Full-bridge resistance strain type pressure sensor and preparation method thereof

Abstract

The present invention discloses a full-bridge resistive strain type pressure sensor and a preparation method thereof, wherein the pressure sensor comprises a substrate and four resistive strain sensing units formed on the substrate, wherein the resistive strain sensing units comprise grooves on the substrate and semiconductor materials filled in the grooves by a molten deposition process, wherein the four resistive strain sensing units are centrally symmetrically distributed on the substrate and are prepared and formed in the same molten deposition process, wherein a metal pad is arranged on the connection node of any two resistive strain sensing units; wherein the resistive strain sensing units comprise a plurality of straight portions and a connection portion connecting the plurality of straight portions in series, wherein the straight portions extend in a direction from one of the metal pads to another adjacent metal pad. The present invention simultaneously prepares four resistive strain sensing units constituting a full-bridge circuit on the substrate by the same molten deposition process, so that the pressure sensor has the advantages of small size and high sensitivity.

Description

Technical Field

[0001] The present invention relates to the technical field of pressure sensors, and in particular to a full-bridge resistance strain type pressure sensor and a preparation method thereof. Background Art

[0002] Strain gauge pressure sensors work based on the principle of resistance strain effect. Resistance strain gauges are divided into two categories: metal strain gauges (metal wire or metal foil) and semiconductor strain gauges. The resistance value of metal strain gauges changes mainly due to changes in shape, while the semiconductor diffusion resistor changes when strain is applied to the lattice, causing the carrier mobility to change and causing the resistance to change significantly. The change in the resistance value of the strain gauge is then used to obtain the corresponding millivolt potential output through a bridge circuit, and the measured pressure is displayed using a millivoltmeter or other recording instrument, thus forming a strain gauge pressure sensor. Semiconductor strain sensors have the advantages of small size, high precision, low cost, good responsiveness, repeatability, and vibration resistance, and are widely used in aerospace, chemical, automotive, medical equipment and other fields.

[0003] Currently, semiconductor strain gauges are mainly silicon strip strain gauges. To make a silicon strip strain gauge into a full-bridge circuit, four silicon strip strain gauges need to be packaged together. The prepared full-bridge circuit is large in size, has high requirements for post-production process, and has low accuracy. Summary of the invention

[0004] In view of this, the present invention provides a full-bridge resistive strain gauge pressure sensor and a preparation method thereof to solve the problem of large size of existing full-bridge pressure sensors based on silicon strip strain gauges.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A full-bridge resistive strain pressure sensor, comprising a substrate and four resistive strain sensing units formed on the substrate and connected end to end in sequence, wherein the resistive strain sensing unit comprises a groove formed on the substrate and a semiconductor material filled in the groove by a molten deposition process, the four resistive strain sensing units are centrally symmetrically distributed on the substrate and are prepared and formed in the same molten deposition process, and a metal pad is provided on the connection node of any two of the resistive strain sensing units;

[0007] The resistive strain sensing unit includes a plurality of straight line portions and a connecting portion that sequentially connects the plurality of straight line portions in series, and the straight line portions extend in a direction from one metal pad to another adjacent metal pad.

[0008] Preferably, a metal connecting strip is deposited on the connecting portion.

[0009] Preferably, the four resistive strain sensing units are distributed on the substrate in a 90° rotationally symmetrical manner.

[0010] Preferably, the substrate is a silicon dioxide substrate, and the semiconductor material is single crystal silicon.

[0011] Preferably, the semiconductor material is doped with oxygen, hydrogen, boron or cobalt, with a doping concentration of 10 10 cm -3 ~10 18 cm -3 .

[0012] Preferably, in the resistive strain sensing unit, the doping concentration of the straight portion is lower than the doping concentration of the connecting portion.

[0013] Preferably, the width of the groove is 10 μm to 20 μm, and the depth of the groove is 5 μm to 25 μm.

[0014] Another aspect of the present invention is to provide a method for preparing the full-bridge resistive strain gauge pressure sensor as described above, comprising:

[0015] Providing a substrate, and etching a corresponding groove structure on the substrate through an etching process according to the shape structure of the resistive strain sensing unit and the distribution structure of the four resistive strain sensing units;

[0016] Depositing the semiconductor material in the groove structure by a molten deposition process to prepare four resistive strain sensing units;

[0017] The full-bridge resistive strain type pressure sensor is obtained by depositing a metal pad on the connection node of any two of the resistive strain sensing units through a metal deposition process.

[0018] Furthermore, the preparation method further comprises: depositing a metal connecting strip on the connecting portion by a metal deposition process, and / or doping oxygen, hydrogen, boron or cobalt into the semiconductor material by an ion implantation process.

[0019] Preferably, the etching process is an ion etching process, the molten deposition process is a suspended zone solution process and a horizontal zone solution process, and the metal deposition process is a 3D printing process.

[0020] The full-bridge resistive strain pressure sensor provided in the embodiment of the present invention is prepared on a substrate through the same molten deposition process to obtain four resistive strain sensing units constituting a full-bridge circuit. The four resistive strain sensing units are integrated on the same substrate, so that the full-bridge resistive strain pressure sensor has the advantages of small size and high sensitivity. In addition, the preparation process of the full-bridge resistive strain pressure sensor is simple and easy to implement, which is conducive to large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic structural diagram of a full-bridge resistive strain gauge pressure sensor in an embodiment of the present invention;

[0022] Figure 2 is a schematic structural diagram of a resistive strain sensing unit in an embodiment of the present invention;

[0023] Figures 3 to 5 It is an exemplary diagram of the preparation process flow of the full-bridge resistive strain pressure sensor in an embodiment of the present invention. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the present invention clearer, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. Examples of these preferred embodiments are illustrated in the accompanying drawings. The embodiments of the present invention shown in the accompanying drawings and described according to the accompanying drawings are merely exemplary, and the present invention is not limited to these embodiments.

[0025] It should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, only structures and / or processing steps closely related to the solutions according to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0026] The embodiment of the present invention first provides a full-bridge resistive strain gauge pressure sensor. Figure 1 and Figure 2 The full-bridge resistive strain pressure sensor includes a substrate 10 and four resistive strain sensing units 20 formed on the substrate 10. The resistive strain sensing unit 20 includes a groove 21 formed on the substrate 10 and a semiconductor material 22 filled in the groove 21 by a molten deposition process.

[0027] Among them, Figure 1As shown, the four resistive strain sensing units 20 are connected end to end in sequence, that is, one end of the first resistive strain sensing unit 20 is connected to one end of the second resistive strain sensing unit 20, the other end of the second resistive strain sensing unit 20 is connected to one end of the third resistive strain sensing unit 20, the other end of the third resistive strain sensing unit 20 is connected to one end of the fourth resistive strain sensing unit 20, and the other end of the fourth resistive strain sensing unit 20 is connected to the other end of the first resistive strain sensing unit 20, thereby the connection mode of the four resistive strain sensing units 20 constitutes a full-bridge circuit connection mode.

[0028] The four resistive strain sensing units 20 are centrally symmetrically distributed on the substrate 10 and are prepared in the same melt deposition process, and a metal pad 30 is provided on the connection node of any two of the resistive strain sensing units 20. In this embodiment, as a preferred technical solution, the four resistive strain sensing units 20 are 90° rotationally symmetrically distributed on the substrate 10, that is, the outer peripheral contour of the layout structure of the four resistive strain sensing units 20 is in the shape of a square.

[0029] Among them, see 1 and Figure 2 The resistance strain sensing unit 20 includes a plurality of straight portions 20a and a connecting portion 20b that sequentially connects the plurality of straight portions 20a in series, and the straight portion 20b extends from one metal pad 30a to another adjacent metal pad 30b. In this embodiment, as a preferred technical solution, Figure 2 As shown, the resistive strain sensing unit 20 includes three straight portions 20a and two connecting portions 20b that connect the three straight portions 20a in series in sequence, one end of the three straight portions 20a connected in series is connected to one of the metal pads 30a, and the other end is connected to another of the metal pads 30b.

[0030] The shape structure of the groove 21 needs to be designed according to the shape structure of the resistive strain sensing unit 20. In a preferred solution, the width of the groove is 10 μm to 20 μm, and the depth of the groove is 5 μm to 25 μm.

[0031] The full-bridge resistive strain pressure sensor as described above is prepared on a substrate through the same molten deposition process to obtain four resistive strain sensing units 20 constituting a full-bridge circuit. The four resistive strain sensing units 20 are integrated on the same substrate 10, so that the full-bridge resistive strain pressure sensor has the advantages of small size and high sensitivity. In addition, the resistive strain sensing units 20 prepared simultaneously based on the same process have a resistivity of 4Ω·m to 15Ω·m, and the resistance values ​​of the four resistive strain sensing units 20 in the full-bridge resistance circuit are basically matched, avoiding the problem of difficulty in matching the resistance values ​​of four single resistor bars or two resistor bars connected in series and difficulty in ensuring the installation position.

[0032] In this embodiment, as a preferred technical solution, Figure 1 and Figure 2 As shown, in the resistive strain sensor unit 20, a metal connecting bar 40 is deposited on the connecting portion 20b.

[0033] In this embodiment, as a preferred technical solution, the substrate 10 is a silicon dioxide substrate, the semiconductor material 22 is single crystal silicon, and the resistance strain sensing unit 20 formed thereby is a silicon strip strain gauge. The thermal expansion coefficients of silicon and carbon dioxide are very small, and they are directly bonded through the interface without other transition layers, thereby avoiding thermal stress caused by temperature fluctuations and improving the mechanical properties and high temperature stability of the sensor.

[0034] In this embodiment, as a preferred technical solution, in the resistive strain sensor unit 20, the semiconductor material 22 is doped with oxygen, hydrogen, boron or cobalt elements, and the doping concentration is 10 10 cm -3 ~10 18 cm -3 By ion implanting oxygen, hydrogen, boron, cobalt and other elements, the resistance value of the silicon strip is modulated to be in a stable performance state, avoiding large sensitivity dispersion (due to the influence of factors such as crystal orientation and impurities) and large nonlinear errors under large strains, which cause product performance fluctuations, making the sensor have high sensitivity and stable performance.

[0035] In a further preferred embodiment, in the resistive strain sensing unit 20, the doping concentration of the straight portion 20a is less than the doping concentration of the connecting portion 20b. In one of the resistive strain sensing units 20, the straight portion 20a has a longer length and can be understood as a transverse silicon strip, and the connecting portion 20b has a relatively shorter length and can be understood as a longitudinal silicon strip. The transverse and longitudinal silicon strips use different doping amounts, and the transverse silicon strip (i.e., the straight portion 20a) is lightly doped with a concentration of 10 10 cm -3 ~10 15 cm -3In order to improve the sensitivity of the silicon strip, the longitudinal silicon strip (i.e., the connecting portion 20b) is heavily doped with a concentration of 10 16 cm -3 ~10 18 cm -3 Therefore, the entire silicon strip of the resistance strain sensing unit 20 has different sensitivities in the horizontal and vertical directions, and at the same time, the longitudinal resistance length is reduced and the transverse resistance length is increased, thereby reducing the noise interference caused by the longitudinal strain.

[0036] The present invention also provides a method for preparing the full-bridge resistive strain gauge pressure sensor as described above. Figures 3 to 5 Combined with Figure 1 and Figure 2 , the preparation method comprises the following steps:

[0037] Step S10: Figure 3 As shown, firstly, a substrate 10 is provided, and then, according to the shape structure of the resistive strain sensing unit 20 and the distribution structure of the four resistive strain sensing units 20 , a corresponding groove structure 10 a is formed on the substrate 10 through an etching process A1.

[0038] For example, in this embodiment, the substrate 10 is a silicon dioxide substrate, and the shape structure of the resistive strain sensing unit 20 is as follows: Figure 2 The structure shown includes three straight portions 20a and two connecting portions 20b that connect the three straight portions 20a in series. The four resistive strain sensing units 20 are distributed on the substrate 10 in a 90° rotational symmetric manner. Therefore, when the groove structure 10a is etched to form the groove structure 10a, the groove 21 corresponding to each resistive strain sensing unit 20 also includes three straight portions and two connecting portions that connect the three straight portions, and the groove structure 10a as a whole is also distributed on the substrate 10 in a 90° rotational symmetric manner.

[0039] In a preferred embodiment, the etching process is an ion etching process. Ion etching is a process that uses high-energy inert gas ions (such as Ar + ) or corrosive gases (such as CHF3 or CF4 / H2) bombard the surface of the etched object (silicon dioxide substrate) to achieve the effect of sputtering etching.

[0040] Step S20: Figure 4 As shown, the semiconductor material 22 is deposited in the groove structure 10 a by a molten deposition process to prepare and form four resistive strain sensing units 20 .

[0041] The resistance strain sensing unit 20 includes three straight portions 20 a and two connecting portions 20 b that sequentially connect the three straight portions 20 a in series.

[0042] The molten deposition process includes a suspension zone solution process A2 and a horizontal zone solution process A3. First, the single-element polycrystalline silicon material locally melted above 1420°C is concentrated in the groove by the suspension zone solution process A2, and a silicon single crystal is formed by controlling a certain continuous temperature gradient field, and then the grain orientation is modulated by the horizontal zone solution process A3.

[0043] The piezoresistive coefficient of single-crystal silicon material is about 1.5 times that of polycrystalline silicon material, which is conducive to obtaining an excellent piezoresistive bridge. Single-crystal silicon has a large piezoresistive anisotropy in each crystal axis direction, and its piezoresistive coefficient is closely related to the crystal orientation. The single-crystal silicon strip is prepared by coupling the suspension zone solution process with the temperature field gradient control. After the molten silicon strip deposited by the suspension zone solution solidifies for a few seconds, the grain orientation is modulated by the horizontal zone solution process A3. Specifically, 10 2 W / mm 2 ~10 6 W / mm 2 A high-energy laser beam is focused on the silicon strip, locally heating it to above 1410°C (below 1723°C) to produce a molten zone. At the same time, the laser beam moves slowly to make the molten zone move synchronously. The molten zone is cooled step by step, directionally crystallized and then solidified under the temperature gradient. The lateral silicon strip is oriented in the

[100] direction. The piezoresistance coefficient of silicon element in the

[100] direction is the largest, that is, the resistivity change caused by bending deformation is the largest, so that the sensor has a higher sensitivity.

[0044] In a further preferred embodiment, see Figure 4 When the semiconductor material 22 is dissolved in the horizontal zone, oxygen, hydrogen, boron or cobalt elements are doped into the semiconductor material 22 through the ion implantation process A4, and the resistance value of the silicon strip is modulated by doping to be in a stable performance state, thereby avoiding a large degree of discrete sensitivity. Among them, by setting the spacing between the working positions of the horizontal zone dissolution process A3 and the ion implantation process A4, the ion implantation process A4 acts on the same position of the silicon strip 1s to 2s later than the horizontal zone dissolution process A3, and the ion implantation process A4 and the horizontal zone dissolution process A3 are performed simultaneously. Therefore, the ion implantation process A4 in the embodiment of the present invention does not require the doping preheating and high-temperature diffusion annealing process in the traditional process, and has high efficiency and stable performance.

[0045] Step S30: Figure 5 As shown, a metal pad 30 is deposited on the connection node of any two of the resistive strain sensing units 20 by a metal deposition process to obtain the full-bridge resistive strain pressure sensor. In a further preferred embodiment, a metal connecting strip 40 is also deposited on the connecting portion 20b in step S30.

[0046] Preferably, the metal deposition process is a 3D printing process. The metal pads and metal connection parts are prepared by 3D printing SLS, 3DP and other technologies, which are firmly bonded to the substrate, with high precision and high efficiency.

[0047] In summary, the full-bridge resistive strain pressure sensor provided in the embodiment of the present invention is prepared on a substrate through the same molten deposition process to obtain four resistive strain sensing units constituting a full-bridge circuit. The four resistive strain sensing units are integrated on the same substrate, so that the full-bridge resistive strain pressure sensor has the advantages of small size and high sensitivity, and the accuracy can be as high as 0.1% to 0.2%. In addition, the preparation process of the full-bridge resistive strain pressure sensor is simple and easy to implement, which is conducive to large-scale industrial production.

[0048] The above is only a specific implementation of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A full-bridge resistive strain gauge pressure sensor, comprising a substrate and four resistive strain gauge sensing units formed on the substrate and connected end to end in sequence, characterized in that: The resistive strain sensing unit includes a groove formed on the substrate and a semiconductor material filled in the groove by a molten deposition process, four resistive strain sensing units are centrally symmetrically distributed on the substrate and are prepared and formed in the same molten deposition process, and a metal pad is provided on the connection node of any two resistive strain sensing units; Wherein, the resistive strain sensing unit comprises a plurality of straight portions and a connecting portion connecting the plurality of straight portions in series in sequence, and the straight portion extends in a direction from one metal pad to another adjacent metal pad; The length of the straight portion is greater than the length of the connecting portion, and in the resistive strain sensing unit, the doping concentration of the straight portion is less than the doping concentration of the connecting portion.

2. The full-bridge resistive strain gauge pressure sensor according to claim 1, characterized in that: A metal connecting strip is deposited on the connecting portion.

3. The full-bridge resistive strain gauge pressure sensor according to claim 1, characterized in that: The four resistance strain sensing units are distributed on the substrate in a 90° rotationally symmetrical manner.

4. The full-bridge resistive strain gauge pressure sensor according to claim 1, characterized in that: The substrate is a silicon dioxide substrate, and the semiconductor material is single crystal silicon.

5. The full-bridge resistive strain gauge pressure sensor according to claim 4, characterized in that: The semiconductor material is doped with oxygen, hydrogen, boron or cobalt elements, and the doping concentration is 10 10 cm -3 ~10 18 cm -3 .

6. The full-bridge resistive strain gauge pressure sensor according to any one of claims 1 to 5, characterized in that: The width of the groove is 10 μm to 20 μm, and the depth of the groove is 5 μm to 25 μm.

7. A method for preparing a full-bridge resistive strain gauge pressure sensor as claimed in any one of claims 1 to 6, characterized in that: include: Providing a substrate, and etching a corresponding groove structure on the substrate through an etching process according to the shape structure of the resistive strain sensing unit and the distribution structure of the four resistive strain sensing units; Depositing the semiconductor material in the groove structure by a molten deposition process to prepare four resistive strain sensing units; The full-bridge resistive strain type pressure sensor is obtained by depositing a metal pad on the connection node of any two of the resistive strain sensing units through a metal deposition process.

8. The method for preparing a full-bridge resistive strain gauge pressure sensor according to claim 7, characterized in that: Also includes: A metal connecting strip is deposited on the connecting portion by a metal deposition process, and / or oxygen, hydrogen, boron or cobalt is doped into the semiconductor material by an ion implantation process.

9. The method for preparing a full-bridge resistive strain gauge pressure sensor according to claim 8, characterized in that: The etching process is an ion etching process, the molten deposition process is a suspended zone solution process and a horizontal zone solution process, and the metal deposition process is a 3D printing process.

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