CN209299229U - A kind of resonance structure SAW filter - Google Patents

Abstract

The utility model relates to a kind of resonance structure SAW filters, carry out isolation reduction treatment on the piezoelectric chip surface of lithium tantalate or lithium columbate crystal, and resonator element electrode is formed on reducing zone.Destruction of the piezo-electric crystal pyroelectric effect to resonator element periodic electrode lines is eliminated using the piezoelectric chip surface of reduction, simultaneously, it is therefore prevented that the decrease being electrically isolated between resonator element caused by the full surface reduction processing of chip.

Description

A kind of resonance structure SAW filter

Technical field

The utility model relates to a kind of resonance structure SAW filters.

Background technique

Now in the base station and mobile terminal of radio communication, make for radio frequency reception/transmitting unit filter to be more With SAW filter, and resonance structure filter is its primary structure form.Resonance structure type SAW filter It is that the multiple SAW resonator units made on the piezoelectric chip with piezoelectric effect are electrically connected, resonator element It is made of periodic electrodes (interdigital transducer IDT and reflecting grating) and bus electrode.In piezoelectric material, lithium tantalate or lithium niobate Crystal due to biggish electromechanical coupling factor, it can be achieved that the filter characteristic of the low decaying of broadband.

In high-frequency sound surface wave filter, superfine metal electrode lines are easy to be discharged by wafer surface accumulation of static electricity Cause to burn, therefore, the piezoelectric chip of high-frequency element mostly uses reduction method to handle now, to improve wafer surface conductivity Eliminate pyroelectric effect, the reliability hidden danger for avoiding Electro-static Driven Comb from bringing.

As field of radio frequency communication is to 5G era development, the centre frequency of used acoustic surface wave filter device is increasingly Height, it is also more stringent to the performance requirement of piezo-electric crystal substrate.Since the lattice defect in piezoelectric crystal material will affect sound table Surface wave transmission performance increases excess loss, therefore in order to reduce the high-frequency loss of SAW device, it is desirable that crystals lattice defect To lack as far as possible.

Piezoelectric crystal material used in SAW device is commonly the congruent niobic acid using Czochralski grown at present The chip that lithium, lithium tantalate are processed.Nearby wafer surface in the effective workspace of surface acoustic wave, the chemical composition of material are same Ingredient lithium tantalate (CLT) or congruent lithium niobate (CLN).And since the lithium tantalum ratio or Li/Nb ratio of CLT or CLN are only 0.486, no Meet the chemical formula ratio (can accurately be measured with x-ray diffraction method or microscopic Raman analytic approach) of 1:1.The content of lithium is insufficient, brilliant Piece surface is there are more lithium vacancy defect, and excessive lithium vacancy defect declines the mechanical-electric coupling ability of piezoelectric material, in turn Lead to the disadvantage for the performances differences such as the insertion loss of the SAW filter produced is big, Out-of-band rejection is small.But near-stoichiometric The lithium niobate of ratio, lithium tantalate wafer are difficult to grow due to the crystal of major diameter, and it is brilliant to be difficult to see 3 cun or more batch produce in the market Piece.

In open source information, rich lithiumation is carried out to wafer surface using gas-liquid equilibrium means of transportation (VTE) and is handled, in chip It is upper to form one layer of rich lithium layer, so that the chemical composition of wafer surface is close to stoichiometric ratio, to improve the electromechanics of wafer material Coupling ability improves the performance of SAW filter.

But currently used rich lithium method treatment process is implemented to the full surface of piezoelectric chip, will cause device heat resistanceheat resistant and releases The reduction of electric energy power, partial offset reduction chip bring benefit.How to take into account mechanical-electric coupling ability and electric energy power is released in heat resistanceheat resistant It is the problem for implementing the manufacture of high-performance high-frequency SAW filter.

Utility model content

In order to solve the shortcomings of the prior art, the utility model provides a kind of resonance structure sound that insertion loss is low Surface wave filter.

One of the utility model resonance structure SAW filter, comprising: piezoelectric chip is arranged in piezoelectric chip Multiple resonator elements and electrical connection metal electrode on surface,

The piezoelectric chip is the congruent lithium niobate for using Czochralski grown, the wafer of monocrystalline lithium tantalate processing and fabricating；

The piezoelectric chip is the reduction chip by reduction treatment；

At least one rich lithium surface district has been made on the piezoelectric chip surface reduction layer；

At least one resonator element is produced in rich lithium surface district.

The lithium niobium component ratio of lithium niobate crystal chip richness lithium surface district is greater than 0.486, and less than 0.5；Lithium tantalate wafer richness lithium table The lithium tantalum component ratio in face area is greater than 0.486, and less than 0.5.

According to IEC standard, lithium niobate crystal chip bulk conductivity are as follows: (1.0 * 10^-12 ~ 1.0* 10 ^-8) S/cm, lithium tantalate Chip bulk conductivity are as follows: (1.0*10^-13~ 1.0*10^-10) S/cm.

Preferably, all resonator elements are produced in rich lithium surface district.The resonator element being directly electrically connected Electrical connection metal electrode structure, can also be produced in rich lithium surface district.

Preferably, the rich lithium surface district where the resonator element of indirect electrical connection is not connected with.

Preferably, rich lithium surface district, can be used silica as the separation layer for making rich lithium surface district technique.

Resonance structure SAW filter resonator element, metal electrode are that single metal or multiple layer metal are constituted 's.The metal generally used is Al, Cu or Al/Cu.

Preferably, piezoelectric chip be equipped with multiple resonator elements and electrical connection metal electrode structure above production have it is more Layer dielectric.

Preferably, multilayer dielectricity film bottom is silica.As temperature-compensating；To reduce filter out-of-band interference, Silicon oxide film surface is graduation.

Preferably, multilayer dielectric film top layer is silicon nitride.In addition to as filter frequencies fine tuning, can also increase device can By property.

The utility model has the beneficial effects that obtaining congruent lithium niobate lithium tantalate piezoelectric chip surface richness lithium processing technique Simultaneously, electric energy power is released in the device heat resistanceheat resistant for maintaining surface reduction technology to advantage, optimizes the performance of radio-frequency filter: reducing insertion Loss promotes Out-of-band rejection, ensure that the reliability of filter.

Detailed description of the invention

Fig. 1 is the schematic diagram of the section structure of resonance structure SAW filter.

Fig. 2 is piezoelectric chip resonator cell electrode structural schematic diagram.

Fig. 3 is the schematic diagram of the section structure of surface acoustic wave resonance Structure Filter.

Fig. 4 is the fabrication process flow figure of resonance structure SAW filter,.

Fig. 5 is the structural schematic diagram of resonance structure SAW filter in embodiment 1.

Fig. 6 is the structural schematic diagram of resonance structure SAW filter in embodiment 2.

Marked in the figure: 1, piezoelectric chip, 2, reduction zone, 3, the area Fu Li, 4, resonator element electrode, 5, silicon dioxide layer, 6, silicon nitride layer, S1, reduction piezoelectric chip, S2, barrier layer and graphical, S3, rich lithium processing, S4, resonator element electricity Pole manufacture, S5, deposit silicon dioxide layer simultaneously planarize, S6, deposit silicon nitride layer.

Specific embodiment

The utility model is described in further detail with reference to the accompanying drawing, but this should not be interpreted as the utility model The range of above-mentioned theme is only limitted to above-described embodiment.

As shown in Figure 1, a kind of isolation area Fu Li of resonance structure SAW filter and cuing open for resonator element electrode Face schematic diagram makes the area You Fuli 3, and resonator element below the resonator element electrode 4 on reduction 1 surface of piezoelectric chip Between be isolation；Make the barrier layer of rich lithium treatment process in piezoelectric chip surface deposition silica, with lithography and etching side Legal system makees figure, exposes the surface for needing rich lithiumation part, then carries out rich lithium processing, shape by high temperature solid-state richness lithiation At the isolation area Fu Li.

As shown in Fig. 2, resonator is that the formation of resonator element electrode 4 is manufactured on piezoelectric chip 1, resonator element electricity The reflecting grating and bus electrode of IDT and both sides that pole is made of intermediate interdigitated form.Resonator element electrode using Al, Cu or The production of the metals such as its alloy, fine lines are processed with light lithography, then produce electrode pattern with etching method or stripping method.

As shown in figure 3, resonance structure SAW filter includes the area Fu Li 3, resonator element electrode 4 and offer temperature The dielectric layer of compensation forms, and dielectric layer is divided into two parts: one is silica (5), is deposited using sputtering method, and its table Face needs to planarize；The other is silicon nitride (6), for improving layer dielectric reliability, and is used for the fine tuning of filter frequencies, It can be deposited with sputtering method.

A kind of surface acoustic wave resonance Structure Filter of the invention can use following two embodiment with mode above Implemented:

Embodiment 1:

Using the congruent lithium tantalate of Czochralski grown (LiTaO3) crystal, produced by processes such as cutting, grinding, polishings Lithium tantalate wafer, and chip obtains reduction chip by reduction treatment；

Then chip is cleaned；

Then silicon dioxide blocking layer is formed with sputtering method, thickness is set as 2 microns；

Lithography and etching method is reused, the airbreak figure for manufacturing rich lithium region is formed；

Followed by, rich lithiumation carried out to chip using rich lithiation process, when rich lithiumation, carries out sheet mode using piece, In, chip face, which contains rich lithium material coating, accompanies and attends to piece, and between the two every 1mm, 550 DEG C of rich lithium temperature keeps the temperature 150 hours；

After the completion of rich lithiumation, chip is cleaned, the pollution such as removal disintegrating slag, particle；

Then multiple groups resonator element electrode pattern is manufactured on the area Fu Li corresponding region using photoetching process, structure is such as Shown in Fig. 5；

Finally in wafer surface deposit for the silicon dioxide layer of temperature-compensating and for the silicon nitride layer of fine tuning.

Embodiment 2:

Congruent lithium niobate (LiNbO3) crystal is formed using czochralski method, is produced by processes such as cutting, grinding, polishings Lithium niobate crystal chip, and chip obtains reduction chip by reduction treatment,

Then chip is cleaned,

Then silicon dioxide blocking layer being formed with sputtering method, thickness is set as 2 microns,

Lithography and etching method is reused, the airbreak figure for manufacturing rich lithium region is formed,

Followed by carrying out rich lithiumation to chip using rich lithium method, when rich lithiumation carries out sheet mode using piece, wherein brilliant Piece face, which contains rich lithium material coating, accompanies and attends to piece, and between the two every 1mm, 1100 DEG C of rich lithium temperature keeps the temperature 100 hours,

After the completion of rich lithiumation, chip is cleaned, the pollution such as removal disintegrating slag, particle,

Then multiple groups resonator element electrode pattern is manufactured on the area Fu Li corresponding region using photoetching process, structure is such as Shown in Fig. 6,

Finally in wafer surface deposit for the silicon dioxide layer of temperature-compensating and for the silicon nitride layer of fine tuning.

Claims (10)

1. a kind of resonance structure SAW filter, comprising: piezoelectric chip, multiple resonators that piezoelectric chip surface is arranged in Unit and electrical connection metal electrode, it is characterized in that:

The piezoelectric chip is the lithium niobate for using Czochralski grown, the wafer of monocrystalline lithium tantalate processing and fabricating；

At least one reduction surface district has been made on the piezoelectric chip surface；

At least one resonator element is produced in reduction surface district；

Reduction surface district where the resonator element of indirect electrical connection is not connected with.

2. resonance structure SAW filter according to claim 1, it is characterized in that: all resonator elements are made Make in reduction surface district.

3. resonance structure SAW filter according to claim 1, it is characterized in that: the resonator list being directly electrically connected The electrical connection metal electrode of member is produced in reduction surface district.

4. resonance structure SAW filter according to claim 1, it is characterized in that: the reduction table on piezoelectric chip surface Face area, the separation layer using silica as production reduction surface district technique.

5. resonance structure SAW filter according to claim 1, it is characterized in that: the metal electrode of resonator element It is that single metal or multiple layer metal are constituted.

6. resonance structure SAW filter according to claim 5, it is characterized in that: the metal electrode of resonator element It is what Al, Cu or Al/Cu were constituted.

7. resonance structure SAW filter according to claim 1, it is characterized in that: further include: it is produced on piezo crystals Multilayer dielectric film above the multiple resonator elements of on piece and electrical connection metal electrode structure.

8. resonance structure SAW filter according to claim 7, it is characterized in that: the bottom of multilayer dielectric film is one Determine the silica of thickness.

9. resonance structure SAW filter according to claim 8, it is characterized in that: silicon oxide film surface is graduation 's.

10. resonance structure SAW filter according to claim 7, it is characterized in that: the top layer of multilayer dielectric film is Certain thickness silicon nitride.