JPH0778780A - Vertical type diffusion furnace tube - Google Patents

Abstract

PURPOSE:To protect the inside of a device and a wafer against contamination caused by reaction product produced when reaction gas is cooled down at an opening. CONSTITUTION:In a vertical diffusion furnace tube, an inner tube 122 which can extend inwards from an opening 110 as far as a prescribed distance is provided, the base 121 of a groove cut between the inner tube 122 and an outer tube 111 is made to slope down towards an exhaust opening 120, reaction product produced on the inner wall of the opening of the core pipe of the vertical diffusion furnace as reaction gas is cooled down is made to fall off into the groove and discharged out through an exhaust opening directly connected to the groove.

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 in a semiconductor substrate.

[0002]

2. Description of the Related Art FIGS. 3 (a) and 3 (b) are a sectional view and an enlarged view of a portion A of a vertical diffusion furnace showing a conventional example. 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 installed perpendicularly to a floor surface.
A boat 313 loaded with wafers 312 and a drive unit 31 for transporting the boat 313 into the furnace core tube 311.
4, a boat pedestal 315 that connects the drive unit 314 and the boat 313 to close the furnace opening of the furnace core tube 311 during heat treatment,
The furnace core tube holder 317 for fixing the furnace core tube 311 was provided.

Next, the operation of this 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 wafers 312
13 is conveyed into the furnace core tube 311. Transport is performed by the drive unit 314.
The operation is performed. 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. Then, after the furnace core tube 311 reaches the processing temperature, the carrier gas (reaction gas) containing the phosphorus oxychloride.
Is introduced into the furnace from the upper part of the furnace core tube 311 through the reaction gas piping 319 through the reaction gas inlet 318, and the wafer 31
Spread to 2. The reaction gas after being diffused in the wafer 312 is exhausted from the exhaust port 320. After diffusion for a certain period of time, the introduction of the reaction gas into the furnace core tube 311 is stopped, the temperature is lowered to the base substrate, and then the boat 31 is operated by the operation of the driving unit 314.
3 and the wafer 312 are transferred to the outside of the furnace core tube 311, and then the wafer 312 is removed from the boat 313, and the processing ends.

As the 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 the reaction gas is introduced from the upper part of the furnace core tube 311 and is exhausted from the exhaust port provided near the lower furnace opening part. Therefore, the reaction gas introduced into the furnace core tube is cooled as it moves out of the heating zone of the heater 316 as it approaches the furnace opening. 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 mouth portion, and this is transmitted along the inner wall of the furnace core tube and accumulates on the end face of the boat rack.

[0006] Therefore, the accumulated reaction products are generated in the boat 3
13 is scattered into the apparatus other than the furnace core tube 311 at the time of entering and exiting the furnace to contaminate or corrode the inside of the apparatus, and further, when the boat is exiting from the reactor, the reaction products are re-vaporized by the heat of the wafer and the wafer itself to re-vaporize the wafer. There is a problem in that abnormal diffusion such as contact with 312 and re-diffusion causes abnormal formation of junction and abnormal concentration of surface impurities. This problem,
This causes a defect due to abnormal electrical characteristics of the semiconductor device, which becomes a serious problem.

Therefore, the object of the present invention is to prevent the reaction products generated by the condensation of the reaction gas from being contaminated and corroded into the apparatus other than the furnace core tube, and to prevent the reaction products from the residual heat of the boat and the wafer itself. It is an object of the present invention to provide a furnace core tube for a vertical diffusion furnace that prevents abnormal diffusion of re-diffusing a wafer with vaporized gas.

[0008]

A feature of the present invention is that it has an opening at the lower end and a gas inlet port at the upper end side, with an opening through which a boat having a plurality of semiconductor substrates mounted thereon is provided with a heater on the outer periphery thereof. In a vertical diffusion furnace core tube having a gas exhaust port at the lower end side, an inner tube portion extending upward from the opening by a predetermined dimension is provided, and a groove formed by sandwiching the inner tube portion and the outer tube portion. Is a furnace core tube for a vertical diffusion furnace, in which the bottom surface of the furnace has a downward gradient and the gas exhaust port and the groove are connected to each other.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

1 (a) and 1 (b) are a longitudinal sectional view and a lateral sectional view of a bottom portion of a furnace core tube for a vertical diffusion furnace showing an embodiment of the present invention. As shown in FIG. 1, this furnace core tube for a vertical diffusion furnace has an inner tube portion 122 extending a predetermined distance from the opening 110 through which a boat platform for loading and unloading a boat carries in and out.
Is provided, and 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. The end portion of the inner tube 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 also inclined toward the outside. Is desirable. Otherwise, it is the same as the conventional example.

By providing the groove having the inclined bottom surface 121 as described above, the reaction product produced by cooling the reaction gas accumulates 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.
After thermal diffusion for a predetermined time, the furnace core tube is cooled 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 process is completed.

FIGS. 2 (a) and 2 (b) are a longitudinal sectional view and a lateral sectional view of the 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 introduction port 112 for introducing nitrogen at a position of the outer pipe portion 111 facing the exhaust port 120.
Other than that 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, Exhaust port 220 for reaction products accumulated in the groove
Works to wash away.

Therefore, in this embodiment, since the reaction product accumulated in the groove is pushed by the N ₂ gas toward the exhaust port 120, the discharge capacity of the reaction product is higher than that of the above-mentioned embodiments. is there. Of course, the gas introduced through the N ₂ gas inlet 222 is not limited to N ₂ gas, and may be an inert gas such as Ar gas.

[0015]

As described above, according to the present invention, the opening 1
A vertical diffusion is provided by providing an inner pipe portion extending from the inner side of the inner pipe portion 10 by a predetermined dimension, and providing a bottom slope of a groove sandwiched between the inner pipe portion and the outer pipe portion 111 toward the exhaust port. The reaction product produced by cooling the reaction gas on the inner wall of the furnace core tube of the furnace falls into the groove, and the reaction product can be discharged from the exhaust port directly connected to the groove. Therefore,
Prevents contamination and corrosion of equipment other than the furnace core tube by the reaction product at the time of boat ingress / egress, and re-evaporates the wafer by revaporizing the reaction product due to heat of the boat and the wafer itself at the time of evacuation of the boat. This has the effect of preventing abnormal diffusion of diffusion.

[Brief description of drawings]

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

FIG. 3 is a sectional view of a vertical diffusion furnace showing a conventional example and FIG.
FIG.

[Explanation of symbols]

110 Opening 111 Outer Pipe 112 N ₂ Gas Inlet 120,320 Exhaust Outlet 121 Bottom 122 Inner Pipe 311 Furnace Core Tube 312 Wafer 313 Boat 314 Drive 315 Boat Mount 316 Heater 317 Furnace Core Hold 318 Reactant Gas Inlet 319 Reaction gas piping

Claims (2)

[Claims] 1. A vertical type having an opening at the lower end for arranging a heater on the outer periphery and carrying in and out a boat mounting a plurality of semiconductor substrates, and having a gas inlet at the upper end and a gas outlet at the lower end. In the core tube for the diffusion furnace, an inner tube portion extending upward from the opening by a predetermined dimension is provided, and the bottom surface of the 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, which has a downward slope and connects the gas exhaust port and the groove. 2. The furnace core tube for a vertical diffusion furnace according to claim 1, further comprising an inert gas inlet for flowing an inert gas along the gradient of the groove.