Semiconductor device manufacturing: process – Gettering of substrate – By vibrating or impacting
Reexamination Certificate
1999-10-01
2001-11-06
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Gettering of substrate
By vibrating or impacting
C438S800000
Reexamination Certificate
active
06313013
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device for protecting semiconductor material and to a method for protecting semiconductor material.
2. The Prior Art
High-purity semiconductor material is required for the production of solar cells or electronic components, such as for example storage elements or microprocessors. It is therefore desired to keep the concentrations of harmful contaminants as low as possible. It is often observed that semiconductor material which has already been produced to a high purity level is contaminated again during further processing to give the target products. For this reason, expensive cleaning steps are required again and again in order to restore the original purity. By way of example, foreign metal atoms which are incorporated in the crystal lattice of the semiconductor material interfere with the charge distribution and may reduce the ability of the subsequent component to function or may even lead to this component failing. Consequently, metallic contamination of the semiconductor material is to be particularly avoided. This is true in particular of silicon, which is the most frequently used semiconductor material in the electronics industry.
High-purity silicon is obtained, for example, by thermal decomposition of silicon compounds which are readily volatile and are therefore easy to purify by distillation methods, such as for example trichlorosilane.
To produce high-purity silicon using the most frequently employed Siemens method, a mixture of trichlorosilane and hydrogen is guided over thin silicon rods, which are heated by direct current passage to approximately 1100° C., in a quartz reactor. The result is polycrystalline silicon in the form of rods with typical diameters of from 70 to 300 mm and lengths of from 500 to 2500 mm. The polycrystalline silicon is used to produce single crystals which are pulled from crucibles, strips and sheets or to produce polycrystalline solar-cell base material.
For the production of these products, it is necessary to melt solid silicon in crucibles. In order to achieve a high filling level in the crucibles and, in this way, to make the melting operation as efficient as possible, the abovementioned polycrystalline silicon rods have to be comminuted and then separated before being melted. Usually, this inevitably entails contamination to the surface of the semiconductor material, since the comminution is carried out using metallic crushing tools, such as jaw crushers or roll crushers, hammers or chisels on bases made from materials such as steel or plastic. Also, the subsequent separation operation usually takes place on screens made from metal or plastic. Therefore, during the comminution operation and the separation step, the silicon is contaminated by metals or carbon from the tools and the base. To eliminate this contamination, the fragments have to be subjected to complex and expensive surface cleaning, such as for example by etching with HF/HNO
3
, before being melted.
Therefore, silicon bases and tools made from silicon or with silicon coatings are used to reduce the contamination during comminution. Screens made from silicon or silicon-coated screens also form part of the prior art for the separation operation. However, these have the drawback that they are damaged or destroyed by the transmission of forces during the comminution operation (striking with hammers) or in the separation operation, and have to be replaced. On average, a base is able to take approximately 10 to 15 batches (corresponding to approximately 10 to 15 t) both during crushing and during screening. Then, broken pieces (approx. 30%) have to be replaced, so that fragments of the base do not enter the material which is to be sold.
Furthermore, these silicon bases have to be disposed of, entailing further costs, since this material is cracked or has been comminuted to undesirable fragment sizes, and therefore can no longer be sold. The production of such a base requires additional deposition of silicon, mechanical operations involved in the production of the shaped parts and complex cleaning thereof, for example by etching with HF/HNO
3
.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to overcome the drawbacks of the prior art and to provide a device and a method which reduce the additional contamination of semiconductor material during comminution, separation or during transport. This object is achieved by means of the invention.
One embodiment of the invention is a device for protecting semiconductor material, wherein semiconductor material is situated on a surface of stabilized ice, produced from ultrapure water and semiconductor particles.
The semiconductor material from which the stabilized layer of ice is produced is advantageously the same material which is to be protected by the device according to the invention.
Examples of semiconductor materials are silicon, germanium or gallium arsenide with silicon, in particular ultrapure polysilicon, being preferred.
The device according to the invention is formed by stabilized ice which can be produced from ultrapure water and particles of semiconductor material. This stabilized ice is preferably situated on the surface of a support, such as for example a substrate made from steel, plastic, a semiconductor material, such as for example silicon, or some other suitable material. However, the stabilized ice made from ultrapure water and semiconductor particles may also form a self-supporting block.
This stabilized ice is produced by being deposited on a support, such as a substrate made from steel, plastic, a semiconductor material, such as for example preferably silicon, or some other suitable material. Pipes are attached to the underside of the support, through which pipes a cooling liquid flows, such as for example preferably an aqueous potassium carbonate solution. In order for the support to be cooled better, the pipes preferably lie in a thermally conductive paste. In order to save energy, that side of the pipes which faces away from the support is usually insulated. In a refrigerating machine, the cooling liquid is cooled to preferably below −10° C. and particularly preferably to below −25° C. and is pumped through the pipes of the support.
During the cooling operation and in the following period, the surface of the base is sprayed with ultrapure water which has a specific conductance of preferably less than 0.01 &mgr;S/cm. During spraying, particles of semiconductor material, in particular in the form of dust or granules, are continuously or entirely discontinuously, as desired, added to the layer of ice which is being formed, for example by being scattered onto the ice. The particles of semiconductor material which are added to the layer of ice are formed preferably having a diameter of from 10 &mgr;m to 5 mm, particularly preferably between 500 &mgr;m and 2000 &mgr;m.
When the layer has grown preferably to a thickness of from 0.5 cm to 30 cm, particularly preferably to 5 cm to 20 cm, in particular to 5 cm to 10 cm, the semiconductor material which is to be protected is placed on the layer of stabilized ice.
This semiconductor material may also be placed onto a block of self-supporting ice made from ultrapure water and semiconductor particles or may be frozen into this block, in order, for example, for it to be transported.
Preferably, in the device according to the invention, the semiconductor particles form between 5 and 70% by weight, particularly preferably between 15 and 35% by weight, of the layer of ice, based upon the total weight of the layer of ice.
Preferably, the semiconductor material, such as for example silicon rods produced using the Siemens method, is placed on the layer of stabilized ice, in order to be comminuted on this ice made from ultrapure water and semiconductor particles using contamination-free crushing methods, such as for example with a hammer made from ultrapure silicon. Comminution between two layers of stabilized ice which are suddenly struck together is a
Ast Gerhard
Flottmann Dirk
Wolf Reinhard
Collard & Roe P.C.
Lindsay Jr. Walter L.
Niebling John F.
Wacker-Chemie GmbH
LandOfFree
Method and device for processing semiconductor material does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and device for processing semiconductor material, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and device for processing semiconductor material will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2586385