Plasma processing equipment

Abstract

To provide a plasma processing apparatus that is not affected by a decrease in intensity of light caused by misalignment of optical axes of an irradiating unit and a light receiving unit.SOLUTION: A plasma processing apparatus includes:a processing chamber in which plasma is formed; a sample stage that is disposed inside the processing chamber and allows a wafer 109 to be placed thereon; a light transmissive dielectric window that is disposed above the sample stage, and allows an electric field for forming the plasma to be transmitted therethrough; an irradiating unit 181 that irradiates the wafer 109 with light and a light receiving unit 182 that receives light irradiated from the irradiating unit 181 and reflected from an upper surface of the wafer 109, the irradiating unit and the light receiving unit being arranged above the dielectric window so as to be spaced apart from each other in a first direction along an upper surface of the sample stage; and a control unit and a storage unit. Each of the irradiating unit 181 and the light receiving unit 182 is configured to be movable in the first direction, and the control unit adjusts a position of the irradiating unit 181 or the light receiving unit 182 such that the intensity of the light received by the light receiving unit 182 is equal to or greater than a threshold value stored in the storage unit.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a plasma processing apparatus or plasma processing method for processing a sample on a substrate such as a semiconductor wafer placed in a processing chamber inside a vacuum vessel using plasma generated in the processing chamber, and more particularly to a plasma processing apparatus that detects the amount of etching during processing using light from the surface of the sample. [Background technology]

[0002] In semiconductor wafer manufacturing, dry etching is widely used to remove layers of various materials formed on the surface of the wafer, especially to remove or pattern layers of dielectric materials. In dry etching equipment, a process gas introduced into a processing chamber inside a vacuum vessel is converted into plasma to generate ions or radicals, which then react with the wafer to etch the wafer.

[0003] In the dry etching process of semiconductor wafers, the emission intensity of a specific wavelength in plasma light changes as the etching of the processed material progresses. Therefore, one conventional method for detecting the remaining film thickness in the etching process of semiconductor wafers is to detect the change in the emission intensity of a specific wavelength from the plasma during the dry etching process and, based on this detection result, to detect the etching endpoint at which the processed material is completely removed by etching.

[0004] In addition, after applying a mask material to the wafer, there is a process of etching the silicon substrate to form grooves in the silicon to electrically isolate elements on the wafer. In this case, it is important to etch the silicon substrate to a predetermined depth and then complete the process.

[0005] One method for this is to observe plasma light using optical emission spectroscopy. In this method, as the etching progresses and the depth of the silicon increases, the dispersed light forms an interference waveform, and this interference signal is used to measure the depth.

[0006] Patent Document 1 (JP 2022-58184 A) describes a technique for measuring the remaining film thickness or etching amount of a film to be processed on a wafer. This measurement is performed by receiving interference light formed by reflection of plasma emission from the wafer surface above the processing chamber during processing of a wafer held on the top surface of a sample stage located in a processing chamber inside a vacuum vessel, and comparing the light intensity pattern of a given wavelength obtained from the received interference light with previously acquired pattern data of interference light intensity versus etching amount for multiple wavelengths, with wavelength as a parameter.

[0007] Patent document 2 (International Publication No. 2021 / 124539) describes a configuration of an apparatus for detecting the remaining film thickness or etching amount on the surface of a wafer during etching processing, in which light from an external light source is irradiated onto the surface at an angle from above the processing chamber. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2022-58184 [Patent Document 2] International Publication No. 2021 / 124539 Summary of the Invention [Problem to be solved by the invention]

[0009] The above-mentioned conventional technology has problems due to insufficient consideration of the following point: It is necessary to consider that the optical axes of the light-emitting unit and the light-receiving unit may be misaligned due to the machining accuracy of the components in the plasma processing apparatus and the machining accuracy of the light-emitting unit and the light-receiving unit. This optical axis misalignment causes the problem that the light intensity required for film thickness detection cannot be obtained.

[0010] An object of the present invention is to provide a plasma processing apparatus that is not affected by a decrease in light intensity due to misalignment of the optical axes of an irradiating section and a light receiving section in a technique for detecting a film thickness on a wafer surface.

[0011] Other objects and novel features will become apparent from the description of this specification and the accompanying drawings. [Means for solving the problem]

[0012] A brief summary of a representative embodiment of the present invention will be given below.

[0013] In one embodiment, a plasma processing apparatus includes a processing chamber disposed within a vacuum vessel in which plasma is generated, a sample stage disposed within the processing chamber and capable of supporting a wafer to be processed by the plasma, a dielectric window member constituting the vacuum vessel and disposed above the sample stage facing the upper surface of the sample stage, the dielectric window member being made of a light-transmitting material and allowing an electric field for generating the plasma to pass through, an irradiator and a light-receiving unit disposed above the window member and spaced apart from each other in a first direction along the upper surface of the sample stage, a controller, and a memory unit connected to the controller. The irradiator irradiates light onto the wafer, and the light-receiving unit receives light irradiated from the irradiator and reflected by the upper surface of the wafer, each of the irradiator and the light-receiving unit being movable in the first direction, and the controller adjusts the position of the irradiator or the light-receiving unit so that the intensity of the light received by the light-receiving unit is equal to or greater than a threshold value stored in the memory unit. [Effects of the Invention]

[0014] The effects obtained by the representative inventions disclosed in this application will be briefly explained as follows.

[0015] According to the present invention, it is possible to provide a plasma processing apparatus that is not affected by a decrease in light intensity due to misalignment of the optical axes of the irradiating section and the light receiving section. [Brief explanation of the drawings]

[0016] [Figure 1] 2 is a cross-sectional view schematically showing the configuration of an irradiation unit, a light receiving unit, and respective position adjustment mechanisms of the plasma processing apparatus according to the embodiment; FIG. [Figure 2] 2 is a cross-sectional view schematically showing the configuration of an irradiation unit and a light receiving unit of the plasma processing apparatus according to the embodiment; FIG. [Figure 3] 1 is a cross-sectional view schematically illustrating a configuration of a position adjustment mechanism for an irradiation unit and a light receiving unit of a plasma processing apparatus according to an embodiment. [Figure 4] 1 is a side view schematically illustrating a configuration of a position adjustment mechanism for an irradiation unit and a light receiving unit of a plasma processing apparatus according to an embodiment. [Figure 5] 1 is a diagram schematically showing a film structure to be processed on the upper surface of a wafer by a plasma processing apparatus according to an embodiment; [Figure 6] 1 is a diagram schematically showing a film structure to be processed on the upper surface of a wafer by a plasma processing apparatus according to an embodiment; [Figure 7] 10 is a graph showing the relationship between the amount of optical axis deviation and the intensity of light reflected on the surface of the wafer. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In all drawings for explaining the embodiments, components having the same functions are designated by the same reference numerals, and repeated explanations thereof will be omitted. Furthermore, in the following embodiments, explanations of identical or similar parts will not be repeated unless specifically required. Furthermore, in the drawings for explaining the embodiments, hatching may be used even in plan views or perspective views to make the configuration easier to understand. Furthermore, in the drawings for explaining the embodiments, hatching may be omitted in cross-sectional views to make the configuration easier to understand.

[0018] (Embodiment) Hereinafter, an embodiment of the present invention will be described with reference to Fig. 1 to Fig. 6. Fig. 1 is a cross-sectional view showing a schematic outline of the configuration of a plasma processing apparatus according to an embodiment of the present invention. Fig. 1 shows a plasma processing apparatus that uses a microwave electric field as an electric field for forming plasma, generates ECR (Electron Cyclotron Resonance) between the microwave electric field and magnetic field to form plasma, and uses the plasma to etch a substrate-like sample such as a semiconductor wafer.

[0019] A plasma processing apparatus (plasma etching apparatus) 100 shown in FIG. 1 will be described. The plasma processing apparatus 100 has a vacuum vessel 101 equipped with a processing chamber 104 inside which plasma is generated. The vacuum vessel 101 has a cylindrical shape, and the top of the cylindrical vessel 101 is open. A dielectric window 103 (made of, for example, quartz) for introducing microwaves is disposed at the top as a cover member, and the inside of the vacuum vessel 101 forms a processing chamber 104 in which the inside and outside are airtightly separated. The dielectric window 103 forms part of the vacuum vessel 101 and is a dielectric window member made of a light-transmitting material that allows the electric field for generating plasma to pass through.

[0020] A vacuum exhaust port 110 is disposed at the bottom of the vacuum vessel 101, and is connected to a vacuum exhaust device (not shown) disposed below the vacuum vessel 101 and connected to the vacuum vessel 101. A shower plate 102, which forms the ceiling surface of a processing chamber 104, is provided below the lower surface of a dielectric window 103 that forms the upper cover member of the vacuum vessel 101. The shower plate 102 has a plurality of gas inlet holes 102a disposed in the center, and etching process gas is introduced into the processing chamber 104 through these gas inlet holes 102a. The shower plate 102 is a circular plate made of a dielectric material such as quartz.

[0021] An electric field and magnetic field generating unit 160 is disposed above and outside the vacuum vessel 101, generating an electric field and a magnetic field for generating the plasma 116. The electric field and magnetic field generating unit 160 is provided in the plasma processing apparatus 100 and includes the following components. The electric field and magnetic field generating unit 160 includes a waveguide 105 disposed above the dielectric window 103, which supplies a high-frequency electric field of a predetermined frequency for generating the plasma 116 into the processing chamber 104. The electric field is transmitted inside the waveguide 105 toward the upper surface of the dielectric window 103. The electric field transmitted inside the waveguide 105 is generated by oscillation in an electric field generating power supply 106. The electric field and magnetic field generating unit 160 includes the waveguide 105 and the electric field generating power supply 106. The frequency of the electric field is not particularly limited, but microwaves of 2.45 GHz are used in this embodiment.

[0022] The plasma processing apparatus 100 includes a control unit 1 disposed outside a vacuum chamber 101. The control unit 1 is connected to an electric field generating power supply 106, a magnetic field generating coil 107, a high frequency power supply 124, a high frequency filter 125, a DC power supply 126, a high frequency power supply 127, a load matching box 128, a matching box 129, and a load impedance variable box 130. A memory unit 2 is connected to the control unit 1.

[0023] Furthermore, magnetic field generating coils 107 for generating a magnetic field are disposed above the dielectric window 103, on the outer sidewall of the vacuum vessel 101 constituting the cylindrical portion of the processing chamber 104, and on the outer periphery of the lower end of the waveguide 105, surrounding these. The magnetic field generating coils 107 are solenoid coils disposed on the outer periphery of the vacuum vessel 101 to surround the processing chamber 104 and the waveguide 105, respectively. The generation of the magnetic field by the magnetic field generating coils 107 is controlled by the control unit 1. An electric field in the microwave band generated by the electric field generating power supply 106 propagates through the inside of the waveguide 105, passes through the dielectric window 103 and the shower plate 102, and is supplied to the processing chamber 104 from above. Furthermore, ECR is generated by the magnetic field generating coils 107 interacting with the magnetic field supplied into the processing chamber 104. Then, atoms or molecules of the processing gas introduced into the processing chamber 104 through the gas introduction holes 102a of the shower plate 102 are excited and dissociated, thereby generating high-density plasma 116 in the processing chamber 104. That is, the plasma 116 is generated by the interaction between the electric field and the magnetic field from the magnetic field generating coil 107.

[0024] Furthermore, a wafer-mounting electrode (first electrode) 120 constituting a sample stage is provided at the bottom of the processing chamber 104, below the space where the plasma 116 is generated. The wafer-mounting electrode 120 has a mounting surface 120a on which a wafer (semiconductor wafer) 109, which is a sample (object to be processed), is mounted. The dielectric window 103 is disposed above the sample stage, facing the upper surface (mounting surface 120a) of the sample stage. The mounting surface 120a, which is the upper surface of the sample stage, is along a horizontal plane, and when the wafer 109 is mounted on the sample stage, the upper surface of the wafer 109 also follows the horizontal plane.

[0025] Furthermore, a high-frequency filter 125 is disposed outside the vacuum vessel 101 and is connected to the conductive film 111. A high-frequency power supply (first high-frequency power supply) 124 and a matching box 129 are disposed closer to the electrostatic attraction electrode (conductive film 111) than the high-frequency filter 125. The high-frequency power supply 124 and the matching box 129 are connected to an electrode substrate 108 made of a conductive material and having a circular or cylindrical shape, which is disposed inside the wafer mounting electrode 120. The high-frequency power supply 124 is electrically connected to the ground 112. High-frequency power (first high-frequency power) of a predetermined frequency is supplied to the electrode substrate 108 via the matching box 129 from the high-frequency power supply 124, and a bias potential is formed above the wafer 109, which is attracted to and held on the upper surface of the wafer mounting electrode 120, during processing of the wafer 109. In other words, the sample stage has a wafer-supporting electrode (first electrode) 120 to which high-frequency power (first high-frequency power) is supplied from a high-frequency power supply 124 while the plasma 116 is being generated.

[0026] The control unit 1 controls the DC power applied to the conductive film 111 from the DC power supply 126. The control unit 1 also controls the high-frequency power supply 124 and the matching box 129 to supply high-frequency power of a predetermined frequency to the electrode substrate 108. At this time, high-voltage high-frequency noise is generated, and this noise may leak into the electrical circuits of peripheral devices and cause damage to the power supply. Therefore, the control unit 1 controls the high-frequency filter 125 to remove the high-frequency noise and protect the peripheral devices.

[0027] Inside the electrode base material 108, in order to remove the transferred heat and cool the wafer mounting electrode 120, multiple coolant flow paths 152 are arranged spirally or concentrically around the central axis in the vertical direction of the electrode base material 108 or the wafer mounting electrode 120. A cooling coolant for cooling the electrode base material 108 flows through these coolant flow paths 152.

[0028] In the plasma processing apparatus 100, an unprocessed wafer 109 is placed on the tip of an arm of a wafer transfer robot disposed in a vacuum transfer chamber, which is a separate vacuum chamber connected to the side wall of the vacuum chamber 101 and whose pressure has been reduced to the same level as that of a processing chamber 104 inside the vacuum transfer chamber. A gate, which is a passage connecting the vacuum transfer chamber and the processing chamber 104, is opened by operating a valve disposed in the vacuum transfer chamber, and the unprocessed wafer 109 placed on the tip of the arm of the robot is transferred into the processing chamber 104. The wafer 109 is then transferred to above a mounting surface 120a of a wafer mounting electrode 120 in the processing chamber 104. The wafer 109 is then transferred onto the lift pins by vertical movement of the lift pins, and is then placed on the mounting surface. The wafer is then attracted to and held on the mounting surface 120a of the wafer mounting electrode 120 by electrostatic force generated by DC power applied from a DC power supply 126.

[0029] In this state, the flow rate or speed of the etching gas is adjusted by a mass flow controller (not shown) and introduced into the space between the dielectric window 103 and the quartz shower plate 102. After diffusing in this space, the gas is introduced into the processing chamber 104 through the gas inlet holes 102a of the shower plate 102. Thereafter, the gas and particles in the processing chamber 104 are exhausted through the vacuum exhaust port 110 by operation of the vacuum exhaust device. Depending on the balance between the amount of gas supplied from the gas inlet holes 102a of the shower plate 102 and the amount of gas exhausted from the vacuum exhaust port 110, the pressure inside the processing chamber 104 is adjusted to a predetermined value within a range suitable for processing the wafer 109.

[0030] Furthermore, while the wafer 109 is being held by suction, a heat-conductive gas such as He (helium) is supplied from an opening (not shown) on the top surface of the dielectric film 140 to the gap between the wafer 109 and the top surface of the dielectric film 140, which is the mounting surface 120a of the wafer mounting electrode 120, thereby promoting heat transfer between the wafer 109 and the wafer mounting electrode 120. A coolant adjusted to a predetermined temperature range circulates through a coolant flow path 152 disposed in the electrode base material 108 of the wafer mounting electrode 120, thereby adjusting the temperature of the wafer mounting electrode 120 or the electrode base material 108 before the wafer 109 is mounted thereon. Therefore, by heat transfer between the wafer mounting electrode 120 or the electrode base material 108, which have large heat capacities, the temperature of the wafer 109 is adjusted to be close to these temperatures before processing, and heat is transferred from the wafer 109 to adjust the temperature of the wafer 109 even after processing has begun.

[0031] In this state, a microwave electric field and magnetic field are supplied into the processing chamber 104, generating plasma 116 using the gas. Once the plasma 116 is formed, a radio frequency (RF) bias power is supplied to the electrode substrate 108 from the high frequency power supply 124. As a result, a bias potential is formed above the upper surface of the wafer 109, and charged particles such as ions in the plasma 116 are attracted to the upper surface of the wafer 109 in response to the potential difference between the bias potential and the potential of the plasma 116. The charged particles then collide with a mask pre-placed on the upper surface of the wafer 109 and the surface of the target film layer of a film structure including the target film layer, thereby performing an etching process. During the etching process, the processing gas introduced into the processing chamber 104 and particles of reaction products generated during the process are exhausted from the vacuum exhaust port 110.

[0032] In the plasma processing apparatus 100 of this embodiment, during plasma processing, a second high-frequency power is supplied from a high-frequency power source (second high-frequency power source) 127 to a conductor ring (second electrode) 131 arranged on the upper outer periphery of the sample stage via a power supply connector 161 (described later) that is provided on the sample stage and has an elastic conductive member.

[0033] In the wafer-mounting electrode 120 of this embodiment, an AC high voltage generated by a radio-frequency power supply (second radio-frequency power supply) 127 is supplied to a conductor ring (second electrode) 131 made of a conductive material and disposed within the susceptor ring 113 via a load matching box 128 and a load impedance variable box 130. This supply of radio-frequency power is performed by the control unit 1 controlling the radio-frequency power supply 127, the load matching box 128, and the load impedance variable box 130. With this configuration, the load impedance variable box 130, which is adjusted to a suitable impedance value, is combined with a relatively high impedance portion disposed above the susceptor ring 113 to relatively reduce the impedance value for radio-frequency power from the radio-frequency power supply 127 through the electrode base material 108 to the outer periphery of the wafer 109. This allows radio-frequency power to be effectively supplied to the outer periphery and outer periphery of the wafer 109, reducing the concentration of the electric field at the outer periphery or outer periphery, and attracting charged particles such as ions in the plasma to the upper surface of the wafer 109 in a desired direction. High frequency power supply 127 is electrically connected to ground 112. The frequency of high frequency power supply 127 in this embodiment is preferably set to the same value as that of high frequency power supply 124 or a constant multiple thereof.

[0034] Discharge chamber 121 above dielectric window 103 is surrounded by a cylindrical member, and this cylindrical member has a top plate 210 that covers the top. The lower end of waveguide 105 is connected to the center of top plate 210, and this cylindrical member and top plate 210 have a diameter larger than that of waveguide 105. Top plate 210 is disposed above dielectric window 103 with discharge chamber 121 between them, and covers the top surface of dielectric window 103. An electric field that has propagated through waveguide 105 spreads within discharge chamber 121, which is the interior of this cylindrical member.

[0035] The plasma processing apparatus 100 is provided with a configuration for detecting the film thickness on a wafer above a top plate 210. An irradiation unit (irradiator, light emitter) 181 that irradiates light from the outside onto the surface of a wafer 109 placed on the upper surface (mounting surface 120a) of a sample stage in the processing chamber 104 from above the discharge chamber 121, and a light receiving unit (light receiver) 182 that receives light from the surface of the wafer 109 and transmits it to a spectroscope 188 are attached to the top surface of the top plate 210. The plasma processing apparatus 100 is provided with the irradiation unit 181 and the light receiving unit 182 above the top plate 210. The irradiation unit 181 and the light receiving unit 182 are provided with adjustment mechanisms 183 and 184 that adjust their respective installation positions in the direction of the irradiation optical axis. The adjustment mechanism 183 is located between the top plate 210 and the irradiation unit 181, and the adjustment mechanism 184 is located between the top plate 210 and the light receiving unit 182.

[0036] Irradiation unit 181 is connected to external light source 187 via optical fiber 185, and irradiates light from external light source 187 transmitted through optical fiber 185 onto discharge chamber 121 through light-passing hole 212 (see FIG. 2) in top plate 210. Irradiation light propagated through optical fiber 185 from external light source 187 is incident downward from irradiation unit 181, passes sequentially through discharge chamber 121, dielectric window 103, shower plate 102, and the interior of processing chamber 104 below, and is irradiated obliquely onto center X (see FIG. 2) of the upper surface of wafer 109. The light irradiated onto the upper surface of wafer 109 is reflected obliquely off the upper surface of wafer 109 and received by light-receiving unit 182.

[0037] Fig. 5 is a diagram schematically showing the film structure on the surface of wafer 109 including mask layer 405 and processing target layer 406 before plasma processing in plasma processing apparatus 100 of Fig. 1. Fig. 6 is a diagram schematically showing the principle of light reflection on the upper surface of the processing target during etching processing of processing target layer 406 on the surface of wafer 109.

[0038] As shown in FIG. 5, when irradiation light 190 is irradiated onto wafer 109 during etching, reflected light 402 from the surface of mask layer 405, reflected light 403 from the surface of layer 406 to be processed, which is the interface between mask layer 405 and layer 406 to be processed, and reflected light 404 from the surface of layer 406 to be processed are generated. Optical path differences occur between the reflected lights 402, 403, and 404, resulting in the formation of interference light. As shown in FIG. 6, the thickness of layer 406 to be processed decreases as etching progresses, causing the optical path differences between the reflected lights to change, resulting in interference phenomena with different periods for each wavelength. Of these multi-wavelength interference light 191 (see FIG. 1), the multi-wavelength interference light 191 received by light-receiving unit 182 is transmitted to spectrometer 188 via optical fiber 186. The light transmitted to the spectrometer 188 is split into light of a predetermined number of wavelengths and detected by the spectrometer 188, and the intensity of the light transmitted at each wavelength is detected by a detector 189 connected to the spectrometer 188. The film thickness of the processing target layer 406 is detected by comparing the detected light intensity at each wavelength with the film thickness obtained in advance and the light intensity at each reference wavelength.

[0039] Next, details of the configuration for detecting the film thickness on the surface of wafer 109 will be described with reference to Figures 2, 3, and 4. Figure 2 is a cross-sectional view schematically showing the configuration of irradiation unit 181 and light receiving unit 182 of the plasma processing apparatus according to the embodiment shown in Figure 1. Dielectric window 103 is not shown in Figure 2.

[0040] 2, in order to detect the film thickness of wafer 109, an irradiation unit 181 equipped with an adjustment mechanism 183 and a light receiving unit 182 equipped with an adjustment mechanism 184 are installed at a predetermined radial position from the center of top plate 210. For example, in a plan view, adjustment mechanism 183 and irradiation unit 181 are installed on the opposite side of the center of top plate 210 from adjustment mechanism 184 and light receiving unit 182. The irradiation unit 181 and light receiving unit 182 are installed above dielectric window 103 and spaced apart from each other in the horizontal direction. Adjustment mechanism 183 is installed above top plate 210, and irradiation unit 181 is installed above adjustment mechanism 183. Furthermore, adjustment mechanism 184 is installed above top plate 210, and light receiving unit 182 is installed above adjustment mechanism 183.

[0041] The installation surfaces of the adjustment mechanisms 183 and 184 are flush with each other, and the heights of the ground surface of the irradiation unit 181 and the installation surface of the light-receiving unit 182 from the top surface of the wafer 109 are the same. That is, the adjustment mechanisms 183 and 184 are disposed at the same height in the up-down direction perpendicular to the horizontal direction. The up-down direction is the direction perpendicular to the top surface (mounting surface 120a) of the sample stage. The direction V in which the positions of the irradiation unit 181 and the light-receiving unit 182 are adjusted by the adjustment mechanisms 183 and 184 is the radial direction from the center of the wafer 109, and the irradiation unit 181 and the light-receiving unit 182 are movable on the same axis. That is, the movement directions V of the adjustment mechanisms 183 and 184 overlap each other when viewed from any direction.

[0042] The irradiation unit 181 is composed of a block 201 having a light passing hole 203 and a light passing hole 216, and a mirror 208 that bends light passing through the light passing hole 203 toward the light passing hole 216. The collimating lens unit 205 is connected to the tip of the optical fiber 185, and is installed in the irradiation unit 181 while being inserted into the light passing hole 203 of the block 201. The light receiving unit 182 is composed of a block 202 having a light passing hole 204 and a light passing hole 217, and a mirror 209 that bends light passing through the light passing hole 217 toward the light passing hole 204. The collimating lens unit 206 is connected to the tip of the optical fiber 186, and is installed in the light receiving unit 182 while being inserted into the light passing hole 204 of the block 202.

[0043] Collimating lens unit 205 includes a cylindrical or disk-shaped flange portion 220 and a collimating lens 219 composed of a disk-shaped convex or concave lens attached to the tip of flange portion 220 with its axis aligned with a through-hole located in the center of flange portion 220. Collimating lens unit 206 also includes a cylindrical or disk-shaped flange portion 222 and a collimating lens 221 composed of a disk-shaped convex or concave lens attached to the tip of flange portion 222 with its axis aligned with a through-hole located in the center of flange portion 222. Adjustment mechanism 183 is located directly below irradiation unit 181 and has a light-passing hole (through-hole) 211 that passes through adjustment mechanism 183 in the vertical direction, and adjustment mechanism 184 is located directly below light-receiving unit 182 and has a light-passing hole (through-hole) 214 that passes through adjustment mechanism 184 in the vertical direction. The top plate 210 has a light-passing hole (through hole) 212 located below the irradiation unit 181 and penetrating the top plate 210 in the vertical direction, and a light-passing hole (through hole) 213 located below the light-receiving unit 182 and penetrating the top plate 210 in the vertical direction.

[0044] Light from an external light source 187 is irradiated onto the wafer 109 from the irradiation unit 181 via optical fiber 185, irradiation light 190 is reflected on the upper surface of the wafer 109, and the reflected interference light 191 is received by the light receiving unit 182 and transmitted to the spectrometer 188 via optical fiber 186. The light from the optical fiber 185 is converted to a predetermined light diameter by the collimating lens unit 205, passes through the light passing hole 203 of the irradiation unit 181 parallel to the axis of the light passing hole 203, is reflected by the mirror 208, passes through the light passing hole 216, and is irradiated at an angle a with respect to the central axis Y of the wafer 109. The central axis Y of the wafer 109 is aligned in the vertical direction.

[0045] Irradiation light 190 emitted from irradiation unit 181 passes through light passing holes 211 and 212, discharge chamber 121, dielectric window 103, shower plate 102, and further through the interior of processing chamber 104 below, before being irradiated onto wafer 109. Irradiation light 190 irradiated onto wafer 109 is reflected at center X of the top surface of wafer 109 at angle a with respect to central axis Y of wafer 109. In this way, the angle of incidence of irradiation light 190 with respect to the top surface of wafer 109 and the angle of reflection of interference light 191 from the top surface of wafer 109 are the same. The reflected interference light 191 passes through the interior of processing chamber 104 below, shower plate 102, dielectric window 103, discharge chamber 121, and light passing holes 213 and 214, in that order, before being received by light receiving unit 182. The light received by the light receiving unit 182 passes through the light passage hole 217, is reflected by the mirror 209, passes through the light passage hole 204, is concentrated by the collimating lens unit 206, and is then transmitted to the spectrometer 188 via the optical fiber 186.

[0046] 3 and 4 show the configuration of the adjustment structure. Each of adjustment mechanisms 183 and 184 is composed of a fixed stage 303, a movable stage 302, a stepping motor 301, a ball screw 305, a ball screw nut 304, a bearing 306, and a guide rail 307. Stepping motor 301, bearing 306, and guide rail 307 are installed on fixed stage 303. A rod-shaped ball screw 305 that passes through ball screw nut 304 is installed on the rotation axis of stepping motor 301. Stepping motor 301 is installed at an end of fixed stage 303. The tip of ball screw 305 is supported by bearing 306, which is installed at one of both ends of fixed stage 303, opposite stepping motor 301. Guide rail 307 shown in FIG. 4 is installed so that the extension direction of the groove (not shown) of the guide rail is the same as the rotation axis of ball screw 305. The movable stage 302 slides along the extending direction of the groove of the guide rail.

[0047] The positions of the irradiation unit 181 and the light receiving unit 182 can be moved in direction V by rotating stepping motors 301 of adjustment mechanisms 183 and 184 and sliding movable stage 302 along guide rails 307 using ball screws 305 and ball screw nuts 304. In other words, the irradiation unit 181 and the light receiving unit 182 move along the axis of ball screw 305, whose axis is arranged parallel to direction V. The irradiation unit 181 and the light receiving unit 182 are each fitted with ball screw 305 and connected to ball screw nut (slider) 304, and move along direction V as ball screw nut 304 moves along that axis. In other words, each of the irradiating unit 181 and the light receiving unit 182 is coupled to a ball screw nut 304 that is fitted into a spiral groove provided on the surface of the ball screw 305 and moves along the axis as the ball screw 305 rotates about the axis, and moves in direction V as the ball screw nut 304 moves along the axis of the ball screw 305. Direction V is a direction along a horizontal plane.

[0048] The control unit 1 is connected to the stepping motor 301. In other words, the control unit 1 is connected to the adjustment mechanisms 183 and 184. The control unit 1 controls the rotation of the stepping motor 301, thereby controlling the movement and position of the irradiation unit 181 and the light receiving unit 182. The adjustment mechanisms 183 and 184 are drive units that move the irradiation unit 181 and the light receiving unit 182, respectively.

[0049] Figure 7 shows the relationship between the amount of optical axis misalignment and the intensity of light reflected from the wafer surface. The horizontal axis of the graph shown in Figure 7 represents the amount of optical axis misalignment in direction V, and the vertical axis represents the light intensity. As the amount of optical axis misalignment between the irradiating unit 181 and the light receiving unit 182 increases, the intensity of light reflected from wafer 109 and received by light receiving unit 182 decreases. The method of adjusting and determining the positions of irradiating unit 181 and light receiving unit 182 to obtain light intensity Z required for film thickness detection on the surface of wafer 109 is as follows.

[0050] Light is irradiated onto the surface of wafer 109 before etching processing, and the intensity of the light reflected by wafer 109 is compared with the light intensity Z required for film thickness detection. If the optical axis misalignment is large and the intensity of the light reflected by wafer 109 becomes value S, which is below the light intensity Z that is the specified value required for film thickness detection, the installation position of irradiating unit 181 or light receiving unit 182 in direction V is adjusted using adjustment mechanism 183 or adjustment mechanism 184 so that the intensity of the reflected light becomes value L, which is a value that exceeds the light intensity Z required for film thickness detection.

[0051] That is, the memory unit 2 stores the light intensity Z as the lower limit (threshold) of the light intensity required for film thickness detection (the intensity of light received by the light receiving unit 182). The control unit 1 adjusts the movement of the irradiation unit 181 or the light receiving unit 182 so that the intensity of the light received by the light receiving unit 182 is within a predetermined allowable range, that is, equal to or greater than the threshold.

[0052] <Effects of this embodiment> In a plasma processing apparatus, it is necessary to consider that misalignment of the optical axes of the light-emitting unit and the light-receiving unit may occur due to the processing accuracy of the components and the processing accuracy of the light-emitting unit and the light-receiving unit. When this misalignment of the optical axis occurs, the light intensity decreases, resulting in a problem that the light intensity required for film thickness detection cannot be obtained. In response to this problem, in this embodiment, the control unit 1 adjusts the movement of the irradiation unit 181 or the light-receiving unit 182 so that the intensity of the light received by the light-receiving unit 182 is equal to or greater than a threshold. This makes it possible to provide a plasma processing apparatus 100 that is not affected by the decrease in light intensity due to misalignment of the optical axes of the irradiation unit 181 and the light-receiving unit 182 in the technology for detecting film thickness on the surface of a wafer.

[0053] The invention made by the present inventors has been specifically described above based on the embodiments, but it goes without saying that the present invention is not limited to the above-described embodiments and can be modified in various ways without departing from the spirit of the invention. [Explanation of symbols]

[0054] 1. Control section 2 Storage section 100 Plasma processing device 101 Vacuum container 103 Dielectric window 104 Processing Room 105 Waveguide 109 wafers 116 Plasma 120a Placement surface 121 Discharge chamber 181 Irradiation unit 182 Light receiving part 183, 184 Adjustment mechanism 185, 186 Optical fiber 187 External light source 190 Irradiation Light 191 Interferometric Light 203, 204, 211~214, 216, 217 Light holes 210 Top Plate

Claims

1. a processing chamber disposed within the vacuum vessel in which plasma is formed; a sample stage disposed within the processing chamber, on the upper surface of which a wafer to be processed by the plasma can be placed; a dielectric window member that constitutes the vacuum vessel and is disposed above the sample stage so as to face an upper surface of the sample stage, the dielectric window member being made of a light-transmitting material and through which an electric field for generating the plasma can pass; an irradiation unit and a light receiving unit disposed above the window member and spaced apart from each other in a first direction along an upper surface of the sample stage; A control unit; a storage unit connected to the control unit; Equipped with the irradiation unit irradiates the wafer with light, the light receiving unit receives light emitted from the irradiation unit and reflected by the upper surface of the wafer; each of the irradiating unit and the light receiving unit is configured to be movable in the first direction; The control unit adjusts the position of the irradiation unit or the light receiving unit so that the intensity of the light received by the light receiving unit is equal to or greater than a threshold value stored in the memory unit.

2. 2. The plasma processing apparatus according to claim 1, The plasma processing apparatus, wherein the irradiation unit and the light receiving unit are disposed at the same height in a vertical direction perpendicular to an upper surface of the sample stage, and are each movable on the same axis.

3. 3. The plasma processing apparatus according to claim 2, a waveguide disposed above the window member, through which the electric field propagates toward an upper surface of the window member; a top plate connected to a lower end of the waveguide, having a diameter larger than that of the waveguide, and covering an upper surface of the window member at a distance; and the light-emitting unit and the light-receiving unit are respectively disposed above a pair of through-holes that pass through the top plate in the up-down direction, The light irradiated from the irradiation unit is irradiated onto the wafer through one of the pair of through holes and the window member, and the light reflected from the surface of the wafer is received by the light receiving unit through the window member and the other of the pair of through holes.

4. 3. The plasma processing apparatus according to claim 1, The plasma processing apparatus is configured such that the irradiation unit and the light receiving unit move along an axis of a rod-shaped member whose axis is arranged parallel to the first direction.

5. 5. The plasma processing apparatus according to claim 4, The plasma processing apparatus, wherein the irradiation unit or the light receiving unit is connected to a slider fitted with the rod-shaped member and moves in the first direction as the slider moves along the axis.

6. 5. The plasma processing apparatus according to claim 4, a nut that is fitted into a spiral groove formed on the surface of the rod-shaped member and moves in the first direction as the rod-shaped member rotates around its axis; The plasma processing apparatus, wherein the irradiation unit or the light receiving unit is connected to the nut and moves in the first direction as the nut moves along the axis.

7. 3. The plasma processing apparatus according to claim 1, the irradiating unit or the light receiving unit is connected to a fiber through which the light from a light source propagates, the light propagating through the fiber is obliquely irradiated onto the upper surface of the wafer from the irradiation unit; The light reflected obliquely from the upper surface of the wafer is received by the light receiving unit.

8. 3. The plasma processing apparatus according to claim 1, a solenoid coil disposed on the outer periphery of the vacuum vessel so as to surround the processing chamber; The plasma processing apparatus is configured such that the plasma is generated by interaction between the electric field having a frequency in the microwave band and the magnetic field from the solenoid coil.

9. 3. The plasma processing apparatus according to claim 1, The control unit is connected to a driving unit that moves each of the irradiation unit and the light receiving unit in the first direction.

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