JP3042208B2 - Microwave plasma processing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave plasma processing apparatus, and more particularly to a microwave plasma processing apparatus used as an etching apparatus for a semiconductor element substrate, a thin film forming processing apparatus, and the like.

[0002]

2. Description of the Related Art A reaction gas and a microwave are introduced into a vessel decompressed near a vacuum to generate a plasma by generating a gas discharge, and the plasma is irradiated on a substrate surface to perform processing such as etching and thin film formation. The microwave plasma processing apparatus to be performed has become indispensable in the manufacture of highly integrated semiconductor elements and the like. Among the,
A microwave plasma processing apparatus capable of independently controlling the generation of plasma and the acceleration of ions in the plasma,
It has become indispensable for the dry etching technique and the embedding technique for forming a thin film, and the research and development thereof have been advanced.

FIG. 5 shows a microwave plasma proposed by the present applicant in Japanese Patent Application No. 3-331269 for the purpose of independently controlling the generation of plasma and the acceleration of ions in the plasma. It is sectional drawing which showed the etching apparatus typically, and 11 has shown the reactor of a hollow rectangular parallelepiped shape in the figure. The reactor 11 is formed of a metal such as stainless steel, and its peripheral wall has a double structure. A cooling water passage 12 is formed inside the reactor, and cooling water flowing through the cooling water passage 12 is provided with a cooling water inlet. The cooling water is supplied from the cooling water outlet 12b. A reaction chamber 13 is formed inside the cooling water passage 12, and the upper part of the reactor 11 is made of quartz glass, Pyrex glass, or the like having microwave permeability, low dielectric loss, and heat resistance. It is hermetically sealed by a microwave introduction window 14 formed using a dielectric plate. A sample holding unit 15 for holding a sample S is provided at a position facing the microwave introduction window 14 in the reaction chamber 13.
a and a sample table 15 on which the sample S is mounted. A high-frequency power supply 18 for generating a bias voltage on the surface of the sample S is connected to the sample holding unit 15a. Suction mechanism such as electrostatic chuck (not shown)
And a cooling mechanism (not shown) for circulating a coolant or the like for cooling the sample S is provided.
An exhaust port 16 connected to an exhaust device (not shown) is formed at a lower wall of the reactor 11, that is, below the reaction chamber 13, and a required reaction gas is provided in the reaction chamber 13 on one side wall of the reactor 11. A gas supply pipe 17 for supplying the gas is connected.

On the other hand, above the reactor 11, a dielectric line 2
1, a metal plate 21a of aluminum (Al) or the like is provided above the dielectric line 21, and the end of the dielectric line 21 is sealed with a metal reflection plate 21b. A dielectric layer 21c is adhered to the lower surface of 21a.
The dielectric layer 21c is formed using a fluororesin, polyethylene, polystyrene, or the like having a small dielectric loss. A microwave oscillator 23 is connected to the dielectric line 21 via a waveguide 22.
From the dielectric line 21 via the waveguide 22
Has been introduced.

In the case where the microwave plasma processing apparatus having the above-described structure is used to perform an etching process on the surface of the sample S placed on the sample holding section 15a, first, the exhaust port 16 is evacuated and the reaction chamber 13 is exhausted. After setting the inside to a required degree of vacuum, a reaction gas is supplied from the gas supply pipe 17 into the reaction chamber 13. Cooling water is supplied from the cooling water inlet 12a and discharged from the cooling water outlet 12b to circulate in the cooling water passage 12. Next, the microwave is oscillated in the microwave oscillator 23, and the microwave is introduced into the dielectric line 21 via the waveguide 22. Then, an electric field is formed below the dielectric line 21, and the formed electric field passes through the microwave introduction window 14 and is supplied to the reaction chamber 13 to generate plasma. At the same time, a high-frequency electric field is applied to the sample holder 15a using the high-frequency power supply 18,
A bias voltage is generated on the surface of the sample S. Then, the plasma is applied to the surface of the sample S while controlling the directionality and acceleration energy of ions in the plasma by the bias voltage,
The surface of the sample S is etched.

[0006]

In the microwave plasma processing apparatus described above, there is no counter electrode when a high-frequency electric field is applied to the sample holder 15a, the ground potential viewed from the plasma is unclear, and the plasma potential (Plasma potential) tends to be unstable. For this reason, there is a problem that the plasma is likely to be unstable, a stable bias voltage is hardly generated on the surface of the sample S, and it is difficult to sufficiently control the directionality and acceleration energy of the ions in the plasma.

The present invention has been made in view of such a problem, and it is possible to stabilize a plasma potential when a high-frequency electric field is applied to a sample holding unit, and to generate a stable bias voltage on the surface of a sample S. It is an object of the present invention to provide a microwave plasma processing apparatus capable of optimizing ion energy in plasma and irradiating a sample surface with ions vertically.

[0008]

In order to achieve the above object, a microwave plasma processing apparatus according to the present invention comprises a microwave oscillator, a waveguide for transmitting microwaves, and a waveguide connected to the waveguide. A microwave plasma processing apparatus comprising: a dielectric line; a reactor having a microwave introduction window disposed to face the dielectric line; and a sample holding unit provided in the reactor. And a means for applying a high-frequency electric field or a direct-current electric field, and a grounded electrode means having a transmission hole is arranged in contact with the microwave introduction window.

Further, the microwave plasma processing apparatus according to the present invention comprises a microwave oscillator, a waveguide for transmitting microwaves, a dielectric line connected to the waveguide, and a dielectric line opposed to the dielectric line. A microwave plasma processing apparatus comprising: a reactor having a microwave introduction window to be provided; and a sample holder provided in the reactor, comprising a means for applying a high-frequency electric field or a DC electric field to the sample holder. A grounded electrode means having a transmission hole is provided at an intermediate position between the microwave introduction window and the sample holding section.

[0010]

In general, when an anode electrode is arranged opposite to a cathode electrode in a plasma region, a bias voltage (V _c ) generated at the cathode electrode by application of a high-frequency electric field or a DC electric field has the following equation (1). It is known to hold.

[0011]

(Equation 1)

Therefore, the bias voltage is affected by the area of the cathode electrode and the area of the anode electrode, and the electrode area is the area in contact with the plasma. Will receive it.

In the apparatus shown in FIG. 5, a large amount of plasma generated by microwaves is generated between the microwave introduction window 14 and the sample holder 15a. On the other hand, when a high-frequency electric field or a direct-current electric field is applied to the sample holding unit 15a, the reaction chamber 1 which is grounded and serves as a counter electrode
The wall of No. 3 is disposed in a peripheral part away from a main generation point of plasma. Therefore, the contact between the wall of the reaction chamber 13 and the plasma may not be sufficient, and at this time, the bias potential to the sample S due to the plasma may not be stable.

In the apparatus according to the present invention, the grounded electrode means is disposed in the vicinity of the main plasma generation location so as to face the sample holder, and thus the cathode and anode contact areas with the plasma are provided. Is stabilized, and the plasma, that is, the plasma potential, and the bias potential to the sample S can be stabilized.

Further, in the apparatus according to the present invention, since a transmission hole through which microwaves and plasma can pass is formed in the grounded electrode means, the shape of the transmission hole (slit shape, circular shape, etc.). By changing the size, the distribution, the transmission of the microwave and the plasma generated by the microwave can be adjusted, and the microwave plasma and the high-frequency plasma (mainly related to the bias potential) are combined in the processing of the sample S. The obtained plasma can be used with good uniformity.

[0016]

Embodiments and Comparative Examples Hereinafter, embodiments of a microwave plasma processing apparatus according to the present invention will be described with reference to the drawings. Note that components having the same functions as those of the conventional example are denoted by the same reference numerals. FIG. 1 is a cross-sectional view schematically showing a microwave plasma processing apparatus according to an embodiment, and 11 in FIG.
Indicates a hollow rectangular reactor. As in the conventional example, the reactor 11 is formed of a metal such as stainless steel, and its peripheral wall has a double structure, inside which a cooling water passage 12 is formed, and cooling water flowing through the cooling water passage 12 is formed. Water is supplied from a cooling water inlet 12a and discharged from a cooling water outlet 12b. Cooling water passage 1
A reaction chamber 13 is formed inside the reactor 2, and an upper part of the reactor 11 is made of a dielectric plate such as quartz glass or Pyrex glass having microwave permeability, low dielectric loss and heat resistance. And hermetically sealed by a microwave introduction window 14 formed by using the same. On the lower surface of the microwave introduction window 14, as shown in FIG. 2 (a), a grounded electrode means 30 made of an Al conductive plate 31 having a plurality of slits 32 is arranged in close contact. , The grounded electrode means 30 is connected to the ground 33 via the reactor 11.
Have been. A sample holder 15a for holding the sample S and a sample table 15 on which the sample S is to be placed are disposed at a position in the reaction chamber 13 opposite to the grounded electrode means 30. Is connected to a driving device (not shown) so as to be able to move up and down. A high-frequency power supply 18 for generating a bias voltage on the surface of the sample S is connected to the sample holding unit 15a, and an adsorption mechanism (not shown) such as an electrostatic chuck is provided for holding the sample S. In addition, a cooling mechanism (not shown) for circulating a coolant or the like for cooling the sample S is provided. An exhaust port 16 connected to an exhaust device (not shown) is formed at a lower wall of the reactor 11, that is, below the reaction chamber 13.
A gas supply pipe 17 for supplying a required reaction gas into the reaction chamber 13 is connected to one side wall of the reactor 11.

On the other hand, above the reactor 11, the dielectric line 2
1, a metal plate 21a of Al or the like is provided on the upper part of the dielectric line 21, and the end of the dielectric line 21 is sealed with a metal reflector 21b. Has a dielectric layer 21c adhered thereto. This dielectric layer 21
c is formed using, for example, a fluorine resin, polyethylene, or polystyrene having a small dielectric loss. The microwave oscillator 2 is connected to the dielectric line 21 via a waveguide 22.
3 are connected so that the microwave generated from the microwave oscillator 23 is introduced into the dielectric line 21 via the waveguide 22.

When, for example, the surface of the sample S mounted on the sample holding unit 15a is subjected to etching using the microwave plasma processing apparatus configured as described above, first, the sample S mounted on the sample table 15 is processed. After the position is adjusted to the predetermined height using the driving device, exhaust is performed from the exhaust port 16 to set the inside of the reaction chamber 13 to a required degree of vacuum. A reaction gas is supplied into the apparatus 13. In addition, cooling water is supplied from a cooling water inlet 12a,
The water is circulated in the cooling water passage 12 by being discharged from the cooling water discharge port 12b. Next, a high-frequency electric field is applied to the sample holder 15 a using the high-frequency power supply 18, and a stable bias voltage is generated on the surface of the sample S by the grounded electrode means 30. At the same time, the microwave oscillator 23
, A microwave is oscillated, and the microwave is introduced into the dielectric line 21 via the waveguide 22. Then, an electric field is formed below the dielectric line 21, and the formed electric field passes through the microwave introduction window 14 and the slit 32 of the electrode means 30 grounded, and generates plasma in the reaction chamber 13. Then, the ions in the plasma are irradiated perpendicularly to the surface of the sample S by the stable bias voltage, and etching is performed while controlling the acceleration energy.

The result of etching a silicon oxide film (SiO ₂ film) using the apparatus shown in FIG. 1 will be described below. In this case, the sample S is using what SiO ₂ film of 1μm was formed on an 8-inch silicon wafer, the discharge gas is approximately 30sccm the CF _4, substantially the CHF ₃ 30sc
cm and Ar were supplied at approximately 100 sccm, and the gas pressure was set at 30 mTorr. Microwaves with a frequency of 2.45 GHz were used to generate plasma with 1 kW of power. Further, a high frequency of 400 kHz was supplied to the sample holder 15a with a power of 600W.

As a result, the average etch rate of the SiO ₂ film was 400 nm / min, and the uniformity of the etch rate on an 8-inch silicon wafer was ± 5%. As a comparative example, when an experiment was performed under the same conditions using an apparatus in which the grounded electrode means 30 was not provided, the average etch rate of the SiO ₂ film was 350 nm / min. In some cases, the etch rate was reduced.

As apparent from the result, in the microwave plasma processing apparatus according to the present embodiment, the sample holder 15
a means for applying a high-frequency electric field to the microwave introducing window 1 having a slit 32 and a grounded electrode means 30.
4, a stable bias voltage can be generated on the surface of the sample S, and the plasma potential of the plasma generated in the reaction chamber 13 by the microwave transmitted through the slit 32 can be stabilized. The ion energy in the sample S can be optimized and the surface of the sample S can be irradiated with ions perpendicularly. Therefore, the silicon wafer can be stably and uniformly etched by the anisotropic and fast etch rate. it can.
In this embodiment, the high-frequency power supply 18 is connected to generate a stable bias voltage on the surface of the sample S. However, in another embodiment, a DC power supply may be used. Further, in this embodiment, the configuration applied to the etching apparatus has been described, but the configuration is not limited to this.
For example, the present invention can be similarly applied to a thin film forming apparatus and the like.

3 and 4 are cross-sectional views schematically showing a microwave plasma processing apparatus according to another embodiment.
FIG. 4 shows a microwave plasma processing apparatus in which the grounded electrode means 40 is disposed at a predetermined position between the microwave introduction window 14 and the sample holder 15a. FIG. A gas supply pipe 17 is provided at a predetermined position between the wave introduction window 14 and the sample holding unit 15a.
Shows a microwave plasma processing apparatus connected to an intermediate portion 43 between the microwave introduction window 14 and the grounded electrode means 40, and all other configurations are the same as those of the apparatus shown in FIG. Is configured. In the case of the microwave plasma processing apparatus shown in FIGS. 3 and 4, the microwave introduction window 14 and the grounded electrode means 1 may be used depending on the operating conditions.
In some cases, plasma is generated in the intermediate portion 43 between the electrode plate 4 and the electrode hole 40 of the grounded electrode means 40, as shown in FIG. It is desirable that a large number of small holes 42 having a diameter are formed.

In the case where the surface of the sample S is etched or a thin film is formed on the surface of the sample S by using the microwave plasma processing apparatus having the above-described configuration, substantially the same effect is obtained by a method substantially similar to that of FIG. Can be obtained.

[0024]

As described in detail above, the microwave plasma processing apparatus according to the present invention is provided with a means for applying a high-frequency electric field or a direct-current electric field to the sample holder, and is provided with a grounded electrode having a transmission hole. Since the means is disposed in contact with the microwave introduction window, the counter electrode to the sample holding unit becomes clear. Therefore, a stable bias voltage can be generated on the sample surface, the plasma potential of the plasma generated in the reaction chamber by the microwave transmitted through the transmission hole is stabilized, the ion energy in the plasma is optimized, and the sample is sampled. The surface can be irradiated with ions perpendicularly.

Further, in the microwave plasma processing apparatus according to the present invention, there is provided a means for applying a high-frequency electric field or a direct-current electric field to the sample holder, and the grounded electrode means having a transmission hole is provided with the microwave introduction window. Since it is disposed at an intermediate position between the sample holding unit and the sample holding unit, the counter electrode to the sample holding unit becomes clearer than in the case of the above apparatus. Therefore, a stable bias voltage can be generated on the sample surface, and the plasma potential of the plasma generated between the microwave introduction window and the grounded electrode means and transmitted through the transmission hole is stabilized,
The ion energy in the plasma can be optimized, and the sample surface can be irradiated with ions perpendicularly.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing an embodiment of a microwave plasma processing apparatus according to the present invention.

FIG. 2 is a front view schematically showing grounded electrode means of the microwave plasma processing apparatus according to the present invention;
(A), the transmission hole is composed of a plurality of slits, (b)
Indicates that the transmission hole is composed of many holes.

FIG. 3 is a cross-sectional view schematically illustrating a microwave plasma processing apparatus according to another embodiment.

FIG. 4 is a cross-sectional view schematically showing a microwave plasma processing apparatus according to another embodiment.

FIG. 5 is a sectional view schematically showing a conventional microwave plasma etching apparatus.

[Explanation of symbols]

 Reference Signs List 11 reactor 14 microwave introduction window 15a sample holder 21 dielectric line 22 waveguide 23 microwave oscillator 30 grounded electrode means 32 transmission hole (slit)

Claims (2)

(57) [Claims] 1. A reactor having a microwave oscillator, a waveguide for transmitting microwaves, a dielectric line connected to the waveguide, and a microwave introduction window disposed opposite to the dielectric line. And a microwave plasma processing apparatus including a sample holding unit provided in the reactor, comprising: a unit for applying a high-frequency electric field or a DC electric field to the sample holding unit;
A microwave plasma processing apparatus, wherein a grounded electrode means having a transmission hole is disposed in contact with the microwave introduction window. 2. A reactor having a microwave oscillator, a waveguide for transmitting microwaves, a dielectric line connected to the waveguide, and a microwave introduction window disposed opposite to the dielectric line. And a microwave plasma processing apparatus including a sample holding unit provided in the reactor, comprising: a unit for applying a high-frequency electric field or a DC electric field to the sample holding unit;
A microwave plasma processing apparatus, wherein a grounded electrode means having a transmission hole is provided at an intermediate position between the microwave introduction window and the sample holder.