JP2723795B2 - Horizontal processing furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a horizontal diffusion furnace in which a long furnace core tube is placed horizontally, and more particularly to a horizontal diffusion furnace in which a plurality of semiconductor wafers (hereinafter simply referred to as wafers) are mounted on a boat and stored. The present invention relates to a horizontal processing furnace for performing processes such as oxidation, impurity diffusion, and vapor phase growth on a wafer surface.

[0002]

2. Description of the Related Art In a horizontal processing furnace of this type, a plurality of wafers are erected and arranged on a boat so that a large number of wafers can be efficiently processed at a time, and the boat is placed in a long furnace core tube. Processing such as required oxidation, impurity diffusion, or film formation by vapor phase growth has been performed. In addition, various improvements have been made in boats on which these wafers are mounted to see how many semiconductor wafers can be mounted and processed uniformly for the purpose of improving productivity.

[0003] However, the boat itself becomes longer and heavier as a large number of wafers can be mounted on the boat, and when the heavy boat is inserted into the furnace core tube, the inner wall of the furnace core tube and the lower part of the boat are separated. This causes dust due to the removal of quartz chips and the vapor-phase growth film attached to the inner wall, and the dust generated when the furnace core tube is evacuated flies up and adheres to semiconductor wafers, causing serious defects in quality. Raises a new problem:

As a method of suppressing the generation of such dust, when a boat is carried into a furnace core tube, the boat is moved in a space without sliding on the furnace core inner wall and reaches a predetermined position. A soft landing method was adopted in which the boat was slowly lowered and placed on the furnace core tube. However, although this method suppresses the generation of dust, it requires a boat loading / unloading mechanism that performs a complicated movement of lifting and moving the boat and slowly lowering it, which not only makes the device itself expensive, but also moves the boat loading / unloading mechanism. Accordingly, the furnace core tube must be enlarged accordingly, and at the same time, a large floor area is required around the furnace core tube for installing the boat loading / unloading mechanism, which is not always an advantageous method.

A horizontal processing furnace having means for removing dust even if dust is generated in addition to the soft landing method is disclosed in Japanese Patent Application Laid-Open No. 60-72225. In this apparatus, a plurality of dust discharge holes are arranged and opened on the passage of a boat in a quartz reaction tube which is a furnace core tube, and a new exhaust pipe including the dust discharge holes is provided at a lower portion of the quartz reaction tube. The quartz reaction tube is connected to a vacuum evacuation device via a valve.

The dust removing action of this device is as follows. First, dust generated when a boat is inserted and discharged is opened by opening the valve, discharged through the dust discharge hole and the exhaust pipe, and discharged by the vacuum exhaust device. After that, the valve is closed, the valve on the quartz reaction tube side is opened, and the quartz reaction tube is evacuated. As described above, dust is effectively removed through the lower exhaust pipe before the quartz reaction pipe is evacuated.

[0007]

However, in the above-mentioned horizontal processing furnace, relatively heavy dust falls into the exhaust pipe from the dust discharge hole and can be removed by the suction force of the vacuum exhaust device, but the fine and small weight is small. The powdery dust does not fall into the dust discharge hole and remains at the bottom of the quartz reaction tube. Ascending, these soaring dusts absorb a little moisture in the air and adhere to the wafer. It is difficult to remove the fine powder dust attached from the wafer unless it is cleaned.
In addition, processing with dust adhered causes a serious defect in quality.

Accordingly, it is an object of the present invention to provide a horizontal processing furnace capable of processing wafers without contaminating the wafers even if dust is generated when the boat is carried in and out of the furnace core tube.

[0009]

A feature of the present invention is that a long elongate furnace which is connected horizontally to a vacuum exhaust device at one end through a first on-off valve and has an opening at the other end. A core tube,
A horizontal processing furnace having a lid provided with a reaction gas inlet and opening and closing the opening, and inserting a boat in which a plurality of semiconductor wafers are placed and stored into the furnace core tube from the opening,
A second opening / closing valve for opening and closing a plurality of air intake ports provided in the upper part of the furnace core pipe in a longitudinal direction, an exhaust pipe connecting an inner wall of the bottom part of the furnace core pipe and one wall part thereof, and an exhaust pipe Is connected to the vacuum pumping device via a third on-off valve, and a pumping speed control mechanism for controlling a pumping speed of the vacuum pumping device.

[0010] It is preferable that a means for introducing dry gas into the furnace core tube from the air inlet is provided.

[0011]

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

1 (a) and 1 (b) are a cross-sectional view and an enlarged view taken on line AA of an embodiment of the horizontal processing furnace of the present invention. As shown in FIG. 1, this horizontal processing furnace is connected to the vacuum pump 2 via a valve 8 at one end and has an opening 18 at the other end, and has a long quartz core inserted horizontally. A tube 1, a lid 17 having a reaction gas inlet 14 for opening and closing an opening 18, a boat 12 inserted through the opening 18 of the furnace core tube 1, on which a plurality of wafers 11 are placed and stored, and a furnace core tube 1 A valve 15 for opening and closing an air intake port 16 provided in the upper portion of the furnace in a longitudinal direction, an exhaust pipe 3 in which an inner wall 4a at the bottom of the furnace core tube 1 and a partial wall 4b thereof are continuous, and an exhaust pipe 3 is connected to the vacuum pump 2 via a valve 9 and has a variable conductance valve 10 for controlling the evacuation speed of the vacuum pump 2.

Further, it is desirable to attach an air purifying filter 13 for removing moisture to the air intake 16 in consideration of the degree of dust and humidity in the room where the apparatus is placed.
Since the room in which this type of device is installed is a room with a high degree of cleanliness, it is desirable that this filter 13 puts a drying agent in favor of humidity rather than dustiness in the room. The desiccant needs to be replaced frequently, but is preferably filled with phosphorus pentoxide having high hygroscopicity.

The furnace core tube 1 is preferably made of a quartz material or a silicon carbide material or a silicon nitride material which can be formed smoothly and has high heat resistance and which is inexpensive. Further, it is desirable to form a groove 4 at the bottom of the furnace core tube 1 formed into a circular tube so that heavy dust falls. In addition, it is to have a downward gradient toward the exhaust pipe 3.

The variable conductance valve 10 serving as an exhaust speed control mechanism controls the exhaust speed of the vacuum pump 2 by changing the conductance according to the opening degree of the vane.
The suction pressure can be reduced by reducing the exhaust speed of the vacuum pump 2. When the back pressure of the variable conductance valve 10 is reduced due to the suppression of the pumping speed of the vacuum pump 2 and the control of the variable conductance valve 10 is not performed smoothly, a variable leak valve is provided at a subsequent stage so as to increase the back pressure. It is desirable that a certain amount of outside air be leaked so that the back pressure becomes constant.

Next, the dust removing action in this horizontal processing furnace will be described. First, valve 15 and valve 9
With the valve 8 closed, the boat 12 is housed in the furnace core tube 1 while the sliding portion 12 a is in contact with the inner wall of the furnace core tube 1, and the opening 18 is closed by the lid 17. Next, the vacuum pump 2 is operated with the opening of the variable conductance valve 10 minimized. Then, the opening of the variable conductance valve 10 is gradually increased, and the evacuation speed of the vacuum pump 2 is gradually increased.

As a result, outside air enters through the air inlet 16 and generates an air flow indicated by an arrow. Dust stagnating in the groove 4 is flowed in the direction of the exhaust pipe 3, passes through the exhaust pipe 3, and passes through the furnace core pipe 1. It is discharged outside. Next, when the degree of opening of the variable conductance valve 10 reaches the maximum, for example, about 排 気, the gas is evacuated for a predetermined time, and then the laser light is applied to the groove 4 to check for the presence of foreign matter. Close 9
The valve 8 is opened to evacuate the furnace core tube to a predetermined degree of vacuum.
Then, a reaction gas is introduced from the reaction gas inlet 14 to process the wafer 11.

With the exhaust speed of the vacuum pump 2 suppressed and the suction pressure reduced in this way, a weak flow of dry air from the air intake 16 to the exhaust pipe 3 is formed, and the intensity of the flow gradually increases. With the increase, the dust in the groove 4 or in the vicinity of the groove 4 is flown toward the exhaust pipe 3 and discharged without rising. When the dust adhering to the wafer 11 was examined in the trial, the number of the dust was about 10 per wafer, which was almost the same as that of the soft landing method.

FIG. 2 is a sectional view showing another embodiment of the horizontal processing furnace of the present invention. In this horizontal processing furnace, as shown in FIG. 2, a dry gas supply device 6 is provided at an air intake 16 at an upper portion of the furnace core tube 1 via a manifold 5 and a valve 7. Other than that, it is the same as the above-mentioned embodiment.

This dry gas supply device comprises a gas cylinder filled with an inert gas such as nitrogen, argon or helium, a pressure regulator and a pressure gauge 19, and introduces a gas at an arbitrary pressure into the furnace core tube 1. can do. Here, nitrogen which is inexpensive and easy to handle is used. Also,
Since nitrogen gas filled in this kind of gas cylinder does not contain moisture at all, by introducing this highly dry nitrogen, moisture adhering to the inner wall of the furnace core tube 1, the wafer 11, the boat 12, or the like is deprived. There is an advantage that dust adhering to these is more easily separated.

Next, the dust removing action in the horizontal processing furnace will be described. First, with the valve 7 and the valve 9 opened and the valve 8 closed, the boat 12 is
The opening 18 is closed with the lid 17. Next, furnace core tube 1
While maintaining the inside at approximately 1 atm, nitrogen is supplied from the dry gas supply device 6 at a pressure of, for example, about 0.05 atm and is introduced from the air intake 16. On the other hand, the opening of the variable conductance valve 10 is adjusted so that the suction pressure of the vacuum pump 2 becomes, for example, about 0.05 atm. As a result, a pressure difference of 0.1 atm is generated between the upper part and the lower part of the furnace core tube 1 to form a flow of air indicated by an arrow. Due to this flow of air, the dust is brought to the side of the exhaust pipe 3 and discharged without soaring.

In this embodiment, since the flow of air can be controlled in one direction by forcibly flowing nitrogen gas, there is an advantage that the flying phenomenon can be further reduced as compared with the above-described embodiment. Further, by using the dried nitrogen gas, the separation and movement of the dust proceed extremely smoothly as compared with the above-described embodiment using the indoor air containing moisture,
Dust can be discharged from the furnace core tube 1 in a shorter time. In the embodiment described above, the boat 11 is carried in and out of the furnace core tube 1 by surface contact between the inner wall of the furnace core tube 1 and the sliding portion 12a of the boat 11. If the wheels are mounted and moved by rolling contact, dust generated by the movement can be further reduced.

[0023]

As described above, according to the present invention, an exhaust pipe is provided on the upper side of the furnace core pipe, and an exhaust pipe is provided on the lower side where an inner wall where dust stays and a part of the wall are continuous. Is connected to a vacuum pumping device via a valve, and has a pumping speed control mechanism for controlling the pumping speed of the vacuum pumping device. Since the dust remaining on the inner wall of the tube can be discharged through the exhaust pipe without soaring, dust does not adhere to the wafer. Also, if necessary,
By introducing the dry gas into the furnace core tube from the outside air intake, there is also an effect that moisture on the inner wall of the furnace core tube or the boat is removed, the separation of dust is promoted, and the dust is discharged in a short time.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a horizontal processing furnace according to the present invention, and is an enlarged view taken on line AA of FIG.

FIG. 2 is a sectional view showing another embodiment of the horizontal processing furnace of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Furnace tube 2 Vacuum pump 3 Exhaust pipe 4 Groove 4a Inner wall 4b Wall 5 Manifold 6 Dry gas supply device 7, 8, 9, 15 Valve 10 Variable conductance valve 11 Wafer 12 Boat 12a Sliding portion 13 Filter 14 Introducing reactive gas Mouth 16 Air intake 17 Lid 18 Opening 19 Pressure gauge

Claims (3)

(57) [Claims] 1. A long furnace core tube having one end connected to a vacuum evacuation device via a first on-off valve and having an opening at the other end, which is placed horizontally, and a reaction gas inlet. A horizontal processing furnace having a lid for opening and closing the opening, and inserting a boat in which a plurality of semiconductor wafers are placed and stored into the furnace core tube through the opening, wherein a plurality of semiconductor wafers are longitudinally disposed above the furnace core tube. A second on-off valve for opening and closing the air intake ports provided side by side, an exhaust pipe connecting the inner wall at the bottom of the furnace core tube and one wall thereof, and connecting the exhaust pipe to the vacuum via a third on-off valve. A horizontal processing furnace, comprising: an exhaust speed control mechanism connected to the exhaust device and controlling an exhaust speed of the vacuum exhaust device. 2. The horizontal processing furnace according to claim 1, wherein an air cleaning filter for removing moisture through the second on-off valve is attached to the air intake. 3. The horizontal processing furnace according to claim 1, wherein a drying gas supply device is provided at the air intake via the second on-off valve.