CN103017946A - Micro-electromechanical system (MEMS) piezoresistive multi-axis force sensor and production method thereof - Google Patents

Abstract

The invention discloses a MEMS piezoresistive multi-axis force sensor and a preparation method thereof. The multi-axis force sensor of the present invention includes: a substrate, a cantilever beam and a piezoresistive strip; wherein, one end of the cantilever beam is fixed on the substrate through an anchor point, and the other end is suspended in the air; the piezoresistive strip is arranged on the vertical plane and the parallel plane of the cantilever beam On, the integrated piezoresistive strip. In the present invention, the piezoresistive strips are prepared by oblique injection, and the integrated piezoresistive strips are simultaneously prepared on the vertical and horizontal planes of the cantilever beam, so that when a certain micro-action force is applied, the cantilever beam passes through sensitive bending in the lateral and vertical directions. The change of resistance value during bending indirectly reflects the situation of micro-forces from vertical and horizontal directions. Therefore, in the case of a relatively small system volume, it can measure more accurate multi-directional micro-forces. It is a relatively small-volume, high-sensitivity sensor. application prospects.

Description

A MEMS piezoresistive multi-axis force sensor and its preparation method

technical field

The invention relates to semiconductor manufacturing technology, in particular to a micro-electro-mechanical system (Micro-Electro-Mechanical Systems) MEMS piezoresistive multi-axis force sensor and a preparation method thereof.

Background technique

The research and development of multi-axis force sensor began in the early 1980s, and it is the second micromechanical sensor to enter the market after the micro pressure sensor. As the core device of the miniature inertial combined measurement system, the multi-axis force sensor is a miniature device that can simultaneously measure multiple axial external forces that are orthogonal to each other. MEMS multi-axis force sensor is the cutting-edge high technology of Micro-Electro-Mechanical Systems (Micro-Electro-Mechanical Systems) MEMS, which applies a variety of disciplines and has strategic significance. Due to the advantages of miniaturization, MEMS multi-axis force sensor is widely used in automobiles, Electronics, home appliances, mechanical and electrical industries and military fields have extremely broad application prospects and will be one of the leading industries in the future.

The MEMS biaxial or triaxial force sensors in the prior art can be divided into two types in terms of structural composition: one is to measure the acceleration of 2 or 3 axial directions on the same silicon chip, and the easiest way is to measure the acceleration of 2 or 3 axes on the same silicon chip. Make 2 or 3 independent sensitive element structures on the silicon chip, and then match the corresponding detection circuit; the other is to place 2 or 3 single-degree-of-freedom sensors orthogonally, and then package them together. Simply a combination module for miniature dual or triaxial force transducers. This kind of multi-axis force sensor simply combines single-degree-of-freedom sensors together, which is not only bulky, but also has low precision. Although, a multi-axis force sensor that uses a sensitive element structure to measure the force vector has also appeared, but it is difficult for this sensor to solve the cross-coupling between the various axes.

Contents of the invention

In view of the deficiencies of the prior art proposed above, the present invention provides a MEMS piezoresistive multi-axis force sensor and its preparation method. The sensor of the present invention has advanced manufacturing technology, high sensitivity, relatively small volume, and a monolithic integrated micro-electromechanical system. (Micro-Electro-Mechanical Systems) MEMS multi-axis force sensor improves the stability and reliability of the sensor's measurement signal during use.

An object of the present invention is to provide a MEMS piezoresistive multi-axis force sensor.

The MEMS piezoresistive multi-axis force sensor of the present invention includes: a substrate, a cantilever beam and a piezoresistive strip; wherein, one end of the cantilever beam is fixed on the substrate through an anchor point, and the other end is suspended in the air; the piezoresistive strip is formed by oblique injection On the vertical plane and the parallel plane of the cantilever beam, the integrated piezoresistive strip.

In order to fix the cantilever beam to the bottom more firmly, the area of the anchor point is increased. The bottom area of the anchor point is rectangular, and the long side is perpendicular to the suspended end of the cantilever beam. Therefore, the horizontal section of the cantilever beam is T-shaped. This structure increases the bottom area of the anchor point, thereby making the fixing of the cantilever beam and the substrate more stable.

The material of the substrate adopts semiconductor material. The obliquely implanted ions use trivalent ions.

The MEMS piezoresistive multi-axis force sensor of the present invention adopts the method of oblique injection, tilts a certain angle with the vertical surface of the cantilever beam, performs ion implantation on the vertical surface of the cantilever beam, and prepares piezoresistive strips, and the vertical surface and the horizontal surface are formed simultaneously The piezoresistive strip, thus forming an integrated piezoresistive strip with a triangular three-dimensional structure in section. The piezoresistive strips are arranged on the vertical surface and the parallel surface of the cantilever beam, so that the pressure in the vertical direction and the parallel direction can be detected simultaneously. Moreover, the piezoresistive strips arranged on the vertical plane and the parallel plane of the cantilever beam in the present invention are integrated, which has simple structure, convenient preparation and higher precision.

Since the maximum stress value associated with each cross-section varies linearly with the distance from the free end, piezoresistive strips should be placed on the surface of the cantilever beam close to the fixed end.

The inclined angle between the oblique injection and the vertical plane of the cantilever beam is 20°-45°.

Further, the MEMS piezoresistive multi-axis force sensor of the present invention is connected to an external circuit, the piezoresistive strip on the cantilever beam and the reference resistor are connected to form a simple Wheatstone resistance bridge, and the signal processing circuit is connected.

There is a certain relationship between the change of the resistance value of the piezoresistive strip on the cantilever beam and the magnitude of the micro force applied on the cantilever beam. The cantilever beam can be bent along the horizontal and vertical directions under the action of external force, and the change of resistance value during bending reflects the micro force from the horizontal and vertical directions. By connecting the piezoresistive strip on the detection cantilever beam and the reference resistor into a simple Wheatstone resistance bridge, and the change of the resistance can be obtained through the signal processing circuit, so as to indirectly calculate the micro force on the cantilever beam.

Another object of the present invention is to provide a method for preparing a MEMS piezoresistive multi-axis force sensor.

The preparation method of the MEMS piezoresistive multi-axis force sensor of the present invention comprises the following steps:

1) Provide semiconductor substrates;

2) The cantilever beam is processed by MEMS technology;

3) Inclining at a certain angle with the vertical surface of the cantilever beam, performing ion implantation on the vertical surface of the cantilever beam to prepare piezoresistive strips;

4) The cantilever beam is fixed on the substrate by bonding through the anchor point to complete the preparation of the MEMS piezoresistive multi-axis force sensor.

Wherein, in step 3), the inclination angle between the ion implantation and the vertical plane of the cantilever beam is 20°-45°.

Beneficial effects of the present invention:

The MEMS piezoresistive multi-axis force sensor of the present invention adopts the oblique injection method to prepare the piezoresistive strip, and simultaneously prepares the integrated piezoresistive strip on the vertical plane and the horizontal plane of the cantilever beam, so that when a certain micro force is applied, the cantilever The beam undergoes lateral and vertical sensitive bending, and the change of resistance value during bending indirectly reflects the situation of micro-forces from the vertical and horizontal directions. Therefore, in the case of a relatively small system volume, it can measure more accurate multi-directional micro-forces. It is a relatively small-volume, high-sensitivity sensor. application prospects.

Description of drawings

Fig. 1 is the structural representation of MEMS piezoresistive multi-axis force sensor of the present invention;

Figure 2 is a cross-sectional view of the cantilever beam along line A-A' in Figure 1(a).

Detailed ways

Below in conjunction with accompanying drawing, further illustrate the present invention through embodiment.

As shown in FIG. 1 , the MEMS piezoresistive multi-axis force sensor of the present invention includes: a substrate 1 , a cantilever beam 2 and a piezoresistive strip 3 ; one end of the cantilever beam 2 is bonded to the substrate 1 through an anchor point 21 .

In this embodiment, the anchor point of the cantilever beam is perpendicular to the suspended end, and the horizontal section of the cantilever beam is T-shaped.

The method of oblique injection is adopted, and the angle of inclination to the vertical plane of the cantilever beam is 30°. The section of piezoresistive strip 3 is triangular, as shown in FIG. 2 .

The preparation method of the MEMS piezoresistive multi-axis force sensor of the present invention:

1) Provide a substrate made of silicon;

2) The cantilever beam is processed by MEMS technology, and the horizontal section of the cantilever beam is T-shaped;

3) The angle of inclination to the vertical surface of the cantilever beam is 30°, and germanium ion implantation is performed on the vertical surface of the cantilever beam to prepare a piezoresistive strip;

4) The cantilever beam is fixed on the substrate by bonding through the anchor point to complete the preparation of the MEMS piezoresistive multi-axis force sensor.

Finally, it should be noted that although this specification describes the specific parameters and structures of the present invention in detail through specific embodiments, those skilled in the art should understand that the implementation of the present invention is not limited to the scope of description of the embodiments, without departing from Various modifications and replacements can be made to the present invention within the essence and spirit scope of the present invention, so the protection scope of the present invention is defined by the scope of claims.

Claims (9)

1. A MEMS piezoresistive multi-axis force sensor, characterized in that the multi-axis force sensor comprises: a substrate (1), a cantilever beam (2) and a piezoresistive strip (3); wherein the cantilever beam One end of (2) is fixed to the substrate (1) through an anchor point (21), and the other end is suspended in the air; the piezoresistive strip (3) is formed on the vertical surface of the cantilever beam (2) by oblique injection On the parallel plane, there is an integral piezoresistive strip (3). 2. The multi-axis force sensor according to claim 1, characterized in that, the material of the substrate (1) is a semiconductor material. 3. The multi-axis force sensor according to claim 1, wherein the obliquely injected ions are trivalent ions. 4. The multi-axis force sensor according to claim 1, characterized in that the angle between the oblique injection and the vertical plane of the cantilever beam (2) is 20°-45°. 5. The multi-axis force sensor according to claim 1, characterized in that, the horizontal section of the cantilever beam (2) is T-shaped. 6. The multi-axis force sensor according to claim 5, characterized in that the multi-axis force sensor is connected to an external circuit, and the piezoresistive strip (3) on the cantilever beam (2) and the reference resistor are connected into a simple The Wheatstone resistance bridge, and connected to the signal processing circuit. 7. The multi-axis force sensor according to claim 1, wherein the piezoresistive strip is placed on the surface of the cantilever beam and close to the fixed end. 8. a preparation method of the MEMS piezoresistive multiaxial force sensor claimed in claim 1, is characterized in that, described method comprises the following steps: 1) Provide semiconductor substrates; 2) The cantilever beam is processed by MEMS technology; 3) Inclining at a certain angle with the vertical surface of the cantilever beam, performing ion implantation on the vertical surface of the cantilever beam to prepare piezoresistive strips; 4) The cantilever beam is fixed on the substrate by bonding through the anchor point to complete the preparation of the MEMS piezoresistive multi-axis force sensor. 9 . The preparation method according to claim 8 , wherein, in step 3), the inclination angle between the ion implantation and the vertical plane of the cantilever beam is 20°-45°.

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