a plurality of DRAs 115 may be distributed across the dielectric plate 112. The DRAs 115 may be similar to the DRAs 115 described above with respect to Figure 1 A. For example, each DRA 115 may comprise a puck and a pin. A housing may also surround the puck and pin of each DRA 115. In the illustrated embodiment, twenty five DRAs 115 are distributed across the dielectric plate 112. Though, it is to be appreciated that one or more DRAs 115 may be included in the lid assembly 110 in other embodiments. In a particular embodiment, nineteen DRAs 115 are provided on the dielectric plate 112.

[0041] In an embodiment, the layout of the plurality of DRAs 115 may include any suitable pattern. In a particular embodiment, the DRAs 115 may be provided in a symmetric pattern about the dielectric plate 112. Embodiments may also include a series of DRA 115 rings that are substantially concentric with each other, as shown in Figure IB. Other packing configurations may also be used in order to provide denser DRA 115 layouts.

[0042] The use of a plurality of DRAs 115 allows for greater control of the processing environment within the chamber 107. That is, the plasma 105 can be controlled with greater spatial variation. This allows for different plasma parameters to be applied to (for example) the center of the substrate 101 and the edge of the substrate 101. Variable control in this manner can lead to improved overall processing uniformity.

[0043] Referring now to Figure 2, a schematic illustration of a microwave power delivery system 220 is shown, in accordance with an embodiment. In an embodiment, the microwave power delivery system 220 may be coupled to a plasma processing tool similar to the tool 100 described in greater detail herein. The microwave power delivery system 220 may be a solid state microwave power delivery system 220. That is, the microwaves may be generated without the use of a magnetron or the like. Accordingly, a plurality of microwave lines 230 may be included within a reasonable form factor. In Figure 2, microwave lines 230A to 230N are provided as an example. The number of microwave lines 230 may be equal to the number of DRAs that are desired for the tool. For example, there may be one or more microwave lines 230, ten or more microwave lines 230, or twenty or more microwave lines 230. In a particular embodiment, there may be nineteen micro wave lines 230.

[0044] In an embodiment, the microwave power delivery system 220 may comprise a power supply 222. A single power supply 222 may supply power to each of the microwave lines 230. For example, coaxial cables 223 may electrically couple the power supply 222 to the plurality of microwave lines 230. The power supply 222 may be an AC / DC power supply in some embodiments. More particularly, the power supply 222 may be a solid state microwave power supply 222. While a single power supply 222 is shown in Figure 2, it is to be appreciated that two or more power supplies 222 may be used in the power delivery system 220 in other embodiments.

[0045] In an embodiment, the microwave lines 230 may each comprise a plurality of components that take the microwave power and deliver it to the plasma processing tool. In an embodiment, the microwave line 230 may comprise a microwave power amplifier 231, such as a solid state microwave power amplifier. The microwave power amplifier may be electrically coupled to an impedance transformer 235 by a coaxial cable 224. The impedance transformer 235 may be a conical impedance transformer (CIT) in some embodiments. A more detailed description of the impedance transformer 235 is provided in greater detail below. In an embodiment, the impedance transformer 235 is electrically coupled to the DRA 215. The DRA 215 may be similar to any of the DRAs described in greater detail herein. For example, the DRA 215 may comprise a puck 216 and a pin 217. The pin 217 may be coupled to the impedance transformer 235 by solder, a connector, or the like. The DRA 215 may be used to couple the microwave power to gasses within the chamber (not shown) in order to initiate and / or sustain a plasma within the chamber.

[0046] The impedance transformer 235 may be used to match an impedance of the DRA 215 to the characteristic impedance of the coaxial cable 224. This is done to reduce (or eliminate) reflected power in the system at a given frequency. For example, at an operating frequency of approximately 2,450MHz, the impedance of the coaxial cable 224 may be approximately 50 Ohms.

[0047] An example of the effect of microwave line 230 that has an impedance mismatch that leads to high reflected power is shown in Figures 3 A and 3B. Figure 3 A is a plot of the forward power in Watts over time, and Figure 3B is a plot of the reflected power in Watts over the same duration. As can be seen, for a given forward power, in each pulse there is a rapid increase in reflected power, as shown by the plurality of peaks 340. Ideally, the reflected power should be zero for each pulse of forward power. However, as shown in Figure 3B, the reflected power increases to a significant percentage of the forward power. In some instances, the reflected power may extend up to over 50% of the forward power. This can lead to multiple issues.

[0048] One problem is that the high reflected power can damage the microwave power delivery system 220. As such, when high values of reflected power are detected, the processing may be halted. This can occur in the middle of a processing recipe. As such, the substrates being processed may not be processed properly. The substrate may need to be scrapped or reworked. Therefore, yields and throughput are negatively impacted.

[0049] Alternatively, if the tool is not stopped in time, the reflected power can damage the microwave power amplifiers 231 or other components. This increases cost of ownership of the tool, as parts need to be replaced more frequently. Replacing components also results in down time for the tool, which can increase cost of ownership and reduce throughput.

[0050] Accordingly, embodiments disclosed herein may include an impedance match tuning process to achieve a low (or perfect) impedance matching condition for a multi-channel microwave plasma tool, such as tool 100. In an embodiment, the impedance match tuning process may include three operations. A first operation may set the input impedance of the pin of the impedance transformer to match the load impedance of the DRA at a resonant frequency of the DRA. The input impedance of the DRA may be set by modulating a pin depth into the DRA. In the case of a multi-channel microwave system, each impedance transformer may be set individually to set a rough level of impedance matching. A second level of impedance matching may be done to account for cross-talk between DRAs in order to refine the input impedance of all impedance transformers to further mitigate reflected power.

[0051] A second operation may include tuning the microwave power amplifier frequency to compensate the shift of resonant frequency of the DRA when plasma is ignited. The DRA’s resonant frequency depends on its geometrical dimension and dielectric constant of the material, and it is optimally designed to operate at center frequency of 2450MHz in vacuum (without plasma). When plasma is ignited, the resonant frequency of DRA can upshift by approximately 10-50 MHz, which depends on gas pressure, gas species, and process chamber condition. When microwave power amplifier frequency is tuned to match the DRA resonant frequency with plasma, this can lead to a low reflected power (e.g., approximately 10% reflected power or less, approximately 5% reflected power or less, or approximately 1% reflected power or less, or no reflected power).

[0052] A third operation may include using the impedance transformer to convert the DRA load impedance with plasma to the characteristic impedance of the coaxial transmission line as well. The impedance transformer may be a fixed matching network, such as a CIT.

[0053] The process may be done in the design phase of the manufacture of the multi-channel microwave plasma tool. Though, one or more of the operations may be modified at a subsequent time. For example, pin depth and microwave power amplifier frequency may be modulated and / or adjusted at a later time.

[0054] Referring now to Figure 4, a cross-sectional illustration of a portion of a lid assembly 410 is shown, in accordance with an embodiment. In an embodiment, the lid assembly 410 may comprise a dielectric plate 412 with a DRA 415 positioned over the lid assembly 410. The DRA 415 may comprise a puck 416 that is similar to any of the pucks described in greater detail herein. In an embodiment, a hole 419 may be provided into a top surface of the puck 416. The hole 419 may be at an axial center of the puck 416. In an embodiment, a pin 417 may be inserted into the hole 419. Controlling the pin depth PD can be used in order to adjust the input impedance of the DRA 415 to match the load impedance of the DRA 415 at a resonant frequency of the DRA 415. For example, the operating resonant frequency of the DRA 415 may be approximately 2,450MHz in some embodiments.

[0055] In an embodiment, a pin depth PD may be up to the entire rod depth RD (i.e. , the total length of the pin 417). For microwave plasma processing tools, the pin depth PD may generally be between 35 mm and 40mm. Though smaller pin depths PD or larger pin depths PD may also be used in other embodiments.

[0056] In an embodiment, the pin depth PD has a significant effect on coupling microwave power into the DRA 415. To achieve maximum coupling efficacy, the pin input impedance and the microwave frequency are substantially equal to the DRA load impedance (with plasma) and the DRA resonant frequency, respectively.

[0057] Referring now to Figures 5A and 5B, a pair of plots showing the input impedance of the DRA with an inserted pin 417 (Figure 5 A) and an Sn parameter of the of the DRA with an inserted pin 417 is shown, in accordance with an embodiment. As shown in Figure 5 A, a set of three pin depths PD are shown with lines 561, 562, and 563. Line 561 is the largest pin depth PD, line 562 is the middle pin depth PD, and line 563 is the smallest pin depth PD. AS shown, the middle pin depth PD of line 562 has a maximum of approximately 50 Ohms. This means by adjusting the pin depth, the impedance transformer (such as a CIT) is able to convert the load impedance of the DRA at a resonant frequency condition, to the characteristic impedance of coaxial cable.

[0058] In Figure 5B, the associated Sn parameters are shown with line 564 corresponding with line 561, line 564 corresponding with line 562, and line 566 corresponding with line 563. As shown, the S 11 parameter of line 565 has the deepest trough. This corresponds to the lowest value of reflected power of the various pin depths PD that are investigated in Figures 5A and 5B. Accordingly, the matched impedance results in the optimal reflected power (e.g., essentially no reflected power).

[0059] In an embodiment, the pin depth PD adjustment may be done on a channel-by-channel basis for a first pass of impedance tuning. After all channels have an initial tuning, the entire multi-channel system can be tuned again. This subsequent tuning process can be used to account for cross-talk between the plurality of DRAs 415 in the multi-channel microwave plasma system.

[0060] After the pin depth tuning operation, the microwave power amplifiers can each be tuned to a frequency to match the resonant frequency of the DRA with plasma. In an embodiment, the tuning process may be executed through the use of a frequency sweep. In an embodiment, the frequency sweep may be between 2,400MHz and 2,500MHz in some embodiments. An example of such a process is shown in Figures 6A - 6C.

[0061] In Figure 6A, the Sn parameter of a vector network analyzer (VNA) is shown across a range of frequencies during a frequency sweep. For example, between 2,400MHz and 2,500MHz a distinct trough is formed along line 671. The bottom of the trough indicates the frequency of the lowest reflected power. More particularly, the region of line 671 that falls below the -20dB line indicates a reflected power of approximately 1% or less. Accordingly, the targeted frequency for the microwave power amplifier is within this range. In the example shown in Figure 6A, the targeted frequency is around 2,435MHz and 2,445MHz.

[0062] Figure 6B shows a plot of the impedance in a complex form of Z=R+jX. Line 672 is the real portion R and line 673 is the reactance X. Ideally, the real portion R will be closely matched to the characteristic impedance (e.g., 50 Ohms) in order to optimize matching in the system. The reactance X should ideally be close to 0 to indicate a resonant condition has been reached. As shown, the frequency that corresponds to an impedance around 50 Ohms and a reactance of 0 is substantially equal to the ideal condition of the S I i parameter in Figure 6A (e.g., between approximately 2,435MHz and 2,445MHz). Accordingly, for the example shown in Figures 6A and 6B, the frequency of the microwave power amplifier can be set between approximately 2, 435MHz and 2,445MHz.

[0063] Figure 6C is a combined plot showing a frequency sweep on the microwave power amplifier (bottom plot) and a reflected power (top plot), in accordance with an embodiment. As shown by the line 675, the point of zero reflected power aligns with a frequency of approximately 2,440MHz (which is within the range predicted in Figures 6A and 6B. Accordingly, the microwave power amplifier frequency can be set to the frequency of line 675 in order to deliver micro wave power from the microwave power amplifier to the processing chamber with no reflected power. While particular frequencies are described with respect to Figures 6A - 6C, it is to be appreciated that changes to component geometries, materials (e.g., with different dielectric constants), processing conditions, and / or the like may result in the position of line 675 being shifted from what is shown in Figures 6A - 6C.

[0064] After the microwave power amplifier frequency is set, the impedance transformer is used to convert the DRA load impedance with plasma to the characteristic impedance of the coaxial transmission line (e.g., approximately 50 Ohms). This can be done through the design of the impedance transformer. An example of an impedance transformer, such as quarter wavelength impedance transforming (e.g., a CIT), is shown in Figure 7.

[0065] Referring now to Figure 7, a CIT 750 is shown, in accordance with an embodiment. In an embodiment, the CIT 750 may comprise a pin 717. The pin 717 of the CIT 750 may be the pin that is inserted into the DRA to a pin depth PD determined in the first operation of the tuning process. In an embodiment, the pin 717 passes through an output side 751 into an interior of a tapered outer conductor 753. The pin 717 may pass through a polymer ring 754, such as a Teflon ring. In an embodiment, the pin 717 may continue through an input side 752 of the CIT 750. A polymer ring 755, such as a Teflon ring, may be provided on the input side 752 of the CIT 750 as well. In an embodiment, the pin 717 is coupled to a connector 756 used to electrically couple the CIT 750 to a coaxial transmission line (not shown in Figure 7). The connector 756 may be an n- connector or the like. In the embodiment shown in Figure 7, the pin 717 is continuous through the entire height of the CIT 750. In other embodiments, the pin 717 may be coupled (e.g., by solder) to an inner conductor within the outer conductor 753. The inner conductor (or the pin 717) may be coupled to the connector 756 with a solder joint or the like as well.

[0066] In an embodiment, the impedance of the CIT 750 may be altered by changing various dimensions and / or geometries of the components of the CIT 750. Generally, the impedance take the form of Zo(0) = ]ZsZLor Zo(0) = L / C where Zs is the source (or input) impedance and ZL is the load (or output) impedance. The inductance L may have the equation L = I In and capacitance C may have the equation C = I — . In an embodiment, a is the radius of the inner In- a conductor (or pin 717 within the outer conductor 753), b is the inner radius of the outer conductor 753, and 1 is the length of the tapered coaxial line section.

[0067] Referring now to Figure 8, a process flow diagram of a process 880 for impedance match tuning for a multi-channel microwave plasma system is shown, in accordance with an embodiment. In an embodiment, the process 880 may begin with operation 881, which comprises setting a pin depth of a pin inserted into a hole in a DRA to adjust an input impedance of the DRA to match a load impedance of the DRA at a resonant frequency of the DRA. In an embodiment, operation 881 may include setting the pin depth for each pin in isolation. After each pin depth is individually set, the pin depth across the entire system can be refined to account for cross-talk between DRAs. More generally, the pin and the DRA may be one pair in a plurality of pairs of pins and DRAs. In such an embodiment, operation 881 may further comprise setting the pin depth for each pair individually, and refining the pin depth for each pair in order to account for cross-talk between DRAs. In an embodiment, the load impedance of the DRA comprises contributions from one or more of the DRA, a chamber wall condition within a chamber coupled to the DRA, process gaps within the chamber, or plasma properties within the chamber. In an embodiment, the hole is at an axial center of the DRA. In an embodiment, the pin depth is set to between 35mm and 40mm.

[0068] In an embodiment, the process 880 may continue with operation 882, which comprises tuning a frequency of a microwave power amplifier that is electrically coupled to the microwave frequency to match the resonant frequency of the DRA. In an embodiment, the frequency of the microwave power amplifier is tuned to between 2,400MHz and 2, 500 MHz. In an embodiment, the microwave power amplifier is a solid state microwave power amplifier.

[0069] In an embodiment, the process 880 may continue with operation 883, which comprises converting the load impedance of the DRA to a characteristic impedance of a coaxial transmission line with an impedance transformer. In an embodiment, the impedance transformer is electrically coupled between the microwave power amplifier and the DRA. In an embodiment the impedance transformer is a C1T or any other suitable quarter wavelength impedance transformer. In some embodiments, the pin may be part of the impedance transformer. In an embodiment, the characteristic impedance of the coaxial transmission line may be approximately 50 Ohms.

[0070] In an embodiment, a similar processes may be implemented to tune an entire multi-channel microwave plasma tool for improved impedance matching. Such an embodiment may include a process that comprises adjusting a load impedance of a plurality of pins with a first adjustment to match a load impedance of each of a plurality of the DRAs at a resonant frequency of each of the DRAs. In an embodiment, the first adjustment is done individually for each pin to DRA pair. In an embodiment, the process may further comprise refining the load impedance of the plurality of pins with a second adjustment, where the second adjustment is done in view of cross-talk between the plurality of DRAs.

[0071] In an embodiment, the process may further comprise tuning a frequency of a plurality of microwave power amplifiers that are each electrically coupled to one of the plurality of pins in order to match the resonant frequency of the DRA. In an embodiment, the process may further comprise converting the load impedance for each of the plurality of DRAs to a characteristic impedance of a coaxial transmission line with one of a plurality of impedance transformers. In an embodiment, each of the plurality of impedance transformers is electrically coupled between different ones of the plurality of microwave power amplifiers and the plurality of DRAs.

[0072] In an embodiment, the plurality of impedance transformers are each conical impedance transformers. In an embodiment, the plurality of DRAs comprises ten or more DRAs. For example, the plurality of DRAs may comprise nineteen DRAs. In an embodiment, the plurality of microwave power amplifiers are solid state devices.

[0073] Referring now to Figure 9, a block diagram of an exemplary computer system 900 of a processing tool is illustrated in accordance with an embodiment. In an embodiment, computer system 900 is coupled to and controls processing in the processing tool. Computer system 900 may be connected (e.g., networked) to other machines in a Local Area Network (LAN), an intranet, an extranet, or the Internet. Computer system 900 may operate in the capacity of a server or a client machine in a client-server network environment, or as a peer machine in a peer- to-peer (or distributed) network environment. Computer system 900 may be a personal computer (PC), a tablet PC, a set-top box (STB), a Personal Digital Assistant (PDA), a cellular telephone, a web appliance, a server, a network router, switch or bridge, or any machine capable of executing a set of instructions (sequential or otherwise) that specify actions to be taken by that machine. Further, while only a single machine is illustrated for computer system 900, the term “machine” shall also be taken to include any collection of machines (e.g., computers) that individually or jointly execute a set (or multiple sets) of instructions to perform any one or more of the methodologies described herein.

[0074] Computer system 900 may include a computer program product, or software 922, having a non- transitory machine-readable medium having stored thereon instructions, which may be used to program computer system 900 (or other electronic devices) to perform a process according to embodiments. A machine-readable medium includes any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computer). For example, a machine- readable (e.g., computer-readable) medium includes a machine (e.g., a computer) readable storage medium (e.g., read only memory (“ROM”), random access memory (“RAM”), magnetic disk storage media, optical storage media, flash memory devices, etc.), a machine (e.g., computer) readable transmission medium (electrical, optical, acoustical or other form of propagated signals (e.g., infrared signals, digital signals, etc.)), etc.

[0075] In an embodiment, computer system 900 includes a system processor 902, a main memory 904 (e.g., read-only memory (ROM), flash memory, dynamic random access memory (DRAM) such as synchronous DRAM (SDRAM) or Rambus DRAM (RDRAM), etc.), a static memory 906 (e.g., flash memory, static random access memory (SRAM), etc.), and a secondary memory 918 (e.g., a data storage device), which communicate with each other via a bus 930.

[0076] System processor 902 represents one or more general-purpose processing devices such as a microsystem processor, central processing unit, or the like. More particularly, the system processor may be a complex instruction set computing (CISC) microsystem processor, reduced instruction set computing (RISC) microsystem processor, very long instruction word (VLIW) microsystem processor, a system processor implementing other instruction sets, or system processors implementing a combination of instruction sets. System processor 902 may also be one or more special-purpose processing devices such as an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a digital signal system processor (DSP), network system processor, or the like. System processor 902 is configured to execute the processing logic 926 for performing the operations described herein.

[0077] The computer system 900 may further include a system network interface device 908 for communicating with other devices or machines. The computer system 900 may also include a video display unit 910 (e.g., a liquid crystal display (LCD), a light emitting diode display (LED), or a cathode ray tube (CRT)), an alphanumeric input device 912 (e.g., a keyboard), a cursor control device 914 (e.g., a mouse), and a signal generation device 916 (e.g., a speaker).

[0078] The secondary memory 918 may include a machine-accessible storage medium 931 (or more specifically a computer-readable storage medium) on which is stored one or more sets of instructions (e.g., software 922) embodying any one or more of the methodologies or functions described herein. The software 922 may also reside, completely or at least partially, within the main memory 904 and / or within the system processor 902 during execution thereof by the computer system 900, the main memory 904 and the system processor 902 also constituting machine-readable storage media. The software 922 may further be transmitted or received over a network 961 via the system network interface device 908. In an embodiment, the network interface device 908 may operate using RF coupling, optical coupling, acoustic coupling, or inductive coupling.

[0079] While the machine- accessible storage medium 931 is shown in an exemplary embodiment to be a single medium, the term “machine-readable storage medium” should be taken to include a single medium or multiple media (e.g., a centralized or distributed database, and / or associated caches and servers) that store the one or more sets of instructions. The term “machine-readable storage medium” shall also be taken to include any medium that is capable of storing or encoding a set of instructions for execution by the machine and that cause the machine to perform any one or more of the methodologies. The term “machine-readable storage medium” shall accordingly be taken to include, but not be limited to, solid-state memories, and optical and magnetic media.

[0080] In the foregoing specification, specific exemplary embodiments have been described. It will be evident that various modifications may be made thereto without departing from the scope of the following claims. The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense.

Claims

CLAIMSWhat is claimed is:

1. A method for impedance match tuning, comprising: setting a pin depth of a pin inserted into a hole in a dielectric resonator antenna (DRA) to adjust an input impedance of the DRA to match a load impedance of the DRA at a resonant frequency of the DRA; tuning a frequency of a microwave power amplifier that is electrically coupled to the DRA to match the resonant frequency of the DRA; and converting the load impedance of the DRA to a characteristic impedance of a coaxial transmission line with an impedance transformer, wherein the impedance transformer is electrically coupled between the microwave power amplifier and the DRA.

2. The method of claim 1, wherein the impedance transformer is a conical impedance transformer (CIT).

3. The method of claim 1, wherein the load impedance of the DRA comprises contributions from one or more of the DRA, a chamber wall condition within a chamber coupled to the DRA, process gaps within the chamber, or plasma properties within the chamber.

4. The method of claim 1, wherein the pin is part of the impedance transformer.

5. The method of claim 1 , wherein the frequency of the micro wave power amplifier is tuned to between 2,400MHz and 2,500MHz.

6. The method of claim 1, wherein the characteristic impedance of the coaxial transmission line is approximately 50 Ohms.

7. The method of claim 1, wherein the pin depth is set to between 35mm and 40mm.

8. The method of claim 1 , wherein the hole is in an axial center of the DRA.

9. The method of claim 1, wherein the pin and the DRA are one pair in a plurality of pairs of pins and DRAs, and wherein the method further comprises: setting the pin depth for each pair individually; and refining the pin depth for each pair in order to account for cross-talk between DRAs.

10. The method of claim 1, wherein the microwave power amplifier is a solid state microwave power amplifier.

11. A processing tool, comprising: a power supply; a plurality of microwave lines coupled to the power supply, wherein each microwave line comprises: a microwave power amplifier;an impedance match electrically coupled to the microwave power amplifier; and a dielectric resonator antenna (DRA) coupled to the impedance match; a chamber; and a lid assembly to seal the chamber, wherein the plurality of DRAs are supported on the lid assembly, and wherein the plurality of impedance matches are tuned to provide less than 5% reflected microwave power along each of the plurality of microwave lines.

12. The processing tool of claim 11, wherein the processing tool is a microwave plasma enhanced atomic layer deposition (PEALD) tool, a microwave plasma enhanced chemical vapor deposition (PECVD) tool, a microwave plasma etching tool, or a microwave plasma treatment tool.

13. The processing tool of claim 11, wherein the impedance transformer is a conical impedance transformer (CIT).

14. The processing tool of claim 11, wherein a pin extending from an output of the impedance transformer is inserted into a hole in the DRA, wherein a pin depth in the hole is between 35mm and 40mm.

15. The processing tool of claim 11, wherein resonant frequencies of the DRAs are between 2, 400MHz and 2,500MHz.

16. The processing tool of claim 11, wherein the plurality of microwave power amplifiers are solid state microwave power amplifiers.

17. A method for impedance match tuning, comprising: adjusting a load impedance of a plurality of pins with a first adjustment to match the load impedance of each of a plurality of dielectric resonator antennas (DRAs) at a resonant frequency of each of the DRAs, wherein the first adjustment is done individually for each pin to DRA pair; refining the load impedance of the plurality of pins with a second adjustment, wherein the second adjustment is done in view of cross-talk between the plurality of DRAs; tuning a frequency of a plurality of microwave power amplifiers that are each electrically coupled to microwave frequency in order to match the resonant frequency of the DRA; and converting the load impedance for each of the plurality of DRAs to a characteristic impedance of a coaxial transmission line with one of a plurality of impedance transformers, wherein each of the plurality of impedance transformers is electrically coupled between different ones of the plurality of microwave power amplifiers and the plurality of DRAs.

18. The method of claim 17, wherein the plurality of impedance transformers are each conical impedance transformers.

19. The method of claim 17, wherein the plurality of DRAs comprises ten or more DRAs.

20. The method of claim 17, wherein the plurality of microwave power amplifiers are solid state devices.

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