CN115816673A - Pretreatment method for cutting irregular semiconductor crystal - Google Patents

Pretreatment method for cutting irregular semiconductor crystal Download PDF

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Publication number
CN115816673A
CN115816673A CN202211497487.XA CN202211497487A CN115816673A CN 115816673 A CN115816673 A CN 115816673A CN 202211497487 A CN202211497487 A CN 202211497487A CN 115816673 A CN115816673 A CN 115816673A
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China
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paraffin
cutting
mold
ingot
adhesive
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CN202211497487.XA
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Chinese (zh)
Inventor
王守志
曹文豪
张雷
王国栋
俞娇仙
徐现刚
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Shandong University
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Shandong University
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Priority to CN202211497487.XA priority Critical patent/CN115816673A/en
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Abstract

The invention belongs to the technical field of processing of irregular polycrystalline crystals, and particularly relates to a pretreatment method for cutting irregular semiconductor crystals. The method comprises the following steps: heating the mould, uniformly coating the inner wall of the mould with paraffin, cooling the mould to room temperature in the air, and completely solidifying the paraffin to form a paraffin buffer layer; placing a block-shaped crystal ingot in a mold, pouring modified acrylate or other high-strength adhesives between the crystal ingot and a paraffin layer, and standing to solidify the adhesives; heating the mold after glue pouring to melt the paraffin and finish demolding; and adhering the ingot after demoulding to a graphite block, and adhering the graphite block to a material plate of the cutting machine to perform subsequent cutting operation. The invention adopts a paraffin-assisted demoulding method, can effectively improve the demoulding efficiency, and can ensure that the encapsulated crystal after demoulding presents a regular shape, thereby facilitating the later processing and being beneficial to maintaining the integrity of the crystal.

Description

Pretreatment method for cutting irregular semiconductor crystal
Technical Field
The invention belongs to the technical field of irregular polycrystalline crystal processing, and particularly relates to a pretreatment method for cutting an irregular semiconductor crystal.
Background
During the crystal growth process, irregular polycrystalline ingots are inevitably grown, and although polycrystals have no high use value, the exploration of the growth mechanism is still crucial, because the single crystal can be better grown only by knowing the source of polycrystals. In order to explore the polycrystal more deeply, the polycrystal is required to be cut, and because a large number of grain boundaries exist in the polycrystal and the bonding force at the grain boundaries is weak, if the polycrystal is directly cut, crystals are easily broken along the grain boundaries and even broken into crystal slag, so that the crystal slag is difficult to collect and study, the cutting process is very important and difficult for ensuring the integrity of the polycrystal ingot. At present, the most effective method for protecting the integrity of the crystal is to wrap and encapsulate the polycrystal by adopting a high-strength adhesive in a mold to form a more regular shape, and then cut the encapsulated crystal. The firm wrapping layer is formed outside the crystal by the high-strength adhesive, and when the wrapped crystal is cut, the wrapping layer applies inward-extruded adhesive force to the crystal, so that the cut wafer is prevented from being broken. However, the high-strength adhesive also has strong adhesion with the mold, so that the demolding process becomes quite difficult. In order to solve the problem of too great difficulty in complete demolding, a method of cutting with a mold is generally adopted, but the Mohs hardness of the mold is generally larger than 5, and a hard material can have serious irreversible influence on a cutting line and even easily cause a line breaking condition, so demolding and cutting are particularly critical to crystal processing.
Therefore, how to demold the crystal more conveniently and simply and under the condition of ensuring the integrity of the adhesive-encapsulated crystal becomes a problem to be solved urgently in crystal cutting.
Disclosure of Invention
In order to solve the problems, the invention provides a pretreatment method for cutting irregular semiconductor crystals, which is characterized in that a filling layer is formed between a mold and a high-strength adhesive by using paraffin, and after the paraffin is heated and melted, the packaged crystals can be rapidly demoulded, so that the regular shape of the crystals coated with an adhesive layer can be kept, the demoulding efficiency can be greatly improved, and the polycrystalline ingots can be effectively cut.
In order to achieve the purpose, the invention adopts the following technical scheme:
a pretreatment method for cutting an irregular semiconductor crystal, comprising the steps of:
s1, uniformly heating a mould to 100-160 ℃, uniformly coating paraffin on the inner surface of the mould, cooling the mould to room temperature in air, and then completely solidifying the paraffin to form a paraffin layer.
S2, putting a blocky irregular semiconductor crystal ingot matched with the size of the mold into the mold with the paraffin layer in the step S1, pouring a high-strength adhesive between the crystal ingot and the paraffin layer, and standing to enable the high-strength adhesive to be tightly adhered to the crystal ingot and the paraffin layer respectively.
And S3, heating the mold filled with the high-strength adhesive in the step S2, and taking out the crystal ingot packaged by the high-strength adhesive from the mold after the paraffin layer is completely melted to finish demolding.
And S4, adhering the ingot after demolding to a graphite block, and adhering the graphite block to a material plate of the cutting machine, namely finishing the pretreatment of cutting the irregular semiconductor crystal. Preferably, the mold in step S1 is a metal mold, but the invention is not limited thereto, and other assembly molds with good thermal conductivity are also applicable.
In the step S1, the paraffin layer mainly plays a role in buffering, a transition layer can be formed between the high-strength adhesive and the mold, and other buffering materials with low melting points are also applicable.
Preferably, the inner shape of the die in step S1 is cylindrical or rectangular, and the inner shape should be adjusted according to the cutting requirement.
Preferably, the high strength adhesive in step S2 is selected from polyethylene or modified acrylate, but not limited thereto, and other curable adhesives or resin materials are also suitable.
Preferably, the heat-resistant temperature of the adhesive is 200-300 ℃, the fluidity is good initially, the crystal can be wrapped completely, and the bonding strength is more than 15MPa after mixing.
Preferably, in the step S3, the temperature of the mold is raised to 100-150 ℃, and the heating time is 10-15min; when other low melting point buffer materials are used to coat the interior surfaces of the mold, the temperature range and heating time of the elevated temperature should be reasonably adjusted depending on the melting point of the selected buffer material.
Preferably, in step S4, the encapsulated ingot is bonded to the graphite block by an adhesive.
Compared with the prior art, the invention has the following advantages:
according to the method, paraffin is adopted to coat the inner wall of the mold, the formed paraffin layer separates the inner wall of the mold from the high-strength adhesive, when the paraffin is melted, the packaged crystal ingot can be rapidly demolded, the residue of the high-strength adhesive on the inner wall of the mold is reduced, and the demolded high-strength adhesive packaged crystal ingot is regular in shape and complete in structure and is convenient for subsequent cutting.
Drawings
FIG. 1 shows a die used for cutting an aluminum nitride ingot in an example.
Fig. 2 is a photograph of the inside of the mold after demolding in example 1.
FIG. 3 shows an ingot of aluminum nitride after pouring and demolding in example 1.
FIG. 4 is a photograph of a fixed cut of an aluminum nitride ingot after the potting and the mold release in example 1.
FIG. 5 shows an aluminum nitride wafer obtained by dicing in example 1.
Fig. 6 is a photograph of the inside of the mold after demolding in comparative example 1.
FIG. 7 is a photograph showing the aluminum nitride ingot bonded to a graphite block after the potting and the mold release in comparative example 1.
FIG. 8 is a photograph of a fixed cut of an aluminum nitride ingot after releasing the potting resin in comparative example 1.
Fig. 9 shows the aluminum nitride wafer obtained by dicing in comparative example 1.
Detailed Description
The invention will be further described with reference to specific embodiments, and the advantages and features of the invention will become apparent as the description proceeds. The examples are illustrative only and do not limit the scope of the present invention in any way. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention, and that such changes and modifications may be made without departing from the spirit and scope of the invention.
Example 1:
a pretreatment method for cutting an aluminum nitride cylindrical crystal ingot adopts a detachable mold as shown in figure 1, and comprises a cylindrical side wall and a bottom plate, wherein the cylindrical side wall is vertically arranged on the bottom plate, the side wall is divided into two parts along the vertical direction, the side wall of the mold is connected with the bottom plate by paraffin, a sealed space is ensured to be formed inside, the mold is not leaked after being poured, and the bottom plate is easy to detach after the mold is heated.
The bottom plate is an iron sheet with the bottom edge size larger than the diameter of the bottom of the cylindrical side wall.
The method specifically comprises the following steps:
s1, heating the side wall of the aluminum alloy cylindrical mold in the figure 1, and after the side wall is heated to 120 ℃, coating paraffin on the inner surface of the side wall of the mold by using a paraffin rod to ensure that paraffin is buffered between the inner wall of the mold and a subsequent adhesive layer; tightly binding the side wall of the mould by using a binding belt, and sealing;
and then heating the iron sheet serving as the bottom plate to 100 ℃, fully coating paraffin on the upper surface of the iron sheet, and adhering the tightly bound side wall of the aluminum alloy cylindrical mold to the iron sheet to obtain the complete mold.
S2, placing an aluminum nitride polycrystalline ingot on the iron sheet, ensuring that the aluminum nitride polycrystalline ingot is in the center of a mold, after the aluminum nitride polycrystalline ingot is cooled to room temperature, forming a sealed space inside the mold, fixing a crystal ingot, and then pouring AB glue (the main component is modified polyacrylate) serving as an encapsulating material into the mold; and standing for 30-40 minutes until the packaging material is fully wrapped with the crystal, and solidifying. After the AB glue is solidified, the ingot is completely wrapped, so that the problem that the cutting ingot is broken and the slag is removed can be solved.
And S3, heating the die to 120 ℃, preserving heat for 15 minutes, and demolding. After heating and heat preservation, paraffin between the modified polyacrylate layer solidified inside and the mould is found to be molten, and then the aluminum nitride polycrystalline ingot wrapped by the modified polyacrylate layer can be completely demoulded easily.
And S4, as shown in figure 4, gluing the aluminum nitride polycrystalline ingot after the casting mold on a graphite block by using AB, and then gluing the graphite block on a material plate to perform the next cutting process, wherein the used multi-wire cutting machine is a crystal jade YBDX160S diamond multi-wire cutting machine.
In the embodiment, the heat-resistant temperature of the AB adhesive is 200-300 ℃, the AB adhesive has good fluidity initially, so that the AB adhesive can completely wrap crystals conveniently, and the bonding strength of the AB adhesive is greater than 15MPa after mixing. The method for assisting demolding by using the paraffin buffer layer is used in the embodiment, the paraffin protective layer is uniformly coated on the inner wall of the mold in contact with the high-strength adhesive, and paraffin is melted into a liquid state through heating, so that the mold is isolated from the high-strength adhesive, and the paraffin plays a role in facilitating demolding. Fig. 2 is a picture of the interior of the mold after demolding. Fig. 3 is a picture of a demoulded ingot after a paraffin buffer layer is adopted, and fig. 4 is a picture of fixedly cutting an aluminum nitride ingot after glue pouring and demoulding. FIG. 5 is a photograph of a sliced aluminum nitride wafer.
Example 2:
a pretreatment method for cutting a gallium nitride ingot, comprising the steps of:
step S1 is the same as step S1 of the embodiment.
S2, placing the gallium nitride polycrystal ingot on an iron sheet to ensure that the gallium nitride polycrystal ingot is in the center of the mold, after cooling to room temperature, forming a sealed space inside the mold, fixing the ingot, and pouring an AB glue (the main component is modified polyacrylate) serving as a packaging material into the mold; and standing for 30-40 minutes until the packaging material is fully wrapped with the crystal, and solidifying. Because the gallium nitride is thin, a plurality of pieces of gallium nitride are adopted for simultaneous encapsulation when the adhesive is wrapped, and the cutting efficiency and precision can be ensured.
And S3, heating the mould to 120 ℃, preserving heat for 5 minutes, demoulding, finding that paraffin between the modified polyacrylate layer solidified inside and the mould is molten after heating and heat preservation, and then completely demoulding the gallium nitride crystal wrapped by the modified polyacrylate layer easily.
And S4, gluing the gallium nitride crystal after the casting mold on a graphite block by using AB glue, and gluing the graphite block on a material plate to perform the next cutting process, wherein the used multi-wire cutting machine is a crystal jade YBDX160S diamond multi-wire cutting machine.
Comparative example 1:
a pretreatment method for cutting an aluminum nitride cylindrical ingot, comprising the steps of:
steps S1 and S2 are the same as steps S1 and S2 in example 1.
And S3, adopting a heating method during demolding, heating the mold to 180 ℃ in the comparative example because the AB glue loses the bonding strength at the temperature of more than 200 ℃, and separating the mold from the glue layer by using a cutter after the mold is heated to the high temperature for 30 minutes.
And S4, gluing the aluminum nitride polycrystalline ingot after the casting mold on a graphite block by using AB glue, gluing the graphite block on a material plate, and carrying out the next cutting process, wherein the used multi-wire cutting machine is a crystal jade YBDX160S diamond multi-wire cutting machine.
Fig. 6 is a picture of the inside of the mold after demolding in the comparative example, and it can be seen that the adhesive layer is basically completely stuck to the mold, the adhesive layer is extremely difficult to completely peel off from the mold, and the adhesive layer is partially softened after heating, so that the shape is extremely irregular, and great additional difficulty is generated in subsequent cutting.
Fig. 7 is a picture of an ingot obtained by the mold release without using the paraffin buffer layer in the comparative example, and the upper part is a graphite block, and it is apparent from the figure that the ingot with rubber obtained by the mold release without using the paraffin buffer layer is extremely irregular in shape, and the surface is formed with many rugged regions whose presence is extremely disadvantageous for cutting, and when the tension of the wire is applied to these portions, the state of cutting becomes uneven, increasing the cutting error. Meanwhile, when a sample with an irregular shape is cut, the leather can easily fall off, the influence of the leather on the cutting process is great, the falling leather is clamped into the roller and then is easily broken, and the roller can also be irreversibly damaged. As can be seen by comparing with the figure 3, the ingot demolded by the method provided by the invention has regular shape and complete structure, can reduce falling off of the material skin and is convenient for subsequent cutting.
FIG. 8 is a photograph of a fixed cut of an aluminum nitride ingot after releasing the potting adhesive in this comparative example.
Fig. 9 is a cut picture of the ingot obtained in the comparative example after demolding without using a paraffin buffer layer, and it can be seen that the aluminum nitride wafer inside is intact, but the shape of the cut aluminum nitride ingot in fig. 5 is more regular, so that the polycrystalline crystal inside can be better protected from cracking, and the formation of cracks during cutting can be reduced.

Claims (7)

1. A pretreatment method for cutting an irregular semiconductor crystal is characterized by comprising the following steps:
s1, heating a mould to 100-160 ℃, uniformly coating paraffin on the inner wall of the mould, cooling the mould to room temperature in the air, and completely solidifying the paraffin to form a paraffin layer;
s2, placing a bulk irregular semiconductor crystal ingot in the mould with the paraffin layer in the step S1, pouring an adhesive between the ingot and the paraffin layer, and standing to enable the adhesive to fill a gap between the ingot and the paraffin layer;
s3, heating the mould which is poured with the adhesive in the step S2, and removing the crystal ingot packaged by the adhesive from the mould after the paraffin layer is completely melted;
and S4, bonding the crystal ingot packaged by the adhesive in the step S3 to a graphite block, and bonding the graphite block to a material plate of a cutting machine to finish the pretreatment of cutting the irregular semiconductor crystal.
2. The pretreatment method for cutting irregular semiconductor crystals, according to claim 1, wherein the mold in the step S1 is a metal mold.
3. The pretreatment method for cutting an irregular semiconductor crystal according to claim 1, wherein the inside shape of the mold in the step S1 is cylindrical or rectangular parallelepiped.
4. The pretreatment method for cutting irregular semiconductor crystals as claimed in claim 1, wherein the adhesive in the step S2 is selected from polyethylene or modified acrylate.
5. The pretreatment method for cutting the irregular semiconductor crystal according to claim 1, wherein the heat-resistant temperature of the modified acrylate adhesive in the step S2 is 200 to 300 ℃, and the bonding strength after mixing is more than 15MPa.
6. The pretreatment method for cutting irregular semiconductor crystals as claimed in claim 1, wherein in the step S3, the temperature of the mold is raised to 100-150 ℃ for 10-15 minutes.
7. The pretreatment method for cutting irregular semiconductor crystals, as set forth in claim 1, wherein the packaged ingot is bonded to the graphite block with an adhesive in the step S4.
CN202211497487.XA 2022-11-28 2022-11-28 Pretreatment method for cutting irregular semiconductor crystal Pending CN115816673A (en)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH03288606A (en) * 1990-04-04 1991-12-18 Toyo Tire & Rubber Co Ltd Manufacture of mold release agent for molding of polyurethane foam and skinless polyurethane foam
CN1606046A (en) * 2003-10-12 2005-04-13 李云建 Process for making jade imitation terrestrial globe
CN105198475A (en) * 2015-09-28 2015-12-30 西北工业大学 Method for producing complex-shaped porous silicon nitride ceramic product
CN106544738A (en) * 2016-10-31 2017-03-29 福建晶安光电有限公司 A kind of manufacture method of crystal bar
CN115351931A (en) * 2022-07-28 2022-11-18 江西新余新材料科技研究院 Crystal cutting method and piezoelectric wafer

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH03288606A (en) * 1990-04-04 1991-12-18 Toyo Tire & Rubber Co Ltd Manufacture of mold release agent for molding of polyurethane foam and skinless polyurethane foam
CN1606046A (en) * 2003-10-12 2005-04-13 李云建 Process for making jade imitation terrestrial globe
CN105198475A (en) * 2015-09-28 2015-12-30 西北工业大学 Method for producing complex-shaped porous silicon nitride ceramic product
CN106544738A (en) * 2016-10-31 2017-03-29 福建晶安光电有限公司 A kind of manufacture method of crystal bar
CN115351931A (en) * 2022-07-28 2022-11-18 江西新余新材料科技研究院 Crystal cutting method and piezoelectric wafer

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
许家云: "环氧树脂脱模剂", 《工程塑料应用》, no. 2, 28 February 1986 (1986-02-28), pages 20 - 23 *

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