JPH10162766A - Focused ion beam processing observation equipment - Google Patents

Abstract

(57) [Summary] [Object] To provide a focused ion beam processing observation apparatus capable of observing a three-dimensional structure of a sample with high resolution. A three-dimensional image is formed after performing a deconvolution process for reducing an influence of a beam distribution of a focused ion beam from a two-dimensional image of a sample.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a processing observation apparatus using a focused ion beam and a failure analysis apparatus for a semiconductor device or the like using the processing observation apparatus.

[0002]

2. Description of the Related Art Conventionally, as a focused ion beam processing observation apparatus capable of observing a three-dimensional structure of a sample, for example, Japanese Patent Application Laid-Open No.
No. 72667 is known. In this apparatus, a method is used in which a plurality of two-dimensional images obtained during scanning and processing the same region on a sample with a focused ion beam are accumulated, and these are reconstructed to form a three-dimensional image of the sample. ing. Since this method always detects secondary particle signals generated from all portions of the sample scraped off by the focused ion beam, it does not overlook defective portions and the like and is excellent in reproducibility of a three-dimensional image.

[0003]

In the above-mentioned prior art, no consideration has been given to a phenomenon in which the topological (topological) reproducibility of a three-dimensional structure is deteriorated in order to increase the resolution. That is, when a narrower focused ion beam is used for a pattern on a sample, there is a phenomenon that the flatness of a processed surface is extremely deteriorated locally due to a difference in sputtering rate of various materials in the sample.

[0004] It is an object of the present invention to provide a focused ion beam processing and observation apparatus capable of observing a three-dimensional structure of a sample with high resolution.

[0005]

An object of the present invention is to provide a focused ion beam processing / observing apparatus which performs a deconvolution process for reducing image blur caused by a beam intensity distribution of a focused ion beam in a two-dimensional image of a sample. This is achieved by providing a function of reconstructing these to form a three-dimensional image. In addition, the problem is better achieved by blowing a deposition gas onto the sample during the processing of the sample.

[0006] When processing a sample, using a focused ion beam that is thicker with respect to the spatial change of the material on the sample keeps the sample processing surface flatter. Therefore, after performing a deconvolution process to reduce image blur caused by the beam intensity distribution of the focused ion beam from the two-dimensional image of the sample obtained by this processing, these two-dimensional images are reconstructed to three-dimensional By forming an image, the reproducibility and resolution of the structure in the three-dimensional image can be increased at the same time. Here, the beam intensity distribution of the focused ion beam is measured in advance.

Further, when a sample is sputtered with a focused ion beam and a small amount of deposition gas is irradiated to such an extent that the sputtering speed is reduced, a large amount of deposits are formed in the portion of the sample which is easily sputtered. Since it functions as a protective film, the flatness of the sample is further improved. Thereby, the reproducibility of the structure in the three-dimensional image is improved.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment for observing a shape defect inside an LSI using the present invention will be described below.

Embodiment 1 FIG. 1 is a configuration diagram of a focused ion beam processing and observation apparatus according to the present invention. The apparatus body 1 mainly includes an ion source 2, a variable aperture 4,
It comprises an electrostatic lens 5, a deflector 6, a sample stage 7, and a secondary particle detector 9. Here, the vacuum container storing these is omitted. Here, the ion source 2 is G
a, the acceleration voltage of the ion beam 3 is 30 kV. The secondary particle detector 9 includes a fluorescent screen and a photomultiplier, and detects secondary electrons. The apparatus main body 1 is connected to a control circuit 20 via a deflection control system 10 and a secondary particle signal control system 11. Here, control systems such as the ion source 2, the variable aperture 4, the electrostatic lens 5, and the sample stage 7 are omitted. Control circuit 20
Includes a display 21, a plurality of two-dimensional image memories 22,
The rendering calculator 23 and the three-dimensional image memory 24 are connected.

The present embodiment is characterized in that a beam distribution memory 25, a deconvolution calculator 26, and a plurality of two-dimensional image memories 27 are further connected to the control circuit 20.

Next, the operation of this device will be described. The beam amount of the ion beam 3 emitted from the ion source 2 is controlled by a variable aperture 4, focused by an electrostatic lens 5, and irradiated onto a sample 8. When the sample 8 is irradiated with the ion beam 3, the portion is sputtered and secondary electrons and secondary ions are generated according to the material and shape of the sample. Here, the secondary particle detector 9 detects secondary electrons and converts them into an electric signal (secondary electron signal). Deflector 6 causes ion beam 3 to be deflected by a scanning deflection signal generated by a scanning circuit in deflection control system 10.
Is deflected to scan over the sample 8. The secondary electron signal stored in the buffer memory in the secondary particle detection system 11 in conjunction with the scanning deflection signal is sent to the display 21 by the control circuit 20, and the SIM that uses the secondary electron signal as a luminance signal
An image (scanning ion microscope image) is displayed.

Usually, the following operation is performed to observe a portion of the sample 8 where a failure analysis is to be performed. As shown in FIG. 2, the SI of the sample 8 displayed on the display 21
While observing the M image 210, the sample stage 7 is moved so that the processing place enters the scanning range. SI including processing location
When the M image is obtained, a processing area is set by a portion shown on the display 21 and surrounded by a cursor (frame) 211, for example. Further, after setting control parameters such as the size of the variable aperture 4 and the processing depth in the control circuit 20, the ion beam 3 is scanned to start processing on the sample 8. As shown in FIG. 2, a SIM image of the sample 8 being processed is displayed on the display 21, and the SIM image is stored in the two-dimensional image memory 22 as a two-dimensional image of the sample.

[0013] In order to obtain a three-dimensional image of the sample 8 after processing is completed, the following has been done conventionally. That is, a plurality of sample images stored in the two-dimensional image memory 22 are reconstructed by the rendering calculator 23 to form a three-dimensional image, and the three-dimensional image is stored in the three-dimensional image memory 24.
To be displayed. Here, the rendering computing unit 23 has a function of classifying each pixel of the sample image into several pixels according to, for example, luminance, and separating each of the pixels by luminance classification to represent the pixels three-dimensionally. The method of classification can be arbitrarily changed. Further, the rendering calculator 23 can form an arbitrary cross-sectional image of the sample.

The feature of this embodiment is that, unlike the conventional case, the sample image stored in the two-dimensional image memory 22 is once sent to a deconvolution calculator 26 for processing and then processed by another two-dimensional image memory 27. To store. Then, the plurality of sample images stored in the two-dimensional image memory 27 are reconstructed by the rendering calculator 23 to form a three-dimensional image. After storing this in the three-dimensional image memory 24, it is displayed on the display 21.

The deconvolution calculator 26 uses the beam distribution of the focused ion beam stored in the beam distribution memory 25 to perform processing for reducing image blur of the sample image stored in the two-dimensional image memory 22. As a result, even if a beam thicker than the pattern on the sample is used, not only a high-resolution image can be obtained, but also the flatness of the processed surface is maintained, so that the original three-dimensional structure is included in the three-dimensional image. It is reproduced well. That is, three-dimensionally high resolution can be obtained.

In this embodiment, when the sample was processed using a beam having a width of 0.2 μm, local irregularities were suppressed to 0.1 μm or less. Further, in the present method, the quadrupling resolution could be improved by the deconvolution calculator, and a resolution of a sample image of 0.05 μm was substantially obtained.

As shown in FIG. 2, a three-dimensional image 213 of the LSI sample obtained in the display 21 is displayed.
Here, only the electrode portion of poly-Si is shown, and it was observed that a portion was missing.

Here, the pattern rule 0.
A three-dimensional image was formed using a 2 μm LSI as a sample. When a beam with a width of 0.05 nm was used to increase the resolution, local irregularities of about 0.6 μm were generated on the sample processing surface, and a microstructure having a thickness of about 3 μm was formed in the obtained three-dimensional image. I can no longer determine.

As described above, according to the present invention, the internal structure of a sample such as a semiconductor element can be three-dimensionally observed with high resolution.
This has the effect of increasing the probability of finding a fine structural abnormality.

In this embodiment, a secondary electron is used for a signal to form a two-dimensional image of a sample. However, when a secondary ion is used for a signal, the SN is inferior but the three-dimensional structure of element distribution is high. There is an effect that can be obtained with the resolution. Further, by interpolating data between a sample image formed by secondary electrons and a sample image formed by secondary ions, a more accurate three-dimensional structure of element distribution can be obtained.

Embodiment 2 The focused ion beam processing and observation apparatus used in this embodiment is the same as that used in the first embodiment.

A feature of the present embodiment is that the sample 8 is processed while the sample 8 is irradiated with the deposition gas 13 by the gas source 12 shown in FIG. Here, the control system of the gas source 12 is omitted, but is connected to the control circuit 20. Gas 13 was produced by heating tungsten carbonyl (W (CO) ₆ ).

Here, in order to obtain a three-dimensional image of the sample 8,
When the sample 13 is sputter-processed with the focused ion beam 3 and a small amount of the gas 13 is irradiated to reduce the sputter processing speed, a large amount of deposits are formed in portions of the sample 8 which are easily sputter-processed. Since it works, the flatness of the processed surface of the sample 8 is improved. Specifically, when the sputter processing speed was reduced to about half, the local unevenness was reduced to half when the same depth was normally sputtered. As a result, when the LSI sample of Example 1 was observed, the strain in the depth direction was 0.05 μm, and the resolution was the same as that in the plane direction.

As described above, according to the present invention, there is an effect that the internal structure of a sample such as a semiconductor element can be three-dimensionally observed without being distorted in the depth direction.

Embodiment 3 FIG. 3 is a configuration diagram of a semiconductor failure analysis system according to the present invention. This system comprises the focused ion beam processing and observation apparatus 30 of the first embodiment and a data display system 40 connected thereto. The data display system 40 includes a control circuit 41, a CAD data buffer 42, a data clipping calculator 43, a rendering calculator 44, a three-dimensional image memory 45, and a display device 46.

In this system, a control circuit 41 takes in a three-dimensional image of a sample from the focused ion beam processing and observation device 30 and displays it on a display device 46, and also sends CAD data of the semiconductor integrated circuit from a computer (not shown) to a CAD data buffer 42. Captured via to form a three-dimensional design image corresponding to the three-dimensional image of the sample,
They are displayed side by side or overlaid on the same display device 46. Here, the control circuit 41 causes the data cut-out calculator 43 to cut out only the portion necessary for display from the CAD data, synthesizes this into a three-dimensional image by the rendering calculator 44, and stores it in the three-dimensional image memory 45. Then, this is sent to the display device 46 to be displayed.

Therefore, according to the present embodiment, it is possible to observe the actual three-dimensional structure of the sample at high resolution and to compare it with the designed three-dimensional structure in detail.

As described above, according to the present embodiment, there is an effect that a dimensional error or a shape defect of a semiconductor integrated circuit can be accurately evaluated in three dimensions.

[0029]

According to the present invention, it is possible to three-dimensionally observe the internal structure of a sample such as a semiconductor device with high resolution, so that there is an effect of improving the probability of finding a minute structural abnormality. In addition, this enables the failure analysis of the semiconductor integrated circuit to be performed in a short time, so that the yield can be improved at an early stage.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a focused ion beam processing and observation apparatus according to one embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating an example of image display according to the embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a semiconductor failure analysis system according to one embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Focused ion beam apparatus main body, 2 ... Ion source, 3 ... Ion beam, 4 ... Aperture, 5 ... Electrostatic lens, 6 ... Electrostatic deflector, 7 ... Sample stage, 8 ... Sample, 9 ... Secondary electron detection , 10 ... deflection control system, 11 ... secondary particle detection system, 12 ...
Gas source, 13: deposition gas, 20: control circuit, 21: display, 22: two-dimensional image memory, 23: rendering calculator, 24: three-dimensional image memory, 25: beam distribution memory, 26: deconvolution calculator , 27: two-dimensional image memory, 30: focused ion beam processing and observation device, 4
0: data display system, 41: control circuit, 42: CA
D data buffer, 43 ... data cutout computing unit, 44
... Rendering operation unit, 45 ... Three-dimensional image memory, 46 ...
display.

Claims (3)

[Claims] 1. A mechanism for acquiring and storing a plurality of two-dimensional images by scanning the same area on a sample with a focused ion beam, and forming a three-dimensional image of the sample by reconstructing the plurality of two-dimensional images. A focused ion beam processing / observing apparatus having a mechanism for displaying a three-dimensional image of the sample and a mechanism for displaying a three-dimensional image of the sample, having a function of reducing image blurring of the plurality of two-dimensional images caused by the beam intensity distribution of the focused ion beam. A focused ion beam processing and observation apparatus characterized by the above-mentioned. 2. A mechanism for scanning a same area on a sample with a focused ion beam to acquire and accumulate a plurality of two-dimensional images, and reconstructing the plurality of two-dimensional images to form a three-dimensional image of the sample. A focused ion beam processing and observation apparatus having a mechanism for displaying a three-dimensional image of the sample and a mechanism for displaying the three-dimensional image of the sample. A focused ion beam processing and observation apparatus characterized by obtaining a two-dimensional image. 3. A means for displaying three-dimensional image data of a semiconductor device obtained by the focused ion beam processing and observation apparatus according to claim 1 and design data of the semiconductor device on a same monitor. A semiconductor failure analysis system characterized by the following.