CN104401932A - AlN piezoelectric film device with duplexer function and preparation method thereof - Google Patents

Abstract

The invention discloses an AlN piezoelectric film device with a duplexer function. The AlN piezoelectric film device comprises a Si substrate, an insulation layer, a bottom electrode, an AlN film layer I, an intermediate electrode, an AlN film layer II and a top electrode from bottom to top, wherein the C axis of the AlN film layer I and the C axis of the AlN film layer II are tilted relative to the Si substrate (1) and in the opposite directions; the thickness of the Si substrate is 300-700 mu m; the insulation layer is an SiO layer, and the thickness is 250-350 nm; the bottom electrode is made of Mo or Ti/Pt; the intermediate electrode is made of Ir or Mo; the thickness of each of the bottom electrode and the intermediate electrode is 120-160 nm; and the top electrode is made of Al, and the thickness is 1,000-1,200 nm. An AlN piezoelectric film layer structure provided with double-layer tilted C axes is provided creatively, the sensitivity of a sensor can be greatly improved by the structure in the liquid phase working environment, two-way communication of a film bulk acoustic wave device is realized, and the size of the device is reduced.

Description

A kind of aluminum nitride piezoelectric film device with duplexer function and its preparation method

technical field

The invention belongs to the field of micro-opto-electromechanical systems, relates to an aluminum nitride piezoelectric film device with a duplexer function, in particular to a double-layer C-axis tilted aluminum nitride ( AlN) piezoelectric thin film device and its preparation method.

Background technique

Aluminum nitride piezoelectric film has the advantages of high sound velocity, high temperature resistance, stable performance, and is compatible with CMOS technology, and has attracted widespread attention at home and abroad. MEMS devices based on the preparation of AlN piezoelectric thin films have been widely used in the fields of sensors, resonators and energy harvesters.

When the thin-film bulk acoustic resonator with silicon-based AlN film preparation as the core technology is applied to liquid detection, if the bulk acoustic wave works in the length stretching mode, a large amount of acoustic wave energy will be lost in the liquid and the detection sensitivity of the sensor will be reduced; When working in the thickness-shear mode, the energy loss of the acoustic wave in the liquid is small, which is conducive to improving the sensitivity and quality factor of the sensor; in addition, the detection system composed of thin-film bulk acoustic wave devices that communicate in a single mode is not only bulky, but also for subsequent Signal processing brings a lot of inconvenience.

Therefore, it is necessary to prepare double-layer C-axis tilted piezoelectric films that can excite the thickness-shear mode and have the function of a duplexer.

Contents of the invention

In view of this, the object of the present invention is to provide an aluminum nitride piezoelectric thin film device with a duplexer function.

To achieve the above object, the present invention provides the following technical solutions:

An aluminum nitride piezoelectric thin film device with a duplexer function, comprising a silicon substrate, an insulating layer, a lower electrode, a first aluminum nitride thin film layer, an intermediate electrode, a second aluminum nitride thin film layer and For the upper electrode, the C axes of the first aluminum nitride thin film layer and the second aluminum nitride thin film layer are inclined to the silicon substrate, and the inclination directions of the two are opposite.

As a preference of the aluminum nitride piezoelectric thin film device of the present invention, the wire bonding area on the upper surface of the lower electrode is also compounded with a metal aluminum layer for wire bonding.

As another preference of the aluminum nitride piezoelectric thin film device of the present invention, the thickness of the silicon substrate is 300-700 um, and the insulating layer is a silicon dioxide layer with a thickness of 250-350 nm.

As another preference of the aluminum nitride piezoelectric thin film device of the present invention, the material of the lower electrode is Mo or Ti/Pt, and its thickness is 120-160 nm.

As a further preference of the aluminum nitride piezoelectric thin film device of the present invention, the material of the intermediate electrode is Ir or Mo, and its thickness is 120-160 nm.

As a further preference of the aluminum nitride piezoelectric thin film device of the present invention, the material of the upper electrode is Al, and its thickness is 1000-1200 nm.

As a further preference of the aluminum nitride piezoelectric thin film device of the present invention, the thicknesses of the first aluminum nitride thin film layer and the second aluminum nitride thin film layer are both 0.8-1.2 μm. The invention also discloses a method for preparing the aluminum nitride piezoelectric thin film device with a duplexer function, comprising the following steps:

1) Take a silicon wafer with a thickness of 300-700um as the substrate;

2) double-sided thermal oxidation 1) the selected substrate, so that _SiO2 layers with a thickness of 250-350nm are formed on the upper and lower surfaces;

3) growing a Mo or Ti/Pt lower electrode layer on the surface of the upper SiO ₂ layer and patterning it, controlling its thickness to be 200-250nm;

4) Using magnetron sputtering technology to sequentially grow the first aluminum nitride thin film layer, Ir or Mo intermediate electrode layer and the second aluminum nitride thin film layer on the Mo or Ti/Pt electrode and pattern them respectively;

5) growing and patterning an Al upper electrode layer on the II aluminum nitride film layer;

6) Etching and removing the _SiO2 layer at the lower part of the silicon substrate first, and then growing and patterning an aluminum layer with a thickness of 80-100 nm on the lower part of the silicon substrate;

7) Using the Al layer as a mask layer, plasma etch the silicon substrate to the upper SiO ₂ layer to form holes through the silicon substrate.

In particular, step 4) controls the thickness of the first aluminum nitride thin film layer and the second aluminum nitride thin film layer to be 0.8-1.2 μm, and the thickness of the Ir or Mo intermediate electrode layer to be 120-160 nm.

The beneficial effects of the present invention are:

The present invention creatively proposes a double-layer C-axis inclined AlN piezoelectric film layer structure, which can greatly improve the sensitivity of the sensor in a liquid-phase working environment, realize two-way communication of the film bulk acoustic wave device and reduce its volume; the present invention Further optimized each layer thickness and raw material of this piezoelectric film layer, this is equally important for obtaining high-performance piezoelectric film layer structure; An intermediate electrode layer is arranged between the aluminum nitride film layers, and the inclination mode of the first and second aluminum nitride film layers is adjusted, so that the device has a two-way communication function; the present invention considers the needs of device wire bonding, and uses aluminum metal as the lead wire Bonded direct contact material.

Description of drawings

In order to make the purpose, technical scheme and beneficial effect of the present invention clearer, the present invention provides the following drawings for illustration:

Fig. 1 is a schematic diagram of the structure of the present invention having a double-layer C-axis tilted AlN piezoelectric film layer;

Fig. 2 is the schematic diagram of step 1) of preparing an aluminum nitride piezoelectric thin film device with duplexer function in embodiment 1;

Fig. 3 is the schematic diagram of step 2) of preparing an aluminum nitride piezoelectric thin film device with duplexer function in embodiment 1;

4 is a schematic diagram of step 3) of preparing an aluminum nitride piezoelectric thin film device with a duplexer function in Example 1;

Fig. 5 is the schematic diagram of step 4) of preparing an aluminum nitride piezoelectric thin film device with a duplexer function in embodiment 1;

6 is a schematic diagram of step 5) of preparing an aluminum nitride piezoelectric thin film device with a duplexer function in Example 1;

FIG. 7 is a schematic diagram of Step 6) of preparing an aluminum nitride piezoelectric thin film device with a duplexer function in Example 1. FIG.

Detailed ways

The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

The following embodiments will disclose a kind of aluminum nitride piezoelectric film device with duplexer function, as shown in Figure 1: comprise silicon substrate 1, insulating layer 2, lower electrode 3, the 1st aluminum nitride successively from bottom to top Thin film layer 4, intermediate electrode 5, the second aluminum nitride thin film layer 6 and upper electrode 7, the C axis of the first aluminum nitride thin film layer 4 and the second aluminum nitride thin film layer 6 is inclined to the silicon substrate 1 and Both tilt in opposite directions. (C-axis tilt means that the angle between the columnar crystal of the aluminum nitride film and the substrate is not at right angles)

Wherein: the lower surface of the silicon substrate 1 is compounded with a metal aluminum layer for wire bonding;

The silicon substrate 1 has a thickness of 300-700um, and the insulating layer 2 is a silicon dioxide layer with a thickness of 250-350nm;

The material of the lower electrode 3 is Mo or Ti/Pt (Ti, Pt composite layer), and its thickness is 120-160nm;

The material of the intermediate electrode 5 is Ir or Mo, and its thickness is 120-160 nm;

The upper electrode 7 is made of Al, and its thickness is 1000-12000nm;

The thicknesses of the first aluminum nitride thin film layer 4 and the second aluminum nitride thin film layer 6 are both 0.8-1.2 μm.

Example 1:

The method for preparing an aluminum nitride piezoelectric thin film device with a duplexer function in this embodiment specifically includes the following steps:

a As shown in Figure 1, first take a 4-inch N-type silicon wafer (100 sides) as the substrate 1 with a thickness of 500um, and then double-sided thermal oxidation 1) The selected substrate is formed so that the upper and lower surfaces are respectively formed with a thickness of 300nm SiO ₂ layer 2;

b As shown in Figure 2, grow and pattern the Mo lower electrode layer 3 on the surface of the upper SiO ₂ layer 2, and control its thickness to 120-160 nm;

c As shown in Figure 3, the first aluminum nitride film layer 4, the Ir intermediate electrode layer 5 and the second aluminum nitride film layer 6 are sequentially grown on the Mo electrode by magnetron sputtering technology and patterned respectively; The sputtering process makes the thickness of the first aluminum nitride thin film layer 4 and the second aluminum nitride thin film layer 6 be 1um respectively, and the thickness of the Ir intermediate electrode layer 5 is 120nm;

d As shown in Figure 4, grow Al upper electrode layer 7 and patterning on the II aluminum nitride film layer 6; Control Al upper electrode layer 7 thickness to be 1000nm; Also compounded with metal aluminum layer for wire bonding)

e as shown in Figure 5, first reactive ion etching removes SiO ₂ layer 2 at the lower part of the silicon substrate, then grows an aluminum layer 8 with a thickness of 100 nm and patterning at the lower part of the silicon substrate;

f As shown in Figure 6, using the Al layer 8 as a mask layer, inductively coupled plasma etching the silicon substrate 1 to the upper SiO ₂ layer 3,

A hole 9 is formed through the silicon substrate.

The present invention creatively proposes a double-layer C-axis inclined AlN piezoelectric film layer structure, which can greatly improve the sensitivity of the sensor in a liquid-phase working environment, realize two-way communication of the film bulk acoustic wave device and reduce its volume; the present invention Further optimized each layer thickness and raw material of this piezoelectric film layer, this is equally important for obtaining high-performance piezoelectric film layer structure; The intermediate electrode layer is arranged between the aluminum nitride thin film layers, and the inclination mode of the first and second aluminum nitride thin film layers is reasonably adjusted; the present invention considers the needs of device wire bonding, and uses aluminum metal as the direct contact of wire bonding Material.

Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that it can be described in terms of form and Various changes may be made in the details without departing from the scope of the invention defined by the claims.

Claims (8)

1. a kind of aluminum nitride piezoelectric film device with duplexer function, it is characterized in that: comprise silicon substrate (1), insulating layer (2), lower electrode (3), the 1st nitride successively from bottom to top Aluminum film layer (4), intermediate electrode (5), the second aluminum nitride film layer (6) and upper electrode (7), the first aluminum nitride film layer (4) and the second aluminum nitride film layer The C-axis of (6) is inclined to the silicon substrate (1) and the inclination directions of the two are opposite. 2. The aluminum nitride piezoelectric film device with duplexer function according to claim 1, characterized in that: the upper surface wire bonding area of the lower electrode (3) is also compounded with metal aluminum for wire bonding layer. 3. The aluminum nitride piezoelectric thin film device with duplexer function according to claim 1, characterized in that: the thickness of the silicon substrate (1) is 300-700um, and the insulating layer (2) is made of The silicon layer has a thickness of 250-350 nm. 4. The aluminum nitride piezoelectric thin film device with duplexer function according to claim 1, characterized in that: the material of the lower electrode (3) is Mo or Ti/Pt, and its thickness is 120-160 nm. 5. The aluminum nitride piezoelectric film device with duplexer function according to claim 1, characterized in that: the material of the middle electrode (5) is Ir or Mo, and its thickness is 120-160nm, and the upper electrode (7) The material is Al, and its thickness is 1000-1200 nm. 6. the aluminum nitride piezoelectric film device with duplexer function according to claim 1, is characterized in that: the 1st aluminum nitride film layer (4) and the 2nd aluminum nitride film layer (6) The thicknesses are all 0.8 to 1.2 μm. 7. The method for preparing the aluminum nitride piezoelectric thin film device with duplexer function as described in any one of claims 1-6, is characterized in that, comprises the following steps: 1) Take a silicon wafer with a thickness of 300-700um as the substrate; 2) double-sided thermal oxidation 1) the selected substrate to form _SiO2 layers with a thickness of 250-350nm on the upper and lower surfaces; 3) growing a Mo or Ti/Pt lower electrode layer on the surface of the upper SiO ₂ layer and patterning it, controlling its thickness to be 200-250nm; 4) Using magnetron sputtering technology to sequentially grow the first aluminum nitride thin film layer, Ir or Mo intermediate electrode layer and the second aluminum nitride thin film layer on the Mo or Ti/Pt electrode and pattern them respectively; 5) growing and patterning an Al upper electrode layer on the II aluminum nitride film layer; 6) Etching and removing the _SiO2 layer at the lower part of the silicon substrate first, and then growing and patterning an aluminum layer with a thickness of 80-100 nm on the lower part of the silicon substrate; 7) Using the Al layer as a mask layer, plasma etch the silicon substrate to the upper SiO ₂ layer to form holes through the silicon substrate. 8. prepare the method for the aluminum nitride piezoelectric film device with diplexer function according to claim 7, it is characterized in that: step 4) control the I aluminum nitride film layer and the II aluminum nitride film layer thickness to be 0.8-1.2 μm, the thickness of the Ir or Mo intermediate electrode layer is 120-160 nm.