阅读说明：本技术 一种加工蓝宝石衬底led晶圆的方法及激光装置 (Method for processing sapphire substrate LED wafer and laser device ) 是由 张一谋 杨深明 柳啸 李福海 尹建刚 高云峰 于 2019-08-22 设计创作，主要内容包括：本发明提供了一种加工蓝宝石衬底LED晶圆的方法及激光装置,加工蓝宝石衬底LED晶圆的方法包括：划线,用划线激光在晶圆蓝宝石表面划线形成初始裂纹；切割,用红外激光沿着初始裂纹对蓝宝石表面加热；沿着初始裂纹对LED晶圆蓝宝石表面冷却。红外激光加热组件包括：红外激光器、红外光束第一反射镜组、红外激光束扩束镜组、光束整形组件和红外光束第二反射镜组。通过在LED蓝宝石晶圆表面用划线激光划线,再用红外激光对划线形成的初始裂纹加热,之后对加热区域进行冷却,使LED蓝宝石晶圆在拉应力和压应力的结合下沿初始裂纹裂开,切割质量更佳,切割端面光滑,利于光线通过,增加边缘强度,提高LED芯片的发光效率和使用寿命。(The invention provides a method for processing a sapphire substrate LED wafer and a laser device, wherein the method for processing the sapphire substrate LED wafer comprises the following steps: scribing, namely scribing on the surface of the sapphire wafer by using scribing laser to form an initial crack; cutting, heating the surface of the sapphire along the initial crack by using infrared laser; the LED wafer sapphire surface is cooled along the initial crack. The infrared laser heating assembly includes: the infrared laser device comprises an infrared laser device, an infrared beam first reflector group, an infrared beam expander group, a beam shaping assembly and an infrared beam second reflector group. Through scribing laser on the surface of the LED sapphire wafer, the initial crack formed by scribing is heated by infrared laser, and then the heating area is cooled, so that the LED sapphire wafer cracks along the initial crack under the combination of tensile stress and compressive stress, the cutting quality is better, the cutting end face is smooth, the light can pass through the cutting end face, the edge strength is increased, and the light emitting efficiency and the service life of an LED chip are improved.)

1. A method for processing a sapphire substrate LED wafer is characterized by comprising the following steps:

scribing: scribing on the surface of the LED wafer sapphire (006) by adopting scribing laser or a hard cutter wheel, and forming an initial crack (003) with the depth within 5um-100um on the surface of the LED wafer sapphire (006);

cutting: heating the surface of the LED wafer sapphire (006) along the extending direction of the initial crack (003) by using infrared laser, so that the heated area of the surface of the LED wafer sapphire (006) forms tensile stress distribution; cooling the heated LED wafer sapphire (006) surface along the extension direction of the corresponding initial crack (003), forming a compressive stress distribution in the cooled region of the LED wafer sapphire (006) surface, and expanding the initial crack (003) downwards along the longitudinal direction of the LED wafer sapphire (006) to form a longitudinal expansion region (005) until the wafer is separated, so that the sapphire substrate LED wafer cracks along the corresponding initial crack (003).

2. The method of claim 1, wherein the scribing laser has a wavelength within a range of 100nm to 1064 nm.

3. The method of claim 1, wherein the infrared laser has a wavelength within a range of 0.1um to 10.6 um.

4. The method for processing the sapphire substrate LED wafer of claim 1, wherein water mist is sprayed on the heated area of the surface of the sapphire (006) of the LED wafer during cooling.

5. The method for processing the sapphire substrate LED wafer of any one of claims 1-4, wherein during processing, after scribing and cutting along a first direction of the surface of the LED wafer sapphire (006) are completed, scribing and cutting along a second direction perpendicular to the first direction of the surface of the LED wafer sapphire (006) are performed, and the cutting lines in the same direction are arranged at equal intervals.

6. The method of processing the sapphire substrate LED wafer of claim 5, wherein in the process of scribing and cutting along the first direction or the second direction, the center line of the LED wafer sapphire (006) is first scribed and cut in the corresponding processing direction to form a first portion and a second portion;

and according to the number of the cutters required to be cut in the direction, scribing and cutting the first part or the second part from the center line to two sides by using the cutting allowance of 32 cutters or 64 cutters until the rest part is less than the cutting allowance of 32 cutters, and forming a corresponding initial cutting block after cutting.

7. The method of processing the sapphire substrate LED wafer of claim 6, wherein the initial cutting block with the cutting margin of 32 or 64 knives is scribed and cut in sequence according to the rule of bisector, quartering, eighty, sixteen, thirty-two and sixty-four;

for the initial cutting block with less than 32 cutting allowance, the cutting allowance is increased by 2ⁿScribing and dividing the cutting allowance (n is a positive integer) until the cutting allowance can not be continuously divided to meet the requirement of 2ⁿFor a cutting margin of 2ⁿThe blocks are scribed and cut at bisected, quartered, eighted and sixteen parts.

8. A laser apparatus for implementing the method of processing a sapphire substrate LED wafer as claimed in any one of claims 1 to 7, comprising: the device comprises a device body, a laser scribing component (1), an infrared laser heating component (2) and a cooling structure (3);

the device body is provided with a rotary working platform (4), and the sapphire substrate LED wafer is fixed on the rotary working platform (4);

the laser scribing component (1) is assembled on the device body, and the laser scribing component (1) is used for generating scribing laser to scribe on the surface of the LED wafer sapphire (006) so as to form an initial crack (003) with the depth within 5-20 um on the surface of the LED wafer sapphire (006);

the infrared laser heating assembly (2) is assembled on the device body, and the infrared laser heating assembly (2) is used for generating infrared laser to heat the surface of the LED wafer sapphire (006) at the rear of the scribing laser scribing direction, so that the heated area of the surface of the LED wafer sapphire (006) forms tensile stress distribution;

the cooling structure (3) is assembled on the infrared laser heating assembly (2), the cooling structure (3) is used for cooling a heated area of the surface of the LED wafer sapphire (006), a compressive stress distribution is formed on the cooled area of the surface of the LED wafer sapphire (006), the initial cracks (003) are made to spread downwards along the longitudinal direction of the LED wafer sapphire (006) until the wafers are separated, and the sapphire substrate LED wafer is made to crack along the corresponding initial cracks (003).

9. Laser device according to claim 8, characterized in that the laser scribing assembly (1) comprises: the laser scribing device comprises a scribing laser (11), a scribing laser beam expander set (12) and a scribing laser beam reflector set (13), wherein the scribing laser (11) is used for generating scribing laser, the scribing laser beam expander set (12) is used for expanding and collimating the scribing laser, and the scribing laser passes through the scribing laser beam expander set (12) and then is reflected to a scribing position by the scribing laser beam reflector set (13);

the infrared laser heating assembly (2) comprises: infrared laser (21), the first speculum group of infrared beam (22), infrared laser beam expander group (23), beam plastic subassembly (24) and infrared beam second mirror group (25), the infrared laser that infrared laser (21) produced by the first speculum group of infrared beam (22) reflect extremely infrared laser beam expander group (23), infrared laser beam expander group (23) are used for expanding the beam collimation to infrared laser, beam plastic subassembly (24) are used for adjusting infrared laser beam's energy distribution, infrared laser passes through in proper order infrared laser beam expander group (23) with behind beam plastic subassembly (24) by infrared beam second mirror group (25) reflect to the position that heats.

10. The laser device according to claim 8, wherein the cooling structure (3) adopts a water mist generator, and the water mist is sprayed by the cooling structure (3) to cool the heated area on the surface of the LED wafer sapphire (006).

Technical Field

The invention belongs to the technical field of LED chips, and particularly relates to a method for processing a sapphire substrate LED wafer and a laser device.

Background

In recent years, a sapphire substrate LED chip has been developed in the future as a new generation illumination light source in the 21 st century because of its advantages of low energy consumption, high luminous efficiency, long life, environmental protection, cold light source, fast response time, and being capable of being used under various severe conditions. With the aging of the III-V semiconductor process, the development of LED chips is continuously moving towards higher efficiency and higher brightness. With the wider application of the GaN-based LED, how to improve the luminous efficiency of the GaN-based LED becomes a focus of attention, factors influencing the luminous efficiency of the LED mainly include internal quantum efficiency and external quantum efficiency, and the improvement of the external quantum efficiency becomes one of the key technologies of the current semiconductor illumination LED.

Because sapphire has excellent performances in the aspects of transparency, thermal conductivity, stability and GaN lattice matching, sapphire is generally used as a GaN-based LED chip substrate in the industry at present, a GaN layer is generally only 3-5um, the thickness of the sapphire substrate is basically 400-500um, and the thickness is still about 100um after thinning, so that the sapphire is cut when the GaN-based LED chip is cut, but the Mohs hardness of the sapphire is 9, which is only inferior to diamond, and is a material which is quite difficult to process.

Sapphire belongs to brittle materials, has a better thermal expansion coefficient of 5.8x10^-6The absorption rate of the material to the infrared laser of 9.6/10.6um wave band is high, which provides possibility for laser stress processing.

The traditional processing mode is as follows: conventional wafer dicing is commonly performed by diamond saw dicing, but the kerf width is limited by the thickness of the cutting edge and the brittleness of the diamond saw blade. In addition, the wide bandgap of typical substrate materials (e.g., sapphire, gan, sic, si, etc.) used in the fabrication of wafers means that these materials are easily broken to cause poor insulation and severe leakage of the LED devices, thereby seriously affecting the yield of the LEDs. With the rapid development of LED applications, chip fabrication density has been increasing to meet cost requirements and yield requirements, scribe lines reserved for dicing have been reduced to 10-20 μm, and the core grain size has been smaller than 0.2 × 0.2 mm. This presents a significant challenge to conventional diamond saw dicing: on one hand, the hardness of hard and brittle materials such as sapphire, silicon carbide and the like is close to that of diamond; on the other hand, the minimum thickness of the diamond saw is about 20 μm, which exceeds the width of the scribe line, and the cutting force of the diamond saw is seriously insufficient, so that the tool wear rate is unacceptable for industrial production.

At present, the mainstream processing mode is as follows: at present, laser processing becomes a mainstream processing mode, common laser cutting is divided into surface cutting and internal cutting (namely invisible cutting), laser with a certain wavelength is focused on the surface or the inside of a wafer, a large amount of heat is released in a very short time, materials are melted and even gasified, cutting traces are formed by matching with relative movement of a laser head or an object, and the purpose of cutting is achieved.

Surface cutting: generally, 355nm or 266nm scribing laser is adopted, the cutting depth is generally within 50um, if the cutting depth is deepened, the laser power is required to be increased or the scribing times are required to be increased, so that the manufacturing cost is increased and the cutting efficiency is influenced, in addition, during surface cutting processing, sputtering objects in a groove often splash, recasting layers are formed on two sides of the surface of the groove, generally gluing protection is required, and the process flow is as follows: the process of chip mounting, protective liquid coating, laser grooving, cleaning, splitting and the like is complicated, the efficiency is reduced when a thicker LED wafer (more than 150um in thickness) is processed, more importantly, the area for damaging the sapphire lattice structure is increased along with the width of the laser cutting modified layer in surface cutting, the LED luminous efficiency is greatly reduced, and the chip leakage is easily caused.

Invisible cutting: generally, 1064nm infrared light or 532nm green light is adopted to form a single light spot or multiple light spots for internal processing, laser is acted on a certain depth inside a chip, and laser scratches, namely discontinuous micro 'explosion spots' are formed along a cutting path.

Generally, single-light-spot stealth cutting can only be performed on a relatively thin LED wafer with the thickness of 80-150 microns, a modified layer is formed by focusing and scribing at a position which is away from the surface 1/3, and then separation is realized by adopting a film expanding or mechanical splitting mode, although a gluing process is avoided, the mode cannot be used for processing a thicker LED wafer because the depth of the single-light-spot modified layer is generally 10-80 microns, the cracking tendency is limited, and inclined cracking or even bicrystal problems are easily caused during mechanical splitting.

The multiple light spots are cut implicitly, the overall cutting depth is often larger than the thickness of a 1/2 chip, although the processing efficiency is improved, the depth of a modified layer is increased, mechanical splitting is not needed, a film can be separated through film expansion, and the problems of inclined cracking and double crystals are avoided, the increase of the modified layer on the side surface of the LED wafer also means that the area for damaging a sapphire crystal lattice structure is increased, the luminous efficiency of the LED is influenced, and chip electric leakage is easy to generate.

Both the surface cutting and the invisible cutting are the modes that laser is directly stripped or modified on the LED chip, the width of a modified layer is often close to the thickness of 1/3-1/2 of the LED chip or larger, and even if technological parameters are optimized, the problems of sputtering, point collapse, inclined crack, double crystal and the like are reduced.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a method for processing a sapphire substrate LED wafer and a laser device, which can effectively reduce the depth of a modified layer, and crack by utilizing stress, so that more than 99% of the end surface of an LED wafer chip is in a mirror surface effect, light can pass through the LED wafer chip easily, and the service life of the LED wafer chip is prolonged.

In order to solve the technical problem, the invention is realized in such a way that a method for processing a sapphire substrate LED wafer comprises: scribing: scribing on the surface of the LED wafer sapphire by adopting laser or a hard cutter wheel, and forming initial cracks with the depth within 5-100 um on the surface of the LED wafer sapphire; cutting: heating the surface of the LED wafer sapphire along the extending direction of the initial crack by using infrared laser, so that a heated area on the surface of the LED wafer sapphire forms tensile stress distribution; and cooling the heated LED wafer sapphire surface along the extension direction of the corresponding initial crack, forming compressive stress distribution in a cooled area of the LED wafer sapphire surface, and enabling the initial crack to downwards expand along the longitudinal direction of the LED wafer sapphire to form a longitudinal expansion area until the wafer is separated, so that the sapphire substrate LED wafer cracks along the corresponding initial crack.

Further, the scribing laser has a wavelength within 100nm to 1064 nm.

Further, the wavelength of the infrared laser is within 0.1um-10.6 um.

Further, water mist is sprayed on the heated area of the sapphire surface of the LED wafer during cooling.

Further, during processing, after scribing and cutting are performed along a first direction of the surface of the LED wafer sapphire, scribing and cutting are performed along a second direction of the surface of the LED wafer sapphire, wherein the second direction is perpendicular to the first direction, and cutting lines in the same direction are arranged at equal intervals.

Further, in the process of scribing and cutting along the first direction or the second direction, firstly scribing and cutting the center line of the sapphire of the LED wafer in the corresponding processing direction to form a first part and a second part; and according to the number of the cutters required to be cut in the direction, scribing and cutting the first part or the second part from the center line to two sides by using the cutting allowance of 32 cutters or 64 cutters until the rest part is less than the cutting allowance of 32 cutters, and forming a corresponding initial cutting block after cutting.

Further, the initial cutting block with the cutting allowance of 32 or 64 knives is divided into bisected parts, quartered parts and eighted parts in sequenceScribing and cutting at sixteen equi-divisions, thirty-two equi-divisions and sixty-four equi-divisions; for the initial cutting block with less than 32 cutting allowance, the cutting allowance is increased by 2ⁿScribing and dividing the cutting allowance (n is a positive integer) until the cutting allowance can not be continuously divided to meet the requirement of 2ⁿFor a cutting margin of 2ⁿThe blocks are scribed and cut at bisected, quartered, eighted and sixteen parts.

Further, a laser device is provided for implementing the method for processing the sapphire substrate LED wafer, which includes: the device comprises a device body, a laser scribing component, an infrared laser heating component and a cooling structure; the device body is provided with a rotary working platform, and the sapphire substrate LED wafer is fixed on the rotary working platform; the laser scribing component is assembled on the device body and used for generating scribing laser to scribe on the surface of the LED wafer sapphire so as to form an initial crack with the depth within 5-20 um on the surface of the LED wafer sapphire; the infrared laser heating assembly is assembled on the device body and used for generating infrared laser to heat the surface of the LED wafer sapphire in the rear direction of the scribing laser scribing direction, so that a tensile stress distribution is formed on a heated area of the surface of the LED wafer sapphire; the cooling structure is assembled on the infrared laser heating assembly and used for cooling a heated area on the sapphire surface of the LED wafer, pressure stress distribution is formed on the cooled area on the sapphire surface of the LED wafer, the initial cracks are made to downwards expand along the longitudinal direction of the sapphire of the LED wafer until the wafer is separated, and the LED wafer with the sapphire substrate is made to crack along the corresponding initial cracks.

Further, the laser scribing assembly comprises: the scribing laser device comprises a scribing laser device, a scribing laser beam expanding lens group and a scribing laser beam reflector group, wherein the scribing laser device is used for generating scribing laser, the scribing laser beam expanding lens group is used for expanding and collimating the scribing laser, and the scribing laser passes through the scribing laser beam expanding lens group and then is reflected to a scribing position by the scribing laser beam reflector group; the infrared laser heating assembly includes: infrared laser, the first speculum group of infrared beam, infrared laser beam expander group, beam plastic subassembly and infrared beam second mirror group, infrared laser that infrared laser produced by the first speculum group of infrared beam reflects extremely infrared laser beam expander group, infrared laser beam expander group is used for expanding the beam collimation to infrared laser, beam plastic subassembly is used for adjusting infrared laser beam's energy distribution, infrared laser passes through in proper order infrared laser beam expander group with behind the beam plastic subassembly by infrared beam second mirror group reflects to heating the position.

Further, the cooling structure adopts a water mist generator, and the water mist is sprayed out of the cooling structure to cool the heated area on the sapphire surface of the LED wafer.

Compared with the prior art, the method for processing the LED wafer with the sapphire substrate and the laser device have the advantages that:

according to the invention, the surface of the LED sapphire wafer is scribed by using laser or a hard cutter wheel, the initial crack formed by scribing is heated by using infrared laser, tensile stress distribution is formed on the heated area of the surface of the LED sapphire wafer, then the heated area is cooled, and compressive stress distribution is formed in the cooled area of the surface of the LED sapphire wafer, so that the LED sapphire wafer is cracked along the initial crack under the combination of tensile stress and compressive stress, the modified layer depth can be effectively reduced, the cracking efficiency by using stress is higher, more than 99% of the end surfaces of the LED wafer chips are in a mirror surface effect, the cutting quality is better, the light can be favorably passed through, the influence on the strength of the single LED chip is reduced by the smaller modified layer depth, the expansion of micro cracks caused by the heating of the LED chips can be slowed down, and the service life of the LED chip is prolonged.

Drawings

FIG. 1 is a schematic diagram of a laser device according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of the cutting principle of the present invention;

FIG. 3 is a schematic view of the processing method in example 1 of the present invention;

fig. 4 is a diagram illustrating the effect of the die-cutting end surface in the embodiment of the present invention. .

In the drawings, each reference numeral denotes: 001. a Gaussian spot of purple outer circle; 002. infrared elliptic Gaussian spots; 003. initiating a crack; 004. water spotting; 005. a longitudinal expansion region; 006. LED wafer sapphire; 1. a laser scribing assembly; 11. a scribing laser; 12. scribing a laser beam expander set; 13. a scribing laser beam mirror group; 2. an infrared laser heating assembly; 21. an infrared laser; 22. a first infrared beam reflector group; 23. an infrared laser beam expander set; 24. a beam shaping component; 25. the infrared beam second reflector group; 3. a cooling structure; 4. and rotating the working platform.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.