JPH0532483A - Vapor-phase growth method and plasma process deivce therefor - Google Patents

Abstract

PURPOSE:To form a high-quality epitaxial growth film having very little pollution and very few defects by lighting a plasma of a gas for vapor-phase growth at a low microwave power at which no plasma is essentially lighted. CONSTITUTION:A method for vapor-phase growth wherein a silicon substrate 33 is washed with a hydrofluoric acid gas, then the silicon substrate 33 is placed on a sample stand 31 arranged in a reaction chamber 11 of an ECR plasma process device 43, an inert gas is introduced into the reaction chamber 11, plasma is lighted at an energy lower than displacement energy of silicon and a gas for vapor-phase growth is introduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vapor phase growth method and a plasma process apparatus, and more particularly to a vapor phase growth method performed in a manufacturing process of semiconductor substrates and the like and a plasma process apparatus used for manufacturing semiconductor substrates and the like.

[0002]

2. Description of the Related Art In epitaxial growth, surface cleaning of a substrate including removal of a surface oxide film is important for obtaining a highly reliable substrate with few defects. Therefore, the first substrate to be put into the LSI manufacturing process is SC-1 cleaning (NH ₄ OH (30%): H ₂ O ₂ (30%): H ₂ O
= 1: 2: 6 (80 ° C)), hydrofluoric acid solution (HF 1%) washing and SC-2 washing (HCl (35%): H ₂ O ₂ (30%): H ₂ O
= 1: 2: 6 (80 ° C.)) is performed to remove metal, organic contaminants, and oxide film on the substrate surface.
After the RCA cleaning, the surface of the substrate is covered with a uniform natural oxide film of about 10 Å. Therefore, the oxide film was removed by performing heat treatment, plasma treatment or the like in a vacuum container immediately before the epitaxial growth.

However, in recent years, dangling bonds on the surface of a silicon wafer are converted to hydrogen atoms or fluorine by simply cleaning the surface of the silicon wafer with a hydrofluoric acid solution after removing the metal, organic contaminants and oxide film on the surface of the silicon wafer by conventional RCA cleaning. It has become clear that the surface is terminated by atoms, and the natural oxidation of the surface is suppressed for nearly 40 minutes (SiO ₂ / Si Interface studie
d by STM M. Niwa and H. Iwasaki, Extended Abstract
sof the 21st Conference on Solid State Device and
Materials, Tokyo 1989 p.213).

Therefore, it has been attempted to carry out a cleaning pretreatment for epitaxial growth by suppressing the natural oxide film itself by performing cleaning with hydrofluoric acid after RCA cleaning (The formation of hydrogen passiv.
ated silicon single-crystal surface using ultravio
let cleaning and HF etching, H kuroda et al., J. Ap
pl. Phys. 64 ( 7) 1988 p.3516). FIG. 2 is a cross-sectional view schematically showing the ECR plasma processing apparatus 50.
After cleaning the silicon substrate 51 with a hydrofluoric acid solution after the CA cleaning, epitaxial growth was performed on the silicon substrate 51 using the ECR plasma processing apparatus 50.
In this method, a silicon substrate 51 treated with a hydrofluoric acid solution is used.
Are immediately loaded into the load lock chamber 52 and a vacuum is drawn. After the evacuation, the reaction chamber 5 was evacuated in advance.
Transport to 3. Then, the plasma generated in the plasma generation chamber 54 is guided to the silicon substrate 51 in the reaction chamber 53, and the substance generated by the reaction in the plasma is deposited on the silicon substrate 51 to form a film. At this time, in forming the epitaxial film having good crystallinity, the silicon substrate 5
The heat treatment of 1 is indispensable.

A sample stage 55 is disposed in the reaction chamber 53 so as to face the plasma extraction window 56, and the silicon substrate 51 is placed on the upper surface of a susceptor 57 placed on the sample stage 55. Below the susceptor 57, a heater 58 composed of a spiral metal tungsten 58a and a heater support 58b is provided with a reaction chamber 53 through a bell jar 59 made of quartz.
The heat treatment is applied to the silicon substrate 51 by radiant heat from the heater 58.

[0006]

In the plasma processing apparatus 50 described above, after cleaning the silicon substrate 51 with the hydrofluoric acid solution, the silicon substrate 51 is placed on the sample stage 55 of the reaction chamber 53 which is evacuated. It will pass through the atmosphere once. In this case, as described above, the formation of the natural oxide film is unlikely to occur, but there is a problem in that the adsorption of oxygen on the surface of the silicon substrate 51 and the adhesion of organic substances and fine particles cause the deterioration of the film quality.

After cleaning the silicon substrate 51, the reaction chamber 5
When epitaxially growing with ECR plasma in No. 3, it is effective to grow with a low microwave power to form a high-quality epitaxial growth film, but silane-based gas (SiH ₄ , Si ₂ H ₆ , Si ₃ H ₈ ) is used. When used, there was a problem that plasma was very difficult to light at low microwave power.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a vapor phase growth method and a plasma processing apparatus capable of growing a high-quality epitaxial film.

[0009]

In order to achieve the above object, in the vapor phase growth method according to the present invention, a silicon substrate is cleaned with hydrofluoric acid gas, and thereafter, the silicon substrate is placed in a reaction chamber of an ECR plasma process apparatus. The silicon substrate is placed on a sample table, an inert gas is introduced into the reaction chamber, plasma is lit at an energy lower than the displacement energy of silicon, and then a gas for vapor phase growth is introduced. .

In order to achieve the above-mentioned object, a plasma process apparatus according to the present invention is a plasma process apparatus including a reaction chamber having a plasma generation chamber and a sample stage, and a vacuum sluice valve is provided in the reaction chamber. And a substrate cleaning chamber is connected.

[0011]

According to the above-mentioned method, the silicon substrate is cleaned with hydrofluoric acid gas, and then the silicon substrate is placed on the sample table provided in the reaction chamber of the ECR plasma process apparatus and the inert gas is removed. It is introduced into the reaction chamber to turn on plasma with energy lower than the displacement energy of silicon, and the gas for vapor phase growth is introduced while maintaining this turned-on state, so even with low microwave power that plasma does not turn on originally. The plasma of the vapor growth gas is turned on, and a good quality epitaxial growth film is obtained.

Further, according to the above structure, in the plasma process apparatus having the reaction chamber in which the plasma generation chamber and the sample stage are installed, the substrate cleaning chamber is connected to the reaction chamber via the vacuum gate valve. Also, when the substrate after cleaning with hydrofluoric acid or the like is conveyed to the plasma processing apparatus, the substrate surface is prevented from being contaminated, the deterioration of the film quality due to contaminants is prevented, and the contamination and defects are of high quality. An epitaxial growth film is obtained.

[0013]

Embodiments of the vapor phase growth method and plasma processing apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing the configuration of a plasma process apparatus according to an embodiment. In FIG. 1, reference numeral 10 denotes a plasma generation chamber formed of stainless steel.
0 is TE113 for microwave of industrial frequency 2.45GHz
It functions as a cylindrical cavity that forms a standing wave of the mode. A microwave introduction window 13 that is hermetically closed by a dielectric such as a circular quartz glass plate 12 is formed in the center of the upper wall of the plasma generation chamber 10. In addition, the plasma generation chamber 1
A plasma extraction window 16 is formed at a position facing the microwave introduction window 13 in the central part of the lower wall of 0, and an excitation coil 15 is concentrically arranged with the plasma generation chamber 10 around the plasma generation chamber 10. It is set up.

One end of a microwave waveguide 14 is connected to the microwave introduction window 13, and the microwave waveguide 14 is connected to the microwave introduction window 13.
The other end of is connected to a high frequency oscillator (not shown). Industrial frequency 2.45 emitted from this high-frequency oscillator
The microwave of GHz is introduced into the plasma generation chamber 10 through the quartz glass plate 12.

The exciting coil 15 is connected to a direct current power source (not shown), and the flow from this direct current power source produces a magnetic flux density of 8.75 × 10 ^-2 T which establishes an electron cyclotron resonance condition by introducing microwaves. A divergent magnetic field that reduces the magnetic flux density toward the reaction chamber 11 side is formed while being supplied to the plasma generation chamber 10, and the plasma generated in the plasma generation chamber 10 is introduced into the reaction chamber 11 side through the plasma extraction window 16. It has become.

Exhaust ports 18, 19 are formed on one side wall of the reaction chamber 11 via a gate valve 17, a turbo molecular pump 20 is connected to the exhaust port 18, and an oil rotary pump 21 is connected to the exhaust port 19. Are connected. A substrate cleaning chamber 23 formed of stainless steel is connected to the other side wall via a vacuum gate valve 22, and a quartz glass plate 24 is mounted inside the substrate cleaning chamber 23. In addition, exhaust ports 25 and 26 are formed on the upper wall and the lower wall of the substrate cleaning chamber 23 at positions facing each other, and these exhaust ports 25 and 26 are connected to a vacuum pump 27. A gas supply pipe 42 for supplying a gas such as hydrofluoric acid is connected to the substrate cleaning chamber 23. A plurality of pipes 44 are connected to the gas supply pipe 42 so that nitrogen gas, HF / H ₂ O, H ₂ O gas or the like can be supplied to the substrate cleaning chamber 23.
A mass flow controller 45 is connected to the pipe 44 so as to maintain a desired gas flow rate. The silicon substrate 3 is placed inside the substrate cleaning chamber 23.
A transfer arm 28 for transferring 3 to the reaction chamber 11 is provided.

On the other hand, a gas supply pipe 2 for introducing a silane-based gas and an inert gas is provided on the upper inner wall of the reaction chamber 11.
9 and 30 are connected to each other, and a cylindrical sample stage 31 having an opening on a side surface is disposed inside the reaction chamber 11 so as to face the plasma extraction window 16. A transparent quartz susceptor 32 is detachably mounted on the sample table 31,
A silicon substrate 33 is placed at the center of the susceptor 32 so as to face the plasma extraction window 16.

The sample stage 31 is made of a silicon in a horizontal plane centered on the center of the silicon substrate 33 by a substrate rotating mechanism 34 composed of a motor 34a, a rotation introducing mechanism 34b to the vacuum side, pinion gears 34c and 34d, and a bearing 34e. It is adapted to be rotationally driven with the substrate 33 placed thereon.

A hole 32a having a diameter slightly smaller than the outer diameter of the silicon substrate 33 is formed in the central portion of the susceptor 32, and the silicon substrate 33 is provided below the susceptor 32.
A heater 35 for heating the silicon substrate 33 is provided from the lower surface of the. The heater 35 includes a Ta wire 35a arranged in parallel with the silicon substrate 33 and a heater support 35b made of transparent alumina magnetic, and the heater 35 can directly heat the silicon substrate 33.
The heating efficiency can be increased. A quartz tube is passed through the Ta wire 35a, and the heater wire is made into a lamp, so that the quartz bell jar 36, which will be described later, is heated by the heater 3.
It is possible to reduce the adhesion of the evaporate from 5.
A water cooling jacket 38 made of stainless steel is provided below the heater support 35b to cool the heater support 35b.

The reaction chamber 11 and the heater 35 side are separated by a quartz bell jar 36 provided on a stainless steel bell jar support 37. When the reaction chamber 11 side and the heater 35 side are evacuated to vacuum, the reaction chamber 1 is prevented from being damaged due to the pressure difference between the two sides.
1 is opened and the sluice valve 39 between the heating heater 35 side is opened, and the oil rotary pump 21 connected to both sides and the oil rotary pump 47 arranged via the oil diffusion pump 40 are evacuated to a pressure on both sides. Is lowered until a molecular flow is formed with respect to the exhaust ports 19 and 41, the sluice valve 39 is closed, the reaction chamber 11 side is the turbo molecular pump 20, and the heating heater 35 side is further oil diffused 40 to exhaust gas. Try to do it.

Next, a method for vapor phase growth on the silicon substrate 33 using this plasma processing apparatus will be described. The silicon substrate 33 from which metal and organic contaminants have been removed by RCA cleaning or the like is carried into the substrate cleaning chamber 23, and 1
After evacuating to less than 00 Pa, nitrogen gas 5SLM is flown into the substrate cleaning chamber 23 to bring the pressure in the substrate cleaning chamber 23 to about 150 Torr, and then hydrofluoric acid gas is flown into the silicon substrate 33 by hydrofluoric acid gas. Wash for about a minute. Since hydrofluoric acid is a liquid at room temperature,
The gas cylinder, the gas supply pipe 42, and the cleaning liquid tank 46 are 50
It must be heated to ~ 55 ° C. After cleaning, exhaust ports 25, 26 connected to the upper and lower parts of the substrate cleaning chamber 23
The substrate cleaning chamber 23 is evacuated to a high vacuum of about 0.1 Pa by the vacuum pump 27, and a rinsing and drying process is performed while maintaining this vacuum state, and then the silicon substrate 33 is transferred by the transfer arm 28 to the reaction chamber of the apparatus main body. 11
Carry it inside. This makes it possible to prevent organic pollution and the like due to the atmosphere after cleaning.

After the silicon substrate 33 is transferred to the reaction chamber 11, an argon gas is flown, plasma is turned on under the conditions of a gas pressure of 0.5 Pa, a microwave power of 25 W, and a coil current of 19.5 A to adsorb oxygen. Immediately after removing
Switch to H ₄ gas. At this time, the flow rate of the SiH ₄ gas is increased while the flow rate of the argon gas is reduced.
When the H ₄ gas reaches a predetermined flow rate, the flow rate of the argon gas is set to 0 at about the same time. As a result, it is possible to shift to low microwave power plasma using SiH ₄ gas without turning off the plasma. Further, there is also an effect that the surface migration at the initial stage of film formation can be promoted by irradiating the substrate with Ar plasma of low microwave power. The vapor phase growth was performed under the conditions that the pressure of SiH ₄ gas was 0.4 Pa, the microwave power was 25 W, and the coil current was 19.5 A.

After the SiH ₄ gas is decomposed by plasma, it is necessary to heat the silicon substrate 33 in order to promote the surface migration of the adsorbed species, while the thermal diffusion of the dopant becomes a problem as the LSI pattern becomes finer. Therefore, it is required to lower the process temperature, and by using the ECR plasma, a good-quality epitaxial film can be obtained even at a low temperature of 700 ° C. (usually about 1100 ° C. in thermal epitaxial growth).

Table 1 shows the relationship between the microwave power of SiH ₄ plasma during growth and EPD (etch pit density: according to dislocation). The growth conditions at this time are that the pressure of SiH ₄ gas is 0.4 Pa and the coil current is 19.5 A.
The EPD evaluation was carried out by a method of observing a hole showing a crystal defect when a grown silicon epitaxial film of about 1 μm was etched back by about 0.2 μm with a microscope. The conditions for etch back are as follows. First, as the first liquid, K ₂ Cr ₂ O ₇ : H ₂ O = 44 g: 100
0 cc (0.15 N) was adjusted, and then 1st liquid: HF
(50%) = 1: 2 (volume ratio) is adjusted to obtain the second liquid. Immediately before etching, the second liquid is 1: 1 (volume ratio).
The substrate on which the silicon epitaxial film was grown in this solution after being mixed with H ₂ O at 60 ° C. was ultrasonically stirred and washed for 60 seconds, and then observed with a microscope.

[0025]

[Table 1]

As described above, it is understood that when epitaxially growing by ECR plasma in the reaction chamber 11, it is effective to grow with low microwave power to form a high quality epitaxial growth film.

When the epitaxial growth film is formed on the silicon substrate 33 by using the vapor phase growth method and the plasma processing apparatus according to this embodiment, the surface of the silicon substrate 33 is washed by hydrofluoric acid and then the conventional method is performed. The silicon substrate 33 is placed in the reaction chamber 11 without being exposed to the atmosphere.
Therefore, contaminants can be prevented from entering the silicon substrate 33. Further, since the inert gas can be turned on with a low microwave power and the plasma can be transferred to a low microwave power plasma with SiH ₄ gas without turning off the plasma, there is very little contamination and defects, and high quality. An epitaxial growth film can be formed.

[0028]

As described above in detail, in the vapor phase growth method according to the present invention, the silicon substrate is cleaned with hydrofluoric acid gas, and then the sample stage is provided in the reaction chamber of the ECR plasma processing apparatus. Since the silicon substrate is placed on the above, inert gas is introduced into the reaction chamber, plasma is lit at an energy lower than the displacement energy of silicon, and then gas for vapor phase growth is introduced, so plasma is originally lit. Even with such a low microwave power, the vapor phase growth gas is turned on and a high quality epitaxial growth film can be formed.

Further, in the plasma process apparatus according to the present invention, in the plasma process apparatus having the plasma generation chamber and the reaction chamber in which the sample stage is installed, the substrate cleaning chamber is provided in the reaction chamber via the vacuum gate valve. Since the substrates are connected, the substrate surface can be prevented from being contaminated when the cleaned substrate is transported to the plasma process apparatus, and the deterioration of the film quality due to contaminants can be prevented.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of an ECR plasma processing apparatus according to the present invention.

FIG. 2 is a schematic sectional view showing a conventional ECR plasma processing apparatus.

[Explanation of symbols]

10 Plasma generation chamber 11 Reaction chamber 22 Vacuum gate valve 23 Substrate cleaning room 31 sample table 33 Silicon substrate 43 Plasma Process Equipment

Claims (2)

[Claims] 1. A silicon substrate is cleaned with a hydrofluoric acid gas, and then the silicon substrate is placed on a sample table provided in a reaction chamber of an electron cyclotron resonance excitation (ECR) plasma process apparatus, and an inert gas is used. Is introduced into the reaction chamber to turn on plasma with energy lower than the displacement energy of silicon, and then a gas for vapor phase growth is introduced. 2. A plasma process apparatus having a reaction chamber in which a plasma generation chamber and a sample stage are internally provided, wherein a substrate cleaning chamber is connected to the reaction chamber via a vacuum sluice valve. apparatus.