JPS614905A - Measuring method of line width - Google Patents

Abstract

PURPOSE:To reduce an error in measurement of line width by guiding light beams which have different direction of polarization in a film of light transmissible material through a prism, calculating the wavelength of light projecting at the same angle of projection from the film through a prism, and finding the line width from the relation among the propagation constant, film shape, and refractive index. CONSTITUTION:A film which a refractive index n1, thickness (t), and line width W is sandwiched between a material 2 with a refractive index n2 and a material 3 (e.g. air) with a refractive index n0, and light 5 with wavelength lambda is guided in the film 1 through a prism 4 with a refractive index n'p and then projected at an angle theta1 of projection through a prism 6 with a refractive index np. Further, the refractive indexes np and n'p are both larger than n0 and n2. Then, the wavelength lambda of light which has specific wavelength lambda and a different direction of polarization and is projected at an angle thetai of projection is measured to find the line width W by solving the relational expression based upon the line width W, refractive indexes n0 and n1, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of 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 light reflectance does not change sharply at the pattern edges, which makes the resulting measured pattern line width equal to the true pattern line width, 0.1
There was an uncertainty on the order of μm.

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

(Structure of the Invention) That is, the present invention allows light to be guided through a prism through a patterned light-transmitting material film on a substrate with a known refractive index and film thickness, and then to be guided. Find the wavelength of the light such that the light and the source with different polarization directions exit from the iron film through the prism at the same exit angle, and find the wavelength between this wavelength and the original propagation constant, film shape, and refractive index. This width measuring method is characterized by determining the processed line width of the film from the Tatsu equation.

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

As shown in Figure 1, the refractive index fil is the line width W at the thickness t.
A film 1 processed with a material 2 (substrate in this case) having a refractive index n and a material 2 (substrate in this case) having a refractive index n. substance (e.g. air or liquid)3
ζ
Light 5 having a wavelength λ is guided into the film 1 through a prism 4 with a refractive index of n, which is placed in close contact with the film 1, and then a prism with a refractive index of n, which is placed in close contact with the film 1. 6, the light is emitted at an emission angle θ1. Note that 1) p+ np' must both be larger than rto and n2.

At this time, regarding the TE wave, there is a relationship between each variable from equation (1) to (
The relationship 5) holds true. βM and β8 are respectively TM waves,
TB wave propagation constant.

k=2π/λ (4
) no/np=th(θp-α)/5frlθI(5)
However, α is the angle between the light exit surface of the prism and the surface where the prism contacts the film 1.

Furthermore, when the TM wave t gets stuck, the above equations (3) to (5) and equations (6) and (7) hold true.

Furthermore, at a specific wavelength λ, equations (1) to (7) hold simultaneously, and light with different polarization directions 1j is emitted from the prism 6 at the same output angle θi. Therefore, the line width W of the pattern can be determined by measuring the wavelength λ of light emitted from the prism 6 with different polarization directions at the same exit angle, and solving the equation (7).

Although FIG. 1 shows an example of measuring the line width of a straight pattern, 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.

Polymethyl methacrylic acid (PMMA) was coated on quartz glass with a refractive index of 1457, and measured by optical analysis.
The refractive index of PMMA was 1,491, and the film thickness was 08 μm. Next, after processing the PMMA into a linear pattern, it was passed through a heavy crown color prism in air (refractive index 1.000), and the total propagation wavelength of the Rhodamitsu B dye laser source was changed in the range of 6000 to 6400 A. When the light was guided through PMMA and emitted from a heavy crown glass prism (α-45°) with a refractive index of 1.587, the wavelength was 63.
At 28 A, TB waves and TM waves were emitted at an emission angle of 34.22 degrees. Therefore, by finding W from equation (]) to (7), the line width of the PMMA pattern after processing is 1°2
It was found to be 2 μm.

(Effects of the Invention) Therefore, according to the present invention, the line width of a pattern can be accurately determined simply by measuring the wavelength of light guided to the pattern using a prism.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a method for measuring the line width after processing a film. 1...Membrane, 2...Flint material, 3
°゛°°°゛Substance with refractive index n, 4...Input prism, 5...Element, 6...Output prism. Akashiro Solo Dialect] Kou Shiuchihara

Claims (1)

[Claims] (1) Light is guided through a prism through a patterned light-transmissive material film with a known refractive index and film thickness on the substrate, and then the guided light and the polarization direction are different from this. Find the wavelength of the light that will be emitted from the film through the prism at the same exit angle, and use the formula between this wavelength, the propagation constant of the light, the shape of the film, and the refractive index to determine the processed line width of the film. A line width measurement method characterized by determining.