JPS6193831A - Preparation of membrane - Google Patents

Abstract

PURPOSE:To form a membrane at a high speed while uniformity is held, by allowing reaction luminous flux to be incident to a substrate in parallel and passing said incident luminous flux along the substrate to be reflected by a reflective mirror while allowing the reflected liminous flux to be again incident to said substrate in parallel. CONSTITUTION:A substrate support part 8 for supporting a substrate 7 is mounted in a reaction container 6 and the substrate 7 is placed on the substrate support part 8 and a substrate heating part 9 for heating the substrate 7 is provided to said support part 8. Further, a gaseous phase substance introducing pipe 10 for introducing a gaseous phase substance into the reaction container 6 is provided in the reaction container 6. In this apparatus, when luminous flux 1 is introduced into the reaction container 6 from the luminous flux introducing window 40 of a liminous flux introducing part 4, reaction luminous flux 1 passes in parallel to the substrate 7 to be guided to a luminous flux reflective part 11. The luminous flux 1 guided to the luminous flux reflective part 11 is reflected by a reaction luminous flux total reflection mirror 110 to be returned to the substrate 7.

Description

[Detailed Description of the Invention] [Field of the Invention] The present invention relates to a method for producing a thin film, and more particularly, to a so-called photovapor phase chemical growth method in which a film of a substance produced by a photochemical reaction is grown on a substrate surface from a gas phase. The present invention relates to a manufacturing method that enables luminous thin film growth while maintaining the film thickness distribution of the formed thin film on a substrate within a required range.

[Background of the invention]

Silane (Sina), disilane (Si2Hs) can be used to form a film using photodecomposition and photoreaction of gas phase substances.
a-5t (SiHa Si+2
H2, Sig Hs 2 Si + 3H2: both reactions by light energy) and silane, nitrous oxide (
5iOs+ (N20 N2) using N20) as raw material
There are many reports on each thin film of +01SiH4+20SiO2+H2). Other methods of forming thin films using light are also described in Japanese Patent Publications No. 56-96704 and Japanese Patent Publication No. 59-87814.

FIG. 1 is a schematic diagram of an apparatus used in a conventional thin film manufacturing method using photoreaction. In the figure, 1 is a reaction light flux, 2 and 3 are optical systems for converting the reaction light flux shape and intensity distribution, 4 is a light flux introduction part, 40 is a window for light flux introduction, 41 is a gas introduction tube for window purging, and 5 is a light flux emission part , 50 is a window for light flux emission, 51 is a window for light flux emission, gas introduction tube for purging, 6 is a reaction vessel, 7 is a substrate, 8 is a substrate support section, 9 is a substrate heating section, and 10 is a gas phase substance introduction tube. .

As is clear from FIG. 1, the reaction light flux l emitted from the light source passes through the conversion optical systems 2 and 3 and enters the reaction vessel 6 through the light flux introduction window 40 of the light flux introduction section 4. The light travels directly above the substrate 7 in the reaction container 6 in parallel to the substrate 7, and is emitted from the reaction container 6 through the light beam emission window 50 of the light beam emission section 5.

The reaction light beam 1 traveling directly above the substrate 7 is introduced from the gas phase substance introduction tube 10 and induces photodecomposition or photoreaction of the gas phase substance distributed near the optical path, and the substrate heated by the substrate heating section 9. The product is annealed on 7 to form a thin film.

Factors that determine the uniformity of the thickness distribution of thin films formed by such methods include the temperature distribution within the substrate plane, the intensity distribution of the reaction light, the concentration distribution of the gaseous substance in the reaction light flux, and the concentration distribution of the gaseous substance in the reaction light flux. There is a light absorption coefficient.

1. In order to make the temperature and concentration distribution uniform, similar techniques such as MOCVD or high-temperature oxidation of the St back surface in an oxidizing atmosphere have been well studied, and it is known that there are many solutions. Furthermore, uniformity of the intensity distribution of the reaction light can be achieved by applying conventional optical techniques.

However, the method of forming a thin film using light has an essential drawback that the film thickness becomes thinner as the distance from the incident end increases due to the absorption of the reaction light by the gas phase substance.

[Summary of the invention]

The present invention has been made in view of the above points, and can be made thinner at high speed while maintaining the required uniformity. ! The purpose of this invention is to provide a method for forming 2.

Therefore, according to the method for producing a thin film according to the present invention, in a method of forming a thin film on a substrate using light decomposition of a gas phase substance, a reaction light beam is incident on the substrate in parallel, and the incident light beam is passed on the substrate. After that, the light is reflected by a reflecting mirror and is made parallel to the substrate again.

According to the present invention, after the reaction light beam is incident on the substrate, it is reflected by the reflecting mirror and then enters the substrate again, so that the intensity distribution of the light beam can be made uniform, and therefore, the thickness distribution of the formed film can be maintained within the required range. It has the advantage of being able to be formed at high speed.

[Detailed description of the invention]

The second tooth is a schematic diagram showing an example of an apparatus for carrying out the method of the present invention, in which the same reference numerals as in FIG. The reflecting portion 110 represents a total reflection mirror for the reaction light beam.

As is clear from this FIG.
A light flux introduction section 4 having a reaction light flux introduction section 4 is provided, and this light flux introduction window 40 has a reaction light flux introduction window material 4 that transmits the light flux l.
2, and a purge gas introduction pipe 41 for introducing purge gas so that soot, which is a gas phase substance, does not adhere to the window material 42 is provided.

A reaction light beam reflection section 11 is located at a position opposite to this light flux introduction section 4.
The reaction light beam reflecting section 11 is equipped with a reaction light beam total reflection mirror 110 for reflecting the reaction light beam, and soot, which is a vapor phase substance, adheres to this total reflection mirror 110, causing the reflection property to deteriorate. A purge gas introduction pipe 111 is provided so as not to lower the temperature.

A substrate support portion 8 for supporting the substrate 7 is provided in the reaction vessel 6.
A number of substrates 7 are placed on this substrate support section 8, and a substrate heating section 9 for heating the substrates 7 is provided on the substrate support section 8. Furthermore, a gas phase substance introduction pipe 10 for introducing a gas phase substance into the reaction vessel 6 is provided in the reaction vessel 6 .

In such an apparatus, when the light flux 1 is introduced into the reaction vessel 6 through the light flux introduction window 40 of the light flux introduction section 4, the reaction light flux 1 passes parallel to the substrate 7 and is guided to the light flux reflection section 11.

The light beam l guided to the reaction light beam reflection section 11 is reflected by a reaction light beam total reflection mirror 110 and returns onto the base 7.

Next, the operation of the present invention will be explained.

The growth rate of the N film based on photolysis or photoreaction is γd, which is proportional to the number of photons absorbed by the gaseous material per unit time, and is determined by the absorption coefficient α of the gaseous material and the distance from the light incident end to the observation point. When using the reflected light of the present invention, the distance χ is expressed by the following equation.

However, numbers 8 and 10 indicate the respective proportionality constants and light intensity at the light incident end.

On the other hand, when the light beam is incident from only one direction using the conventional method, the thin film formation rate γd' is expressed by the following equation.

In fact, the present inventors investigated the formation of SiO thin films using silane (SiHa) and nitrous oxide (N20) as raw material gases and ArF excimer laser, and found that the relationship between growth rate and absorption coefficient is (1). and (2) and good (consistent).

Figure 3 shows a ^rF excimer laser (oscillation wavelength 1) as a light source.
93 nn+), N2 dilution 5i as gas phase substance for reaction
Ha 5%, N t O 100%, N as window purge gas
2, each flow rate of the gas phase substance is set to 0.2.1°0.
．． O and the solid line in the figure 0, which shows the relationship between the light absorption coefficient (193 nm) in the reaction vessel 6 and the growth rate at the center of the substrate (Z=L/2) at 0.81/min, indicate the reflected light of the present invention. It shows experimental values and calculated values when used.
and the broken line show experimental values and calculated values in the case of conventional unidirectional incidence.

FIG. 4 shows the film thickness distribution within the plane of the substrate in the case of the conventional method. The horizontal axis indicates the distance from the light incident side end of the substrate, and the vertical axis indicates the film thickness ratio with respect to the light incident end. In the figure, (a) to (d) show the film thickness distribution when the absorption coefficient α is o, oi, and 0.02.0.05.0.1, respectively.

As can be understood from FIG. 4, the uniformity of the film thickness distribution deteriorates rapidly as the absorption coefficient increases.

In SiOt IIR, which is used for gate oxide films and the like in integrated circuit formation technology, the permissible range of film thickness distribution within the wafer surface is about ±5% at most, preferably ±2% or less. The allowable range of film thickness distribution within a 5 cm wide substrate is set to 1.
In order to make it 5% or less, the absorption coefficient needs to be 0.02 cm' or less. However, as the absorption coefficient is decreased, the growth rate of the film decreases, as can be seen in FIG.

FIG. 5 shows the film thickness distribution in the optical path direction in the case of bidirectional incidence according to the present invention. Here, the diameter of the reaction container is 20 cm, and the distribution on a substrate with a width of 5 cm placed in the center of the container is shown. In the figure, (a), (b), and (C1) each show the distribution when α is 0.01.0.1.0.5.

As is clear from the comparison between Figure 4, which shows the film thickness distribution by the single-side incidence method, and Figure 5, which shows the film thickness distribution by the two-way incidence method, the growth rate can be increased by the two-direction incidence method up to a large absorption coefficient region. , it can be seen that the film thickness is made uniform.

As described above, the gas phase substance used in the thin film growth method according to the present invention is basically not limited.

For example, silicon, boron, germanium, aluminum, phosphorus, gallium, indium, titanium, tungsten,
One or more substances containing molecules containing hafnium, zinc, calcium, tantalum, niobium, zirconium, potassium, lead, barium, sodium, or antimony, or one or more of these substances combined with nitrous oxide, nitrogen dioxide, or carbon oxide. , carbon dioxide, and oxygen molecules. Furthermore, a photodecomposition or photoreaction sensitizer can be added to the above-mentioned gas phase substance to increase the deposition rate.

Although the light source according to the present invention has been explained using an ArF excimer laser in the above description, it is clear that the present invention is not limited to this.

Examples of the present invention will be described below along with comparative examples.

Comparative Example In the apparatus shown in FIG. 1, the reaction light beam 1 is incident on one side, and a Si wafer with a diameter of 50 mm is used as the substrate 7. In order to keep the film thickness distribution within ±2.5%, the absorption coefficient α is 0.01c
A SiOg film was formed with a thickness of less than m'.

Formation conditions were: substrate temperature 200°C, N2 dilution 5iH 45%
, Nt 0100%, the flow rate of N-2 gas for window purging was 0.2.1.0.0.812/+win, and the light source was an ArF excimer laser 10-.

At this time, the film formation rate at the center of the wafer was 700 (person/person).
The film thickness ratio between the end and the center on the light incident side and the light exit side was 1,024.0.977, respectively.

EXAMPLE Using an apparatus having the configuration shown in FIG. 2, a Si02 film was formed by utilizing the reflected light of the reaction light flux. absorption coefficient 0.03
The SiO
A film of @ was formed.

At this time, the film formation rate at the center was 2700 persons/min, and the film thickness distribution was within ±2.5%.

From the above results, it was confirmed that the present invention is effective in forming a thin film at high speed while maintaining the required uniformity.

〔Effect of the invention〕

As explained above, by re-injecting the reaction luminous flux onto the substrate, the intensity distribution of the luminous flux on the substrate can be made uniform. This method has the advantage that a thin film can be formed at high speed while maintaining the film thickness distribution within a required range.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of a conventional thin film forming apparatus, Fig. 2 is a schematic diagram of an example of an apparatus for implementing the thin film forming method according to the present invention, and Fig. 3 is a schematic diagram of an example of an apparatus for carrying out the thin film forming method according to the present invention. A diagram showing the relationship, Fig. 4. A diagram showing the thickness distribution of the thin [*(7)Ill] formed by one side incidence of the reaction light beam, Fig.
The figure shows a film thickness distribution formed from the film thickness scale shown in FIG. 2. 1...Reaction luminous flux, 6...Reaction volume N, 7...
・Substrate, 11... Reaction light beam reflecting section, 110...
Reactive beam total reflection mirror. Applicant's agent: Masaki Amemiya Figure 2 Figure 3 Eyesight 1 thread (cm') Figure 4

Claims (1)

[Claims] (1) In a method of forming a thin film on a substrate using light decomposition of a gas phase substance, a reaction light beam is incident on the substrate in parallel, and this incident light beam is passed over the substrate and then reflected by a reflecting mirror. A method for producing a thin film, characterized by making the light incident parallel to the substrate again.