Summary of the invention
The purpose of this invention is to provide a kind of adopt wafer level packaging that silicon substrate reduction process technology realizes based on hot type wind speed wind direction sensor of reduction process and preparation method thereof, the sensor construction of design and packing forms help when guaranteeing big sensitive signal amplitude, and sensing system has lower power consumption.
The present invention adopts following technical scheme:
A kind of hot type wind speed wind direction sensor based on reduction process, comprise the attenuate silicon, the back side of described attenuate silicon is connected with ceramic substrate by heat-conducting glue, be provided with the N trap in the front of attenuate silicon, on the N trap, be provided with oxide layer, be provided with 4 diffusion resistance heating elements and 4 hot sensing temperature elements at the middle part of N trap, 4 hot sensing temperature elements be the thermocouple temperature measurement element and be distributed in 4 diffusion resistance heating elements around, be provided with electricity at the fringe region of oxide layer and draw pad, the electricity that the electricity of 4 diffusion resistance heating elements is drawn pad and 4 hot sensing temperature elements is drawn pad and is drawn pad by metal lead wire and electricity respectively and be connected, be provided with hot isolation channel between 4 diffusion resistance heating elements and 4 hot sensing temperature elements, described heat is isolated in groove depth and the attenuate silicon substrate.
A kind of preparation method of the hot type wind speed wind direction sensor based on reduction process is as described below:
The first step, the preparation of silicon
Step 1 is at silicon surface heat first thermal oxide layer of growing;
Step 2, chemical vapor deposition silicon nitride layer on first thermal oxide layer;
Step 3 utilizes the RIE technology that silicon is carried out etching, the definition active area;
Step 4, chemical vapor deposition second oxide layer;
Step 5 utilizes the CMP technology that silicon is carried out polishing;
Step 6, wet etching is removed silicon nitride layer, and field oxide is finished in preparation;
Step 7, phosphonium ion injects, preparation N trap;
Step 8, heat growth gate oxide;
Step 9, the boron ion injects, an end of preparation heating element and hot sensing temperature element;
Step 10, chemical vapor deposition the 3rd oxide layer, wherein first thermal oxide layer, second oxide layer and the 3rd oxide layer are merged into an oxide layer;
Step 11 utilizes dry etch process to prepare on the hot sensing temperature element through hole on the through hole and heating element;
Step 12 is utilized sputtering technology preparation electricity to draw with another end and the heating element electricity of aluminum pad and hot sensing temperature element and is drawn pad;
Step 13 utilizes dry etch process to prepare hot isolation channel between heating element and hot sensing temperature element;
Second step, attenuate and encapsulation
Step 1 is coated with paraffin layer in the front of silicon;
Step 2 adheres to microslide by paraffin layer in the front of silicon under 80 ℃ of environment temperatures;
Step 3, utilize reduction process to the substrate of silicon carry out attenuate until substrate thickness be 80 microns to 100 micrometer ranges, obtain the attenuate silicon;
Step 4 is coated with heat-conducting glue at the attenuate silicon back side, and sticks ceramic substrate, under 100 ℃ of environment temperatures heat-conducting glue is cured;
Step 5 is removed microslide and paraffin layer under 80 ℃ of environment temperatures;
In the 3rd step, the preparation of wind speed wind direction sensor is finished in scribing.
The present invention utilizes CMOS technology to prepare heating element and hot sensing temperature element on silica-based, utilize the DRIE dry etch process between heating element and hot sensing temperature element, to prepare 50 microns dark hot isolation channels, be used to reduce the transverse heat transfer effect between heating element and the hot sensing temperature element; Utilize the reduction process of silicon substrate mechanical lapping and polishing that the silicon substrate that comprises heating element and hot sensing temperature element is carried out attenuate, remove most silicon substrate until the thickness of silicon substrate at 80 microns to 100 micrometer ranges, can reduce the thermal capacity of chip so to a great extent, the response time that in the sensitivity that improves chip, can reduce sensor; The ceramic substrate that utilization has certain thermal conductivity seals to the back side of attenuate silicon by heat-conducting glue; ceramic substrate is protected the attenuate silicon to avoid the pollution of external environment on the one hand and mechanical support is provided, and realizes the heat interchange of attenuate silicon and external environment on the other hand as middle heat transfer medium.The silicon substrate is being carried out in the process of attenuate, at first utilize paraffin that silicon is labelled on the microslide, utilize microslide to provide necessary mechanical support to the attenuate silicon, the attenuate silicon that utilizes heat-conducting glue will still post microslide then seals to ceramic substrate, fuse paraffin at last again, remove microslide, finish the preparation of sensor, such preparation process can prepared the sensor chip of substrate thickness at 80 microns to 100 microns, and the chip structure to fragility provides necessary mechanical support in the whole last handling process of sensor package and scribing.
The present invention conducts in the ceramic substrate by the substrate of attenuate silicon and the heat-conduction effect of heat-conducting glue by the heat that the heating element of preparation in the attenuate silicon produces, in ceramic substrate, set up a temperature field, the ceramic substrate upper surface is exposed in the external environment, the temperature field that the variation of external environment apoplexy can influence in the ceramic substrate distributes, transmission by heat-conducting glue can distribute the temperature field that changes in the ceramic substrate and be transmitted back in the attenuate silicon substrate, and the silicon substrate of the hot sensing temperature element in the attenuate silicon after by attenuate measured this temperature field variation in temperature distribution situation.Under the calm condition in the external world, the distribution in temperature field presents the state of complete symmetry.When the external world has wind out-of-date from the ceramic substrate upper surface blown, wind will be taken away the heat of part in the mode of thermal convection from the ceramic substrate upper surface, and in ceramic substrate, set up a temperature gradient distribution field along the wind direction direction, hot sensing temperature element after by attenuate silicon substrate and the conduction of heat of heat-conducting glue measure the variation that this temperature field distributes, and then can calculate the size of wind speed and direction.
In sensor construction, seal to the ceramic substrate at the attenuate silicon back side by heat-conducting glue and to be used to protect the attenuate silicon of lower floor on the one hand and necessary mechanical support is provided, on the other hand again as the sensitive element of the variation of the extraneous wind of impression.Whole sensor has only the upper surface of ceramic substrate and the environment of wind to contact, and other elements are all isolated by ceramic substrate and external environment, therefore can avoid being subjected to the pollution of external environment.The structure of sensor of the present invention is applicable to the wind speed wind direction sensor of preparation two dimension.
In this sensor design scheme, in the preparation of first step silicon, utilize standard CMOS process to prepare heating element and hot sensing temperature element; In the preparation of hot isolation channel of second step, utilize the DRIE dry etch process; In the 3rd step silicon substrate thinning, utilize the reduction process of silicon substrate mechanical lapping and polishing; The 4th step ceramic substrate seals in the encapsulation, utilizes the technology that is coated with that heat-conducting glue is coated with the back side to ceramic substrate, and the back side to the attenuate silicon seals then; The 5th step, scribing.Whole sensor preparation process and standard CMOS process compatibility, and can realize the wafer level packaging of sensor chip.
The present invention obtains following effect:
1. the present invention utilizes the DRIE dry etch process to prepare 50 microns dark hot isolation channels between silicon front surface heating element and hot sensing temperature element, can effectivelyly reduce the transverse heat transfer effect between heating element and the hot sensing temperature element; Utilize the reduction process of silicon substrate mechanical lapping and polishing that the silicon substrate that comprises heating element and hot sensing temperature element is carried out attenuate, remove most silicon substrate until the thickness of silicon substrate at 80 microns to 100 micrometer ranges, the thermal capacity of chip be can reduce so greatly, the thermal response time of sensor and the sensitivity that improves sensor reduced.
The chip structure form that attenuate silicon front surface has a hot isolation channel can make the heat overwhelming majority that heating element produces by the silicon substrate vertical conduction behind the attenuate to the attenuate silicon back side, can completely cut off the transverse heat transfer between heating element and the hot sensing temperature element to a great extent, so greatly degree reduces because the unnecessary power consumption that the heat-conduction effect of silicon substrate causes.
3. the silicon substrate carries out in the process of attenuate, at first utilize paraffin that the silicon front is labelled on the microslide, attenuate silicon after utilizing microslide to attenuate provides necessary mechanical support, the attenuate silicon back side that utilizes heat-conducting glue will still post microslide then seals to ceramic substrate, under 80 ℃ of-100 ℃ of environment, fuse paraffin at last, remove microslide, finish the preparation of sensor, such preparation process can prepare substrate thickness in the whole process of 80 microns to 100 microns attenuate silicon and sensor package and scribing all the chip structure to fragility necessary mechanical support is provided
4. the ceramic substrate that utilization of the present invention has certain thermal conductivity seals to the thin film silicon chip back by heat-conducting glue; necessary mechanical support can be provided for the chip structure of fragility; and protect sensor to avoid the pollution of external environment, simultaneously for providing heat passage between attenuate silicon and the external environment.
Traditional CMOS integrated anemograph, aspect the heat conduction of reduction silicon-based substrate, a kind of method is to utilize wet corrosion technique to prepare heat insulation cavity at the silicon back side and heating element corresponding region, its shortcoming is that the thermoinduction film of preparing is too fragile, thermal stress is bigger to the influence of input, and can't realize the encapsulation of sensor.Another kind method is a preparation porous silicon thermofin below heating element, and so preparation technology and standard CMOS process are incompatible, and preparation technology's consistance of porous silicon is relatively poor, have improved the difficulty of rear end sensor signal conditioning.The sensor construction that the present invention proposes adopts the standard CMOS process preparation, prepare hot isolation channel and can reduce heat that the sensor heating element produces effectively because the thermal loss that heat-conduction effect causes makes most heats carry out the variation that heat interchange comes wind speed and direction in the perception external environment by ceramic substrate and air the structural design that the silicon substrate carries out attenuate; Prepare the sensitivity that very thin attenuate silicon substrate can improve sensor greatly, therefore can under lower power consumption, obtain bigger output signal.The form of this wafer level packaging is compared with the wind speed wind direction sensor of traditional single-chip package, greatly reduce the packaging cost of MEMS device on the one hand, guarantee the consistance of the deviation that sensor package causes on the other hand to a great extent, reduced the cost of sensor back end signal conditioning.
Embodiment
Embodiment 1
A kind of preparation method of the hot type wind speed wind direction sensor based on reduction process is as follows:
The first step, the preparation of silicon
Step 1 is at silicon 1 surface heat first thermal oxide layer 2 of growing;
Step 2, chemical vapor deposition silicon nitride layer 3 on first thermal oxide layer 2;
Step 3 utilizes the RIE technology that silicon 1 is carried out etching, definition active area 4;
Step 4, chemical vapor deposition second oxide layer 5;
Step 5 utilizes the CMP technology that silicon 1 is carried out polishing;
Step 6, wet etching is removed silicon nitride layer 3, and field oxide 6 is finished in preparation;
Step 7, phosphonium ion injects, preparation N trap 7;
Step 8, heat growth gate oxide 8;
Step 9, the boron ion injects, an end 10 of preparation heating element 9 and hot sensing temperature element 15;
Step 10, chemical vapor deposition the 3rd oxide layer, wherein first thermal oxide layer 2, second oxide layer 5 and the 3rd oxide layer are merged into oxide layer 11;
Step 11 utilizes dry etch process to prepare on the hot sensing temperature element 15 through hole 17 on the through hole 12 and heating element 9;
Step 12 is utilized sputtering technology preparation electricity to draw with another end 13 and heating element 9 electricity of aluminum pad 14 and hot sensing temperature element 15 and is drawn pad 18;
Step 13 utilizes dry etch process to prepare hot isolation channel 16 between heating element 9 and hot sensing temperature element 15;
Second step, attenuate and encapsulation
Step 1 is coated with paraffin layer 19 in the front of silicon 1;
Step 2 adheres to microslide 20 by paraffin layer 19 in the front of silicon 1 under 80 ℃ of environment temperatures;
Step 3, utilize reduction process to the substrate of silicon 1 carry out attenuate until substrate thickness be 80 microns to 100 micrometer ranges, obtain attenuate silicon 21;
Step 4 is coated with heat-conducting glue 22 at attenuate silicon 21 back sides, and sticks ceramic substrate 23, under 100 ℃ of environment temperatures heat-conducting glue is cured;
Step 5 is removed microslide 20 and paraffin layer 19 under 80 ℃ of environment temperatures;
In the 3rd step, the preparation of wind speed wind direction sensor is finished in scribing.
The present invention is the scheme of a kind of CMOS of realization integrated anemograph preparation and wafer level packaging.The side that sensor chip contacts with wind facies in the external environment is the upper surface of ceramic substrate 23, by setting up hot tie-in between heat-conducting glue 22 and the attenuate silicon 21, because stupalith has certain pyroconductivity, silicon substrate and the heat-conducting glue 22 of the heat that heating element 9 in the attenuate silicon 21 produces after by attenuate conducts to ceramic substrate 23, sets up the distribution in certain temperature field at the upper surface of ceramic substrate 23.This temperature field is symmetrical distribution around ceramic substrate 23 centers on ceramic substrate 23 under calm condition; Exist in external environment under the condition of certain wind speed, this symmetrical distribution is broken, and generates a temperature gradient field, and the direction of gradient direction and wind direction is consistent.4 hot sensing temperature elements 15 be symmetric configuration be distributed in heating element 9 on the attenuate silicon 21 around, between heating element 9 and hot sensing temperature element 15, be provided with hot isolation channel 16, be used to reduce the transverse heat transfer effect between them, increase the useful signal of sensor.The temperature field of ceramic substrate 23 upper surfaces can utilize the thermal conduction characteristic of heat-conducting glue 22 to pass to attenuate silicon 21, conducts to hot sensing temperature element 15 by silicon substrate again, and then measures the change of temperature field situation of ceramic substrate 23 upper surfaces.Output signal to 4 hot sensing temperature elements 15 is handled, and just can obtain the information of wind speed and direction in the external environment.
Traditional CMOS integrated anemograph, the form and the ceramic substrate that generally directly utilize flip chip bonding upside-down mounting or heat-conducting glue to attach are realized encapsulation.Because the thermal conductivity far of silicon is much larger than the thermal conductivity of pottery, therefore the heat overwhelming majority that heating element produces on the silicon of encapsulation back dissipates in heat conducting mode from silicon substrate, only have only a spot of heat to produce the thermal convection heat exchange by ceramic substrate and air, greatly reduce signal of sensor so on the one hand, improve the operating power of sensor on the other hand, reduced the usefulness of sensor.Based on this problem, forefathers propose at silicon substrate back side making cavity or make the heat conduction that one deck porous silicon is used to reduce silicon substrate under heating elements, so just the encapsulation of sensor or the consistance and the CMOS processing compatibility of technology have been proposed challenge.
Among the present invention, utilize CMOS technology to prepare sensor chip; Utilize the DRIE dry etch process at the hot isolation channel of the positive preparation of sensor chip, be used to increase the useful signal of sensor and reduce the interference that heat-conduction effect causes useful signal; The reduction process of utilization and CMOS process compatible carries out attenuate to the substrate of sensor chip, can lower greatly because the sensitivity of useless power consumption that heat conduction effectiveness causes and increase sensor; Utilize ceramic substrate sensor chip to be encapsulated by the sensor chip back side that heat-conducting glue seals to the attenuate.
Embodiment 2
A kind of hot type wind speed wind direction sensor based on reduction process, it is characterized in that, comprise attenuate silicon 21, the back side of described attenuate silicon 21 is connected with ceramic substrate 23 by heat-conducting glue 22, be provided with N trap 7 in the front of attenuate silicon 21, on N trap 7, be provided with oxide layer 11, be provided with 4 diffusion resistance heating elements 9 and 4 hot sensing temperature elements 15 at the middle part of N trap 7,4 hot sensing temperature elements 15 for the thermocouple temperature measurement element and be distributed in 4 diffusion resistance heating elements 9 around, be provided with electricity at the fringe region of oxide layer 11 and draw pad 14, the electricity that the electricity of 4 diffusion resistance heating elements 9 is drawn pad 18 and 4 hot sensing temperature elements 15 is drawn pad 13 and is drawn pad 14 by metal lead wire and electricity respectively and be connected, between 4 diffusion resistance heating elements 9 and 4 hot sensing temperature elements 15, be provided with hot isolation channel 16, described hot isolation channel 16 dark reaching in attenuate silicon 21 substrates.