JP5077511B2 - Semiconductor thin film manufacturing method and manufacturing apparatus, beam shaping mask, and thin film transistor - Google Patents

Description

  The present invention particularly relates to a method and apparatus for manufacturing a semiconductor thin film with controlled grain boundaries, and a thin film transistor.

  As a switching element constituting a pixel in a liquid crystal display device, a thin film transistor (hereinafter referred to as “TFT”) formed on a glass substrate is used. In recent years, in addition to the realization of high-definition liquid crystal display devices, there has been a growing demand for higher TFT operation speeds in order to realize system-on-glass, and high-quality laser-annealed polycrystalline silicon TFT formation technology has attracted attention. I'm bathing.

  The above-described TFT is usually manufactured as shown in FIG. For example, as shown in FIG. 13A, amorphous silicon 1201 is formed on an insulating film 1202 formed on the surface of a glass substrate 1203. Subsequently, as shown in FIG. 13B, the surface of the amorphous silicon 1201 is irradiated with laser light 1204 to form polycrystalline silicon 1201 ′. Subsequently, as shown in FIG. 13 (3), the obtained polycrystalline silicon 1201 ′ has a source region 1207, a drain region 1209, and a channel (active layer) 1208 sandwiched between the source region 1207 and the drain region 1209. A gate insulating film 1212 and a gate electrode 1206 are formed thereon. After the interlayer insulating film 1211 is formed so as to cover the gate electrode 1206 and the gate insulating film 1212, a contact hole penetrating the interlayer insulating film 1211 and the gate insulating film 1212 is formed. Then, a source electrode 1205 connected to the contact hole in the source region 1207 and a drain electrode 1206 connected to the contact hole in the drain region 1209 are formed on the interlayer insulating film 1211 to complete the TFT.

  In recent years, there has been a demand for increasing the operation speed of polycrystalline TFTs. The larger the carrier (electron or hole) mobility in the channel, the faster the operation. However, when there are many crystal grain boundaries in the channel, there is a problem that the carrier mobility is lowered. For this reason, a technique for improving the carrier mobility by reducing the number of crystal grain boundaries in the channel by controlling crystal growth during laser annealing has been proposed as follows.

[First conventional technology]
Non-Patent Document 1 discloses a technique for forming a huge crystal grain in the scanning direction by scanning a thin beam. This technique will be described below.

  First, as shown in FIG. 14A, pulse laser light is shaped into a fine line beam 1302 using a predetermined mask, and the shaped thin line beam 1302 is irradiated along the substrate while irradiating the amorphous silicon 1301 on the substrate. Thereby, the amorphous silicon 1301 is sequentially heated (annealed).

  As shown in FIG. 14B, crystallization of the melted amorphous silicon film proceeds as follows by irradiating the thin beam 1302 for the first time. First, each crystal grows toward the center of the melting region, starting from the scanning direction (beam width direction) end of the thin line beam that forms a solid-liquid interface with the adjacent non-melting region. As a result, the solidified portion becomes crystallized polycrystalline silicon 1301 ′. Each crystal collides in the vicinity of the central portion and stops growing, and a crystal grain boundary is formed in this portion. In the direction perpendicular to the scanning direction (beam length direction), a large number of crystal grain boundaries are formed along the scanning direction.

  Subsequently, as shown in FIG. 14 (3), the second thin beam 1302 ′ is irradiated. The scanning amount of the second thin beam 1032 'is equal to or smaller than the grain size of crystal grains crystallized along the scanning direction of the first thin beam 1302'.

  Subsequently, as shown in FIG. 14 (4), crystal growth is performed by using the crystal grains grown by the first irradiation as seeds in association with the second irradiation of the fine wire beam 1302 ′.

  By sequentially scanning the laser irradiation region and repeating melting and crystallization of the amorphous silicon 1301, crystal grains 1303 extending along the scanning direction can be formed as shown in FIG.

[Second prior art]
In Patent Document 1, using a light shielding mask having a light shielding part 1402 and a zigzag pattern transmission part 1401 shown in FIG. 15 (1), the beam is passed through the transmission part 1401 and shaped into a zigzag beam shape and scanned. A technique for irradiating is disclosed. In this technique, crystal growth is performed not only in the scanning direction but also in the direction perpendicular to the scanning direction starting from the apex of the beam pattern. As a result, as shown in FIG. 15 (2), it has been reported that position-controlled crystal grains 1502 can be formed corresponding to the period of the zigzag pattern. In FIG. 15B, 1501 indicates a high density grain boundary region, and 1503 indicates a crystal grain boundary.
“Sequential lateral solidification of thin silicon films on SiO2”, Robert S. Sposili and James S. Im, Appl. Phys. Lett. 69 (19) 1996 pp.2864-2866. Japanese Patent Laid-Open No. 11-64883

  In the case of the laser annealing method described in the first prior art, it is possible to extend the crystal grains in the laser beam scanning direction (beam width direction). However, since there is no temperature gradient in the direction (beam length direction) orthogonal to the laser beam scanning direction, crystal grain boundaries are randomly generated in the beam length direction. Therefore, there are problems that crystal grain growth may be interrupted and that the grain size in the beam length direction becomes as short as about 1 μm. As a result, when a TFT is manufactured by providing a channel so that carriers move in parallel with the scanning direction, since the grain boundary position is not controlled, there is a grain boundary in the channel, and the carrier mobility. There arises a problem that the mobility and threshold voltage fluctuate greatly. In addition, when a TFT is manufactured by providing a channel so that carriers move in the direction perpendicular to the scanning direction, since the position of the crystal grain boundary is not controlled, the crystal grain boundary is blocked so as to block the carrier movement in the channel. Presents a problem that carrier mobility is lowered, and mobility and threshold voltage fluctuations are large.

  In addition, a projection is generated along the crystal grain boundary at each scanning step. Since crystal grain boundaries in the beam width direction are randomly formed, the arrangement of protrusions in the beam width direction is random. In a TFT including a protrusion in the channel, the electric field during operation is concentrated on the protrusion, and the threshold voltage fluctuates. That is, in the TFT manufactured by the first prior art in which the arrangement and number of protrusions in the channel are random, the threshold voltage varies greatly.

  In the laser annealing method using the light shielding mask as described in the second prior art, the beam shape on the light shielding mask is generally rectangular (laser irradiation region 1403) shown in FIG. Therefore, when the laser is passed through a mask having a zigzag pattern for use in the second prior art, the transmittance of the laser light is reduced as compared with the case of forming a fine beam used in the first prior art. As a result, since the length of the beam irradiated on the substrate is shortened, a polycrystalline region obtained by one scanning irradiation is narrowed, and thus there is a problem that the time required for the substrate processing is lengthened.

  Further, in the obtained crystal, there is a problem that a high density grain boundary region 1501 as shown in FIG. 15B is generated in a wide range at the irradiation start position and the irradiation end position. Further, in the mask manufacturing process, forming a complicated zigzag pattern increases the cost as compared with the case of a linear pattern. Further, in order to form a zigzag pattern beam, an optical system requiring high resolution is required for the laser annealing apparatus.

  An object of the present invention is to provide a method for manufacturing a semiconductor thin film that enables position control of crystal grain boundaries formed in the semiconductor thin film when the crystal film is formed, a beam shaping mask used in the method for manufacturing a semiconductor thin film, An object of the present invention is to provide a semiconductor thin film manufacturing apparatus for manufacturing a semiconductor thin film using a beam shaping matrix, and a thin film transistor manufactured by the manufacturing apparatus.

In order to achieve the above object, a method of manufacturing a semiconductor thin film according to the present invention includes: irradiating a semiconductor thin film formed on an insulating substrate with a laser beam to form crystal grains in the semiconductor thin film. ,
In the laser beam shaping step, a part of the irradiation pattern of the laser beam irradiated on the precursor film is shaped into a control pattern.

  According to the present invention, a temperature gradient is generated on the semiconductor thin film by the control pattern shaped into a part of the irradiation pattern. Due to this temperature gradient, the crystal film continuously grows on the semiconductor thin film, the position of the crystal grain boundary is controlled reliably, and a crystal film having an area sufficient to form an active layer is obtained. It is done.

  The irradiation pattern is shaped into a rectangular shape having the control pattern on one side. A band-like crystal grain is grown on the semiconductor thin film while controlling the position of the crystal grain boundary by the control pattern. Thereby, the growth of the band-like crystal grains is not interrupted, and the position control of the crystal grain boundaries can be surely performed.

  The present invention is not limited to the case where the crystal film is formed on the semiconductor thin film by a single shot that does not scan the laser beam. When scanning with a laser beam, by irradiating the semiconductor thin film with a laser beam of the irradiation pattern including the control pattern while scanning the laser beam, a band-like crystal grain is formed in a region sandwiched between parallel crystal grain boundaries. A band-shaped crystal region is formed. In this case, the laser beam is shaped by forming the control pattern on the side opposite to the side of the laser beam in the scanning direction.

  Similarly, when the laser beam is scanned in this manner, the semiconductor thin film is given a temperature gradient to grow a band-like crystal grain, and the position of the crystal grain boundary is controlled to form an active layer (channel). The region of the crystal film can be enlarged. Furthermore, compared with the zigzag pattern, the transmittance of the laser beam is large, so that the beam length can be increased, and by increasing the scanning irradiation area once, the laser annealing processing time per substrate is increased. Shortened. Further, by reducing the beam recess width of the concave pattern, it is possible to narrow the high density grain boundary region generated at the irradiation start position as compared with the zigzag pattern. In addition, since the front half end of the beam is a straight line perpendicular to the scanning direction, the high-density grain boundary region generated at the irradiation end position is about the crystal growth distance in one irradiation. It becomes narrower than the pattern. The high density region generated at the irradiation end position in the case of the zigzag pattern is about the sum of the scanning direction length of the zigzag pattern and the crystal growth distance in one irradiation. Further, by shaping the control pattern into a concave shape, the pattern does not have an acute angle, the manufacturing cost is reduced as compared with a zigzag pattern, and the laser annealing optical system does not require high resolution. In addition, a TFT manufactured using the obtained semiconductor thin film can improve carrier mobility and can suppress variations in mobility and threshold voltage.

  The length of the beam concave portion in the length direction of the control pattern is set to be equal to or smaller than the width of the beam concave portion in the width direction of the control pattern in which the crystal growth width of the band-like crystal grains is maximized. The width of the beam recess in the width direction of the control pattern is set to be equal to or greater than the width of the beam recess in the width direction of the control pattern at which the crystal growth width of the band-like crystal grains is maximized.

By doing so, the position of the crystal grain boundary formed starting from the beam recess can be controlled, and the area of the crystal film forming the active layer can be expanded. Furthermore, it is possible to continuously form the band-like crystal regions with reduced grain boundaries.

  At least one of the control patterns is shaped on the one side. The period for shaping the control pattern is set to be equal to or shorter than the crystal growth width of the band-like crystal grains. Thus, the position control of the crystal grain boundary can be reliably performed by the arrangement of the control pattern.

In order to reliably control the position of the crystal grain boundary, it is desirable to configure the mask as follows. That is, the beam shaping mask according to the present invention is a beam shaping mask for shaping a laser beam applied to a semiconductor thin film.
The main body of the mask is constructed so as to have a light shielding pattern for shielding the laser beam in a part of a transmission region that transmits the laser beam.

  In this case, the transmission region is formed in an opening shape that is rectangular and has the shielding pattern on one side thereof. The shielding pattern may be formed in the shape of a convex pattern that protrudes from the shielding region of the laser beam toward the transmitting region. Further, the length of the concave portion in the length direction of the shielding pattern is set to be equal to or smaller than the width of the concave portion of the shielding pattern in which the crystal growth width of the band-like crystal grains is maximized. The width of the concave portion in the width direction of the shielding pattern is set to be equal to or larger than the width of the concave portion of the shielding pattern that maximizes the crystal growth width of the band-like crystal grains. In this case, one or more shielding patterns are provided. The shielding pattern may be provided periodically. It is desirable to set the period of the shielding pattern to be equal to or less than the length of the crystal growth width of the band-like crystal grains.

  When the opening width in the width direction of the transmission region is A, the recess width in the width direction of the shielding pattern is B, and the maximum crystal growth distance of the band-like crystal grains in the width direction is L, these dimensional relationships are 2L. ≦ A−B may be set. In this case, when 2L> A-B is set, crystal growth on the side on the control pattern side is hindered by crystal growth that occurs from the opposite side, and the growth width of the single crystal film in the width direction of the transmission region is narrowed. On the other hand, when 2L ≦ A−B, the crystal growth from the control pattern side is not hindered by the crystal growth from the opposite side, and the growth of the single crystal film in the width direction of the transmission region is prevented. The width can be increased.

  When the length of the concave portion in the length direction of the shielding pattern is C, the length of the convex portion that is an interval between the shielding patterns is D, and the maximum crystal growth distance of the band-like crystal grains in the width direction of the transmission region is L, The dimensional relationship may be set to a relationship of 2L ≧ C + D. In this case, when 2L <C + D is set, many crystal grain boundaries are generated between the crystal grains forming the band-like single crystal film. On the other hand, when the relationship of 2L ≧ C + D is set, the band-like crystal grains can be formed side by side by having a radial temperature gradient centering on the control pattern.

  The opening width in the width direction of the transmission region is A, the recess width in the width direction of the shielding pattern is B, the recess length in the length direction of the shielding pattern is C, and the projection length that is an interval between the shielding patterns is D. In this case, these dimensional relationships may be set to a relationship of AB ≧ C + D. According to this setting, both the effect of setting 2L ≦ A−B and the effect of setting 2L ≧ C + D can be achieved, and the area of the crystal film in the length direction and width direction of the laser beam can be increased. it can.

An apparatus for manufacturing a semiconductor thin film according to the present invention is an apparatus for manufacturing a semiconductor thin film in which a precursor film made of a semiconductor thin film formed on an insulating substrate is irradiated with a laser beam and single crystal grains are grown on the precursor film. ,
A beam shaping mask for shaping the laser beam;
The mask main body has a light-shielding pattern that shields the laser beam in a part of a transmission region that transmits the laser beam.

  According to the present invention, the formation position of the crystal grain boundary can be controlled, and the band-like crystal region extending in the length direction of the crystal grain boundary can be formed in the region sandwiched between the parallel crystal grain boundaries.

A thin film transistor using a semiconductor thin film according to the present invention is a thin film transistor having an active layer for carriers to move,
Having a band-shaped crystal region formed in a region sandwiched between parallel crystal grain boundaries,
At least one of a first active layer in which the carrier moving direction is set in the length direction of the crystal grain boundary and a second active layer in which the carrier moving direction is set in a direction crossing the crystal grain boundary. One active layer is formed in the band-like crystal region.

  In the case of having the first active layer, the first active layer is formed in a band-shaped crystal region sandwiched between the parallel crystal grain boundaries, and the drain region and the source region are defined as the active region. It is formed along the length direction of the crystal grain boundary with a layer interposed therebetween. Further, when the second active layer is provided, the second active layer is formed in a band-shaped crystal region sandwiched between the parallel crystal grain boundaries, and the drain region and the source region are formed as described above. The active layer is formed along a direction intersecting the length direction of the crystal grain boundary. When the first active layer and the second active layer are included, the first active layer and the second active layer are band-shaped sandwiched between the parallel crystal grain boundaries. Forming a drain region and a source region of the first active layer along a direction intersecting a length direction of the crystal grain boundary with the active layer interposed therebetween, A drain region and a source region of the active layer are formed along a direction intersecting a length direction of the crystal grain boundary with the active layer interposed therebetween.

  The source region and the drain region of the first active layer are formed including the crystal grain boundary and the band crystal region. The source region and the drain region of the first active layer are formed only in the band-shaped crystal region. The source region and the drain region of the second active layer are formed including the crystal grain boundary and the band-like crystal region. Further, protrusions are scattered only in the crystal grain boundaries.

The thin film transistor according to the present invention includes a semiconductor thin film made of granular crystal grains,
Band-shaped crystal grains made of crystal grains having a grain size larger than the granular crystal grains formed along one direction of the semiconductor thin film, and an active layer is formed on each of the semiconductor thin film and the band-shaped crystal grains. It is good also as a structure.

  According to the present invention, since the crystal grain boundary is not included in the active layer, high carrier mobility and high on-current can be realized.

  According to the manufacturing method and the manufacturing apparatus of the present invention, the number of crystal grain boundaries in the semiconductor thin film can be reduced, and a semiconductor thin film in which the direction of the crystal grain boundary is controlled can be manufactured. Furthermore, since the laser beam transmittance is larger than that of the zigzag pattern, the beam length can be increased, so that the laser annealing processing time per substrate can be increased by widening the scanning irradiation area once. Can be shortened. Also, by reducing the beam recess width of the concave pattern, it is possible to narrow the high density grain boundary region generated at the irradiation start position as compared with the zigzag pattern. In addition, since the front half end of the beam is a straight line perpendicular to the scanning direction, the high-density grain boundary region generated at the irradiation end position is about the crystal growth distance in one irradiation. It becomes narrower than the pattern. In addition, the concave pattern is easier in the mask manufacturing process than the zigzag pattern, and the manufacturing cost is reduced. In addition, forming the beam shape of the concave pattern does not require high resolution in the laser annealing optical system as compared with the case of forming the zigzag pattern beam shape. In addition, a TFT manufactured using the obtained semiconductor thin film can improve carrier mobility and suppress variation in mobility and threshold voltage.

  Furthermore, by improving the transmittance of the optical system, the laser annealing treatment time is shortened compared to the case of the zigzag pattern, the high density grain boundary region generated at the irradiation start position and the irradiation end position is narrowed, and the mask is manufactured. An object is to realize cost reduction and resolution reduction of an optical system for laser annealing. It is another object of the present invention to improve the operation speed of a TFT manufactured using the obtained semiconductor thin film, and suppress variations in operation speed and threshold voltage.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Laser annealing is performed using the laser annealing apparatus shown in FIG. In this figure, a precursor described later is formed on a substrate 110, and this substrate 110 is placed on a substrate stage 111 in a chamber 109. A laser oscillator 101 is disposed outside the chamber 109. The laser oscillator 101 oscillates and outputs XeCl excimer laser light (beam 102) having a wavelength of 308 nm in a pulse shape. The laser light (beam 102) is guided to the homogenizer 104 by the mirrors 103a and 103b, and is adjusted to a rectangular beam profile by the homogenizer 104. The shaped beam 102 has an optical path bent downward by the mirror 103c, and has a beam shape when irradiating the precursor of the substrate 110 through the mask 105 on the mask stage 106. Further, the beam (laser light) 102 is appropriately reduced by a reduction lens 107 and irradiated onto the surface of the precursor on the substrate 110 via a window 108 provided in the chamber 109. The substrate 110 can be moved in the direction of the arrow in FIG. 1 together with the substrate stage 111, that is, in the direction intersecting the beam 102, and the beam 102 and the substrate 110 move relative to each other, so that the beam 102 The surface is scanned in the moving direction of the substrate 110. In this apparatus, the beam 102 and the substrate 110 are relatively moved by the substrate stage 111 and the beam 102 is scanned on the surface of the substrate 110. However, the present invention is not limited to this. You may make it scan on the fixed board | substrate 110 by moving the mask stage 106 to a horizontal direction.

  The mask 105 has a transmission region that transmits laser light made of quartz and a non-transmission region that is formed of chromium on the surface of the quartz and blocks light from the laser light. Note that. For example, by forming a material that shields laser light such as aluminum, molybdenum, chromium, tungsten silicide, and stainless steel on a material that transmits laser light, and patterning the formed light shielding material into a necessary shape, It is also possible to form a non-transmissive region. Further, a transparent film such as a chromium oxide film serving as a protective film may be laminated on a light shielding film having an opening through which laser light is transmitted, and the opening may be covered with the transparent film. As the light shielding film member, a single-layer or multilayer dielectric film may be patterned. Further, the shape of the beam 102 may be shaped by using a phase shift mask instead of the light shielding mask. The above-described mask may be disposed at any position in the laser optical path from the laser oscillator 101 to the precursor.

  In the above embodiment, the XeCl excimer laser is used as the laser oscillator 101. However, the present invention is not limited to this. The laser oscillator 101 may be another excimer laser such as a KrF laser, a solid-state laser such as an Nd: YAG laser, an Nd: YLF laser, or an Nd: YVO4 laser, or a gas laser such as a carbon dioxide laser or an argon gas laser. There may be.

  In the substrate 110, an insulating film and an amorphous silicon film are sequentially formed on a glass substrate.

In the present invention, scanning irradiation is performed using a mask having a shape in which convex light-shielding patterns and concave patterns are periodically formed as shown in FIG. That is, as shown in FIG. 2A, the light-shielding film 206 is formed with a rectangular transmission portion 207 having an opening length 201 and an opening width 203. Further, the light shielding film 206 includes a comb-like convex light shielding pattern 206 a protruding into the transmission part 207. The convex light-shielding pattern 206a is a rectangle having a concave width 204 and a concave length 202, and is formed in a convex shape.The convex light-shielding pattern 206a has an opening length 201 with an interval of the convex length 205 from each other. It is formed in a line in the length direction, and a concave pattern is formed between the convex light shielding patterns 206a. The beam 306 transmitted through the light shielding film 206 shown in FIG. 2A has a beam length 301 and a beam width 303 as shown in FIG. 2B, and is opposite to the side 306a on the scanning direction (one direction) side. The side 306b is shaped into a rectangular shape having a plurality of concave patterns 306c. The concave pattern 306c has a beam convex portion length 305 and a beam width 303, and is arranged in a row on the side 306b with a beam concave portion length 302. In FIG. 2 (2), the scanning direction of the beam is indicated by an arrow.

  In FIG. 3A, amorphous silicon is used as a precursor film made of a semiconductor film formed on an insulating substrate. As shown in FIG. 3A, when the amorphous silicon 311 is irradiated with the first beam 312 (corresponding to the beam 306 in FIG. 2B), the concave pattern 312a (see FIG. 2B) of the beam 312 is irradiated. A temperature gradient is formed radially in the region of the amorphous silicon 311 irradiated with the beam 312 around the tip of the concave pattern 306c. Therefore, as shown in FIG. 3 (2), the region of amorphous silicon 311 corresponding to the tip of the concave pattern 312a includes not only the beam width direction (the direction of the beam width 303 in FIG. 2 (2)) but also the beam length. Crystal grains 313 that grow in the direction (the direction of the beam length 301 in FIG. 2B) are also formed. When irradiation with the beam 312 for the second and subsequent times is performed, crystal grains 313 are repeatedly grown using the crystal nucleus 314 formed in the amorphous silicon 311 as a seed corresponding to the tip of the concave pattern 312a. As a result, compared to the case of the conventional thin beam, wide band-like crystal grains 313 are formed in the amorphous silicon 311 starting from the tip of the concave pattern 312a.

  Further, if the size of the concave pattern 312a having the beam concave width 304 and the beam concave length 302 is equal to or smaller than the crystal grain size in the beam scanning direction and the direction intersecting this direction (vertical direction), it intersects the beam scanning direction. The band-like crystal grains 313 can be continuously arranged in the direction. At this time, it is not necessary to set the beam convex portion length 305 that is the dimension between the adjacent concave patterns 312a to be equal, and the concave patterns 312a may be appropriately arranged so as to form the band-like crystal grains 313 at desired positions. As described above, in this embodiment, as shown in FIG. 3C, the number of crystal grain boundaries 315 in the semiconductor thin film is reduced, and a semiconductor thin film in which the formation direction of the crystal grain boundaries 315 is controlled to a parallel positional relationship is manufactured. It is possible to solve the problems of the conventional thin beam.

  Further, as shown in FIG. 3 (3), dot-like projections 317 are formed along the crystal grain boundaries 315 at intervals of beam scanning steps. Therefore, in the present embodiment, a semiconductor film in which the protrusions 317 are formed in a grid pattern is obtained. When a TFT is manufactured on such a semiconductor thin film, the arrangement and number of protrusions 317 in the channel can be controlled. Therefore, a TFT manufactured with a conventional thin wire beam in which the arrangement and number of protrusions in the channel are random In comparison, variation in threshold voltage is reduced. Further, by forming the channel while avoiding the protrusion 317, variation in threshold voltage can be further suppressed. In FIG. 3 (3), three band crystal regions 318 divided by the crystal grain boundaries 315 are formed along the length direction of the parallel crystal grain boundaries 315. The band-like crystal region 318 is not limited to three rows. Each band-like crystal region 318 is formed of a single crystal.

  Furthermore, compared to the zigzag pattern, the laser beam transmittance is large, so the beam length can be increased. Therefore, the laser annealing processing time per substrate is shortened by widening the scanning irradiation area. Is done. Further, by reducing the beam recess width (beam recess width 304 in FIG. 2) of the concave pattern 312a, the high density grain boundaries generated in the amorphous silicon 311 corresponding to the irradiation start position of the beam compared to the zigzag pattern. Region 316 can be narrowed. Further, as shown in FIG. 2B, the front side 306a of the beam 306 is a straight line extending in a direction perpendicular to the scanning direction, and therefore, a high beam generated at the irradiation end position of the beam on the amorphous silicon 311. The density grain boundary region 316 is about the crystal growth distance in one irradiation. Note that the high-density grain boundary region generated at the beam irradiation end position in the case of the zigzag pattern becomes wide because it is about the sum of the scanning direction length of the zigzag pattern and the crystal growth distance in one irradiation. Further, the concave pattern 306c is easier to manufacture the mask than the zigzag pattern, and the manufacturing cost is reduced. Further, forming the concave pattern 306c of the beam 306 does not require high resolution in the laser annealing optical system as compared with the case of forming the zigzag pattern beam shape. From the above, the problems of the conventional zigzag pattern beam can be solved.

  In addition, a TFT manufactured using the obtained semiconductor thin film can improve carrier mobility and suppress variations in mobility and threshold voltage. In the present embodiment, an example in which the concave pattern 306c has a rectangular shape is shown, but the present invention is not limited to this. The concave pattern 306c may be a polygon such as a triangle, a semicircular shape, a semielliptical shape, or the like.

  In summary, the embodiment of the present invention irradiates a semiconductor thin film (311, 1603) formed on an insulating substrate (110) with a laser beam (102, 1602), and crystallizes the semiconductor thin film. It is intended for semiconductor thin film manufacturing methods for growing films. In the laser beam shaping process, a part of the laser beam irradiation pattern irradiated on the semiconductor thin film is shaped into a control pattern (concave pattern 312a). It is characterized by doing. In this case, the crystal growth may be performed by making the grain size of the semiconductor thin film different from the grain size of the crystal film.

  When shaping the irradiation pattern in which the laser beam is irradiated onto the semiconductor thin film into a rectangular shape (FIGS. 2 and 4), the irradiation pattern has a rectangular shape and has the control pattern on one side thereof. Shape it. Then, the position of the crystal grain boundary is controlled by the control pattern to grow the band-like crystal grains.

  The embodiment of the present invention is applied to either the case where the band-like crystal grains are formed on the semiconductor thin film by single shot without scanning the laser beam (102) or the case where the band-like crystal grains are formed while scanning the laser beam. can do. When scanning with a laser beam, a band-shaped crystal grain is grown by irradiating a semiconductor thin film with a laser beam of the irradiation pattern including the control pattern. In this case, the position of the crystal grain boundary is controlled by the control pattern formed on the side opposite to the side in the scanning direction of the laser beam to grow a band-like crystal grain. When scanning with a laser beam, a band-like crystal grain is formed between crystal grain boundaries whose positions are controlled each time the laser beam is irradiated, and a region sandwiched between parallel crystal grain boundaries by these band-like crystal grains. A band-like crystal region (318) is formed on the surface.

  The beam shaping mask used in the method for manufacturing a semiconductor thin film according to the embodiment of the present invention has a light shielding pattern (206a, 406a) that shields the laser beam in a part of a transmission region (transmission portion 207) that transmits the laser beam. It is set as the structure which has. When the transmission region is formed in a rectangular shape, it is formed in an opening shape having the shielding pattern on one side (FIGS. 2 and 4). The shielding pattern is formed in the shape of a convex pattern protruding from the shielding region of the laser beam toward the transmitting region.

  An opening width (opening width 203, 402) in the width direction of the transmission region (transmission portions 207, 407) is A, and a concave width (204, 403) in the width direction of the shielding pattern (206a, 406a) is B, When the maximum growth distance of the band-like crystal grains in the width direction is L, it is desirable to set these dimensional relationships to 2L ≦ A−B. Further, the concave length (202, 404) in the length direction of the shielding pattern (206a, 406a) is C, the convex length (205), which is an interval between the shielding patterns, is D, and the width direction (beam width 303) of the transmission region. , 502), when the maximum growth distance of the band-like crystal grains is L, it is desirable to set these dimensional relationships as 2L ≧ C + D.

  The opening width (203, 402) in the width direction of the transmission region is A, the recess width (204, 403) in the width direction of the shielding pattern is B, and the recess length (202, 404) in the length direction of the shielding pattern. Where C is C and the convex portion length (205), which is the interval between the shielding patterns, is D, these dimensional relationships may be set such that AB ≧ C + D.

  Next, examples that further embody the embodiment of the present invention will be described.

  Laser annealing is performed using the laser annealing apparatus shown in FIG. The method, mask and laser are as described in the description of the above embodiment. In addition, with respect to the openings and transmission portions formed in the mask, a large number of very narrow slits may be arranged as openings or the like, or a large number of holes may be densely formed as openings or the like. In these cases, the energy of the laser beam can be adjusted by changing the number of slits, the number of holes, and the density. The substrate will be described. Non-alkali glass was used as the glass substrate. An insulating film for preventing the diffusion of impurities from the glass was formed on the glass substrate. On the insulating film, an amorphous silicon film as a precursor film was formed to a thickness of 60 nm by using a low pressure chemical vapor deposition (LP-CVD) method.

  In this example, scanning irradiation was performed using a mask having the shape shown in FIG. Table 1 shows the irradiation conditions. The irradiation intensity is a value on the substrate. The step width of the laser beam scanning is a distance on the substrate scanned by the laser beam between the irradiations of the rectangular laser beams. The mask shown in FIG. 4A has a structure having a convex pattern (convex light-shielding pattern) 406a having a concave length 404 and a concave width 403 in an opening having dimensions of an opening width 402 and an opening length 401. Yes. The beam that has passed through the mask has the shape shown in FIG. That is, the beam 505 has a beam length 501 and a beam width 502, and is shaped into a shape having one concave pattern (control pattern) 505c on the side 505b opposite to the side 505a on the scanning direction (one direction) side. . The concave pattern 505c has dimensions of a beam recess length 504 and a beam recess width 503. In FIG. 4B, the beam scanning direction is indicated by an arrow. The beam size on the substrate is 1/3 of the beam size on the mask. That is, the beam width 502 is 10 μm, the beam recess length 504 is 1 μm, and the beam recess width 503 is 5 μm.

[Table 1] Example 1
Irradiation intensity (mJ / cm ² ) 600
Step width (μm) 0.5
Opening width (μm) 30
Concave length (μm) 3
Concave width (μm) 15

  FIG. 5 shows the SEM observation results after Secco etching. A band-like crystal region having a crystal growth width of 2 μm was formed in a region sandwiched between crystal grain boundaries parallel to the beam scanning direction (horizontal direction in FIG. 5). It was confirmed that the band-like crystal region corresponds to the position of the concave pattern 505c. An oblique grain boundary was formed around the band-shaped crystal grains formed in the direction intersecting the beam scanning direction with respect to the scanning direction. Further, as seen in the case of a conventional thin beam, crystal grain boundaries were randomly generated around the band-like crystal grains in the beam length direction. Since a temperature gradient is radially formed on the amorphous silicon around the position corresponding to the tip of the concave pattern 505c, crystal growth is also performed in the beam length direction (direction intersecting the beam scanning direction), and the conventional thin beam The crystal growth width of the band-like crystal grains in the beam length direction becomes longer. As described above, according to the manufacturing method according to the embodiment of the present invention, the region in the beam scanning direction is wider in the region sandwiched between the grain boundaries whose positions are controlled compared to the case of the conventional thin beam. It was confirmed that it is possible to form a band-like crystal region that grows in the length direction. The crystal growth width in the beam length direction is simply referred to as crystal growth width.

  Using the same laser annealing apparatus as in Example 1 and the mask having the shape shown in FIG. 4A, the beam recess length was changed to 1.5 μm, 3 μm, 6 μm, and 12 μm, and scanning irradiation was performed. Table 2 shows the irradiation conditions. The irradiation intensity is a value on the substrate. The step width is the distance on the substrate scanned between each irradiation. The opening width 402, recess length 404, and recess width 403 in the table are values on the mask. The beam that has passed through the mask has the shape shown in FIG. 7B on the substrate. The beam size on the substrate is 1/3 of the beam size on the mask. That is, the beam width 502 is 10 μm, the beam recess length 504 is 0.5 μm, 1 μm, 2 μm, and 4 μm, and the beam recess width 503 is 5 μm.

[Table 2]
Example 2-1 Example 2-2 Example 2-3 Example 2-4
Irradiation intensity (mJ / cm ² ) 600 600 600 600
Step width (μm) 0.5 0.5 0.5 0.5
Opening width (μm) 30 30 30 30
Concave length (μm) 1.5 3 6 12
Concave width (μm) 15 15 15 15

  FIG. 6 shows the SEM observation results after Secco etching. In the recess length of 1.5 μm (beam recess length of 0.5 μm) (Example 2-1), the band-like crystal region was formed in the scanning direction starting from the tip of the recess pattern. The crystal growth width was 1.6 μm.

  In the recess length of 3 μm (beam recess length of 1 μm) (Example 2-2), as in the case of the recess length of 1.5 μm, the band-like crystal regions were formed in regions sandwiched between parallel crystal grain boundaries. In this case, the crystal growth width of the band-like crystal grains was 2.0 μm, which was enlarged as compared with the case where the recess length was 1.5 μm.

  In the concave portion length of 6 μm (beam concave portion length of 2 μm) (Example 2-3), in the region where the concave pattern was scanned, a large number of crystal grain boundaries were generated partially and obliquely with respect to the scanning direction. As the recess length becomes wider, a large number of crystal nuclei are generated in the semiconductor thin film corresponding to the tip of the recess pattern 505c, and the temperature gradient in the beam length direction becomes gentle at the center of the recess pattern 505c in the beam length direction. This is thought to be the cause.

  In the concave portion length of 12 μm (beam concave portion length of 4 μm) (Example 2-4), the concave portion length further widened, so that the grain boundary in the beam length direction as seen with a conventional thin beam at the central portion of the concave portion beam length direction. Formed randomly.

  From the above, when the beam recess length 504 of the concave pattern 505c is set to be equal to or less than the beam recess width 503 where the crystal growth width of the band-shaped crystal grains is maximum, a band-shaped crystal region in which the grain boundary position is well controlled is formed. be able to.

  Under the irradiation conditions of this example, when the beam recess length 504 is set to 3 μm (beam recess width 503; 1 μm) or less, a band-like crystal region in which the grain boundary position is well controlled can be formed. A TFT with high mobility and small performance variation can be manufactured. However, since the preferable beam recess length also changes if the film thickness of the precursor film, the film forming method, the beam irradiation intensity, or the resolution of the optical system changes, the beam recess length may be appropriately designed according to the conditions.

  Scanning irradiation was performed using the same laser annealing apparatus as in Example 1 and a mask having a shape in which concave patterns 306c were periodically formed as shown in FIG. Table 3 shows the irradiation conditions. The irradiation intensity is a value on the substrate. The step width is the distance on the substrate scanned between each irradiation. The opening width 204, the concave portion length 202, the concave portion width 204, and the convex portion length 205 in the table are values on the mask. The beam that has passed through the mask has the shape shown in FIG. 2B on the substrate. The beam size on the substrate is 1/3 of the beam size on the mask. That is, the beam width 303 is 6 μm, the beam concave portion length 302 is 1 μm, the beam concave portion width 304 is 3 μm, and the beam convex portion length 305 is 1 μm.

[Table 3] Example 3
Irradiation intensity (mJ / cm ² ) 600
Step width (μm) 0.2
Opening width (μm) 18
Concave length (μm) 3
Concave width (μm) 9
Convex length (μm) 3

  FIG. 7A shows the SEM observation result after Secco etching. A band-shaped crystal region having a crystal growth width of 2 μm was formed in parallel to the scanning direction from the tip of each concave pattern. When the results of FIG. 5 (Example 1) and FIG. 7 (1) (Example 3) are compared, no change is observed in the size and crystal state of the band-like crystal region. It can be said that even if the concave patterns are arranged periodically, there is no effect on the crystal state of the band-like crystal grains formed. Furthermore, band-like crystal regions can be formed side by side in a region sandwiched between parallel crystal grain boundaries, and a plurality of band-like crystal regions can be formed by a single scanning irradiation. In this embodiment, an example of a periodic pattern is shown. However, it is not necessary to form the concave pattern at equal intervals, and it may be designed as appropriate so as to form a band-like crystal region at a desired position. These band-like crystal regions along the length direction of the crystal grain boundaries are formed from band-like crystal grains grown in a direction crossing the length direction of the crystal grain boundaries (beam scanning direction).

  Using the same laser annealing apparatus as in Example 1 and a mask having a shape in which concave patterns are periodically formed as shown in FIG. 2A, the projection length was changed to 6 μm and 3 μm, and scanning irradiation was performed. . Table 4 shows the irradiation conditions. The irradiation intensity is a value on the substrate. The step width is the distance on the substrate scanned between each irradiation. The opening width 203, concave portion length 202, concave portion width 204, and convex portion length 205 in the table are values on the mask. The beam that has passed through the mask has the shape shown in FIG. 2B on the substrate. The beam size on the substrate is 1/3 of the beam size on the mask. That is, the beam width 303 is 10 μm, the beam concave portion length 302 is 1 μm, the beam concave portion width 304 is 5 μm, and the beam convex portion length 305 is 1 μm and 2 μm.

[Table 4]
Example 4-1 Example 4-2
Irradiation intensity (mJ / cm ² ) 600 600
Step width (μm) 1 1
Opening width (μm) 30 30
Concave length (μm) 3 3
Concave width (μm) 15 15
Convex length (μm) 6 3

  FIG. 7B shows the SEM observation result after Secco etching. In the convex part length 6 μm (beam convex part length 2 μm) (Example 4-1), the band-like crystal grains grown from the tip of the beam concave part are formed at a period of 3 μm in the direction perpendicular to the beam scanning direction. A large number of parallel grain boundaries were generated. As shown in Example 2-2, the crystal growth width of the band-like crystal grains with the recess length of 3 μm (beam recess length of 1 μm) is approximately 2 μm. It is considered that a large number of crystal grain boundaries were generated because the period of the concave pattern was longer than the crystal growth width of the band-like crystal grains.

  In the convex part length of 3 μm (beam convex part length of 1 μm) (Example 4-2), the many crystal grain boundaries formed in Example 4-1 disappear, and the band-like crystal grains having a crystal growth width of 2 μm are perpendicular to the scanning direction. It was formed with a period of 2 μm continuously in the direction. This is presumably because the period of the concave pattern was less than the crystal growth width of the band-like crystal grains.

  From the above results, if the period of the concave pattern in the beam planar shape on the precursor film is less than or equal to the length of the crystal growth width of the band-shaped crystal grains, the band-shaped crystal grains are continuous in the direction perpendicular to the scanning direction. The band-like crystal region can be efficiently formed in a region sandwiched between parallel crystal grain boundaries. Further, when a TFT having a channel length and channel width longer than the crystal growth width of the band-shaped crystal grains can be manufactured without including many crystal grain boundaries in the channel, the TFT has high mobility and small performance variation. It can be made.

  Using the same laser annealing apparatus as in Example 1 and a mask having a shape in which a concave pattern is periodically formed as shown in FIG. 2A, the concave width is changed to 15 μm, 9 μm, and 3 μm, and scanning irradiation is performed. went. Table 5 shows the irradiation conditions. The irradiation intensity is a value on the substrate. The step width is the distance on the substrate scanned between each irradiation. The opening width 203, concave portion length 202, concave portion width 204, and convex portion length 205 in the table are values on the mask. The beam that has passed through the mask has the shape shown in FIG. 2B on the substrate. The beam size on the substrate is 1/3 of the beam size on the mask. That is, the beam width 303 is 8 μm and 6 μm, the beam recess length 302 is 1 μm, the beam recess width 304 is 3 μm, 1 μm, and the beam protrusion length is 1 μm.

[Table 5]
Example 5-1 Example 5-2
Irradiation intensity (mJ / cm ² ) 600 600
Step width (μm) 1 1
Opening width (μm) 24 18
Concave length (μm) 3 3
Concave width (μm) 9 3
Convex length (μm) 3 3

  FIG. 8 (1) shows the SEM observation results after Secco etching. In Example 5-2 (recess width 3 μm (beam recess width 1 μm)), more crystal grain boundaries were formed than in Example 5-1 (recess width 9 μm (beam recess width 3 μm)). This is considered to be because the effect of forming the band-like crystal grains by the concave pattern was reduced because the width of the concave portion was shorter than that of Example 5-1.

  From the above results, if the recess width is greater than or equal to the recess width that maximizes the crystal growth width of the band-like crystal grains, that is, if the recess width is 9 μm (beam recess width of 3 μm) or more in the irradiation conditions of this embodiment A band-like crystal region in which the grain boundary position is well controlled can be formed, and this makes it possible to manufacture a TFT with high mobility and small performance variation. However, if the film thickness of the precursor film, the film forming method, the irradiation intensity of the beam, or the resolution of the optical system changes, the preferable beam recess length also changes. Therefore, the beam recess length may be appropriately designed according to the conditions.

  Scanning irradiation was performed using the same laser annealing apparatus as in Example 1 and a mask having a shape in which a concave pattern was periodically formed as shown in FIG. Table 6 shows the irradiation conditions. The irradiation intensity is a value on the substrate. The step width is the distance on the substrate scanned between each irradiation. The opening width 203, concave portion length 202, concave portion width 204, and convex portion length 205 in the table are values on the mask. The beam that has passed through the mask has the shape shown in FIG. 2B on the substrate. The beam size on the substrate is 1/3 of the beam size on the mask. That is, the beam width 303 is 6 μm, the beam concave portion length 302 is 1 μm, the beam concave portion width 304 is 1 μm, and the beam convex portion length 305 is 1 μm.

[Table 6] Example 6
Irradiation intensity (mJ / cm ² ) 600
Step width (μm) 1
Opening width (μm) 18
Concave length (μm) 3
Concave width (μm) 3
Convex length (μm) 3

  Under the irradiation conditions of this example, even when the recess width is 3 μm (beam recess width 1 μm), the crystal grain boundary position is well controlled, that is, a band-like crystal region is formed in a region sandwiched between parallel crystal grain boundaries. be able to. In the present example, it has been found that even when the beam recess width is as small as 1 μm, band-like crystal grains can be formed in the direction intersecting the length direction of the crystal grain boundaries. Thereby, although the band-like crystal grains can be formed at a desired position, the device transmittance equivalent to that of the conventional thin beam can be realized. In addition, the high density grain boundary region can be narrowed at the scanning start position and the end position. At this time, the transmittance of the mask was 62% (laser transmittance 9%). Further, the transmittance of the zigzag pattern mask at an angle of 60 ° was 43% (laser transmittance 6%). From this, it is apparent that the pattern according to the present invention has a high transmittance of laser light, so that the beam length can be increased and processing can be performed in a short time.

  Using the same laser annealing apparatus as in Example 1 and a mask having a shape in which a concave pattern is periodically formed as shown in FIG. 2A, scanning irradiation is performed over 300 μm, and the direction perpendicular to the scanning direction A polycrystalline region in which band-like crystal grains having a crystal growth width of 2 μm were continuously arranged was formed. Table 7 shows the irradiation conditions. The irradiation intensity is a value on the substrate. The step width is the distance on the substrate scanned between each irradiation. The opening width 203, concave portion length 202, concave portion width 204, and convex portion length 205 in the table are values on the mask. The beam that has passed through the mask has the shape shown in FIG. 2B on the substrate. The beam size on the substrate is 1/3 of the beam size on the mask. That is, the beam width 303 is 6 μm, the beam concave portion length 302 is 1 μm, the beam concave portion width 304 is 3 μm, and the beam convex portion length 305 is 1 μm.

[Table 7] Example 7
Irradiation intensity (mJ / cm ² ) 600
Step width (μm) 1
Opening width (μm) 30
Concave length (μm) 3
Concave width (μm) 15
Convex length (μm) 3

  As described in the embodiment, the obtained semiconductor thin film had protrusions 317 formed only on the crystal grain boundaries 315 in a grid pattern as shown in FIG. A thin film transistor was manufactured using the semiconductor thin film obtained by the example of the present invention shown in FIG. Specifically, as shown in FIG. 9 (1), the semiconductor thin film according to the embodiment of the present invention has a crystal grain boundary 603 formed in parallel along the scanning direction in which the laser beam is scanned. A single crystal region (band crystal region) 602 is formed in the region sandwiched by the boundaries 603 along the scanning direction. This indicates that according to the embodiment of the present invention, the positions of the crystal grain boundaries 603 are controlled, and these crystal grain boundaries 603 are formed in parallel with the scanning direction of the laser beam.

As shown in FIG. 9A, an island 601 is formed in a region including the single crystal regions 602, 602a, and 602b and the crystal grain boundary 603. The island 601 was formed in a rectangular shape having a length of 10 μm in the scanning direction and a length of 4 μm in the direction orthogonal to the scanning direction. Further, as shown in FIG. 9B, the single crystal region 602 sandwiched between the crystal grain boundaries 603 is used as an active layer, and carriers move in the active layer (602) in the laser beam scanning direction. Therefore, a drain region 703 and a source region 701 are formed in the scanning direction across the active layer (602). Then, a contact 704 that connects a drain electrode (not shown) and the drain region 703 is formed on an insulating film (not shown). Similarly, a contact 705 for connecting a source electrode (not shown) and the source region 701 is formed on an insulating film (not shown). A gate electrode 702 was formed. As a result, the carrier moving direction was the scanning direction, and an n-type TFT and a p-type TFT having a channel length of 4 μm and a channel width of 4 μm of the active layer 602 were fabricated. The carrier mobility in the obtained TFT was 410 cm ² / Vs for n-type and 150 cm ² / Vs for p-type. The variation in threshold voltage for 100 n-type TFTs was 0.2V.

  Here, for comparison, using the same laser annealing apparatus as in Example 1, using a fine line pattern mask without a concave pattern (opening length 270 μm (90 μm on the substrate), opening width 9.9 μm (on the substrate) 3.3 μm)) The shaped beam was scanned for a length of 300 μm to produce a polycrystalline film.

The semiconductor thin film obtained by the comparative example had protrusions formed randomly. The irradiation intensity is 600 mJ / cm ² on the substrate, and the step width is 0.2 μm on the substrate. An n-type TFT and a p-type TFT having a channel length of 4 μm and a channel width of 4 μm were prepared by using this polycrystal as an active layer and providing a channel so that carriers move in parallel with the scanning direction. Mobility of the TFT is an n-type is 320cm ² / Vs, p-type was 120 cm ² / Vs. The variation in threshold voltage for 100 n-type TFTs was 1V.

  From the mobility comparison of the above two types of TFTs, it is clear that a TFT satisfying the requirements of the present invention can provide higher mobility than a TFT manufactured by a conventional thin beam, and the present invention provides high performance. TFTs can be provided. In addition, according to the TFT satisfying the requirements of the present invention, it is possible to obtain a TFT having a small variation in threshold voltage as compared with a TFT using a semiconductor thin film having a random protrusion manufactured by a conventional thin beam. Clearly, the present invention can provide a high-performance TFT.

  Using the same laser annealing apparatus as in Example 1 and a mask having a shape in which concave patterns are periodically formed as shown in FIG. 2A, scanning irradiation is performed over 300 μm, and the direction perpendicular to the scanning direction A band-like crystal grain having a crystal growth width of 2 μm arranged continuously was prepared. Table 7 shows the irradiation conditions. The irradiation intensity is a value on the substrate. The step width is the distance on the substrate scanned between each irradiation. The opening width, recess length, recess width, and protrusion length in the table are values on the mask. The beam that has passed through the mask has the shape shown in FIG. 2B on the substrate. The beam size on the substrate is 1/3 of the beam size on the mask. That is, the beam width 303 is 6 μm, the beam concave portion length 302 is 1 μm, the beam concave portion width 304 is 3 μm, and the beam convex portion length 305 is 1 μm.

  As described in the embodiment, the obtained semiconductor thin film had protrusions 317 formed only on the crystal grain boundaries 315 in a grid pattern as shown in FIG. A thin film transistor was manufactured using the semiconductor thin film obtained by the example of the present invention shown in FIG. Specifically, as shown in FIG. 10 (1), the semiconductor thin film according to the embodiment of the present invention has a crystal grain boundary 803 formed in parallel along the scanning direction in which the laser beam is scanned. A single crystal region (band crystal region) 802 is formed in the region sandwiched between the boundaries 803 along the scanning direction. This indicates that according to the embodiment of the present invention, the positions of the crystal grain boundaries 803 are controlled, and these crystal grain boundaries 803 are formed in parallel with the scanning direction of the laser beam.

  As shown in FIG. 10A, an island 801 is formed only in the single crystal region 802 sandwiched between the crystal grain boundaries 803. 9 is different from that of FIG. 9 in that the island 801 is formed avoiding the single crystal regions 802a and 802b and the crystal grain boundaries 803. The island 801 was formed in a rectangular shape having a length of 5 μm in the scanning direction and a length of 4 μm in a direction orthogonal to the scanning direction. Further, as shown in FIG. 10B, the single crystal region 802 sandwiched between the crystal grain boundaries 803 is used as an active layer, and carriers move in the active layer (802) in the laser beam scanning direction. Therefore, a drain region 903 and a source region 902 are formed in the scanning direction with the active layer (802) interposed therebetween. Then, a contact 904 for connecting a drain electrode (not shown) and the drain region 903 was formed on an insulating film (not shown). Similarly, a contact 905 for connecting a source electrode (not shown) and the source region 902 is formed on an insulating film (not shown). Then, the carrier movement direction was the scanning direction, and an n-type TFT and a p-type TFT having a channel length of 1.4 μm and a channel width of 1.4 μm of the active layer 802 were fabricated.

Mobility of carriers in the obtained TFT is n-type is 520cm ² / Vs, p-type was 200 cm ² / Vs. Here, in order to form a channel in the band-shaped single crystal region 802 having a crystal grain width of 2 μm, the channel width is desirably 2 μm or less, preferably 1.8 μm or less. The variation in threshold voltage for 100 n-type TFTs was 0.2V.

  Here, for comparison, using the same laser annealing apparatus as in Example 1, using a fine line pattern mask without a concave pattern (opening length 270 μm (90 μm on the substrate), opening width 9.9 μm (on the substrate) 3.3 μm)) The shaped beam was scanned for a length of 300 μm to produce a polycrystalline film.

The semiconductor thin film obtained by the comparative example had protrusions formed randomly. The irradiation intensity is 600 mJ / cm ² on the substrate, and the step width is 0.2 μm on the substrate. A channel was provided so that carriers moved in parallel with the scanning direction, and an n-type TFT and a p-type TFT having a channel length of 1.4 μm and a channel width of 1.4 μm were manufactured. Since the grain boundary position was not controlled, there was a grain boundary in the channel. Mobility of the resulting TFT has n-type is 320cm ² / Vs, p-type was 120 cm ² / Vs. The variation in threshold voltage for 100 n-type TFTs was 0.15V.

  From the mobility comparison of the above two types of TFTs, it is clear that a TFT satisfying the requirements of the present invention can provide a TFT with higher mobility than conventional TFTs, and the present invention provides a high-performance TFT. be able to. In addition, since the mobility is higher than that of the TFT shown in Example 7, it is apparent that a higher performance TFT can be obtained by forming a channel in the band-like crystal grains in the present invention. . In addition, according to the TFT satisfying the requirements of the present invention, it is possible to obtain a TFT having a small variation in threshold voltage as compared with a TFT using a semiconductor thin film having a random protrusion manufactured by a conventional thin beam. Clearly, the present invention can provide a high-performance TFT.

  Using the same laser annealing apparatus as in Example 1, scanning irradiation is performed over 300 μm using a mask having a shape in which concave patterns are periodically formed as shown in FIG. 2A, and is perpendicular to the scanning direction. Band-like crystal grains having a crystal growth width of 2 μm continuously arranged in various directions were produced. Table 7 shows the irradiation conditions. The irradiation intensity is a value on the substrate. The step width is the distance on the substrate scanned between each irradiation. The opening width 203, concave portion length 202, concave portion width 204, and convex portion length 205 in the table are values on the mask. The beam that has passed through the mask has the shape shown in FIG. 2B on the substrate. The beam size on the substrate is 1/3 of the beam size on the mask. That is, the beam width 303 is 6 μm, the beam concave portion length 302 is 1 μm, the beam concave portion width 304 is 3 μm, and the beam convex portion length 305 is 1 μm.

  As described in the examples, the obtained semiconductor thin film had protrusions 317 formed only on the crystal grain boundaries 315 in a grid pattern as shown in FIG. A thin film transistor was manufactured using the semiconductor thin film obtained by the example of the present invention shown in FIG. More specifically, as shown in FIG. 11 (1), the semiconductor thin film according to the embodiment of the present invention has crystal grain boundaries 1003 formed in parallel along the scanning direction in which the laser beam is scanned. A single crystal region (band crystal region) 1002 is formed in the region sandwiched by the boundaries 1003 along the scanning direction. This indicates that according to the embodiment of the present invention, the positions of the crystal grain boundaries 1003 are controlled, and these crystal grain boundaries 1003 are formed in parallel with the scanning direction of the laser beam.

  As shown in FIG. 11A, an island 1001 is formed in a region including single crystal regions 1002, 1002a, 1002b and a crystal grain boundary 1003. The island 1001 was formed in a rectangular shape having a length of 4 μm in the scanning direction and a length of 5 μm in a direction orthogonal to the scanning direction. Further, as shown in FIG. 11B, the single crystal region 1002 sandwiched between the crystal grain boundaries 1003 is used as an active layer, and carriers move in the active layer (1002) in a direction perpendicular to the scanning direction of the laser beam. Like that. Therefore, a drain region 1102 and a source region 1101 are formed in a direction perpendicular to the scanning direction with the active layer (1002) interposed therebetween. Then, a contact 1105 for connecting a drain electrode (not shown) and the drain region 1102 was formed on an insulating film (not shown). Similarly, a contact 1104 that connects a source electrode (not shown) and the source region 1101 was formed on an insulating film (not shown). A gate electrode 1103 was formed. As a result, the carrier movement direction was perpendicular to the scanning direction, and an n-type TFT and a p-type TFT having a channel length of 1.4 μm and a channel width of 4 μm of the active layer 1002 were fabricated.

Mobility of the resulting TFT has n-type is 520cm ² / Vs, p-type was 200 cm ² / Vs. Here, in order to form a channel in the grain of a band-like crystal grain having a crystal grain width of 2 μm, the channel length is desirably 2 μm or less, preferably 1.8 μm or less. The variation in threshold value for 100 n-type TFTs was 0.15V.

Here, for comparison, using the same laser annealing apparatus as in Example 1, using a fine line pattern mask without a concave pattern (opening length 270 μm (90 μm on the substrate), opening width 9.9 μm (on the substrate) 3.3 μm)) The shaped beam was scanned for a length of 300 μm to produce a polycrystalline film. Protrusions were randomly formed on the obtained semiconductor thin film. The irradiation intensity is 600 mJ / cm ² on the substrate, and the step width is 0.2 μm on the substrate.

A channel was provided so that carriers moved in parallel with the scanning direction, and an n-type TFT and a p-type TFT having a channel length of 1.4 μm and a channel width of 4 μm were manufactured. Since the grain boundary position was not controlled, there was a grain boundary in the channel so as to block carrier movement. Mobility of the resulting TFT has n-type is 150cm ² / Vs, p-type was 100 cm ² / Vs. The variation in threshold voltage for 100 n-type TFTs was 0.15V.

  From the mobility comparison of the above two types of TFTs, it is clear that a TFT satisfying the requirements of the present invention can provide a TFT with higher mobility than conventional TFTs, and the present invention provides a high-performance TFT. be able to. Since the mobility is higher than that of the TFT shown in Example 7, when the crystal growth width is longer than the channel length and shorter than the channel width as in this example, the carrier traveling direction is the scanning direction. If the TFT is designed to be in a vertical direction, a channel can be formed in the band-like crystal, and a higher performance TFT can be obtained. In addition, according to the TFT satisfying the requirements of the present invention, it is possible to obtain a TFT having a small variation in threshold voltage as compared with a TFT using a semiconductor thin film having a random protrusion manufactured by a conventional thin beam. Clearly, the present invention can provide a high-performance TFT.

An insulating film was formed on the alkali-free glass, and an amorphous silicon film 1601 was formed on the insulating film by a reduced pressure chemical vapor deposition method to a thickness of 60 nm. Then, as shown in FIGS. 12A and 12B, the amorphous silicon film 1601 is scanned with a beam 1602 of XeCl excimer laser at an energy density of 360 mJ / cm ² and a step width of 50 μm. Granular polycrystalline silicon having a diameter of 0.1 to 1 μm was formed. The granular crystal grains are small-diameter crystal grains compared to the band-shaped crystal grains described later, and in this specification, the granular crystal grains are referred to as granular crystal grains 1603 in order to be distinguished from the band-shaped crystal grains. In this embodiment, an XeCl excimer laser is used, but the laser used may be another excimer laser such as a KrF laser, and may be an Nd: YAG laser, an Nd: YLF laser, an Nd: YVO4 laser, or the like. A gas laser such as a solid-state laser, a carbon dioxide gas laser, or an argon gas laser may be used.

  Next, in a region where high mobility is required, for example, in a drive circuit region in an image display device including an active matrix substrate, a mask having a shape in which concave patterns shown in FIG. As shown in FIGS. 12 (3) and 12 (4), the scanning growth of the beam 1604 is selectively performed, and the crystal growth width as shown in FIG. 12 (4) continuously arranged in the direction perpendicular to the scanning direction. 2 μm band-like crystal grains 1605 were produced.

  The irradiation conditions at this time are as shown in Table 7. The irradiation intensity is a value on the substrate. The step width is the distance on the substrate scanned between each irradiation. The opening width 203, concave portion length 202, concave portion width 204, and convex portion length 205 in the table are values on the mask in FIG. The beam that has passed through the mask has the shape shown in FIG. 2B on the substrate. The beam size on the substrate is 1/3 of the beam size on the mask. That is, in FIG. 2B, the beam width 303 is 6 μm, the beam concave portion length 302 is 1 μm, the beam concave portion width 304 is 3 μm, and the beam convex portion length 305 is 1 μm.

  Next, after the substrate is rotated by 90 degrees, as shown in FIGS. 12 (5) and 12 (6), a mask having a shape in which the concave pattern shown in FIG. 2 (1) is periodically formed is used. Scanning irradiation was performed. The irradiation conditions are as shown in Table 7. Note that irradiation may be performed by rotating the scanning direction by 90 degrees without rotating the substrate by 90 degrees.

A TFT was fabricated using the obtained granular crystal grains 1603 and band-shaped crystal grains 1605 as an active layer. In the TFT using the band-like crystal grain 1605, the channel direction and the scanning direction were made parallel. As a result, 520cm ² / Vs, high mobility of 200 cm ² / Vs at the p-type was obtained at n-type. High mobility can be obtained regardless of whether the channel direction of the TFT using the band-like crystal grain 1605 as the active layer is the scanning direction or the direction perpendicular to the scanning direction. Therefore, the laser scanning direction and the TFT channel direction may be appropriately designed.

  In this way, by selectively performing the beam scanning irradiation having the concave pattern that needs to reduce the step width to the region that requires high mobility, compared with the case where the entire surface of the substrate is irradiated, The processing speed can be improved.

  The thin film transistor according to the embodiment of the present invention described above will be summarized. A thin film transistor according to an embodiment of the present invention has a band-like crystal region (602, 802, 1002) formed in a region sandwiched between parallel crystal grain boundaries (603, 803, 1003), and the moving direction of the carrier At least one of the first active layer set in the length direction of the crystal grain boundary and the second active layer set in the direction crossing the crystal grain boundary in the carrier movement direction. The single crystal film is formed.

  In the case of having the first active layer, the drain region (703, 903) and the source region (701, 902) of the first active layer have the crystal grain boundary sandwiching the active layer. It is formed along the length direction of (603, 803). In this case, the source region and the drain region of the first active layer are formed including the crystal grain boundary and the band-like crystal region. Alternatively, the source region and the drain region of the first active layer are formed only within the region of the band-shaped crystal region.

  In the case of having the second active layer, the drain region (1102) and the source region (1101) of the second active layer have the crystal grain boundary (1003) sandwiched between the active layers. It is formed along the direction intersecting the length direction. In this case, the source region and the drain region of the second active layer are formed including the crystal grain boundary and the band crystal region.

  In the case where the first active layer and the second active layer are included, the drain region and the source region of the first active layer have a length of the crystal grain boundary across the active layer. The drain region and the source region of the second active layer are formed along a direction intersecting the length direction of the crystal grain boundary with the active layer interposed therebetween. The

  A thin film transistor according to an embodiment of the present invention includes a semiconductor thin film (1603) made of granular crystal grains, and a belt-like shape made of crystal grains having a grain size larger than the granular crystal grains formed along one direction of the semiconductor thin film. And an active layer may be formed on each of the semiconductor thin film and the band-shaped crystal grains.

It is a figure which shows the laser annealing apparatus which concerns on this invention. FIG. 2 (1) is a plan view showing a first example of a mask according to the present invention, and FIG. 2 (2) is a plan view showing its beam shape. It is a figure which shows the laser annealing process which concerns on this invention, and a process progresses in order of Fig.3 (1)-(3). FIG. 4A is a plan view showing a second example of the mask according to the present invention, and FIG. 4B is a plan view showing the beam shape. 2 is a diagram showing an SEM image of the surface of a polycrystalline film formed in Example 1. FIG. 6 is a diagram showing an SEM image of the surface of a polycrystalline film formed in Example 2. FIG. FIG. 7 (1) is a diagram showing an SEM image of the surface of the polycrystalline film formed in Example 3, and FIG. 7 (2) is a diagram showing an SEM image of the surface of the polycrystalline film formed in Example 4. is there. FIG. 8A is a diagram showing an SEM image of the surface of the polycrystalline film formed in Example 5, and FIG. 8B is a diagram showing an SEM image of the surface of the polycrystalline film formed in Example 6. is there. FIG. 9A is a schematic diagram of the surface of the polycrystalline film formed in Example 7, and FIG. 9B is a schematic diagram showing the TFT of Example 7. FIG. 10A is a schematic view of the surface of the polycrystalline film formed in Example 8, and FIG. 10B is a diagram showing the TFT in Example 8. FIG. 11 (1) is a schematic view of the surface of the polycrystalline film formed in Example 9, and FIG. 11 (2) is a diagram showing the TFT in Example 9. FIG. 12 is a plan view showing Example 10, and the process proceeds in the order of FIGS. It is sectional drawing which shows the manufacturing process of the conventional TFT, and a process progresses in order of FIG. 13 (1)-(3). It is a top view which shows the laser annealing process of 1st prior art, and a process progresses in order of FIG. 14 (1)-(5). FIG. 15A is a plan view showing the mask of the second prior art, and FIG. 15B is a schematic view of the surface of the polycrystalline film of the second prior art.

Explanation of symbols

101 laser oscillator
102 beam
103 mirror
104 Homogenizer
105 mask
106 Mask stage
107 Reduction lens
108 windows
109 chamber
110 substrates
111 Substrate stage
201, 401 Opening length
202, 404 Concave length
203, 402 Opening width
204, 403 Recess width
205 Convex length
206,405 Shading part
207,406 Transmission part
301, 501 Beam length
302,504 Beam recess length
303,502 Beam width
304, 503 Beam recess width
305 Beam convex length
306, 505 beam
601, 801, 1001 island
602, 802, 1002 Band crystal region
603, 803, 1003 Grain boundary
701, 902, 1101 source
702, 901, 1103 Gate
703, 903, 1102 drain
704, 904, 1104 contacts

Claims (21)

In a method of manufacturing a semiconductor thin film in which a semiconductor thin film formed on an insulating substrate is irradiated with a laser beam to grow crystal grains in the semiconductor thin film,
In the laser beam shaping step, a semiconductor thin film manufacturing method is characterized in that an irradiation pattern of a laser beam irradiated on the semiconductor thin film is shaped into a rectangular shape having a control pattern on one side thereof. Method.   2. The method of manufacturing a semiconductor thin film according to claim 1, wherein band-like crystal grains are grown on the semiconductor thin film while controlling a position of a crystal grain boundary according to the control pattern.   By irradiating the semiconductor thin film with a laser beam having the irradiation pattern including the control pattern while scanning with a laser beam, a band-shaped crystal region composed of band-shaped crystal grains is formed in a region sandwiched between parallel crystal grain boundaries. The method for producing a semiconductor thin film according to claim 1.   4. The method of manufacturing a semiconductor thin film according to claim 3, wherein the laser beam is shaped by forming the control pattern on a side opposite to the side in the scanning direction of the laser beam.   The method for manufacturing a semiconductor thin film according to claim 1, wherein the control pattern is shaped into a concave shape.   6. The semiconductor according to claim 5, wherein the length of the beam concave portion in the length direction of the control pattern is set to be equal to or smaller than the width of the beam concave portion in the width direction of the control pattern that maximizes the crystal growth width of the band-like crystal grains. Thin film manufacturing method.   6. The semiconductor thin film according to claim 5, wherein the width of the beam recess in the width direction of the control pattern is set to be equal to or greater than the width of the beam recess in the width direction of the control pattern that maximizes the crystal growth width of the band-like crystal grains. Manufacturing method.   2. The method of manufacturing a semiconductor thin film according to claim 1, wherein at least one of the control patterns is shaped on the one side.   9. The method of manufacturing a semiconductor thin film according to claim 8, wherein a period for shaping the control pattern is set to be equal to or shorter than a crystal growth width of the band-like crystal grains.   The semiconductor thin film made of granular crystal grains is irradiated with a laser beam having an irradiation pattern having the control pattern, and band-like crystal grains made of crystal grains larger than the crystal grains of the semiconductor thin film are grown on the semiconductor thin film. The method for producing a semiconductor thin film according to claim 1. In a beam shaping mask for shaping a laser beam for growing crystal grains in a semiconductor thin film,
The mask body is characterized in that the mask body is formed with a transmission region transmitting a laser beam in a rectangular shape and having an opening shape having a shielding pattern on one side thereof.   12. The beam shaping mask according to claim 11, wherein the shielding pattern is formed in the shape of a convex pattern protruding from the laser beam shielding region toward the transmission region.   13. The beam shaping mask according to claim 12, wherein the length of the concave portion in the length direction of the shielding pattern is set to be equal to or smaller than the width of the concave portion of the shielding pattern that maximizes the crystal growth width of the band-like crystal grains.   13. The beam shaping mask according to claim 12, wherein the width of the concave portion in the width direction of the shielding pattern is set to be equal to or larger than the width of the concave portion of the shielding pattern that maximizes the crystal growth width of the band-like crystal grains.   The beam shaping mask according to claim 11, wherein at least one shielding pattern is provided.   The beam shaping mask according to claim 15, wherein the shielding pattern is provided periodically.   The beam shaping mask according to claim 11, wherein a period of the shielding pattern is set to be equal to or shorter than a crystal growth width of the band-shaped crystal grains.   When the opening width in the width direction of the transmission region is A, the recess width in the width direction of the shielding pattern is B, and the maximum crystal growth distance of the band-like crystal grains in the width direction is L, these dimensional relationships are 2L. The beam shaping mask according to claim 11, wherein ≦ A−B is set.   When the length of the concave portion in the length direction of the shielding pattern is C, the length of the convex portion that is an interval between the shielding patterns is D, and the maximum crystal growth distance of the band-like crystal grains in the width direction of the transmission region is L, The beam shaping mask according to claim 11, wherein the dimensional relationship is set to a relationship of 2L ≧ C + D.   The opening width in the width direction of the transmission region is A, the recess width in the width direction of the shielding pattern is B, the recess length in the length direction of the shielding pattern is C, and the projection length that is an interval between the shielding patterns is D. 12. The beam shaping mask according to claim 11, wherein the dimensional relationship is set to a relationship of AB ≧ C + D. In a semiconductor thin film manufacturing apparatus in which a precursor film made of a semiconductor thin film formed on an insulating substrate is irradiated with a laser beam to grow crystal grains on the precursor film,
A beam shaping mask for shaping the laser beam;
2. The semiconductor thin film manufacturing apparatus according to claim 1, wherein the beam shaping mask is formed by forming a transmission region that transmits a laser beam into a rectangular shape having an opening shape having a shielding pattern on one side thereof.

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