CN115555734A - Laser slicing method and device for silicon carbide crystal ingot - Google Patents

Abstract

The invention provides a laser slicing method and a laser slicing device for a silicon carbide crystal ingot. And moving the focus of the short pulse laser beam to a certain range above the layer with the set depth, enabling the short pulse laser beam to penetrate through the crack modification forming region and then focus on the hole modification forming region for scattering propagation, enabling the crack in the crack modification forming region to grow outwards in the transverse direction, and scanning to enable the cracks in any adjacent hole modification forming regions in the hole modification layer to be connected together through the transverse growth. The amount and the length of the cracks in the modifying layer along the longitudinal extension of the silicon carbide crystal ingot are reduced, the number of transverse crack growth and the growth length of the cracks are increased, the cutting loss thickness is reduced, and the waste is reduced.

Description

Laser slicing method and device for silicon carbide crystal ingot

Technical Field

The invention relates to the technical field of silicon carbide crystal ingots, in particular to a laser slicing method and a laser slicing device for the silicon carbide crystal ingots.

Background

In the third generation semiconductor materials, siC (silicon carbide) has the characteristics of large forbidden bandwidth, high breakdown electric field, high saturated electron drift velocity, large thermal conductivity and the like, and can be applied to high-voltage environments of over 1200 volts, so that the SiC has obvious advantages in severe environments. The SiC substrate processing technology is an important basis for manufacturing devices, the quality and the precision of surface processing of the SiC substrate directly affect the quality of an epitaxial film and the performance of the devices, and therefore the surface of a wafer is required to be ultra-smooth, defect-free and damage-free in application, and the surface roughness value is below a nanometer level.

However, the processing of SiC wafers is very difficult due to the high hardness, high brittleness, good wear resistance and extremely stable chemical properties of SiC crystals. The ultra-precision machining process of the SiC single crystal wafer mainly comprises the following steps according to the machining sequence: directional cutting, grinding (rough grinding, fine grinding), polishing (mechanical polishing), and ultra-precision polishing (chemical mechanical polishing).

In the traditional method, cutting is a process of cutting the SiC crystal bar into crystal slices along a certain direction. The SiC crystal bar is cut into wafers with small warpage, uniform thickness and low cutting loss, and is vital to subsequent grinding and polishing. Compared with the traditional inner circle and outer circle cutting, the multi-line cutting has the advantages of high cutting speed, high processing precision, high efficiency, long service life and the like, and is widely applied to the high-efficiency cutting of wafers. The multi-wire cutting process is to cut the crystal ingot into cutting pieces with thickness not more than 1mm, flat surface and uniform thickness according to a certain crystal direction so as to facilitate the subsequent grinding processing. The basic principle is that a high-quality steel wire moves back and forth on the surface of an ingot at a high speed, and diamond particles in cutting fluid attached to the steel wire generate violent friction on the ingot, so that the material is cracked and falls off from the surface of a matrix, and the cutting effect is achieved. The disadvantages are high cutting abrasion, and high processing difficulty and much abrasion when cutting the silicon carbide due to the extremely high hardness of the silicon carbide. The high cost of time and complex processing make the silicon carbide substrate costly, limiting the amount of silicon carbide that can be used. In addition, the larger the wafer size, the greater the difficulty of the growth and processing techniques of the corresponding crystal, and the higher the manufacturing efficiency and lower the unit cost of downstream devices.

There are techniques in the prior art for cutting silicon ingots using a laser. On the one hand, however, silicon carbide ingots have the characteristics of high hardness, high brittleness, good wear resistance and extremely stable chemical properties compared with silicon ingots, and very thin wafers cannot be cut from the silicon carbide ingots by the existing laser cutting process. On the other hand, in the conventional process of cutting a silicon ingot by laser, a modified layer is formed at a position with a certain thickness in the silicon ingot by laser modification, then the modified layer is heated by the laser to grow and diffuse cracks in the modified layer, and then stripping is performed. In the process, the thickness of the modified layer formed by modifying the laser is thicker, when the modified layer is heated by using the laser subsequently, the laser focus is focused in the modified layer, the fluctuation of the height difference of the laser focus is larger, and the focusing position of the laser focus is not well designed, so that cracks in the modified layer are longer and more longitudinally expanded along the silicon ingot, the cutting loss thickness is larger, and a large amount of waste is caused.

Disclosure of Invention

The invention provides a laser slicing method and a laser slicing device for a silicon carbide crystal ingot, which reduce the amount and the length of cracks in a modifying layer expanding along the longitudinal direction of the silicon carbide crystal ingot, increase the number of transverse crack growth and the growth length of the cracks, reduce the cutting loss thickness and reduce the waste.

In a first aspect, the present invention provides a laser slicing method of a silicon carbide ingot, the laser slicing method comprising:

focusing the focus of the ultrashort pulse laser beam on a set depth layer position of a silicon carbide crystal ingot to be cut so as to respectively generate a cavity modification forming region and a crack modification forming region above the set depth layer position; wherein, the cavity modification forming region is positioned between the position of the set depth layer and the crack modification forming region;

controlling the focus of the ultrashort pulse laser beam to scan on a set depth layer of the silicon carbide crystal ingot so as to form a cavity modified layer and a crack modified layer above the set depth layer respectively; the crack modifying layer consists of a plurality of crack modifying forming regions, and the cavity modifying layer is positioned between the set depth layer and the crack modifying layer;

after the short pulse laser beam penetrates through the crack modification forming region, focusing the short pulse laser beam on the cavity modification forming region, and scattering and propagating the short pulse laser beam in the cavity modification forming region to enable the crack in the cavity modification forming region to grow outwards in the transverse direction;

controlling the focus of the short pulse laser beam to scan on the cavity modification layer so as to enable cracks in any adjacent cavity modification forming area in the cavity modification layer to be connected together through transverse growth;

and taking the hollow modified layer as an interface to strip part of the silicon carbide crystal ingot to generate the silicon carbide wafer.

In the above scheme, the ultrashort pulse laser is first used, the focus of the ultrashort pulse laser beam is focused on the set depth layer position of the silicon carbide crystal ingot, so as to generate a cavity modification forming region and a crack modification forming region above the set depth layer position respectively, and the focus of the ultrashort pulse laser beam is controlled to scan on the set depth layer of the silicon carbide crystal ingot, so as to form a cavity modification layer and a crack modification layer. After the ultrashort pulse level laser stealth cutting processing, short pulse level laser with slightly wide pulse width is adopted, the focus of the short pulse laser beam is moved to a position above a set depth layer within a certain range, the short pulse laser beam penetrates through a crack modification forming region, then is focused on the hole modification forming region and is scattered and propagated in the hole modification forming region, so that the heat of the short pulse laser beam mainly acts on the hole modification forming region, cracks in the crack modification forming region grow outwards in the transverse direction, and the focus of the short pulse laser beam is controlled to scan on the hole modification layer, so that the cracks in any adjacent hole modification forming regions in the hole modification layer are connected together through the transverse growth.

Compared with the existing process for cutting the silicon ingot by adopting the laser, due to the adoption of the ultrashort pulse laser, a cavity modification forming region and a crack modification forming region can be respectively generated above the position of a set depth layer where the focus of the ultrashort pulse laser beam is located, and the cavity modification layer and the crack modification layer are respectively formed through scanning, so that the modification layers in the prior art are refined and distinguished. Then, when a short pulse laser beam is used, the focal point of the short pulse laser beam is focused on the cavity modifying formation region, the focal point of the short pulse laser beam is positioned above the focal point of the ultrashort pulse laser beam, but not at the same depth position in the prior art, so that the short pulse laser beam can penetrate through the crack modifying formation region, then is focused on the cavity modifying formation region, scatters and propagates in the cavity modifying formation region, causes the crack in the cavity modifying formation region to grow outwards in the transverse direction, and causes the cracks in any adjacent cavity modifying formation region in the cavity modifying layer to be connected together through the transverse growth through scanning. In addition, in the process of heating the cavity modifying formation region by focusing the short pulse laser beam through the crack modifying formation region in the cavity modifying formation region, the crack modifying formation region can stop the growth of the crack, so that the upward growth length of the crack in the cavity modifying formation region can be limited to a region below the crack modifying formation region, the longitudinal growth length of the crack can be limited to a small height range, the crack extension efficiency can be improved, the longitudinal extension degree of the crack can be reduced as much as possible, and the slicing loss can be reduced as much as possible. The modified layer is divided into a cavity modified layer and a crack modified layer through thinning, then the short pulse laser beam is focused on the cavity modified layer, the focal position of the short pulse laser beam is designed more accurately and reasonably, the fluctuation of the height difference of the upper part and the lower part of the focal point of the short pulse laser beam is small (because the height difference of the upper part and the lower part of the cavity modified forming region is always smaller than the height difference of the modified layer formed by the crack modified forming region and the cavity modified forming region), the focal point of the short pulse laser beam is focused on the modified layer to be optimized to be focused on the cavity modified layer, the crack modified forming region on the modified layer blocks the crack in the cavity modified forming region from growing upwards longitudinally, the length of the crack growing longitudinally is limited in a smaller height range, the focal position of the short pulse laser beam is optimized, the amount and the length of the crack in the modified layer extending longitudinally along a silicon carbide ingot are reduced, so that more laser energy acts on the crack to grow outwards transversely, the number of the crack growing and the crack growing length can be increased, the thinner silicon carbide ingot can be cut, and the cutting loss thickness of the same silicon carbide ingot can be reduced.

In a specific embodiment, the ultrashort pulse laser beam is a subpicosecond pulse width laser beam, a picosecond pulse width laser beam, or a femtosecond pulse width laser beam, so as to generate a cavity modification forming region and a crack modification forming region with better effect above a focal point of the ultrashort pulse laser beam.

In one embodiment, the ultrashort pulse laser beam has a pulse width of 243fs to 900fs and a wavelength of 500nm to 1100nm, thereby further improving the modifying effect of the cavity modifying-forming region and the crack modifying-forming region generated above the focal point of the ultrashort pulse laser beam.

In a specific embodiment, the short pulse laser beam is a sub-nanosecond laser beam to increase the number and length of crack lateral growth.

In a specific embodiment, the pulse width of the short pulse laser beam is 500ps-1ns, and the wavelength of the short pulse laser beam is 500-1100nm, so that the amount and the length of the crack in the modifying layer extending along the longitudinal direction of the silicon carbide crystal ingot can be reduced better, the laser energy is applied to the transverse direction of the crack to grow outwards, and the number of the transverse crack growth and the crack growth length are increased.

In a specific embodiment, the focus point of the short pulse laser beam is 1-4.5um higher than that of the ultrashort pulse laser beam, so that the focus position of the short pulse laser beam is better optimized.

In one specific embodiment, the method of transmitting a short pulse laser beam through a crack modifying formation region, focusing the short pulse laser beam on a cavity modifying formation region, and scattering and propagating the short pulse laser beam in the cavity modifying formation region to grow a crack laterally outward in the cavity modifying formation region includes: the polarization state of the short pulse laser beam is adjusted, so that the electron propagation direction is expanded along the direction of the silicon carbide crystal lattice of the silicon carbide crystal ingot, a transverse growth crack of 3-5 degrees is formed, the amount and the length of the crack in the modifying layer, which is longitudinally expanded along the silicon carbide crystal ingot, are reduced better, more laser energy is applied to the transverse outward growth of the crack, and the number of the transverse crack growth and the crack growth length are increased.

In one embodiment, controlling the focus of the ultrashort pulse laser beam to scan a set depth layer of the silicon carbide ingot comprises: and controlling the focus of the ultrashort pulse laser beam to scan a plurality of parallel first cutting channels on a set depth layer of the silicon carbide crystal ingot, wherein the interval between any two adjacent first cutting channels is 10-25 mu m. Controlling the focal point of the short pulse laser beam to scan the cavity modifying layer includes: and controlling the focus of the short pulse laser beam to scan a plurality of parallel second cutting channels on the cavity modified layer, wherein each second cutting channel is positioned right above one first cutting channel, so that the silicon carbide explosion point interval with proper width can be conveniently set, and the scanning difficulty is simplified.

In one embodiment, controlling the focal point of the short pulse laser beam to scan a plurality of parallel second scribe lines on the hole modifying layer comprises: the number of times of scanning the focus of the short pulse laser beam at each second cutting channel is controlled to be more than or equal to three times, the connection of the explosion point cracks is realized by adopting the short pulse laser beam to process continuous heat injection for multiple times, the transverse growth amount and length of the cracks in the crack modification forming region are improved, the cracks extending out of the adjacent second cutting channels are connected together more quickly, and the aim of separating the silicon carbide crystal ingot into a plurality of silicon carbide crystal wafers is fulfilled conveniently by a concealed cutting crack induced growth mode.

In a second aspect, the present invention also provides a laser slicing apparatus for a silicon carbide ingot, the laser slicing apparatus comprising: the system comprises an object stage, an ultrashort pulse laser system, a first scanning system, a short pulse laser system, a second scanning system and a separation system. Wherein the stage is for holding thereon a silicon carbide ingot to be cut. The ultrashort pulse laser system is used for providing an ultrashort pulse laser beam and focusing the focus of the ultrashort pulse laser beam at the set depth layer position of the silicon carbide crystal ingot to be cut so as to respectively generate a cavity modification forming region and a crack modification forming region above the set depth layer position; wherein the cavity modifying formation region is located between the predetermined depth layer position and the crack modifying formation region. The first scanning system is used for controlling the focus of the ultrashort pulse laser beam to scan at a set depth layer of the silicon carbide crystal ingot so as to respectively form a cavity modified layer and a crack modified layer above the set depth layer; the cavity modified layer is composed of a plurality of cavity modified forming regions, the crack modified layer is composed of a plurality of crack modified forming regions, and the cavity modified layer is located between the set depth layer and the crack modified layer. The short pulse laser system is used for providing a short pulse laser beam, and the short pulse laser system is also used for focusing the short pulse laser beam on the cavity modification forming region after the short pulse laser beam penetrates through the crack modification forming region, and scattering and propagating the short pulse laser beam in the cavity modification forming region to enable the crack in the cavity modification forming region to grow outwards in the transverse direction. And the second scanning system is used for controlling the focus of the short pulse laser beam to scan on the cavity modification layer so as to enable the cracks in any adjacent cavity modification forming regions in the cavity modification layer to be connected together through transverse growth. The separation system is used for taking the hollow modification layer as an interface to strip a part of the silicon carbide crystal ingot to generate the silicon carbide wafer.

In the above scheme, the ultrashort pulse laser is first used, the focus of the ultrashort pulse laser beam is focused on the set depth layer position of the silicon carbide crystal ingot, so as to generate a cavity modification forming region and a crack modification forming region above the set depth layer position respectively, and the focus of the ultrashort pulse laser beam is controlled to scan on the set depth layer of the silicon carbide crystal ingot, so as to form a cavity modification layer and a crack modification layer. After the ultrashort pulse-level laser stealth cutting processing, short pulse-level laser with slightly wider pulse width is adopted, the focus of the short pulse laser beam is moved to a position above a set depth layer within a certain range, the short pulse laser beam penetrates through the crack modification forming region, then is focused on the hole modification forming region, and is scattered and propagated in the hole modification forming region, so that the heat of the short pulse laser beam mainly acts on the hole modification forming region, cracks in the crack modification forming region grow outwards in the transverse direction, and the focus of the short pulse laser beam is controlled to scan in the hole modification layer, so that the cracks in any adjacent hole modification forming region in the hole modification layer are connected together through the transverse growth.

Compared with the existing process for cutting the silicon ingot by adopting the laser, due to the adoption of the ultrashort pulse laser, a cavity modification forming region and a crack modification forming region can be respectively generated above the position of a set depth layer where the focus of the ultrashort pulse laser beam is located, and the cavity modification layer and the crack modification layer are respectively formed through scanning, so that the modification layers in the prior art are refined and distinguished. Then, when a short pulse laser beam is used, the focal point of the short pulse laser beam is focused on the cavity modifying formation region, the focal point of the short pulse laser beam is positioned above the focal point of the ultrashort pulse laser beam, but not at the same depth position in the prior art, so that the short pulse laser beam can penetrate through the crack modifying formation region, then is focused on the cavity modifying formation region, scatters and propagates in the cavity modifying formation region, causes the crack in the cavity modifying formation region to grow outwards in the transverse direction, and causes the cracks in any adjacent cavity modifying formation region in the cavity modifying layer to be connected together through the transverse growth through scanning. In addition, in the process of heating the cavity modifying formation region by focusing the short pulse laser beam through the crack modifying formation region in the cavity modifying formation region, the crack modifying formation region can stop the growth of the crack, so that the upward growth length of the crack in the cavity modifying formation region can be limited to a region below the crack modifying formation region, the longitudinal growth length of the crack can be limited to a small height range, the crack extension efficiency can be improved, the longitudinal extension degree of the crack can be reduced as much as possible, and the slicing loss can be reduced as much as possible. The modified layer is divided into a cavity modified layer and a crack modified layer through thinning, then the short pulse laser beam is focused on the cavity modified layer, the focal position of the short pulse laser beam is designed more accurately and reasonably, the fluctuation of the height difference of the upper part and the lower part of the focal point of the short pulse laser beam is small (because the height difference of the upper part and the lower part of the cavity modified forming region is always smaller than the height difference of the modified layer formed by the crack modified forming region and the cavity modified forming region), the focal point of the short pulse laser beam is focused on the modified layer to be optimized to be focused on the cavity modified layer, the crack modified forming region on the modified layer blocks the crack in the cavity modified forming region from growing upwards longitudinally, the length of the crack growing longitudinally is limited in a smaller height range, the focal position of the short pulse laser beam is optimized, the amount and the length of the crack in the modified layer extending longitudinally along a silicon carbide ingot are reduced, so that more laser energy acts on the crack to grow outwards transversely, the number of the crack growing and the crack growing length can be increased, the thinner silicon carbide ingot can be cut, and the cutting loss thickness of the same silicon carbide ingot can be reduced.

Drawings

FIG. 1 is a flow chart of a method of laser slicing a silicon carbide ingot according to an embodiment of the present invention;

fig. 2 to 7 are schematic structural cross-sectional views of steps in a method for laser slicing a silicon carbide ingot according to an embodiment of the present invention, in which fig. 3 is a diagram of an actual sample of a cavity modification formation region and a crack modification formation region processed by using an ultrashort pulse laser beam according to an embodiment of the present invention, and fig. 6 is a schematic diagram of a scattering effect of laser when the short pulse laser beam provided by an embodiment of the present invention acts on the cavity modification formation region;

FIG. 8 is a schematic view of an apparatus for laser slicing a silicon carbide ingot in accordance with an embodiment of the present invention;

fig. 9 is a flowchart of a method of laser slicing a silicon carbide ingot based on the apparatus for laser slicing a silicon carbide ingot provided in fig. 8.

Reference numerals are as follows:

10-silicon carbide ingot 21-set depth layer 22-void modified layer 23-crack modified layer

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, 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.

In order to facilitate understanding of the laser slicing method for silicon carbide crystal ingots provided by the embodiments of the present invention, an application scenario of the laser slicing method provided by the embodiments of the present invention, which is applied in a process of separating silicon carbide wafers from silicon carbide crystal ingots, is first described below. The method for laser slicing the silicon carbide ingot will be described in detail below with reference to the accompanying drawings.

Referring to fig. 1 to 7, a method for laser slicing a silicon carbide ingot according to an embodiment of the present invention includes:

step10: focusing the focus of the ultrashort pulse laser beam on the position of a set depth layer 21 of the silicon carbide crystal ingot 10 to be cut so as to respectively generate a cavity modification forming region and a crack modification forming region above the position of the set depth layer 21; wherein the cavity modification forming region is located between the position of the set depth layer 21 and the crack modification forming region;

step20: controlling the focus of the ultrashort pulse laser beam to scan on the set depth layer 21 of the silicon carbide crystal ingot 10 so as to form a cavity modification layer 22 and a crack modification layer 23 above the position of the set depth layer 21 respectively; wherein the cavity modified layer 22 is composed of a plurality of cavity modified forming regions, the crack modified layer 23 is composed of a plurality of crack modified forming regions, and the cavity modified layer 22 is located between the set depth layer 21 and the crack modified layer 23;

step30: after the short pulse laser beam penetrates through the crack modification forming region, focusing the short pulse laser beam on the cavity modification forming region, and scattering and propagating the short pulse laser beam in the cavity modification forming region to enable the crack in the cavity modification forming region to grow outwards in a transverse direction;

step40: controlling the focus of the short pulse laser beam to scan on the cavity modified layer 22, so that the cracks in any adjacent cavity modified forming region in the cavity modified layer 22 are connected together through lateral growth;

step50: a silicon carbide wafer is grown by peeling off a part of the silicon carbide ingot 10 with the hollow reformed layer 22 as an interface.

In the above-described embodiment, the ultrashort pulse laser is first used, the focus of the ultrashort pulse laser beam is focused on the position of the set depth layer 21 of the silicon carbide ingot 10, so as to generate a cavity modified formation region and a crack modified formation region above the position of the set depth layer 21, and the focus of the ultrashort pulse laser beam is controlled to scan the set depth layer 21 of the silicon carbide ingot 10, so as to form the cavity modified layer 22 and the crack modified layer 23. After the ultrashort pulse level laser stealth cutting processing, short pulse level laser with a slightly wider pulse width is adopted, the focus of the short pulse laser beam is moved to a position above the set depth layer 21 within a certain range, the short pulse laser beam penetrates through the crack modification forming region, then is focused on the hole modification forming region, and is scattered and propagated in the hole modification forming region, so that the heat of the short pulse laser beam mainly acts on the hole modification forming region, cracks in the crack modification forming region grow outwards in the transverse direction, and the focus of the short pulse laser beam is controlled to scan on the hole modification layer 22, so that cracks in any adjacent hole modification forming regions in the hole modification layer 22 are connected together through the transverse growth.

Compared with the existing process of cutting silicon ingots by adopting laser, due to the adoption of the ultrashort pulse laser, a cavity modification forming region and a crack modification forming region can be respectively generated above the position of the set depth layer 21 where the focus of the ultrashort pulse laser beam is located, and the cavity modification layer 22 and the crack modification layer 23 are respectively formed through scanning, so that the modification layers in the prior art are refined and distinguished. Then, when a short pulse laser beam is used, the focal point of the short pulse laser beam is focused on the cavity modifying formation region, and the focal point of the short pulse laser beam is located above the focal point of the ultrashort pulse laser beam, rather than at the same depth position in the prior art, so that the short pulse laser beam can pass through the crack modifying formation region, then be focused on the cavity modifying formation region, and scatter and propagate in the cavity modifying formation region, so that the crack in the cavity modifying formation region grows laterally outward, and the cracks in any adjacent cavity modifying formation region in the cavity modifying layer 22 are connected together by lateral growth through scanning. In addition, in the process of heating the cavity modifying formation region by focusing the short pulse laser beam on the cavity modifying formation region through the crack modifying formation region, the crack modifying formation region can stop the growth of the crack, so that the upward growth length of the crack in the cavity modifying formation region can be limited to a region below the crack modifying formation region, the longitudinal growth length of the crack can be limited to a small height range, the crack extension efficiency can be improved, the longitudinal extension degree of the crack can be reduced as much as possible, and the slicing loss can be reduced as much as possible. The modified layer is divided into a cavity modified layer 22 and a crack modified layer 23 through thinning, then the short pulse laser beam is focused on the cavity modified layer 22, the focal position of the short pulse laser beam is designed more accurately and reasonably, the fluctuation of the height difference of the upper part and the lower part of the focal point of the short pulse laser beam is small (the height difference of the cavity modified forming region is smaller than that of the modified layer formed by the crack modified forming region and the cavity modified forming region), the focal point of the short pulse laser beam is focused on the modified layer 22, the crack modified forming region on the modified layer blocks the crack in the cavity modified forming region from growing upwards longitudinally, the length of the crack growing longitudinally is limited in a smaller height range, the focal position of the laser beam is optimized through short pulse, the amount and the length of the crack in the modified layer extending longitudinally along the silicon carbide 10 are reduced, so that more laser energy acts on the crack to grow outwards transversely, the number and the length of the crack can be increased, thinner silicon carbide ingots can be cut, and more waste of silicon ingots can be reduced. The above steps will be described in detail with reference to the accompanying drawings.

First, referring to fig. 1, 2 and 3, the focus of the ultrashort pulse laser beam is focused on the position of the set depth layer 21 of the silicon carbide ingot 10 to be cut, so as to generate a cavity modified formation region and a crack modified formation region above the position of the set depth layer 21, wherein the cavity modified formation region is located between the position of the set depth layer 21 and the crack modified formation region. The intensity at the focal volume of the ultrashort pulsed laser beam causes nonlinear absorption of the laser energy by the material through multiphoton ionization, tunnel ionization, and avalanche ionization. Because of the nonlinear absorption, the focal position produces highly excited plasmas of very small size, which can vary from nanometer to submicron size for different crystal materials. And thus large-sized material damage in the laser incident direction is not generated.

The depth layer 21 is set during the processing process, and specifically relates to the thickness of the peeled wafer, the thickness of the peeling loss, and the like. The focus of the ultrashort pulse laser beam can be accurately focused on the position of the set depth layer 21 of the silicon carbide crystal ingot 10 through a triaxial galvanometer, a height gauge and the like.

As shown in fig. 2 to 4, the crack modifying formation region and the cavity modifying formation region generated above the position of the set depth layer 21 both occupy a certain thickness space, the sizes of the crack modifying formation region and the cavity modifying formation region are related to the energy of the ultrashort pulse laser beam, and the sizes of the crack modifying formation region and the cavity modifying formation region both increase with the increase in the laser energy. As shown in fig. 2 to 4, the cavity modification forming region may be located at a region 1 to 5um above the focal point of the ultrashort pulse laser beam, and the crack modification forming region may be located at a region 10 to 30um above the cavity modification forming region, so that the cavity modification forming region and the crack modification forming region are located at different depth layers, and the cavity modification layer 22 and the crack modification layer 23 can be clearly distinguished.

When the ultrashort pulse laser beam is selected, the ultrashort pulse laser beam can be a subpicosecond pulse width laser beam, a picosecond pulse width laser beam or a femtosecond pulse width laser beam, and a cavity modification forming region and a crack modification forming region with better effects can be conveniently generated above the focus of the ultrashort pulse laser beam. For example, the pulse width of the ultrashort pulse laser beam may be set to any value between 243fs and 900fs, and the modifying effect of the cavity modifying region and the crack modifying region generated above the focal point of the ultrashort pulse laser beam is further improved. In a more preferred embodiment, the wavelength of the ultrashort pulse laser beam can be controlled to be 500-1100nm, and specifically, the wavelength of the ultrashort pulse laser beam can be 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm, 1100nm, and any value between 500-1100nm. It is convenient to generate a cavity modification forming region and a crack modification forming region with better effect above the focus of the ultrashort pulse laser beam.

Next, referring to fig. 1 and 4, controlling the focus of the ultrashort pulse laser beam to scan the set depth layer 21 of the silicon carbide ingot 10 to form a cavity modified layer 22 and a crack modified layer 23 above the position of the set depth layer 21, respectively; the cavity modified layer 22 is composed of a plurality of cavity modified forming regions, the crack modified layer 23 is composed of a plurality of crack modified forming regions, and the cavity modified layer 22 is located between the set depth layer 21 and the crack modified layer 23.

Specifically, the mode of controlling the focus of the ultrashort pulse laser beam to scan the set depth layer 21 of the silicon carbide ingot 10 may adopt various modes, so as to form the cavity modified layer 22 and the crack modified layer 23 in the silicon carbide ingot 10, respectively, so that the cavity modified layer 22 in the cavity modified layer 22 is paved with the cavity modified layer 22 region at intervals, and the crack modified layer 23 in the crack modified layer 23 is paved with the crack modified layer 23 region at intervals. For example, a spiral scanning mode may be adopted, and a mode of scanning a plurality of cutting tracks at parallel intervals may also be adopted. Illustratively, the focus of the ultrashort pulse laser beam can be controlled to scan a plurality of parallel first cutting lanes on the set depth layer 21 of the silicon carbide ingot 10, and the interval between any two adjacent first cutting lanes can be 10-25um, specifically, the interval between any two adjacent first cutting lanes can be any value between 10-25um such as 10um, 15um, 20um, 25um, and the like, and the characteristics that the size of the cavity modification forming region is smaller than that of the crack modification forming region and the crack growth range is lower are considered, so that the interval between adjacent cavity modification forming regions is properly reduced, the difficulty of transverse growth and connection of subsequent cracks is simplified, the silicon carbide explosion point interval with proper width is conveniently set, the slicing efficiency is improved, and the scanning difficulty is simplified.

Next, referring to fig. 1, 5, 6, and 7, the short pulse laser beam is transmitted through the crack modifying formation region, focused on the cavity modifying formation region, and scatters and propagates in the cavity modifying formation region, thereby growing a crack in the cavity modifying formation region laterally outward. The pulse width of the short pulse laser beam is larger than that of the ultrashort pulse laser beam, and the pulse width of the short pulse laser beam does not reach the nanosecond pulse width degree and is in the sub-nanosecond wavelength level of picosecond magnitude. That is, the short pulse laser beam is focused on the cavity modified formation region after passing through the crack modified formation region by moving upward one time relative to the focal point focusing position of the ultra-short pulse laser beam. The focus of the short pulse laser beam moves upwards within a certain range relative to the focus of the ultrashort pulse laser beam, after the short pulse laser beam acts on the cavity modification forming region, the scattering property of the laser focal spot of the laser in the cavity modification forming region is realized by utilizing the laser self-scattering property of free ions after the laser passes through the crack modification region, and the laser focal spot scatters and propagates in the cavity modification forming region to drive the crack of the cavity modification forming region to crack and grow.

Early laser machining process, 10 ^-15 The laser energy of s pulse width order is absorbed in the material, and for different action materials (conductors, semiconductors, insulators and the like), the essence of the laser is that the laser introduces the free electron distribution of a non-equilibrium state, and the energy is transferred through the interaction between electrons, crystal lattices and phonons. The plasma was then in subpicosecond (10) ^-9 s) is initiated, with an inherent process of evaporation and melting, in which the energy and the transfer rate between the crystal lattices are related to the intrinsic properties of the material, and the material begins to change its phase state at this stage as the laser energy continues to act. After which the impact radiation is generated, which process exists over a large time span (typically occurring at 10) ^-12 s to 10 ^-3 s) the thermal effect of the material gradually dominates the main factor, thereby creating a thermal front and an evaporation front resulting in a gradual increase of the back momentum, with the concomitant occurrence of weaker secondary radiative processes. The processing method shown in the step is taken from the initial stage of the material to generate the heat effect, and the heat accumulation effect is generated.

Further, when the short pulse laser beam passes through the crack modification formation region, the beam is widened, dithered, and bent due to the modification of the material. However, since the crack modifying formation region and the cavity modifying formation region are close to each other in distance, most of the laser light can still act on the cavity modifying formation region. Although the focus spot flickers and drifts, the coherence of the laser beam is deteriorated. However, the laser after phase change can generate self-scattering in the cavity modification forming region, and electronic waves are radiated in all directions along with the vibration of electromagnetic waves, so that the laser scattered in multiple directions is at the focus of the laser, surrounding materials are ionized and absorbed to form a high-energy and high-pressure region, the cavity region is further exploded and grown under the action of the laser, cracks grow along the direction of a silicon carbide crystal lattice in order under the control of the polarization direction of the laser, and the peeling of the wafer is finally realized along with the connection of the cracks in all cutting channels.

The cavity modification forming region is a modification region, a cavity is not formed yet, and when the focused short pulse laser beam capable of penetrating through the material is subsequently loaded, when the photon energy of the short pulse laser beam is focused on the material and is high enough, the laser photon can directly break off the chemical bond of the sample, so that the volume of the local region rapidly expands and explodes. The short pulse width is long enough so that the photon energy, after being transferred to an electron, can be coupled into the silicon carbide lattice immediately and the photon energy will be converted into thermal energy, resulting in an increase in the temperature of the sample. When the temperature rises, the physicochemical properties of the sample further change, the coefficient of an optical system changes and causes stress to be generated in the sample, and the stress is continuously superposed along with the extension of the pulse width, after the chemical bond in the cavity modification forming area processed by the previous ultrashort pulse laser beam is broken, the cracks between the carbon element and the silicon element which are respectively formed further guide outward radiation.

It should be explained that the pulse width broadening of the short pulse laser beam is expected to have more light dwell time and generate more thermal effect than that of the ultrashort pulse laser beam, so that the crack grows longer, after multiple continuous irradiation of the short pulse laser beam, the multiple irradiation can be 1-3 times or 3-5 times, and the crack can grow in the horizontal direction by more than 200 microns. The growth will be different according to the material, the material type, the doping implantation condition, the power pulse width wavelength of different laser parameters, etc.

When the short pulse laser beam is selected, the short pulse laser beam can be a subnanosecond laser beam, and the number and the length of the transverse growth of cracks are increased. For example, the pulse width of the short pulse laser beam may be any value between 500ps and 1ns to facilitate better reduction in the amount and length of crack propagation within the modifying layer in the longitudinal direction of silicon carbide ingot 10, thereby allowing more laser energy to act on the cracks to grow laterally outward, increasing the number of lateral crack growths and the crack growth length. In a more preferred embodiment, the short pulse laser beam may have a wavelength of 500 to 1100nm, and specifically, the short pulse laser beam may have a wavelength of 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm, 1100nm, or any value between 500 and 1100nm. Facilitating a better reduction in the amount and length of crack propagation in the modified layer along the longitudinal direction of silicon carbide ingot 10, thereby allowing more laser energy to act on the cracks to grow laterally outward, increasing the number of lateral crack growths and the crack growth length.

When the focus of the short pulse laser beam is focused on the cavity modifying formation region, in a more preferable mode, the focus of the short pulse laser beam can be focused at a position 1-4.5um higher than the focus of the ultrashort pulse laser beam, so that the focus position of the short pulse laser beam can be better optimized. It is needless to say that any method of focusing the focal point of the short pulse laser beam on the cavity modifying formation region is within the scope of the present patent.

In addition, the control of the explosion energy diffusion direction of the cavity modification formation region can be realized by controlling the polarization state of the short pulse laser beam, and the crack growth at a certain angle of the explosion point of the short pulse laser beam can also be realized. After the short pulse laser beam penetrates through the crack modifying formation region, the short pulse laser beam is focused on the cavity modifying formation region and is scattered and propagated in the cavity modifying formation region, so that in the process of transversely outwards growing the crack in the cavity modifying formation region, the polarization state of the short pulse laser beam can be adjusted, the electron propagation direction is expanded along the silicon carbide crystal lattice direction of the silicon carbide crystal ingot 10, a transversely grown crack of 3-5 degrees is formed, the amount and the length of the crack in the modifying layer longitudinally expanded along the silicon carbide crystal ingot 10 can be better reduced, more laser energy acts on the transverse outwards growing of the crack, and the transverse crack growth quantity and the crack growth length are increased. For example, the polarization state of the short pulse laser beam may be adjusted so that the growth direction of the laterally grown crack is at an angle of 3-5 ° with respect to the scribe line direction.

Next, referring to fig. 1, 5, and 7, the focal point of the short pulse laser beam is controlled to scan the cavity-modified layer 22 so that cracks in any adjacent cavity-modified formation region in the cavity-modified layer 22 are connected together by lateral growth. Specifically, the mode of controlling the scanning of the focal point of the short-pulse laser beam on the cavity modifying layer 22 is related to the mode of controlling the scanning of the focal point of the ultra-short-pulse laser beam on the set depth layer 21. For example, when the spiral scanning method is adopted to control the focus of the ultrashort pulse laser beam to scan the set depth layer 21, the spiral scanning method is also adopted to control the focus of the short pulse laser beam to scan the cavity-modified layer 22. When the mode of controlling the focus of the ultrashort pulse laser beam to scan in the set depth layer 21 adopts a mode of a plurality of parallel first cutting channels, the mode of controlling the focus of the second short pulse laser beam to scan in the cavity modified layer 22 may specifically be: the focus of the short pulse laser beam is controlled to scan a plurality of parallel second cutting channels on the hollow modified layer 22, and each second cutting channel is located right above one first cutting channel, so that the scanning difficulty is simplified.

In addition, when the focus of the short pulse laser beam is controlled to scan a plurality of parallel second cutting channels on the cavity modified layer 22, the number of times that the focus of the short pulse laser beam is scanned at each second cutting channel can be controlled to be more than or equal to three times, the shot crack connection is realized by adopting the multiple processing continuous heat injection of the short pulse laser beam, the transverse growth amount and length of the crack in the crack modified forming region are improved, the cracks extending from the adjacent second cutting channels are connected together more quickly, and the aim of separating the silicon carbide crystal ingot 10 into a plurality of silicon carbide wafers through the implicit cutting crack induced growth mode is fulfilled.

Next, referring to fig. 1, a silicon carbide wafer is grown by peeling off a part of silicon carbide ingot 10 with hollow modified layer 22 as an interface. Specifically, in a mode of peeling off a part of the silicon carbide ingot 10 to produce a silicon carbide wafer with the hollow modified layer 22 as an interface, a wafer above the hollow modified layer 22 may be peeled off from the silicon carbide ingot 10 by means of stretching, rotation, or the like.

Further, a grown wafer may be peeled from a part of the silicon carbide ingot 10 with the hollow modified layer 22 as an interface. And performing line cutting on the hole modified layer by adopting a diamond wire saw, taking the hole modified layer as an interface, and stripping a part of the silicon carbide crystal ingot to generate the silicon carbide wafer. A hollow modified layer is formed at a predetermined depth layer position by first focusing a laser beam at a predetermined depth layer from the interior of the silicon carbide ingot and scanning. In the process of forming the cavity modified layer, the energy density at the laser focus exceeds the ablation threshold of the silicon carbide, the material temperature rises suddenly, the silicon carbide is decomposed under the high-temperature condition, and amorphous silicon or monocrystalline silicon or a mixture of the amorphous silicon and the monocrystalline silicon and carbon are generated, wherein the specific amorphous silicon and the monocrystalline silicon are determined by the laser energy density. When the laser energy is large, monocrystalline silicon is produced, and when the laser energy is small, amorphous silicon is produced. And then, carrying out wire cutting on the hole modified layer by adopting a diamond wire saw, taking the hole modified layer as an interface, and stripping a part of the silicon carbide crystal ingot to generate the silicon carbide wafer. Because the materials of the cavity modified layer are monocrystalline silicon, amorphous silicon and carbon, the hardness of the cavity modified layer is much lower than that of silicon carbide, and the abrasion of the diamond wire saw can be reduced in the process of adopting the diamond wire saw to carry out wire cutting on the cavity modified layer, so that the loss of the diamond wire saw is reduced, and the wire cutting difficulty is reduced. Therefore, a thinner diamond wire saw can be selected, the loss of the silicon carbide crystal ingot is reduced, and the slicing yield of the silicon carbide crystal ingot is improved. Meanwhile, the cutting mode of the diamond wire saw is adopted, so that the silicon carbide wafer is not easy to crack due to uneven stress. Compared with a method of laser cutting and mechanical stripping, the method has the advantages that the diamond wire saw is adopted to cut the cavity modified layer, the silicon carbide wafer is stripped from the modified silicon carbide crystal ingot, a mechanical stripping mode is not needed, the phenomenon that the silicon carbide wafer is cracked due to uneven stress in the mechanical stripping process can be avoided, and the product yield and the stripping efficiency are improved.

After the silicon carbide wafer is peeled from the silicon carbide ingot, before the silicon carbide wafer is polished, a step of immersing the silicon carbide wafer in a chemical solution to etch the interface of the modified layer of the silicon carbide wafer may be added, and the interface of the modified layer of the silicon carbide wafer is etched by using the chemical solution, whereby defects such as residual stress, dislocation, and crack generated in the silicon carbide wafer peeling step can be removed. And then grinding the modified layer interface of the silicon carbide wafer, wherein no residual stress or less residual stress exists on the modified layer interface of the silicon carbide wafer, so that defect increment of a grinding process is avoided, the phenomenon that the residual stress is increased due to extrusion of the grinding process so as to cause continuous growth of cracks can be relieved, a damaged layer can be completely removed by grinding less materials, the ingot loss is reduced, and the quality of the wafer is improved. And the modified layer interface corroded by the chemical solution has better flatness, the subsequent grinding difficulty can be reduced, and the grinding efficiency is improved.

In the above-described embodiments, the ultrashort pulse laser beam is first used, the focus of the ultrashort pulse laser beam is focused on the position of the set depth layer 21 of the silicon carbide ingot 10, so that the cavity modified formation region and the crack modified formation region are generated above the position of the set depth layer 21, and the focus of the ultrashort pulse laser beam is controlled to scan the set depth layer 21 of the silicon carbide ingot 10, so that the cavity modified layer 22 and the crack modified layer 23 are formed. After the ultrashort pulse level laser stealth cutting processing, short pulse level laser with a slightly wider pulse width is adopted, the focus of the short pulse laser beam is moved to a position above the set depth layer 21 within a certain range, the short pulse laser beam penetrates through the crack modification forming region, then is focused on the hole modification forming region, and is scattered and propagated in the hole modification forming region, so that the heat of the short pulse laser beam mainly acts on the hole modification forming region, cracks in the crack modification forming region grow outwards in the transverse direction, and the focus of the short pulse laser beam is controlled to scan on the hole modification layer 22, so that cracks in any adjacent hole modification forming regions in the hole modification layer 22 are connected together through the transverse growth.

Compared with the existing process for cutting silicon ingots by adopting laser, due to the adoption of the ultrashort pulse laser, a cavity modification forming region and a crack modification forming region can be respectively generated above the position of the set depth layer 21 where the focus of the ultrashort pulse laser beam is located, and the cavity modification layer 22 and the crack modification layer 23 are respectively formed through scanning, so that the modification layers in the prior art are refined and distinguished. Then, when a short pulse laser beam is used, the focal point of the short pulse laser beam is focused on the cavity modifying formation region, and the focal point of the short pulse laser beam is located above the focal point of the ultrashort pulse laser beam, rather than at the same depth position in the prior art, so that the short pulse laser beam can pass through the crack modifying formation region, then be focused on the cavity modifying formation region, and scatter and propagate in the cavity modifying formation region, so that the crack in the cavity modifying formation region grows laterally outward, and the cracks in any adjacent cavity modifying formation region in the cavity modifying layer 22 are connected together by lateral growth through scanning. In addition, in the process of heating the cavity modifying formation region by focusing the short pulse laser beam through the crack modifying formation region in the cavity modifying formation region, the crack modifying formation region can stop the growth of the crack, so that the upward growth length of the crack in the cavity modifying formation region can be limited to a region below the crack modifying formation region, the longitudinal growth length of the crack can be limited to a small height range, the crack extension efficiency can be improved, the longitudinal extension degree of the crack can be reduced as much as possible, and the slicing loss can be reduced as much as possible. The modified layer is divided into a cavity modified layer 22 and a crack modified layer 23 through thinning, then the short pulse laser beam is focused on the cavity modified layer 22, the focal position of the short pulse laser beam is designed more accurately and reasonably, the fluctuation of the height difference of the upper part and the lower part of the focal point of the short pulse laser beam is small (the height difference of the cavity modified forming region is smaller than that of the modified layer formed by the crack modified forming region and the cavity modified forming region), the focal point of the short pulse laser beam is focused on the modified layer 22, the crack modified forming region on the modified layer blocks the crack in the cavity modified forming region from growing upwards longitudinally, the length of the crack growing longitudinally is limited in a smaller height range, the focal position of the laser beam is optimized through short pulse, the amount and the length of the crack in the modified layer extending longitudinally along the silicon carbide 10 are reduced, so that more laser energy acts on the crack to grow outwards transversely, the number and the length of the crack can be increased, thinner silicon carbide ingots can be cut, and more waste of silicon ingots can be reduced.

In addition, an embodiment of the present invention further provides a laser slicing apparatus for a silicon carbide ingot, and referring to fig. 1 to 8, the laser slicing apparatus includes: an object stage, an ultrashort pulse laser system, a first scanning system, a short pulse laser system, a second scanning system, and a separation system. Wherein the stage is used to hold a silicon carbide ingot 10 to be cut thereon. The ultrashort pulse laser system is used for providing an ultrashort pulse laser beam, and focusing the focus of the ultrashort pulse laser beam at the position of the set depth layer 21 of the silicon carbide crystal ingot 10 to be cut so as to respectively generate a cavity modification forming region and a crack modification forming region above the position of the set depth layer 21; the cavity modification formation region is located between the position of the set depth layer 21 and the crack modification formation region. The first scanning system is used for controlling the focus of the ultrashort pulse laser beam to scan the set depth layer 21 of the silicon carbide crystal ingot 10 so as to respectively form a cavity modified layer 22 and a crack modified layer 23 above the position of the set depth layer 21; the cavity modified layer 22 is composed of a plurality of cavity modified forming regions, the crack modified layer 23 is composed of a plurality of crack modified forming regions, and the cavity modified layer 22 is located between the set depth layer 21 and the crack modified layer 23. The short pulse laser system is used for providing a short pulse laser beam, and the short pulse laser system is also used for focusing the short pulse laser beam on the cavity modification forming region after the short pulse laser beam penetrates through the crack modification forming region, and scattering and propagating the short pulse laser beam in the cavity modification forming region to enable the crack in the cavity modification forming region to grow outwards in the transverse direction. The second scanning system is used for controlling the focus of the short pulse laser beam to scan the cavity modified layer 22, so that the cracks in any adjacent cavity modification forming region in the cavity modified layer 22 are connected together through lateral growth. The separation system is used to peel off a portion of silicon carbide ingot 10 to produce a silicon carbide wafer with hollow modifying layer 22 as an interface.

In an apparatus for laser slicing of a silicon carbide ingot as shown in fig. 8, the first scanning system and the second scanning system may each be implemented by a three-axis motion stage to which the stage is fixed. The ultra-short pulse laser system and the short pulse laser system can respectively adopt different lasers, different laser systems can share part of optical devices, and optical switches are arranged on different light paths so as to carry out switching. The parameter setting manner of the ultrashort pulse laser beam provided by the ultrashort pulse laser system can refer to the description of the relevant part of the laser slicing method of the silicon carbide crystal ingot 10, and is not described herein again. The parameter setting manner of the short pulse laser beam provided by the short pulse laser system can refer to the description of the relevant part of the laser slicing method of the silicon carbide crystal ingot 10, and is not repeated herein. Referring to fig. 8, a CCD camera and a light source may also be provided on a different laser system to observe the condition of the processing position in real time.

As shown in fig. 9, which is a flowchart of a laser slicing operation mode of the laser slicing apparatus based on the silicon carbide ingot shown in fig. 8, all the operation steps of any one of the laser slicing methods shown above can be completed according to the operation flowchart shown in fig. 9.

In the above-described embodiment, the ultrashort pulse laser is first used, the focus of the ultrashort pulse laser beam is focused on the position of the set depth layer 21 of the silicon carbide ingot 10, so as to generate a cavity modified formation region and a crack modified formation region above the position of the set depth layer 21, and the focus of the ultrashort pulse laser beam is controlled to scan the set depth layer 21 of the silicon carbide ingot 10, so as to form the cavity modified layer 22 and the crack modified layer 23. After the ultrashort pulse-level laser stealth cutting process, a short pulse-level laser with a slightly wider pulse width is used to move the focus of the short pulse laser beam to a position above the set depth layer 21 within a certain range, so that the short pulse laser beam passes through the crack modification forming region, is focused on the hole modification forming region, and is scattered and propagated in the hole modification forming region, so that the heat of the short pulse laser beam mainly acts on the hole modification forming region, the crack in the crack modification forming region grows laterally outwards, and the focus of the short pulse laser beam is controlled to scan on the hole modification layer 22, so that the cracks in any adjacent hole modification forming regions in the hole modification layer 22 are connected together through lateral growth.

Compared with the existing process of cutting silicon ingots by adopting laser, due to the adoption of the ultrashort pulse laser, a cavity modification forming region and a crack modification forming region can be respectively generated above the position of the set depth layer 21 where the focus of the ultrashort pulse laser beam is located, and the cavity modification layer 22 and the crack modification layer 23 are respectively formed through scanning, so that the modification layers in the prior art are refined and distinguished. Then, when the short pulse laser beam is used, the focal point of the short pulse laser beam is focused on the cavity modified formation region, and the focal point position of the short pulse laser beam is located above the focal point position of the ultra-short pulse laser beam, rather than at the same depth position in the prior art, so that the short pulse laser beam can pass through the crack modified formation region, then be focused on the cavity modified formation region, and scatter and propagate in the cavity modified formation region, so that the crack in the cavity modified formation region grows laterally outward, and the crack in any adjacent cavity modified formation region in the cavity modified layer 22 is connected together through lateral growth by scanning. In addition, in the process of heating the cavity modifying formation region by focusing the short pulse laser beam through the crack modifying formation region in the cavity modifying formation region, the crack modifying formation region can stop the growth of the crack, so that the upward growth length of the crack in the cavity modifying formation region can be limited to a region below the crack modifying formation region, the longitudinal growth length of the crack can be limited to a small height range, the crack extension efficiency can be improved, the longitudinal extension degree of the crack can be reduced as much as possible, and the slicing loss can be reduced as much as possible. The modified layer is divided into a cavity modified layer 22 and a crack modified layer 23 through thinning, then the short pulse laser beam is focused on the cavity modified layer 22, the focal position of the short pulse laser beam is designed more accurately and reasonably, the fluctuation of the height difference of the upper part and the lower part of the focal point of the short pulse laser beam is small (the height difference of the cavity modified forming region is smaller than that of the modified layer formed by the crack modified forming region and the cavity modified forming region), the focal point of the short pulse laser beam is focused on the modified layer 22, the crack modified forming region on the modified layer blocks the crack in the cavity modified forming region from growing upwards longitudinally, the length of the crack growing longitudinally is limited in a smaller height range, the focal position of the laser beam is optimized through short pulse, the amount and the length of the crack in the modified layer extending longitudinally along the silicon carbide 10 are reduced, so that more laser energy acts on the crack to grow outwards transversely, the number and the length of the crack can be increased, thinner silicon carbide ingots can be cut, and more waste of silicon ingots can be reduced.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are also within the scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims (10)

1. A method of laser slicing a silicon carbide ingot, comprising:

focusing the focus of an ultrashort pulse laser beam on a set depth layer position of a silicon carbide crystal ingot to be cut so as to respectively generate a cavity modification forming region and a crack modification forming region above the set depth layer position; wherein the cavity modification formation region is located between the set depth layer position and the crack modification formation region;

controlling the focus of the ultrashort pulse laser beam to scan in a set depth layer of the silicon carbide crystal ingot so as to form a cavity modification layer and a crack modification layer above the set depth layer respectively; wherein the cavity modified layer is composed of a plurality of the cavity modification forming regions, the crack modified layer is composed of a plurality of the crack modification forming regions, and the cavity modified layer is located between the set depth layer and the crack modified layer;

after transmitting the short pulse laser beam through the crack modifying formation region, focusing the short pulse laser beam on the cavity modifying formation region, and scattering and propagating the short pulse laser beam in the cavity modifying formation region to enable the crack in the cavity modifying formation region to grow outwards in the transverse direction;

controlling the focus of the short pulse laser beam to scan on the cavity modifying layer so as to enable cracks in any adjacent cavity modifying forming region in the cavity modifying layer to be connected together through lateral growth;

and taking the hollow modification layer as an interface to strip a part of the silicon carbide crystal ingot to generate a silicon carbide wafer.

2. The laser dicing method of claim 1, wherein the ultrashort pulse laser beam is a subpicosecond pulse width laser beam, a picosecond pulse width laser beam, or a femtosecond pulse width laser beam.

3. The laser dicing method of claim 2, wherein a pulse width of the ultrashort pulse laser beam is 243fs-900fs, and a wavelength of the ultrashort pulse laser beam is 500-1100nm.

4. The laser dicing method of claim 1, wherein the short pulse laser beam is a sub-nanosecond laser beam.

5. The laser dicing method of claim 4, wherein the short pulse laser beam has a pulse width of 500ps to 1ns and a wavelength of 500nm to 1100nm.

6. The laser dicing method of claim 1, wherein a focal point of the short pulse laser beam is 1-4.5um higher than a focal point of the ultra-short pulse laser beam.

7. The laser dicing method according to claim 1, wherein the transmitting of the short pulse laser beam through the crack modifying formation region, focusing on the cavity modifying formation region, and scattering and propagating in the cavity modifying formation region to grow the crack laterally outward in the cavity modifying formation region comprises:

and adjusting the polarization state of the short pulse laser beam to expand the electron propagation direction along the silicon carbide crystal lattice direction of the silicon carbide crystal ingot to form a transverse growth crack of 3-5 degrees.

8. The laser slicing method of claim 1 wherein said controlling the focus of said ultrashort pulse laser beam to scan a set depth slice of said silicon carbide ingot comprises:

controlling the focus of the ultrashort pulse laser beam to scan a plurality of parallel first cutting channels on a set depth layer of the silicon carbide crystal ingot, wherein the interval between any two adjacent first cutting channels is 10-25um;

the controlling of the focal point of the short pulse laser beam to scan at the hole modifying layer includes:

and controlling the focus of the short pulse laser beam to scan a plurality of parallel second cutting channels on the cavity modifying layer, wherein each second cutting channel is positioned right above one first cutting channel.

9. The laser dicing method of claim 8, wherein the controlling of the focal point of the short pulse laser beam to scan a plurality of parallel second streets on the hole modifying layer comprises:

and controlling the number of times that the focal point of the short pulse laser beam scans at each second cutting track to be more than or equal to three.

10. An apparatus for laser slicing a silicon carbide ingot, comprising:

an object stage for holding thereon a silicon carbide ingot to be cut;

the ultra-short pulse laser system is used for providing an ultra-short pulse laser beam and focusing the focus of the ultra-short pulse laser beam at a set depth layer position of a silicon carbide crystal ingot to be cut so as to respectively generate a cavity modification forming region and a crack modification forming region above the set depth layer position;

a first scanning system, which is used for controlling the focus of the ultrashort pulse laser beam to scan at a set depth layer of the silicon carbide crystal ingot so as to respectively form a cavity modification layer and a crack modification layer above the set depth layer; wherein the cavity modified layer is composed of a plurality of the cavity modification forming regions, the crack modified layer is composed of a plurality of the crack modification forming regions, and the cavity modified layer is located between the set depth layer and the crack modified layer;

the short pulse laser system is used for providing a short pulse laser beam, and the pulse width of the short pulse laser beam is greater than that of the ultrashort pulse laser beam; the short pulse laser beam is focused on the cavity modifying formation region after penetrating through the crack modifying formation region, and is scattered and propagated in the cavity modifying formation region, so that the crack in the cavity modifying formation region grows outwards in the transverse direction;

a second scanning system for controlling the focus of the short pulse laser beam to scan on the cavity modifying layer so as to connect the cracks in any adjacent cavity modifying formation region in the cavity modifying layer together through lateral growth;

and the separation system is used for taking the hollow modification layer as an interface to strip a part of the silicon carbide crystal ingot to generate the silicon carbide wafer.

Images