JPH01182710A - Thickness measuring apparatus for semiconductor layer - Google Patents

Abstract

PURPOSE:To project light beams having the desired sizes of the spots, by providing a control means, which can change the sizes of the spots of two incident light beams that are projected on a semiconductor layer to be measured. CONSTITUTION:Two light beams having the different wavelengths are projected 8 on a semiconductor layer body 4 to be measured as two incident light beams from a light source 7. The intensities of the light beams are detected 12 through transmission. The thickness of the semiconductor layer body 4 is operated 13 based on the outputs of the detectors 12 and the absorption coefficient for one light beam. At this time, a light projecting device 11 of the projecting means 8 has a condensing lens system 21. An optical distance between the device 11 and the semiconductor layer body 4 is varied and controlled with a suitable moving means 22. Thus, the size of the spots of the incident light beam on the semiconductor layer 1 can be changed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor layer thickness measuring device used for measuring the thickness of a semiconductor layer.

[Prior Art I Conventionally, a light source that can obtain first and second lights that can be absorbed by a semiconductor layer to be measured but have mutually different wavelengths;
The first and second lights obtained from the light source are respectively
and a light irradiation means for irradiating the semiconductor layer to be measured as a second incident light beam, and first and second light beams obtained by transmitting the first and second incident light beams through the semiconductor layer to be measured, respectively.
a photodetector for electrically detecting the emitted light beam as first and second emitted light beam outputs; the first and second emitted light beam outputs; and a second incident light beam on the semiconductor layer to be measured. and a second absorption coefficient output representing the absorption coefficient of the semiconductor layer to be measured. Thickness measuring device is special 1 1986-21993
This is proposed in Publication No. 9.

According to such a semiconductor layer thickness measuring device, it is possible to measure the thickness of a semiconductor layer to be measured using the semiconductor layer thickness measuring method described below.

That is, the thickness of the semiconductor layer to be measured is t, and the intensities of the first and second incident light beams irradiating the semiconductor layer to be measured by the light irradiation means are respectively Iil and . The first obtained by passing through
and the intensity of the second emitted light beam is 01 and 1, respectively.
02, the first and second absorption coefficients of the semiconductor layer to be measured for the first and second incident light beams are α1 and α2, respectively.
When the thickness t of the semiconductor layer to be measured is the first and second
Intensities of the incoming light beams 111 and 1 Intensities of the first and second outgoing light beams 12 birds! as well as! and the first and second absorption coefficients α0102
~1 and α2, when the first and second incident light beams irradiate the semiconductor layer to be measured, the first and second intensities R1 based on the first and second incident light beams and R2, respectively, the wavelengths λ1 and λ2 of the first and second incident light beams are defined as the difference IR1−R,,l between the intensities R and R2 of the first and second reflected light beams. If we choose in advance a value sufficient to obtain a negligible value, then (Io, 2/ I, 2) / (Io1/ I, 1
)=0-(α,-α+H ・・・・・・・・・・・・・・・(1) relationship,
In addition, when the first and second incident light beams irradiate the semiconductor layer to be measured and the above-mentioned first and second reflected lights are not equal to 1, the first and second wavelengths λ and λ2 are set to the above-mentioned wavelengths. Even if the values are not selected in advance, the relationship of equation (1) described above is maintained, so that in the arithmetic processing unit, the electrical values representing the intensities 11 and Ii2 of the first and second incident lights, respectively, are the first and second incident light outputs and the first and second output light intensities I; The first one represents 1 and 102 respectively.
and the second output light output and the first and second absorption coefficients α1
and α2, an electrical thickness output representing the thickness t of the semiconductor layer to be measured can be obtained, and thus the thickness t of the semiconductor layer to be measured can be measured.

Also, let the first and second wavelengths λ and λ2 be α2〉〉α
1, the first and second incident light outputs, the first and second output light outputs, and the second absorption Coefficient α2
can be used to obtain an electrical thickness output representative of the thickness t of the semiconductor layer to be measured, thus making it possible to measure the thickness t of the semiconductor layer to be measured.

As is clear from the above, the semiconductor layer thickness measuring device described above can be used to destroy the semiconductor layer to be measured without exposing the cross section of the semiconductor layer to the outside. Since it is possible to measure the thickness of the semiconductor layer to be measured without having to do anything, the thickness of the semiconductor layer to be actually used can also be easily measured with high precision.

[Problems to be Solved by the Invention] In the case of the conventional semiconductor layer thickness measuring device described above, it is difficult to determine the size of the spot on the semiconductor layer to be measured of the first and second incident light beams that irradiate the semiconductor layer to be measured. The smaller the value, the higher the resolution of the thickness of the semiconductor layer to be measured.

However, as the spot sizes of the first and second incident light beams are made smaller, the intensity of the output light beam becomes different depending on the surface condition of the semiconductor layer to be measured. This causes an error in the thickness of the semiconductor layer to be measured.

Therefore, it has been desired to be able to irradiate the semiconductor layer to be measured with the first and second incident light beams with desired spot sizes.

Therefore, it is an object of the present invention to propose a novel semiconductor layer thickness measuring device that can satisfy the above-mentioned desired matters.

[Means for Solving the Problems] The semiconductor layer thickness measuring device according to the present invention, like the conventional semiconductor layer thickness measuring device described above, can both be absorbed by the semiconductor layer to be measured, but can be absorbed by the semiconductor layer to be measured. a light source from which first and second lights having different wavelengths are obtained; and the first and second lights obtained from the light source are applied to the semiconductor layer to be measured as first and second incident light beams, respectively. a light irradiation means for irradiating the semiconductor layer; and a light irradiation unit that electrically controls the intensity of the first and second output light beams obtained by transmitting the first and second incident light beams through the semiconductor layer to be measured. a photodetecting means for detecting the second output light beam output; a second detection means for detecting the first and second output light beam outputs; and a second output light beam representing the absorption coefficient of the semiconductor layer under test for the second incident light beam. and an arithmetic processing device that uses at least the absorption coefficient output to obtain an electrical thickness output representing the thickness of the semiconductor layer to be measured.

However, in the semiconductor layer thickness measuring apparatus according to the present invention, the light irradiation means is configured to irradiate the first and second incident light beams that irradiate the semiconductor layer to be measured. , comprising an incident light beam spot size control means for varying the spot size on the semiconductor layer to be measured.

[Function] According to the semiconductor layer thickness measuring device according to the present invention, the thickness of the semiconductor layer can be measured as described above, except that the light irradiation means has the above-mentioned incident light beam spot size control means. It has the same configuration as the measurement device.

Therefore, it can be used to destroy the semiconductor layer to be measured without exposing the cross section of the semiconductor layer to the outside, as in the case of the conventional semiconductor layer thickness measuring device described above. Since the thickness of the semiconductor layer to be measured can be measured without using a semiconductor layer, the thickness of the semiconductor layer to be actually used can also be easily measured with high precision.

However, according to the semiconductor layer thickness measuring device according to the present invention, since the light irradiation means has the above-mentioned incident light beam spot size control means, the first and second incident light beams are directed toward the semiconductor layer to be measured. , since the desired spot size can be irradiated, the thickness of the semiconductor layer to be measured can be
It has high resolution and small error and can be easily measured.

[Example] Next, with reference to FIG. 1, an example of a semiconductor layer thickness measuring device according to the present invention will be described together with an example of a semiconductor layer thickness measuring device using the device, and a semiconductor layer to be measured will be described. Assume that the semiconductor layer 1 is made of a single-crystal lnQaASP system having an energy band gap corresponding to a wavelength of 1.55 μm. Other semiconductor layers 2 and 3 made of crystalline 1nP are arranged, and these semiconductor layers 2
A case will be described in which a semiconductor stacked body 4 is formed by 3 and 3 and the semiconductor layer 1.

The semiconductor laminate 4 described above is placed on a stand 5 having a window 6 so that the window 6 is closed.

Thus, from the semiconductor layer 3 side to the semiconductor stack 4,
The lights LA and LA2 obtained from the light source 7 sequentially or simultaneously are converted into an incident light beam 1B through a light irradiation means 8.
And LB2 is irradiated.

In this case, the lights LA and LA2 are applied to the semiconductor layer 1 as the semiconductor layer to be measured of the semiconductor stack body 4.

can be absorbed, but have mutually different wavelengths λ1 and λ2, which cannot be absorbed substantially by the other semiconductor layers 2 and 3, respectively, and the light source sections M and Obtained from M2.

Further, an example of the light irradiation means 8 is the light L obtained from the light source 8.
A and LA2 are guided to the optical coupler 9 via the optical transmission lines U and F2, respectively, and then guided from the optical coupler 9 to the optical projector 11 via the optical transmission line 10, and the light projector 11 It has a configuration in which the incident light beams LB and LB2 are emitted from the light beams.

In this case, the light projector 11 has a focusing lens system 21 whose optical distance to the semiconductor stack 4 is variably controlled by a suitable movable means 22.

When the semiconductor stack 4 is irradiated with the incident light beams LB1 and LB2, the incident light beams LB1 and LB2 pass through the semiconductor stack 4 as output light beams LC and LC2. In this case, if the intensities of the incident light beams LB1 and LB2 are Iil and Ii2, respectively, the incident light beams LB1 and LB2 are absorbed by the semiconductor layer 1 as the semiconductor layer to be measured of the semiconductor stack 4, so the output light beam L.C.
and LC2 have an intensity ■ that is weaker than the intensities ■il and Ii2 of the incident light beams LB1 and LB2, respectively. 1 and ■. 2
It can be obtained with

By irradiating the semiconductor stack 4 with the incident light beams LB and LB2, the output light beam LC
, and LC2, so that its intensities I and I. 2
are electrically detected as output light beam outputs E and EO2 by the photodetection means 12.

In this case, various types of light detection means 12 that are known per se can be used, but in the case where the lights LΔ1 and LA2 are obtained in time sequence, and therefore the output light beams LC and LC2 are obtained in time sequence, 1 , output light beam output E. 1 and E. 2 as one time-sequential output and connect it to one output line H
1 can be used, and the light L
If A and LA2 are obtained simultaneously, and therefore output light beams LC1 and LC2 are obtained simultaneously, the output light beams LC1 and LC2 are separated from each other using a spectrometer, and then the output light beam output E is obtained, respectively. . 1 and E. 2 and simultaneously outputting them to the output lines H1 and F2, respectively, can be used.

Furthermore, the output light beam output E obtained from the photodetection means 12
. 1 and E. 2 via output line H1 or output r
It is supplied to the arithmetic processing unit 13 via AH and F2.

On the other hand, the light LA1 and 1-Δ obtained from the light source 7 described above
2, the intensities 11 and I:2 of the incident light beams LB1 and LB2 that are irradiating the semiconductor stack 4 are electrically detected as the incident light beam output Ei by another light detection means 14.
1 and Ei2. In this case, as the light detection means 14, various known ones can be used, but the light L
If A1 and LA2 are obtained sequentially in time, their light L
A and LA are detected as incident light beam outputs E and E1□ by photodetectors F1 and F2, respectively, and these are obtained as one time-sequential output, which is output to one output line G1. In addition, when the lights LA and LA2 are obtained at the same time, it has a configuration in which the incident light beam outputs Ei1 and Ei2 obtained from the above-mentioned photodetectors F and F2 are outputted to the outputs 1i1G and G2, respectively. You can use whatever you want.

Thus, the incident light beam outputs Ei1 and F12 obtained from the photodetecting means 14 described above are transmitted via the output line G.
Or it is supplied to the arithmetic processing unit 13 mentioned above via the output lines G2 and G2.

In this case, the arithmetic processing unit 13 may have various configurations that are known per se; It has a configuration in which the absorption coefficient output E (xl and E expressed as α2 It has a configuration that can perform calculation processing on the light beam outputs E.1 and E.2 and the incident light beam outputs Eil and Ei2 supplied from the photodetection means 14. In this case, the calculation processing device 13
and light source 7 are synchronized with each other so that the arithmetic processing described above by arithmetic processing unit 13 is performed in synchronization with light LA1 and LA2 obtained from light source 7.

By the way, when the semiconductor layered body 4 is irradiated with the incident light beams LB1 and LB2 as described above, a portion of the incident light beams LB1 and LB2 is applied to the semiconductor layer 3.
are reflected as reflected lights N and N12 having intensities R11 and R12, respectively, on the surface of the semiconductor layer 2 opposite to the semiconductor layer 111I, and with intensities R and R22, respectively, on the surface of the semiconductor layer 2 opposite to the semiconductor layer 1 side. Reflected light N12 with
and reflected as N22, but between semiconductor m3 and 1,
And if no reflected light is reflected at the interface between semiconductor layers 1 and 2, the incident light beams LB and L
The wavelengths λ and λ2 of B are expressed as the difference between the intensities R and R21 of the reflected lights N and N 11 21
1fIR-Rl, and the difference 1R12-R221 between the intensities R12 and R22 of reflected light "12 and N22" is selected in advance to be a value sufficient to obtain a negligible value, R1
1+R12=R1, R12+R22=R2, and output light outputs E01 and E. 2, respectively.
Since it corresponds to 01 and 2002, each is marked ■. 1 and ■. 2, and let the incident light beam outputs Ei1 and Eio be Eil and Eio, respectively, since they correspond to Iil and 112, respectively, and let the absorption coefficient outputs E and E be respectively P: r11 α1 α2 Absorption coefficients α1 and α2 for incident lights LB1 and LB2
, respectively, so if α1 and α2 are respectively expressed, then equation (1) described above in the section of action can be obtained.

Therefore, in the arithmetic processing unit 13, the wavelengths λ1 and λ2 of the lights LA1 and LA2 obtained by the light source 7, and therefore the wavelengths λ1 and λ2 of the incident light beams L81 and LB2, are ignored by the above-mentioned differences lR11-R211 and 1J2-R221. The output light outputs EO1 and EO2, the input light outputs Ei1 and Ei2, and the absorption coefficient outputs Ea1 and E are preselected to values sufficient to obtain the obtained values. 2 to perform the calculation corresponding to the operation n for determining the thickness t using the above-mentioned equation (1).

In this case, the arithmetic processing unit 13 obtains a thickness output Et representing the thickness t of the semiconductor layer 1 as the semiconductor layer to be measured of the semiconductor stack 4.

Furthermore, the wavelengths λ1 and λ2 of the lights LA1 and LA2 described above are
By selecting , so that the relationship α1>>α2 is obtained, the thickness output E, which represents the thickness t of the semiconductor layer 1 of the semiconductor stack 4, can be obtained by the arithmetic processing unit 13 without using α1. can get.

-E As mentioned above, according to the configuration of the semiconductor layer thickness measuring device according to the present invention described above, it is possible to measure the thickness t of the semiconductor layer 1 as the half-diameter layer to be measured. In the irradiation means 8, the optical distance between the focusing lens system 21 and the semiconductor layer 1 can be variably controlled using the movable means 21. Then, the optical distance between the focusing lens system 21 and the semiconductor layer 1 is variably controlled m+
If the semiconductor B1 of the incident light beam LSI and LB2
You can change the size of the spot on the top. Therefore, the light irradiation means 8 has an incident light beam spot size control means for varying the spot size of the incident light beams L81 and LB2 on the semiconductor layer 1 as the semiconductor layer to be measured.

Therefore, by the light irradiation game 8, the incident light beam LB,
and LB2 can be irradiated onto the semiconductor layer 1 with a desired spot size, so the thickness of the semiconductor layer 1 can be
It has high resolution and small error and can be easily measured.

[Brief explanation of the drawing]

The figure is a schematic diagram showing an embodiment of the semiconductor layer thickness measuring device according to the present invention. 1.2.3 ...... Semiconductor layer 4 ...... Semiconductor laminate 5 ...... Mounting table 6 ...... - Window 7... Light source Ml/M2... Light source section 8... Light irradiation means u 1 u, i. ...... Optical transmission line 9 ...... Optical coupler 11 ...... Light projectors 12, 14 ...... Light detection means 13... Arithmetic processing unit 15.16... Synchronization control line 17... Drive device 21... ...Focusing lens system 22...
...Mobile means applicant Nippon Telegraph and Telephone Corporation agent Patent attorney 1) Masaharu Naka

Claims (1)

[Claims] 1. A light source from which first and second lights, both of which can be absorbed by a semiconductor layer to be measured, have mutually different wavelengths, and first and second lights obtained from the light source; a light irradiation means for irradiating the semiconductor layer to be measured as first and second incident light beams, respectively; 1st and 2nd
a photodetecting means for electrically detecting the intensity of the emitted light beam as first and second emitted light beam outputs, the first and second emitted light beam outputs, and the first and second emitted light beams of the semiconductor layer to be measured. an arithmetic processing device for obtaining an electrical thickness output representing the thickness of the semiconductor layer to be measured, using at least second absorption coefficient outputs representing absorption coefficients for the two incident light beams; In the semiconductor layer thickness measuring device, the light irradiation means varies the size of a spot on the semiconductor layer to be measured of the first and second incident light beams that irradiate the semiconductor layer to be measured. A device for measuring the thickness of a semiconductor layer, comprising means for controlling the size of an incident light beam spot.