JP3173697B2 - Vertical heat treatment 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 vertical heat treatment apparatus.

[0002]

2. Description of the Related Art One of the heat treatment processes in a semiconductor wafer manufacturing process is a low pressure CVD (chemical vapor deposition).
There is a process called. The low pressure CVD is a method of forming a film forming component in a processing gas on a surface of a semiconductor wafer (hereinafter, referred to as “wafer”) by a gas phase reaction under a low pressure.
As such a device, a vertical heat treatment device with little air entrainment is becoming mainstream.

As shown in FIG. 5, a conventional vertical low-pressure CVD apparatus has a double-walled reaction tube 1 composed of an inner tube 1a and an outer tube 1b made of quartz, and surrounds the reaction tube 1. It has a heater 11 provided and a stainless steel manifold 12 provided on the lower side of the reaction tube 1. A plurality of gas introduction tubes are provided around the manifold 12 so that a plurality of types of processing gases can be introduced. 13 (only one is shown in the figure) and an exhaust pipe 14 are connected. And CV
In performing D, a large number of wafers W are stacked on the wafer boat 15, the boat elevator 16 is raised to load the wafers W, and the inside of the reaction tube 1 is heated to a predetermined temperature and maintained at a predetermined degree of vacuum. While the processing gas is being supplied to the reaction tube 1
And a thin film is formed on the surface of the wafer W by CVD.

[0004]

When performing low-pressure CVD, stainless steel manifolds 12 are used to cope with a plurality of types of processing, so that they have corrosion resistance. When a gas having a large value is used, corrosion is promoted. Therefore, at high temperatures, there is a problem that the type of gas used is limited.

Further, the present inventors have proposed an oxidation / diffusion treatment and a reduced pressure C
We are studying a vertical heat treatment system that can perform VD and VD in a common furnace.
(Hydrogen chloride) may be mixed into the processing gas. This HCl has the advantage of removing impurities to the outside and obtaining a high-quality film. However, in the presence of H ₂ O, it exhibits extremely strong corrosiveness, corrodes the inner peripheral surface of the stainless steel manifold 12, and generates particles and heavy metals. It becomes a source of pollution.
If the manifold is made of quartz, the problem of corrosion can be solved. However, it is difficult to manufacture and the price is high, and it is difficult to join the external piping and the intake / exhaust port.

The present invention has been made under such circumstances, and an object of the present invention is to provide a vertical heat treatment apparatus having a high degree of freedom in processing.

[0007]

According to a first aspect of the present invention, a metal manifold to which a gas supply pipe and an exhaust pipe are connected is provided at a lower portion of a vertical reaction tube, and a large number of objects to be processed are provided. In a vertical heat treatment apparatus mounted on a holder and carried into a reaction tube from a lower end opening of a manifold, a cover made of a heat-resistant material provided so as to cover an inner peripheral surface of the manifold, and an inner periphery of the cover and the manifold And an inert gas introducing means for introducing an inert gas into a gap between the surface and the surface.

According to a second aspect of the present invention, in the first aspect of the present invention, the cover is made of quartz, and a pipe fitting hole is formed in a side peripheral surface of the cover, and the periphery of the pipe fitting hole is made flat. The inner end portion of the gas supply pipe and / or the exhaust pipe is made of quartz and fitted into the pipe fitting hole.

According to a third aspect of the present invention, in the second aspect of the present invention, the cylindrical body made of quartz having a flange portion is provided on an inner surface or an outer surface of a flat portion around a hole for fitting a pipe. The gas supply pipe and / or the exhaust pipe are inserted into the cylindrical body while being fitted into a pipe fitting hole so as to make contact with the pipe.

According to a fourth aspect of the present invention, in the second aspect of the present invention, a flange portion made of quartz is integrally formed at an inner end portion of the gas supply pipe and / or the exhaust pipe, and the flange portion is used for fitting a pipe. The inner end portion is inserted into a hole for fitting a pipe so that the inner surface or the outer surface of the flat portion around the hole is in surface contact.

[0011]

According to the first aspect of the present invention, since a cover made of a heat-resistant material is provided so as to cover the inner peripheral surface of the manifold and an inert gas is supplied to a gap therebetween, the manifold is purged with the inert gas. Is prevented from coming into contact with the processing gas, and corrosion of the manifold can be prevented.

According to the second or fourth aspect of the present invention,
A through-hole is formed in the cover made of quartz, and the periphery of the through-hole is flat, and the quartz pipe on the inner end side of the gas pipe (gas supply pipe and exhaust pipe) is fitted to the flat face. The gap can be reduced and the manufacture is easy. In this case, if the gas pipe is inserted into the cylindrical body as in the third aspect of the invention, and the flange portion of the cylindrical body is brought into surface contact with the flat portion, the diameter of the quartz tube and the through hole of the cover can be reduced. No high position accuracy is required.

[0013]

FIG. 1 is a view showing a vertical heat treatment apparatus according to an embodiment of the present invention, and FIGS. 2 and 3 are a cross-sectional view and an exploded perspective view showing a main part of the vertical heat treatment apparatus of FIG. 1, respectively. . Reaction tube 2
Is an inner tube 2a made of a heat-resistant material, for example, quartz, both ends of which are open and arranged in the vertical direction, and a bottomed cylindrical shape, for example, quartz, which is concentrically arranged via a gap so as to surround the inner tube 2a. And an outer tube 2b composed of

Outside the reaction tube 2, a heating furnace 23, which is constituted by attaching a heater 22 made of a resistance heating wire inside the heat insulator 21, is disposed so as to surround the reaction tube 2. The reaction tube 2 is held by a manifold 3 fixed to a base plate 30.
Is made of, for example, stainless steel. A cap 31 made of, for example, stainless steel is provided at the lower end opening of the manifold 3 so as to be openable and closable, and when closed, the opening is hermetically sealed via an O-ring (not shown).

The cap portion 31 is disposed on a boat elevator 24 which is lifted and lowered by, for example, a ball screw. On the cap portion 31, a wafer boat 26 made of, for example, quartz is placed via a heat retaining tube 25. . The wafer boat 26 is for holding a large number of wafers W stacked one above the other in a horizontal state. However, in the example of FIG. 2, a rotation mechanism 28 having a rotation shaft 27 is attached to the boat elevator 24, and the heat retaining cylinder 25 is connected to the rotation shaft 2.
7 and is mounted on a turntable 29 that rotates.

A cover 4 made of a heat-resistant material such as quartz is provided inside the manifold 3 so as to cover the inner peripheral surface of the manifold 3. The cover 4 has a smaller diameter on the lower side than the diameter on the upper side, and a step portion in the middle thereof contacts the annular projecting piece 32 formed on the inner peripheral surface of the manifold 3. The outer edge of the upper end is engaged with the inner edge of the upper end of the manifold 3.

A ring member 33 made of a heat-resistant material such as quartz is provided on the upper surface of the cap portion 31.
Is embedded concentrically with respect to the ring member 3.
The outer edge portion and the inner edge portion of 3 have upstanding pieces 34 and 35 (see FIG. 2) that are bent upright. The lower end of the cover 4 is provided with an upright piece 34 on the outer edge side of the ring member 33.
And at a constant interval (0.05 to 0.7 cm). At the bottom of the heat retaining cylinder 25, a leg 25a is formed in an annular shape, and the leg 25a of the thermal retaining cylinder 25 is spaced apart from the outside of the upright piece 35 on the inner edge side of the ring member 33 by a predetermined distance (0.05). ０．７0.7 cm).

On the side of the manifold 3, an inner pipe 2a is provided.
A first gas supply pipe 5 for supplying a processing gas to a region inside the first pipe is connected to a first exhaust pipe 6 for exhausting the processing gas from a gap between the inner pipe 2a and the outer pipe 2b. Have been. The gas supply pipe 5 and the exhaust pipe 6 are piping systems used for low-pressure CVD, and a gas supply source and a vacuum pump (not shown) are connected to outer ends of the gas supply pipe 5 and the exhaust pipe 6, respectively. .

Further, a second gas supply pipe 7 for supplying a processing gas to a gap between the inner pipe 2a and the outer pipe 2b is provided on a side surface of the manifold 3 separately from a piping system for reduced pressure CVD. And a second exhaust pipe 7 for exhausting the processing gas from a region inside the inner pipe 2a. The second gas supply pipe 7 and the exhaust pipe 8 are piping systems used for oxidation treatment, and include a gas supply pipe 7 and an exhaust pipe 8.
Are connected to a gas supply pipe and an exhaust pump (not shown), respectively.

Here, the connection structure between the pipe system and the cover 4 will be described with reference to FIGS. For example, in the first gas supply pipe 5, an inner end portion extending from the intake port 51 to the inside of the manifold 3 is constituted by a quartz tube 52, and the inner end of the quartz tube 52 is bent upward, and Outside from 51 is stainless steel tube 53
It consists of.

On the other hand, a circular through-hole 41 (see FIG. 3) corresponding to the first gas supply pipe 5 is formed on the side peripheral surface of the cover 4, and the through-hole 41 is formed in the through-hole 41. 41
A quartz plate (in this example, formed in a ring shape as can be seen from FIG. 3) 54 which has a shape conforming to the above and forms a flat surface having a thickness sufficient to close the through hole 41 is formed. Mated and welded. A hole 55 (see FIG. 3) for fitting a pipe is formed in the quartz plate 54, a flange 56 is formed on the inner end side, and the inside diameter of the quartz tube 52 is
A cylindrical body 57 made of quartz suitable for the diameter of the tube is fitted into the hole 55 of the quartz plate, and the inner surface of the flange 56 is in surface contact with the inner surface of the quartz plate 54. The hole 55 is larger than the outer diameter of the cylindrical body 57 by about 4 mm.
And the cover 4 can absorb the axial misalignment. Further, a quartz tube 52 is inserted into the cylindrical body 57,
Thus, in this example, the quartz tube 52 is fitted to the pipe fitting hole 55 of the quartz plate 54 via the tubular body 57.

The second gas supply pipe 7 and the exhaust pipe 8 are connected to the cover 4 in the same manner, but in this example, the first exhaust pipe 6 does not use a cylindrical body. It is different from the piping connection structure. That is, the tube wall of the inner end portion of the quartz tube in the first exhaust pipe 6 is cut off from the outside and reduced in diameter, and the reduced diameter portion 6a is fitted into the through hole 65 of the quartz plate 64 and the tube wall is formed. The step portion 6 b is in contact with the inner peripheral surface of the quartz plate 64.

2 and 3, reference numerals 42 to 44 denote through holes, 6
1, 81 are exhaust ports, 71 is intake ports, 62, 7
2, 82 are quartz tubes, 63, 73, 83 are stainless steel tubes,
64, 74 and 84 are quartz plates welded to the cover 4;
5, 75 and 85 are holes for fitting pipes, 76 and 86 are flanges,
Numerals 77 and 87 are cylindrical bodies made of quartz.

On the upper and lower sides of the manifold 3, an inert gas such as N ₂ gas is introduced into the gap S between the inner peripheral surface of the manifold 3 and the cover 4 to prevent the processing gas from entering. Gas supply means, for example, gas supply pipes 40a and 40b are connected respectively.

The cap 31 has a cap 31
A gas supply pipe 40c for introducing N ₂ gas is connected to a gap between the heat insulation cylinder 25 and the gas supply pipe 40c.

Next, the operation of the above embodiment will be described.
First, the inside of the reaction tube 2 is heated to, for example, a uniform temperature of 780 ° C. by the heater 22, and the wafer W to be processed is
The wafers are held in a wafer boat 35 in a shelf shape and loaded into the reaction tube 2 by a boat elevator 33. Next, the inside of the reaction tube 2 is evacuated to a reduced pressure on the order of, for example, 10 ⁻³ Torr by a vacuum pump (not shown) through the first exhaust pipe 6, and then the processing gas, for example, ammonia (ammonia) is passed through the first gas supply pipe 5. NH ₃ ) gas and dichlorosilane (SiH)
₂ Cl ₂ ) gas at a flow rate of, for example, 0.03 l / min and 0.03 l / min.
To the area inside.

The pressure inside the reaction tube 2 is maintained at a reduced pressure of, for example, 1 Torr while controlling the inner tube 2a.
The gas is evacuated from the gap between the outer tube 2b and the outer tube 2b through the exhaust tube 6, and a Si ₃ N ₄ film is formed on the surface of the wafer W. At this time, the gas supply pipes 40a to 40c supply N ₂ gas into the gap S between the cover 4 and the manifold 3 and the gap between the cap portion 31 and the heat retaining cylinder 25 to prevent the processing gas from entering the gap. Preventing. In this embodiment, the cover 4 is placed in the manifold 3 and the heat retaining cylinder 25 is merely placed on the cap portion 31. Therefore, there is a gap between them and N ₂ gas (nitrogen gas). A part of the gas flows out from the gap toward the inside of the furnace with respect to the cover 4, and the other part is sucked into the stainless steel pipe 63 through a gap between the exhaust port 61 and the quartz pipe 62 in the exhaust pipe 6.

Thereafter, the atmosphere in the reaction tube 2 is changed to, for example, N ₂
The temperature inside the reaction tube 2 is raised to about 1000 ° C. at a rate of, for example, 50 ° C./min while replacing with the gas. The replacement with the N ₂ gas is performed by the first exhaust pipe 6 while supplying the N ₂ gas from the gas supply pipe (not shown) provided in the manifold 3 to the inside of the inner pipe 2 a, similarly to the first gas supply pipe 4. This is performed by evacuating.

Then, after the evacuation is stopped, for example, H ₂ gas is supplied between the inner pipe 2 a and the outer pipe 2 b by the second gas supply pipe 6.
O and HCl are supplied at a flow rate of 10 liters / minute and 1 liter / minute, respectively, and are evacuated from the inside of the inner tube 2a through the second exhaust tube 8 to bring the inside of the reaction tube 2 to normal pressure. Thus, the surface of the Si ₃ N ₄ film is oxidized to
An iO ₂ film is formed. Even during this oxidation process, N ₂ gas is purged into the gap S from the gas supply pipe 40.

According to the above-described embodiment, the inner peripheral surface of the manifold is covered with the cover 4 made of quartz, and the gap S between the cover 4 and the manifold 3 is supplied with N ₂ gas for purging. _{The two} gases shut off the manifold 3 and the processing gas atmosphere, and the corrosion of the manifold 3 is prevented even when a highly corrosive gas is used at a high temperature. Therefore, for example, using a gas for oxidation treatment including HCl gas, 1000
Even if the oxidation treatment is performed at a high temperature of not less than ° C., the corrosion of the manifold 3 does not progress, so that it can be used as a device that can share the CVD and the oxidation treatment.

Then, through holes 41 to 4 are formed in the side peripheral surface of the cover 4.
4 and quartz plates 54, 64, 74, 84
And the connection structure between the gas pipes (5 to 8) and the cover 4 can be minimized, and the through holes 41 to 44 can be minimized. Is easy to manufacture because the positional accuracy of the device may be low. That is, when the quartz tubes 52, 62, 72, and 82 are integrated with the cover 4, the height position and the circumferential position of each of the intake port and the exhaust port of the manifold 3 are different. Although it is extremely difficult to attach 52, 62, 72, and 82, as described above, if the quartz tube 52 is inserted into the tubular body 57 with some margin, for example, the flange 56 and the quartz plate 74 are inserted. And the gap between the intake port or the exhaust port and the through hole is absorbed, and the flange 56 and the quartz plate 74 are in surface contact with each other, so that the gap can be reduced.

Also, when the stepped portion 6b is formed at the inner end of the quartz tube 62 and is inserted into the quartz plate 64 with some margin as in the case of the first exhaust pipe 6, the stepped portion 6b and the quartz plate 6
By the rubbing with No. 4, the displacement can be similarly absorbed. In this case, by making each of the quartz tubes 52, 62, 72, 82 slightly smaller than the diameter of the intake port (or the exhaust port), the above-mentioned displacement can be sufficiently absorbed. In addition, since the cap portion 31 also covers the space between the heat retaining cylinder 25 and the cover 4 with the quartz ring member 33, corrosion due to the processing gas is suppressed.

Further, since the film forming process and the oxidizing process are performed by using the common reaction tube 2, the throughput is remarkably improved and the space occupied by the device is greatly improved as compared with the case where the processes are performed by separate devices as in the prior art. It can be made narrower, and there is no possibility that the wafer W may be damaged due to the transfer of the wafer W.
After the formation of the Si ₃ N ₄ film, the SiO ₂ film is formed without carrying the wafer W out of the reaction tube 2, so that an unnecessary oxide film is not formed between these thin films. Also, impurities such as moisture are not mixed.

In the above description, the connection structure between the gas pipes (5 to 8) and the cover 4 may be a structure other than the above-described embodiment. For example, as shown in FIG. A flange 91 made of quartz is integrally formed on the outer surface of the manifold 4, while the periphery of the pipe fitting hole 45 of the manifold 4 is a flat surface 46, and the flange 91 is in surface contact with the inner surface or the outer surface of the flat surface 46. Alternatively, the inner end portion may be inserted into the hole 45. Note that such a structure may be applied to a case where the exhaust pipe is attached to the manifold. The material of the cover 4 is not limited to quartz, and the gap S between the cover 4 and the manifold 3 is not limited to quartz.
The inert gas supplied to the gas may be a gas other than the N ₂ gas.

Further, in the present invention, instead of having a structure in which the oxidation / diffusion furnace and the CVD furnace are combined as described above, a structure dedicated to the CVD furnace may be used.

[0036]

According to the first aspect of the present invention, since a cover made of a heat-resistant material is provided so as to cover the inner peripheral surface of the manifold and an inert gas is supplied to a gap therebetween, corrosion of the manifold is prevented. Thus, restrictions on the type of processing gas and the processing temperature can be relaxed.

According to the second and fourth aspects of the present invention, a pipe fitting hole is formed in a cover made of quartz, a flat surface is formed around the hole, and a gas pipe (gas supply pipe and exhaust pipe) is formed in the flat portion. Since the quartz tube on the inner end side of (2) is fitted, the gap between the gas pipe and the cover can be reduced, and the production is easy. In this case, the gas pipe is inserted into the cylindrical body as in the invention of claim 3, and the flange of the cylindrical body is brought into surface contact with the quartz plate, so that the diameter of the quartz pipe and the hole for fitting the pipe of the cover are formed. Since the positional accuracy of the is not so high, the manufacture is easy.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a sectional view showing a main part of the embodiment of the present invention.

FIG. 3 is an exploded perspective view showing a main part of the embodiment of the present invention.

FIG. 4 is an exploded perspective view showing a part of another embodiment of the present invention.

FIG. 5 is a cross-sectional view showing a conventional vertical heat treatment apparatus.

[Explanation of symbols]

2 Reaction tube 26 Wafer boat 3 Manifold 31 Cap part 4 Cover 5,7 Gas supply tube 6,8 Exhaust tube 51,61,71,81 Quartz tube 54,64,74,84 Quartz plate 57,67,87 Flange 40 Gas (N ₂ gas) introduction pipe S gap

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Akito Yamamoto 1 Toshiba-cho, Komukai Toshiba-cho, Saisaki-ku, Kawasaki City, Kanagawa Prefecture (56) References JP-A-2-86120 (JP, A) Kaihei 2-138730 (JP, A) JP-A 5-77933 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/31 H01L 21/205

Claims (4)

(57) [Claims] 1. A metal manifold to which a gas supply pipe and an exhaust pipe are connected is provided at a lower side of a vertical reaction tube, and a large number of workpieces are mounted on a holder, and a lower end opening of the manifold is provided. In a vertical heat treatment apparatus carried into a reaction tube, a cover made of a heat-resistant material provided so as to cover an inner peripheral surface of the manifold, and an inert gas is supplied to a gap between the cover and the inner peripheral surface of the manifold. A vertical heat treatment apparatus comprising: an inert gas introduction means for introducing. 2. A cover is made of quartz, a hole for fitting a pipe is formed on a side peripheral surface of the cover, and a periphery of the hole for fitting a pipe is a flat portion, and the inside of a gas supply pipe and / or an exhaust pipe is formed. 2. The vertical heat treatment apparatus according to claim 1, wherein an end portion is made of quartz and fitted into the pipe fitting hole. 3. A tubular body made of quartz having a flange portion is fitted into a pipe fitting hole such that the flange portion comes into surface contact with an inner surface or an outer surface of a flat portion around the pipe fitting hole. 3. The vertical heat treatment apparatus according to claim 2, wherein the gas supply pipe and / or the exhaust pipe are inserted into the cylindrical body. 4. A flange portion made of quartz is integrally formed on an inner end portion of the gas supply pipe and / or the exhaust pipe, and the flange portion faces an inner surface or an outer surface of a flat portion around a hole for fitting a pipe. The vertical heat treatment apparatus according to claim 2, wherein the inner end portion is inserted into a hole for fitting a pipe so as to be in contact with the pipe.