Abstract: In silicon single crystal growth by the Czochralski method using a quartz crucible, a silicon single crystals with a uniform distribution of oxygen concentration can be produced in high yield without being affected by changes of crystal diameter and initial amount of melt feedstock. The oxygen concentration is adjusted by estimating oxygen concentration during growth on the basis of a relationship among three parameters: crucible rotation rate (?), crucible temperature (T), and the ratio (?) of contact area of molten silicon with the inner wall of the crucible and with atmospheric gas, and by associating the temperature (T) with the ratio (?) by the function 1/?×Exp(?E/T) where E is the dissolution energy (E) of quartz into molten silicon to control at least one of the rotation rate (?) and temperature (T) to conform the estimated oxygen concentration to a target concentration.

Abstract: An active layer side silicon wafer is heat-treated in an oxidizing atmosphere to thereby form a buried oxide film therein. The active layer side silicon wafer is then bonded to a supporting side wafer with said buried oxide film interposed therebetween thus to fabricate an SOI wafer. Said oxidizing heat treatment is carried out under a condition satisfying the following formula: [Oi]?2.123×1021exp(?1.035/k(T+273)), where, T is a temperature of the heat treatment, and [Oi] (atmos/cm3) is an interstitial oxygen concentration.

Abstract: There are disclosed a silicon seed crystal which is composed of silicon single crystal and used for the Czochralski method, wherein oxygen concentration in the seed crystal is 15 ppma (JEIDA) or less, a silicon seed crystal which is used for the Czochralski method, wherein the silicon seed crystal does not have a straight body, and a method for producing a silicon single crystal by the Czochralski method comprising using said seed crystal, bringing a tip end of the seed crystal into contact with a silicon melt to melt the tip end of the seed crystal, with or without performing necking operation, and growing a silicon single crystal. The method is capable of improving the rate of success in making crystals dislocation-free and the productivity of single crystal rods regardless of the use of necking operation.

Abstract: A process for producing nitrogen-doped semiconductor wafers has the nitrogen being derived from a dopant gas which contains NH3. The process includes pulling a single crystal from a melt of molten semiconductor material, feeding the dopant gas to the semiconductor material, and cutting the nitrogen-doped semiconductor wafers off the pulled single crystal. The dopant gas is fed to the semiconductor material at most until pulling begins for that part of the single crystal from which the semiconductor wafers are cut.

Abstract: A process for producing silicon wafers with low defect density is one wherein a) a silicon single crystal having an oxygen doping concentration of at least 4*10.sup.17 /cm.sup.3 is produced by molten material being solidified to form a single crystal and is then cooled, and the holding time of the single crystal during cooling in the temperature range of from 850.degree. C. to 1100.degree. C. is less than 80 minutes; b) the single crystal is processed to form silicon wafers; and c) the silicon wafers are annealed at a temperature of at least 1000.degree. C. for at least one hour. Also, it is possible to prepare a silicon single crystal based upon having an oxygen doping concentration of at least 4*10.sup.17 /cm.sup.3 and a nitrogen doping concentration of at least 1*10.sup.14 /cm.sup.3 for (a) above.

Abstract: A method for controlling oxygen precipitation (106) in a silicon crystal (12) grown according to the Czochralski silicon crystal growing technique which includes the steps of forming a cylindrical portion (22) of the silicon crystal (12) from a reservoir of molten silicon (24) according to the Czochralski silicon crystal growing technique. The method includes the steps of terminating the Czochralski silicon crystal growing technique by forming a first tapered portion (101) in silicon crystal (12) at a predetermined rate. A second tapered portion (102) includes a cascaded middle portion (108) that connects to the first tapered portion (101) and that concentrates oxygen precipitation (106) within cascaded middle portion (108) and away from the cylindrical portion (22) of silicon crystal (12). At least a third tapered portion (104) is formed for separating silicon crystal (12) from molten silicon (24).

Abstract: A method for controlling oxygen precipitation (106) in a silicon crystal (12) grown according to the Czochralski silicon crystal growing technique which includes the steps of forming a cylindrical portion (22) of the silicon crystal (12) from a reservoir of molten silicon (24) according to the Czochralski silicon crystal growing technique. The method includes the steps of terminating the Czochralski silicon crystal growing technique by forming a first tapered portion (101) in silicon crystal (12) at a predetermined rate. A second tapered portion (102) includes a cascaded middle portion (108) that connects to the first tapered portion (101) and that concentrates oxygen precipitation (106) within cascaded middle portion (108) and away from the cylindrical portion (22) of silicon crystal (12). At least a third tapered portion (104) is formed for separating silicon crystal (12) from molten silicon (24).

Abstract: The amount of Group-V element included in a melt 6 has the close relationship with the oxygen concentration of the melt 6. This relationship is utilized for controlling the oxygen concentration of a single crystal 8 at a high level. The content of Group-V element is calculated from the weight of the melt 6 gauged by a gravimeter 11 and compared with a preset value in a control unit 12. When the calculated content is smaller than the preset value, the control signal to additionally supply Group-V element to the melt 6 is outputted from the control unit 12 to a feeder 14. When the calculated content is larger than the preset value, the control signal to supply a raw material to the melt 6 is outputted to another feeder 13.

Abstract: A method for controlling oxygen precipitation (106) in a silicon crystal (12) grown according to the Czochralski silicon crystal growing technique which includes the steps of forming a cylindrical portion (22) of the silicon crystal (12) from a reservoir of molten silicon (24) according to the Czochralski silicon crystal growing technique. The method includes the steps of terminating the Czochralski silicon crystal growing technique by forming a first tapered portion (101) in silicon crystal (12) at a predetermined rate. A second tapered portion (102) includes a cascaded middle portion (108) that connects to the first tapered portion (101) and that concentrates oxygen precipitation (106) within cascaded middle portion (108) and away from the cylindrical portion (22) of silicon crystal (12). At least a third tapered portion (104) is formed for separating silicon crystal (12) from molten silicon (24).