Sumitomo Metal Industries, Inc.

Sumitomo Mitsubishi Silicon Corporation

Tokuji Maeda

Keiichi Takanashi

Ken Hamada

Masato Tabuchi

Toshiyuki Yamamoto

Masahiko Mizuta

Masahiro Ogawa

Kazuo Hiramoto

Yoshiyuki Kashiwara

An apparatus is used to pull a single crystal, wherein a flow of an inert gas to the single crystal to be grown, a pressure in an apparatus body, and a temperature environment are always kept constant by keeping a melt level at a prescribed position in spite of changes in volume of a quartz crucible between batches and thermal deformation of the quartz crucible, so that high quality single crystals can be pulled. The apparatus has a reference reflector arranged inside an apparatus body, a level position measuring unit to measure an actual level position by detecting a mirror image position of the reference reflector reflected in the melt surface using a one-dimensional CCD camera arranged outside the apparatus body, a crucible ascent speed adjustment value calculating unit to calculate an adjustment value of the crucible ascent speed based on an output from the level position measuring unit, an adjustment value adding unit to add the adjustment value to the crucible ascent speed, and a level position controlling unit to control the level position in the crucible by controlling a motor for crucible lifting based on an output from the adjustment value adding means to control the crucible ascent speed.

Method for pulling a single crystal

In pulling a single crystal by CZ method, stable pulling up is carried out in a pulling rate as fast as possible while a crystal deformation is controlled to an aimed value and density of grown-in defects is suppressed to a value below an upper limit value. As an index of deformation of the single crystal from a perfect circle, the aimed value of the crystal deformation is previously determined. The upper limit value of a pulling rate necessary to suppress a defect density to an allowable range is previously calculated from distribution of grown-in defects in the crystal section, the single crystal is pulled up according to a predetermined pulling rate, and then deviation of the achieved value from the aimed value of the crystal deformation in pulling is calculated. The deviation is converted to a correction of the pulling rate. This correction is added to a set value of the pulling rate in the pulling and the result is used as a temporary set value of the pulling rate in the next pulling. The temporary set value is compared with the upper limit value of the above described pulling rate and the smaller value is determined as the pulling rate in the next runs.

Method for producing single crystal

A method of measuring a crystal section shape of a crystal being pulled from a crystal melt while rotating, including taking an image of the base of the crystal in horizontal and vertical directions with a two-dimensional camera set at an upper oblique position over the crystal; setting at least two horizontal light measuring lines in the image taken by the two-dimensional camera, being arranged in parallel in the vertical direction; detecting pairs of intersection points, at which a fusion ring intersects the two horizontal light measuring lines; transforming a position of each of the intersection points into a position of a point located on a line passing through a crystal center; determining diameters of the crystal based on the transformed positions and on time lags between two intersection points of each of the pairs of intersection points.

Crystal section shape measuring method

In a conventional method, it is difficult to reject a stray light component with certainty, so that it is difficult to accurately measure the temperature of the melt surface. Since a temperature measuring device and a computing means are expensive, the cost of the measurement tends to be high. Modifications to an existing apparatus for pulling a single crystal are required, which is an inconvenience. In order to solve the above problems, a CCD camera is used for detecting the radiation light luminance distribution of the melt surface, the minimum radiation light luminance L,is determined based on the radiation light luminance distribution data measured using the CCD camera, and the temperature T,of the melt surface within an apparatus for pulling a single crystal is computed based on the minimum radiation light luminance L,.

Methods and a device for measuring melt surface temperature within apparatus for pulling a single crystal

In the pulling of a single crystal, hitherto, it is difficult to reduce the OSF density while the deformation rate is held down within the tolerance, so that it is difficult to improve the quality and productivity. In the present invention, a deviation from a true circle in each part of a single crystal S.sub.n-1 which was pulled in the preceding batch is found and the pulling speed pattern f.sub.pn-1 (L.sub.1) in the preceding batch is updated (f.sub.pn (L.sub.1)) before a single crystal S.sub.n is pulled, in order to pull the single crystal as fast as possible so that the OSF density is small while the deviation is within the tolerance.

Growing community of inventors

Kishima-gun, Japan

Tokuji Maeda