JPH0217639A - Method of forming silicon oxide film - Google Patents

Abstract

PURPOSE:To make it possible to accumulate insulation films inside a groove of high aspect ratio and simplify the control and device by setting a pressure inside a reaction container and a substrate temperature to be processed for a condition that a product from the reaction of feedstock gas and reactive gas becomes a liquid. CONSTITUTION:A processed substrate 15 on which surface is formed a groove is housed in a reaction container 11 capable of vacuum-discharged. At least feedstock gas representing by SiHaXb (where, X is at least one kind of halogen atom selected from F, Cl, Br, a=0 to 4, b=0 to 4, a+b=4) and reactive gas containing oxygen capable of chemically reacting with the feedstock gas are introduced in the reaction container at the same time. For a condition such that the feedstock gas, the reactive gas, or the product from the reaction of the two gas become a liquid on the above processed substrate, the pressure inside the reaction container and the temperature of the processed substrate are set, and a silicon oxide film is buried in the grooved on the surface of the processed substrate. As a reactive gas containing oxygen capable of chemically reacting with the feedstock gas, for example, it should preferably be H2O, O2, NO, NO2, CO, CO2 or an organic compound gas containing at least silicon and oxygen.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a method for forming a silicon oxide film used in the manufacture of semiconductors such as VLSI devices.

(Prior art) Thin film forming methods used in the manufacture of semiconductors such as VLSI devices can be roughly divided into chemical vapor deposition methods (CheIIli
cal Vapor Deposition:CVD)
and physical vapor deposition method.
Deposition: PVD). The CVD method is a method of forming a thin film on a substrate by utilizing a chemical reaction on the surface of the substrate or in a gas phase, and is mainly used for forming an insulating film such as a silicon oxide film or a silicon nitride film. The PVD method is a method of forming 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, for example, conventional Braz TCVD method (e.g. J
, L., Vossen & W., Kern; ThinF.
ilmProcess;Academic Pres
When, for example, a silicon oxide film 3 is buried in the groove 2 formed on the surface of the silicon substrate 1 as shown in FIG. As a result, it becomes increasingly difficult for the deposited species to enter the bottom of the groove 2, creating a cavity inside the groove 2 and deteriorating the step coverage characteristics.

A technique called bias sputtering, which is one of the PVD methods, is known as a method for improving the step coverage shape (for example, T, Mogami, Morlmoto &0
Extended abstrac
ts 1ath conf', 5oldState
Devices & Materials, Kobe
, 19114. p. 43).

In this method, Ar ions are used to physically sputter the substrate surface to remove deposited species, and a competitive reaction with the deposited species is used to deposit, for example, a silicon oxide film. For this reason,
Unlike the plasma CVD method, deposition does not occur near the corners of the silicon substrate, but only on the flat areas (2! board surface and trench bottom), making it possible to deposit an insulating film inside the trench. Become.

However, in this method, the deposited species in the gas phase enter the groove obliquely, so it is still difficult to fill the groove with an aspect ratio>1. Furthermore, since a competitive reaction between removal of deposited species by physical sputtering and deposition is used, the effective deposition rate is slow and productivity is extremely low. Furthermore, irradiation damage in plasma is also unavoidable.

Therefore, recently, the ECR bias sputtering method (for example, 1.
0ikava；SEMITECIINOLOGY SY
M, 1980 E3-1) has been proposed. However, although this method also alleviates the above-mentioned problem, it is not an essential solution.

In addition, for example, the thermal decomposition method of TE01 (for example, R, D,
Rang, Y, Moll1ose & Y, Naga
kubo; IEDM, TECH.

DIG, 1982. When a silicon oxide film is formed using a silicon oxide film (p, 237), large movement of the deposited species occurs on the surface, so as shown in FIG. The silicon oxide film 3 shown here exhibits excellent step coverage characteristics. However, with this method, groove 2
After embedding the silicon oxide film 3 in the silicon oxide film 3, cleaning treatment is performed using, for example, a diluted HF solution, as shown in FIG.
Silicon oxide film 3 is formed on the upper surface of the central part of groove 2 (indicated by X in the figure).
The removal speed becomes abnormally fast, and as a result, buried flattening cannot be achieved.

The reason for this is thought to be that distortions between the silicon oxide films 3 that have grown from the sidewalls of the groove 3 remain near the center of the groove 3.

As described above, even with the method of forming a thin film in a conformable manner, it was thought to be extremely difficult to bury an insulating film such as a silicon oxide film into a trench with a high aspect ratio.

To solve these problems, tetramethylsilane (S i (CH3)4; TMS) gas is reacted with oxygen atoms excited by microwave discharge, and the substrate is cooled to below the boiling point of the reaction product. Therefore, a method (liquid phase oxidation method) of depositing a silicon oxide film in a trench with a high aspect ratio is known (for example, S, Nogu
chi et al; SSDM 5-11-13 (1
987)451). According to this method, FIG.
As shown in (C), since the silicon oxide film 3 is deposited from the bottom of the groove 2 formed on the surface of the silicon substrate 1, it is possible to easily fill the silicon oxide film 3 into the groove 2 having a high aspect ratio. can. However, since this method oxidizes the source gas with oxygen atoms activated by microwave discharge, there are many deposition parameters such as the distance between the microwave discharge section and the sample wafer, microwave discharge power, and microwave discharge pressure. However, there are problems in that the apparatus becomes complicated and the control of the deposition parameters becomes complicated.

(Problem to be Solved by the Invention) As mentioned above, the conventional liquid phase oxidation method using microwave discharge has the advantage of being able to deposit a silicon oxide film in a trench with a high aspect ratio. There is a problem in that the number of deposition parameters related to the method increases, making deposition control complicated.

An object of the present invention is to provide a method that can deposit a silicon oxide film in a high aspect ratio trench by a liquid phase oxidation method without using microwave discharge, and that allows easy control of deposition parameters and equipment. It is in.

[Structure of the Invention] (Means and Effects for Solving the Problems) The method for forming a silicon oxide film of the present invention includes accommodating a substrate to be processed having grooves formed on its surface in a reaction vessel that can be evacuated;
3iH, Xb (X is Fs Ci'
Contains a raw material gas represented by a small number (both one type of halogen atom, a -0 to 4, b-0 to 4, a + b to 4) selected from SBr and oxygen that can chemically react with the raw material gas. Reactive gas is introduced at the same time, and raw material gas,
By setting the pressure inside the reaction vessel and the temperature of the substrate to be treated so that the reactive gas or the reaction product with both becomes liquid on the substrate, silicon is deposited in the grooves on the surface of the substrate to be treated. It is characterized by embedding an oxide film.

In the present invention, the reactive gas containing oxygen that can chemically react with the source gas includes, for example, H2O, 0□, NO,
Examples include NO2, Co, CO2, or an organic compound gas containing at least silicon and oxygen.

To illustrate the raw material gas and reactive gas used in the method of the present invention and their reactions, for example, SiCΩ as the raw material gas
4. When H2O is used as the reactive gas, S 1C4) 4 + 2H20S t 02 +4H
A hydrolysis reaction called C11 occurs. Furthermore, when a siloxane compound having a functional group -0-Y is used instead of H2O as the reactive gas, the following condensation polymerization reaction occurs.

These reactions are violent chemical reactions, and the microwave number is 7.
Since the reaction occurs even without using active species excited by u, the pressure inside the reaction vessel and the substrate to be treated must be adjusted so that the raw material gas, the reactive gas, or the reaction product of both become liquid on the substrate to be treated. By setting a temperature of , it is possible to embed a thin silicon oxide film into the grooves on the surface of the substrate to be processed. Therefore, according to the method of the present invention, unlike the conventional liquid phase oxidation method using microwave discharge, it is possible to control the deposition parameters when depositing a silicon oxide film in a high aspect ratio trench by the liquid oxidation method. It can be done easily.

In the present invention, the pressure inside the reaction vessel and the temperature of the substrate to be processed cannot be absolutely limited because the conditions for turning into a liquid vary depending on the type of raw material gas, reactive gas, or the reaction product of both. For example, for the reaction of SiCΩ4 and H2O mentioned above, the pressure inside the reaction vessel is set to about 2 Torr.
In this case, the temperature of the substrate to be processed may be 0°C or lower, preferably -15°C or lower; Higher temperatures can be set by increasing the pressure within the container.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram of a reaction apparatus for carrying out the method of the present invention. In FIG. 1, a sample holder 12 is installed in a reaction vessel 11, a heater 13 is provided to this sample holder 12, and a cooling pipe 14 is connected to the sample holder 12. Sample 1
It is possible to control the temperature of No. 5 in the range of -100°C to 600°C. This device uses nitrogen gas cooled by liquid nitrogen as a cooling medium. The inside of the reaction vessel 11 is evacuated by a vacuum evacuation device 1G, and the internal pressure can be adjusted by a conductance valve 17. There is an inlet 18.1 in the reaction vessel 11.
A raw material gas and a reactive gas are respectively introduced from 9 and supplied to the surface of the sample 15. Then, among the raw material gas, the reactive gas, and the reaction products thereof, residual gas that did not participate in the deposition is exhausted by the vacuum evacuation device 16.

Next, an example in which a silicon oxide film was actually deposited using this apparatus will be described.

Example 1 In this example, silicon tetrachloride (810g4
), water (H20) was used as the reactive gas. A silicon substrate in which a groove with an aspect ratio of 5 was formed was housed in a reaction vessel 11, and a flow rate of S i C (14 was 12 sccaSS).
i Partial pressure ratio of CΩ4 and H2O (SiCΩ4/H20
) was set to 1/2, the pressure inside the reaction vessel 11 was set to 2 Torr, and the deposition rate and shape of the silicon oxide film were investigated when the substrate temperature was changed. FIG. 2 shows the relationship between substrate temperature, deposition rate, and deposition shape.

As shown in FIG. 2, the temperature of the silicon substrate 1 is 0°C.
In the above case, the silicon oxide film 3 was deposited in an overhanging state at the trench 2l portion, and a cavity was formed in the trench 2. On the other hand, when the temperature of the silicon substrate 1 is lowered to below -15°C, the silicon oxide film 3 is formed from the bottom of the groove 2, and even a groove with an aspect ratio of 5 can be easily filled, and the surface is completely flattened. .

The reaction mechanism between the raw material gas and the reactive gas in this example will be considered. Here, Fig. 3 shows the phase diagram of H2O,
FIG. 4 shows state diagrams of S i Cf74. Under the above conditions, the partial pressure of H2O is approximately 1.3 Torr,
The partial pressure of S i CD 4 is approximately 0.7 Torr.

However, from Figures 3 and 4, on a substrate at 15°C, H
It is thought that neither 2O nor 810g4 becomes liquid. Therefore, these gases are 5iCJL+H2O5t(Jh (OH) + HC
i)S 1c1)4 +2H20→S i Cjl)
2 (OH) 2 +2HCNS t C1' 4
+ 3 H20→S i C1' (OH) 3
+ 3 HCf1S t CN 4 +4H20→S
Through the reaction i (OH) 4 +4HCN, S i C1) 3 (OH), S i CN 2
(OH)2, Si CΩ (OH)3, Si
A reaction intermediate called (OH)4 is produced, and these reaction intermediates liquefy and flow into the groove, and further S i C1l
3 (OH) +H20→SiO□+3HC1! S
i C(12(OR) 2 + H20→SiO□+
2HCD+ H20sicg(OH)3 +H20→
5i02+ HCl1+2H20S t (OH) 4
+H20→S i 02 +3 It is thought that hydrolysis occurs as shown in H20, and a silicon oxide film is formed.

In addition, when the infrared absorption spectrum of this deposited film was examined, it was found that immediately after deposition, it was S i-0 and S i -OH.

It was found that the film was a silicon oxide film in which 0-H bonds existed. However, by performing annealing at a low temperature of 300° C., the 5t-OH and O-H bonds were eliminated, resulting in a complete silicon oxide film.

In addition, although the case where SiCΩ4 is used as the raw material gas and H2O is used as the reactive gas is explained above, SiF
The same deposition shape and film quality as above can be obtained with each combination of 4 and H2O, S i Br, and H2O.

Example 2 In this example, silicon tetrachloride (SiCII) was used as the raw material gas.
4), tetramethoxysilane (S f
(OCH3) 4) was used. A silicon substrate in which a groove with an aspect ratio of 5 was formed was placed in the reaction vessel 11, and the flow rate of 5iCN4 was set to 12 sec + asS i C1l.
4 and S i (OCH3)4 (SiCΩ4
/St (OCH3)4) was set to 1, the pressure inside the reaction vessel 11 was set to 2 Torr, and the deposition rate and shape of the silicon oxide film were investigated when the substrate temperature was changed. FIG. 5 shows the relationship between substrate temperature and deposition rate.

As shown in FIG.
When the temperature was 0° C. or higher, the silicon oxide film 3 was deposited in an overhanging state in the groove 2l portion, and a cavity was formed in the groove 2. On the other hand, when the temperature of the silicon substrate 1 is lowered to -50°C or less, the silicon oxide film 3 is formed from the bottom of the groove 2, and the groove 2 with an aspect ratio of 5 can be easily filled.
The surface was completely flattened.

The reaction mechanism between the raw material gas and the reactive gas in this example will be considered. Under the above conditions, SiCΩ4 and S
The partial pressure of i (OCH3)a is also approximately I Torr. From Figure 4, on silicon substrate 1 at -50°C, 5iC
It is thought that 114 becomes a liquid.

Therefore, 5LCN4 liquefies and flows into the groove, S 1cj) 4 +S i (OCHi) a→2
It is thought that the silicon oxide film 3 is formed by a polycondensation reaction of Si02+4CH,CD.

Furthermore, when we examined the infrared absorption spectrum of this deposited film, we found that there were bonds of 5t-0 and SiOH%0-H immediately after deposition, but there were no bonds such as 5t-CSC-0, indicating that carbon It turned out that it was a silicon oxide film that did not contain any.

However, by performing annealing at a low temperature of 300°C, Si-OH.

Each 0-H bond disappeared and a complete silicon oxide film was formed.

In addition, although the case where S I CD 4 was used as the raw material gas and S i (OCH3)4 as the reactive gas was explained above, S i C04 and S i (OC2H5), SiF4 and S i (OCHi )4, SiF4 and 5j (OC2H
The same deposition shape and film quality as above can be obtained with each combination of 1) and 4.

[Effects of the Invention] As detailed above, according to the method of the present invention, it is easy to control the deposition parameters when depositing a silicon oxide film in a high aspect ratio trench by a liquid oxidation method, and its industrial value is improved. is big.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a reaction apparatus used in an example of the present invention, and FIG. 2 shows the relationship between the temperature of a silicon substrate and the deposition rate and shape of a silicon oxide film in Example 1 of the present invention. Characteristic diagram, Figure 3 is the phase diagram of H2O, Figure 4
The figure is a state diagram of SiCΩ4, Figure 5 is a characteristic diagram showing the relationship between the temperature of the silicon substrate and the deposition rate and shape of the silicon oxide film in Example 2 of the present invention, and Figure 6 is a diagram of the conventional plasma CVD method. A cross-sectional view of a silicon substrate showing the problem,
FIGS. 7(a) and (b) are cross-sectional views of a silicon substrate showing problems in the conventional thermal decomposition method of TE01, and FIGS. 8(a) to (
c) is a cross-sectional view of a silicon substrate showing a conventional liquid phase oxidation method. DESCRIPTION OF SYMBOLS 1... Silicon substrate, 2... Groove, 3... Silicon oxide film, 11... Reaction container, 12... Sample holder,
13...Heater, 14...Cooling pipe, 15...Sample, 1G...Evacuation device, 17...Conductance valve, 18.19...Inlet. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Board temperature (°C) @ 4 U grave soak (0C) Board 1 width (°C) Figure 6 No. 8

Claims (2)

[Claims] (1) A substrate to be processed with grooves formed on the surface is housed in a reaction vessel that can be evacuated, and SiH_aX_b is placed inside the reaction vessel.
(However, X is at least one halogen atom selected from F, Cl, and Br, a=0-4, b=0-4, a+b
A raw material gas represented by =4) and a reactive gas containing oxygen capable of chemically reacting with the raw material gas are simultaneously introduced, and the raw material gas, the reactive gas, or the reaction product of both is on the substrate to be treated. A method for forming a silicon oxide film, which comprises embedding a silicon oxide film in a groove on the surface of the substrate to be processed by setting the pressure inside the reaction vessel and the temperature of the substrate to be a liquid. (2) The reaction gas is H_2O, O_2, NO, NO_2,
2. The method for forming a silicon oxide film according to claim 1, wherein the gas is CO, CO_2, or an organic compound gas containing at least silicon and oxygen.