Gallium arsenide chip laser processing device and method thereof

Abstract

The invention relates to a gallium arsenide chip laser processing device and method, the output end of a laser is sequentially provided with a beam expander and a spatial light modulator, the output end of the spatial light modulator is sequentially provided with a first lens, a first reflector and a second lens, and the output light path of the second lens is provided with a second reflector; a processing objective lens is arranged on a reflection light path of the second reflector and is opposite to the gallium arsenide chip on the motion platform; light spots of light beams output by the laser device are amplified and collimated through the beam expander, an effective window of the spatial light modulator is covered, the spatial light modulator loads an aberration correction holographic phase diagram, then the light beams sequentially pass through the first lens, the first reflector, the second lens and the second reflector, and the first reflector and the second reflector are used for changing the light path transmission direction. The first lens and the second lens form a 4f system for transmitting an image to a light inlet of the processing objective lens, and output laser forms a focusing light spot in the gallium arsenide chip for processing, so that the cutting efficiency and the cutting quality are improved.

Description

Technical Field

[0001] The invention relates to a gallium arsenide chip laser processing device and a method thereof, belonging to the technical field of laser processing. Background Art

[0002] Gallium arsenide (GaAs) is a compound synthesized from gallium and arsenic. It belongs to the III to V group of compound semiconductor materials. Compared with traditional silicon semiconductor materials, it has the characteristics of high electron mobility, large bandgap, and low power consumption. It plays a vital role in the civil and military fields. GaAs wafers are highly brittle, and the yield strength and elastic limit of the material are close. Compared with silicon wafers, traditional grinding wheel cutting and diamond knife cutting will cause serious cracking of GaAs wafers. Due to the high hardness of the material, grinding wheels, diamond knives and other tools wear out quickly, making their cost high and the cutting efficiency low.

[0003] Laser cutting is a new type of cutting technology that has emerged with the development of laser technology. There are two main methods: laser surface ablation and invisible cutting. Laser surface ablation is to focus a laser with a certain energy density and wavelength on the chip surface to burn a scratch, and then use a chip splitter to split along the scratch to form several small chips. The laser directly acts on the surface of the gallium arsenide material, which is easy to produce some toxic and polluting dust. Therefore, laser surface ablation cutting is not widely used in the cutting operation of gallium arsenide wafers.

[0004] The laser invisible cutting method is to focus the laser beam to a certain depth inside the material. The material absorbs the laser energy in a short period of time, causing local heating, melting and vaporization, and finally forming a modified layer inside the material, which is then separated by slicing. As a non-contact processing, the laser invisible cutting method has significant advantages in gallium arsenide wafer cutting, such as high efficiency and low loss. The Chinese patent with patent publication number CN117483972A discloses a laser cutting method for gallium arsenide-based chips, which adopts a laser invisible cutting method. Compared with traditional grinding wheel cutting, it improves the cutting efficiency and cutting quality to a certain extent. The patent publication number CN101165877A discloses a laser processing method for gallium arsenide wafers, which adopts laser surface ablation cutting, and cannot avoid the problems of cracking and dust pollution on the surface of gallium arsenide.

[0005] In the process of laser invisible cutting, when the converged laser beam passes through the interface between the air medium and the material with different refractive indexes, a strong spherical aberration phenomenon will be caused due to the refractive index mismatch. The spherical aberration phenomenon leads to significant focus shift, stretching and distortion of the focal spot, and the spherical aberration phenomenon will become more significant as the processing depth increases. These phenomena have an adverse effect on processing consistency, and aberration correction becomes increasingly important in the process of laser invisible cutting. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a gallium arsenide chip laser processing device and method thereof, aiming to improve the efficiency and quality of gallium arsenide chip laser cutting.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] The gallium arsenide chip laser processing device is characterized in that: a beam expander and a spatial light modulator are arranged in sequence at the laser output end, a first lens, a first reflector and a second lens are arranged in sequence at the output end of the spatial light modulator, a second reflector is arranged on the output light path of the second lens, a processing objective lens is arranged on the reflected light path of the second reflector, the processing objective lens is directly facing the gallium arsenide chip on the moving platform, and the output laser forms a focusing spot inside the gallium arsenide chip for processing.

[0009] Furthermore, in the above-mentioned gallium arsenide chip laser processing device, the laser has an emission wavelength of 1000nm to 1100nm, an emission laser frequency of 10KHz to 100KHz continuously adjustable, an average power of 0 to 30W adjustable, and a pulse width of 1ns to 100ns adjustable.

[0010] Furthermore, in the above-mentioned gallium arsenide chip laser processing device, the laser is a laser with an emission wavelength of 1064nm, a pulse width of 100ns, an average power of 1W, and a repetition frequency of 10KHz to 100KHz.

[0011] Furthermore, in the above-mentioned gallium arsenide chip laser processing device, the spatial light modulator is a spatial light modulator with a wavelength range of 300nm to 1100nm and a pixel number of not less than 500,000.

[0012] Furthermore, in the above-mentioned gallium arsenide chip laser processing device, the spatial light modulator is a spatial light modulator with a pixel size of 1920×1080 and an effective area of ​​15.4 mm×8.6 mm.

[0013] Furthermore, in the above-mentioned gallium arsenide chip laser processing device, the focal length of the first lens is twice the focal length of the second lens, forming a 4f system.

[0014] Furthermore, in the above-mentioned gallium arsenide chip laser processing device, the numerical aperture of the processing objective lens is 0.85 and the magnification is 100 times.

[0015] The invention discloses a method for processing a gallium arsenide chip by laser. The light beam output by the laser is passed through a beam expander to enlarge and collimate the light spot, covering the effective window of a spatial light modulator. The spatial light modulator is loaded with an aberration-corrected holographic phase diagram, and then passes through a first lens, a first reflector, a second lens, and a second reflector in sequence. The first reflector and the second reflector are used to change the transmission direction of the light path. The first lens and the second lens form a 4f system to transmit the image to the light inlet of the processing objective lens. The laser output by the processing objective lens forms a focused light spot inside the gallium arsenide chip for processing.

[0016] Furthermore, in the above-mentioned gallium arsenide chip laser processing method, the spatial light modulator performs aberration correction phase modulation, generates a spherical aberration correction holographic phase map through an aberration correction formula, loads it into the spatial light modulator, and focuses it inside the gallium arsenide chip for processing.

[0017] Furthermore, in the above-mentioned GaAs chip laser processing method, the aberration correction phase map is loaded into the spatial light modulator, the phase light field of the incident light is modulated to achieve compensation for spherical aberration, and the laser focus focused on the inside of the GaAs chip to be processed is phase modulated. The spherical aberration compensation formula is:

[0018]

[0019] Where λ is the laser wavelength, ρ is the normalized pupil radius of the laser emission, and d nom is any depth inside the GaAs chip to be processed, n1=1 is the refractive index of air, n2 is the refractive index of GaAs material, NA is the numerical aperture of the laser output lens, Correct phase for spherical aberration;

[0020] Substitute each parameter and use MATLAB software or PYTHON software to calculate the aberration correction phase map.

[0021] Compared with the prior art, the present invention has significant advantages and beneficial effects, which are specifically embodied in the following aspects:

[0022] ① The laser beam of the present invention is subjected to aberration correction phase modulation by a spatial light modulator, and then reaches the processing objective lens after passing through the 4f system and is focused inside the gallium arsenide chip to generate an aberration correction focus spot for processing, thereby improving the cutting efficiency and cutting quality of the gallium arsenide chip;

[0023] ②Use laser invisible cutting technology to cut gallium arsenide chips, greatly improving existing efficiency and reducing chip surface contamination;

[0024] ③ The aberration correction algorithm generated by the spatial light modulator is used for gallium arsenide chip cutting, which greatly improves the cutting quality. It can be extended to the processing of semiconductor materials such as silicon wafers, diamonds, indium phosphide and gallium nitride.

[0025] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or be understood by practicing the specific embodiments of the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0027] Figure 1 : Schematic diagram of the optical path structure of the device of the present invention;

[0028] Figure 2 : Schematic diagram of aberration correction;

[0029] Figure 3 : Comparison of the cross-section photo of the GaAs chip without aberration correction and the cross-section photo of the GaAs chip with aberration correction;

[0030] Figure 4 : Comparison of the surface photos of the GaAs chip without aberration correction and the surface photos of the GaAs chip with aberration correction. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The components of the embodiments of the present invention generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present invention.

[0032] It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings. At the same time, in the description of the present invention, directional terms and order terms are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0033] like Figure 1As shown, in the gallium arsenide chip laser processing device, a beam expander 2 and a spatial light modulator 3 are arranged in sequence at the output end of the laser 1, a first lens 4, a first reflector 5 and a second lens 6 are arranged in sequence at the output end of the spatial light modulator 3, a second reflector 7 is arranged on the output light path of the second lens 6, a processing objective lens 8 is arranged on the reflected light path of the second reflector 7, the processing objective lens 8 is facing the gallium arsenide chip 9 on the moving platform 10, and the output laser forms a focusing spot inside the gallium arsenide chip 9 for processing.

[0034] The laser 1 is a laser with an emission wavelength of 1000nm to 1100nm, an emission laser frequency of 10KHz to 100KHz which is continuously adjustable, an average power of 0 to 30W which is adjustable, and a pulse width of 1ns to 100ns which is adjustable.

[0035] Preferably, the laser 1 is a laser with an emission wavelength of 1064 nm, a pulse width of 100 ns, an average power of 1 W, and a repetition frequency of 10 KHz to 100 KHz.

[0036] The spatial light modulator 3 is a spatial light modulator with a wavelength range of 300nm to 1100nm, a pixel of not less than 500,000, a pixel of 1920×1080, and an effective area of ​​15.4mm×8.6mm. As a new type of programmable optical shaping device, the role of the spatial light modulator in laser processing is becoming more and more significant. It can flexibly control the optical parameters such as the amplitude, phase and polarization of the laser beam in a programmable manner, and cooperate with the external optical path system to obtain arbitrary light field intensity distribution inside the material. Different laser spots are focused inside the gallium arsenide chip, which has different effects on the modification and expansion of the material, and will have different effects on improving the efficiency and quality of gallium arsenide chip cutting.

[0037] The focal length of the first lens 4 is twice that of the second lens 6, forming a 4f system.

[0038] The numerical aperture of the processing objective lens 8 is 0.85, and the magnification is 100 times.

[0039] In specific applications, the light beam output by the laser 1 passes through the beam expander 2 to enlarge and collimate the light spot, covering the effective window of the spatial light modulator 3. The spatial light modulator 3 is loaded with an aberration-corrected holographic phase image, and then passes through the first lens 4, the first reflector 5, the second lens 6, and the second reflector 7 in sequence. The first reflector 5 and the second reflector 7 are used to change the transmission direction of the light path. The first lens 4 and the second lens 6 form a 4f system to transmit the image to the light entrance of the processing objective lens 8. The laser output by the processing objective lens 8 forms a focused light spot inside the gallium arsenide chip 9 for processing.

[0040] The spatial light modulator 3 performs aberration correction phase modulation, generates a spherical aberration correction holographic phase map through an aberration correction formula, loads it into the spatial light modulator, and focuses it inside the gallium arsenide chip for processing.

[0041] like Figure 2 As shown, during the laser invisible cutting process, when the converged laser beam passes through the interface between the air medium and the gallium arsenide material with different refractive indices, a strong spherical aberration phenomenon will be caused due to the refractive index mismatch. The spherical aberration phenomenon causes significant focus shift, stretching and distortion of the focal spot, and the spherical aberration phenomenon will become more significant as the processing depth increases. In order to compensate for the spherical aberration caused by the refractive index mismatch, the present invention loads the aberration correction phase map generated by the computer onto the spatial light modulator to realize the phase light field modulation of the incident light to realize the compensation of the spherical aberration.

[0042] The aberration correction phase map is loaded into the spatial light modulator 3, and the phase light field of the incident light is modulated to achieve compensation for the spherical aberration. The laser focus focused on the inside of the gallium arsenide chip to be processed is phase modulated. The spherical aberration compensation formula is:

[0043]

[0044] Where λ is the laser wavelength, ρ is the normalized pupil radius of the laser emission, and d nom is any depth inside the GaAs chip to be processed, n1=1 is the refractive index of air, n2 is the refractive index of GaAs material, NA is the numerical aperture of the laser output lens, Correct phase for spherical aberration;

[0045] Substituting various parameters, the aberration-corrected phase map was calculated using MATLAB software or PYTHON software, with a resolution of 1920×1080 and a bit depth of 8.

[0046] like Figure 3 , the cross section of the GaAs chip without aberration correction (left) is compared with the cross section of the GaAs chip with aberration correction (right). The GaAs chip is cut by laser stealth cutting. Without aberration correction, the laser modification state of the cross section is relatively messy, and the laser focus point presents a disordered elongated spot state. With aberration correction, the laser modification state of the cross section is relatively orderly, and the laser focus point presents a clear and uniform focused spot state, which directly leads to the following Figure 4 As shown, the surface of a gallium arsenide chip without aberration correction (left side) is compared with the surface of a gallium arsenide chip with aberration correction (right side). The corresponding surface quality of the gallium arsenide chip is that the cutting straightness of the chip surface without aberration correction is very poor, and the chip has many chip edge breakages, while the cutting straightness of the chip surface with aberration correction is very good, and there is no chip edge breakage, and the cutting quality is significantly improved.

[0047] In summary, the laser beam of the present invention is phase modulated by aberration correction through a spatial light modulator, and reaches the processing objective lens after passing through the 4f system to focus on the inside of the gallium arsenide chip to generate an aberration correction focus spot for processing, thereby improving the cutting efficiency and cutting quality of the gallium arsenide chip. The gallium arsenide chip is cut using laser invisible cutting technology, which greatly improves the existing efficiency and reduces chip surface contamination. The aberration correction algorithm generated by the spatial light modulator is used for gallium arsenide chip cutting, which greatly improves the existing cutting quality and can be extended to the processing technology of semiconductor materials such as silicon wafers, diamonds, indium phosphide and gallium nitride.

[0048] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention. It should be noted that similar numbers and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings.

[0049] The above is only a specific implementation of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

[0050] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

Claims

1. A gallium arsenide chip laser processing device, characterized in that: The output end of the laser (1) is sequentially provided with a beam expander (2) and a spatial light modulator (3); the output end of the spatial light modulator (3) is sequentially provided with a first lens (4), a first reflector (5) and a second lens (6); a second reflector (7) is arranged on the output light path of the second lens (6); a processing objective lens (8) is arranged on the reflection light path of the second reflector (7); the processing objective lens (8) is directly opposite to a gallium arsenide chip (9) on a moving platform (10); and the output laser forms a focused light spot inside the gallium arsenide chip (9) for processing.

2. The gallium arsenide chip laser processing device according to claim 1, characterized in that: The laser (1) is a laser with an emission wavelength of 1000nm to 1100nm, an emission laser frequency of 10KHz to 100KHz which is continuously adjustable, an average power of 0 to 30W which is adjustable, and a pulse width of 1ns to 100ns which is adjustable.

3. The gallium arsenide chip laser processing device according to claim 2, characterized in that: The laser (1) is a laser with an emission wavelength of 1064nm, a pulse width of 100ns, an average power of 1W, and a repetition frequency of 10KHz to 100KHz.

4. The gallium arsenide chip laser processing device according to claim 1, characterized in that: The spatial light modulator (3) is a spatial light modulator with a wavelength range of 300nm to 1100nm and a pixel number of not less than 500,000.

5. The gallium arsenide chip laser processing device according to claim 4, characterized in that: The spatial light modulator (3) is a spatial light modulator with 1920×1080 pixels and an effective area of ​​15.4 mm×8.6 mm.

6. The gallium arsenide chip laser processing device according to claim 1, characterized in that: The focal length of the first lens (4) is twice the focal length of the second lens (6), forming a 4f system.

7. The gallium arsenide chip laser processing device according to claim 1, characterized in that: The numerical aperture of the processing objective lens (8) is 0.85, and the magnification is 100 times.

8. A method for laser processing of gallium arsenide chips using the device of claim 1, characterized in that: The light beam output by the laser (1) passes through a beam expander (2) to enlarge and collimate the light spot, covering the effective window of the spatial light modulator (3). The spatial light modulator (3) is loaded with an aberration-corrected holographic phase diagram, and then passes through a first lens (4), a first reflector (5), a second lens (6), and a second reflector (7) in sequence. The first reflector (5) and the second reflector (7) are used to change the transmission direction of the light path. The first lens (4) and the second lens (6) form a 4f system to transmit the image to the light entrance of the processing objective lens (8). The laser output by the processing objective lens (8) forms a focused light spot inside a gallium arsenide chip (9) for processing.

9. The gallium arsenide chip laser processing method according to claim 8, characterized in that: The spatial light modulator (3) performs aberration correction phase modulation, uses an aberration correction formula to generate a spherical aberration correction holographic phase map, loads it into the spatial light modulator, and focuses it inside the gallium arsenide chip for processing.

10. The gallium arsenide chip laser processing method according to claim 8, characterized in that: The aberration correction phase map is loaded into the spatial light modulator (3), and the phase light field of the incident light is modulated to achieve compensation for the spherical aberration. The laser focus focused on the inside of the gallium arsenide chip to be processed is phase modulated. The spherical aberration compensation formula is: Where λ is the laser wavelength, ρ is the normalized pupil radius of the laser emission, and d nom is any depth inside the GaAs chip to be processed, n1=1 is the refractive index of air, n2 is the refractive index of GaAs material, NA is the numerical aperture of the laser output lens, Correct phase for spherical aberration; Substitute each parameter and use MATLAB software or PYTHON software to calculate the aberration correction phase map.

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