阅读说明：本技术 应用于近场扫描微波显微镜的扫描区域平面纠斜的方法 (Scanning area plane inclination correction method applied to near-field scanning microwave microscope ) 是由 彭斌 黄和 鞠量 曾慧中 张万里 于 2019-08-20 设计创作，主要内容包括：一种近场扫描微波显微镜的扫描区域平面纠斜的方法,属于薄膜材料测试技术领域。本发明通过三点测试法,仅需测试三点处针尖与薄膜接触时,位移台在z轴上的移动距离,即可确定待测样品斜面的平面方程并得到面内各点z轴的坐标值,进而控制每一扫描点处针尖-样品表面的距离保持一致,有效解决了测量时的样品平面倾斜影响测量结果准确性的问题,消除了样品倾斜放置所导致的测量结果误差。(A method for correcting the plane of a scanning area of a near-field scanning microwave microscope belongs to the technical field of thin film material testing. According to the invention, by a three-point testing method, only when the needle point at three points is in contact with the film, the moving distance of the displacement table on the z axis is required to be tested, the plane equation of the inclined plane of the sample to be tested can be determined, the coordinate value of each point in the plane on the z axis can be obtained, and further the distance between the needle point at each scanning point and the surface of the sample is controlled to be consistent, so that the problem that the accuracy of the measurement result is influenced by the plane inclination of the sample during measurement is effectively solved, and the error of the measurement result caused.)

1. A method for correcting the plane tilt of a scanning area of a near-field scanning microwave microscope is characterized by comprising the following steps:

step 1, preparing metal films at four corners of a sample to be detected respectively, sequentially marking the metal films as a film A, a film B, a film C and a film D, measuring and recording the size of the sample to be detected, wherein the length is B, and the width is D;

step 2, placing a sample to be detected on a sample table, moving a displacement table to enable the probe tips to be respectively positioned right above a film A, a film B, a film C and a film D, then inserting the probe until a resonance peak disappears, enabling the probe tips to be in contact with a metal film, and respectively recording the moving distances of the displacement tables corresponding to the film A, the film B, the film C and the film D in the vertical direction;

step 3, selecting the film with the largest moving distance in the step 2, and setting the central coordinate of the film as (0, 0, z)_max) Then, establishing a three-dimensional coordinate system by the point;

step 4, obtaining (0, 0, z) according to the coordinate system established in the step 3 and the dimension parameters recorded in the step 1_max) The central points of the adjacent films are respectively (b, 0, z)₁) And (0, d, z)₂) And establishing a plane coordinate equation according to the coordinates of the three points:

wherein (x, y, z) is the coordinate of any point in the plane of the sample to be measured,is the normal vector of the plane of the sample to be measured;

according to the formula (1), the coordinates (x, y, z) of any point in the plane of the sample to be measured satisfy:

and 5, assuming that the test height is h, for any scanning point (x, y), the moving distance of the z-axis displacement table relative to the original point at the point is z-h, and the distance from the needle point to the surface of the sample can be kept to be h by adjusting the moving distance of the z-axis displacement table.

2. The method for plane rectification of the scanning area of a near-field scanning microwave microscope as claimed in claim 1, wherein the areas of the film A, the film B, the film C and the film D in the step 1 are larger than the area of the probe tip.

Technical Field

The invention belongs to the technical field of thin film material testing, and particularly relates to a method for correcting scanning area plane deflection of a near-field scanning microwave microscope.

Background

Near-Field Scanning Microwave Microscopy (NSMM) is a combination of Microwave measurement and Scanning probe measurement. The working mode is as follows: a sample to be measured is placed in the near field range of the microwave probe, so that the microwave field collected by the probe tip of the microwave probe interacts with the sample, and the properties of the sample, such as the surface structure, the dielectric property and the like, are represented by measuring the variation of the obtained feedback signal (resonance frequency, quality factor, phase position, amplitude).

The NSMM system has the advantages of nondestructive scanning, high spatial resolution and the like, so that the NSMM system is very suitable for performing nondestructive measurement on dielectric properties of all positions on the surface of a film sample. The actual measurement shows that the factors influencing the measurement result mainly have two aspects: dielectric properties at each measurement point on the surface of the film sample and the distance between the needle tip and the sample. Experiments show that the influence of the distance between the needle point and the sample on the measurement result is related to the material property, namely the influence of the two factors on the measurement result is highly coupled and is difficult to separate; while the change in the cavity parameters is more sensitive to changes in the tip-to-sample distance as the tip is closer to the sample, as shown in figure 2. Therefore, when scanning and measuring electromagnetic parameters at various positions in the plane of the film sample, the distance from the needle point to each measuring point in the plane of the film needs to be ensured to be consistent. At present, in order to control the distance between the needle tip and the sample, the adopted methods are soft contact testing, tuning fork distance measurement and the like, but the application limitations of the methods are large, and the methods can only be applied to certain specific scenes. For example, the soft contact test is implemented by directly contacting a needle tip with a sample under the action of a soft spring, but when the probe is contacted with a metal sample, the resonance peak disappears, and the soft contact test cannot be used for measuring the metal material; and the test system of the tuning fork ranging method is complicated, and the probe is difficult to assemble when extending out of the cavity for a short time.

Disclosure of Invention

The invention aims to provide a method for correcting the plane of a scanning area of a near-field scanning microwave microscope aiming at the defects in the background technology, effectively solves the problem that the plane inclination of a sample during measurement influences the accuracy of the measurement result, and eliminates the error of the measurement result caused by the inclined placement of the sample.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a method for correcting the plane tilt of a scanning area of a near-field scanning microwave microscope is characterized by comprising the following steps:

step 1, preparing metal films at four corners of a sample to be detected respectively, sequentially marking the metal films as a film A, a film B, a film C and a film D, measuring and recording the size of the sample to be detected, wherein the length is B, and the width is D;

step 2, placing a sample to be detected on a sample table, moving a displacement table to enable the probe tips to be respectively positioned right above the film A, the film B, the film C and the film D, then inserting the probe until the resonance peak disappears, enabling the probe tips to be in contact with the metal film, respectively recording the moving distance of the displacement table corresponding to the film A, the film B, the film C and the film D in the vertical direction (z axis), and recording the moving distance as z₁、z₂、z₃、z_max；

Step 3, selecting the film with the largest moving distance in the step 2, and setting the coordinates of the center point of the film as (0, 0, z)_max) Then, establishing a three-dimensional coordinate system by the point, and representing all scanning points in the plane of the sample to be detected by the three-dimensional coordinate system as (x, y, z);

step 4, obtaining (0, 0, z) according to the coordinate system established in the step 3 and the dimension parameters recorded in the step 1_max) The central points of the adjacent films are respectively (b, 0, z)₁) And (0, d, z)₂) And establishing a plane coordinate equation according to the coordinates of the three points:

wherein (x, y, z) is the coordinate of any point in the plane of the sample to be measured,is the normal vector of the plane of the sample to be measuredPerpendicular to the plane, thereforeThe dot product with any vector in the plane is zero, so that the above formula can be obtained;

according to the formula (1), the coordinates (x, y, z) of any point in the plane of the sample to be measured satisfy:

and 5, assuming that the test height is h, for any scanning point (x, y), the moving distance of the z-axis displacement table relative to the original point at the point is z-h, and the distance from the needle point to the surface of the sample can be kept to be h by adjusting the moving distance of the z-axis displacement table.

Further, the areas of the film A, the film B, the film C and the film D in the step 1 are larger than the area of the probe tip.

Further, the metal film in step 1 is gold, silver, aluminum or copper.

Compared with the prior art, the invention has the beneficial effects that:

the invention provides a method for correcting the plane of a scanning area of a near-field scanning microwave microscope, which is applied to a scanning area of a near-field scanning microwave microscope.

Drawings

FIG. 1 is a schematic diagram of a system architecture of a near field scanning microwave microscope; the system comprises a sample analyzer, a Z-axis displacement table support frame, an xy-axis displacement table, a Z-axis displacement table, a sample to be detected, a resonant cavity, a probe, a vector network analyzer and a computer, wherein 1 is the Z-axis displacement table support frame, 2 is the xy-axis displacement table, 3 is the Z-axis displacement table, 4 is the sample to be detected, 5 is the resonant; the resonant cavity and the probe are enlarged for clearly showing the structure of the system;

FIG. 2 is a graph of resonant frequency of a resonant cavity as a function of tip-sample distance;

FIG. 3 is a schematic diagram of a sample to be tested;

FIG. 4 is a test scan image using a constant height measurement method;

FIG. 5 is a test scan image of an embodiment employing the method of the present invention.

Detailed Description

The invention is further illustrated by the following figures and examples:

the invention provides a method for correcting the plane of a scanning area of a near-field scanning microwave microscope, which comprises the following steps:

step 1, respectively carrying out single-point test on several known materials, and analyzing to find that for different material samples, the variation of feedback signals (resonance frequency, quality factor, phase and amplitude) obtained by measurement of the different material samples is different along with the variation curve of the needle point-sample distance, which undoubtedly increases the analysis difficulty; but when the probe tip touches the metal sample, the resonant peak of the cavity disappears. The invention realizes plane rectification by utilizing the property, metal films are plated at four corners of a sample to be measured, the area of the metal films is preferably just larger than the diameter of a probe, the metal films are sequentially marked as a film A, a film B, a film C and a film D, the size of the sample to be measured is measured and recorded, the length of the sample to be measured is B, the width of the sample to be measured is D, and the sample to be measured is a film formed on a rectangular substrate;

step 2, placing a sample to be tested on a sample table, accurately positioning the A, B, C, D positions set in the step 1 and sequentially enabling the A, B, C, D positions to be located under the needle point, then inserting the needle with the minimum step length until the resonance peak disappears, enabling the needle point to be in contact with the metal film at the moment, and respectively recording the moving distance of a displacement table corresponding to the A, B, C, D in the vertical direction (z axis);

step 3, selecting the point (namely the lowest position of the inclined plane) of the A, B, C, D four-point z-axis displacement table moving distance maximum in the step 2, and setting the coordinate of the point as (0, 0, z)_max) Then, a three-dimensional coordinate system is established by the coordinates of the point, all scanning points in the plane of the sample to be measured are expressed by the three-dimensional coordinate system and are marked as (x, y, z), and the plane of the sample to be measured is marked as (x, y, z)Expressing a plane equation in a three-dimensional coordinate system, and then carrying out test analysis on the plane equation;

step 4, obtaining (0, 0, z) according to the coordinate system established in the step 3 and the dimension parameters recorded in the step 1_max) Two adjacent points are (b, 0, z)₁) And (0, d, z)₂) And establishing a plane coordinate equation according to the coordinates of the three points:

wherein (x, y, z) is the coordinate of any point in the plane of the sample to be measured,is the normal vector of the plane of the sample to be measuredPerpendicular to the plane, thereforeThe dot product with any vector in the plane is zero, so that the above formula can be obtained;

according to the formula (1), the coordinates (x, y, z) of any point in the plane of the sample to be measured satisfy:

and 5, determining the number of scanning points, the coordinates of the scanning points and the passing sequence of the points according to the substrate size, the test precision and the scanning track requirement, setting the test height to be h, and then, for any scanning point (x, y) in the plane to be tested, setting the moving distance of the z-axis displacement table at the point relative to the original point to be z-h, and adjusting the moving distance of the z-axis displacement table to ensure that the distance from the needle point to the surface of the sample is kept to be h.