JP3130710B2 - Furnace tube for vertical diffusion furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a furnace core tube used in a vertical diffusion furnace for thermally diffusing impurities into a semiconductor substrate.

[0002]

2. Description of the Related Art FIGS. 3A and 3B are a cross-sectional view and an enlarged view of a portion A of a vertical diffusion furnace showing an example of the prior art. As shown in FIG. 3, a conventional vertical diffusion furnace for thermally diffusing impurities into a semiconductor substrate (hereinafter, referred to as a wafer) includes a heater 316 and a furnace core tube 311 which are installed perpendicularly to a floor, and
A boat 313 loaded with wafers 312 and a driving unit 31 for transporting the boat 313 into a furnace core tube 311
4, a boat mount 315 that connects the drive unit 314 and the boat 313 and closes the furnace port of the furnace core tube 311 during heat treatment;
A furnace core tube holder 317 for fixing the furnace core tube 311 was provided.

Next, the operation of the vertical diffusion furnace will be described by taking phosphorus diffusion using phosphorus oxychloride (POCl ₃ ) as an example. First, the boat 3 loaded with the wafer 312
13 is conveyed into the furnace core tube 311. The transport is performed by the drive unit 314
The operation is performed by the following operation. At this time, the inside of the furnace core tube 311 is previously heated and maintained at a base temperature of 500 to 800 ° C. by the heater 316. After entering the furnace, the wafer 312 is heated from the base temperature to a target processing temperature, for example, 1000 ° C. After the furnace core tube 311 reaches the processing temperature, the carrier gas (reactive gas) containing the phosphorus oxychloride is used.
Is introduced into the furnace from the upper part of the furnace core tube 311 through the reaction gas pipe 319 through the reaction gas inlet 318 and the wafer 31
Spread to 2. Here, the reaction gas diffused into the wafer 312 is exhausted from the exhaust port 320. After the diffusion for a certain period of time, the introduction of the reaction gas into the furnace core tube 311 is stopped and the temperature is lowered to the base substrate.
The wafer 312 and the wafer 312 are conveyed out of the furnace core tube 311. Thereafter, the wafer 312 is removed from the boat 313, and the processing is completed.

As an impurity source, phosphorus tribromide (PBr ₃ ) and the like have been used in addition to phosphorus oxychloride (POCl ₃ ).

[0005]

The conventional vertical diffusion furnace described above has a structure in which a reaction gas is introduced from the upper part of the furnace core tube 311 and exhausted from an exhaust port installed near the lower furnace port. Therefore, the reaction gas introduced into the furnace core tube is cooled as it moves away from the heating zone of the heater 316 as it approaches the furnace port. For this reason, the reaction gas is liquefied before being exhausted from the exhaust port, and the liquid reaction product adheres to the inner wall of the furnace core tube at the furnace opening, and propagates along the inner wall of the furnace core tube and accumulates on the end surface of the boat gantry.

For this reason, the accumulated reaction product is generated in the boat 3
At the time of entering and exiting the furnace 13, it scatters into equipment other than the furnace core tube 311 and contaminates and corrodes the inside of the equipment. There is a problem that abnormal diffusion of contact and re-diffusion occurs to cause abnormal junction formation and abnormal surface impurity concentration. This problem,
Failures due to abnormal electrical characteristics of the semiconductor device occur, which is a serious problem.

Accordingly, an object of the present invention is to prevent the reaction products generated by the condensation of the reaction gas from being contaminated and corroded in equipment other than the furnace core tube, and to reduce the reaction products due to residual heat of the boat and the wafer itself. An object of the present invention is to provide a furnace core tube for a vertical diffusion furnace which prevents abnormal diffusion of re-diffusion of a wafer with a vaporized gas.

[0008]

SUMMARY OF THE INVENTION A feature of the present invention is that a heater is provided on the outer periphery and an opening for a boat carrying a plurality of semiconductor substrates to be carried in and out is provided at a lower end, and a gas inlet is provided on an upper end. In the furnace core tube for a vertical diffusion furnace provided, an inner tube portion extending upward from the opening by a predetermined dimension is provided, and the bottom surface of a groove sandwiched between the inner tube portion and the outer tube portion is provided as the gas exhaust port. This is a vertical diffusion furnace core tube having a downward slope and connecting the gas exhaust port and the groove. Also, the slope of the groove
Provide an inert gas inlet through which inert gas flows
Is desirable.

[0009]

Next, the present invention will be described with reference to the drawings.

FIGS. 1A and 1B are a vertical sectional view and a horizontal sectional view of a bottom portion of a core tube for a vertical diffusion furnace showing an embodiment of the present invention. As shown in FIG. 1, this vertical diffusion furnace core tube has an inner tube portion 122 extending from the opening 110 into and out of which a boat base for loading a boat is carried in and out by a predetermined dimension toward the back.
The bottom surface 121 of the groove sandwiched between the inner pipe portion 122 and the outer pipe portion 111 has a downward slope toward the exhaust port 120. In addition, the end of the inner pipe portion 122 is formed so as to be inclined toward the exhaust port 120 so that the falling reaction product does not get on, and the edge portion is formed so as to be inclined toward the outside. It is desirable. Otherwise, it is the same as the conventional example.

By providing the groove having the inclined bottom surface 121, the reaction products generated by cooling the reaction gas accumulate in the groove. Since the bottom surface 121 of the groove is inclined toward the exhaust port 120, the reaction product flows toward the exhaust port 120 and is discharged. These operations are performed during the thermal diffusion of phosphorus to the wafer.
Then, after performing the thermal diffusion for a predetermined time, the temperature of the furnace core tube is lowered to a base temperature of 500 to 800 ° C. at the time of entering the furnace, the boat and the wafer are taken out of the furnace core tube, and the processing is completed.

FIGS. 2 (a) and 2 (b) are a longitudinal sectional view and a transverse sectional view of a bottom portion of a furnace core tube for a vertical diffusion furnace showing another embodiment of the present invention. As shown in FIG. 2, the furnace core tube for a vertical diffusion furnace is provided with an N ₂ gas inlet 112 for introducing nitrogen at a position of an outer tube portion 111 facing an exhaust port 120.
Other than that, it is the same as the above-mentioned embodiment.

[0013] The angle for the boat and out furnace direction of the furnace core tube of the N ₂ gas inlet 112 is at the same angle as the bottom surface 121, N ₂ gas introduced from the N ₂ gas inlet 222, The reaction product that has accumulated in the groove is exhausted 220
It works to flush away.

Therefore, in this embodiment, since the reaction products accumulated in the grooves are flushed toward the exhaust port 120 by the N ₂ gas, there is an advantage that the reaction product discharge ability is higher than that of the above-described embodiment. is there. Of course, the gas introduced from the N ₂ gas inlet 222 is not particularly limited to N ₂ gas, but may be an inert gas such as Ar gas.

[0015]

As described above, according to the present invention, the opening 1
By providing an inner pipe extending from the base 10 to the back by a predetermined dimension, and making the bottom surface of the groove sandwiched between the inner pipe and the outer pipe 111 downward toward the exhaust port, the vertical diffusion is achieved. The reaction product generated by cooling the reaction gas into the inner wall of the furnace port of the furnace core tube falls into the groove, and the reaction product can be discharged from an exhaust port directly connected to the groove. Therefore,
Prevents contamination and corrosion of the reaction products at the time of entering / leaving the boat into equipment other than the furnace core tube, and re-vaporizes the reaction products due to heat of the boat and the wafer itself at the time of leaving the boat, thereby re-evaporating the wafer. This has the effect of preventing the abnormal diffusion of diffusion.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view and a transverse sectional view of a bottom portion of a furnace core tube for a vertical diffusion furnace showing an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view and a transverse sectional view of a bottom part of a furnace core tube for a vertical diffusion furnace showing another embodiment of the present invention.

FIG. 3 is a cross-sectional view of a vertical diffusion furnace showing one example of the related art, and FIG.
It is a part enlarged view.

[Explanation of symbols]

110 opening 111 outer tube portion 112 N ₂ gas inlet 120, 320 outlet 121 bottom 122 inside tube 311 core tube 312 wafer 313 Boat 314 driver 315 boat pedestal 316 heater 317 core tube retainer 318 reaction gas inlet 319 Reaction gas piping

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Claims (2)

(57) [Claims] 1. A vertical type in which a heater is provided on an outer peripheral portion and has an opening at a lower end where a boat for mounting a plurality of semiconductor substrates is loaded and unloaded, a gas inlet at an upper end, and a gas exhaust at a lower end. In the furnace core tube for a diffusion furnace, an inner tube portion extending upward from the opening by a predetermined dimension is provided, and a bottom surface of a groove sandwiched between the inner tube portion and the outer tube portion is directed toward the gas exhaust port. A furnace core tube for a vertical diffusion furnace, characterized in that the gas exhaust port is connected to the groove with a downward slope. 2. A vertical diffusion furnace muffle according to claim 1, characterized in that it comprises an inert gas inlet for flowing the inert gas along the gradient of the groove.