Single-crystal – oriented-crystal – and epitaxy growth processes; – Processes of growth from liquid or supercritical state – Having pulling during growth
Reexamination Certificate
2001-09-27
2003-05-27
Hiteshew, Felisa (Department: 1765)
Single-crystal, oriented-crystal, and epitaxy growth processes;
Processes of growth from liquid or supercritical state
Having pulling during growth
C117S014000, C117S030000, C117S032000, C117S202000, C117S208000
Reexamination Certificate
active
06569236
ABSTRACT:
TECHNICAL FIELD
This invention relates to a device and method for producing single-crystal ingot (particularly silicon single-crystal ingots) by the Czochralski method (CZ method).
BACKGROUND ART
The method for pulling single-crystals by the CZ method is commonly known art, and CZ method devices for producing single-crystal ingot are in wide use. In obtaining a single-crystal by the CZ method, the single-crystal is pulled up from the liquid surface of the raw material. The pulling speed and other conditions are variously set so as to reduce crystal defects and the like in the single-crystal that is pulled. What is being done more recently includes performing rapid cooling through the temperature region of defect formation, thereby diminishing the size of crystal defect, and making the wafer surface layer a defectless layer in subsequent heat treatment. By performing rapid cooling, the efficiency of producing single-crystal ingots can be enhanced.
As to performing the rapid cooling of single-crystals being pulled, there is a technology in which a cooler is disposed in the CZ furnace (WO93/00462 publication (Japanese Patent No. 2,562,245)). As is indicated in that publication, for the coolers used to perform the rapid cooling, cooling pipelines through which cooling water flows are generally adopted in the interest of ease of use and general purpose characteristics of the construction.
However, when a cooling pipeline through which cooling water flows is used as a cooler, there is a problem in that enormous damage will be inflicted on the device if and when the cooling pipeline fails and cooling water leaks out. When such an accident as this occurs, not only is the single-crystal ingot pulling environment adversely affected, but sometimes such an accident will lead to a situation wherein the production process is stopped, and the stable supply of single-crystal ingots is impeded.
DISCLOSURE OF THE INVENTION
In view of such problems as noted above, an object of the present invention is to effect improvements, in a single-crystal ingot producing device equipped with a cooler comprising a pipeline system through which cooling water is made to flow, to reduce device malfunctions caused by water leakage, and, simultaneously, to implement conditions for achieving maximum production efficiency.
As a result of assiduous research conducted by the inventors with a view to the problems noted in the foregoing, it was discovered that the cooler used to control crystal defects in single-crystal ingots being pulled need not be disposed in an extensive region inside the furnace, but need only be disposed in a limited narrow region. At the same time, it was confirmed that, by appropriately setting the cooling water flow volume and flow speed and the pipe diameter, etc., even when a cooler is disposed in such a limited narrow region, such a cooler functions adequately well as a cooler for raising the single-crystal ingot pulling speed and enhancing production efficiency, which leads to the completion of the present invention.
More specifically, the present invention provides the following device and method.
[Czochralski method silicon single-crystal ingot producing device]
First, the present invention provides Czochralski method silicon single-crystal ingot producing devices such as described below.
(1) A Czochralski method (hereinafter “CZ method”) single-crystal ingot producing device for pulling, inside a furnace, single-crystal ingots from a raw material melt in a crucible, comprising a thermal shielding element that encloses a single-crystal ingot being pulled (hereinafter “being-pulled single-crystal ingot”) and blocks radiant heat from liquid surface of the melt; and a cooler, disposed on inside of the thermal shielding element, for cooling a prescribed portion of the being-pulled single-crystal ingot, the thermal shielding element and the cooler being provided inside the furnace, wherein the cooler comprises a cooling pipeline through which cooling water flows, and is disposed in a portion of inside of the thermal shielding element.
(2) The CZ method single-crystal ingot producing device as described above, wherein the cooler is a cooling pipeline through which cooling water flows, and encloses the being-pulled single-crystal ingot; and inner diameter of the cooler is larger than inner diameter of the thermal shielding element.
(3) The CZ method single-crystal ingot producing device as described above, wherein lower end of the cooling pipeline is positioned at a position 150 mm or less from liquid surface of the melt.
(4) The CZ method single-crystal ingot producing device as described above, further comprising at least one of detection means noted below, either singly or in combination:
{circle around (1)} a temperature sensor provided inside a gas exhaust pathway of a CZ furnace;
{circle around (2)} tracking means for tracking intake volume of a pump for exhausting gas inside the CZ furnace; and
{circle around (3)} an infrared absorbance measuring sensor provided inside the CZ furnace or inside the exhaust path of the CZ furnace.
(5) The CZ method single-crystal ingot producing device as described above, further comprising magnetic field application means for applying a magnetic field into a raw material melt inside the crucible.
(6) The CZ method single-crystal ingot producing device as described above, wherein the magnetic field application means are magnetic field application means for generating an isometrically symmetrical and radially formed cusp magnetic field inside the raw material melt.
[Pipeline Setting Method for CZ Method Single-crystal Ingot Producing Device]
(7) A method for setting a pipeline for a CZ method single-crystal ingot producing device for causing a cooling fluid to flow through a pipeline in a CZ furnace so as to rapidly cool a single-crystal ingot being pulled, wherein position of a lower end of the pipeline through which the cooling fluid flows is set low and inner diameter of the pipeline is made small, and flow speed of the cooling fluid is controlled in accordance with diameter of the being-pulled single-crystal ingot, whereby temperature gradient of the being-pulled single-crystal ingot in pulling direction is increased, device stability is enhanced, and flexibility for arranging the pipeline is enhanced.
(8) The method as describe above, wherein the pipeline used for the rapid cooling is disposed in a portion on the inside of the heat shield in the furnace.
Here, when the inner diameter of the cooling pipeline is small, even if it should happen that a water leak occurs, the volume of leaking water will be small compared to the case of a large inner diameter. Furthermore, it was confirmed by the inventors that, in that portion that is 150 mm or less (and particularly the portion that is 100 mm or less) from the liquid surface of the silicon melt, if the inner diameter of the cooling pipeline is made smaller, there is no great change in the cooling effect contributing to the temperature gradient in the pulling direction. Accordingly, making the inner diameter of the cooling pipeline smaller in that portion means that device malfunctions caused by water leakage can be reduced while maintaining the cooling effect for contributing to the control of the temperature gradient in the pulling direction. This also, at the same time, leads to the realization of improvements in production efficiency by upping the pulling speed.
According to the present invention, the flexibility the pipeline can be enhanced. This is because, if the pipeline is narrow, the accommodation volume capacity of the pipeline may be made smaller, and bending and other processing are made easier. What is significant in the present invention, however, is that the flexibility in the arrangement of the pipeline can be enhanced without diminishing the cooling effect, and in a condition of enhanced safety. That significance is particularly great when the pipeline is disposed in a portion on the inside of the thermal shielding element.
[Temperature Gradient Controlling Met
Ebi Daisuke
Kotooka Toshirou
Monden Hiroshi
Morimoto Shigeo
Hiteshew Felisa
Komatsu Denshi Kinzoku Kabushiki Kaisha
Varndell & Varndell PLLC
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