CN100563101C - Acoustic resonator and filter - Google Patents
Acoustic resonator and filter Download PDFInfo
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- CN100563101C CN100563101C CNB2006800237896A CN200680023789A CN100563101C CN 100563101 C CN100563101 C CN 100563101C CN B2006800237896 A CNB2006800237896 A CN B2006800237896A CN 200680023789 A CN200680023789 A CN 200680023789A CN 100563101 C CN100563101 C CN 100563101C
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Abstract
Between baseplate part (40) and the 2nd support (20), be provided with the 1st support (30).The 1st support (30) is by the film that formed by the material with acoustic impedance higher than piezoelectrics (11) and baseplate part (40) or the formations such as film that formed than piezoelectrics (11) and the little material of baseplate part (40) by the Q value.Insertion by the 1st support (30), from most be reflected (arrow (a)) of the 2nd support (20), and prevent to be returned (arrow (b)) by the bottom reflection of baseplate part (40) to the direction of vibration section (10) to the vibration that baseplate part (40) transmits from the 2nd support (20) towards the vibration of baseplate part (40).
Description
Technical field
The present invention relates to acoustic resonator and filter, relate in particular to and to suppress to look genuine the acoustic resonator of generation of vibration and the filter that uses this acoustic resonator.
Background technology
Be built in part requirement miniaturization and lightweight in the electronic equipments such as portable set.For example, the filter that uses in portable set requires miniaturization, and requirement can be carried out the fine adjustment of frequency characteristic.As satisfying one of filter of these requirements, the known filter (with reference to patent documentation 1～3) that the use acoustic resonator is arranged.
Below, with reference to Figure 13 A～Figure 13 D, the acoustic resonator in the past of patent documentation 1 record is described.
Figure 13 A is a profile of representing the essential structure of acoustic resonator in the past.Acoustic resonator in the past is the structure by upper electrode 102 and lower electrode 103 clamping piezoelectrics 101.This acoustic resonator in the past is positioned on the substrate 105 that is formed with cavity 104 and uses.Can utilize the microfabrication method to carry out local etching, form cavity 104 from the back side of substrate 105.This acoustic resonator in the past applies electric field by upper electrode 102 and lower electrode 103 on thickness direction, produce the vibration of thickness direction.Then, utilize the thickness compressional vibration of infinite slab to carry out the action specification of acoustic resonator in the past.
Figure 13 B is the schematic stereogram that is used for illustrating the action of acoustic resonator in the past.In the acoustic resonator in the past,, be mechanical energy with transformation of electrical energy then by piezoelectrics 101 if between upper electrode 102 and lower electrode 103, apply electric field.The mechanical oscillation that are energized are thickness direction stretching vibrations, stretch on the direction identical with electric field.Generally, acoustic resonator in the past utilizes the synchronous vibration of the thickness direction of piezoelectrics 101, equals the resonance action of the frequency of half-wavelength with thickness.Cavity 104 shown in Figure 13 A utilizes in order to ensure the thickness compressional vibration of these piezoelectrics 101.
The equivalent circuit of this acoustic resonator in the past is the equivalent circuit that has resonance series and parallel resonance simultaneously shown in Figure 13 D.This equivalence circuit constitutes by the resonance series portion that is made of capacitor C1, inductor L1 and resistance R 1 with capacitor C0 that resonance series portion is connected in parallel.By this circuit structure, the admittance frequency characteristic of equivalent circuit is shown in Figure 13 C, and admittance becomes maximum under resonance frequency fr, and admittance becomes minimum under antiresonant frequency fa.Here, resonance frequency fr and antiresonant frequency fa have following relation.
fr＝1/{2π√(L1×C1)}
fa＝fr√(1+C1/C0)
Have in use under the situation of acoustic resonator in the past as filter of such admittance frequency characteristic, owing to utilize the synchronous vibration of piezoelectrics 101, so can realize small-sized and low-loss filter.
Here, influencing the piezoelectric membrane of acoustic resonator characteristic significantly, high-quality piezoelectric membrane is used in expectation.Therefore, the various manufacture methods (with reference to patent documentation 4) that are used for realizing high-quality piezoelectric membrane have been proposed.Figure 14 is the figure that is used for illustrating the order of the manufacture method of disclosed acoustic resonator in the past in patent documentation 4.
At first, etching substrates 111 forms the depression (Figure 14 (a)) as cavity 112 then on substrate 111.Then, on whole of substrate 111, form alternative corrosion layer 115 (Figure 14 (b)).Then, carry out planarization so that the surface of substrate 111 becomes double altitudes (Figure 14 (c)) with the surface of alternative corrosion layer 115.Then, distinguish stacked lower electrode 121, piezoelectric membrane 122 and upper electrode 123 at an upper portion thereof, form vibration section 120 (Figure 14 (d)).At last, remove alternative corrosion layer 115 by etching cavity 112 is set, acoustic resonator is finished (Figure 14 (c)).In this patent documentation 4, in order to improve the crystallinity of piezoelectric membrane, by thickness and the flatness of regulation as the molybdenum (Mo) of lower electrode 121, the high-quality piezoelectric membrane when having realized using sputtering method.
Patent documentation 1: Japanese kokai publication sho 60-68711 communique
Patent documentation 2: TOHKEMY 2003-158309 communique
Patent documentation 3: No. 5587620 specification of United States Patent (USP)
Patent documentation 4: No. 2800905 communique of Japan's special permission
Patent documentation 5: No. 6060818 specification of United States Patent (USP)
Above-mentioned acoustic resonator in the past is that a part is fixed on the structure on the substrate 105, so in any case the part of the vibration that the vibration section produced also can be delivered to substrate 105.Be delivered to the unnecessary vibration of this substrate 105, turn back to vibration plate side, so bring influence (the arrow e of Figure 15) can for the primary resonance vibration of vibration section at the bottom reflection of substrate 105.
This influence produces the vibration of looking genuine between the resonance frequency of vibration section and antiresonant frequency shown in Figure 16 A.As Figure 16 B, be connected in parallel and form filter if will have such acoustic resonator that looks genuine vibration, then shown in Figure 16 C, undesirable characteristic of passing through occurs in the part of passband.Should cause communication quality to reduce by characteristic.
In addition, according to manufacture method in the past, the crystallinity of piezoelectric membrane is subjected to the substrate considerable influence.Therefore, for material, require high crystalline and high flatness as substrate.Thus, complicated if vibration section that is made of piezoelectric membrane and upper/lower electrode and the structure between the substrate become, then crystallinity and the flatness to the basilar memebrane of piezoelectric membrane exerts an influence.Therefore,, before the film forming of piezoelectric membrane, need to carry out the technology of flatening process etc., the technology complicated problems that becomes is arranged for example for flatness.
In addition, in order to realize high-quality piezoelectric membrane, known film forming with the use sputtering method is compared, and uses the film forming of organic metal vapour phase epitaxy flop-in method (mocvd method) better.But, in this mocvd method, need the technology under 1000 ℃ of left and right sides high temperature.Therefore, under the situation of as the manufacture method of above-mentioned acoustic resonator in the past, carrying out film forming and stacked manufacture method successively, there is the problem that has limited electrode material etc. for the high-temperature technology that bears mocvd method from the bottom.Problem about this high-temperature technology, though can consider not to carry out successively the manufacture method of film forming and stacked other, for example become the manufacture method of membrane electrode etc. after with the piezoelectric membrane film forming from the substrate inner face, also not be implemented in the practical effective manufacture method that from the bottom.
Summary of the invention
Therefore, the purpose of this invention is to provide and a kind ofly can prevent the unnecessary vibration of returning and the acoustic resonator and the filter of the generation of the vibration that suppresses to look genuine at the bottom reflection of substrate.
In addition, another object of the present invention provides a kind of manufacture method of acoustic resonator, the technology of utilizing baseplate-laminating is in the film forming of laggard column electrode of film forming of piezoelectric membrane etc., even the structure of support is complicated shape, also can make the acoustic resonator that has used the higher piezoelectric membrane of crystal type.
The present invention relates to acoustic resonator with the assigned frequency vibration.And to achieve these goals, acoustic resonator of the present invention possesses: substrate; The 1st support is located on the substrate; The 2nd support is located on the 1st support; The vibration section is located on the 2nd support, upper electrode that comprise piezoelectrics at least, is provided with at the upper surface of piezoelectrics and the lower electrode that is provided with at the lower surface of piezoelectrics; The 1st support is by having than piezoelectricity height, and the material of the acoustic impedance higher than substrate constitutes.
Preferably, the 1st support is made of the material with acoustic impedance higher than substrate as eutectic crystallization of Jin Yuxi etc.In addition, be provided with at upside under the situation of the 2nd support, with respect to the wavelength X of the resonance frequency that is encouraged by the vibration section, the thickness of the 1st support is preferably λ/4.On the other hand, be provided with at upside under the situation of sound reflector portion, with respect to the wavelength X of the resonance frequency that is encouraged by the vibration section, the thickness of the 1st support is preferably beyond λ/4.
Above-mentioned acoustic resonator of the present invention is individually as filter performance function, but so long as any or combination and trapezoidal with being connected to more than two, just can realize the filter of various frequency characteristics.In addition, above-mentioned filter can use in communication equipment with switched input signal and the switch of exporting etc.
In addition, the present invention relates to the manufacture method of acoustic resonator.And the manufacture method of acoustic resonator of the present invention realizes above-mentioned purpose by carrying out following processing successively.
On alternative corrosion substrate, make the piezoelectric membrane film forming.Stacked the 1st electrode layer on piezoelectric membrane.With the 1st electrode layer composition, form the lower electrode of acoustic resonator.The stacked the 1st substitutes corrosion layer on piezoelectric membrane and lower electrode.Substitute the corrosion layer composition with the 1st, be formed in the alternative corrosion portion of back of removing as the cavity performance function of acoustic resonator.Substituting the maintenance layer that is used for keeping piezoelectric thin film resonator on corrosion portion, lower electrode and the piezoelectric membrane by film forming formation.At the surperficial laminated semiconductor substrate that keeps layer.After the operation of fitting, will substitute the corrosion substrate and peel off from semiconductor substrate.Stacked the 2nd electrode layer on the piezoelectric membrane that after peeling off, exposes.With the 2nd electrode layer composition, the upper electrode of acoustic resonator is shaped.To substitute corrosion portion removes and forms the cavity.
Keep the surface of layer also can before the operation of laminated semiconductor substrate, carry out planarization.In addition, keep the planarization of laminar surface to be preferably, surface roughness is below the 1000ARMS.
In this bonding process, both can also can utilize eutectic to engage and fit keeping layer and semiconductor substrate to fit by adhesive linkage.The preferred silicide that uses molybdenum or tungsten in substituting corrosion layer.In addition, in the operation of film forming piezoelectric membrane, also can on alternative corrosion substrate, substitute corrosion layer and make the piezoelectric membrane film forming across the 2nd.Substitute preferred gallium nitride or the molybdenum of using in the corrosion layer the 2nd.
In addition, the manufacture method of acoustic resonator of the present invention also can realize above-mentioned purpose by carrying out following processing successively.
On alternative corrosion substrate, make the piezoelectric membrane film forming.Stacked the 1st electrode layer on piezoelectric membrane.With the 1st electrode layer composition, form the lower electrode of acoustic resonator.On lower electrode and piezoelectric membrane, will be used for keeping the maintenance layer film forming of piezoelectric thin film resonator.Keeping forming reflector layer on the layer.Laminated semiconductor substrate on reflector layer.After the operation of fitting, will substitute the corrosion substrate and peel off from semiconductor substrate.Stacked the 2nd electrode layer on the piezoelectric membrane that after peeling off, exposes.With the 2nd electrode layer composition, the upper electrode of acoustic resonator is shaped.
Keep the surface of layer also can before the operation of laminated semiconductor substrate, carry out planarization.In addition, keep the planarization on the surface of layer to be preferably, surface roughness is below the 1000ARMS.
In this bonding process, both reflector layer and semiconductor substrate can be fitted by adhesive linkage, also can utilize eutectic to engage and fit.In addition, in the operation of film forming piezoelectric membrane, also can substitute on the corrosion substrate across alternative corrosion layer the piezoelectric membrane film forming.In addition, in the operation of film forming piezoelectric membrane, also can substitute on the corrosion substrate across alternative corrosion layer the piezoelectric membrane film forming.Preferred gallium nitride or the molybdenum of using in substituting corrosion layer.
According to the acoustic resonator of the invention described above, can prevent at the bottom reflection of baseplate part and turn back to the unnecessary generation of vibration of vibration plate side.Thus, can access the good admittance frequency characteristic of the vibration of between the resonance frequency of vibration section and antiresonant frequency, not looking genuine.
In addition, according to the invention described above, owing to utilize the baseplate-laminating technology, so can use single crystallization base plate as basal substrate during the film forming of the piezoelectric membrane that influences significantly in characteristic to acoustic resonator, perhaps can use the high-temperature technology of mocvd method etc., so can access the higher piezoelectric membrane of crystallinity.In addition,, also after the film forming of piezoelectric membrane, carry out, so there is not crystalline influence such as the crystallinity, flatness of support etc. piezoelectric membrane in the formation of cavity and the formation of support.And then, owing in the formation of cavity, use to substitute corrosion layer, behind strippable substrate, will substitute corrosion layer and remove by etching, so the barrier film of lifting from vibration section in the operation at laser can not sustain damage, can improve rate of finished products.
In addition, the present invention relates to acoustic resonator with assigned frequency vibration.And to achieve these goals, acoustic resonator of the present invention possesses: substrate; Support is located on the substrate; Sound reflector portion is located on the support, alternately is laminated with low impedance layers and high impedance layer; The vibration section is located in the sound reflector portion, upper electrode that comprise piezoelectrics at least, is provided with at the upper surface of piezoelectrics and the lower electrode that is provided with at the lower surface of piezoelectrics; Support is made of the material with acoustic impedance higher than substrate; Make gold form support with the tin eutectic crystallization.
Description of drawings
Fig. 1 is the section of structure of the acoustic resonator that relates to of the 1st execution mode of the present invention.
Fig. 2 is another section of structure of the acoustic resonator that relates to of the 1st execution mode of the present invention.
Fig. 3 is another section of structure of the acoustic resonator that relates to of the 1st execution mode of the present invention.
Fig. 4 is another section of structure of the acoustic resonator that relates to of the 1st execution mode of the present invention.
Fig. 5 is the section of structure of the acoustic resonator that relates to of the 2nd execution mode of the present invention.
Fig. 6 A is the figure of the embodiment of the expression filter that uses acoustic resonator of the present invention.
Fig. 6 B is the figure of another embodiment of the expression filter that uses acoustic resonator of the present invention.
Fig. 7 is the figure of the another embodiment of the expression filter that uses acoustic resonator of the present invention.
Fig. 8 represents to use the figure of embodiment of the device of acoustic resonator of the present invention.
Fig. 9 A is to use the figure of the acoustic resonator that the manufacture method of the 1st example makes.
Fig. 9 B is the section of structure of the acoustic resonator of Fig. 9 A.
Figure 10 A is the process chart that is used for illustrating the manufacture method of the 1st example.
Figure 10 B is the process chart that is used for illustrating the manufacture method of the 1st example.
Figure 10 C is the process chart that is used for illustrating the manufacture method of the 1st example.
Figure 11 is to use the knot of acoustic resonator of the manufacture method manufacturing of the 2nd example to make profile.
Figure 12 A is the process chart that is used for illustrating the manufacture method of the 2nd example.
Figure 12 B is the process chart that is used for illustrating the manufacture method of the 2nd example.
Figure 12 C is the process chart that is used for illustrating the manufacture method of the 2nd example.
Figure 13 A is the figure that is used for illustrating acoustic resonator in the past.
Figure 13 B is the figure that is used for illustrating acoustic resonator in the past.
Figure 13 C is the figure that is used for illustrating acoustic resonator in the past.
Figure 13 D is the figure that is used for illustrating acoustic resonator in the past.
Figure 14 is the figure that the manufacture method of acoustic resonator in the past is described.
Figure 15 is the figure that is used for illustrating the problem that produces in acoustic resonator in the past.
Figure 16 A is the figure that is used for illustrating the problem that produces in acoustic resonator in the past.
Figure 16 B is the figure that is used for illustrating the problem that produces in acoustic resonator in the past.
Figure 16 C is the figure that is used for illustrating the problem that produces in acoustic resonator in the past.
Reference numeral
10 vibration sections
11,101 piezoelectrics
12,102 upper electrodes
13,103 lower electrodes
20,30 supports
21,104 cavitys
40,105 substrates
50 sound reflector portions
51 low impedance layers
52 high impedance layer
61,62,71 piezoelectric resonators
81,82 antennas
84 filters
91,92 substitute corrosion layer
Embodiment
[the 1st execution mode]
Fig. 1 is the figure of the structural profile of the acoustic resonator that relates to of the 1st execution mode of the present invention.In Fig. 1, the acoustic resonator that the 1st execution mode relates to comprises baseplate part 40, be located at the 1st support 30 on the baseplate part 40, be located at the 2nd support 20 on the 1st support 30 and be located at vibration section 10 on the 2nd support 20.The 2nd support 20 has the cavity 21 of the shape that connects the 2nd support 20 in order to ensure the compressional vibration of vibration section 10.The 2nd support 20 is to be used for vibration section 10 is bearing in supporting course on the baseplate part 40.Vibration section 10 comprises the piezoelectrics 11 that form with aluminium nitride piezoelectrics such as (AlN), be located at the upper electrode 12 of piezoelectrics 11 upper surfaces and be located at the lower electrode 13 of piezoelectrics 11 lower surfaces.Upper electrode 12 and lower electrode 13 are for example formed by molybdenum (Mo).This vibration section 10 make lower electrode 13 for downside be positioned on the 2nd support 20.
The 1st support 30 is to be used for the interlock of the 2nd support 20 vibration section 10 being bearing in supporting course on the baseplate part 40, and also is damping layer.The 1st support 30 has the film that the material of the acoustic impedance higher than piezoelectrics 11 and substrate 40 forms by utilization or utilizes film that the Q value forms than piezoelectrics 11 and baseplate part 40 little materials etc. to constitute.The material of the 1st support 30 both can be that insulating material also can be an electric conducting material.Under the situation of using electric conducting material, also the 1st support 30 can be used as wiring layer.The 1st support 30 of high impedance for example can make gold and tin eutectic crystallization form.In the 1st support 30 of low reactance-resistance ratio, can use for example bonding agent of polymer etc.
In the acoustic resonator that the 1st execution mode of said structure relates to, by being located at the effect of the 1st support 30 between baseplate part 40 and the 2nd support 20, the feature that performance is following.
The 1st, (arrow of Fig. 1 a) by 30 reflections of the 1st support towards the major part of the vibration of baseplate part 40 from the 2nd support 20.The 2nd, even the vibration seldom of transmitting to baseplate part 40 from the 2nd support 20 turns back to the direction of vibration section 10 at the bottom reflection of baseplate part 40, also in 30 reflections (the arrow b of Fig. 1) of the 1st support.The acoustic impedance that this means the 1st support 30 is than baseplate part 40 and the 2nd support 20 height.
In addition, the degree of depth of the thickness of the 2nd support 20, cavity 21 and the thickness of the 1st support 30 also can be made Fig. 2～structure shown in Figure 4 except structure shown in Figure 1.
Fig. 2 is the embodiment of acoustic resonator that is provided with the cavity 21 of the shape that does not connect the 2nd support 20.Fig. 3 is with respect to the wavelength X by the resonance frequency of vibration section 10 excitation, makes the thickness of the thickness of the 2nd support 20 and the 1st support 30 be respectively the embodiment of the acoustic resonator of λ/4.Fig. 4 is the wavelength X with respect to the resonance frequency that is encouraged by vibration section 10, and the thickness that makes the 2nd support 20 is that the thickness of the/2, the 1st support 30 is the embodiment of the acoustic resonator of λ/4.Certainly, in the structure of this Fig. 3 and Fig. 4, also can make the structure that cavity 21 does not connect the 2nd support 20.
[the 2nd execution mode]
Fig. 5 is the figure of the structural profile of the acoustic resonator that relates to of the 2nd execution mode of the present invention.In Fig. 5, the acoustic resonator that the 2nd execution mode relates to comprises baseplate part 40, be located at support 30 on the baseplate part 40, be located at the sound reflector portion 50 on the support 30 and be located at vibration section 10 in the sound reflector portion 50.The acoustic reflecting layer of sound reflector portion 50 formations are alternately stacked low impedance layers 51 and high impedance layer 52.In this sound reflector portion 50, guaranteed the compressional vibration of vibration section 10.Vibration section 10 comprises the piezoelectrics 11 that form with aluminium nitride piezoelectrics such as (AlN), be located at the upper electrode 12 of piezoelectrics 11 upper surfaces and be located at the lower electrode 13 of piezoelectrics 11 lower surfaces.Upper electrode 12 and lower electrode 13 are formed by for example molybdenum (Mo).This vibration section 10 make lower electrode 13 for downside be positioned on the 2nd support 20.
In the acoustic resonator that the 2nd execution mode of said structure relates to, by being located at the effect of the support 30 between baseplate part 40 and the sound reflector portion 50, the feature that performance is following.
The 1st, be supported portion's 30 reflections (the arrow c of Fig. 5) from sound reflector portion 50 towards the major part of the vibration of baseplate part 40.The 2nd, even the less vibration of transmitting to baseplate part 40 from sound reflector portion 50 turns back to the direction of vibration section 10 at the bottom reflection of baseplate part 40, also be supported portion's 30 reflections (the arrow d of Fig. 5).The acoustic impedance that this means support 30 is than baseplate part 40 and sound reflector portion 50 height.
In the structure of the acoustic resonator that the 2nd execution mode relates to, its characteristic point is, the low impedance layers 51 of sound reflector portion 50 and the thickness of high impedance layer 52 be respectively acoustic resonator vibration wavelength λ 1/4, still, the thickness of support 30 is beyond λ/4.At this moment, also can make mounting the thickness of support 30 of part of vibration section 10 different with the thickness of the support 30 of the part that does not have mounting vibration section 10.By these features, can further bring into play damping.In addition, resonance frequency and vibration section 10 resonance frequency in addition by changing vibration section 10 can be enclosed in energy in the vibration section 10, can expect better damping.
In addition, support 30 has the formed film of material of the acoustic impedance higher than piezoelectrics 11 and substrate 40 by utilization or utilizes Q value material formed film littler than piezoelectrics 11 and baseplate part 40 etc. to constitute.The material of this support 30 both can be that insulating material also can be an electric conducting material.Under the situation of using electric conducting material, also support 30 can be used as wiring layer.The support 30 of high impedance for example can make gold and tin eutectic crystallization form.In the support 30 of low reactance-resistance ratio, can use for example bonding agent of polymer etc.
More than, according to the acoustic resonator that the of the present invention the 1st and the 2nd execution mode relates to, can prevent at the bottom reflection of baseplate part 40 and turn back to the unnecessary generation of vibration of vibration section 10.Thus, can access the good admittance frequency characteristic of the vibration of between the resonance frequency of vibration section 10 and antiresonant frequency, not looking genuine.
In addition, the acoustic resonator that relates to of the above-mentioned the 1st and the 2nd execution mode can obtain filter by making up one or more.Below, the filter to making up when a plurality of and use the device of this filter to describe.
(using the 1st embodiment of the filter of acoustic resonator)
Fig. 6 A is the figure of the 1st embodiment of the expression filter that uses acoustic resonator of the present invention.Filter shown in Fig. 6 A is the ladder-type filter that acoustic resonator is connected with the L type.Be connected with acoustic resonator 61, it moves as the resonance series device.That is, be connected in series between input terminal 63 and the lead-out terminal 64.Be connected with acoustic resonator 62, it moves as the parallel resonance device.That is, be connected from input terminal 63 between the path and ground wire of lead-out terminal 64.Here, if set the resonance frequency of acoustic resonator 61 than the resonance frequency height of acoustic resonator 62, then can realize having the ladder-type filter of bandpass characteristics.Preferably, the resonance frequency by making acoustic resonator 61 is consistent in fact with the antiresonant frequency of acoustic resonator 62 or be set at approachingly, can realize with the good ladder-type filter of logical flatness.
In addition, in above-mentioned the 1st embodiment, the ladder-type filter of illustration L type structure is illustrated, but if the ladder-type filter of other T type structures or π type structure or the ladder-type filter of grid type structure also can access same effect.In addition, ladder-type filter can be 1 level structure as Fig. 6 A both, can be multilevel hierarchy as Fig. 6 B also.
(using the 2nd embodiment of the filter of acoustic resonator)
Fig. 7 is the figure of the 2nd embodiment of the expression filter that uses acoustic resonator of the present invention.Filter shown in Figure 7 is the filter of stacked.Acoustic resonator 71 is connected in series between input terminal 73 and the lead-out terminal 74.The target of acoustic resonator 71 is connected on the ground wire.Like this, if use the acoustic resonator 71 of the vibration of not looking genuine, then can realize the stacked filter that bandpass characteristics is good.Certainly, ladder-type filter both can be 1 level structure as shown in Figure 7, also can be multilevel hierarchy.
(using the embodiment of the device of acoustic resonator)
Fig. 8 is the figure of the embodiment of the expression device that uses acoustic resonator of the present invention.Device shown in Figure 8 is to use the communication equipment of Fig. 6 A, Fig. 6 B and filter shown in Figure 7.This device comprises two antennas 81 and 82, is used for switching the switch 83 and the filter 84 of two frequency signals.By such structure, can realize low-loss communication equipment.
(the 1st example of the manufacture method of acoustic resonator)
Fig. 9 A is to use an example of the vertical view of the acoustic resonator that the 1st execution mode of the manufacture method manufacturing of the 1st example relates to.Fig. 9 B is the X-X profile of the acoustic resonator shown in Fig. 9 A.In the manufacture method of the 1st example, the method for two baseplate-laminatings is made acoustic resonator by using.Below, with further reference to Figure 10 A～Figure 10 C, the order of the manufacture method of the 1st example is described.
At first, (Figure 10 A, operation a) substituting on the corrosion substrate 92 stacked alternative corrosion layer 91.Then, on alternative corrosion layer 91, form piezoelectric membrane 11a (Figure 10 A, operation b) by film forming.Here, so-called alternative corrosion substrate 92 is interim substrates that use in forming the process of acoustic resonator, is the structure in the acoustic resonator that is not included in after the manufacturing.Should substitute corrosion substrate 92 for example is made of sapphire.To substitute corrosion layer 91 and be in order bonding process described later after, to substitute and corrode substrate 92 and peel off and the resilient coating that is provided with from piezoelectric membrane 11a.Should substitute corrosion layer 91 for example is made of gallium nitride (GaN).Piezoelectric membrane 11a is made of aluminium nitride (AlN), by the mocvd method film forming on alternative corrosion layer 91.Like this,, membranous good piezoelectric body layer can be formed, broadband and high Q value and the higher acoustic resonator of reliability can be made by using mocvd method.
In addition, mocvd method carries out under 1050 ℃ high temperature.But in the present embodiment, the gallium nitride of use materials with high melting point is corrosion layer 91 as an alternative, can fully bear 1050 ℃ high temperature.Thereby, in the film forming of piezoelectric membrane 11a, use mocvd method, on manufacturing process without any problem.In addition, in alternative corrosion layer 91, except gallium nitride, also can use molybdenum.
Then, stacked electrode layer 13a (Figure 10 A, operation c) on piezoelectric membrane 11a as electric conductor.Then, stacked electrode layer 13a is carried out composition, with lower electrode 13 shapings (Figure 10 A, operation d).Then, stacked alternative corrosion layer 21a (Figure 10 A, operation e) on lower electrode 13 that is shaped and piezoelectric membrane 11a.At this moment, with substitute corrosion layer 21a stacked be than lower electrode 13 thick layer.Then, this stacked alternative corrosion layer 21a is carried out composition, will substitute 21 shapings (Figure 10 A, operation f) of corrosion layer portion.Should substitute corrosion portion 21 is to form the part that is removed in the operation at cavity described later, by being removed the cavity 21 that forms acoustic resonator.As the material of this alternative corrosion layer 21a, can use silicide of molybdenum for example or tungsten etc.In addition, in the case, in the material of lower electrode 13, use molybdenum aluminium in addition etc.
Then, stacked the 2nd supporting course 20 (Figure 10 B, operation g) on alternative corrosion portion 21, lower electrode 13 and piezoelectric membrane 11a.The 2nd supporting course 20 is preferably silica (SiO
2) or silicon nitride (Si
3N
4) insulator that waits.Then, carry out planarization, making does not have step (Figure 10 B, operation h) on the surface of this 2nd stacked supporting course 20.By this planarization, make and in follow-up bonding process, substrate 40 whole faces can be fitted equably smoothly.Can use CMP etc. in planarization, be below the RMS2000A by the roughness that makes the surface, can fit uniformly.
Then, on the surface of the 1st supporting course 30, will be formed with the substrate 40 of the 1st supporting course 30 that the alloy by golden tin constitutes and the 2nd supporting course 20 fit (Figure 10 B, operation i).This substrate 40 for example is made of silicon.At this moment, also can between substrate 40 and the 1st supporting course 30, form the insulator layer that constitutes by silicon nitride or silica.In the 1st example, form the alloy film of golden tin as the 1st supporting course 30 by film forming, the applying that has utilized the eutectic of golden tin to engage.Particularly, make that to substitute corrosion substrate 92 opposed with substrate 40,, two plate bases are fitted by applying the temperature 10 minutes that applies 375 ℃ under the pressure status of 15N/cm2.In addition, so long as the material that can eutectic engages also can access same effect by the alloy beyond the golden tin.
Then, from substituting back side illuminaton yttrium-aluminium-garnet (YAG) laser of corrosion substrate 92,, will substitute corrosion substrate 92 and peel off (Figure 10 B, operation j) with substrate 40 by cutting off the joint of the alternative corrosion layer 91 that constitutes by the less aluminium nitride of band gap.At this moment, be formed on than alternative corrosion layer 91 by piezoelectric membrane 11a, the lower electrode 13 of upside, substitute corrosion portion 21 and the 2nd supporting course 20 is transferred on the substrate 40.In addition, the YAG laser that in peeling off, uses, according to the alternative corrosion substrate 92 that uses and the mould that substitutes corrosion layer 91 is thick and kind is selected optical maser wavelength, also can tackle band gap variation that the thickness that substitutes corrosion layer 91 causes or the situation of having selected other materials.
Then, on the piezoelectric membrane 11a that exposes on the surface being stripped from, stacked electrode layer 12a (Figure 10 C, operation k) as electric conductor.Then, stacked electrode layer 12a is carried out composition, with upper electrode 12 shapings (Figure 10 C, operation l).And then, as required with piezoelectric membrane 11a composition, make piezoelectrics 11 shapings (Figure 10 C, operation m).At last, will substitute corrosion portion 21 and remove, form cavity 21 (Figure 10 C, operation n) by etching etc.Thus, finish the acoustic resonator shown in Fig. 9 B.
As mentioned above, in the manufacture method of the 1st example, utilize the baseplate-laminating technology.Therefore, when the film forming of piezoelectric membrane, can in substrate, use single crystallization base plates such as silicon, obtain high-quality piezoelectric membrane even in the membrane structure (support structure) of complexity, also can eliminate the influence of substrate.In addition, when piezoelectric membrane forms, can use high temperature technologies such as mocvd method, can access the piezoelectric membrane of epitaxial growth.
In addition, in the formation of cavity, use to substitute corrosion layer, behind strippable substrate, will substitute corrosion layer and remove,, can improve rate of finished products so the barrier film of lifting from vibration section in the operation at laser can not come to harm by etching.In addition, because can be with substrate with whole applying, so manufacturing process is oversimplified.
In addition, according to laminating condition, also can omit the planarization operation (Figure 10 B, operation h) of the 2nd support 20.Do not carrying out under the situation of planarization like this, because vibration section 10 leaves from binding face, thus bring influence can not for the characteristic of acoustic resonator, and can make acoustic resonator easily.
In addition, because the binding face of the 2nd support 20 and substrate 40 10 leaves from the vibration section, so also can use bonding agents etc. at the 1st support 30.In the case, do not need to improve the roughness on surface, can omit planarization operation (Figure 10 B, operation g), can make acoustic resonator more easily, and the damping by the 1st support 30 that constitutes by bonding agent, can decay expeditiously passes to the vibration of substrate 40.
In addition, in substituting corrosion substrate 92, except sapphire substrate,, also can use the substrate of silicon or carborundum (SiC) etc. as long as can make piezoelectric membrane 11a film forming.In addition, in alternative corrosion layer 91, except gallium nitride, also can use the material that easily to peel off from substrate, can the film forming piezoelectric body layer.For example, by using molybdenum corrosion layer 91 as an alternative, can utilize hydrogen peroxide more easily from forming strippable substrate.In the case, in strippable substrate operation (lifting from operation corresponding to laser in the present embodiment), using under the situation of Wet-type etching etc., because vibration section 10 covered by the 2nd support 20, so lower electrode 13 can not sustain damage yet.
In addition, the film build method as piezoelectric membrane 11a is not limited to mocvd method, uses sputtering method also to have same effect certainly.And then, in piezoelectric membrane 11a, except utilizing the aluminium nitride that mocvd method forms, also can use the PZT material of the lead titanates (PbTiO3) of having implemented high-temperature process or lead zirconate titanate (PbTiZrO) etc. etc.But, when being shaped these films, because must be in the high-temperature process of carrying out under the carrier of oxygen environment about 800 ℃, so in substituting corrosion layer, need thermal endurance in the materials used.
In addition, as the strippable substrate operation, represented that laser lifts from the example of operation, but so long as behind bonding process, can substitute the method that corrosion substrate 92 is removed, corrode substrate as an alternative and remove operation, can consider to utilize etching etc. will substitute the method that corrosion substrate 92 is removed.For example, under the situation of Wet-type etching, can use nitric acid to remove substituting under the situation that corrosion substrate 92 is silicon substrates, utilize dry-etching etc. also can similarly remove.
(the 2nd example of the manufacture method of acoustic resonator)
Figure 11 is to use an example of the structural section of the acoustic resonator that the manufacture method of the 2nd example makes.The manufacture method of the 2nd example also can be made acoustic resonator with the method for two baseplate-laminatings by adopting.Below, refer again to Figure 12 A～Figure 12 C, the order of the manufacture method of the 2nd example is described.
At first, substituting stacked alternative corrosion layer 91 (Figure 12 A, operation A) on the corrosion substrate 92.Then, on alternative corrosion layer 91, make piezoelectric membrane 11a film forming (Figure 12 A, process B).Then, stacked electrode layer 13a (Figure 12 A, operation C) on piezoelectric membrane 11a as electric conductor.Then, with stacked electrode layer 13a composition, make lower electrode 13 shapings (Figure 12 A, step D).Then, stacked acoustic impedance layer 51 (Figure 12 A, operation E) on lower electrode 13 that is shaped and piezoelectric membrane 11a.Be laminated into than lower electrode 13 thick layer with acoustic impedance layer 51 this moment.Then, carry out planarization, making does not have step (Figure 12 A, operation F) on the surface of this stacked acoustic impedance layer 51.Then, stacked low acoustic impedance layer 52 (Figure 12 B, operation G) on the acoustic impedance layer 51 of planarization.Repeat repeatedly this operation F and operation G, form sound reflector layer 50 (Figure 12 B, step H).In Figure 12 B, represented with acoustic impedance layer 51 and low acoustic impedance layer 52 alternately stacked 3 grades the example of sound reflector layer 50.
Then, the substrate 40 harmony reflector layers 50 that will be formed with the 1st supporting course 30 that the alloy by golden tin constitutes fit (Figure 12 B, operation I) with face with the 1st supporting course 30.Then, from substituting the back side illuminaton yag laser of corrosion substrate 92,, will substitute corrosion substrate 92 and peel off (Figure 12 C, operation J) with substrate 40 by cutting off the joint of the alternative corrosion layer 91 that constitutes by the less gallium nitride of band gap.At this moment, be formed on than piezoelectric membrane 11a, lower electrode 13 and the sound reflector layer 50 of alternative corrosion layer 91 and be transferred on the substrate 40 by upside.Then, on the piezoelectric membrane 11a that exposes on the surface being stripped from, stacked electrode layer 12a (Figure 12 C, operation K) as electric conductor.At last, with stacked electrode layer 12a composition, make upper electrode 12 shapings (Figure 12 C, operation L).Thus, finish acoustic resonator shown in Figure 11.
As mentioned above, in the 2nd example, utilize the baseplate-laminating technology.Therefore, the high-temperature technology of mocvd method etc. can be when piezoelectric membrane forms, adopted, the higher piezoelectric membrane of crystallinity can be accessed.
In addition, in the operation E of above-mentioned Figure 12 A, the example of direct stacked acoustic impedance layer 51 on lower electrode 13 and piezoelectric membrane 11a has been described, but also can have formed the maintenance layer that the insulator by silica and silicon nitride etc. constitutes before this.
Acoustic resonator of the present invention and filter can be used in portable phone, radio communication or wireless internet connection etc., the look genuine situation etc. of admittance frequency characteristic of vibration that being particularly suitable for has wanted to be inhibited.
In addition, manufacture method of the present invention can be useful under the situation of wanting to utilize the higher piezoelectric membrane of crystallinity to realize broadband and low-loss acoustic resonator etc. as the uses such as manufacture method of the acoustic resonator that uses in the high-frequency circuit of the mobile communication terminal of portable phone and WLAN etc. especially.
Claims (6)
1, a kind of acoustic resonator, the frequency vibration with regulation is characterized in that,
This acoustic resonator possesses:
Substrate (40);
The 1st support (30) is located on the aforesaid substrate (40);
The 2nd support (20) is located on above-mentioned the 1st support (30);
Vibration section (10) is located on above-mentioned the 2nd support (20), upper electrode (12) that comprise piezoelectrics (11) at least, is provided with at the upper surface of piezoelectrics (11) and the lower electrode (13) that is provided with at the lower surface of piezoelectrics (11);
Above-mentioned the 1st support (30) is by having than above-mentioned piezoelectrics (11) height, and the material of the acoustic impedance higher than aforesaid substrate (40) constitutes.
2, acoustic resonator as claimed in claim 1 is characterized in that, makes gold form above-mentioned the 1st support (30) with the tin eutectic crystallization.
3, acoustic resonator as claimed in claim 1 is characterized in that, with respect to the wavelength X of the resonance frequency that is encouraged by above-mentioned vibration section (10), the thickness of above-mentioned the 1st support (30) is λ/4.
4, a kind of filter constitutes the described acoustic resonator of plural claim 1 with trapezoidal connection.
5, a kind of communication equipment possesses the described filter of claim 4.
6, a kind of acoustic resonator, the frequency vibration with regulation is characterized in that,
This acoustic resonator possesses:
Substrate (40);
Support (30) is located on the aforesaid substrate (40);
Sound reflector portion (50) is located on the above-mentioned support (30), alternately is laminated with low impedance layers (51) and high impedance layer (52);
Vibration section (10) is located in the above-mentioned sound reflector portion (50), upper electrode (12) that comprise piezoelectrics (11) at least, is provided with at the upper surface of piezoelectrics (11) and the lower electrode (13) that is provided with at the lower surface of piezoelectrics (11);
Above-mentioned support (30) is made of the material with acoustic impedance higher than aforesaid substrate (40);
Make gold form above-mentioned support (30) with the tin eutectic crystallization.
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| JP2005192516 | 2005-06-30 | ||
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