High-optical-power MEMS infrared light source capable of balancing stress and manufacturing method of high-optical-power MEMS infrared light source

Abstract

The invention discloses a stress-balanced high-optical-power MEMS infrared light source and a manufacturing method thereof, and belongs to the field of infrared radiation sources. The MEMS infrared light source comprises a tube shell, a nickel plating layer is arranged in a cavity of the tube shell, the nickel plating layer is connected with an infrared light source electrode through a connecting layer, and a cover plate used for blocking an opening of the tube shell is arranged at the top of the tube shell; the infrared light source electrode is a hollow snakelike beam electrode and comprises an electrode body, the electrode body is longitudinally divided into a plurality of electrode areas, the middle areas of the adjacent electrode areas are connected in a penetrating mode, and a hollow structure is arranged in each electrode area. And two ends of the electrode main body are respectively provided with a connecting end. According to the MEMS infrared light source, the stress generated by the electrodes can be effectively balanced while the high optical power of the MEMS infrared light source is kept. For example, the stress balance structure design is carried out on the light source electrode, the high light power of the light source is kept, meanwhile, the overall heat mass of the light source is reduced, structural fatigue caused by heat circulation is relieved, and the service life of the light source is prolonged.

Description

Technical Field

[0001] The present invention relates to the field of infrared radiation sources, and particularly to a novel high-light-power MEMS infrared light source with balanced stress and a manufacturing method thereof. Background Art

[0002] A microelectromechanical system (MEMS) infrared light source is a miniaturized infrared radiation device manufactured based on micro-nano processing technology, and is widely used in fields such as gas sensing, infrared spectroscopy analysis, thermal imaging, security monitoring, etc. Compared with traditional infrared light sources (such as blackbody radiation sources, laser diodes, etc.), MEMS infrared light sources have advantages such as small volume, low power consumption, fast response, and batch manufacturability.

[0003] In recent years, with the rapid development of fields such as gas sensing and environmental monitoring, the demand for high-performance MEMS infrared light sources by gas sensors based on non-dispersive infrared (NDIR) technology has become increasingly urgent. As a core component, the light power, thermal stability, and reliability of MEMS infrared light sources directly affect the detection accuracy and lifespan of sensors. However, there are still problems in the prior art such as low light power, stress concentration, and insufficient structural reliability:

[0004] The multilayer thin film structure of MEMS devices is prone to residual stress due to differences in the thermal expansion coefficients of the materials, causing the film to warp or even break. Existing technologies, such as the patent with application number CN201310500968.6, use front release technology to form a micro-cantilever beam to support the infrared light source to reduce heat loss, and reduce structural stress by pre-burying a dielectric layer of silicon nitride under the heating layer. However, the thermal mass of the structure is large, resulting in slow thermal response speed and limited modulation frequency, making it difficult to meet high-dynamic detection requirements. The patent with application number CN202121010008.8 provides a MEMS infrared light source. The heating source structure used can not only improve heating efficiency and provide sufficient heat for the light source, but also effectively heat the conductor to reduce the risk of conductor breakage due to different thermal deformation in different areas; improve the stability of the infrared light source and extend its service life; the preparation process is relatively simple, the production cost is low, and it is suitable for mass production, but there are still problems such as uneven stress distribution and structural fatigue under long-term thermal cycles. Patent application number CN202410609278.2 sandwiches a heating electrode with a porous structure in the infrared component to improve heating efficiency and structural stability. The porous structure of the infrared component reduces the thermal conduction loss of the film and the power consumption of the light source, reducing the thermal mass of the infrared component to accelerate the thermal response and modulation frequency of the infrared light source. However, the overall resistance of the heating electrode structure is low, which reduces the optical power of the infrared light source. Patent application number CN202410751326.1 reduces the heat loss from the infrared light source chip to the base by adding a gasket packaging method, reducing the power consumption of the MEMS infrared light source. The gasket packaging allows the air below the infrared light source radiation area to be connected to the outside world, greatly reducing the vibration amplitude of the supporting film when the MEMS infrared light source is working, thereby improving the long-term reliability of the MEMS infrared light source. However, the light source electrode still has the problem of uneven heating. Summary of the Invention

[0005] The purpose of the present invention is to provide a stress-balanced high-power MEMS infrared light source and a manufacturing method thereof, so as to solve the problems of low optical power, stress concentration and insufficient structural reliability of MEMS infrared light sources in the prior art.

[0006] The technical solution adopted by the present invention is:

[0007] A stress-balanced high-power MEMS infrared light source comprises a tube shell, a nickel-plated layer is provided inside a cavity of the tube shell, the nickel-plated layer is connected to an infrared light source electrode via a connecting layer, and a cover plate for sealing the opening is provided on the top of the tube shell; the infrared light source electrode is a hollow serpentine beam electrode, comprising an electrode body, which is longitudinally divided into a plurality of electrode zones, with intermediate regions of adjacent electrode zones being through-connected, and a hollow structure being provided inside each electrode zone; and connecting terminals are provided at both ends of the electrode body.

[0008] Preferably, the hollow structure includes strip-shaped holes which are arranged along the longitudinal center line of the electrode region. First triangular holes are symmetrically arranged at both ends of the strip-shaped holes. A plurality of second triangular holes are symmetrically arranged on both sides of the strip-shaped holes. All the second triangular holes on each side are arranged in a longitudinal row, and two adjacent second triangular holes in each row are arranged in a reverse cross pattern.

[0009] Preferably, the distance between the strip-shaped hole in the electrode region and the edge of the electrode region is called the beam width, and the beam width of the electrode region in the middle area of the electrode body gradually decreases towards the beam width of the electrode regions in the areas on both sides of the electrode body.

[0010] Preferably, the electrode region in the middle area of the electrode body is the first electrode region. The second electrode regions are on both sides of the first electrode region. The third electrode regions are on both sides of the second electrode regions, and so on. The Nth electrode regions are on both sides of the (N - 1)th electrode region. Moreover, the difference in beam width between the first electrode region and the second electrode region, the difference in beam width between the second electrode region and the third electrode region, and the difference in beam width between the (N - 1)th electrode region and the Nth electrode region are equal.

[0011] Preferably, one of the vertices of the first triangular hole faces the strip-shaped hole. The orientation arrangement of the second triangular holes is perpendicular to that of the first triangular holes, and the area of the first triangular holes is larger than that of the second triangular holes.

[0012] Preferably, the package shell is a cermet package shell. The nickel plating layer is arranged at the middle position of the inner sides of both edges of the cermet package shell. The nickel plating layer is connected to the connection end of the infrared light source electrode through a connection layer.

[0013] Preferably, the connection layer is an active metal layer, which is made of Ag, Cu, and / or Ti active brazing filler metals. The cover plate is a silicon cover plate. As a vacuum packaging cover plate, it is connected to the cermet package shell to ensure the internal vacuum tightness of the light source.

[0014] The manufacturing method of the high-light-power MEMS infrared light source with balanced stress as described above includes the following steps:

[0015] S01. Process the infrared light source electrode;

[0016] S02. Perform ultrasonic cleaning on the surface of the cermet package shell, and nickel plate locally to form a nickel plating layer on the package shell. Adopt the active metal brazing technology to connect the infrared light source electrode to the nickel plating layer of the cermet package shell;

[0017] S03. Adopt the vacuum eutectic process to package the silicon cover plate and the cermet package shell.

[0018] Preferably, step S01 includes the following steps:

[0019] S011. Clean the silicon substrate with a cleaning solution, and then bond the nickel-chromium electrode material to the surface of the silicon substrate;

[0020] S012. Use photolithography and etching processes to fabricate the required planar microstructures;

[0021] S013. Use micro-nano processing technology to divide the entire electrode into independent micro-units;

[0022] S014. Peel off the electrode micro-units from the silicon substrate with the aid of a micro-operation assembly system;

[0023] S015. Use the glancing angle evaporation process to process the electrode surface to form a radiation layer.

[0024] Preferably, in step S02: Use Ag-Cu-Ti active solder to bond the infrared light source electrode and the nickel-plated layer of the metal-ceramic package in a vacuum brazing furnace;

[0025] In step S03: Use Au-Si eutectic solder to complete the hermetic welding of the silicon cover plate and the metal-ceramic package in a vacuum chamber; Suppress thermal stress by stepwise cooling, and the airtightness retention rate of the packaged device is >99% under thermal shock at -20 to 150 °C.

[0026] The beneficial technical effects of the present invention are as follows:

[0027] (1) While maintaining the high light power of the MEMS infrared light source, the present invention can effectively balance the stress generated by the electrodes. Specifically, by designing the structure of the light source electrodes, not only a small structural thermal mass is maintained, the high light power of the infrared light source is maintained, but also the stress generated during the operation of the light source is balanced, greatly improving the service life of the light source.

[0028] (2) By adopting the novel hollow serpentine electrode design, the present invention increases the effective length and resistance of the electrodes while significantly reducing the overall thermal mass, achieving high light power of the infrared light source and solving the problems of low resistance and low light power of traditional MEMS infrared light sources.

[0029] (3) The symmetric structure of the serpentine electrodes adopted in the present invention can effectively disperse the thermal expansion stress, and the design of its winding path makes the thermal deformation directions of adjacent units cancel each other out, slowing down the structural fatigue caused by thermal cycling during long-term operation of the light source.

[0030] (4) By designing different beam widths, the present invention makes the temperature distribution on the surface of the light source electrodes uniform, balances the stress distribution of the light source electrodes, and extends the service life of the light source.

[0031] (5) The processing technology of the present invention makes the connections between the components in the MEMS infrared light source tight and stable, with better bonding, and can effectively improve the airtightness of the light source, etc.

[0032] In summary, based on the MEMS processing technology, the present invention designs a stress balance structure for the light source electrode, which reduces the overall thermal mass of the light source while maintaining high light power of the light source, slows down the structural fatigue caused by thermal cycling, and extends the service life of the light source. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a cross-sectional structure diagram of a high-light-power MEMS infrared light source with balanced stress according to the present invention;

[0034] Figure 2 It is a three-dimensional connection diagram of the electrode and the cermet package in a high-light-power MEMS infrared light source with balanced stress according to the present invention;

[0035] Figure 3 It is a structural schematic diagram of an infrared light source electrode with balanced stress according to the present invention;

[0036] Figure 4 It is a flow chart of a manufacturing method of a high-light-power MEMS infrared light source with balanced stress according to the present invention.

[0037] In the figure: 1, cermet package; 2, nickel plating layer; 3, active metal layer; 4, infrared light source electrode; 5, silicon cover plate.

[0038] 401 - electrode main body; 402 - electrode area; 403 - connection end; 404 - strip hole; 405 - first triangular hole; 406 - second triangular hole. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] The purpose of the present invention is to provide a novel high-light-power MEMS infrared light source with balanced stress and a manufacturing method thereof to solve the problems of low light power, stress concentration and insufficient structural reliability of the MEMS infrared light source in the prior art methods. As Figure 1 、 Figure 2 shown, a high-light-power MEMS infrared light source with balanced stress includes a cermet package 1. A nickel plating layer 2 is arranged inside the chamber of the cermet package 1. The nickel plating layer 2 is connected to an infrared light source electrode 4 through an active metal layer 3. A silicon cover plate 5 is arranged on the top of the cermet package 1.

[0040] As Figure 3As shown, the infrared light source electrode 4 is a hollow serpentine beam electrode, including an electrode main body 401. The electrode main body 401 is longitudinally divided into several electrode regions 402. The middle regions of adjacent electrode regions are connected through. A hollow structure is provided inside each electrode region. Connection ends 403 are respectively arranged at both ends of the electrode main body 401. The hollow structure includes strip holes 404. The strip holes 404 are arranged along the longitudinal center line of the electrode region. First triangular holes 405 are symmetrically arranged at both ends of the strip hole; several second triangular holes 406 are symmetrically arranged on both sides of the strip hole. All the second triangular holes on each side are arranged in a longitudinal row, and two adjacent second triangular holes in each row are arranged in a reverse cross pattern.

[0041] The distance between the strip hole 404 and the edge of the electrode region in the above-mentioned electrode region 402 is called the beam width, and the beam width of the electrode region located in the middle region of the electrode main body gradually decreases towards the beam width of the electrode region located in the two side regions of the electrode main body. More specifically, the electrode region located in the middle region of the electrode main body is the first electrode region. The second electrode regions are on both sides of the first electrode region. The third electrode regions are on both sides of the second electrode region, and so on. The Nth electrode regions are on both sides of the (N - 1)th electrode region; and the difference in beam width between the first electrode region and the second electrode region, the difference in beam width between the second electrode region and the third electrode region, and the difference in beam width between the (N - 1)th electrode region and the Nth electrode region are equal. Figure 3 The case where the independent micro unit includes 5 electrode regions is shown in [Figure], that is, the first electrode region is in the middle, the second electrode regions are on both sides, and the third electrode regions are on both sides of the second electrode regions. From the middle to both sides, the beam width of the electrode region gradually decreases.

[0042] One of the vertices of the above-mentioned first triangular hole 405 faces the strip hole. The orientation arrangement of the second triangular hole 406 is perpendicular to that of the first triangular hole, and the area of the first triangular hole is larger than that of the second triangular hole.

[0043] By adopting the novel hollow serpentine electrode design, the present invention significantly reduces the overall thermal mass while increasing the effective length and resistance of the electrode, realizes high light power of the infrared light source, and solves the problems of low resistance and low light power of the traditional MEMS infrared light source. The symmetric structure of the serpentine electrode adopted by the present invention can effectively disperse the thermal expansion stress. The design of its winding path enables the thermal deformation directions of adjacent units to cancel each other out, and slows down the structural fatigue caused by thermal cycling during the long-term operation of the light source. By designing different beam widths, the present invention makes the temperature distribution on the surface of the light source electrode uniform, balances the stress distribution of the light source electrode, and prolongs the service life of the light source.

[0044] The MEMS infrared light source designed by the present invention has high light power, stable and reliable structure, and can effectively solve the problem of stress concentration.

[0045] The above nickel plating layer 2 is arranged at the middle position between the inner edges on both sides of the cermet shell, and the nickel plating layer 2 is connected to the connection end 403 of the infrared light source electrode 4 through the active metal layer 3 or the connection layer. The active metal layer is made of Ag, Cu, and / or Ti active solders. The active metal layer 3 can withstand temperatures above 700 °C. The silicon cover plate serves as a vacuum packaging cover plate and is connected to the cermet shell to ensure the internal vacuum tightness of the light source.

[0046] As Figure 1 shown, the cermet shell 1 serves as the infrared light source packaging shell. At the nickel plating layer of the shell, high-purity nickel is plated, and through the active metal layer 3, it is connected to the stress-balancing electrode, namely the infrared light source electrode 4. Above the cermet shell is the silicon cover plate 5, which is packaged by the eutectic method, and a vacuum is maintained inside the cermet shell 1. As Figure 2 shown, it is the overall structure of the light source. The nickel plating layer is only inside the shell and does not affect the connection between the shell and the silicon cover plate. As Figure 3 shown, for the electrodes of the hollow serpentine beam, by adjusting the beam width, the effect of adjusting the current density can be achieved, so as to make the temperature of the light source electrodes balanced and the stress distribution balanced.

[0047] As Figure 4 shown, the present invention also provides a method for manufacturing a high-light-power MEMS infrared light source with balanced stress, which specifically includes the following steps:

[0048] S01. Pretreatment of the silicon substrate and electrode bonding; use Piranha solution (H2SO4:H2O2 = 3:1) to ultrasonically clean the silicon substrate for 10 minutes at 40 kHz to remove surface organic pollutants and particles. Through the thermocompression bonding process, at a temperature of 300 °C, a pressure of 10 MPa, and under the protection of argon, the nickel-chromium alloy (Ni80Cr20) electrode film is wafer-level bonded to the silicon substrate.

[0049] S02. Lithography forming of the planar micro-structure: Spin-coat positive photoresist, and use ultraviolet lithography to define the micro-structure pattern on the electrode layer; combine reactive ion etching and wet etching (HF:HNO3 = 1:3) to achieve a hollow micro-structure.

[0050] S03. Division of the micro-electrode array: Use the deep reactive ion etching Bosch process to divide the whole electrode into independent micro-units. As Figure 3 shown, it is an independent micro-unit.

[0051] S04. Separation of the micro-electrode units: Use an auxiliary micromanipulator, combined with local laser heating of 50 mW to weaken the adhesion layer, to achieve non-destructive peeling of the electrode units.

[0052] S05. Gradient evaporation coating of the radiation layer: Using electron beam evaporation technology, deposit the blackbody radiation layer at a grazing angle of 83°. Achieve nanoscale surface roughness through angle control, and increase the radiation efficiency to 85%. Then, perform vacuum annealing at 400 °C for 2 hours to optimize the crystallinity of the film layer and reduce the temperature coefficient of resistance drift.

[0053] S06. Encapsulation of the cermet tube shell and the electrode: Perform plasma cleaning on the Al2O3 cermet tube shell, and locally nickel-plate it using a vacuum coating process; Use Ag-Cu-Ti active brazing filler metal to achieve the bonding of the electrode and the tube shell under the conditions of 950 °C and 10 -3 Pa in a vacuum brazing furnace.

[0054] S07. Vacuum eutectic sealing integration: Use Au-Si eutectic solder to complete the sealing welding of the silicon cover plate and the tube shell in a vacuum chamber; Suppress thermal stress by stepwise cooling (5 °C / min). After encapsulation, the airtightness retention rate of the device is > 99% under thermal shock from -20 to 150 °C.

[0055] For the parts not described in the above methods, the existing technologies can be adopted or borrowed to achieve the purpose.

[0056] The above only illustrates several specific embodiments of the present invention, but it cannot be regarded as the protection scope of the present invention. Any equivalent changes, modifications, equal-proportion enlargements or reductions, etc. made according to the design spirit of the present invention should be considered to fall within the protection scope of the present invention.

Claims

1. A high-light-power MEMS infrared light source for balancing stress, characterized in that: It includes a package. Inside the chamber of the package, a nickel plating layer is provided. The nickel plating layer is connected to the infrared light source electrode through a connection layer. At the top of the package, a cover plate is provided for sealing its opening. The infrared light source electrode is a hollow serpentine beam electrode, which includes an electrode body. The electrode body is longitudinally divided into several electrode regions. The middle regions of adjacent electrode regions are connected through. Inside each electrode region, a hollow structure is provided. At both ends of the electrode body, connection ends are respectively provided.

2. The high-light power MEMS infrared light source for balancing stress according to claim 1, wherein: The hollow structure includes strip-shaped holes. The strip-shaped holes are arranged along the longitudinal center line of the electrode region. At both ends of the strip-shaped holes, first triangular holes are symmetrically arranged. On both sides of the strip-shaped holes, several second triangular holes are symmetrically arranged. All the second triangular holes on each side are arranged in a longitudinal row, and adjacent two second triangular holes in each row are arranged in a reverse cross pattern.

3. The high-light-power MEMS infrared light source for balancing stress according to claim 2, characterized in that: The distance between the strip-shaped hole in the electrode region and the edge of the electrode region is called the beam width. And the beam width of the electrode regions located in the middle region of the electrode body gradually decreases towards the beam width of the electrode regions located in the regions on both sides of the electrode body.

4. A high-light-power MEMS infrared light source for balancing stress according to claim 3, characterized in that: The electrode regions located in the middle region of the electrode body are the first electrode regions. On both sides of the first electrode regions are the second electrode regions. On both sides of the second electrode regions are the third electrode regions, and so on. On both sides of the (N - 1)th electrode region are the Nth electrode regions. And the difference in beam width between the first electrode region and the second electrode region, the difference in beam width between the second electrode region and the third electrode region, and the difference in beam width between the (N - 1)th electrode region and the Nth electrode region are equal.

5. A high-light-power MEMS infrared light source for balancing stress according to claim 2, characterized in that: One of the vertices of the first triangular hole faces the strip-shaped hole. The orientation arrangement of the second triangular hole is perpendicular to that of the first triangular hole, and the area of the first triangular hole is larger than that of the second triangular hole.

6. The high-light power MEMS infrared light source with balanced stress according to claim 1, characterized in that: The package is a cermet package. The nickel plating layer is arranged at the middle position between the inner two side edges of the cermet package. The nickel plating layer is connected to the connection ends of the infrared light source electrode through a connection layer.

7. The high-light power MEMS infrared light source for balancing stress according to claim 1, wherein: The connection layer is an active metal layer, which is made of Ag, Cu, and / or Ti active brazing filler metals. The cover plate is a silicon cover plate. As a vacuum packaging cover plate, it is connected to the cermet package to ensure vacuum tightness inside the light source.

8. The manufacturing method of the high-light-power MEMS infrared light source with balanced stress according to any one of claims 1-7, characterized in that It includes the following steps: S01. Process the infrared light source electrode. S02. Ultrasonically clean the surface of the cermet package and locally nickel plate it to form a nickel plating layer on the package. Adopt the active metal brazing technology to connect the infrared light source electrode to the nickel plating layer of the cermet package. S03. Adopt the vacuum eutectic process to package the silicon cover plate and the cermet package.

9. The manufacturing method of a high-light-power MEMS infrared light source for balancing stress according to claim 8, wherein Step S01 includes the following steps: S011. Clean the silicon substrate with a cleaning solution, and then bond the nickel-chromium electrode material to the surface of the silicon substrate. S012. Use the photolithography etching process to process the required planar microstructures. S013. Adopt the micro-nano processing technology to divide the whole electrode into independent micro-units. S014. Peel the electrode micro-units from the silicon substrate with the aid of a micro-operation assembly system. S015. Adopt the grazing incidence evaporation process to process on the surface of the electrode to form a radiation layer.

10. The manufacturing method of a high-light-power MEMS infrared light source for balancing stress according to claim 8, wherein, In step S02: Use Ag-Cu-Ti active brazing filler metal to combine the infrared light source electrode and the nickel plating layer of the cermet package in a vacuum brazing furnace. In step S03: An Au-Si eutectic solder is used to complete the hermetic welding of the silicon cover plate and the cermet package in a vacuum chamber; thermal stress is suppressed by stepwise cooling, and the airtightness retention rate of the packaged device is >99% under thermal shock at -20 to 150 °C.

Images