JPH09312296A - Heat treatment method and device for substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the processing time per substrate by eliminating or reducing, in comparison with a conventional technique, the time for gas purge in a heat treatment furnace after transport of the substrate into the heat treatment furnace and sealing of the heat treatment furnace in the case where the substrate is to be heat-treated by single wafer processing. SOLUTION: In switching the flow rate of a gas fed into a heat treatment furnace 10 from a first flow rate at the time of transport of the substrate into and out of the furnace to a second flow rate for heat treatment which is smaller than the first flow rate, a control signal inputted to a mass flow controller 44 is changed gradually, not linearly, so that the actual flow rate of the gas fed into the heat treatment furnace 10 is prevented from being lower than the second flow rate and thus prevented from causing under shoot.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat treatment method for a substrate, such as a lamp annealing apparatus, which heats various substrates such as semiconductor wafers one by one by heating means such as light irradiation, and a method for implementing the method. The present invention relates to a heat treatment apparatus for substrates.

[0002]

2. Description of the Related Art A heat treatment apparatus for heating a substrate, for example, a semiconductor wafer, by heating means such as light irradiation has a structure shown in a schematic side sectional view in FIG. The apparatus shown in FIG. 1 is a light irradiation type heat treatment apparatus, and this heat treatment apparatus includes a heat treatment furnace 10 having an opening 12 on the front side for loading and unloading a semiconductor wafer W. The furnace wall of the heat treatment furnace 10 is formed of, for example, quartz glass having infrared transparency. Opening 1 of heat treatment furnace 10
On the second side, a furnace port block 14 is provided so as to be connected to the heat treatment furnace 10. The front opening of the furnace port block 14 is closed by a movable flange 16 so as to be openable and closable.
A susceptor 18 that supports the wafer W in a horizontal posture is integrally fixed to the inner surface of the movable flange 16, and the wafer W supported by the susceptor 18 is moved by reciprocating the movable flange 16 in the horizontal direction. It is carried in and out of the heat treatment furnace 10. Then, the movable flange 16 moves toward the heat treatment furnace 10 side and comes into contact with the furnace mouth block 14, thereby closing the front opening of the furnace mouth block 14 and the wafer W supported by the susceptor 18 inside the heat treatment furnace 10. It is arranged at a predetermined position.

In the vertical direction of the heat treatment furnace 10, a light irradiation light source 20 composed of a lamp group such as a halogen lamp and a xenon lamp is disposed so as to face the upper wall surface and the lower wall surface of the heat treatment furnace 10, respectively. Further, reflectors (reflecting plates) 22 are arranged behind the light sources 20 and on both sides and the rear of the heat treatment furnace 10 so as to surround the heat treatment furnace 10. The inner surface side of each reflector 22 is
It is mirror-polished to enable efficient reflection of light. The light source 20 for light irradiation may be arranged only above the heat treatment furnace 10.

In the heat treatment furnace 10, the gas introduction passage 2 is provided on the rear side.
4 is formed, and its gas introduction path 24 is connected to a gas introduction device 28 as shown in FIG. 2 for introducing a processing gas, for example, nitrogen gas into the heat treatment furnace 10. The gas introduction device 28 includes a nitrogen gas supply source 30,
A stop valve 34, a check valve 36, a filter 38, a regulator 40, a pressure gauge 42, a mass flow controller (hereinafter referred to as “MFC”) 44, and air are provided in a gas supply path 32 that connects the nitrogen gas supply source 30 and the heat treatment furnace 10. An operating valve 46 is provided in between. A CPU 48 that sends a control signal to the MFC 44 of the gas introduction device 28 to control the MFC 44 is connected to the MFC 44. Although not shown, the furnace port block 14 is provided with a gas exhaust passage. Further, in order to keep the airtightness inside the heat treatment furnace 10 high, an O-ring 26 is attached to each of the furnace port blocks 14.

To heat the semiconductor wafer W in a single wafer by using the light irradiation type heat treatment apparatus having the above-described structure, the gas introduction device 28 introduces gas while the opening 12 side of the heat treatment furnace 10 is opened. Heat treatment furnace 1 through path 24
Nitrogen gas was introduced into the heat treatment furnace 10
The wafer W supported by the susceptor 18 is inserted into the heat treatment furnace 10 while flowing out from the opening 12 side through the opening surface of the furnace port block 14. The flow rate of nitrogen gas introduced into the heat treatment furnace 10 is adjusted by controlling the MFC 44 by the CPU 48, and a desired constant flow rate of nitrogen gas is introduced into the heat treatment furnace 10 through the MFC 44. The gas flow rate at this time is such that the outside air is not drawn into the heat treatment furnace 10 from the opening 12 side, for example, the internal volume of the heat treatment furnace 10 is 2.4 l and the area of the opening 12 is 65 cm ₂ . In this case, it is set to 30 to 50 l / min.

The movable flange 16 moves as the wafer W is inserted into the heat treatment furnace 10, and the opening surface of the furnace port block 14 is closed by the movable flange 16. During this process, the wafer W in the heat treatment furnace 10 is closed. When the insertion of
The MFC 44 is controlled by the control signal from the CPU 48, and the flow rate of the nitrogen gas introduced into the heat treatment furnace 10 is switched to the flow rate for heat treatment. The gas flow rate after switching is smaller than the above-mentioned flow rate, for example, 5 to 10 l / m.
It is set to about in and is maintained at the flow rate of the introduced gas during the heat treatment. When the opening surface of the furnace port block 14 is airtightly closed by the movable flange 16, the wafer W is irradiated and heated to a desired temperature programmed in advance by a wafer temperature detection device and a temperature controller (not shown). When the heat treatment is completed, the wafer W is cooled to a desired temperature in the heat treatment furnace 10 and then unloaded from the heat treatment furnace 10. At this time, the MFC 44 is controlled by the control signal from the CPU 48, and the flow rate of the nitrogen gas introduced into the heat treatment furnace 10 is again the first 30 to 50 l / min.
Is switched to.

[0007]

In the heat treatment of semiconductor wafers using the light irradiation type heat treatment apparatus, the flow rate of the nitrogen gas introduced into the heat treatment furnace 10 is such that the wafer W is loaded into the heat treatment furnace 10. A relatively large flow rate (30 to 50 l / min in the above example) to the extent that the outside air is not entrained into the inside 10 through the opening 12 side, and a relatively small flow rate for the heat treatment of the wafer W (5 to 5 in the above example. 10 l /
min) and at least two types of flow rates are controlled.
In this case, in order to shorten the processing time per wafer W, after the wafer W is inserted into the heat treatment furnace 10, the flow rate of the nitrogen gas introduced into the heat treatment furnace 10 is set to the heat treatment of the wafer W. The heat treatment may be started immediately after changing to a smaller flow rate. However, switching of the gas flow rate causes pulsation in the gas flow in the heat treatment furnace 10, so that the flow rate of the nitrogen gas introduced into the heat treatment furnace 10 is changed to M
Even if it is controlled by FC44, as shown in FIG.
A phenomenon occurs in which the gas flow rate actually introduced into the heat treatment furnace 10 is transiently lower than the minimum gas flow rate required for the outside air not to be drawn into the heat treatment furnace 10 through the opening 12 side. In FIG. 5, the solid line a indicates the heat treatment furnace 10.
The actual flow rate of the gas introduced into the chamber is indicated by the broken line b
The gas flow rate corresponding to the control signal sent from U48 to MFC44 is shown. Further, the gas flow rate at the level indicated by the reference sign c indicates that the wafer W is carried into the heat treatment furnace 10 and the heat treatment furnace 1
The introduction gas flow rate when the wafer W is unloaded from 0 is shown, and the gas flow rate at the level indicated by the symbol d shows the introduction gas flow rate during the heat treatment of the wafer W.

As described above, as a result of the undershoot of the flow rate of the gas introduced into the heat treatment furnace 10, the heat treatment furnace 10
Outside air enters the inside through the opening 12 side. Therefore, in order to expel the outside air that has entered the heat treatment furnace 10 from the inside of the heat treatment furnace 10 through the gas exhaust path of the furnace mouth block 14, the opening surface of the furnace mouth block 14 is hermetically closed and then the heat treatment of the wafer W is started. Before, the inside of the heat treatment furnace 10 was purged with nitrogen gas for an appropriate time. Then, the inside of the heat treatment furnace 10 is completely replaced with nitrogen gas,
After improving the gas purity in the heat treatment furnace 10, the wafer W
The heat treatment was started. As described above, conventionally, it is necessary to perform gas purging after airtightly closing the inside of the heat treatment furnace 10, so that the processing time per wafer is long.

The present invention has been made in view of the above circumstances, and in the case of heat-treating a substrate by a single-wafer method, the substrate is carried into the heat treatment furnace, the inside of the heat treatment furnace is sealed, and then the inside of the heat treatment furnace is closed. To provide a substrate heat treatment method capable of improving the treatment efficiency by eliminating the gas purging time or shortening the gas purging time as compared with the conventional one, and shortening the treatment time per substrate, and the method is preferably used. It is an object of the present invention to provide a substrate heat treatment apparatus that can be implemented.

[0010]

The invention according to claim 1 is
A heat treatment furnace that has an opening for loading and unloading the substrate and that accommodates the substrate in a single wafer is controlled so that outside air is not entrained in the heat treatment furnace through the opening by controlling the gas flow rate controller. While introducing a gas at a first flow rate and letting the gas flow from the inside of the heat treatment furnace through the opening, the substrate is carried into the heat treatment furnace through the opening, and then the opening of the heat treatment furnace is closed. , The gas flow rate controller is controlled to switch to a second flow rate for heat treatment that is lower than the first flow rate, and after the opening of the heat treatment furnace is airtightly closed, the second flow rate is changed into the heat treatment furnace. In a substrate heat treatment method of heating a substrate in a heat treatment furnace while introducing gas, the flow rate of the gas introduced into the heat treatment furnace is switched from the first flow rate to the second flow rate. In addition, the control signal input to the gas flow rate controller is gradually changed so as to prevent or suppress an undershoot in which the actual gas flow rate introduced into the heat treatment furnace is lower than the second flow rate and is lower than the second flow rate. It is characterized by

According to a second aspect of the present invention, there is provided a heat treatment furnace which has an opening for loading and unloading the substrate, and which accommodates the substrate in a single wafer, and a heat treatment furnace for loading the substrate into the heat treatment furnace through the opening. Substrate loading / unloading means for unloading a substrate from inside through an opening, opening closing means for hermetically closing the opening of the heat treatment furnace, heating means for heating the substrate held in the heat treatment furnace, and a gas flow rate controller. Gas introducing means for introducing a desired flow rate of gas into the heat treatment furnace,
When the substrate is carried into the heat treatment furnace through the opening, the flow rate of the gas introduced into the heat treatment furnace is set to a first flow rate such that outside air is not drawn into the heat treatment furnace through the opening. When the opening of the heat treatment furnace is closed by the opening closing means and the substrate in the heat treatment furnace is heated by the heating means for heat treatment, the flow rate of the gas introduced into the heat treatment furnace is less than the first flow rate. In a substrate heat treatment method, comprising: a flow rate control unit that controls a gas flow rate controller of the gas introduction unit so as to obtain a second flow rate for heat treatment, the flow rate of the gas introduced into the heat treatment furnace is At the time of switching from the first flow rate to the second flow rate, undershoot in which the actual gas flow rate introduced into the heat treatment furnace falls below the second flow rate and is below that is prevented or suppressed. As the flow rate control means,
It has a control program for gradually changing a control signal inputted to the gas flow rate controller of the gas introducing means.

According to the substrate heat treatment method of the invention of claim 1 having the above-mentioned structure, the flow rate of the gas introduced into the heat treatment furnace changes from the first flow rate to a value lower than the first flow rate due to the closing of the opening of the heat treatment furnace. When switching to the smaller second flow rate, the control signal input to the gas flow rate controller does not change linearly as in the past, but the actual gas flow rate introduced into the heat treatment furnace causes undershoot. The input control signal to the gas flow controller gradually changes so as not to exist or to suppress it. FIG. 4 is a diagram showing this state, in which the solid line A indicates the actual gas flow rate introduced into the heat treatment furnace, and the broken line B indicates the gas corresponding to the input control signal to the gas flow rate controller. Flow rates are indicated respectively, and a gas flow rate at a level C indicates an introduction gas flow rate when the substrate is loaded into the heat treatment furnace, and a gas flow rate at a level D indicates an introduction gas flow rate during the heat treatment of the substrate, respectively. Shows. Therefore, when switching the gas flow rate, pulsation does not occur in the gas flow in the heat treatment furnace, and outside air is prevented or reduced from entering the heat treatment furnace through the opening. Therefore, it is not necessary to carry out gas purging inside the heat treatment furnace after the substrate is carried into the heat treatment furnace and airtightly closed inside the heat treatment furnace, or the gas purging time can be shortened, and immediately or immediately after closing the inside of the heat treatment furnace. Then, the heat treatment of the substrate can be started.

In the heat treatment apparatus for a substrate according to the second aspect of the present invention having the above structure, the flow rate of the gas introduced into the heat treatment furnace from the flow rate control means to the gas flow rate controller of the gas introduction means is changed from the first flow rate. A control signal that is gradually changed so that the actual gas flow rate introduced into the heat treatment furnace when switching to the second flow rate does not cause or suppress undershoot is input. Therefore, when switching the gas flow rate, pulsation does not occur in the gas flow in the heat treatment furnace, and outside air is prevented or reduced from entering the heat treatment furnace through the opening. Therefore, it is not necessary to carry out gas purging inside the heat treatment furnace after the substrate is carried into the heat treatment furnace and airtightly closed inside the heat treatment furnace, or the gas purging time can be shortened, and immediately or immediately after closing the inside of the heat treatment furnace. Then, the heat treatment of the substrate can be started.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described below.

The structure of the heat treatment apparatus used to carry out the substrate heat treatment method according to the present invention is basically the same as the conventional one, and is as already described with reference to FIGS. 1 and 2. , The description is omitted. This heat treatment method is characterized by a control method when switching the flow rate of the process gas introduced into the heat treatment furnace 10, for example, nitrogen gas. Further, as a device, it is characterized by a control program for sending a control signal from the CPU 48 to the MFC 44.

In this heat treatment method, in the state where the opening 12 side of the heat treatment furnace 10 is opened, the flow rate is controlled by the MFC 44, and a constant flow rate is passed from the gas introduction device 28 through the gas introduction passage 24, for example, the internal volume of the heat treatment furnace 10. Is 2.
When the area of the opening 12 is 4 cm and the area of the opening 12 is 65 cm ₂ , a processing gas having a constant flow rate of 30 to 50 l / min, for example, nitrogen gas is introduced into the heat treatment furnace 10, and the nitrogen gas is used to open the heat treatment furnace 10. It is made to flow out from the 12 side through the opening surface of the furnace port block 14. At this time, the outside air is not entrained in the heat treatment furnace 10 from the opening 12 side.
In this state, the semiconductor wafer W supported by the susceptor 18 is inserted into the heat treatment furnace 10. This heat treatment furnace 10
When the wafer W is inserted into the heat treatment furnace 10, the opening surface of the furnace opening block 14 is closed by the movable flange 16. However, when the wafer W is completely inserted into the heat treatment furnace 10, the MFC 44 is controlled by the control signal from the CPU 48. The flow rate of the nitrogen gas introduced into the heat treatment furnace 10 is switched to a constant flow rate for heat treatment, for example, a constant flow rate of 5 to 10 l / min. This switching of the gas flow rate is performed by the MFC 44 so that the actual gas flow rate introduced into the heat treatment furnace 10 is temporarily below the flow rate for the heat treatment so as not to cause or suppress undershoot. It is performed based on a control program that gradually changes the input control signal instead of linearly. Therefore, when the gas flow rate is switched, the pulsation of the gas flow in the heat treatment furnace 10 is prevented, and the outside air is prevented from entering the heat treatment furnace 10 through the opening 12 side.

The insertion of the wafer W into the heat treatment furnace 10 is completed, the flow rate of the nitrogen gas introduced into the heat treatment furnace 10 is switched, and the opening surface of the furnace port block 14 is completely closed so that the inside of the heat treatment furnace 10 is closed. When kept airtight, the heat treatment of the wafer W is immediately performed by the same method as the conventional method while continuously introducing the nitrogen gas at a constant flow rate of 5 to 10 l / min into the heat treatment furnace 10. In this way, the heat treatment of the wafer W can be immediately performed without gas purging the inside of the heat treatment furnace 10, so that the time can be shortened by about 10 seconds as compared with the conventional case. When the heat treatment of the wafer W is completed, the wafer W is cooled to a desired temperature in the heat treatment furnace 10, and then the wafer W supported by the susceptor 18 is unloaded from the heat treatment furnace 10. As the wafer W is unloaded from the heat treatment furnace 10, the movable flange 16 moves to open the opening surface of the furnace port block 14, but at this time, CP
MFC44 is controlled by the control signal from U48,
The flow rate of the nitrogen gas introduced into the heat treatment furnace 10 is 30 again.
The flow rate is switched to a constant flow rate of 50 l / min. This switching of the gas flow rate is performed by an input control signal to the MFC 44 so that the actual gas flow rate introduced into the heat treatment furnace 10 temporarily exceeds the flow rate and does not cause or overshoot. It is performed based on a control program that changes gradually, not linearly. Therefore, even if the flow rate of the gas introduced into the heat treatment furnace 10 rapidly increases, the abnormal increase in the pressure inside the heat treatment furnace 10 is prevented.

FIG. 3A shows the state of change in the flow rate of nitrogen gas introduced into the heat treatment furnace 10 in the above heat treatment equipment. Further, FIG. 3B shows the state of change in the flow rate of the introduced gas in the conventional heat treatment method for comparison. In FIG. 3, the solid line indicates the actual gas flow rate introduced into the heat treatment furnace 10, and the broken line indicates the CPU 48 to the MF.
The gas flow rate corresponding to the control signal sent to C44 is shown.

In the above description of the embodiment, the wafer W is carried into the heat treatment furnace 10 by supporting the wafer W on the susceptor 18 and driving the movable flange 16, but the handling arm is used. The wafer is loaded into the heat treatment furnace by the above, and the wafer is placed on the wafer support fixed in the heat treatment furnace.The wafer is left in the heat treatment furnace and the handling arm is withdrawn from the heat treatment furnace. The method of the present invention can also be applied to a heat treatment apparatus having a mechanism for closing the opening of the heat treatment furnace. Further, although the light irradiation type heat treatment apparatus is shown in the above-described embodiment, the heat source is not limited to the light source, and may be a heat treatment apparatus that heats the substrate by various heaters.

[0020]

According to the substrate heat treatment method of the first aspect of the present invention, when the substrate is heat-treated by the single wafer method, the substrate is carried into the heat treatment furnace, the inside of the heat treatment furnace is sealed, and then the inside of the heat treatment furnace is gas-purged. Then, it is not necessary to replace the gas, or the gas purge processing time can be shortened as compared with the conventional case, so that the processing time per substrate can be shortened, and therefore the processing efficiency can be improved.

By using the substrate heat treatment apparatus according to the second aspect of the present invention, the heat treatment method of the first aspect of the present invention can be preferably performed, and the processing time per substrate can be shortened. Therefore, the processing efficiency of the device can be improved.

[Brief description of drawings]

FIG. 1 is a schematic side sectional view showing an example of a configuration of a substrate heat treatment apparatus.

FIG. 2 is a schematic piping diagram showing an example of a configuration of a gas introduction device of the heat treatment apparatus shown in FIG.

FIG. 3 (a) is a diagram showing a change state of the flow rate of gas introduced into the heat treatment furnace in the substrate heat treatment method according to the present invention, and FIG. 3 (b) is a change of introduced gas flow rate in the conventional heat treatment method. It is a figure which shows the state of.

FIG. 4 is a diagram showing a change state of a flow rate of gas introduced into the heat treatment furnace in the heat treatment method for a substrate according to the present invention.

FIG. 5 is a diagram showing how the flow rate of introduced gas into the heat treatment furnace changes in the conventional heat treatment method.

[Explanation of symbols]

 10 Heat Treatment Furnace 12 Heat Treatment Furnace Opening 14 Furnace Mouth Block 16 Movable Flange 18 Susceptor 20 Light Source for Light Irradiation 22 Reflector (Reflector) 24 Gas Introducing Channel 28 Gas Introducing Device 30 Nitrogen Gas Supplying Source 32 Gas Supplying Channel 44 Mass Flow Controller (MFC) ) 48 CPU W semiconductor wafer

Claims (2)

[Claims] 1. A heat treatment furnace which has an opening for loading and unloading a substrate and which accommodates the substrate in a single-wafer manner. By controlling a gas flow controller, outside air is passed through the opening into the heat treatment furnace. A substrate is carried into the heat treatment furnace through the opening while introducing a gas at a first flow rate that is not caught in the heat treatment furnace and allowing the gas to flow out of the heat treatment furnace through the opening. While closing the opening, the gas flow rate controller is controlled to switch to the second flow rate for heat treatment, which is lower than the first flow rate, and after the opening of the heat treatment furnace is airtightly closed, the gas is introduced into the heat treatment furnace. In the substrate heat treatment method of heating a substrate in a heat treatment furnace while introducing a gas at a second flow rate, the flow rate of the gas introduced into the heat treatment furnace is changed from the first flow rate to the second flow rate. When switching to the heat treatment furnace, the control signal input to the gas flow rate controller is controlled so as to prevent or suppress an undershoot in which the actual gas flow rate introduced into the heat treatment furnace falls below the second flow rate and becomes lower than the second flow rate. A method for heat-treating a substrate, characterized by gradually changing. 2. A heat treatment furnace having an opening for loading and unloading a substrate and containing the substrate in a single wafer, and a substrate is loaded into the heat treatment furnace through the opening and the substrate is loaded from the inside of the heat treatment furnace through the opening. Substrate carry-in / out means for carrying out, opening closing means for hermetically closing the opening of the heat treatment furnace, heating means for heating the substrate held in the heat treatment furnace, and gas flow controller into the heat treatment furnace When the substrate is carried into the heat treatment furnace through the opening and a gas introduction unit that introduces a gas at a desired flow rate, the flow rate of the gas introduced into the heat treatment furnace is such that the outside air is entrained through the opening into the heat treatment furnace. When the substrate is heated in the heat treatment furnace by the heating means so that the opening of the heat treatment furnace is closed by the opening closing means so that the first flow rate does not exceed A substrate heat treatment method, comprising: a flow rate control unit that controls a gas flow rate controller of the gas introduction unit so that a flow rate of the introduced gas becomes a second flow rate for heat treatment that is lower than the first flow rate. In, when the flow rate of the gas introduced into the heat treatment furnace is switched from the first flow rate to the second flow rate, the actual gas flow rate introduced into the heat treatment furnace is lower than the second flow rate. In order to prevent or suppress undershoot that is less than that, the flow rate control means has a control program for gradually changing a control signal input to the gas flow rate controller of the gas introduction means. Heat treatment equipment.