JPH10302697A - Charged particle beam microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a vibration from being generated on a scanning image on a monitor, by vibrating a sample by use of a piezoelectric actuator so as to cancel the resonance vibration of a stage or a mirror column. SOLUTION: A drive signal having an optional frequency component is imparted to a piezoelectric actuator 9 to vibrate a sample 6, whereby the vibration generated on a scanning image on a monitor is canceled. A small-sized piezoelectric actuator 9 having a sufficiently high resonance frequency to a stage 8 or a mirror column 5 is provided between the stage 8 and a sample holder 7, and the sample holder 7 is driven at a frequency conformed to the resonance frequency of the stage 8 or the mirror column 5, whereby the relative position of the sample 6 and a scanning electron beam 2 is corrected. The amplitude and phase of the drive signal are controlled while observing the image displayed on a monitor 15. Thus, the vibration generated when a disturbance having a complicated phase such as noise is inputted can be easily corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art The configuration of a charged particle beam microscope is shown in FIG. 2 using an electron microscope as an example. In FIG. 2, the left-right direction of the paper is defined as an X direction, and the front-rear direction is defined as a Y direction. An electron beam 2 generated from an electron gun 1 is applied to a deflector 3 installed in a mirror column 5.
Are deflected in the X and Y directions, converged on the surface of the sample 6 by an electron optical system such as the objective lens 4, and irradiated while scanning the surface of the sample 6. Here, the input current of the deflector 3 in each of the X and Y directions is provided by a scanning current source 16, and each scanning current is controlled by the controller 14. The sample 6 is fixed to a sample holder 7 and can be moved to an arbitrary position by a stage 8 having functions of horizontal movement, inclination and rotation. The mirror column 5 and the stage 8 are fixed to the sample chamber 10. Further, the sample chamber 10 is fixed to the base plate 11 directly or via a vibration isolator. Secondary electrons 12 generated when the electron beam 2 irradiates the sample 6 are detected by the secondary electron detector 13, and a scanned image of the surface of the sample 6 is formed on the monitor 15.

[0003]

In a conventional charged particle beam apparatus, vibrations appear in a scanned image when the apparatus is installed in a place such as a semiconductor factory clean room where noise is large. This vibration causes the sample chamber 10 to slightly vibrate when the sound pressure of the noise is input to the surface of the sample chamber 10, and this slight vibration causes the stage 8 to resonate. Alternatively, the sound pressure is generated to vibrate the electron source 1 when the sound pressure is input to the column 5 and the column 5 resonates. Since the sound pressure of the above-described noise is directly input to the sample chamber 10 and the mirror column 5, it is difficult to attenuate the vibration using a mechanical attenuator.
In order to attenuate the vibration generated by the sound pressure, there has been proposed a method of providing a soundproof wall covering the entire apparatus, a sound insulating plate covering the sample chamber 10 and the mirror column 5, and attenuating the sound pressure of noise input to the apparatus. (Japanese Patent Application No. 7-245762).

However, the vibration frequency of the scan image in question is 50 to 300H, which is the resonance frequency of the stage 8.
low frequency of z. In order to attenuate the low-frequency noise and completely prevent the sample chamber from vibrating, a large-scale device such as a soundproof wall that completely covers the device is required, and it is practically difficult to realize it.

[0005] An object of the present invention is to provide an electron microscope that prevents vibrations from appearing in a scanned image without using a large-scale soundproof wall or the like.

[0006]

In order to solve the above problems, the present invention clarifies that the vibration appearing in the scanned image is the resonance of the stage 8 and the mirror column 5,
Even if the stage 8 and the mirror column 5 resonate, no vibration appears in the scanned image displayed on the monitor 15. When the stage 8 and the mirror column 5 do not resonate, the stage 8 and the mirror column 5 vibrate integrally with the sample chamber 10, and no vibration appears in the scanned image. However, when the stage 8 resonates, the vibration of the stage 8 is
Since it becomes large with respect to the vibration of the mirror column 5, the vibration appears in the scanned image. On the other hand, when the mirror column 5 resonates, the scanning electron beam 2 relatively vibrates with respect to the sample 6, so that a vibration appears in the scanned image. Even when the stage 8 and the mirror column 5 are resonating, if the relative position between the sample 6 and the scanning electron beam 2 can be corrected so as not to vibrate, vibration can be prevented from appearing in the scanned image. .

According to the present invention, a small-sized piezoelectric actuator 9 having a resonance frequency sufficiently higher than the resonance frequency of the stage 8 and the mirror column 5 is provided between the stage 8 and the sample holder 7 and the sample holder 7 is mounted on the stage 8 or the sample holder 7. The relative position between the sample 6 and the scanning electron beam 2 is corrected by driving the mirror column 5 at the same frequency as the resonance frequency. Since the amplitude and phase of the drive signal at this time are controlled while observing the image displayed on the monitor 15, the vibration generated when a disturbance having a complicated phase such as noise is input can be easily corrected.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described using the electronic device of FIG. 1 as an example. In FIG. 1, the left-right direction of the paper is defined as an X direction, and the front-rear direction is defined as a Y direction. A mirror column 5 composed of an electron optical system such as an electron gun 1, a deflector 3, and an objective lens 4 is fixed to an upper surface of a sample chamber 10. The electron beam 2 generated by the electron gun 1 is deflected in the X and Y directions by the deflector 3, scans the surface of the sample 6, detects secondary electrons 12 generated at this time by the secondary electron detector 13, and controls the control circuit. A scanning image of the surface of the sample 6 is formed on the monitor 15 by the monitor 14. The stage 8 is fixed to the lower surface of the sample chamber 10 and is built therein. The sample 6 is fixed to a sample holder 7. Further, the sample holder 7 is attached to a stage 8 via a piezoelectric actuator 9. Here, the stage 8 has a function of moving, rotating, and tilting the sample 6 to an arbitrary position. Further, the piezoelectric actuator 9 is connected to the signal generation circuit 1.
8, driven by a drive control circuit 17 composed of a drive voltage source 19. The drive control circuit 17 has a function of oscillating the sample 6 and the sample holder 7 at an arbitrary frequency, amplitude, and phase in the X and Y directions.

In the present invention, a driving signal having an arbitrary frequency component is given to the piezoelectric actuator 9 to vibrate the sample 6, thereby canceling the vibration generated in the scanned image on the monitor 15. Here, the drive signal is output from the drive control circuit 17. Here, the signal generation circuit of the drive control circuit 17 can arbitrarily set the frequency, amplitude, and phase of the drive signal. Here, the drive signal is set so that the vibration of the scanned image on the monitor 15 is minimized, and its frequency matches the resonance frequency of the stage 8 or the mirror column. The piezoelectric actuator used in this embodiment has a resonance frequency sufficiently higher than the resonance frequency of the stage 8 and the mirror column 5.

In this embodiment, since the waveform of the drive signal can be set arbitrarily, it is possible to cope with the case where the resonance frequency of the stage 8 changes due to the movement or inclination of the stage 8 and the frequency of image vibration changes. it can. Further, image vibrations generated when a disturbance having an unstable phase such as noise is input can be canceled by changing the phase of the drive signal as needed.

[0011]

According to the present invention, since the sample is vibrated by the piezoelectric actuator so as to cancel the resonance vibration of the stage 8 or the mirror column 5, the vibration does not appear in the scanned image on the monitor.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention.

FIG. 2 is an explanatory view of a conventional electron microscope.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electron gun, 2 ... Scanning electron beam, 3 ... Deflector, 4 ... Objective lens, 5 ... Mirror column, 6 ... Sample, 7 ... Sample holder, 8
... Stage, 9 ... Piezoelectric actuator, 10 ... Room, 11
... Base plate, 12 ... Secondary electron, 13 ... Secondary electron detector, 14 ... Control device, 15 ... Monitor, 16 ... Scan current source, 17 ... Drive control circuit, 18 ... Signal generation circuit, 19 ...
Drive voltage source.

Claims (2)

[Claims] 1. A charged particle source for generating a charged particle beam, a deflector for scanning the charged particle beam on a sample, and an electron optical system of an objective lens for converging the charged particle beam on the sample. Mirror column, a sample holder for fixing the sample, a stage for moving, rotating, and tilting the sample to an arbitrary position, a sample chamber containing the stage, and irradiating the sample with the charged particle beam. In a charged particle beam microscope that detects generated secondary charged particles, transmitted charged particles, reflected charged particles, and the like, and observes the above detection signal as an image on a monitor, the sample is corrected so that vibrations generated on the image are corrected. A charged particle beam microscope having a function of driving. 2. A charged particle beam microscope which drives the sample holder according to claim 1 while controlling frequency, amplitude and phase using a piezoelectric actuator.