JPH02201921A - Semiconductor heat treatment furnace using pocl3 - Google Patents

Abstract

PURPOSE:To simplify the device and facilitate maintenance and eliminate disadvantage of highly corrosive acid generation by providing a door on an inner tube to make independent space therein. CONSTITUTION:A door 11 is provided at an opening of an inner tube 2 opened to the interior of an outer tube 2. Further an SiC puddle 12, capable of extending through a door 5 of the outer tube 1 into the inner tube 2, is provided, and the door 11 for blocking the opening of the inner tube 2 is provided at the half-way position of the puddle 12. Preferably, the door 11 is fixed to the puddle 12, and the door 5 of the outer tube 1 is so constructed that it can tightly close the opening of the outer tube 1 by an SiC cantilever. Thus, P2O5, generated within the inner tube 2, is prevented from adhering to the door 5, and disadvantage of generation of highly corrosive acid can be eliminated.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention is directed to POCJ! ! The present invention relates to a semiconductor heat treatment furnace for forming a P diffusion layer on the surface layer of a semiconductor substrate using gas.

(Prior Art) Conventionally, as a semiconductor heat treatment furnace using POC4, for example, as shown in Figure 1, an inner tube made of quartz with one end open is provided inside an airtight outer tube a made of quartz. The outer pipe a has an inlet C for carrier gas such as N2 gas.
, a door e for loading and unloading the semiconductor substrate d, and an exhaust pipe f.
In order to provide a
A source inlet g for introducing a source gas mixed with, for example, 02 gas is provided, and the semiconductor substrate d and the source gas, which are placed on a boat h and housed in the inner tube, are transferred to the outer tube a. It is known that a P diffusion layer is formed on the surface layer of the semiconductor substrate d by heating with a heater j provided on the outer periphery.

In this diffusion furnace, the P2O5 component that did not adhere to the substrate d is discharged from the inner tube to the outer tube a, and the P2O
5 is discharged from the exhaust pipe f together with the carrier gas without cooling it. The exhaust pipe f1 is provided with a pressure sensor 0 such as a diaphragm gauge, a pressure controller k, and a water-cooled trap l to control the pressure inside the exhaust pipe f and trap P2O5. The boat h and the boat n carrying the dummy semiconductor substrates m are taken in and out in a soft landing style, in which the boat h and the boat n carrying the dummy semiconductor substrates m are gently placed in the inner tube and gently taken out from the inner tube by an unillustrated unloader means.

According to this diffusion furnace, it is possible to form a P diffusion layer with an accuracy of 25Ω±2% or less on each of 100 semiconductor substrates d having 3000 layers of polysilicon on the surface.

(Problem to be Solved by the Invention) In the conventional diffusion furnace, the end of the inner pipe is open, and the boat h%n is taken in and taken out from the opening, but the N2 carrier flowing inside the outer pipe a from the opening There is a drawback that the gas is drawn into the inner tube and it is difficult to precisely control the concentration of the source gas at the opening.

Furthermore, since the diffusion process must be carried out while maintaining the atmospheric pressure inside the outer tube a, the pressure at the opening of the inner tube must be precisely controlled within a range of several mmAq.
For this reason, a high-precision pressure sensor 0 is provided, but this high-precision pressure sensor 0 is prone to many troubles and has many disadvantages in terms of maintainability due to matching with the pressure controller, etc.

In addition, PzOs from the inner pipe adheres to the inner surface of the door e on the way to the exhaust pipe f, but when the door e is opened, it absorbs moisture from the atmosphere and becomes highly corrosive phosphoric acid. There is an inconvenience that the liquid drips in the vicinity of the door e and causes corrosion, for example, in a portion of the scavenger installed in the vicinity of the door e.

The present invention aims to eliminate the above-described drawbacks and inconveniences of semiconductor thermal diffusion furnaces caused by using POCl3 as a source gas.

(Means for Solving the Problem) In the present invention, an inner tube made of quartz is provided in an airtight outer tube made of quartz, and the outer tube has a gas inlet for introducing a carrier gas into the inner tube and a port for carrying out the semiconductor substrate. In addition to providing a door for entry and an exhaust pipe, the inner pipe is provided with a POCj! A source inlet for introducing a source gas containing three gases is provided, and the semiconductor substrate accommodated in the inner tube and the introduced source gas are heated by a heater provided on the outer periphery of the outer tube to diffuse P into the semiconductor substrate. In the case where layers are formed, the above object is achieved by providing the inner tube with a door that seals the inside of the inner tube into an independent space.

Semiconductor substrates are carried into and out of the inner tube by placing them on paddles inserted through the doors of the inner tube and the outer tube.

(Function) When the semiconductor substrate is housed in the inner tube, the inner tube is closed by a door to create an independent space inside the inner tube, and the door of the outer tube is further closed. Next, the heater on the outer periphery of the outer tube is activated, and a carrier gas such as N2 is introduced into the inner tube from the gas inlet of the outer tube, and a mixed gas of POC4 gas and 0□ gas is introduced from the source inlet of the inner tube. Then, exhaust operation from the exhaust pipe starts.

The flow rates of the carrier gas and source gas are controlled to maintain atmospheric pressure inside the outer tube and the inner tube. As a result, the P component in the source gas in the inner tube diffuses and permeates from the surface of the heated semiconductor substrate to the inside thereof in a layered manner.
When the heat treatment is completed, the introduction of the source gas is stopped, the door of the inner tube is opened, and the source gas in the inner tube is blown out from the exhaust tube by the carrier gas. Next, the carrier gas and exhaust from the exhaust pipe are stopped, the door of the outer pipe is opened, and the processed semiconductor substrate is taken out.

In this case, the carrier gas in the outer tube is not blocked by the door provided in the inner tube and drawn into the inner tube, and the concentration of the source gas in the inner tube is prevented from changing due to the carrier gas. Control accuracy is improved. Also, during processing, the inside of the inner pipe is closed by a door and becomes an independent space, and is not connected to the exhaust pipe, so there is no need to install a pressure sensor or pressure controller in the exhaust pipe system, and the source gas introduced into the inner pipe It is possible to maintain atmospheric pressure inside the inner tube simply by controlling the amount of . Since the inside of the inner pipe is independent, even if a large amount of carrier gas is introduced into the outer pipe and discharged from the exhaust pipe, there will be no change in the pressure or gas concentration inside the inner pipe, allowing a large amount of carrier gas to flow. This makes it possible to exhaust the P2O5 component in the outer pipe to the water-cooled trap, thereby increasing the efficiency of exhausting the P2O5 component in the outer pipe to the water-cooled trap. Although the P20S component is present in the inner tube during heat treatment, the inner tube and its door are
The P20S component is maintained at a high temperature that makes it difficult for the five components to adhere, and when the door is opened after the heat treatment, the P20S component can be almost completely discharged to the exhaust pipe by the carrier gas flowing in a large amount in the outer pipe. Done, put P on the inner tube door.
Almost no 2O5 components adhere to it, and even if the door of the inner tube is exposed to the atmosphere when the semiconductor substrate is taken out of the outer tube, highly corrosive acids will not be generated there, and the area near the door of the outer tube will not be affected. This eliminates the inconvenience of corroding a portion of the scavenger.

(Embodiment) An embodiment of the present invention will be explained based on FIG. 2, in which reference numeral (1) indicates an airtight outer tube made of quartz, and (2)
indicates an inner tube made of quartz provided within the outer tube (1) with a space between it and the inner wall thereof, and the outer tube (1) has an inlet (3) at one end for a carrier gas such as N2 gas. )
is provided, and a silicon semiconductor substrate (4
) is provided, and an exhaust pipe (6) is connected to the wall of the outer pipe (1). Also,
A source inlet (D) is provided at one end of the inner tube (2) to pass through the tube wall of the outer tube (1) and lead out to the outside, and for example, POCJg gas and 02 A mixture of gases is introduced into the inner pipe (2). (8) is a cylindrical heater provided on the outer periphery of the outer pipe (1), and (8) is a cylindrical heater provided in the middle of the exhaust pipe (6). The trap (9) is a water-cooled trap installed at the end of the exhaust pipe (6), and the trap (9) removes water-soluble gas components when the gas in the outer pipe (1) is sucked and exhausted by a vacuum pump or blower installed at the tip of the exhaust pipe (6). Collect. (IQ is the door (5) of the outer tube (1)
) shows part of the scavenger covering the outer periphery of the

The above configuration is almost the same as that of a conventional semiconductor heat treatment furnace, but in the present invention, a door (+1) is provided at the opening of the inner tube (2) into the outer tube (1). In the illustrated example, the door (5) of the outer pipe (1)
S that extends into the inner tube (2) by inserting it so that it can appear and retract freely.
A paddle (121) made of iC was provided, and a door 01 was provided in the middle of the paddle (2) to close the opening of the inner tube (2).

It is preferable that the door av is fixed to the paddle 0, and the door (5) of the outer tube (1) is configured to seal the opening of the outer tube (1) with a cantilever made of SiC, for example.

The semiconductor substrate (4) is placed upright on the tip of the paddle (2) with a gap in between, and the inner tube (2) is inserted by inserting the paddle (6b) into the outer tube (1) in the axial direction from the opening thereof. ), but before the semiconductor substrate (4) reaches the proper position, the door (5) is closed and the outer tube (1)
By flowing carrier gas from the inlet (3) to the exhaust pipe (6), the inside of the outer pipe (1) and the inner pipe (2) are removed.
) to eliminate the air inside. Next, the semiconductor substrate (4) is brought to the proper position in the inner tube (2), and when the inner tube (2) is blocked by the door (IV), the heater (8) is activated and the inner tube is removed from the source inlet (7). The source gas is introduced so that the inside of the tube (2) is at atmospheric pressure.The source gas is thereby decomposed, and heat treatment is performed to diffuse and infiltrate the P component in the gas component into the surface layer of the substrate (4). Since the carrier gas does not mix into the inner tube (2), the concentration and pressure of the source gas can be precisely controlled.

When the prescribed heat treatment is completed, the source inlet (7) into the inner tube (2) is closed to stop the introduction of the source gas, the paddles G are slightly pulled out from the inner tube (2), the door a1 is opened, and the outer tube is closed. The carrier gas flowing through the tube (1) transfers the source gas components to the outer tube (1) and the inner tube (2).
) into the exhaust pipe (6). After this, stop the carrier gas, open the door (5) of the outer tube (1),
Take out the 11 paddles to the outside and replace the board (4).

During the heat treatment, make sure that the door (5) of the outer tube (1) is not contaminated with P2O generated in the inner tube (2), and that the carrier gas is sufficiently supplied when the door (It) of the inner tube (2) is opened. By circulating P2O5 to the exhaust pipe (6)
It is possible to eliminate the components and prevent them from adhering to the door (IV), and there is no inconvenience caused by contact between the P2O5 components and the atmosphere and the formation of highly corrosive acids.

(Effect of the invention) As described above, according to the present invention, P
In a semiconductor heat treatment furnace equipped with an inner tube into which OCl3 gas is introduced, a door is provided on the inner tube to create an independent space inside the inner tube, so that the concentration and pressure of the source gas inside the inner tube can be controlled from the source. This can be done when gas is introduced, there is no need to specially install a pressure sensor or pressure controller in the exhaust pipe, the equipment is simplified and maintenance is easier, and the inconvenience of producing highly corrosive acids can be eliminated. There is an effect.

[Brief explanation of the drawing]

FIG. 1 is a cut side view of the conventional example, and FIG. 2 is a cut side view of the embodiment of the present invention. (1)...Outer tube (2)...Inner tube (3)...Gas inlet (4)...Semiconductor substrate (5) (TD...Door (6)...Exhaust Pipe (1)... Source inlet (8)... Heater 0... Paddle Patent applicant

Claims (1)

[Claims] 1. A quartz inner tube is provided in an airtight outer tube made of quartz, and the outer tube includes a gas inlet for introducing a carrier gas into the outer tube and a door for carrying in and out semiconductor substrates. and an exhaust pipe, and a PO inside the inner pipe.
A source inlet for introducing a source gas containing Cl_3 gas is provided, and the semiconductor substrate housed in the inner tube and the introduced source gas are heated by a heater provided on the outer periphery of the outer tube to diffuse P into the semiconductor substrate. POCl_3, characterized in that the inner tube is provided with a door that seals the inside of the inner tube into an independent space, in which a layer is formed.
A semiconductor heat treatment furnace that uses 2. A semiconductor using POCl_3 according to claim 1, characterized in that a paddle is provided to be inserted through the door provided on the inner tube and the door provided on the outer tube, and a semiconductor substrate is placed on the paddle. Heat treatment furnace.