JP2854786B2 - Silicon wafer manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a silicon wafer used for manufacturing a semiconductor device, and more particularly, to a method for irradiating a silicon wafer with neutrons to form atomic vacancies.

[0002]

2. Description of the Related Art Conventionally, as a method of manufacturing a silicon wafer of this type, a silicon wafer is irradiated with neutrons in a heavy water reactor in which a value obtained by dividing a thermal neutron dose by a fast neutron dose is 1000, and the thickness of the silicon wafer is measured in the thickness direction. Has attempted to obtain a uniform resistance distribution.

[0003]

However, in such a method for manufacturing a silicon wafer, when a semiconductor device is formed near the surface of the silicon wafer, the characteristics of the semiconductor device are significantly deteriorated, and the yield of the semiconductor device is reduced. Had a problem of a great decrease.

[0004] In other words, neutrons irradiated in a heavy water reactor with a value obtained by dividing the thermal neutron dose by the fast neutron dose are 1000, because the fast neutron dose is small, the number of atomic vacancies taken into the silicon wafer is reduced. Therefore, even when the heat treatment is performed, the precipitation of oxygen inside the silicon wafer is not easily promoted. As a result, it is difficult to form an oxygen precipitate layer inside the silicon wafer, and crystal defects caused by the oxygen precipitate layer are reduced. Therefore, when a semiconductor device is formed in the vicinity of the surface of a silicon wafer, the crystal defects inside the device become I
It became difficult to function as a G layer. Therefore, when a semiconductor device is formed near the surface of a silicon wafer, the characteristics of the semiconductor device are significantly deteriorated, and the production yield of the semiconductor device is reduced.

[0005]

Accordingly, an object of the present invention is to form a defect-free layer near the surface of an NTD (neutron irradiation) silicon wafer and form a crystal defect functioning as an IG layer therein. To provide a method for manufacturing a silicon wafer.

[0006]

According to the present invention, an oxygen concentration of 0.9 to 1.3 × 10 ¹⁸ atoms / cm ³ (former AS
TM, the same applies hereinafter), and neutrons are irradiated on the silicon wafer in a heavy water reactor having a value obtained by dividing the thermal neutron dose by the fast neutron dose of 100 to 600, and then at 600 to 1200 ° C. for 1 hour or more. This is a method for producing a silicon wafer that has been subjected to the above heat treatment.

[0007]

[Action] The oxygen concentration is 0.9 to 1.3 × 10 ¹⁸ atoms.
The silicon wafer of s / cm ³ is formed, for example, from a silicon single crystal rod pulled up by the Czochralski method.
This silicon wafer is irradiated with a predetermined amount of neutrons in a heavy water reactor whose value obtained by dividing the thermal neutron dose by the fast neutron dose is 100 to 600. By this neutron irradiation, point defects (atomic vacancies) are uniformly taken in the silicon wafer in the thickness direction. 600-120
Heat treatment is performed at a temperature of 0 ° C. for 1 hour or more. At this time,
Oxygen precipitates inside and near the surface of the silicon wafer. The precipitation of oxygen inside this silicon wafer is
It is promoted by the presence of the vacancy. As a result, an oxygen precipitation layer is formed inside the silicon wafer. On the other hand, in the vicinity of the surface of the silicon wafer, the vacancies are diffused outward by the heat treatment. Therefore, in the vicinity of the surface of the silicon wafer, the precipitation of oxygen is not promoted.
As a result, a defect-free layer is formed near the surface of the silicon wafer.

A semiconductor device having a pn junction or the like in a defect-free layer near the surface of the silicon wafer manufactured as described above is formed. At this time, crystal defects caused by the oxygen precipitate layer inside the silicon wafer function as an IG layer. As a result, this silicon wafer greatly improves its production yield.

A value obtained by dividing the thermal neutron dose by the fast neutron dose to a silicon wafer having an oxygen concentration outside the range of the present invention and less than 0.6 × 10 ¹⁸ atoms / cm ³ is 1.
Irradiate neutrons in a heavy water reactor of 00 to 600,
Heat treatment at a temperature of 00 ° C. for 1 hour or more. At this time, since the oxygen concentration of the silicon wafer is low, the precipitation amount of oxygen inside decreases. As a result, even if the precipitation of oxygen is promoted by the presence of atomic vacancies, an oxygen precipitate layer inside the silicon wafer is not easily formed, and crystal defects caused by this oxygen precipitate layer are reduced. Therefore, when a semiconductor device is formed in the vicinity of the surface of a silicon wafer, crystal defects inside the semiconductor device hardly function as an IG layer, and the production yield of the semiconductor device is reduced.

Further, a silicon wafer having an oxygen concentration exceeding 1.3 × 10 ¹⁸ atoms / cm ³ , which is outside the scope of the present invention, is subjected to a heavy water reactor having a value obtained by dividing a thermal neutron dose by a fast neutron dose of 100 to 600. Irradiate neutrons, 600-1
Heat treatment is performed at a temperature of 200 ° C. for 1 hour or more. At this time, since the oxygen concentration of the silicon wafer is high, precipitation of oxygen near the surface of the silicon wafer increases. For this reason, sufficient oxygen remains for precipitation even in the case of out-diffusion of atomic vacancies near the surface of the silicon wafer. As a result, crystal defects due to oxygen occur near the surface of the silicon wafer. Therefore, when a semiconductor device is formed near the surface of a silicon wafer, the manufacturing yield of the semiconductor device decreases.

Further, neutrons in heavy water reactors in which the value obtained by dividing the thermal neutron dose outside the scope of the present invention by the fast neutron dose exceeds 600, and the oxygen concentration is 0.6 to 1.3 × 10 ¹⁸ atoms
When irradiating a silicon wafer of s / cm ³ , atomic vacancies taken into the silicon wafer are reduced due to a small fast neutron dose. Therefore, even if heat treatment is performed at a temperature of 600 to 1200 ° C. for 1 hour or more, precipitation of oxygen inside the silicon wafer is not easily promoted. As a result, an oxygen precipitate layer inside the silicon wafer is hardly formed,
Crystal defects caused by the oxygen precipitate layer are reduced. Therefore, when a semiconductor device is formed in a defect-free layer near the surface of a silicon wafer, the crystal defects inside the semiconductor device hardly function as an IG layer, and the production yield of the semiconductor device is reduced.

Further, neutrons in a heavy water reactor having a value obtained by dividing a thermal neutron dose outside the scope of the present invention by a fast neutron dose of less than 100 and an oxygen concentration of 0.6 to 1.3 × 10 ¹⁸ atoms are obtained.
/ Cm ³ of silicon wafers, the irradiation damage due to neutron irradiation is large, that is, the fast neutron dose is large. For this reason, the number of atomic vacancies taken into the silicon wafer increases. For this reason, even if heat treatment is performed at a temperature of 600 to 1200 ° C. for 1 hour or more, atomic vacancies remain near the surface of the silicon wafer due to outward diffusion of atomic vacancies. These vacancies promote the deposition of oxygen near the surface of the silicon wafer. As a result, in the vicinity of the surface of the silicon wafer, the amount of crystal defects caused by the oxygen becomes too large. Therefore, when a semiconductor device is formed near the surface of a silicon wafer, the manufacturing yield of the semiconductor device decreases.

The oxygen concentration is 0.6-1.3 × 10 ¹⁸
A silicon wafer of atoms / cm ³ is irradiated with a predetermined amount of neutrons in a heavy water reactor having a value obtained by dividing a thermal neutron dose by a fast neutron dose of 100 to 600. This silicon wafer is subjected to a heat treatment for one hour or more at a temperature of less than 600 ° C., which is outside the scope of the present invention. At this time, since the heat treatment temperature is low, the amount of oxygen deposited inside the silicon wafer decreases. As a result, even if the precipitation of oxygen is promoted by the presence of atomic vacancies, an oxygen precipitate layer inside the silicon wafer is not easily formed, and crystal defects caused by this oxygen precipitate layer are reduced. Therefore, when a semiconductor device is formed in the vicinity of the surface of a silicon wafer, the crystal defect inside the device becomes IG.
It becomes difficult to function as a layer, and the production yield of semiconductor devices decreases.

The oxygen concentration is 0.6-1.3 × 10 ¹⁸
A silicon wafer of atoms / cm ³ is irradiated with a predetermined amount of neutrons in a heavy water reactor having a value obtained by dividing a thermal neutron dose by a fast neutron dose of 100 to 600. This silicon wafer is subjected to a heat treatment at a temperature higher than 1200 ° C., which is outside the scope of the present invention, for one hour or more. At this time, since the heat treatment temperature is high, the amount of supersaturation of oxygen decreases, and an oxygen precipitate layer is hardly formed. For this reason, crystal defects caused by the oxygen precipitate layer are reduced. Therefore, when a semiconductor device is formed in the vicinity of the surface of a silicon wafer, crystal defects inside the semiconductor device hardly function as an IG layer, and the production yield of the semiconductor device is reduced.

The oxygen concentration is 0.6 to 1.3 × 10 ¹⁸
A silicon wafer of atoms / cm ³ is irradiated with a predetermined amount of neutrons in a heavy water reactor having a value obtained by dividing a thermal neutron dose by a fast neutron dose of 100 to 600. This silicon wafer is subjected to a heat treatment at a temperature of 600 to 1200 ° C., which is shorter than one hour, which is outside the scope of the present invention. At this time, since the heat treatment time is short, near the surface of the silicon wafer,
Atomic vacancies do not diffuse outward sufficiently. For this reason, atomic vacancies remain near the surface of the silicon wafer. These vacancies promote the deposition of oxygen near the surface of the silicon wafer. As a result, in the vicinity of the surface of the silicon wafer, the amount of crystal defects caused by the oxygen becomes too large. Therefore, when a semiconductor device is formed near the surface of a silicon wafer, the manufacturing yield of the semiconductor device decreases.

[0016]

An embodiment of the present invention will be described below. First,
A silicon single crystal rod is grown by the Czochralski method (CZ method). Then, a silicon wafer is formed from the silicon single crystal rod. The oxygen concentration [Oi] of this silicon wafer is 0.6 to 1.3 × 10 ¹⁸ atoms / cm.
Set the pulling conditions etc. so that ³ .

Then, the silicon wafer is irradiated with neutrons in a heavy water reactor having a value obtained by dividing the thermal neutron dose by the fast neutron dose of 400. Thereafter, the silicon wafer is subjected to a heat treatment at 1000 ° C. for 64 hours or more.

FIG. 1 shows the resulting cleavage section of the silicon wafer. FIG. 1 is a photograph substituted for a drawing, which is obtained by using a heavy water reactor having a value obtained by dividing a thermal neutron dose by a fast neutron dose of 400. In the same figure, (A) is a central portion of the silicon wafer, (B) is a portion at a position of R (radius) / 2, (C)
Indicates a peripheral portion (outer peripheral portion) thereof. The thickness of the formed DZ is 50 to 100 μm.

On the other hand, in FIG. 2, neutron irradiation is performed in a heavy water reactor having a value obtained by dividing a thermal neutron dose by a fast neutron dose of 1000 as a comparative example, and then the silicon wafer is heated to 1000 ° C. 5 shows a photograph as a substitute for a drawing, showing a cleavage cross section of a silicon wafer when heat treatment is performed for 64 hours or more. FIG. 1A shows the central portion of the silicon wafer, FIG. 2B shows the position of about half the radius, and FIG. 1C shows the peripheral portion (outer peripheral portion).

[0020]

According to the present invention, a defect-free layer (DZ) is formed near the surface of a silicon wafer, and an IG layer is formed therein. As a result, semiconductor devices can be manufactured with a high yield.

[Brief description of the drawings]

FIG. 1 is a drawing-substitute photograph showing a crystal structure of a cleavage plane of a silicon wafer according to one embodiment of the present invention.

FIG. 2 shows a crystal structure similar to FIG. 1 showing a comparative example of the present invention.
It is a drawing substitute photograph shown .

──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Koichiro Takashima 3-8-16 Iwamotocho, Chiyoda-ku, Tokyo Inside Mitsubishi Materials Silicon Corporation (72) Inventor Hiroshi Yasuda 3-816 Iwamotocho, Chiyoda-ku, Tokyo No. Mitsubishi Materials Silicon Corporation (56) References JP-A-62-257723 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01L 21/322 H01L 21/261

Claims (1)

(57) [Claims] An oxygen concentration of 0.9 to 1.3 × 10 ¹⁸ a
Using a silicon wafer of toms / cm ³ (former ASTM), the value obtained by dividing the thermal neutron dose by the fast neutron dose is 100 to 6.
A method for manufacturing a silicon wafer, comprising irradiating the silicon wafer with neutrons in a heavy water reactor of No. 00, and thereafter performing a heat treatment at 600 to 1200 ° C. for 1 hour or more.