JP2002083851A - Quality evaluation method of semiconductor substrate and its quality evaluation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately evaluate impurity, defects, etc., in a semiconductor substrate by detecting quantitatively the life time of a semiconductor substrate whose life time is long. SOLUTION: A first chopper 21 between a laser device 14 and a semiconductor substrate 11 makes an excitation light 13 turn on and off at a prescribed frequency. A second chopper 22 between the first chopper and the semiconductor substrate makes the excitation light turn on and off at a variable frequency higher than that of the first chopper. A photoluminescence light 16 which is generated by the semiconductor substrate when irradiation of the excitation light to the semiconductor substrate is turned on and off is introduced in a spectroscope 17. A controller 23 detects an attenuation time constant T of the photoluminescence light from the change of mean intensity of the photoluminescence light at the time when the on-off frequency of the excitation light is increased gradually by controlling the second chopper, and calculates the life time of the semiconductor substrate from a formula τ=T/C (where C is a constant).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for quantitatively evaluating the quality of a semiconductor substrate, that is, impurities and defects existing in the semiconductor substrate.

[0002]

2. Description of the Related Art Conventionally, as an evaluation method of this kind, an excitation light is irradiated on an epitaxial wafer for a light emitting device which is a compound semiconductor, and photoluminescence light generated by excitation of carriers in an active layer of the wafer is detected. A method for evaluating an epitaxial wafer for a light-emitting element, which derives a non-light-emitting lifetime from a rate of change in the intensity of photoluminescence light when the time-dependent change in intensity of the photoluminescence light is constant (Japanese Patent Laid-Open No. 2000-2000) No. 101145). In the method for evaluating the epitaxial wafer for a light-emitting element configured as described above, the non-light-emitting lifetime is a property value independent of the excited carrier density. Good correlation holds. As a result, the non-light-emitting lifetime in the active layer can be accurately and easily measured without depending on the excited carrier density, so that an epitaxial wafer having high luminous efficiency can be reliably selected and the production yield of the epitaxial wafer can be improved. It has become.

On the other hand, a semiconductor layer having a band gap smaller than the p-type cladding layer and the n-type cladding layer is sandwiched between the p-type cladding layer and the n-type cladding layer, and a forward direction is provided between the p-type cladding layer and the n-type cladding layer. A method for evaluating a semiconductor device in which the decay time constant of photoluminescence light is measured based on photoluminescence light obtained by irradiating a semiconductor layer with pulsed light while applying a bias voltage (Japanese Unexamined Patent Application, First Publication No. H10-260,1992). 10-135291
issue). In this evaluation method, the decay time constant of the photoluminescence light is calculated by subtracting the light emission intensity when the excitation light is not irradiated and the bias voltage is applied from the light emission intensity. The method for evaluating a semiconductor device configured in this manner is suitable for a semiconductor device having a pn junction, particularly a light emitting element such as an LED or a compound semiconductor laser, and the excitation light is irradiated from the intensity of the photoluminescence light when irradiated with the excitation light. By applying a bias voltage in the forward direction to the pn junction without irradiation and reducing the effect of the tilt of the energy band of the semiconductor layer, the intensity of the photoluminescence light is subtracted, so that the photoluminescence light of the light emitting element is reduced. Find the decay time constant. As a result, even if the excitation intensity changes, the slope of the energy band hardly changes and the decay time constant of the photoluminescence light does not vary, so that the decay time constant can be measured more accurately. Accuracy can be improved, and defective factors can be detected early.

[0004]

However, in the above-described conventional method for evaluating an epitaxial wafer for a light emitting device disclosed in Japanese Patent Application Laid-Open No. 2000-101145, the lifetime of an epitaxial wafer (compound semiconductor) used for a light emitting device is limited. Although it is considered that light is emitted in the excitation light irradiation region because it is sufficiently small (in nanoseconds), excitation light is applied to a semiconductor substrate such as an indirect transition type silicon substrate having a long lifetime (microseconds). Therefore, unless the diffusion of the excited carriers in the semiconductor substrate is taken into account, there is a problem that the accurate lifetime cannot be measured. In the conventional method of evaluating a semiconductor device disclosed in Japanese Patent Application Laid-Open No. Hei 10-135291, since the object to be measured is a compound semiconductor having a double hetero structure having a short attenuation time constant, the semiconductor device is measured in a forward direction with respect to the pn junction. By applying a bias voltage to reduce the effect of the tilt of the energy band of the semiconductor layer, the decay time constant can be obtained relatively accurately. However, in the case of a semiconductor substrate such as an indirect transition type silicon substrate having a long life time, Unless the diffusion of the excited carriers in the semiconductor substrate is taken into account, there is a problem that the decay time constant cannot be measured accurately. An object of the present invention is to accurately evaluate impurities, defects, and the like in a semiconductor substrate by quantitatively determining a lifetime of a semiconductor substrate having a long lifetime without destroying and contacting the semiconductor substrate. It is an object of the present invention to provide a semiconductor substrate quality evaluation method and a quality evaluation device therefor.

[0005]

In measuring the lifetime of a semiconductor substrate by the photoluminescence method, the present inventors have found that a semiconductor substrate having a long lifetime (several tens of microseconds to several hundreds) is used as a polished silicon substrate. μs) When a substrate is used, the attenuation of the photoluminescence light emitted from the semiconductor substrate cannot follow the intermittent frequency of the excitation light even at the commonly used intermittent frequency of the excitation light (several tens Hz to several hundreds of Hz), and the intermittent frequency of the excitation light It was considered that when the frequency was gradually increased from a low frequency to a high frequency, the photoluminescence light changed from intermittent light emission having a large fluctuation width to light emission having a small fluctuation width. The intermittent frequency dependence of the photoluminescence light was expected to be different due to the difference in the photoluminescence light decay time constant of each semiconductor substrate. In other words, it has been found that the decay time constant of the photoluminescence light can be obtained from the difference in the intermittent frequency of the excitation light when the photoluminescence light changes from intermittent light emission to continuous light emission. Then, the present inventors have considered the transient response of the photoluminescence light and derived the lifetime from the decay time constant of the photoluminescence light.

According to the first aspect of the present invention, as shown in FIG. 1, the surface of a semiconductor substrate 11 is irradiated with excitation light 13 intermittently. When the photoluminescence light 16 is attenuated by converting the intensity of the photoluminescence light 16 emitted from the photoluminescence light 16 into an electric signal and gradually increasing the intermittent frequency of the excitation light 13 to change the average intensity of the photoluminescence light 16 converted into the electric signal. This is a semiconductor substrate quality evaluation method in which a constant T is obtained, and a lifetime τ, which is an index of quality evaluation of the semiconductor substrate 11, is calculated from the equation τ = T / C (where C is a constant). According to the method for evaluating the quality of a semiconductor substrate according to the first aspect, the lifetime τ of the semiconductor substrate 11 can be quantitatively determined without breaking the semiconductor substrate 11 and without contacting the semiconductor substrate 11. The obtained lifetime τ is a value that quantitatively and accurately represents impurities and defects in the semiconductor substrate 11. This quality evaluation method is suitable for obtaining the lifetime τ of the semiconductor substrate 11 having a long lifetime τ.

According to a third aspect of the present invention, as shown in FIG. 1, a laser device 14 for irradiating a surface of a semiconductor substrate 11 with excitation light 13 and a semiconductor device provided between the laser device and the semiconductor substrate 11 are provided. A first chopper 21 for interrupting the irradiated excitation light 13 at a predetermined frequency and generating a pulse signal at the predetermined frequency; a first chopper and the semiconductor substrate 11
And a second chopper 22 capable of changing the frequency of the excitation light 13 at a frequency higher than that of the first chopper 21 and intermittently, and emitting the excitation light 13 to the semiconductor substrate 11 when the semiconductor substrate 11 is intermittently emitted. Photoluminescence light 16
, A photodetector 18 that converts the intensity of the photoluminescence light 16 introduced into the spectrometer into an electric signal, an electric signal converted by the photodetector,
A lock-in amplifier 19 that takes in and amplifies the pulse signal generated by the chopper 21 and reads an electric signal and a pulse signal amplified by the lock-in amplifier and controls the second chopper 22 to reduce the intermittent frequency of the pump light 13. A quality evaluation device for a semiconductor substrate, comprising: a controller that controls the second chopper to gradually increase the intermittent frequency of the pumping light; The decay time constant T of the photoluminescence light 16 is obtained from the change in the average intensity of the luminescence light 16, and the lifetime τ, which is the evaluation criterion of the semiconductor substrate 11, is expressed by the formula τ = T / C (where C is a constant). Is calculated from the following. In the semiconductor substrate quality evaluation apparatus according to the third aspect, similarly to the first aspect, the lifetime τ of the semiconductor substrate 11 is quantitatively determined without breaking the semiconductor substrate 11 and without contacting the semiconductor substrate 11. The obtained lifetime τ is a value that quantitatively and accurately represents impurities and defects in the semiconductor substrate 11. The quality evaluation device 12 is suitable for obtaining the lifetime τ of the semiconductor substrate 11 having a long lifetime τ.

[0008]

Embodiments of the present invention will now be described with reference to the drawings. As shown in FIG.
The quality evaluation device 12 includes a laser device 14 for irradiating the surface of the semiconductor substrate 11 with excitation light 13, a first chopper 21 provided between the laser device and the semiconductor substrate 11, a first chopper 21 A spectroscope 17 into which the photoluminescence light 16 emitted from the semiconductor substrate 11 when the irradiation of the semiconductor substrate 11 with the excitation light 13 is cut off is provided. A photodetector 18 for converting the intensity of the photoluminescence light 16 introduced into the detector into an electric signal; a lock-in amplifier 19 for receiving and amplifying the electric signal converted by the photodetector; And a controller 23 for reading the electric signal. Examples of the semiconductor substrate 11 include a polished silicon substrate and an epitaxial substrate having a long lifetime τ, and examples of the laser device 14 include a gas laser such as an argon ion laser, a solid-state laser such as YAG, and a semiconductor laser such as AlGaAs. Can be

The first chopper 21 rotates about the first axis 21 and has an opaque first disk 21c having a plurality of first small holes 21b formed on the same circumference around the first axis. First
It has a first driven gear 21d fixed to a shaft, a first drive gear 21e meshing with the first driven gear, and a first motor 21f for driving the first drive gear. The first motor 21f rotates the first disk 21c at a predetermined rotation speed, and the excitation light 13 applied to the semiconductor substrate 11 is blocked by the first disk 21c or passed through the first small hole 21b. The excitation light 13 is configured to be intermittent at a predetermined frequency. Further, the first chopper 21 is provided with a transmitter 21g that emits a pulse signal having the same frequency as the intermittent frequency of the excitation light 13 that is intermittently applied to the semiconductor substrate 11. The intermittent frequency of the excitation light 13 by the first chopper 21 is a predetermined frequency in the range of 0.5 to 10 Hz, preferably 4 to 6 Hz.

The second chopper 22 rotates about a second shaft 22a and a plurality of second choppers are arranged on the same circumference around the second shaft.
The opaque second disk 22c having the small hole 22b formed therein, the second driven gear 22d fixed to the second shaft, the second driving gear 22e meshing with the second driven gear, and the second driving gear are driven. And a second motor 22f. The second disk 22c
Is formed to have a larger diameter than the first disk 21c, and the second small holes 22b
Are formed more than the first small holes 21b. Second motor 22
f to rotate the second disk 22c by changing the rotation speed,
The excitation light 13 applied to the semiconductor substrate 11 is
The excitation light 13 is interrupted at a frequency higher than that of the first chopper 21 by changing the frequency by blocking or passing through the second small holes 22b at c.
In addition, the intermittent frequency of the excitation light 13 by the second chopper 22 is configured to be changeable in a range of 50 to 4000 Hz.
The change range of the intermittent frequency of the pumping light 13 by the second chopper 22 is set to 50 to 4000 Hz, which is higher than the intermittent frequency of the pumping light by the first chopper 21, because the upper limit of the mechanical chopper is 4000 Hz. However, in principle, if a high-frequency chopper is used, a smaller attenuation time constant can be measured.

The excitation light 13 that has passed through the second small holes 22b of the second disk 22c is reflected by the condenser mirror 24 and is irradiated on the surface of the semiconductor substrate 11. As the condenser mirror 24, a concave mirror, a plane mirror, or the like is used. Focal length 130
When a focusing mirror 24 (concave mirror) of about mm is used, the spot size (diameter) of the excitation region of the semiconductor substrate 11 is about 0.5 mm, and the focusing mirror 24 (plane mirror) having an infinite focal length is used. When used, the spot size (diameter) is about 1.5 mm.

Although the spectroscope 17 is not shown, the semiconductor substrate 11
Has an entrance-side slit for passing the photoluminescence light 16 emitted by the light-emitting device, a grating for dispersing the photoluminescence light 16 passing through the entrance-side slit, and an exit-side slit for passing the photoluminescence light 16 dispersed by the grating. The grating preferably has 600 slits / mm. Note that the photoluminescence light 1 emitted from the semiconductor substrate 11 is
6 is collected by two parallel quartz lenses 26 and 27 and then introduced into a spectroscope 17.

The lock-in amplifier 19 is configured to take in and amplify a pulse signal generated by a transmitter 21g provided in the first chopper 21 together with the electric signal converted by the photodetector 18. The electrical signal and the pulse signal amplified by the lock-in amplifier 19 are input to the control input of the controller 23, respectively.
The control output of No. 3 is the laser device 14, the first motor 21,
It is connected to a motor 22 and a display 23 (display, monitor, etc.).

A method for evaluating the quality of the semiconductor substrate 11 using the quality evaluation device 12 configured as described above will be described. First, after turning on the laser device 14, the controller 23 controls the first motor 21f to rotate the first disk 21c at a predetermined rotation speed, and further controls the second motor 22f to intermittently emit the excitation light 13. Irradiation is performed on the surface of the semiconductor substrate 11. When the semiconductor substrate 11 is irradiated with the excitation light 13 intermittently, and when the irradiation of the excitation light 13 to the semiconductor substrate 11 is interrupted, the photoluminescence light 16 emitted from the semiconductor substrate 11 emits two quartz lenses. The light is split by the spectroscope 17 through 26 and 27. The intensity of the split photoluminescence light 16 is converted into an electric signal by a photodetector 18, and the electric signal is amplified by a lock-in amplifier 19 together with a pulse signal generated by a transmitter 21 g and is supplied to a control input of a controller 23. Is entered.

Next, the controller 23 controls the second motor 22f.
Is controlled to gradually increase the intermittent frequency of the pump light 13, the photoluminescence light 16 emitted from the semiconductor substrate 11 cannot follow the intermittent cycle of the pump light 13, so that Changes to a small light emission. The controller 23 controls the photoluminescence light 1
6 (a change in the average intensity of the photoluminescence light 16 converted into an electric signal by the photodetector 18, amplified by the lock-in amplifier 19, and further input to the control input of the controller 23). An attenuation time constant T of the luminescence light 16 is obtained. Furthermore, the controller 23
Calculates the lifetime τ, which is an evaluation criterion of the semiconductor substrate 11, from the above-mentioned decay time constant T from the equation (1) τ = T / C (1) and displays the value on the display 28. The lifetime τ obtained in this manner is a value that quantitatively and accurately represents impurities and defects in the semiconductor substrate 11, and the quality evaluation method and apparatus of the semiconductor substrate 11 are based on the lifetime τ of a polished silicon substrate or the like. Long semiconductor substrate 11
Is suitable for obtaining the lifetime τ of

C in the above equation (1) is obtained by measuring the frequency response of the photoluminescence light 16 emitted from the semiconductor substrate 11 by the intermittent excitation light 13 and deriving an analytical solution of this frequency response. The decay time constant T is determined by the response measurement results and the analysis solution fitting.
Is calculated, and μ-PCD (microwave photoconductivedec
The lifetime τ of the semiconductor substrate 11 is measured by the ay) method, and is obtained by comparing the decay time constant T and the lifetime τ. C is a predetermined value in the range of (0.45 to 0.55). The reason why C is limited to a predetermined value in the range of (0.45 to 0.55) is that although C is theoretically 0.5, the C value is measured at the time of measuring the frequency response of the photoluminescence light 16 or at μ. The reason is that the deviation is caused by an experimental error generated when the lifetime τ is measured by the PCD method.

[0017]

As described above, according to the present invention, the surface of the semiconductor substrate is intermittently irradiated with the excitation light, and the photoluminescence light emitted from the semiconductor substrate when the excitation light is intermittently applied to the semiconductor substrate. The intensity is converted into an electric signal, the intermittent frequency of the excitation light is gradually increased, and the decay time constant T of the photoluminescence light is obtained from the change in the average intensity of the photoluminescence light converted into the electric signal. The lifetime τ, which is an index of evaluation, is expressed by the formula τ = T /
Since C is calculated from C (where C is a constant), the lifetime of the semiconductor substrate can be quantitatively determined without breaking the semiconductor substrate and without contacting the semiconductor substrate, and the calculated lifetime is obtained. The lifetime is a value that quantitatively and accurately represents impurities and defects in the semiconductor substrate. This quality evaluation method is suitable for determining the lifetime of a semiconductor substrate having a long lifetime.

A first chopper between the laser device and the semiconductor substrate interrupts the excitation light applied to the semiconductor substrate at a predetermined frequency, and a second chopper between the first chopper and the semiconductor substrate transmits the excitation light from the first chopper. When the photoluminescence light is attenuated at a high variable frequency, the controller controls the second chopper to gradually increase the intermittent frequency of the excitation light, and the change in the average intensity of the photoluminescence light converted into the electric signal. A constant T is obtained, and a lifetime τ, which is an evaluation criterion of a semiconductor substrate, is calculated by an equation τ = T /
If it is configured to calculate from C (where C is a constant), it is possible to quantitatively determine the lifetime of the semiconductor substrate without destroying and contacting the semiconductor substrate as described above. The obtained lifetime is a value that quantitatively and accurately represents impurities and defects in the semiconductor substrate. Further, the quality evaluation apparatus is suitable for determining the lifetime of a semiconductor substrate having a long lifetime.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a semiconductor substrate quality evaluation apparatus according to an embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 11 semiconductor substrate 12 quality evaluation device 13 excitation light 14 laser device 16 photoluminescence light 17 spectroscope 18 photodetector 19 lock-in amplifier 21 first chopper 22 second chopper 23 controller

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[Procedure amendment]

[Submission date] April 9, 2001 (2001.4.9)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0001

[Correction method] Change

[Correction contents]

[0001]

TECHNICAL FIELD The present invention relates to a silicon wafer
The present invention relates to a method and an apparatus for quantitatively evaluating the quality of a semiconductor substrate, that is, impurities, defects and the like existing in the semiconductor substrate.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0003

[Correction method] Change

[Correction contents]

On the other hand, a semiconductor layer having a band gap smaller than the p-type cladding layer and the n-type cladding layer is sandwiched between the p-type cladding layer and the n-type cladding layer, and a forward direction is provided between the p-type cladding layer and the n-type cladding layer. A method for evaluating a semiconductor device in which the decay time constant of photoluminescence light is measured based on photoluminescence light obtained by irradiating a semiconductor layer with pulsed light while applying a bias voltage (Japanese Unexamined Patent Application, First Publication No. H10-260,1992). 10-135291
issue). In this evaluation method, the decay time constant of the photoluminescence light from the light emitting intensity is calculated by subtracting the emission intensity at the time of applying a and bias voltage without irradiating the excitation light. The method for evaluating a semiconductor device configured in this manner is suitable for a semiconductor device having a pn junction, particularly a light emitting element such as an LED or a compound semiconductor laser, and the excitation light is irradiated from the intensity of the photoluminescence light when irradiated with the excitation light. By applying a bias voltage in the forward direction to the pn junction without irradiation and subtracting the intensity of the photoluminescence light in a state where the influence of the energy band inclination of the semiconductor layer is reduced, the photoluminescence light of the light emitting element is reduced. Obtain the decay time constant of As a result, even if the excitation intensity changes, the slope of the energy band hardly changes and the decay time constant of the photoluminescence light does not vary, so that the decay time constant can be measured more accurately. Accuracy can be improved, and defective factors can be detected early.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction contents]

[0008]

Embodiments of the present invention will now be described with reference to the drawings. As shown in FIG.
The quality evaluation device 12 includes a laser device 14 for irradiating the surface of the semiconductor substrate 11 with excitation light 13, a first chopper 21 provided between the laser device and the semiconductor substrate 11, a first chopper 21 A spectroscope 17 into which the photoluminescence light 16 emitted from the semiconductor substrate 11 when the irradiation of the semiconductor substrate 11 with the excitation light 13 is cut off is provided. A photodetector 18 for converting the intensity of the photoluminescence light 16 introduced into the detector into an electric signal; a lock-in amplifier 19 for receiving and amplifying the electric signal converted by the photodetector; And a controller 23 for reading the electric signal. Examples of the semiconductor substrate 11 include a polished silicon wafer and an epitaxial wafer having a long lifetime τ.
4 is a gas laser such as an argon ion laser,
Examples include a solid-state laser such as YAG and a semiconductor laser such as AlGaAs.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction contents]

The first chopper 21 rotates about a first shaft 21a and a plurality of first choppers are arranged on the same circumference around the first shaft.
Driving the first opaque first disk 21c in which the small hole 21b is formed, the first driven gear 21d fixed to the first shaft, the first driving gear 21e meshing with the first driven gear, and the first driving gear And a first motor 21f. The first motor 21f rotates the first disk 21c at a predetermined rotation speed, and the excitation light 13 applied to the semiconductor substrate 11 is blocked by the first disk 21c or passed through the first small hole 21b. The excitation light 13 is configured to be intermittent at a predetermined frequency. Further, the first chopper 21 is provided with a transmitter 21g that emits a pulse signal having the same frequency as the intermittent frequency of the excitation light 13 that is intermittently applied to the semiconductor substrate 11. The intermittent frequency of the excitation light 13 by the first chopper 21 is a predetermined frequency in the range of 0.5 to 10 Hz, preferably 4 to 6 Hz.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction contents]

The second chopper 22 rotates about a second shaft 22a and a plurality of second choppers are arranged on the same circumference around the second shaft.
The opaque second disk 22c having the small hole 22b formed therein, the second driven gear 22d fixed to the second shaft, the second driving gear 22e meshing with the second driven gear, and the second driving gear are driven. And a second motor 22f. The second disk 22c
Is formed to have a larger diameter than the first disk 21c, and the second small holes 22b
The number of formed greater than the number of the first small holes 21b. The second disk 22c is rotated at a different rotation speed by the second motor 22f, and the excitation light 13 applied to the semiconductor substrate 11 is changed to the second rotation.
By blocking or passing through the second small hole 22b by the disk 22c, the excitation light 13 is configured to be intermittent at a higher frequency than the first chopper 21 and by changing the frequency. In addition, the intermittent frequency of the excitation light 13 by the second chopper 22 is configured to be changeable in a range of 50 to 4000 Hz. The change range of the intermittent frequency of the pump light 13 by the second chopper 22 is set to 50 to 4000 Hz and the first chopper 21
Is higher than the intermittent frequency of the excitation light due to the upper limit of 4000 Hz in the mechanical chopper. However, in principle, if a high-frequency chopper is used, a smaller attenuation time constant can be measured.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction contents]

The lock-in amplifier 19 is configured to take in and amplify a pulse signal generated by a transmitter 21g provided in the first chopper 21 together with the electric signal converted by the photodetector 18. The electrical signal and the pulse signal amplified by the lock-in amplifier 19 are input to the control input of the controller 23, respectively.
Control output 3 the laser system 14, the first motor 21 f, are connected to the second motor 22 f and a display 2 8 (such as a display or monitor).

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction contents]

A method for evaluating the quality of the semiconductor substrate 11 using the quality evaluation device 12 configured as described above will be described. First, after turning on the laser device 14, the controller 23 controls the first motor 21f to rotate the first disk 21c at a predetermined rotation speed, and further controls the second motor 22f to rotate the second disk 22c to a predetermined speed. And the surface of the semiconductor substrate 11 is irradiated with the excitation light 13 intermittently. A time intermittent illumination of the semi-conductor substrate 11 of the excitation light 13, when the irradiation of the semiconductor substrate 11 of the excitation light 13 is interrupted, photoluminescence 16 two quartz emitted from the semiconductor substrate 11 Spectroscope 1 through lenses 26 and 27
It is split at 7. The intensity of the split photoluminescence light 16 is converted into an electric signal by a photodetector 18,
More transmitter 21 the electrical signal to the lock-in amplifier 19
The signal is amplified together with the pulse signal generated by g and input to the control input of the controller 23.

[Procedure amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction contents]

[0015] Next, controller 23 is the second motor 22f
To increase the rotation speed of the second disk 22c.
Accordingly, when the above-mentioned intermittent frequency of the excitation light 13 is gradually increased, the photoluminescence light 1 emitted from the semiconductor substrate 11 is increased.
6 cannot follow the intermittent cycle of the excitation light 13 and changes from intermittent light emission having a large fluctuation width to light emission having a small fluctuation width.
The controller 23 changes the average intensity of the photoluminescence light 16 (converted into an electric signal by the photodetector 18, amplified by the lock-in amplifier 19, and further transmitted to the control input of the controller 23). The decay time constant T of the photoluminescence light 16 is determined from the average intensity change). Further, the controller 23 calculates a lifetime τ, which is an evaluation criterion of the semiconductor substrate 11, from the equation (1) τ = T / C (1) from the decay time constant T, and displays the value on the display 28. . The lifetime τ obtained in this manner is a value that quantitatively and accurately represents impurities and defects in the semiconductor substrate 11, and the quality evaluation method and apparatus of the semiconductor substrate 11 are based on the lifetime τ of a polished silicon substrate or the like. Long semiconductor substrate 11
Is suitable for obtaining the lifetime τ of

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Hiroyuki Shiraki F-term (reference) in Mitsubishi Materials Silicon Co., Ltd. 1-5-1, Otemachi, Chiyoda-ku, Tokyo 2G043 AA03 CA05 EA01 FA03 HA12 JA01 KA08 KA09 LA01 NA01 2G051 AA65 AB02 AB06 BA10 BB03 BC03 CB01 CC07 CC09 CC15 4M106 AA01 AA10 BA05 CA09 CA18 CB11 CB19 DH12 DH32

Claims (4)

[Claims] A semiconductor substrate (11) is irradiated with excitation light (13) intermittently, and the semiconductor substrate (11) emits light when the excitation light (13) is irradiated on the semiconductor substrate (11) intermittently. Luminescent light (16)
Of the photoluminescence light (16) from the change in the average intensity of the photoluminescence light (16) converted to the electric signal by gradually increasing the intermittent frequency of the excitation light (13). A method for evaluating the quality of a semiconductor substrate, comprising: determining a decay time constant (T); and calculating a lifetime (τ), which is an index of the quality evaluation of the semiconductor substrate (11), from Expression (1). τ = T / C (1) where C is a constant. 2. The method according to claim 1, wherein C in the formula (1) is a predetermined value within a range of 0.45 to 0.55. 3. A laser device (14) for irradiating the surface of the semiconductor substrate (11) with excitation light (13); and a laser device provided between the laser device and the semiconductor substrate (11) for irradiating the semiconductor substrate. A first chopper (21) for interrupting the pumping light (13) at a predetermined frequency and emitting a pulse signal at the predetermined frequency; and the pumping light provided between the first chopper and the semiconductor substrate (11). The second chopper (2) capable of changing the frequency of the light (13) at a higher frequency than the first chopper (21) and intermittently.
2), the photoluminescence light (16) emitted from the semiconductor substrate during the intermittent irradiation of the excitation light (13) to the semiconductor substrate (11)
And the photoluminescence light (1) introduced into the spectroscope.
6) a photodetector (18) for converting the intensity into an electric signal, and a lock-in for taking in and amplifying the electric signal converted by the photodetector and the pulse signal generated by the first chopper (21). An amplifier (19), a controller (23) that reads the electric signal and the pulse signal amplified by the lock-in amplifier and controls the second chopper (22) to change the intermittent frequency of the pump light (13). ), The controller (23) controlling the second chopper (22) to gradually increase the intermittent frequency of the excitation light (13), The photoluminescence light converted into a signal (1
6) From the change in the average intensity of the photoluminescence light (1
6) determining a decay time constant (T) of the semiconductor substrate (11) and calculating a lifetime (τ) which is an evaluation standard of the semiconductor substrate (11) from Expression (1). Quality evaluation device. τ = T / C (1) where C is a constant. 4. The semiconductor substrate quality evaluation apparatus according to claim 3, wherein C in equation (1) is a predetermined value within a range of 0.45 to 0.55.