JP2019110028A - Plasma processing apparatus - Google Patents

Abstract

To provide a plasma processing apparatus improving the processing yield of a specimen.SOLUTION: A plasma processing apparatus includes: a processing chamber 11 in which first plasma 101 is formed; a circular waveguide 6 for transmitting an electric field of microwave to the processing chamber 11; a stage 19 placed in the processing chamber 11, and having a specimen 18 placed on its upper face; a partition plate 9 placed between the circular waveguide 6 and the processing chamber 11, and through which the electric field of microwave permeates for forming the first plasma 101; and a microwave introduction window 8 placed between the circular waveguide 6 and the partition plate 9, and through which the electric field of microwave permeates. Furthermore, plasma processing apparatus is provided with a discharge space 12 for forming second plasma 102, between the microwave introduction window 8 and the partition plate 9.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a plasma processing apparatus for processing a substrate-like sample such as a semiconductor wafer disposed in a vacuum processing chamber using plasma, such as etching, ashing, chemical vapor deposition (CVD), etc., and more particularly to ECR (Electron Cyclotron Resonance). Etching apparatus for forming a plasma using the etching method and etching a film to be processed.

  Plasma processing such as plasma etching, plasma CVD, plasma ashing and the like is widely used in semiconductor device manufacturing. In the etching apparatus which is one of the plasma processing apparatuses, coexistence of anisotropic processing and isotropic processing is calculated | required by one etching apparatus from a viewpoint of device mass productivity. Anisotropic processing is an ion assist reaction mainly composed of ions vertically incident on a wafer, and can be realized by a chemical reaction mainly diffused by isotropic radicals diffused on isotropic processing and incident on a wafer.

  In general, ion density is high at low pressure and ion-based etching is possible, and radical density is high at high pressure and radical-based etching can be performed. Therefore, it is desirable that the etching apparatus can operate in a wide pressure range from a low pressure of about 0.1 Pa to a high pressure of several tens of Pa. Furthermore, in order to ensure device mass productivity, it is necessary to be able to etch uniformly in the wafer surface in such a wide pressure range. In the state-of-the-art device manufacturing, the diameter of a wafer is increased to improve mass productivity, and the technical difficulty of performing plasma processing uniformly in the wafer surface is increasing.

  As a technique for generating plasma, one using ECR, one using inductive coupling, capacitive coupling and the like is known. In ECR, it is known that plasma can be efficiently generated at a low pressure of 1 Pa or less, which is difficult with other techniques such as inductive coupling and capacitive coupling.

  ECR is called electron cyclotron resonance. When a magnetic field is applied to the vacuum device, electrons in the magnetic field perform rotational movement called cyclotron movement around magnetic field lines. When a microwave of a frequency matched to the speed of rotation is incident there, energy resonance between the cyclotron motion and the electric field occurs, and the electric field energy is absorbed by the electrons. This is called electron cyclotron resonance, and electrons can be effectively accelerated to give large energy. These high energy electrons collide with gas molecules or atoms, and are ionized and dissociated to generate plasma. The plasma generated in this manner is called ECR plasma.

  If the pressure in the processing chamber is relatively low, the electron mean free path is long enough to accelerate the electrons sufficiently with ECR and then collide with the molecules or atoms of the gas so that the atoms or molecules are efficient Can be ionized and dissociated. And, in the case of forming plasma using ECR at low pressure, as a result, high density plasma is generated in the vicinity of the equimagnetic field surface satisfying the condition of ECR.

  Usually, the equi-magnetic field satisfying the ECR condition due to the magnetic field formed by the electromagnetic coils arranged above and to the side of the processing chamber spreads in a horizontal direction in the processing chamber, so the plasma by ECR in the processing chamber It is formed in the area which spreads like a plane. Therefore, it is supposed that relatively uniform plasma processing can be realized.

  However, when the pressure in the processing chamber is relatively high, the mean free path of the electrons becomes short, and electrons moving along the electric field travel a short distance and collide with atoms or molecules of the gas to be ionized or dissociated. Will occur. For this reason, the region in the processing chamber where the plasma is generated is not in the vicinity of the equimagnetic field surface satisfying the ECR condition but in the processing chamber just below the dielectric window to which electromagnetic waves are incident and directly below the waveguide. It localizes near the central axis. Therefore, when the pressure is relatively high, the etching rate of the film to be processed has a convex distribution in the in-plane direction of the wafer, and the etching amount becomes uneven in the wafer surface. That is, the etching variation in the central portion of the wafer is larger than that in the outer peripheral portion.

  A conventional technique for solving the problem that the high density or high intensity portion of the plasma is concentrated in the vicinity of the central axis of the processing chamber and the processing characteristics in the in-plane direction of the sample surface become uneven. Examples thereof include JP-A-9-148097 (PTD 1) and JP-A 2013-211270 (PTD 2).

  The plasma processing apparatus using the ECR method of Patent Document 1 includes a dielectric window disposed between a discharge chamber (processing chamber) and an electromagnetic wave transmission unit, an electromagnetic wave reflection plate disposed under the dielectric window, It has with the auxiliary reflector. Then, an electromagnetic wave is made to enter the discharge chamber from a ring-shaped electromagnetic wave emission port formed between the electromagnetic wave reflection plate and the auxiliary reflection plate, and a ring-like plasma is generated on the ECR surface to form uniform plasma covering the sample. doing. Thus, highly uniform plasma processing is realized.

  Further, Patent Document 2 relates to a plasma processing apparatus in which plasma is generated only by microwaves without using a magnetic field. The plasma processing apparatus is disposed above the processing container (chamber), and a waveguide through which the microwave electric field propagates inside, and the upper part of the processing container, the transmitted microwave electric field transmits through the inside of the processing container Of the dielectric window introduced into the ring, an annular ring slot disposed between the waveguide and the dielectric window, and the microwave transmitted through the dielectric window disposed on the processing container side of the dielectric window And a shielding plate for shielding an electric field. By providing the shielding plate, formation of plasma with high density or intensity in the central portion in the processing container is suppressed, and nonuniformity of plasma processing is reduced in the in-plane direction of the sample.

JP-A-9-148097 JP, 2013-211270, A

  It turned out that the patent documents 1 and 2 have room for further improvement.

  That is, in the plasma processing apparatus using ECR, it is technically difficult to equalize the characteristics of the plasma processing, for example, the etching rate in a wide pressure range of 0.1 to several tens Pa. In particular, under conditions where the pressure in the processing chamber is relatively high, plasma with high density or strength is formed in the processing chamber in the region directly below the waveguide, and etching in the radial direction from the center of the sample surface toward the outer peripheral side The rate is a so-called convex distribution in which the central portion is high and becomes smaller toward the outer periphery, and it has been confirmed that the variation in shape after processing becomes large and the yield of the etching process is lowered.

  For example, as described in Patent Document 1 and Patent Document 2, in the configuration in which a shielding plate for shielding microwaves is aligned with the central axis in the processing chamber and arranged, the etching rate Nonuniformity can be improved. However, the inventors of the present application have found that problems occur under relatively low pressure in the processing chamber due to the presence of the shielding plate. That is, due to the presence of the shielding plate, a plasma in which a region having high plasma density or intensity is distributed in a ring shape is formed in the processing chamber, and the etching rate becomes a concave distribution increasing from the center toward the outer periphery. It was found that the yield of the etching process was lowered.

  In such a case, in order to reduce variation in plasma processing characteristics in the radial direction of the sample surface in a wide pressure range and to make the characteristics uniform, the arrangement of the shielding plate is changed according to the pressure in the processing chamber. Or, it is necessary to attach and detach. In that case, it is necessary to open the air to the inside of the processing chamber at atmospheric pressure or a pressure that can be regarded as the same every time the shielding plate is attached and removed, and to change the arrangement and to reduce the pressure inside the processing chamber again after attachment and detachment. As a result, the non-operating time during which plasma processing can not be performed increases.

  Also, consider an example in which a shielding plate is disposed at a location on the air side immediately above the dielectric window. The dielectric window generally has a thickness of several tens of mm or more in order to obtain strength to withstand an external force caused by a pressure difference between inside and outside the processing container (vacuum container). Since the electric field of the microwaves propagates inside the dielectric window and wraps around to the center of the processing chamber, a region with high plasma density and intensity is formed at the center of the processing chamber, resulting in non-uniform plasma processing. For example, there has been the problem that the yield of the etching process is reduced.

  The present invention provides a plasma processing apparatus that enables uniform plasma processing in a sample (wafer) plane over a wide pressure range.

  In order to solve the above problems, the plasma processing apparatus according to one embodiment is disposed in a processing chamber in which a first plasma is formed, a circular waveguide for transmitting an electric field of microwaves to the processing chamber, and a processing chamber. A stage on which the sample is placed, a partition plate disposed between the circular waveguide and the processing chamber, and through which a microwave electric field is transmitted to form a first plasma; And a microwave introduction window disposed between the partition plate and through which a microwave electric field is transmitted. The plasma processing apparatus further includes a discharge space for forming a second plasma between the microwave introduction window and the partition plate.

  ADVANTAGE OF THE INVENTION According to this invention, the plasma processing apparatus which improves the processing yield of a sample in the plasma processing in a wide pressure range can be provided.

It is sectional drawing which shows typically the outline of a structure of the plasma processing apparatus which concerns on Example 1 of this invention. It is a graph which shows distribution of the etching rate in the surface direction of the sample etched in the inside of the plasma processing apparatus which concerns on Example 1 of this invention. FIG. 7 is a cross-sectional view schematically showing a configuration of a portion of a plasma processing apparatus in accordance with a first modification; FIG. 10 is a plan view schematically showing a configuration of a portion of a plasma processing apparatus in accordance with a second modification; FIG. 13 is a cross-sectional view schematically showing a configuration of a portion of a plasma processing apparatus in accordance with a third modification; FIG. 16 is a cross-sectional view schematically showing a configuration of a portion of a plasma processing apparatus in accordance with a fourth modification;

  Embodiments of the present invention will be described below using the drawings.

Example 1
Example 1 will be described below with reference to FIGS. 1 and 2.

  FIG. 1 is a cross-sectional view schematically showing the configuration of a plasma processing apparatus according to a first embodiment of the present invention. FIG. 2 is a graph showing the distribution of the etching rate in the in-plane direction of the sample to be etched in the plasma processing apparatus according to the first embodiment of the present invention.

  In Example 1, when the pressure in the process chamber is a relatively low pressure (1 Pa or less), the etching process is performed without generating the second plasma, and the pressure in the process chamber is a relatively high pressure (several Pa or more) In this case, the present invention relates to a plasma processing apparatus which generates a second plasma and carries out an etching process.

  The plasma processing apparatus 100 shown in FIG. 1 is, for example, a plasma etching processing apparatus. The plasma processing apparatus 100 has a vacuum vessel (chamber) 26 having a cylindrical shape, and in the vacuum vessel 26, a microwave introduction window 8, a second discharge space 12, a partition plate 9, a processing chamber 11 and the like are provided. It is done. In the processing chamber 11, a shower plate 10 having a plurality of through holes and a stage 19 are provided. A substrate-like sample 18 such as a semiconductor wafer to be subjected to plasma etching is disposed on the stage 19. An insulating layer (or a conductor layer) which is a film to be processed is formed on the sample 18, and a mask layer (for example, a photoresist film) having a desired pattern is formed on the film to be processed. There is. Then, when the sample 18 is subjected to plasma etching, the film to be processed in the region exposed from the mask layer is removed, and the film to be processed is selectively left in the region covered by the mask layer.

  The plasma processing apparatus 100 is disposed above and to the side of the vacuum vessel 26 and includes a plasma forming unit that generates an electric field and a magnetic field supplied to form the first plasma 101 in the processing chamber; And an exhaust unit including a vacuum pump 21 such as a turbo molecular pump that exhausts particles in the processing chamber 11 in communication with the exhaust opening 27 disposed at the bottom of the processing chamber 11. The means for generating the electric field and the magnetic field constituting the plasma forming portion of the first embodiment is disposed under the atmosphere outside the vacuum vessel 26 and treated with the electric field of a predetermined frequency from the upper side of the vacuum vessel 26. A waveguide 28 introduced into the chamber 11 and a static magnetic field generator 24 disposed around the processing chamber 11 around the waveguide 28 are provided.

  The waveguide 28 is a rectangular waveguide 2 whose axis extends in the horizontal direction and whose cross section has a rectangular shape, and is connected to the rectangular waveguide 2 so that the axis extends in the vertical direction, and the cross section is circular. And a circular waveguide 6 which is a conduit having a circular shape, and a microwave electric field transmitted in the rectangular waveguide 2 disposed between the rectangular waveguide 2 and the circular waveguide 6. A circular-rectangular converter 5 directed to the waveguide 6 is provided.

  At one end of the rectangular waveguide 2, a microwave source 1 such as a magnetron formed by oscillating the electric field of microwave used in the first embodiment is disposed, and at the other end of the rectangular waveguide 2, a circular rectangle is formed. The transducers 5 are arranged and connected. The automatic matching device 3 and the isolator 4 are provided between the microwave source 1 and the circular rectangular converter 5 of the rectangular waveguide 2, and the electric field of the microwave oscillated by the microwave source 1 is the automatic matching device 3 and the isolator 4 And is transmitted to the circular waveguide 6 through the circular-rectangular converter 5.

  In the first embodiment, a 2.45 GHz magnetron which is often used as an industrial frequency is used as the microwave source 1. However, the present invention is not limited to this frequency, and electromagnetic waves of several tens of MHz to several tens of GHz may be used.

  The automatic matching machine 3 adjusts the load impedance, and the electric field of the microwaves propagating toward the processing chamber 11 is reflected and propagates toward the microwave source 1 in the circular waveguide 6 or the rectangular waveguide 2 The waves are suppressed to improve the efficiency of supplying the electric field of the microwaves into the processing chamber 11. In addition, the isolator 4 has a function of protecting the microwave source 1 from reflected waves.

  The diameter of the circular waveguide 6 is selected such that the electric field propagated downward inside is only the circular TE11 mode which is the fundamental mode. This is because when the higher order mode is included, the stability and uniformity in generating the first plasma 101 may be adversely affected. The lower end portion of the circular waveguide 6 is connected to the hollow portion 7, and the hollow portion 7 has the same size as the inside of the processing chamber 11 above the vacuum vessel 26 or a size close to the size that can be regarded as this. It has a cylindrical shape. The electric field propagated in the circular waveguide 6 and introduced into the cavity 7 is adjusted so as to have a distribution of intensity suitable for plasma processing inside the cavity 7 with the increased diameter.

  A microwave introduction window 8 made of a dielectric material and a partition plate 9 are disposed below the cavity 7 and between the processing chamber 11 and the upper end of the side wall of the vacuum vessel 26 having a cylindrical shape. And the discharge space 12 is shielded from the atmosphere outside the vacuum vessel 26. Below the partition plate 9, a shower plate 10 having a disk shape that constitutes the ceiling surface of the processing chamber 11 is disposed.

  The microwave introduction window 8, the partition plate 9 and the shower plate 10 efficiently transmit microwaves, and quartz having plasma resistance is used. Alternatively, as a material having high plasma resistance and transmitting microwaves, yttria, alumina, yttrium fluoride, aluminum fluoride, aluminum nitride or the like may be used.

  The microwave introduction window 8 and the partition plate 9 each having a disk shape are disposed in the vertical direction with a gap in between, and the microwave introduction window 8 and the partition plate 9 constitute a lid on the upper part of the vacuum vessel 26. The microwave introduction window 8 and the partition plate 9 are window members through which the electric field of the microwaves passes. The space between these is shielded from the outside of the vacuum vessel 26 and the atmosphere of the processing chamber 11 to constitute the discharge space 12. The microwave introduction window 8 is disposed above the discharge space 12 so as to cover it, and constitutes another window member that divides the inside of the discharge space 12 from the outside. That is, the microwave introduction window 8 isolates the discharge space 12 from the atmosphere outside the vacuum vessel 26, and the partition plate 9 isolates the discharge space 12 from the atmosphere of the processing chamber 11.

  The discharge space having a cylindrical or disc shape is connected to and communicated with the second gas supply unit 13 and the second gas supply passage 31 at one end thereof, and the second discharge space is formed at the other end. The gas exhaust unit 15 and the second gas exhaust passage 32 are connected and communicated with each other. On the second gas exhaust passage 32, a conductance adjustment unit 14 and a pressure sensor 16 for detecting the pressure in the discharge space 12 are provided. The second gas supplied from the second gas supply unit 13 is introduced into the discharge space 12 from the second gas supply passage 31 connected to the vacuum vessel 26 and dispersed therein, and then the second gas is supplied. The gas is exhausted by the second gas exhaust unit 15 through the exhaust passage 32 and via the conductance adjustment unit 14.

  As a second type of gas, an inert gas is used in which the surface of the microwave introduction window 8 and the partition plate 9 is not scraped by chemical reaction or the formation of a deposited film does not occur. For example, it is desirable to use a noble gas such as He or Ar as the inert gas. The second gas supply unit 13 includes a flow rate regulator such as a mass flow controller, and has a function of adjusting the flow rate of the second gas introduced into the discharge space 12 or the speed thereof to a value within a desired range. doing.

  As the second gas exhaust unit 15, for example, a dry pump for roughing, such as a rotary pump, is used. In addition, as the conductance adjustment unit 14, a throttle such as an orifice or a variable valve that increases / decreases the flow passage cross-sectional area of the second gas exhaust passage 32 depending on the opening degree is used. By adjusting the conductance in the second gas exhaust passage 32 in this manner, the second gas can be uniformly dispersed in the discharge space 12 to suppress the nonuniformity of the internal pressure, which will be described later. The plasma intensity or density can be realized in a desired distribution.

  Further, the pressure of the discharge space 12 is detected by a pressure sensor 16 disposed upstream of the conductance adjustment unit 14 of the second gas exhaust passage 32. Then, the control unit 29 receives the output from the pressure sensor 16, and the computing unit disposed in the control unit 29 is stored in advance in a storage device such as a memory or a hard disk or a CD-ROM disposed in the control unit 29. A command signal calculated according to the value of pressure detected according to the recorded software algorithm is sent to the mass flow controller or conductance adjustment unit 14 of the second gas supply unit 13 to adjust its operation. That is, according to the detection result of the pressure of the discharge space 12, the control unit 29 adjusts the operation of the second gas supply unit 13, the second gas supply unit 13, or the conductance adjustment unit 14 to obtain the second gas flow rate. By adjusting the pressure of the discharge space 12 to a desired value.

  When a variable valve is used as the conductance adjustment unit 14, the pressure of the discharge space 12 may be adjusted by increasing or decreasing the opening degree of the variable valve according to the command signal from the control unit 29. Further, in order to bring the pressure in the discharge space 12 into a predetermined range, a pressure sensor 16 may be used. For example, after the control unit 29 detects that the pressure in the discharge space 12 is within the predetermined allowable range, the control unit 29 detects the output from the pressure sensor 16, and then the variable valve of the conductance adjustment unit 14 is controlled by the command signal from the control unit 29. May be driven, the second gas exhaust passage 32 may be closed, and the supply of the second gas from the second gas supply unit 13 may be stopped.

  A gap between the partition plate 9 and the disk-shaped shower plate 10 is connected and communicated via the first gas supply unit 17 and the first gas supply passage 33. The processing first gas supplied from the first gas supply unit 17 is dispersed inside the gap and passes downward through the plurality of through holes disposed in the central portion of the shower plate 10 into the processing chamber 11. Supplied. The plurality of through holes disperse the first gas from the shower plate 10 and cause the first gas to flow into the processing chamber 11, thereby reducing the nonuniformity of the amount of the first gas supplied to the processing chamber 11.

  A stage 19 is provided below the processing chamber 11, and a sample 18 is adsorbed and held on the stage 19 by electrostatic force. An exhaust opening 27 is disposed on the bottom of the processing chamber 11, and the stage 19 is held at an intermediate position in the height direction between the exhaust opening 27 and the shower plate 10. Each has a space to configure.

  The exhaust opening 27 is an upper end of the exhaust path constituting the exhaust unit and is an opening communicating with the processing chamber 11, and is connected on the exhaust path connecting and communicating between the exhaust opening 27 and the inlet of the vacuum pump 21. The conductance control valve 20 is disposed. The conductance adjustment valve 20 is driven by a command signal from the control unit 29 to increase or decrease the conductance of the exhaust gas passing through the exhaust path. Then, the flow rate or the speed of exhaust of particles such as gas, plasma, reaction product and the like from the processing chamber 11 by the operation of the vacuum pump 21 is adjusted.

  The center of each of the processing chamber 11 having a cylindrical shape, the stage 19 and the exhaust opening 27 having a circular shape in plan view coincides with or approximates to the central axis CA of the plasma processing apparatus 100. It is placed in position. Therefore, the flow of the first gas supplied into the processing chamber 11 from the plurality of through holes of the shower plate 10 and the particles of the formed first plasma 101 to the exhaust opening 27 is symmetrical with respect to the central axis CA. It has become. That is, the flow rates and velocities of the first gas and particles are balanced in the circumferential direction with respect to the central axis CA, and the variation is reduced. Of course, the center of the sample 18 is also placed on the stage 19 so as to coincide with the central axis CA.

  Further, a disc or cylindrical electrode made of a conductive material such as metal (not shown) is provided inside the stage 19, and the electrode is automatically matched with a bias power supply 23 supplying high frequency power to form a bias potential above the upper surface of the sample 18. It is electrically connected via the machine 22. In the first embodiment, a frequency of 400 kHz is used as the frequency of the high frequency power from the bias power supply 23, but the frequency is selected according to the purpose required for the plasma processing such as 13.56 MHz.

  Further, a metal base material disposed in the stage 19 is connected to a temperature control unit (not shown) inside, and a refrigerant flow supplied with the refrigerant whose temperature is adjusted to a value within a predetermined range by the temperature control unit The road is arranged. The refrigerant exchanges heat with the sample or the sample 18 placed on the substrate or the stage 19 or the upper surface thereof while flowing through the refrigerant channel, is discharged from the refrigerant channel, returns to the temperature control unit again and is temperature-controlled again. The temperature of the sample 18 is adjusted to a value in the range suitable for the etching process by the circulation supplied to the flow path and the temperature of the substrate or stage 19 being adjusted to the value in the predetermined range. .

  The processing chamber 11 is formed around the cylindrical sidewall of the vacuum vessel 26 surrounding the processing chamber 11 having a cylindrical shape, the outer periphery of the upper cavity 7 and the outer periphery of the circular waveguide 6 above the cavity 7. A static magnetic field generator 24 provided with a solenoid coil and an electromagnet such as a yoke for forming a magnetic field supplied therein is disposed. The direct current supplied to the static magnetic field generator 24 is appropriately adjusted by the control unit 29 so that the strength of the magnetic field and the distribution thereof satisfy the condition of the magnetic flux density necessary for causing ECR in the processing chamber 11. To be realized.

  For a microwave electric field with a frequency of 2.45 GHz, the flux density required to cause ECR is 875 G. In particular, under the condition that the pressure in the processing chamber 11 is a low pressure, the static magnetic field distribution is adjusted to form the 875 G equal magnetic field surface at an arbitrary position in the processing chamber 11, whereby the first plasma 101 is generated. It is possible to adjust the position (especially the position in the height direction) of the area to be

  Further, by adjusting the distribution of the static magnetic field, it is possible to adjust the distribution of the diffusion of the particles in the plasma 101 and the distribution of the density of the particles with respect to the sample 18. A plurality of coils of the electromagnet used as the static magnetic field generator 24 are disposed in a plurality, in particular, in the upper and lower directions in order to facilitate control of the region where the first plasma 101 is generated and diffusion of the first plasma 101. It is desirable to be done.

  The etching of the film to be processed disposed on the surface of the sample 18 is performed using the first plasma 101. The first plasma 101 is formed by the microwave source 1 and is generated by the electric field and the static magnetic field generator 24 of the microwaves propagated through the waveguide 28 and supplied into the processing chamber 11 and supplied into the processing chamber 11 The first gas introduced into the processing chamber 11 is excited, dissociated or ionized to form using the ECR generated by the generated magnetic field. Then, charged particles such as ions present in the first plasma 101 are attracted to the surface of the sample 18 by the bias potential formed by the high frequency power supplied to the stage 19, and reactive particles such as radicals and the like are processed The film to be processed is etched by promoting the reaction with the film.

  So far, the etching method in the case where the processing chamber 11 has a low pressure of 1 Pa or less has been described, but next, the etching method in the case where the processing chamber 11 has a high pressure of several Pa or more will be described.

  When the processing chamber 11 has a high pressure of several Pa or more, a region of high strength of the first plasma 101 is formed in the vicinity of the central axis CA of the processing chamber 11. The etching rate becomes high, and the distribution of the etching rate becomes a so-called middle-high (convex) shape. However, in the first embodiment, the second plasma 102 is formed in the discharge space 12 and the density distribution of the first plasma 101 is appropriately adjusted, so that the radial distribution of the etching rate is made uniform from the convex shape. It is Furthermore, if necessary, the rate of the outer peripheral portion from the central portion can be adjusted to a high concave distribution. By this function, the etching rate can be made to approach uniformly in a wide range of the pressure of the processing chamber 11.

  First, generation of the second plasma 102 in the discharge space 12 will be described. In order to generate the second plasma 102, as indicated by Paschen's law, the strength of the electric field of the microwave, the pressure, and the size of the second space in the discharge space 12 are set to values within an appropriate range. It will be necessary.

  Typically, assuming that the distance between the flat microwave introduction window 8 and the partition plate 9, that is, the length (height) of the cylindrical or disc-shaped discharge space 12 in the central axis CA direction is several mm, The range of pressure at which discharge can be started in the discharge space 12 is 100 to 1000 Pa. Also, due to the strength of the electric field of the microwave in the circular TE 11 mode of the circular waveguide 6 becoming stronger at the central portion compared to the peripheral portion, the strength of the electric field of the microwave is the central axis of the discharge space 12 and its It tends to be high in nearby places.

  From the above, by realizing the value of the parameter such as pressure that satisfies Paschen's law, the second plasma 102 is generated in the central axis CA of the discharge space 12 and in the vicinity thereof. Furthermore, the density of the second plasma 102 can be adjusted by increasing or decreasing the pressure in the discharge space 12. In order to measure the pressure in the discharge space 12, a spectroscope and a photodetector (not shown) can be used. For example, the light emitted from the second plasma 102 is received by a spectroscope, and the light detector detects the intensity of light of an arbitrary wavelength. The control unit 29, which receives the detection result output from the light detector, uses the intensity of light emission calculated from the received signal as information indicating the density of the second plasma 102, and the pressure in the discharge space 12 and the gas supply amount Alternatively, the displacement may be adjusted. Alternatively, means for detecting a change in the magnitude of the reflected wave of the electric field of the microwave from the second plasma 102 with the passage of time may be used. When the second plasma 102 is not generated (that is, in the case of etching in which the pressure in the processing chamber 11 is lowered), the pressure in the discharge space 12 is sufficiently smaller than the pressure suitable for discharge, Or you can make it high enough.

  By forming the second plasma 102 in the discharge space 12 disposed on the propagation path of the microwave electric field between the cavity 7 and the processing chamber 11, the microwaves supplied from the microwave source 1 can be obtained. A part of the electric field is absorbed or reflected by the second plasma 102, and the other part is supplied to the processing chamber 11. Therefore, the electric field of the microwave supplied to the processing chamber 11 changes with the magnitude of the density of the second plasma 102. That is, by adjusting the density of the second plasma 102, it is possible to adjust the transmittance of the microwave electric field of the cavity 7 from the cavity 7 to the central axis CA of the processing chamber 11 and a region in the vicinity thereof. it can.

  By performing such adjustment during the process of the sample 18, the distribution of the density of the first plasma 101 in the process chamber 11 in the radial direction (direction orthogonal to the central axis CA) of the process chamber 11 is adjusted, The distribution of the etching rate of the film to be processed on the surface of the sample 18 is adjusted. This will be described below with reference to FIG.

  First, when the second plasma 102 is not generated, the radial distribution of the etching rate of the film to be processed on the surface of the sample 18 processed by the first plasma 101 is that the central portion is closer than the outer peripheral portion It becomes a high middle high (convex) one (Fig. 2 (a)). This is because the electric field of the microwave in the cavity 7 is transmitted through the inside of the discharge space 12 without causing a large interaction and propagates into the processing chamber 11. The first plasma 101 formed by the electric field of the microwave has a portion having a larger strength than the portion on the outer peripheral side in the vicinity of the central axis CA of the processing chamber 11. That is, FIG. 2A shows the distribution of the etching rate of the comparative example with respect to the first embodiment.

  Next, when the second plasma 102 is formed in the discharge space 12 and the size of the density is appropriately adjusted, the electric field of the microwave in the central axis CA of the processing chamber 11 and the vicinity thereof is generated. The intensity (in other words, the high density of the first plasma 101) is reduced. As a result, the distribution of the etching rate in the radial direction of the film to be processed on the surface of the sample 18 is alleviated and the distribution of the medium height is made to be uniform ((b) in FIG. 2).

  That is, the electric field of the microwaves supplied from the hollow portion 7 of FIG. 1 to the processing chamber 11 through the microwave introduction window 8, the discharge space 12 and the partition plate 9 is the central axis CA of the discharge space 12 and the vicinity thereof. It is absorbed by the second plasma 102 formed with a region of high density. On the other hand, since the rate of absorption of the electric field of the microwaves transmitted through the outer peripheral side of the discharge space 12 is small, the intensity of the electric field of the microwaves transmitted to the central axis CA of the processing chamber 11 and a region in the vicinity thereof is It becomes smaller compared to that of the outer peripheral area.

  As a result, in the central axis CA of the processing chamber 11 and in the vicinity thereof, a portion having a higher intensity or density than that of the portion on the outer peripheral side is concentrated to form a medium-high distribution. . Then, the phenomenon that the distribution of the etching rate in the radial direction from the center of the sample 18 becomes high is also suppressed. Furthermore, when the density of the second plasma 102 is adjusted to the cut-off density or more according to the command signal from the control unit 29, the microwave introduction window 8 toward the inside of the processing chamber 11 from the hollow portion 7 Since the electric field of the microwaves transmitted through is not transmitted through the second plasma 102 but is reflected, the electric field of the microwaves is selectively introduced to the discharge space 12 and the outer peripheral side portion of the partition plate 9 It permeate | transmits and is supplied in the processing chamber 11 from the outer peripheral side part. As a result, the electric field of the microwave and the intensity or density of the first plasma 101 become a so-called distribution of outside heights, in which the places where they are high are concentrated on the outer peripheral side portion of the processing chamber 11 (FIG. (C)). In this case, the etching rate of the film to be processed on the upper surface of the sample 18 to be treated by the first plasma 101 can also be an external height distribution in which the outer peripheral side is higher than the central side.

  When the pressure in the processing chamber 11 is set to a value of 1 Pa or less, the first plasma 101 is generated on an isomagnetic field surface of 875 G that satisfies the ECR condition. The power supplied to the static magnetic field generator 24 is adjusted in accordance with the command signal from the control unit 29 to adjust the shape and position of the equi-magnetic field surface of 875 G by the generated magnetic field. As a result, the diffusion of the particles of the first plasma 101 along the position where the first plasma 101 is generated and the magnetic lines of force is adjusted, and the value of the etching rate of the film to be processed and its distribution can also be adjusted. In this case, although the generation of the second plasma 102 is not necessarily required to adjust the distribution shape of the etching rate, the density of the second plasma 102 may be adjusted to adjust the distribution of the etching rate of the film to be processed, if necessary. You may.

  According to the above-described first embodiment, the processing chamber is controlled by adjusting the intensity or density distribution of the first plasma 101 using the second plasma 102 in accordance with the conditions of processing of the film to be processed of the sample 18. It is possible to provide a plasma processing apparatus which realizes, for example, a desired etching rate distribution in a wide range from a low value to a high value of the pressure in 11.

<Modification 1>
Next, a modified example of the first embodiment will be described with reference to FIG. FIG. 3 is a cross-sectional view schematically showing a configuration of a portion of a plasma processing apparatus 100a in accordance with the first modification. The modification 1 is different from the first embodiment in the configuration of the microwave introduction window 8 a constituting the discharge space 12 a 1. Descriptions of components having the same configuration and operation as those of the first embodiment are omitted.

  As shown in FIG. 3, the microwave introduction window 8 a has a recess 30 on the surface facing the partition plate 9. Although not shown, the recess 30 is located at the center of the microwave introduction window 8a and has a circular shape. The center of the circular recess 30 overlaps the central axis CA. The film thickness of the microwave introduction window 8 a is thin in the region where the recess 30 is formed and is thick in the region around the recess 30. That is, the thick film portion of the microwave introduction window 8 a surrounds the periphery of the thin film portion corresponding to the recess 30.

  The microwave introduction window 8 a faces the partition plate 9 with the space 12 a 2 or the discharge space 12 a 1 interposed therebetween. As shown in FIG. 3, a discharge space 12 a 1 is formed in a region where the recess 30 is located, and a space 12 a 2 is formed around the discharge space 12 a 1. In other words, the discharge space 12a1 is formed between the thin film portion of the microwave introduction window 8a and the partition plate 9, and the space 12a2 is formed between the thick film portion of the microwave introduction window 8a and the partition plate 9 . The discharge space 12a1 has a height H1 suitable for generating the second plasma 102, and the space 12a2 has a height H2 within a range where discharge or plasma can not be generated or suppressed by the electric field of the microwave. . The heights H1 and H2 have a relationship of H1> H2, and as a typical example, the height H1 is about 1 to 10 mm and the height H2 is less than 1 mm.

  In the first modification, since the second plasma 102 is formed in the discharge space 12a1 located at the center of the microwave introduction window 8a, the second gas supply unit 13 is formed in a part of the space 12a2 on the outer peripheral side. The second gas exhaust unit 15 is in communication via the second gas exhaust passage 32 at another portion on the outer peripheral side. The conductance adjustment unit 14, the pressure sensor 16, and the control unit 29 are the same as those in the first embodiment.

  Also in the first modification, the pressure suitable for discharge in the discharge space 12a1 is about 100 to 1000 Pa, and the operation of the second gas supply unit 13, the conductance adjustment unit 14, or the second gas exhaust unit 15 is the control unit 29. As a result of being adjusted according to the command signal from the control unit, the pressure in the discharge space 12a1 is adjusted to a value within a predetermined range. According to the frequency of the electric field of the microwave used in the microwave source 1 and the size, shape, and structure of the second discharge space 12a1 and the space 12a2, the pressure which can form an internal discharge or the pressure which can prevent discharge, values of H1 and H2 The appropriate pressure, H1 and H2 are not limited to the illustrated values, as the appropriate range of H changes.

  In the first modification having such a configuration, the central portion in which the height of the gap between the microwave introduction window 8a and the partition plate 9 is increased constitutes the discharge space 12a1, and the second plasma 102 is a discharge. It is formed only in the area inside diameter D1 of space 12a1 (space of height H1), and is formed to extend over the entire area inside discharge space 12a1. The density of the second plasma 102 is adjusted in accordance with the command signal from the control unit 29 so that the micro-propagates from the upper cavity 7 in the area of the diameter D1 around the central axis CA of the processing chamber 11. The transmittance of the electric field of the wave is adjusted, and the value of the density or intensity of the first plasma 101 generated in the processing chamber 11 from the central axis in the radial direction and the distribution thereof are adjusted. Here, it is important to make the diameter D1 of the recess 30 larger than the diameter D2 of the circular waveguide 6 (D1> D2). In other words, it is important that the area where the circular waveguide 6 is projected from above is located inside the outer peripheral edge of the second plasma 102. This is because the electric field of the microwave is high immediately below the circular waveguide 6 compared to its surroundings. Therefore, it is important to form the second plasma 102 (in other words, the recess 30) so as to completely cover the area where the circular waveguide 6 is projected from above.

  Further, since the second plasma 102 is not formed in the space 12a2 of the outer peripheral side portion of the discharge space 12a1, the microwaves are efficiently transmitted to the outer peripheral side portion of the processing chamber 11 through the outer peripheral side portion of the partition plate 9 below. An electric field is supplied to efficiently form the first plasma 101 of high intensity or density around the outer periphery.

  The diameter D1 of the cylindrical recess 30 constituting the discharge space 12a1 is desirably smaller than the diameter D3 of the sample 18 having a disk shape. In other words, it is desirable that the area where the second plasma is projected from above be smaller than the diameter D3 of the sample 18. This is because when the diameter D1 of the recess 30 is increased, the distribution of the etching rate becomes an outer height shown in FIG. 2 (c).

  In the first modification, the recess 30 is provided in the microwave introduction window 8a, but the recess 30 may be provided in the partition plate 9 instead of the microwave introduction window 8a.

<Modification 2>
Next, still another modification of the first embodiment will be described with reference to FIG. FIG. 4 is a plan view schematically showing the configuration of a portion of a plasma processing apparatus 100b according to the second modification, and in particular, the microwave introduction window 8 and the second gas supply unit 13 and the second gas exhaust unit 15 Is schematically shown. The second modification relates to the improvement of the space 12a2 of the first modification. In FIG. 4, descriptions of components having the same configuration and operation as those of the first embodiment or the first modification are omitted.

  As shown in FIG. 4, the microwave introduction window 8 b is provided with a recess 30 and a plurality of grooves 34 a and 34 e on the surface facing the partition plate 9. The bottoms of the recess 30 and the plurality of grooves 34a and 34e do not penetrate in the thickness direction of the microwave introduction window 8b, and the depths of the recess 30 and the plurality of grooves 34a and 34e are equal to the microwave introduction window 8b. Less than the film thickness of The recess 30 is provided at the central portion of the microwave introduction window 8 b as in the first modification, and has a circular shape. The plurality of grooves 34 a and 34 e extend radially from the recess 30 toward the outer periphery of the circular microwave introduction window 8 b. The plurality of grooves 34a are connected to the second gas supply unit 13 at the outer periphery of the circular microwave introduction window 8b, and the plurality of grooves 34b are second at the outer periphery of the circular microwave introduction window 8b. It is connected to the gas exhaust unit 14. That is, the plurality of grooves 34a and 34e form a flow path for the second gas, and the second gas is supplied to the recess 30 through the plurality of grooves 34a, and the second gas is exhausted from the plurality of grooves 34b. Exhausted to part 15. The grooves 34a and the grooves 34b are alternately arranged, and in the region between the adjacent grooves 34a and the grooves 34b, the microwave introduction windows 8b and the partition plate 9 are in contact with each other.

  In the second modification, the recess 30 and the plurality of grooves 34a and 34b are formed in the microwave introduction window 8b, but may be formed in the partition plate 9 instead of the microwave introduction window 8b. In addition, it may be formed on both the microwave introduction window 8 b and the partition plate 9.

<Modification 3>
Next, still another modification of the first embodiment will be described with reference to FIG. FIG. 5 is a cross-sectional view schematically showing the configuration of a portion of a plasma processing apparatus 100c according to the third modification, and particularly shows the configuration of the microwave introduction window 8c and the waveguide 28 thereabove. Also in FIG. 5, the configuration of the microwave introduction window 8c constituting the discharge space 12b is different from that of the first embodiment, and the description of the same configuration and operation as the first embodiment is omitted.

  As shown in FIG. 5, an injection and suction unit 25 of a conductive liquid is connected to the microwave introduction window 8c, and is connected to and communicated with the discharge space 12b. In the third modification, the partition plate 9 is omitted, and the discharge space 12b is disposed at the center of the inside of the microwave introduction window 8c, and a plurality of flow paths 35 radially extending in communication with the discharge space 12b on the outer peripheral side. Is arranged. A conductive liquid flows into the discharge space 12 b from the liquid injection and suction unit 25. In addition, the liquid in the discharge space 12 b is discharged to the injection and suction unit 25 as necessary. The liquid injection and suction unit 25 may be configured as, for example, a syringe. The conductive liquid 103 may use, for example, an ionic liquid as mercury which is a liquid which is liquid at normal temperature, or a salt which is present as a liquid at normal temperature.

  When the discharge space 12 b is filled with the conductor liquid 103, the electric field of the microwaves propagated from the microwave source 1 and transmitted from the cavity 7 is reflected by the conductor liquid 103 inside the discharge space 12 b. The electric field propagated downward from the outer peripheral portion of the hollow portion 7 passes through the microwave introduction 8c and is supplied from above to the outer peripheral side of the processing chamber 11 (see FIG. 1). As a result, the electric field of the microwave in the processing chamber 11 and the electric field generated thereby. Therefore, as in the first embodiment, the first plasma 101 has a portion with high density or strength formed in the outer peripheral side portion of the processing chamber 11, so that the distribution of the inside and the outside of the etching rate is reduced. Etching variation of the film is suppressed.

  On the other hand, when the conductive liquid 103 is sucked from the discharge space 12 b by the injection and suction unit 25 and the amount of the conductive liquid 103 inside is reduced, it permeates the discharge space 12 b and permeates to the central portion of the processing chamber 11. And the density or intensity of the first plasma 101 in the vicinity of the central axis of the processing chamber 11 is increased, and the etching rate of the central portion of the upper surface of the lower sample 18 is on the outer peripheral side. It rises relatively to the department. As described above, the radial distribution of the density of the first plasma 101 is adjusted by the increase or decrease or the presence or absence of the amount (thickness, height) of the conductive liquid 103 stored in the discharge space 12. That is, the distribution of the etching rate in the radial direction of the sample 18 is adjusted to a desired one according to the operation of the injection and suction unit 25 in accordance with the command signal from the control unit 29.

<Modification 4>
Next, another modification of the first embodiment will be described with reference to FIG. FIG. 6 is a cross-sectional view schematically showing a configuration of a portion of a plasma processing apparatus 100 d according to the fourth modification. The fourth modification can be said to be a modification of the first modification. Also in FIG. 6, the configurations of the microwave introduction window 8d and the partition plate 9 that constitute the discharge space 12c1 and the space 12c2 are different from those of the first embodiment or the first modification, and are the same as the first embodiment or the first modification. Descriptions of components having actions are omitted.

  As shown in FIG. 6, the microwave introduction window 8 d has a recess 30 a on the surface facing the partition plate 9. Although not shown, the recess 30a has a ring shape in plan view. In addition, the recess 30 a is separated from the area where the circular waveguide 6 is projected from above. A space 12c2 and a discharge space 12c1 are formed between the microwave introduction window 8d and the partition plate 9. The heights of the discharge space 12c1 and the space 12c2 are the same as the discharge space 12a1 and the space 12a2 of the first modification. Unlike the first modification, the discharge space 12c1 is disposed outside the projection area where the circular waveguide 6 is projected from above, away from the projection area and surrounding the projection area. The fourth modification is effective, for example, when a mode of a microwave electric field in which the strength of the electric field is increased on the outer periphery side of the processing chamber 11 (see FIG. 1) or the waveguide 28 is formed. It becomes.

  In the case of the circular TE01 mode, if the second plasma 102 is not formed inside the ring-shaped discharge space 12c1, the intensity of the electric field at the outer peripheral portion of the waveguide 28 is increased, and the electric field is formed in the processing chamber 11 A portion of the first plasma 101 having a large density or strength in an outer peripheral side portion is in a ring shape. For this reason, the distribution of the etching rate of the film to be processed on the upper surface of the sample 18 is easily obtained with an outside height. On the other hand, when the second gas 102 is supplied from the second gas supply unit 13 and the second plasma 102 is generated in a ring shape in the discharge space 12c1, the electric field of the microwave is absorbed by the second plasma 102. In addition, since the light is reflected, it becomes difficult for the electric field of the microwave to reach the outer peripheral side of the processing chamber 11.

  Therefore, the strength or density of the first plasma 101 generated is reduced at the outer peripheral side portion of the processing chamber 11, and as a result, a region of high density is formed at the outer peripheral side of the processing chamber 11, resulting in an outer height. The distribution of the etching rate of the film to be processed is relaxed, and the variation in processing in the radial direction is reduced.

  The fourth modification has the same concept as the first embodiment described above, and the discharge space 12c1 of the microwave introduction window 8d can be used as a micro in the processing chamber 11 so that the localization of the first plasma 101 generation can be suppressed. It is to be disposed above the point where the strength or density of the electric field of the wave increases.

  The present invention is not limited to the above-described embodiment, but includes various modifications. For example, the embodiments described above are described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the configurations described. Also, part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. In addition, with respect to a part of the configuration of each embodiment, it is possible to add, delete, and replace other configurations.

CA central axis 1 microwave source 2 square waveguide 3 automatic matching device 4 isolator 5 circular rectangular converter 6 circular waveguide 7 cavity 8, 8a, 8b microwave introduction window 9 partition plate 10 shower plate 11 processing chamber 12, processing chamber 12, 12a1, 12b, 12c1 Discharge space 12a2, 12c2 Space 13 second gas supply unit 14 conductance adjustment unit 15 second gas exhaust unit 16 pressure sensor 17 first gas supply unit 18 sample 19 stage 20 conductance adjustment valve 21 vacuum pump 22 Automatic alignment machine 23 Bias power supply 24 Static magnetic field generator 25 Injection and suction part 26 Vacuum vessel (chamber)
27 exhaust opening 28 waveguide 29 control unit 30 concave portion 31 second gas supply passage 32 second gas exhaust passage 33 first gas supply passage 34 a, 34 e groove 35 passage 100, 100 a, 100 b, 100 c, 100 d plasma treatment Apparatus 101 first plasma 102 second plasma 103 conductive liquid

Claims (11)

A processing chamber in which a first plasma is formed;
A circular waveguide for transmitting a microwave electric field to the processing chamber;
A stage disposed in the processing chamber and on which the sample is placed on the top surface thereof;
A first window member disposed between the circular waveguide and the processing chamber and transmitting the electric field of the microwave for forming the first plasma;
A second window member disposed between the circular waveguide and the first window member for transmitting the electric field of the microwave;
Have
A plasma processing apparatus, comprising a discharge space for forming a second plasma between the first window member and the second window member. The plasma processing apparatus according to claim 1,
The plasma processing apparatus, wherein a region where the second plasma is projected from above is located inside the outer peripheral edge of the sample. The plasma processing apparatus according to claim 1 or 2, wherein
A plasma processing apparatus, wherein a region obtained by projecting the circular waveguide from above is located inside an outer peripheral edge of the second plasma. The plasma processing apparatus according to any one of claims 1 to 3, wherein
further,
A gas supply unit for supplying a gas to the discharge space;
A gas exhaust unit for exhausting the gas from the discharge space;
An adjustment unit that adjusts the flow rate of the gas;
, A plasma processing apparatus. The plasma processing apparatus according to claim 4,
The said adjustment part is a plasma processing apparatus arrange | positioned in the gas exhaust passage which connects the said process chamber and the said gas exhaust part. The plasma processing apparatus according to claim 5, wherein
further,
A pressure sensor disposed in the gas exhaust passage;
A control unit that controls the gas supply unit, the gas exhaust unit, and the adjustment unit based on information of the pressure sensor;
, A plasma processing apparatus. The plasma processing apparatus according to claim 4,
further,
A space between the first window member and the second window member and surrounding the discharge space in plan view;
Have
The plasma processing apparatus, wherein the height of the space is lower than the height of the discharge space. The plasma processing apparatus according to claim 7, wherein
The space is formed between a plurality of grooves formed in the second window member and the first window member,
The plurality of grooves extend from the discharge space to the outer periphery of the second window member,
The first groove of the plurality of grooves is in communication with the gas supply unit,
The second groove adjacent to the first groove is in communication with the gas exhaust unit. The plasma processing apparatus according to claim 1,
The plasma processing apparatus, wherein the discharge space is located outside a region where the circular waveguide is projected from above. A processing chamber in which a first plasma is formed;
A circular waveguide for transmitting a microwave electric field to the processing chamber;
A stage disposed in the processing chamber and on which the sample is placed on the top surface thereof;
A window member disposed between the circular waveguide and the processing chamber for transmitting the electric field of the microwave for forming the first plasma;
A space formed inside the window member;
An injector communicating with the space and supplying a conductive liquid into the space;
, A plasma processing apparatus. The plasma processing apparatus according to claim 10, wherein
An area where the circular waveguide is projected from above is located inside the space.

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