JPH05211053A - Charged particle ray device - Google Patents

Abstract

PURPOSE:To provide good images even if a screen is composed of the intricacies of cross section parts, surface parts, and edge parts which are the boundaries thereof by allowing at least either the contrast or brightness of images to be automatically adjusted. CONSTITUTION:There is provided an image quality automatic adjustment function wherein secondary charged particle signals from each of a plurarity of divided beam scanning areas are weighted and used as automatic adjustment feedback signals which adjust either the contrast or brightness of images. That is, in a dynamic memory as an observation sample, the screen displaying a cross section 3 near a contact part including the periphery of machined holes is divided into a central part region 5 (an image quality automatic adjustment region) and other regions and only image signals from the region 5 are used to automatically adjust the contrast. SIM images (cross section photographs) providing good cross section images which allow the circumstances to be simulataneously understood are obtained by adjusting at least either the contrast or brightness of images.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for obtaining a high-resolution microscope image using a charged particle beam, and more particularly to a charged particle beam apparatus suitable for observing a cross-sectional image of a device after cross-section processing.

[0002]

2. Description of the Related Art The prior art is the Proceedings of International Reliability Physics Symposium, (1989) pp. 43-52.
ysics Symposium, (1989) pp. 43-52).

In the above-mentioned paper, as shown in FIG. 2, an example of obtaining a device cross-section photograph (SIM image) shown in FIG. 3 by using the FIB to process the cross-section of the device and using the SIM function is shown.

The processing procedure described in the paper will be described with reference to FIG.

(1) A rough processing area (area surrounded by a broken line) is set based on the SIM image.

(2) Large current FIB with a current value of 2 to 5 nA
The rectangular hole is processed at high speed by sputtering.
The cross-section after rough processing is not in a state where the device cross-sectional structure can be observed due to the sag of the cross-section and the redeposited film of sputter particles.

(3) The observed cross section is FIB with a current of 400 pA.
Finish processing by.

The above-mentioned conventional technique can be evaluated in that a plurality of beam currents (beam diameters) are used properly and a cross section is formed efficiently.

As shown in FIG. 3, the paper shows a low-magnification SIM image (1) in which a processed rectangular hole enters the field of view and a high-magnification SIM image (2) including a target observation location. High magnification SI
The angle of view of the M image is indicated by a white frame within the low-magnification SIM image. A close look at this screen configuration reveals that the high-magnification SIM image is composed of the device cross section at the top of the screen and the device surface at the bottom of the screen. As described above, the observation screen is often configured to include not only the area near the important observation point but also other areas. By inserting information other than the observation point, for example, the relative position and size of the observation point can be clarified, and the composition as an image can be adjusted.

[0010]

In the above conventional technique, S
There is no description of automatic adjustment of contrast and brightness in IM image observation. For example, in the above conventional technique, if automatic contrast adjustment that is generally performed by SEM or the like is performed, a problem occurs due to the following reason. (1) Generally, automatic contrast adjustment is
The entire screen is roughly scanned, and the gain of the signal detection system is automatically adjusted by the feedback circuit so that the peak value of the secondary electron signal becomes constant (set value).

(2) In the case of observing the cross section of a device, the screen structure often has a complicated cross section, the surface, and the edge of the boundary between them, resulting in a high contrast screen.

Therefore, if (1) is simply applied to (2),
Although an image with good contrast can be obtained as a whole, the cross-sectional portion becomes darker than the others, resulting in an image lacking cross-sectional information.

The automatic adjustment of contrast and the like is indispensable in order to take a high-resolution photograph of a cross section beautifully and without failure, and it is a problem to realize this in a cross section observation apparatus.

The object of the present invention is to provide an automatic image quality that can obtain a good image (without losing the information of the sectional structure) even in the case of a screen configuration in which the sectional part, the surface part, and the edge part of the boundary are complicated. It is to provide a device having an adjusting function.

[0015]

In order to achieve the above object, a plurality of beam scanning regions are provided in an apparatus for forming a cross section on a device by using FIB and obtaining a microscope image including the cross section by SIM or SEM. An image quality automatic adjustment function is provided for automatically adjusting at least one of contrast and brightness of an image including a cross-section by weighting secondary charged particle signals generated from each region.

[0016]

In the screen configuration in which the cross-section portion, the surface portion, and the edge portion of the boundary thereof are intricately divided, for example, the screen is divided into a partial area of the cross-section (mainly including the portion to be observed) and other areas, If the weights (contributions to the image quality adjustment function) of the other regions are set to zero, the image quality can be adjusted only by the signals from some regions of the cross section. Thereby, even in the case of a screen configuration in which the cross-section part, the surface part, and the edge part of the boundary thereof are complicated, a good image (information of the cross-section structure is not lost) can be obtained.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 4 is a block diagram of the FIB device used in the embodiment.
Ions emitted from the liquid metal ion source 100 are focused on the sample 112 by the condenser lens 101 and the objective lens 107. The beam acceleration voltage is 30 kV. A variable aperture 102, an aligner / stigmer 103, a blanker 104, a blanking aperture 105, and a deflector 106 are arranged between the lenses.
The sample 112 can be moved by the stage 108. The stage is controlled in five axis directions of x, y, z, tilt and rotation. Secondary electrons generated from the sample 112 by FIB irradiation are detected and amplified by the secondary electron detector 109, and are synchronized with the deflection control, so that the CRT of the computer is detected.
Displayed as a SIM image on top.

FIG. 1 is an explanatory diagram of an embodiment (observation of device cross section) using the present invention. Since the method of forming the cross section is similar to the conventional technique, the description thereof will be omitted.

The SIM image was taken by inclining the sample by 60 °. The observation sample was a dynamic memory, and the cross section 3 near the contact portion 1 was photographed including the periphery of the processed hole. The screen was divided into an area 5 (mainly an area to be observed) surrounded by a dotted line in the center and other areas, and automatic contrast adjustment was performed only with the former image signal. The configuration of the automatic contrast adjustment circuit is shown in FIG. The operation will be described with reference to the drawings.

The secondary electrons 10 emitted from the sample are converted into light by the scintillator 11 and current-amplified by the photomultiplier tube 12. The amplified current is converted into a voltage signal by the preamplifier 13. This signal is sent to A / via the limiter 14.
It is supplied to the D converter 15 and stored in the image memory 16. This content is displayed as a grayscale image on the CRT of the computer.

The signal (having brightness information) output from the preamplifier 13 is supplied to the gate circuit 17, and only the signal in the image quality automatic adjustment area 5 (area surrounded by a broken line) shown in FIG. It is supplied to the hold circuit 18. This part is a characteristic part of the present invention. The highest luminance signal is held in the image quality automatic adjustment area 5, and the error amplifier 19 amplifies the difference voltage from the reference voltage (setting value),
The signal changes the output voltage of the high voltage power supply for the multiplier. Since the amplification factor of the photomultiplier tube 12 is controlled by this high voltage, feedback control is performed, and the condition where the output of the peak hold circuit 18 and the reference voltage become equal is settled down. That is, the contrast of the image quality automatic adjustment area 5 shown in FIG. 1 is feedback-controlled to an appropriate value (value designated by the reference voltage). When the SIM image was retaken while the output voltage of the high-voltage power source 20 for the multiplier was held, a SIM image having a good cross-sectional image and capable of simultaneously grasping the surrounding conditions was obtained.

In the present embodiment, the above operation was performed after the SIM image, which is the base for setting the image quality automatic adjustment area, was photographed by manual adjustment. In this way, if a SIM image that can be used for area setting is taken in advance, the image quality can be efficiently and accurately adjusted automatically.

Further, the gate circuit shown in FIG. 5 is always turned on.
In this state, a normal image quality automatic adjustment circuit (for the entire scanning area) is set. In this state, a SIM image for area setting is captured in advance, and the image quality automatic adjustment area is set based on that image. Then, a good SIM image can be taken again.

When a cross section is formed on the device by FIB and the cross section is observed, it is possible to estimate the cross section of the cross section observation image by using numerical calculation from the position data of the finished surface used during the cross section processing. If this is done, the image quality automatic adjustment area can also be set automatically, resulting in a system with good usability.

[0025]

According to the present invention, even in a screen configuration in which the device cross section, the surface, and the edge of the boundary between them are complicated, the contrast of a highly important part (for example, a part of the cross section) is controlled by automatic control. Image quality) is good, and
A SIM image in which there are other parts that serve as a reference is also obtained. In particular, there is an effect that high-resolution photography can be taken beautifully and without failure.

[Brief description of drawings]

FIG. 1 is an explanatory diagram (CRT image) of an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a device cross-section processing procedure described in a known example.

FIG. 3 is a view showing a device cross-sectional photograph of a known example.

FIG. 4 is a configuration diagram of an FIB device used in an example.

FIG. 5 is a configuration diagram of an image quality automatic adjustment circuit used in the embodiment.

[Explanation of symbols]

1 ... Contact part, 2 ... Wiring pattern, 3 ... Observation section (finished surface), 4 ... Machining hole side wall (non-finished surface), 5 ... Image quality automatic adjustment area, 6 ... CRT image, 10 ...
Secondary electron, 11 ... Scintillator, 12 ... Photomultiplier tube, 13 ... Preamplifier, 14 ... Limiter, 15 ... A / D
Converter, 16 ... Image memory, 17 ... Gate circuit, 18
... Peak / hold circuit, 19 ... Error amplifier, 20 ... High voltage power supply for multiplier, 100 ... Liquid metal ion source, 101 ...
Condenser lens, 102 ... Variable aperture, 10
3 ... Aligner Stigmar, 104 ... Blanker,
105 ... Blanking aperture, 106 ... Deflector, 107 ... Objective lens, 108 ... Stage, 109
... secondary electron detector, 112 ... sample.

Claims (6)

[Claims] 1. A charged particle beam apparatus for obtaining a microscope image by focusing a charged particle beam to scan on a sample and detecting the intensity of secondary particles emitted from the sample in synchronization with the scanning, A signal obtained by dividing the beam scanning region into a plurality of regions and weighting the secondary charged particle signals generated from each region was used as a feedback signal for automatic adjustment for adjusting at least one of contrast and brightness of the image. A charged particle beam device having an automatic image quality adjustment function. 2. The charged particle beam is a focused ion beam (Focused)
Ion Beam: FIB for short. After cross-section processing using sputtering, the cross-section is scanned with a scanning ion microscope (Sc
The charged particle beam apparatus according to claim 1, wherein the observation is performed by an anning ion microscope (abbreviated as SIM). 3. An apparatus capable of irradiating a sample with a FIB and an electron beam, characterized in that a cross-section is processed by the FIB and an observation image is obtained by a scanning electron microscope (SEM for short). Item 1. The charged particle beam device according to Item 1. 4. A system for storing and displaying image information in a memory, characterized by further comprising means for designating an area for automatic image quality adjustment based on an image already taken. The charged particle beam device according to any one of 1 to 3. 5. The beam scanning region is divided into a region including an important observation point (for example, a portion of a device cross section) and another portion.
The charged particle beam device according to claim 1, wherein the charged particle beam device is divided and the weight of other portions is set to 0. 6. A cross-section processing step by FIB and an image observing step by SIM or SEM are interlocked to automatically specify an area (related to automatic image quality adjustment) in the observed image from processing position data used for cross-section processing. Claim 2 characterized by the above
6. The charged particle beam device according to claim 1.