阅读说明：本技术 音叉型原子力显微镜探头和应用 (Tuning fork type atomic force microscope probe and application ) 是由 宋志军 杨楚宏 姬忠庆 吕力 于 2019-03-29 设计创作，主要内容包括：本发明提供了一种音叉型原子力显微镜探头,所述探头包括石英音叉、电流放大器及补偿电路。还提供了该探头的应用。既可以实现对分布电容的补偿又可以在10mK温度对通过石英音叉的电流信号进行放大,从而可以降低驱动电压的幅度,以期望提高测量的分辨率。(The invention provides a tuning fork type atomic force microscope probe, which comprises a quartz tuning fork, a current amplifier and a compensation circuit. Applications of the probe are also provided. The compensation of the distributed capacitance can be realized, and the current signal passing through the quartz tuning fork can be amplified at the temperature of 10mK, so that the amplitude of the driving voltage can be reduced, and the measurement resolution ratio is expected to be improved.)

1. A tuning fork type atomic force microscope probe, characterized in that the probe comprises a quartz tuning fork, a current amplifier and a compensation circuit, preferably the probe further comprises an I-V converter.

2. The probe of claim 1, wherein the material of the current amplifier is selected from one or more of the following: the transistor comprises a germanium-silicon heterojunction transistor, a junction field effect transistor, a metal-semiconductor contact field effect transistor, a metal-oxide semiconductor field effect transistor, a high electron mobility transistor, an insulated gate bipolar transistor and a silicon-based integrated operational amplifier; preferably a silicon germanium heterojunction transistor; more preferably, the germanium-silicon heterojunction transistor is a germanium-silicon bipolar transistor NESG3031T 1K.

3. The probe of claim 1 or 2, wherein the branches of the compensation network of the compensation circuit are in opposite phase to the current of the branches of the parasitic capacitance of the equivalent circuit of the quartz tuning fork.

4. The probe of any one of claims 1 to 3, wherein the compensation circuit comprises an inverting amplifier and a compensation circuit capacitance, the product of the multiple of the inverting amplifier and the compensation circuit capacitance being equal to the parasitic capacitance of the quartz tuning fork equivalent circuit.

5. The probe of claim 4, wherein the material of the inverting amplifier is selected from one or more of: the transistor comprises a high electron mobility transistor, a germanium-silicon heterojunction transistor, a junction field effect transistor, a metal-semiconductor contact field effect transistor, a metal-oxide semiconductor field effect transistor, an insulated gate bipolar transistor and a silicon-based integrated operational amplifier; preferably a high electron mobility transistor.

6. The probe of any one of claims 1 to 5, wherein the equivalent circuit of the quartz tuning fork is connected in parallel with the compensation circuit and then connected in series with the current amplifier.

7. The probe of claim 6, wherein the I-V converter is in series with the current amplifier.

8. The probe of any one of claims 1 to 7, wherein the total power consumption of the current amplifier and the compensation circuit is less than 10uW, preferably less than 4 uW.

9. An atomic force microscope, characterized in that it comprises a tuning fork-type atomic force microscope probe according to any one of claims 1 to 8.

10. A method for detecting the morphology of micro-nano devices at extremely low temperature, characterized in that the method uses a tuning fork atomic force microscope probe according to any one of claims 1 to 8, wherein the extremely low temperature is a milli-boiling temperature zone, preferably of the order of 10 mK.

Technical Field

The invention belongs to the field of atomic force microscopes, and particularly relates to an atomic force microscope probe capable of working at extremely low temperature (10mK magnitude) and application, which are integrally developed by utilizing a tuning fork, a silicon-germanium bipolar transistor capable of working at extremely low temperature and a high electron mobility transistor.

Background

An Atomic Force Microscope (AFM) system is characterized in that a cantilever with a needle point is arranged on piezoelectric ceramics, the needle point is driven to vibrate periodically by exciting the piezoelectric ceramics, the vibration mode of the cantilever can be changed due to the action of the atomic force of the needle point and a sample to be detected, the vibration change of the cantilever is detected by utilizing a beam deflection method, and the appearance of the surface of the sample is further obtained. The atomic force microscope has transverse and longitudinal ultrahigh resolution capability, and can obtain a two-dimensional image of a sample to be detected and height information of the surface of the sample, so that the atomic force microscope is widely used for measuring the appearance of a micro-nano device in the semiconductor chip industry. In the basic research field, for example, in the current popular research direction of quantum computing experiments, atomic force microscopy is also used for performing morphology analysis and positioning on quantum devices in extremely low temperature environments.

Conventional AFMs are complex in structure and are not suitable for implementation at extremely low temperatures due to the need for optical components to detect cantilever vibration. In 1995, k.karrai et al, germany, proposed that a self-induced AFM probe could be developed with a quartz tuning fork to detect the change in the amplitude of the cantilever by the tuning fork itself outputting an electrical signal. The traditional optical detection component is not needed, so that the system is simple in structure and can work in an extremely low temperature environment, and the appearance of the sample can be measured in a frequency modulation or amplitude modulation mode by using a phase locking technology and a PID (proportion integration differentiation) technology as long as the probe is provided.

Disclosure of Invention

It is therefore an object of the present invention to overcome the disadvantages of the prior art and to provide a tuning fork atomic force microscope probe and application that is usable at very low temperatures (mK).

Before setting forth the context of the present invention, the terms used herein are defined as follows:

the term "I-V conversion" means: current-to-voltage conversion.

To achieve the above object, a first aspect of the present invention provides a tuning fork type atomic force microscope probe, which comprises a quartz tuning fork, a current amplifier and a compensation circuit, and preferably further comprises an I-V converter.

The probe according to the first aspect of the present invention, wherein the material of the current amplifier is selected from one or more of: germanium-silicon heterojunction transistors (HBT), Junction Field Effect Transistors (JFET), metal-semiconductor contact field effect transistors (MESFET), metal-oxide semiconductor field effect transistors (MOSFET), High Electron Mobility Transistors (HEMT), Insulated Gate Bipolar Transistors (IGBT) and silicon-based integrated operational amplifiers. Preferably a silicon germanium heterojunction transistor; more preferably, the germanium-silicon heterojunction transistor is a germanium-silicon bipolar transistor NESG3031T 1K.

The probe according to the first aspect of the invention, wherein the compensating network branch of the compensating circuit is in opposite phase with the current of the parasitic capacitance branch of the equivalent circuit of the quartz tuning fork.

The probe according to the first aspect of the invention, wherein the compensation circuit comprises an inverting amplifier and a compensation circuit capacitance, and a product of a multiple of the inverting amplifier and the compensation circuit capacitance is equal to a parasitic capacitance of an equivalent circuit of the quartz tuning fork.

The probe according to the first aspect of the invention, wherein the material of the inverting amplifier is selected from one or more of: high Electron Mobility Transistors (HEMTs), silicon germanium heterojunction transistors (HBTs), Junction Field Effect Transistors (JFETs), metal-semiconductor contact field effect transistors (MESFETs), metal-oxide semiconductor field effect transistors (MOSFETs), Insulated Gate Bipolar Transistors (IGBTs), and silicon-based integrated operational amplifiers. Preferably a high electron mobility transistor.

According to the probe of the first aspect of the invention, the equivalent circuit of the quartz tuning fork is connected in parallel with the compensation circuit and then connected in series with the current amplifier.

The probe according to the first aspect of the invention, wherein the I-V converter is connected in series with the current amplifier.

The probe according to the first aspect of the present invention, wherein the total power consumption of the current amplifier and the compensation circuit is less than 10uW, preferably less than 4 uW.

A second aspect of the invention provides an atomic force microscope comprising a tuning fork-type atomic force microscope probe according to the first aspect.

A third aspect of the present invention provides a method for detecting the morphology of a micro-nano device at an extremely low temperature, wherein the method uses the tuning fork atomic force microscope probe according to the first aspect, and the extremely low temperature is a milli-boiling temperature region, preferably 10mK magnitude.

A tuning fork-based atomic force microscope probe generally needs to be added with a compensation circuit to compensate the influence of the distributed capacitance of a tuning fork vibrator. In the room temperature AFM system, the compensation circuit is easy to realize, and in the cryogenic dilution refrigerator, the tuning fork has a long input/output measuring coaxial line and a large distributed capacitance. In order to improve the signal-to-noise ratio of the measurement, only the tuning fork needs to be applied with a relatively high driving voltage, so that the output signal is larger than the noise floor of the system. An excessive excitation voltage may cause the amplitude of the tuning fork vibration to be too large, which may reduce the sensitivity of the tuning fork vibration. In order to improve the measurement sensitivity, the voltage amplitude of the active drive needs to be reduced as much as possible, and the reduction of the voltage amplitude can cause the current passing through the quartz tuning fork crystal oscillator to be reduced. If the output end of the quartz tuning fork is connected with a current amplifier, the signal-to-noise ratio and the sensitivity of measurement can be provided under low active driving voltage.

The atomic force microscope probe of the invention can have the following beneficial effects:

the invention utilizes the low-power consumption silicon-germanium bipolar transistor NESG3031T1K which can work at 10mK, the high electron mobility transistor HEMT and the quartz tuning fork to be matched for use, thereby not only realizing the compensation of the distributed capacitance, but also amplifying the current signal passing through the quartz tuning fork at the temperature of 10mK, and further reducing the amplitude of the driving voltage so as to hopefully improve the resolution ratio of measurement. The commercial Attocube tuning fork AFM does not incorporate an extremely low temperature (mK) amplifier and an extremely low temperature compensation circuit.

Drawings

Embodiments of the invention are described in detail below with reference to the attached drawing figures, wherein:

FIG. 1 shows a quartz tuning fork after a commercial two-pin passive 32.768kHz crystal oscillator has been stripped of its outer shell;

FIG. 2 shows the structure and working principle of a tuning fork probe;

FIG. 3 shows an equivalent circuit of a 32.768kHz quartz tuning fork (shown within the dashed box);

FIG. 4 shows the output current I (f) as a function of frequency f for a quartz tuning fork with an excitation voltage of 1V;

FIG. 5 shows a quartz tuning fork signal detection and phase compensation circuit commonly used at room temperature;

FIG. 6 illustrates I-V conversion with and without a phase compensation circuitOutput voltage V of the device_out(f)；

Fig. 7 shows the operating characteristics of the NESG 10mK for the NESG3031T1K sige bipolar transistor;

FIG. 8 shows a 10mK operating characteristic curve for a custom HEMT;

FIG. 9 shows an input-output noise spectrum measurement circuit with a very low temperature 10mK quartz tuning fork followed by a NESG3031T1K current amplifier and without a current amplifier;

FIG. 10 shows the output noise spectral relationship of a 10mK low temperature current amplifier with NESG3031T1K and without current amplification;

FIG. 11 shows a HEMT simulation analysis 10mKAFM quartz tuning fork compensation circuit;

FIG. 12 shows the results of simulation analysis of compensation of a very low temperature 10mKAFM quartz tuning fork using HEMTs;

fig. 13 shows a schematic diagram of a 10mK probe design of a quartz tuning fork based AFM, where G is a gate static operation bias terminal of a HEMT low-temperature phase compensation circuit, D is a power supply terminal of the HEMT low-temperature phase compensation circuit, B is a base bias terminal of a low-temperature NESG3031 current amplifier, and E is a power supply terminal of the low-temperature NESG3031 current amplifier.

Detailed Description

The invention is further illustrated by the following specific examples, which, however, are to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.

This section generally describes the materials used in the testing of the present invention, as well as the testing methods. Although many materials and methods of operation are known in the art for the purpose of carrying out the invention, the invention is nevertheless described herein in as detail as possible. It will be apparent to those skilled in the art that the materials and methods of operation used in the present invention are well within the skill of the art, provided that they are not specifically illustrated.

The materials and instruments used in the following examples are as follows:

a two-pin passive 32.768kHz crystal oscillator manufactured by ECS inc.

NESG3031T1K manufactured by Easter Laboratories, Inc. of California;

HEMTs are manufactured by Avago Technologies, Inc.;

the current amplifier at the room temperature end is made of a common integrated operational amplifier manufactured by Analog Devices.