JP2009058273A - Crystallinity evaluation device of silicon semiconductor thin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crystallinity evaluation device of a silicon semiconductor thin film capable of rapidly and accurately evaluating the crystallinity of the silicon semiconductor thin film. <P>SOLUTION: The crystallinity evaluation device of the silicon semiconductor thin film includes an exciting light laser 3, an infrared laser 4, a metal film 6 having a small hole 6a, which has a diameter smaller than the wavelength of infrared rays, and irradiating the silicon semiconductor thin film 2b with the infrared rays thrown on one opening of the small hole 6a as the near field light L1 bled out of the other opening of the small hole 6a, a photodetector 23 for detecting the intensity of the reflected light reflected on this side of the other opening of the small hole 6a out of the infrared rays emitted from the infrared laser 4 to output its detection signal, and a signal processor 26 for forming data for use in evaluating the crystallinity of the thin film 2b on the basis of the detection signal. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an apparatus for evaluating the crystallinity of a silicon semiconductor thin film, and more particularly to an apparatus for evaluating the crystallinity of a silicon semiconductor thin film formed on a base material such as a glass substrate.

  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 into 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 grain size and crystal orientation, can be produced 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 conditions. Therefore, in the manufacture of a p-Si thin film, the crystallinity of the p-Si thin film is evaluated on the production line in a short time on the production line in order to obtain a stable quality product with a high yield. There has been a demand for a method capable of promptly feeding back the manufacturing conditions of the 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 complete or a sample to be measured by destroying the measurement target, 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 is known.
JP 2004-226260 A

  The method for evaluating the crystallinity of a silicon semiconductor thin film using Raman spectroscopy is excellent in that it does not require the measurement sample to be adjusted by destroying the measurement target.

  However, the intensity of the Raman scattered light detected by the crystallinity evaluation method using Raman spectroscopy is very weak. Therefore, in order to obtain an accurate evaluation result, it is necessary to integrate the measurement results by a plurality of measurements, which is an insufficient measurement method from the viewpoint of obtaining an accurate evaluation result quickly. In particular, the method is insufficient in that the formed thin film is evaluated on-line on the production line and the evaluation result is quickly fed back to the production conditions.

  This invention makes it a subject to provide the crystallinity evaluation apparatus of the silicon semiconductor thin film which solves the said problem.

  In order to solve the above problems, the present inventor irradiates excitation light with so-called near-field light, which is light that oozes out from the hole when infrared light is irradiated to a hole having a diameter smaller than the wavelength. When the excitation region of the silicon semiconductor thin film is irradiated, there is a correlation between the magnitude of the influence of the near-field light from the thin film and the intensity of the infrared light reflected at the position on the near side of the hole. Paying attention, the following invention was completed.

  That is, the present invention is an apparatus for evaluating the crystallinity of a silicon semiconductor thin film formed on a substrate, and an excitation light for exciting carriers to a predetermined excitation region on the surface of the silicon semiconductor thin film. Excitation light irradiating means for irradiating, infrared light radiating means for radiating infrared light, and a hole having a diameter smaller than the wavelength of the infrared light, and one of the holes from the infrared light radiating means Near-field light forming means capable of irradiating the excitation region with near-field light that radiates to the aperture of the aperture as near-field light that oozes out from the other aperture of the hole, and emitted from the infrared light radiation means. Reflected light intensity detecting means for detecting the intensity of reflected light reflected from the front side of the other opening of the hole and outputting a detection signal thereof, and the silicon semiconductor thin film based on the detection signal Create data to evaluate the crystallinity of That a data creation means for providing a crystalline evaluation apparatus of a silicon semiconductor thin film characterized.

  According to the present invention, of the irradiated infrared light emitted from the infrared light emitting means, the near-field light oozing out from the hole is irradiated to the excitation region, and the reflected light reflected at the position in front of the hole Since the intensity is detected, the influence of the near-field light from the silicon semiconductor thin film can be specified based on the reflected light intensity correlated with the influence. And since the influence which the said near-field light receives is a value which fluctuates according to the crystallinity of a silicon semiconductor thin film, by detecting the reflected light intensity, the amount of carriers in the excitation region, that is, the silicon semiconductor thin film The crystallinity can be evaluated.

  Specifically, the influence on the reflectance of infrared light decreases as the amount of the carrier increases. On the other hand, the amount of carrier increases as the crystallinity of the silicon semiconductor thin film increases. The higher the crystallinity, the lower the effect on the surface.

  Furthermore, the influence on the reflectance of the infrared light also depends on the temperature of the thin film. That is, the influence on the reflectance of infrared light becomes larger as the temperature of the silicon semiconductor thin film is higher. Here, 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 lower the amount of heat energy given locally to the substrate, resulting in a lower influence on the reflectance of infrared light.

  Thus, since the influence on the reflectance of infrared light increases or decreases depending on the crystallinity of the silicon semiconductor thin film, the crystallinity of the thin film is evaluated based on the intensity of the reflected light as in the present invention. The evaluation can be performed quickly and accurately.

  In particular, in the present invention, since the silicon semiconductor thin film is irradiated with near-field light that oozes out from the hole of the near-field light forming means, more accurate evaluation of crystallinity can be performed. In other words, near-field light, unlike propagating light, has a characteristic of being localized in a region near the other opening of the hole and smaller than the diameter of the hole. By using localized near-field light, the range of irradiation with infrared light can be limited to a smaller range, and the spatial resolution of crystallinity evaluation can be further increased.

  Further, in the present invention, the phrase “diameter smaller than the wavelength of infrared light” is not intended to limit the hole to a circular cross-sectional shape, but the widest opening width in the cross-sectional shape (which may be a rectangular opening shape). In other words, the longitudinal dimension) is shorter than the wavelength of infrared light.

  The silicon semiconductor thin film crystallinity evaluation apparatus preferably further includes a light guide member capable of guiding the infrared light emitted from the infrared light emitting means to one of the openings.

  In this way, since the infrared light can be guided to one opening of the hole by the light guide member, it is compared with the case of transmitting the infrared light (spreading in space) without using such a light guide member. Thus, it is possible to reduce the loss of infrared light guided in the direction other than the one opening.

  Specifically, the light guide member is made of an optical fiber having a core extending in a specific axial direction and a clad surrounding the core around the axis, and the tip of the core is formed by a hole of the near-field light forming means. It can be set as the structure protruded in the said axial direction rather than the front end surface of a clad | crud so that it may arrange | position inside.

  In this way, by guiding the infrared light along the core of the optical fiber to the tip thereof, the infrared light can inevitably be guided to the hole of the near-field light forming means.

  In the silicon semiconductor thin film crystallinity evaluation apparatus, a holding means for holding the near-field light forming means so as to be able to contact and separate from the silicon semiconductor thin film, and a control means for controlling the operation of the holding means. The control means further comprises a silicon semiconductor thin film so that a reflected light intensity equal to or higher than a preset reference intensity is obtained based on the intensity of the reflected light of the infrared light obtained by the reflected light intensity detecting means. It is preferable to adjust the distance of the near-field light forming means with respect to.

  In this way, by adjusting the distance between the silicon semiconductor thin film and the near-field light forming means, it is possible to ensure the reflected light intensity that is equal to or higher than the reference intensity. That is, as the near-field light forming means gets closer to the thin film, the scattering of the near-field light on the surface of the thin film increases and the energy is deprived, so the influence on infrared light (propagation light) (that is, reflected light intensity) On the other hand, when the near-field light forming means and the thin film are moved away to a range where the near-field light does not reach the thin film, the reflected light intensity is not detected. Accordingly, when the reference intensity is below a preset reference intensity, the near-field light forming means is separated from the thin film, whereas when the reference intensity is exceeded, the near-field light forming means is brought close to the thin film so as not to fall below the reference intensity. The distance between the thin film and the near-field light forming means can be adjusted so that the reflected light intensity exceeding the intensity can be obtained.

  In the crystallinity evaluation apparatus for a silicon semiconductor thin film, the near-field light forming means preferably has a hole having a diameter smaller than the wavelengths of the excitation light and infrared light as the hole.

  In this way, both the excitation light and the infrared light can be irradiated to the thin film as near-field light by the common near-field light forming means, so that the excitation light and the infrared light can be used to irradiate the near-field light. The cost can be reduced as compared with the case where a separate near-field light forming means is provided for each.

  Further, the present invention is an apparatus for evaluating the crystallinity of a silicon semiconductor thin film formed on a substrate, and excitation light for exciting carriers to a predetermined excitation region on the surface of the silicon semiconductor thin film Excitation light irradiating means for radiating infrared light, infrared light radiating means for emitting infrared light, and an optical fiber for guiding the excitation light and infrared light from the excitation light irradiating means and infrared light radiating means to the excitation region And a condensing means for condensing excitation light and infrared light provided between the optical fiber and the silicon semiconductor thin film and guided by the optical fiber, and infrared light irradiated by the condensing irradiation means A reflected light intensity detecting means for detecting the intensity of the reflected light reflected by the silicon semiconductor thin film and outputting a detection signal thereof, and a decipher for evaluating the crystallinity of the silicon semiconductor thin film based on the detection signal. It provides crystalline evaluation apparatus of a silicon semiconductor thin film characterized comprising a data generating means for generating data.

  According to the present invention, the silicon semiconductor thin film is irradiated with excitation light and infrared light is emitted to the excitation region, and the crystallinity of the silicon semiconductor thin film is evaluated based on the reflected light intensity of the infrared light. Therefore, the crystallinity can be evaluated quickly and accurately.

  Specifically, in the present invention, a predetermined region of the silicon semiconductor thin film formed on the substrate using the excitation light irradiation means is irradiated with light (excitation light) having a band gap or more to excite the carrier of the silicon semiconductor thin film. In addition, the region where the carriers are excited is irradiated with infrared light using an infrared light emitting means, an optical fiber, and a light collecting means.

  Part of the infrared light irradiated in this way is reflected by the silicon semiconductor thin film, but the reflectance of the infrared light depends on the amount of excited carriers present in the region. That is, while the reflectance of infrared light decreases as the amount of the carrier increases, the amount of carrier increases as the crystallinity of the silicon semiconductor thin film increases. Therefore, the reflectance of infrared light is high in crystallinity. It becomes so low.

  Furthermore, the reflectance of the infrared light reflected by the silicon semiconductor thin film formed on the substrate also depends on the temperature of the thin film. That is, the reflectance of infrared light increases as the temperature of the silicon semiconductor thin film increases. Here, 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 infrared light reflectance.

  As described above, since the reflectance of infrared light increases or decreases depending on the crystallinity of the silicon semiconductor thin film, the crystallinity of the thin film is evaluated based on the intensity of infrared light reflected by the silicon semiconductor thin film as in the present invention. If so, the evaluation can be performed quickly and accurately.

  In particular, as in the present invention, the pumping light and infrared light are guided to the pumping region using a common optical fiber, and the pumping light and infrared light are condensed by a condensing means and irradiated into the pumping region. Thereby, the radiation direction and radiation distribution of the excitation light and infrared light guided from the optical fiber to the excitation region can be matched between the excitation light and the infrared light. Therefore, the irradiation conditions of the excitation light and infrared light irradiated on the region can be made constant, and measurement with high reproducibility becomes possible.

  In the silicon semiconductor thin film crystallinity evaluation apparatus, the condensing means includes a condensing lens having different aberration characteristics depending on the difference between the wavelength of the excitation light and the wavelength of the infrared light. It is preferable that the focus of the external light and the focus of the excitation light are set at different positions in the optical axis direction.

  In this way, when the focus of infrared light is set on the surface of the silicon semiconductor thin film, the focus of the excitation light is set on the front side (condenser lens side) or the back side of the silicon semiconductor thin film, so that the silicon semiconductor Since the irradiation diameter of the excitation light on the thin film can be made wider than the irradiation diameter of the infrared light, the infrared light is within the irradiation range of the excitation light while using a condensing lens common to the excitation light and the infrared light. The crystallinity can be more reliably evaluated by reliably irradiating.

In addition, as a wavelength of the infrared light radiated | emitted by the said infrared light radiation | emission means in this invention, it is preferable that it is 1-10 micrometers. 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. Therefore, it is preferable that the wavelength of the measurement light is longer from the viewpoint of detection accuracy, but if the wavelength is 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 infrared light to the target portion while maintaining such high spatial resolution. When infrared light having a wavelength in such a range is used, it is possible to easily collect and irradiate even an area where the irradiation diameter is 10 μm or less with a normal optical lens, and has high spatial resolution. Thus, the crystallinity can be accurately evaluated.

  On the other hand, 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 measurement errors corresponding to the thickness of the material are likely to occur, the interference is less likely to occur when broadband infrared light is used, so that stable measurement values can be obtained regardless of the thickness of the substrate. .

  According to the present invention, the silicon semiconductor thin film is irradiated with excitation light, infrared light is emitted to the irradiated region, and the crystallinity of the silicon semiconductor thin film is evaluated based on the reflected light intensity of the infrared light. Therefore, the crystallinity can be evaluated quickly and accurately.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic diagram showing the overall configuration of a silicon semiconductor thin film crystallinity evaluation apparatus according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view of the tip of the optical fiber of FIG.

  Referring to FIGS. 1 and 2, the crystallinity evaluation apparatus 1 is for evaluating the crystallinity of a silicon semiconductor thin film 2b formed on a substrate 2a. Here, the silicon semiconductor thin film 2b 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 1 includes an excitation light laser (excitation light irradiation means) 3 that irradiates the surface of the silicon semiconductor thin film 2b with excitation light, an infrared light laser (infrared light emission means) 4 that emits infrared light, and , An optical fiber (light guide member) 5 for guiding the excitation light and infrared light to the silicon semiconductor thin film 2b, a metal film (near-field light forming means) 6 provided on the optical fiber 5, and the excitation An optical system 7 provided between the optical laser 3 and the infrared light laser 4 and the optical fiber 5, a holding device 8 for holding the substrate 2a and the optical fiber 5, the excitation light laser 3 and the infrared light And a control device 9 for controlling the laser 4 and the holding device 8.

  The excitation light laser 3 is composed of an ultraviolet semiconductor laser that emits light having a wavelength of 375 nm as excitation light for carrier excitation of the silicon semiconductor thin film 2b.

  The infrared laser 4 is composed of a semiconductor infrared laser that emits light of 1550 nm.

  The optical system 7 includes a lens 10, a lens 11 and a lens 12, a dichroic mirror 14, a mirror 15 and a mirror 16, and excitation light and infrared light emitted from the excitation light laser 3 and the infrared light laser 4. Is guided to the optical fiber 5. Specifically, the excitation light emitted from the excitation light laser 3 is collimated (parallelized) by the lens 10, reflected by the dichroic mirror 14, collected by the lens 11, and then the base end of the optical fiber 5. 5a. Infrared light emitted from the infrared laser 4 is collimated by the lens 12, passes through the dichroic mirror 14, is collected by the lens 11, and is guided to the proximal end 5 a of the optical fiber 5. .

  On the other hand, the excitation light returning from the distal end 5 b of the optical fiber 5 is guided to the lens 11 from the proximal end 5 a of the optical fiber 5, collimated by the lens 11, reflected by the dichroic mirror 14, and further reflected by the mirror 15. The light is reflected and guided to the photodetector 24 described later. The infrared light returned from the distal end 5b of the optical fiber 5 is guided to the lens 11 from the proximal end 5a of the optical fiber 5, collimated by the lens 11, and transmitted through the dichroic mirror 14, and then the mirror 16 And is guided to the photodetector 23 described later.

  The optical fiber 5 includes a core 17 extending from the proximal end 5a to the distal end 5b, and a clad 18 surrounding the core 17 around its axis, and the difference in refractive index between the core 17 and the clad 18 is utilized. Light is guided in the core 17. In addition, the core 17 of this embodiment has a diameter of 5 μm.

  The core 17 is made of a material such as glass that can transmit light, and can also be formed of plastic. The core 17 of the present embodiment is made of quartz glass. On the other hand, the clad 18 is made of a metal material. When the core 17 is formed of glass as in the present embodiment, the clad 18 can be formed of glass having a refractive index lower than that of the core 17. The purpose of the cladding 18 is to confine light within the core 17.

  As shown in FIG. 2, the metal film 6 is provided on the tip 5 b of the optical fiber 5. Specifically, the metal film 6 is formed in a truncated cone shape and is provided so as to surround the truncated cone tip portion 17a of the core 17 protruding to the tip side from the cladding 18 in the axial direction thereof. . In other words, the truncated cone tip portion 17 a is exposed to the outside of the metal film 6 through a small hole 6 a formed in the metal film 6. The small hole 6a is a hole that penetrates the metal film 6 from the optical fiber 5 side to the distal end side, and the opening area on the distal end side is smaller than the opening area on the optical fiber 5 side according to the shape of the truncated cone distal end portion 17a. It is formed as follows.

  The small holes 6a of the present embodiment have a circular opening shape having a diameter D1 of 0.1 μm smaller than the wavelength of infrared light (1550 nm) and the wavelength of excitation light (375 nm). Therefore, most of the infrared light and the excitation light guided through the core 17 are not irradiated to the outside through the small holes 6a as propagating light, and most of them are reflected light L2 on the base end 5a side. However, infrared light and excitation light other than the reflected light L2 ooze out from the small holes 6a as near-field light L1. Specifically, the near-field light L1 is localized from the small hole 6a of the metal film 6 (tip surface of the truncated cone tip portion 17a) to a region that is approximately centered on the diameter dimension D1. In the present embodiment, the crystallinity of the thin film 2b is evaluated by irradiating the silicon semiconductor thin film 2b with near-field light L1 of excitation light and infrared light.

  That is, as shown in FIG. 2, when the near-field light L1 of excitation light and infrared light is irradiated to the silicon semiconductor thin film 2b, the carrier of the silicon semiconductor thin film 2b is excited by the excitation light in the near-field light L1. At the same time, the infrared light of the near-field light L1 is irradiated to the irradiated portion. The infrared light in the near-field light L1 varies depending on the crystallinity of the silicon semiconductor thin film 2b. Specifically, the larger the amount of carriers present in the silicon semiconductor thin film 2b, the smaller the variation, and the greater the amount of carriers the higher the crystallinity of the silicon semiconductor thin film 2b. It will be small. This variation also causes a change in the reflected light L2 that interacts with the near-field light L1 through the small hole 6a. Therefore, this change is detected by the infrared light detector 23 described later. Thus, the crystallinity of the silicon semiconductor thin film 2b can be evaluated.

  When the clad 18 of the optical fiber 5 is formed of metal, the clad 18 and the metal film 6 can be made of the same material. In this case, the optical fiber 5 having the metal film 6 can be manufactured by the method described below.

  First, the tip of the glass core 17 is dipped in hydrochloric acid or the like to sharpen the tip. Next, the entire surface of the core 17 is coated with a metal material that becomes the clad 18 and the metal film 6 after completion. Thereafter, a treatment such as melting the tip of the coated material with a chemical or the like is performed to flatten the tip as shown in FIG. Thereby, the clad 18 and the metal film 6 can be formed simultaneously with the same metal material.

  Referring to FIGS. 1 and 2 again, the holding device 8 is attached to the stage 19 for placing the base material 2a, the clamp 20 for holding the tip 5b of the optical fiber 5, and the stage 19. And a lifting device 21 that lifts and lowers the clamp 20 (optical fiber 5). The stage 19 can be moved in a horizontal direction (a direction parallel to the surface of the substrate 2a) by a driving mechanism (not shown) with the substrate 2a with the silicon semiconductor thin film 2b facing upward. ing. The clamp 20 holds the optical fiber 5 in a posture in which the optical fiber 5 faces downward so that the truncated cone tip 17a faces the base material 2a placed on the stage 19. The elevating device 21 is capable of adjusting the distance between the truncated cone tip portion 17a of the optical fiber 5 held by the clamp 20 and the silicon semiconductor thin film 2b by moving the clamp 20 up and down.

  The control device 9 includes an oscillator 22, an infrared light detector 23 and an excitation light detector 24 that detect reflected light of infrared light or excitation light, and electrical signals from the oscillator 22 and infrared light detector 23. From the input amplifier 25, a signal processing device 26 for processing an electric signal input from the amplifier 25, a computer 27 for receiving an electric signal from the signal processing device 26 and the excitation light detector 24, and from the computer 27 And a controller 28 that controls the driving of the holding device 8.

  The oscillator 22 is for periodically modulating the intensity of the excitation light emitted by the excitation light laser 3. The reason why the intensity is modulated in this manner is that many carriers can be generated instantaneously, so that the signal intensity obtained by the infrared light detector 23 described later can be increased.

  The infrared light detector 23 receives reflected light of the infrared light guided by the optical system 7 (mirror 16), and outputs a voltage signal (detection signal) corresponding to the intensity to the amplifier 25. It has become. Similarly, the excitation light detector 24 receives reflected light of the excitation light guided from the mirror 15 and outputs a voltage signal corresponding to the intensity to the computer 27.

  The amplifier 25 removes unnecessary frequency components from the electrical (voltage) signal obtained by the infrared light detector 23 by referring to the electrical signal relating to the intensity modulation input from the oscillator 22. ing. Therefore, a detection signal with a high S / N ratio can be obtained. The amplifier 25 outputs the detection signal obtained as described above to the signal processing device 26.

  The signal processing device 26 is data for evaluating the crystallinity of the silicon semiconductor thin film 2b based on the detection signal input from the amplifier 25, for example, a signal waveform indicating a time change of the detection signal as shown in FIG. Create In FIG. 3, p-Si is a 50-nm thick p-Si thin film formed on a glass substrate, a-Si is a 50-nm thick a-Si thin film, and Bulk-Si is a crystallinity evaluation of a highly crystalline silicon ingot. Results are shown. In FIG. 3, the detection signal is shown as a negative polarity when the intensity of infrared light is increased (reflectance is increased) as compared to that before excitation light irradiation, and is positive when it is decreased. . As shown in the figure, the reflectivity of Bulk-Si, which has high crystallinity due to excitation light irradiation, is significantly reduced, whereas the reflectivity of a-Si thin film, which has low crystallinity, significantly increases. Yes. In addition, in the p-Si thin film obtained by crystallizing the a-Si thin film, the level of increase in reflectance is lower than that of a-Si.

  The computer 27 calculates an appropriate distance between the optical fiber 5 and the silicon semiconductor thin film 2b based on the electrical (voltage) signal input from the excitation light detector 24. That is, the computer 27 stores a reference reflection intensity set in advance for the reflected light of the excitation light, and the optical fiber 5 and the silicon semiconductor thin film 2b for making the reference reflection intensity equal to or higher than the actual reflection light intensity. Calculate the interval. Specifically, referring to FIG. 2, when the distance between the optical fiber 5 (the truncated cone tip portion 17a) and the silicon semiconductor thin film 2b is shortened, the scattering of the near-field light L1 in the thin film 2b is increased by the shortened distance. Since the energy is deprived, the intensity of the reflected light L2 is reduced. On the other hand, when the optical fiber 5 moves away to a range where the near-field light L1 does not reach the thin film 2b, the reflected light intensity is not detected (becomes 0). ). Therefore, the computer 27 calculates the distance for separating the optical fiber 5 and the thin film 2b within a range where the intensity does not become zero when the intensity falls below the reference reflection intensity, while not exceeding the reference reflection intensity. The distance at which the optical fiber 5 is brought close to is calculated. Then, the computer 27 outputs a command regarding the distance calculated in this way to the controller 28 as an electrical signal. Further, the computer 27 has an operation means (not shown) capable of inputting the horizontal position of the substrate 2a with respect to the optical fiber 5, and the position information input by the operation means is also output to the controller 28 as an electrical signal. The

  The controller 28 drives the elevating device 21 or a drive device (not shown) for the stage 19 in accordance with an electrical signal input from the computer 27. That is, the controller 28 drives the elevating device 21 in accordance with the command regarding the distance between the optical fiber 5 and the thin film 2b input from the computer 27, and is input from the computer 27 in accordance with the operation of the operating means (not shown). The stage 19 is driven according to a command related to the position information.

  As described above, according to the embodiment, the near-field light L1 that has oozed out of the hole 6a out of the infrared light emitted from the infrared laser 4 is applied to the thin film 2b and before the hole 6a. Since the intensity of the reflected light L2 reflected at the position is detected, the influence of the near-field light L1 received from the silicon semiconductor thin film 2b is specified based on the intensity of the reflected light L2 correlated with this influence. Can do. Since the influence of the near-field light L1 varies depending on the crystallinity of the silicon semiconductor thin film 2b, the amount of carriers in the thin film 2b, that is, the silicon semiconductor is detected by detecting the intensity of the reflected light L2. The crystallinity of the thin film 2b can be evaluated.

  Specifically, the influence on the reflectance of infrared light decreases as the amount of the carrier increases. On the other hand, the amount of carrier increases as the crystallinity of the silicon semiconductor thin film 2b increases. The higher the crystallinity, the lower the effect on the rate.

  Furthermore, the influence on the reflectance of the infrared light reflected by the silicon semiconductor thin film 2b formed on the substrate 2a also depends on the temperature of the thin film 2b. That is, the influence on the reflectance of infrared light becomes larger as the temperature of the silicon semiconductor thin film 2b is higher. Here, when the carriers of the silicon semiconductor thin film 2b are excited with excitation light, the relaxation time of the excited carriers is longer as the crystallinity of the thin film 2b is higher. In addition, the higher the crystallinity, the higher the diffusibility of excited carriers, and the higher the diffusibility of heat generated by recombination of excited carriers, the higher the diffusibility of heat generated by recombination of excited carriers. 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 2a, resulting in a lower influence on the reflectance of infrared light. .

  Thus, since the influence on the reflectance of infrared light increases or decreases according to the crystallinity of the silicon semiconductor thin film 2b, the crystallinity of the thin film 2b is evaluated based on the intensity of the reflected light L2 as in the above embodiment. If so, the evaluation can be performed quickly and accurately.

  In particular, in the above-described embodiment, since the near-field light L1 that oozes out from the small hole 6a of the metal film 6 is irradiated to the silicon semiconductor thin film 2b, accurate and rapid evaluation of crystallinity can be performed. That is, the near-field light L1, unlike the propagation light, has a characteristic of being localized in a region near the small hole 6a and smaller than the diameter of the small hole 6a. By using the localized near-field light L1, the range irradiated with infrared light can be limited to a small range, and the spatial resolution of the crystallinity evaluation can be enhanced.

  As in the above-described embodiment, the configuration including the optical fiber 5 capable of guiding the infrared light to the hole 6a of the metal film 6 allows the infrared light to propagate without using the optical fiber 5 and is red. Compared with the case where external light is guided to the hole 6a, the loss of infrared light guided in the direction other than the hole 6a can be reduced. Specifically, the core 17 of the optical fiber 5 is formed so as to protrude from the front end surface of the clad 18 so that the tip 17a of the core 17 of the optical fiber 5 is disposed inside the hole 6a. By guiding infrared light to the tip portion 17a along the line, the infrared light can inevitably be guided to the hole 6a.

  If the control device 9 for controlling the operation of the holding device 8 is provided as in the above-described embodiment, the silicon semiconductor thin film 2b and the metal film 6 are provided so that the reflected light intensity equal to or higher than a preset reference intensity can be obtained. Can be automatically adjusted to an appropriate distance.

  If the small hole 6a is configured to have a diameter smaller than the wavelengths of the excitation light and the infrared light as in the above embodiment, both the excitation light and the infrared light are transmitted by the common metal film 6 in the near field. Since the thin film 2b can be irradiated as the light L1, the cost can be reduced compared to the case where a separate metal film 6 (optical fiber 5) is provided for each of the excitation light and infrared light.

  In the above-described embodiment, the configuration in which the near-field light L1 for the excitation light and the infrared light is applied to the silicon semiconductor thin film 2b has been described. However, the excitation light and the infrared light are applied to the thin film 2b as propagating light. Similarly, the crystallinity can be evaluated.

  FIG. 4 is a schematic diagram showing the overall configuration of the crystallinity evaluation apparatus according to the second embodiment of the present invention. In addition, about the structure same as embodiment mentioned above, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  The crystallinity evaluation apparatus 30 according to this embodiment includes the excitation light laser 3, the infrared light laser 4, the optical fiber 5, and the excitation light laser 3, the infrared light laser 4, and the optical fiber 5. A second optical system 31 provided, a holding device 32 for holding the substrate 2a, a third optical system 33 provided between the optical fiber 5 and the holding device 32, the excitation light laser 3, And a control device 34 for controlling the infrared laser 4 and the holding device 32.

  The second optical system 31 has the same configuration as the optical system 7 except that the second optical system 31 does not have the mirrors 15 and 16. That is, the second optical system 31 includes the lenses 10, 11, and 12 and the dichroic mirror 14, and the excitation light and infrared light emitted from the excitation light laser 3 and the infrared light laser 4 are used as the basis of the optical fiber 5. It leads to the end 5a.

  The third optical system 33 includes four lenses 35 to 38 and a beam splitter 39, and the excitation light and infrared light irradiated from the tip 5 b of the optical fiber 5 are held by the holding device 32. The silicon semiconductor thin film 2b and the photodetectors 41 and 42 to be described later are guided respectively. Specifically, the ultraviolet light and infrared light derived from the tip 5b of the optical fiber 5 are collimated by the lens 35, and a part thereof is reflected by the beam splitter 39 and collected by the lens 38. While being guided to the first detector 41, the light transmitted through the beam splitter 39 is condensed by the lens 36 and then guided to the silicon semiconductor thin film 2b. The infrared light and excitation light reflected by the silicon semiconductor thin film 2 b are collimated by the lens 36, reflected by the beam splitter 39, collected by the lens 37, and then guided to the second detector 42. The lens 36 has different aberration characteristics depending on the difference between the wavelength of excitation light (375 nm) and the wavelength of infrared light (1550 nm). Specifically, the focal point of the infrared light by the lens 36 is set at a position closer to the surface of the silicon semiconductor thin film 2b (far from the optical fiber 5) than the focal point of the excitation light by the lens 36, and in this embodiment. The aberration characteristics of the lens 36 are set so that the irradiation diameter of the excitation light applied to the thin film 2b is 10 μm and the irradiation diameter of the infrared light is 3 μm.

  The holding device 32 includes the stage 19, a lifting / lowering holding device 40 that holds the lens 36 so as to be movable up and down with respect to the stage 19, and a surface position of the substrate 2 a with respect to the stage 19 (surface of the silicon semiconductor thin film 2 b And a surface position detection sensor 46 for detecting the position). The surface position detection sensor 46 is a fire contact sensor for detecting a relative distance from the surface position of the stage 19 on the optical axis of the lens 36 to the surface position of the silicon semiconductor thin film 2b. Moreover, the raising / lowering holding | maintenance apparatus 40 adjusts the said irradiation diameter of the excitation light and infrared light with respect to the thin film 2b by raising / lowering the lens 36. As shown in FIG.

  The control device 34 includes the oscillator 22, the first detector 41 and the second detector 42, the amplifier 25, and the electric signals input from the amplifier 25, the first detector 41 and the second detector 42. A signal processing device 43 for processing, a computer 44 for transmitting and receiving electrical signals to and from the signal processing device 43, and a controller 45 for controlling the driving of the holding device 32 in response to an instruction from the computer 44. Yes.

  The first detector 41 detects excitation light and infrared light that have not been irradiated onto the silicon semiconductor thin film 2b, and outputs an electrical signal corresponding to the detection result to the signal processing device 43. On the other hand, the second detector 42 detects excitation light and infrared light reflected from the silicon semiconductor thin film 2b, and outputs an electrical signal corresponding to the detection result to the amplifier 25 and the signal processing device 43. ing.

  The signal processing device 43 shows data for evaluating the crystallinity of the silicon semiconductor thin film 2b based on the detection signal input from the amplifier 25, for example, the time change of the detection signal as shown in FIG. Create a signal waveform. In addition, since the detection signal about the excitation light before irradiating the thin film 2b is input from the first detector 41 to the signal processing device 43 of this embodiment, the second detection is performed by referring to this detection signal. An unnecessary frequency component can be removed from the detection signal obtained by the detector 42. Therefore, in this case, a detection signal having a high S / N ratio can be obtained without removing unnecessary frequency components in the amplifier 25.

  The computer 44 calculates an appropriate distance between the lens 36 and the silicon semiconductor thin film 2 b based on the electrical signal input from the surface position detection sensor 46. That is, the computer 44 stores in advance a relative distance between the lens 36 having an excitation light irradiation diameter of 10 μm and an infrared light irradiation diameter of 3 μm, and the surface of the silicon semiconductor thin film 2b, and detects the surface position. Based on the relative distance detected by the sensor 46, the distance that the lens 36 should move is calculated.

  The controller 45 drives the lifting / lowering holding device 40 or the driving device (not shown) of the stage 19 in accordance with an electrical signal input from the computer 44.

  As described above, according to the embodiment, the silicon semiconductor thin film 2b is irradiated with excitation light, and infrared light is emitted to the irradiated region, and the silicon semiconductor is based on the reflected light intensity of the infrared light. Since the crystallinity of the thin film 2b is evaluated, the crystallinity can be evaluated quickly and accurately.

  Specifically, in the above-described embodiment, a predetermined region of the silicon semiconductor thin film 2b formed on the substrate 2a is irradiated with excitation light having a band gap or more using the excitation light laser 3 to excite the carriers of the thin film 2b. The infrared light is irradiated to the region where the carriers are excited using the infrared light laser 4.

  A part of the infrared light irradiated in this way is reflected by the silicon semiconductor thin film 2b, but the reflectance of the infrared light depends on the crystallinity of the thin film 2b. As described above, since the reflectance of infrared light increases or decreases according to the crystallinity of the silicon semiconductor thin film 2b, the crystal of the thin film 2b is based on the intensity of infrared light reflected by the silicon semiconductor thin film 2b as in this embodiment. If sex is evaluated, the evaluation can be performed quickly and accurately.

  In particular, as in this embodiment, the pumping light derived from the optical fiber 5 by guiding the pumping light and infrared light to the silicon semiconductor thin film 2b using the common optical fiber 5 and irradiating the thin film 2b. And the radiation direction and radiation distribution of infrared light can be matched between the excitation light and infrared light. Therefore, the irradiation conditions of the excitation light and infrared light irradiated on the thin film 2b can be made constant, and measurement with high reproducibility becomes possible.

  If the configuration in which the focal point of the infrared light by the lens 36 is set closer to the surface of the silicon semiconductor thin film 2b than the focal point of the excitation light by the lens 36 as in the above embodiment, the excitation to the silicon semiconductor thin film 2b is performed. Since the irradiation diameter of light can be made wider than the irradiation diameter of infrared light, infrared light is reliably irradiated within the irradiation range of excitation light while using a condensing lens common to excitation light and infrared light. Thus, the crystallinity can be more reliably evaluated.

  Specifically, when the focus of the infrared light is set on the surface of the silicon semiconductor thin film 2b, the focus of the excitation light is set on the front side (lens 36 side) or the back side of the silicon semiconductor thin film 2b, whereby the silicon semiconductor thin film The irradiation diameter of the excitation light with respect to 2b can be made wider than the irradiation diameter of the infrared light.

  In addition, as the infrared laser 4 in each said embodiment, the semiconductor laser etc. which radiate | emit infrared light with a wavelength of about 1.3-1.6 micrometers are used preferably, for example.

  Furthermore, 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 L3 in FIG. 5, when an SLD (Super Luminescent Diode) is employed as the infrared light emitting means, infrared light having a wavelength spread of about 30 nm as its half-value width can be irradiated. Here, the “half-value width” refers to the spread (width) of the wavelength at half the peak value of the oscillation light intensity in the oscillation spectrum (the intensity indicated by the broken line in FIG. 5). In addition, L4 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 on the silicon semiconductor thin film 2b interferes with the infrared light reflected by the bottom surface of the base material 2a under the thin film 2b, While a measurement error corresponding to the thickness of the substrate 2a is likely to occur, the interference is less likely to occur when broadband infrared light is used, and thus a stable measurement value is obtained regardless of the thickness of the substrate 2a. be able to.

It is the schematic which shows the whole structure of the crystallinity evaluation apparatus of the silicon semiconductor thin film which concerns on embodiment of this invention. It is sectional drawing which expands and shows the front-end | tip part of the optical fiber of FIG. It shows an example of data created by the signal processing apparatus of FIG. It is the schematic which shows the whole structure of the crystallinity evaluation apparatus which concerns on 2nd embodiment of this invention. It is a graph which shows the example of the infrared light used for evaluation of crystallinity.

Explanation of symbols

D1 Diameter dimension L1 Near-field light L2 Reflected light 1, 30 Crystallinity evaluation apparatus 2a Base material 2b Silicon semiconductor thin film 3 Excitation light laser (excitation light irradiation means)
4 Infrared laser (infrared light irradiation means)
5 Optical fiber (light guide member)
5a Base end 5b Tip 6 Metal film (Near-field light forming means)
6a Small hole 23 Infrared light detector (reflected light intensity detection means)
26, 43 Signal processing device (data creation means)
42 Second detector (reflected light intensity detecting means)

Claims (8)

An apparatus for evaluating the crystallinity of a silicon semiconductor thin film formed on a substrate,
Excitation light irradiation means for irradiating excitation light for exciting carriers to a predetermined excitation region on the surface of the silicon semiconductor thin film;
Infrared light emitting means for emitting infrared light;
Near-field light having a hole having a diameter smaller than the wavelength of the infrared light, and the infrared light radiated from the infrared light emitting means to one opening of the hole oozes from the other opening of the hole A near-field light forming means capable of irradiating the excitation region as
Reflected light intensity detecting means for detecting the intensity of reflected light reflected on the near side of the other opening of the hole from the infrared light emitted from the infrared light emitting means and outputting the detection signal;
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 crystal of a silicon semiconductor thin film according to claim 1, further comprising a light guide member capable of guiding infrared light radiated from the infrared light radiating means to one opening of the hole. Sex evaluation device.   The light guide member is composed of an optical fiber having a core extending in a specific axial direction and a clad surrounding the core around the axial line, and a tip portion of the core projects in the axial direction from a tip surface of the clad, 3. The apparatus for evaluating crystallinity of a silicon semiconductor thin film according to claim 2, wherein the crystallinity evaluation apparatus is disposed inside a hole of the near-field light forming means.   The apparatus further comprises holding means for holding the near-field light forming means so as to be able to contact and separate from the silicon semiconductor thin film, and control means for controlling the operation of the holding means. Based on the intensity of the reflected infrared light obtained by the intensity detecting means, the distance of the near-field light forming means with respect to the silicon semiconductor thin film is adjusted so that a reflected light intensity exceeding a preset reference intensity can be obtained. The crystallinity evaluation apparatus for a silicon semiconductor thin film according to any one of claims 1 to 3, wherein:   5. The silicon semiconductor thin film according to claim 1, wherein the near-field light forming unit has a hole having a diameter smaller than a wavelength of the excitation light and infrared light as the hole. Crystallinity evaluation apparatus. An apparatus for evaluating the crystallinity of a silicon semiconductor thin film formed on a substrate,
Excitation light irradiation means for irradiating excitation light for exciting carriers to a predetermined excitation region on the surface of the silicon semiconductor thin film;
Infrared light emitting means for emitting infrared light;
An optical fiber that guides the excitation light and infrared light irradiated from the excitation light irradiation means and infrared light radiation means to the vicinity of the excitation region and irradiates the excitation region;
A condensing unit that is provided between the optical fiber and the silicon semiconductor thin film and collects the excitation light and infrared light guided by the optical fiber;
Reflected light intensity detecting means for detecting the intensity of reflected light reflected on the silicon semiconductor thin film from the infrared light irradiated by the optical fiber and outputting the detection signal;
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.   The condensing means comprises a condensing lens having different aberration characteristics according to the difference between the wavelength of the excitation light and the wavelength of the infrared light, and the focal point of the infrared light and the focal point of the excitation light by the condensing lens are 7. The crystallinity evaluation apparatus for a silicon semiconductor thin film according to claim 6, wherein the crystallinity evaluation apparatus is set at different positions in the optical axis direction.   The crystallinity evaluation apparatus for a silicon semiconductor thin film according to any one of claims 1 to 7, wherein the infrared light emitting means emits broadband infrared light having a spread of 10 nm or more in wavelength.

Images