CN117001174A

CN117001174A - Double-laser beam thinning method

Info

Publication number: CN117001174A
Application number: CN202311177376.5A
Authority: CN
Inventors: 周锐; 袁公发
Original assignee: Xiamen University
Current assignee: Xiamen University
Priority date: 2023-09-13
Filing date: 2023-09-13
Publication date: 2023-11-07

Abstract

The application provides a double laser beam thinning method, which comprises the following steps: step 1, fixing a sample to be processed, and then controlling the dual laser beams to focus on the surface of the sample to be processed; step 2, obtaining the diameter of a light spot and the frequency of laser formed by irradiating the surface of the sample to be processed with the double laser beams; step 3, adjusting the relative positions of two light spots formed by light beams in the double laser beams according to the light spot diameters, and ensuring that the edges of the two light spots of the double laser beams are tangent; step 4, determining an initial scanning speed according to the diameter of the light spot and the laser frequency; step 5, according to the thinning requirement, adjusting the thinning operation parameters of the sample to be processed and taking the thinning operation parameters as the double laser beam processing parameters; and 6, carrying out line parallel scanning on the surface of the sample to be processed according to the double laser beam processing parameters so as to finish the thinning work of the sample to be processed.

Description

Double-laser beam thinning method

Technical Field

The application relates to the technical field of material surface thinning, in particular to a double-laser-beam thinning method.

Background

Thinning is an important surface treatment technique and has wide application in the field of material processing. In the semiconductor industry, the method is widely used in chip manufacturing, and is used for improving the heat dissipation effect of chips, reducing the difficulty of a later packaging process and improving the quality and performance of the chips; in the brittle material industry, the glass is widely applied to photoelectric glass thinning, is suitable for 'thinning' of electronic products, improves the flexibility of the materials, can be bent to a certain extent, and improves the expressive force of the products; in the metal material industry, the metal alloy is widely applied to thinning of parts of aerospace, medical appliances and the like, can improve the processability, electrical conductivity, magnetism, thermal conductivity and the like of metal, and plays an important role in developing new materials and new processes. Existing methods for thinning the surface of materials (including semiconductor materials, brittle materials, metal materials, etc.) include mechanical grinding, chemical mechanical polishing, ion implantation, and the like. The mechanical grinding mode is simple to operate and low in equipment cost, but the problems of flatness and breakage rate of the material surface are considered. The chemical mechanical polishing and ion implantation modes are relatively complex, the cost is high, and the thinning effect with higher precision can be achieved, but the processing efficiency of the method is low. Currently, in order to improve the thinning efficiency of products, when thinning a material surface, a nanosecond laser is generally used to thin the surface of a workpiece to be processed. However, when the nanosecond laser is used for the thinning treatment, if the laser energy is high, a large roughness is generated on the surface of the sample during the thinning treatment, and the surface processing quality is reduced, so that the control of the time-space domain distribution of the laser energy is very critical, and a new process method for thinning the material surface by the laser is needed.

Disclosure of Invention

Aiming at the problems in the prior art and the defects in the prior art, the application mainly aims to provide a double-laser beam thinning method which aims to solve the problems of low efficiency, poor quality and the like of a laser thinned sample to be processed.

In order to solve the technical problems, the application provides a double-laser beam thinning method, which adopts the following technical scheme:

the double laser beam thinning method includes laser and light splitting device for splitting the laser beam emitted by the laser into two laser beams to form double laser beam, and the method includes the following steps:

step 1, fixing a sample to be processed, and then controlling the dual laser beams to focus on the surface of the sample to be processed;

step 2, obtaining the diameter of a light spot and the frequency of laser formed by irradiating the surface of the sample to be processed with the double laser beams;

step 3, adjusting the relative positions of two light spots formed by light beams in the double laser beams according to the light spot diameters, and ensuring that the edges of the two light spots of the double laser beams are tangent;

step 4, determining an initial scanning speed according to the spot diameter and the laser frequency, wherein when the overlapping degree of two spots of the double laser beams is 40% -70%, the corresponding scanning speed is the initial scanning speed;

step 5, according to the thinning requirement, adjusting the thinning operation parameters of the sample to be processed and taking the thinning operation parameters as the double laser beam processing parameters;

and 6, carrying out line parallel scanning on the surface of the sample to be processed according to the double laser beam processing parameters so as to finish the thinning work of the sample to be processed.

In a preferred embodiment, in step 2, the spot diameter is a spot diameter corresponding to energy of a laser beam used in laser thinning; the measuring mode of the spot diameter is that an optical microscope is used for shooting a spot picture processed by double laser beams on the surface of a sample to be processed, and then the spot diameter of the processed spot picture is measured;

the spot diameter is the average value of the spot diameters measured at 3 different angles.

In a preferred embodiment, in step 3, the edges of the two light spots are tangent, and whether the edges of the two light spots of the dual laser beams are tangent is determined according to a picture taken by an optical microscope, wherein the space position of the tangent is a line in the scanning direction, and the central connecting line of the two light spots is parallel to the line scanning direction.

In a preferred embodiment, in step 4, the line spacing of the scanning between the dual laser beams is determined according to the spot diameter, so that the two spots of the dual laser beams have an overlapping degree of 40% -70%;

the overlapping degree is the overlapping degree of light spots corresponding to laser beams with larger intensity in the double laser beams; the line interval is the center line distance of the two light spots of the double laser beams.

In a preferred embodiment, the laser includes, but is not limited to, an ultraviolet pulse laser, an infrared pulse laser, a green pulse laser.

In a preferred embodiment, the beam splitting device includes a beam expander, a half-wave plate, a first polarization splitting prism, a second polarization splitting prism and a galvanometer, which are sequentially arranged along the laser emission line;

the beam expander expands the passed laser; the half-wave plate carries out polarization adjustment on the passed laser; the first polarization beam splitting prism divides the passing laser into two laser beams; and the second polarization splitting prism combines the two passed laser beams.

In a preferred embodiment, at least one pair of mirrors is disposed on the optical paths of the two laser beams, for adjusting the optical paths, so that the two laser beams are combined by the second polarization splitting prism.

In a preferred embodiment, at least one pair of reflectors is arranged on the optical path of the two combined laser beams, and the reflectors are used for adjusting the optical path so that the two combined laser beams are injected into the vibrating mirror and then are emitted to thin the sample to be processed.

In a preferred embodiment, the half-wave plate adjusts the energy ratio of the two laser beams so that the energy of one laser beam accounts for 10% -50% of the total energy of the laser beams.

In a preferred embodiment, in step 6, the line parallel scanning is divided into a line scanning along a vertical direction and a line scanning along a horizontal direction;

the scanning direction is line scanning along the vertical direction and line scanning along the horizontal direction sequentially.

In summary, the application has the following beneficial effects:

1. the application provides a double-laser beam thinning method, which is used for controlling double laser beams to focus on the surface of a sample to be processed, carrying out line parallel scanning on the surface of the sample to be processed to realize the thinning operation of the sample to be processed, and carrying out shaping and modification on the surface of the sample to be processed, so that the surface evenness of the sample to be processed is better, the processing efficiency is higher, and the processing quality can be improved.

2. According to the double-laser-beam thinning method provided by the application, the laser is controlled to uniformly scan the surface of the sample to be processed, so that the surface of the sample to be processed is thinned efficiently. The laser thinning method is safe and reliable, saves energy, and has high flexibility, high controllability and high accuracy. The flatness of the thinned surface of the substrate material is within an allowable range, and the thinning efficiency of the substrate material is improved.

3. The double laser beam thinning technology provided by the application is expected to realize high-quality processing. The method comprises the steps of introducing two laser beams to thin the surface of a sample, wherein the laser beams are divided into a high-energy laser beam and a low-energy laser beam, the low-energy laser beam preheats the surface of a material, and the high-energy laser beam follows the material to thin the surface of the sample; on the premise of preheating treatment, the laser ablation threshold is lowered, so that the sample surface can be thinned by adopting a high-energy laser beam with energy lower than that of a single laser beam. And meanwhile, as the energy of the laser used for thinning is lower, less scraps are generated, and the surface processing quality is improved.

4. Compared with single laser beam processing, the double laser beam has the following two main advantages, namely that the surface processing quality can be improved, and the processed surface is subjected to plastic modification to make the surface smoother. The low-energy laser beam preheats the workpiece to be processed, reduces the ablation threshold of the laser, and processes the preheated surface by the high-energy laser beam, so that the sample surface can be processed by the laser beam with lower energy than the single laser beam. Meanwhile, as the laser beam energy adopted by the processing is lower, the generated processing scraps are less, and the surface processing quality is improved. Meanwhile, when the surface of the sample piece is processed for a plurality of times, the low-energy laser beam can be used for recasting and shaping small particles on the surface of the sample piece, so that the surface is smoother. Therefore, the dual laser beam processing method is expected to solve the problems existing in the single laser thinning and further improve the thinning efficiency.

Drawings

FIG. 1 is a schematic diagram of a system structure of a dual laser beam thinning method employed in the present application;

FIG. 2 is a schematic flow chart of a method for preparing a dual laser beam thin film according to the present application;

FIG. 3 is a schematic diagram of the application using dual laser beams to scan the spot position and scanning pattern of a sample to be processed;

FIG. 4 is a schematic three-dimensional morphology of a silicon-based sample prepared by a dual laser beam thinning method according to a first embodiment;

fig. 5 is a schematic view showing a thinning depth of a silicon-based sample prepared by a dual laser beam thinning method according to the first embodiment.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application; it is apparent that the described embodiments are only some embodiments of the present application, not all embodiments, and that all other embodiments obtained by persons of ordinary skill in the art without making creative efforts based on the embodiments in the present application are within the protection scope of the present application.

In the description of the present application, it should be noted that the positional or positional relationship indicated by the terms such as "upper", "lower", "inner", "outer", "top/bottom", etc. are based on the positional or positional relationship shown in the drawings, are merely for convenience of describing the present application and simplifying the description, and do not indicate or imply that the apparatus or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present application. Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present application, unless explicitly specified and limited otherwise, the terms "mounted," configured to, "" engaged with, "" connected to, "and the like are to be construed broadly, and may be, for example," connected to, "wall-mounted," connected to, removably connected to, or integrally connected to, mechanically connected to, electrically connected to, directly connected to, or indirectly connected to, through an intermediary, and may be in communication with each other between two elements, as will be apparent to those of ordinary skill in the art, in view of the detailed description of the terms herein.

The application is described in further detail below with reference to fig. 1-3.

The embodiment of the application discloses a double-laser-beam thinning method, which comprises a laser and a beam splitting device, wherein the beam splitting device is used for splitting laser emitted by the laser into two beams of laser so as to form double laser beams.

The specific implementation mode is as follows:

the double laser beam thinning method provided by the embodiment comprises the following steps:

step 4, determining an initial scanning speed according to the spot diameter and the laser frequency, wherein when the overlapping degree of two spots of the double laser beams is 40% -70%, the corresponding scanning speed is the initial scanning speed (wherein, the setting of the corresponding spot diameter of the laser beams and the setting of the laser frequency are adjusted according to the actual thinning processing requirement and the thinning process requirement of the corresponding material);

In order to implement the above-mentioned method for thinning the dual laser beams, the surface of the sample to be processed is thinned, and this embodiment provides a processing structure of a laser and a beam splitting device as shown in fig. 1, where the beam splitting device includes a beam expander 1, a half-wave plate 2, a first polarization beam splitter prism 3, a second polarization beam splitter prism 9, and a galvanometer 10, which are sequentially arranged along the laser emission line.

The beam expander 1 expands the passing laser beam; the half-wave plate 2 carries out polarization adjustment on the passed laser; the first polarization splitting prism 3 divides the passing laser into two laser beams; the second polarization splitting prism 9 combines the two laser beams passing through.

And at least one pair of reflectors are arranged on the optical paths of the two laser beams for optical path adjustment, so that the two laser beams are combined through the second polarization splitting prism 9. At least one pair of reflectors are arranged on the optical path of the two laser beams after beam combination, and are used for optical path adjustment so that the two laser beams after beam combination are incident into the vibrating mirror 10, and then the light is emitted to thin the sample 11 to be processed.

In this embodiment, the laser is an ultraviolet pulse laser. It should be noted that, the lasers in the present embodiment include, but are not limited to, the lasers proposed in the present embodiment, and other lasers, such as an infrared pulse laser, a green pulse laser, etc., are all simple alternatives to the present embodiment. The half wave plate can adjust the energy ratio of the two laser beams, so that the energy of one laser beam accounts for 10% -50% of the total energy of the laser beams.

The specific light path route of the beam splitting device is that the beam is expanded through the beam expander 1, the polarized beam splitter prism 3 divides the beam into two beams of laser beams P and S, the energy ratio of the two beams of laser beams is adjusted through the half-wave plate 2 at the outlet of the rotary laser, one beam of laser beam is subjected to light path adjustment through the first reflecting mirror 6 and the second reflecting mirror 7, the other beam of laser beam is adjusted through the third reflecting mirror 4 and the fourth reflecting mirror 5, the two beams of laser beams are injected into the second polarized beam splitter prism 9 for beam combination after being adjusted through the reflecting mirrors, and then are injected into the vibrating mirror 10 after being adjusted through the fifth reflecting mirror 8, and further the light is emitted to thin the sample 11 to be processed.

In this embodiment, in step 1, the step of fixing the sample to be processed includes: clamping the sample to be processed; and detecting the current clamping state of the sample to be processed.

The step of controlling the double laser beams to focus on the surface of the sample to be processed comprises the step of controlling a laser to emit laser; and starting a focusing lens to focus and irradiate the laser on the surface of the sample to be processed.

Wherein the double laser beams are homologous laser beams. The laser beam can be emitted by pulse lasers such as ultraviolet, infrared, green light and the like, and then divided into two beams of P and S laser by a polarization beam splitter prism.

In this embodiment, in step 2, the diameter of the light spot formed by irradiating the surface of the sample to be processed with the dual laser beams is the diameter of the light spot corresponding to the energy used for laser thinning, and the measurement method is to take a picture of the light spot processed by the dual laser beams on the surface of the sample by using an optical microscope, measure the diameter of the light spot formed on the surface of the silicon wafer, select different angles to measure the two light spots three times respectively, and average the two light spots to obtain the diameter of the light spot of the two laser beams.

In this embodiment, in step 3, the edges of the two light spots of the dual laser beam are tangent, and it is determined whether the edges of the two light spots of the dual laser beam are tangent according to the image captured by the optical microscope, and the spatial position of the tangent is along the line scanning direction 16, and the center line of the two light spots is parallel to the line scanning direction, as shown in fig. 3.

In this embodiment, in step 4, the line spacing 14 scanned between the dual laser beams is determined according to the spot diameter, so that the two spots of the dual laser beams overlap by between 40% and 70%, wherein the overlap is optimally set at 50%; the overlapping degree is the overlapping degree of light spots corresponding to laser beams with larger intensity in the double laser beams; the line interval is the center line connecting distance 15 between two light spots of the dual laser beams, and when the center line connecting distance 15 between two light spots is the radius length of the light spot corresponding to the laser beam, the corresponding overlapping degree is the overlapping degree of the light spots, as shown in fig. 3.

Specifically, the line spacing of the dual laser beam scanning is determined according to the spot diameter, the line spacing 14 is the scanning line spacing of the light spots, as shown in fig. 3, the diameter of the light spot 12 corresponding to the high-energy laser beam is 13 μm-18 μm, and the diameter of the light spot 13 corresponding to the low-energy laser beam is 8 μm-15 μm.

In this embodiment, in step 6, the line parallel scanning is divided into a line scanning in a vertical direction and a line scanning in a horizontal direction; the scanning direction is line scanning along the vertical direction and line scanning along the horizontal direction sequentially. As shown in fig. 3, the surface of the silicon wafer is scanned in a line parallel manner according to the double laser beam processing parameters, the silicon wafer is scanned in a line manner along the vertical direction 16, and the silicon wafer is sequentially scanned in a line manner along the horizontal direction 17.

The dual laser beam thinning method provided in the present embodiment may be used for thinning the surfaces of semiconductor materials, metal materials, brittle materials, and the like. The overlapping degree of two light spots of the double laser beams can be adjusted between 40% and 70% according to the composition of the surface material of the sample to be processed so as to meet the requirements of surface processing of different brittle materials, semiconductor materials, metal materials and the like, and meanwhile, the overlapping degree can be adjusted according to the thickness requirement of thinning when the surface of the brittle materials is thinned so as to meet the thickness requirement of thinning when the surface of the brittle materials is thinned.

Specifically, the present embodiment provides a processing method for performing surface thinning of a dual laser beam using a silicon-based material as an example, as a first embodiment, and is specifically implemented as follows:

a method for thinning the surface of a silicon-based material by double laser beams is provided, which comprises the following steps:

1. clamping the silicon-based sample to be processed; and detecting the current clamping state of the silicon-based sample to be processed.

2. Controlling a laser to emit laser; and starting a focusing lens to focus and irradiate the laser on the surface of the silicon-based sample to be processed (wherein the energy ratio of two laser beams is adjusted by rotating a half-wave plate 2 at the outlet of the laser so that the energy of one laser beam accounts for 20% of the total energy of the laser beams).

3. And adjusting the diameter of a light spot of the laser irradiated on the surface of the silicon-based sample to be processed, so that the diameter of a light spot 12 corresponding to one light spot corresponding to a high-energy laser beam formed on the surface of the silicon-based sample to be processed is 15 mu m, the diameter of a light spot 13 corresponding to the other light spot corresponding to the energy laser beam is 10 mu m, and the laser frequency is set at 50kHz.

4. And adjusting the relative position of the double laser beam spots according to the spot diameter to ensure the edge tangency of the laser spots.

5. The initial scanning speed determined according to the spot diameter and the laser frequency is 400mm/s.

6. And determining the line spacing of laser scanning according to the light spot diameter, determining the light spot overlapping degree corresponding to the high-energy laser beam according to the line spacing, adjusting the light spot overlapping degree to be about 50%, and optimally setting the overlapping degree to be 50%.

7. According to the silicon-based thinning requirement, the thinning operation parameters of the silicon-based sample to be processed are adjusted, and the laser processing parameters adopted in the embodiment are as described above, and the double laser beam scanning times are 30 times;

8. and carrying out thinning treatment on the surface of the silicon-based sample to be processed according to the double laser beam processing parameters, carrying out line scanning along the vertical direction 16, and carrying out line scanning processing in sequence along the horizontal direction 17 to finish the thinning work of the silicon-based sample to be processed.

In this embodiment, in step 2, the dual laser beam processing parameters are: the total power of the laser is 1.50W, the powers of the two laser beams are 1.2W and 0.30W respectively, the center distance of the light spots of the two laser beams is 12.5 mu m, the wavelength is 355nm, the laser pulse frequency is 50kHz, the pulse duration is less than 20ns, and the scanning speed is 400mm/s.

As shown in fig. 4, a three-dimensional morphology of a sample prepared by the dual laser beam silicon-based thinning method according to the present application is shown, wherein the red region is an un-thinned silicon-based region, and the blue region is a thinned silicon-wafer region.

As shown in FIG. 5, a schematic view of the thinning depth of the sample prepared by the dual laser beam silicon-based thinning method according to the present application is shown, wherein the thinning depth is 100.44 μm, and the height difference between the lowest point and the highest point is 6.05. Mu.m.

The above embodiments are not intended to limit the scope of the present application, so: all equivalent changes in structure, shape and principle of the application should be covered in the scope of protection of the application.

Claims

1. A double laser beam thinning method is characterized in that: the method comprises the following steps of:

2. A dual laser beam thinning method according to claim 1 and characterized in that: in the step 2, the diameter of the light spot is the diameter of the light spot corresponding to the energy of the laser beam adopted in laser thinning; the measuring mode of the spot diameter is that an optical microscope is used for shooting a spot picture processed by double laser beams on the surface of a sample to be processed, and then the spot diameter of the processed spot picture is measured;

3. A dual laser beam thinning method according to claim 1 and characterized in that: in step 3, the edges of the two light spots are tangent, whether the edges of the two light spots of the double laser beams are tangent or not is judged according to the picture shot by the optical microscope, the tangent space position is a line in the scanning direction, and the central connecting line of the two light spots is parallel to the line scanning direction.

4. A dual laser beam thinning method according to claim 1 and characterized in that: in step 4, determining the line interval of scanning between the double laser beams according to the spot diameter so that the two spots of the double laser beams have 40% -70% overlapping degree;

5. A dual laser beam thinning method according to claim 1 and characterized in that: including but not limited to ultraviolet pulsed lasers, infrared pulsed lasers, green pulsed lasers.

6. A dual laser beam thinning method according to claim 1 and characterized in that: the beam splitting device comprises a beam expanding lens, a half wave plate, a first polarization beam splitting prism, a second polarization beam splitting prism and a vibrating lens which are sequentially arranged along laser emission rays;

7. A dual laser beam thinning method according to claim 6 and characterized in that: at least one pair of reflectors are arranged on the optical path of the two laser beams and used for optical path adjustment, so that the two laser beams are combined through the second polarization beam splitting prism.

8. A dual laser beam thinning method according to claim 7 and characterized in that: at least one pair of reflectors are arranged on the optical path of the two laser beams after beam combination and used for optical path adjustment so that the two laser beams after beam combination are injected into the vibrating mirror and then are emitted out to thin the sample to be processed.

9. A dual laser beam thinning method according to claim 6 and characterized in that: the half-wave plate adjusts the energy ratio of the two laser beams, so that the energy of one laser beam accounts for 10% -50% of the total energy of the laser beams.

10. A dual laser beam thinning method according to claim 1 and characterized in that: in step 6, the line parallel scanning is divided into a line scanning along a vertical direction and a line scanning along a horizontal direction;