JPS6013299B2 - Heat treatment method for semiconductor devices - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of arranging a plurality of wafers in parallel in a furnace and performing heat treatment such as impurity diffusion.

Conventionally, when forming a diffusion layer on a semiconductor wafer by diffusing impurities or growing a thermal oxide film, multiple semiconductor wafers are lined up on a diffusion boat with their surfaces facing in a certain direction. 1000 in a heating furnace
Heat treatment is performed at a high temperature of o0 or higher, but this heat treatment must be repeated several times until the semiconductor wafer has a predetermined function.

However, in this case, an impurity diffusion layer is often formed on the back surface of the semiconductor wafer during the previous heat treatment process, and as a result, impurity scattering (zero-core tdiffusion) occurs from the wafer surface, especially from the wafer back surface, during the subsequent heat treatment. However, such scattering phenomenon has a negative effect on the characteristics of the obtained semiconductor wafer. For example, when an impurity source having an opposite conductivity type (N type) is deposited on a specific location on the surface of a substrate having one conductivity type (for example, a P type substrate) and an N type diffusion layer is formed by thermal diffusion, the previous N-type impurities formed on the back surface of the semiconductor wafer due to heat treatment scatter to the surface of the opposing semiconductor wafer, and a diffusion layer of N-type impurities is formed in areas other than the predetermined diffusion layer formation area, which adversely affects the characteristics of the semiconductor wafer. It is. The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a method for heat treatment of semiconductor wafers that can avoid the adverse effects caused by the scattering phenomenon during heat treatment of semiconductor wafers as described above.

That is, the present invention is a method of arranging a plurality of semiconductor wafers in a diffusion boat in parallel and heat-treating them in a diffusion furnace, in which two adjacent semiconductor wafers are arranged in a diffusion boat in a parallel state with their back surfaces facing each other. The present invention also provides a method of heat treatment for a semiconductor device, characterized in that heat treatment is performed to form a diffusion layer or an oxide film by diffusion of impurities.

Hereinafter, the present invention will be explained with reference to illustrated specific examples.

In the figure, reference numeral 11 denotes a diffusion furnace, and a diffusion boat 13 containing a plurality of semiconductor wafers 12 is housed therein. These semiconductor wafers 12 are arranged in pairs with their back surfaces 12a facing each other, and have a distance A between the back surfaces 12a.
are arranged in parallel so that the distance 8 between the surfaces 12b of the semiconductor wafers 2 is narrower than that between the surfaces 12b. When heat treatment such as impurity diffusion is performed with the semiconductor wafers 12 arranged on the diffusion boat 13 in this manner, even if impurities are scattered from the back surface 12a of the semiconductor wafers 12, such impurity scattering will be prevented. Most of them act only between the back surfaces 12a of the semiconductor wafers, as shown in FIG. Since it can be made larger than the conventional one, the influence of scattering from the wafer surface 12b is reduced, and the influence on the semiconductor wafer surface 12b, which governs the characteristics of semiconductor devices, is significantly reduced.

FIG. 3 shows the method of the present invention in which the spacing A between the backsides of semiconductor wafers is set to 1. As a matter of fact, the distance B between the semiconductor wafer surfaces is 6
．． The characteristics of a diode obtained by performing impurity diffusion as zero ribs are compared with the characteristics of a diode obtained by performing impurity diffusion under the same conditions with the surface of a conventional semiconductor wafer oriented in a certain direction and arranged at equal intervals. This is a comparison using the current IR evaluation method.

Among these, distribution 14 shows the case of the conventional method, and distribution 15 shows the case of the present invention.As is clear from these results, the semiconductor device obtained by the present invention is less affected by the scattering phenomenon of impurities than the conventional method. As you can see, it becomes significantly less painful. The present invention is characterized in that the spacing between the back surfaces of the semiconductor wafers arranged in parallel on the diffusion boat is narrower than the spacing between the front surfaces.

At the same time, it is preferable to make the distance between the back surfaces of the semiconductor wafers as small as possible in order to reduce the adverse effects caused by the scattering phenomenon of impurities. In addition, in the above example, the diameter is 2
I explained about inch wafers, but if the diameter of the wafer changes, the degree of influence of impurity scattering will naturally change.
It is preferable that the above-mentioned intervals A and B also be changed. For example 2.
For a 5-inch diameter wafer, A = 1.5 sails, B = 9
For a wafer with a diameter of 3.0 inches, A=2
It can be said that 8 = 12 side is appropriate.

[Brief explanation of drawings]

Fig. 1 shows a specific example of the method of the present invention. Fig. 2 is a cross-sectional view showing a part of the interior of the diffusion furnace. Fig. 2 is a side view showing an enlarged view of the part shown in Fig. 1. FIG. 3 is a diagram showing the invention in comparison with a conventional example. In the figure, 11 is a diffusion furnace, 12 is a semiconductor wafer, 12a is the back side of the semiconductor wafer, 12b is the front side of the semiconductor wafer, 3
is a diffusion boat. Figure hFigure 2Figure 3

Claims (1)

[Claims] 1 In a method of arranging a plurality of semiconductor wafers in a diffusion boat and heat-treating them in a diffusion furnace, the back surfaces of two adjacent semiconductor wafers are arranged in parallel to face each other, and the distance between the front surfaces is smaller than the gap between the back surfaces. A method for heat treatment of a semiconductor device, characterized by placing the semiconductor device in a large state in a diffusion boat and performing heat treatment.