WO2020258639A1

WO2020258639A1 - System and method for testing discharge of electric spark at nanoscale gap

Info

Publication number: WO2020258639A1
Application number: PCT/CN2019/115731
Authority: WO
Inventors: 佟浩; 权冉; 孔全存; 李勇; 李俊杰
Original assignee: 清华大学
Priority date: 2019-06-25
Filing date: 2019-11-05
Publication date: 2020-12-30
Also published as: CN110275097A; CN110275097B

Abstract

A system (10) and method for testing discharge of an electric spark at a nanoscale gap. The system (10) comprises: a micro tool electrode (100) used as a tool electrode for micro electric spark discharge; a silicon wafer (200) used as a workpiece electrode for micro electric spark discharge, wherein a prepared insulation film having a pre-configured thickness and located on a conductive film of the silicon wafer (200) is used as a breakdown medium to provide a target nanoscale discharge gap; a one-dimensionally movable platform (300) used to fix, move, and position the silicon wafer (200) such that the insulation film on the silicon wafer (200) contacts the micro tool electrode (100), and a suspended conductive wire twists by a target angle; and a torque suspension system (400) used to generate torque by using the twisting of the conductive wire by the target angle, such that the micro tool electrode (100) lightly contacts the insulation film on the silicon wafer (200) without piercing the insulation film, thereby acquiring a performance test result of a small energy pulsed discharge power supply at a target nanoscale gap. The system (10) has a simple and easy operating process and low costs, is reliable, and performs automated control and testing easily.

Description

Nanometer gap electric spark discharge test system and method

Cross references to related applications

This application claims the priority of the Chinese Patent Application No. “201910557063.X” filed by Tsinghua University on June 25, 2019, with the title of “Nano-Gap Electric Spark Discharge Test System and Method”.

Technical field

The invention relates to the technical field of micro-special processing, in particular to a nano-level gap electric spark discharge test system and method.

Background technique

The micro-EDM technology can realize high-precision machining of micro-holes, micro-grooves, and micro-three-dimensional structures on conductive materials such as metal alloys. It has the advantage of not being restricted by the mechanical properties of the strength, stiffness and hardness of the workpiece material. Precision processing and manufacturing play an important role.

With the in-depth research on the removal of micro-EDM at the nanometer scale, it is necessary to realize the research of micro-EDM with nano-level gaps, which urgently needs to solve the performance test and optimization of the more micro-energy pulse discharge power supply under the given nano-level gap. problem. The smaller energy pulse power supply can obtain the required smaller energy by reducing the pulse width of a single discharge to the order of nanoseconds. However, it is challenging and technically difficult to repeatedly and accurately specify the nano-gap between the tool electrode and the workpiece.

At present, there are few studies on the performance test and optimization of a given nanometer discharge gap for micro-energy pulsed power supplies with nanosecond pulse widths. The commonly used method to accurately control the nano-gap is to use a piezoelectric ceramic-driven nano-positioning platform, which is to accurately control the feed step by the piezoelectric effect to achieve nanosecond positioning accuracy to adjust the distance, but this piezoelectric positioning platform is not only the entire system It is complex and expensive, the operation and control process is complicated, and it is easily affected by mechanical vibration, rigidity and other internal and external factors. It is difficult to achieve repeatability and precise setting of nano-level gaps with very high consistency.

In order to realize the performance test of a pulsed discharge power supply with lower energy under the condition of a given nanometer gap, there is still a lack of a simple, highly accurate and reliable system and method for a given nanometer discharge gap.

Summary of the invention

The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

For this reason, an object of the present invention is to provide a nano-level gap electric spark discharge test system, which has simple and convenient operation process, low cost, high reliability, and easy realization of automatic control and test processes.

Another object of the present invention is to provide a nanometer gap spark discharge test method.

In order to achieve the above objective, one aspect of the present invention proposes a nano-gap electric spark discharge test system, which includes: a micro tool electrode, used as a tool electrode for micro spark discharge; a silicon wafer, used as a workpiece electrode for micro spark discharge Spark discharge, an insulating film prepared with a predetermined thickness on the conductive film of the silicon wafer is used as a breakdown medium to provide a target nano-scale discharge gap; a one-dimensional mobile platform is used to fix and move the silicon wafer to make The insulating film on the silicon wafer is in contact with the electrode of the micro tool and causes the suspended conductive wire to twist at a target angle; a torque suspension system is used to generate torque by using the twist of the conductive wire at the target angle to make the micro tool The electrode is in micro-force contact with the insulating film on the silicon wafer, and does not pierce the insulating film, so as to obtain the performance test result of the pulse discharge power supply with a smaller energy under the target nanometer gap.

The nano-level gap electric spark discharge test system of the embodiment of the present invention precisely controls the nano-level discharge gap by accurately and controllably preparing an insulating film with a nano-level thickness, and can realize the precise and repeated discharge test of the same nano-level discharge gap; The size is ensured by adjusting the thickness of the prepared insulating film. Since the thickness of the insulating film can be precisely adjusted to the order of 1nm, it is convenient to accurately adjust the size of the nano-level gap; through the torque suspension system, the micro-tool electrode and the insulating film are in micro-force contact, thereby Ensure the precise size of the nano-level gap, such a physical contact method is not easily affected by external factors such as vibration, and improves the repeatability and reliability of nano-level gap control; the operation process is simple and convenient, low cost, high reliability, and easy to implement Automated regulation and testing process.

In addition, the nano-gap electric spark discharge test system according to the foregoing embodiment of the present invention may also have the following additional technical features:

Further, in an embodiment of the present invention, it further includes: a dual-channel digital oscilloscope for displaying the discharge waveform in the performance test.

Further, in an embodiment of the present invention, the conductive film may be a gold-plated film, and the insulating film may be an aluminum oxide film.

In order to achieve the above objective, another embodiment of the present invention proposes a nanoscale gap electric spark discharge test method, which adopts the test system described in the above embodiment, wherein the method includes: preparing the micro tool electrode and the electrode The conductive film and insulating film of the silicon wafer; use dilute acid to remove half of the insulating film; build the torque suspension system, and fix the silicon wafer on the one-dimensional mobile platform; conduct the test system Circuit, and move the silicon chip to twist the conductive wire; obtain the performance test result of the pulse discharge power supply with a smaller energy under the target nanometer gap.

The nano-level gap electric spark discharge test method of the embodiment of the present invention precisely controls the nano-level discharge gap by precisely and controllably preparing an insulating film with a nano-level thickness, and can realize the precise and repeated discharge test of the same nano-level discharge gap; The size is ensured by adjusting the thickness of the prepared insulating film. Since the thickness of the insulating film can be precisely adjusted to the order of 1nm, it is convenient to accurately adjust the size of the nano-level gap; through the torque suspension system, the micro-tool electrode and the insulating film are in micro-force contact, thereby Ensure the precise size of the nano-level gap, such a physical contact method is not easily affected by external factors such as vibration, and improves the repeatability and reliability of nano-level gap control; the operation process is simple and convenient, low cost, high reliability, and easy to implement Automated regulation and testing process.

In addition, the nano-gap electric spark discharge test method according to the foregoing embodiment of the present invention may also have the following additional technical features:

Further, in an embodiment of the present invention, the method further includes: turning on the power of the dual-channel digital oscilloscope to observe the discharge waveform through the dual-channel digital oscilloscope.

The additional aspects and advantages of the present invention will be partly given in the following description, and partly will become obvious from the following description, or be understood through the practice of the present invention.

Description of the drawings

The above and/or additional aspects and advantages of the present invention will become obvious and easy to understand from the following description of the embodiments in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic diagram of the structure of a nano-scale gap electric spark discharge test system according to an embodiment of the present invention;

2 is a physical schematic diagram of a nano-scale gap electric spark discharge test system according to an embodiment of the present invention;

3 is a schematic diagram and a physical diagram of a thin film on a silicon wafer according to an embodiment of the present invention;

4 is a flowchart of a nano-gap electric spark discharge test method according to an embodiment of the present invention;

Fig. 5 is a flowchart of a nano-gap electric spark discharge test method according to an embodiment of the present invention;

Fig. 6 is a waveform diagram of a nano-gap electric spark discharge test according to an embodiment of the present invention.

Detailed ways

The embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings, in which the same or similar reference numerals indicate the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary, and are intended to explain the present invention, but should not be construed as limiting the present invention.

The following describes the nano-gap electric spark discharge test system and method according to the embodiments of the present invention with reference to the drawings. First, the nano-gap electric spark discharge test system according to the embodiments of the present invention will be described with reference to the drawings.

Fig. 1 is a schematic structural diagram of a nano-gap electric spark discharge test system according to an embodiment of the present invention.

As shown in FIG. 1, the nanometer gap electric spark discharge test system 10 includes: a micro tool electrode 100, a silicon wafer 200, a one-dimensional mobile platform 300 and a torque suspension system 400.

Among them, the fine tool electrode 100 is used as a tool electrode for fine spark discharge. The silicon wafer 200 is used as a workpiece electrode for fine spark discharge, and an insulating film prepared with a predetermined thickness on the conductive film of the silicon wafer 200 is used as a breakdown medium to provide a target nanometer-scale discharge gap. The one-dimensional mobile platform 300 is used to fix and move the silicon wafer 200 to make the insulating film on the silicon wafer 200 contact the micro tool electrode 100 and cause the suspended conductive wire to twist at a target angle. The torque suspension system 400 is used to generate torque by using the torsion of the conductive wire at the target angle, so that the micro tool electrode 100 and the silicon wafer 200 insulating film are in micro force contact without piercing the insulating film, so as to obtain a smaller energy under the target nanometer gap Pulse discharge power supply performance test results. The operation process of the system 10 of the embodiment of the present invention is simple and convenient, low in cost, high in reliability, and easy to realize automatic control and testing processes.

Among them, those skilled in the art can set the preset thickness according to the actual situation, which is not specifically limited here. The conductive wire may be a slender conductive wire, for example, a slender steel wire, wherein the diameter of the conductive wire should be small enough to ensure that the torque generated when it has a small twist angle is small enough.

Further, in an embodiment of the present invention, the conductive film may be a gold-plated film, and the insulating film may be an aluminum oxide film. Of course, both the conductive film and the insulating film may also be films of other materials. The specific material needs to be selected, which is only used as an example here, without specific restrictions.

Specifically, a preparation process of conductive film and insulating film is: depositing a conductive film (a gold film as an example) on a silicon wafer with a smooth surface by physical vapor deposition or chemical vapor deposition; Atomic layer deposition method deposits an insulating film with a given nanometer thickness (taking aluminum oxide film as an example); immersing the silicon wafer vertically in a dilute acid solution (taking dilute sulfuric acid as an example) to wash away a part of the insulating film ; Finally, use deionized water to clean the remaining silicon wafer and dry it.

Further, in an embodiment of the present invention, the system 10 of the embodiment of the present invention further includes: a dual-channel digital oscilloscope. Among them, a dual-channel digital oscilloscope is used to display the discharge waveform in the performance test.

It is understandable that the nanometer gap spark discharge test system 10 is mainly composed of a micro tool electrode 100, a silicon wafer 200 covered with a conductive film (a gold film as an example) and an insulating film (alumina film as an example), a one-dimensional It consists of a mobile platform 300, a torque suspension system 400, and a dual-channel digital oscilloscope. The micro tool electrode 100 is used as the tool electrode for micro spark discharge; the conductive film on the silicon wafer 200 is used as the workpiece electrode for micro spark discharge, and the insulating film prepared with a given thickness on the conductive film is used as a breakdown medium, with a given nanometer One-dimensional discharge gap; the one-dimensional mobile platform 300 is used to fix and move the silicon chip, so that the insulating film on the silicon chip is in contact with the micro tool electrode and the elongated conductive wire (take the elongated steel wire as an example) is produced Slightly twisted; the torque suspension system uses the tiny torque generated by the small twisting of the slender conductive wire to ensure that the micro tool electrode is in contact with the insulating film on the silicon chip and does not pierce the film.

Specifically, as shown in FIG. 1 and FIG. 2, the main components of the system 10 of the embodiment of the present invention include: (1) Micro tool electrode 100: as a tool electrode for micro spark discharge; (2) Cover thin film silicon wafer 200: It is covered with a conductive film to be used as a workpiece electrode for fine spark discharge. A gold film is used as an example to improve conductivity, and then a nano-thickness insulating film is covered with a given nano-level discharge gap, and an aluminum oxide film is used as an example for breakdown Medium, remove part of the aluminum oxide film to expose the gold film, as shown in Figure 3; (3) One-dimensional mobile platform 300: used to fix and move the silicon wafer; (4) Torque suspension system 400: insulate the silicon wafer The membrane is in contact with the micro tool electrode and hangs it on the slender conductive wire. The slender conductive wire takes a slender steel wire as an example. The slender steel wire is used to provide a small twist angle to generate a small torque to ensure that the tip of the micro tool electrode and silicon The on-chip insulating film is in contact with little force and does not pierce the film; (5) Dual-channel digital oscilloscope: used to observe the discharge waveform between the micro tool electrode and the gold film on the silicon wafer.

In summary, cover the smooth surface of the silicon wafer with gold or silver film, and then cover the gold or silver film with a certain thickness of insulating film as a breakdown medium, and use acid to wash away a part of the insulating film to expose the gold or silver film connection The negative pole of the pulse power supply; the one-dimensional mobile platform is used to fix and move the silicon wafer; the torque suspension system uses the slender filament to twist at a small angle to adjust the tiny torque to ensure that the micro tool electrode is in contact with the insulating film on the silicon wafer and does not penetrate the film. The nano-thickness insulating film is the discharge breakdown gap. This method is used to simulate the nano-scale discharge gap to test the discharge characteristics of the micro-EDM pulse power supply at a given nano-gap.

According to the nano-level gap electric spark discharge test system proposed by the embodiment of the present invention, the nano-level discharge gap can be precisely controlled by accurately and controllably preparing an insulating film of nano-level thickness, which can realize the precise and repeated discharge test of the same nano-level discharge gap; The size of the gap is ensured by adjusting the thickness of the prepared insulating film. Since the thickness of the insulating film can be precisely adjusted to the order of 1nm, it is convenient to accurately adjust the size of the nano-level gap; the micro-tool electrode and the insulating film can be contacted by a torque suspension system. , So as to ensure the precise size of the nano-level gap, such a physical contact method is not easily affected by external factors such as vibration, and improves the repeatability and reliability of nano-level gap control; the operation process is simple and convenient, low cost, and high reliability. It is easy to realize automatic control and testing process.

Next, the nano-gap electric spark discharge test method proposed according to the embodiment of the present invention will be described with reference to the accompanying drawings.

Fig. 4 is a flowchart of a nano-gap spark discharge test method according to an embodiment of the present invention.

As shown in FIG. 4, the nano-scale gap electric spark discharge test method adopts the test system of the above-mentioned embodiment, wherein the method includes the following steps:

In step S401, the conductive film and insulating film of the micro tool electrode and the silicon wafer are prepared.

In step S402, a half area of the insulating film is removed with dilute acid.

It is understandable that the existing micro-machining method (take the micro electrochemical machining method as an example) is used to prepare a micro tool electrode with a micro-nano-scale tip. First deposit a conductive film (a gold film as an example) on a silicon wafer with a smooth surface, then deposit an insulating film with a given nanometer thickness (aluminum oxide film as an example), and then remove a part of the insulating film to expose the conductive film .

In step S403, a torque suspension system is built, and the silicon wafer is fixed on a one-dimensional mobile platform.

It is understandable that the micro tool electrode is fixed to one end of a slender metal rod (take a tungsten rod as an example), and two slender conductive wires (take a slender steel wire as an example) are used to hang the slender metal rod on the fixed rod. , Adjust the fixed position to keep the slender metal rod in balance, connect the slender conductive wire to the positive electrode of the pulse power supply for electric discharge machining and one end of the oscilloscope; fix the silicon wafer on the one-dimensional mobile platform, and connect the exposed conductive film to the electric spark The negative pole of the pulse power supply for machining discharge and the other end of the oscilloscope.

In step S404, the circuit of the test system is turned on, and the silicon chip is moved to twist the conductive wire.

It is understandable that the one-dimensional moving platform is adjusted to make the insulating film on the silicon chip contact the micro tool electrode and cause the elongated conductive wire to produce a small twist angle.

In step S405, the performance test result of the pulse discharge power supply with a smaller energy under the target nanometer gap is obtained.

Further, in an embodiment of the present invention, the method of the embodiment of the present invention further includes: turning on the power of the dual-channel digital oscilloscope to observe the discharge waveform through the dual-channel digital oscilloscope.

It is understandable that the pulse power supply for EDM discharge is turned on and the discharge waveform is observed through an oscilloscope.

The following will further illustrate the nanometer gap spark discharge test method through specific embodiments.

As shown in Figure 5, the operation flow of the nanometer gap electric spark discharge test method is:

(1) Use the micro electrochemical machining method to prepare the micro tool electrode, and the diameter of the needle tip of the micro tool electrode is ~ 4 μm;

(2) Deposit a 50nm thick gold film on a silicon wafer with a surface roughness of Ra0.1nm by evaporation, and then deposit a 20nm thick aluminum oxide film on the gold film by atomic layer deposition;

(3) Configure 2mol/L dilute sulfuric acid solution, immerse the silicon wafer covered with the thin film in the dilute sulfuric acid solution vertically, take out the silicon wafer after 2 minutes, and rinse the silicon wafer from the aluminum oxide film to the gold film with deionized water , Drying at 60°C for 10 minutes, the structure of the film-covered silicon wafer is shown in Figure 3;

(4) Fix the silicon wafer on a one-dimensional mobile platform, and electrically connect the exposed gold film part of the silicon wafer with the negative electrode of the pulse power supply for electric discharge machining and one end of the oscilloscope;

(5) Fix the micro tool electrode on one end of a tungsten rod with a length of 10cm and a diameter of 0.4mm. Use two slender wires with a length of 15cm and a diameter of 0.12mm to hang the tungsten rod on the fixed rod to adjust the fixing of the wire Position the long and thin tungsten rod to maintain balance, connect the long and thin steel wire to the positive pole of the pulse power supply for electric discharge machining and the other end of the oscilloscope. The experimental system is shown in Figure 2;

(6) Adjust the one-dimensional mobile platform so that the aluminum oxide film on the silicon wafer is in contact with the micro tool electrode, and the slender steel wire produces a torsion angle of ~1° and maintains a balance;

(7) Turn on the pulse power supply for EDM discharge and observe the waveform of the oscilloscope. The waveform obtained before the gap discharge breakdown is shown in Figure 6(a), and the waveform obtained during the gap discharge breakdown is shown in Figure 6(b).

According to the nano-level gap electric spark discharge test method proposed by the embodiment of the present invention, the nano-level discharge gap can be precisely controlled by accurately and controllably preparing an insulating film of nano-level thickness, which can realize the precise and repeated discharge test of the same nano-level discharge gap; The size of the gap is ensured by adjusting the thickness of the prepared insulating film. Since the thickness of the insulating film can be precisely adjusted to the order of 1nm, it is convenient to accurately adjust the size of the nano-level gap; the micro-tool electrode and the insulating film can be contacted by a torque suspension system. , So as to ensure the precise size of the nano-level gap, such a physical contact method is not easily affected by external factors such as vibration, and improves the repeatability and reliability of nano-level gap control; the operation process is simple and convenient, low cost, and high reliability. It is easy to realize automatic control and testing process.

In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features defined with "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise specifically defined.

In the description of this specification, descriptions with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean specific features described in conjunction with the embodiment or example , Structure, materials or features are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine the different embodiments or examples and the characteristics of the different embodiments or examples described in this specification without contradicting each other.

Although the embodiments of the present invention have been shown and described above, it can be understood that the above-mentioned embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can comment on the foregoing within the scope of the present invention. The embodiment undergoes changes, modifications, substitutions and modifications.

Claims

A nanometer gap electric spark discharge test system is characterized in that it comprises:

Micro tool electrode, used as a tool electrode for micro spark discharge;

A silicon wafer is used as a workpiece electrode for fine spark discharge, and an insulating film prepared with a predetermined thickness on the conductive film of the silicon wafer is used as a breakdown medium to provide a target nanometer-scale discharge gap;

A one-dimensional mobile platform for fixing and moving the silicon wafer so that the insulating film on the silicon wafer contacts the micro tool electrode and the suspended conductive wire is twisted at a target angle;

The torque suspension system is used to generate torque using the twisting of the conductive wire at the target angle, so that the micro tool electrode is in contact with the insulating film on the silicon wafer without piercing the insulating film to obtain the The performance test results of a smaller energy pulse discharge power supply under the target nanometer gap.
The test system according to claim 1, further comprising:

Dual-channel digital oscilloscope, used to display the discharge waveform in the performance test.
The test system according to claim 1, wherein:

The conductive film is a gold-plated film, and the insulating film is an aluminum oxide film.
A nano-level gap electric spark discharge test method, characterized in that the test system according to any one of claims 1 to 3 is used, wherein the method comprises:

Preparing the conductive film and insulating film of the micro tool electrode and the silicon wafer;

Use dilute acid to remove half of the insulating film;

Build the torque suspension system, and fix the silicon wafer on the one-dimensional mobile platform;

Turn on the circuit of the test system, and move the silicon chip to twist the conductive wire; and

Obtain the performance test result of the pulse discharge power supply with a smaller energy under the target nanometer gap.
The method according to claim 4, further comprising:

Turn on the power of the dual-channel digital oscilloscope to observe the discharge waveform through the dual-channel digital oscilloscope.