The microphone chip that girder-type diaphragm is formed
Technical field
The present invention relates to the mike technique field, particularly semicoductor capacitor formula microphone chip is the microphone chip that a kind of girder-type diaphragm is formed.
Background technology
The history in existing more than 20 year of semiconductor microphone chip research, during miscellaneous microphones on silicon chip, realized successively by exploitation.Wherein, main the most popular a kind of be capacitance type silicon microphone.Characteristics such as capacitance type silicon microphone has not only that volume is little, highly sensitive, good frequency response, noise are low the more important thing is to have very wide working temperature, applicable to automatic production line operation and bad working environment such as SMT.
Capacitance type microphone chip is the capacitance structure that is formed by vibrating diaphragm, backplane, and report and patent adopt two membrane capacitance structures mostly at present, on silicon chip, utilizes micromachining technology to make vibrating diaphragm and the two membrane capacitance structures of backplane.Research, report for the single membrane capacitance type silicon microphone are rare, document Fabrication of silicon condenser microphone using single wafer technology, Journal of microelectromechanical systems; VOL.1.No.3,1992, p147-154; Reported a kind of single membrane capacitance type silicon microphone; Utilize vibrating diaphragm edge and silicon base to form capacitance structure, silicon base is as backplane, and backplane center macropore is as the sound hole.This report exists deficiency; Because the vibrating diaphragm edge links to each other with periphery, when receiving sound wave, maximum vibration is at the center of vibrating diaphragm; The vibration at vibrating diaphragm edge is less; Because the vibrating diaphragm center is over against backplane sound hole, the mechanical sensitivity of amplitude maximum region does not obtain utilizing, and the vibrating diaphragm mechanical sensitivity is little to sensitivity of microphone contribution; U.S. Pat 5,870,482 have described the beam type vibrating diaphragm; Cantilever beam one end is fixed; Utilize free end edge and backplane to constitute electric capacity, this construction machine sensitivity is very big to sensitivity of microphone contribution, but the structure fabrication more complicated; Cantilever beam three ends are free simultaneously, and the attitude and the reliability of vibrating diaphragm are more difficult to get assurance; U.S. publication US2006/0093170A1; The equally distributed monofilm structure of overarm has been proposed; Utilize vibrating diaphragm edge and backplane to form electric capacity, overarm has improved the contribution of mechanical sensitivity to the microphone output sensitivity, but can not realize described vibrating diaphragm translational Motion Model.
Summary of the invention
The objective of the invention is in order to solve the problem that exists in the single membrane capacitance type microphone chip technology that has now; Deficiency to current existence; The microphone chip that a kind of girder-type diaphragm is formed has been proposed; The single membrane capacitance type microphone chip that girder-type diaphragm is formed effectively improves sensitivity, and improves its performance and reliability.
For achieving the above object, technical solution of the present invention is:
A kind of girder-type diaphragm is used for capacitance type microphone chip, comprises vibrating diaphragm, outer overarm, the frame of hanging oneself from a beam outward; Its vibrating diaphragm is the beam type strip, and two ends respectively are provided with overarm outside at least one on the longitudinal direction of vibrating diaphragm, and outer overarm fully is connected for balanced symmetrical structure and with vibrating diaphragm and is used for vibrating diaphragm maintenance horizontal equilibrium state, and vibrating diaphragm is connected through outer overarm and outer overarm frame; The girder-type diaphragm central part is a sheet, in the vibrating diaphragm outer edge region, is provided with most holes at the sheet edge.
The microphone chip that a kind of described girder-type diaphragm is formed, be vibrating diaphragm last, backplane under the single membrane capacitance type structure, comprise substrate, insulating barrier, conductive layer, bottom electrode, top electrode; Substrate is as backplane, and there is the hole at the substrate center, and upper surface of substrate is connected with insulating barrier, and insulating barrier comprises at least two outer overarm supports and all edge insulating layers, and all edge insulating layer upper surfaces are connected with conductive layer, and upper surface of substrate also is provided with bottom electrode; At least two outer overarm frames of its girder-type diaphragm are connected in outer overarm respectively and support upper surface, and wherein an outer overarm frame upper surface is connected with top electrode, and the sheet central part covering sound hole of girder-type diaphragm is established bore region and substrate and constituted electric capacity on the vibrating diaphragm.
Described microphone chip, its said substrate is a semiconductor silicon.
Described microphone chip, its said insulating barrier are PSG, LTO, TEOS silica.
Described microphone chip, its said top electrode and bottom electrode are metallic gold or aluminium.
Capacitance type microphone chip of the present invention, vibrating diaphragm are girder structure, and the vibrating diaphragm two ends are affixed on the longitudinal direction of beam, and vibrating diaphragm is free on the direction vertical with beam, and the edge of vibrating diaphragm and substrate form capacitance structure.During the vibrating diaphragm vibration, the maximum displacement of vibrating diaphragm is at the midline position of beam, and the maximum machine sensitivity of vibrating diaphragm is contributed to output sensitivity.Substrate has a macropore as backplane in the middle of the backplane---and the sound hole, vibrating diaphragm is overlying on this hole.The countless apertures that vibrating diaphragm is provided with outside the scope of sound hole, these apertures cooperate backplane sound holes to discharge original sacrifice layer between vibrating diaphragms and the backplane, and the Frequency Response of microphone is had the improvement effect.
The vibrating diaphragm two ends are fixed in substrate, can select for use various ways to connect, and the advantage of this girder-type diaphragm has been for given play to the mechanical sensitivity of vibrating diaphragm to greatest extent, promptly under sensitivity meets the requirements of prerequisite, can effectively guarantee reliabilities such as vibrating diaphragm is anti-drop; Substrate has very strong rigidity as backplane.The microphone chip of this structure is simple in structure, technology difficulty is low, cost is low, reliability is high.
The present invention proposes the girder-type diaphragm structure, the vibrating diaphragm two ends on the longitudinal direction of beam are fixed, and the direction vibrating diaphragm vertical with beam is free.Vibrating diaphragm edge and substrate form capacitance structure, and beam direction vibrating diaphragm midline amplitude is maximum, make full use of the mechanical sensitivity of vibrating diaphragm amplitude maximum.
Description of drawings
Fig. 1 has the girder-type diaphragm microphone chip vertical view of herringbone overarm for the present invention;
Fig. 2 has the profile of the girder-type diaphragm microphone chip of herringbone overarm along Fig. 1 dotted line for the present invention;
Fig. 3 has insulating barrier vertical view in the girder-type diaphragm microphone chip of herringbone overarm for the present invention;
Fig. 4 has the girder-type diaphragm microphone chip upward view of herringbone overarm for the present invention;
The girder-type diaphragm capacitance type microphone chip vertical view of Fig. 5 double font overarm for the present invention has;
The girder-type diaphragm capacitance type microphone chip of Fig. 6 double font overarm for the present invention has is along the profile of Fig. 5 dotted line;
Fig. 7 has the girder-type diaphragm capacitance type microphone chip vertical view of in-line overarm for the present invention;
Fig. 8 has the profile of the girder-type diaphragm capacitance type microphone chip of in-line overarm along Fig. 7 dotted line for the present invention;
Embodiment
The present invention has multiple multi-form embodiment, and Fig. 1-8 is depicted as one embodiment of the present invention, is elaborated in the face of this embodiment down.
Girder-type diaphragm capacitance type microphone chip structure of the present invention; Shown in Fig. 1-4; Its characteristics are fixed for vibrating diaphragm two ends on the longitudinal direction of girder-type diaphragm, and the vertical direction vibrating diaphragm becomes free state with it, sound hole, substrate center; Vibrating diaphragm edge and substrate form electric capacity, and this structure is from bottom to top: substrate 21, insulating barrier 22, conductive layer 23, bottom electrode 24, top electrode 25.
Wherein, there is through hole at substrate 21 centers, are sound hole 26.Substrate 21 is conductor or semi-conducting material, as the backplane of capacitance structure.Semi-conducting material can be a silicon, and for silicon materials, the sound hole 26 of substrate 21 central parts can use bulk silicon etching technology to form, and is as shown in Figure 4.Also can adopt dry etching to form column sound hole.
Substrate 21 upper surfaces are fixed with insulating barrier 22, and insulating barrier 22 supports 22a by outer overarm and all edge insulating layer 22b constitute, and is as shown in Figure 3.Week edge insulating layer 22b circlewise, outer overarm is supported 22a and within circular periphery layer 22b and each other, is isolated, sound hole 26 upper sheds are within all edge insulating layer 22b.A side has a through hole on ringed perimeter insulating barrier 22b, is bottom electrode hole 27.In bottom electrode hole 27, the affixed metal electrode of substrate 21 upper surfaces is bottom electrode 24, and bottom electrode 24 can be gold, aluminium.Insulating barrier 22 can be a silica, is PSG, LTO, TEOS.
Conductive layer 23 by girder-type diaphragm 23a, outward hang oneself from a beam 23b, hang oneself from a beam frame 23c and peripheral conductive layer 23d constitutes outward, and be as shown in Figure 1.Vibrating diaphragm 23a links to each other with outer overarm frame 23c through outer overarm 23b, and it is affixed that the 22a upper surface is supported in hang oneself from a beam outward frame 23c and outer overarm; Vibrating diaphragm 23a is covered on 26 upper sheds of hole, and vibrating diaphragm 23a is greater than the area of sound hole 26 upper sheds, and vibrating diaphragm 23a edge and substrate 21 form capacitance structure; Vibrating diaphragm 23a can be circular hole, square hole or other polygonal hole over against several apertures 28 are arranged outside 26 openings of sound hole; Vibrating diaphragm 23a, hang oneself from a beam 23b and hang oneself from a beam frame 23c outward in all edge insulating layer 22b annular extent outward, and gapped 29.Periphery conductive layer 23d is fixed in all edge insulating layer 22b upper surfaces, and shape is consistent.The fixed metal electrode of outer overarm frame 23c upper surface is top electrode 25, and top electrode 25 can be gold, aluminium.Conductive layer 23 can be the low stress polysilicon, and through mixing phosphorus or boron, forms n type or p type conductive layer.When vibrating diaphragm 23a produced vibration under the effect of sound wave, frame of broken lines position amplitude was bigger among Fig. 1, provides the major part of sensitivity.
In order to make the sensitivity of vibrating diaphragm 23a midline position consistent, discharge residual stress, make vibrating diaphragm keep the horizontal equilibrium state simultaneously, outer overarm need be selected balanced symmetrical structure for use and fully is connected with vibrating diaphragm.Fig. 1-4 hangs oneself from a beam outward for herringbone; The double font of Fig. 5-6 is hung oneself from a beam outward; Fig. 7-8 hangs oneself from a beam outward for in-line, and these in-lines are hung oneself from a beam outward, and width reduces successively from the centre to both sides.
Substrate 21 forms capacitance structure with vibrating diaphragm 23a edge, and spacing is the 2-5 micron.When the time spent of doing that vibrating diaphragm 23a receives sound wave, vibrating diaphragm 23a center aporate area is stressed, drives whole vibrating diaphragm 23a balance vibration, and the distortion of vibrating diaphragm 23a midline position is maximum, and the deflection of vibrating diaphragm 23a converts the variation of capacitance to, thereby realizes the function of transducer.Owing to adopt the girder-type diaphragm structure among the present invention, utilize the maximum area contribution sensitivity of vibrating diaphragm 23a distortion, therefore, on the basis that sensitivity meets the demands, can effectively increase reliability, improve rate of finished products.