JP2018107202A - Plasma processing apparatus and plasma control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress occurrence of abnormality in plasma processing for wafer.SOLUTION: A plasma processing apparatus 100 has an upper top plate 16b functioning as an electrode, an irradiation unit 81, and a detector 82. The upper top plate 16b faces a plasma processing space, and an infrared reflection layer 85 is provided on the reverse face for the plasma processing space or in the plasma processing space. The irradiation unit 81 irradiates the upper top plate 16b with infrared radiation during plasma processing. The detector 82 detects signal intensity of infrared radiation reflected on the reflection layer 85. The plasma processing apparatus 100 measures the thickness of a reaction product produced on the upper top plate 16b based on the detected signal intensity of infrared radiation, and controls plasma so as to suppress reduction in the thickness of the reaction product or increase in the thickness of the reaction product, when the measured thickness of the reaction product exceeds a threshold level.SELECTED DRAWING: Figure 1

Description

  Various aspects and embodiments of the present invention relate to a plasma processing apparatus and a plasma control method.

  2. Description of the Related Art Conventionally, plasma processing apparatuses that perform plasma processing on an object to be processed such as a wafer using plasma are known. In such a plasma processing apparatus, for example, a processing gas is injected into a processing container, a voltage is applied to an electrode to generate plasma, and various types of etching and film formation are performed on a target object. Perform plasma treatment.

  In the plasma processing apparatus, a phenomenon in which a reaction product is deposited on the inner wall of the processing container occurs due to the plasma processing. The deposited reaction product is also referred to as a depot. The reaction product deposited on the inner wall of the processing container may be peeled off due to temperature change, pressure change, transporting operation of the object to be processed, and attached to the object to be processed, resulting in foreign matter. Therefore, a technique is known in which the inner wall of the processing container is irradiated with infrared light, and the film thickness of the reaction product deposited on the inner wall is monitored from the reflected light of the infrared light on the inner wall (see, for example, Patent Document 1 below) ).

JP 2000-3905 A

  However, the conventional technology may not be able to suppress the occurrence of abnormality in the plasma processing.

  In the plasma processing apparatus, reaction products are also deposited on the electrodes by the plasma processing. In the plasma processing apparatus, conditions change due to reaction products deposited on the electrodes, and abnormalities such as deterioration of process characteristics and generation of particles occur.

  In the conventional technology, since the deposition state of the reaction product on the electrode cannot be grasped, the change in the condition in the processing container cannot be grasped, and the occurrence of abnormality in the plasma processing cannot be suppressed.

  In one embodiment, the disclosed plasma processing apparatus includes an electrode, an irradiation unit, a detection unit, a measurement unit, and a plasma control unit. The electrode faces the plasma processing space, and an infrared reflection layer is provided on the back surface or inside the plasma processing space. The irradiation unit irradiates the electrode with infrared light during the plasma processing. The detection unit detects the signal intensity of the infrared light reflected by the reflective layer. A measurement part measures the film thickness of the reaction product which arises on an electrode based on the signal intensity | strength of the infrared light detected by the detection part. The plasma control unit controls the plasma so as to reduce the reaction product thickness or suppress the increase in the reaction product thickness when the thickness of the reaction product measured by the measurement unit exceeds a threshold value.

  According to one aspect of the disclosed plasma processing apparatus, it is possible to suppress the occurrence of abnormality in the plasma processing.

FIG. 1 is a schematic cross-sectional view showing a plasma processing apparatus according to an embodiment. FIG. 2 is a diagram showing a detailed configuration in the vicinity of the shower head. FIG. 3 is a diagram showing the polarization direction of infrared light. FIG. 4 is a diagram illustrating an example of a signal intensity distribution. FIG. 5 is a diagram illustrating an example of a distribution of signal intensity as a difference from the measurement start (Initial). FIG. 6 is a diagram illustrating an example of the relationship between the difference signal intensity and the film thickness. FIG. 7 is a flowchart showing an example of the flow of the plasma control method.

  Hereinafter, embodiments of a plasma processing apparatus and a plasma control method disclosed in the present application will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals. Moreover, the invention disclosed by this embodiment is not limited. Each embodiment can be appropriately combined as long as the processing contents do not contradict each other.

[Configuration of plasma processing apparatus]
FIG. 1 is a schematic cross-sectional view showing a plasma processing apparatus according to an embodiment. In one embodiment, the plasma processing apparatus 100 is an apparatus that performs a plasma etching process on an object to be processed. A plasma processing apparatus 100 shown in FIG. 1 has a processing chamber 1 that is hermetically configured and is electrically grounded. The processing chamber 1 has a cylindrical shape, and is made of, for example, aluminum having an anodized film formed on the surface thereof. In the processing chamber 1, a mounting table 2 that horizontally supports a semiconductor wafer W that is an object to be processed is provided.

  The mounting table 2 has a base 2a made of a conductive metal, such as aluminum, and has a function as a lower electrode. The mounting table 2 is supported by a conductor support 4 via an insulating plate 3. A focus ring 5 made of, for example, single crystal silicon is provided on the outer periphery above the mounting table 2. Further, a cylindrical inner wall member 3 a made of, for example, quartz is provided around the mounting table 2 and the support table 4 so as to surround the mounting table 2 and the support table 4.

  A first high frequency power source 10a is connected to the base material 2a of the mounting table 2 via a first matching unit 11a, and a second high frequency power source 10b is connected via a second matching unit 11b. Yes. The first high-frequency power source 10a is for generating plasma, and high-frequency power of a predetermined frequency (for example, 60 MHz) is supplied from the first high-frequency power source 10a to the base material 2a of the mounting table 2. Yes. The second high frequency power supply 10b is for ion penetration (for bias), and the second high frequency power supply 10b has a high frequency power having a predetermined frequency (for example, 400 kHz) lower than that of the first high frequency power supply 10a. Is supplied to the base material 2 a of the mounting table 2. On the other hand, a shower head 16 having a function as an upper electrode is provided above the mounting table 2 so as to face the mounting table 2 in parallel. The shower head 16 and the mounting table 2 have a pair of electrodes ( Upper electrode and lower electrode). A plasma processing space in which plasma is generated and plasma processing is performed is defined between the shower head 16 and the mounting table 2.

  An electrostatic chuck 6 for electrostatically attracting the semiconductor wafer W is provided on the upper surface of the mounting table 2. The electrostatic chuck 6 is configured by interposing an electrode 6a between insulators 6b, and a DC power source 12 is connected to the electrode 6a. When the DC voltage is applied from the DC power source 12 to the electrode 6a, the semiconductor wafer W is attracted by the Coulomb force.

  A refrigerant channel 2b is formed inside the mounting table 2, and a refrigerant inlet pipe 2c and a refrigerant outlet pipe 2d are connected to the refrigerant channel 2b. The support 4 and the mounting table 2 can be controlled to a predetermined temperature by circulating a coolant such as Galden in the coolant channel 2b. Further, a backside gas supply pipe 30 for supplying a cooling heat transfer gas (backside gas) such as helium gas is provided on the back surface side of the semiconductor wafer W so as to penetrate the mounting table 2 and the like. The backside gas supply pipe 30 is connected to a backside gas supply source (not shown). With these configurations, the semiconductor wafer W attracted and held on the upper surface of the mounting table 2 by the electrostatic chuck 6 can be controlled to a predetermined temperature.

  The shower head 16 described above is provided on the top wall portion of the processing chamber 1. The shower head 16 includes a main body portion 16 a and an upper top plate 16 b that forms an electrode plate, and is supported on the upper portion of the processing chamber 1 via an insulating member 45. The main body portion 16a is made of a conductive material, for example, aluminum whose surface is anodized, and is configured such that the upper top plate 16b can be detachably supported at the lower portion thereof. The upper top plate 16b is formed of a silicon-containing material, for example, silicon. The upper top plate 16b is an example of an electrode.

  Gas diffusion chambers 16c and 16d are provided inside the main body portion 16a, and a large number of gas flow holes 16e are formed at the bottom of the main body portion 16a so as to be positioned below the gas diffusion chambers 16c and 16d. Has been. The gas diffusion chamber is divided into two parts: a gas diffusion chamber 16c provided in the central portion and a gas diffusion chamber 16d provided in the peripheral portion. The supply state of the processing gas is independently determined in the central portion and the peripheral portion. It can be changed.

  The upper top plate 16b is provided with a gas introduction hole 16f penetrating the upper top plate 16b in the thickness direction so as to overlap the gas flow hole 16e. With such a configuration, the processing gas supplied to the gas diffusion chambers 16c and 16d is dispersed and supplied into the processing chamber 1 through the gas flow holes 16e and the gas introduction holes 16f. ing. The main body 16a and the like are provided with a pipe (not shown) for circulating the refrigerant so that the temperature of the shower head 16 can be controlled to a desired temperature during the plasma etching process.

  In the main body 16a, two gas inlets 16g and 16h for introducing the processing gas into the gas diffusion chambers 16c and 16d are formed. Gas supply pipes 15a and 15b are connected to the gas inlets 16g and 16h, and a processing gas supply source 15 for supplying a processing gas for etching is connected to the other ends of the gas supply pipes 15a and 15b. Has been. The processing gas supply source 15 is an example of a gas supply unit. The gas supply pipe 15a is provided with a mass flow controller (MFC) 15c and an on-off valve V1 in order from the upstream side. The gas supply pipe 15b is provided with a mass flow controller (MFC) 15d and an on-off valve V2 in order from the upstream side.

  Then, a processing gas for plasma etching is supplied from the processing gas supply source 15 to the gas diffusion chambers 16c and 16d through the gas supply pipes 15a and 15b, and gas flow holes are provided from the gas diffusion chambers 16c and 16d. 16e and the gas introduction hole 16f are distributed and supplied into the processing chamber 1 as a shower. For example, the processing gas supply source 15 supplies a processing gas used for etching the silicon oxide film, a cleaning gas used for cleaning, and the like.

  A variable DC power source 52 is electrically connected to the shower head 16 as the upper electrode through a low-pass filter (LPF) 51. The variable DC power supply 52 can be turned on / off by an on / off switch 53. The current / voltage of the variable DC power supply 52 and the on / off of the on / off switch 53 are controlled by a control unit 60 described later. As will be described later, when a high frequency is applied from the first high frequency power supply 10a and the second high frequency power supply 10b to the mounting table 2 to generate plasma in the processing space, the control unit 60 turns on as necessary. The off switch 53 is turned on, and a predetermined DC voltage is applied to the shower head 16 as the upper electrode.

  A cylindrical ground conductor 1 a is provided so as to extend upward from the side wall of the processing chamber 1 above the height position of the shower head 16. The cylindrical ground conductor 1a has a top wall at the top.

  An exhaust port 71 is formed at the bottom of the processing chamber 1, and an exhaust device 73 is connected to the exhaust port 71 via an exhaust pipe 72. The exhaust device 73 has a vacuum pump. By operating this vacuum pump, the inside of the processing chamber 1 can be depressurized to a predetermined degree of vacuum.

  In the figure, reference numerals 76 and 77 denote depot shields that are detachable. The deposition shield 76 is provided along the inner wall surface of the processing chamber 1 and has a role of preventing reaction products (depots) from adhering to the processing chamber 1. A conductive member (GND block) 79 connected to the ground in a DC manner is provided at substantially the same height as the semiconductor wafer W of the deposition shield 76, thereby preventing abnormal discharge.

  On the side wall of the processing chamber 1, a window 80 a and a window 80 b are provided at positions facing each other via the mounting table 2. The window 80a and the window 80b are sealed by fitting a member having transparency to infrared light such as quartz. An irradiation unit 81 that irradiates infrared light is provided outside the window 80a. A detection unit 82 capable of detecting infrared light is provided outside the window 80b. The positions of the window 80a and the irradiation unit 81 are adjusted so that the infrared light irradiated from the irradiation unit 81 is irradiated to the upper top plate 16b through the window 80a. The positions of the window 80b and the detection unit 82 are adjusted so that the infrared light reflected by the upper top plate 16b enters the detection unit 82 through the window 80b. Further, a loading / unloading port (not shown) for loading / unloading the semiconductor wafer W is provided on a side wall different from the windows 80a and 80b of the processing chamber 1. The loading / unloading port is provided with a gate valve for opening and closing the loading / unloading port.

  FIG. 2 is a diagram showing a detailed configuration in the vicinity of the shower head. The upper top plate 16b functioning as an upper electrode is provided with a reflective layer 85 that reflects infrared rays on the back surface with respect to the plasma processing space. The reflection layer 85 may be formed in any way as long as it can reflect infrared rays. For example, the reflective layer 85 may be a layer made of a material that reflects infrared rays, such as tungsten or aluminum, or may be a layer in a space that satisfies the conditions for totally reflecting infrared rays. In the present embodiment, the reflective layer 85 is a tungsten metal layer. The material of the upper top plate 16b may be any material having conductivity, and examples thereof include Si and Qz. In the present embodiment, the upper top plate 16b is assumed to be formed of Si. The upper top plate 16b preferably has a thickness of 500 μm or less, more preferably 1 μm or less, in order to suppress infrared absorption by the upper top plate 16b. The reflective layer 85 may be provided inside the upper top plate 16b. That is, the reflective layer 85 may be included in the upper top plate 16b.

  The irradiation unit 81 is arranged so that the irradiated infrared light strikes a predetermined region near the center of the upper top plate 16b through the window 80a. The detector 82 is arranged so that infrared light reflected by a predetermined region near the center of the upper top plate 16b is incident through the window 80b.

  The plasma processing apparatus 100 according to the present embodiment obtains the absorbance for each wavelength of the infrared light reflected by the reflection layer 85 of the upper top plate 16b by infrared spectroscopy (IR), thereby obtaining the upper ceiling. The film thickness of the reaction product generated on the plate 16b is measured. Specifically, the plasma processing apparatus 100 obtains the absorbance for each wavelength of the reflected infrared light by Fourier transform infrared spectroscopy (FT-IR) to obtain the upper top plate 16b. The film thickness of the resulting reaction product is measured.

  The irradiation unit 81 has a built-in optical element such as a light source that emits infrared light, a mirror, and a lens, and can irradiate the interfered infrared light. For example, the irradiation unit 81 splits an intermediate portion of the optical path until infrared light generated by the light source is emitted to the outside into two optical paths using a half mirror or the like, and sets one optical path length to the other optical path length. On the other hand, by varying the optical path difference and causing interference, infrared light of various interference waves having different optical path differences is irradiated.

  The irradiation unit 81 has a built-in polarizing element and can switch the polarization direction of infrared light emitted from the light source. For example, the irradiation unit 81 can individually irradiate two directions of infrared light having different polarization directions by using a photoelastic modulator. For example, the irradiation unit 81 switches and irradiates infrared light in the horizontal direction whose polarization direction is the same as the surface of the upper top plate 16b and infrared light in the vertical direction whose polarization direction is orthogonal to the horizontal direction. The irradiation unit 81 is provided with a plurality of light sources, and controls infrared light of each light source with an optical element to switch between infrared light whose polarization direction is horizontal and infrared light whose polarization direction is vertical. Irradiation may be possible.

  FIG. 3 is a diagram showing the polarization direction of infrared light. FIG. 3A shows infrared light in the horizontal direction with the y direction constituting the surface of the upper top plate 16b as the polarization direction. FIG. 3A shows infrared light in the vertical direction with the z direction (perpendicular to the surface of the upper top plate 16b) orthogonal to the horizontal direction as the polarization direction.

  The irradiation unit 81 switches the polarization direction between the horizontal direction and the vertical direction, and irradiates infrared light of various interference waves having different optical path differences.

  The detection unit 82 detects the signal intensity of the infrared light of various interference waves reflected by the reflection layer 85 of the upper top plate 16b in the horizontal direction and the vertical direction, respectively.

[Configuration of control unit]
Returning to the description of FIG. The operation of the plasma processing apparatus 100 configured as described above is comprehensively controlled by the control unit 60. The control unit 60 includes a process controller 61 that includes a CPU and controls each unit of the plasma processing apparatus 100, a user interface 62, and a storage unit 63.

  The process controller 61 is connected to the irradiation unit 81 and the detection unit 82 via an interface (not shown) that inputs and outputs data, and inputs and outputs various types of information. The process controller 61 controls the irradiation unit 81 and the detection unit 82. For example, the irradiation unit 81 switches between infrared light whose polarization direction is horizontal and infrared light whose polarization direction is vertical based on control information from the process controller 61, and thereby various interference waves having different optical path differences. Irradiate. In addition, information on the signal intensity of the infrared light detected by the detection unit 82 is input to the process controller 61.

  The user interface 62 includes a keyboard that allows a process manager to input commands to manage the plasma processing apparatus 100, a display that visualizes and displays the operating status of the plasma processing apparatus 100, and the like. The user interface 62 accepts various operations. For example, the user interface 62 receives a predetermined operation for instructing the start of plasma processing.

  The storage unit 63 stores a control program (software) for realizing various processes executed by the plasma processing apparatus 100 under the control of the process controller 61, and a recipe storing process condition data and the like. . Note that recipes such as control programs and processing condition data may be stored in a computer-readable computer recording medium (eg, hard disk, CD, flexible disk, semiconductor memory, etc.), or It is also possible to transmit the data from other devices as needed via a dedicated line and use it online.

  The process controller 61 has an internal memory for storing programs and data, reads the control program stored in the storage unit 63, and executes the processing of the read control program. The process controller 61 functions as various processing units when the control program operates. For example, the process controller 61 has functions of a plasma control unit 61a and a measurement unit 61b. In the plasma processing apparatus 100 according to the present embodiment, the case where the process controller 61 has the functions of the plasma control unit 61a and the measurement unit 61b will be described as an example. However, the plasma control unit 61a and the measurement unit 61b are different controllers. The function may be realized with.

  The plasma control unit 61a reads a recipe or the like from the storage unit 63 according to an instruction received via the user interface 62, and controls the plasma processing of the plasma processing apparatus 100 based on the read recipe or the like.

  The measurement unit 61b measures the film thickness of the reaction product generated on the upper top plate 16b at a predetermined cycle during the plasma processing by the plasma control unit 61a. For example, the measurement unit 61b outputs control information to the irradiating unit 81 at a predetermined cycle, and switches the polarization direction between the horizontal direction and the vertical direction from the irradiating unit 81, thereby causing various interference waves having different optical path differences. Of infrared light. Thereby, the detection unit 82 detects the signal intensity of the infrared light of various interference waves reflected by the reflection layer 85 of the upper top plate 16b in the horizontal direction and the vertical direction, respectively. It is output to the process controller 61.

  The measurement unit 61b measures the film thickness of the reaction product generated on the upper top plate 16b based on the signal intensity of the infrared light of each interference wave detected by the detection unit 82. For example, the measurement unit 61b converts the signal intensity of the infrared light of each interference wave into the signal intensity of the infrared light of each wave number component by Fourier transforming the polarization direction for each horizontal and vertical directions. The wave number has a relationship of wave number k = 2π / wavelength λ with the wavelength. For this reason, the measurement unit 61b converts the signal intensity of the infrared light of each wave number component into the signal intensity of the infrared light for each absorbed wavelength, and uses the signal intensity of the infrared light for each wavelength, You may calculate the film thickness of the reaction product which arises on the top plate 16b.

  Incidentally, noise is generated in the signal intensity of the infrared light detected by the detector 82 due to various influences on the optical path of the infrared light.

  Therefore, the measurement unit 61b uses the signal intensity of the infrared light in the horizontal direction as a reference, divides the signal intensity of the infrared light in the horizontal direction from the signal intensity of the infrared light in the vertical direction for each wave number, and In addition, the signal intensity of the infrared light in the vertical direction with respect to the infrared light in the horizontal direction is calculated.

  The polarization direction of the horizontal infrared light is lateral to the upper top plate 16b. For this reason, the signal intensity of the infrared light in the horizontal direction includes many influences of reaction products on the surface portion of the upper top plate 16b. On the other hand, the infrared light in the vertical direction has a vertical polarization direction with respect to the upper top plate 16b. For this reason, the signal intensity of the infrared light in the vertical direction includes information on the inner portion of the upper top plate 16b, and the influence of reaction products on the surface portion is small. Therefore, by dividing the signal intensity of the infrared light in the horizontal direction from the signal intensity of the infrared light in the vertical direction for each wave number, the measurement unit 61b is the reaction product of the surface portion of the upper top plate 16b. It is possible to accurately measure the effect of light absorption.

  Moreover, since the infrared light in the horizontal direction and the infrared light in the vertical direction pass through the same optical path, similar noise components are included. Therefore, by dividing the signal intensity of the infrared light in the horizontal direction from the signal intensity of the infrared light in the vertical direction for each wave number, the measurement unit 61b suppresses the influence of noise in the optical path of the infrared light to be small. The film thickness of the reaction product can be accurately measured.

[Example of signal strength distribution]
FIG. 4 is a diagram illustrating an example of a signal intensity distribution. The example of FIG. 4 is obtained by performing plasma processing using C4F8 / Ar gas. In this case, the carbon-based reaction product is accumulated in the upper top plate 16b as a deposit. In the example of FIG. 4, the measurement is started at a predetermined timing when the plasma processing is started, and the measurement is started (Initial) at each time point of 4 seconds, 8 seconds, 12 seconds, 24 seconds, 36 seconds, 48 seconds, and 60 seconds. The distribution of signal strength is shown. The wavelength of infrared light increases as the wavelength is shorter. When infrared light is reflected, the wavelength of absorbed infrared light differs depending on the substance. For example, when the upper top plate 16b is made of Si, as shown in FIG. 4, infrared light is largely absorbed in the vicinity of a wave number of 1250 [cm-1]. In FIG. 4, as time passes, infrared light is absorbed even in the vicinity of a wave number of 1280 [cm−1]. The signal intensity in the vicinity of the wave number of 1280 [cm-1] has a correlation with the film thickness of the carbon-based reaction product accumulated in the upper top plate 16b. Therefore, the film thickness of the reaction product can be calculated from the signal intensity in the vicinity of the wave number of 1280 [cm-1].

  The measuring unit 61b measures the film thickness of the reaction product from the difference between the signal intensity at the start of the plasma processing and the signal intensity during the plasma processing. For example, the measurement unit 61b stores the signal intensity at the start of measurement, subtracts the signal intensity at the start of measurement from the signal intensity at each timing measured thereafter, and then generates a reaction product from the signal intensity at the difference from the measurement start. Measure the film thickness.

  FIG. 5 is a diagram illustrating an example of a distribution of signal intensity as a difference from the measurement start (Initial). The example of FIG. 5 is a signal obtained by subtracting the signal strength at the start of measurement (Initial) from the signal strength at each time point of 4 seconds, 8 seconds, 12 seconds, 24 seconds, 36 seconds, 48 seconds, and 60 seconds for each wave number. The intensity distribution is shown. In the example of FIG. 5, the signal intensity increases with the passage of time when the wave number is around 1280 [cm−1]. This is because the film thickness of the carbon-based reaction product accumulated on the upper top plate 16b has increased.

  FIG. 6 is a diagram illustrating an example of the relationship between the difference signal intensity and the film thickness. The example of FIG. 6 shows the difference in signal intensity between the measurement start (Initial) and the case where the plasma treatment is performed using C4F8 / Ar gas and the case where the plasma treatment is performed using C4F8 / Ar / O2 gas. The result of having measured the film thickness of the reaction product (depot) accumulate | stored in the upper top plate 16b is shown. As shown in FIG. 6, there is a positive correlation between the difference signal intensity and the film thickness. Therefore, the film thickness of the reaction product can be measured from the difference signal intensity.

  When the thickness of the reaction product measured by the measuring unit 61b exceeds the threshold, the plasma control unit 61a decreases the thickness of the reaction product attached to the upper top plate 16b or increases the thickness of the reaction product. The plasma is controlled to suppress this. The threshold value is determined in accordance with the deterioration of process characteristics and the film thickness at which particles start to be generated. The threshold value may be set or changed from the outside (for example, the user interface 62). Further, the plasma control unit 61a may determine a plurality of threshold values in a stepwise manner, and control the plasma so that the reaction product does not adhere to the upper top plate 16b as the thickness of the reaction product increases.

  For example, when the film thickness of the reaction product exceeds a threshold value, the plasma control unit 61a performs DC voltage applied to the shower head 16 including the upper top plate 16b, high-frequency power applied to the shower head 16, and cleaning used for plasma processing. By controlling at least one of the gas flow rates, the plasma is controlled so as to reduce the thickness of the reaction product attached to the upper top plate 16b or suppress the increase in the thickness of the reaction product. For example, the plasma control unit 61 a controls the variable DC power supply 52 so as to increase the DC voltage applied to the shower head 16. For example, when a negative voltage is applied to the shower head 16, the plasma control unit 61 a controls the variable DC power supply 52 so as to apply a larger negative voltage. Thereby, since it becomes difficult for a reaction product to adhere to the upper top plate 16b, an increase in the film thickness of the reaction product attached to the upper top plate 16b can be suppressed. Further, for example, the plasma controller 61a reduces the thickness of the reaction product attached to the upper top plate 16b or suppresses the increase in the thickness of the reaction product from the first high-frequency power source 10a or the second high-frequency power source. The voltage, frequency, and timing of the high frequency power applied from at least one of 10b are controlled. For example, the plasma control unit 61a controls to apply high frequency power in a pulse form from the first high frequency power supply 10a. The upper top plate 16b is sputtered while the high frequency power is off. For this reason, the film thickness of the reaction product adhering to the upper top plate 16b can be reduced or the increase in the film thickness of the reaction product can be suppressed. Further, for example, the plasma control unit 61a controls the processing gas supply source 15 so as to contain the cleaning gas or increase the content of the cleaning gas. For example, the plasma control unit 61a controls the processing gas supply source 15 so that O 2 is added as a cleaning gas at a flow rate of 5% or more. Thereby, since the reaction product adhering to the upper top plate 16b can be cleaned with the cleaning gas, the film thickness of the reaction product adhering to the upper top plate 16b can be reduced or the increase in the film thickness of the reaction product can be suppressed.

  As described above, the plasma processing apparatus 100 irradiates the upper top plate 16b with infrared light during plasma processing, detects the signal intensity of the infrared light reflected by the reflective layer 85, and detects the detected signal intensity. The film thickness of the reaction product generated on the upper top plate 16b is measured. Thereby, the plasma processing apparatus 100 can grasp the change in the condition in the processing chamber 1.

  Further, when the film thickness of the reaction product exceeds the threshold value, the plasma processing apparatus 100 decreases the film thickness of the reaction product attached to the upper top plate 16b or suppresses the increase in the film thickness of the reaction product. Thereby, the plasma processing apparatus 100 can suppress generation | occurrence | production of abnormality, such as deterioration of a process characteristic and generation | occurrence | production of a particle.

[Flow of plasma control]
Next, a plasma control method using the plasma processing apparatus 100 according to the embodiment will be described. FIG. 7 is a flowchart showing an example of the flow of the plasma control method.

  When the process controller 61 receives a predetermined operation for instructing the start of plasma processing from the user interface 62, for example, the process controller 61 performs the following control.

  The plasma control unit 61a reads a recipe or the like from the storage unit 63 in accordance with an instruction received via the user interface 62 (step S100). The plasma controller 61a controls each device of the plasma processing apparatus 100 based on the read recipe and the like, and starts plasma processing (step S101).

  The measuring unit 61b initializes the variable n to 1 (step S102). The measurement unit 61b determines whether or not the film thickness measurement timing has come (step S103). For example, the measurement unit 61b determines the timing of a predetermined cycle, such as the timing of every 4 seconds, as the measurement timing. If it is not the measurement timing of the film thickness (step S103: No), the process proceeds to step S103 again.

  On the other hand, when the measurement timing of the film thickness comes (step S103: Yes), the measurement unit 61b outputs control information to the irradiation unit 81, and the irradiation unit 81 changes the polarization direction between the horizontal direction and the vertical direction. Switching is performed to irradiate infrared light of various interference waves having different optical path differences (step S104). Thereby, the detection unit 82 detects the signal intensity of the infrared light of various interference waves reflected by the reflection layer 85 of the upper top plate 16b in the horizontal direction and the vertical direction, respectively. It is output to the process controller 61.

  The measurement unit 61b converts the signal intensity of the infrared light of each interference wave into the signal intensity of the infrared light of each wave number component by Fourier transforming the polarization direction for each of the horizontal direction and the vertical direction (step S105). Then, the measurement unit 61b divides the signal intensity of the infrared light in the horizontal direction from the signal intensity of the infrared light in the vertical direction for each wave number, and uses the infrared light in the horizontal direction as a reference for each wave number. The signal intensity of the infrared light in the vertical direction is calculated (step S106).

  The measurement unit 61b determines whether the value of the variable n is 1 (step S107). When the value of the variable n is 1 (step S107: Yes), the measurement unit 61b stores the signal intensity of infrared light for each wave number calculated in step S106 as data of signal intensity at the start of measurement (step S108). . The measurement unit 61b adds 1 to the value of the variable n (step S109), and proceeds to step S114 described later.

  On the other hand, when the value of the variable n is not 1 (step S107: No), the measurement unit 61b subtracts the signal intensity at the start of measurement from the signal intensity of the infrared light for each wave number calculated in step S106, and starts measurement. The difference signal intensity with respect to time is calculated, and the film thickness of the reaction product is calculated from the difference signal intensity (step S110). The measuring unit 61b adds 1 to the value of the variable n (step S111).

  The plasma control unit 61a determines whether or not the film thickness of the reaction product has exceeded the threshold value (step S112). When the film thickness of the reaction product does not exceed the threshold (step S112: No), the process proceeds to step S114 described later.

  On the other hand, when the calculated film thickness of the reaction product exceeds the threshold value (step S112: Yes), the plasma control unit 61a reduces the film thickness of the reaction product adhering to the upper top plate 16b or the reaction product. Plasma is controlled so as to suppress an increase in film thickness (step S113).

  The plasma controller 61a determines whether to end the plasma processing (step S114). For example, when the plasma processing based on the read recipe or the like is completed, the plasma control unit 61a determines to end the plasma processing. When the plasma process is not finished (step S114: No), the process proceeds to the above-described step S103. On the other hand, when the plasma processing is terminated (step S114: Yes), the processing is terminated.

  As described above, the plasma processing apparatus 100 according to the embodiment includes the upper top plate 16b that functions as an electrode, the irradiation unit 81, and the detection unit 82. The upper top plate 16b faces the plasma processing space, and an infrared reflection layer 85 is provided on the back surface or inside the plasma processing space. The irradiation unit 81 irradiates the upper top plate 16b with infrared light during the plasma processing. The detection unit 82 detects the signal intensity of the infrared light reflected by the reflective layer 85. The plasma processing apparatus 100 measures the film thickness of the reaction product generated on the upper top plate 16b based on the detected signal intensity of the infrared light. When the measured reaction product film thickness exceeds the threshold value, the plasma processing apparatus 100 controls the plasma so as to reduce the reaction product film thickness or suppress the reaction product film thickness increase. Thereby, the plasma processing apparatus 100 can suppress the occurrence of abnormality in the plasma processing.

  Further, the plasma processing apparatus 100 according to the embodiment has a DC voltage applied to the upper top plate 16b, a high-frequency power applied to the upper top plate 16b, and a cleaning used for plasma processing when the film thickness of the reaction product exceeds a threshold value. The plasma is controlled to control at least one of the gas flow rates to reduce the reaction product film thickness or suppress the reaction product film thickness increase. Thereby, the plasma processing apparatus 100 can reduce the thickness of the reaction product deposited on the upper top plate 16b or suppress the increase in the thickness of the reaction product even during the plasma processing.

  Moreover, the irradiation part 81 which concerns on embodiment switches and irradiates two directions of infrared light with the vertical direction orthogonal to a horizontal direction and the horizontal direction where the polarization direction is the same as the surface of the upper top plate 16b, respectively. The detector 82 detects the signal intensity of the infrared light in two directions reflected by the reflective layer 85. The plasma processing apparatus 100 measures the film thickness of the reaction product from the difference between the detected signal intensities of the two directions of infrared light. Thereby, the plasma processing apparatus 100 can suppress the influence of the noise in the optical path of infrared light small, and can measure the film thickness of the reaction product with high accuracy.

  In addition, the plasma processing apparatus 100 according to the embodiment measures the film thickness of the reaction product from the difference between the signal intensity at the start of the plasma processing and the signal intensity during the plasma processing. Thereby, the plasma processing apparatus 100 can obtain | require the change of the film thickness of the reaction product adhering to the upper top plate 16b by plasma processing accurately.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be made to the above-described embodiment. In addition, it is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

  For example, the reaction product adhering to the upper top plate 16b has different wavelengths of infrared light to be absorbed depending on the substance, and has different wavelengths at which the signal intensity changes according to changes in the film thickness. For example, a carbon-based reaction product has a signal intensity that varies depending on the film thickness in the vicinity of a wave number of 1280 [cm −1]. Therefore, the irradiating unit 81 irradiates infrared light having a wavelength in the wavelength range where the change in signal intensity is large with respect to the film thickness of the reaction product to be detected, or infrared light having any wavelength in the wavelength range. May be. The measurement unit 61b may measure the film thickness of the reaction product to be detected based on the signal intensity of the infrared light detected by the detection unit 82. For example, when a carbon-based reaction product is to be detected, infrared light having a wavelength in the vicinity of 1280 [cm-1] or infrared light having a wavenumber of 1280 [cm-1] is used. The film thickness of the reaction product may be measured. In general, light molecular bonds vibrate faster and heavy molecular bonds vibrate slower. For example, in CH, the signal intensity around the wave number of 3000 [cm-1] changes. In C-F, the signal intensity around a wave number of 1200 [cm-1] changes. In C-Br, the signal intensity changes in the vicinity of a wave number of 600 [cm-1]. The irradiation unit 81 is configured to emit infrared light having a wavelength in a wavelength range where the change in signal intensity is large relative to the film thickness of the reaction product substance attached to the upper top plate 16b, or infrared light having any wavelength in the wavelength range. May be irradiated only.

  Moreover, although said embodiment demonstrated the case where the film thickness of the reaction product which reflects infrared light in the center vicinity of the upper top plate 16b and adheres to the upper top plate 16b was measured, it is not limited to this. For example, the film thickness of the reaction product adhering to the vicinity of the upper top plate 16b may be measured by reflecting infrared light in the vicinity of the upper top plate 16b. Further, for example, the film thickness of the reaction product adhering to each of the plurality of portions of the upper top plate 16b may be measured by reflecting infrared light at a plurality of locations such as the vicinity of the center and the vicinity of the upper top plate 16b. Good.

  Moreover, although said embodiment demonstrated the case where the reflection layer 85 was provided in the front surface of the back surface of the upper top plate 16b, it is not limited to this. The reflective layer 85 may be provided corresponding to a region that reflects infrared light. For example, the reflective layer 85 may be provided only near the center of the upper top plate 16b. In addition, when measuring the film thickness of the reaction product attached by reflecting infrared light near the periphery of the upper top plate 16b, in order to suppress non-uniform electrical characteristics in the circumferential direction of the upper top plate 16b, The reflective layer 85 is preferably provided in the entire circumferential direction with the width of the region that reflects infrared light.

DESCRIPTION OF SYMBOLS 1 Processing chamber 10a 1st high frequency power supply 10b 2nd high frequency power supply 15 Process gas supply source 52 Variable DC power supply 60 Control part 61 Process controller 61a Plasma control part 61b Measurement part 62 User interface 63 Storage part 80a Window 80b Window 81 Irradiation part 82 Detection Unit 85 Reflective Layer 100 Plasma Processing Apparatus W Semiconductor Wafer

Claims (5)

An electrode that faces the plasma processing space and has an infrared reflective layer provided on the back surface or inside the plasma processing space;
An irradiation unit for irradiating the electrode with infrared light during plasma treatment;
A detection unit for detecting the signal intensity of infrared light reflected by the reflective layer;
Based on the signal intensity of the infrared light detected by the detection unit, a measurement unit that measures the film thickness of the reaction product generated in the electrode,
A plasma control unit for controlling the plasma so as to reduce the thickness of the reaction product or suppress the increase in the thickness of the reaction product when the thickness of the reaction product measured by the measurement unit exceeds a threshold;
A plasma processing apparatus comprising: The plasma control unit controls at least one of a direct-current voltage applied to the electrode, a high-frequency power applied to the electrode, and a flow rate of a cleaning gas used for plasma processing when the film thickness of the reaction product exceeds a threshold value. The plasma processing apparatus according to claim 1, wherein the plasma is controlled so as to reduce a film thickness of the reaction product or suppress an increase in the film thickness of the reaction product. The irradiation unit switches and irradiates infrared light in two directions with a polarization direction that is the same as the surface of the electrode and a vertical direction orthogonal to the horizontal direction,
The detection unit detects the signal intensity of the infrared light in the two directions reflected by the reflection layer,
The measurement unit divides the signal intensity of the horizontal infrared light from the signal intensity of the infrared light in the vertical direction detected by the detection unit for each wave number to obtain a signal of infrared light in the vertical direction. The plasma processing apparatus according to claim 1, wherein the intensity is corrected, and the film thickness of the reaction product is measured based on the corrected value. The said measurement part measures the film thickness of a reaction product from the difference of the signal strength at the time of the start of plasma processing, and the signal strength during plasma processing. Plasma processing equipment. An electrode that faces the plasma processing space and has an infrared reflective layer provided on the back surface or inside the plasma processing space;
An irradiation unit for irradiating the electrode with infrared light;
A detection unit for detecting the signal intensity of infrared light reflected by the reflective layer;
A plasma control method for a plasma processing apparatus comprising:
Irradiate infrared light from the irradiation unit during plasma processing,
Based on the signal intensity of infrared light detected by the detection unit, measure the film thickness of the reaction product generated in the electrode,
A plasma control method comprising: controlling plasma so as to reduce a reaction product film thickness or suppress an increase in a reaction product film thickness when a measured reaction product film thickness exceeds a threshold value.

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