JPS62135710A - Inspecting method for minute pattern - Google Patents

Abstract

PURPOSE:To form a minute pattern with high accuracy by analyzing a variation factor influencing on a line width variation in an inspecting process of the minute pattern existing on a substrate. CONSTITUTION:A resist applied on the silicon substrate is exposed while connecting with the maximum rectangular length about 1.0mum using variable rectangular electron beams and scanned with the electron beams with the accelerating voltage about 1KV so as to cross the developed resist pattern (RP). Then, a slice level is set at the position of 50% of a vale of signal waveform (A) obtained by detecting the secondary beams reflecting from the RP in each scanning line. The line width of the minute pattern is defined by an interval of a point where the slice level crosses the wavefrom A. The line width is developed to dispersive high-speed Fourier series in connection with the electron beam scanning position and a power spectrum is calculated from a value of Fourier coefficients in each component of a line width variation period. An maximum value of the spectrum exists in the line width variation period 1.0mum. Since this variation period is conformed to the maximum length of the rectangular beams in the exposure of the electron beams, it is analyzed that the connecting adjustment of the rectangular beams of an exposer it not sufficient.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of inspecting the line width of fine nonaturns formed on a substrate using a low acceleration voltage scanning electron microscope.

[Conventional technology]

Conventionally, when inspecting the line width of fine/main turns formed on a substrate using a low acceleration voltage scanning electron microscope,
This was done by the method described below.

In other words, the first method scans an electron beam across one part of the fine pattern, detects secondary electrons or backscattered electrons reflected from the pattern, and processes the resulting signal waveform to detect the fine pattern. The second method is to repeat the first method while moving the scanning position in the direction perpendicular to the scanning line direction at a constant scanning line interval on the fine no-no-turn. This is a method of calculating the average line width of a fine pattern and mark deviation of line width distribution from the line width of the fine pattern at each scanning line position (JEOL News, Vol. 23, No. 2, 1983).
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[Problem that the invention seeks to solve]

BACKGROUND OF THE INVENTION The dimensions and shapes of various fine patterns formed on a substrate during the manufacturing process of semiconductor devices vary from the designed dimensions due to factors specific to the material and manufacturing method of the fine patterns. For example, in a fine pattern made of a material with a large particle size, the pattern size changes with the period of the particle size. Furthermore, in the resist pattern, the line width varies periodically due to the residue after development that exists at the bottom of the pattern. As mentioned above, the line width of the six clusters of fine patterns fluctuates with a unique periodic component, so when inspecting the line width of such fine patterns,
The conventional method causes the following problems.

In the first method, the line width of the fine pattern is measured only at one location, so it is not possible to determine the variation in the line width of the fine pattern.

Furthermore, in the second method, although it is possible to obtain the standard deviation of variations in line width of a fine pattern, it is not possible to separate and obtain line width variation components that exist periodically for each period.

An object of the present invention is to provide a method for inspecting fine patterns that solves the above problems.

[Failure to solve the problem]

The present invention includes a step of repeating scanning while moving the scanning position of the electron beam in a direction perpendicular to the scanning line direction at a constant scanning line interval when scanning an electron beam across a fine pattern existing on a substrate; Processing the signal waveform obtained by detecting secondary electrons or backscattered electrons reflected from the fine pattern in each scanning line to define the line width of the fine/main turn; A method for inspecting fine/turn roofing comprising the step of calculating the Fourier coefficient for the line width variation cycle of the fine pattern by expanding the line width of the fine pattern into a Fourier series with respect to the position of each scanning line. It is.

[For production]

As shown in FIG. 2, the line width of the fine pattern on the substrate varies at a specific period. In the diagram, fine 1? Line width W of N fliffi at equal intervals ΔX on the turn. , Wl.

. . . When wN-1 is obtained, the following holds true by discrete Fourier series expansion regarding the n-th line width Wn. The Fourier coefficient Wk is kWk=ΣWnexp(−j2πd) n=O. Here, j2=-1.

At this time, the worth vector IWk+ of the line width having the fluctuation period Tk=N·Δx/k can be found as follows. Here, R8Wk and Xrnwk represent the real part and imaginary part of Wk, respectively.

The fine no-turn line width is amazing! Since it fluctuates with a specific period due to the material and manufacturing method of the turn, the spectral value of that period becomes large.

Therefore, it is expected that by determining the overall spectral distribution, it will be possible to estimate the main factors that cause linewidth fluctuations.

[Example] Hereinafter, a method for inspecting a fine pattern according to the present invention will be explained with reference to an example.

FIG. 1(a) is a top view of a resist pattern coated on a silicon substrate, which is connected with a maximum rectangular length of 1.0 μm using a variable rectangular electron beam, exposed from the inside, and then developed. . An electron beam with an acceleration voltage of 1 kV is scanned across this Rennost pattern. The scanning line interval is 0.01 μm, and the number of scanning lines is 1024. By detecting the secondary electrons reflected from the z4 turn in each scanning line, a signal waveform as shown in Figure 1 (bl) is obtained.The maximum value of the signal waveform is 100%, and the minimum value is 0%. Then, a slice level is set at the 50th position, and the line width of the fine and main turns is defined by the interval between the points where the slice level and the signal waveform intersect. This shows the line width of a fine pattern defined at a scanning position as a function of the scanning position. The average value and standard deviation of the line width distribution can be determined from this figure, but the line width for each fluctuation period cannot be determined.
It is difficult to analyze the main factors affecting line width variations. Figure 1 (at) is obtained by expanding the line width of the resist pattern found in Figure 1 (c) into a discrete fast Fourier series with respect to the electron beam scanning position, and calculating the value of the Fourier coefficient at each component of the line width variation period. Figure 1 (line width variation period 1.0 from dl).
It was found that the maximum value of the /4' Worth vector exists in μm. This line width variation period coincides with the maximum length of the rectangular beam in electron beam exposure, which indicates that the rectangular beam connection adjustment of the electron beam exposure machine was not sufficient. In this way, we were able to analyze the main factors in mother turn manufacturing that affect line width variations in resist patterns.

The fine pattern inspection method according to the present invention is applicable not only to the resist pattern shown in the above example but also to any pattern formed on a substrate in semiconductor device manufacturing.

〔Effect of the invention〕

The method of the present invention makes it possible to analyze the fluctuation factors that affect the line width variation of the fine pattern in the process of inspecting the fine pattern existing on the substrate.

By feeding and packing the analysis results to the fine pattern manufacturing process, the optimum ratio is carried out, and it is possible to form highly accurate fine patterns.

[Brief explanation of drawings]

Figure 1 shows an example in which the line width of each turn of a fine resist formed on a substrate was examined using the inspection method according to the present invention. across the resist pattern formed by
(b) is a diagram showing the relationship between the waveform of the secondary electron signal reflected from the resist pattern and the line width of the resist pattern; (C) ) is a diagram depicting the measured resist pattern width with respect to the scanning position of the electron beam, fdl is a four-Worth vector diagram obtained by performing discrete fast Fourier transform on the resist pattern width with respect to the scanning position of the electron beam, and The figure shows inherent periodic line width fluctuations that exist in fine patterns on a substrate. C(1) Fig. 1 Scanning position of electron beam) (C) Period of line width fluctuation C, ttm) Cd) Fig. 1 Fig. 2

Claims (1)

[Claims] (1) When scanning an electron beam across a fine pattern existing on a substrate, a process of repeating scanning while moving the scanning position of the electron beam in a direction perpendicular to the scanning line direction at a fixed scanning line interval; The process of defining the line width of the fine pattern by processing the signal waveform obtained by detecting secondary electrons or backscattered electrons reflected from the fine pattern in the scanning line, and the process of defining the line width of the fine pattern defined in each scanning line. A method for inspecting a fine pattern, comprising the step of calculating a Fourier coefficient for a line width variation cycle of the fine pattern by expanding the line width into a Fourier series with respect to the position of each scan ψ.