JP2000173797A - Microwave plasma treating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the size of a device as a whole and carry out uniform plasma treatment even when a substrate to be treated is large in diameter by generating standing waves in microwaves propagated inside a tubular member and distributing concentrically a plurality of high electric field strength areas, based on the standing waves in the radial direction of the tubular member. SOLUTION: Microwaves generated from a microwave oscillator 20 are introduced from an introducing part 13 of an antenna 11 toward an annular part 12 via a waveguide tube 21 and propagated in a dielectric body inside the annular pat 12 as oppositely directed traveling waves. In the annular part 12, both traveling waves collide mutually in the position facing an inlet port 13A so as to generate standing waves. In this way, electric current showing a maximum value at a fixed interval flows on the inside face of the annular part 12, and on both sides of a slit 15, a potential difference is generated between the inside and the outside of the annular part 12, so that an electric field is radiated to a microwave introducing plate 4 from the slit 15. The respective slits 15 are positioned radially between the adjacent strong electric field strength areas, the electric field of a strong electric field strength leaks from each of the slits 15, and this electric field penetrates the microwave inlet plate 4 to be introduced uniformly to all the areas of a treating container 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for generating plasma in a processing vessel using microwaves, and etching, ashing, or the like of an object to be processed such as a semiconductor substrate or a glass substrate for a liquid crystal display by the generated plasma. CV
The present invention relates to a microwave plasma processing apparatus for performing processing such as D (Chemical Vapor Deposition) and a microwave plasma processing method.

[0002]

2. Description of the Related Art FIG. 9 is a front sectional view schematically showing a conventional microwave plasma processing apparatus, and FIG. 10 is a schematic plan view of the same apparatus shown in FIG. Processing container 31
Are made of a metal conductor, and define a processing chamber 32. A sealing plate formed by using a dielectric plate made of quartz glass, alumina (Al ₂ O ₃ ), or the like, which has heat resistance and microwave permeability, and has a small dielectric loss, is provided vertically above the processing container 31. 34 seals in an airtight state.

[0003] A cover member 40 for covering the upper portion of the processing container 31 is connected to the processing container 31. This cover member 4
A dielectric line 41 is attached to the ceiling portion inside 0.
An air gap 4 is provided between the dielectric line 41 and the sealing plate 34.
3 are formed. The dielectric line 41 is made of a dielectric such as fluorocarbon resin such as Teflon (registered trademark), polyethylene resin, polystyrene resin, or quartz, and is tapered from the width of the waveguide 51 to a width enough to cover the processing vessel 31. It is formed in a pentagon.

A mounting table 33 for mounting a substrate W as a sample is provided at a position facing the sealing plate 34 in the processing container 31.
Is provided, and an exhaust port 38 connected to an exhaust device (not shown) is formed in the bottom wall 31B of the processing container 31.
A gas supply pipe 35 for supplying a required reaction gas is connected to a side wall 31A of the processing container 31.

[0005] When, for example, the semiconductor substrate W mounted on the mounting table 33 is subjected to, for example, an etching process using the microwave plasma processing apparatus configured as described above, the processing vessel is evacuated through the exhaust port 38. After setting the inside of the chamber 31 to a required degree of vacuum, a reaction gas is supplied from the gas supply pipe 35. Next, the microwave is oscillated in the microwave oscillator 50, and is introduced into the dielectric line 41 including the tapered portion 41A in order to uniformly spread and propagate the microwave through the waveguide 51. Then, a uniform electric field is formed below the dielectric line 41, and the formed electric field is transmitted through the air gap 43 and the sealing plate 34 and supplied into the processing container 31 to generate a uniform plasma. A uniform process such as etching is performed on the surface of the substrate W.

[0006]

In the conventional microwave plasma processing apparatus as described above, the edge of the sealing plate 34 and the edge of the processing container 31 are required to uniformly spread and propagate the microwave on the dielectric line 41. A tapered portion 41A protruding horizontally from a position corresponding to the tapered portion is provided.
1A is set to a predetermined size according to the area of the rectangular portion of the dielectric line 41, that is, the size of the processing chamber 32. Therefore, when installing the conventional microwave plasma processing apparatus, it is necessary to secure extra horizontal space for storing the tapered portion 41A protruding from the peripheral edge of the processing container 31.

By the way, as the diameter of the substrate W, which is a sample, becomes larger, a microwave plasma processing apparatus in which the size of the processing chamber 32 is further increased is required, and at the same time, it is required to reliably perform uniform plasma processing. I have. At this time, it is also required that there is no place where the device is installed, that is, it can be installed in a space as small as possible. However, in the conventional apparatus, since the size of the tapered portion 41A is determined according to the diameter of the processing container 31, these requirements described above cannot be satisfied at the same time.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and can reduce the size of the entire apparatus as much as possible even if the diameter of a substrate to be processed is large, and can be installed in a small space. It is another object of the present invention to provide a microwave plasma processing apparatus capable of more reliably performing uniform plasma processing.

[0009]

In order to achieve the above object, a microwave plasma processing apparatus according to the first aspect of the present invention accommodates a sample W to be processed using plasma, as shown in FIG. A processing container 1; a sealing member 4 for sealing the processing container 1 and transmitting the microwaves for generating the plasma and introducing the microwaves into the processing container 1; An annular tubular member 12 opened at; and between the tubular member 12 and the sealing member 4, disposed opposite to the sealing member 4 and the tubular member 12;
Predetermined slits 15, 15 through which the microwave passes;
… Provided with a slit plate 10; tubular member 12
Generates a standing wave in the microwave propagating in the tubular member 12; a plurality of regions where the electric field strength of the standing wave is relatively strong are distributed in the radial direction of the tubular member 12 and are substantially concentric. It is characterized by being configured to be distributed.

[0010] The annular tubular member is typically formed by annularly forming a channel-like member in which a part of a longitudinal section of a tubular member is open, and a slit plate closes the open portion. It is configured to The slit plate may be formed integrally with the annular tubular member, or may be formed as a separate member. When integrally formed, a tubular member having a closed cross section is constituted by a tubular member and a slit plate having a part of the vertical cross section opened. An antenna is configured including the annular tubular member and the slit plate.

The microwaves incident on the annular tubular member from the microwave inlet become traveling waves traveling in opposite directions in the tubular member and propagate through the tubular member. And collides with each other at a position opposing to the stationary wave to form a standing wave.

Due to the standing wave, a current that reaches a maximum at predetermined intervals flows through the wall surface of the tubular member. Under the tubular member, a slit is formed in a slit plate provided opposite to the sealing member and the tubular member, and a potential difference is generated between the inside and outside of the tubular member with the slit interposed therebetween due to the above-described current, and this potential difference is generated. As a result, an electric field is uniformly radiated from the slit to the sealing member. That is, the microwave propagates from the tubular member to the sealing member, and the microwave propagates inside the sealing member from the periphery to the center. The microwave passes through the sealing member and is introduced into the processing chamber, and plasma is generated by the microwave. The plasma spreads from the periphery to the center of the region inside the processing chamber, while maintaining the plasma at a high density and uniformity in a region directly below the tubular member.

[0013] Since the microwave can be directly incident into the tubular member in this manner, the tubular member does not protrude from the processing vessel that defines the processing chamber, and thus the horizontal dimension of the plasma processing apparatus is reduced. It can be as small as possible. On the other hand, since the microwave is guided from the tubular member to substantially the entire region of the processing chamber and is radiated from the slit, the microwave can be uniformly introduced into the processing chamber. Further, by setting the inner diameter and the outer diameter of the tubular member to required dimensions, that is, by setting the width of the tubular member to the required dimensions, a mode having a radial order of 2 or more in the tubular member (when the electric field (A propagation mode having two or more antinodes in each direction) can be formed. Thereby, energy loss can be reduced as much as possible, and the width of the tubular member can be increased.

A standing wave of a mode having a second or higher order in the radial direction is generated therein, and a plurality of regions where the electric field intensity is relatively strong due to the standing wave are distributed in the radial direction of the annular tubular member, and are substantially formed. When the annular tubular member is formed so as to be formed concentrically, the width thereof is larger than the width of the annular tubular member formed so as to generate only the fundamental mode standing wave. Therefore, the area of the plasma generated in opposition to the annular tubular member becomes relatively large, so that it is possible to easily cope with a large-diameter sample, and at the same time, the plasma density corresponding to the central portion of the annular tubular member. Reduction is suppressed.

According to a second aspect of the present invention, there is provided a microwave plasma processing apparatus according to the first aspect, wherein the annular tubular member includes a dielectric material for propagating the introduced microwave. It is characterized by fitting.

The microwave incident on the annular tubular member decreases the relative permittivity of the dielectric by εr and its wavelength by 1 / (εr) ^0.5 by the dielectric. Therefore, when using an annular tubular member having the same outer diameter and the same inner diameter, the inner wall surface of the annular tubular member is better when the dielectric is installed than when the dielectric is not installed. There are many positions where the flowing current is maximized, so that many slits can be opened. Therefore, the microwave can be more uniformly introduced into the processing container.

Further, at this time, since the annular tubular member itself becomes a dielectric line, the electric field intensity radiated from the dielectric facing the slit opening surface is significantly higher than when no dielectric is inserted. In addition, more microwave energy is stored in the dielectric line. Therefore,
When the same power is applied, the ignitability and the degree of dissociation of the plasma are greatly improved, and the stability of the plasma is also significantly increased.

According to a third aspect of the present invention, there is provided the microwave plasma processing apparatus according to the first or second aspect, wherein the slit is provided in the radial direction of the tubular member so that the electric field intensity is increased. Are formed in the same number as the number of relatively strong regions distributed in the radial direction; in the circumferential direction of the tubular member, the regions are formed between the adjacent regions.

Due to a standing wave having a mode of second or higher order in the radial direction formed in the annular tubular member, a current which reaches a maximum at predetermined intervals flows through a flat surface in the annular tubular member. . By forming a slit at this position, a potential difference is generated on a flat surface across the slit, and the potential difference causes an electric field to be radiated from the slit to the sealing member. That is, the microwave propagates from the annular tubular member to the sealing member. The microwave passes through the sealing member and is introduced into the processing container, and plasma is generated by the microwave. Further, in the annular tubular member, there are radially as many points as the order of the mode in the radial direction where the current becomes maximum. If the number of slits in the radial direction is the same as the radial order of the mode in the annular tubular member, the microwaves can be efficiently transmitted through the slits while suppressing the energy loss as much as possible and transmitting the microwaves to the circumferential direction. Electric power can be supplied to the plasma.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding members are denoted by the same or similar reference numerals, and duplicate description is omitted.

FIG. 1 is a schematic front sectional view showing the structure of a plasma processing apparatus according to a first embodiment of the present invention. FIG. 2 is a schematic plan view of the plasma processing apparatus shown in FIG. As shown in FIGS. 1 and 2, the plasma processing apparatus of the present embodiment includes a processing vessel 1 having a bottomed cylindrical shape entirely made of aluminum. The processing chamber 1 defines a processing chamber 2 in which processing of a substrate W as a sample is performed. A microwave introduction window is opened at the top of the processing container 1 in the vertical direction, and the microwave introduction window has a diameter of 38 mm.
It is hermetically sealed with a microwave introduction plate 4 as a sealing member having a thickness of 0 mm and a thickness of 20 mm. The microwave introduction plate 4 is formed of a dielectric material such as quartz glass or alumina having heat resistance and microwave permeability and low dielectric loss.

The upper surface and the outer peripheral side surface of the above-described microwave introduction plate 4 are covered with a cover member 10 made of a conductive metal in a lid shape, and the cover member 10 is fixed on the processing vessel 1. . On the upper surface of the cover member 10, the processing container 1
An antenna 11 for introducing microwaves into the inside is provided. The antenna 11 includes an annular portion 12 as a tubular member fixed to the upper surface of the cover member 10 and formed into an annular shape having an inner circumference circle and an outer circumference circle whose centers coincide with each other. The part facing the annular part 12 of the cover member 10
There are zero slits 15, 15,... Therefore, the cover member 10 also serves as a slit plate. Details of the slit will be described later.

The annular portion 12 is provided slightly inside the inner peripheral surface of the processing container 1 and concentric with the central axis of the processing container 1. Further, a rod-shaped introduction portion 13 for introducing microwaves to the annular portion 12 is horizontally arranged in a diameter direction of the annular portion 12 at an introduction port 13A as a microwave introduction port provided on the outer peripheral surface of the annular portion 12. , Are connected to the annular portion 12. The antenna 11 includes the annular portion 12, the introduction portion 13, and the slit 15. A dielectric 14 such as a fluororesin such as Teflon (registered trademark), a polyethylene resin, or a polystyrene resin (preferably, Teflon) is charged in substantially the entire internal space of the introduction portion 13 and the annular portion 12. The waveguide 2 horizontally disposed in the introduction portion 13
1 is connected, and the microwave oscillator 20 is connected to the waveguide 21.

By inserting the dielectric 14 into the annular portion 12, the wavelength in the tube can be shortened, many slits can be opened, and the microwave can be uniformly supplied into the processing chamber 2. Since the annular portion 12 itself serves as a dielectric line, the dielectric 1 in contact with the opening surfaces of the slits 15, 15,.
The electric field intensity radiated from 4 is much higher than when the dielectric 14 is not inserted, and the ignitability and dissociation degree of the plasma when the same power is applied is improved. In addition, since the insertion of the dielectric 14 shortens the guide wavelength, the same effect as increasing the vertical cross-sectional area of the annular portion 12 without changing the guide wavelength has the same effect as that of transmitting large power to the annular portion 12. Therefore, it is possible to easily cope with processing of a substrate having a large diameter.

The microwave oscillated by the microwave oscillator 20 enters the introduction portion 13 of the antenna 11 via the waveguide 21. This incident wave is introduced from the introduction part 13 to the annular part 12. The microwaves introduced into the annular portion 12 propagate through the dielectric 14 in the annular portion 12 as traveling waves traveling in the annular portion 12 in opposite directions. Both traveling waves collide at a position facing the inlet 13A of the annular portion 12, and a standing wave is generated.

Due to the standing wave, a current having a maximum value flows through the inner surface of the annular portion 12 at predetermined intervals. This current causes the annular portion 12 to sandwich the slits 15, 15,.
A potential difference is generated inside and outside the slit, and this potential difference causes the slit 1
An electric field is radiated from 5, 15, ... to the microwave introduction plate 4. That is, an electric field is radiated from the annular portion 12 to the microwave introduction plate 4.

The microwave frequency is 2.45 GHz,
The dimensions of the annular portion 12 are such that the height of the inner wall is 27 mm and the width is 12
When the center line C is determined to be 6 mm, the diameter of the center line C (see FIG. 3) is set to 211 mm, and a Teflon having a relative dielectric constant εr = 2.1 is inserted into the introduction portion 13 and the annular portion 12, a simulation calculation described later shows. As described above, a microwave having a second-order mode in the radial direction is generated, and propagates through the dielectric 14 (Teflon of εr = 2.1) in the annular portion 12 with little loss of energy. Here, the above-mentioned center line C is the annular portion 1
2, inner diameter 148 mm and outer diameter 274 mm
And a diameter obtained by dividing by 2 and concentric with the inner and outer circles.

FIG. 4 shows the result of determining the size of the annular portion 12 and obtaining the intensity of the distributed electric field by simulation as described above. As shown in FIG. 4, two regions in the radial direction of the annular portion 12 and 10 regions in the circumferential direction where the electric field intensity is strong are:
A on substantially concentric, longitudinal intersection of the inlet port 13A side of the center line and an extension line L formed by extending the center line C of the above P _0, and ring the center of the annular portion 12 of the inlet section 13 is rod-shaped body It is formed on the dielectric 14 so as to be symmetrical about an axis passing through O (see FIG. 3). The radial direction of the annular portion 12 refers to the radial direction of the ring of the annular portion 12, and the circumferential direction of the annular portion 12 refers to the circumferential direction of the ring of the annular portion 12.

A center line C connecting the center of the annular portion 12 in the width direction.
If the diameter of the inner wall is 211 mm and the height and width of the inner wall are determined as described above, the microwaves generate resonance in the annular portion 12, and the electric field has 10 antinodes in the circumferential direction and two antinodes in the radial direction. A standing wave in the propagation mode having the antenna, the electric field has an antinode at a diagonal position of the inlet 13A, a high voltage / low current at each antinode position, a low voltage / high current at each node position, and the antenna 11 Is improved. That is, the amplitude of the standing wave formed in the antenna 11 increases, and the microwave having a high electric field strength is
Are emitted to the processing container 1 from 5, 15,.

FIGS. 5 and 6 show distributions of regions where the electric field intensity is high when only the width of the annular portion 12 is changed. FIG. 5 shows the result of simulation calculation when the width is 100 mm (when the width is too narrow), and FIG. 6 shows the result of simulation calculation when the width is 165 mm (when the width is too wide). In FIGS. 5 and 6, the distribution of the region where the electric field intensity is strong is different from the distribution in FIG. In such a case, it is difficult to accurately open the slit at an appropriate position as described below, that is, at a position between adjacent regions where the electric field strength is strong, and the electric field is efficiently placed in the processing chamber 1. And it cannot radiate uniformly.

FIG. 7 shows that the frequency of the microwave, the dielectric to be inserted are the same as those described above, and the diameter of the center line C is 273 m.
m, the circumferential length is 858 mm, and the width of the annular portion 12 is 19
The distribution of the region where the electric field strength is strong according to the result of the simulation calculation in the case of 0 mm is shown. In this case, a standing wave of a propagation mode is generated in which three regions with a strong electric field strength are arranged radially and twelve in the circumferential direction and are arranged substantially concentrically. in this case,
Since the width of the annular portion 12 can be made wider, uniform plasma can be easily generated over a wider area (larger area). Therefore, a sample having a larger diameter can be easily and uniformly processed.

FIG. 3 shows the slit 1 shown in FIG. 1 and FIG.
It is explanatory drawing explaining 5, 15, .... As shown in FIG. 3, ten rectangular (rectangular) slits 15, 15,
Are opened so that the length direction is orthogonal to the diameter direction of the annular portion 12, that is, the traveling direction of the microwave propagating in the annular portion 12.

Each of the slits 15, 15,.
Microwave incident into annular portion 12 from A
2, from the position where they collide with each other in the opposite directions, that is, the introduction port at two points where the extension line L extending the longitudinal center line of the introduction section 13 and the above-mentioned circular center line C intersect. The two slits 15 and 15 are placed at positions separated by λg / 4 (λg is the wavelength of the microwave propagating in the antenna) in both directions along the circle C from the intersection P1 on the side separated from 13A. Opened, both slits 1
A plurality of other slits 15, 15,... Are respectively formed from 5, 5 in both directions along the circle C at a pitch interval of λg / 2, and a total of 10 slits are formed radially in the circumferential direction. Have been.

Each of the above-mentioned slits 15, 15,... Is located between adjacent regions having a strong electric field strength, and an electric field with a strong electric field strength leaks from each of the slits 15, 15,. The light passes through the wave introduction plate 4 and is introduced into the processing container 1. That is, microwaves for generating plasma are introduced into the processing chamber 1. Since the slits 15, 15,... Are provided substantially radially on the cover member 10 as described above, the microwave is uniformly introduced into the entire region in the processing container 1.

As shown in FIG. 1, the antenna 11 is provided on the cover member 10 having the same diameter as the processing container 1 without protruding from the periphery of the cover member 10.
Even if the diameter of the processing container 1 is large, the size of the microwave plasma processing apparatus other than the processing container 1 can be reduced. Therefore, the microwave plasma processing apparatus can be installed in a small space.

The side wall 1A of the processing vessel 1 is provided with a gas nozzle 6 which extends horizontally through the side wall 1A, and a required gas is introduced into the processing chamber 2 from a gas introduction pipe 5 connected to the gas nozzle 6. . At the center of the bottom wall 1B of the processing chamber 2, a substrate holding table 3 on which the substrate W is placed is provided. Alternatively, an exhaust port 18 is provided in the bottom wall 1B of the processing container 1 so that the gas in the processing chamber 2 is exhausted from the exhaust port 18.

The substrate holder 3 has a matching box 16
The high frequency power supply 7 is connected via the. Therefore, a bias potential is generated on the substrate W placed on the substrate holding table 3, the bias potential is controlled by controlling the power of the high frequency power supply 7, and the energy of the ions in the plasma is independently controlled, thereby controlling the substrate W. Processability (etching shape, etc.) of the substrate can be improved.

FIG. 8 shows another embodiment of the present invention.
As shown in the figure, there are radially maximum points in the annular portion 12 where the secondary mode occurs in the number of modes in the radial direction, so that the number of slits in the radial direction is equal to the mode order in the annular portion 12. It is good to be the same 2. This embodiment is the same as the first embodiment except that the slit is divided into two in the radial direction. For example, the size of the annular portion 12 is set to 27 mm in height of the inner wall and 126 mm in width. The center line C has a diameter of 211 mm. In this embodiment, the microwave power can be efficiently supplied to the plasma through the two slits while the microwave is propagated in the circumferential direction while suppressing the energy loss as much as possible.

[0039]

As described above, according to the present invention, since the antenna having the annular tubular member and the slit plate provided with the slit is provided, the portion other than the processing container of the apparatus can be miniaturized. The device can be installed in a small space. Furthermore, if a standing wave having a radial order of 2 or more is formed inside the annular tubular member, the width of the annular tubular member can be increased, and the area of plasma facing the annular tubular member can be increased. can do. Therefore, since it is possible to cope with a large-diameter sample, it is possible to suppress a decrease in the density of plasma corresponding to the central portion of the annular tubular member, and it is possible to reliably perform uniform plasma processing.

[Brief description of the drawings]

FIG. 1 is a schematic front sectional view of a plasma treatment apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic front view of the plasma processing apparatus shown in FIG.

3 is an explanatory view of a slit of a cover member of the plasma processing apparatus shown in FIG.

FIG. 4 is a view showing an electric field intensity distribution in an annular portion of the plasma processing apparatus shown in FIG. 1 (Example of the present invention).

FIG. 5 is a view showing an electric field intensity distribution when the width of the annular portion of the plasma processing apparatus shown in FIG. 1 is changed (comparative example).

6 is a diagram showing an electric field intensity distribution when the width of the annular portion of the plasma processing apparatus shown in FIG. 1 is changed (comparative example).

FIG. 7 is a diagram showing an electric field intensity distribution of the annular portion of the plasma processing apparatus shown in FIG. 1 when the diameter and width of the center line are changed.

FIG. 8 is an explanatory view of a slit of a cover member of a microwave plasma processing apparatus according to another embodiment of the present invention.

FIG. 9 is a schematic front sectional view of a conventional microwave plasma processing apparatus.

FIG. 10 is a schematic plan view of a conventional microwave plasma processing apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Processing container 1A Side wall 1B Bottom wall 2 Processing chamber 3 Substrate holder 4 Microwave introduction plate 5 Gas introduction pipe 6 Gas nozzle 7 High frequency power supply 10 Cover member 11 Antenna 12 Annular part 13 Introduction part 13A Inlet 14 Dielectric 15 Slit 16 Matching Box 18 Exhaust port 20 Microwave transmitter 21 Waveguide C Center line L Extension line O Center P ₀ intersection P ₁ intersection W Substrate

Claims (3)

[Claims] A processing container for storing a sample to be processed using plasma; a sealing member for sealing the processing container and transmitting the microwaves for generating the plasma into the processing container through the microwave; An annular tubular member having a microwave inlet opening on a peripheral surface for introducing the microwave;
A slit plate provided between the tubular member and the sealing member so as to face the sealing member and the tubular member, and having a predetermined slit through which the microwave passes; The member causes the microwave propagating in the tubular member to generate a standing wave; a plurality of regions where the electric field strength of the standing wave is relatively strong are distributed in the radial direction of the tubular member and are substantially concentric. A microwave plasma processing apparatus. 2. The microwave plasma processing apparatus according to claim 1, wherein the annular tubular member is fitted with a dielectric that propagates the introduced microwave. 3. The slit is formed in the radial direction of the tubular member in the same number as the number of regions where the electric field strength is relatively strong in the radial direction; and the slits are adjacent in the circumferential direction of the tubular member. The microwave plasma processing apparatus according to claim 1, wherein the microwave plasma processing apparatus is provided between the regions.