Plasma generating device and plasma generating method

Abstract

To provide a plasma generation device capable of performing a deposition over a wide range, and a plasma generation method.SOLUTION: A plasma generation device includes: a waveguide coaxial converter 11 through which a microwave passes; an antenna 13 connected to a coaxial-side end of the waveguide coaxial converter; a cylindrical chamber 14 having a space for making a raw material into plasma by the microwave emitted from the antenna 13; and a substrate stage 17 on which a substrate for depositing the raw material made into plasma is mounted. An inner diameter of the chamber 14 is 1.25 to 1.72 times a wavelength of the microwave.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a plasma generating apparatus and a plasma generating method used in semiconductor processes. [Background technology]

[0002] In the field of semiconductor manufacturing processes, there is a demand for larger wafer sizes and improved manufacturing efficiency. However, as wafer sizes increase, it becomes necessary to deposit films over a wider area.

[0003] Regarding this point, Japanese Patent Laid-Open Publication No. 9-289099 (Patent Document 1) discloses a technique for generating a ring-shaped plasma and depositing a film over a wide area. According to Patent Document 1, uniform plasma can be generated over a wide area.

[0004] However, since Patent Document 1 generates a ring-shaped plasma, it is not sufficient in terms of plasma uniformity. Therefore, there is a need for a new technology for forming a film over a wide area, in particular a technology that has a high power density and can form a film over a large area. Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in view of the above-mentioned problems in the prior art, and has an object to provide a plasma generating apparatus and a plasma generating method that are capable of forming films over a wide range. [Means for solving the problem]

[0006] That is, according to the present invention, a waveguide coaxial converter through which microwaves pass; an antenna connected to a coaxial end of the waveguide-coaxial converter; a cylindrical chamber having a space for converting a raw material into plasma by the microwaves emitted from the antenna; a substrate stage for placing a substrate on which a film is to be formed using the plasma-converted raw material; Including, The inner diameter of the cylindrical chamber is 1.25 to 1.72 times the wavelength of the microwave. A plasma generating device is provided. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a plasma generating apparatus and a plasma generating method that are capable of forming a wide range of films. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing the configuration of a plasma generating device according to the prior art. [Figure 2] FIG. 1 is a diagram showing the configuration of a plasma generation device according to an embodiment of the present invention. [Figure 3] FIG. 3 is a diagram showing dimensional parameters of the plasma generation device of the present embodiment. [Figure 4] 5A and 5B are diagrams showing simulation results of the electric field distribution generated by the plasma generating device of the present embodiment. [Figure 5] 5A and 5B are diagrams showing simulation results of the electric field distribution generated by the plasma generating device of the present embodiment. [Figure 6] 5A and 5B are diagrams illustrating examples of vectors showing electric field distribution in the present embodiment. [Figure 7] 3A and 3B are diagrams showing typical examples of plasma shapes generated by the plasma generating device of the present embodiment. [Figure 8] FIG. 2 is a diagram showing a diamond film formed using the plasma generating apparatus of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention will be described below with reference to embodiments, but the present invention is not limited to the embodiments described below. In the drawings referred to below, the same reference numerals will be used for common elements, and their description will be omitted as appropriate.

[0010] Here, the prior art that is the premise for explaining this embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram showing the configuration of a plasma generation device 1' in the prior art.

[0011] As shown in FIG. 1, a plasma generating device 1' according to the prior art includes a TM mode converter 51, a quartz window 52, ​​a chamber 53, and a substrate stage .

[0012] The TM mode converter 51 is connected to a microwave power supply (not shown) and introduces microwaves into the chamber 53. The microwaves introduced into the chamber 53 react with the raw material gas to generate plasma P.

[0013] The plasma P reacts with the substrate S placed on the substrate stage 54 to form a thin film on the substrate S. In the conventional plasma generator 1', as shown in FIG. 1, a substantially spherical plasma P is generated. Therefore, the area of ​​contact between the substrate S and the plasma P is small, and the area on which a film can be formed is narrow. For this reason, the conventional plasma generator 1' cannot be applied to large-area substrates S, which has been a factor hindering improvements in manufacturing efficiency. For example, in the case of a conventional 5 kW, 2.45 GHz band plasma generator 1', film formation on a substrate with a diameter of approximately 50 mm was typical.

[0014] Therefore, in this embodiment, a plasma generator 1 is provided that generates plasma that can increase the area of ​​the film formation range. Fig. 2 is a diagram showing the configuration of the plasma generator 1 in this embodiment. Fig. 2(a) is a schematic cross-sectional view of the plasma generator 1 of this embodiment, and Fig. 2(b) is a cross-sectional view showing the detailed structure in the vicinity of the waveguide coaxial converter 11.

[0015] As shown in FIG. 2(a), the plasma generator 1 of this embodiment includes a waveguide-coaxial converter 11, a quartz ring 12, an antenna 13, a chamber 14, a top cover 15, a gas inlet 16, a substrate stage 17, and a reflector 18. The plasma generator 1 of this embodiment can be used as a CVD apparatus for film deposition, for example, to deposit diamond films, but this is not a limitation of the embodiment. Therefore, the plasma generator 1 may also be used to deposit thin films other than diamond. In the embodiment described below, the plasma generator 1 is shown as depositing a film using microwaves in the 5 kW, 2.45 GHz band, but this is just an example, and microwaves of other powers and frequency bands may also be used.

[0016] The waveguide-coaxial converter 11 is connected to a 5 kW, 2.45 GHz microwave power supply (not shown). The antenna 13 is connected to the inner conductor 19 of the waveguide-coaxial converter 11. The inner conductor 19 to which the antenna 13 is connected is supported at its upper part by a clamp 23 (see FIG. 2(b)), thereby fixing the position of the antenna 13. A quartz ring 12 together with an O-ring (not shown) is inserted between the antenna 13 and the top lid 15. This insulates the antenna 13 from the chamber 14 and maintains the vacuum-tightness of the internal space of the chamber 14. Microwaves output from the microwave power supply are output from the antenna 13 into the chamber 14.

[0017] The chamber 14 can accommodate various components, a substrate S, and the like. The chamber 14 in this embodiment can be cylindrical, and an airtight space is defined by an upper lid 15, providing a generation chamber. The upper lid 15 is provided with a gas inlet 16, which allows gas to be supplied into the chamber 14 from a raw material gas container connected to the outside.

[0018] The microwaves output from the antenna 13 into the chamber 14 react with the raw material gas supplied from the gas inlet 16 to generate plasma. The plasma generated in the plasma generator 1 of this embodiment has, for example, a flattened spherical shape, which allows the area on the substrate S to be increased. Note that the shape of the plasma generated in the plasma generator 1 of this embodiment is not limited to a flattened spherical shape, and can also be a non-spherical shape that is expanded relative to the surface of the substrate S.

[0019] The substrate stage 17 is a stage on which the substrate S is placed. The substrate stage 17 in this embodiment can move up and down, that is, in the height direction of the cylindrical chamber 14. This allows the substrate S to be moved to a predetermined position (for example, a position where plasma with high power density and a large film formation area is generated) in the film formation process.

[0020] The reflector 18 can reflect the microwaves output from the antenna 13. In this embodiment, the reflector 18 can be moved vertically, i.e., in the height direction of the cylindrical chamber 14, allowing for appropriate control of the electric field distribution within the chamber 14. In this embodiment, the position of the reflector 18 contributes to the generation of plasma. By changing the position of the reflector 18, the axial length of the cylindrical space of the chamber 14 can be changed. By changing the position of the reflector 18, the axial length can be increased to lower the resonant frequency, and the axial length can be decreased to increase the resonant frequency. Therefore, resonance occurs by matching the resonance point with the microwave frequency. This generates a standing wave, which maximizes the electric field amplitude, thereby generating plasma.

[0021] A vacuum pump (not shown) can be connected to the chamber 14 to reduce the pressure inside the chamber. The film formation process is carried out after the air inside the chamber 14 has been sufficiently evacuated by the vacuum pump. If the chamber 14 is not sufficiently evacuated, impurities resulting from residual gas will be contained in the material being formed, affecting the product yield. After the chamber 14 has been sufficiently evacuated, a source gas is introduced into the chamber 14. The amount of source gas can be controlled by a mass flow controller (not shown). Gas can be introduced into the chamber 14 at a mass flow rate set by the mass flow controller. When plasma is generated to form a film, the pressure inside the chamber 14 can be measured and the opening of the valve in the exhaust line can be controlled to maintain a constant pressure inside the chamber 14 during film formation.

[0022] The coaxial portion of the waveguide-coaxial converter 11 and the antenna 13 are configured as shown in Fig. 2(b). That is, microwaves that pass through the waveguide portion of the waveguide-coaxial converter 11 pass through the coaxial line of the waveguide-coaxial converter 11 and reach the antenna 13. The coaxial line is composed of an inner conductor 19 and an outer conductor 20 and has a constant impedance. The inner conductor of the coaxial line passes through a hole provided in the top lid 15 and reaches the internal space of the chamber 14.

[0023] 2(b), the inner conductor 19 is electrically connected to the antenna 13 in the chamber 14. The antenna 13 has a larger diameter than the inner conductor 19 and is cylindrical in shape. That is, the impedance of the antenna 13 is lower than that of the coaxial line and is constant.

[0024] The coaxial line and antenna 13 of the waveguide-coaxial converter 11 of this embodiment may be configured as a hollow structure, and a viewport 21 may be provided. As shown in FIG. 2(b), the provision of the viewport 21 allows the state inside the chamber 14 to be observed through a window 22 at the top of the plasma generator 1. This allows, for example, visual observation of the state of the plasma P and the substrate S during the film formation process. In particular, in this embodiment, the configuration shown in FIG. 2(b) allows observation from directly above the film formation region, which provides the advantage of being able to observe the in-plane distribution when measuring the substrate temperature with a radiation thermometer or measuring the reflection coefficient with laser measurement.

[0025] 3 is a diagram showing the dimensional parameters of the plasma generator 1 of this embodiment. The plasma generator 1 can adjust various dimensional parameters to generate a flattened spherical plasma P. Examples of dimensional parameters that can be adjusted for the plasma generator 1 of this embodiment include the stage height hs, the chamber inner diameter D, and the chamber axial length h.

[0026] The stage height hs is the distance in the axial direction of the chamber 14 from the upper surface of the reflector 18 to the substrate placement surface of the substrate stage 17. In this embodiment, the stage height hs can be changed as desired by moving the substrate stage 17 up and down.

[0027] The chamber inner diameter D is the inner diameter of the cylindrical chamber 14. In this embodiment, as will be described later, by setting the inner diameter D to 1.25 to 1.72 times the wavelength of the microwave, a flattened spherical plasma P is generated, and the film formation area on the substrate S can be increased.

[0028] The stage height hs and the chamber inner diameter D are parameters that mainly affect the shape of the plasma P. By selecting an appropriate stage height hs and chamber inner diameter D, the plasma generator 1 of this embodiment can introduce TM mode microwaves in which a ring-shaped electric field is distributed inside the chamber 14, and can generate plasma with a flattened spherical shape. Therefore, in the embodiment to be described, the plasma generator 1 can generate plasma P with a desired shape by adjusting the stage height hs and the chamber inner diameter D, as shown in FIG. 3.

[0029] In order to generate a flattened spherical plasma, it is possible to use a method such as adjusting the height dimension of the antenna 13. However, in this embodiment, from the viewpoints of device manufacturing and impedance matching, the substrate stage 17 is moved.

[0030] The chamber axial length h is the distance in the axial direction of the chamber 14 from the top surface of the reflector 18 to the bottom surface of the top lid 15. In this embodiment, the chamber axial length h can be changed arbitrarily by moving the reflector 18 up and down. The chamber axial length h is a parameter mainly used to align the resonance point of the microwave. The chamber axial length h can be adjusted by moving the reflector 18, and plasma can be generated by appropriately adjusting the chamber axial length h so as to align the resonance point of the microwave.

[0031] The following describes the results of a simulation of the electric field distribution in the plasma generator 1 of this embodiment. Figures 4 and 5 are diagrams showing the results of a simulation of the electric field distribution generated by the plasma generator of this embodiment. The electric field distribution was simulated using HFSS by ANSYS. In the simulation, the stage height was kept constant, and the chamber inner diameter D was varied to calculate the electric field distribution at the axial length h at resonance. Generally, when generating plasma, there is a correlation between the inner diameter of the chamber 14 and the stage height, and there is an optimal stage height for a certain inner diameter. In Figures 4 and 5, simulations were performed for stage heights of 55 mm and 40 mm, respectively, to determine the inner diameter at which an appropriate electric field distribution was generated, and the appropriate range of inner diameters was determined based on the trend. The simulations shown in Figures 4 and 5 calculate behavior at 5 kW and 2.45 GHz microwaves.

[0032] Figure 4 shows the simulation results when the stage height hs is 55 mm. Figure 4(a) plots the axial length h and inner diameter D at which resonance occurs when the stage height hs is 55 mm. Figure 4(b) shows the electric field distribution when the inner diameter D is 110 mm, Figure 4(c) shows the electric field distribution when the inner diameter D is 150 mm, Figure 4(d) shows the electric field distribution when the inner diameter D is 182.5 mm, Figure 4(e) shows the electric field distribution when the inner diameter D is 190 mm, and Figure 4(f) shows the electric field distribution when the inner diameter D is 210 mm.

[0033] 4, when the inner diameter D was 110 mm, no strong electric field distribution was observed near the substrate stage 17 (see FIG. 4(b)), but when the inner diameter D was 150 mm or more, a strong electric field distribution spreading laterally (in the radial direction of the chamber 14) was observed near the substrate stage 17 (see the region indicated by the dashed lines in FIGS. 4(c) to 4(f)). This shows that by introducing the source gas into the chamber 17 under the conditions of FIGS. 4(c) to 4(f), a flattened spherical plasma P can be generated.

[0034] Figure 5 shows the simulation results when the stage height hs is 40 mm. Figure 5(a) plots the axial length h and inner diameter D at which resonance occurs when the stage height hs is 40 mm. Figure 5(b) shows the electric field distribution when the inner diameter D is 110 mm, Figure 5(c) shows the electric field distribution when the inner diameter D is 150 mm, Figure 5(d) shows the electric field distribution when the inner diameter D is 180 mm, Figure 5(e) shows the electric field distribution when the inner diameter D is 210 mm, Figure 5(f) shows the electric field distribution when the inner diameter D is 220 mm, and Figure 5(g) shows the electric field distribution when the inner diameter D is 230 mm.

[0035] As shown in Figure 5, when the inner diameter D was 110 mm and 230 mm, no strong electric field distribution was observed near the substrate stage 17 (see Figures 5(b) and 5(h)), but when the inner diameter D was 150 mm to 220 mm, a strong electric field distribution spreading laterally (in the radial direction of the chamber 14) was observed near the substrate stage 17 (see the regions indicated by dashed lines in Figures 5(c) to 5(g)). This shows that by introducing the source gas into the chamber 17 under the conditions of Figures 5(c) to 5(g), a plasma P with a flattened spherical shape can be generated.

[0036] 4 and 5 show that the chamber inner diameter D is preferably about 1.5 times the microwave wavelength, and more preferably 1.25 to 1.72 times the microwave wavelength. That is, in the case of microwaves in the 2.45 GHz band, the chamber inner diameter D is preferably 155 mm to 210 mm.

[0037] By setting the chamber inner diameter D within the above range, it is possible to form a high power density and a ring-shaped TM mode electric field distribution near the substrate stage 17. Therefore, when the source gas is introduced, a stable flattened spherical plasma P can be generated near the surface of the substrate S, and the film formation area can be increased.

[0038] Next, the electric field distribution of this embodiment will be explained using vectors. Fig. 6 is a diagram of an example of vectors showing the electric field distribution in this embodiment. Fig. 6 shows the vectors of the electric field distribution when viewed from a cross section cut along a plane including the central axis of the chamber 14. Therefore, in reality, the vectors shown in Fig. 6 extend in the circumferential direction of the chamber 14.

[0039] In this embodiment, the electric field distribution is as shown by the arrows in FIG. 6 . That is, on the antenna 13 side, there is a strong electric field distribution from the end of the lower surface of the antenna 13 (antenna edge) toward the inner wall of the chamber 14 (arrow A pointing diagonally downward in FIG. 6 ), but there is no electric field distribution near the center of the antenna 13. Here, the state of the electric field near the antenna 13 is such that, while there is an electric field distribution as shown by arrow A, there is no electric field distribution near the center of the antenna 13, and therefore a ring-shaped electric field distribution is formed from the antenna 13. Furthermore, on the stage 15 side, there is a strong electric field distribution toward the vertical direction (vertically upward direction) at the center of the stage 15 (arrow B pointing from the stage 15 toward the antenna 13 in FIG. 6 ). On the stage side, there is also an electric field distribution from the end of the upper surface of the stage 15 (stage edge) toward the inner wall of the chamber 14 (arrow C pointing diagonally upward in FIG. 6 ). By bringing the stage 15 closer to the antenna 13, the electric field distribution on the antenna 13 side is reinforced. Then, a non-spherical flat electric field distribution is formed by combining the ring-shaped electric field distribution on the antenna 13 side caused by the electric field of arrow A and the hemispherical electric field distribution on the stage 15 side caused by the electric field of arrow B. Therefore, when the electric field distribution shown in Fig. 6 is generated, the plasma generated by this electric field distribution has a flattened spherical shape. That is, in the plasma generator 1 of this embodiment, a strong electric field is widely distributed over the substrate S, so that it is possible to generate plasma having a shape that allows for a large film formation area.

[0040] The plasma generator 1 of this embodiment can generate plasma P that can increase the area of ​​film formation on the substrate S. Here, the plasma shape that can increase the area of ​​film formation can be a non-spherical plasma shape. Figure 7 is a diagram showing a typical example of the shape of plasma generated by the plasma generator 1 of this embodiment.

[0041] In this embodiment, the plasma generator 1 can generate plasma P having a flattened spherical shape that spreads in the radial direction of the substrate S, for example, as shown in Fig. 7(a). As another example of the plasma shape, the plasma generator 1 can generate plasma P having a disk shape with a recessed center, as shown in Fig. 7(b).

[0042] 7 is an example and does not limit the embodiment. Therefore, the shape of the plasma generated by the plasma generator 1 of this embodiment may be a non-spherical shape other than that shown in FIG.

[0043] Next, an example of film formation using the above-mentioned plasma generator 1 is shown. Figure 8 is a diagram showing a diamond film formed using the plasma generator 1 of this embodiment. Here, a diamond film was formed on a tungsten substrate with a diameter of 80 mm and a thickness of 4 mm using the plasma generator 1 of this embodiment. The experimental conditions for film formation are as follows:

[0044] Specifically, as a pretreatment, diamond powder (Diamond Powder MD80 manufactured by Tomei Diamond Co., Ltd., average particle size 75 nm) and ethanol were placed on a tungsten substrate and applied to the substrate surface. Applying diamond powder in this way facilitates diamond film formation on the tungsten substrate. The source gases introduced were H2, CH4, and O2 at 100 SCCM, 11 SCCM, and 5 SCCM, respectively. During the film formation process, the pressure inside chamber 14 was 9.3 kPa, the microwave output was 4.2 kW, the substrate temperature was 1090°C, and the film formation time was 20 hours.

[0045] When a diamond film was formed under the above conditions, the film shown in Figure 8(a) was formed. Figure 8(a) shows images of the substrate near the center and near the edge, observed with an optical microscope (attached to the Raman spectrometer). As shown in Figure 8(a), polycrystalline diamond was formed near both the center and the edge, and the film quality was similar near the center and the edge. The film thickness was approximately 73 micrometers near the center and approximately 95 micrometers near the edge.

[0046] Figure 8(b) shows the Raman spectrum of the deposited diamond film, evaluated using a Raman spectrometer. As shown in Figure 8(b), peaks are observed near 1333 cm^-1, which corresponds to the Raman shift peak of diamond, both near the center and near the edges. This demonstrates that a uniform diamond film was deposited over the entire substrate using the plasma generator 1 of this embodiment.

[0047] 8, by using the plasma generator 1 of this embodiment, a uniform film was formed over the entire surface of a relatively large substrate. That is, it was demonstrated that the plasma generator 1 of this embodiment can form a uniform film over a wide area.

[0048] According to the embodiments of the present invention described above, it is possible to provide a plasma generation device and a plasma generation method that are capable of forming films over a wide range.

[0049] Although the present invention has been described above with reference to embodiments, the present invention is not limited to the above-described embodiments, and any embodiment that can be conceived by a person skilled in the art is included in the scope of the present invention as long as it exhibits the functions and effects of the present invention. [Explanation of symbols]

[0050] 1, 1'...plasma generator, 11...waveguide coaxial converter, 12...quartz ring, 13...antenna, 14...Chamber, 15...Top lid, 16...gas inlet, 17...Substrate stage, 18...reflector, 19...inner conductor, 20...outer conductor, 21...viewport, 22...window, 23...Clamp, 51...TM mode converter, 52...quartz window, 53...Chamba, 54...substrate stage, P...plasma, S...Substrate [Prior art documents] [Patent documents]

[0051] [Patent Document 1] Japanese Patent Application Publication No. 9-289099

Claims

1. a waveguide coaxial converter through which microwaves pass; an antenna connected to a coaxial end of the waveguide-coaxial converter and outputting a ring-shaped electric field distribution in TM mode; a reflector that reflects the microwaves emitted from the antenna; a cylindrical chamber having a space for converting a raw material into plasma by the microwaves emitted from the antenna; a substrate stage for placing a substrate on which a film is to be formed using the plasma-converted raw material; Including, The inner diameter of the cylindrical chamber is 1.25 to 1.72 times the wavelength of the microwave. Plasma generator.

2. a waveguide coaxial converter through which microwaves pass; an antenna connected to a coaxial end of the waveguide-coaxial converter; a cylindrical chamber having a space for converting a raw material into plasma by the microwaves emitted from the antenna; a substrate stage for placing a substrate on which a film is to be formed using the plasma-converted raw material; Including, The inner diameter of the cylindrical chamber is 1.25 to 1.72 times the wavelength of the microwaves; the antenna has a constant impedance that is lower than the impedance of the waveguide-coaxial converter; Plasma generator.

3. The antenna outputs a ring-shaped electric field distribution in TM mode. The plasma generating device according to claim 2 .

4. The shape of the plasma generated in the cylindrical chamber is non-spherical. The plasma generating device according to claim 3 .

5. the microwaves are microwaves in the 2.45 GHz band, The inner diameter of the cylindrical chamber is 155 mm to 210 mm. The plasma generating device according to claim 1 .

6. The reflector is configured to be movable in the height direction of the cylindrical chamber. The plasma generating device according to claim 1 .

7. a waveguide coaxial converter through which microwaves pass; an antenna connected to a coaxial end of the waveguide-coaxial converter; a cylindrical chamber having a space for converting a raw material into plasma by the microwaves emitted from the antenna; a substrate stage for placing a substrate on which a film is to be formed using the plasma-converted raw material; A plasma generation method performed by a plasma generation device, comprising: outputting a ring-shaped electric field distribution in TM mode by the antenna; Including, The shape of the plasma generated in the cylindrical chamber is non-spherical. Plasma generation method.

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