JPH11316115A - Scanning electron microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the precision of measurement of form or size to pattern by a scanning electron microscope by performing a dimensional measurement on the basis of the result obtained by adding and averaging the scanning lines in the area between a plurality of regulated boundary lines. SOLUTION: The emitted electron beam 2 of an electron source 1 is converged by a convergent lens 3 or an objective lens 5 and focused on a sample 6. The beam 2 is two-dimensionally deflected by a deflection coil 4 operated according to the signal of a deflection generator 9 according to the control command by an electronic computer 13 to scan the sample 6. The signal of the secondary electron 7 generated from the sample 6 is detected by a detector 8, stored in an image memory 10 after A/D conversion, and also D/A converted to image-display it on a CRT 14 as a luminance modulation signal. In an automatic measurement by a scanning microscope, addresses of upper and lower ends in an area to be averaged are calculated according to a prescribed expression. Since the form or size of a pattern or the state of the patter edge can be confirmed by a test image, and the setting of area is allowed to perform the comparison with a sample image, the measurement precision can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning electron microscope, and more particularly to a fine pattern width on a wafer displayed on an image display section.
The present invention relates to a scanning electron microscope provided with means suitable for measuring dimensions such as pitch.

[0002]

2. Description of the Related Art Conventional scanning electron microscopes used for dimension measurement of wafers, as described in Japanese Utility Model Laid-Open No. 24606/1986, have a signal and a pattern edge having a good S / N ratio. When measuring the length using a signal whose roughness is averaged, the signal around the designated position is averaged. The averaging is to add and average the upper and lower signals in the dimension measurement direction and the vertical direction.

However, the display does not indicate the range of the area to be averaged. Therefore, the operator needs to confirm the range of the area.
A method of calculating a designated area and applying a difference or the like to a screen to confirm the difference is employed. For this reason, an extra load is imposed on the operator and there is a problem in terms of throughput.

FIG. 5 is a diagram showing a CRT display example in the conventional automatic length measurement.

In the conventional automatic length measurement, a command is sent from a computer to a cursor generator, and a pattern 21 and a cursor 22 are first displayed on a CRT as shown in FIG. The cursor 22 can be moved to the length measurement position by controlling the movement by an external operation (for example, an operation of a trackball).
Can be overlaid and displayed.

[0006] Next, as shown in FIG.
(A) With the cursor 22 being the designated length measurement position as the center, the averaging is performed based on the addition number n and the line-to-line interval s set in advance in the i direction which is a direction perpendicular to the length measurement direction. I do. That is, assuming that addition is performed at intervals of s in the i direction and the current number of additions is n, the value of the m-th pixel is the addition value up to (n-1)

[However, A (i, m) is the i-th pixel of the m-th pixel.
Direction value] and the n-th A (n, m) are added and averaged. This process is performed for all pixels at the designated measurement position,
Using the signal thus obtained, an automatic length measurement process is performed using an electronic computer. Here, as an implementation method, the averaging of the signal once taken into the image memory has been described, but there is no problem if this is implemented by a hardware method.

As a result, as shown in FIG. 5C, the cursors 23 and
24 and 25 are displayed, and the length measurement value is automatically calculated by the computer based on the interval 1 between the cursors 24 and 25.

As described above, the cursor 22 indicated at the length measurement position
Since only the display is performed, the average area or the average area is not clear. For this reason, as described above, there is a task of calculating which region the operator averages and confirming it with a finger or the like, which places an extra burden on the operator.

On the other hand, Japanese Patent Application Laid-Open No. Sho 59-210312 discloses a technique of displaying two cursors on a screen in order to specify the averaged area.
However, it is not enough to be applied to length measurement of various shapes and sizes of patterns formed on a semiconductor device.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a scanning electron microscope having a length measuring function suitable for improving the accuracy of length measurement for patterns of various shapes and sizes.

[0012]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides
In a scanning electron microscope having a length measuring function of scanning a sample with an electron beam and displaying a sample image on a display device based on a signal generated by the sample, a scanning line in a designated area is averaged, and based on the result, Means for performing dimension measurement by means of: a means for displaying two boundary lines indicating the designated area and the other area on the sample image; a means for adjusting the position of the two boundary lines; Means for displaying the adjusted two boundary lines, wherein dimension measurement is performed based on the result of averaging the scanning lines in the area within the adjusted two boundary lines. A scanning electron microscope having a function is provided.

According to such a configuration, the region to be averaged can be set while confirming the shape and size of the sample on the sample image.

In the case where the edge of the line pattern varies, by measuring the length based on the scanning lines in a certain wide area, the variation of the measured values can be averaged, and the length of the pattern can be measured. Accuracy can be improved.

Further, when measuring the length of a locally provided pattern or a pattern having a characteristic in a certain specific portion, it is necessary to limit the area to be averaged to the characteristic portion.
Among the limited areas, securing the area to be averaged to the maximum can further improve the pattern length measurement accuracy.

According to the structure of the present invention, the averaging area can be set arbitrarily while the state of the pattern is confirmed on the sample image, so that the length measurement accuracy can be improved.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the embodiment shown in FIG. 1 and FIGS. FIG. 1 is a configuration diagram showing one embodiment of the scanning electron microscope of the present invention. In FIG. 1, an electron beam 2 emitted from an electron source 1 is finely converged by a converging lens 3 and an objective lens 5 and focused on a sample 6. The electron beam 2 is two-dimensionally deflected by a deflection coil 4 that operates according to a signal from a deflection generator 9 in accordance with a control command from an electronic computer 13, and scans the sample 6. At this time, signals of secondary electrons 7 and the like generated from the sample 6 are detected by the detector 8, A / D-converted and stored in the image memory 10. Image display is performed as a modulation signal. By the way, in the present invention, as shown in FIG. 2A showing a CRT display in the automatic length measurement by the scanning electron microscope, the addresses of the upper end and the lower end of the area to be averaged are measured by the number n of additions and the interval s. Using the long center position P, the upper end address = P− (n × s) / 2 (1) The lower end address = P + (n × s) / 2 (2) However, the cursors 16 and 17 are displayed by the cursor generator 12. In addition, 11 is an adder.

These cursors 16 and 17 are connected to an external operation, for example, a trackball 15 to count the number of pulses generated by moving the trackball 15 and move these cursors 16 and 17 up and down based on the count. At a constant width (m × s; n is the number of additions, and s is an interval). After the automatic length measurement, as shown in FIG.
Cursors 18 and 19 indicating the averaged area are displayed on CRT 14
To be displayed.

Further, the number of added areas and the interval can be set in advance by the operator for the area to be averaged, and the width of the area displayed on the CRT 14 can be changed correspondingly.

According to the above-described embodiment of the present invention, an averaged area or an averaged area can be easily confirmed.

When it is desired to measure the average dimension of the entire pattern, as shown in FIG.
When it is desired to measure the local dimension by setting the number of additions and the interval so as to be wide as between 21 and 21, the area to be averaged is set between the cursors 20 and 21 as shown in FIG. What is necessary is just to set the number of additions and the interval so as to narrow the number. Therefore, when changing the area to be averaged according to the application, the operator can easily work while checking on the CRT 14, and the burden on the operator can be reduced.

Further, in the case of a shape as shown in FIG. 4A which is an explanatory view of another application example of the present invention, FIG.
If the area to be averaged is widened as shown in FIG. 4A, it is not possible to obtain an appropriate length measurement value. Therefore, as shown in FIG. Although it is necessary, it can be said that it is an effective display method in such a case.

However, the number and type of cursors (for example, points, solid lines, etc.) need not be limited to those shown in the embodiment.

[0024]

As described above, according to the present invention,
The shape and size of the pattern or the state of the pattern edge can be confirmed in the sample image, and the area for averaging the scanning lines can be set based on this sample image. Can be compared, so that it is possible to provide a scanning electron microscope having a length measuring function capable of easily realizing improvement in length measuring accuracy.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of a scanning electron microscope of the present invention.

FIG. 2 is a view showing a CRT display in the automatic length measurement by the scanning electron microscope of FIG.

FIG. 3 is an explanatory diagram of an application example of the present invention.

FIG. 4 is an explanatory diagram of an application example of the present invention.

FIG. 5 is a view showing a CRT display in a conventional automatic length measurement by a scanning electron microscope.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electron source, 2 ... Electron beam, 3 ... Converging lens, 4 ... Deflection coil, 5 ... Objective lens, 6 ... Sample, 7 ... Secondary electron,
8 Detector, 9 Deflection generator, 10 Image memory, 11
... adder, 12 ... cursor generator, 13 ... electronic computer,
14 ... CRT, 15 ... Trackball, 16, 17 ... Cursor.

Claims (1)

[Claims] 1. A scanning electron microscope having a length measurement function of scanning a sample with an electron beam and displaying a sample image on a display device based on a signal generated by the sample, and averaging scanning lines in a designated area. Means for performing dimension measurement based on the result, means for displaying two boundary lines indicating the designated area and the other area on the sample image, and adjusting the position of the two boundary lines Means for displaying the adjusted two boundary lines, and performing dimension measurement based on the result of averaging the scanning lines in the area within the adjusted two boundary lines. Scanning electron microscope with a feature of length measurement.