SU1619015A1 - Method of checking thickness of material - Google Patents

Abstract

The invention relates to a measurement technique and can be used in etching or forming layers of semiconductor materials. The purpose of the invention is to improve the accuracy of monitoring semiconductor layers by eliminating interference effects. A photosensitive photodetector layer is performed such that the long-wave slope of its spectral sensitivity characteristics is located in the wavelength region bounded by the edge of the fundamental absorption band of the monitored semiconductor material. which eliminates interference effects from the measurement process. 2 Il.

Description

The invention relates to a measurement technique and can be used in etching or forming layers of semiconductor materials for thickness control.

The purpose of the invention is to improve the accuracy of the control semiconductor layers by eliminating interference effects.

FIG. 1 shows a diagram of a device implementing a control method; in fig. 2 - the characteristic of the spectral sensitivity of the photosensitive layer of the photodetector y (L) and the spectral characteristic of the light transmission of the monitored material T (I).

The device contains a broadband optical radiation source 1, a photodetector 2, located in the radiation beam that passes through the monitored material layer 3 of the semiconductor material, the photodetector 2 is connected to the means 4 for recording and processing the photodetector signal. In addition, the indicated wavelength I (Fig. 2),

the long-wave slope of the characteristic 5 of the spectral sensitivity of the photosensitive layer of the photodetector, the edge of the fundamental absorption band 6 of the monitored semiconductor material (interval Yat – H2).

The material of the photosensitive layer of the photodetector 2 is made so that the long-wave slope of the characteristic 5 of its spectral sensitivity is located in the wavelength region bounded by the edge of the fundamental absorption band 6 of the controlled semiconductor material.

The method is implemented as follows.

The luminous flux from the broadband optical radiation source 1 passes through the controlled semiconductor layer 3, and the shortwave component of the specified luminous flux is spectrally limited in accordance with the T (X) curve. Then the luminous flux enters the photodetector 2, which is spectrally

Yo

limits the controlled light flux from the long-wave side in accordance with the characteristic 5 of the spectral sensitivity of the photosensitive layer of the photodetector # (A). Thus, a spectral band of the detected light flux is formed in the region of the edge of the fundamental absorption band 6 of the monitored semiconductor material (At - Ar).

When the thickness of the controlled semiconductor layer 3 changes, the angle of inclination T (A) changes according to the Bouguer – Lambert – Beer law. In accordance with this, the signal taken from the photodetector 2 and going further to the means of recording and processing the signal of the photodetector 4 also changes.

An increase in the monitoring power is a result of the broadband of the measured optical signal associated with the monitored thickness of the semiconductor layer, i.e., insensitivity to interference effects.

In general, the magnitude of the photo receiver signal can be represented as

A2 l0 (A) S0 (A) (A) ,,

where U is the magnitude of the photodetector signal;

10 (A) - radiation intensity of a broadband source at a given wavelength A

S is the integrated sensitivity of the photodetector;

p (A) is the spectral sensitivity of the photosensitive layer of the photodetector;

(A), I A I, in accordance with the Bouguer-Lambert-Beer law, the transmittance value of the monitored semiconductor layer at a given wavelength;

K (A) is the absorption coefficient of the monitored semiconductor layer at a given wavelength;

I - thickness of the controlled semiconductor layer.

When using the material of the photosensitive layer of a photodetector of a material identical to the controlled one, the spectral sensitivity in the region of the edge of the fundamental absorption band is $ 0 (A) (A) a, where a is a constant determined by the photodetector design. Then

ten

U С

l (l + a)

where C is a constant, defined by the type of controlled material, parameters

optical radiation source, integrated sensitivity of the photosensitive photodetector layer.

The material identity of the photosensitive layer of the photodetector and the monitored layer simplifies the selection of a pair of a photodetector layer, since in this case the long-wave slope of the spectral sensitivity of the photosensitive photodetector layer is located in the wavelength region bounded by the edge of the fundamental semiconductor material's fundamental absorption band.

In other cases, the type of dependence U –U (I) is determined experimentally.

Claims (1)

Invention Formula The method of controlling the thickness of the material, which consists in directing the luminous flux to the material, using a spectral device, register the value the intensity transmitted through the material of the luminous flux, and the results of processing are judged on the thickness, which differs from the fact that, in order to improve the accuracy of control of semiconductor layers, to record the intensity of the transmitted luminous flux, a photodetector with a long-wave slope is selected as the spectral instrument spectral sensitivity located in the wavelength region bounded by the edge of the fundamental absorption band of the layer. Y ////////////////// A Sh then yes 7 FIG. one Wv / 5 V / / m)