JP5295924B2 - Semiconductor carrier lifetime measuring apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor carrier life measuring device and method allowing measurement in a production line, and allowing more accurate measurement of the carrier life with no need of preliminary pretreatment and assumption of a diffusion coefficient as conventionally performed. <P>SOLUTION: The semiconductor carrier life measuring device A utilizes a microwave photo-conduction attenuating method. When a measured sample X of a semiconductor is in a first surface recombination velocity state, the measured sample X is irradiated with at least two kinds of lights having mutually different wavelengths by a light application section 1 and is irradiated with measuring waves by a measuring wave input/output section 2 to obtain a first difference in a time-based relative change of reflected waves or transmitted waves detected by a detection section 3, a second difference in a second surface recombination velocity state is obtained like the first difference, and the carrier life of the measured sample X is obtained based on the first difference and the second difference. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a semiconductor carrier lifetime measuring apparatus and a semiconductor carrier lifetime measuring method for measuring a carrier lifetime in a semiconductor.

  With the recent development of electronics, semiconductor products are used in various fields. Since semiconductor products are generally manufactured from a semiconductor wafer, quality control of the semiconductor wafer is important for improving the performance of the semiconductor product. One of the indexes for evaluating the quality of a semiconductor wafer is a carrier lifetime in the semiconductor. In particular, in recent years, solar cells (PV) have attracted attention as clean energy sources. In this solar cell, it is important for achieving high photoelectric conversion efficiency that carriers (electrons and holes) generated by light irradiation reach the electrode without recombination in the middle. For this reason, it is necessary to evaluate the carrier lifetime even in the semiconductor wafer for PV. By selecting the semiconductor wafer for PV which does not reach the required specification (spec) by this carrier life evaluation in the manufacturing process, the yield of solar cells can be improved, and as a result, cost reduction can also be achieved. .

  A microwave photoconductive decay method (μ-PCD method) is known as one method for measuring the carrier lifetime. This microwave photoconductive decay method generates excess carriers by irradiating light to a semiconductor to be measured (semiconductor sample, sample to be measured), and this excess carrier is recombined with a carrier lifetime determined by the physical properties of the semiconductor sample. In this method, the disappearance process is detected by the time change of the reflectance of the microwave or the time change of the transmittance. Since the generation of excess carriers increases the conductivity of the semiconductor, the microwaves irradiated to the semiconductor part (part, region) where excess carriers are generated by photoexcitation have a density of excess carriers that reflects or transmits. It changes corresponding to. This microwave photoconductive decay method measures the carrier lifetime by utilizing this phenomenon.

  In general, crystal irregularities exist on the surface of a semiconductor wafer, which causes so-called surface recombination in which carriers recombine on the semiconductor surface. For this reason, the measurement result of the carrier lifetime includes not only the carrier lifetime due to recombination inside the semiconductor wafer (bulk carrier lifetime) but also the carrier lifetime due to this surface recombination (surface carrier lifetime). Bulk carrier life is important for quality control of the semiconductor wafer, and carrier life due to surface recombination becomes a measurement error. For this reason, normally, a semiconductor sample is heat-treated before measurement, and an oxide film is formed on the surface of the semiconductor sample, so that the occurrence of the surface recombination is suppressed, or the semiconductor sample contains, for example, iodine before the measurement. By soaking, the so-called dangling bonds that cause surface recombination are passivated. Such pre-treatment requires labor and time, and the heat treatment causes the semiconductor wafer to deteriorate due to performance deterioration or chemical immersion. For this reason, a method of measuring the bulk carrier lifetime in a semiconductor wafer in a simpler manner is desired. For example, there are technologies disclosed in Patent Literature 1 and Patent Literature 2 and technology disclosed in Non-Patent Literature 1.

  In this carrier lifetime measuring method disclosed in Patent Document 1, excess carriers are injected by photoexcitation in the vicinity of the surface of a semiconductor substrate in a thermal equilibrium state, and the decay time of the excess carrier concentration is regarded as a change in conductance, and the time of the amount of reflection of microwaves. Carrier lifetime measurement method by photoexcitation method that detects and measures a change in the state, and prior to the measurement of the carrier lifetime, an insulating film is provided on the surface of the semiconductor substrate, a charge layer is formed thereon, and the semiconductor substrate Corona discharge is used to deposit positive or negative charges on the provided insulating film surface to form the charge layer.

  In the carrier lifetime measuring method disclosed in Patent Document 1, since the charge layer generated by corona discharge under the insulating layer is easily discharged, surface recombination occurs during the lifetime measurement of the semiconductor carrier. As a result, it is difficult to accurately measure the lifetime of a semiconductor carrier.

  For this reason, the semiconductor carrier lifetime measuring device disclosed in Patent Document 2 measures the reflection or transmitted wave change of a predetermined measurement wave applied to the semiconductor when the semiconductor is irradiated with pulsed light. A device for measuring a lifetime of a semiconductor carrier for measuring a lifetime of a waveguide, wherein the waveguide guides the measurement wave to a surface of the semiconductor, and is provided in or near a portion of the waveguide adjacent to the semiconductor. And a first electrode that corona discharges when a predetermined voltage is applied during measurement of the reflected wave or transmitted wave of the measurement wave.

  Further, in the lifetime measurement method disclosed in Non-Patent Document 1, at least two types of pulsed light having different wavelengths and different penetration lengths are irradiated onto a semiconductor, thereby generating photoexcited carriers in the semiconductor, and thereafter photoexcited carriers. The relative change in the reflected wave or the transmitted wave that decreases by recombination and the difference between them are detected. According to the lifetime measurement method disclosed in Non-Patent Document 1, regardless of the surface recombination velocity on the wafer surface, carrier annihilation on the surface and carrier annihilation on the bulk can be analytically divided. Non-Patent Document 1 shows that the bulk carrier lifetime can be extracted.

JP 07-240450 A JP 2004-006756 A

J. Appl. Phys. Vol. 69, (9), 6495 (1991)

  By the way, the semiconductor carrier measuring device disclosed in Patent Document 2 does not require a pre-processing step such as heating oxide film formation or the like, and maintains the charged state in the measurement wave irradiation portion of the semiconductor during measurement. This is advantageous in terms of points, but if the charge state changes due to the discharge during measurement, a measurement error occurs. For this reason, it takes time to stabilize the charged state, and the semiconductor carrier disclosed in Patent Document 2 is selected during the manufacturing process, that is, in order to select the semiconductor wafer by measuring the carrier life in the manufacturing line. The measuring device is not suitable. For these reasons, there is room for improvement in the semiconductor carrier measurement device disclosed in Patent Document 2.

When the surface recombination velocity is S and the diffusion coefficient is D, the value obtained from the measurement result of the lifetime measurement method disclosed in Non-Patent Document 1 is S / D. The lifetime measurement method disclosed in (1) determines the surface recombination velocity S by assuming D = 30 cm ² / s, and then determines the carrier lifetime. However, when the electron and hole carrier concentrations are n and p, respectively, and the electron and hole diffusion coefficients are Dn and Dp, respectively, the actual diffusion coefficient is (n + p) / (n / Dp + p / Dn) It depends on the carrier concentration and conductivity type, and is not a constant. Furthermore, when the surface recombination velocity S is relatively large, such as when no pretreatment is performed in advance, the measured (observed) carrier lifetime is small compared to the bulk carrier lifetime, and The change also becomes smaller and the measurement error becomes larger.

  The present invention has been made in view of the above circumstances, and its purpose is to enable measurement of carrier life even in the production line, and to determine the value of the diffusion coefficient without performing prior pretreatment as in the prior art. It is an object to provide a semiconductor carrier lifetime measuring apparatus and a semiconductor carrier lifetime measuring method capable of measuring the carrier lifetime more accurately than before without assuming it.

  As a result of various studies, the present inventor has found that the above object is achieved by the present invention described below. That is, a semiconductor carrier lifetime measuring apparatus according to one aspect of the present invention includes a light irradiation unit that irradiates a measurement target semiconductor with at least two types of light having different wavelengths, and irradiates the measurement target semiconductor with a predetermined measurement wave. A measurement wave irradiation unit, a detection unit that detects a reflected wave of the measurement wave reflected by the semiconductor to be measured or a transmitted wave of the measurement wave that has passed through the semiconductor of the measurement target, and a semiconductor to be measured In the first surface recombination velocity state, the light irradiation unit irradiates the measurement target semiconductor with the at least two types of light and the measurement wave irradiation unit applies the measurement wave to the measurement target semiconductor. The first difference in the temporal relative change of the reflected wave or the transmitted wave that has been irradiated and detected by the detection unit, and the semiconductor to be measured is in the first surface recombination velocity state. When the second surface recombination velocity state is different from the above, the at least two types of light are irradiated onto the measurement target semiconductor by the light irradiation unit, and the measurement wave is irradiated to the measurement target by the measurement wave irradiation unit. A calculation unit that obtains a carrier lifetime in the semiconductor to be measured based on a second difference in time-dependent relative change of the reflected wave or the transmitted wave that is irradiated on the semiconductor and detected by the detection unit. Features.

  The semiconductor carrier lifetime measurement method according to another aspect of the present invention includes a light irradiation step of irradiating a semiconductor to be measured with at least two types of light having different wavelengths, and a predetermined measurement wave on the semiconductor to be measured. A measurement wave irradiation step of irradiating the measurement object, a detection step of detecting a reflected wave of the measurement wave reflected by the semiconductor of the measurement object or a transmission wave of the measurement wave transmitted through the semiconductor of the measurement object, In the case where the semiconductor is in the first surface recombination velocity state, the at least two kinds of light are irradiated on the semiconductor to be measured by the light irradiation step, and the measurement wave is irradiated on the measurement target by the measurement wave irradiation step. A first difference in a temporal relative change of the reflected wave or the transmitted wave detected by the detecting step after being irradiated on the semiconductor, and the semiconductor to be measured is the first surface When the second surface recombination velocity state is different from the coupling velocity state, the at least two kinds of light are irradiated to the measurement target semiconductor by the light irradiation step, and the measurement wave is emitted by the measurement wave irradiation step. A calculation step of obtaining a carrier lifetime in the semiconductor to be measured based on a second difference of the relative change in time of the reflected wave or the transmitted wave that has been irradiated to the semiconductor to be measured and detected in the detection step; It is characterized by providing. In another aspect, in the semiconductor carrier lifetime measurement method described above, preferably, the carrier lifetime is obtained based on detection results of the semiconductor to be measured in two states of the first and second surface recombination velocity states. Therefore, the calculation step obtains a carrier lifetime in the semiconductor to be measured by obtaining a ratio between a diffusion coefficient and a surface recombination velocity in the semiconductor to be measured based on the first difference and the second difference. That is.

    Then, in the semiconductor carrier lifetime measurement method according to another aspect of the present invention, when the measurement target semiconductor is in the first surface recombination velocity state, while irradiating the measurement target semiconductor with the predetermined measurement wave, By irradiating at least two types of light having different wavelengths, the time relative of the reflected wave of the measurement wave reflected by the semiconductor to be measured or the transmitted wave of the measurement wave that has passed through the semiconductor of the measurement object A first difference measurement step for measuring a first difference of change, and a first difference measurement step measured by the first difference measurement step when the surface recombination velocity in the semiconductor to be measured is S and the diffusion coefficient is D. Based on the first S / D calculation step for obtaining the S / D in the first surface recombination velocity state based on the difference, and the S / D in the first surface recombination velocity state obtained in the first S / D calculation step. Diffusion coefficient And a surface recombination velocity state changing step of changing the semiconductor to be measured from the first surface recombination velocity state to a second surface recombination velocity state different from the first surface recombination velocity state. And when the measurement target semiconductor is in a second surface recombination velocity state, irradiating the measurement target semiconductor with at least two types of light having different wavelengths while irradiating the measurement target semiconductor, A second difference measuring step of measuring a second difference of a reflected wave of the measurement wave reflected by the measurement target semiconductor or a temporal relative change of the transmission wave of the measurement wave transmitted through the measurement target semiconductor; A second S / D calculation step for obtaining S / D in the second surface recombination velocity state based on the second difference measured in the second difference measurement step, and a second surface obtained in the second S / D calculation step A surface recombination rate calculating step for obtaining a surface recombination rate S based on S / D in a bonding rate state, and a semiconductor to be measured based on the surface recombination rate S obtained in the surface recombination rate calculating step And a lifetime calculation step for obtaining a carrier lifetime.

  In the semiconductor carrier lifetime measuring apparatus and the semiconductor carrier lifetime measuring method configured as described above, when the semiconductor to be measured is in the first surface recombination velocity state, at least two types of light are irradiated onto the semiconductor to be measured. A measurement wave is applied to the semiconductor to be measured to determine a first difference in a temporal relative change of the reflected wave or the transmitted wave, and the second surface re-differentiation of the semiconductor to be measured is different from the first surface recombination velocity state. In the case of the coupling speed state, at least two kinds of light are irradiated onto the measurement target semiconductor and the measurement wave is irradiated onto the measurement target semiconductor, and the second relative change in time of the reflected wave or the transmitted wave is obtained. The difference is obtained, and the carrier lifetime in the semiconductor to be measured is obtained based on the first difference and the second difference.

  Therefore, the semiconductor carrier lifetime measuring apparatus and the semiconductor carrier lifetime measuring method having such a configuration need only obtain the first difference and the second difference as described above, and can therefore measure the carrier lifetime in the production line. In addition, it is not necessary to perform pre-processing as in the prior art, and the carrier life can be measured with higher accuracy than in the prior art. Since the first difference and the second difference need only be obtained in this way, it is not necessary to assume the value of the diffusion coefficient in the semiconductor to be measured, and the carrier lifetime can be measured more accurately than in the past. .

  According to another aspect, in the above-described semiconductor carrier lifetime measuring apparatus, it is preferable that the wavelength difference between the at least two types of light is large. Therefore, the at least two types of light are first light having wavelengths in the infrared region. Preferably, the second light has a wavelength in the ultraviolet region, or the at least two types of light are first light having a wavelength in the infrared region and third light having a wavelength in the visible light region. preferable.

  When the semiconductor is irradiated with light, this light (incident light) penetrates into the semiconductor, and the penetration length depends on the wavelength of the incident light. According to this configuration, since the wavelength difference between the at least two types of light is large, the penetration length difference between them is also large. As a result, the reflected wave of the measurement wave or the transmission of the measurement wave by each of the at least two types of light. It becomes possible to greatly change the ratio of the influence of surface recombination included in the wave. Therefore, according to this configuration, the carrier lifetime can be measured with higher accuracy than in the past.

  Here, the penetration length is the distance (depth) from the surface irradiated with light to the point where the light intensity of the light becomes 1 / e of the incident intensity. Usually, the longer the wavelength of the light, the more the penetration occurs. The length becomes longer (becomes larger and deeper).

  Further, in another aspect, in the above-described semiconductor carrier lifetime measuring apparatus, a surface recombination velocity state change that changes the semiconductor to be measured from the first surface recombination velocity state to the second surface recombination velocity state. It further has a section.

  According to this configuration, the surface recombination speed state changing unit can change the surface recombination speed state in the semiconductor to be measured from the first state to the second state.

  According to another aspect, in the above-described semiconductor carrier lifetime measuring apparatus, the surface recombination velocity changing unit applies a corona discharge to a measurement wave irradiation region of a semiconductor irradiated with a measurement wave by the measurement wave irradiation unit. It is a corona discharge imparting part.

  According to this configuration, the second recombination velocity state can be realized by corona discharge. And since the 2nd surface recombination speed state is implement | achieved by corona discharge, the physicochemical property in the semiconductor of a measuring object can be returned by complete | finishing provision of corona discharge.

  In another aspect, in the above-described semiconductor carrier lifetime measuring apparatus, the semiconductor to be measured is in a state where a natural oxide film is provided as the first surface recombination rate state.

  Prior to use, a semiconductor wafer usually has a natural oxide film formed on its surface through a cleaning process that removes contamination such as dirt. According to this configuration, since the natural oxide film exposed by this cleaning process is brought into the first surface recombination rate state, the process for realizing the first surface recombination rate state can also be used as this cleaning process. It becomes possible to reduce man-hours.

  According to another aspect, the above-described semiconductor carrier lifetime measuring apparatus further includes a power generation light irradiation unit that irradiates the measurement target semiconductor with light for power generation.

  According to this configuration, since the power generation light irradiation unit is provided, it is possible to measure the actual characteristics of the measurement target semiconductor in a state where light is irradiated to generate power with higher accuracy.

  The semiconductor carrier lifetime measuring apparatus and the semiconductor carrier lifetime measuring method according to the present invention enable the carrier lifetime to be measured even in the production line, and assume the value of the diffusion coefficient without performing prior pretreatment as in the prior art. Therefore, the carrier lifetime can be measured with higher accuracy than in the past.

It is a figure which shows the surface recombination dependence of the time change of the relative output in the reflected wave of a measurement wave about two each light from which a wavelength mutually differs. It is a figure which shows the time change of the relative output difference of the reflected wave of the measurement wave in two each light from which a wavelength mutually differs. It is a figure which shows the structure of the semiconductor carrier lifetime measuring apparatus of embodiment. It is a flowchart which shows an example of operation | movement of the semiconductor carrier lifetime measuring apparatus of embodiment. It is a flowchart which shows operation | movement of the semiconductor carrier lifetime measuring apparatus in the case of calculating | requiring a diffusion coefficient. It is a figure which shows the time change of the relative output of a reflected measurement wave about two each light from which a wavelength mutually differs in an analysis example. It is a figure which shows the time change of the relative output difference of the reflected measurement wave in two each light from which a wavelength mutually differs in the analysis example. It is a figure which shows the relationship between the diffusion coefficient in the case of S / D = 4000, and a bulk carrier lifetime.

  Hereinafter, an embodiment according to the present invention will be described with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted suitably. Further, in this specification, when referring generically, it is indicated by a reference symbol without a suffix, and when referring to an individual configuration, it is indicated by a reference symbol with a suffix.

  First, the measurement principle in the carrier lifetime measuring apparatus according to the present embodiment will be described. FIG. 1 is a diagram showing the surface recombination dependence of the temporal change of the relative output in the reflected wave of the measurement wave for each of two lights having different wavelengths. The horizontal axis in FIG. 1 is the elapsed time expressed in μs (microseconds) with the origin at the end of each light irradiation, and the vertical axis is the relative output (the reflected wave relative intensity of the measurement wave). . In FIG. 1, the surface recombination velocity S is 20 (solid line), 100 (dashed line), 1000 (dashed line), and 10000 for infrared light (thick line) at a wavelength of 904 nm and ultraviolet light (thin line) at a wavelength of 349 nm, respectively. For each case of (two-dot chain line), the time change of the relative output in the reflected wave of the measurement wave is shown. Here, δ is defined by Equation 4 described later. FIG. 2 is a diagram showing a change over time in the relative output difference of the reflected wave of the measurement wave in each of two lights having different wavelengths. The horizontal axis in FIG. 2 is the same as the horizontal axis in FIG. 1, and the vertical axis is the relative output difference δ of the reflected wave of the measurement wave in each light. For each case where the surface recombination velocity S is 20 (solid line), 100 (dashed line), 1000 (one-dot chain line), and 10,000 (two-dot chain line), the relative reflected wave of the measurement wave in each of the two lights having different wavelengths from each other The time change of the output difference is shown.

  In the microwave photoconductive decay method, the intensity (relative output) in the reflected wave of the measurement wave decreases sequentially with time as shown in FIG. As shown in FIG. 1, the profile depends on the wavelength of light applied to the semiconductor to be measured, and further depends on the surface recombination velocity S. In particular, when the surface recombination velocity S is 1000 or 10000, the change is relatively large for each light.

For such a measurement result, when the carrier lifetime actually observed in the measurement by the microwave photoconductive decay method is τ1, the bulk carrier lifetime is τb, and the diffusion coefficient is D, Equation 1 is established.
1 / τ1 = 1 / τb + α ² × D (1)
Here, α is given as the lowest order solution of the characteristic equation 2 that defines α. Note that d is the thickness of the semiconductor in the region irradiated with light.
(Α × D / S) = cot (α × d / 2) (2)

Therefore, when the surface recombination rate states are different, the carrier lifetime actually observed in the measurement in the first surface recombination rate state is τ11, and α in this case is α1, and the first surface recombination rate is In the second surface recombination velocity state different from the state, when the carrier lifetime actually observed in the measurement is τ12 and α in this case is α2, Equations 1a and 1b hold.
1 / τ11 = 1 / τb + α1 ² × D (1a)
1 / τ12 = 1 / τb + α2 ² × D (1b)

Therefore, by erasing the diffusion coefficient D from the two expressions 1a and 1b, expression 3 is obtained, and the bulk carrier lifetime τb is obtained without depending on the diffusion coefficient D.
τb = (α1 ² −α2 ² ) / (α1 ² / τ12−α2 ² / τ11) (3)

  Based on such a measurement principle, the carrier lifetime measuring apparatus according to the present embodiment can determine the bulk carrier lifetime τb by calculating τ11, τ12, α1, and α2.

  Here, τ11 and τ12 are values actually observed in the measurement, while α1 and α2 are values given by Equation 2. According to Equation 2, since the semiconductor thickness d can be measured, α1 and α2 are obtained by obtaining D / S. By the way, S / D, which is the reciprocal of this D / S, is a value correlated with the difference δ in time relative change of the reflected wave of the measurement wave in each light, and this difference δ in time relative change. S / D can be obtained based on the above. In addition, S / D is evaluated by the excitation measurement of 2 wavelengths so that the detail may mention later using Formula 4 etc. As shown in FIG. 2, the difference δ in relative change with time depends on the surface recombination velocity, but becomes a substantially constant value as time elapses. Therefore, α1 and α2 can also be obtained by obtaining the difference δ of the temporal relative change.

  In addition, in the evaluation of semiconductors, in addition to the bulk carrier lifetime τb, it is also important to evaluate the surface recombination velocity S indicating the carrier lifetime on the surface. This S can be obtained by multiplying (S / D) by D.

  Next, the carrier lifetime measuring apparatus according to this embodiment will be described more specifically. FIG. 3 is a diagram illustrating a configuration of the semiconductor carrier lifetime measuring apparatus according to the embodiment. FIG. 3A is a diagram showing the overall configuration, and FIG. 3B is a partially enlarged view showing the tip portion of the waveguide antenna.

  As shown in FIG. 3A, for example, the semiconductor carrier lifetime measuring apparatus A of the present embodiment includes a light irradiation unit 1, a measurement wave input / output unit 2, a detection unit 3, a control unit 4, and a discharge unit. 5.

  The light irradiation unit 1 is an apparatus for emitting at least two types of light having different wavelengths to a semiconductor wafer (sample to be measured) X such as a silicon wafer to be measured, in order to make the penetration lengths different from each other. . In the semiconductor carrier lifetime measuring apparatus A of the present embodiment, the light irradiation unit 1 is configured to emit two different types of light, as shown in FIG. A first light source unit 11-1 that emits first light having a first wavelength according to the control of the control unit 4, and the first light emitted from the first light source unit 11-1 is directed toward the sample X to be measured, and its optical path is changed. A first mirror 12-1 that bends about 90 degrees and a second mirror that bends the optical path of the second light emitted from the second light source section 11-2 toward the sample X to be measured according to the control of the control section 4 by about 90 degrees. 12-2.

  The first and second light source units 11-1 and 11-2 may be, for example, a light source device including a lamp and a wavelength filter, but in this embodiment, a laser beam that can obtain a relatively large output. And a laser light source device that emits light. The first light and the second light are monochromatic lights, and the wavelength difference is larger (the gap is wider) so that a larger penetration length difference (penetration length difference at a wider interval) occurs. Preferably, for example, the first light source unit 11-1 is a device that emits laser light having a predetermined wavelength in the infrared region, that is, infrared laser light, and the second light source unit 11-2 is a laser having a predetermined wavelength in the ultraviolet region. It is a device that emits light, that is, ultraviolet laser light. The second light source unit 11-2 may be a device that emits laser light having a predetermined wavelength in the visible light region, that is, visible light laser light. Each wavelength of the 1st and 2nd light source parts 11-1 and 11-2 is suitably selected according to the kind of sample X to be measured, for example. For example, in the case where the sample X to be measured is a silicon wafer, each of the first and second light source units 11-1 and 11-2 is considered in addition to the above point of view from the viewpoint of improving the efficiency of light excitation and reducing the cost of the light source 11. The wavelength is preferably a combination of 904 nm and 349 nm, or a combination of 904 nm and 523 nm. The first and second lights generate carriers (electrons and holes) by photoexcitation in the sample by irradiating the sample to be measured, and the semiconductor carrier lifetime measuring apparatus A uses the generated carriers. Therefore, it is preferable that the first and second lights shift from the lighting state to the extinguishing state in a stepped manner. In this embodiment, for example, pulsed light, more specifically, Is a pulsed laser beam.

  The first and second mirrors 12-1 and 12-2 are configured such that the second mirror 12-2 transmits the first light, and the first light whose optical path is bent by the first mirror 12-1 is the first light. Although it may be arranged to reach the sample to be measured via the two mirrors 12-2, in the present embodiment, for example, the first optical path of the first light whose optical path is bent by the first mirror 12-1 It arrange | positions so that the 2nd optical path of the 2nd light bent by the 2nd mirror 12-2 may cross | intersect the light irradiation surface (light irradiation area | region) of the to-be-measured sample X, and may become V shape.

  The measurement wave input / output unit 2 is an apparatus for injecting a predetermined measurement wave to the light irradiation surface of the sample X to be measured and emitting a measurement wave that has received a predetermined interaction with the sample X to be measured. This corresponds to an example of a wave irradiation unit. In the semiconductor carrier lifetime measuring apparatus A of the present embodiment, the measurement wave input / output unit 2 includes a measurement wave generation unit 21, a waveguide antenna 22, an E-H tuner 23, as shown in FIG. A waveguide 24 and a circulator 25 are provided.

  The measurement wave generation unit 21 is a device that generates the predetermined measurement wave according to the control of the control unit 4. In the semiconductor carrier lifetime measuring apparatus A of the present embodiment, the predetermined measurement wave may be an electromagnetic wave in order to take out the change in the conductivity of the semiconductor that occurs during the generation and disappearance process of the carrier by the change in the intensity of the measurement wave. In the embodiment, it is a microwave, and the measurement wave generating unit 21 includes a microwave oscillator that generates a microwave. The measurement wave generator 21 is connected to one terminal of the circulator 25, and the measurement wave radiated from the measurement wave generator 21 is incident on the circulator 25.

  The circulator 25 has three or more terminals (ports), and irreversibly outputs the input of one terminal to the other terminals cyclically. An optical element that includes a third terminal, emits a measurement wave incident on the first terminal to the second terminal, and emits a measurement wave incident on the second terminal to the third terminal. The first terminal of the circulator 25 is connected to the measurement wave generating unit 21, the second terminal is connected to the waveguide 24, and the third terminal is connected to the measurement wave detecting unit 31.

  The waveguide 24 is a member that forms a propagation path for guiding a measurement wave. The second terminal of the circulator 25 is connected to one end of the waveguide 24 and the waveguide antenna 22 is connected to the other end. In the present embodiment, since the measurement wave is a microwave, the waveguide 24 is a microwave waveguide.

  The waveguide antenna 22 radiates the measurement wave propagating through the waveguide 24 to the sample to be measured, and receives the measurement wave interacting with the sample to be measured and guides it to the waveguide 24. It is. The waveguide antenna 22 is disposed along the normal direction of the sample to be measured, and has one end connected to the waveguide 24 and the other end provided with an opening 22a. The opening 22a is an opening for radiating the measurement wave to the sample to be measured and receiving the measurement wave that has interacted with the sample to be measured. In addition, an opening 22 b for guiding the first and second light radiated from the light irradiation unit 1 into the waveguide antenna 22 is provided at one end of the waveguide antenna 22. In the present embodiment, since the measurement wave is a microwave, the waveguide antenna 22 is a microwave antenna.

  The E-H tuner 23 is interposed in the waveguide 24 between the circulator 25 and the waveguide antenna 22, and the measurement wave detector 31 detects the measurement wave that has interacted with the sample to be measured better. It is a device that adjusts the magnetic field and electric field of the measurement wave so that it can be performed.

  The detection unit 3 is a device that detects a measurement wave that has interacted with the sample to be measured, and includes, for example, a measurement wave detection unit 31 that detects the intensity of the measurement wave that has interacted with the sample X to be measured. Composed. In the present embodiment, since the measurement wave is a microwave, the measurement wave detection unit 31 includes a microwave detector.

  The control unit 4 is a device that performs overall control of the semiconductor carrier lifetime measuring device A, and includes, for example, a microcomputer including a macro processor and a memory. The control unit 4 includes a calculation unit 41 that calculates the carrier lifetime based on the intensity of the measurement wave that is detected by the measurement wave detection unit 31 and that interacts with the sample X to be measured. For example, the calculation unit 41 is functionally executed by executing a carrier lifetime calculation program that calculates the carrier lifetime based on the intensity of the reflected wave (reflection measurement wave) of the measurement wave detected by the measurement wave detection unit 31. The first state calculation unit 411, the second state calculation unit 412, the life calculation unit 413, the diffusion coefficient storage unit 414, and the δ-S / D table storage unit 415 are provided.

  When the sample X to be measured is in the first surface recombination velocity state, the first state calculation unit 411 irradiates the sample X with the first and second lights by the light irradiation unit 1 and inputs and outputs measurement waves. The measurement wave is irradiated onto the sample X to be measured by the unit 2 and the first difference of the temporal relative change in the reflected wave of the measurement wave detected by the detection unit 3 is obtained. More specifically, in the present embodiment, the first state calculation unit 411 obtains a first difference in the temporal relative change, and based on the obtained first difference, in the first surface recombination velocity state. S / D is obtained, and the diffusion coefficient D is obtained based on the obtained S / D in the first surface recombination velocity state. The obtained diffusion coefficient D is stored in the diffusion coefficient storage unit 414 for use in the next measurement of the same type of sample X to be measured.

  The second state calculation unit 412 is configured so that the first and second light beams are measured by the light irradiation unit 1 when the sample X to be measured is in a second surface recombination velocity state different from the first surface recombination velocity state. X is irradiated with the measurement wave by the measurement wave input / output unit 2 and the second difference of the temporal relative change in the reflected wave of the measurement wave detected by the detection unit 3 is obtained. is there. More specifically, in the present embodiment, the second state calculation unit 412 calculates the second difference in the temporal relative change, and in the second surface recombination velocity state based on the calculated second difference. The S / D is obtained, and the surface recombination velocity S is obtained based on the obtained S / D in the second surface recombination velocity state and the diffusion coefficient D obtained by the first state calculation unit 411. .

  The lifetime calculator 413 calculates the bulk carrier lifetime τb based on the surface recombination velocity S calculated by the second state calculator 412.

  The diffusion coefficient storage unit 414 stores the diffusion coefficient D obtained by the first state calculation unit 412.

The δ-S / D table storage unit 415 stores a δ-S / D table. The δ-S / D table is a so-called look-up table showing the correspondence between δ values and S / D values, and is obtained and created in advance, for example, by simulation. As shown in Equation 4, the difference δ in time relative change is the first light (long wavelength) with respect to the reflected measurement wave intensity detected by the measurement wave detector 31 and irradiated with the second light (short wavelength light). It is the natural logarithm of the reflected measurement wave intensity due to irradiation of light.
δ = ln ((first light (long wavelength light) reflected measurement wave intensity) / (second light (short wavelength light) reflected measurement wave intensity)) (4)

  The discharge unit 5 is a device for changing the surface recombination velocity of the sample X to be measured from the first surface recombination velocity state to the second surface recombination velocity state according to the control of the control unit 4. Is a device for bringing the surface of the surface into at least two different surface recombination speed states, and corresponds to an example of a surface recombination speed changing unit. In this embodiment, for example, the discharge unit 5 generates a corona discharge, and the corona discharge is applied to the measurement wave irradiation region (light irradiation region) of the sample X to be measured that is irradiated with the measurement wave by the measurement wave input / output unit 2. It is a corona discharge generator to be applied, and corresponds to an example of a corona discharge application unit. For example, as shown in FIG. 3A, the discharge unit 5 is a first corona wire 51 that is a first electrode that corona discharges by applying a high voltage in the vicinity of the opening 22 a of the waveguide antenna 22. And a second electrode that corona discharges by applying a high voltage in the vicinity of the back surface (back surface region) of the sample X to be measured facing the measurement wave irradiation region of the sample X to be measured irradiated with the measurement wave. 2 corona wires 52, a power source 53 for generating the high voltage, and a second corona wire 52 in the vicinity of the back surface region in order to supply the high voltage to the first and second corona wires 51 and 52, respectively. And an attachment member 54 to be attached.

  The first and second corona wires 51 and 52 are, for example, tungsten wires having a wire diameter of 0.1 mm. In FIG. 3 (B), the waveguide antenna 22 is, for example, a rectangular tube, a part of each of the two opposing surfaces of the opening 22a is cut out, and a predetermined part is formed in each of the cut out parts. An insulator 51a is provided. The first corona wire 51 is attached so as to cross the center of the opening 22a across the two opposing insulators 51a (FIG. 3B shows the insulator 51a). Only one is shown). Further, the first corona wire 51 is connected to the power supply unit 53 by a connection line 51b, whereby the first corona wire 51 and the waveguide antenna 22 are insulated. The second corona wire 52 is similarly insulated and attached to the attachment member 54. Further, in order to place the sample X to be measured between the first corona wire 51 and the second corona wire 52, a support member (not shown) that supports the sample X to be measured is provided. With this configuration, the corona discharge generated by applying a predetermined voltage by the power supply unit 53 to the electrodes of the first and second corona wires 51 and 52 provided so as to be close to the sample X to be measured. Is applied to the sample X to be measured.

  The semiconductor carrier lifetime measuring apparatus A having such a configuration measures the semiconductor bulk carrier lifetime τb by operating as follows, for example. FIG. 4 is a flowchart illustrating an example of the operation of the semiconductor carrier lifetime measuring apparatus according to the embodiment. FIG. 5 is a flowchart showing the operation of the semiconductor carrier lifetime measuring apparatus when obtaining the diffusion coefficient. FIG. 6 is a diagram illustrating a temporal change in the relative output of the reflected measurement wave for each of two lights having different wavelengths from each other in the analysis example. The horizontal axis in FIG. 6 is the elapsed time expressed in microseconds, and the vertical axis is the relative output (the reflected wave relative intensity of the measurement wave). The intensity of the reflected measurement wave when irradiated with light having a wavelength in the infrared region is indicated by a thick line (YA1 (IR)), and the intensity of the reflected measurement wave when irradiated with light having a wavelength in the ultraviolet region is indicated by a thick line (YA1 (UR )). FIG. 7 is a diagram illustrating a temporal change in the relative output difference of the reflected measurement wave in each of the two lights having different wavelengths in the analysis example. The horizontal axis in FIG. 7 is the same as the horizontal axis in FIG. 6, and the vertical axis is the relative output difference δ of the reflected wave of the measurement wave in each light. FIG. 8 is a diagram showing the relationship between the diffusion coefficient and the bulk carrier lifetime when S / D = 4000. The horizontal axis in FIG. 8 is the diffusion coefficient D expressed in units of cm / s2, and the vertical axis is the bulk carrier lifetime τb expressed in units of s (seconds).

  In FIG. 4, first, dirt, surface damage, etc. on the surface of a semiconductor wafer to be measured are removed in advance by, for example, so-called chemical etching (cleaning process), and a natural oxide film is applied (S11). The state to which the natural oxide film is applied is the first surface recombination velocity state. Then, the cleaned semiconductor wafer is placed on the support member as the sample X to be measured, and is set at a predetermined measurement position sandwiched between the first corona wire 51 and the second corona wire 52.

  Subsequently, the S / D when the sample X to be measured is in the first surface recombination velocity state is obtained, and the diffusion coefficient D is obtained based on the obtained S / D (S12).

  More specifically, the measurement wave input / output unit 2 irradiates the measurement wave irradiation region (light irradiation region) of the sample X to be measured and the measurement wave reflected by the sample X to be measured is controlled by the control unit 4. The detection unit 3 detects the detection result, and the detection result is output from the detection unit 3 to the control unit 4. More specifically, the measurement wave generator 21 generates a measurement wave according to the control of the controller 4, and the generated measurement wave is incident on the first terminal of the circulator 25. The measurement wave incident from the first terminal exits from the second terminal of the circulator 25, enters the waveguide 24, and propagates through the waveguide 24. The measurement wave propagating in the waveguide 24 is guided in order to irradiate the measurement wave irradiation region of the sample X to be measured, by adjusting the electric field and magnetic field via the EH tuner 23 provided in the middle. The light is emitted from the opening 22a of the tube antenna 22 toward the measurement wave irradiation region. Then, the measurement wave (reflection measurement wave) reflected by the sample X to be measured is incident from the opening 22 a of the waveguide antenna 22 and received by the waveguide antenna 22. The reflected measurement wave propagates through the waveguide 24 via the EH tuner 23 and is incident on the second terminal of the circulator 25. The reflected measurement wave incident from the second terminal is emitted from the third terminal of the circulator 25, is incident on the detection unit 3, and its intensity is detected by the measurement wave detection unit 31 of the detection unit 3. The detected intensity of the reflected measurement wave is output from the measurement wave detection unit 31 of the detection unit 3 to the calculation unit 41 of the control unit 4.

  On the other hand, under the control of the control unit 4, the light irradiation unit 1 irradiates the light irradiation region (measurement wave irradiation region) of the sample X to be measured in a time-sharing manner. More specifically, first, firstly, the first light source unit 11-1 emits the first light of the pulsed laser light according to the control of the control unit 4, and the emitted first light is the first mirror. The optical path is bent at 12-1, enters the opening 22 b of the waveguide antenna 22, propagates through the waveguide antenna 22, and irradiates the light irradiation region of the sample X to be measured. The light is emitted from the opening 22a toward the light irradiation region. Next, secondly, the second light source unit 11-2 emits the second light of the pulse laser beam in accordance with the control of the control unit 4, and the emitted second light is transmitted by the second mirror 12-2. The optical path is bent, enters the opening 22 b of the waveguide antenna 22, propagates through the waveguide antenna 22, and irradiates the light irradiation region of the sample X to be measured. To the light irradiation region. Note that the irradiation order of the first light and the second light may be opposite to the above.

  As a result, when the measurement sample X is irradiated with the first light when the measurement target X is irradiated with the first light, the intensity change of the reflected measurement wave due to the first light is transmitted via the measurement wave detector 31. If the sample X is irradiated with the measurement wave when the measurement object 41 is irradiated with the second light, the intensity change of the reflected measurement wave due to the second light is measured. The data is taken into the calculation unit 41 via the wave detection unit 31. Normally, as shown in FIG. 5, the measurement wave is irradiated to the sample X to be measured (S21), and the first light (or the second light) of the pulse laser beam is irradiated while the measurement wave is irradiated to the sample X to be measured. As a result, the intensity change of the reflected measurement wave immediately after irradiation (immediately after extinction) of the first light (or second light) of the pulse laser beam is measured (S22), and the measurement sample X is irradiated with the measurement wave. However, by irradiating the second light (or the first light) of the pulse laser light, the intensity change of the reflected measurement wave immediately after the irradiation of the second light (or the first light) of the pulse laser light (immediately after the light is turned off) is measured. (S23). Then, since the wavelengths of the first and second light are different from each other, their penetration lengths into the sample X to be measured are also different from each other. As a result, each reflected measurement wave by irradiation of the first and second lights having different penetration lengths is obtained. Can be obtained.

  For example, as shown in FIG. 6, the intensity of the reflected measurement wave decreases with the passage of time, and eventually the carrier becomes in a thermal equilibrium state and becomes substantially constant. In the process of decreasing the reflected measurement wave intensity, the reduction rate (reduction speed, reduction amount per unit time) is relatively large in the initial stage and decreases with time. Further, the temporal intensity change of the reflected measurement wave due to the first infrared laser beam (IR) is smaller than the temporal intensity change of the reflected measurement wave due to the second ultraviolet laser beam (UV). Then, as shown in FIG. 7, the difference δ between the intensity of the reflected measurement wave by the first infrared laser beam (IR) and the intensity of the reflected measurement wave by the second ultraviolet laser beam (UV) at each time point. Decreases with the passage of time and eventually becomes substantially constant. 6 and 7 are analysis examples in the case where the sample X to be measured is a semiconductor wafer after cleaning with hydrofluoric acid, the surface recombination velocity S is 9000 cm / s, and the bulk carrier lifetime τb is 79 μs.

  Subsequently, the first state calculation unit 411 of the calculation unit 41 calculates a δ value based on the output of the measurement wave detection unit 31, calculates a value at which the δ value becomes substantially constant as described above, and δ -By referring to the δ-S / D table of the S / D table storage unit 415, the S / D corresponding to the value at which the δ value becomes substantially constant is obtained (S24).

  Subsequently, the first state calculation unit 411 of the calculation unit 41 obtains α1 in the first surface recombination state by using the obtained S / D in Equation 2 (S25).

Subsequently, the first state calculation unit 411 of the calculation unit 41 obtains the diffusion coefficient D by evaluating the bulk carrier lifetime τb with respect to the diffusion coefficient in the sample X to be measured by using Equation 5 obtained by modifying Equation 1. The diffusion coefficient D is stored in the diffusion coefficient storage unit 414 (S26). In this process, α in Equation 5 is α1.
τb = 1 / ((1 / τ1) −α2 × D) (5)

  When the bulk carrier lifetime τb is a relatively large value such as 100 μs, preferably 1000 μs (= 1 ms), the diffusion coefficient D is a value that matches the peak value of Equation 5.

  For example, when S / D = 4000 and the measurement result τ1 = 4 μs, the bulk carrier lifetime τb according to Equation 5 is set to a predetermined range in which the diffusion coefficient D includes a peak, for example, from 0 to 30 When the calculation is performed within the range, the graph shown in FIG. 8 is obtained, and the bulk carrier lifetime τb according to Equation 5 has a peak at one point. The value at this peak (about 15.6 in the example of FIG. 8) is the diffusion coefficient D.

  By each of these processes, the S / D when the sample X to be measured is in the first surface recombination velocity state is obtained, and the diffusion coefficient D is obtained based on the obtained S / D.

  Returning to FIG. 4, subsequently, the surface treatment of the sample X to be measured is performed based on the obtained diffusion coefficient D (about 15.6 in the example of FIG. 8) (S13). This surface treatment preferably includes, for example, corona discharge treatment, oxidation treatment, passivation treatment by forming silicon nitride, amorphous silicon and an alumina film. In this embodiment, since the surface treatment can be temporarily performed for the time required for the measurement and the original property can be restored after the measurement, the corona discharge treatment is adopted as the surface treatment of the sample X to be measured. . More specifically, the power supply unit 53 applies high voltages having different polarities to the first and second corona wires 51 and 52 according to the control of the control unit 4. As a result, corona discharge is applied from both the first and second corona wires 51 and 52 to both main surfaces of the sample X to be measured, and surface treatment is performed.

  Subsequently, the S / D when the sample to be measured X is in the second surface recombination velocity state is obtained, and the surface recombination velocity S is obtained based on the obtained S / D (S14).

  More specifically, while applying a high voltage to the first and second corona wires 51 and 52 by the power supply unit 53, the same processes as the processes S21 to S23 described above with reference to FIG. A change in the intensity of the reflected measurement wave due to one light is detected by the measurement wave detector 31, and a change in the intensity of the reflected measurement wave due to the second light is detected by the measurement wave detector 31. It is taken into the calculation unit 41.

  Subsequently, the second state calculation unit 412 of the calculation unit 41 obtains a δ value based on the output of the measurement wave detection unit 31 by a process similar to the process S24 described above with reference to FIG. By obtaining a constant value and referring to the δ-S / D table of the δ-S / D table storage unit 415, an S / D corresponding to the value at which the δ value becomes substantially constant is obtained. .

  Subsequently, the first state calculation unit 412 of the calculation unit 41 obtains the surface recombination velocity S by multiplying the obtained S / D by the diffusion coefficient D obtained above.

  By each of these processes, the S / D when the sample X to be measured is in the second surface recombination speed state is obtained, and the surface recombination speed S is obtained based on the obtained S / D.

  Subsequently, the lifetime calculation unit 413 of the calculation unit 41 calculates the bulk carrier lifetime τb by using Equations 1 and 2 based on the obtained surface recombination velocity S (S15).

  Then, the semiconductor carrier lifetime measuring apparatus A outputs the obtained bulk carrier lifetime τb to an output device (not shown) such as a display device or a printing device.

  In the second and subsequent measurements, by using the diffusion coefficient D stored in the diffusion coefficient storage unit 414, the processing S11 and the processing S12 may be omitted, and the measurement may be started from the processing S13.

  As described above, the semiconductor carrier lifetime measuring apparatus A of the present embodiment has the first difference in the temporal relative change of the reflected measurement wave in the first surface recombination velocity state and the reflected measurement wave in the second surface recombination velocity state. Since it is only necessary to obtain the second difference in the relative change in time of the carrier, it is possible to measure the carrier life in the production line, and it is not necessary to perform a prior pretreatment as in the prior art, and the carrier life Can be measured with higher accuracy than in the past. Since the first difference and the second difference need only be obtained in this way, it is not necessary to assume the value of the diffusion coefficient in the semiconductor to be measured, and the carrier lifetime can be measured more accurately than in the past. .

  In general, when light is incident on a semiconductor, this light (incident light) penetrates into the semiconductor, and the penetration length depends on the wavelength of the incident light. In the semiconductor carrier lifetime measuring apparatus A of the present embodiment, the first light having the wavelength in the infrared region and the second light having the wavelength in the ultraviolet region, or the wavelength in the infrared region as the light irradiated to the semiconductor of the sample X to be measured. First light having a wavelength and third light having a wavelength in the visible light region are used. For this reason, since the wavelength difference between these lights is large, the penetration length difference between them is also large, and as a result, the ratio of the influence of surface recombination included in the reflected measurement wave by each of these lights is greatly different. Is possible. Therefore, the semiconductor carrier lifetime measuring apparatus A of the present embodiment can measure the carrier lifetime more accurately than the conventional one.

  Further, in the semiconductor carrier lifetime measuring apparatus A of the present embodiment, the surface recombination velocity state changing unit that changes the surface recombination velocity state of the sample X to be measured from the first surface recombination velocity state to the second surface recombination velocity state. As an example, a discharge unit 5 that applies corona discharge to the measurement wave irradiation region of the sample X to be measured is provided. For this reason, the semiconductor carrier lifetime measuring apparatus A of this embodiment changes the surface recombination velocity state in the sample X to be measured from the first state to the second state by the discharge unit 5 as an example of the surface recombination velocity state changing unit. And a second recombination rate state can be realized by corona discharge. In addition, since the second surface recombination velocity state is realized by corona discharge, the physicochemical properties of the sample X to be measured can be restored by terminating the application of corona discharge.

  Prior to use, a semiconductor wafer usually has a natural oxide film formed on its surface through a cleaning process that removes contamination such as dirt. In the semiconductor carrier lifetime measuring apparatus A of the present embodiment, the natural oxide film exposed by this cleaning process is brought into the first surface recombination speed state, so that the process for realizing the first surface recombination speed state is performed by this cleaning process. It is possible to reduce the man-hours.

  Next, the measurement error in the semiconductor carrier lifetime measuring apparatus A of this embodiment will be examined.

  The temporal relative change difference δ is used to determine the S / D ratio. When the diffusion coefficient D is unknown, the surface recombination velocity S is not determined, and the bulk carrier lifetime τb is not determined. Become. In particular, for a semiconductor wafer that is not subjected to a so-called surface treatment, for example, a cleaning process such as chemical etching, the surface recombination rate S that is measured (observed) is generally about 10,000 cm / s, and therefore, the lifetime of the bulk τb is about several microseconds. Therefore, in this case, even if the diffusion coefficient D is accurately obtained, an accuracy of 0.01% is required for estimating the first-order mode lifetime τ, which is not practical. Furthermore, it is expected that the diffusion coefficient D is different for each wafer separated from the same ingot of the semiconductor.

  On the other hand, in the semiconductor carrier lifetime measuring apparatus A of the present embodiment, the surface to reduce the surface recombination velocity S is first obtained by first measuring the sample X to be measured in the state of a natural oxide film by a cleaning process, and then reducing the surface recombination rate S. Processing (corona discharge) is performed, and the sample X to be measured is measured again in this state. The measurement accuracy (deviation from the true value;%) of the first-order mode lifetime τ in such measurement is as shown in Tables 1 to 3. For example, the bulk lifetime τb is obtained with an accuracy of about 10%. Therefore, the measurement accuracy of the primary mode lifetime may be about 1%. Table 1 shows the case where the measurement accuracy of the primary mode lifetime is ± 10%, Table 2 shows the case where the measurement accuracy of the primary mode lifetime is ± 1%, and Table 3 shows This is a case where the measurement accuracy of the primary mode lifetime is ± 0.1%.

  In the above-described embodiment, in order to more accurately measure the actual characteristics of the solar cell semiconductor wafer (PV semiconductor wafer) in a state where light is applied to generate power, the semiconductor carrier lifetime measuring apparatus A is As shown by a broken line in FIG. 3, it may be configured to further include a power generation light irradiation unit 6 that irradiates the measurement target sample X with power generation light. For example, the power generation light irradiation unit 6 emits power generation light (bias light) having a predetermined spectral distribution set in advance according to the control of the control unit 4, and the third light source unit 61 emits light. And a light guide member 62 such as an optical fiber that guides the biased light toward the light irradiation region (measurement wave irradiation region) of the sample X to be measured, and is emitted from the third light source unit 61. The biased light is applied to the light irradiation region of the sample X to be measured via the light guide member 62. As a result, the PV semiconductor wafer as the sample X to be measured is biased by the power generation light. The predetermined spectral distribution is appropriately determined according to the photoexcited carrier of the PV semiconductor wafer to be measured. From the viewpoint of measuring the carrier lifetime of the PV semiconductor wafer with sunlight with higher accuracy, the third light source unit 61 may be an illumination device that illuminates light simulating the same spectral spectrum and irradiance as sunlight. Further, from the above viewpoint, the third light source unit 61 is preferably light corresponding to 1 SUN, and more preferably light having a pseudo-sunlight spectrum. In the measurement of the bulk carrier lifetime τb, each of the above-described processes is performed while irradiating the sample to be measured X with bias light by the power generation light irradiation unit 6. By further including such a power generation light irradiation unit 6, the semiconductor carrier lifetime measuring device A can measure the actual characteristics of the PV semiconductor wafer in a state where light is irradiated to generate power more accurately. It becomes. The PV semiconductor wafer has a relatively wide range of specific resistance, and when the actual power generation characteristics are evaluated, the PV semiconductor wafer is thus irradiated with light. However, it is difficult to estimate the diffusion coefficient of the semiconductor wafer for PV, but the semiconductor carrier lifetime measuring apparatus A of the present embodiment operates as described above. Measurement can be performed with higher accuracy than in the past.

  In the above-described embodiment, the detection unit 3 detects the reflected wave of the measurement wave irradiated to the sample X to be measured, but is configured to detect the transmitted wave of the measurement wave irradiated to the sample X to be measured. Also good. For example, the transmitted wave of the measurement wave is placed in the vicinity of the back surface (back surface region) of the sample to be measured facing the measurement wave irradiation region of the sample X to be measured irradiated so as not to interfere with the second corona wire 52. A waveguide for guiding is provided, and the detection unit 3 guides the transmission wave of the measurement wave to the measurement wave detection unit 31 of the detection unit 3 by this waveguide and detects the intensity of the transmission wave of the measurement wave. Composed. Even with such a configuration, the semiconductor carrier lifetime measuring apparatus A can measure the bulk carrier lifetime τb by the same processes as in the case of measuring the reflected wave of the measurement wave.

  In order to express the present invention, the present invention has been properly and fully described through the embodiments with reference to the drawings. However, those skilled in the art can easily change and / or improve the above-described embodiments. It should be recognized that this is possible. Therefore, unless the modifications or improvements implemented by those skilled in the art are at a level that departs from the scope of the claims recited in the claims, the modifications or improvements are not covered by the claims. To be construed as inclusive.

A Semiconductor carrier lifetime measurement apparatus X Sample to be measured 1 Irradiation unit 2 Measurement wave input / output unit 3 Detection unit 4 Control unit 5 Discharge unit 6 Power generation light irradiation unit 11-1 First light source 11-2 Second light source 21 Measurement wave generation unit 31 Measurement Wave Detection Unit 41 Calculation Unit 51 First Corona Wire 52 Second Corona Wire 53 Power Supply Unit 61 Third Light Source Unit 411 First State Calculation Unit 412 Second State Calculation Unit 413 Lifetime Calculation Unit 414 Diffusion Coefficient Storage Unit 415 δ− S / D table storage

Claims (10)

A light irradiation unit that irradiates the semiconductor to be measured with at least two types of light having different wavelengths;
A measurement wave irradiation unit that irradiates the measurement target semiconductor with a predetermined measurement wave; and
A detection unit that detects a reflected wave of the measurement wave reflected by the semiconductor to be measured or a transmitted wave of the measurement wave that has passed through the semiconductor to be measured;
In the case where the measurement target semiconductor is in the first surface recombination velocity state, the light irradiation unit irradiates the measurement target semiconductor with the at least two types of light and the measurement wave irradiation unit generates the measurement wave. A first difference in a temporal relative change of the reflected wave or the transmitted wave that is detected by the detection unit after being irradiated on the measurement target semiconductor; and the measurement target semiconductor is in the first surface recombination velocity state. In the case of different second surface recombination velocity states, the light irradiation unit irradiates the measurement target semiconductor with the at least two types of light and the measurement wave irradiation unit converts the measurement wave into the measurement target semiconductor. Based on the second difference of the temporal relative change of the reflected wave or the transmitted wave detected by the detection unit. And an arithmetic unit for obtaining the A life,
The difference in relative change with time is the first light of the at least two types of light and the second light having a shorter wavelength than the first light, the intensity of the reflected wave due to the irradiation of the second light. natural logarithm of the intensity of the reflected wave by irradiation of the first light, or Ru natural logarithm der of the intensity of the transmitted wave by irradiation of the first light to the intensity of the transmitted wave by irradiation of the second light A semiconductor carrier lifetime measuring apparatus characterized by the above. Wherein the at least two kinds of light, the semiconductor carrier lifetime measuring apparatus according to claim 1, characterized in that the ultraviolet light having a wavelength of infrared and ultraviolet light region having a wavelength in the infrared region. Wherein the at least two kinds of light, the semiconductor carrier lifetime measuring apparatus according to claim 1, characterized in that a visible light having a wavelength of infrared and visible light region having a wavelength in the infrared region. The surface recombination velocity state changing unit that changes the semiconductor to be measured from the first surface recombination velocity state to the second surface recombination velocity state is further provided. The semiconductor carrier lifetime measuring apparatus according to claim 1. The said surface recombination speed change part is a corona discharge provision part which provides a corona discharge to the measurement wave irradiation area | region of the semiconductor with which a measurement wave is irradiated by the said measurement wave irradiation part. Semiconductor carrier lifetime measuring device. The semiconductor carrier lifetime measuring apparatus according to claim 4, wherein the semiconductor to be measured is in a state in which a natural oxide film is provided as the first surface recombination velocity state. The semiconductor carrier lifetime measuring apparatus according to claim 1, further comprising a power generation light irradiation unit configured to irradiate the measurement target semiconductor with power generation light. A light irradiation step of irradiating the semiconductor to be measured with at least two types of light having different wavelengths;
A measurement wave irradiation step of irradiating the semiconductor to be measured with a predetermined measurement wave;
A detection step of detecting a reflected wave of the measurement wave reflected by the semiconductor to be measured or a transmitted wave of the measurement wave transmitted through the semiconductor of the measurement object;
When the semiconductor to be measured is in the first surface recombination velocity state, the at least two types of light are irradiated to the semiconductor to be measured by the light irradiation step, and the measurement wave is generated by the measurement wave irradiation step. A first difference in temporal relative change of the reflected wave or the transmitted wave that is detected in the detection step after being irradiated on the semiconductor to be measured, and the semiconductor to be measured is in the first surface recombination velocity state. In the case of different second surface recombination velocity states, the at least two types of light are irradiated to the measurement target semiconductor by the light irradiation step, and the measurement wave is irradiated to the measurement target semiconductor by the measurement wave irradiation step. And the second difference of the temporal relative change of the reflected wave or the transmitted wave detected in the detection step and the semiconductor to be measured And a calculation step of obtaining a definitive carrier lifetime,
The difference in relative change with time is the first light of the at least two types of light and the second light having a shorter wavelength than the first light, the intensity of the reflected wave due to the irradiation of the second light. natural logarithm of the intensity of the reflected wave by irradiation of the first light, or Ru natural logarithm der of the intensity of the transmitted wave by irradiation of the first light to the intensity of the transmitted wave by irradiation of the second light A semiconductor carrier lifetime measuring method characterized by the above. The calculating step obtains a carrier lifetime in the semiconductor to be measured by obtaining a ratio between a diffusion coefficient and a surface recombination velocity in the semiconductor to be measured based on the first difference and the second difference. The semiconductor carrier lifetime measuring method according to claim 8, wherein the semiconductor carrier lifetime is measured. When the measurement target semiconductor is in the first surface recombination velocity state, the measurement target is irradiated with at least two types of light having different wavelengths while irradiating the measurement target semiconductor with the predetermined measurement wave. A first difference measuring step of measuring a first difference of a reflected wave of the measurement wave reflected by the semiconductor or a transmitted wave of the measurement wave transmitted through the semiconductor to be measured;
When the surface recombination velocity in the semiconductor to be measured is S and the diffusion coefficient is D, S / in the first surface recombination velocity state based on the first difference measured by the first difference measurement step. A first S / D calculation step for obtaining D;
A diffusion coefficient calculation step for obtaining a diffusion coefficient D based on the S / D in the first surface recombination velocity state obtained in the first S / D calculation step;
A surface recombination velocity state changing step of changing the semiconductor to be measured from the first surface recombination velocity state to a second surface recombination velocity state different from the first surface recombination velocity state;
In the case where the semiconductor to be measured is in a second surface recombination velocity state, the measurement is performed by irradiating the semiconductor to be measured with at least two types of light having different wavelengths while irradiating the semiconductor to be measured. A second difference measuring step for measuring a second difference of a reflected wave of the measurement wave reflected by the target semiconductor or a transmitted wave of the measurement wave transmitted through the measurement target semiconductor;
A second S / D calculation step for obtaining S / D in the second surface recombination velocity state based on the second difference measured by the second difference measurement step;
A surface recombination rate calculating step for determining a surface recombination rate S based on S / D in the second surface recombination rate state determined in the second S / D calculation step;
A life calculation step for obtaining a carrier life in the semiconductor to be measured based on the surface recombination velocity S obtained in the surface recombination velocity calculation step,
The difference in relative change with time is the first light of the at least two types of light and the second light having a shorter wavelength than the first light, the intensity of the reflected wave due to the irradiation of the second light. natural logarithm of the intensity of the reflected wave by irradiation of the first light, or Ru natural logarithm der of the intensity of the transmitted wave by irradiation of the first light to the intensity of the transmitted wave by irradiation of the second light A semiconductor carrier lifetime measuring method characterized by the above.

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