CN110098816A - A kind of piezo-electric resonator of narrow support frame high quality factor - Google Patents

Abstract

The invention discloses a piezoelectric resonator with a narrow support frame and high quality factor. Grooves are formed on the surface of the substrate and the support layer is fixed on the surface of the substrate. The gap between the support layer and the groove is The air gap is formed between them and the air gap is filled with air, the bottom electrode is fixed on the surface of the support layer, the piezoelectric layer is fixed on the surface of the bottom electrode, and the piezoelectric layer is fixed on the surface The upper electrode is fixed, and a plurality of high-impedance material layers and low-impedance material layers are arranged below the support layer, and the high-impedance material layers and low-impedance material layers are arranged at intervals, and the high-impedance material layers and low-impedance material layers are arranged at intervals. The number of material layers is the same, the high-impedance material is fixed on the substrate, and the support layer is fixed on the upper surface of the low-impedance material. Method for the preparation of electric resonators. The invention has higher mechanical strength and higher quality factor.

Description

A High Quality Factor Piezoelectric Resonator with a Narrow Support Frame

technical field

The invention relates to the technical field of resonators, in particular to a piezoelectric resonator with a narrow support frame and high quality factor.

Background technique

Thin film bulk acoustic resonators are layered structures similar to sandwiches, that is, there is a piezoelectric film layer between the upper electrode and the lower electrode. The back of the silicon substrate uses etching technology to form an air cavity or uses the surface micromachining technology to form an air cavity on the upper surface of the silicon by filling the animal material, so as to use the approximately zero impedance of air to limit the sound wave or energy from the piezoelectric Layer leaks. The biggest disadvantage of TFBAR is that the removal of a large number of silicon substrates leads to a significant reduction in the mechanical fastness of the resonator. Generally speaking, a layer of silicon nitride or silicon dioxide is placed on the lower surface of the bottom electrode as a support layer to increase the mechanical fastness of TFBAR, but this seriously reduces the quality factor Q value of TFBAR.

Contents of the invention

(1) Solved technical problems

Aiming at the deficiencies of the prior art, the invention provides a piezoelectric resonator with a narrow support frame and high quality factor and a preparation method thereof, which solves the problems of low mechanical fastness and low quality factor of the existing resonator.

(2) Technical solution

In order to achieve the above object, the present invention provides the following technical solutions: a piezoelectric resonator with a narrow support frame and high quality factor, including a substrate, a support layer, a bottom electrode, an air gap, an upper electrode and a piezoelectric layer, the substrate There is a groove on the surface of the substrate and the support layer is fixed on the surface of the substrate, the air gap is formed between the support layer and the groove, and the air gap is filled with air, the support layer The bottom electrode is fixed on the surface of the bottom electrode, the piezoelectric layer is fixed on the surface of the bottom electrode, the upper layer electrode is fixed on the surface of the piezoelectric layer, and a plurality of high-impedance materials are arranged below the support layer. layer and a low-resistance material layer, the high-resistance material layer and the low-resistance material layer are arranged at intervals and the number of layers of the high-resistance material layer and the low-resistance material layer is the same, and the high-resistance material layer is fixed on the substrate , the support layer is fixed on the upper surface of the low resistance material layer.

Preferably, the piezoelectric layer is an AlN piezoelectric film, the substrate is made of silicon dioxide, and the material used for the bottom electrode and the top electrode is one of Au, Mo, W, and Pt.

Preferably, the air gap makes the lower surface of the support layer in direct contact with the air, and confines the acoustic wave energy within the working area.

A method for preparing a piezoelectric resonator with a narrow support frame and high quality factor according to the above scheme, characterized in that it includes the following steps:

(1): The standard RCA process is used to clean the double-sided polished Si sheet, the Si sheet is the substrate material, and then the high-impedance material layer and the low-impedance material layer are pasted at intervals, and then PECVD is deposited on both sides of the Si sheet A 100nm/100nm thick SiN ₄ /SiO ₂ thin film;

(2): Then use DC magnetron sputtering to deposit 100nm/10nm Pt/Ti as the bottom electrode, and use photolithography and stripping to form the bottom electrode pattern;

(3): After removing the glue, use radio frequency magnetron reactive sputtering to prepare AlN piezoelectric film under optimized sputtering conditions. The AlN piezoelectric film is used as the piezoelectric layer with a thickness of about 1.8 μm. Ammonium hydroxide solution is used as an etching solution to etch the piezoelectric layer pattern;

(4): Then adopt the DC magnetron sputtering method to deposit the Au upper electrode of 300nm, and the Au upper electrode is used as the upper layer electrode;

(5): Finally, photolithographically etch the SiN ₄ /SiO ₂ film on the back of the substrate and use a reactive ion etching process to form a cavity window to be etched, and the cavity window is an air gap; then use KOH solution and isopropanol The mixed solution of the solution is an etching solution, and the Si wafer substrate under the window is etched to obtain a back cavity, and the back cavity is an air gap.

Preferably, in step (5), air is filled in the air gap, the lower surface of the substrate is coated with a conductive silver paste, and the surface of the conductive silver paste is pasted with a quartz glass sheet, two After bonding, it is cured in an environment with a constant temperature of 20°C.

Preferably, the thickness of the conductive silver paste is 40-60 μm.

(3) Beneficial effects

The invention provides a piezoelectric resonator with a narrow support frame and high quality factor, which has the following beneficial effects: the invention sets a support layer, a high-impedance material layer and a low-impedance material layer on the surface of the substrate. Silicon nitride or silicon dioxide is set on the surface of the support layer to increase the mechanical fastness of the resonator, and then a high-impedance material layer and a low-impedance material layer are set on the bottom of the support layer, and the high-impedance material layer and the low-impedance material layer are separated It is set and the high-impedance material layer and the low-impedance material layer form an acoustic mirror to prevent sound waves or energy from entering the substrate layer. Another angle achieves an equivalent approximately zero-impedance medium to a certain extent, and its mechanical firmness is much stronger than that of ordinary Resonator, the present invention strengthens the mechanical fastness of resonator by arranging support layer and high-impedance material layer and low-impedance material layer, acts as reflection medium by high-impedance material layer and low-impedance material layer and air in addition, can improve the resonator like this Quality factor.

Description of drawings

Fig. 1 is a structural representation of the present invention;

In the figure: 1. Substrate; 2. Quartz glass sheet; 3. Conductive silver paste; 4. Air gap; 5. Support layer; 6. High impedance material layer; 7. Low impedance material layer; 8. Bottom electrode; 9. Piezoelectric layer; 10. Upper electrode.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

As shown in Figure 1, the following embodiments are now proposed:

A piezoelectric resonator with a narrow support frame and high quality factor, comprising a substrate 1, a support layer 5, a bottom electrode 8, an air gap 4, an upper electrode 10, and a piezoelectric layer 9, and the surface of the substrate 1 is provided with a concave Groove and the surface of the substrate 1 is fixed with the support layer 5, the air gap 4 is formed between the support layer 5 and the groove, and the air gap 4 is filled with air, the support layer The bottom electrode 8 is fixed on the surface of the bottom electrode 8, the piezoelectric layer 9 is fixed on the surface of the bottom electrode 8, the upper layer electrode 10 is fixed on the surface of the piezoelectric layer 9, the bottom of the support layer 5 A plurality of high-resistance material layers 6 and low-resistance material layers 7 are provided, and the high-resistance material layers 6 and low-resistance material layers 7 are arranged at intervals and the number of layers of the high-resistance material layers 6 and low-resistance material layers 7 is the same, The high resistance material layer 6 is fixed on the substrate 1 , and the support layer 5 is fixed on the upper surface of the low resistance material layer 7 .

In this embodiment, the piezoelectric layer 9 is an AIN piezoelectric film, the substrate 1 is made of silicon dioxide, and the materials used for the bottom electrode 8 and the upper electrode 10 are Au, Mo, W, Pt, etc. kind of.

In this embodiment, the air gap 4 makes the lower surface of the support layer 5 in direct contact with the air, and confines the sound wave energy in the working area.

According to the preparation method of a piezoelectric resonator with a narrow support frame and high quality factor described in the above scheme, the method comprises the following steps:

(1): The standard RCA process is used to clean the double-sided polished Si sheet, the Si sheet is the substrate material, and then the high-impedance material layer 6 and the low-impedance material layer 7 are pasted at intervals, and then PECVD is used on both sides of the Si sheet The method deposits a layer of 100nm/100nm thick SiN ₄ /SiO ₂ film;

(2): Then deposit 100nm/10nm Pt/Ti as the bottom electrode 8 by DC magnetron sputtering method, and form the bottom electrode pattern with photolithography and stripping process;

(3): After removing the glue, use radio frequency magnetron reactive sputtering to prepare AlN piezoelectric film under optimized sputtering conditions. The AlN piezoelectric film is used as the piezoelectric layer 9 with a thickness of about 18 μm. Ammonium hydroxide solution is used as an etching solution to etch the piezoelectric layer pattern;

(4): Then adopt the DC magnetron sputtering method to deposit the Au upper electrode of 300nm, and the Au upper electrode is used as the upper layer electrode 10;

(5): Finally, photolithography is performed on the back of the substrate 1 and the SiN ₄ /SiO ₂ film is etched by a reactive ion etching process to form a cavity window to be etched, and the cavity window is an air gap 4; The mixed solution of propanol solution is an etching solution, and the Si wafer substrate under the etching window is obtained to obtain a back cavity, which is an air gap 4, and air is filled in the air gap 4, and the substrate 1 A 40-60 μm conductive silver paste 3 is coated on the lower surface of the bottom surface, and the surface of the conductive silver paste 3 is pasted with a quartz glass sheet 2. After the two are bonded, they are cured in an environment with a constant temperature of 20°C.

In the present invention, a support layer 5, a high-impedance material layer 6, and a low-impedance material layer 7 are arranged on the surface of the substrate. First, silicon tetranitride or silicon dioxide is arranged on the surface of the substrate 1 as the support layer 5 to increase the mechanical strength of the resonator. Fastness, then the high resistance material layer 6 and the low resistance material layer 7 are arranged at the bottom of the support layer 5, and the high resistance material layer 6 and the low resistance material layer 7 are arranged at intervals and the high resistance material layer 6 and the low resistance material layer 7 are composed Acoustic mirrors are used to prevent sound waves or energy from entering the substrate 1, and at another angle, an equivalent approximately zero-impedance medium is realized to a certain extent, and the mechanical firmness is much stronger than that of a general resonator. The present invention sets the support layer 5 and The high-impedance material layer 6 and the low-impedance material layer 7 strengthen the mechanical fastness of the resonator, and in addition, the high-impedance material layer 6, the low-impedance material layer 7 and air act as a reflection medium, which can improve the quality factor of the resonator

It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is a relationship between these entities or operations. There is no such actual relationship or order between them. Furthermore, the term "comprises", "comprises" or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, article, or apparatus comprising a set of elements includes not only those elements, but also includes elements not expressly listed. other elements of or also include elements inherent in such a process, method, article, or device. Without further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article or apparatus comprising said element.

Although the embodiments of the present invention have been shown and described, those skilled in the art can understand that various changes, modifications and substitutions can be made to these embodiments without departing from the principle and spirit of the present invention. and modifications, the scope of the invention is defined by the appended claims and their equivalents.

Claims (6)

1. a kind of piezo-electric resonator of narrow support frame high quality factor, it is characterised in that: including substrate (1), support layer (5), bottom Layer electrode (8), air-gap (4), upper electrode (10) and piezoelectric layer (9), the surface of the substrate (1) are provided with groove and described The surface of substrate (1) is fixed with the support layer (5), and the air-gap (4) are formed between the support layer (5) and the groove And air is filled in the air-gap (4), the surface of the support layer (5) is fixed with the bottom electrode (8), the bottom The surface of electrode (8) is fixed with the piezoelectric layer (9), and the surface of the piezoelectric layer (9) is fixed with the upper electrode (10), institute The lower section for stating support layer (5) is equipped with multiple highly-resistant material layers (6) and low resistivity materials layer (7), the highly-resistant material layer (6) and low resistivity materials layer (7) interval is arranged and the number of plies of the highly-resistant material layer (6) and low resistivity materials layer (7) Identical, the highly-resistant material layer (6) is fixed on the substrate (1), and the upper surface of the low resistivity materials layer (7) is fixed with The support layer (5).

2. a kind of piezo-electric resonator of narrow support frame high quality factor according to claim 1, it is characterised in that: the pressure Electric layer (9) is AIN piezoelectric membrane, and the substrate (1) is earth silicon material, the bottom electrode (8) and upper electrode (10) Material used is one of Au, Mo, W, Pt.

3. a kind of piezo-electric resonator of narrow support frame high quality factor according to claim 1, it is characterised in that: the sky Air gap (4) contacts the lower surface of the support layer (5) directly with air, and acoustic wave energy is limited in workspace.

4. a kind of preparation side of the piezo-electric resonator of narrow support frame high quality factor according to claim 1-3 Method, characterized by the following steps:

(1): using the Si piece of standard RCA technique cleaning twin polishing, Si piece is substrate material, is then pasted at interval described Highly-resistant material layer (6) and low resistivity materials layer (7) then all use PECVD method to deposit one layer of 100nm/ on Si piece two sides The SiN of 100nm thickness₄/SiO₂Film；

(2): then use DC magnetron sputtering method deposition 100nm/10nm Pt/Ti as bottom electrode (8), and with photoetching, Stripping technology forms hearth electrode figure；

(3): after removing photoresist, using superconducting RF, AlN piezoelectric membrane being prepared with the sputtering condition of optimization, AlN piezoelectricity is thin For film as piezoelectric layer (9), thickness is about 1.8 μm, is etched later using diluted tetramethyl ammonium hydroxide solution as etching liquid Piezoelectricity layer pattern；

(4): and then again using the Au top electrode of DC magnetron sputtering method deposition 300nm, Au top electrode is as upper electrode (10)；

(5): finally etching SiN in the back photoetching of substrate (1) and with reactive ion etching process₄/SiO₂Film is formed to be etched Cavity window is lost, cavity window is air-gap (4)；Again using the mixed solution of KOH solution and aqueous isopropanol as etching liquid, etching Si piece substrate under window, obtains back cavity, and back cavity is air-gap (4).

5. a kind of preparation method of the piezo-electric resonator of narrow support frame high quality factor according to claim 4, feature It is: in step (5), air is inserted in the air-gap (4), the lower surface of the substrate (1) is coated with a conductive silver The surface mount of rubber cement (3), the conductive silver rubber cement (3) has quartz glass plate (2), and after the two bonding, it is in constant temperature 20 DEG C environment in solidified.

6. a kind of preparation method of the piezo-electric resonator of narrow support frame high quality factor according to claim 5, feature Be: the conductive silver rubber cement (3) with a thickness of 40-60 μm.