In-situ electric field detection method and apparatus

Abstract

An embodiment of the present disclosure includes an electric field measurement system including a first light source, a first optical sensor configured to receive electromagnetic energy transmitted from the first light source, an electro-optical sensor, and a controller. The electro-optical sensor can include a package having a first electro-optical crystal disposed within a body thereof, and at least one optical fiber. The optical fiber is configured to transmit the electromagnetic energy transmitted from the first light source to a surface of the first electro-optical crystal and transmit at least a portion of the electromagnetic energy transmitted to the surface of the first electro-optical crystal and then passing through at least a portion of the first electro-optical crystal to the first optical sensor. The first optical sensor is configured to generate a signal based on an attribute of the electromagnetic energy received by the first optical sensor from the at least one optical fiber. The controller is configured to generate a command signal based on the signal received from the first optical sensor.

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE Embodiments of the present disclosure generally relate to systems and methods used during semiconductor device manufacturing. More particularly, embodiments provided herein generally include apparatus and methods for measuring electric fields generated in a plasma processing chamber for purposes of diagnosing and controlling the generated plasma formed in the plasma processing chamber. [Background technology]

[0002] Reliable fabrication of high aspect ratio features is one of the key technological challenges for next-generation semiconductor devices. One method of forming high aspect ratio features uses a plasma-assisted etching process, such as a reactive ion etch (RIE) plasma process, to form high aspect ratio openings in a material layer (e.g., a dielectric layer) of a substrate. In a typical RIE plasma process, a plasma is formed in a processing chamber, and ions from the plasma are accelerated toward the substrate surface to form openings in a material layer disposed beneath a mask layer formed on the substrate surface.

[0003] A typical reactive ion etching (RIE) plasma processing chamber includes a radio frequency (RF) bias generator that supplies an RF voltage to a power electrode (more commonly called a “cathode”), such as a metal plate positioned near an “electrostatic chuck” (ESC) assembly. The power electrode can be capacitively coupled to the processing system plasma through a thick layer of dielectric material (e.g., ceramic material) that is part of the ESC assembly. In a capacitively coupled gas discharge, the plasma is generated using a radio frequency (RF) generator coupled to the power electrode or a separate power electrode positioned outside the ESC assembly within the processing chamber through an RF matching network (“RF match”) that adjusts the apparent load to 50 Ω to minimize reflected power and maximize power delivery efficiency. Application of an RF voltage to the power electrode creates an electron-repellent plasma sheath over the processing surface of a substrate placed on the substrate support surface of the ESC assembly during processing. The nonlinear, diode-like nature of the plasma sheath results in rectification of the applied RF field, creating a direct-current (DC) voltage drop, or "self-bias," between the substrate and the plasma, making the substrate potential negative with respect to the plasma potential. This voltage drop determines the average energy of the plasma ions accelerating toward the substrate, resulting in anisotropic etching. More specifically, the ion directionality, feature profile, and etch selectivity to mask and stop layers are controlled by the ion energy distribution function (IEDF). In plasmas that include an RF bias, the IEDF typically has two non-discrete peaks, one at low energy and one at high energy, with an ion population ranging in energy between the two peaks. The existence of an ion population between the two peaks of the IEDF reflects the fact that the voltage drop between the substrate and the plasma varies with the RF bias frequency.When a lower-frequency RF bias generator is used to achieve a higher self-bias voltage, the energy difference between the two peaks can lead to process-related problems, such as bowing of the walls of the etched features formed on the substrate surface. Compared to high-energy ions, low-energy ions are less effective in reaching the bottom corners of the etched features (e.g., due to charging effects), but they sputter less mask material. This is important in high-aspect-ratio etching applications, such as hard mask opening or dielectric mold etching. As feature sizes continue to shrink and aspect ratios increase, the requirement for feature profile control becomes more stringent, while it becomes more desirable to have the substrate bias, and therefore the IEDF, properly controlled at the substrate surface during processing.

[0004] Conventional RF plasma-assisted etching processes simply apply an RF signal comprising a sinusoidal waveform to one or more electrodes in a plasma processing chamber at conventional plasma-generating bias levels, but have been found to not adequately or desirably control the sheath characteristics and generated ion energy, leading to undesirable plasma processing results, which can include excessive sputtering of mask layers and the occurrence of sidewall defects in high aspect ratio features.

[0005] Furthermore, substrate potential, or the self-bias that occurs during plasma processing, is an important parameter for ensuring controllable and desirable plasma processing results. Determining substrate potential during plasma processing of a substrate can be used to improve plasma processing results achieved on the substrate being processed and subsequent substrates in the processing chamber. For example, determining substrate potential in real time can be used to better control the actual bias voltage developed at the substrate due to capacitive coupling of waveforms applied to nearby bias electrodes and to correct for drift in substrate potential due to changes in the processing environment. In other examples, determining substrate potential can be used for plasma process diagnostics and optimization, as well as for controlling electrostatic chucking and dechucking of substrates during plasma processing. Conventionally, substrate potential can only be estimated using empirical models or cannot be experimentally measured using wired, non-production level dummy substrates or experimental probes using offline, non-production level diagnostic process test methods. Thus, using conventional processes, it is not possible to directly measure substrate potential in real time during plasma processing of semiconductor devices, including production substrates, and to control substrate potential in real time based on the measurements.

[0006] Therefore, there is a need in the art for a plasma processing apparatus and biasing method that can at least address the problems outlined above. Summary of the Invention

[0007] An embodiment of the present disclosure includes an electric field measurement system. The electric field measurement system also includes a first light source configured to transmit electromagnetic energy at one or more wavelengths and a first optical sensor configured to receive the transmitted electromagnetic energy at the one or more wavelengths. The system also includes at least one electro-optical sensor, which may include a package that may include a body, a first electro-optical crystal disposed within the body, and at least one optical fiber configured to transmit the electromagnetic energy transmitted from the first light source to a surface of the first electro-optical crystal and to transmit at least a portion of the electromagnetic energy transmitted to the surface of the first electro-optical crystal and then passing through at least a portion of the first electro-optical crystal to the first optical sensor. The first optical sensor is configured to generate a signal that varies based on at least a portion of an attribute of the electromagnetic energy received by the first optical sensor from the at least one optical fiber. The system also includes a controller configured to receive the signal generated from the first optical sensor and to generate a command signal based on the received signal. Other embodiments of this aspect include corresponding computer systems, devices, and computer programs stored on one or more computer storage devices, each configured to perform the operations of the method.

[0008]

[0006] Embodiments of the present disclosure may further include a method for performing electric field measurements using an electric field measurement system, the method including detecting an electric field generated by a first component using a first electro-optic sensor, the first electro-optic sensor including a package that may include a body, a first electro-optic crystal disposed within the body such that the generated electric field passes through at least a portion of the first electro-optic crystal, and at least one optical fiber. The method also includes transmitting electromagnetic energy using a first light source to a surface of the first electro-optic crystal via the at least one optical fiber while the electric field is generated by the first component. The method also includes transmitting at least a portion of the electromagnetic energy transmitted to the surface of the first electro-optic crystal and then passing through at least a portion of the first electro-optic crystal to a first optical sensor via the at least one optical fiber. The method also includes generating, by the first optical sensor, a first measurement signal that varies based on at least a portion of an attribute of the electromagnetic energy received by the first optical sensor from the at least one optical fiber. The method also includes generating, by the controller, a command signal based on the generated first measurement signal, the command signal configured to provide information used to adjust a setting of a process parameter of a plasma process performed in the plasma processing chamber. Other embodiments of this aspect include corresponding computer systems, apparatus, and computer programs stored on one or more computer storage devices, each configured to perform the operations of the method.

[0009] An embodiment of the present disclosure includes a method of performing electric field measurements using an electric field measurement system, the method including detecting an electric field generated by a first component using a first electro-optic sensor, the first electro-optic sensor including a package including a body, a first electro-optic crystal disposed within the body such that the generated electric field passes through at least a portion of the first electro-optic crystal, and at least one optical fiber. The method also includes using a first light source to transmit electromagnetic energy to a surface of a first electro-optic crystal via at least one optical fiber while the electric field is generated by the first component; transmitting at least a portion of the electromagnetic energy transmitted to the surface of the first electro-optic crystal and then passing through at least a portion of the first electro-optic crystal to a first optical sensor via the at least one optical fiber; generating, by the first optical sensor, a first measurement signal that varies based on attributes of at least a portion of the electromagnetic energy received by the first optical sensor from the at least one optical fiber; and generating, by a controller, a command signal based on the generated first measurement signal, the command signal being configured to provide information used to adjust settings of process parameters of a plasma process performed in the plasma processing chamber.

[0010] An embodiment of the present disclosure includes an electric field measurement system. The electric field measurement system may also include a first light source configured to transmit electromagnetic energy at one or more wavelengths, a first optical sensor configured to receive the transmitted electromagnetic energy at one or more wavelengths, at least one electro-optical sensor, and a controller. The at least one electro-optical sensor may include a package including a body, a first electro-optical crystal disposed within the body, and at least one optical fiber. The optical fiber may include at least one optical fiber configured to transmit the electromagnetic energy transmitted from the first light source to a surface of the first electro-optical crystal and transmit at least a portion of the electromagnetic energy transmitted to the surface of the first electro-optical crystal and then passing through at least a portion of the first electro-optical crystal to the first optical sensor. The first optical sensor is configured to generate a signal that varies based on at least a portion of an attribute of the electromagnetic energy received by the first optical sensor from the at least one optical fiber. The controller is configured to receive the generated signal from the first optical sensor and generate a command signal based on the received signal.

[0011] So that the above-mentioned features of the present disclosure may be understood in detail, a more particular description of the present disclosure briefly summarized above will be had by reference to embodiments, some of which are illustrated in the accompanying drawings. It should be noted, however, that the accompanying drawings depict only exemplary embodiments and therefore should not be considered as limiting the scope of the present disclosure, as other equally effective embodiments may also be permitted. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic cross-sectional view of a processing system configured to perform the methods described herein, according to one embodiment. [Figure 2] 1 is a schematic diagram of a portion of a signal detection assembly according to one embodiment. [Figure 3A] FIG. 1 is a top perspective view of a sensing assembly including a signal detection assembly according to one or more embodiments. [Figure 3B] FIG. 3B is a side cross-sectional view of the sensing assembly shown in FIG. 3A according to one embodiment. [Figure 3C] FIG. 3B is a side cross-sectional view of an alternative version of the sensing assembly shown in FIG. 3A, according to one embodiment. [Figure 3D] FIG. 1 is a cross-sectional side view of a sensing assembly according to one embodiment. [Figure 4] FIG. 1 illustrates a method for real-time wafer potential measurement in a plasma processing system according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] To facilitate understanding, wherever possible, like reference numerals have been used to designate like elements common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

[0014] FIELD OF THE DISCLOSURE Embodiments of the present disclosure generally relate to systems and methods used during semiconductor device manufacturing. More specifically, embodiments provided herein generally include apparatus and methods for measuring and controlling, in real time, the electrical potentials formed on a substrate or plasma-generating components disposed within a plasma processing chamber during processing. The measured electrical potentials can be used for plasma process monitoring, apparatus calibration, process and apparatus performance diagnostics, process chamber design optimization, and plasma processing chamber safety enhancement.

[0015] Electro-optic (EO) effect sensing devices, including electro-optic sensing elements (e.g., EO crystals), have been found to offer significant advantages over other conventional techniques used to detect electrical potentials generated within one or more regions of a plasma processing chamber. Typical conventional measurement techniques require circuits containing devices and conductive elements that typically modify and / or interfere with various electromagnetic fields generated within the plasma processing chamber during processing. Electromagnetic fields are typically generated by providing radio frequency (RF) signals and / or pulsed direct current (DC) voltage signals that are used to generate and control a plasma within a processing region of the processing chamber during operation. FIG. 1 illustrates an example of a plasma processing system 10 and controller 126 configured to perform a plasma processing method. 2 is a simplified schematic diagram of a signal detection assembly 225, which forms part of a sensing assembly 184 that may be positioned within a region of the plasma processing system 10 to sense the electric field strength E, thereby determining the voltage (V) generated within the region (i.e., electric field E=-dV / ds, where "s" is the distance the electric field extends), which may be used to control one or more aspects of the plasma process. The signal detection assembly 225 includes a laser 210 and a photodetector 211 optically coupled to one or more fiber optic sensors 250 (e.g., quartz crystals) using one or more optical fibers. The one or more optical fibers may include a first optical fiber 213 and a second optical fiber 214. The laser 210 is connected to the fiber optic sensor 250 via the first fiber optic cable 213. The fiber optic sensor 250 is connected to the photodetector 211 via the second fiber optic cable 214. When the optical fiber sensor 250 is disposed between the first electrode 203 and the second electrode 204, the optical fiber sensor can be used to detect the electric field formed between the first electrode 203 and the second electrode 204.Fiber optic sensor 250 includes an electro-optic (EO) effect sensing element, such as electro-optic crystal 290, configured to detect the magnitude of an electric field E passing through it, such as the electric field E generated between first electrode 203 and second electrode 204 during plasma processing. In one embodiment, the EO effect sensing element includes a crystal that utilizes the Pockels effect, where the birefringence of the crystal changes in proportion to an electric field applied to the optical crystal in fiber optic sensor 250. In some embodiments, electro-optic crystal 290 includes a crystalline material, such as a crystal including lithium niobate (LiNbO), LiTaO, potassium dihydrogen phosphate (KDP) and its isomorphs, beta-barium borate (BBO), a III-V semiconductor, or other non-centrosymmetric media, such as an electric-field poled polymer or glass. Any change in the electric field will alter the characteristics of the light received by detector 211 due to the effect of the change in the electric field on the EO effect sensing element, and the light transmitted through the EO effect sensing element is generated by laser 210. In some embodiments, laser 210 is configured to transmit light at a wavelength between approximately 200 and 14,000 nanometers (nm). A value associated with the change in the characteristics of the light received by photodetector 211 may then be relayed to controller 126 to determine the potential or voltage formed across the electric field-generating element in the region of plasma processing system 10 in which fiber optic sensor 250 is located.

[0016] However, it has been found that the electric field strength measurements made by most EO effect sensor designs are temperature dependent and also dependent on the orientation of the sensing crystal relative to the direction of the generated electric field lines. Accordingly, the embodiments of the present disclosure provided herein are configured to compensate for these additional measurement variables. FIGS. 3A and 3B illustrate one embodiment of a sensing assembly 184 including a sensing assembly 301 that includes multiple fiber optic sensors 250, such as a first fiber optic sensor 320 and a second fiber optic sensor 321, mounted within a package 310. The package 310 includes a body that can support and retain each of the multiple fiber optic sensors 250 and can include a dielectric material; in some embodiments, the body can include a ceramic material, a polymer material, or other material that does not interfere with the operation of the fiber optic sensors and does not significantly degrade when exposed to high temperatures, electric fields, or plasma processing environments. In one embodiment, first fiber optic sensor 320 includes a pair of optical fibers 341 and 342, each in optical communication with the surface of electro-optic crystal 290 at one end and in optical communication with first photo-detection assembly 350A at the other end. Similarly, second fiber optic sensor 321 includes a pair of optical fibers 343 and 344, each in optical communication with the surface of electro-optic crystal 290 at one end and in optical communication with second photo-detection assembly 350B at the other end. Optical fibers 341, 342 and 343, 344 are each disposed within a support sleeve 311 that extends between the surface of the body of package 310 and photo-detection assemblies 350A, 350B and is used to protect the optical fibers from the external environment and to prevent damage during installation and / or use. The sleeve 311 can be further protected using ceramic beads, flexible metal tubing, or other useful materials that can provide chemical and thermal insulation and / or resistance to the elements to which the sleeve 311 will be exposed during processing.

[0017] During operation, the light emitting assembly 351 within the light detecting assembly 350 includes a laser 210 configured to transmit electromagnetic radiation (e.g., coherent light) to input optical fibers 341, 343, which transmit the generated radiation to and through the electro-optic crystal 290, which, in some configurations, reflects and / or returns a majority of the generated radiation to output optical fibers 342, 344, which then transmit the generated radiation to the photodetector 352, which is configured to detect aspects of the received radiation (e.g., intensity, polarization, etc.) and transmit information regarding the detected aspects of the received radiation to the controller 126. The photodetector 352 is configured to receive the electromagnetic radiation provided by the light emitting assembly 351 and then provide a signal including information regarding the detected aspects of the received electromagnetic radiation. The optical detector 352 may include an optoelectronic device, such as a photoelectric sensor (e.g., a photodiode, a photomultiplier tube), a photoconductive sensor, a photorefractive sensor, or any other useful device configured to convert electromagnetic energy into a signal usable by the controller 126. The controller 126 may then use the signal received from the optical detector 352 to generate a command signal to control an aspect of a process running in the processing chamber 100 or to control the use of a piece of hardware in the processing chamber 100. In general, the controller 126 will analyze and use information provided in the signal received from the optical detector 352 to monitor certain aspects of the plasma process, aid in the calibration and / or performance improvement of one or more processing chamber components, optimize processing chamber design, and ensure the safety of the plasma processing chamber, as described further below. The analysis performed by the controller 126 may include comparing the information provided in the signal to system configuration data stored in the memory of the controller 126. The system configuration data may include previously generated benchmark data from previous process runs and / or user-defined thresholds defined to ensure portions of the processing chamber are functioning properly.

[0018] 3A and 3B, the first and second fiber optic sensors 320, 321 are spaced a fixed distance apart in a direction (e.g., the X direction) so that each of the electro-optic crystals 290 in each fiber optic sensor 250 can detect a different portion of the electric field E passing through various components in the detection assembly 301 during processing. Generally, it is desirable that the surfaces 325, 326 of the first and second fiber optic sensors 320, 321, respectively, be oriented in a desired direction relative to the generated electric field E. In one example, the surfaces 325, 326 of the first and second fiber optic sensors 320, 321, which may align with features (e.g., crystal faces) in the electro-optic crystal 290, are oriented orthogonal to the direction of the dominant electric field E lines (e.g., the Z direction). In some embodiments, it is desirable for the detection assembly 301 to include three or more fiber optic sensors 250. In one example, package 310 includes a first fiber optic sensor 320, a second fiber optic sensor 321, and a third fiber optic sensor (not shown) that are oriented to separately measure the electric field E in three different orthogonal directions, such that each major surface (e.g., surfaces 325, 326) of each fiber optic sensor is oriented orthogonal to a separate one of the X, Y, and Z coordinate directions.

[0019] To compensate for temperature drift or variations in the measured electric field strength, and therefore the measured voltage, the measurements provided in the signals received by the controller 126 from the photodetector 352 can be adjusted using fiber optic sensor calibration data stored in the memory of the controller 126. In one embodiment, the effect of temperature on the measurements from each of the fiber optic sensors 320, 321 can be stored in a time-varying form or as data in a look-up table created based on known processing sequences. In one example, variations in the optical properties of the electro-optic crystal 290 are collected and stored in memory for multiple standard plasma processing sequences performed in a first plasma processing chamber, and the stored data is used in a subsequent plasma processing sequence to help adjust measurements made in a similarly configured second plasma processing chamber performing one of the multiple standard plasma processing sequences. In another embodiment, the effect of temperature changes on the measurement results can be determined by synchronizing the cessation or withdrawal of the electric field-generating signal to the electrode, radio frequency (RE) coil, or electric field-generating element for a short period of time to allow the fiber optic sensor 250 to collect at least one measurement in the absence of the electric field E, whereby changes in the optical properties of the electro-optic crystal 290 can be collected by comparing the measurement taken while the electric field E is turned off with a previous measurement taken when the electric field was not present. In one example, the optical properties of the electro-optic crystal 290 are measured at one or more intervals when the generated electric field E is turned off and compared to the optical properties of the electro-optic crystal 290 taken at a time before the start of the plasma process. In one example process, the photodetector 352 is adapted to provide a measurement signal to the controller 126 in real time, the measurement signal including a first portion where the electric field is sensed by the fiber optic sensor 250 and a second portion where the electric field is not sensed by the fiber optic sensor 250, thereby allowing the effect of temperature to be determined by comparing the two portions of the measurement signal.In any of the above cases, a temperature effect correction factor determined by use of a formula, data in a look-up table, or by comparison of measurements taken at various times, can then be used to adjust the optical data collected by one or more fiber optic sensors and improve the accuracy of the derived voltage measurements.

[0020] 3C illustrates one embodiment of a sensing assembly 184 that includes a detection assembly 301 that includes at least one fiber optic sensor 250 (i.e., first fiber optic sensor 320) configured to detect variations in an electric field and at least one fiber optic sensor 250 (i.e., second fiber optic sensor 321) that is similarly configured but shielded from the electric field E through the use of a shielding element 360. The shielding element 360 may include a conductive layer (e.g., a metal layer) disposed within the body of the package 310 that is sized to act as a Faraday shield for the shielded fiber optic sensor. In this configuration, due to the proximity of the two fiber optic sensors 250 and their thermal coupling to each other due to their positions within the package 310, the measured optical properties of the electro-optic crystal 290 within the shielded fiber optic sensor are substantially unaffected by the presence of the electric field E passing through the body of the package 310 and can be used as a baseline value to adjust measurements made by the other fiber optic sensor that is exposed to the electric field E. In one example, the measurement baseline value measured by the shielded second optical fiber sensor 321 can be subtracted from the measurement obtained by the first optical fiber sensor 320, thus eliminating the effect of temperature changes on the measurement results.

[0021] 3D illustrates one embodiment of the sensing assembly 184, including a detection assembly 301 including at least one fiber optic sensor 250 (i.e., first fiber optic sensor 320) configured to detect variations in the electric field E and at least one optical temperature measurement assembly 370 configured to measure the temperature of the electro-optic crystal 290 while the fiber optic sensor 250 acquires measurements of the electric field E. The optical temperature measurement assembly 370 can include an optical fiber 371 arranged to collect radiation emitted from the electro-optic crystal 290 at one end and transmit the collected electromagnetic radiation to a detector disposed in an optical detection assembly 372 disposed at the opposite end. In this case, a temperature measurement signal generated by electronics in the optical detection assembly 372 due to received radiation emitted from the surface 327 of the electro-optic crystal 290 can be provided to the controller 126, so that measurements collected by the fiber optic sensor 250 can be adjusted based on previous calibration data stored in memory to compensate for variations in the temperature of the electro-optic crystal 290. Conventional optical temperature measurement assemblies configured to measure within the desired temperature range to which the electro-optic crystal 290 will be exposed during processing are available from Omega Engineering, Inc. of Norwalk, Connecticut, USA, or Advanced Energy Inc. of Fort Collins, Colorado, USA.

[0022] In some alternative embodiments, a temperature sensor (e.g., an optical temperature sensor probe) external to the detection assembly 301 and not affected by the electric field E may be used. In this case, the temperature signal generated by the external temperature sensor is sent to the controller 126 for processing and electric field compensation.

[0023] Measuring device and processing method As described above, the sensing assembly 184 includes, for example, a detection assembly 301 including a package 310 containing one or more fiber optic sensors 250, and an optical detection assembly 350A optically coupled to the fiber optic sensors 250 via optical fibers 341, 342. Returning to FIG. 1 , each sensing assembly 184 is communicatively connected to the controller 126 via communication line 165. In this case, the controller 126 can use the output signals received from each of the optical detection assemblies to display measurements performed by the fiber optic sensors 250 and / or control portions of the processing chamber 100 during processing. As described in further detail below, the processing chamber 100 can include one or more sensing assemblies 184 positioned to detect the electric field, and therefore the generated voltage, within a region of the processing chamber 100 and provide feedback to the controller 126. Changes in the sensed parameters detected by the fiber optic sensors 250 are communicated from the sensing assembly 184 to the controller 126. The controller 126 can then use the input received from the sensing assembly 184 to modify one or more plasma processing variables, such as the characteristics of the RF signal or the pulse voltage (PV) waveform generated by the pulse voltage (PV) waveform generator 175 and / or the amount of current supplied from the current source 177 to the bias electrode 104 in the processing chamber 100.

[0024] 1 is a schematic cross-sectional view of a plasma processing system 10 that can be configured to perform one or more plasma processing methods. In some embodiments, the plasma processing system 10 is configured for a plasma-assisted etching process, such as a reactive ion etching (RIE) plasma process. The plasma processing system 10 can also be used for other plasma-assisted processes, such as plasma-enhanced deposition processes (e.g., plasma-enhanced chemical vapor deposition (PECVD) processes, plasma-enhanced physical vapor deposition (PEPVD) processes, plasma-enhanced atomic layer deposition (PEALD) processes, plasma processing, plasma-based ion implantation processes, or plasma doping (PLAD) processes. In one configuration, as shown in FIG. 1 , the plasma processing system 10 is configured to form a capacitively coupled plasma (CCP). However, in some embodiments, the plasma can alternatively be generated by an inductively coupled source positioned above a processing region of the plasma processing system 10. In this configuration, an RF coil can be positioned above a ceramic lid (vacuum boundary) of the plasma processing system 10.

[0025] The plasma processing system 10 includes a processing chamber 100, a substrate support assembly 136, a gas system 182, a DC power system 183, an RF power system 189, one or more sensing assemblies 184, and a controller 126. The processing chamber 100 includes a chamber body 113, which includes a chamber lid 123, one or more sidewalls 122, and a chamber base 124. The chamber lid 123, the one or more sidewalls 122, and the chamber base 124 collectively define a processing space 129. The one or more sidewalls 122 and the chamber base 124 generally comprise a material (e.g., aluminum, an aluminum alloy, or a stainless steel alloy) sized and shaped to provide structural support for the elements of the processing chamber 100 and configured to withstand the pressures and additional energy applied thereto while a plasma 101 is generated in a vacuum environment maintained within the processing space 129 of the processing chamber 100 during processing. A substrate 103 is loaded into and removed from the processing space 129 through an opening (not shown) in one of the sidewalls 122. The opening is sealed by a slit valve (not shown) during plasma processing of the substrate 103. A gas system 182 connected to the processing space 129 of the processing chamber 100 includes a process gas source 119 and a gas inlet 128 disposed through the chamber lid 123. The gas inlet 128 is configured to supply one or more process gases from the multiple process gas sources 119 to the processing space 129.

[0026] The processing chamber 100 further includes a chamber lid 123, an RF coil 181, and a lower electrode (e.g., substrate support assembly 136) disposed within the processing space 129. The chamber lid 123 and the lower electrode are disposed opposite one another. As seen in FIG. 1 , in one embodiment, a radio frequency (RF) source 171 is electrically coupled to the lower electrode. The RF source 171 is configured to provide an RF signal to generate and maintain a plasma (e.g., plasma 101) between the upper and lower electrodes. In some alternative configurations, the RF source can also be electrically coupled to the upper electrode. For example, the RF source can be electrically coupled to the chamber lid. In other examples, the RF source can also be electrically coupled to the substrate support base 107.

[0027] The substrate support assembly 136 includes a substrate support 105, a substrate support base 107, an insulating plate 111, a ground plate 112, a plurality of lift pins 186, and a bias electrode 104. Each lift pin 186 is disposed through a through-hole 185 formed in the substrate support assembly 136 and is used to facilitate movement of the substrate 103 onto and off the substrate support surface 105A of the substrate support 105. The substrate support 105 is formed of a dielectric material. The dielectric material may include a bulk-sintered ceramic material, a corrosion-resistant metal oxide (e.g., aluminum oxide (AlO), titanium oxide (TiO), yttrium oxide (YO)), a metal nitride material (e.g., aluminum nitride (AlN), titanium nitride (TiN)), a mixture thereof, or a combination thereof.

[0028] The substrate support base 107 is formed of an electrically conductive material (e.g., aluminum, an aluminum alloy, or a stainless steel alloy). The substrate support base 107 is electrically insulated from the chamber base 124 by an insulating plate 111 and a grounded plate 112 interposed between the insulating plate 111 and the chamber base 124. In some embodiments, the substrate support base 107 is configured to regulate the temperature of both the substrate support 105 and the substrate 103 placed on the substrate support 105 during substrate processing. In some embodiments, the substrate support 105 includes a heater (not shown) for heating the substrate support 105 and the substrate 103 placed on the substrate support 105.

[0029] A bias electrode 104 is embedded in the dielectric material of the substrate support 105. Typically, the bias electrode 104 is formed of one or more conductive components. The conductive components typically include a mesh, a foil, a plate, or a combination thereof. Here, the bias electrode 104 functions as a chuck pole (i.e., an electrostatic chuck electrode) used to secure (e.g., electrostatically chuck) the substrate 103 to the substrate support surface 105A of the substrate support 105. Generally, a parallel plate-like structure is formed by the bias electrode 104 and a layer of dielectric material disposed between the bias electrode 104 and the substrate support surface 105A. The dielectric material typically has an effective capacitance C of about 5 nF to about 50 nF. EThe layer of dielectric material (e.g., aluminum nitride (AlN), aluminum oxide (Al2O3), etc.) may have an effective capacitance. Typically, the layer of dielectric material (e.g., aluminum nitride (AlN), aluminum oxide (Al2O3), etc.) has a thickness of about 0.05 mm to about 5 mm, such as about 0.1 mm to about 3 mm, such as about 0.1 mm to about 1 mm, or even about 0.1 mm to about 0.5 mm. The bias electrode 104 is electrically coupled to a clamping network that supplies a chucking voltage. The clamping network includes a direct current (DC) voltage supply 173 (e.g., a high-voltage DC supply) that is coupled to a filter 178A of a filter assembly 178 disposed between the DC voltage supply 173 and the bias electrode 104. In one example, the filter 178A is a low-pass filter configured to prevent radio frequency signals and pulse voltage (PV) waveform signals provided by other bias components found in the processing chamber 100 from reaching the DC voltage supply 173 during plasma processing. In one configuration, the static DC voltage is between about −5000V and about 5000V and is supplied using an electrical conductor (such as coaxial power feed 160).

[0030] In some configurations, the substrate support assembly 136 further includes an edge control electrode 115. The edge control electrode 115 is formed of one or more conductive components. The conductive components typically include a mesh, a foil, a plate, or a combination thereof. The edge control electrode 115 is disposed below the edge ring 114 and surrounds and / or is spaced a distance from the center of the bias electrode 104. Typically, for a processing chamber 100 configured to process a circular substrate, the edge control electrode 115 is annular in shape, made of a conductive material, and configured to surround at least a portion of the bias electrode 104. As can be seen in FIG. 1 , the edge control electrode 115 is disposed within the region of the substrate support 105 and is energized using a pulsed voltage (PV) waveform generator 175.

[0031] The DC power system 183 includes a DC voltage supply 173, a pulsed voltage (PV) waveform generator 175, and a current source 177. The RF power system 189 includes a radio frequency (RF) waveform generator 171, a match 172, and a filter 174. As previously described, the DC voltage supply 173 provides a constant chucking voltage, the RF waveform generator 171 provides an RF signal to the processing region, and the PV waveform generator 175 generates a PV waveform at the bias electrode 104. By applying a sufficient amount of RF power to an electrode, such as the substrate support base 107, a plasma 101 is formed in the processing region 129 of the processing chamber 100. In one configuration, the RF waveform has a frequency range of about 1 MHz to about 200 MHz.

[0032] In some embodiments, the power supply system 183 further includes a filter assembly 178 for electrically isolating one or more components included within the power supply system 183. As shown in FIG. 1 , power supply line 167 electrically connects the output of RF waveform generator 171 to impedance match circuit 172, RF filter 174, and substrate support base 107. Power supply line 160 electrically connects the output of voltage supply 173 to filter assembly 178. Power supply line 161 electrically connects the output of PV waveform generator 175 to filter assembly 178. Power supply line 162 connects the output of current source 177 to filter assembly 178. In some embodiments, current source 177 is selectively coupled to bias electrode 104 using a switch (not shown) located in supply line 162 so that current source 177 can supply a desired current to bias electrode 104 during one or more phases (e.g., ion current phases) of the voltage waveform generated by PV waveform generator 175. In one example, the voltage waveform provided by PV waveform generator 175 can include a plurality of asymmetric voltage pulses, each having a peak voltage in the range of ±5000 V, a pulse on-time of 10%-90% of the asymmetric voltage pulse period, and a pulse repetition frequency of 100 kHz-500 kHz. As seen in FIG. 1 , filter assembly 178 can include a plurality of separate filter components (i.e., separate filters 178A-178C), each electrically connected to an output node via power supply line 164. Power supply lines 160-164 can include electrical conductors, including combinations of coaxial cables, such as rigid coaxial cables and flexible coaxial cables connected in series, insulated high-voltage corona-resistant hook-up wires, bare wires, metal rods, electrical connectors, or any combination of the above.

[0033] The controller 126, also referred to herein as a process chamber controller, includes a central processing unit (CPU) 133, memory 134, and support circuits 135. The controller 126 is used to control the process sequence used to process the substrate 103. The CPU is a general-purpose computer processor configured for use in an industrial setting to control the process chamber and its associated sub-processors. The memory 134, as described herein, is generally non-volatile memory and may include random access memory, read-only memory, a hard disk drive, or other suitable forms of local or remote digital storage. The support circuits 135 are conventionally connected to the CPU 133 and include cache, clock circuits, input / output subsystems, power supplies, etc., as well as combinations thereof. Software instructions (programs) and data for instructing the processor in the CPU 133 may be coded and stored in the memory 134. The software programs (or computer instructions) readable by the CPU 133 in the controller 126 determine which tasks are executable by the components in the plasma processing system 10.

[0034] Typically, a program readable by CPU 133 in controller 126 includes code that, when executed by CPU 133, performs tasks related to the plasma processing schemes described herein. The program may include instructions used to control various hardware and electrical components within plasma processing system 10 to perform various process tasks and various process sequences used to carry out the methods described herein. In one embodiment, the program includes instructions used to perform one or more of the steps described below in connection with FIG. 4.

[0035] The controller 126 communicates with the pulsed voltage (PV) waveform generator 175 and the radio frequency (RF) waveform generator 171, thereby enabling one or more command signals provided by the controller 126 to control aspects (e.g., waveform characteristics) of the output signals provided by the pulsed voltage (PV) waveform generator or the radio frequency (RF) waveform generator during processing.

[0036] Processing method example 4 illustrates a method for real-time wafer potential measurement of a substrate or plasma-generating component disposed within a plasma processing chamber. Method 400 includes generating a plasma in a processing region of the processing chamber, monitoring electrical characteristics of sensors disposed within detection assemblies 301 within sensing assembly 184, forming a set of adjustment parameters based on the electrical characteristics, and adjusting one or more plasma processing parameters based on the monitored electrical characteristics of the sensors. Prior to performing method 400, one or more detection assemblies 301, and thus one or more fiber optic sensors 250 disposed within the body of the package 310 of each detection assembly 301, are positioned within one or more regions of processing chamber 100 and aligned to detect a portion of the electric field formed therein.

[0037] At activity 402, the method 400 includes forming a plasma 101 in the processing chamber 100 due, at least in part, to an RF signal provided from an RF waveform generator 171 of an RF power system 189 being provided to an electrode in the processing chamber 100. In some embodiments of activity 402, an asymmetric voltage waveform is also provided from a PV waveform generator 175 to an electrode (e.g., bias electrode 104) disposed in the processing chamber 100.

[0038] At activity 404, method 400 includes measuring one or more sensed parameters based on measurements collected by one or more sensors disposed within process chamber 100. The one or more sensed parameters may include one or more of the following: electric field strength measured by fiber optic sensor 250, changes in optical properties of electro-optic crystal 290, and, in some cases, changes in temperature measurements provided by a temperature sensor. In some embodiments, the sensed parameters include real-time measurements of the generated electric field E in a region of process chamber 100 using one or more of fiber optic sensors 250 in sensing assembly 184. Activity 404 may include measuring the generated electric field E in a region of RF coil 181 ( FIG. 1 ) to detect regions of RF coil 181 that contain higher or lower electric field E than expected and are therefore prone to arcing or plasma non-uniformities. The measurements for the region of RF coil 181 being measured are relayed to controller 126 via communication line 165 for analysis. Prior to measurements being taken during activity 404, the detection assembly 301, and thus one or more fiber optic sensors 250 disposed within the body of the package 310, are positioned and aligned so that a surface of the one or more fiber optic sensors 250 (e.g., surfaces 325, 326 shown in FIG. 3B) is aligned in a desired orientation to detect the electric field E generated by a region of the RF coil 181.

[0039] Additionally or alternatively, during activity 404, measurements of the electric field E generated within a region of the RF matcher 172 or filter assembly 178 are performed to detect regions of the RF matcher 172 or filter assembly 178 containing higher or lower electric fields E than expected. These regions containing higher or lower electric fields may be a signal that an arc may be more likely to occur or that a field-generating component may be at risk of premature failure. Measurements of the regions of the RF matcher 172 or filter assembly 178 being measured during processing are relayed to the controller 126 via communication line 165 for analysis. It is contemplated that detecting that the electric fields generated by various electrical components within the RF matcher 172 and filter assembly 178, such as fixed or variable inductors, variable capacitors, and grounding elements (e.g., grounding straps), are outside of desired ranges may be useful in preventing any of these electrical components from causing variations in process results or damage to portions of the processing chamber 100.

[0040] Additionally or alternatively, during activity 404, measurements of the electric field E generated within the processing region 129 of the processing chamber 100 are performed using a movable probe assembly (not shown) configured to be adjustably positioned within various regions of the processing region 129 of the processing chamber 100 using an articulated arm (not shown) attached to the wall of the processing chamber 100 during plasma processing. The movable probe assembly can be used to map the electric field E generated within various regions of the processing chamber 100. The mapped electric field can then be used to adjust the power or characteristics of the electrical signals supplied to the plasma generating components and / or to further physically adjust the plasma generating components to alter plasma uniformity and / or prevent arcing or other undesirable attributes of the processing chamber design.

[0041] Additionally or alternatively, during activity 404, measurements of the electric field E generated at the surface of the substrate 103 are performed using an instrumented substrate. The instrumented substrate includes one or more detection assemblies 301 aligned, oriented, and distributed in an array across the surface of the substrate to detect the amount of generated electric field E in each region of the substrate surface to determine the amount of plasma non-uniformity and / or skew in plasma density formed across the various regions of the substrate surface. Referring to FIG. 1 , in some embodiments, the support sleeve 311 and its associated optical fiber are connected to a vacuum-compatible connector 137 configured to transfer optical signals passing between portions of the optical fiber inside and outside the processing chamber, and between the optical fiber sensor 250 and the optical detection assembly 350. Measurements of the electric field E in the various regions of the substrate surface being measured are relayed to the controller 126 via communication line 165 for analysis.

[0042] In some alternative configurations, measurements of the electric field E generated at the surface of the substrate 103 are performed using an array of fiber optic sensors 250 (not shown) that are aligned, oriented, and embedded within the substrate support 105, such as in the region between the bias electrode 104 and the substrate support surface 105A. In this configuration, the support sleeve 311 and its associated optical fiber may be positioned to exit the bottom of the substrate support assembly 136 for connection to an associated optical detection assembly 350 configured to provide a signal to the controller 126.

[0043] At activity 406, method 400 includes monitoring and analyzing changes in a sensed parameter detected by one or more fiber optic sensors 250 and other sensing elements (e.g., optical temperature measurement assembly 370) in one or more sensing assemblies 184. During activity 406, controller 126 compares data received from one or more fiber optic sensors 250 and other sensing elements with information stored in memory of controller 126 or other received sensor data to determine a desired correction amount needed to compensate for temperature drift occurring in one or more fiber optic sensors 250. The stored information may include an equation or lookup table configured to provide a correction amount based on data related to temperature fluctuations received by controller 126 using one of the techniques described above. In one example, the sensed parameter is a change in electric field strength over time between times when no electric field E is present within a region of process chamber 100. In another example, the sensed parameter is determined by the difference in electric field E detected by first fiber optic sensor 320 and second fiber optic sensor 321, which is shielded from the electric field E using shielding element 360. The controller 126 then analyzes and uses the data received over time to determine the amount of adjustment needed to the measurement of the electric field E to compensate for temperature variations.

[0044] In activity 408, the controller 126 then uses the determined adjustment amount and the obtained adjusted measurement data to generate a command signal, which is used to adjust one or more plasma processing parameters based on the adjusted measurement. The plasma processing parameters may include any plasma processing variable that will affect the process results seen on the substrate during or after plasma processing, and may include, but are not limited to, RF power levels provided by the RF source, PV power levels provided by the PV source, actions to stop the plasma process, gas flow rates, process chamber pressure, and substrate temperature. In one example, the controller 126 determines that the adjusted set of measurement data provided by the detection assembly 301 is higher than expected by comparing the adjusted measurement data with stored system configuration data, and then generates a command signal that is used to stop a process running in the processing chamber due to the possibility of arcing occurring in the processing chamber. In some embodiments of activity 408, the controller may also calculate an adjusted voltage measurement based on the determined adjusted electric field E measurement and display information related to the measurement on a graphical user interface (GUI) or store the result in memory for later use. In one example, the controller 126 determines, by comparing the adjusted set of measurement data provided by the detection assembly 301 in a region of the plasma processing chamber, that the adjusted set of measurement data is higher or lower than expected by comparing the adjusted measurement data with stored system configuration data, and then generates a command signal that is used to provide information to a user that the electric field E in that region of the chamber is outside of a desired range and therefore may need to adjust, service, or replace one or more chamber components.

[0045] The embodiments of the present disclosure described herein can be used to measure and control, in real time, the electrical potentials formed on a substrate or plasma-generating components disposed within a plasma processing chamber during processing. As described herein, the measured electrical potentials can be used for plasma process monitoring, equipment calibration, process and equipment performance diagnostics, process chamber design optimization, and plasma processing chamber safety enhancement.

[0046] While the foregoing specification is directed to embodiments of the present disclosure, other and additional embodiments of the disclosure may be devised without departing from the basic scope thereof, the scope of which is defined by the claims that follow.

Claims

1. 1. An electric field measurement system, comprising: a first light source configured to transmit electromagnetic energy at one or more wavelengths; a first optical sensor configured to receive the electromagnetic energy transmitted at the one or more wavelengths; at least one electro-optical sensor; The at least one electro-optical sensor comprises: A package containing the body, a first electro-optic crystal disposed within the body; and at least one optical fiber, directing the electromagnetic energy transmitted from the first light source to a surface of the first electro-optic crystal; and transmitting at least a portion of the electromagnetic energy transmitted to the surface of the first electro-optic crystal and then passing through at least a portion of the first electro-optic crystal to the first photosensor. at least one optical fiber configured to perform Including, the first optical sensor is configured to generate a signal that varies based on an attribute of the at least a portion of the electromagnetic energy received by the first optical sensor from the at least one optical fiber; The electric field measurement system further comprises: a controller configured to receive the generated signal from the first optical sensor and generate a command signal based on the received signal; An electric field measurement system comprising:

2. a second light source configured to transmit electromagnetic energy at one or more wavelengths; a second optical sensor configured to receive the electromagnetic energy transmitted at the one or more wavelengths; Furthermore, The at least one electro-optical sensor comprises: a second electro-optic crystal disposed within the body; and at least one optical fiber, directing the electromagnetic energy transmitted from the second light source to a surface of the second electro-optic crystal; and transmitting at least a portion of the electromagnetic energy transmitted to the surface of the second electro-optic crystal and then passing through at least a portion of the second electro-optic crystal to the second photosensor. at least one optical fiber configured to perform Including, the second optical sensor is configured to generate a signal that varies based on an attribute of the at least a portion of the electromagnetic energy received by the second optical sensor from the at least one optical fiber; 2. The electric field measurement system of claim 1, wherein the controller is further configured to receive the generated signal from the second optical sensor and to generate the command signal based on the signals received from the first optical sensor and the second optical sensor.

3. The at least one electro-optical sensor comprises: a shielding element disposed over the second electro-optic crystal and configured to shield the second electro-optic crystal from an electric field E passing through the body; The electric field measurement system of claim 2 further comprising:

4. 2. The electric field measurement system of claim 1, wherein the controller is configured to communicate with at least one of a pulse voltage (PV) waveform generator and a radio frequency (RF) waveform generator, and the command signal is configured to cause the pulse voltage (PV) waveform generator or the radio frequency (RF) waveform generator to adjust an output signal provided therefrom.

5. 10. The electric field measurement system of claim 1, wherein the controller comprises a processor configured to execute computer-readable instructions that cause the system to measure an electric field strength over time within a region of a plasma processing chamber using the at least one electro-optical sensor.

6. The controller has a processor configured to execute computer readable instructions, the computer readable instructions providing the system with: applying a first radio frequency (RF) waveform to a first electrode using an RF generator; measuring an electric field strength over time within a region of a plasma processing chamber using the at least one electro-optical sensor; modifying the first RF waveform generated by the RF generator based on the measured field strength; The electric field measurement system according to claim 1 ,

7. The controller has a processor configured to execute computer readable instructions, the computer readable instructions providing the system with: applying a first voltage waveform to a first electrode using a pulsed voltage (PV) waveform generator; measuring an electric field strength over time within a region of a plasma processing chamber using the at least one electro-optical sensor; modifying a pulse voltage (PV) waveform generated by the pulse voltage (PV) waveform generator based on the measured electric field strength; The electric field measurement system according to claim 1 ,

8. 2. The electric field measurement system of claim 1, wherein the at least one electro-optical sensor is disposed within an RF matcher, the RF matcher having an input coupled to an output of an RF generator and an output adapted for coupling to an electrode disposed within a plasma processing chamber, and the at least one electro-optical sensor is disposed to detect an electric field generated by one or more components within the RF matcher.

9. 10. The electric field measurement system of claim 1, wherein the at least one electro-optical sensor is positioned near a portion of an RF coil disposed in a plasma processing chamber, the at least one electro-optical sensor being positioned to detect an electric field generated by at least the portion of the RF coil during a process performed in the plasma processing chamber.

10. 10. The electric field measurement system of claim 1, wherein the at least one electro-optical sensor further comprises an array of electro-optical sensors disposed on a surface of a substrate configured to be mounted on a substrate support in the plasma processing chamber during a process performed in the plasma processing chamber.

11. 1. A method of performing electric field measurements using an electric field measurement system, comprising: detecting an electric field generated by a first component using a first electro-optical sensor, the first electro-optical sensor comprising: A package containing the body, a first electro-optic crystal disposed within the body such that the generated electric field passes through at least a portion of the first electro-optic crystal; and At least one optical fiber detecting an electric field, transmitting electromagnetic energy using a first light source through the at least one optical fiber to a surface of the first electro-optic crystal while the electric field is generated by the first component; transmitting at least a portion of the electromagnetic energy transmitted to the surface of the first electro-optic crystal and then passing through at least a portion of the first electro-optic crystal to a first optical sensor via the at least one optical fiber; generating, by the first optical sensor, a first measurement signal that varies based on an attribute of at least a portion of the electromagnetic energy received by the first optical sensor from the at least one optical fiber; generating, by a controller, a command signal based on the generated first measurement signal, the command signal being configured to provide information used to adjust a setting of a process parameter of a plasma process being performed in the plasma processing chamber; A method comprising:

12. 12. The method of claim 11, wherein the processing parameters include modifying a first voltage waveform generated by a pulse voltage (PV) waveform generator or a radio frequency (RF) waveform generated by an RF generator.

13. The method of claim 12 , wherein the first component is selected from the group consisting of a component in an RF match box, a component in a filter assembly, and a portion of an RF coil.

14. Generating the first measurement signal comprises: generating a first portion of the first measurement signal during a first time period; generating a second portion of the first measurement signal during a second time period, wherein the electric field generated by the first component is generated during the first time period and no electric field is generated by the first component during the second time period; Including, Generating the command signal based on the generated first measurement signal includes: comparing the first portion of the first measurement signal with the second portion of the first measurement signal; modifying the information provided in the command signal used to adjust processing parameter settings based on the comparison; and The method of claim 12 further comprising:

15. detecting an electric field generated by the first component using a second electro-optical sensor; While the electric field is being generated by the first component, transmitting electromagnetic energy using a second light source through the at least one optical fiber to a surface of a second electro-optic crystal disposed within the body of the package; transmitting at least a portion of the electromagnetic energy transmitted to the surface of the second electro-optic crystal and then passing through at least a portion of the second electro-optic crystal to a second optical sensor via the at least one optical fiber; generating, by the second optical sensor, a second measurement signal that varies based on an attribute of at least a portion of the electromagnetic energy received by the second optical sensor from the at least one optical fiber; further comprising generating the command signals by the controller comparing the first measurement signal with the second measurement signal; modifying the information provided in the command signal used to adjust processing parameter settings based on the comparison; and The method of claim 11 further comprising:

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