JPH0812862B2 - Heat treatment method for semiconductor silicon wafers - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION In a device process, when a silicon wafer having a defect-free layer (hereinafter referred to as a DZ layer) on the surface and a defect layer (gettering layer) inside is manufactured, a DZ layer is formed. For high temperatures (for example,
(1100 ° C or higher) Heat treatment method without heat treatment.

[0002]

2. Description of the Related Art Conventionally, there is a defect-free layer on the surface, while
In order to obtain a silicon wafer in which a defect layer having a gettering effect is formed, in a device process, for example, Czochralski (hereinafter referred to as CZ)
By heating the silicon wafer manufactured by the method to a high temperature of 1100 ° C or higher, oxygen is once diffused outward,
A method in which a DZ layer is formed and then oxygen precipitation nuclei for forming nuclei for internal defects are formed by heat treatment at about 700 ° C. is implemented.

[0003]

In the conventional DZ layer formation as described above, since the high temperature heat treatment as described above is required, generation of warp, slip, etc. due to the high temperature treatment will occur in the future as the diameter of the wafer becomes larger. Is a problem. At present, in order to solve the warp and slip of the wafer, the number of wafers to be loaded is reduced to make the temperature distribution uniform, but this lowers the productivity.

[0004]

The present invention provides the above-mentioned conventional D
The present invention provides a DZ layer forming technique that does not use high-temperature treatment, in order to solve the problems of the heat treatment method for forming the Z layer. That is, the present invention provides semiconductor silicon wafers with 400-
It is characterized in that a defect- free layer is formed on the surface and a minute defect is formed inside by repeatedly performing heat treatment at a temperature of 700 ° C.

[0005]

In general, when the heat treatment temperature is as high as over 1100 ° C., the longer the time, the deeper the DZ layer formed on the wafer surface. On the contrary, when the treatment is performed at a temperature lower than that, the longer the time, the higher the internal microdefect (hereinafter referred to as BMD) density. However, even considering this fact, the formation mechanism of the DZ layer in the present invention is still unclear. That is, unlike the prior art, by removing oxygen atoms, which will be the nucleus of future defects on the wafer surface, by out diffusion at a high temperature of 1100 ° C. or higher, it is different from the action of forming a DZ layer. It is considered to be a thing. This is because outward diffusion of oxygen is not expected in the temperature range of 400 to 700 ° C. used in the present invention.

However, FIG. 3 shows the relationship between the DZ layer in the wafer and the BMD density after heat treatment at a low temperature of 650 ° C.
It becomes clear that the DZ layer can be formed to some extent even at a temperature of 00 ° C. or lower. In this case, even if the temperature is similarly low, the DZ layer formation depth becomes deeper when the heat treatment is repeatedly performed than when the temperature is kept constant, as compared with the same BMD density. Conversely, the same D
Comparing the Z layer depths, the BMD density in the wafer is higher in the case of repeated heat treatment than in the case of holding and heat treatment at a constant temperature. Therefore, at a temperature of 1000 ° C or less that does not cause distortion, warpage, or slip on the wafer,
It becomes clear that repeated heat treatment may be performed to secure the required BMD density and to efficiently form the DZ layer.

The present invention utilizes such an effect which has not been found hitherto. In order to investigate the state of BMD in the heat-treated wafer, after heat treatment, for example, by heat treatment at 1000 ° C. for 16 hours, oxygen precipitation nuclei in the wafer are grown and visualized (so-called simulation). Of course, heat treatment as heat treatment is necessary.

Hereinafter, the present invention will be disclosed in more detail with reference to Examples.

[0009]

[Example] A wafer (conductivity type: N, crystal axis: (100), resistivity: 3 to 5 which was mirror-finished from CZ single crystal silicon containing oxygen concentration: about 16 × 10 ¹⁷ atoms / cc (Old ASTM)
450 for (Ω · cm), diameter; 150 mm, thickness; 625 μm)
℃, 5hr (N ₂ atmosphere), 650 ℃, 2hr. (Dry O ₂ atmosphere)
Was repeatedly heat-treated (FIG. 1).

The purpose of this heat treatment is to create minute oxygen precipitation nuclei, and it becomes possible to control the BMD density and the formation state of the DZ layer by changing the heat treatment time and the number of repetitions. There are four repeating patterns A to D in FIG. 1, and the manner of forming the DZ layer and the like in each pattern is shown in FIG. Of these four patterns, A is only 450 for comparison with the present invention.
The treatment is performed only once at ℃. As described above, in order to visualize the BMD, the heat treatment of this example is followed by heat treatment at 1000 ° C. for 16 hours.

As a result, no warp or slip was found on any of the 100 wafers used in this example.

[0012]

[Comparative example] Oxygen concentration: Wafer mirror-finished from CZ single crystal silicon containing about 16 × 10 ¹⁷ atoms / cc (Old ASTM) (conductivity type; P, crystal axis; (100), resistivity; 3-5
(Ω · cm, diameter; 150 mm, thickness; 625 μm), 1175 ° C
After outward diffusion of interstitial oxygen near the wafer surface in (N ₂ atmosphere), a two-step heat treatment was performed at 700 ° C. (dry O ₂ atmosphere) by the conventional method of forming oxygen precipitation nuclei (FIG. 4). ). The formation of the DZ layer and the like is shown in FIG. As described above, in order to visualize BMD, the heat treatment of this reference example is followed by heat treatment at 1000 ° C. for 16 hours.

1 out of 100 wafers used in this comparative example
Warp and slip were observed on 0 sheets.

As is clear from the above, the DZ layer can be effectively formed on the wafer surface by repeating the heat treatment even in the low temperature region. Moreover, since high temperature is not used, no warp or slip on the wafer occurs.

[0015]

As described above, according to the present invention, since the high temperature heat treatment is not used as a method for forming the DZ layer on the wafer surface, warp and slip are prevented from occurring and the yield is improved. Further, the number of loaded sheets in the heat treatment can be increased, and the productivity is improved.

Further, since high temperature is not adopted, deterioration of jigs and deterioration of accuracy are reduced, and an economic effect is expected.

[Brief description of drawings]

FIG. 1 is a diagram showing a heat treatment pattern of the present invention.

FIG. 2 is a cross-sectional cleavage view of a wafer that has been heat treated according to the present invention.

FIG. 3 is a diagram showing a relationship between a BMD density in a wafer and a DZ layer.

FIG. 4 is a diagram showing a heat treatment pattern according to a conventional method.

FIG. 5 is a cross-sectional cleavage diagram of a wafer that has been heat-treated by a conventional method.

[Explanation of symbols]

A Heat treatment of 450 ° C only once B Heat treatment of 450 ° C → 650 ° C only once C Heat treatment of 450 ° C → 650 ° C two times D Heat treatment of 450 ° C → 650 ° C 3 times X 1175 ° C → 700 ° C (short time) ) Heat treatment only once Y 1175 ° C → 700 ° C (medium time) Heat treatment only once Z 1175 ° C → 700 ° C (long time) Heat treatment only once

Claims (1)

[Claims] 1. A semiconductor silicon wafer, 400-70.
A heat treatment method for a semiconductor silicon wafer, characterized in that a defect-free layer is simultaneously formed on the surface of the semiconductor wafer by repeatedly performing heat treatment in a temperature range of 0 ° C., and minute defects are formed therein.