JPH01115044A - Fine beam length measuring device - Google Patents

Abstract

PURPOSE:To prevent detectors from having an effect of their position on measurement by mounting a plurality of detectors on a scanning electronic microscope and combining signals obtained from the respective detectors or by using signals single according to materials or shapes of an object te be measured. CONSTITUTION:Electron beams 103 emitted from an electron gun 102 are detected by an electronic lens system 104 and made incident to a sample 106. Secondary electrons 107 emitted from the sample 106 are detected from a right detector 108 and a left detector 109. These signals are processed by a computer 111 to display their scanning wave forms and images on a display 112. In the case of measuring a surface shape, detectors to be used are selected on the basis of knowledge obtained from theoretical considerations on a positional relation between the detectors and the sample or knowledge about the desirable positional relation obtained in advance by experiments. A signal which always reflects a fine shape even on observing any portion of the sample can be thus obtained to enable high precision measurement.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for measuring line 11I on a semiconductor surface, and more particularly to a minute line width measuring device that provides highly accurate measurement results.

[Conventional technology]

With the miniaturization of semiconductors, high-resolution scanning electronics V11 mirrors have come to be used for line 11M measurements for controlling the manufacturing process. The conventional device is
As described in Japanese Patent No. 9-112217, it basically has a configuration in which an image signal storage section and an arithmetic control section are added to a normal scanning electron microscope that has been used for biological samples Min. For electronic lens systems, electron guns, etc., semiconductor Ii! !
Many of them have been improved to be suitable for scanning, but only one detector for detecting secondary electrons was used, as in the case of JP-A-59-112217, which is the same as in ordinary scanning electron microscopes. However, no special consideration was given to the positional relationship between the detector and the sample to be measured.

[Problem that the invention seeks to solve]

The above conventional technology does not take into consideration the fact that when observing minute shapes such as the surface shape of a semiconductor using a scanning electron microscope**, the obtained image depends on the orientation of the detector. There was a problem in that measured values such as line width differed depending on the orientation of the detector. In other words, 1. A commonly used scanning electron microscope has about four locations where the detector can be attached, and the one facing the detector produces a brighter image. This effect is known as the illumination effect. It is being Similarly, areas that are shaded from the detector are also known to be dark.

An object of the present invention is to obtain a minute line width measuring device that is not affected by the position of the detector.

[Means for solving problems]

The above object is achieved by attaching a plurality of detectors to a scanning electron microscope and using signals obtained from each detector in combination or singly depending on the material and shape of the object to be measured.

[Effect]

Depending on the relative relationship between the positions of each of the plurality of detectors and the sample surface shape, there are detector signals that well reflect the minute features of a certain part and detector signals that do not reflect the minute features. Therefore, when measuring a certain surface shape, it is necessary to use knowledge obtained from theoretical considerations regarding the positional relationship between the detector and the sample, or to conduct experiments in advance and determine the desired position of the detector and sample. Select the detector to use based on knowledge of the relationship. As a result, no matter which part of the sample is inspected, a signal reflecting the minute shape can always be obtained, making it possible to perform highly accurate measurements.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 4. FIG. 1 is a hardware configuration diagram of an embodiment of the scanning electron microscope*nm length system according to the present invention, in which two detectors are attached to an ordinary scanning electron microscope, and arithmetic control is performed by a computer. . An electron beam 103 emitted from an electron gun 102 in a mirror body 101 is deflected by an electron lens system 104 and is directed toward a sample 106 on a sample stage 105.
incident on the Correspondingly, secondary electrons 107 emitted from the sample 106 are detected by the right detector 108 and the left detector 109, respectively.

These signals are processed by a computer 111 controlled by a keyboard 1.10, and the scanning waveforms and images are displayed on a display 112 either alone or after being subjected to calculations.

FIG. 2(a) is a cross-sectional view of a typical semiconductor surface pattern, and FIG. 2(b) is the scanning signal waveform of each detector and its sum signal obtained when the surface is scanned with the above hardware configuration. represents the waveform of

The object of measurement is the sample cross section 201 in Fig. 2(a).
The distance between the lower edge 202 and the lower edge 203, and the interval between the upper edge 204 and the upper edge 205. When this is scanned, the right side signal waveform 207 . Left side signal waveform 208 by left side detector 109
, and a sum signal waveform 206 which is the sum of both. Among the feature points on these waveforms, the right signal waveform feature point 209 is located at the lower edge 202, the left signal waveform feature point 211 is located at the lower edge 203, and the left signal waveform feature point 209 is located at the upper edge 204. The signal waveform feature point 212 is at the upper edge 205,
Since three or more right signal waveform feature points 210 correspond well to each other, highly accurate measurement can be performed by using the above feature points as each edge position when determining PAg.

The measurement procedure of this example will be explained below using the flowchart of FIG. 3 and FIG. 4. In block 301, the sum signal image is displayed, and in block 302, the part to be measured is specified. At this time, which detector's signal is to be used, and whether to measure the upper edge or the lower edge. Specify.

The operations from block 303 to block 306 are performed twice for the edges at both ends. In block 30:3, an edge determination algorithm is selected according to the specification in block 302. This specific algorithm will be explained with respect to the right signal waveform 207 in FIG. Figure 4(a)
2 is a diagram illustrating an algorithm for finding right signal waveform feature points 210. FIG. Oblique approximation straight line 4 of right side signal waveform 207
01 and a horizontal approximation straight line 402, and the intersection thereof is defined as the right signal waveform feature point 210. FIG. 4(b) is a diagram illustrating an algorithm for determining the right signal waveform feature point 209. Right side signal waveform 207 is obliquely approximated straight line 403
and a horizontal approximation straight line 404, and the intersection thereof is defined as the right signal waveform feature point 209. To find the feature points from the left signal waveform, reverse the left and right sides of Fig. 4,
A similar operation may be performed, and in block 304, a signal to be used for measurement is input. That is, according to the algorithm selected above, the right signal waveform 207 or the left signal waveform 2
Enter either 08. In block 305, the fourth
The input waveform is linearly approximated according to the algorithm explained in the figure. In block 306, the intersection of the approximate straight lines is found, and the horizontal coordinate value is used as the edge position. In block 307, the difference between the coordinate values determined at both edges is taken, and the distance between the edges is calculated by taking this and the magnification of the microscope into account. At block 308, the calculation results are displayed.

〔Effect of the invention〕

According to the present invention, since measurement can be performed using a waveform that is not affected by the positional relationship between the detector and the sample, there is an effect that highly accurate minute line width measurement can be performed.

[Brief explanation of the drawing]

Figure 1 is a hardware configuration diagram of the present invention-embodiment;
Figure 1 shows a cross-sectional view of a sample used in an embodiment of the present invention;
The corresponding scanning waveform diagram, FIG. 3 is a flowchart of processing of an embodiment of the present invention, and FIG. 4 is an algorithm used in an embodiment of the present invention. 3 Figure No. 47

Claims (1)

[Claims] 1. In a scanning electron microscope that irradiates a measurement sample with an electron beam and detects electrons emitted from the sample to obtain surface information such as images and scanning waveforms, a plurality of detectors for the emitted electrons are provided. , a minute linewidth measurement device that measures minute shapes on the surface of a sample based on information from the plurality of detectors according to the local shape, material, etc. on the sample.