Preparation method and performance optimization method of pressure sensor based on silicon wafer material metastable contact

Abstract

The application relates to the technical field of electronic devices and sensors, and particularly discloses a preparation method and a performance optimization method of a metastable contact pressure sensor, which comprises the following steps: S1, selecting two silicon wafers, processing the two silicon wafers to form a main area for constructing a force-sensitive contact area and a lead area for leading electrodes; S2, performing surface cleaning treatment on the processed silicon wafers, and depositing a metal electrode layer on the surface of the lead area to form an ohmic contact electrode with low contact resistance; and S3, stacking the polished surfaces of the two silicon wafers in a facing direction and aligning the two silicon wafers, so that the main areas are overlapped to form the force-sensitive contact area, and the lead areas are exposed for external electrical connection, thereby obtaining the metastable contact pressure sensor based on the silicon wafer material. The sensor prepared by the application realizes high-sensitivity modulation of the carrier tunneling behavior by constructing a metastable contact interface between the two silicon wafers and regulating the interval between the interface under the external pressure, so that the electrical detection of the slight pressure change is realized.

Description

Technical Field

[0001] This invention relates to the field of electronic devices and sensors, specifically to a method for fabricating and optimizing the performance of a pressure sensor based on metastable contacts in silicon wafers. Background Technology

[0002] Pressure sensors are key devices used to convert external mechanical pressure or stress signals into electrical signals, and they have a wide range of applications in industrial automation control, medical testing equipment, consumer electronics products, and structural health monitoring.

[0003] Among existing pressure sensors, piezoelectric pressure sensors have attracted widespread attention in applications such as vibration detection, dynamic pressure, and ultrasonic detection due to their fast response speed and high electromechanical conversion efficiency. However, the piezoelectric effect mainly exists in crystals lacking centrosymmetry, and it is difficult to directly generate an effective piezoelectric response for commonly used centrosymmetric semiconductor materials such as silicon (Si) and germanium (Ge). Furthermore, even in some materials with piezoelectric potential, the excitation of the piezoelectric effect often depends on shear stress in a specific direction or complex external loading conditions, making them unsuitable for conventional vertical pressure detection scenarios. Existing commonly used piezoelectric materials such as zinc oxide (ZnO) and gallium nitride (GaN) typically face problems such as lattice mismatch, thermal expansion coefficient mismatch, and insufficient interfacial chemical stability when integrated with silicon-based processes, thus limiting their large-scale application in mainstream silicon-based microelectronics manufacturing systems.

[0004] Besides the piezoelectric effect, the piezoresistive effect is another electromechanical coupling mechanism widely used in pressure sensing. The piezoresistive effect is prevalent in various materials, and related device structures are mature and have been industrialized. Among them, silicon-based piezoresistive pressure sensors, due to their good process maturity and stability, are widely used in process control and microelectromechanical systems (MEMS). However, the working principle of this type of sensor mainly relies on the small changes in the material's band structure or carrier transport characteristics caused by external pressure. Its intrinsic resistance changes within a limited range, resulting in relatively low overall device sensitivity. To achieve effective signal detection, complex signal amplification and processing circuits are usually required, which not only increases system power consumption and structural complexity but also limits its widespread adoption in low-power, miniaturized applications.

[0005] In summary, existing pressure sensing technologies generally suffer from the following shortcomings: First, some high-sensitivity sensing mechanisms have stringent requirements on material systems and stress loading methods, making them difficult to integrate with silicon-based integrated circuit processes; second, silicon-based pressure sensors based on the traditional bulk effect have limited sensitivity, making it difficult to meet the high-precision detection requirements for minute pressure changes; and third, the external circuitry introduced to compensate for insufficient sensitivity increases system complexity and energy consumption. Therefore, there is an urgent need to propose a novel pressure sensing technology that is simple in structure, highly sensitive, and well-compatible with existing silicon-based semiconductor processes to overcome the aforementioned deficiencies of existing technologies. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a method for fabricating and optimizing the performance of a pressure sensor based on metastable contact in silicon wafers. The fabricated sensor constructs a metastable contact interface between two silicon wafers and utilizes external pressure to regulate the interface spacing, thereby achieving highly sensitive modulation of carrier tunneling behavior and enabling ultra-sensitive electrical detection of minute pressure changes.

[0007] The technical solution of this invention is a method for fabricating a pressure sensor based on metastable contact of silicon wafer material, comprising the following steps: S1. Select two silicon wafers and process them to form the main area for constructing the force-sensitive contact area and the lead area for leading out the electrode. S2. Perform surface cleaning on the processed silicon wafer and deposit a metal electrode layer on the surface of the lead area to form an ohmic contact electrode with low contact resistance. S3. Stack and align the polished surfaces of two silicon wafers facing each other, so that the main body areas overlap to form a force-sensitive contact area, and expose the lead area for external electrical connection, thus obtaining a pressure sensor based on metastable contact of silicon wafer material.

[0008] Furthermore, the silicon wafer is one or two of p-type silicon wafers, n-type silicon wafers, or n++-type silicon wafers.

[0009] Furthermore, the silicon wafer may be replaced with a metallic material, other semiconductor materials, a polymer or composite material system with resistive properties.

[0010] Furthermore, the main body area in S1 is circular, and the lead area is rectangular.

[0011] Furthermore, in S2, the wafer is ultrasonically cleaned sequentially with alcohol, acetone, and deionized water, and then dried with inert gas.

[0012] Furthermore, the metal electrode layer deposited by S2 is made of aluminum and is deposited by magnetron sputtering, with a deposition thickness of 50~200 nm.

[0013] Furthermore, in S1, one side of the silicon wafer is a polished surface, and the main body area and lead area are located on this polished surface.

[0014] The present invention also relates to a pressure sensor obtained by the above-described preparation method.

[0015] This invention also relates to a method for optimizing the performance of the aforementioned pressure sensor, comprising the following steps: 1) Apply a fixed bias voltage to the ohmic contact electrode of the pressure sensor and perform initial electrical tests on the device under no external force conditions; 2) Apply pressure to the main body area of ​​the sensor gradually through an external loading device, and measure the IV characteristic curve of the device under different pressure conditions; 3) Extract the current values ​​under different pressure conditions from the IV characteristic curve and plot the response curve of current versus pressure; calculate the relative pressure sensitivity of the sensor under different pressure conditions based on the current-pressure response relationship and plot the sensitivity-pressure response curve; evaluate the dynamic response performance of the device by periodically applying dynamic pressure and monitoring the device output current in real time; optimize the sensor's operating range, sensitivity, and stability by adjusting the doping concentration of the silicon wafer, the type of electrode material, and structural parameters to meet the needs of different application scenarios.

[0016] Preferably, in step 2), as the pressure gradually increases, the gap between the two silicon wafers gradually shrinks to the nanoscale range, the tunneling barrier narrows significantly, the tunneling current increases exponentially with the pressure, and the sensor enters the metastable contact working region. During this stage, the current exhibits high response sensitivity to pressure changes.

[0017] The present invention has the following beneficial effects: This invention addresses the problems of insufficient sensitivity, limited material systems, and poor compatibility with silicon-based processes in existing pressure sensors by proposing an ultra-high sensitivity pressure sensor based on a metastable contact structure of silicon wafers. This sensor constructs a metastable contact interface between two silicon wafers and utilizes external pressure to control the interface spacing, achieving highly sensitive modulation of carrier tunneling behavior, thereby enabling ultra-high sensitivity electrical detection of minute pressure changes. The metastable contact refers to an intermediate contact state between two opposing wafer materials, where the interface is neither a stable ohmic contact nor a completely non-contact state. In this state, a controllable nanoscale gap is formed between the surfaces of the two materials, allowing carriers to be transported across this gap via quantum tunneling. Since the tunneling current has an exponential dependence on the tunneling barrier width, even a small change in the interface gap can cause a significant change in the current.

[0018] In the pressure sensor provided by this invention, by arranging the polished surfaces of two silicon wafers opposite each other to form a force-sensitive contact area, under the condition of applying a fixed bias voltage, when external pressure is applied to the force-sensitive contact area, the contact gap between the wafers undergoes reversible modulation with the pressure change, thereby achieving highly sensitive control of the tunneling current. During the transition of the pressure sensor from an off state to a stable on state, the tunneling current rapidly jumps from a nearly immeasurable minimum value to a stable finite value within a small pressure change range. This rapid current change range can be used to achieve ultra-high sensitivity pressure sensing, with a maximum pressure sensitivity of up to 995 kPa. - ¹.

[0019] The technical solution of this invention also possesses excellent material versatility. Metastable contact, as a physical phenomenon universally present at the interface of solid materials, does not depend on the intrinsic piezoelectric effect or special crystal structure of the material. Therefore, by employing a metastable contact structure design, this invention is not only applicable to silicon wafer materials, but can also be extended to metals, other semiconductor materials, and polymer or composite material systems with resistive properties, thereby significantly broadening the range of materials that can be selected for pressure sensors.

[0020] The working characteristics of the pressure sensor of the present invention can be adjusted by a variety of parameters, including the doping type and concentration of the semiconductor material, the contact interface structure, the selection of electrode materials, and the bias voltage conditions, so that the sensitivity, working pressure range and output characteristics can be designed in a targeted manner according to different application scenarios, and it has good scalability and adaptability.

[0021] The pressure sensor of this invention can operate stably over a wide pressure range, with a relative pressure sensitivity of 1–10 kPa. - ¹, and exhibits good repeatability and stability during multiple loading and unloading processes, meeting the reliability requirements of high-sensitivity pressure detection. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the pressure sensor based on metastable contact described in this invention; Figure 2 This is a schematic diagram illustrating the changes in the working state of the pressure sensor described in this invention under different pressures. Figure 3 The current-voltage (IV) characteristic curves of n-Si / n-Si structure devices under different pressure conditions are shown. Figure 4 The current-voltage (IV) characteristic curves of n++-Si / n++-Si structure devices under different pressure conditions are shown. Figure 5The current-voltage (IV) characteristic curves of p-Si / n-Si structure devices under different pressure conditions are shown. Figure 6 The current-pressure response characteristics of n-Si / n-Si structure devices under different bias voltage conditions are shown in the figure. Figure 7 The current-pressure response characteristics of n++-Si / n++-Si structure devices under different bias voltage conditions are shown in the figure. Figure 8 The current-pressure response characteristics of p-Si / n-Si structure devices under different bias voltage conditions are shown in the figure. Figure 9 The sensitivity-pressure response characteristics of n-Si / n-Si structure devices under different bias voltage conditions are shown in the figure. Figure 10 Sensitivity-pressure response characteristic curves of n++-Si / n++-Si structure devices under different bias voltage conditions; Figure 11 The sensitivity-pressure response characteristics of p-Si / n-Si structure devices under different bias voltage conditions are shown in the figure. Figure 12 The current response curve of an n-Si / n-Si structure device under periodic dynamic pressure is shown as a function of time. Detailed Implementation

[0023] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, all raw materials and reagents used are commercially available.

[0024] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention.

[0025] Example 1 Fabrication of a pressure sensor based on metastable contacts on silicon wafers: S1. Material Selection Silicon wafers are selected as the core semiconductor material for the sensor, including p-type, n-type, and n++ type silicon wafers. The silicon wafers can be doped with boron, arsenic, or phosphorus, and the doping concentration can be selected according to the actual application requirements. In this embodiment, the silicon wafer used is a single-sided polished wafer with a thickness of approximately 0.5 mm. For n-Si, the carrier concentration is approximately 4.6 × 10⁻⁶. 16 cm -3 For heavily doped n + -Si, with a carrier concentration of approximately 6.3 × 10⁻⁶. 20 cm-3 For p-Si, the carrier concentration is approximately 1.4 × 10⁻⁶. 15 cm -3 For heavily doped p + -Si, with a carrier concentration of approximately 1.3 × 10⁻⁶. 21 cm -3 .

[0026] It should be noted that the present invention is not limited to specific suppliers or wafer sizes. Any silicon material that meets the requirements of p-type, n-type doping or has good electrical properties can be used to implement the technical solution of the present invention.

[0027] S2, Wafer Processing The silicon wafer is processed into a predetermined shape using a wafer dicing machine, including forming a circular main body region for constructing a force-sensitive contact area and a rectangular lead region for electrode extraction. In this embodiment, the diameter of the circular main body region is approximately 6 mm, and the size of the lead region is approximately 3 mm × 2 mm. The above dimensions are only examples and can be scaled up or down according to specific application scenarios.

[0028] S3, Surface cleaning treatment The processed silicon wafers were sequentially subjected to ultrasonic cleaning in alcohol, acetone, and deionized water to remove residual organic contaminants and particulate impurities from the wafer surface. They were then dried using inert gas to ensure the cleanliness of the wafer surface.

[0029] S4, Ohmic electrode preparation A metal thin film is deposited on the surface of the silicon wafer lead area using magnetron sputtering to form an ohmic contact electrode. In this embodiment, aluminum is used as the metal material, and the deposition thickness is approximately 100 nm. The metal electrode can form good low-resistance ohmic contacts with p-type, n-type, and n++ type silicon materials.

[0030] S5, Device Assembly Two silicon wafers are mechanically stacked and precisely aligned face-to-face, with their polished surfaces overlapping to form a unified force-sensitive contact area. The lead area is exposed for external electrical connections. Depending on the doping type of the selected silicon wafer, n-Si / n-Si, n... ++ -Si / n ++ -Si and p-Si / n-Si basic devices are used to design pressure sensors.

[0031] Example 2: Pressure Sensor Performance Optimization 1) Determining the initial working state A fixed bias voltage (2 V in this embodiment) is applied across the device (between the ohmic electrodes of the two silicon wafers), and initial electrical testing is performed on the device under conditions of no or minimal external force. At this time, a large gap is maintained between the two silicon wafers, the tunneling barrier width is large, the output current is close to zero, and the device is in the off state. Figures 1-2 As shown.

[0032] 2) Current-voltage characteristic test Pressure was gradually applied to the device using an external loading device, and the IV characteristic curves of the device were measured under different pressure conditions. Taking an n-Si / n-Si structure as an example, as the pressure gradually increased, the IV curve gradually changed from an unstable state to a stable and rapidly rising state. Within a small pressure variation range, the current could change by several orders of magnitude (see...). Figure 3 ).

[0033] For n ++ -Si / n ++ When performing similar tests on the -Si structure, due to its higher carrier concentration, the output current in the stable conduction state is significantly higher than that of the lightly doped structure, and significant current changes can be achieved within a smaller pressure variation range (see...). Figure 4 ).

[0034] For p-Si / n-Si structures, due to the rectification characteristics of the pn junction, the current response under forward bias is significantly higher than that under reverse bias, and it also exhibits high sensitivity to pressure changes (see...). Figure 5 ).

[0035] 3) Current-pressure response relationship analysis Current values ​​under different pressure conditions were extracted from the IV characteristic curves, and the current response curves as a function of pressure were plotted. The results show that within the metastable contact region where the device transitions from the off state to the stable on state, the current exhibits a rapid increasing trend with pressure (see...). Figures 6 to 8 ).

[0036] 4) Sensitivity characteristic calculation Based on the current-pressure response relationship, the relative pressure sensitivity of the device under different pressure conditions was calculated, and sensitivity-pressure response curves were plotted. The results show that the n++-Si / n++-Si structure exhibits the highest sensitivity in the low-pressure range, reaching approximately 995 kPa. - ¹, while n-Si / n-Si and p-Si / n-Si structures also exhibit high sensitivity within their respective pressure ranges (see...). Figures 9 to 11 ).

[0037] 5) Dynamic stability test The dynamic response performance of the device was evaluated by periodically applying dynamic pressure and monitoring the device's output current in real time. Test results show that the device's current response exhibits good repeatability and stability during multiple loading and unloading processes (see...). Figure 12 ).

[0038] 6) Performance optimization By adjusting the doping concentration of the silicon wafer, the type of electrode material, and the structural parameters, the operating range, sensitivity, and stability of the device can be further optimized to meet the needs of different application scenarios.

[0039] The above embodiments describe preferred embodiments of the present invention, but the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other way. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A method for fabricating a metastable contact pressure sensor, characterized in that, Includes the following steps: S1. Select two silicon wafers and process them to form the main area for constructing the force-sensitive contact area and the lead area for leading out the electrode. S2. Perform surface cleaning on the processed silicon wafer and deposit a metal electrode layer on the surface of the lead area to form an ohmic contact electrode with low contact resistance. S3. Stack and align the polished surfaces of two silicon wafers facing each other, so that the main body areas overlap to form a force-sensitive contact area, and expose the lead area for external electrical connection, thus obtaining a pressure sensor based on metastable contact of silicon wafer material.

2. The preparation method according to claim 1, characterized in that: The silicon wafer is one or two of p-type silicon wafers, n-type silicon wafers, or n++ type silicon wafers.

3. The preparation method according to claim 1, characterized in that: The silicon wafer is replaced by a metallic material, other semiconductor materials, a polymer with resistive properties, or a composite material system with resistive properties.

4. The preparation method according to claim 1, characterized in that: The main body area in S1 is circular, and the lead area is rectangular.

5. The preparation method according to claim 1, characterized in that: In S2, the wafer is ultrasonically cleaned sequentially with alcohol, acetone, and deionized water, and then dried with inert gas.

6. The preparation method according to claim 1, characterized in that: The S2 deposited metal electrode layer is made of aluminum and is deposited by magnetron sputtering, with a thickness of 50 ~ 200 nm.

7. The preparation method according to any one of claims 1 to 6, characterized in that: In S1, one side of the silicon wafer is a polished surface, and the main body area and lead area are located on the polished surface.

8. A pressure sensor obtained by the preparation method according to any one of claims 1 to 7.

9. The method for optimizing the performance of a pressure sensor according to claim 7, characterized in that, Includes the following steps: 1) Apply a fixed bias voltage to the two ohmic contact terminals of the pressure sensor and perform initial electrical tests on the device under no external force conditions; 2) Apply pressure gradually to the main body area of ​​the sensor using an external loading device, and measure the IV characteristic curve of the device under different pressure conditions; 3) Extract the current values ​​under different pressure conditions from the IV characteristic curve and plot the response curve of current versus pressure; calculate the relative pressure sensitivity of the sensor under different pressure conditions based on the current-pressure response relationship and plot the sensitivity-pressure response curve; evaluate the dynamic response performance of the device by periodically applying dynamic pressure and monitoring the device output current in real time; optimize the sensor's operating range, sensitivity, and stability by adjusting the doping concentration of the silicon wafer, the type of electrode material, and structural parameters to meet the needs of different application scenarios.

10. The method for optimizing the performance of a pressure sensor according to claim 9, characterized in that: In step 2), as the pressure gradually increases, the gap between the two silicon wafers gradually shrinks to the nanoscale range, the tunneling barrier narrows significantly, and the tunneling current increases exponentially with the pressure. The sensor enters the metastable contact working region, during which the current exhibits high response sensitivity to pressure changes.

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