System and method for measuring displacement

Abstract

To provide a system and a method for properly measuring displacement of an object by using light.SOLUTION: A system that measures displacement includes: a light source; a lens configured to converge light generated by the light source; a beam splitter configured to irradiate the object with the light converged by the lens and receive reflected light from the object; an image sensor configured to receive the reflected light from the object via the beam splitter and acquire an intensity distribution of the reflected light; and a control unit configured to acquire a size of a beam diameter of the reflected light on the basis of the intensity distribution of the reflected light acquired by the image sensor, and output displacement information of the object on the basis of the acquired beam diameter and a relation acquired in advance between the size of the beam diameter and the displacement information of the object.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] SUMMARY OF THE DISCLOSURE Exemplary embodiments of the present disclosure relate to systems and methods for measuring displacement. [Background technology]

[0002] Patent Document 1 discloses an optical interference system. The optical interference system emits light from a source onto an object and receives returning light from the front and back surfaces of the object. The thickness of the object is measured based on the waveform obtained by Fourier transforming the intensity distribution of the returning light. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-96858 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides systems and methods for suitably measuring displacement of an object using light. [Means for solving the problem]

[0005] One aspect of the present disclosure is a system for measuring the displacement of an object. The system includes a light source, a lens, a beam splitter, an image sensor, and a controller. The lens is configured to converge light generated by the light source. The beam splitter is configured to irradiate the object with the light converged by the lens and to receive reflected light from the object. The image sensor is configured to receive the reflected light from the object via the beam splitter and acquire an intensity distribution of the reflected light. The controller is configured to acquire a beam diameter of the reflected light based on the intensity distribution of the reflected light acquired by the image sensor, and to output displacement information of the object based on the acquired beam diameter and a previously acquired relationship between the beam diameter and displacement information of the object. [Effects of the Invention]

[0006] According to the present disclosure, the displacement of an object can be appropriately measured using light. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram illustrating an example of a processing system according to an example embodiment. [Figure 2] FIG. 2 is a diagram schematically illustrating an example of a substrate processing apparatus according to an exemplary embodiment. [Figure 3] FIG. 3 is a diagram schematically illustrating an example of the mounting position of the sensor head. [Figure 4] FIG. 4 is a diagram illustrating a schematic diagram of an example of a displacement measurement system according to an exemplary embodiment. [Figure 5] FIG. 5 is a graph showing an example of the relationship between the power and wavelength of light in a light source. [Figure 6] FIG. 6 is a diagram schematically illustrating an example of optical paths of light of a plurality of wavelengths. [Figure 7] FIG. 7 is an example of an image of the intensity distribution acquired by the image sensor. [Figure 8] FIG. 8 is an example of an intensity distribution acquired by an image sensor. [Figure 9] FIG. 9 is a graph showing an example of the relationship between the beam diameter and the displacement of the object. [Figure 10] FIG. 10 is a flow chart of a method for using a displacement measurement system. [Figure 11] FIG. 11 shows an example of measuring a tilted wafer. [Figure 12] FIG. 12 shows an example of an image of the intensity distribution when measuring a tilted wafer. [Figure 13] FIG. 13 is a diagram schematically illustrating an example of a displacement measuring system according to a modified example. [Figure 14] FIG. 14 is a diagram showing an example of a region where sensitivity decreases. [Figure 15]FIG. 15 is a graph showing an example of the relationship between sensitivity and position. [Figure 16] FIG. 16 is a diagram schematically illustrating an example of a displacement measuring system according to a modified example. [Figure 17] FIG. 17 is a graph showing an example of the relationship between the beam diameter of a single wavelength and the displacement of an object. DETAILED DESCRIPTION OF THE INVENTION

[0008] Various exemplary embodiments are described below.

[0009] An optical interference system can not only measure the thickness of an object based on the returned light, but also measure the displacement of the object. The displacement of the object is the distance from the light-emitting unit to the object. In order to accurately measure the thickness and displacement of an object, the optical interference system must receive the returned light with as little loss as possible. In other words, to achieve the target measurement accuracy, the orientation of the object is restricted so that the returned light is properly coupled to the optical fiber (restrictions on the angular tolerance of the object). The present disclosure provides a technology that relaxes the restrictions on the orientation of the object and properly measures the displacement of the object using light.

[0010] One aspect of the present disclosure is a system for measuring the displacement of an object. The system includes a light source, a lens, a beam splitter, an image sensor, and a controller. The lens is configured to converge light generated by the light source. The beam splitter is configured to irradiate the object with the light converged by the lens and to receive reflected light from the object. The image sensor is configured to receive the reflected light from the object via the beam splitter and acquire an intensity distribution of the reflected light. The controller is configured to acquire a beam diameter of the reflected light based on the intensity distribution of the reflected light acquired by the image sensor, and to output displacement information of the object based on the acquired beam diameter and a previously acquired relationship between the beam diameter and displacement information of the object.

[0011] In this system, light generated by a light source is converged by a lens and irradiated onto an object by a beam splitter. Light reflected from the object is incident on the beam splitter and then on an image sensor, where the intensity distribution of the reflected light is acquired. The beam diameter of the reflected light is acquired based on the intensity distribution of the reflected light. The relationship between the beam diameter and displacement information of the object is acquired in advance. Displacement information of the object is output based on the beam diameter acquired by measurement and the known relationship. In this way, since displacement information of the object can be output based on the beam diameter acquired from the intensity distribution of the reflected light acquired by the image sensor, there is no need to appropriately couple the returned light into an optical fiber. Therefore, this system relaxes restrictions on the object's orientation and can appropriately measure the object's displacement using light.

[0012] In one embodiment, the light source may be a broadband light source, the lens may have chromatic aberration, and the image sensor may be configured to acquire the intensity distribution of the reflected light for each wavelength. In this case, the system may acquire different beam diameters for each wavelength that the broadband light source can output, and output displacement information of the object based on the multiple beam diameters. Therefore, the system may improve the accuracy of the displacement information of the object compared to when the displacement information of the object is output based on a single beam diameter.

[0013] In one embodiment, the light source may be configured to output light obtained by combining multiple single-wavelength light beams, the lens may have chromatic aberration, and the image sensor may be configured to acquire the intensity distribution of the reflected light for each wavelength. In this case, the system may acquire different beam diameters for each wavelength of the combined light beam that the light source can output, and output displacement information of the object based on the multiple beam diameters. Therefore, the system may improve the accuracy of the displacement information of the object compared to when the displacement information of the object is output based on a single beam diameter.

[0014] In one embodiment, the light source is configured to be able to output multiple single-wavelength light beams with time delays, and the lens may have chromatic aberration. In this case, the system can obtain different beam diameters for each wavelength of light that the light source can output, and output displacement information of the object based on the multiple beam diameters. Therefore, the system can improve the accuracy of the displacement information of the object compared to when the displacement information of the object is output based on a single beam diameter.

[0015] In one embodiment, the control unit may be configured to acquire the position and shape of the beam diameter of the reflected light based on the intensity distribution of the reflected light, and calculate the tilt of the object based on the acquired position and shape of the beam diameter. In this case, the system can calculate the tilt of the object based on the position and shape of the beam diameter.

[0016] In one embodiment, the beam splitter is a rectangular parallelepiped and may be arranged so that its longitudinal direction is perpendicular to the direction in which the object and the image sensor face each other. In this case, the range of the beam splitter that receives reflected light from a tilted object is expanded, and therefore the system can more easily accommodate restrictions on the orientation of the object.

[0017] Another aspect of the present disclosure is a method using a system for measuring the displacement of an object. The system includes a light source, a lens, a beam splitter, an image sensor, and a control unit. The lens is configured to converge light generated by the light source. The beam splitter is configured to irradiate the object with the light converged by the lens and to receive reflected light from the object. The image sensor is configured to receive the reflected light from the object via the beam splitter and acquire an intensity distribution of the reflected light. The method includes an acquiring step and an outputting step. In the acquiring step, a beam diameter of the reflected light is acquired based on the intensity distribution of the reflected light acquired by the image sensor. In the outputting step, displacement information of the object is output based on the acquired beam diameter and a previously acquired relationship between the beam diameter and displacement information of the object. This method achieves the same effects as the above-mentioned system.

[0018] Various embodiments will be described in detail below with reference to the drawings. In the following description and in each drawing, the same or equivalent elements are designated by the same reference numerals, and redundant description will not be repeated. The dimensional ratios of the drawings do not necessarily match those in the description. The terms "upper," "lower," "left," and "right" are based on the illustrated state and are for convenience.

[0019] [Processing system overview]

[0020] FIG. 1 is a diagram illustrating an example of a processing system according to an exemplary embodiment. The processing system 100 illustrated in FIG. 1 includes a processing device for processing an object, a transport device for transporting the object to the processing device, and a displacement detection system capable of detecting displacement of the object. The object is a disk-shaped object to be processed by the processing device, such as a wafer (substrate). The wafer may or may not have already been subjected to a processing process or plasma treatment.

[0021] The processing system 100 includes stages 2a to 2d, containers 4a to 4d, a loader module LM, load lock chambers LL1 and LL2, process modules PM1 to PM6, and a transfer chamber TC.

[0022] The stages 2a to 2d are arranged along one edge of the loader module LM. The containers 4a to 4d are mounted on the stages 2a to 2d, respectively. The containers 4a to 4d are configured to accommodate wafers W, respectively.

[0023] The loader module LM has a chamber wall that defines a transfer space therein under atmospheric pressure. The loader module LM has a transfer device TU1 in this transfer space. The transfer device TU1 is configured to transfer wafers W between the containers 4a to 4d and the load lock chambers LL1 and LL2.

[0024] The load lock chambers LL1 and LL2 are each provided between the loader module LM and the transfer chamber TC. Each of the load lock chambers LL1 and LL2 serves as a preliminary decompression chamber.

[0025] The transfer chamber TC is connected to the load lock chambers LL1 and LL2 via gate valves. The transfer chamber TC provides a decompression chamber that can be decompressed, and the transfer device TU2 is housed in the decompression chamber. The transfer device TU2 is configured to transfer wafers W between the load lock chambers LL1-LL2 and the process modules PM1-PM6, and between any two of the process modules PM1-PM6.

[0026] The process modules PM1 to PM6 are connected to the transfer chamber TC via gate valves. Each of the process modules PM1 to PM6 is a processing apparatus configured to perform a dedicated process, such as a plasma process, on the wafer W.

[0027] The series of operations when a wafer W is processed in the processing system 100 is exemplified as follows: The transfer device TU1 of the loader module LM removes the wafer W from one of the containers 4a to 4d and transfers the wafer W to one of the load lock chambers LL1 and LL2. Next, one of the load lock chambers reduces the pressure in the preliminary decompression chamber to a predetermined pressure. Next, the transfer device TU2 of the transfer chamber TC removes the wafer W from one of the load lock chambers and transfers the wafer W to one of the process modules PM1 to PM6. Then, one or more of the process modules PM1 to PM6 processes the wafer W. Then, the transfer device TU2 transfers the processed wafer from the process module to one of the load lock chambers LL1 and LL2. Next, the transfer device TU1 transfers the wafer W from one of the load lock chambers to one of the containers 4a to 4d.

[0028] The processing system 100 further includes a control device MC. The control device MC may be a computer including a processor, a storage device such as a memory, a display device, an input / output device, a communication device, etc. The series of operations of the processing system 100 described above is realized by the control device MC controlling each part of the processing system 100 in accordance with a program stored in the storage device.

[0029] [Outline of substrate processing equipment] Next, a substrate processing apparatus, which is an example of the process modules PM1 to PM6, will be described. FIG. 2 is a diagram schematically illustrating a substrate processing apparatus according to an exemplary embodiment. The plasma processing apparatus 10 (an example of a substrate processing apparatus) illustrated in FIG. 2 is a capacitively coupled plasma etching apparatus. The plasma processing apparatus 10 includes a chamber body 12. The chamber body 12 has a substantially cylindrical shape and provides an internal space 12s. The chamber body 12 is formed of, for example, aluminum. The inner wall surface of the chamber body 12 is subjected to a treatment to impart plasma resistance. For example, the inner wall surface of the chamber body 12 is subjected to an anodizing treatment. The chamber body 12 is electrically grounded.

[0030] A passage 12p is formed in the sidewall of the chamber body 12. The workpiece passes through the passage 12p when being loaded into or unloaded from the internal space 12s. The passage 12p can be opened and closed by a gate valve 12g.

[0031] A support 13 is provided on the bottom of the chamber body 12. The support 13 is made of an insulating material. The support 13 has a generally cylindrical shape. The support 13 extends vertically from the bottom of the chamber body 12 within the internal space 12s. The support 13 supports a stage 14. The stage 14 is provided within the internal space 12s.

[0032] The stage 14 has a lower electrode 18 and an electrostatic chuck 20. The stage 14 may further include an electrode plate 16. The electrode plate 16 is made of a conductive material such as aluminum and has a substantially disc shape. The lower electrode 18 is provided on the electrode plate 16. The lower electrode 18 is made of a conductive material such as aluminum and has a substantially disc shape. The lower electrode 18 is electrically connected to the electrode plate 16.

[0033] The electrostatic chuck 20 is provided on the lower electrode 18. A workpiece is placed on the upper surface of the electrostatic chuck 20. The electrostatic chuck 20 has a body made of a dielectric material. A film-like electrode is provided within the body of the electrostatic chuck 20. The electrode of the electrostatic chuck 20 is connected to a power supply 22 via a switch. The power supply 22 may be a DC power supply or an AC power supply. When a voltage from the power supply 22 is applied to the electrode of the electrostatic chuck 20, an electrostatic attractive force is generated between the electrostatic chuck 20 and the workpiece. The generated electrostatic attractive force attracts the workpiece to the electrostatic chuck 20 and the workpiece is held by the electrostatic chuck 20.

[0034] An edge ring ER is disposed on the stage 14 so as to surround the edge of the workpiece. The edge ring ER is provided to improve the in-plane etching uniformity. The edge ring ER may be made of silicon, silicon carbide, quartz, or the like.

[0035] A flow path 18f is provided inside the lower electrode 18. A coolant is supplied to the flow path 18f from a chiller unit 26 disposed outside the chamber body 12 via a pipe 26a. The coolant supplied to the flow path 18f is returned to the chiller unit 26 via a pipe 26b. In the plasma processing apparatus 10, the temperature of the workpiece placed on the electrostatic chuck 20 is adjusted by heat exchange between the coolant and the lower electrode 18.

[0036] The plasma processing apparatus 10 is provided with a gas supply line 28. The gas supply line 28 supplies a heat transfer gas, for example, He gas, from a heat transfer gas supply mechanism to between the upper surface of the electrostatic chuck 20 and the back surface of the workpiece.

[0037] The plasma processing apparatus 10 further includes an upper electrode 30. The upper electrode 30 is provided above the stage 14. The upper electrode 30 includes an electrode plate 34. The lower surface of the electrode plate 34 is the lower surface on the internal space 12s side and defines the internal space 12s. The electrode plate 34 can be formed from a low electrical resistance conductor or semiconductor that generates little Joule heat. As an example, the electrode plate 34 is made of silicon. A plurality of gas discharge holes 34a are formed in the electrode plate 34. The plurality of gas discharge holes 34a penetrate the electrode plate 34 in the plate thickness direction.

[0038] A cooling plate 37 that holds the electrode plate 34 is disposed above the electrode plate 34. The cooling plate 37 includes a cooling plate main body 37A. The cooling plate main body 37A may be made of a conductive material such as aluminum. The cooling plate 37 includes an electrostatic chuck 35 on the underside of the cooling plate main body 37A. The electrostatic chuck 35 exerts an attraction force to bring the electrode plate 34 into close contact with the cooling plate main body 37A. The electrostatic chuck 35 also exerts an attraction force to support the electrode plate 34 on the upper part of the chamber body 12. The member 32 and the locking portion 39 are support members that support the electrode plate 34 from below and prevent the electrode plate 34 from falling. The member 32 and the locking portion 39 are made of, for example, an insulating material. The locking portion 39 may be configured to be rotatable downward.

[0039] A flow path 37c is provided inside the cooling plate main body 37A. A coolant is supplied to the flow path 37c from a chiller unit (not shown) disposed outside the chamber body 12. The coolant supplied to the flow path 37c is returned to the chiller unit. This adjusts the temperature of the cooling plate main body 37A. In the plasma processing apparatus 10, the temperature of the electrode plate 34 is adjusted by heat exchange with the cooling plate main body 37A.

[0040] A plurality of gas inlet passages 37a are provided inside the cooling plate main body 37A, extending downward. A plurality of gas diffusion chambers 37b are provided between the upper surface of the electrode plate 34 and the lower surface of the cooling plate main body 37A, corresponding to the plurality of gas inlet passages 37a. A plurality of gas supply passages 37e are provided, extending in the thickness direction from the gas diffusion chambers 37b toward the electrode plate 34. The gas supply passages 37e supply process gas to the plurality of gas discharge holes 34a of the electrode plate 34. A plurality of gas inlet ports 37d are formed in the cooling plate main body 37A, which introduce process gas into the plurality of gas diffusion chambers 37b. Gas supply pipes 38 are connected to the gas inlet ports 37d.

[0041] A gas supply unit GS is connected to the gas supply pipe 38. In one embodiment, the gas supply unit GS includes a gas source group 40, a valve group 42, and a flow rate controller group 44. The gas source group 40 is connected to the gas supply pipe 38 via the flow rate controller group 44 and the valve group 42. The gas source group 40 includes a plurality of gas sources. The valve group 42 includes a plurality of on-off valves. The flow rate controller group 44 includes a plurality of flow rate controllers. Each of the plurality of flow rate controllers is a mass flow controller or a pressure-controlled flow rate controller. The plurality of gas sources in the gas source group 40 are connected to the gas supply pipe 38 via the corresponding valves in the valve group 42 and the corresponding flow rate controllers in the flow rate controller group 44.

[0042] In the plasma processing apparatus 10, a shield 46 is detachably provided along the inner wall of the chamber body 12. The shield 46 is also provided on the outer periphery of the support part 13. The shield 46 prevents etching by-products from adhering to the chamber body 12. The shield 46 is formed, for example, by coating an aluminum member with a ceramic such as Y2O3.

[0043] A baffle plate 48 is provided between the support 13 and the side wall of the chamber body 12. The baffle plate 48 is made, for example, by coating an aluminum member with a ceramic such as Y2O3. A plurality of through holes are formed in the baffle plate 48. An exhaust port 12e is provided below the baffle plate 48 and at the bottom of the chamber body 12. An exhaust device 50 is connected to the exhaust port 12e via an exhaust pipe 52. The exhaust device 50 has a pressure control valve and a vacuum pump such as a turbomolecular pump.

[0044] The plasma processing apparatus 10 further includes a first high-frequency power supply 62 and a second high-frequency power supply 64. The first high-frequency power supply 62 is a power supply that generates a first high-frequency wave (high-frequency power) for generating plasma. The frequency of the first high-frequency wave is, for example, within a range of 27 MHz to 100 MHz. The first high-frequency power supply 62 is connected to the lower electrode 18 via a matching box 66 and the electrode plate 16. The matching box 66 has a circuit for matching the output impedance of the first high-frequency power supply 62 with the input impedance on the load side (lower electrode 18 side). The first high-frequency power supply 62 may be connected to the upper electrode 30 via the matching box 66.

[0045] The second high frequency power supply 64 is a power supply that generates a second high frequency for attracting ions into the workpiece. The frequency of the second high frequency is lower than the frequency of the first high frequency. The frequency of the second high frequency is, for example, within a range of 400 kHz to 13.56 MHz. The second high frequency power supply 64 is connected to the lower electrode 18 via a matching box 68 and the electrode plate 16. The matching box 68 has a circuit for matching the output impedance of the second high frequency power supply 64 with the input impedance on the load side (lower electrode 18 side).

[0046] The plasma processing apparatus 10 may further include a DC power supply unit 70. The DC power supply unit 70 is connected to the upper electrode 30. The DC power supply unit 70 is capable of generating a negative DC voltage and applying the DC voltage to the upper electrode 30.

[0047] The plasma processing apparatus 10 may further include a control unit Cnt. The control unit Cnt may be a computer including a processor, a storage unit, an input device, a display device, etc. The control unit Cnt controls each unit of the plasma processing apparatus 10. The control unit Cnt allows an operator to input commands, etc., to manage the plasma processing apparatus 10 using the input device. The control unit Cnt also allows the display device to visualize and display the operating status of the plasma processing apparatus 10. Furthermore, the storage unit of the control unit Cnt stores control programs and recipe data for the processor to control various processes executed in the plasma processing apparatus 10. The processor of the control unit Cnt executes the control programs and controls each unit of the plasma processing apparatus 10 according to the recipe data, thereby performing the method described below in the plasma processing apparatus 10.

[0048] [Displacement measurement system overview] The displacement measurement system 1 measures the displacement of an object placed in a chamber of a plasma processing apparatus 10. In the following, the object is assumed to be a wafer placed in the chamber as an example, but the object is not limited to a wafer and may be any part placed in the chamber. As an example, the wafer is made of silicon. Furthermore, as an example, the electromagnetic wave generated by the light source is light.

[0049] The displacement measurement system 1 includes, as an example, a sensor head 80. The displacement measurement system 1 places the sensor head 80 in the internal space 12s and uses light to measure the displacement of the object. FIG. 3 is a diagram schematically illustrating an example of the mounting position of the sensor head. As shown in FIG. 3, the sensor head 80 is provided, for example, at the tip of the transfer device TU2. This allows the sensor head 80 to be placed in the internal space 12s without opening the internal space 12s to the atmosphere. When the object is a wafer W or an edge ring ER, the sensor head 80 is configured to irradiate light downward. When the object is an upper electrode or the like, the sensor head 80 may be configured to irradiate light upward. The sensor head 80 receives light reflected from the object and outputs information about the reflected light to a control device (an example of a control unit) described later.

[0050] 4 is a diagram schematically illustrating an example of a displacement measurement system according to an exemplary embodiment. As shown in FIG. 4, the displacement measurement system 1 measures a distance (displacement D) to a wafer W, which is an object. The displacement measurement system 1 includes a light source 71, a sensor head 80, and a control device 90.

[0051] The light source 71 is, for example, a broadband light source. A broadband light source is a light source that generates light over a wide wavelength range. FIG. 5 is a graph showing an example of the relationship between the power and wavelength of light in a light source. The horizontal axis represents wavelength, and the vertical axis represents power. As shown in FIG. 5, the light source 71 is capable of generating light over a wide range of wavelengths, rather than generating light of only a certain wavelength. A broadband light source generates light in a wavelength range of, for example, 400 nm to 1100 nm. Examples of broadband light sources include an SLD (Super luminescent diode) and an LED (Light-emitting diode).

[0052] 4, the sensor head 80 includes a lens 81, a beam splitter 82, and an image sensor 83. The sensor head 80 includes a case body. The lens 81, the beam splitter 82, and the image sensor 83 are housed in the case body.

[0053] The lens 81 is connected to the light source 71 via an optical fiber 72. Light generated by the light source 71 propagates through the optical fiber 72 and is emitted from the tip of the optical fiber 72 to the lens 81. The lens 81 is configured to converge the light generated by the light source 71. The lens 81 has chromatic aberration. In other words, the lens 81 has a different focal length for each wavelength.

[0054] The light converged by the lens 81 is incident on the beam splitter 82. The beam splitter 82 is configured to irradiate the light converged by the lens 81 onto the wafer W, which is an object. The beam splitter 82 is configured, for example, by combining two right-angle prisms. The beam splitter 82 splits the incident light into two at the prism combining surface and changes the direction of one of the lights. Here, the beam splitter 82 bends the horizontally incident light by 90 degrees at the prism combining surface and emits it downward. The beam splitter 82 receives reflected light (return light) from the wafer W. The beam splitter 82 splits the reflected light from the wafer W into two and transmits one of the lights as is. The beam splitter 82 may include a half mirror that achieves a nearly 1:1 ratio between the intensity of the reflected light and the intensity of the transmitted light.

[0055] The image sensor 83 receives reflected light from the wafer W via the beam splitter 82. For this reason, the image sensor 83 is disposed above the beam splitter 82, with the beam splitter 82 positioned between the image sensor 83 and the wafer W. The image sensor 83 is configured to receive reflected light from an object and acquire the intensity distribution of the reflected light. The intensity distribution is the relationship between the light receiving position (X, Y) and the light intensity. The image sensor 83 can output the intensity distribution of the reflected light as image information. The measurement results of the image sensor 83 are output to the control device 90 via a communication network 84.

[0056] The control device 90 may be a computer equipped with a processor, a storage device such as a memory, a display device, an input / output device, a communication device, etc. A series of operations of the displacement measurement system is realized by control by the control device 90 in accordance with a program stored in the storage device.

[0057] The control device 90 acquires the beam diameter of the reflected light based on the intensity distribution of the reflected light acquired by the image sensor 83. The beam diameter is the diameter of the cross section of the light. The control device 90 acquires the beam diameter from the imaged intensity distribution of the reflected light. Alternatively, the control device 90 may acquire the beam diameter based on the distribution range of the intensity distribution of the reflected light. The relationship between the beam diameter and the displacement D of the wafer W is acquired in advance and stored in the storage device 91. The control device 90 outputs the displacement D of the wafer W based on the beam diameter acquired by the sensor head 80 and the known relationship stored in the storage device 91. The details of the calculation will be described later.

[0058] Next, the difference in the beam diameter received for each wavelength of measurement light will be outlined. Fig. 6 is an enlarged view of only the lens 81, beam splitter 82, and image sensor 83 of the displacement measurement system 1 shown in Fig. 4, and schematically illustrates an example of the optical paths of light of multiple wavelengths. The light source 71 is, for example, a broadband light source, and generates a first light L1 having a first wavelength, a second light L2 having a second wavelength, and a third light L3 having a third wavelength. Because the lens 81 has chromatic aberration, the first light L1, the second light L2, and the third light L3 are converged at different focal lengths. As a result, the light reaches the wafer W via the beam splitter 82, is reflected by the wafer W, returns to the beam splitter 82, passes through the beam splitter 82, and is received by the image sensor 83. At this time, due to the difference in focal length, the beam diameters of the first light L1 (R1), the second light L2 (R2), and the third light L3 (R3) decrease in this order.

[0059] FIG. 7 is an example of an image of intensity distribution acquired by an image sensor. Image G1 is obtained by converting the light intensity detected at each pixel position of the image sensor 83 into pixel values. As shown in FIG. 7, the beam diameter (R1) of the first light L1, the beam diameter (R2) of the second light L2, and the beam diameter (R3) of the third light L3 are detected in an overlapping manner. FIG. 8 is an example of intensity distribution acquired by an image sensor. The horizontal axis represents position, and the vertical axis represents light intensity. As shown in FIG. 8, the waveform has a different beam diameter for each wavelength. In this way, the image sensor 83 can acquire the intensity distribution of reflected light for each wavelength.

[0060] The beam diameter depends on the displacement of the object. FIG. 9 is a graph showing an example of the relationship between the beam diameter and the displacement of the object. The horizontal axis represents the displacement of the object, and the vertical axis represents the beam diameter. The graph shown in FIG. 9 was obtained by measuring the object as a wafer W in advance, for example, during maintenance. As shown in FIG. 9, the beam diameters of the first light L1, the second light L2, and the third light L3 all change depending on the displacement of the wafer W. Therefore, by observing at least two beam diameters, the displacement of the wafer W can be uniquely determined. A method for measuring one beam diameter will be described later. The relationship shown in FIG. 9 is stored in advance in a storage device 91 and referenced by a control device 90.

[0061] [Displacement measurement method] Fig. 10 is a flowchart of a method using the displacement measurement system. As shown in Fig. 10, in the method MT, first, a preparation step (step S10) is performed. In the preparation step, the gate valve 12g is opened, and the transfer device TU2 places the sensor head 80 in the internal space 12s maintained at a predetermined vacuum level.

[0062] Next, an acquisition process (step S12) is performed. In the acquisition process, the light source 71 generates light. The optical fiber 72 propagates the light, and the light is irradiated from the end of the optical fiber 72 onto the lens 81. The lens 81 converges the light and irradiates it onto the beam splitter 82. The beam splitter 82 bends the incident light and irradiates it onto the wafer W. The beam splitter 82 transmits the light reflected from the wafer W. The image sensor 83 receives the light that has transmitted through the beam splitter 82. The image sensor 83 detects the light intensity for each pixel position and acquires the intensity distribution. The control device 90 acquires the size of the beam diameter for each wavelength based on the intensity distribution of the reflected light.

[0063] Next, an outputting step (step S14) is executed. The control device 90 outputs the displacement D of the wafer W based on the beam diameter acquired in step S12 and the relationship shown in Fig. 9 that is pre-stored in the storage device 91. When step S14 is completed, the method MT shown in Fig. 10 is completed.

[0064] [Summary of the embodiment] In the displacement measurement system 1, light generated by the light source 71 is converged by a lens 81 and irradiated onto the wafer W by a beam splitter 82. The light reflected from the wafer W is incident on the beam splitter 82 and then incident on an image sensor 83, where the intensity distribution of the reflected light is acquired. The beam diameter of the reflected light is acquired based on the intensity distribution of the reflected light. The relationship between the beam diameter and the displacement of the wafer W is acquired in advance. The displacement D of the wafer W is output based on the beam diameter acquired by measurement and the known relationship. In this way, the displacement D of the wafer W can be output based on the beam diameter acquired from the intensity distribution of the reflected light acquired by the image sensor 83, eliminating the need to appropriately couple the returned light to an optical fiber. The image sensor 83 can receive the reflected light even if the wafer W is tilted to some extent. Therefore, the displacement measurement system 1 relaxes restrictions on the orientation of the wafer W and can appropriately measure the displacement of the wafer W using light.

[0065] Furthermore, in the principle of conventional optical interferometers, the angular tolerance of the target object (the range of tilt angles at which returning light can be coupled into the fiber) is proportional to the numerical aperture (NA) of the lens used in the sensor head 80. Therefore, a small sensor head has a small numerical aperture, making it difficult to measure displacement accurately enough to evaluate wear and tear. In contrast, the displacement measurement system 1 measures the beam diameter rather than the light intensity itself, making it possible to perform measurements with sufficient accuracy even if the lens numerical aperture (NA) is small and the spot diameter is small. Therefore, the displacement measurement system 1 can perform displacement measurements with a small spot diameter, high angular tolerance, and compact size.

[0066] (Variation) It will be understood that various modifications can be made to the embodiments of the present disclosure without departing from the scope and spirit of the present disclosure. Accordingly, the various embodiments disclosed herein are not intended to be limiting, with the true scope and spirit being indicated by the appended claims.

[0067] For example, the object may be the edge ring ER or the upper electrode 30. The control device 90 may acquire an image of the object for each displacement in advance, match the image acquired during measurement with the image acquired in advance, and determine the displacement of the object based on the matching result.

[0068] The displacement measurement system 1 can also measure the posture (tilt) of an object when the displacement D of the object is known. FIG. 11 shows an example of measuring a tilted wafer. The configuration shown in FIG. 11 is the same as the configuration shown in FIG. 4 except that the wafer W is tilted. As shown in FIG. 11, when the wafer W is tilted, the light receiving position of the image sensor 83 is offset compared to when the wafer W is not tilted (FIG. 4).

[0069] FIG. 12 is an example of an intensity distribution image obtained when measuring a tilted wafer. Image G2 is obtained by converting the light intensity detected at each pixel position of the image sensor 83 into pixel values. As shown in FIG. 12, the beam diameters of the first light L1, second light L2, and third light L3 are detected as overlapping beams. The dashed circle in the figure represents the measurement result of a non-tilted wafer W (FIG. 7). As shown in FIG. 12, when the wafer W is tilted, the light receiving position is offset, and the position of the beam diameter fluctuates. Furthermore, the shape of the beam diameter (circle) is flattened in the direction of movement. In other words, by plotting and acquiring the position (offset amount) and shape of the beam diameter of the reflected light in advance, the control device 90 can calculate the tilt of the wafer W based on the acquired position and shape of the beam diameter.

[0070] The displacement measurement system 1 may be modified to expand the range of allowable tilt of the wafer W. FIG. 13 is a diagram schematically illustrating an example of a displacement measurement system according to a modified example. The configuration illustrated in FIG. 13 is the same as the configuration illustrated in FIG. 11 except that it includes an extended beam splitter 82A and image sensor 83A. The beam splitter 82A is a rectangular parallelepiped and is disposed so that the longitudinal direction of the beam splitter 82A is perpendicular to the direction in which the wafer W and the image sensor 83A face each other. The image sensor 83A is also extended in the same direction as the beam splitter 82A. This allows the displacement measurement system 1A to determine the displacement of the wafer W even if the offset amount increases due to tilt of the wafer W.

[0071] In the configuration shown in FIG. 13, the control device 90 may correct the intensity distribution after measurement to improve the accuracy of the displacement of the object. FIG. 14 is a diagram showing an example of a region where sensitivity decreases. As shown in FIG. 14, depending on the light receiving position of the image sensor 83A, light that does not pass through the prism coupling surface of the beam splitter 82A is received. In the region H surrounded by the dashed line, light passes through the prism coupling surface of the beam splitter 82A, so the sensitivity (intensity) decreases. FIG. 15 is a graph showing an example of the relationship between sensitivity and position. The horizontal axis represents position, and the vertical axis represents sensitivity. As shown in FIG. 15, the sensitivity "B" at the position corresponding to region H is lower than the sensitivity "A" at positions other than region H. The control device 90 performs correction so that the difference between sensitivity "A" and sensitivity "B" is eliminated. The control device 90 may positively correct the sensitivity at the position corresponding to region H, or may negatively correct the sensitivity at positions other than region H.

[0072] The light source 71 is not limited to a broadband light source. FIG. 16 is a diagram schematically illustrating an example of a displacement measurement system according to a modified example. The configuration illustrated in FIG. 16 is identical to the configuration illustrated in FIG. 4 except for the inclusion of a light source 71A. The light source 71A is configured to output light obtained by multiplexing multiple single-wavelength light beams. For example, the light source 71A includes a first light source 711 that emits a first light beam L1 having a first wavelength, a second light source 712 that emits a second light beam L2 having a second wavelength, and a third light source 713 that emits a third light beam L3 having a third wavelength. The multiplexer 714 is connected to the first light source 711, the second light source 712, and the third light source 713 and multiplexes the light beams from the respective light sources. The image sensor 83 is configured to acquire the intensity distribution of the reflected light for each wavelength. Even with this configuration, the displacement measurement system 1B can determine the displacement of the wafer W.

[0073] The displacement measurement system 1B may be configured with a selector switch instead of the multiplexer 714. In this case, the displacement measurement system 1B is configured to be able to output multiple single-wavelength light beams with a time delay. The image sensor 83 is configured to acquire the intensity distribution of the reflected light for each wavelength. Even with this configuration, the displacement measurement system 1B can determine the displacement of the wafer W.

[0074] In the exemplary embodiment described above, the displacement of the wafer W is uniquely determined by observing at least two beam diameters. However, the displacement measurement system 1 does not necessarily need to acquire at least two beam diameters. FIG. 17 is a graph showing an example of the relationship between the beam diameter of a single wavelength and the displacement of an object. The horizontal axis represents the displacement of the object, and the vertical axis represents the beam diameter. In the graph shown in FIG. 17, the solid line represents the beam diameter of the single-wavelength fourth light L4. The beam diameters of the first light L1, second light L2, and third light L3 shown in FIG. 9 are also shown for comparison. As shown in FIG. 17, when only the fourth light L4 is used, even if the beam diameter is determined, there are two candidates: one larger than the focal length P and one smaller than the focal length P, making it impossible to uniquely determine the displacement of the object. Therefore, when using light of a single wavelength, the focal length P must be determined before measurement, and measurement must be performed within a range not exceeding the focal length P or beyond the focal length P. This makes it possible to determine the displacement of the object using light of a single wavelength.

[0075] The present disclosure also includes the following aspects. [Article 1] A light source and a lens configured to converge light generated by the light source; a beam splitter configured to irradiate an object with the light converged by the lens and to receive reflected light from the object; an image sensor configured to receive reflected light from the object via the beam splitter and acquire an intensity distribution of the reflected light; a control unit configured to acquire a beam diameter of the reflected light based on the intensity distribution of the reflected light acquired by the image sensor, and output displacement information of the object based on the acquired beam diameter and a previously acquired relationship between the beam diameter and displacement information of the object; A system for measuring displacement comprising: [Clause 2] the light source is a broadband light source; the lens has chromatic aberration; 10. The system of claim 1, wherein the image sensor is configured to acquire the intensity distribution of the reflected light for each wavelength. [Article 3] the light source is configured to be capable of outputting light obtained by combining a plurality of single-wavelength light beams; the lens has chromatic aberration; 10. The system of claim 1, wherein the image sensor is configured to acquire the intensity distribution of the reflected light for each wavelength. [Article 4] the light source is configured to be able to output a plurality of single wavelength light beams with a time difference; 10. The system of claim 1, wherein the lens has chromatic aberration. [Article 5] The system described in any one of clauses 1 to 4, wherein the control unit is configured to acquire the position and shape of the beam diameter of the reflected light based on the intensity distribution of the reflected light, and calculate the tilt of the object based on the acquired position and shape of the beam diameter. [Article 6] 6. The system of any one of clauses 1 to 5, wherein the beam splitter is a rectangular parallelepiped and is arranged so that the longitudinal direction of the beam splitter is perpendicular to the direction in which the object and the image sensor face each other. [Article 7] 1. A method of using a system for measuring displacement, comprising: The system includes a light source, a lens configured to converge light generated by the light source, a beam splitter configured to irradiate an object with the light converged by the lens and to receive reflected light from the object, and an image sensor configured to receive the reflected light from the object via the beam splitter and acquire an intensity distribution of the reflected light, acquiring a beam diameter of the reflected light based on an intensity distribution of the reflected light acquired by the image sensor; outputting displacement information of the object based on the acquired beam diameter and a previously acquired relationship between the size of the beam diameter and displacement information of the object; A method for measuring displacement, comprising: [Explanation of symbols]

[0076] 1, 1A, 1B... displacement measurement system, 71... light source, 80... sensor head, 81... lens, 82... beam splitter, 83... image sensor, 90... control device (an example of a control unit).

Claims

1. A light source and a lens configured to converge light generated by the light source; a beam splitter configured to irradiate an object with the light converged by the lens and to receive reflected light from the object; an image sensor configured to receive reflected light from the object via the beam splitter and acquire an intensity distribution of the reflected light; a control unit configured to acquire a beam diameter of the reflected light based on the intensity distribution of the reflected light acquired by the image sensor, and output displacement information of the object based on the acquired beam diameter and a previously acquired relationship between the beam diameter and displacement information of the object; A system for measuring displacement comprising:

2. the light source is a broadband light source; the lens has chromatic aberration; The system of claim 1 , wherein the image sensor is configured to acquire an intensity distribution of the reflected light for each wavelength.

3. the light source is configured to be capable of outputting light obtained by combining a plurality of single-wavelength light beams; the lens has chromatic aberration; The system of claim 1 , wherein the image sensor is configured to acquire an intensity distribution of the reflected light for each wavelength.

4. the light source is configured to be able to output a plurality of single wavelength light beams with a time difference; The system of claim 1 , wherein the lens has chromatic aberration.

5. The system according to any one of claims 1 to 4, wherein the control unit is configured to acquire a position and a shape of a beam diameter of the reflected light based on an intensity distribution of the reflected light, and to calculate a tilt of the object based on the acquired position and shape of the beam diameter.

6. The system according to any one of claims 1 to 4, wherein the beam splitter is a rectangular parallelepiped and is arranged so that the longitudinal direction of the beam splitter is perpendicular to the direction in which the object and the image sensor face each other.

7. 1. A method of using a system for measuring displacement, comprising: The system includes a light source, a lens configured to converge light generated by the light source, a beam splitter configured to irradiate an object with the light converged by the lens and to receive reflected light from the object, and an image sensor configured to receive the reflected light from the object via the beam splitter and acquire an intensity distribution of the reflected light, acquiring a beam diameter of the reflected light based on an intensity distribution of the reflected light acquired by the image sensor; outputting displacement information of the object based on the acquired beam diameter and a previously acquired relationship between the size of the beam diameter and displacement information of the object; A method for measuring displacement, comprising:

Images