JPS597226A - Measuring method for incidence angle of polarization analyzing monitor - Google Patents

Abstract

PURPOSE:To determine simply and accurately an incidence angle of a polarization analyzing monitor, by measuring a polarization analyzing parameter of a sample by using the bulk sample having a known optical constant. CONSTITUTION:First, an incidence angle is roughly set and the polarization analyzing parameters psi, DELTA of the sample are measured basing on equations by a polarization analyzing monitor having an optical axis adjusted by using the parameter sample having a known optical constant and then, the incidence angle is determined accurately from these values.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for measuring the angle of incidence of an ellipsometry monitor.

Emission spectroscopy, atomic absorption spectroscopy,
Voltage change method, reflectance change method, mass spectrometry, etc. have been widely used in the past, but recently ellisymmetry has been replaced by the above methods due to its shortcomings in obtaining higher measurement specificity. has come to be used. Ellipsometry is a method that can accurately determine the thickness and optical constants of thin films by measuring the changes in the state that occur when polarized light is reflected on the sample surface. The device normally has a light source section, a light receiving section, and a sample holder integrally constructed by a precision-machined pedestal, and the incident angle is set on this pedestal. Therefore, when incorporating such a device into a vacuum process device, it is actually difficult to integrate and adjust the entire device, and it is difficult to integrate the entire monitor device into a vacuum process device.
, the accuracy of the incident angle setting angle will also deteriorate.

Therefore, this invention provides a new method for measuring the angle of incidence that allows the angle of incidence of the polarization analysis monitor to be roughly set without being precisely set in advance, and the angle of incidence can be easily and accurately determined when incorporating the vacuum process equipment K. It is about providing law.

By the way, considering the reflection of light by a thin film, as shown in FIG. 7, the refractive index of the substrate is ns.

If the refractive index of the thin film is n and the film thickness is d, and a monochromatic parallel ray is incident on the sample from vacuum at an incident angle ψ, then the direction parallel to the plane including the normal to the incident ray, that is, the p direction, and the above-mentioned plane. The reflectance of each component of warpage in the vertical direction, that is, the S direction, is expressed by the refraction angle within the thin film.

r1p+rla is vacuum and thin film s r* 9@rx
S is the Fresnel reflection coefficient at the thin film and substrate, respectively.

, where 91 is the refraction angle within the substrate. What determines the change in the polarization state between the incident light and the reflected light is the ratio of /Rp and 1S, that is, the ratio of the polarization p component and the reflectance of the three components is expressed as 3tanF'Δ. Therefore, tanW=-Δ=δp-δ.

It can be expressed as R,s, and V and Δ are called ellipsometry parameters, and it is recognized that these parameters have a certain relationship with the optical constants of the surface, the film thickness, and the angle of incidence. Therefore, if the film thickness d and refractive index n of the thin film are known, the polarization analysis parameters V and Δ can be obtained by calculating in the order of the above equation (2) b ('') b (3).

Therefore, in the incident angle measurement method according to the present invention.

First, a rough angle of incidence is set, and the polarization analysis parameters V and Δ of the sample are measured based on the above formula using a polarization analysis monitor with the optical axis adjusted using a Norouruk sample with known optical constants. The angle of incidence is determined accurately from these values.

An embodiment of the present invention will be described below with reference to FIG. 1 of the accompanying drawings.

In the illustrated embodiment, a case will be considered in which the incident angle is determined using a raw silicon wafer as a sample. The optical constant n of silicon at the He--Ne laser light wavelength (1, 32r A) is n = 3rj -0, 0, 2i.

The polarization analysis parameter V of this sample, Δ is the incident angle, ψ=7
Measure near 00. Considering that there is a natural oxide film on the raw silicon wafer, the refractive index n = /,
'l! Assuming that the film has a thickness d, the ellipsometry parameters V and Δ were calculated for each incident angle o and i', and the results are shown in the diagram of FIG. In Figure 2, the arrows indicate the accuracy range of W and Δ obtained with a normal polarization analyzer, and the accuracy is ±0 for the parameter yt.
．． Oj0. Further, the parameter Δ is set to ±0910.

Therefore, the polarization analysis data ξ as shown in Figure 2.
The incident angle ψ and the thickness d of the natural oxide film can be determined from the values of the parameters V and Δ. The refractive index n of the natural oxide film is still
K:t: 0. Even if there is an error of
= /, j! As shown in , the error for the angle of incidence ψ found is extremely small.

As described above, according to the method of the present invention, the ellipsometry parameters V,
By measuring ΔK, the angle of incidence of the ellipsometric monitor can be determined simply and accurately.

[Brief explanation of drawings]

FIG. 1 is a diagram showing light interference due to a single layer film, and FIG. 2 is a graph showing an embodiment of the method of the present invention. Figure 1 1 13

Claims (1)

[Claims] Measure the polarization analysis parameters V and Δ of a Norouruk sample with known optical constants using a polarization analysis monitor with optical axis adjustment, and calculate the incident angle from the values of the polarization analysis parameters V and Δ. An incident angle measurement method for an ω ellipsometry monitor.