JPH01235259A - Formation of silicon oxide film - Google Patents

Abstract

PURPOSE:To decrease an amount of dopant in a silicon oxide film buried in a groove so that the silicon oxide film of good quality can be buried in the groove having a high aspect ratio in a desirable manner, by selecting, as a gas used in the liquid-phase oxidation, a silicon compound in which oxygen atoms are directly bonded to all the four hands of a silicon atom. CONSTITUTION:A groove having a high aspect ratio is formed on the surface of an Si substrate 12. A base 13 can be heated by a heater and cooled by nitrogen gas cooled by liquid nitrogen. Raw gas is supplied into a vessel 11 through a gas inlet port 14 and discharged through a gas exhaust port 15. Reactive gas excited by a microwave discharge tube 16 is also supplied into the vessel 11 through an inlet port 17 and evacuated through an exhaust port 15. Tetramethoxy silane having four oxygen atoms bonded around an Si atom is used as the raw gas. The raw gas is introduced into the vessel 11 as it is, without being excited by electric discharge. Oxygen used as the reactive gas is excited by microwave discharge and active species of oxygen produced thereby are introduced into the vessel 11.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a thin film deposition method used in the manufacture of semiconductors such as VLSI devices, and in particular relates to a method for embedding a silicon oxide film in a trench. The present invention relates to a method of forming a silicon oxide film.

(Conventional technology) Thin film forming methods can be roughly divided into chemical vapor deposition (Chemistry)
Mical Vapor Deposition;
CVD) and physical vapor deposition (Physical
Vapor Depositslon (PVD). The CVD method is a method of depositing a thin film on a substrate using chemical reactions on the substrate surface or in a gas phase, and is mainly used for forming insulating films such as silicon oxide films and silicon nitride films. Furthermore, the PVD method forms a thin film by colliding deposited particles generated in a gas phase with a substrate, and is mainly used for forming metal films.

On the other hand, in recent VLSI devices, thin film deposition technology in trenches with a high aspect ratio (depth 7 width) is becoming essential. However, the Braz vCVD method, which is one of the CVD methods (
For example, J.L., Vossen & W.

Kern: Th1n Film Process;
When a SiO□ film 83 is deposited in a deep groove 82 formed in a Si substrate 81 as shown in FIG. As the amount of sedimentation increases, it becomes increasingly difficult for the deposited species to enter the bottom of the groove, creating a cavity 84 and deteriorating the step coverage characteristics.

As a method for improving the step coverage shape, a technique called bias sputtering, which is one of the PVD methods, is used (for example, T, Moaose, etc.).

Morimoto & 0kabayashi:
Extended abstract slath
eon', 5olid 5tate Devices
& Materials.

Kobe, 1984. p43), this method A: ``For example, a silicon oxide film is formed while physically sputtering the substrate surface with ions, so deposition does not occur at the corners but only on the flat areas.Therefore, the formation of cavities. However, since the deposited species in the gas phase enter the groove obliquely, embedding becomes difficult when the aspect ratio is >1.

Furthermore, since a competitive reaction between removal of the deposited film by physical sputtering and deposition is used, the net deposition rate is low and productivity is extremely poor. Further, irradiation in plasma cannot be avoided. Recently, the ECR bias sputtering method (for example, 11
．． 01kawa; SEMITECNOLOGY SYM
, 19861E3-1) has also been proposed, but although it alleviates the above problem, it does not provide an essential solution.

In addition, for example, TEO3O thermal decomposition method (for example, R, D,
Rang, Y., Moaose & Y., Nagaku.
bo; lEDM, TEctl.

DIG, 19g2. When a silicon oxide film is formed using a silicon oxide film (p, 237), it exhibits excellent step coverage characteristics as shown in FIG. 10(b) due to large surface movement of deposited species.

However, if the oxide film 83 buried in the trench is cleaned using a diluted HF solution using this method, then
As shown in C), the removal rate of the oxide film 83 in the central portion 85 becomes abnormally fast, and as a result, buried planarization cannot be realized. The reason for this is thought to be that distortions between the oxide films that have grown from both sides of the trench wall remain near the center. As described above, even with the method of forming a thin film in a conformable manner, it was considered extremely difficult to fill the trench with a high aspect ratio.

In order to solve the above problem, tetramethylsilane (S
A method of depositing a silicon oxide film in high aspect ratio trenches by cooling the substrate below the dew point of the reaction product of oxygen atoms excited by a microwave discharge (CHI) gas and oxygen atoms excited by a microwave discharge (liquid phase oxidation method) (for example, S, NOguehiet at,; S
SDM S-1-13 (1987) 451), by liquefying reaction products on the substrate surface, the silicon oxide film is gradually removed from the bottom of the groove as shown in Figures 11(a) to (C). This is the embedding method. Here, 91 in the figure is S
A t-substrate, 92 is a groove, and 93 is a silicon oxide film.

However, in the film deposited by this method, as shown in the infrared absorption spectrum in Fig. 12 (,5i-CHi
bonds exist, and many methyl groups are incorporated (A in the figure). By annealing this deposited film at a temperature of 300°C, as shown in B in the figure (the St-OH bond disappears and the hydrogen in the film is removed by the dehydration reaction. However, the S1-CH3 bond is Almost no change occurs, and the methyl groups in the film cannot be removed, making it difficult to obtain a pure silicon oxide film.

(Problem to be Solved by the Invention) As described above, the conventional method of filling the trench with a silicon oxide film or the like using the liquid phase oxidation method has the disadvantage that the deposited film contains many impurities. Ta.

For example, in liquid phase oxidation using tetramethylsilane as a raw material gas, there is a problem in that the deposited film contains many methyl groups.

The present invention has been made in consideration of the above circumstances, and its purpose is to be able to deposit a silicon oxide film that does not contain impurities by a liquid phase oxidation method, and to deposit a high quality silicon oxide film in a trench. It is an object of the present invention to provide a method for forming a silicon oxide film that can be buried well.

[Structure of the Invention (Means for Solving the Problems) The gist of the present invention is to reduce impurities in the silicon oxide film embedded in the trench by selecting a gas to be used in the liquid phase oxidation method. be.

That is, in the present invention, a substrate to be processed having grooves formed on its surface is housed in a reaction vessel, a reactive gas (for example, oxygen) excited in a region other than the vessel is introduced into the vessel, and at the same time Introducing a raw material gas (for example, tetramethoxysilane) into the container, and setting the temperature of the substrate to be treated and the pressure in the reaction container within a range in which the raw material gas or the reaction product of the raw material gas and the reactive gas is liquefied, In a method for forming a silicon oxide film in which a silicon oxide film is filled in a groove on the surface of a substrate to be processed by liquefying and adhering a raw material gas or a reaction product to the surface of the substrate to be processed, silicon atoms are used as the source gas. 4
This method uses a silicon compound in which oxygen atoms are directly bonded to all of the bonds.

Further, the present invention accommodates a substrate to be processed having grooves formed on its surface in a reaction vessel, and contains a reactive gas (for example, oxygen) and a source gas (for example, tetraethoxyoxygenate) excited in a region other than the vessel. At the same time, the temperature of the substrate to be treated and the pressure in the reaction vessel are set within a range where the raw material gas or the reaction product of the raw material gas and the reactive gas is liquefied, and the raw material gas or In a method for forming a silicon oxide film in which a silicon oxide film is filled in the grooves on the surface of a substrate by liquefying a reaction product and depositing the reaction product, oxygen atoms are added to all four bonds of silicon atoms as the raw material gas. This method uses a silicon compound to which are directly bonded.

(Function) According to the present invention, when depositing a thin film by a liquid phase oxidation method or the like, all four bonds of Si atoms are supplied with O as a source gas.
By using a silicon compound in which atoms are directly bonded, it is possible to deposit a silicon oxide film that does not contain impurities such as methyl groups in the deposited film. For example, tetramethylsilane.

When a silicon organic compound containing no substituents such as dimethyldimethoxysilane or hexamethylsilane is used as a raw material gas, there is a 5i-C bond, and this bond is cut with oxygen gas excited by microwave discharge to form a complete silicon oxide film. As shown in the infrared absorption spectrum using tetramethylsilane in FIG. 12, the film contains many methyl groups. However, when a silicon organic compound in which four OR (R is an organic group) substituents are bonded to silicon as a raw material gas, 5i-0 (bond energy: 106Kc) is formed among the 5t-0-C bonds.
0-, which has a lower binding energy than al/mol)
C (Binding energy: 85.5Kcal/aoi)
is cleaved by the O atom, as shown in the infrared absorption spectrum when using tetramethoxysilane in Figure 5.
A silicon oxide film that does not contain C can be deposited.

(Example) Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

FIG. 1 is a schematic diagram showing a thin film forming apparatus for carrying out a method according to an embodiment of the present invention. In the figure, reference numeral 11 denotes a reaction vessel, and a sample stage 13 on which a Si substrate 12 as a substrate to be processed is placed is accommodated within this vessel 11. The Si substrate 12 has high aspect ratio grooves formed on its surface.

The sample stage 13 can be heated by a heater and cooled by nitrogen gas cooled by liquid nitrogen, and the temperature of the substrate 12 placed thereon is controlled.

A raw material gas is supplied into the container 11 from a gas inlet 14, and this gas is exhausted from a gas exhaust port 15. Also,
A reactive gas excited by a microwave discharge tube 16 is supplied into the container 11 through a gas inlet 17, and this gas is also exhausted through a gas exhaust port 15. In addition, in the figure, 18 indicates a microwave power source, and 21 and 22 each indicate a valve.

Next, a method for forming a thin film using the apparatus shown in FIG. 1 will be explained. Tetramethoxysilane (TM01
), and this gas was introduced into the container 11 as it was without being excited by discharge. Further, oxygen, which is a reactive gas, was excited by microwave discharge, and the generated active species of oxygen were introduced into the container 11. The inside of the container 11 was previously evacuated to 10-' Torr or less using a turbo molecular pump, and then the above-mentioned source gas and reactive gas were introduced to deposit a thin film.

FIG. 2 shows the relationship between the deposition rate and the deposition shape with respect to the substrate temperature. The flow rate of oxygen is 168scca+, the partial pressure ratio of tetramethoxysilane and oxygen is 0.2, and the pressure inside the container is 2To.
It was set as rr. The deposition rate reaches its maximum (0.5 μm/1ln) when the substrate temperature is around 30°C, and reaches approximately zero at 10°C, reaching 1
It becomes approximately constant above 00°C. Also, the temperature of the substrate is 70℃.
At temperatures above 70°C, the deposited shape overhangs and the trench cannot be filled with a silicon oxide film, but at temperatures below 70°C, a silicon oxide film is formed to collect liquid from the bottom of the trench, resulting in a high aspect ratio. groove was completely filled.

FIG. 3 shows the relationship between the deposition rate and the deposition shape with respect to the pressure inside the container. A silicon oxide film was formed from the bottom of the trench when the pressure was higher than 0.3 Torr and lower than 1 Q Torr. At 0.3 Torr or less, the deposition shape was overhanging, and this is thought to be because the partial pressure of the substance liquefied on the substrate became lower than its equilibrium vapor pressure. Also, when the temperature is 1QTorr or more, there is a diameter of 3mm on the board.
Powder of approximately 000A was attached.

FIG. 4 shows the relationship between the deposition rate and the deposition shape with respect to the partial pressure ratio of tetramethoxysilane and oxygen. The silicon oxide film was formed from the bottom of the trench when the partial pressure ratio was greater than 0.655, and when the partial pressure ratio was less than 0.55, the deposition shape was overhanging. Furthermore, when the partial pressure ratio was 0.3 or more, the deposition rate became approximately zero, making it impossible to fill the groove.

Therefore, in this embodiment, the substrate temperature is 30°C and the pressure is 2 Torr.
A silicon oxide film was deposited on the St substrate in which the grooves were formed, with the partial pressure ratio of tetramethoxysilane and oxygen set to 0.2. As a result, the grooves on the surface of the Si substrate are flattened and filled with a silicon oxide film. FIG. 5 shows the infrared absorption spectrum of the silicon oxide film at this time. Although there are peaks due to OH, there are almost no peaks due to 5i-C, and there is no peak due to C, which was present in the infrared absorption spectrum (Figure 12) when deposited using tetramethylsilane. I understand. Furthermore, as a result of measuring the Auger spectrum of this silicon oxide film, there was no peak due to C, and it is thought that the C content in this film was ~ several atmlc% or less.

In this way, according to the method of this embodiment, 4
By using tetramethoxysilane with two 0 atoms bonded as a raw material gas, 5 in the bond of 81-〇-C
O-C, which has a lower bond energy than i-0, can be cleaved by the 0 atom. As a result, a silicon oxide film containing no C as an impurity could be deposited.

Therefore, it becomes possible to fill the grooves formed on the surface of the Si substrate with a high-quality silicon oxide film, which is extremely useful in semiconductor manufacturing technology.

FIG. 6 is a schematic diagram showing a thin film forming apparatus used in another embodiment of the present invention. Note that the same parts as in FIG. 1 are given the same reference numerals, and detailed explanation thereof will be omitted. This apparatus differs from the apparatus shown in FIG. 1 in that the raw material gas is excited by microwaves and introduced into the reaction vessel in the same way as the reactive gas. That is, the source gas is supplied to the microwave discharge tube 16 together with the reactive gas, excited within the discharge tube 16, and introduced into the container 11.

In this example, tetraethoxysilane (
TE01), using oxygen as a reactive gas, a silicon oxide film was deposited on the surface of a Si substrate in the same manner as in the previous example.

FIG. 7 shows the relationship between deposition rate and substrate temperature. The flow rate of oxygen was 168 scca+%, the partial pressure ratio of tetraethoxysilane to oxygen was 0.67, and the pressure inside the container was 2 Torr. The deposition rate increases as the substrate temperature decreases. Also, if the substrate temperature is 0°C or higher, no deposition occurs. However, at lower temperatures, a silicon oxide film was formed to collect liquid from the bottom of the groove, completely filling the high aspect ratio groove. In addition, the deposited shapes were all good with no overhang.

FIG. 8 shows the relationship between the deposition rate and the pressure inside the container. No deposition was observed at a pressure of 9 Torr or higher, but at a pressure lower than that, a silicon oxide film was formed on the bottom of the trench, and the lower the pressure, the faster the deposition rate. In addition, regarding the deposition rate with respect to the partial pressure ratio of tetraethoxysilane and oxygen, no deposition was observed when the partial pressure ratio was less than 0.1.
At higher pressures, a silicon oxide film was formed from the bottom of the trench, and the higher the partial pressure ratio, the faster the deposition rate. In this case as well, regardless of the partial pressure ratio, the deposition shape was good with no overhang.

Figure 9 shows a substrate temperature of -40'C and a pressure inside the container of 2 Torr.
.

This figure shows an infrared absorption spectrum of a silicon oxide film deposited at a partial pressure ratio of tetraethoxysilane and oxygen of 0.67. 5
Although there is a peak due to t-0, there is almost no peak due to the presence of OH, and there is no peak due to C that was present in the infrared absorption spectrum when deposited using tetramethylsilane. I understand. In this way, S
By using tetraethoxysilane in which four O atoms are bonded around an i atom as a source gas, it was possible to deposit a silicon oxide film that does not contain any C as an impurity.

Note that the present invention is not limited to the methods of each embodiment described above. For example, the raw material gas is not limited to tetramethoxysilane, tetraethoxysilane,
Tetraacetoxysilane.

Tetrapropoxysilane, tetraisopropoxysilane, tetrakis(2-ethylbutoxy)silane.

A silicon compound such as tetraphenoxysilane, tetrakis(2-ethylhexyloxy)silane, etc., in which an oxygen atom is directly bonded to all four bonds of a silicon atom, can be used. That is, a silicon compound represented by the general formula % can be used.

However, R is an alkyl group, an alkoxy group, an aryl group, etc.

Furthermore, even if the weight loss gas is excited using hydrogen, nitrogen, a gas containing halogen gas such as chlorine or fluorine, or an inert gas such as argon, or a mixture thereof as a reactive gas, the raw material gas itself Since it contains a large amount of oxygen, it is also possible to form a silicon oxide film that does not contain impurities. Further, conditions such as the substrate temperature, the pressure inside the container, and the partial pressure ratio between the raw material gas and the reactive gas can be changed as appropriate within a range where no overhang occurs in the silicon oxide film buried in the trench. In addition, various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] As detailed above, according to the present invention, by selecting a silicon compound in which oxygen atoms are directly bonded to all four bonds of silicon atoms as the gas used in the liquid phase oxidation method, , it is possible to reduce impurities in the silicon oxide film buried in the trench, and it is possible to satisfactorily bury a high-quality silicon oxide film in the trench with a high aspect ratio.

[Brief explanation of the drawing]

1 to 5 are for explaining a method according to an embodiment of the present invention. FIG. 1 is a schematic configuration diagram showing a thin film forming apparatus used in the method of the embodiment, and FIG. A characteristic diagram showing the relationship between the deposition rate and the deposition shape. Figure 3 is a characteristic diagram showing the relationship between the deposition rate and the deposition shape with respect to the pressure inside the container. Figure 4 is a characteristic diagram showing the relationship between the deposition rate and the deposition shape with respect to the partial pressure ratio. , FIG. 5 is a characteristic diagram showing the infrared absorption spectrum of the silicon oxide film formed by the method of the same example, and FIG.
9 to 9 are for explaining other embodiment methods of the present invention, FIG. 6 is a schematic configuration diagram showing a thin film forming apparatus, and FIG. 7 is a characteristic showing the relationship between substrate temperature and deposition rate. Figure, 8th
The figure is a characteristic diagram showing the relationship between the pressure inside the container and the deposition rate.
The figure is a characteristic diagram showing an infrared absorption spectrum, and FIGS. 10 to 12 are diagrams for explaining the problems of the conventional technology. 11... Reaction container, 12.81.91... Si substrate (substrate to be processed), 13... Sample stand, 14.17...
Gas inlet, 15... Gas exhaust port, 16... Microwave discharge tube, 18... Microwave power supply, 21.22.
...Valve, 82.92...Groove, 83.93...Silicon oxide film, 84...Cavity. Applicant's representative Patent attorney Takehiko Suzue Substrate degree (''C) - Figure 2 Liquid yield (cm'') - Figure 6 Substrate 1tL (''C) - Figure 7 f: f7 (Torr) → Figure 8 Wasted revenue (cm-1) - Figure 10, Figure 11!!!

Claims (4)

[Claims] (1) A substrate to be processed with grooves formed on its surface is housed in a reaction vessel, and a reactive gas excited in a region other than the vessel is introduced into the vessel, and at the same time, a raw material gas is introduced into the vessel. In addition, the temperature of the substrate to be treated and the pressure in the reaction vessel are set within a range in which the raw material gas or the reaction product of the raw material gas and the reactive gas is liquefied, and the raw material gas or the reaction product is applied to the surface of the substrate to be treated. In a method for forming a silicon oxide film, in which a silicon oxide film fills grooves on the surface of a substrate to be processed by liquefying and depositing the film, oxygen atoms are directly bonded to all four bonds of silicon atoms as the source gas. A method for forming a silicon oxide film, characterized in that it uses a silicon compound that is (2) A substrate to be processed with grooves formed on its surface is housed in a reaction vessel, a reactive gas and source gas excited in a region other than the vessel are introduced into the vessel, and the temperature of the substrate to be processed is By setting the pressure in the reaction vessel to a range in which the raw material gas or the reaction product of the raw material gas and the reactive gas liquefies, and liquefying and attaching the raw material gas or the reaction product to the surface of the substrate to be treated, In a method for forming a silicon oxide film in which grooves on the surface of a substrate to be processed are filled with a silicon oxide film, a silicon compound in which oxygen atoms are directly bonded to all four bonds of silicon atoms is used as the source gas. A method for forming a silicon oxide film characterized by: (3) Tetramethoxysilane is used as the source gas, oxygen gas is used as the reactive gas, the partial pressure ratio of tetramethoxysilane to oxygen gas is greater than 0.55, the temperature of the substrate to be treated is less than 70°C, and the pressure inside the container is 0.3 Torr
3. The method of forming a silicon oxide film according to claim 1, wherein the grooves on the surface of the substrate to be processed are filled with a silicon oxide film containing no impurities at a pressure exceeding 10 Torr. (4) Tetraethoxysilane is used as the raw material gas, oxygen gas is used as the reactive gas, the partial pressure ratio of tetraethoxysilane to oxygen gas is greater than 0.1, the temperature of the substrate to be treated is less than 0°C, and the inside of the container is 3. The method of forming a silicon oxide film according to claim 1, wherein the pressure is less than 10 Torr, and the trenches on the surface of the substrate to be processed are filled with a silicon oxide film containing no impurities.