JPH04188553A - Section observing device - Google Patents

Abstract

PURPOSE:To store three-dimensional image data in memory and provide possibil ity of reproducing a section image by sensing charged particles sputtered from a specimen at the same time as processing of a certain desired part with a converging ion beam. CONSTITUTION:With a condenser lens 3 and an objective lens 6, an ion beam is converged on the surface of a specimen 7, and a deflecting electrode 5 deflects this ion beam to scan the specimen surface in the X- and Y-directions. In this maner the converging ion beam makes scanning in steps in the X-and Y- directions in certain periods, and all sensing signals are stored in a memory device 12 in correspondence to the scan to build the data of one picture field for the specimen surface. The sputtered amount of the specimen surface per scan is decided, and the image data of internal layers are stored with proceeding with the number of scanning passes. Thereby the section image of the desired inclined surface can be reproduced by setting the cross-section with a desired function in the X- and Y directions.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to the collection of three-dimensional image data of a micro-side cross-section observation device used for failure analysis of LSIs and the like.

[Prior Art] The application of focused ion beams in the semiconductor field is well known as described in the above-mentioned documents. The functions of a focused ion beam include (1) an enlarged image of the surface obtained by scanning the sample surface, (2) microfabrication by sputtering, i.e., wiring pattern correction, drilling, wiring cutting, etc., and (3) tungsten, etc. Additional wiring can be added by metal film deposition. In recent years, LSI devices have become increasingly miniaturized, and focused ion beams and ion beams are attracting attention as processing methods on the submicron order. For example, S
The size of the cell in I is 0.6 μmXl, 04 m, the pattern is 0.3 μm wide, the interlayer connection hole diameter is 0.3 μmφ, and the insulation film thickness is 0.0171 m, all on the submicron order. 1. For pattern correction and failure analysis during SI development, processing means of the above order are naturally required. On the other hand, a needle is wetted with liquid metal such as gallium and a strong electric field is applied2 to generate an ion beam with a diameter of several tens of μm.
The beam diameter of the focused ion beam obtained with the aperture and electrostatic lens is about 0.03 μmφ, and -1-L S
Although it is not sufficient to clearly display the phenomenon of T, it is extremely effective as a surface processing means. This is because the wiring pattern inside an LSI is multi-layered, so surface images alone are not helpful in defect analysis, and it is necessary to perform partial etching to excavate the parts that are thought to be defective. Focused ion beams are extremely effective at this point.

[Problems to be Solved by the Invention] - Conventional focused ion beam technology involves irradiating the surface of a sample with an ion beam to process a desired portion, and then tilting the sample to obtain a cross-sectional image. However, processing with a focused ion beam means sputtering and destroying the target sample.
This is an operation that cannot be processed incorrectly. In particular, if the pattern of the sample to be processed is large and the beam diameter of the focused ion beam is much smaller than that and operates stably, there is no problem. When the diameter and stability become too large to ignore, the possibility of machining errors increases, which becomes a serious problem.

Furthermore, since the sample surface is etched from time to time while observing the cross section of a desired region, the region most desired to be observed may be etched too much.

An object of the present invention is to solve the above problems.

[Means for solving the problem] In order to achieve the above object, a large-capacity storage device capable of storing three-dimensional image data is provided, and at the same time a desired part is processed with a focused ion beam, sputtering is performed from a sample. charged particles are detected, and the signal thereof is stored in the storage device. A desired cross-sectional image is then obtained by rearranging the stored image data. Furthermore, the performance of the apparatus is improved by improving image quality through image processing.

Then, by collecting a plurality of three-dimensional image data in a time-division manner, the drift of the focused ion beam of the apparatus is corrected to obtain more accurate data.

[Operation 1] The focused ion beam is scanned stepwise in the X and Y directions at regular intervals, and all detection signals corresponding to the scans are stored in a storage device to obtain data for one screen of the sample surface. On the other hand, the amount of sputtering on the sample surface determined by one scan is determined by the material on the sample surface, the type of ion beam, the energy level, and the dose. By repeating the number of scans, the image data of the inner layer is stored.

That is, the step in the depth direction is proportional to the number of scans.

In this way, it can be stored as three-dimensional image data in the X, Y directions, and depth direction.

Next, this stored three-dimensional image data is
When data in the Y direction and depth direction, where the directional address is constant, is displayed, a cross-sectional image parallel to the Y direction is obtained. Also, X
, Y, and the depth direction, it is possible to recreate a cross-sectional image of a desired inclined surface.

[Example] Hereinafter, an example of the present invention will be described with reference to FIG. A high voltage is applied to the ion source 1 whose needle is wetted with liquid metal serving as the ion source material, and a strong electric field is generated between it and the extraction electrode 2 to generate a highly accurate ion beam from the tip of the needle. The condenser lens 3 and the objective lens 6 are electrostatic lenses that focus the ion beam on the surface of the sample 7.

The aperture 4 changes the diameter of the ion beam.

The deflection electrode 5 scans the ion beam on the sample surface in the X and Y directions. Sample 7 is placed on stage 8, and x, y,
Any part of the sample surface can be moved to the ion beam irradiation position in the z direction, rotation, tilt, etc. The charged particle detector 9 emitted by irradiating the sample surface with an ion beam is a scintillator photomultiplier when the charged particles are electrons, and a multi-dynode, quadrupole mass separator, etc. when the charged particles are ions. It is. In the control system, a controller 14 sets the period of the scan signal generator 15, the amount of deflection in the X and Y directions, and the irradiation position of the ion beam. A scan signal from the scan signal generator 15 is converted into an analog quantity by a D/A converter 16, voltage amplified by an amplifier 17, and applied to the deflection electrode 5 of the mirror body. The image signal from the charged particle detector 9 is sent to an amplifier 10.
The signal is amplified by the A/D converter, converted into a digital quantity by the A/D converter, and stored in the storage device 12 in synchronization with the scan signal. The image data stored in the storage device 12 is reproduced on the display device 13 to obtain the desired cross-sectional image.

FIG. 2 shows a sample processed with a focused ion beam. By repeatedly scanning the sample surface with an ion beam in the X and Y directions at regular intervals, the surface of the sample can be carved into squares.

When viewed from an angle, a specific cross section can be observed. This is a conventional cross-sectional observation device using a focused ion beam. The disadvantage of this method is that when the object to be observed becomes minute and the size and fluctuations of the ion beam affect it, it is not possible to accurately obtain the cross section of the desired part, and when observing the cross section, the sample must be tilted and reprocessed. If they are returned to their original positions, alignment becomes extremely complicated due to stage bala crashes and ion beam fluctuations.

FIG. 3 shows an example of three-dimensional image data of the present invention. X
If the ion beam is scanned not only in this direction but also in the Y direction, image data on the XY plane can be obtained. When this scan is repeated, a considerable amount of sputtering is generated on the sample surface with each scan, so there is a correlation between the depth direction and the number of scans, and three-dimensional image data can be obtained. When the three-dimensional image data is regenerated with a constant value in the X direction, an image of the cross section indicated by the dotted line in the figure is obtained. It is also possible to recreate the cross-sectional image at any position in the X, Y, and depth directions and at any angle.

FIG. 4 is an example in which the deflection range of the focused ion beam is set wide to reduce the influence of processing etching, and the image data capture range is narrowed to improve the quality of the data.

FIG. 5 shows how the data acquisition position drifts due to fluctuations in the focused ion beam during measurement, and these fluctuations in the device can be corrected by the known structure of the part.

[Effects of the Invention] According to the present invention, since three-dimensional image data is stored,
Since it is possible to recreate a cross-sectional image at any position and at any angle, it is extremely effective for cross-sectional observation of minute parts. In addition, image quality can be improved through three-dimensional image processing, which is also effective in improving performance. Furthermore, fluctuations in devices such as focused ion beams can be easily corrected by data processing.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a diagram showing an example of processing on a sample surface to explain cross-sectional observation of a conventional focused ion beam, and FIG. 3 is a diagram stored in the storage device of the present invention. FIG. 4 is a diagram showing the relationship between the deflection range of the focused ion beam and the data acquisition range, and FIG. 5 is a diagram showing the relationship between the deflection range of the focused ion beam and the data acquisition range. FIG. 4 is a diagram showing an example of three-dimensional image data in which the data tightness position has changed due to drift during measurement. DESCRIPTION OF SYMBOLS 1... Ion source, 2... Extraction electrode, 3... Condenser lens, 4... Aperture, 5... Deflection electrode, 6... Objective lens, 7... Sample, 8... ... Stage, 9... Charged particle detector, 10... Preamplifier,
11... A/D converter, 12... Storage device, 13.
...Display device, 14...Controller, 15...Scan signal generator, 16...D/A converter, 17...
・Voltage amplifier. $1rlA? Figure 2

Claims (1)

[Claims] 1. The ion beam finely focused on the surface of the sample is deflected in the X and Y directions at regular intervals, the charged particles emitted from the sample surface are detected, and the signals are stored in a storage device as three-dimensional image data. A cross-sectional observation device characterized by being able to accumulate images of any cross-section and reproduce them on a display device. 2. Wetting a needle with liquid ionic material, applying a strong electric field to generate an ion beam, and focusing the ion beam on the sample surface using an electrostatic lens, etc. to reduce the ion beam diameter to 0.1 μmφ or less. The cross-sectional observation device according to claim 1, characterized in that: 3. The cross-sectional observation apparatus according to claim 1, wherein the period and the amount of ion beam deflection in the X direction and the Y direction can be set in advance. 4.Independently of the amount of deflection of the ion beam in the X and Y directions,
4. The cross-sectional observation apparatus according to claim 3, wherein the data acquisition range in the Y direction can be set in advance. 5. The cross-sectional observation device according to claim 1, wherein the cross-sectional observation device detects secondary electrons, secondary ions, or both secondary electrons and secondary ions as the charged particles emitted from the sample surface. 6. The cross-sectional observation device according to claim 1, wherein a plurality of three-dimensional image data can be acquired simultaneously. 7. The cross-sectional observation apparatus according to claim 6, wherein three-dimensional image data of a known cross-sectional structure site and an unknown cross-sectional structure site are collected in a time-sharing manner. 8. The cross-sectional observation device according to claim 1, wherein drift during measurement of the focused ion beam is calibrated using three-dimensional image data of a known cross-sectional structure.