The low temperature airtightness packaging method of a kind of wafer level micro machinery device or photoelectric device
Technical field
The present invention relates to the low temperature airtightness packaging method of a kind of wafer level micro machinery device or photoelectric device, specifically, be a kind of benzocyclobutene (BCB) material that utilizes at through wet etching or the semi-conducting material of dry etching or the air-tightness bonding that glass carries out low-temperature wafer-level, thereby realize the low-temperature wafer-level air-tight packaging of micro mechanical device and photoelectric device.Belong to micro mechanical device, photoelectric device and Micrometer-Nanometer Processing Technology field.
Background technology
Part MEMS (microelectromechanical systems) device very easily sustains damage in scribing and assembling process owing to comprise some moving parts on its structure; Materials such as the dust in the long simultaneously contact working environment, air-flow, steam, mechanical admixture also can influence the service life of device.The MEMS device of these specific uses (as resonant mode MEMS device, micro-acceleration gauge, little gyro, low-grade fever radiation gauge etc.), since the requirement of its physics operation principle, stable operation and low drift, strict especially air-tight packaging.Along with semiconductor technology to systematization, integrated development, the temperature for bonding in device fabrication processes has also proposed lower requirement.The encapsulation of wafer level has higher manufacturing benefit, and the yield rate height can reduce production costs better.One of important technology that so wafer level low temperature airtightness encapsulation technology is the MEMS area research always to be explored.
Present existing wafer level air-tightness bonding encapsulation technology mainly contains following four kinds:
(1) anode linkage (anodic bonding claims electrostatic bonding, silicon-glass bonding again): be with MEMS silicon wafer and the glass substrate method for sealing commonly used of sealing-in mutually.Usually with sending lux glass (Pyrex) to make glass substrate, because it and silicon have the close coefficient of expansion.During bonding, silicon chip places on the anode heating plate, and glass is connected with negative electrode.Bonding temperature 300 ~ 450 ℃ of (representative temperature is 400 ℃), voltages are 300 ~ 1000V, pressure 100 ~ 300kPa.The glass heavy doping sodium that anode linkage is used, therefore usually incompatible with the MEMS sensor of integrated CMOS-IC.
Anode linkage is the same with the glass bonding to be nonconducting, airtight, heat-staple and chemically stable, and the mechanical strength height.During with silicon chip and Pyrex glass anode linkage, because the coefficient of expansion that is close, the thermal stress that sealing-in caused is smaller.But also occur the cracking problem in the actual production often, show as: come off after (1) silicon chip and the sheet glass sealing-in; (2) sheet glass bursts.Causing the reason that comes off is that material polishing flatness is not enough, cleans unclean before the sealing-in.The reason of cracking is original crack and crack splitting, and causes stress to concentrate.Thermal cycle during sealing-in causes the propagation of crackle and cracking again.Owing to need very smooth plane to obtain high-quality bonding, limited the application of anode linkage.
(2) silicon-Si direct bonding (silicon fusion bonding): silicon fusion bonding does not need the intermediate layer.Bonding process: need carry out hydrophilic cleaning to the silicon wafer that has polished, carry out room temperature or low temperature then and fit, at high temperature at last (up to 1000 ℃) carry out the bonding of several hrs.Long time treatment under high temperature like this makes this technology can not be applied to contain the silicon wafer of CMOS (CMOS) circuit.Also have the low-temperature-direct-bonding technology of silicon-silicon in addition, but high requirement is arranged for the planarization of silicon chip surface.
(3) melten glass sealing-in (Glass frit bonding): in the frit bonding, lead borate or " scolder " glass provide with powder type, are mixed into the body of paste that can carry out serigraphy then.When the glass alkalinity that uses lower, when fusing point is also lower, with the CMOS technical compatibility.Before actual bond, undertaken after the degasification, can form vacuum chamber and obtain good level Hermetic Package by heat treatment method.For example, in the pressure sensor (absolute pressure), by the bonding formation vacuum chamber of silicon and silicon substrate.Being bonded under the vacuum environment and carrying out, is one deck glass sealing material between silicon and the silicon.
(4) scolder bonding: the scolder bonding techniques has been widely used in the microelectronics Packaging field.According to the difference of material, can be subdivided into two kinds of eutectic bonding (hard solder bonding) and slicken solder bondings again.Hard solder is defined on the phasor corresponding to solder compositions, the scolder of its liquidus curve between 315 ℃-425 ℃.Au/Si, Au/Sn are the eutectic bonding materials of using always.But gold may cause heavy metal pollution to cmos circuit, and this is undesirable.The gold silicon eutectic bonding also has very big defective: be difficult to obtain complete large tracts of land bonding, and the existence of natural oxide also can stop the carrying out of bonding.Slicken solder is defined in the phasor corresponding to solder compositions, and its liquidus curve is lower than 315 ℃ brazing metal.The kind of slicken solder is a lot, as Pb/Sn, Pb/In, In/Sn scolder etc.Can use Pb/Sn and Ni/Au not to have scaling powder welding (250 ℃), promptly in vacuum drying oven and under the effect of infra-red radiation, form annular seal space.Two kinds of scolders have pluses and minuses separately, and promptly hard solder bonding temperature height can at high temperature use, the intensity height; But residual thermal stress is big after the cooling.The slicken solder bonding temperature is low, and fatigue easily takes place non-refractory, and intensity is lower slightly; But cooling back residual stress is less, can the absorption portion thermal stress.
Benzocyclobutene (benzo-cyclo-butene, BCB) material is since the commercialization nineties, it is a kind of advanced person's electronic package material, be generally used for rerouting of integrated circuit, now just be used for the technique for sticking (compatible mutually with IC technology) of MEMS device gradually, BCB has low dielectric constant, the calorifics that is as good as, chemistry and mechanical stability, when being used for the wafer level bonding, advantage is as follows: the leveling ability of height; Solidification temperature is lower, does not need catalyst in the solidification process, does not have byproduct, and shrinkage factor can be ignored in the solidification process; Good adhesive property; BCB can also carry out photoetching or etching, can carry out PASTE SPECIAL; The BCB that solidifies can be used for optics to visible transparent; The erosion that the BCB that solidifies can resist multiple acid, alkali and solvent is fit to the application of fluid aspect; Water absorption rate is very low, and is favourable to level Hermetic Package; Dielectric constant is lower, and is favourable to wafer level packaging such as RF-MEMS; Do not influence the lead-in wire of device and circuit in the encapsulation process.BCB has two types: Photosensitive (negative glue behavior) and non-photosensitivity type (claiming the dry etching type again).The monomer of BCB is a liquid, and what be transformed into solid-state dependence by liquid state is the mechanism that heating produce to be solidified.The monomer of BCB and mechanism of polymerization are as shown in Figure 1.The BCB monomer is by a series of diene synthetic reaction, and final formation is polymerization and crosslinked BCB solid polymer highly.
For this reason, the present invention attempts special physics and the chemical property in conjunction with benzocyclobutene (BCB) material, realizes the low-temperature wafer-level air-tightness bonding encapsulation of micro mechanical device under 250 ℃ of situations or photoelectric device.
Summary of the invention:
The object of the present invention is to provide the low temperature airtightness packaging method of a kind of wafer level micro machinery device or photoelectric device.It mainly utilizes the specific physical of benzocyclobutene (BCB) material, wet etching or the dry etching technology that chemical property is carried out low-temperature wafer-level material bonding and semi-conducting material, realizes the low-temperature wafer-level air-tightness bonding encapsulation of micro mechanical device, photoelectric device under 250 ℃ of situations.
The objective of the invention is to reach by the following method:
(1) at first finishes the making of micro mechanical device and photoelectric device by the MEMS fine process.
(2) on semi-conducting material, produce seal chamber by method such as burn into gluing mask openings, corrosion in gluing mask etching or oxidation, protection, the BOE corrosive liquid, the selection of material is so long as can graphically produce the material of cavity and get final product, as silicon, GaAs, indium phosphide, gallium nitride, indium nitride, diamond, aluminium nitride or aluminium oxide etc.; Described BOE corrosive liquid is NH
4The mixed liquor of F and HF is a kind of silicon dioxide etching liquid of normal businessization.
(3) at the bonding surface spin coating of making cavity or spraying BCB glue (available from DOW chemicalcompany), concrete coating technique parameter is as follows: 1. earlier at bonding face spin coating tackifier AP3000 (available from DOW chemical company), tackifier can make the disk adhesion strength improve one times nearly.Select the 800 rev/mins of spin coatings 20 seconds of uncapping for use, close and cover 2500 rev/mins of spin coatings 20 seconds.2. spin coating BCB glue on tackifier.Parameter is: 1000-5000 rev/min of spin coating 20-30 second, bondline thickness 5.5 μ m ~ 2.5 μ m.3. remove the BCB glue of silicon chip edge, avoid polluting the bonding machine, can by before the gluing at the edge of glass or structure pasted with high temperature-resistant adhesive tape, take off adhesive tape behind the gluing, thereby overflow when preventing BCB glue bonding and pollute the bonding machine.4. heat dish oven dry: purpose is that organic solvent is vapored away, to obtain not have the BCB glue bond layer of hole.Select for use concrete coating technique parameter as follows during element manufacturing: 1., to select the 800 rev/mins of spin coatings 20 seconds of uncapping for use, close and cover 2500 rev/mins of spin coatings 20 seconds at bonding face spin coating tackifier AP3000.2. spin coating BCB glue on tackifier selects to uncap 800 rev/mins of spin coatings 20 seconds in the experiment, closes and covers 1500 rev/mins of spin coatings 20 seconds, and bondline thickness is approximately 4-5 μ m.
(4) carry out the wafer level low-temperature bonding in the bonding machine, the major parameter in the bonding process has: bonding temperature and heating curve; The bonding on-load pressure; Vacuum.The solidification temperature of BCB is between 200-300 ℃, and standard technology is 250 ℃ of insulation 1h; When temperature is lower than 250 ℃, need the insulation several hrs; And temperature is then solidified rapidly when being higher than 250 ℃.Keep certain vacuum or needed gaseous environment simultaneously, and load certain bonding pressure (1 ~ 3 * 10
5Pa), thus the wafer level of finishing gas box make.Select for use concrete technological parameter as follows during element manufacturing, 1. temperature: 100 ℃ of insulation 10min, 150 ℃ of insulation 10min, 200 ℃ of insulation 10min, 250 ℃ of insulation 1h, coolings naturally; 2. silicon chip is applied (1-3) * 10
5The bonding on-load pressure of Pa; 3. vacuum condition (10
-1Pa).Compare with existing method, the method has following characteristics:
(1) technological temperature is relatively low, can effectively reduce the damage or the damage of the device that causes owing to heating up, and lower technological temperature effectively raises the processing compatibility (with the CMOS process compatible) of this method simultaneously, is beneficial to the residual thermal stress that reduces device.
(2) do not need added electric field, only the BCB material need be heated up to solidify and promptly finish the bonding encapsulation.
(3) this method belongs to the organic gel adhesive bond, so can the disk of various materials be bondd.
(4) this method does not need disk surfaces is carried out specially treated, can tolerate that the surface exists structure or particle, and can will give prominence to structure (as aluminum steel) or wherein particle studded.
(5) this method be a kind of relatively simply, reliably, technology cheaply.
(6) do not need catalyst in this method solidification process, do not have byproduct, shrinkage factor can be ignored in the BCB material cured process, has good adhesive property.
(7) the BCB material can also carry out photoetching, etching and serigraphy, so can carry out graphical PASTE SPECIAL bonding encapsulation.
(8) the BCB material after the curing can be used for optics to visible transparent.
(9) erosion that can resist multiple acid, alkali and solvent of the BCB material after solidifying, the application of suitable fluid aspect.
(10) the BCB material water absorption rate after the curing is very low, and is favourable to level Hermetic Package.
(11) the BCB material dielectric constant after the curing is lower, and is favourable to wafer level packaging such as RF-MEMS.
By BCB bonding package experiment, verified that using air-tightness, shear strength, the thermal cycle reliability that the BCB material carries out micro mechanical device, photoelectric device encapsulation satisfies the encapsulation requirement of practical product fully, as Fig. 2, shown in 3,4.Air tightness test is finished by Varian 947 Helium leak detectors, and test result shows that BCB glue seal chamber air-tightness reaches 2.1 ~ 5.9 * 10
-4Pa cm
3/ s He is better than one of military standard more than the order of magnitude.Shear strength is finished by Dage Series 4000 bond strength test machines, and test result all more than 4.65MPa, has reached the encapsulation standard of microelectronic component fully.(numbering: 03-523) finish, test result also reaches the practical standard of electronic device to the thermal shock experimental machine of thermal cycle reliability testing by KSONInstrument Technology company fully.
Use this method to make the MEMS device of some specific use, as: resonant mode MEMS device, micro-acceleration gauge, little gyro, low-grade fever radiation gauge etc., can effectively reduce the damping of device, improve the quality factor (Q value) of device system, thereby improve the sensitivity of senser element.In view of the above-mentioned advantage of this method, this method is effective low-temperature wafer-level airtight packaging method of micro mechanical device, low-light electrical part, and can produce in batches, has a wide range of applications.
Description of drawings:
Fig. 1: BCB material monomer structure and Principles of Polymerization
Fig. 2: 250 ℃ of air-tightness contrasts (each two groups of data) of adopting BCB material bonding and 300 ℃ of anode linkage samples
Ordinate: the logarithm value of leak detection test data
Abscissa: the seal chamber perforate length of side
Fig. 3: 250 ℃ of shear strength contrasts of adopting BCB material bonding and 300 ℃ of anode linkage samples
Ordinate: shear strength test data
Abscissa: the seal chamber perforate length of side
Fig. 4: the air-tightness of BCB material bonding sample is adopted in temperature shock circulation back
Ordinate: the logarithm value of leak detection test data
Abscissa: the seal chamber perforate length of side
Fig. 5: gas box cavity manufacture craft flow process
(a) silicon chip
(b) silicon chip after the two-sided thermal oxide
(c) silicon chip behind the top layer gluing
(d) photoetching forms the silicon chip of corrosion top layer silicon dioxide mask
(e) top layer silicon dioxide goes out the silicon chip of window by the BOE solution corrosion
(f) remove the silicon chip with top layer silicon dioxide mask of top layer photoresist mask
(g1) the micro-mechanical movable component packages cover plate silicon chip after the KOH corrosion perforate
(g2) the low-light electrical part encapsulation cover plate silicon chip after the KOH corrosion perforate
(h1) the micro-mechanical movable component packages cover plate silicon chip about BOE removes behind the silica
(h2) the low-light electrical part encapsulation cover plate silicon chip about BOE removes behind the silica
(i) the low-light electrical part encapsulation cover plate structure behind the anode linkage
(j1) the micro-mechanical movable component packages cover plate silicon chip behind the spin coating BCB glue
(j2) the low-light electrical part encapsulation cover plate structure behind the spin coating BCB glue
(k1) the micro-mechanical movable parts device schematic diagram by the BCB material package
(k2) the low-light electrical part schematic diagram by the BCB material package
Fig. 6: BCB material whirl coating thickness technological parameter curve
Ordinate: bondline thickness
Abscissa: gluing rotating speed
Fig. 7: the BCB material standard is solidified heating curve
Ordinate: temperature
Abscissa: time
Among the figure: 1: semi-conductor silicon chip
2: top layer mask silica
3: bottom layer silicon dioxide
4: photoresist
The 5:Pyrex7740 sheet glass
6: benzocyclobutene (BCB)
7: mechanical movable member (comprising micro-resonance type movable member, micro-acceleration gauge movable member, little gyro movable member, micro bolometer movable member)
8: low-light electricity structure member
The specific embodiment:
Illustrate that below by embodiment part of the present invention specifically uses, semiconductor medium material selection silicon chip, but application of the present invention is not limited only to silicon materials, also is not limited only to embodiment.This method is made the seal chamber that seal chamber, dry etching seal chamber and additive method produce for wet etching and all is suitable for, below embodiment be example only all with the wet etching preparation method because this kind method cost is minimum relatively.
Embodiment 1: resonant mode MEMS device (resonating device that comprises resonance beam type and other modes) is carried out the low-temperature wafer-level air-tight packaging, and concrete technological process as shown in Figure 5.Implementation method is as follows:
(1) selects semi-conducting material such as silicon chip 1 (the two throwing silicon chips of common N type (100), thickness 420 ± 15 μ m, resistivity 3-8 (Ω cm)), carry out oxidation, obtain top layer mask silica 2 and bottom layer silicon dioxide 3, as Fig. 5 (b).
(2) resist coating 4 (adopting the trade mark 1912 type photoresists of Shipley company in this experiment), and graphical exposure, development obtain the structure as Fig. 5 (d), form the mask to top layer silicon dioxide 2 perforates.
(3) corrosion top layer mask silica 2 in the BOE corrosive liquid for it opens corrosion window, removes photoresist 4, subsequently as Fig. 5 (f).
(4) in KOH or other anisotropic silicons or isotropic etch liquid,, obtain cavity body structure as Fig. 5 (g1) by the window corrosion of silicon.
(5) in the BOE corrosive liquid, remove top layer mask silica 2 and protective underlayer silica 3 fully, obtain protection cavity body structure as Fig. 5 (h1).
(6) as top layer face spin coating of Fig. 5 (h1) cavity body structure or spraying BCB glue 6, concrete coating technique parameter is as follows: 1. at bonding face spin coating tackifier AP3000, select the 800 rev/mins of spin coatings 20 seconds of uncapping in the experiment for use, close and cover 2500 rev/mins of spin coatings 20 seconds.2. spin coating BCB glue on tackifier selects to uncap 800 rev/mins of spin coatings 20 seconds in the experiment, closes and covers 1500 rev/mins of spin coatings 20 seconds, and bondline thickness is approximately 4-5 μ m, and gluing thickness as shown in Figure 6.3. remove the BCB glue of silicon chip edge, avoid polluting the bonding machine.4. heat dish oven dry.Obtain structure as Fig. 5 (j1).
(7) at last by bonding machine (for example Karl Suss SB6 type bonding machine), carry out the low-temperature wafer-level air-tightness bonding encapsulation of Fig. 5 (j1) cavity body structure and resonance type micromechanical movable member 7, the technological parameter of selecting in the experiment: 1. temperature: 100 ℃ of insulation 10min, 150 ℃ of insulation 10min, 200 ℃ of insulation 10min, 250 ℃ of insulation 1h, cooling naturally, as shown in Figure 7; 2. silicon chip is applied 3 * 10
5The bonding on-load pressure of Pa; 3. vacuum condition (10
-1Pa).Finally obtain encapsulated device as Fig. 5 (k1).
Embodiment 2: micro-acceleration gauge device (comprising journey high-precision accelerometer, high-range acceleration meter, the micro-acceleration gauge of vertical direction motion and the micro-acceleration gauge of horizontal slip in a small amount) is carried out the low-temperature wafer-level air-tight packaging, specific implementation method is with reference to step among the embodiment 1: (1) ~ (7), the mechanical movable member that just the cavity interior resonance declined replaces with micro-acceleration gauge movable member 7.
Embodiment 3: little gyro (comprising little gyroes such as micro-mechanical capacitance type, pressure resistance type) is carried out the low-temperature wafer-level air-tight packaging, specific implementation method is with reference to step among the embodiment 1: (1) ~ (7), the mechanical movable member that just the cavity interior resonance declined replaces with little gyro movable member 7.
Embodiment 4: low-grade fever radiation gauge device is carried out the low-temperature wafer-level air-tight packaging, specific implementation method is with reference to step among the embodiment 1: (1) ~ (7), movable member or light that the mechanical movable member that just the cavity interior resonance declined replaces with low-grade fever radiation gauge device detect movable member 7.
Embodiment 5: photoelectric device is carried out the low-temperature wafer-level air-tight packaging, and specific implementation method is as follows, and step (1) ~ (3) are with reference to step among the embodiment 1: (1) ~ (3);
(4) in KOH or other anisotropic silicons or isotropic etch liquid,, obtain cavity body structure as Fig. 5 (g2) by the window corrosion of silicon.
(5) in the BOE corrosive liquid, remove top layer mask silica 2 and protective underlayer silica 3 fully, obtain protection cavity body structure as Fig. 5 (h2).
(6) (380 ℃ of temperature, voltage ± 800V) are carried out the anode linkage of structure 5 (h2) and Pyrex7740 glass 5, obtain as Fig. 5 (i) under arm's length standard technology.
(7) as top layer face spin coating of Fig. 5 (i) cavity body structure or spraying BCB glue 6, concrete coating technique parameter obtains the structure as Fig. 5 (j2) with reference to step (6) among the embodiment 1.
(8) at last by the bonding machine, carry out the low-temperature wafer-level air-tightness bonding encapsulation of Fig. 5 (j2) cavity body structure and photoelectric device 8, the technological parameter of selecting in the experiment finally obtains the encapsulated device as Fig. 5 (k2) with reference to step (7) among the embodiment 1.