JPH0372599B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a technique for performing oxidation treatment or diffusion treatment in a wet oxygen atmosphere.
For example, regarding heat treatment technology, Electronic
It is introduced on pages 48 to 50 of Integrated Circuits (written by J. Allison).

In the oxidation/diffusion process of semiconductor thin plates (wafers) in the manufacture of semiconductor devices, hydrogen (H ₂ ), oxygen (O ₂ Wet oxygen generation method (burning method) by direct reaction of )
is generally adopted. As a method of producing wet oxygen of this type, a pyrogenic hydrogen combustion mechanism as shown in FIG. 1 is known. That is,
A hydrogen supply tube 3 made of quartz glass is inserted into a narrow tail tube 2 of a process tube 1 made of quartz glass in an airtight state through mutual rubbing surfaces to supply hydrogen ( H ₂ ). In addition, a technical tube 4 is made at the closed end of the furnace core tube 1 in parallel with the tail tube 2, and the furnace core tube 1 is connected through this technique tube 4.
Oxygen (O ₂ ) is supplied inside. Further, a heater section 5 consisting of a soaking tube, a heater, etc. is disposed around the outer periphery of the furnace core tube 1, and heats a processing chamber 6 within the furnace core tube 1 to an appropriate temperature. When forming an oxide film on the wafer, the silicon wafer is placed into the processing chamber 6 heated to a predetermined temperature using a heat treatment jig (not shown), and then oxygen is supplied from the technique tube 4 to the processing chamber 6. At the same time, hydrogen is supplied into the processing chamber 6 from the hydrogen supply pipe 3. Since the inside of the processing chamber 6 has reached a predetermined temperature and hydrogen and oxygen are each sent into the processing chamber 6 at a predetermined ratio, the hydrogen and oxygen burn without exploding (flame 7 is shown). Oxygen containing water vapor, that is, wet oxygen, is supplied toward the center of the reactor core tube 1 to thermally oxidize (SiO ₂ ) on the wafer surface.
Formation of a film is being carried out.

However, such a mechanism has the following drawbacks.

(1) The temperature of the elongated reactor core tube is generally controlled by three heaters A, B, and C arranged in series, and as shown in Figure 2, the temperature distribution is constant in the central part. In addition, in order to maintain a constant temperature distribution over a constant length, heaters A and C located at both ends keep the temperature at both ends of the core tube slightly higher than that at the center. controlled so that However, when hydrogen and oxygen are reacted and burned at the closed end of the core tube, the back of the core tube becomes the second
As shown by the two-dot chain line in the figure, the temperature rises locally, impairing the uniform temperature distribution within the reactor core tube, and making the formation of an oxide film uneven. Note that, in general, the central heater B only plays the role of raising and lowering a constant temperature, and does not have the function of correcting the temperature difference between the two ends of the reactor core tube.

(2) It is necessary to check the ignition (combustion) state in order to confirm safety and whether an oxide film is being formed properly. Combustion takes place inside the core tube, and the outside of the core tube is heated. To check the ignition (flame 7), one must look through the opening of the core tube. However, because the wafers are inserted into the reactor core tube in a row, it is difficult to confirm ignition (combustion).

(3) If an explosion occurs due to a change in the mixture ratio of hydrogen and oxygen or the temperature in the processing chamber becomes low, the reactor core tube is made of quartz glass, so it will break into powder and scatter into the surrounding area, creating a dangerous situation. In addition, it has the disadvantage of damaging the wafer and heater section.

(4) Especially in the case of a diffusion furnace, it is common to install a new technical tube in addition to the tail tube at the closed end of the reactor core tube in order to supply the reactant gas. However, in the above-mentioned method, the structure of the furnace core tube becomes complicated and the manufacturing cost becomes high. In addition, because there are two thin and easily broken tail tubes and two tip tubes at one end of the furnace core tube, handling is more troublesome than the conventional furnace core tube that only has a tail tube.

Therefore, an object of the present invention is to provide a heat treatment technique in wet oxygen that does not disturb the temperature distribution within the processing chamber.

Another object of the present invention is to provide a device that allows easy confirmation of the ignition state and is highly safe.

In order to achieve these objects, the present invention provides a heat treatment method that can eliminate adverse effects on wafers and the like by burning oxygen and hydrogen outside a reaction tube.

FIG. 3 is a schematic diagram showing a wet oxygen generating apparatus and a diffusion furnace including the wet oxygen generating apparatus used in one embodiment of the present invention. The figure shows an airtight container (box) 8 made of quartz glass. This container 8 is housed in a doping box 9 of a diffusion furnace.
Further, the container 8 has a three-layer structure, and the innermost layer box 10 is made of quartz glass so that it does not generate impurities and can withstand high temperatures. The outermost box 11 is made of a metal container, such as stainless steel, which has a strength that will not cause damage even if an explosion occurs inside the container. Further, a heat insulating material such as quartz wool is inserted between the outermost box 11 and the innermost box 10 to enhance the heat insulating effect, forming a heat insulating layer 12.

A plurality of pipes 13 are integrally attached to the innermost box 10 on its upper surface and side portions. That is, one side wall has a hydrogen supply pipe 14 for introducing it into the hydrogen gas container 8 and a pipe for introducing oxygen gas into the container 8.
An oxygen supply pipe 15 is provided to introduce the oxygen into the inside.
The hydrogen supply pipe 14 extends into the container through the innermost box 10, and its tip protrudes below the center of the ceiling of the innermost box 10. Also, container 8
A spiral-shaped heater 16 is installed in the hydrogen supply pipe 14 portion inside.
is wrapped around the innermost box 1 at both ends.
0, the heat insulating layer 12, the outermost box 11, and extends outside the container, and is connected to a predetermined power source (not shown). The heater 16 is covered on the outside with quartz glass and is welded to the innermost box 10 via the quartz glass to maintain airtightness of the insertion portion. Further, the upper part of the spiral part 17 of the heater 16 extends over the extension of the nozzle part 18 at the tip of the hydrogen supply pipe 14, and heats the area around the nozzle part 18.

Further, a conduit 19 is provided on the ceiling of the innermost box 10 facing the nozzle part 18, and water vapor generated by the combustion reaction between the hydrogen gas spouted from the nozzle part 18 and the oxygen gas filling the container. (indicated by scattered dots in the figure) is led out of the container 8 together with oxygen. Further, in order to detect the temperature of the flame 20 due to combustion, a thermocouple terminal 21 is connected to the flame 20.
from outside the container. This thermocouple terminal 21 is connected to the innermost box 10 whose inner end is closed.
It is covered with a protective tube 22 made of quartz glass that extends from the quartz glass. Further, a drain pipe 23 made of quartz glass is attached to the lower side of the container 8 to drain water accumulated at the bottom of the container. This drain pipe 23 is provided with a drain pot 24. Although not shown, the container 8 is provided with a reaction gas supply pipe for processing the object to be processed.
Further, the outermost box 11 and the heat insulating layer 12 are partially removed to form an observation window 25 so that the flame 20 burning inside the container 8 can be observed from outside the container. Note that a transparent protective plate with excellent heat resistance may be attached to the observation window 25 to serve as a protective plate when the innermost box 10 explodes. Furthermore, the innermost box 10 and the heat insulating layer 12 are constructed to be sequentially removable from the outermost box 11.

On the other hand, a conduit 19 protruding from the container 8 is connected to a narrow tail tube 27 of a standard type core tube 26 via an auxiliary conduit 28 made of a tube made of fluororesin or the like. Incidentally, a connector 29 for connecting this type of pipe, which is generally known, is used in each of the connecting portions. Furthermore, a ribbon heater 30 is wrapped around the outer periphery of the connector 29 and the auxiliary conduit 28 to prevent the water vapor flowing inside the auxiliary conduit 28 from becoming water droplets, and to constantly supply wet oxygen at a constant temperature to the reactor core tube. There is. Further, numeral 31 in the figure is a heater section that heats the furnace core tube 26.

Next, the operation of supplying wet oxygen to the reactor core 26 will be explained. The vicinity of the nozzle portion 18 of the hydrogen supply pipe 14 is heated to a predetermined temperature by the heater 16, and oxygen gas is injected from the oxygen supply pipe 15 into the container 8 to fill it with oxygen. Also,
Hydrogen gas is injected from the nozzle part 18. In addition,
The hydrogen gas and oxygen gas are supplied in a predetermined ratio. As a result, the hydrogen injected from the nozzle portion 18 reacts with oxygen and burns, generating water vapor. Since the pressure inside the vessel 8 is high, the oxygen in the steam in the vessel (and reactant gases such as diffusion impurities, if necessary) pass through the conduit 19 and the auxiliary conduit 28 into the core tube 26. Supplied sequentially.

According to such an embodiment, the following effects are achieved.

(1) Wet oxygen supplied to the reactor core tube is always maintained at a constant temperature by a ribbon heater and then supplied to the reactor core tube. Therefore, the temperature distribution in the furnace tube is stabilized, so that wafer processing with excellent quality and reliability can be performed, and yields can also be improved.

(2) Since the combustion status can be easily observed through the observation window of the vessel, it can be confirmed whether steam is being reliably sent to the reactor core tube. Therefore, it is also possible to avoid performing wafer processing in a state where water vapor is not applied.

(3) Even if an explosion occurs inside the container, the outermost layer of the container is pressure-resistant and strong, so fragments of quartz glass will not scatter outside the container, unlike conventional methods. Therefore, it is safe. Furthermore, since the wafer is not damaged by flying quartz glass pieces as in the conventional case, there is no possibility of a decrease in holding capacity. Furthermore, since the heater part is not destroyed by flying quartz glass pieces, the life of each part of the heat treatment furnace apparatus is extended, which also leads to a reduction in product processing costs.

(4) Since a standard core tube with a tail tube can be used, equipment costs are also low.

[Brief explanation of drawings]

Figure 1 is a partial sectional view showing a wet oxygen generation mechanism that supplies wet oxygen to the core tube of a conventional diffusion furnace, Figure 2 is a temperature curve diagram showing the temperature distribution in the core tube, and Figure 3 is a diagram of the present invention. 1 is a cross-sectional view showing a wet oxygen generation device and a diffusion furnace including the same. 1... Furnace core tube, 3... Hydrogen supply pipe, 5... Heater section, 6... Processing chamber, 7... Flame, 8... Container, 1
0... Innermost layer box, 11... Outermost layer box, 12... Heat insulation layer, 14... Hydrogen supply pipe, 15
... Oxygen supply pipe, 16 ... Heater, 18 ... Nozzle section, 19 ... Conduit, 20 ... Flame, 21 ... Thermocouple terminal, 25 ... Observation window, 26 ... Reactor core tube, 27
... tail pipe, 28 ... auxiliary conduit, 30 ... ribbon heater, 31 ... heater section.

Claims (1)

[Claims] 1. When heat-treating semiconductor wafers in a wet oxygen atmosphere, oxygen and hydrogen are burned outside the reaction tube to generate a wet oxygen atmosphere, and this wet oxygen atmosphere is passed through a conduit connected to the tail tube of the reaction tube. A method for heat treating a semiconductor wafer, which method comprises introducing the semiconductor wafer into the reaction tube.