DE1138353B - Device for dividing crystals, in particular for cutting up semiconductor crystals - Google Patents

Description

In semiconductor technology, for the production of semiconductor crystals, in particular of semiconductor single crystals, Process used in which the semiconductor material is in the form of larger crystal rods receives. For further processing into semiconductor crystal components, it is then necessary these rods into smaller pieces, e.g. B. slices to be divided. Because semiconductor materials as used for semiconductor devices are used, are very expensive to manufacture, the question plays in the division after the cutting losses a large role, so that the application of too little cutting losses leading sawing tool is of great importance. The use of circular saws, e.g. B. Diamond saws or fretsaws, generally leads to large cutting losses because of the rigidity of these saws.

It was now known to use a band-shaped or thread-shaped sawing tool for dividing crystals is moved in the longitudinal direction, whereby the crystal at the cut surface through the solvent carried along by the sawing tool is slowly dissolved. It was also used for sawing Stones known to use a cable or a wire as a sawing tool, on which one from a device supplied, moistened abrasive is applied. It was known about this after all Purpose of using a saw made of a wire or cable, the one with a softer sheath is provided to facilitate the adhesion of an abrasive.

The invention relates to a device for dividing crystals, in particular for cutting of semiconductor crystals, with a thin saw wire moved only in the longitudinal direction Tensile strength stretched over at least two guide rollers and covered with an abrasive is.

According to the invention it is proposed that the saw wire consists of a core made of hard, magnetizable Material, especially steel, with a sheath made of copper or silver, that one the Saw wire magnetizing device in front of the work place and demagnetizing device behind the work place and an abrasive made of powdery, magnetizable material, in particular ferrite feeding device are provided.

The use of a thread covered with a solvent as a sawing tool provides a Range of materials to be sawn gives satisfactory results. However, it appears in some In some cases it is advisable to refrain from using a solvent and sawing the crystal Device for dividing crystals,

especially for cutting

of semiconductor crystals

Applicant:

Siemens & Halske Aktiengesellschaft,
ίο Berlin and Munich,

Munich 2, Wittelsbacherplatz 2

Kurt Eltze, Dr.-Ing. Heinz executioner

and Dipl.-Ing. Fritz-Adolf Mentzel, Munich,

have been named as inventors

on a purely mechanical basis. It was found in the investigations leading to the invention show that the use of a tensile strength, surrounding with a softer jacket Wire as a sawing tool with simultaneous use of an abrasive also when sawing Semiconductor crystals consistently delivers satisfactory results with regard to cutting losses, if the sawing tool has the structure taught according to the invention. In particular, it allows use a high-tensile saw wire covered with copper or silver to compensate for pressure differences, due to the different size and position of the grains of the abrasive on the sawing tool caused, so that the inevitably caused by the cutting process crystal disturbances the cut surfaces penetrate the crystal much less than when using a homogeneous, the required tensile strength, but generally very hard sawing tool is the case were.

On the other hand, in the interest of the uniformity of the sawing process, it appears expedient if the Saw tool in a known manner only in its longitudinal direction over or through the to be cut Crystal is moved. Since then, however, guides such. B. roles, necessary for the sawing tool is due to adhering to the sawing tool

Abrasives an unevenness of the guides and possibly damage to these guides possible. For this reason it appears

209 677/42

beneficial if the abrasive is removed from the sawing tool before entering the guides will.

Accordingly, according to the teaching of the invention, the sawing tool consists of a wire made of magnetizable wire High tensile strength material, e.g. B. made of steel or iron, with a sheath made of copper or silver. The abrasive also consists of a magnetizable material, e.g. B. Ferrite powder. Before passing the interface, the tool is magnetized and in contact with the Brought abrasive, which as a result adheres well to the sawing tool. After passing the interface the tool is demagnetized again, causing the abrasive to fall off.

In the drawing is an embodiment of the Device according to the invention shown. 1 means a rod-shaped semiconductor single crystal to be divided. The sawing tool consists of an endless one with a copper or silver jacket Wire 2, which is guided over a roller arrangement 9, 10, 11, the roller 11 with a (not shown) drive is provided. Furthermore, the wire 2 runs before it reaches the semiconductor rod 1 via a roller 5, which draws magnetizable abrasive material made of ferrite powder from a container 6 and brings this into contact with the wire 2. By a magnetizing head 7, the wire 2, the moves in the direction of arrow 8, magnetized, so that the ferrite powder on the wire 2 when leaving the roller 5 sticks. 12 is a demagnetizing head which demagnetizes the wire 2. Consequently the grinding powder falls off the wire between the demagnetizing head 12 and the roller 9 again, whereby a destruction of the rollers 9, 11 and 10 is avoided.

Instead of the type of application of the magnetizable abrasive powder shown in the figure the saw tool can this z. B. can also be dusted on. It is also possible, in addition to that Abrasive an etchant, e.g. B. to apply an etching liquid. In this case, the cutting effect by applying an electrical voltage between the sawing tool and the semiconductor rod 1 if the voltage is chosen so that an electrolytic dissolution of the semiconductor material takes place through the etchant; but this is not the subject of the invention. Also through excitement of the grinding wire by means of longitudinal vibrations, in particular ultrasound, in the grinding direction the grinding and cutting effect is increased. Instead of the endless wire, one of wire unwound from an unwinding drum can be used. It can be advantageous to use the wire at increased speed after it has been unwound from the drum without cutting action this back to carry out the cutting process in one direction only can.

The wire thickness is expediently dimensioned to an amount below 0.5 mm. Even better Effects can be achieved with a sawing tool thickness of 0.2 mm or less.

Claims (2)

PATENT CLAIMS: 1. A device for dividing crystals, in particular for cutting semiconductor crystals, with a thin saw wire of high tensile strength which is moved only in the longitudinal direction, is stretched over at least two guide rollers and covered with an abrasive, characterized in that the saw wire consists of a core made of hard, magnetizable material, in particular steel, with a sheath made of copper or silver, that a device magnetizing the saw wire in front of the job and demagnetizing behind the job as well as an abrasive feeding device consisting of powdery, magnetizable material, in particular ferrite, are provided. 2. Apparatus according to claim 1, characterized in that in addition a saw wire to longitudinal - ζ. Β. Ultrasonic vibrations - stimulating, known device provided is. Considered publications:
German Patent Nos. 215 162, 523 885;
French Patent No. 363,436;
U.S. Patent No. 2,515,331. Earlier patent considered:
German Patent No. 951 798. 1 sheet of drawings © 209 677/42 10.