Semiconductor device manufacturing: process – Coating of substrate containing semiconductor region or of... – By reaction with substrate
Reexamination Certificate
2002-09-11
2004-07-27
Nhu, David (Department: 2818)
Semiconductor device manufacturing: process
Coating of substrate containing semiconductor region or of...
By reaction with substrate
C438S770000
Reexamination Certificate
active
06767848
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a silicon semiconductor substrate and a method for the production thereof. More particularly, the invention relates to a silicon semiconductor substrate which originates in a silicon semiconductor substrate so shaped as to permit easy extinction of void type defects by a heat treatment with a view to obtaining a defect-free region in a void type product and which, in consequence of a subsequent heat treatment, forms a deep defect-free surface layer, excels in device characteristics, and enjoys a satisfactory gettering property and to a method for the production thereof.
2. The Prior Art
Heretofore, as regards the improvement of the defect-freeness of the surface layer of the semiconductor substrate, the technique of heat-treating a given semiconductor substrate in an atmosphere of hydrogen gas at a temperature of 1200° C. for a duration of not less than one hour thereby inducing expansion of a defect-free layer devoid of oxygen precipitate defects to a depth of 10 &mgr;m from the surface layer has been reported (JP-A-06-252,154). This technique has been known to effect the extinction of void type defects (i.e. “empty hole” type defects) to a depth of 1 to 3 &mgr;m. Recently, the technique of effecting the extinction of the void type defects to a deeper region from the surface layer by decreasing the void type defects in size at a high density in consequence of the addition of nitrogen has been reported (JP-A-11-135,511 and JP-A-2000-256,092). In the latter invention, it is reported that the change in form of void type defects attracted interest and the addition of nitrogen in a pertinent shape of the defects proved effective.
The prior art mentioned above has barely unveiled the effect of the addition of nitrogen on the change of form manifested in the void type defects. Regarding the heat treatment which is performed for the purpose of effecting extinction of the void type defects, it has not imposed any limitation on the effective nitrogen concentration, the oxygen concentration, and the cooling rate to be used while the silicon single crystal being pulled passes through a temperature zone of 1100° C. (hereinafter referred to simply as “cooling rate”). Specifically, in the void type defects, the voids which are point defects are diffused through the surface of the void type defects during the extinction thereof by the heat treatment. The diffusion in this case is proportional to the surface area forming the peripheral parts of the void type defects. The mere mention of the effect in the change of form does not deserve to be deemed as imposing a necessary limitation on the extinction of void type defects.
In fact, the heat treatment contemplated by the prior art induces extinction of the defects barely to the extent of recording a residual ratio on the order of percent at a depth of 0.5 &mgr;m from the surface layer. It has not imposed on the void type defects a limitation enough for effecting extinction of the void type defects to such a density that the manufacture of a device under production conditions excelling in commercial productivity will not be adversely affected.
Owing to the current demand to produce silicon single crystals in increased diameters, the void type defects possibly gain unduly in growth, depending on the relevant production conditions. In the light of this fact, the prior art is suspected of manifesting its effect only insufficiently unless the addition of nitrogen is made in an adequate amount. From the viewpoint of permitting manufacture of a commercially useful silicon semiconductor substrate enjoying extinction of void type defects throughout to a deep region from the surface layer, therefore, the prior art is at a disadvantage in lacking limitations of conditions.
SUMMARY OF THE INVENTION
It is, therefore, an object of this invention to provide a novel silicon semiconductor substrate and a method for the production thereof in view of such drawbacks of the prior art as mentioned above.
To be specific, this invention is capable of effecting extinction of void type defects to a deep region from the surface layer, the feature which has not been attained by the prior art. For a fixed temperature of the heat treatment, this invention is capable of attaining the extinction of the void type defects to a region of a greater depth than the prior art.
This invention is directed to providing a method of production which enables a silicon semiconductor substrate possessing a defect-free layer of a required depth to be manufactured by performing a heat treatment for a shorter duration than the prior art in forming the defect-free layer in a fixed depth. The objects mentioned above are accomplished by the following items (1)~(10).
(1) A silicon semiconductor substrate derived from a silicon single crystal grown by the Czochralski method or the magnetic field-applied Czochralski method, characterised by satisfying the relation, 0.2≧V/S/R, providing V denotes the volume of void type defects, S the surface area thereof, and R the radius of spherical defects presumed to have the same volume as the void type defects having the volume of V.
(2) A silicon semiconductor substrate set forth in item (1) above, which contains nitrogen at a concentration of not less than 1×10
14
atoms/cm
3
and not more than 1×10
16
atoms/cm
3
.
(3) A silicon semiconductor substrate set forth in item (1) above, wherein the void type defects in the silicon semiconductor substrate having an oxygen concentration of not more than 9.5×10
17
atoms/cm
3
and a nitrogen concentration of not less than 5×10
14
atoms/cm
3
and not more than 1×10
16
atoms/cm
3
, when presumed to have spherical volumes, have a radius R satisfying R≦30 nm.
(4) A silicon semiconductor substrate set forth in item (1) above, wherein the void type defects in the silicon semiconductor substrate having an oxygen concentration of not more than 8.5×10
17
atoms/cm
3
and a nitrogen concentration of not less than 5×10
14
atoms/cm
3
and not more than 1×10
16
atoms/cm
3
, when presumed to have spherical volumes, have a radius R satisfying R≦75 nm.
(5) A method for the production of a silicon semiconductor substrate, characterised by causing a silicon semiconductor substrate set forth in item (1) above as derived from a silicon single crystal grown by the Czochralski method or the magnetic field-applied Czochralski method using a cooling rate of not less than 1° C./min while the silicon single crystal being pulled passes through a temperature zone of 1100° C. to be heat-treated in a non-oxidising atmosphere at a temperature of not less than 1150° C. for not less than one hour at least.
(6) A method for the production of a silicon semiconductor substrate, characterised by causing a silicon semiconductor substrate set forth in item (2) above as derived from a silicon single crystal grown by the Czochralski method or the magnetic field-applied Czochralski method using molten silicon containing nitrogen at a concentration of not less than 1×10
17
atoms/cm
3
and not more than 1.5×10
19
atoms/cm
3
and using a cooling rate of not less than 1° C./min while the silicon single crystal being pulled passes through a temperature zone of 1100° C. to be heat-treated in a non-oxidising atmosphere at a temperature of not less than 1150° C. for not less than one hour at least.
(7) A method for the production of a silicon semiconductor substrate, characterised by causing a silicon semiconductor substrate set forth in item (3) above as derived from a silicon single crystal grown by the Czochralski method or the magnetic field-applied Czochralski method using molten silicon containing nitrogen at a concentration of not less than 5×10
17
atoms/cm
3
and not more than 1.5×10
19
atoms/cm
3
and using a cooling rate of not less than 5° C./min while the silicon single crystal being pulled passes through a temperature zone of 1100° C. to be heat-treated in a non-oxidising atmosphere at
Ishisaka Kazunori
Tachikawa Akiyoshi
Nhu David
Wacker Siltronic Gesellschaft Für Halbleiter Materialien AG
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