Method of measuring micro-structure, micro-structure measurement apparatus, and micro-structure analytical system

Abstract

This invention provides a method and an apparatus of measuring a micro-structure, capable of evaluating a geometry of a micro-structure formed typically on the surface of a semiconductor substrate, in a non-destructive, easy, precise and quantitative manner. A reflection spectrum of a sample having a known dimension of a target micro-geometry is measured (A1), features (waveform parameters) which strongly correlate to a dimension of the measured micro-geometry are determined (A2), a relation between the dimension of the micro-geometry and the waveform parameters is found (A3), and a dimension of the micro-structure having an unknown dimension is finally determined using this relation and based on the reflection spectrum obtained therefrom (A4, A5).

Description

[0001] This application is based on Japanese patent application No. 2004-105903 the content of which is incorporated hereinto by reference. DISCLOSURE OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to a method of measuring a micro-structure, a micro-structure measurement apparatus, and a micro-structure analytical system, and in particular to a method of measuring a micro-structure, a micro-structure measurement apparatus, and a micro-structure analytical system preferably applicable to optical measurement of structures of nanometer level. [0004] 2. Related Art [0005] It has conventionally been important in semiconductor fabrication processes such as lithography, etching and so forth, aimed at forming fine patterns of a 0.1 μm (micrometer) level, to precisely control dimensions of the patterns at the nanometer level, so that it has been believed as essential to readily and precisely measure dimensions of the patterns, when conditions for the l...

AI Technical Summary

Benefits of technology

[0051] According to the present invention, it is made possible to readily and accurately measure geometry of micro-structures in a non-destructive manner, which must have been observed under a SEM in a destructive manner in the prior art. The present invention applied to a periodic structure makes it possible to precisely measure height, duty ratio and periodicity of the periodic structure in a non-destructive manner.

[0052] According to the present invention, it is also made possible to provide a generally-adoptable, simple and high-precision method of measurement, adoptable to production processes in which dimension of micro-structures to be fabricated is predictable to a certain degree, and in which dimensional control to as precise as sub-micrometer or nanometer level is necessary.

[0053] It is therefore made possible to provide a general-purpose method and an apparatus of measuring a micro-structure, and a micro-structure analytical system, capable of readily, precisely and quantitatively evaluating geometry of the micro-structure formed typically on the surface of semiconductor, through measurement of wavelength dependence of intensity of the reflected light (reflection spectrum) obtained when a measurement sample is irradiated by a measuring beam.

[0054] It is also made possible to provide a general-purpose method and an apparatus of measuring a micro-structure, and a computer program and a system, preferably applicable to process control or the like in the mass production, and capable of realizing a simple and precise measurement.

Problems solved by technology

Insufficient precision in the control of the lithographic process or etching process may fail in obtaining a stable single-mode oscillation, fail in obtaining oscillation threshold value or optical output satisfactory in view of product standards, or result in a lowered yield ratio.

Measurement under a scanning electron microscope, however, raises a problem in that observation of the sectional shape inevitably needs cutting of the sample, so that the measurement will never be applicable to the samples which cannot be subjected to destructive inspection.

On the other hand, non-destructive observation of the surface state under a CD-SEM raises difficulty in measurement of correct shape, because depth-wise information cannot be obtained.

Another problem of the measurement under the electron microscope resides in that it takes a long time due to need of setting of the sample in vacuo, so that the measurement is not fully applicable to the mass production process.

The methods of measuring line width of a periodic structure described in Japanese Laid-Open Patent Publication No. 11-211421 and ditto No. 2001-217291, however, raise a problem in that only a limited amount of reflection characteristic data is measurable, and in that information on the height cannot be obtained, because the line width of the periodic structure is an only measurable parameter, without considering any influences of multiple reflection, or reflection in directions other than that normal to the incident light.

Another problem resides in that there is no clear explanation on the method applied to measurement of other geometries such as typically having a slope or the like, so that the method is not readily applicable.

The method is, however, only applicable to the measurement of line width of the periodic structure, and cannot readily be applied to the measurement of height, for example, of the periodic structure.

On the other hand, the method of measuring surface profile of an irregular substrate based on the spectral ellipsometry described in Japanese Laid-Open Patent Publication No. 2001-217291 pays no regard to reflection on surfaces other than those in parallel with the sample to be measured, and consequently pays no regard to influences of scattered light which depends on geometry of the target object to be measured, and this results in only a limited accuracy in the measurement.

More specifically, measured results shown in FIG. 13 of Japanese Laid-Open Patent Publication No. 2001-217291 are found to differ by a maximum of approximately 30% or more from results of the SEM observation, and this raises a problem of insufficient accuracy in the measurement.

What is worse, no information is available on density of the irregular geometry (corresponded to periodicity of the periodic structure pattern), which is a target object to be measured, and any changes in the density may further worsen the accuracy of the measurement.

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