DE1142420B - Method for producing platelet-shaped semiconductor bodies for semiconductor components from a single semiconductor crystal - Google Patents

Description

The invention relates to a method for producing platelet-shaped semiconductor bodies from Semiconductor components made from single crystals, e.g. B. consist of germanium. The platelet-shaped Semiconductor bodies are used z. B. for the formation of rectifiers or transistors.

In the production of platelet-shaped semiconductor bodies, the procedure is usually such that cut a disk from a semiconductor crystal and then cut it into pieces of usually rectangular shape Form is disassembled, which can be built into the rectifier or transistor. The decomposition of the Disc into the individual parts is done by grinding tools, e.g. B. a wheel set with diamonds or by the reciprocating motion of a thin wire that is provided with an abrasive and is guided back and forth over the disc. The flake-form semiconductor bodies produced in this way have rough edges that are under internal mechanical stresses. This can be done later too breaking the body or at least causing it to break easily if they are one be exposed to further stress.

It is already known that in the manufacture of transistors on the correct crystal orientation of the Germanium must be taken into account because some properties of germanium, e.g. B. the Zener voltage. the distribution coefficient and the attack of the etchant depends on this orientation.

Cutting grooves into the semiconductor material is also a process step that is known per se the material is removed to a significant extent. The remaining surfaces of the semiconductor material should be covered with paraffin or another wax so that an etchant is only applied to the grooves Attacks material and thereby causes individual platelets to be broken up. The etchant can e.g. B. be a mixture of nitric acid and hydrofluoric acid.

The disadvantage of the known method is that either by mechanical processing of the semiconductor changes the structure of the surface areas and thereby the electrical Properties of the final semiconductor component are deteriorated or one additional Protective substances, such as wax or paraffin, must use, their detachment from the semiconductor additional work or cause difficulties.

Such a method for producing platelet-shaped semiconductor bodies from semiconductor components from a semiconductor single crystal is improved according to the invention in that of the semiconductor single crystal a disc parallel to its main process to manufacture

of platelet-shaped semiconductor bodies

of semiconductor components

from a semiconductor single crystal

Applicant:

Associated

Electrical Industries (Woolwich) Limited,
London

Representative: Dr.-Ing. W. Reichel, patent attorney,
Frankfurt / M. 1, Parkstrasse 13th

Claimed priority:
Great Britain June 10, 1958 (No. 18 536)

Roland Freestone and Mary Teresa Weir,
Harlow, Essex (UK),
have been named as inventors

level, e.g. B. the [lll] -plane, is cut off that a pattern is scratched into one surface of the disc, which marks the dividing lines between the represents platelet-shaped semiconductor bodies, and that then the scratched disk with an etchant so is etched for a long time until the wafer disintegrates into the platelet-shaped semiconductor body and the desired Thickness of the semiconductor body is reached.

With the method according to the invention, therefore, it is possible to produce platelet-shaped semiconductor bodies whose mechanically disturbed surface areas without the use of a protective material completely up to the desired one Thickness are etched away. The etchant used is a mixture, e.g. B. of hydrogen peroxide and potassium hydroxide, which, in contrast to the known mixtures, has an alkaline reaction. In addition, the semiconductor bodies produced in this way have smooth edges without internal mechanical stresses on.

The invention will now be explained in more detail with reference to the drawings in connection with exemplary embodiments.

1 shows a view of the scribing of the wafer made of semiconductor material;

Fig. 2 shows a plan view of a wafer of the semiconductor material after scribing, and

209 758/183

Fig. 3 shows a cross section of a wafer after etching.

In Fig. 1, a disc 1 made of monocrystalline semiconductor material, e.g. B. from a germanium single crystal, shown. This single crystal is cut from a bar of germanium single crystal, the z. B. obtained by pulling a crystal from a mass of molten germanium is. The method for producing such an ingot is known per se. The bar becomes transverse to its longitudinal axis by suitable means, e.g. B. by a grinding wheel, cut so that a disc 1 arises. The disc can be about 0.5 mm thick and is preferably cut out of the ingot in such a way that that the surface of the disc is parallel to a main plane, preferably the [111] plane. of the crystal lies. The disc is then lapped to a thickness of 0.15 mm. Such Disk 1 is shown in the drawing. When the slices are cut so thin from the start then the subsequent lapping process is not required. The disc is then during immersed in an etching bath for a predetermined period of time, removed again, and then the Thickness measured so that the etching rate of the bath can be determined.

The disc 1 is then scored by drawing a sharp tool 2 across the surface of the disc will. One suitable tool is to create irregularities in the crystal have been. As a result of this process, there are deep cuts along the scratched lines or column 4, seen from Figure 3, so that the disk breaks up into the desired sections. Further etching will only reduce the thickness of the wafer and hence leave the process so long continue until the desired thickness is obtained.

A suitable means for the preparation of the etching bath ίο for the treatment of germanium consists, for. B. off the following components:

15 ecm 100 ^u / "hydrogen peroxide, 15 ecm potassium hydroxide solution (20 ⁰ O).

The temperature of the bath should be between 70 and 80 ° C. Stirring the etchant during of etching is appropriate. The etching speed was found to be between 0.005 and 0.0075 mm per minute fluctuates, but that at a certain one

zo combination of bath and disc material within of the above temperature range, the etching rate is constant. Temperatures below 70 ° C and above 80 ° C reduce or increase the etching speed. When a caustic bath up to the creation of the etchant is used, then one can also influence the temperature and the time Do without factors of the process.

It was found that disks with an initial strength of 0.15 mm when inserted into the above

z. B. from a sharp diamond. During the 30 mentioned etching bath to a thickness of 0.05 mm in one Ritzens the disc on a base plate 3 z. B. by paraffin wax or a suitable one Adhesive attached. The scribing is carried out in such a way that a pattern is created that defines the dividing lines represents between the individual platelets that are to be produced from the disk. In Fig. 2 is z. B. a pattern is shown in which the scribed lines form a rectangular grid. Since several parallel Lines for making this grid can be carved into several sharp works witnesses can be used at the same time. Several discs can also be attached to the base plate 3, so that they can be scratched one after the other. The disks can be arranged so that make two separate 45 passages under the scoring tool in mutually perpendicular directions.

As mentioned above, the thickness of the disks should be about 0.15 mm before scribing. If the Slice of the monocrystalline ingot in a row is cut parallel to the [100] plane of the crystal, then it is useful to adjust the thickness of the slices to choose larger, namely about 0.3 mm

After the scratching, the disc is removed from the blanket layer 3 and the scratched disc is then immersed in the etching bath for so long that its thickness decreases to a value of 0.05 mm. the Time required for the etching process can be estimated from the etching speed of the bath, which results from the reduction in the thickness of the wafer during the initial etching, in which the Disc was immersed in the bath for a predetermined period of time.

When the etched wafer is inserted into the etch bath, then the scribed lines are preferred attacked by the etchant, as the time of about 20 minutes decrease when the bath is used was kept at a temperature between 70 and 80 ° C. The dismantling of the disc into individual parts Platelet was also achieved within this time.

Claims (3)

Claim f.: 1. Process for the production of platelet-shaped semiconductor bodies of semiconductor components of a semiconductor single crystal, characterized in that of the semiconductor single crystal a disk parallel to a main plane, e.g. B. the J1! 1] -plane, is cut off, that one surface of the disc is scratched a pattern which defines the dividing lines between the puittchen-shaped semiconductor bodies shown, and that then the scratched disk with an etchant is etched until the disk into the platelet-shaped semiconductor body disintegrates and the desired thickness of the semiconductor body is reached. 2. The method according to claim! characterized, that vertically intersecting dividing lines are carved into the disc. 3. The method according to claim J. characterized in that that in the etchant approximately equal proportions of hydrogen peroxide and potassium hydroxide can be used and that a temperature between 70 and 80 "C during the etching is adhered to. Documents considered: German Patent No. 823 470; British Patent No. 699,050; Journal of Electrochemistry. Vol. 58, 1954. No. 8. Pp. 283 to 327. 1 sheet of drawings