Optical interference system and substrate processing device

Abstract

The present invention provides an optical interference system and a substrate processing device. A technology for measuring the physical properties of a measurement object using a simple structure is provided. In an exemplary embodiment, an optical interference system is provided. The optical interference system includes: a light source configured to generate measurement light; an optical fiber configured to transmit the measurement light; and a measuring unit. The optical fiber includes a single-mode optical fiber, a multimode optical fiber, and a connecting portion connecting the single-mode optical fiber and the multimode optical fiber. The top end of the optical fiber is composed of a multimode optical fiber. The end face of the top end of the optical fiber is configured to emit measurement light toward the measurement object and to receive reflected light from the measurement object. The measuring unit is configured to measure the physical properties of the measurement object based on the reflected light.

Description

Technical Field

[0001] Exemplary embodiments of the present disclosure relate to an optical interference system and a substrate processing apparatus. Background Art

[0002] Patent Document 1 discloses an optical interferometer system. The system includes a light source that generates measurement light, a collimator, an optical fiber connecting the light source and the collimator, and a computing device. The collimator collimates the measurement light into parallel beams and then emits the collimated measurement light toward the object being measured. The collimator then receives reflected light from the object. The computing device measures the thickness or temperature of the object based on the reflected light.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2013-242267 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] The present disclosure provides a technology for measuring physical properties of a measurement object with a simple structure.

[0008] Solutions for solving problems

[0009] In one exemplary embodiment, an optical interferometer system is provided. The optical interferometer system includes: a light source configured to generate measurement light; an optical fiber configured to transmit the measurement light; and a measuring unit. The optical fiber includes a single-mode optical fiber, a multimode optical fiber, and a connector that connects the single-mode optical fiber and the multimode optical fiber. The tip of the optical fiber is formed of a multimode optical fiber. The end face of the tip of the optical fiber is configured to emit measurement light toward a measurement object and receive reflected light from the measurement object. The measuring unit is configured to measure physical properties of the measurement object based on the reflected light.

[0010] Effects of the Invention

[0011] According to an exemplary embodiment, physical properties of a measurement object can be measured with a simple configuration. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 FIG. 1 is a diagram illustrating the structure of an optical interference system according to an exemplary embodiment.

[0013] Figure 2 FIG. 1 is a partially enlarged view of a cross section of an optical fiber according to an exemplary embodiment.

[0014] Figure 3FIG. 1 is a partially enlarged view of a cross section of an optical fiber with a cover according to an exemplary embodiment.

[0015] Figure 4 FIG. 1 is a partially enlarged view of a cross section of an optical fiber having a cover and an anti-reflection member according to an exemplary embodiment.

[0016] Figure 5 FIG. 1 is a partially enlarged view of a cross section of an optical fiber having an inclined end face at the tip according to an exemplary embodiment.

[0017] Figure 6 This is a graph showing an example of the relationship between the incident angle of measurement light with respect to the measurement object and the measurement result based on the reflected light.

[0018] Figure 7 It is a cross-sectional view illustrating the structure of a substrate processing apparatus according to another exemplary embodiment.

[0019] Figure 8 FIG. 1 is a partially enlarged view of a cross section of an optical fiber in a substrate processing apparatus according to an exemplary embodiment.

[0020] Figure 9 FIG. 1 is a partially enlarged view of a cross section of an optical fiber in a substrate processing apparatus according to an exemplary embodiment.

[0021] Description of Reference Numerals

[0022] 1: Optical interferometer system; 2: Substrate processing apparatus; 10: Light source; 20: Optical fiber; 21: Single-mode optical fiber; 22: Multimode optical fiber; 23: Connector; 24: Cover; 25: Antireflection member; 30: Measurement unit; 40: Measurement object; 100: Chamber body. FR: Focus ring; W: Semiconductor wafer. DETAILED DESCRIPTION

[0023] Various exemplary embodiments are described below.

[0024] When the optical interferometer system includes a probe with a collimator or a focuser, the measurement light emitted from the probe with the collimator is adjusted to parallel light, and the measurement light emitted from the probe with the focuser is adjusted to focused light. Parallel light refers to light that travels in a straight line without spreading. When the measurement light is parallel light, the optical axis of the collimator must be adjusted so that the parallel light enters the measurement object, and then the light reflected from the measurement object enters the collimator. This adjustment is difficult due to the parallel light. On the other hand, focused light refers to non-parallel light that is focused at a specific, designed distance. When the measurement light is focused light, the optical axis of the focuser must be adjusted so that the focused light enters the measurement object, and then the light reflected from the measurement object enters the focuser. This adjustment is not as difficult as for parallel light, but the angle tolerance is not necessarily large. In typical adjustment procedures, the collimator or focuser is mounted on an optical mount, and the optical mount's function is used to fine-tune the emission angle. Therefore, sufficient space for the optical mount is required.

[0025] In one exemplary embodiment, an optical interferometer system is provided. The optical interferometer system includes: a light source configured to generate measurement light; an optical fiber configured to transmit the measurement light; and a measuring unit. The optical fiber includes a single-mode optical fiber, a multimode optical fiber, and a connector that connects the single-mode optical fiber and the multimode optical fiber. The tip of the optical fiber is formed of a multimode optical fiber. The end face of the tip of the optical fiber is configured to emit measurement light toward a measurement object and receive reflected light from the measurement object. The measuring unit is configured to measure physical properties of the measurement object based on the reflected light.

[0026] In the above embodiment, the measurement light is transmitted through a connector to a multimode optical fiber having a core thicker than that of a single-mode optical fiber. The transmitted measurement light is emitted directly from the end face of the multimode optical fiber toward the object to be measured. Reflected light from the object to be measured is incident on the end face of the multimode optical fiber. According to the above embodiment, the core of the multimode optical fiber is thicker than that of the single-mode optical fiber, making it easier to recouple, and even if the measurement light is not set as a parallel beam, a sufficient amount of reflected light can be obtained. Since this optical interferometer system does not require an optical fixture for adjusting the optical axis, it does not require space for the installation of the optical fixture. Therefore, this optical interferometer system can measure the physical properties of the object to be measured with a simpler structure than previous structures.

[0027] In one exemplary embodiment, the connection portion may have a tapered core connecting the core of the multimode optical fiber and the core of the single-mode optical fiber. In this case, the optical interference system can reduce the reduction in the amount of measurement light in the connection portion.

[0028] In one exemplary embodiment, the optical fiber may include a cover for protecting the end face of the optical fiber, the cover being made of a material that transmits the measurement light and being provided on the end face of the optical fiber. In this case, the optical interferometer system can protect the end face of the optical fiber.

[0029] In an exemplary embodiment, the cover and the end face of the distal end of the optical fiber may be bonded together by an adhesive that transmits the measurement light.

[0030] In one exemplary embodiment, the optical fiber may include an anti-reflection member to prevent the cover from reflecting the measurement light, with the anti-reflection member being disposed between the end face of the optical fiber's tip and the cover. In this case, the optical interference system can reduce reflections of the measurement light caused by the interface between the end face of the optical fiber's tip and the cover. Alternatively, the anti-reflection member may also be disposed on the end face of the cover facing the object to be measured. In this case, the optical interference system can also reduce reflections of the measurement light caused by the interface between the end face of the cover facing the object to be measured and the vacuum or atmospheric space within the processing chamber.

[0031] In one exemplary embodiment, the end face of the optical fiber tip may be tilted relative to a plane perpendicular to the axis of the multimode optical fiber. In this case, the optical interferometer system can reduce reflected light generated at the interface between the medium transmitting the measurement light and the medium through which the measurement light is transmitted, by tilting the end face.

[0032] In another exemplary embodiment, a substrate processing apparatus is provided, comprising: an optical interference system; and a chamber body configured to be vacuum-exhausted and configured to accommodate a measurement object. The optical interference system comprises: a light source configured to generate measurement light; an optical fiber configured to transmit the measurement light; and a measuring unit. The optical fiber includes a single-mode optical fiber, a multimode optical fiber, and a connecting portion connecting the single-mode optical fiber and the multimode optical fiber. The top end of the optical fiber is formed of a multimode optical fiber. The end face of the top end of the optical fiber is configured to emit measurement light toward the measurement object and to receive reflected light from the measurement object. The measuring unit is configured to measure the physical properties of the measurement object based on the reflected light.

[0033] In the above embodiment, the measuring light is transmitted through the connecting portion to a multimode optical fiber having a core thicker than that of a single-mode optical fiber. The transmitted measuring light is emitted directly from the end face of the multimode optical fiber toward the object to be measured. The reflected light from the object to be measured is incident on the end face of the multimode optical fiber. According to the above embodiment, the core of the multimode optical fiber is thicker than that of the single-mode optical fiber and the end face of the multimode optical fiber is close to the object to be measured. Therefore, even if the measuring light is not set as a parallel light beam, the amount of reflected light can be sufficiently obtained. The substrate processing device obtains the reflected light without adjusting the optical axis. Compared with the previous structure, the substrate processing device can more easily measure the physical properties of the object to be measured. In addition, the substrate processing device does not require a collimator, so it can be miniaturized compared with the previous structure.

[0034] In an exemplary embodiment, a stage is disposed within the chamber body. The stage includes a plate to which high-frequency power is applied, and an electrostatic chuck mechanism disposed on the plate for adsorbing an object to be measured, with the stage having a measurement hole formed therein that passes through the plate and the electrostatic chuck mechanism. The optical fiber includes a cover and a cylindrical coating. The cover is made of a material that transmits measurement light and is bonded to the end face of the optical fiber's tip with an adhesive that allows the measurement light to pass through, thereby protecting the tip of the optical fiber. The cylindrical coating is made of a conductive material and extends along the axis of the optical fiber, covering the adhesive and the cover. The optical fiber passes through the measurement hole so that the object to be measured, which is placed on the stage, faces the cover. The coating passes through the measurement hole together with the optical fiber, and is interposed between the optical fiber and the stage. In this case, in the substrate processing apparatus, the surface area of ​​the exposed adhesive is reduced, and the surface of the optical fiber is covered by the conductive coating, thereby preventing abnormal discharge from occurring between the optical fiber and the stage.

[0035] In one exemplary embodiment, a coating may be interposed between the inner surface of the measurement hole formed in the electrostatic chuck mechanism and the optical fiber. In this case, the coating can prevent abnormal discharge from occurring between the electrostatic chuck mechanism and the optical fiber.

[0036] In one exemplary embodiment, the covering member may include an annular cover portion extending radially along the optical fiber on the surface of the cover facing the object to be measured, thereby covering the adhesive and the cover. In this case, the exposed adhesive surface area is reduced, and the covering member including the cover can effectively prevent abnormal discharge between the optical fiber and the mounting table.

[0037] In an exemplary embodiment, the distance between the end face at the distal end of the optical fiber and the object to be measured may be arranged to be greater than or equal to 0.5 mm and less than or equal to 1.5 mm.

[0038] Below, exemplary embodiments of the present disclosure are described with reference to the accompanying drawings. In the following description, identical or equivalent elements are denoted by the same reference numerals, and repeated descriptions are omitted. The dimensional ratios in the drawings do not necessarily correspond to those in the description. The terms "upper," "lower," "left," and "right" are based on the illustrated conditions and are provided for ease of description.

[0039] Figure 1 FIG is a diagram illustrating the structure of an optical interference system 1 according to an exemplary embodiment. Figure 1 As shown, the optical interferometer system 1 utilizes optical interference to measure a physical property value of an object 40. The physical property value is, for example, thickness or temperature. Since measuring the thickness of the object 40 and measuring the temperature of the object 40 can be accomplished using substantially the same operations, the following description will use the optical interferometer system 1 measuring the temperature of the object 40 as an example for ease of understanding.

[0040] The optical interferometer system 1 measures temperature using optical interference and includes a light source 10 , an optical fiber 20 , and a measuring unit 30 .

[0041] Light source 10 generates measurement light having a wavelength that transmits through object 40. For example, an SLD (Super Luminescent Diode) is used as light source 10. Furthermore, object 40 is, for example, in the form of a plate and has a first principal surface and a second principal surface 42 facing first principal surface 41. Hereinafter, first principal surface 41 will be referred to as front surface 41, and second principal surface 42 as back surface 42, as appropriate. Object 40 to be measured may be made of, for example, SiO2 (quartz) or Al2O3 (sapphire), in addition to Si (silicon).

[0042] The optical fiber 20 includes a single-mode optical fiber 21, a multimode optical fiber 22, and a connecting portion 23. The single-mode optical fiber 21 and the multimode optical fiber 22 are both examples of optical fibers. The optical fiber includes a core and a cladding with different refractive indices. The core is arranged at the center, and the cladding is arranged to cover the core. Light incident on the optical fiber is totally reflected at the interface between the core and the cladding for transmission. The diameter of the core of the multimode optical fiber 22 is larger than the diameter of the core of the single-mode optical fiber 21. As an example, the diameter of the core of the single-mode optical fiber 21 is As an example, the core diameter of the multimode optical fiber 22 is or The connection portion 23 connects the single-mode optical fiber 21 and the multi-mode optical fiber 22. Details of the connection portion 23 will be described later.

[0043] Furthermore, the multimode optical fiber 22 may be either an SI (Step Index) fiber or a GI (Graded Index) fiber. The refractive index of a GI fiber core gradually changes between the center and the periphery. Compared to SI fiber, GI fiber reduces noise by transmitting measurement light with a smaller phase difference.

[0044] The distal end of the optical fiber 20 is formed of a multimode optical fiber 22. The end face of the distal end of the optical fiber 20 formed of the multimode optical fiber 22 is configured to emit the measurement light generated by the light source 10 toward the measurement object 40 and to receive the reflected light from the measurement object 40. Details of the distal end of the optical fiber 20 will be described later.

[0045] The optical circulator 11 is connected to the optical fiber 20. The optical circulator 11 transmits the measurement light generated by the light source 10 to the end face of the optical fiber 20. The optical circulator 11 emits the reflected light incident from the end face of the optical fiber 20 to the measurement unit 30.

[0046] The measuring unit 30 measures the temperature of the measurement object 40 based on the reflected light spectrum. The measuring unit 30 may include, for example, a measuring unit 31 and a computing device 32. The measuring unit 31 measures the spectrum of the reflected light obtained from the optical circulator 11. The reflected light spectrum represents the intensity distribution depending on the wavelength or frequency of the reflected light.

[0047] The measuring unit 31 includes, for example, a light dispersing element and a light receiving unit. The light dispersing element is, for example, a diffraction grating, which is an element that disperses light at a predetermined dispersion angle for each wavelength. The light receiving unit acquires the light dispersed by the light dispersing element. As the light receiving unit, for example, a CCD (Charge Coupled Device) is used in which a plurality of light receiving elements are arranged in a grid. The number of light receiving elements is the number of samples. In addition, the wavelength span is specified based on the dispersion angle of the light dispersing element and the distance between the light dispersing element and the light receiving element. As a result, the reflected light is dispersed for each wavelength or frequency, and the intensity is acquired for each wavelength or frequency. The measuring unit 31 outputs the reflected light spectrum to the computing device 32.

[0048] The computing device 32 measures the temperature of the measurement object 40 based on the reflected light spectrum. The computing device 32 includes an optical path length calculation unit, a temperature calculation unit, and temperature calibration data. The optical path length calculation unit performs Fourier transform, data interpolation, and center of gravity position calculation on the reflected light spectrum to calculate the optical path length of the measurement object 40. The temperature calculation unit calculates the temperature of the measurement object 40 based on the optical path length. The temperature calculation unit calculates the temperature of the measurement object 40 with reference to the temperature calibration data. The temperature calibration data is pre-measured data that represents the relationship between temperature and optical path length. With the above structure, the optical interference system 1 uses optical interference between the surface 41 and the back surface 42 of the measurement object 40 to measure the temperature (FFT frequency domain method).

[0049] Figure 2 FIG. 1 is a partially enlarged view of a cross section of an optical fiber 20 according to an exemplary embodiment. Figure 2 The diagram shows the operation of measuring light emitted from end face 22a at the distal end of optical fiber 20, reflected by object 40, and incident on end face 22a as reflected light. Core 22b of multimode optical fiber 22 is connected to core 21b of single-mode optical fiber 21 via core 23b of connector 23. Cores 21b, 22b, and 23b are each surrounded by a cladding layer 20a.

[0050] exist Figure 2 In the example shown, connector 23 has a tapered core 23b. Connector 23 connects core 22b of multimode optical fiber 22 and core 21b of single-mode optical fiber 21 via tapered core 23b. The tapered core 23b has a diameter that gradually decreases from multimode optical fiber 22 toward single-mode optical fiber 21. The gradual change in diameter of core 23b reduces coupling loss during light transmission. Consequently, the tapered core 23b minimizes a decrease in light intensity in connector 23.

[0051] The connector 23 is not limited to a member integrally formed with the single-mode optical fiber 21 and the multimode optical fiber 22. For example, the connector 23 may be a member integrally formed with either the single-mode optical fiber 21 or the multimode optical fiber 22. The connector 23 may also be a member independent of the single-mode optical fiber 21 or the multimode optical fiber 22.

[0052] Figure 3This is a partially enlarged view of a cross-section of an optical fiber 20 having a cover 24 according to an exemplary embodiment. The cover 24 is provided on the end face 22a at the tip of the optical fiber 20. The cover 24 is made of a material that transmits the measurement light and reflects the light. Examples of materials for the cover 24 include Si, SiO2, Al2O3, and YAG (Yttrium Aluminum Garnet). The cover 24 can be, for example, approximately 1.0 mm thick. The thickness of the cover 24 is not limited to approximately 1.0 mm. The cover 24 is designed so that the position where the signal generated after the high-speed Fourier transform at the optical interface of the gap between the cover 24 and the measurement object 40 does not overlap with the signal generated after the high-speed Fourier transform of the measurement object 40. The cover 24 protects the end face 22a at the tip of the optical fiber 20 from being consumed and contaminated by plasma. As an example, the cover 24 and the end face 22a can be bonded together using an adhesive that transmits the measurement light. The adhesives are of acrylic, epoxy, and silicone types, for example, and are cured by ultraviolet irradiation, heating, or a curing agent.

[0053] Figure 4 This is a partially enlarged view of a cross-section of an optical fiber 20 having a cover 24 and an anti-reflection member 25 according to an exemplary embodiment. The anti-reflection member 25 is disposed between the end face 22a at the top of the optical fiber 20 and the cover 24. The anti-reflection member 25 is composed, for example, of a thin film of Al2O3 or MgF2 (magnesium fluoride) coated on the cover 24. The anti-reflection member 25 suppresses reflection at the interface between the cover 24 and the core 22b. Specifically, it suppresses Fresnel reflection at the interface between the core 22b and the cover 24 of the multimode optical fiber 22 having different refractive indices. The anti-reflection member 25 can also be disposed on the end face 24a of the cover 24 on the object to be measured side. In this case, the anti-reflection member 25 is selected from a material that is plasma-resistant and does not cause contamination within the processing chamber 102. When the anti-reflection member 25 is disposed on both the interface between the cover 24 and the core 22b and the end face 24a of the cover 24 on the object to be measured side, reflection caused by the interface of the cover 24 is suppressed. The reflected light from the cover 24 reduces the S / N ratio of the reflected light from the measurement object 40, thereby increasing the variation in the temperature measured by the measurement unit 30. Therefore, the anti-reflection member 25 reduces the variation in the temperature measured by the measurement unit 30 by suppressing the reflection of the measurement light by the cover 24.

[0054] Figure 5 FIG. 2 is a partially enlarged view of a cross section of an optical fiber 20 with an inclined end face 22a at the tip according to an exemplary embodiment. Figure 5 In FIG. 2 , the optical fiber 20 has a cover 24 . The cover 24 is provided on the inclined end face 22 a . The end face 22 a at the tip of the optical fiber 20 is provided so as to be inclined relative to a plane perpendicular to the axial direction of the multimode optical fiber 22 .

[0055] Measurement light L1, propagating axially through the core 22b of the multimode optical fiber 22, is emitted toward the cover 24 at an incident angle θ1. The inclination θ1 of the cover 24 geometrically matches the incident angle θ1 of the measurement light L1. The measurement light L1 is refracted at the interface between the end face 22a and the cover 24, transforming into measurement light L2. A portion of the measurement light L1 is reflected at the interface between the end face 22a and the cover 24, and reflected light R1 is incident on the core 22b.

[0056] The measurement light L2 propagating within the cover 24 is emitted into the external space at an incident angle θ2. The external space is a vacuum or a space filled with any gas. The measurement light L2 is refracted at the interface between the end face 24a and the external space, changing into the measurement light L3. The measurement light L3 propagating in the external space is emitted toward the measurement object 40 at an incident angle θ3. The measurement light L3 is reflected by the front surface 41 and the back surface 42 (not shown), and reflected light R3 is incident on the cover 24. A portion of the measurement light L2 is reflected by the interface between the end face 24a and the external space, and reflected light R2 is incident on the cover 24. The reflected light R2 also enters the core 22b.

[0057] When the inclination θ1 of the end face 22a relative to the plane perpendicular to the axis of the multimode optical fiber 22 is 0 degrees and the end face 22a is not tilted, the reflected light R1 and reflected light R2 incident on the core 22b reduce the S / N ratio of the reflected light R3 from the measurement object 40. When the end face 22a is tilted, the incident angle of the reflected light R1 and reflected light R2 incident on the core 22b increases with respect to the interface between the core 22b and the cladding 20a, preventing them from reaching the measurement unit 30. Therefore, the S / N ratio of the reflected light R3 is not affected. Therefore, the tilted end face 22a suppresses the reflected light R1 and reflected light R2 from reaching the measurement unit 30, thereby improving the accuracy of the temperature measured by the measurement unit 30.

[0058] Figure 6 3 is a graph showing an example of the relationship between the incident angle θ3 of the measurement light L3 with respect to the measurement object 40 and the measurement result obtained from the measurement unit 30 . Figure 6 The signal intensity and temperature stability 3σ shown are obtained based on the reflected light R3 obtained by irradiating the measurement object 40 with the measurement light L3 at an incident angle θ3. Figure 6 In the figure, white circles represent signal strength, with the numerical value represented by the right vertical axis. Black circles represent temperature stability 3σ, with the numerical value represented by the left vertical axis. Both signal strength and temperature stability 3σ vary with the incident angle θ3.

[0059] The signal intensity is a value digitized by the measuring unit 30 based on the reflected light R3, and is a value that increases as the amount of reflected light R3 increases. When the incident angle θ3 increases, part of the reflected light R3 is reflected again by the end surface 24a and the end surface 22a, so the signal intensity decreases. The signal intensity shows a maximum value when the incident angle θ3 is 0 degrees and the end surface 22a is not tilted. The signal intensity decreases exponentially with the increase in the incident angle θ3. When the incident angle θ3 exceeds 4 degrees, the signal intensity drops to approximately 10 a.u. At least if the incident angle θ3 is within the range of greater than 0 degrees and less than 2 degrees, the optical interferometer system 1 can measure the temperature of the measurement object 40 with sufficient accuracy.

[0060] Temperature stability 3σ indicates the range of error in the temperature of the measurement object 40 calculated by the measurement unit 30 based on the reflected light R3. 3σ refers to data within the 3σ range of the standard deviation. For example, the temperature measured by the measurement unit 30 varies with each measurement. This variation includes both extremely large and extremely small variations. Therefore, temperature stability 3σ indicates the variation in the measurement results based on the measurement results within the 3σ range. When the incident angle θ3 is 0 degrees and the end face 22a is not tilted, the temperature stability 3σ shows a minimum value of ±0.5°C. Since the signal intensity decreases as the incident angle θ3 increases, the temperature stability 3σ deteriorates as the incident angle θ3 increases. When the incident angle θ3 is 2 degrees, the temperature stability 3σ changes by ±1.0°C. When the incident angle θ3 is greater than 2 degrees, the temperature stability 3σ deteriorates exponentially. For example, when the incident angle θ3 is 4 degrees, the temperature stability 3σ changes by ±2.0°C. When the incident angle θ3 is set within a range of greater than 0 degrees and not more than 2 degrees, the rate of degradation of the temperature stability 3σ can be reduced.

[0061] The relationship between the angles of incidence θ1, θ2, and θ3 is shown below as an example. When the inclination θ1 of the end face 22a relative to the plane perpendicular to the axis of the multimode optical fiber 22 is 4.0 degrees, the angle of incidence θ1 is 4.0 degrees. In this case, the measurement light L2 is refracted at the interface of the end face 22a, so the angle of incidence θ2 is 3.3 degrees. The measurement light L3 is refracted at the interface of the end face 24a, and the angle of incidence θ3 becomes 2.0 degrees. The angle of incidence θ3 is approximately half of the angle of incidence θ1. Therefore, when the angle of incidence θ3 is within 4.0 degrees, the inclination θ1 is within a range of greater than 0 degrees and within 8.0 degrees. When the angle of incidence θ3 is within 2.0 degrees, the inclination θ1 is within a range of greater than 0 degrees and within 4.0 degrees.

[0062] The distance between the end face 22a at the tip of the optical fiber 20 and the object 40 to be measured can be set to be between 0.5 mm and 1.5 mm. Specifically, the distance between the first principal surface 41 of the object 40 to be measured and the end face 22a at the tip of the optical fiber 20 can be set to be between 0.5 mm and 1.5 mm. This arrangement ensures the required accuracy of signal strength.

[0063] In addition, when a cover 24 is provided on the end face 22a at the top end of the optical fiber 20, the thickness of the cover is designed so that the position where the signal after the high-speed Fourier transformation is generated based on the optical interface of the optical path length of the cover 24 and the gap between the cover 24 and the measured object 40 does not overlap with the signal after the high-speed Fourier transformation of the measured object 40.

[0064] Figure 7 This is a cross-sectional view illustrating the structure of a substrate processing apparatus 2 according to an exemplary embodiment. Here, as an application example of the optical interferometer system 1 in a substrate processing apparatus 2 such as a plasma etching apparatus, the case of measuring the temperature of a wafer or a focus ring is described.

[0065] like Figure 7 As shown, the substrate processing apparatus 2 includes a chamber body 100 that accommodates a semiconductor wafer W as a substrate and processes the semiconductor wafer W using plasma.

[0066] The interior of the chamber body 100 is defined as a processing chamber 102. The processing chamber 102 is configured to be vacuum evacuable. A mounting table 120 for mounting a semiconductor wafer W is provided in the processing chamber 102. The mounting table 120 includes an RF plate 120a made of a conductive material to which high-frequency power is applied, and an electrostatic chuck mechanism 120b disposed on the RF plate 120a for absorbing the semiconductor wafer W. The center portion of the RF plate 120a is connected to a power supply rod 120c, which is electrically connected to a high-frequency power supply (not shown).

[0067] A partition plate 130 formed in an annular shape is provided around the stage 120 so as to surround the stage 120. An annular exhaust space 140 is formed at the bottom of the partition plate 130 for uniformly exhausting air from around the stage 120. In addition, a base plate 150 is provided at the bottom of the chamber body 100, and a gap 101 is formed between the RF plate 120a and the base plate 150. The gap 101 has a sufficient width for insulating the RF plate 120a from the base plate 150. In addition, a driving mechanism (not shown) for a push pin is provided in the gap 101. The push pin is used to receive the semiconductor wafer W from the transfer arm and place the semiconductor wafer W on the stage 120, or to lift the semiconductor wafer W from the stage 120 and hand it over to the transfer arm. In addition, the gap 101 is not a vacuum atmosphere but an atmospheric atmosphere.

[0068] A counter electrode 110 is disposed above the mounting table 120, spaced apart from the mounting table 120 and facing the mounting table 120. This counter electrode 110 comprises a so-called showerhead, configured to supply a predetermined processing gas in a shower-like manner to the semiconductor wafer W mounted on the mounting table 120. This counter electrode 110 is set to ground potential or has high-frequency power applied thereto. Furthermore, a focus ring FR is disposed around the semiconductor wafer W on the mounting table 120. This focus ring FR is used to improve the in-plane uniformity of the plasma processing of the semiconductor wafer W.

[0069] The chamber body 100 is configured such that the space above the stage 120, i.e., the processing chamber 102, is in a vacuum atmosphere, while the space 101 below the stage 120 is in a normal pressure atmosphere. Thus, the stage 120 forms a portion of a partition wall separating the vacuum atmosphere from the normal pressure atmosphere. Furthermore, a plurality of temperature measurement holes 121, 122, 123, and 124 are formed in the stage 120. The temperature measurement holes 121, 122, 123, and 124 are configured to allow the optical fiber 20 of the optical interferometer system 1 to communicate through the upper and lower surfaces of the stage 120 and are hermetically sealed by a fiber feedthrough.

[0070] In one exemplary embodiment, among the temperature measurement holes 121, 122, 123, and 124, the temperature measurement hole 124 provided at the outermost circumference of the mounting table 120 is used to measure the temperature of the focus ring FR. The other temperature measurement holes 121, 122, and 123 are used to measure the temperature of the semiconductor wafer W.

[0071] On the bottom plate 150, through holes 151, 152, 153 and 154 are provided corresponding to the above-mentioned temperature measurement holes 121, 122, 123 and 124. Optical fibers 201, 202, 203 and 204 as part of the optical interference system 1 are fixed in these through holes. In addition, instead of the through holes 151, 152, 153 and 154, a through hole may be provided in which the optical fibers 201, 202, 203 and 204 are collectively fixed. In addition, a connecting member 160 for connecting the bottom plate 150 and the mounting table 120 (RF plate 120a) is provided in the gap 101 between the bottom plate 150 and the mounting table 120 (RF plate 120a). In addition, in Figure 7 Although only one connecting member 160 is shown in the figure, a plurality of connecting members 160 (eg, four or more) are arranged along the circumferential direction. These connecting members 160 are used to suppress deformation and vibration of the mounting table 120 .

[0072] The optical fibers 201, 202, 203, and 204 described above are exemplary embodiments of the optical fiber 20. In this case, the optical fiber 20 may also include an optical switch between the optical circulator 11 and the tip of the optical fiber 20. As an example, the optical switch has one input and four outputs. The input is connected to the optical circulator 11. The four outputs are connected to the optical fibers 201, 202, 203, and 204, respectively. The optical switch is configured to switch the output destination. The optical switch alternately transmits light from the optical circulator 11 from the input to the four outputs.

[0073] In the optical interferometer system 1, measurement light is emitted from the end faces of the respective top ends of the optical fibers 201, 202, 203, and 204, and is reflected by the semiconductor wafer W and the focus ring FR, which are the measurement objects, on the mounting table 120. The reflected light from the semiconductor wafer W and the focus ring FR is then incident on the end faces of the respective top ends of the optical fibers 201, 202, 203, and 204. The optical switch alternately transmits the reflected light from the optical fibers 201, 202, 203, and 204 to the optical circulator 11.

[0074] Figure 8 FIG. 1 is a partially enlarged view of a cross section of an optical fiber in a substrate processing apparatus according to an exemplary embodiment. Figure 8 As an example, a cross-section of optical fiber 201 fixed to temperature measurement hole 121 is enlarged. The optical fiber may be any of optical fibers 201, 202, 203, and 204, and the temperature measurement hole may be any of temperature measurement holes 121, 122, 123, and 124. Sleeve 240 penetrates temperature measurement hole 121. Sleeve 240 secures optical fiber 201 to temperature measurement hole 121. If optical fiber 201 can be directly fixed to temperature measurement hole 121, sleeve 240 may not be provided.

[0075] The optical fiber 201 includes a structure 210 and a cover 220. The structure 210 covers the periphery of the optical fiber 201 and extends along the axis of the optical fiber 201. The material of the structure 210 is, for example, alumina ceramic or sapphire. The structure 210 fixes the optical fiber 201 so that the optical fiber 201 extends along the temperature measurement hole 121. The cover 220 is an exemplary embodiment of the cover 24. The cover 220 is bonded to the end face 201a at the top of the optical fiber 201 by an adhesive B. The measuring light passes through the adhesive B. The adhesive B is, for example, acrylic, epoxy, and silicone, and is cured by ultraviolet irradiation, heating, or a curing agent. The cover 220 is bonded to the end face 201a at the top of the optical fiber 201 and is also bonded to the end face 210a of the structure 210 located on the same plane as the end face 201a.

[0076] The optical fiber 201 also has a cylindrical coating 230. The coating 230 is made of a conductive material, for example, Si or SiC. The cylindrical coating 230 extends along the axial direction of the optical fiber 201 in a manner that covers the adhesive B and the cover 220. Specifically, the coating 230 covers the adhesive B that bonds the end face 201a and the end face 210a to the cover 220. The coating 230 also extends from the cover 220 in a manner that covers the structural member 210. The coating 230 is located between the inner surface of the temperature measurement hole 121 formed in the electrostatic chuck mechanism 120b and the optical fiber 201. The coating 230 may also be located between the inner surface of the temperature measurement hole 121 formed in the RF plate 120a and the optical fiber 201.

[0077] By enclosing adhesive B and cover 220 with coating 230, the area of ​​adhesive B exposed in the vacuum atmosphere of processing chamber 102 is reduced. This reduces the amount of gas volatilized from adhesive B. Therefore, during plasma processing, coating 230 can prevent abnormal discharge between optical fiber 201 and mounting table 120. Coating 230 extends along the electrostatic chuck mechanism 120b that penetrates temperature measurement hole 121, thereby preventing abnormal discharge between optical fiber 201 and electrostatic chuck mechanism 120b.

[0078] Furthermore, by passing the conductive coating 230 through the temperature measurement hole 121, the space for electron acceleration in the temperature measurement hole 121 is reduced. Therefore, the coating 230 can prevent abnormal discharge from occurring between the optical fiber 201 and the mounting table.

[0079] Figure 9 FIG. 1 is a partially enlarged view of a cross section of an optical fiber in a substrate processing apparatus according to an exemplary embodiment. Figure 9As an example, a cross section of the optical fiber 201 having the coating 231 fixed to the temperature measurement hole 121 is enlarged. The coating 231 is a modified example of the coating 230 .

[0080] The covering member 231 includes a cover portion 231a. The cover portion 231a extends radially along the optical fiber 201 on the surface of the cover 220 facing the semiconductor wafer W, covering the adhesive B and the cover 220. Specifically, the cover portion 231a extends radially inward along the end face 220a of the cover 220. A hole is formed in the radial center of the cover portion 231a, through which the end face 220a of the cover 220 is exposed. The diameter of the hole is, for example, 0.3 mm.

[0081] In this case, the surface area of ​​the exposed adhesive B is smaller, and thus the coating member 231 including the cover portion 231 a can more effectively prevent abnormal discharge generated between the optical fiber 201 and the mounting table 120 .

[0082] As described above, by incorporating the optical interferometer system 1 into the substrate processing apparatus 2, it is possible to measure the thickness and temperature of the semiconductor wafer W, as well as the thickness and temperature of the focus ring FR. Furthermore, when chamber components such as the focus ring FR housed within the processing chamber are used as measurement targets, the chamber components are formed from a material that is transparent to the measurement light. For example, Si, SiO2, SiC, and Al2O3 are used as materials for the chamber components.

[0083] Based on the above description, it should be understood that various embodiments of the present disclosure can be modified in various ways without departing from the scope and spirit of the present disclosure. Therefore, the various embodiments disclosed in this specification are not intended to be limiting, and the true scope and spirit are shown by the appended claims.

Claims

1. An optical interference system, characterized in that: have: a light source configured to generate measurement light; an optical fiber configured to transmit the measurement light, the optical fiber comprising a single-mode optical fiber, a multimode optical fiber, and a connection portion connecting the single-mode optical fiber and the multimode optical fiber, the tip of the optical fiber being formed of the multimode optical fiber, the end face of the tip of the optical fiber being configured to emit the measurement light toward the measurement object and to receive reflected light from the measurement object; as well as The measuring unit is configured to measure a physical property of the measurement object based on the reflected light.

2. The optical interferometer system according to claim 1, wherein: The connecting portion has a tapered core that connects the core of the multimode optical fiber and the core of the single-mode optical fiber.

3. The optical interferometer system according to claim 1, wherein: The optical fiber has a cover for protecting the end face of the tip of the optical fiber. The cover is made of a material that transmits the measurement light and is provided on an end face at the distal end of the optical fiber.

4. The optical interference system according to claim 3, characterized in that The cover and the end face of the distal end of the optical fiber are bonded together by an adhesive that transmits the measurement light.

5. The optical interference system according to claim 3, wherein: The optical fiber has an anti-reflection member for preventing the cover from reflecting the measurement light. The anti-reflection member is provided between the end face of the distal end of the optical fiber and the cover.

6. The optical interference system according to claim 3, wherein: The end face at the distal end of the optical fiber is provided so as to be inclined with respect to a plane perpendicular to the axial direction of the multimode optical fiber.

7. The optical interferometer system according to claim 1, wherein: The distance between the end face of the distal end of the optical fiber and the object to be measured is arranged to be 0.5 mm or more and 1.5 mm or less.

8. A substrate processing device, characterized in that: have: optical interferometry systems; and The chamber body is configured to be vacuum-exhausted and to accommodate the object to be measured. Wherein, the optical interference system comprises: a light source configured to generate measurement light; an optical fiber configured to transmit the measurement light, the optical fiber including a single-mode optical fiber, a multimode optical fiber, and a connection portion connecting the single-mode optical fiber and the multimode optical fiber, the tip of the optical fiber being formed of the multimode optical fiber, the end face of the tip of the optical fiber being configured to emit the measurement light toward the measurement object and to receive reflected light from the measurement object; and The measuring unit is configured to measure a physical property of the measurement object based on the reflected light.

9. The substrate processing apparatus according to claim 8, wherein: A mounting table is arranged inside the chamber body. The mounting table includes: a plate to which high-frequency power is applied; and an electrostatic chuck mechanism provided on the plate for adsorbing the object to be measured, and the mounting table is formed with a measurement hole penetrating the plate and the electrostatic chuck mechanism. The optical fiber has: a cover made of a material that transmits the measurement light, bonded to the end face of the tip of the optical fiber by an adhesive that allows the measurement light to pass, and used to protect the tip of the optical fiber; as well as A cylindrical covering member is made of a conductive material and extends along the axial direction of the optical fiber in a manner covering the adhesive and the cover. The optical fiber passes through the measurement hole so that the measurement object placed on the mounting table faces the cover. The coating member passes through the measurement hole together with the optical fiber.

10. The substrate processing apparatus according to claim 9, wherein: The coating member is interposed between the inner surface of the measurement hole formed in the electrostatic chuck mechanism and the optical fiber.

11. The substrate processing apparatus according to claim 9 or 10, wherein: The coating member includes an annular cover portion extending in the radial direction of the optical fiber on a surface of the cover facing the object to be measured so as to cover the adhesive and the cover.

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