Komatsu Electronic Metals Co., Ltd.

Komatsu Corporation

Toshimichi Kubota

Makoto Kamogawa

Junsuke Tomioka

Toshirou Kotooka

Yoshiyuki Shimanuki

Toshiro Kotooka

Toshiaki Saishouji

Kouzou Nakamura

Toshiaki Saishoji

Tetsuhiro Iida

Takashi Yokoyama

Hiroshi Inagaki

Kozo Nakamura

Hirotaka Nakajima

Ayumi Suda

An apparatus for fabricating single-crystal silicon easily controlling a temperature gradient based on the Czochralski (CZ) method, and more particularly preventing as-grown defects created in order to obtain high-quality single-crystal silicon. The above-mentioned apparatus includes a first thermal shield member surrounding the pulling single-crystal silicon and a second thermal shield member inside the first thermal shield member, surrounding the pulling single-crystal silicon. The second thermal shield member is fixed on the first thermal shield member by a support located on the external surface of the second thermal shield member and connected to the first thermal shield member. The surroundings of a solid-liquid interface are extremely cooled by using the first thermal shield member, thereby a stable shape of the single-crystal silicon is formed. The temperature gradient of the temperature region of 1000.degree. C..about.1200.degree. C. where the single-crystal silicon passes is decreased by using the second thermal shield member so as to reduce the crystal defect density, thereby obtaining single-crystal silicon having a stronger oxide film voltage breakdown characteristic. If the support length is changed, the second thermal shield member can be adjusted in the upper or lower direction in order to make the expected portion of single-crystal silicon cool slowly.

Apparatus for fabricating single-crystal silicon

The cooling speed of the portion near the rear part of a single-crystal body and passing through the defect-forming temperature zone is kept the same as that of the front portion of the single-crystal body. Namely, the heater is kept in operation while pulling the single crystal silicon subsequent to forming the tail of the single crystal silicon and the cooling speed throughout the whole single-crystal body in the defect-forming temperature zone is kept below 15.degree. C./min (levels A and B). Furthermore, the length of the tail is preset in the process of pulling the single crystal silicon so that the single-crystal body cools down slowly while passing through the defect-forming temperature zone (level C). In addition, the temperature of the portion near the rear part of the single-crystal body under pulling is below the minimum temperature of the defect-forming temperature zone by shortening the distance between melted liquid surface and the portion passing through the defect-forming temperature zone of the single-crystal, and by increasing the temperature gradient along the single-crystal axis (level D).

Method of fabricating a silicon single crystal

An apparatus and a method for fabricating a single-crystal semiconductor by means of CZ method are provided for improving the quality control through the modification of thermal cycle of a pulled single-crystal semiconductor. The apparatus includes a ring after heater which is capable of elevation. The method decreases a temperature gradient to smaller than 20.degree. C./cm, and preferably under 15.degree. C./cm, when the pulled single-crystal semiconductor is cooled from 1200.degree. C. to 1000.degree. C. The after heater therefore heats the single-crystal semiconductor where there is a temperature of 100-300.degree. C. lower than the range of 1200-1000.degree. C. A thermal shelter is provided to retain a temperature gradient of larger than 20.degree. C./cm when the single-crystal semiconductor is within the temperature range between the melting point and 1250.degree. C. The after heater and the shelter can be raised to an upper portion when polysilicon blocks are charged and a twisting step is carried out.

Method for fabricating a single-crystal semiconductor

A method for fabricating a single-crystal semiconductor by means of CZ method is disclosed. The method separates the single-crystal semiconductor from the melt by increasing the lift rate when the growth of a crystal body is finished. By controlling the lift rate, the single-crystal semiconductor is then gradually cooled within a range of an arbitrary crystal temperature, thereby forming a concave separated surface. The single-crystal semiconductor is cooled at a rate of lower than 35.degree. C./min when the temperature of the separated surface is within a range between the melting point and 1000.degree. C., or by keeping the temperature of the separated surface within a range between 1250.degree. C. and 1000.degree. C. for more than 30 minutes. Therefore, no dislocation is introduced in the crystal body, and productivity is improved.

When the pulling speed is V(mm/min), the temperature gradient along the crystal axis within the temperature range from the melting point of silicon to 1300.degree. C. is G1 (.degree. C./mm), the temperature gradient along the crystal axis within the temperature range from 1150.degree. to 1080.degree. C. is G2 (.degree. C./mm), and the octahedral-shaped void density is d (pieces/cm.sup.3), crystals are grown under a condition satisfying:

Method of fabricating silicon single crystals

When the silicon single crystal is pulled up, the nucleation rate of the void cluster is obtained from the forming energy of the cluster of the vacancies in the silicon single crystal. The growth shrinkage of the cluster is obtained basing on the deviation of the flowing-into amount to the cluster of the vacancies and the self-interstitials, and the pulling-up speed or the temperature distribution of the furnace is modified to inhibit the growth of the cluster so as to inhibit the grown-in defects of the silicon single crystal.

Method of controlling defects of a silicon single crystal

An cylindrical after-heater surrounding a single crystal being lifted and a cylindrical heat-retaining cylinder installed between the after-heater and the single crystal are provided above a reversed frustrated heat-shielding sleeve disposed near the melted liquid. The heat history of the single crystal can be controlled by adjusting the output of the after-heater and the location of the heat-retaining cylinder. By such an arrangement, rapid respond to the change of the heat environment in a furnace can be made and control of the temperature gradient of the single crystal can be achieved. The single crystal, throughout the whole length, is maintained in the range of from 1000.degree. C. to 1200.degree. C. for more than one hour during lifting operation.

Apparatus for manufacturing semiconductor single crystals

This invention provides a method and apparatus for fabricating semiconductor single crystals. By using the method of this invention, the temperature gradient of the single crystal being lifted can be easily controlled. The as-grown defect density can be reduced, and it is possible to manufacture high quality semiconductor single crystals with high oxidation-film breakdown strength. A shield cylinder is used for surrounding the semiconductor single crystal 7 being lifted, the shield cylinder is made to be of the telescopic type and consists of a first shield duct 4, a second shield duct 5, a third shield duct 6. A wire 8 wrapping around a wind-up reel 10 is engaged with the third shield duct 6, and the shield cylinder can be driven to extend or retract by rotating the wind-up reel 10. An ascend and descend rod 3 is connected with the first duct 4, and the shield cylinder can be driven to move upward or downward by lifting or lowering the ascend and descend rod 3. The wind-up reel 10 is driven to retract part of the shield cylinder so that the lapped portion of the shield cylinder keeps a predetermined portion of the semiconductor single crystal 7 being lifted warm, and the temperature gradient of the semiconductor single crystal 7 can be reduced when it passes through the zone whose temperature is within a range from 1000.degree. C. to 1200.degree. C.

Method and apparatus for fabricating semiconductor single crystal

The object of this invention is to provide a method and a device for manufacturing semiconductor single crystals by the CZ method in response to the increase in the weight of semiconductor single crystal produced. The necked portion formed beneath the reduced portion can be held and the single crystal under lifting can be re-melted.

Apparatus and method for lifting single crystals

An apparatus and a method for fabricating a single-crystal semiconductor by means of a CZ method are provided for improving the quality through modification of the thermal cycle of a pulled single-crystal semiconductor. The apparatus includes a ring-shaped after heater which is capable of elevation. The method decreases the temperature gradient to smaller than 20.degree. C./cm, and preferably under 15.degree. C./cm, when the pulled single-crystal semiconductor is cooled from 1200.degree. C. to 1000.degree. C. The after heater therefore heats the single-crystal semiconductor where there is a temperature of 100.degree.-300.degree. C. lower than the range of 1200.degree.-1000.degree. C. A thermal baffle (or shield) is provided to retain a temperature gradient of larger than 20.degree. C./cm when the single-crystal semiconductor is within the temperature range between the melting point and 1250.degree. C. The after heater and the baffle (or shield) can be raised to an upper portion when polysilicon blocks are charged and a twisting step is carried out.

Apparatus for fabricating a single-crystal semiconductor

In the manufacture of a single crystal using a semiconductor single-crystal pulling apparatus equipped with a radiation screen, the time of passage of the single crystal through the high-temperature region of 1050.degree. C. and above is made to be long and the time of passage of the single crystal through the temperature region of about 900.degree. C.-500.degree. C. is made to be short. The semiconductor single-crystal pulling apparatus is so constructed that a radiation screen comprises an upper screen of 3-layer construction consisting of a heat-insulating member made of graphite or ceramics fiber clad with outer members made of graphite and a lower screen 3 of single-layer construction made of graphite, quartz or fine ceramics. Radiant heat from the molten liquid heats the lower part of single crystal as it passes through lower screen, thereby prolonging its period of passage through the high-temperature region. The radiant heat cannot reach single crystal when it is surrounded by upper screen, so it is cooled comparatively abruptly and can pass through the temperature region of about 900-500.degree. C. in a short time.

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Hiratsuka, Japan

Toshimichi Kubota