CN115647599B

CN115647599B - Micro groove laser processing device and method

Info

Publication number: CN115647599B
Application number: CN202211421374.1A
Authority: CN
Inventors: 徐少林; 邱佩; 郭杨; 黄凌羽
Original assignee: Southern University of Science and Technology
Current assignee: Southern University of Science and Technology
Priority date: 2022-11-14
Filing date: 2022-11-14
Publication date: 2024-12-10
Anticipated expiration: 2042-11-14
Also published as: CN115647599A

Abstract

The present application discloses a micro-groove laser processing device and method, which relates to the field of micro-groove processing technology, including: a laser light source, the laser light source is used to emit a laser beam, the laser beam includes an initial polarized light; a beam shaping module, the beam shaping module includes a half-wave plate, a spatial light modulator, and a first polarizer, the spatial light modulator is provided with a binary phase diagram, the half-wave plate is used to modulate the initial polarized light into an inclined polarized light, the spatial light modulator is used to deflect the inclined polarized light into a deflected polarized light perpendicular to each other in the selected area and the non-selected area through the binary phase diagram, the first polarizer is used to filter the deflected polarized light in the non-selected area, so as to obtain a light spot composed of the deflected polarized light in the selected area; a laser focusing module, the laser focusing module is used to control the light spot to focus on the corresponding position of the material to be processed. The present application can improve the shape freedom of micro-groove processing while improving the processing efficiency.

Description

Micro-groove laser processing device and method

Technical Field

The application relates to the technical field of groove processing, in particular to a micro-groove laser processing device and method.

Background

In the related art, a micro-scale groove, abbreviated as a micro-groove, is applied to a plurality of fields, for example, in the semiconductor field, a micro-groove array can be used as a heat dissipation structure, the cross section shape of the micro-groove can influence the heat dissipation performance of a semiconductor device, in the micro-fluid field, as a part in direct contact with fluid, the influence of the groove shape on the pressure distribution of the fluid determines the flow performance of the micro-fluid, and therefore, the processing method of the cross section shape of the micro-groove is particularly important. Currently, a method of machining a micro groove is generally a method of machining or spark-machining a raw material by using a machining tool adapted to a target groove shape. However, both the above-mentioned processing methods are contact processing methods, the shape of the processing tool is limited due to the problems of process, material and the like, so that the shape of the micro-groove is also limited, and the degree of freedom of the shape of the micro-groove is low. Therefore, how to improve the shape freedom and the processing efficiency of the micro-groove during processing is a technical problem to be solved.

Disclosure of Invention

The present application aims to solve at least one of the technical problems existing in the prior art. Therefore, the application provides a micro-groove laser processing device and a micro-groove laser processing method, which can improve the shape freedom degree and the processing efficiency of micro-groove processing.

An embodiment of the micro groove laser processing apparatus according to the first aspect of the present application includes:

The laser source is used for emitting a laser beam, wherein the laser beam is initially polarized light;

The light beam shaping module comprises a half-wave plate, a spatial light modulator and a first polaroid, wherein the spatial light modulator is provided with a binary phase diagram, the half-wave plate is used for modulating the initial polarized light into oblique polarized light, the spatial light modulator is used for deflecting the oblique polarized light into deflection polarized light with a selected area and a non-selected area which are perpendicular to each other through the binary phase diagram, and the first polaroid is used for filtering the deflection polarized light of the non-selected area so as to obtain a light spot formed by the deflection polarized light in the selected area;

And the laser focusing module is used for controlling the light spot to focus on the corresponding position of the material to be processed.

The micro-groove laser processing device at least has the following beneficial effects that by arranging the laser light source, the beam shaping module and the laser focusing module, when the laser light source emits a laser beam formed by initial polarized light, the beam shaping module shapes a plurality of initial polarized lights to obtain a target spot shape, and finally, the laser focusing module focuses the spot on a corresponding position of a material to be processed. According to the micro-groove laser processing device, laser is shaped into a specific light spot shape, and a material to be processed is processed through focusing the light spot to obtain corresponding micro-grooves, in the first aspect, different micro-groove shapes can be obtained through shaping by a light beam shaping module, and are obtained through processing, a processing tool with a specific structure is not needed to be additionally arranged, in a long-time processing state, a new processing tool is not needed to be replaced due to a wear problem, and the processing efficiency is improved. In summary, the micro-groove laser processing device can improve the degree of freedom of the micro-groove processing shape and the processing efficiency.

According to some embodiments of the application, the micro-groove laser processing device further comprises a light spot center adjusting module and a semi-transparent and semi-reflective lens, wherein the light spot center adjusting module comprises a second reflecting mirror, a first convex lens, a beam quality analyzer and an angle adjusting module, the semi-transparent and semi-reflective lens is used for reflecting part of laser beams corresponding to the light spots to the second reflecting mirror so that the second reflecting mirror reflects part of the light spots to the beam quality analyzer through the first convex lens, the beam quality analyzer is used for analyzing part of the light spots to obtain a light intensity distribution diagram, and the angle adjusting module is used for adjusting angles of the laser beams emitted by the laser source according to the light intensity distribution diagram so that centers of the laser beams coincide with centers of binary phase diagrams loaded by the spatial light modulator when the laser beams pass through the binary phase diagrams.

According to some embodiments of the application, the micro-groove laser processing device further comprises a liquid film control module, wherein the liquid film control module is used for covering a liquid film on the surface of the material to be processed according to a set thickness, and the laser focusing module is further used for controlling the light spot to penetrate through the liquid film and focus on a corresponding position of the material to be processed with the set liquid film thickness.

According to some embodiments of the application, the liquid film control module comprises a peristaltic pump, a displacement table and a flow needle, wherein the displacement table is provided with a water tank, the water tank is used for fixing the material to be processed and containing liquid which circularly flows on the surface of the material to be processed, the peristaltic pump is used for conveying the liquid to the surface of the material to be processed, and the flow needle is used for controlling the thickness of the liquid film on the surface of the material to be processed to be a set thickness.

According to some embodiments of the application, the micro-groove laser processing device further comprises a focus detection module, a dichroic mirror and a focusing modulation module, wherein the focus detection module comprises an objective lens, the focus detection module comprises a coaxial light source, a beam splitter, a camera and a first reflecting mirror, the coaxial light source is used for emitting monochromatic light so that the monochromatic light sequentially passes through the dichroic mirror and the objective lens after being reflected by the beam splitter and irradiates the surface of a material to be processed, the camera is used for capturing the monochromatic light reflected by the surface of the material to be processed and sequentially passes through the objective lens, the dichroic mirror, the beam splitter and the first reflecting mirror to form an image corresponding to the surface of the material to be processed, and the focusing modulation module is used for moving the objective lens in the vertical direction according to the image so that the focus formed by the light spot after passing through the objective lens is focused on the surface of the material to be processed.

The micro-groove laser processing method according to the embodiment of the second aspect of the present application is applied to a micro-groove laser processing apparatus including:

A laser light source for emitting a laser beam, wherein the laser beam comprises an initial polarization;

The laser focusing module is used for controlling the light spots to focus on the corresponding positions of the material to be processed;

the micro-groove laser processing method comprises the following steps:

emitting the laser beam;

modulating the initial polarization light into the oblique polarization light;

deflecting the obliquely polarized light into the deflected polarized light with the selected and non-selected areas perpendicular to each other;

filtering the deflected polarized light of the non-selected region to obtain the light spot formed by the deflected polarized light in the selected region;

and focusing the light spots on the surface of the material to be processed and processing to obtain the micro-groove.

According to some embodiments of the application, the micro-groove laser processing device further comprises a light spot center adjusting module and a semi-transparent and semi-reflective lens, wherein the light spot center adjusting module comprises a second reflecting mirror, a first convex lens, a beam quality analyzer and an angle adjusting module, the semi-transparent and semi-reflective lens is used for reflecting part of laser beams corresponding to the light spots to the second reflecting mirror so that the second reflecting mirror reflects part of the light spots to the beam quality analyzer through the first convex lens, the beam quality analyzer is used for analyzing part of the light spots to obtain a light intensity distribution map, and the angle adjusting module is used for adjusting angles of the laser beams emitted by the laser source according to the light intensity distribution map so that the centers of the laser beams coincide with the centers of the binary phase maps loaded by the spatial light modulator when the laser beams pass through the binary phase maps;

The micro-groove laser processing method further comprises the following steps of adjusting the center of the light spot to enable the center of the laser beam to coincide with the center of the binary phase diagram loaded by the spatial light modulator;

The center of the light spot is adjusted so that the center of the laser beam coincides with the center of the binary phase diagram loaded by the spatial light modulator, and the method comprises the following steps:

reflecting part of the light spots to obtain part of the light spots;

Analyzing part of the light spots to obtain the light intensity distribution map;

And adjusting the angle of the laser beam emitted by the laser source according to the light intensity distribution diagram so as to enable the center of the laser beam to coincide with the center of the binary phase diagram loaded by the spatial light modulator.

According to some embodiments of the application, the micro-groove laser processing device further comprises a liquid film control module, wherein the liquid film control module is used for covering a liquid film on the surface of the material to be processed according to a set thickness;

The micro-groove laser processing method further comprises the step of covering the liquid film on the surface of the material to be processed according to a set thickness.

According to some embodiments of the application, the liquid film control module comprises a peristaltic pump, a displacement table and a flow needle, wherein the displacement table is provided with a water tank, the water tank is used for fixing the material to be processed and containing liquid which circularly flows on the surface of the material to be processed, the peristaltic pump is used for conveying the liquid to the surface of the material to be processed, and the flow needle is used for controlling the thickness of the liquid film on the surface of the material to be processed to be a set thickness;

the liquid film is covered on the surface of the material to be processed according to a set thickness, and the method comprises the following steps:

Delivering the liquid to the surface of the material to be processed in the water tank;

and controlling the thickness of the liquid film on the surface of the material to be processed to be a set thickness.

According to some embodiments of the application, the micro-groove laser processing device further comprises a focus detection module, a dichroic mirror and a focusing modulation module, wherein the focus detection module comprises an objective lens, the focus detection module comprises a coaxial light source, a beam splitter, a camera and a first reflecting mirror, the coaxial light source is used for emitting monochromatic light, the monochromatic light sequentially passes through the dichroic mirror and the objective lens after being reflected by the beam splitter and irradiates the surface of a material to be processed, the camera is used for capturing the monochromatic light reflected by the surface of the material to be processed and sequentially passes through the objective lens, the dichroic mirror, the beam splitter and the first reflecting mirror to form an image corresponding to the surface of the material to be processed, and the focusing modulation module is used for moving the objective lens in the vertical direction according to the image so that the focus formed by the light spot after passing through the objective lens is focused on the surface of the material to be processed;

The micro-groove laser processing method further comprises the steps of adjusting the focusing position of the light spot;

The adjusting the focusing position of the light spot comprises the following steps:

Irradiating the monochromatic light on the surface of the material to be processed;

Capturing the monochromatic light reflected by the surface of the material to be processed to form the image corresponding to the surface of the material to be processed;

And moving the objective lens in the vertical direction according to the image so as to enable the focus formed after the light spot passes through the objective lens to be focused on the surface of the material to be processed.

Additional aspects and advantages of the application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the application.

Drawings

The application is further described with reference to the accompanying drawings and examples, in which:

FIG. 1 is a schematic structural view and a schematic optical path diagram of a micro-groove laser processing apparatus according to an embodiment of the present application;

FIG. 2 is a schematic view of the polarization direction of polarized light detected by the polarization detection bit shown in FIG. 1;

FIG. 3 is a schematic diagram of a processing process in which a material to be processed is processed by light spots;

FIG. 4 is a schematic illustration of spot shapes corresponding to different ablation areas;

FIG. 5 is a schematic diagram illustrating the relationship between the shape of a light spot and the ablation depth during micro-groove processing;

FIG. 6 is a schematic structural view of a cross section of a micro-trench;

fig. 7 is a flow chart of a micro-groove laser processing method.

Reference numerals:

a laser light source 100;

a beam shaping module 200, a half-wave plate 210, a spatial light modulator 220, a first polarizer 230, a first polarization detection bit 240, a second polarization detection bit 250, a third polarization detection bit 260, a fourth polarization detection bit 270;

a laser focusing module 300, an objective lens 310, a second convex lens 320;

A spot center adjusting module 400, a second reflecting mirror 410, a first convex lens 420, and a beam quality analyzer 430;

A half mirror 500;

a liquid film control module 600, a displacement table 610, a water tank 611, and a liquid 612;

A focus detection module 700, a coaxial light source 710, a beam splitter 720, a camera 730, a first mirror 740;

A dichroic mirror 800;

the material 900 to be processed.

Detailed Description

Embodiments of the present application are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative only and are not to be construed as limiting the application.

In the description of the present application, it should be understood that references to orientation descriptions such as upper, lower, front, rear, left, right, etc. are based on the orientation or positional relationship shown in the drawings, are merely for convenience of description of the present application and to simplify the description, and do not indicate or imply that the apparatus or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus should not be construed as limiting the present application.

In the description of the present application, the meaning of a number is one or more, the meaning of a number is two or more, and greater than, less than, exceeding, etc. are understood to exclude the present number, and the meaning of a number is understood to include the present number. The description of the first and second is for the purpose of distinguishing between technical features only and should not be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated or implicitly indicating the precedence of the technical features indicated.

In the description of the present application, unless explicitly defined otherwise, terms such as arrangement, installation, connection, etc. should be construed broadly and the specific meaning of the terms in the present application can be reasonably determined by a person skilled in the art in combination with the specific contents of the technical scheme.

In the description of the present application, the descriptions of the terms "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

In the field of semiconductors, an array of micro-grooves is commonly used as a heat dissipation device, wherein the cross-sectional shape characteristics of the array affect the heat dissipation performance of a device, in the field of microfluidics, the micro-grooves are used as parts in direct contact with fluid, the influence of the groove shape on the distribution of fluid pressure determines the flow performance of the microfluidics, and in addition, the micro-grooves are also applied to devices such as a gas proportion detector, diffraction optics and the like. Therefore, in the above field, processing to obtain a micro-groove structure meeting the requirements is a key technical means for realizing the corresponding function of the micro-groove. At present, machining of the micro-grooves with controllable cross sections is usually performed by adopting a mechanical machining method or an electrolytic machining method, and tools with shapes corresponding to the designed grooves are needed to be adopted in the two methods, for example, V-shaped grooves are machined, and V-shaped tools or electrodes are needed. Wear of the working tool directly affects the shape accuracy of the groove. In addition, for hard and brittle materials such as third-generation semiconductors, the traditional processing mode cannot effectively remove the materials, and the processing quality or the processing efficiency are poor.

As a machining method, the diamond cutter has the defects that larger contact stress is generated and edge breakage is easily generated at the edge of a hard and brittle semiconductor material to reduce the quality of a machined surface; the electric discharge machining method is also a contact machining method, and requires that the object to be machined has conductivity, and is not suitable for machining a nonconductive material. In both the above-mentioned contact machining methods, wear deformation of the tool or the electrode directly leads to a reduction in the accuracy of the groove shape.

The laser ablation trench technology solves the shortcomings of contact processing and material selectivity of the two methods. The laser processing technology is used as a non-contact processing method with low material selectivity and high processing precision, and can be suitable for high-precision processing of various materials. However, since the initial light spot energy is in gaussian distribution, the shape of the micro-groove finally obtained by adjusting the laser processing parameters by single laser scanning is limited to a symmetrical U-shape or V-shape, and the cross section profile cannot be freely regulated. The processing method of designing the scanning path according to the cross-sectional profile requires multiple scans of the laser beam, which not only reduces the processing efficiency, but also limits the groove width to at least several times the spot diameter.

Specifically, based on the above-mentioned problems, a technical means for obtaining micro grooves by laser processing has been developed, and the laser processing technology is used as a contactless processing method with low material selectivity and high processing precision, which is applicable to various processing situations with high difficulty, especially in situations where the material to be processed is difficult to process, and can realize high-precision processing of the processed material. However, the gaussian energy distribution characteristic of the conventional light spot is limited, and the control of the groove type is usually performed by adjusting the focal plane of the laser or adjusting laser processing parameters, including single pulse energy and pulse overlapping rate, so as to change the cross-sectional shape of the ablated groove. This change in parameters also yields only U-shaped or V-shaped micro-grooves for a single scan. These laser processing methods cannot achieve a more abundant trench morphology, such as a trench with a T-shaped or stepped cross-sectional shape.

In addition, the laser beam can be scanned for multiple times on the basis of single scanning, and the multiple scanning processing is effective in controlling the groove type, for example, the movement amplitude of the laser beam during back and forth reciprocating movement is controlled in a mode of adding a beam deflection component on a laser processing light path, so that the ablation linewidth is controlled. The other groove control method is to deduce the path of laser scanning for multiple times according to the depth, width and cross section profile of the target micro groove shape and the fitting algorithm of the ablation function, and then to operate the laser beam to scan according to the path, so as to obtain the micro groove with the target width and cross section profile.

Generally, in the related art, the process of laser ablation of the micro-groove is limited by the spot shape, only the U-shaped or V-shaped micro-groove can be processed by a single scanning, and the micro-groove with the size of several micrometers cannot be processed due to the low processing efficiency of the method of designing the path and overlapping the scanning path. Based on the method, the application provides a micro-groove laser processing device and a micro-groove laser processing method, which can process the micro-groove with controllable cross section shape through single laser scanning, and control energy distribution by adopting a mode of shaping an initial light spot, so that the purpose of ablating the micro-groove with controllable cross section shape through single laser scanning is achieved.

A micro groove laser processing apparatus according to an embodiment of the present application is described below with reference to fig. 1.

As can be appreciated, as shown in fig. 1, the micro groove laser processing apparatus according to the present application includes:

A laser light source 100, the laser light source 100 being configured to emit a laser beam, wherein a polarization of the laser beam is an initial polarized light;

A beam shaping module 200, the laser beam including an initial polarized light, the beam shaping module 200 including a half-wave plate 210, a spatial light modulator 220, and a first polarizer 230, the spatial light modulator 220 being provided with a binary phase diagram, the half-wave plate 210 being configured to modulate the initial polarized light into an oblique polarized light, the spatial light modulator 220 being configured to deflect the oblique polarized light into a deflected polarized light in which a selected area and a non-selected area are perpendicular to each other through the binary phase diagram, the first polarizer 230 being configured to filter the deflected polarized light in the non-selected area to obtain a spot of the deflected polarized light in the selected area;

the laser focusing module 300, the laser focusing module 300 is used for controlling the light spot to focus on the corresponding position of the material 900 to be processed.

By providing the laser light source 100, the beam shaping module 200 and the laser focusing module 300, when the laser light source 100 emits a laser beam composed of initial polarized light, the beam shaping module 200 shapes a plurality of initial polarized lights to obtain a target spot shape, and finally, focuses the spot on a corresponding position of the material 900 to be processed by the laser focusing module 300. The micro-groove laser processing device of the application obtains corresponding micro-grooves by shaping laser into a specific light spot shape and processing a material 900 to be processed by focusing the light spot, wherein in the first aspect, different micro-groove shapes can be obtained by shaping the light beam shaping module 200 to obtain different light spot shapes and processing the light spot shapes, a processing tool with a specific structure is not needed to be additionally arranged, in a long-time processing state, a new processing tool is not needed to be replaced due to a wear problem, the processing efficiency is improved, and in the second aspect, the material 900 to be processed can be processed by shaping the light spot to obtain more various micro-grooves, so that the shape of the micro-groove has a larger degree of freedom and is not limited to the specific shape any more. In summary, the micro-groove laser processing device can improve the degree of freedom of the micro-groove processing shape and the processing efficiency.

It should be noted that, the laser light source 100 may be an ultrafast laser or other pulse laser, and the laser beam may be a gaussian ultrafast pulse laser beam emitted by the ultrafast laser or other pulse laser.

The initial polarized light is horizontally polarized light, and is understood to be polarized light parallel to the horizontal plane.

It can be understood that, as shown in fig. 1, the micro-groove laser processing apparatus further includes a spot center adjustment module 400, a half-mirror 500, where the spot center adjustment module 400 includes a second mirror 410, a first convex lens 420, a beam quality analyzer 430, and an angle adjustment module, the half-mirror 500 is configured to reflect a portion of a laser beam corresponding to a spot to the second mirror 410, so that the second mirror 410 reflects a portion of the spot to the beam quality analyzer 430 through the first convex lens 420, the beam quality analyzer 430 is configured to analyze the portion of the spot to obtain a light intensity distribution diagram, and the angle adjustment module is configured to adjust an angle of the laser beam emitted by the laser source 100 according to the light intensity distribution diagram, so that when the laser beam passes through the binary phase diagram, a center of the laser beam coincides with a center of the binary phase diagram loaded by the spatial light modulator 220.

It will be appreciated that, as shown in fig. 1, the micro-groove laser processing apparatus further includes a liquid film control module 600, where the liquid film control module 600 is configured to cover the liquid film on the surface of the material 900 to be processed according to a set thickness, and the laser focusing module 300 is further configured to control the light spot to pass through the liquid film and focus on a corresponding position of the material 900 to be processed having the set liquid film thickness.

It will be appreciated that, as shown in fig. 1, the liquid film control module 600 includes a peristaltic pump, a displacement stage 610, and a flow needle, where the displacement stage 610 is provided with a water tank 611, the water tank 611 is used to fix the material 900 to be processed and hold the liquid 612 circulating on the surface of the material 900 to be processed, the peristaltic pump is used to convey the liquid 612 to the surface of the material 900 to be processed, and the flow needle is used to control the thickness of the liquid film on the surface of the material 900 to be processed to a set thickness.

It will be appreciated that, as shown in fig. 1, the micro-groove laser processing apparatus further includes a focus detection module 700, a dichroic mirror 800, and a focus modulation module, the laser focus module 300 includes an objective lens 310, the focus detection module 700 includes a coaxial light source 710, a beam splitter 720, a camera 730, and a first mirror 740, the coaxial light source 710 is configured to emit monochromatic light, so that the monochromatic light sequentially passes through the dichroic mirror 800 and the objective lens 310 after being reflected by the beam splitter 720 and irradiates the surface of the material 900 to be processed, the camera 730 is configured to capture the monochromatic light reflected by the surface of the material 900 to be processed and sequentially passes through the objective lens 310, the dichroic mirror 800, the beam splitter 720, and the first mirror 740 to form an image corresponding to the surface of the material 900 to be processed, and the focus modulation module is configured to move the objective lens 310 in a vertical direction according to the image, so that the focus formed by the spot passing through the objective lens 310 is focused on the surface of the material 900 to be processed.

A micro groove laser processing apparatus according to an embodiment of the present application will be described with reference to fig. 1 to 6.

As shown in fig. 1, a propagation path of a laser beam is obtained by fig. 1, and processing is performed through this path, and thus, also referred to as a processing optical path, the laser light source 100 in fig. 1 is an ultrafast laser, and a gaussian ultrafast pulse laser beam is generated using the ultrafast laser. As shown in fig. 2 (a), the gaussian ultrafast pulse laser beam emitted from the laser source 100 is a horizontally polarized laser beam, the polarized light in the direction of 45 ° is converted into polarized light in the direction of 45 ° by the half-wave plate 210, that is, the polarized light in the direction of 45 ° is modulated into a light spot pattern shown in fig. 2 (c) by a binary phase diagram loaded on the spatial light modulator 220, and the polarized light in one direction of the light spots is filtered by the first polarizer 230, so as to obtain polarized light shown in fig. 2 (d). Among them, the ultrafast laser is not limited to a solid laser having a center wavelength of 520 nanometers (nm), and the pulse width of the gaussian ultrafast pulse laser beam is not limited to 300 femtoseconds (fs).

In some embodiments, the laser light source 100 is controlled to have a single pulse energy of 8. Mu.J, a beam diameter of 6mm before focusing, a laser repetition rate of 5kHz, and a scanning speed of 100 μm/s. The binary phase diagram loaded on spatial light modulator 220 is a right triangle pattern.

It should be noted that, the shaped right triangle laser beam, referred to as a light spot, passes through a 4f system, that is, the laser focusing module 300, where the laser focusing module 300 includes the objective lens 310 and the second convex lens 320, and is focused on the surface of the material 900 to be processed. Wherein the dichroic mirror is used to reflect the right triangle laser beam to the objective lens 310, so that the objective lens 310 focuses the right triangle laser beam on the material 900 to be processed for processing. Because the focal length of objective 310 is fixed, the up-and-down movement can cause the focal point of objective 310 to fall exactly on the sample surface, and thus, by controlling the up-and-down movement of objective 310, the focal point of the right triangle laser beam is moved to the surface of the material 900 to be processed. The material 900 to be processed is placed in a water tank 611, and the water tank 611 is placed on a displacement table 610, wherein the displacement table 610 may be a triaxial precision displacement table 610.

It should be noted that, the coaxial light source 710 may be an LED light source, and monochromatic light emitted by the LED light source is reflected by the beam splitter 720 and then sequentially passes through the dichroic mirror 800 and the objective 310 to illuminate the surface of the material 900 to be processed. Light reflected by the material to be processed 900 sequentially passes through the objective 310, the dichroic mirror 800, the beam splitter 720 and the first reflecting mirror 740, and enters the camera 730 to image, so as to obtain a photograph of the surface of the sample, wherein the camera 730 is a CMOS camera 730. The focal position imaged by the camera 730 and the laser focusing position are coaxially processed, so that laser focusing modulation is conveniently performed by a focusing modulation module, wherein the focusing modulation module is visual software, and specifically, the movement of the objective lens 310 is controlled up and down by the focusing modulation module.

In the light beam shaping example, referring to fig. 2, four types of polarized light in fig. 2 are sequentially detected by the first polarization detection bit 240, the second polarization detection bit 250, the third polarization detection bit 260, and the fourth polarization detection bit 270, respectively. The initial polarization is first modulated to linear polarization in the 45 polarization direction, i.e., transition from (a) to (b) of fig. 2. The polarization of the laser beam outside the pattern is then rotated by 90 ° by the binary phase diagram loaded on the spatial light modulator 220, forming a laser beam with orthogonal polarization inside and outside the pattern, i.e., transition to (c) in fig. 2 (b), and finally, the polarized light outside the pattern is blocked by the first polarizer 230, only the laser beam inside the pattern can pass through, and the same laser pattern as the phase diagram is obtained, i.e., transition to (d) in fig. 2 (c). The binary phase diagram is designed according to the gray level of the spatial light modulator 220, and the relationship between the phase delay of the spatial light modulator 220 and the gray level diagram, that is, the numerical relationship between the phase and the gray level value is determined, and then the gray level values of the pattern are respectively set inside and outside the design pattern, so that the two gray level values inside and outside the pattern exactly correspond to the phase delay of 0 and pi, thereby realizing the rotation operation of polarized light.

It should be noted that whether liquid 612 is used to aid ablation may be selected based on the material. For the processing object with ablation fragments such as silicon carbide and silicon, the liquid 612 is used for assisting the ablation, and the interference of the ablation product is eliminated by using a laser-induced micro-jet assisted ablation method, so that the grooves with the specific shapes can be processed by the superposition scanning of the shaping light spots.

Specifically, the water tank 611 may be an open quartz container, and the material 900 to be processed is placed in the open quartz container to be fixed in use. The open quartz vessel is used to hold an auxiliary liquid 612 in a laser-induced micro-jet assisted ablation process. The liquid 612 is circularly supplied by a peristaltic pump, wherein the peristaltic pump is a micro-flow pump, an outlet of the peristaltic pump is connected with a flow needle, the liquid 612 is ejected from the flow needle to the surface of the material 900 to be processed, and a thin film of the liquid 612 with dynamic stable thickness is formed on the surface of a processing area.

It will be appreciated that as shown in fig. 3, the shaped laser beam is focused by objective 310 at the surface of the material 900 to be processed covered by the thin film of liquid 612 produced in the above-described manner. The area and thickness of the liquid 612 film formed in the processing area are controlled by changing the flow rate of the pump and the diameter of the outlet of the needle head, and the requirement that the thickness of the liquid 612 film is smaller than the diameter of the cavitation bubbles induced by laser is satisfied, so that the condition of forming laser-induced micro-jet is achieved.

It should be noted that the principle of forming the cross section of the trench is that the energy deposited on the surface of the material 900 to be processed determines the depth of ablation, and the amount of the deposited energy is determined by the number of deposited laser pulses and the energy of each pulse. During the laser scanning ablation process, the energy of the laser pulse is kept unchanged, so that the deposited pulse number at each position on the surface of the material can ablate different depths at different positions. Referring to the schematic diagram of the effective pulse number calculation principle given in fig. 4, when the spot shape is a triangular spot as in fig. 4 (e), the effective pulse number N at each position of the ablation region in fig. 4 (f) can be calculated according to the following formula,

N=h□f/v

Wherein H is the size of the triangular light spot corresponding to each position of the material ablation area in the scanning direction, the scanning direction is the length direction of the micro groove, namely the y-axis direction, f is the repetition frequency of laser, namely the number of laser pulses in one second time, v is the scanning speed of the laser, H is the right-angle side length of the triangular light spot in the length direction, W is the right-angle side length of the triangular light spot in the width direction, and the width direction can be understood as the x-axis direction.

Specifically, taking a triangular light spot as an example, the length of the light spot in the scanning direction varies linearly, with the result that the effective pulse number at each position of the material ablation area also varies linearly. Under the condition that the energy of a single pulse is unchanged, the ablation depth correspondingly and linearly changes, and finally, the triangular groove is formed by ablation.

It should be noted that, the triangular light spot in fig. 4 may be scattered in the x direction and simplified into three-stage stepped light spots, as shown in the structural arrangement shown in (g) of fig. 5, where h1, h2, and h3 respectively represent lengths of different rows of light spots, and each row controls the pulse number of the different rows through the length of h.

It should be noted that, assuming that the superimposed schematic diagram of the light spot in the scanning direction as shown in (h) in fig. 5, that is, the superimposed schematic diagram of the light spot scanning three steps along the positive y-axis direction, c1, c2, c3, b1, b2, b3, a1, a2, a3 are used to indicate the number of pulses that have been superimposed in different processing regions, the number of pulses is controlled by the length of h. The number of pulses which are overlapped at the three positions a1, b1 and c1 shown in (h) in fig. 5 is 1,2 and 3 respectively, and the number of pulses which are finally overlapped at the subsequent scanning of a2, b2, c2, a3, b3 and c3 is 1,2 and 3 respectively. Since the ablation depth of each pulse is equal, the more the number of superimposed pulses, the deeper the ablation depth is, so that a structure having different depths in the z direction as shown in fig. 5 (i) can be obtained.

The micro-grooves shown in fig. 6 are ablated on 200 μm thick single crystal silicon carbide wafers by using the micro-groove laser processing device to perform beam shaping and liquid 612 assisted ablation, designing the spot shape and adjusting the proper laser pulse energy and scanning parameters, wherein (j) and (n) are a group, (k) and (o) are a group, (l) and (p) are a group, (m) and (q) are a group, respectively representing triangular, W-shaped, stepped and T-shaped micro-grooves.

The micro-groove laser processing device provided by the invention can realize the laser scanning processing of the micro-groove with the controllable cross section according to the method implemented by the micro-groove laser processing device, reduce recasting and ablation product adhesion, improve the ablation quality of the micro-groove, and realize the micro-groove processing with freely adjustable cross section shape.

A micro-groove laser processing method according to an embodiment of the present application is described below with reference to fig. 7.

It will be appreciated that as shown in fig. 7, there is provided a micro-groove laser processing method applied to a micro-groove laser processing apparatus, the micro-groove laser processing apparatus comprising:

The laser focusing module 300, the laser focusing module 300 is used for controlling the light spot to focus on the corresponding position of the material 900 to be processed;

The micro-groove laser processing method comprises the following steps:

Emitting a laser beam;

Modulating the initial polarization light into oblique polarization light;

Deflecting the obliquely polarized light into deflected polarized light having the selected area and the non-selected area perpendicular to each other;

filtering the polarized light deflected in the non-selected area to obtain a light spot formed by the polarized light deflected in the selected area;

and focusing the light spot on the surface of the material 900 to be processed and processing to obtain the micro-groove.

It can be understood that the micro-groove laser processing device further comprises a light spot center adjusting module 400 and a semi-transparent and semi-reflective lens 500, wherein the light spot center adjusting module 400 comprises a second reflecting mirror 410, a first convex lens 420, a beam quality analyzer 430 and an angle adjusting module, the semi-transparent and semi-reflective lens 500 is used for reflecting a part of laser beams corresponding to light spots to the second reflecting mirror 410 so that the second reflecting mirror 410 reflects a part of the light spots to the beam quality analyzer 430 through the first convex lens 420, the beam quality analyzer 430 is used for analyzing the part of the light spots to obtain a light intensity distribution diagram, and the angle adjusting module is used for adjusting angles of the laser beams emitted by the laser source 100 according to the light intensity distribution diagram so that when the laser beams pass through the binary phase diagram, the centers of the laser beams coincide with the centers of the binary phase diagram loaded by the spatial light modulator 220;

The micro-groove laser processing method further includes the steps of adjusting the center of the spot so that the center of the laser beam coincides with the center of the binary phase diagram loaded by the spatial light modulator 220;

The center of the spot is adjusted so that the center of the laser beam coincides with the center of the binary phase diagram loaded by the spatial light modulator 220, comprising the steps of:

reflecting part of the light spots to obtain part of the light spots;

analyzing part of the light spots to obtain a light intensity distribution map;

the angle at which the laser source 100 emits the laser beam is adjusted according to the light intensity profile so that the center of the laser beam coincides with the center of the binary phase diagram loaded by the spatial light modulator 220.

It can be understood that the micro-groove laser processing device further comprises a liquid film control module 600, wherein the liquid film control module 600 is used for covering the liquid film on the surface of the material 900 to be processed according to a set thickness, and the laser focusing module 300 is also used for controlling the light spot to pass through the liquid film and focus on the corresponding position of the material 900 to be processed with the set liquid film thickness;

The micro-groove laser processing method further comprises the step of covering the liquid film on the surface of the material 900 to be processed according to the set thickness.

It may be appreciated that the liquid film control module 600 includes a peristaltic pump, a displacement stage 610, and a flow needle, where the displacement stage 610 is provided with a water tank 611, the water tank 611 is used for fixing the material 900 to be processed and accommodating the liquid 612 circularly flowing on the surface of the material 900 to be processed, the peristaltic pump is used for delivering the liquid 612 to the surface of the material 900 to be processed, and the flow needle is used for controlling the thickness of the liquid film on the surface of the material 900 to be processed to a set thickness;

the liquid film is covered on the surface of the material 900 to be processed according to the set thickness, and the method comprises the following steps:

delivering the liquid 612 to the surface of the material 900 to be processed in the trough 611;

the thickness of the liquid film on the surface of the material 900 to be processed is controlled to be a set thickness.

It can be understood that the micro-groove laser processing apparatus further comprises a focus detection module 700, a dichroic mirror 800, and a focus modulation module, wherein the laser focus module 300 comprises an objective lens 310, the focus detection module 700 comprises a coaxial light source 710, a beam splitter 720, a camera 730, and a first mirror 740, the coaxial light source 710 is used for emitting monochromatic light so that the monochromatic light sequentially passes through the dichroic mirror 800 and the objective lens 310 after being reflected by the beam splitter 720 and irradiates on the surface of the material 900 to be processed, the camera 730 is used for capturing the monochromatic light which is reflected by the surface of the material 900 to be processed and sequentially passes through the objective lens 310, the dichroic mirror 800, the beam splitter 720, and the first mirror 740 to form an image corresponding to the surface of the material 900 to be processed, and the focus modulation module is used for moving the objective lens 310 in a vertical direction according to the image so that a focus formed by a light spot passing through the objective lens 310 is focused on the surface of the material 900 to be processed;

the micro-groove laser processing method also comprises the steps of adjusting the focusing position of the light spot;

the focusing position of the light spot is adjusted, which comprises the following steps:

irradiating monochromatic light on the surface of the material 900 to be processed;

Capturing monochromatic light reflected by the surface of the material 900 to be processed to form an image corresponding to the surface of the material 900 to be processed;

objective 310 is moved in a vertical direction according to the image so that a focal point formed after the spot passes through objective 310 is focused on the surface of material 900 to be processed.

The focus detection module 700 of the present invention can keep the plane (focal plane for short) on which the focus of the laser beam is located on the sample surface, regardless of whether the sample surface is covered with the liquid film. Because the positioning of the laser focal plane is achieved by one coaxial light source 710 and camera 730, i.e. the combined positioning of a coaxial illumination LED (center wavelength 650 nm) and one CMOS camera 730, it has the same focal plane as the focused laser beam (center wavelength 520 nm). The laser focal plane can thus be guaranteed to be on the sample surface.

The laser processing method of the micro-groove of the present application is further described below.

The invention aims to solve the key technical problem of controllable processing of the cross section profile of the micro groove. The method solves the problems that the ablation product stays in a laser processing area to affect the subsequent laser energy deposition, and the method reshapes the light spots and adjusts the pulse overlapping rate of each part of the groove through the shape of the light spots. Therefore, the invention provides a groove processing device and a groove processing method for shaping laser-induced micro-jet assisted ablation, which can rapidly discharge ablation products, avoid deposition of ablation particles and obtain a groove section similar to a light spot shape.

The specific operation steps are as follows:

Step one, generating an ultrafast pulsed Gaussian laser beam by using an ultrafast laser.

And step two, the half wave plate 210 is adopted to modulate the initial polarized light output by the laser light source 100 into polarized light with an included angle of 45 degrees with the horizontal direction.

Step three, a binary phase diagram is loaded on the spatial light modulator 220, and gray values inside and outside the pattern on the binary phase diagram are different and correspond to 180 DEG and 0 DEG of phase delay of the phase type spatial light modulator 220 respectively. The linear polarized laser light of 45 ° in the second step is irradiated to the area where the binary phase diagram is loaded by the spatial light modulator 220, and after the laser light inside and outside the area undergoes different phase delays, the polarization direction is correspondingly deflected. The spot pattern finally modulated by the spatial light modulator 220 has polarized light perpendicular to each other inside and outside.

And step four, screening the modulated laser polarization by adopting a first polaroid 230. The first polarizer 230 allows only one direction of polarization to pass through, and can completely retain only the polarization inside or outside the pattern, resulting in the same laser spot as the design pattern.

The laser beam shaping method includes not only a method of loading binary phases by the spatial light modulator 220. Other ways such as loading the holographic phase diagram by the spatial light modulator 220 to generate a spot of a specific shape, and scanning the cross section of the groove with this shaped spot uses the same principle of ablation pulse superposition, and is also a derivative method of the present invention.

And fifthly, when a liquid film is required to be paved for processing, forming a liquid film with a specific thickness in a processing area of the material 900 to be processed by using the liquid film control module 600. First, a peristaltic pump is used to pump the liquid 612 contained in the open quartz vessel into a liquid 612 jet, the liquid 612 in the jet is ejected through a flow needle, and the liquid 612 passes through the jet at a specific flow rate to form a controllable-speed liquid 612 jet. The jet of liquid 612 impinges on the surface of the material 900 to be processed at an angle that will form a dynamically stable thin film of liquid, the thickness of the stable film of liquid 612 being one tenth of the diameter of the nozzle. The invention adjusts the thickness of the processed liquid film by selecting the diameter of the spray pipe, so that the processed liquid film is matched with the laser monopulse energy, and finally, the cavitation bubbles induced by laser can be asymmetrically collapsed under the thickness of the liquid film. The asymmetric collapse specifically means that the thickness of the liquid film is smaller than the diameter of the cavitation bubbles induced by laser, in this case, the upper surface of the spherical cavitation bubbles generated by the laser breakdown of the liquid 612 is located at the interface between the air and the liquid 612, and the movement of the bubbles and the surrounding flow field thereof is changed so as to meet the corresponding boundary conditions. Thus, when the bubble moves near the boundary, the pressure generated by the boundary will cause the bubble to preferentially collapse in a direction perpendicular to the boundary, i.e., an asymmetric collapse phenomenon.

Step six, the shaped laser beam is focused on the surface of the material 900 to be processed covered by the thin liquid film through a 4f system formed by the second convex lens 320 and the objective lens 310, namely, the laser focusing module 300. The laser beam irradiates the surface of the material 900 to be processed, causing ablation of the material 900 to be processed. Meanwhile, as shown in fig. 3, the laser induces cavitation bubbles in the liquid 612, and the cavitation bubbles collapse asymmetrically under the action of the free boundary, so as to generate high-speed microjet opposite to the scanning direction of the laser. The microjet carries debris and residual bubbles from the ablation back away from the ablation area.

And seventhly, under the processing environment without scraps and residual bubbles, scanning and processing by utilizing the shaped light spots, wherein the accumulated effective pulse numbers at different positions of the scanning section are linearly related to the light spot size. The locally accumulated number of effective pulses is different, resulting in a consequent variation of the ablation depth at various locations of the trench cross-section.

The micro-groove laser processing method can also detect and adjust the energy distribution of the light spots, and aims to ensure that the laser center coincides with the center of the binary phase diagram and utilize the energy of the light spot center as much as possible. The specific implementation steps are as follows:

Step one, reflecting a part of the shaped facula energy from a main light path to a beam quality analyzer 430 by using a semi-transparent semi-reflective lens 500;

Collecting reflected light energy by using a light beam quality analyzer 430 to form a light intensity distribution image;

And thirdly, adjusting the angle between the incident laser and the spatial light modulator 220 through an angle adjusting module, so that the laser center coincides with the pattern center of the binary phase diagram, and a shaping light spot with uniformly distributed energy is obtained.

It should be noted that, the half mirror 500 of the present invention reflects a part of light to the beam quality analyzer 430, and by on-line observation of the energy intensity of the reflected light spot, the coincidence of the light spot and the pattern center of the binary phase diagram can be accurately controlled.

Based on the above description, the present invention has the following effects:

In contrast to conventional machining, electro-discharge machining, etc., the present invention has no loss of machining tools and the shape of the grooves can be changed according to the loaded phase diagram without the need for custom-made special tools.

In a second aspect, in contrast to techniques for ablating grooves by varying laser processing parameters, the shape of the groove that can be processed by the present invention is not limited to U-shape and V-shape, and the degree of freedom in shape is greater.

In the third aspect, compared with the multi-scanning laser ablation of overlapping scanning paths, the method can process the micron-sized controllable groove through single scanning forming, and improves the processing efficiency.

The embodiments of the present application have been described in detail with reference to the accompanying drawings, but the present application is not limited to the above embodiments, and various changes can be made within the knowledge of one of ordinary skill in the art without departing from the spirit of the present application. Furthermore, embodiments of the application and features of the embodiments may be combined with each other without conflict.

Claims

1. Micro-groove laser beam machining device, its characterized in that includes:

The laser device comprises a laser light source, a light source and a light source, wherein the laser light source is used for emitting a laser beam, and the polarization of the laser beam is initial polarized light;

the micro-groove laser processing device further comprises a light spot center adjusting module and a semi-transparent semi-reflective lens, wherein the light spot center adjusting module comprises a second reflecting mirror, a first convex lens, a beam quality analyzer and an angle adjusting module, the semi-transparent semi-reflective lens is used for reflecting part of laser beams corresponding to the light spots to the second reflecting mirror so that the second reflecting mirror reflects part of the light spots to the beam quality analyzer through the first convex lens, the beam quality analyzer is used for analyzing part of the light spots to obtain a light intensity distribution diagram, and the angle adjusting module is used for adjusting angles of the laser beams emitted by the laser source according to the light intensity distribution diagram so that the centers of the laser beams coincide with the centers of the binary phase diagram when the laser beams pass through the binary phase diagram.

2. The micro-groove laser processing device according to claim 1, further comprising a liquid film control module for covering a liquid film on the surface of the material to be processed according to a set thickness, wherein the laser focusing module is further used for controlling the light spot to penetrate through the liquid film and focus on a corresponding position of the material to be processed with the set liquid film thickness.

3. The micro-groove laser processing apparatus according to claim 2, wherein the liquid film control module comprises a peristaltic pump, a displacement table, and a flow needle, the displacement table is provided with a water tank, the water tank is used for fixing the material to be processed and containing liquid flowing circularly on the surface of the material to be processed, the peristaltic pump is used for conveying the liquid to the surface of the material to be processed, and the flow needle is used for controlling the thickness of the liquid film on the surface of the material to be processed to be a set thickness.

4. The micro-groove laser processing device according to claim 1, further comprising a focus detection module, a dichroic mirror and a focusing modulation module, wherein the focus detection module comprises an objective lens, the focus detection module comprises a coaxial light source, a beam splitter, a camera and a first reflecting mirror, the coaxial light source is used for emitting monochromatic light, the monochromatic light sequentially passes through the dichroic mirror and the objective lens after being reflected by the beam splitter and irradiates the surface of a material to be processed, the camera is used for capturing the monochromatic light reflected by the surface of the material to be processed and sequentially passes through the objective lens, the dichroic mirror, the beam splitter and the first reflecting mirror to form an image corresponding to the surface of the material to be processed, and the focusing modulation module is used for moving the objective lens in the vertical direction according to the image so that a focus formed after the light spot passes through the objective lens is focused on the surface of the material to be processed.

5. The micro-groove laser processing method is characterized by being applied to a micro-groove laser processing device, wherein the micro-groove laser processing device comprises:

the micro-groove laser processing method comprises the following steps:

emitting the laser beam;

modulating the initial polarization light into the oblique polarization light;

Focusing the light spots on the surface of the material to be processed and processing the light spots to obtain micro grooves;

The micro-groove laser processing device further comprises a light spot center adjusting module and a semi-transparent and semi-reflective lens, wherein the light spot center adjusting module comprises a second reflecting mirror, a first convex lens, a beam quality analyzer and an angle adjusting module, the semi-transparent and semi-reflective lens is used for reflecting part of laser beams corresponding to the light spots to the second reflecting mirror so that the second reflecting mirror reflects part of the light spots to the beam quality analyzer through the first convex lens, the beam quality analyzer is used for analyzing part of the light spots to obtain a light intensity distribution diagram, and the angle adjusting module is used for adjusting angles of the laser beams emitted by the laser source according to the light intensity distribution diagram so that the centers of the laser beams coincide with the centers of the binary phase diagrams loaded by the spatial light modulator when the laser beams pass through the binary phase diagrams;

reflecting part of the light spots to obtain part of the light spots;

6. The micro-groove laser processing method according to claim 5, wherein the micro-groove laser processing device further comprises a liquid film control module, wherein the liquid film control module is used for covering a liquid film on the surface of the material to be processed according to a set thickness;

7. The micro-groove laser processing method according to claim 6, wherein the liquid film control module comprises a peristaltic pump, a displacement table and a flow needle, the displacement table is provided with a water tank, the water tank is used for fixing the material to be processed and containing liquid which circularly flows on the surface of the material to be processed, the peristaltic pump is used for conveying the liquid to the surface of the material to be processed, and the flow needle is used for controlling the thickness of the liquid film on the surface of the material to be processed to be a set thickness;

8. The micro-groove laser processing method according to claim 5, wherein the micro-groove laser processing device further comprises a focus detection module, a dichroic mirror and a focusing modulation module, wherein the laser focusing module comprises an objective lens, the focus detection module comprises a coaxial light source, a beam splitter, a camera and a first reflecting mirror, the coaxial light source is used for emitting monochromatic light, the monochromatic light sequentially passes through the dichroic mirror and the objective lens after being reflected by the beam splitter and irradiates the surface of a material to be processed, the camera is used for capturing the monochromatic light reflected by the surface of the material to be processed and sequentially passes through the objective lens, the dichroic mirror, the beam splitter and the first reflecting mirror to form an image corresponding to the surface of the material to be processed, and the focusing modulation module is used for moving the objective lens in the vertical direction according to the image so that a focus formed by the light spot after passing through the objective lens is focused on the surface of the material to be processed;