JPH05259153A - Method and apparatus for manufacture of silicon oxide film - Google Patents

Abstract

PURPOSE:To enable the formation at a low temperature of an oxide film of quality having a higher dielectric breakdown strength by jetting radical hydrogen atoms to a heated Si substrate in vacuum to reduce and clean the substrate and then jetting radical oxygen atoms to the Si substrate to oxidize it. CONSTITUTION:A processing chamber 1 is evacuated to vacuum. Meanwhile, hydrogen gas is introduced into a hydrogen radical source 7, and further high-frequency power is increased, until the plasma is pinched, to produce neutral radical hydrogen atoms. The radical hydrogen atoms are to a silicon substrate 5 heated in vacuum. The silicon substrate 5 is then reduced to be cleaned. Subsequently, oxygen gas is introduced into an oxygen radical source 8, and further high-frequency power is increased, until the plasma is pinched, to produce neutral radical oxygen atoms. The radical oxygen atoms are made to strike the silicon substrate 5 heated in vacuum to oxidize it.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for producing a high-quality silicon oxide film having high dielectric breakdown strength.

A silicon (Si) oxide film is widely used as a gate insulating film of a MOS transistor, an interlayer insulating film of a semiconductor device having a multilayer structure, an insulating film for separating elements, and the like.
As the degree of integration is improved, the thickness of the insulating film is as thin as several nm to 20 nm. Therefore, a high-quality oxide film with high dielectric breakdown strength.
It is necessary to form (SiO ₂ ).

[0003]

2. Description of the Related Art A conventional oxide film such as a gate insulating film of a MOS transistor is formed by a thermal oxidation method.

Here, there are a dry oxidation method and a wet oxidation method as the thermal oxidation method. A Si wafer is installed in a quartz furnace core tube, and the dry oxidation method is performed in an atmosphere of oxygen (O ₂ ) or air. In wet oxidation, the Si wafer was heated to 1000 ° C in a steam atmosphere.
Made by heating to a degree.

However, the heat treatment performed in the device forming process such as the formation of the gate insulating film is accompanied by the diffusion of the constituent elements and causes the deterioration of the characteristics. Therefore, as the device becomes finer, it is desired to lower the heat treatment temperature. What is being done,
Heating at least about 700 ℃ is necessary, but the film quality is not good.

This is because the energy required to oxidize Si is insufficiently applied. Also, as a semiconductor device
A thin film of another semiconductor element such as germanium (Ge) and a cumulative layer may be formed on the Si substrate, and an oxide film may be formed on the uppermost Si film, but in this case also a good oxide film is formed at low temperature. There is a need to.

Therefore, a vapor phase growth method (CVD method) and a sputtering method have been studied as a method for forming an oxide film having a good film quality at a low temperature, but it is difficult to remove impurities at the interface of the oxide film and a dense oxide film is formed. However, there is a problem that it is difficult to obtain, and at present, there is no one suitable for practical use.

On the other hand, whether oxygen plasma is used as a method of using an oxidant that causes a sufficient oxidation reaction with Si even at low temperature,
There are methods such as anodic oxidation in plasma or oxidation using oxygen radicals generated by ultraviolet irradiation.

However, the Si oxide film thus formed is damaged by the impact of ions and electrons in the plasma, and in the case of the gate insulating film of the MOS transistor, the fluctuation of the threshold voltage and the increase of the leak current, It is known that switching speed is reduced.

For these reasons, the practical application of a technique for forming a high-quality Si oxide film by low-temperature treatment is desired.

[0011]

With the improvement in the integration of semiconductor devices, it is desired that the Si oxide film used for the gate insulating film and the interlayer isolation film has a low processing temperature and excellent film quality. However, it is an issue to put the manufacturing method into practical use.

[0012]

[Means for Solving the Problems] The above-mentioned problems face a Si substrate mounted on a heating source in an apparatus having an exhaust system, a discharge tube formed of an insulating material, and a discharge tube formed outside the discharge tube. There is a hydrogen radical source and an oxygen radical source equipped with a high frequency coil. While evacuating the processing chamber, first, while introducing hydrogen gas into the hydrogen radical source, increase the high frequency power until the plasma is pinched and neutralize. Of the hydrogen radicals / atoms are generated, and the hydrogen radicals / atoms are sprayed onto a heated Si substrate in a vacuum to reduce and clean the Si substrate, and then oxygen gas is introduced into the oxygen radical source. , Increase the high frequency power until the plasma is pinched and neutral oxygen radicals
This can be solved by configuring a method for producing a Si oxide film, which is characterized by generating atoms and injecting the oxygen radicals / atoms onto a Si substrate that has been heated in a vacuum to oxidize the Si substrate.

After forming a Si film or a cumulative layer having a Si film as the uppermost layer on a Si substrate by vapor phase epitaxy or molecular beam epitaxy, the neutral oxygen radicals are continuously kept in a vacuum atmosphere. This can be solved by oxidizing the surface of the Si film with atoms.

[0014]

The present invention utilizes the generation of neutral radicals / atoms by high frequency discharge as a method for forming a Si oxide film on a Si wafer at a low temperature.

According to this method, a water-cooled high-frequency coil is wound on the outside of an insulating discharge tube, and the gas pressure inside the discharge tube is 1 to 10 Pa.
As a result, plasma is generated by energizing. Here, it is important to increase the high-frequency power until the plasma in the discharge tube is pinched. At this time, the plasma emits a strong emission, and the emission spectrum from the ions is hardly observed. It is known that only radicals and atoms are included. (For example, Vacuum Volume 31, Volume 4
The present invention is intended to form a high-quality Si oxide film without damage due to ion bombardment by using the neutral radicals / atoms thus generated.

For a thin Si oxide film having a thickness of several nm, the electrical characteristics such as dielectric breakdown strength form the oxide film.
It is closely related to contamination of the Si substrate and surface irregularities, and it is necessary to form a film on a clean flat surface as the oxide film becomes thinner.

That is, when an oxide film is formed on a Si substrate, a flat surface is necessary because the unevenness of the substrate continues to grow up to a film thickness of about 20 nm. From the diffusion of the oxide to the oxide film surface,
The Si substrate needs to be free of contamination.

The inventor has found that contamination of the substrate due to gas adsorption or water vapor adsorption occurs when the substrate is exposed to the atmosphere. Therefore, in order to obtain a good quality thin oxide film, it is necessary to consistently manufacture the substrate without exposing it to the atmosphere. I realized that.

Therefore, in order to form an oxide film on the substrate,
First, since it is necessary to form a film after cleaning the substrate surface, the present invention reduces the oxide film formed on the substrate surface by using neutral hydrogen radicals / atoms to clean it, and then , Supply oxygen radicals / atoms to oxidize.

FIG. 1 shows an apparatus configuration for performing such steps. That is, the processing chamber 1 is a vacuum chamber capable of high vacuum exhaust by the exhaust system 2 having a large exhaust amount, and is connected to the load lock chamber 4 for loading / unloading the substrate through the gate valve 3.

Here, in the processing chamber 1, a substrate manipulator 6 for holding the Si substrate 5 at an appropriate position and heating it, a hydrogen radical source 7 for cleaning the Si substrate 5, and an oxide film are formed. An oxygen radical source 8 is provided.

The hydrogen radical source 7 and the oxygen radical source 8 are discharge tubes 9 and 9'for generating plasma, and water cooled copper high frequency (RF) coils 10 and 10, respectively.
', Apertures 11 and 11', and a shield tube that covers them
12 and 12 ', each configured to supply H ₂ and O ₂ from a gas introduction system.

As the operation procedure, first, the chemically cleaned Si substrate 5 is loaded into the load lock chamber 4 and exhausted using an exhaust system (not shown). And the load lock chamber 4
When the temperature becomes high, the gate valve 3 is opened, and the Si substrate 5 is attached to the heater section 34 by a transfer mechanism (not shown).
Heat to 550-600 ° C with a heater.

On the other hand, the hydrogen radical source 7 and the oxygen radical source 8 are sufficiently exhausted by the exhaust system 15. The hydrogen radical source 7 and the oxygen radical source 8 are leak valves V ₁ , V ₄ ,
Pressure reducing valves 16 and 16 ', H ₂ gas cylinder 17 through the valve _{V 2, V 3, V 5} , V 6
And is connected to an O ₂ cylinder 18.

First, the valve V ₃ , the pressure reducing valve 16, the leak valve V
The H ₂ gas from the H ₂ cylinder 17 is introduced into the discharge tube 9 of the hydrogen radical source 7 through the gas line ₁ and when the pressure in the discharge tube 9 reaches several tens mtorrr to several 100 mtorr, the matching circuit 20 is supplied from the RF power source 19 Then, RF power is supplied to the RF coil 10 to generate glow discharge.

For example, when H ₂ is introduced so that the degree of vacuum in the processing chamber 1 is 10 ⁻⁷ torr, glow discharge is generated when about 170 W is input as RF power.
When the power is increased to 0 W, the plasma is suddenly pinched to generate strong light emission due to arc discharge, and once the plasma is pinched, the power is maintained even if the power is reduced, so that stable operation can be performed with the applied power of 250 W.

Next, the Si substrate 5 is rotated by the rotating mechanism of the substrate manipulator 6, and a substrate shutter (not shown) is opened to irradiate hydrogen radicals / atoms. As a result, the natural oxide film, carbon, metal, etc. on the substrate surface can be removed without damaging the Si substrate 5.

After the cleaning of the Si substrate 5 is completed in this way, the valve is switched and the oxygen radical source 8 is operated in the same procedure as the hydrogen radical source 7. For O ₂ ,
The glow discharge occurred at 150 W, for example, and at 220 W the plasma was pinched.

In this way, by irradiating oxygen radicals / atoms, an oxide film having good film quality and high dielectric breakdown strength can be formed on the Si substrate. A feature of the present invention is that such an oxide film is formed following vapor phase epitaxy (CVD) or molecular beam epitaxial growth (MBE).

That is, conventionally, a semiconductor layer such as Si is formed by CVD or MBE, and this is taken out into the atmosphere,
Contamination of the semiconductor layer occurs because of the step of heating to form an oxide film, which makes it difficult to form an oxide film having excellent film quality.

Therefore, the present invention is to obtain a semiconductor device having excellent characteristics by incorporating this oxide film forming step using neutral oxygen radicals / atoms into a CVD apparatus or an MBE apparatus.

It is more efficient to irradiate hydrogen radicals / atoms to reduce and remove the oxide film on the Si substrate before performing epitaxial growth or heteroepitaxial growth on the Si substrate by the CVD method or the MBE method. In addition, in the present invention, a CVD apparatus and an MBE apparatus are provided with a hydrogen radical source and an oxygen radical source for irradiating hydrogen radicals / atoms and oxygen radicals / atoms.

[0033]

【Example】

Example 1 (Example of application to CVD apparatus) FIG. 2 shows a configuration of a CVD apparatus to which the present invention is applied.

Hereinafter, the same substances as those in FIG. 1 will be described by using the same numbers. The CVD apparatus shown in FIG. 2 has a load chamber 20 for loading a substrate, a cleaning chamber 21 for irradiating the substrate with neutral hydrogen radicals / atoms to clean it, a main chamber 22 for growing a CVD film on the substrate, and a CVD film. It consists of an oxidation chamber 23 that irradiates and oxidizes neutral oxygen radicals and atoms, and an unload chamber 24 that stores and takes out the substrate.

The cleaning chamber 21 is provided with a hydrogen radical source 7 and a substrate manipulator 25 for driving the substrate. Further, in the main chamber 22, a substrate manipulator 26 for driving the substrate and a vertical reactor for performing CVD on the substrate
There is an RF coil 28 on the outside of the reactor 27, and an Si coil on the susceptor 14 driven by the substrate manipulator 26.
The substrate 5 is mounted, and a plurality of (four in this case) gas introduction lines 29 are provided above the reaction furnace 27.

Further, the oxidation chamber 23 is provided with an oxygen radical source 8 and a substrate manipulator 30 for driving the substrate.
As the operation procedure, the substrate carried in from the load chamber 20 is low-temperature cleaned by irradiation of neutral hydrogen radicals / atoms in the cleaning chamber 21, and then handed over to the substrate manipulator 26 in the backbone chamber 22 by the substrate transport mechanism. It

The substrate is carried into the vertical reactor 27 by the linear introduction mechanism of the substrate manipulator 26, and heated by the graphite susceptor 14 by the induction heating of the RF coil 28. The susceptor 14 is rotated during growth by the rotation introducing mechanism of the substrate manipulator 26.

A gas introduction line is used for CVD growth of Si.
Silane (SiH ₄ ) or disilane (Si ₂ H ₆ ) is supplied from 29 to maintain the vacuum in the furnace at ~ 10 ^-5 torr and the substrate temperature to 550.
Keep at ~ 700 ℃.

Next, the substrate is transferred to the oxidation chamber 23 by the substrate transport mechanism, the substrate temperature is set to 600 ° C., and neutral oxygen radicals / atoms are irradiated from the oxygen radical source 8 to form an oxide film. Moved to load room 24.

As a result of consistently forming the gate oxide film on the Si substrate in this manner, the breakdown voltage is lower than that of the conventional 9 MV / cm.
It could be improved to 11.5 MV / cm. Second Embodiment: (Application Example to MBE Device) FIG. 3 is a configuration diagram of an MBE device to which the present invention is applied.

The MBE apparatus is a load lock chamber 30 for loading and unloading a substrate, a processing chamber for irradiating the substrate with neutral hydrogen radicals / atoms for cleaning, and for irradiating the substrate with neutral oxygen radicals / atoms for oxidation. 31 and a growth chamber 32 for MBE.

Here, there is a substrate manipulator for driving the substrate in the upper part of the processing chamber 31, and an oxygen radical source 8 and a hydrogen radical source 7 in the lower part. A substrate manipulator is provided above the growth chamber 32 adjacent to the gate valve 35.
35, which drives the heater unit 34 on which the Si substrate 5 is mounted.

In the lower part of the growth chamber 32, there are electron beam evaporators 36, 37 and molecular beam sources 38, 39 for dopant evaporation.
Further, the inner wall of the growth chamber 32 has the liquid N ₂ shroud 40. As an operating procedure, the substrate in the load lock chamber 30 is
In FIG. 3, after being cleaned at low temperature by neutral hydrogen radicals / atoms irradiated from the hydrogen radical source 7, the substrate is held by the substrate manipulator 35 in the growth chamber 32 by a substrate transport mechanism (not shown).

After that, the Si substrate 5 reaches a predetermined temperature of 300 to 700 ° C. by heating from the heater portion 34, and then MBE growth is performed using the electron beam vapor deposition devices 36 and 37 and the molecular beam sources 38 and 39. ..

Next, the Si substrate 5 is again transported to the processing chamber 31 and is irradiated with neutral oxygen radicals / atoms from the oxygen radical source 8 to be oxidized. Thus, an oxide film having excellent film quality can be manufactured by performing a series of processes of forming the semiconductor layer and oxidizing the surface thereof with the MBE apparatus.

[0046]

According to the present invention, a good quality Si oxide film can be formed at a low temperature, and an oxide film can be formed subsequent to the CVD growth or MBE growth process, thus eliminating the risk of contamination. You can

Therefore, the performance of the semiconductor device can be improved by implementing the invention.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an oxide film manufacturing apparatus according to the present invention.

FIG. 2 is a configuration diagram of a CVD apparatus to which the present invention is applied.

FIG. 3 is a configuration diagram of an MBE device to which the present invention is applied.

[Explanation of symbols]

 1,31 Processing chamber 4 Load lock chamber 5 Si substrate 6 Substrate manipulator 7 Hydrogen radical source 8 Oxygen radical source 21 Cleaning chamber 22 Core chamber 23 Oxidation chamber 27 Vertical reactor 32 Growth chamber 36,37 Electron beam evaporator 38,39 Molecular beam source

Claims (6)

[Claims] 1. A heater section (3) in an apparatus equipped with an exhaust system (2)
4) Discharge tubes (9) and (9 ') made of an insulator and a high-frequency coil around the discharge tubes (9) and (9') facing the silicon substrate (5)
There is a hydrogen radical source (7) and an oxygen radical source (8) equipped with (10) and (10 '), and while evacuating the processing chamber (1), first, hydrogen gas is supplied to the hydrogen radical source (7). As it is introduced, the high frequency power is increased until the plasma is pinched to generate neutral hydrogen radicals / atoms, and the hydrogen radicals / atoms are jetted onto the silicon substrate (5) heated in a vacuum. After reducing and cleaning the silicon substrate (5), while introducing oxygen gas into the oxygen radical source (8), increase the high-frequency power until the plasma pinches to generate neutral oxygen radicals / atoms. A method for producing a silicon oxide film, characterized in that the silicon substrate (5) heated in vacuum is irradiated with the oxygen radicals / atoms to oxidize the silicon substrate (5). 2. A silicon substrate (5) driven by a substrate manipulator (6) and placed on a heater section (34), and a hydrogen radical source (7) and an oxygen radical source facing the substrate (5).
At least a processing chamber (1) provided with (8), a load lock chamber (4) for supplying and storing a substrate through a gate valve (3), and an exhaust system (2) for vacuum exhaust. It is configured and the substrate (5) supplied from the load lock chamber (4) is processed in the processing chamber.
It is characterized in that it is transported to (1), reduced by neutral hydrogen radicals / atoms, oxidized by neutral oxygen radicals / atoms, and stored in the load lock chamber (4) after forming an oxide film. Silicon oxide film growth equipment. 3. The neutral oxygen radical according to claim 1, wherein after a silicon film or a cumulative film having a silicon film as an uppermost layer is formed on a silicon substrate by a vapor phase growth method, the oxygen film is continuously kept in a vacuum atmosphere. A method for manufacturing a silicon oxide film, which comprises oxidizing the surface of the silicon film with atoms. 4. A silicon substrate mounted on a susceptor (14).
Driving the gas introduction line (29) for supplying the reaction gas to the upper part of the (5) and the vertical reactor (27) equipped with the high frequency coil (28) on the outside and the substrate (5) A main chamber (22) equipped with a substrate manipulator (26) is located in the center, and a cleaning chamber (21) and a load chamber (20) equipped with a hydrogen radical source (7) and a substrate manipulator (25) are provided on one side through a gate valve. ) And an oxygen chamber with oxygen radical source (8) and substrate manipulator (30) on the other side through a gate valve
(23) and unload chamber (24), the silicon substrate supplied from the load chamber (20) in the cleaning chamber (21),
After reducing by neutral hydrogen radicals / atoms to clean the surface of the substrate, the substrate is moved to the basic chamber (22) for vapor phase growth, and then neutral oxygen radicals / atoms in the oxidation chamber (23) are used. Oxidation is performed by the unloading chamber (24) after the oxide film is formed.
A vapor phase growth apparatus characterized by being stored in. 5. The neutral oxygen radical according to claim 1, wherein a silicon film or a cumulative film having a silicon film as an uppermost layer is formed on a silicon substrate by a molecular beam epitaxial growth method, and then continued in the vacuum atmosphere. A method for manufacturing a silicon oxide film, which comprises oxidizing the surface of the silicon film with atoms. 6. A silicon substrate (5) driven by a substrate manipulator (35) and placed on a heater section (34), and an electron beam vapor deposition device (6) for vapor deposition of a semiconductor material facing the substrate (5). 36), (37) and a growth chamber (32) each equipped with a plurality of molecular beam sources (38), (39) for dopant deposition, and a gate valve (35)
Silicon substrate supplied from the load lock chamber (30), consisting of a substrate manipulator, a processing chamber (31) equipped with a hydrogen radical source (7) and an oxygen radical source (8), and a load lock chamber (30). After transporting (5) to the processing chamber (31) and reducing it with neutral hydrogen radicals / atoms, molecular beam epitaxial growth is performed in the growth chamber (32) and then returning to the processing chamber (31) again. A molecular beam epitaxial growth apparatus characterized in that it is oxidized by a reactive oxygen radical / atom and stored in a load lock chamber (30) after forming an oxide film.