JPS63295493A - Method for pulling up single crystal - Google Patents

Abstract

PURPOSE:To improve the productivity of a single crystal having uniform quality by determining the rising speed of a crucible by the output signals from a pulling up speed detector and single crystal diameter detector and pulling up the single crystal. CONSTITUTION:Raw materials are put into the crucible 3 and are heated to a high temp. to form a raw material melt 2. The single crystal 1 is grown by rotating and pulling up the single crystal by a pulling up shaft 4. The pulling up speed is determined by the number of revolutions of a pulling up motor 7 and the pulling up speed signal is taken out by the rotating speed detector 8 of a motor 7. On the other hand, the fluctuation in the diameter of the single crystal is detected by the outside diameter detector 16 consisting of an optical means and the output signal is inputted together with the pulling up speed signal to an arithmetic processor 17. The arithmetic processor 17 calculates the rising speed in accordance with the input signals and the signal thereof is put through a signal amplifier 14 to a motor controller 12 for lifting the crucible. The motor 10 for lifting the crucible is driven by the motor controller 12, by which the crucible 3 is raised and the liquid level position of the molten raw materials is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in a method for pulling single crystals of compound semiconductors and the like.

[Conventional technology and its problems]

Among the semiconductor single crystal manufacturing methods, the pulling method involves melting the semiconductor raw material in a crucible using high frequency or resistance heating, attaching a single crystal seed to the tip of the pulling shaft, and contacting the molten semiconductor with the seed. Once it is familiar, slowly pull it up while rotating the pulling shaft. At this time, as the crystal is pulled up, the semiconductor raw material decreases, the crystal growth area, ie, the surface position of the molten raw material liquid changes, and therefore the heating temperature conditions etc. also change. If there is any disturbance in the temperature distribution or flow of the melt at the interface between the liquid surface and the crystal, defective crystals will form that cannot be used as devices. In order to prevent such changes in crystal growth conditions, it is necessary to raise the crucible as the molten raw material decreases to keep the melt surface position constant. When pulling a crystal, the newly grown crystal that follows the seed crystal is elongated and neck-shaped, and the next growing crystal gradually becomes thicker and takes on the shape of a shoulder. It is desirable that the diameter of the body remains constant during the growth of the body.In the actual pulling process, the pulling speed and crystal diameter vary between manufacturing lots and even within the same lot, so the rising speed of the crucible is controlled. The problem arises as to how to keep the surface position of the molten raw material liquid constant.

The present invention has been made in view of the above points.
The purpose is to provide a single crystal pulling method that detects the pulling speed and crystal diameter and controls the crucible rising speed.

[Means and effects for solving the problem] In order to achieve the above object, according to the present invention, a raw material melt is prepared in a crucible, a seed crystal is brought into contact with the melt, and then gradually pulled up. A single crystal pulling method for growing a crystal following a seed crystal, comprising a pulling speed detector and a single crystal diameter detector, inputting output signals from each of the detectors to an arithmetic processor,
A method for pulling a single crystal is provided, characterized in that a crucible rising speed is determined based on an output signal from the arithmetic processor.

The diameter of the single crystal is d, its change is Δd, and the outer diameter of the crucible is D
, the pulling speed is V, and in order to keep the molten raw material liquid surface position constant, the crucible lifting speed v2 is as shown in the following equation.

From the above formula, if the single crystal outer diameter is constant, the crucible lifting speed should be proportional to the pulling speed at a constant ratio.
Furthermore, when the single crystal outer diameter varies, the second term in the above equation is corrected.

〔Example〕

The present invention will be described below based on embodiments shown in the drawings.

In the drawing, a raw material is put into a crucible (3) to form a raw material melt (2) at high temperature, and a single crystal (1) is grown by rotating and pulling it up using a pulling shaft (4). As the single crystal grows, the raw material melt (2) decreases, so the liquid surface position 09 lowers, but in order to keep the heating conditions by the heater (6) constant, the crucible is pushed up by the crucible push-up shaft (5). 3) Increase.

The pulling speed is determined by the rotational speed of the pulling motor (7), and a pulling speed signal is taken by a rotational speed detector (8) of said motor, e.g. a tachogenerator, while variations in the single crystal diameter are determined externally by optical means. Diameter detector 0
ω is detected, and its output signal is input to the arithmetic processor θ″r) together with the lifting speed signal.The arithmetic processor calculates the crucible lifting speed according to equation (1) based on the input signal, The signal enters the crucible push-up motor controller Oz through the signal amplifier 04).The motor controller a'IJ drives the crucible push-up motor 0[D to raise the crucible (3) and adjust the liquid level of the molten raw material. Control.

If the diameter of the single crystal (1) is approximately constant, the rising speed of the crucible is simply proportional to the pulling speed according to equation (1), so the calculation process can be done by a simple proportional calculation, using a potency meter or an amplifier. can do. If a specific crucible lifting speed is required, the crucible lifting speed can be set separately from the control system using the independent/interlocked switch +131.

〔Effect of the invention〕

As explained above, according to the present invention, a pulling speed detector and a single crystal diameter detector are provided, and the output signals from each of the detectors are inputted into an arithmetic processor, and the output signal from the arithmetic processor is used to control the crucible. Since the rising speed is determined, the crucible rising speed follows the pulling speed well, and the surface of the raw material melt is maintained at a constant position. Therefore, the quality of the single crystal is uniform, and its productivity is improved. have an effect.

[Brief explanation of the drawing]

The drawing is an explanatory diagram of the single crystal pulling method according to the present invention. 1... Single crystal, 2... Raw material melt, 3... Crucible, 4... Pulling shaft, 5... Crucible pushing shaft,
6... Heater, 7... Pulling motor,
8, 11... Rotation speed detector, 9, 12...
Motor controller, lO... Crucible push-up motor, 13... Independent/interlocked switching device, 14...
Amplifier in signal term, 15... Raw material melt surface, 16
... Outer diameter detector, 17... Arithmetic processor, 18.
...Independent speed setting device.

Claims (1)

[Claims] In a single crystal pulling method in which a raw material melt is created in a crucible, a seed crystal is brought into contact with the melt, and then gradually pulled up to grow a crystal following the seed crystal, a pulling speed detector and a single crystal diameter detector are used. A method for pulling a single crystal, characterized in that the output signals from each of the detectors are inputted into an arithmetic processor, and the crucible rising speed is determined based on the output signals from the arithmetic processor.