JPH10172486A - Beam shift constolling method of charged particle beam microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To release an operator from complicated work by enabling observation while consecutively changing an observation point without restraint of a limit shift quantity of a charged particle beam at a viewing field of high magnification. SOLUTION: When an attempt is made to move observation point on a sample by 100 micrometers, for example, a movement distance L of a beam irradiation position is 100 micrometers, and assuming that a limit shift quantity D of a charged particle beam microscope being used is 30 micrometers, a movement distance of the irradiation position at the completion of a first (n=1) beam shift operation is 30 micrometers. Similarly, the movement distance of the irradiation position at the completion of a second (n=2) beam shift operation is 30 micrometers, resulting in 60 micrometers in total. The total movement distance of the irradiation position at the completion of a third (n=3) beam shift operation is 90 micrometers. Since an observation point is moved by 100 micrometers, if 10 micrometers is added by a fourth (n=4) beam shift operation, a target observation point is reached. At this time, a beam shift quantity is 10 micrometers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a beam shift control method for a scanning charged particle beam microscope.

[0002]

2. Description of the Related Art In a scanning charged particle beam microscope represented by a scanning electron microscope, when the observation position of a sample is changed, a stage on which the sample is mounted is driven or a charged particle beam is applied to a magnetic field of a deflection coil. "Beam shift" is used. Usually, for low-magnification observation, a stage drive with a large moving distance is used, and for high-magnification observation, the moving distance of the beam irradiation position is as small as several tens of μm, but a beam shift that enables precise positioning is used. Have been.

[0003] In general, the driving amount (driving distance) of a stage depends on the size of the stage, but is several tens of mm.
The beam shift amount is as small as about ± 30 μm in order to maintain the resolution. When moving the point to be observed on the sample and observing the point in detail, first drive the stage with a low magnification field of view, roughly locate the point to be observed, switch to the high magnification field of view, and beam shift Observe with stricter positioning. Subsequently, when observing another point, the operation of switching to the low magnification field of view again and driving the stage was repeated.

[0004]

However, as described above, when different points on the sample are observed one after another, the magnification must be frequently switched between a low-magnification visual field and a high-magnification visual field. Increases the burden on the operator. If the observation position can be moved and accurate positioning can be performed while maintaining the high magnification field of view, such a complicated operation becomes unnecessary, and the burden on the operator is reduced.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a beam shift control method capable of solving the above-mentioned problems and smoothly moving an observation position while maintaining a high-magnification field of view, and enabling accurate positioning.

[0006]

According to the first aspect of the present invention, there is provided a beam shifter for a charged particle beam microscope which moves and positions the irradiation position of a charged particle beam on a sample mounted on a stage. In the control method, the irradiation position is moved by a beam shift operation, and when the movement distance reaches a limit shift amount which is a maximum shift amount of the charged particle beam, the stage is beam-shifted by the limit shift amount. The operation of driving in the opposite direction to the shift direction and the operation of returning the irradiation position to the origin position are automatically performed,
This operation is repeatedly performed until the movement of the irradiation position is completed. "

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is a beam shift control method for a charged particle beam microscope capable of moving an irradiation position of a charged particle beam and performing accurate positioning only by a beam shift operation. The movement of the irradiation position uses both the beam shift and the driving of the stage on which the sample is placed.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the flowchart shown in FIG. FIG. 1 is a flowchart showing a beam shift control method according to the embodiment of the present invention. Although the beam shift control method shown in the flowchart of FIG. 1 is one-dimensional (for example, in the X-axis direction on the sample) for clarity of description, it is needless to say that the beam shift control method is not limited to one-dimensional but also two-dimensional (for example, on the sample). XY
Plane).

In the flow chart of FIG. 1, the moving distance of the irradiation position of the charged particle beam is L, the limit shift amount which is the maximum shift amount of the charged particle beam is D, and the charged particle beam having the limit shift amount as a limit. 1 beam shift operation
Count the times. Therefore, when the movement distance of the irradiation position is long, the number of beam shift operations increases by one, such as 1, 2, 3,..., N.

In the flowchart of FIG. 1, first, S1
In step 1, the charged particle beam is set at the origin position. This is a state where the magnetic field of the deflection coil is zero. The observation magnification is set to, for example, a high magnification of 1000 times or more. The position of the stage may be arbitrary as long as it can be driven. In S12, the first (n = 1) beam shift operation is performed to change the observation point, that is, to move the irradiation position of the charged particle beam. The moving direction of the irradiation position is instructed by a direction indicating device on the console, and the beam shift operation is performed in accordance with the instruction. Any of a trackball, a joystick, a keyboard and the like may be used as the direction indicating device.

In S13, it is determined whether or not the moving distance of the irradiation position has reached the limit shift amount D of the charged particle beam. If it has reached, the process proceeds to S14, and if the movement of the irradiation position is terminated in a state where it has not reached, the process proceeds to S17. In S14, the stage on which the sample is placed is moved by D. The moving direction of the stage is opposite to the beam shifting direction. That is, shifting the charged particle beam in the + X direction on the sample is equivalent to driving the stage in the -X direction.

In S15, the charged particle beam is reset to the origin position. That is, the magnetic field of the deflection coil is returned to zero. The beam irradiation position at this time is in the initial state S11.
That is, it has moved by D from the time. In S16, the operator determines whether to continuously move the irradiation position. When the movement is continued, the process returns to S13, and the second (n = 2) beam shift operation is performed. Hereinafter, while the operator continues to move the irradiation position, S13 to S
The steps up to 16 are repeated.

If the movement is to be ended in S16, the process proceeds to S17.
Proceed to. This completes the nth beam shift operation,
In this case, the (n + 1) -th beam shift operation is not performed. At this time, the total movement distance of the stage is n × D, and the beam irradiation position is just at the origin, so that the beam shift is zero. . In S17, since the stage is not moved any more, the stage remains fixed. At this point, the total travel distance of the stage is (n-
1) xD. The irradiation position of the charged particle beam is in the middle of the n-th beam shift operation, and the shift amount of the charged particle beam is L- (n-1) D.

For example, when it is desired to move the observation point by 100 μm on the sample, the moving distance L of the beam irradiation position is 100 μm.
m and the limit shift amount D = 30 μm of the charged particle beam microscope used, the moving distance of the irradiation position is 30 μm at the time of completing the first (n = 1) beam shift operation. Similarly, the movement distance of the irradiation position at the time of completion of the second (n = 2) beam shift operation is also 30 μm, and the total
60 μm. The total movement distance of the irradiation position when the third (n = 3) beam shift operation is completed is 90 μm. Because we want to move the observation point by 100 μm,
= 4) By adding 10 μm by the beam shift operation, the target observation point is reached. The beam shift amount at this time is of course 10
μm.

The above steps proceed automatically and continuously except for the beam shifting operation by the operator, so that the operator does not need to switch the observation magnification and does not need to frequently adjust the focus. This eliminates the need for complicated operations such as driving the stage and resetting the charged particle beam to the origin position. In the beam shift control method of the present invention, since the irradiation position of the charged particle beam can be moved while maintaining the high magnification field of view, the observation is performed while continuously changing the observation point without being limited by the limit shift amount of the charged particle beam. can do.

[0016] Actually, the positioning accuracy of the stage is inferior to the positioning accuracy of the charged particle beam. Therefore, it is necessary to slightly correct the irradiation position. However, since the positioning accuracy of the stage is usually about 1 μm, the correction is easy. Can be.

[0017]

As described above, in the beam shift control method according to the present invention, the observation point can be continuously changed without being limited by the limit shift amount of the charged particle beam while maintaining the high magnification field of view. Can be observed. Therefore, the operator can concentrate only on the beam shift operation and the monitor screen observation, and the observation point can be changed at any time.
Further, since the driving of the stage and the reset of the charged particle beam to the origin position are automatically performed, the operator can
The operability is improved by being released from such complicated work.

In addition, since the change of the observation point, that is, the movement and positioning of the irradiation position of the charged particle beam on the sample is performed based on the beam shift, high-precision positioning is finally possible.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating a beam shift control method of a charged particle beam according to an embodiment of the present invention.

Claims (1)

[Claims] 1. A beam shift control method for a charged particle beam microscope for moving and positioning an irradiation position of a charged particle beam on a sample placed on a stage, wherein the irradiation position is moved by a beam shift operation. When the moving distance reaches the limit shift amount which is the maximum shift amount of the charged particle beam, an operation of driving the stage in the direction opposite to the beam shift direction by the limit shift amount, and setting the irradiation position to the origin. A beam return control method for the charged particle beam microscope, wherein the operation of returning to the position is automatically performed, and the operation is repeatedly performed until the movement of the irradiation position is completed.