Plasma processing apparatus

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 by using plasma formed in the processing chamber, and more particularly to a plasma processing apparatus for detecting the amount of etching during processing by using light from the surface of the sample. [Background technology]

[0002] In the manufacture of semiconductor wafers, dry etching is widely used to remove layers of various materials formed on the surface of the wafer, especially to remove layers of dielectric materials or to form patterns. In a dry etching apparatus for performing dry etching, a process gas introduced into a process chamber inside a vacuum vessel is turned into plasma to produce ions or radicals, and the ions or radicals are reacted with the wafer to etch the wafer.

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

[0004] In addition, after applying a mask material onto the wafer, for example, a process may be performed in which the silicon substrate is etched to form grooves in the silicon for electrically isolating elements on the wafer. In this case, it is important to etch the silicon substrate to a specified depth and then terminate the process.

[0005] One method for this is to observe the 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 technology 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 on the surface of the wafer during processing of a wafer held on the upper surface of a sample stage arranged in a processing chamber inside a vacuum vessel at the top of the processing chamber, and comparing the pattern of light intensity of an arbitrary wavelength obtained from the received interference light with data of a pattern of the intensity of interference light for the etching amount obtained in advance for multiple wavelengths, with the wavelength as a parameter.

[0007] Patent document 2 (WO 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] 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] In the above-mentioned conventional technology, problems arise because the following points were not sufficiently considered. That is, it is necessary to take into consideration that the optical axes of the light emitting part and the light receiving part may be misaligned due to the processing accuracy of the components in the plasma processing apparatus and the processing accuracy of the light emitting part and the light receiving part. The occurrence of this optical axis misalignment causes a problem in which 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 surface of a wafer.

[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 outline of a representative embodiment of the present invention will be described below.

[0013] A plasma processing apparatus according to one embodiment includes a processing chamber disposed inside a vacuum vessel in which plasma is generated, a sample stage disposed inside the processing chamber and capable of placing a wafer to be processed by the plasma on an upper surface thereof, a dielectric window member disposed above the sample stage and facing the upper surface of the sample stage, through which an electric field for generating the plasma can pass and made of a material having translucency, an irradiation unit and a light receiving unit disposed above the window member at a distance from each other in a first direction along the upper surface of the sample stage, a control unit, and a storage unit connected to the control unit. Here, the irradiation unit irradiates light onto the wafer, the light receiving unit receives light irradiated from the irradiation unit and reflected by the upper surface of the wafer, each of the irradiation unit and the light receiving unit is configured to be movable in the first direction, and 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 storage unit. Effect of the Invention

[0014] The effects obtained by the representative inventions among those disclosed in this application will be briefly described 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 an irradiating section and a light receiving section. [Brief description of the drawings]

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

[0017] Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings. In all the drawings for explaining the embodiments, the same reference numerals are used for the members having the same functions, and the repeated explanations are omitted. In addition, in the following embodiments, the explanations of the same or similar parts are not repeated in principle, except when particularly necessary. In addition, in the drawings for explaining the embodiments, hatching may be used even in plan views or perspective views, etc., in order to make the configuration easier to understand. Furthermore, in the drawings for explaining the embodiments, hatching may be omitted in cross-sectional views in order 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 which uses a microwave electric field as an electric field for forming plasma, generates ECR (Electron Cyclotron Resonance) between the electric field and magnetic field of the microwave 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 with a processing chamber 104 therein where plasma is generated. The vacuum vessel 101 has a cylindrical shape, and the upper part of the cylindrical shape is open. A dielectric window 103 (made of, for example, quartz) for introducing microwaves is arranged at the upper part as a cover member, and the inside of the vacuum vessel 101 forms a processing chamber 104 in which the inside and the outside are airtightly separated. The dielectric window 103 forms the vacuum vessel 101, and is a dielectric window member made of a light-transmitting material through which an electric field for generating plasma passes.

[0020] Furthermore, 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. Furthermore, a shower plate 102 forming the ceiling surface of a processing chamber 104 is provided below the lower surface of a dielectric window 103 forming a cover member at the top of the vacuum vessel 101. The shower plate 102 has a plurality of gas introduction holes 102a disposed in the center, and etching gas is introduced into the processing chamber 104 through the plurality of gas introduction 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 forming unit 160 for forming an electric field and a magnetic field for generating plasma 116 is disposed at an upper portion outside vacuum vessel 101. Electric field and magnetic field forming unit 160 is provided in plasma processing apparatus 100 and includes the following configuration. That is, electric field and magnetic field forming unit 160 includes a waveguide 105 disposed above dielectric window 103 and for supplying a high frequency electric field of a predetermined frequency for generating plasma 116 into processing chamber 104. Inside waveguide 105, the electric field is transmitted toward the upper surface of dielectric window 103. The electric field transmitted inside waveguide 105 is generated by oscillation in electric field generating power supply 106. Electric field and magnetic field forming unit 160 includes waveguide 105 and electric field generating power supply 106. The frequency of the electric field is not particularly limited, but in this embodiment, microwaves of 2.45 GHz are used.

[0022] The plasma processing apparatus 100 includes a control unit 1 disposed outside a vacuum vessel 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 storage unit 2 is connected to the control unit 1.

[0023] Moreover, a magnetic field generating coil 107 for generating a magnetic field is disposed above the dielectric window 103, on the outer side wall 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, so as to surround these. The magnetic field generating coil 107 is a solenoid coil disposed on the outer periphery of the vacuum vessel 101 so as to surround the processing chamber 104 and the waveguide 105. The generation of the magnetic field by the magnetic field generating coil 107 is controlled by the control unit 1. Then, the microwave band electric field generated by the electric field generating power supply 106 propagates inside 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, the magnetic field generating coil 107 generates an ECR by 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] Further, a wafer mounting electrode (first electrode) 120 constituting a sample stage is provided at the bottom of the processing chamber 104 and below the space in which 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 (processing target), is mounted. The dielectric window 103 is disposed above the sample stage and 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 is also along the horizontal plane.

[0025] Further, a high-frequency filter 125 is disposed outside the vacuum vessel 101 and is connected to the conductive film 111. A high-frequency power source (first high-frequency power source) 124 and a matching box 129 are disposed at a location closer to the electrostatic attraction electrode (conductive film 111) than the high-frequency filter 125. The high-frequency power source 124 and the matching box 129 are connected to an electrode substrate 108 having a circular or cylindrical shape and made of a conductive material, which is disposed inside the wafer mounting electrode 120. The high-frequency power source 124 is electrically connected to the ground 112. A high-frequency power (first high-frequency power) of a predetermined frequency is supplied from the high-frequency power source 124 to the electrode substrate 108 via the matching box 129, and a bias potential is formed above the wafer 109 that is attracted 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 source 124 while the plasma 116 is being generated.

[0026] The control unit 1 controls the DC power applied from the DC power supply 126 to the conductive film 111. 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 get into the electrical circuits of the 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 in a spiral or concentric manner 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 the coolant flow paths 152.

[0028] In such a plasma processing apparatus 100, in a vacuum transfer chamber that is a separate vacuum container connected to the side wall of the vacuum container 101 and that is depressurized to the same pressure as that of the processing chamber 104 inside a vacuum transfer container, an unprocessed wafer 109 is placed on the tip of an arm of a robot for wafer transfer arranged in the vacuum transfer chamber. Then, a gate that is a passage that communicates between the vacuum transfer chamber and the processing chamber 104 is opened by the operation of a valve arranged in the vacuum transfer chamber, and the unprocessed wafer 109 is transferred into the processing chamber 104 while being placed on the tip of the arm of the robot. Furthermore, the wafer 109 that has been transferred to above the mounting surface 120a of the wafer mounting electrode 120 in the processing chamber 104 is transferred onto the lift pins by the vertical movement of the lift pins, and is then placed on the mounting surface, and is then attracted to and held on the mounting surface 120a of the wafer mounting electrode 120 by the electrostatic force generated by the DC power applied from the DC power source 126.

[0029] In this state, the etching gas has its flow rate or speed adjusted by a mass flow controller (not shown) and is introduced into the space between the dielectric window 103 and the quartz shower plate 102, and after diffusing in this space, 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 the 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 inside of the processing chamber 104 is adjusted to a predetermined value within a range suitable for processing the wafer 109.

[0030] While the wafer 109 is being held by suction, a thermally 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. The temperature of the wafer mounting electrode 120 or the electrode base material 108 is adjusted in advance before the wafer 109 is mounted by circulating a coolant adjusted to a temperature within a predetermined range through a coolant flow path 152 arranged in the electrode base material 108 of the wafer mounting electrode 120. Therefore, by transferring heat between the wafer mounting electrode 120 or the electrode base material 108, which have a large heat capacity, the temperature of the wafer 109 is adjusted to be close to these temperatures before processing, and even after processing begins, heat is transferred from the wafer 109 to adjust the temperature of the wafer 109.

[0031] In this state, an electric field and a magnetic field of microwaves are supplied into the processing chamber 104, and plasma 116 is generated using the gas. When plasma 116 is formed, radio frequency (RF) bias power is supplied from a high frequency power supply 124 to the electrode substrate 108. 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 according to the potential difference between the bias potential and the potential of the plasma 116. Furthermore, the charged particles collide with a mask arranged in advance on the upper surface of the wafer 109 and a surface of the film layer to be processed of a film structure including the film layer to be processed, 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 a 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 part of the outer periphery of the sample stage through 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 from a high frequency power source (second high frequency power source) 127 is supplied to a conductor ring (second electrode) 131 made of a conductor disposed in the susceptor ring 113 via a load matching box 128 and a load impedance variable box 130. The supply of this high frequency power is performed by the control unit 1 controlling the high frequency power source 127, the load matching box 128, and the load impedance variable box 130. With this configuration, the impedance value for the high frequency power from the high frequency power source 127 through the electrode base material 108 to the outer periphery of the wafer 109 is relatively low by a combination of the load impedance variable box 130 adjusted to a suitable impedance value and a relatively high impedance portion disposed on the upper part of the susceptor ring 113. This allows the high frequency power to be effectively supplied to the outer periphery and outer periphery of the wafer 109, and the concentration of the electric field on the outer periphery or outer periphery to be alleviated, thereby 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 upper part. 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 upper surface of dielectric window 103. An electric field propagated through waveguide 105 spreads inside discharge chamber 121, which is the inside of this cylindrical member.

[0035] The plasma processing apparatus 100 is provided with a configuration for detecting the film thickness on the wafer on the top plate 210. An irradiation unit (irradiator, light-emitting unit) 181 that irradiates light from the outside onto the surface of the wafer 109 arranged on the top surface (mounting surface 120a) of the sample stage in the processing chamber 104 from above the discharge chamber 121, and a light-receiving unit (light-receiving unit) 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 an irradiation unit 181 and a light-receiving unit 182 on the top plate 210. The irradiation unit 181 and the light-receiving unit 182 are provided with adjustment mechanisms 183 and 184 that adjust the installation positions of the irradiation unit 181 and the light-receiving unit 182 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 to discharge chamber 121 through light passing hole 212 (see FIG. 2) of top plate 210. Irradiation light propagated through optical fiber 185 from external light source 187 is incident downward from irradiation unit 181, passes through discharge chamber 121, dielectric window 103, shower plate 102, and the interior of processing chamber 104 below, and is irradiated obliquely to center X (see FIG. 2) of the upper surface of wafer 109. The light irradiated to the upper surface of wafer 109 is reflected obliquely from the upper surface of wafer 109 and received by light receiving unit 182.

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

[0038] As shown in FIG. 5, when the wafer 109 undergoing etching is irradiated with the irradiation light 190, the reflected light 402 from the surface of the mask layer 405, the reflected light 403 from the surface of the layer 406 to be processed, which is the boundary between the mask layer 405 and the layer 406 to be processed, and the reflected light 404 from the surface of the layer 406 to be processed are generated. An optical path difference occurs between the reflected lights 402, 403, and 404 to be generated, and thus an interference light is formed. As shown in FIG. 6, the thickness of the layer 406 to be processed decreases as the etching progresses, so that the optical path difference of each reflected light changes, and an interference phenomenon with a different period occurs for each wavelength. Of these multi-wavelength interference lights 191 (see FIG. 1), the multi-wavelength interference light 191 received by the light receiving unit 182 is transmitted to the spectrometer 188 via the 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 transmitted light for 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 for each wavelength with a film thickness obtained in advance and the light intensity for 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 that shows a schematic 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 omitted from Figure 2.

[0040] As shown in FIG. 2, in order to detect the film thickness of the wafer 109, an irradiation unit 181 having an adjustment mechanism 183 and a light receiving unit 182 having an adjustment mechanism 184 are installed at a predetermined radial position from the center of the top plate 210. For example, in a plan view, the adjustment mechanism 183 and the irradiation unit 181 are arranged on the opposite side of the center of the top plate 210 from the adjustment mechanism 184 and the light receiving unit 182. The irradiation unit 181 and the light receiving unit 182 are arranged above the dielectric window 103 with a distance between them in the horizontal direction. The adjustment mechanism 183 is installed on the top of the top plate 210, and the irradiation unit 181 is installed on the top of the adjustment mechanism 183. The adjustment mechanism 184 is installed on the top of the top plate 210, and the light receiving unit 182 is installed on the top of the adjustment mechanism 183.

[0041] The installation surfaces of the adjustment mechanisms 183 and 184 are the same, 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 a 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 a radial direction from the center of the wafer 109, and the irradiation unit 181 and the light receiving unit 182 can move on the same axis. That is, the directions V in which the adjustment mechanisms 183 and 184 move overlap each other when viewed from any direction.

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

[0043] The collimating lens unit 205 includes a cylindrical or disc-shaped flange portion 220 and a collimating lens 219 configured with a disc-shaped convex or concave lens attached to the tip of the flange portion 220 with its axis aligned with a through hole arranged in the center of the flange portion 220. The collimating lens unit 206 also includes a cylindrical or disc-shaped flange portion 222 and a collimating lens 221 configured with a disc-shaped convex or concave lens attached to the tip of the flange portion 222 with its axis aligned with a through hole arranged in the center of the flange portion 222. The adjustment mechanism 183 is located directly below the irradiation portion 181 and has a light-passing hole (through hole) 211 penetrating the adjustment mechanism 183 in the vertical direction, and the adjustment mechanism 184 is located directly below the light-receiving portion 182 and has a light-passing hole (through hole) 214 penetrating the adjustment mechanism 184 in the vertical direction. The top plate 210 is located below the irradiation section 181 and has a light passage hole (through hole) 212 that penetrates the top plate 210 in the vertical direction, and a light passage hole (through hole) 213 that is located below the light receiving section 182 and penetrates 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 the 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 the 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, 212, discharge chamber 121, dielectric window 103, shower plate 102, and further through the interior of processing chamber 104 below, in that order, and is irradiated onto wafer 109. Irradiation light 190 irradiated onto wafer 109 is reflected at center X of the upper surface of wafer 109 at angle a with respect to central axis Y of wafer 109. In this manner, the angle of incidence of irradiation light 190 with respect to the upper surface of wafer 109 and the angle of reflection of interference light 191 from the upper 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, light passing holes 213 and 214, in that order, and is received by light receiving unit 182. The light received by the light receiving unit 182 passes through the light passing hole 217, is reflected by the mirror 209, passes through the light passing 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 the 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. The stepping motor 301, the bearing 306, and the guide rail 307 are installed on the fixed stage 303. A rod-shaped ball screw 305 that penetrates the ball screw nut 304 is installed on the rotation axis of the stepping motor 301. The stepping motor 301 is installed at an end on the fixed stage 303. The tip of the ball screw 305 is supported by a bearing 306, and the bearing 306 is installed at one of both ends on the fixed stage 303, the end opposite the stepping motor 301. The 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 the ball screw 305. The movable stage 302 slides along the extending direction of the groove of the guide rail.

[0047] Each of the irradiation unit 181 and the light receiving unit 182 can move its position in the direction V by rotating the stepping motor 301 of the adjustment mechanisms 183, 184 and sliding the movable stage 302 along the guide rail 307 by the ball screw 305 and the ball screw nut 304. That is, the irradiation unit 181 and the light receiving unit 182 move along the axis of the ball screw 305, whose axis is arranged parallel to the direction V. Each of the irradiation unit 181 and the light receiving unit 182 is fitted with the ball screw 305 and connected to the ball screw nut (slider) 304, and moves along the direction V in conjunction with the movement of the ball screw nut 304 along the axis. In other words, each of the irradiation 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 each of the irradiation unit 181 and the light receiving unit 182. The adjustment mechanisms 183 and 184 are drive units that move each of the irradiation unit 181 and the light receiving unit 182.

[0049] Fig. 7 shows the relationship between the amount of optical axis misalignment and the intensity of light reflected on the surface of the wafer. The horizontal axis of the graph shown in Fig. 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 on the wafer 109 and received by the light receiving unit 182 decreases. The method of adjusting the positions of the irradiating unit 181 and the light receiving unit 182 and determining the positions in order to obtain the light intensity Z required for film thickness detection on the surface of the wafer 109 are 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 irradiation 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 a 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 take into consideration 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 and the machining accuracy of the light emitting unit and the light receiving unit. When this optical axis misalignment occurs, the light intensity decreases, and a problem occurs in that the light intensity required for film thickness detection cannot be obtained. In response to this, 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 higher than a threshold value. This makes it possible to provide a plasma processing apparatus 100 that is not affected by the decrease in light intensity due to the optical axis misalignment between the irradiation unit 181 and the light receiving unit 182 in the film thickness detection technology on the surface of the wafer.

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

[0054] 1. Control section 2 Storage section 100 Plasma treatment device 101 Vacuum container 103 Dielectric window 104 Processing Room 105 Waveguide 109 Wafer 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 Interference light 203, 204, 211~214, 216, 217 Light holes 210 Tabletop

Claims

1. a processing chamber disposed within the vacuum vessel and in which plasma is formed; a sample stage disposed within the processing chamber and capable of mounting a wafer to be processed by the plasma on an upper surface thereof; 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 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 irradiated from the irradiating unit and reflected from an 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 a 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 and 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 disposed above a pair of through holes that pass through the top plate in the up-down direction, A plasma processing apparatus, wherein 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, A plasma processing apparatus, wherein 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 in association with the movement of the slider along the axis.

6. 5. The plasma processing apparatus according to claim 4, The rod-shaped member further includes a nut that is fitted into a groove that is spirally provided on a surface of the rod-shaped member and moves in the first direction in response to rotation of the rod-shaped member about its axis. A plasma processing apparatus, wherein the irradiation unit or the light receiving unit is connected to the nut and moves in the first direction in association with movement of the nut along the axis.

7. 3. The plasma processing apparatus according to claim 1, The irradiation 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 with respect to the upper surface of the wafer is received by the light receiving section.

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, wherein the plasma is generated by interaction between the electric field having a frequency in the microwave band and a 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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