Patent Application
20180226282
Embodiments of the present disclosure generally relate to substrate processing equipment.
In conventional substrate processing chambers, the substrate processing temperature is controlled by providing heat exchangers around or in a substrate support for holding one or more substrates during processing. In a plasma environment, the temperature of the substrate might differ from the temperature of the heat exchanger provided in the process chamber. Accordingly, typical high vacuum and plasma processing chambers include apparatus for measuring and monitoring the substrate temperature. However, substrate temperature measurement in high vacuum and plasma processing chambers is not possible with contact methods, such as with thermocouples and the like. Consequently, current high vacuum and plasma processing chambers include apparatus and methods for performing a non-contact substrate temperature sensing and measurement. However, the inventors have discovered that the current non-contact substrate temperature measuring apparatus, such as infra-red pyrometers and the like have diminished accuracy when the transmittance and emissivity of the substrate changes due to changes in temperature. The inventors have also discovered that the current non-contact substrate temperature measurement methods are characterized by long signal sampling times which results in delayed temperature correction and poor film deposition.
Therefore, the inventors have provided improved apparatus and methods for non-contact measurement of substrate temperature during processing in a process chamber.
Methods and apparatus for measuring the temperature of substrates in substrate processing systems are provided herein. In some embodiments, an apparatus for processing substrates includes: a substrate processing chamber; a substrate support within the chamber to support a substrate for processing; a light source directly coupled to a light isolator and configured to deliver incident light to and through a first surface of the substrate when disposed on the substrate support; an optical fiber having a first end spaced apart a first distance from the first surface and a second end directly coupled to the light source via a coupling element; a photodetector directly coupled to the second end of the optical fiber via the coupling element and configured to receive a first reflected light beam reflected off the first surface and a second reflected light beam reflected off an inner boundary of a second surface of the substrate, opposite the first surface; and a signal processor to determine a temperature of the substrate based on the first and second reflected light beams.
In some embodiments, a method for method measuring a temperature of a substrate includes: (a) irradiating a substrate inside a processing chamber with light; (b) receiving a first reflection of the light from a first surface of the substrate; (c) receiving a second reflection of the light through the substrate from an inner boundary of a second surface opposite the first surface; and (d) determining a substrate temperature based on a spectral analysis of an interference pattern of the first and second reflections.
In some embodiments, a non-transitory computer readable medium having instructions stored thereon that, when executed, cause a method for measuring the temperature of a substrate to be performed. The method may include any of the embodiments disclosed herein.
Other and further embodiments of the present disclosure are described below.
Embodiments of the present disclosure, briefly summarized above and discussed in greater detail below, can be understood by reference to the illustrative embodiments of the disclosure depicted in the appended drawings. However, the appended drawings illustrate only typical embodiments of the disclosure and are therefore not to be considered limiting of scope, for the disclosure may admit to other equally effective embodiments.
To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. The figures are not drawn to scale and may be simplified for clarity. Elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.
Embodiments of the present disclosure provide improved measurement and monitoring of the temperature of one or more substrates disposed in a process chamber. The disclosed methods and apparatus advantageously facilitate fast (e.g., real-time) and accurate measurements of the temperature of a substrate disposed or undergoing processing in a process chamber. Faster and more accurate measurements of the substrate temperature advantageously enable improved process uniformity by decreasing the time delay between a deviation from the set-temperature and the corrective action. Furthermore, the disclosed methods and apparatus facilitate improved substrate thickness control by providing a more robust temperature measurement technique.
The substrate processing system 100 includes a process chamber 102 enclosing an inner volume defined by the sidewalls, a bottom portion, and a top portion of the process chamber. A substrate support 104 is disposed in the inner volume of the process chamber 102. The substrate support 104 includes a base 106 and a support member 108. A top portion of the base 106 includes a substrate support surface 110 configured to receive and support a substrate 112. The substrate 112 has a first surface 113 and a second surface 115 opposite the first surface.
The temperature measurements in accordance to some embodiments of the present disclosure may be performed on one or more bare or coated substrates. In some embodiments, the temperature of a bare or coated substrate having a thickness of about 10 μm to about 900 μm, for example about 760 μm, may be measured. Suitable substrates include but are not limited to bare silicon, metal coated silicon, and silicon substrates coated with other suitable materials.
In some embodiments, the substrate support 104 may optionally include a heating apparatus 114 disposed in the base 106, for providing heat to the base 106. In some embodiments, the heating apparatus 114 is a resistive heater disposed in the base 106. Alternatively or in combination, in some embodiments, the heating apparatus is one or more of an infra-red, an ultra-violet, or a microwave heat source.
In some embodiments, the base 106 may further include a cooling apparatus 116. In some embodiments, the cooling apparatus 116 includes one or more passageways for flowing a heat transfer medium, for example, coolant for cooling the base 106.
The substrate support 104 may also include a temperature monitor 118 for monitoring the temperature of the base 106, and a thermal profile across the base 106 and the substrate support surface 110. In some embodiments, the temperature monitor 118 may be a thermocouple disposed in the base 106.
In some embodiments, the substrate support 104 may be a vacuum or an electrostatic chuck (ESC). In some embodiments, the substrate support 104 may further include processing apparatus such as electrodes for RF bias, pulsed DC bias, and the like. In the exemplary embodiment depicted in
An opening 122 having an inner wall 124 is formed in the support member 108, through a central axis of the substrate support 104 and perpendicular to the substrate support surface 110. The opening 122 may be disposed in any suitable location that will be covered by the substrate 112 when disposed on the substrate support surface 110. In some embodiments, the opening 122 is disposed in the center of the substrate support surface 110 (or in a location corresponding to the center of the substrate 112 when disposed on the substrate support surface 110). In some embodiments, the opening 122 is a gas hole provided to direct one or more gases to the backside of substrate 112 when disposed on the substrate support surface 110.
The substrate support 104 further includes a plurality of holes 126 formed through the base 106 and spaced apart from the opening 122. In some embodiments, the holes 126 are disposed about the opening 122 and proximate to the periphery of the base 106. In some embodiments, for example in a substrate support designed for handling 300 mm wafers or similar substrates, each of the holes 126 may be located about 127 mm from the opening 122. Other radial locations may also be used, in particular in substrate supports designed for operation with substrates having other dimensions.
A plurality of lift pins 128 are movably disposed through the holes 126. The lift pins 128 are configured to be light-permeable in the vertical direction. In some embodiments, the lift pins 128 may be hollow. The lift pins 128 are vertically movable with respect to the base 106. The lift pins 128 are configured to extend through the holes 126 to transfer a substrate 112 onto or away from the substrate support surface 110.
In some embodiments, the process chamber 102 may include a dielectric ring 130 (e.g., a deposition ring) which may be used to shield the periphery of the substrate 112 from deposition. For example, the dielectric ring 130 may be disposed about a peripheral edge of the substrate support 104 and adjacent to the substrate support surface 110 as illustrated in
An optical fiber 132 (three optical fibers shown in
The coupling element 140 (e.g., a coupler) is provided to provide coupling between one or more optical fibers provided to send and receive light into the process chamber (e.g., optical fibers 132a, 132b, 132c) and optical fibers provided to either carry light from a light providing unit of (e.g., light source 202, shown in
In the exemplary embodiment depicted in
The first ends 134 of the optical fibers 132 are respectively disposed in the opening 122 or one of the holes 126. In embodiments where the optical fibers 132 are disposed in the holes 126, the first end 134 may optionally further be disposed within a lift pin 128. The first end 134 of each optical fiber 132 is coupled to an optical probe 144, as illustrated in
In embodiments where the optical probe 144 is disposed in the opening 122, one or more probe holders may be disposed between the inner wall 124 of the opening 122 and the optical probe 144. When provided, the probe holders vertically align and retain the optical probe 144 within the opening 122. In some embodiments, the probe holders are further configured to allow passage of gases around the optical probe 144.
In some embodiments, the light source 202 is configured to provide light having a suitable wavelength, such as between about 1100 nm and about 1700 nm. In some embodiments, the wavelength is selected according to the first distance 136. For example, in some embodiments the light source 202 may provide light having a wavelength about 1300 nm where the first distance 136 is about 155 mm. In some embodiments, the light source 202 may provide an incident light spot size of about 60 μm2.
In some embodiments, the light source 202 may be an amplified spontaneous emission (ASE) light source. For example, in some embodiments, the light source 202 may be a superluminiscent diode (SLD). In some embodiments, the light source 202 may be suitable for low-coherence interferometry.
The isolating element 204 is provided to allow the transmission of light in only the direction, e.g., from the light source 202 to the coupling element 140. The isolating element 204 prevents unwanted light from entering the light source or interfering with the light provided by the light source. For example, the isolating element 204 can be an infrared (IR) fiber optic isolator with an operating wavelength range of about 1295 to about 1325 nm. The isolating element typically can provide isolation of greater than or equal to about 29 dB.
The optical fiber 132 further operatively couples the optical probe 144 to a photodetector 208. The photodetector 208 (e.g., a light detector) detects light reflected from the substrate 112, for example a first reflected beam from the first surface 113, and a second reflected beam from an inner boundary of the second surface 115. Reflected light beams travel the length of the optical fiber 132, from the first end 134 to the second end 138 to be detected and received by the photodetector 208.
The photodetector 208 is coupled to a signal processor 210. In some embodiments the photodetector 208 is directly coupled to the signal processor 210. In some embodiments, the signal processor 210 includes a spectrum analyzer configured to perform spectral interferometry of the reflected light beams, for example, by curve-fitting, Fast Fourier Transform (FFT), or similar methods.
In some embodiments, the measurement equipment 142 further includes a multiplexing unit 212 disposed between the coupling element 140 and the second end 138 of each optical fiber 132 (e.g., optical fibers 132a, 132b, 132c). Although one optical fiber 132 and optical probe 144 is shown in
The de-multiplexer is operatively coupled to the light source 202 and provided to split a light beam from the light source 202 into separate light beams for delivery to one or more different locations of the substrate support surface 110 (e.g., areas on the first surface 113 disposed above the first end 134 of optical fibers 132a, 132b, and 132c, when provided).
The multiplexer is operatively coupled to the photodetector 208. The multiplexer is a signal selector that selectively passes reflected light beams from the one or more different locations to the photodetector 208. For example, in some embodiments, the multiplexer may include a rotary switch.
In some embodiments, the multiplexing unit 212 may be a wavelength-division multiplexing (WDM) system. In some embodiments, the multiplexing unit 212 may be a polarization-division multiplexing (PDM) system.
In some embodiments, the multiple-substrate holder 300 includes a bottom member 302 having one or more vertical supports 304 extending from the bottom member 302. A plurality of vertically spaced apart substrate support planes are attached to the vertical supports. Each substrate support plane is configured to hold a substrate such that multiple substrates can be disposed in the process chamber. For example, in some embodiments, the vertical supports 304 may further include one or more mounting holes 306 for receiving a peripheral member 308. The peripheral members 308 may be configured to support a substrate, for example, proximate the peripheral edge of the substrate. In some embodiments, the bottom member 302 and the vertical supports may be fabricated from aluminum or other suitable process-compatible material.
One or more fasteners 310 are provided, for example, along with the peripheral member 308 to fasten the peripheral member 308 to the vertical supports 304 through the mounting holes 306.
The multiple-substrate holder 300 is configured to hold a plurality of substrates. In some embodiments, the plurality of substrates may be arranged in a stack configured to grow from a first substrate at one end closest to the first end 134 of the optical fiber 132 to an Nth substrate at an opposite end furthest from the first end 134.
In some embodiments having vertically arranged substrates, the top substrate may be designated a first substrate, for example, if the first end 134 is disposed above the stack. In other embodiments having vertically arranged multiple substrates, the bottom substrate may be designated the first substrate, for example, if the first end 134 is disposed beneath the stack. Accordingly, in the exemplary embodiment depicted in
In some embodiments, the peripheral member 308 may include a plurality of vertically arranged substrate support members 309. The plurality of substrate support members 309 include a blade region 312 disposed beneath and radially inward of a plate region 314. In some embodiments, the blade region 312 may be made of ceramic or other suitable process-compatible material. In some embodiments, the plate region 314 may be made from a nickel-based alloys (such as an alloy comprising nickel, iron, and cobalt), for example KOVAR®.
In the exemplary embodiment depicted in
The plurality of substrate support members 309 are spaced apart to define a series of gaps d1 to dN, between adjacent surfaces of plural substrates, when present. For example, a gap d1 is defined between the second surface 115a of the first substrate 112a and the first surface 113b of the second substrate 112b. Similarly, respective gaps are formed between successive adjacent substrates and a gap dN is defined between the Nth-1 and Nth substrate. In some embodiments, the gaps d1 to dN may have different lengths. In other embodiments, the gaps d1 to dN may be equal in length. For example, in some embodiments, the gaps d1 to dN may each be about 400 μm.
The index of refraction of the material disposed in the gaps d1 to dN is different from the index of refraction of the substrate material. In accordance with some embodiments of the present disclosure, the index of refraction of the material disposed in the gaps d1 to dN may be lower than the index of refraction of the substrate material. For example, the gaps d1 to dN may comprise air or process gases within the process chamber 102.
In operation, as illustrated in
To measure the temperature of a single substrate at a single location (e.g., the center of substrate 112), the light source 202 sends a light beam to the isolating element 204. The isolating element 204 allows the light from the light source to pass the coupling element 140. The isolating element 204 further prevents any of the light from flowing back towards the light source 202 or in any direction other than into the coupling element 140. At the multiplexing unit 212, the light passes through in a single beam, without any de-multiplexing, because the light is intended to be incident on a single spot of the substrate. Alternatively or optionally, the multiplexing unit 212 may be bypassed or omitted from the light path circuit. Therefore, light leaving the coupling element 140 propagates directly into one optical fiber directed to a particular location of the substrate to be measured (e.g., optical fiber 132a disposed in the opening 122, for measuring the temperature at the center of a substrate 112, when present). After exiting the optical fiber through the first end 134 (optionally, via the optical probe 144), the light traverses the first distance 136 and irradiates the first surface 113.
Upon irradiating the first surface 113 at a first time (t1), a portion of the incident light is reflected by the first surface 113 to form a first reflected light beam. The rest of the incident light is transmitted through the first surface 113 and travels a further distance equal to the thickness of the substrate 112. At a later second time (t2), some of the transmitted light is reflected by an inner boundary of the second surface 115 to form a second reflected beam.
The first and second reflected light beams travel the first distance 136 and are received by the first end 134 for transmission in the optical fiber 132, towards the coupling element 140. However, due to the delay of the second reflected light beam (i.e., t2>t1), the two reflected light beams will be out of phase and will interfere with each other when they combine during propagation. The coupling element 140 directs the reflected light beams into the photodetector 208. The photodetector 208 senses and transmits the interference signal to the signal processor 210. The signal processor 210 performs a spectral analysis of the interference signal to determine the temperature of the substrate.
The inventors observed that in some processes, for example plasma processing, the temperature profile of the substrate may be non-uniform, for example, the temperature at periphery of the substrate may be different than the temperature at the center of the substrate. Hence, in some embodiments, the substrate processing system 100 may be configured to measure the temperature at different points of the substrate 112.
To measure the temperature a single substrate (e.g., substrate 112 shown in
In some embodiments, pairs of reflected light beams (i.e., the first and second reflected light) beams produced at each irradiated location of the substrate 112 are received by the first end 134 of a corresponding optical fiber (e.g., 132a, 132b, and 132c) for propagation towards coupling element 140. The first and second reflected light beams from each substrate location interfere with each other when they combine during propagation into the multiplexing unit 212 before entering the coupling element 140.
The multiplexing unit 212, via the multiplexer, selects and allows the combined reflected light beams from one substrate location at a time. Thus, the photodetector 208 senses and receives discrete interference signals, each due to a pair of reflected light beams from each one of the substrate locations.
The photodetector 208 transmits the discrete interference signals to the signal processor 210. The signal processor 210 performs spectral interferometry on each discrete signal to determine the temperature of the substrate 112 at the different locations. Measuring temperature at different locations of the substrate provides information about the temperature distribution across the substrate 112.
The temperature of multiple substrates stacked one a substrate support may be measured in accordance with some embodiments of the present disclosure. To measure the temperature of each substrate (e.g., 112a, 112b, 112c shown in
Upon exiting the optical fiber through the first end 134 or, optionally, via the optical probe 144, the light traverses the first distance 136 and irradiates the first surface 113 of the first substrate (e.g., first surface 113a of substrate 112a). A portion of the incident light is reflected by the first surface 113 of the first substrate to form a first reflected light beam. An un-reflected portion of the incident light forms a first transmitted light beam is transmitted through the first surface 113 and across the thickness of the first substrate to reach the second surface 115 of the first substrate (e.g., second surface 115a of substrate 112a). At the second surface 115 of the first substrate, a portion of the first transmitted light beam is reflected by an inner boundary of the second surface 115 of the first substrate (e.g., inner boundary of second surface 115a of substrate 112a) to form a second reflected light beam.
Accordingly, the optical path length of the second reflected light beam is longer than the optical path length of the first reflected light beam by a length corresponding to the thickness of the first substrate (e.g., the thickness of substrate 112a).
An un-reflected portion of the first transmitted light beam becomes a second transmitted light beam and enters the first gap d1 between the first substrate and the second substrate (e.g., substrate 112a and substrate 112b). Due to refraction, the second transmitted light beam propagates through the first gap d1 and is incident upon the first surface 113 of the second substrate (e.g., first surface 113b of substrate 112b). A portion of the second transmitted light beam is reflected by the first surface 113 of the second substrate (e.g., first surface 113b of substrate 112b).
The light reflected by the first surface 113 of the second substrate is refracted through the first gap d1 to be incident on the second surface 115 of the first substrate (e.g., of second surface 115a of substrate 112a). A portion of the light that is incident on the second surface 115 of the first substrate (e.g., substrate 112a) is transmitted across the thickness of the first substrate (e.g., substrate 112a) to form a third reflected light beam. The optical path length of the third reflected light beam is longer than the optical path of the first reflected light beam by twice the distance of the first gap d1 plus twice the distance of the thickness of the first substrate (e.g., substrate 112a).
An un-reflected portion of the second transmitted light beam becomes a third transmitted light beam which is incident on the first surface 113 of the second substrate (e.g., first surface 113b of substrate 112b). The third transmitted light beam is transmitted through the first surface 113 (e.g., first surface 113b of substrate 112b) and across the thickness of the second substrate (e.g., thickness of substrate 112b) to reach an inner boundary of the second surface 115 of the second substrate (e.g., inner boundary of second surface 115b of substrate 112b). At the inner boundary of the second surface 115 of the second substrate (e.g., second surface 115b of substrate 112b), a portion of the third transmitted light beam is reflected.
The light reflected by the inner boundary of the second surface 115 of the second substrate (e.g., inner boundary of second surface 115b of substrate 112b) is refracted through the first gap d1 to be incident on the second surface 115 of the first substrate (e.g., second surface 115a of substrate 112a). A portion of the light that is incident on the second surface 115 of the first (e.g., inner boundary of second surface 115a of substrate 112a) is transmitted across the thickness of the first substrate (e.g., substrate 112a) to form a fourth reflected light beam. The optical path length of the fourth reflected light beam is longer than the optical path of the second reflected light beam by twice the distance of the first gap d1 plus twice the thickness of the second substrate (e.g., substrate 112b). Accordingly, the optical path length of the fourth reflected light beam is longer than the optical path length of the third reflected light beam by a length corresponding to the thickness of the second substrate (e.g., thickness of substrate 112b).
An un-reflected portion of the third transmitted light beam becomes a fourth transmitted light beam and the operation continues until a pair of reflected light beams are reflected from the first and second surfaces of the Nth substrate.
Each pair of reflected light beams due to the first to the Nth substrate travels the first distance 136 and is received by the first end 134 of the optical fiber 132 for transmission in the optical fiber 132, towards the coupling element 140. However, due to the delay of the reflected light beam from the second surface 115 of each substrate, the two reflected light beams from each substrate will be out of phase and will interfere with each other when they combine during propagation. The coupling element 140 directs the reflected light beams into the photodetector 208. The photodetector 208 senses and transmits the interference signal to the signal processor 210. The signal processor 210 performs a spectral analysis of the interference signal to determine the temperature of the first to the Nth substrate (e.g., substrates 112a, 112b, and 112c).
In some embodiments, temperature of multiple substrates (e.g., substrates a, 112b, 112c shown in
The method begins at 402 by loading a substrate into the process chamber and onto the substrate support. Optionally, as shown at 404, substrate processing may be started in the process chamber. At 406, the substrate on the substrate support is irradiated with an incident light beam. At 408, a first reflection of the incident light is bounced off a first surface 113 of the substrate 112. At 410, a second reflection of the first incident light is bounced off an inner boundary of a second surface 115 opposite the first surface 113. At 412, a temperature of the substrate 112 is determined from a spectral interferometry of the first and second reflections.
To measure the temperature of multiple substrates, for example according to
The configuration of the measurement equipment 142 disclosed herein advantageously addresses the inaccuracy, unreliability, and lack of repeatability associated with typical light-based measuring systems, including those utilizing mechanical scanning and light polarization. Consequently, the non-contact substrate temperature measurement technique disclosed herein is more accurate, more robust, and faster than most common thermo-optical measurement methods.
For example, in some embodiments, the temperature of a substrate may be performed in less than about 1 second/data point. In some embodiments, for example, for substrates having a thickness more than about 500 μm, the sampling rate of the temperature measurement may be about 22.2 ms/point, with a measurement accuracy of about +/−0.1%. In some embodiments, for example, for substrates having a thickness less than about 500 μm, the sampling rate of the temperature measurement may be about 16.7 ms/point, with a measurement accuracy of about +/−0.5%.
A controller 146 may be provided and coupled to various components of the substrate processing system 100 to control the operation of the substrate processing system 100. The controller 146 includes a central processing unit (CPU) 148, support circuits 150 and a memory or computer readable medium 152. The controller 146 may control the substrate processing system 100 directly, or via computers (or controllers) associated with particular process chamber and/or support system components. The controller 146 may be any form of general-purpose computer processor that can be used in an industrial setting for controlling various chambers and sub-processors. The memory, or computer readable medium, 152 of the controller 146 may be one or more of readily available memory such as random access memory (RAM), read only memory (ROM), floppy disk, hard disk, optical storage media (e.g., compact disc or digital video disc), flash drive, or any other form of digital storage, local or remote. The support circuits 150 are coupled to the CPU 148 for supporting the processor in a conventional manner. These circuits include cache, power supplies, clock circuits, input/output circuitry and subsystems, and the like. Inventive methods as described herein, such as the method for measuring a temperature of a substrate, may be stored in the memory 152 as software routine 154 that may be executed or invoked to control the operation of the substrate processing system 100 in the manner described herein. The software routine may also be stored and/or executed by a second CPU (not shown) that is remotely located from the hardware being controlled by the CPU 148.
Thus, improved substrate temperature measuring systems and substrate supports incorporating such substrate temperature measuring systems have been provided herein. The substrate temperature measuring systems disclosed herein provide accurate, robust, and real-time temperature measurements of one or more substrates disposed in a process chamber.
While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof.
This application claims benefit of U.S. provisional patent application Ser. No. 62/454,642, filed Feb. 3, 2017, which is herein incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62454642 | Feb 2017 | US |
