In-SITU microwave plasma impedance measurement system

Abstract

Embodiments disclosed herein include an apparatus that comprises a microwave power delivery channel, and an impedance measurement system electrically coupled to the microwave power delivery channel. In an embodiment, the impedance measurement system includes a dual directional coupler (DDC), and a detector electrically coupled to the DDC. In an embodiment, a first interconnect between the DDC and the detector is configured to supply a forward power signal to the detector, and a second interconnect between the DDC and the detector is configured to supply a reflected power signal to the detector. The detector may be configured to measure an amplitude and a phase between the forward power signal and the reflected power signal.

Description

[0001] IN-SITU MICROWAVE PLASMA IMPEDANCE MEASUREMENT SYSTEM

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims priority to U.S. Patent Application No. 63 / 560,453, 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 an in-situ microwave plasma impedance measurement 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 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 include an apparatus that comprises a microwave power delivery channel, and an impedance measurement system electrically coupled to the microwave power delivery channel. In an embodiment, the impedance measurement system includes a dual directional coupler (DDC), and a detector electrically coupled to the DDC. In an embodiment, a first interconnect between the DDC and the detector is configured to supply a forward power signal to the detector, and a second interconnect between the DDC and the detector is configured to supply a reflected power signal to the detector. The detector may be configured to measure an amplitude and a phase between the forward power signal and the reflected power signal. Embodiments may also include an apparatus, including a power supply, and a plurality of micro wave power delivery channels, where each of the plurality of microwave power delivery channels is electrically coupled to the power supply. In an embodiment, the apparatus may include a plurality of impedance measurement systems, where each of the plurality of impedance measurement systems is electrically coupled to one of the plurality of microwave power delivery channels. Tn an embodiment, each of the plurality of impedance measurement systems comprises a dual directional coupler (DDC), and a detector electrically coupled to the DDC. In an embodiment, a first interconnect between the DDC and the detector is configured to supply a forward power signal to the detector, and a second interconnect between the DDC and the detector is configured to supply a reflected power signal to the detector. In an embodiment, the detector is configured to measure an amplitude and a phase between the forward power signal and the reflected power signal. In an embodiment, the apparatus further comprises a chamber coupled to the plurality of microwave power delivery channels. In an embodiment, the plurality of microwave power delivery channels are configured to couple microwave power into the chamber to ignite and / or sustain a plasma within the chamber.

[0011] Embodiments may also include a method for determining a plasma load impedance of a plasma in a microwave plasma tool with an in-situ impedance measurement system. In an embodiment, the method includes initiating a plasma in the multi-channel microwave plasma tool, where the microwave plasma tool comprises a dual directional coupler that is electrically coupled between a micro wave power amplifier and a fixed match. In an embodiment, the method may further comprise feeding a reflected power signal and a forward power signal to a detector electrically coupled to the dual directional coupler, and measuring an amplitude and a phase between the reflected power signal and the forward power signal with the detector. In an embodiment, the method further comprises calculating the plasma load impedance from the amplitude and the phase.

[0012] BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A is a cross-sectional illustration of a semiconductor processing tool for generating a microwave plasma using a plurality of dielectric resonator antennas (DRAs), in accordance with an embodiment.

[0014] 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 illustration of the microwave power delivery system of a semiconductor processing tool for generating a microwave plasma, in accordance with an embodiment.

[0015] Figure 3A is a plot of the forward power over time of a microwave power delivery system, in accordance with an embodiment.

[0016] Figure 3B is a plot of the reflected power over time of a microwave power delivery system with a poor impedance match, in accordance with an embodiment.

[0017] Figure 4 is a schematic illustration of a tool with a plurality of microwave power delivery channels, where each channel includes an in-situ plasma impedance measurement system, in accordance with an embodiment.

[0018] Figure 5 is a schematic diagram of the plasma impedance measurement system with a dual directional coupler (DDC) and a detector for measuring the amplitude and the phase between a reflected power signal and a forward power signal, in accordance with an embodiment.

[0019] Figure 6 is a schematic diagram of impedance sources within a plasma processing tool, in accordance with an embodiment.

[0020] Figure 7 is a cross-sectional illustration of a conical impedance transformer, in accordance with an embodiment.

[0021] Figure 8 is a process flow diagram of a process for determining a plasma impedance in a plasma tool using an in-situ impedance measurement process, in accordance with an embodiment. 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.

[0022] DETAILED DESCRIPTION

[0023] Embodiments described herein include apparatuses and processes for in-situ microwave plasma impedance measurement. 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.

[0024] 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. 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.

[0025] 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.

[0026] 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.

[0027] 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., micro wave plasma enhanced chemical vapor deposition (PECVD), a microwave plasma enhanced atomic layer deposition (PEALD), etc.), a microwave plasma etching tool, a microwave 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.

[0028] 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.

[0029] 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 116 and a pin 117 that is inserted into a hole into the top surface of the puck 116.

[0030] 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.

[0031] 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.

[0032] In the illustrated embodiment, the DRA 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.

[0033] 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 1 10 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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 (also referred to herein as microwave channels) 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 microwave lines 230.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] An example of a microwave line 230 with poor impedance matching 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.

[0042] 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.

[0043] 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.

[0044] Accordingly, it is necessary to use impedance monitoring in order to provide the proper matching within the tool. In-situ monitoring of the plasma impedance (i.e., monitoring changes to plasma impedance during the operation of the tool) is critical in order to protect the tool and provide efficient operation of the tool. One common plasma impedance measurement solution is to use a voltage / current (V / I) sensor or probe. These sensors work well for RF plasma systems, but are not able to adequately monitor microwave plasmas. Particularly, the frequency of microwave plasmas is significantly higher than the frequency of RF plasmas. As such, the wavelength of the microwave signals is significantly smaller than the wavelength of RF signals. Accordingly, it is difficult to obtain reliable separation of capacitive components (V) and magnetic components (I) in order to obtain the necessary impedance measurements for microwave systems. Typically, the signal needs to be down converted to lower frequencies in order to make the measurements.

[0045] Some impedance measurement techniques have been used for microwave systems. One solution is to use a waveguide with multiple probes inserted into the waveguide. These waveguides are bulky and occupy a large amount of space. In the case of a slotted line approach, a pickup probe is moved back and forth along the waveguide to detect a standing wave pattern. In a rotating probe approach, the probes need to be rotated within the waveguide.

[0046] Due to the size of the components for these techniques, both waveguide based solutions are not suitable for in-situ measurements of a microwave plasma system. Further, when a multi-channel approach is used, the number of waveguides increases. This leads to even larger form factors with a greater degree of design complexity.

[0047] Accordingly, embodiments disclosed herein may include an in-situ plasma impedance measurement system that is compatible with microwave plasma tools. Particularly, the plasma impedance measurement system may be a solid state architecture so that bulky waveguides are omitted. This allows for integration with a multi-channel plasma tool without significantly increasing form factor. The in-situ approach also allows for the monitoring plasma impedance variation during processing operations in order to provide a more controllable and efficient tool. In an embodiment, the plasma impedance measurement system may include a dual directional coupler (DDC) and a detector for measuring amplitude and gain. The DDC provides a reflected power signal and a forward power signal to the detector, and the detector is configured to measure the amplitude and the phase between the two signals. The amplitude and the phase can then be used in order to calculate the plasma impedance of the system. Accordingly, the plasma impedance can be measured without the need to down convert signals from the microwave regime, and the form factor is not significantly increased. In an embodiment, the DDC is electrically coupled to the microwave power delivery channel between the power amplifier and the impedance transformer.

[0048] Referring now to Figure 4, a schematic illustration of a plasma processing tool 400 is shown, in accordance with an embodiment. As shown, a chamber 407 is electrically coupled to a plurality of microwave lines 430A - 430N. The chamber 407 may be a chamber similar to any of the chambers described in greater detail herein. For example, the chamber 407 may be a part of a microwave PECVD tool, a microwave PEALD, a microwave plasma etching tool, a microwave plasma treatment tool, and / or the like. In an embodiment, the number of microwave lines 430 may be one or more lines, five or more lines, ten or more lines, or twenty of more lines. In a particular embodiment, there may be nineteen microwave lines 430.

[0049] In an embodiment, each of the plurality of microwave lines 430 may comprise a microwave power amplifier 431, an impedance transformer 435 (e.g., a fixed match), and a DRA 415. The microwave power amplifier 431 may be a solid state device. The impedance transformer 435 may be a CIT in some embodiments. The DRA 415 may comprise a dielectric puck with a pin inserted into a hole into the axial center of the top surface of the dielectric puck. In an embodiment, a power supply 422 may be electrically coupled to the microwave power amplifier 431. A single power supply 422 may be coupled to all of the microwave power amplifiers 431 in the tool 400, or two or more power supplies 422 may be used.

[0050] In an embodiment, the plasma impedance measurement system 450 (or just “measurement system” for short) may be electrically coupled to the main microwave line 430. For example, the measurement system 450 may be electrically coupled between the microwave power amplifier 431 and the impedance transformer 435. In a particular embodiment, the DDC 451 of the measurement system 450 is directly coupled to the microwave power amplifier 431 and the impedance transformer 435 (e.g., by coaxial cables). The DDC 451 has a pair of outputs for delivering the attenuated microwave signals to the detector 454. A first output 452 may deliver a forward power signal to the detector 454 along an interconnect (e.g., a coaxial cable), and a second output 453 may deliver a reflected power signal to the detector 454 along an interconnect (e.g., a coaxial cable).

[0051] In an embodiment, the detector 454 may be a solid state device that is configured to receive the forward power signal and the reflected power signal and measure a gain (also referred to as amplitude) and a phase between the two signals. A more detailed description of the circuitry of the detector 454 is shown in greater detail below. The resulting amplitude |T| and phase 0 are shown in block 455. The amplitude and phase values can then be used to calculate a plasma impedance (Z Load) 456. In an embodiment, the plasma impedance is calculated on a computing system (not shown) that is communicatively coupled to the measurement system 450, the microwave line 430, and / or the tool 400.

[0052] In an embodiment, each microwave line 430 includes its own measurement system 450. That is, a number of measurement systems 450 in the tool may equal a number of microwave lines 430. However, due to the small form factor and solid state design of the measurement systems 450, the overall increase in the form factor of the tool 400 is minimal.

[0053] Referring now to Figure 5, a schematic illustration of a measurement system 550 is shown, in accordance with an embodiment. As shown, the measurement system 550 comprises a DDC 551 that feeds a forward power signal 552 along Channel A to the detector 554 and a reflected power signal 553 along Channel B to the detector 554. In an embodiment, detector 554 includes a first log amplifier detector 562 at the forward power signal 552 input and a second log amplifier detector 561 at the reflected power signal 553 input. The log amplifiers 562 and 561 are used to condition the signals for further processing (e.g., mixing, summing, etc.).

[0054] In an embodiment, a mixer 563 is fed the conditioned signals from the first log amplifier 562 along line 558 and from the second log amplifier 561 along line 557. The mixer 563 outputs a mixed signal along line 568 to a first amplifier 565. The output of the first amplifier is the phase of the compared forward power signal 552 and the reflected power signal 553. More specifically, the phase may refer to the phase shift between the forward power signal 552 and the reflected power signal 553.

[0055] In an embodiment, a summation point 564 is fed the conditioned signals from the first log amplifier 562 along line 560 and from the second log amplifier 561 along line 559. The summation point 564 outputs a summation of the signals along line 567 to a second amplifier 566. The output of the second amplifier is the gain (or amplitude) of the compared forward power signal 552 and the reflected power signal 553. More specifically, the gain (or amplitude) may refer to the ratio between the two input ports of the detector 554, respectively, for the forward power signal 552 and the reflected power signal 553. Referring now to Figure 6, an equivalent circuit diagram 670 of the microwave plasma system is shown, in accordance with an embodiment. In an embodiment, for a given set-point, the microwave power amplifier (i.e., the source (S)) 631 has a maximum output power coupled to the coaxial cable when its source impedance 671 is equal to the characteristic impedance of the coaxial cabling of the system. The microwave power amplifier 631 may be grounded 673. In some embodiments, the source impedance 671 (Zs) may be approximately 50 Ohms. In an embodiment, the source impedance 671 continues to the impedance transformer 635 (which may be a fixed match, such as a CIT). After the impedance transformer 635, the load impedance 672 is provided. The chamber body of processing tool may be coupled to ground 674. In an embodiment, the load impedance 672 may be the plasma impedance that is desired to be measured by the measurement system. The load impedance ZL may be defined by the equation ZL= R + jX . Arrow 675 indicates the reflection coefficient T of the microwave signal at a point (along the dashed line) before the impedance transformer 635.

[0056] In an embodiment, it is desired to calculate the load impedance 672 through the use of a measurement system similar to any of the measurement systems described in greater detail herein. The reflection coefficient T may be defined by the equation T = (ZL— Z^) / ZL+ Zs). Rearranged, this provides the equation Z = Zs(l + T) / (l — T). Since the source impedance 671 is generally known (e.g., approximately 50 Ohms) and the reflection coefficient and the phase are known from the measurement system, the load impedance ZL is easily calculated. Knowledge of the load impedance ZL during operation of the system (i.e., through in-situ measurement) provides greater control and efficiency of the system.

[0057] Referring now to Figure 7, a CIT 735 that may be used as the impedance transformer or match in any of the microwave plasma tools described herein is shown, in accordance with an embodiment. In an embodiment, the CIT 735 may comprise a pin 717. The pin 717 of the CIT 735 may be the pin that is inserted into the DR A. In an embodiment, the pin 717 passes through an output side 781 into an interior of a tapered outer conductor 783. The pin 717 may pass through a polymer ring 784, such as a Teflon ring. In an embodiment, the pin 717 may continue through an input side 782 of the CIT 735. A polymer ring 785, such as a Teflon ring, may be provided on the input side of the CIT 735 as well. In an embodiment, the pin 717 is coupled to a connector 786 used to electrically couple the CIT 735 to a coaxial transmission line (not shown in Figure 7). The connector 786 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 735. In other embodiments, the pin 717 may be coupled (e.g., by solder) to an inner conductor within the outer conductor 783. The inner conductor (or the pin 717) may be coupled to the connector 786 with a solder joint or the like as well. Referring now to Figure 8, a process flow diagram of a process 890 for measuring a plasma load impedance in a microwave plasma system is shown, in accordance with an embodiment. In an embodiment, the process 890 may begin with operation 891, which comprises initiating a plasma in a microwave plasma tool that comprises a DDC that is electrically coupled between a microwave power amplifier and a fixed match. In an embodiment, the fixed match may be an impedance transformer, such as a CIT. The microwave plasma tool may be similar to any of the microwave plasma tools described in greater detail herein. For example, the microwave plasma tool may comprise a microwave PECVD tool, a microwave PEALD, a microwave plasma etching tool, a microwave plasma treatment tool, or the like.

[0058] In an embodiment, the process 890 may continue with operation 892, which comprises feeding a reflected power signal and a forward power signal to a detector electrically coupled to the DDC. In an embodiment, the detector may be a solid state device. Further, the detector may be configured to measure a phase and an amplitude between the forward power signal and the reflected power signal.

[0059] In an embodiment, the process 890 may continue with operation 893, which comprises measuring the amplitude and the phase between the reflected power signal and the forward power signal. In an embodiment, the measurement circuitry may be similar to the circuitry described in greater detail herein with respect to Figure 5. For example, the detector may comprise a log amplifier for each input, a mixer, a summation point, and a pair of amplifiers (one for phase and one for amplitude).

[0060] In an embodiment, the process 890 may continue with operation 894, which comprises calculating the plasma load impedance from the amplitude and the phase. The calculation may use methods and / or equations such as those described in greater detail herein. In an embodiment, the calculation may be executed by a processor, computing system, or the like that is communicatively coupled to the detector.

[0061] After the plasma load impedance has been measured the microwave plasma tool may make adjustments to one or more components (e.g., match settings, microwave power amplifier frequency, etc.) or to one or more process conditions (e.g., gas flow rates, biases, etc.) to bring the plasma load impedance closer to the characteristic impedance of the system (i.e., to reduce reflected power). In some embodiments, such an in-situ plasma impedance measurement allows for improved processing and greater protection to the tool.

[0062] Process 890 is generally described as a measurement of the plasma impedance along a single microwave power delivery channel (also referred to as a microwave power delivery line or micro wave line for short). However, it is to be appreciated that embodiments may also include a plurality of microwave power delivery channels. In such an embodiment, a similar plasma impedance measurement system may be provided along each microwave power delivery channel in order to monitor the performance of each channel during operation of the tool.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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).

[0068] 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.

[0069] 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.

[0070] 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. An apparatus, comprising: a microwave power delivery channel; and an impedance measurement system electrically coupled to the microwave power delivery channel, wherein the impedance measurement system comprises: a dual directional coupler (DDC); and a detector electrically coupled to the DDC, wherein a first interconnect between the DDC and the detector is configured to supply a forward power signal to the detector, wherein a second interconnect between the DDC and the detector is configured to supply a reflected power signal to the detector, and wherein the detector is configured to measure an amplitude and a phase between the forward power signal and the reflected power signal.

2. The apparatus of claim 1, wherein the microwave power delivery channel is coupled to a plasma chamber.

3. The apparatus of claim 2, wherein the plasma chamber is a microwave plasma enhanced atomic layer deposition (PEALD) chamber, a microwave plasma enhanced chemical vapor deposition (PECVD) chamber, a microwave plasma etching chamber, or a microwave plasma treatment chamber.

4. The apparatus of claim 1, wherein the microwave power delivery channel comprises: a microwave power amplifier; an impedance transformer; and a dielectric resonator antenna (DR A).

5. The apparatus of claim 4, wherein the DDC is electrically coupled between the microwave power amplifier and the impedance transformer.

6. The apparatus of claim 4, wherein the microwave power amplifier is a solid state device.

7. The apparatus of claim 4, wherein the DRA comprises a dielectric puck with a hole into an axial center of a top surface of the dielectric puck, and wherein a pin is inserted into the hole.

8. The apparatus of claim 4, wherein the impedance transformer is a conical impedance transformer (CIT).

9. The apparatus of claim 1, wherein the amplitude and the phase are used to calculate an impedance.

10. The apparatus of claim 1, wherein the microwave power delivery channel is one of a plurality of micro wave power delivery channels.

11. An apparatus, comprising:a power supply; a plurality of microwave power delivery channels, wherein each of the plurality of micro wave power delivery channels is electrically coupled to the power supply; a plurality of impedance measurement systems, wherein each of the plurality of impedance measurement systems is electrically coupled to one of the plurality of microwave power delivery channels, and wherein each of the plurality of impedance measurement systems comprises: a dual directional coupler (DDC); and a detector electrically coupled to the DDC, wherein a first interconnect between the DDC and the detector is configured to supply a forward power signal to the detector, wherein a second interconnect between the DDC and the detector is configured to supply a reflected power signal to the detector, and wherein the detector is configured to measure an amplitude and a phase between the forward power signal and the reflected power signal; and a chamber coupled to the plurality of microwave power delivery channels, wherein the plurality of microwave power delivery channels are configured to couple microwave power into the chamber to ignite and / or sustain a plasma within the chamber.

12. The apparatus of claim 11, wherein each of the plurality of microwave power delivery channels comprises: a microwave power amplifier; an impedance transformer; and a dielectric resonator antenna (DR A).

13. The apparatus of claim 12, wherein the DDC of each impedance measurement system is electrically coupled between the microwave power amplifier and the impedance transformer of a respective one of the plurality of microwave power delivery channels.

14. The apparatus of claim 12, wherein the microwave power amplifier is a solid state device.

15. The apparatus of claim 12, wherein the impedance transformer is a conical impedance transformer (CIT).

16. The apparatus of claim 12, wherein the amplitude and the phase are used to calculate an impedance of the plasma within the chamber.

17. A method for determining a plasma load impedance of a plasma in a multi-channel microwave plasma tool with an in-situ impedance measurement system, comprising: initiating a plasma in the multi-channel microwave plasma tool, wherein the multichannel microwave plasma tool comprises a dual directional coupler that is electrically coupled between a microwave power amplifier and a fixed match; feeding a reflected power signal and a forward power signal to a detector electricallycoupled to the dual directional coupler; measuring an amplitude and a phase between the reflected power signal and the forward power signal with the detector; and calculating the plasma load impedance from the amplitude and the phase.

18. The method of claim 17, wherein the detector comprises a first log amplifier, a second log amplifier, a mixer, a summation point, a first amplifier, and a second amplifier.

19. The method of claim 17, wherein the microwave power amplifier and the fixed match are electrically coupled to a dielectric resonator antenna that couples microwave power into a chamber to generate the plasma in the chamber.

20. The method of claim 17, wherein the microwave power amplifier is a solid state device.

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