CN112404747B - Wafer stripping method and wafer stripping device - Google Patents

Wafer stripping method and wafer stripping device Download PDF

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Publication number
CN112404747B
CN112404747B CN202011242999.2A CN202011242999A CN112404747B CN 112404747 B CN112404747 B CN 112404747B CN 202011242999 A CN202011242999 A CN 202011242999A CN 112404747 B CN112404747 B CN 112404747B
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ingot
wafer
cooling fluid
laser beam
region
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CN112404747A (en
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王宏建
赵卫
何自坚
杨涛
王自
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XiAn Institute of Optics and Precision Mechanics of CAS
Songshan Lake Materials Laboratory
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XiAn Institute of Optics and Precision Mechanics of CAS
Songshan Lake Materials Laboratory
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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
    • B23K26/36—Removing material
    • B23K26/38—Removing material by boring or cutting
    • 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
    • B23K26/36—Removing material
    • B23K26/40—Removing material taking account of the properties of the material involved
    • B23K26/402—Removing material taking account of the properties of the material involved involving non-metallic material, e.g. isolators
    • 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
    • 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
    • B23K26/703—Cooling arrangements
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/67—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere
    • H01L21/67005—Apparatus not specifically provided for elsewhere
    • H01L21/67011—Apparatus for manufacture or treatment

Abstract

A wafer stripping method and a wafer stripping device belong to the technical field of semiconductor material processing. The wafer stripping method comprises the following steps: dividing a processing surface in the ingot into a plurality of regions, sequentially processing the plurality of regions by using a laser beam to form a modified layer, and stripping to obtain a wafer when the modified layer penetrates through the ingot. The laser beam is processed in each zone by spraying a cooling fluid around the surface of the ingot to cool the edge and/or the outer side of the edge of the zone being processed. The cooling fluid is adopted to surround the surface of the sprayed ingot and act on the edge of the processed region to form an annular flow field, so that when the laser beam forms the modified layer of each region, the energy of the laser beam acting on the inner part of the ingot is more concentrated in the modified layer forming region, and the influence of the energy on the unprocessed region is reduced. The method realizes more accurate processing of the modified layer, is beneficial to the generation of the induced stress layer in the crystal ingot, thereby improving the stripping quality of the wafer and obtaining the high-quality wafer.

Description

Wafer stripping method and wafer stripping device
Technical Field
The application relates to the technical field of semiconductor material processing, in particular to a wafer stripping method and a wafer stripping device.
Background
Wafer lift-off is one of the core technologies in the field of semiconductor manufacturing. In the traditional method, a diamond wire is used for cutting to obtain a wafer from a crystal ingot, and the method not only is long in time consumption, but also has large loss and damage to materials and high cost.
The laser stealth processing is a research hotspot in recent years to peel off wafers from ingots. However, processing a desired modified layer inside an ingot by using a laser is a difficult problem in wafer lift-off. Patent cn201511020496.x discloses a laser lift-off method for silicon wafers, which adopts laser to form explosive dots in the silicon wafers, and then pulls the wafers in the opposite direction under low temperature condition to realize seamless separation of the silicon wafers. The method is difficult to control the generation of explosion points in the laser processing process, and is easy to cause irreparable damage to materials.
Disclosure of Invention
The application provides a wafer peeling method and a wafer peeling device, which can enable cooling fluid to act on the periphery of a modified layer generated in an ingot, realize more accurate modified layer processing and are beneficial to obtaining high-quality wafers.
The embodiment of the application is realized as follows:
in a first aspect, the present application provides a wafer lift-off method, comprising: dividing a processing surface in the ingot into a plurality of regions, sequentially processing the plurality of regions by using a laser beam to form a modified layer, and stripping to obtain a wafer when the modified layer penetrates through the ingot.
The laser beam is processed in each zone by spraying a cooling fluid around the surface of the ingot to cool the edge and/or the outer side of the edge of the zone being processed.
In the above technical solution, the wafer lift-off method divides the processing surface of the ingot into a plurality of regions, processes the plurality of regions in sequence by using the laser beam, and when each region is processed, forms an annular flow field by spraying a cooling fluid around the surface of the ingot to cool the edge and/or the outer side of the edge of the region being processed, so that when the modified layer of each region is formed by the laser beam, the energy of the laser beam acting on the inner part of the ingot is more concentrated on the modified layer to form the modified region, thereby reducing the influence of the energy on the unprocessed region. And the annular flow field formed by the cooling fluid can form gradient stress in crystal ingots with different depths, so that the processing controllability of the modified layer in the crystal ingots is improved, and the processing of the more accurate modified layer is realized. Meanwhile, the intersection of the thermal action of the laser beam and the cold action of the fluid is in the processing area and the non-processing area, which is beneficial to the generation of the induced stress layer in the crystal ingot, thereby improving the stripping quality of the wafer and obtaining the high-quality wafer.
With reference to the first aspect, in a first possible example of the first aspect of the present application, the cooling fluid acts on the outer side of the machining area, and a distance between a position where the cooling fluid acts on the machining surface and an edge of the machining area is 1 to 5 mm.
In the above example, the cooling fluid does not directly act on the machining area, but acts on the position which is 1-5 mm away from the machining area, so that the cooling fluid does not affect the area of the laser beam for forming the modified layer, and the laser beam acts on the machining area through heat transfer, and the intersection of the thermal action of the laser beam and the cold action of the fluid is realized in the machining area.
In a second possible example of the first aspect of the present application in combination with the first aspect, an angle of the cooling fluid jet directed toward the processing surface is 10 to 90 ° with respect to the processing surface of the ingot.
In the above example, the surrounding injection of the cooling fluid is achieved by adjusting the injection angle of the cooling fluid and the self-rotation of the ingot.
In a third possible example of the first aspect of the present application in combination with the first aspect, the shape of the plurality of regions includes any one or more of a circle, a square, a rectangle, and a rhombus.
In a fourth possible example of the first aspect of the present application in combination with the first aspect, the cooling fluid includes water or alcohol.
Optionally, the temperature of the cooling fluid is 5-40 ℃.
Optionally, the pressure of the cooling fluid is 0.1-0.5 MPa.
Optionally, the cooling fluid has a circulating velocity of 50-200 mm/s.
With reference to the first aspect, in a fifth possible example of the first aspect of the present application, the thickness of the wafer is 200 to 600 μm.
In a sixth possible example of the first aspect of the present application in combination with the first aspect, the laser beam has a pulse width of 200fs to 10ns, a wavelength of 355 to 1064nm, a power of 1 to 10W, and a scanning speed of 50 to 500 mm/s.
In a second aspect, the present application provides a wafer lift-off device for implementing the wafer lift-off method described above, which includes a stage, a laser, and a nozzle.
The ingot is placed on a platform.
A laser is disposed on an upper side of the stage to enable a laser beam emitted from the laser beam to act on a processing surface of the ingot to form a modified layer.
The nozzle is movably installed at an upper side of the stage so that the cooling fluid sprayed from the nozzle can spray the surface of the ingot and cool the processed surface.
In the above technical solution, the laser beam moves relative to the ingot in a process in which the laser beam forms the modified layer inside the ingot. At the same time, the nozzles spray cooling fluid at an angle coordinated to rotate relative to the ingot so that the cooling fluid can be sprayed around the surface of the ingot to cool the edge and/or the outer side of the edge of the area being processed.
In a first possible example of the second aspect of the present application in combination with the second aspect, the nozzle has a hole diameter of 50 to 300 μm.
Optionally, the nozzle can rotate within an angle range of 10-90 degrees by taking a mounting point of the nozzle as a fulcrum.
With reference to the second aspect, in a second possible example of the second aspect of the present application, the wafer lift-off device further includes a control system, where the platform includes a precision motion platform, and the control system is connected to the precision motion platform and the nozzle respectively, and is configured to control the motion of the precision motion platform and the rotation angle of the nozzle, so that the laser beam can sequentially process the interiors of the multiple regions to form modified layers, and the laser beam can process each region, and the cooling fluid ejected from the nozzle can cool around the edge of the region being processed.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained from the drawings without inventive effort.
FIG. 1 is a schematic view of a cooling fluid-sprayed ingot of an embodiment of the present application;
FIG. 2 is a schematic structural diagram of a wafer lift-off device according to an embodiment of the present disclosure;
FIG. 3 is a first schematic view of a nozzle injecting cooling fluid in accordance with an embodiment of the present application;
FIG. 4 is a second schematic illustration of the nozzle injecting cooling fluid in accordance with an embodiment of the present application;
FIG. 5 is a third schematic view of the nozzle of the present application injecting cooling fluid.
Icon: 10-a wafer lift-off device; 100-a platform; 200-a laser; 210-a laser beam; 300-a nozzle; 400-ingot; 410-modified layer; 420-processing the noodles; 500-cooling fluid; 510-cooling fluid action zone; 600-a wafer; 700-a beam expander; 800-a mirror; 900-focusing mirror.
Detailed Description
Embodiments of the present application will be described in detail below with reference to examples, but those skilled in the art will appreciate that the following examples are only illustrative of the present application and should not be construed as limiting the scope of the present application. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
The following is a detailed description of a wafer peeling method and a wafer peeling apparatus according to an embodiment of the present application:
the application provides a wafer stripping method, which comprises the following steps: dividing a processing surface in the ingot into a plurality of regions, sequentially processing the plurality of regions by using a laser beam to form a modified layer, and stripping to obtain a wafer when the modified layer penetrates through the ingot.
The laser beam is processed in each zone by spraying a cooling fluid around the surface of the ingot to cool the edge of the zone being processed and/or the cooling fluid ingot outside the edge.
The present application divides a processing surface inside an ingot into a plurality of regions of suitable size, and causes a laser beam to set a processing route in the order of the regions. When the laser beam is processed in each region, an annular flow field is formed by surrounding the surface of the sprayed ingot with cooling fluid to cool the edge of the region being processed and/or the cooling fluid ingot outside the edge, so that when the laser beam forms the modified layer of each region, the heat action of the laser beam and the cold action of the fluid intersect in the region being processed, and when the laser beam forms the modified layer of each region, the energy of the laser beam acting on the inner part of the ingot is more concentrated in the modified layer forming region, so that the influence of the energy on the unprocessed region is reduced. And the annular flow field formed by the cooling fluid can form gradient stress in crystal ingots with different depths, so that the processing controllability of the modified layer in the crystal ingots is improved, and the processing of the more accurate modified layer is realized.
It should be noted that the farthest distance from the center to the edge of each area cannot be too large or too small, and the too large distance results in that the cooling effect of the cooling fluid cannot cover the whole area, and thus there is still a case of energy concentration in the center of the area; too small a region makes it difficult to achieve cooling fluid that strictly surrounds the surface of the sprayed ingot and acts on the edge of the region being processed.
Optionally, the shape of the plurality of regions comprises any one or more of a circle, a square, a rectangle, and a diamond.
In one embodiment of the present application, the plurality of regions may be all circular. In other embodiments of the present application, the plurality of regions may also be partially circular and partially square; or part of the material can be rectangular and part of the material can be square; or the part of the diamond-shaped part can be a square and the part of the diamond-shaped part can be a rectangle.
Of course, at the edge of the ingot, some irregular shapes can be designed so that the formed modified layer penetrates through the ingot.
When the shape of the plurality of regions comprises a circle, the diameter of each circle region is 0.1-5 mm;
when the shape of the plurality of areas comprises a square, the side length of each square area is 0.1-5 mm;
when the plurality of regions are rectangular, each rectangular region has a length of 0.1-10 mm, a width of 0.1-5 mm, and an area of 0.01-50 mm or less2；
When the shape of the plurality of regions comprises a rhombus, the side length of each rhombus region is 0.1-5 mm.
When the shapes of the areas comprise irregular shapes, the farthest distance from the center point of the irregular-shaped area to the contour line is less than or equal to 2-12 mm.
Referring to fig. 1, when the shape of the plurality of regions includes a circular shape, the laser beam is applied to the processed surface to form modified layer 410, and the cooling fluid is injected around the surface of ingot 400 and applied to the edge of the region being processed to form cooling fluid application region 510.
In order to avoid the influence of the cooling fluid on the area of the laser beam forming the modified layer and to enable the cooling fluid to be transmitted to the area being processed through the cold action, the intersection of the heat action of the laser beam and the cold action of the fluid is realized in the area being processed, and the cooling fluid does not directly act on the area being processed, but acts on the position with the distance of 1-5 mm from the edge of the area being processed. Continuing with FIG. 1, L is the distance between the cooling fluid and the region being processed.
The included angle between the spray angle of the cooling fluid towards the processing surface and the processing surface of the crystal ingot is 10-90 degrees.
The surrounding injection of the cooling fluid is achieved by adjusting the injection angle of the cooling fluid and the self-rotation of the ingot.
The cooling fluid comprises water or alcohol.
Optionally, the temperature of the cooling fluid is 5-40 ℃.
Optionally, the pressure of the cooling fluid is 0.1-0.5 MPa.
Optionally, the cooling fluid has a circulating velocity of 50-200 mm/s.
It should be noted that the cooling fluid includes liquid water or liquid alcohol, and the minimum temperature of the cooling fluid in the liquid state is preferably maintained.
The ingot comprises silicon, silicon carbide, sapphire, or gallium nitride.
The pulse width of the laser beam is 200 fs-10 ns, the wavelength is 355-1064 nm, the power is 1-10W, and the scanning speed is 50-500 mm/s.
The thickness of the wafer obtained by peeling is 200 to 600 μm.
Referring to fig. 2, the present application further provides a wafer lift-off apparatus 10 for implementing the wafer lift-off method, which includes a stage 100, a laser 200 and a nozzle 300.
Wherein ingot 400 is disposed on platform 100.
Laser 200 is disposed on the upper side of stage 100 to allow laser beam 210 emitted from laser beam 210 to act on processing surface 420 of ingot 400 to form modified layer 410.
In the embodiment shown in FIG. 1, the platform 100 comprises a precision motion platform. The laser beam 210 acts on the processing surface 420 inside the crystal ingot 400, the laser beam 210 does not move, and the moving precision motion platform moves along the X axis and the Y axis, namely the laser beam 210 moves relative to the crystal ingot 400 and continuously acts on the crystal ingot 400 to form the modified layer 410. In other embodiments of the present application, movement of laser beam 210 relative to ingot 400 may be accomplished without movement of stage 100, but with movement of laser beam 210.
The nozzle 300 is movably installed at an upper side of the precision motion stage so that the cooling fluid 500 sprayed from the nozzle 300 can act on the machining surface 420.
During the processing of the laser beam 210, the precision motion stage moves along the X-axis and the Y-axis, so that the laser beam 210 is sequentially processed in the divided regions to form the modified layer 410.
For example, the processing surface 420 of the entire ingot 400 is divided into 20 processing regions, and the first region and the second region are sequentially processed using the laser beam 210 until the twentieth region is completed.
During the processing of each region by laser beam 210, the precision motion stage is rotated about the Z-axis to rotate ingot 400 about the Z-axis, at which time nozzle 300 adjusts its spray angle so that cooling fluid 500 sprays around the surface of ingot 400 and against the edge of the region being processed.
For example, when the laser beam 210 is processed in the first area, the nozzle 300 is rotated by its own angle and the Z-axis of the precision motion stage, so that the cooling fluid 500 ejected from the nozzle 300 acts around the edge of the area being processed.
Optionally, the aperture of the nozzle 300 is 50-300 μm.
Optionally, the nozzle 300 can rotate within an angle range of 10-90 ° with its mounting point as a fulcrum.
Referring to fig. 3, when the edge of the region being processed is located directly below the nozzle 300, the nozzle 300 maintains the spray angle perpendicular to the modified layer 410, and the cooling fluid 500 is sprayed perpendicularly to the upper surface of the ingot 400 to act on the edge of the region being processed.
Referring to fig. 4 and 5, when the edge of the region being processed is located obliquely below the nozzle 300, the nozzle 300 rotates and maintains an inclined spray angle to the modified layer 410, and the cooling fluid 500 is sprayed obliquely to the upper surface of the ingot 400 to act on the edge of the region being processed.
The wafer stripping apparatus 10 further comprises a control system connected to the precision motion stage and the nozzle 300 respectively for controlling the motion of the precision motion stage and the rotation angle of the nozzle 300, so that the laser beam 210 can sequentially process the inside of a plurality of regions to form the modified layer 410, and the cooling fluid 500 sprayed from the nozzle 300 can surround the surface of the sprayed ingot 400 to cool the edge of the region being processed and/or the outside of the edge when the laser beam 210 processes each region.
The wafer peeling apparatus 10 further includes a beam expander 700, a reflector 800, and a focusing mirror 900, wherein the beam expander 700, the reflector 800, and the focusing mirror 900 are sequentially disposed on the path of the laser beam 210.
After being emitted from the laser 200, the laser beam 210 passes through the beam expander 700, the reflector 800, and the focusing mirror 900 in sequence and is focused on the processing surface 420 in the ingot 400.
The wafer stripping apparatus 10 further comprises a monitoring device (not shown) including an acoustic emission and CCD system. The monitoring device feeds back the crack propagation state of the modified layer 410 in real time through the transmission of the acoustic signal and the image of the modified layer 410.
The ingot 400 to be stripped is placed on a precision motion stage, the X-axis and Y-axis of the precision motion stage are moved to define a machining region, and the Z-axis is moved such that the focal plane of the laser beam 210 from the laser 200 is located at the machining surface 420 inside the ingot 400.
The laser beam 210 sequentially forms modified layers 410 in the processed region of the processed surface 420 of the ingot 400 by computer analysis and dividing the processed surface 420 of the ingot 400 into a plurality of regions and designing the movement trajectories of the precision motion stage along the X-axis and the Y-axis. The spray angle of the nozzle 300 and the rotation trajectory of the precision motion stage about the Z-axis are designed such that the cooling fluid 500 may act around the edge of the processing region of the ingot 400.
The laser 200 is turned on, the laser beam 210 is focused on the focal plane of the ingot 400 through the upper surface of the ingot 400, the laser beam 210 is sequentially processed in a plurality of regions to form modified layers 410 during the movement of the precision motion stage along the X-axis and the Y-axis, and the cooling fluid 500 sprayed from the nozzle 300 is circumferentially sprayed on the surface of the ingot 400 and applied to the edge of the region being processed during the rotation of the nozzle 300 and the rotation of the precision motion stage about the Y-axis during the processing of each region by the laser beam 210.
The formation state of the modified layer 410 in the ingot 400 is monitored in real time by a monitoring device, and the wafer 600 is obtained by peeling when the modified layer 410 penetrates the peeling surface of the entire ingot 400.
A wafer peeling method and a wafer peeling apparatus 10 according to the present application are described in further detail below with reference to embodiments.
Example 1
The embodiment of the application provides a wafer stripping method, which comprises the following steps:
the silicon carbide ingot 400 to be stripped is placed on a precision motion stage, the X-axis and Y-axis of the precision motion stage are moved to define a machining region, and the Z-axis is moved such that the focal plane of the laser beam 210 from the laser 200 is located at the machining surface 420 inside the silicon carbide ingot 400.
The laser beam 210 sequentially forms modified layers 410 in the processed region of the processed surface 420 of the ingot 400 by computer analysis and dividing the processed surface 420 of the ingot 400 into a plurality of regions and designing the movement trajectories of the precision motion stage along the X-axis and the Y-axis. The spray angle of the nozzle 300 and the rotation trajectory of the precision motion stage about the Z-axis are designed such that the cooling fluid 500 may act around the edge of the processing region of the ingot 400.
The laser 200 is turned on, a laser beam 210 having a pulse width of 4ns, a wavelength of 1064nm and a power of 2W is focused on a focal plane of the silicon carbide ingot 400 through the upper surface of the silicon carbide ingot 400, the laser beam 210 is sequentially processed in a plurality of regions at a scanning rate of 300mm/s while the precision motion stage moves along the X-axis and the Y-axis to form modified layers 410, and cooling water having a temperature of 10 ℃ and a pressure of 0.2MPa is sprayed from the nozzle 300 around the surface of the silicon carbide ingot 400 at a speed of 100mm/s and applied to the edge of the region being processed while each region is being processed by the laser beam 210, while the nozzle 300 is rotated and the precision motion stage is rotated around the Y-axis.
The state of formation of the modified layer 410 in the silicon carbide ingot 400 is monitored in real time by a monitoring device, and when the modified layer 410 penetrates the entire surface of the silicon carbide ingot 400 to be peeled, the silicon carbide wafer 600 is obtained.
Example 2
The embodiment of the application provides a wafer stripping method, which comprises the following steps:
the silicon ingot 400 to be stripped is placed on a precision motion stage, and the X-axis and Y-axis of the precision motion stage are moved to determine a processing area while the Z-axis is moved so that the focal plane of the laser beam 210 emitted from the laser 200 is located at the processing surface 420 inside the silicon ingot 400.
The laser beam 210 sequentially forms modified layers 410 in the processed region of the processed surface 420 of the ingot 400 by computer analysis and dividing the processed surface 420 of the ingot 400 into a plurality of regions and designing the movement trajectories of the precision motion stage along the X-axis and the Y-axis. The spray angle of the nozzle 300 and the rotation trajectory of the precision motion stage about the Z-axis are designed such that the cooling fluid 500 may act around the edge of the processing region of the ingot 400.
The laser 200 is turned on, a laser beam 210 with a pulse width of 300fs, a wavelength of 1030nm and a power of 2W is focused on a focal plane of the silicon ingot 400 through the upper surface of the silicon ingot 400, the laser beam 210 is sequentially processed in a plurality of regions at a scanning rate of 150mm/s during the movement of the precision motion stage along the X-axis and the Y-axis to form modified layers 410, and cooling alcohol with a temperature of 5 ℃ and a pressure of 0.1MPa is sprayed from the nozzle 300 around the surface of the silicon ingot 400 at a speed of 75mm/s and is applied to the edge of the region being processed during the rotation of the nozzle 300 and the rotation of the precision motion stage around the Y-axis when the laser beam 210 processes each region.
The state of formation of the modified layer 410 in the silicon ingot 400 is monitored in real time by a monitoring device, and when the modified layer 410 penetrates the entire peeling surface of the silicon ingot 400, the silicon wafer 600 is peeled off.
Example 3
The embodiment of the application provides a wafer stripping method, which comprises the following steps:
the sapphire ingot 400 to be peeled is placed on a precision motion stage, and the X-axis and Y-axis of the precision motion stage are moved to determine a processing region while the Z-axis is moved so that the focal plane of the laser beam 210 emitted from the laser 200 is located at a processing surface 420 inside the sapphire ingot 400.
The laser beam 210 sequentially forms modified layers 410 in the processed region of the processed surface 420 of the ingot 400 by computer analysis and dividing the processed surface 420 of the ingot 400 into a plurality of regions and designing the movement trajectories of the precision motion stage along the X-axis and the Y-axis. The spray angle of the nozzle 300 and the rotation trajectory of the precision motion stage about the Z-axis are designed such that the cooling fluid 500 may act around the edge of the processing region of the ingot 400.
The laser 200 is turned on, a laser beam 210 with a pulse width of 300f, a wavelength of 1030nm and a power of 1.5W is focused on a focal plane of the sapphire ingot 400 through the upper surface of the sapphire ingot 400, the laser beam 210 is sequentially processed in a plurality of regions at a scanning rate of 70mm/s during the movement of the precision motion stage along the X-axis and the Y-axis to form modified layers 410, and cooling water with a temperature of 7 ℃ and a pressure of 0.15MPa is sprayed from the nozzle 300 around the surface of the sapphire ingot 400 at a speed of 120mm/s and acts on the edge of the region being processed during the rotation of the nozzle 300 and the rotation of the precision motion stage around the Y-axis when the laser beam 210 processes each region.
The formation state of the modified layer 410 in the sapphire ingot 400 is monitored in real time by a monitoring device, and when the modified layer 410 penetrates through the peeling surface of the whole sapphire ingot 400, the sapphire wafer 600 is obtained by peeling.
Comparative example 1
The comparative example of the present application provides a wafer lift-off method, which includes:
the silicon carbide ingot 400 to be stripped is placed on a precision motion stage, the X-axis and Y-axis of the precision motion stage are moved to define a machining region, and the Z-axis is moved such that the focal plane of the laser beam 210 from the laser 200 is located at the machining surface 420 inside the silicon carbide ingot 400.
The laser beam 210 sequentially forms modified layers 410 in the processed region of the processed surface 420 of the ingot 400 by computer analysis and dividing the processed surface 420 of the ingot 400 into a plurality of regions and designing the movement trajectories of the precision motion stage along the X-axis and the Y-axis.
And starting the laser 200, focusing the laser beam 210 with the pulse width of 4ns, the wavelength of 1064nm and the power of 2W on the focal plane of the silicon carbide crystal ingot 400 through the upper surface of the silicon carbide crystal ingot 400, and sequentially processing the laser beam 210 in a plurality of areas at the scanning speed of 300mm/s to form modified layers 410 in the process that the precision motion platform moves along the X axis and the Y axis.
The state of formation of the modified layer 410 in the silicon carbide ingot 400 is monitored in real time by a monitoring device, and when the modified layer 410 penetrates the entire surface of the silicon carbide ingot 400 to be peeled, the silicon carbide wafer 600 is obtained.
Test example 1
Comparing the above embodiments with the comparative examples, embodiments 1 to 3 using the annular cooling fluid 500 can form gradient stress in the interior of the ingot 400 at different depths, the processing of each region of the processing surface 420 of the ingot 400 is relatively independent, and the processing of the modified layer 410 in the interior of the ingot 400 can be controlled within a range of 80 μm. Comparative example 1 due to the absence of the annular cooling fluid 500, the processing of the regions of the processing surface 420 of the ingot 400 were affected by each other and the controllability of the processing of the modified layer 410 inside the ingot 400 was poor, ranging over 150 μm.
In summary, according to the wafer peeling method and the wafer peeling apparatus 10 of the embodiment of the present application, the processing surface 420 of the ingot 400 is divided into a plurality of regions, the plurality of regions are sequentially processed by the laser beam 210, and an annular flow field is formed around the surface of the ingot 400 by spraying the cooling fluid 500 to cool the edge of the region being processed and/or the outer side of the edge when each region is processed, so that the energy of the laser beam 210 applied to the inner portion of the ingot 400 is more concentrated on the region where the modified layer 410 is formed when the modified layer 410 of each region is formed by the laser beam 210, thereby reducing the influence of the energy on the unprocessed region. In addition, the annular flow field formed by the cooling fluid 500 can form gradient stress in the crystal ingot 400 at different depths, so that the processing controllability of the modified layer 410 in the crystal ingot 400 is improved, and the processing of the modified layer 410 is more accurate. Meanwhile, the intersection of the thermal action of the laser beam 210 and the cold action of the fluid in the machining region and the non-machining region facilitates the generation of the induced stress layer inside the ingot 400, thereby improving the peeling quality of the wafer 600 to obtain a high-quality wafer 600.
The foregoing is illustrative of the present application and is not to be construed as limiting thereof, as numerous modifications and variations will be apparent to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims (14)

1. A wafer peeling method is characterized by comprising the following steps: dividing a processing surface in the ingot into a plurality of areas, sequentially processing the areas by using laser beams to form a modified layer, and stripping to obtain a wafer when the modified layer penetrates through the stripping surface in the whole ingot;
the laser beam is sprayed around the surface of the ingot with a cooling fluid to cool the edge of the region being processed and/or the outside of the edge as each region is processed.
2. The wafer peeling method according to claim 1, wherein the cooling fluid acts on the outer side of the processing area, and a distance between a position where the cooling fluid acts on the processing surface and an edge of the processing area is 1 to 5 mm.
3. The wafer peeling method as claimed in claim 1, wherein an angle of spraying the cooling fluid toward the processing surface is 10 to 90 ° to the processing surface of the ingot.
4. The wafer peeling method as claimed in claim 1, wherein the shape of the plurality of regions includes any one or more of a circle, a square, a rectangle, and a diamond.
5. The wafer stripping method as claimed in claim 1, wherein the cooling fluid comprises water or alcohol.
6. The wafer stripping method as claimed in claim 5, wherein the temperature of the cooling fluid is 5-40 ℃.
7. The wafer stripping method as claimed in claim 5, wherein the pressure of the cooling fluid is 0.1-0.5 MPa.
8. The wafer lift off method of claim 5, wherein the cooling fluid has a circulating velocity of 50 to 200 mm/s.
9. The wafer lift off method as claimed in any one of claims 1 to 8, wherein the thickness of the wafer is 200 to 600 μm.
10. The wafer lift-off method as claimed in any one of claims 1 to 8, wherein the laser beam has a pulse width of 200fs to 10ns, a wavelength of 355 to 1064nm, a power of 1 to 10W, and a scanning speed of 50 to 500 mm/s.
11. A wafer peeling apparatus for carrying out the wafer peeling method according to claim 1, characterized in that the wafer peeling apparatus comprises:
a stage on which the ingot is placed;
a laser disposed on an upper side of the stage to enable the laser beam emitted from the laser to act on the processing surface of the ingot to form the modified layer;
a nozzle movably installed at an upper side of the stage to allow the cooling fluid sprayed from the nozzle to spray a surface of the ingot and cool the processed surface.
12. The wafer stripping apparatus as claimed in claim 11, wherein the nozzle has an aperture of 50-300 μm.
13. The wafer stripping apparatus as claimed in claim 12, wherein the nozzle is rotatable within an angle range of 10-90 ° about a pivot point at a mounting point thereof.
14. The wafer stripping apparatus as claimed in claim 11, further comprising a control system, wherein the platform comprises a precision motion platform, and the control system is connected to the precision motion platform and the nozzle respectively, and is configured to control the motion of the precision motion platform and the rotation angle of the nozzle, so that the laser beam can sequentially process the inside of the plurality of regions to form modified layers, and the laser beam can process each region, and the cooling fluid ejected from the nozzle can cool around the edge of the region being processed.
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