Method and apparatus for processing a substrate

Abstract

Methods and apparatuses for processing a substrate are provided herein. For example, a processing chamber for processing a substrate includes a chamber body defining a processing volume; a radio frequency (RF) power source configured to transmit RF energy to a processing space for processing a substrate; a substrate support including an electrode; an AC power source configured to supply power to the processing chamber; an RF filter circuit connected between the electrode and the AC power source; and a controller configured to monitor, at the RF filter circuit, an RF voltage induced into the electrode during operation by the RF power source and configured to determine a processing condition in the processing volume based on the monitored RF voltage.

Description

TECHNICAL FIELD

[0001] Embodiments of the present disclosure generally relate to methods and apparatuses for processing a substrate, and more particularly, to methods and apparatuses configured to monitor a state of a plasma used during processing of a substrate.

[0002] BACKGROUND

[0003] Plasma processing chambers for processing substrates are known, but processing substrates with plasma becomes increasingly challenging, for example, when substrate critical features are less than 30 nm. Accordingly, it is a critical need to monitor and / or diagnose a state of a plasma during processing of a substrate near an electrostatic chuck (ESC) / susceptor region within a plasma processing chamber, for example. Conventional methods and apparatuses monitor the plasma using voltage or current measurements provided by corresponding voltage and current sensors at an output of an impedance matching network of the plasma processing chamber. Although this approach can be easy to implement, there is a potential loss of information due to RF wave propagation through a transmission line connecting the impedance matching circuit to an RF electrode in the ESC / susceptor. SUMMARY

[0004] Methods and apparatuses for processing a substrate are provided herein. In some embodiments, an apparatus for processing a substrate includes a chamber body defining a processing volume; a radio frequency (RF) power source configured to transmit RF energy to the processing volume for processing a substrate; a substrate support including an electrode; an AC power source configured to supply power to the processing chamber; an RF filter circuit connected between the electrode and the AC power source supply; and a controller configured to monitor an RF voltage induced into the electrode during operation by the RF power source indirectly at the RF filter circuit, and configured to determine a processing state in the processing volume based on the monitored RF voltage.

[0005] According to at least some embodiments, a method of monitoring a processing condition in a processing volume of a processing chamber includes supplying radio frequency (RF) power from an RF power source to the processing volume for processing a substrate; monitoring an RF voltage induced into the electrode by the RF power source indirectly at an RF filter circuit; and determining a processing state in the processing volume based on the RF voltage.

[0006] According to at least some embodiments, a non-transitory computer readable storage medium having stored thereon instructions which, when executed by a processor, perform a method of monitoring a process condition in a process volume of a process chamber. The method includes supplying radio frequency (RF) power from an RF power source to a process volume for processing a substrate; monitoring an RF voltage induced into an electrode from the RF power source at an RF filter circuit; and determining a process state in the process volume based on the RF voltage.

[0007] Other and further embodiments of the present disclosure are described below. BRIEF DESCRIPTION OF DRAWINGS

[0008] Embodiments of the present disclosure, briefly summarized above and discussed in detail below, can be understood by reference made to the illustrative embodiments of the disclosure depicted in the drawings. However, the drawings merely provide illustration of the typical embodiments of this disclosure, and therefore are not to be considered limiting of its scope, as the disclosure can admit to other equally functional embodiments.

[0009] Figure 1 is a cross-sectional schematic view of a process chamber in accordance with at least some embodiments of the present disclosure.

[0010] Figure 2 is a cross-sectional schematic view of a substrate support of a process chamber in accordance with at least some embodiments of the present disclosure Figure 1

[0011] Figure 3 is a diagram of an equivalent lumped circuit model of RF coupling between an RF electrode of Figure 2 and an embedded resistive heater of a substrate support in accordance with at least some embodiments of the present disclosure.

[0012] Figure 4 is a method of monitoring a process condition in a process volume of a process chamber in accordance with at least some embodiments of the present disclosure.

[0013] To facilitate the understanding of this disclosure, like reference numerals have been used, where possible, to designate identical elements in the figures. The figures are not drawn to scale and may be simplified for the sake of clarity. Elements and features of one embodiment can be beneficially incorporated into other embodiments without further description. DETAILED DESCRIPTION

[0014] ​Embodiments of methods and apparatuses for processing a substrate are provided herein. For example, the methods and apparatuses described herein use a low pass RF filter including a pair of RF capacitive coupled ports configured to receive an RF voltage induced from an RF electrode coupled to a substrate support and used to heat a substrate. In at least some embodiments, the amount of RF voltage induced from the RF electrode, the RF waveform associated with the RF voltage induced from the RF electrode, or other information about the induced RF voltage is used to monitor the state of the plasma in the processing volume. Unlike conventional methods and apparatuses that use voltage and / or current sensors, which can be expensive and difficult to install, the methods and apparatuses described herein use the induced RF voltage to the pair of RF capacitive coupled ports, which is inexpensive and easy to install. Moreover, because the pair of RF capacitive coupled ports are positioned adjacent to the RF electrode, opposite the output of the impedance matching network, potential loss of information due to the propagation of RF waves through the transmission line connecting the impedance matching network to the RF electrode will be reduced if not eliminated. As such, the methods and apparatuses described herein provide a more accurate understanding of the state of the plasma during operation when compared to conventional methods and apparatuses.

[0015] Figure 1 A schematic cross-sectional view of a processing chamber 100, which can be in accordance with one example of the present disclosure. The processing chamber 100 includes a chamber body 101 and a lid 102 disposed thereon to together define an interior volume. The chamber body 101 is typically coupled to an electrical ground 103.

[0016] The processing chamber 100 can be one of an inductively coupled plasma (ICP) chamber and / or a capacitively coupled plasma (CCP) chamber. For example, in at least some embodiments, the processing chamber 100 is a chamber that includes a CCP device 107 at the top. In at least some embodiments, the top of the processing chamber 100 can be grounded. The CCP device 107 generates a plasma of reactive species in the processing chamber 100, and a controller 108 (e.g., a system controller) is adapted to control the systems and subsystems of the processing chamber 100, as will be described in greater detail below.

[0017] The CCP device 107 is disposed above the lid 102 and is configured to capacitively couple RF power into the processing chamber 100 to generate a plasma 116 in the processing chamber 100. The CCP device 107 can be adjusted as desired to control the distribution or density of the plasma 116 formed. The CCP device 107 is coupled to an RF power source 121 via an RF feed structure 124 through a matching network 122. The RF power source 121 is capable of generating up to about 60,000 W (but not limited to about 60,000 W) at an adjustable frequency in the range from 50 kHz to 150 MHz, although other frequencies and powers can be utilized as desired for a particular application.

[0018] In certain examples, a power splitter (not shown), such as a dividing capacitor, can be disposed between the RF feed structure 124 and the RF power source 121 to control the relative amounts of RF power provided. For example, a power splitter can be used in embodiments when the processing chamber 100 includes an ICP device. In such embodiments, the power splitter can be incorporated into the matching network 122.

[0019] A heater element 128 can be disposed on the lid 102 to facilitate heating the interior of the processing chamber 100. The heater element 128 can be disposed between the lid 102 and a plasma device, such as the CCP device 107. In some examples, the heater element 128 can comprise a resistive heating element and can be coupled to a power source 130, such as an AC power supply, configured to provide sufficient energy to control the temperature of the heater element 128 to be within a desired range, as described in greater detail below.

[0020] The substrate support assembly 104 is disposed in the interior volume to support a substrate 105 thereon during processing (use). An edge ring 106 is positioned around an outer periphery of the substrate 105 on the substrate support assembly 104. The edge ring 106 is disposed on and surrounds the substrate support surface of the ESC.

[0021] The substrate support assembly 104 includes one or more electrodes, such as a first electrode 109 and a second electrode, such as a ring electrode 111 surrounding the first electrode 109. The first electrode 109 is coupled to an attraction power source 114 to facilitate attraction of the substrate 105 to the upper surface 160 during processing.

[0022] The AC power source 113 is configured to supply power to the processing chamber 100 to energize one or more components associated therewith. Unlike an RF power source, which operates at a much higher frequency (e.g., 13.56 MHz) and requires a matching circuit for impedance matching, the AC power source 113 operates at a much lower frequency and does not require such a matching circuit. For example, the AC power source 113 can be configured to supply 110v or 220v, for example, at one or more suitable frequencies. For example, in at least some embodiments, the AC power source 113 can be configured to supply up to 220v and about 40 amps to the processing chamber 100 at 50 Hz or 60 Hz.

[0023] In at least some embodiments, a DC power source 131 can be connected to the substrate support assembly 104 (e.g., to the ring electrode 111) and configured to provide a clamping force to clamp the edge ring 106 to the substrate support (e.g., to a ceramic ring 250 disposed on the substrate support, as described below) to, for example, enhance thermal control of the edge ring 106 during operation.

[0024] The first electrode 109 and the ring electrode 111 are each coupled to an RF power source 110 to provide one or more frequencies through a matching network 112 (similar to the matching network 122) and an edge tuning circuit 155 (e.g., hereafter simply referred to as edge tuning circuit 155) including variable capacitors and inductors. The matching network 112 ensures that the output of the RF power source 110 is effectively coupled to the plasma to maximize energy coupled to the plasma. The matching network 112 generally matches 50 ohms to the complex impedance of the plasma. To facilitate dynamic matching as plasma characteristics change during processing, the matching network 112 can be adjusted as necessary to ensure that the match is maintained throughout processing. The matching network 122 is similarly configured and operated with respect to the RF energy provided by the RF power source 121.

[0025] The edge tuning circuit 155 is an RF circuit that operates near resonance, which is capable of adjusting voltages that are higher and / or lower than the source voltage. The substrate 105 disposed on the upper surface 160 of the substrate support assembly 104 is biased with the RF power source 110. The RF power source 110 can illustratively be a source of RF energy up to about 10,000 W (but not limited to about 10,000 W), which can be provided at one or more frequencies, such as 400 kHz, 2 MHz, 13.56 MHz, 27 MHz, 40 MHz, or 60 MHz. The RF power source 110 can include two or more independent RF power sources configured to provide RF energy at two or more corresponding frequencies. For example, in at least some embodiments, the RF power source 110 can include a first RF power source and a second RF power source configured to provide RF energy at corresponding frequencies (e.g., 400 kHz and 2 MHz), respectively, and an optional third RF power source can be provided and can be configured to provide RF energy at frequencies of 400 kHz, 2 MHz, and / or 40 MHz. The RF power source 110 can be capable of generating either or both continuous or pulsed power.

[0026] During operation, a substrate 105, such as a semiconductor wafer or other substrate suitable for plasma processing, is placed on the substrate support assembly 104. A substrate lift pin 146 is movably disposed in the substrate support assembly 104 to assist in transferring the substrate 105 onto the substrate support assembly 104. After positioning of the substrate 105, a process gas is supplied from the gas panel 132 through the inlet port 134 into the interior volume of the chamber body 101. The process gas is ignited into a plasma 116 in the processing chamber 100 by applying power from the RF power source 121 to the CCP device 107. In some examples, power from the RF power source 110 can also be provided through the matching network 112 to the first electrode 109 and / or the edge ring 106 in the substrate support assembly 104. Alternatively or additionally, power from the RF power source 110 can also be provided through the matching network 112 to a bottom plate and / or other electrode in the substrate support assembly 104.

[0027] The pressure in the interior of the processing chamber 100 can be controlled using the valve 136 and the vacuum pump 138. The temperature of the chamber body 101 can be controlled using fluid-containing conduits (not shown) that pass through the chamber body 101.

[0028] The processing chamber 100 includes a controller 108 to control the operation of the processing chamber 100 during processing. The controller 108 includes a central processing unit (CPU) 140, memory 142 (e.g., non-transitory computer readable storage medium), and support circuits 144 for the CPU 140 and facilitates control of the components of the processing chamber 100. The controller 108 can be one of any form of general purpose computer processor that can be used in an industrial setting for controlling various chambers and sub-processors. The memory 142 stores software (source or object code) that can be executed or called upon to control the operation of the processing chamber 100 in the manner described herein. For example, during operation, the software of the memory 142 includes software (source or object code) for manipulating the various RF circuits provided herein to monitor the RF voltage indirectly induced at the output of the RF filter circuit by the RF power source 110, and determine a processing state in the processing volume based on the RF voltage, as explained in greater detail below.

[0029] RF filter circuit 115 (e.g., a low-pass filter) is connected between the electrode (e.g., heater) and AC power source 113. RF filter circuit 115 includes one or more electronic components, including, but not limited to, resistors, inductors, capacitors, and the like. For example, in at least some embodiments, RF filter circuit 115 includes a series-connected inductor and capacitor 117 combination (e.g., a shunt capacitor) configured to act as a low-pass frequency filter on AC power transmission line 119, e.g., to block one or more frequencies at which RF power source 110 is configured to operate. For example, some of the frequencies blocked by the low-pass frequency filter may include, but are not limited to, 400 kHz or greater, 2 MHz or greater, 13.56 MHz or greater, 27 MHz or greater, 40 MHz or greater, or 60 MHz or greater. RF filter circuit 115 also includes one or more capacitive coupling ports that are capacitively coupled to AC power transmission line 119. For example, in at least some embodiments, RF filter circuit 115 includes capacitive coupling port 123. Capacitive coupling port 123 may have any suitable capacitive coupling power. For example, in at least some embodiments, the capacitively coupled port 123 can have a capacitively coupled power of about -40 dB to about -47 dB.

[0030] Figure 2 Shown in accordance with at least some embodiments of the present disclosure Figure 1 1. An enlarged schematic side view of a portion of the substrate support assembly 104 is shown in FIG. The substrate support assembly 104 includes a ground plate 200 surrounding an insulating layer 205, an electrode 210 (e.g., an RF electrode configured as a facility or backplane), and an electrostatic chuck 215 assembled in a vertical stack.

[0031] The electrostatic chuck 215 includes one or more adsorption electrodes (e.g., the first electrode 109) embedded therein for adsorption of the substrate 105 to the support surface of the electrostatic chuck 215. A quartz tubular ring 220 surrounds the electrode 210 and the electrostatic chuck 215 to insulate the electrostatic chuck 215 from the ground plate 200. A plasma shield 225 is disposed on an upper surface of the quartz tubular ring 220 to facilitate confinement of the plasma within the processing chamber 100 (e.g., Figure 1 A quartz ring 230 is positioned on the upper surface of the plasma sheath 225 .

[0032] The electrostatic chuck 215 includes one or more channels 235 formed in a first material 236 through which fluid is provided to facilitate temperature control of the substrate support assembly 104. The first material 236 is a metallic material, such as aluminum. The electrostatic chuck 215 includes the first electrode 109 embedded in a second material 240. The second material 240 is a dielectric material, such as a ceramic material, such as aluminum oxide or aluminum nitride.

[0033] Electrode 210 can be made of an electrically conductive material, such as aluminum or other suitable electrically conductive material, and is positioned between a lower portion of ground plate 200 and electrostatic chuck 215. Electrode 210 is coupled to RF power source 110 and is configured to heat substrate 105 using RF energy. Electrode 210 can also be configured to route fluids and / or gases from an input location (e.g., at a bottom thereof, not shown) to an output location (e.g., at a top thereof, not shown).

[0034] Electrode 245, surrounded by or embedded in a ceramic layer 246 (e.g., aluminum oxide or aluminum nitride), is disposed adjacent to or in electrostatic chuck 215 to facilitate temperature control of substrate 105. Electrode 245 can be, for example, a resistive heater having a plurality of resistive heating elements embedded therein. Electrode 245 is coupled to AC power source 113 via AC power transmission line 119.

[0035] A ceramic ring 250 is disposed on electrostatic chuck 215 (e.g., on first material 236 or heater electrode) and surrounds a radially outward edge of second material 240. Ceramic ring 250 can be made of, for example, aluminum oxide or aluminum nitride and can have a thickness in a range of about 1 millimeter to about 20 millimeters. One or more O-rings 221 can be disposed between ceramic ring 250 and second material 240 to protect any adhesive material from being exposed therebetween.

[0036] Ring electrode 111 can be a component of ceramic ring 250 or separate from ceramic ring 250. For example, in the illustrated embodiment, ring electrode 111 is embedded in ceramic ring 250. Ring electrode 111 can be positioned about 0.3 millimeters to about 1 millimeter, such as about 0.75 millimeters, from an upper surface of ceramic ring 250. Ring electrode 111 can have a width of about 3 millimeters to about 20 millimeters, such as about 15 millimeters.

[0037] Ring electrode 111 is positioned radially outward from a perimeter of substrate 105 and below edge ring 106. In one example, ring electrode 111 can have an inner diameter that is greater than 200 millimeters, or greater than 300 millimeters, or greater than 450 millimeters. Ring electrode 111 is electrically coupled to ground and / or matching network 112 by edge conditioning circuit 155, which can include one or more capacitors and / or inductors. Ring electrode 111 can be coupled to edge conditioning circuit 155 by a plurality of transmission lines 265 (shown as two). For example, ring electrode 111 can be coupled to edge conditioning circuit 155 by three transmission lines 265 that are spaced apart around substrate support assembly 104 at uniform intervals (e.g., 120 degrees).

[0038] Figure 3 is a schematic diagram of a substrate support assembly 104 in accordance with at least some embodiments of the present disclosure Figure 2FIG. 2 is a diagram of an equivalent lumped circuit model 300 of RF coupling between an RF electrode (e.g., electrode 210) and an embedded resistive heater (e.g., electrode 245) of a substrate support assembly 104. Figure 4 FIG. 4 is a flowchart of a method 400 of monitoring processing conditions in a processing volume of a processing chamber, in accordance with at least some embodiments of the present disclosure.

[0039] The inventors have discovered that due to the embedding of electrode 245 in ceramic layer 246, electrode 210 and electrode 245 can behave as a transformer 302. For example, electrode 210 can behave as a primary winding 304 of transformer 302, and electrode 245 can behave as a secondary winding 306 of transformer 302. RF energy supplied to electrode 210 by RF power source 110 is coupled to electrode 245. The RF energy coupled to electrode 245 travels along AC power transmission line 119, and decays (e.g., attenuates) due in part to the resistance and inductance associated with AC power transmission line 119, which can be represented by inductor and resistor combination 318, shown at both the input and output of AC power source 113.

[0040] At 402, radio frequency (RF) power from an RF power source is supplied to a processing volume for processing a substrate. For example, RF power source 110 can be used to provide RF energy to electrode 210. The RF energy provided to electrode 210 can be used to heat, for example, substrate 105 supported on substrate support assembly 104. Some of the RF energy is inductively induced (RF coupled) into electrode 245, and travels along AC power transmission line 119.

[0041] At 404, the induced RF voltage from electrode 245 is monitored (e.g., measured) at the capacitively coupled port 123 of RF filter circuit 115. For example, the RF voltage, which is the portion of the RF voltage induced into electrode 245 that decays (e.g., due to decay along AC power transmission line 119), can be measured by controller 108. For example, controller 108 can use one or more devices suitable for monitoring the coupled RF voltage. For example, in at least some embodiments, an oscilloscope, a spectrum analyzer, or the like can be used to monitor / measure the coupled RF voltage at capacitively coupled port 123. In at least some embodiments, monitoring the RF voltage includes monitoring the RF voltage peak-to-peak (Vpp). Controller 108 can be configured to monitor the RF Vpp according to one or more control schemes. For example, controller 108 can be configured to continuously or periodically (e.g., over a certain timeframe) monitor the RF Vpp. For example, in at least some embodiments, controller 108 can be configured to continuously monitor the RF Vpp at capacitively coupled port 123 while processing a substrate (e.g., in real-time).

[0042] At 406, a processing state in the processing volume can be determined based on the monitored RF voltage. For example, the controller 108 is configured to compare the measured / monitored RF voltage to previously measured / monitored RF voltages stored in, for example, the memory 142. Based on the measured / monitored RF voltage, the controller 108 can determine a processing state, for example, a state of the plasma 116 in the processing volume of the processing chamber 100. For example, a sudden change in Vpp of the measured / monitored RF voltage can indicate non-stable or stable plasma conditions.

[0043] Furthermore, to avoid damage to the AC power source 113 and / or the AC power transmission line 119 that can be caused by the relatively high RF current associated with the RF voltage, a combination of inductor and capacitor 117 can be used to pass only relatively low RF (e.g., about 60 Hz to about 100 Hz).

[0044] While the foregoing relates to embodiments of the present disclosure, other and further embodiments of the present disclosure can be devised without departing from the basic scope thereof.

Claims

1. A process chamber for processing a substrate, comprising: a chamber body defining a process volume; a radio frequency (RF) power source configured to transmit RF energy to the process volume for processing a substrate; a substrate support comprising an electrode; an AC power source configured to supply power to the process chamber; an RF filter circuit connected between the electrode and the AC power source; and a controller configured to monitor at the RF filter circuit an RF voltage induced into the electrode during operation by the RF power source indirectly, and configured to determine a process condition in the process volume based on the monitored RF voltage, wherein the monitored RF voltage is an attenuated portion of the RF voltage induced into the electrode, the RF filter circuit is connected to an AC power supply transmission line of the AC power source, and comprises: a capacitive coupling port coupled to the controller and configured to provide a measurement of the RF voltage to the controller; and an inductor and a capacitor connected in series and configured as a low pass frequency filter, and the monitored RF voltage is attenuated due to resistance and inductance associated with the AC power supply transmission line. the capacitive coupling port is configured to provide a capacitive coupled power of about -40 dB to about -47 dB. the monitored RF voltage is a voltage peak-to-peak.

2. The processing chamber of claim 1, wherein, the process condition in the process volume comprises a plasma condition in the process volume.

3. The processing chamber of claim 1, wherein, the electrode is a resistive heater having a plurality of resistive heating elements embedded in a ceramic layer of the substrate support.

4. The processing chamber of claim 1, wherein, 6. A method of monitoring a process condition in a process volume of a process chamber, comprising the steps of:

5. The process chamber of any of claims 1, 3, or 4, wherein, supplying radio frequency (RF) power from an RF power source to the process volume for processing a substrate; monitoring at an RF filter circuit an RF voltage induced into an electrode by the RF power source indirectly, wherein the RF voltage at the RF filter circuit is an attenuated portion of the RF voltage induced into the electrode, the RF voltage monitored at the RF filter circuit; and determining a process condition in the process volume based on the RF voltage at the RF filter circuit, wherein the RF filter circuit is connected to an AC power supply transmission line of an AC power source configured to supply power to the process chamber, and comprises: a capacitive coupling port coupled to a controller of the process chamber and configured to provide a measurement of the RF voltage to the controller; and an inductor and a capacitor connected in series and configured as a low pass frequency filter, and the RF voltage at the RF filter circuit is attenuated due to resistance and inductance associated with the AC power supply transmission line. the capacitive coupling port is configured to provide a capacitive coupled power of about -40 dB to about -47 dB. ​ 7. The method of claim 6, wherein, ​ 8. The method of claim 6, wherein, Monitoring the RF voltage includes monitoring an RF voltage peak-to-peak.

9. The method of claim 6, wherein, The process condition in the process volume includes a plasma condition in the process volume.

10. The method of claim 6, 8 or 9, wherein, The electrode is a resistive heater having a plurality of resistive heating elements embedded in a ceramic layer of a substrate support of the process chamber.

11. A non-transitory computer readable storage medium having stored thereon instructions which, when executed by a processor, perform a method of monitoring a process condition in a process volume of a process chamber, the method comprising: supplying radio frequency (RF) power from an RF power source to the process volume for processing a substrate; monitoring an RF voltage induced into an electrode indirectly from the RF power source at an RF filter circuit, wherein the RF voltage at the RF filter circuit is an attenuated portion of the RF voltage induced into the electrode, the RF voltage monitored at the RF filter circuit; and determining a process condition in the process volume based on the RF voltage at the RF filter circuit, wherein the RF filter circuit is connected to an AC power supply transmission line of an AC power source configured to supply power to the process chamber, and includes: a capacitive coupling port coupled to a controller of the process chamber and configured to provide a measurement of the RF voltage to the controller; and an inductor and a capacitor connected in series and configured as a low pass frequency filter, and the RF voltage at the RF filter circuit is attenuated due to resistance and inductance associated with the AC power supply transmission line.

12. The non-transitory computer-readable storage medium of claim 11, wherein, the capacitive coupling port is configured to provide a capacitive coupled power of about -40 dB to about -47 dB.

13. The non-transitory computer-readable storage medium of claim 11, wherein, Monitoring the RF voltage includes monitoring an RF voltage peak-to-peak.

14. The non-transitory computer-readable storage medium of claim 11, wherein, The RF voltage at the RF filter circuit is an attenuated portion of the RF voltage induced into the electrode.

15. The non-transitory computer readable storage medium of any one of claims 11 or 13, wherein, The process condition in the process volume includes a plasma condition in the process volume.

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