JP5308395B2 - Semiconductor carrier lifetime measuring apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor carrier lifetime measuring apparatus and a method therefor, by which a lifetime of carriers can be measured with good precision. <P>SOLUTION: A semiconductor carrier lifetime measuring apparatus Xa includes: a light-irradiation unit 1 for irradiating first and second different regions in a semiconductor as a measurement sample SW with first and second lights having different wavelengths; a measurement wave input/output unit 2 for irradiating the first and second regions with predetermined measurement waves respectively, and for using a first reflected or transmitted wave and a second reflected or transmitted wave with no changes to generate a difference-measurement wave which is a difference between the first reflected or transmitted wave of the measurement wave from the first region and the second reflected or transmitted wave of the measurement wave from the second region; a detection unit 3 for detecting the difference-measurement wave of the measurement wave input/output unit 2; and a calculation-control unit 4 for determining a carrier lifetime in the semiconductor of the measurement sample SW based on a result of detection by the detection unit 3. <P>COPYRIGHT: (C)2012,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. On the other hand, in recent years, a solar cell (PV) has attracted attention as a clean energy source. 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 life 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.

  Further, generally, there is a crystalline irregularity on the surface of the 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). In the measurement of the carrier lifetime of the semiconductor wafer, it is necessary to consider such circumstances, and in particular, the measurement of the bulk carrier lifetime is important for the quality control of the semiconductor wafer.

  As a method for measuring the carrier lifetime in such a semiconductor wafer, for example, there are a technique disclosed in Patent Document 1 and a technique disclosed in Non-Patent Document 1.

  The semiconductor wafer characteristic measuring method disclosed in Patent Document 1 is irradiated with a light beam or an electron beam on one surface and / or the other surface of the semiconductor wafer, and is instantaneously excited by the irradiation of the light beam or the electron beam. The surface recombination velocity on one side of the semiconductor wafer, the surface recombination velocity on the other side by detecting the change in conductivity time of the semiconductor wafer based on at least two different spatial distributions due to the difference in carrier excitation conditions of excess carriers. And the bulk lifetime are measured separately.

  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-A-57-054338

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

  The methods disclosed in Patent Document 1 and Non-Patent Document 1 are methods for measuring the carrier lifetime by using the difference between the measurement results obtained under different conditions. For this reason, when the difference between the measurement results is small, the number of effective digits in the difference between the measurement results is small, and as a result, it is difficult to accurately measure the carrier lifetime.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a semiconductor carrier lifetime measuring apparatus and a semiconductor carrier lifetime measuring method capable of measuring the carrier lifetime more accurately.

  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 an aspect of the present invention includes a light irradiation unit that irradiates at least two types of light having different wavelengths to different first and second regions in a semiconductor to be measured; A measurement wave irradiating unit that irradiates each of the first and second regions with a predetermined measurement wave, and a first reflected wave of the measurement wave reflected by the first region or a first of the measurement wave transmitted through the first region. A difference measurement wave, which is a difference between one transmitted wave and the second reflected wave of the measurement wave reflected by the second region or the second transmitted wave of the measurement wave transmitted through the second region, is converted into the first reflected wave. A difference measurement wave generator generated by using the wave or the first transmitted wave as it is and using the second reflected wave or the second transmitted wave as it is, and a difference measurement generated by the difference measurement wave generator Detection unit for detecting waves , Characterized in that it comprises a computing unit for determining the carrier lifetime in the measurement target semiconductor based on the detected portion detected detection result.

  The semiconductor carrier lifetime measurement method according to another aspect of the present invention includes a light irradiation step of irradiating at least two types of light having different wavelengths to different first and second regions in a semiconductor to be measured; A measurement wave irradiation step of irradiating each of the first and second regions with a predetermined measurement wave, and the first reflected wave of the measurement wave reflected by the first region or the measurement wave transmitted through the first region A difference measurement wave that is a difference between the first transmitted wave of the second reflected wave of the measurement wave reflected by the second region or the second transmitted wave of the measurement wave transmitted by the second region, A difference measurement wave generating step that is generated by using the first reflected wave or the first transmitted wave as it is and using the second reflected wave or the second transmitted wave as it is, and the difference measurement wave generating step. Detect difference measurement wave A detecting step that, characterized in that it comprises a calculation step of the detection process on the basis of the detection result by determining the carrier lifetime in the semiconductor of the measurement target.

  In the semiconductor carrier lifetime measuring apparatus and method having such a configuration, the first reflected wave of the measurement wave reflected by the first region or the first transmitted wave of the measurement wave transmitted through the first region and the second reflected wave are reflected by the second region. The second reflected wave of the measured wave or the difference measured wave that is the difference between the measured wave transmitted through the second region and the second transmitted wave is used as the first reflected wave or the first transmitted wave and the second reflected wave. The difference measurement wave is generated by being used as the wave or the second transmitted wave, and the carrier life is determined based on the detection result. For this reason, the first measurement result obtained by measuring the first reflected wave or the first transmitted wave with a predetermined detector and the second reflected wave or the second transmitted wave obtained by measuring with the detector. Each measurement obtained by directly measuring the difference measurement wave itself with the detector rather than the number of significant digits in the difference between the measurement results calculated by obtaining the difference from the obtained second measurement result The number of significant digits of the detection result corresponding to the difference between the results becomes larger because the difference measurement wave is directly detected using the entire dynamic range in the detector. Therefore, the semiconductor carrier lifetime measuring apparatus and method having such a configuration can measure the carrier lifetime more accurately.

  According to another aspect, in the above-described semiconductor carrier lifetime measuring apparatus, the at least two types of light include a first light having a wavelength in the infrared region, a second light having a wavelength in the visible light region, and a wavelength in the ultraviolet region. These are two lights selected from the third light having

  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, the first and second initial states generated when each of the first and second regions is irradiated with at least two types of light having different wavelengths. A light intensity control unit is further provided for controlling the light intensity of at least one of the at least two types of light so that the two excess carrier amounts are equal to each other.

  According to this configuration, the initial first and second excess carrier amounts generated when the at least two types of light are irradiated to each of the first and second regions are substantially equal to each other. When the coupling speed is zero, the output signal level of the detector can be zero, and the carrier life can be measured with higher accuracy.

  According to another aspect, in the above-described semiconductor carrier lifetime measuring apparatus, the apparatus further includes a surface recombination velocity state changing unit that changes a surface recombination velocity state in the semiconductor to be measured, and the calculation unit includes the measurement When the target semiconductor is in the first surface recombination speed state, the first detection result detected by the detection unit, and the second surface recombination speed in which the measurement target semiconductor is different from the first surface recombination speed state The carrier lifetime in the semiconductor to be measured is obtained based on the second detection result detected by the detector in the state.

  According to this configuration, when the semiconductor to be measured is in the first surface recombination velocity state, the detection unit detects the first detection result, and the semiconductor to be measured is different from the first surface recombination velocity state. In the case of the two-surface recombination velocity state, the detection unit measures the second detection result, and based on the first and second detection results, the carrier lifetime in the semiconductor to be measured is obtained. Therefore, since the semiconductor carrier lifetime measuring apparatus having such a configuration only needs to obtain the first and second detection results in this way, it is not necessary to assume or measure the value of the diffusion coefficient in the semiconductor to be measured. The lifetime can be measured more easily and more accurately than in the past.

  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. For this reason, the semiconductor carrier lifetime measuring apparatus having such a configuration can be used in a production line, and the yield of products is improved by selecting semiconductor wafers that do not meet the required specifications in the production process. It becomes possible to make it.

  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. Therefore, the semiconductor carrier lifetime measuring apparatus having such a configuration is suitable for measuring the carrier lifetime of a PV semiconductor wafer, for example.

  The semiconductor carrier lifetime measuring apparatus and the semiconductor carrier lifetime measuring method according to the present invention can measure the carrier lifetime more accurately.

It is a figure which shows the structure of the semiconductor carrier lifetime measuring apparatus in 1st Embodiment. It is a perspective view which shows the structure of the magic T used for the semiconductor carrier lifetime measuring apparatus in 1st Embodiment. It is a figure which shows the structure of the part regarding irradiation of the light in the semiconductor carrier lifetime measuring apparatus of 1st Embodiment. It is a figure which shows the change of the time relative output in the reflected wave of a measurement wave. It is a figure which shows the time change of the relative output difference (difference measurement wave) of the reflected wave of the measurement wave obtained when infrared light and ultraviolet light are each irradiated to a semiconductor. It is a figure which shows the structure of the semiconductor carrier lifetime measuring apparatus in 2nd Embodiment. It is a figure which shows the structure of the calculation control part 4 in the semiconductor carrier lifetime measuring apparatus of 2nd Embodiment. It is a flowchart which shows an example of operation | movement of the semiconductor carrier lifetime measuring apparatus of 2nd Embodiment. It is a flowchart which shows operation | movement of the semiconductor carrier lifetime measuring apparatus of 2nd Embodiment in the case of calculating | requiring a diffusion coefficient. It is a figure which shows the relationship between the diffusion coefficient in the case of S / D = 4000, and a bulk carrier lifetime. It is a figure which shows the structure of the semiconductor carrier lifetime measuring apparatus in 3rd Embodiment.

  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 embodiment)
FIG. 1 is a diagram showing the configuration of the semiconductor carrier lifetime measuring apparatus in the first embodiment. FIG. 2 is a perspective view showing the configuration of the magic T used in the semiconductor carrier lifetime measuring apparatus in the first embodiment. FIG. 3 is a diagram illustrating a configuration of a portion related to light irradiation in the semiconductor carrier lifetime measuring apparatus according to the first embodiment.

  The semiconductor carrier lifetime measuring apparatus Xa of the first embodiment is an apparatus for measuring the carrier lifetime of a semiconductor by a so-called microwave photoconductive decay method, and generates excess carriers for different first and second regions in the semiconductor. Therefore, at least two types of light having different wavelengths are irradiated, and in order to detect the annihilation process of the excess carriers, a measurement wave such as a microwave is irradiated, and measurement from the first region obtained thereby is performed. The difference (difference measurement wave) between the reflected wave of the wave or the transmitted wave and the reflected wave of the measurement wave from the second region or the transmitted wave is directly generated, and the directly generated difference (difference measurement) is generated. (Wave) itself is measured by a detector using the entire dynamic range, and the carrier lifetime of the semiconductor is obtained based on the detection result.

  Such a semiconductor carrier lifetime measuring apparatus Xa according to the first embodiment includes, for example, a light irradiation unit 1 (1A, 1B), a measurement wave input / output unit 2, a detection unit 3, and a calculation as shown in FIG. The control part 4 is comprised, Furthermore, the moving part 5 is provided in order to move a measurement location.

  The light irradiation unit 1 includes at least two types of wavelengths different from each other in order to make the penetration wavelengths different in different first and second regions in a semiconductor wafer (measurement sample) SW such as a silicon wafer to be measured. It is an apparatus for irradiating light. In the semiconductor carrier lifetime measuring apparatus Xa of the present embodiment, the light irradiation unit 1 irradiates the first region of the sample SW to be measured with the first light of the first wavelength and the second of the second wavelength different from the first wavelength. In order to irradiate light to a second region different from the first region in the sample SW to be measured, for example, as shown in FIG. 1, a first light irradiation unit 1A and a second light irradiation unit 1B are provided. .

  These first and second regions define the measurement range measured by the semiconductor carrier lifetime measuring apparatus Xa, and the center position of the first region (for example, the light of the first light irradiated on the first region) The distance between the center position of the intensity) and the center position of the second region (for example, the center position of the light intensity of the second light irradiated on the second region) defines the spatial resolution of the semiconductor carrier lifetime measuring device Xa. To do. Therefore, the first and second regions are set so as to be adjacent to each other, and the distance is a predetermined length that is appropriately set according to the specifications relating to the spatial resolution of the semiconductor carrier lifetime measuring apparatus Xa. In order to make the resolution high, it is preferable that the first and second regions are as short as possible. The distance is limited to, for example, several millimeters because it is also limited by the size of a first waveguide antenna 24a and a second waveguide antenna 25a described later in the measurement wave input / output unit 2.

  The first light irradiator 1A emits first light having a first wavelength according to the control of the arithmetic controller 4 and the first light emitted from the first light source 10A to the sample SW to be measured. The first mirror 12A that bends its optical path by about 90 degrees and the first light reflected by the first mirror 12A has a lens function that adjusts the light irradiation diameter and light intensity distribution on the surface of the sample SW to be measured. The first light that is configured to include the first lens 13A and receives the lens action by the first lens 13A is irradiated to the first region of the sample SW to be measured through the third waveguide 24, as will be described later. .

  Similarly, the second light irradiating unit 1B measures the second light emitted from the second light source unit 10B and the second light source unit 10B that emits the second light having the second wavelength according to the control of the arithmetic control unit 4. A second mirror 12B that bends its optical path toward the sample SW by about 90 degrees and a second lens 13B that imparts the lens action to the second light reflected by the second mirror 12B are configured, and the second lens 13B As described later, the second light that has received the lens action is irradiated to the second region of the sample SW to be measured through the fourth waveguide 25.

  The first and second light source units 10A and 10B may be, for example, a light source device including a lamp and a wavelength filter, but in the present embodiment, a relatively large output is obtained, for example, emitting laser light. A laser light source device such as a semiconductor laser or a YAG laser is provided. 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 10A is a device that emits laser light having a predetermined wavelength in the infrared region, that is, infrared laser light (IR laser light), and the second light source unit 10B has a predetermined wavelength in the ultraviolet region. It is a device that emits laser light, that is, ultraviolet laser light (UV laser light). Note that one of the first and second light source units 10A and 10B may be a device that emits laser light having a predetermined wavelength in the visible light region, that is, visible light laser light. The wavelengths of the first and second light source units 10A and 10B are appropriately selected according to the type of the sample SW to be measured, for example. For example, in the case where the sample SW to be measured is a silicon wafer, the first and second light source units 10A and 10B can be used in addition to the above viewpoints from the viewpoint of improving the efficiency of light excitation and reducing the cost of the light sources 10 (10A and 10B). Each 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 irradiate the sample SW to be measured to cause photoexcited carriers (electrons and holes) to be generated in the sample SW to be measured, and the semiconductor carrier lifetime measuring apparatus Xa generates this. Since it is an apparatus for measuring the life of a carrier (carrier life), it is preferable that the first and second lights shift from a lighting state to a light-off state in a stepped manner. In this embodiment, for example, pulsed light is more specifically used. Is a pulsed laser beam.

  In this embodiment, the light irradiation unit 1 of the semiconductor carrier lifetime measuring device Xa irradiates each of the first and second regions of the sample SW to be measured with at least two types of light having different wavelengths. In order to make the generated initial first and second excess carrier amounts equal to each other, the first light irradiation unit 1A further includes a first light intensity adjuster 11A, and the second light irradiation unit 1B includes a second light intensity adjuster 11B. Is further provided.

  The first light intensity adjuster 11A is configured to include, for example, an optical attenuator (optical attenuator) that attenuates the light intensity of incident light and emits the light. The first region of the sample SW to be measured from the first light source unit 10A. In the optical path reaching the surface, in the example shown in FIG. 1, the optical path is arranged (inserted) in the optical path between the first light source unit 10A and the first mirror 12A. Similarly, the second light intensity adjuster 11B is configured to include, for example, an optical attenuator, and in the example shown in FIG. 1 in the optical path from the second light source unit 10B to the second region surface of the sample SW to be measured. The second light source unit 10B and the second mirror 12B are disposed (inserted) in the optical path.

  The measurement wave input / output unit 2 irradiates each of the first and second regions of the sample SW to be measured with a predetermined measurement wave, and the first reflected wave of the measurement wave reflected by the first region or the The difference between the first transmitted wave of the measurement wave transmitted through the first region and the second reflected wave of the measurement wave reflected at the second region or the second transmitted wave of the measurement wave transmitted through the second region The difference measurement wave is generated by using the first reflected wave or the first transmitted wave as it is and using the second reflected wave or the second transmitted wave as it is. As described above, in the semiconductor carrier lifetime measuring apparatus Xa of the first embodiment, the function as a measurement wave irradiation unit that irradiates each of the first and second regions in the sample SW to be measured with a predetermined measurement wave, and the first A first reflected wave of the measurement wave reflected by a region, a first transmitted wave of the measurement wave transmitted through the first region, and a second reflected wave of the measurement wave reflected by the second region or the second The difference measurement wave, which is the difference between the measurement wave transmitted through the region and the second transmission wave, is used as the first reflection wave or the first transmission wave, and the second reflection wave or the second transmission wave is used. The function as the difference measurement wave generation unit that is generated by using as it is is realized by being integrally configured as the measurement wave input / output unit 2.

  As shown in FIG. 1, the measurement wave input / output unit 2 includes, for example, a measurement wave generation unit 20, a branch unit 21, first to fifth waveguides 22 to 26, and a branch synthesis unit 27. It has.

  The measurement wave generator 20 is a device that generates the predetermined measurement wave according to the control of the arithmetic control unit 4. In the semiconductor carrier lifetime measuring apparatus Xa 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 extinction process of excess carriers by the change in the intensity of the measurement wave. In the embodiment, it is a microwave, and the measurement wave generation unit 20 includes a microwave oscillator configured to generate a microwave, which includes, for example, a 26 GHz Gunn diode. The measurement wave generation unit 20 is connected to the branch unit 21.

  The branching unit 21 is a device that branches (distributes) an incident measurement wave into two, and includes a directional coupler such as a 10 dB coupler, for example. This directional coupler is, for example, a waveguide having three first to third ports, and the microwaves incident on the first port are respectively transmitted to the third and fourth ports at a constant intensity ratio. Is injected from. The branching unit 21 is connected to the branching / combining unit 27 through the first waveguide 22 and is connected to the detecting unit 3 through the second waveguide 23.

  The first to fifth waveguides 22 to 26 are members that form a propagation path for guiding a measurement wave. In this embodiment, the measurement wave is a microwave, and thus the first to fifth waveguides 22 are used. ˜26 are microwave waveguides.

  The branching / combining unit 27 radiates the measurement wave to each of the first and second regions of the sample SW to be measured, and the measurement wave (the one of the ones) incident from the branching unit 21 via the first waveguide 22 is measured. (Measurement wave) is branched (distributed) into two, and the first reflected wave of the measurement wave reflected by the first region of the sample SW to be measured or the first transmitted wave of the measurement wave transmitted through the first region and A difference measurement wave, which is a difference between the second reflected wave of the measurement wave reflected by the second region in the sample SW to be measured or the second transmitted wave of the measurement wave transmitted through the second region, is converted into the first reflected wave. It is an apparatus which generates by using the wave or the first transmitted wave as it is and using the second reflected wave or the second transmitted wave as it is. In the present embodiment, in order to configure the branching / combining unit 27 with a smaller number of parts, the branching / combining unit 27 of the present embodiment radiates a measurement wave to each of the first and second regions in the sample SW to be measured. The measurement wave (the one measurement wave) incident from the branch part 21 via the first waveguide 22 is branched (distributed) into two, and the measurement is reflected in the first region of the sample SW to be measured. A difference measurement wave that is a difference between the first reflected wave of the wave and the second reflected wave of the measurement wave reflected by the second region in the sample SW to be measured is used as the first reflected wave and the second reflected wave. It is a device that generates by using the reflected wave as it is. Such a branching and synthesizing unit 27 may be configured by combining a plurality of branching waveguides. However, in the semiconductor carrier lifetime measuring apparatus Xa of the present embodiment, for example, it is a magic T-type waveguide 27. The magic T-type waveguide 27 is, for example, a four-opening element having four first to fourth ports 27a to 27d, as shown in FIG. This is a structure in which a branching waveguide is combined. The microwaves incident on the second port 27b are distributed and emitted from the third and fourth ports 27c and 27d in equal phase with equal power, and conversely, the third and fourth ports 27c and 27d. Each of the microwaves incident on the difference between the microwaves is emitted from the second port 27b, and the sum thereof is emitted from the first port 27a. As described above, the magic T-type waveguide 27 can generate a microwave having a difference between the microwaves in a microwave state (as it is). The first waveguide 27 is connected to the first port 27a of the magic T-type waveguide 27, the fifth waveguide 26 is connected to the second port 27b, and the third port 27c is connected to the first port 27a. The third waveguide 24 is connected, and the fourth waveguide 25 is connected to the fourth port 27d.

  The third waveguide 24 guides the one measurement wave to radiate (transmit) one measurement wave branched by the branching / combining unit 27 to the first region of the sample SW to be measured, and also measures the measurement target. The measurement wave that interacts with the sample SW, in this embodiment, the first reflected wave of the measurement wave reflected by the first region of the sample SW to be measured is received (received), and the received measurement wave The first reflected wave or the first transmitted wave is again guided to the branching / combining unit 27. Therefore, the first waveguide antenna 24 a is provided at the end of the third waveguide 24. The first waveguide antenna 24a radiates the one measurement wave that has propagated through the third waveguide 24 to the sample SW to be measured, and the measurement wave that has interacted with the sample SW to be measured. An antenna that receives the wave and guides it to the third waveguide 24. As shown in FIG. 3, the first waveguide antenna 24a is disposed along the normal direction of the sample SW to be measured, and the third waveguide 24 is extended on the side surface of one end. The other end is provided with an opening 24b. The opening 24b is an opening for radiating (transmitting) the one measurement wave to the sample SW to be measured and receiving the measurement wave interacting with the sample SW to be measured. In order to guide the first light emitted from the first light irradiation unit 1A together with the one measurement wave to the first region of the sample SW to be measured, the one end portion of the first waveguide antenna 24a has An opening 24c is provided for guiding the first light emitted from the first light irradiation unit 1A into the first waveguide antenna 24a. In the present embodiment, since the measurement wave is a microwave, the first waveguide antenna 24a is a microwave antenna.

  Similarly, the fourth waveguide 25 guides the other measurement wave to radiate (transmit) the other measurement wave branched by the branching / combining unit 27 to the second region of the sample SW to be measured. The measurement wave that interacted with the sample SW to be measured, in this embodiment, the second reflected wave of the measurement wave reflected by the second region of the sample SW to be measured was received (received) and received. The second reflected wave or the second transmitted wave of the measurement wave is again guided to the branching / combining unit 27. For this reason, the end of the fourth waveguide 25 has a second waveguide antenna 25a. The second waveguide antenna 25a radiates the other measurement wave propagating through the fourth waveguide 25 to the sample SW to be measured, and transmits the measurement wave that has interacted with the sample SW to be measured. An antenna that receives the wave and guides it to the fourth waveguide 25. Similar to the first waveguide antenna 24a, the second waveguide antenna 25a is disposed along the normal direction of the sample SW to be measured, and the fourth waveguide 25 is provided on the side surface of one end. Is provided with an opening 25b at the other end. The opening 25b is an opening for radiating (transmitting) the other measurement wave to the sample SW to be measured and receiving the measurement wave interacting with the sample SW to be measured. Then, in order to guide the second light emitted from the second light irradiation unit 1B together with the other measurement wave to the second region of the sample SW to be measured, the one end of the second waveguide antenna 25a includes An opening 25c for guiding the second light emitted from the second light irradiation unit 1B into the second waveguide antenna 25a is provided. In the present embodiment, since the measurement wave is a microwave, the second waveguide antenna 25a is a microwave antenna.

  The fifth waveguide 26 is connected to the branching / combining unit 27, in this embodiment, the second port 27 b of the magic T-type waveguide 27, and from the third waveguide 24 and the fourth waveguide 25. The difference measurement wave of the reflected microwave is guided to the detection unit 3.

  The detection unit 3 is a device that detects the difference measurement wave generated by the measurement wave input / output unit 2 and includes, for example, a mixer 30 and a detector 31. The detection result of the difference measurement wave detected by the detection unit 3 (the intensity of the difference measurement wave) is output to the calculation control unit 4.

  The mixer 30 is connected to the branching unit 21 via the second waveguide 23, connected to the branching / combining unit 27 via the fifth waveguide 26, and guided by the second waveguide 23. The difference measurement wave is detected by the measurement wave by mixing (multiplying, multiplexing) the measurement wave from the measurement wave generator 20 and the difference measurement wave guided by the fifth waveguide 26. It is. The detector 31 is connected to the mixer 30 and detects the intensity of the detection signal detected by the mixer 30. Thereby, the intensity of the difference measurement wave is detected. The detector 31 outputs this detection result to the arithmetic control unit 4.

  The arithmetic control unit 4 is a device that controls the entire semiconductor carrier lifetime measuring device Xa by controlling each unit of the semiconductor carrier lifetime measuring device Xa according to the function of the unit. It is provided with a microcomputer provided. Then, the calculation control unit 4 obtains the carrier life in the sample SW to be measured based on the detection result detected by the detection unit 3.

  The moving unit 5 is a device that moves the sample SW to be measured in the XY plane (horizontal plane) according to the control of the calculation control unit 4 in order to move the measurement location, and includes, for example, a stage 50 and a stage control unit 51. Configured. The stage 50 is a mechanism on which the sample SW to be measured is placed and moves the sample SW to be measured in the XY plane. The stage control unit 51 has a predetermined position in the sample SW to be measured according to the control of the arithmetic control unit 4. The stage 50 is driven and controlled so as to be measured.

  Note that the first transmitted wave of the measurement wave transmitted through the first region is received (received) at a position facing the opening 24b of the first waveguide antenna 24a via the sample SW to be measured. A three-waveguide antenna is provided, and the second transmitted wave of the measurement wave transmitted through the second region is received at a position facing the opening 25b of the second waveguide antenna 25a via the sample SW to be measured. A fourth waveguide antenna for receiving (receiving) a wave; a first transmitted wave of the measurement wave received by the third waveguide antenna; and a second of the measurement wave received by the fourth waveguide antenna. A difference measurement wave that is generated by using a difference measurement wave that is a difference from the transmitted wave as it is as the first transmitted wave and as it is used as the second transmitted wave is provided. May be guided to the mixer 30 of the detection unit 3.

  The semiconductor carrier lifetime measuring apparatus Xa having such a configuration measures the semiconductor carrier lifetime by operating as follows, for example. First, dirt or surface damage on the surface of a semiconductor wafer to be measured is removed in advance by, for example, so-called chemical etching (cleaning process), and a natural oxide film is applied. Then, the semiconductor wafer after the cleaning treatment is placed on the stage 50 as the sample SW to be measured.

  For example, when a start switch for inputting a measurement start instruction (not shown) to the semiconductor carrier lifetime measuring apparatus Xa is operated, measurement of the carrier lifetime of the sample SW to be measured by the semiconductor carrier lifetime measuring apparatus Xa is started. In order to measure a predetermined measurement point, the stage 50 is driven and controlled by the stage controller 51 according to the control of the arithmetic control unit 4, and the sample SW to be measured is moved to a predetermined position.

  Subsequently, when the sample SW to be measured is moved to a predetermined position by the moving unit 5, the measurement wave is input to the first and second regions of the sample SW by the measurement wave input / output unit 2 according to the control of the arithmetic control unit 4. The first and second light beams are emitted to the first and second regions of the sample X to be measured, respectively, according to the control of the arithmetic control unit 4. A difference measurement wave that is a difference between a measurement wave that interacts with the sample SW to be measured in the first region and a measurement wave that interacts with the sample SW to be measured in the second region is directly generated. The difference measurement wave is detected by the detection unit 3, and the detection result is output from the detection unit 3 to the calculation control unit 4.

  More specifically, in the measurement wave input / output unit 2, a measurement wave is generated by the measurement wave generation unit 20 according to the control of the arithmetic control unit 4, and the generated measurement wave is transmitted from the measurement wave generation unit 20 to the branching unit 21. Is injected into. This measurement wave is branched into two at the branching section 21, and one of the measurement waves (the eleventh measurement wave) is emitted to the branching / combining section 27 through the first waveguide 22, and the other measurement wave is measured. (Twelfth measurement wave) is emitted to the mixer 30 of the detection unit 3 through the second waveguide 23. The measurement wave (eleventh measurement wave) incident on the branching / combining unit 27 (the first port 27a of the magic T-type waveguide 27) via the first waveguide 22 from the branching unit 21 is in phase and equal power. One of the branched measurement waves (the 21st measurement wave) is branched and emitted from the branching / combining unit 27 (the third port 27c of the magic T-type waveguide 27) to the third waveguide 24. The other measured wave (22nd measured wave) is emitted from the branching / combining unit 27 (the fourth port 27d of the magic T-type waveguide 27) to the fourth waveguide 25. The one measurement wave (21st measurement wave) branched by the branching / combining unit 27 is guided by the third waveguide 24 and radiated from the first waveguide antenna 24a to the first region of the sample SW to be measured. Then, the other measurement wave (the 22nd measurement wave) branched by the branching / combining unit 27 is guided by the fourth waveguide 25 and the second region of the sample SW to be measured from the second waveguide antenna 25a. To be emitted.

  The measurement wave that has interacted with the sample SW to be measured in the first region, and in the configuration shown in FIG. 1, the first reflected wave of the measurement wave reflected in the first region is received by the first waveguide antenna 24a. The wave is guided by the third waveguide 24 and is incident again on the branching / combining unit 27 (the third port 27 c of the magic T-type waveguide 27). The measurement wave that has interacted with the sample SW to be measured in the second region, and in the configuration shown in FIG. 1, the second reflected wave of the measurement wave reflected in the second region is received by the second waveguide antenna 25a. The wave is guided by the fourth waveguide 25 and is incident again on the branching / combining unit 27 (the fourth port 27d of the magic T-type waveguide 27). Then, the first reflected wave and the second reflected wave are synthesized while being in the microwave state by the branching and synthesizing unit 27 (magic T-type waveguide 27), and the first reflected wave and the second reflected wave are combined. A difference measurement wave which is a difference is emitted from the branching / combining unit 27 (the second port 27b of the magic T-type waveguide 27) to the mixer 30 of the detecting unit 3 through the fifth waveguide 26.

  In the detection unit 3, the measurement wave (twelfth measurement wave) guided from the measurement wave generation unit 20 guided by the second waveguide 23 and the difference measurement wave guided by the fifth waveguide 26 Are mixed (multiplied and combined) by the mixer 30, and the difference measurement wave is detected by the measurement wave. The detection signal detected by the mixer 30 is emitted to the detector 31, and its intensity (level) is detected. Thereby, the intensity (level) of the difference measurement wave is detected. The intensity (detection result) of the difference measurement wave detected by the detector 31 is output to the arithmetic control unit 4.

  On the other hand, in the light irradiation unit 1, the first light irradiation unit 1 </ b> A generates the first light by the first light source unit 10 </ b> A according to the control of the arithmetic control unit 4, and the generated first light is the first light source unit. 10A is emitted to the first light intensity adjuster 11A. The light intensity of the first light is adjusted by the first light intensity adjuster 11A so that the initial first excess carrier amount by the irradiation of the first light becomes equal to the initial second excess carrier amount by the irradiation of the second light. (Level) is adjusted to a predetermined light intensity, and the adjusted first light is emitted from the first light intensity adjuster 11A to the first mirror 12A. The first light is reflected by the first mirror 12A having its optical path bent by approximately 90 degrees toward the sample SW to be measured, and the reflected first light is emitted from the first mirror 12A to the first lens 13A. Is done. The first light is subjected to a lens action by the first lens 13A, and the first light that has received this lens action passes through the first waveguide antenna 24a of the third waveguide 24 to the first region of the sample SW to be measured. Is irradiated. Due to the lens action of the first lens 13A, the first region of the sample SW to be measured is irradiated with the first light in a substantially uniform and substantially wide area irradiation. For this reason, the semiconductor carrier lifetime measuring apparatus Xa can reduce the diffusion of excess carriers in the in-plane direction.

  Similarly, in the 2nd light irradiation part 1B, 2nd light is produced | generated by the 2nd light source part 10B according to control of the calculation control part 4, and this produced | generated 2nd light is 2nd light from 2nd light source part 10B. It is injected into the intensity adjuster 11B. The light intensity of the second light is adjusted by the second light intensity adjuster 11B so that the initial second excess carrier amount due to the second light irradiation is equal to the initial first excess carrier amount due to the first light irradiation. (Level) is adjusted to a predetermined light intensity, and the adjusted second light is emitted from the second light intensity adjuster 11B to the second mirror 12B. The second light is reflected by the second mirror 12B having its optical path bent by approximately 90 degrees toward the sample SW to be measured, and the reflected second light is emitted from the second mirror 12B to the second lens 13B. Is done. This second light is subjected to a lens action by the second lens 13B, and the second light that has received this lens action passes through the second waveguide antenna 25a of the fourth waveguide 25 to the second region of the sample SW to be measured. Is irradiated. Due to the lens action of the second lens 13B, the second region of the sample SW to be measured is irradiated with the first light in a substantially uniform and substantially wide area irradiation. For this reason, the semiconductor carrier lifetime measuring apparatus Xa can reduce the diffusion of excess carriers in the in-plane direction.

  Note that the first light intensity adjuster 11A and the second light intensity adjuster 11B are initially generated when at least two types of light having different wavelengths are irradiated to each of the first and second regions in the sample SW to be measured. The first and second excess carrier amounts are adjusted in advance before the measurement, for example, by actually irradiating the sample SW to be measured with the first light and the second light.

  As a result, when the first and second light is irradiated to the first and second regions of the sample SW to be measured, and the measurement wave is irradiated to the sample SW, the first region by the first light. The first reflected wave of the measurement wave at is received by the first waveguide antenna 24 a of the third waveguide 24, and the branching / combining unit 27 (magic T-type waveguide 27 is passed through the third waveguide 24. ) And the second reflected wave of the measurement wave in the second region by the second light is received by the second waveguide antenna 25a of the fourth waveguide 25, and the fourth waveguide 25 is received. Is guided to the branching / combining unit 27 (magic T-type waveguide 27). Then, the first reflected wave and the second reflected wave of the measurement wave when the first and second regions are irradiated to the first and second regions of the sample SW to be measured by the branching / combining unit 27 (magic T-type waveguide 27), respectively. The two reflected waves are combined into a difference measurement wave that is the difference between the first reflected wave and the second reflected wave of the measurement wave while remaining in the microwave state. The difference measurement wave is emitted to the detection unit 3 through the fifth waveguide 26, detected by the detection unit 3, and the intensity of the detected difference measurement wave is taken into the arithmetic control unit 4. Usually, the measurement wave is irradiated to the sample SW to be measured, and the first and second light of the pulsed laser beam is irradiated to the first and second regions of the sample SW to be measured, respectively, The intensity change of the difference measurement wave is measured immediately after the irradiation of the first and second light of the pulse laser beam is turned off (immediately after the irradiation and the light is turned off).

  Subsequently, the carrier life of the object to be measured is calculated by the calculation control unit 4 based on the difference measurement wave by a known conventional means. As a result, the carrier lifetime at the predetermined location in the sample SW to be measured is measured, and the semiconductor carrier lifetime measurement apparatus Xa follows the control of the arithmetic control unit 4 to measure the carrier lifetime at the next predetermined location in the sample SW to be measured. The stage 50 is driven and controlled by the stage controller 51, the sample SW to be measured is moved to the next predetermined position, and the above-described operation is repeated. Thereby, the semiconductor carrier lifetime measuring device Xa scans the entire surface of the sample SW to be measured at a predetermined interval, and measures the carrier lifetime over the entire surface of the sample SW to be measured. This carrier lifetime is a measured value of a region including the first and second regions.

  Then, the semiconductor carrier lifetime measuring device Xa outputs the calculated carrier lifetime to an unillustrated output device such as a display device or a printing device.

  FIG. 4 is a diagram showing a temporal relative output change in the reflected wave of the measurement wave. The horizontal axis in FIG. 4 indicates the elapsed time, and the vertical axis indicates the relative output intensity (level) on a logarithmic scale. In FIG. 4, the solid line indicates the time change of the relative output when the semiconductor is irradiated with infrared light, and the broken line indicates the time change of the relative output when the semiconductor is irradiated with ultraviolet light. FIG. 5 is a diagram showing the time change of the relative output difference (difference measurement wave) of the reflected wave of the measurement wave obtained when the semiconductor is irradiated with infrared light and ultraviolet light, respectively. The horizontal axis in FIG. 5 indicates the elapsed time, and the vertical axis indicates the intensity (level) of the relative output difference (difference measurement wave).

  In general, as shown in FIG. 4, the intensity (relative output) of the reflected wave of the measurement wave is maximized almost immediately after light irradiation and extinguishing, and then decreases with the passage of time, and the carrier eventually reaches a thermal equilibrium state. It becomes almost constant. In the process of decreasing the reflected wave intensity, the reduction rate (reduction rate, reduction amount per unit time) is relatively large in the initial stage and decreases with the passage of time. Further, the temporal intensity change of the reflected wave due to the first infrared laser beam (IR, solid line in FIG. 4) is the time of the reflected wave due to the second ultraviolet laser beam (UV, broken line in FIG. 4). Smaller than the typical intensity change. Then, as shown in FIG. 5, the difference between the intensity of the reflected wave by the first infrared laser beam (IR) and the intensity of the reflected wave by the second ultraviolet laser beam (UV) at each time ( The intensity of the difference measurement wave (δ) decreases with the passage of time and eventually becomes substantially constant. 4 and 5 are normalized by the maximum value almost immediately after the light irradiation and extinction.

The difference (intensity of the difference measurement wave) δ depends on the surface recombination velocity S. The larger the difference (intensity of the difference measurement wave) δ, the larger the surface recombination velocity S, and the difference (difference measurement wave). The surface recombination velocity S can be determined from the intensity of δ. More specifically, generally, a relationship (δ-S / D table) between the difference (intensity of the difference measurement wave) δ and S / D obtained by dividing the surface recombination velocity S by the diffusion velocity D is obtained in advance. The value at which the δ value is substantially constant as described above is obtained, and the S / D corresponding to the substantially constant δ value is referred to from the δ-S / D table to obtain the S / D. By multiplying this by a previously obtained diffusion coefficient D, for example, D = 30 cm ² / s, the surface recombination velocity S is obtained, and the carrier lifetime is obtained.

  Conventionally, the detector detects the first reflected wave of the measurement wave, subsequently detects the second reflected wave of the measurement wave, and the δ value is obtained from the difference between these detection results. Therefore, each of the first and second reflected waves of the measurement wave is measured over the entire dynamic range of the detector. That is, the range from the zero level to the maximum level of the first reflected wave of the measurement wave is measured over the entire dynamic range of the detector. As a result, as shown in FIG. 4, when each of the first and second reflected waves of the measurement wave is measured in the range R2 in the entire dynamic range of the detector, the difference between these detection results is the range. The range R3 (R3 <R2) is smaller (narrower) than R2, and the entire dynamic range of the detector cannot be used effectively. For example, when the range R2 is 10 bits (= 1024), the range R3 is several bits, for example, 3 bits (= 8). The range R3 becomes smaller as the difference between the intensity of the first reflected wave and the intensity of the second reflected wave is smaller, and the entire dynamic range of the detector cannot be used effectively.

  On the other hand, in the semiconductor carrier lifetime measuring apparatus Xa of the present embodiment, a difference measurement wave that is a difference between the first reflected wave and the second reflected wave is generated as a microwave, and the difference measurement wave of the microwave is generated. It is detected by the detector. That is, the range from the zero level to the maximum level of the difference measurement wave is measured over the entire dynamic range of the detector. Accordingly, as shown in FIG. 5, this difference measurement wave can be detected using the entire dynamic range of the detector, and can be detected in a range R1 equivalent to the range R2 in the entire dynamic range of the detector. it can. That is, as compared with the above example, this difference measurement wave is detected with 10 bits (= 1024) equivalent to the range R2.

  As described above, in the semiconductor carrier lifetime measuring apparatus Xa of this embodiment, the first reflected wave of the measurement wave reflected by the first region in the sample SW to be measured or the first transmitted wave of the measurement wave that has passed through the first region and A difference measurement wave, which is a difference between the second reflected wave of the measurement wave reflected by the second region in the sample SW to be measured or the second transmitted wave of the measurement wave transmitted through the second region, is generated by the branching and combining unit 27. The first reflected wave or the first transmitted wave is used as it is and the second reflected wave or the second transmitted wave is used as it is, and this difference measurement wave is detected by the detection unit 3. The carrier lifetime is determined based on the detection result. Therefore, the first measurement result obtained by measuring the first reflected wave or the first transmitted wave with a predetermined detector, and the second reflected wave or the second transmitted wave measured with the detector. It is obtained by directly measuring the difference measurement wave itself with the detector rather than the effective number of digits in the difference between the respective measurement results calculated by obtaining the difference between the second measurement result obtained by The detected number of significant digits of the detection result corresponding to the difference between the measurement results is directly detected by using the entire dynamic range in the detector as described above. So become more. Therefore, the semiconductor carrier lifetime measuring apparatus Xa of this embodiment can measure the carrier lifetime more accurately.

  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 Xa of this embodiment, the first and second lights are infrared light having a wavelength in the infrared region, visible light having a wavelength in the visible light region, and ultraviolet light having a wavelength in the ultraviolet region. Are two lights selected from For this reason, since the wavelength difference between these lights is large, the penetration length difference also becomes large. As a result, the ratio of the influence of the surface recombination included in the first and second reflected waves of the measurement wave is greatly different. It becomes possible to make it. Alternatively, it is possible to greatly vary the ratio of the influence of surface recombination included in the first and second transmitted waves of the measurement wave. Therefore, the semiconductor carrier lifetime measuring apparatus Xa according to the present embodiment can measure the carrier lifetime more accurately than the conventional one.

  Further, in the semiconductor carrier lifetime measuring apparatus Xa of the present embodiment, the initial first and second excess carrier amounts generated when the first and second lights are respectively irradiated on the first and second regions are equal to each other. Thus, the light intensities of the first and second lights are adjusted by the first and second light intensity adjusters 11A and 11B, respectively. For this reason, since the first and second excess carrier amounts are substantially equal to each other in the initial stage, for example, the output signal level of the detector 31 when the surface recombination velocity S is zero can be zero. The carrier life can be measured with higher accuracy. Further, in such a case, as R << Δ1, Δ2, the intensity R1 of the first reflected wave is expressed as R1 = R + Δ1, and the intensity R2 of the second reflected wave is expressed as R2 = R + Δ2. In the initial stage, R1 and R2 substantially coincide (R1 to R2), so δ = ln (R1 / R2) = ln ((R + Δ1) / (R + Δ2)) to ln (R−Δ) Δ = Δ1−Δ2, and δ can be calculated directly from the detection result of the difference measurement wave. Note that “˜” in this paragraph means that both are mathematically approximated.

  Next, another embodiment will be described.

(Second Embodiment)
In the semiconductor carrier lifetime measuring apparatus Xa of the first embodiment, as described above, the surface recombination velocity is obtained by using a known value of the diffusion coefficient D, for example, D = 30 cm ² / s, for the obtained S / D. S is required, and carrier life is required. However, the diffusion coefficient D may not always be known. In particular, the diffusion coefficient D is actually D = (n + p) / (n when the electron and hole carrier concentrations are n and p, respectively, and the electron and hole diffusion coefficients are Dn and Dp, respectively. / Dp + p / Dn) and depends on the carrier concentration and the conductivity type. Therefore, the semiconductor carrier lifetime measuring apparatus Xb of the second embodiment is configured as follows, and also measures the diffusion coefficient D to obtain the carrier lifetime with higher accuracy.

First, the measurement principle in the carrier lifetime measuring apparatus Xb according to the present embodiment will be described. In the microwave photoconductive decay method, the intensity (relative output) of the reflected wave of the measurement wave decreases sequentially with the passage of time as shown in FIG. The profile depends on the wavelength of light applied to the semiconductor of the sample to be measured, and further depends on the surface recombination velocity S. Equation 1 holds 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.
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 Xb 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. The difference δ of the relative change over 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. The surface recombination velocity S can be obtained by multiplying S / D by the diffusion coefficient D as described above.

  Next, the carrier lifetime measuring device Xb according to the second embodiment will be described more specifically. FIG. 6 is a diagram showing the configuration of the semiconductor carrier lifetime measuring apparatus in the second embodiment. 6A shows the overall configuration, and FIG. 6B is a partially enlarged perspective view showing the distal end portion of the waveguide antenna. FIG. 7 is a diagram illustrating a configuration of an arithmetic control unit in the semiconductor carrier lifetime measuring apparatus according to the second embodiment.

  The semiconductor carrier lifetime measuring device Xb in the second embodiment includes, for example, a light irradiation unit 1 (1A, 1B), a measurement wave input / output unit 2, a detection unit 3, as shown in FIG. A calculation control unit 4b and a discharge unit 6 are provided, and a moving unit 5 (not shown in FIG. 6) is further provided to move the measurement location. The light irradiation unit 1 (1A, 1B), the measurement wave input / output unit 2, the detection unit 3 and the moving unit 5 in the semiconductor carrier lifetime measuring apparatus Xb of the second embodiment are the same as those of the semiconductor carrier lifetime measuring apparatus Xa of the first embodiment. The light irradiation unit 1 (1A, 1B), the measurement wave input / output unit 2, the detection unit 3 and the moving unit 5 in FIG. In the carrier life measuring apparatus Xb of the second embodiment, the moving unit 5 arranges the corona wires 62 not only on the front surface but also on the back surface of the sample SW to be measured, as will be described later. The structure is such that the sample SW to be measured is supported by the edge portion of the sample SW, and includes, for example, a hollow cylindrical body such as a horizontal section circle or rectangle.

  The discharge unit 6 changes the surface recombination velocity of the sample SW 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 according to the control of the arithmetic control unit 4b. Is a device for bringing the surface of the sample SW to be measured into at least two different surface recombination velocity states, and corresponds to an example of a surface recombination velocity changing unit. In the present embodiment, for example, the discharge unit 6 generates a corona discharge, and applies the corona discharge to the first and second regions of the sample SW to be measured that are irradiated with the measurement wave by the measurement wave input / output unit 2. It is a discharge generator and corresponds to an example of a corona discharge application unit. In this embodiment, the discharge unit 6 includes a first corona discharge unit 6A that applies corona discharge to the first region of the sample SW to be measured in order to apply corona discharge to the two regions of the first and second regions. And a second corona discharge section 6B for applying corona discharge to the second region of the sample SW to be measured. For example, as shown in FIGS. 6 (A) and 6 (B), the first corona discharge section 6A is a first corona discharge that applies a high voltage to the vicinity of the opening 24b of the third waveguide antenna 24a. By applying a high voltage in the vicinity of the eleventh corona wire 61A that is one electrode and the back surface (back surface region) of the sample SW to be measured facing the first region of the sample SW to be measured, the corona is applied. A twelfth corona wire 62A as a second electrode to be discharged, a power supply unit 63 for generating the high voltage to supply the high voltage to each of the eleventh and twelfth corona wires 61A, 62A, and a twelfth corona wire An attachment member 64A for attaching 62A in the vicinity of the rear surface region is provided. Similarly, as shown in FIG. 6A, the second corona discharge part 6B is a first electrode that corona discharges by applying a high voltage in the vicinity of the opening 25b of the fourth waveguide antenna 25a. A corona discharge is caused by applying a high voltage in the vicinity of a certain 21st corona wire 61B and the back surface (back surface region) of the sample SW to be measured facing the second region of the sample SW to be measured. In order to supply the twenty-second corona wire 62B, which is two electrodes, and the high voltage to each of the twenty-first and twenty-second corona wires 61B, 62B, the power supply unit 63 that generates the high voltage and the twenty-second corona wire 62B And an attachment member 64B attached in the vicinity of the back surface region.

  These eleventh, twelfth, twenty-first and twenty-second corona wires 61A, 62A; 61B, 62B are, for example, tungsten wires having a wire diameter of 0.1 mm. In FIG. 6 (B), the waveguide antenna 24a is, for example, a rectangular tube, a part of each of the two opposing surfaces of the opening 24b is cut out, and a predetermined part is provided in each of the cut out parts. An insulator 61Aa is provided. The eleventh corona wire 61A is attached so as to cross the center of the opening 24b across the two opposing insulators 61Aa (FIG. 6B shows the insulator 61Aa. Only one is shown). The eleventh corona wire 61 is connected to the power supply unit 63 by a connection line 61Ab, whereby the eleventh corona wire 61 and the waveguide antenna 24a are insulated. The twelfth corona wire 62A is similarly insulated and attached to the attachment member 64. The same applies to the 21st corona wire 61B and the 22nd corona wire 62B. Further, the sample SW to be measured is arranged such that the sample SW to be measured is disposed between the eleventh corona wire 61A and the twelfth corona wire 62A and between the twenty-first corona wire 61B and the twenty-second corona wire 62B. The stage 5 (not shown) to be supported is provided. With this configuration, the eleventh and twelfth corona wires 61A and 62A provided so as to be close to the sample SW to be measured and the 21st provided so as to be close to the sample SW to be measured. The corona discharge generated by applying a predetermined voltage to the electrodes of the 22nd corona wires 61B and 62B by the power source 63 is applied to the sample SW to be measured.

  Similar to the calculation control unit 4, the calculation control unit 4b is a device that performs overall control of the semiconductor carrier lifetime measuring device Xb, and includes, for example, a microcomputer including a macro processor and a memory. Then, as shown in FIG. 7, the arithmetic control unit 4 b calculates the carrier lifetime based on the intensity of the difference measurement wave detected by the detection unit 3, which is the difference between the measurement waves interacted with the sample SW to be measured. A calculation unit 41 for calculating is provided. For example, by executing a carrier life calculation program that calculates the carrier life based on the intensity of the difference measurement wave detected by the detection unit 3, the calculation unit 41 functionally includes the first state calculation unit 411 and 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 SW to be measured is in the first surface recombination velocity state, the first state calculation unit 411 causes the light irradiation unit 1 to send the first and second lights to the first and second regions of the sample SW to be measured, respectively. The first surface recombination is performed on the basis of the first difference measurement wave that is irradiated and irradiated with the measurement wave to the first and second regions of the sample SW to be measured by the measurement wave input / output unit 2 and detected by the detection unit 3. The S / D in the velocity state 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 to be used when measuring the same type of sample SW to be measured next.

  When the sample SW to be measured is in a second surface recombination velocity state different from the first surface recombination velocity state, the second state calculation unit 412 converts the first and second lights to be measured by the light irradiation unit 1. Second difference measurement in which the first and second regions of SW are respectively irradiated and the measurement wave is irradiated by the measurement wave input / output unit 2 to the first and second regions of the sample SW to be measured and detected by the detection unit 3 Based on the wave, the S / D in the second surface recombination velocity state is obtained, and the S / D in the obtained second surface recombination velocity state and the diffusion coefficient D obtained by the first state calculation unit 411 are calculated. Based on this, the surface recombination velocity S is obtained.

  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 a correspondence relationship between δ values and S / D values, and is obtained in advance by simulation or the like, for example. As shown in Equation 4, the difference δ in time relative change is the intensity of the reflected wave due to the irradiation of the first light (long wavelength light) with respect to the intensity of the reflected wave due to the irradiation of the second light (short wavelength light). Natural logarithm.
δ = ln ((first light (long wavelength light) reflected measurement wave intensity) / (second light (short wavelength light) reflected measurement wave intensity)) (4)

  The semiconductor carrier lifetime measuring apparatus Xb having such a configuration measures the semiconductor bulk carrier lifetime τb by operating as follows, for example. FIG. 8 is a flowchart showing an example of the operation of the semiconductor carrier lifetime measuring apparatus according to the second embodiment. FIG. 9 is a flowchart showing the operation of the semiconductor carrier lifetime measuring apparatus according to the second embodiment when obtaining the diffusion coefficient. FIG. 10 is a diagram showing the relationship between the diffusion coefficient and the bulk carrier lifetime when S / D = 4000. The horizontal axis in FIG. 10 represents the diffusion coefficient, and the vertical axis represents the bulk lifetime.

  In FIG. 8, first, a semiconductor wafer to be measured is subjected to the cleaning process in advance, 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 stage 50 (not shown in FIG. 6) of the moving unit 5 as the sample SW to be measured, and is sandwiched between the eleventh corona wire 61A and the twelfth corona wire 62A. At the same time, it is set at a predetermined arrangement position sandwiched between the 21st corona wire 61B and the 22nd corona wire 62B.

  Then, for example, when the start switch (not shown) is operated, the measurement of the carrier life of the sample SW to be measured by the semiconductor carrier life measuring device Xb is started, and the arithmetic control unit 4b The stage 50 is driven and controlled by the stage controller 51 according to the control, and the sample SW to be measured is moved to a predetermined position.

  Subsequently, the S / D when the sample SW 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, when the sample SW to be measured is moved to a predetermined position by the moving unit 5, the measurement wave is measured by the measurement wave input / output unit 2 according to the control of the arithmetic control unit 4b as shown in FIG. The first and second light beams are emitted to the first and second regions of the sample SW (S21), and the first and second light beams are measured by the first and second light irradiation units 1A and 1B, respectively, according to the control of the calculation control unit 4b. The measurement wave irradiated to each of the first and second regions and interacted with the sample SW to be measured in the first region and the measurement wave interacted with the sample SW to be measured in the second region A difference measurement wave, which is a difference between the two, is directly generated, and the difference measurement wave is detected by the detection unit 3 (S22), and the detection result is output from the detection unit 3 to the calculation control unit 4b.

Then, the first state calculation unit 411 of the calculation unit 41 obtains a δ value based on the output of the detection unit 3, obtains a value at which this δ value becomes substantially constant as described above, and δ−S / By referring to the δ-S / D table of the D table storage unit 415, the S / D corresponding to the value at which the δ value becomes substantially constant is obtained (S23). 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 (S24). 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 D in the sample SW to be measured by Expression 5 obtained by modifying Expression 1. The obtained diffusion coefficient D is stored in the diffusion coefficient storage unit 414 (S25). In this process, α in Equation 5 is α1.
τb = 1 / ((1 / τ1) −α ² × D) (5)

  Here, 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. 10 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. 10) is the diffusion coefficient D.

  With each of these processes, the S / D when the sample SW 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. 8, the surface treatment of the sample SW to be measured is subsequently performed based on the obtained diffusion coefficient D (about 15.6 in the example of FIG. 10) (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 the present 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 SW to be measured. . More specifically, the power supply unit 63 applies high voltages having different polarities to the eleventh and twelfth corona wires 61A and 62A and controls the twenty-first and twenty-second corona wires 61B and 62B according to the control of the arithmetic control unit 4b. Are applied with high voltages having different polarities. Accordingly, corona discharge is applied from both the eleventh and twelfth corona wires 61A and 62A to both main surfaces of the sample SW to be measured on the first region, surface treatment is performed, and the twenty-first and twenty-second corona wires are applied. Corona discharge is applied from both 61B and 62B to both main surfaces of the sample SW to be measured in the second region, and surface treatment is performed.

  Subsequently, the S / D when the sample SW 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 (S14).

  More specifically, while applying a high voltage to the eleventh, twelfth and twenty-first and twenty-second corona wires 61A, 62A; 61B, 62B by the power source 63, the processing S21 and the processing S22 described above with reference to FIG. By the same processing as each of the above, the difference measurement wave by the first and second lights is detected by the detection unit 3 and taken into the calculation unit 41 of the calculation control unit 4b.

  Subsequently, by the same process as the process S23 described above with reference to FIG. 9, the second state calculation unit 412 of the calculation unit 41 obtains a δ value based on the output of the detection unit 3, and the δ value is substantially constant. Then, by referring to the δ-S / D table in the δ-S / D table storage unit 415, the S / D corresponding to the value at which the δ value becomes substantially constant is obtained.

  Subsequently, the second 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 SW 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 device Xb outputs the obtained bulk carrier lifetime τb to a not-shown output device 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 Xb of the present embodiment irradiates the semiconductor of the sample SW to be measured with a predetermined measurement wave when the semiconductor of the sample SW to be measured is in the first surface recombination velocity state. By irradiating at least two types of light having different wavelengths, the first and second lights in the present embodiment, the first reflected wave or the first transmitted wave of the measurement wave in the first region of the sample SW to be measured; A first difference measurement step of measuring a first difference measurement wave that is a difference between a second reflected wave or a second transmitted wave of a measurement wave in a second region of the sample SW to be measured; When the coupling speed is S and the diffusion coefficient is D, the first S / D for obtaining the S / D in the first surface recombination speed state based on the first difference measurement wave measured by the first difference measurement step. D calculation step, the first S A diffusion coefficient calculation step for obtaining a diffusion coefficient D based on S / D in the first surface recombination velocity state obtained in the D calculation step, which is different from the first surface recombination velocity state from the first surface recombination velocity state. A surface recombination velocity state changing step for changing the semiconductor to be measured to the second surface recombination velocity state, and a predetermined measurement wave is measured when the semiconductor of the sample SW to be measured is in the second surface recombination velocity state By irradiating the semiconductor of the sample SW with at least two types of light having different wavelengths, in this embodiment, the first and second lights, the first wave of the measurement wave in the first region of the sample SW to be measured is irradiated. A second difference measurement step of measuring a second difference measurement wave that is a difference between the reflected wave or the first transmitted wave and the second reflected wave or the second transmitted wave of the measurement wave in the second region of the sample SW to be measured; Second difference measuring step Accordingly, the second S / D calculation step for obtaining the S / D in the second surface recombination velocity state based on the measured second difference measurement wave, the second surface recombination velocity state obtained in the second S / D calculation step Surface recombination velocity calculation step for obtaining surface recombination velocity S based on S / D at the surface, carrier lifetime in semiconductor of sample SW to be measured based on surface recombination velocity S obtained in surface recombination velocity calculation step Each process of the lifetime calculation process which calculates | requires is performed.

  Since the semiconductor carrier lifetime measuring apparatus Xb of this embodiment only needs to obtain each difference measurement wave in the first and second surface recombination velocity states, the value of the diffusion coefficient D in the semiconductor of the sample SW to be measured is obtained. There is no need to make assumptions, and the carrier life can be measured more accurately than in the past.

  Further, in the semiconductor carrier lifetime measuring apparatus Xb of the present embodiment, as an example of a surface recombination velocity state changing unit that changes the surface recombination velocity state of the sample SW to be measured between a plurality of states, the first measurement sample SW of the sample SW to be measured is used. And the discharge part 6 which provides a corona discharge to the 2nd area | region is provided. For this reason, the semiconductor carrier lifetime measuring apparatus Xb of this embodiment can change the surface recombination velocity state in the sample SW to be measured from the first state to the second state by the discharge unit 6, and the corona A second recombination velocity state can be achieved by the discharge. In addition, since the second surface recombination velocity state is realized by corona discharge, the physicochemical properties of the sample SW to be measured can be restored by terminating the application of the corona discharge. In order to change the surface recombination velocity state, it is not necessary to perform prior processing, and since there is almost no change in the physicochemical properties before and after the carrier lifetime measurement, the carrier lifetime can be measured in the production line. It becomes possible.

  In addition, a semiconductor wafer is usually in a state where a natural oxide film is generated on the surface thereof through a cleaning process for removing contamination such as dirt before use. In the semiconductor carrier lifetime measuring apparatus Xb of the present embodiment, the natural oxide film exposed by this cleaning process is set to the first surface recombination speed state. Therefore, the process for realizing the first surface recombination speed state is performed by this cleaning process. When the sample SW to be measured is a semiconductor wafer, the number of man-hours can be reduced.

  Further, in the second embodiment of the example shown in FIG. 6 described above, the detection unit 3 detects the reflected wave of the measurement wave irradiated to the sample SW to be measured, but the first of the measurement waves irradiated to the sample SW to be measured. And the second transmitted wave may be used. For example, the first transmission of the measurement wave so as not to interfere with the twelfth corona wire 62A in the vicinity of the back surface (back surface region) of the measurement sample SW opposed to the first region of the measurement sample SW irradiated with the measurement wave. A waveguide for guiding the wave is provided, and interferes with the 22nd corona wire 62B near the back surface (back surface region) of the sample SW to be measured facing the second region of the sample SW to be measured irradiated with the measurement wave. In order to avoid this, a waveguide for guiding the second transmitted wave of the measurement wave is provided, and a difference measurement wave which is a difference between the first and second transmitted waves of the measurement wave guided by each of the waveguides is provided. A synthesizing unit that is generated by using the first transmitted wave as it is and using the second transmitted wave as it is is provided so that the difference measurement wave synthesized by the synthesizing unit is guided to the mixer 30 of the detecting unit 3. May be configured. Even with such a configuration, the semiconductor carrier lifetime measuring apparatus Xb can measure the bulk carrier lifetime τb by the same processing as that when measuring the reflected wave of the measurement wave.

  Next, another embodiment will be described.

(Third embodiment)
When the sample SW to be measured is a solar cell semiconductor wafer (PV semiconductor wafer), it is more practical to measure the characteristics of the PV semiconductor wafer in a state where light is irradiated to generate power. The semiconductor carrier lifetime measuring device Xc of the third embodiment is the same as that of the semiconductor carrier lifetime measuring devices Xa and Xb of the first and second embodiments described above, in which the semiconductor wafer for solar cells is irradiated with light to generate power. In order to measure the actual characteristics of the (PV semiconductor wafer) with higher accuracy, the apparatus further includes a power generation light irradiation section 7 that irradiates the measurement target SW with power generation light.

  Here, the semiconductor carrier lifetime measuring device Xc of the third embodiment in which the semiconductor carrier lifetime measuring device Xa of the first embodiment is further provided with the power generation light irradiation unit 7 will be described, but the semiconductor carrier lifetime measuring device of the second embodiment will be described. The semiconductor carrier lifetime measuring apparatus Xc according to the third embodiment in which the power generation light irradiation unit 7 is further added to Xb can be similarly described.

  FIG. 11 is a diagram showing the configuration of the semiconductor carrier lifetime measuring apparatus in the third embodiment. In FIG. 11, the semiconductor carrier lifetime measuring device Xc of the third embodiment includes a light irradiation unit 1 (1A, 1B), a measurement wave input / output unit 2, a detection unit 3, an arithmetic control unit 4, and a moving unit 5. And a power generation light irradiation unit 7. The light irradiation unit 1 (1A, 1B), the measurement wave input / output unit 2, the detection unit 3, the calculation control unit 4 and the moving unit 5 in the semiconductor carrier lifetime measuring apparatus Xc of the third embodiment are the same as those of the semiconductor device of the first embodiment. Since it is the same as the light irradiation part 1 (1A, 1B), the measurement wave input / output part 2, the detection part 3, the calculation control part 4, and the movement part 5 in the carrier lifetime measurement apparatus Xa, the description thereof is omitted.

  The power generation light irradiation unit 7 includes, for example, a third light source unit 71 that emits power generation light (bias light) having a predetermined spectral distribution set in advance under the control of the arithmetic control unit 4, and a third light source unit 71. A bias emitted from the third light source unit 71 is configured to include a light guide member 72 such as an optical fiber for guiding the emitted bias light toward the first and second regions of the sample SW to be measured. Light is applied to the first and second regions of the sample SW to be measured via the light guide member 72. As a result, the PV semiconductor wafer as the sample SW 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 71 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 71 is preferably light corresponding to 1 SUN, and more preferably light having a pseudo sunlight spectrum. In the measurement of the carrier lifetime, each of the above-described processes is performed while irradiating the measured sample SW with the bias light by the power generation light irradiation unit 7. By further including such a power generation light irradiation unit 7, the semiconductor carrier lifetime measuring device Xc of the present embodiment measures the actual characteristics of the PV semiconductor wafer in a state where light is irradiated to generate power more accurately. It becomes possible to do.

  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. It is difficult to estimate the diffusion coefficient of the semiconductor wafer for PV, and in particular, the third embodiment is further provided with the power generation light irradiation unit 7 in the semiconductor carrier lifetime measuring device Xb of the second embodiment. Since the semiconductor carrier lifetime measuring apparatus Xc operates as described in the second embodiment, the bulk carrier lifetime τb can be measured more accurately than in the past.

  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.

Xa, Xb, Xc Semiconductor carrier lifetime measuring device 1 Light irradiation unit 2 Measurement wave input / output unit 3 Detection unit 4, 4b Operation control unit 5 Moving unit 6 Discharge unit 7 Power generation light irradiation unit 61, 62 Corona wire 411 First state calculation Unit 412 second state calculation unit 413 life calculation unit 414 diffusion coefficient storage unit 415 δ-S / D table storage unit

Claims (8)

A light irradiation unit that irradiates at least two types of light having different wavelengths to different first and second regions in a semiconductor to be measured;
A measurement wave irradiation unit that irradiates each of the first and second regions with a predetermined measurement wave;
The first reflected wave of the measurement wave reflected by the first region, the first transmitted wave of the measurement wave transmitted through the first region, and the second reflected wave of the measurement wave reflected by the second region or A difference measurement wave, which is a difference between the measurement wave transmitted through the second region and a second transmission wave, is used as the first reflection wave or the first transmission wave, and the second reflection wave or the second reflection wave is used. A difference measurement wave generator that is generated by using the transmitted wave as it is;
A detection unit for detecting the difference measurement wave generated by the difference measurement wave generation unit;
A semiconductor carrier lifetime measuring apparatus comprising: an arithmetic unit that calculates a carrier lifetime in the semiconductor to be measured based on a detection result detected by the detector. The at least two types of light are two lights selected from a first light having a wavelength in the infrared region, a second light having a wavelength in the visible light region, and a third light having a wavelength in the ultraviolet region. The semiconductor carrier lifetime measuring apparatus according to claim 1. The first and second excess carrier amounts generated when the first and second regions are irradiated with at least two types of light having different wavelengths are made equal to each other so that the first and second excess carrier amounts are equal to each other. The semiconductor carrier lifetime measuring apparatus according to claim 1, further comprising a light intensity control unit that controls at least one of the light intensities. A surface recombination velocity state changing unit for changing a surface recombination velocity state in the semiconductor to be measured;
The calculation unit includes a first detection result detected by the detection unit when the semiconductor to be measured is in a first surface recombination velocity state, and the semiconductor to be measured is in the first surface recombination velocity state. 4. The carrier lifetime in the semiconductor to be measured is obtained based on the second detection result detected by the detection unit in the case of different second surface recombination velocity states. 5. The semiconductor carrier lifetime measuring apparatus of any one of Claims. 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 any one of claims 1 to 6, further comprising a power generation light irradiation unit that irradiates the measurement target semiconductor with power generation light. A light irradiation step of irradiating different first and second regions in a semiconductor to be measured with at least two types of light having different wavelengths;
A measurement wave irradiation step of irradiating each of the first and second regions with a predetermined measurement wave;
The first reflected wave of the measurement wave reflected by the first region, the first transmitted wave of the measurement wave transmitted through the first region, and the second reflected wave of the measurement wave reflected by the second region or A difference measurement wave, which is a difference between the measurement wave transmitted through the second region and a second transmission wave, is used as the first reflection wave or the first transmission wave, and the second reflection wave or the second reflection wave is used. A differential measurement wave generating step generated by using the transmitted wave as it is,
A detection step of detecting the difference measurement wave generated in the difference measurement wave generation step;
And a calculation step for obtaining a carrier lifetime in the semiconductor to be measured based on the detection result detected in the detection step.

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