Wafer laser implicit cutting system and method

Abstract

The invention provides a wafer laser implicit cutting system and a wafer laser implicit cutting method. The double-reflector assembly is arranged corresponding to a pulse string emitting position of the laser emitter; the first laser polarization adjusting part is arranged at the reflected light output position of the double-reflector assembly; the beam expander and the PBS are both arranged below the first laser polarization adjusting part, and the beam expander is arranged above the PBS; a second laser polarization adjusting part and a single reflection part, the second laser polarization adjusting part is arranged on one side of the PBS and is arranged corresponding to the pulse string output position of the PBS, and the single reflection part is arranged on the side, away from the PBS, of the second laser polarization adjusting part; the longitudinal moving shaft is arranged below the single reflection part, and a focusing objective lens is arranged on the longitudinal moving shaft; and the moving platform is used for placing a wafer and is arranged below the longitudinal moving shaft. The problem of thermal damage of the wafer is avoided, the cutting precision can be improved, and the final quality and the product yield of the wafer are effectively improved.

Description

Technical Field

[0001] The present invention relates to the field of chip processing technology, and in particular to a wafer laser hidden cutting system and method. Background Art

[0002] In recent years, LED technology has been widely used, among which GaN-based LED chips generally use sapphire substrates due to their excellent physical and chemical properties, such as high hardness, good electrical insulation, wear resistance, high thermal conductivity and chemical stability. However, the high hardness and brittleness of sapphire pose challenges to the cutting of LED chips.

[0003] Traditional mechanical processing is gradually marginalized by the market due to the problems of easy generation of waste chips, edge collapse, cracks, etc., and the high tool loss and high cost. At the same time, its wide cutting path and low efficiency also limit its application. Although chemical etching is feasible, the process is cumbersome, inefficient and has great environmental pollution.

[0004] To meet these challenges, laser precision processing technology has emerged and become the new favorite for cutting sapphire substrates. Laser beams with high peak power density can achieve high-speed and precise cutting, while the cutting path is narrower, significantly improving the processing accuracy and yield rate of wafers.

[0005] Among the existing technologies, wafer laser cutting technology mostly uses MHz-level pulsed lasers for processing. Although this type of laser can achieve basic cutting functions, due to its long pulse train interval (hundreds of nanoseconds), it leads to significant heat accumulation during the cutting process, which in turn causes thermal damage to the material, rough cutting edges, poor straightness and other problems, affecting the final quality of the wafer and product yield. Summary of the invention

[0006] Based on this, the purpose of the present invention is to provide a wafer laser stealth cutting system and method to at least solve the above-mentioned deficiencies in the prior art.

[0007] In a first aspect, the present invention provides a wafer laser stealth cutting system, comprising:

[0008] Laser transmitter;

[0009] A double reflector assembly is arranged on one side of the laser transmitter and is arranged corresponding to the location where the pulse train of the laser transmitter is emitted;

[0010] A first laser polarization adjustment unit is arranged at the output of the reflected light of the double reflector assembly;

[0011] A beam expander and a PBS are both arranged below the first laser polarization adjustment unit and corresponding to the pulse train output of the first laser polarization adjustment unit, and the beam expander is arranged above the PBS;

[0012] A second laser polarization adjustment unit and a single reflection unit, wherein the second laser polarization adjustment unit is arranged at one side of the PBS and corresponds to the pulse train output of the PBS, and the single reflection unit is arranged at a side of the second laser polarization adjustment unit away from the PBS;

[0013] A longitudinal moving axis is arranged below the single reflection part, and a focusing objective lens is arranged on the longitudinal moving axis;

[0014] A movable platform for placing wafers, arranged below the longitudinal movable axis;

[0015] Wherein, the laser emitter is used to emit a pulse train, which is reflected by the double reflector assembly to the first laser polarization adjustment unit and emitted from the focusing objective lens via the beam expander, the PBS, the first laser polarization adjustment unit and the single reflector, and the focusing position of the focusing objective lens is adjusted by the longitudinal moving axis to perform hidden cutting on the wafer on the moving platform.

[0016] Compared with the prior art, the beneficial effects of the present invention are: a pulse train is emitted by a laser transmitter, and the polarization direction of the pulse train can be adjusted by the first laser polarization adjustment unit and the second laser polarization adjustment unit, the beam expander can perform on the pulse train, and the PBS can further improve the polarization extinction ratio of the pulse train, thereby effectively preventing the problem of heat accumulation of the pulse train during the hidden cutting of the wafer, avoiding the problem of thermal damage to the wafer, and being able to improve the cutting accuracy, effectively improving the final quality of the wafer and the product yield.

[0017] Furthermore, the dual reflector assembly includes a first reflector and a second reflector, and the first reflector and the second reflector are arranged on one side of the laser emitter at a preset angle, wherein the laser emitted by the laser emitter is reflected to the first reflector via the second reflector, and is reflected to the first laser polarization adjustment unit via the first reflector.

[0018] Furthermore, the first laser polarization adjustment unit and the second laser polarization adjustment unit are both half-wave plates.

[0019] Furthermore, the single reflection part is a third reflection mirror.

[0020] Furthermore, a coaxial CCD is provided above the single reflection portion, and the coaxial CCD is used to monitor the focusing objective lens on the longitudinal movement axis.

[0021] Furthermore, the movable platform is provided with a base for placing the wafer.

[0022] Furthermore, a paraxial CCD is provided on one side of the longitudinal moving axis, and the paraxial CCD is used to observe the wafer cutting effect on the moving platform.

[0023] Furthermore, the laser emitter is an ultrafast laser system, the pulse train width output by the laser emitter is less than 15 picoseconds, the output power of the laser emitter is greater than 2W, the pulse train output by the laser emitter includes a GHz pulse train and a kHz pulse train, the number of the GHz pulse trains is 2 to 20, and the frequency of the kHz pulse train is 50kHz to 200kHz.

[0024] Furthermore, the magnification of the beam expander is 1.1 to 3.0.

[0025] In a second aspect, the present invention provides a wafer laser hidden cutting method, which is applied to the above-mentioned wafer laser hidden cutting system, and the method comprises:

[0026] Sending a pulse train through the laser transmitter;

[0027] By means of the double reflector assembly, the first laser polarization adjustment unit, the beam expander, the PBS, the second laser polarization adjustment unit and the single reflector, the light polarization state and the light spot shaping of the pulse train are adjusted;

[0028] The focusing position of the focusing objective lens is adjusted by the longitudinal moving axis that moves longitudinally, and the position of the wafer is adjusted by the moving platform so that the pulse train can perform hidden cutting on the wafer. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the structure of the wafer laser hidden cutting system in the first embodiment of the present invention;

[0030] Figure 2 A schematic diagram of a GHz pulse train in the first embodiment of the present invention;

[0031] Figure 3 Flow chart of the wafer laser stealth cutting method in the second embodiment of the present invention.

[0032] Description of main component symbols:

[0033] 10. Laser transmitter;

[0034] 20. Double reflector assembly; 21. First reflector; 22. Second reflector;

[0035] 30. A first laser polarization adjustment unit;

[0036] 40. Beam expander;

[0037] 50. PBS;

[0038] 60. A second laser polarization adjustment unit;

[0039] 70. Single reflection part;

[0040] 80, longitudinal movement axis; 81, focusing objective lens; 82, coaxial CCD; 83, paraxial CCD;

[0041] 90. Mobile platform; 91. Base.

[0042] The following specific implementation manner will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0043] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. Several embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0044] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0046] Embodiment 1

[0047] See also Figure 1 , shown is a wafer laser stealth cutting system in the first embodiment of the present invention, including a laser emitter 10, a double reflector assembly 20, a first laser polarization adjustment unit 30, a beam expander 40, a PBS 50, a second laser polarization adjustment unit 60, a single reflector 70, a longitudinal moving axis 80 and the moving platform 90.

[0048] The double reflector assembly 20 is arranged on one side of the laser emitter 10, and is arranged corresponding to the pulse string output of the laser emitter 10. The first laser polarization adjustment unit 30 is arranged at the reflected light output of the double reflector assembly 20. The beam expander 40 and the PBS 50 are both arranged below the first laser polarization adjustment unit 30, and are arranged corresponding to the pulse string output of the first laser polarization adjustment unit 30. The beam expander 40 is arranged above the PBS 50. The second laser polarization adjustment unit 60 is arranged on one side of the PBS 50, and is arranged corresponding to the pulse string output of the PBS 50. The single reflector 70 is arranged at the second laser polarization adjustment unit 60 away from the PBS On one side of S50, the longitudinal moving axis 80 is arranged below the single reflection part 70, and a focusing objective lens 81 is provided on the longitudinal moving axis 80. The moving platform 90 is used to place a wafer, and the moving platform 90 is arranged below the longitudinal moving axis 80, wherein the laser emitter 10 is used to emit a pulse train, which is reflected to the first laser polarization adjustment part 30 by the double reflector assembly 20 and emitted from the focusing objective lens 81 via the beam expander 40, the PBS50, the first laser polarization adjustment part 30 and the single reflection part 70, and the focusing position of the focusing objective lens 81 is adjusted by the longitudinal moving axis 80 to perform hidden cutting on the wafer on the moving platform 90.

[0049] It can be understood that the pulse train is adjusted through the double mirror assembly 20, the first laser polarization adjustment unit 30, the beam expander 40, the PBS50, the second laser polarization adjustment unit 60 and the single reflection unit 70 to adjust the light polarization state and the spot shaping of the pulse train, so that the adjusted pulse train can avoid heat accumulation during the cutting process when the wafer is cut, thereby effectively avoiding the final quality and yield of the wafer from being affected.

[0050] It should be noted that the laser emitter 10 is an ultrafast laser system, the pulse train width output by the laser emitter 10 is less than 15 picoseconds, the output power of the laser emitter 10 is greater than 2W, the pulse train output by the laser emitter 10 includes a GHz pulse train and a kHz pulse train, the number of the GHz pulse trains is 2, and the frequency of the kHz pulse train is 50kHz. In this embodiment, the adjusted pulse interval is 0.15, the interval of the GHz pulse train is 6.67, and the scribing power is 0.532W, and the scribing power refers to the power under the focusing objective lens 81.

[0051] It should be explained that the ultrafast laser system contains a laser output with a pulse interval of less than 1ns (GHz repetition frequency), and the number of GHz pulses is greater than 2, forming a GHz pulse train. In addition, the interval between the envelopes of the GHz pulse train is at the us level (kHz repetition frequency). The laser system can output GHz and kHz pulses at the same time. In order to achieve the "cold processing" effect, the pulse width of the laser output must be less than 15 picoseconds or even at the femtosecond level. In addition, the average power of the laser output is greater than 2W, so that the energy density after the external optical path loss is higher than the modification threshold of the wafer.

[0052] It is worth mentioning that please refer to Figure 2 , as shown in the GHz pulse train used in this embodiment, the number of pulses is 12.

[0053] Specifically, in the present embodiment, the dual reflector assembly 20 includes a first reflector 21 and a second reflector 22, and the first reflector 21 and the second reflector 22 are arranged on one side of the laser emitter 10 at a preset angle, wherein the laser emitted by the laser emitter 10 is reflected to the first reflector 21 via the second reflector 22, and is reflected to the first laser polarization adjustment unit 30 via the first reflector 21, the first laser polarization adjustment unit 30 and the second laser polarization adjustment unit 60 are both half-wave plates, and the single reflection unit 70 is a third reflector.

[0054] It can be understood that the output of the laser emitter 10 is directed toward the second reflector 22, and the pulse output by the laser emitter 10 is reflected by the second reflector 22 to the first reflector 21, and is emitted downward from the first reflector 21 in a vertical direction. The polarization direction is adjusted by the first laser polarization adjustment unit 30, that is, the first half-wave plate, so that it can pass through the PBS 50 with minimum loss, and then the pulse train is amplified by the beam expander 40, which is used to expand the beam diameter to the required size. In this embodiment, the beam expansion factor is 1.1, and the PBS 50 is to further increase the beam diameter. In order to increase the polarization extinction ratio of the light beam, after being reflected and output from the PBS 50, the light beam passes through the second laser polarization adjustment unit 60, that is, the second half-wave plate, to adjust the polarization direction, and then passes through the single reflection unit 70, that is, the third reflection mirror, to reflect the light beam to the focusing objective lens 81 on the longitudinal moving axis 80. By moving the longitudinal moving axis 80, the focusing objective lens 81 can cut the wafer on the moving platform 90, and the moving platform 90 can move in the horizontal direction and in the direction perpendicular to the horizontal direction on the plane, so as to achieve the purpose of accurately cutting the wafer.

[0055] In addition, it is worth mentioning that a base 91 for placing a wafer is provided on the mobile platform 90, so that the wafer can be stably set on the mobile platform 90 through the base 91, and the base 91 can also rotate on the mobile platform 90. In addition, the base 91 includes a function of vacuum adsorption to fix the wafer to be processed. The vertical moving shaft 80 that moves vertically up and down accurately focuses the vertically captured laser beam into the inside of the wafer to achieve internal damage to the wafer, forming a row of modified points along the cutting direction, and using a series of modified points as seven dividing points to generate cracks on the front and back sides of the wafer, respectively, to achieve wafer cutting, which is also called hidden cutting.

[0056] It needs to be explained that when the laser pulse is precisely focused inside the wafer, the wafer crystals in the focal area undergo a local melting process. It is worth noting that the density of the wafer in the molten state will increase compared to its crystallized state. This change causes tiny vacuum pores to form in the molten area. As the temperature in this area gradually decreases, below the melting point of the wafer, part of the molten wafer will recrystallize, while the rest will remain amorphous. This transformation forms a high density of dislocation points inside the wafer, the so-called "modified points". This series of linearly arranged modified points serves as the starting point, and under the action of stress, natural cracking occurs from the inside of the wafer to the front and back sides. This method of crack generation from the inside to the outside avoids the generation of debris on the surface of the wafer, thereby eliminating the traditional deionized water cleaning step, which not only simplifies the production process, but also effectively reduces production costs and improves overall processing efficiency.

[0057] Furthermore, in this embodiment, a coaxial CCD is provided above the single reflection part 70, and the coaxial CCD82 is used to monitor the focusing objective lens 81 on the longitudinal moving axis 80. A paraxial CCD83 is provided on one side of the longitudinal moving axis 80, and the paraxial CCD83 is used to observe the wafer cutting effect on the moving platform 90.

[0058] It should be explained that the focus accuracy of the focusing lens 81 can be observed through the coaxial CCD82, and the cutting effect at different depths inside the wafer after cutting can be observed through the paraxial CCD83. For details on the straightness of the cutting edge of the wafer, please refer to Table 1.

[0059] Embodiment 2

[0060] The wafer laser hidden cutting system provided in the second embodiment of the present invention is different from the wafer laser hidden cutting system in the first embodiment in that:

[0061] The pulse train output by the laser transmitter 10 includes a GHz pulse train and a kHz pulse train, the number of the GHz pulse trains is 2, and the frequency of the kHz pulse train is 50kHz. In this embodiment, the adjusted pulse interval is 0.25, the interval of the GHz pulse train is 4.00, and the scribing power is 0.521W. The scribing power refers to the power under the focusing objective lens 81. In this embodiment, the beam expansion multiple of the beam expander 40 is 1.5. For details on the straightness of the cutting edge of the wafer, please refer to Table 1.

[0062] Embodiment 3

[0063] The pulse train output by the laser transmitter 10 includes a GHz pulse train and a kHz pulse train, the number of the GHz pulse trains is 2, and the frequency of the kHz pulse train is 50kHz. In this embodiment, the adjusted pulse interval is 0.45, the interval of the GHz pulse train is 2.22, and the scribing power is 0.521W. The scribing power refers to the power under the focusing objective lens 81. In this embodiment, the beam expansion multiple of the beam expander 40 is 1.8. For details on the straightness of the cutting edge of the wafer, please refer to Table 1.

[0064] Embodiment 4

[0065] The pulse train output by the laser transmitter 10 includes a GHz pulse train and a kHz pulse train, the number of the GHz pulse trains is 2, and the frequency of the kHz pulse train is 50kHz. In this embodiment, the adjusted pulse interval is 0.7, the interval of the GHz pulse train is 1.43, and the scribing power is 0.545W. The scribing power refers to the power under the focusing objective lens 81. In this embodiment, the beam expansion multiple of the beam expander 40 is 2.1. For details on the straightness of the cutting edge of the wafer, please refer to Table 1.

[0066] Embodiment 5

[0067] The pulse train output by the laser transmitter 10 includes a GHz pulse train and a kHz pulse train, the number of the GHz pulse trains is 2, and the frequency of the kHz pulse train is 50kHz. In this embodiment, the adjusted pulse interval is 1.1, the interval of the GHz pulse train is 0.91, and the scribing power is 0.565W. The scribing power refers to the power under the focusing objective lens 81. In this embodiment, the beam expansion multiple of the beam expander 40 is 2.5. For details on the straightness of the cutting edge of the wafer, please refer to Table 1.

[0068] Embodiment 6

[0069] The pulse train output by the laser transmitter 10 includes a GHz pulse train and a kHz pulse train, the number of the GHz pulse trains is 2, and the frequency of the kHz pulse train is 50kHz. In this embodiment, the adjusted pulse interval is 2.3, the interval of the GHz pulse train is 0.43, and the scribing power is 0.605W. The scribing power refers to the power under the focusing objective lens 81. In this embodiment, the beam expansion multiple of the beam expander 40 is 3.1. For details on the straightness of the cutting edge of the wafer, please refer to Table 1.

[0070] Comparative Example 1

[0071] Comparative Example 1 uses a MHz pulse train, the number of pulse trains is 8, and the pulse train interval is 40MHz, that is, the pulse interval is 25ns. The test results are shown in Table 1, and the wafer straightness is not as good as the processing effect of the GHz pulse train. This is because the duration of the MHz pulse train is 25ns*7=175ns, which is much longer than the duration of the GHz pulse train in this implementation case, which is 0.45ns*11=4.95ns. The longer pulse train duration leads to significant heat accumulation during the cutting process, which in turn causes problems such as thermal damage to the material, rough cutting edges, and poor straightness, affecting the final quality of the wafer and product yield.

[0072] Table 1

[0073]

[0074] As shown in Table 1, as the GHz pulse interval increases, the wafer appearance straightness increases from ±1um to ±4um. From the test results, the GHz pulse interval can maintain a good wafer straightness effect in the range of 0.15 to 0.45ns. Among them, the dicing power refers to the power under the focusing objective lens 81.

[0075] In summary, the wafer laser stealth cutting system in the above-mentioned embodiment of the present invention emits a pulse train through the laser transmitter 10, and the polarization direction of the pulse train can be adjusted through the first laser polarization adjustment unit 30 and the second laser polarization adjustment unit 60, the beam expander 40 can perform on the pulse train, and the PBS50 can further improve the polarization extinction ratio of the pulse train, thereby effectively preventing the problem of heat accumulation of the pulse train during the stealth cutting of the wafer, avoiding the problem of thermal damage to the wafer, and being able to improve the cutting accuracy, effectively improving the final quality of the wafer and the product yield.

[0076] Embodiment 7

[0077] See also Figure 3 , which shows a wafer laser hidden cutting method in a seventh embodiment of the present invention, the method comprises steps S1 to S3:

[0078] S1, emitting a pulse train through the laser transmitter 10;

[0079] S2, adjusting the light polarization state and spot shaping of the pulse train through the double reflector assembly, the first laser polarization adjustment unit, the beam expander, the PBS, the second laser polarization adjustment unit and the single reflector;

[0080] S3, adjusting the focusing position of the focusing lens 81 by the longitudinally moving longitudinal moving axis 80, and adjusting the position of the wafer by the moving platform 90, so that the pulse train performs hidden cutting on the wafer.

[0081] Among them, the first laser polarization adjustment unit 30 and the second laser polarization adjustment unit 60 are half-wave plates. The pulse train is adjusted by the double reflector assembly 20, the first laser polarization adjustment unit 30, the beam expander 40, the PBS50, the second laser polarization adjustment unit 60 and the single reflector 70, so that the laser emitted by the laser transmitter 10 can be transmitted along a specified path. The beam expander 40 can expand the laser beam to a required size so that it can reach a sufficiently small size after passing through the focusing objective lens 81. The PBS50 can further improve the extinction ratio of the laser. The half-wave plate rotates the polarization direction of the laser beam to achieve the best processing effect.

[0082] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0083] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A wafer laser stealth cutting system, characterized in that: include: Laser transmitter; A double reflector assembly is arranged on one side of the laser transmitter and is arranged corresponding to the location where the pulse train of the laser transmitter is emitted; A first laser polarization adjustment unit is arranged at the output of the reflected light of the double reflector assembly; A beam expander and a PBS are both arranged below the first laser polarization adjustment unit and corresponding to the pulse train output of the first laser polarization adjustment unit, and the beam expander is arranged above the PBS; A second laser polarization adjustment unit and a single reflection unit, wherein the second laser polarization adjustment unit is arranged at one side of the PBS and corresponds to the pulse train output of the PBS, and the single reflection unit is arranged at a side of the second laser polarization adjustment unit away from the PBS; A longitudinal moving axis is arranged below the single reflection part, and a focusing objective lens is arranged on the longitudinal moving axis; A movable platform for placing wafers, arranged below the longitudinal movable axis; Wherein, the laser emitter is used to emit a pulse train, which is reflected by the double reflector assembly to the first laser polarization adjustment unit and emitted from the focusing objective lens via the beam expander, the PBS, the first laser polarization adjustment unit and the single reflector, and the focusing position of the focusing objective lens is adjusted by the longitudinal moving axis to perform hidden cutting on the wafer on the moving platform.

2. The wafer laser stealth cutting system according to claim 1, characterized in that: The dual reflector assembly includes a first reflector and a second reflector, wherein the first reflector and the second reflector are arranged at a preset angle on one side of the laser emitter, wherein the laser emitted by the laser emitter is reflected to the first reflector via the second reflector, and is reflected to the first laser polarization adjustment unit via the first reflector.

3. The wafer laser stealth cutting system according to claim 1, characterized in that: The first laser polarization adjustment unit and the second laser polarization adjustment unit are both half-wave plates.

4. The wafer laser stealth cutting system according to claim 1, characterized in that: The single reflection part is a third reflection mirror.

5. The wafer laser stealth cutting system according to claim 4, characterized in that: A coaxial CCD is arranged above the single reflection part, and the coaxial CCD is used to monitor the focusing objective lens on the longitudinal moving axis.

6. The wafer laser stealth cutting system according to claim 1, characterized in that: The movable platform is provided with a base for placing wafers.

7. The wafer laser stealth cutting system according to claim 1, characterized in that: A paraxial CCD is provided on one side of the longitudinal moving axis, and the paraxial CCD is used to observe the wafer cutting effect on the moving platform.

8. The wafer laser stealth cutting system according to claim 1, characterized in that: The laser emitter is an ultrafast laser system. The width of the pulse train output by the laser emitter is less than 15 picoseconds. The output power of the laser emitter is greater than 2W. The pulse train output by the laser emitter includes a GHz pulse train and a kHz pulse train. The number of the GHz pulse trains is 2 to 20, and the frequency of the kHz pulse train is 50kHz to 200kHz.

9. The wafer laser stealth cutting system according to claim 1, characterized in that: The magnification of the beam expander is 1.1 to 3.

0.

10. A wafer laser hidden cutting method, characterized in that: The wafer laser stealth cutting system according to any one of claims 1 to 9, wherein the method comprises: Sending a pulse train through the laser transmitter; By means of the double reflector assembly, the first laser polarization adjustment unit, the beam expander, the PBS, the second laser polarization adjustment unit and the single reflector, the light polarization state and the light spot shaping of the pulse train are adjusted; The focusing position of the focusing objective lens is adjusted by the longitudinal moving axis that moves longitudinally, and the position of the wafer is adjusted by the moving platform so that the pulse train can perform hidden cutting on the wafer.

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