Plasma device and substrate processing method using coaxial waveguide

Abstract

An example of a plasma device includes: a coaxial waveguide having an inner conductor and an outer conductor surrounding the inner conductor, wherein a first gap is provided between the outer conductor and the inner conductor, the coaxial waveguide having a shape branched at a plurality of branch portions; a plurality of rods having a conductor and a dielectric surrounding the conductor, wherein a second gap is provided between the dielectric and the conductor, the plurality of rods connecting both ends of the coaxial waveguide branched at the branch portion to connect the first gap and the second gap; and a conductive post provided at a branch portion of the coaxial waveguide obtained by branching at the branch portion, the conductive post being insertable into and removable from the first gap.

Description

Technical Field

[0001] The described examples relate to a plasma apparatus using a coaxial waveguide and a substrate processing method using the plasma apparatus. Background Art

[0002] As disclosed in WO2011 / 021607, in some plasma devices, microwaves are used as a plasma source. The plasma device has a pile member that can extend from the outer conductor side to the inner conductor side. The inner conductor is displaced in position relative to the center of the outer conductor, and since the radial gap between the inner conductor and the outer conductor is not uniform, this makes the microwave intensity non-uniform. The pile member is provided to alleviate the adverse effects caused by the position displacement.

[0003] There is a plasma device having a basic structure different from that of WO2011 / 021607. Specifically, a coaxial waveguide having a branched shape is connected by a rod covered with a dielectric, and microwaves are supplied from the coaxial waveguide into the dielectric. That is, microwaves guided from a microwave introduction portion of the coaxial waveguide are transmitted through the branched structure of the coaxial waveguide, and finally reach a plurality of rods. The electric field generated by the dielectric of the rod causes plasma to be generated. Such a plasma device that generates plasma by using a plurality of rods cannot control the ratio of microwave power supplied to the plurality of rods. Summary of the invention

[0004] Some examples described herein can solve the above problems.Some examples described herein can provide a plasma device and a substrate processing method capable of controlling plasma distribution.

[0005] In some examples, a plasma device includes: a coaxial waveguide having an inner conductor and an outer conductor surrounding the inner conductor, wherein a first gap is provided between the outer conductor and the inner conductor, the coaxial waveguide having a shape branched at a plurality of branch portions; a plurality of rods having a conductor and a dielectric surrounding the conductor, wherein a second gap is provided between the dielectric and the conductor, the plurality of rods connecting both ends of the coaxial waveguide branched at the branch portion to connect the first gap and the second gap; and a conductive post provided at a branch portion of the coaxial waveguide obtained by branching at the branch portion, the conductive post being insertable into and removable from the first gap. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 is a perspective view showing a configuration example of a plasma device;

[0007] Figure 2A is a partial cross-sectional view of a plasma device;

[0008] Figure 2B is a cross-sectional view of a coaxial waveguide;

[0009] Figure 2C is a cross-sectional view of the rod;

[0010] Figure 3 is a plan view of the plasma device;

[0011] Figure 4 It is a perspective view of the branch section;

[0012] Figure 5 is a cross-sectional view of a portion of a coaxial waveguide;

[0013] Figure 6 A pile according to another example is shown;

[0014] Figure 7 A pile according to yet another example is shown;

[0015] Figure 8 It is a top view of the pile;

[0016] Fig. 9 An example of a pile arrangement is shown;

[0017] Fig.10 is a diagram showing the results of electromagnetic field simulation;

[0018] Fig.11 The electric field strength of the rod is shown;

[0019] Fig.12 shows the electric field strength of the rod; and

[0020] Fig.13 The electric field strength of the rod is shown. DETAILED DESCRIPTION

[0021] A plasma apparatus and a substrate processing method will be described with reference to the accompanying drawings. The same reference numerals may be used for the same or corresponding components, thereby omitting redundant descriptions.

[0022] Figure 1 1 is a perspective view showing a configuration example of a plasma device. The plasma device includes a microwave introduction portion 10. A coaxial waveguide 12 is connected to the microwave introduction portion 10. Microwaves are supplied to the coaxial waveguide 12 from a microwave generator outside the plasma device via the microwave introduction portion 10. A tuner 11 is provided near the microwave introduction portion 10. The tuner 11 causes the reflected wave in the microwave introduction portion 10 to advance to the coaxial waveguide 12 again.

[0023] The coaxial waveguide 12 includes an introduction waveguide 12A, a center waveguide 12B, and an edge waveguide 12C. The introduction waveguide 12A is a waveguide extending in the z direction. The edge waveguide 12C branching from the introduction waveguide 12A in the positive and negative x directions is connected to the introduction waveguide 12A. The edge waveguide 12C branches from the introduction waveguide 12A at a branch portion 12D, and then branches again, thereby connecting to the side surface of the housing 14. The branch portion 12D serves as a first branch portion, which branches the microwaves guided from the microwave introduction portion 10 to the coaxial waveguide 12 in three directions.

[0024] Another branch portion is provided below the branch portion 12D of the introduction waveguide 12A, and the center waveguide 12B branched in the positive and negative x directions is connected at the other branch portion. The center waveguide 12B branches multiple times and then connects to the side surface of the housing 14.

[0025] Figure 1 It is shown that six ends 12E of the coaxial waveguide 12 are connected to the left side of the housing 14. In addition, six ends 12E of the coaxial waveguide 12 are connected to the right side of the housing 14. Therefore, the coaxial waveguide 12 has a microwave introduction portion 10 and a plurality of ends 12E obtained by branching at a plurality of branch portions. The branch portion closest to the microwave introduction portion 10 among the plurality of branch portions is the first branch portion, i.e., the branch portion 12D. According to another example, the number of ends can be increased or decreased by increasing or decreasing the number of branches of the coaxial waveguide 12. The chamber 16 is disposed below the housing 14.

[0026] Figure 2A : is a partial cross-sectional view of a plasma device. The figure shows a cross-section of a coaxial waveguide 12 and a rod, in which a part of the device is omitted or simplified. The introduction waveguide 12A has an inner conductor 12a′ and an outer conductor 12a″ surrounding the inner conductor 12a′, wherein a first gap 13 is provided between the outer conductor 12a″ and the inner conductor 12a′. The center waveguide 12B has an inner conductor 12b′ and an outer conductor 12b″ surrounding the inner conductor 12b′, wherein a first gap 13 is provided between the outer conductor 12b″ and the inner conductor 12b′. The edge waveguide 12C also has an inner conductor and an outer conductor surrounding the inner conductor, wherein a first gap is provided between the outer conductor and the inner conductor. Therefore, in this example, the entire coaxial waveguide 12 having a shape branched at a plurality of branch portions has an inner conductor and an outer conductor. The inner conductor, the outer conductor and the shell 14 are metal.

[0027] exist Figure 2A , a susceptor 26 disposed in the chamber 16 is shown. On the susceptor 26, a substrate to be processed is mounted. According to one example, the susceptor 26 may be disposed below the plurality of rods 24. Depending on the processing content, a gas is supplied from a gas source 27 to the chamber 16. The gas in the chamber 16 may be exhausted, for example, through an exhaust port below the susceptor 26.

[0028] Figure 2B is a cross-sectional view of the coaxial waveguide 12. Any portion of the coaxial waveguide 12 has a first gap 13 between the inner conductor and the annular outer conductor.

[0029] like Figure 2A As shown, rods 24 are provided inside the housing 14. Each rod 24 has a conductor 20 and a dielectric 22 surrounding the conductor 20, wherein a second gap 21 is provided between the dielectric 22 and the conductor 20. Each rod 24 connects both ends of the coaxial waveguide branched at the branching portion, thereby connecting the first gap 13 and the second gap 21.

[0030] Figure 2C is a cross-sectional view of the rod 24. The material of the dielectric 22 may be, for example, ceramic, such as alumina (Al2O3) or aluminum nitride (AlN).

[0031] Figure 3 1 is a plan view of the plasma device. The rods 24 in the housing 14 are indicated by dotted lines. The plurality of rods 24 are arranged substantially in parallel, and are divided into a central rod and two edge rods sandwiching the central rod. Specifically, the four central rods 24 of the six rods 24 are central rods that connect the central waveguides 12B to each other. The two rods 24 at the two ends of the six rods 24 are edge rods that connect the edge waveguides 12C to each other. In this example, all the rods 24 have the same Figure 2C The same structure as the cross section illustrated in FIG.

[0032] The inner conductor of the coaxial waveguide 12 and the conductor of the rod 24 are not particularly limited as long as they are metal: for example, they may be silver-coated copper. The outer conductor of the coaxial waveguide 12 is not particularly limited as long as it is metal: for example, it may be aluminum.

[0033] exist Figure 3 In the example, the outer edge of the base 26 is drawn by alternate long and short dashes. In this example, all rods 24 are located just above the base 26.

[0034] exist Figure 1 In the example shown, the central waveguide 12B branches twice in both the positive and negative x directions, thereby allowing four central rods to be provided. However, any number of central rods may be provided by varying the number of branches of the central waveguide 12B.

[0035] exist Figure 1 In the example shown, the edge waveguide 12C branches once in both the positive and negative x directions, thereby allowing two edge rods to be provided. However, any number of edge rods may be provided by varying the number of branches of the edge waveguide 12C.

[0036] Figure 412C is a perspective view of the branch portion 12D. The edge waveguide 12C includes an inner conductor 12c' and an outer conductor 12c". Figure 4 , the inside of the outer conductors 12a" and 12c" are visualized. The post 30 is provided at the branch portion 12D as the first branch portion. The post 30 is formed of a conductor such as metal, for example. Figure 4 In the example of FIG. 1 , a plurality of cylindrical posts 30 are shown. The posts 30 can be inserted into and removed from the first gap 13. The posts 30 can be fitted into, for example, a hole of the outer conductor 12a' without a gap.

[0037] Figure 5 3 is a cross-sectional view of a portion of the coaxial waveguide 12 provided with the pile 30. Figure 5 In the example of FIG. 1 , six piles 30 are arranged in a ring shape. The number of the piles 30 may be one; although a plurality of piles may be provided. In a plan view, a plurality of piles 30 may surround the inner conductor 12a'. The protrusion amount "d" of the piles 30 in the direction of the inner conductor 12a' is defined by the distance between the position of each pile 30 closest to the inner conductor 12a' and the inner wall of the outer conductor 12a".

[0038] Figure 4 Arrows in the positive and negative directions of x in denoted microwaves supplied to the edge waveguide 12C. Figure 4 The arrow in the negative z direction in represents the microwave provided to the central waveguide 12B without branching at the branch portion 12D. Therefore, the branch portion 12D branches the microwave power provided from the microwave introduction portion 10 in three directions. In addition, the branch portion 12D as the first branch portion determines whether the microwave introduction portion 10 is connected to the central rod or the microwave introduction portion 10 is connected to the edge rod. The ratio between the microwave power to the central rod and the microwave power to the edge rod can be adjusted according to the protrusion amount d of the above-mentioned pile 30. The continuous change of the protrusion amount d of the pile 30 leads to the continuous change of the above-mentioned ratio. Adjusting the ratio between the microwave power to the central rod and the microwave power to the edge rod allows the plasma generation rate outside the rod to be controlled by the central rod and the edge rod. Therefore, the protrusion amount d of the pile is changed, thereby changing the plasma distribution.

[0039] Figure 6 A pile according to another example is shown. In this example, the pile 32 is prismatic. Figure 7 A post according to yet another example is shown. In this example, two posts 34 are provided. The surface of each post 34 facing the inner conductor 12a' has the same shape as the surface of the inner conductor 12a'. Figure 8 yes Figure 734. The stake 34 is moved in the direction of the arrow to change its protrusion amount. The surface 34A of each stake 34, that is, the surface 34A facing the inner conductor 12a', is made to have a shape that is the same as or similar to the surface shape of the inner conductor 12a', thereby allowing most of the first gap 13 to be closed by the stake 34.

[0040] Therefore, various shapes of stakes can be used. The shape of the stake can be freely set according to, for example, ease of manufacturing, ease of insertion and removal from the first gap 13, the shielded area of ​​the first gap 13, and the like.

[0041] Fig. 9 An arrangement example of the piles is shown. In this example, in addition to the pile 30 described above, piles 36 and 38 are provided to the edge waveguide 12C. The piles 36 and 38 are inserted into or removed from the first gap 13 in the edge waveguide 12C. In this configuration example, the protrusion amount of the piles 30, 36, and 38 toward the first gap 13 is adjusted, thereby allowing the distribution of plasma to be changed. According to yet another example, the piles 36 and 38 may be provided and the pile 30 may be omitted.

[0042] In the above example, the configuration is such that a stake is provided at the branch portion 12D as the first branch portion when viewed from the microwave introduction portion 10, so that the ratio of microwave power between the center rod and the edge rod can be adjusted. However, a stake may be provided at any branch portion of the coaxial waveguide 12 obtained by branching at the branch portion. For example, a stake may be provided at the second or third branch portion when viewed from the microwave introduction portion 10.

[0043] A substrate processing method using the above-mentioned plasma device will be described. Figure 2A The gas source 27 shown supplies gas into the chamber 16. In a state where the gas has been supplied into the chamber 16 or when the gas is being supplied into the chamber 16, plasma is generated in the chamber 16. Specifically, the power of the microwaves guided from the microwave introduction portion 10 is distributed by inserting the stakes into the branch portions of the coaxial waveguide 12, and then the microwaves are supplied to the space covered by the dielectric 22 of the plurality of rods 24. Then, the microwaves permeating from the dielectric 22 cause plasma to be generated outside the dielectric 22. The plasma diffuses in the chamber 16, resulting in plasma being generated in the space surrounded by the chamber 16 outside the dielectric 22. By using the plasma, the substrate on the susceptor 26 is processed. The substrate processing is, for example, film formation, etching, or film modification.

[0044] When the protrusion amount d of the pile is 0, the plasma uniformity is generally uneven. The degree of unevenness depends on the processing conditions. When the pile is not inserted into the first gap 13, there is a situation where the plasma is unevenly distributed, which leads to the following results: Fig.10The non-uniformity of the electric field strength shown. In this case, the piles can be used to control the ratio of power and adjust the plasma non-uniformity. When the piles are made to protrude from the inner wall of the outer conductor in the direction of the inner conductor, the ratio of the power distribution to the multiple rods changes, thereby making the electric field strength of the multiple rods non-uniform. Making the electric field strength of the rods non-uniform can compensate for the non-uniformity in the process, such as the non-uniformity of the plasma density, thereby improving the process uniformity. In other words, the non-uniform plasma distribution can provide process uniformity. In order to achieve the above-mentioned purpose, the electric field strength of the center rod can be made higher than the electric field strength of the edge rods, and the electric field strength of the center rod can also be made lower than the electric field strength of the edge rods.

[0045] Fig.10 : is a graph showing the results of electromagnetic field simulation. The horizontal axis represents the protrusion amount d of the pile, and the vertical axis represents the ratio of the power absorption amount between the center rod and the edge rod. As a simulation model, it is assumed that the plasma density in the chamber 16 is uniform, and the above-mentioned plasma device with relatively simple conditions is used. As the structure of the pile, Figure 7 The calculation is performed on the pile 34 shown. For a plasma density, that is, an electron density of 5.00E+17 (1 / m 3 ) and for plasma density 7.00E+17(1 / m 3 ) is used to perform this simulation.

[0046] In this simulation, a trend can be seen for both plasma densities that as the pile protrusion increases, the power absorption at the center rod also increases. More specifically, the pile protrusion gradually increases, thereby allowing the state where the power absorption of the edge rod is greater than the center rod to be transformed into a state where the power absorption of the edge rod is less than the center rod. Therefore, when the initial processing result indicates that "the plasma density at the edge is high", the pile protrusion is increased in order to increase the power absorption of the center rod, thereby making the plasma substantially uniform. The inventors have confirmed that using Figure 4 and 6 The same trend can be achieved with the pile shape shown. Figures 11 to 13 The electric field intensity of the rod when the pile protrusion amount is changed is shown. Regarding the rod, the electric field intensity of the dark blue part is lower than that of the red part. The electric field intensity of the red area is the highest, and the electric field intensity of the dark blue area is the lowest. Figures 11 to 13 The results are consistent with the above trend: as the pile protrusion increases, the power absorption of the center rod increases.

[0047] The above-mentioned plasma apparatus and substrate processing method can be modified in various forms. For example, the means for inserting and removing the pile into and from the branch portion in the coaxial waveguide can be manual operation, electronic control, or screw operation. When inserting and removing the pile by manual operation, the pile protrusion amount can be correctly grasped by providing a scale on the side surface of the pile. In the case of a screw-type pile, the pile protrusion amount can be correctly grasped by the screw rotation amount.

Claims

1. A plasma device, comprising: a coaxial waveguide having an inner conductor and an outer conductor surrounding the inner conductor, wherein a first gap is provided between the outer conductor and the inner conductor, the coaxial waveguide having a shape branched at a plurality of branch portions; a plurality of rods having a conductor and a dielectric surrounding the conductor, wherein a second gap is provided between the dielectric and the conductor, the plurality of rods connecting both ends of the coaxial waveguide branched at the branch portion to connect the first gap and the second gap; as well as a conductive post provided at a branch portion of the coaxial waveguide obtained by branching at the branch portion, the conductive post being insertable into and removable from the first gap, Wherein, the coaxial waveguide has a microwave introduction portion and a plurality of ends, and the plurality of ends are obtained by branching at a plurality of branch portions; Wherein, the conductive pile is arranged in the first branch portion, and the first branch portion is the branch portion closest to the microwave introduction portion among the multiple branch portions; and The conductive posts are formed to protrude from the inner wall of the outer conductor in the direction of the inner conductor, thereby allowing the electric field strength of the plurality of rods to be non-uniform.

2. The plasma device according to claim 1, wherein: The first branching portion branches the microwaves guided from the microwave introduction portion to the coaxial waveguide in three directions.

3. The plasma device according to claim 1 or 2, wherein: The plurality of rods are arranged substantially in parallel and are divided into a central rod and two edge rods sandwiching the central rod; and The first branch portion is a branch portion that determines whether the microwave introduction portion is connected to the center rod or the microwave introduction portion is connected to the edge rod.

4. The plasma device according to claim 1 or 2, comprising a susceptor disposed below the plurality of rods.

5. The plasma device according to claim 1 or 2, wherein: The conductive piles are provided in plurality.

6. The plasma device according to claim 1 or 2, wherein: In a plan view, the plurality of conductive posts surround the inner conductor.

7. The plasma device according to claim 1 or 2, wherein: The conductive pile is cylindrical or prism-shaped.

8. The plasma device according to claim 1 or 2, wherein: A surface of the conductive post facing the inner conductor has the same shape as a surface shape of the inner conductor.

9. A substrate processing method, comprising: providing a gas into the chamber; The power of the microwaves is distributed by inserting the stakes into the branch parts of the coaxial waveguide, the microwaves are guided from the microwave introduction part, and then the microwaves are provided to the space covered by the dielectric of the plurality of rods so that plasma is generated in the space surrounded by the chamber outside the dielectric; wherein the plurality of rods have a conductor and a dielectric surrounding the conductor and a second gap is provided between the dielectric and the conductor, and the plurality of rods connect two ends of the coaxial waveguide branched at the branching portion; wherein a conductive post is provided at a branch portion of the coaxial waveguide obtained by branching at the branch portion, the conductive post being insertable into and removable from a first gap between an inner conductor and an outer conductor of the coaxial waveguide; Wherein, the coaxial waveguide has a microwave introduction portion and a plurality of ends, and the plurality of ends are obtained by branching at a plurality of branch portions; Wherein, the conductive pile is arranged in the first branch portion, and the first branch portion is the branch portion closest to the microwave introduction portion among the multiple branch portions; and causing the conductive posts to protrude from the inner wall of the outer conductor in the direction of the inner conductor, thereby allowing the electric field strength of the plurality of rods to be non-uniform; and The substrate is treated with plasma.

10. The substrate processing method according to claim 9, wherein: The plurality of rods are arranged substantially in parallel, and are divided into a central rod and two edge rods sandwiching the central rod.

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