Plasma Processing Equipment

Abstract

To provide a plasma processing apparatus capable of detecting a change in light in a narrow region.SOLUTION: A plasma processing apparatus includes a chamber, a gas supply portion capable of supplying gas to the interior of the chamber, a mount portion in which a workpiece can be mounted, and a pressure-reducing portion capable of reducing the internal pressure of the chamber, a window which is provided to the chamber and faces the mount portion, a plasma generation portion which is provided outside the chamber and capable of generating plasma inside the chamber, an optical path changing portion that is locally provided inside the window and has a surface that is inclined with respect to the central axis of the chamber, and a detection unit for detecting the state of the workpiece through the optical path changing portion. The window has, on a side surface thereof, a flat surface that is parallel to the surface of the optical path changing portion and is inclined with respect to a line perpendicular to the central axis of the chamber, and the flat surface refracts the optical path of light emitted from the detection portion.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] An embodiment of the present invention relates to a plasma processing apparatus. [Background technology]

[0002] A plasma processing apparatus used for dry etching or the like is provided with a detection unit that detects the state of the processing object. For example, in detecting the end point of plasma processing, the end point of processing is detected based on a change in the scattering intensity of light irradiated on the surface of the processing object. In addition, in detecting the end point of plasma processing, the end point of processing may be detected based on a change in the emission spectrum of the plasma. In addition, in detecting the end point of plasma processing, the end point of processing may be detected based on reflected light or transmitted light in the processing area of ​​the processing object. That is, in general, the end point of plasma processing is detected based on an optical change that occurs during the plasma processing.

[0003] Here, a plasma processing apparatus has been proposed that includes a detection window (transmission window) provided on the side of the chamber and a detection unit provided outside the chamber that detects plasma emission through the detection window. Also, a plasma processing apparatus has been proposed that includes a plate-shaped window provided on the ceiling of the chamber and a detection unit that detects light that enters the window from inside the chamber, propagates inside the window, and is emitted from the side of the window. These detection units detect emission over a wide range, such as the entire area where plasma is generated. In this case, the intensity of the light that enters the detection unit is the average value of the light intensity over the wide range, making it difficult to detect slight changes in the surface of the processing object.

[0004] In recent years, the processed parts have become finer, and the opening ratio of the unevenness or holes formed may be 1% or less. In such cases, the amount of material removed is small, and the amount of change in light is very small. Therefore, if light emission is detected over a wide area, it becomes even more difficult to detect slight changes in the surface of the processed object.

[0005] In this case, if a change in light in a narrow area can be detected, the end point of even fine processing can be detected with high accuracy, and therefore fine processing can be performed with high accuracy. Therefore, there has been a demand for the development of a plasma processing apparatus capable of detecting changes in light in a narrow area. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2007-66935 A Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a plasma processing apparatus capable of detecting a change in light in a narrow area. [Means for solving the problem]

[0008] A plasma processing apparatus according to an embodiment includes a chamber capable of maintaining an atmosphere reduced in pressure below atmospheric pressure, a gas supply unit capable of supplying gas into the chamber, a mounting unit provided inside the chamber and capable of mounting an object to be processed, a pressure reduction unit capable of reducing the pressure inside the chamber, a window provided in the chamber and facing the mounting unit, a plasma generation unit provided outside the chamber on a surface of the window opposite to the mounting unit side and capable of generating plasma inside the chamber, an optical path changing unit provided locally inside the window and having a surface inclined with respect to the central axis of the chamber, and a detection unit provided outside the chamber and detecting the state of the object to be processed via the optical path changing unit. There is The central axis of the chamber Hanging For a straight line 、 The optical sensor has an inclined flat surface, and the flat surface refracts the optical path of the light emitted from the detection unit. Effect of the Invention

[0009] According to an embodiment of the present invention, a plasma processing apparatus capable of detecting a change in light in a narrow area is provided. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic cross-sectional view illustrating a plasma processing apparatus according to an embodiment of the present invention. [Diagram 2] 1 is a schematic perspective view for illustrating a placement module; FIG. [Diagram 3] 4 is a schematic cross-sectional view illustrating an optical path changing unit. FIG. [Figure 4] 13A and 13B are schematic cross-sectional views illustrating modified examples of the optical path changing unit. [Diagram 5] 13A to 13C are schematic cross-sectional views illustrating other modified examples of the optical path changing unit. [Figure 6] 13 is a schematic plan view illustrating the relationship between a flat surface provided on a side surface of a window and an optical axis adjustment portion. FIG. [Figure 7] 10A to 10C are schematic plan views for illustrating the relationship between a flat surface provided on a side surface of a window and the optical path changing unit, and between the flat surface and the detection unit. [Figure 8] FIG. 11 is a schematic plan view illustrating a case where the first angle and the spread angle are the same angle. [Figure 9] 1A and 1B are schematic plan views illustrating the relationship between a detection unit that irradiates inspection light having a cross-sectional area derived from the aperture diameter and has a light-receiving area derived from the aperture diameter, and a flat surface provided on the side of the window. [Figure 10] FIG. 9(b) is a schematic enlarged view of the periphery of the light spread at the spread angle of FIG. [Figure 11] 2(θ1-θ3), tan2(θ1-θ3), and APr / tan2(θ1-θ3). [Figure 12] 11A to 11C are schematic plan views illustrating modified examples of flat surfaces provided on the side surfaces of the windows. [Figure 13]11A to 11C are schematic plan views illustrating modified examples of flat surfaces provided on the side surfaces of the windows. [Figure 14] 13A and 13B are schematic cross-sectional views illustrating an optical path changing unit according to another embodiment. [Figure 15] 11 is a schematic cross-sectional view illustrating a plasma processing apparatus according to another embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and detailed description thereof will be omitted as appropriate. In each drawing, the arrows X, Y, and Z represent three directions that are perpendicular to each other. For example, the arrows X and Y represent the horizontal direction, and the arrow Z represents the vertical direction. Fig. 1 is a schematic cross-sectional view illustrating a plasma processing apparatus 1 according to this embodiment. Fig. 2 is a schematic perspective view illustrating a mounting module 3. As shown in FIG. 1, a plasma processing apparatus 1 can be provided with a chamber 2, a mounting module 3, a power supply unit 4, a power supply unit 5, a pressure reducing unit 6, a gas supply unit 7, a processing state detecting unit 8, and a control unit 9.

[0012] The chamber 2 may have an airtight structure capable of maintaining an atmosphere at a pressure lower than atmospheric pressure. The chamber 2 can have a main body 21, a top plate 22, and a window 23. The main body 21 has a substantially cylindrical shape, and a bottom plate 21a is integrally provided at one end. The other end of the main body 21 is open. The main body 21 can be made of a metal such as an aluminum alloy. The main body 21 can be grounded. An area 21b where plasma P is generated is provided inside the main body 21. The main body 21 can be provided with a loading / unloading port 21c for loading / unloading the workpiece 100. The loading / unloading port 21c can be closed airtightly by a gate valve 21c1.

[0013] The processing object 100 may be, for example, a photomask, a mask blank, a wafer, a glass substrate, etc. However, the processing object 100 is not limited to the above-mentioned examples.

[0014] The top plate 22 has a plate shape and can be provided so as to cover the opening of the main body 21. The top plate 22 can be provided so as to face the bottom plate 21a. A hole 22a penetrating the thickness direction can be provided in the central region of the top plate 22. The center of the hole 22a can be provided on the central axis 2a of the chamber 2 (main body 21). The hole 22a can be provided to transmit electromagnetic waves radiated from an electrode 51 described below. The top plate 22 can be formed from a metal such as an aluminum alloy.

[0015] The window 23 has a plate shape and can be provided on the top plate 22. The window 23 can be provided so as to cover the hole 22a. That is, the window 23 is provided in the chamber 2 and faces a mounting portion 31 described below. The window 23 can be made of a material that can transmit light and an electromagnetic field and is difficult to be etched during an etching process. The window 23 can be made of a dielectric material such as quartz.

[0016] An optical path changing section 81, which will be described later, is provided inside the window 23. A flat surface 23a, which corresponds to a flat surface, is provided on the side surface of the window 23 (see FIG. 7). The optical path changing section 81 and the flat surface 23a will be described later.

[0017] 1 and 2, the mounting module 3 may have a mounting part 31, a support part 32, and a cover 33. The mounting module 3 may have a cantilever structure that protrudes from a side surface of the chamber 2 (main body part 21) into the chamber 2 (main body part 21) and has the mounting part 31 provided at the tip side. The treatment object 100 may be mounted on the mounting part 31. The mounting part 31 is located below the region 21b where the plasma P is generated.

[0018] The mounting portion 31 can have an electrode 31a, an insulating ring 31b, and a base 31c. The electrode 31a can be made of a conductive material such as metal. An upper surface of the electrode 31a can be a mounting surface for mounting the object 100 to be treated. The electrode 31a can be fixed to a base 31c, for example, by screws. The electrode 31a can also include a pickup pin 31a1 (see FIG. 2), a temperature control unit, and the like. A plurality of pickup pins 31a1 can be provided.

[0019] The plurality of pickup pins 31a1 are rod-shaped and can be provided so as to be able to protrude from the upper surface of the electrode 31a. The plurality of pickup pins 31a1 can be used when transferring the workpiece 100. For this reason, the plurality of pickup pins 31a1 can be caused to protrude from the upper surface of the electrode 31a and retracted into the electrode 31a by a drive unit (not shown). The number and arrangement of the plurality of pickup pins 31a1 can be appropriately changed depending on the size, planar shape, etc. of the workpiece 100.

[0020] The temperature control unit can be, for example, a refrigerant circulation line (flow path), a heater, etc. The temperature control unit can control the temperature of the electrode 31a, and further the temperature of the treatment object 100 placed on the electrode 31a, based on, for example, the output from a temperature sensor (not shown).

[0021] The insulating ring 31b is ring-shaped and can cover the side surface of the electrode 31a. The insulating ring 31b can be made of a dielectric material such as quartz. The pedestal 31c can be provided between the electrode 31a and the mounting portion 32a of the support portion 32. The pedestal 31c can be provided to provide insulation between the electrode 31a and the support portion 32. The pedestal 31c can be made of a dielectric material such as quartz. The pedestal 31c can be fixed to the mounting portion 32a of the support portion 32 by, for example, a screw.

[0022] The support portion 32 can support the mounting portion 31 in the internal space of the chamber 2. The support portion 32 can extend between a side surface of the chamber 2 and the lower portion of the mounting portion 31. The support portion 32 may have an attachment portion 32a, a beam 32b, and a flange 32c. The attachment portion 32a, the beam 32b, and the flange 32c may be formed from, for example, an aluminum alloy.

[0023] The mounting portion 32a can be located below the mounting portion 31 in the internal space of the chamber 2. The mounting portion 32a can be provided so that the center of the mounting portion 32a is located on the central axis 2a of the chamber 2. The mounting portion 32a has a cylindrical shape, and a hole 32a1 can be provided in the end face on the mounting portion 31 side. A hole 32a2 can be provided in the end face opposite the mounting portion 31 side. The bus bar 42c, piping for a coolant, etc. can be connected to the electrode 31a via the hole 32a1.

[0024] The holes 32a2 can be used for connecting the bus bar 42c or piping for a refrigerant, or for performing maintenance on the electrode 31a. The mounting portion 31 (pedestal 31c) can be provided on the end face of the mounting portion 32a on the mounting portion 31 side. Therefore, the planar shape of the mounting portion 32a can be the same as the planar shape of the mounting portion 31. The planar dimensions of the mounting portion 32a can be approximately the same as or slightly larger than the planar dimensions of the mounting portion 31.

[0025] One end of the beam 32b can be connected to the side of the mounting portion 32a. The other end of the beam 32b can be connected to the flange 32c. The beam 32b can extend from the side of the chamber 2 toward the central axis 2a of the chamber 2 through the internal space of the chamber 2. The beam 32b can have a rectangular cylindrical shape. The internal space of the beam 32b can be connected to the external space (atmospheric space) of the chamber 2 through a hole 32c1 provided in the flange 32c. Therefore, the bus bar 42c can be in contact with the atmospheric space. If the internal space of the beam 32b is connected to the external space of the chamber 2, the pressure in the internal space of the beam 32b becomes the same as the pressure in the external space of the chamber 2 (for example, atmospheric pressure). In addition, the internal space of the beam 32b can be connected to the internal space of the mounting portion 32a. In this case, the pressure in the internal space of the support portion 32 becomes the same as the pressure in the external space of the chamber 2 (for example, atmospheric pressure).

[0026] The flange 32c may have a plate shape and may have a hole 32c1 penetrating in the thickness direction. The flange 32c may be attached to the outer wall of the chamber 2, for example, by screws.

[0027] A hole 2b can be provided on the side surface of the chamber 2. The hole 2b can have a size and shape that allows the placement unit 31 attached to the attachment unit 32a to pass through. Therefore, the placement module 3 provided with the placement unit 31 can be removed from the chamber 2 or the placement module 3 provided with the placement unit 31 can be attached to the chamber 2 via the hole 2b.

[0028] That is, through the hole 2b, the mounting portion 32a and the beam 32b on which the mounting portion 31 is provided can be carried into and out of the chamber 2. Note that a slider can be provided on the outer wall of the chamber 2 to facilitate attachment and detachment of the mounting module 3.

[0029] The cover 33 can be provided on the end surface of the mounting portion 32a opposite to the mounting portion 31 side. The cover 33 can be screwed to the mounting portion 32a, for example. By attaching the cover 33 to the mounting portion 32a, the hole 32a2 can be closed airtight. There is no particular limitation on the shape of the cover 33, and the cover 33 may be a dome-shaped cover or a plate-shaped cover 33. The cover 33 can be formed from, for example, an aluminum alloy.

[0030] Here, if the support part 32 has a cantilever structure, a space can be provided below the mounting part 31 in the internal space of the chamber 2, so that the pressure reducing part 6 can be arranged directly below the mounting part 31. If the pressure reducing part 6 can be arranged directly below the mounting part 31, the effective exhaust speed is high, and it is easy to perform axially symmetrical exhaust without bias. In addition, if the support part 32 has a cantilever structure, the support part 32 on which the mounting part 31 is provided can be removed from the chamber 2 from the horizontal direction, and the support part 32 on which the mounting part 31 is provided can be attached to the chamber 2. Therefore, maintenance of the plasma processing apparatus is easier than when the mounting part is fixed to the bottom surface of the chamber 2.

[0031] However, the mounting portion 31 is provided with a metal electrode 31a. The mounting portion 31 is also provided with a pickup pin 31a1 and its drive unit, a refrigerant circulation line, a temperature control unit such as a heater, and the like. This makes the mounting portion 31 heavy. Since the support portion 32 has a cantilever structure, if the weight of the mounting portion 31 provided on the tip side becomes heavy, the load is biased, and the tip of the beam 32b supporting the mounting portion 31 may bend downward. If the tip of the beam 32b bends downward, the mounting portion 31 may tilt. For example, the weight of the mounting portion 31 may be 56 to 70 kgf (kilogram force). In such a case, the tip of the mounting module 3 may drop downward by about 0.2 mm.

[0032] Since the processing object 100 is placed on the mounting part 31, the mounting surface on which the processing object 100 is placed needs to have an area at least equal to or larger than the area of ​​the main surface of the processing object 100. This increases the planar dimensions of the mounting part 31. If the mounting part 31, which has a large planar dimension, is tilted, the gas flow in the chamber 2 may be disturbed or the plasma density may become non-uniform, which may result in non-uniform processing characteristics.

[0033] In this case, if the cross-sectional dimensions of the beams 32b supporting the mounting portion 31 are increased in order to suppress the inclination of the mounting portion 31, exhaust may be hindered, the effective exhaust speed may decrease, or it may become difficult to perform axially symmetrical exhaust without bias. In this case, if the beams 32b supporting the mounting portion 31 are provided in a plurality of places, the cross-sectional dimensions of each beam 32b may be reduced, and the decrease in the effective exhaust speed may be suppressed. In addition, if the arrangement of the plurality of beams 32b is devised, it may be possible to perform axially symmetrical exhaust. However, if the beams 32b are provided in a plurality of places, the dimensions of the portion fixed to the side surface of the chamber 2 may become large, making it difficult to attach and detach the support portion 32, and this may reduce maintainability.

[0034] Therefore, the support part 32 according to this embodiment is provided with a beam 32b having a space therein. As described above, the internal space of the beam 32b is connected to the space outside the chamber 2. That is, the pressure in the internal space of the beam 32b is the same as the pressure in the space outside the chamber 2 (for example, atmospheric pressure). In addition, when the thickness of the side part (upper side part) of the beam 32b on the mounting part 31 side is t1 and the thickness of the side part (lower side part) of the beam 32b opposite to the mounting part 31 side is t2, "t1>t2".

[0035] Therefore, when performing plasma processing, a uniformly distributed load according to the difference between the pressure inside the beam 32b and the pressure outside the beam 32b is applied to the upper side and the lower side of the beam 32b. In this case, the uniformly distributed load applied to the upper side and the lower side of the beam 32b is equal. Therefore, if "t1>t2", the amount of deflection of the upper side of the beam 32b is larger than the amount of deflection of the lower side of the beam 32b. As a result, the tip of the beam 32b is deflected upward, so that the downward deflection due to the weight of the mounting part 31 can be offset by the upward deflection due to the pressure difference. The specific dimensions of the thicknesses t1 and t2 can be appropriately determined by performing experiments and simulations.

[0036] Next, returning to FIG. 1, the power supply unit 4, the power supply unit 5, the pressure reducing unit 6, the gas supply unit 7, the processing state detecting unit 8, and the control unit 9 will be described. The power supply unit 4 may be a so-called high-frequency power supply for bias control. That is, the power supply unit 4 may be provided to control the energy of ions attracted to the object 100 on the mounting unit 31.

[0037] The power supply unit 4 may include a power supply 41 and a matching unit 42 . The power supply 41 can output high-frequency power having a frequency suitable for attracting ions (for example, a frequency of 27 MHz to 1 MHz). The matching section 42 may include a matching circuit 42a, a fan 42b, and a bus bar 42c. The matching circuit 42a can be provided to match the impedance on the power source 41 side with the impedance on the plasma P side. The matching circuit 42a can be electrically connected to the power source 41 and the electrode 31a via a bus bar (wiring member) 42c. That is, the power source 41 can be electrically connected to the electrode 31a provided on the mounting portion 31 via the bus bar 42c. The fan 42b can send air into the inside of the support part 32. The fan 42b can be provided to cool the bus bar 42c and the matching circuit 42a provided inside the support part 32.

[0038] Furthermore, the alignment part 42 can be provided on the flange 32c of the support part 32. If the alignment part 42 is provided on the flange 32c, the placement module 3 and the alignment part 42 can be moved together when removing the placement module 3 from the chamber 2 (main body part 21) or attaching the placement module 3 to the chamber 2 (main body part 21). This improves maintainability. In addition, the internal space of the beam 32b is connected to the external space of the chamber 2 (main body 21) via the matching portion 42. Therefore, the pressure in the internal space of the beam 32b can be made the same as the pressure in the external space of the chamber 2 (for example, atmospheric pressure).

[0039] The power supply unit 5 can be a high-frequency power supply for generating the plasma P. That is, the power supply unit 5 can be provided to generate the plasma P by causing a high-frequency discharge inside the chamber 2. In this embodiment, the power supply unit 5 is provided outside the chamber 2 on the surface of the window 23 opposite the mounting unit 31 side, and serves as a plasma generating unit that generates plasma P inside the chamber 2.

[0040] The power supply unit 5 may include an electrode 51, a power supply 52, a matching circuit 53, and a Faraday shield 54. The electrode 51 can be provided outside the chamber 2 and on the window 23. The electrode 51 can have a plurality of conductor parts and a plurality of capacitive parts (capacitors) that generate an electromagnetic field. The power source 52 can output high frequency power having a frequency of about 100 KHz to 100 MHz. In this case, the power source 52 can output high frequency power having a frequency (for example, a frequency of 13.56 MHz) suitable for generating plasma P. The power source 52 can also change the frequency of the high frequency power it outputs.

[0041] The matching circuit 53 can be provided to match the impedance on the power supply 52 side with the impedance on the plasma P side. The matching circuit 53 can be electrically connected to the power supply 52 and the electrode 51 via wiring 55. The matching circuit 53 can also be electrically connected to the power supply 52 and the electrode 51 via a bus bar.

[0042] The Faraday shield 54 can be provided between the window 23 and the electrode 51. The Faraday shield 54 has a plate shape and can be made of a conductive material such as a metal. The Faraday shield 54 can have a plurality of slits extending radially from the center. An insulating film made of an insulating material can be provided on the surface of the Faraday shield 54 facing the electrode 51. The portion of the Faraday shield 54 made of a conductive material can be grounded.

[0043] The plasma processing apparatus 1 illustrated in FIG. 1 is a dual-frequency plasma processing apparatus having an inductively coupled electrode at its upper portion and a capacitively coupled electrode at its lower portion. However, the method of generating plasma is not limited to the example given. The plasma processing apparatus 1 may be, for example, a plasma processing apparatus using inductively coupled plasma (ICP) or a plasma processing apparatus using capacitively coupled plasma (CCP).

[0044] The pressure reducing section 6 is located below the mounting section 31, and is capable of reducing the pressure inside the chamber 2 to a predetermined pressure. The pressure reducing section 6 may include a pump 61 and a valve 62 . The pump 61 can be provided outside the chamber 2. The pump 61 can be connected to a hole 21a1 provided in the bottom plate 21a of the chamber 2. The pump 61 can exhaust gas inside the chamber 2. The pump 61 can be, for example, a turbo molecular pump (TMP). Note that a roots type dry pump can also be connected to the turbo molecular pump as a back pump.

[0045] The valve 62 can have a valve body 62a and a drive portion 62b. The valve body 62a has a plate shape and can be provided inside the chamber 2. The valve body 62a can face the hole 21a1. The planar dimensions of the valve body 62a can be larger than the planar dimensions of the intake port 61a of the pump 61. When the valve body 62a is viewed from the direction of the central axis 2a, the valve body 62a can cover the intake port 61a of the pump 61.

[0046] The driving unit 62b can change the position of the valve body 62a in the direction of the central axis 2a of the chamber 2 (main body 21). That is, the driving unit 62b can raise and lower the valve body 62a. The driving unit 62b can include a shaft 62a1 connected to the valve body 62a and a control motor (e.g., a servo motor) that moves the shaft 62a1. The valve 62 can be a so-called poppet valve.

[0047] When the position of the valve body 62a inside the chamber 2 changes, the distance between the valve body 62a and the bottom plate 21a of the chamber 2 changes. The space between the valve body 62a and the bottom plate 21a of the chamber 2 becomes an exhaust flow path. Therefore, changing the dimensions of this portion changes the conductance, so that it is possible to control the exhaust amount, exhaust speed, and the like. The control unit 9 can change the position of the valve body 62a by controlling the drive unit 62b based on the output of a vacuum gauge (not shown) that detects the internal pressure of the chamber 2, for example. The vacuum gauge can be a diaphragm-type capacitance manometer, or the like.

[0048] The gas supply unit 7 can supply the gas G to the region 21b inside the chamber 2 where the plasma P is generated. The gas supply unit 7 may have a gas storage unit 71, a gas control unit 72, and an on-off valve 73. The gas storage unit 71, the gas control unit 72, and the on-off valve 73 may be provided outside the chamber 2. The gas storage unit 71 can store gas G and supply the stored gas G to the inside of the chamber 2. The gas storage unit 71 can be, for example, a high-pressure cylinder that stores gas G. The gas storage unit 71 and the gas control unit 72 can be connected via piping.

[0049] The gas control unit 72 can control the flow rate and pressure of the gas G supplied from the gas storage unit 71 to the inside of the chamber 2. The gas control unit 72 can be, for example, an MFC (Mass Flow Controller). The gas control unit 72 and the on-off valve 73 can be connected via piping.

[0050] The on-off valve 73 can be connected to the gas supply port 22b provided in the chamber 2 via a pipe. Note that a plurality of gas supply ports 22b may be provided so that the gas G is evenly supplied from a plurality of directions to the region 21b where the plasma P is generated. The on-off valve 73 can control the start and stop of the supply of the gas G. The on-off valve 73 can be, for example, a two-port solenoid valve. Note that the function of the on-off valve 73 can be imparted to the gas control unit 72.

[0051] The gas G may be one that generates desired radicals or ions when excited and activated by the plasma P. For example, when the plasma processing is an etching processing, the gas G may be one that generates radicals or ions that can etch the exposed surface of the processing object 100. In this case, the gas G may be, for example, a gas containing chlorine, a gas containing fluorine, or the like. The gas G may be, for example, a mixed gas of chlorine gas and oxygen gas, a mixed gas of CHF3, CHF3 and CF4, a mixed gas of SF6 and helium gas, or the like.

[0052] The processing state detection unit 8 can detect the state of the processing object 100 based on an optical change that occurs during the plasma processing. For example, the processing state detection unit 8 can detect the end point of the plasma processing. The processing state detection unit 8 can include an optical path changing unit 81 and a detection unit 82 .

[0053] The optical path changing section 81 can be provided inside the window 23. The optical path changing section 81 changes the optical path of the incident light between a direction from the window 23 toward the mounting section 31 (thickness direction of the window 23) and a direction perpendicular to the direction from the window 23 toward the mounting section 31 (direction perpendicular to the thickness direction of the window 23). For example, the optical path changing section 81 may be provided locally inside the window 23 and may have a surface (reflective surface) that is inclined with respect to the central axis 2a of the chamber 2.

[0054] FIG. 3 is a schematic cross-sectional view illustrating the optical path changing unit 81. As shown in FIG. 3 may be a recess that opens onto the surface of the window 23 opposite the mounting portion 31. For example, the bottom surface of the recess that is the optical path changing portion 81 is a flat surface, and the bottom surface is a reflective surface 81a. The angle between the surface 81a and the central axis 2a of the chamber 2 may be set to 45°. The outer shape of the recess may be, for example, a cylinder or a polygonal prism.

[0055] 3, the optical path changing unit 81 can reflect the incident light La so that the angle between the optical path of the incident light La and the optical path of the output light Lb is 90°. That is, the angle of incidence of the incident light La on the surface 81a can be set to 45°. The reflection angle can be set to 45°.

[0056] 3 illustrates an example in which light is incident from the thickness direction of the window 23 (light is incident on the light path changing unit 81 from the mounting unit 31 side), but the traveling direction of the inspection light is also changed by the light path changing unit 81 when the inspection light is incident on the side surface (circumferential end surface side) of the window 23. The traveling direction of the inspection light emitted from the light path changing unit 81 and reflected by the processing object 100 is also changed by the light path changing unit 81, similarly to the incident light La. In this case as well, the angle of incidence of the light traveling from the detection unit 82 to the surface 81a can be 45°. The reflection angle can be 45°.

[0057] The optical path changing section 81 illustrated in FIG. 3 is a recess as described above. The inside of the optical path changing section 81 may be a space or may be filled with a gas, liquid, or solid. Also, a film containing a material with high reflectivity (for example, a film containing titanium oxide) may be formed on the surface 81a. When filling the inside of the optical path changing section 81 with a gas, liquid, or solid, or providing a film on the surface 81a, it is preferable to use an insulating gas, liquid, or solid. In this way, it is possible to suppress the optical path changing section 81 from affecting the electromagnetic field formed by the power supply section 5. In addition, if surface 81a has irregularities, the irregularities will scatter light, so it is preferable to increase the flatness of surface 81a. For example, the surface roughness of surface 81a can be reduced to Ra 0.02 or less by optical polishing.

[0058] 4A and 4B are schematic cross-sectional views illustrating modified examples of the optical path changing unit. As shown in FIG. 4(a), the optical path changing portion 81b can have a small depth dimension d. If the depth dimension d is small, the length of the cutting tool used to cut the recess that becomes the optical path changing portion 81b can be shortened. The shorter the length of the cutting tool, the higher the rigidity of the cutting tool can be. This reduces the vibration of the cutting tool, improving the flatness of the bottom surface (surface 81ba) of the recess that becomes the optical path changing portion 81b. For example, when the surface 81ba is circular, the depth dimension d is preferably 0.5 to 1.0 times the diameter of the surface. When the surface 81ba is rectangular, the depth dimension d is preferably 0.5 to 1.0 times the diameter of the inscribed circle of the surface 81ba.

[0059] Also, as shown in FIG. 4(b), the optical path changing portion 81c can have a large area of ​​the bottom surface (surface 81ca). By increasing the area of ​​the surface 81ca, a cutting tool with a large cross-sectional area can be used. The rigidity of the cutting tool can be increased by the amount of the cross-sectional area of ​​the cutting tool. This reduces vibration of the cutting tool, and improves the flatness of the bottom surface (surface 81ca) of the recess that becomes the optical path changing portion 81c. Alternatively, the depth of the recess may be reduced and the area of ​​the bottom surface of the recess may be increased. In this way, the flatness of the bottom surface can be further improved. In addition, optical polishing becomes easier, so that the flatness of the bottom surface can be more easily adjusted to a desired value.

[0060] Here, the cross-sectional area of ​​the optical path changing section 81 in the direction perpendicular to the central axis 2a (see "D" in FIG. 7) is preferably 1.95% or less of the area of ​​the surface of the window 23 on the side opposite to the mounting section 31. Alternatively, it is preferable that the load applied to the optical path changing section 81 is 9.8% or less of the allowable load of the window 23. If the load applied to the optical path changing section 81 is at this level, the durability of the window 23 with the optical path changing section 81 can be considered to be substantially equivalent to the durability of a window without the optical path changing section 81. In other words, by doing so, the strength (vacuum resistance strength) of the window 23 can be maintained.

[0061] Moreover, it is more preferable that the cross-sectional area of ​​the optical path changing section 81 in the direction perpendicular to the central axis 2a (see "D" in FIG. 7) is 0.5% or less of the area of ​​the face of the window 23 on the side opposite to the mounting section 31. Alternatively, it is more preferable that the load applied to the optical path changing section 81 is 5.0% or less of the allowable load of the window 23. In this way, the change in the capacitance of the window 23 can be made small, and therefore the influence of the optical path changing section 81 on the electromagnetic field formed by the power supply section 5 can be suppressed.

[0062] FIG. 5 is a schematic cross-sectional view illustrating another modified example of the optical path changing portion. The optical path changing section 81d illustrated in FIG. 5 is a polygonal prism-shaped (e.g., quadrangular prism-shaped) recess having a flat side surface 81da. The side surface 81da of the optical path changing section 81d is inclined at an angle of 45° with respect to the upper surface of the window section 23 (the surface opposite to the mounting section 31 side). In this way, the incident light La that is incident on the side surface 81da from a direction perpendicular to the upper surface of the window section 23 can be made into the outgoing light Lb that is reflected toward a direction parallel to the upper surface of the window section 23. In this case, the side surface of the recess can be easily made larger in area than the bottom surface of the recess, which makes it easier to perform optical polishing.

[0063] Here, a part of the light that enters the inside of the window 23 from the surface of the window 23 facing the placement portion 31 is reflected inside the window 23 and exits to the outside from a flat surface 23a provided on the side of the window 23. Therefore, the light exiting to the outside from the side of the window 23 can also be detected by the detection portion 82. However, in this case, the intensity of the light that enters the detection portion 82 is the average value of the light intensity in a relatively wide range, making it difficult to detect slight changes in the surface of the workpiece 100 to be treated.

[0064] In recent years, the processed parts have become finer, and the opening ratio of the unevenness or holes formed may be 1% or less. In such cases, the amount of material removed is small, and the amount of change in light is very small. Therefore, if light emission is detected over a wide area, it becomes even more difficult to detect slight changes in the surface of the processed object 100.

[0065] As described above, the electrode 51, the Faraday shield 54, and the like are provided on the window 23. Therefore, when detecting light emitted in the thickness direction of the window 23, the electrode 51, the Faraday shield 54, and the like may get in the way, making it impossible to detect light in appropriate positions.

[0066] As described above, the cross-sectional area of ​​the optical path changing section 81 can be reduced, and the optical path changing section 81 can be provided at any position in the window 23. This makes it possible to detect changes in light in a narrow area (detection area) at an appropriate position. As a result, even in fine processing, the end point of the plasma processing can be detected with high accuracy, and thus fine processing can be performed with high accuracy.

[0067] In addition, since the angle between the optical path of the incident light and the optical path of the outgoing light can be set to 90°, the detection unit 82 can be disposed on the flat surface 23a provided on the side surface of the window 23. Therefore, it becomes possible to dispose the detection unit 82 in an appropriate position regardless of the shapes and positions of the electrodes 51, the Faraday shield 54, etc.

[0068] The detection unit 82 may have a light-projecting unit and a light-receiving unit. The light-projecting unit can irradiate the surface of the processing object 100 with inspection light via the light path changing unit 81. The light-receiving unit can receive light reflected from the surface of the processing object 100 and traveling toward the light-receiving unit via the light path changing unit 81, and interference light of light emitted from the light-projecting unit. For example, the detection unit 82 irradiates light onto the surface of the processing object 100 via the surface 81a of the light path changing unit 81. The light reflected from the surface of the processing object 100 and further reflected by the surface 81a of the light path changing unit 81 enters the detection unit 82. In this case, the detector 82 can detect the state of the workpiece 100 (for example, the end point of the plasma processing) based on the change in the interference light.

[0069] The detector 82 is not limited to the one exemplified above, and may be any detector capable of detecting an optical change. For example, the detector 82 may further include a spectroscope. If a spectroscope is provided, it is possible to extract light having a predetermined wavelength, thereby improving the detection accuracy.

[0070] In addition, it is preferable that most of the light reflected by the surface of the processing object 100 is incident on the surface 81a of the light path changing unit 81. In other words, it is preferable that the optical axis of the inspection light bent by the light path changing unit 81 and the optical axis of the inspection light reflected by the surface of the processing object 100 are substantially the same. For this purpose, it is preferable that the window 23 and the mounting unit 31 are substantially parallel. However, as described above, when the support unit 32 that supports the mounting unit 31 has a cantilever structure, the mounting unit 31 may tilt. For this reason, when using the detection unit 82 having a light projecting unit and a light receiving unit and the mounting unit 31 having a cantilever structure, it is preferable that the thickness (t1) of the upper side of the beam 32b is thicker than the thickness (t2) of the lower side of the beam 32b (t1>t2). If "t1>t2", it becomes easy to make the window 23 and the mounting portion 31 approximately parallel, so that the optical axis of the inspection light bent by the optical path changing portion 81 and the optical axis of the inspection light reflected on the surface of the workpiece 100 can be made approximately the same.

[0071] 1 and 6, the light path changing unit 81 and the detection unit 82 can also be connected via a light guiding unit 83 and an optical axis adjustment unit 84. In this case, the tip of the light guiding unit 83 is connected to the optical axis adjustment unit 84. The light guiding unit 83 can be, for example, an optical fiber. The light guiding unit 83 is not necessarily required, and the detection unit 82 may be provided in the optical axis adjustment unit 84. However, if the light guiding unit 83 is provided, it becomes easier to provide the detection unit 82 at a desired position.

[0072] The optical axis adjustment unit 84 is a member that adjusts the optical axis of the inspection light. For example, the tip of the light guiding unit 83 is disposed at a position where the optical axis of the inspection light emitted from the tip of the light guiding unit 83 does not overlap with a perpendicular line to the flat surface 23a provided on the side surface of the window 23. Specifically, the tip of light guiding section 83 or detection section 82 can be moved in the X and Y directions, and can be rotated on a plane perpendicular to central axis 2a (XY plane).

[0073] The optical axis adjustment unit 84 includes, for example, a rotation drive unit 84a and a movement unit 84b. Rotation drive unit 84a can be rotated by a rotational force of a rotating device (not shown). Rotation drive unit 84a is connected to, for example, the tip of light guiding unit 83. The rotation axis of rotation drive unit 84a is parallel to central axis 2a. Therefore, the tip of light guiding unit 83 can be rotated on the XY plane. The moving unit 84b is, for example, a two-axis table capable of two-axis control. The moving unit 84b is connected to the rotation drive unit 84a and moves the rotation drive unit 84a in the X direction and the Y direction.

[0074] The optical axis adjustment unit 84 is not necessarily required, and the detection unit 82 may be provided at a position where the optical axis of the inspection light emitted from the tip of the detection unit 82 does not overlap with a perpendicular line to the flat surface 23a provided on the side surface of the window 23. However, if the optical axis adjustment unit 84 is provided, it becomes easy to provide the detection unit 82 or the light guiding unit 83 at a desired position.

[0075] Incidentally, when inspection light is irradiated onto flat surface 23a provided on the side surface of window 23, the light is split into light that travels inside window 23 and light that is reflected by flat surface 23a. When inspection light is irradiated from a direction perpendicular to flat surface 23a, the light reflected by flat surface 23a enters the light receiving section of detection unit 82. When light other than the light reflected by the surface of object 100 containing information about the surface of object 100 enters detection unit 82, the signal-to-noise ratio of the signal output from detection unit 82 deteriorates.

[0076] Therefore, as described above, the detection unit 82 is disposed at a position where the optical axis of the inspection light does not overlap with the perpendicular line to the flat surface 23a provided on the side surface of the window 23. In other words, the detection unit 82 irradiates the inspection light onto the flat surface 23a provided on the side surface of the window 23 from an inclined position.

[0077] 7 is a schematic plan view illustrating the relationship between the flat surface 23a provided on the side surface of the window and the optical path changing unit 81, and the relationship between the flat surface 23a and the detection unit 82. For the sake of simplicity, it is assumed that the inspection light includes inspection light L1 parallel to the optical axis, and inspection light L2 and inspection light L3 that spread from the inspection light L1 at a spread angle θ3.

[0078] As shown in FIG. 7, the detection unit 82 irradiates the inspection light from a position inclined by a first angle θ1 with respect to a perpendicular line 23b to a flat surface 23a provided on a side surface of the window 23. In this way, the optical path of the inspection light L1 intersects with the perpendicular line 23b at a position where the optical path of the inspection light L1 hits the flat surface 23a, and the angle between the optical path of the inspection light L1 and the perpendicular line 23b forms the first angle θ1. In other words, the angle between the inspection light L1 and the perpendicular line 23b becomes the first angle θ1. Note that the inspection light L2 that spreads from the inspection light L1 at a spread angle θ3 intersects with the perpendicular line 23b at a position where the optical path of the inspection light L2 hits the flat surface 23a, and the angle between the optical path of the inspection light L1 and the perpendicular line 23b becomes an angle smaller than the first angle θ1. In addition, the inspection light L3 that spreads from the inspection light L1 at a spread angle θ3 intersects with the perpendicular line 23b at the position where the optical path of the inspection light L2 hits the flat surface 23a, and the angle between the optical path of the inspection light L3 and the perpendicular line 23b is greater than the first angle θ1.

[0079] In this embodiment, by irradiating the inspection light from a position inclined at a first angle θ1 with respect to the perpendicular 23b to the flat surface 23a provided on the side of the window 23, it is possible to prevent the light reflected from the flat surface 23a from entering the light receiving section of the detection unit 82.

[0080] There are two positions inclined by the first angle θ1 with respect to the perpendicular line 23b. The position at which the detection unit 82 is provided may be a position where the optical axis of the inspection light L1 refracted by the flat surface 23a overlaps with the center of the surface 81a. For example, the position at which the detection unit 82 is provided may be a position where the light from a light-emitting diode is irradiated onto the flat surface 23a and the irradiated light is directed toward the surface 81a.

[0081] The inspection light emitted from the detection unit 82 has a spread angle θ3. Fig. 8 is a schematic plan view illustrating a case where the first angle θ1 and the spread angle θ3 are the same angle. For the sake of simplicity, the inspection light is assumed to include inspection light L1 parallel to the optical axis, and inspection light L2 and inspection light L3 that spread from the inspection light L1 at a spread angle θ3.

[0082] As shown in FIG. 8, when the first angle θ1 and the spread angle θ3 are the same angle, the inspection light L2 is parallel to the perpendicular line 23b. That is, the inspection light L2 is incident perpendicularly to the flat surface 23a provided on the side of the window 23. The reflected light L1a of the inspection light L1 reflected by the flat surface 23a and the reflected light L3a of the inspection light L3 reflected by the flat surface 23a do not enter the light receiving section of the detection unit 82. However, the reflected light L2a of the inspection light L2 passes through the same optical path as the inspection light L2 and reaches the detection unit 82. Since light other than the reflected light reflected by the surface of the processing object 100, which has information on the surface of the processing object 100, enters the detection unit 82, the signal-to-noise ratio deteriorates. Therefore, it is preferable that the spread angle θ3 is smaller than the first angle θ1.

[0083] Returning to Fig. 7, the flat surface 23a of the window 23 will be described. A line 23c parallel to the flat surface 23a of the window 23 is parallel to the surface 81a of the optical path changing section 81, but is not parallel to a line 81f perpendicular to the central axis 2a. The angle between the line 23c and the line 81f forms a second angle θ2. In other words, the flat surface 23a is inclined by the second angle θ2 with respect to the line 81f.

[0084] The flat surface 23a of the window 23 can be produced, for example, by providing a notch on the side surface of the window 23. When providing the notch, the window 23 may be processed so that the surface of the notch is parallel to the surface 81a of the optical path changing section 81 and forms a second angle θ2 with a line 81f perpendicular to the central axis 2a. However, the window 23 is airtightly connected to the top plate 22 via a sealing member (not shown) at the outer periphery of the window 23. Therefore, if the second angle is large, the notch also becomes large, and there is a risk that the sealing member (not shown) may protrude from the window 23. Therefore, the second angle θ2 is preferably set to 5 degrees to 10 degrees.

[0085] Incidentally, it is preferable that the first angle θ1 of the detection unit 82 is adjusted so that the refraction angle θn of the light that transmits through the flat surface 23a of the window 23, out of the inspection light irradiated onto the flat surface 23a of the window 23, is the same as the second angle θ2. By adjusting the detection unit 82 in this manner, the light that transmits through the flat surface 23a is made to be perpendicularly incident on the surface 81a of the optical path changing unit 81.

[0086] Here, if the refractive index of the atmosphere outside the device in which the detection unit 82 is provided is n1 and the refractive index of the window 23 is n2, the relationship between the first angle θ1, which is the angle of incidence, and the refraction angle θn can be considered to be given by equation (1) according to Snell's law. n2 / n1=Sinθ1 / Sinθn … (1)

[0087] As described above, if the refraction angle θn is the same as the second angle θ2, and the second angle θ2 is 10 degrees or less, the Sinθ1 / Sinθn part of equation (1) can be transformed into equation (2). Sinθ1 / Sinθ2=θ1 / θ2 … (2)

[0088] Substituting equation (2) into equation (1) and rearranging it gives equation (3). θ1=θ2×n2 / n1 … (3)

[0089] Here, since the atmosphere outside the device where the detection unit 82 is provided is atmospheric air, the value of n1 can be approximated to 1. Substituting n1=1 into equation (3), the following equation is obtained. θ1=θ2×n2 … (4)

[0090] 7, the inspection light is a point light source. However, in reality, the inspection light is irradiated from the aperture of the detection unit 82, and the light reflected from the surface of the processing object 100 is incident on the aperture via the optical path changing unit 81. In other words, the inspection light is light having a cross-sectional area derived from the aperture diameter, and the light receiving unit also has a light receiving area derived from the aperture diameter.

[0091] Figure 9(a) and (b) show the aperture diameter AP r The inspection light having a cross-sectional area derived from the aperture diameter AP r 2 is a schematic plan view illustrating the relationship between a detection unit 182 having a light receiving area derived from the above and a flat surface 23a provided on a side surface of the window. As shown in FIG. 9(a), the aperture has a thickness AP t The detection unit 182 has a thickness AP t The light source is disposed at a position where the inspection light L2 and the inspection light L3 that spread from the inspection light L1 at a spread angle θ3 are not blocked. r The diameter of the inspection light having a cross-sectional area derived from the aperture diameter AP r Less than.

[0092] As shown in Figure 9(a), if the distance S between the flat surface 23a on the side of the window 23 and the detection unit 182 is sufficiently large, the reflected light L2a reflected by the flat surface 23a out of the light L2 that spreads at a spread angle θ3 and the reflected light L3a reflected by the flat surface 23a out of the light L3 that spreads at a spread angle θ3 will not enter the light receiving unit through the aperture.

[0093] However, as shown in FIG. 9(b), when the distance S between the flat surface 23a on the side of the window 23 and the detection unit 182 is short, of the light L3 that spreads at a spread angle θ3, reflected light L3a reflected by the flat surface 23a enters the light receiving unit through the aperture.

[0094] FIG. 10 is a schematic enlarged view of the periphery of the light L3 that spreads at a spread angle θ3 in FIG. 9(b). 10, the angle GDB is a first angle θ1, and the angle ECF is a third angle θ3.

[0095] The length of the line segment AC is the aperture diameter AP r The length of the line segment AH is the diameter of the inspection light having a cross-sectional area derived from the aperture diameter AP. rThe inspection light L1 is a light that travels perpendicular to the aperture and passes through the center of the aperture. Therefore, the length of the line segments AB and BH is half the length of the line segment AH. As mentioned above, the aperture diameter AP r The diameter of the inspection light having a cross-sectional area derived from the aperture diameter AP r Therefore, the line segment BC is shorter than the line segment BH. The line segments DG and FB are lines perpendicular to the flat surface 23a. The line segment CE is a straight line parallel to the line segment BD.

[0096] Angle BDE is (90-θ1) degrees. Since angles BDE and CEF are similar figures, angle CEF is also (90-θ1) degrees. As mentioned above, angle ECF is θ3 degrees. The sum of the interior angles of triangle CEF is 180 degrees. Therefore, angle CFE is [180-{(90-θ1)+θ3}] degrees. Rearranging the parts in [], angle CFE becomes (90+θ1-θ3) degrees.

[0097] Here, angle EFB is 90 degrees. Angle BFC can be found by subtracting angle EFB from angle CFE. Therefore, angle BFC is (θ1-θ3) degrees. Since angles BFC and AFB are the angles of incidence and reflection, angle AFB is also (θ1-θ3) degrees. Therefore, angle AFC is 2(θ1-θ3) degrees.

[0098] Now, if we call the right-angled triangle AFC', the following relationship holds: tan2(θ1-θ3)=line segment AC' / line segment FC' … (4)

[0099] As shown in FIG. 9, the length of the line segment AC' is smaller than the length of the line segment AH. In other words, the length of the line segment AC' is smaller than the aperture diameter AP r The length S' of the line segment FC' is approximately the same as the distance S between the flat surface 23a on the side surface of the window 23 and the detection unit 182. r By substituting the line segment FC'=S into equation (4), the following equation holds: S=APr / tan2(θ1-θ3) … Equation (5)

[0100] The length of the line segment AC' is AP r Therefore, if the value of S is greater than the value on the right side of equation (5), it is possible to prevent light L3a reflected by flat surface 23a from entering the light receiving portion of detection unit 182. Therefore, the distance S between detection unit 182 and flat surface 23a provided on the side surface of window 23 can be calculated from the following equation. S>AP r / tan2(θ1-θ3) … Equation (6)

[0101] Here, the refractive index n2 of the window 23 is 1.44, and the aperture diameter AP r Assuming the value of φ5mm, AP r The value of / tan2(θ1-θ3) was calculated. Figure 11 shows the relationship between 2(θ1-θ3), tan2(θ1-θ3) and AP r 11 is a table illustrating the relationship of / tan2(θ1-θ3).

[0102] As described above, the second angle θ2 is preferably set to 5 degrees to 10 degrees. Therefore, by substituting θ2 and n2 into formula (4), θ1 becomes 7.2 degrees to 14.4 degrees. As described above, the spread angle θ3 is preferably smaller than the first angle θ1. Therefore, the value of tan2(θ1-θ3) was calculated when the value of 2(θ1-θ3) was between 1 degree and 28 degrees.

[0103] As shown in FIG. 11, when the value of 2(θ1-θ3) increases, the value of tan2(θ1-θ3) also increases. In other words, tan2(θ1-θ3) is proportional to 2(θ1-θ3). Also, AP r Since is a constant value, AP r / tan2(θ1-θ3) is inversely proportional to tan2(θ1-θ3). In other words, AP r / tan2(θ1-θ3) is inversely proportional to 2(θ1-θ3). Therefore, when the value of 2(θ1-θ3) is between 1 degree and 28 degrees, the value of 2(θ1-θ3), the value of tan2(θ1-θ3), and AP r Intermediate values ​​of / tan2(θ1-θ3) are omitted.

[0104] When the difference between the first angle θ1 and the third angle θ3 is greater than 1 degree, if the distance S between the flat surface 23a on the side of the window 23 and the detection unit 182 is set to 150 mm or more, the light reflected by the flat surface 23a among the light that spreads at the spread angle θ3 will not enter the light receiving unit through the aperture.

[0105] The intensity of the reflected light incident on the light receiving unit is proportional to the intensity of the inspection light irradiated by the detection unit 182. The intensity of the inspection light irradiated by the detection unit 182 increases as the distance between the detection unit 182 and the flat surface 23a provided on the side surface of the window 23 decreases. As shown in Fig. 11, the larger the value of 2(θ1-θ3), the greater the AP r The value of / tan2(θ1-θ3) becomes smaller. Therefore, the greater the difference between the first angle and the third angle, the smaller the distance L between the flat surface 23a provided on the side surface of the window 23 and the detection unit 182 can be. In other words, the smaller the value of θ3, the more preferable.

[0106] Therefore, it is preferable to provide a collimator at the tip of detection unit 182 or light guiding unit 83. By providing a collimator, the third angle θ3 can be made smaller than 1 degree. Therefore, it is not necessary to consider the third angle θ3, and formula (6) can be expressed as follows. S>AP r / tan2θ1 (7.2≦θ1≦14.4) … Equation (7)

[0107] When a collimator is installed, if the value of θ1 is 8 degrees, the AP rThe value of / tan2θ1 is 35.6 mm. Therefore, if the value of the distance S between the flat surface 23a provided on the side surface of the window 23 and the detection unit 182 is set to 40 mm or more, the light reflected by the flat surface 23a of the light that spreads at the spread angle θ3 will not enter the light receiving unit through the aperture.

[0108] In addition, if surface 23a has unevenness, the unevenness will scatter light, so it is preferable to increase the flatness of surface 23a, similar to surface 81a. For example, the surface roughness of surface 23a can be reduced to Ra 0.02 or less by optical polishing.

[0109] Furthermore, the light guide unit 83 can have a plurality of optical fibers. The detection unit 82 can have a plurality of spectrometers. And, one optical fiber can be connected to one spectrometer. In this way, it becomes easy to detect the interference light described above.

[0110] It is also possible to provide a plurality of optical path changing units 81. If a plurality of optical path changing units 81 are provided, it is possible to know the processing states at a plurality of locations, and by selecting an optical path changing unit 81 to be used for detection, it is possible to know the processing states at a plurality of locations without increasing the number of detection units 82.

[0111] The control unit 9 may include a calculation unit such as a CPU (Central Processing Unit) and a storage unit such as a memory. Based on a control program stored in the storage unit, the control unit 9 can control the operation of each element provided in the plasma processing apparatus 1. For example, the control unit 9 can end the plasma processing based on an output from the processing status detection unit 8 (detection unit 82).

[0112] 7 is easy to process and is therefore preferable, but the shape of the flat surface 23a of the window 23 is not limited to this. 12, for example, a recess 123 is provided on the side surface of a circular plate at a position intersecting the optical axis of the inspection light. A bottom surface 123a of the recess 123 is provided such that a line 123c parallel to the bottom surface 123a of the recess 123 and a line 81f parallel to the surface 81a, which is the reflecting surface of the optical path changing unit 81, and perpendicular to the central axis 2a form a second angle θ2.

[0113] 13, for example, a convex portion 223 is provided on the side surface of a circular plate at a position intersecting the optical axis of the inspection light. A surface 223a of the convex portion 223 is provided so that the surface 223a of the convex portion 223 and a line 81f that is parallel to the surface 81a, which is the reflecting surface of the optical path changing unit 81, and perpendicular to the central axis 2a form a second angle θ2.

[0114] By providing the protrusion 223 on the window 23, it is not necessary to consider interference between a sealing member (not shown) that airtightly seals the window 23 and the top plate 22 and the surface 223a of the protrusion 223. Therefore, the second angle θ2 can be increased to about 40 degrees. Accordingly, the first angle θ1 can also be increased to a maximum of 55 degrees. Therefore, the value of the distance S between the flat surface 23a provided on the side surface of the window 23 and the detection unit 82 can be reduced. Therefore, the intensity of the reflected light incident on the light receiving unit can be increased. The second angle θ2 is 45 degrees or less in order to prevent the light reflected from the surface of the processing object 100 and traveling toward the light receiving part via the optical path changing part 81 from being totally reflected from the flat surface 23a.

[0115] 14A and 14B are schematic cross-sectional views illustrating an optical path changing unit 181 according to another embodiment. 14(a) and (b), the light path changing part 181 can be provided inside the window 23. The light path changing part 181 has a flat end surface 181a, and the angle between the end surface 181a and the central axis 2a of the chamber 2 can be set to 45°.

[0116] 14(a), the optical path changing section 181 can be embedded inside the window 23. For example, the optical path changing section 181 can be embedded when forming the window 23. For example, the optical path changing section 181 can be formed by irradiating the window 23 with a laser and processing the inside of the window 23.

[0117] As shown in FIG. 14(b), a recess 181b may be provided in the window 23, and an optical path changing section 181 may be provided inside the recess 181b. The optical path changing section 181 is preferably formed from a material having high reflectance and insulating properties. For example, the optical path changing section 181 may be formed by processing the inside of the window 23, or may be a film containing titanium oxide. If the optical path changing section 181 is formed to have insulating properties, it is possible to suppress the optical path changing section 181 from affecting the electromagnetic field formed by the power supply section 5.

[0118] FIG. 15 is a schematic cross-sectional view illustrating a plasma processing apparatus 101 according to another embodiment. 15, the plasma processing apparatus 101 can be provided with a chamber 102, a mounting unit 103, a power supply unit 4, a power supply unit 5, a pressure reduction unit 106, a gas supply unit 7, a processing state detection unit 8, and a control unit 109. In the plasma processing apparatus 101, the power supply unit 5 also serves as a plasma generating unit that generates plasma P inside the chamber 102.

[0119] The chamber 102 may have an airtight structure capable of maintaining an atmosphere at a pressure lower than atmospheric pressure. The chamber 102 can have a body portion 102 a and a window 23 . The main body 102a may be an integrated unit of a top plate, a bottom plate, and a substantially cylindrical side portion. The main body 102a may be made of a metal such as an aluminum alloy. The main body 102a may be grounded. An area 102b where plasma P is generated is provided inside the main body 102a. The main body 102a may be provided with an inlet / outlet 102c for carrying in and out the workpiece 100. The inlet / outlet 102c may be airtightly closed by a gate valve 102d.

[0120] The mounting portion 103 can be provided inside the chamber 102 (main body portion 102a) on the bottom surface of the main body portion 102a. The mounting portion 103 can have an electrode 103a, a base 103b, and an insulating ring 103c. The inside of the mounting portion 103 can be connected to the external space (atmospheric space).

[0121] The electrode 103a can be provided below the region 102b where the plasma P is generated. The upper surface of the electrode 103a can be a mounting surface for mounting the object 100 to be treated. The electrode 103a can be made of a conductive material such as a metal. Similarly to the above-mentioned electrode 31a, the electrode 103a can have a plurality of pickup pins, a temperature control unit, and the like built therein.

[0122] The base 103b can be provided between the electrode 103a and the bottom surface of the main body 102a. The base 103b can be provided to insulate the electrode 103a from the main body 102a. The base 103b can be made of a dielectric material such as quartz.

[0123] The insulating ring 103c has a ring shape and can be provided so as to cover the side surface of the electrode 103a and the side surface of the base 103b. The insulating ring 103c can be made of a dielectric material such as quartz.

[0124] The plasma processing apparatus 101 according to this embodiment can also be provided with the power supply unit 4 described above. As described above, the power supply unit 4 can be a so-called high-frequency power supply for bias control. The matching circuit 42a can be electrically connected to the power supply 41 and the electrode 103a via the bus bar 42c. Since the inside of the mounting unit 103 is connected to the atmospheric space, the bus bar 42c can be in contact with the atmospheric space.

[0125] The plasma processing apparatus 101 may also be a dual frequency plasma etching apparatus having an inductively coupled electrode in the upper portion and a capacitively coupled electrode in the lower portion. However, the method of generating plasma is not limited to the example given. The plasma processing apparatus 101 may be, for example, a plasma processing apparatus using inductively coupled plasma (ICP) or a plasma processing apparatus using capacitively coupled plasma (CCP).

[0126] The pressure reducing section 106 may include a pump 106a and a pressure control section 106b. The pressure reducing unit 106 can reduce the pressure inside the chamber 102 to a predetermined pressure. The pump 106a can be, for example, a turbo molecular pump. Note that a roots type dry pump can be connected to the turbo molecular pump as a back pump. The pump 106a and the pressure control unit 106b can be connected via piping.

[0127] The pressure control unit 106b can control the internal pressure of the chamber 102 to a predetermined pressure based on the output of a vacuum gauge (not shown) that detects the internal pressure of the chamber 102. The vacuum gauge can be a diaphragm-type capacitance manometer or the like. The pressure control unit 106b can be, for example, an APC (Auto Pressure Controller) or the like. The pressure control unit 106b can be connected to an exhaust port 102e provided in the main body 102a via a pipe.

[0128] The control unit 109 may include a calculation unit such as a CPU and a storage unit such as a memory. The control unit 109 may control the operation of each element provided in the plasma processing apparatus 101 based on a control program stored in the storage unit. For example, the control unit 109 may end the plasma processing based on an output from the processing status detection unit 8 (detection unit 82). The plasma processing apparatus 101 according to this embodiment is also provided with the processing state detection unit 8, and therefore can enjoy the above-mentioned effects.

[0129] Although the embodiments have been described above, the present invention is not limited to these descriptions. Any modifications to the above-described embodiments made by those skilled in the art are also encompassed within the scope of the present invention as long as they incorporate the features of the present invention. For example, the shapes, materials, arrangements, and the like of the components included in the plasma processing apparatuses 1 and 101 are not limited to those exemplified, and can be changed as appropriate. Furthermore, the elements of each of the above-described embodiments can be combined to the greatest extent possible, and combinations of these are also included within the scope of the present invention as long as they include the features of the present invention. [Explanation of symbols]

[0130] REFERENCE SIGNS LIST 1 plasma processing apparatus, 2 chamber, 2a central axis, 3 placement module, 4 power supply unit, 5 power supply unit, 6 pressure reduction unit, 7 gas supply unit, 8 processing state detection unit, 9 control unit, 23 window, 23a flat surface, 31 placement unit, 81 light path changing unit, 81a surface, 82 detection unit, 83 light guide unit, 100 processing object, 101 plasma processing apparatus, 102 chamber, 103 placement unit, 106 pressure reduction unit

Claims

1. A chamber capable of maintaining an atmosphere reduced in pressure below atmospheric pressure; a gas supply unit capable of supplying a gas into the chamber; a placement part provided inside the chamber, on which an object to be treated can be placed; a pressure reducing unit capable of reducing the pressure inside the chamber; a window provided in the chamber and facing the placement portion; a plasma generating unit that is provided outside the chamber, on a surface of the window opposite to the placement portion, and that is capable of generating plasma inside the chamber; an optical path changing unit provided locally inside the window and having a surface inclined with respect to a central axis of the chamber; a detection unit provided outside the chamber and detecting a state of the object to be processed through the optical path changing unit; Equipped with the window has a flat surface on a side surface thereof that is inclined with respect to a line that is parallel to the surface of the optical path changing unit and perpendicular to a central axis of the chamber, The flat surface refracts the optical path of light irradiated from the detection unit.

2. The detection unit is provided on a side surface of the window, The plasma processing apparatus according to claim 1 , wherein the detection unit irradiates the light from a position inclined at a first angle with respect to a perpendicular line to the flat surface.

3. the flat surface of the window is inclined at a second angle with respect to a line that is parallel to the surface of the optical path changing section and perpendicular to a central axis of the chamber; the first angle is greater than or equal to 8 degrees and less than or equal to 55 degrees; 3. The plasma processing apparatus according to claim 2, wherein the second angle is equal to or greater than 5 degrees and equal to or less than 40 degrees.

4. The flat surface of the window is inclined at a second angle with respect to a line that is parallel to the surface of the optical path changing section and perpendicular to a central axis of the chamber; the second angle is greater than or equal to 5 degrees and less than or equal to 10 degrees; a refraction angle of the light refracted at the flat surface is equal to the second angle; The plasma processing apparatus according to claim 2 , wherein the first angle can be calculated by multiplying the second angle by a refractive index of the window.

5. The light emitted by the detection unit has a spread angle, 5. The plasma processing apparatus according to claim 2, wherein the divergence angle is smaller than the first angle.

6. The detection unit has an aperture through which the light is irradiated or incident, 6. The plasma processing apparatus according to claim 5, wherein the following formula is satisfied when the first angle is θ1, the spread angle is θ3, the diameter of the aperture is AP, and the distance between the flat surface and the detection unit is S: S>AP / tan2(θ1-θ3)

7. 7. The plasma processing apparatus according to claim 1, wherein the surface of the optical path changing part is a flat surface, and an angle between the surface and a central axis of the chamber is 45 degrees.

8. 8. The plasma processing apparatus according to claim 1, wherein the light traveling from the detection unit toward the surface has an incident angle of 45° and a reflection angle of 45° on the surface.

9. 9. The plasma processing apparatus according to claim 1, wherein the optical path changing section is a recess that opens onto a surface of the window opposite to the placement section.

10. 10. The plasma processing apparatus according to claim 1, further comprising a light guiding section provided between the flat surface and the detection section.

11. The light guide portion includes a plurality of optical fibers, The detection unit has a plurality of spectroscopes, 11. The plasma processing apparatus according to claim 10, wherein one of the optical fibers is connected to one of the spectrometers.

12. A plasma processing apparatus as described in claim 10 or 11, further comprising an optical axis adjustment unit that can adjust the direction of the optical axis of the light by rotating or moving the detection unit or the light-guiding unit on a plane perpendicular to the central axis of the chamber.

13. 13. The plasma processing apparatus according to claim 10, wherein the detection section or the light guiding section further comprises a collimator.

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