JPH03186711A - Microdimension length measuring device - Google Patents

Abstract

PURPOSE:To obtain an image whose visual field is wide and whose contrast is strong and to facilitate the detection of a length measuring part by providing not only a length measuring electron gun but a length measuring part detecting electron gun, and executing the length measurement and the detection of the length measuring part by each separate electron gun. CONSTITUTION:The detection of a length measuring part is executed by an electron beam 12 from a length measuring part detecting electron gun 11. At the time of detecting the length measuring part, magnification is lowered in order to display a wide visual field on a display device 8. That is, the electron beam 12 is allowed to scan a wide range on the surface of a sample 9. This electron beam 12 is made incident obliquely on the surface of the sample 9, therefore, even by low magnification, an image whose contrast is strong is obtained. Subsequently, after the length measuring part is detected, a position of a sample base 7 is adjusted so that its part comes to the center of a visual field. Also, length between two points in the length measuring part is measured by an electron beam from a measuring electron gun 2. This electron beam 3 is made incident vertically on the surface of the sample 9, therefore, the length measuring accuracy is high.

Description

[Detailed description of the invention] [Industrial application field]

TECHNICAL FIELD The present invention relates to a micro-dimension measuring device for measuring the dimensions of microscopic parts such as patterns of large-scale integrated circuits (hereinafter referred to as rLsIJ).

[Conventional technology]

The minute dimension measuring device is used, for example, to measure the dimension (the length between two points) of an LSI pattern formed on a semiconductor substrate. However, with the miniaturization of LSIs, even greater precision in length measurement is required, and in recent years, minute dimension measurement devices that use electron beams rather than light (lasers) have been developed. This type of minute dimension measuring instrument is the length measuring SEM (SEM:
Scanning Electron Micros
Due to practical requirements, it is equipped with an automatic length measurement function (a function that first finds the measurement point and then measures the length). FIG. 2 shows such a conventional minute dimension measuring device. In FIG. 2, 1 is an electron gun drive unit, 2 is a length measurement electron gun,
3 is an electron beam, 4 is a secondary electron beam, 5 is a sample chamber, 6 is a secondary electron detector, 7 is a sample stage, 8 is a display device, 9 is L
This is a sample of SI etc. The electron gun drive section 1 houses a power supply circuit and the like for emitting an electron beam 3 from the length measurement electron gun 2. When the sample 9 is irradiated with electrons m3, secondary electrons are emitted. The secondary electron beam 4 is an electron beam generated by this secondary electron. The ejected secondary electrons are detected by a secondary electron detector 6, subjected to processing such as amplification, and displayed on a display device 8. The brightness of the point displayed on the display device 8 at this time corresponds to the amount of secondary electrons emitted at the point on the sample 9 that is irradiated with the electron beam 3. That is, when the amount of emission is large, it is bright, and when it is small, it is dark (note that the display can be reversed, such as making it dark when the amount of emission is large and bright when it is small). When the electron beam 3 is scanned and irradiates another point on the sample 9,
Secondary electrons are emitted depending on the material at that point. Therefore,
When sample 9 is an LSI substrate, the surface material is:
The image of the jiSI pattern is displayed on the display device 8 because it varies depending on the location depending on the LSI pattern being formed. Based on this displayed image, the length of the desired point is measured. By the way, prior to measuring the length, a location where the length should be measured is detected. To detect the length measurement point, the electron vA3 is scanned over a wide range of the sample 9 in order to cover a wide range in the field of view. The display device 8 displays an image corresponding to the wide range. In other words, the magnification in this case is small. When the length measurement point is detected by looking at the image displayed on the display device 8, the length measurement point is placed in the center of the field of view (that is, the image of the length measurement point is placed in the center of the display device 8). Move the sample stage 7. After that, a narrow range including the length measurement point is scanned. On the display device 8, the narrow range is displayed on the entire screen. In other words, the image of the length measurement location is displayed at a high magnification. In this way, minute lengths can be measured. Note that documents related to this type of technology include, for example:
Sakae Miyauchi, Takao Ise, Karl L, Harri
s “Practical Application of Dimension Control in Process Automation Lines” (Monthly Sem1conductor World
d 1987+ 6°P130-134).

[Problem to be solved by the invention]

(Problem) However, the conventional micro-dimension measuring device described above has a problem in that it is difficult to detect the length measurement point. (Explanation of the problem) When measuring the length as described above using an electron beam, 75I
It is known that measurements can be made more accurately when an electron beam is incident perpendicularly to an object that is to be elongated than obliquely. By the way, before measuring the length, a wide range of the surface of the sample 9 is scanned to detect the length measurement point, but in conventional micro-dimension measuring instruments, a length-measuring electron gun is also used for this detection. 2 was used. In order to detect the length measurement point, it is desirable to obtain an image with strong contrast between light and dark. However, when the magnification of the micro-dimension measuring device is kept the same, the contrast of the image obtained is worse when the electron beam 3 is incident perpendicularly to the sample 9, and worse when the electron beam 3 is incident obliquely to the sample 9. is known to be better. It is also known that the contrast becomes stronger when the magnification is increased. For length measurement point detection, it is more convenient to make the light incident obliquely so that the contrast is strong. However, priority was given to improving length measurement accuracy, and conventionally, as shown in FIG. The structure is such that I3 is incident vertically. Therefore, the length measurement point must be detected using vertical electron &@3. In order to quickly detect the length measurement point, it is necessary to lower the magnification and widen the field of view, but the contrast with the vertical electron beam 3 is weak, making it difficult to detect the length measurement point. Increasing the magnification can increase the contrast, but the field of view becomes narrower and the probability that the length measurement point will be out of the field of view increases.For these reasons, it becomes difficult to detect the length measurement point. was. An object of the present invention is to solve the above-mentioned problems.

[Means to solve the problem]

In order to solve the above problems, the present invention provides a length measurement electron gun that irradiates a sample to be measured with an electron beam, a secondary electron detector that detects secondary electrons emitted from the sample, and a secondary electron detector that detects secondary electrons emitted from the sample. An electron gun for detecting a length measurement point that emits an electron beam that is obliquely incident on the surface of the sample in a micro-dimension measuring device that includes a display device that displays an image of the sample surface based on a signal from an electron detector. We decided to set up a.

[For production]

According to the above configuration, since the length measurement point detection electron gun is provided in addition to the length measurement electron gun, it is possible to measure the length and detect the length measurement point using separate electron guns. The electron beam emitted from the electron gun for length measurement point detection is incident obliquely to the surface of the sample, so even when scanning a wide range of the sample surface (in other words, when the magnification is low), it can produce strong contrast. An image is obtained. In other words, an image with a wide field of view and strong contrast can be obtained.
It becomes easy to detect the length measurement point.

【Example】

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows a minute dimension measuring device according to an embodiment of the present invention. Components with the same symbols as in FIG. 2 correspond to those in FIG. 10 is an electron gun drive unit, 11 is an electron gun for length measurement point detection, and 12 is an electron beam. The difference in configuration from conventional micro-dimension measuring instruments is that a length-measuring point detection electron gun 11 is provided, which is a dedicated electron gun for detecting length-measuring points. The electron gun drive unit 10 houses a power supply circuit and the like for the length measurement point detection electron gun 11. The length measurement point detection electron gun 11 is arranged at such a position that the electron beam 12 emitted therefrom is incident obliquely (for example, at an angle of 30° to 60°) with respect to the surface of the sample 9. Detection of a length measurement location and length measurement using the minute dimension length measuring device of the present invention are performed as follows. (1) Detection of the length measurement point Detection of the length measurement point is performed using the electron beam 12 from the length measurement point detection electron gun 11. In order to detect the length measurement point, it is necessary to display a wide field of view on the display device 8. Therefore, reduce the magnification. That is, the electron beam 12 scans a wide range on the surface of the sample 9. Since the electron beam 12 is obliquely incident on the surface of the sample 9, an image with strong contrast can be obtained even at low magnification. In this way, since an image with a wide field of view and strong contrast can be obtained on the display device 8, the length measurement point can be easily detected. After detecting the length measurement point, the position of the sample stage 7 is adjusted so that the point is in the center of the field of view. (2) Length measurement To measure the length between two points at the length measurement location, use the length measurement electron gun 2.
This is done using an electron beam 3 from . Since the electron beam 3 is incident perpendicularly to the surface of the sample 9, the length measurement accuracy is high. Increase the magnification of the micro-dimension measuring device according to the length to be measured. If the length measurement point is within the field of view but is shifted from the center of the field of view, the position of the sample stage 7 may be finely adjusted and moved to the center. Note that even if the electron beam 3 is incident perpendicularly, the contrast required for length measurement can be obtained because the magnification is large.

【Effect of the invention】

As described above, according to the present invention, the electron gun for detecting the length measurement point is separately provided, and the detection of the length measurement point is performed with an electron beam incident obliquely to the surface of the sample. Even when scanning a wide range (that is, at low magnification), images with strong contrast can be obtained. Therefore, an image with a wide field of view and strong contrast can be obtained, and the length measurement point can be easily detected.

[Brief explanation of drawings]

Fig. 1: Microscopic length measuring device according to an embodiment of the present invention Fig. 2: In the diagram of a conventional microscopic length measuring device, ■ is an electron gun drive section, 2 is an electron gun for length measurement, and 3
is an electron beam, 4 is a secondary electron beam, 5 is a sample chamber, 6 is a secondary electron detector, 7 is a sample stage, and 8 is a display'! ! ! Device,
9 is a sample, 10 is an electron gun drive unit, 11 is an electron gun for length measurement point detection, and 12 is an electron beam.

Claims (1)

[Claims] A length measurement electron gun that irradiates the sample to be measured with an electron beam, a secondary electron detector that detects secondary electrons emitted from the sample, and an image of the sample surface based on the signal from the secondary electron detector. A micro-dimension measuring device comprising a display device for displaying a display device, characterized in that the micro-dimension measuring device is provided with an electron gun for detecting a length measurement point that emits an electron beam obliquely incident on the surface of the sample. Long vessels.