CN115818556A - MEMS infrared light source with improved photoelectric conversion efficiency - Google Patents

MEMS infrared light source with improved photoelectric conversion efficiency Download PDF

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Publication number
CN115818556A
CN115818556A CN202211310539.8A CN202211310539A CN115818556A CN 115818556 A CN115818556 A CN 115818556A CN 202211310539 A CN202211310539 A CN 202211310539A CN 115818556 A CN115818556 A CN 115818556A
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layer
substrate
light source
heating electrode
infrared light
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刘军林
吕全江
侯海港
刘桂武
乔冠军
郝俊操
夏松敏
陈杰
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Weijidian Technology Suzhou Co ltd
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Weijidian Technology Suzhou Co ltd
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Priority to CN202211310539.8A priority Critical patent/CN115818556A/en
Priority to PCT/CN2022/132886 priority patent/WO2024087270A1/en
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B81MICROSTRUCTURAL TECHNOLOGY
    • B81BMICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
    • B81B7/00Microstructural systems; Auxiliary parts of microstructural devices or systems
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B81MICROSTRUCTURAL TECHNOLOGY
    • B81BMICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
    • B81B7/00Microstructural systems; Auxiliary parts of microstructural devices or systems
    • B81B7/02Microstructural 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]

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Abstract

The invention belongs to the technical field of photoelectricity, and particularly relates to an MEMS infrared light source with improved photoelectric conversion efficiency. The light source comprises a substrate, a supporting layer, a heating electrode layer and an infrared emission layer which are sequentially stacked from bottom to top; and two heat generating electrode pads electrically connected to the heat generating electrode layer. The upper surface of the substrate is provided with a pit which is sunken downwards and comprises a horizontal bottom surface and a slope-shaped side wall. The substrate is in a four-side fixed support structure and is connected with the supporting layer above the substrate, and a cavity structure is formed between the substrate and the supporting layer. The enclosing area of the upper opening of the pit is positioned on the inner sides of the two heating electrode pads, and the distribution area along the extension direction of the heating electrode pads exceeds the range of the heating electrode pads. At least one through sacrificial window is provided in the support layer. And complete reflecting layers are arranged on the bottom surfaces and the side walls of the pits. The invention solves the problems of increased heat capacity, poor anti-inversion performance and durability and the like of devices possibly caused by the structural design of the substrate and the reflecting layer in the existing MEMS infrared light source.

Description

MEMS infrared light source with improved photoelectric conversion efficiency
Technical Field
The invention belongs to the technical field of photoelectricity, and particularly relates to an MEMS infrared light source with improved photoelectric conversion efficiency.
Background
Infrared sensing technology has been widely used in the fields of atmospheric quality detection, temperature monitoring, industrial process control, space monitoring, information communication, medicine, military and the like. Infrared light sources are important components of infrared sensing technology and commonly used emission wavelengths are 3-5 microns and 8-14 microns. The traditional heat radiation infrared light source such as an incandescent lamp has low electro-optic conversion efficiency and poor modulation characteristics; the infrared diode with the wavelength of 3-5 microns has low luminous efficiency and low output power, so that the application of the infrared diode is limited; quantum cascade infrared lasers are capable of emitting high-intensity narrow-band infrared laser light, but are also inefficient and expensive to manufacture. The MEMS infrared light source manufactured by utilizing the Micro Electro Mechanical System (MEMS) technology is a novel thermal radiation infrared light source, has the characteristics of high electro-optic conversion efficiency, small size, low energy consumption and the like, can easily cover the range of 2-20 micrometers by a spectrum, has higher modulation frequency, is widely applied to the field of infrared sensing, and becomes a trending technology of the infrared light source.
The MEMS infrared light source with the conventional structure comprises a substrate, wherein a supporting layer is arranged on the substrate, the supporting layer and the substrate are connected by adopting a four-side fixed supporting structure, and a heating electrode layer is arranged on the supporting layer. Joule heat is generated by energizing the heat-generating electrode layer, so that the heat-generating 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 source mainly emerges from two directions: one is to radiate from above the heat-generating electrode layer, and the part of the infrared radiation in the forward direction belongs to the effective radiation of the infrared sensor. The other is radiation transmitted from the heating electrode layer to the substrate through the supporting layer, and the infrared radiation is absorbed by packaging materials, the substrate and the like after the MEMS infrared light source is packaged, so that the radiation cannot be effectively utilized, and the radiation belongs to energy loss of devices. Therefore, one approach to improving the photoelectric conversion efficiency of a device is to enhance the "forward radiation" of the device and suppress the "backward radiation" of the device.
In order to enhance the "forward radiation" above the heat-generating electrode layer, a skilled person will usually select a material with high emissivity to make the heat-generating electrode layer or add an infrared emission layer with higher infrared emissivity on the surface of the heat-generating electrode layer. In order to suppress the energy loss caused by bottom radiation in the infrared light source; the existing MEMS infrared light source adopts a substrate hollowing technology as shown in FIG. 1, and the substrate material is hollowed from the bottom surface upwards, so that the volume and the mass of the substrate material can be reduced, and the heat capacity generated by the supporting layer and the substrate in the device is reduced; finally, the electro-optic conversion efficiency of the MEMS infrared light source is improved, and the heating power consumption is reduced. Meanwhile, the undercut of the substrate is easy to realize in process, and the generation of various functional layers above the substrate and the product performance are not influenced.
In addition, some technicians also provide a reflective layer in the device to further suppress the "bottom radiation" of the device. For example, in the technical solution of fig. 2 provided in chinese patent application publication No. CN114249292a, a reflective layer is disposed on the bottom surface of the substrate, and the infrared rays radiated from the heating electrode layer to the substrate portion via the supporting layer are reflected back and then radiated upward via the heating electrode layer. Although the scheme reduces the energy loss generated by bottom radiation of the device to a certain extent, the scheme also causes new technical problems. For example, the reflective layer directly and closely attached to the substrate itself may form a "communication" with the supporting layer, and absorb part of the energy, thereby increasing the heat capacity of the device and generating heat loss. Meanwhile, due to the structural design of the joint of the reflecting layer and the supporting layer, a violent thermal strain effect can be caused due to the large difference of the thermal expansion coefficients of different functional layer materials in the switching stage of the device, so that the risk of breakage or falling of the reflecting layer is increased, and the photoelectric conversion performance and the service life of a light source are influenced.
Disclosure of Invention
The MEMS infrared light source aims at solving the problems that the structural design of a reflecting layer in the existing MEMS infrared light source possibly causes the increase of the heat capacity of a device, poor anti-inversion performance and durability and the like; the invention provides an MEMS infrared light source with improved photoelectric conversion efficiency.
The invention is realized by adopting the following technical scheme:
an MEMS infrared light source with improved photoelectric conversion efficiency comprises a substrate, a supporting layer, a heating electrode layer and an infrared emission layer which are sequentially stacked from bottom to top; and two heat generating electrode pads electrically connected to the heat generating electrode layer.
The upper surface of the substrate is provided with a pit which is sunken downwards and comprises a horizontal bottom surface and a slope-shaped side wall. The substrate is in a four-side fixed support structure and is connected with the supporting layer above the substrate, and a cavity structure is formed between the substrate and the supporting layer. The surrounding area of the upper opening of the pit covers the infrared emission layer; the enclosing area of the upper opening of the pit is positioned on the inner sides of the two heating electrode pads, and the distribution area of the enclosing area of the upper opening of the pit along the extension direction of at least one end of each heating electrode pad exceeds the length range of the heating electrode pad.
The area of the supporting layer is larger than the upper opening of the pit and the heating electrode layer; at least one through sacrificial window is arranged in the supporting layer and is communicated with a pit in the substrate below the sacrificial window; the distribution position of the sacrificial window is tangent to or separated from the distribution position of the heating electrode layer.
The bottom and the side wall of the pit are provided with complete reflecting layers which are prepared by materials with high reflectivity for infrared rays with the wavelength range of 2-14 microns.
As a further improvement of the invention, the depth of the cavity structure is 1-50 μm.
As a further improvement of the invention, the reflecting layer adopts a metal coating film prepared by any one of Ag, au, cu and Al. Or a dielectric film bragg reflector layer is adopted. Or a multilayer composite film formed by overlapping any plurality of single metal coating films according to a specified sequence.
As a further improvement of the invention, the substrate material comprises silicon and other materials which can be used as substrates of infrared light sources.
As a further improvement of the invention, the support layer is made of a single material composed of silicon oxide or silicon nitride or a multi-layer composite material composed of the silicon oxide or the silicon nitride arranged in an overlapped mode at intervals.
As a further improvement of the invention, the infrared emission layer is made of a material with high infrared emissivity, and the thickness of the infrared emission layer is 50-1000nm. Wherein the material with high infrared emissivity comprises NiCr alloy, tiN, tiAlN, amorphous carbon, siC, niCrO compound and ZrO 2 、HfO 2 、La 1-x Ca x CrO 3 (x is more than or equal to 0 and less than or equal to 0.5) and any one or more of carbon nanotubes.
In the invention, the emission surface of the infrared emission layer is in a rough surface structure;
as a further improvement of the invention, the material of the heating electrode layer adopts Pt, mo, niCr alloy, polysilicon, siC, cu, W and HfB 2 PtSi and SnO 2 Any one of the above;
a transition layer for improving the interface adhesion between the heating electrode layer and the supporting layer can be added between the heating electrode layer and the supporting layer. The transition layer is selected from any one of Ti, cr, and Ni depending on the material of the heat generating electrode layer and the supporting layer used.
As a further improvement of the invention, two heating electrode pads are parallel to each other and are electrically connected on the upper surface of the heating electrode layer; the infrared emission layer is positioned between the two heating electrode pads;
in the invention, the heating electrode pad is prepared from any one of AlSi alloy, au, al, niCr alloy and NiV alloy.
As a further improvement of the present invention, the heat-generating electrode layer and the infrared-emitting layer are further provided with a separation layer for blocking the effect of electric conduction therebetween. The isolation layer is made of one or a combination of any more of silicon oxide, silicon nitride and aluminum oxide.
As a further improvement of the invention, the infrared light source is also provided with a protective layer which covers the area of 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 combination of more of silicon oxide, silicon nitride, aluminum oxide and hafnium oxide.
The technical scheme provided by the invention has the following beneficial effects:
the MEMS infrared light source with improved photoelectric conversion efficiency improves the structure of the substrate, and the pit with a special shape is arranged above the substrate, so that a cavity positioned below the heating electrode layer and the infrared emission layer is formed between the pit and the supporting layer, and meanwhile, a complete reflection layer is formed on the wall surface of the pit. The MEMS infrared light source with the special structure can simultaneously inhibit the ineffective heat conduction of the device and the energy consumption generated by the ineffective infrared radiation, and reduce the heat capacity of the device; thereby greatly improving the photoelectric conversion efficiency of the device.
In addition, the MEMS infrared light source with the special structure provided by the invention also has strong thermal stability and structural strength; the service life and various weather resistance of the device are also enhanced. Compared with the traditional device, the device has outstanding performance advantages and is suitable for large-scale commercial popularization.
Drawings
FIG. 1 is a schematic diagram of a longitudinal section structure of a MEMS infrared light source prepared by a substrate hollowing technology in the background art.
FIG. 2 is a schematic diagram of a longitudinal cross-sectional structure of a MEMS infrared light source of the prior art in which a reflective layer is disposed at the bottom of a hollowed substrate.
Fig. 3 is a schematic view of an overall structure of the MEMS infrared light source provided in embodiment 1 of the present invention.
Fig. 4 is a schematic structural diagram of a substrate including a pit of the MEMS infrared light source provided in embodiment 1 of the present invention.
Fig. 5 is a schematic cross-sectional structure view of a MEMS infrared light source provided in embodiment 1 of the present invention.
Fig. 6 is a layered explosion diagram of a specific structure of the MEMS infrared light source provided in embodiment 1 of the present invention.
Fig. 7 is a schematic cross-sectional structure diagram of a MEMS infrared light source including a transition layer provided in embodiment 1 of the present invention.
Fig. 8 is a schematic cross-sectional view of a MEMS infrared light source with an isolation layer according to embodiment 1 of the present invention.
Fig. 9 is a schematic cross-sectional view of a MEMS infrared light source with a protective layer according to embodiment 1 of the present invention.
Fig. 10 is a manufacturing method for manufacturing the MEMS infrared light source in embodiment 1, according to embodiment 2 of the present invention.
Fig. 11 is a schematic cross-sectional view of the MEMS infrared light source of fig. 5 from a two-sided view, where the sacrificial window inside the support layer can be seen in a longitudinal section.
Fig. 12 is a schematic view of an end product obtained after the "mask processing of the substrate" step in embodiment 2 is completed.
FIG. 13 is a schematic representation of the end of the product obtained after the "etch window preparation" step in example 2.
FIG. 14 is a schematic view showing the end of the product obtained after the "anisotropic etching" step in example 2.
FIG. 15 is a schematic view showing the end of the product obtained after the "preparation of reflective layer" step in example 2.
FIG. 16 is a schematic view showing the end of the product obtained after the "one-shot polishing" step in example 2.
Fig. 17 is a schematic view of the end of the product obtained after the "sacrificial layer preparation" step in example 2.
FIG. 18 is a schematic view showing the end of the product obtained after the "secondary polishing" step in example 2.
FIG. 19 is a schematic representation of the end of the product obtained after the "support layer preparation" step in example 2.
FIG. 20 is a schematic view showing the end of the product obtained after the "heat-generating electrode layer preparation" step in example 2.
FIG. 21 is a schematic view showing the end of the product obtained after the "preparation of the separator" step in example 2.
Fig. 22 is a schematic view showing the end of the product obtained after the "heat-generating electrode pad preparation" step in embodiment 2.
FIG. 23 is a schematic diagram of the end of the product obtained after the "preparation of infrared emission layer" step in example 2.
FIG. 24 is a schematic view showing the end of the product obtained after the "protective layer preparation" step in example 2.
FIG. 25 is a schematic representation of the end of the product obtained after the "sacrificial window preparation" step in example 2.
Fig. 26 is a schematic view of the end of the product obtained after the "sacrificial layer removal" step in embodiment 2 is completed.
Labeled in the figure as:
100. a pit; 101. a substrate; 201. masking; 301. a reflective layer; 401. a sacrificial layer; 501. a support layer; 601. a heat generating electrode layer; 701. an isolation layer; 801. a heat generating electrode pad; 901. an infrared emitting layer; 1001. a protective layer; 1002. a sacrificial window; 5011. and a transition layer.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Example 1
Fig. 1 and 2 are schematic longitudinal cross-sectional views of MEMS infrared light sources in two prior art solutions mentioned in the background. The two technical schemes are the same as the traditional infrared light source, and both comprise 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. Such a device having a stacked structure can be manufactured by a process of sequentially forming different functional layers on the substrate 101. The substrate 101 is a base for forming various functional layers thereon, and provides stable adhesion of the layers and good support. The support layer 501 is an intermediate layer between the substrate 101 and the heat generating electrode layer 601, and plays a good role in supporting, and particularly when the substrate 101 is subjected to special etching processing, the support layer 501 can play a good role in supporting the upper functional layers, and uniformly disperse the load generated by the compressive stress of the upper parts.
The heating electrode layer 601 is connected with the heating electrode pad 801, the heating electrode pad 801 is used for connecting a lead wire to supply power to the heating electrode, the material of the heating electrode layer 601 is a functional layer capable of converting electric energy into internal energy, and the heating electrode layer 601 can rapidly heat up and heat in a conductive state; and infrared radiation is generated outwardly. The infrared emission layer 901 is a functional layer made of a material with ultrahigh infrared emissivity, and the functional layer can emit received internal energy in the form of infrared radiation at a high temperature.
Since the main functions of the heat generating electrode layer 601 are to generate infrared radiation and heat the upper direct contact infrared emission layer 901 by means of heat conduction, the infrared emission layer 901 can maintain an emission state. However, since the bottom surfaces of the support layer 501 and the infrared electrode layer are also in direct contact, the heat generated by heating the electrode layer is also conducted to the support layer 501 and the substrate 101. For the MEMS infrared light source, the energy consumption of the heat conducted to the supporting layer 501 and the substrate 101 is not converted into effective infrared radiation, and belongs to the ineffective power consumption (a type of loss) of the device, and the ineffective power consumption of the device can significantly reduce the photoelectric conversion efficiency of the MEMS infrared light source. On the other hand, the infrared radiation generated by the infrared emitting layer 901 will radiate both upwards and downwards, the upwards radiation is the effective radiation emitted, while the downwards radiation part cannot be effectively modulated and applied, and is the ineffective radiation (second type loss), and the generated ineffective radiation is another important reason for reducing the photoelectric conversion efficiency of the device.
The technical scheme provided in fig. 1 is mainly that on the basis of a multilayer stacked MEMS infrared light source, the bottom of the substrate 101 is hollowed out at a position corresponding to the infrared emission layer 901, the contact surface between the hollowed substrate 101 and the support layer 501 is reduced, and the volume and mass of the substrate 101 are greatly reduced; and further, the energy loss caused by heat conduction when the device works can be effectively reduced, namely the loss of the device is reduced. Meanwhile, since the hollow portion is located on the bottom surface of the substrate 101, the processing and forming of the functional layers above the hollow portion are not affected. However, it should be noted that: since the substrate 101 is used as a support during the device fabrication process, the substrate 101 must be hollowed out by photolithography, etching, etc. after all the functional layers are formed.
The technical scheme of fig. 2 is a further improvement of the scheme of fig. 1 proposed by the present inventors. The improvement point is that a reflecting layer 301 is added to the bottom hollowed part of the substrate 101; the reflective layer 301 is made of a material having a high reflectivity to infrared radiation. Thus, the reflective layer 301 can reflect back the downward infrared radiation generated by the upper infrared-emitting layer 901, converting some of the non-effective radiation into effective radiation. Thereby reducing the second class loss of the device. The solution of fig. 2 has some disadvantages while reducing the second-class loss of the device. The details of the disadvantages of the scheme of fig. 2 will be described in detail later when the advantages of the improved scheme provided by the present embodiment are introduced.
Specifically, on the basis of the technical solutions shown in fig. 1 and fig. 2, the present embodiment further provides a novel MEMS infrared light source with improved photoelectric conversion efficiency. The overall structure of the light source provided by this embodiment is shown in fig. 3, and the MEMS infrared light source includes a substrate 101, a supporting layer 501, a heat-generating electrode layer 601, and an infrared emission layer 901, which are sequentially stacked from bottom to top; and two heat generating electrode pads 801 electrically connected to the heat generating electrode layer 601. It should be emphasized that fig. 3 and the following text and figures of this embodiment are mainly illustrated in the form of a rectangular light source when describing the present application. However, the shape of the light source is not a limiting feature of the present embodiment, and the present embodiment provides a technical solution that 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, even an oval, a long strip and any other irregular forms.
The main difference between the technical scheme provided by the embodiment and the existing scheme is as follows: as shown in fig. 4, a concave pit 100 is formed on an upper surface of a substrate 101 of the MEMS infrared light source, where the concave pit 100 includes a horizontal bottom surface and a slope-shaped sidewall. The substrate 101 is connected with the upper supporting layer 501 in a four-side clamped structure, and a cavity structure is formed between the two. As can be seen from fig. 5, in the MEMS infrared light source provided in this example, the enclosed area of the upper opening of the pit 100 covers the infrared emitting layer 901. I.e. the distribution area of the upper opening of the pit 100 can completely cover the infrared emitting layer 901 above, it can be understood that the whole infrared emitting layer 901 in the light source of the embodiment is "suspended" above the pit 100.
With reference to fig. 6, in the substrate 101 of the MEMS infrared light source provided in this embodiment, the surrounding area of the upper opening of the pit 100 is located inside the two heat generating electrode pads 801, and the distribution area of the surrounding area of the upper opening of the pit 100 along the extending direction of at least one end of the heat generating electrode pads 801 exceeds the length range of the heat generating electrode pads 801. In a colloquial manner, taking a rectangular light source as an example, the length of the pit 100 in a direction parallel to the extending direction of the heat generating electrode pad 801 is longer than that of the upper infrared-emitting layer 901 (and the heat generating electrode layer 601). And the width of the pit 100 in the direction perpendicular to the extending direction of the heat generating electrode pad 801 is shorter than the infrared emitting layer 901 (and the heat generating electrode layer 601) therebelow. When the light source takes other shapes, this definition should be fulfilled, namely: the pit 100 must be "sandwiched" between two heat generating electrode pads 801, but slightly longer than the heat generating electrode pads 801.
Meanwhile, as shown in fig. 5, the area of the support layer 501 of the MEMS infrared light source provided by this embodiment is larger than the upper opening of the pit 100 and the heat generating electrode layer 601. And as shown in fig. 3 and 6, at least one sacrificial window 1002 extending therethrough is provided in the support layer 501, the sacrificial window 1002 communicating with the recess 100 in the underlying substrate 101. The distribution position of the sacrificial window 1002 is tangent to or separated from the distribution position of the heat generating electrode layer 601. Specifically, the support layer 501 completely "caps" the recesses 100 on the substrate 101. And the heat generating electrode layer 601 is just covered over the support layer 501 at the position facing the pit 100. Meanwhile, the sacrificial windows 1002 communicating with the underlying pits 100 are provided in the support layer 501, and the sacrificial windows 1002 must be distributed at positions on the support layer 501 that are not blocked by the heat generating electrode layer 601 and the infrared emission layer 901.
In the MEMS infrared light source provided by this embodiment, the complete reflective layer 301 is disposed on the bottom surface and the sidewall of the pit 100 of the substrate 101, and the reflective layer 301 is made of a material having a high reflectivity for infrared rays in a wavelength range of 2-14 μm.
The working principle and performance advantages of the MEMS light source provided by the present embodiment will be described in detail below with reference to the above technical features of the light source.
First, the light source provided by this embodiment has a "hollow" structure similar to the solution of fig. 2, i.e. the pits 100 in this case. Therefore, the substrate 101 of the present invention can also have the effect of reducing the heat capacity of the MEMS infrared light source and reducing the heat conduction from the heat generating electrode layer 601 to the substrate 101. Thereby reducing one class of losses in the device. However, the present well 100 is again "hollowed out" in a manner different from that of the substrate 101 of FIG. 2. In particular, the recess 100 is located above the substrate 101, which results in a cavity between the substrate 101 and the support layer 501. The hollow cavity structure in this embodiment has the following two functions: 1. the cavity can effectively block the downward heat conduction path of the combination of the heating electrode layer 601 and the supporting layer 501, and the first effect of reducing heat radiation is achieved. 2. The gas medium in the cavity is equivalent to a heat preservation cover formed by a layer of poor heat conductor, and heat is prevented from being transferred to the substrate 101 and being dissipated from a larger surface of the substrate 101.
Secondly, the structure of the pit 100 in this case is a shape with a large upper opening and a small lower opening, and particularly, as shown in fig. 4 to 6, the longitudinal section of the pit 100 is approximately in a shape of a 'canal'. The desired reflective layer 301 is created taking into account the walls and floor of the pit 100. Such a sloped pocket 100 wall thus includes at least the following advantages:
(1) The reflective layer 301 material is primarily generated by a sputtering or evaporation process. The sloped walls of the recess 100 may facilitate better deposition of the reflective layer 301 material. The dispersion effect and continuity of the reflective layer 301 in the pits 100 are improved to obtain a uniform and complete reflective layer 301. Enhancing the reflection of infrared radiation by the reflective layer 301.
(2) The horizontal bottom surface of the pit 100 corresponds to a plane mirror, and can completely reflect the bottom radiation of the upper infrared emission layer 901 above the infrared emission layer 901.
(3) The pressure-receiving surface of the support layer 501 is located just above the slope wall surface of the recess 100, and is also a supporting point of the heat-generating electrode pad 801. In the scheme, the slope wall surface as shown in fig. 5 is equivalent to a trapezoidal 'bank' with a small upper bottom and a large lower bottom, and has good pressure-resistant and impact-resistant effects. Therefore, the device of the MEMS infrared light source has stronger shock resistance and pressure resistance; the service life of the product is prolonged.
(4) The pits 100 need to be formed by anisotropic etching or photolithography. The pit 100 with the special shape is also just suitable for the process characteristics of chemical corrosion and laser etching and is very easy to process; the production cost of the product can be reduced.
In addition, in the technical solution of the present embodiment providing the MEMS infrared light source, the distribution area of the pits 100 (i.e. the distribution area of the reflective layer 301) is just "shrunk" to the inner sides of the two heating electrode pads 801, so that the heating electrode pads 801 can just overlap the slope of the pits 100, and a good supporting effect is maintained. The infrared emitting layer 901 between the heating electrode pads 801 can completely hang above the pit 100, so that all bottom radiation of the infrared emitting layer 901 can reach the emitting layer in the pit 100, the reflectivity of the bottom radiation is further improved, and the power of second-class loss is suppressed to the maximum extent.
One needs to be particularly emphasized: in the technical solution provided by this embodiment, the substrate 101 has a cavity formed by the recess 100 between the substrate and the supporting layer 501; the reflective layer 301, which is disposed on the walls of the cavity, has the following advantages: because the reflective layer 301 is isolated from the heat generating region of the MEMS light source by the cavity, when the MEMS is frequently switched, the temperature of the reflective layer 301 is relatively low and stable, so the thermal expansion between the substrate 101 and the reflective layer 301 is not significant, and the reflective layer 301 does not deform or fall significantly. That is, in the embodiment of the present invention, the heat resistance of the reflective layer 301 is good, and even if the device is used for a long time, the reflective layer 301 is not easily damaged, and the service life of the device is long, so that the optimal photoelectric conversion performance of the device can be maintained to the maximum extent.
In the conventional scheme shown in fig. 2, when the MEMS infrared light source is frequently switched, the reflective layer 301 and the supporting layer 501 are in direct contact (which is equivalent to being in direct contact with a heating region of the MEMS), and at this time, the temperature of the reflective layer 301 changes dramatically during use, so that the substrate 101 and the reflective layer 301 may thermally expand to different degrees, and the adhesion effect of the interface between the substrate 101 and the reflective layer 301 is poor, and the reflective layer 301 may be damaged in severe cases. Since the reflective layer 301 of fig. 2 is located under the substrate 101, once the reflective layer 301 is broken, the reflective layer 301 may be partially peeled off, the uniformity and integrity of the reflective layer 301 may be damaged, and the reflection of infrared radiation may be lost. Thereby causing the photoelectric conversion efficiency of the MEMS infrared light source to be reduced.
Meanwhile, one of the important functions of the processes of 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. (note: heat capacity refers to the absorption and storage capacity of the object for heat energy; the higher the heat capacity, the lower the temperature rise amplitude for absorbing the same heat energy, and the heat capacity is related to the volume/mass of the object, the type of material, and other properties.) the reflective layer 301 is located under the cavity and does not contact the supporting layer 501, so the heat capacity of the device is hardly affected. Whereas in the arrangement of fig. 2, the reflective layer 301 is in direct contact with the support layer 501, the reflective layer 301 increases the thermal capacitance of the device. This is disadvantageous in improving the photoelectric conversion efficiency of the device.
Finally, the main function of the sacrificial window 1002 with a special shape and position reserved on the support layer 501 in the present embodiment is to facilitate the processing of the product. As is well known, each functional layer above the substrate 101 is actually a micro-or nano-scale plating or film. Therefore, these functional layers cannot be directly grown on the upper surface of the substrate 101 with the pits 100; otherwise, each functional layer is obtained and is also provided with pits and cannot be in a plane state. Therefore, the pits 100 can be processed only after the formation of the respective functional layers. However, it is not technically feasible to create a pit 100 in the "center" of the device by etching after the functional layer is formed.
Aiming at the problem, the invention designs a special production process which is specially used for producing the MEMS infrared light source with the special structure provided by the embodiment. A key technical means of the processing process provided in this embodiment is to use a material having a certain specificity and being selectively removable by a specific method as the sacrificial layer 401, fill the sacrificial layer 401 in the processed pit 100 in advance, and remove the material of the sacrificial layer 401 from the pit 100 after the functional layers above the pit 100 are formed. And the sacrificial window 1002 reserved in the support layer 501 is used to remove the material of the sacrificial layer 401 in the pit 100.
In particular, the sacrificial window 1002 of the present embodiment is designed to communicate with the recess 100 in the underlying substrate 101, thereby facilitating the removal of the sacrificial layer 401 material in the recess 100. But also needs to be tangent to or separated from the distribution position of the heating electrode layer 601; thereby ensuring that the integrity of the functional layer above cannot be damaged and the function of each functional layer above cannot be influenced. While also avoiding the blocking or shadowing of the sacrificial window 1002 by the overlying functional layers.
In practical applications, at least one sacrificial window 1002 may be provided, and the sacrificial window 1002 may be a through hole with any shape, such as a circular hole, a stripe, etc. In the most preferred embodiment, the sacrificial windows 1002 should be symmetrically disposed on the support layer 501, and located on both sides of the heat generating electrode layer 601. This can ensure that the support layer 501 is balanced by the stress-strain effect, thereby improving the production yield and prolonging the service life. By popularization, the optimal scheme of the MEMS infrared light source provided by this embodiment is to maintain good structural symmetry in the design of the overall structure (including each functional layer). So as to improve the structural strength, stress resistance and various performances of the device.
In the MEMS infrared light source provided by this embodiment, the depth of the cavity structure is 1-50 μm. The cavity of the device can exert the best technical effect under the condition of the depth range. When the cavity depth is lower than the preferred range, the substrate 101 is almost equivalent to no pit 100, and the support layer 501 and the substrate 101 are very close to each other, so that the above technical effect cannot be exerted. When the depth of the cavity is larger than the optimal interval, the processing difficulty is improved when the depth of the cavity is too large, and meanwhile, the reflection effect of the reflection layer 301 on infrared radiation is poor.
In this embodiment, a metal plating film made of any one of Ag, au, cu, and Al may be used as the reflective layer 301. Or a dielectric film bragg reflector layer 301. Or a multilayer composite film formed by overlapping any plurality of single metal coating films according to a specified sequence. Ag. Au, cu, al are materials having high infrared reflectance. The dielectric film bragg emission layer is a common laminated optical film composed of high-refractive index and low-refractive index dielectric materials in a certain order, can generate strong reflection to infrared rays with specific wavelengths or infrared rays with wide spectrum through film layer design, and can also be used as a reflection film in the embodiment.
Considering that the cost of different materials is different, the cost of the Ag and Au reflecting layer 301 is much higher than that of Cu and Al; therefore, in practical applications, different materials can be layered on the substrate 101 as required to form the composite reflective layer 301 film. For example, cu is used as a base of the reflective layer 301, and a thin Au plating layer is formed on the upper surface to form the desired reflective layer 301. The composite reflection layer 301 can not only maintain high infrared radiation reflectivity, but also achieve better technical effects in the aspects of production cost of the MEMS infrared light source and comprehensive properties such as material strength, toughness, wear resistance and the like.
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, and the like. In the case where silicon is used as a material of the substrate 101, a silicon (100) surface is generally used as a work surface for forming the pits 100 and the functional layers, and in this case, the shape of the pits 100 having an inverted trapezoidal shape (large opening and small bottom surface) can be very easily realized by anisotropic etching of silicon.
In this embodiment, the support layer 501 is made of a single material of silicon oxide or silicon nitride or a multi-layer composite material of silicon oxide or silicon nitride arranged in an overlapping manner. The silicon oxide and the silicon nitride are both inorganic non-metallic materials with high strength, high hardness, poor thermal conductivity, insulation, high temperature resistance and corrosion resistance; the material is very suitable for being used as the material of the supporting layer 501 in the MEMS light source.
The infrared emitting layer 901 in the MEMS light source of this embodiment is made of a material with high infrared emissivityThe thickness is 50-1000nm. Wherein the material with high infrared emissivity comprises NiCr alloy, tiN, tiAlN, amorphous carbon, siC, niCrO compound and ZrO 2 、HfO 2 、La 1-x Ca x CrO 3 (x is more than or equal to 0 and less than or equal to 0.5) and any one or more of carbon nanotubes.
In particular, the emission surface of the infrared emission layer 901 of the present embodiment has a rough surface structure. The rough surface structure improves the infrared emission capability of the MEMS infrared light source.
In this embodiment, the material of the heat generating electrode layer 601 is Pt, mo, niCr alloy, polysilicon, siC, cu, W, hfB 2 PtSi and SnO 2 Any one of the above; the above materials are all the existing materials for manufacturing the resistance heating unit, and the heating electrode layer 601 prepared by the materials can convert the electric energy into the internal energy for heating more efficiently after being electrified.
As shown in fig. 7, in a more preferred embodiment of the present invention, a transition layer 5011 for improving the adhesion between the heat generating electrode layer 601 and the supporting layer 501 may be further added. The transition layer 5011 is selected from any one of Ti, cr, and Ni depending on the materials of the heat generating electrode layer 601 and the support layer 501. For example, when the heat generating electrode layer 601 is made of Pt material and the support layer 501 is made of SiO 2 During material preparation, an ultrathin Cr coating can be added on the upper surface of the supporting layer 501 in the manufacturing process, so that the interface adhesive force strength of the supporting layer and the supporting layer is remarkably improved. The heating electrode layer 601 and the supporting layer 501 are prevented from displacing in the using process, and the comprehensive performance of the product is improved.
In this embodiment, two heating electrode pads 801 are parallel to each other, and are electrically connected to the upper surface of the heating electrode layer 601; the infrared emission layer 901 is located between the two heat generating electrode pads 801. The heating electrode pad 801 is made of any one of an AlSi alloy, au, al, niCr alloy, and NiV alloy. The main function of the heat-generating electrode pad 801 is to induce directionally transported electron migration on the heat-generating electrode layer 601, thereby causing the heat-generating electrode layer 601 to generate heat. Therefore, the material of the heating electrode pad 801 adopted in this embodiment is a material having high electrical conductivity, high thermal stability, and high weldability.
As shown in fig. 8, in a more preferable configuration of this embodiment, the heat generating electrode layer 601 and the infrared emission layer 901 are further provided with an isolation layer 701 for blocking an electric conduction effect therebetween. The material of the isolation layer 701 is one or a combination of any more of silicon oxide, silicon nitride, and aluminum oxide.
The spacer layer 701 is typically only used when the infrared emitting layer 901 material is also electrically conductive, if the infrared emitting layer 901 is made of an insulating material, such as ZrO 2 、HfO 2 、La 1-x Ca x CrO 3 (x is not less than 0 and not more than 0.5), etc., it is not necessary to provide the spacer layer 701 between the heat generating electrode layer 601 and the infrared emitting layer 901. The isolation layer 701 works as follows: when the infrared emission layer 901 is made of a conductive material, if the infrared emission layer 901 is not electrically isolated from the heating electrode layer 601, a current also passes through the infrared emission layer 901, which may cause a change in resistance of the heating electrode layer 601, and under the condition that the applied voltage is the same, the temperature obtained by the MEMS light source may deviate greatly from a design value, and thus the working requirement cannot be met. The above problem can be solved by providing an insulating isolation layer 701 therebetween.
As shown in fig. 9, in a more preferable embodiment of the present invention, the infrared light source is further provided with a protective layer 1001, and the protective layer 1001 covers the area of the upper surface of the MEMS infrared light source except for the heat generating electrode pad 801. The protection layer 1001 plays a role in protecting the internal structure, and in this embodiment, according to the performance requirements of the device, the protection layer 1001 is mainly made of a material having a relatively high infrared radiation transmittance and a relatively high strength and hardness; the material with stronger corrosion resistance and heat resistance. Specifically, the material of the protection layer 1001 selected in this embodiment includes any one or a combination of more of silicon oxide, silicon nitride, aluminum oxide, and hafnium oxide.
Example 2
The embodiment further provides a manufacturing method specially used for producing the device, aiming at the MEMS infrared light source with a special structure and improved photoelectric conversion efficiency in the embodiment 1. The manufacturing process designed in this embodiment adopts the following steps according to the core structure characteristics of the device: firstly etching the pit 100, then filling the pit 100 by using a sacrificial layer 401 material, then generating each functional layer on a plane, and finally after the functional layers are completely processed, replacing the sacrificial layer 401 in the pit 100 by using a sacrificial window 1002 which is formed and communicated with the pit 100 to complete the product manufacturing. In particular, the process provides for selective removal of the sacrificial layer 401 by disposing a sacrificial window 1002 on the support layer 501 proximate to the recess 100 in the substrate 101.
Scheme one
As shown in fig. 10, for a liquid crystal display device including only the substrate 101, the support layer 501, the heat generating electrode layer 601, and the infrared emitting layer 901; and a special-shaped cavity is arranged between the substrate 101 and the supporting layer 501, and the MEMS infrared light source with the reflecting layer 301 in a specific shape is distributed in the cavity. The manufacturing method provided by the embodiment comprises the following processing steps:
(1) Mask processing of the substrate:
providing a substrate 101, and depositing a preset amount of the material of the mask 201 layer on the surface to be processed of the substrate 101 to form the required mask 201 layer.
In particular, the substrate 101 of the present embodiment may be made of any material. The preferred material of the substrate 101 is silicon, and the (100) crystal plane of silicon is used as the plane 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.
(2) Preparing a corrosion window:
according to the size and the shape of the preset window, a part of the mask 201 layer on the surface to be processed is removed by utilizing the photoetching technology to form an etching window on the substrate 101. The etching window is designed according to the shape of the upper opening of the pit 100 of the designed MEMS infrared light source, and the exposed area below the etching window is the area of the substrate 101 needing etching.
(3) Anisotropic etching:
the substrate 101 is chemically etched by an anisotropic etching process to form a pit 100 with a gradually decreasing diameter recessed toward the inside of the substrate 101 in an etching window region in the substrate 101.
In this example, TMAH aqueous solution, KOH aqueous solution, naOH aqueous solution, mixed aqueous solution of ethylenediamine and catechol, NH were used 4 Any one of the OH aqueous solutions is used as the anisotropic etching solution for the silicon substrate 101 as necessary. During the etching process, the etching process needs to be controlled so that the depth of etching is controlled to be 1-50 μm.
(4) Preparing a reflecting layer:
a predetermined amount of reflective layer 301 material is deposited in the recesses 100 in the surface of the substrate 101 using a physical vapor deposition process to form the desired reflective layer 301. The reflective layer 301 is a single metal plating layer made of one of Ag, au, cu, and Al. Or the reflecting layer 301 is made of multiple materials of Ag, au, cu and Al through layer-by-layer deposition to form a composite metal coating. Or a dielectric film bragg plated layer is prepared as the desired reflective layer 301.
(5) Primary polishing:
and polishing the surface to be processed of the substrate 101, and removing the surface coatings of the other areas of the surface of the substrate 101 except the pits 100, wherein the surface coatings comprise the material of the corrosion mask 201 and the material of the reflecting layer 301. The polishing treatment adopts a wet etching method or a chemical mechanical polishing method. When wet etching is used, the etch mask 201 is removed and the reflective layer 301 material is stripped away from the etch mask 201 by selective etching of the etch mask 201 and other structures (reflective layer 301 and substrate 101), thus leaving the reflective layer 301 in the pit 100 and exposing the upper surface of the substrate 101 in areas outside the pit 100. When chemical mechanical polishing is used, the material of the reflective layer 301 and the material of the etch mask 201 are removed from the areas outside the pits 100, exposing the upper surface of the substrate 101 in the areas outside the pits 100, while leaving the reflective layer 301 in the pits 100.
(6) Preparing a sacrificial layer:
the pits 100 in the substrate 101 are filled with a sacrificial layer 401 material that can be selectively removed by any one of a number of means. The material of the sacrificial layer 401 is SiO 2 One of phosphosilicate glass, silica gel, polyimide, SU-8, polydimethylsiloxane (PDMS), gelatin, polyethylene glycol, parylene and benzocyclobutene.
(7) And (3) secondary polishing:
and performing secondary polishing treatment on the surface to be processed of the substrate 101 filled with the material of the sacrificial layer 401, so that the material of the sacrificial layer 401 in the pit 100 is flush with the surrounding surface of the substrate 101. The polishing treatment adopts a dry etching or chemical mechanical polishing method.
(8) Preparing a support layer:
the required support layer 501 is created on the surface of the substrate 101 on the side containing the sacrificial layer 401, and the support layer 501 completely covers the underlying substrate 101 and sacrificial layer 401. The supporting layer 501 is generated by adopting a physical vapor deposition or chemical vapor deposition process; the support layer 501 is a single coating layer made of silicon oxide or silicon nitride, or a multi-layer composite coating layer made of silicon oxide or silicon nitride deposited layer by layer according to a predetermined sequence.
(9) Preparing a heating electrode layer:
a desired heat generating electrode layer 601 is prepared on the surface of the support layer 501, and the heat generating electrode layer 601 is located at a position corresponding to the position above the pit 100 in the substrate 101. The left and right sides of the heat generating electrode layer 601 completely cover the recess 100, and the front and rear sides are located in the region opposite to the inner side of the recess 100 and do not cover the recess 100. The heat generating electrode layer 601 is generated by a physical vapor deposition or chemical vapor deposition process; the material of the heat generating electrode layer 601 is any one selected from Pt, mo, niCr alloy, polycrystalline silicon, siC, cu, W, hfB2, ptSi, and SnO 2.
In order to improve the interface adhesion between the support layer 501 and the heat generating electrode layer 601, in a more optimized embodiment, a transition layer 5011 made of a specific material may be deposited on the surface of the support layer 501; and then a desired heat generating electrode layer 601 is regenerated. The transition layer 5011 is selected from any one of Ti, cr, and Ni depending on the materials used for the heat generating electrode layer 601 and the support layer 501.
(10) Preparing a heating electrode pad:
two parallel long heating electrode pads 801 not exceeding the distribution area of the heating electrode layer 601 are prepared above the heating electrode layer 601. Wherein, the distribution areas of the two heating electrode pads 801 are separated from or circumscribed with the surrounding area of the upper opening of the pit 100.
The heat generating electrode pad 801 is electrically connected to the heat generating electrode layer 601, and the material for preparing the heat generating electrode pad 801 is selected from any one of an AlSi alloy, au, al, niCr alloy, and NiV alloy.
(11) Preparing an infrared emission layer:
a desired infrared emitting layer 901 is prepared above the heat generating electrode layer 601 inside the heat generating electrode pad 801. The infrared emission layer 901 is located in the wiring region of the four end points of the heat generating electrode pad 801.
The required ir-emitting layer 901 is made of a material with high ir-emissivity. The thickness of the prepared infrared emission layer 901 is 50-1000nm. Wherein the adopted material with high infrared emissivity comprises NiCr alloy, tiN, tiAlN, amorphous carbon, siC, niCrO compound and ZrO 2 、HfO 2 、La 1-x Ca x CrO 3 (x is more than or equal to 0 and less than or equal to 0.5) and any one or more of carbon nanotubes.
In particular, in other more preferred embodiments, the emission surface of the processed infrared emission layer 901 has a rough surface structure.
(12) Preparing a sacrificial window:
the material of the support layer 501 is etched by photolithography, and at least one through sacrificial window is processed in a selected specific area on the basis of not damaging the upper heating electrode layer 601 and the infrared emission layer 901, so as to expose the material of the sacrificial layer 401 in the pit 100 below. Fig. 11 is a schematic cross-sectional view of the MEMS infrared light source of fig. 5 along two side views, which can more visually see the relative positions of the sacrificial window, the supporting layer 501 and the pit 100.
(13) Sacrificial layer 401 removal:
selectively removing all the material of the sacrificial layer 401 filled in the pit 100 by adopting a specific technical means according to the specificity of the selected sacrificial material so as to form a required cavity structure; and then the required MEMS infrared light source is prepared.
And (3) adopting a solvent or solution capable of directionally corroding the sacrificial layer 401 material as selective corrosive liquid to carry out immersion treatment, wherein the corrosive liquid is diffused into the cavity through the sacrificial window, and the sacrificial layer 401 material in the cavity is completely removed. The product is also cleaned and dried after the sacrificial layer 401 is removed.
The finally prepared MEMS infrared light source comprises four structural layers, namely a substrate 101, a supporting layer 501, a heating electrode layer 601 and an infrared emitting layer 901; and a special-shaped cavity is arranged between the substrate 101 and the support layer 501, and the reflective layer 301 with a specific shape is distributed in the cavity.
Scheme two
On the basis of the first embodiment, when the prepared infrared emission layer 901 has conductivity, a step of preparing the isolation layer 701 is added between the steps (9) and (10). And after preparing the isolation layer 701, the heat generating electrode pad 801 preparation step of step (10) requires first removing the isolation layer 701 for disposing a partial region of the heat generating electrode pad 801 by a photolithography peeling method so that the heat generating electrode pad 801 is electrically connected to the heat generating electrode layer 601 therebelow; and in step (11), the infrared emission layer 901 is located on the upper surface of the isolation layer 701.
Specifically, the isolation layer 701 is formed by using a physical vapor deposition or chemical vapor deposition process, and the material is one or a combination of any more of silicon oxide, silicon nitride, and aluminum oxide.
The overall structure of the MEMS light source prepared at this time includes, from bottom to top, a substrate 101, a support layer 501, a heat-generating electrode layer 601, an infrared emission layer 901, and a heat-generating electrode pad 801. Wherein a cavity is arranged at the interface of the substrate 101 and the support layer 501, and a complete reflecting layer 301 is arranged on the inner wall of the cavity close to one side of the substrate 101.
Scheme three
On the basis of the second scheme, in order to improve the weather resistance such as corrosion resistance of the product, a step of preparing a protective layer 1001 is added between the step (11) and the step (12), and the prepared protective layer 1001 completely covers the upper surfaces of the infrared emission layer 901, the infrared electrode layer and the support layer 501. And the sacrificial window opened in step (12) effectively removes both the protective layer 1001 and the support layer 501, since the protective layer 1001 also covers the support layer 501 where the sacrificial window area is opened.
In this embodiment, the protection layer 1001 is formed by a physical vapor deposition or chemical vapor deposition process, and the material is selected from any one or a combination of silicon oxide, silicon nitride, aluminum oxide, and hafnium oxide.
The following are specifically mentioned: in the manufacturing method provided by this embodiment, the protection layer 1001 is not only used as the outer protection layer 1001 of the whole MEMS light source product. And also as an outer cladding layer covering the heat-generating electrode layer 601, the isolation layer 701 and the infrared-emitting layer 901 when the substrate 101 is removed by the selective etchant in step (13). At this point, selective solvent can only enter the pits 100 of the substrate 101 from the sacrificial window. When the etchant is selected, a solvent that can etch the sacrificial layer 401 but does not affect the materials of the support layer 501, the substrate 101, the reflective layer 301, and the protective layer 1001 may be selected.
In order to more clearly show the manufacturing process provided in this embodiment, the complete manufacturing process of the complete product including the substrate 101, the supporting layer 501, the heat generating electrode layer 601, the isolation layer 701, the infrared emission layer 901, the heat generating electrode pad 801, and the protection layer 1001 in the third embodiment is described below with reference to a series of continuous drawings from fig. 12 to 26. Fig. 12-26 show the morphological changes of the semi-finished product or product obtained after the completion of the different manufacturing process steps.
1. Masking of substrates
The mask 201 on the substrate 101 is shaped as shown generally in fig. 12, where the mask 201 is seen to be located on top of the substrate 101.
2. Etch window preparation
The etch window is successfully formed and the mask 201 includes a notch, as shown generally in FIG. 13.
3. Anisotropic etching
After the anisotropic etching, the substrate 101 is not affected by the mask 201, the exposed substrate 101 is etched, and the pits 100 are etched in a state where the upper opening is larger and the lower opening is smaller as shown in fig. 14 because the anisotropic etching is used.
4. Preparation of the reflective layer
Since the reflective layer 301 is formed by a sputtering or evaporation deposition process in this embodiment, the reflective layer 301 is deposited on the upper surfaces of the substrate 101 and the mask 201 in fig. 15.
5. One-time polishing
The goal of the primary polishing is to remove the mask 201 material and the reflective layer 301 material from the surface of the substrate 101 except at the pits 100. The state as in fig. 16 is reached.
6. Preparation of sacrificial layer
Sacrificial layer 401 is filled directly into the recess 100. To ensure that sacrificial layer 401 is completely filled, sacrificial layer 401 is typically left "over" as shown in fig. 17.
7. Secondary polishing
The secondary polishing aims to remove the overflowing sacrificial layer 401 and to re-expose the substrate 101 outside the pit 100; the effect of fig. 18 is achieved so that a little more can be ground away during polishing, ensuring that the sacrificial layer 401 material in the recess 100 remains flush with the surrounding substrate 101 surface.
8. Support layer preparation
In fig. 19, it can be seen that a complete support layer 501 is grown over the sacrificial layer 401 and the substrate 101.
9. Preparation of heating electrode layer
As can be seen from fig. 20, a heat generating electrode layer 601 is formed above the support layer 501, and the heat generating electrode layer 601 is shorter than the support layer 501. Meanwhile, the lengths of the left and right sides of the electrode layer are longer than the pits 100 in the current view, but the heat generating electrode layer 601 is slightly shorter than the pits 100 in order to reserve sacrificial windows in the view corresponding to the front and rear sides of the drawing.
10. Preparation of isolation layer
This embodiment provides a complete spacer layer 701 over the heat generating electrode layer 601, and as shown in fig. 21, the spacer layer 701 is as large as the heat generating electrode layer 601.
11. Heating electrode pad preparation
This embodiment prepares heat generating electrode pad 801 on insulating layer 701, as seen in fig. 22, and removes insulating layer 701 at heat generating electrode pad 801 to electrically connect heat generating electrode pad 801 directly with heat generating electrode layer 601 therebelow. Note that the heat generating electrode pads 801 are substantially elongated, which is not seen from the perspective of fig. 22.
12. Preparation of Infrared emitting layer
As can be seen from fig. 23, this embodiment prepares an infrared emission layer 901 on the isolation layer 701 between the two heat generating electrode pads 801.
13. Preparation of protective layer
As shown in fig. 24, the infrared emission layer 901 is located at the uppermost layer of the device, and since the layers are not uniform in size and take the shape of a "multi-layer cake" that shrinks step by step, the protection layer 1001 covers the infrared emission layer 901, the isolation layer 701, the heat generating electrode layer 601 and the support layer 501.
14. Sacrificial window preparation
In this embodiment, the feature areas of the protection layer 1001 and the support layer 501 are punched through to connect the pits 100 therebelow, and expose the sacrificial layer 401. The sacrificial window is not visible from the corresponding viewing angles of fig. 12-24, and a schematic view of a specific sacrificial window can be seen in the top view of fig. 25.
15. Sacrificial layer removal
With the sacrificial window 1002 in place, the sacrificial layer 401 material in the recess 100 can be completely removed by using a specific solvent, and the final MEMS infrared light source product as shown in fig. 26 can be obtained.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims (10)

1. An MEMS infrared light source with improved photoelectric conversion efficiency comprises a substrate, a supporting layer, a heating electrode layer and an infrared emission layer which are sequentially stacked from bottom to top; and two heating electrode pads electrically connected to the heating electrode layer; the method is characterized in that:
the upper surface of the substrate is provided with a pit which is sunken downwards, and the pit comprises a horizontal bottom surface and a slope-shaped side wall; the substrate is connected with the supporting layer above the substrate in a four-side fixed support structure, and a cavity structure is formed between the substrate and the supporting layer; the enclosed area of the upper opening of the pit covers the infrared emission layer; the enclosing area of the upper opening of the pit is positioned on the inner sides of the two heating electrode pads, and the distribution area of the enclosing area of the upper opening of the pit along the extending direction of at least one end of each heating electrode pad exceeds the length range of the heating electrode pad;
the area of the supporting layer is larger than that of the upper opening of the pit and the heating electrode layer; at least one through sacrificial window is arranged in the supporting layer and is communicated with the pit in the substrate below the sacrificial window; the distribution position of the sacrificial window is tangent to or separated from the distribution position of the heating electrode layer above the sacrificial window;
the bottom surface and the side wall of the pit are provided with complete reflecting layers, and the reflecting layers are made of materials with high reflectivity for infrared rays with the wavelength range of 2-14 microns.
2. The MEMS infrared light source with improved photoelectric conversion efficiency according to claim 1, wherein: the depth of the cavity structure is 1-50 μm.
3. The MEMS infrared light source with improved photoelectric conversion efficiency according to claim 1, wherein: the reflecting layer is a metal coating film prepared from any one of Ag, au, cu and Al; or a dielectric film Bragg reflecting layer is adopted; or a multilayer composite film formed by overlapping any plurality of single metal coating films according to a specified sequence.
4. The MEMS infrared light source with improved photoelectric conversion efficiency according to claim 1, wherein: the substrate material includes silicon and other materials that can be used as substrates for infrared light sources.
5. The MEMS infrared light source with improved photoelectric conversion efficiency according to claim 1, wherein: the supporting layer is made of a single material composed of silicon oxide or silicon nitride or a multi-layer composite material composed of the silicon oxide or the silicon nitride which are arranged in an overlapped mode at intervals.
6. The MEMS infrared light source with improved photoelectric conversion efficiency according to claim 1, wherein: the infrared emission layer is made of a material with high infrared emissivity, and the thickness of the infrared emission layer is 50-1000nm; wherein the material with high infrared emissivity comprises NiCr alloy, tiN, tiAlN, amorphous carbon, siC, niCrO compound and ZrO 2 、HfO 2 、La 1-x Ca x CrO 3 (x is more than or equal to 0 and less than or equal to 0.5) and any one or more of carbon nanotubes; and/or the emission surface of the infrared emission layer is in a rough surface structure.
7. The MEMS infrared light source with improved photoelectric conversion efficiency according to claim 1, wherein: the heating electrode layer is made of Pt, mo, niCr alloy, polysilicon, siC, cu, W and HfB 2 PtSi and SnO 2 Any one of the above;
and/or
A transition layer for improving the interface adhesion between the heating electrode layer and the supporting layer is added between the heating electrode layer and the supporting layer; the transition layer is selected from any one of Ti, cr and Ni according to different materials of the heating electrode layer and the supporting layer.
8. The MEMS infrared light source with improved photoelectric conversion efficiency according to claim 1, wherein: 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 positioned between the two heating electrode bonding pads;
and/or
The heating electrode bonding pad is prepared from any one of AlSi alloy, au, al, niCr alloy and NiV alloy.
9. The MEMS infrared light source with improved photoelectric conversion efficiency according to claim 1, wherein: the heating electrode layer and the infrared emission layer are also provided with isolation layers for blocking the electric conduction effect between the heating electrode layer and the infrared emission layer; the isolation layer is made of one or a combination of any more of silicon oxide, silicon nitride and aluminum oxide.
10. The MEMS infrared light source with improved photoelectric conversion efficiency according to claim 1, wherein: the infrared light source is also provided with a protective layer, and the protective layer covers the area of the upper surface of the MEMS infrared light source except the heating electrode pad;
and/or
The material of the protective layer is selected from any one or combination of more of silicon oxide, silicon nitride, aluminum oxide and hafnium oxide.
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