WO2024087270A1 - 一种光电转换效率提升的mems红外光源 - Google Patents

一种光电转换效率提升的mems红外光源 Download PDF

Info

Publication number
WO2024087270A1
WO2024087270A1 PCT/CN2022/132886 CN2022132886W WO2024087270A1 WO 2024087270 A1 WO2024087270 A1 WO 2024087270A1 CN 2022132886 W CN2022132886 W CN 2022132886W WO 2024087270 A1 WO2024087270 A1 WO 2024087270A1
Authority
WO
WIPO (PCT)
Prior art keywords
layer
heating electrode
light source
pit
substrate
Prior art date
Application number
PCT/CN2022/132886
Other languages
English (en)
French (fr)
Inventor
刘军林
吕全江
侯海港
刘桂武
乔冠军
郝俊操
夏松敏
陈杰
Original Assignee
微集电科技(苏州)有限公司
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 微集电科技(苏州)有限公司 filed Critical 微集电科技(苏州)有限公司
Publication of WO2024087270A1 publication Critical patent/WO2024087270A1/zh

Links

Images

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B81—MICROSTRUCTURAL TECHNOLOGY
    • B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
    • B81B7/00—Microstructural systems; Auxiliary parts of microstructural devices or systems
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B81—MICROSTRUCTURAL TECHNOLOGY
    • B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
    • B81B7/00—Microstructural systems; Auxiliary parts of microstructural devices or systems
    • B81B7/02—Microstructural systems; Auxiliary parts of microstructural devices or systems containing distinct electrical or optical devices of particular relevance for their function, e.g. microelectro-mechanical systems [MEMS]

Definitions

  • the present invention belongs to the field of optoelectronic technology, and in particular relates to a MEMS infrared light source with improved photoelectric conversion efficiency.
  • Infrared sensing technology has been widely used in the fields of air quality detection, temperature monitoring, industrial process control, space monitoring, information communication, medicine and military.
  • Infrared light source is an important component of infrared sensing technology, and the commonly used luminous wavelengths are 3-5 microns and 8-14 microns.
  • Traditional thermal radiation infrared light sources such as incandescent lamps, have low electro-optical conversion efficiency and poor modulation characteristics; infrared diodes with a wavelength of 3-5 microns have low luminous efficiency and low output power, which limits their application; quantum cascade infrared lasers can emit high-intensity narrow-band infrared lasers, but their efficiency is not high and their manufacturing cost is high.
  • MEMS infrared light source made using micro-electromechanical system (MEMS) technology is a new type of thermal radiation infrared light source with high electro-optical conversion efficiency, small size, and low energy consumption.
  • the spectrum can easily cover the range of 2-20 microns, and it also has a faster modulation frequency. It has been widely used in the field of infrared sensing and has become a trending technology for infrared light sources.
  • the conventional structure of the MEMS infrared light source includes a substrate, a support layer is provided on the substrate, the support layer and the substrate are connected by a four-side fixed support structure, and a heating electrode layer is provided on the support layer. Joule heat is generated by energizing the heating electrode layer, so that the heating electrode layer is heated to a specific temperature (determined according to the required infrared emission wavelength and radiation amount), thereby generating infrared radiation.
  • the infrared radiation of the MEMS infrared light source is mainly emitted from two directions: one is radiated outward from the top of the heating electrode layer, and this part of the forward infrared radiation belongs to the effective radiation of the infrared sensor.
  • the other is the radiation transmitted from the heating electrode layer to the substrate via the support layer.
  • This part of the infrared radiation will be absorbed by the packaging material and substrate after the MEMS infrared light source is packaged, and cannot be effectively used, which belongs to the energy loss of the device. Therefore, the way to improve the photoelectric conversion efficiency of the device is to enhance the "forward radiation" of the device and suppress the "backward radiation” of the device.
  • the existing MEMS infrared light source will use the substrate hollowing technology shown in Figure 1. "Hollowing out” the substrate material from the bottom to the top can reduce the volume and mass of the substrate material, and reduce the heat capacity generated by the support layer and the substrate as a whole in the device; ultimately improving the electro-optical conversion efficiency of the MEMS infrared light source and reducing heating power consumption.
  • the hollowing out of the bottom of the substrate is also easier to achieve in terms of technology, and will not affect the generation of the various functional layers above the substrate and the product performance.
  • a reflective layer in the device to further suppress the "bottom radiation" of the device.
  • a reflective layer is set on the bottom surface of the substrate to reflect the infrared rays radiated from the heating electrode layer to the substrate part through the support layer, and then radiate upward through the heating electrode layer.
  • this solution reduces the energy loss caused by the "bottom radiation” of the device to a certain extent, it will also cause new technical problems.
  • the reflective layer that is directly and tightly attached to the substrate will also form a "connected" whole with the support layer, absorbing part of the energy, thereby increasing the heat capacity of the device and generating heat loss.
  • the structural design of the reflective layer and the support layer will cause a severe thermal strain effect during the switching stage of the device due to the large difference in the thermal expansion coefficients of the materials of the different functional layers, thereby increasing the risk of damage or shedding of the reflective layer, affecting the photoelectric conversion performance and service life of the light source.
  • the present invention provides a MEMS infrared light source with improved photoelectric conversion efficiency.
  • a MEMS infrared light source with improved photoelectric conversion efficiency comprises a substrate, a support layer, a heating electrode layer, an infrared emission layer stacked in sequence from bottom to top; and two heating electrode pads electrically connected to the heating electrode layer.
  • the upper surface of the substrate is provided with a pit that is sunken downward, and the pit includes a horizontal bottom surface and a sloped sidewall.
  • the substrate is in a four-sided fixed support structure connected to the upper support layer, and a cavity structure is formed between the two.
  • the enclosed area of the upper opening of the pit covers the infrared emitting layer; the enclosed area of the upper opening of the pit is located on the inner side of the two heating electrode pads, and the distribution area of the enclosed area of the upper opening of the pit along the extension direction of at least one end of the heating electrode pad exceeds the length range of the heating electrode pad.
  • the area of the support layer is larger than the upper opening of the pit and the heating electrode layer; and at least one penetrating sacrificial window is provided in the support layer, the sacrificial window is connected to the pit in the substrate below; the distribution position of the sacrificial window is tangent to or separated from the distribution position of the heating electrode layer.
  • a complete reflective layer is arranged on the bottom surface and side wall of the pit, and the reflective layer is made of a material with high reflectivity to infrared rays in the wavelength range of 2-14 microns.
  • the depth of the cavity structure is 1-50 ⁇ m.
  • the reflective layer is a metal coating film made of any one of Ag, Au, Cu, and Al, or a dielectric film Bragg reflective layer, or a multilayer composite film composed of any multiple single metal coating films stacked in a specified order.
  • the substrate material includes silicon and other materials that can be used as infrared light source substrates.
  • the support layer is made of a single material consisting of silicon oxide or silicon nitride, or a multi-layer composite material consisting of the two being alternately arranged and overlapped.
  • the infrared emitting layer is made of a material with high infrared emissivity and has a thickness of 50-1000 nm, wherein the material with high infrared emissivity includes any one or more mixtures of NiCr alloy, TiN, TiAlN, amorphous carbon, SiC, NiCrO compound, ZrO 2 , HfO 2 , La 1-x Ca x CrO 3 (0 ⁇ x ⁇ 0.5) and carbon nanotubes.
  • the emitting surface of the infrared emitting layer is a rough surface structure
  • the material of the heating electrode layer is any one of Pt, Mo, NiCr alloy, polysilicon, SiC, Cu, W, HfB 2 , PtSi and SnO 2 ;
  • a transition layer for improving the interface adhesion between the heating electrode layer and the support layer of the invention can be added.
  • the transition layer can be selected from any one of Ti, Cr and Ni according to the different materials of the heating electrode layer and the support layer.
  • the two heating electrode pads are parallel to each other and are electrically connected to the upper surface of the heating electrode layer; the infrared emission layer is located between the two heating electrode pads;
  • the heating electrode pad is made of any one of AlSi alloy, Au, Al, NiCr alloy and NiV alloy.
  • the heating electrode layer and the infrared emission layer are further provided with an isolation layer for blocking the electrical conduction effect between the two.
  • the isolation layer is made of one or a combination of any of silicon oxide, silicon nitride and aluminum oxide.
  • the infrared light source is further provided with a protective layer, which covers the area on the upper surface of the MEMS infrared light source except the heating electrode pad.
  • the material of the protective layer is selected from any one or more combinations of silicon oxide, silicon nitride, aluminum oxide, and hafnium oxide.
  • the MEMS infrared light source with improved photoelectric conversion efficiency provided by the present invention improves the structure of the substrate, and a specially shaped pit is opened on the substrate, so that a cavity located below the heating electrode layer and the infrared emission layer is formed between the pit and the support layer, and a complete reflection layer is generated on the wall of the pit.
  • the MEMS infrared light source with a special structure can simultaneously suppress the ineffective heat conduction of the device and the energy consumption generated by the ineffective infrared radiation, reduce the heat capacity of the device, and thus greatly improve the photoelectric conversion efficiency of the device.
  • the MEMS infrared light source with a special structure provided by the present invention also has strong thermal stability and structural strength; the life of the device and various weather resistance properties are also enhanced. Compared with traditional devices, the device has very outstanding performance advantages and is suitable for large-scale commercial promotion.
  • FIG. 1 is a schematic diagram of the longitudinal cross-sectional structure of a MEMS infrared light source prepared by substrate hollowing technology in the background art.
  • FIG. 2 is a schematic diagram of the longitudinal section structure of a MEMS infrared light source in the background art in which a reflective layer is arranged at the bottom of a hollowed-out substrate.
  • FIG3 is a schematic diagram of the overall structure of the MEMS infrared light source provided in Example 1 of the present invention.
  • FIG. 4 is a schematic structural diagram of a substrate including pits of a MEMS infrared light source provided in Example 1 of the present invention.
  • FIG5 is a schematic diagram of the cross-sectional structure of the MEMS infrared light source provided in Example 1 of the present invention.
  • FIG. 6 is a layered exploded diagram of the specific structure of the MEMS infrared light source provided in Example 1 of the present invention.
  • FIG. 7 is a schematic diagram of the cross-sectional structure of a MEMS infrared light source including a transition layer provided in Example 1 of the present invention.
  • FIG8 is a schematic diagram of the cross-sectional structure of a MEMS infrared light source with an isolation layer provided in Example 1 of the present invention.
  • FIG. 9 is a schematic cross-sectional structure diagram of a MEMS infrared light source with a protective layer provided in Example 1 of the present invention.
  • FIG. 10 is a method for manufacturing the MEMS infrared light source in Example 1 provided in Example 2 of the present invention.
  • FIG. 11 is a schematic diagram of the cross-sectional structure of the MEMS infrared light source of FIG. 5 from two side viewing angles.
  • the sacrificial window inside the support layer can be seen by longitudinal sectioning from this side.
  • FIG12 is a schematic diagram of the product structure obtained after the step of “masking the substrate” in Example 2 is completed.
  • FIG13 is a schematic diagram of the product structure obtained after the “corrosion window preparation” step in Example 2 is completed.
  • FIG14 is a schematic diagram of the product structure obtained after the “anisotropic etching” step in Example 2 is completed.
  • FIG15 is a schematic diagram of the product structure obtained after the step of “reflective layer preparation” in Example 2 is completed.
  • FIG16 is a schematic diagram of the product structure obtained after the “primary polishing” step in Example 2.
  • FIG17 is a schematic diagram of the product structure obtained after the “sacrificial layer preparation” step in Example 2 is completed.
  • FIG18 is a schematic diagram of the product structure obtained after the “secondary polishing” step in Example 2.
  • FIG19 is a schematic diagram of the product structure obtained after the “support layer preparation” step in Example 2 is completed.
  • FIG20 is a schematic diagram of the product structure obtained after the step of “preparing the heating electrode layer” in Example 2 is completed.
  • Figure 21 is a schematic diagram of the product structure obtained after the "isolation layer preparation" step in Example 2 is completed.
  • Figure 22 is a schematic diagram of the product structure obtained after the "heating electrode pad preparation" step in Example 2 is completed.
  • Figure 23 is a schematic diagram of the product structure obtained after the "infrared emission layer preparation" step in Example 2 is completed.
  • Figure 24 is a schematic diagram of the product structure obtained after the "protective layer preparation" step in Example 2 is completed.
  • Figure 25 is a schematic diagram of the product structure obtained after the "sacrificial window preparation" step in Example 2 is completed.
  • FIG26 is a schematic diagram of the product structure obtained after the “sacrificial layer removal” step in Example 2.
  • 100 pit; 101, substrate; 201, mask; 301, reflective layer; 401, sacrificial layer; 501, support layer; 601, heating electrode layer; 701, isolation layer; 801, heating electrode pad; 901, infrared emitting layer; 1001, protective layer; 1002, sacrificial window; 5011, transition layer.
  • Fig. 1 and Fig. 2 are schematic diagrams of the longitudinal cross-sectional structure of the MEMS infrared light source in the two existing schemes mentioned in the background technology. These two technical schemes are the same as the traditional infrared light source, and both include a substrate 101, a support layer 501, a heating electrode layer 601, an isolation layer 701, an infrared emission layer 901 and a heating electrode pad 801.
  • the device of this laminated structure can be processed and manufactured by the process of sequentially generating different functional layers on the substrate 101.
  • the substrate 101 is the basis for generating each functional layer above, which plays a role in providing stable attachment of each layer and providing good support.
  • the support layer 501 is an intermediate layer between the substrate 101 and the heating electrode layer 601, which plays a good supporting role, especially when the substrate 101 is subjected to special etching processing, the support layer 501 can provide a good supporting effect for each functional layer above, and evenly disperse the load generated by the compressive stress of each part above.
  • the heating electrode layer 601 is connected to the heating electrode pad 801.
  • the heating electrode pad 801 is used to connect the lead wire to power the heating electrode.
  • the heating electrode layer 601 material is a functional layer that can convert electrical energy into its own internal energy.
  • the heating electrode layer 601 will quickly heat up and generate infrared radiation in the conductive state.
  • the infrared emission layer 901 is a functional layer made of a material with ultra-high infrared emissivity. The functional layer will emit the received internal energy in the form of infrared radiation in a high temperature state.
  • the heating electrode layer 601 Since the main function of the heating electrode layer 601 is to generate infrared radiation and heat the infrared emission layer 901 directly in contact with the upper part by heat conduction, the infrared emission layer 901 can maintain the emission state. However, since the support layer 501 and the bottom surface of the infrared electrode layer are also in direct contact, the heat generated by the heating electrode layer will also be conducted to the support layer 501 and the substrate 101. For the MEMS infrared light source, the energy consumption of this part of the heat conducted to the support layer 501 and the substrate 101 is not converted into effective infrared radiation, which belongs to the ineffective power consumption of the device (a type of loss). The ineffective power consumption of the device will significantly reduce the photoelectric conversion efficiency of the MEMS light source.
  • the infrared radiation generated by the infrared emission layer 901 will radiate both upward and downward.
  • the upward radiation belongs to the effective radiation emitted, while the downward radiation cannot be effectively modulated and applied, which belongs to the ineffective radiation (a type of loss).
  • the generated ineffective radiation is another important reason for reducing the photoelectric conversion efficiency of the device.
  • the technical solution provided in FIG. 1 is mainly based on a multi-layer stacked MEMS infrared light source, and the position corresponding to the infrared emission layer 901 at the bottom of the substrate 101 is hollowed out.
  • the contact surface between the hollowed-out substrate 101 and the support layer 501 is reduced, and the volume and mass of the substrate 101 are greatly reduced; thus, the energy loss caused by heat conduction when the device is working can be effectively reduced, that is, a type of loss of the device is reduced.
  • the hollowed-out part is located on the bottom surface of the substrate 101, it will not affect the processing and forming of the functional layers above. However, it should be noted that: since the substrate 101 plays a supporting role in the device processing process, the substrate 101 must be hollowed out by photolithography, etching, etc. after all functional layers are formed.
  • the technical solution of Figure 2 is a further improvement of the solution of Figure 1 proposed by the inventor of this case.
  • the improvement mainly adds a reflective layer 301 to the hollowed-out portion of the bottom surface of the substrate 101; the reflective layer 301 is made of a material with high reflectivity for infrared radiation. Therefore, the reflective layer 301 can reflect the downward infrared radiation generated by the upper infrared emitting layer 901 back, and convert part of the invalid radiation into effective radiation. Thereby reducing the type II loss of the device.
  • the technical solution of Figure 2 reduces the type II loss of the device, it also has some disadvantages. The details of the shortcomings of the solution of Figure 2 will be specifically explained later when introducing the advantages of the improved solution provided in this embodiment.
  • this embodiment further provides a new type of MEMS infrared light source with improved photoelectric conversion efficiency.
  • the overall structure of the light source provided in this embodiment is shown in Figure 3.
  • the MEMS infrared light source includes a substrate 101, a support layer 501, a heating electrode layer 601, and an infrared emission layer 901 stacked in sequence from bottom to top; and two heating electrode pads 801 electrically connected to the heating electrode layer 601.
  • Figure 3 and the text and pictures in the following text of this embodiment mainly use rectangular light sources as examples when introducing this case.
  • the shape of the light source is not a restrictive technical feature of the solution of this embodiment, and the technical solution provided in this embodiment is not limited to any one shape.
  • the MEMS infrared light source with improved photoelectric conversion efficiency can adopt a rectangular light source, a circular light source, or even an elliptical, long strip, and any other irregular shape.
  • the upper surface of the substrate 101 of the MEMS infrared light source implemented in this embodiment is provided with a downwardly recessed pit 100, and the pit 100 includes a horizontal bottom surface and a sloped side wall.
  • the substrate 101 is in a four-sided fixed support structure connected to the upper support layer 501, and a cavity structure is formed between the two.
  • the enclosed area of the upper opening of the pit 100 covers the infrared emission layer 901. That is, the distribution area of the upper opening of the pit 100 can completely cover the upper infrared emission layer 901, which can be understood as the entire infrared emission layer 901 in the light source of this embodiment is "suspended" above the pit 100.
  • the enclosed area of the upper opening of the pit 100 is located on the inner side of the two heating electrode pads 801, and the distribution area of the enclosed area of the upper opening of the pit 100 along the extension direction of at least one end of the heating electrode pad 801 exceeds the length range of the heating electrode pad 801.
  • the length of the pit 100 along the extension direction parallel to the heating electrode pad 801 is longer than the infrared emission layer 901 (and the heating electrode layer 601) above.
  • the width of the pit 100 perpendicular to the extension direction of the heating electrode pad 801 is shorter than the infrared emission layer 901 (and the heating electrode layer 601) below.
  • this limitation should be met, that is, the pit 100 must be "sandwiched" between the two heating electrode pads 801, but slightly longer than the heating electrode pad 801.
  • the area of the support layer 501 of the MEMS infrared light source provided in this embodiment is larger than the upper opening of the pit 100 and the heating electrode layer 601.
  • at least one penetrating sacrificial window 1002 is provided in the support layer 501, and the sacrificial window 1002 is connected to the pit 100 in the substrate 101 below.
  • the distribution position of the sacrificial window 1002 is tangent to or separated from the distribution position of the heating electrode layer 601.
  • the support layer 501 completely "covers" the pit 100 on the substrate 101.
  • the heating electrode layer 601 just covers the support layer 501 at the position opposite to the pit 100.
  • the support layer 501 is provided with a sacrificial window 1002 that is connected to the pit 100 below, and the sacrificial window 1002 must be distributed at a position on the support layer 501 that will not be blocked by the heating electrode layer 601 and the infrared emission layer 901.
  • a complete reflective layer 301 is provided on the bottom surface and side walls of the pit 100 of the substrate 101.
  • the reflective layer 301 is made of a material with high reflectivity for infrared rays in the wavelength range of 2-14 microns.
  • the light source provided in this embodiment has a "hollowed out” structure similar to that of the scheme in FIG. 2, namely, the pit 100 in this case. Therefore, the substrate 101 in this case can also have the effect of reducing the heat capacity of the MEMS infrared light source and reducing the heat conduction from the heating electrode layer 601 to the substrate 101 part. Thus, a type of loss of the device is reduced.
  • the pit 100 in this case is different from the "hollowed out" method of the substrate 101 in FIG. 2.
  • the pit 100 in this case is located above the substrate 101, which forms a cavity between the substrate 101 and the support layer 501.
  • the functions of the cavity structure in this embodiment include the following two points: 1.
  • the cavity can effectively block the downward heat conduction path of the combination composed of the heating electrode layer 601 and the support layer 501, and play the first effect of reducing thermal radiation.
  • the gas medium in the cavity is equivalent to a "thermal blanket" composed of a layer of poor thermal conductor, which prevents heat from being transferred to the substrate 101 and dissipated from the larger surface of the substrate 101.
  • the structure of the pit 100 in this case is in the shape of a large upper opening and a small lower opening, as shown in FIGS. 4-6 , and the longitudinal cross-section of the pit 100 is roughly in the shape of a “water channel”.
  • the sloped wall of the pit 100 has at least the following advantages:
  • the material of the reflective layer 301 is mainly generated by sputtering or evaporation.
  • the sloped wall of the pit 100 can be conducive to better deposition of the reflective layer 301 material.
  • the dispersion effect and continuity of the reflective layer 301 in the pit 100 are improved to obtain a uniform and complete reflective layer 301.
  • the reflective effect of the reflective layer 301 on infrared radiation is enhanced.
  • the horizontal bottom surface of the pit 100 is equivalent to a plane reflector, which can completely reflect the bottom radiation of the infrared emission layer 901 above to the top of the infrared emission layer 901.
  • the sloped wall surface of the pit 100 is just above the pressure-bearing surface of the support layer 501, and is also the bearing support point of the heating electrode pad 801.
  • the sloped wall surface as shown in FIG5 is equivalent to a trapezoidal "bank" with a small upper bottom and a large lower bottom, which has a good pressure and impact resistance effect. This can make the MEMS infrared light source device have strong anti-seismic and pressure resistance performance and improve the service life of the product.
  • the pit 100 needs to be generated by various processes such as anisotropic etching or photolithography during processing.
  • This special shape of the pit 100 is also compatible with the process characteristics of chemical etching and laser etching, and is very easy to process; it can reduce the production cost of the product.
  • the distribution area of the pit 100 i.e., the distribution area of the reflective layer 301 just "shrinks" inside the two heating electrode pads 801, so that the heating electrode pads 801 can just overlap on the slope of the pit 100, maintaining a good support effect.
  • the infrared emission layer 901 between the heating electrode pads 801 can be completely “suspended” above the pit 100, so that all bottom radiation of the infrared emission layer 901 can reach the emission layer in the pit 100, thereby improving the reflectivity of the bottom radiation and suppressing the power of the second type of loss to the greatest extent.
  • the reflective layer 301 arranged on the wall of the cavity has the following advantages: since there is a cavity between the reflective layer 301 and the heating area of the MEMS light source, when the MEMS is frequently switched on and off, the temperature of the reflective layer 301 is relatively low and relatively stable, so the thermal expansion between the substrate 101 and the reflective layer 301 is not obvious, and the reflective layer 301 will not be significantly deformed or fall off.
  • the reflective layer 301 has good heat resistance, and even if the device is used for a long time, the reflective layer 301 is not easily damaged, the device has a long service life, and the device can maintain the best photoelectric conversion performance to the greatest extent.
  • the reflective layer 301 is in direct contact with the support layer 501 (equivalent to direct contact with the heating area of the MEMS).
  • the temperature of the reflective layer 301 changes dramatically during use, and the substrate 101 and the reflective layer 301 may undergo different degrees of thermal expansion, which may lead to a deterioration in the interface adhesion between the two, and in severe cases, may cause the reflective layer 301 to be damaged. Since the reflective layer 301 in FIG.
  • the reflective layer 301 is damaged, it may cause the reflective layer 301 to partially fall off, the uniformity and integrity of the reflective layer 301 to be destroyed, and the reflective effect of infrared radiation is lost. This leads to a decrease in the photoelectric conversion efficiency of the MEMS infrared light source.
  • one of the important functions of the processes such as hollowing out the cavity and the substrate 101 is to reduce the heat capacity of the device, thereby improving the photoelectric conversion efficiency of the device.
  • Heat capacity refers to the ability of an object to absorb and store thermal energy; the higher the heat capacity, the lower the temperature rise when absorbing the same amount of thermal energy.
  • the heat capacity is related to the volume/mass of the object, as well as the type of material and other properties.
  • the reflective layer 301 in this case is located under the cavity and does not contact the support layer 501, so it has almost no effect on the heat capacity of the device. In the solution in Figure 2, the reflective layer 301 is in direct contact with the support layer 501, and the reflective layer 301 increases the heat capacity of the device. This is not conducive to improving the photoelectric conversion efficiency of the device.
  • each functional layer above the substrate 101 is actually a layer of micron or nanometer-level coating or film. Therefore, these functional layers cannot be directly grown on the upper surface of the substrate 101 with the pit 100; otherwise, each functional layer will also have pits and cannot be in a planar state. Therefore, the pit 100 can only be processed after each functional layer is formed. However, after the functional layer is formed, it is technically not feasible to generate a pit 100 in the "center" of the device by etching.
  • the present invention has designed a special production process, which is specially used to produce the MEMS infrared light source with a special structure provided in this embodiment.
  • a key technical means of the processing technology provided in this embodiment is to use a material with certain specificity that can be selectively removed by a specific method as a sacrificial layer 401, and fill the sacrificial layer 401 in the processed pit 100 in advance, and then remove the sacrificial layer 401 material from the pit 100 after the functional layers above the pit 100 are formed.
  • the reserved sacrificial window 1002 on the support layer 501 is used to remove the sacrificial layer 401 material in the pit 100.
  • the sacrificial window 1002 designed in this embodiment is connected to the pit 100 in the substrate 101 below, so as to facilitate the removal of the sacrificial layer 401 material in the pit 100. It also needs to be tangent to or away from the distribution position of the heating electrode layer 601, thereby ensuring that the integrity of the functional layer above is not damaged and the functions of each functional layer above are not affected. At the same time, it is also necessary to avoid the functional layer above blocking or shielding the sacrificial window 1002.
  • the sacrificial window 1002 can be a through hole of any shape, such as a circular hole, a strip, etc.
  • the sacrificial window 1002 should be symmetrically arranged on the support layer 501, located on both sides of the heating electrode layer 601. This can ensure that the support layer 501 is balanced under stress and strain, and improve production yield and service life.
  • the best solution for the MEMS infrared light source provided in this embodiment is also to maintain good structural symmetry in the design of the overall structure (including each functional layer). To improve the structural strength, stress resistance and various performances of the device.
  • the depth of the cavity structure is 1-50 ⁇ m.
  • the cavity of the device can exert the best technical effect under the condition of this depth range.
  • the cavity depth is lower than the preferred interval, the substrate 101 is almost equivalent to the non-pit 100, and the support layer 501 and the substrate 101 are very close, and the above technical effect cannot be exerted.
  • the cavity depth is greater than the preferred interval, when the depth of the cavity is too large, the difficulty of processing is increased, and the reflection effect of the reflective layer 301 on infrared radiation will deteriorate.
  • the reflective layer 301 can be a metal coating film made of any one of Ag, Au, Cu, and Al.
  • a dielectric film Bragg reflective layer 301 can be used.
  • a multilayer composite film composed of any number of single metal coating films stacked in a specified order can be used.
  • Ag, Au, Cu, and Al are all materials with high infrared reflectivity.
  • the dielectric film Bragg emission layer is a common laminated optical film composed of high and low refractive index dielectric materials in a certain order. It can generate strong reflection of infrared rays of a specific wavelength or infrared rays of a wide spectrum through film layer design, and can also be used as a reflective film in this embodiment.
  • the cost of Ag and Au reflective layers 301 is much higher than that of Cu and Al; therefore, in practical applications, different materials can be layered on the substrate 101 as needed to form a composite reflective layer 301 thin film.
  • Cu is used as the base of the reflective layer 301, and a thinner Au coating is generated on the upper surface to form the required reflective layer 301.
  • the composite reflective layer 301 can not only maintain a high infrared radiation reflectivity, but also achieve better technical effects in terms of the production cost of the MEMS infrared light source and the comprehensive performance of material strength, toughness, wear resistance, etc.
  • the substrate 101 material in this embodiment includes silicon and other materials that can be used as the infrared light source substrate 101, such as quartz, glass, sapphire, etc.
  • silicon when silicon is used as the required substrate 101 material, the silicon (100) surface is usually used as the working surface for forming the pit 100 and various functional layers.
  • the anisotropic etching of silicon can be easily used to realize the pit 100 shape of an inverted trapezoid (large opening and small bottom surface).
  • the support layer 501 is made of a single material composed of silicon oxide or silicon nitride or a multilayer composite material composed of the two being arranged alternately and overlapped. Both silicon oxide and silicon nitride are inorganic non-metallic materials with high strength, high hardness, poor thermal conductivity, insulation, high temperature resistance, and corrosion resistance; they are very suitable for use as the support layer 501 material in the MEMS light source.
  • the infrared emission layer 901 in the MEMS light source of this embodiment is made of a material with high infrared emissivity and has a thickness of 50-1000 nm.
  • the material with high infrared emissivity includes any one or more of NiCr alloy, TiN, TiAlN, amorphous carbon, SiC, NiCrO compound, ZrO 2 , HfO 2 , La 1-x Ca x CrO 3 (0 ⁇ x ⁇ 0.5) and a mixture of carbon nanotubes.
  • the emission surface of the infrared emission layer 901 of this embodiment has a rough surface structure.
  • the rough surface structure improves the infrared emission capability of the MEMS infrared light source.
  • the material of the heating electrode layer 601 is any one of Pt, Mo, NiCr alloy, polysilicon, SiC, Cu, W, HfB2 , PtSi and SnO2 ; the above materials are all existing materials used to manufacture resistance heating units.
  • the heating electrode layer 601 prepared by these materials can convert electrical energy into internal energy more efficiently to generate heat after being powered on.
  • a transition layer 5011 for improving the interfacial adhesion between the heating electrode layer 601 and the support layer 501 can be added.
  • the transition layer 5011 is selected from any one of Ti, Cr, and Ni according to the different materials of the heating electrode layer 601 and the support layer 501.
  • an ultra-thin Cr coating can be added to the upper surface of the support layer 501 during the manufacturing process, so that the interfacial adhesion strength between the two is significantly improved. Avoid displacement of the heating electrode layer 601 and the support layer 501 during use, and improve the comprehensive performance of the product.
  • heating electrode pad 801 are parallel to each other and electrically connected to the upper surface of the heating electrode layer 601; the infrared emission layer 901 is located between the two heating electrode pads 801.
  • the heating electrode pad 801 is made of any one of AlSi alloy, Au, Al, NiCr alloy, and NiV alloy.
  • the main function of the heating electrode pad 801 is to introduce directional transmission electron migration on the heating electrode layer 601, thereby causing the heating electrode layer 601 to generate heat. Therefore, the material of the heating electrode pad 801 used in this embodiment is a material with high electrical conductivity, high thermal stability, and high weldability.
  • the heating electrode layer 601 and the infrared emission layer 901 are further provided with an isolation layer 701 for blocking the electrical conduction effect therebetween.
  • the isolation layer 701 is made of one or a combination of silicon oxide, silicon nitride and aluminum oxide.
  • the isolation layer 701 is usually used only when the material of the infrared emission layer 901 is also conductive. If the infrared emission layer 901 is made of insulating materials, such as ZrO 2 , HfO 2 , La 1-x Ca x CrO 3 (0 ⁇ x ⁇ 0.5), etc., there is no need to set the isolation layer 701 between the heating electrode layer 601 and the infrared emission layer 901.
  • the working mechanism of the isolation layer 701 is as follows: when the infrared emission layer 901 is made of conductive materials, if it is not electrically isolated from the heating electrode layer 601, then the current will also pass through the infrared emission layer 901, which will cause the resistance of the heating electrode layer 601 to change. Under the same external voltage, the temperature obtained by the MEMS light source will deviate greatly from the design value and cannot meet the working requirements.
  • the above problems can be solved by setting an insulating isolation layer 701 between the two.
  • the infrared light source is further provided with a protective layer 1001, and the protective layer 1001 covers the area on the upper surface of the MEMS infrared light source except for the heating electrode pad 801.
  • the protective layer 1001 plays a role in protecting the internal structure.
  • the material of the protective layer 1001 is mainly made of materials with strong infrared radiation transmittance, high strength and hardness; strong corrosion resistance and heat resistance.
  • the material of the protective layer 1001 selected in this embodiment includes any one or more combinations of silicon oxide, silicon nitride, aluminum oxide, and hafnium oxide.
  • this embodiment further provides a manufacturing method specifically for producing such a device.
  • the manufacturing process designed in this embodiment adopts the following steps based on the core structural features of the device: first, the pit 100 is etched out, and then the pit 100 is filled with the sacrificial layer 401 material, and then each functional layer is generated on the plane. Finally, after the functional layer is completely processed, the sacrificial window 1002 connected to the pit 100 is opened to replace the sacrificial layer 401 in the pit 100 to complete the product manufacturing.
  • the sacrificial window 1002 is set on the support layer 501 closest to the pit 100 in the substrate 101.
  • a MEMS infrared light source that only includes a substrate 101, a support layer 501, a heating electrode layer 601, and an infrared emission layer 901; and contains a cavity of a special shape between the substrate 101 and the support layer 501, and a reflective layer 301 of a specific shape is distributed in the cavity.
  • the manufacturing method provided in this embodiment includes the following process steps:
  • a substrate 101 is provided, and a preset amount of mask 201 layer material is deposited on the surface of the substrate 101 to be processed to form a required mask 201 layer.
  • the substrate 101 of this embodiment can be made of various existing materials.
  • the preferred material of the substrate 101 is silicon, and the silicon (100) crystal plane is used as the surface to be processed.
  • the material of the mask 201 layer is selected from any one of silicon oxide, silicon nitride, Cr, Au, Pt and NiCr alloy.
  • etching window is specifically designed according to the shape of the upper opening of the pit 100 of the designed MEMS infrared light source, and the area exposed below the etching window is the substrate 101 area that needs to be etched.
  • the substrate 101 is chemically etched by an anisotropic etching process to form a pit 100 in an etching window region of the substrate 101 that is recessed toward the inside of the substrate 101 and has a gradually decreasing diameter.
  • any one of TMAH aqueous solution, KOH aqueous solution, NaOH aqueous solution, ethylenediamine and catechol mixed aqueous solution, and NH 4 OH aqueous solution is used as the required anisotropic etching solution for the silicon substrate 101.
  • the etching process needs to be controlled so that the etching depth is controlled to be 1-50 ⁇ m.
  • a preset amount of reflective layer 301 material is deposited in the pit 100 on the surface of the substrate 101 by a physical vapor deposition process to form the required reflective layer 301.
  • the reflective layer 301 is a single metal coating made of one material among Ag, Au, Cu, and Al.
  • the reflective layer 301 is a composite metal coating made of multiple materials among Ag, Au, Cu, and Al deposited layer by layer.
  • a dielectric film Bragg coating is prepared as the required reflective layer 301.
  • the surface to be processed of the substrate 101 is polished to remove the surface coating of the substrate 101 in other areas except the pit 100, including the material of the etching mask 201 layer and the material of the reflective layer 301.
  • the polishing process adopts a wet etching method or a chemical mechanical polishing method.
  • wet etching is adopted, the etching mask 201 layer and other structures (reflective layer 301 and substrate 101) are selectively etched to remove the etching mask 201 layer and the reflective layer 301 material above it, so that the reflective layer 301 is retained in the pit 100, and the upper surface of the substrate 101 in the area outside the pit 100 is exposed.
  • the reflective layer 301 material and the etching mask 201 layer material in the area outside the pit 100 are polished off, the upper surface of the substrate 101 in the area outside the pit 100 is exposed, and the reflective layer 301 in the pit 100 is retained.
  • the pit 100 in the substrate 101 is filled with a sacrificial layer 401 material that can be selectively removed by any means.
  • the sacrificial layer 401 material is selected from SiO2 , phosphosilicate glass, silica gel, polyimide, SU-8, polydimethylsiloxane (PDMS), gelatin, polyethylene glycol, polyparaxylene, and benzocyclobutene.
  • the surface to be processed of the substrate 101 filled with the sacrificial layer 401 material is subjected to secondary polishing treatment, so that the sacrificial layer 401 material in the pit 100 is kept flush with the surrounding surface of the substrate 101.
  • the polishing treatment adopts dry etching or chemical mechanical polishing method.
  • the required support layer 501 is generated on the surface of the substrate 101 on the side containing the sacrificial layer 401, and the support layer 501 completely covers the substrate 101 and the sacrificial layer 401 below.
  • the support layer 501 is generated by physical vapor deposition or chemical vapor deposition process; the generated support layer 501 is a single coating composed of silicon oxide or silicon nitride, or a multi-layer composite coating composed of silicon oxide or silicon nitride deposited layer by layer in a preset order.
  • the required heating electrode layer 601 is prepared on the surface of the support layer 501, and the heating electrode layer 601 is located above the corresponding pit 100 in the substrate 101.
  • the left and right sides of the heating electrode layer 601 completely cover the pit 100, and the front and back sides are located in the area inside the pit 100 and do not cover the pit 100.
  • the heating electrode layer 601 is generated by physical vapor deposition or chemical vapor deposition process; the material of the heating electrode layer 601 is selected from any one of Pt, Mo, NiCr alloy, polysilicon, SiC, Cu, W, HfB2, PtSi and SnO2.
  • a transition layer 5011 composed of a specific material can be deposited on the surface of the support layer 501 first, and then the required heating electrode layer 601 is generated.
  • the transition layer 5011 is selected from any one of Ti, Cr, and Ni according to the different materials of the heating electrode layer 601 and the support layer 501.
  • Two parallel long strip heating electrode pads 801 are prepared above the heating electrode layer 601 and do not exceed the distribution area of the heating electrode layer 601.
  • the distribution areas of the two heating electrode pads 801 are separated from or circumscribed to the enclosed area of the upper opening of the pit 100.
  • the heating electrode pad 801 is electrically connected to the heating electrode layer 601 , and the material for preparing the heating electrode pad 801 is selected from any one of AlSi alloy, Au, Al, NiCr alloy, and NiV alloy.
  • the required infrared emission layer 901 is prepared on the heating electrode layer 601 inside the heating electrode pad 801.
  • the infrared emission layer 901 is located in the connection area of the four ends of the heating electrode pad 801.
  • the required infrared emission layer 901 is prepared by a material with high infrared emissivity.
  • the thickness of the prepared infrared emission layer 901 is 50-1000nm.
  • the material with high infrared emissivity includes any one or more mixtures of NiCr alloy, TiN, TiAlN, amorphous carbon, SiC, NiCrO compound, ZrO2 , HfO2 , La1 - xCaxCrO3 (0 ⁇ x ⁇ 0.5) and carbon nanotubes.
  • the emitting surface of the processed infrared emitting layer 901 has a rough surface structure.
  • the support layer 501 material is etched by photolithography technology, and at least one penetrating sacrificial window is processed in a specific area without damaging the heating electrode layer 601 and the infrared emission layer 901 above, so as to expose the sacrificial layer 401 material in the pit 100 below.
  • FIG11 is a schematic diagram of the cross-sectional structure of the MEMS infrared light source of FIG5 from the perspective of both sides, which can more intuitively show the relative position relationship between the sacrificial window and the support layer 501 and the pit 100.
  • a specific technical means is used to selectively remove all the sacrificial layer 401 materials filled in the pit 100 to form the required cavity structure; thereby preparing the required MEMS infrared light source.
  • a solvent or solution that can directionally etch the sacrificial layer 401 material is used as a selective etching liquid for immersion treatment, and the etching liquid diffuses into the cavity through the sacrificial window to completely remove the sacrificial layer 401 material in the cavity. After the sacrificial layer 401 is removed, the product is also cleaned and dried.
  • the final MEMS infrared light source includes four structural layers: substrate 101, support layer 501, heating electrode layer 601 and infrared emission layer 901; and there is a special-shaped cavity between the substrate 101 and the support layer 501, and a reflective layer 301 of a specific shape is distributed in the cavity.
  • a step of preparing the isolation layer 701 is added between steps (9) and (10).
  • the step of preparing the heating electrode pad 801 in step (10) needs to first remove the isolation layer 701 of a part of the area used to set the heating electrode pad 801 by a photolithography stripping method, so that the heating electrode pad 801 is electrically connected to the heating electrode layer 601 below; and in step (11), the infrared emission layer 901 is located on the upper surface of the isolation layer 701.
  • the isolation layer 701 is formed by physical vapor deposition or chemical vapor deposition process, and the material is one of silicon oxide, silicon nitride, and aluminum oxide, or a combination of any multiple thereof.
  • the overall structure of the prepared MEMS light source includes, from bottom to top, a substrate 101, a support layer 501, a heating electrode layer 601, an infrared emission layer 901, and a heating electrode pad 801.
  • a cavity is provided at the interface between the substrate 101 and the support layer 501, and a complete reflection layer 301 is provided on the inner wall of the cavity close to the substrate 101.
  • a step of preparing a protective layer 1001 is added between step (11) and step (12), and the prepared protective layer 1001 completely covers the upper surface of the infrared emission layer 901, the infrared electrode layer and the support layer 501.
  • the sacrificial window opened in step (12) actually removes the protective layer 1001 and the support layer 501 at the same time, because the protective layer 1001 also covers the support layer 501 in the area where the sacrificial window is opened.
  • the protective layer 1001 is formed by physical vapor deposition or chemical vapor deposition process, and the material is selected from any one or more combinations of silicon oxide, silicon nitride, aluminum oxide, and hafnium oxide.
  • the protective layer 1001 not only serves as the outer protective layer 1001 of the entire MEMS light source product produced, but also serves as the outer cladding covering the heating electrode layer 601, the isolation layer 701 and the infrared emission layer 901 when the substrate 101 is removed by a selective etchant in step (13).
  • the selective solvent can only enter the pit 100 of the substrate 101 from the sacrificial window.
  • Figures 12 to 26 show the complete manufacturing process of the complete product of Scheme 3 including the substrate 101, the support layer 501, the heating electrode layer 601, the isolation layer 701, the infrared emission layer 901, the heating electrode pad 801, and the protective layer 1001.
  • Figures 13 to 27 show the morphological changes of the semi-finished products or products obtained after the completion of different manufacturing process steps.
  • the mask 201 on the substrate 101 is processed and formed, it is roughly as shown in FIG. 12 , in which it can be seen that the mask 201 is located on the upper layer of the substrate 101 .
  • the etching window is successfully prepared, and the mask 201 includes a gap, as shown in FIG. 13 .
  • the substrate 101 at the mask 201 is not affected, and the exposed substrate 101 is etched. Moreover, because the anisotropic etching is adopted, the etched pit 100 is in a state of having a larger upper opening and a smaller lower opening as shown in FIG. 14 .
  • the reflective layer 301 is prepared by a sputtering or evaporation deposition process in this embodiment, the reflective layer 301 material is deposited on the upper surfaces of the substrate 101 and the mask 201 in FIG. 15 .
  • the goal of the first polishing is to remove the mask 201 material and the reflective layer 301 material on the surface of the substrate 101 except for the pit 100, so as to reach the state shown in FIG.
  • the sacrificial layer 401 is directly filled in the pit 100 .
  • the sacrificial layer 401 is usually allowed to “overflow” a little, as shown in FIG. 17 .
  • the goal of the secondary polishing is to remove the overflowed sacrificial layer 401 and re-expose the substrate 101 outside the pit 100; to achieve the effect shown in Figure 18, so a little more can be appropriately polished off during polishing to ensure that the sacrificial layer 401 material in the pit 100 remains flush with the surrounding substrate 101 surface.
  • a complete supporting layer 501 is grown on the sacrificial layer 401 and the substrate 101 .
  • a heating electrode layer 601 is formed on the support layer 501, and the heating electrode layer 601 is shorter than the support layer 501.
  • the length of the left and right sides of the electrode layer is longer than the pit 100, but at the viewing angles corresponding to the front and back sides of the figure, in order to reserve the sacrificial window, the heating electrode layer 601 is slightly shorter than the pit 100.
  • a complete isolation layer 701 is disposed above the heat-generating electrode layer 601 . As shown in FIG. 21 , the isolation layer 701 is as large as the heat-generating electrode layer 601 .
  • a heating electrode pad 801 is prepared on the isolation layer 701, as can be seen in FIG22, and the isolation layer 701 at the heating electrode pad 801 is removed, so that the heating electrode pad 801 is directly electrically connected to the heating electrode layer 601 below. It should be noted that the heating electrode pad 801 is actually in the shape of a long strip, which cannot be seen from the perspective of FIG22.
  • an infrared emitting layer 901 is prepared on the isolation layer 701 between two heating electrode pads 801 .
  • the infrared emission layer 901 is located at the top layer of the device, and because the sizes of the layers are inconsistent, it is in the shape of a “multi-layer cake” that shrinks step by step, so the protective layer 1001 will cover the infrared emission layer 901 , the isolation layer 701 , the heating electrode layer 601 and the support layer 501 .
  • the characteristic areas of the protective layer 1001 and the support layer 501 are penetrated to connect the pit 100 below and expose the sacrificial layer 401.
  • the sacrificial window cannot be seen from the corresponding viewing angles of Figures 12 to 24.
  • the schematic diagram of the specific sacrificial window can be seen in the top view of Figure 25.
  • the sacrificial layer 401 material in the pit 100 can be completely removed by using a specific solvent to obtain the final MEMS infrared light source product as shown in FIG. 26 .

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Micromachines (AREA)

Abstract

一种光电转换效率提升的MEMS红外光源，属于光电技术领域。光源包括从下至上依次叠加的衬底（101）、支撑层（501）、发热电极层（601）、红外发射层（901）以及与发热电极层（601）电连接的两条发热电极焊盘（801）。衬底（101）的上表面设有向下凹陷的凹坑（100），凹坑（100）包括一个水平的底面以及呈坡面状的侧壁。衬底（101）呈四边固支结构与上方的支撑层（501）相接，并在二者之间形成空腔结构。凹坑（100）上口的围合区域位于两条发热电极焊盘（801）的内侧，且沿发热电极焊盘（801）的延伸方向上的分布区域超出发热电极焊盘（801）的范围。支撑层（501）中设有至少一个贯穿的牺牲窗口（1002）。凹坑（100）底面和侧壁上设有完整的反射层（301）。光电转换效率提升的MEMS红外光源解决了现有MEMS红外光源中衬底和反射层的结构设计可能造成的器件热容升高、抗逆性和耐用性较差等问题。

Description

一种光电转换效率提升的MEMS红外光源 技术领域
本发明属于光电技术领域，具体涉及一种光电转换效率提升的MEMS红外光源。
背景技术
红外传感技术已经被广泛应用于大气质量检测、温度监控、工业过程控制、空间监控、信息通信、医学及军事等领域。红外光源是红外传感技术的重要元件，常用的发光波长为3-5微米以及8-14微米。传统热辐射红外光源如白炽灯，其电光转换效率低、调制特性差；而波长在3-5微米的红外二极管发光效率低，输出功率小，限制了其应用；量子级联红外激光器能够发射高强度的窄带红外激光，但效率也不高，且制造成本高昂。利用微机电系统(MEMS)技术制作的MEMS红外光源是一种新型的热辐射红外光源，具有电光转换效率高、体积小、能耗低等特点，同时光谱很容易覆盖2-20微米范围，还具有较快的调制频率，已经被广泛应用于红外传感领域，成为红外光源的趋势性技术。
常规结构的MEMS红外光源包含衬底，在衬底上设有支撑层，支撑层和衬底采用四边固支结构连接，在支撑层上设有发热电极层。通过给发热电极层通电产生焦耳热，使发热电极层升温至特定温度(根据所需红外发射波长和辐射量确定)，进而产生红外辐射。MEMS红外光源的红外辐射主要从两个方向出射：一个是从发热电极层上方向外辐射，这部分前向的红外辐射属于红外传感器的有效辐射。另一个是从发热电极层经由支撑层向衬底传递的辐射，这部分红外辐射在MEMS红外光源封装后将被封装材料和衬底等吸收，无法有效利用，属于器件的能量损耗。因此，提高器件的光电转换效率的途径就是增强器件的“前向辐射”并抑制器件的“后向辐射”。
为了增强发热电极层上方的“前向辐射”，技术人员通常会选择具有高发射率的材料制作发热电极层或者在发热电极层表面增设具有更高红外发射率的红外发射层。为了抑制红外光源中“底向辐射”造成的能量损失；现有MEMS红外光源会采用如图1所示的衬底掏空技术，将衬底材料从底面向上“掏空”可以减小衬底材料的体积和质量，降低器件中由支撑层和衬底整体产生的热容；最终提升了MEMS红外光源的电光转换效率并降低加热功耗。同时，衬底底部掏空在工艺上也较易实现，不会对衬底上方的各个功能层的生成和产品性能造成影响。
此外，部分技术人员还会在器件中设置反射层，以达到进一步抑制器件“底向辐射”的目的。例如在中国发明专利申请公开号CN114249292A提供的如图2的技术方案中，在衬底底面设置反射层，将发热电极层经由支撑层向衬底部分辐射的红外线反射回去，再经过发热电极层向上辐射。该方案虽然在一定程度降低了器件“底向辐射”产生的能量损耗，但是也会造成新的技术问题。例如，与衬底直接紧密贴合的反射层本身也会和支撑层构成一个“联通”的整体，吸收部分能量，进而增大器件的热容，产生热损耗。同时，反射层与支撑层贴合的结构设计，在器件开关阶段会因不同功能层材料热膨胀系数差异较大而导致剧烈的热应变效应，进而增大反射层破损或脱落的风险，影响光源光电转换性能和使用寿命。
发明内容
为了解决现有MEMS红外光源中反射层的结构设计可能造成的器件热容升高、抗逆性和耐用性较差等问题；本发明提供了一种光电转换效率提升的MEMS红外光源。
本发明采用以下技术方案实现：
一种光电转换效率提升的MEMS红外光源，其包括从下至上依次叠加的衬底、支撑层、发热电极层、红外发射层；以及与发热电极层电连接的两条发热电极焊盘。
衬底的上表面设有向下凹陷的凹坑，凹坑包括一个水平的底面以及呈坡面状的侧壁。衬底呈四边固支结构与上方的支撑层相接，并在二者之间形成空腔结构。凹坑上口的围合区域覆盖红外发射层；凹坑上口的围合区域位于两条发热电极焊盘的内侧，且凹坑上口围合区域沿发热电极焊盘的至少一端的延伸方向上的分布区域超出发热电极焊盘的长度范围。
支撑层的面积大于凹坑的上口以及发热电极层；且支撑层中设有至少一个贯穿的牺牲窗口，牺牲窗口与下方的衬底中的凹坑连通；牺牲窗口的分布位置与发热电极层的分布位置相切或相离。
凹坑底面和侧壁上设有完整的反射层，反射层由对2-14微米波长范围的红外线具有高反射率的材料制备而成。
作为本发明进一步的改进，空腔结构的深度为1-50μm。
作为本发明进一步的改进，反射层采用由Ag、Au、Cu、Al中的任意一种制备而成的金属镀层薄膜。或采用介质膜布拉格反射层。或采用由任意多种单一的金属镀层薄膜按照指定顺序叠加构成的多层复合薄膜。
作为本发明进一步的改进，衬底材料包括硅以及其它可作为红外光源衬底的材料。
作为本发明进一步的改进，支撑层采用由氧化硅或氮化硅构成的单一材料或由二者间隔交叠设置构成的多层复合材料。
作为本发明进一步的改进，红外发射层为由高红外发射率的材料制备而成，厚度为50-1000nm。其中，高红外发射率的材料包括NiCr合金、TiN、TiAlN、非晶碳、SiC、NiCrO化合物、ZrO 2、HfO 2、La 1-xCa xCrO 3(0≤x≤0.5)以及碳纳米管中的任意一种或多种的混合物。
本发明中，红外发射层的发射面呈粗糙面结构；
作为本发明进一步的改进，发热电极层的材料采用Pt、Mo、NiCr合金、多晶硅、SiC、Cu、W、HfB 2、PtSi以及SnO 2中的任意一种；
在发明的发热电极层与支撑层之间还可以增加用于提高二者界面附着力的过渡层。过渡层根据采用的发热电极层和支撑层材料的不同而选自Ti、Cr、Ni中的任意一种。
作为本发明进一步的改进，两条发热电极焊盘相互平行，二者电连接在发热电极层的上表面；红外发射层位于两条发热电极焊盘之间；
在本发明中，发热电极焊盘采用AlSi合金、Au、Al、NiCr合金、NiV合金中的任意一种材料制备而成。
作为本发明进一步的改进，发热电极层和红外发射层还设置有用于阻断二者之间的电传导效应的隔离层。隔离层的材料采用氧化硅、氮化硅、氧化铝中的一种或任意多种的组合。
作为本发明进一步的改进，红外光源还设置有保护层，保护层覆盖在MEMS红外光源上表面中除所述发热电极焊盘以外的区域。所述保护层的材料选自氧化硅、氮化硅、氧化铝、氧化铪中的任意一种或多种的组合。
本发明提供的技术方案，具有如下有益效果：
本发明提供的光电转换效率提升的MEMS红外光源对衬底的结构进行了改进，在衬底上方开设了特殊形状的凹坑，进而使得凹坑和支撑层间形成了一个位于发热电极层和红外发射层下方的空腔，同时还在凹坑的壁面生成了完整的反射层。该特殊结构的MEMS红外光源可以同时抑制器件的无效热传导以及无效的红外辐射产生的能耗，降低器件的热容；进而大幅提高器件的光电转换效率。
此外，本发明提供的特殊结构的MEMS红外光源还具有很强的热稳定性和结构强度；器件的寿命和各项耐候性能也得到了增强。相对传统器件而言，该器件具有非常突出的性能优势，适合进行大规模的商用推广。
附图说明
图1为背景技术中衬底掏空技术制备的MEMS红外光源的纵剖面结构示意图。
图2为背景技术中在掏空衬底底部设置反射层的MEMS红外光源的纵剖面结构示意图。
图3为本发明实施例1中提供的MEMS红外光源的整体结构示意图。
图4为本发明实施例1中提供的MEMS红外光源的包含凹坑的衬底的结构示意图。
图5为本发明实施例1中提供的MEMS红外光源的剖面结构示意图。
图6为本发明实施例1中提供的MEMS红外光源具体结构的分层爆炸图。
图7为本发明实施例1中提供的包含过渡层的MEMS红外光源的剖面结构示意图。
图8为本发明实施例1中提供的带有隔离层的MEMS红外光源的剖面结构示意图。
图9为本发明实施例1中提供的带有保护层的MEMS红外光源的剖面结构示意图。
图10为本发明实施例2中提供的一种制造实施例1中的MEMS红外光源的制造方法。
图11为图5的MEMS红外光源的沿两侧视角下的剖面结构示意图，从该侧进行纵剖可以看到支撑层内部的牺牲窗口。
图12为实施例2中“衬底的掩膜处理”步骤结束后得到的产品结示意图。
图13为实施例2中“腐蚀窗口制备”步骤结束后得到的产品结示意图。
图14为实施例2中“各向异性腐蚀”步骤结束后得到的产品结示意图。
图15为实施例2中“反射层制备”步骤结束后得到的产品结示意图。
图16为实施例2中“一次抛光”步骤结束后得到的产品结示意图。
图17为实施例2中“牺牲层制备”步骤结束后得到的产品结示意图。
图18为实施例2中“二次抛光”步骤结束后得到的产品结示意图。
图19为实施例2中“支撑层制备”步骤结束后得到的产品结示意图。
图20为实施例2中“发热电极层制备”步骤结束后得到的产品结示意图。
图21为实施例2中“隔离层制备”步骤结束后得到的产品结示意图。
图22为实施例2中“发热电极焊盘制备”步骤结束后得到的产品结示意图。
图23为实施例2中“红外发射层制备”步骤结束后得到的产品结示意图。
图24为实施例2中“保护层制备”步骤结束后得到的产品结示意图。
图25为实施例2中“牺牲窗口制备”步骤结束后得到的产品结示意图。
图26为实施例2中“牺牲层去除”步骤结束后得到的产品结示意图。
图中标记为：
100、凹坑；101、衬底；201、掩膜；301、反射层；401、牺牲层；501、支撑层；601、发热电极层；701、隔离层；801、发热电极焊盘；901、红外发射层；1001、保护层；1002、牺牲窗口；5011、过渡层。
具体实施方式
为了使本发明的目的、技术方案及优点更加清楚明白，以下结合附图及实施例，对本发明进行进一步地详细说明。应当理解，此处所描述的具体实施例仅用以解释本发明，并不用于限定本发明。
实施例1
图1和图2是背景技术中提及的两个现有方案中的MEMS红外光源的纵向剖面结构示意图。这两种技术方案和传统红外光源相同，都包括衬底101、支撑层501、发热电极层601、隔离层701、红外发射层901和发热电极焊盘801。这种叠层结构的器件可以通过在衬底101上依次生成不同功能层的工艺来加工制造。其中，衬底101是生成上方的各个功能层的基础，起到供各层稳定附着，以及提供良好的支撑作用等效果。支撑层501是衬底101和发热电极层601之间的中间层，起到良好的支撑作用，尤其是在衬底101进行特殊的蚀刻加工时，支撑层501可以为上方各功能层起到良好的支撑效果，均匀分散上方各部分的压应力产生的负荷。
发热电极层601和发热电极焊盘801相接，发热电极焊盘801用于接引线进而为发热电极供电，发热电极层601材料是一种可将电能转换为自身内能功能层，发热电极层601在导 电状态会迅速升温发热；并向外产生红外辐射。红外发射层901则是由具有超高红外发射率的材料制备而成的功能层，该功能层在高温状态下会将接收到的内能以红外辐射的形式发射出去。
由于发热电极层601的主要功能就是产生红外辐射以及通过热传导的方式对上方直接接触红外发射层901进行加热，使得红外发射层901可以保持发射状态。但是由于支撑层501和红外电极层底面也是直接接触的，因此加热电极层产生的热量也会传导至支撑层501以及衬底101部分。而对于MEMS红外光源来说，传导至支撑层501和衬底101部分的这部分热量的能耗是并未转化为有效的红外辐射的，属于器件的无效功耗(一类损耗)，器件的无效功耗会显著降低MEMS光源的光电转换效率。另一方面，红外发射层901产生的红外辐射既会向上辐射，也会向下辐射，向上辐射的属于发射出去的有效辐射，而向下辐射的部分无法进行有效调制和应用，属于无效辐射(二类损耗)，产生的无效辐射是降低器件的光电转换效率的另一个重要原因。
图1提供的技术方案主要是在多层堆叠式MEMS红外光源的基础上，将衬底101底部对应红外发射层901的位置掏空，掏空后的衬底101与支撑层501的接触面减小，衬底101的体积和质量大幅缩小；进而可以有效降低器件工作时因热传导产生的能量损失，即减小器件的一类损耗。同时，由于掏空部分位于衬底101的底面，所有不会影响上方各功能层的加工成型。但是需要说明的是：由于衬底101在器件加工过程中起支撑作用，所以衬底101必须要在所有功能层成型后再通过光刻、腐蚀等方式掏空。
图2的技术方案是本案发明人提出的对图1方案的进一步改进。改进点主要是在衬底101的底面掏空部分增加了一个反射层301；反射层301采用对红外辐射具有高反射率的材料制备而成。因此，反射层301可以将上方红外发射层901产生的向下的红外辐射反射回去，将部分无效辐射转化为有效辐射。进而降低器件的二类损耗。图2的技术方案在降低器件的二类损耗的同时，也会存在一些弊端。图2方案的缺点的详细内容将在后续介绍本实施例提供的改进方案的优势时进行针对性说明。
具体地，本实施例在图1和图2对应的技术方案的基础上，更进一步提供一种新型的光电转换效率提升的MEMS红外光源。本实施例提供的光源的整体结构如图3所示，该MEMS红外光源包括从下至上依次叠加的衬底101、支撑层501、发热电极层601、红外发射层901；以及与发热电极层601电连接的两条发热电极焊盘801。需要强调的是，图3以及本实施例后文的文字和图片部分在对本案进行介绍时，主要是以矩形光源形态进行举例说明的。但是光源的形状并不是本实施例方案的一个限制性技术特征，本实施例提供的技术方案并不局限于任意一种形状。该光电转换效率提升的MEMS红外光源可以采用矩形光源、也可以采用圆形光源，甚至是椭圆形、长条形，以及其它任意不规则形态。
本实施例提供技术方案与现有方案的主要区别在于：如图4所示，本实施的MEMS红外光源的衬底101的上表面设有向下凹陷的凹坑100，凹坑100包括一个水平的底面以及呈坡面状的侧壁。衬底101呈四边固支结构与上方的支撑层501相接，并在二者之间形成空腔结构。结合图5可知，在本实例提供的MEMS红外光源中，凹坑100上口的围合区域覆盖红外发射层901。即凹坑100上口的分布区域可以完整覆盖住上方的红外发射层901，可以理解为本实施例方案光源中的整个红外发射层901是“悬”在凹坑100上方的。
请结合图6，在本实施例提供的MEMS红外光源的衬底101中，凹坑100上口的围合区域位于两条发热电极焊盘801的内侧，且凹坑100上口围合区域沿发热电极焊盘801的至少一端的延伸方向上的分布区域超出发热电极焊盘801的长度范围。通俗来说，以矩形光源为例，凹坑100沿平行于发热电极焊盘801延伸方向上的长度要比上方的红外发射层901(以及发热电极层601)要长。而凹坑100垂直于发热电极焊盘801延伸方向上的宽度要比下方的红外发射层901(以及发热电极层601)要短。当光源采用其它形状时，应当满足这一限定，即：凹坑100必须“夹”在两条发热电极焊盘801之间，但是要比发热电极焊盘801略 长一点。
同时，如图5所示，本实施例提供的MEMS红外光源的支撑层501的面积大于凹坑100的上口以及发热电极层601。且如图3和图6所示，支撑层501中设有至少一个贯穿的牺牲窗口1002，牺牲窗口1002与下方的衬底101中的凹坑100连通。牺牲窗口1002的分布位置与发热电极层601的分布位置相切或相离。具体来说就是，支撑层501完整“盖住”衬底101上的凹坑100。且发热电极层601恰好罩在正对凹坑100处的支撑层501上方。同时，支撑层501中设置有与下方的凹坑100相通的牺牲窗口1002，且牺牲窗口1002必须分布在支撑层501上不会被发热电极层601和红外发射层901遮挡的位置。
本实施例提供的MEMS红外光源中，衬底101的凹坑100底面和侧壁上设有完整的反射层301，反射层301由对2-14微米波长范围的红外线具有高反射率的材料制备而成。
以下结合本实施例提供的MEMS光源的上述技术特征对该光源产品的工作原理和性能优势进行详细的说明。
首先，本实施例提供的光源中存在和图2方案相似的“掏空”结构，即本案中的凹坑100。因此本案的衬底101也可以具有降低MEMS红外光源的热容，减少发热电极层601向衬底101部分的热传导的效果。进而降低器件的一类损耗。但是，本案的凹坑100又和图2中的衬底101“掏空”方式不一样。特别地，本案中的凹坑100是位于衬底101上方的，这使得衬底101和支撑层501之间会形成一个空腔。本实施中空腔结构的功能包括以下两点：1、空腔可以有效阻隔发热电极层601和支撑层501构成的组合体向下的热传导路径，起到第一重削减热辐射的效果。2、空腔中气体介质又相当于一层热的不良导体构成的“保温被”，避免热量传递到衬底101上从衬底101上较大的表面散失掉。
其次，本案中凹坑100的结构呈上口大下口的小的形状，具体如图4-6所示，凹坑100纵向截面大致呈“水渠”状。考虑到凹坑100的壁面和底面会生成所需反射层301。因此这种带有斜坡的凹坑100壁面至少包括以下几个优势：
(1)反射层301材料主要是通过溅射或者蒸发工艺生成的。凹坑100的斜坡型壁面可以有利于更好的沉积反射层301材料。提高反射层301在凹坑100内的分散效果和连续性，得到一个均一的完整的反射层301。增强反射层301对红外辐射的反射效果。
(2)凹坑100的水平底面相当于一个平面反射镜，可以完整地将上方的红外发射层901的底向辐射反射到红外发射层901上方。
(3)凹坑100的斜坡壁面的正上方恰好是支撑层501的受压面，也是发热电极焊盘801的承载支点。本案中如图5的斜坡壁面则相当于一个上底小下底大的梯形“堤岸”，起到了良好的耐压和耐冲击效果。这可以使得MEMS红外光源的器件具备较强的抗震和耐压性能；提高产品的使用寿命。
(4)凹坑100在加工中需要通过各项异性腐蚀或光刻加工等工艺生成。这种特殊形状的凹坑100也恰好和化学腐蚀以及激光蚀刻的工艺特点相适应，非常容易加工出来；可以降低产品的生产成本。
另外，本实施例提供MEMS红外光源的技术方案中，凹坑100分布区域(即反射层301分布区域)恰好“收缩”在两条发热电极焊盘801内侧，这使得发热电极焊盘801可以恰好搭接在凹坑100的坡面上，保持良好的支撑效果。而发热电极焊盘801之间的红外发射层901又可以完整“悬”在凹坑100上方，这使得红外发射层901的所有底向辐射均能到达凹坑100内的发射层上，进而提高底向辐射的反射率，最大幅度抑制二类损耗的功率。
需要特别强调一点：在本实施例提供的技术方案中，衬底101由于和支撑层501之间具有一个有凹坑100形成的空腔；设置在空腔壁面上的反射层301，就会具有如下的优势：由于反射层301与MEMS光源的发热区中间有空腔隔离，因此当MEMS频繁开关时，反射层301的温度相对比较低且比较稳定，所以衬底101和反射层301之间热膨胀不明显，反射层301不会发生明显的变形或脱落。即本实施例的方案中，反射层301的耐热性能较好，即使 器件长时间使用，反射层301也不容易损坏，器件的使用寿命较长，也可以最大程度保持器件最佳的光电转换性能。
而对于图2中的现有方案而言，当MEMS红外光源频繁开关时，反射层301与支撑层501之间直接接触(相当于与MEMS的发热区直接接触)，此时反射层301在使用过程中的温度变化剧烈，衬底101和反射层301可能会发生不同程度的热膨胀，进而导致二者界面附着效果变差，严重时会导致反射层301破损。由于图2反射层301是位于衬底101下方的，一旦反射层301破损，就可能导致反射层301局部脱落、反射层301的均一性和完整性被破坏，失去红外辐射的反射作用。进而导致MEMS红外光源的光电转换效率降低。
同时，空腔和衬底101掏空等工艺的其中一个重要作用都是降低器件的热容，进而提高器件的光电转换效率。(注：热容指物体对热能的吸收和储蓄能力；热容越高，吸收相同热能的温度升高幅度越低，热容与物体的体积/质量，以及材料类型等属性相关。)而本案的反射层301位于空腔下，不与支撑层501接触，所以对器件的热容几乎没有影响。而图2中的方案，反射层301是与支撑层501直接接触，反射层301增大了器件的热容。这对于提高器件的光电转换效率是不利的。
最后，本实施例在支撑层501上预留的具有特殊形状和位置的牺牲窗口1002的主要作用是便于产品的加工。众所周知，衬底101上方的各个功能层实际上都是一层微米或纳米级别的镀层或薄膜。因此这些功能层是无法直接生长在带有凹坑100的衬底101上表面的；否则得到各个功能层也是带有凹坑的，无法呈平面状态。因此，凹坑100只能在各个功能层形成之后再进行加工。但是，功能层形成后，再通过蚀刻在器件“中央”生成一个凹坑100在技术上并不可行。
针对这一问题，本发明设计了一种特殊的生产工艺，专门用于生产本实施例提供的具有特殊结构的MEMS红外光源。本实施例提供的加工工艺的一个关键技术手段就是采用具有某种特异性可以通过特定方法选择性去除的材料作为牺牲层401，预先将牺牲层401填在加工出的凹坑100中，待凹坑100上方的各功能层形成后，再将牺牲层401材料从凹坑100内去除。而支撑层501上的预留的牺牲窗口1002就是用来去除凹坑100内的牺牲层401材料的。
特别地，本实施例设计的牺牲窗口1002既与下方的衬底101中的凹坑100连通，便于对凹坑100中的牺牲层401材料进行去除。又需要和发热电极层601的分布位置相切或相离；进而保证不会对上方的功能层的完整性造成破坏，不影响上方各个功能层的功能。同时也要避免上方的功能层对牺牲窗口1002造成堵塞或者遮挡。
在实际应用中，牺牲窗口1002至少有一个，牺牲窗口1002可以采用任意形状的通孔，例如圆孔状、条状等等。在最优的方案中，牺牲窗口1002应当在支撑层501上对称设置，位于发热电极层601的两侧。这可以保证支撑层501受到应力应变作用保持平衡，提高生产良率和使用寿命。推广开来，本实施例提供的MEMS红外光源的最佳方案也是在整体结构(包括各个功能层)的设计上保持良好的结构对称性。以提升器件的结构强度、抗逆性和各项性能。
在本实施例提供的MEMS红外光源中，空腔结构的深度为1-50μm。器件的空腔在该深度范围条件下能够发挥最佳的技术效果。当空腔深度低于该优选区间时，衬底101几乎等同于无凹坑100，支撑层501和衬底101非常靠近，无法发挥上述技术效果。当空腔深度大于该优选区间时，空腔的深度过大时，提升了加工的难度，同时反射层301对红外辐射的反射效果会变差。
在本实施例中，反射层301可以采用由Ag、Au、Cu、Al中的任意一种制备而成的金属镀层薄膜。或采用介质膜布拉格反射层301。或采用由任意多种单一的金属镀层薄膜按照指定顺序叠加构成的多层复合薄膜。Ag、Au、Cu、Al都是具有高红外反射率的材料。介质膜布拉格发射层是一种常见的由高低折射率介质材料按照一定次序组成的叠层光学薄膜，可以 通过膜层设计对特定波长的红外线或者宽光谱红外线产生强反射，也可以作为本实施例中的反射膜。
考虑到不同材料的成本不一样，Ag、Au反射层301的成本比Cu、Al高很多；因此在实际应用中还可以根据需要将不同材料分层设置在衬底101上，以形成复合反射层301薄膜。例如以Cu为反射层301基底，在上表面生成较薄的Au镀层，构成所需的反射层301。复合反射层301不仅可以保持较高的红外辐射反射率，还可以在MEMS红外光源的生产成本和材料强度、韧性、耐磨性等综合性能方面达到更好的技术效果。
本实施例中的衬底101材料包括硅以及其它可作为红外光源衬底101的材料，如石英、玻璃、蓝宝石等等。其中，使用硅作为所需的衬底101材料时，通常将采用硅(100)面作为形成凹坑100以及各功能层的作业面，此时可以非常容易地采用硅的各项异性腐蚀实现倒梯形(开口大，底面小)的凹坑100形状。
在本实施例中，支撑层501采用由氧化硅或氮化硅构成的单一材料或由二者间隔交叠设置构成的多层复合材料。氧化硅和氮化硅均为强度高、硬度大、导热性差、绝缘、耐高温、耐腐蚀的无机非金属材料；非常适合作为MEMS光源中的支撑层501材料使用。
本实施例的MEMS光源中的红外发射层901为由高红外发射率的材料制备而成，厚度为50-1000nm。其中，高红外发射率的材料包括NiCr合金、TiN、TiAlN、非晶碳、SiC、NiCrO化合物、ZrO 2、HfO 2、La 1-xCa xCrO 3(0≤x≤0.5)以及碳纳米管中的任意一种或多种的混合物。
特别地，本实施例的红外发射层901的发射面呈粗糙面结构。粗糙面结构提高MEMS红外光源的红外发射能力。
在本实施例中，发热电极层601的材料采用Pt、Mo、NiCr合金、多晶硅、SiC、Cu、W、HfB 2、PtSi以及SnO 2中的任意一种；以上材料都是现有的用于制造电阻发热单元的材料，这些材料制备的发热电极层601在通电后可以将电能更大效率地转换成内能进行发热。
如图7所示，在本发明更优化的技术方案中，发热电极层601与支撑层501之间还可以增加用于提高二者界面附着力的过渡层5011。过渡层5011根据采用的发热电极层601和支撑层501材料的不同而选自Ti、Cr、Ni中的任意一种。例如当发热电极层601采用Pt材料制备而成，而支撑层501采用SiO 2材料时，可以在制造过程中在支撑层501上表面增加一层超薄的Cr镀层，从而使得二者的界面附着力强度显著提升。避免发热电极层601和支撑层501在使用过程中发生位移，提高产品的综合性能。
本实施例中，两条发热电极焊盘801相互平行，二者电连接在发热电极层601的上表面；红外发射层901位于两条发热电极焊盘801之间。发热电极焊盘801采用AlSi合金、Au、Al、NiCr合金、NiV合金中的任意一种材料制备而成。发热电极焊盘801的主要作用就是在发热电极层601上引入定向传输的电子迁移，进而使得发热电极层601产热。因此本实施例采用的发热电极焊盘801的材料为具有较高的电导率、高热稳定性、可焊性高的材料。
如图8所示，在本实施例更优化的方案中，发热电极层601和红外发射层901还设置有用于阻断二者之间的电传导效应的隔离层701。隔离层701的材料采用氧化硅、氮化硅、氧化铝中的一种或任意多种的组合。
隔离层701通常仅在红外发射层901材料也具有导电性时才采用，如果红外发射层901采用绝缘材料生产，如ZrO 2、HfO 2、La 1-xCa xCrO 3(0≤x≤0.5)等时，则无需在发热电极层601和红外发射层901之间设置隔离层701。隔离层701的工作机理如下：当红外发射层901采用导电材料时，如果不和发热电极层601进行电气隔离，那么电流也会经过红外发射层901，这会导致发热电极层601的电阻发生变化，在外加电压相同的情况下，MEMS光源所获得的温度会与设计值发生较大偏差，无法满足工作需求。而在二者之间设置绝缘的隔离层701则可以解决以上问题。
如图9所示，在本实施例更优化的方案中，红外光源还设置有保护层1001，保护层1001 覆盖在MEMS红外光源上表面中除所述发热电极焊盘801以外的区域。保护层1001起到对内部结构进行保护的作用，在本实施例中，根据对器件的性能要求，保护层1001材料主要采用具有较强的红外辐射透过率，较高的强度和硬度；较强的耐腐蚀性能和耐热性能的材料制备而成。具体地，本实施例中选择的保护层1001的材料包括氧化硅、氮化硅、氧化铝、氧化铪中的任意一种或多种的组合。
实施例2
针对实施例1中具有特殊结构的光电转换效率提升的MEMS红外光源，本实施例进一步提供了一个专用于生产该类器件的制造方法。本实施例设计的制造工艺根据器件的核心结构特征采用：先蚀刻出凹坑100，再通过牺牲层401材料对凹坑100进行填平，然后在平面上生成各功能层，最后在功能层完全加工出来后，再通过开设的连通凹坑100的牺牲窗口1002置换掉凹坑100内的牺牲层401的工艺完成产品制造。特别地，该工艺为了实现牺牲层401的选择性移除，将牺牲窗口1002设置在了最接近衬底101中凹坑100的支撑层501上。
方案一
如图10所示，对于仅包含衬底101、支撑层501、发热电极层601和红外发射层901；且在衬底101和支撑层501之间含有特殊形态的空腔，空腔内分布有特定形状反射层301的MEMS红外光源。本实施例提供的制造方法包括如下工艺步骤：
(1)衬底的掩膜处理：
提供衬底101，在衬底101的待加工面上沉积预设量的掩膜201层材料，构成所需的掩膜201层。
特别地，本实施例的衬底101材料可以选择现有各类材料。其中，衬底101的优选材料为硅，并将硅(100)晶面作为待加工面。掩膜201层的材料选自氧化硅、氮化硅、Cr、Au、Pt和NiCr合金中的任意一种。
(2)腐蚀窗口制备：
按照预设的窗口尺寸和形状，利用光刻技术去除待加工面上的部分掩膜201层以在衬底101上形成腐蚀窗口。腐蚀窗口按照设计的MEMS红外光源的凹坑100上口的形状进行针对性设计，腐蚀窗口的下方露出的区域即为需要进行腐蚀的衬底101区域。
(3)各向异性腐蚀：
通过各向异性腐蚀的工艺对所述衬底101进行化学腐蚀，以在衬底101中的腐蚀窗口区域形成向衬底101内部凹陷且口径逐渐缩小的凹坑100。
本实施例中，采用TMAH水溶液、KOH水溶液、NaOH水溶液、乙二胺和邻苯二酚混合水溶液、NH 4OH水溶液中的任意一种作为所需的硅衬底101各向异性腐蚀液。在腐蚀过程中，需要对腐蚀过程进行控制，以使得腐蚀的深度控制为1-50μm。
(4)反射层制备：
采用物理气相沉积工艺在衬底101表面的凹坑100中沉积预设量的反射层301材料，构成所需的反射层301。反射层301采用Ag、Au、Cu、Al中的一种材料制成的单一金属镀层。或反射层301采用Ag、Au、Cu、Al中的多种材料逐层沉积制成复合金属镀层。或者制备介质膜布拉格镀层作为所需的反射层301。
(5)一次抛光：
对衬底101的待加工面进行抛光处理，去除衬底101表面除凹坑100以外的其它区域的表面镀层，包括腐蚀掩膜201层材料和反射层301材料。抛光处理采用湿法腐蚀或者化学机械抛光的方法。当采用湿法腐蚀时，通过对腐蚀掩膜201层和其他结构(反射层301和衬底101)的选择性腐蚀，去除腐蚀掩膜201层并剥离掉其上方的反射层301材料，这样便在凹坑100中保留了反射层301，而露出了凹坑100以外区域的衬底101上表面。当采用化学机械抛光时，则是抛掉凹坑100以外区域的反射层301材料和腐蚀掩膜201层材料，露出凹坑100以外区域的衬底101上表面，而保留凹坑100内的反射层301。
(6)牺牲层制备：
在衬底101中的凹坑100中填充可通过任意一种手段选择性移除的牺牲层401材料。牺牲层401材料选择SiO 2、磷硅玻璃、硅胶、聚酰亚胺、SU-8、聚二甲基硅氧烷(PDMS)、明胶、聚乙二醇、聚对二甲苯、苯并环丁烯中的一种。
(7)二次抛光：
对填充有所述牺牲层401材料的衬底101的待加工面进行二次抛光处理，以使得凹坑100中的牺牲层401材料与周围的衬底101表面保持齐平。抛光处理采用干法刻蚀或者化学机械抛光的方法。
(8)支撑层制备：
在衬底101中含有牺牲层401一侧的表面生成所需的支撑层501，支撑层501完整覆盖下方的衬底101和牺牲层401。支撑层501采用物理气相沉积或化学气相沉积工艺生成；生成的支撑层501为氧化硅或氮化硅构成的单一镀层，或由氧化硅或氮化硅按照预设顺序逐层沉积构成的多层复合镀层。
(9)发热电极层制备：
在支撑层501表面制备所需的发热电极层601，发热电极层601位于对应衬底101中凹坑100上方的位置。发热电极层601的左右两侧完整覆盖凹坑100，前后两侧位于相对凹坑100内侧的区域，未覆盖凹坑100。发热电极层601通过物理气相沉积或化学气相沉积工艺生成；发热电极层601的材料选自Pt、Mo、NiCr合金、多晶硅、SiC、Cu、W、HfB2、PtSi以及SnO2中的任意一种。
为了提高支撑层501和发热电极层601之间的界面附着力，在更优化的实施例中，还可以先在支撑层501表面沉积一层由特定材料构成的过渡层5011；然后再生成所需的发热电极层601。其中，过渡层5011根据采用的发热电极层601和支撑层501材料的不同而选自Ti、Cr、Ni中的任意一种。
(10)发热电极焊盘制备：
在发热电极层601上方制备两条相互平行的不超过发热电极层601分布区域的长条状的发热电极焊盘801。其中，两条发热电极焊盘801的分布区域与凹坑100上口的围合区域相离或外切。
发热电极焊盘801与发热电极层601形成电连接，制备发热电极焊盘801的材料选自AlSi合金、Au、Al、NiCr合金、NiV合金中的任意一种。
(11)红外发射层制备：
在发热电极焊盘801内侧的发热电极层601上方制备所需的红外发射层901。红外发射层901位于发热电极焊盘801四个端点的连线区域内。
通过高红外发射率的材料制备所需的红外发射层901。制备出的红外发射层901的厚度为50-1000nm。其中，采用的高红外发射率的材料包括NiCr合金、TiN、TiAlN、非晶碳、SiC、NiCrO化合物、ZrO 2、HfO 2、La 1-xCa xCrO 3(0≤x≤0.5)以及碳纳米管中的任意一种或多种的混合物。
特别地，在其它更优化的实施例中，加工出的红外发射层901的发射面呈粗糙面结构。
(12)牺牲窗口制备：
通过光刻技术对支撑层501材料进行蚀刻，在不破坏上方的发热电极层601和红外发射层901的基础上，选择特定区域加工出至少一个贯穿的牺牲窗口，以露出下方凹坑100中的牺牲层401材料。图11为图5的MEMS红外光源的沿两侧视角下的剖面结构示意图，可以更加直观的看到牺牲窗口与支撑层501及凹坑100的相对位置关系。
(13)牺牲层401去除：
根据选择的牺牲材料的特异性，采用特定的技术手段选择性去除凹坑100内的填充的所有牺牲层401材料，以形成所需的空腔结构；进而制备出所需的MEMS红外光源。
采用可定向腐蚀牺牲层401材料的溶剂或溶液作为选择性腐蚀液进行浸渍处理，腐蚀液通过牺牲窗口扩散到空腔内，完全去除空腔内的牺牲层401材料。牺牲层401去除后还对产品进行清洗和干燥。
最终制备出的MEMS红外光源中包含衬底101、支撑层501、发热电极层601和红外发射层901四个结构层；且在衬底101和支撑层501之间含有特殊形态的空腔，空腔内分布有特定形状反射层301。
方案二
在方案一的基础上，当制备出的红外发射层901具有导电性时，在步骤(9)、(10)之间增加一个制备隔离层701的步骤。且在制备隔离层701之后，步骤(10)的发热电极焊盘801制备步骤需要首先通过光刻剥离方法去除用于设置发热电极焊盘801的部分区域的隔离层701，以使得发热电极焊盘801与下方的发热电极层601电连接；且步骤(11)中红外发射层901位于隔离层701的上表面。
具体地，隔离层701采用物理气相沉积或化学气相沉积工艺生成，材料采用氧化硅、氮化硅、氧化铝中的一种或任意多种的组合。
此时制备出的MEMS光源的整体结构从下向上包括衬底101、支撑层501、发热电极层601、红外发射层901，以及发热电极焊盘801。其中衬底101和支撑层501的界面处设有空腔，空腔中靠近衬底101一侧的内壁上设有完整的反射层301。
方案三
在方案二的基础上，为了提高产品的耐腐蚀等耐候性能，在步骤(11)和步骤(12)之间，增加一个制备保护层1001的步骤，制备出的保护层1001完整覆盖在红外发射层901、红外电极层和支撑层501的上表面。且在步骤(12)中开设的牺牲窗口事实上同时去除了保护层1001和支撑层501，因为保护层1001也覆盖在开设牺牲窗口区域的支撑层501上方。
在本实施例中，保护层1001采用物理气相沉积或化学气相沉积工艺生成，材料选自氧化硅、氮化硅、氧化铝、氧化铪中的任意一种或多种的组合。
需要特别说明的是：本实施例提供的制造方法中，保护层1001不仅作为生产出的整个MEMS光源产品的外保护层1001。而且还作为步骤(13)中通过选择型腐蚀剂去除衬底101时，覆盖在发热电极层601、隔离层701和红外发射层901外的外包层。此时，选择性溶剂只能从牺牲窗口进入到衬底101的凹坑100内。选择腐蚀剂时，只要选择可以腐蚀牺牲层401，但是不会对支撑层501、衬底101、反射层301和保护层1001材料造成影响的溶剂即可。
为了对本实施例中提供的制造工艺进行更清楚的展示，以下结合从图12-26的一组连续动图，来说明方案三中包含衬底101、支撑层501、发热电极层601、隔离层701、红外发射层901、发热电极焊盘801，以及保护层1001的完整产品的完整制造过程。图13-27展示的是不同制造工艺步骤完成后得到的半成品或产品的形态变化图。
1、衬底的掩膜处理
衬底101上的掩膜201加工成型后大致如图12所示，图中可见掩膜201位于衬底101上层。
2、腐蚀窗口制备
腐蚀窗口制备成功，掩膜201上包含了一个缺口，大致如图13所示。
3、各向异性腐蚀
各向异性腐蚀后，掩膜201处衬底101不受影响，露出的衬底101被腐蚀，并且因为采用各向异性腐蚀，所以腐蚀出的凹坑100呈如图14的上口大下口小的状态。
4、反射层制备
因为本实施例中制备反射层301采用了溅射或者蒸发的沉积工艺，所以图15中衬底101和掩膜201上表面都沉积上了反射层301材料。
5、一次抛光
一次抛光的目标是为了去除衬底101表面的除凹坑100处以外的掩膜201材料和反射层301材料。达到如图16的状态。
6、牺牲层制备
牺牲层401是直接填在凹坑100内的，为了保证牺牲层401完全填满，通常要让牺牲层401“溢出来”一些，如图17所示。
7、二次抛光
二次抛光的目标是去除溢出来的牺牲层401，将凹坑100以外的衬底101重新暴露出来；达到如图18的效果，因此在抛光时可以适当多磨掉一点，保证凹坑100中的牺牲层401材料与周围的衬底101表面保持齐平。
8、支撑层制备
图19中可见，牺牲层401和衬底101上方又生长出了一层完整的支撑层501。
9、发热电极层制备
图20可见，支撑层501上方形成了发热电极层601，发热电极层601比支撑层501短。同时，当前视角下，电极层左右两侧的长度比凹坑100要长，但是在对应该图前后两侧的视角下，为了预留牺牲窗口，发热电极层601反而比凹坑100略短。
10、隔离层制备
本实施例在发热电极层601上方设置了完整的隔离层701，如图21所示，隔离层701和发热电极层601一样大。
11、发热电极焊盘制备
本实施例在隔离层701上制备发热电极焊盘801，图22中可见，并去除了发热电极焊盘801处的隔离层701，使发热电极焊盘801直接和下方的发热电极层601电连接。需要说明，发热电极焊盘801实际上是长条形的，这点从图22视角看不出来。
12、红外发射层制备
从图23中可知，本实施例在两条发热电极焊盘801之间的隔离层701上制备了红外发射层901。
13、保护层制备
如图24所示，红外发射层901位于器件最上层，并且由于各层大小不一致，呈一个逐级收缩的“多层蛋糕”状，所以保护层1001会覆盖红外发射层901、隔离层701、发热电极层601和支撑层501。
14、牺牲窗口制备
本实施例将保护层1001和支撑层501的特点区域打穿，连通下方的凹坑100，暴露出牺牲层401。在图12-图24对应视角下是看不到牺牲窗口的，具体的牺牲窗口的示意图可以参见图25俯视图。
15、牺牲层去除
有了牺牲窗口1002之后，采用特定溶剂可以将凹坑100内的牺牲层401材料完整去除，得到如图26的最终的MEMS红外光源产品。
以上所述仅为本发明的较佳实施例而已，并不用以限制本发明，凡在本发明的精神和原则之内所作的任何修改、等同替换和改进等，均应包含在本发明的保护范围之内。

Claims (10)

  1. 一种光电转换效率提升的MEMS红外光源，其包括从下至上依次叠加的衬底、支撑层、发热电极层、红外发射层；以及与所述发热电极层电连接的两条发热电极焊盘；其特征在于：
    所述衬底的上表面设有向下凹陷的凹坑，所述凹坑包括一个水平的底面以及呈坡面状的侧壁；所述衬底呈四边固支结构与上方的所述支撑层相接，并在二者之间形成空腔结构；所述凹坑上口的围合区域覆盖所述红外发射层；所述凹坑上口的围合区域位于两条所述发热电极焊盘的内侧，且凹坑上口围合区域沿所述发热电极焊盘的至少一端的延伸方向上的分布区域超出所述发热电极焊盘的长度范围；
    所述支撑层的面积大于所述凹坑的上口以及所述发热电极层；且所述支撑层中设有至少一个贯穿的牺牲窗口，所述牺牲窗口与下方的所述衬底中的凹坑连通；牺牲窗口的分布位置与上方的所述发热电极层的分布位置相切或相离；
    所述凹坑底面和侧壁上设有完整的反射层，所述反射层由对2-14微米波长范围的红外线具有高反射率的材料制备而成。
  2. 如权利要求1所述的光电转换效率提升的MEMS红外光源，其特征在于：所述空腔结构的深度为1-50μm。
  3. 如权利要求1所述的光电转换效率提升的MEMS红外光源，其特征在于：所述反射层采用由Ag、Au、Cu、Al中的任意一种制备而成的金属镀层薄膜；或采用介质膜布拉格反射层；或采用由任意多种单一的金属镀层薄膜按照指定顺序叠加构成的多层复合薄膜。
  4. 如权利要求1所述的光电转换效率提升的MEMS红外光源，其特征在于：所述衬底材料包括硅以及其它可作为红外光源衬底的材料。
  5. 如权利要求1所述的光电转换效率提升的MEMS红外光源，其特征在于：所述支撑层采用由氧化硅或氮化硅构成的单一材料或由二者间隔交叠设置构成的多层复合材料。
  6. 如权利要求1所述的光电转换效率提升的MEMS红外光源，其特征在于：所述红外发射层为由高红外发射率的材料制备而成，厚度为50-1000nm；其中，所述高红外发射率的材料包括NiCr合金、TiN、TiAlN、非晶碳、SiC、NiCrO化合物、ZrO 2、HfO 2、La 1-xCa xCrO 3(0≤x≤0.5)以及碳纳米管中的任意一种或多种的混合物；且/或所述红外发射层的发射面呈粗糙面结构；
  7. 如权利要求1所述的光电转换效率提升的MEMS红外光源，其特征在于：所述发热电极层的材料采用Pt、Mo、NiCr合金、多晶硅、SiC、Cu、W、HfB 2、PtSi以及SnO 2中的任 意一种；
    且/或
    在所述发热电极层与支撑层之间增加用于提高二者界面附着力的过渡层；所述过渡层根据采用的发热电极层和支撑层材料的不同而选自Ti、Cr、Ni中的任意一种。
  8. 如权利要求1所述的光电转换效率提升的MEMS红外光源，其特征在于：两条所述发热电极焊盘相互平行，二者电连接在所述发热电极层的上表面；所述红外发射层位于两条所述发热电极焊盘之间；
    且/或
    所述发热电极焊盘采用AlSi合金、Au、Al、NiCr合金、NiV合金中的任意一种材料制备而成。
  9. 如权利要求1所述的光电转换效率提升的MEMS红外光源，其特征在于：所述发热电极层和所述红外发射层还设置有用于阻断二者之间的电传导效应的隔离层；所述隔离层的材料采用氧化硅、氮化硅、氧化铝中的一种或任意多种的组合。
  10. 如权利要求1所述的光电转换效率提升的MEMS红外光源，其特征在于：所述红外光源还设置有保护层，所述保护层覆盖在所述MEMS红外光源上表面中除所述发热电极焊盘以外的区域；
    且/或
    所述保护层的材料选自氧化硅、氮化硅、氧化铝、氧化铪中的任意一种或多种的组合。
PCT/CN2022/132886 2022-10-25 2022-11-18 一种光电转换效率提升的mems红外光源 WO2024087270A1 (zh)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CN202211310539.8A CN115818556A (zh) 2022-10-25 2022-10-25 一种光电转换效率提升的mems红外光源
CN202211310539.8 2022-10-25

Publications (1)

Publication Number Publication Date
WO2024087270A1 true WO2024087270A1 (zh) 2024-05-02

Family

ID=85525399

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CN2022/132886 WO2024087270A1 (zh) 2022-10-25 2022-11-18 一种光电转换效率提升的mems红外光源

Country Status (2)

Country Link
CN (1) CN115818556A (zh)
WO (1) WO2024087270A1 (zh)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117776089A (zh) * 2024-02-27 2024-03-29 北京中科海芯科技有限公司 一种红外光源器件、红外光源阵列及其制作方法

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103332648A (zh) * 2013-04-10 2013-10-02 南京曼莫斯电子科技有限公司 电调制mems 红外光源及其制备方法
CN104291263A (zh) * 2014-08-25 2015-01-21 厦门脉科优芯电子科技有限公司 一种金刚石桥膜结构微型红外光源芯片及制备方法
CN105004694A (zh) * 2015-05-29 2015-10-28 苏州诺联芯电子科技有限公司 基于mems技术的阵列式红外光源器件及其制备方法
CN109231154A (zh) * 2018-08-27 2019-01-18 杭州北芯传感科技有限公司 一种硅-玻璃密封的黑硅表面红外光源芯片及制备方法
US20210278282A1 (en) * 2018-11-28 2021-09-09 Korea Advanced Institute Of Science And Technology Mems device having curved reflective layer and method for manufacturing mems device
CN114249292A (zh) * 2021-11-29 2022-03-29 江苏大学 一种mems红外光源及其制造方法

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN100483255C (zh) * 2004-09-01 2009-04-29 中国科学院电子学研究所 基于微电子机械系统技术的红外光源及制备方法
CN102384789B (zh) * 2010-08-30 2013-06-26 中国科学院微电子研究所 红外焦平面阵列器件及其制作方法
CN106276773B (zh) * 2016-08-31 2018-06-29 中国科学院微电子研究所 悬浮结构的mems红外光源及其制备方法
CN106629577B (zh) * 2016-12-30 2019-02-05 中国科学院微电子研究所 一种mems红外光源及其制作方法
TW201924086A (zh) * 2017-11-15 2019-06-16 南韓商Ａｕｋ公司 改善反射率的光反射型紅外線發光二極體晶片及其製造方法
US10636777B2 (en) * 2017-12-22 2020-04-28 Ams Sensors Uk Limited Infra-red device
CN212030738U (zh) * 2020-06-12 2020-11-27 北京泊菲莱科技有限公司 一种高功率红外辐射光源结构
CN113358596B (zh) * 2021-06-07 2024-03-22 大连理工大学 一种双层气室的微型ndir集成红外气体传感器
CN114671397A (zh) * 2021-12-31 2022-06-28 深圳市美思先端电子有限公司 一种硅基mems红外光源及其制备方法

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103332648A (zh) * 2013-04-10 2013-10-02 南京曼莫斯电子科技有限公司 电调制mems 红外光源及其制备方法
CN104291263A (zh) * 2014-08-25 2015-01-21 厦门脉科优芯电子科技有限公司 一种金刚石桥膜结构微型红外光源芯片及制备方法
CN105004694A (zh) * 2015-05-29 2015-10-28 苏州诺联芯电子科技有限公司 基于mems技术的阵列式红外光源器件及其制备方法
CN109231154A (zh) * 2018-08-27 2019-01-18 杭州北芯传感科技有限公司 一种硅-玻璃密封的黑硅表面红外光源芯片及制备方法
US20210278282A1 (en) * 2018-11-28 2021-09-09 Korea Advanced Institute Of Science And Technology Mems device having curved reflective layer and method for manufacturing mems device
CN114249292A (zh) * 2021-11-29 2022-03-29 江苏大学 一种mems红外光源及其制造方法

Also Published As

Publication number Publication date
CN115818556A (zh) 2023-03-21

Similar Documents

Publication Publication Date Title
US7704764B2 (en) Fabrication method of GaN power LEDs with electrodes formed by composite optical coatings
JP5511114B2 (ja) 光抽出を向上させた微小発光ダイオードアレイ
JP5770143B2 (ja) 発光素子及びその製造方法
TWI420693B (zh) 發光二極體及其製程
TWI411124B (zh) 發光二極體裝置及其製造方法
JP6839668B2 (ja) 電流遮断層を有する発光素子
WO2024087270A1 (zh) 一种光电转换效率提升的mems红外光源
CN101641847A (zh) 光子晶体激光器及其制造方法
CN104576857B (zh) 一种高反射层倒装led芯片结构及其制作方法
CN114249292A (zh) 一种mems红外光源及其制造方法
JP2011166146A (ja) 分布ブラッグ反射器を有する発光ダイオードチップ及びその製造方法
KR100917792B1 (ko) 반사판을 구비한 마이크로 히터 및 그 제조방법
TWI429110B (zh) 具有自我複製式光子晶體之發光元件與其製造方法
JP2001160654A (ja) 光学素子、レーザアレイ、および光学素子の製造方法
CN110176525A (zh) 亚波长垂直结构发光二极管及其制备方法
CN113555484A (zh) 高光萃取率的高光效倒装led芯片及其制备方法
KR20050070854A (ko) 반도체 ｌｅｄ 소자
JP2006086254A (ja) 発光素子およびその製造方法ならびにその発光素子を用いた照明装置
CN218202203U (zh) 一种mems红外光源的衬底结构
CN116040574A (zh) 一种mems红外光源的制造方法
WO2022094801A1 (zh) 谐振腔发光二极管及其制备方法
CN115642209A (zh) 一种Micro-LED芯片结构及其制备方法
CN221093749U (zh) 一种高性能的新型mems红外光源
JP5243817B2 (ja) 赤外線放射素子
CN209150487U (zh) 一种垂直腔面发射激光器

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 22963249

Country of ref document: EP

Kind code of ref document: A1