A fan-shaped ion focusing lens based on a MEMS process and a preparation method thereof

Abstract

The application discloses a fan-shaped ion focusing lens based on a MEMS process and a preparation method thereof, and relates to the field of mass spectrometers. In view of the problems of difficult processing and insufficient unidirectional focusing of the existing micro ion lens, the application adopts a first wafer, a second wafer and a third wafer laminated bonding structure, the third wafer is provided with a hollow area to form an ion flow channel, the first wafer and the second wafer are provided with three groups of fan-shaped ion focusing electrodes on the inner sides, and the TGV electrode and the pad are electrically connected. The preparation method comprises wafer micropore and electrode manufacturing, intermediate layer through hole processing and femtosecond laser wafer level packaging. The application realizes wafer level miniaturization and batch manufacturing of the ion lens, utilizes the multi-stage fan-shaped ion focusing electrode to form a non-uniform electrostatic field in the horizontal and vertical directions, realizes bidirectional focusing of the ion beam, effectively reduces the beam spot size, improves the transmission efficiency, and is convenient for integration with other planar mass spectrometry components.

Description

Technical Field

[0001] This invention patent relates to the field of mass spectrometer design and manufacturing, specifically to a fan-shaped ion focusing lens based on MEMS technology and its fabrication method. Background Technology

[0002] Ion lenses are key ion optical components in mass spectrometry systems, enabling ion beam transmission, shaping, focusing, and energy control. Their performance directly affects ion transmission efficiency, beam spot size, spatial divergence angle, and the resolution and sensitivity of subsequent mass analyzers. Ion lenses in existing mass spectrometers typically employ cylindrical electrodes, ring electrodes, perforated electrodes, plate electrodes, electrostatic deflection electrodes, or multi-level three-dimensional ion optical structures formed by combinations of multiple independent electrodes. By applying preset voltages to different electrodes, an electrostatic field or alternating electric field is generated within the ion transmission region, thereby altering the direction of ion movement and spatial distribution.

[0003] With the development of microelectromechanical systems (MEMS) technology, mass spectrometers are gradually moving towards miniaturization, planarization, low power consumption, and high integration. However, existing miniature ion lenses still face significant challenges in the MEMS process. First, traditional three-dimensional ion lens structures typically rely on complex coaxial cylindrical or curved electrodes, requiring high precision in fabrication, assembly, and alignment, making them difficult to reproduce in batches using planar MEMS processes. Second, as the size of the ion lens decreases, the influence of electrode edge fields, fabrication errors, and electrode gap deviations on ion trajectories significantly increases, easily leading to ion beam divergence, increased aberrations, and decreased transmission efficiency. Third, conventional miniature ion lenses often only achieve effective focusing in a single direction, lacking sufficient control over ion divergence in the other direction, making it difficult to simultaneously meet the requirements of two-dimensional ion beam confinement, spatial compression, and efficient transmission. For miniature mass spectrometry systems, this lack of unidirectional focusing capability further limits ion implantation efficiency and the overall performance of the mass analyzer.

[0004] Therefore, it is necessary to provide a planar ion lens structure compatible with MEMS processes to achieve multi-directional focusing and transmission of ion beams in a smaller space, reduce processing complexity, and facilitate chip integration with other simple functional components. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a fan-shaped ion focusing lens based on MEMS technology and its fabrication method. By introducing a planar fan-shaped ion optical structure, this invention achieves bidirectional focusing of the ion beam while remaining compatible with MEMS technology, thereby improving the ion utilization rate and overall analytical performance of the micro-mass spectrometry system.

[0006] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a fan-shaped ion focusing lens chip based on MEMS technology, which is formed by stacking and bonding three wafers; The three wafers are a first wafer 1, a second wafer 2, and a third wafer 3, respectively; wherein the first wafer 1 and the second wafer 2 serve as the upper substrate and the lower substrate, respectively, and the third wafer 3 is located between the first wafer 1 and the second wafer 2. The third wafer 3 has a hollow area extending through its thickness direction. This hollow area, together with the first wafer 1 and the second wafer 2, forms an ion flow channel for the ion beam to pass through and be focused and controlled. Fan-shaped ion focusing electrodes 4 are provided on the opposite inner surfaces of the first wafer 1 and the second wafer 2. The fan-shaped ion focusing electrodes 4 on the first wafer 1 and the second wafer 2 are symmetrically distributed facing each other, located above and below the ion flow channel, respectively, to form an electrostatic field with spatial focusing effect in the channel. The fan-shaped ion focusing lens chip also includes a pad 5 and a TGV electrode 6; the TGV electrode 6 is used to connect the fan-shaped ion focusing electrode 4 located on the inner side of the first wafer 1 and the second wafer 2 to the pad 5 located on the outer side of the first wafer 1 and the second wafer 2, thereby realizing electrical connection with an external power supply.

[0007] Furthermore, the fan-shaped ion focusing electrode 4 is composed of three thin-film electrodes arranged sequentially along the ion transport direction in a fan shape, a fan ring shape, or an approximate fan shape. Each fan-shaped ion focusing electrode 4 is insulated from the others and is connected to different DC bias voltages to form a continuous or quasi-continuous electrostatic field distribution in the ion flow channel.

[0008] Furthermore, the first wafer 1, the second wafer 2, and the third wafer 3 can all simultaneously form multiple device units during wafer-level processing, with each device unit corresponding to a MEMS fan-shaped ion focusing lens group structure. After the three wafers are aligned and bonded, multiple independent MEMS fan-shaped ion focusing lens chips can be obtained through dicing, cutting, or laser separation, thereby achieving wafer-level mass production. This wafer-level mass production method not only significantly improves production efficiency and reduces the manufacturing cost of individual devices, but also significantly improves the consistency and yield between devices.

[0009] In a second aspect, the present invention provides a method for fabricating a fan-shaped ion focusing lens chip based on MEMS technology, for fabricating the fan-shaped ion focusing lens chip described in the first aspect, comprising the following steps: a first wafer 1 and a second wafer 2 processing step, a third wafer 3 processing step, and a wafer-level packaging step; Furthermore, the processing steps for the first wafer 1 and the second wafer 2 include the following steps: Glass wafers are selected as the substrates of the first wafer 1 and the second wafer 2. The preset glass micro-hole pattern and preset alignment mark pattern on the first wafer 1 and the second wafer 2 are modified by infrared picosecond laser to obtain the modified first wafer 1 and the second wafer 2. The modified first wafer 1 and second wafer 2 are placed in a hydrofluoric acid solution for ultrasonic etching to form glass micro-vias and alignment marks; The TGV electrode 6 is prepared by filling the glass micro-pores with metal using screen printing or electroplating processes, wherein the metal is selected from copper or silver. A fan-shaped electrode pattern is formed on the opposite inner surfaces of the first wafer 1 and the second wafer 2 by homogenization, photolithography, and development. Then, a metal film is deposited by magnetron sputtering and the photoresist is stripped off to complete the fabrication of the fan-shaped ion focusing electrode 4. The pad pattern is formed on the outer surfaces of the first wafer 1 and the second wafer 2 by homogenization, photolithography and development. Then, a metal film is deposited by magnetron sputtering and the photoresist is stripped off to complete the fabrication of the pad 5. Furthermore, the third wafer 3 processing step includes the following steps: A glass wafer is selected as the substrate of the third wafer 3, and the preset alignment mark pattern on the third wafer 3 is modified by infrared picosecond laser to obtain the modified third wafer 3. The modified third wafer 3 was placed in a hydrofluoric acid solution for ultrasonic etching to form alignment marks; A 16mm×12mm square glass through-hole was machined using CNC on the third wafer 3, and then double-sided grinding and polishing was performed. Furthermore, the wafer-level packaging process includes the following steps: The first wafer 1 is aligned with the third wafer 3, the second wafer 2 is aligned with the third wafer 3, and the three wafers are welded together using an ultrafast femtosecond laser. The three wafers are then diced, cut, or separated by laser to obtain multiple independent fan-shaped ion focusing lens chips.

[0010] Furthermore, the glass wafers used as substrates for the first wafer 1 and the second wafer 2 have a diameter of 4 inches, 6 inches, or 8 inches and a thickness of 400~1000 μm. The substrate of the third wafer 3 is selected from glass wafers with a diameter of 4 inches, 6 inches, or 8 inches and a thickness of 2 to 2.5 mm, further, with a thickness of 2 mm; the size of the square through hole is 16 mm × 12 mm.

[0011] Furthermore, the alignment marks obtained in the processing steps of the first wafer 1 and the second wafer 2 include the first alignment mark 7 and the second alignment mark 10 on the first wafer 1, the fifth alignment mark 9 and the sixth alignment mark 12 on the second wafer 2; the alignment marks obtained in the processing step of the third wafer 3 include the third alignment mark 8 and the fourth alignment mark 11.

[0012] Furthermore, the infrared picosecond laser has a power of 50~70 W and a scanning speed of 150~250 mm / s; further, the infrared picosecond laser has a power of 60 W and a scanning speed of 200 mm / s. The hydrofluoric acid solution has a mass percentage of 4-6%.

[0013] Furthermore, the parameters for the screen printing include: squeegee pressure of 0.1–0.3 MPa, printing speed of 50–200 mm / s, and curing temperature of 120–180°C; The electroplating process for filling copper has the following parameters: current density of 1-3 A / dm², temperature of 50-60℃, pH value of 8-10, and electroplating time of 30-120 min.

[0014] Furthermore, the process parameters for spin coating, photolithography, and development include: a pre-baking temperature of 90–120°C after spin coating, an exposure power of 30–80 mJ / cm², an exposure wavelength of 365 nm, and a post-baking temperature of 110–130°C; the developer is a 2.38% TMAH aqueous solution, the development time is 30–90 s, and the development temperature is 20–25°C.

[0015] Furthermore, in the fabrication of the fan-shaped ion focusing electrode 4, the deposited metal film is a Cr-Au or Ti-Au composite structure, wherein the thickness of the Cr or Ti layer is 20-100 nm, the thickness of the Au layer is 900-1000 nm, and further, the thickness of the Au layer is 1000 nm. In the fabrication of the pad 5, the deposited metal film is a Cr-Au or Ti-Au composite structure, wherein the thickness of the Cr or Ti layer is 20-50 nm and the thickness of the Au layer is 300-800 nm.

[0016] Further, the alignment of the first wafer 1 with the third wafer 3 is based on the first alignment mark 7 and the second alignment mark 10 coinciding with the third alignment mark 8 and the fourth alignment mark 11, respectively; the alignment of the second wafer 2 with the third wafer 3 is based on the fifth alignment mark 9 and the sixth alignment mark 12 coinciding with the third alignment mark 8 and the fourth alignment mark 11, respectively; after alignment, a preset pressure of 0.2~0.5 MPa is applied; further, the preset pressure is 0.3 MPa.

[0017] Furthermore, the parameters of the ultrafast femtosecond laser are as follows: wavelength 1064 nm, repetition rate 300 kHz, pulse width 15 ps, pulse energy 11.7 μJ, maximum output power 12.78 W, and spot size 40±2 μm.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Achieve wafer-level miniaturization and mass production of ion lens structures. This invention employs a structure in which a first wafer, a third wafer, and a second wafer are stacked sequentially, and fan-shaped thin-film electrodes are formed on the opposing inner surfaces of the first and second wafers. These fan-shaped thin-film electrodes can be fabricated through photolithography, thin-film deposition, and patterning processes, reducing the machining, positioning, and assembly steps required for independent three-dimensional electrodes. This reduces the size of the ion lens structure perpendicular to the wafer and in the chip plane, providing a structural basis for the miniaturization, thinning, and chip-based fabrication of ion lenses. Simultaneously, this structure allows for the simultaneous formation of multiple device units during wafer-level fabrication. After overall alignment, bonding, and dicing, multiple independent MEMS fan-shaped ion focusing lens chips can be obtained, significantly improving device manufacturing consistency and mass production capabilities.

[0019] 2. It facilitates bidirectional focusing of the ion beam in two directions. Existing micro-ion lenses mostly rely on a single-directional electrostatic field to confine the ion beam, typically only allowing for unidirectional collimation or focusing, making it difficult to simultaneously suppress ion divergence in both the planar and vertical directions. This invention, through a fan-shaped ion focusing electrode structure correspondingly positioned on the inner surfaces of the first and second wafers, and the spatial constraint effect of a hollowed-out ion flow channel on the third wafer, forms a controllable electrostatic field within the ion transport region. This electric field can both bend, compress, and converge the ion trajectory within the chip plane, and constrain the ion beam in the vertical direction through the potential distribution between the upper and lower corresponding electrodes, thereby achieving bidirectional focusing of the ion beam in both directions, effectively reducing the beam spot size and improving ion transport efficiency.

[0020] 3. Stepwise adjustment of ion trajectory through multi-stage electrodes. In this invention, three sector-shaped ion focusing electrodes are arranged sequentially along the ion transport direction, and each is subjected to a predetermined DC voltage. These three sector-shaped ion focusing electrodes and their edge regions together constitute a multi-level electrostatic lens region, allowing continuous adjustment of the lateral motion state of ions as they pass through the electric field regions corresponding to different electrodes. By adjusting the potential difference and voltage ratio between the three sector-shaped ion focusing electrodes, the convergence degree of the ion beam in the x and z directions can be changed, and the focusing position, exit beam spot size, and exit divergence angle can be adjusted. Compared to structures with only a single planar electrode or a single-level aperture electrode, this invention has more degrees of freedom in electric field adjustment, enabling adaptive adjustment of the ion beam focusing state based on the ion's charge polarity, initial kinetic energy, mass-to-charge ratio, initial position, and incident angle.

[0021] 4. TGV vertical interconnects can reduce the amount of wiring occupied on the chip surface. This invention incorporates a TGV vertical interconnect structure in both a first and second wafer, extending a fan-shaped thin-film electrode located on the inner surface of the wafer and within the ion flow channel to the outer surface. External voltage is transmitted to the corresponding fan-shaped ion focusing electrode via pads on the outer surface, the TGV vertical interconnect structure, and inner leads, eliminating the need to extend the leads of each electrode to the chip edge. This structure reduces the space occupied by leads and pads on the inner working surface and chip edge, providing more layout space for the fan-shaped ion focusing electrode, ion flow channel, and bonding sealing area, and facilitating a reduction in the chip's lateral dimensions. Furthermore, the TGV vertical interconnect structure allows the electrode working area and the external electrical connection area to be located on different surfaces of the wafer, facilitating vertical integration between the ion optical structure and the driving circuitry.

[0022] 5. Improve ion implantation accuracy and subsequent mass analysis performance. In miniature mass spectrometry systems, the coupling efficiency between the ion source, ion lens, mass analyzer, and detector directly affects the system's sensitivity and resolution. Traditional miniature ion optical structures are limited by fabrication errors, edge field effects, and unidirectional focusing capabilities, easily leading to ion beam divergence, offset, and loss. This invention utilizes a fan-shaped ion focusing electrode array working in synergy, enabling ions from different initial positions and incident angles to reconverge in a predetermined focal region, entering the subsequent mass analyzer with a smaller beam size and lower divergence angle. Therefore, this invention improves ion implantation conditions, increases effective ion utilization, and consequently enhances the detection sensitivity, signal-to-noise ratio, and analytical stability of the miniature mass spectrometry system.

[0023] 6. Facilitates chip-level integration with other planar mass spectrometry components. This invention employs planar thin-film electrodes, multilayer wafers, and a TGV vertical interconnect structure. Its fabrication method is compatible with MEMS fabrication processes for components such as planar ion sources, planar quadrupoles, planar ion traps, miniature ion guides, and miniature detectors. The MEMS fan-shaped ion focusing lens can be mounted as an independent chip within the mass spectrometry system, or it can be housed with the ion source, mass analyzer, or detector on the same packaging substrate, the same wafer assembly, or multiple wafers bonded together. This shortens the transmission distance between different ion optical components, reduces the mechanical connections and alignment structures of independent components, and provides conditions for constructing planar, miniaturized, and highly integrated mass spectrometry analysis systems. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the overall structure of a MEMS fan-shaped ion focusing lens. Figure 2 Top view of the MEMS fan-shaped ion focusing lens electrode structure; Figure 3 Top view of the upper surface of a MEMS fan-shaped ion focusing lens; Figure 4 Side view of a MEMS fan-shaped ion focusing lens; Figure 5 This is a schematic diagram of the first wafer 1; Figure 6 This is a schematic diagram of the third wafer 3; Figure 7 This is a schematic diagram of the wafer for a MEMS fan-shaped ion focusing lens. Figure 8 This is the overall structural diagram of Example 2.

[0026] Among them, 1-first wafer, 2-second wafer, 3-third wafer, 4-three sets of fan-shaped ion focusing electrodes, 5-pad, 6-TGV electrode, 7-first alignment mark, 8-third alignment mark, 9-fifth alignment mark, 10-second alignment mark, 11-fourth alignment mark, 12-sixth alignment mark, 13-ion source, 14-fan-shaped flat ion lens, 15-planar ion trap mass analyzer. Detailed Implementation

[0027] The present invention will be further described below with reference to embodiments, but the scope of protection of the present invention is not limited thereto. It should be noted that the implementation steps in the embodiments can be further adjusted according to the specific experimental environment, and the implementation steps not specified are usually conditions in conventional experiments.

[0028] Example 1 This embodiment provides a fan-shaped ion focusing lens chip based on MEMS technology. The overall structure diagram of the lens chip is shown below. Figure 1 As shown, the top view of the structure is as follows: Figure 2 and Figure 3 As shown, the side view is as follows Figure 4 As shown, its preparation method specifically includes the following three steps: First step: Fabrication process of first wafer 1 and second wafer 2 Step 1: First, select a 4-inch wafer 1 and a wafer 2 with a thickness of 500 μm. Use an infrared picosecond laser to modify the glass micro-hole area and the alignment mark area. The laser power is set to 60 W and the scanning speed is 200 mm / s.

[0029] Step 2: Place the modified first wafer 1 and second wafer 2 into a 5% hydrofluoric acid solution and perform ultrasonic etching for 1 hour to obtain glass micro-vias and alignment marks, namely alignment mark 7 on the first wafer 1, second alignment mark 10, fifth alignment mark 9 and sixth alignment mark 12 on the second wafer 2.

[0030] Step 3: Fill the glass micro-perforations with metallic copper using an electroplating filling process to prepare TGV electrode 6; the commonly used parameters for electroplating copper filling are: current density 2 A / dm², electrolyte temperature 55℃, pH value 9, and filling time 60 min.

[0031] Step 4: Coating is performed on the inner surfaces of the first wafer 1 and the second wafer 2, followed by photolithography and development to obtain the pattern of the fan-shaped ion focusing electrode; wherein, the pre-baking temperature after coating is 100℃, the exposure power is 50 mJ / cm², the exposure wavelength is 365nm (i-line), and the post-baking temperature after exposure is 120℃; the developer is a 2.38% TMAH aqueous solution, the development time is 60s, and the development temperature is 23℃.

[0032] Step 5: Deposit a metal film on the first wafer 1 and the second wafer 2 using magnetron sputtering. The metal film is a Cr-Au composite structure, wherein the thickness of the Cr layer is 100 nm and the thickness of the Au layer is 1000 nm.

[0033] Step 6: Clean the photoresist in acetone solution to achieve metal stripping and complete the fabrication of the fan-shaped ion focusing electrode 4.

[0034] Step 7: Apply photoresist to the outer surfaces of the first wafer 1 and the second wafer 2, and perform photolithography and development to obtain the pattern of the pad 5; the photolithography and development parameters are the same as in step 4.

[0035] Step 8: Deposit a metal film on the first wafer 1 and the second wafer 2 using magnetron sputtering. The metal film is a Cr-Au composite structure, wherein the thickness of the Cr layer is 30 nm and the thickness of the Au layer is 500 nm.

[0036] Step 9: Clean the photoresist in acetone solution to achieve metal stripping, fabricate pad 5, and complete the first wafer 1. Figure 5 As shown.

[0037] Second step: Fabrication process of the third wafer 3 Step 1: Select a 4-inch, 2 mm thick third wafer 3 and perform routine cleaning.

[0038] Step 2: Modify the preset hollow area pattern and preset alignment mark pattern on the third wafer 3 using an infrared picosecond laser to obtain the modified third wafer 3; wherein, the laser power is set to 60 W and the scanning speed is 200 mm / s; the modified third wafer 3 is placed in a 5% hydrofluoric acid solution for ultrasonic etching for 1 hour to form the third alignment mark 8 and the fourth alignment mark 11.

[0039] Step 3: A 16mm × 12mm square glass via is CNC machined on the third wafer 3, and then double-sided grinding and polishing are performed to achieve a surface roughness at the nanometer level. The completed third wafer 3 is shown below. Figure 6 As shown.

[0040] Third process: Wafer-level packaging process Wafer-level packaging is achieved using ultrafast femtosecond lasers, specifically including: Step 1: The lower surface of the first wafer 1 and the upper surface of the third wafer 3 are aligned before welding, and a preset pressure of 0.3 MPa is applied. The alignment is judged by the overlap of the first alignment mark 7, the second alignment mark 10, the third alignment mark 8, and the fourth alignment mark 11. Step 2: The lower surfaces of the second wafer 2 and the third wafer 3 are aligned before welding, and a preset pressure of 0.3 MPa is applied. The alignment is determined by the overlap between the fifth alignment mark 9, the sixth alignment mark 12 and the third alignment mark 8, the fourth alignment mark 11. Step 3: Weld three glass wafers using an ultrafast femtosecond laser. The laser beam parameters are: wavelength 1064 nm, repetition rate 300 kHz, pulse width 15 ps, pulse energy 11.7 uJ, maximum output power 12.78 W (Gaussian beam), and spot size 40 μm.

[0041] After the above packaging is completed, multiple independent MEMS fan-shaped ion focusing lens chips are obtained by dicing, cutting, or laser separation, such as... Figure 7 As shown.

[0042] Example 2 This embodiment provides an application method of a fan-shaped flat plate ion lens in a planar ion trap mass spectrometer.

[0043] like Figure 8 As shown, in this embodiment, the fan-shaped flat ion lens 14 is disposed between the ion source 13 and the planar ion trap mass analyzer 15. It is used to focus, collimate and control the transmission direction of the diverging ion beam generated by the ion source 13, so that the ion beam can enter the effective capture area of ​​the planar ion trap mass analyzer 15 with a smaller beam spot size and a suitable incident angle.

[0044] The ion source 13 can be an electrospray ion source, an electron bombardment ion source, a chemical ionization ion source, a photoionization ion source, or other ion sources capable of generating ion beams. The planar ion trap mass analyzer 15 is composed of multiple planar electrodes arranged on the same plane or opposite to each other. By applying radio frequency voltage, DC voltage, or a combination thereof to different electrodes, an electric field for ion capture, cooling, mass selection, and expulsion is formed inside the ion trap.

[0045] The working principle of the MEMS fan-shaped ion focusing lens provided in this embodiment is as follows: During operation, the ion beam generated by ion source 13 enters through the inlet of the ion transport channel and propagates forward along the central axis of the ion transport channel. In this embodiment, the main transport direction of the ion beam is defined as the y-direction, the direction located in the wafer plane and perpendicular to the y-direction is defined as the x-direction, and the direction perpendicular to the wafer plane is defined as the z-direction. The focusing of the ion beam in the xy-plane corresponds to its focusing in the x-direction, and the focusing of the ion beam in the yz-plane corresponds to its focusing in the z-direction.

[0046] Three sector-shaped ion focusing electrodes 4 are respectively disposed on the inner surfaces of the first wafer 1 and the second wafer 2. The three sector-shaped ion focusing electrodes on the first wafer 1 and the three sector-shaped ion focusing electrodes on the second wafer 2 are symmetrically distributed vertically, thus forming three pairs of sector-shaped ion focusing electrodes arranged sequentially along the y-direction. A preset DC bias voltage is applied to each of the three pairs of sector-shaped ion focusing electrodes 4, so that a potential difference is formed between adjacent sector-shaped ion focusing electrodes, and a three-dimensional non-uniform electrostatic field varying along the y-direction is formed in the ion transport channel.

[0047] When the ion beam enters the focusing region corresponding to the fan-shaped ion focusing electrode, the transverse electric field component in the three-dimensional non-uniform electrostatic field modulates the motion of ions deviating from the central axis. Specifically, the contour of the fan-shaped ion focusing electrode 4 within the wafer plane and its edge electric field create a potential distribution that varies along the x-direction within the ion transport channel, thereby correcting the x-direction displacement and x-direction velocity of the ions, causing ions deviating from the central axis to gradually converge towards the central axis in the xy-plane.

[0048] Meanwhile, the corresponding sector-shaped ion focusing electrodes 4 on the first wafer 1 and the second wafer 2 are located on both sides of the ion transport channel, and the electric field they jointly form is basically symmetrical about the central transport surface of the ion transport channel. When the ions deviate from the central transport surface in the z-direction, the vertical electric field components generated by the upper and lower corresponding electrodes and the edge electric field adjust the z-direction displacement and z-direction velocity of the ions, so that the ions gradually converge towards the central transport surface in the yz plane.

[0049] Since the three pairs of sector-shaped ion focusing electrodes 4 are arranged sequentially along the ion transport direction, the first pair of sector-shaped ion focusing electrodes first performs preliminary shaping on the ion beam entering the focusing region, reducing the divergence of the ion beam in the x and z directions; the second pair of sector-shaped ion focusing electrodes further adjusts the lateral motion state of the ions, enhancing the convergence of the ion beam in the xy and yz planes; the third pair of sector-shaped ion focusing electrodes further corrects and collimates the trajectory of the ions, so that the ion beam obtains net lateral momentum pointing towards the central axis in both the x and z directions after passing through the entire focusing region.

[0050] Thus, ions with different initial positions and incident angles, under the influence of the non-uniform electrostatic field formed by the three pairs of fan-shaped ion focusing electrodes 4, gradually reduce their range of motion in the x and z directions, and their trajectories continuously converge towards the central axis of the ion transmission channel, thereby achieving bidirectional focusing of the ion beam in the xy and yz planes. The focused ion beam has a smaller beam spot size and a lower spatial divergence angle, and enters the subsequent mass analyzer, ion trap, ion guide, or ion detection unit from the exit end of the ion transmission channel.

[0051] The specific usage method of the MEMS fan-shaped ion focusing lens provided in this embodiment is as follows: First, the MEMS fan-shaped ion focusing lens chip formed by stacking and cutting the first wafer 1, the second wafer 2, and the third wafer 3 is installed in the vacuum chamber, with its ion inlet aligned with the outlet of the ion source 13, and its ion outlet aligned with the inlet of the subsequent mass analyzer, ion trap, detector, or other ion optical unit. Secondly, a predetermined voltage is applied to the three sector-shaped ion focusing electrodes 4 by means of an external DC voltage source, a voltage divider resistor array, or a multi-channel voltage control module; Next, the potential of each electrode is adjusted so that the ion beam forms a predetermined bending trajectory within the fan-shaped focusing area defined by the hollow area of ​​the third wafer 3 and forms the minimum beam spot near the exit. Finally, the focused ion beam is input into the subsequent quality analysis or detection unit to improve ion transport efficiency, ion implantation accuracy, and system detection sensitivity.

[0052] The specific working process of a planar ion trap mass spectrometer system is as follows: The ion beam generated by the ion source 13 first enters the fan-shaped flat ion lens 14. By applying a preset voltage to each fan-shaped ion focusing electrode 4 in the fan-shaped flat ion lens 14, a non-uniform electrostatic field distributed along the ion propagation path is formed inside the fan-shaped ion channel. Under the action of the radial electric field force, the diverging ions gradually converge towards the predetermined transmission axis and change their propagation direction along the fan-shaped ion channel, thereby achieving the focusing, collimation, and deflection transmission of the ion beam.

[0053] After being controlled by the fan-shaped flat ion lens 14, the ion beam enters the planar ion trap mass analyzer 15 from the lens exit. Because the beam spot size of the ion beam is reduced, the spatial distribution is more concentrated, and the ion propagation direction matches the entrance direction of the planar ion trap mass analyzer 15, collision losses of ions at the entrance electrode and ineffective capture area can be reduced, thereby increasing the number of ions entering the effective capture area of ​​the ion trap.

[0054] In this embodiment, the fan-shaped flat ion lens 14 is fabricated using MEMS technology and includes an upper substrate, an intermediate layer, and a lower substrate stacked along the thickness direction. The intermediate layer has a through-hole fan-shaped area. Multiple fan-shaped ion focusing electrodes 4 are respectively disposed on the side of the upper and lower substrates facing the intermediate layer. The upper and lower substrates and the intermediate layer together form a fan-shaped ion transport channel. Each fan-shaped ion focusing electrode 4 is connected to an external voltage source. By applying the same or different electrostatic voltages to different electrodes, an electric field with focusing and deflection functions is formed inside the fan-shaped ion channel.

[0055] Both the fan-shaped planar ion lens 14 and the planar ion trap mass analyzer 15 adopt a planar electrode structure, which can be integrated into a single unit through wafer-level processing, bonding, and packaging. Compared with the traditional structure combining a cylindrical ion lens with a three-dimensional ion trap, this embodiment can reduce the size of the ion optical system, shorten the ion transmission distance, reduce divergence and loss during ion transmission, and improve ion implantation efficiency, ion capture efficiency, and mass spectrometry detection sensitivity. It is more suitable for miniaturized, chip-based planar ion trap mass spectrometry systems.

Claims

1. A fan-shaped ion focusing lens chip based on MEMS technology, characterized in that, It is composed of three wafers stacked and bonded together; The three wafers are a first wafer (1), a second wafer (2), and a third wafer (3); wherein the first wafer (1) and the second wafer (2) serve as the upper substrate and the lower substrate, respectively, and the third wafer (3) is located between the first wafer (1) and the second wafer (2); The third wafer (3) has a hollow area that runs through its thickness direction. The hollow area, together with the first wafer (1) and the second wafer (2), forms an ion flow channel for the ion beam to pass through and be focused and controlled. Fan-shaped ion focusing electrodes (4) are provided on the opposite inner surfaces of the first wafer (1) and the second wafer (2); the fan-shaped ion focusing electrodes (4) on the first wafer (1) and the second wafer (2) are symmetrically distributed facing each other, located above and below the ion flow channel, respectively, to form an electrostatic field with spatial focusing effect in the channel; The fan-shaped ion focusing lens chip also includes a pad (5) and a TGV electrode (6); the TGV electrode (6) is used to connect the fan-shaped ion focusing electrode (4) located on the inner side of the first wafer (1) and the second wafer (2) to the pad (5) located on the outer side of the first wafer (1) and the second wafer (2).

2. The fan-shaped ion focusing lens chip according to claim 1, characterized in that, The fan-shaped ion focusing electrode (4) consists of three thin film electrodes arranged sequentially along the ion transport direction in a fan shape, fan ring shape or approximately fan shape. Each fan-shaped ion focusing electrode (4) is insulated from each other and connected to different DC bias voltages to form a continuous or quasi-continuous electrostatic field distribution in the ion flow channel.

3. A method for fabricating a fan-shaped ion focusing lens chip based on MEMS technology, used to fabricate the fan-shaped ion focusing lens chip as described in claim 1 or 2, characterized in that, The process includes: the processing of the first wafer (1) and the second wafer (2), the processing of the third wafer (3), and the wafer-level packaging process; The processing steps for the first wafer (1) and the second wafer (2) include the following steps: Glass wafers are selected as the substrates of the first wafer (1) and the second wafer (2). The preset glass micro-hole pattern and preset alignment mark pattern on the first wafer (1) and the second wafer (2) are modified to obtain the modified first wafer (1) and the second wafer (2). The modified first wafer (1) and second wafer (2) are ultrasonically etched to form glass micro-vias and alignment marks; A TGV electrode (6) is prepared by filling the glass micropores with metal, wherein the metal is selected from copper or silver. A fan-shaped electrode pattern is formed on the opposite inner surfaces of the first wafer (1) and the second wafer (2) by homogenization, photolithography and development. Then, a metal film is deposited and the photoresist is stripped off to complete the fabrication of the fan-shaped ion focusing electrode (4). The pad pattern is formed on the outer surfaces of the first wafer (1) and the second wafer (2) by homogenization, photolithography and development, then a metal film is deposited and the photoresist is stripped off to complete the fabrication of the pad (5); The third wafer (3) processing steps include: A glass wafer is selected as the substrate of the third wafer (3), and the preset alignment mark pattern on the third wafer (3) is modified to obtain the modified third wafer (3). The modified third wafer (3) is ultrasonically etched to form alignment marks; Square glass through-holes are processed on the third wafer (3), and double-sided grinding and polishing are performed; The wafer-level packaging process includes the following steps: The first wafer (1) is aligned with the third wafer (3), the second wafer (2) is aligned with the third wafer (3), and the three wafers are welded together. The three wafers after welding are diced, cut or laser separated to obtain multiple independent fan-shaped ion focusing lens chips.

4. The preparation method according to claim 3, characterized in that, The substrates of the first wafer (1) and the second wafer (2) are selected from glass wafers with a diameter of 4 inches, 6 inches or 8 inches and a thickness of 400~1000 μm; The substrate of the third wafer (3) is selected from glass wafers with a diameter of 4 inches, 6 inches or 8 inches and a thickness of 2 to 2.5 mm.

5. The preparation method according to claim 3, characterized in that, The alignment marks obtained in the processing steps of the first wafer (1) and the second wafer (2) include the first alignment mark (7) and the second alignment mark (10) on the first wafer (1), the fifth alignment mark (9) and the sixth alignment mark (12) on the second wafer (2); the alignment marks obtained in the processing step of the third wafer (3) include the third alignment mark (8) and the fourth alignment mark (11).

6. The preparation method according to claim 3, characterized in that, The process parameters for spin coating, photolithography, and development include: a pre-baking temperature of 90–120°C after spin coating, an exposure power of 30–80 mJ / cm², and a post-baking temperature of 110–130°C after exposure; the developer is a TMAH aqueous solution, the development time is 30–90 s, and the development temperature is 20–25°C.

7. The preparation method according to claim 3, characterized in that, In the fabrication of the fan-shaped ion focusing electrode (4), the deposited metal film is a Cr-Au or Ti-Au composite structure, wherein the thickness of the Cr or Ti layer is 20-100 nm and the thickness of the Au layer is 900-1000 nm.

8. The preparation method according to claim 3, characterized in that, In the fabrication of the pad (5), the deposited metal film is a Cr-Au or Ti-Au composite structure, wherein the thickness of the Cr or Ti layer is 20-50 nm and the thickness of the Au layer is 300-800 nm.

9. The preparation method according to claim 5, characterized in that, The alignment of the first wafer (1) with the third wafer (3) is based on the first alignment mark (7) and the second alignment mark (10) coinciding with the third alignment mark (8) and the fourth alignment mark (11), respectively; the alignment of the second wafer (2) with the third wafer (3) is based on the fifth alignment mark (9) and the sixth alignment mark (12) coinciding with the third alignment mark (8) and the fourth alignment mark (11), respectively; a preset pressure is applied after alignment.

10. The preparation method according to claim 9, characterized in that, The preset pressure is 0.2~0.5 MPa.

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