JP2845105B2 - Thin film vapor deposition equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a horizontal thin film vapor phase growth apparatus. The thin film vapor phase growth apparatus introduces a source gas onto a heated substrate, causes a gas phase reaction between the source gases, and deposits a reaction product on the substrate to form a thin film. The substrate is a crystal of silicon Si, gallium arsenide GaAs, zinc selenide ZnSe, or the like. A glass-like object may be used as the substrate. Source gas varies depending on the purpose. For example, when the substrate is gallium arsenide and the thin film is gallium arsenide, a hydride of arsenic and an organometallic compound of gallium are used together with hydrogen gas. Or the thin film is Z
In the case of nSe, a raw material is an organometallic compound of Zn and a hydride of Se.

[0002]

2. Description of the Related Art There are two types of thin film vapor phase growth apparatuses, a horizontal type and a vertical type. This is a classification based on the direction of gas flow. The vertical type apparatus uses a cylindrical reaction vessel and flows a raw material gas from above. The substrate is horizontally supported by the susceptor. The susceptor rotates about an axis of rotation. This is to improve the uniformity of circumferential thin film growth. Since the substrate is horizontal and rotates, the uniformity of thin film growth is good. However, the source gas collides perpendicularly with the substrate and the gas flow is not smooth. Since the flow path is wide and the gas flow cannot be increased, there is a disadvantage that the growth rate is low.

[0003] The horizontal thin film vapor phase growth apparatus uses a reaction vessel (reactor) that is long horizontally. An inclined susceptor such as graphite is provided inside. Place the substrate on the susceptor. The substrate and the susceptor are heated by a lamp or a heater. Source gas is introduced into the reaction vessel from one end. The source gas flows in the horizontal direction. The source gas causes a gas phase reaction near the substrate. The reaction product is deposited on the substrate to form a thin film. Either format is used. Each has advantages and disadvantages. The horizontal type vapor phase growth apparatus has an advantage that the flow of the source gas is smooth and the contact of the source gas with the substrate is soft. Since the flow path can be narrowed, the speed of the source gas increases. Growth rate can be increased.

[0004]

When a ZnSe thin film is grown on a gallium arsenide GaAs substrate or a ZnSe substrate, an organic metal of Zn and a hydride of Se are used as source gases. Examples of the organic metal of Zn include DMZ (dimethyl Zn) and DEZ (diethyl Zn). This reacts with the hydride of Se even at room temperature. Then, when the two source gases are mixed at the inlet of the reaction vessel, a reaction occurs there. In order to avoid this, it has been proposed to extend a pipe of one source gas to the vicinity of the substrate, from which the source gas is ejected toward the substrate. Since the gas flow is unidirectional, it means that the two gases are mixed only immediately before the substrate. Then, the reaction occurs very close to the substrate, and the reaction product is deposited on the substrate as a thin film.

However, there is still a drawback in the case where the one material gas supply port is provided very close to the substrate. One is a case where several thin films of different types are formed one after another. In this case, a dead space where the movement of gas is slow occurs at the front end on the entrance side of the reaction vessel. In order to form a multilayer film, the source gas must be switched in a short time. However, if there is a large dead space, the previous gas remains in the dead space. It takes time for the newly switched feed gas to drive out the old gas and fill this space. The thin film grown during this time contains a mixture of the previous material and the current material. Therefore, the change in composition at the boundary of the multilayer film becomes slow. Steep boundaries cannot be obtained.

Another difficulty is that the gas flow is disturbed when the gas is switched, because the conventional inlet for the source gas has a simple circular cross section. When the gas becomes turbulent, the gas phase reaction becomes spatially nonuniform, and the composition and thickness of the thin film become nonuniform.

There is provided a vapor phase growth apparatus which overcomes such difficulties, does not generate dead space, does not generate turbulence even when a source gas is switched, and can grow a thin film having a uniform film quality. That is the object of the present invention.

[0008]

In the vapor phase growth apparatus of the present invention, nozzles for blowing a source gas are provided in upper and lower stages, one of which extends to the vicinity of the substrate and is opened, and the other nozzle is opened. Open more rearward. Further, a purge gas blowing port is provided at the front end of the nozzle, and the purge gas is blown from the front end of the nozzle. It is desirable that the two-stage nozzle shape be similar to the cross-sectional shape of the reaction vessel.

[0009]

A source gas nozzle for introducing two types of source gases is brought close to the substrate. Since the source gas does not mix until the substrate approaches the substrate, a gas phase reaction in front of the substrate can be prevented. Although the purge gas is blown from the front end of the nozzle, the source gas does not stay or recede due to the purge gas, and reaches the substrate after leaving the nozzle while maintaining a laminar flow state. Dead space cannot be created by the action of purge gas. Therefore, when the source gas is switched to form a multilayer film, the previous source gas does not remain in the reaction vessel, and the composition change at the boundary of the thin film is fast. Since the source gas reaches the substrate in a laminar flow state, a highly uniform thin film can be grown. The purge gas is, for example, hydrogen or nitrogen. In the case of gallium arsenide or ZnSe, the purge gas is hydrogen.

If the shape of the nozzle is the same as the shape of the reaction vessel, the flow path of the flow path of the purge gas becomes uniform, so that the flow of the purge gas is uniform and does not disturb the flow of the source gas.

[0011]

FIG. 1 is a schematic sectional view of a thin film vapor phase growth apparatus according to an embodiment of the present invention. FIGS. 2, 3, and 4 correspond to X in FIG.
It is -X, YY, ZZ sectional drawing. Horizontal reaction vessel 1
Is a cylindrical container. Made of quartz tube. A susceptor 2 inclined forward is provided at the tip of the support shaft 3 inside. A high frequency heating coil 4 for heating the susceptor 2 is provided on an outer peripheral portion thereof.

A nozzle mechanism for introducing a source gas and a purge gas is provided in front of the reaction vessel 1. A nozzle flange 6 is fixed to a front flange 5 of the reaction vessel 1 via an O-ring 7. The nozzle flange 6 is a cylindrical container, in which a two-stage nozzle body 8 is mounted. Although the nozzle body 8 is securely supported by the nozzle flange 6, illustration of a support rod and the like is omitted here. The nozzle flange 6 has a circulating gas passage 9 on the outside.

A purge gas introduction pipe 10 for introducing a purge gas from the outside is provided in the circulation gas passage 9. A plurality of purge gas inlets 11 are bored in the inner wall of the nozzle flange 6 in the radial direction. The purge gas passes from the purge gas introduction pipe 10 through the orbiting gas passage 9 and into the front outer peripheral space 12 which is the outermost area in front of the reaction vessel 1 via the purge gas inlet 11. The purge gas proceeds in this space as a laminar flow. The purge gas is hydrogen, nitrogen, or the like. The type of purge gas should be selected according to the purpose.

A substrate 13 is placed on the susceptor 2. The substrate 13 is inclined with respect to the source gas, so that the gas is soft.

The nozzle body 8 has a two-stage nozzle structure that opens toward the substrate 13. FIG. 5 is a perspective view of only the nozzle body 8. The upper nozzle is referred to as an A nozzle 14.
The lower nozzle is called a B nozzle 15. Each of them has a rectangular cross section near the substrate and a substantially uniform cross sectional area. However, in the vicinity of the nozzle flange 6, the two flow paths are narrow and form a circular mounting base 16. Mounting base 16
Are opened at the end face of each of the nozzles 17 and 18 communicating with the A nozzle 14 and the B nozzle 15. An O-ring 19 is interposed in order to separate these two blowing ports.

The A nozzle 14 and the B nozzle 15 are completely separated from the blowing port to the upper opening 20 and the lower opening 21 on the substrate side. The nozzle body 8 has two flow paths,
An upper plate 22, a middle plate 23, a lower plate 24, a side plate 25, and a side plate 26 are formed. In both the A nozzle 14 and the B nozzle 15, the cross-sectional areas of the flow paths increase in the middle. This reduces the velocity of the gas, resulting in a constant velocity rectification. O-ring 19
Then, the nozzle body 8 is attached to the nozzle flange 6 via the O-ring 27. An A gas inlet 28 and a B gas inlet 29 are perforated in the end face of the nozzle flange 6.

When the nozzle body 8 is attached to the nozzle flange 6, three different gas flow paths are formed. One is an A gas inlet 28, a blowing port 17, an A nozzle 14, and an upper opening 20.
And a gas passage reaching the position above the substrate 13. The other is a gas passage that reaches the position below the substrate 13 through the B gas introduction port 29, the blowing port 18, the B nozzle 15, and the lower opening 21. The last one is a purge gas introduction pipe 1
0, a circulation gas passage 9, a purge gas inlet 11, a front outer space 12, and a gas passage passing through the periphery of the reaction vessel 1.

The A nozzle 14 is made to pass, for example, an organometallic gas of Zn. A hydride gas such as Se or sulfur S is passed through the B nozzle 15. These gases come into contact for the first time in a space closer to the substrate than the upper opening 20 extending further to the substrate. Here, the gas phase reaction occurs for the first time. The reason why the shapes of the A nozzle 14 and the B nozzle 15 are planar is that the source gases flowing out of the nozzles are mixed in a short time, and the mixed gas uniformly contacts the substrate 13. For this reason, the width W of the openings 20 and 21 of the A nozzle 14 and the B nozzle 15 is made larger than the diameter of the substrate. The substrate 13 is completely open 20;
If the gas enters the opening 21, the gas exiting from the openings 20 and 21 uniformly contacts the substrate surface. If the cross-sectional areas of the openings of the A nozzle 14 and the B nozzle 15 are made proportional to the gas flow rate, the flow at the outlet will not be disturbed.

The nozzle 8 has a small diameter at the beginning, expands as it advances forward, and becomes flat and square in cross section. A variant nozzle, which can be made from a quartz tube. Alternatively, it can be made of stainless steel. In the case of high-frequency heating, the reaction vessel is made of a quartz tube or the like. In this case, the reaction vessel is also the nozzle body 8
Is also quartz. However, the heater may have a built-in resistance heater. In this case, the reaction vessel can be made of metal such as stainless steel.

Since the A nozzle 14 is open closer to the substrate, it mixes with the material of the B nozzle 15 immediately before the substrate. Therefore, it does not react in a low-temperature region until reaching the substrate and cause loss of material. In addition, since the reaction product does not adhere to the space in front of the reaction vessel, there is no possibility that the thin film is contaminated.

The dead space will be described. When both the A nozzle 14 and the B nozzle 15 are inserted deep into the reaction vessel 1 as described above, a dead space should be created on the upstream side of the reaction vessel. However, in the present invention, since the purge gas flows from the upstream side of the reaction vessel 1, the gas flow does not flow backward. Since the purge gas is always flowing, the source gas does not flow backward through the reaction vessel and stay in the front part. In addition to eliminating the dead space, the purge gas has the advantage that the reaction product can be prevented from adhering to the wall surface.

The height H and the width W of the nozzle opening are parameters that can be freely set.

[0023]

The vapor phase growth apparatus of the present invention has two gas nozzles vertically, one of which is open near the substrate and the other is also open near the substrate. Further, a purge gas is blown from the outer peripheral portion at the front end of the reaction vessel. This has the following effects. 1. Since the purge gas is blown, no dead space is generated in the reaction vessel. 2. The gas flow becomes laminar. 3. When the source gas is switched, no residual gas remains, and the gas in the reaction vessel is rapidly replaced by a new gas. It is possible to grow a multilayer film in which the composition change at the boundary is clear.

4. Two gases can be mixed immediately before the substrate. 5. By optimizing the shape of the nozzle outlet, it is possible to form a film with good film thickness uniformity. 6. Since the purge gas is supplied, it is possible to prevent the reaction product from adhering to the inner wall of the reaction vessel. This prevents impurities from being included in the thin film, and enables formation of a high-purity thin film.

[Brief description of the drawings]

FIG. 1 is an overall sectional view of a thin film vapor phase growth according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line XX of FIG.

FIG. 3 is a sectional view taken along line YY of FIG. 1;

FIG. 4 is a sectional view taken along the line ZZ in FIG. 1;

FIG. 5 is a perspective view of a nozzle body.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 reaction vessel 2 susceptor 3 support shaft 4 high-frequency heating coil 5 front flange 6 nozzle flange 7 O-ring 8 nozzle body 9 orbiting gas passage 10 purge gas introduction pipe 11 purge gas inlet 12 front outer peripheral space 13 substrate 14 A nozzle 15 B nozzle 16 Mounting base 17 Inlet 18 Inlet 19 O-ring 20 Upper opening 21 Lower opening 22 Upper plate 23 Middle plate 24 Lower plate 25 Side plate 26 Side plate 27 O-ring 28 A gas inlet 29 B gas inlet

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-266621 (JP, A) JP-A-5-226257 (JP, A) JP-A-6-13331 (JP, A) JP-A-6-13331 216030 (JP, A) JP-A-5-90161 (JP, A) JP-A-4-279024 (JP, A) JP-A-4-10667 (JP, A) JP-A-63-313826 (JP, A) JP-A-62-226887 (JP, A) JP-A-62-266622 (JP, A) JP-A-1-125368 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01L 21/205 C23C 16/44 C30B 25/14 H01L 21/365

Claims (2)

(57) [Claims] 1. A horizontally elongated reaction vessel 1, a susceptor 2 accommodated in the reaction vessel 1 and holding a substrate 13, and a susceptor 2
A heater for heating the raw material, a nozzle body 8 composed of an A-nozzle 14 and a B-nozzle 15 which are inserted into the reaction vessel from the upstream side of the reaction vessel 1 and are arranged in two stages, and a source gas is supplied to the A-nozzle 14. A, a B gas inlet for supplying a different source gas to the B nozzle 15, and a purge gas inlet pipe for introducing a purge gas to the periphery of the reaction vessel 1. The opening of the A nozzle 14 is located just before the substrate. And that the opening of the B nozzle 15 is also near the substrate, different source gases are mixed immediately before the substrate, and the purge gas flows around the nozzle body 8 to prevent the source gas from flowing back and stagnation. Characteristic thin-film vapor deposition equipment. 2. A horizontally elongated reaction vessel 1, a susceptor 2 accommodated in the reaction vessel 1 and holding a substrate 13, and a susceptor 2
And an A-nozzle 1 which is concentrically inserted into the reaction vessel from the upstream side of the reaction vessel 1 and has two upper and lower stages.
Nozzle body 8 consisting of nozzle 4 and B nozzle 15 and A nozzle 14
A gas inlet for supplying a source gas to the reactor, a B gas inlet for supplying a different source gas to the B nozzle 15, and a purge gas inlet pipe for introducing a purge gas to a peripheral portion of the reaction vessel 1; 8 has a cross section similar to that of the reaction vessel, in the vicinity of the opening, the A nozzle 14 and the B nozzle 15 have a flat rectangular cross section, the opening of the A nozzle 14 is located immediately before the substrate, and the opening of the B nozzle 15 is also A thin film vapor phase growth apparatus characterized in that different source gases are mixed immediately before the substrate near the substrate, and the purge gas flows around the nozzle body 8 to prevent backflow and stagnation of the source gas.