JP2007287866A - Method for manufacturing semiconductor crystal thin film and manufacturing apparatus thereof, photomask, and semiconductor element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of semiconductor crystal thin film that can use large crystal grain size and can improve characteristic thereof, and also provide a manufacturing apparatus and photomask used in the same manufacturing method. <P>SOLUTION: The manufacturing method of semiconductor crystal thin film using an apparatus and a photomask comprises the steps of: forming a semiconductor crystal thin film through crystallization of the semiconductor thin film using a first laser for emitting the laser beam onto a semiconductor thin film to form a slit beam group and a second laser for emitting the laser beam to an radiation region including the slit beam group; and reducing height of a ridge generated on the semiconductor crystal thin film through radiation of the rectangular shape laser beam including the radiation region of the second laser using the first laser. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a semiconductor crystal thin film using a laser as an energy beam, a manufacturing apparatus used therefor, a photomask, and a semiconductor element.

  In recent years, flat display devices using liquid crystal or organic electroluminescence (organic EL) are often used as display displays for personal computers and mobile phones. In a display device using liquid crystal or organic EL, a thin film transistor using amorphous or polycrystalline silicon as an active layer is used to switch display of a pixel. These thin film transistors are formed on a glass substrate, and a thin and lightweight display device can be obtained.

  Among these, polycrystalline silicon thin film transistors have many advantages over amorphous silicon thin film transistors because they have higher mobility of carriers such as electrons and holes than transistors using amorphous silicon. is doing.

  For example, since the mobility of carriers such as electrons and holes is high, it is possible to manufacture a high-performance transistor, thereby not only forming a switching element in the pixel portion but also on the glass substrate in the pixel peripheral portion. Accordingly, a driver circuit that requires a higher performance transistor and a peripheral circuit having functions such as image processing can be formed. For this reason, it is not necessary to mount a driver IC or a drive circuit board on a glass substrate, and a display device can be provided at a low price.

  Further, as another advantage, since the mobility of carriers such as electrons and holes is high, the size of the transistor can be miniaturized. Therefore, the switching element formed in the pixel portion can be made small, so that a high aperture ratio can be achieved. This makes it possible to provide a display device with high brightness even with high definition.

  A polycrystalline silicon thin film having the above-described advantages can be usually manufactured by forming an amorphous silicon thin film on a glass substrate by CVD or the like and then performing a process of polycrystallizing amorphous silicon. it can.

  As a process for crystallizing amorphous silicon, there is an annealing method in which the entire substrate is kept at a high temperature of 600 to 1000 ° C. or more to convert amorphous to crystalline. However, in the annealing method, an inexpensive glass substrate cannot be used, and it is necessary to use an expensive quartz substrate that can withstand the above-described high temperature, which has been an impediment to reducing the cost of the display device.

  In recent years, therefore, a technique for crystallizing amorphous silicon at a low temperature of 600 ° C. or lower using a laser has been generalized in the production of a polycrystalline silicon thin film, and a polycrystalline silicon transistor is formed on a low-cost glass substrate. Display devices can be provided at a low price. This laser crystallization technique is generally a method of continuously irradiating a glass substrate with a linear laser beam having a length of about 200 to 400 mm and a width of about 0.2 to 1.0 mm. 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 is melted by the energy of the laser beam and then solidified to become a crystal, and the electron mobility can be improved by several orders of magnitude compared to amorphous silicon. .

  In the method using this laser, the first amorphous silicon film is not melted over the entire thickness direction, but is melted industrially by leaving a part of the amorphous region at the bottom of the film. Useful crystals can be obtained. However, in this method, crystal nuclei are generated everywhere in the entire laser irradiation region, and the crystal grows toward the outermost layer of the silicon thin film, thereby forming crystal grains with random orientation. When a large number of crystal grains are formed on the substrate in this way, there are innumerable grain boundaries in the film. Therefore, when a transistor is formed and electrically driven, carriers such as electrons and holes are generated. It will be scattered by the grain boundaries, and only about a fraction of the electron mobility can be obtained compared to a single crystal substrate. In view of such a background, in order to obtain a high-performance display device capable of realizing performance close to that of a single crystal by increasing the crystal grain size of polycrystalline silicon and controlling the crystal orientation, Research and development has been done.

  As one of the characteristic improvement techniques, for example, Japanese Patent No. 3204986 (Patent Document 1) discloses a technique called super lateral growth. In the method described in Patent Document 1, crystallization is performed by irradiating a thin silicon film with a pulse laser having a fine width, and melting and solidifying the thin silicon film over the entire thickness direction of the laser irradiation region. For example, by laser irradiation with a fine width of 2 to 3 μm, the laser irradiation region is melted, and a crystal grows laterally from the boundary of the unmelted region (that is, a direction substantially perpendicular to the thickness direction of the substrate). Crystals grown from both sides collide with each other, and the growth is completed. The laser irradiation region is usually in a fine stripe shape (strip shape), the crystal grows along the short direction of the stripe shape, and the crystal grown from both sides of the melted region central portion has the stripe shape. Will collide on the center line in the longitudinal direction.

  This method can also be performed by a plurality of pulsed laser irradiations. When laser pulses are sequentially irradiated so as to overlap a part of the needle-like crystal formed by the previous laser irradiation, It has the feature that a crystal having a longer orientation is obtained by taking over the already grown crystal as a seed for the next crystal growth, thereby growing a longer needle-like crystal.

  In addition, attempts to improve characteristics using a plurality of beams are described in Japanese Patent Application Laid-Open No. 8-186268 (Patent Document 2), Japanese Patent Application Laid-Open No. 2001-176797 (Patent Document 3), and the like. However, the techniques described in Patent Documents 2 and 3 do not incorporate the concept of lateral growth.

Further, an attempt to improve the flatness of the surface is described in Japanese Patent Laid-Open No. 2003-142402 (Patent Document 4).
Japanese Patent No. 3204986 JP-A-8-186268 JP 2001-176797 A JP 2003-142402 A

  However, in any of the conventional methods, it is not easy to increase the size of crystal grains and improve the characteristics of the obtained semiconductor crystal thin film. This is because the conventional method described above cannot sufficiently increase the size of the crystal grains, and the surface of the semiconductor crystal thin film becomes uneven in the process of melting-solidification, so that the semiconductor crystal This is because variation in characteristics of the semiconductor element formed in the thin film (particularly the threshold value of the thin film transistor) is increased.

  The present invention has been made to solve the above-described problems, and the object of the present invention is to provide a semiconductor crystal capable of increasing the crystal grain (can increase the crystal length) and improving the characteristics thereof. A thin film manufacturing method, and a manufacturing apparatus and a photomask used therefor are provided. Another object of the present invention is to provide a semiconductor device using a semiconductor crystal thin film having large crystal grains and improved characteristics.

  The present invention is a method for producing a semiconductor crystal thin film by irradiating a semiconductor thin film formed on a substrate with a laser, wherein a first laser beam is irradiated so as to form a slit beam group on the semiconductor thin film. Crystallizing a semiconductor thin film by using a laser and a second laser that irradiates a laser beam to an irradiation region including the slit beam group, and using the first laser And a step of reducing the height of the ridge generated in the semiconductor crystal thin film by irradiating a rectangular laser beam including the irradiation region of the second laser.

Here, it is preferable to use a carbon dioxide laser as the second laser.
The method for manufacturing a semiconductor crystal thin film according to the present invention includes: a plurality of aperture groups arranged so that the slit laser beam can be formed by a first laser; and a rectangular laser beam emitted from the first laser. A semiconductor laser is irradiated with a first laser through a photomask having a rectangular opening. In the step of crystallizing the semiconductor thin film to form a semiconductor crystal thin film, the first laser The semiconductor thin film is irradiated with the slit beam group through the opening group of the photomask, and the irradiation region including the slit beam group of the semiconductor thin film is irradiated with the second laser to reduce the height of the ridge. In the process, the rectangular laser is applied to the region of the semiconductor thin film that is not included in the irradiation region of the second laser through the rectangular opening of the photomask. Irradiating the Zabimu, by repeating the movement of the laser irradiation and photomask, the be sequentially performing process and steps to reduce the height of the ridge to form a semiconductor crystal thin film, preferred.

  The photomask used in the method for producing a semiconductor crystal thin film of the present invention preferably has a region that does not transmit laser between the opening group and the rectangular opening.

  In the method for producing a semiconductor crystal thin film of the present invention, it is preferable that the irradiation intensity of the first laser is lower than the irradiation intensity at which the entire thickness direction of the semiconductor thin film is melted and recrystallized.

  The present invention is also an apparatus used for manufacturing a semiconductor crystal thin film by irradiating a semiconductor thin film formed on a substrate with a laser, and irradiating a slit beam group and a rectangular laser beam on the semiconductor thin film. Forming a slit beam group by a first laser for irradiation, a second laser for irradiating a laser beam to an irradiation region including a slit beam group by the first laser on a semiconductor thin film, and the first laser There is also provided a semiconductor crystal thin film manufacturing apparatus comprising a plurality of aperture groups arranged in such a manner and a photomask having a rectangular aperture for irradiating a rectangular laser beam with a first laser.

Here, the second laser is preferably a carbon dioxide laser.
In the semiconductor crystal thin film manufacturing apparatus of the present invention, it is preferable that the photomask has a region that does not transmit laser between the opening group and the rectangular opening.

  The irradiation intensity of the first laser in the semiconductor crystal thin film manufacturing apparatus of the present invention is preferably set lower than the irradiation intensity at which the entire thickness direction of the semiconductor thin film is melted and recrystallized.

  The present invention is also a photomask used for manufacturing a semiconductor crystal thin film from a semiconductor thin film formed on a substrate, and a plurality of slit beams arranged so that the slit beam group can be formed by a first laser. A photomask having an aperture group, a rectangular aperture for irradiating a rectangular laser beam with a first laser, and a region formed between the aperture group and the rectangular aperture that does not transmit a laser Also provide.

  In the photomask of the present invention, it is preferable that the transmittance of the rectangular opening is lower than the transmittance of the opening group.

  The present invention further includes a semiconductor element formed in a semiconductor crystal thin film on a substrate, the semiconductor element having a ridge linearly extending substantially perpendicular to a direction in which the semiconductor crystal thin film is grown, and the height of the ridge being a semiconductor There is also provided a semiconductor element having a thickness of twice or less the thickness of the crystalline thin film.

  According to the present invention, even if the semiconductor thin film is crystallized under the condition that a very large crystal grain is formed using the second laser, a semiconductor crystal thin film with less unevenness can be obtained. A semiconductor element having large grains (long crystal length) and excellent characteristics (particularly, a transistor with small variation in threshold value) can be manufactured.

  FIG. 1 is a schematic view for explaining a preferred example of the method for producing a semiconductor crystal thin film of the present invention. The method for producing a semiconductor crystal thin film according to the present invention is a method for producing a semiconductor crystal thin film by irradiating a semiconductor thin film formed on a substrate with a laser, and (1) forming a slit beam group on the semiconductor thin film. The semiconductor thin film is formed by crystallizing the semiconductor thin film using the first laser for irradiating the laser beam and the second laser for irradiating the irradiation region including the slit beam group with the laser beam. (Hereinafter referred to as “crystallization step”), and (2) the first laser was used to irradiate a rectangular laser beam including the irradiation region of the second laser, thereby generating the semiconductor crystal thin film. And a step of reducing the height of the ridge (hereinafter referred to as “ridge reduction step”).

  According to the method of manufacturing a semiconductor crystal thin film of the present invention having the crystallization process and the ridge reduction process as described above, the slit laser beam is irradiated by the first laser and the second laser is used in the crystallization process. Even if the semiconductor thin film is crystallized under such a condition that a very large crystal grain is formed, the height of the ridge formed in the ridge reduction process can be reduced. Thus, a semiconductor crystal thin film having large crystal grains (long crystal length) and few irregularities can be manufactured. By using the semiconductor crystal thin film thus obtained, it is possible to manufacture a semiconductor element having large crystal grains and excellent characteristics (particularly, a transistor having a small variation in threshold value).

  The first laser used in the present invention is not particularly limited as long as a pulsed energy beam can be emitted and silicon can be melted. For example, an excimer laser and a YAG laser are representative. A light source having a wavelength in the ultraviolet region such as various solid-state lasers or harmonics thereof can be preferably used.

  The second laser used in the present invention may be any laser capable of effectively assisting the process of melting and solidifying the semiconductor thin film by the first laser 1. For example, a carbon dioxide laser, a YAG laser, or the like is used. In particular, a carbon dioxide laser can be preferably used because it has a wavelength with a high absorptivity with respect to a glass substrate and can increase the substrate temperature instantaneously.

  In the method for producing a semiconductor crystal thin film of the present invention, it is preferable that the first laser is applied to the semiconductor thin film formed on the substrate through a photomask having a specific shape as shown in FIG. That is, as a photomask, a plurality of aperture groups arranged so that the slit beam group can be formed by a first laser, and a rectangular aperture for irradiating a rectangular laser beam by the first laser, In the crystallization process, the semiconductor laser thin film is irradiated with the slit beam group through the opening group of the photomask and the second laser includes the slit beam group of the semiconductor thin film. The irradiation region is irradiated with a laser beam, and in the ridge reduction process, a rectangular laser is applied to a region not included in the irradiation region of the semiconductor thin film by the first laser through the rectangular opening of the photomask. It is preferably realized to irradiate the beam. Furthermore, in the method for producing a semiconductor crystal thin film of the present invention, it is preferable to sequentially perform the crystallization process and the ridge reduction process as described above by repeatedly performing laser irradiation and photomask movement. In other words, the crystallization process and the ridge reduction process are simultaneously performed in separate areas on the semiconductor thin film (the irradiation area including the slit beam group and the area irradiated with the rectangular laser beam), respectively. It is preferable that the crystallization process and the ridge reduction process are sequentially performed over the entire surface of the semiconductor thin film by the movement.

  Hereinafter, first, the crystallization process will be specifically described. In FIG. 1, for example, a photomask 11 in which two opening groups 12 a and 12 b (hereinafter collectively referred to as “opening group 13”) is formed is used, and the first mask is interposed through the photomask 11. In this example, a laser beam is irradiated onto a semiconductor thin film by a laser so that a slit beam group is formed on the semiconductor thin film by the first laser in the crystallization step. By irradiating the semiconductor thin film with a plurality of slit beam images (collectively referred to as “slit beam group”) through the opening group 13 formed in the photomask 11, the semiconductor thin film is melted and solidified to be crystallized. Cause super lateral growth. This method itself is a method of causing lateral crystal growth in the in-plane direction of the substrate described in Patent Document 1 described above. As will be described later, the present invention is a very effective method for improving the crystal characteristics during the lateral growth.

  In the example shown in FIG. 1, for example, a photomask 11 is used in which an opening group 13 is formed such that a plurality of openings having a length L, a pitch P, and a width D are arranged in the width direction of each opening. ing. As a result, a slit beam image corresponding to the opening group 13 of the photomask 11 is formed on the semiconductor thin film, and is melted and solidified with the width D ′ of the slit beam image corresponding to the width D of each opening of the opening group 13. And crystal growth occurs, and a crystal 4 is formed from the edge of the slit beam image inward (in the example shown in FIG. 1, toward the directions S1 and S2 of white arrows). Here, the width D of each aperture of the aperture group 13 and the width D ′ of the slit beam image are appropriately determined according to the magnification determined by the design of the optical system described later, and are not particularly limited. Further, the length L and the pitch P of each aperture of the aperture group 13 are also imaged on the semiconductor thin film at a magnification substantially equal to the above magnification.

At this time, the length of the generated crystal 4 varies depending on conditions. For example, an amorphous silicon thin film having a thickness of 50 nm formed on a glass substrate is irradiated with an excimer laser having a wavelength of 308 nm with an energy of about 500 mJ / cm ^2. When given at 50 ns, it is approximately between 1 and 2 microns. As can be seen from the above, in the method disclosed in Patent Document 1, since the crystal length grown by one irradiation is very small, it is not practical for manufacturing a device as it is.

  Therefore, in the crystallization step in the method for producing a semiconductor crystal thin film of the present invention, the slit beam group is irradiated onto the semiconductor thin film by the first laser as described above, and the second laser is used to irradiate the semiconductor thin film on the semiconductor thin film. A laser beam is irradiated to an irradiation region including the slit beam group. As a result, a crystal 4 having a remarkably long crystal length can be obtained as compared with irradiation using the first laser alone.

  For example, a slit beam group is formed on a semiconductor thin film (amorphous silicon thin film or silicon thin film) formed on a glass substrate using an excimer laser having a wavelength of 308 nm as the first laser under the above-described conditions. When irradiation is performed, and the irradiation region including the slit beam group is irradiated with light having a wavelength of 10.6 microns using a carbon dioxide gas laser as the second laser, the crystal length of 5 to 10 microns or more is usually several times to 10 times. About a crystal length can be obtained. This is because the semiconductor thin film has no absorption with respect to the wavelength of 10.6 microns oscillated by the carbon dioxide laser and has a large absorption with respect to the substrate. This is considered to be because it is possible to heat the vicinity of the interface between the substrate and the semiconductor thin film.

  As described above, when an excimer laser is used as the first laser and irradiation is performed with the first laser alone without using the second laser, a sufficient crystal length cannot be obtained. This is because the excimer laser used as the first laser usually has a pulse width of 10 to 1000 ns, and after melting in an extremely short time, cooling is performed in a short time, resulting in a crystal length of 1 This is because only a value limited to micron can be obtained. On the other hand, in addition to the irradiation with the first laser as in the present invention, the temperature of the substrate is maintained even after the semiconductor thin film is melted by irradiating the irradiation region with the second laser. The result is that crystal growth continues and large crystals grow. In the example shown in FIG. 1, the semiconductor thin film is irradiated with a light source image of a narrow slit beam having a width of about 10 microns, and crystals are grown in the lateral direction from the peripheral portion of the image.

  The irradiation conditions of the first laser and the second laser in the crystallization process can be set as follows, for example.

First, as for the irradiation intensity, the irradiation intensity of the first laser is preferably such that the semiconductor thin film formed on the substrate can be heated so as not to melt in the entire thickness direction by the energy of the first laser alone. The irradiation intensity of the second laser is preferably such that the semiconductor thin film formed on the substrate can be heated so that it is not melted by the energy of the second laser alone. Specifically, the irradiation intensity of the first laser is preferably in the range of 150 to 450 mJ / cm ² , more preferably in the range of 200 to 350 mJ / cm ² , and the irradiation intensity of the second laser is in the range of 10~500W / mm ^2, more preferably in the range of 100 to 200 W / mm ^2. By setting the irradiation intensity of the first laser and the second laser in this way, the semiconductor thin film to which both energies are applied is melted in the entire thickness direction.

  Next, with respect to the irradiation timing, the irradiation start time and irradiation end time of the first laser, and the irradiation start time and irradiation end time of the second laser can be set as appropriate.

  As a preferable first example of the irradiation timing, there is a case where the irradiation of the first laser is started at the same time as the irradiation of the second laser is completed after the irradiation of the second laser is started. When irradiation is performed at the timing according to the first example, since the first laser is irradiated at the same time as the substrate reaches the maximum temperature by the second laser irradiation, the heat input to the substrate is minimized. There is an advantage that the crystallization of the semiconductor thin film can be performed to the maximum in such a manner as to be suppressed.

  As a second preferable example of the irradiation timing, there is a case where irradiation of the first laser is started after at least irradiation of the second laser is started. In this case, the second laser may continue irradiation after the first laser irradiation ends, or may end before the first laser irradiation starts. When the irradiation is performed at the timing according to the second example as described above, the heat input to the substrate by the second laser is increased as compared with the first example described above, but the first laser irradiation is performed. Since the substrate temperature can be continuously raised even in the process of melting and recrystallization of the semiconductor thin film, there is an advantage that larger crystal grains can be obtained.

  As a third preferable example of the irradiation timing, there is a case where the irradiation of the second laser is started after the irradiation of the first laser is started. In this case, the second laser may continue irradiation after the first laser irradiation ends, or may end before the first laser irradiation ends, In order to sufficiently exhibit the above-described effect by using the second laser together, it is preferable to continue the irradiation of the second laser even when the irradiation of the first laser is almost completed. When irradiating at the timing according to the third example, paying attention mainly to the solidification process after melting of the semiconductor thin film by the first laser irradiation, the second laser is turned on after the first laser irradiation is completed. Irradiation is advantageous in that the solidification time can be extended and the crystal grains can be enlarged.

  Note that in any of the above cases, if the semiconductor laser is irradiated on the semiconductor thin film for a long time, the temperature of the substrate on which the semiconductor thin film is formed may be excessively increased and the substrate may be damaged. The degree of heating with a laser should be kept to a minimum.

  In order to crystallize the entire surface of the semiconductor thin film by the crystallization process, for example, as shown in FIG. 1, the opening group 13 is formed so that two opening groups 12a and 12b are adjacent to each other in the length direction. Thus, it is preferable to use a photomask 11 in which a plurality of openings having the same length L, width D, and pitch P are arranged. The photomask 11 in the example shown in FIG. 1 is formed by arranging the openings of the two opening groups 12a and 12b in the length direction so as to be partially offset and shifted from each other in the width direction.

  Using such a photomask 11, a slit beam group is irradiated onto the semiconductor thin film by the first beam through the aperture group 12a (first irradiation), and then the slit beam is projected in the length direction X of the slit beam. And the slit beam group through the aperture group 12b is irradiated onto the semiconductor thin film. By repeating this sequentially according to the size of the semiconductor thin film, the semiconductor thin film can be crystallized over the entire surface. At that time, by setting the irradiation region of the second laser so as to include the slit beam groups corresponding to the two aperture groups 12a and 12b described above, the crystal length can be dramatically increased as described above. Can do.

  Here, FIG. 2 is a cross-sectional view showing stepwise the change from the semiconductor thin film to the semiconductor crystal thin film by the crystallization step in the method of manufacturing a semiconductor crystal thin film of the present invention. In FIG. 2, the direction perpendicular to the paper surface of FIG. 2 corresponds to the length direction of each opening of the opening group 13 in the example shown in FIG.

  First, FIG. 2A shows a structure in which the semiconductor thin film 1 is formed on the substrate 2 in a state before the semiconductor crystal thin film manufacturing method of the present invention is performed. As the semiconductor thin film 1, for example, a silicon thin film or an amorphous silicon thin film is used. As the substrate 2, a glass substrate, a quartz substrate, or the like is used, and is not particularly limited, but a glass substrate is preferably used from the viewpoint of heat resistance. Further, normally, as shown in the example shown in FIG. 2A, it is formed of silicon dioxide or the like between the substrate 2 and the semiconductor thin film 1 for the purpose of preventing the diffusion of impurities from the substrate 2 to the semiconductor thin film 1. The underlying layer 3 is interposed.

  Next, as described above, the irradiation of the slit beam group by the first laser and the irradiation of the second laser to the irradiation region through the opening group 12a of the photomask 11 (first irradiation), FIG. As shown in (b), the crystal 4 is formed only in the region of the semiconductor thin film 1 that has been irradiated with the slit beam group corresponding to the opening group 12a. The crystal 4 is crystallized from both ends of the region irradiated with the slit beam group in opposite directions S1 and S2, and the crystal 4 collides at the center. As a result, the central portion of the region where the crystal 4 is formed A raised portion (ridge 5) called a ridge is generated. The position where the ridge 5 occurs is on the center line in the width direction of the region where the crystal 4 is formed, and this center line is substantially equal to the line along the length direction passing through the center in the width direction of each slit beam.

  Next, after moving the photomask 11 of the example shown in FIG. 1 by the length of the slit beam on the semiconductor thin film 1 corresponding to the length L of the opening in the direction X, the first laser and the first laser are again formed. Irradiation is performed using laser No. 2 (second irradiation). At this time, by the movement of the photomask 11, irradiation with the first laser is performed through the aperture group 12b in which the apertures are arranged with respect to the aperture group 12a with respect to the width direction. Here, the deviation in the width direction between each opening of the opening group 12a and each opening of the opening group 12b is that the position where crystallization is performed by the slit beam group formed by the second irradiation is the first irradiation described above. Set between the crystallized regions so that they are in the middle of the region that was not crystallized by the first irradiation, and crystallized by re-irradiation with the region crystallized by the first irradiation. It is necessary to set so that it overlaps with the area. Specifically, as described above, it can be generally achieved by making the width D of each opening of the opening group 13 in the photomask 11 larger than 1/2 of the pitch P in the width direction of the opening.

  In this way, two irradiation groups using the photomask 11 in which the two opening groups 12a and 12b which are shifted in the width direction are formed adjacent to each other in the longitudinal direction of the opening are repeatedly superimposed on the entire surface of the semiconductor thin film. By doing so, as shown in FIG. 2C, a semiconductor crystal thin film whose entire surface is crystallized can be formed.

  However, after the entire surface of the semiconductor thin film is crystallized by the crystallization process to form the semiconductor crystal thin film, as shown in FIG. 2C, a ridge 5 is generated at each central portion of the crystallized region. . The ridge 5 has an extremely large influence on the characteristics of the formed semiconductor element (particularly, the threshold voltage fluctuation of the thin film transistor). In general, it is desirable that the threshold voltage of the thin film transistor to be formed is constant, and if variation occurs due to the influence of the ridge 5, it becomes difficult to lower the power supply voltage. For example, when this is applied to a liquid crystal display element It is difficult to reduce power consumption.

  The inventors of the present invention have made a prototype of a semiconductor element in which this raised portion is included in the channel region of the thin film transistor and a semiconductor element that is not included, and compared the characteristics. We found that there was little and the variation was small. That is, it was confirmed that the characteristics of the semiconductor element formed there were better as there was no raised portion or the height of the raised portion was lower.

  Further, the present inventors examined the relationship between the height of the ridge and the length of the crystal formed by lateral growth formed at that time, and found the relationship shown in the graph of FIG. Turned out to show. In the graph of FIG. 3, the vertical axis represents the height of the ridge, and the horizontal axis represents the crystal length in the horizontal direction. In addition, regarding the horizontal axis of the graph of FIG. 3, it shows that irradiation intensity | strength by a 2nd laser is so large that the crystal length of a horizontal direction is large. As can be seen from the dotted line shown in the graph of FIG. 3, the crystal length and the height of the ridge are closely related, and the height of the ridge increases in proportion to the crystal length. In other words, when the crystal length is short, the height of the ridge is low (for example, the state at point B in FIG. 3), and the longer the crystal length is, the more the condition becomes longer (in other words, irradiation by the second laser). The higher the strength, the higher the ridge, and the tendency from the state of point B to the state of point C shown in FIG.

  It has also been found that the crystal length and the irradiation intensity of the second laser show a relationship like the graph shown in FIG. In the graph of FIG. 4, the vertical axis represents the crystal length in the horizontal direction, and the horizontal axis represents the irradiation intensity of the second laser. From the graph of FIG. 4, it can be seen that the crystal length obtained tends to increase at an accelerated rate by increasing the irradiation intensity of the second laser.

  Further, in the graph shown in FIG. 3, when the crystal length becomes D ′ / 2 (that is, ½ of the width D ′ of the slit beam shown in FIG. 1) (the state at the point C in FIG. 3), it is theoretical. However, if the irradiation intensity of the second laser is further increased, the crystal length will eventually increase. This is because the melting region is expanded due to the energy of the second laser dosed excessively on the semiconductor thin film, and the melting region is expanded beyond the width of the slit beam, resulting in a longer crystal length. is there. In this case, the height of the ridge shows a tendency that the gradient of the dotted line becomes larger from the point C to the point A, not on the extension of the dotted line from the point B to the point C shown in FIG. That is, if crystallization is performed under an irradiation condition that extends longer than ½ of the width D ′ of the slit beam, the height of the ridge is excessively increased.

  Also, in order to crystallize normally to the center of the slit beam width and to crystallize stably (that is, to avoid fluctuations in irradiation intensity, film thickness fluctuations, reflectance fluctuations, etc.), irradiation is slightly excessive. It is necessary to determine the strength. Therefore, the ridge height is generated under the condition of point A shown in FIG.

  Therefore, in the method for producing a semiconductor crystal thin film of the present invention, a rectangular laser beam including an irradiation region of the second laser on the semiconductor thin film is formed using the first laser after the crystallization step described above. Irradiation is performed to reduce the height of the ridge generated in the semiconductor crystal thin film. As described above, in the method of manufacturing a semiconductor crystal thin film according to the present invention, in order to reduce the ridge height, the entire crystallized region including the ridge generated under the condition of the point A in FIG. The ridge height is reduced. In this case, the condition at point A in FIG. 3 generally corresponds to the condition at point D in FIG. That is, this is a case where the irradiation intensity of the second laser is large and the crystal length of the lateral growth is large.

  Thus, after the crystallization step, the first laser was used to irradiate the rectangular laser beam including the irradiation region of the second laser, thereby forming the film under the condition of point A in FIG. The entire crystallization region including the ridge is irradiated with a laser beam with an irradiation intensity that does not melt and recrystallize in the entire thickness direction of the semiconductor crystal thin film. As a result, the ridge having a large thickness of the semiconductor crystal thin film is partially melted and solidified, and the height of the ridge can be reduced. Note that the irradiation intensity of the rectangular laser beam by the first laser is very low (or zero) as shown in FIG. Corresponds to irradiation under non-growing conditions.

  FIG. 5 is a cross-sectional view showing how the ridge is reduced by the ridge reduction process of the present invention, and FIG. 6 is a top perspective view of FIG. 5 (b). FIG. 5A shows the semiconductor crystal thin film before the ridge reduction process, and the height of the ridge 5 is indicated by H1. The height H1 of the ridge 5 is measured from, for example, the difference in height between the protrusion and the flat portion with an atomic force microscope, and is usually in the range of 150 to 250 nm. The semiconductor crystal thin film having the ridge 5 having such a height is irradiated with the rectangular laser beam 10 with an irradiation intensity that does not melt and recrystallize in the entire thickness direction of the semiconductor crystal thin film using the first laser. .

  As a result, as shown in FIG. 5B, the ridge 5 in the semiconductor crystal thin film is partially melted and solidified by the irradiation of the rectangular laser beam 10, and the ridge 6 reduced to the height H2 is formed. . Here, the height H2 of the ridge 6 after the ridge reduction process has a value measured in the same manner as the height H1 of the ridge 5 described above within a range of 50 to 100 nm, preferably within a range of 20 to 50 nm. Become. As described above, the ridge 6 having the height H2 which is preferably reduced to not more than twice the film thickness of the semiconductor crystal thin film can be formed through the ridge reduction process of the present invention. Then, as shown in FIG. 6 which is a top perspective view of FIG. 5B, the semiconductor crystal thin film after the ridge reduction process has a ridge that is linearly connected substantially perpendicular to the crystal growth direction. It will have a typical appearance. As described above, the semiconductor crystal thin film manufactured by the method of the present invention can reduce the height of the ridge as well as the unevenness, and when a semiconductor element such as a transistor is formed thereon. Can obtain a semiconductor element with improved characteristics.

  Irradiation of the rectangular beam is performed using a photomask 11 having a rectangular opening 14 adjacent to the opening group 12b corresponding to the slit beam group described above, for example, as shown in FIG. 1, and through the opening group 12b. After the crystallization process by the irradiation of the first laser beam and the irradiation of the second laser beam to the irradiation region, the photomask 11 is moved in the direction X by the length of the slit beam on the semiconductor thin film corresponding to the length L of the opening. Then, the rectangular beam 10 is irradiated onto the semiconductor crystal thin film through the rectangular opening 14. Here, as described above, since the rectangular beam irradiates the region including the region irradiated with the slit beam group in the crystallization process, the rectangular opening 14 in the photomask 11 has the opening groups 12a and 12b. Are formed so as to have a length longer than the total length in the width direction and at least equal to the length L of each opening of the opening groups 12a and 12b (same length L in the example shown in FIG. 1). Is done.

  Here, in the case where the photomask 11 shown in FIG. 1 is used, in separate regions on the semiconductor thin film (that is, an irradiation region including a slit beam group and a region irradiated with a rectangular laser beam), respectively. The crystallization process and the ridge reduction process are performed at the same time, and the crystallization process and the ridge reduction process are sequentially performed over the entire surface of the semiconductor thin film by moving the photomask 11. That is, when the photomask 11 as shown in FIG. 1 is used, the slit laser beam is irradiated by the first laser through the aperture group 13 and the irradiation region including the slit beam group is irradiated by the second laser. A region not included in the region on the semiconductor thin film to be subjected to the irradiation is irradiated with a rectangular laser beam through the rectangular opening 14 by the first laser, and the laser irradiation and the movement of the photomask 11 And repeat. In this way, by performing the crystallization step and the ridge reduction step simultaneously in separate regions on the semiconductor thin film, only the portion of the ridge 5 having a large height is selectively melted and solidified in the ridge reduction step. Can be formed.

  By irradiating a rectangular laser beam so as to be outside the irradiation region by the second laser in this way, the crystallization step and the ridge reduction step are simultaneously performed in separate regions on the semiconductor thin film, thereby providing an effect. In particular, the height of the ridge can be reduced. In particular, increasing the irradiation intensity of the second laser within an appropriate range indicates that a large crystal can be formed by a single irradiation, and therefore, a semiconductor device using a semiconductor crystal thin film having a large crystal formed therein. This has the effect of improving the characteristics. In this case, the throughput can be dramatically improved as compared with the case where crystals of the same size are formed without using the second laser. According to the method for manufacturing a semiconductor crystal thin film of the present invention, even when the second laser having a high irradiation intensity within such an appropriate range is used, it is outside the region irradiated with the second laser. By irradiating a rectangular laser beam as described above, the crystallization process and the ridge reduction process are simultaneously performed in separate regions on the semiconductor thin film, so that the irradiation condition of the rectangular beam for reducing the ridge height is achieved. Can be set to conditions that can effectively reduce the ridge height. As a result, the height of the ridge can be prevented from deteriorating the characteristics of the thin film transistor (especially variations in threshold voltage), and as a result, a high-quality semiconductor crystal thin film with high throughput can be produced more flatly. be able to.

  FIG. 7 is a schematic diagram for explaining another preferred example of the method for producing a semiconductor crystal thin film of the present invention. The semiconductor crystal thin film of the present invention may be subjected to the above-described crystallization step and ridge reduction step using the photomask 21 as shown in FIG. 7 instead of the photomask 11 as shown in FIG. Good. The photomask 21 in the example shown in FIG. 7 has the same structure as the photomask 11 in the example shown in FIG. 1 except for a part thereof, and the same reference numerals are used for the parts having the same structure. A description thereof will be omitted.

  The photomask 21 of the example shown in FIG. 7 irradiates a rectangular laser beam with an opening group 12b for irradiating the slit beam group with the first laser in the crystallization process and with the first laser in the ridge reduction process. 1 is different from the photomask 11 of the example shown in FIG. 1 in that an area region 22 that does not transmit laser is provided between the opening 14 and the rectangular opening 14. Here, the second laser irradiated to the irradiation region including the slit beam group usually has a distribution in which the intensity distribution is not sharp at the edge of the irradiation region. Therefore, as shown in the example shown in FIG. 7, by using the photomask 21 having the region 22 as described above between the opening 12b and the rectangular opening 14, the region irradiated with the second laser on the semiconductor thin film Even when the intensity distribution at the edge of the substrate has a change, it is possible to prevent the edge from overlapping with the irradiation region of the rectangular laser beam. As a result, the region on which the crystallization process is performed on the semiconductor thin film can be irradiated with the second laser at a uniform intensity on the irradiation region including the slit beam group, and the ridge reduction process is performed. In the region, the irradiation intensity of the second laser in the region irradiated with the rectangular laser beam 10 can be set to substantially zero.

  In the photomask 21 shown in FIG. 7, the length of the region 22 is preferably set to a length L equal to the length L of each opening of the opening groups 12a and 12b for irradiating the slit beam. Thus, in the region where the crystallization process is performed, the slit laser beam irradiation by the first laser and the irradiation region by the second laser are performed every time the semiconductor thin film corresponding to the length L moves in the direction X. In the region where the ridge reduction process is performed, the rectangular laser beam 10 through the rectangular opening 14 is irradiated so as to match the crystallization region formed in the crystallization process. Can be reduced.

  FIG. 8 is a schematic diagram for explaining still another preferred example of the semiconductor crystal thin film of the present invention. The semiconductor crystal thin film of the present invention may be subjected to the above-described crystallization step and ridge reduction step using a photomask 31 as in the example shown in FIG. 8 instead of the photomask 11 in the example shown in FIG. Good. The photomask 31 in the example shown in FIG. 8 has the same structure as the photomask 11 in the example shown in FIG. 1 except for a part thereof, and the same reference numerals are used for the parts having the same structure. A description thereof will be omitted.

  The photomask 31 of the example shown in FIG. 8 has four opening groups 32a, 32b, 32c, and 32d that are formed in stages for forming a slit beam group on a semiconductor thin film in a crystallization process (these generic names). Is referred to as “aperture group 33”). Unlike the aperture group 13 in the photomask 11 of the example shown in FIG. 1, the aperture group 33 is sequentially shifted in the width direction from the aperture group 32a toward the adjacent aperture groups 32b, 32c, and 32d in the longitudinal direction. The amount of displacement in the width direction is set to approximately 1/4 to 1/2 of the width of the opening.

  FIG. 9 is a cross-sectional view showing step-by-step changes when the method for producing a semiconductor crystallized thin film of the present invention is performed using the photomask 31 of the example shown in FIG. First, as shown in FIG. 9A, a region irradiated with the slit beam group on the semiconductor thin film corresponding to the opening group 32a by irradiation of the slit beam group with the first laser through the opening group 32a. Crystallization forms a crystal 34. Here, in the photomask 31, the opening group 32b is formed so as to be deviated from the opening group 32a by approximately D / 4 in the width direction. Therefore, in the crystallization process via the photomask 31, the photomask 31 is irradiated on the semiconductor thin film corresponding to the length L in the direction X after the irradiation of the slit beam group by the first laser via the opening group 32a. When the slit beam group is irradiated through the aperture group 32b after being moved by the length of the slit beam, the slit beam width D ′ corresponding to the width of the aperture group 32a is passed through the aperture group 32b. The slit beam group is irradiated with a deviation of about D ′ / 4 with respect to the width direction of the slit beam group through the aperture group 32a (FIG. 9B). For this reason, the ridge 35 near the center of the crystallization region formed by the irradiation of the slit beam group through the aperture group 32a by the first laser in the stage of FIG. 9A is formed in the stage of FIG. 9B. As a result of forming the slit beam group through the aperture group 32b by the first laser so as to overlap the ridge 35, the ridge 35 is melted and a new ridge 36 is formed from the original ridge 35 in the width direction of the slit beam group. A crystal 37 is formed which is shifted by D ′ / 4 and grows long in the lateral direction. Subsequently, the slit beam group by the first laser through the aperture groups 32c and 32d is further irradiated by sequentially shifting by D ′ / 4. As a result, the slit beam group corresponding to the aperture group 32d is related to the longitudinal direction. A ridge is formed only at the center line, and the crystal 37 grows further in the lateral direction (direction of deviation with respect to the width direction). The photomask 31 is moved to the ridge thus formed by the length of the slit beam on the semiconductor thin film corresponding to the length L in the direction X, and the rectangular shape is formed by the first laser through the rectangular opening 14. The height of the finally formed ridge is reduced by performing the ridge reduction process by irradiating the beam. By performing the semiconductor crystal thin film manufacturing method of the present invention using such a photomask 31, it is possible to reduce the ridge height even when larger crystal grains are formed as compared with the case described above. There is an advantage that a semiconductor crystal thin film having a uniform thickness can be obtained.

  In the method of manufacturing a semiconductor crystal thin film of the present invention, the above-described conditions are only exemplary for the conditions of laser irradiation and the shape of the photomask used (number of openings, size, position, shape, etc.). This is not a limitation. Further, the case where the irradiation of the rectangular laser beam in the ridge reduction process is performed once has been described as an example, but it is of course possible to irradiate the rectangular laser beam a plurality of times with the first laser. By irradiating the rectangular beam a plurality of times, only the ridge having a large thickness of the semiconductor thin film can be melted and solidified a plurality of times, and the ridge height can be further reduced. In such a case, for example, a photomask in which a rectangular laser beam by the first laser is formed with a plurality of rectangular openings can be used.

  The semiconductor crystal thin film manufacturing method of the present invention described above can be carried out in combination with a conventionally known appropriate device, and the device used in the manufacturing method is not particularly limited. The present invention also provides an apparatus that can be suitably used for the above. That is, the present invention is an apparatus used for producing a semiconductor crystal thin film by irradiating a semiconductor thin film formed on a substrate with a laser, and irradiating a slit beam group and a rectangular laser beam on the semiconductor thin film. A second laser for irradiating a laser beam onto an irradiation region including a slit beam group by the first laser on the semiconductor thin film, and the slit beam group by the first laser. An apparatus for manufacturing a semiconductor crystal thin film, comprising a photomask having a plurality of aperture groups arranged so as to be formed and a rectangular aperture for irradiating a rectangular laser beam with a first laser provide.

  FIG. 10 is a diagram conceptually showing a semiconductor crystal thin film manufacturing apparatus 51 as a preferred example of the present invention. The apparatus 51 of the example shown in FIG. 10 basically includes a first laser 52, a second laser 53, and a photomask (for example, the photomask 11 of the example shown in FIG. 1). The semiconductor thin film 1 formed on the substrate is irradiated with the laser beam from 52 through the photomask 11 described above, and the semiconductor thin film 1 is also irradiated with the laser beam from the second laser 53. It is comprised so that. With the apparatus 51 having such a basic configuration, as described above, the first laser 52 irradiates the slit thin film on the semiconductor thin film through the opening group 13 of the photomask 11 and the second laser 53. The above-described crystallization step of irradiating the irradiation region including the slit beam group with a laser beam and the irradiation region on the semiconductor thin film through the rectangular opening 14 of the photomask 11 with the first laser 52 The method for producing a semiconductor crystal thin film of the present invention, which includes a ridge reduction step of irradiating a rectangular laser beam containing

  In the semiconductor crystal thin film manufacturing apparatus 51 of the present invention, the first laser 52 is not particularly limited as long as it can emit a pulsed energy beam and melt silicon as described above. However, a light source having a wavelength in the ultraviolet region, such as various solid-state lasers typified by excimer lasers and YAG lasers, or harmonics thereof, can be preferably used. Specifically, an excimer laser having a wavelength of 308 nm is exemplified. The As the first laser 52, it is preferable to use a laser whose irradiation intensity is set lower than the irradiation intensity at which the entire thickness direction of the semiconductor thin film is melted and recrystallized as described above.

  In the semiconductor crystal thin film manufacturing apparatus 51 of the present invention, as the second laser 53, as long as it can effectively assist the process of melting and solidifying the semiconductor thin film 1 by the first laser 52 as described above, it is particularly preferable. Although not limited, for example, a carbon dioxide laser, a YAG laser, or the like can be used, and a carbon dioxide laser can be particularly preferably used.

  Further, as a photomask used in the semiconductor crystal thin film manufacturing apparatus 51 of the present invention, FIG. 10 shows an example using the photomask 11 of the example shown in FIG. 1, but it is not limited to this. As long as it can be preferably applied to the method for producing a semiconductor crystal thin film of the present invention as described above. In particular, for example, as shown in FIG. 7, when a photomask 21 in which a region 22 that does not transmit laser is formed between the opening group 12 b and the rectangular opening 14 is used, an irradiation region by the second laser 53 is used. Even when the intensity distribution at the edge of the substrate has a change, it can be prevented that the edge overlaps the irradiation region of the rectangular laser beam, and the slit beam group by the first laser 52 is included in the crystallization process. The irradiation area can be irradiated with the second laser 53 with a uniform intensity, and the irradiation intensity of the second laser at the rectangular opening 14 can be set to substantially zero during the ridge reduction process. There is an advantage that it can be performed, which is preferable.

  In the apparatus 51 of the example shown in FIG. 10, mask surface uniform irradiation elements 54 and 55, a field lens 56, and a folding mirror 57 are interposed as an optical system between the first laser 52 and the photomask 11. An objective lens 58 is interposed between the photomask 11 and the semiconductor thin film 1. Further, a second laser irradiation optical system 59 is interposed between the second laser 53 and the semiconductor thin film 1. In addition to the above, the apparatus of the present invention is not shown in FIG. 10, but includes a variable attenuator that corrects the beam intensity, a beam shaping element that corrects the beam shape, a drive system that scans the substrate or the optical system, and the like. Of course, a control system for controlling the above may be provided as appropriate.

  In the example shown in FIG. 10, the mask surface uniform irradiation elements 54 and 55 interposed between the first laser 52 and the photomask 11 uniformly distribute the laser beam emitted from the first laser 52 to the mask 11 surface. It has a function to irradiate. As such mask surface uniform irradiation elements 54 and 55, for example, a cylindrical lens array can be used, whereby the laser beam from the first laser 52 having a Gaussian intensity distribution is divided and superimposed on the mask surface. By illuminating, mask illumination with a uniform intensity distribution can be obtained.

  In the example shown in FIG. 10, the laser beam that has passed through the mask surface uniform irradiation elements 54 and 55 passes through the field lens 56 and is then irradiated onto the photomask 11 via the folding mirror 57. Here, the field lens 56 has a function of causing the principal ray transmitted through the photomask 11 to enter the imaging plane on the semiconductor thin film 1 perpendicularly. Further, the folding mirror 57 is used for folding the laser beam, and FIG. 10 shows an example of the arrangement between the field lens 56 and the photomask 11. It is not limited, and can be appropriately arranged according to the optical design and mechanism design of the apparatus. The laser beam from the first laser 52 after passing through the photomask 11 forms an image having a shape corresponding to the aperture group 13 on the photomask 11, and this image is formed on the semiconductor thin film 1 via the objective lens 58. An image is formed at a predetermined magnification and irradiated as a slit beam group. Thus, the mask pattern of the photomask is imaged on the semiconductor thin film at a constant magnification, and the mask pattern and the image irradiated on the semiconductor thin film are similar. Thereby, as described above, the semiconductor thin film 1 is melted and solidified to be crystallized, thereby causing super lateral growth.

  In the example shown in FIG. 10, the laser beam from the second laser 53 is irradiated onto the semiconductor thin film 1 through the second laser illumination optical system 59. The second laser illumination optical system 59 optimizes the shape and intensity distribution of the beam of the second laser 53 so that the most effective irradiation can be performed on the semiconductor thin film 1. It is realizable using the means of.

  The present invention also provides a photomask suitably used in the above-described method and apparatus for producing a semiconductor crystal thin film of the present invention. That is, the photomask of the present invention is a photomask for use in irradiation with a first laser and a second laser for producing a semiconductor crystal thin film from a semiconductor thin film formed on a substrate, A plurality of aperture groups arranged so that the slit beam group can be formed by a laser, a rectangular aperture for irradiating a rectangular laser beam by the first laser, and the aperture group and the rectangular aperture And a region which does not transmit the laser formed between the two. As a preferred example of the photomask of the present invention, there can be mentioned the photomask 21 as shown in FIG. 7 as described above, but it is of course not limited thereto. The photomask of the present invention uses a conventionally known material such as chrome so that the portions other than the opening group and the rectangular opening described above (including the region 22 in the example shown in FIG. 7) do not transmit the laser. The formed one can be used.

  In the photomask of the present invention, an opening group for irradiating a slit beam group on a semiconductor thin film by a first laser and a rectangular shape for irradiating a rectangular laser beam on a semiconductor crystal thin film by a first laser are provided. The aperture is not particularly limited with respect to the transmittance, but it is preferable that the transmittance of the rectangular aperture is realized to be lower than the transmittance of the aperture group. This ensures that the semiconductor crystal thin film crystallized by irradiation with the slit beam group is melted over the entire thickness direction by the laser beam irradiated through the rectangular opening, and a fine polycrystal is formed. There is an advantage that can be prevented.

  In this case, the difference between the transmittance of the rectangular opening in the photomask and the transmittance of the aperture group is preferably in the range of 10 to 60%, and more preferably in the range of 20 to 40%. When the difference between the transmittance of the rectangular aperture in the photomask and the transmittance of the aperture group is less than 10%, as described above, the laser beam is irradiated by the rectangular aperture and the slit beam group is irradiated first. The formed semiconductor crystal thin film tends to melt again in the entire thickness direction to form fine polycrystals, and there is a difference between the transmittance of the rectangular opening and the transmittance of the aperture group in the photomask. If it exceeds 60%, the laser irradiation intensity by the rectangular opening is weak, and the ridge reduction of the semiconductor crystal thin film formed by irradiation of the previous slit beam group tends to be insufficient. Specifically, the transmittance of the rectangular opening in the photomask is preferably 40 to 90%, and the transmittance of the aperture group is 100%, which is preferably realized so as to have a difference within the above range. The transmittance was calculated from, for example, the ratio of the laser energy value measured on the irradiated surface when a photomask was not installed on the optical path to the laser energy value measured on the irradiated surface with the photomask installed. Points to the value. Further, the transmittance of the aperture group and the rectangular aperture in the photomask is realized to be within the above-mentioned range by appropriately forming, for example, a fine pattern less than the optical resolution in the aperture region and forming a halftone shape. can do.

  The present invention further provides a semiconductor element using the semiconductor crystal thin film produced by the above-described method for producing a semiconductor crystal thin film of the present invention. As described above, the semiconductor crystal thin film manufactured by the method of manufacturing a semiconductor crystal thin film of the present invention has a characteristic appearance of having ridges that are linearly connected substantially perpendicular to the crystal growth direction. (See FIG. 6). In the semiconductor device of the present invention, the semiconductor crystal thin film has a ridge that is linearly connected substantially perpendicular to the crystal growth direction, and the height of the ridge is not more than twice the film thickness of the semiconductor crystal thin film (preferably 1 or less). The semiconductor element of the present invention formed on such a semiconductor crystal thin film has characteristics that are remarkably improved as compared with the conventional one.

  Specific examples of the semiconductor element of the present invention include a thin film transistor, a driving circuit for the thin film transistor, and the like. In particular, the semiconductor element is preferably realized as a thin film transistor from the viewpoint that characteristics of variation in threshold voltage are improved. The semiconductor element of the present invention can be suitably applied to a display device or the like.

It is a schematic diagram for demonstrating a preferable example of the manufacturing method of the semiconductor crystal thin film of this invention. It is sectional drawing which shows the change from a semiconductor thin film to a semiconductor crystal thin film in steps by the crystallization process in the manufacturing method of the semiconductor crystal thin film of this invention. It is a graph which shows the relationship between the height of a ridge and the length of the crystal formed by the lateral growth formed at that time, the vertical axis is the height of the ridge, and the horizontal axis is the crystal length in the horizontal direction . It is a graph which shows the relationship between crystal length and the irradiation intensity | strength of a 2nd laser, a vertical axis | shaft is the crystal length of a horizontal direction, and a horizontal axis | shaft is the irradiation intensity of a 2nd laser. It is sectional drawing which shows a mode that a ridge is reduced by the ridge reduction process of this invention in steps. FIG. 6 is a perspective view of FIG. It is a schematic diagram for demonstrating the other preferable example of the manufacturing method of the semiconductor crystal thin film of this invention. It is a schematic diagram for demonstrating another preferable example of the semiconductor crystal thin film of this invention. It is sectional drawing which shows the change at the time of performing the manufacturing method of the semiconductor crystallized thin film of this invention using the photomask 31 of the example shown in FIG. It is a figure which shows notionally the manufacturing apparatus 51 of the semiconductor crystal thin film of a preferable example of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Semiconductor thin film, 2 Substrate, 3 Underlayer, 4,34,37 Crystal, 5, 6, 35, 36 Ridge, 10 Rectangular beam, 11, 21, 31 Photomask, 12a, 12b, 13, 32a, 32b, 32c, 32d, 33 aperture group, 14 rectangular aperture, 22 regions, 51 semiconductor crystal thin film manufacturing apparatus, 52 first laser, 53 second laser, 54, 55 mask surface uniform irradiation element, 56 field lens, 57 Folding mirror, 58 objective lens, 59 Second laser irradiation optical system.

Claims (12)

A method of manufacturing a semiconductor crystal thin film by irradiating a semiconductor thin film formed on a substrate with a laser,
A semiconductor thin film is crystallized using a first laser that irradiates a laser beam so as to form a slit beam group on the semiconductor thin film, and a second laser that irradiates a laser beam to an irradiation region including the slit beam group. Forming a semiconductor crystal thin film,
A step of reducing a height of a ridge generated in the semiconductor crystal thin film by irradiating a rectangular laser beam including an irradiation region of the second laser with the first laser. Thin film manufacturing method.   The method according to claim 1, wherein a carbon dioxide laser is used as the second laser. Through a photomask having a plurality of aperture groups arranged so that the slit laser beam can be formed by a first laser and a rectangular aperture for irradiating a rectangular laser beam by the first laser. The first laser is applied to the semiconductor thin film,
In the step of crystallizing the semiconductor thin film to form the semiconductor crystal thin film, the first laser irradiates the semiconductor thin film with a slit beam group through the opening group of the photomask, and the second laser emits the semiconductor thin film. Irradiate the irradiation area including the slit beam group with a laser beam,
In the step of reducing the height of the ridge, the first laser irradiates a rectangular laser beam to a region not included in the irradiation region of the semiconductor thin film through the rectangular opening of the photomask. And
3. The method according to claim 1, wherein the step of forming the semiconductor crystal thin film and the step of reducing the height of the ridge are sequentially performed by repeatedly performing laser irradiation and photomask movement. 4. .   The method according to claim 3, wherein the photomask has a region that does not transmit a laser between the opening group and the rectangular opening.   The method according to claim 1, wherein the irradiation intensity of the first laser is lower than the irradiation intensity at which the entire thickness direction of the semiconductor thin film is melted and recrystallized. An apparatus used for manufacturing a semiconductor crystal thin film by irradiating a semiconductor thin film formed on a substrate with a laser,
A first laser for irradiating the semiconductor thin film with a slit beam group and a rectangular laser beam;
A second laser for irradiating a laser beam onto an irradiation region including a slit beam group of the first laser on a semiconductor thin film;
A photomask having a plurality of aperture groups arranged so as to form the slit beam group by a first laser and a rectangular aperture for irradiating a rectangular laser beam by the first laser; An apparatus for manufacturing a semiconductor crystal thin film.   The apparatus according to claim 6, wherein the second laser is a carbon dioxide laser.   The apparatus according to claim 6 or 7, wherein the photomask has a region that does not transmit a laser between the opening group and the rectangular opening.   9. The apparatus according to claim 6, wherein the irradiation intensity of the first laser is set lower than the irradiation intensity at which the entire thickness direction of the semiconductor thin film is melted and recrystallized. A photomask used for manufacturing a semiconductor crystal thin film from a semiconductor thin film formed on a substrate,
A plurality of aperture groups arranged to form the slit beam groups with a first laser;
A rectangular opening for irradiating a rectangular laser beam with the first laser;
A photomask comprising: a region formed between the opening group and a rectangular opening that does not transmit a laser.   The photomask according to claim 10, wherein the transmittance of the rectangular opening is lower than the transmittance of the opening group.   A semiconductor element formed on a semiconductor crystal thin film on a substrate, having a ridge linearly extending substantially perpendicular to a direction of crystal growth of the semiconductor crystal thin film, the height of the ridge being a film thickness of the semiconductor crystal thin film 2 or less of the semiconductor element.

Images