Photoelectrochemical laser direct writing etching apparatus and maskless etching process

Abstract

This invention provides a photoelectrochemical laser direct writing etching apparatus and a maskless etching method. The photoelectrochemical laser direct writing apparatus includes a laser source, an acousto-optic modulator, a mirror, a lens, a spatial filter module, a filter objective, a dichroic mirror-beam splitter, and a focusing objective; an illumination source, a beam splitter, and an industrial camera; a motion controller and a moving sample stage. The moving sample stage is used to place the wafer to be etched. The laser generated by the laser source is redirected by a first and second mirror, then passes sequentially along a second straight line through the filter objective and the spatial filter module. The laser then passes through a third and fourth mirror before being emitted to the dichroic mirror-beam splitter. The reflected laser light passes sequentially through the dichroic mirror-beam splitter and the focusing objective, and is then emitted onto the wafer to be etched on the moving sample stage. This invention provides a maskless, high-efficiency, low-cost, and easy-to-operate photoelectrochemical laser direct writing method, which can realize the fabrication of complex free-form surface micro-optical components.

Description

Technical Field

[0001] This invention relates to the field of photoelectrochemical laser direct writing, and more particularly to a photoelectrochemical laser direct writing etching apparatus and a maskless etching process. Background Technology

[0002] Semiconductor freeform surface micro-optical elements possess advantages such as small size, light weight, flexible design, and high optical efficiency, and have broad potential applications in fields such as artificial intelligence, information processing, aerospace, biomedicine, and laser technology. However, fabricating three-dimensional freeform surface micro-optical elements with complex shapes is very difficult.

[0003] Photolithography is a key core technology in semiconductor manufacturing. Photolithography refers to the process of creating a pattern on a photosensitive substrate by exposing a designed pattern to sunlight. The photolithography process mainly includes steps such as resist coating, exposure, development, and etching, and is relatively complex. Among existing photolithography technologies, mask lithography and maskless lithography are the two main types. Although mask lithography is a mature technology, its smaller feature size means expensive mask processing costs, and the characteristics of masks determine their immutability, lacking versatility and flexibility.

[0004] In contrast, maskless lithography, with its high flexibility and variability, has attracted much attention and become a current research hotspot. Laser direct writing technology is one of the fastest-developing maskless lithography techniques. It reduces the energy beam to the micrometer and nanometer scale, then moves the substrate or energy beam to modify the photosensitive material at different locations on the substrate. This creates differences in the solubility of the exposed and unexposed areas in a special developing solution, thereby removing the patterned areas. Although maskless lithography has made significant progress in improving lithographic resolution, achieving nanometer-level resolution, its exposure efficiency is relatively low, and it has extremely high requirements for the working environment, resulting in high overall costs. Therefore, to further promote the development of freeform surface micro-optical components made of semiconductor materials and improve the integration of micro- and nano-manufacturing, developing a simple, easy-to-use, efficient, low-cost, and highly flexible maskless lithography technique is particularly important. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide a photoelectrochemical laser direct writing etching apparatus and a maskless etching process. Through photoelectrochemical laser direct writing, which is maskless, photoresist-free, highly efficient, low-cost, and easy to operate, the fabrication of free-form surface micro-optical components can be achieved.

[0006] To address the aforementioned technical problems, this invention provides a photoelectrochemical laser direct-write etching apparatus, comprising: a laser processing optical path, a microscopic and monitoring optical path, a host computer control system, and an electric displacement platform; wherein:

[0007] The laser processing optical path includes a laser source (1), an acousto-optic modulator (2), a first reflector (3), a filter objective (4), a spatial filter module (5), a second reflector (6), a third reflector (7), a fourth reflector (8), a dichroic mirror-beam splitter (9), and a focusing objective (10).

[0008] The microscopic and observation optical path includes an illumination source (11), a first lens (12), a second lens (13), a beam splitter (14), a third lens (15), and an industrial camera (16);

[0009] The electric displacement platform includes a motion controller (17) and a motion sample stage (18);

[0010] The moving sample stage is used to place the electrolytic cell (22) and the wafer to be etched (19), with the wafer to be etched (19) placed at the bottom of the electrolytic cell (22);

[0011] The control system includes a host computer (20) and a data acquisition card (DAQ) (21);

[0012] The laser generated by the laser source (1) passes through the acousto-optic modulator (2), is redirected by the reflector (3), and then passes through the filter objective (4) and the spatial filter module (5) in sequence along the second straight line. After passing through the first reflector (6), the second reflector (7), and the third reflector (8), the laser is emitted to the dichroic mirror-beam splitter (9). The reflected laser passes through the dichroic mirror-beam splitter (9) and the focusing objective (10) in sequence and is emitted to the wafer (19) to be etched on the moving sample stage (18).

[0013] The illumination light generated by the illumination source (11) is emitted sequentially through the first lens (12), the second lens (13), the beam splitter (14), the dichroic mirror-beam splitter (9), and the focusing objective (10) onto the wafer (19) to be etched on the moving sample stage (18). The illumination light reflected by the wafer (19) is emitted sequentially through the focusing objective (10), the dichroic mirror-beam splitter (9), the beam splitter (14), and the third lens (15) onto the industrial camera (16).

[0014] The host computer (20) is connected to the data acquisition card (DAQ) (21), and the laser light source (1), acousto-optic modulator (2), moving sample stage (18), and industrial camera (16) are all connected to the host computer (20) for communication.

[0015] In a preferred embodiment, the laser light source (1), the acousto-optic modulator (2), and the first reflector (3) are arranged sequentially along a first straight line in the horizontal direction;

[0016] The first reflecting mirror (3), the filter objective (4), the spatial filter module (5), and the second reflecting mirror (6) are arranged in sequence along the second straight line in the horizontal direction; the second reflecting mirror (6) and the third reflecting mirror (7) are arranged in sequence along the second straight line perpendicular to the horizontal direction; the third reflecting mirror (7) and the fourth reflecting mirror (8) are arranged in sequence along the first straight line in the direction of gravity; the fourth reflecting mirror (8) and the dichroic mirror-beam splitter (9) are arranged in sequence along the third straight line in the horizontal direction; the dichroic mirror-beam splitter (9), the focusing objective (10), and the moving sample stage (18) are arranged in sequence along the second straight line in the direction of gravity.

[0017] In a preferred embodiment, the industrial camera (16), the third lens (15), and the beam splitter (14) are arranged sequentially along a second straight line in the direction of gravity;

[0018] The industrial camera (16), the third lens (15), and the beam splitter (14) are located above the dichroic mirror-beam splitter (9), the focusing objective (10), and the moving sample stage (19); the illumination source (11), the first lens (12), the second lens (13), and the beam splitter (14) are arranged sequentially along the fourth straight line in the horizontal direction.

[0019] In a preferred embodiment, an active focusing procedure is also included, wherein the active focusing procedure adjusts the distance between the wafer to be etched (19) and the focusing objective lens (10) by moving the sample stage in the Z direction based on the image sharpness evaluation function via the host computer (20) and the sharpness of the surface image of the wafer to be etched (19) acquired by the industrial camera (16).

[0020] In a preferred embodiment, the moving sample stage (18) includes a high-precision piezoelectric ceramic displacement stage for carrying the wafer (19) to be etched and driving the wafer (19) to be etched to move in the XY direction.

[0021] The present invention also provides a maskless etching method, utilizing the photoelectrochemical laser direct writing etching apparatus described above, the maskless etching method comprising the following steps:

[0022] Step 1: Start the laser source (1), acousto-optic modulator (2), motion controller (17), industrial camera (16), and host computer (20);

[0023] Step 2: Place the wafer (19) to be etched at the bottom of the photoelectrochemical system electrolytic cell (22), and then place the electrolytic cell (22) on the horizontally moving sample stage (18) in the XY direction;

[0024] Step 3: Inject photoelectrochemical etching solution into the electrolytic cell (22) so that the etching solution covers the wafer (19) to be etched;

[0025] Step 4: Control the focusing objective (10) to approach the wafer (19) to be etched, and observe the clarity of the surface image of the wafer (19) to be etched by the industrial camera (16) through the host computer (20). Adjust the distance between the focusing objective (10) and the wafer (19) to be etched in the Z direction until the image is clear and the focusing is completed.

[0026] Step 5: Based on the three-dimensional topography data of the pre-processed freeform surface (x i y i , z i ) and calculate the processing data (x) based on the proportional relationship. i y i E i ), where E i The focused laser source (1) moves to (x) the surface of the wafer (19) to be etched. i y i The corresponding laser source (1) power control voltage signal; the proportional relationship is the height data z of the three-dimensional topography of the pre-processed freeform surface. i With laser source (1) power intensity I i The relationship between the ratio of the etching scan rate v and the etching scan rate v is expressed by the expression. Calculations are performed, where the value of a1 ranges from 0.001 to 10, and the value of b1 ranges from 0.001 to 10; the power intensity I of the laser source (1) ranges from 10. -4 ~10 6 W / cm 2 The power intensity I of the laser source (1) i The corresponding control voltage signal E i The correspondence between them is expressed by the expression E. i =a2×I i The calculation is performed using +b2, where the value of a2 ranges from 0.001 to 10, and the value of b2 ranges from 0.001 to 10.

[0027] Step 6: The focused laser source on the surface of the wafer (19) to be etched performs a scanning motion relative to the wafer (19) along a preset trajectory. The power intensity of the laser source (1) and the scanning motion trajectory are modulated in real time according to the calculated processing data (xi, yi, Ei). Finally, a predetermined free-form three-dimensional micro-nano structure is processed on the wafer (19) to be etched.

[0028] In a preferred embodiment, in step two, the material of the wafer to be etched (19) is silicon, germanium, gallium arsenide, gallium phosphide, indium phosphide, zinc sulfide or cadmium telluride, or a combination of at least two of the above materials.

[0029] In a preferred embodiment, in step three, the photoelectrochemical etching solution is composed of an etchant and a supporting electrolyte; the etchant is at least one selected from FeCl3, HNO3, HF, KMnO4, K2S2O8, and bromide, and the concentration of the etchant is 0.001–0.3 mol / L; the supporting electrolyte is at least one selected from hydrochloric acid, sulfuric acid, phosphate, and L-cysteine, and the concentration of the supporting electrolyte is 0.1–2 mol / L; the mass ratio of the etchant to the supporting electrolyte is 1:1 to 1:100.

[0030] In a preferred embodiment, in step four, the industrial camera (16) acquires images in real time and sends the acquired images to the host computer (20). The host computer (20) processes the images and monitors the photoelectrochemical laser direct writing process.

[0031] In a preferred embodiment, in step five, the scanning speed of the etching scanning motion is 0.001–10 mm / s.

[0032] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0033] (1) The purpose of this invention is to provide a photoelectrochemical laser direct writing etching device and a maskless etching process, which only requires a three-dimensional manipulation device, signal communication and related auxiliary facilities to complete the three-dimensional morphology processing of free-form surfaces. Compared with electron beam lithography and LIGA technology, this method does not require complex equipment and the processing technology is simple and easy to implement.

[0034] (2) The purpose of this invention is to provide a photoelectrochemical laser direct writing etching device and a maskless etching process. Compared with the three-beam direct writing technology, this method does not require expensive energy beam equipment and has low cost.

[0035] (3) The purpose of this invention is to provide a photoelectrochemical laser direct writing etching device and a maskless etching process. Since it is a photoelectrochemical induced process, the process is carried out in a solution, the environment is mild, and the surface and subsurface damage of the workpiece can be avoided.

[0036] (4) The purpose of this invention is to provide a photoelectrochemical laser direct writing etching device and a maskless etching process. During the process, the laser source does not contact the wafer to be etched, the wafer to be etched can avoid mechanical damage, and there are no special requirements for the properties of the wafer to be etched, so hard and brittle materials can be processed.

[0037] (5) The purpose of this invention is to provide a photoelectrochemical laser direct writing etching device and a maskless etching process, which is a single exposure and one-time forming process, thereby greatly reducing the processing complexity and improving the processing efficiency. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the photoelectrochemical laser direct writing device according to a specific embodiment of the present invention;

[0039] Figure 2 This is a schematic diagram of the processing steps according to a specific embodiment of the present invention;

[0040] Figure 3 This is a height map of the three-dimensional structure to be processed in Embodiment 1 of the present invention;

[0041] Figure 4 This is a diagram of the analog signal data of the processing voltage during the processing in Embodiment 1 of the present invention.

[0042] Figure 5 The image shows the surface morphology of gallium arsenide after processing in Example 1 of a specific embodiment of the present invention.

[0043] Figure 6 This is a microscope image of the processed gallium arsenide surface in Example 1 of a specific embodiment of the present invention.

[0044] Figure Labels

[0045] 1: Laser source; 2: Acousto-optic modulator; 3: First reflecting mirror; 4: Filter objective; 5: Spatial filter module; 6: Second reflecting mirror; 7: Third reflecting mirror; 8: Fourth reflecting mirror; 9: Dichroic mirror-beam splitter; 10: Focusing objective; 11: Illumination source; 12: First lens; 13: Second lens; 14: Beam splitter; 15: Third lens; 16: Industrial camera; 17: Motion controller; 18: Motion sample stage; 19: Wafer to be etched; 20: Host computer; 21: Data acquisition card (DAQ); 22: Electrolytic cell. Detailed Implementation

[0046] To make the technical solution and features of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. After reading the present invention, any modifications of the present invention in various equivalent forms by those skilled in the art fall within the scope defined by the appended claims.

[0047] like Figure 1As shown, the present invention provides a photoelectrochemical laser direct writing etching apparatus, which includes a laser source 1, an acousto-optic modulator 2, a first reflector 3, a filter objective 4, a spatial filter module 5, a second reflector 6, a third reflector 7, a fourth reflector 8, a dichroic mirror-beam splitter 9, and a focusing objective 10; the microscopic and observation optical path includes an illumination source 11, a first lens 12, a second lens 13, a beam splitter 14, a third lens 15, and an industrial camera 16; the electric displacement platform includes a motion controller 17 and a moving sample stage 18; the moving sample stage is used to place the wafer to be etched 19; the control system includes a host computer 20 and a data acquisition card DAQ 21.

[0048] Furthermore, in combination Figure 1 As shown, the laser source 1 and the acousto-optic modulator 2 are arranged sequentially along the first straight line. The generated laser light is redirected by the first reflecting mirror 3 and then passes sequentially along the second straight line through the filter objective lens 4 and the spatial filter module 5. After passing through the second reflecting mirror 6, the third reflecting mirror 7, and the fourth reflecting mirror 8, the laser light is emitted to the dichroic mirror-beam splitter 9. The reflected laser light passes sequentially through the dichroic mirror-beam splitter 9 and the focusing objective lens 10 and is emitted to the wafer 19 to be etched on the moving sample stage 18.

[0049] Furthermore, in combination Figure 1 As shown, the laser source 1, acousto-optic modulator 2, and first reflector 3 are arranged sequentially along a first straight line in the horizontal direction. The first reflector 3, filter objective 4, spatial filter module 5, and second reflector 6 are arranged sequentially along a second straight line in the horizontal direction. The second reflector 6 and third reflector 7 are arranged horizontally along a second straight line perpendicular to the horizontal direction. The third reflector 7 and fourth reflector 8 are arranged sequentially along a first straight line in the direction of gravity. The fourth reflector 8 and dichroic mirror-beam splitter 9 are arranged sequentially along a third straight line in the horizontal direction. The dichroic mirror-beam splitter 9, focusing objective 10, and moving sample stage 18 are arranged sequentially along a second straight line in the direction of gravity to ensure a collimated optical path with uniform energy distribution and a sufficiently small spot size focused on the sample surface.

[0050] Furthermore, in combination Figure 1As shown, the industrial camera CCD 16, the third lens 15, and the beam splitter 14 are arranged sequentially along the second straight line in the direction of gravity, and are located above the dichroic mirror-beam splitter 9, the focusing objective lens 10, and the moving sample stage 18. The illumination source 11, the first lens 12, the second lens 13, and the beam splitter 14 are arranged sequentially along the fourth straight line in the horizontal direction. The illumination light generated by the illumination source 11 is emitted sequentially through the first lens 12, the second lens 13, the beam splitter 14, the dichroic mirror-beam splitter 9, and the focusing objective lens 10 onto the wafer 19 to be etched on the moving sample stage 18. The illumination light reflected by the wafer 19 is emitted sequentially through the focusing objective lens 10, the dichroic mirror-beam splitter 9, the beam splitter 14, and the third lens 15 onto the industrial camera CCD 16, ensuring that the laser direct writing process can be monitored in real time by the camera CCD, while making the laser direct writing lithography device sufficiently compact.

[0051] Furthermore, in combination Figure 1 As shown, the photoelectrochemical laser direct writing etching device for processing three-dimensional micro-nano structures also includes an active focusing program. The active focusing program adjusts the distance between the wafer 19 to be etched and the focusing objective lens 10 based on the image sharpness evaluation function of the host computer 20 according to the sharpness of the image of the surface of the wafer 19 to be etched acquired by the industrial camera CCD 16, so as to ensure real-time focusing and guarantee processing accuracy.

[0052] Furthermore, in combination Figure 1 As shown, the motion sample stage 18 includes a high-precision piezoelectric ceramic displacement stage, which is used to support the wafer 19 to be etched and drive the wafer 19 to be etched to move in the XY direction, thereby realizing the processing of the preset free-form surface microstructure.

[0053] Furthermore, in combination Figure 1 As shown, the control system includes a host computer 20 and a data acquisition card DAQ21. The host computer 20 is connected to the data acquisition card DAQ21. The laser light source 1, the acousto-optic modulator 2, the moving sample stage 18, and the industrial camera 16 are all connected to the host computer 20 to ensure mutual communication of optical signals, electrical signals, and parameter signals, so as to realize the coordinated operation of each component.

[0054] like Figure 1 and Figure 2 As shown, this embodiment describes a maskless etching process using the aforementioned photoelectrochemical laser direct writing etching apparatus. The maskless etching process includes the following steps:

[0055] Step 1: Start the laser source, acousto-optic modulator, moving sample stage, industrial camera, and host computer;

[0056] Step 2: Place the wafer to be etched at the bottom of the photoelectrochemical system electrolytic cell, and then place the electrolytic cell on the horizontally moving sample stage in the XY direction;

[0057] Step 3: Inject photoelectrochemical etching solution into the electrolytic cell, ensuring the etching solution covers the wafer to be etched;

[0058] Step 4: Control the focusing objective lens to approach the wafer to be etched, observe the clarity of the image of the wafer surface captured by the industrial camera through the host computer, and adjust the distance between the focusing objective lens and the wafer to be etched in the Z direction until the image is clear, thus completing the focusing process.

[0059] Step 5: Based on the three-dimensional topography data x of the pre-processed freeform surface i y i , z i And calculate the processing data x based on the proportional relationship. i y i E i Where Ei is the focused laser source moving to x on the surface of the wafer to be etched. i y i The corresponding laser source power control voltage signal;

[0060] Step Six: The focused laser source on the surface of the wafer to be etched performs a scanning motion along a preset trajectory relative to the wafer, based on the calculated processing data x. i y i E i The laser source power intensity and scanning trajectory are modulated in real time to ultimately fabricate a predetermined free-form three-dimensional micro / nano structure on the wafer to be etched.

[0061] Furthermore, in combination Figure 2 As shown, in step two, the material of the wafer 19 to be etched is silicon, germanium, gallium arsenide, gallium phosphide, indium phosphide, zinc sulfide, or cadmium telluride, or a combination of at least two of these materials. This invention allows for the selection of different semiconductor materials for processing based on the specific laser light source wavelength.

[0062] Furthermore, in combination Figure 2 As shown, in step three, the photoelectrochemical etching solution is composed of an etchant and a supporting electrolyte. The etchant is at least one selected from FeCl3, HNO3, HF, KMnO4, K2S2O8, and bromide, and its concentration is 0.001–0.3 mol / L. The supporting electrolyte is at least one selected from hydrochloric acid, sulfuric acid, phosphate, and L-cysteine, and its concentration is 0.1–2 mol / L. The mass ratio of the etchant to the supporting electrolyte is 1:1 to 1:100. This invention allows for the selection of a suitable etching solution for different wafer materials to be etched.

[0063] Furthermore, in combination Figure 2 As shown, in step five, based on the three-dimensional topography data x of the pre-processed freeform surface... i y i , z i And calculate the processing data x based on the proportional relationship. i y i E i E i The focused laser source for etching the wafer surface is moved to x i y i The corresponding laser source power control voltage signal; the proportional relationship is the height data z of the three-dimensional topography of the pre-processed freeform surface. i With laser source 1 power intensity I i The relationship between the ratio of the etching scan rate v and the etching scan rate v is expressed by the expression. Calculations are performed, where the value of a1 ranges from 0.001 to 10, and the value of b1 ranges from 0.001 to 10; the power intensity I of the laser source 1 ranges from 10. -4 ~10 3 W / cm 2 The power intensity I of the laser source 1 i The corresponding control voltage signal E i The correspondence between them is expressed by the expression E. i =a2×I i The calculation is performed using +b2, where the value of a2 ranges from 0.001 to 10, and the value of b2 ranges from 0.001 to 10. This invention selects appropriate parameters based on the specific electrochemical system and the wafer material to be etched, and then processes the wafer to be etched.

[0064] Furthermore, in combination Figure 2 As shown, in step five, the etching scanning motion speed is 0.001–10 mm / s. This invention allows for the selection of appropriate scanning speeds based on different chemical systems and processing efficiencies, enabling efficient and rapid processing.

[0065] Example 1: Figure 3 A three-dimensional height map of the process to be processed according to the present invention is given. Figure 5 The surface morphology of gallium arsenide after processing according to the present invention is shown in the figure. Figure 6 Microscopic images of the gallium arsenide surface after processing according to this invention are provided. Processing conditions: the solution used contained 0.275 mol / L nitric acid and 0.870 mol / L HCl; before processing, the three-dimensional height map to be processed was prepared according to the formula... Converted into a processing signal diagram as follows Figure 4In the Z-direction, to ensure positioning accuracy, the moving sample stage in this embodiment is a piezoelectric ceramic displacement stage, which brings the focusing objective close to the wafer to be etched until it is focused. The moving sample stage is controlled to scan relative to the focusing laser source in the XY directions at a scanning speed of 50 μm / s. Simultaneously, the laser power and the displacement of the moving sample stage are adjusted according to the processing simulation voltage signal diagram described above. All movements in all directions are controlled by a motion controller via host computer software, and the laser source power is changed by an acousto-optic modulator controlled by host computer software. After the scanning movement is completed, the focusing objective is moved away from the wafer to be etched, thus obtaining a three-dimensional micro / nano structure consistent with the desired three-dimensional morphology.

[0066] The above is only one specific embodiment of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantial modifications made to the present invention using this concept shall be deemed as infringing the protection scope of the present invention.

Claims

1. A maskless etching process, characterized in that... A photoelectrochemical laser direct-write etching apparatus is used, comprising: a laser processing optical path, a microscopic and monitoring optical path, a host computer control system, and an electric displacement platform; wherein: The laser processing optical path includes a laser source (1), an acousto-optic modulator (2), a first reflector (3), a filter objective (4), a spatial filter module (5), a second reflector (6), a third reflector (7), a fourth reflector (8), a dichroic mirror-beam splitter (9), and a focusing objective (10). The microscopic and monitoring observation optical path includes an illumination source (11), a first lens (12), a second lens (13), a beam splitter (14), a third lens (15), and an industrial camera (16); The electric displacement platform includes a motion controller (17) and a motion sample stage (18); The moving sample stage is used to place the electrolytic cell (22) and the wafer to be etched (19), with the wafer to be etched (19) placed at the bottom of the electrolytic cell (22); The control system includes a host computer (20) and a data acquisition card (DAQ) (21); The laser generated by the laser source (1) is redirected by the reflector (3) after passing through the acousto-optic modulator (2) and then passes through the filter objective (4) and spatial filter module (5) in sequence along the second straight line. After passing through the second reflector (6), the third reflector (7) and the fourth reflector (8), the laser is emitted to the dichroic mirror-beam splitter (9). The reflected laser passes through the dichroic mirror-beam splitter (9) and focusing objective (10) in sequence and is emitted to the wafer (19) to be etched on the moving sample stage (18). The illumination light generated by the illumination source (11) is emitted sequentially through the first lens (12), the second lens (13), the beam splitter (14), the dichroic mirror-beam splitter (9), and the focusing objective (10) onto the wafer (19) to be etched on the moving sample stage (18). The illumination light reflected by the wafer (19) is emitted sequentially through the focusing objective (10), the dichroic mirror-beam splitter (9), the beam splitter (14), and the third lens (15) onto the industrial camera (16). The host computer (20) is connected to the data acquisition card (DAQ) (21), and the laser light source (1), acousto-optic modulator (2), moving sample stage (18), and industrial camera (16) are all connected to the host computer (20) for communication. The maskless etching process includes the following steps: Step 1: Start the laser source (1), acousto-optic modulator (2), motion controller (17), industrial camera (16), and host computer (20); Step 2: Place the wafer (19) to be etched at the bottom of the photoelectrochemical system electrolytic cell (22), and then place the electrolytic cell (22) on the horizontally moving sample stage (18) in the XY direction; Step 3: Inject photoelectrochemical etching solution into the electrolytic cell (22) until the etching solution covers the wafer (19) to be etched; Step 4: Control the focusing objective (10) to approach the wafer (19) to be etched, and observe the clarity of the surface image of the wafer (19) to be etched by the industrial camera (16) through the host computer (20). Adjust the distance between the focusing objective (10) and the wafer (19) to be etched in the Z direction until the image is clear and the focusing is completed. Step 5: Based on the three-dimensional topography data of the pre-processed freeform surface (x i y i , z i ) and calculate the processing data (x) based on the proportional relationship. i y i E i ), where E i The focused laser source (1) moves to (x) the surface of the wafer (19) to be etched. i y i The corresponding laser source (1) power control voltage signal; the proportional relationship is the height data z of the three-dimensional topography of the pre-processed freeform surface. i The relationship between the ratio of the power intensity of the laser source (1) and the etching scanning speed v is calculated using an expression, where the value of a1 ranges from 0.001 to 10, and the value of b1 ranges from 0.001 to 10; the power intensity I of the laser source (1) ranges from 10. -4 ~10 6 W / cm²; the control voltage signal E corresponding to the power intensity of the laser source (1) i The correspondence between them is calculated using an expression, where the value of a2 ranges from 0.001 to 10, and the value of b2 ranges from 0.001 to 10. Step Six: The focused laser source on the surface of the wafer (19) to be etched performs a scanning motion along a preset trajectory relative to the wafer (19), based on the calculated processing data (x... i y i E i The power intensity and scanning trajectory of the laser source (1) are modulated in real time, and the predetermined free-form three-dimensional micro-nano structure is finally processed on the wafer (19) to be etched.

2. The maskless etching process according to claim 1, characterized in that: In step two, the material of the wafer to be etched (19) is silicon, germanium, gallium arsenide, gallium phosphide, indium phosphide, zinc sulfide or cadmium telluride, or a combination of at least two of the above materials.

3. The maskless etching process according to claim 2, characterized in that: In step three, the photoelectrochemical etching solution is composed of an etchant and a supporting electrolyte; the etchant is at least one selected from FeCl3, HNO3, HF, KMnO4, K2S2O8, and bromide, and the concentration of the etchant is 0.001~0.3 mol / L; the supporting electrolyte is at least one selected from hydrochloric acid, sulfuric acid, phosphate, and L-cysteine, and the concentration of the supporting electrolyte is 0.1~2 mol / L; the mass ratio of the etchant to the supporting electrolyte is 1:1~1:

100.

4. The maskless etching process according to claim 1, characterized in that: In step four, the industrial camera (16) acquires images in real time and sends the acquired images to the host computer (20). The host computer (20) processes the images and monitors the photoelectrochemical laser direct writing process.

5. The maskless etching process according to claim 1, characterized in that: In step five, the scanning speed of the etching scanning motion is 0.001~10mm / s.

6. The maskless etching process according to claim 1, characterized in that: The laser source (1), the acousto-optic modulator (2), and the first reflector (3) are arranged sequentially along a first straight line in the horizontal direction; The first reflecting mirror (3), the filter objective (4), the spatial filter module (5), and the second reflecting mirror (6) are arranged in sequence along the second straight line in the horizontal direction; the second reflecting mirror (6) and the third reflecting mirror (7) are arranged in sequence along the second straight line perpendicular to the horizontal direction; the third reflecting mirror (7) and the fourth reflecting mirror (8) are arranged in sequence along the first straight line in the direction of gravity; the fourth reflecting mirror (8) and the dichroic mirror-beam splitter (9) are arranged in sequence along the third straight line in the horizontal direction; the dichroic mirror-beam splitter (9), the focusing objective (10), and the moving sample stage (18) are arranged in sequence along the second straight line in the direction of gravity.

7. The maskless etching process according to claim 1, characterized in that: The industrial camera (16), the third lens (15), and the beam splitter (14) are arranged sequentially along the second straight line in the direction of gravity; The industrial camera (16), the third lens (15), and the beam splitter (14) are located above the dichroic mirror-beam splitter (9), the focusing objective (10), and the moving sample stage (18); the illumination source (11), the first lens (12), the second lens (13), and the beam splitter (14) are arranged sequentially along the fourth straight line in the horizontal direction.

8. The maskless etching process according to claim 1, characterized in that: It also includes an active focusing program, which adjusts the distance between the wafer to be etched (19) and the focusing objective lens (10) by moving the sample stage in the Z direction based on the image sharpness evaluation function of the host computer (20) according to the sharpness of the image of the surface of the wafer to be etched (19) acquired by the industrial camera (16).

9. The maskless etching process according to claim 1, characterized in that: The moving sample stage (18) includes a high-precision piezoelectric ceramic displacement stage, which is used to support the wafer (19) to be etched and drive the wafer (19) to be etched to move in the XY direction.

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