JPS6039822A - Thin film forming device - Google Patents

Abstract

PURPOSE:To unify the film thickness of overall surface of a wafer by means of widening the space between the periphery of wafer and a supporter. CONSTITUTION:The grooves 19 almost concentrially circular with a wafer 16 is spot-faced at the positions corresponding to the periphery of the wafer 16 on each wafer holding position of each supporter 15 of a thin film forming device to make the wafer 16 afloat from the bottom of the grooves 19. In such a constitution, e.g. in the deposition of plasma oxide film, there exists a gap between the periphery of the wafer 16 and the bottom of the grooves 19, accordingly the oxygen contained in the nitrous oxide as plasma producing gas is consumed by carbon contained in the graphite material of the susceptor 15 to form a carbide eliminating the phenomenon to make the film thickness of the plasma oxide on the periphery of the wafer 16 thinner than that of the central part further unifying the film thickness of the overall surface of the wafer 16.

Description

[Detailed description of the invention] [Technical part! l! F] The present invention relates to a thin film formation technique, and in particular to a technique for depositing CvDllili onto a wafer using plasma.

[Background technology] In the manufacturing process of semiconductor devices, diffusion furnace type plasma CV
When depositing a CVD film on a silicon (Si) wafer using the D apparatus, as shown in FIG. It is conceivable that the wafer 3 is supported by two wafer support claws 2 provided perpendicularly to the wafer.

However, in this susceptor structure, in addition to the susceptor 1 having a flat plate shape, there is a wafer 3 on the surface of the susceptor 1.
Since only a small narrow tweezers insertion recess 4 for inserting the tweezers holding the wafer 3 is formed, the wafer 3 is supported in close contact with the surface of the susceptor 1 over almost its entire surface. In addition, since graphite is used as the material of the susceptor 1, when depositing a plasma oxide film (P-si□ film) on the wafer 3, the graphite material of the susceptor 1 is Oxygen in (N20) is consumed and the wafer 3
The inventors have discovered that there is a problem in that the film thickness decreases at the periphery of the wafer, and the film thickness becomes non-uniform between the central part and the periphery of the wafer.

[Object of the Invention] An object of the present invention is to provide a thin film forming technique that can obtain a uniform film thickness over the entire surface of a wafer.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Summary of the Invention] A brief overview of typical inventions disclosed in this application is as follows.

That is, by increasing the distance between the wafer, especially its periphery, and the support, or by forming the support from a material to which at least a portion of aluminum or silicon is added, the film thickness on the wafer can be reduced over the entire surface of the wafer. It can be made uniform.

[Example 1] Fig. 2 is a schematic cross-sectional view in the middle direction of a thin film forming apparatus which is an embodiment of the present invention, Fig. 3 is a schematic longitudinal cross-sectional view thereof, and Fig. 4 is an enlarged view of the wafer susceptor. FIG.

The thin film forming furnace in this example is configured as a diffusion furnace type plasma CVD apparatus with a multilayer electrode structure, and the reactor IO made of a quartz tube is configured so that a vacuum can be maintained by a front door 11. An exhaust pipe 12 is connected to the rear part of the furnace for evacuating the inside of the furnace. On the other hand, in the front part of the reactor 10, silane (S
Gas supply pipes 13 and 14 for supplying nitrous oxide (L H4) and nitrous oxide (N20) G into the furnace are connected.

Further, in the reactor 10, a plurality of wafer boats, ie, susceptors 15, which are made of graphite and also serve as electrodes, are disposed in the longitudinal direction and in the vertical direction so as to be removable.

On the opposing surface of each susceptor 15, a plurality of silicon (Si)
) is held vertically by supporting its lower side with two wafer support claws 17 (FIG. 4). Each susceptor 15 also serves as an electrode, and is connected to a high frequency power source 18, respectively.

Furthermore, at each wafer holding position of each susceptor 15,
A groove 19 approximately concentric with the wafer 16 is formed at a position corresponding to the periphery of the wafer 16 by, for example, counterboring. Therefore, in this embodiment, the wafer holding surface of the susceptor 15 and the wafer 16 are in contact with each other at the circular island-like portion inside the groove 19, but at least the depth of the groove 19 is The wafers 16 are separated from each other by a certain amount, so that the wafers 16 are floating above the bottom surface of the grooves 19, so to speak.

Next, the operation of this embodiment will be explained.

First, the semiconductor wafer 16 is loaded at a predetermined position on the opposing surface of the susceptor 15, which also serves as an electrode, and is held substantially vertically by the wafer support claws 17. After that, the door 11 is closed and the exhaust pipe 12 is closed.
By evacuating the inside of the reactor 10 through the reactor 10, the inside of the reactor 10 is brought into a vacuum state, and SiH4 and N20 are introduced into the reactor 10 as plasma generation gases from the gas supply pipes 13, 14.

When high frequency power from the high frequency power supply 18 is applied between the susceptors 15 in this state, gas plasma is generated in the reactor IO, and due to the action of this plasma, the wafer 16
A desired plasma oxide film (P-3iO film) can be deposited thereon.

In the deposition of this plasma oxide film, in this embodiment, a substantially concentric groove I9 on the left side of the wafer 16 is provided at the wafer holding position of the susceptor 15, so that the wafer 1
6 is spaced apart from the bottom of the groove 19, oxygen in nitrous oxide, which is a plasma generating gas, is consumed by the carbon in the graphite material of the susceptor 15 and forms a compound with carbon. This eliminates the phenomenon that the plasma oxide film at the periphery of the wafer 16 becomes thinner than the center, thereby making the film thickness uniform over the entire surface of the wafer 16.

[Example 2] In Example I, a case was explained in which substantially concentric grooves were formed at the wafer holding position of the susceptor, but the present inventor achieved the same purpose by using a specific material for the susceptor. I found out what I can achieve.

That is, when the present inventor conducted an experiment on the relationship between the material of the susceptor on the side facing the wafer and the rate of plasma oxide film formation, the results shown in FIG. 5 were obtained.

In FIG. 5, the left column shows the case where a plasma oxide film is generated with a silicon wafer held on the opposing surfaces of two graphite susceptors, and the generation rate at the center C of the wafer. is large, but the production rate in the left side portion R and the right side portion R, which are the peripheral portions, is low, and the uniformity of the film thickness is somewhat difficult.

In the middle column of FIG. 5, plasma deposition was performed with a silicon wafer held only on one side of two graphite susceptors, and the plasma oxide film formation rate was low overall.

The reason for such a decrease in the production rate is considered to be that the carbon in the graphite of the susceptor consumes the oxygen in the N20 and a compound of oxygen and carbon is produced.

The column on the right side of Figure 5 shows a susceptor made of two graphite that holds a soricon wafer and an aluminum (AI) foil on the opposing surfaces. The difference in production rate depending on surface position was relatively small.

From the results shown in Figure 5, if the material of the susceptor facing the wafer contains at least a portion of aluminum,
It is clear that good plasma deposition can be obtained in terms of film formation rate and film thickness uniformity.

[Example 3] FIG. 6 shows the results of an experiment conducted by the present inventor on the relationship between the material difference of the wafer peripheral support surface of the susceptor and the formation rate and uniformity of the film thickness of the plasma oxide film.

First, the left column of Figure 6 shows the experimental results when the entire surface of the wafer support surface is made of graphite. There are some difficulties.

The middle column in Figure 6 shows the gap between the left peripheral part of the wafer and the wafer support surface of the graphite susceptor.
1) This is an example in which plasma deposition was performed with a foil interposed. In this case, the film formation rate on the left side R with the AI foil interposed is the same as that on the right side R with no AI foil interposed.
It is higher than that of fluorine, and the difference with the central part C is small, so
Uniform film thickness can be obtained. This improvement in the film formation rate on the left side is considered to be because the carbon in the graphite of the susceptor is covered with the AI foil.

The right column of FIG. 6 shows the case where plasma deposition was performed with another silicon wafer interposed between the left peripheral part of the silicon wafer and the wafer support surface. In this case as well, it can be seen that the generation rate of the plasma oxide film on the left side of the wafer is significantly higher than on the right side R, and a uniform film thickness can be obtained. This improvement in the film formation rate on the left side of the wafer is thought to be due to the carbon in the graphite of the susceptor being covered by the silicon wafer.

From the experimental results shown in Figure 6, it is clear that if the susceptor that supports the wafer is made of a material to which at least a portion of aluminum or silicon is added, a plasma oxide film with uniform thickness and high production rate can be obtained. be.

[Effects] (1) By providing a groove in the wafer support to create a gap between the periphery of the wafer and the support surface of the support, oxygen, etc. in the plasma generation gas is supported. The film is not consumed by body material, and a uniform film thickness can be obtained over the entire wafer surface.

(2) By forming the wafer support from a material to which at least a portion of aluminum or silicon is added, a uniform film thickness can be obtained over the entire surface of the wafer.

(3) By combining the above (1) and (2), a synergistic film thickness uniformization effect can be obtained.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the Examples and can be modified in various ways without departing from the gist thereof. Nor.

For example, the support may be made of aluminum or silicon, or may be made of a mixture of graphite and aluminum or silicon. moreover,
The core of the support may be made of graphite, and part or all of its surface may be coated with aluminum or silicon.

Further, the shape of the spacing grooves formed in the support is not limited to the above-described one, and the support may be formed of a material to which at least a portion of aluminum or silicon is added, and the spacing grooves may be formed in the support. By forming this, it is possible to synergistically achieve uniform film thickness.

[Field of Application] The above explanation has mainly focused on the case where the invention made by the present inventor is applied to the production of a plasma oxide film on the surface of a wafer, which is the field of application that formed the background of the invention.
The present invention is not limited thereto, and can be widely applied to other thin film formations, such as the production of other plasma films, for example.

[Brief explanation of drawings]

FIG. 1 is a partial perspective view of a possible wafer susceptor, FIG. 2 is a schematic cross-sectional view in the middle direction of a thin film forming apparatus that is an embodiment of the present invention, and FIG. 3 is a schematic cross-sectional view in the longitudinal direction thereof. Figure 4 is an enlarged partial perspective view of the wafer susceptor, Figure 5 is a diagram showing the relationship between the material of the susceptor facing the wafer and the film formation rate, and Figure 6 is the relationship between the material of the wafer support surface of the susceptor and the film formation rate. FIG. DESCRIPTION OF SYMBOLS 10... Reactor, 11... Door, 12... Exhaust pipe, 13.14... Gas supply pipe, 15... Susceptor (
16... Wafer, 17... Wafer support claw, 18... High frequency power supply, 19... Groove. Agent Patent Attorney Akira Takahashi Mistake 1 Figure 2

Claims (1)

[Claims] 1. In an apparatus for forming 81 m on a wafer using plasma, a groove is provided in a wafer support to create a space between the Pi side of the wafer and the support surface of the support. A thin film forming apparatus characterized by being provided with. 2. The thin film forming apparatus according to claim 1, wherein the groove is a groove formed on the wafer support surface of the support body substantially concentrically with the wafer. 3. A thin film forming apparatus for forming a thin film on a wafer using plasma, characterized in that the surface of the wafer support is formed from a member whose main component is aluminum or silicon.