JPS6298624A - Heat-treatment furnace - Google Patents

Abstract

PURPOSE:To enable the atmosphere surrounding semiconductor substrates to be controlled with high precision in the case they are inserted into or pulled out of a furnace core tube by a method wherein a control chamber to control the internal atmosphere is provided connecting to the furnace core tube wherein semiconductor substrates are inserted or whereof they are pulled out. CONSTITUTION:A furnace core tube 2 and a control chamber 5 are connected to each other while an entrance door thereof can be opened and closed freely by a cut-off plate 8. Besides, the control chamber 5 is provided with a semiconductor carrying-in port 6 also freely opened and closed to carry in and out the semiconductor substrates. The semiconductor substrates 3 and a boat 4 can be shifted inside the control chamber 5 and the furnace core tube 2 using a pull out bar 7. Through these procedures, the atmosphere in the furnace core tube 2 can be controlled to be non oxidative N2 atmosphere even in the case the semiconductor substrates are inserted into or pulled out of the furnace core tube 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a heat treatment furnace, and more particularly to a furnace for heat treating a workpiece such as a semiconductor substrate.

[Background of the invention]

Heat treatment of semiconductor substrates is usually performed by inserting the semiconductor substrates side by side on a quartz jig into a transparent quartz tube built into an electric furnace, and if the heat treatment involves oxidation, the semiconductor substrates are placed in an oxidizing atmosphere. This is done by sending 9 times.

At this time, it is necessary to replace the inside of the furnace core tube with non-oxidizing gas when inserting and withdrawing the semiconductor substrate.

In the conventional furnace structure, the furnace core tube port through which the semiconductor substrate is pushed in and pulled out is usually an open end.

Therefore, when inserting or pulling out a semiconductor substrate, the atmosphere outside the furnace flows back into the furnace, making it difficult to control the atmosphere inside the furnace core tube. Therefore, insert the semiconductor substrate,
A to the jig to pull out! Measures such as installing cutting plates are being taken. Related equipment in this building includes:
Examples include published utility model publication No. 59-95625, published patent publication No. 57-89219, and the like. However, even in the equipment in this building, it is difficult to prevent the backflow of outside air at the moment the semiconductor substrate passes through the furnace opening. Further, when a large number of semiconductor substrates are inserted side by side, the atmosphere of the outside air between the semiconductor substrates is directly taken into the furnace core tube, and the atmosphere inside the furnace core tube is contaminated by the outside air. When a semiconductor substrate is subjected to heat treatment under such conditions, there is a drawback that the processing characteristics become unstable. When the heat treatment is oxidation, the oxide film formed on the semiconductor substrate has large variations in film thickness and film thickness.

[Purpose of the invention]

An object of the present invention is to eliminate the drawbacks of the above-mentioned conventional techniques, and to achieve stable heat treatment by being able to control the atmosphere inside the furnace core tube even when objects to be processed, such as semiconductor substrates, are inserted into and pulled out of the furnace core tube. The purpose of the present invention is to provide a heat treatment furnace that can be used for heat treatment.

[Summary of the invention]

In order to achieve the above six objectives, the heat treatment furnace of the present invention is provided with a control chamber that is connected to the furnace core tube port on the side into which semiconductor substrates are inserted and pulled out, and is capable of controlling the internal atmosphere. This makes it possible to control the atmosphere of the semiconductor substrate with high precision even when the semiconductor substrate is taken in and out of the furnace core tube.

[Embodiments of the invention]

Examples of the present invention will be described in detail below.

Example 1 FIG. 1 shows the structure of one embodiment of the present invention.

In Fig. 1, symbol 1 indicates a heater, 2 indicates a furnace core tube,
Reference numeral 5 indicates a control room, and reference numeral 8 indicates a blocking plate. The furnace core tube 2 and the control chamber 5 are connected, and the entrance and exit between the furnace core tube 2 and the control chamber 5 can be opened and closed by a blocking plate 8. In addition, control room 3
A substrate loading port 6 is provided for loading and unloading semiconductor substrates.

The main substrate loading port 6 can also be opened and closed. FIG. 1 shows a state in which the shielding plate 8 is closed, and also shows a state in which a semiconductor substrate 3 and a substrate transfer boat 4 are introduced into the furnace core tube. The semiconductor substrate 3 and the boat 4 are connected by a pull-out rod 7.
The inside of the control chamber 5 and the inside of the furnace core tube 2 can be moved. Symbol 9゜11.12 is the gas inlet, and 10.
Reference numeral 13 indicates a waste discharge port. Hereinafter, each step of the process of carrying in the semiconductor substrate, the process of oxidizing it, and the process of carrying it out will be explained.

First, the semiconductor substrate 3 is carried in by loading the semiconductor substrate 3 onto the substrate transfer boat 4 which is carried from the board holder 6 into the control room 5. At this time, the block &8 is closed!
Nitrogen was supplied from gas inlet ports 9, 11 and 12. Subsequently, after closing the board/port 6 and purging the inside of the control room 5 with nitrogen, the shield plate 8 is opened, and then the semiconductor board, the cell 3 and the boat 4 are removed from the furnace core tube 2 using the pull-out rod 7. Push it inside, take out only the pull-out rod 7, and close the blocking plate 8 again.

In this state, the gas introduced from the gas inlet 9 is changed from nitrogen to an oxidizing gas, and an oxide film is grown on the semiconductor substrate 3. After growing the desired oxide film, the gas introduced from the gas inlet 9 is changed to nitrogen again to complete the oxidation process. For the semiconductor substrate (6), shut off &8 while introducing nitrogen from gas inlet ports 9, 11, and 12.
Open the door, use the drawer 7 to move the semiconductor Go & 7 and the boat 4 into the control room, and close the shutoff & 8. after that,
4. The semiconductor substrate 3 is taken out from the loading port 6.

According to this embodiment, even when a semiconductor substrate is inserted into the furnace core tube or pulled out of the furnace core tube,
The atmosphere within the furnace core tube can be controlled to a desired non-oxidizing atmosphere.

In the present invention, as an example of the stability of the atmosphere inside the furnace core tube of the oxidation furnace, FIG. 3 shows measurement results regarding the distribution of water vapor mystery inside the furnace core tube. The figure also shows the case of a conventional oxidation furnace for comparison. In addition,
The measurement was performed immediately after the semiconductor substrate was transferred into the furnace core tube. In addition, Peckman (13eckm) is used to measure moisture content.
Trace Moisture Analyzer manufactured by an)
was used. As shown in the figure, in a conventional oxidation furnace, the furnace core tube opening has a
On the other hand, the moisture content in the oxidation furnace in this example is extremely small, about 1 ppm from the mouth of the furnace tube to the vicinity of the center of the furnace tube, and can be stably controlled. It is clear that it can be done.

Next, the characteristics of the oxide film formed using the oxidation furnace according to this example will be described below. The sample used was MOS
(Metal Oxide Sem1conducto
r) A capacitor with the structure was created using the following procedure.

As a semiconductor saw board, P type (100) plane, specific resistance 10Ω
(7), using a silicon wafer with a diameter of about 75 ctn,
A silicon wafer is oxidized in a dry oxygen atmosphere at about 1000 C using the oxidation furnace of the present invention to form a silicon oxide film of about 20 nm, on which an AI film is deposited by a well-known vapor deposition method, and then an ordinary photoresist is applied. A by processing and etching
lg was processed into a predetermined pattern. The CV (capacitance-voltage) characteristics of the MOS capacitor thus produced were measured, and the fixed charge density Nt was derived. This fixed charge density is
It represents the fixed charge density at the interface between the semiconductor substrate and the oxide film and in the oxide film, and it can be judged that the smaller this value is, the better the performance of the MO8 element is. Table 1 shows the fixed charge density of the MOS capacitor produced using the oxidation furnace of this example and the fixed charge density of the MOS capacitor produced by the conventional method.

As is clear from Table 1, when the oxidation furnace according to the present 1M example is used, the fixed charge density can be reduced to about 1/2 compared to when a conventional oxidation furnace is used.

Embodiment 2 The structure of an oxidation furnace which is a second embodiment of the present invention is shown in FIG. Of the structure of the oxidation furnace shown in the figure, the structure other than the furnace core tube is the same as the structure of the oxidation furnace in the invention of Example 1 shown in FIG. In the present invention, as shown in FIG.
The wall of the furnace core tube 20 has a double structure and includes a gas inlet 14 and a gas outlet 15. In this oxidation furnace,
Nitrogen gas can be introduced from the gas inlet when the semiconductor substrate is inserted into the furnace core tube, when it is pulled out, and during oxidation, so that nitrogen can flow between the walls of the double structure.

According to this fruitful example, it is possible to reduce impurities that penetrate the wall of the furnace core tube and enter the tube, and it is possible to maintain a stable atmosphere inside the tube. In addition, the amount of water in the oxidation furnace according to this embodiment can be reduced to a pitifully small value of 1 ppm or less from the furnace core tube mouth to the vicinity of the furnace core tube center. In addition, MO in which a silicon oxide film was formed using the oxidation furnace according to this practical example
The fixed charge density of the S capacitor is 9.6X10'Crn-
“It is.

MOS capacitor with oxide film formed in a conventional oxidation furnace
It was 15 or less.

〔Effect of the invention〕

According to the present invention, the atmosphere inside the furnace core tube can be stably controlled even when the semiconductor substrate is inserted into the furnace core tube, when it is pulled out from the furnace core tube, and during oxidation, and high quality semiconductor substrates can be produced. It is possible to do so.

In the previous embodiment, the content of the heat treatment was shown for oxidation, but the present invention has similar effects in heat treatments such as nitriding, diffusion, and annealing.

[Brief explanation of drawings]

1 and 2 are longitudinal cross-sectional views showing different embodiments of the present invention, respectively. FIG. 3 is a diagram showing the effects of the present invention.

Claims (1)

[Claims] 1. In a heat treatment furnace, which has a furnace core tube for heat-treating the object to be treated, and an opening at one end of the furnace core tube through which the object to be treated is carried in and taken out, the inner A heat treatment furnace comprising: a control chamber capable of controlling the atmosphere; and means for blocking the opening of the furnace core tube.