JPH07118289B2 - Two-dimensional analyzer for sample surface - Google Patents

Description

TECHNICAL FIELD The present invention relates to a surface analyzer of the type that scans a sample surface with a particle beam.

(Prior Art) An analysis in which a particle beam such as an electron beam is focused on a sample surface to scan the sample surface to detect secondary radiation emitted from the sample has a high positional resolution, and therefore the concentration of elements on the sample surface is high. It is suitable for measuring distributions and state distributions in detail and displaying images. For this reason, the color content mapping method has been conventionally used in which the element concentration distribution on the sample surface is converted into a color image and displayed using EPMA, but the shape of the scanning range on the sample surface is defined by the scanning widths in the x and y directions. Since it is decided by setting, it is usually limited to a square. In particular, there has been proposed a method of setting a scanning range in a parallelogram so as to be circumscribed with a distorted amorphous region to be analyzed (Japanese Patent Laid-Open No. 59-79946). In addition, the sample surface is scanned at high speed and appropriate secondary radiation is detected to determine whether or not the area requires analysis.
Various methods have been proposed to reduce the analysis time by scanning only the area requiring analysis over time.
Since the required analysis range is not known in advance, fast-forward on the scan line to reach the required analysis area and suddenly switch to slow-forward, it is impossible for the scanning mechanism, and even in the area that does not require analysis. Since the scanning mechanism is driven, the total amount of movement of the scanning mechanism is larger than the amount of movement of the scanning mechanism in only the analysis required area, which shortens the life of the mechanism.

(Problems to be Solved by the Invention) In the above-described sample surface analysis method, it is necessary to take a certain amount of time per pixel in order to improve analysis accuracy. For example, the sample is irradiated with an electron beam, and the element concentration measurement for spectrally detecting the X-rays emitted from the sample takes about 1 second per pixel. Therefore, when measuring the sample surface by dividing it into 500 pixels vertically and horizontally, the number of pixels is 500 x 500 = 250,000, and approximately 70
It will take time. On the other hand, the sample has various cross-sectional shapes, and when measuring a quadrangle that circumscribes such a sample surface as its outer shape as a scanning range, it takes a lot of time for unnecessary points in analysis. Especially, as mentioned above, when the measurement of one surface takes several tens of hours, it is an important issue to eliminate this useless measurement time. An object of the present invention is to improve the efficiency of surface analysis by an apparatus of a type that scans a sample surface with a particle beam.

(Means for Solving the Problem) In the two-dimensional scanning of the sample surface, a predetermined range is scanned along one straight line, and then the position of the scanning line is slightly moved in the direction perpendicular to the scanning line. Is repeated. Now, let us say that the direction of the above-mentioned scanning line is the x direction and the direction orthogonal thereto is the y direction, and the x axis and the y axis are determined for each of the x and y directions, and the position on the sample surface is represented by the xy coordinate value.

The present invention comprises means for storing in the storage device the x-coordinate values of the start and end points of the scan in the x-direction as a function of the y-coordinate value.
The sample surface analyzer is provided with scanning control means for performing scanning in the x direction from the scanning start point to the scanning end point in the x direction for each scanning line within the scanning range in the y direction based on the data stored in the storage device.

Further, in the case where the region requiring analysis is an arbitrarily curved strip-shaped region, means for storing in the storage device x, y coordinate data representing a curve passing through the center of the width of the strip-shaped region, and the stored data Scanning points were set on the curve at appropriate intervals, and a scanning control program for scanning a range including the belt-like region along a straight line passing through each of the scanning points and orthogonal to the curve was given to the scanning control means.

(Operation) According to the present invention, a region that requires analysis by connecting the line connecting the scan start points and the line connecting the end points by means for storing the start point and the end point of the scan in the x direction as a function of y You can make a closed curve that surrounds and surrounds
Since the scanning measurement will be performed only in this closed curve,
The time required for the measurement is shortened as compared with the measurement within the four sides circumscribing the area requiring analysis.

In addition, when the analysis area is in the shape of an arbitrarily curved strip, the width of the strip area is scanned along the scanning line that is orthogonal to the curve that passes through the center of the width of this strip area, so measurement is performed without scanning an extra area. The time required is reduced.

(Embodiment) FIG. 1 shows an embodiment of the present invention. E is an electron beam microanalyzer (EPMA), and S is a sample, which is set on the x, y-direction moving stage T. C is a crystal for X-ray spectroscopy, D is an X-ray detector for detecting dispersed X-rays, and P is a secondary electron detector for detecting secondary electrons emitted from the sample. Further, M is an objective concave mirror of an optical microscope arranged coaxially with the optical axis of the EPMA electron optical system, and L is an eyepiece lens of the microscope. Tx is an x drive device that moves the stage T in the x direction, and Ty is a y drive device. dx and dy are deflection coils for deflecting the electron beam e in the x and y directions, respectively, and Dx and Dy are scanning signal generation circuits in the x and y directions, respectively. This scanning signal is also applied as a scanning signal to a CRT for displaying a sample image, and the output of the secondary electron detector P is applied as a luminance signal to the CRT to generate a secondary electron image on the sample surface. Displayed on CRT. The CPU is a computer for controlling the operation of the device, K is a keyboard for inputting various data or commands to the CPU, and J is a joystick on the keyboard. Joyce Tech J is CP
When operating the stage T drive instruction to U, the stage T can be moved in the direction in which the joystick is tilted. When the CPU issues an electron beam movement instruction, the center point of the sample surface scanning by the electron beam. Can be moved.
m1 is a scanning range storage memory, and m2 is a measurement data storage memory.

The operation in the case of analyzing the sample cross section as shown in FIG. When the sample cross section is relatively large, specify the analysis range using an optical microscope. While observing the sample through the eyepiece L, the appropriate point A is set as the starting point along the outer periphery of the sample, and the joystick is operated so that the point A is in the center of the visual field of the microscope, and the stage T is moved.
A memory instruction is given to U to store the x, y movement amount of the stage T at that time, that is, the x, y coordinates. The chain line F surrounding the sample thereafter
Operate joystick J so that the upper point is in the center of the field of view, and follow chain line F to reach point B, while giving CPU instructions as appropriate to the memory and giving x, y coordinates of many points on chain line F. C
Store in PU. When the above operation is completed, the CPU draws the chain line F from the coordinate data of many points on the chain line closed curve F surrounding the sample cross section.
Is reconstructed with broken lines, the minimum value and the maximum value of the y coordinate of the scanning range are obtained, and the y coordinate of each scanning line is determined by dividing the value by a predetermined number of scanning lines, and the data of the reconstructed chain line F From the above, the x-coordinate of the point intersecting with the chain line F is calculated for each scanning line, and the x-coordinate data thus calculated is used as the scanning start point end point on each scanning line and as one table together with the y coordinate data of each scanning line. Store in memory m1. After that, when the analysis operation is started, the CPU reads the y-coordinate of the scanning line from the memory m1, drives the stage T in the y-direction, and then the y-axis.
The stage T is x by the data of the x coordinate corresponding to the coordinate.
Driving in the direction, the analysis operation is performed over a predetermined scanning range over time. In this way, scanning is performed only within the area surrounded by the chain line F. When the sample cross section is small, the setting operation is easier to perform by using the secondary electron image on the CRT than by using the optical microscope for setting the scanning area. In this case, the CPU may be instructed to move the joystick J with the electron beam, and thereafter, setting scanning may be performed while observing the sample cross-sectional image on the CRT in the same manner as described above. Instead of moving the sample image with the joystick, the sample cross-sectional image on the CRT may be kept still, and a closed curve may be drawn around the sample cross-sectional image with the light pen to specify the scanning region. Even in the case of using the optical microscope, it goes without saying that the optical microscope image can be captured by the television camera and displayed on the CRT, and the scanning area can be designated by the light pen.

In the above-mentioned embodiment, the scanning area of the sample is a single connection area,
When the sample is tubular or has a cross section as shown in FIG. 3, the scanning region is a multi-connection region such as double or triple. In this case, one scan line corresponds to an even number of x-coordinates of 2 or more. The CPU reads these x-coordinates in ascending order, determines that the smallest value is the scan start point, the next is the scan end point, and the third is the scan start point again, and the next scan from the scan end point. Fast-forward the stage until the starting point.

Next, another operation mode of the apparatus shown in FIG. 1 will be described. When the cross section of the sample has a curved shape with a narrow width as shown in FIG. 4, it is specifically suitable for the analysis of the side surface of the tape-shaped sample and the cross section of the plating layer on the surface of the article having an arbitrary cross section. This is an analysis operation. Even in such a case, the above-described operation mode can be applied, but in such a case, the scanning line X having a constant length l is drawn in the direction orthogonal to the curve G passing through the center of the width of the curved strip region. This is advantageous because it is easier to set the scanning area, and the number of times the stage is fast-forwarded and the distance are reduced during actual analysis. When this operation is performed, the CPU is instructed to scan the curve in advance, the center line G of the sample width is traced by the center point of the visual field while observing the optical microscope, and the shape of the center line G of the sample width is used as a relation table of x and y. Store in CPU. CP
From this relational table, U determines scanning points on the center line G at regular intervals and obtains their x and y coordinates. Next, at each scanning point, the direction orthogonal to the center line is calculated as the y-direction movement amount of the unit movement amount of the stage T in the x-direction, and the x, y coordinates and direction data (y-direction movement amount for the x-direction unit movement amount) are calculated. Amount) is stored in the memory m1. Separately, the scanning width 1 is set by the keyboard K. The CPU uses the data in the memory m
For each scanning point, the x, y coordinates of the starting point and the x coordinate of the ending point of the scanning line and the above-mentioned direction data are made into a table and stored again in the memory.
Store in m1. After that, when the analysis operation is started, CP
The U reads the contents of the memory m1, moves the stage T to the starting point of the scanning line, performs the analysis while moving the stage in the x and y directions at a predetermined ratio according to the direction data, and the stage position is x at the end point of the scanning line. When the coordinate values are reached, the stage is fast-forwarded to the starting point position of the next scanning line and the analysis is repeated along the next scanning line.

In the above example, the y-direction movement amount for the x-direction unit movement amount of the stage is used as the scanning line direction data. However, when the scanning line direction is close to the y-axis direction, the value of the direction data becomes large, which is inconvenient. When the inclination of the stage is 45 ° or more with respect to the x-axis, it is better to set the movement amount in the x direction to the unit movement amount in the y direction of the stage. This is just a programming problem. Similarly, the method of defining the end point of the scanning line is such that only the x coordinate is specified in the above example.
When the scanning line direction is close to the y-axis direction, the difference between the x-coordinates of the scanning start point and the end point becomes small and the positional accuracy of the end point deteriorates. Therefore, the end point is defined by the y-coordinate at the 45 ° direction. Better. Further, when the center line of the width of the sample is stored in the CPU, it is sufficient to store it by broken line approximation without storing it as an accurate curve. Further, in the above example, scanning is performed by moving the stage, but in this case, since the scanning width is small, the sample is moved by the stage T so that the center line passes on the optical axis of the electron optical system, and the center line is moved. The orthogonal scanning may be performed by oscillating an electron beam.

(Effects of the Invention) According to the present invention, since the surface analysis of the sample surface is performed only in the necessary area, the analysis efficiency is improved, and the effect becomes larger as the variation of the actual area of the analysis area becomes smaller. Further, since the scanning mechanism is moved only within the range that requires analysis, it is possible to reduce the total movement amount of the scanning mechanism and prolong the life of the scanning mechanism.

[Brief description of drawings]

FIG. 1 is a block diagram of an apparatus according to an embodiment of the present invention, FIG. 2 is an explanatory diagram of how to set a scanning region when an analysis region is a single connected region, and FIG. 3 is a diagram of an analysis region of a multiple connected region. , 4th
The figure is an explanatory view of a sample surface scanning state according to the second invention of the present application. E: EPMA, S: sample, T: sample moving stage, T
z, Ty: x-direction and y-direction driving device for the moving stage T, Dx, Dy: electron beam scanning signal generation circuit, m1: scanning range storage memory, m2: measurement data storage memory,
K ... Keyboard, J ... Joystick, L ... Eyepiece of optical microscope.

Claims (2)

[Claims] 1. In an analyzer of a type that scans a sample surface with a particle beam and detects secondary radiation emitted from the sample, a scanning range in a direction orthogonal to the scanning line and a scanning start point on each scanning line. And means for storing one or a plurality of pairs of end points in the scanning line direction in the storage device in correspondence with the positions in the direction orthogonal to the scanning line, and the direction orthogonal to the scanning line by the data stored in the storage device. From the start point to the end point of the scanning range, the scanning control means is provided for fast-forwarding a section that does not require scanning from the first scanning start point to the last scanning end point in the scanning direction for each scanning line. A two-dimensional analyzer for a sample surface, which is characterized in that 2. An analyzer which scans a sample surface with a particle beam and detects secondary radiation emitted from the sample. Means for storing coordinate data representing an arbitrary curve on the scan surface in a storage device. And scanning by setting scanning points on the curve at appropriate intervals according to the data in the storage device, and scanning a range of a designated length around the scanning point along a straight line orthogonal to the curve at each scanning point. A two-dimensional analysis apparatus for a sample surface, which is provided with a control means.