JPS6228606A - Film thickness measuring instrument - Google Patents

Abstract

PURPOSE:To easily and accurately measure the thickness of a film, by providing at least two pairs of a light source which irradiates rays of light at different incident angles and a detector for detecting reflecting light and irradiating rays of light of the same wavelength from each light source. CONSTITUTION:Two sets of light sources 1a and 1b and two sets of reflecting light detectors 2a and 2b are provided. Rays of light having the same wavelength are used as those irradiated from the light sources 1a and 1b. The reflecting lights from the two light sources 1a and 1b are respectively detected with the detectors 2a and 2b and arithmetic units 5a and 5b perform prescribed operation processes on the detected data. The periodicity values thus obtained are compared with each other at a relational arithmetic unit 6 and the one when the two values coincide with each other is used as the true thickness of a film. The value of the true film thickness thus obtained is displayed through a display device 7. Therefore, the thickness of a film can be measured easily and accurately.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to thin films such as oxide films, nitride films, and polycrystalline silicon films formed on semiconductor wafers, etc., and film types with short ellipsometry periods. The present invention relates to a film thickness measuring device that measures film thickness.

[Technical background of invention■ and its problems]

FIG. 3 shows a conventional example of a film thickness measuring device using an ellipsometry. A pair of light sources 1 that emit light of a constant wavelength and detectors 2 that detect reflected light are provided. The sample 3 is placed on a sample stage 4, and a thin film is formed on the surface of the sample 3. However, with this device, during measurement, the operator changes the angle of the light source to change the incident angle of the light ray, as shown by the dotted line in Figure 3, and the ellipsometry period obtained by measuring at each angle is From the film thickness value, a measured value with the same numerical value must be determined as the film thickness. Therefore, the operation is complicated.

In addition to such devices, there are two pairs of light sources that emit light of different wavelengths and detectors that detect the reflected light from each light source.

Traditionally used. However, with this device,
The light of one wavelength among the irradiated light beams is stable, but the light of the other wavelength is unstable, has a short lifetime, and lacks reliability.

[Purpose of the invention]

The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a film thickness measuring device that can easily and accurately measure the thickness of a film formed on a sample surface. There is.

[Summary of the invention]

In order to achieve the above object, the present invention includes at least two pairs of light sources arranged so that the incident angles of the irradiated light rays are different, and at least two pairs of detectors for detecting each reflected light. The present invention provides a film thickness measuring device that irradiates light beams of the same wavelength and measures the film thickness from the numerical values obtained with each light irradiation.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

In the embodiment shown in FIG. 1, two light sources ia and 1b are provided, and two reflected light detectors 2a and 2b are provided.

That is, there are two sets of light 11a, lb and detection W2a, 2b.
It is arranged against. All of these are fixed above a sample 3 such as a semiconductor wafer 8 placed on a sample stage 4, and one light source 1a is configured to irradiate a light beam at an incident angle of 70 degrees with respect to the normal line of the sample 3. The other light source 1b is set to emit light at an incident angle of 30 degrees with respect to the normal line. Therefore, the detectors 2a and 2b that detect the reflected lights corresponding to the eight lights Ft1a and ib are also set at similar angles to the normal.

The light rays emitted from the light sources 1a and lb are reflected by the i9 film formed on the upper surface of the sample 3 and the sample surface, and are directed to the detector 2a.
, 2b, and the film thickness is thereby measured. Here, the light beams emitted from the eight lights 11a and 1b are of the same wavelength. As this wavelength light, one having good stability and good reflectivity is used; for example, helium-neon laser light is selected. Using stable wavelength light enables accurate measurements and extends the life of the light source.

The film thickness is measured by ellipsometry.

That is, as shown in FIG. 2, two light sources 1a.

1b is detected by detectors 2a and 2b, and arithmetic units 5a and 5b perform a predetermined operation τ) on the detected data. The periodic values obtained in this manner are compared by the comparison calculation device 6, and the one where the respective numerical values match can be determined as the true film thickness. This true film thickness value is displayed on the display device 7. In this case, since the measurement method is the same as the conventional method, measurement control and data processing can be easily performed by simply changing the program of the personal computer etc. that constitutes the arithmetic units 5a, 5b and the comparison arithmetic unit 6. can.

Next, a heliumone A laser with a wavelength of 6,328 people was applied to the sample 3 at an incident angle of 30 degrees and 70 degrees.
A film with a refractive index of 1.45 and a film thickness of 6000 was formed on a silicon wafer 3 using an apparatus in which
A case will be explained in which the thickness of an oxide film on a person is measured. light source 1b
The numbers detected by detector 2b of the light irradiated from the sample at an incident angle of 30 degrees and reflected by the sample were 1,351 and 3,675, respectively.

6000 people, 8325 people, etc., resulting in a cycle of 2325 people. The numbers detected by the detector 2a of the reflected light emitted from the light source 1a at an incident angle of 70 degrees were 270 and 3135 people.

6,000 people, 8,865 people, etc., resulting in a cycle to 2,865. Therefore, the film thickness determined by measurement is 6000, which is the same as the above two values.
Accurate film thickness data will be obtained.

In addition, in the present invention, three or more pairs of light sources and detectors may be provided, thereby making it possible to improve accuracy and shorten measurement time. Also, the incident angle of the light beam is limited to the illustrated embodiment.
Various changes are possible.

〔Effect of the invention〕

As described above, according to the present invention, light beams are emitted at different angles of incidence.
By reducing the number of light sources and detectors for detecting reflected light and arranging two or more pairs, each light source emits light of the same wavelength, making it possible to easily and accurately measure rIQ thickness. It is possible to obtain a fixed setup for all film thicknesses that allows rapid continuous measurement.

[Brief explanation of drawings]

FIG. 1 is a front view of a main part of an embodiment of the present invention, FIG. 2 is a block diagram showing the configuration of the same embodiment, and FIG. 3 is a front view of a main part of an example of a conventional device. 1a, 1b...light source, 2a, 2b...detector, 3.
··sample. Applicant's agent: Sato-O P) 1 Figure also 2 Figure 53 Figure

Claims (1)

[Claims] a sample stage on which a sample having a thin film formed on its surface is placed; a first light irradiation means for irradiating the sample on the sample stage with light at a first incident angle; a first detection means for detecting light from the first light irradiation means; and a second detection means for irradiating the sample on the sample stage with light having the same wavelength as that of the first light irradiation means at a second incident angle. ellipsometry based on the output signals of the first and second detection means; A film thickness measuring device comprising a calculation means for calculating a film thickness value for each period, and a comparison means for comparing the calculation results of the calculation means to obtain a true film thickness value.