JP2545266C - - Google Patents

Description

Description of the Invention The present invention relates to a material for the rod-shaped, in particular caused by sawing the crystals cowpea is relates to how to remove the debris of the sawing aid slices. Rod-shaped materials, in particular, for example, glass, quartz, gallium-cadolinium-garnet,
Oxide materials such as sapphire and spinel, or silicon, germanium,
It is known to saw crystal bars made of a semiconductor material such as gallium arsenide or indium phosphide with a saw into thin slices. In many cases, an undisputed way to separate the slices from the material is to assist with sawing aids. For example, in German Patent Publication No. 106628 or equivalent US Pat. No. 3,078,549, assistance is provided by surrounding the material with a synthetic resin jacket comprising an epoxide resin. In German Patent Publication No. 3010866, some rods are joined with a synthetic resin to provide support as a rod bundle. In German Offenlegungsschrift 3216200 or its equivalent in U.S. Pat.No. 4,513,544, a plurality of inner peripheral blades are provided by gluing the material onto a cutting plate made of, for example, graphite or ceramic material, using a suitable adhesive. Holds slices separated in a saw-tooth manner. The same cutting plate is used when the inner peripheral blade is sawed with a single blade arrangement, particularly when a slice or a group of slices is completely cut by sawing and then taken out using a take-out device. Before further processing the resulting slices, for example by coarse or fine polishing,
The debris of such sawing aids must be removed. In this first publication for this purpose, the slices are placed in trichlorethylene or acetone, where the plastic rings surrounding the slices begin to swell and dissolve. Similarly, the remnants of the cutting patch attached to the slices with a common epoxide resin adhesive are also usually removed in the trichlorethylene solution. However, the use of solvents such as trichlorethylene or acetone is associated with long-known problems. An important point in this case is the health hazard to workers that can be derived from these solvents, which generally requires expensive safety precautions and exhaust equipment. Moreover, in order to achieve rapid release of debris, the baths are usually operated at high temperatures near the boiling point, so that the above-mentioned means and facilities are particularly necessary. Furthermore, waste disposal of such solvents is difficult. For example, used trichlorethylene cannot be broken down by microorganisms. Therefore, it must be cleaned, for example, by burning. In many cases, beware of fire hazards and low flash points of many organic solvents. An object of the present invention can achieve a good effect than or comparable to the use of the solvent by using, moreover does not have the disadvantages of the solvent gives the removal how the sawing aid remnants slices It is in. The object is to contact the slice with an aqueous solution of one or more carboxylic acids containing 1 to 3 carbon atoms at a temperature of 60 to 90 ° C. until the bond between the slice and the sawing assisting means is broken. The problem is solved by a method characterized by maintaining contact with the aqueous solution. As this carboxylic acid, a monocarboxylic acid, a dicarboxylic acid or a tricarboxylic acid can be used. Illustrative of such suitable carboxylic acids are formic acid, acetic acid, Ru Oh <br/> propionic acid. Among them, monocarboxylic acids having one to three C atoms are particularly effective. Preferably, formic acid, which has been shown to be particularly effective over other acids, is used. The acids selected in each case take the form of an aqueous solution in a wide concentration range, and the acids may be used alone or in a mixture. Basically, for carboxylic acids which are liquid at the chosen operating temperature, for example formic acid or acetic acid, the use of highly concentrated solutions with an acid proportion of about 98 to 99% by weight is not excluded. However, in the case of the above-mentioned high concentration, the smell is strong, the risk of ignition is high, and the cost is high. Therefore, the concentration of such an acid is further reduced. Therefore, it is generally advantageous to use an aqueous solution having an acid concentration of 0.5 to 70% by weight, preferably 5 to 50% by weight. In general, to finalize the working concentration,
It is considered that the higher the concentration, on the one hand, the shorter the required operating time, but on the other hand, the higher the required amount of material and the higher the cost of the device. Often, preliminary experiments are performed to determine these parameters and harmonize with each other. The operating time required for the removal of the sawing aid debris of the respectively selected aqueous carboxylic acid solution is influenced by the temperature. The solution Ru is used in 60 to 90 ° C.. In this case, the higher the temperature, the shorter the action time. Generally, above the upper limit of this range, losses due to evaporation of the solution become unacceptable. In contrast, below 20 ° C., the effectiveness is markedly reduced. In this onset bright, can be added to the selected solution, pKa values not affected the slice to be processed smaller inorganic acids than the value of the pKa of the carboxylic acid or carboxylic acid mixture to coexist. In the case of a suitable aqueous solution of formic acid (pKa about 3.7) and slices of silicon or germanium, for example hydrochloric acid, hydrobromic acid, hydroiodic acid, phosphoric acid or sulfuric acid are suitable. In this case as well, care must be taken to avoid possible contamination of the slices with doping substances. In many cases, it is sufficient to add each selected inorganic acid at a concentration of up to 5% by weight of the total solution. Other One variant has the carboxylic acid aqueous solution, to sell an inorganic acid addition, for example, alkyl sulfonates, alkylaryl sulfonates, salts of long-chain carboxylic acids, or the nature of such surfactants Adafuto ethylene oxide The substance is present in an amount up to about 10% by weight, preferably up to about 5% by weight. With such a solution, cleaning of the slice surface is achieved with the removal of the sawing aid. Sometimes an aqueous carboxylic acid solution, in particular an aqueous formic acid solution, containing said additive is placed in one or several previously separated forms, preferably in a heatable bath, in which the slices to be treated are sometimes successively immersed. It is appropriate to leave the sawing assisting means remaining until it is released. In that case, the slice and the solution in the bath can be relatively moved.
For example, moving the slice or circulating the bath solution. Another suitable method of contacting the slice with the aqueous carboxylic acid solution is to rinse the slice with the aqueous solution or to apply a jet of the aqueous solution directly to the previously inspected slice and the remaining separation points. The use of one or several baths has the advantage that the slices can be provided in a processing grid of an apparatus, such as can be used for a surface cleaning treatment. In that case,
Of course, care must be taken to ensure that this grid, which can accommodate 25 slices, is made of a material that will withstand the chemicals in the bath. Such materials include, for example, synthetic resins such as polytetrafluoroethylene or polypropylene. The use of metallic materials, such as, for example, high-grade steel, is not ruled out, but when processing semiconductor slices, there is the danger of unacceptable contamination of the slice surfaces. In order to avoid this contamination, it is appropriate that at least only the inner wall of the container for receiving the aqueous solution to be used is made of the above-mentioned resistant material. Due to the action of the selected carboxylic acid aqueous solution, the bond between the edge of the slice and the sawing aid remnant, generally due to the adhesive action of the adhesive, is progressively weakened, eventually leading to complete unraveling and sawing aid. The instrument debris separates from the slice. The method of the present invention is characterized in that the bond to the sawing aid is made by a reactive adhesive based on the composition of epoxide resin, phenolic resin, acrylate resin, cyanoacrylate, polyester resin, It is also particularly suitable for use, sometimes even when the cured adhesive itself is the sawing aid. A typical example is when a crystal rod of a semiconductor or oxide material is cut into thin slices with an internal saw, made mainly of an epoxide resin adhesive, for example, a ceramic material, glass, or carbon before sawing. This is the case where a stick is adhered to the cut backing plate and fixed to the support. For example, when cutting a block from coarse crystalline silicon for a solar cell with a saw blade, a sawing assisting means such as a glass prism is often adhered to the block, and the remaining pieces are fixed to the obtained slice. It remains. Further, dividing an optical material such as glass into slices may be mentioned as an example. Often a cutting patch is attached to the material to assist in the sawing process. Of course, it is obvious that the examples given above should not be construed as limiting the inventive idea of the present invention. The aqueous carboxylic acid solution, particularly the aqueous solution based on formic acid, used to remove the debris of the sawing aid from the slices obtained by the method of the present invention is compared to organic solvents used to date such as trichloroethylene or acetone. Then, it has almost the same or higher effectiveness. In addition, these solutions have the advantage that the risk of ignition is significantly reduced or negligible and the health risks to the workers are significantly reduced. In addition, the solution can generally be degraded by microorganisms, so there are fewer problems with disposal. The method of the present invention is described in more detail by the following examples. Example 1 A silicon rod (about 10 cm in diameter and about 100 cm in length) obtained by a crucible crystal pulling method using Czochralski was sliced into a thin slice having a thickness of about 400 μm using a commercially available inner peripheral saw. Cut and divided. To assist sawing process, the adhesive stick using adhesives based on epoxy resin commercially available as "ARALDITE" the trade name graphite cutting caul (cross-sectional area of about 12 × 25 mm ²⁾ did. This serves as an aid in the installation of the bar and at the same time helps prevent breakage at the end of each cut. In this case, a residual fragment of the cutting patch remained on the outer peripheral edge of each separated slice. In all
120 slices were obtained. Next, to remove any attached residual fragments, each 10 of these slices are immersed in a bath filled with a drug suitable for removal and left in the bath until the slices release all residual fragments. Left. In this case, for each slice, the required working time between dipping and release of the cutting patch debris was measured, and finally an average value was obtained from this measurement for a total of 10 slices. In this case, aqueous solutions having various concentrations of formic acid, acetic acid and propionic acid were used at about 90 ° C., respectively. For comparison, ten slices were processed in a bath filled with trichlorethylene maintained at the boiling point (about 87 ° C.). Formic acid,
Various concentrations of acetic acid, propionic acid and citric acid in water
Cutting in 400μm thick silicon slices in 100% ethylene oxide solution
The time required to release the patch debris was measured.
Aqueous solution is nearly as effective or more effective than trichlorethylene solution
Was found to have Monocarboxylic acids having 1 to 3 carbon atoms are especially
It was effective, especially formic acid. Example 2: Ten slices each sawed according to Example 1 were brought into a bath kept at room temperature (about 25 ° C). In this case, the bath solution used was 50% by weight formic acid in the first case, 50% by weight acetic acid in the second case, and trichloroethylene in the third case. About 1 hour in formic acid bath, about 3 hours in acetic acid bath,
For the first time in a trichlorethylene bath, at approximately 10 hours, all residual fragments had detached from the slice. Example 3 Two baths (bath temperature 65 ° C. each) containing 15% by weight of formic acid were prepared. In one of the baths, about 2% by weight of a commercial surfactant based on alkyl sulfonates was added to the bath liquor. Next, ten soiled silicon slices with dark sawing marks on the surface were cycled in the two baths for about one minute. During this treatment, the remaining pieces of the cutting patch were released in the two slice groups.
No visible streaks were left on the surface of the slices treated in the bath containing the surfactant. In contrast, slices treated in a surfactant-free bath showed streaks on the surface.

Claims (1)

Claims: 1) From a semiconductor material obtained by sawing a rod-shaped material, especially a crystal rod,
In a method for removing debris of a sawing assisting means, one or more kinds of the slices may be used.
Contact with an aqueous solution of a carboxylic acid containing 1 to 3 carbon atoms and having a temperature of 60 to 90 ° C.
And maintain contact until the bond between the slice and the remnant of the sawing aid is loosened.
A method comprising: 2) The method according to claim 1, wherein formic acid is used as the carboxylic acid.
. 3) that the ratio of the carboxylic acid in the aqueous solution is adjusted to 0.5 to 70% by weight;
A method according to claim 1 or 2, characterized in that: 4) up to 10% by weight of surfactant and up to 5% by weight of pKa
Add inorganic acids whose values are lower than the pKa value of the carboxylic acid used and do not attack the slices
The method according to any one of claims 1 to 3, wherein the method is performed.