JP5283889B2 - Crystallinity evaluation system for silicon semiconductor thin films - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for evaluating crystallinity of a semiconductor thin film, capable of evaluating the crystallinity of the semiconductor thin film, without destroying a sample and evaluating, quickly online, the thin film formed on a manufacture line for forming the thin film. <P>SOLUTION: A crystallinity evaluation device for a silicon semiconductor thin film is for evaluating the crystallinity of the silicon semiconductor thin film and comprises an exciting light irradiation means for irradiating the prescribed region of the silicon semiconductor thin film with a carrier exciting light; an infrared light irradiation means for irradiating the prescribed region with infrared light; a range-adjusting means for adjusting the irradiation range with the infrared light so that the irradiation range to the surface of the thin film is a preset range; a reflected light intensity detection means for detecting the intensity of reflected light reflected on the silicon semiconductor thin film, and a data preparation means for preparing data for evaluating the crystallinity from the detected signal. <P>COPYRIGHT: (C)2009,JPO&amp;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 substrate 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 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.

  In recent years, a technique for producing polysilicon only in a minute region (about 5 μm) for producing a TFT circuit has been developed, and the need for local crystallinity evaluation is also increasing.

  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.
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 prepared 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.

  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 problems, the present invention is an apparatus for evaluating the crystallinity of a silicon semiconductor thin film formed on a substrate, and excites carriers in a predetermined region on the surface of the silicon semiconductor thin film. Excitation light irradiating means for irradiating excitation light to cause the infrared light irradiation means to irradiate infrared light in the predetermined region, and the irradiation range to the surface of the silicon semiconductor thin film is a preset range As described above, the range adjusting means for adjusting the irradiation range of the infrared light and the intensity of the reflected light reflected on the silicon semiconductor thin film out of the infrared light irradiated in the predetermined region are detected and detected. and the reflected light intensity detecting means for outputting a signal, and data generating means for generating data for processing said detection signal to evaluate the crystallinity of the silicon semiconductor film, wherein the predetermined from the infrared light irradiating means And a focusing means for focusing the infrared light irradiated on the region, the focusing means along with has a lens for condensing the infrared light, the range adjusting means, wherein A moving means for moving the lens along the optical axis of the infrared light; a measuring means for measuring a distance between the lens and the surface of the silicon semiconductor thin film; and a distance measured by the measuring means. based on, a silicon semiconductor thin film characterized that you have a control means for controlling the movement of the lens by the moving means so that the irradiation range of the infrared light to the surface of the silicon semiconductor thin film becomes equal to a preset range A crystallinity evaluation apparatus is provided.

  A predetermined 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, and in the region where the carriers are excited. When infrared light is irradiated using infrared light irradiation means, a part of infrared light is reflected by the silicon semiconductor thin film. The reflectance of infrared light at this time depends on the amount of excited carriers present in the 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 semiconductor band gap of the semiconductor thin film to excite carriers, and infrared light is irradiated in the region irradiated with the excitation light. In general, 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.

  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 the infrared light emitted by the infrared light irradiation 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 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.

  As described above, in the crystallinity evaluation apparatus according to the present invention, the crystallinity is evaluated based on the intensity of the reflected light from the silicon semiconductor thin film. Therefore, the conditions for obtaining the reflected light are set for each evaluation. If it can be kept constant, the result of the evaluation can be obtained stably. And in this invention, since the irradiation range of infrared light is adjusted so that the irradiation range with respect to a silicon semiconductor thin film may turn into the preset range, the stable evaluation result can be obtained.

The crystal evaluation apparatus of a silicon semiconductor thin film according to the present invention, the infrared light irradiated on the predetermined area from the infrared light irradiating means further comprises a condensing means for condensing.

According to the present invention , infrared light can be condensed and the irradiation range can be narrowed, so that the crystallinity can be evaluated with high spatial resolution. When narrowing the irradiation range in this way, if the position of the focal point and the surface of the silicon semiconductor thin film deviate, fluctuation (enlargement) of the irradiation range of infrared light occurs, and the reflected light intensity at the evaluation target point becomes weak, and evaluation accuracy However, in the present invention, since the irradiation range of the infrared light is adjusted to be a preset range by the range adjustment unit as described above, it is stable with high spatial resolution. Evaluation can be performed.

Specifically, the condensing unit has a lens for condensing infrared light, and the range adjusting unit is a moving unit for moving the lens along the optical axis of the infrared light. And a measuring means for measuring a distance between the lens and the surface of the silicon semiconductor thin film, and an irradiation range of the infrared light on the surface of the silicon semiconductor thin film based on the distance measured by the measuring means in advance. Control means for controlling the movement of the lens by the moving means so as to be in the set range .

Therefore , it is possible to adjust the irradiation range of infrared light by adjusting the distance between the lens and the silicon semiconductor thin film.

  Furthermore, in the crystallinity evaluation apparatus for a silicon semiconductor thin film, the range adjusting means can be configured to be able to adjust the irradiation range of the excitation light to the silicon semiconductor thin film.

  In this way, since the irradiation range of excitation light as well as infrared light can be adjusted by the range adjusting means, the crystallinity evaluation of the silicon semiconductor thin film can be performed more stably. In other words, there is a positive correlation between the excitation density (excitation light energy per unit area) and the peak value of the signal based on the intensity of the reflected light, so the crystallinity evaluation stability can be maintained by keeping the excitation density constant. However, this excitation density can be stabilized by keeping the excitation light irradiation range constant. Therefore, in the said structure, the stability of crystallinity evaluation can be improved by adjusting the irradiation range of excitation light, keeping excitation density stable.

Further, the crystallinity evaluation device of the silicon semiconductor film, wherein the lens is both infrared light and the excitation light is condensed, said moving means, said lens along an optical axis of the infrared light and the excitation light moves The range adjusting means is preferably configured to adjust the irradiation range of the infrared light and the excitation light by moving the lens by the moving means.

  According to this configuration, the irradiation range of the infrared light and the excitation light can be adjusted only by moving the common lens. Therefore, when the lenses are provided for the excitation light and the infrared light to move them, In comparison, it is possible to adjust the irradiation range of both excitation light and infrared light with a simpler and smaller configuration.

  In the silicon semiconductor thin film crystallinity evaluation apparatus, the silicon semiconductor thin film crystallinity evaluation apparatus can hold the silicon semiconductor thin film in a state in which the surface thereof is open and is substantially parallel to the surface. It is preferable to further comprise holding means movable along a flat plane.

  In this way, when the surface of the silicon semiconductor thin film is continuously evaluated according to the movement of the holding means, the irradiation range of the infrared light on the surface of the silicon semiconductor thin film held by the holding means is Since it is maintained within a certain range, a stable evaluation result can be obtained.

  In particular, in recent years, a large-sized substrate such as an LTPS (Low-Temperature Poly-Silicon TFT) substrate is sometimes evaluated, and a silicon semiconductor is used when continuously evaluating the entire surface of such a substrate. Although it is difficult to keep the irradiation range of infrared light on the surface of the thin film (for example, the distance between the semiconductor surface and the condenser lens) constant, according to the above configuration, the variation of the irradiation range is suppressed. Stable evaluation is possible.

In the crystallinity evaluation apparatus for a silicon semiconductor thin film, it is preferable that the lens and the measuring unit can be moved together by the moving unit.

In the silicon semiconductor thin film crystallinity evaluation apparatus, it is preferable that the measurement unit has a support portion on which the lens is held, and the moving unit moves the measurement unit.

  In the crystallinity evaluation apparatus for a silicon semiconductor thin film of the present invention, it is preferable that the base material, the excitation light irradiation means, and the light condensing means are configured as follows.

  That is, it is preferable that the base material is fixed to base material support means provided with positioning means such as a stage controller controlled by a computer or the like. By using such a substrate support means, it is possible to accurately irradiate a predetermined region on the substrate with excitation light and infrared light.

  The excitation light irradiation means includes excitation light emission means for emitting excitation light and excitation light irradiation direction adjusting means for irradiating the substrate with excitation light emitted from the excitation light emission means. Is preferred. Examples of the excitation light irradiation direction adjusting means include a movable mirror that can adjust the reflection direction of the excitation light, and a means that can freely adjust the radiation direction provided in the excitation light emitting means. By providing the excitation light irradiation means with the excitation light irradiation direction adjusting means, the excitation light irradiation means can accurately and accurately place a predetermined region on the substrate regardless of the position where the excitation light emission means is disposed. Excitation light can be irradiated.

  Further, as the light condensing means, a condensing lens provided above the base material fixed to the base material supporting means, for condensing infrared light emitted by the infrared light irradiation means, It is preferable to include means for causing infrared light emitted from the infrared light irradiation means to enter the condenser lens from above. With such a configuration, the infrared light emitted from the infrared light irradiating means is incident on the condenser lens, and the infrared light can be irradiated to an accurate position on the substrate.

  An apparatus such as a beam splitter capable of changing the traveling direction of the infrared light is used as the means for causing the infrared light emitted from the infrared light irradiation means to enter from above. When such an apparatus is used, infrared light can be accurately incident on the condenser lens regardless of the position where the infrared light irradiation means is disposed.

  An example of the crystallinity evaluation apparatus for a silicon semiconductor thin film having the above-described configuration will be described below based on the crystallinity evaluation apparatus as shown in FIG.

  In FIG. 1, the base material 5b is supported at a specific position by the base material stage 17 which is the base material support means, and a condensing lens 4 for condensing infrared light is provided above the base material 5b. Means such as a laser splitter 12 for allowing infrared light emitted from infrared light irradiation means such as the infrared light laser 10 to enter the condenser lens 4 from above is provided. On the other hand, the excitation light irradiation means includes excitation light emission means such as an excitation pulse laser 1 that emits excitation light, and further transmits excitation light that is transmitted through the infrared light and emitted from the excitation light emission means. A mirror 6 that reflects toward the substrate 5b is provided above the condenser lens 4. Then, the excitation light reflected by the mirror 6 passes through the condenser lens 4 and irradiates the silicon semiconductor thin film 5a formed on the base material 5b, and infrared light incident on the condenser lens 4 is irradiated. The said base material support means with respect to the support position of the said base material so that it may irradiate in the irradiation area | region of the said excitation light in the silicon semiconductor thin film 5a formed by the condensing lens 4 on the base material 5b. A relative position between the lens and the mirror is set. With such a configuration, the silicon semiconductor thin film crystallinity evaluation apparatus of the present invention can be configured more efficiently.

  Then, the intensity of the reflected light with respect to the thin film of the infrared light condensed and irradiated as described above is detected by the reflected light intensity detecting means. Then, the crystallinity is evaluated by data creation means for creating data comprising a computer or the like having a data operation processing means such as a CPU for processing the detected detection signal to evaluate the crystallinity of the silicon semiconductor thin film. By creating data for the purpose and outputting the result, the crystallinity of the thin film can be quickly evaluated in a short time.

  The data generating means uses the light whose intensity periodically varies as the excitation light in the excitation light irradiating means, and the infrared light synchronized with the intensity fluctuation period of the light whose intensity varies periodically. It is preferable to create data on light reflectance changes. As described above, the light whose intensity varies periodically as the excitation light is used, and the data generation means uses the infrared light reflectivity change synchronized with the period of fluctuation of the intensity of the light whose intensity varies periodically. By creating data, the S / N ratio of the detected reflected light intensity can be increased. In addition, by periodically modulating the intensity of the excitation light and detecting only the same period component using a lock-in amplifier or the like, unnecessary noise frequency components can be removed, and the S / N ratio can be increased. High accuracy can be realized.

  Further, the excitation light irradiation means further includes a timing detection means for detecting the fluctuation timing of the intensity of the excitation light to be irradiated. In this case, the data generation means is detected by the timing detection means. It is preferable to generate data for evaluating the crystallinity of the silicon semiconductor thin film by collecting the detection signal of the reflected light intensity detection means at a timing synchronized with the fluctuation timing of the intensity of the excitation light. In this way, the timing detection means detects the intensity variation timing of the excitation light, and synchronizes the period during which the intensity of the excitation light is high and the period for data collection of the reflected light, thereby reducing the S / N ratio of the data to be created. Can be increased.

  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.

  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 the silicon semiconductor thin film 5a formed on the substrate 5b, and a substrate stage (holding means) 17 that supports the substrate 5b. And excitation light irradiating means, infrared light irradiating means, condensing means, range adjusting means, reflected light intensity detecting means, timing detecting means, and data creating means.

  In this embodiment, a glass substrate 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 stage controller 16.

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

  The excitation pulse 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 pulse 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 irradiation with excitation light whose intensity periodically varies can generate a large number of carriers instantaneously. It is preferable from the point that the signal intensity can be increased. The excitation light whose intensity varies periodically is not necessarily pulsed light, and may be any light whose intensity is periodically modulated.

  The excitation light may be “light having a wavelength having energy at least equal to the band gap of the semiconductor thin film”. Specifically, in the case of the silicon semiconductor thin film 5a, the excitation light is light having a wavelength of about 1100 nm or less. Good.

  In addition, ultraviolet light is used as the excitation light because the thin film 5a is very thin (for example, 50 nm) and has a large absorption at the ultraviolet wavelength. This is because it can be excited. In other words, if the efficiency is extrapolated, light other than ultraviolet light can be used as excitation light.

  The beam adjuster 2 is composed of a combination lens, and adjusts the divergence angle of the pulsed light beam transmitted from the excitation pulse 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, toward the base material 5, and passes through a condenser lens 4 described later, for example, an irradiation diameter of 0.01 to 1 mm. Irradiate to a certain area.

  The infrared light irradiation means is for irradiating infrared light within a range irradiated with excitation light on the surface of the silicon semiconductor thin film 5a. In this embodiment, the infrared light laser 10; A beam adjuster 11, a beam splitter 12, a λ / 2 polarizing plate 20, and a λ / 4 polarizing plate 21 are provided. As the infrared laser 10, for example, a semiconductor laser that emits infrared light having a wavelength of about 1.3 to 1.6 μm is preferably used. 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 infrared light laser 10. The beam splitter 12 reflects the infrared light that has passed through the beam adjuster 11 and the λ / 2 polarizing plate 20 to the substrate 5b side, and the infrared light irradiated to the substrate 5b through the λ / 4 polarizing plate 21. The reflected light, that is, the infrared light that has passed through the λ / 4 polarizing plate 21 twice is transmitted to the photodetector 13 described later.

  Further, as the infrared light emitted from the infrared laser 10, a broadband light having a spread of 10 nm or more in wavelength can be employed. For example, as shown by L1 in FIG. 3, when an SLD (Super Luminescent Diode) is employed as the infrared laser 10, infrared light having a wavelength broadening of about 30 nm can be irradiated as its half-value width. 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. The measurement error corresponding to the thickness of the base material 5b is likely to occur, but when the broadband infrared light is used, the interference is difficult to occur. Therefore, a stable measurement value is obtained regardless of the thickness of the base material 5b. Can be obtained.

  The said condensing means is for condensing the infrared light radiated | emitted from the said infrared light radiation means, and contains the said condensing lens 4 in this embodiment. 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 is adjusted by a range adjusting means to be described later. For example, it is preferable to adjust the irradiation diameter to about 2 to 10 μm from the viewpoint of maintaining a high spatial resolution.

  Note that 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 range adjusting means adjusts the distance between the lens 4 and the silicon semiconductor thin film 5a so that the irradiation range of infrared light and ultraviolet light on the silicon semiconductor thin film 5a becomes a preset reference range. Is. The reference range may be set substantially the same for infrared light and ultraviolet light, but from the viewpoint of reliably irradiating the excitation range with infrared light, the ultraviolet light irradiation range is higher than the infrared light irradiation range. Is preferably set larger. For example, the diameter dimension of the irradiation range defined as the reference range for ultraviolet light can be set to be not less than 2 times and not more than 20 times the diameter dimension of the irradiation range defined as the reference range for infrared light.

  As a specific configuration, the range adjusting unit includes a sensor (measuring unit) 22 that holds the condenser lens 4, a drive mechanism (moving unit) 23 that can move the sensor 22 and the lens 4 up and down, A computer (control means) 15 that drives and controls the drive mechanism 23 based on an input signal from the sensor 22 is provided.

  The sensor 22 holds the condensing lens 4 in a support portion 24 extending sideways, detects the distance between the condensing lens 4 and the surface of the silicon semiconductor thin film 5a, and sends the detection result to the computer 15. It is configured to output. Specifically, the sensor 22 can use a well-known detection means, for example, a sensor using triangulation, a quadrant sensor used for a pickup lens of an optical disk, or the like. Comparing these sensors using triangulation with the quadrant sensor, the quadrant sensor is advantageous from the viewpoint of miniaturization, but the quadrant sensor has a side where the dynamic range is narrowed. On the other hand, a sensor using triangulation is not suitable for downsizing, but has a characteristic of a wide dynamic range.

  In the present embodiment, as shown in FIG. 1, a sensor 22 configured to hold the condenser lens 4 and move up and down integrally with the condenser lens 4 is disclosed. Assuming that the distance between 4 and the surface of the silicon semiconductor thin film 5a can be measured, the arrangement position of the sensor 22 is not limited. For example, the sensor 22 may be provided independently of the condenser lens 4 and the drive mechanism 23. On the contrary, as shown in FIG. 1, the distance can be measured more accurately by adopting a configuration in which the lens 4 is driven in the vicinity of the condenser lens 4.

  The drive mechanism 23 moves the condenser lens 4 and the sensor 22 as a unit according to a control signal output from the computer 15. For example, the drive mechanism 23 has a ball screw (not shown) and a motor (not shown) for rotationally driving the ball screw, and the ball screw is attached to a nut attached to the sensor 22. Inserted (screwed). As the ball screw rotates in accordance with the driving of the motor, the nut moves relative to the ball screw. As a result, the sensor 22 and the condenser lens 4 move up and down with respect to the substrate stage 17. The drive mechanism 23 is not limited to the combination of the above-described ball screw and motor, and may be any configuration that can move the condenser lens 4 and the sensor 22 as a unit other than the ball screw. In the present embodiment, the sensor 22 and the condenser lens 4 are moved up and down in parallel with the optical axes of infrared light and excitation light.

  The computer 15 controls the drive of the drive mechanism 23 so that the distance between the condenser lens 4 detected by the sensor 22 and the surface of the silicon semiconductor thin film 5a falls within a preset allowable range.

  Specifically, the computer 15 stores the permissible range, and compares the permissible range with a distance detected by the sensor 22 (hereinafter referred to as a detection distance), so that the detection distance is within the permissible range. When it is determined that, the drive mechanism 23 is held as it is (that is, the sensor 22 and the condensing lens 4 are set as they are). On the other hand, when the computer 15 determines that the detection distance is out of the allowable range, the computer 15 calculates the amount of movement of the condenser lens 4 to be within the allowable range, and outputs an electric signal based on the amount of movement. Output to the drive mechanism 23. This process is performed every predetermined period in accordance with an instruction from the computer 15.

  The tolerance defined as the distance between the condenser lens 4 and the silicon semiconductor thin film 5a is based on the position of the condenser lens 4 at which the focal point of the condenser lens 4 coincides with the surface of the silicon semiconductor thin film 5a. Is a range of distances where an upper and lower intersection is provided. Therefore, when the processing is executed by the computer 15, the irradiation range of the infrared light and the excitation light collected by the condenser lens 4 to the silicon semiconductor thin film 5a is adjusted to an appropriate range according to the allowable range. Will be.

  In the present embodiment, the irradiation range of the infrared light and the excitation light to the silicon semiconductor thin film 5a is adjusted by moving the condenser lens 4 up and down with respect to the substrate stage 17. It is also possible to adjust the irradiation range by bringing the substrate stage 17 into and out of contact with the optical lens 4.

  The reflected light intensity detecting means is for detecting the intensity of the reflected light reflected on the silicon semiconductor thin film out of the infrared light irradiated by the light collecting means and outputting the detection signal. In the embodiment, the light detector 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 pulse 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 pulse 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.

  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 also control the driving of the substrate stage (holding means) 17. This drive control enables, for example, measurement at any position on the substrate 5 and mapping measurement.

  In the present embodiment, the silicon semiconductor thin film 5a is moved two-dimensionally with respect to the condenser lens 4 by the movement of the substrate stage 17, but this two-dimensional movement is performed by the substrate stage 17. This can also be realized by moving the condensing lens 4 with respect to. Specifically, the drive mechanism 23 can be provided not only with the above-described lifting function of the condensing lens 4 but also with a two-dimensional movement function along the surface of the silicon semiconductor thin film 5a.

  Next, the operation of this apparatus will be described.

  Of the pulsed light emitted from the excitation pulsed 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. Then, the silicon semiconductor thin film 5a on the substrate 5 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, infrared light emitted from the infrared laser 10 passes through the beam adjuster 11, the beam splitter 12, the dichroic mirror 6, and the condenser lens 4 in the irradiation region of the excitation light to the silicon semiconductor thin film 5 a. The central part is focused and irradiated.

  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. That is, the distance between the condenser lens 4 and the surface of the silicon semiconductor thin film 5a is detected by the sensor 22 every predetermined time, and the drive mechanism 23 is operated by the computer 15 so that the detected distance is within the reference range. As a result, the irradiation range of infrared light is maintained at an appropriate radius. In this embodiment, since the condensing lens 4 is used for both infrared light and excitation light, the irradiation range of the excitation light becomes appropriate by the control by the computer 15.

  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.

  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 pulse 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 pulse laser 1, and the pulsed light from the excitation pulse laser 1 passes through the beam splitter 3, and the beam adjuster 2 The divergence angle was adjusted, reflected by the dichroic mirror 6, transmitted through the condenser lens 4, and irradiated onto the surfaces of various samples with an irradiation diameter of 1 mm.

  On the other hand, a semiconductor laser that emits infrared light having a wavelength of 1.55 μm was used as the infrared light laser 10 included in the infrared light irradiation means. 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. (That is, drive control for the drive mechanism 23 by the computer 15 is performed based on the allowable range set so that the irradiation diameter is 5 μm ± several%).

  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.

  In the embodiment described above, the reflected light from the sample is guided to the photodetector 13 as it is, but the reflected light from the sample is divided into two light beams as shown in FIG. It can also be configured to detect.

  In this embodiment, a beam splitter 25 for dividing the reflected light into two light beams, and a photodetector 26 and an amplifier 27 provided separately from the photodetector 13 and the amplifier 8 are provided.

  In this embodiment, the reflected light is separated into two light beams, and one light beam is guided to the photodetector 13 while the other light beam is guided to the photodetector 26. The photodetector 13 detects an AC component included in the reflected light (that is, a component that varies when irradiated with ultraviolet light), and the photodetector 26 detects a DC component (irradiated with ultraviolet light) included in the reflected light. Reflected light in a state in which it is not performed (always a constant value for a specific sample) is detected, and these detected values are guided to the signal processing unit 9 via amplifiers 8 and 27, respectively.

  The signal processing unit 9 calculates the maximum fluctuation amplitude of the reflectance of infrared light based on the measured values of the AC component and the DC component. That is, the maximum value of the increase rate of the AC component with respect to the DC component is calculated. Specifically, when the detected value of the DC component is Va and the peak value of the AC component is Vb, the signal processing unit 9 calculates Vb / Va. As described above, the reason why the maximum value of the increase ratio of the AC component with respect to the DC component is calculated is that the DC component value may be different for each sample. This is because an absolute evaluation cannot be performed even if compared.

  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.

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 figure which expands and shows a part of crystallinity evaluation apparatus which concerns on another embodiment of this invention.

DESCRIPTION OF SYMBOLS 1 Excitation pulse laser 2 Beam adjustment device 3 Beam splitter 4 Condensing lens 5b Base material 5a Silicon semiconductor thin film 6 Dichroic mirror 7 Optical detector 8 Amplifier 9 Signal processing apparatus 10 Infrared light laser 11 Beam adjustment device 12 Beam splitter 13 Optical detection 15 Computer (control means)
16 stage controller 17 substrate stage 22 sensor (measuring means)
23 Drive mechanism (moving means)

Claims (6)

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 in a predetermined region of the surface of the silicon semiconductor thin film;
Infrared light irradiating means for irradiating infrared light in the predetermined region;
Range adjusting means for adjusting the irradiation range of the infrared light so that the irradiation range on the surface of the silicon semiconductor thin film is a preset range;
Reflected light intensity detecting means for detecting the intensity of reflected light reflected on the silicon semiconductor thin film from the infrared light irradiated in the predetermined region and outputting the detection signal;
Data creation means for processing the detection signal and creating data for evaluating the crystallinity of the silicon semiconductor thin film ;
Condensing means for condensing infrared light emitted from the infrared light irradiating means into the predetermined region;
Equipped with a,
The condensing means has a lens for condensing infrared light, and the range adjusting means includes a moving means for moving the lens along an optical axis of infrared light, and the lens A measuring means for measuring the distance between the surface of the silicon semiconductor thin film and a range in which the irradiation range of the infrared light on the surface of the silicon semiconductor thin film is set in advance based on the distance measured by the measuring means moving means silicon semiconductor thin film of crystalline evaluation apparatus characterized that you have a control means for controlling the movement of the lens according to the. 2. The crystallinity evaluation apparatus for a silicon semiconductor thin film according to claim 1, wherein the range adjusting means is configured to be able to adjust an irradiation range of the excitation light to the silicon semiconductor thin film. Sex evaluation device. 3. The silicon semiconductor thin film crystallinity evaluation apparatus according to claim 2, wherein the lens condenses both infrared light and excitation light, and the moving means places the lens on the optical axes of infrared light and excitation light. And the range adjusting means is configured to adjust the irradiation range of infrared light and excitation light by moving the lens by the moving means. Sex evaluation device. The crystallinity evaluation apparatus for a silicon semiconductor thin film according to any one of claims 1 to 3, wherein the silicon semiconductor thin film can be held in a state in which the surface thereof is open and substantially parallel to the surface. An apparatus for evaluating crystallinity of a silicon semiconductor thin film, further comprising holding means movable along a flat surface. 5. The silicon semiconductor thin film crystallinity evaluation apparatus according to claim 1, wherein the lens and the measuring unit can be moved integrally by the moving unit. Crystallinity evaluation device. 6. The silicon semiconductor thin film crystallinity evaluation apparatus according to claim 5, wherein said measuring means has a support part holding said lens, and said moving means moves said measuring means. Semiconductor thin film crystallinity evaluation system.

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