JP4355441B2 - Heat treatment apparatus, heat treatment method, and semiconductor device manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heat treatment apparatus, and more particularly to a heat treatment apparatus equipped with a vertical furnace.
[0002]
[Prior art]
In the market, higher integration of semiconductor devices is required, and more inexpensive semiconductor devices are required.
[0003]
As a device for manufacturing a semiconductor device, there is a heat treatment apparatus such as a vertical diffusion / CVD apparatus, and this heat treatment apparatus performs processing such as formation of a thin film and diffusion of impurities on a silicon wafer.
[0004]
In such a heat treatment apparatus, in order to perform substrate processing so as to meet market demands, it is necessary to reduce the thermal budget of the wafer and to suppress the formation of a natural oxide film and to improve the throughput. Must be done.
[0005]
In the substrate processing, the temperature raising and lowering steps of the heat treatment furnace are inevitable, but the temperature raising and lowering time for film forming varies depending on the film type, but occupies 40 to 60% of the processing cycle time. . This temperature increase / decrease time is a waste time from the viewpoint of throughput, and from the viewpoint of device characteristics, a long time heat load is applied, which causes an adverse effect.
[0006]
For this reason, it is necessary to insert the wafer into the heat treatment furnace at a low temperature, raise the temperature to the treatment temperature in a short time, and then lower the temperature to a temperature that can be taken out from the heat treatment furnace quickly after the heat treatment. As a result, the thermal load is reduced, the quality is improved, the throughput is improved as the cycle time is shortened, and the cost reduction of the semiconductor device can be expected.
[0007]
An RHC (Rapid Heating Canister) furnace is known as such a furnace having high speed temperature rise and high temperature drop performance.
[0008]
A conventional RHC furnace will be described with reference to FIG.
[0009]
In the figure, reference numeral 1 denotes a quartz reaction tube. The reaction tube 1 is provided concentrically inside a SiC heat equalizing tube 2, and the heat equalizing tube 2 is surrounded by a cylindrical heater 3. The heater 3 heats the inside of the reaction tube 1 and the soaking tube 2 through the soaking tube 2. The heater 3 is usually composed of a resistance heating wire, and heating spots are eliminated by heating through the soaking tube 2. Further, the heater 3 is a Kanthal heater wire (Fe, Al, Cr alloy wire), and emits metal ions such as Fe ions, Cu ions, Al ions, Cr ions, Li ions, etc. at high temperatures. Since SiC used for the soaking tube 2 captures metal ions, it has a function of preventing metal contamination.
[0010]
A boat 4 is loaded into and withdrawn from the reaction tube 1 by a boat elevator (not shown), and wafers 5 are held in multiple stages in the boat 4 in a horizontal posture. An exhaust duct 6 communicates with the upper end of the heater 3, and a damper 7, a cooler 8 and a blower 9 are provided on the exhaust duct 6 from the heater 3 side.
[0011]
In the processing of the wafer 5, the boat 4 loaded with the wafer 5 is loaded into the reaction tube 1 and heated to a predetermined temperature by heating of the heater 3. A reaction gas is introduced from a reaction gas inlet (not shown) while being heated by the heater 3, and a required heat treatment is performed.
[0012]
When the processing is completed, in order to prevent natural oxidation of the wafer 5 when the boat 4 is pulled out, a furnace, a reaction tube, and the like are rapidly cooled, and the temperature is lowered to a predetermined temperature.
[0013]
The rapid cooling is performed by opening the damper 7, driving the blower 9, and sucking and exhausting the air in the heater 3. Air outside the furnace is sucked from the lower end of the heater 3, flows between the heater 3 and the soaking tube 2, cools the heater 3 and the soaking tube 2, and the soaking tube 2 is cooled. The reaction tube 1 and the wafer 5 are cooled. The air heated by cooling is cooled by the cooler 8 and exhausted through the blower 9.
[0014]
After the soaking tube 2, the reaction tube 1, and the wafer 5 are cooled to a predetermined temperature, the boat 4 is pulled out, and the wafer 5 is transferred from the boat 4.
[0015]
Another conventional example will be described with reference to FIGS.
[0016]
4 and 5, the same reference numerals are given to the same components as those shown in FIG. 3, and the description thereof is omitted.
[0017]
The heater 3 has a heat insulating material 10 and a heat generating wire 11 spirally provided along the inner surface of the heat insulating material 10, and the heat generating wire 11 is a hollow tube as shown in FIG. The wire 11 is formed in a coil shape centered on the axis of the reaction tube 1. A number of gas blowing holes 12 are formed at a required pitch at a position facing the coil center of the heating wire 11. Both ends of the heating wire 11 are closed, and gas introduction pipes 13 communicate with the heating wire 11 at a plurality of locations at appropriate intervals along the axial direction of the heating wire. A cooling gas is supplied from the gas introduction pipe 13.
[0018]
When the processing of the wafer 5 is completed and cooling is performed, the damper 7 is opened, the blower 9 is driven, and the air in the heater 3 is sucked and exhausted. Cooling gas is introduced into the heating wire 11 from the gas introduction pipe 13, and the introduced gas uniformly flows into the entire inner surface of the heater 3 through the numerous gas blowing holes 12.
[0019]
Thus, the cooling gas having a low temperature uniformly flows into the heater 3 to cool the soaking tube 2 evenly. The soaking tube 2 is uniformly cooled, so that the reaction tube 1 and the wafer 5 on the boat 4 are uniformly cooled and cooled.
[0020]
[Problems to be solved by the invention]
In the former case of the conventional example shown in FIG. 3, the air outside the furnace flows into the heater 3 from the lower end portions of the heater 3 and the soaking tube 2 and rises and is exhausted from the upper portion. It is lower at the lower end and higher at the upper end. For this reason, there was a problem that the soaking tube 2 first started to cool from the lower part of the furnace port through which air close to room temperature passes, and the upper part where the heat effect from the lower part was large was not easily cooled. Further, if the temperature lowering rate of the soaking tube 2 during the rapid cooling is different in the vertical direction of the reaction tube 1, the temperature lowering rate is also different due to the difference in the vertical position of the wafer 5 in the reaction tube 1. Further, since the temperature of the wafer 5 is lowered through the heat equalizing tube 2 having a large heat capacity, the influence is further increased. Therefore, there is a problem that the film forming characteristics in the vertical direction of the wafer 5 are affected.
[0021]
In the latter case of the conventional example shown in FIGS. 4 and 5, the cooling gas is allowed to flow out from the entire surface of the heater 3, so that the uniformity of the temperature drop rate in the vertical direction of the soaking tube 2 can be ensured. However, the wafer 5 is also cooled through the soaking tube 2, and a large temperature drop rate of the wafer 5 is not obtained.
[0022]
In the latter conventional example, when 150 8-inch wafers are loaded into the furnace, the temperature drop rate of the soaking tube 2 is 30 to 40 ° C./min at a practical cooling gas flow rate (−10 m 3 / min), The temperature lowering rate of the wafer 5 was 25 to 35 ° C./min.
[0023]
Accordingly, it has been difficult to obtain a wafer cooling rate (up to 50 ° C./min or more) that is currently required.
[0024]
In view of such a situation, the present invention is intended to obtain a large cooling rate while maintaining a uniform cooling rate in the vertical direction of the wafer.
[0025]
[Means for Solving the Problems]
The present invention is a heat treatment apparatus in which a reaction tube, a soaking tube, and a heater are provided concentrically, and a substrate is heat-treated inside the reaction tube, and a first space is formed between the reaction tube and the soaking tube, A second space is formed between the soaking tube and the heater, supplying cooling gas to the first space, exhausting from the upper end of the soaking tube, and supplying cooling gas from the outer periphery of the heater to the second space In addition, the present invention relates to a heat treatment apparatus configured to discharge from the upper end of the heater.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0027]
In FIG. 1, the same components as those shown in FIG.
[0028]
A cylindrical heater 16 is erected on the heater base 15, a soaking tube 17 and a reaction tube 1 are provided concentrically inside the heater 16, and a second cylinder is provided between the heater 16 and the soaking tube 17. A space 19 is formed, and a first cylindrical space 18 is formed between the soaking tube 17 and the reaction tube 1. A boat 4 for holding wafers 5 in a horizontal multi-stage can be inserted into and removed from the reaction tube 1.
[0029]
A heater case 21 is provided outside the heater 16 so as to form a third cylindrical space 22. The heater 16 has a cylindrical heat insulating material 23, and a heating wire provided in a coil shape on the inner peripheral surface of the cylindrical heat insulating material 23. 11 and the upper ends of the heater 16 and the heater case 21 are closed by an upper heat insulating material 24.
[0030]
A required number of gas blowout ports 25 communicating the third cylindrical space 22 and the second cylindrical space 19 are formed in substantially the upper half of the cylindrical heat insulating material 23 so as to have an even distribution. A lower portion of the third cylindrical space 22 is connected to a cooling gas supply source (not shown) through a flow rate adjusting valve 29 at a required position. The third cylindrical space 22 is set so that the pressure loss on the supply side of the cooling gas at each connection position is equal so that the cooling gas is supplied uniformly over the entire circumference.
[0031]
An exhaust port 26 is formed at the upper end of the soaking tube 17. The exhaust port 26 is provided concentrically with the soaking tube 17 and protrudes upward in a nozzle shape. A lower portion of the first cylindrical space 18 is connected to a cooling gas supply source (not shown) through a flow rate adjusting valve 31 at a required location. Also in the first cylindrical space 18, the pressure loss on the supply side of the cooling gas at each connection position is set to be equal so that the cooling gas is supplied uniformly.
[0032]
The upper heat insulating material 24 is formed with an elbow-shaped exhaust conduit 27 that opens to the lower surface and the side surface. The lower surface opening 28 of the exhaust conduit 27 is concentric with the exhaust port 26 and is sufficiently larger than the exhaust port 26. It has an area and communicates with the first cylindrical space 18 and the second cylindrical space 19.
[0033]
Since the wafer processing is the same as that of the conventional example, the description thereof will be omitted, and the temperature lowering action of the wafer will be described below.
[0034]
The flow rate adjustment valve 31 and the flow rate adjustment valve 29 are opened to supply a cooling gas (air or an inert gas such as nitrogen gas).
[0035]
The cooling gas flowing into the first cylindrical space 18 is a mainstream cooling gas flow in the temperature lowering action, and simultaneously cools the reaction tube 1 and the soaking tube 17 in the process of ascending the first cylindrical space 18. . The cooling gas is exhausted from the exhaust conduit 27 through the exhaust port 26.
[0036]
The cooling gas supplied to the third cylindrical space 22 is a secondary cooling gas flow, flows into the second cylindrical space 19 through the gas outlet 25, and is substantially in the upper half of the heat equalizing pipe 17. The part is cooled from the outer surface, and after cooling, it flows into the exhaust conduit 27 and is exhausted.
[0037]
As described above, the mainstream cooling gas is introduced into the first cylindrical space 18 and the reaction tube 1 having a small heat capacity is directly cooled, so that the cooling effect on the wafer 5 is great and the wafer 5 is rapidly cooled.
[0038]
In the process in which the cooling gas rises in the first cylindrical space 18, the temperature rises due to heat absorption from the reaction tube 1 and the soaking tube 17, and the cooling effect on the upper portion of the reaction tube 1, that is, the upper wafer 5 is obtained. However, since the upper half of the soaking tube 17 is cooled by the secondary cooling gas, the wafer is cooled uniformly throughout the entire area by the synergistic cooling effect of the cooling by the secondary cooling gas and the main cooling gas. Is done.
[0039]
The cooling state will be described with reference to FIG. In FIG. 2 (B), the B line shows the cooling effect by the main flow cooling gas, and in FIG. 2 (B), the C line shows the cooling effect by the side flow cooling gas. The cooling effect of the mainstream cooling gas is reduced at the top of the furnace.
[0040]
In FIG. 2 (A), the A line has shown the synthetic | combination cooling effect by a mainstream and a substream cooling gas. It can be seen that the substream cooling gas supplements the reduction of the cooling effect on the flow path of the mainstream cooling gas, and the uniform cooling effect is obtained as a whole.
[0041]
Next, the effect of suppressing wafer metal contamination in the present embodiment will be described.
[0042]
The phenomenon of metal contamination is that the heating wire 11 serving as a heater source becomes hot, metal ions are released, and move due to the diffusion phenomenon. The moved metal ions are absorbed by the portion (member) having a low temperature.
[0043]
The present invention utilizes such a metal ion diffusion phenomenon. The temperature of the exhaust port 26 is lowered, the metal ions are captured at the exhaust port 26, and the metal ions do not diffuse into the soaking tube 17. It is a thing.
[0044]
In the exhaust port 26, the mainstream cooling gas that has flowed through the first cylindrical space 18 is throttled by the effect of the nozzle shape of the exhaust port 26 and is discharged from the exhaust conduit 27. Further, the sub-flow cooling gas that has risen through the second cylindrical space 19 is throttled, and is guided to the exhaust conduit 27 and discharged by the nozzle shape of the exhaust port 26 with less resistance. Therefore, the main flow cooling gas and the side flow cooling gas flowing through the exhaust port 26 have a large flow velocity, and the exhaust port 26 has a larger cooling effect than the other portions. Further, the exhaust port 26 is located away from the heating wire 11 and is difficult to receive heat from the heating wire 11.
[0045]
According to the actual measurement, the heater temperature is 1000 ° C. and the vicinity of the exhaust port 26 of the upper heat insulating material 24 is about 130 ° C. Therefore, the temperature difference between the exhaust port 26 and the upper heat insulating material 24 is taken into consideration. Even so, the data that the temperature of the exhaust port 26 is around 180 ° C. is obtained. This temperature is sufficiently lower than the wafer temperature, and a sufficient effect of absorbing metal ions can be obtained.
[0046]
Further, since the upper portion of the soaking tube 17 is narrowed and the exhaust port 26 is opened, the escape of heat from the wafer 5 is suppressed, and soaking of the wafer 5 is possible.
[0047]
According to the present invention, the temperature decrease rate is obtained when 150 8-inch process wafers are processed, and a temperature decrease rate of 50 to 60 ° C./min is obtained.
[0048]
In the embodiment described above, the flow rate adjusting valve 29 and the flow rate adjusting valve 31 are adjusted to control the cooling gas flow rate in the first cylindrical space 18 and the second cylindrical space 19, thereby cooling the wafer 5. Can be controlled. Further, it is possible to select the distribution state of the gas outlets 25, for example, increasing the number upward, and the gas outlets 25 are provided over the entire surface of the cylindrical heat insulating material 23, You may make it select a distribution state suitably.
[0049]
【The invention's effect】
As described above, according to the present invention, in a heat treatment apparatus in which a reaction tube, a soaking tube, and a heater are provided concentrically and a substrate is heat-treated inside the reaction tube, a second step is provided between the reaction tube and the soaking tube. A first space is formed, a second space is formed between the soaking tube and the heater, a cooling gas is supplied to the first space, discharged from the upper end of the soaking tube, and the second from the outer periphery of the heater. Since the cooling gas is supplied to the space and discharged from the upper end of the heater, the reaction tube having a small heat capacity is directly cooled by the cooling gas, so that the cooling effect on the substrate is large, and the soaking tube is simultaneously provided with the reaction tube. Since it is directly cooled, a large temperature drop rate can be obtained. Furthermore, since the heat equalizing tube is auxiliaryly cooled from the outside, the cooling mode is selected. For example, if the upper part is partially cooled, it is possible to make the heat distribution even when the temperature is lowered. Demonstrate the effect.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of the present invention.
FIG. 2 is a diagram showing a temperature distribution during a temperature drop in the same embodiment.
FIG. 3 is a schematic sectional view of a conventional example.
FIG. 4 is a cross-sectional view of another conventional example.
FIG. 5 is a partial view of the other conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Reaction tube 4 Boat 5 Wafer 16 Heater 17 Heat equalizing tube 18 1st cylindrical space 19 2nd cylindrical space 23 Cylindrical heat insulating material 24 Upper heat insulating material 25 Gas outlet 26 Exhaust 27 Exhaust conduit 29 Flow rate adjustment valve 31 Flow rate adjustment valve

Claims (3)

In a heat treatment apparatus in which a reaction tube, a soaking tube, and a heater are provided concentrically and a substrate is heat-treated inside the reaction tube, a first space is formed between the reaction tube and the soaking tube, A second space is formed between the heater, the upper portion of the heat equalizing tube is throttled, an exhaust port is opened concentrically with the heat equalizing tube at the throttled upper end, and a lower opening is formed in the upper heat insulating material at the upper end of the heater. An exhaust conduit that is concentric with the exhaust port is formed, the lower surface opening has a larger opening area than the exhaust port, and communicates with the first space and the second space. Cooling gas is introduced into the first space. Supply and discharge from the exhaust port, supply cooling gas from the outer periphery of the heater to the second space, and discharge the cooling gas in the first space and the cooling gas in the second space from the lower surface opening . Heat treatment apparatus characterized by having a configuration A reaction tube, a soaking tube, and a heater are provided concentrically, a first space is formed between the reaction tube and the soaking tube, a second space is formed between the soaking tube and the heater, and the soaking tube is formed. heat tube top squeezed, squeezed the homogeneous heat pipes at the top and concentrically with the exhaust port is opened, the exhaust conduit in the upper insulation heater upper end is formed, the exhaust port on the lower surface of the exhaust Kishirubero A heat treatment method for treating a substrate inside the reaction tube, wherein the lower surface opening is formed concentrically and having a larger opening area than the exhaust port and communicated with the first space and the second space , Cooling gas is supplied to the first space, discharged from the lower surface opening through the exhaust port, and cooled gas is supplied from the outer periphery of the heater to the second space, and discharged from the lower surface opening from the periphery of the exhaust port. Heat treatment method characterized by comprising the steps of: A reaction tube, a soaking tube, and a heater are provided concentrically, a first space is formed between the reaction tube and the soaking tube, a second space is formed between the soaking tube and the heater, and the soaking tube is formed. heat tube top squeezed, squeezed the homogeneous heat pipes at the top and concentrically with the exhaust port is opened, the exhaust conduit in the upper insulation heater upper end is formed, the exhaust port on the lower surface of the exhaust Kishirubero A lower surface opening communicating with the first space and the second space and having a larger opening area than the exhaust port and processing a substrate inside the reaction tube. The cooling gas is supplied to the first space, discharged from the lower surface opening through the exhaust port, and the cooling gas is supplied from the outer periphery of the heater to the second space, and the lower surface from the periphery of the exhaust port. Characterized by having a step of discharging from the opening A method of manufacturing a semiconductor device that.

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