JP2009058274A - Crystallinity evaluation device of silicon semiconductor thin film and crystallinity evaluation method using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crystallinity evaluation method of a silicon semiconductor thin film capable of suppressing the deterioration of crystallinity evaluating precision caused by the irregularity of the thickness dimension of a base material having light perviousness. <P>SOLUTION: This crystallinity evaluation device of the silicon semiconductor thin film includes an exciting laser 1 for irradiating a predetermined irradiation region of the silicone semiconductor thin film 5a with carrier excitation light, a semiconductor laser 10 for radiating infrared rays, a high frequency pulse power supply 18 capable of irradiating the semiconductor laser 10 with a plurality of kinds of different infrared rays by supplying a current modified in intensity to the semiconductor laser 10, a photodetector 13 which detects the intensity of the reflected light reflected by the silicone semiconductor thin film 5a or the base material 5b and contains at least two kinds of the infrared rays of a plurality of kinds of infrared rays to output its detection signal, and a signal processor 9 for forming data for evaluating the crystallinity of the silicon semiconductor thin film 5a on the basis of the detection signal. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an apparatus and method for evaluating the crystallinity of a silicon semiconductor thin film, and in particular, to evaluate the crystallinity of a silicon semiconductor thin film formed on a light-transmitting substrate such as a glass substrate. The present invention relates to an apparatus and a method.

  In recent years, as a thin film transistor (TFT) used in a liquid crystal display device, a polycrystalline silicon (p-Si) thin film is used instead of a conventional amorphous silicon semiconductor thin film transistor (a-Si TFT) using an amorphous silicon (a-Si) thin film. A polycrystalline silicon semiconductor thin film transistor (p-Si TFT) using the above is used. The p-Si TFT is a silicon semiconductor thin film having a high electron mobility, and can realize high definition, high image quality, and high response speed of the liquid crystal display device.

  A p-Si thin film used for the p-Si TFT is formed on the surface of a glass substrate or the like used for a liquid crystal display device. As a method for forming a p-Si thin film on the surface of the base material, a method is used in which an a-Si thin film previously formed on the surface of the base material is melt-crystallized to change to a p-Si thin film. As a method for melting and crystallizing an a-Si thin film into a p-Si thin film, an excimer laser annealing method (ELA method) in which the a-Si thin film is annealed by irradiating it with an excimer laser is frequently used. . However, the crystal structure of the p-Si thin film obtained by the excimer laser annealing method, such as the crystal particle diameter and crystal orientation, is subject to manufacturing conditions such as variations in the thickness of the pre-formed a-Si thin film and pulse fluctuations of the excimer laser to be irradiated. Varies depending on Therefore, in order to obtain a stable product with high yield in the production of p-Si thin film, the crystallinity of the obtained p-Si thin film is evaluated on-line in the production line in a short time, and the result is There has been a demand for a method capable of promptly feeding back to the manufacturing conditions of the p-Si thin film.

  As methods for evaluating the crystallinity of a p-Si thin film, methods using an X-ray diffraction method, Rutherford backscattering method, transmission electron diffraction method, and the like have been conventionally known. All of these methods are measured. Because it is a destructive test that requires a relatively long time to prepare a measurement sample by destroying the measurement object, it is difficult to evaluate on-line in the production line in a short time. It was difficult to feed back to manufacturing conditions quickly.

  As a method for solving the above problem, for example, a method for evaluating crystallinity of a silicon semiconductor thin film using Raman spectroscopy as described in Patent Document 1 below is known.

In this evaluation method using Raman spectroscopy, a silicon thin film formed on a glass substrate is irradiated with excitation light, Raman scattered light from the polycrystalline silicon thin film is received, and crystals are crystallized based on the Raman scattered light. We are going to evaluate sex.
JP 2004-226260 A

  However, in the crystallinity evaluation method using Raman spectroscopy, it is difficult to obtain an accurate evaluation result because it is necessary to detect very weak intensity of Raman scattered light.

  In recent years, it has been required to evaluate a silicon semiconductor thin film with high accuracy even when there is an error in the thickness dimension of a light-transmitting base material such as a glass substrate.

  It is an object of the present invention to provide an evaluation apparatus and an evaluation method for crystallinity of a silicon semiconductor thin film that solve the above problems.

  In order to solve the above-described problems, the present invention provides an apparatus for evaluating the crystallinity of a silicon semiconductor thin film formed on a light-transmitting base material, wherein a predetermined surface on the surface of the silicon semiconductor thin film is formed. From excitation light irradiating means for irradiating excitation light to excite carriers in the irradiation region, infrared light radiating means capable of emitting a plurality of types of infrared light having different wavelengths, and the infrared light radiating means Condensed irradiating means for irradiating the irradiated area in the state where the emitted infrared light is condensed, and reflected by the silicon semiconductor thin film or the substrate among the infrared light irradiated by the condensed irradiating means Reflected light intensity detecting means for detecting the intensity of reflected light of the plurality of types of infrared light and outputting the detection signal, and evaluating the crystallinity of the silicon semiconductor thin film based on the detection signal Data to create It provides crystalline evaluation apparatus of a silicon semiconductor thin film characterized comprising a data creation means that.

  A predetermined irradiation region on the surface of the silicon semiconductor thin film formed on the substrate using the excitation light irradiation means is irradiated with light having a band gap or more to excite carriers in the silicon semiconductor. When infrared light is irradiated using the light emitting means and the condensing irradiation means, a part of the infrared light is reflected by the silicon semiconductor thin film. The reflectance of the infrared light at this time depends on the amount of excited carriers existing in the irradiation region. As the amount of the carrier increases, the reflectance of infrared light reflected near the thin film decreases. In a silicon semiconductor thin film, the higher the crystallinity, the greater the amount of excited carriers present. Therefore, the higher the crystallinity, the lower the reflectivity.

  On the other hand, in the silicon semiconductor thin film formed on the substrate, the reflectance of the reflected infrared light generally depends on the temperature of the thin film. The reflectance increases as the temperature of the thin film increases.

  When the carriers of the silicon semiconductor thin film are excited with excitation light, the relaxation time of the excited carriers is longer as the crystallinity of the thin film is higher. Further, since the diffusibility of excited carriers is higher as the crystallinity is higher, the diffusibility of heat generated by recombination of excited carriers is higher. Therefore, the higher the crystallinity, the lower the degree of local temperature rise, and the less the amount of heat energy given locally to the substrate, resulting in a decrease in the reflectance of infrared light.

  As described above, a predetermined region on the surface of the silicon semiconductor thin film is irradiated with excitation light that exceeds the band gap of the semiconductor of the semiconductor thin film to excite carriers, and an infrared region is irradiated in the irradiation region irradiated with the excitation light. When light is irradiated, generally, the lower the crystallinity, the higher the reflectance, and the higher the crystallinity, the lower the reflectance. Therefore, the crystallinity of the thin film can be evaluated by measuring the reflectance.

  Furthermore, in the present invention, the infrared light radiating means emits a plurality of types of infrared light having different wavelengths, and the intensity of reflected light including at least two types of infrared light among the plurality of types of infrared light. Since the data for evaluating the crystallinity of the silicon semiconductor thin film is created based on the above, it is possible to prevent the crystallinity evaluation accuracy from deteriorating due to variations in the thickness dimension of the substrate. Details thereof will be described below.

  Since the thickness dimension of the silicon semiconductor thin film formed on a light-transmitting base material such as a glass base material is shorter than the wavelength of the infrared light to be irradiated, The portion is transmitted through the silicon semiconductor thin film. Furthermore, since the infrared light transmitted through the silicon semiconductor thin film has little absorption in the base material particularly when its wavelength is several μm or less, it also passes through the base material and is reflected on the back surface of the base material. Therefore, the reflected light from the silicon semiconductor thin film includes the reflected light from the back surface of the base material in addition to the reflected light from the surface of the silicon semiconductor thin film.

  And among the reflected light from the silicon semiconductor thin film, between the light reflected by the surface of the silicon semiconductor thin film and the light reflected by the back surface of the base material, cancellations caused by the different optical path lengths. Interference phenomena such as strengthening will occur. For this reason, the intensity of reflected light from the silicon semiconductor thin film changes depending on the thickness dimension of the base material and the wavelength of infrared light.

  This change in reflected light intensity changes periodically according to the thickness of the substrate when the wavelength of infrared light is fixed (see FIG. 5), and this change is for evaluating crystallinity. This affects the intensity of reflected light.

  Therefore, in the present invention, the silicon semiconductor thin film is irradiated with a plurality of types of infrared light having different wavelengths, and based on the intensity of reflected light including at least two types of infrared light among the plurality of types of infrared light. Compared to the case where the crystallinity is evaluated only by the reflected light intensity of single-wavelength infrared light, the crystallinity is evaluated. High crystallinity evaluation can be performed.

  In the crystallinity evaluation apparatus for a silicon semiconductor thin film, the infrared light emitting means supplies a semiconductor laser that emits infrared light, and an intensity-modulated current to the semiconductor laser, thereby providing a wavelength of the semiconductor laser. It is preferable to include a current supply unit capable of irradiating different types of infrared light.

  According to this configuration, by supplying an intensity-modulated current to the semiconductor laser, it is possible to irradiate the silicon semiconductor thin film with a plurality of types of infrared light having different wavelengths by a mode hop phenomenon peculiar to the semiconductor laser.

  In the silicon semiconductor thin film crystallinity evaluation apparatus, the current supply means is configured to supply the semiconductor laser with a current whose intensity is modulated at a frequency within a period within the decay time of relaxation oscillation in the semiconductor laser. It is preferable.

  Here, “attenuation time of relaxation oscillation” means that the supply current to the semiconductor laser is changed abruptly, resulting in non-steady emission due to the delay time to light emission and the transient nonuniformity of the supply current (carrier). This is the time during which the phenomenon occurs. Within this relaxation oscillation decay time, the carrier concentration of the semiconductor laser is larger than that in the steady state, so that the wavelength band that can be oscillated is widened. As a result, a plurality of laser beams having different wavelengths can be oscillated simultaneously. (Multimode oscillation).

  According to the above configuration, since the current whose intensity is modulated at the frequency of the period within the decay time of the relaxation oscillation is supplied, the semiconductor laser is caused to perform the multimode oscillation, and a plurality of different wavelengths are provided. Laser light can be oscillated simultaneously.

  In the silicon semiconductor thin film crystallinity evaluation apparatus, the infrared light reflected on the surface of the silicon semiconductor thin film is guided into the detection range of the reflected light intensity detecting means, while the infrared light reflected on the back surface of the base material is reflected. It is preferable that light guide means for guiding the reflected light intensity detection means to outside the detection range is further provided.

  According to this configuration, it is possible to exclude the infrared light reflected on the back surface of the base material unnecessary for the crystallinity evaluation from the detection target of the reflected light intensity detection unit, so that the accuracy of the crystallinity evaluation can be further improved. it can.

  In the crystallinity evaluation apparatus for a silicon semiconductor thin film, the light guide means has a focal point set on the surface of the silicon semiconductor thin film, and reflects light from the surface of the silicon semiconductor thin film within a detection range of the reflected light intensity detection means. The lens can also be used as the condensing irradiation means for condensing the infrared light emitted from the infrared light emitting means on the surface of the silicon semiconductor thin film. preferable.

  According to this configuration, the infrared light is condensed on the surface of the silicon semiconductor thin film, and the reflected light from the surface is guided into the detection range of the reflected light intensity detecting means using the common lens. be able to.

  As the excitation light used for the excitation light irradiation means in the present invention, using pulsed light can instantaneously generate many carriers and increase the intensity change of reflected light of infrared light. It is preferable from the point.

  On the other hand, the wavelength of infrared light emitted by the infrared light emitting means in the present invention is preferably 1 to 10 μm. When infrared light having a short wavelength such as less than 1 μm is irradiated, carriers are also excited by the infrared light, so that the reflectance detection accuracy depending on the amount of excited carriers tends to decrease. In addition, the longer the wavelength of the infrared light, the stronger the interaction with the excited carrier, so the longer the wavelength of the measurement light, the better the detection accuracy. However, if the wavelength becomes too long, the light is condensed on the thin film. Irradiation becomes difficult. When evaluating the crystallinity of a p-Si thin film formed by excimer laser annealing, a high spatial resolution of several tens of μm or less, preferably 10 μm or less is usually required. Therefore, it is preferable to use infrared light having a wavelength of 10 μm or less in order to accurately irradiate the focused portion with the focused infrared light while maintaining such high spatial resolution. When infrared light having a wavelength in such a range is used, it is possible to easily and accurately irradiate the light with an irradiation diameter of 10 μm or less even with a normal optical lens, and accurately with high spatial resolution. The crystallinity can be evaluated.

  The infrared light includes, for example, broadband light having a spread of 10 nm or more in wavelength. When such broadband infrared light is used, the coherence can be weakened compared to the case where infrared light with a narrower band is used, so the evaluation of crystallinity is more stable. Can be done. That is, when narrow-band infrared light is adopted, the infrared light irradiated on the silicon semiconductor thin film and the infrared light reflected on the bottom surface of the base material under the semiconductor thin film interfere with each other, and the base While it is easy for reflectance fluctuations to occur depending on the thickness of the material, the interference is less likely to occur when broadband infrared light is used, so a stable measurement value can be obtained regardless of the thickness of the substrate. it can.

  By using the silicon semiconductor thin film crystallinity evaluation apparatus and method of the present invention, the crystallinity of the semiconductor thin film can be evaluated without destroying the sample. In addition, since the crystallinity of the thin film can be evaluated quickly and non-destructively, the formed thin film is evaluated online even on a production line for forming the thin film on a substrate. Quick feedback to manufacturing conditions.

  Furthermore, according to the present invention, the crystallinity can be evaluated with high accuracy even when the thickness of the base material varies as compared with the case where the crystallinity is evaluated only by the reflected light intensity of single-wavelength infrared light. It can be performed.

  Hereinafter, the present invention will be described more specifically.

  FIG. 1 shows an example of the overall configuration of a silicon semiconductor thin film crystallinity evaluation apparatus according to an embodiment of the present invention.

  The crystallinity evaluation apparatus shown in FIG. 1 is for evaluating the crystallinity of a silicon semiconductor thin film 5a formed on a substrate 5b. Here, the silicon semiconductor thin film 5a to be evaluated for crystallinity is a silicon semiconductor thin film made of polysilicon having a thickness of several nanometers to several tens of nanometers, or a silicon semiconductor thin film made of single crystal silicon having a thickness of several micrometers or less. A typical example is given.

  The crystallinity evaluation apparatus includes a substrate stage 17 that supports the substrate 5b, excitation light irradiation means, infrared light emission means, focused light irradiation means, reflected light intensity detection means, and timing detection means. And data creation means.

  In this embodiment, a glass substrate having a thickness of 0.5 mm is used for the base material 5b, and the base material 5b is placed on the base material stage 17 in a horizontal state. The substrate stage 17 is driven in the horizontal direction under the control of the controller 16.

  The excitation light irradiation means irradiates a predetermined irradiation region on the surface of the silicon semiconductor thin film 5a formed on the substrate 5b on the substrate stage 17 with excitation light that excites carriers in the silicon semiconductor thin film. , An excitation laser 1, a beam conditioner 2, and a dichroic mirror 6.

  The excitation laser 1 emits pulsed light (for example, wavelength 355 nm, pulse width 10 ns) as excitation light. In this embodiment, an ultraviolet pulse laser is used as the excitation laser 1 in order to efficiently absorb the excitation light in the thin film sample. In the present invention, the excitation light does not necessarily need to be pulsed light, but when the instantaneous light intensity is large, more carriers can be generated instantaneously, so that the signal intensity of the detection signal described later is increased. It is preferable because it is possible. The excitation light whose intensity varies periodically is not necessarily pulsed light, and may be any light whose intensity is periodically modulated.

  The beam adjuster 2 is composed of a combination lens, and adjusts the divergence angle of the pulsed light beam transmitted from the excitation laser 1 through a beam splitter 3 described later. The dichroic mirror 6 reflects the excitation light, the divergence angle of which has been adjusted by the beam adjuster 2, to the base material 5 b side, and transmits the condenser lens 4 described later, for example, an irradiation diameter of 0.01 to 1 mm. Irradiate to a certain area.

  The infrared light emitting means is for emitting infrared light. In this embodiment, the semiconductor laser 10 is provided. As this semiconductor laser 10, for example, a laser that emits infrared light having a wavelength of about 1.3 to 1.6 μm is used.

  Further, as the infrared light emitted by the infrared light emitting means, a broadband light having a spread of 10 nm or more in wavelength can be adopted. For example, as shown by L1 in FIG. 3, when an SLD (Super Luminescent Diode) is adopted as the infrared light emitting means, infrared light having a wavelength broadening of about 30 nm as its half-value width can be irradiated. Here, the “half-value width” refers to a spread (width) of a wavelength at an intensity half the peak value of the oscillation light intensity in the oscillation spectrum (intensity indicated by a broken line in FIG. 3). In addition, L2 of the figure shows the case where a laser diode (monochromatic light) is adopted as the infrared light emitting means, and in this case, infrared light having a wavelength spread of about 1 nm as its half-value width is shown. Will be irradiated. When broadband infrared light is used like the SLD, the coherence can be weakened compared to the case where a narrow-band laser diode or the like is used, so the evaluation of crystallinity is more stable. Can be done. That is, when narrow-band infrared light is employed, the infrared light irradiated onto the silicon semiconductor thin film 5a and the infrared light reflected from the bottom surface of the base material 5b under the semiconductor thin film 5a interfere with each other. Since the reflectance fluctuation according to the thickness of the base material 5b is likely to occur, the interference is less likely to occur when broadband infrared light is used. Therefore, a stable measurement value regardless of the thickness of the base material 5b. Can be obtained.

  In the present embodiment, a high frequency pulse power supply (current supply means) 18 for supplying a high frequency pulse current to the semiconductor laser 10 is provided. The high-frequency pulse power supply 18 suddenly supplies a high-frequency pulse current having a frequency of 200 MHz to the semiconductor laser 10 to cause a mode hop phenomenon peculiar to the semiconductor laser. That is, by supplying the high-frequency pulse current, the semiconductor laser 10 changes from a single mode oscillation which is a normal oscillation state shown in FIG. 4A to a plurality of different wavelengths as shown in FIG. Transition to multi-mode oscillation that simultaneously emits (seven types) of infrared light.

  The condensing irradiating means is for condensing infrared light emitted from the infrared light radiating means and irradiating it in the irradiation region. In the present embodiment, A beam splitter 12 and the condenser lens 4 are included. The beam adjuster 11 is composed of a combination lens similarly to the beam adjuster 2 and adjusts the divergence angle of the infrared light emitted from the semiconductor laser 10. The beam splitter 12 reflects the infrared light that has passed through the beam adjuster 11 toward the substrate 5b. The condenser lens 4 is disposed at a position immediately above the base material 5b placed on the base material stage 17, and condenses the infrared light transmitted from the beam splitter 12 through the dichroic mirror 6. Then, the central portion of the irradiation region of the excitation light is irradiated. The irradiation diameter can be set as appropriate, but for example, it is preferable to adjust the irradiation diameter to about 5 μm from the viewpoint of maintaining high spatial resolution.

  The intensity of the detection signal depends on the density of excited carriers and the degree of temperature increase in the region irradiated with excitation light, and the density of excited carriers and the degree of temperature increase depend on the intensity of excitation light and the irradiation diameter. The optimum excitation light intensity and irradiation diameter for crystallinity evaluation are appropriately selected according to the form of the sample to be measured (the type of substrate, the thickness, and the thickness of the thin film).

  The reflected light intensity detecting means is a reflected light reflected on the silicon semiconductor thin film or the base material 5b among the infrared light irradiated by the focused light irradiating means, and a plurality of types emitted from the semiconductor laser 10 This is for detecting the intensity of reflected light including at least two types of infrared light and outputting the detection signal. In this embodiment, the light detection unit 13 is used. The photodetector 13 is disposed at a position immediately above the beam splitter 12, and receives reflected light transmitted from the silicon semiconductor thin film 5a through the condenser lens 4, the dichroic mirror 6, and the beam splitter 12, and receives the reflected light. A voltage signal (detection signal) corresponding to the intensity is output.

  The timing detection means detects the fluctuation timing of the intensity of the excitation light that the excitation laser 1 irradiates on the silicon semiconductor thin film 5a formed on the surface of the substrate 5b (in this embodiment, the on / off timing of the pulsed light). And includes a beam splitter 3 and a photodetector 7. The beam splitter 3 guides part of the excitation light to the photodetector 7 side at a position between the excitation laser 1 and the beam adjuster 2. The photodetector 7 receives the pulsed light that is the excitation light and outputs an irradiation timing detection signal of the pulsed light.

  The data creation means creates data for evaluating the crystallinity of the silicon semiconductor thin film by processing the detection signal, and includes an amplifier 8 and a signal processing device 9. The amplifier 8 amplifies the detection signal output from the photodetector 13 and inputs it to the signal processing device 9. The signal processing device 9 is configured by, for example, a digital oscilloscope, and receives an input of a timing detection signal output from the photodetector 7 and an amplification detection signal output from the amplifier 8. Data for evaluating the crystallinity of the silicon semiconductor thin film based on the amplification detection signal is taken in only when the timing detection signal is on, that is, when the pulsed light is on. For example, a signal waveform indicating a time change of the amplified detection signal as shown in FIG. 2 is created. If the excitation light is not pulse light but light whose intensity is periodically modulated, for example, the signal level and phase of the component having the same period as the reflected light may be measured.

  As will be described in detail later, the signal processing device 9 receives from the silicon semiconductor thin film 5a corresponding to two or more infrared lights having different wavelengths emitted from the semiconductor laser 10 based on the detection signal output from the amplifier 8. Data for evaluating crystallinity is created based on the average intensity of reflected light and the sum of the intensities.

  The signal waveform is taken into the computer 15 and is appropriately output by means such as screen display or printing.

  The computer 15 plays a role of outputting a command signal to the stage controller 16 to perform drive control of the substrate stage 17. This drive control enables measurement and mapping measurement at an arbitrary position on the base material 5b, for example.

  Next, the operation of this apparatus will be described.

  Of the pulsed light emitted from the excitation laser 1, the pulsed light that has passed through the beam splitter 3 passes through the beam adjuster 2, is reflected downward by the dichroic mirror 6, and passes through the condenser lens 4. The silicon semiconductor thin film 5a on the substrate 5b is irradiated with a predetermined irradiation diameter. The pulsed light (excitation light) excites semiconductor carriers of the silicon semiconductor thin film 5a, and then relaxes by recombination while diffusing. The existence time of the excited carriers increases as the crystallinity of the silicon semiconductor thin film 5a increases. become longer. Therefore, after a certain period of time, the higher the crystallinity, the more excited carriers are present. In addition, since the relaxation of the excited carriers is performed through an exothermic process, the temperature rises in the thin film. However, the higher the crystallinity, the higher the diffusibility of the excited carriers, and thus the degree of local temperature rise becomes smaller.

  On the other hand, as shown in FIG. 4B, a plurality of types of infrared light having different wavelengths are emitted from the semiconductor laser 10, and these infrared lights are emitted from the beam adjuster 11 and the beam splitter 12, respectively. Through the dichroic mirror 6 and the condenser lens 4, the silicon semiconductor thin film 5 a is condensed and irradiated to the central portion of the irradiation region of the excitation light.

  The irradiated infrared light is focused on the silicon semiconductor thin film 5a while being focused by the focusing lens 4 and adjusted in focus.

  The condensed infrared light is reflected by the silicon semiconductor thin film 5a. The amount of excited carriers in the region of the silicon semiconductor thin film 5a is larger, and the temperature of the thin film is lower. As a result, the intensity of the reflected light of the infrared light decreases as the crystallinity of the silicon semiconductor thin film 5a increases.

  Here, as shown in FIG. 5, the reflectance of the infrared light periodically changes as the thickness dimension of the substrate 5b increases or decreases. That is, as a result of interference between the infrared light reflected on the surface of the silicon semiconductor thin film 5a and the infrared light reflected on the back surface of the base material 5b, the difference between these optical path lengths, that is, the change in the thickness dimension of the base material 5b. Accordingly, the reflected light intensity changes periodically. Therefore, when only the infrared light of one wavelength is emitted and the reflected light intensity is detected, the detection result is greatly affected by the thickness dimension of the base material 5b. Specifically, it has been found that the reflected light intensity fluctuates by 20% or more even if the thickness dimension error of the substrate 5b is 1 μm or less.

  Therefore, in this embodiment, as shown in FIG. 4B, a plurality of types of infrared light having different wavelengths are simultaneously emitted from the semiconductor laser 10. Therefore, the reflected light intensity in this case differs for each infrared light having a different wavelength, as shown in FIG. In FIG. 6, the solid line indicates the reflected light intensity of infrared light having a wavelength of 1.550 μm, the two-dot chain line indicates the reflected light intensity of infrared light having a wavelength of 1.549 μm, and the broken line indicates The reflected light of infrared light having a wavelength of 1.551 μm is shown. As described above, when a plurality of infrared lights having different wavelengths are radiated, even if the reflected light intensity of the infrared light having one wavelength is greatly affected by the error in the thickness dimension of the base material 5b. Since interpolation can be performed based on the reflected light intensity of infrared light having other wavelengths, the influence of the reflected light intensity received by the thickness dimension of the base material 5b can be reduced.

  The reflected light passes through the condenser lens 4, the dichroic mirror 6, and the beam splitter 12 and is received by the photodetector 13. The photodetector 13 outputs a voltage signal corresponding to the intensity of the reflected light as a detection signal. This detection signal is amplified by the amplifier 8 and taken into the signal processing device 9 comprising a digital oscilloscope.

  On the other hand, the beam splitter 3 guides a part of the excitation light (pulse light) emitted from the excitation laser 1 to the photodetector 7. The photodetector 7 outputs a timing detection signal corresponding to the on / off timing of the pulsed light and inputs it to the signal processing device 9. The signal processing device 9 collects a detection signal in synchronization with the on / off timing of the pulsed light detected by the timing detection signal, creates a signal waveform as shown in FIG.

  Hereinafter, the present invention will be described more specifically with reference to examples. In addition, this invention is not limited at all by the Example.

  A polycrystalline silicon (p-Si) thin film having a thickness of 50 nm formed on a glass substrate obtained by an excimer laser annealing method using the apparatus having the configuration shown in FIG. 1, and an amorphous silicon having a thickness of 50 nm before the annealing. The crystallinity of the (a-Si) thin film and the silicon wafer (Bulk-Si) as a comparison were evaluated.

  In this embodiment, an ultraviolet pulse laser having a wavelength of 355 nm and a pulse width of 10 ns is used as the excitation laser 1, the pulsed light from the excitation laser 1 is transmitted through the beam splitter 3, and the beam divergence angle is obtained by the beam adjuster 2. Was adjusted, reflected by the dichroic mirror 6, transmitted through the condenser lens 4, and irradiated onto the surface of various samples with an irradiation diameter of 1 mm.

  On the other hand, as the infrared light emitting means, a semiconductor laser 10 that emits infrared light having a wavelength of 1.55 μm was used. The infrared light passes through the beam adjuster 11 and the beam splitter 12, is reflected by the dichroic mirror 6, is condensed by the condenser lens 4, and has an irradiation diameter of 5 μm in the region irradiated with the pulsed light of the sample. It was irradiated to become.

  And the reflected light of the infrared light from the said various samples permeate | transmits the condensing lens 4, the dichroic mirror 6, and the beam splitter 12, and detected the intensity | strength of the said reflected light as a voltage signal with the photodetector 13. FIG. The voltage signal was amplified by an amplifier 8 and taken into a signal processing device 9 having a digital oscilloscope. In the digital oscilloscope, a signal waveform was collected in synchronization with the emission timing of the excitation pulse laser, and the waveform was captured by the computer 15 and displayed on the screen and printed.

  FIG. 2 shows the evaluation results of the apparatus having the series of configurations.

  In FIG. 2, p-Si is a p-Si thin film with a thickness of 50 nm formed on a glass substrate, a-Si is an a-Si thin film with a thickness of 50 nm, and Bulk-Si is a crystallinity evaluation of a highly crystalline silicon ingot. Results are shown. In FIG. 2, the detection signal is shown as a negative polarity when the intensity of infrared light is increased (reflectance is increased) compared to that before excitation light irradiation, and is positive when the intensity is decreased.

  As shown in FIG. 2, the reflectivity of Bulk-Si having high crystallinity due to irradiation with excitation light is significantly reduced, whereas the reflectivity of the a-Si thin film having low crystallinity is significantly increased. In addition, in the p-Si thin film obtained by crystallizing the a-Si thin film, the level of increase in reflectance was lower than that of a-Si. Therefore, it was confirmed from the above results that the crystallinity of the silicon semiconductor thin film can be evaluated by measuring the detection signal.

  Note that the reflectance measured as described above varies depending on the thickness and type of the thin film and the base material due to the light interference effect in the base material. Thus, the crystallinity can be quickly evaluated.

  FIG. 7 is a partially enlarged view showing another embodiment of the present invention. In addition, about the structure similar to the said embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  In the present embodiment, a partition plate 19 and a lens 20 are further provided as light guide means. The partition plate 19 is provided between the beam splitter 12 and the photodetector 13. The partition plate 19 is provided with a pinhole 19a penetrating in the thickness direction. On the other hand, the lens 20 is provided between the partition plate 19 and the beam splitter 12, and guides the infrared light L3 reflected by the surface of the silicon semiconductor thin film 5a to the photodetector 13 through the pinhole 19a. Infrared light L4 reflected by the back surface of the substrate 5b is guided to the outside of the pinhole 19a. Further, the condensing lens 4 in the present embodiment has its focal point set on the surface of the silicon semiconductor thin film 5a, and is also used as a light guiding unit and a condensing irradiation unit.

  The operation of this embodiment will be described. Infrared light emitted from the semiconductor laser 10 is reflected by the dichroic mirror 6 and condensed by the condenser lens 4 on the surface of the silicon semiconductor thin film 5a. The infrared light L3 reflected by the surface of the silicon semiconductor thin film 5a passes through the condenser lens 4, the dichroic mirror 6 and the beam splitter 12, and is condensed by the lens 20, so that it passes through the pinhole 19a and is detected. Guided to vessel 13. On the other hand, the infrared light L4 transmitted through the silicon semiconductor thin film 5a and the base material 5b is reflected by the back surface of the base material 5b, passes through the condenser lens 4 and the beam splitter 12, and is outside the pinhole 19a by the lens 20. Led to.

  In the embodiment, a plurality of types of infrared light having different wavelengths are simultaneously emitted by supplying a high-frequency current, and the crystallinity is evaluated based on the average intensity and the sum of the intensities of reflected light of these infrared lights. However, it is also possible to change the wavelength of infrared light with the passage of time by supplying a low-frequency current. In this case, the reflected light intensity obtained within a predetermined time is averaged and used. In addition, the influence of interference with infrared light reflected on the back surface of the substrate 5b can be reduced.

  FIG. 8 shows an example of the overall configuration of a silicon semiconductor crystallinity evaluation apparatus according to still another embodiment of the present invention. In addition, about the structure similar to the crystallinity evaluation apparatus based on the said embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  In the present embodiment, an ultraviolet semiconductor laser (390 nm, 30 mW) is used as the pumping laser 1, and the current supplied to the pumping laser 1 is modulated by the modulator 24, so that the intensity of the pumping light is increased by a frequency of 10 kHz, for example. It is modulated.

  In the present embodiment, an AC power source 21 and a bias power source 22 for supplying an AC current to the semiconductor laser 10 are provided instead of the RF pulse power source 18 for supplying a high-frequency pulse current to the semiconductor laser 10. Yes. The AC power supply 21 supplies a current having a frequency T1 of 1 MHz to the semiconductor laser 10. As a result, as shown in FIG. 9, the infrared light reflected by the silicon semiconductor thin film 5a can also be obtained as intensity changing at the frequency T1. Although the reflected light intensity in the figure is slightly varied, the wavelength of the infrared light emitted from the semiconductor laser 10 changes with time due to the supply of the alternating current. This is because the influence of interference occurs as shown in FIG. 5 above due to the relationship between the wavelength and the thickness dimension of the substrate 5b.

  The reflected light from the silicon semiconductor thin film 5a is detected by the photodetector 13 and output as an electrical signal, and this electrical signal is sent to the lock-in amplifier 26 through the amplifier 8 and the filter 25. The filter 25 can perform an averaging process by cutting a frequency component of 1 MHz or more from the reflected light intensity shown in FIG. 9 to obtain a reflected light intensity S indicated by a broken line in FIG. Since the reflected light intensity S includes a frequency component (10 kHz) due to the excitation light, the infrared light reflectance change due to the excitation light is measured by extracting this frequency component. Can do. The lock-in amplifier 26 creates data for evaluating the crystallinity of the silicon semiconductor thin film 5a based on a signal of a specific frequency component (10 kHz) using the modulation signal output from the photodetector 7 as a reference signal. It has become. That is, in the present embodiment, the filter 25 and the lock-in amplifier 26 constitute an example of a data creation unit.

An example of the whole structure of the crystallinity evaluation apparatus of the silicon semiconductor thin film which concerns on embodiment of this invention is shown. The data for evaluating the crystallinity obtained by the examples are shown. It is a graph which shows the example of the infrared light used for evaluation of crystallinity. It is a graph which shows the radiation | emission state of a semiconductor laser, (a) is the single mode oscillation, (b) has each shown the state of multimode oscillation. It is a graph which shows the relationship between a base material thickness and a reflectance. It is a graph which shows the reflectance of 3 infrared rays from which a wavelength differs. It is a partially expanded view which shows another embodiment of this invention. The example of the whole structure of the crystallinity evaluation apparatus of the silicon semiconductor which concerns on another embodiment of this invention is shown. It is a graph which shows the reflected light intensity when a high frequency current is supplied to a semiconductor laser.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Excitation laser 4 Condensing lens 5a Silicon semiconductor thin film 5b Base material 9 Signal processing apparatus 10 Semiconductor laser 13 Photo detector 18 High frequency pulse power supply 19a Pinhole 20 Lens 21 AC power supply 25 Filter 26 Lock-in amplifier

Claims (6)

An apparatus for evaluating the crystallinity of a silicon semiconductor thin film formed on a substrate having optical transparency,
Excitation light irradiation means for irradiating excitation light for exciting carriers to a predetermined irradiation region on the surface of the silicon semiconductor thin film;
Infrared light emitting means capable of emitting a plurality of types of infrared light having different wavelengths;
Condensing irradiation means for irradiating the irradiation area with the infrared light emitted from the infrared light emitting means being condensed;
Of the infrared light irradiated by the condensing irradiation means, the reflected light reflected by the silicon semiconductor thin film or the substrate, and the intensity of the reflected light of the plurality of types of infrared light is detected, and the detection signal Reflected light intensity detection means for outputting,
A crystallinity evaluation apparatus for a silicon semiconductor thin film, comprising: data creation means for creating data for evaluating the crystallinity of the silicon semiconductor thin film based on the detection signal.   2. The crystallinity evaluation apparatus for a silicon semiconductor thin film according to claim 1, wherein the infrared light emitting means supplies a semiconductor laser that emits infrared light and an intensity-modulated current to the semiconductor laser. An apparatus for evaluating crystallinity of a silicon semiconductor thin film, comprising: current supply means capable of irradiating a semiconductor laser with a plurality of types of infrared light having different wavelengths.   3. The crystallinity evaluation apparatus for a silicon semiconductor thin film according to claim 2, wherein the current supply means supplies the semiconductor laser with a current whose intensity is modulated at a frequency having a period within an attenuation time of relaxation oscillation in the semiconductor laser. An apparatus for evaluating crystallinity of a silicon semiconductor thin film, comprising:   In the crystallinity evaluation apparatus for a silicon semiconductor thin film according to any one of claims 1 to 3, while guiding the infrared light reflected on the surface of the silicon semiconductor thin film into a detection range of the reflected light intensity detection means, An apparatus for evaluating crystallinity of a silicon semiconductor thin film, further comprising light guide means for guiding infrared light reflected by the back surface of the base material to the outside of a detection range of the reflected light intensity detection means.   5. The crystallinity evaluation apparatus for a silicon semiconductor thin film according to claim 4, wherein the light guide means has a focal point set on a surface of the silicon semiconductor thin film, and the reflected light from the surface of the silicon semiconductor thin film is detected by the reflected light intensity. A lens capable of being guided into the detection range of the means, and this lens may be used as the condensing irradiation means for condensing the infrared light emitted from the infrared light emitting means on the surface of the silicon semiconductor thin film. An apparatus for evaluating crystallinity of a silicon semiconductor thin film, which is also used.   The crystallinity evaluation apparatus for a silicon semiconductor thin film according to any one of claims 1 to 5, wherein the infrared light radiating means emits broadband infrared light having a spread of 10 nm or more in wavelength. For evaluating the crystallinity of silicon semiconductor thin films.

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