JPS63138206A - Minute distance measuring system - Google Patents

Abstract

PURPOSE:To execute a minute distance measurement which does not depend on a material, by deriving a distance between feature points of a sample extracted on a scanning waveform generated from the quantity calculated from a prescribed equation to the same point of an image obtained from a detector, or a waveform which has brought said waveform to an arithmetic processing. CONSTITUTION:An electron beam 103 emitted from an electron gun 102 in a mirror body 101 is deflected and converged onto a sample 106 by an electron lens system 104. An emitted secondary electron 107 is detected by right and left detectors 108, 109, a detecting signal passes through an A/D converter 110 and inputted to a memory of a computer 111, and the result of calculation and an image are displayed on a display 113. On the other hand, the computer 111 derives a scanning waveform which does not depend on a material by using the quantity calculated by a numerator/denominator homogeneous equation, (Il-I)/2(Il-I)<1/2>=(Fl-F)/2(FlF)<1/2>2, and derives a distance between feature points on its waveform. In this regard, ratios of secondary electrons for reaching the right and left detectors, and detecting signals are denoted as F, Fl, and I, Il, respectively.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to the inspection of microfabricated objects such as semiconductors.

In particular, it relates to highly accurate small distance measurement methods.

[Conventional technology]

With the miniaturization of semiconductors, high-resolution scanning electron microscopes have come to be used to measure line widths during the control of the manufacturing process. Conventionally, to measure minute distances such as semiconductor line widths, one line is scanned over the sample, and two straight lines are drawn around the characteristic points in the waveform, as shown in Japanese Patent Laid-Open No. 112217/1983. The distances between the plurality of feature points were measured using the approximation and the intersection point as the position of the feature point.

[Problem that the invention seeks to solve]

The above conventional technology does not take into consideration the fact that the scanning waveform produced by a scanning electron microscope depends on the material, and even if the shape is the same, the scanning waveform will differ greatly depending on the material. The problem with the extraction method is that it can only be applied to some materials.

An object of the present invention is to provide a minute distance measurement method for extracting feature points and measuring length, which does not depend on the material.

[Means for solving problems]

The above objectives are included in the scanning electron microscope signal.

This is achieved by removing the contrast component due to the material, creating a signal containing only the contrast component depending on the shape, and extracting features on the scanning waveform made of this signal.

[Effect]

The signal of a scanning electron microscope is emitted from the surface of the sample2
It is determined by the total number of secondary electrons and the allocation of the emitted secondary electrons reaching the detector. The former.

Roughly, it can be written as the product of a constant η, which depends on the material, and F8, which depends on the shape of the point, the acceleration pressure of the incident electron beam, etc., but does not depend on the material. Assuming that there are two detectors on the left and right, and the ratio of reaching the left and right detectors is written as F and Ft, respectively, the signal 11F and process 6 obtained from the left and right detectors are calculated by the following formula % Equation % Here, if a homogeneous equation of the denominator and numerator of It and I is created, the constant η that depends on the material is eliminated, as shown in the following equation, for example.

By using a quantity calculated using a rational formula with one denominator and numerator homogeneity in this manner, a scanning waveform that does not depend on the material can be obtained.

Therefore, by recognizing feature points on this scanning waveform, distance measurement that does not depend on the material can be performed.

[Embodiment] 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 a semiconductor line width measurement method that is an embodiment of the present invention. Electron gun 1 in mirror body 101
The electron beam 103 emitted from the electron lens system 104
As a result, the deflection is focused on the sample 106 on the sample stage 105,
Correspondingly, secondary electrons 107 are emitted, and the right detector 10
8 and the left detector 109. The detected signal is.

A/L) is digitized by a converter and the keyboard 112
The computer 111 is manually inputted into the memory of the computer 111, which operates according to one of the instructions. The images and measurement results created from these signals are
It is displayed on the display 113.

Next, FIG. 2 is a flowchart of processing in an embodiment of the present invention. In block 201, right detector 108° left detector 1
09), input the signal for one line. block 20
In step 2, a homogeneous rational expression is operated on the signal input in block 201. In this embodiment, the same equation (3) t- as described in the section of the above-mentioned operation is used. This formula expresses the inclination of one plane, so the material A301 in Fig. 3(a)
When a cross section of a semiconductor consisting of two layers of material B502 and B502 is observed using the hardware of this embodiment, the left detector signal is
Scanning waveform 303 in figure (b). The right detector signal is shown in Figure 3 (
The scanning waveform 304 shown in C) is obtained, but the result of the calculation of the homogeneous rational expression is shown as the waveform 305 shown in FIG. 3(d). Next, in block 203, feature points are extracted.

In this embodiment, the right edge 3 of the line butter/ in FIG.
The purpose is to find the distance between 06 and the left edge 3070. Therefore, in FIG. 4, a threshold value 401 and a threshold value 402 are set for the a-type 305, and the outer intersections are set at the left measurement edge position 403 and the right measurement edge position t.
1404. Block 204 calculates the distance between the two measurement edges. In block 205 the result'
Display jt.

〔Effect of the invention〕

According to the present invention, since feature points can be extracted on a waveform that does not depend on the material, there is an effect that highly accurate length measurement can be performed even on samples made of various materials.

[Brief explanation of the drawing]

FIG. 1 is a software configuration diagram according to an embodiment of the present invention, and FIG. 2 is a flowchart of processing according to an embodiment of the present invention. 3 and 4 are diagrams showing the output waveform of the block 203 in FIG. 2.

Claims (1)

[Claims] 1. In a scanning electron microscope equipped with multiple detectors, a scanning waveform created from a quantity calculated from the denominator and numerator homogeneous equation of the image density for the same point of the image obtained from each detector, or this scanning waveform A micro-distance measurement method that extracts feature points on a sample from a waveform that has been subjected to processing such as addition, and calculates the distance between multiple feature points.