JPH04236307A - Detecting device of three-dimensional shape of pattern - Google Patents

Abstract

PURPOSE:To measure a three-dimensional shape of a transparent minute pattern on a substrate efficiently and accurately. CONSTITUTION:Since laser light S1 and a laser light S2 transmitted through an objective lens 10 and entering a transparent pattern are different in wavelength from each other, a difference occurs between refractive indexes thereof and they proceed on different optical paths in the pattern 1. When the objective lens 10 is moved minutely in directions A of the Fig. 1 along the direction of the optical axis, strong light signals reach a photodetector 13 and a photodetector 23 respectively in the case when the laser light S1 and the laser light S2 converge in the upper surface of a substrate 2 respectively. The thickness of the pattern 1 is calculated from a distance of movement of the objective lens 10, angles of incidence of the laser light S1 and the laser light S2 on the pattern 1 and the indexes of refraction of the laser light 1 and the laser light 2 in the pattern 1 on the occasion.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for inspecting fine patterns on a substrate, and more particularly to a pattern three-dimensional shape detecting apparatus for efficiently and accurately measuring the three-dimensional shape of a transparent fine pattern.

0002

2. Description of the Related Art A conventional method for measuring the shape of a three-dimensional pattern is, for example, Japanese Patent Application Laid-Open No. 2-31103.

FIG. 4 is a diagram showing the principle of a conventional method for detecting the three-dimensional shape of a transparent fine pattern. In FIG. 4, 101 is the substrate 10
The substrate 102 is a transparent pattern with a thickness of about several μm formed on the substrate 102, and the substrate 102 is placed on the XY table 109. Reference numeral 110 designates an objective lens that can be moved slightly along the optical axis S in the direction A in the figure (in the vertical direction on the paper), 111 designates a converging lens on the detection side, 112 designates a pinhole, and 113 designates a photodetector. Further, 114 indicated by a dotted line is a polarizing beam splitter, and 115 is a light projecting lens.

Here, laser beams 201 having wavelengths of λ1 and λ2 and parallel light are emitted from the light projection lens 115.
and laser beam 202 are simultaneously emitted and both are reflected in the direction of pattern 101 by polarizing beam splitter 114. After the reflected laser beams 201 and 202 pass through the objective lens 110, the laser beam 1 with a wavelength λ1 becomes pattern 1.
01, focuses at a predetermined position F on the lower surface of the pattern, that is, the surface of the substrate 102, and is reflected to become a laser beam 201'. After that, the objective lens 110 and the polarizing beam splitter 1
Each optical system is arranged so that the light passes through the light beam 14, is further converged by the converging lens 111, focuses at the position F1 of the pinhole 112, and enters the photodetector 113 as a strong light signal.

On the other hand, a laser beam 202 with a wavelength λ2 enters the transparent pattern 101 in the same way as the laser beam 201, but since the wavelength is different, there is a difference in the refractive index within the pattern 101, and the laser beam 202 is different from the laser beam 201. Follow the light path. That is, the laser beam 202 is focused at a position F within the pattern 101 in FIG.

Therefore, the laser beam 202' reflected from the lower surface of the pattern, that is, the surface of the substrate 102, passes through the objective lens 110 and the polarizing beam splitter 114, and then passes through the converging lens 1.
11, the photodetector 11 does not converge at the position of the pinhole 112 but, for example, at the position F1'.
Only a weak optical signal reaches 3.

[0007] Here, when the objective lens 110 is slightly moved in the optical axis direction to align the focal position F' of the laser beam 202 inside the pattern 101 with the point F on the substrate 102, the laser beam that is the reflected light of the laser beam 202 is Since the laser beam 202' follows almost the same optical path as the laser beam 201', it converges at the position F1 of the pinhole 112, allowing a strong optical signal to be incident on the photodetector 113.

This means that by moving the objective lens 110, strong optical signals reach the photodetector 113 for both the laser beam 201 and the laser beam 202, and the objective lens 11 at this time reaches the photodetector 113.
The thickness of the transparent pattern 101 can be calculated from the movement distance of 0.

Here, the moving distance of the objective lens 110 mentioned above is u, the incidence of each of the laser beams 201 and 202 on the pattern 101 is θ, the refraction angle of the laser beam 201 in the pattern 101 is α, and the refractive index is n1. If the refraction angle of the laser beam 202 in the pattern 101 is β and the refractive index is n2, then the thickness of the transparent pattern 101 is h.

[
0010

[0011] Here, sinα=n1・sinθ Equation 5 sinβ=n2
・sin θ Equation 6. By determining the moving distance u of the objective lens 110 from Equation 4, the pattern 101 is
The thickness h and cross-sectional shape of the can be detected.

FIG. 5 is a block diagram of a conventional pattern three-dimensional shape detection device. Transparent pattern 1 on the XY table 109
A substrate 102 on which 01 is formed is mounted. 120
, 121 are laser light sources with wavelengths λ1 and λ2, respectively, 122a and 122b are filters, 123 is a polarizing beam splitter that makes the two laser beams coaxial and sends them out as a specific polarized component, and 124 reflects only a specific polarized component. a polarizing beam splitter that transmits other polarized light components;
25 is an objective lens that can be moved slightly in the optical axis direction, 126 is a reflection mirror, 127 is a converging lens, 128 is a pinhole, 12
9 is a photodetector, 130 is a photodetector 12
9 shows a monitor image that is displayed after processing the signal of No. 9.

In FIG. 5, by slightly moving the objective lens 125 in the direction A' in the drawing using a moving mechanism (not shown), the photodetector 129 detects the laser beam 201 from the laser light source 120 and the laser beam 202 from the laser light source 202.
It is possible to detect the peak as an optical signal for each of the following. FIG. 6 shows an example of a detection signal in the monitor image 30 of FIG.
The moving distance of 25 and the vertical axis Y represent the amount of light received by the photodetector 129. At this time, the objective lens 125
The curve obtained by the movement shows two peaks as shown in FIG. 6, and the thickness of the pattern 101 is calculated from Equation 4, Equation 5, and Equation 6 from the movement distance u between these two peak values.

[0014]

The above-described conventional method for detecting the three-dimensional shape of a transparent fine pattern has the disadvantage that highly accurate detection cannot be performed for the following reasons.

The moving distance u of the objective lens 110 is determined from two peak values of the amount of light received by the photodetector 113. The relationship between the moving distance of the objective lens and the amount of received light at this time is as shown in FIG.

However, as the thickness of the pattern 101 becomes thinner, the two peaks approach each other and the waveforms overlap, as shown in FIG. The measurement accuracy of the thickness h of the film is reduced.

[0017]

[Means for Solving the Problems] The pattern three-dimensional shape detection device of the present invention includes two laser light sources that emit light of different wavelengths, and two laser beams emitted from these two laser light sources that are arranged facing the sample. a coaxial optical system including at least two polarizing beam splitters for guiding the emitted laser beam to one objective lens; the emitted laser beam is separated from the optical path of the emitted laser beam by one polarizing beam splitter in the coaxial optical system A dichroic mirror separates the two reflected laser beams that are reflected by the sample and travel backward through the objective lens, and each of the two reflected laser beams separated by the dichroic mirror is converged by a converging lens and then focused. It is characterized in that it includes two confocal optical systems that detect what passes through the hole with a photodetector, and that the objective lens can be moved slightly along the optical axis.

[0018]

[Operation] FIG. 1 is a diagram illustrating the principle of the present invention.

In FIG. 1, reference numeral 1 denotes a transparent pattern with a thickness of about several μm formed on a substrate 2, which is placed on an XY table 9. As shown in FIG. Laser light 51 and laser light 52 having wavelengths of λ1 and λ2 and which are parallel lights are emitted from the projection lens 15. 10 can be slightly moved along the optical axis S in the direction A shown in the figure (in the vertical direction on the paper), and has a wavelength λ1.
, λ2, 11 is a converging lens on the laser beam 51 side, 12 is a pinhole, and 13 is a photodetector.
The distance between and the pinhole 12 is the wavelength λ1 of the converging lens 11.
Make it equal to the focal length.

21 is a converging lens on the laser beam 52 side; 22
23 is a pinhole, and 23 is a photodetector. Similarly to the laser beam 1 side, the distance between the converging lens 21 and the pinhole 22 is set equal to the focal length of the converging lens 21 at wavelength λ2.

Further, 14 is a polarizing beam splitter, 15 is a projecting lens, and 16 is a dichroic mirror for separating the laser beam 51 and the laser beam 52.

The wavelengths λ1 and λ1 are emitted from the light projection lens 15, respectively.
Laser light 51 and laser light 52, which have a wavelength of λ2 and are parallel lights, are simultaneously emitted and both are reflected in the direction of pattern 1 by polarizing beam splitter 14. The reflected laser beams 51 and 52 have wavelengths λ after passing through the objective lens 10.
One laser beam 51 enters the pattern 1, focuses at a predetermined position F on the lower surface of the pattern, that is, the surface of the substrate 2, and is reflected to become a laser beam 51'. After that, it passes through an objective lens 10 and a polarizing beam splitter 14, and then passes through a dichroic mirror 16.
Transmit. Furthermore, each optical system is arranged so that the light is converged by the converging lens 11, focused at the position F1 of the pinhole 12, and is incident on the photodetector 13 as a strong optical signal.

On the other hand, the laser beam 52 with the wavelength λ2 enters the transparent pattern 1 in the same way as the laser beam 51, but since the wavelength is different, there is a difference in the refractive index within the pattern 1, and the laser beam 52 is different from the laser beam 1. Follow the light path. That is, the laser beam 52 is focused at a position F' within the pattern 1 in FIG.

Therefore, the laser beam 52' reflected from the lower surface of the pattern, that is, the surface of the substrate 2, passes through the objective lens 10 and the polarizing beam splitter 14, is reflected by the dichroic mirror 16, and is further converged by the converging lens 21. Since the light does not converge at the position F1', for example, only a weak optical signal reaches the photodetector 23.

Here, when the objective lens 10 is slightly moved in the optical axis direction to align the focal position F' of the laser beam 52 inside the pattern 1 with the point F on the substrate 2, the reflected light of the laser beam 2, the laser beam 2 ' will converge at the position F2 of the pinhole 22, allowing a strong optical signal to be incident on the photodetector 23.

This means that by moving the objective lens 10, strong optical signals reach the photodetector 13 and the photodetector 23 for the laser beam 51 and the laser beam 52, respectively.
The thickness of the transparent pattern 1 can be calculated from the moving distance of the objective lens 10.

Here, for example, the moving distance of the objective lens 10 is u, the incident angle of the laser beam 51 and the laser beam 52 with respect to the pattern 1 is θ, and the pattern 1 of the laser beam 51 is
The refraction angle at is α, the refractive index is n1, and the laser beam 52
When the refraction angle in pattern 1 is β and the refractive index is n2, the thickness h of transparent pattern 1 is

[0028]

[0029] Here, sinα=n1・sinθ Equation 2 sinβ=n2
- sin θ Equation 3, θ, n1, n2 are known, and u is a measured value, so the thickness h and cross-sectional shape of the pattern 1 can be detected by finding the moving distance u of the objective lens 10. can.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the drawings.

FIG. 2 is a block diagram of an embodiment of the present invention.

FIGS. 3(1) and 3(2) are examples of detection signals from the photodetector 13 and photodetector 23 in FIG. 2.

In FIG. 2, a substrate 2 on which a transparent pattern 1 is formed is placed on an X-Y table 9. 27 and 29 are laser light sources that emit laser light with wavelengths λ1 and λ2, respectively; for example, the laser light source 27 has a wavelength of 632.8n.
m He-Ne laser light source, the laser light source 29 has a wavelength of 51
This is a 4.5 nm Ar laser light source.

26 and 28 are filters; 25 is a polarizing beam splitter that coaxializes the two laser beams from the laser light sources 27 and 29 and sends out only a specific polarized component; and 24 is a polarizing beam splitter that reflects only a specific polarized component and transmits other polarized components. 10 is an objective lens that can be moved slightly in the optical axis direction, 16 is a dichroic mirror, 11 is a converging lens,
12 is a pinhole, 13 is a photodetector, 21 is a converging lens, 22 is a pinhole, 23 is a photodetector, 30 is a photodetector 13 and a photodetector 23
This is an arithmetic unit that calculates the thickness h of pattern 1 by processing the signal. Here, the distances between the converging lens 11 and the pinhole 12 and between the converging lens 21 and the pinhole 22 are the same as in the case of FIG.

The two laser beams emitted from the laser light source 27 and the laser light source 29 are turned into two coaxial beams having a specific polarization component by the beam splitter 25, further reflected by the polarizing beam splitter 24, and converged by the objective lens 10 to form a transparent pattern. 1. At this time, the laser beam 61 from the laser light source 27 focuses on the lower surface of the pattern 1, that is, the upper surface of the substrate 2, and when reflected, the reflected laser beam 61' passes through the objective lens 10 and becomes parallel light, and the dichroic mirror 1
6 , is focused at the pinhole 12 position by the converging lens 11 , and enters the photodetector 13 . At this time, when the objective lens 10 is slightly moved in the direction A in the figure by a moving mechanism (not shown), the relationship between the moving distance of the objective lens 10 at that time and the amount of light received by the photodetector 13 becomes, for example, as shown in FIG. 3(1).

Further, the relationship between the moving distance of the objective lens 10 and the amount of light received by the photodetector 23 at that time is shown in FIG. 3, for example.
As shown in (2), the laser beam 2 is focused on the upper surface of the substrate 2 and becomes parallel light at the objective lens 10, and the pinhole 22
The peak value is reached when the image is brought into focus. In this case, Figure 3 (
Objective lens 1 corresponding to the difference in peak position between 1) and Fig. 3 (2)
From the movement distance u of 0, the thickness of pattern 1 is calculated using equations 1, 2, and 3.

[0037]

[Effects of the Invention] The pattern three-dimensional shape detection device of the present invention has the following features:
By installing a dichroic mirror to separate the laser beam reflected from the sample surface, we can separate the laser beams of different wavelengths and use two confocal optical systems instead of one, consisting of a converging lens, a pinhole, and a photodetector to receive the light. Since two laser beams are provided, the peaks of the amount of reflected light and the amount of received light of two laser beams of different wavelengths can be individually measured, and the shape of a transparent fine pattern can be measured with high precision.

[Brief explanation of the drawing]

FIG. 1 is a principle diagram explaining the present invention.

FIG. 2 is a configuration diagram showing an embodiment of the present invention.

3(1) is a diagram showing the relationship between the moving distance of the objective lens 10 and the amount of received light in the photodetector 13 of FIG. 2, FIG.
(2) is a diagram showing the relationship between the moving distance of the objective lens 10 in the photodetector 23 and the amount of light received.

FIG. 4 is a principle diagram of a conventional pattern three-dimensional shape detection method.

FIG. 5 is a configuration diagram of a conventional pattern three-dimensional shape detection device.

6 is a diagram showing detection signals of the monitor image 130 in FIG. 5. FIG.

FIG. 7 is a diagram showing a detection signal of the monitor image 130 when the transparent pattern 101 is thin.

[Explanation of symbols]

1 Pattern 2　　　　Substrate 9 XY table 10 Objective lens 11 Convergent lens 12 Pinhole 13 Photo detector 14 Polarizing beam splitter 16 Dichroic mirror 21 Convergent lens 22 Pinhole 23 Photodetector 24 Polarizing beam splitter 25 Polarizing beam splitter 26 Filter 27 Laser light source 28 Filter 29 Laser light source 30 Arithmetic unit 101 Transparent pattern 102 Board 110 Objective lens 112 Pinhole 113 Photodetector 114 Polarizing beam splitter 120 Laser light source 121 Laser light source 122a Filter 122b filter 123 Polarizing beam splitter 124 Polarizing beam splitter 125 Objective lens 126 Reflection mirror 127 Convergent lens 128 Pinhole 129 Photodetector 130 Monitor image

Claims (1)

[Claims] 1. Two laser light sources that emit light of different wavelengths, and at least two polarized beams for guiding two emitted laser beams from the two laser light sources to one objective lens placed facing a sample. a coaxial optical system including a beam splitter; and one polarizing beam splitter in the coaxial optical system, where the emitted laser light is separated from the optical path of the emitted laser light, is reflected by the sample, and travels backward through the objective lens. A dichroic mirror for separating two reflected laser beams, and two confocal points for each of the two reflected laser beams separated by this dichroic mirror to be converged by a converging lens and then passed through a pinhole and detected by a photodetector. 1. A pattern three-dimensional shape detection device, comprising: an optical system, and the objective lens can be moved slightly along an optical axis.