JPS614906A - Measuring method of line width - Google Patents

Abstract

PURPOSE:To reduce an error in measurement of line width by generating light beams which differ in direction of polarization in a light transmissible material film and guiding them to one grating, calculating the wavelength of the light beams projected from the other at the same angle of projection, and calculating the line width from the relation among the wavelength, a propagation constant, film shape, and refractive indexes. CONSTITUTION:A film 1 which has a refractive index n1 and thickness (t) is sandwiched between a material 2 with a refractive index n2 and a material 3 (e.g. air) with a refractive index n0, and a grating 4 with a period S' and a grating 5 with a period S are formed on the surface of the film 1. Further, light 6 which has a different direction of polarization and wavelength lambda is guided in the film 1 from the grating 4 and the wavelength lambda of the light projected at the same angle theta of projection is measured. Further, the line width W is calculated from a relational expression which holds for the line width W, refractive indexes n0 and n1, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for measuring line width of a pattern formed by microfabrication.

(Prior art and its problems) Conventionally, in order to measure the line width of a pattern obtained by microfabrication, it is necessary to irradiate focused light from above the pattern and measure the reflectance of light from each part of the pattern. It has been done. However, the reflectance of light does not change sharply at the pattern edge, and for this reason, the measured value of the pattern line width obtained is not equal to the true pattern line width, and is 0.1 μm.
There was an uncertainty of about m.

(Objective of the Invention) An object of the present invention is to eliminate the above-mentioned drawbacks and provide a line width measuring method with small measurement errors.

(Structure of the Invention) That is, in the present invention, gratings are formed in two places on a patterned light-transmitting material film of known refractive index and film thickness on a substrate, and an iron film is formed through one of the gratings. Waveguide the light, then find the wavelength and length of the light such that the guided light and light with a different polarization direction exit from the iron film through the other grating at the same exit angle.
This line width measurement method is characterized by determining the processed line width of the film from the equation formed between this wavelength, the propagation constant of light, the shape of the film, and the refractive index.

(Principle of the present invention) The present invention will be explained below with reference to the drawings.

As shown in FIG. 1, a film 1 processed to have a line width W with a refractive index n1 and a thickness t is made up of a material 2 with a refractive index n2 (in this case, the substrate) and a material with a refractive index n0 (for example, air or liquid). ) 3, first, a grating 4 with a period S' and a grating 5 with a period S are formed on the surface of the film 1. Next, light 6 with a wavelength λ is transmitted through the grating 4 to the film 1. The light is guided through the grating 5 and is emitted at an emission angle θ. Incidentally, the grating periods S and S' are l+λ/S and l+λ/S' are "O
It is necessary that r'' is greater than 2 and that λ/8 and λ/S' be less than n.

At this time, for the TE wave, the functions of equations (1) to (4) hold between each variable, /M and /9E are respectively T
Propagation constant of M wave and TE wave.

(A/k)” + UM/k door”j = S”θ+
λ/S −(3)k−2π/λ
-(4) Also, regarding the TM wave, the above formula (3) (
4) and formula +5) (6) holds true.

Further, at a specific wavelength λ, equations (1) to (6) hold simultaneously, and lights with different polarization directions are emitted through the grating 5 at the same exit light angle θ. Therefore, the wavelength λ
The line width W of the pattern can be determined by changing the wavelength λ at which light with different polarization directions exits at the same exit angle through the grating 5 and solving equations (1) to (6).

Although FIG. 1 shows an example in which the line width of a straight pattern is measured, it is also possible to measure a crooked pattern as long as the line width is constant.

(Example) Examples of the present invention will be described below.

When polymethyl methacrylic acid (PMMA) was coated on quartz glass with a refractive index of 1.457 and measured using ellipsometry, the refractive index of PMMA was 1,491, [thickness is 0].
．． It was 8 μm. Next, after processing the PMMA into a linear pattern, gratings of 1 μm in diameter are formed on the PMMA surface at two locations. Next, air (refractive index i, ooo
> From the middle, Rhodamine B dye laser light was guided into PMMA with the wavelength changed in the range of 6000 to 6400 A through one grating, and the light was emitted from the other grating, where it was TE at a wavelength of 6328 A.
The waves and TM waves were emitted at an emission angle of 54.51 degrees. Therefore, by finding W from equation +1+ (6), it was found that the line width of the PMMA pattern after processing was 1.22 μm.

(Effects of the Invention) Therefore, according to the present invention, it is possible to accurately determine the line width of a pattern by simply measuring the wavelength of light guided into the pattern using a grating. be.

[Brief explanation of drawings]

FIG. 1 is a perspective view for explaining a method of measuring the line width after processing a film. DESCRIPTION OF SYMBOLS 1... Film to be measured, 2... Substance with refractive index n2, 3... Substance with refractive index no, 4... Incoming grating, 5... Outgoing grating, 6... Light. −〇− Representative Patent Attorney Susumu Uchihara 7. 2' 71-1 Figure

Claims (1)

[Claims] (1) Gratings are formed at two locations on a patterned light-transmitting material film with a known refractive index and film thickness on a substrate, and light is guided to the film through one grating, Next, find the wavelength of the light such that the guided light and the light with a different polarization direction exit from the film through the other grating at the same exit angle, and calculate this wavelength, the light propagation constant, and the film's wavelength. A line width measuring method characterized by determining the processed line width of a film from an equation established between shape and refractive index.