JP7085828B2 - Plasma processing equipment - Google Patents

Description

The present invention relates to a plasma processing apparatus for processing a substrate-like sample such as a semiconductor wafer arranged in a vacuum processing chamber using plasma such as etching, ashing, and CVD (Chemical Vapor Deposition), and particularly ECR (Electron Cyclotron Response). ) Is used to form plasma to etch the film to be processed.

Plasma processing such as plasma etching, plasma CVD, and plasma ashing is widely used in semiconductor device manufacturing. In an etching device, which is one of the plasma processing devices, from the viewpoint of device mass productivity, it is required to achieve both anisotropic processing and isotropic processing with one etching device. Anisotropic processing can be realized by an ion assist reaction mainly composed of ions vertically incident on the wafer, and isotropic processing can be realized by a chemical reaction mainly composed of radicals diffused isotropically and incident on the wafer.

In general, at low pressure, the ion density becomes high and ion-based etching can be performed, and at high pressure, the radical density becomes high 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. Further, in order to ensure mass productivity of the device, it is necessary to be able to uniformly etch in the wafer surface in such a wide pressure range. In the manufacture of state-of-the-art devices, the wafer diameter has been increased in order to improve mass productivity, and the technical difficulty of uniformly performing plasma treatment on the wafer surface has increased.

As a technique for generating plasma, a technique using ECR, an inductive coupling, a capacitive coupling, or the like is known. It is known that ECR can efficiently generate plasma 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 a vacuum device, the electrons in the magnetic field make a rotational motion called cyclotron motion around the magnetic force lines. When a microwave having a frequency matching the speed of its rotation is incident therein, 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 it can effectively accelerate electrons and give them a large amount of energy. These high-energy electrons collide with gas molecules or atoms and ionize and dissociate to generate a plasma. The plasma generated in this way is called ECR plasma.

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

Normally, the equimagnetic field surface that satisfies the ECR condition due to the magnetic field formed by the electromagnetic coils arranged above and to the side of the processing chamber spreads horizontally in the processing chamber, so the plasma generated by the ECR in the processing chamber is also this. It is formed in a region that extends in a horizontal pattern along the surface. Therefore, it is said that relatively uniform plasma processing can be realized.

However, when the pressure in the processing chamber is relatively high, the mean free path of electrons becomes short, and the electrons moving along the electric field travel a short distance and collide with gas atoms and molecules to ionize or dissociate. Will occur. Therefore, the region where plasma is generated in the processing chamber is not in the vicinity of the equimagnetic field surface satisfying the ECR condition, but directly under the dielectric window in which the electromagnetic wave is incident, and in the processing chamber directly under the waveguide. 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 non-uniform 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.

Conventional technique for solving the problem that the portion having high plasma density or intensity is concentrated and formed in the vicinity of the central axis of such a processing chamber and the processing characteristics in the in-plane direction of the sample surface become non-uniform. Examples thereof include Japanese Patent Application Laid-Open No. 9-148097 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2013-21270 (Patent Document 2).

The plasma processing apparatus using the ECR method of Patent Document 1 includes a dielectric window arranged between a discharge chamber (processing chamber) and an electromagnetic wave transmission unit, an electromagnetic wave reflecting plate arranged below the dielectric window, and an electromagnetic wave reflecting plate. It has an auxiliary reflector. Then, an electromagnetic wave is incident into the discharge chamber from a ring-shaped electromagnetic wave emitting port formed between the electromagnetic wave reflecting plate and the auxiliary reflecting plate, and a ring-shaped plasma is generated on the ECR surface to form a uniform plasma covering the sample. is doing. In this way, plasma processing with high uniformity is realized.

Further, Patent Document 2 relates to a plasma processing apparatus of a type that generates plasma only by microwaves without using a magnetic field. The plasma processing device consists of a waveguide that is located above the processing container (chamber) and where the electric field of the microwave propagates inside, and the microwave electric field that constitutes the upper part of the processing container and propagates through the inside of the processing container. The dielectric window introduced in, the annular ring slot arranged between the waveguide and the dielectric window, and the microwave arranged on the processing container side of the dielectric window and transmitted through the dielectric window. It is provided with a shielding plate that shields an electric field. By providing the shielding plate, it is possible to suppress the formation of high-density or high-intensity plasma in the central portion of the processing container, and to reduce the non-uniformity of plasma processing in the in-plane direction of the sample.

Japanese Unexamined Patent Publication No. 9-148097 Japanese Unexamined Patent Publication No. 2013-21270

It was found that Patent Documents 1 and 2 have room for further improvement.

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

For example, as described in Patent Document 1 and Patent Document 2, in the configuration in which the shielding plate that shields microwaves is arranged so as to match the central axis of the processing chamber, the etching rate is high under the condition that the pressure in the processing chamber is relatively high. Non-uniformity can be improved. However, it has been found by the inventor of the present application that the problem occurs under the condition that the pressure in the processing chamber is relatively low due to the existence of the shielding plate. In other words, the presence of the shielding plate creates a plasma in which the plasma density or high intensity region is distributed in a ring shape in the processing chamber, resulting in a concave distribution in which the etching rate increases from the center toward the outer peripheral side. , It was found that the yield of etching treatment was reduced.

In such a case, in order to reduce the variation in the plasma processing characteristics in the radial direction of the sample surface over a wide pressure range and bring it closer to uniform, the arrangement of the shielding plate is changed according to the pressure in the processing chamber. , Or it is necessary to put on and take off. In that case, it is necessary to open the inside of the processing chamber to atmospheric pressure or a pressure that can be regarded as atmospheric pressure each time the shielding plate is attached or detached, and to reduce the pressure inside the processing chamber again after changing the arrangement or attaching or detaching. Therefore, the non-operating time during which plasma processing cannot be performed increases.

In addition, an example of arranging a shielding plate on the atmosphere side directly above the dielectric window will be examined. 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 the inside and outside of the processing container (vacuum container). Since the microwave electric field propagates inside the dielectric window and wraps around the center of the processing chamber, a region with high plasma density and intensity is formed in the center of the processing chamber, resulting in non-uniform plasma processing. It becomes impossible to reduce the density, and for example, there is a problem that the yield of the etching treatment process is reduced.

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

In order to solve the above problems, the plasma processing apparatus of one embodiment is arranged in a processing chamber in which a first plasma is formed, a circular waveguide in which a microwave electric field is transmitted to the processing chamber, and a processing chamber. A stage on which the sample is placed, a partition plate that is placed between the circular waveguide and the processing chamber and that allows the microwave electric field to pass through to form the first plasma, and the circular waveguide. It has a microwave introduction window, which is arranged between the partition plate and allows a microwave electric field to pass through. The plasma processing apparatus further includes a discharge space for forming a second plasma between the microwave introduction window and the partition plate.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a plasma processing apparatus that improves the processing yield of a sample in plasma processing in a wide pressure range.

It is sectional drawing which shows the outline of the structure of the plasma processing apparatus which concerns on Example 1 of this invention schematically. It is a graph which shows the distribution of the etching rate in the in-plane direction of the sample which is etched inside the plasma processing apparatus which concerns on Example 1 of this invention. It is sectional drawing which shows typically the structure of the part of the plasma processing apparatus which concerns on modification 1. FIG. It is a top view schematically showing the structure of a part of the plasma processing apparatus which concerns on modification 2. FIG. It is sectional drawing which shows typically the structure of the part of the plasma processing apparatus which concerns on modification 3. FIG. It is sectional drawing which shows typically the structure of the part of the plasma processing apparatus which concerns on modification 4.

Embodiments of the present invention will be described below with reference to 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 an outline of the configuration of the plasma processing apparatus according to the 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 inside the plasma processing apparatus according to the first embodiment of the present invention.

In Example 1, when the pressure in the processing chamber is relatively low (1 Pa or less), the etching process is performed without generating the second plasma, and the pressure in the processing chamber is relatively high (several Pa or more). In the case, the present invention relates to a plasma processing apparatus that generates a second plasma and performs 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 the vacuum vessel 26 is provided with a microwave introduction window 8, a second discharge space 12, a partition plate 9, a processing chamber 11, and the like. Has been done. The treatment chamber 11 is provided with a shower plate 10 and a stage 19 having a plurality of through holes. A substrate-like sample 18 such as a semiconductor wafer to be plasma-etched is arranged on the stage 19. An insulating layer (or 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. When the sample 18 is subjected to plasma etching treatment, the work film in the region exposed from the mask layer is removed, and the work film is selectively left in the region covered with the mask layer.

The plasma processing apparatus 100 is arranged above and to the side of the vacuum vessel 26, and has a plasma forming unit that generates an electric field and a magnetic field supplied to form a first plasma 101 in the processing chamber, and a vacuum vessel 26. It is provided with an exhaust unit including a vacuum pump 21 such as a turbo molecular pump which communicates with an exhaust opening 27 arranged at the bottom of the processing chamber 11 and exhausts particles inside 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 arranged in an atmosphere created at atmospheric pressure outside the vacuum vessel 26, and an electric field having a predetermined frequency is processed from above the vacuum vessel 26. It includes a waveguide 28 to be introduced into the chamber 11 and a static magnetic field generator 24 arranged around the waveguide 28 so as to surround the processing chamber 11.

The waveguide 28 has a rectangular waveguide 2 whose axis extends in the horizontal direction and has a rectangular cross section, and a waveguide 28 which is connected to the square waveguide 2 and whose axis extends in the vertical direction and has a circular cross section. The circular waveguide 6 which is a conduit having a It is provided with a circular rectangular converter 5 that faces the waveguide 6.

A microwave source 1 such as a magnetron formed by oscillating an electric field of microwaves used in the first embodiment is arranged at one end of a square waveguide 2, and a circular rectangle is arranged at the other end of the square waveguide 2. The converter 5 is arranged and connected. An automatic matching machine 3 and an 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 machine 3 and the isolator 4. It is transmitted to the circular waveguide 6 via the circular rectangular converter 5.

In Example 1, a 2.45 GHz magnetron, which is often used as an industrial frequency, was used as the microwave source 1. However, the present invention is not limited to this frequency, and an electromagnetic wave 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 microwave propagating toward the processing chamber 11 is reflected and reflected in the circular waveguide 6 or the square waveguide 2 toward the microwave source 1. The wave is suppressed to improve the efficiency of supplying the microwave electric field into the processing chamber 11. Further, the isolator 4 has a function of protecting the microwave source 1 from the reflected wave.

The diameter of the circular waveguide 6 is selected so that the electric field propagating downward inside is only in the circular TE11 mode, which is the basic 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 of the circular waveguide 6 is connected to the cavity 7, and the cavity 7 has the same diameter as or similar to the inside of the processing chamber 11 above the vacuum vessel 26. It has a cylindrical shape. The electric field propagating in the circular waveguide 6 and introduced into the cavity 7 is adjusted so as to have an intensity distribution suitable for plasma processing inside the cavity 7 having an increased diameter.

A microwave introduction window 8 made of a dielectric material and a partition plate 9 are arranged below the cavity 7 and between the processing chamber 11, and these are the upper ends of the side wall having a cylindrical shape of the vacuum vessel 26. The processing chamber 11 whose internal space is depressurized and the discharge space 12 are shielded from the outside atmosphere of the vacuum vessel 26. Below the partition plate 9, a shower plate 10 having a disk shape constituting the ceiling surface of the processing chamber 11 is arranged.

Quartz, which efficiently transmits microwaves and has plasma resistance, is used for the microwave introduction window 8, the partition plate 9, and the shower plate 10. Alternatively, ytria, alumina, yttrium fluoride, aluminum fluoride, aluminum nitride or the like may be used as a material having high plasma resistance and transmitting microwaves.

The microwave introduction window 8 and the partition plate 9 each having a disk shape are arranged with a gap in the vertical direction, and the microwave introduction window 8 and the partition plate 9 form a lid on the upper part of the vacuum container 26. Further, the microwave introduction window 8 and the partition plate 9 are window members through which a microwave electric field is transmitted. The gap between them is shielded from the outside of the vacuum vessel 26 and the atmosphere of the processing chamber 11, and constitutes the discharge space 12. The microwave introduction window 8 is arranged above the discharge space 12 so as to cover it, and constitutes another window member that separates the inside and the outside of the discharge space 12. That is, the microwave introduction window 8 shields the discharge space 12 from the atmosphere outside the vacuum vessel 26, and the partition plate 9 blocks the discharge space 12 from the atmosphere of the processing chamber 11.

The discharge space having a cylindrical or disk shape is connected and communicated with a second gas supply unit 13 via a second gas supply path 31 at one end thereof, and at a second end portion thereof. It is connected and communicated with the gas exhaust portion 15 of the above via a second gas exhaust passage 32. A conductance adjusting unit 14 and a pressure sensor 16 for detecting the pressure inside the discharge space 12 are provided on the second gas exhaust passage 32. The second gas supplied from the second gas supply unit 13 is introduced into the discharge space 12 from the second gas supply path 31 connected to the vacuum vessel 26, dispersed internally, and then the second gas. It is exhausted by the second gas exhaust unit 15 through the exhaust passage 32 and the conduction adjustment unit 14.

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

As the second gas exhaust unit 15, for example, a dry pump for roughing such as a rotary pump is used. Further, as the conductance adjusting unit 14, a throttle such as an orifice or a variable valve that increases or decreases the cross-sectional area of the flow path 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 way, it is possible to uniformly disperse the second gas in the discharge space 12 and suppress the non-uniformity of the internal pressure, which will be described later. The intensity or density of the plasma can be achieved in the desired distribution.

Further, the pressure in the discharge space 12 is detected by the pressure sensor 16 arranged on the upstream side of the conductance adjusting unit 14 of the second gas exhaust passage 32. Then, the control unit 29 receives the output from the pressure sensor 16, and the arithmetic unit arranged inside the control unit 29 is stored in the memory, hard disk, CD-ROM, or other storage device arranged inside the control unit 29 in advance. A command signal calculated according to the pressure value detected according to the recorded software algorithm is transmitted to the mass flow controller or the conductance adjusting unit 14 of the second gas supply unit 13 to adjust the operation. That is, the control unit 29 adjusts the operation of the second gas supply unit 13, the second gas supply unit 13, or the conduction adjustment unit 14 according to the pressure detection result of the discharge space 12, and the second gas flow rate. By adjusting the pressure of the discharge space 12, the pressure of the discharge space 12 can be adjusted to a desired value.

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

The gap between the partition plate 9 and the shower plate 10 having a disk shape is connected and communicated with the first gas supply unit 17 via the first gas supply path 33. The first gas for treatment supplied from the first gas supply unit 17 to the gap is dispersed inside the gap, passes through a plurality of through holes arranged in the central portion of the shower plate 10, and downwards into the treatment chamber 11. Will be supplied. The plurality of through holes reduce the non-uniformity of the amount of the first gas supplied to the processing chamber 11 by dispersing the first gas from the shower plate 10 and flowing it into the processing chamber 11.

A stage 19 is provided in the lower part of the processing chamber 11, and the sample 18 is adsorbed and held on the stage 19 by an electrostatic force. An exhaust opening 27 is arranged on the bottom surface 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, and the processing chambers 11 are placed above and below the stage 19. Each has its own space.

The exhaust opening 27 is the upper end of the exhaust path constituting the exhaust portion, which is an opening communicating with the processing chamber 11, and is on the exhaust path connecting and communicating between the exhaust opening 27 and the inlet of the vacuum pump 21. The conductance adjusting valve 20 is arranged in the vehicle. The conductance adjustment valve 20 is driven by the 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 the exhaust of particles such as gas, plasma, and reaction products from the processing chamber 11 is adjusted by the operation of the vacuum pump 21.

In a plan view, the centers of the cylindrical processing chamber 11, the stage 19, and the circular exhaust opening 27 are aligned with or approximated to the central axis CA of the plasma processing apparatus 100. It is placed in a 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 disk or a cylindrical electrode made of a conductor such as a metal (not shown) is provided inside the stage 19, and the electrode is automatically matched with a bias power supply 23 that supplies high frequency power that forms 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 other frequencies such as 13.56 MHz are selected according to the purpose required for plasma processing.

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

The processing chamber 11 is located on the outer circumference of the cylindrical side wall of the vacuum vessel 26 surrounding the processing chamber 11 having a cylindrical shape, the outer circumference of the upper cavity portion 7, and the outer circumference of the circular waveguide 6 above the cavity portion 7. A static magnetic field generator 24 including a solenoid coil forming a magnetic field supplied therein and an electromagnet such as a yoke is arranged. The direct current supplied to the static magnetic field generator 24 is appropriately adjusted by the control unit 29, and the strength and distribution of the magnetic field are adjusted so as to satisfy the conditions of the magnetic flux density required to generate ECR in the processing chamber 11. It will be realized.

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

Further, by adjusting the distribution of the static magnetic field, the direction of diffusion of the particles in the plasma 101 and the distribution of the density of the particles can be adjusted with respect to the sample 18. The coils of the electromagnet used as the static magnetic field generator 24 are arranged in a plurality, particularly in a stepwise manner in the vertical direction, in order to facilitate the control of the region where the first plasma 101 is generated and the diffusion of the first plasma 101. It is desirable to be done.

The etching of the film to be processed arranged on the surface of the sample 18 is performed by using the first plasma 101. The first plasma 101 is formed by the microwave supply source 1, is generated by the microwave electric field and the static magnetic field generator 24 propagated through the waveguide 28 and supplied into the processing chamber 11, and is supplied into the processing chamber 11. The ECR generated by the generated magnetic field is used to excite, dissociate or ionize the first gas introduced into the processing chamber 11 to form it. Then, charged particles such as ions existing 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 are processed with the reactive particles such as radicals. The film to be processed is etched by promoting the reaction with the film.

Up to this point, the etching method when the processing chamber 11 has a low pressure of 1 Pa or less has been described, but next, the etching method when the processing chamber 11 has a high pressure of several Pa or more will be described.

When the pressure of the processing chamber 11 is set to a high pressure of several Pa or more, a high-strength region of the first plasma 101 is formed in the vicinity of the central axis CA of the treatment chamber 11, and the high-strength region of the film to be processed is formed. The etching rate becomes high, and the distribution of the etching rate becomes a so-called medium-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 to make the radial distribution of the etching rate uniform from the convex shape. It is something to do. Further, if necessary, the rate of the outer peripheral side portion can be adjusted to a concave distribution higher than that of the central portion. With this function, the etching rate can be made uniform in a wide range of pressure in the processing chamber 11.

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

Typically, assuming that the distance between the flat plate-shaped microwave introduction window 8 and the partition plate 9, that is, the length (height) of the cylindrical or disk-shaped discharge space 12 in the CA direction of the central axis is several mm. The range of pressure at which discharge can be started in the discharge space 12 is 100 to 1000 Pa. Further, due to the fact that the strength of the microwave electric field in the circular TE11 mode of the circular waveguide 6 is stronger in the central portion than in the peripheral portion, the strength of the microwave electric field becomes stronger in the central axis of the discharge space 12 and its portion. It tends to be high in the vicinity.

From the above, by realizing the values of parameters such as pressure that satisfy Paschen's law, the second plasma 102 is generated in the central axis CA of the discharge space 12 and its vicinity. Further, the density of the second plasma 102 can be adjusted by increasing or decreasing the pressure in the discharge space 12. A spectroscope and a photodetector (not shown) can be used to measure the pressure in the discharge space 12. For example, the light emitted from the second plasma 102 is received by a spectroscope, and the intensity of light having an arbitrary wavelength is detected by a photodetector. The control unit 29, which has received the detection result output by the photodetector, uses the intensity of light emission calculated from the received signal as information indicating the density of the second plasma 102, and the pressure and gas supply amount in the discharge space 12. Alternatively, the displacement may be adjusted. Further, a 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. Further, 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 it should be high enough.

The second plasma 102 is formed in the discharge space 12 arranged on the propagation path of the microwave electric field between the cavity 7 and the processing chamber 11, so that the microwave supplied from the microwave source 1 is formed. 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 depending on the magnitude of the density of the second plasma 102. That is, by adjusting the density of the second plasma 102, the transmittance of the microwave electric field of the cavity 7 transmitted from the cavity 7 to the central axis CA of the processing chamber 11 and the region in the vicinity thereof can be adjusted. can.

By making such an adjustment during the processing of the sample 18, the distribution of the density of the first plasma 101 in the processing chamber 11 in the radial direction (direction orthogonal to the central axis CA) of the processing 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 etching rate of the film to be processed on the surface of the sample 18 treated by the first plasma 101 is such that the central portion is from the outer peripheral side portion. It is a high medium-high (convex type) ((a) in FIG. 2). This is because the microwave electric field in the cavity 7 permeates the inside of the discharge space 12 without causing a large interaction and propagates in the processing chamber 11. The first plasma 101 formed by the electric field of the microwave has a portion having a higher intensity than the portion on the outer peripheral side thereof in the central axis CA of the processing chamber 11 and its vicinity. 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 magnitude of the density thereof is appropriately adjusted, the electric field of the microwave in the central axis CA of the processing chamber 11 and the region in the vicinity thereof is formed. 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 relaxed and the distribution of the middle and high heights is relaxed, and the distribution becomes closer to a uniform one ((b) in FIG. 2).

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

As a result, the localization of the first plasma 101, in which the central axis CA of the processing chamber 11 and the vicinity thereof are concentrated with higher intensities or densities than those on the outer peripheral side, and the distribution is medium and high, is alleviated. .. Further, the phenomenon that the distribution of the etching rate in the radial direction from the center of the sample 18 becomes medium and high is also suppressed. Further, when the density of the second plasma 102 is adjusted to be equal to or higher than the cutoff density in response to the command signal from the control unit 29, the microwave introduction window 8 from the cavity 7 toward the inside of the processing chamber 11 Since the electric field of the microwave transmitted through the plasma 102 cannot be transmitted through the second plasma 102 and is reflected, the electric field of the microwave is selectively introduced into the discharge space 12 and the outer peripheral side portion of the partition plate 9. It is transmitted and supplied into the processing chamber 11 from the outer peripheral side portion thereof. As a result, the electric field of the microwave and the intensity or density of the first plasma 101 have a so-called outer height distribution in which high portions are concentrated on the outer peripheral side portion of the processing chamber 11 (FIG. 2). (C)). In this case, the etching rate of the film to be processed on the upper surface of the sample 18 treated by the first plasma 101 can also be an outer height distribution in which the outer peripheral side is higher than the value on the central side.

Further, 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 the isomagnetic field surface of 875 G satisfying the ECR condition. The shape and position of the isomagnetic field surface of 875G are adjusted by the magnetic field generated by adjusting the electric power supplied to the static magnetic field generator 24 according to the command signal from the control unit 29. As a result, the position where the first plasma 101 is generated and the diffusion of the particles of the first plasma 101 along the magnetic force lines are adjusted, and the value of the etching rate of the film to be processed and its distribution can also be adjusted. In this case, it is not always necessary to generate the second plasma 102 to adjust the distribution shape of the etching rate, but the density of the second plasma 102 is adjusted as necessary to adjust the distribution of the etching rate of the film to be processed. You may.

According to the above-mentioned Example 1, the processing chamber is adjusted by adjusting the distribution of the intensity or density of the first plasma 101 by using the second plasma 102 according to the treatment conditions of the film to be processed of the sample 18. It is possible to provide a plasma processing apparatus that 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 example 1>
Next, a modified example of the above-mentioned Example 1 will be described with reference to FIG. FIG. 3 is a cross-sectional view schematically showing the configuration of a part of the plasma processing apparatus 100a according to the first modification. In the first modification, the configuration of the microwave introduction window 8a constituting the discharge space 12a1 is different from that of the first embodiment. Those having the same configuration and operation as those of the first embodiment are omitted from the description.

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

The microwave introduction window 8a faces the partition plate 9 with the space 12a2 or the discharge space 12a1 interposed therebetween. As shown in FIG. 3, a discharge space 12a1 is formed in the region where the recess 30 is located, and a space 12a2 is formed around the discharge space 12a1. In other words, a discharge space 12a1 is formed between the thin film portion of the microwave introduction window 8a and the partition plate 9, and a 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 in which discharge or plasma cannot be generated or suppressed by the microwave electric field. .. 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 placed in a part of the space 12a2 on the outer peripheral side thereof. It is communicated via the gas supply passage 31 of No. 2, and the second gas exhaust portion 15 is communicated via the second gas exhaust passage 32 at the other portion on the outer peripheral side. The conductance adjusting 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 conduction 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 pressure in the discharge space 12a1 is adjusted to a value within a predetermined range. Depending on the frequency of the electric field of the microwave used in the microwave source 1 and the dimensions, shape, and structure of the second discharge space 12a1 and space 12a2, the pressure that can form an internal discharge, the pressure that can prevent the discharge, and the values of H1 and H2. The appropriate pressures, H1 and H2, are not limited to the illustrated values because the appropriate range of is variable.

In the modified example 1 having such a configuration, the central portion where 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 discharged. It is formed only in the inner region of the diameter D1 of the space 12a1 (the space of the height H1), and is formed so as to spread over the entire inner region of the discharge space 12a1. By adjusting the density of the second plasma 102 according to the command signal from the control unit 29, the microwave propagating from the upper cavity portion 7 in the region 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 in the radial direction from the central axis of the density or intensity of the first plasma 101 generated in the processing chamber 11 and its distribution 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 region 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 higher directly under the circular waveguide 6 than in the surroundings. Therefore, it is important to form the second plasma 102 (in other words, the recess 30) so as to completely cover the region projected from above the circular waveguide 6.

Further, since the second plasma 102 is not formed in the space 12a2 on the outer peripheral side portion of the discharge space 12a1, the microwave passes through the outer peripheral side portion of the partition plate 9 below the discharge space 12a1 and efficiently reaches the outer peripheral side portion of the processing chamber 11. The electric field of the above is supplied, and the first plasma 101 having high intensity or density is efficiently formed on the outer peripheral portion.

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

Although the modification 1 shows an example in which the recess 30 is provided in the microwave introduction window 8a, the recess 30 may be provided in the partition plate 9 instead of the microwave introduction window 8a.

<Modification 2>
Next, another modification of Example 1 will be described with reference to FIG. FIG. 4 is a plan view schematically showing the configuration of a part of the plasma processing apparatus 100b according to the modified example 2, and in particular, the microwave introduction window 8 and the second gas supply unit 13 and the second gas exhaust unit 15. The configuration of is schematically shown. Modification 2 relates to the improvement of the space 12a2 of modification 1. In FIG. 4, the description of the one having the same configuration and operation as that of the first embodiment or the first modification is omitted.

As shown in FIG. 4, the microwave introduction window 8b is provided with a recess 30 and a plurality of grooves 34a and 34e on the surface facing the partition plate 9. The bottom of the recess 30 and the plurality of grooves 34a and 34e does not penetrate in the thickness direction of the microwave introduction window 8b, and the depth of the recess 30 and the plurality of grooves 34a and 34e is the depth of the microwave introduction window 8b. Is smaller than the film thickness of. The recess 30 is provided in the central portion of the microwave introduction window 8b and has a circular shape, as in the first modification. The plurality of grooves 34a and 34e extend radially from the recess 30 toward the outer periphery of the circular microwave introduction window 8b. The plurality of grooves 34a are connected to the second gas supply unit 13 at the outer peripheral portion of the circular microwave introduction window 8b, and the plurality of grooves 34b are connected to the second gas supply unit 13 at the outer peripheral portion 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 are flow paths for the second gas, 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. It is exhausted to the part 15. The grooves 34a and the grooves 34b are arranged alternately, and the microwave introduction window 8b and the partition plate 9 are in contact with each other in the region between the adjacent grooves 34a and the groove 34b.

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. Further, it may be formed on both the microwave introduction window 8b and the partition plate 9.

<Modification 3>
Next, 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 part of the plasma processing apparatus 100c according to the modified example 3, and in particular, shows the configuration of the microwave introduction window 8c and the waveguide 28 above the microwave introduction window 8c. 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 one having the same configuration and operation as that of the first embodiment is omitted.

As shown in FIG. 5, a conductive liquid injection and suction unit 25 is connected to the microwave introduction window 8c, and is connected to and communicates with the discharge space 12b. In the third modification, the partition plate 9 is omitted, the discharge space 12b is arranged in the central portion inside the microwave introduction window 8c, and a plurality of flow paths 35 communicating with the discharge space 12b and extending radially on the outer peripheral side thereof. Is placed. The conductive liquid flows into the discharge space 12b from the liquid injection and suction unit 25. Further, if necessary, the liquid in the discharge space 12b is discharged to the injection and suction unit 25. The liquid injection and suction unit 25 may be configured as, for example, a syringe. As the conductive liquid 103, for example, mercury may be used as a metal that becomes liquid at room temperature, or an ionic liquid may be used as a salt that exists as a liquid at room temperature.

When the discharge space 12b is filled with the conductor liquid 103, the electric field of the microwave propagating from the microwave source 1 and transmitted through the cavity 7 is reflected by the conductor liquid 103 inside the discharge space 12b. The electric field propagating downward from the outer peripheral side portion of the cavity 7 is transmitted from above to the outer peripheral side portion of the processing chamber 11 (see FIG. 1) through the microwave introduction 8c. This causes the microwave electric field in the processing chamber 11 and thereby. Therefore, as in the first embodiment, in the first plasma 101, a portion having a high density or strength is formed on the outer peripheral side portion of the processing chamber 11, so that the distribution of the middle and high etching rates is reduced, and the processing is performed. Etching variation of the film is suppressed.

On the other hand, when the conductive liquid 103 is sucked from the discharge space 12b by the injection and suction unit 25 and the amount of the conductive liquid 103 inside is reduced, it penetrates through the discharge space 12b and penetrates into the central portion of the processing chamber 11. The transmittance of the electric field of the microwave is increased, the density or intensity of the first plasma 101 in the central axis of the processing chamber 11 and its vicinity 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 relative to the part. In this way, the radial distribution of the density of the first plasma 101 is adjusted by increasing or decreasing 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 value according to the injection according to the command signal from the control unit 29 and the operation of the suction unit 25.

<Modification example 4>
Next, another modification of the above-mentioned Example 1 will be described with reference to FIG. FIG. 6 is a cross-sectional view schematically showing the configuration of a part of the plasma processing apparatus 100d according to the modified example 4. The modified example 4 can be said to be a modified example of the modified example 1. Also in FIG. 6, the configurations of the microwave introduction window 8d and the partition plate 9 constituting the discharge space 12c1 and the space 12c2 are different from those of the first embodiment or the first modification, and the configurations are the same as those of the first embodiment or the first modification. The explanation is omitted for those having an action.

As shown in FIG. 6, the microwave introduction window 8d has a recess 30a on the surface facing the partition plate 9. Although not shown, the recess 30a has a ring shape in a plan view. Further, the recess 30a is separated from the region 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 those of the discharge space 12a1 and the space 12a2 of the first modification. Unlike the first modification, the discharge space 12c1 is arranged outside the projection region in which the circular waveguide 6 is projected from above, away from the projection region, and surrounding the projection region. Modification 4 is effective when a microwave electric field mode in which the electric field strength is increased is formed on the outer peripheral side of the processing chamber 11 (see FIG. 1) or the waveguide 28, for example, as in the circular TE01 mode. Will be.

In the case of the circular TE01 mode, if the second plasma 102 is not formed inside the ring-shaped discharge space 12c1, the strength of the electric field on the outer peripheral side portion of the waveguide 28 becomes large and is formed in the processing chamber 11. The first plasma 101 has a ring shape at a portion having a high density or strength on the outer peripheral side portion thereof. Therefore, it is easy to obtain a sample 18 having an outer height as the etching rate distribution of the film to be processed on the upper surface. On the other hand, when the second gas 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. Or because it is reflected, it becomes difficult for the microwave electric field to reach the outer peripheral side portion of the processing chamber 11.

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

The modified example 4 has the same concept as that of the first embodiment, and the discharge space 12c1 of the microwave introduction window 8d is set to the micro in the processing chamber 11 so that the localization of the first plasma 101 generation can be suppressed. It is placed above the place where the strength or density of the electric field of the wave is high.

The present invention is not limited to the above-described embodiment, and includes various modifications. For example, the above-described embodiment has been described in detail in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to the one including all the described configurations. Further, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Further, it is possible to add / delete / replace a part of the configuration of each embodiment with another configuration.

CA Central axis 1 Microwave source 2 Square waveguide 3 Automatic matching machine 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, 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 matching 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 Recess 31 Second gas supply path 32 Second gas exhaust path 33 First gas supply path 34a, 34e Groove 35 Flow path 100, 100a, 100b, 100c, 100d Plasma processing Device 101 First plasma 102 Second plasma 103 Conductive liquid

Claims (8)

A processing chamber in which the first plasma is formed, and
A circular waveguide that transmits a microwave electric field to the processing chamber,
A stage arranged in the processing chamber and a sample placed on the upper surface thereof,
A first window member arranged between the circular waveguide and the processing chamber and through which the electric field of the microwave for forming the first plasma is transmitted.
A second window member arranged between the circular waveguide and the first window member and through which the electric field of the microwave is transmitted ,
A discharge space provided between the first window member and the second window member for forming a second plasma , and
A gas supply unit that supplies gas to the discharge space and
A gas exhaust unit that exhausts the gas from the discharge space,
An adjusting unit that adjusts the flow rate of the gas,
A space between the first window member and the second window member that surrounds the discharge space in a plan view.
Have,
The height of the space is lower than the height of the discharge space,
The space is formed between the 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 among the plurality of grooves is communicated with the gas supply unit.
The second groove adjacent to the first groove is a plasma processing device communicating with the gas exhaust portion . The plasma processing apparatus according to claim 1.
The region where the second plasma is projected from above is a plasma processing apparatus located inside the outer peripheral edge of the sample. The plasma processing apparatus according to claim 1 or 2.
The region obtained by projecting the circular waveguide from above is a plasma processing apparatus located inside the outer peripheral edge of the second plasma. The plasma processing apparatus according to claim 1 .
The adjusting unit is a plasma processing device arranged in a gas exhaust path communicating the processing chamber and the gas exhaust unit. The plasma processing apparatus according to claim 4 .
moreover,
The pressure sensor arranged in the gas exhaust passage and
A control unit that controls the gas supply unit, the gas exhaust unit, and the adjustment unit based on the information of the pressure sensor.
Has a plasma processing device. The plasma processing apparatus according to claim 1.
The discharge space is a plasma processing device located outside the region where the circular waveguide is projected from above. A processing chamber in which the first plasma is formed, and
A circular waveguide that transmits a microwave electric field to the processing chamber,
A stage arranged in the processing chamber and a sample placed on the upper surface thereof,
A window member arranged between the circular waveguide and the processing chamber and through which the electric field of the microwave for forming the first plasma is transmitted.
The space formed inside the window member and
An injection unit that communicates with the space and supplies a conductive liquid into the space.
Has a plasma processing device. The plasma processing apparatus according to claim 7 .
The region where the circular waveguide is projected from above is a plasma processing device located inside the space.

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