Sensors for Semiconductor Processing Tools

Abstract

Described herein is a pedestal assembly comprising a platen and a sensor support plate below the platen. In at least one embodiment, the sensor support plate comprises a sensor compartment and a waveguide temperature sensor in the sensor compartment. In at least one embodiment, the waveguide temperature sensor comprises a temperature sensor comprising a first reflector structure and a second reflector structure. In at least one embodiment, the first reflector structure and the second reflector structure are separated by a gauge length.

Description

[Technical field]

[0001] Claiming priority This application claims priority to U.S. Provisional Patent Application No. 63 / 268,336, entitled "ULTRASONIC DISTRIBUTED TEMPERATURE SENSORS FOR SEMICONDUCTOR PROCESSING TOOLS," filed February 22, 2022, which is incorporated by reference in its entirety. [Background technology]

[0002] Processing tools are used to perform processes such as deposition and etching of films on substrates such as semiconductor wafers. For example, deposition may be performed to deposit conductive films, dielectric films, or other types of films using chemical vapor deposition (CVD), plasma-enhanced CVD (PECVD), atomic layer deposition (ALD), plasma-enhanced ALD (PEALD), and / or other deposition processes. Deposition may be performed in a wafer processing chamber, such as a PECVD chamber with multiple stations for processing multiple wafers at once.

[0003] Accurately and precisely sensing the temperature of vital components such as the wafer pedestal assembly and showerhead is important for process control. Currently, wafer pedestal assembly or showerhead heater input control at any given set point is achieved by a single thermocouple (TC) or resistance temperature detector (RTD). These TCs are typically spring loaded and depend on the integrity of the joints (joint failure is likely). Deformation of the components during heating changes this contact pressure, resulting in temperature variations. To measure the spatial variation in temperature, multiple TCs must be incorporated into the system, which is cumbersome and sometimes difficult to accommodate.

[0004] To measure spatial temperature variations within the wafer pedestal assembly, it is possible to use a wafer TC with multiple TCs integrated into the wafer substrate. The wafer TC may be mounted on top of the wafer pedestal assembly. While this method gives accurate temperature variations on the surface of the wafer pedestal assembly, it cannot be used in-situ during processing conditions (especially in the presence of plasma). Currently, there is no practical solution for multi-point temperature measurement on other areas of the substrate processing tool, such as in the showerhead or chamber walls. With multi-zone heater wafer pedestal assemblies under development, it is important to understand the temperature distribution in dynamic process conditions, and thus there is a need for multi-point temperature sensing for good process control. To be most effective, it may be necessary to independently monitor zone temperatures within the multi-zone wafer pedestal assembly (and other process components). Individual TCs or RTDs can be mounted at strategic locations within the wafer pedestal assembly or other process tool components, but these solutions may not be robust for some microelectronic device fabrication processes. As mentioned above, TCs or RTDs generally may not be compatible with plasma-enhanced deposition or etch processes due to the electromagnetic environment that dominates the process chamber. In another example, particle defects in deposition layers can occur due to thermal gradients across the showerhead faceplate, wafer pedestal assembly, or chamber surface walls. A multi-point temperature sensing approach can help identify cold / hot spots for potential troubleshooting. Currently, multi-point temperature sensing in wafer pedestal assemblies and showerheads is not commonly implemented in components that are integral to semiconductor processing, such as wafer pedestal assemblies, showerheads, shields, and chambers. Thus, a need exists for multi-point temperature sensing that can be used in-situ during many types of semiconductor (and other material) device fabrication processes in various parts of a substrate processing tool. [Brief description of the drawings]

[0005] The materials described herein are illustrated by way of example, and not by way of limitation, in the accompanying figures. For simplicity and clarity of illustration, elements shown in the figures are not necessarily drawn to scale. For example, dimensions of some elements may be exaggerated relative to other elements for clarity. Also, for clarity of illustration, various physical features may be represented in their simplified "ideal" forms and geometries, but it will nevertheless be understood that actual implementations may only approximate the illustrated ideals. For example, smooth surfaces and square intersections may be depicted while ignoring finite roughness, rounded corners, and imperfect angular intersections that are characteristic of structures formed by nanofabrication techniques. Additionally, where considered appropriate, reference labels are repeated among the figures to indicate corresponding or similar elements.

[0006] [Figure 1A] FIG. 1A is an exploded isometric view of a base assembly according to at least one embodiment.

[0007] [Figure 1B] FIG. 1B is an assembled isometric view of the pedestal assembly of FIG. 1A according to at least one embodiment.

[0008] [Figure 1C] FIG. 1C is a top view of the base assembly of FIG. 1A according to at least one embodiment.

[0009] [Figure 2A] FIG. 2A is a cross-sectional view of a temperature sensor strip assembly secured to a sensor support plate and a platen according to at least one embodiment.

[0010] [Figure 2B] FIG. 2B is a cross-sectional view of the temperature sensor strip assembly of FIG. 2A according to at least one embodiment.

[0011] [Diagram 3] FIG. 3 is a top view of the temperature sensor strip assembly of FIG. 2A according to at least one embodiment.

[0012] [Figure 4] FIG. 4 is an isometric 3D view of a base assembly with a serpentine temperature sensor strip according to at least one embodiment.

[0013] [Figure 5A] FIG. 5A is an isometric 3D view of a base assembly with a helical spiral temperature sensor strip according to at least one embodiment.

[0014] [Figure 5B] FIG. 5B is an orthogonal cross-sectional view of the pedestal assembly of FIG. 5A according to at least one embodiment.

[0015] [Figure 5C] FIG. 5C is an isometric 3D view of a base assembly with a double helical spiral temperature sensor strip according to at least one embodiment.

[0016] [Figure 5D] FIG. 5D is an orthogonal cross-sectional view of the pedestal assembly of FIG. 5C according to at least one embodiment.

[0017] [Figure 6] FIG. 6 is a top view of a base assembly with a folded temperature sensor strip according to at least one embodiment.

[0018] [Figure 7] FIG. 7 is a top view of a base assembly with a partial temperature sensor strip according to at least one embodiment.

[0019] [Figure 8]FIG. 8 is a top view of a base assembly with a circular temperature sensor strip according to at least one embodiment.

[0020] [Figure 9A] FIG. 9A is a partial side view of the temperature sensor strip of FIG. 1A according to at least one embodiment.

[0021] [Figure 9B] FIG. 9B is an echogram of the temperature sensor strip of FIG. 9A according to at least one embodiment.

[0022] [Figure 10] FIG. 10 illustrates an exemplary calibration curve, according to at least one embodiment.

[0023] [Figure 11A] FIG. 11A is a 3D view of a symmetric groove, according to at least one embodiment. [Figure 11B] FIG. 11B is a 3D view of a single asymmetric groove, according to at least one embodiment.

[0024] [Figure 11C] FIG. 11C is a three-dimensional view of a cylindrical acoustic waveguide temperature sensor according to at least one embodiment. [Figure 11D] FIG. 11D is a three-dimensional view of a cylindrical acoustic waveguide temperature sensor according to at least one embodiment.

[0025] [Figure 12] FIG. 12 is a top view of a showerhead with a waveguide temperature sensor according to at least one embodiment.

[0026] [Figure 13] FIG. 13 illustrates an embodiment of a waveguide temperature sensor in a process tool in accordance with at least one embodiment.

[0027] [Figure 14] FIG. 14 is a process flow diagram summarizing an exemplary method of operation of an ultrasonic waveguide temperature sensor coupled to a process tool according to at least one embodiment.

[0028] [Figure 15] FIG. 15 illustrates a system that includes a process tool in accordance with at least one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Numerous specific details, such as construction schemes, are described herein to provide a thorough understanding of one or more embodiments. It will be apparent to one of ordinary skill in the art that the embodiments may be practiced without these specific details. In other instances, well-known features, such as gas line fittings, heating elements, and snap switches, are not described in particular detail so as not to unnecessarily obscure the embodiments of the present disclosure. Furthermore, it should be understood that the various embodiments shown in the figures are illustrative representations and may not be drawn to scale.

[0030] In some cases, well-known methods and devices are shown in block diagram form rather than in detail to avoid obscuring the disclosure. Throughout this specification, reference to "one embodiment" or "one embodiment" or "at least one embodiment" or "some embodiments" means that a particular feature, structure, function, or characteristic described in connection with an embodiment is included in at least one embodiment. Thus, the phrases "in one embodiment" or "in at least one embodiment" or "in one embodiment" or "some embodiments" appearing in various places throughout this specification do not necessarily refer to the same embodiment. Furthermore, features, structures, functions, or characteristics can be combined in any suitable manner in one or more embodiments. For example, a first embodiment may be combined with a second embodiment, unless the features, structures, functions, or characteristics associated with the two embodiments are mutually exclusive.

[0031] Here, "coupled" and "connected," along with their derivatives, may be used herein to describe a functional or structural relationship between components. These terms are not intended as synonyms for each other. Rather, in certain embodiments, "connected" may be used to indicate that two or more elements are in direct physical, optical, or electrical contact with each other. "Coupled" may be used to indicate that two or more elements are in direct or indirect (with other elements between them) physical, electrical, or magnetic contact with each other and / or that two or more elements cooperate or interact with each other (e.g., in a causal relationship).

[0032] Here, "on," "under," "between," and "on" as used herein refer to the relative location of one component or material with respect to other components or materials for which such physical relationship is noteworthy. Unless these terms are modified with "direct" or "directly," one or more intervening components or materials may be present. A similar distinction is made with respect to component assemblies. As used throughout this specification and claims, a list of items linked by the terms "at least one of" or "one or more of" can mean any combination of the listed terms.

[0033] As used herein, "adjacent" may generally refer to the location of an object that is next to (e.g., immediately adjacent or nearby with one or more objects between) or in close proximity to (e.g., abutting) another object.

[0034] As used herein, "pedestal assembly" may generally refer to one or more components of a pedestal used in a process tool.

[0035] As used herein, "pedestal" may generally refer to a platform for supporting a wafer substrate. In at least one embodiment, the pedestal may comprise a pedestal assembly according to at least one embodiment.

[0036] As used herein, "platen" may generally refer to a flat portion of a pedestal assembly operable to support a wafer substrate for processing within a process tool.

[0037] Here, the term "sensor support plate" may generally refer to a component of the pedestal assembly that resides below the platen. In at least one embodiment, the sensor support plate may provide a housing for a waveguide temperature sensor.

[0038] Here, "sensor compartment" may generally refer to a component of the base assembly that is a cavity in the sensor support plate.

[0039] Here, a "waveguide temperature sensor" may generally refer to an acoustic or optical waveguide strip, wire, or optical fiber with reflector structures distributed along the length of the waveguide. In at least one embodiment, the segment of the waveguide between adjacent reflector structures is a temperature sensor.

[0040] Herein, a "temperature sensor strip" may refer to an acoustic waveguide temperature sensor having a generally rectangular cross-section.

[0041] Here, a "reflector structure" may generally refer to one or more discontinuities along an acoustic or optical waveguide. In at least one embodiment, the reflector structure may be a groove or a notch. In at least one embodiment, the discontinuity may cause reflection of an ultrasonic or optical signal launched into the waveguide.

[0042] Here, "gauge length" may generally refer to the distance between adjacent discontinuities. In at least one embodiment, the gauge length may be associated with temperature sensors distributed along the waveguide temperature sensor.

[0043] Here, a "temperature sensor" may generally refer to a segment of a waveguide temperature sensor that extends between adjacent reflector structures. In at least one embodiment, the temperature structure comprises a segment of a waveguide temperature sensor and includes reflector structures adjacent opposite ends of the waveguide segment.

[0044] Here, "strip" may generally refer to a waveguide temperature sensor having a rectangular cross-section.

[0045] Here, "acoustic signal" may generally refer to an ultrasonic excitation emitted from a transducer to an acoustic waveguide temperature sensor.

[0046] Here, a "transducer" may generally refer to a converter that converts energy from one form to another. In at least one embodiment, the transducer may be a piezoelectric transducer capable of generating mechanically excited shear waves (e.g., by vibration perpendicular to the contact surface) at frequencies up to several megahertz. In at least one embodiment, ultrasonic shear wave excitation may be coupled to the waveguide temperature sensor by mechanical contact with the transducer.

[0047] As used herein, "ultrasonic transducer" may generally refer to a device operable to couple an ultrasonic signal into a waveguide and to receive a reflected ultrasonic signal returning from the waveguide.

[0048] As used herein, "spiral geometry" may generally refer to the spiral form of a waveguide temperature sensor.

[0049] Here, a "straight segment" may generally refer to a temperature sensor strip having one or more interconnected segments that are straight. In at least one embodiment, the straight segments may extend at different angles to one another.

[0050] Here, "folding" may generally refer to a transition between straight line segments, and the temperature sensor strip may be folded to form a straight line segment.

[0051] Here, a "unit" may generally refer to a temperature sensor strip that is divided into separate smaller temperature sensor strips.

[0052] Here, "surface" may generally refer to a surface of a component of a base assembly. In at least one embodiment, the surface may be the floor of a sensor compartment of a sensor support plate.

[0053] Here, "groove" may generally refer to a track in a surface into which a temperature sensor strip may be placed.

[0054] Here, "top edge" may generally refer to the upper edge of a vertically oriented temperature sensor strip.

[0055] Here, "bottom edge" may generally refer to the lower edge of a vertically oriented temperature sensor strip.

[0056] Here, a "frame segment" may generally refer to a rigid guide that is attached to an edge of a vertically oriented temperature sensor strip. In at least one embodiment, the frame segment may allow the temperature sensor strip to be secured to a surface.

[0057] Here, "upper frame segment" may generally refer to the frame segment that is attached to the top edge of the temperature sensor strip.

[0058] Here, "lower frame segment" may generally refer to the frame segment that is attached to the lower edge of the temperature sensor strip.

[0059] Herein, a "helical spiral" may generally refer to a helix having a decreasing diameter along its axis.

[0060] Here, "sidewall" may generally refer to the broad wall of the temperature sensor strip.

[0061] Here, "wavelength" may generally refer to the distance between the crests or troughs of a wave.

[0062] Here, "shear modulus" may generally refer to a physical property of a material. In at least one embodiment, the shear modulus may be related to the lateral strain in a solid bar of the material.

[0063] As used herein, "optical fiber" may generally refer to an optical waveguide in the form of a thin fiber.

[0064] Here, the term "Bragg grating reflector structure" may generally refer to a reflector structure on an optical fiber.

[0065] As used herein, "thermographic phosphor" may generally refer to molecules that exhibit a change in refractive index property with changes in temperature.

[0066] Herein, a "vacuum chamber" may generally refer to a chamber operable to hold a high vacuum. In at least one embodiment, the vacuum chamber may be a component of a process tool. In at least one embodiment, the vacuum chamber may enable the fabrication of semiconductor devices by vacuum processes.

[0067] Here, "terminal lead" may generally refer to a portion of a waveguide temperature sensor that is coupled to an acoustic transducer, such as an ultrasonic transducer.

[0068] As used herein, "showerhead" may generally refer to a process gas distribution manifold used in a vacuum chamber.

[0069] Here, "faceplate" can generally refer to the perforated flat plate of the showerhead. In at least one embodiment, process gases can flow through openings in the faceplate of the showerhead.

[0070] Here, "return signal" may generally refer to a reflected pulse or echo of an ultrasonic or optical pulse launched into a waveguide temperature sensor.

[0071] Here, "time of flight" (TOF) may generally refer to a measurement of the time required for a pulse signal to propagate a distance. In at least one embodiment, TOF may be measured for an ultrasonic pulse to propagate to a reflector structure and return to its source.

[0072] Here, "difference" may generally refer to the difference between TOF measurements emanating from two or more reflector structures.

[0073] Unless otherwise specified by the explicit context in which they are used, "substantially equal," "about equal," and "approximately equal" herein mean that there is only incidental variation between the two items so described. In at least one embodiment, such variation is typically no more than + / - 10% of the reference value.

[0074] To address the various limitations described herein, a waveguide temperature sensor for multi-point temperature sensing is disclosed. In at least one embodiment, the waveguide temperature sensor may be a waveguide with different propagation properties with changing temperature. In at least one embodiment, the waveguide temperature sensor may include multiple reflecting structures that reflect the propagating waves. In at least one embodiment, the time of flight (TOF) of the reflected waves is measured to determine a relationship between the temperature of the waveguide and the speed (or other property) of the reflected waves. In at least one embodiment, the waveguide temperature sensor may comprise an acoustic or optical waveguide having, for example, a length to width or diameter ratio greater than 5:1. In at least one embodiment, the waveguide temperature sensor may comprise a strip waveguide with one or more waveguide segments extending between reflector structures. In at least one embodiment, in contrast to individual temperature sensors, the waveguide temperature sensor is not affected by the harsh conditions of RF plasma or chemicals in the vacuum chamber of the process tool.

[0075] In at least one embodiment, the reflector structure may generally be a structural and / or material discontinuity. In at least one embodiment, the reflector structure may be a groove or notch machined into the sidewall of the waveguide. In at least one embodiment, the groove or notch may provide an abrupt change in the cross section of the waveguide at one or more points along the length of the waveguide. In at least one embodiment, the waveguide segment extending between a pair of adjacent reflector structures may be defined as a distributed temperature sensor. In at least one embodiment, the temperature sensor may include a pair of adjacent reflector structures at the end of the waveguide segment. In at least one embodiment, the temperature sensor may also be characterized by its gauge length, defined as the length of the waveguide segment to the pair of adjacent reflector structures.

[0076] In at least one embodiment, the multiple points can each reflect a portion of the incident wave energy injected into the waveguide by an acoustic or optical transducer that propagates down the waveguide. In at least one embodiment, the reflected wave energy can propagate back toward the energy source, typically where it is recoupled into the transducer. For example, in at least one embodiment, an optical or ultrasonic transducer can be attached to one end of the waveguide as a wave energy source that both transmits and receives energy. In at least one embodiment, the reflected wave energy can return to the source end of the waveguide, while the incident energy continues to the opposite end of the waveguide. In at least one embodiment, the incident wave can eventually be reflected at the end of the waveguide.

[0077] In at least one embodiment, the waveguide temperature sensor may be incorporated on or in some process tool components. In at least one embodiment, the one or more waveguide temperature sensors may be incorporated inside a pedestal assembly used in process tools for fabricating devices from semiconductors and other materials. In at least one embodiment, the one or more waveguide temperature sensors may be incorporated in a process gas distribution showerhead that is also part of a process tool used in CVD and PECVD processes or plasma etching processes (e.g., dry reactive ion etching [DRIE] processes). In at least one embodiment, the one or more waveguide temperature sensors may be incorporated along an interior surface in a vacuum chamber of a process tool (e.g., deposition or etching). In at least one embodiment, the waveguide temperature sensor may be used on the exterior surface of a semiconductor process chamber or other components outside the chamber. In at least one embodiment, the waveguide temperature sensor may be attached to heated gas lines, vessels, and other components.

[0078] In at least one embodiment, the waveguide temperature sensors may be distributed along the length of the waveguide. In at least one embodiment, discontinuities may be fabricated along the waveguide to reflect the transmitted acoustic or optical energy back towards the transducer, which is also the signal source. In at least one embodiment, the time of flight (TOF) of the reflected acoustic wave may be measured and correlated with the local temperature of individual temperature sensors distributed along the waveguide. In at least one embodiment, TOF may be defined as the travel time of a signal injected into the waveguide (e.g., referred to as the incident signal, or forward signal) to reach the reflector structure and be reflected back towards the source. In at least one embodiment, the round trip time between the forward signal and the reflected signal may be referred to as the "time of flight," TOF. In at least one embodiment, for acoustic signals, TOF may generally be governed by the speed of sound in the material of the waveguide. In at least one embodiment, optical signals may travel at substantially the speed of light in the material of the optical waveguide, typically an optical fiber. In at least one embodiment, the material properties that govern the speed of sound or light, such as Young's modulus or refractive index, may change with temperature.

[0079] In at least one embodiment, for optical waveguide temperature sensors, the spectral shift of the reflected white light component traveling in the optical fiber waveguide can be measured and correlated with the local temperature of the individual waveguide temperature sensors using fiber Bragg gratings (FBGs). In at least one embodiment, the FBGs can exhibit temperature-dependent changes in the local refractive index of the grating, as well as temperature-induced changes in the grating distance. In at least one embodiment, other suitable temperature-sensitive optical detection methods can also be used, such as using the heat-sensitive luminescence decay lifetime of a thermographic phosphor as a coating on the optical fiber.

[0080] In at least one embodiment, temperature-induced changes in signal velocity (e.g., sound or light velocity) may cause a shift in the TOF of the reflected signal (e.g., return signal) returning to the source in both optical and acoustic waveguides. In at least one embodiment, the TOF shift can be correlated with the temperature of the waveguide segment between adjacent pairs of reflector structures. In at least one embodiment, a calibration curve can be obtained by such correlation, allowing automated multi-point temperature measurement with a single waveguide temperature sensor with multiple temperature sensors along the length of the waveguide. In at least one embodiment, the waveguide temperature sensor can be molded to place individual temperature sensors at selected locations on the surface of a process tool. In at least one embodiment, individual temperature sensors can be placed at predetermined measurement points to measure local temperatures in the vicinity of the individual temperature sensors.

[0081] In at least one embodiment, the local temperature may be the temperature of a surface in contact with the temperature sensor. In at least one embodiment, the waveguide temperature sensor may detect local temperature variations within a component of a process tool, such as a pedestal used in semiconductor device manufacturing. In at least one embodiment, multi-point temperature detection may provide detection of local hot or cold spots, as well as temperature gradients. In at least one embodiment, the process tool components may include, non-exhaustively, a chuck, a showerhead, and a vacuum chamber surface.

[0082] In at least one embodiment, the spatial resolution of temperature measurements obtained by a waveguide temperature sensor may be related to the gauge length of the individual temperature sensors distributed along its length. In at least one embodiment, the gauge length may be defined for purposes of this disclosure as the spacing between pairs of discontinuities. In at least one embodiment, the time of flight of the reflected signal may be measured and correlated with the local temperature in the vicinity of the corresponding discontinuity.

[0083] In at least one embodiment, implementation of a waveguide temperature sensor can provide advantages over deployment of individual temperature sensors, such as thermocouples and resistance temperature detector (RTD) sensors, within a process tool. Incorporating individual temperature sensors can significantly increase material and labor costs in tool manufacturing. In addition, individual temperature sensors can be difficult to deploy in sufficient numbers for high-resolution spatial temperature mapping. In at least one embodiment, a single WDT sensor can advantageously perform multi-point temperature measurements within a process tool at low material and manufacturing costs. In at least one embodiment, a single ultrasonic transducer or optical coupling can be used to inject wave pulses and detect reflected waves from the multi-point waveguide temperature sensor, which can further reduce costs. In at least one embodiment, the waveguide temperature sensor may generally not interact with radio frequency (RF) fields that are commonly used to initiate and sustain plasmas in PECVD and plasma etch process tools.

[0084] In at least one embodiment, the wave propagation mode may be determined by the orientation of the transducer relative to the waveguide axis. In at least one embodiment, the transducer may generate transverse or longitudinal waves when the excitation of the transducer is parallel or orthogonal to the longitudinal (or transverse) axis of the waveguide. In at least one embodiment, the acoustic waveguide temperature device may have a rectangular strip geometry. In at least one embodiment, an acoustic wave propagation mode specific to the rectangular geometry may be selected to minimize dispersion and loss due to leakage of acoustic energy from the waveguide to surrounding structures or to the air coupled to the waveguide. In at least one embodiment, in a strip waveguide, the fundamental shear horizontal mode (SH0) may be selected to have the lowest loss and dispersion compared to other modes in the strip waveguide. In at least one embodiment, the rectangular cross section of the strip waveguide may have dimensions of at least 5:1 to allow for substantially exclusive propagation of the SH0 mode. In at least one embodiment, some dimensions are related to the wavelength of the acoustic wave.

[0085] In at least one embodiment, the acoustic waveguide device may have a cylindrical geometry. In at least one embodiment, the cylindrical geometry may comprise a circular or suitable non-circular cross-section, such as, for example, an oval, elliptical, square, hexagonal, or octagonal cross-section. In a cylindrical waveguide, a fundamental transverse mode (e.g., T0) may exhibit the most desirable acoustic propagation characteristics. In at least one embodiment, the cross-section of the cylindrical waveguide may be designed to support the propagation of the T0 mode. In at least one embodiment, a transducer may be coupled to the cylindrical waveguide accordingly.

[0086] In at least one embodiment, the waveguide temperature sensor can be folded into different shapes to fit within limited spaces in process tool components without substantially affecting performance. In at least one embodiment, two or more waveguide temperature sensors may be nested in different configurations and have a variety of geometric shapes.

[0087] In at least one embodiment, the dimensions of the waveguide may be limited by spatial constraints within the processing tool. In at least one embodiment, the waveguide temperature sensor may be wired onto the surface of a shield or chamber wall of the substrate processing tool. In some embodiments, the wiring of the waveguide temperature sensor may involve dimensional constraints. To address these constraints, in one embodiment, the wavelength of the ultrasound may be 3 mm or less. In at least one embodiment, frequencies of 1 megahertz (MHz) or greater may be used to optimize the sensor to accommodate dimensional constraints. In at least one embodiment, in aluminum, 1 MHz ultrasound has a wavelength of approximately 3 mm.

[0088] In at least one embodiment, the acoustic waveguide may include metal, plastic, or ceramic materials. In at least one embodiment, the shape of the waveguide may be a solid rectangular strip, a cylinder, or a tube. In at least one embodiment, the discontinuities may include periodic or non-periodic grooves, or pre-induced geometric variations such as bends. In at least one embodiment, the mounting of the waveguide temperature sensor may minimize contact between the waveguide and surrounding structures. In at least one embodiment, the temperature sensor strip may include rails along segments of the waveguide edge to minimize attenuation of ultrasonic energy due to leakage to surrounding structures.

[0089] FIG. 1A illustrates an exploded isometric view of a pedestal assembly 100 according to at least one embodiment. In at least one embodiment, the pedestal assembly 100 may be used in a wafer processing station of a semiconductor processing tool. In at least one embodiment, the semiconductor processing tool may be a deposition tool or an etching tool with a vacuum chamber. In at least one embodiment, both deposition and etching may use a radio frequency environment to initiate and maintain a plasma for, for example, a plasma enhanced chemical vapor deposition (PECVD) process or a plasma etching process. In at least one embodiment, other deposition processes are within the scope of the description. In at least one embodiment, the pedestal assembly 100 may be a multi-component structure comprising a sensor support plate 102 and a heater support plate 104. In at least one embodiment, the heater support plate is stacked below the sensor support plate 102. In at least one embodiment, the sensor support plate 102 and the heater support plate 104 are fastened together by bolts or screws (not shown). In at least one embodiment, the sensor support plate 102 comprises a sensor section 106. In at least one embodiment, a temperature sensor strip 108 is housed within the sensor compartment 106. In at least one embodiment, a width w of the temperature sensor strip 108 is vertically oriented (e.g., aligned in the z-direction) within the sensor compartment 106, and the temperature sensor strip 108 may be in edge contact with a floor 114 of the sensor compartment. In at least one embodiment, a bottom edge 109 of the temperature sensor strip 108 may be in thermal contact with the floor 114 of the sensor compartment 106. In at least one embodiment, to accommodate spatial constraints, the dimensions of the sensor compartment 106, the temperature sensor strip 108 may be folded into a spiral configuration to fit within the sensor compartment 106, as shown.

[0090] In at least one embodiment, the temperature sensor strip 108 comprises a solid strip waveguide structure having a rectangular cross section with a high aspect ratio as shown (see, e.g., FIG. 6). In at least one embodiment, the high aspect ratio is at least a ratio of 10:1. In at least one embodiment, the temperature sensor strip 108 may also comprise a solid cylindrical wire waveguide for conducting ultrasonic waves. In at least one embodiment, the temperature sensor strip 108 may comprise, for example, a tubular waveguide with a core of air or other fluid. In at least one embodiment, the core may comprise a solid material. In at least one embodiment, an optical waveguide with optical fibers may be used in place of the temperature sensor strip 108. In at least one embodiment, structural components similar to the temperature sensor strip 108 may be used inside or outside the process tool. In at least one embodiment, the heated gas line may be modified to include discontinuities, such as grooves, that may cause wave reflections.

[0091] 1A, in at least one embodiment, the temperature sensor strip 108 comprises a plurality of temperature sensors (TS) 110 distributed along the temperature sensor strip 108. In at least one embodiment, the temperature sensor strip 108 is an acoustic waveguide whereby an acoustic (ultrasonic) excitation travels longitudinally along the temperature sensor strip 108. In at least one embodiment, the temperature sensor strip 108 comprises a material with high acoustic transmission (low acoustic attenuation), which allows for substantially non-dispersive acoustic propagation modes in a strip waveguide (e.g., shear horizontal mode SH0) or transverse modes in a cylindrical waveguide (e.g., T 0,1 ) In at least one embodiment, suitable materials include, but are not limited to, aluminum, stainless steel, tungsten, titanium, silica, borosilicate glass, aluminum oxide, titanium oxide, aluminum nitride, and some organic polymers.

[0092] In at least one embodiment, the temperature sensor 110 extends between a pair of adjacent grooves 112. In at least one embodiment, materials of construction can be selected to meet interrelated design criteria. In at least one embodiment, the temperature sensor strip 108 may need to accommodate the dimensional constraints of the device into which it may be incorporated. In at least one embodiment, the temperature sensor strip 108 may need to have a width that can fit within the height constraints (e.g., height h) of the sensor compartment 106. In at least one embodiment, to meet this design criteria, materials can be selected based at least in part on the phase velocity of sound in the material.

[0093] In at least one embodiment, the operating criteria for the temperature sensor strip 108 may be single mode excitation and propagation of the lowest order shear horizontal mode (SH0). In at least one embodiment, the SH0 mode includes a vibration displacement (e.g., a maximum and minimum amplitude) across the thickness of the strip waveguide (e.g., vibration parallel to the plane of the strip waveguide along the width dimension across the thickness dimension). In at least one embodiment, the lowest order shear horizontal mode (SH0) may be selected due to its dispersive characteristics in a particular material. In at least one embodiment, the SH0 mode in the strip waveguide becomes substantially non-dispersive (e.g., phase velocity is substantially constant with frequency) above a threshold excitation frequency. In at least one embodiment, the threshold frequency may be approximately 1 MHz for materials (e.g., aluminum, stainless steel) with bulk shear velocities of approximately 3000 m / s. In at least one embodiment, in materials such as aluminum or steel (or other materials with approximately the same bulk shear rate), the shear rate of the SH0 excitation mode is substantially constant at frequencies above approximately 1 MHz.

[0094] In at least one embodiment, the sound velocity of the SH0 mode can be selected to meet this operating criterion for a strip waveguide, since in many materials the sound velocity exhibits negligible dispersion and loss above a threshold frequency (e.g., shear velocity is substantially constant above 1 MHz). In at least one embodiment, any convenient frequency above 1 MHz can be selected as the operating frequency. In at least one embodiment, other modes such as the A0 mode of the Lamb wave mode (oscillating displacement across the width surface) can also be considered. In at least one embodiment, the A0 mode can be less dispersive than other modes, but still more dispersive than the SH0 mode, and approaches the bulk shear velocity of the material slower than the SH0 mode. In at least one embodiment, the temperature sensor 110, which may be a waveguide segment, may have a uniform or non-uniform gauge length, the gauge length being the distance between a pair of adjacent grooves 112.

[0095] In at least one embodiment, the grooves 112 can extend transversely to the long axis of the temperature sensor strip 108. In at least one embodiment, the grooves 112 constitute structural discontinuities that can act as reflector structures. In at least one embodiment, the grooves 112 can be considered as abrupt structural or material changes along the length of the temperature sensor strip 108 with discontinuities. In at least one embodiment, such structures can cause reflection of ultrasonic waves excited in the temperature sensor strip 108, as described below. In at least one embodiment, the temperature is measured as the time of flight (TOF) of acoustic reflections from the grooves 112.

[0096] In at least one embodiment, multiple reflections may be recorded from a single pulse of ultrasound. In at least one embodiment, the reflected ultrasound pulses may be correlated with individual grooves 112 by TOF measurements. In at least one embodiment, other types of reflector structures that may cause acoustic reflections may be used in place of the grooves 112. In at least one embodiment, such reflector structures are discontinuities and may non-exhaustively include grooves, notches, abrupt changes in dimensions and / or material including bulges, bends, protrusions, blocks of dissimilar materials that are machined, etched, or fabricated into the sidewalls of the temperature sensor strip 108. In at least one embodiment, the reflector structures may be positioned at regular or irregular intervals along the temperature sensor strip 108.

[0097] In at least one embodiment, due to the non-dispersive nature of the SH0 (or A0) mode, the time of flight may be substantially independent of frequency above a threshold frequency (e.g., above 1 MHz). In at least one embodiment, it may be possible to freely select a suitable operating frequency. In at least one embodiment, the SH0 mode may be generated by a suitable ultrasonic transducer coupled to the temperature sensor strip 108. In at least one embodiment, the transducer excites ultrasonic horizontal shear waves that vibrate along a plane parallel to the width dimension of the waveguide, which may propagate through the waveguide as the SH0 mode.

[0098] In at least one embodiment, to select single-mode propagation that is advantageous for the SH0 mode, the temperature sensor strip 108 can conform to design criteria that are advantageous for SH0 propagation within the strip waveguide. In at least one embodiment, for substantially exclusive SH0 mode excitation, the design rules of the waveguide can require that the width of the temperature sensor strip 108 be at least 5λ (e.g., w>5λ), where λ is the wavelength of the excitation frequency within the material of the waveguide. In at least one embodiment, since λ = c / f, the parameter c is the propagation speed of the SH0 mode wave within the material. In at least one embodiment, the speed c can have a threshold that satisfies the design criterion of 5λ < h for a desired operating frequency f. In at least one embodiment, the selected material can exhibit a shear speed close to c.

[0099] In at least one embodiment, the width of the temperature sensor strip 108 is selected so as not to exceed the height h of the sensor section 106. In at least one embodiment, the minimum width of the temperature sensor strip 108 can be 5λ. In at least one embodiment, for a design criterion using a maximum width of 10 mm, the shear wavelength λ of the ultrasonic wave can be 2 mm or less within an aluminum waveguide. In at least one embodiment, for an operating frequency of approximately 1.5 MHz, a material that exhibits a shear speed of at least 3000 m / s can be selected as the temperature sensor strip 108 so that λ can be approximately 2 mm. In at least one embodiment, materials that exhibit a shear speed close to 3000 m / s can include aluminum, steel, nickel, titanium, tungsten, molybdenum, and borosilicate glass.

[0100] In at least one embodiment, the operating frequency of the temperature sensor strip 108 supporting the SH0 mode propagation may be determined at least in part from the frequency dimension product, which is a figure of merit derived from an analysis of the dispersion relations in the strip waveguide. In at least one embodiment, the dimension may be the thickness of the temperature sensor strip 108, where for the SH0 mode, frequency x thickness ≥ 1.565 MHz-mm. In at least one embodiment, there may also be a design rule for the thickness of the temperature sensor strip 108 based on the frequency x thickness product. In at least one embodiment, the operating frequency may be at least approximately 1.5 MHz when the thickness is 1 mm or less. In at least one embodiment, the operating frequency may be further limited by a susceptibility to mode conversion and energy leakage that occurs at frequencies less than approximately 1 MHz. In at least one embodiment, the mode propagation may be further limited by a low frequency cutoff where the mode cannot propagate in the material. In at least one embodiment, the SH0 mode may have a cutoff of approximately 500 kHz in aluminum or steel with a width of approximately 7 or 8 mm.

[0101] Referring again to FIG. 1A, the plurality of grooves 112 are shown as being substantially uniform, however, in at least one embodiment, some individual grooves 112 may have substantially different dimensions than other grooves. In at least one embodiment, the grooves 112 may be combined with other types of structural discontinuities, such as bulges, bends, and interfaces with other materials, as described above. In at least one embodiment, other structural materials that may be integrated into the temperature sensor strip 108 may have a shear modulus that is different from the bulk shear modulus of the waveguide. In at least one embodiment, the grooves 112 may partially reflect the injected ultrasonic energy back to the source as it passes through the waveguide to the end of the waveguide. In at least one embodiment, some losses may occur due to friction and leakage of energy from the side walls. In at least one embodiment, the partially attenuated acoustic energy may be totally reflected from the end of the waveguide back to the source, which may be an ultrasonic transducer, as described below. In at least one embodiment, multiple attenuated reflections may appear as echoes at the source.

[0102] In at least one embodiment, the groove 112 extends across the entire width w of the temperature sensor strip 108, as shown. In at least one embodiment, the groove 112 can extend partially across the width w. In at least one embodiment, the groove 112 has a rectangular cross-section (example shown in FIG. 11A). In at least one embodiment, the groove 112 can have a round cross-section. In at least one embodiment, the groove 112 can be symmetrically positioned on both sides of the temperature sensor strip 108, as shown. In at least one embodiment, the groove 112 can be asymmetrically positioned. In at least one embodiment, the groove 112 can be present on one side with no opposing groove.

[0103] In at least one embodiment, a pair of adjacent grooves 112 can define a gauge length (e.g., a lengthwise extent) of an individual temperature sensor 110. In at least one embodiment, the gauge length of an individual temperature sensor 110 can coincide with a temperature zone within the pedestal assembly 100 (or other process component). In at least one embodiment, adjacent temperature sensors 110 can be in different temperature zones. In at least one embodiment, heat transfer by any or all of conductive, convective, or radiative paths can allow an individual temperature sensor 110 to thermally equilibrate with the current surrounding environment. In at least one embodiment, an approximate average zone temperature can be calculated as an average of the temperatures from a pair of adjacent grooves 112. In at least one embodiment, the spatial resolution of the temperature sensors 110 can be modified by adjusting the gauge length of some or all of the temperature sensors 110.

[0104] In at least one embodiment, the grooves 112 may be positioned at predetermined temperature measurement points distributed in a two-dimensional pattern on the sensor support plate 102. In at least one embodiment, the temperature sensor strip 108 may be incorporated into the sensor compartment 106 in a number of suitable geometric shapes. In at least one embodiment, the temperature sensor strip 108 may be wound into a spiral having a suitable diameter to fit within the sensor compartment 106. Other suitably shaped implementations are described below. In at least one embodiment, the coordinates of the location may be predetermined xy or radial coordinates of the sensor compartment 106. In at least one embodiment, the gauge length of the individual temperature sensors 110 may also be adjusted as desired to increase or decrease the spatial resolution of the temperature measurement.

[0105] In at least one embodiment, the temperature sensor strip 108 may be wound to fit within the sensor compartment 106. In at least one embodiment, a particular coil spiral may place a groove 112 at a predetermined temperature probe location along the floor 114 of the sensor compartment 106, as shown. In at least one embodiment, the spiral geometry of the temperature sensor strip 108 may include a number of turns and a winding pitch to position the temperature sensor 110 at a particular location within the sensor compartment 106 to obtain a temperature measurement. In at least one embodiment, a two-dimensional mapping of the temperature distribution on the sensor support plate 102 and within the pedestal assembly 100 may be determined by collecting TOF data of reflected ultrasonic pulses. In at least one embodiment, the temperature mapping data may be continuously interrogated and updated by firing pulses of ultrasonic energy at the temperature sensor strip 108.

[0106] In at least one embodiment, the temperature sensor strip 108 can perform multi-point measurements with a single device (e.g., a metal waveguide strip or wire) to eliminate the need for multiple installations of individual sensors to map temperature in two- or three-dimensional space. In at least one embodiment, such installation requirements may include complex cabling and electronic interfaces. In at least one embodiment, the thermocouples and RTDs should not be exposed to the RF environment (or subsequent plasma) without special shielding. In at least one embodiment, the temperature sensor strip 108 is robust to the RF and plasma environments. In at least one embodiment, the temperature sensor strip 108 can be easily installed using relatively simple cabling and electronic interfaces. In at least one embodiment, the multi-point temperature measurements may be included in a feedback circuit that dynamically controls the heat output of a heating element, for example, to maintain spatial uniformity of the temperature of the substrate during a deposition or etching process.

[0107] In at least one embodiment, the temperature sensor strip 108 may include a tail lead 116. In at least one embodiment, the tail lead 116 may not have a reflective structure such as a notch or groove. In at least one embodiment, the tail lead 116 may extend perpendicular to the sensor support plate 102. In at least one embodiment, the tail lead 116 may be angled by bending the temperature sensor strip 108 in a desired direction. In at least one embodiment, the tail lead 116 may be routed through an opening 118 in the floor 114 of the sensor support plate 102. In at least one embodiment, the tail lead 116 may be coupled to an ultrasonic transceiver (not shown) further below the pedestal assembly 100.

[0108] In at least one embodiment, the heater support plate 104 includes a heater element 120 disposed on a top surface 113 of the heater support plate 104. In at least one embodiment, the heater element is operable to provide heat to the base assembly 100. In at least one embodiment, the heater element 120 can be a resistive element that can be coupled to a power source. In at least one embodiment, the heater element 120 can be between the heater support plate 104 and the sensor support plate 102. In at least one embodiment, a groove (shown in dashed hidden lines) that follows the contour of the heater element 120 is on the bottom surface 121 of the sensor support plate 102 to allow seating of an upper portion of the heater element 120 against the sensor support plate 102. In at least one embodiment, such a groove can increase thermal contact between the heater element 120 and the sensor support plate 102. In at least one embodiment, the heater element 120 can provide a heat source to the platen 128 to raise the temperature of the wafer substrate and enable surface reactions to occur at a desired rate during a deposition or etch process. In at least one embodiment, temperature gradients, as well as hot or cold spots, can exist across the plate and wafer substrate, which can affect the quality and uniformity of the deposition or etch.

[0109] In at least one embodiment, power and electrical connections for the electric heating element and electrodes may be provided by cables and wires that may be routed through pedestal stem 122. In at least one embodiment, pedestal stem 122 extends from a base 124 of heater support plate 104. In at least one embodiment, pedestal stem 122 is a tubular structure that may be routed through tail lead 116 and heater element lead 126. In at least one embodiment, pedestal stem 122 may include a flange (not shown) for mounting to a support post.

[0110] 1B illustrates an assembled isometric view of pedestal assembly 100, according to at least one embodiment. In at least one embodiment, pedestal assembly 100 further comprises a platen 128. In at least one embodiment, platen 128 is operable to support a semiconductor wafer. In at least one embodiment, platen 128 comprises a metal, such as aluminum, or a dielectric material, such as aluminum nitride. In at least one embodiment, platen 128 comprises a plasma electrode (not shown) embedded within platen 128 below upper surface 130. In at least one embodiment, platen 128 comprises an electrostatic clamping electrode (not shown) for clamping a wafer to upper surface 130.

[0111] In at least one embodiment, the platen 128 may be mounted on a rim 132 of the sensor support plate 102. In at least one embodiment, the width w of the temperature sensor strip 108 may be approximately equal to the height h between the floor 114 and the rim 132 of the sidewall 134 of the sensor compartment 106. In at least one embodiment, the upper edge 136 of the temperature sensor strip 108 is in thermal contact with the platen 128. In at least one embodiment, electrodes may be included within the platen 128 for electrostatically clamping the wafer substrate and / or for generating an RF plasma.

[0112] In at least one embodiment, the pedestal stem 122 can also provide conduits for routing power conductors for an electrostatic clamping (ESC) electrode and radio frequency (RF) conductors for supplying the ESC and plasma electrodes, respectively, within the platen 128. Referring again to Figures 1A and 1B, the description of the implementation of the temperature sensor strip 108 may be in the context of the pedestal assembly 100, although similar features may be common to other possible implementations, such as a process gas delivery showerhead (e.g., showerhead 1200, Figure 12) or chamber surface (e.g., process tool 1300, Figure 13).

[0113] 1C shows a top view of the base assembly 100, according to at least one embodiment. In at least one embodiment, the inset shows a close-up of the grooves 112, illustrating the rectangular cross-sectional shape for the grooves 112a and 112b. In at least one embodiment, the grooves 112a and 112b occur on opposing sidewalls 138 and 140 of the temperature sensor strip 108. In at least one embodiment, the grooves 112 may be asymmetrically positioned (see, e.g., FIG. 11B), as described below.

[0114] In at least one embodiment, the grooves 112a and 112b may have a circular cross-section. In at least one embodiment, certain design rules may be applied to the width dimension L of the grooves 112a and 112b. In at least one embodiment, L may be determined by taking the wavelength λ of the SH0 wave divided by six (e.g., λ / 6). In at least one embodiment, the grooves 112 may have a width L that is substantially equal to or greater than 1 / 6 of the wavelength of the acoustic signal propagated in the waveguide. In at least one embodiment, the depth of the grooves 112 may be approximately 100-300 microns. In at least one embodiment, the thickness t of the temperature sensor strip 108 may be 1 mm or less.

[0115] In at least one embodiment, the temperature sensor strips 108 can be mechanically coupled to the floor 114 by gluing the temperature sensor strips 108 and / or to an opposing top plate (e.g., platen 128, FIG. 1B). In at least one embodiment, the sensor support plate 102 can be heated by convection, conduction, and / or radiative heat transfer from the heater elements 120. In at least one embodiment, a temperature gradient can be generated within the sensor compartment 106 along the surfaces of the sensor support plate 102 and platen 128.

[0116] In at least one embodiment, the temperature sensor strip 108 can be optimally shaped to place the temperature sensors 110 at predetermined locations in the central portion and periphery of the sensor compartment 106. In at least one embodiment, the intermediate region may not be in direct contact with the temperature sensor strip 108. In at least one embodiment, the lateral temperature gradient can be interpolated, for example, by measuring the temperatures at the center and periphery.

[0117] 2A illustrates a cross-sectional view of a temperature sensor strip assembly 200 secured to the sensor support plate 102 and the platen 128, according to at least one embodiment. In at least one embodiment, the temperature strip assembly 200 includes an upper frame segment 202 and a lower frame segment 204. In at least one embodiment, the lower edge 109 and upper edge 136 of the temperature sensor strip 108 may be seated within grooves (shown in dashed lines) in the lower and upper support frame segments 204 and 202.

[0118] In at least one embodiment, the floor 114 of the sensor support plate 102 and the surface 205 of the platen 128 include grooves 206 and 208, respectively. In at least one embodiment, the upper frame segment 202 is seated in the groove 208. In at least one embodiment, the lower frame segment 204 is seated in the groove 206. In at least one embodiment, the lower frame segment 204 and the upper frame segment 202 can increase the structural rigidity of the temperature sensor strip 108 and can be press fit or brazed to the side walls of the grooves 206 and 208, respectively. In at least one embodiment, the upper frame segment 202 and the lower frame segment 204 can have any suitable length. In at least one embodiment, the upper and lower frame segments 202 and 204 can extend lengthwise between the grooves 112 of the temperature sensor strip 108. In at least one embodiment, the upper and lower frame segments 202 and 204 extend over the groove 112. In at least one embodiment, the upper and lower frame segments 202 and 204 may be adhered onto flat surfaces on the floor 114 of the sensor support plate 102 and the surface 205 of the platen 128, respectively.

[0119] FIG 2B illustrates a cross-sectional view of the temperature sensor strip assembly 200, according to at least one embodiment. In at least one embodiment, FIG 2B illustrates an orthogonal view (relative to FIG 2A) of the temperature sensor strip 108 secured within the base assembly 100. In at least one embodiment, the upper edge 136 and the lower edge 109 of the temperature sensor strip 108 may be press-fit into grooves in the upper and lower frame segments 202 and 204, respectively, without permanent adhesion. In at least one embodiment, the temperature sensor strip 108 may be adhered to the side walls of the grooves 210 and 212 of the upper and lower frame segments 202 and 204, respectively, by brazing or an adhesive coating.

[0120] In at least one embodiment, adjacent temperature sensors (e.g., temperature sensor 110, FIG. 1A) may be supported by upper and lower frame segments 202 and 204. In at least one embodiment, upper and lower frame segments 202 and 204 may be mechanically coupled to every third, fourth, or fifth temperature sensor (110). In at least one embodiment, coverage of sidewalls 138 and 140 by upper and lower frame segments 202 and 204 may be limited to reduce leakage of ultrasonic energy from temperature sensor strip 108. In at least one embodiment, height h3 of lower frame segment 204 or upper frame segment 202 may be limited to cover only 10%-20% of the surface of sidewalls 138 and 140 to avoid measurable energy loss and possible mode conversion.

[0121] In at least one embodiment, grooves 206 and 208 are shown in cross section to show width w and depth d. In at least one embodiment, width w can be between 2 and 4 mm, and depth d can be between 1 mm and 5 mm. In at least one embodiment, grooves 206 and 208 can be machined into sensor support plate 102 and platen 128 to a desired shape and dimensions during manufacturing. In at least one embodiment, grooves 206 and 208 can provide guided mounting of temperature sensor strip 108.

[0122] FIG. 3 illustrates a top view of the temperature sensor strip assembly 200, according to at least one embodiment. In at least one embodiment, the lower frame segment 204 can bend to follow the curvature of the groove 206 in the sensor support plate 102, as shown. In at least one embodiment, the groove 206 can be in the form of a spiral groove in the sensor support plate 102, which facilitates assembly of the temperature sensor strip 108 to the pedestal assembly 100. In at least one embodiment, the curvature of the lower frame segment 204 illustrated in FIG. 3 can substantially match the spiral curvature of the corresponding groove, although the lower frame segment 204 can have any suitable curvature or linearity that matches the particular geometry of the temperature sensor strip 108. In at least one embodiment, the shape of the groove 206 can guide the attachment of the temperature sensor strip 108 to the sensor support plate 102 in any suitable geometry. In at least one embodiment, the upper frame segment 202 mounted on the top edge 136 of the temperature sensor strip 108 may be similarly curved to follow the spiral curvature of a similar groove (208) in the platen 128.

[0123] 4 illustrates an isometric 3D view of a pedestal assembly 400 comprising a temperature sensor strip 402 supported on a sensor support plate 102, according to at least one embodiment. In at least one embodiment, the temperature sensor strip 402 comprises multiple straight segments 404 joined by folded segments 406 to form a serpentine geometric shape. In at least one embodiment, the temperature sensor strip 402 is shaped to fit within the sensor compartment 106. In at least one embodiment, the straight segments 404 and the folded segments 406 are oriented such that the width w is parallel (flat) to the plane of the floor 114 of the sensor support plate 102. In at least one embodiment, the serpentine shape may allow multiple temperature sensors 410 (e.g., segments of the temperature sensor strip 402 between grooves 412) to be arranged in a rectangular grid pattern.

[0124] In at least one embodiment, the grooves 412 may be symmetric across the upper 408 and lower 414 sidewalls of the temperature sensor strip 402, as shown in the inset, with a groove 412a on the upper 408 sidewall and an opposing groove 412b on the lower 414 sidewall. In at least one embodiment, some or all of the grooves 412 may be asymmetrically distributed. In at least one embodiment, one of the upper or lower sidewalls 408 or 414 may include a groove (e.g., one of grooves 412a or 412b).

[0125] In at least one embodiment, the temperature sensor strip 402 may be coupled to an ultrasonic transducer (not shown) that is coupled to one or both of the terminals 416 or 418. In at least one embodiment, the terminals 416 and 418 extend below the sensor support plate 102 as described above (see FIGS. 1A and 1B). In at least one embodiment, one of the terminals 416 or 418 may be a dead terminal that allows for terminal reflection of ultrasonic energy excited by the transducer.

[0126] FIG. 5A shows an isometric 3D view of a pedestal assembly 500 according to at least one embodiment. In at least one embodiment, a temperature sensor strip 502 may be housed within the sensor compartment 106 of the sensor support plate 102. In at least one embodiment, the temperature sensor strip 502 is formed as a helical spiral. In at least one embodiment, the temperature sensor strip 502 is oriented such that the width w is aligned in the xy plane of the figure (e.g., flat to the plane of the floor 114). In at least one embodiment, the temperature sensor strip 502 may have a three-dimensional structure, whereby the temperature sensor strip 502 occupies multiple planes within the sensor compartment 106. In at least one embodiment, the helical structure may allow for mapping of temperature in three-dimensional space within the sensor compartment 106. In at least one embodiment, multiple temperature sensors 510 may be positioned at desired three-dimensional coordinates within the sensor compartment 106. In at least one embodiment, adjusting the gauge length of the temperature sensor 510, as well as adjusting the radius and pitch of the spiral along the helical axis A-A', can allow for flexible placement of the temperature sensor 510. In at least one embodiment, the temperature sensor 510 extends between adjacent grooves 512.

[0127] 5B illustrates an orthogonal cross-sectional view of the pedestal assembly 500, according to at least one embodiment. In at least one embodiment, the spiral structure of the temperature sensor strip spans approximately the height h3 of the sensor section 106. As noted above, the temperature sensor strip 502 can enable sensing of temperature in three dimensions. In at least one embodiment, the temperature sensor strip 502 has a decreasing diameter along the central axis AA, enabling temperature measurements at multiple x,y coordinates within the sensor section 106.

[0128] FIG. 5C illustrates an isometric 3D view of the pedestal assembly 500, according to at least one embodiment. In at least one embodiment, the temperature sensor strip 502 comprises two separate sections, temperature sensor strip 502a and temperature sensor strip 502b. In at least one embodiment, both the temperature sensor strip 502a and the temperature sensor strip 502b may have a helical spiral configuration, as shown. In at least one embodiment, the temperature sensor strip 502a is coaxial with the temperature sensor strip 502b. In at least one embodiment, separating the temperature sensor strip 502 into two or more sections may enable a higher quality of the reflected signal returning to the transducer. In at least one embodiment, the attenuation of the reflected signal may be a function of the length of the temperature sensor strip 502. In at least one embodiment, dividing the temperature sensor strip 502 into two or more units reduces the overall signal path length of any one of the sensor strips. In at least one embodiment, the signal to noise ratio may be improved, for example.

[0129] In at least one embodiment, temperature sensor strips 502a and 502b can share a common helical axis A-A'. In at least one embodiment, the helical axis can further coincide with a central axis of the sensor support plate 102. In at least one embodiment, temperature sensor strip 502a can have a smaller lateral span than temperature sensor strip 502b. In at least one embodiment, temperature sensor 510a and temperature sensor 510b can have the same gauge length.

[0130] 5D illustrates an orthogonal cross-sectional view of the pedestal assembly 500, according to at least one embodiment. In at least one embodiment, the temperature sensor strip 502a may be stacked on top of the temperature sensor strip 502b in a coaxial configuration. In at least one embodiment, the temperature sensor strips 502a and 502b include terminal leads 520a and 520b, respectively. In at least one embodiment, the terminal leads 520a and 520b extend below the sensor support plate 102, for attachment to a transducer, for example. In at least one embodiment, the terminal leads 520a and 520b may be routed through the pedestal stem 122.

[0131] FIG. 6 illustrates a plan view of a base assembly 600 including a temperature sensor strip 602, according to at least one embodiment. In at least one embodiment, the base assembly 600 includes a temperature sensor strip 602 in a sensor compartment 106 of a sensor support plate 102. In at least one embodiment, the temperature sensor strip 602 includes a plurality of straight segments 604. In at least one embodiment, the straight segments 604 extend between folds 606. In at least one embodiment, the folds 606 have a radius of curvature of at least 1 mm. In at least one embodiment, the folds 606 can be bent at an angle of at least 90 degrees. In at least one embodiment, the segments 604 have a uniform width w2. In at least one embodiment, the segments 604 are oriented flat such that the width w2 is aligned with the xy plane of the figure. In at least one embodiment, adjacent straight segments 604 can be oriented at an acute or obtuse angle relative to one another. In at least one embodiment, the temperature sensor strip 602 is flat, substantially planar, and has an overall height of 1-2 mm. In at least one embodiment, several temperature sensor strips 602 may be deployed at multiple vertical levels within the sensor compartment 106.

[0132] In at least one embodiment, the temperature sensor strip 602 comprises two sections, temperature sensor strip 602a and temperature sensor strip 602b. In at least one embodiment, the temperature sensor strips 602a and 602b may be juxtaposed within the sensor compartment 106 such that the terminal leads 608a and 608b are adjacent. In at least one embodiment, the terminal leads 608a and 608b may extend vertically (e.g., in the z-direction) through an opening 610 below the sensor support plate 102 (e.g., into the pedestal stem 122, FIGS. 1A and 1B). The temperature sensor strips 602a and 602b may be coupled to an ultrasonic transducer located therein.

[0133] In at least one embodiment, the temperature sensor 612 extends between the grooves 614. In at least one embodiment, the grooves 614 are the primary reflector structure in the temperature sensor strips 602a and 602b. In at least one embodiment, the folds 606 may not measurably reflect acoustic energy and do not impede reflection from the grooves 614.

[0134] In at least one embodiment, the temperature sensor strip 602 may be configured by folding as shown in FIG. 6, although other folding configurations are possible for optimal temperature sampling. In at least one embodiment, the temperature sensor strips 602a and 602b may be positioned by adjusting the position of the temperature sensor 612 near a measurement point, such as the measurement point indicated by the black dot in FIG. 6. In at least one embodiment, the measurement point may be predetermined. In at least one embodiment, the measurement point may be near a heater element, such as heater element 120 (FIG. 1B), indicated by the dashed outline below the floor 114 of the sensor support plate 102.

[0135] FIG. 7 illustrates a top view of a pedestal assembly 700 including a temperature sensor strip 702, according to at least one embodiment. In at least one embodiment, the temperature sensor strip 702 includes two separate temperature sensor strips 702a and 702b. In at least one embodiment, the temperature sensor strip 702 can be split into two or more smaller temperature sensor strips to reduce acoustic signal path length to improve signal quality. In at least one embodiment, the temperature sensor strips 702a and 702b include terminal leads 704a and 704b, respectively, that can be routed through an opening 706 in the floor 114. In at least one embodiment, the terminal leads 704a and 704b can extend vertically (e.g., in the z-direction) below the sensor support plate 102. In at least one embodiment, the terminal leads 704a and 704b can be attached to an ultrasonic transducer that transmits pulses and receives reflected pulses (echoes) from the temperature sensor strips 702a and 702b, respectively.

[0136] In at least one embodiment, the temperature sensor strips 702a and 702b include a straight segment 708. In at least one embodiment, the straight segment 708 extends between creases 710. In at least one embodiment, the straight segment 708 may have any suitable length. In at least one embodiment, the straight segment 708 may have any suitable angle relative to adjacent straight segments 708. In at least one embodiment, the straight segment 708 includes at least one temperature sensor 712. In at least one embodiment, the temperature sensor 712 extends between grooves 714. In at least one embodiment, the grooves 714 are the primary reflector structures in the temperature sensor strips 702a and 702b. The creases 710 may have a bend radius adjusted to not cause a measurable reflection. In at least one embodiment, the creases 710 may have a bend radius of 1 mm or greater.

[0137] In at least one embodiment, the temperature sensor strip 702a at least partially surrounds the temperature sensor strip 702b. In at least one embodiment, the temperature sensor strip 702a can be folded into a quasi-hexagonal configuration. In at least one embodiment, the temperature sensor strip 702a surrounds the temperature sensor strip 702b. In at least one embodiment, the temperature sensor strip 702b can be folded into a compact shape confined to a central portion of the sensor compartment 106. In at least one embodiment, the temperature sensor strip 702a extends through a peripheral region of the sensor compartment 106. In at least one embodiment, the temperature sensor 712 can be positioned to sample temperatures near the sampling points indicated by the black dots in the diagram.

[0138] FIG. 8 illustrates a top view of a pedestal assembly 800 including a temperature sensor strip 802, according to at least one embodiment. In at least one embodiment, the temperature sensor strip 802 includes two smaller temperature sensor strip units, a temperature sensor strip 802a and a temperature sensor strip 802b. In at least one embodiment, the temperature sensor strips 802a and 802b are configured as arcs. In at least one embodiment, the temperature sensor strip 802a may follow the arc of the sensor support plate 102 within the peripheral region of the sensor compartment 106. In at least one embodiment, the sensor support plate 102 may follow the inner arc of the sensor support plate 102. In at least one embodiment, the arc configuration of both temperature sensor strips 802a and 802b distributes the temperature sensors 804a and 804b near sample points, shown as black dots, in both the peripheral and inner portions of the sensor support plate 102.

[0139] In at least one embodiment, temperature sensors 804a and 804b are distributed along temperature sensor strips 802a and 802b, respectively. In at least one embodiment, temperature sensors 804a and 804b extend between grooves 806. In at least one embodiment, temperature sensors 804a and 804b are curved segments of temperature sensor strips 802a and 802b, respectively. In at least one embodiment, temperature sensors 804a and 804b can have similar or different lengths. In at least one embodiment, the length of temperature sensors 804a and 804b can be determined by sensor layout constraints related to the number and location of sampling points. Exemplary sampling points are indicated by black dots.

[0140] In at least one embodiment, temperature sensor strips 802a and 802b include terminal leads 808a and 808b, respectively. In at least one embodiment, terminal leads 808a and 808b can be routed through openings 810 in the floor 114 of the sensor support plate 102.

[0141] 9A illustrates a partial side view of a temperature sensor strip 108, according to at least one embodiment. In at least one embodiment, the temperature sensor strip 108 includes a temperature sensor 110 between grooves 112a and 112b. The upper edge 136 and lower edge 109 of the temperature sensor 110 are attached to lower and upper frame segments 202 and 204, respectively. Reference to the type of discontinuity embodied by grooves 112a and 112b is indicated by the labels notch 1 and notch 2. In at least one embodiment, the upper and lower frame segments 202 and 204, respectively, may extend between grooves 112a and 112b, as shown, or may be omitted. Here, arrows indicate the direction of forward and reflected ultrasonic signals excited and received by transducer 902. In at least one embodiment, transducer 902 may be coupled to a terminal lead of the temperature sensor strip 108, as shown. In at least one embodiment, the transducer 902 may be a piezoelectric transducer capable of generating mechanically excited shear waves (e.g., by vibration perpendicular to the contact surface) at frequencies up to several megahertz. In at least one embodiment, the ultrasonic shear wave excitation may be coupled to the temperature sensor strip 108 by mechanical contact with the transducer 902. In at least one embodiment, the transducer 902 may be attached or mounted to a sidewall of the temperature sensor strip 108. The transducer 902 may be electrically coupled to a signal pulser / receiver unit (not shown).

[0142] In at least one embodiment, the reflected waves may be detected as echoes of the transmitted pulse by the same piezoelectric crystal that generates the excitation or by a separate piezoelectric crystal. In at least one embodiment, the grooves 112a and 112b may each reflect a portion of the transmitted energy, e.g., 10%-30%, depending on the type and size of the discontinuity. In at least one embodiment, the return signal, including the returning vibration, may excite a voltage of the same frequency in the piezoelectric crystal, which is amplified by amplifier electronics in the pulser / receiver unit. In at least one embodiment, the transducer 902 may be mounted on a strip waveguide to excite shear waves perpendicular to the longitudinal axis of the waveguide. In at least one embodiment, if longitudinal excitation is desired, the transducer 902 may be rotated 90 degrees to excite waves along the longitudinal axis of the waveguide. In at least one embodiment, a couplant containing a highly viscous liquid is used to increase the coupling efficiency of ultrasound into the waveguide.

[0143] Here, the large arrow emanating from the transducer 902 may represent a forward burst of ultrasonic shear energy at time 0 that moves the strip wave toward the end 904 of the temperature sensor strip 108. In at least one embodiment, the pulse may encounter a groove 112a that reflects a portion of the energy back to the transducer 902, as shown by the inverted arrow labeled "Notch 1 Reflection" in the echo. In at least one embodiment, the travel time of the forward and reflected waves is the Time of Flight (TOF). In at least one embodiment, the TOF is labeled TOF1 and may be measured in nanoseconds or microseconds depending on the distance and shear rate between the groove 112a and the transducer 902. Exemplary data is shown in the TOF echogram of FIG. 9B.

[0144] In at least one embodiment, the unreflected energy of the forward traveling pulse continues through Notch 1 (e.g., groove 112a) and propagates along the gauge length of the temperature sensor strip 108 where it encounters Notch 2 (e.g., groove 112b). At Notch 2, a portion of the energy is reflected again to form a second echo that travels back towards the transducer 902. This is indicated by the arrow labeled Notch 2 reflection. For clarity, the arrow indicating the reflected wave has a dark grey shading and the arrow indicating the forward wave is black. In at least one embodiment, the echo from Notch 2 is associated with a TOF2, which is the time of flight of the second echo that may be recorded by a receiver unit coupled to the transducer 902.

[0145] In at least one embodiment, the second echo arrives at a later time (TOF2) than the first echo (relative to TOF1). In at least one embodiment, the difference TOF2-TOF1 may be expressed as δTOF. In at least one embodiment, the TOF data may show a measurable dependence on local temperature within the vicinity of notches 1 and 2 (e.g., grooves 112a and 112b, respectively). In at least one embodiment, the local temperature may be measured by calculating the difference TOF2-TOF1 at different temperatures.

[0146] In at least one embodiment, sound propagation parameters of solid materials, such as Young's modulus and shear modulus, have a temperature dependence that modifies the speed of sound in solid materials. In at least one embodiment, this temperature dependence accounts for a shift in TOF. In at least one embodiment, as temperature increases, the speed of sound decreases, resulting in longer measured TOF values. In at least one embodiment, a temperature-induced difference in TOF is measured from each groove 112a and 112b. In at least one embodiment, the calculated temperature may be considered a composite (e.g., average) temperature over the gauge length of the temperature sensor strip 108. In at least one embodiment, when the temperature gradient is large, the measurement resolution local temperature may be increased by shortening the gauge length of the temperature sensor 110.

[0147] In at least one embodiment, a portion of the transmit pulse that strikes notch 2 may continue to the end 904 of the temperature sensor strip 108. In at least one embodiment, the signal may be nearly completely reflected and return to the transducer 902 as a third echo. In at least one embodiment, a third TOF, TOF3, may be recorded by a receiver unit coupled to the transducer 902. In at least one embodiment, a small portion of the energy striking the end 904 may be absorbed by the waveguide material or leak into the surroundings. In at least one embodiment, TOF3 may not be included in the temperature determination.

[0148] FIG. 9B illustrates an echogram 910 according to at least one embodiment. In at least one embodiment, the echogram 910 illustrates time-of-flight (TOF) measurements at two separate temperatures from the temperature sensor strip 108 illustrated in FIG. 9A. In at least one embodiment, the pulse echoes from grooves 112a and 112b are designated as notch 1 and notch 2, respectively. Here, the pulse packets shaded gray indicate TOF data measured at temperature T1 (e.g., T1=30° C.), and the pulse packets with black shading indicate TOF data measured at temperature T2>>T1 (e.g., T2=300° C.). With reference to the echogram 910, signal packet 912 represents an ultrasonic pulse injected into the temperature sensor strip 108 at time zero (t0). Signal packet 914 is the reflected signal from notch 1, and signal packet 916 is the reflected signal from notch 2. The TOFs of signal packets 916 and 918, respectively, may be indicated by a time scale in microseconds, where a TOF measurement may be made at T1. In at least one embodiment, signal packet 918 may represent a reflection from end 904 of temperature sensor strip 108.

[0149] In at least one embodiment, the shift in TOF data with temperature (δTOF) is shown by signal packets 920, 922, and 924 for notches 1 and 2 (e.g., grooves 112a and 112b), respectively, measured at T2. In at least one embodiment, the measured TOF shift (e.g., δTOF) can be approximately a 10 microsecond increase in TOF between T1 and T2 (e.g., from 30° C. to 300° C.). In at least one embodiment, the calculation of δTOF can include the TOF shift at an increased temperature T2 (e.g., 300° C.) from a reference temperature T1 (e.g., 30° C.). In at least one embodiment, δTOF=(TOF2-TOF1). T2 -(TOF2-TOF1) T 1 where TOF2 and TOF1 refer to the time-of-flight measurements from reflections from notch 2 and notch 1, respectively.

[0150] 10 shows an exemplary calibration curve 1000, according to at least one embodiment. In at least one embodiment, the calibration curve 1000 may be derived from δTOF measurements, exemplified by echogram 910, relating temperature to the measured δTOF. In at least one embodiment, the calibration curve 1000 may include measurements from a temperature sensor strip 108 with a symmetric or asymmetric groove discontinuity (see, e.g., FIGS. 11A and 11B). In at least one embodiment, the data points from both variations of the discontinuity (symmetric and asymmetric) substantially coincide, as shown by the two sets of data points in the calibration curve 1000.

[0151] Figures 11A and 11B show 3D views of symmetric grooves 1102, 1104 and a single asymmetric groove 1110, respectively, according to at least one embodiment. In at least one embodiment, Figure 11A shows symmetric grooves 1102 and 1104 facing each other on opposing sidewalls 1106 and 1108 of a temperature sensor strip 108. In at least one embodiment, Figure 11B shows an asymmetric groove 1110 on the sidewall 1108 of the temperature sensor strip 108.

[0152] FIG. 11C illustrates a three-dimensional view of a cylindrical acoustic waveguide temperature sensor 1120 (shown as a segment) according to at least one embodiment. In at least one embodiment, the cylindrical acoustic waveguide temperature sensor includes symmetrical notches 1122 and 1124, respectively. In at least one embodiment, the symmetrical notches 1122 and 1124 are opposed across a plane of symmetry along the axis of the cylindrical acoustic waveguide temperature sensor 1120 (shown as a dashed line). The symmetrical notches 1122 and 1124 can form discontinuities in a reflector such as groove 112 (FIGS. 1A and 1B). FIG. 11D illustrates a three-dimensional view of a cylindrical acoustic waveguide 1128 with a single asymmetrical notch 1130 according to at least one embodiment.

[0153] FIG. 12 illustrates a top view of a showerhead 1200 according to at least one embodiment. In at least one embodiment, the showerhead 1200 includes one or more waveguide temperature sensors 1202. In at least one embodiment, the waveguide temperature sensor 1202 may be a temperature sensor strip, such as the temperature sensor strip 108. In at least one embodiment, the waveguide temperature sensor 1202 may be an optical sensor. In at least one embodiment, the showerhead 1200 may include a plurality of openings 1206 in a faceplate 1204. In at least one embodiment, the openings 1206 may distribute deposition vapors and gases onto a substrate mounted on one or more wafer pedestal assemblies. In at least one embodiment, the openings 1206 may be arranged in a hexagonal close-packed configuration as shown. In at least one embodiment, the openings 1206 may be arranged in other configurations, such as, but not limited to, a square, a rectangle, a circle, or other suitable configurations.

[0154] In at least one embodiment, the temperature of the faceplate may be controlled by a heating wire attached to the inner surface of the faceplate 1204. In at least one embodiment, the heating wire may meander between the openings 1206. In at least one embodiment, one or more waveguide temperature sensors 1202 may be attached to the inner surface of the faceplate 1204 to monitor the temperature of portions of the showerhead 1200. In at least one embodiment, the waveguide temperature sensor 1202 may extend across one or more diameters of the faceplate 1204 as shown. In at least one embodiment, the waveguide temperature sensor 1202 may include a meander between the openings 1206 as shown in the inset. In at least one embodiment, two waveguide temperature sensors 1202 are shown, although any suitable number of sensors may be included. In at least one embodiment, by including multiple waveguide temperature sensors 1202 at various angles on the faceplate 1204, it is possible to measure angular and radial temperature gradients.

[0155] FIG. 13 illustrates an implementation of a waveguide temperature sensor 1302 in a process tool 1300 shown in a plan view, according to at least one embodiment. In at least one embodiment, the process tool 1300 may be a single processing module with a single pedestal, such as pedestal assembly 100 (e.g., FIGS. 1A and 1B). In at least one embodiment, the process tool 1300 includes multiple processing stations arranged in a quad configuration. In at least one embodiment, each processing station may include a single pedestal. In at least one embodiment, pedestals 1304, 1306, 1308, or 1310 may be assigned to one of four processing stations. In at least one embodiment, one or more of the pedestals 1304, 1306, 1308, or 1310 can receive a wafer substrate introduced into the process tool 1300 via a robot indexer arm (not shown) used to transfer wafer substrates between the pedestals 1304, 1306, 1308, or 1310.

[0156] In at least one embodiment, multiple showerheads may be included in each processing station. In at least one embodiment, one or more of the pedestals 1304, 1306, 1308, or 1310 may be combined with a showerhead, allowing separate process steps to be performed at each processing station. In at least one embodiment, one or more of the pedestals 1304, 1306, 1308, or 1310 may be independently heated and / or cooled to perform the process steps being performed. In at least one embodiment, the inclusion of a waveguide temperature sensor 1302 in one or more of the pedestals may facilitate precise control of the pedestal temperature. In at least one embodiment, the waveguide temperature sensor 1302 is a temperature sensor strip, such as the temperature sensor strip 108. In at least one embodiment, the waveguide temperature sensor 1302 may be an optical temperature sensor. A reflector structure 1322 is shown as a mark distributed along the waveguide temperature sensor 1302. In at least one embodiment, the reflector structure 1322 can be a groove, such as groove 112 (FIG. 1A).

[0157] In at least one embodiment, process station surfaces 1312, 1314, 1316, and 1318 may be heated to prevent deposition of films on such surfaces due to process gas precursor spray-over. In at least one embodiment, the surface temperature may be monitored by a waveguide temperature sensor 1302. In at least one embodiment, multiple waveguide temperature sensors 1302 may be wired onto each of the process station surfaces 1312-1318 as shown. In at least one embodiment, the waveguide temperature sensor 1302 may be coupled at one end (e.g., terminal lead 1324) to a transducer 1320 (e.g., an ultrasonic transducer or a light source coupler).

[0158] 14 illustrates a process flow chart 1400 summarizing an exemplary method of operation of an ultrasonic waveguide temperature sensor coupled to a process tool, according to at least one embodiment. In at least one embodiment, the process flow chart 1400 includes major operations of the method. Some major operations may be preceded or followed by support operations that may be understood as routine or minor. In at least one embodiment, these operations may be implied or omitted from the description of the major operations below.

[0159] In at least one embodiment, the following examples may be applied to a semiconductor processing tool (e.g., process tool 1300), as described above. In at least one embodiment, the processing tool may include one or more processing stations comprising a showerhead (e.g., showerhead 1200) and a pedestal (e.g., pedestals 1304-1310, FIG. 13). In at least one embodiment, wafer substrates may be transferred between the processing stations by a robotic indexer.

[0160] In at least one embodiment, one or more acoustic waveguide temperature sensors (e.g., temperature sensor strips 108) may be incorporated into any or all process stations within the process chamber. In at least one embodiment, waveguide temperature sensors may also be included in the showerhead (e.g., waveguide temperature sensor 1202), pedestals, and chamber surfaces in the process stations. Waveguide temperature sensors can be either acoustic or optical types, although in at least one embodiment, any suitable combination of both types may be used.

[0161] In at least one embodiment, in operation 1402, an acoustic signal is generated by an ultrasonic transducer and coupled to a waveguide temperature sensor (e.g., temperature sensor strip 108 or cylindrical acoustic waveguide temperature sensor 1120) in a process station. In at least one embodiment, the ultrasonic transducer may be mechanically contacted to a waveguide portion of the temperature sensor strip at or on a terminal lead (e.g., transducer 902 in FIG. 9A). In at least one embodiment, the transducer may comprise a piezoelectric crystal electrically coupled to an electronic pulse generator and a receiver. In at least one embodiment, in the case of a strip waveguide, the transducer may be oriented such that mechanical vibrations can inject shear waves into the waveguide substantially perpendicular to the axis of the strip waveguide. In at least one embodiment, acoustic pulses having a frequency of approximately 1 MHz or greater may be injected into the strip waveguide at preset intervals (e.g., fractions of a second to minutes) to favor horizontal shear modes (e.g., SH0 modes). In at least one embodiment, in a cylindrical waveguide, a similar frequency can be selected for the shear wave mode (eg, the T0 mode) that exhibits the greatest temperature sensitivity for the desired dimensions of the waveguide.

[0162] In at least one embodiment, the injected acoustic pulse can travel along the length of the waveguide at the speed of sound of the waveguide material. In at least one embodiment, acoustic shear waves can travel in aluminum or steel strip waveguides at shear velocities of approximately 3000 m / sec. In at least one embodiment, the acoustic waves can then reflect from discontinuities distributed along the length of the waveguide. In at least one embodiment, the acoustic waves can reflect from discontinuities in the groove (e.g., grooves 112 formed on the sidewalls of the waveguide temperature sensor). In at least one embodiment, the optical waveguide (e.g., fiber optic waveguide) can support Bragg reflection of white light that can be optically transferred to a spectrometer to measure the wavelength shift of individual spectral lines for temperature measurement.

[0163] In at least one embodiment, a signal can be injected into the waveguide temperature sensor at some initial time t0 at a reference temperature T0, which in at least one embodiment can be room temperature (e.g., 20° C.-25° C.) or some other initial temperature of a part of a process.

[0164] In at least one embodiment, in operations 1404 and 1406, in at least one embodiment, a reference temperature can be established to determine the elevated temperature. In at least one embodiment, the reference temperature can be measured at room temperature according to at least one embodiment. In at least one embodiment, the calculation of the elevated temperature is referred to as the reference temperature. In at least one embodiment, the reflected acoustic wave signal can return to the transducer as a return signal and couple to a piezoelectric crystal to convert the acoustic return signal to an analog electrical return signal.

[0165] In at least one embodiment, the return signal may be measured and stored in an electronic control unit associated with the transducer. In at least one embodiment, the return signal reflected from a reflector structure, such as groove 112 in the temperature sensor strip 108, may arrive at the transducer at times t1, t2, etc., where t2>t1>t0. The reflected signal may be detected and recorded at times t1 and t2. In at least one embodiment, t1 and t2 may be tens to hundreds of microseconds depending on the distance of each reflector (e.g., groove) from the transducer. In at least one embodiment, the difference between t1-t0 and t2-t0 may be recorded as time-of-flight data TOF1 and TOF2, respectively, of the acoustic energy reflected from successive discontinuities (e.g., notch 1 and notch 2). In at least one embodiment, δTOF corresponding to a segment of the waveguide temperature sensor between adjacent grooves (or other discontinuities) may be calculated as δTOF=TOF2-TOF1. In at least one embodiment, the WDT sensor can include multiple adjacent DTS segments, each segment being a temperature sensor. In at least one embodiment, the temperature of an individual temperature sensor on the waveguide temperature sensor can be determined by measuring the δTOF at different temperatures and correlating the data to temperature via a predefined calibration curve (e.g., calibration curve 1000) that relates the δTOF data for a particular sensor to local temperature.

[0166] In at least one embodiment, return signals from successive sensor segments (e.g., temperature sensor 110, FIGS. 1A and 1B) can be measured simultaneously and correlated with the local temperature in the environment of each successive sensor. In at least one embodiment, the location of individual sensor segments within one or more pedestals, showerheads, or on the chamber surfaces is known so that local temperatures can be mapped accordingly.

[0167] In at least one embodiment, the measurements from operations 1404 and 1406 can be repeated in operations 1408, 1410, and 1412 to measure increasing temperatures, for example, during a temperature ramp-up or temperature cool-down phase. In at least one embodiment, the temperature can reach a steady state at the target temperature. In at least one embodiment, increasing the temperature can shift the TOF data by slowing down the speed of sound in the material, which can shift the TOF to a longer time. In at least one embodiment, thermal expansion can cause an increase in the distance between the reflectors, as well as changes in Young's modulus and shear modulus, resulting in a delay in the TOF of the acoustic signal. In at least one embodiment, as described above, a 10-fold temperature change from 30° C. to 300° C. can cause a 10 microsecond delay in the TOF. In at least one embodiment, increasing the temperature can cause a change in the refractive index in an optical waveguide temperature sensor. In at least one embodiment, thermal expansion can increase the distance between discontinuities in the lattice. In at least one embodiment, such changes can cause a shift in the angular or linear position of the spectral lines. In at least one embodiment, such temperature-induced spectral shifts can be linearly or quasi-linearly correlated with temperature within the range of interest, allowing for the creation of a calibration curve.

[0168] In at least one embodiment, in operation 1414, the TOF data can be correlated to the elevated temperature by applying the formula δTOF=(TOF2-TOF1)T1-(TOF2-TOF1)T2, where TOF1 and TOF2 refer to discontinuities in the continuous reflector (e.g., groove 112, Figures 1A and 1B).

[0169] FIG. 15 illustrates a system 1500 including a process tool, according to at least one embodiment. In at least one embodiment, the system 1500 may be a semiconductor process tool used for CVD and / or PECVD. In at least one embodiment, the system 1500 includes a vacuum chamber 1502. In at least one embodiment, the vacuum chamber 1502 includes a showerhead 1504. In at least one embodiment, the showerhead 1504 includes a faceplate 1505 above and adjacent to a pedestal 1506 (e.g., pedestal assembly 100, FIGS. 1A and 1B). In at least one embodiment, the showerhead 1504 may be substantially identical to the showerhead 1200 described above. In at least one embodiment, the pedestal 1506 may include a platen 1508 and a stem 1509 coupled to the platen 1508. In at least one embodiment, the pedestal 1506 includes a sensor section 1510. In at least one embodiment, a temperature sensor strip 1512 is located within the sensor compartment 1510. In at least one embodiment, the temperature sensor strip 1512 is substantially identical to the temperature sensor strip 108 (FIG. 1A) described above. In at least one embodiment, other waveguide temperature sensors than those described herein may be used as well, such as the cylindrical acoustic waveguide temperature sensor 1120.

[0170] In at least one embodiment, a transducer 1514 may be mechanically coupled to the temperature sensor strip 1512. In at least one embodiment, the transducer 1514 is mounted on the outside of the base 1506. In at least one embodiment, the transducer 1514 may be mounted within the sensor compartment 1510. In at least one embodiment, the transducer 1514 may physically contact a sidewall of the temperature sensor strip 1512, for example, by a layer of grease or paste, to enhance acoustic coupling to the temperature sensor strip 1512. In at least one embodiment, the orientation of the vibration may determine a dominant acoustic mode, for example, SH0 or longitudinal mode.

[0171] In at least one embodiment, the temperature sensor strip 1512 can include a reflector structure 1516. In at least one embodiment, the reflector structure 1516 can be substantially identical to the groove 112 (FIGS. 1A and 1B). In at least one embodiment, the reflector structure 1516 can also be any suitable discontinuity, as described above.

[0172] In at least one embodiment, the transducer 1514 can inject acoustic waves into the temperature sensor strip 1512 and receive a reflected return signal from the reflector structure 1516. In at least one embodiment, the transducer 1514 can comprise a piezoelectric crystal or polycrystal oscillator capable of generating mechanical vibrations and converting the mechanical vibrations into a voltage signal.

[0173] Examples illustrating at least one embodiment are provided in the following paragraphs, where these examples may be combined with other examples. Thus, at least one embodiment may be combined with at least another embodiment without changing the scope of the at least one embodiment.

[0174] Example 1 is a base assembly comprising: a platen; and a sensor support plate below the platen, the sensor support plate comprising a sensor compartment and a waveguide temperature sensor within the sensor compartment, the waveguide temperature sensor comprising a temperature sensor, the temperature sensor comprising a first reflector structure and a second reflector structure, the first reflector structure and the second reflector structure being separated by a gauge length.

[0175] Example 2 includes all of the features of example 1, wherein the waveguide temperature sensor comprises a strip having a rectangular cross-section, the rectangular cross-section having a width and a length, the length being at least 10 times the width.

[0176] Example 3 includes all of the features of example 2, wherein the width is at least 5 times a wavelength of an acoustic signal propagated within the waveguide temperature sensor.

[0177] Example 4 includes all of the features of example 1, wherein the waveguide temperature sensor has a spiral geometry.

[0178] Example 5 includes all of the features of example 1, wherein the waveguide temperature sensor comprises a plurality of straight segments, adjacent straight segments being joined by folds.

[0179] Example 6 includes all of the features of example 1, wherein the waveguide temperature sensor comprises an arc.

[0180] Example 7 includes all of the features of example 1, wherein the waveguide temperature sensor comprises a first unit and a second unit.

[0181] Example 8 includes all of the features of example 1, wherein the waveguide temperature sensor is adhered to a surface of the sensor compartment.

[0182] Example 9 includes all of the features of example 8, wherein the waveguide temperature sensor is in a groove in the surface of the sensor compartment.

[0183] Example 10 includes all of the features of example 9, wherein the waveguide temperature sensor has an upper edge coupled to an upper frame segment and a lower edge coupled to a lower frame segment, the lower frame segment being mechanically coupled to the surface of the sensor compartment.

[0184] Example 11 includes all of the features of example 10, wherein the upper frame segment is coupled to the platen.

[0185] Example 12 includes all of the features of example 1, wherein the waveguide temperature sensor comprises a helical spiral.

[0186] Example 13 includes all of the features of example 1, wherein the waveguide temperature sensor comprises a first helical spiral portion and a second helical spiral portion on the first helical spiral portion, the second helical spiral portion being coaxial with the first helical spiral portion.

[0187] Example 14 includes all of the features of example 1, wherein the first reflector structure and the second reflector structure comprise first and second grooves, respectively, on a sidewall of the waveguide temperature sensor, the first and second grooves having a length that is at least a portion of a first width of the waveguide temperature sensor, and the first and second grooves have a second width that is substantially greater than or equal to ⅙ of a wavelength of an acoustic signal propagated within the waveguide temperature sensor.

[0188] Example 15 includes all of the features of example 1, wherein the waveguide temperature sensor comprises a first material, the first reflector structure and the second reflector structure comprise a second material, the first material having a first shear modulus, and the second material having a second shear modulus different from the first shear modulus.

[0189] Example 16 includes all of the features of example 15, wherein the first material includes any one of aluminum, stainless steel, tungsten, titanium, silica, borosilicate glass, aluminum oxide, titanium oxide, or aluminum nitride.

[0190] Example 17 includes all of the features of example 1, wherein the waveguide temperature sensor is substantially cylindrical.

[0191] Example 18 includes all of the features of example 1, wherein the waveguide temperature sensor is an optical fiber, the optical fiber comprising a plurality of fiber Bragg grating reflector structures or a coating including a thermographic phosphor.

[0192] Example 19 is a system comprising: a vacuum chamber; a showerhead in the vacuum chamber; a pedestal in the vacuum chamber below the showerhead, the pedestal comprising a sensor compartment; and a waveguide temperature sensor in the sensor compartment, the waveguide temperature sensor comprising at least one temperature sensor, the at least one temperature sensor comprising a first reflector structure and a second reflector structure, the first reflector structure and the second reflector structure being separated by a gauge length, the at least one temperature sensor comprising: a waveguide temperature sensor disposed within the sensor compartment to coincide with one or more measurement locations; and a transducer coupled to a terminal lead of the waveguide temperature sensor.

[0193] Example 20 includes all of the features of example 19, wherein the transducer is operable to couple a signal to the waveguide temperature sensor and receive one or more return signals, the one or more return signals reflected from the first reflector structure and the second reflector structure to the transducer.

[0194] Example 21 includes all of the features of example 19, wherein the waveguide temperature sensor is a first waveguide temperature sensor and the showerhead comprises a second waveguide temperature sensor adjacent a faceplate of the showerhead.

[0195] Example 22 includes all of the features of example 21, wherein a third waveguide temperature sensor is thermally coupled to at least one surface of the vacuum chamber.

[0196] Example 23 is a method for measuring a temperature of a process, the method including: coupling a signal pulse to a waveguide temperature sensor in a pedestal assembly, the waveguide temperature sensor comprising a temperature sensor, the temperature sensor comprising a first reflector structure and a second reflector structure, the first reflector structure and the second reflector structure being separated by a gauge length; receiving first and second return signals reflected from the first and second reflector structures; measuring a first time of flight (TOF) of the first return signal and a second TOF of the second return signal; calculating a difference between the second TOF and the first TOF; and correlating the difference with a temperature of one or more surfaces.

[0197] Example 24 includes all of the features of example 23, wherein measuring a first TOF of the first return signal and a second TOF of the second return signal includes correlating the first return signal and the second return signal with the first reflector structure and the second reflector structure, and the TOFs of the first and second return signals are a function of a local pedestal temperature near the reflector structure.

[0198] Example 25 includes all of the features of Example 23, and further includes increasing the temperature of the one or more surfaces of the base assembly to a second temperature, the temperature being a first temperature and the second temperature being greater than the first temperature.

[0199] Example 26 includes all of the features of example 25, wherein the difference is a first difference, and the method further includes receiving a third return signal and a fourth return signal at the second temperature; measuring a third TOF of the third return signal and a fourth TOF of the fourth return signal, the third TOF and the fourth TOF being measured at the second temperature; calculating a second difference between the fourth TOF and the third TOF; calculating a third difference between the first difference and the second difference; and correlating the third difference with the second temperature.

[0200] Besides those described herein, various modifications can be made to the at least one embodiment without departing from the scope thereof, and therefore, the description of the at least one embodiment herein should be construed as an example and not as a limitation on the scope of the at least one embodiment.

Claims

1. 1. A pedestal assembly comprising: A platen; a sensor support plate below the platen, A sensor compartment; and a waveguide temperature sensor in the sensor compartment, the waveguide temperature sensor comprising a temperature sensor, the temperature sensor comprising a first reflector structure and a second reflector structure, the first reflector structure and the second reflector structure being separated by a gauge length; a sensor support plate having A pedestal assembly comprising:

2. 2. The base assembly of claim 1, A pedestal assembly, wherein the waveguide temperature sensor comprises a strip having a rectangular cross-section, the rectangular cross-section having a width and a length, the length being at least ten times the width.

3. 3. The base assembly of claim 2, A pedestal assembly, wherein the width is at least five times the wavelength of an acoustic signal propagated within the waveguide temperature sensor.

4. 2. The base assembly of claim 1, The waveguide temperature sensor has a spiral geometry.

5. 2. The base assembly of claim 1, A base assembly, wherein the waveguide temperature sensor has a plurality of straight segments, adjacent straight segments being joined by folds.

6. 2. The base assembly of claim 1, The waveguide temperature sensor comprises an arc.

7. 2. The base assembly of claim 1, The waveguide temperature sensor includes a first unit and a second unit.

8. 2. The base assembly of claim 1, A base assembly, wherein the waveguide temperature sensor is adhered to a surface of the sensor compartment.

9. 9. The base assembly of claim 8, A base assembly, wherein the waveguide temperature sensor is in a groove in the surface of the sensor compartment.

10. 10. The base assembly of claim 9, the waveguide temperature sensor having an upper edge coupled to an upper frame segment and a lower edge coupled to a lower frame segment; A pedestal assembly, wherein the lower frame segment is mechanically coupled to the surface of the sensor compartment.

11. 11. The base assembly of claim 10, The upper frame segment is coupled to the platen. A base assembly.

12. 2. The base assembly of claim 1, The waveguide temperature sensor includes a helical spiral.

13. 2. The base assembly of claim 1, the waveguide temperature sensor having a first helical spiral portion and a second helical spiral portion on the first helical spiral portion; The second helical spiral portion is coaxial with the first helical spiral portion.

14. 2. The base assembly of claim 1, the first reflector structure and the second reflector structure have a first groove and a second groove, respectively, on a sidewall of the waveguide temperature sensor; the first groove and the second groove have a length that is at least a portion of a first width of the waveguide temperature sensor; the first groove and the second groove have a second width that is substantially greater than or equal to 1 / 6 of a wavelength of an acoustic signal propagated within the waveguide temperature sensor.

15. 2. The base assembly of claim 1, the waveguide temperature sensor includes a first material; the first reflector structure and the second reflector structure include a second material; the first material has a first shear modulus; The second material has a second shear modulus different from the first shear modulus.

16. 16. The base assembly of claim 15, The pedestal assembly, wherein the first material comprises any one of aluminum, stainless steel, tungsten, titanium, silica, borosilicate glass, aluminum oxide, titanium oxide, or aluminum nitride.

17. 2. The base assembly of claim 1, The waveguide temperature sensor is substantially cylindrical.

18. 2. The base assembly of claim 1, the waveguide temperature sensor is an optical fiber; The optical fiber comprises a plurality of fiber Bragg grating reflector structures or a coating including a thermographic phosphor.

19. 1. A system comprising: A vacuum chamber; a showerhead in the vacuum chamber; a pedestal within the vacuum chamber below the showerhead, the pedestal comprising a sensor compartment; a waveguide temperature sensor in the sensor compartment, the waveguide temperature sensor having at least one temperature sensor, the at least one temperature sensor having a first reflector structure and a second reflector structure, the first reflector structure and the second reflector structure being separated by a gauge length, the at least one temperature sensor being positioned within the sensor compartment to coincide with one or more measurement locations; a transducer coupled to a terminal lead of the waveguide temperature sensor; A system comprising:

20. 20. The system of claim 19, the transducer is operable to couple a signal to the waveguide temperature sensor and receive one or more return signals; The one or more return signals are reflected from the first reflector structure and the second reflector structure back to the transducer.

21. 20. The system of claim 19, the waveguide temperature sensor is a first waveguide temperature sensor and the showerhead comprises a second waveguide temperature sensor adjacent a faceplate of the showerhead.

22. 22. The system of claim 21, A third waveguide temperature sensor is thermally coupled to at least one surface of the vacuum chamber.

23. 1. A method for measuring the temperature of a process, comprising: coupling the signal pulse to a waveguide temperature sensor in a pedestal assembly, the waveguide temperature sensor having a temperature sensor, the temperature sensor having a first reflector structure and a second reflector structure, the first reflector structure and the second reflector structure being separated by a gauge length; receiving a first return signal and a second return signal reflected from the first reflector structure and the second reflector structure; Measuring a first time of flight (TOF) of the first return signal and a second TOF of the second return signal; calculating a difference between the second TOF and the first TOF; correlating said difference with a temperature of one or more surfaces; A method comprising:

24. 24. The method of claim 23, Measuring the first TOF of the first return signal and the second TOF of the second return signal includes correlating the first return signal and the second return signal with the first reflector structure and the second reflector structure; A method, wherein the TOF of the first return signal and the second return signal is a function of a local pedestal temperature in the vicinity of the reflector structure.

25. 24. The method of claim 23, The method, further comprising increasing the temperature of the one or more surfaces of the pedestal assembly to a second temperature, the temperature being a first temperature and the second temperature being greater than the first temperature.

26. 26. The method of claim 25, The difference is a first difference, and the method further comprises: receiving a third return signal and a fourth return signal at the second temperature; measuring a third TOF of the third return signal and a fourth TOF of the fourth return signal, the third TOF and the fourth TOF being measured at the second temperature; calculating a second difference between the fourth TOF and the third TOF; calculating a third difference between the first difference and the second difference; correlating the third difference with the second temperature; and The method further comprising:

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