JP2502692B2 - Diffusion furnace device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diffusion furnace device used for thermal oxidation, thermal diffusion, etc. in the manufacture of semiconductor devices.

2. Description of the Related Art In recent years, the diameter of silicon wafers used in the manufacture of semiconductor devices has increased, and 6-inch wafers are now the mainstream. Along with that, semiconductor device manufacturing equipment has been improved and advanced so as to be compatible with a large diameter. Diffusion furnaces used for thermal diffusion and thermal oxidation in the manufacture of semiconductor devices are also being improved by increasing the diameter of the tube that houses the wafer, increasing the diameter of the heater, and extending the life of the heater.

A typical example of a conventional diffusion furnace is shown in FIG. The tube 2 is inserted into the heater 1, and the front end of the tube and the tail tube are housed in the furnace body. Here, a gas such as oxygen is introduced into the tube from the tail tube portion of the tube through the gas introduction tube 4 to oxidize the silicon wafer. The front end of the tube is closed by a shutter 9, the gas in the tube is exhausted from an opening provided in the shutter 9, and further an exhaust duct 3 provided in the furnace body.
Is exhausted outside the furnace body. The flow of gas inside and outside the tube is shown by arrows in FIG. The amount of gas exhausted is adjusted by a damper 10 provided in the exhaust duct 3.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In the diffusion furnace apparatus by this method, the flow rate of the exhaust gas is adjusted by the damper provided in the exhaust duct. Therefore, when the pulling amount of the exhaust duct changes, the gas flow in the tube Will be affected. Further, the pressure inside the tube also changes depending on the flow rate of the introduced gas.

As a result, the reproducibility of the heat treatment process is lost and, for example, variations in the oxide film thickness occur, making it impossible to perform a stable process.

Means for Solving the Problems In order to solve the above problems, the diffusion furnace apparatus according to the present invention has the following structure.

That is, first, a cap that completely seals the front end of the tube is provided, and the cap has a differential pressure gauge that detects the pressure difference between the inside and outside of the tube, and an opening having a variable opening area. Further, it has a control device for controlling the opening area of the opening by inputting the output from the differential pressure gauge, and operates so as to always keep the tube internal pressure constant.

Action With this configuration, the pressure in the tube and the gas flow can be kept constant at all times, and a stable and highly reproducible manufacturing process can be performed.

Embodiment An embodiment of the diffusion furnace apparatus according to the present invention will be described below with reference to the drawings.

FIG. 1 shows a diffusion furnace apparatus in one embodiment of the present invention. In FIG. 1, 1 is a heater, 2 is a tube, 3 is an exhaust duct, 4 is a gas introduction pipe, 5 is a cap,
Reference numeral 6 is a differential pressure gauge inside and outside the tube, 7 is an opening portion provided in the cap and having a variable opening area, and 8 is a control device for inputting an output from the differential pressure gauge and controlling the area of the opening portion 7. The arrows in the figure show the flow of gas inside and outside the tube.

The cap 5 is made of stainless steel and has O
Completely seal the tube with a ring. A differential pressure gauge 6 for detecting the pressure difference between the inside and the outside of the tube and an opening portion 7 with a variable opening area are provided on the cap 5, and the output from the differential pressure gauge 6 is input to the opening area control device 8. The pressure in the tube is always kept constant by controlling the area of the opening 7 by the input value.

As described above, according to this embodiment, the tube internal pressure and the gas flow can be always kept constant. Thereby, for example, variations in oxide film thickness can be eliminated and a stable manufacturing process can be realized.

EFFECTS OF THE INVENTION The present invention provides a differential pressure gauge inside and outside a tube, and a control device for controlling the area of the opening by inputting the output from the opening having a variable opening area and the differential pressure gauge. It is possible to realize an excellent diffusion furnace device that can always keep the flow constant.

[Brief description of drawings]

FIG. 1 is a perspective view of a diffusion furnace apparatus in one embodiment of the present invention, and FIG. 2 is a perspective view of a conventional diffusion furnace apparatus. 1 ... Heater, 2 ... Tube, 3 ... Exhaust duct,
4 ... Gas introduction pipe, 5 ... Cap, 6 ... Differential pressure gauge, 7
…… Aperture, 8 …… Aperture area control device, 9 …… Shutter, 10 …… Damper.

Claims (1)

(57) [Claims] 1. A differential pressure gauge for detecting a pressure difference between the inside and outside of the furnace, an opening having a variable opening area for discharging gas inside the furnace to the outside of the furnace, and an output of the differential pressure gauge. And a control device for controlling the area of the opening by inputting the diffusion furnace device.