JPS62219939A - Measuring method for thickness of semiconductor layer and apparatus employed therefor - Google Patents

Abstract

PURPOSE:To enable the highly precise measurement of the thickness of a semiconductor layer to be measured, by using first and second outgoing beam outputs and first and second absorption coefficient outputs with regard to incident light beams. CONSTITUTION:Incident light beams LB1 and LB2 are applied to a semiconductor laminate 4, and thereby outgoing beams LC1 and LC2 are obtained. Therefore, the intensities I01 and I02 thereof are detected electrically as outgoing beam outputs E01 and E02 by a light detecting means 12. The outgoing beam outputs E01 and E02 obtained from the light detecting means 12 are supplied to an arithmetic operation unit 13. The arithmetic operation unit 13 sets internally absorption coefficient outputs Ealpha1 and Ealpha2 which represent electrically absorption coefficients alpha1 and alpha2 for the incident light beams LB1 and LB2 to a semiconductor layer 1 of the semiconductor laminate 4. Accordingly, an operation is executed by using the outgoing beam outputs E01 and E02, incident beam outputs Ei1 and Ei2 and the absorption coefficient outputs Ealpha1 and Ealpha2, and a thickness output representing the thickness of the semiconductor layer 1 can be obtained therefrom.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to a method for measuring the thickness of a semiconductor layer and an apparatus used therefor.

[Kanritsu Blue Ni] Conventionally, when measuring the thickness of a semiconductor layer to be measured, a cross-section of the semiconductor layer to be measured is exposed to the outside, and the exposed cross-section is measured using an optical microscope, scanning microscope, etc. A method has been proposed in which the thickness of a semiconductor layer to be measured is measured by actually measuring the thickness using a semiconductor layer.

Problems to be Solved by the Invention 1 However, when using such a method for measuring the thickness of a semiconductor layer, it is difficult to obtain a clear and flat cross section of the semiconductor layer to be measured. The drawback is that the thickness of the semiconductor layer cannot be measured with high accuracy of 0.1 μm or less.

In addition, since the cross section of the semiconductor layer to be measured must be exposed to the outside, the semiconductor layer whose thickness has been measured cannot be destroyed and the semiconductor layer cannot be used for actual use.
This method has the disadvantage that it is not possible to measure the thickness of the semiconductor layer actually used.

Furthermore, since the cross-section of the semiconductor layer to be measured must be exposed to the outside at a speed U, it is difficult to measure the thickness of the semiconductor layer at multiple positions. The disadvantage was that it was difficult to measure the distribution.

By taking one step towards solving the problem, the present invention proposes a new method for measuring the thickness of semiconductor layers and a new device for use therein, which does not have the above-mentioned drawbacks.

The method for measuring the thickness of a semiconductor layer according to the first invention of the present application is to apply first and second lights to the semiconductor layer to be measured, respectively, which can be absorbed by the semiconductor layer to be measured but have mutually different wavelengths. and the second incident light is irradiated, and the first and second incident light are transmitted through the semiconductor layer to be measured to obtain 1
! The intensities of the first and second emitted lights are electrically detected as the first and second emitted light outputs, and the first and second emitted light outputs and the first and second emitted light outputs of the semiconductor layer to be measured are Electrical first and second absorption coefficient outputs representing the first and second absorption coefficients, respectively, for the second incident light are used to measure the thickness of the semiconductor layer to be measured.

Further, the semiconductor layer thickness measuring device according to the 21st invention of the present application includes a light source that can obtain first and second lights that can both be absorbed by the 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 that irradiates the semiconductor layer to be measured as the second incident light, and first and second output lights obtained by transmitting the first and second incident lights through the semiconductor layer to be measured, respectively,
A photodetecting means for electrically detecting first and second emitted light outputs, the first and second emitted light outputs, and absorption coefficients for the first and second input points of the semiconductor layer to be measured. and an arithmetic processing device that obtains an electrical thickness output representing the thickness of the semiconductor layer to be measured using the first and second absorption coefficient outputs respectively representing the thickness of the semiconductor layer to be measured.

Roughly speaking, the method for measuring the thickness of a semiconductor layer according to the third invention of the present application is as follows:
using first and second incident light beams, respectively, and
The first and second incident light beams are irradiated to the same position of the semiconductor layer to be measured, so that the V of the semiconductor layer to be measured is defined as the thickness at the position irradiated by the first and second incident light beams. Measure.

Further, in the semiconductor layer thickness measuring device according to the fourth invention of the present application, in the above-mentioned semiconductor layer thickness measuring device according to the second invention of the present application, in the light source, the first and second
are respectively 1!7 beams of light,
Accordingly, the light irradiation means irradiates the first and second incident light beams onto the same position of the semiconductor layer to be measured, and the light detection means irradiates the same position of the semiconductor layer to be measured with the first and second incident light beams. The intensities of the first and second emitted light beams obtained by passing through the semiconductor layer are electrically detected as the first and second emitted light beam outputs; an electrical thickness output 41q representing the thickness at the location illuminated by the first and second incident light beams;
Ru.

Furthermore, in the method for measuring the thickness of a semiconductor layer according to the fifth invention of the present application, in the method for measuring the thickness of a semiconductor layer according to the first invention of the invention described above, as the first and second incident light, Similarly to the method for measuring the thickness of a semiconductor layer according to the second invention of the present application, first and second incident light beams are used, respectively, and the first and second incident light beams are applied to the semiconductor layer to be measured. While irradiating the same position on the layer,
The semiconductor layer to be measured and the first and second incident light beams are moved relative to each other, so that the thickness of the semiconductor layer to be measured is changed to the first and second incident light beams.
and a plurality of radias at a plurality of locations illuminated by a second incident light beam.

Further, the semiconductor layer thickness measuring bag U according to the sixth invention of the present application is provided in the semiconductor layer thickness measuring device according to the second invention of the present application described above, in which the first and second light sources are used.
As in the case of the semiconductor layer thickness measuring device according to the fourth aspect of the present invention, the first and second light beams each emit 1q of light, and accordingly, the light irradiation means irradiate the incident light beam to the same position of the semiconductor layer to be measured,
It has a moving means for relatively moving the semiconductor layer to be measured and the light irradiation means, and further, the light detection means transmits the first and second incident light beams through the semiconductor layer to be measured, respectively. and the intensity of the second emitted light beam is electrically controlled by the first
and detected as the output of the second emitted light beam, and also processed]! I! A plurality of electrical thickness outputs are obtained, each representing a thickness of the semiconductor layer to be measured at a plurality of locations illuminated by the first and second incident light beams.

According to the method for measuring the thickness of a semiconductor layer according to the first invention of the present application, the thickness of the semiconductor layer to be measured is t, and the intensities of the first and second incident lights that irradiate the semiconductor layer to be measured are respectively 11 and ■12, 1 after passing through the semiconductor layer to be measured! ? The intensities of the first and second emitted lights are respectively r. 1 and l. 2. When the first and second absorption coefficients of the semiconductor layer to be measured for the first and second incident light are α1 and α2, respectively,
The thickness t of the semiconductor layer to be measured is the intensity li1 and li2 of the first and second incident lights, and the intensity I of the first and second outgoing lights.

1 and ■. 2, and the first and second absorption coefficients α and α
2, when the first, second, and second incident lights irradiate the semiconductor layer to be measured, the first and second intensities R and R2 based on the first and second incident lights are calculated. The wavelengths λ of the first and second incident lights are 1q if each reflected light has 1q
and λ2 are selected in advance to be sufficient values such that the difference lR1-R21 between the intensities R and R2 of the first and second reflected lights is equal to (!1), then (Io1/ l11)(Io2/l12)=0-(α,-
αr H ・・・・・・・・・・・・・・・ It has the relationship of (1), and when the first and second incident lights irradiate the semiconductor layer to be measured, the above-mentioned first If the first and second wavelengths 21 and λ2 cannot be obtained, the first and second wavelengths 21 and λ2 may be preselected to the above-mentioned values. Intensities Ii1 and 1 of the first and second incident lights
Since the absorption coefficients α1 and α2 of the first and second absorption coefficients α1 and α2 can be determined in advance, the intensities I and Ii2 of the first and second incident lights are expressed as 1.1/I, 2=K (
K is a constant), so the first
and measuring the thickness t of a semiconductor layer to be measured without using electrical first and second incident light outputs representing the intensities 'N and 12 of the second incident light, respectively. Gadesa・
Ru.

Further, according to the semiconductor layer thickness measuring device according to the second invention of the present application, the thickness of the semiconductor layer to be measured can be measured using the device. It is clear from the above description of the thickness measurement method.

Furthermore, according to the method for measuring the thickness of a semiconductor layer according to the third invention of the present application, the first and second incident light beams irradiate the same position of the semiconductor layer to be measured. It is clear that it is possible to measure the thickness of the semiconductor layer to be measured at the position irradiated by the first and second incident light beams for reasons analogous to those described above for the method for measuring the thickness of a semiconductor layer.

Further, according to the semiconductor layer thickness measuring device according to the fourth aspect of the present invention, the thickness of the semiconductor layer to be measured is measured at the position irradiated with the first and second incident light beams. It is clear from the above description of the third invention of the present application that this is possible.

Furthermore, according to the method for measuring the thickness of a semiconductor layer according to the fifth invention of the present application, the first and second incident light beams irradiate the same position of the semiconductor layer to be measured, Since the layer and the first and second incident light beams move relative to each other, the thickness of the semiconductor layer to be measured is It is clear that a plurality of thicknesses can be measured at a plurality of locations illuminated by the first and second incident light beams.

Further, according to the semiconductor layer thickness measuring device according to the sixth invention of the present application, the thickness measurement device measures the thicknesses of the semiconductor layer to be measured at the plurality of positions irradiated with the first and second incident light beams. It is clear from the above description of the fifth invention of the present application that it can be measured.

Effects of the Invention According to the semiconductor layer thickness measuring method according to the first invention of the present application and the semiconductor layer thickness measuring apparatus according to the second invention of the present application, the cross section of the semiconductor layer to be measured is not exposed to the outside. Therefore, since the thickness of the semiconductor layer to be measured can be measured without destroying the semiconductor layer to be measured, the thickness of the semiconductor layer to be actually used can be easily measured with high precision. be able to.

Further, according to the semiconductor layer thickness measuring method according to the third invention of the present application and the semiconductor layer thickness measuring device according to the eleventh invention of the present application, the cross section of the semiconductor layer to be measured can be exposed to the outside. Therefore, the thickness of the semiconductor layer to be measured at the position irradiated by the first and second incident light beams can be measured without destroying the semiconductor to be measured m. Therefore, the thickness at the position irradiated by the first and second incident light beams (a) can be easily measured with high accuracy.

Furthermore, according to the method for measuring the thickness of a semiconductor layer according to the invention of the present invention and the device for measuring the thickness of a semiconductor layer according to the sixth invention of the present application, the cross section of the semiconductor layer to be measured can be measured without exposing the cross section to the outside. Therefore, the thicknesses of the semiconductor layer to be measured at the positions irradiated by the first and second incident light beams can be reduced to 1l without destroying the semiconductor layer to be measured.
Since l11 can be specified, the actual value of l'
Regarding physical strength, it is possible to easily measure a plurality of thicknesses at a plurality of positions irradiated by the first and second incident light beams with high precision.

Example 1 Next, an example of the method for measuring the thickness of a semiconductor layer according to the invention of No. 1 [1] of the present application will be described with reference to FIG. In the first embodiment,
Assuming that the semiconductor layer to be measured is a semiconductor layer 1 made of a single crystal E nGaASP system that absorbs light in a wavelength band of 1°5 μm,
However, single-crystal InGaAs has an energy band gap on both ends of the semiconductor layer 1 that is narrower than that of the semiconductor layer 1.
Other P-based semiconductor layers 2 and 3 are arranged, and these semiconductor layers 2 and 3 and the semiconductor layer 1 form a semiconductor stack 4.
Let's discuss the case where it forms.

The semiconductor stack 4 described above is placed on the mounting table 5 with the window 6 turned to the right so that the window 6 is closed.

Therefore, light LA1 obtained from the light source 7 sequentially or simultaneously from the side of the half-layer 3 of the semiconductor 85
and LA2 are irradiated as incident lights LB1 and LB2 through the light irradiation means 8.

In this case, the light beams A1 and 1-A2 can be absorbed by the semiconductor y11 as the semiconductor layer to be measured in the semiconductor stack 4, but are substantially absorbed by the other semiconductor layers 2 and 3. Different wavelengths λ1 and A2 are set on the right side of the light source 7, respectively.
For example, the light source parts M and M2 each include a semiconductor laser and its driving circuit.

Further, an example of the light irradiation means 8 is the light L obtained from the light source 8.
A and LA2 are optical transmission lines U and 1, respectively,
from the optical coupler 9 via the optical transmission line 10 to the optical projector 11, and from the optical projector 11, the incident light beams LB and LB2 are emitted. has.

When the semiconductor stack 4 is irradiated with incident lights LB1 and LB2, the incident lights 181 and LB2G,t,'l are transmitted through the conductive stack 4 as output lights LC and LC2.

In this case, the intensities of the incident lights LB1 and LB2 are respectively
11 and Ii2, the incident lights LB and LB2 are absorbed by the semiconductor layer 1 as the semiconductor layer to be measured of the semiconductor stack 4, so the output lights LC1 and LC2 have the intensities 'il and Ii2 of the incident lights L81 and 182, respectively. 'Intensity I is weaker than i2. 1 and 1°2.

In this way, the incident light 181 and LB2 are applied to the semiconductor stack 4.
Since the output lights LC and LC2 are obtained by irradiating the light, the intensities 1ol and (.2) are electrically detected as the output light outputs E.1 and E.2 by the photodetecting means 12.

In this case, the light detection means 42 may be of a type known per se, but if the lights LA1 and LΔ2 are obtained in time order, and therefore the emitted lights LC1 and LC2 are obtained in time order, Output light output E and E. 2 can be used as one time-sequential output ql and one output 11H1, and the optical LAI and L
A 2 is obtained at the same time, therefore, the output beams LCi and LC
2 are obtained simultaneously, the output lights LC1 and LC2 are separated from each other using a spectrometer, and then each output light output E. 1 and EO2 and simultaneously output them to the output line H1 and above, respectively.

Further, the output light outputs EOI and E obtained from the light detection means 12. 2 via output line H1 or output)] line T1
and is supplied to the arithmetic processing unit 13 via the above.

On the other hand, the lights LA1 and LA2 obtained from the light source 8 mentioned above
Incident light LB1 that has irradiated the semiconductor stack 4 using
The intensities 11 and li2 of LB2 and LB2 are electrically detected as incident light outputs E and Ei2 by another light detection means 14.

In this case, the light detecting means 14 can use various types known per se, but the lights LA1 and LA2 are sequentially 1!
? When the light beams LA1 and LA2 are converted to the incident light output E by the photodetector 1:1 and the above, respectively.
It is possible to use the configuration of b, which has the configuration of detecting i1 and Ei2, obtaining them as one time-sequential output, and outputting it to one output v; 1. E-described photodetector F1 and incident light outputs Ei1 and Ei obtained from the above, respectively.
2 to the output lines G1 and G2, respectively.

Thus, the incident light outputs Ei1 and Ei2 obtained from the above-mentioned photodetecting means 14 are supplied to the above-mentioned arithmetic processing unit 13 via the output line G1 or via the outputs ll11G and G2.

In this case, the arithmetic processing unit 13 may have various configurations that are known per se; Absorption coefficient output Ea1 expressed in
and σEa2 can be internally set, and the absorption coefficient outputs E and Ea2α1 set in this way and the output light outputs EOl and E supplied from the light detection means 12. 2 and the incident light outputs Ei1 and Ei2 supplied from the photodetecting means 14. In this case, the arithmetic processing device 13 and the light source 7 are synchronized with each other so that the above-mentioned arithmetic processing by the arithmetic processing device 13 is performed in synchronization with the lights LA1 and L/'2 obtained from the light source 7. There is.

By the way, when the semiconductor stack 4 is irradiated with the incident lights LB1 and LB2 as described above, a part of the incident lights LB1 and LB2 is applied to the semiconductor layer 3 on the side opposite to the semiconductor layer 1 side. are reflected as reflected lights N11 and ``12, which have strong If
12 and R are reflected as "12 and N22" between the semiconductor layers 3 and 1 and between the semiconductor layers 1 and 2.
If no reflected light is reflected at the interface between them, the wavelengths λ and A2 of the incident light LB and L82 are expressed as the difference I between the intensities R11 and R21121 of the reflected light N11 and "21", N22
J3 is preselected to a value sufficient for the difference lR12-R221 between the intensities R12 and R22 to be reduced by 1q to an acceptable value.
Then, R11+R12=R-R, 2+R22-R2, and output light output E. 1 and E. 2, each of them ■. 1 and 102, respectively. 1 and Io2, and the incident light output Ei1
and Ei.

(They correspond to ril and ]A1, respectively, so let them be Eil and Eio respectively, and roughly,
The absorption coefficient outputs E and E are α1 and α2, respectively, since they represent the absorption coefficients α1 and α2 for the incident lights LB and LB2 of the semiconductor WJ1, respectively.
If α1 and α2 are α1 and α2, then (1
) formula is obtained.

Therefore, in the arithmetic processing unit 13, the wavelengths λ1 and A2 of the lights LA1 and [A2 obtained by the light source 7, and therefore the incident light L
The wavelengths λ1 and A2 of B and LB2 are determined by the above-mentioned difference IR
, , -R2,1 and 1-Rl2-R221 are preselected to sufficient strands to obtain negligible values,
Outgoing light output E and E Incoming light output Ei1 and Ei2
and absorption coefficient output E and Ea2, α
Further, the calculation corresponding to the calculation for calculating the thickness t is performed using the 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.

Example 2 Next, a second example of the method for measuring the thickness of a semiconductor layer according to the present invention using the second example of the device for measuring the thickness of a semiconductor layer according to the present invention will be explained with reference to FIG. Let me explain.

In Figure 2, parts corresponding to those in Figure 1 are designated by the same reference numerals (
=JL, detailed explanation will be omitted.

A second embodiment of the method for measuring the thickness of a semiconductor layer according to the present invention using a second embodiment of the device 2 for measuring the thickness of a semiconductor layer according to the present invention is shown in FIG. L.A.
and LA2 are light beams・LA' and LA2'
19, and accordingly, the incident light beams LB1 and LB2 that irradiate the semiconductor stacked body 4 are incident light beams 1B' and 182' that irradiate the same position of the semiconductor V4FM body 4.
In addition, the output lights LC1 and LC2 obtained by passing through the semiconductor stack 4 are output light beams L01' and LC2.
', and furthermore, the output light output E from the light detection means 12 17. 1 and EO2 become the exits (light beam outputs E' and E', and the incident light outputs E11 and Ei2 obtained from the optical detector [14] become the incident light beam outputs Ei1' and E, / , is the same as in FIG.

Therefore, although further detailed explanation will be omitted, semiconductor V4
It is possible to measure the thickness of the semiconductor Vvi as the semiconductor layer to be measured at the position irradiated by the incident light beams LB,' and L82'.

Next, a third embodiment of the method for measuring the thickness of a semiconductor layer according to the present invention using the third embodiment of the device for measuring the thickness of a semiconductor layer according to the present invention will be explained with reference to FIG. Let me explain.

In Figure 3, parts corresponding to those in Figure 2 are designated by the same reference numerals (
=J and detailed explanation will be omitted.

A third embodiment of the semiconductor layer thickness measuring method according to the present invention using the third embodiment of the semiconductor layer thickness measuring device according to the present invention is shown in FIG. 2, except that the light irradiation means 8 is driven by a drive device 17 which operates synchronously with the light irradiation means 13 through a synchronization control line 16.

Therefore, although further detailed explanation will be omitted, the semiconductor layer 1 as the semiconductor layer to be measured of the semiconductor stack 4 is irradiated by the incident light beams LB1' and LB2', and a plurality of light beams that may or may not be connected to IζH. The thickness of the position can be measured.

Incidentally, in the above description, only a few examples have been shown regarding both the semiconductor layer thickness measuring method according to the present invention and the semiconductor layer thickness measuring apparatus according to the present invention, and for example, FIGS. As shown in FIG. 3, the output of the light detection means 14)
. 1 and E. 2 (or E 01' and E. 2'),
Output E. 1 and E o2 (or E.1' and E'
) may be fed back to the light source 7 so that the light is turned on at a constant level, and various other modifications and changes may be made without departing from the spirit of the present invention.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a first embodiment of a method for measuring the thickness of a semiconductor layer according to the present invention and a first embodiment of an apparatus used therefor. FIG. 2 is a schematic diagram showing a second embodiment of the method for measuring the thickness of a semiconductor layer according to the present invention and a second embodiment of the apparatus used therefor. FIG. 3 is a schematic diagram showing a third embodiment of the method for measuring the thickness of a semiconductor layer according to the present invention and a third embodiment of the apparatus used therefor. 1.2.3 ...... Semiconductor layer 4 ...... Semiconductor fa notification body 5 ...... Mounting table 6 ...... ...Window 7...Light source Ml/M2...Light source section 8...Light irradiation means U % U % Ul 10... ...... Optical transmission line 9 ...... Optical coupler 11 ...... Light projectors 12, 14 ...... Light detection means 13...8J1f:'J processing device 15.
16 ...... Synchronous control line 17 ...... Drive system Applicant: Nippon Telegraph and Telephone Corporation Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. First and second lights that can be absorbed by the semiconductor layer to be measured but have mutually different wavelengths are applied to the semiconductor layer to be measured as first and second incident lights, respectively. , and the intensities of the first and second output lights obtained by transmitting the first and second incident lights through the semiconductor layer to be measured, respectively,
electrically detecting the output as first and second emitted light outputs, A method for measuring the thickness of a semiconductor layer, characterized in that the thickness of the semiconductor layer to be measured is measured using electrical first and second absorption coefficient outputs each representing an absorption coefficient. 2. A light source that can obtain first and second lights that can both be absorbed by the semiconductor layer to be measured but have mutually different wavelengths; a light irradiation means for irradiating the semiconductor layer to be measured as the second incident light; and first and second output lights obtained by transmitting the first and second incident lights through the semiconductor layer to be measured, respectively. a photodetector for electrically detecting intensity as first and second emitted light outputs; the first and second emitted light outputs; and the first and second incident light on the semiconductor layer to be measured. and an arithmetic processing device for obtaining an electrical thickness output representing the thickness of the semiconductor layer to be measured using the first and second absorption coefficient outputs respectively representing the absorption coefficient for the semiconductor layer to be measured. Features: Semiconductor layer thickness measuring device. 3. First and second light beams that can be absorbed by the semiconductor layer to be measured but have mutually different wavelengths at the same position of the semiconductor layer to be measured are used as first and second incident light beams, respectively; The intensities of the first and second emitted light beams obtained by transmitting the first and second incident light beams through the semiconductor layer to be measured are electrically determined by the first and second emitted light beams. an electric current detected as a beam power and representing the first and second output light beam powers and first and second absorption coefficients of the semiconductor layer to be measured for the first and second incident light beams, respectively; measuring the thickness of the semiconductor layer to be measured at a position irradiated by the first and second incident light beams using the first and second absorption coefficient outputs. Method for measuring the thickness of semiconductor layers. 4. A light source that obtains first and second light beams that can both be absorbed by the semiconductor layer to be measured but have mutually different wavelengths; and a light irradiation means for irradiating the same position of the semiconductor layer to be measured as a second incident light beam; and a first light beam obtained by transmitting the first and second incident light beams through the semiconductor layer to be measured, respectively. and a photodetector for electrically detecting the intensity of the second emitted light beam as first and second emitted light beam outputs; the first and second emitted light beam outputs; and the semiconductor layer to be measured. first and second beams representing absorption coefficients for said first and second incident light beams, respectively;
an arithmetic processing device for obtaining an electrical thickness output representing the thickness of the semiconductor layer to be measured at a position irradiated by the first and second incident light beams using the absorption coefficient output of the semiconductor layer; A device for measuring the thickness of a semiconductor layer, comprising: 5. First and second light beams that can both be absorbed by the semiconductor layer to be measured but have mutually different wavelengths at the same position of the semiconductor layer to be measured, as first and second incident light beams, respectively; moving the semiconductor layer to be measured and the first and second incident light beams relative to each other while irradiating the same position of the semiconductor layer to be measured; electrically detecting the intensities of the first and second emitted light beams obtained by transmitting the beams through the semiconductor layer to be measured as first and second emitted light beam outputs; and a first output of the semiconductor layer to be measured relative to the first and second incident light beams.
and electrical first and second absorption coefficient outputs representing a second absorption coefficient, respectively, of the semiconductor layer to be measured that is irradiated by the first and second incident light beams. A method for measuring the thickness of a semiconductor layer, the method comprising measuring a plurality of thicknesses at a plurality of positions. 6. A light source that obtains first and second light beams that can both be absorbed by the semiconductor layer to be measured but have mutually different wavelengths; and a light irradiation means for irradiating the same position of the semiconductor layer to be measured as a second incident light beam; a moving means for relatively moving the semiconductor layer to be measured and the light irradiation means; Photodetection that electrically detects the intensities of the first and second emitted light beams obtained by transmitting the second incident light beam through the semiconductor layer to be measured as the first and second emitted light beam outputs. means; first and second output light beam powers; first and second light beams representing absorption coefficients of the semiconductor layer to be measured for the first and second incident light beams, respectively;
and absorption coefficient outputs of the measured semiconductor layer to obtain a plurality of electrical thickness outputs each representing a thickness of the semiconductor layer under test at a plurality of locations illuminated by the first and second incident light beams. 1. A semiconductor layer thickness measuring device, comprising: an arithmetic processing device.