JPH02132309A - Sectional shape detecting method - Google Patents

Abstract

PURPOSE:To reflect cutting light completely on the surface of a light- transmissive material and to accurately detect its sectional shape by dipping the light transmissive body in liquid whose refractive index is larger than the refractive index of the light transmissive body. CONSTITUTION:The light transmissive body (e.g., resist pattern) 101 which has the refractive index n2 is formed on a substrate 100. When the sectional shape of this body 101 is detected, this body 101 is dipped in the liquid 102 which has the refractive index n1 larger than the refractive index n2. Then optical cutting is performed by projecting linearly-sectioned cutting light 103, but the incidence angle theta1 of the cutting light 103 incident on the light transmissive body 101 from the liquid 102 is set to such a value that the total reflection condition is satisfied on the surface of the body 101. Consequently, the cutting light 103 never enters the body 101 internal reflected light is therefore ceased completely; and only surface reflected light 104 is detected and the sectional shape of the body 101 is accurately detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a cross-sectional shape detection method using optical sectioning.

[Conventional technology]

Conventionally, for example, when detecting the cross-sectional shape of a resist pattern formed on a silicon wafer, a cross-sectional shape detection method using a light cutting method has been adopted.

In this cross-sectional shape detection method, a light beam with a straight cross section (hereinafter referred to as cutting light) is irradiated obliquely onto the surface of the object to be detected, a light cutting line is projected onto the surface of the object to be detected, and the light is reflected For example, by guiding light to a two-dimensional optical sensor,
A light section image corresponding to the cross-sectional contour of the object to be detected is obtained.

[Problem to be solved by the invention]

However, in such conventional cross-sectional shape detection methods, when the object to be detected has optical transparency, the cutting light 1 is reflected by the surface of the object to be detected 2, as shown in FIG. 3(a). Not only is it reflected, but it is also reflected inside the object 2 to be detected.

As a result, both the surface reflected light 3 and the internally reflected light 4 are introduced into the two-dimensional optical sensor (not shown), and the third
As shown in Figure (b), in addition to the light section line 5 caused by the surface reflected light 3, a light section line 6 caused by the internal reflection light appears in the light section image, which makes it possible to accurately detect the cross-sectional shape. The problem was that it was not possible.

The present invention has been made in order to solve the above-mentioned problems, and its purpose is to provide a cross-sectional shape that can accurately detect the cross-sectional shape of an object to be detected even when the object has optical transparency. An object of the present invention is to provide a shape detection method.

[Means to solve the problem]

FIG. 1 shows a principle diagram of the cross-sectional shape detection method according to the present invention.

In FIG. 1, a substrate (e.g. silicon wafer) 10
A light-transmissive object (for example, a resist pattern) 101 having a refractive index n2 is formed on the surface.

In such a state, when detecting the cross-sectional shape of the light-transmitting object 101 using the light cutting method, the present invention performs this as follows.

That is, first, the light-transmitting object 101 has a refractive index n1 (n 1 > n
s+).

Thereafter, the light cutting method is carried out in the same manner as in the conventional method, but at this time, the incident angle θ1 of the cutting light 103 entering the light-transmitting object 101 from the liquid 102 is determined as shown in the following equation (1). , is set to a value that satisfies the total reflection condition on the surface of the light-transmitting object 101.

[Effect]

According to such a configuration, the cutting light 10B is completely reflected on the surface of the light-transmitting object 101 and does not penetrate into the interior of the light-transmitting object 101.

Therefore, the internal reflected light completely disappears, and the surface reflected light 104
It becomes possible to detect only

〔Example〕

FIG. 2 shows an embodiment of the cross-sectional shape detection method according to the present invention.

In this embodiment, it is assumed that the cross-sectional shape of a resist pattern (refractive index n2=1..5) 8 formed on a silicon wafer 7 is detected using an optical cutting method.

As shown in FIG. 2, the laser beam 10 that has passed through the slits 1 and 9 is focused onto the resist pattern 8 to be detected by the action of the objective lens 11, and a light cutting line 12 is formed on the surface of the resist pattern 8. be painted. In this case, the slit 9 is so small that it is affected by the diffraction phenomenon of light, so it is arranged so as to be perpendicular to the light cutting line 12.

This light cutting line 12 is focused by the action of the objective lens 13 and formed into an image on the light receiving surface of the two-dimensional photosensor 14, and as a result, an optical cross-sectional image of the resist pattern 8 is obtained from the two-dimensional photosensor 14. That will happen.

In addition to the above basic configuration, the gap between the objective lenses 11 and 13 and the resist pattern 8 has a refractive index n1 larger than the refractive index n2 (n2-1.5) of the resist pattern 8 to be detected. It is filled with liquid 15.

Examples of the liquid 15 include α-monochloronaphthalene (n L = 1.6 3 6) and α-monobromnaphthalene (n L = 1-6 6 2).
, methyl iodide (n 1-1- . 7 4 1.
) etc. are available.

Further, the incident angle θ1 of the cutting light incident from the liquid 15 onto the resist 1 pattern 8 to be detected is set to an angle such that a total reflection condition is satisfied on the surface of the resist pattern 8.

For example, when methyl iodide is used as the liquid 15, the incident angle θ1 of the laser beam for forming the optical cutting line is determined as follows.

The optical refractive index of the liquid (methyl iodide) is 01-1.741, and the optical refractive index of the resist pattern to be detected is n2-1.
．． 5, the total reflection condition is: 1 θ>Sin import/n) (2) = sin '(1..5/1.741) = 59.
49, it is sufficient to set θl=60°.

That is, if the incident angle is 01=60°, the cutting light is completely reflected on the surface of the resist l/pattern 8 and does not penetrate into its interior.

Therefore, internally reflected light is completely eliminated, and only surface reflected light can be detected.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, when detecting a cross-sectional shape using the optical cutting method, even if the target object has light transparency, the cross-sectional shape can be accurately detected. It becomes possible.

[Brief explanation of drawings]

Fig. 1 is a diagram explaining the principle of the present invention, Fig. 2 is a diagram showing an embodiment of the present invention, Fig. 3(a) is a diagram showing the relationship between surface reflected light and internally reflected light, Fig. 3 ( b) is a diagram showing a light section image of a light-transmitting object. 100...Substrate 101...Light-transmitting object 102...Liquid 103...Cutting light 104...Surface reflected light FIG.

Claims (1)

[Claims] In a cross-sectional shape detection method of detecting the cross-sectional shape of a light-transmitting object (101) using a light sectioning method, the light-transmitting object (101) has a refractive index larger than the refractive index (n_2) of the light-transmitting object (n_2). (n_1), and the incident angle (
A cross-sectional shape detection method characterized by setting θ_1) to an angle such that a total reflection condition is satisfied on the surface of the light-transmitting object (101).