CN104236723A - Three-dimensional thermopile infrared detector structure of MEMS (micro-electromechanical system) - Google Patents
Three-dimensional thermopile infrared detector structure of MEMS (micro-electromechanical system) Download PDFInfo
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- CN104236723A CN104236723A CN201410520500.8A CN201410520500A CN104236723A CN 104236723 A CN104236723 A CN 104236723A CN 201410520500 A CN201410520500 A CN 201410520500A CN 104236723 A CN104236723 A CN 104236723A
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Abstract
The invention discloses a three-dimensional thermopile infrared detector structure for MEMS (micro-electromechanical systems). Thermocouples are serially connected to one another to form three-dimensional thermopile structures which are radially distributed around a vertical center of a heat-insulation cavity; two thermocouple units of a serially connected thermocouple pair are arranged on an upper layer and a lower layer which are different from each other; hot junctions of the thermocouples are positioned at positions which are close to an upper position of a heat-absorbing layer; cold junctions of the thermocouples are buried in a heat-conduction material which is arranged on the lower portion of the structure; heat received by the thermocouples can be rapidly transferred into a substrate so that the cold junctions are not easily affected by environment temperature and heat junctions positioned in a heat-insulation environment of the heat-insulation cavity cannot be dissipated easily; the size of a heat absorbing area can be reduced relatively; the length of a heat end portion of each thermocouple is increased; and the response ratio and the detectivity of a detector are comprehensively improved by setting the suitable quantity of the thermocouples, so that the temperature resolution and the stability of the thermopile detector are improved.
Description
Technical field
The present invention relates to technical field of microelectronic mechanical systems, particularly a kind of infrared eye with the MEMS thermoelectric pile of three-dimensional structure.
Background technology
Thermocouple is a kind of temperature sensor of widespread use, is also used to thermal potential difference to be converted to electric potential difference.Its principle of work be based on Thomas Seebeck in 1821 find thermoelectric effect or Seebeck effect: in the loop be made up of two kinds of different metal material A and B, if the temperature of these two kinds of metals at node place is different, then will produce a thermoelectromotive force in this loop.
The voltage produced by Seebeck effect can be expressed as:
Wherein, S
aand S
bbe respectively the Seebeck coefficient of above-mentioned two kinds of metal material A and B, it depends on the molecular structure of temperature and material, is usually approximately temperature independent material behavior.
Just thermoelectric pile is defined when being together in series by multiple thermocouple.When the identical temperature difference, the Open Output Voltage of thermoelectric pile is the thermoelectromotive force sum of all series connection thermocouples (number represents with n).Under identical electrical signal detection condition, the minimum temperature difference that thermoelectric pile can detect is the 1/n of single thermocouple, thus enhances its resolution characteristic to temperature.
Flourish along with microelectric technique and large scale integrated circuit, proposes the concept of microelectromechanical systems (micro-electro-mechanical system, MEMS).Putting before this, semiconductor material reaches its maturity as the scheme of thermopile IR detector matrix, and has developed MEMS thermopile IR detector thus.MEMS thermopile IR detector has the incomparable advantage of conventional detectors: volume is little, quality is light, low in energy consumption, reliability is high, excellent performance, thus the micro of detector can be realized, can be applied in portable equipment, and due to can integrated a large amount of thermocouple, the resolution to temperature sensing therefore can be improved further.
MEMS thermopile IR detector is a kind of infrared eye based on Seebeck effect, does not usually need refrigeration, can work at normal temperatures, and even to the infrared optical response in a big way.Because its cost of manufacture is lower, can realize production in enormous quantities, therefore, have a wide range of applications in security monitoring, therapeutic treatment, life detection etc.Responsiveness, detectivity and response time are several important performance indexes of infrared eye.
Existing MEMS thermopile IR detector is substantially all utilize CMOS technology technically, by thermocouple to being made into planar structure, and the cold junction top layer that be directly placed in device same with hot junction of thermoelectric pile.This structure is comparatively vulnerable to the impact of environment temperature residing for device, causes the decline of thermopile IR detector temperature resolution and stability.
Summary of the invention
The object of the invention is to the above-mentioned defect overcoming prior art existence, a kind of three-dimensional MEMS thermopile IR detector structure is provided, by two the thermocouple unit formed by two kinds of thermocouple materials right for the thermocouple of connecting in thermopile structure are produced on levels different up and down, the thermojunction of thermocouple is made to be positioned at the comparatively top position of close heat-sink shell, and cold junction is embedded in the Heat Conduction Material be arranged in compared with below, each thermocouple is connected the Three Dimensional Thermal electric pile structure being formed and distribute radially around the vertical center of insulated cavity mutually, cold junction is made not to be subject to the impact of environment temperature, and the heat of thermojunction also not easily scatters and disappears, thus improve temperature resolution and the stability of thermopile detector.
For achieving the above object, technical scheme of the present invention is as follows:
A kind of three-dimensional MEMS thermopile IR detector structure, comprise Semiconductor substrate, the first heat-conducting layer, the second heat-conducting layer, insulating protective layer from bottom to top, and being surrounded by insulated cavity, described insulating protective layer is coated with heat-sink shell, and has the opening of the described insulated cavity of middle part connection, some thermocouples distribute radially around the vertical center of described insulated cavity and connect and are integrated formation thermoelectric pile, the second thermocouple unit that each described thermocouple comprises setting up and down the first thermocouple unit formed by the first thermocouple material and formed by the second thermocouple material, described second thermocouple unit upwards connects described first thermocouple unit by its extension, and the thermojunction of described thermocouple is formed in junction, described first thermocouple unit connects the described second thermocouple unit of adjacent described thermocouple downwards by its extension, and the cold junction of described thermocouple is formed in junction, two kinds of thermocouple materials of each thermocouple form thermocouple pair, wherein, the Outboard Sections that each described thermocouple comprises the described extension of described first thermocouple unit is arranged in described second heat-conducting layer, form the cold junction of described thermoelectric pile, the inboard portion comprising the described extension of described second thermocouple unit is suspended at the described types of flexure in described insulated cavity, form the hot junction of described thermoelectric pile, described heat-sink shell is positioned at above the described hot junction of described thermoelectric pile, and is contacted with the described hot junction of described thermoelectric pile by described insulating protective layer.
Preferably, described infrared eye is the right cylinder of diameter 0.1 ~ 10 millimeter, height 0.5 ~ 2 millimeter, and described insulated cavity is circular cavity, and the described opening of described insulating protective layer is the circular hole of diameter 5 ~ 100 microns.
Preferably, the described first thermocouple unit of each described thermocouple and the shape of described second thermocouple unit are vertical bar shaped, and level is crisscross arranged up and down, forms the angle of 5 ~ 60 degree.
Preferably, the described second thermocouple unit of each described thermocouple is arranged towards the vertical center of described insulated cavity, and each described first thermocouple unit is crisscross arranged towards the homonymy direction of described second thermocouple unit and described second thermocouple unit.
Preferably, the described first thermocouple unit of each described thermocouple and the shape of described second thermocouple unit are respectively the Z-shaped of bending, the Z-shaped hypomere part of the described second thermocouple unit of each described thermocouple is arranged towards the vertical center of described insulated cavity, and the Z-shaped upper portion of described first thermocouple unit is connected by the described extension of described second thermocouple unit, the Z-shaped hypomere part of described first thermocouple unit connects the Z-shaped upper portion of the described second thermocouple unit of adjacent described thermocouple by the described extension of described first thermocouple unit.
Preferably, the Z-shaped hypomere part of described second thermocouple unit and center section part divide perpendicular, upper portion and center section part to be divided into 100 ~ 150 degree of angles to arrange; The Z-shaped epimere of described first thermocouple unit, stage casing, the vertical setting mutually respectively of hypomere part.
Preferably, the Z-shaped hypomere part of described second thermocouple unit is divided with the Z-shaped center section part of described first thermocouple unit and is paralleled.
Preferably, the length of the Z-shaped hypomere part of described second thermocouple unit is 10 ~ 100 microns, and the described Z-shaped epimere of the first thermocouple unit and the length of hypomere part are 5 ~ 50 microns.
Preferably, described thermoelectric pile by 5 ~ 30 described thermocouples around described insulated cavity vertical center radially even level distribute and connect to be integrated and form.
As can be seen from technique scheme, the present invention is by being produced on levels different up and down by right for the thermocouple of connecting in thermopile structure two thermocouple unit, the thermojunction of thermocouple is made to be positioned at the comparatively top position of close heat-sink shell, and cold junction is embedded in the Heat Conduction Material be arranged in compared with below, after the cold junction of thermoelectric pile is connected with reference edge, the heat that thermocouple receives can be delivered to rapidly in substrate, namely cold junction is not subject to the impact of environment temperature, and the heat being in the thermojunction in insulated cavity adiabatic environment also not easily scatters and disappears; Each thermocouple mutually connect formed around insulated cavity vertical center radially even level distribution Three Dimensional Thermal electric pile structure, compare traditional being connected by thermocouple and form the thermoelectric pile of square structure, can relative decrease heat absorption district size, extend thermocouple hot junction part (overhanging portion that thermocouple is right) length, and by setting suitable thermocouple quantity, comprehensively improve responsiveness and the detectivity of detector, thus improve temperature resolution and the stability of thermopile detector.
Accompanying drawing explanation
Fig. 1 is the sectional structure schematic diagram of a kind of three-dimensional MEMS thermopile IR detector of the present invention structure;
Fig. 2 is the thermoelectric pile perspective view in one embodiment of the invention;
Fig. 3 is the thermoelectric pile planar structure schematic diagram in one embodiment of the invention;
Fig. 4 is the thermoelectric pile perspective view in another embodiment of the present invention;
Fig. 5 is the thermoelectric pile planar structure schematic diagram in another embodiment of the present invention;
Fig. 6 a ~ Fig. 6 o a kind ofly makes the device architecture schematic diagram that in the method for three-dimensional MEMS thermopile IR detector structure of the present invention, each step is corresponding.
Embodiment
Below in conjunction with accompanying drawing, the specific embodiment of the present invention is described in further detail.
It should be noted that, in following embodiment, when describing embodiments of the present invention in detail, in order to clearly represent structure of the present invention so that explanation, special to the structure in accompanying drawing not according to general scale, and carried out partial enlargement, distortion and simplify processes, therefore, should avoid being understood in this, as limitation of the invention.
In following embodiment, refer to Fig. 1, Fig. 1 is the sectional structure schematic diagram of a kind of three-dimensional MEMS thermopile IR detector of the present invention structure.As shown in Figure 1, three-dimensional MEMS thermopile IR detector structure of the present invention, comprises Semiconductor substrate 1, first heat-conducting layer 2, second heat-conducting layer 4, insulating protective layer 8 from bottom to top.First heat-conducting layer 2, second heat-conducting layer 4 is annular, with the substrate 1 of below and above insulating protective layer 8 be combined after, i.e. the insulated cavity 10 of square one-tenth detector on substrate 1.Such as, conglobate insulated cavity 10 can be enclosed.Insulating protective layer 8 is coated with heat-sink shell 9, and middle part has opening 11, and opening 11 is communicated with insulated cavity 10.This opening 11 is as the release window of the release process adopted when forming insulated cavity 10.Opening 11 can be made into the circular hole form of such as diameter 5 ~ 100 microns.The profile of infrared eye such as can be right cylinder, and its diameter is 0.1 ~ 10 millimeter, be highly 0.5 ~ 2 millimeter.
Please continue to refer to Fig. 1.Thermoelectric pile is connected by some thermocouples 12 and is formed, and some thermocouples 12 distribute radially around the vertical center of described insulated cavity and connect and are integrated formation thermoelectric pile, such as, adopt 5 ~ 30 thermocouples 12 to connect and formed.Each thermocouple 12 is around vertical center even level's distribution radially of insulated cavity 10, and series connection is integrated (concrete form refers to Fig. 2 to Fig. 5, and is described in detail later).The second thermocouple unit 3 that each thermocouple 12 comprises setting up and down the first thermocouple unit 7 formed by the first thermocouple material and formed by the second thermocouple material.Second thermocouple unit 3 upwards connects the first thermocouple unit 7 by its extension 5, and forms the thermojunction of thermocouple in junction; First thermocouple unit 7 connects the second thermocouple unit of adjacent thermocouple downwards by its extension, and forms the cold junction of thermocouple in junction.Understand from schematic structure, the first thermocouple unit 7-1 being an adjacent thermocouple connects the second thermocouple unit 3 of the thermocouple be adjacent downwards by its extension 6, and forms the cold junction of thermocouple in junction.Two kinds of thermocouple materials of each thermocouple 12 form thermocouple pair.Wherein, the Outboard Sections that each thermocouple comprises the extension 6 of the first thermocouple unit 7-1 is arranged in the second heat-conducting layer 4, forms the cold junction of thermoelectric pile; The inboard portion comprising the extension 5 of the second thermocouple unit 3 is suspended at above the substrate 1 in insulated cavity 10, form the hot junction of thermoelectric pile, namely a part for each thermocouple 12 of thermoelectric pile is embedded in the second heat-conducting layer 4, forms cantilevered fashion and stretches in insulated cavity 10.The heat-sink shell 9 be coated in insulating protective layer 8 is ring-type, is positioned at the hot junction upper of thermoelectric pile, not the cold junction part of cover heating pile.Heat-sink shell 9 is contacted with the hot junction part of thermoelectric pile by insulating protective layer 8, and the part being namely positioned at hot junction with the first thermocouple unit 7 contacts.
In one embodiment of this invention, refer to Fig. 2 and Fig. 3, Fig. 2 is the thermoelectric pile perspective view in one embodiment of the invention; Fig. 3 is the thermoelectric pile planar structure schematic diagram in one embodiment of the invention.As shown in Figure 2 (represent each structure in figure for clear, this figure have employed transparent form and draws), three-dimensional MEMS thermopile IR detector of the present invention is cylindrical, comprises the substrate 1 of bottom, is linked as the first overall heat-conducting layer 2 and the second heat-conducting layer 4.The Outboard Sections of the thermoelectric pile of annular is arranged in the second heat-conducting layer 4, and being connected by 15 thermocouple head and the tail is formed.Heat-sink shell 9 is ring-type, is positioned at the hot junction upper of thermoelectric pile, not the cold junction part of cover heating pile.Each thermocouple comprises the first thermocouple unit 7 formed by the first thermocouple material of lower leaf setting and the second thermocouple unit 3 formed by the second thermocouple material.The shape of the first thermocouple unit 7 and the second thermocouple unit 3 is vertical bar shaped, and thickness is 0.3 ~ 10 micron.Second thermocouple unit 3 has vertical extension 5 by the end inside thermoelectric pile, and upwards connecting the first thermocouple unit 7 by extension 5, its junction forms the thermojunction 12 (marking the extension place of a second thermocouple unit of opposite side in the drawings) of thermocouple.Second thermocouple unit 3 and its extension 5 use the second same thermocouple material to be formed.First thermocouple unit 7-1 also has vertical extension 6 by the end outside thermoelectric pile, and the second thermocouple unit 3 of another thermocouple adjacent is connected downwards by extension 6, its junction forms the cold junction 13 (marking the extension place of another the first thermocouple unit bottom-right in the drawings) of thermocouple.First thermocouple unit 7-1 and its extension 6 use the first same thermocouple material to be formed.The extension of two thermocouple unit is cylindrical, also can be other cylindricalitys.
Incorporated by reference to consulting Fig. 3.Be in series by cylindrical extension to enable each thermocouple unit of vertical bar shaped, need the first thermocouple unit 7 and the second thermocouple unit about 3 level to be crisscross arranged, and make the first thermocouple unit 7 and the second thermocouple unit 3 form the relative deflection angle of 5 ~ 60 degree in vertical projection direction.Preferably deflect angle and such as can be 18 degree.Simultaneously, second thermocouple unit 3 of each thermocouple is arranged towards the vertical center of insulated cavity 10, and each first thermocouple unit 7 is crisscross arranged towards the homonymy direction (being illustrated as clockwise direction deflection to the right) of the second thermocouple unit 3 with the second thermocouple unit 3.15 thermocouples (instant heating couple) head and the tail series connection of composition thermoelectric pile, forms the radial loop configuration of horizontal homogeneous distribution centered by the vertical central shaft of insulated cavity 10.
Like this, be divided into upper and lower two layers of setting by the first thermocouple unit of each thermocouple and the second thermocouple unit, hot junction be in adiabatic insulated cavity, and make thermojunction be positioned at higher position; And cold junction is embedded in the heat-conducting layer formed by Heat Conduction Material, and cold junction is made to be positioned at lower position.After being connected with reference edge by the cold junction of thermoelectric pile, the heat that thermocouple receives can be delivered to rapidly in substrate, makes cold junction not be subject to the impact of environment temperature; And the thermojunction be in insulated cavity adiabatic environment can receive rapidly the heat from heat-sink shell, and heat also not easily scatters and disappears.Three Dimensional Thermal electric pile structure of the present invention forms ring-type, and the thermocouple hot junction being positioned at inner side is in state of aggregation, be positioned at the thermocouple cold junction in outside is in divergent state.Compare the thermoelectric pile of traditional square structure formed that distributed along square heat-sink shell by some thermocouple series connection, can relative decrease heat absorption district size, extend thermocouple hot junction part (overhanging portion that thermocouple is right) length, and by setting suitable thermocouple quantity, comprehensively improve responsiveness and the detectivity of detector, thus improve temperature resolution and the stability of thermopile detector.
In another embodiment of the invention, refer to Fig. 4 and Fig. 5, Fig. 4 is the thermoelectric pile perspective view in another embodiment of the present invention; Fig. 5 is the thermoelectric pile planar structure schematic diagram in another embodiment of the present invention.As shown in Figure 4, three-dimensional MEMS thermopile IR detector of the present invention is similarly cylindrical, and thermoelectric pile is connected by 15 thermocouple head and the tail and formed.Each thermocouple comprises the first thermocouple unit 7 formed by the first thermocouple material of lower leaf setting and the second thermocouple unit 3 formed by the second thermocouple material.First thermocouple unit 7 and the shape of the second thermocouple unit 3 are bend by three sections of vertical bar shapeds the English alphabet shape be combined into that is connected, and thickness is 0.3 ~ 10 micron.First thermocouple unit 7 is different with the Z-shaped direction of the second thermocouple unit 3, and wherein, the Z-shaped inner side towards thermoelectric pile of the first thermocouple unit 7 is just put, and the Z-shaped inner side towards thermoelectric pile of the second thermocouple unit 3 is horizontal.Second thermocouple unit 3 end in the inner part has vertical extension 5, and upwards connects the first thermocouple unit 7 by extension 5, and its junction forms the thermojunction 12 (marking the extension place of a second thermocouple unit of opposite side in the drawings) of thermocouple.Second thermocouple unit 3 and its extension 5 use the second same thermocouple material to be formed.First thermocouple unit 7-1 end in the outer part also has vertical extension 6, and the second thermocouple unit 3 of another thermocouple adjacent is connected downwards by extension 6, its junction forms the cold junction 13 (marking the extension place of another the first thermocouple unit on right side in the drawings) of thermocouple.First thermocouple unit 7-1 and its extension 6 use the first same thermocouple material to be formed.The extension of two thermocouple unit is cylindrical, also can be other cylindricalitys.
Please continue combination and consult Fig. 5.The Z-shaped hypomere part 3-3 of the second thermocouple unit of each thermocouple is arranged towards the vertical center of insulated cavity 10, and its length is 10 ~ 100 microns, and connects the Z-shaped upper portion 7-2 of the first thermocouple unit by the extension of the second thermocouple unit.The Z-shaped hypomere part 7-4 of the first thermocouple unit connects the Z-shaped upper portion of the second thermocouple unit of another thermocouple adjacent by the extension of the first thermocouple unit.The Z-shaped hypomere part 3-3 of the second thermocouple unit is perpendicular with stage casing part 3-2, upper portion 3-1 becomes 100 ~ 150 degree of angles to arrange with stage casing part 3-2, preferably arranges with the angle of 115 degree; Z-shaped upper portion 3-1, the stage casing part 3-2 of the second thermocouple unit, the length of hypomere part 3-3 increase setting successively.Z-shaped upper portion 7-2, the stage casing part 7-3 of the first thermocouple unit, hypomere part 7-4 are mutually vertical respectively to be arranged, and the length of its Z-shaped epimere and hypomere part 7-2,7-4 is short compared with stage casing part 7-3, is 5 ~ 50 microns.The Z-shaped hypomere part 3-3 of the second thermocouple unit parallels setting with the Z-shaped stage casing part 7-3 of the first thermocouple unit.
Thermoelectric pile spatial structure in another embodiment of the present invention, except there is the advantage identical with foregoing first embodiment, compared with first embodiment, due to thermocouple is Z-shaped to being designed to, more increase the length of cold junction, therefore, not only can more promptly the heat of thermocouple is delivered in substrate, and enhance the structural stability that cantilevered thermocouple (namely imbeds the part in heat-conducting layer) in detector, make detector be not easy to be damaged.
Below by Fig. 6 a ~ Fig. 6 o, the method making three-dimensional MEMS thermopile IR detector structure of the present invention is illustrated.Fig. 6 a ~ Fig. 6 o a kind ofly makes the device architecture schematic diagram that in the method for three-dimensional MEMS thermopile IR detector structure of the present invention, each step is corresponding.
First, please refer to Fig. 6 a, Semiconductor substrate 201 deposits the first heat-conducting layer 202.The material of substrate 201 can be silicon, germanium or germanium silicon.First heat-conducting layer can be SiO
2film, BN film, AlN film or undoped monocrystalline silicon thin film.Preferably, substrate 201 is monocrystalline substrate, and the first heat-conducting layer 202 is BN film.
Please refer to Fig. 6 b, the first heat-conducting layer 202 deposits the second thermocouple material, and graphically, to form the second thermocouple layer 203 with some second thermocouples unit.Second thermocouple material can be the poor polysilicon membrane of thermal conductivity or amorphous silicon membrane, and thickness is 0.3 ~ 10 micron.Preferably, polysilicon membrane can be adopted.
Please refer to Fig. 6 c ~ 6g, on the second thermocouple layer 203, make thermocouple extension by twice single Damascus technics.
Specifically, first as fig. 6 c, the first heat-conducting layer 202 and the second thermocouple layer deposit the second heat-conducting layer 204.Second heat-conducting layer 204 can be SiO
2film, BN film, AlN film or undoped monocrystalline silicon thin film.Preferably, the second heat-conducting layer 204 and the first heat-conducting layer 202 are all BN film.
Then, as shown in fig 6d, carry out graphically to the second heat-conducting layer 204, form the second thermocouple through hole that bottom extends to the second thermocouple layer.According to the difference of the second heat-conducting layer 204 material, can select, to the second thermocouple layer, there is different etching method compared with high selectivity.To the graphical employing wet etching of BN film, liquid used is the mixed solution of the concentrated sulphuric acid and hydrogen peroxide.
Please refer to Fig. 6 e again, in the second thermocouple through hole, fill the second thermocouple material and carry out planarization by CMP (chemically mechanical polishing) technique, making the upper surface of the second thermocouple material in the second thermocouple through hole concordant with the upper surface of the second heat-conducting layer 204.The second thermocouple material in second thermocouple through hole forms the second thermocouple unit extension 205.
Please continue to refer to Fig. 6 f, similar with step shown in Fig. 6 d, carry out graphically to the second heat-conducting layer 204 again, form the first thermocouple through hole that bottom extends to the second thermocouple layer.Same, to the graphical employing wet etching of the second heat-conducting layer 204BN film, liquid used is the mixed solution of the concentrated sulphuric acid and hydrogen peroxide.
Finally, please refer to Fig. 6 g, similar with step shown in Fig. 6 e, in the first thermocouple through hole, fill the first thermocouple material, and carry out planarization by CMP, make the upper surface of the first thermocouple material in the first thermocouple through hole concordant with the upper surface of the second heat-conducting layer 204.The first thermocouple material in first thermocouple through hole forms the first thermocouple unit extension 206.Wherein, the first thermocouple material can be the good Al film of thermal conductivity, Cu film or W film, and thickness is 0.3 ~ 10 micron.
Next, the second thermocouple unit extension 205 and the first thermocouple unit extension 206 form the first thermocouple layer formed by the first thermocouple unit with corresponding second thermocouple element number, specifically please refer to Fig. 6 h ~ 6j.
First, concordant the second thermocouple unit extension, the first thermocouple unit extension and the second heat-conducting layer of upper surface deposits the 3rd heat-conducting layer again; The material of the 3rd heat-conducting layer is identical with the second heat-conducting layer (continuity being exactly in fact the second heat-conducting layer deposits, and therefore have employed identical mark 204).Afterwards, in the 3rd heat-conducting layer 204, the figure of the first thermocouple layer is etched by photoetching, etching technics; The graph position of the first thermocouple layer and thermocouple unit extension one_to_one corresponding, contact with thermocouple unit extension upper surface bottom it.Then, deposit the first thermocouple material, and carry out planarization by CMP, form the first thermocouple layer 207.The upper surface of the first thermocouple layer 207 is concordant with the upper surface of described 3rd heat-conducting layer 204, and is connected with the first thermocouple unit extension with the second thermocouple unit extension.So, complete the second thermocouple layer 203, thermoelectric pile agent structure that thermocouple unit extension 205 and 206, first thermocouple layer 207 is formed.Wherein, the first thermocouple unit that each thermocouple of the first thermocouple layer 207 is right and the second thermocouple unit extension 205 connecting place are the thermojunction of thermocouple, and the second thermocouple unit connecting place that another thermocouple adjacent of the first thermocouple unit extension 206 and the second thermocouple layer 207 is right is the cold junction of thermocouple.Because cold junction is embedded in bottom the second heat-conducting layer 204, therefore, the impact by environment temperature is not easy.
Next, the step forming heat-sink shell is carried out.Heat-sink shell is coated by insulating protective layer institute, to prevent the heat loss at thermojunction place better.Please refer to Fig. 6 k, the 3rd heat-conducting layer 204 and the first thermocouple layer 207 deposit the first insulating protective layer 208.Insulation protection layer material is silicon oxide film or silicon nitride film, and preferably, insulating protective layer 208 is the silicon oxide film adopting PECVD method deposition.
Then, as shown in Fig. 6 l, the first insulating protective layer 208 grows heat-sink shell 209 and graphically, heat-sink shell 209 is positioned at above hot junction.Heat-sink shell, for receiving infrared radiation, is infrared absorption characteristic preferably membraneous material, and as silicon nitride film, Ti or TiAlN thin film, Ta or TaN film, thickness is 100 dust ~ 5 micron.Preferred heat-sink shell 209 is the TiAlN thin film of square resistance close to free space impedance (about 377ohms/square).
And then, patterned heat-sink shell 209 deposits one deck second insulating protective layer 208a again, heat-sink shell is wrapped up completely, as shown in Fig. 6 m.
Then, please refer to Fig. 6 n, insulating protective layer 208,208a are carried out graphically, and form the release window running through insulating protective layer.Now, heat-sink shell is still completely wrapped in insulating protective layer, thus the heat in hot junction also not easily scatters and disappears.
Finally, please refer to Fig. 6 o, carry out release process by release window, form final MEMS thermopile IR detector structure.In preferably release process, the mixed solution wet method of the concentrated sulphuric acid and hydrogen peroxide is adopted to remove the expendable material boron nitride of the heat-conducting layer 204 and 202 below hot junction.Wet method release process adopts time controling, the second heat-conducting layer (with the 3rd heat-conducting layer) after making to discharge around the second thermocouple unit extension 205 and the first heat-conducting layer below the second thermocouple unit extension are all removed, and the heat-conducting layer around the first thermocouple unit extension still retains.Optionally, when heat-conducting layer material is SiO
2during film, wet processing adopts BOE liquid; When heat-conducting layer material is BN film, wet processing adopts the mixed solution of the concentrated sulphuric acid and hydrogen peroxide; When heat-conducting layer material is AlN film, wet processing adopts strong phosphoric acid, and temperature is 120 ~ 200 degrees Celsius.
Above-describedly be only the preferred embodiments of the present invention; described embodiment is also not used to limit scope of patent protection of the present invention; therefore the equivalent structure that every utilization instructions of the present invention and accompanying drawing content are done changes, and in like manner all should be included in protection scope of the present invention.
Claims (9)
1. a three-dimensional MEMS thermopile IR detector structure, it is characterized in that, comprise Semiconductor substrate, the first heat-conducting layer, the second heat-conducting layer, insulating protective layer from bottom to top, and be surrounded by insulated cavity, described insulating protective layer is coated with heat-sink shell, and has the opening of the described insulated cavity of middle part connection; Some thermocouples distribute radially around the vertical center of described insulated cavity and connect and are integrated formation thermoelectric pile, the second thermocouple unit that each described thermocouple comprises setting up and down the first thermocouple unit formed by the first thermocouple material and formed by the second thermocouple material, described second thermocouple unit upwards connects described first thermocouple unit by its extension, and the thermojunction of described thermocouple is formed in junction, described first thermocouple unit connects the described second thermocouple unit of adjacent described thermocouple downwards by its extension, and forms the cold junction of described thermocouple in junction; Wherein, the Outboard Sections that each described thermocouple comprises the described extension of described first thermocouple unit is arranged in described second heat-conducting layer; form the cold junction of described thermoelectric pile; the inboard portion comprising the described extension of described second thermocouple unit is suspended at the described types of flexure in described insulated cavity; form the hot junction of described thermoelectric pile; described heat-sink shell is positioned at above the described hot junction of described thermoelectric pile, and is contacted with the described hot junction of described thermoelectric pile by described insulating protective layer.
2. MEMS thermopile IR detector structure according to claim 1; it is characterized in that; described infrared eye is the right cylinder of diameter 0.1 ~ 10 millimeter, height 0.5 ~ 2 millimeter; described insulated cavity is circular cavity, and the described opening of described insulating protective layer is the circular hole of diameter 5 ~ 100 microns.
3. MEMS thermopile IR detector structure according to claim 1, is characterized in that, the described first thermocouple unit of each described thermocouple and the shape of described second thermocouple unit are vertical bar shaped, and level is crisscross arranged up and down, forms the angle of 5 ~ 60 degree.
4. MEMS thermopile IR detector structure according to claim 3, it is characterized in that, the described second thermocouple unit of each described thermocouple is arranged towards the vertical center of described insulated cavity, and each described first thermocouple unit is crisscross arranged towards the homonymy direction of described second thermocouple unit and described second thermocouple unit.
5. MEMS thermopile IR detector structure according to claim 1, it is characterized in that, the described first thermocouple unit of each described thermocouple and the shape of described second thermocouple unit are respectively the Z-shaped of bending, the Z-shaped hypomere part of the described second thermocouple unit of each described thermocouple is arranged towards the vertical center of described insulated cavity, and the Z-shaped upper portion of described first thermocouple unit is connected by the described extension of described second thermocouple unit, the Z-shaped hypomere part of described first thermocouple unit connects the Z-shaped upper portion of the described second thermocouple unit of adjacent described thermocouple by the described extension of described first thermocouple unit.
6. MEMS thermopile IR detector structure according to claim 5, is characterized in that, the Z-shaped hypomere part of described second thermocouple unit and center section part divide perpendicular, upper portion and center section part to be divided into 100 ~ 150 degree of angles to arrange; The Z-shaped epimere of described first thermocouple unit, stage casing, the vertical setting mutually respectively of hypomere part.
7. MEMS thermopile IR detector structure according to claim 5, is characterized in that, the Z-shaped hypomere part of described second thermocouple unit is divided with the Z-shaped center section part of described first thermocouple unit and paralleled.
8. the MEMS thermopile IR detector structure according to claim 5 ~ 7 any one, it is characterized in that, the length of the Z-shaped hypomere part of described second thermocouple unit is 10 ~ 100 microns, and the described Z-shaped epimere of the first thermocouple unit and the length of hypomere part are 5 ~ 50 microns.
9. the MEMS thermopile IR detector structure according to claim 1,3 or 5, is characterized in that, described thermoelectric pile by 5 ~ 30 described thermocouples around described insulated cavity vertical center radially even level distribute and connect to be integrated and form.
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