JPH03195019A - Gas supply apparatus for semiconductor diffusion furnace use - Google Patents

Abstract

PURPOSE:To prevent that ultrapure water to be liquefied inside a gas supply pipe flows into a diffusion furnace by a method wherein a hermetically sealed liquid storage container is installed at a halfway part of the gas supply pipe which is connected to the diffusion furnace. CONSTITUTION:Steam, of ultrapure water 6, which is generated by using an apparatus is supplied through a gas supply pipe 8; oxygen 9 is supplied to the gas supply pipe 8. Even when the steam is cooled and liquefied at a halfway part of a divided long gas supply pipe 11 on one side, the liquefied ultrapure water flows and drops into a hermetically sealed liquid storage container 10 and is stored there. The steam and the oxygen once flow into the hermetically sealed liquid container; after that, they are supplied into a diffusion furnace through a divided short gas supply pipe 12 on the other side. Consequently, a pulsatory movement of the Iiquefied ultrapure water inside the gas supply pipe is not caused; the steam of a definite amount is always fed into the diffusion furnace. Thereby, the liquefied ultrapure water 6 is not supplied into the diffusion furnace 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement of a gas supply device for a semiconductor diffusion furnace for forming an oxide film on a semiconductor substrate by a steam oxidation method.

[Prior Art] Conventionally, in order to form an oxide film on a semiconductor substrate by a steam oxidation method, a semiconductor substrate 2 is supported by a jig 3 and put into a diffusion furnace 1 as shown in FIG. 4 flasks 5
The ultrapure water 6 in the interior is heated with a heater 7 to generate water vapor, and this water vapor is supplied into the diffusion furnace 1 through a gas supply pipe 8 made of a quartz tube or a Teflon tube, and at the same time, the gas supply pipe 8 is Oxygen is sent through an oxygen supply pipe 9 connected in the middle, and is supplied together with water vapor into the diffusion furnace 1 through a gas supply pipe 8 to form an oxide film on the semiconductor substrate 2 by steam oxidation.

[Problems to be Solved by the Invention] By the way, in the conventional gas supply means described above, the ultrapure water in the flask S is heated, and the evaporated water vapor is cooled before being supplied into the diffusion furnace 1 through the gas supply pipe 8. water droplets adhere to the inner wall of the pipe and begin to grow and block the inside of the pipe.The cross-sectional area of the opening becomes extremely small, making it difficult for water vapor to pass through, and eventually the inside of the pipe becomes completely blocked. A part of the liquefied ultrapure water is supplied into the diffusion furnace 1 due to the pressure of oxygen and water vapor flowing through the pipe, and the inside of the pipe is partially opened and the water vapor is supplied into the diffusion furnace 1 again, although the amount of water vapor is small. Repeated pulsations of liquefied ultrapure water occur. Therefore, if sufficient water vapor is not sent into the diffusion furnace 1, or if liquefied ultrapure water is supplied directly to the diffusion furnace 1, the semiconductor substrate 2 may be abnormally oxidized, resulting in variations in oxide film thickness and oxidation step. This leads to a problem in that the electrical characteristics of the semiconductor device are adversely affected.

For this reason, it is conceivable to heat the gas supply pipe 8 with a heater to maintain it at an appropriate temperature, but the structure becomes complicated and proper temperature adjustment and maintenance are troublesome.

For this reason, it has recently been proposed to cover the gas supply pipe with a radiant heat reflective cover to maintain the gas supply pipe at a temperature sufficient to prevent the generation of water droplets. (
(Refer to Japanese Patent Application Laid-Open No. 60-154627.) However, even if the gas supply pipe is covered with a radiant heat reflective cover in this way, if the gas supply pipe is long, water vapor will become supersaturated while passing through the gas supply pipe and condense. There is a problem in that water droplets are created and these droplets enter the diffusion furnace.

Therefore, the present invention aims to provide a gas supply device for a semiconductor diffusion furnace in which ultrapure water liquefied in a gas supply pipe never flows into the diffusion furnace.

[Means for Solving the Problems] In order to solve the above problems, the gas supply device for a semiconductor diffusion furnace of the present invention places a semiconductor substrate in a diffusion furnace, supplies water vapor and oxygen, and processes the semiconductor substrate by a steam oxidation method. In a gas supply device for a semiconductor diffusion furnace for forming an oxide film, a gas supply pipe having an oxygen supply pipe of the gas supply device communicating with the diffusion furnace is divided in the middle at a position close to the diffusion furnace, and the divided portion is The present invention is characterized in that a closed liquid storage container is provided, and each of the divided gas supply pipes is connected to the closed liquid storage container at an angle.

[Function] According to the gas supply device for a semiconductor diffusion furnace configured as described above, when ultrapure water vapor generated by the gas supply device is supplied through the gas supply pipe and oxygen is supplied to the gas supply pipe, Even if water vapor is cooled and liquefied in the middle of one of the long gas supply pipes, this liquefied ultrapure water flows into the sealed liquid reservoir and is stored, and the water vapor and oxygen are temporarily stored in the sealed liquid reservoir. After entering the container, the gas is supplied into the diffusion furnace through the other short gas supply pipe. Therefore, the pulsation of the liquefied ultrapure water in the gas supply pipe is eliminated, and a constant amount of water vapor is always sent into the diffusion furnace.Also, since the liquefied ultrapure water is not supplied into the diffusion furnace, the diffusion The semiconductor substrate set in the furnace will not be abnormally oxidized, the oxide film thickness will be constant, and the oxidation yield will be improved.

[Example] A first example of the gas supply device for a semiconductor diffusion furnace of the present invention is described below.
To explain with reference to the drawings, reference numeral 1 denotes a diffusion furnace into which a semiconductor substrate 2 is supported by a jig 3 made of quartz as shown in the figure. Reference numeral 4 denotes a gas supply device that heats the ultrapure water 6 in the flask 5 with a heating heater 7 to generate water vapor. The gas supply pipe 8 that communicates the flask 5 of the gas supply device 4 with the diffusion furnace 1 is divided in the middle at a position close to the diffusion furnace 1, and a sealed liquid storage container 10 made of quartz is provided at the divided part.
The divided gas supply pipes 11 and 12 are communicated with each other. A long gas supply pipe 11 from one of the divided flasks 5 is slanted slightly downward and is supported through the upper outer periphery of the closed liquid storage container 10, and a short gas supply pipe 12 to the other divided diffusion furnace 1 is It is bent downward in an L-shape, and its vertical portion is penetratingly supported through the center of the upper surface of the closed liquid storage container 10, and its horizontal portion is slightly inclined toward the closed liquid storage container 10 side. Sealed liquid storage container 1
A drain port 14 having a drain cock 13 is provided at the bottom of the tank. An oxygen supply pipe 9 is connected in the middle of the gas supply pipe 11 .

The operation of the gas supply device for a semiconductor diffusion furnace according to the embodiment configured as described above will be explained. The ultrapure water 6 in the flask 5 of the gas supply device 4 is heated by the heater 7 to generate water vapor, and this water vapor is supplied through the gas supply pipe 11 and oxygen is supplied from the oxygen supply pipe 9 to the gas supply pipe 11. When water vapor is supplied, even if it is cooled and liquefied in the middle of the long gas supply pipe 11, this liquefied ultrapure water flows along the slightly inclined inner wall of the gas supply pipe 11 and flows into the closed liquid storage container 10. The water vapor and oxygen that fall and are stored once enter the closed liquid storage container 10 and then are supplied into the diffusion furnace 1 through the short gas supply pipe 12. Water vapor does not liquefy in the middle of this gas supply pipe 12, and even if it does, it is tilted toward the closed liquid storage container 10, so the diffusion furnace 1
There is no way to go inside. Therefore, the pulsation of the liquefied ultrapure water in the gas supply pipe 11 is eliminated, and a constant amount of water vapor is always fed into the diffusion furnace 1, and the liquefied ultrapure water is also supplied into the diffusion furnace 1. Therefore, the semiconductor substrate 2 set in the diffusion furnace 1 is no longer subject to abnormal oxidation. As a result, the oxide film thickness and oxidation yield of the semiconductor substrate 2 are
Compared to the conventional gas supply system for semiconductor diffusion furnaces shown in the figure, improvements were made as shown in the table below.

[Effects of the Invention] As can be seen from the above description, according to the gas supply device for a semiconductor diffusion furnace of the present invention, ultrapure water vapor and oxygen can be supplied to the semiconductor diffusion furnace, and liquefied ultrapure water can be supplied to the semiconductor diffusion furnace. Since the semiconductor substrate set in the diffusion furnace is not supplied to the interior of the diffusion furnace, the semiconductor substrate set in the diffusion furnace is not abnormally oxidized, the thickness of the oxide film formed on the semiconductor substrate is constant, and the oxidation yield is improved.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of a gas supply device for a semiconductor diffusion furnace according to the present invention, and FIG. 2 is a diagram showing a conventional gas supply device for a semiconductor diffusion furnace. 1...Diffusion furnace 2...Semiconductor substrate 3...
・Jig 4... Gas supply device 5... Flask 6... Ultrapure water 7... Heater 8... Gas supply pipe 9... Oxygen supply pipe
10... Sealed liquid storage container 11.12... Divided gas supply pipe

Claims (1)

[Claims] 1) In a gas supply device for a semiconductor diffusion furnace in which a semiconductor substrate is placed in a diffusion furnace and water vapor and oxygen are supplied to form an oxide film on the semiconductor substrate by a steam oxidation method, a gas supply device communicating with the diffusion furnace is provided. A gas supply pipe having an oxygen supply pipe is divided in the middle at a position close to the diffusion furnace, a sealed liquid reservoir is provided at the divided part, and each of the divided gas supply pipes is connected to the closed liquid reservoir by tilting it. A gas supply device for a semiconductor diffusion furnace, characterized by: