JPH02253550A - Charged particle beam scanning equipment - Google Patents

Abstract

PURPOSE:To permit observing a large-sized sample in a small sample room by rotating and plane-moving the sample in a plane for being parted into four quadrants to be observed. CONSTITUTION:A sample 3 is placed on a rotary table 10 placed on a movable table 11 making planar movements in a plane vertical to the rotation axis of the table 10. Operation of the rotary table 10 by a rotary drive mechanism 12, operation of the movable table 11 by a movable drive mechanism 13 and scanning of electron beams(EB) by a scanning signal generator circuit 4 are all made via a control unit 8. Consequently, the sample 3 is parted into four quadrants for permitting to scan each of the quadrants in the same direction. Moreover, a boundary area (R) having its width equal to the size of the maximum visual field of a scanning electron microscope image is provided to each of boundary portions between the respectively adjacent guadrants, so that the sample 3 can be continuously observed even if a changeover to each adjacent quadrant is made.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a charged particle beam apparatus such as a scanning electron microscope that scans a charged particle beam over a sample and observes an image of the sample.

(Conventional technology) Semiconductor wafers are observed using scanning electron microscopes, etc., but the size of wafers has been increasing year by year, and currently,
The 6-inch ones are mainly observed. It is predicted that the size of this wafer will increase to 8 inches to 10 inches in the near future.

By the way, in a scanning electron microscope, a stage on which a sample is placed is moved two-dimensionally to observe the entire surface of the sample. In this case, in order to observe the entire surface of the sample, the stage needs a movement span equal to the diameter of the sample. In other words, the sample chamber needs to be twice the diameter of the sample.

(Problem to be solved by the invention) As described above, the sample chamber needs to be twice as long as the diameter of the sample, but if a wafer is used as a sample, as the wafer becomes larger, scanning The sample chamber of an electron microscope will become significantly larger. As a result, the following problems arise.

■The vacuum pump becomes larger in order to evacuate the large-capacity sample chamber to a high vacuum.

■The sample stage must be manufactured with a high precision of several μm, but it is difficult to manufacture a large stage with such high precision.

■As the sample chamber becomes larger, the installation area of the scanning electron microscope also becomes larger.

■As the sample chamber and vacuum pump become larger, the cost of the equipment increases significantly.

The present invention has been made in view of these points, and its purpose is to realize a charged particle beam device that can reduce the size of the sample chamber even when observing a large sample.

(Means for Solving the Problems) A charged particle beam device according to claim 1 of the present invention includes a focusing lens for focusing a charged particle beam on a target, and a focusing lens for two-dimensionally scanning the charged particle beam on the target. a first table that moves on a plane; a second table that is rotatably arranged on the first table and on which a target is placed; and a drive means that drives the first table. , comprising a rotational drive means for rotating the second table every 90 degrees, and a control system for rotating the scanning direction of the charged particle beam by the deflector in synchronization with the rotation of the second table by the rotational drive means. , virtually divide the area on the target into four quadrants, and
By rotation every 0° and plane movement of the first table,
It is characterized by a configuration in which four quadrants are observed using a charged particle beam.

A charged particle beam device according to claim 2 of the present invention includes a focusing lens for focusing a charged particle beam on a target, a deflector for two-dimensionally scanning the charged particle beam on the target, and a a first table that moves the target; a second table that is rotatably arranged on the first table and on which the target is placed; a drive means that drives the first table; and a control system that rotates the scanning direction of the charged particle beam by the deflector in synchronization with the rotation of the second table by the rotation drive means, and a control system that rotates the scanning direction of the charged particle beam by the deflector in synchronization with the rotation of the second table by the rotation drive means. Divided into four quadrants, 9 of the second table
By rotation every 0° and plane movement of the first table,
The four quadrants are configured to be observed by the charged particle beam, and the control system is arranged such that if there is an observation point in the quadrant boundary region, the second table remains on the observation point after being rotated by 90°. It is characterized by having a function of moving the second table so that scanning of the charged particle beam is performed.

(Function) In the invention of claim 1, the sample is placed on a rotary table,
The rotary table is rotated every 90@, the sample surface is virtually divided into four quadrants, and each quadrant is moved two-dimensionally horizontally to observe the entire surface of the sample.

In the invention of claim 2, the sample is placed on a rotary table,
The rotary table is rotated every 90 degrees, the sample surface is virtually divided into four quadrants, two-dimensional horizontal movement is performed for each quadrant, the entire surface of the sample is observed, and each quadrant is The boundary area of the quadrant can be observed in any of the adjacent quadrants, and if the sample is rotated 90 degrees while observing the quadrant boundary area, the table should be set so that the observation point can be continuously observed after rotation. Move horizontally.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a scanning electron microscope that is an embodiment of the present invention. An electron beam EB from an electron gun 1 is narrowly focused onto a sample 3 by a focusing lens 2. The electron beam irradiation point on the sample 3 can be changed by supplying a scanning signal from the scanning signal generating circuit 4 to the deflector 5. For example, 2
The secondary electrons are detected by a secondary electron detector 6.

The signal detected by the detector 6 is amplified by the amplifier 7 and then sent to the scanning signal generation circuit 4 via the control device 8.
The scanning signal is supplied to the cathode ray tube 9 as a brightness modulation signal.

The sample 3 is placed on the rotary table 10,
Rotary table 10 is rotatably mounted on movable table 11. The rotary table 10 is rotated by a rotation drive mechanism 12, and the moving table 11 is moved horizontally by a horizontal movement drive mechanism 13. The rotational drive mechanism 12 includes a quadrant changeover switch 14
The rotary table 10 is driven by the switching of the rotary table 10, thereby causing the rotary table 10 to rotate. The movement drive mechanism 13 is driven by an instruction from the movement instruction circuit 15, and the movement table 11 is thereby moved.

The operation of the above-described configuration is as follows. The observation range of sample 3 is virtually divided into four quadrants as shown in FIG. Figure 2(a) shows the initial state, and sample 3 is divided into four quadrants (1) to (4).
The electron beam is irradiated onto a first quadrant (1) marked with diagonal lines.

Observation of each part in this first quadrant (1) is carried out by moving the moving table in the direction of the arrow by pressing any of the four arrow buttons of the movement instruction circuit 15, and by this mechanical movement. This is performed by two-dimensional scanning of the electron beam EB after the movement.

That is, after pressing one of the arrow buttons on the movement instruction circuit 15 to move the movement table 11 to place a desired area of the sample under the electron beam optical axis, the control device 8 controls the scanning signal generation circuit 4 to A scanning signal is supplied to the deflector 5, and a desired area on the sample 3 is two-dimensionally scanned by the electron beam. Secondary electrons generated by the electron beam irradiation are detected by a detector 6 and sent to an amplifier 7.
Since the scanning signal is amplified by the scanning signal generating circuit 4 and then supplied to the cathode ray tube 9 to which the scanning signal is supplied,
A secondary electron image of the sample is displayed on the cathode ray tube 9. In addition,
In the electron beam length measuring device, length measurements such as the width of the observation pattern are performed in the control device 8 based on the detection signal.

Next, the observation in the first quadrant (1) is completed, and the observation in the second quadrant (2) is completed.
When observing the quadrant switch 14,
) press the switch. When this switch (2) is pressed, the control device 8 drives the rotary drive mechanism 12 to rotate the rotary table 10 by 90@, so that it is aligned on the electron beam optical axis as shown in FIG. 2(b). The second quadrant (2) of sample 3 is placed. In this state, observations are made in the second quadrant, and the third
When observing the quadrant, press the quadrant selector switch 14 (
The switch 3) is pressed, and the sample 3 is further rotated by 90'' as shown in FIG. Then, as shown in FIG. 2(d), the sample 3 is rotated.

In this way, we rotated sample 3 every 90 degrees and moved the sample horizontally in each of the four virtually divided quadrants to observe the entire surface of the sample. The span can be reduced to half the diameter of the sample, and the moving table and moving mechanism can be made smaller, as well as the size of the sample chamber.

In addition, when pressing the right arrow button in the first quadrant of the arrow buttons of the movement instruction circuit 15 and moving the sample in the X direction of the sample's absolute coordinates, for example, when rotating the sample by 90 degrees, Even if only the right arrow is pressed on the movement instruction circuit, the sample is still controlled to move in the X direction of the sample's absolute coordinates. With this kind of control, the operator can move the sample without being aware of the rotation of the sample, i.e.
You can move your field of view.

Next, the rotation of the sample 3 and the scanning direction of the electron beam will be explained. As shown in Figure 3(a), when observing the first quadrant (1), the electron beam is
Scanning is performed in the X direction in the coordinates of the deflector 5. Next, when the sample is rotated 90'' and the second quadrant (2) is observed as shown in FIG. 3(b), the scanning signal from the scanning signal generation circuit 4 is As shown in the figure, the electron beam is scanned in the X direction of the coordinates of the deflector 5.As a result, even if the sample is rotated 900 times, the scanning of the electron beam on the sample always follows the absolute coordinates of the sample. This is done in the X direction, and rotation of the direction of the image during image observation on the cathode ray tube is prevented.

Next, another embodiment of the present invention will be described based on FIG.

In this embodiment, a boundary region R of a constant width, indicated by diagonal lines in the figure, is provided at each quadrant boundary of four quadrants (1) to (4). That is, the moving ranges of the moving table 11 overlap by several degrees at the boundary. This width is equal to the maximum field size of a scanning electron microscope image.

Now, observing inside the first quadrant (1), the observation field enters the boundary area between the first quadrant and the second quadrant, and becomes point A in the figure.
When starting observation of the second quadrant (2) from this point A, the electron beam will always be at A, even if the rotation table 10 rotates.
The control device 8 controls the moving drive mechanism 13 in synchronization with the rotation so as to scan from a point. As a result, sample 3 was 90
``Even if the observation of the second quadrant is started after rotation, the first
The observation field in the quadrants is displayed on the cathode ray tube 9, and the sample can be observed continuously even by switching from the first quadrant to the second quadrant.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to these embodiments. For example, when switching quadrants, the field of view shifts significantly, so a portion of the screen of the cathode ray tube 9 is shown in Figure 5(a) so that the operator can always check which part of the sample is currently being observed. It is effective to display a diagram of the sample 3 and display the observation point indicated by a point P in the diagram as a spot, as shown in FIG. When the sample 3 is rotated 90 degrees and the second quadrant is observed, the spot position indicating this observation point moves to point P' as shown in FIG. 5(b). In addition, although the explanation was given using a scanning electron microscope as an example, the sample is irradiated with an ion beam, and secondary ions and secondary ions from the sample are detected.
The present invention can also be applied to a device configured to detect secondary electrons.

(Effects of the Invention) As described above in detail, in the invention of claim 1, the sample is placed on a rotary table, and the rotary table is rotated every 90 degrees, so that the sample surface is virtually divided into four quadrants. Since the entire surface of the sample can be observed by moving horizontally in two dimensions in each quadrant, the horizontal movement span of the sample can be set to half the diameter of the sample. The mechanism is compact and the moving mechanism can be manufactured with high precision. Furthermore, since the length of the sample chamber is reduced to 3/4 and the area to 1/2 of that of the conventional sample chamber, it becomes easier to evacuate to a high vacuum and the vacuum pump can be made smaller. Furthermore, the installation area of the device can be reduced, and the overall cost can be lowered.

In the invention of claim 2, the sample is placed on a rotary table,
The rotary table is rotated every 90'', the sample surface is virtually divided into four quadrants, and each quadrant is moved two-dimensionally horizontally to observe the entire surface of the sample. The boundary of the quadrant can be observed in any of the adjacent quadrants, and if the sample is rotated 90 degrees while observing the quadrant boundary area, the table should be set so that the observation point can be continued after rotation. Since it is configured to move in the horizontal direction, in addition to the effects of claim 1, observation across different quadrants can be performed continuously without any jump in the field of view.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a scanning electron microscope which is an embodiment of the present invention, FIG. 2 is a diagram for explaining a sample observation method using an apparatus based on the present invention, and FIG. 3 is a diagram showing rotation of a sample. FIG. 4 and FIG. 5 are diagrams for explaining other embodiments of the present invention. 1... Electron gun 2... Focusing lens 3...
Sample 4...Scanning signal generation circuit 5...Deflector 6...Detector 7...Amplifier
8...Control device 9...Cathode ray tube 10...
Rotary table 11...Movement table 12...Rotary drive mechanism 13...Movement drive mechanism 14...Quadrant changeover switch 15...Movement instruction circuit 2 Fig. 3 Fig. 5

Claims (2)

[Claims] (1) A focusing lens for focusing a charged particle beam on a target, a deflector for two-dimensionally scanning the charged particle beam on a target, a first table that moves on a plane, and a first rotatably placed on the table of
A second table on which a target is placed, a drive means for driving the first table, a rotation drive means for rotating the second table every 90 degrees, and a rotation drive means for rotating the second table by the rotation drive means. A control system that synchronously rotates the scanning direction of the charged particle beam by the deflector, virtually divides the area on the target into four quadrants, and rotates the second table every 90 degrees and the first table. A charged particle beam device configured to observe four quadrants with a charged particle beam by moving the plane of the charged particle beam. (2) a focusing lens for focusing the charged particle beam on the target; a deflector for two-dimensionally scanning the charged particle beam on the target; a first table that moves on a plane; rotatably placed on the table of
A second table on which a target is placed, a drive means for driving the first table, a rotation drive means for rotating the second table every 90 degrees, and a rotation drive means for rotating the second table by the rotation drive means. A control system that synchronously rotates the scanning direction of the charged particle beam by the deflector, virtually divides the area on the target into four quadrants, and rotates the second table every 90 degrees and the first table. The four quadrants are configured to be observed by the charged particle beam by plane movement of the second table, and when the observation point is in the quadrant boundary area, the control system A charged particle beam device having a function of moving the second table so that scanning of the charged particle beam is still performed over the observation point.