JPS61266939A - Pulverous particles measuring instrument using scanning type electron microscope - Google Patents

Abstract

PURPOSE:To facilitate an operation and to improve its efficiency by computing many measurement positions distributed uniformly on a sample surface by a computer and moving each measurement position to an observation position automatically. CONSTITUTION:A filter film F which collects particulates is set on a sample table 15. The sample table is moved to find coordinate values of three optional points A, B, and C on the periphery of the filter film, and the coordinates of the center P of the sample F are calculated on the basis of said values. Then, many measurement positions distributed uniformly on the surface of the filter film are computed on the basis of the deviation values of coordinates between the center point P of the filter film F and the center point Q of the sample table 15, the desired number of measurement positions to be distributed uniformly on the filter film, and the area of the filter film. Pulse motors 17 and 20 are controlled to move each measurement position to the center of a cathode-ray tube 6 and the focus is adjusted by the automatic focusing mechanism 4 of an electron microscope to photograph the image on the display 5 by a camera 2. The film is taken up automatically after the photographing and the many measurement positions are photographed in order under the control of the computer 3.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention provides a scanning electron microscope for measuring the number of fine particles contained in ultrapure water for semiconductors and other types of samples. Regarding the particulate measuring device used.

(Prior art) Conventionally, for example, as a method for measuring the number of particles in ultrapure water, a unit amount of ultrapure water is filtered through a filtration membrane, the particles are collected on the filtration membrane, and the size of the particles is 0.2. If the size is more than a micrometer, an optical microscope is used, and if it is less than that, a scanning electron microscope (hereinafter referred to as an electron microscope) is used. A method is used in which the number of particles appearing in each field of view is counted with the naked eye while the field of view (measurement position) is slowly moved sequentially to the observation position by carefully rotating the knob by the measurement staff. However, with this conventional method, since there are very few particles in ultrapure water, it is necessary to measure about 50 fields of view (number of measurement positions) at a magnification of 1500 even with an optical microscope, so even an expert can complete the measurement. In addition, in the case of an electron microscope, when the magnification is increased, the field area per field of view becomes smaller, so the number of fields of view must be increased, for example, 20.
When set to 0, it takes about 8 hours to complete the measurement, especially when using an electron microscope. The result was a great deal of fatigue.

On the other hand, when the field of view becomes narrower in measurements using an electron microscope, it becomes important to distribute the measurement positions uniformly over the entire surface of the filter membrane in order to ensure measurement accuracy. However, with conventional measurement methods, it is extremely difficult to accurately align the center of the filtration membrane with the center of the sample stage. The position will deviate from the center of the sample stage, and therefore the position protruding from the filtration membrane may have to be moved to the center of the electron microscope lens barrel. Although it is necessary to move the position accurately, there are drawbacks such as the fact that it takes a considerable amount of time to uniformly move the measurement position for each micrometer.

(Problems to be Solved by the Invention) The first invention of the present application is capable of accurately moving a large number of measurement positions uniformly distributed on the surface of a sample such as a filtration membrane to the center point of the lens barrel of an electron microscope, and at the same time being efficient. The purpose of the present invention is to provide a particle measuring device using a scanning electron microscope that can achieve improved performance.

In addition to the object of the first invention, the second invention of the present application aims to provide a particle measuring device using a scanning electron microscope that can eliminate fatigue of the measurer.

(Means for Solving the Problems) In order to achieve the above object, the first invention of the present application is equipped with a scanning electron microscope having an automatic focusing mechanism and a computer, and the electron microscope has two orthogonal X-axes and a computer. A sample stand on which a sample is to be set is supported movably in the Y-axis direction, and the sample stand is connected to the
a sample stage moving mechanism having an X-direction pulse motor and a Y-direction pulse motor for driving in both axial directions;
The computer has the center point of the cathode ray tube display when the sample stage of the electron microscope is aligned with the reference position, and the X, Y
In a coordinate system with axes as coordinate axes.

A mechanism for calculating coordinate values of a center point of a sample surface set on the sample stage.

Based on the area of the sample surface, the deviation value on the coordinates between the center point of the sample surface and the center point of the sample stage, and the desired number of multiple measurement positions, multiple measurement positions uniformly distributed on the sample surface are determined by the deviation value. a mechanism for correcting the values and calculating them as coordinate values, and a mechanism for moving each of the measurement positions to the center point of the lens barrel of the electron microscope in the X and Y directions based on the coordinate values of the multiple measurement positions. and a pulse control mechanism that generates a pulse signal necessary to rotate both pulse motors and transmits it to each of the pulse motors, and the second invention of the present application is the same as the first invention of the present invention. In addition to the structure, an automatic film winding camera is placed in front of the cathode ray tube display of the electron microscope, and a shutter control mechanism for operating the camera is provided in the computer.

The present invention will be described in detail below with reference to the drawings.

In FIG. 1, the particle measuring device of this example is equipped with a scanning electron microscope (1), an automatic film winding camera (2), and a personal computer (3), and the electron microscope (1) has an automatic focusing mechanism. (4), a cathode ray tube display for photography (5), a cathode ray tube display for AM (6), and a sample stage moving mechanism (7) with a pulse motor for moving each measurement position of the sample; (2) is the cathode ray tube display (5
) is set in front of the cathode ray tube display (5), and the computer (3) is equipped with a mechanism for calculating the center point of the sample and a large number of measurement positions uniformly distributed on the sample surface. A mechanism for calculating, a pulse control mechanism for transmitting signals to the pulse motor of the sample stage moving mechanism (7), an operation control mechanism for the automatic focusing mechanism (4) of the electron microscope, and for operating the camera (2). It has a shutter control mechanism. Note that the cathode ray tube display (5) only has a smaller screen than the cathode ray tube display (6), and both display the same image.

First, the sample stage moving mechanism (7) of the electron microscope (1) will be explained. In Fig. 2, two guide rails (9), (9) extending in the X-axis direction are laid on the main plate (8), and the lower pedestal (1) is placed on the guide rails (9), (9).
0) is slidably supported in the X-axis direction, and two guide rails (11), (11) extending in the Y-axis direction are laid on the lower pedestal (10).
1), an upper pedestal (12) is supported slidably in the Y-axis direction on top of (11), and a column (13) is vertically erected at the center of the upper surface of this upper pedestal (12). ) has a male threaded portion (14) protruding from the center of the upper end surface, and a female threaded portion (14) has a female threaded portion (14) from the center of the lower surface of the sample stage (15) made of a square plate.
6) are screwed together.

As a driving means for sliding the lower pedestal (10) in the X-axis direction, an X-direction pulse motor (17) is installed on the main plate (8), and a female screw block (18) is installed on the negative side of the lower pedestal (10). is fixed in the X-axis direction, and an X-direction rotation drive shaft (19) consisting of a male threaded rod screwed into the female threaded block (18) is connected to the output shaft of the pulse motor (17), Further, as a driving means for sliding the upper pedestal (12) in the Y-axis direction, a Y-direction pulse motor (20) is used.
is installed on the main plate (8), and a female screw block (21) is fixed to the side surface of the upper right pedestal (12) facing the Y-axis direction, and consists of a male screw thread that is screwed into the female screw block (21). The Y direction rotation drive shaft (22) is connected to the lower pedestal (10).
Brackets (23), (23) protruding from the other side are rotatably supported at the open end, and the rotary drive shaft (2
2) (7) A worm wheel (24) is fixed to one end, and an interlocking shaft (26) supported by brackets (25) and (25) protruding from the other side of the lower pedestal (10).
A worm (27) is fixed to one end of the worm (27).
7) is engaged with the worm wheel (24), and the other end of the interlocking shaft (26) is connected to the output shaft of the pulse motor (20) via the universal joint (28). (29) and (30) are the motors mentioned above (
17) and (20) are hand-cranked handles.

On the sample stage (15), in this example, as a sample, a circular filtration membrane (
F) with their centers approximately aligned and set by conventional means.

Next, the sample center point calculation mechanism of the personal computer (3) is as follows. Prior to calculation, first, the sample stage (15) is aligned with the reference position. The reference position is set in advance for each electron microscope, and the reference position is set in advance for each electron microscope.
) is the position where the cathode ray tube lens barrel faces the center. Next, a coordinate system is set whose origin is the center of the cathode ray tube display (6) when the sample stage (15) is aligned with the reference position, and whose coordinate axes are the X and Y axes that are orthogonal to each other. Below, as shown in the third figure, arbitrary three points A, B, on the circumference of the filter membrane (F) set on the sample stage (15),
Coordinate values of C (X y work), (x z, yz), (Xi,
Find y3). This requires an electron microscope of 100 to 20
Adjust to low magnification of 0x.

The handles (29) and (30) of the sample stage moving mechanism (7)
) is obtained by the respective X and Y coordinate values when the three points A, B, and C are moved to the center of the cathode ray tube display (6). A point equidistant from these three points A, B, and C is the center of the filter membrane (F). In other words, for example, the intersection of the perpendicular bisector of line segment AB and the perpendicular bisector of line segment AC is Since it is the center of a circle circumscribing the triangle ABC, if the center of one circle, that is, the center of the sample is P (xo, yo), the coordinates of the center can be determined from the following expansion formula.

Vo=-3'a V
I Y2 '11 In addition, the measurement position calculation mechanism for uniform distribution on the sample surface is based on the relationship between the center point (P) of the filter membrane CF) and the center point (Q) of the sample stage (15) as shown in Figure 4. From the deviation value on the coordinates between, the desired number of measurement positions to be uniformly distributed on the surface of the filtration membrane (F), and the area of the filtration membrane (F), the filtration membrane (, F ) are calculated using coordinate values with the deviation values corrected.

Furthermore, the pulse control mechanism is configured to control the pulse control mechanism at each of the measurement positions (S).
--- Each measurement position (S) is moved to the center point of the CRT display (6).
The number of pulses necessary to rotate both the pulse motors (17) and (20) in the X and Y directions is generated based on the X and Y coordinate values of
0) respectively. In this example, one pulse moves one micrometer.

In the measurement, one measurement position (S
) from the pulse control mechanism to the X-direction and Y-direction pulse motors (17), (2
o) and rotated by a required angle, thereby moving the measuring position (S) to the center of the cathode ray tube display (6). Automatic focusing mechanism of electron microscope after movement (4)
The focus is adjusted using the shutter control mechanism, and then a shutter release signal is sent to the camera (2) from the shutter control mechanism to take an image on the cathode ray tube display (5). Camera after shooting (
2) automatically winds the film and prepares for the next shot.

The computer (3) repeats the above control to sequentially move one of the measurement positions (S) to the camera (2).
I'm going to take pictures.

When all measurement positions (S) have been photographed, the film is developed and the particles are measured using the film.

(Effects of the Invention) According to the particle measuring device using the scanning electron microscope of the first invention of the present application, a computer calculates a large number of measurement positions uniformly distributed on the sample surface, and a pulse motor in the X direction and Y direction By sending the required pulse signals to the sensor, each of the above measurement positions can be accurately and automatically moved to the observation position.

This eliminates the complicated manual operation required in the past, making work easier and more efficient.

In particular, the computer calculates the center point of the sample surface, corrects the deviation value between the center point and the center point of the sample stage, and calculates each of the above measurement positions, so each measurement point can be accurately positioned with respect to the sample surface. The combination of these features makes it possible to achieve highly accurate particulate measurement.

According to the particle measuring device using a scanning electron microscope of the second invention of the present application, in addition to the effects of the first invention, images of each measurement position projected on a cathode ray tube display are sequentially photographed by an automatic film winding camera, By measuring fine particles using those photographs, compared to the conventional method,
This greatly reduces the fatigue of the measurer and enables more accurate measurements.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is an overall block diagram, FIG. 2 is a perspective view of the sample stage moving mechanism with the sample stage separated, and FIG. 3 is an explanation showing a method for calculating the center point of a filtration membrane. FIG. 4 is an explanatory diagram showing the center point deviation between the filtration membrane and the sample stage, and FIG. 5 is an explanatory diagram showing measurement positions arranged on the filtration membrane surface. 1-111 scanning electron microscope, 2-111 automatic film winding camera, 3-111 personal computer. 4-111 automatic focus mechanism, 5----Cathode-ray tube display for photographing, 6----Cathode-ray tube display for observation, 7----Sample stage moving mechanism, 15----Sample stage,
17---X direction pulse motor, 2O---Y direction pulse motor, F-111 filtration membrane.

Claims (2)

[Claims] (1) The electron microscope is equipped with a scanning electron microscope having an automatic focusing mechanism and a computer, and the above-mentioned electron microscope is equipped with a sample stage on which a sample is set, which is supported movably in mutually orthogonal X-axis and Y-axis directions; a sample table moving mechanism having an X-direction pulse motor and a Y-direction pulse motor for driving the sample table in both the X and Y axis directions, and the computer moves the sample table of the electron microscope to a reference position. The origin is the center point of the cathode ray tube display when set to
In a coordinate system with the axis as the coordinate axis, a mechanism for calculating the coordinate values of the center point of the sample surface set on the sample stage, an area of the sample surface, a center point of the sample surface, and a center point of the sample stage. a mechanism that corrects the deviation value and calculates each of the multiple measurement positions uniformly distributed on the sample surface as coordinate values based on the deviation value on the coordinates and the desired number of multiple measurement positions; and the lens barrel of the electron microscope. In order to move each measurement position to the center point of the measurement position, a pulse signal necessary to rotate both the pulse motors in the X direction and the Y direction is generated based on the coordinate values of the multiple measurement positions. and a pulse control mechanism for transmitting signals to the respective pulses. A particle measurement device using a scanning electron microscope. (2) Equipped with a scanning electron microscope having an automatic focusing mechanism, an automatic film winding camera, and a computer, the electron microscope is capable of handling a sample supported movably in the mutually perpendicular X-axis and Y-axis directions. The automatic film winding camera has a sample stage to be set, and a sample stage moving mechanism having an X-direction pulse motor and a Y-direction pulse motor for driving the sample stage in both the X and Y directions, respectively. The computer is placed in front of the cathode ray tube display of the electron microscope, and the computer uses the center point of the cathode ray tube display when the sample stage of the electron microscope is aligned with the reference position as the origin, and
In a coordinate system with the axis as the coordinate axis, a mechanism for calculating the coordinate values of the center point of the sample surface set on the sample stage, an area of the sample surface, a center point of the sample surface, and a center point of the sample stage. a mechanism that corrects the deviation value and calculates each of the multiple measurement positions uniformly distributed on the sample surface as coordinate values based on the deviation value on the coordinates and the desired number of multiple measurement positions; and the lens barrel of the electron microscope. In order to move each measurement position to the center point of the measurement position, a pulse stop signal necessary to rotate both the pulse motors in the X direction and the Y direction is generated based on the coordinate values of the multiple measurement positions, and both pulses are generated. a pulse control mechanism that sends signals to each motor; a shutter control mechanism that operates the camera;
A particle measuring device using a scanning electron microscope.