JPH0669196A - Method of forming insulating film - Google Patents

Abstract

PURPOSE:To improve accumulation speed and give margin to the condition of flow stack formation on the step having a high aspect ratio by adding alkanol to the ozone, the oxygen, and the alkoxysilane as the reactive gas used for formation of a silicon oxide film by CVD method. CONSTITUTION:A working pressure CVD device is provided with a heater 1, a susceptor 2, a material blow-out port 4, a 100 deg.C heater and warmer 5, an ozone generator, a tetraethoxysilane(TEOS) bubbling container 7, and a heating and warming container 8. In addition to these, it is provided with a alkanol, for example, ethanol bubbling container 9, and its heating and warming container 10. When forming a silicon oxide film on a substrate 3, a CVD film is grown using the reactive gas where ethanol is added to it besides ozone, oxygen, and TEOS. Hereby, the stacking speed increases, and the stacking of flow shape to the step improves.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a silicon thin film by a CVD method. The formed silicon oxide film is mainly used as an interlayer insulating film and a passivation film of a semiconductor device.

[0002]

2. Description of the Related Art Conventionally, various methods have been proposed as a method for forming a silicon oxide film by a CVD method. on the other hand,
As semiconductor devices become highly integrated and highly functional, temperature restrictions on respective steps in the manufacturing process become strict, and the process temperature is being lowered. Under such a background, as a method capable of forming a silicon oxide film at a low temperature, typically, atmospheric pressure CVD using SiH ₄ and O ₂ raw materials is performed.
Plasma CVD methods using SiH ₄ and N ₂ O raw materials have been used. Further, plasma CVD using TEOS (tetraethoxysilane), which is an organic metal raw material, as a raw material
Method and atmospheric pressure CVD method using TEOS raw material and ozone have been studied. However, among the above methods, atmospheric pressure C
In the VD method, the step coverage of the formed film is poor and the miniaturized LS is used.
Since it cannot be applied to I and the plasma CVD method is a film forming process using charged particles, there is a concern that the device may be damaged. On the other hand, the atmospheric pressure CVD method of TEOS-ozone is an expected film forming method because it has many advantages such as no problem of damage and easy structure of the film forming apparatus. Further, the atmospheric pressure CVD method of TEOS-ozone has a feature that the deposition shape becomes a flow shape, and VLSI with advanced steps and finer aspect ratio
A very large contribution can be expected to the steps of flattening and smoothing the surface of the interlayer insulating film, which are required in the above.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention As mentioned above, T
The atmospheric pressure CVD method of EOS-ozone is a very excellent method for forming an insulating thin film applied to VLSI. An object of the present invention is to provide a method for forming an insulating thin film, which further improves the deposition rate of this thin film forming method and has a margin in the conditions for forming a flow deposition shape on a step having a high aspect ratio. .

[0004]

The present invention will be described in brief. The present invention relates to a method for forming an insulating thin film, in which ozone, oxygen, and alkoxysilane are used as reaction gases.
In the method for forming a silicon oxide film by the VD method, alkanol is added.

In the atmospheric pressure CVD method of TEOS-ozone which has been reported so far, only TEOS and ozone are used as CVD raw materials, and nitrogen is used to supply TEOS which is an organic metal raw material. At that time, the deposition rate showed a dependency on the ozone concentration as shown in FIG. That is, FIG. 2 is a graph showing the ozone concentration dependence of the deposition rate. The substrate temperature is 400 ° C., the nitrogen carrier gas flow rate is 18 liters, the TEOS bubbling temperature is 65 ° C., and the carrier gas is 3 liters. The ozone concentration (%) in the oxygen flow rate 7.5 liters is the horizontal axis, and the vertical axis is the deposition. The speed (Å / min). On the other hand, it is known that it is better to increase the ozone concentration so that the deposition shape on the step, which is a feature of TEOS-ozone CVD, becomes a flow shape. That is, under the condition that the flow shape is obtained, there is a problem that a waste amount is generated in the supplied ozone and the waste amount does not contribute to the film characteristics.

In view of such a situation, the present invention provides a CV
It was conducted as a result of a study for further optimizing the D condition and improving efficiency. By increasing the ozone utilization rate and keeping the flow shape easy to obtain, by preventing a decrease in the deposition rate, The productivity is improved without losing the smoothness of the substrate, which is important in the VLSI manufacturing process.

When the present raw material system is used, it is considered that the first stage of the reaction mechanism is the oxidation reaction of ozone of the organometallic raw material and radical formation. A chain reaction due to the generated radicals occurs, and a flow-shaped formation, which is a feature of the present CVD, occurs on the stepped substrate. On the other hand, since it is a chain reaction by radicals, the radicals generated in the reaction process may accelerate or suppress the film formation reaction. The present invention controls this radical chain reaction by adding an alkanol to the reaction system.
By adding an alkanol, a CVD reaction is controlled by generating a substance that generates or deactivates a radical that starts or continues a chain reaction.

The case where ethanol is used as the additive alkanol will be described. FIG. 3 is a schematic view of a conventional device. That is, FIG. 3 shows the conventional atmospheric pressure CVD.
1 is a schematic view of the apparatus, in which reference numeral 1 is a heater, 2 is a susceptor, 3 is a substrate, 4 is a raw material outlet, 5 is heat insulation at 100 ° C., 6 is an ozone generator, 7 is a TEOS bubbling container,
Reference numeral 8 is a heating / heat retaining container. The raw material vaporized through the bubbling mechanism is supplied from the raw material outlet to the heated and held substrate. For example, the TEOS raw material is in the raw material reservoir kept at 65 ° C., and is mixed with oxygen partially ozoned by the silent discharge immediately before the raw material outlet. TEOS
In order to prevent re-liquefaction of the raw material, the raw material supply pipe is 100 ° C.
It is heated and kept warm to some extent.

A film was formed by adding the ethanol mixing mechanism as shown in FIG. 1 to the above apparatus. That is,
FIG. 1 is a schematic view of a conventional device in which an alkanol addition mechanism and piping are added to FIG. 3, and reference numerals 1 to 8 are synonymous with FIG.
Reference numeral 9 is an ethanol bubbling container, and 10 is a heating / heat insulating container. As shown in FIG. 1, ethanol was held in a bubbling container similar to TEOS, and nitrogen gas was supplied as a carrier gas.

In the following examples, the case where ethanol was used as the alkanol was described, but the same effect was confirmed when methanol, propyl alcohol, isopropyl alcohol, tert-butyl alcohol, etc. were used. If ethanol molecules with very similar molecular structure to a substituent ethoxy (-OCH ₂ CH ₃₎ this was considered the most preferred. Moreover, tetramethoxysilane Si is used as an organic metal.
When (OCH ₃ ) ₄ was used, the effect became remarkable by using methanol.

[0011]

EXAMPLES The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 Using the apparatus shown in FIG. 1, ethanol was held in a bubbling container similar to TEOS, and nitrogen gas was supplied as a carrier gas. Since ethanol has a high vapor pressure, it is not necessary to keep it at a high temperature, and in Example 1, it was set to 30 ° C.

FIG. 4 shows a substrate temperature of 350.degree.
8 liters / min, oxygen flow rate 7.5 liters / min
(The ozone concentration in the oxygen supply is 4.6%), showing the dependence of the deposition rate of the silicon oxide film formed on the carrier gas flow rate of TEOS and the carrier gas flow rate of ethanol. The vertical axis represents a deposition rate value (D _EtOH / D ₀ ) obtained by normalizing the deposition rate D _EtOH when ethanol is added to the deposition rate D ₀ when ethanol is not added, and the horizontal axis represents nitrogen of ethanol. The carrier gas flow rate (liter / min). The symbol in the figure indicates the flow rate of the carrier gas for supplying TEOS to 0.5 l / min.
Is a circle, 1.0 liter / min is a square, 2.0 liter / min is a triangle, and 3.0 liter / min is a cross. TEOS carrier gas flow rate is 0.5
In the case of liter / min and 1.0 liter / min, 2 liter / mi was added with the addition of ethanol.
The maximum deposition rate was shown at n / l / min. It can be seen that the effect of increasing the deposition rate due to the addition of ethanol becomes more significant as the mixing ratio of O _{3 to} TEOS increases.

The effect of the addition of ethanol is not only the film-forming rate, but the flow-shaped deposition on the step is improved as the deposition rate is increased. On the other hand, if excess alkanol is added, the deposition rate will decrease, but at the same time, the deposition shape on the step can be made isotropic. Thus, the addition of alkanol improved the use efficiency of ozone during the film formation reaction and showed the effect of improving the film characteristics and the step coverage shape.

[0015]

According to the present invention, ozone TEOS atmospheric pressure CVD, which is considered as a promising method for forming an interlayer insulation of VLSI, is proposed.
The raw material utilization efficiency of the method can be improved and the deposition rate can be improved, and the atmospheric pressure CVD method using the TEOS-ozone-based raw material can be easily applied to the formation of the interlayer insulating film and the passivation film.

[Brief description of drawings]

FIG. 1 is a schematic view of an example of an apparatus used in the method of the present invention, in which an alkanol addition mechanism and piping are added to a conventional atmospheric pressure CVD apparatus.

FIG. 2 is a graph showing the ozone concentration dependence of the deposition rate.

FIG. 3 is a schematic view of a conventional atmospheric pressure CVD apparatus.

FIG. 4 is a graph showing the ethanol addition amount dependency of the value obtained by normalizing the deposition rate when ethanol is added and the deposition rate when ethanol is not added.

[Explanation of symbols]

1: Heater, 2: Susceptor, 3: Substrate, 4: Raw material outlet, 5: 100 ° C heat insulation, 6: Ozone generator, 7:
TEOS bubbling container, 8 and 10: heating / heat retaining container, 9: ethanol bubbling container.

Claims (1)

[Claims] 1. A method for forming an insulating thin film, which comprises adding an alkanol in a method for forming a silicon oxide film by a CVD method using ozone, oxygen and alkoxysilane as reaction gases.