Method for accurately controlling metal single crack

Abstract

The invention discloses a method for accurately controlling a metal single crack, and relates to the technical field of crack strain sensors, and the method comprises the following steps: 1, carrying out fluorination treatment on a silicon wafer in a closed container for 3 hours; 2, fully mixing a PMDS main agent and a curing agent according to a mass ratio of 10: 1, carrying out air exhaust defoaming in a vacuum box for 30 min, carrying out spin coating on a silicon wafer at a speed of 150 r / min for 60 s, and drying in a drying oven at 80 DEG C for 2 h to obtain a PDMS film; 3, cutting the PDMS film into long strips with the length of 30mm and the width of 7mm, attaching a metal mask to the central position of the PDMS, and sequentially depositing a 5nm Cr brittleness induction layer and a 40nm Au conductive layer through electron beams; the method comprises the following steps: designing a stress induction structure on a metal mask, then carrying out electron beam deposition on a middle adhesion layer and a conductive layer, finally removing the metal mask, and controlling single crack initiation and expansion on a micron stretching table. According to the method, the evolution length, the forming position and the micromorphology of the crack can be accurately controlled.

Description

Technical Field

[0001] The present invention relates to the technical field of crack strain sensors, and in particular to a method for accurately controlling a single metal crack. Background Art

[0002] Metal crack strain sensor is a sensor that converts external strain signals into resistance signals. Its structure consists of a flexible substrate and a conductive layer with cracks. When the external strain causes the substrate to deform, the cracks in the conductive layer open or close, and the resistance changes. Controlling cracks can regulate sensor performance. Generally speaking, channel cracks are characterized by high sensitivity and low strain, which is conducive to capturing various weak signals; network cracks are characterized by low sensitivity and high strain, which are suitable for whole-body motion monitoring.

[0003] However, the existing crack control methods are still not accurate enough, which is mainly limited by the differences of multiple cracks. At present, the angles of crack control are mainly to control the micro-nano structure stress of the substrate, the bonding stress of the interface, and the material stress distribution of the conductive layer. For example, laser etching, photolithography, and template methods are used to prepare micro-nano structures on the substrate and in the conductive layer, and adhesion layers or plasma treatments are introduced at the interface to change the stress distribution. However, they only macro-control the overall morphology of the cracks and cannot ensure the precise control of all cracks, which is not conducive to the standardized preparation of sensors. Therefore, there is a practical need to eliminate the mutual influence of multiple cracks and accurately control single metal cracks. Therefore, the present invention proposes a method for accurately controlling single metal cracks. Summary of the invention

[0004] The purpose of the present invention is to solve the defects in the prior art and propose a method for accurately controlling a single metal crack. The problem that metal multiple crack sensors are difficult to accurately control cracks can be solved by designing a stress-inducing structure in the metal layer and allowing the crack to grow slowly, thereby accurately controlling the length, position and microscopic morphology of a single crack.

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

[0006] A method for accurately controlling a single crack in a metal, the method comprising the following steps:

[0007] Step 1: The silicon wafer is subjected to fluorination treatment in a sealed container for 3 hours;

[0008] Step 2: The PMDS main agent and the curing agent were fully mixed in a mass ratio of 10:1, degassed in a vacuum box for 30 minutes, spin-coated on a silicon wafer at a speed of 150 r / min for 60 seconds, and dried in an oven at 80°C for 2 hours to obtain a PDMS film;

[0009] Step 3: Cut the PDMS film into strips with a length of 30 mm and a width of 7 mm, attach a metal mask to the center of the PDMS, and deposit a 5 nm Cr brittle inducing layer and a 40 nm Au conductive layer in sequence by electron beam; rate: Air pressure: 9.0x10 -4 Pa;

[0010] Step 4: Use alcohol droplets to soak the contact surface between the metal mask and the flexible substrate, then use tweezers to slowly remove the metal mask, dry it naturally and set it aside;

[0011] Step 5: Fix the distance between the sensors on the micron stretching table to 20 mm, use liquid metal as the electrode, and stretch the sensor in 1 μm steps. After each 1 μm stretch, stop for 5 seconds and then stretch again to control the slow evolution of a single crack.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] The present invention designs a stress-inducing structure on a metal mask, then deposits an intermediate adhesion layer and a conductive layer by electron beam, and finally removes the metal mask to control the initiation and expansion of a single crack on a micron stretching table. The present invention can accurately control the evolution length, formation position and microscopic morphology of the crack. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0015] Figure 1 This is a schematic diagram of the process of accurately controlling the generation of a single crack in the present invention;

[0016] Figure 2 Schematic diagram of the single crack sensing characteristics generated by precise control of the present invention. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention;

[0018] Reference Figure 1-2 , a method for accurately controlling a single crack in a metal, the method comprising the following steps:

[0019] Step 1: The silicon wafer is subjected to fluorination treatment in a sealed container for 3 hours;

[0020] Step 2: The PMDS main agent and the curing agent were fully mixed in a mass ratio of 10:1, degassed in a vacuum box for 30 minutes, spin-coated on a silicon wafer at a speed of 150 r / min for 60 seconds, and dried in an oven at 80°C for 2 hours to obtain a PDMS film;

[0021] Step 3: Cut the PDMS film into strips with a length of 30 mm and a width of 7 mm. Attach the pre-designed metal mask to the center of the PDMS. Deposit a 5-nm Cr brittle induction layer and a 40-nm Au sensing layer successively by electron beam; rate: Air pressure: 9.0x10 -4 Pa;

[0022] Step 4: Moisten the contact surface between the metal mask and the flexible substrate with alcohol droplets, and then slowly remove the metal mask with tweezers to avoid premature crack generation. After natural drying, it is reserved for use;

[0023] Step 5: Fix the distance between the clamps of the sensor on the micrometer stretching table to 20 mm. Use liquid metal as the electrode. Stretch the sensor with a 1-μm step. For each 1-μm stretch, stop for 5 s and then stretch again to control the slow evolution of a single crack.

[0024] Adopt a brittle intermediate layer to induce cracks in the sensing layer; adopt a ductile metal as the sensing layer to avoid brittle fracture of the cracks.

[0025] Deposit a metal layer using a metal mask, and construct a stress concentration structure in the metal layer. Its geometric feature is a pair of stress concentration notches, so as to control the crack initiation position, quantity and growth length.

[0026] From Figure 1 - Figure 2 it can be seen that as the displacement of the micrometer stretching table slowly increases, due to the stress concentration effect of the notch, a single crack appears between the notches. At the initial stretching, an unpenetrated single crack is formed, and a large number of metal bridges and void cracks are generated. At this stage, a large number of conductive paths make the response show a low resistance change; as the stretching increases, the bridges gradually break, and the final fracture process based on the ductile metal Au forms atomic-level point contacts. The conductive path becomes a single channel, and at this time the conductive channel is a quantized ballistic transport channel. Therefore, the strain response characteristic is a conductance jump related to nG 0 related, Figure 2 The point contact section shows a conductance jump of about 0 G - 1 G at a strain of 0.790%; 0 As the stretching displacement further increases, the single crack completely penetrates and the conductive path is almost disconnected. The strain response characteristic is a high switching characteristic.

[0027] The present invention provides a method for precise control of a single crack. Its precision is manifested in the length, quantity, position at the macroscopic level and three different stages at the microscopic level, which can provide more in-depth theoretical guidance and practical operation guidelines for the precise regulation of cracks.

Claims

1. A method for accurately controlling a single crack in a metal, characterized in that: The method comprises the following steps: Step 1: The silicon wafer is subjected to fluorination treatment in a sealed container for 3 hours; Step 2: The PMDS main agent and the curing agent were fully mixed in a mass ratio of 10:1, degassed in a vacuum box for 30 minutes, spin-coated on a silicon wafer at a speed of 150 r / min for 60 seconds, and dried in an oven at 80°C for 2 hours to obtain a PDMS film; Step 3: Cut the PDMS film into strips with a length of 30 mm and a width of 7 mm, attach a metal mask to the center of the PDMS, and deposit a 5 nm Cr brittle induction layer and a 40 nm Au sensing layer in sequence by electron beam; Step 4: Use alcohol droplets to soak the contact surface between the metal mask and the flexible substrate, then use tweezers to slowly remove the metal mask, dry it naturally and set it aside; Step 5: Fix the distance between the sensors on the micron stretching table to 20 mm, use liquid metal as the electrode, and stretch the sensor in 1 μm steps. After each 1 μm stretch, stop for 5 seconds and then stretch again to control the slow evolution of a single crack.

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