Preparation method of photon chip integrated microfluidic channel based on chemical mechanical polishing

Abstract

The invention discloses a preparation method of a photon chip integrated microfluidic channel based on chemical mechanical polishing. Comprising the following steps: plating a silicon dioxide film on a thin-film lithium niobate photon chip by chemical vapor deposition, plating a chromium film by magnetron sputtering, directly writing a chromium mask by femtosecond laser, chemically and mechanically polishing, grinding and etching a microfluidic channel structure, carrying out wet etching on the mask, packaging with an ultraviolet curing adhesive and the like. According to the method disclosed by the invention, chemical mechanical polishing etching is used for replacing traditional photoetching, and the ultra-precision machining advantage of chemical mechanical polishing and the technical characteristics of low cost, high efficiency and the like of the femtosecond laser direct writing mask are utilized, so that a high-precision and low-roughness two-dimensional complex microfluidic channel structure can be prepared on a photon chip on a large scale; the method can be applied to the fields of on-chip optical fluid sensing, photochemical analysis, environment monitoring and the like.

Description

Technical Field

[0001] This invention belongs to the interdisciplinary field of photonic integration and microfluidics, and involves the research and development and manufacturing of high-performance functional chips that integrate photonics and microfluidics, including photofluid sensing, integrated optical device packaging, and photonics and microfluidics. In particular, it relates to a method for preparing photonic chip integrated microfluidic channels based on chemical mechanical polishing. Background Technology

[0002] With the integration of photonics and microfluidics, photofluidic chips have become core devices for biosensing. Thin-film lithium niobate, due to its excellent optical properties and compatibility with optical waveguides, is an ideal substrate material, and its optical waveguides provide a high-quality platform for photofluid interactions. Currently, the integration of photonic chips and microfluidic channels mostly adopts traditional techniques such as photolithography, but bottlenecks are prominent when fabricating complex two-dimensional channels: photolithography relies on masks, and the development of complex patterns is costly and time-consuming, and the patterning accuracy on the silicon dioxide coating is insufficient; plasma etching easily damages the sidewalls of the channels, and ion bombardment can also damage the performance of the optical waveguides; the thickness of the silicon dioxide layer between the microfluidic channel and the optical waveguide is also difficult to control precisely, affecting the efficiency of photofluid interaction or damaging the device. In addition, problems such as poor packaging and sealing and difficulties in mask layer removal are also common. These defects jointly restrict the performance improvement and industrialization process of photofluidic chips, and there is an urgent need to develop a fabrication process for photonic chips integrating complex two-dimensional microfluidic channels based on chemical mechanical polishing. Summary of the Invention

[0003] The purpose of this invention is to overcome the problem of insufficient precision in the integrated application of photon transmission and fluid manipulation achieved by traditional photolithography, and to provide an alternative technical route for scenarios with stringent requirements for photofluid synergy performance, such as biomolecular detection, environmental monitoring, and photochemical analysis. It also provides core fabrication support for the development of high-sensitivity, miniaturized photofluid functional devices and promotes their industrial application.

[0004] The technical solution for achieving the objective of this invention is as follows:

[0005] A method for fabricating photonic chip integrated microfluidic channels based on chemical mechanical polishing includes the following steps:

[0006] Step 1: Prepare a thin-film lithium niobate photonic chip and deposit a silicon dioxide film:

[0007] 1-1, The thin-film lithium niobate photonic chip comprises three layers: the top layer is a lithium niobate single crystal thin film with a thickness of 300nm-900nm and an optical waveguide structure, the middle layer is a silicon dioxide layer with a thickness of 2μm-8μm, and the bottom layer is a single crystal silicon substrate with a thickness of 500μm-800μm.

[0008] The thickness of the lithium niobate single crystal thin film is selected according to the actual light source wavelength and evanescent field leakage requirements;

[0009] 1-2, On the surface of the thin-film lithium niobate photonic chip, a 4μm-10μm silicon dioxide film is deposited as a microfluidic channel structure layer using chemical vapor deposition.

[0010] Step 2: Chemically and mechanically polish the silicon dioxide film and then plate it with a chromium film.

[0011] 2-1. The thin-film lithium niobate photonic chip with a silicon dioxide film coated on its surface is bonded and fixed on the grinding adsorption plate of the grinding machine. A hard polishing pad and a large abrasive particle size polishing liquid are selected to coarsely polish the silicon dioxide film at a uniform speed. The polishing time is set to 45-90 seconds, the rotation speed is 25-40 revolutions per minute, and the pressure is 100-140 Torr. The protruding parts of the silicon dioxide film are removed to make the overall thickness uniform.

[0012] 2-2. Select a soft polishing pad and a small abrasive particle size polishing fluid to finely polish the silica film after coarse polishing in step 2-1 at a uniform speed. Set the polishing time to 20-40 seconds, the rotation speed to 10-20 revolutions per minute, and the pressure to 80-100 Torr to reduce the surface roughness of the silica film.

[0013] 2-3, A 100nm-500nm chromium film was deposited on the polished silicon dioxide film surface using magnetron sputtering as a mask layer for the microfluidic channel structure;

[0014] Step 3, Femtosecond laser direct writing of microfluidic channel structure mask layer:

[0015] The thin-film lithium photonic chip is fixed on a three-dimensional motion platform based on precise computer programming control. A femtosecond laser is focused onto the surface of the microfluidic channel structure mask layer. The three-dimensional motion platform is controlled, and the microfluidic channel structure mask pattern is constructed on the chromium film using femtosecond laser direct writing technology.

[0016] Step 4: Chemical mechanical polishing, grinding, and etching of the microfluidic channel structure:

[0017] 4-1. Fix the thin-film lithium photonic chip on the grinding adsorption plate of the grinding machine, select a hard polishing pad and a polishing slurry with a large abrasive particle size, set the polishing time to 150-360 seconds, the rotation speed to 25-40 revolutions per minute and the pressure to 100-140 Torr, and perform coarse polishing and grinding on the silicon dioxide film, so that the silicon dioxide film protected by the microfluidic channel structure mask pattern is not ground and etched, and the other silicon dioxide films not protected by the microfluidic channel structure mask pattern are ground and etched until the thickness of the silicon dioxide film above the optical waveguide is 50-100nm, forming a microfluidic channel structure;

[0018] 4-2. Select a soft polishing pad and a small abrasive particle size polishing slurry, set the polishing time to 30-50 seconds, the rotation speed to 10-20 revolutions per minute and the pressure to 80-100 Torr, and perform fine polishing, grinding and etching on the silicon dioxide film until the thickness of the silicon dioxide film above the optical waveguide is 10-20 nm, to ensure that an appropriate amount of evanescent field of the optical waveguide can leak into the microfluidic channel and reduce the surface roughness in the microfluidic channel;

[0019] Step 5: Chemically etch the chromium film of the microfluidic channel structure mask:

[0020] The thin-film lithium photonic chip polished and ground in step 4-1 was placed in a chromium etching solution. The etching time was controlled within 20 to 40 minutes and the temperature within 40 to 60 degrees Celsius. Combined with ultrasonic assistance, the remaining chromium film of the microfluidic channel structure mask layer after polishing and grinding was removed.

[0021] Step 6, Top cover plate coating and sealing:

[0022] 6-1. The thin film lithium niobate photonic chip after wet etching is observed in real time by dripping ultraviolet light curing adhesive into the non-microfluidic channel structure area of ​​the silicon dioxide film that has not been ground and polished.

[0023] 6-2. Select a glass cover plate with the same size as the thin-film lithium niobate photonic chip and a thickness of 0.5mm-1mm, polished on both sides. Move it to the top of the thin-film lithium niobate photonic chip described in step 6-1 and attach it tightly. Then, bond the cover plate to the thin-film lithium niobate photonic chip to obtain the integrated two-dimensional complex microfluidic channel of the photonic chip.

[0024] Furthermore, the optical waveguide cross-section of the lithium niobate single crystal thin film is rectangular or ridge-shaped.

[0025] The optical waveguide of the lithium niobate single crystal thin film is a straight strip, ribbed, micro-ring cavity, meandering, spiral, or racetrack-shaped waveguide.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] This invention uses chemical mechanical polishing (CMP) etching as the core method for microfluidic channel formation, directly replacing the photolithography process relied upon in traditional technologies. It also employs a combination of a chromium film metal mask layer and femtosecond laser direct writing, enabling the rapid and high-precision fabrication of complex two-dimensional microfluidic channels with significant cost and efficiency advantages.

[0028] 1) It provides an integrated fabrication route that is perfectly compatible with thin-film lithium niobate photonic chip substrates and can handle any two-dimensional complex microfluidic channel structure, solving the problem of the difficulty in accurately controlling the channel depth in traditional processes.

[0029] 2) A preparation method is provided, which optimizes the performance such as the uniformity of the microfluidic channel, the inner wall roughness, and the optical fluid coupling efficiency, and plays an important role in the characteristics such as optical fluid sensing and optical detection in integrated photonics.

[0030] 3) A complete process system from substrate treatment to cover plate packaging is provided. The packaging has strong sealing and high reliability, solves the problem of easy liquid leakage in traditional packaging, improves the service life of the chip, and lays a foundation for the industrial application of optical fluid chips. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic flow chart of the preparation method of the present invention;

[0032] Figure 2 It is a schematic structural diagram of a lithium niobate photonic chip with a micro-ring resonator and an "I"-shaped microfluidic channel;

[0033] Figure 3 It is a schematic structural diagram of an "I"-shaped microfluidic channel;

[0034] Figure 4 It is a three-dimensional schematic diagram after the "I"-shaped microfluidic channel is packaged with a cover plate;

[0035] Figure 5 It is a schematic structural diagram of a lithium niobate photonic chip with an array of straight waveguides and a rib-shaped microfluidic channel;

[0036] Figure 6 It is a schematic structural diagram of a rib-shaped microfluidic channel;

[0037] Figure 7 It is a three-dimensional schematic diagram after the rib-shaped microfluidic channel is packaged with a cover plate;

[0038] Figure 8 It is a schematic structural diagram of a lithium niobate photonic chip with a rib-shaped long waveguide and a stepped microfluidic channel;

[0039] Figure 9 It is a schematic structural diagram of a stepped microfluidic channel;

[0040] Figure 10 It is a three-dimensional schematic diagram after the stepped microfluidic channel is packaged with a cover plate.

[0041] In the figure, 1-deposit a silicon dioxide film on the surface of the thin-film lithium niobate photonic chip, 2-chemically mechanically polish the silicon dioxide film and deposit a chromium film, 3-femtosecond laser direct writing of the microfluidic channel structure mask layer, 4-chemically mechanically polishing and etching the microfluidic channel structure, 5-chemically etching the chromium film of the microfluidic channel structure mask layer, 6-top cover plate coating and sealing, 7-lithium niobate photonic chip, 8-lithium niobate thin film, 9-silicon dioxide layer, 10-single crystal silicon substrate, 11-silicon dioxide film, 12-chromium film, 13-UV curing adhesive, 14-cover plate, 15-lithium niobate optical waveguide structure, 16-microfluidic channel structure. Detailed Implementation

[0042] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the scope of protection of the present invention.

[0043] Example 1

[0044] like Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, the present invention discloses a method for integrating an "I"-shaped microfluidic channel into a thin-film lithium niobate microring cavity photonic chip using chemical mechanical polishing, comprising the following steps:

[0045] 1) Prepare a thin-film lithium niobate microring cavity (MRR) photonic chip and deposit a silicon dioxide film on its surface: The MRR photonic chip 7 is prepared by femtosecond lithography-assisted chemical mechanical polishing. The MRR photonic chip consists of a 300nm thick single-crystal X-cut lithium niobate thin film 8, a 2μm thick silicon dioxide layer 9 and a 500μm thick single-crystal silicon substrate 10. A 4μm thick silicon dioxide film 11 is deposited on the surface of the lithium niobate thin film 8 by chemical vapor deposition.

[0046] 2) Chemical mechanical polishing of silica film and chromium plating: The MRR chip with silica film deposited on its surface is fixed on the adsorption plate of the polishing machine by paraffin bonding. Diamond polishing pad and alumina polishing liquid are selected. The polishing time is set to 45 seconds, the rotation speed is 25 rpm, and the pressure is 100 Torr by computer program. The polishing machine is driven to perform coarse polishing of silica film 11 at a uniform speed. After correcting the surface flatness, a wool polishing pad and nano silica polishing liquid are selected. The polishing time is set to 20 seconds, the rotation speed is 10 rpm, and the pressure is 80 Torr for fine polishing to reduce surface roughness. Then, a 100nm chromium film 12 is magnetron sputtered on silica film 11.

[0047] 3) Femtosecond laser direct writing of microfluidic channel chromium mask: The MRR chip after chromium film is deposited is fixed on a three-dimensional motion platform. To ensure the focusing accuracy during the processing, the surface morphology of the chromium film layer is scanned in advance using a focus tracking system. The femtosecond laser is focused on the chromium film surface through a 0.7 numerical aperture objective lens. The lower computer and the femtosecond laser switch are controlled by software programming to complete the photolithography writing according to the preset "I" shaped microfluidic channel structure chromium mask pattern.

[0048] 4) Chemical Mechanical Polishing (CMP) Etching: The MRR chip is fixed on the adsorption plate of the polishing machine. A diamond polishing pad and an alumina polishing slurry are selected, and the polishing time is set to 150 seconds, the rotation speed is 25 rpm, and the pressure is 100 Torr to perform coarse polishing and grinding of the silicon dioxide film 11 to form a microfluidic channel structure. The thickness of the silicon dioxide film 11 above the optical waveguide without the protection of the chromium mask is 50 nm. Then, a wool polishing pad and a nano-silica polishing slurry are selected, and the polishing time is set to 30 seconds, the rotation speed is 10 rpm, and the pressure is 80 Torr to perform fine polishing to reduce the surface roughness in the groove of the microfluidic channel until the thickness of the silicon dioxide film 11 above the optical waveguide is 10 nm, so that an appropriate amount of evanescent field of the MRR chip optical waveguide can leak into the microfluidic channel.

[0049] 5) Wet etching of the mask film: The polished MRR chip is placed in a chromium etching solution, and the etching time is controlled within 20 to 40 minutes and the temperature is controlled within 40 to 60 degrees Celsius. Combined with ultrasonic assistance, the chromium film of the microfluidic channel structure mask layer on the surface is removed.

[0050] 6) Top cover plate coating and sealing: After wet etching, the MRR chip is placed under a microscope for real-time observation. An appropriate amount of UV-curable adhesive is applied to the non-microfluidic channel structure area of ​​the silicon dioxide film 11 using an automatic dispensing machine. A double-sided polished glass with the same size as the MRR chip and a thickness of 500μm is used as the cover plate 14. The cover plate is moved above the MRR chip and tightly attached using a precision displacement platform. The UV-curable adhesive is then irradiated with a UV light source to bond the cover plate to the MRR chip, thus creating an integrated "I"-shaped microfluidic channel on the lithium niobate micro-cavity photonic chip.

[0051] Example 2

[0052] See Figure 1 , Figure 5 , Figure 6 and Figure 7 This invention discloses a method for integrating ribbed microfluidic channels on a lithium niobate array waveguide photonic chip using chemical mechanical polishing, comprising the following steps:

[0053] 1) Prepare a thin-film lithium niobate array waveguide photonic chip and deposit a silicon dioxide film on its surface: Prepare an ultra-low loss array waveguide photonic chip 7 using femtosecond lithography-assisted chemical mechanical polishing technology. The array waveguide photonic chip consists of a 500nm thick single-crystal X-cut lithium niobate thin film 8, a 4.7μm thick silicon dioxide layer 9 and a 600μm thick single-crystal silicon substrate 10. A 7μm thick silicon dioxide film 11 is deposited on the surface of the lithium niobate thin film 8 by chemical vapor deposition.

[0054] 2) Chemical mechanical polishing of silica film and chromium plating: The array waveguide chip with silica film deposited on its surface is fixed on the adsorption plate of the polishing machine by paraffin wax. Diamond polishing pad and alumina polishing liquid are selected. The polishing time is set to 60 seconds, the rotation speed is 30 rpm, and the pressure is 120 Torr by computer program. The polishing machine is driven to perform coarse polishing of silica film 11 at a uniform speed. After correcting the surface flatness, a wool polishing pad and nano silica polishing liquid are selected and the polishing time is set to 30 seconds, the rotation speed is 15 rpm, and the pressure is 90 Torr for fine polishing to reduce surface roughness. Then, a 300nm chromium film 12 is magnetron sputtered on silica film 11.

[0055] 3) Femtosecond laser direct writing of microfluidic channel chromium mask: The array waveguide chip after chromium film is deposited is fixed on a three-dimensional motion platform. To ensure the focusing accuracy during the processing, the surface morphology of the chromium film layer is scanned in advance using a focus tracking system. The femtosecond laser is focused on the chromium film surface through a 0.7 numerical aperture objective lens. The lower computer and the femtosecond laser switch are controlled by software programming to complete the photolithography writing according to the preset rib-shaped microfluidic channel structure chromium mask pattern.

[0056] 4) Chemical mechanical polishing, grinding, and etching: The array waveguide chip is fixed on the adsorption plate of the polishing machine. A diamond polishing pad and an alumina polishing slurry are selected, and the polishing time is set to 260 seconds, the rotation speed is 30 rpm, and the pressure is 120 Torr to perform rough polishing and grinding on the silicon dioxide film 11 to form a microfluidic channel structure. The thickness of the silicon dioxide film 11 above the optical waveguide without the protection of the chromium mask is 70 nm. Then, a wool polishing pad and a nano-silica polishing slurry are selected, and the polishing time is set to 40 seconds, the rotation speed is 15 rpm, and the pressure is 90 Torr to perform fine polishing to reduce the surface roughness in the groove of the microfluidic channel until the thickness of the silicon dioxide film 11 above the optical waveguide is 15 nm, so that an appropriate amount of evanescent field of the array waveguide chip can leak into the microfluidic channel.

[0057] 5) Wet etching of the mask film: The polished array waveguide chip is placed in a chromium etching solution, and the etching time is controlled within 20 to 40 minutes and the temperature is controlled within 40 to 60 degrees Celsius. Combined with ultrasonic assistance, the chromium film of the microfluidic channel structure mask layer on the surface is removed.

[0058] 6) Top cover plate coating and sealing: After wet etching, the array waveguide chip is placed under a microscope for real-time observation. An appropriate amount of UV-curable adhesive is applied to the non-microfluidic channel structure area of ​​the silicon dioxide film 11 using an automatic dispensing machine. A double-sided polished glass with a thickness of 700μm and the same size as the array waveguide chip is used as the cover plate 14. The cover plate is moved above the array waveguide chip and tightly attached using a precision displacement platform. The UV-curable adhesive is then irradiated with a UV light source to bond the cover plate to the array waveguide chip, thus creating an integrated ribbed microfluidic channel on the lithium niobate array waveguide photonic chip.

[0059] Example 3

[0060] See Figure 1 , Figure 8 , Figure 9 and Figure 10 This invention discloses a method for integrating a stepped microfluidic channel pattern on a lithium niobate ribbed long-waveguide photonic chip using chemical mechanical polishing, comprising the following steps:

[0061] 1) Prepare a thin-film lithium niobate ribbed long waveguide photonic chip and deposit a silicon dioxide film on its surface: Prepare an ultra-low loss ribbed long waveguide photonic chip 7 using femtosecond lithography-assisted chemical mechanical polishing technology. The ribbed long waveguide photonic chip consists of a 900nm thick single-crystal Z-cut lithium niobate thin film 8, an 8μm thick silicon dioxide layer 9 and an 800μm thick single-crystal silicon substrate 10. A 10μm thick silicon dioxide film 11 is deposited on the surface of the lithium niobate thin film 8 by chemical vapor deposition.

[0062] 2) Chemical mechanical polishing of silicon dioxide film and chromium plating: The ribbed long waveguide chip with silicon dioxide film deposited on its surface is fixed on the adsorption plate of the polishing machine by paraffin wax. Diamond polishing pad and alumina polishing liquid are selected. The polishing time is set to 90 seconds, the rotation speed is 40 rpm, and the pressure is 140 Torr by computer program. The polishing machine is driven to perform coarse polishing of silicon dioxide film 11 at a uniform speed. After correcting the surface flatness, a wool polishing pad and nano silicon dioxide polishing liquid are selected and the polishing time is set to 40 seconds, the rotation speed is 20 rpm, and the pressure is 100 Torr for fine polishing to reduce the surface roughness. Then, a 500nm chromium film 12 is magnetron sputtered on silicon dioxide film 11.

[0063] 3) Femtosecond laser direct writing of microfluidic channel chromium mask: The ribbed long waveguide chip after chromium film is deposited is fixed on a three-dimensional motion platform. To ensure the focusing accuracy during the processing, the surface morphology of the chromium film layer is scanned in advance using a focus tracking system. The femtosecond laser is focused on the chromium film surface through a 0.7 numerical aperture objective lens. The lower computer and the femtosecond laser switch are controlled by software programming to complete the photolithography writing according to the preset stepped microfluidic channel structure chromium mask pattern.

[0064] 4) Chemical mechanical polishing, grinding, and etching: The ribbed long waveguide chip is fixed on the adsorption plate of the polishing machine. A diamond polishing pad and an alumina polishing slurry are selected, and the polishing time is set to 360 seconds, the rotation speed is 40 rpm, and the pressure is 140 Torr to perform rough polishing and grinding on the silicon dioxide film 11 to form a flow channel structure. The thickness of the silicon dioxide film 11 above the optical waveguide without the protection of the chromium mask is 100 nm. Then, a wool polishing pad and a nano-silica polishing slurry are selected, and the polishing time is set to 50 seconds, the rotation speed is 20 rpm, and the pressure is 100 Torr to perform fine polishing to reduce the surface roughness in the groove of the microfluidic channel until the thickness of the silicon dioxide film 11 above the optical waveguide is 20 nm, so that an appropriate amount of evanescent field of the ribbed long waveguide chip's optical waveguide can leak into the microfluidic channel.

[0065] 5) Wet etching of the mask layer: The polished ribbed long waveguide chip is placed in a chromium etching solution. The etching time is controlled within 20 to 40 minutes and the temperature is controlled within 40 to 60 degrees Celsius. Combined with ultrasonic assistance, the chromium film of the microfluidic channel structure mask layer on the surface is removed.

[0066] 6) Top cover plate coating and sealing: After wet etching, the ribbed long waveguide chip is placed under a microscope for real-time observation. An appropriate amount of UV-curable adhesive is applied to the non-microfluidic channel structure area of ​​the silicon dioxide film 11 using an automatic dispensing machine. A double-sided polished glass with the same size as the ribbed long waveguide chip and a thickness of 1 mm is used as the cover plate 14. The cover plate is moved above the ribbed long waveguide chip and tightly attached using a precision displacement platform. The UV-curable adhesive is then irradiated with a UV light source to bond the cover plate to the ribbed long waveguide chip, thus creating an integrated stepped microfluidic channel on the lithium niobate ribbed long waveguide photonic chip.

Claims

1. A method for fabricating photonic chip integrated microfluidic channels based on chemical mechanical polishing, comprising the following steps: Step 1: Prepare a thin-film lithium niobate photonic chip and deposit a silicon dioxide film: 1-1, The thin-film lithium niobate photonic chip (7) comprises three layers: the top layer is a lithium niobate single crystal thin film (8) with a thickness of 300nm-900nm and an optical waveguide structure, the middle layer is a silicon dioxide layer (9) with a thickness of 2μm-8μm, and the bottom layer is a single crystal silicon substrate (10) with a thickness of 500μm-800μm. 1-2, A 4μm-10μm silicon dioxide film (11) is deposited on the surface of the thin-film lithium niobate photonic chip (7) as a microfluidic channel structure layer; Step 2: Chemically and mechanically polish the silicon dioxide film and then plate it with a chromium film. 2-1, the thin-film lithium niobate photonic chip (7) with a silicon dioxide film coated on its surface is bonded and fixed on the grinding adsorption plate of the grinding machine. A hard polishing pad and a large abrasive particle size polishing liquid are selected to coarsely polish the silicon dioxide film (11) at a uniform speed. The polishing time is set to 45-90 seconds, the rotation speed is 25-40 revolutions per minute and the pressure is 100-140 Torr. The protruding part of the silicon dioxide film (11) is removed to make the overall thickness uniform. 2-2. Select a soft polishing pad and a small abrasive particle size polishing liquid to polish the silica film (11) after rough polishing in step 2-1 at a uniform speed. Set the polishing time to 20-40 seconds, the rotation speed to 10-20 revolutions per minute and the pressure to 80-100 Torr to reduce the surface roughness of the silica film (11). 2-3, A 100nm-500nm chromium film (12) is deposited on the surface of the polished silicon dioxide film (11) using magnetron sputtering as a mask layer for the microfluidic channel structure; Step 3, Femtosecond laser direct writing of microfluidic channel structure mask layer: The thin-film lithium photonic chip (7) is fixed on a three-dimensional motion platform based on precise computer programming control. A femtosecond laser is focused onto the surface of the microfluidic channel structure mask layer. The three-dimensional motion platform is controlled, and the microfluidic channel structure mask pattern is constructed on the chromium film layer (12) using the femtosecond laser direct writing process. Step 4: Chemical mechanical polishing, grinding, and etching of the microfluidic channel structure: 4-1. Fix the thin-film lithium photonic chip (7) on the grinding adsorption plate of the grinding machine, select a hard polishing pad and a large abrasive particle size polishing liquid, set the polishing time to 150-360 seconds, the rotation speed to 25-40 revolutions per minute and the pressure to 100-140 Torr, and perform rough polishing and grinding on the silicon dioxide film (11) so that the silicon dioxide film (11) protected by the microfluidic channel structure mask pattern is not ground and etched, and the other silicon dioxide films (11) not protected by the microfluidic channel structure mask pattern are ground and etched until the thickness of the silicon dioxide film (11) above the optical waveguide is 50-100nm, forming a microfluidic channel structure; 4-2. Select a soft polishing pad and a small abrasive particle size polishing slurry, set the polishing time to 30-50 seconds, the rotation speed to 10-20 revolutions per minute and the pressure to 80-100 Torr, and perform fine polishing, grinding and etching on the silicon dioxide film (11) until the thickness of the silicon dioxide film (11) above the optical waveguide is 10-20 nm, to ensure that an appropriate amount of evanescent field of the optical waveguide can leak into the microfluidic channel and reduce the surface roughness in the microfluidic channel; Step 5: Chemically etch the chromium film of the microfluidic channel structure mask: The thin-film lithium photonic chip (7) after polishing and grinding in step 4-1 was placed in a chromium etching solution. The etching time was controlled within 20 to 40 minutes and the temperature was controlled within 40 to 60 degrees Celsius. With the aid of ultrasound, the remaining microfluidic channel structure mask layer chromium film (12) after polishing and grinding was removed. Step 6, Top cover plate coating and sealing: 6-1. Real-time observation of the thin film lithium niobate photonic chip (7) after wet etching, and drop UV curing adhesive (13) onto the non-microfluidic channel structure area of ​​the silicon dioxide film (11) that has not been ground and polished; 6-2. Select a glass with the same size as the thin-film lithium niobate photonic chip (7) and a thickness of 0.5mm-1mm with double-sided polishing as a cover plate (14). Move it to the top of the thin-film lithium niobate photonic chip (7) described in step 6-1 and attach it tightly. Then, bond the cover plate (14) to the thin-film lithium niobate photonic chip (7) to obtain the photonic chip integrated two-dimensional complex microfluidic channel.

2. The method for fabricating photonic chip integrated microfluidic channels according to claim 1, characterized in that, The thickness of the lithium niobate single crystal thin film (8) is selected according to the actual light source band and evanescent field leakage requirements.

3. The method for fabricating photonic chip integrated microfluidic channels according to claim 1, characterized in that, The optical waveguide cross section of the lithium niobate single crystal thin film (8) is rectangular or ridge-shaped.

4. The method for fabricating photonic chip integrated microfluidic channels according to claim 1, characterized in that, The optical waveguide of the lithium niobate single crystal thin film (8) is a straight strip, ribbed, micro-ring cavity, meandering, spiral or racetrack-shaped waveguide.

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