JP2002353206A - Equipment for plasma treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an equipment for plasma treatment, with which nitriding can be carried out with reduced contamination. SOLUTION: The plasma treatment equipment comprises a chamber 1, a micro wave generator 6 for generating plasma by micro wave discharge and an antenna section 3. A susceptor 7 for carrying a substrate 12 is installed in the chamber 1. An antenna section 3 is mounted at the upper portion of the chamber through a quartz plate 15. A silicon crystal 2 is disposed on the inside wall face of the chamber 1 from the side face of the chamber 1 exposed in a plasma generation region 13 that is a position on which the substrate 12 is mounted through the upper portion of the chamber 1 on which the antenna portion 3 is mounted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a plasma processing apparatus, and more particularly, to a plasma processing apparatus used for nitriding a gate oxide film.

[0002]

2. Description of the Related Art For example, in order to meet the demand for low power consumption in portable terminals, the thickness of a gate insulating film in a transistor is urgently reduced. As part of this, the silicon nitride film has a higher dielectric constant than the silicon oxide film, and the silicon nitride film is denser than the silicon oxide film. Techniques have been developed to reduce the leakage current and prevent the penetration of boron while reducing the thickness of the film.

[0003] A plasma processing apparatus has been applied for nitriding the surface of a gate oxide film. Therefore, an example of a conventional plasma processing apparatus used for such nitriding will be described. As shown in FIG. 2, the plasma processing apparatus includes a chamber 1 for receiving a substrate 112 and performing a predetermined process.
And a microwave generator 106 and an antenna unit 103 for generating plasma by microwave discharge in the chamber 101.

In the chamber 101, a susceptor 107 for mounting a substrate 112 is provided. An antenna unit 103 is attached to the upper part of the chamber 101 via a quartz plate 115 so as to face the substrate 112 placed thereon.

[0005] The antenna section 103 includes a flat conductor 103a, an aluminum nitride plate 3b, and a slot electrode 3c.

The microwave generated by the microwave generator 106 is applied to the waveguide 105 and the coaxial waveguide converter 10.
4 to the antenna unit 103. Antenna unit 1
The microwave guided to 03 passes through the quartz plate 115 from the aluminum nitride plate 3b via the slot electrode 3c and is radiated almost uniformly into the chamber 101.

The chamber 101 is provided with a gas inlet 114 for sending nitrogen gas or the like for nitriding into the chamber 101. Also, the chamber 101
Has a vacuum pump 1 for exhausting the inside of the chamber 101.
09 is attached, and the pressure in the chamber 101 is adjusted by the pressure controller 108.

A rectifying plate 111 for uniformly exhausting the gas in the chamber 101 is provided between the susceptor 107 and the inner wall of the chamber 101. A focus ring 110 is provided around the susceptor 107 to prevent the substrate from shifting.

The conventional plasma processing apparatus is configured as described above. In this plasma processing apparatus, particularly, the chamber 101 and the current plate 11 are formed by processing aluminum. The focus ring 110 is formed of ceramics or quartz.

When the chamber 101 is formed from aluminum, the wall surface of the chamber 101 easily becomes a ground potential (ground plane) because it is a conductor, and plasma can be generated relatively uniformly in the chamber 101. Further, aluminum has relatively high thermal conductivity and excellent heat dissipation, so that, for example, O 2 for sealing the inside and outside of the chamber 101 is used.
Deterioration of a ring (not shown) and the like can be suppressed, and temperature control including the chamber 101 can be relatively easily performed.

On the other hand, in addition to a chamber made of aluminum, a plasma processing apparatus having a chamber made of quartz has been proposed.

[0012] Quartz has been widely used in diffusion furnaces and the like, and its cleaning technology has been established to some extent. Therefore, in such a plasma processing apparatus, impurities attached to the inner wall of the chamber or the like can be relatively easily cleaned and removed.

[0013]

However, the above-described plasma processing apparatus has the following problems. First, in a chamber made of aluminum, when polishing aluminum, iron (Fe) is likely to adhere to the surface of aluminum as an impurity. Further, sodium (Na) also easily adheres to the surface of aluminum through human hands.

If the plasma treatment is performed with such impurities such as iron and sodium adhered to the inner wall of the chamber 101, the adhered impurities such as iron and sodium are exposed by exposing the inner wall of the chamber 101 to plasma. Easily desorbs. The desorbed impurities sometimes adhere to the surface of the substrate 112 and contaminate the substrate 112 in some cases.

In particular, formation of a gate oxide film is a very important step that affects the characteristics of a transistor. For this reason,
If such impurities adhere to the surface of the substrate 112 where the gate oxide film is being nitrided, the electrical characteristics of the transistor fluctuate significantly.

On the other hand, in a chamber made of quartz, the wall surface of the chamber cannot be easily set to the ground potential (ground plane) because it is an insulator, and the generated plasma tends to be non-uniform. Therefore, particularly when nitriding is performed, the degree of nitridation of the gate oxide film sometimes varies in the substrate surface.

In the case of quartz, since the heat conductivity is relatively low and heat is not sufficiently released, the sealing member such as an O-ring tends to be easily deteriorated. Further, there has been a problem that the temperature control of the chamber tends to be unstable.

The present invention has been made in order to solve the above problems, and has as its object to provide a plasma processing apparatus capable of performing a nitriding treatment while reducing contamination.

[0019]

A plasma processing apparatus according to the present invention is a plasma processing apparatus for generating a plasma in a reaction chamber and performing a predetermined process on a substrate introduced into the reaction chamber. A silicon crystal is provided in a portion of the inner wall of the reaction chamber facing the plasma generation region.

The silicon crystal can easily remove impurities such as a metal adhered to the surface by an acid, for example. Therefore, according to this plasma processing apparatus, the cleanliness of the surface exposed to the plasma can be increased by providing the silicon crystal in the portion facing the plasma, and the adhered impurities are desorbed by the plasma to remove the substrate. Will not re-adhere. As a result, a treatment with less contamination can be performed on the substrate. Further, a silicon crystal, which is a semiconductor, is more likely to have a ground potential than an insulator such as quartz. Thereby, the propagation of the microwave along the wall surface of the silicon crystal is suppressed, and uniform plasma can be generated. As a result, the predetermined processing can be performed uniformly in the substrate surface. For example, when performing the nitriding treatment of the gate oxide film, the nitriding in the substrate surface can be performed uniformly. Furthermore, since the silicon crystal has better heat dissipation than quartz, for example, temperature control can be easily performed, and deterioration of the seal member and the like can be suppressed.

More specifically, the silicon crystal is formed on the inner wall portion of the reaction chamber facing a region (space) located on the side of the plasma generation region from the position of the substrate introduced into the reaction chamber. It is preferable to be provided so as to surround.

As a result, the silicon crystal is disposed at a portion substantially exposed to the plasma generation region.

It is preferable that the silicon crystal contains at least one impurity selected from the group consisting of boron, phosphorus and arsenic.

As a result, the silicon crystal contains P-type or N-type impurities, the resistance of the silicon crystal is reduced, and the silicon crystal comes closer to the properties as a conductor. As a result, the silicon crystal is more likely to be at the ground potential, and the plasma generation region can be formed more uniformly.

Further, when such an impurity is contained, the impurity concentration of the impurity on the surface of the silicon crystal body facing the plasma generation region is preferably lower than the impurity concentration inside.

Thus, it is possible to prevent the impurities from being detached from the silicon crystal by the plasma and re-adhering to the surface of the substrate.

A stage for mounting a substrate, and a rectifying plate mounted between the stage and the inner wall of the reaction chamber so as to surround the stage in a circumferential direction, and for stabilizing a gas flow. It is preferable that a silicon crystal is formed on at least the surface of the current plate.

Further, it is preferable that a ring member is provided along the outer edge of the stage section so as to surround the substrate to be mounted, and a silicon crystal is formed on at least the surface of the ring member.

Such a rectifying plate and a ring member also face the plasma generation region. By providing a silicon crystal in these rectifier plates and the ring member, impurities can be effectively removed by washing, and a process with high cleanliness can be performed. Can be applied.

As means for generating plasma, it is preferable to provide a microwave discharge unit for generating plasma by microwave discharge.

More specifically, the microwave discharge unit is attached to the reaction chamber so as to substantially face the substrate, and a microwave generator for generating microwaves. And a plate-shaped antenna portion for radiating the light into the reaction chamber.

In a plasma processing apparatus provided with a microwave discharge section having such a flat antenna, a substrate having a relatively large area is targeted, and in particular, a silicon crystal is provided on the inner wall of a reaction chamber of this type. So, as mentioned above,
A uniform plasma can be generated, and the processing in the substrate surface can be performed more uniformly.

Alternatively, as means for generating plasma, a high-frequency discharge unit for generating plasma by high-frequency discharge may be provided.

This makes it possible to perform a process with high cleanliness on a so-called inductively coupled plasma processing apparatus, a parallel plate type plasma processing apparatus, and the like.

[0035]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A plasma processing apparatus according to an embodiment of the present invention will be described. As shown in FIG. 1, the plasma processing apparatus includes a chamber 1 for housing a substrate 12 and performing predetermined processing, and a microwave generator 6 for generating plasma in the chamber 1 by microwave discharge.
And an antenna unit 3.

In the chamber 1, a susceptor 7 for mounting a substrate 12 is provided. A quartz plate 15 is placed on the upper part of the chamber 1 so as to face the placed substrate 12.
The antenna unit 3 is attached via the.

Each of the antenna portions 3 has a flat conductor 3
a, an aluminum nitride plate 3b and a slot electrode 3c. A plurality of openings are provided in the slot electrode 3c.

A waveguide 5 and a coaxial waveguide converter 4 for guiding the microwave generated in the microwave generator 6 toward the antenna section 3 are provided between the microwave generator 6 and the antenna section 3. Have been.

The chamber 1 has a gas inlet 1 for introducing nitrogen gas for nitriding into the chamber 1.
4 and an argon gas inlet (not shown) for introducing, for example, argon as a plasma gas. Further, a vacuum pump 9 for exhausting the inside of the chamber 1 is attached to the chamber 1, and the pressure in the chamber 1 is adjusted by the pressure controller 8.

Between the susceptor 7 and the inner wall of the chamber 1, a rectifying plate 11 for uniformly exhausting the gas in the chamber 1 is mounted. A focus ring 1 around the susceptor 7 for preventing the substrate from shifting or the like.
0 is provided.

In this plasma processing apparatus, the silicon crystal 2 is provided particularly on the side surface of the chamber 1 exposed to the plasma generation region 13. More specifically, the silicon crystal 2 is disposed on the inner wall surface of the chamber 1 from the position where the substrate 12 is mounted to the upper part of the chamber 1 where the antenna unit 3 is mounted. The silicon crystal body 2 is formed in a tubular shape by, for example, hollowing out a central portion of a silicon ingot, and is provided so as to surround the plasma generation region 13.

Next, the operation of the above-described plasma processing apparatus will be described with reference to an example of a nitriding process of a gate oxide film.

First, the substrate 12 on which the gate oxide film to be subjected to the nitriding treatment is formed is accommodated in the chamber 1 by the transfer arm (not shown), and the substrate 12 is moved up and down by the lifter pins (not shown). 7 on the upper surface.

The inside of the chamber 1 is evacuated by the vacuum pump 9 and the pressure in the chamber 1 is maintained in a predetermined pressure range by the pressure controller 8.
L / min) of argon gas is introduced into the chamber 1 from the argon gas inlet and the flow rate is about 20 sccm.
(0.02 L / min) nitrogen gas is introduced into the chamber 1 from the gas inlet 14.

On the other hand, the microwave generator 6 generates a microwave having a frequency of 2.45 GHz. The generated microwave is guided to the antenna unit 3 via the waveguide 5 and the coaxial waveguide converter 4. The microwave guided to the antenna section 3 is propagated to the entire area of the aluminum nitride plate 3b, transmitted through the quartz plate 15 from the opening provided in the slot electrode 3c, and radiated substantially uniformly into the chamber 1.

When the microwave is radiated into the chamber 1, the argon gas existing in the chamber 1 is dissociated, and a plasma generation region 13 is formed in a space between the substrate 12 and the quartz plate 15. The nitrogen gas is activated to generate nitrogen radicals. The portion near the surface of the silicon oxide film formed on the substrate 12 is nitrided by the generated nitrogen radicals.

After the substrate 12 has been subjected to the nitriding treatment, the substrate 12 is taken out of the chamber 1 and a series of nitriding treatments is completed.

In the above-described plasma processing apparatus, as shown in FIG.
Is provided with a silicon crystal body 2 on the side surface portion. Silicon is a material that is generally widely used as a semiconductor substrate. That is, since the semiconductor is a semiconductor, the wall surface of the silicon crystal body 2 is more likely to be at the ground potential (earth surface) than an insulator such as quartz. Thereby, the propagation of the microwave along the wall surface of the silicon crystal body 2 is suppressed, and a uniform plasma generation region is formed above the substrate 12.

As a result, when the nitriding treatment is performed,
Variations in the degree of nitridation of the gate oxide film in the plane can be suppressed.

Further, since the cleaning technology of a silicon substrate as a semiconductor substrate has been advanced, such a cleaning technology can be applied to the silicon crystal 2 made of the same material. For example, impurities such as metals attached to the surface of the silicon crystal 2 can be easily removed using an acid such as sulfuric acid or nitric acid.

As a result, the cleanliness of the portion exposed to the plasma is improved, and the adhered impurities do not desorb and re-adhere to the surface of the substrate as in the conventional plasma processing apparatus. As a result, nitriding treatment with low contamination and high cleanliness can be performed on the gate oxide film, and the electrical characteristics of the transistor are stabilized.

Further, since the silicon crystal body 2 has better heat dissipation than quartz, deterioration of, for example, an O-ring (not shown) for sealing the inside and the outside of the chamber 1 can be suppressed. Further, the temperature control of the chamber 1 is relatively easy to perform as compared with the quartz chamber.

In addition, an appropriate conductive type impurity such as boron or phosphorus may be introduced into silicon crystal body 2. By introducing such a suitable conductivity type impurity into the silicon crystal 2 to lower the resistance of the silicon crystal 2, the silicon crystal 2 comes closer to the properties as a conductor.
As a result, the silicon crystal body 2 tends to be at the ground potential (ground plane), and the plasma generation region can be formed more uniformly.

In the case where impurities such as boron or phosphorus are introduced into the silicon crystal 2, in order to prevent boron or phosphorus or the like from being detached from the silicon crystal 2 by plasma and re-adhering to the surface of the substrate. It is desirable that the impurity concentration on the surface of silicon crystal body 2 facing plasma generation region 13 be set lower than the impurity concentration inside.

In this plasma processing apparatus, the current plate 11 and the focus ring 10 are formed of a silicon crystal. By using the current plate 11 made of silicon crystal as compared with the conventional current plate made of aluminum, as described above, it is possible to suppress the impurities attached to the surface of aluminum from contaminating the inside of the chamber. .

Further, as compared with a conventional focus ring made of an insulator made of ceramics or quartz, the focus ring 10 made of a silicon crystal has semiconductor properties. As a result, as described above, the plasma can be uniformly formed in the space above the substrate 12.

The above-described effects can be obtained by providing the silicon crystal body at least on the surfaces of the current plate 11 and the focus ring 10.

Although the quartz plate 15 is provided between the antenna unit 3 and the reaction chamber, an aluminum nitride plate can be used as a material of the portion through which microwaves pass, in addition to the quartz plate.

Next, in the above-described plasma processing apparatus and a conventional plasma processing apparatus having a chamber made of aluminum, plasma processing was performed to evaluate contamination of the substrate. An 8-inch wafer was used as a substrate. Also,
Each impurity attached to the wafer was measured by ICP-MS (inductively coupled plasma method).

First, in a wafer subjected to plasma processing by a conventional plasma processing apparatus, aluminum (Al)
Is 5 × 10 ¹⁰ atoms / cm ² and sodium (N
The amount of a) is 1 × 10 ¹⁰ atoms / cm ² and copper (Cu)
Was 1 × 10 ¹⁰ atoms / cm ² , and the amount of iron (Fe) was 1 × 10 ¹⁰ atoms / cm ² .

On the other hand, it was confirmed that the above-mentioned impurity elements were all reduced in the wafer which was subjected to the plasma processing by the present plasma processing apparatus having the silicon crystal 2.

In the above-described embodiment, a description has been given by taking as an example a plasma processing apparatus in which plasma is generated using the microwave generator 3 and the flat antenna unit 3. This type is a so-called microwave-excited type plasma processing apparatus. In addition, as a micro-excited type plasma processing apparatus, for example, an ECR (Electron Cyclotr
The silicon crystal can be applied to a plasma processing apparatus such as an on-resonance type.

As a plasma processing apparatus other than the microwave excitation type, for example, an inductive coupling type (ICP: Inductio
The silicon crystal can be applied to a plasma processing apparatus such as an n-coupling plasma or a parallel plate type. In particular,
In an inductively coupled or parallel plate type plasma processing apparatus,
Applying a silicon crystal is highly significant from the viewpoint of effectively removing impurities adhering to the inner wall of the chamber.

Further, although the nitriding of the gate oxide film has been described as an example of the processing by the plasma processing apparatus, the above-described plasma processing apparatus can be applied to processes other than the nitriding of the gate oxide film.

The embodiment disclosed this time is an example in all respects, and should not be considered as limiting. The present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[0066]

According to the plasma processing apparatus of the present invention, by providing a silicon crystal at a portion facing the plasma, the surface of the portion exposed to the plasma can be improved in cleanliness, and the adhered impurities can be reduced. Elimination by plasma does not cause re-adhesion to the substrate. As a result, a treatment with less contamination can be performed on the substrate. Further, a silicon crystal, which is a semiconductor, is more likely to have a ground potential than an insulator such as quartz. Thereby, the propagation of the microwave along the wall surface of the silicon crystal is suppressed, and uniform plasma can be generated. As a result, the predetermined processing can be performed uniformly in the substrate surface. For example, when performing the nitriding treatment of the gate oxide film, the nitriding in the substrate surface can be performed uniformly. Furthermore, since the silicon crystal has better heat dissipation than quartz, for example, temperature control can be easily performed, and deterioration of the seal member and the like can be suppressed.

More specifically, the silicon crystal is formed on the inner wall portion of the reaction chamber facing a region (space) located on the side of the plasma generation region from the position of the substrate introduced into the reaction chamber. Is provided so as to surround the silicon crystal, so that the silicon crystal is disposed in a portion substantially exposed to the plasma generation region.

Further, since the silicon crystal contains at least one of impurities selected from the group consisting of boron, phosphorus and arsenic, the resistance of the silicon crystal is lowered, and the silicon crystal has a property as a conductor. You will get closer. As a result, the silicon crystal is more likely to be at the ground potential, and the plasma generation region can be formed more uniformly.

Further, when such an impurity is contained, the impurity concentration of the impurity on the surface of the silicon crystal body facing the plasma generation region is preferably lower than the impurity concentration in the inside, whereby the impurity is reduced. Accordingly, it is possible to prevent separation from the silicon crystal and re-adhesion to the surface of the substrate.

Further, by providing a silicon crystal body also in the current plate and the ring member, impurities can be effectively removed by washing, and a process with high cleanliness can be performed.

As means for generating plasma, it is preferable to provide a microwave discharge unit for generating plasma by microwave discharge.

More specifically, the microwave discharge unit is attached to the reaction chamber so as to be substantially opposed to the substrate, the microwave generator for generating microwaves, and the microwave generated by the microwave generator. And a plate-shaped antenna section for radiating into the reaction chamber,
In a plasma processing apparatus including a microwave discharge unit having such a flat antenna, a substrate having a relatively large area is targeted, and in particular, by providing a silicon crystal on an inner wall of a reaction chamber of this type, As described above, uniform plasma can be generated, and processing in the substrate surface can be performed more uniformly.

Alternatively, a high frequency discharge unit for generating plasma by high frequency discharge may be provided as a means for generating plasma, whereby a so-called inductively coupled plasma processing apparatus or a parallel plate type plasma processing apparatus is provided. For example, it is possible to perform a process with high cleanliness.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view of a conventional plasma processing apparatus.

[Explanation of symbols]

1 chamber, 2 silicon crystal, 3 antenna section,
3a conductor, 3b aluminum nitride plate, 3c
Slot electrode, 4 coaxial waveguide converter, 5 waveguide, 6
Microwave generator, 7 susceptor, 8 pressure controller, 9
Vacuum pump, 10 focus ring, 11 gas dispersion plate, 12 substrate, 13 plasma generation region, 14 gas inlet, 15 quartz plate.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G075 AA24 AA30 CA47 DA02 EB41 EB42 EB44 FA12 FB01 FC11 FC13 FC20 5F045 BB02 BB14 EB03 EH08 EH09 EH10 EH11 EH12 EH16

Claims (9)

[Claims] 1. A plasma processing apparatus for generating plasma in a reaction chamber and performing a predetermined process on a substrate introduced into the reaction chamber, wherein the plasma processing apparatus includes a plasma generation region on an inner wall of the reaction chamber. A plasma processing apparatus in which a silicon crystal body is provided in a facing part. 2. The silicon crystal body surrounds a plasma generation region on an inner wall portion of the reaction chamber facing a region located on the side of a plasma generation region from a position of a substrate surface introduced into the reaction chamber. The plasma processing apparatus according to claim 1, wherein the plasma processing apparatus is provided as follows. 3. The plasma processing apparatus according to claim 1, wherein said silicon crystal body contains at least one impurity selected from the group consisting of boron, phosphorus, and arsenic. 4. The plasma processing apparatus according to claim 3, wherein an impurity concentration of the impurity on a surface of the silicon crystal body facing a plasma generation region is lower than an impurity concentration in the inside. 5. A stage for mounting a substrate, mounted between the stage and the reaction chamber wall so as to surround the stage in a circumferential direction, and for stabilizing a gas flow. The plasma processing apparatus according to claim 1, further comprising a rectifying plate, wherein a silicon crystal is formed on at least a surface of the rectifying plate. 6. A ring member mounted along an outer edge of the stage section so as to surround a substrate to be mounted, and a silicon crystal is formed on at least a surface of the ring member. The plasma processing apparatus according to any one of claims 1 to 5, 7. The plasma processing apparatus according to claim 1, further comprising a microwave discharge unit for generating plasma by microwave discharge. 8. The microwave discharge unit is attached to the reaction chamber so as to substantially face a substrate, and a microwave generator for generating microwaves. The microwave discharge unit converts the microwaves generated by the microwave generator. The plasma processing apparatus according to claim 7, further comprising a flat antenna unit for radiating light into the reaction chamber. 9. The plasma processing apparatus according to claim 1, further comprising a high-frequency discharge unit for generating plasma by high-frequency discharge.