Leybold Aktiengesellschaft

Leybold Systems Gmbh

Balzers Und Leybold

Burkhard Altekruger

Joachim Aufreiter

Dieter Bruss

Klaus Kalkowski

Roland Gesche

Martin Flachsel

A device for controlling crystal growth processes which run through various process phases, for instance, melting or cool-down, and in which the shape of the crystal has different areas during growth, for instance, a neck and/or a shoulder. Certain process parameters and target values, as well as input values and output values, for instance, a certain gas pressure or a certain rotational speed, are also associated with each of these areas and phases. The linking of these parameters is accomplished by function generators or tables. With the aid of the control device, it is made possible to generate a specially adapted linking of the respectively necessary input and output parameters for each of the special process phases and crystal sections with an essentially uniform construction and a comprehensible structure. This permits an optimized process operation with high reproducibility, in which manual interventions by the operating personnel during the entire process and also during the transition phases between different process steps are not necessary.

Device for controlling crystal growth processes

An image of the meniscus ring (21) between the crystal (20) and the melt (4) is formed by optical means (12, 24) on a sensor, the signals of which yield the actual value for the diameter of the crystal. Two optical measuring devices are provided, the optical paths of which are defined by base points on the meniscus ring (21) and two planes which are offset by 90.degree. to each other and which are parallel to the main axis of the crystal and in tangential contact with the meniscus ring (21). The two optical paths are preferably set up to intersect, their intersection being in the viewing window.

Apparatus for drawing single crystals by the czochralski method

A source (1) is equipped with a conveying device (4) for discharging the particles (2, 2a) at adjustable rates per unit time. A crystal (16), formed from doped particles, is withdrawn from the melting crucible (13) at a predetermined rate per unit time. So that the control process can be conducted smoothly over prolonged periods of time with precise doping, the particles (2, 2a) are fed single file to the melting crucible (13) and counted by at least one sensor (21, 22). The sequence of count pulses is sent to a counter (25) and compared there with a corresponding sequence of reference input pulses. The comparison signal formed from the count pulses and the reference input pulses is used, in accordance with its sign, as a control signal for adjusting the amount of particles being discharged per unit time from source (1) to correspond to the reference value.

Controlled feeding Czochralski apparatus

A crucible is situated in a vacuum chamber and provided with a feeder for granulate material, heating elements for melting the material, and a crystal puller above the crucible. Measuring elements provide signals for a controller including a fuzzy processor utilizing an empirically determined data field to output a signal for the material feeder.

Method and apparatus for pulling monocrystals from a melt

A prefusing crucible in a closed prefusing tank is provided above a melting crucible in a closed vacuum container. Prefusing the charge material prevents thermal shock to the melt in the crucible from which monocrystals are drawn. A cover provided over the overflow from the prefusing crucible acts as a dust trap.

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Alzenau, Germany

Burkhard Altekruger