JPH09306899A - Gas phase reactor - Google Patents

Abstract

(57) Abstract: A plasma CVD apparatus capable of efficiently performing self-cleaning is provided. A reactor is provided, and at least a shower electrode and a susceptor are provided in the reactor, and the shower electrode is supported by an insulating ring and is connected to a high frequency power source. In a vapor phase reactor having a soaking plate on its upper surface and an insulating cover surrounding the soaking plate, two types of pressure sensors, a film forming pressure sensor and a cleaning pressure sensor, are installed in the reaction furnace. A gas-phase reactor characterized by being present.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a gas phase reaction apparatus such as a plasma CVD apparatus. More specifically, the present invention relates to a plasma CVD apparatus and a cleaning method therefor capable of smoothly and quickly performing a cleaning operation after a film forming process.

[0002]

2. Description of the Related Art In manufacturing a semiconductor IC, there is a step of forming a thin film of silicon oxide on the surface of a substrate. Chemical vapor deposition (CVD) is used as a method of forming a thin film. There are three CVD methods, an atmospheric method, a decompression method and a plasma method, but the plasma method is attracting attention as a suitable method for a recent ultra LSI that requires a high quality and highly accurate thin film. .

[0003] In the plasma method, a high-frequency voltage is applied to a reaction gas injected in a vacuum to form a plasma to obtain energy required for the reaction. The uniformity of the film thickness and good film quality are obtained. Moreover, it is excellent in many points such as a high film formation speed.

[0004] For example, SiH ₄ has been used as a material for forming a silicon oxide film by the plasma method. However, a decrease in step coverage (step coverage) has become a problem with the miniaturization of semiconductor devices. Liquid tetraethylorthosilicate (TEOS) [Si (OC ₂ H ₅ ) ₄ ] has recently been used in place of this monosilane gas. This is because TEOS can form a dense film having excellent step coverage. When a silicon oxide film is formed using TEOS, TEOS is heated and vaporized to form TEOS gas, which is mixed with oxygen gas and supplied to the reaction furnace.

FIG. 2 is a schematic configuration diagram of an example of a conventional plasma CVD apparatus 1. In the figure, a reaction furnace (chamber) 10 is made airtight, a metal nozzle portion 30 is fixed to a lid plate 102 of the reaction furnace 10, and an aluminum lower portion is provided therewith, and a large number of minute holes 41 penetrating from the upper surface to the lower surface are provided. The disk-shaped shower electrode 40 is supported by the insulating ring 103. This is the upper electrode 32. A high frequency power supply 7 for applying a high frequency voltage to the shower electrode 40 is provided.

A lower electrode 20 is provided so as to face the upper electrode 32. The lower electrode 20 is supported by columns 25. The susceptor 22 is arranged on the upper part of the pillar 25,
A heater unit 21 is provided below the susceptor 22, and a heater cover 23 is provided around the susceptor 22 and the heater unit 21.

In the reaction process, the side surface 1 of the reaction furnace 10 is used.
05, the gate 51 of the loading / unloading path 50 is opened, the substrate 6 is loaded by the carrier 52, and the susceptor 2 is loaded.
It is placed on the upper surface of the No. 2 approximately at the center. After the gate is closed and the duct 104 is evacuated to bring the inside of the reaction furnace to a predetermined degree of vacuum, the heater unit 21 heats the susceptor 22, and when the substrate 6 placed on the susceptor 22 reaches a predetermined temperature, the inlet is closed. 31 to a predetermined reaction gas (for example, TE
OS and oxygen gas) are fed into the reaction furnace. The gas passes through the nozzle portion 30 and is jetted toward the substrate through the minute holes 41 of the shower electrode 40.

However, as the film forming process progresses, in addition to the surface of the substrate, the inner wall surface of the reaction furnace, the shower electrode 40,
Reaction products also adhere to the wall surfaces of various members such as the susceptor 22 and the heater cover 23. If such a reaction product is left as it is and the film forming process is continued, the product eventually peels off and becomes a cause of foreign matter. Further, the impedance in the furnace changes, which adversely affects the high-frequency output and the like, and as a result, the film thickness distribution and film quality characteristics of the plasma CVD film formed on the substrate surface may be deteriorated, which may cause product defects. For this reason, in the case of a single-wafer apparatus, the inside of the furnace is always cleaned when the film forming process for several to several tens of substrates is completed, and after the cleaning is completed, a new substrate is loaded into the furnace and a new film is formed. I'm trying to start the process.

In the conventional plasma CVD apparatus, a CFC-based gas (for example, CF ₄ , CCl) is introduced from the inlet 31.
₂ F ₂ , C ₂ F ₆ or NF ₃ and O ₂ ) are introduced into the furnace,
Self-cleaning of the inner wall surface of the furnace has been performed by a plasma dry etching method in which a high frequency voltage is applied to generate fluorine radicals in a plasma atmosphere, and foreign substances are decomposed and removed by the fluorine radicals.

[0010]

However, in the CVD process using high-density plasma, film formation is performed at a low pressure of the order of several mTorr, but if self-cleaning in the reaction furnace is performed in the same pressure band, cleaning time And increase in throughput, which causes a decrease in throughput.

Accordingly, an object of the present invention is to provide a gas phase reaction apparatus and a cleaning method therefor capable of smoothly and quickly performing self-cleaning in a reaction furnace.

[0012]

Means for Solving the Problems The above problem has a reaction furnace in which at least a shower electrode and a susceptor are disposed, and the shower electrode is supported by an insulating ring and has a high frequency. In a gas phase reaction apparatus connected to a power source, the susceptor having a heat equalizing plate on its upper surface and an insulating cover surrounding the heat equalizing plate, a film forming pressure sensor and a cleaning pressure sensor are provided in the reaction furnace. This is solved by a gas phase reaction device characterized in that two types of pressure sensors are installed.

Further, the above object is to have a reaction furnace in which at least a shower electrode and a susceptor are arranged, and the shower electrode is supported by an insulating ring and connected to a high frequency power source. The susceptor has a soaking plate on its upper surface and an insulating cover surrounding the circumference of the soaking plate, and supplies electric power from the high-frequency power source to the reaction furnace through the upper electrode at the same time. A cleaning method in which a freon-based gas is fed into the furnace and fluorine radicals are generated in a plasma atmosphere to remove unnecessary film formation formed inside the reaction furnace to clean the inside of the reaction furnace. , 1 Torr ~ 9
It is also solved by a method for cleaning a gas phase reaction device, characterized in that the showerhead electrode is cleaned at an atmospheric pressure within a range of Torr, and the inside of the reaction furnace other than the shower electrode is cleaned at an atmospheric pressure within a range of 1 mTorr to 90 mTorr. To be done.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail with reference to specific examples.

FIG. 1 is a schematic sectional view showing the structure of the plasma CVD apparatus of the present invention. The configuration itself of the plasma CVD apparatus of the present invention shown in FIG. 1 is almost the same as that of the conventional plasma CVD apparatus shown in FIG. Therefore, the following description will be made using the reference numerals shown in FIG.

Unlike the conventional plasma CVD apparatus shown in FIG. 2, the plasma CVD apparatus of the present invention has a reaction furnace 10
A film forming pressure sensor 60 and a cleaning pressure sensor 6
2 are provided. The locations of the sensors 60 and 62 are not limited to the illustrated side wall portions. The reaction furnace 10 may be provided at any suitable place as long as the pressure inside the furnace can be accurately detected. For example, it may be arranged on the cover plate 102. The sensors 60, 62 are connected to the reactor 10 by suitable conduits 64.

The film forming pressure sensor 60 has an order of several mTorr to several tens of mTorr, for example, 1 mTorr to 90 m.
The one that can detect the pressure within the range of Torr is used. On the other hand, the cleaning pressure sensor 62 is several T
An orr order, for example, one capable of detecting a pressure within the range of 1 Torr to 9 Torr is used. Therefore, in the plasma CVD apparatus of the present invention, the sensor is used by switching between film formation and cleaning. Examples of the sensor that can be used for such a purpose include a baratron gauge, a BA gauge, a thermocouple gauge, and a Pirani gauge.

In the CVD process using high-density plasma, film formation is carried out at a low pressure on the order of millimetres. However, if self-cleaning in the reaction furnace is carried out in the same pressure band, the cleaning time will be increased and this will be a factor of lowering the throughput. . However, at an atmospheric pressure of several mTorr, the plasma discharge diffuses to the surroundings, which is extremely convenient for cleaning the portion other than the shower electrode. Therefore, according to the present invention, after the film formation, while maintaining the pressure in the reaction furnace at the state of several mTorr at the time of film formation, the inlet 31 through the C
A fluorine-based gas such as ₂ F ₆ or CF ₄ is introduced into the furnace, a high frequency is applied to the upper electrode 32 to cause plasma discharge, and the inside of the reaction furnace other than the shower electrode is self-cleaned. Then, the pressure in the furnace is increased to several Torr.
At such a high atmospheric pressure, the plasma discharge concentrates on the local area, which is extremely convenient for cleaning the local area rather than the large area in the furnace. Therefore, according to the present invention, when the cleaning of the inside of the reaction furnace at a low pressure is completed, the pressure in the furnace is increased by about two orders of magnitude higher than the pressure at the time of film formation, and the fluorine-based gas is added under the atmospheric pressure of several Torr. Is introduced into the furnace, the plasma density is increased, and high-speed self-cleaning of the showerhead electrode is performed.

Regardless of the two-step cleaning method of the present invention, even if the pressure inside the furnace is increased immediately after film formation and a fluorine-based gas is introduced into the furnace under an atmospheric pressure of several Torr to cause plasma discharge. Since the plasma concentrates locally, the cleaning of the shower electrode part is performed quickly, but the interior of other reaction furnaces is not sufficiently cleaned. On the other hand, cleaning with only low pressure is convenient for cleaning a large area in the furnace because plasma diffuses to the surroundings, but cleaning of the shower electrode is rarely performed. Therefore, the two-step cleaning method of the present invention is most effective for sufficiently cleaning a large area in the furnace together with a local area such as a shower electrode within a short time.

The cleaning method of the present invention is most preferably carried out in a plasma CVD apparatus having a so-called parallel plate type electrode in which an upper electrode and a lower electrode face each other. In the bias ECR-CVD apparatus, cleaning cannot be performed because plasma discharge does not occur at a pressure of several Torr. If it is a parallel plate type plasma CVD apparatus,
In addition to the high-density plasma film forming process at a low pressure of several mTorr, plasma discharge can be generated not only in the cleaning operation at a high pressure of several Torr.

In the device of the present invention, the insulating ring 103 supporting the shower electrode 40 is formed of an aluminum nitride ceramic material. An insulating ring made of aluminum nitride ceramic is particularly preferable because it has high electric insulation and is resistant to thermal shock. If desired, only the outer peripheral surface of the insulating ring 103 and the contact portion of the shower ring can be lined with an aluminum nitride ceramic material.

Further, in the susceptor 20, the soaking plate 22
It is particularly preferred that the insulating cover 23 surrounding it and its surroundings be made of an aluminum nitride ceramic material.
If desired, the closure 24 enclosing the heater 21 and the legs 25 of the susceptor may also be formed of or lined with an aluminum nitride ceramic material.

In the plasma CVD apparatus of the present invention, at least a soaking plate in the reaction furnace and an insulating cover around it,
The insulating ring supporting the shower electrode and the heater closure are preferably formed of an aluminum nitride ceramic material. The reason is that these parts are intensively exposed to plasma and are most susceptible to attack by fluorine ion radicals.

Further, in order to further improve the fluorine resistance of these members formed of the aluminum nitride ceramic material, AlF ₃ is formed on the surface of the aluminum nitride ceramic material.
It is also possible to form a dense layer of. The presence of the AlF ₃ layer can prevent the progress of corrosion. Although the AlF ₃ layer can be artificially formed in advance, it is also generated in the plasma self-cleaning process using CF ₄ .

If desired, the inner wall surfaces of the lid plate 102, the base 101, and the body portion 105 of the reaction furnace 10 can be made of an aluminum nitride (AlN) ceramic material. The lid plate 102, the base 101, and the body 105 can be entirely formed of an aluminum nitride ceramic material, or can be lined with a plate-shaped aluminum nitride ceramic material having an appropriate thickness.

[0026]

As described above, according to the plasma CVD apparatus and the two-step cleaning method of the present invention, it is possible to sufficiently clean a large area in the furnace together with a local part such as a shower electrode within a short time. . as a result,
Throughput of the entire film formation process can be improved.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an example of a plasma CVD apparatus according to the present invention.

FIG. 2 is a schematic sectional view of an example of a conventional plasma CVD apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plasma CVD apparatus 6 Wafer 7 High frequency power supply 10 Enclosure (reactor) 101 Base 102 Cover plate 103 Insulation ring 104 Exhaust port 105 Body part 20 Susceptor 21 Heater 22 Soaking plate 23 Insulation cover 24 Heater closure 25 Leg part 30 Nozzle part 31 Inlet 32 Upper Electrode 40 Shower Electrode 41 Injection Hole 50 Carrying In / out Path 51 Gate 52 Carriage

Claims (5)

[Claims] 1. A reaction furnace is provided, and at least a shower electrode and a susceptor are disposed in the reaction furnace, the shower electrode is supported by an insulating ring, and is connected to a high frequency power source. The susceptor is a vapor-phase reactor having an equalizing plate on its upper surface and an insulating cover surrounding the equalizing plate, and two types of pressure sensors, a film forming pressure sensor and a cleaning pressure sensor, are installed in the reaction furnace. A gas-phase reaction device characterized in that 2. The film forming pressure sensor is 1 mTorr to 90.
The gas phase reaction apparatus according to claim 1, wherein a pressure within a range of mTorr can be detected, and the cleaning pressure sensor can detect a pressure within a range of 1 Torr to 9 Torr. 3. The gas phase reactor according to claim 1, wherein the sensor is a Baratron gauge. 4. The gas phase reaction apparatus according to claim 1, which is a plasma CVD apparatus. 5. A reaction furnace is provided, and at least a shower electrode and a susceptor are disposed in the reaction furnace, the shower electrode is supported by an insulating ring, and is connected to a high frequency power source. The susceptor is a gas-phase reaction apparatus having a soaking plate on its upper surface and an insulating cover surrounding the soaking plate, and supplies electric power from the high-frequency power source to the reaction furnace through the upper electrode, and at the same time, makes a chlorofluorocarbon inside the furnace. A cleaning method for cleaning an inside of the reaction furnace by removing an unnecessary film formed inside the reaction furnace by supplying a system gas and generating fluorine radicals in a plasma atmosphere, wherein The showerhead electrode is cleaned at an atmospheric pressure within the range of 9 Torr,
A method for cleaning a gas phase reaction apparatus, comprising cleaning the inside of a reaction furnace other than a shower electrode with an atmospheric pressure within a range of orr.