JP4088437B2 - Charged particle beam equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a charged particle beam apparatus, and more particularly to a charged particle beam apparatus suitable for easily setting optimum operating conditions according to observation conditions.
[0002]
[Prior art]
In a charged particle beam apparatus typified by a scanning electron microscope, desired information (for example, a sample image) is obtained from a sample by scanning a finely focused charged particle beam on the sample. Among such charged particle beam devices, particularly in a device with high resolution, in order to operate the objective lens with a very strong lens action, the charged particle beam is increased as the acceleration voltage increases due to the physical limitation of the lens operation. WD that can converge is increased. FIG. 6 shows the relationship between the acceleration voltage and the minimum WD that can be focused. As shown in FIG. 6, when the acceleration voltage is small, the minimum focusable WD is constant regardless of the operation of the objective lens, but when the acceleration voltage exceeds a certain value, the physical limit of the lens operation is reached. As a result, the minimum WD becomes longer. Therefore, in order to use the apparatus under the observation condition that provides the highest resolution, it is necessary to select the minimum WD according to the acceleration voltage. Further, when the sample is tilted, the usable WD is limited according to the tilt angle in order to avoid contact between the sample and the objective lens. Furthermore, when a detector disposed between the objective lens and the sample is used, the usable WD is limited in order to avoid contact between the sample and the detector.
[0003]
Conventionally, a protective function for preventing contact between the sample and the objective lens or the sample and a detector disposed below the objective lens when setting the WD and the sample inclination angle has been provided.
[0004]
[Problems to be solved by the invention]
However, there is no protection function on the device side for the X-ray analysis that requires a specific WD or the range of WD that is restricted according to the acceleration voltage. WD was judged. However, for example, in the case of a manually operated stage, the user needs to determine the optimum WD taking into account all the constraints due to acceleration voltage, sample tilt, detectors used, etc. There is a problem that the lens is brought into contact with the parts in the apparatus (objective lens, detector, etc.) or the focus is not adjusted. Alternatively, in order to avoid damage to the apparatus due to such an erroneous operation, the stage is always fixed to a long and safe WD. However, in this case, there is a problem that the maximum performance inherent in the apparatus cannot be obtained.
[0005]
The object of the present invention is to display the WD most suitable for the designated condition by designating the observation condition and the purpose of the observation, or to automatically set the WD, thereby preventing an erroneous operation. It is another object of the present invention to provide a charged particle beam apparatus suitable for using the apparatus under the highest performance conditions.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, by specifying the acceleration voltage, the sample inclination angle, and the detector to be used, which are the minimum necessary for the observation purpose, means for displaying the WD most suitable for achieving the object, and a stage on the WD A means for moving is provided.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0008]
FIG. 1 is a schematic configuration diagram of a scanning electron microscope which is an example of the present invention. A voltage is applied between the cathode 1 and the first anode 2 by a high voltage control power source 20 controlled by a computer 40, and the primary electron beam 4 is extracted from the cathode 1 with a predetermined emission current. An acceleration voltage is applied between the cathode 1 and the second anode 3 by a high-voltage control power source 20 controlled by a computer 40, and the primary electron beam 4 emitted from the cathode 1 is accelerated and proceeds to the subsequent lens system. . The primary electron beam 4 is converged by the converging lens 5 controlled by the lens control power source 21, and after the unnecessary region of the primary electron beam is removed by the diaphragm plate 8, the converging lens 6 controlled by the lens control power source 22, And the objective lens 7 controlled by the objective lens control power source 23 is converged as a minute spot on the sample 10. The objective lens 7 can take various forms such as an in-lens system, an out-lens system, and a snorkel system (semi-in-lens system). A retarding method is also possible in which a negative voltage is applied to the sample to decelerate the primary electron beam. Furthermore, each lens may be composed of an electrostatic lens composed of a plurality of electrodes.
[0009]
The primary electron beam 4 is scanned two-dimensionally on the sample 10 by the scanning coil 9. The secondary signal 12 such as secondary electrons generated from the sample 10 by the irradiation of the primary electron beam travels to the upper part of the objective lens 7 and is then separated from the primary electrons by the orthogonal electromagnetic field generator 11 for secondary signal separation. And detected by the secondary signal detector 13. The signal detected by the secondary signal detector 13 is amplified by the signal amplifier 14 and then transferred to the image memory 25 and displayed on the image display device 26 as a sample image.
[0010]
A two-stage electric visual field moving coil 51 is arranged at the same position as the scanning coil 9, and the position (observation visual field) of the primary electron beam 4 on the sample 10 can be controlled two-dimensionally.
[0011]
The stage 15 can move the sample 10 in at least two directions (X direction and Y direction), a vertical direction (Z direction), and a tilt direction (T direction) in a plane perpendicular to the primary electron beam. At least in the Z direction, the motor is controlled by the computer.
[0012]
From the input device 42, the user can input or select an acceleration voltage, a sample tilt angle, a detector, and the like.
[0013]
In this embodiment, when an acceleration voltage, a sample tilt angle, and a detector are designated, a WD optimum for observation is displayed in conjunction with the designated state, and the stage can be moved to the WD. An example of means for displaying and moving the WD will be described with reference to FIGS.
[0014]
FIG. 2 shows an example of a GUI screen that can be operated by the user for specifying an acceleration voltage, a sample tilt angle, a detector, displaying a WD optimum for observation, and moving the stage to the optimum WD. When the observation condition is selected by the acceleration voltage selection unit 32, the sample inclination angle selection unit 33, and the detector selection unit 34 in the screen, the acceleration voltage shown in FIG. 6 registered in the computer 40 or the storage device 41 in advance. From the relationship of the observable WD with respect to various observation conditions such as the relationship between the WD and the minimum WD that can be focused, the range of the WD that can be observed under all the conditions selected in 32 to 34 is obtained. Here, since the WD needs to be as small as possible in order to use the apparatus under the observation condition where the highest resolution can be obtained, the minimum value in the observable WD range is the optimum WD for observation. The optimum WD obtained in this way is displayed on the optimum WD display unit 35. Further, when the movement button 36 is pressed, the stage 15 is moved in the Z direction by the motor 52 controlled by the computer 40 so that Z = (optimum WD). In addition, when the contents of the condition selection units 32 to 34 are changed and the optimum WD is changed, if the automatic stage Z movement check box 37 is checked, the stage Z is automatically selected without pressing the movement button 36 every time. Move. When all operations are completed, the Close button 38 is pressed to close the screen.
[0015]
Here, the GUI screen may be displayed together with the sample image on the image display device 26 or may be output to another display device. In addition, each of the condition selection units 32 to 34 may select from a plurality of options, or may input a condition from the input device 42.
[0016]
FIG. 3 shows an optimum WD display in this embodiment and a flow for moving the stage to the optimum WD. According to the present embodiment, the user can instantly obtain a safe and maximum performance condition WD simply by specifying the observation condition. In addition, even if the observation conditions are frequently changed, the stage automatically moves in the Z direction so that the optimum WD is always achieved. Therefore, the optimum observation conditions can be easily set without erroneous operation.
[0017]
FIG. 4 is a schematic view of another embodiment of the present invention, which is a scanning electron microscope in which a detector is disposed between an objective lens and a sample. Components having substantially the same structure as in FIG. 1 are denoted by the same reference numerals.
[0018]
In this embodiment, a detector 62 for detecting reflected electrons from the sample is disposed between the objective lens 7 and the sample 10. A reflected electron signal 61 generated from the sample 10 by irradiation of the primary electron beam 4 directly reaches the detector 62 and is detected. The signal detected by the detector 62 is amplified by the signal amplifier 63, transferred to the image memory 25, and displayed on the image display device 26 as a sample image using the reflected electron signal. This detector is, for example, a YAG type backscattered electron detector using a YAG (Yttrium Aluminum Garnet) single crystal in the scintillator section. Usually, this type of detector is inserted directly above the sample when used, and has a mechanism for pulling back because it obstructs secondary signal image observation when not used. In this embodiment, detector position control means 64 controlled by the computer 40 is provided for inserting and pulling back the detector. In this embodiment, the detector 62 is a detector that detects reflected electrons, but the present invention is not limited in its effect by the type of detector.
[0019]
The computer 40 has the function of the GUI screen shown in FIG. 2 or a function equivalent thereto, and the user can specify the acceleration voltage, the sample tilt angle, and the detector.
[0020]
In this embodiment, when the acceleration voltage, the sample tilt angle, and the detector are designated, the optimum WD display for observation, the stage is moved to the optimum WD, and the automatic position control of the detector is performed in conjunction with the designated state. It can be carried out. An example of this operation will be described below.
[0021]
When the user selects an observation condition by the acceleration voltage selection unit 32, the sample tilt angle selection unit 33, and the detector selection unit 34, the optimal WD is determined by the computer 40 by the method shown in the above-described embodiment. Displayed on the display unit 35. Thereafter, the computer 40 determines what kind of detector is selected by the detector selection unit 34. Here, when the detector 62 closer to the sample 10 than the objective lens 7 is selected, the stage 15 is first moved in the Z direction so that Z = (optimum WD). Next, it is determined whether or not the detector 62 is inserted. If the detector 62 is not inserted, the detector 40 is controlled by the computer 40 and the detector 62 is inserted. On the other hand, when the detector 13 which selects the detector 13 on the cathode 1 side from the objective lens 7 is selected, it is first determined whether or not the detector 62 is pulled out, and if it is not pulled out, the computer 40 detects it. The detector position control means 64 is controlled and the detector 62 is pulled out. Next, the stage 15 is moved in the Z direction so that Z = (optimum WD).
[0022]
FIG. 5 shows the flow for performing the optimum WD display, moving the stage to the optimum WD, and controlling the position of the detector in the embodiment described above. In this embodiment, since the order of execution is considered in the automatic movement of the stage in the Z direction and the automatic control of the insertion / extraction of the detector 62, damage such as contact between the sample and the apparatus is not caused. . For this reason, in this embodiment, the user can easily set the WD that realizes the optimum observation condition without having to be aware of the position of the detector only by specifying the observation condition.
[0023]
【The invention's effect】
According to the present invention, it is possible to easily set a WD that is most suitable for the purpose without any erroneous operation only by designating the minimum condition necessary for the purpose of observation.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a scanning electron microscope according to an embodiment of the present invention.
FIG. 2 is a GUI screen for setting observation conditions and displaying an optimum WD.
FIG. 3 is a flowchart for carrying out an embodiment of the present invention.
FIG. 4 is a schematic configuration diagram of a scanning electron microscope according to another embodiment of the present invention.
FIG. 5 is a flowchart for carrying out another embodiment of the present invention.
FIG. 6 is a diagram for explaining a relationship between an acceleration voltage and a focusable minimum WD.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Cathode, 2 ... First anode, 3 ... Second anode, 4 ... Primary electron beam, 5 ... First convergent lens, 6 ... Second convergent lens, 7 ... Objective lens, 8 ... Diaphragm plate, 9 ... Scanning coil DESCRIPTION OF SYMBOLS 10 ... Sample, 11 ... Orthogonal electromagnetic field (EXB) generator for secondary signal separation, 12 ... Secondary signal, 13 ... Detector for secondary signal, 14 ... Signal amplifier, 15 ... Stage, 20 ... High voltage control power supply , 21 ... first convergent lens control power supply, 22 ... second convergent lens control power supply, 23 ... objective lens control power supply, 24 ... scanning coil control power supply, 25 ... image memory, 26 ... image display device, 27 ... electrical field control Power source 32 ... Acceleration voltage selection unit 33 ... Sample tilt angle selection unit 34 ... Detector selection unit 35 ... Optimum WD display unit 36 ... Move button 37 ... Auto stage Z move check box 38 ... Close button 40 ... computer, 41 ... memory device , 42 ... input apparatus, 51 ... electric field moving coil, 52 ... motor, 61 ... reflected electron signal, 62 ... detector, 63 ... signal amplifier, 64 ... detector position control means.

Claims (3)

A cathode,
An electron optical system for converging the primary electron beam emitted from the cathode and scanning the sample;
A sample stage capable of moving the sample at least in the horizontal direction (X-axis, Y-axis), vertical direction (Z-axis), and tilt direction (T-axis);
Detecting means for detecting electrons generated from the sample by scanning the primary electron beam ,
In a scanning electron microscope that forms a sample image based on electrons detected by the detection means,
Specifying the accelerating voltage of the primary electron beam, the tilt angle of the sample, and the observation condition designating either the detector disposed between the objective lens and the sample or the detector disposed on the cathode side of the objective lens Means,
The usable working distance range for the specified acceleration voltage, the usable working distance range for the sample tilt angle, and when the detector is inserted between the sample and the objective lens. A storage device that stores a range of working distance when no
When a detector disposed between the objective lens and the sample is designated by the observation condition designating means, a working distance range that can be used in all the observation conditions designated by the observation condition designating means, The sample stage is moved to a position in the Z-axis direction of the sample stage that is the smallest working distance in the range of working distance in which the AND condition can be taken,
When the detector arranged between the objective lens and the cathode is designated by the observation condition designating means, it is determined whether the detector arranged between the objective lens and the sample is inserted. If there is not, the Z of the sample stage that is the range of working distance that can be used in all the observation conditions specified by the observation condition specifying means and that is the minimum working distance in the range of working distances in which the AND condition can be taken. the axial position, a scanning electron microscope, characterized in Rukoto moving the sample stage. The scanning electron microscope according to claim 1,
A scanning electron microscope comprising a drive mechanism for driving the sample stage in the Z-axis direction and controlling the drive mechanism in conjunction with a designated state of the observation condition designating means. The scanning electron microscope according to claim 1 or 2,
One or a plurality of detectors on the sample side with respect to the objective lens, and detector position control means for controlling the positions of these detectors are provided, and the detectors are interlocked with the specified state of the observation condition specifying means. A scanning electron microscope characterized by controlling the position of the scanning electron microscope .

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