Adjustment of power supply signal for electrostatic chuck

Abstract

An exemplary semiconductor processing system may include a processing chamber and an electrostatic chuck at least partially disposed within the processing chamber. The electrostatic chuck may include at least one electrode and a heater. The semiconductor processing system may include a power supply that supplies a signal to the electrode to provide an electrostatic force that secures a substrate to the electrostatic chuck. The system may also include a filter communicatively coupled between the power supply and the electrode. The filter is configured to remove or reduce noise introduced into the chuck signal by operating the heater while the electrostatic force on the substrate is maintained. The filter may include active circuitry, passive circuitry, or both, and may include an adjustment circuit for setting the gain of the filter so that an output signal level from the filter corresponds to an input signal level of the filter.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of and priority to U.S. patent application Ser. No. 17 / 036,048, filed Sep. 29, 2020, entitled "POWER SUPPLY SIGNAL CONDITIONING FOR AN ELECTROSTATIC CHUCK," the entire contents of which are incorporated herein by reference.

[0002]

[0002] The present technology relates to components and apparatus for semiconductor manufacturing. More particularly, the present technology relates to electrostatic chuck components and other semiconductor processing equipment. Background technology

[0003]

[0003] Integrated circuits are realized through processes that fabricate intricately patterned layers of material on a substrate surface. Fabricating patterned materials on a substrate requires methods for controlled formation and removal of exposed material. As device sizes shrink, deposited materials can impart stress to the substrate, resulting in substrate warpage. During subsequent deposition steps, wafer warpage can affect contact across the substrate support, potentially affecting heating. Non-uniform heating profiles across the substrate can affect subsequent deposition steps, causing non-uniform deposition across the substrate surface.

[0004]

[0004] Therefore, there is a need for improved systems and methods that can be used to manufacture high quality devices and structures. These and other needs are addressed by the present technique. Summary of the Invention

[0005] An exemplary semiconductor processing system may include a processing chamber and an electrostatic chuck at least partially disposed within the processing chamber. The electrostatic chuck may include at least one electrode and a heater. The semiconductor processing system may include a power supply that provides a signal to the electrode to provide an electrostatic force that secures a substrate to the electrostatic chuck. The semiconductor processing system may also include a filter communicatively coupled between the power supply and the electrode. The filter is configured to filter out noise caused by operating the heater while the electrostatic force on the substrate is maintained.

[0006] In some embodiments, the filter may include a passive circuit including a plurality of resistors and capacitors, inductors, or both. The filter may include a circuit configured to apply at least 40 dB of attenuation at a design frequency of 45 Hz to 65 Hz while a heater maintains a substrate temperature of 550° C. to 650° C. The filter may include a twin-T band rejection circuit, where a first T circuit includes at least one resistor having a resistance value approximately twice the resistance value of a resistor in a second T circuit and a capacitor having a capacitance value approximately twice the capacitance value of at least one capacitor in the second T circuit. The filter may include both a passive stage and an active stage. The active stage may include an operational amplifier and an adjustment circuit communicatively coupled to the operational amplifier for setting the gain of the filter so that an output signal level from the filter corresponds to an input signal level of the filter.

[0007] Some embodiments of the present technique include a method for processing a semiconductor. The method may include applying a chucking voltage to an electrostatic chuck supporting a substrate in a semiconductor processing chamber and applying a voltage to a heater to increase the temperature of the substrate. The method may also include filtering a power supply signal providing the chucking voltage to remove noise introduced into the power supply signal by the heater while an electrostatic force on the substrate is maintained. The method may further include setting a gain applied to the power supply signal during filtering such that an output signal level corresponds to an input signal level. The method may also include processing the substrate in the semiconductor processing chamber. In some embodiments, the filtering may be achieved using one or more of the filter circuits and configurations described above.

[0008] An exemplary power supply system may include a power supply configured to provide a signal to an electrode of an electrostatic chuck and a filter communicatively coupled to the power supply. The filter is configured to filter noise caused by operating a heater of the electrostatic chuck while an electrostatic force on the substrate is maintained. The filter may include an operational amplifier and a conditioning circuit communicatively coupled to the operational amplifier to set a gain of the filter such that an output signal level from the filter corresponds to an input signal level. The filter may include any of the filter circuits and configurations described above. In some embodiments, a power supply referred to as part of the exemplary power supply system and / or as part of the exemplary semiconductor processing system may be configured to provide a time-varying voltage as a square wave with a frequency of approximately 20 Hz, a duty cycle of approximately 20%, a magnitude of approximately ±1000 V, and an offset of substantially 0 V.

[0009] A further understanding of the nature and advantages of the disclosed technology may be realized by reference to the remaining portions of the specification and the drawings. [Brief explanation of the drawings]

[0010] [Figure 1]1 is a schematic cross-sectional view of an exemplary processing system according to some embodiments of the present technique; [Figure 2] 1 is a schematic cross-sectional view illustrating an exemplary electrostatic chuck and an exemplary power supply system in accordance with some embodiments of the present technique; [Figure 3] FIG. 1 is a schematic diagram illustrating an exemplary filter circuit in accordance with some embodiments of the present technology. [Figure 4] FIG. 10 is a schematic diagram illustrating another exemplary filter circuit in accordance with some embodiments of the present technology. [Figure 5] 10A-10C are schematic diagrams illustrating additional exemplary filter circuits in accordance with some embodiments of the present technology. [Figure 6] FIG. 1 is a flow diagram illustrating a method for powering an electrode of an electrostatic chuck in accordance with some embodiments of the present technique. [Figure 7] 10A-10C illustrate the effect of filtering the power supplied to an electrostatic chuck in accordance with some embodiments of the present technique; DETAILED DESCRIPTION OF THE INVENTION

[0011]

[0017] Some of the figures are included as schematic diagrams. It should be understood that the figures are for illustrative purposes and should not be considered to scale unless the scale is explicitly stated. Furthermore, the schematic diagrams are provided to aid in understanding and may not include all aspects or information compared to realistic representations. The figures may include exaggerated material for illustrative purposes.

[0012]

[0018] In the accompanying figures, similar components and / or features may be labeled with the same reference labels. Furthermore, electronic components of the same type may be distinguished by the use of letters and numbers to distinguish between similar components.

[0013]

[0019] Many material deposition processes can be temperature sensitive. In various processing systems, the substrate support can act as a heat source for the substrate during deposition. As manufacturing processes are performed, multiple material layers may be formed on the substrate, potentially imparting multiple stresses to the substrate. These stresses often cause the substrate to warp to some degree. Chucking with an electrostatic chuck (ESC) can counteract many of the warping effects, maintaining a flatter substrate, which in turn maintains more uniform contact across the substrate support, thereby maintaining more uniform heating across the substrate.

[0014]

[0020] Ceramic heaters in processing chambers are semiconductive when operating at high temperatures. For example, the resistance of aluminum nitride ceramic materials can drop to approximately 20 kΩ when current is passed through the wafer and ESC surfaces to ground. This drop in resistance can create a noise path between the heater and chuck power system components. Heater elements typically carry AC voltage and current, e.g., 208 VAC RMS at 60 Hz. The AC voltage and current flowing through portions of the semiconductive material can couple to the ESC power supply through the ESC electrodes and affect power supply regulation. Some of the AC power, voltage, and current used by the heater element can be superimposed on the chuck voltage and current, causing misregulation of the chuck power supply and potentially causing perturbations in the chucking force. Such perturbations can ultimately lead to unintended deformation of the substrate and resulting deposition incompleteness.

[0015]

[0021] The present technology overcomes these challenges by using one or more chucking force adjustment mechanisms to remove unwanted voltage and current noise in the chucking force. For example, a filter can be provided. The filter is configured to remove or reduce noise introduced into the chucking signal by operating the heater. The filter may include active circuitry, passive circuitry, or both, and may include an adjustment circuit that sets the filter gain so that the output signal level from the filter corresponds to the input signal level of the filter. Therefore, improved film formation and removal, as well as improved film properties, can be achieved.

[0016]

[0022] While the remainder of the disclosure will always identify specific deposition processes using the disclosed technology, it will be readily understood that the present systems and methods are equally applicable to other deposition and cleaning chambers and processes that may be performed in the described chambers. Accordingly, the present technology should not be considered limited for use with only these specific deposition processes or chambers. This disclosure will describe one possible system and chamber that may include lid stack components according to embodiments of the present technology, before describing additional modifications and adjustments to this system according to embodiments of the present technology.

[0017]

[0023] 1 is a schematic cross-sectional view illustrating an exemplary semiconductor processing system according to some embodiments of the present technique. As shown, the processing system 100 may be an etch chamber suitable for etching a substrate 121. The processing system 100 may be used for various plasma processes. For example, the processing system 100 may be used to perform dry etching using one or more etchants. The processing system may be used to etch precursor C. x F y (where x and y represent values ​​of known compounds), O, NF, or combinations thereof. In another embodiment, the processing chamber 100 can be used for plasma enhanced chemical vapor deposition (PECVD) processes using one or more precursors.

[0018]

[0024] The system includes a processing chamber 120 having a chamber body 102, a lid assembly 106, and an electrostatic chuck 101. The electrostatic chuck 101 includes a support stem 107 and a chuck body 228. While a portion of the support stem may protrude from the chamber, the electrostatic chuck is at least partially contained within the processing chamber during operation. The lid assembly 106 is positioned at an upper end of the chamber body 102. The chuck body 228 may be contained within the chamber body 102, and the lid assembly 106 may be coupled to the chamber body 102 to enclose the chuck body 228 within the processing chamber. The chamber body 102 may include a transfer port 126, which may include a slit valve, formed in a sidewall of the chamber body 102. The transfer port 126 may be selectively opened and closed to allow access to the interior of the processing chamber 120 by a substrate handling robot (not shown) for substrate transfer.

[0019]

[0025] The electrode 108 may be provided as part of the lid assembly 106. The electrode 108 may also function as a gas distributor plate 112 having a plurality of openings 118 for admitting process gas into the processing chamber 120. The process gas may be supplied to the processing chamber 120 through a conduit 114, and the process gas may enter a gas mixing region 116 before flowing through the openings 118. The electrode 108 may be coupled to a power source such as an RF generator 109. An isolator 110 may contact the electrode 108 and electrically and thermally isolate the electrode 108 from the chamber body 102. The isolator 110 may be constructed using a dielectric material such as aluminum oxide, aluminum nitride, and / or other ceramic or metal oxides. A heater 119 may be coupled to the gas distributor plate 112. The heater 119 may also be coupled to an AC power source (not shown).

[0020]

[0026] The chuck body 104 can be formed from a metallic or ceramic material. For example, metal oxides, nitrides, or oxide / nitride mixtures, such as aluminum, aluminum oxide, aluminum nitride, aluminum oxide / aluminum nitride mixtures, and / or other similar materials, can be used. In a typical implementation, one or more pedestal electrodes can be included in the chuck body 104. The one or more pedestal electrodes (not shown) can be configured to supply RF energy to a plasma within the processing chamber 120.

[0021]

[0027] The electrostatic chuck 101 is configured to support and hold a substrate to be processed. In one embodiment, the electrostatic chuck 101 may include at least one electrode 223 to which a voltage is applied to electrostatically clamp the substrate thereon. The electrode 223 is powered by a power supply 276 connected to the electrode 223 via an interface circuit 177. The electrostatic chuck 101 may be monopolar, bipolar, tripolar, DC, interdigitated, strip, etc.

[0022]

[0028] In one embodiment, the electrostatic chuck 101 may include a heating element, such as a resistive element, for heating a substrate positioned thereon to a desired process temperature. Alternatively, the electrostatic chuck 101 may be heated by an external heating element, such as a lamp assembly. The RF source 109 is coupled to the electrode 108 through an impedance match circuit 173. The electrode 223 may provide both a ground path for the RF source 109 and an electrical bias from a power supply 276 to enable electrostatic clamping of the substrate 121.

[0023]

[0029] The RF source 109 can include a high frequency radio frequency (HFRF) power source, such as a 13.56 MHz RF generator, and a low frequency radio frequency (LFRF) power source, such as a 300 kHz RF generator. The LFRF power source provides both low frequency generation and a fixed matching element. The HFRF power source is designed for use with a fixed matching element to regulate the power delivered to the load and eliminate concerns about forward and reflected power.

[0024]

[0030] In certain embodiments, characteristics of a substrate 121 secured on the chuck body 104 may be monitored during a plasma process. In certain embodiments, the characteristics can be monitored by measuring the characteristics of the electrostatic chuck 101 to which the substrate is secured. The characteristics of the electrostatic chuck 101 may be measured by a sensor 174 connected to the distributor plate 112. The sensor 174 may be a VI probe connected between the distributor plate 112 and the impedance match circuit 173. In some embodiments, the sensor 174 may be configured to measure the capacitance between the distributor plate 112 and the electrode 223 because the capacitance between the distributor plate 112 and the electrode 223 is affected by the flatness of the substrate 121. The capacitive reactance of an electrostatic chuck may increase if the substrate placed thereon becomes uneven. If the substrate is uneven, for example, if it is deformed by the heat of the plasma, the distribution of the air gap between the substrate and the electrostatic chuck is uneven. Therefore, a change in the flatness of the substrate on the electrostatic chuck results in a change in the capacitance of the plasma reactor, which can be measured. In such a case, the sensor 174 may be configured to measure the impedance of the electrostatic chuck 101 by measuring the voltage and current across a capacitor formed by the distributor plate 112 and the electrode 223, thereby monitoring the flatness of a substrate secured thereon.

[0025]

[0031] During plasma processing, a substrate positioned on an electrostatic chuck may experience increased curvature due to deformation caused by heating, an increase in the thickness of a deposited film, a loss of chucking force, or a combination thereof. Substrate deformation can increase process non-uniformity. In one embodiment, the flatness of the substrate being processed can be monitored by measuring the characteristics of the electrostatic chuck that secures the substrate. Depending on predetermined conditions, the chucking voltage of the electrostatic chuck can be adjusted to correct for substrate deformation. Sensors 174 can be connected to the system controller 175. The system controller 175 can be configured to calculate and adjust the flatness of the substrate 121 being processed in the system 100. In one embodiment, the system controller 175 can calculate the flatness or chucking condition of the substrate 121 by monitoring characteristics such as the imaginary impedance of the electrostatic chuck 101. If the impedance measurement indicates that the flatness of the substrate 121 is decreasing, the system controller 175 can increase the chucking force by adjusting the power supply 276.

[0026]

[0032] FIG. 2 is a schematic cross-sectional view illustrating an exemplary electrostatic chuck according to some embodiments of the present technology. The electrostatic chuck 200 includes a chuck body 228 coupled to a support stem 226. The body 228 has a top surface 202 configured to support and clamp a substrate 121 during processing. The body 228 of the electrostatic chuck 200 includes an electrode 223 coupled to a conductive member 286. The electrode 223 may be a metal electrode of a size comparable to that of the substrate within the body 228 and may be constructed to be substantially parallel to the substrate 121 held against the top surface 202 of the body 228. The electrodes 223 may be arranged in any configuration or pattern such that the electrodes are uniformly distributed across the top surface 202. For example, the electrodes 223 may be arranged in a grid, pixel, or dot configuration. The conductive member 286 may be a rod, tube, wire, or the like, and may be made of a conductive material such as molybdenum (Mo), tungsten (W), or another material having a coefficient of expansion substantially similar to that of another material comprising the body 228. In some embodiments, the top surface 202 of the body 228 may have various patterns of surface contacts 290 that may be positioned near the back surface region of the substrate 121 and / or may contact the substrate 121 to affect chucking force and timing performance.

[0027]

[0033] In one embodiment, the electrostatic chuck uses a single electrode 223 to maintain a substantially uniform voltage between the electrode 223 and the substrate 121. Alternatively, the electrostatic chuck may use a bipolar ESC, in which multiple chuck electrodes with different voltages are used to generate a clamping force. In some embodiments, the electrostatic chuck 200 may have a bias electrode embedded or disposed in the body 228 that provides an electrical bias to the substrate to facilitate or enhance electrostatic clamping of the substrate. Alternatively, the electrode 223 may provide both a ground path for radio frequency (RF) power (e.g., RF source 109 in FIG. 1 ) and an electrical bias to the substrate 121 to enable electrostatic clamping of the substrate.

[0028]

[0034] To provide an electrical bias to the substrate 121, the electrode 223 may be in communication with a power supply system 280 that provides a bias voltage to the electrode 223. The power supply system 280 includes a power supply 276, which may be a direct current (DC) power supply that provides a DC signal to the electrode 223. In one embodiment, the power supply 276 is a 24V DC power supply, and the electrical signal may provide a positive or negative bias.

[0029]

[0035] Alternatively or additionally, the power supply 276 may be an alternating current (AC) power supply that supplies a time-varying, regulated signal to the electrode 223. In such an embodiment, the AC power supply supplies the signal to the electrode. The signal includes a control waveform with a specific frequency, duty cycle, offset relative to ground, and peak-to-peak value. All of these parameters can be adjusted to obtain the best results, taking into account the desired heating profile and deposition characteristics. In one example, the substrate temperature is controlled to remain within the same temperature range while the substrate is on a chuck having a ceramic heater 288 maintained at a temperature between 550°C and 650°C. The substrate is chucked to the surface of the ceramic heater by electrostatic forces generated between the wafer and the electrode 223. In this example, the voltage signal varies over time as a square wave with a 20 Hz frequency, a 20% duty cycle, ±1000 V, and a 0 V offset. These values ​​are not absolute. In this example, approximate values, for example, within 10%, are also included.

[0030]

[0036] In one embodiment, the power supply 276 is coupled to the electrode 223 through an interface circuit 177 that includes a power amplifier 279 and a filter 277. An example circuit that can be communicatively coupled between the power supply 276 and the electrode 223 and function as the filter 277 is described below. The power supply 276 can be coupled to the power amplifier 279 to amplify the electrical signal from the power supply. The amplified electrical signal passes through the filter 277 to remove noise from the bias voltage from the power supply system 280 and any RF currents from the amplified electrical signal. The amplified and filtered electrical signal is provided to the conductive member 286 by a connector 282. The amplified and filtered electrical signal is provided to the electrode 223 and the substrate 121 to enable electrostatic clamping of the substrate 121. The electrode 223 can also function as an RF ground, with RF power being coupled to ground by a connector 281. A capacitor 278 can be coupled to the ground path to prevent the bias voltage from conducting to ground. In this manner, the electrode 223 functions as a substrate bias electrode and an RF return electrode.

[0031]

[0037] In some embodiments, the body 228 may include one or more embedded heaters 288 that apply heat to the body 228. The heat from the heaters 288 is then transferred to the substrate 121 to enhance a fabrication process, such as a deposition process. The heaters 288 may or may not be positioned parallel to the electrode 223. While the heater 288 is shown below the electrode 223, the electrode may be positioned along the same plane as the heater 288 or above the heater 288. The heater 288 may be a single continuous metal wire or may be in the form of separate metal wires. The heater 288 may be any heating device suitable for providing inductive or resistive heating to the electrostatic chuck. A temperature sensor (not shown), such as a thermocouple, may be embedded in the body 228. The temperature sensor may be connected to a temperature controller (not shown) that provides a control signal to the power supply 283 to control the temperature of the body 228.

[0032]

[0038] The heater 288 is coupled to a heater power supply 283 through the support stem 226 to provide power to the heater 288. The power supply 283 may include a direct current (DC) power supply, an alternating current (AC) power supply, or a combination of both. In one embodiment, the power supply 283 is an alternating current (AC) power supply that provides an AC signal to the heater 288. The heater 288 may be constructed of a resistive metal, a resistive metal alloy, or a combination of the two. Suitable materials for the heating element include those with high thermal resistance, such as tungsten (W), molybdenum (Mo), or titanium (Ti). Additionally, the heater 288 may be fabricated from a material having thermal properties, e.g., a thermal expansion coefficient, substantially similar to those of the material comprising the body 228 to reduce stress caused by thermal expansion mismatch.

[0033]

[0039] Generally, the resistivity of AlN material changes with temperature, potentially increasing coupling between the embedded chuck electrode 223 and the heater 288 due to their close physical proximity. Therefore, low-frequency signals and harmonic noise primarily found on the AC line side of the heater circuit that can couple through the AlN dielectric chuck material to the chuck electrode and affect the chucking voltage can be filtered by the filter 277. Examples of low-frequency signals include frequencies between 45 Hz and 65 Hz, including the standard line frequencies of 50 Hz and 60 Hz. Note that the positioning of the filter 277 shown in FIG. 2 is merely an example. The filter 277 can be placed in any suitable location relative to the electrostatic chuck, whether inside or outside the chamber environment, nearby, or remotely further from the noise source.

[0034]

[0040] To reduce leakage current through the heater, an isolation transformer 246 may be disposed between the heater 288 and the heater power supply 283. The isolation transformer 246 is used to interrupt the ground current path. In this case, the isolation transformer 246 may include a primary coil winding 247 and a secondary coil winding 249. The primary coil winding 247 may be connected to the power supply 283, and the secondary coil winding 249 may be connected to the electrical load to be protected (i.e., the heater 288). Thus, the heater 288 may be electrically isolated from the AC voltage source and any transients from external sources, reducing leakage current. In most cases, the isolation transformer 246 should be designed to withstand the maximum ESC voltage without failure while not allowing DC current across its primary and secondary coil windings. However, AC current may pass freely between the primary and secondary coil windings of the isolation transformer 246. Depending on the configuration of the heater 288, the isolation transformer 246 may be a single-zone or multi-zone isolation transformer. If the electrostatic chuck includes multiple heating zones, multiple transformers, or a single transformer with multiple primary and / or secondary coil windings, may be used to maintain DC isolation from the heater to ground.

[0035]

[0041] The filter 277 can include various passive and active circuits for filtering AC noise, depending on the spectrum of noise frequencies that need to be filtered out. The filter 277 can filter out noise caused by operating a ceramic heater while maintaining an electrostatic force on the substrate. In some embodiments, the filter can target AC line frequency components based on a 50 Hz or 60 Hz power line frequency, including harmonics of these frequencies up to several kHz. Such filters can have various configurations, including low-pass, high-pass, band-pass, band-rejection, and notch filters. As a further example, consider AC noise coupled into a DC or low-frequency square-wave chuck signal during the deposition of a 3.4 μm carbon film at 630°C. The AC noise components can affect the chuck signal level. When measured, such noise typically appears periodic or contains a specific frequency or multiple frequency components. For example, noise consisting of 60 Hz switching noise typically contains harmonic frequencies up to several kHz.

[0036]

[0042] In one embodiment, filter 277 is a passive circuit with an iron-core inductor having an inductance of 25 mH, although various inductances can be used. For 60 Hz switching noise, a 25 mH iron-core inductor provides attenuation factors of 50 dB, 13.8 dB, and 1.4 dB at frequencies of 13.56 MHz, 1800 Hz, and 180 Hz, respectively, which is about 7% of the ESC current noise level tested in the chamber and process described above, i.e., 25±2 mA.

[0037]

[0043] FIG. 3 is a schematic diagram illustrating another exemplary passive filter circuit according to some embodiments of the present technology. Circuit 300 is a passive twin-T band rejection filter. This filter includes resistive and capacitive elements forming a network of two T circuits with a noise attenuation factor of over 40 dB at the design frequency. The attenuation value and frequency response are related to the specific values ​​of the resistors and capacitors. In one embodiment, the first T circuit includes resistors R1 and R2 and capacitor C1, and the second T circuit includes resistor R3 and capacitors C2 and C3. In this example, the resistance value of each of resistors R1 and R2 in the first T circuit is approximately twice the resistance value of resistor R3 in the second T circuit. Similarly, the capacitance value of capacitor C1 in the first T circuit is approximately twice the capacitance value of capacitors C2 and C3 in the second T circuit. In this example, these relative values ​​are set as close as possible to accommodate standard values ​​of widely available components and a 5% tolerance.

[0038]

[0044] In one embodiment, the above-mentioned filter is implemented with resistance values ​​of 10 MΩ and 5 MΩ and capacitance values ​​of 530 pF and 260 pF. These values ​​provide filtering for, for example, a 60 Hz fundamental, 7.8 VDC + 4 Vpp (50%) noise signal, providing attenuation to 2.55 VDC + 0.06 Vpp (2%). Such a noise signal may occur, for example, during a chemical vapor deposition process at temperatures between 550°C and 650°C. The ESC power supply current and voltage fluctuations are measured at the output terminal V O The output impedance of circuit 300 is approximately 100 kΩ, which matches the impedance of typical isolation amplifier circuits that may be used in ESCs.

[0039]

[0045] FIG. 4 is a schematic diagram illustrating an exemplary active filter circuit according to some embodiments of the present technology. The filter circuit 400 includes an active stage built around an operational amplifier 402 and a passive stage including the passive filter circuit described above. The operational amplifier 402 adjusts the gain applied to the input signal so that the DC or peak output signal level from the filter corresponds to the DC or peak input signal level. This signal level matching allows the filter to be transparent to the operation of the power system or to have no effect other than providing noise attenuation. In the example shown in FIG. 4, the gain is set by using the operational amplifier 402 as a voltage follower with a high input impedance set by a regulation circuit including resistors R4 and R5. Alternatively, the gain can be set by connecting a resistive voltage divider network to the operational amplifier.

[0040]

[0046] In one embodiment, such a circuit includes a resistor and capacitor in a passive stage with the values ​​described above. The filter is applied to reduce noise having a fundamental frequency of approximately 60 Hz and measurable harmonics up to approximately 3 kHz. R4 has a value of approximately 5 MΩ. R5 is adjustable and, in the exemplary system described herein, may be set to approximately 228 kΩ. The active filter response exhibits a notch centered at approximately 56 Hz. The active filter circuit may be configured to filter the ESC current, the ESC voltage, or both. Gain adjustment can be performed, for example, via firmware in the power system's system controller (such as system controller 175), via an operator-accessible variable resistor control, or by designing the power system for a particular known operating environment. The filter is transparent, meaning that not only is the steady-state chuck signal largely unaffected, but the rise and fall times of the AC chuck signal also remain substantially unchanged. The filter also operates without substantially slowing the rise time of the chucking voltage or the fall time of the dechucking voltage when processing a substrate.

[0041]

[0047] FIG. 5 is a schematic diagram illustrating another exemplary active filter circuit according to some embodiments of the present technology. The filter circuit 500 also includes an active stage built around an operational amplifier 402 and a passive stage including a passive filter circuit. The operational amplifier 402 adjusts the gain applied to the input signal for signal level matching. In the example shown in FIG. 5, the gain is set by adjusting the value of R5 in any of the ways previously described. V CC The operational amplifier 402 is supplied by two 208 VAC to 10 VDC power supplies 502 and 504 to achieve the required current. Alternatively, a single power supply with sufficient current capability could be used. These power supplies are connected to a voltage clamp circuit including R7, R8, C4, and diode VR1 to provide overvoltage protection. R7 and R8 are used in parallel to allow for more precise adjustment of the total resistance using off-the-shelf resistors. The passive filter portion of circuit 500 also includes two parallel resistors, R3a and R3b, to provide the resistance of R3 shown in the previous diagram. Again, off-the-shelf components allow for more precise setting of the resistance. A capacitor C5 is added to the input of circuit 500 to act as a low-pass filter.

[0042]

[0048] FIG. 6 is a flow diagram illustrating a method for powering an electrode of an electrostatic chuck according to some embodiments of the present technique. Method 600 may be performed in one or more chambers, including those previously described herein. Method 600 may be used with the electrostatic chucks previously described herein, along with the filters and other components shown. Method 600 may include optional steps or conditions that may or may not be particularly relevant to some embodiments of the present technique. For example, many of the steps are described to provide a broader range of uses for the structure, but may be performed by alternative methodologies that are not critical to the present technique or that will be readily understood. As will be appreciated from the description of gain settings below, in some embodiments, the semiconductor processing system may be designed to allow active monitoring and adjustment of gain, either through an automated feedback process or manually by an operator.

[0043]

[0049] In step 602 of method 600, a chucking voltage is applied to the chucking electrode 223. This voltage may be DC or AC, e.g., a square wave with a particular duty cycle, offset, etc. In step 604, a voltage is applied to the ceramic heater 288 to raise and maintain the temperature of the substrate being processed. In step 608, the power signal is filtered to remove noise while the electrostatic force on the substrate 121 is maintained. In some embodiments, the filtering is achieved in part by applying at least 40 dB of attenuation at a design frequency of 45 Hz to 65 Hz while the substrate is maintained at a temperature of 550°C to 650°C. The filter may include passive stages, active stages, or both. The filter may also be inductor-based. In step 610, a gain applied to the power signal during filtering is set so that the filter output signal level corresponds to the filter input signal level. Optionally, in step 612, the signal level may be monitored. If the signal level changes, the gain can be reset by repeating step 610. If not, in step 614, the substrate 121 is processed in a chamber of the semiconductor processing system.

[0044]

[0050] 7 is a graph illustrating the effect of filtering power supplied to an electrostatic chuck according to some embodiments of the present technique. Voltage waveform graph 700 shows an example of ESC current and voltage noise attenuation before and after the implementation of the above-described active noise filter in a semiconductor processing system having a chamber with a ceramic heater temperature of 550°C to 575°C. Waveform 702 represents the unfiltered ESC current, and waveform 704 represents the unfiltered ESC voltage. Waveform 706 represents the filtered ESC current, and waveform 708 represents the unfiltered ESC voltage. The high-signal and low-signal voltages are 550V and 350V, respectively. The original noise current variation of the high-voltage signal is approximately 2.5 mA at 0V, and the noise current variation of the low-voltage signal is less than 3 mA at 0V.

[0045]

[0051] In the above description, for purposes of explanation, numerous details are set forth in order to provide an understanding of various embodiments of the present technology. However, it will be apparent to one skilled in the art that certain embodiments may be practiced without some of these details or with additional details.

[0046]

[0052] While several embodiments have been disclosed, those skilled in the art will recognize that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the embodiments. Moreover, in order to avoid unnecessarily obscuring the technology, many well-known processes and elements have not been described. Therefore, the above description should not be deemed to limit the scope of the technology.

[0047]

[0053] Where a range of values ​​is provided, it is understood that each intervening value, to the smallest fraction of the unit of the lower limit, between the upper and lower limit of that range is also specifically disclosed, unless the context clearly dictates otherwise. Any narrower range between any stated value or unstated intervening value in a stated range and any other stated or intervening value in that stated range is also included. The upper and lower limits of these smaller ranges may independently be included or excluded, and each range in which one, both, or neither of the smaller ranges is included is also included within the technology, subject to any specifically excluded limit in the stated range. Where a stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included.

[0048]

[0054] As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Thus, for example, a reference to "a heater" includes a plurality of such heaters; a reference to "the filter" includes a reference to one or more filters and equivalents thereof known to those skilled in the art; and so forth.

[0049]

[0055] Also, as used in this specification and the following claims, the terms "comprise," "comprising," "contain," "containing," "include," and "including" specify the presence of stated features, integers, components, or steps, but do not exclude the presence or addition of one or more other features, integers, components, steps, operations, or groups. The terms "coupled," "connected," "arranged," and similar terms may refer to a direct connection or arrangement between components, or to or between intervening components.

Claims

1. 1. A semiconductor processing system comprising: a processing chamber; an electrostatic chuck disposed at least partially within the processing chamber, the electrostatic chuck including at least one electrode and a heater; a power supply that supplies a signal to the at least one electrode to provide an electrostatic force that secures a substrate to the electrostatic chuck; a filter communicatively coupled between the power supply and the at least one electrode, the filter configured to filter noise caused by operating the heater while the electrostatic force on the substrate is maintained; Passive stage and an active stage communicatively coupled to the passive stage, an operational amplifier; an active stage including an adjustment circuit communicatively coupled to the operational amplifier for setting a gain of the filter such that an output signal level from the filter corresponds to an input signal level of the filter; A semiconductor processing system comprising:

2. 10. The semiconductor processing system of claim 1, wherein the filter comprises a passive circuit including at least one of a plurality of resistors and capacitors, or an inductor.

3. 10. The semiconductor processing system of claim 1, wherein the filter comprises circuitry configured to apply at least 40 dB of attenuation at a design frequency of 45 Hz to 65 Hz while the heater maintains a temperature of the substrate between 550°C and 650°C.

4. 4. The semiconductor processing system of claim 3, wherein the filter includes a twin-T band rejection circuit, a first T circuit including at least one resistor having a resistance value approximately twice the resistance value of a resistor in a second T circuit, and a capacitor having a capacitance value approximately twice the capacitance value of at least one capacitor in the second T circuit.

5. 10. The semiconductor processing system of claim 1, wherein the power supply is configured to provide a voltage that varies over time as a square wave with a frequency of approximately 20 Hz, a duty cycle of approximately 20%, a magnitude of approximately ±1000 V, and an offset of substantially 0 V.

6. 1. A method for processing a substrate in a semiconductor processing system, comprising: applying a chucking voltage to an electrostatic chuck supporting the substrate in a semiconductor processing chamber; applying a voltage to a heater to increase the temperature of the substrate; filtering a power supply signal providing the chucking voltage to remove noise introduced into the power supply signal by the heater while an electrostatic force on the substrate is maintained; setting a gain applied to the power supply signal during said filtering such that an output signal level corresponds to an input signal level; processing the substrate in the semiconductor processing chamber; A method comprising:

7. The method of claim 6 , wherein the power supply signal is filtered using a passive circuit including at least one of a plurality of resistors and capacitors, or an inductor.

8. 7. The method of claim 6, wherein filtering the power supply signal further comprises applying at least 40 dB of attenuation at a design frequency of 45 Hz to 65 Hz while the substrate is maintained at a temperature of 550° C. to 650° C.

9. 7. The method of claim 6, wherein the power supply signal is filtered using a twin-T band rejection circuit, a first T circuit including at least one resistor having a resistance value approximately twice the resistance value of a resistor in a second T circuit and a capacitor having a capacitance value approximately twice the capacitance value of at least one capacitor in the second T circuit.

10. The method of claim 6 , wherein the power supply signal is filtered using a filter including a passive stage and an operational amplifier communicatively coupled to the passive stage.

11. 7. The method of claim 6, wherein the chucking voltage is time-varying as a square wave with a frequency of approximately 20 Hz, a duty cycle of approximately 20%, a magnitude of approximately ±1000 V, and an offset of substantially 0 V.

12. 1. A power supply system for an electrostatic chuck in a semiconductor processing chamber, comprising: a power supply configured to provide a signal to an electrode of the electrostatic chuck; a filter communicatively coupled to the power supply and configured to filter noise caused by operating a heater of the electrostatic chuck while an electrostatic force on a substrate is maintained; The filter includes an active stage and a passive stage, the active stage comprising: an operational amplifier; an adjustment circuit communicatively coupled to the operational amplifier for setting a gain of the filter such that an output signal level from the filter corresponds to an input signal level of the filter; Including filters and A power supply system comprising:

13. The power supply system of claim 12 , wherein the filter includes a passive circuit including at least one of a plurality of resistors and capacitors, or an inductor.

14. 13. The power system of claim 12, wherein the filter includes circuitry configured to apply at least 40 dB of attenuation at a design frequency of 45 Hz to 65 Hz while the heater maintains a temperature of the substrate between 550° C. and 650° C.

15. 15. The power supply system of claim 14, wherein the filter includes a twin-T band rejection circuit, a first T circuit including at least one resistor having a resistance value approximately twice the resistance value of a resistor in a second T circuit, and a capacitor having a capacitance value approximately twice the capacitance value of at least one capacitor in the second T circuit.

16. The power system of claim 12 , further comprising a power amplifier communicatively coupled between the power supply and the filter.

17. 13. The power supply system of claim 12, wherein the power supply is configured to provide a voltage that varies over time as a square wave with a frequency of approximately 20 Hz, a duty cycle of approximately 20%, a magnitude of approximately ±1000 V, and an offset of substantially 0 V.

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