JPH0658204B2 - Sample plane position measuring device - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a sample surface height measuring device for optically measuring the position of a sample surface, and particularly to the position of a sample surface such as a wafer or a mask in a semiconductor manufacturing apparatus. The present invention relates to a sample surface position measuring device suitable for measuring the.

[Technical background of the invention and its problems]

In an LSI manufacturing apparatus such as an electron beam exposure apparatus,
When a pattern is formed by drawing on a sample such as a semiconductor wafer or a mask substrate, if the position of the sample surface (distance to the optical system) changes due to warpage of the sample or other factors, an error occurs in the drawing pattern. Therefore, conventionally, a method has been adopted in which the amount of fluctuation of the surface of the sample is measured and the correction is performed according to the amount of fluctuation.

As a sample plane position measuring device, there is one using an optical method as shown in FIG. 6 (Japanese Patent Laid-Open No. 56-2632). In this apparatus, the light emitted from the laser light source L is focused in a spot shape by the lens L ₁ and irradiated on the sample surface, and the reflected light is imaged on the detector D by the lens L ₂ . The height position of the sample surface is measured by calculating the detection output of the detector D.

Conventionally, a laser light source is used as a light source as in the above example, and an S deflection parallel to the surface to be measured and a P deflection perpendicular thereto
It used a light source that is the sum of the deflection. However, when the resist film formed on the surface to be measured is exposed, P
The deflection is larger in the amount of light entering the resist film than in the amount of light reflected on the surface of the resist film. At this time, when the state of the semiconductor substrate under the resist film is aluminum with high reflectance, the amount of light reflected on the resist surface is summed with the reflected light on the Al surface to obtain accurate surface information. There was a drawback that it could not be obtained.

As one method for preventing such a defect, Japanese Patent Laid-Open No.
Although there is a method of measuring only the S-deflection on the surface to be measured as shown in Japanese Patent Laid-Open No. 101112, there is a drawback that the deflection filter must be placed on the incident light side.

[Object of the Invention]

In view of the above problems, the present invention is to provide an optical system that irradiates light mainly for S-polarization without inserting a polarization filter.

[Outline of Invention]

In order to achieve the object of the present invention, a semiconductor laser is used as a light source, paying attention to the emission characteristics of this semiconductor laser, and changing the installation method of the semiconductor laser to reduce the above problems. is there.

〔The invention's effect〕

According to the present invention, since the same effect can be obtained without separating the light source consisting of P-deflection and S-deflection into only S-deflection by the deflection filter, the structure is simple and the effect of reducing the transmittance by the filter does not occur. A sample surface position measuring device can be provided.

Example of Invention

FIG. 1 shows a generally used oblique-incidence type specimen surface measuring device. The light emitted from the light source 11 passes through the slit 12 and is mirrored.
It is reflected by 13 and is condensed by the lens 15 to form a slit image on the sample surface.

The light reflected from the sample surface is condensed again by the lens 32, reflected by the mirror 33, and incident on the detector 35.

Here, as shown a light source commonly circular deflection line summer in Figure 2 when used in the apparatus shown in FIG. 1, curve reflectance for S-polarized component R _s, the curve reflectivity of P polarized component R _P Becomes

In general, the incident angle is 20-
About 80 ° is used. Therefore, as shown in the figure, since it is used in a region where the reflectance of the P-polarized component is low, that is, the transmittance is high, for example, as shown in FIG. 3, the surface of the resist film lower layer is coated with Al or the like having high reflectance. If so, there is reflectance and the P-polarized component enters the detector 35, and accurate position measurement cannot be performed.

Therefore, a P-deflection is cut using a deflection filter, but in the present invention, the problem is solved by using a semiconductor laser for the light source 11. That is, note that the light emitted from the semiconductor laser is linearly polarized,
As shown in FIG. 5, the semiconductor laser is mounted so that it can be freely rotated around the radiation optical axis.

The semiconductor laser is rotated and adjusted so that the amount of light incident on the detector 35 is maximized with respect to the surface to be measured, for example, on a very thick glass surface (as shown in FIG. 4).

In this case, the S-polarized reflected wave is returned as described above.

By paying attention to the fact that the semiconductor laser is linearly deflected in this way and freely setting the direction, the conventional problems can be solved.

Such a sample surface position measuring device can be used in various devices for manufacturing semiconductors.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a sample surface position measuring device, FIG. 2 is a characteristic diagram showing reflectance of S deflection and P deflection, FIG. 3 is an explanatory diagram of errors due to reflected light, and FIG. FIG. 5 is a schematic diagram showing a conventional measuring device, and FIG. 6 is a schematic diagram showing a known measuring device. 11 …… light source, 12 …… aperture, 13 …… Mira 15 …… lens, 16 …… incident light, 21 …… table 22 …… sample, 31 …… reflected light, 32 …… lens 33 …… mirror, 34 …… Slit, 35 …… Detector.

Claims (1)

[Claims] 1. A light irradiation section for irradiating the surface of a sample to be measured with focused light from an oblique direction, and a light detection section for detecting reflected light reflected on the surface of the sample, and photoelectrically reflecting the reflected light. In a sample surface position measuring device that measures the position of a sample surface by receiving light by a detection unit, a semiconductor laser having linear deflection is used as a light source in a light irradiation unit, and the linear deflection direction of this semiconductor laser is parallel to the sample surface. A device for measuring the position of a sample surface, wherein the semiconductor laser is mounted by adjusting the rotation.