Laser cutting method for lithium niobate crystal and lithium niobate crystal grain

Abstract

The invention relates to the technical field of semiconductor manufacturing, and discloses a laser cutting method of a lithium niobate crystal and a lithium niobate crystal grain, the method comprises the following steps: infrared laser performs focusing processing in the lithium niobate crystal gradually upwards from the bottom surface of the lithium niobate crystal to the top surface of the lithium niobate crystal, and a plurality of cavity modified columns are formed in the lithium niobate crystal; each cavity modification column comprises a plurality of cavity modification points which are arranged at intervals along the thickness direction, and each plurality of cavity modification columns form a cavity modification surface; the ultraviolet laser device is used for processing the lithium niobate crystal according to a preset cutting channel interval, so that ultraviolet laser is focused on the top surface of the lithium niobate crystal, cutting grooves with preset depths are formed by processing from the top surface of the lithium niobate crystal to the interior of the lithium niobate crystal, and each cutting groove corresponds to one cavity modified surface; and a chopper of the mechanical splitting equipment sequentially aligns to each cavity modified surface from the bottom surface of the lithium niobate crystal to carry out splitting processing so as to obtain lithium niobate crystal grains. The machining efficiency is high, and the quality of cut finished products is good.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor manufacturing technology, and in particular to a laser cutting method for lithium niobate crystals and lithium niobate grains. Background Art

[0002] Lithium niobate (LiNbO3) crystal is an important optoelectronic material with excellent piezoelectric, electro-optical and nonlinear optical properties. It is widely used in surface acoustic wave devices, optical modulators, lasers, optical waveguides, etc. The Mohs hardness of lithium niobate crystal is 5. The conventional cutting method of lithium niobate crystal is mechanical cutting method with diamond cutter wheel and wire cutting. However, due to the hard and brittle characteristics of lithium niobate crystal, the vibration of the tool and the deviation of the wire will not only cause edge collapse and cracks of several microns to tens of microns, but also cause wear and tear of the tool after long-term service. In order to solve the above problems, laser cutting technology has become a new cutting method due to its high precision, high efficiency and flexibility. Laser invisible cutting technology and Bessel laser cutting method are common means to solve the cutting of hard and brittle materials, but because lithium niobate crystal belongs to the trigonal crystal system and has a triple rotation axis, the physical properties are anisotropic in the triple axis and the direction perpendicular to the triple axis. For example, in optical properties, lithium niobate crystal has different refractive indices for light waves in specific directions, which causes the light waves passing through the crystal to split into ordinary light and extraordinary light during propagation. The refractive index of ordinary light is not affected by the crystal orientation, while the refractive index of extraordinary light is significantly affected by the crystal orientation. The thermal expansion coefficient of lithium niobate crystals shows significant differences in different crystal orientation axes. The thermal expansion coefficient along the X-axis is about 16.7×10^-6℃^-1 (at 300℃), while the thermal expansion coefficient along the Z-axis is about 2.5×10^-6℃^-1 (at 300℃). This anisotropy causes the crystal to respond differently to temperature changes in different directions, thereby affecting the formation and expansion of cracks. The above-mentioned laser invisible cutting and Bessel laser cutting methods can only cut along specific crystal directions. Cutting in other directions will produce oblique cracks, and uncontrollable edge collapse will occur when splitting. In addition, for lithium niobate splitting links with special requirements of thickness exceeding 1000μm and narrow strip width within 1.5mm cutting spacing, quality defects such as large edge collapse and cutting film splitting and damage often occur. Summary of the invention

[0003] Based on the above, the purpose of the present invention is to provide a laser cutting method for lithium niobate crystals and lithium niobate grains, which have high processing efficiency, good quality of cut products, and can achieve narrow spacing cutting of thick lithium niobate crystals.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A laser cutting method for lithium niobate crystal, comprising:

[0006] Fixing a lithium niobate crystal to be processed on a processing table of an infrared laser device, and processing the lithium niobate crystal according to a preset cutting track spacing, so that the infrared laser is focused and processed inside the lithium niobate crystal from the bottom surface of the lithium niobate crystal to the top surface of the lithium niobate crystal, so as to form a plurality of cavity modification columns inside the lithium niobate crystal, each of the cavity modification columns comprising a plurality of cavity modification points spaced apart along the thickness direction of the lithium niobate crystal, wherein a plurality of the cavity modification columns form a cavity modification surface;

[0007] Fixing the lithium niobate crystal processed by infrared laser on a processing platform of ultraviolet laser device, processing the lithium niobate crystal according to the preset cutting track spacing, focusing the ultraviolet laser on the top surface of the lithium niobate crystal, and processing from the top surface of the lithium niobate crystal to the inside of the lithium niobate crystal to form a cutting groove of a preset depth, each of the cutting grooves corresponding to one of the cavity modified surfaces;

[0008] The lithium niobate crystal processed by ultraviolet laser is fixed to a mechanical splitting device, and the splitting knife of the mechanical splitting device is aligned with each of the cavity modified surfaces from the bottom surface of the lithium niobate crystal to split the crystal in turn to obtain narrow lithium niobate grains.

[0009] As a preferred embodiment of a laser cutting method for a lithium niobate crystal, the infrared laser device gradually focuses upward inside the lithium niobate crystal and stops when it reaches a preset position, and the ultraviolet laser device processes from the top surface of the lithium niobate crystal toward the inside of the lithium niobate crystal and stops when it reaches a preset distance from the preset position, and the preset distance is greater than 0 and does not exceed 60 μm.

[0010] As a preferred embodiment of the laser cutting method of lithium niobate crystal, the pulse width of the infrared laser emitted by the infrared laser device is not less than 10 ps, ​​and the single pulse energy of the infrared laser emitted by the infrared laser device is not less than 1 μJ; the pulse width of the ultraviolet laser emitted by the ultraviolet laser device is not greater than 100 ps, ​​and the single pulse energy of the ultraviolet laser emitted by the ultraviolet laser device is not greater than 10 μJ.

[0011] As a preferred embodiment of a laser cutting method for a lithium niobate crystal, before the ultraviolet laser device performs surface cutting processing on the lithium niobate crystal according to the preset cutting path spacing, a processing drawing of the ultraviolet laser device is drawn, and the ultraviolet laser device marks the top surface of the lithium niobate crystal according to the processing drawing to form a plurality of cutting grooves with a preset width and a preset depth arranged according to the preset cutting path spacing, and the center plane of each cutting groove along its width direction is coplanar with each of the cavity modified surfaces.

[0012] As a preferred solution of a laser cutting method for a lithium niobate crystal, the preset cutting track spacing is no greater than 1.5 mm.

[0013] As a preferred solution of a laser cutting method for a lithium niobate crystal, the length direction of the cutting groove is consistent with or inconsistent with the X-principal crystal axis direction of the lithium niobate crystal.

[0014] As a preferred solution of a laser cutting method for lithium niobate crystal, the width of the cutting groove is no greater than 20 μm.

[0015] As a preferred embodiment of a laser cutting method for lithium niobate crystals, the spacing between each adjacent two cavity modification points in each cavity modification column is a first preset spacing, and the spacing between the centers of each adjacent two cavity modification points in the lateral direction in each cavity modification surface is a second preset spacing, the first preset spacing is 0 to 10um, and the second preset spacing is 10 to 20um.

[0016] As a preferred solution of a laser cutting method for a lithium niobate crystal, fixing the lithium niobate crystal to be processed in front of a processing table of an infrared laser device also includes:

[0017] Placing the lithium niobate crystal to be processed on a film laminating machine, and the film laminating machine performs a film laminating operation on the lithium niobate crystal so that one side of the lithium niobate crystal is in close contact with the cutting film;

[0018] Fix the lithium niobate crystal on a processing table of an infrared laser device with one side of the lithium niobate crystal close to the cutting film facing downward;

[0019] The split lithium niobate crystal is placed on a wafer expander for expansion, so that the cut film is separated from the lithium niobate crystal to obtain a plurality of narrow lithium niobate grains.

[0020] A lithium niobate crystal grain, characterized in that it is obtained by the laser cutting method of the lithium niobate crystal described in any of the above technical solutions.

[0021] The beneficial effects of the present invention are:

[0022] The present invention provides a laser cutting method for lithium niobate crystals, wherein the interior of the lithium niobate crystals is processed by an infrared laser device to form cavity modified points distributed at regular intervals inside the lithium niobate crystals, and the surface of the lithium niobate crystals is processed by an ultraviolet laser device to form cutting grooves on the surface of the lithium niobate crystals, and each cutting groove corresponds to each cavity modified surface, so that when the lithium niobate crystals are split, they can be smoothly cleaved and fractured along the cutting grooves and the cavity modified surfaces, and the cutting edge straightness is good, and the cutting quality is controllable; at the same time, the combination of the above infrared laser cutting method and the ultraviolet laser cutting method can realize the cutting of the lithium niobate crystals in any cutting direction, without the limitation that the traditional laser invisible cutting and Bessel laser cutting can only cut along the crystal direction. And after the two laser cutting, mechanical splitting is used for splitting, so that the lithium niobate crystals can be better fractured along the cutting grooves and the cavity modified surfaces to obtain lithium niobate grains without edge collapse.

[0023] The present invention also provides a lithium niobate crystal grain, which is obtained by the above-mentioned laser cutting method of the lithium niobate crystal and has good edge flatness and good quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the contents of the embodiments of the present invention and these drawings without paying any creative work.

[0025] Figure 1 The process of a laser cutting method of lithium niobate crystal provided by an embodiment of the present invention is Figure 1 ;

[0026] Figure 2 is a cross-sectional view of a lithium niobate crystal processed by infrared laser and ultraviolet laser according to an embodiment of the present invention;

[0027] Figure 3 is a schematic structural diagram of mechanical splitting of a lithium niobate crystal provided by an embodiment of the present invention;

[0028] Figure 4 The process of the laser cutting method of lithium niobate crystal provided by the embodiment of the present invention is Figure 2 .

[0029] In the figure:

[0030] 1. lithium niobate crystal; 101. top surface; 102. bottom surface; 2. cavity modified surface; 21. cavity modified column; 20. cavity modified point; 30. cutting groove; 4. cleaver receiving platform; 5. cleaver. DETAILED DESCRIPTION

[0031] In the embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0032] In the embodiments of the present application, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise specified, "plurality" means two or more.

[0033] The term "at least one" in this application means one or more, and the term "multiple" in this application means two or more, for example, multiple second messages means two or more second messages. The terms "system" and "network" are often used interchangeably herein.

[0034] It should be understood that the terms used in the description of the various examples herein are only for describing specific examples and are not intended to be limiting. As used in the description of the various examples and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0035] It should also be understood that the term "and / or" used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. The term "and / or" is a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this application generally indicates that the associated objects before and after are in an "or" relationship.

[0036] It should also be understood that in the various embodiments of the present application, the size of the serial number of each process does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0037] It should be understood that determining B based on A does not mean determining B only based on A. B can also be determined based on A and / or other information.

[0038] It should also be understood that the term “comprise” (also known as “includes,” “including,” “comprises” and / or “comprising”) when used in this specification specifies the presence of stated features, integers, steps, operations, elements, and / or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0039] It should also be understood that the term "if" may be interpreted to mean "when" or "upon" or "in response to determining" or "in response to detecting." Similarly, the phrase "if it is determined that ..." or "if [a stated condition or event] is detected" may be interpreted to mean "upon determining that ..." or "in response to determining that ..." or "upon detecting [a stated condition or event]" or "in response to detecting [a stated condition or event]," depending on the context.

[0040] It should be understood that the references to "one embodiment", "an embodiment", or "a possible implementation" throughout the specification mean that specific features, structures, or characteristics related to the embodiment or implementation are included in at least one embodiment of the present application. Therefore, the references to "in one embodiment" or "in an embodiment", or "a possible implementation" appearing throughout the specification do not necessarily refer to the same embodiment. In addition, these specific features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0041] The Mohs hardness of lithium niobate crystal is 5. The conventional cutting method of lithium niobate crystal is mechanical cutting method of diamond blade and wire cutting. However, due to the hard and brittle characteristics of lithium niobate crystal, the vibration of the tool and the deviation of the wire will not only cause edge collapse and cracks of several microns to tens of microns, but also the tool will cause wear and tear after long-term service. In order to solve the above problems, laser cutting technology has become a new cutting method due to its high precision, high efficiency and flexibility. Laser invisible cutting technology and Bessel laser cutting method are common means to solve the cutting of hard and brittle materials, but because lithium niobate crystal belongs to the trigonal crystal system and has a triple rotation axis, each physical property is anisotropic in the triple axis and the direction perpendicular to the triple axis. For example, in optical properties, lithium niobate crystal has different refractive indices for light waves in specific directions, which causes the light waves passing through the crystal to split into ordinary light and extraordinary light during propagation. The refractive index of ordinary light is not affected by the crystal orientation, while the refractive index of extraordinary light is significantly affected by the crystal orientation. The above-mentioned laser invisible cutting and Bessel laser cutting methods can only cut along a specific crystal direction. Cutting in other directions will produce oblique cracks, and uncontrollable edge collapse will occur during the splitting process. In addition, for lithium niobate splitting links with special requirements of thickness exceeding 1000μm and narrow strip width within 1.5mm cutting spacing, large edge collapse, cutting film splitting and damage often occur.

[0042] Based on the above technical issues, such as Figures 1 to 4 As shown, this embodiment provides a laser cutting method for lithium niobate crystals, which is mainly used for narrow-pitch cutting of thick lithium niobate crystals with a thickness of about 1000 μm, for example, the cutting pitch is 1.2-1.5 mm, for example, 1.3 mm, etc. Of course, it can also be applied to the cutting of lithium niobate crystals with a thickness less than 1000 μm or the cutting pitch greater than 1.5 mm, and specifically includes the following steps:

[0043] S1: Infrared laser processing: fix the lithium niobate crystal 1 to be processed on the processing table of the infrared laser device, and the infrared laser device processes the lithium niobate crystal 1 according to the preset cutting path spacing, so that the infrared laser is focused from the bottom surface 102 of the lithium niobate crystal 1 to the top surface 101 of the lithium niobate crystal 1 and gradually upwards inside the lithium niobate crystal 1 to form a plurality of cavity modified columns 21 inside the lithium niobate crystal 1, each cavity modified column 21 includes a plurality of cavity modified points 20 arranged at intervals along the thickness direction of the lithium niobate crystal 1, wherein each plurality of cavity modified columns 21 forms a cavity modified surface 2, that is, each cutting path processed by the infrared laser forms a corresponding cavity modified surface 2.

[0044] In this embodiment, before the lithium niobate crystal 1 to be processed is fixed on the processing table of the infrared laser device, a cutting film is first attached to the lithium niobate crystal 1. Specifically, the lithium niobate crystal 1 to be processed is placed on a film laminating machine, and the film laminating machine performs a film laminating operation on the lithium niobate crystal 1 so that one side of the lithium niobate crystal 1 is in close contact with the cutting film; then, the lithium niobate crystal 1 is fixed on the processing table of the infrared laser device with the side in close contact with the cutting film facing downward, specifically, it is placed on the vacuum ceramic suction cup of the processing table of the infrared laser device, and vacuum adsorption is turned on so that the lithium niobate crystal 1 is firmly adsorbed on the vacuum ceramic suction cup of the processing table of the infrared laser device.

[0045] Specifically, before or after the lithium niobate crystal 1 to be processed is fixed on the processing table of the infrared laser device, the processing program and processing parameters of the infrared laser device are set, such as setting the spacing of the laser cutting paths, that is, the spacing between each two adjacent cutting paths. In this embodiment, the preset cutting path spacing is less than or equal to or 1.5 mm, and the series of Z-axis cutting height, power, and cutting speed information of a single cutting path of the infrared laser are set at the same time; after the lithium niobate crystal 1 is fixed on the processing table of the infrared laser device, the infrared laser processes the inside of the lithium niobate crystal 1 according to the preset processing parameters.

[0046] Among them, the pulse width of the infrared laser emitted by the infrared laser device is not less than 10ps, and the single pulse energy of the infrared laser emitted by the infrared laser device is not less than 1μJ.

[0047] The infrared laser is focused from the bottom surface 102 of the lithium niobate crystal 1 to the top surface 101 of the lithium niobate crystal 1 and gradually moves upwards to perform processing inside the lithium niobate crystal 1 until it ends at a distance of 20-80 μm from the top surface 101 of the lithium niobate crystal 1, for example, at a distance of 20 μm, 40 μm, 60 μm or 80 μm from the top surface 101 of the lithium niobate crystal 1, which is specifically set according to actual needs.

[0048] By focusing the lithium niobate crystal 1 with an infrared laser, a cavity modification point 20 arranged in a uniform array is formed inside the lithium niobate crystal 1, so that a plurality of cavity modification surfaces 2 can be formed, and each cavity modification surface 2 corresponds to a cutting path, so that when the lithium niobate crystal 1 is subsequently split from the cutting path, it can be cleaved and fractured along the cavity modification surface 2 composed of a plurality of cavity modification columns 21, reducing the possibility of oblique cracking and improving the uniformity of the fracture surface, thereby ensuring the integrity and high quality of the narrow strip width lithium niobate grains finally obtained. At the same time, the infrared laser only forms the cavity modification point 20 inside the lithium niobate crystal 1, rather than performing linear cutting processing inside the lithium niobate crystal 1, so that the cutting processing of the lithium niobate crystal 1 is not limited to its crystal direction, and the cutting direction of the lithium niobate crystal 1 can be set arbitrarily according to needs, which is more practical.

[0049] After the infrared laser device completes processing of the lithium niobate crystal 1, the vacuum ceramic chuck of the processing table of the infrared laser device is closed, and then the lithium niobate crystal 1 is removed, and the following steps are performed:

[0050] S2: UV laser processing: fix the lithium niobate crystal 1 after infrared laser processing on the processing platform of the ultraviolet laser device, and the ultraviolet laser device scribes the lithium niobate crystal 1 according to the preset cutting line spacing, so that the ultraviolet laser is focused on the top surface 101 of the lithium niobate crystal 1, and scribes from the top surface 101 of the lithium niobate crystal 1 to the inside of the lithium niobate crystal 1 to form a cutting groove 30 of a preset depth, each cutting groove 30 corresponds to a cavity modified surface 2.

[0051] Preferably, the spacing between each two adjacent cavity modification points in each cavity modification column is a first preset spacing. It should be noted that the distance between the closest points of each two adjacent cavity modification points is the first preset spacing. The spacing between each two adjacent cavity modification columns in each cavity modification surface is a second preset spacing. It should be noted that the distance between the center points of the two cavity modification points between two adjacent cavity modification columns is defined as the second preset spacing, that is, the spacing between the centers of each two adjacent cavity modification points in the transverse direction in each cavity modification surface is the second preset spacing. Maintaining an appropriate spacing between each two adjacent cavity modification points ensures smooth subsequent fracture and effectively avoids the phenomenon of oblique cracks on the subsequent fracture surface caused by the connection of two or more cavity modification points.

[0052] Among them, the first preset spacing is 0~10um, for example, the first preset spacing is 0, 2um, 4um, 6um, 8um, 10um, etc., and the second preset spacing is 10~20um, for example, the second preset spacing is 10um, 12um, 14um, 16um, 18um, 20um, etc.

[0053] In this embodiment, the lithium niobate crystal 1 is fixed on the processing table of the ultraviolet laser device with one side close to the cutting film facing downward, specifically placed on the vacuum ceramic suction cup of the ultraviolet laser device processing table, and vacuum adsorption is turned on so that the lithium niobate crystal 1 is firmly adsorbed on the vacuum ceramic suction cup of the ultraviolet laser device processing table.

[0054] Specifically, before or after the lithium niobate crystal 1 is fixed on the processing table of the ultraviolet laser device, the processing program and processing parameters of the ultraviolet laser device are set, such as setting the spacing of the laser cutting paths, that is, setting the preset cutting path spacing. The spacing of the ultraviolet laser cutting paths set here is the same as the spacing of the infrared laser cutting paths, and the cutting path positions are exactly the same, ensuring the flatness of the subsequent fracture surface. At the same time, the processing drawings, cutting power, cutting speed and other information of the ultraviolet laser are set; after the lithium niobate crystal 1 is fixed on the processing table of the ultraviolet laser device, the ultraviolet laser processes the top surface 101 of the lithium niobate crystal 1 according to the preset processing parameters.

[0055] The length direction of the cutting groove is consistent with or inconsistent with the X main crystal axis direction of the lithium niobate crystal.

[0056] The width of each cutting groove 30 is not greater than 20 μm, for example, the width of the cutting groove 30 is 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm, etc., to avoid the cutting groove 30 being too wide to affect the subsequent flatness of the cleavage surface.

[0057] It can be understood that the processing drawing of the ultraviolet laser means that when processing each cutting groove 30, the ultraviolet laser is used to laser scribing at the cutting groove position with the cutting path as the center position, and the lines are symmetrically scribing on the left and right sides of the cutting groove according to the processing drawing, and the cutting groove 30 is formed by repeatedly scribing near the cutting groove. That is, the ultraviolet laser device is used to scribing on the top surface 101 of the lithium niobate crystal 1 according to the processing drawing, so as to form a plurality of cutting grooves 30 with a preset width and a preset depth arranged according to the preset cutting groove spacing, and the center plane of each cutting groove 30 along its width direction is coplanar with the center plane of each cavity modified surface 2, so that when the lithium niobate crystal 1 is subsequently split at each cutting path, the lithium niobate crystal 1 can be smoothly broken along the cavity modified surface 2 and the cutting groove 30.

[0058] Among them, the pulse width of the infrared laser emitted by the ultraviolet laser device is not less than 100ps, and the single pulse energy of the infrared laser emitted by the ultraviolet laser device is not less than 10μJ. Ultrashort pulses are conducive to ensuring that the heat-affected area is small during the cutting process, thereby achieving high-precision processing effects without edge collapse.

[0059] When the ultraviolet laser is focused from the top surface 101 of the lithium niobate crystal 1 to the inside of the lithium niobate crystal 1, the processing depth is set to 20 to 80 μm according to the thickness of the lithium niobate and product requirements, for example, the processing depth is 20 μm, 40 μm, 60 μm or 80 μm, which is set according to actual needs.

[0060] In this embodiment, when the infrared laser device gradually focuses upward inside the lithium niobate crystal 1, it stops when it reaches a preset position. When the ultraviolet laser device processes from the top surface 101 of the lithium niobate crystal 1 to the inside of the lithium niobate crystal 1, it stops when it reaches a preset distance from the preset position. The preset distance is greater than 0 and does not exceed 60μm, for example, the preset distance is 40μm, 45μm, 50μm, 55μm, etc. That is, there is a blank area between the processing end position of the infrared laser and the processing end position of the ultraviolet laser to avoid the cavity modification point 20 formed by the infrared laser processing and the cutting groove 30 formed by the ultraviolet laser processing from communicating with each other to affect the flatness of the subsequent fracture surface. The preset distance is no more than 60μm, which can effectively avoid the blank area being too large, resulting in unsmooth splitting or oblique cracking. Accurately controlling the depth of the cutting groove 30 and the spacing between the two laser processes can effectively prevent the stress in the laser processing process from being transmitted to the surface of the lithium niobate crystal 1 to cause oblique cracks and avoid edge collapse.

[0061] After the ultraviolet laser processing, the vacuum ceramic chuck of the ultraviolet laser device processing table is closed, and then the lithium niobate crystal 1 is removed, and the lithium niobate crystal 1 can be split as follows:

[0062] S3: Mechanical splitting: Fix the lithium niobate crystal 1 after UV laser processing onto the mechanical splitting equipment, specifically place it on the splitting knife 5 receiving platform 4 of the mechanical splitting equipment, so that the top surface 101 of the lithium niobate crystal 1 is close to the splitting knife 5 receiving platform 4, and the splitting knife 5 of the mechanical splitting equipment presses down to split the lithium niobate crystal 1 at each cutting path in turn, that is, splits each cavity modified surface 2 from the bottom surface 102 of the lithium niobate crystal 1 in turn to obtain narrow strip width lithium niobate grains.

[0063] Specifically, after the lithium niobate crystal 1 is placed on the splitting knife 5 receiving platform 4, the infrared camera of the mechanical splitting equipment obtains the internal structure of the lithium niobate crystal 1 to obtain the position of each cavity modified surface 2 inside the lithium niobate crystal 1, and the mechanical splitting equipment moves the splitting knife 5 according to the position information obtained by the infrared camera, so that the splitting knife 5 is aligned with one of the cavity modified surfaces 2; at the same time, the grain movement step distance of the splitting knife 5 of the mechanical splitting equipment, the spacing between the splitting knife 5 receiving platforms 4 and the displacement parameters of the splitting knife 5 pressed down are set, the mechanical splitting equipment executes the splitting related parameters, the splitting knife 5 is pressed down, and the lithium niobate crystal 1 is cleaved and fractured along the cavity modified surface 2 and the cutting groove 30 aligned with the splitting knife 5; the splitting knife 5 moves to align with each cavity modified surface 2 in turn, and completes the fracture of the lithium niobate crystal 1 along all cutting paths.

[0064] More specifically, after the splitting is completed, the split lithium niobate crystal 1 is placed on a wafer expander for film expansion, so that the cut film is separated from the lithium niobate crystal 1 to obtain a plurality of separated lithium niobate grains.

[0065] The laser cutting method of lithium niobate crystal provided in this embodiment adopts a combination of infrared laser, ultraviolet laser and mechanical splitting to achieve narrow cutting path cutting of lithium niobate crystal 1 in any direction, and has high processing efficiency. In particular, for lithium niobate crystals with a thickness greater than 1000μm, narrow spacing cutting can be achieved to obtain narrow strip width lithium niobate grains, and the obtained lithium niobate grains have no edge collapse, no oblique cracks, and the straight edge is within 15μm, with good straightness.

[0066] This embodiment also provides a lithium niobate crystal grain, which is produced by the above-mentioned laser cutting method of lithium niobate crystal, and has the advantages of no edge chipping, no oblique cracks, and good edge straightness.

[0067] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A laser cutting method for lithium niobate crystal, characterized in that: include: Fixing a lithium niobate crystal to be processed on a processing table of an infrared laser device, and processing the lithium niobate crystal according to a preset cutting track spacing, so that the infrared laser is focused and processed inside the lithium niobate crystal from the bottom surface of the lithium niobate crystal to the top surface of the lithium niobate crystal, so as to form a plurality of cavity modification columns inside the lithium niobate crystal, each of the cavity modification columns comprising a plurality of cavity modification points spaced apart along the thickness direction of the lithium niobate crystal, wherein a plurality of the cavity modification columns form a cavity modification surface; Fixing the lithium niobate crystal processed by infrared laser on a processing platform of ultraviolet laser device, processing the lithium niobate crystal according to the preset cutting track spacing, focusing the ultraviolet laser on the top surface of the lithium niobate crystal, and processing from the top surface of the lithium niobate crystal to the inside of the lithium niobate crystal to form a cutting groove of a preset depth, each of the cutting grooves corresponding to one of the cavity modified surfaces; The lithium niobate crystal processed by ultraviolet laser is fixed to a mechanical splitting device, and the splitting knife of the mechanical splitting device is aligned with each of the cavity modified surfaces from the bottom surface of the lithium niobate crystal to split the crystal in turn to obtain lithium niobate grains.

2. The narrow-pitch laser cutting method of thick lithium niobate crystal according to claim 1, characterized in that: When the infrared laser device gradually focuses upward inside the lithium niobate crystal, it stops when it reaches a preset position. When the ultraviolet laser device processes from the top surface of the lithium niobate crystal to the inside of the lithium niobate crystal, it stops when it reaches a preset distance from the preset position. The preset distance is greater than 0 and does not exceed 60 μm.

3. The narrow-pitch laser cutting method of thick lithium niobate crystal according to claim 1, characterized in that: The pulse width of the infrared laser emitted by the infrared laser device is not less than 10 ps, ​​and the single pulse energy of the infrared laser emitted by the infrared laser device is not less than 1 μJ; the pulse width of the ultraviolet laser emitted by the ultraviolet laser device is not greater than 100 ps, ​​and the single pulse energy of the ultraviolet laser emitted by the ultraviolet laser device is not greater than 10 μJ.

4. The narrow-pitch laser cutting method of thick lithium niobate crystal according to claim 1, characterized in that: Before the ultraviolet laser device performs surface cutting processing on the lithium niobate crystal according to the preset cutting path spacing, a processing drawing of the ultraviolet laser device is drawn. The ultraviolet laser device marks the top surface of the lithium niobate crystal according to the processing drawing to form a plurality of cutting grooves with a preset width and a preset depth arranged according to the preset cutting path spacing, and the center plane of each cutting groove along its width direction is coplanar with each of the cavity modified surfaces.

5. The narrow-pitch laser cutting method of thick lithium niobate crystal according to claim 1, characterized in that: The preset cutting track spacing is no greater than 1.5 mm.

6. The narrow-pitch laser cutting method of thick lithium niobate crystal according to claim 1, characterized in that: The length direction of the cutting groove is consistent with or inconsistent with the X main crystal axis direction of the lithium niobate crystal.

7. The narrow-pitch laser cutting method of thick lithium niobate crystal according to claim 1, characterized in that: The width of the cutting groove is not greater than 20μm.

8. The narrow-pitch laser cutting method of thick lithium niobate crystal according to claim 1, characterized in that: The spacing between each adjacent two cavity modification points in each cavity modification column is a first preset spacing, and the spacing between the centers of each adjacent two cavity modification points in the lateral direction in each cavity modification surface is a second preset spacing, the first preset spacing is 0 to 10um, and the second preset spacing is 10 to 20um.

9. The narrow-pitch laser cutting method of thick lithium niobate crystal according to claim 1, characterized in that: Fixing the lithium niobate crystal to be processed on the processing table of the infrared laser device also includes: Placing the lithium niobate crystal to be processed on a film laminating machine, and the film laminating machine performs a film laminating operation on the lithium niobate crystal so that one side of the lithium niobate crystal is in close contact with the cutting film; Fix the lithium niobate crystal on a processing table of an infrared laser device with one side of the lithium niobate crystal close to the cutting film facing downward; The split lithium niobate crystal is placed on a wafer expander for expansion, so that the cut film is separated from the lithium niobate crystal to obtain a plurality of lithium niobate grains.

10. A lithium niobate grain, characterized in that: The lithium niobate crystal is prepared by the laser cutting method of any one of claims 1 to 9.

Images