JPH0953179A - Gas introducing structure and cvd device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a gas introducing structure promoting the gas mixing and decomposing reaction by improving the method for introducing reaction gases, improving the uniformity of the film thickness in batch treatment by reducing the dispersion of the mixing and decomposing reaction and furthermore improving the treating capacity by reducing the approach distance or space region or reducing the number of sacrificial dummies and to obtain a CVD device. SOLUTION: This is a vertical low pressure CVD device using two kinds of reaction gases. In a reaction tube 1 for forming a desired thin film on a semiconductor wafer by a CVD method, a feed nozzle 5 for one reaction gas has an approximately L shape and a feed nozzle 6 for the other has an I shape, and the feed nozzles 5 and 6 for two kinds of reaction gases are arranged in such a manner that their tips are made extremely close. A large flow rate of reaction gas of SiH4 is fed from the feed nozzle 5 having an approximately L shape, a small flow rate of reaction gas of PH3 is fed from the feed nozzle 6 having an I shape, and the two kinds of reaction gases are mixed near the tips of the feed nozzles 5 and 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor thin film forming technique, for example, CVD using two or more kinds of reaction gases.
In the gas introduction structure of (Chemical Vapor Deposition) method, in particular, this gas introduction structure is used in a vertical low-pressure CVD apparatus to improve the film thickness uniformity of the processing result and further to improve the processing capacity, and the gas introduction structure is used. The present invention relates to a technique effectively applied to a CVD device.

[0002]

2. Description of the Related Art For example, as a technique studied by the inventor, in a manufacturing process of a semiconductor integrated circuit device, a plurality of semiconductor wafers aligned and held by a jig or the like are collectively accommodated in a reaction tube and a predetermined amount of semiconductor wafers are accommodated. There is a CVD apparatus which performs a thin film forming process by a chemical vapor deposition reaction or the like in a batch process under conditions of temperature and a reaction gas atmosphere.

In such a CVD apparatus, for example, a low pressure CV using a vertical reaction tube for increasing the wafer mounting density is used.
There is a D device, and this system enables high-density wafer filling because semiconductor wafers are horizontally loaded on a vertical wafer boat. The problem of this system is how to uniformly supply the reaction gas to each semiconductor wafer in the reaction tube.

In the low pressure CVD apparatus using the vertical reaction tube, for example, as a method of introducing two kinds of reaction gases into the reaction tube, there is a structure in which the reaction gas is introduced toward the exhaust direction by separate supply nozzles. It is commonly used. Therefore, a method has been adopted in which the reaction gas is sufficiently mixed by providing a sufficient run-up distance until the reaction gas is mixed, or by providing a sacrificial dummy of the semiconductor wafer or a space region where the semiconductor wafer is not loaded. .

A technique relating to such a CVD apparatus is described in documents such as "LSI Handbook" P307 to P318 published by Ohmsha Co., Ltd., edited by The Institute of Electronics and Communication Engineers on November 30, 1984. ing.

[0006]

By the way, in the structure in which the two kinds of reaction gases are introduced from separate supply nozzles as described above, the mixing and decomposition reactions of the reaction gases in the vicinity of the gas introduction portion are not sufficient. Therefore, it is difficult to make the film thickness of all the semiconductor wafers uniform by ensuring these conditions. In particular, it becomes remarkable in the case of two kinds of reaction gases having a large difference in reactivity.

For example, only about 2/3 of the film thickness uniformity of the semiconductor wafers loaded on the wafer boat can be obtained, and the number of processed semiconductor wafers is limited.
Therefore, the limitation of the number of wafers to be processed due to such a variation in the film thickness of the processing result is greatly related to the processing capacity, and further affects the price problem.

Therefore, an object of the present invention is to improve the method of introducing the reaction gas to further promote the mixing / decomposing reaction of the reaction gas in the gas introducing section and to reduce the variation of the mixing / decomposing reaction, thereby performing the batch processing. The film thickness uniformity in
Another object of the present invention is to provide a gas introduction structure capable of reducing the run-up distance or space region or reducing the number of sacrificial dummies to improve the processing capacity, and a CVD apparatus using the same.

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

[0010]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

That is, the gas introduction structure of the present invention is applied to the CVD method using two or more kinds of reaction gases, and the tips of the supply nozzles of the two or more kinds of reaction gases are arranged as close as possible to each other and supplied. The reaction gas is mixed and introduced near the nozzle tip.

Another gas introduction structure is one in which reaction gases are mixed and introduced in a supply nozzle for two or more kinds of reaction gases or in a gas pipe connected to the supply nozzles.

Particularly, as the two or more kinds of reaction gases,
Gases having greatly different reactivities or gases having greatly different flow rates are used.

Further, the CVD apparatus of the present invention uses the above-mentioned gas introduction structure to introduce two or more kinds of reaction gases into the reaction tube, and the CVD method is performed on the semiconductor wafer accommodated in the reaction tube. To form a desired thin film.

In particular, this CVD apparatus is used as a low pressure CVD apparatus using a vertical reaction tube, and a plurality of semiconductor wafers horizontally loaded on a wafer boat are accommodated inside the vertical reaction tube, and the plurality of semiconductor wafers are batch processed. Thus, the thin film forming process is collectively performed, and the wafer boat can be rotated.

[0016]

The above-mentioned gas introduction structure and CV using the same
According to the apparatus D, the tip of the reaction gas supply nozzle is arranged as close as possible, or the reaction gas is mixed inside the supply nozzle or inside the gas pipe, so that, for example, C
It is possible to promote the mixing / decomposition reaction of two or more kinds of reaction gases in the gas introduction part of the reaction tube of the VD device.

As a result, the inside of the reaction tube is made uniform by accelerating the mixing / decomposing reaction of the reaction gas, so that the variation in the mixing / decomposing reaction can be reduced and the uniformity of the film thickness can be improved. Further, by promoting the reaction gas mixing / decomposition reaction, the run-up distance or the space region can be reduced, or the number of sacrificial dummies can be reduced, so that the number of processed wafers can be improved.

Particularly, the reactivity or the flow rate is greatly different.
When using more than one kind of reaction gas, when using a vertical reaction tube for forming thin films of a plurality of semiconductor wafers by batch processing, and when using a low-pressure CVD device capable of rotating a wafer boat, Since the film thickness can be made uniform and the number of processed films can be increased, the throughput in the thin film forming process can be improved.

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(Embodiment 1) FIG. 1 is a schematic view showing the structure of a CVD apparatus which is an embodiment of the present invention, and FIGS. 2 (a) and 2 (b) are plan sectional views of a reaction tube in the CVD apparatus of this embodiment. FIG. 3 is a schematic diagram showing a side cross section.

First, the structure of the CVD apparatus of this embodiment will be described with reference to FIG.

The CVD apparatus of this embodiment is a vertical low-pressure CVD apparatus using, for example, two types of reaction gases.
A reaction tube 1 for forming a desired thin film on a semiconductor wafer by a method, a heater 2 for heating from the outside of the reaction tube 1, and a transfer chamber 3 for transferring a semiconductor wafer loaded on a wafer boat into the reaction tube. , A transfer robot 4 for transferring semiconductor wafers between a cassette and a wafer boat.

In the reaction tube 1, as shown in FIG. 2 (a), for example, one reaction gas supply nozzle 5 has a substantially L-shape and the other supply nozzle 6 has an I-shape. The tips of the reaction gas supply nozzles 5 and 6 are arranged as close to each other as possible. For example, a large flow rate of reaction gas is supplied from the substantially L-shaped supply nozzle 5, and a small flow rate of reaction gas is supplied from the I-shaped supply nozzle 6.

Further, as shown in FIG. 2, the inside of the reaction tube 1 is composed of an inner tube 7 and an outer tube 8.
A wafer boat 10 in which a semiconductor wafer 9 is loaded is housed in the inner tube 7 which is sealed from the outside by an O-ring or the like in a heavy structure. A heat retaining cylinder 11 is arranged below the wafer boat 10, and the heat retaining cylinder 11 is provided as a preheating region.

Further, inside the reaction tube 1,
Two kinds of reaction gases supplied from the two supply nozzles 5 and 6 are heated and supplied to the inside of the inner tube 7 in which the wafer boat 10 is housed, and a thin film is accumulated on the semiconductor wafer 9 by a thermal decomposition reaction. The residual gas passes through the upper part inside the reaction tube 1, between the inner tube 7 and the outer tube 8 and is discharged to the outside by a vacuum pump.

The heater 2 adopts a hot wall system by resistance heating or induction heating, for example, and heating from the outside of the reaction tube 1 promotes decomposition reaction of the reaction gas by thermal energy.

The transfer chamber 3 is, for example, a boat elevator 1
2, the wafer boat 10 on which the semiconductor wafers 9 are loaded is moved up and down, the wafer boat 10 is moved up into the reaction tube 1 for the thin film forming process, and is lowered into the transfer chamber 3 after the process is completed. Then, the semiconductor wafer 9 is transferred.

The transfer robot 4 is, for example, a robot that vacuum-sucks the semiconductor wafers 9 in a depressurized state, and one or several semiconductor wafers 9 before thin film formation processing are housed in a cassette (not shown). Boat 10
Wafer boat 10 after completion of processing.
To be transferred to a cassette.

Next, regarding the operation of this embodiment, SiH ₄
A case where a doped polysilicon film such as a gate electrode is formed by using two kinds of reaction gases, i.e., PH ₃ and PH ₃ , will be described.

In the thin film forming process, first, the transfer robot 4 transfers a plurality of semiconductor wafers 9 from the cassette to the wafer boat 1 inside the transfer chamber 3 from a cassette one by one or several cassettes.
Then, the wafer boat 10 on which a plurality of semiconductor wafers 9 are loaded is transferred from the inside of the transfer chamber 3 to the inside of the reaction tube 1 by the boat elevator 12.

Further, inside the reaction tube 1, a temperature of about 600 ° C. is obtained from the outside of the reaction tube 1 by heating with the heater 2, and two kinds of reaction gases for forming a thin film are introduced, and a predetermined temperature and reaction are performed. A plurality of semiconductor wafers 9 loaded on the wafer boat 10 under the gas atmosphere condition
A desired thin film is deposited on the surface of the substrate by the CVD method.

In this case, a large flow rate of SiH ₄ gas is supplied to the inside of the reaction tube 1 from the substantially L-shaped supply nozzle 5 toward the tip direction of the I-shaped supply nozzle 6, and the I-shaped supply nozzle 6 is supplied. A small flow rate of PH ₃ gas is supplied from the mold supply nozzle 6. As a result, the high flow rate SiH ₄ gas is easily mixed with the low flow rate PH ₃ gas, and two types of reaction gases are supplied to the supply nozzle 5,
It can be sufficiently mixed near the tip of 6.

Then, the sufficiently mixed SiH ₄ gas and PH ₃ gas are supplied to the inside of the inner tube 7 in which the wafer boat 10 is accommodated, and pyrolyzed under the conditions of a predetermined temperature and a reaction gas atmosphere. By the reaction, a doped polysilicon film of polysilicon doped with P is formed on the semiconductor wafer 9 loaded on the wafer boat 10.

As a result, with respect to the semiconductor wafers 9 loaded on the wafer boat 10, a sufficiently mixed reaction gas can be supplied to the semiconductor wafers 9 loaded on the lower side of the wafer boat 10. It is possible to promote the mixing / decomposition reaction in all the semiconductor wafers 9 loaded on the wafer boat 10 and reduce the variation.

Furthermore, after the doped polysilicon film is formed on the plurality of semiconductor wafers 9 inside the inner tube 7, residual gas from the two reaction gases after the treatment is removed from the reaction tube 1 by the reaction gas. It is discharged from the upper part of the inside through a space between the inner tube 7 and the outer tube 8 to the outside by a vacuum pump.

After that, the wafer boat 10 on which the plurality of semiconductor wafers 9 for which the thin film forming process has been completed is loaded is moved from the inside of the reaction tube 1 to the transfer chamber 3 by the boat elevator 12.
After that, the plurality of semiconductor wafers 9 are transferred one by one or several semiconductor wafers 9 from the wafer boat 10 to the cassette by the transfer robot 4. As a result, the thin film forming process for the plurality of semiconductor wafers 9 in one cassette is completed, and the above process is repeated for each cassette thereafter.

Therefore, according to the CVD apparatus of this embodiment,
By making the SiH ₄ gas supply nozzle 5 substantially L-shaped and the PH ₃ gas supply nozzle 6 I-shaped so that the tips of the supply nozzles 5 and 6 are as close as possible to each other, the tips of the supply nozzles 5 and 6 are close to each other. Since the decomposition reaction is promoted by the sufficient mixing of the gas in (1), the gas supply and accumulation state in the preheating region is improved, and the film thickness uniformity of the thin film on the semiconductor wafer 9 can be improved over a wide range.

In particular, a large flow rate of SiH ₄ gas is used for a small flow rate of P
High flow rate of SiH by supplying toward H ₃ gas
It is possible to sufficiently mix the ₄ gas and the PH ₃ gas with a small flow rate in the vicinity of the tips of the supply nozzles 5 and 6.

Further, since the preheating area can be reduced,
Since the run-up distance or the space area can be reduced or the number of sacrificial dummies can be reduced, the number of processed semiconductor wafers 9 can be increased by about 15%.

(Embodiment 2) FIG. 3 is a schematic view showing a plane cross section of a reaction tube in a CVD apparatus which is another embodiment of the present invention.

The CVD apparatus of the present embodiment is a vertical low pressure CVD apparatus using two kinds of reaction gases as in the case of Embodiment 1. The difference from Embodiment 1 is the gas introduction structure into the reaction tube. It is a point. That is, the reaction tube 1a of this embodiment has a structure in which two kinds of reaction gases are mixed inside the supply nozzles 5a and 6a before the reaction gas is introduced into the reaction tube 1a. As shown in FIG. ₃ , the tip of the SiH ₄ gas supply nozzle 5a and the PH ₃ gas supply nozzle 6a are connected to each other, so that a sufficiently mixed reaction gas can be supplied into the reaction tube 1a.

Therefore, according to the CVD apparatus of this embodiment,
By connecting the tips of the SiH ₄ gas supply nozzle 5a and the PH ₃ gas supply nozzle 6a to each other, the gas supply and accumulation state in the preheating region is improved in the same manner as in Example 1, and the thin film film on the semiconductor wafer is widely spread. Since the thickness uniformity can be improved and the preheating area can be reduced, the number of processed semiconductor wafers can be increased.

(Embodiment 3) FIG. 4 is a schematic view showing a side cross section of a reaction tube in a CVD apparatus which is still another embodiment of the present invention.

The CVD apparatus of this embodiment is a vertical low-pressure CVD apparatus using two kinds of reaction gases as in the case of Embodiments 1 and 2. In addition to the gas introduction structure of Embodiments 1 and 2, a wafer is further added. The structure is such that the boat is rotated. That is, in the reaction tube 1b of this example,
At the same time when the reaction gas is introduced into the reaction tube 1b, as shown in FIG.
As shown in, the wafer boat 10b on which a plurality of semiconductor wafers are loaded can be rotated.

Therefore, according to the CVD apparatus of this embodiment,
Since the wafer boat 10b can rotate, the first embodiment
Since it is possible to further promote the mixing of two kinds of reaction gases as compared with 2 and 2, it is possible to further improve the gas supply and accumulation state in the preheating region and further improve the film thickness uniformity of the thin film on the semiconductor wafer in a wide range. Moreover, since the preheating area can be reduced, the number of processed semiconductor wafers can be further increased.

Although the invention made by the present inventor has been specifically described based on the first to third embodiments, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. It goes without saying that it is possible.

For example, with respect to the CVD apparatus of the above-mentioned embodiment, the case where a doped polysilicon film such as a gate electrode is formed by using two kinds of reaction gases of SiH ₄ and PH ₃ has been described. Insulating film such as HTO (High-Temperature-Oxide) film by two kinds of reaction gas of SiH ₄ and PH ₃ ,
It can be widely applied to an insulating film such as a nitride film, an oxide film or a PSG film, and other metal CVD film.

Needless to say, when three kinds of reaction gases are used, it can be widely applied as a gas introduction structure when more reaction gases are used.

In the above description, the case where the invention made by the present inventor is mainly applied to the vertical low-pressure CVD apparatus, which is the field of use thereof, has been described, but the present invention is not limited to this, and other CVD such as horizontal CVD is used. Equipment, two more
It is also widely applicable to other devices that use more than one type of reaction gas.

[0050]

Advantageous effects obtained by typical ones of the inventions disclosed in the present application will be briefly described.
It is as follows.

(1). By disposing the tip of the reaction gas supply nozzle as close as possible, it is possible to sufficiently mix and introduce two or more kinds of reaction gases near the tip of the supply nozzle. It becomes possible to promote the mixing / decomposition reaction of two or more kinds of reaction gases.

(2). By mixing the reaction gas in the reaction gas supply nozzle or in the gas pipe to which this supply nozzle is connected, as in the above (1), the gas in the gas introduction part
It becomes possible to promote the mixing / decomposition reaction of more than one kind of reaction gas.

(3). In particular, by using reaction gases whose reactivities or flow rates greatly differ from each other, mixing of two or more kinds of reaction gases
Even if the difference in the decomposition reaction becomes noticeable, it is possible to reduce the variation in the mixing / decomposition reaction by homogenizing the reaction gas by promoting the mixing / decomposition reaction.

(4). When used in a CVD apparatus for forming a desired thin film on a semiconductor wafer by a CVD method, the inside of the reaction tube is cleaned by accelerating the mixing / decomposition reaction of the reaction gas in the gas introducing part of the reaction tube. Since it can be made uniform, it is possible to improve the uniformity of the film thickness by reducing the variation in the mixing / decomposition reaction.

(5) By the above (4), the reaction gas mixing / decomposition reaction is promoted, so that the supply / accumulation state of the reaction gas is improved in a wide range inside the reaction tube, and the running distance or the space region is reduced. Alternatively, the number of sacrificial dummies can be reduced, so that the number of processed sheets can be improved.

(6) Especially when a low pressure CVD apparatus using a vertical reaction tube is used as the CVD apparatus or when a wafer boat on which a plurality of semiconductor wafers are horizontally loaded is rotated,
It becomes possible to collectively perform a thin film forming process of a uniform film thickness on a plurality of semiconductor wafers by batch processing.

(7) By the above (1) to (6), it is possible to further improve the mixing / decomposition reaction of the reaction gas in the gas introducing section in the structure for introducing two or more kinds of reaction gas and the CVD apparatus using the structure. The uniformity of the film thickness in the batch process is improved by promoting the dispersion and reducing the variation of the mixing / decomposition reaction.
Moreover, since the number of processed sheets can be increased, the throughput in the thin film forming process can be improved.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the configuration of a CVD apparatus that is Embodiment 1 of the present invention.

2 (a) and 2 (b) are schematic views showing a plane cross section and a side cross section of a reaction tube in the CVD apparatus of Example 1. FIG.

FIG. 3 is a schematic view showing a plane cross section of a reaction tube in a CVD apparatus that is Embodiment 2 of the present invention.

FIG. 4 is a schematic view showing a side cross-section of a reaction tube in a CVD apparatus that is Embodiment 3 of the present invention.

[Explanation of symbols]

 1, 1a, 1b Reaction tube 2 Heater 3 Transfer chamber 4 Transfer robot 5,5a Supply nozzle 6,6a Supply nozzle 7 Inner tube 8 Outer tube 9 Semiconductor wafer 10, 10b Wafer boat 11 Heat retaining tube 12 Boat elevator

Claims (7)

[Claims] 1. A gas introduction structure for a CVD method using two or more kinds of reaction gases, wherein the tip of a supply nozzle for the two or more kinds of reaction gases is arranged as close as possible, and the two or more kinds of reaction gases are A gas introduction structure characterized by being mixed and introduced near the tip of a supply nozzle. 2. A gas introduction structure of a CVD method using two or more kinds of reaction gas, wherein the two kinds are provided in a supply nozzle for the two or more kinds of reaction gas or in a gas pipe to which the supply nozzle is connected. A gas introduction structure characterized in that the above reaction gases are mixed and introduced. 3. The gas introducing structure according to claim 1 or 2, wherein the two or more kinds of reactive gases are gases having greatly different reactivities. 4. The gas introducing structure according to claim 1, 2 or 3, wherein the two or more kinds of reaction gases have different flow rates from each other. 5. A CVD apparatus using the gas introduction structure according to claim 1, wherein the two or more kinds of reaction gases are introduced into a reaction tube, and the reaction tube is introduced into the reaction tube. A CVD apparatus in which a desired thin film is formed on a contained semiconductor wafer by a CVD method. 6. The CVD apparatus according to claim 5, wherein the CVD apparatus is a low pressure CVD apparatus using a vertical reaction tube, and a plurality of semiconductors horizontally loaded on a wafer boat inside the vertical reaction tube. A CVD apparatus, in which wafers are accommodated, and a plurality of semiconductor wafers are collectively subjected to thin film formation processing by batch processing. 7. The CVD apparatus according to claim 6, wherein a wafer boat on which the plurality of semiconductor wafers are horizontally loaded is rotatable.