CN114523220A - Silicon carbide wafer stripping method and stripping device - Google Patents
Silicon carbide wafer stripping method and stripping device Download PDFInfo
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- CN114523220A CN114523220A CN202210407355.7A CN202210407355A CN114523220A CN 114523220 A CN114523220 A CN 114523220A CN 202210407355 A CN202210407355 A CN 202210407355A CN 114523220 A CN114523220 A CN 114523220A
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- 229910010271 silicon carbide Inorganic materials 0.000 title claims abstract description 216
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 title claims abstract description 212
- 238000000034 method Methods 0.000 title claims abstract description 70
- 239000013078 crystal Substances 0.000 claims abstract description 199
- 238000005530 etching Methods 0.000 claims abstract description 117
- 239000007788 liquid Substances 0.000 claims abstract description 74
- 230000001678 irradiating effect Effects 0.000 claims abstract description 13
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 21
- 229910052814 silicon oxide Inorganic materials 0.000 claims description 18
- 238000010438 heat treatment Methods 0.000 claims description 17
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 16
- 239000007800 oxidant agent Substances 0.000 claims description 10
- 238000002791 soaking Methods 0.000 claims description 10
- 230000001590 oxidative effect Effects 0.000 claims description 9
- 238000010521 absorption reaction Methods 0.000 claims description 8
- 229910052697 platinum Inorganic materials 0.000 claims description 8
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 6
- 229910018540 Si C Inorganic materials 0.000 claims description 6
- 229910008045 Si-Si Inorganic materials 0.000 claims description 6
- 229910006411 Si—Si Inorganic materials 0.000 claims description 6
- 230000003287 optical effect Effects 0.000 claims description 6
- 238000001914 filtration Methods 0.000 claims description 4
- 229910052757 nitrogen Inorganic materials 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 abstract description 4
- 239000010410 layer Substances 0.000 description 170
- 235000012431 wafers Nutrition 0.000 description 37
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 21
- 239000000243 solution Substances 0.000 description 21
- 230000007797 corrosion Effects 0.000 description 12
- 238000005260 corrosion Methods 0.000 description 12
- 238000006243 chemical reaction Methods 0.000 description 9
- QPJSUIGXIBEQAC-UHFFFAOYSA-N n-(2,4-dichloro-5-propan-2-yloxyphenyl)acetamide Chemical compound CC(C)OC1=CC(NC(C)=O)=C(Cl)C=C1Cl QPJSUIGXIBEQAC-UHFFFAOYSA-N 0.000 description 7
- 229910003460 diamond Inorganic materials 0.000 description 5
- 239000010432 diamond Substances 0.000 description 5
- 229910021417 amorphous silicon Inorganic materials 0.000 description 4
- -1 hydrogen ions Chemical class 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 229910052681 coesite Inorganic materials 0.000 description 3
- 229910052906 cristobalite Inorganic materials 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 239000000377 silicon dioxide Substances 0.000 description 3
- 229910052682 stishovite Inorganic materials 0.000 description 3
- 229910052905 tridymite Inorganic materials 0.000 description 3
- 229910003481 amorphous carbon Inorganic materials 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000000227 grinding Methods 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 2
- 229910052753 mercury Inorganic materials 0.000 description 2
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 2
- 239000004810 polytetrafluoroethylene Substances 0.000 description 2
- 238000006722 reduction reaction Methods 0.000 description 2
- 229910052724 xenon Inorganic materials 0.000 description 2
- FHNFHKCVQCLJFQ-UHFFFAOYSA-N xenon atom Chemical compound [Xe] FHNFHKCVQCLJFQ-UHFFFAOYSA-N 0.000 description 2
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000013532 laser treatment Methods 0.000 description 1
- 230000031700 light absorption Effects 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910021421 monocrystalline silicon Inorganic materials 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- LIVNPJMFVYWSIS-UHFFFAOYSA-N silicon monoxide Chemical compound [Si-]#[O+] LIVNPJMFVYWSIS-UHFFFAOYSA-N 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- 230000001052 transient effect Effects 0.000 description 1
- 238000011282 treatment Methods 0.000 description 1
- 229910021642 ultra pure water Inorganic materials 0.000 description 1
- 239000012498 ultrapure water Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/50—Working by transmitting the laser beam through or within the workpiece
- B23K26/53—Working by transmitting the laser beam through or within the workpiece for modifying or reforming the material inside the workpiece, e.g. for producing break initiation cracks
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/70—Auxiliary operations or equipment
- B23K26/702—Auxiliary equipment
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
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Abstract
The invention relates to the technical field of silicon carbide wafer manufacturing, and discloses a silicon carbide wafer stripping method and a silicon carbide wafer stripping device, which comprise the following steps: connecting a silicon carbide crystal ingot serving as an anode with a voltage output end through a conducting layer on the silicon carbide crystal ingot, and arranging a cathode in etching liquid to be connected with the voltage input end; focusing laser at a preset depth in the silicon carbide crystal ingot, scanning inwards from the edge of the silicon carbide crystal ingot to form an amorphous layer, and simultaneously irradiating the surface of the silicon carbide crystal ingot with incident light larger than the critical value of the wavelength of absorbed light corresponding to single crystal layers on two sides of the surface of the amorphous layer; and providing a positive constant potential for the silicon carbide crystal ingot in the irradiation process to etch the amorphous layer, and rapidly realizing the peeling of the single crystal layer to obtain the silicon carbide wafer. The etching process method adopted by the invention can quickly obtain the silicon carbide wafer with controllable thickness.
Description
Technical Field
The invention relates to the technical field of silicon carbide wafer manufacturing, in particular to a silicon carbide wafer stripping method and a silicon carbide wafer stripping device.
Background
At present, the method for producing the silicon carbide wafer generally adopts a diamond wire saw slicing process. Although high-yield silicon carbide wafers can be obtained, each diamond wire causes the kerf loss thickness of the silicon carbide material to exceed 180 μm and the diamond wire is severely lost. On the other hand, mechanical vibration and stress generated during the diamond wire sawing process may cause a large amount of mechanical damage such as scratches and cracks on the wafer surface, and further removal of the surface layer having a total thickness of about 150 μm is required to eliminate the influence of the wire sawing process. Thus, to produce a silicon carbide wafer having a thickness of about 350 μm, a silicon carbide material about 330 μm thick is consumed.
In the silicon carbide ingot slicing procedure, a mode of combining a laser slicing technology with a photoelectrochemical corrosion technology is a novel method for producing silicon carbide wafers, and is expected to replace the traditional diamond wire saw slicing process. Under a dry environment, pulse laser is focused on a cutting surface parallel to a basal plane through a laser slicing technology, high-density dislocation is generated by local transient high temperature, and a very thin (less than 50 mu m) amorphous layer mixed with amorphous silicon, amorphous carbon and amorphous silicon carbide is formed. Because the forbidden bandwidth of the amorphous layer is lower than that of the single crystal silicon carbide, the selective corrosion is carried out on the amorphous layer by utilizing the photoelectrochemistry corrosion technology in the forbidden bandwidth to obtain the silicon carbide wafer with a wafer level, a surface damage-free layer and a stress residue, and the difficulty of the next grinding process can be obviously reduced. However, since the photoelectrochemical etching of the amorphous layer proceeds from the edge of the layer to the inside of the layer, and the narrow etching area severely limits the material transfer rate during the reaction, the etching rate of the amorphous layer is low, which is not favorable for rapid peeling, and thus further improvement of the etching rate is required.
Disclosure of Invention
The invention aims to overcome the problem of low efficiency of the existing stripping method and provides a silicon carbide wafer stripping method and a silicon carbide wafer stripping device.
In order to achieve the above object, the present invention provides a method for peeling a silicon carbide wafer, comprising the steps of:
providing a silicon carbide crystal ingot, and soaking the silicon carbide crystal ingot into etching liquid, wherein the bottom of the silicon carbide crystal ingot is also provided with a conducting layer, the silicon carbide crystal ingot is used as an anode and is connected with a voltage output end through the conducting layer, and a cathode is also arranged in the etching liquid and is connected with a voltage input end;
in the process of soaking the silicon carbide crystal ingot in the etching liquid, focusing laser at a preset depth inside the silicon carbide crystal ingot, and scanning inwards from the edge of the silicon carbide crystal ingot to form an amorphous layer, wherein the amorphous layer formed by scanning is positioned at the preset depth inside the silicon carbide crystal ingot, the two sides of the amorphous layer are respectively a first single crystal layer and a second single crystal layer of the silicon carbide crystal ingot, the first single crystal layer is a silicon carbide crystal wafer to be stripped, and the conductive layer is specifically arranged on the outer side surface of the second single crystal layer;
focusing laser at a preset depth in the silicon carbide crystal ingot, scanning inwards from the edge of the silicon carbide crystal ingot to form an amorphous layer, irradiating the surface of the silicon carbide crystal ingot with incident light which is larger than a light absorption wavelength critical value corresponding to the first single crystal layer in the laser scanning process, irradiating the surface of the amorphous layer with the incident light through the first single crystal layer on the surface of the silicon carbide crystal ingot, and forming photo-generated hole-electron pairs on the surface of the amorphous layer;
and providing a positive constant potential to the silicon carbide crystal ingot in the process of irradiation by adopting incident light, transferring photo-generated electrons on the surface of the amorphous layer to the cathode along current to react with etching liquid, and selectively etching the surface of the amorphous layer with photo-generated holes by the etching liquid to realize the stripping of the first single crystal layer so as to obtain the silicon carbide wafer.
As an implementation mode, the laser wavelength for laser scanning is 530-1030 nm, and the frequency is 1-600 kHz; the laser scanning adopts a Mach-Zehnder type double-pulse optical device to realize double-pulse output, the time delay between double pulses is +2 picoseconds to +70 picoseconds, and the pulse duration is 10 femtoseconds to 6 picoseconds; the laser focus focused in the silicon carbide crystal ingot scans at the speed of 10-100 μm/s, and the distance between adjacent laser writing tracks is 5-50 μm.
As an implementation mode, the process of providing the positive constant potential to the silicon carbide crystal ingot further comprises the step of carrying out microwave heating on the etching liquid.
As an implementation mode, the microwave output power during microwave heating is 100-300W, and the temperature of the corresponding etching liquid is 30-90 ℃.
As an implementable mode, the silicon carbide crystal ingot is used as an anode and connected with a voltage output end through the conducting layer, and a cathode is arranged in the etching solution, and the silicon carbide crystal ingot is used as an anode and connected with the voltage output end through the conducting layer and a cathode is arranged in the etching solution on the basis of a two-electrode system, or the silicon carbide crystal ingot is used as an anode and connected with the voltage output end through the conducting layer and a cathode is arranged in the etching solution on the basis of a three-electrode system.
As an embodiment, the etching liquid comprises an oxidant and a silicon oxide etching liquid; the method comprises the following steps that photo-generated electrons on the surface of the amorphous layer are transferred to the cathode along with current to react with etching liquid, and the process of selectively etching the surface of the amorphous layer with photo-generated holes by the etching liquid specifically comprises the following steps:
and transferring photo-generated electrons on the surface of the amorphous layer onto the cathode along with current to react with the oxidant, reacting residual photo-generated holes on the surface of the amorphous layer with Si-C and Si-Si on the surface of the amorphous layer to generate silicon oxide, and reacting the silicon oxide etching solution with the silicon oxide so as to selectively etch the surface of the amorphous layer.
In one embodiment, the outside of the conductive layer is further provided with an insulating layer, the cathode is a platinum mesh, and the silicon carbide ingot has a nitrogen doping concentration in the range of 5 × 1014～3×1019 /cm3The thickness of the silicon carbide crystal ingot ranges from 0.5 mm to 50 mm, the size of the silicon carbide crystal ingot ranges from 2 inches to 8 inches, the thickness of the amorphous layer ranges from 2 microns to 50 microns, the depth of the amorphous layer ranges from 5 microns to 600 microns, and the distance from the amorphous layer to the upper side surface of the first single crystal layer ranges from 5 microns to 600 microns; the voltage range for providing a positive constant potential to the silicon carbide crystal ingot is 1-8V;the height range of a light source for emitting incident light from the surface of the etching liquid is 5-10 cm; the flow rate range of the etching liquid is 1-5 mL/min, and the concentration range of the etching liquid is 1-20%.
Correspondingly, the invention also provides a silicon carbide wafer stripping device, which comprises an electrolytic bath, a light source and a laser head;
the electrolytic tank is used for containing etching liquid, and a mounting structure is arranged in the etching liquid and used for mounting a silicon carbide crystal ingot and a cathode; the laser head is arranged above the silicon carbide crystal ingot, a conducting layer is further arranged at the bottom of the silicon carbide crystal ingot, the silicon carbide crystal ingot is used as an anode and is connected with a voltage output end through the conducting layer, and a cathode is further arranged in the etching liquid and is connected with a voltage input end;
in the process of soaking the silicon carbide crystal ingot in the etching liquid, the laser head focuses laser on a preset depth inside the silicon carbide crystal ingot and scans inwards from the edge of the silicon carbide crystal ingot to form an amorphous layer, wherein the amorphous layer formed by scanning is located at the preset depth inside the silicon carbide crystal ingot, the two sides of the amorphous layer are respectively a first single crystal layer and a second single crystal layer of the silicon carbide crystal ingot, the first single crystal layer is a silicon carbide crystal wafer to be stripped, and the conducting layer is specifically arranged on the outer side surface of the second single crystal layer;
incident light emitted by the light source and larger than the critical value of the absorption wavelength corresponding to the first single crystal layer is irradiated on the surface of the amorphous layer through the first single crystal layer on the surface of the silicon carbide crystal ingot in the laser scanning process, so that photo-generated hole-electron pairs are formed on the surface of the amorphous layer, a positive constant potential is provided for the silicon carbide crystal ingot in the irradiation process by adopting the incident light, the photo-generated electrons on the surface of the amorphous layer are transferred to the cathode along with current to react with etching liquid, and the etching liquid selectively etches the surface of the amorphous layer with the photo-generated holes, so that the first single crystal layer is peeled off, and a silicon carbide crystal wafer is obtained.
In an implementation mode, the light source is further provided with a light filter used for filtering so that the wavelength of incident light reaching the surface of the silicon carbide crystal ingot is larger than the wavelength critical value of absorbed light corresponding to the single crystal layer.
As an implementation, further comprising: and the microwave device is used for carrying out microwave heating on the etching liquid in the process of providing positive constant potential for the silicon carbide crystal ingot.
The invention has the beneficial effects that: the invention provides a silicon carbide wafer stripping method and a silicon carbide wafer stripping device.A silicon carbide crystal ingot is used as an anode and is connected with a voltage output end through a conducting layer on the silicon carbide crystal ingot, and a cathode is arranged in etching liquid and is connected with a voltage input end; focusing laser at a preset depth in the silicon carbide crystal ingot, scanning inwards from the edge of the surface of the silicon carbide crystal ingot to form an amorphous layer, and simultaneously irradiating the surface of the silicon carbide crystal ingot with incident light larger than the wavelength critical value of absorbed light corresponding to single crystal layers on two sides of the surface of the amorphous layer; and in the irradiation process, simultaneously providing a positive constant potential for the silicon carbide crystal ingot to etch the amorphous layer, so as to realize the peeling of the single crystal layer and obtain the silicon carbide wafer. The existing etching process method is that an amorphous layer is formed at a preset depth in a silicon carbide crystal ingot, and then the silicon carbide crystal ingot with the formed amorphous layer is placed into etching liquid for selective etching.
Drawings
FIG. 1 is a schematic diagram illustrating a step of a method for peeling a silicon carbide wafer according to an embodiment of the present invention.
FIG. 2 is a schematic view showing the structure of a laser head and a silicon carbide ingot on which an amorphous layer is formed in a method for peeling a silicon carbide wafer according to an embodiment of the present invention.
FIG. 3 is a schematic structural diagram of a silicon carbide wafer lift-off device according to an embodiment of the present invention.
Description of reference numerals: 1 silicon carbide ingot, 100 first single crystal layer, 110 conductive layer, 120 insulating layer, 200 amorphous layer, 300 second single crystal layer, 400 laser head, 2 platinum net, 3 stirrer, 4 anode interface, 5 cathode interface, 7 electrolytic bath, 8 etching liquid inlet and 9 etching liquid outlet.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, the present embodiment provides a technical solution: a method for peeling a silicon carbide wafer comprises the following steps:
step S100, providing a silicon carbide crystal ingot, and soaking the silicon carbide crystal ingot into etching liquid, wherein the bottom of the silicon carbide crystal ingot is also provided with a conducting layer, the silicon carbide crystal ingot is used as an anode and is connected with a voltage output end through the conducting layer, and a cathode is also arranged in the etching liquid and is connected with a voltage input end;
step S200, in the process of soaking the silicon carbide crystal ingot in the etching liquid, focusing laser at a preset depth inside the silicon carbide crystal ingot, and scanning inwards from the edge of the silicon carbide crystal ingot to form an amorphous layer, wherein the amorphous layer formed by scanning is positioned at the preset depth inside the silicon carbide crystal ingot, the two sides of the amorphous layer are respectively a first monocrystalline layer and a second monocrystalline layer of the silicon carbide crystal ingot, the first monocrystalline layer is a silicon carbide wafer to be stripped, and the conductive layer is specifically arranged on the outer side surface of the second monocrystalline layer;
step S300, focusing laser at a preset depth inside the silicon carbide crystal ingot, scanning inwards from the edge of the silicon carbide crystal ingot to form an amorphous layer, irradiating the surface of the silicon carbide crystal ingot with incident light which is larger than a threshold value of a wavelength of absorbed light corresponding to the first single crystal layer in the laser scanning process, irradiating the surface of the amorphous layer with the incident light through the first single crystal layer on the surface of the silicon carbide crystal ingot, and forming photo-generated hole-electron pairs on the surface of the amorphous layer;
step S400, providing a positive constant potential to the silicon carbide crystal ingot in the process of irradiation by adopting incident light, transferring photo-generated electrons on the surface of the amorphous layer to the cathode along current to react with etching liquid, and selectively etching the surface of the amorphous layer with photo-generated holes by the etching liquid to realize the stripping of the first single crystal layer to obtain the silicon carbide wafer.
Step S100 is executed, the concentration range of the etching liquid for soaking the silicon carbide crystal ingot into the etching liquid is 1-20%, the etching liquid comprises an oxidant and a silicon oxide etching liquid, and the oxidant is hydrogen ions H+The silicon oxide etching solution is hydrofluoric acid HF, and specifically, the etching solution is prepared by mixing 40% hydrofluoric acid HF and ultrapure water according to a ratio of 1: 1-1: 39, and stirring to prepare 1-20% hydrofluoric acid HF aqueous solution, wherein in the corrosion process, the flow rate of the etching solution ranges from 1 mL/min to 5 mL/min, and the etching solution can fully react through a stirrer, wherein the rotating speed of the stirrer ranges from 300 r/min to 500 r/min.
Connecting the silicon carbide crystal ingot as an anode with a voltage output end through the conducting layer and setting a cathode connection voltage input end in the etching solution, specifically, connecting the silicon carbide crystal ingot as an anode with the voltage output end through the conducting layer and setting a cathode connection voltage input end in the etching solution based on a two-electrode system, or connecting the silicon carbide crystal ingot as an anode with the voltage output end through the conducting layer and setting a cathode connection voltage input end in the etching solution based on a three-electrode system; when the two-electrode system is used, the silicon carbide ingot is used as an anode, i.e. a working electrode, and is connected to a voltage output end through the conductive layer, and the cathode, i.e. a counter electrode, is connected to a voltage input end, wherein an insulating layer is further arranged on the outer side of the conductive layer, the cathode is specifically a platinum mesh, the conductive layer 110 is specifically conductive silver paste, and the insulating layer 120 is specifically a polytetrafluoroethylene film.
In the embodiment, an etching process through a two-electrode system is adopted, so that the silicon carbide crystal ingot is completely exposed to visible light, and meanwhile, the silicon carbide crystal ingot is connected with a voltage output end through a conducting layer, all photo-generated electrons of an amorphous layer can be led out of a body, the stripping efficiency is better, in addition, compared with a three-electrode system, the damage of hydrofluoric acid (HF) to a reference electrode in the three-electrode system is larger, and the two-electrode system is utilized to obtain a better effect in the embodiment.
Step S200 is executed, as shown in fig. 2, which is a schematic diagram of an amorphous layer 200 formed by laser scanning the surface of the silicon carbide ingot 1 by a laser head 400 in the laser direction as shown in the figure during the process of irradiating the incident light in the incident light direction as shown in the figure, and a first single crystal layer 100 and a second single crystal layer 300 on both side surfaces of the amorphous layer, and it can be seen that in the present embodiment, the amorphous layer 200 is etched simultaneously during the process of laser scanning, and the first single crystal layer 100 is a silicon carbide wafer to be stripped, and the outer side surface of the second single crystal layer 300 is further provided with a conductive layer 110 and an insulating layer 120 in sequence, wherein the nitrogen doping concentration range of the silicon carbide ingot is 5 × 1014～3×1019 /cm3The thickness of the silicon carbide crystal ingot ranges from 0.5 mm to 50 mm, the size of the silicon carbide crystal ingot ranges from 2 inches to 8 inches, the depth of the amorphous layer 200 ranges from 5 microns to 600 microns, and the thickness of the amorphous layer ranges from 2 microns to 50 microns.
Wherein the forming process of the amorphous layer comprises the following steps: focusing laser light on a cutting surface which is positioned at a preset depth of the silicon carbide crystal ingot and is parallel to the basal plane of the silicon carbide crystal ingot, and locally heating the silicon carbide crystal ingot to generate high-density dislocation so as to form an amorphous layer at the preset depth of the silicon carbide crystal ingot, wherein the amorphous layer comprises amorphous silicon, amorphous carbon and amorphous silicon carbide.
And step S300 is executed, the height range of a light source for emitting incident light from the surface of the etching liquid is 5-10cm, the light source is a xenon lamp, a mercury lamp or an led ultraviolet lamp, and an optical filter is adopted on the light source for filtering, so that the wavelength of the incident light reaching the surface of the silicon carbide crystal ingot is larger than the critical value of the wavelength of the absorbed light corresponding to the single crystal layer.
The step of irradiating the surface of the silicon carbide crystal ingot with incident light larger than the absorption light wavelength critical value corresponding to the first single crystal layer specifically includes vertically irradiating the surface of the silicon carbide crystal ingot with incident light larger than the absorption light wavelength critical value corresponding to the first single crystal layer and the second single crystal layer, wherein when the adopted crystal form of the single crystal layer is 4H type or 6H type, the absorption light wavelength critical values corresponding to the 4H type and the 6H type are 380nm and 410nm, respectively.
The laser wavelength for laser scanning is 530-1030 nm, and the frequency is 1-600 kHz; the laser scanning adopts a Mach-Zehnder type double-pulse optical device to realize double-pulse output, the time delay between double pulses is +2 picoseconds to +70 picoseconds, and the pulse duration is 10 femtoseconds to 6 picoseconds; the laser focus focused in the silicon carbide crystal ingot scans at the speed of 10-100 μm/s, and the distance between adjacent laser writing tracks is 5-50 μm.
Step S400 is executed, in the irradiation process, the voltage range of the positive constant potential is 1-8V, wherein the photogenerated electrons on the surface of the amorphous layer are transferred to the cathode along the current to react with the etching liquid, and the step of selectively etching the surface of the amorphous layer with the photogenerated holes by the etching liquid specifically comprises the following steps: and transferring the photo-generated electrons on the surface of the amorphous layer to the cathode along with the current to react with the oxidant, and selectively etching the surface of the amorphous layer with photo-generated holes by the silicon oxide etching solution:
specifically, photo-generated electrons on the surface of the amorphous layer are transferred to the cathode along with current to react with the oxidant, residual photo-generated holes on the surface of the amorphous layer react with Si-C and Si-Si on the surface of the amorphous layer to generate silicon oxide, and the silicon oxide corrosion solution reacts with the silicon oxide, so that the surface of the amorphous layer is selectively etched.
The above-mentionedThe oxidant being hydrogen ions H+The silicon oxide etching solution is hydrofluoric acid (HF), and the reaction process that photo-generated electrons on the surface of the amorphous layer are transferred to the cathode along with current to react with the oxidant comprises the following steps: h+And the photo-generated electron e-A reduction reaction occurs, wherein the chemical formula of the reduction reaction occurs as follows:
(ii) a The residual photo-generated holes on the surface of the amorphous layer react with Si-C and Si-Si on the surface of the amorphous layer to generate silicon oxide, and the reaction process of the silicon oxide etching solution reacting with the silicon oxide comprises the following steps: photo-generated holes h left on the surface of the amorphous layer+Reacts with Si-C and Si-Si on the surface of the amorphous layer to generate SiO2Wherein holes h are generated+The chemical formula for the reaction with Si-C is:
(ii) a Photoproduction cavity h+The chemical formula for the reaction with Si-Si is:
(ii) a Formation of SiO2Then, SiO2Reacting with the hydrofluoric acid HF, wherein SiO is2The chemical formula for the reaction with hydrofluoric acid HF is as follows:
。
in the process of providing positive constant potential for the silicon carbide crystal ingot, microwave heating is further carried out on the etching liquid, the output power of the microwave is 100-300W, and the temperature of the corresponding etching liquid is 30-90 ℃.
Wherein, the microwave is an electromagnetic wave, the frequency is about 2.45GHz, the wavelength is about 122mm, the microwave can cause the positive and negative charge centers in the water molecules to vibrate and be absorbed, so that the temperature inside and outside the etching liquid can be rapidly increased at the same time. For photoelectrochemical corrosion reaction of an amorphous layer in a silicon carbide crystal ingot, high temperature generated by microwave is beneficial to accelerating reaction rate, promoting the transfer of reactants and products on the surface of the amorphous layer and improving reaction kinetics. In addition, the silicon carbide material can not absorb the microwave with the wavelength in centimeter level, thereby eliminating the interference on the selectivity of the photoelectrochemistry corrosion forbidden band. Therefore, the invention adopts microwave to assist rapid photoelectrochemistry corrosion to strip the silicon carbide single crystal, thereby greatly improving the stripping efficiency.
As shown in fig. 3, the silicon carbide ingot 1 is placed in an electrolytic bath 7, an etching liquid is further contained in the electrolytic bath 7, the silicon carbide ingot 1 and the platinum mesh 2 are immersed in the etching liquid, a laser head 400 is further arranged above the silicon carbide ingot 1, in the process of irradiating the silicon carbide ingot 1, laser is focused by the laser head at a predetermined depth inside the silicon carbide ingot to scan to form an amorphous layer, and simultaneously, a positive constant potential is provided for a conductive layer of the silicon carbide ingot 1, so that the etching rate is increased, the formation of the amorphous layer and the selective etching of the amorphous layer can be simultaneously performed, and the technical problems that the amorphous layer formed after laser treatment is corroded from outside to inside in the photoelectrochemical corrosion process, the corrosion rate is low, and the rapid peeling of the silicon carbide wafer is not facilitated are solved.
According to the technical scheme provided by the embodiment of the invention, a silicon carbide crystal ingot is used as an anode and is connected with a voltage output end through a conducting layer on the silicon carbide crystal ingot, and a cathode is arranged in etching liquid and is connected with the voltage input end; focusing laser light at a predetermined depth inside the silicon carbide crystal ingot, scanning inwards from the edge of the surface of the silicon carbide crystal ingot to form an amorphous layer, and simultaneously irradiating the surface of the silicon carbide crystal ingot with incident light of which the wavelength is larger than a critical value of a corresponding absorption light wavelength of the first single crystal layer; and providing a positive constant potential to the silicon carbide crystal ingot while irradiating by adopting incident light to realize the peeling of the first single crystal layer and the second single crystal layer and obtain a silicon carbide wafer; the photoelectrochemical etching process method adopted by the invention can quickly obtain the silicon carbide wafer with controllable thickness, does not need thinning and grinding treatment, has no damage layer and no stress residue on the surface or the subsurface of the single crystal, is simple to operate, has low cost and further improves the photoelectrochemical corrosion rate.
In the embodiment, the amorphous layer is simultaneously corroded in the process of forming the amorphous layer, so that the efficiency of stripping the silicon carbide wafer is improved; in the embodiment, microwave heating is adopted, so that heating is more uniform, the corrosion efficiency is improved, compared with a traditional heat conduction type heating mode, microwave heating can be carried out on a molecular level, a temperature gradient does not exist, heating is uniform, and rapid oxidation of an amorphous layer can be realized; if adopt other modes heating, because the inhomogeneity of heating all has very high requirements to conditions such as the velocity of flow of etching solution, be unfavorable for the application at the in-process that carborundum peeled off, and this embodiment has adopted the mode of microwave heating, has reached the experiment purpose, and has fine effect.
Correspondingly, based on the same invention concept, the embodiment also provides a silicon carbide wafer stripping device, which comprises an electrolytic bath, a light source and a laser head;
the electrolytic tank is used for containing etching liquid, and a mounting structure is arranged in the etching liquid and used for mounting a silicon carbide crystal ingot and a cathode; the laser head is arranged above the silicon carbide crystal ingot, a conducting layer is further arranged at the bottom of the silicon carbide crystal ingot, the silicon carbide crystal ingot is used as an anode and is connected with a voltage output end through the conducting layer, and a cathode is further arranged in the etching liquid and is connected with a voltage input end;
in the process of soaking the silicon carbide crystal ingot in the etching liquid, the laser head focuses laser on a preset depth inside the silicon carbide crystal ingot and scans inwards from the edge of the silicon carbide crystal ingot to form an amorphous layer, wherein the amorphous layer formed by scanning is located at the preset depth inside the silicon carbide crystal ingot, the two sides of the amorphous layer are respectively a first single crystal layer and a second single crystal layer of the silicon carbide crystal ingot, the first single crystal layer is a silicon carbide crystal wafer to be stripped, and the conducting layer is specifically arranged on the outer side surface of the second single crystal layer;
incident light emitted by the light source and larger than the critical value of the absorption wavelength corresponding to the first single crystal layer is irradiated on the surface of the amorphous layer through the first single crystal layer on the surface of the silicon carbide crystal ingot in the laser scanning process, so that photo-generated hole-electron pairs are formed on the surface of the amorphous layer, a positive constant potential is provided for the silicon carbide crystal ingot in the irradiation process by adopting the incident light, the photo-generated electrons on the surface of the amorphous layer are transferred to the cathode along with current to react with etching liquid, and the etching liquid selectively etches the surface of the amorphous layer with the photo-generated holes, so that the first single crystal layer is peeled off, and a silicon carbide crystal wafer is obtained.
The light source is also provided with an optical filter, the optical filter is used for filtering, so that the wavelength of incident light reaching the surface of the silicon carbide crystal ingot is larger than the absorption light wavelength critical value corresponding to the first single crystal layer, and the light source is a xenon lamp, a mercury lamp or an led ultraviolet lamp.
Further comprising: and the microwave device is used for carrying out microwave heating on the etching liquid in the process of providing positive constant potential for the silicon carbide crystal ingot.
Specifically, as shown in fig. 3, the silicon carbide wafer peeling device includes an electrolytic tank 7 and a light source above the electrolytic tank 7, an etching solution is contained in the electrolytic tank, a silicon carbide ingot 1 serving as an anode and a platinum mesh 2 serving as a cathode are arranged in the etching solution, a conductive layer and an insulating layer are further sequentially arranged on the lower surface of the silicon carbide ingot, a stirrer 3 is further arranged below the platinum mesh 2 for enabling the etching solution to fully react, the conductive layer arranged on the lower surface of the silicon carbide ingot 1 is connected to a voltage output end arranged outside the electrolytic tank 7, namely, a positive power supply electrode, through an anode interface 4 formed by a lead, and the platinum mesh 2 serving as the cathode is connected to a voltage input end arranged outside the electrolytic tank 7, namely, a negative power supply electrode, through a cathode interface 5 formed by a lead.
The left side and the right side of the electrolytic cell 7 are respectively provided with an etching liquid outlet 9 and an etching liquid inlet 8, etching liquid enters the electrolytic cell 7 through the etching liquid inlet 8 and then flows out of the electrolytic cell through the etching liquid outlet 9, wherein the electrolytic cell can be a polytetrafluoroethylene electrolytic cell.
Although the present invention has been described with reference to the preferred embodiments, it is not intended to limit the present invention, and those skilled in the art can make variations and modifications of the present invention without departing from the spirit and scope of the present invention by using the methods and technical contents disclosed above.
Claims (10)
1. A method for peeling a silicon carbide wafer is characterized by comprising the following steps:
providing a silicon carbide crystal ingot, and soaking the silicon carbide crystal ingot into etching liquid, wherein the bottom of the silicon carbide crystal ingot is also provided with a conducting layer, the silicon carbide crystal ingot is used as an anode and is connected with a voltage output end through the conducting layer, and a cathode is also arranged in the etching liquid and is connected with a voltage input end;
in the process of soaking the silicon carbide crystal ingot in the etching liquid, focusing laser at a preset depth inside the silicon carbide crystal ingot, and scanning inwards from the edge of the silicon carbide crystal ingot to form an amorphous layer, wherein the amorphous layer formed by scanning is positioned at the preset depth inside the silicon carbide crystal ingot, the two sides of the amorphous layer are respectively a first single crystal layer and a second single crystal layer of the silicon carbide crystal ingot, the first single crystal layer is a silicon carbide crystal wafer to be stripped, and the conductive layer is specifically arranged on the outer side surface of the second single crystal layer;
in the process of laser scanning, irradiating the surface of the silicon carbide crystal ingot with incident light which is larger than the wavelength critical value of the absorbed light corresponding to the first single crystal layer, wherein the incident light is irradiated on the surface of the amorphous layer through the first single crystal layer on the surface of the silicon carbide crystal ingot, and a photo-generated hole-electron pair is formed on the surface of the amorphous layer;
and providing a positive constant potential to the silicon carbide crystal ingot in the process of irradiation by adopting incident light, transferring photo-generated electrons on the surface of the amorphous layer to the cathode along current to react with etching liquid, and selectively etching the surface of the amorphous layer with photo-generated holes by the etching liquid to realize the stripping of the first single crystal layer so as to obtain the silicon carbide wafer.
2. The method for peeling the silicon carbide wafer as set forth in claim 1, wherein the laser scanning is performed at a wavelength of 530 to 1030nm and a frequency of 1 to 600 kHz; the laser scanning adopts a Mach-Zehnder type double-pulse optical device to realize double-pulse output, the time delay between double pulses is +2 picoseconds to +70 picoseconds, and the pulse duration is 10 femtoseconds to 6 picoseconds; the laser focus focused in the silicon carbide crystal ingot scans at the speed of 10-100 μm/s, and the distance between adjacent laser writing tracks is 5-50 μm.
3. The silicon carbide wafer lift-off method of claim 1 further comprising microwave heating the etching liquid during the providing of the positive constant potential to the silicon carbide ingot.
4. The method for peeling the silicon carbide wafer according to claim 3, wherein the microwave output power during the microwave heating is 100 to 300W, and the temperature of the etching solution is 30 to 90 ℃.
5. The silicon carbide wafer stripping method as set forth in claim 1 wherein the silicon carbide ingot is connected as an anode through the conductive layer to a voltage output and a cathode in the etching solution is connected to a voltage input, in particular, the silicon carbide ingot is connected as an anode through the conductive layer to a voltage output and a cathode in the etching solution is connected to a voltage input based on a two-electrode system, or the silicon carbide ingot is connected as an anode through the conductive layer to a voltage output and a cathode in the etching solution is connected to a voltage input based on a three-electrode system.
6. The silicon carbide wafer lift-off method of claim 1 wherein the etching solution comprises an oxidizing agent and a silicon oxide etching solution; the method comprises the following steps that photo-generated electrons on the surface of the amorphous layer are transferred to the cathode along with current to react with etching liquid, and the process of selectively etching the surface of the amorphous layer with photo-generated holes by the etching liquid specifically comprises the following steps:
and transferring photo-generated electrons on the surface of the amorphous layer onto the cathode along with current to react with the oxidant, reacting residual photo-generated holes on the surface of the amorphous layer with Si-C and Si-Si on the surface of the amorphous layer to generate silicon oxide, and reacting the silicon oxide etching solution with the silicon oxide so as to selectively etch the surface of the amorphous layer.
7. The silicon carbide wafer stripping method as set forth in claim 1 wherein an insulating layer is further provided on the outside of the conductive layer, the cathode is a platinum mesh, and the silicon carbide ingot has a nitrogen doping concentration in the range of 5 x 1014～3×1019 /cm3The thickness of the silicon carbide crystal ingot ranges from 0.5 mm to 50 mm, the size of the silicon carbide crystal ingot ranges from 2 inches to 8 inches, the depth of the amorphous layer ranges from 5 microns to 600 microns, the thickness of the amorphous layer ranges from 2 microns to 50 microns, and the distance from the amorphous layer to the upper side surface of the first single crystal layer ranges from 5 microns to 600 microns; the voltage range for providing a positive constant potential to the silicon carbide crystal ingot is 1-8V; the height range of a light source for emitting incident light from the surface of the etching liquid is 5-10 cm; the flow rate range of the etching liquid is 1-5 mL/min, and the concentration range of the etching liquid is 1-20%.
8. A silicon carbide wafer stripping device is characterized by comprising an electrolytic bath, a light source and a laser head;
the electrolytic tank is used for containing etching liquid, and a mounting structure is arranged in the etching liquid and used for mounting a silicon carbide crystal ingot and a cathode; the laser head is arranged above the silicon carbide crystal ingot, a conducting layer is further arranged at the bottom of the silicon carbide crystal ingot, the silicon carbide crystal ingot is used as an anode and is connected with a voltage output end through the conducting layer, and a cathode is further arranged in the etching liquid and is connected with a voltage input end;
in the process of soaking the silicon carbide crystal ingot in the etching liquid, the laser head focuses laser on a preset depth inside the silicon carbide crystal ingot and scans inwards from the edge of the silicon carbide crystal ingot to form an amorphous layer, wherein the amorphous layer formed by scanning is located at the preset depth inside the silicon carbide crystal ingot, the two sides of the amorphous layer are respectively a first single crystal layer and a second single crystal layer of the silicon carbide crystal ingot, the first single crystal layer is a silicon carbide crystal wafer to be stripped, and the conducting layer is specifically arranged on the outer side surface of the second single crystal layer;
incident light emitted by the light source and larger than the critical value of the absorption wavelength corresponding to the first single crystal layer is irradiated on the surface of the amorphous layer through the first single crystal layer on the surface of the silicon carbide crystal ingot in the laser scanning process, so that photo-generated hole-electron pairs are formed on the surface of the amorphous layer, a positive constant potential is provided for the silicon carbide crystal ingot in the irradiation process by adopting the incident light, the photo-generated electrons on the surface of the amorphous layer are transferred to the cathode along with current to react with etching liquid, and the etching liquid selectively etches the surface of the amorphous layer with the photo-generated holes, so that the first single crystal layer is peeled off, and a silicon carbide crystal wafer is obtained.
9. The silicon carbide wafer stripping apparatus as set forth in claim 8 wherein the light source is further provided with a filter for filtering light incident on the surface of the silicon carbide ingot at a wavelength greater than the critical wavelength of the absorbed light corresponding to the first monocrystalline layer.
10. The silicon carbide wafer debonding apparatus of claim 8, further comprising: and the microwave device is used for carrying out microwave heating on the etching liquid in the process of providing positive constant potential for the silicon carbide crystal ingot.
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