JPS6224130A - Refractive index measuring apparatus - Google Patents

Abstract

PURPOSE:To enable the measurement of the refractive index of a transparent thin film at a high accuracy, by gauging the refractive index of the film with the known thickness handily in a wide range of wavelength from ultraviolet to infrared rays. CONSTITUTION:The title apparatus is provided with a substrate 1, a transparent thin film 2, a holder 3, a support base 4, a scale 5, an auxiliary scale 6, a laser 9 a photo detector (PD) 10, a laser driving source 11, an output monitor 12 and the like. Then, with the incident angle and the reflection angle theta set, for example, at 15Deg, this monitors the output of the DP 10 with time, moving to the side of larger at the rate of 6[Deg/min] synchronizing mobile bases 7 and 8. Here, the laser 9 oscillates continuously. Thus, the refractive index of the thin film can be measured at a relatively high accuracy with a simple and inexpensive equipment construction.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a vapor deposition method, a sputtering method, a plasma G method, a thermal C
Dielectrics and organic resins formed on substrates by dry methods such as the VD method or wet methods such as the spin code method.

This relates to a device for measuring the refractive index of transparent conductors, etc.
The present invention provides a refractive index measuring device that is particularly useful when the film thickness is known.

[Technical background of the invention and its problems]

An ellipsometer is a typical device for measuring the refractive index of transparent thin films! 7. The refractive index can be measured accurately even for samples with unknown film thickness, but the problems with the ellipsometer are (1) the equipment cost is high (
1) Data processing is complicated (limited to 11 measurement wavelengths, in particular cannot measure long wavelengths (for example, semiconductor laser wavelengths such as 780 nm, 833r1m, etc.).Among these problems.

In particular, the drawback of not being able to measure the refractive index for light semiconductor laser wavelengths means that it cannot be used as a tool for optimizing the media structure of optical recording media, for example, which severely limits its field of practical application. As a method to derive the refractive index of a thin film without using an ellipsometer,
For example, there is a method in which transparent thin films of different thicknesses are formed on a reflective substrate made of the same material, and the two-side constant wavelength is calculated from the relationship between the reflectance for normal incidence and the film thickness. In this case, samples with different flVl olfactory thicknesses must be formed and prepared as separate badges, so it is impossible to avoid the influence of variations in membrane quality between patches.

(■) Plot the relationship between reflectance R and film thickness t, and calculate t
Since min must be read graphically, there is a drawback that the error is large.

[Purpose of the invention]

The present invention was made in view of the above-mentioned problems with conventional refractive index measuring devices and methods. The purpose of this invention is to provide a refractive index device that can easily measure in the wavelength region.

[Summary of the invention]

The simple measuring device for transparent thin films of the present invention uses an optically flat reflecting surface, especially when the wavelength dependence of the refractive index is required, the spectral reflectance distribution of the reflecting surface is close to flat A/, i, Nl,
0 (DeF ) ~
90 (Deal), the measurement monochromatic light is incident, the intensity of the reflected light from the object to be measured is detected, and the refractive index of the transparent thin film is measured from the incidence angle dependence of this intensity. The configuration includes 1, for example, a semiconductor laser as a measurement light source, a jig for adjusting the incident angle, a support base for fixing the object to be measured, 1 a PIN-photodiode for detecting the amount of reflected light, and a photoelectric conversion for converting the output of the diode into an electrical signal. element,
It is sufficient to have a meter for measuring the angle of incidence, and it is simple. The refractive index n of the transparent thin film of the object to be measured is unknown, but it is usually 1.0 (n (3,0, i3), and the thickness of the transparent thin film in this case t [mi] (cos θ〈1〕 For example, it is sufficient if it is about 8331100A or more.Also, even if the value is less than 1100A, if θ is made sufficiently large, measurement is possible (however, the thinner the thickness, the lower the measurement accuracy).

In addition, there is no particular upper limit to the film thickness, but if the resolution of the incident angle is not very good, it is preferably 1 μm or less, preferably 300 μm or less.
If it is 0 A or less, the mouth can be measured from the first-order extinction angle, resulting in high accuracy.

〔Effect of the invention〕

According to the simple refractive index measuring device for transparent thin films of the present invention, the refractive index of transparent thin films can be measured with relatively high accuracy using a single wire and inexpensive device configuration.

[Embodiments of the invention]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A simple refractive index measuring device for transparent thin films according to the present invention will be explained in detail below with reference to one drawing. FIG. 1 is a block diagram of an embodiment of the present invention.

In Fig. 1, (1) is a Si polished substrate, (2) is a 5lx of 91500A modeled on it by thermal CVD method.
OyNz 11% (3) is a fixing pawl, (4) is a support base, (5) is a semicircular scale with angle graduations in 1 (Den) increments, (6) is an auxiliary semicircular scale Jig, (7
) is a laser moving table that has a motor and a rubber wheel that is rotated by this motor and is in contact with scale (5), (8) is a PD moving table that has the same function as (7) % (9) has a wavelength of 833 [1 m] (1) is a PIN photodetector (PD), (11 is a laser drive source,
(12) is a time change monitor of PD output. According to the above configuration, first, the incident angle and the reflection angle θ are set to 15De
jl, and synchronize the moving table +7>, f8) to 6
While moving toward the larger θ side at a speed of [DeJF/m1n), the output of the PD was monitored over time. At this time, the laser (9) was continuously oscillated at 2 mW. Figure 2 shows the relationship between the photodetector's output R and θ by converting the horizontal axis of the monitor (12) into the incident angle θ. .

θ was measured in the range from the initial value of 15 Dew to a maximum of 60 Del. The value of θmin at which R becomes the minimum is 39 (
When n is derived from t: film thickness, λ: wavelength, Rho 1.7
It becomes 9. In order to examine the validity of the measured quantities, we performed the same olfactory FT-IR analysis (the substrate was FZ-・S1
When a wafer was used, the main absorption peak wavelength was 10.
7 μm, [Reference] J, Elec-trochem
, 8 QC: 80LID 5TATE 5CIFn
(J, vol15°No, 3.p311.Marc
This was consistent with the experimental results of Brown et al.

In the above embodiment, an 833 [nm] semiconductor laser was used as the light source, but the present invention is not limited by the wavelength of the measurement light.
Ar+ laser, He-Ne laser, excimer laser-1
A laser such as a color chart laser, a nitrogen laser, or a wavelength variable light source that is a combination of a halogen lamp and a monochromator can be used. Further, the structure shown in FIG. 81!1, which was specifically produced as a prototype as a - implementation sequence, can be freely changed without departing from the spirit of the present invention.

[Brief explanation of drawings]

This is an example of the results of a mental measurement using the device. 1...Base, 2...Transparent light smell, 3...Suppression, 4
...Support stand, 5...Scale, 6...Auxiliary scale, 9...Laser, 10...Photodetector,
11... Laser drive source, 12... Output monitor. Agent Patent Attorney Noriyuki Chika Yudo Kikuo Takehana Figure 1 Figure 2

Claims (1)

[Scope of Claims] An object to be measured in which a transparent thin film of known thickness is formed on an optically smooth substrate surface that reflects monochromatic light, and a holder for fixing this object to be measured. , means for making monochromatic light incident on the side of the surface of the object to be measured on which the transparent thin film is formed from a variable direction in the range of 0 [Deg] to 90 [Deg] with respect to the direction perpendicular to the film surface; A refractive index measuring device that measures the refractive index of a transparent thin film by detecting the intensity of reflected light from a measuring object.