JP3398403B2 - Sample image display method for scanning electron microscope - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for displaying a sample image of a scanning electron microscope, and in particular, in observing a sample structure in a semiconductor wafer manufacturing process or the like, a portion that cannot be seen from the electron beam irradiation direction is also observed. The present invention relates to a technique effectively applied to a sample image display method of a scanning electron microscope which is capable of

[0002]

2. Description of the Related Art Generally, a scanning electron microscope uses an electron beam as an alternative to the "human eye". For example, as shown in FIG.
Is a device for irradiating the sample, forming a sample image by using the secondary electrons 3 generated as a result of the interaction between the electron beam 2 and the sample 1, and observing the sample image.

Therefore, in the conventional scanning electron microscope,
Only the "portion where the eye can reach", that is, the portion directly irradiated with the electron beam 2 is displayed as a sample image and can be observed.

For example, a hole structure 4 as shown in FIG. 2 (a).
When the electron beam 2 is irradiated to the sample 1a having the electron beam 2 and observed, the secondary electron 3 as an image signal shows the secondary electron 3 in the vicinity of the irradiated portion.
Since the light is emitted only from the surface of a, a sample image as shown in FIG. 2 (b) is observed.

Similarly, the embankment structure 5 as shown in FIG.
When the sample 1b having the above is observed, the sample image as shown in FIG. 3 (b) is obtained, and further, as shown in FIG. 4 (a), the sample 1c in which the internal structure 6 is hidden under the surface is obtained. Is
The sample image is shown in Fig. 4 (b).

[0006]

However, in the prior art as described above, for example, the hole structure 4 shown in FIG. 2 (a).
In the case of observing the sample 1a having the following, the hole bottom portion behind the electron beam 2 on the side wall of the hole is not displayed as a sample image,
I can't observe. Similarly, also in the case of the sample 1b having the levee structure 5 of FIG. 3 (a), the side wall located behind the electron beam 2 cannot be observed.

Furthermore, as shown in FIG. 4 (a), the sample 1c in which the internal structure 6 is hidden under the surface is shown in FIG. 4 (b).
As shown in, no contrast appears on the sample image, and it is not possible to even infer that the internal structure 6 exists.

Therefore, in the observation of the sample structure as shown in FIGS. 2 (a) to 4 (a), the electron beam 2 is behind the electron beam 2 as shown in FIGS. 2 (c) to 4 (c). The information obtained from the sample image can be used to display the bottom of the hole, the side wall of the embankment, or the internal part that is buried in order to understand what the sample 1 is to be observed and what is hidden. The amount will increase dramatically.

For example, in the case of the sample 1d having the conical hole structure 7 as shown in FIG. 5 (a), the sample image shown in FIG.
A circular image like (b) is displayed. From this circular image, the hole is "well-shaped or conical?" I can't answer the question, "How big is it?"

However, if it is known how the hidden portion looks as shown in FIG. 5 (c), the cone shape, the incident angle θ of the electron beam 2 and the image observation magnification / image The actual depth of the hole can be obtained from the depth d of the hole, and such a question can be solved.

Therefore, an object of the present invention is to make a portion which cannot be seen in such a conventional scanning electron microscope image visible and to widen and deepen the knowledge obtained from the sample image. To provide a display method.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0013]

Among the inventions disclosed in the present application, a brief description will be given to the outline of typical ones.
It is as follows.

That is, the sample image display method for the scanning electron microscope of the present invention irradiates the sample with an electron beam for scanning, and the secondary electrons resulting from the interaction between the electron beam and the sample are used as image signals. A scanning electron microscope that forms a sample image, and displays the sample image of the sample part that is visible from the electron beam irradiation direction and the sample image of the sample part that is not visible from the electron beam irradiation direction in an overlapping manner. is there.

Further, as an image signal source of the sample portion which cannot be seen from the irradiation direction of the electron beam, information generated from the sample with the irradiation of the electron beam is used.

In this case, as the information generated from the sample in association with the irradiation of the electron beam, information on secondary electrons produced by X-rays, reflected electrons or reflected electrons scattered inside the sample is used. Is.

Further, as the image signal source of the sample portion which cannot be seen from the irradiation direction of the electron beam, computer graphics utilizing design information relating to the structure of the sample is used.

[0018]

According to the above-described method for displaying the sample image of the scanning electron microscope, the sample image of the sample portion visible from the irradiation direction of the electron beam and the sample image of the invisible sample portion, for example, the irradiation of the electron beam The information that is generated from the sample as it is, or the information after processing, or the sample image by computer graphics using the design information related to the structure of the sample is displayed in an overlapping manner, so that the sample image displayed by the conventional technique is It is possible to display the portion which is hidden and not displayed in the conventional technique in an overlapping manner.

As a result, a portion that cannot be seen in the conventional scanning electron microscope image can be visualized and observed, whereby more information such as a three-dimensional shape and a three-dimensional dimension can be obtained.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing the principle of signal detection in a sample image display method for a scanning electron microscope which is an embodiment of the present invention.

First, the principle of signal detection in the sample image display method of the scanning electron microscope of this embodiment will be described with reference to FIG.

The sample image display method of the scanning electron microscope of the present embodiment is, for example, in observing a sample structure in a manufacturing process of a semiconductor wafer, a sample image of a sample portion seen from the irradiation direction of an electron beam and an electron beam This is a method of superimposing and displaying a sample image of a sample portion that cannot be seen from the irradiation direction. The sample 1 is irradiated with an electron beam 2a for scanning, and a secondary generated as a result of the interaction between the electron beam 2a and the sample 1. A sample image is formed using the electrons 3 and 3a as an image signal.

In this case, an electron beam 2a which is much faster than the conventional one is used, and the signal of the secondary electron 3a produced by the reflected electrons scattered inside the sample 1 is used as it is together with the ordinary secondary electron 3. The sample image of the sample portion that is invisible from the irradiation direction of the electron beam 2a is displayed so as to be superimposed on the sample image of the sample portion that is visible from the irradiation direction of the electron beam 2a displayed by the conventional technique.

Next, the operation of this embodiment will be described by comparison with the prior art.

First, in the prior art, since the electron beam 2 having a relatively low speed was used, a shadow portion of the electron beam 2 was formed, and the shadowed hole bottom 8 and internal structure 9 as shown in FIG. Is the generation of secondary electrons 3a created by reflected electrons?
Alternatively, the amount generated was extremely small and it was not possible to observe it as an image.

However, when the high-speed electron beam 2a is used as in the present invention, the irradiated electron has sufficient kinetic energy, so that the electron beam 2a passes through the sample 1 as shown in FIG. After being reflected by 8 and internal structure 9,
The sample 1 can be escaped again.

In addition, when the sample 1 escapes, a large number of secondary electrons 3a produced by backscattered electrons are generated. The generation amount of the secondary electrons 3a depends on the amount and energy of the irradiated electron beam 2a. However, since the reflected electron beam 2a has the information of the hole bottom 8 and the internal structure 9, the secondary electron 3a is generated. An image of the hole bottom 8 or the internal structure 9 can be obtained by detecting as an image signal.

That is, the secondary electrons 3 and the secondary electrons 3a formed by the backscattered electrons scattered inside the sample 1 are detected together, so that the prior art displays FIGS. 2 (b) to 5 (b). 2 (c) to FIG. 5 (c), the hole bottom part, the side wall part of the embankment, the buried inner part or the conical hole part, which are behind the electron beam 2a, are displayed in accordance with the sample image of FIG. It is possible to display the portion including the portion that cannot be seen from the irradiation direction of the electron beam 2a as indicated by the diagonal line in ().

Here, examples of photographs of sample images taken by the method of the present invention will be described in comparison with examples of photographs by a conventional scanning electron microscope with reference to FIGS.

In this case, the shade of black and white is determined corresponding to the generation amount of the secondary electrons 3 and 3a, and the larger the generation amount of the secondary electrons 3 and 3a is, the lighter the color can be captured, and conversely the smaller. Sometimes it can be taken in dark colors.

First, in the photograph of FIG. 6, as a sample 1a having a hole structure 4 corresponding to the structure of FIG. 2, for example, a hole on the resist is observed by a scanning electron microscope after forming a resist pattern on a semiconductor wafer. Is.

In this case, conventionally, as shown in FIG. 6 (a), the edge of the hole and the side wall portion visible from the irradiation direction of the electron beam 2a are photographed in a light color, and the resist at the bottom of the hole and the resist around the hole is taken. The part was taken in a dark color. in this way,
In the present embodiment, the bottom of the hole, which is the shadow of the electron beam 2a, is not displayed as a sample image on the side wall of the hole.
As shown in (b), it is possible to take an image of the sample in which the light-colored hidden bottom part of the hole is combined.

Also in the case of the sample 1b having the earth bank structure 5 as shown in FIG. 3, the semiconductor wafer after the resist pattern formation was observed as in the photograph of FIG. 6, and as shown in the photograph of FIG. In addition, the side wall on the opposite side of the resist located behind the electron beam 2a can be observed in a lighter color than in the conventional case. In addition, in the case of the photograph of FIG. 7, the recessed portion of the contact hole, which is the internal structure, can be photographed in a darker color than the resist portion on the surface.

Further, the photograph of FIG. 8 is taken, for example, after processing a wiring pattern in which wiring is formed in a two-layer structure. In the conventional technique, only the side wall of the wiring on the surface is shown as shown in FIG. 8 (a). It was taken in a light color, and it was not possible to infer that there was no light and shade in the internal structure, but in this embodiment, as shown in FIG. In accordance with this, the subsurface wiring buried inside can be photographed in a lighter color than the surroundings for observation.

Therefore, according to the sample image display method of the scanning electron microscope of the present embodiment, the reflected electrons scattered inside the sample 1 together with the ordinary secondary electrons 3 are produced by using the extremely high-speed electron beam 2a. By using the signal of the secondary electron 3a as it is, the sample image of the sample portion visible from the irradiation direction of the electron beam 2a displayed by the conventional technique is changed to the sample image of the sample portion invisible from the irradiation direction of the electron beam 2a. Since they can be displayed in an overlapping manner, it is possible to display and observe a part that cannot be seen in the conventional scanning electron microscope image.

Although the invention made by the present inventor has been concretely described above based on the embodiments, the present invention is not limited to the embodiments and various modifications can be made without departing from the scope of the invention. Needless to say.

For example, in the sample image display method of the scanning electron microscope of this embodiment, the reflection scattered inside the sample 1 is used as an information source used for displaying a portion invisible from the irradiation direction of the electron beam 2a. The case where the signal of the secondary electron 3a produced by the electron is used as it is has been described.
The present invention is not limited to the above embodiment, but can be widely applied to other methods as described below.

That is, as in the above embodiment, as an information source used for displaying a portion which cannot be seen in the scanning electron microscope image, reflected electrons or X-rays generated from the sample by the irradiation of the electron beam are used as an image signal. If you do
A method of processing a signal such as a reflected electron or X-ray and then using it for image display is also possible.

In this case, for example, an X-ray image is captured in accordance with a normal secondary electron sample image, and information on a hidden portion such as an internal structure is calculated from a comparison between the two images to obtain a normal image. It can be displayed by being superimposed on the image by the secondary electrons.

A method of utilizing design information such as LSI pattern / structure data as an image signal is also possible. For example, pattern data and device structure information related to a sample are stored in a database in advance, and an image is observed at the time of observation. Detects the observation direction, position, and area information of the observation field,
This is possible by reading out the data of the visual field from the database and converting it into computer graphics.

Furthermore, when displaying such a sample image, it is possible to display the hidden portion by characterizing such as color display or contour display.

In the above description, the invention mainly made by the present inventor is applied to the scanning electron microscope used in the manufacturing process of the semiconductor wafer which is the field of use thereof, but the invention is not limited to this. It is also widely applicable to related devices using scanning electron microscopes or similar devices, and all fields that utilize these devices, and in particular, observation including the sample part invisible from the electron beam irradiation direction is required. It can be applied well in case.

[0043]

The effects obtained by the typical ones of the inventions disclosed in the present application will be briefly described as follows.
It is as follows.

That is, a normal secondary electron image is obtained by superimposing and displaying the sample image of the sample portion visible from the electron beam irradiation direction and the sample image of the sample portion invisible from the electron beam irradiation direction. Since it is possible to display a portion that cannot be seen only by itself, it is possible to obtain more information such as a three-dimensional shape and a three-dimensional size.

As a result, it is possible to obtain a sample image display method for a scanning electron microscope which makes it possible to broaden and deepen the knowledge obtained from the sample image by revealing a portion that cannot be seen in the conventional scanning electron microscope image. You can

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a signal detection principle in a sample image display method for a scanning electron microscope which is an embodiment of the present invention.

FIGS. 2A to 2C are explanatory views showing display examples of a perspective cross-sectional view of a main part of a sample having a hole structure, a sample image according to a conventional technique and a sample image according to the present invention when the sample is observed. It is a figure.

3 (a) to (c) show a perspective view of a main part of a sample having a levee structure, and a display example of a sample image according to the prior art and a sample image according to the present invention when the sample is observed. FIG.

4A to 4C are explanatory views showing display examples of a perspective cross-sectional view of a main part of a sample having an internal structure, a sample image according to the prior art and a sample image according to the present invention when the sample is observed. It is a figure.

5 (a) to 5 (c) show a perspective view of a sample having a conical hole structure, a display example of a sample image according to the prior art and a sample image according to the present invention when the sample is observed. FIG.

6 (a) and 6 (b) are photographs of a sample image according to the prior art and a sample image according to the present invention obtained by scanning a semiconductor wafer after forming a resist pattern with a scanning electron microscope as a sample having a hole structure. .

7 (a) and 7 (b) are photographs of a sample image according to the prior art and a sample image according to the present invention obtained by scanning a semiconductor wafer after forming a resist pattern with a scanning electron microscope as a sample having a bank structure. is there.

8 (a) and 8 (b) are photographs of a sample image according to the prior art and a sample image according to the present invention taken by a scanning electron microscope of a semiconductor wafer after a wiring pattern is processed as a sample having an internal structure. .

FIG. 9 is a configuration diagram showing a signal detection principle in a sample image display method of a scanning electron microscope which is an example of a conventional technique.

[Explanation of symbols]

1, 1a to 1d sample 2 electron beam 2a electron beam (extremely high-speed electron beam) 3 secondary electron 3a secondary electron (secondary electron created by backscattered electrons scattered inside the sample) 4 hole structure 5 levee structure 6 Internal structure 7 Conical hole structure 8 Hole bottom 9 Internal structure

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Sadao Terakado 882, Imo, Katsuta-shi, Ibaraki Hiritsu Mfg. Co., Ltd., Measuring Instruments Division (72) Inventor, Katsuhiro Kuroda 1-280, Higashikoigakubo, Kokubunji, Tokyo Hitachi, Ltd. Factory Central Research Laboratory (72) Inventor Ken Ninomiya 1-280 Higashi Koigakubo, Kokubunji City, Tokyo Hitachi Ltd. Central Research Laboratory (72) Inventor Tokuo Kugaku 1-280 Higashi Koigakubo, Kokubunji City, Tokyo Hitachi Research Center In-house (56) Reference JP-A-5-258700 (JP, A) JP-A-6-103950 (JP, A) JP-A-61-53553 (JP, A) JP-A-6-111748 (JP, A) JP-A-5-290786 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01J 37/22 H01J 37/28

Claims (3)

(57) [Claims] 1. A scanning an electron beam to the sample, a scanning electron microscope for forming a sample image of the resulting Ru electronic interaction with the a electron beam sample as an image signal, the electronic From the sample part visible from the beam irradiation direction
Before passing through the emitted electrons and a part of the sample,
From the irradiation direction of the electron beam to the invisible part of the sample surface
Emitted from the sample based on the arrival of the electron beam.
By the electrons, the electron beam and the specimen image of the specimen portion irradiated visible from the direction of the electron beam scanning electron and displaying by overlapping the sample image of the sample surface invisible part from the irradiation direction of the Display method of sample image of microscope. 2. The irradiation of the electron beam according to claim 1,
The part of the sample surface that cannot be seen from the direction of irradiation is the electron beam
The bottom of the hole or the side wall of the embankment that is shaded with respect to the irradiation direction
査型electron microscope sample image display method of run you comprising a portion. 3. The electron beam according to claim 1,
Enter from the part visible from the electron beam irradiation direction
The electron beam through the part of the sample.
Sufficient to reach the invisible sample surface from the shooting direction
Features and to that run査型electron microscope sample image display method that the high-speed electron beam that.