JPH0444324A - Heat treatment of semiconductor wafer - Google Patents

Abstract

PURPOSE:To prevent deterioration of characteristic generated when a semiconductor wafer is taken out, by tanking out a semiconductor wafer under the condition that temperature of a process pipe is lowered than the specific value while inert gas is supplied at the specified flow rate in the pipe after completion of the heat treatment process. CONSTITUTION:After completion of heat treatment process, a cover 6 is opened under the condition that temperature of a process pipe 1 is lowered to 700 deg.C or lower, while an inert gas, for example, nitrogen gas is supplied at the flow rate corresponding to 10 to 25 cm/min within the pipe, a fork 5 is inserted into the process pipe 1 and a semiconductor wafer board 3 on which semiconductor wafers 4 are placed is taken out from the process pipe 1 in the reverse sequence of introduction of semiconductor wafers.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of heat treating semiconductor wafers used in the manufacture of semiconductor devices.

[Conventional technology]

FIG. 1 shows the structure of a heat treatment apparatus for semiconductor wafers used in the present invention and the conventional heat treatment method.
al is a vertical cross-sectional view, and -) is a cross-sectional view taken along B-B of (1). Hereinafter, the conventional heat treatment method will be explained with reference to this figure. As you can see from this figure, process tube 1 made of quartz
has a cylindrical shape, and is heated to a predetermined temperature by a heater 2 provided so as to surround the cylinder. One end surface of the process tube 1 is closed, and a predetermined gas is supplied from an air supply port IA provided at this one end surface. Process tube 1
The other end surface is open, and a lid 6 that can be opened and closed with a hinge 6A is provided on this other end surface. The semiconductor wafer 4 to be heat-treated is first vertically placed on the semiconductor wafer board 3 at a predetermined interval by a guide (not shown) outside the process tube I, and a fork 5 made of quartz is placed along with the semiconductor wafer board 3. Next, open the lid 6, insert the fork 5 into the process tube 1, carry the semiconductor wafer board 3 on which the semiconductor wafer 4 is placed to the center of the process tube 1, and then insert the fork 5 into the process tube 1. lower the fork 5 and place the semiconductor wafer board 3 in the process tube 1 (the semiconductor wafer board 3 and the fork 5 are shown in this state. After pulling out only the fork 5 from inside the process tube 1, closing the lid 6, and purging the inside of the process tube 1 by supplying an inert gas, such as nitrogen gas, from the air supply port 1^, a predetermined amount of air is applied to the semiconductor wafer 4. When the heat treatment process is completed, the lid 6 is opened, the fork 5 is inserted into the process tube 1, and the semiconductor wafer board on which the semiconductor wafer 4 is placed is carried out in the reverse order to the above-mentioned procedure for loading the semiconductor wafer. At this time, the temperature of the process tube 1 is set to be close to the heat treatment temperature, for example, 800° C. or higher, in order to shorten the heat treatment step.

[III to be solved by the invention] In the above-described semiconductor wafer heat treatment method, when the semiconductor wafer is taken out from the process tube after the completion of the heat treatment process, the process from the time when the fork is inserted into the process tube until the time when the fork is taken out from the process tube is Since the lid remains open, outside air is drawn into the process tube due to convection due to the temperature difference between the inside and outside of the tube. This entrainment of outside air affects the interfacial charge density of the silicon oxide film on the semiconductor wafer or the lifetime of the semiconductor wafer, and is a factor in deteriorating the characteristics of the semiconductor device. In recent years, semiconductor wafers have become larger in diameter, and along with this, the diameter of process tubes has also become larger.
The amount of outside air being drawn into the process tube is increasing, and the deterioration of characteristics due to this drawing of outside air is becoming more and more significant.

For example, to deal with the deterioration of characteristics due to the entrainment of outside air,
The so-called nitrogen gas curtain method has been considered, in which multiple nozzles are installed at the mouth of the process tube and the semiconductor wafer is taken out while blowing nitrogen gas from the nozzles.
It is necessary to modify the main body of the heat treatment equipment, which increases costs.

The present invention solves the above-mentioned problems and provides a method for heat treatment of semiconductor wafers that prevents characteristic deterioration that occurs when taking out the semiconductor wafer after the completion of the heat treatment process without modifying the main body of the heat treatment apparatus.

[Means to solve the problem]

In order to solve the above-mentioned problems, in the present invention, one open tube end surface is provided with a lid, and the other closed tube end surface is provided with a small diameter air supply port and has a cylindrical shape with an inner diameter larger than the diameter of semiconductor wafer 1. In a semiconductor wafer heat treatment method, the semiconductor wafer is taken out after a predetermined heat treatment process that is applied while supplying a predetermined gas from the air supply port after loading the semiconductor wafer into a process tube, wherein the semiconductor wafer is taken out. Thereafter, while supplying an inert gas at a flow rate in the tube of 10 to 25 centimeters per minute, the temperature of the process tube is lowered to 700 DEG C. or lower, and the semiconductor wafer is taken out.

[Effect]

In the semiconductor wafer heat treatment method of the present invention, after the heat treatment process is completed, the temperature of the process tube is lowered to 700°C or lower while supplying an inert gas at a flow rate of 10 to 25 centimeters per minute inside the tube. Semiconductor wafers are taken out from the process tube. When the temperature of the process tube at the time of unloading the semiconductor wafer is set to 700° C. or lower, the generation of guinea pigs due to lattice defects is suppressed, and the charge density at the silicon oxide film interface, which is one of the characteristics deterioration, is rapidly reduced.

Moreover, when the flow rate of the inert gas, such as nitrogen gas, in the process tube is in the range of lO to 25 cm per minute,
Diffusion of nitrogen gas into semiconductor wafers, such as silicon wafers, is minimized and lifetime to silicon wafers is extended. As a result, semiconductor wafers with good characteristics can be obtained without modifying the main body of the heat treatment apparatus.

〔Example〕

An embodiment of the semiconductor wafer heat treatment method according to the present invention will be explained in detail using the semiconductor wafer heat treatment apparatus shown in FIG. It is heated to a predetermined temperature by a heater 2 provided at. A temperature needle 7 is attached to the process tube 1, and measures the temperature of the process tube 1. One end surface of the process tube 1 is closed, and a predetermined gas is supplied from an air supply port IA provided at this one end surface.

Reference numeral 8 denotes a flow rate needle attached to this air supply port l^, which measures the flow rate of gas supplied into the process tube 1. The other end surface of the process tube 1 is open, and a hinge 6 is attached to this other end surface.
A lid 6 that can be opened and closed with ^ is provided. Place the semiconductor wafer 4 as the object to be heat treated on the semiconductor wafer board 3,
The procedure of transporting the process tube 1 to the center of the tube using a fork 5 made of quartz and performing the heat treatment process is the same as in the conventional method. While supplying an inert gas, for example, nitrogen gas, at a flow rate equivalent to 1.0 m, the temperature of the process tube 1 is lowered to 700 degrees Celsius or lower, the opening 16 is opened, the fork 5 is inserted into the process tube 1, and the semiconductor wafer is The semiconductor wafer board 3 on which the semiconductor wafer 4 is placed is taken out from the process tube 1 in the reverse order of the loading procedure.

Figure 2 shows the experimental results of the relationship between "process tube temperature when taking out a semiconductor wafer" and "silicon oxide film interface charge density." According to this figure, the process tube temperature when taking out a semiconductor wafer is 700°C. It can be seen that at or below that, the silicon oxide film interface charge density, which is one of the characteristics deterioration, decreases rapidly. This is considered to be because the generation of diving bonds based on lattice defects is suppressed while the temperature is lowered to 700° C. or lower. In addition, Figure 3 shows the flow rate of inert gas in the process pipe and
According to this figure, when the flow rate of an inert gas, such as nitrogen gas, in the process tube is in the range of lO to 25 cm per minute, the life time of a semiconductor wafer, e.g. , the life time to silicon wafer is the longest. This is considered to be because within this range, diffusion of nitrogen into the silicon wafer is minimized.

As described above, a semiconductor wafer with good characteristics can be obtained by the semiconductor wafer heat treatment method of the present invention.

〔Effect of the invention〕

In the semiconductor wafer heat treatment method of the present invention, after the heat treatment process is completed, the temperature of the process tube is lowered to 700°C or lower while supplying an inert gas at a flow rate of 10 to 25 centimeters per minute inside the tube. Semiconductor wafers were taken out.

As a result, it was possible to obtain a good semiconductor wafer in which the charge density at the silicon oxide film interface was improved by one order of magnitude and the lifetime of the silicon wafer substrate was improved by about 15 microseconds compared to conventional manufacturing methods. By using this semiconductor wafer, the flat band voltage characteristics of MOS IC, C
The dark current characteristics of optical sensor ICs for CDs, autofocus, etc. can be improved.

[Brief explanation of drawings]

FIG. 1 shows the structure of a semiconductor wafer heat treatment apparatus according to a method according to an embodiment of the present invention, where la+ is a vertical cross-sectional view, and crests are (
A cross-sectional view of Ml along A-A, FIG. 2 is a characteristic diagram showing the relationship between "process tube temperature at the time of taking out a semiconductor wafer" and "silicon film interface charge density" according to the present invention, and FIG. 3 is a characteristic diagram according to the present invention. FIG. 2 is a characteristic diagram showing the relationship between "the lifetime of a semiconductor (silicon) wafer" and the "in-process pipe flow rate of inert gas (nitrogen gas)" related to the process.

Claims (1)

[Claims] 1) One open tube end face is provided with a lid, and the other closed tube end face is provided with a small diameter air supply port, and after the semiconductor wafer is carried into a cylindrical process tube whose inner diameter is larger than the diameter of the semiconductor wafer, the air supply is carried out. In a heat treatment method for a semiconductor wafer, in which a predetermined gas is supplied through a port and the semiconductor wafer is taken out after completion of a predetermined heat treatment process, after the completion of the heat treatment process, the flow rate in the tube is 10 to 2 per minute.
A method for heat treatment of semiconductor wafers, characterized in that the semiconductor wafers are taken out while the temperature of the process tube is lowered to 700°C or lower while supplying 5 cm of inert gas.