JP2005353823A - Method of manufacturing thin crystalline semiconductor film and semiconductor device using the film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a thin crystalline semiconductor film with which a thin film semiconductor device having uniform characteristics can be manufactured, and to provide a semiconductor device using the thin crystalline semiconductor film manufactured by the method. <P>SOLUTION: The method of manufacturing the thin crystalline semiconductor film includes a step of forming a substrate and a thin semiconductor film provided with a foundation layer and a semiconductor layer, a step of forming a reflection adjusting film pattern having reflectivity which is different from that of the surface of the thin semiconductor film, and a step of irradiating at least one light to the surface of the thin semiconductor film containing the reflection adjusting film pattern. The distance D between the end of the area irradiated with the light and the reflection adjusting film pattern and the length W of the reflection adjusting film pattern have the relation of D>W. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a crystalline semiconductor thin film used for a display device and the like, and a semiconductor device using the crystalline semiconductor thin film as an active layer.

  A thin film transistor used for a display device using liquid crystal or electroluminescence (EL) uses amorphous or polycrystalline silicon as an active layer. Among them, a polycrystalline silicon thin film transistor has many advantages over an amorphous silicon thin film transistor because of its high electron mobility.

  For example, not only a switching element can be formed in the pixel portion, but also a driver circuit and a part of the peripheral circuits can be formed on a single substrate in the peripheral portion of the pixel. For this reason, it is not necessary to separately mount a driver IC or a drive circuit board on the display device, so that the display device can be provided at a low price.

  Further, as another advantage, since the size of the transistor can be miniaturized, a switching element formed in the pixel portion can be reduced and a high aperture ratio can be achieved. Therefore, it is possible to provide a display device with high brightness and high definition.

  As a method for producing a polycrystalline silicon thin film, an amorphous silicon thin film is formed on a glass substrate by a CVD method or the like, and then a separate step for polycrystallizing amorphous silicon is required. Usually, when the annealing process for crystallization is performed by a high-temperature annealing method at 600 ° C. or higher, it is necessary to use an expensive substrate that can withstand high temperatures, which has been an impediment to reducing the cost of display devices. . In recent years, a technique for crystallizing amorphous silicon at a low temperature of 600 ° C. or lower using a short-pulse oscillation excimer laser has been generalized, and a display device in which a polycrystalline silicon transistor is formed on a low-cost glass substrate is low in price. It can be provided at.

  The laser crystallization technique is a linear laser having a length of about 200 to 400 mm and a width of about 0.2 to 1.0 mm while heating a glass substrate on which an amorphous silicon thin film is formed to about 400 ° C. and scanning the glass substrate. A method of continuously irradiating a beam on a glass substrate is common. By this method, crystal grains having a grain size of about 0.2 to 0.5 μm are formed. At this time, the portion of the amorphous silicon irradiated with the laser does not melt over the entire thickness direction, but melts while leaving a part of the amorphous region. Nuclei are generated, crystals grow toward the outermost layer of the silicon thin film, and randomly oriented crystal grains are formed. However, in the above method, a transistor having excellent characteristics can be obtained as compared with an amorphous silicon thin film transistor, but it cannot be said that the crystal grain size is sufficiently large with respect to the channel region of the thin film transistor. In addition, since there are a large number of grain boundaries, the mobility is smaller than that of single crystal silicon, and there is a problem in that it tends to appear as variations in transistor characteristics.

  Therefore, in order to obtain a display device with higher performance, it is necessary to increase the crystal grain size of polycrystalline silicon and control the crystal orientation, with the aim of obtaining performance close to that of single crystal silicon. In recent years, a lot of research and development has been done.

For example, in crystallization by laser irradiation, a state in which a SiO ₂ cap is formed on the surface in order to reduce reflectance and improve energy efficiency, or to suppress generation of irregularities on the surface due to laser irradiation. In many cases, laser irradiation is performed. In addition to the above purpose, the SiO ₂ cap functions as a heat insulating film for the molten silicon thin film, and the crystallinity is improved as a whole. However, the improvement in homogenization still remains a problem.

Therefore, Patent Document 1 below discloses a technique for increasing the crystal grain size with good reproducibility by patterning the SiO ₂ cap having the antireflection function and forming it at an arbitrary position and then performing laser irradiation. ing. This technique will be described with reference to FIG. FIG. 10 is a schematic cross-sectional view showing a conventional method for producing a semiconductor thin film. As shown in FIG. 10, that through the SiO ₂ cap pattern 74 is irradiated simultaneously laser 75 and a portion in which the amorphous silicon film 73 are covered with the SiO ₂ cap pattern 74 amorphous silicon film 73 is exposed Thus, the crystallization region 76 having a large crystal grain size is arbitrarily formed by crystallization in a direction perpendicular to the film thickness (hereinafter referred to as a transverse direction) from both ends of the SiO ₂ cap pattern 74 toward the center. The crystallization region 76 is used as an active layer of a thin film transistor.

  In the prior art as described above, in order to crystallize from the end of the cap pattern to the center and obtain a lateral crystal in the entire area under the cap pattern, the cap film thickness that prevents reflection from the laser is set. In addition, proper setting of parameters such as the cap pattern width, laser irradiation energy, and amorphous silicon film thickness is extremely important. For example, according to the contents described in Patent Document 1 below, the cap pattern width is 5 μm or less, preferably 0.5 μm to 2 μm, and within this range, the lateral crystal growth from the end of the cap pattern is the cap pattern. Proceeding to the center, a symmetrical crystal structure is obtained with respect to the center of the cap pattern. When the width is larger than the above pattern width, lateral crystal growth occurs from the end of the cap, but cooling in the substrate thickness direction is dominant in the vicinity of the central portion rather than crystallization by cooling in the lateral direction of the substrate, and is made of fine crystals. Since the polycrystalline layer is formed, the lateral crystal growth from the end of the cap pattern does not proceed to the center.

  Even within the range of the cap pattern width, it is important to set the laser irradiation energy appropriately. Based on the inventor's experience, the amorphous silicon film under the cap pattern is formed in the thickness direction by laser irradiation. The portion where the amorphous silicon layer is exposed is in a partially melted state and in the melted state over the entire layer depending on the laser irradiation energy. Exists. In order to ensure the lateral crystal growth to the center of the cap pattern, the portion where the amorphous silicon film is exposed is melted over the entire layer, especially when the cap pattern width is increased. It is necessary to use laser irradiation conditions.

  However, in the crystallization conditions as described above, as described above, since the amorphous silicon film is completely melted even in the exposed portion, in addition to the temperature distribution formation between the cap pattern end and the amorphous silicon exposed portion, Lateral crystal growth occurs due to the formation of a temperature distribution at the boundary between the edge of the laser irradiation region and the non-laser irradiation region. In this case, the boundary between the amorphous silicon film in the laser irradiation region and the amorphous silicon film in the non-laser irradiation region is higher than the temperature between the amorphous silicon film under the cap pattern and the amorphous silicon film exposure in the laser irradiation region. Since the temperature formation is lower, the lateral crystal growth proceeds first at the boundary between the laser irradiation region end and the laser non-irradiation region. At this time, depending on the width of the exposed portion of the amorphous silicon film in the laser irradiation region, the lateral crystal growth that has proceeded prior to the boundary of the laser irradiation region continuously takes over the crystal growth at the end of the cap pattern. If the width of the exposed portion of the amorphous silicon film in the laser irradiation area on both sides of the cap pattern is set to be different (that is, if the center axis of the cap pattern is shifted from the center axis of the laser irradiation area and laser irradiation is performed asymmetrically) In some cases, the crystal structure is asymmetric with respect to the central portion of the cap pattern.

The above phenomenon will be exemplarily described in more detail based on the lateral temperature distribution of the amorphous silicon film cross section. FIG. 5 is a diagram showing the temperature distribution in the lateral direction of the amorphous silicon film with the distance from the center of the cap pattern as the horizontal axis. The left end in the figure, the position where the lateral position is 0 μm is the center of the cap pattern. As shown in FIG. 5, the amorphous silicon film and the amorphous silicon film under the cap pattern are exposed through the cap pattern 64 having an antireflection function on the amorphous silicon film 63 on the glass substrate 61 and the SiO ₂ base film 62. Crystallization is performed by irradiating the portion with laser. FIG. 5 shows the temperature when the width of the cap pattern 64 is 4 μm, the laser irradiation region is sufficiently wider than the cap pattern 64, and the end of the laser irradiation region is sufficiently far from the end of the cap pattern 64. Distribution. The amorphous silicon film 63 is melted and crystallized over the entire layer by the laser irradiation. However, in the portion where the amorphous silicon film 63 sufficiently separated from the end of the cap pattern 64 is exposed, the amorphous silicon film 63 is mainly directed toward the substrate, that is, downward in the figure. Since heat escapes, there is almost no temperature gradient in the lateral direction, and the crystal grows mainly from the bottom to the top to become a fine crystal, and a polycrystalline layer 65 made of the fine crystal is formed. On the other hand, a temperature gradient in the lateral direction is formed in the amorphous silicon film 63 by the antireflection effect of the cap pattern 64 around the end of the cap pattern 64, here, at a portion about 1 μm away from the end of the cap pattern 64, thereby Since heat is transferred with respect to the direction, the lateral crystal grows from this portion toward the center of the cap pattern 64. The lateral crystal region 66 progresses to the center of the cap pattern 64, collides with the lateral crystal that progresses in the same manner from the vicinity of the other end of the cap pattern 64, and the crystallization is completed. The length of the crystal is about 3 μm. In the case as shown in FIG. 5 described above, both ends of the cap pattern 64 are sufficiently separated from the ends of the laser irradiation region, so that the starting point of the lateral crystal is relative to the center of the cap pattern 64 as shown in FIG. 6 and the time required for lateral crystallization start and the time required for lateral crystallization, that is, the cooling time are exactly the same, so that the crystals that have advanced from both ends collide with the center of the cap pattern 64, and as a result, as shown in FIG. Crystals having exactly the same grain size are formed symmetrically in the width direction under the cap pattern 64. Here, FIG. 6 is a schematic diagram showing the crystal grown in the lateral direction under the cap pattern in FIG.

  FIG. 7 shows that the cap pattern width in FIG. 5 is 4 μm and the laser irradiation area is 3 μm away from one end of the cap pattern. Note that the width of the irradiation region on the other end side of the cap pattern is made sufficiently wide as in FIGS. In this case, similarly to the above-described example, the amorphous silicon film 63 is melted over the entire laser irradiation region, but the portion where the amorphous silicon film 63 irradiated with the laser beam is exposed at the end of the laser irradiation region and the laser. A temperature gradient is formed with the amorphous silicon film 63 that has not been irradiated, and a lateral crystal grows toward the center of the cap pattern 64 starting from the periphery of the end of the laser irradiation region. Further, the lateral crystal growth is succeeded by the lateral crystal growth due to the temperature gradient around the end of the cap pattern caused by the antireflection effect of the cap pattern 64, and the growth of the lateral crystal 66 from the end of the laser irradiation region is the cap. The process proceeds continuously to the center of the pattern.

  On the other hand, the other end of the cap pattern 64 has a sufficient distance from the other end of the laser irradiation region, so that the lateral crystal generated at the other end of the laser irradiation region is the same as the example of FIG. The growth is not inherited by the lateral crystal growth that occurs at the other end of the cap pattern 64, and the lateral crystal growth occurs only by the formation of a temperature gradient by the cap pattern 64. In addition, since the laser irradiation area width is sufficiently wide on the other side, it is harder to cool than the one side (approx. 3 μm irradiation area) where the laser irradiation area is narrow, and the crystal growth time is compared with one side. And slow down. Therefore, before the crystal grows from the other side, the crystal grows from one side, and the lateral crystal 66 from the one side passes through the center of the cap pattern 64 and grows toward the other side. It collides with the lateral crystal grown from the periphery of the other end at a location on the other side shifted from the center of the cap pattern 64. That is, as shown in FIG. 8, crystals grown from both sides of the cap pattern do not collide at the center, and crystals having different crystal lengths are formed asymmetrically in the width direction under the cap pattern 64. Here, FIG. 8 is a schematic view of the lateral crystal growth under the cap pattern in FIG.

When a transistor is manufactured using a semiconductor thin film whose crystallization is not symmetrical at the center under such a cap pattern, there may be a problem. For example, as shown in FIG. 9A, a channel is formed along the width direction of the cap pattern using the crystal 66 grown in the lateral direction with the center portion of the cap pattern as a boundary, and the boundary of the center portion is formed. When the two transistors 67 are manufactured by avoiding any of the transistors from crossing the grain boundary in the channel direction, uniform transistor characteristics can be obtained. However, as shown in FIG. When the transistor 67 similar to that shown in FIG. 9A is formed in a state where the boundary of the crystal 66 is deviated from the center of the cap pattern, since the grain boundary is included in the channel of one transistor, the transistor characteristics are deteriorated and uniform. Sexually deteriorates.
JP 2000-260709 A

  The present invention has been made in order to solve the above-described problems of the prior art, and an object of the present invention is to provide a method for manufacturing a crystalline semiconductor thin film capable of forming a thin film semiconductor device having uniform characteristics, and to manufacture the same. Another object of the present invention is to provide a semiconductor device using the formed crystalline semiconductor thin film.

  The present invention includes a step of forming a semiconductor thin film including a substrate, a base film and a semiconductor layer, a step of forming a reflection control film pattern having a reflectance different from that of the semiconductor thin film surface on the semiconductor thin film, and a reflection control film pattern Irradiating at least one light on the surface of the semiconductor thin film, the manufacturing method of the crystalline semiconductor thin film, the distance D between the edge of the region irradiated with the light and the reflection control film pattern, and the reflection control There is provided a method for producing a crystalline semiconductor thin film, wherein the length W of the film pattern has a relationship of D> W.

  Preferably, the reflection adjusting film has a rectangular shape or a linear shape.

  Preferably, the crystal grows from the periphery of the edge of the reflection control film pattern toward the center of the reflection control film by the light irradiation step.

  Preferably, the central portion is an end point of the crystal grown from both ends of the reflection control film pattern.

  The present invention also provides a semiconductor device using, as an active region, a crystallized region immediately below a reflection control film pattern among the crystalline semiconductor thin films manufactured by the above-described method for manufacturing a crystalline semiconductor thin film.

  According to the present invention, on the amorphous semiconductor thin film, a reflection control film pattern that selectively transmits laser light and reduces the reflectance when the surface is irradiated with laser light is selectively formed. In the step of irradiating the amorphous semiconductor thin film with laser light through the reflection control film pattern and crystallizing from the periphery of the end of the reflection control film pattern toward the center of the reflection control film, the laser light By manufacturing the semiconductor thin film with the relationship between the distance D between the edge of the region irradiated with the reflection adjusting film pattern and the length W of the reflection adjusting film pattern being D> W, the central portion of the reflection adjusting film is Symmetrically, crystals having the same grain size in the width direction of the reflection control film can be formed, and by using the crystallized region immediately below the reflection control film pattern as an active region of the thin film semiconductor device, uniform characteristics can be obtained. Thin film It is possible to manufacture the conductor arrangement.

  The method for producing a crystalline semiconductor thin film according to the present invention includes a step of forming a semiconductor thin film having a substrate, a base film and a semiconductor layer, and a step of forming a reflection control film pattern having a reflectance different from that of the surface of the semiconductor thin film on the semiconductor thin film. And a step of irradiating at least one light on the surface of the semiconductor thin film including the reflection control film pattern, and a method for producing a crystalline semiconductor thin film, wherein the irradiated region end and the reflection control film pattern And the length W of the reflection control film pattern have a relationship of D> W. Here, crystallinity means that an amorphous semiconductor material is crystallized. Here, in the rectangular or linear reflection control film pattern, the width in the short side direction of the reflection control film is defined as W, and laser light is irradiated to at least one reflection control film. The distance between the irradiation region end and the long side of the reflection control film is defined as D.

  According to the method for manufacturing a crystalline semiconductor thin film of the present invention, since the relationship of D> W is satisfied, crystals grown from both ends collide with each other at the center of the reflection control film pattern. Symmetrically grown crystals can be obtained. When a semiconductor device is manufactured using the crystallized semiconductor thin film, uniform characteristics can be imparted to the semiconductor device. Hereinafter, the present invention will be described in detail with reference to FIGS.

  First, with reference to FIG. 1, the manufacturing process of the crystalline semiconductor thin film of this invention is demonstrated. FIG. 1 is a schematic sectional view of a semiconductor thin film of the present invention.

  As shown in FIG. 1A, a base film 12 is formed on a substrate 11 made of a glass material to be a thin film transistor (TFT) substrate. In the present invention, the base film 12 can use an inorganic insulating film, particularly a silicon dioxide film, as an impurity diffusion prevention layer, and this formation can be performed using various known methods such as vapor deposition, sputter film formation, and CVD. Is possible. The base film 12 made of a silicon dioxide material is provided to prevent the diffusion of impurities from the substrate 11, and other materials can be used instead of silicon dioxide.

  Next, a semiconductor layer 13 is provided on the base film 12 made of the silicon dioxide material. The material used for the semiconductor layer 13 is usually amorphous silicon and is formed by CVD, but as a film formation method, sputtering, vapor deposition, or the like can be used. The thickness of the semiconductor layer 13 made of an amorphous silicon material varies depending on the required transistor characteristics, process conditions, etc., but is generally in the range of several tens of nanometers to several hundreds of nanometers, particularly typically in the range of 30 nm to 100 nm. In this embodiment, the film thickness is set to 50 nm.

  In the present invention, as described above, the base film 12 is formed on the substrate 11, and the semiconductor layer 13 is formed on the base film 12 to form a semiconductor thin film.

  Subsequently, as shown in FIG. 1B, a reflection control film 14 made of a silicon dioxide material having a thickness of, for example, 50 nm is formed on the semiconductor layer 13 made of the amorphous silicon material. In this case, the thickness of the reflection control film 14 made of a silicon dioxide material is such that the wavelength of the laser beam in the laser irradiation process on the semiconductor thin film surface using a laser annealing method later is λ, and the refractive index of the reflection control film 14 is n. In this case, the antireflection film for the laser beam is set to a value satisfying d≈λ / 4n. At this time, the reflectance periodically changes in accordance with the film thickness of the reflection adjusting film 14, and when the thickness of the reflection adjusting film 14 is made of a silicon dioxide material having a thickness of 50 nm, reflection prevention is performed at a wavelength of 308 nm. It acts as a film and its reflectance is 30.5%. Compared with the reflectance of the semiconductor layer, the reflectance of the amorphous silicon layer at the wavelength of 308 nm is 57.2%. Therefore, the reflectance is large due to the action of the reflection control film 14 as an antireflection film. Will be reduced.

  Further, by patterning the reflection adjustment film 14 made of the silicon dioxide material, a reflection adjustment film pattern 15 having a reflection adjustment film pattern width W as shown in FIG. 1C is formed, and then the substrate is formed. 11 is subjected to a laser annealing process using ultraviolet laser light in a wavelength region that is easily absorbed by the semiconductor layer 13 made of an amorphous silicon material, for example, Xe-Cl excimer laser light 16.

  Here, an apparatus used for the laser annealing process will be described with reference to FIG. This apparatus includes a stage 27 that is driven by mounting at least a laser oscillator 21, an imaging lens 25, and a glass substrate 26. If necessary, an optical element group 22 such as a homogenizer or an expander, and a field lens 24 are provided. Is provided. On the stage 27, a substrate on which a multilayer thin film shown in FIG.

  The laser oscillator 21 is not particularly limited as long as it emits a pulsed energy beam and can melt silicon. For example, ultraviolet light such as various solid-state lasers typified by excimer laser and YAG laser can be used. A light source having a wavelength in the range is desirable. In the case of using an excimer laser, the pulse width is 10 ns to several tens ns, and the film is melted almost instantaneously, but then cooled rapidly, and crystallization occurs in the process.

  The beam emitted from the laser oscillator 21 is converted to an appropriate beam size by an expander (not shown), the irradiance is uniformized in the beam cross section by a homogenizer, reflected by a mirror 23, and field lens. Then, the light enters the imaging lens 25. Here, the beam expander is an optical system having a telephoto system or a reduction system, and determines the size of an incident area to the imaging lens 25. The homogenizer is composed of a lens array or a cylindrical lens array, and divides the beam and recombines it to make the irradiance uniform within the irradiation area on the mask. The field lens 24 has a function of causing the principal ray emitted from the oscillator to enter the imaging lens 25 perpendicularly.

  The light passing through the homogenizer and the field lens 24 is imaged on the surface of the substrate 26 by the imaging lens 25. By imaging the principal ray emitted from the oscillator on the substrate by the imaging lens 25, the film is melted by the laser power, and when the pulse irradiation is completed, it is rapidly cooled and crystallized.

  That is, in the present invention, as shown in FIG. 1C, Xe-Cl excimer laser light 16 having a wavelength of 308 nm is irradiated from the side of the reflection control film pattern 15 made of silicon dioxide material, thereby being made of an amorphous silicon material. The semiconductor layer 13 is crystallized. In the present invention, the distance D between the one end portion of the semiconductor layer irradiated with the Xe-Cl excimer laser beam 16 and the reflection control film pattern 15 made of silicon dioxide material, and the shortness of the reflection control film pattern 15. The side width W is characterized by having a relationship of D> W.

  The temperature distribution along the crystal growth direction in the semiconductor layer when crystallization is performed in the relationship of D> W will be further described with reference to FIG. FIG. 3 is a diagram showing the temperature distribution in the semiconductor layer during crystallization. In the graph, the vertical axis shows the temperature, and the horizontal axis shows the distance from the center of the reflection control film pattern. In FIG. 3, the lateral position 0 μm represents the center of the reflection control film pattern 44, and the lateral position 6 μm is one end of the Xe—Cl excimer laser light irradiation region. 3 represents a schematic cross section of the semiconductor thin film. A base film 42 is formed on the substrate 41, a semiconductor layer 43 is formed on the base film 42, and the semiconductor layer 43 is formed on the semiconductor layer 43. A reflection control film pattern 44 is formed. In FIG. 3, there are a plurality of curves, because this is plotted while changing the time.

  In this embodiment, the width W of the short side of the reflection adjusting film pattern 44 is 4 μm, and the distance D between one end of the Xe-Cl excimer laser beam and the reflection adjusting film pattern 44 is 4 μm, and crystallization is performed. And

  Due to the laser irradiation, the semiconductor layer 43 in FIG. 3 is melted in almost the entire irradiation region, and then the semiconductor layer 43 made of an amorphous silicon material irradiated with the laser is exposed at the end of the Xe—Cl excimer laser light irradiation region. A temperature gradient is formed between the exposed portion and the semiconductor layer 43 that has not been irradiated with the laser, and starts from the periphery of the Xe-Cl excimer laser beam irradiation region toward the center of the reflection control film pattern 44 made of a silicon dioxide material. A lateral crystal 45 grows. More specifically, the starting point of the growth of the lateral crystal 45 in this embodiment is a position about 5.7 μm from the center of the reflection control film pattern 44 made of a silicon dioxide material, that is, the end of the Xe—Cl excimer laser light irradiation region. The position is about 0.3 μm inside from the part. The lateral crystal 45 grows toward the center of the reflection adjusting film pattern 44, and is about 3 μm to 3.5 μm from the center of the reflection adjusting film pattern 44, that is, about 1 μm to the end of the reflection adjusting film pattern 44. In the region of 1.5 μm, as shown in FIG. 3, the heat escaping downward is more dominant than the heat escaping in the lateral direction. Therefore, the semiconductor layer 43 is cooled from the substrate direction, and a large number of fine crystals are formed. Since the crystal layer 46 is formed, the growth of the lateral crystal 45 stops at about 3.5 μm from the center of the reflection control film pattern 44.

  On the other hand, the reflection adjusting film pattern 44 having a thickness of 50 nm satisfies the relationship of 50 nm≈308 nm / 4n (n is a reflectance) with respect to the wavelength 308 nm of the Xe—Cl excimer laser beam. The reflection control film pattern 44 made of a material acts as an antireflection film, and the incident energy increases at the lower part of the reflection control film pattern 44 and the temperature rises. A temperature gradient is formed in the semiconductor layer 43. Accordingly, apart from the lateral crystal 45 grown from the end of the laser light irradiation region, the lateral crystal 47 grows again from the periphery of the end of the reflection control film pattern 44 toward the center of the reflection control film pattern 44. . More specifically, the growth start point of the lateral crystal 47 in this embodiment is a position about 3 μm from the center of the reflection control film pattern 44, that is, a position of about 1 μm from the end of the reflection control film pattern 44. The direction crystal 47 reaches the center of the reflection control film pattern 44.

  The state of crystal growth in the semiconductor layer at this time is shown in FIG. As shown in FIG. 4, from the vicinity of the other end of the reflection control film pattern 44, crystal growth proceeds at the same crystal grain size and crystal growth rate as the lateral crystal 47, and the lateral crystal 47 The crystal growth ends at the center of the reflection control film pattern 44, that is, the end point is reached, so that crystal grains of the same size can be obtained with the center of the reflection control film pattern 44 as the axis of symmetry. By using as the active region of the thin film semiconductor device, a thin film semiconductor device having uniform characteristics can be produced.

  The reason why a symmetric crystal can be obtained centering on the reflection adjusting film pattern 44 as described above is that the distance D between one end of the laser beam and the reflection adjusting film pattern and the short side of the silicon dioxide film pattern are The width W can be realized by satisfying the relationship of D> W. For example, when the relationship is not satisfied, for example, when the silicon dioxide film pattern width W is 4 μm and D is 3 μm, As described in the explanation of the technique, the crystal structure is asymmetric with respect to the central portion of the reflection control film pattern, which leads to deterioration in characteristics and uniformity of the thin film semiconductor device.

  Here, the reason why the relationship D> W is satisfied will be further described with reference to FIG. Under various experimental conditions conducted by the present inventors, for example, with respect to the width W of the reflection adjusting film pattern 44, the laser irradiation energy, the thickness of the semiconductor layer, the film thickness of the reflection adjusting film made of a silicon dioxide film material, etc. In this change, the starting point of the growth of the lateral crystal 47 from the periphery of the end of the reflection adjusting film pattern 44 does not become W / 4 or more outside the end of the reflection adjusting film pattern 44, and laser irradiation is performed. It has been clarified that the growth distance of the lateral crystal 45 from the end of the region does not become larger than the growth distance of the lateral crystal 47 from the periphery of the end of the reflection control film pattern 44, that is, W / 2 + W / 4. , D> W / 4 + W / 2 + W / 4 = W, so that a crystal structure in which the center portion of the silicon dioxide film pattern is symmetrical can be obtained.

  In the embodiment for explaining the present invention, an example in which crystallization is performed with one excimer laser beam is described in detail. However, the laser beam is not limited to one. In addition to the crystallization laser, the second laser is additionally used to increase the temperature of the entire substrate or the semiconductor thin film and increase the melting time of the semiconductor thin film for the purpose of further increasing the crystal grain size. In the same manner, when the relationship between the reflection adjusting film pattern width W and the distance D between the laser beam end and the reflection adjusting film pattern end is D> W, the particle size is uniform. A crystal can be obtained, and the present invention is also effective when the second laser is used.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a schematic sectional drawing which shows the manufacturing process of the crystalline semiconductor thin film of this invention. It is the schematic of the apparatus used for a laser annealing process. It is a figure which shows the temperature distribution in the semiconductor layer in the case of crystallization. It is the schematic which shows the state of the crystal growth in a semiconductor layer. It is a figure which shows the horizontal direction temperature distribution of the amorphous silicon film in a prior art. FIG. 6 is a schematic view showing a crystal grown in the lateral direction under the cap pattern in FIG. 5. It is a figure which shows the horizontal direction temperature distribution of the amorphous silicon film in a prior art. FIG. 8 is a schematic view of lateral crystal growth under a cap pattern in FIG. 7. It is the schematic which shows the crystal | crystallization grown under the cap pattern. It is a schematic sectional drawing which shows the manufacturing method of the conventional semiconductor thin film.

Explanation of symbols

  10, 40, 60 Semiconductor thin film, 11 Substrate, 12, 62 Base film, 13 Semiconductor layer, 14 Reflection control film, 15 Reflection control film pattern, 16 Excimer laser light, 21 Laser oscillator, 22 Optical element group, 23 Mirror, 24 Field lens, 25 Imaging lens, 26 substrate, 27 stage, 41 substrate, 42 base film, 43 semiconductor layer, 44 reflection control film pattern, 45 lateral crystal, 46 polycrystalline layer, 47 lateral crystal, 61 glass substrate, 62 Base film, 63, 73 Amorphous silicon film, 64, 74 Cap pattern, 65 Polycrystalline layer, 66 Lateral crystal region, 67 Transistor, 75 Laser, 76 Crystallized region.

Claims (5)

Forming a semiconductor thin film comprising a substrate, a base film and a semiconductor layer;
Forming a reflection adjusting film pattern having a reflectance different from that of the semiconductor thin film surface on the semiconductor thin film;
Irradiating at least one light on the surface of the semiconductor thin film including the reflection control film pattern, and a method for producing a crystalline semiconductor thin film,
The distance D between the edge of the region irradiated with the light and the reflection control film pattern and the length W of the reflection control film pattern have a relationship of D> W, Production method.   The method of manufacturing a crystalline semiconductor thin film according to claim 1, wherein the reflection control film is rectangular or linear.   3. The crystalline semiconductor thin film according to claim 1, wherein a crystal grows from the periphery of the end of the reflection control film pattern toward the center of the reflection control film by the light irradiation step. Production method.   The method for producing a crystalline semiconductor thin film according to claim 1, wherein the central portion is an end point of a crystal grown from both ends of the reflection control film pattern.   5. A semiconductor device using, as an active region, a crystallized region immediately below the reflection control film pattern among the crystalline semiconductor thin films produced by the method for producing a crystalline semiconductor thin film according to claim 1.

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