CN110943156B - Pressure sensor based on piezoelectric material and preparation method - Google Patents

Abstract

The invention provides a pressure sensor based on piezoelectric materials and a preparation method thereof, wherein the pressure sensor takes silicon on an insulator as a substrate, and d33 mode piezoelectric materials and junction field effect transistors which are interconnected through metal electrodes and are arranged alternately are arranged on the substrate. The invention does not need additional power supply, can greatly simplify subsequent circuits and has high measurement precision.

Description

Pressure sensor based on piezoelectric material and preparation method

Technical Field

The invention relates to a pressure sensor based on a piezoelectric material, belongs to the field of microelectronic devices, and particularly relates to a pressure sensor based on a piezoelectric material and a preparation method thereof.

Background

The pressure sensor is widely applied to the fields of electronic technology, instruments and meters, Internet of things and the like, and is responsible for converting pressure mechanical quantity in the environment into electrical quantity which can be processed by an electronic system. The existing pressure sensing solution is of a resistance type and a capacitance type, and the two solutions are respectively applied to the field of consumer electronics in the last century and the early century, especially the fields of touch screens, fingerprint identification, electronic scales and the like. In recent years, with the breakthrough of the research on piezoelectric materials, it is possible to introduce the piezoelectric materials into a planar process, and the design and research on pressure sensors based on the piezoelectric effect are increasing.

The resistive and capacitive pressure sensors require an additional power supply in conversion between mechanical quantity and electrical quantity, the resistive pressure sensors require a direct current signal for detecting the change of resistance, which brings additional power consumption, the capacitive pressure sensors require an alternating current type for detecting the change of impedance, the detection signals interfere other equipment while bringing additional power consumption, and the additional signal sources of the two signals also cause the increase of circuit scale.

Disclosure of Invention

The invention aims to: the invention provides a pressure sensor based on piezoelectric materials and a preparation method thereof, aiming at the problems in the prior art, the invention realizes the direct conversion of pressure mechanical quantity and electrical quantity through piezoelectric effect, converts the pressure mechanical quantity into the voltage electrical quantity through piezoelectric effect, outputs the voltage electrical quantity after amplifying the voltage electrical quantity through adjacent junction field effect tubes, and obtains the corresponding pressure value through the measurement of structures such as an analog-digital converter of an external circuit.

The invention aims to be realized by the following technical scheme:

a pressure sensor based On piezoelectric materials is characterized in that SOI (Silicon On Insulator) is used as a substrate of the pressure sensor, d33 mode piezoelectric materials and JFETs (Junction Field-Effect transistors) which are arranged at intervals in a staggered mode are arranged On the substrate, and in two-dimensional arrangement, one JFET is staggered among sensors in different rows so as to improve the accuracy of a large-area sensor.

The junction field effect transistor can be an N-channel junction field effect transistor or a P-channel junction field effect transistor, an external circuit has two outputs, namely a Source electrode and a Drain electrode, and the two can be interchanged under a specific electrical environment.

The piezoelectric material works in a d33 mode, and has three electrodes including a middle common electrode COM and output electrodes Gate at two sides, wherein the common electrode COM is directly grounded, and the output electrodes are simultaneously used as the gates of the junction field effect transistors at two sides.

The output electrode of the piezoelectric material and the grid structure of the adjacent junction field effect transistor are the same electrode which is directly connected electrically, and the electrode is connected with the silicon substrate on the insulator through ohmic contact. The polarization direction of the piezoelectric material is determined according to the type of the selected junction field effect transistor, and the difference of the polarization directions can cause the polarity of the potential difference generated by the output electrode when the pressure sensor is stressed and relative to the common electrode to be different, and the potential difference can be a positive value or a negative value.

The piezoelectric material is ZnO, PZT-5 series or AlN. When the pressure sensor is subjected to external pressure, the output electrode of the piezoelectric material generates voltage, the voltage is directly applied to the grid electrode of the field effect tube, current is generated between the source electrode and the drain electrode, and the external circuit can detect the change of the external pressure by measuring the current between the source electrode and the drain electrode.

A method of making a piezoelectric material based pressure sensor, the method comprising the steps of:

a) providing a P-type doped silicon-on-insulator substrate;

b) doping N-type impurities at the position of the field effect transistor N well to form a channel of the junction field effect transistor;

c) doping N-type impurities at the positions of a source electrode and a drain electrode of the field effect transistor to form a high-concentration source region and a high-concentration drain region;

d) depositing a layer of insulating material, and performing surface planarization treatment through CMP after the deposition is finished;

e) etching the insulating material at the position of the piezoelectric material;

f) depositing a piezoelectric material, performing surface planarization treatment through CMP after the deposition is finished, and simultaneously downwards grinding the redundant piezoelectric material until the top insulating material is exposed;

g) etching the insulating material and the piezoelectric material at the position of the metal electrode;

h) sputtering a metal material, wherein the metal forms an electrode in the piezoelectric material layer and the insulating material layer, ohmic contact is formed between the metal and the silicon material below, and after sputtering is finished, surface planarization treatment is carried out through CMP, and a metal film with a certain thickness is reserved;

i) and etching the redundant metal material except the metal lead.

Compared with the prior art, the invention has the following advantages:

1. the electric signal generated by the piezoelectric effect can be directly output, an additional power supply is not needed for conversion between mechanical quantity and electrical quantity, the resistance-type sensor needs a direct-current signal for testing the change of the resistance, and the capacitance screen needs an alternating-current signal for measuring the change of the impedance;

2. the piezoelectric effect can directly output the electric signals, so that the subsequent circuit can obtain the magnitude of the pressure value only by measuring the quantity of the part of the electric signals without measuring the impedance change, and the design of the subsequent circuit and the scale and the design difficulty of the whole system are simplified;

3. the electric signal generated by the piezoelectric material after being subjected to external pressure can be directly amplified by the junction field effect transistor beside and then output, so that the measurement precision is improved;

4. the piezoelectric material can directly output the electric quantity, so that the dynamic pressure change can be conveniently output;

5. compact structure and high integration level.

Drawings

Fig. 1 is a block diagram of a single row pressure sensor of the present invention.

Fig. 2 shows the material layer distribution and the doping distribution of the silicon material under the condition of the N-channel JFET according to the present invention.

Fig. 3 is an equivalent circuit diagram of the pressure sensing unit of the present invention.

Fig. 4-12 are process flow diagrams illustrating the fabrication of an N-channel JFET according to the present invention, wherein fig. 4 provides a P-type SOI substrate; FIG. 5 is doping to form an N-well; FIG. 6 is a doping process to form a high concentration N well; FIG. 7 illustrates the deposition of a layer of insulating material; FIG. 8 is a region where the piezoelectric material is etched; FIG. 9 illustrates the deposition of piezoelectric material; FIG. 10 illustrates an area where a metal material is etched; FIG. 11 is a sputtering of a metallic material; fig. 12 illustrates the formation of metal leads by etching (the material is illustrated in the same manner as in fig. 2).

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments.

Examples

Referring to fig. 1, the pressure sensor based on the d33 piezoelectric material and the jfet of the present invention uses SOI as a substrate, and d33 mode piezoelectric materials and jfet are arranged on the substrate at intervals in a staggered manner;

referring to fig. 1, the pressure sensor based on the d33 piezoelectric material and the jfet of the present invention has a jfet which may be an N-channel jfet or a P-channel jfet, and has two outputs, a Source electrode and a Drain electrode, which are interchangeable in a specific electrical environment;

referring to fig. 1, the piezoelectric material of the pressure sensor based on the d33 piezoelectric material and the jfet of the present invention works in a d33 mode, and has three electrodes in total, including a middle common electrode COM and output electrodes Gate at two sides, wherein the common electrode COM is directly grounded, and the output electrodes are simultaneously used as the gates of the jfets at two sides;

referring to fig. 1, when a plurality of rows of sensors are required to be arranged in parallel to form a two-dimensional array (for example, a system requiring a large area and high precision, such as fingerprint recognition), the arrangement between adjacent rows is staggered by one jfet, so as to improve the performance of the pressure sensor in a large area, as shown in table 1:

TABLE 1 two-dimensional array arrangement of sensors

Referring to fig. 2, in the structure of the pressure sensor based on the d33 piezoelectric material and the JFET of the present invention, taking an N-channel JFET as an example, the pressure sensing device uses a P-type doped SOI as a substrate, an N region is doped on the substrate to form a channel of the fet, a higher concentration N region is doped in a source-drain region to form a source-drain region, an insulating material, a piezoelectric material and a metal material are disposed on a semiconductor layer, an output electrode of the piezoelectric material is also a gate of the fet and is directly connected to the P-type substrate through ohmic contact, and the source-drain region is connected to a source and a drain through ohmic contact. Furthermore, the pressure sensor based on the P-channel JFET takes the N-type doped SOI as a substrate, a P-type region is doped on the substrate to form a channel of the field effect transistor, a P region with higher concentration is doped in a source-drain region to form a source-drain region, and the rest structure is the same as that of the sensor based on the N-channel JFET;

referring to fig. 2 and 3, in the pressure sensor based on the d33 piezoelectric material and the jfet of the present invention, when the piezoelectric material is subjected to external pressure, a stress in a plane direction is generated, and the output ends at two ends of the piezoelectric material and the middle common end generate charges with different polarities, because the common end is grounded, a potential difference is generated between the output end and the common end, depending on whether the voltage of the output end in a polarization direction is positive or negative relative to the common end, and because the output end is the gate of the fet, the change of current between the source and the drain of the fet is caused by the pressure change of the piezoelectric material, and the pressure change of the pressure sensor can be obtained by detecting the current change;

referring to fig. 3, in the pressure sensor based on the d33 piezoelectric material and the jfet of the present invention, a single pressure sensing unit has only three output electrodes, which are a common electrode (generally grounded) of the piezoelectric material, and a source electrode and a drain electrode of the fet, and the source electrode and the drain electrode are connected to an external circuit to transmit a converted electrical signal;

the invention also provides a preparation method of the pressure sensor based on the d33 piezoelectric material and the junction field effect transistor, taking the N-type field effect transistor as an example, the method comprises the following steps:

a) referring to fig. 4, a P-type doped SOI substrate is provided;

b) referring to fig. 5, N-type impurities are doped at the position of the N well of the fet to form a channel of the jfet;

c) referring to fig. 6, N-type impurities are doped at the source and drain of the fet to form high-concentration source and drain regions;

d) referring to fig. 7, an insulating material is deposited, and a surface planarization process is performed by CMP after the deposition is completed;

e) referring to fig. 8, the insulating material at the location of the piezoelectric material is etched;

f) referring to fig. 9, a piezoelectric material is deposited, and after the deposition is completed, a surface planarization process is performed by CMP while polishing down the excess piezoelectric material until the top insulating material is exposed;

g) referring to fig. 10, the insulating material and the piezoelectric material at the position of the metal electrode are etched;

h) referring to fig. 11, a metal material is sputtered, the metal forms an electrode in the piezoelectric material layer and the insulating material layer, and simultaneously forms ohmic contact with the underlying silicon material, and after the sputtering is completed, surface planarization treatment is performed by CMP, and a metal film with a certain thickness is retained;

i) referring to fig. 12, the excess metal material outside the metal leads is etched.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, it should be noted that any modifications, equivalents and improvements made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (4)

1. A pressure sensor based on piezoelectric materials is characterized in that silicon on an insulator is used as a substrate, and d33 mode piezoelectric materials and junction field effect transistors which are connected with each other through metal electrodes and are arranged in a staggered mode at intervals are arranged on the substrate; the piezoelectric material works in a d33 mode, and comprises a common electrode in the middle and output electrodes on two sides, wherein the common electrode is directly grounded; the output electrode of the piezoelectric material and the grid structure of the adjacent junction field effect transistor are the same electrode which is directly connected electrically, and the electrode is connected with the silicon substrate on the insulator through ohmic contact.

2. The piezoelectric material-based pressure sensor as claimed in claim 1, wherein the jfet is an N-channel jfet or a P-channel jfet.

3. A piezoelectric material based pressure sensor as claimed in claim 1, wherein the piezoelectric material is ZnO, PZT-5 series or AlN.

4. A method for preparing a pressure sensor according to claim 1, comprising the steps of:

a) providing a P-type doped silicon-on-insulator substrate;

b) doping N-type impurities at the position of the field effect transistor N well to form a channel of the junction field effect transistor;

c) doping N-type impurities at the positions of a source electrode and a drain electrode of the field effect transistor to form a high-concentration source region and a high-concentration drain region;

d) depositing a layer of insulating material, and performing surface planarization treatment through CMP after the deposition is finished;

e) etching the insulating material at the position of the piezoelectric material;

f) depositing a piezoelectric material, performing surface planarization treatment through CMP after the deposition is finished, and simultaneously downwards grinding the redundant piezoelectric material until the top insulating material is exposed;

g) etching the insulating material and the piezoelectric material at the position of the metal electrode;

h) sputtering a metal material, wherein the metal forms an electrode in the piezoelectric material layer and the insulating material layer, ohmic contact is formed between the metal and the silicon material below, and after sputtering is finished, surface planarization treatment is carried out through CMP, and a metal film with a certain thickness is reserved;

i) and etching the redundant metal material except the metal lead.

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