JPS63199432A - Gas dispersing head for cvd device - Google Patents

Abstract

PURPOSE:To obtain a device, cost of which is low and which is assembled easily and enables the deposition of doped polysilicon and deposition under decompression of an oxide film when the device is used for a decompression CVD device, by a method wherein a gas path is formed by a plurality of capillaries, the capillaries are bundled while the lower ends of the capillaries are cut to the same plane shape and a gas dispersing head is constituted. CONSTITUTION:A gas path introducing a gas is shaped by a plurality of capillaries 17, and the capillaries 17 are bundled while the lower ends of the capillaries are out to the same plane shape, thus organizing a gas dispersing head 4. A large number of the capillaries 17 made of stainless having an outside diameter of 1mm and an inside diameter of 0.8mm are divided into two of a group of capillaries 17a for silane gas, upper ends of which are employed as gas introducing ports for silane gas and the insides of which are used as paths, and a group of capillaries 17b for oxygen gas, upper ends of which are employed as gas introducing ports for oxygen gas and the insides of which are used as paths, while the capillaries 17 are bundled by a rectangular frame-shaped bundling band 18, the bundled section is formed to approximately 400X100mm, and the lower ends of the capillaries are shaped to a plane shape, thus constructing the gas dispersing head 4.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention releases a reactive gas consisting of silane (S iHa ) gas, oxygen gas, etc., and by this reduction and oxidation action, the surface of a silicon substrate is and a silicon oxide film (S
This invention relates to a gas dispersion head that is optimal for use in introducing gas in a CVD (vapor phase oxide deposition) device that deposits i02) by vapor phase growth.

(Prior Art) Conventionally, the above-mentioned CVD apparatus for depositing a silicon oxide film on a semiconductor substrate under normal pressure has a heater 2 built into a substrate support 1, as shown in FIGS. 5 and 6, for example. ,
It is generally known that a silicon substrate 3 placed on the top surface of the substrate support 1 is heated to about 400° C. by the heater 2, and a gas dispersion head 4 is placed vertically to the silicon substrate 3. It is being

This gas dispersion head 4 has a large number of stacked dispersion plates 5, and has a plurality of vertically communicating slits 6 formed therein as gas passages, and the silane gas and oxygen gas are dispersed and released from the slits 6. Then, a silicon oxide film is deposited by vapor phase growth on the upper surface of the silicon substrate 3 and its vicinity using a reactive gas 7 which is a mixture of both gases.

The width of this slit 6 is usually 1 to 2 mm, and the distance between the gas dispersion head 4 and the silicon substrate 3 is 3 to 5n++n.
The slit length (length perpendicular to the width direction) is 400 to 500.
It was about mm.

In this case, the film thickness variation in the length direction of the slit 6 is good, but the film thickness variation in the width direction perpendicular to this is not good, so the silicon substrate 3 or the gas dispersion head 4 is The uniformity of the film thickness was improved by moving the film.

Moreover, FIG. 7 shows a conventional low pressure CVD apparatus, in which a heater 9 for heating the silicon substrate 3 to be coated is arranged outside a reaction tube 8 made of a quartz tube that can reduce the pressure. One end of 8 is connected to an exhaust device 10, and the other end is provided with a door 12 that can be opened and closed for loading and unloading the silicon substrate 3 and a substrate holder 11 for holding it. 13 is interposed to ensure airtightness. Gases used as reaction gases are introduced from the respective cylinders 14 and 15, pass through the door 12, and are discharged into the reaction tube 8.

This released gas is transferred to the dispersion plate 1 placed in front of it.
6 and is dispersed, and is exhausted through the gap between the silicon substrate 3 and the reaction tube 8. A reactive gas is supplied to the surface of the silicon substrate 3 by being diffused from this exhaust flow.

Since the oxide film is deposited in this way, the gap between the silicon substrate 3 and the reaction tube 8 and the distance between the silicon substrates 3 are important in the low pressure CVD apparatus in order to obtain a uniform film thickness. It is.

(Problems to be Solved by the Invention) However, the gas dispersion head shown in FIGS. 5 and 6 above is constructed by stacking a large number of dispersion plates 5 to form a plurality of rows of slits 6. Because of this, it is not only necessary to provide many counterbores and holes, but also requires high assembly precision, making it quite expensive.

Historically, a great deal of labor and sophisticated assembly techniques were required even when disassembling and cleaning.

In addition, in the case shown in FIG. 7, the reaction gas introduced into the reaction tube 8 is sequentially thermally decomposed and exhausted, so a concentration gradient of the reaction gas occurs between the inlet port and the exhaust port. This may result in non-uniformity in film thickness. To prevent this,
It has been attempted to improve the uniformity of the film thickness by providing a temperature gradient to the heater 9.

However, in undoped polysilicon films that do not contain any impurities, good results can be obtained by creating this temperature gradient, but in the case of doped polysilicon films that are doped with impurities such as phosphorous or arsenic, A concentration gradient of impurities occurs, making it impossible to achieve both uniformity of the film pieces and uniformity of concentration.

Also, in order to deposit a silicon oxide film, silane (S I
When a film is deposited by introducing H,i) and oxygen gas, there is a problem that good film thickness uniformity cannot be obtained because the silane gas thermally decomposes quickly.

-41 In view of the above, the present invention is not only inexpensive and easy to assemble, but also can be used in a low pressure CVD apparatus to deposit doped polysilicon and oxide films under reduced pressure. It was made with the purpose of providing.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention forms a gas passage through which gas is introduced using a plurality of thin tubes, bundles the thin tubes, and cuts the lower ends of the thin tubes into the same plane. The gas dispersion head is used in a CVD apparatus with its flat lower end facing a substrate to be deposited, and gas is discharged perpendicularly to the substrate to be deposited.

(Function) By configuring a gas dispersion head by bundling a plurality of thin tubes that introduce gas into the interior, assembly, disassembly and cleaning, etc. can be facilitated, costs can be reduced, and the lower end can be covered. It is made to face the deposition substrate so that gas is discharged vertically to the deposition substrate, so that it can also be used in a low pressure CVD apparatus.

(Embodiment) Figures 1 and 2 show an embodiment of the present invention, in which a large number of stainless steel thin tubes 17 with an outer diameter of 1 m+n and an inner diameter of 0.8 m+n are used, with the upper end being a gas inlet for silane gas. A group of thin tubes 17a for silane gas with the inside as a passage and a group of thin tubes 17b for oxygen gas with the upper end as a gas inlet for oxygen gas and the inside as a passage. Bundle, the cross section of this bundle is approximately 400X
The gas dispersion head 4 is made to have a length of about 100 mm, and the lower end is made flat.

The silane gas thin tube 17a and the oxygen gas thin tube 17b are bundled in parallel so as to form rows.

By configuring the gas dispersion head 4 in this manner, it is possible to facilitate assembly, disassembly and cleaning, and also to significantly reduce costs by using the generally inexpensive thin tube 17.

Figure 3 shows another embodiment, in which a capillary tube for silane gas 1
The thin tubes 7a and 17b for oxygen gas are mutually arranged in a checkerboard pattern, and the cross section of the bundle is approximately the same shape as the silicon substrate which is the deposited substrate.

This arrangement improves in-plane uniformity.
This makes it possible to eliminate the need to move the gas dispersion head 4 and the silicon substrate while keeping them facing each other.

In the embodiment shown in FIG. 1, the silane gas thin tubes 17a and the oxygen gas thin tubes 17b of each rectangular group are bundled in a rectangular shape, but as shown in FIG. The silane gas thin tube 17a and the oxygen gas thin tube 17b may be bundled in a circle with a circular frame-shaped binding band 18'.

Note that a cylindrical tube may be used as the thin tube 17, but the present invention is not limited to this; for example, a polygonal tube such as a square or hexagonal cross section may be used to avoid gaps between the tubes.

Furthermore, it is not necessary that all the bundled thin tubes 17 be used for gas discharge, and some of the thin tubes may be used for gas exhaust.

Further, as the material for the thin tube 17, stainless steel is desirable from an economic standpoint, but from the standpoint of heat resistance and corrosion resistance, glass such as quartz, glassy carbon, and other metals may also be used.

FIG. 5 shows an example in which the gas dispersion head 4 is used in a reduced pressure CVD apparatus.

The gas dispersion head 4 in the figure has an outer diameter of 1 mm and an inner diameter of 0.8 nm.
The cross section of bundled stainless steel tubes 17 of +m has a diameter of 1
．． The length is about 60 mm.

This gas dispersion head 4 is airtightly attached to a reaction tube 8 via a seal 19, and this reaction tube 8 can be connected to an exhaust device (not shown) to create a vacuum. It is something.

Inside this reaction tube 8, a substrate support 20 made of carbon is arranged facing the lower surface of the gas dispersion head 4, and on the upper surface of this substrate support 20, there is a
A recess for placing the silicon substrate 3 of 0+++n+ is provided, and when the silicon substrate 3 is placed in this recess, this surface faces the lower surface of the gas dispersion head 4, and the gas supplied from there. is arranged to emit perpendicular to this surface.

An infrared lamp 2 for heating the silicon substrate 3 placed inside the reaction tube 8 is disposed outside the reaction tube 8. Instead of this infrared lamp 21, an induction heating method using a high frequency power source may be adopted.

Then, the infrared lamp 21 illuminates the silicon substrate 3.
is heated and maintained at 450°C, silane gas and oxygen gas are released from the gas dispersion spatula F' 4, and the reaction tube 8
The internal pressure was set to 0.5 Torr, and a silicon oxide film was deposited on this surface with a uniformity of 2%.

A preliminary chamber 22.23 is connected to the left and right sides of the L reaction tube 8, and the silicon substrate 3 is loaded using the preliminary chamber 22.23 without exposing the reaction tube 8 to the atmosphere, and a silicon oxide film is deposited. It is configured to be unloaded later.

Note that by changing the introduced gas, a doped polysilicon film, a silicon nitride film, a tungsten film, a tungsten silicide film, or the like can be deposited.

This doped polysilicon film is deposited by setting the temperature of the silicon substrate 3 to 700°C, using silane gas as the gas type, and arsine (As Ha) as the impurity gas, thereby reducing the concentration variation in the AS film. It can be suppressed to 1% or less.

The silicon nitride film can be deposited by using silane gas and ammonia at a temperature of 720° C. for the silicon substrate 3, or by using an organic metal gas.

In order to improve the uniformity of the film thickness and film quality, the gas dispersion head 4 or the silicon substrate 3 may be moved or rotated, and the gas introduced into the thin tube 17 may be turned on or off, or the type of gas may be changed. It may also be possible to switch.

〔Effect of the invention〕

Since the present invention has the above-mentioned configuration, it is not only structurally simple and easy to assemble, but also uses relatively inexpensive thin tubes, which significantly reduces costs and reduces the need for disassembly and cleaning. A simple gas dispersion head can be provided.

Furthermore, by using it in a low pressure CVD apparatus, the gradient (unevenness) of gas concentration can be minimized, and a homogeneous film can be deposited with high uniformity even on a large coating substrate, such as a large diameter one.

In addition, since the distance from the gas outlet to the silicon substrate is small, even gases that are easily thermally decomposed can be deposited by raising the temperature of the silicon substrate, and it is also possible to improve step force rayage. effective.

[Brief explanation of the drawing]

1 and 2 show one embodiment of the present invention, FIG. 1 is a perspective view, FIG. 2 is a cross-sectional view showing main parts, and FIG. 3 is equivalent to FIG. 2 showing another embodiment. 4 is a perspective view showing still another embodiment, FIG. 5 is a vertical sectional view showing an example of use of the present invention, FIGS. 6 and 7 show a conventional example, and FIG. 6 is a CVD apparatus. FIG. 7 is a perspective view showing the gas dispersion head, FIG.
The figure is a longitudinal sectional view showing another conventional CVD apparatus. 3... Silicon substrate, 4... Gas dispersion head, 17
...tubule, 18. 18'... Bundling obi, 20...
Board support stand, 21...infrared lamp. Applicant's agent Sato -O = 12-1N Kaichi UG3-199432 (6)

Claims (1)

[Claims] 1. A gas passage for introducing gas is formed by a plurality of thin tubes,
A CV characterized in that a gas dispersion head is constructed by bundling these thin tubes and cutting their lower ends into the same plane.
Gas dispersion head for D equipment. 2. The gas dispersion head for a CVD apparatus according to claim 1, wherein the planar lower end faces the substrate to be deposited so that gas is emitted perpendicularly to the substrate to be deposited.