JPH01182711A - Method and apparatus for measuring thickness of semiconductor layer - Google Patents

Abstract

PURPOSE:To facilitate obtaining two light beams from a light source, by providing a control means, by which the two light beams can be selectively obtained. CONSTITUTION:Two light beams having the different wavelengths to each other are inputted into a semiconductor layer body 4 to be measured as two incident light beams from a light source 7. The intensities of the emitted light beams through transmission are detected 12. The thickness of the semiconductor layer body 4 is operated 13 based on the output of the detectors 12 and the absorption coefficient of one incident light beam. At this time, the light beams LA1 and LA2, which are oscillated and outputted from the semiconductor laser in the light source 7 and have wavelengths of lambda1 and lambda2, are controlled with a control means so that the light beams can be selectively obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for measuring the thickness of a semiconductor layer and an improvement in an apparatus used therefor.

[Prior Art] Conventionally, a semiconductor layer to be measured is irradiated with first and second lights that can be absorbed by the semiconductor layer to be measured but have mutually different wavelengths, as the first and R2 incident lights, respectively. , the intensities of the first and second emitted light obtained by transmitting the first and second incident light through the semiconductor layer to be measured are electrically detected as the first and first and second emitted light outputs. , the first
and an electrical second representing the second output light output and the second absorption coefficient of the semiconductor layer to be measured for the second incident light.
Japanese Patent Laid-Open No. 62-219939 proposes a semiconductor layer thickness measuring method in which the thickness of a semiconductor layer to be measured is measured using at least the absorption coefficient output of .

Conventionally, a light source is used to obtain first and second lights that can both be absorbed by a semiconductor layer to be measured but have true wavelengths, and a first and second light source, respectively, is used to obtain first and second lights that can be absorbed by a semiconductor layer to be measured. and 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 photodetecting means for electrically detecting first and second emitted light outputs; a second photodetection means representing the first and second emitted light outputs and an absorption coefficient of the semiconductor layer to be measured for the second incident light; and an arithmetic processing device that obtains an electrical thickness output representing the thickness of the semiconductor layer to be measured using at least the absorption coefficient output of the semiconductor layer thickness measuring device.
Special feature 1m [proposed in Publication No. 62-219939q.

According to the method for measuring the thickness of a semiconductor layer described above, the thickness of the semiconductor layer to be measured is determined by t1 ml for irradiating the semiconductor layer to be measured and the second
The intensity of the incident light, respectively! 1. and U I i2, the intensity of R41 obtained by passing through the semiconductor layer to be measured, and the intensity of the second emitted light are represented by ■, respectively. 1 and 1°2, and when the first and second absorption coefficients of the semiconductor layer to be measured for the first and second incident lights are α1 and α2, respectively, the thickness t of the semiconductor layer to be measured is Intensities 111 and 1 of the second incident light
, the intensities of the first and second emitted lights '01 and 1 and the first and second absorption coefficients α1 and α2, when the first and second incident lights irradiate the semiconductor layer to be measured, , the first and second intensities R based on the first and second incident lights
7 and R2 respectively, then #
! The wavelengths λ and λ2 of the first and second incident lights are expressed as tklR, -R of the intensities R and R2rm of the first and second reflected lights.
21 is selected in advance to a value sufficient to obtain a negligible value, then (1/I)/(1°,/IH)-8-(α2-
α1) [・・・・・・・・・・・・・・・has the relationship of (1),
In addition, when the first and second reflected lights mentioned above are not obtained when the first and second incident lights irradiate the semiconductor layer to be measured, the first and second wavelengths λ and λ2 are changed to the above-mentioned wavelengths λ and λ2. 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 The first and second incident light outputs and the first and second output light intensities I and IO2 are respectively represented.
and the first and second absorption coefficients α1 and 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.

Moreover, the first and second wavelengths λ1 and λ2 are α 〉〉α
By selecting such that the relationship is obtained, 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 representing the thickness t of the semiconductor layer to be measured, and thus the thickness t of the semiconductor layer to be measured can be measured.

Further, according to the above-mentioned semiconductor layer thickness measuring device, the thickness of the semiconductor layer to be measured can be measured using the above-mentioned method for measuring the thickness of the semiconductor layer to be measured. It is clear from the above description of the method for measuring the thickness of a semiconductor layer.

As is clear from the above, according to the semiconductor layer thickness measurement method and the semiconductor layer thickness measurement device used therein, it is possible to measure the thickness of a semiconductor layer without exposing the cross section of the semiconductor layer to be measured to the outside. Since the thickness of the semiconductor layer to be measured can be measured without destroying the semiconductor layer to be measured, it is possible to measure the thickness of the semiconductor layer actually used.
Can be easily measured with high precision.

[5? ! Ming tries to solve:! Title I].

In the case of the conventional semiconductor layer thickness measuring method and semiconductor layer thickness measuring apparatus described above, the semiconductor layer to be measured has a first and an E1 second layer.
It has been desired to easily obtain first and second light to be irradiated as incident light from a light source.

Therefore, the method for measuring the thickness of a semiconductor layer according to the present invention is a novel semiconductor layer thickness measurement method that can measure the thickness of a semiconductor layer to be measured using the first and second lights easily obtained from a light source. This paper aims to propose a thickness measurement method.

Moreover, the semiconductor layer thickness measuring device according to the present invention is intended to propose a novel semiconductor layer thickness measuring device having a light source that can easily obtain ml and second light.

[Means for Solving the Problems] The method for measuring the thickness of a semiconductor & according to the present invention is similar to the conventional method for measuring the thickness of a semiconductor layer described above. irradiate the semiconductor layer to be measured with first and second lights that can be absorbed by the semiconductor layer but have different wavelengths as the first and second incident lights, respectively. The intensities of the first and second emitted lights obtained by transmitting the are electrically detected as the first and second emitted light outputs, and the intensities of the first and second emitted light outputs and the measured object are detected as the first and second emitted light outputs. The thickness of the semiconductor layer to be measured is measured using at least an electrical second absorption coefficient output representing a second absorption coefficient of the semiconductor layer for the second incident light.

Further, the semiconductor layer thickness measuring device 2 according to the present invention also has a first and second semiconductor layer that can be absorbed by the semiconductor layer to be measured, but have mutually different wavelengths, as in the case of the conventional semiconductor layer thickness measuring device described above. a light source for obtaining second light; a light irradiation means for irradiating the semiconductor layer to be measured with first and second light reflected from the light source as first and second incident light, respectively; a photodetection means for electrically detecting the intensities of the first and second emitted light obtained by transmitting the first and second incident light through the semiconductor layer to be measured as the first and second emitted light outputs; and the first and second emitted light outputs, and a second absorption coefficient output representing the absorption coefficient of the semiconductor layer to be measured for the second incident light. and a processing unit for obtaining an electrical thickness output representative of the thickness of the layer.

However, the method for measuring the thickness of a semiconductor layer according to the present invention
In a semiconductor layer thickness measurement method similar to the conventional semiconductor layer thickness measurement method described above, the first and second lights are applied to the semiconductor layer to be measured as first and second incident lights, respectively. , for irradiation, the first light is obtained from a semiconductor laser, the first light is irradiated to the semiconductor layer to be measured as the first incident light, and then the second light is irradiated to the semiconductor layer to be measured. The second light obtained from the semiconductor laser is irradiated onto the semiconductor layer to be measured as the second incident light.

Further, the semiconductor layer thickness measuring device according to the present invention is a semiconductor layer thickness measuring device similar to the conventional semiconductor layer thickness measuring device described above, in which the light source includes a semiconductor laser; and control means for controlling the first and second lights to be selectively obtained.

In this case, the tIIJw means is
It can be used as a temperature control means for controlling I knitting. Also, 1II
III1 means, the driving current of the semiconductor laser is 113
The drive current control means may be 1 m long.

[Function] According to the method for measuring the thickness of a semiconductor layer according to the present invention, the first and second lights are emitted onto the semiconductor layer to be measured, respectively.
The method for measuring the thickness of a semiconductor layer is the same as the conventional method for measuring the thickness of a semiconductor layer, except that the semiconductor layer to be measured is sequentially irradiated with the first and second lights as incident light. Therefore, as in the case of conventional semiconductor layer thickness measurement methods, the thickness of the semiconductor layer to be measured can be measured without exposing the cross section of the semiconductor layer to the outside, and therefore without destroying the semiconductor layer to be measured. Since the thickness of the semiconductor layer can be measured, the thickness of the semiconductor layer actually used can also be easily measured with high viscosity.

Furthermore, according to the present invention for measuring the thickness of a semiconductor layer'@Kasumi, the light source is a semiconductor laser as described above, and it is @Ij
The semiconductor layer thickness measuring apparatus according to the present invention has the same configuration as the conventional semiconductor layer thickness measuring apparatus described above, except that it has a conventional semiconductor layer thickness measuring apparatus. In the case of a@ and the case of mis, the thickness of the semiconductor layer to be measured can be measured by the above-mentioned method for measuring the thickness of the semiconductor layer.

However, according to the method for measuring the thickness of a semiconductor layer according to the present invention, the semiconductor layer to be measured is irradiated with the first and second lights as the first and second incident lights, respectively. Since the light is sequentially irradiated onto the semiconductor layer to be measured, the first and second lights can be easily obtained from the light source, and can be used to determine the thickness of the semiconductor layer to be measured. can be easily measured.

Further, according to the semiconductor layer thickness measuring device according to the present invention, since the light source includes the semiconductor laser and its control means as described above, it is possible to easily emit the first and second lights from the light source. Obtainable.

[Example J] Next, an example of the method for measuring the thickness of a semiconductor layer according to the present invention will be described with reference to FIG.
& Beast Example, the semiconductor layer to be measured is 1.55 μm
Assume that the semiconductor layer 1 is made of a single crystal 1 nQaASP system having an energy band gap corresponding to the wavelength of
A case will be described in which other semiconductor layers 2 and 3 are arranged, and a semiconductor stack 4 is formed by these semiconductors 1, 2 and 3 and the semiconductor JI11.

The above-mentioned semiconductor laser 4 is placed on a turret 5 having a window 6 so that the window 16 is closed.

Thus, from the semiconductor layer 3 side to the semiconductor stack 4,
Lights LA and LA2 controlled time-sequentially from the light source 7,
Through the light irradiation means 8, the incident lights LB and LB2 are sequentially applied to ff1l.

In this case, the lights LA and LA2 can be absorbed by the semiconductor H1 as the semiconductor layer to be measured of the semiconductor multilayer fan 4, but cannot be qualitatively absorbed by the other semiconductors 1, 2 and 3. They each have true wavelengths A1 and λ2.

In addition, the lights LA1 and LA2 are sequentially removed from the light 11i7.
The light source 7 generates light L having wavelengths λ1 and A2, respectively.
A, and a semiconductor laser 21 that can oscillate and output LA2.
and the semiconductor laser 21, and then the lights LA1 and L
It has a control means 22 for controlling so that A2 is selectively obtained.

In this case, the control means 22 controls the oscillation wavelength of the semiconductor laser 21 to be a second wavelength with respect to the ambient temperature for the semiconductor laser 21.
Since the relationship shown in FIG. Therefore, it can be used as the drive w1 flow control means 24 for controlling the drive current of the semiconductor laser 21. In addition, in FIGS. 2 and 3, λ. indicates a wavelength corresponding to the energy bandgap of the semiconductor mi.

Further, an example of the light irradiation means 8 transmits the lights LAI and LA2 sequentially emitted from the light 17 to the light projection 2S via the optical transmission path U.
11, and from the light projector 11, the incident light beams L8 and LB2 are sequentially emitted.

If the semiconductor stack 4 is irradiated with the incident lights LB and LB2, the incident lights LB1 and LB2 will be applied to the semiconductor stack 4.
are transmitted as output lights LC1 and LC2. In this case, if the intensities of the incident lights LB and LB2 are respectively Ii and the second, then the input ()I lights LB1 and LB2/JtM4
1t [Semiconductor FIJ as the semiconductor layer to be measured of FHk4
1, the outgoing lights LC and LC2 have weak intensities '01 and 'i2, respectively, compared to the intensities i1 and 'i2 of the incident lights LB and LB2. Obtained in 2.

In this way, the incident light LB enters the semiconductor 1111 body 4.

and LB2, the output lights LC and LC2 are obtained, so their intensity is 1. , and '02,
The second light detection means electrically detects the emitted light outputs E and EO2.

In this case, the light detection means 42 may be of any known type, but it obtains the emitted light outputs EOI and EO2 as one time-sequential output, and outputs them as one output 1118.
A device with a configuration that allows output to be used is used.

Further, the output light output E is sequentially increased from the second light detection means.
and "02" to the fraud processing device 1 via the output glH.
3.

On the other hand, the above-mentioned light f! The intensity of the incident lights LB1 and LB2 that illuminate the semiconductor laser 4 using the lights A and LA2 that are sequentially emitted from 7 onwards.

and 1 and 2 are electrically detected as incident light outputs Ei and Ei2 by another light detection means 14. In this case, the first stage of photodetection 14 may be of various types known per se;
and F2, the incident light output Ei and Ei
It is possible to use a device having a configuration of sequentially detecting 2 and 2, obtaining them as one time-sequential output, and outputting it to one output IIaG.

Thus, the sequential incident light outputs ε11 and Ei2 obtained from the above-mentioned photodetecting means 14 are supplied to the above-mentioned arithmetic processing wave H13 via the output IIaG1.

In this case, the input light LB of the semiconductor WJ1 of the semiconductor stack 4 may be used as the control processing device 13, although various configurations that are known per se may be used.

It has a configuration in which absorption coefficient outputs Ea and Ea2 electrically representing absorption coefficients α and α2 for LB2 can be set, and absorption coefficient outputs Ea and Ea2 set in this way can be set. , the output light outputs E and E sequentially supplied from the second photodetector means. 2 and the incident light outputs E.sub.2 and E:2 sequentially supplied from the photodetecting means 14. in this case,! The a-guchi processing unit 13 and the light gi7 are mutually connected to the same unit so that the above-mentioned dark processing by the processing vi unit 13 is performed in synchronization with the light units A1 and LA2 controlled by the light 'IQ7. 1.

By the way, when the semiconductor stacked body 4 is irradiated with the incident lights LB and LB2 as described above, a part of the incident lights L81 and LB2 is applied to them on the surface of the semiconductor FIJ3 opposite to the semiconductor FJ1 side. Strength R11 and R4 respectively
2, and is reflected as reflected lights "2" and "N22" having intensities R2 and R22, respectively, on the surface of the semiconductor Ji2 opposite to the semiconductor El1 side. If no reflected light is reflected at the interface between the semiconductor layer 3 and IFJ, and the semiconductors WJ1 and 2, the wavelengths λ and λ2 of the incident lights LB1 and El2 are changed to the intensity R1 of the reflected lights N11 and N21.
1 and R21, the difference IRf1-R2,1, and the reflected light N
Strong fl of 2nd and N22 [R difference between 2nd and R22 lR
If the value is selected in advance to be sufficient to obtain the 2nd -R2□1 with a negligible value, then R71+R2nd -R1, R2''
R22"R2, and output light outputs EO1 and EO
2 as '01 and I, respectively, since they correspond to '01 and 102, respectively. 2, and the incident light output E1. and El.

Since they correspond to fil and second, respectively, let them be El and Eio, respectively, and let the absorption coefficient outputs εα1 and Eα2 be the absorption coefficients for the incident light LB and El2 of the semiconductor layer 1. α1 and α2
, respectively, so if α and α2 are respectively expressed, then equation (1) described above in the section of action can be obtained.

Therefore, in the arithmetic processing unit t13, the wavelengths λ1 and λ2 of the lights LA and LA obtained by the light source 7, and therefore the wavelengths λ1 and λ of the incident lights LB and El2, are converted into the above-mentioned differences IR, 1-R2, l and 1R. Using the output light outputs EOI and EO2, the input light outputs Eil and El2, and the absorption coefficient outputs Ea1 and El2, with the values set in advance to be sufficient to obtain the second-R221 with a negligible value. ,
A computation corresponding to the computation for determining the thickness t is performed 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.

In addition, the wavelengths λ and λ2 of the lights LA and LA2 are α
By choosing so that the relationship 2〉〉α1 is obtained,
Arithmetic processing unit without using α1! At F13, a thickness output Et representing the thickness t of the semiconductor 111 is obtained.

As described above, according to the semiconductor layer thickness measuring method according to the present invention and the semiconductor layer thickness measuring device 2 used therein, the thickness of the semiconductor layer to be measured can be measured. In this case, the light source 7 includes a semiconductor laser 21 and an I control means 22 (temperature I11 control means 23, or current l
llIw means 24), the light beams 111 and the second lights LA and LA2 can be easily obtained from the light source 7, and the lights LA1 and LA2 can be sequentially incident on the semiconductor to be measured. Since the light can be irradiated as light LB1 and El2, the thickness of the semiconductor layer to be measured can be easily measured.

[Brief explanation of the drawing]

FIG. 1 is according to the present invention! l! 1 is a schematic diagram showing an example of a method for measuring the thickness of a conductor layer and an example of a device for measuring the thickness of a semiconductor layer used therein; FIG. FIG. 2 is a diagram showing the relationship between the oscillation wavelength of the semiconductor laser and the ambient temperature of the semiconductor laser used for the displacement. FIG. 3 shows the NIl of a semiconductor laser used for explaining the present invention.
FIG. 3 is a diagram showing the relationship between the oscillation wavelength of a semiconductor laser and the l1wi flow. 1.2.3 ......Semiconductor layer 4...Semiconductor stacked body 5---...4 units 6... ...Window 7---Light source M,, M2...Light WA section 8---Light irradiation means U... . . . Optical transmission line 11 - . . . Light projector No. 2.14 . . . Light detection means 13 . . . Arithmetic processing IB! Device 21...
...Semiconductor laser 22...Ill 111 means 23...
...4 degree control means 24 ....... Drive Ti flow control means Applicant
Nippon Telegraph and Telephone Corporation. Flute 1-

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. , the intensities of the first and second emitted light obtained by transmitting the first and second incident light through the semiconductor layer to be measured are electrically determined as the first and second emitted light outputs. and detecting the first and second emitted light outputs and an electrical second absorption coefficient output representing a second absorption coefficient of the semiconductor layer to be measured with respect to the second incident light. In the semiconductor layer thickness measurement method for measuring the thickness of the semiconductor layer to be measured, the first and second lights are applied to the semiconductor layer to be measured as first and second incident lights, respectively. For irradiation, the first light is obtained from a semiconductor laser, the first light is irradiated to the semiconductor layer to be measured as the first incident light, and then the second light is irradiated to the semiconductor layer to be measured. from the semiconductor laser, and directing the second light to the semiconductor layer to be measured,
A method for measuring the thickness of a semiconductor layer, characterized in that irradiation is performed as the second incident light. 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 photodetection means for electrically detecting intensity as first and second emitted light outputs, the first and second emitted light outputs, and an absorption coefficient of the semiconductor layer to be measured for the second incident light; and a second absorption coefficient output representing the thickness of the semiconductor layer to be measured. Measurement of the thickness of a semiconductor layer, wherein the light source includes a semiconductor laser and a control means for controlling the semiconductor laser so that the first and second lights are selectively obtained from the semiconductor laser. Device. 3. The semiconductor layer thickness measuring device according to claim 2, wherein the control means is a temperature control means for controlling the ambient temperature of the semiconductor laser. measuring device. 4. The semiconductor layer thickness measuring device according to claim 2, wherein the control means is a drive current control means for controlling the drive current of the semiconductor laser. measuring device.