JP2007299911A - Method of manufacturing semiconductor film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor film which is planarized without increasing manufacturing processes and manufacturing time. <P>SOLUTION: The manufacture method of the semiconductor film includes a process to prepare an amorphous semiconductor film, a process to crystallize to obtain a crystalline semiconductor film by irradiating a crystallizing laser beam to at least a part of the amorphous semiconductor film, and a process to planarize a surface of the crystalline semiconductor film by irradiating a planarizing laser beam to the crystalline semiconductor film continuously from the crystallizing process. The planarizing process includes the first planarizing process and the second planarizing process, wherein in the first planarizing process, the first planarizing laser beam is irradiated to a plurality of first unit regions of the crystalline semiconductor film, while in the second planarizing process, the second planarizing laser beam is irradiated to a plurality of second unit regions in which at least a part is different from the first unit regions of each of the crystalline semiconductor films. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a semiconductor film, and more particularly to a method for manufacturing a semiconductor film using a laser beam.

  In recent years, semiconductor elements typified by thin film transistors (hereinafter sometimes referred to as “TFTs”) and diodes have been widely used. The TFT uses, as an active layer, a semiconductor film with a thickness of several tens to several hundreds of nanometers formed on an insulating substrate by using a CVD (Chemical Vapor Deposition) method, for example. As an application field of TFT, there is an active matrix type liquid crystal display device. In an active matrix liquid crystal display device, one or more TFTs are arranged in each of hundreds of thousands or more of pixel electrodes arranged in rows and columns (matrix), and the amount of electric charge supplied to the pixel electrodes Is controlled by the TFT.

  An amorphous semiconductor film, which is one of the semiconductor films, can be easily manufactured. However, since the amorphous semiconductor film has low carrier mobility, an amorphous semiconductor film is used for a TFT that requires high-speed operation. A crystalline semiconductor film capable of realizing higher carrier mobility is preferably used. Examples of the crystalline semiconductor film include a polycrystalline semiconductor film and a microcrystalline semiconductor film.

  A crystalline semiconductor film is obtained by crystallizing an amorphous semiconductor film. For example, a crystalline semiconductor film can be obtained in a very short time by melting and solidifying an amorphous semiconductor film by irradiating a laser beam.

  However, since a crystalline semiconductor film having sufficient characteristics may not be obtained by only irradiating the amorphous semiconductor film with the laser beam once, a method of irradiating the laser beam twice has been proposed ( For example, Patent Documents 1 and 2).

  Patent Document 1 discloses that laser beam irradiation is performed twice in order to manufacture a crystalline silicon film including a large number of crystal grains with <100> orientation suitable for TFTs having high mobility. In the method disclosed in Patent Document 1, the amorphous silicon film having a thickness of 50 nm is irradiated with a laser beam and then further irradiated with a continuous wave laser beam, which is suitable for a TFT having high mobility < A semiconductor film including a large number of crystal grains having a 100> orientation is manufactured.

  Patent Document 2 discloses that laser beam irradiation is performed twice in order to flatten the surface of a crystalline semiconductor film.

  Hereinafter, the reason why the surface of the crystalline semiconductor film needs to be planarized will be described.

  In order to obtain a crystalline semiconductor film by irradiating the amorphous semiconductor film with a laser beam, oxygen of a predetermined concentration or more is required in the atmosphere in the laser irradiation chamber during crystallization, or amorphous It is necessary that an oxide film be provided on the semiconductor film. As described above, when a laser beam is irradiated on an amorphous semiconductor film having an oxide film thereon in a relatively high oxygen concentration atmosphere, a crystalline semiconductor film having good crystallinity is obtained. However, protrusions (ridges) are formed on the surface of the crystalline semiconductor film, and the surface roughness becomes very large.

  In the case of manufacturing a TFT using a crystalline semiconductor film having such a large ridge formed on the surface, if the thickness of the gate insulating film is set to 100 nm or less in order to improve the electrical characteristics of the TFT, the thickness of the gate insulating film is reduced. Inconsistent electrical characteristics can cause large variations in electrical characteristics, leading to poor insulation. Therefore, in order to improve the electrical characteristics of a semiconductor device such as a TFT, it is flattened to such an extent that it has good crystallinity and does not have any problem in the uniformity and coverage of the thickness of the gate insulating film provided thereon. A crystalline semiconductor film is required.

Therefore, in the method disclosed in Patent Document 2, the amorphous silicon film is crystallized by irradiating a laser beam, and then the oxide layer formed on the surface of the crystalline silicon film is treated with a hydrofluoric acid-based etching solution. After that, the laser beam was scanned again in an atmosphere with a significantly low oxygen concentration so that the laser beam irradiation overlaps by 95 percent, and this had good crystallinity and the surface was flattened. A polycrystalline silicon film is obtained.
JP 2003-151904 A JP 2001-60551 A

  In the method disclosed in Patent Document 1, it is not specified whether the surface of the crystalline semiconductor film is flattened by the second laser beam irradiation, and it is assumed that the second laser beam is formed by this method. Even if the surface of the crystalline semiconductor film is flattened by the irradiation, new ridges are randomly formed by the second laser beam irradiation, and sufficient planarization cannot be performed.

  Further, in the method disclosed in Patent Document 2, in order to planarize the surface of the crystalline semiconductor film, after irradiation with a laser beam for crystallizing the amorphous semiconductor film, the laser beam is irradiated. This is not preferable because the oxide layer formed on the surface of the polycrystalline semiconductor film needs to be removed, and the manufacturing process and manufacturing time increase. The removal of the oxide layer is generally performed by immersion in hydrofluoric acid. If there are small holes (pits) in the semiconductor layer due to dust in the apparatus during the formation of the amorphous semiconductor film, the oxide layer is removed from the holes. Hydrofluoric acid enters and reaches the quartz substrate, a hole opens at the semiconductor film / quartz substrate interface, and the subsequent laminated structure collapses due to the hole. For example, a defect such as disconnection of the electrode wiring material may occur. is there.

  The present invention has been made in view of the above problems, and an object thereof is to provide a method for manufacturing a planarized semiconductor film without increasing the manufacturing time and manufacturing process.

  The method of manufacturing a semiconductor film of the present invention includes a step of preparing an amorphous semiconductor film, and crystallization for obtaining a crystalline semiconductor film by irradiating at least a part of the amorphous semiconductor film with a crystallization laser beam. And a planarization step of planarizing the surface of the crystalline semiconductor film by irradiating the crystalline semiconductor film with a planarizing laser beam continuously with the crystallization step. In the manufacturing method, the planarization step includes a first planarization step of irradiating a plurality of first unit regions of the crystalline semiconductor film with a first planarization laser beam, and the crystalline semiconductor film, respectively. Includes a second planarization step of irradiating a second planarization laser beam to a plurality of second unit regions that are at least partially different from the first unit region.

  In one embodiment, each of the plurality of first and second unit regions has a polygonal shape as viewed from the normal direction of the surface of the crystalline semiconductor film.

  In one embodiment, the plurality of first unit regions are arranged in a first pattern so that sides of the polygonal shape do not overlap each other, and the plurality of second unit regions are formed in the polygonal shape. They are arranged in a second pattern so that the sides do not overlap each other.

  In one embodiment, the first planarization step includes a step of forming the first planarization laser beam using a first mask having a light transmitting region and a light shielding region, and the second planarization step includes And forming the second planarized laser beam using a second mask having a light transmitting region and a light shielding region.

  In one embodiment, the second planarization step includes a step of using a mask different from the first mask as the second mask.

  In one embodiment, the second planarization step includes a step of using the first mask as the second mask by moving the first mask relative to the crystalline semiconductor film.

  In one embodiment, a side of the polygonal shape of the first unit region is in contact with a region not irradiated with the first planarizing laser beam, and a side of the polygonal shape of the second unit region is And a region not irradiated with the second planarizing laser beam.

  In one embodiment, the polygonal shape is a regular polygonal shape.

  In one embodiment, the distance between the center of each regular polygon and each side is 2 μm or less.

  In one embodiment, the length of one side of the regular polygon shape is 1.0 μm or more and 6.9 μm or less.

  In one embodiment, the regular polygon is any one of a regular triangle, a square, and a regular hexagon.

  In one embodiment, each of the plurality of second unit regions is a region that has not been irradiated by the first planarizing laser beam.

  In one embodiment, the second planarization step includes a step of using the same laser beam as the first planarization laser beam as the second planarization laser beam.

  In one embodiment, the flattening step irradiates a third flattening laser beam to a plurality of third unit regions each of which is at least partially different from the second unit region in the crystalline semiconductor film. The process further includes.

  In one embodiment, the third planarization step includes a step of using, as the third planarization laser beam, a laser beam having a reduced energy density of the second planarization laser beam.

  In one embodiment, the third unit region partially overlaps the first unit region and the second unit region.

  In one embodiment, the first unit region has a polygonal shape as viewed from the normal direction of the surface of the crystalline semiconductor film, and the second unit region is irradiated with the first planarizing laser beam. The third unit region is a region that has not been formed and has a polygonal shape as viewed from the normal direction of the surface of the crystalline semiconductor film, and the third unit region is viewed from the normal direction of the surface of the crystalline semiconductor film. It has a polygonal shape and includes ridges formed in the first and second unit regions in the first and second planarization steps at positions other than the center.

  In one embodiment, the second unit region partially overlaps the first unit region.

  In one embodiment, the second unit region is a region partially different from the first unit region, and has a polygonal shape when viewed from the normal direction of the surface of the crystalline semiconductor film, The third unit region has a polygonal shape as viewed from the normal direction of the surface of the crystalline semiconductor film, and other than the ridge formed in the second unit region in the second planarization step. Included in the position.

  In one embodiment, the crystallization step includes a step of crystallizing the amorphous semiconductor film under a predetermined element composition and a predetermined pressure in an atmosphere in a laser irradiation chamber, and the planarization step includes the step of crystallizing the amorphous semiconductor film. A step of performing planarization without changing the predetermined element composition and the predetermined atmospheric pressure in the atmosphere in the laser irradiation chamber in the crystallization step.

  In one embodiment, the crystallization step includes a step of forming an oxide layer in which a surface of the semiconductor film is oxidized as the amorphous semiconductor film is crystallized, and the planarization step includes the crystallization step. After the step, the method includes a step of performing planarization without removing the oxide layer.

  In one embodiment, the planarization step includes a step of reducing surface roughness of a region irradiated with the planarization laser beam in the crystalline semiconductor film.

  In one embodiment, the planarizing laser beam has an energy density that partially melts the crystalline semiconductor film.

  In one embodiment, the planarization step includes a step of using a pulsed laser beam as the planarization laser beam.

  In one embodiment, the planarization step includes a step of using, as the planarization laser beam, a laser beam having a reduced energy density of the crystallization laser beam.

  According to the present invention, a planarized semiconductor film can be manufactured without increasing the manufacturing time and manufacturing process.

(Embodiment 1)
Hereinafter, a first embodiment of a semiconductor film manufacturing method according to the present invention will be described.

  First, the manufacturing process of this embodiment will be described with reference to FIG.

As shown in FIG. 1A, an amorphous semiconductor film 102 is prepared. For example, an amorphous silicon film 102 having a thickness of 50 nm is formed on a quartz substrate 101 having an insulating surface by low pressure CVD using Si ₂ H ₆ gas.

  As shown in FIG. 1B, a crystalline semiconductor film 103 is obtained by irradiating at least part of the amorphous semiconductor film 102 with a laser beam LA. The crystalline semiconductor film 103 is, for example, a polycrystalline silicon film.

In the following description of this specification, the process of performing crystallization in this way is also referred to as a crystallization process. In addition, the laser beam LA used in the crystallization process may be referred to as a crystallization laser beam. The crystallization laser beam LA is, for example, an excimer laser beam that is a kind of pulsed laser beam. The crystallization laser beam LA is shaped to have a short side of 400 μm and a long side of 450 mm, and the crystallization laser beam LA scans by 20 μm in the same direction every time it is irradiated. The energy density of the crystallization laser beam LA is, for example, 380 mJ / cm ² . Note that the crystallization laser beam LA may be a continuous wave laser beam.

  In the crystallization step, the amorphous semiconductor film 102 is relatively scanned with the crystallized laser beam LA while the amorphous semiconductor film 102 is irradiated with the crystallized laser beam LA. Here, scanning is performed by moving the substrate provided with the amorphous semiconductor film 102 while fixing the beam source of the crystallization laser beam LA, but the reverse may be possible. In the present embodiment, only a part of the amorphous semiconductor film 102 may be crystallized without crystallizing the entire amorphous semiconductor film 102. Crystallization of the amorphous semiconductor film 102 is performed in a laser irradiation chamber (not shown). For example, the atmospheric pressure in the laser irradiation chamber is 1 atm, the oxygen concentration in the atmosphere in the laser irradiation chamber is 20%, and the concentrations of other molecules are 80%, which is the same as in normal air.

  A crystalline semiconductor film 103 obtained by crystallizing the amorphous semiconductor film 102 is obtained by irradiation with the crystallization laser beam LA. Along with this crystallization, a ridge is formed on the surface of the crystalline semiconductor film 103, and the crystal An oxide layer 104 is formed on the surface of the crystalline semiconductor film 103. For example, when the thickness of the amorphous silicon film 102 is 50 nm, ridges with a height of about 60 nm are formed on the surface of the crystallized crystalline semiconductor film 103 at random or in a straight line with a period of about 300 nm. Often formed side by side. In the crystalline semiconductor film 103, the Ra value indicating the surface roughness is 8 nm.

  Next, as shown in FIGS. 1C and 1D, the surface of the crystalline semiconductor film 103 is irradiated by sequentially irradiating the crystalline semiconductor film 103 with laser beams LB1 and LB2 in succession to the crystallization process. To flatten. By performing the planarization, the ridge formed on the surface of the crystalline semiconductor film 103 is planarized. In the following description of this specification, the process of performing the planarization in this way is also referred to as a planarization process. Further, the laser beams LB1 and LB2 used in the planarization process may be referred to as planarization laser beams. As the planarizing laser beams LB1 and LB2, for example, a beam obtained by reducing the energy density of the excimer laser beam used in the crystallization process may be used.

  In the planarization step, the planarized laser beams LB1 and LB2 are relatively scanned with respect to the crystalline semiconductor film 103 while the crystalline semiconductor film 103 is irradiated with the planarized laser beams LB1 and LB2. In this case as well, scanning is performed by moving the substrate provided with the crystalline semiconductor film 103 while fixing the beam sources of the planarizing laser beams LB1 and LB2, but the scanning may be reversed.

  The planarizing laser beams LB1 and LB2 have an energy density that partially melts the crystalline semiconductor film 103. When the energy density of the flattening laser beams LB1 and LB2 is such that the crystalline semiconductor film is completely melted, the crystalline semiconductor film is remelted, and there is no crystallization process for obtaining the crystalline semiconductor film. It makes sense and is not preferred.

  In the present embodiment, the planarization step is performed without changing the element composition and the atmospheric pressure in the atmosphere in the laser irradiation chamber as in the crystallization step. In the present embodiment, unlike the method disclosed in Patent Document 2, the planarization step is performed after the crystallization step without removing the oxide layer 104. In the present embodiment, a ridge having a height of about 60 nm was formed on the surface of the crystalline semiconductor film 103 before the planarization step. On the other hand, by performing planarization as shown below, Even without removing the layer 104, the ridge on the surface of the crystalline semiconductor film 103 can be reduced to about 20 nm in height, and the Ra value can be reduced to about 3 nm.

  Hereinafter, the planarization process in the present embodiment will be described.

First, as shown in FIG. 1C, the crystalline semiconductor film 103 is irradiated with a laser beam LB1 on a plurality of unit regions. In the following description, this laser beam LB1 may be referred to as a first flattening laser beam, and a step of performing flattening using the first flattening laser beam LB1 may be referred to as a first flattening step. Further, the unit region irradiated with the first planarizing laser beam LB1 may be referred to as a first unit region. Energy density of the first planarization laser beam LB1 is an energy density to melt the crystalline semiconductor film 103 partially, for example, 360 mJ / cm ^2.

  FIG. 2 shows the surface of the crystalline semiconductor film 103 irradiated with the first planarizing laser beam LB1. As shown in FIG. 2, each of the plurality of first unit regions 151 irradiated with the first planarizing laser beam LB1 has an equilateral triangular shape with a side of 6 μm as viewed from the normal direction of the surface of the crystalline semiconductor film 103. The plurality of first unit regions 151 are regularly arranged in a pattern. Thereby, only the corners of the first unit region 151 overlap with the corners of the adjacent first unit region 151, and the sides of the first unit region 151 do not overlap with the sides of the adjacent first unit region 151.

  In FIG. 2, the non-irradiation region 152 that has not been irradiated by the first planarizing laser beam LB1 is indicated by hatching. Here, each non-irradiation region 152 has an equilateral triangular shape having the same size as the first unit region 151, and the plurality of non-irradiation regions 152 are regularly arranged in a pattern. The plurality of first unit regions 151 and the plurality of non-irradiation regions 152 are arranged so as to form a spotted pattern.

  The first planarizing laser beam LB1 is shaped as shown below using a mask (not shown) installed in the laser irradiation apparatus. The overall size of the mask is, for example, a square of 60 mm × 60 mm, and the light transmitting region and the light shielding region of the mask have the same shape as the first unit region 151 and the non-irradiated region 152 shown in FIG. Yes. The length of one side of the light transmitting region and the light shielding region of the mask is, for example, 30 μm, and is reduced to 1/5 size on the sample surface by the lens. That is, the entire area of 12 mm × 12 mm is irradiated by one irradiation, and the length of one side of each equilateral triangle is 6 μm. For example, the mask is made of chromium in the same manner as a photomask used in a general photolithography process. The mask placed in this way transmits a part of the laser beam emitted from the beam source (not shown), thereby forming the first flattened laser beam LB1. Note that the first planarizing laser beam LB1 scans the crystalline semiconductor film 103 while being shifted by 12 mm in the X direction or the Y direction.

  FIG. 3 shows a ridge 155 formed in the first unit region 151 by irradiation with the first planarizing laser beam LB1. By irradiating the first planarizing laser beam LB1, the ridge formed by the irradiation of the crystallization laser beam LA disappears, and instead, as shown in FIG. A ridge 155 having a thickness of 20 nm is formed. A vertex 156 exists at the intersection of the ridges 155 at the center of the equilateral triangle, and its height is 30 nm.

  The reason why the ridge is formed from the corner of the equilateral triangle to the center in this way is that the melting and solidifying speeds in the first unit region 151 irradiated with the first planarizing laser beam LB1 are different. . Specifically, when the first planarizing laser beam LB1 is irradiated, the first unit region 151 absorbs the energy of the first planarizing laser beam LB1 and is partially melted. Since each side of the equilateral triangle of the first unit region 151 is in contact with the non-irradiation region 152, heat is transferred from each side of the equilateral triangle to the non-irradiation region 152. For this reason, the temperature of the first unit region 151 decreases more rapidly on each side than on the center of the equilateral triangle, solidification starts from each side of the equilateral triangle, and solidification proceeds from each side of the equilateral triangle to the center. In order. Accordingly, the ridge 155 is formed from the corner of the regular triangle toward the center, and forms a vertex 156 in the vicinity of the center of the first unit region 151.

  As described above, the ridge 155 is formed by the irradiation of the first planarizing laser beam LB1, and the height of the ridge 155 is about 30 nm. In the first unit region 151, the first planarizing laser beam LB1 is irradiated with the first planarizing laser beam LB1. It is flattened compared to the ridge with a height of 60 nm before irradiation.

  Next, as shown in FIG. 1D, a plurality of unit regions of the crystalline semiconductor film 103 are irradiated with a laser beam LB2. In the following description, this laser beam LB2 may be referred to as a second planarizing laser beam, and the step of performing planarization using the second planarizing laser beam LB2 may be referred to as a second planarizing step. In addition, the unit region irradiated with the second planarizing laser beam LB2 may be referred to as a second unit region.

The second planarization laser beam LB2 is, for example, an excimer laser beam used in the first planarization process. The energy density of the second planarizing laser beam LB2 is also an energy density that partially melts the crystalline semiconductor film 103, and is, for example, 360 mJ / cm ² . The irradiation of the second planarizing laser beam LB2 is performed without changing the atmosphere and the atmospheric pressure in the laser irradiation chamber when the first planarizing laser beam LB1 is irradiated.

  FIG. 4 shows the surface of the crystalline semiconductor film 103 irradiated with the second planarizing laser beam LB2. As shown in FIG. 4, each of the plurality of second unit regions 161 irradiated with the second planarizing laser beam LB2 has an equilateral triangle shape with a side of 6 μm when viewed from the normal direction of the surface of the crystalline semiconductor film 103. The plurality of second unit regions 161 are regularly arranged in a pattern.

  In FIG. 4, the non-irradiation region 162 that has not been irradiated with the second planarizing laser beam LB2 is indicated by hatching. Each non-irradiation region 162 has an equilateral triangle shape having the same size as the second unit region 161, and the plurality of non-irradiation regions 162 are regularly arranged in a pattern. The plurality of second unit regions 161 and the plurality of non-irradiation regions 162 are regularly arranged so as to form a spotted pattern.

  The second unit region 161 is arranged at the same position as the equilateral triangular non-irradiation region 152 (see FIG. 2) that has not been irradiated by the first planarization laser beam LB1 in the first planarization step. The size of the second unit region 161 is equal to the size of the first unit region 151 in the first planarization step.

  The second planarizing laser beam LB2 is shaped using a mask (not shown) installed in the laser irradiation apparatus. This mask has the same pattern as the mask used in the first planarization step. In the present embodiment, the alignment between the mask used in the first and second planarization steps and the crystalline semiconductor film 103 is performed using an alignment pattern separately provided around the substrate. A ridge similar to that in FIG. 3 is also formed in the second unit region 161 by the second planarizing laser beam LB2.

  FIG. 5 shows a ridge 165 formed in the crystalline semiconductor film 103 after irradiation with the second planarizing laser beam LB2. The ridge 165 is formed by irradiation with the first and second planarizing laser beams LB1 and LB2. In FIG. 5, one first unit region 151 and one second unit region 161 are indicated by broken lines for reference.

  As shown in FIG. 5, the ridge 165 formed by the irradiation of the first planarizing laser beam LB1 has the center of the regular triangle of the first unit region 151 as the vertex 166 having a height of 30 nm, and each of the vertex 166 and each of the regular triangles. It is formed to connect corners. Similarly, the ridge 165 formed by the second planarizing laser beam LB2 connects the vertex 166 and each corner of the equilateral triangle with the position of the center of the equilateral triangle of the second unit region 161 as the vertex 166. Is formed.

  As described above, in the present embodiment, a region within a certain range is flattened by the flattened laser beam LB1, and the region that is not irradiated by the flattened laser beam LB1 within the range by the second flattened laser beam LB2. Is flattened. When a semiconductor film is irradiated with a laser beam having a large beam spot, ridges are randomly formed, and as a result, high vertices are formed and flattening may not be sufficiently performed. Since the first unit region 151 is flattened by irradiation with the first flattening laser beam LB1, and then the second unit region 161 is flattened by irradiation with the second flattening laser beam LB2, ridges 165 are formed randomly. This can be suppressed, and a sufficiently planarized crystalline semiconductor film 103 can be obtained without removing the oxide layer as in the manufacturing method disclosed in Patent Document 2. Further, by performing the planarization process continuously after the crystallization process, the planarized crystalline semiconductor film 103 can be manufactured without increasing the manufacturing process and the manufacturing time. Further, since the planarization can be performed without removing the oxide layer, the occurrence of connection failure can be suppressed.

  In the above description, the semiconductor film is a silicon film, but the present invention is not limited to this. The semiconductor film may be a germanium film or a mixed film of germanium and silicon (silicon / germanium film).

  In the above description, the length of one side of the first and second unit regions 151 and 161 is 6 μm, but the present invention is not limited to this. However, the length of one side of the first and second unit regions 151 and 161 is desirably 1.0 μm or more and 6.9 μm or less. If it is less than 1.0 μm, it is difficult to resolve an equilateral triangle. On the other hand, if it is larger than 6.9 μm, random solidification occurs near the center earlier than solidification from each side, and as a result, a random ridge is formed near the center and flattening may be insufficient. . When the length of one side of the regular triangle is 1.0 μm or more and 6.9 μm or less, the distance between the center of the regular triangle and each side is 0.29 μm or more and 2.0 μm or less.

  In the above description, the first unit region 151 and the second unit region 161 have an equilateral triangle shape, but the present invention is not limited to this. However, the first and second unit regions 151 and 161 are formed on the surface of the crystalline semiconductor film 103 so that the entire surface of the crystalline semiconductor film 104 can be planarized by two irradiations of the planarizing laser beam. It is preferably a regular polygonal shape as viewed from the normal direction. In this case, the distance between the center of the regular polygon and each side is preferably 2 μm or less, and the length of each side of the regular polygon is preferably 1.0 μm or more. This is because if the length of the side is less than 1.0 μm, the image may not be accurately resolved.

  In the above description, the second unit region 161 is the same region as the non-irradiated region 152 in the first planarization step, but the second unit region 161 is a region that is at least partially different from the first unit region 151. It may be. The second unit region 161 can be easily changed by changing or moving the mask.

  Hereinafter, a method for manufacturing a TFT using the semiconductor film 103 obtained by the above-described method will be described with reference to FIG.

  By performing normal photolithography processes such as resist coating, exposure, and development on the semiconductor film 103 formed on the quartz substrate 101, the semiconductor film 103 is formed into a region 105, a region 106, and a region as shown in FIG. Patterned to 107. The regions 105, 106, and 107 are a TFT source region, a channel region, and a drain region, respectively. Here, the oxide layer 104 shown in FIG. 1 is not shown.

  As shown in FIG. 6B, a gate insulating film 112 having an oxide film thickness of about 50 nm is formed to cover the semiconductor film by an atmospheric pressure chemical vapor deposition (APCVD) method. To do. Strictly speaking, since the oxide layer 104 (see FIG. 1) formed by the crystallization process remains on the semiconductor film, the gate insulating film 112 is formed on the oxide layer 104. Next, as shown in FIG. 6C, a conductive film 114 made of aluminum having a thickness of about 300 nm is formed on the gate insulating film 112.

  As shown in FIG. 6D, when the p-type TFT is formed after forming the gate electrode 114 ′ by patterning the conductive film 114, the gate electrode 114 ′ is used as a mask. Boron ions are implanted into the drain regions 105 and 107. Next, as shown in FIG. 6E, an interlayer insulating film 116 is formed by depositing an oxide film having a thickness of 500 nm on the entire surface of the quartz substrate 101 including the patterned gate electrode 114 ′ by the APCVD method. .

  As shown in FIG. 6 (f), a contact hole is formed on the interlayer insulating film 116 on the source / drain regions 105 and 107, and a conductive material is deposited on the contact hole by a sputtering method. By patterning the conductive material, an extraction electrode 118 that is in ohmic contact with the source / drain regions 105 and 107 is formed. The TFT is manufactured as described above. Further, a semiconductor device using this TFT as a switching element is further manufactured.

  Since the semiconductor device manufactured as described above uses a semiconductor film having a flat surface, even if the gate insulating film is thin, the thickness of the gate insulating film of each TFT is made uniform so that the electrical characteristics of the TFT can be obtained. Can be made uniform, and insulation failure can be suppressed.

When a p-type TFT was produced as described above and its carrier mobility was measured, a value of 150 cm ² / V · s was obtained. The gate insulating film 112 was 50 nm thick, but no insulation failure occurred.

(Embodiment 2)
Hereinafter, a second embodiment of the semiconductor film manufacturing method according to the present invention will be described with reference to FIGS.

  The manufacturing method of this embodiment is different from the manufacturing method of Embodiment 1 in that the laser beam is irradiated three times in the planarization step. In the following description, in order to avoid redundancy, the description overlapping with that of the first embodiment is omitted.

First, as shown in FIG. 7A, an amorphous silicon film 202 having a thickness of 50 nm is formed on a quartz substrate 201 by a low pressure CVD method using Si ₂ H ₆ gas.

Next, as shown in FIG. 7B, the amorphous silicon film 202 is crystallized by irradiating the amorphous silicon film 202 with a crystallization laser beam LA. Here, an excimer laser beam is used as the crystallization laser beam LA. The crystallization laser beam LA is shaped to have a short side of 400 μm and a long side of 450 mm, and the crystallization laser beam LA scans by 20 μm in the same direction every time it is irradiated. The energy density of the crystallization laser beam LA is 380 mJ / cm ² . The crystallization process is performed in a laser irradiation chamber. The oxygen concentration in the atmosphere in the laser irradiation chamber is 20%, and the concentrations of other molecules are 80%, which are the same as those in normal air.

  A polycrystalline silicon film 203 obtained by crystallizing the amorphous silicon film 202 is obtained by irradiation with the crystallization laser beam LA. Along with this crystallization, a large number of ridges are formed on the surface of the polycrystalline silicon film 203. An oxide layer 204 is formed on the surface of the polycrystalline silicon film 203. For example, when the thickness of the amorphous silicon film 202 is 50 nm, a ridge having a height of about 60 nm is formed on the surface of the polycrystalline silicon film 203. The Ra value of the polycrystalline silicon film 203 is 8 nm.

Next, as shown in FIG. 7C, a plurality of first unit regions of the polycrystalline silicon film 203 are irradiated with a first planarizing laser beam LB1. The irradiation with the first planarizing laser beam LB1 is performed continuously to the crystallization process. For example, the irradiation with the first planarizing laser beam LB1 is performed without changing the atmosphere and the atmospheric pressure in the laser irradiation chamber when irradiating the crystallization laser beam LA, and after the irradiation with the crystallization laser beam LA. This is done without removing the oxide layer 204 formed on the surface of 203. The energy density of the first planarizing laser beam LB1 is an energy density that partially melts the polycrystalline silicon film 203, and is, for example, 360 mJ / cm ² . The first planarizing laser beam LB1 is shaped using a mask (not shown) installed in the laser irradiation apparatus.

  FIG. 8 shows the surface of the polycrystalline silicon film 203 irradiated with the first planarizing laser beam LB1. As shown in FIG. 8, each of the plurality of first unit regions 251 irradiated with the first planarizing laser beam LB1 has a square shape with a side of 4 μm when viewed from the normal direction of the surface of the polycrystalline silicon film 203. The plurality of first unit regions 251 are regularly arranged in a pattern. Accordingly, only the corners of the first unit region 251 overlap with the adjacent first unit region 251, and the sides of the first unit region 251 do not overlap with the adjacent first unit region 251. Since the length of one side of the square is 4 μm, the distance between the center of the square and each side is 2 μm.

  In FIG. 8, the non-irradiation region 252 that has not been irradiated by the first planarizing laser beam LB1 is indicated by hatching. Each non-irradiation region 252 has a square shape having the same size as the first unit region 251, and the plurality of non-irradiation regions 252 are regularly arranged in a pattern. The plurality of first unit regions 251 and the plurality of non-irradiation regions 252 are regularly arranged so as to form a spotted pattern.

  FIG. 9 shows a ridge 255 formed in the first unit region 251 by irradiation with the first planarizing laser beam LB1. As shown in FIG. 9, a vertex 256 exists at the intersection of the ridges 255 at the center of the square, and its height is 30 nm.

  As shown in FIG. 9, the ridge 255 has a ridge formed from a square corner toward the center. This is because the melting and solidifying speeds in the first unit region 251 irradiated with the first planarizing laser beam LB1 are different. Specifically, when the first planarizing laser beam LB1 is irradiated, the first unit region 251 absorbs the energy of the first planarizing laser beam LB1 and is partially in a molten state. Since each square side of the first unit region 251 is in contact with the non-irradiated region 252, heat is transferred from each square side to the non-irradiated region 252. For this reason, the temperature of the first unit region 251 decreases more rapidly at each side than at the center of the square, solidification starts from each side of the square, and solidification is performed in order from each side of the square toward the center. proceed. Accordingly, the ridge 255 is formed from the corner of the square toward the center, and forms a vertex 256 near the center of the first unit region 251.

Next, as shown in FIG. 7D, a plurality of second unit regions of the polycrystalline silicon film 203 are irradiated with a second planarizing laser beam LB2. The energy density of the second planarizing laser beam LB2 is, for example, 360 mJ / cm ² .

  FIG. 10 shows the surface of the polycrystalline silicon film 203 irradiated with the second planarizing laser beam LB2. As shown in FIG. 10, each of the plurality of second unit regions 261 irradiated with the second planarizing laser beam LB2 has a square shape with a side of 4 μm when viewed from the normal direction of the surface of the polycrystalline silicon film 203. The plurality of second unit regions 261 are regularly arranged in a pattern. In FIG. 10, the non-irradiation region 262 that has not been irradiated with the second planarizing laser beam LB2 is indicated by hatching. Each non-irradiation region 262 has a square shape having the same size as the second unit region 261, and the plurality of non-irradiation regions 262 are regularly arranged in a pattern. The plurality of second unit regions 261 and the plurality of non-irradiation regions 262 are regularly arranged so as to form a spotted pattern.

  The second unit region 261 is arranged at the same position as the non-irradiated region 252 (see FIG. 9) having a square shape that has not been irradiated by the first planarization laser beam LB1 in the first planarization step. The size of the unit region 261 is equal to the size of the first unit region 251 in the first planarization step. The second planarizing laser beam LB2 is shaped using a mask (not shown) installed in the laser irradiation apparatus. The second planarizing laser beam LB2 forms a ridge in the second unit region 261 as well as the first unit region 251 shown in FIG.

  As described above, the surface of the polycrystalline silicon film 203 is entirely planarized by irradiating the first planarizing laser beam LB1 and the second planarizing laser beam LB2, but the first planarizing laser A low ridge is formed on the surface of the polycrystalline silicon film 203 by irradiation with the beam LB1 and the second planarizing laser beam LB2.

  FIG. 11 shows a ridge 265 formed on the polycrystalline silicon film 203 after irradiation with the second planarizing laser beam LB2. The ridge 265 is formed by irradiation with the first planarizing laser beam LB1 and the second planarizing laser beam LB2. In FIG. 11, one first unit region 251 and one second unit region 261 are indicated by broken lines for reference. As shown in FIG. 11, the ridge 265 is formed in a square shape with a side of 2.8 μm inclined 45 degrees from the square of the first and second unit regions 251 and 261.

  Next, as shown in FIG. 7E, a plurality of unit regions are irradiated with a laser beam LB3. Thereby, the surface of the polycrystalline silicon film 203 can be further planarized. This laser beam LB3 may also be referred to as a third planarizing laser beam, and the step of performing planarization using the third planarizing laser beam LB3 may also be referred to as a third planarizing step. Further, the unit region irradiated with the third planarizing laser beam LB3 may be referred to as a third unit region.

Here, an excimer laser beam similar to the second planarizing laser beam LB2 is used as the third planarizing laser beam LB3. The energy density of the third planarizing laser beam LB3 is an energy density that partially melts the polycrystalline silicon film 203, and is, for example, 350 mJ / cm ² . The energy density of the third planarizing laser beam LB3 is lower than that of the second planarizing laser beam LB2. The third planarizing laser beam LB3 is shaped using a mask (not shown) installed in the laser irradiation apparatus.

  FIG. 12 shows the surface of the polycrystalline silicon film 203 irradiated with the third planarizing laser beam LB3. As shown in FIG. 12, each of the plurality of third unit regions 271 irradiated with the third planarizing laser beam LB3 has a square shape with a side of 3.2 μm as viewed from the normal direction of the surface of the polycrystalline silicon film 203. The plurality of third unit regions 271 are regularly arranged in a pattern so that corners of adjacent third unit regions 271 overlap each other.

  In FIG. 12, the ridge 265 before irradiation with the third planarizing laser beam LB3 described with reference to FIG. 11 is indicated by a broken line, but as shown in FIG. They are arranged to include a square surrounded by a ridge 265 having a side of 2.8 μm. In FIG. 12, the non-irradiation region 272 that has not been irradiated by the third planarizing laser beam LB3 is indicated by hatching. Each non-irradiation region 272 has a square shape with a side of 2.4 μm that is smaller than the third unit region 271, and the plurality of non-irradiation regions 272 are patterned so as not to contact with the adjacent non-irradiation regions 272. Are regularly arranged. The plurality of third unit regions 271 and the plurality of non-irradiation regions 272 are regularly arranged so as to form a spotted pattern.

  FIG. 13 shows a ridge 275 formed on the polycrystalline silicon film 203 by irradiation with the third planarizing laser beam LB3. As shown in FIG. 13, the ridge 265 (see FIG. 11) formed by the irradiation of the second planarizing laser beam LB2 is eliminated by the irradiation of the third planarizing laser beam LB3, and a ridge 275 is formed instead. The The height of the ridge 275 formed by the irradiation with the third planarizing laser beam LB3 is 10 nm, and the apex 276 is also 15 nm in height, and the height before irradiation with the third planarizing laser beam LB3 is 30 nm. It is further flattened than the vertex 266 of.

  Here, the reason why the surface of the polycrystalline silicon film 203 is further planarized by the irradiation with the third planarizing laser beam LB3 will be described.

  As understood from FIG. 12, the third unit region 271 includes a ridge 265 formed by irradiation with the second planarizing laser beam LB2, and the third unit region 271 includes the ridge 265 and its apex. 266 is arranged at a position other than the center of the square of the third unit region 271, for example, relatively outside the square of the third unit region 271. When the third planarizing laser beam LB3 is irradiated, the third unit region 271 absorbs the energy of the third planarizing laser beam LB3 and is partially melted. Since each square side of the third unit region 271 is in contact with the non-irradiation region 272, heat is transferred from each side of the square to the non-irradiation region 272. For this reason, the temperature of the third unit region 271 decreases more rapidly at each side than at the center of the square, solidification starts from each side of the square, and solidification is performed in order from each side of the square toward the center. The ridge 275 is formed from the corner of the square toward the center of the square, and forms a vertex 276 near the center of the square of the third unit region 271.

  In the third planarization step, since solidification starts from the vicinity of the ridge 265 relatively outside the square of the third unit region 271, the silicon atom forming the ridge 265 is sufficiently formed to the newly formed ridge 275. The vertex 276 of the ridge 275 is formed by irradiation with the third planarizing laser beam LB3 in the lower portion before the irradiation with the third planarizing laser beam LB3. Therefore, the height of the ridge 275 formed by the irradiation with the third planarizing laser beam LB3 can be made lower than the ridge 265 formed before the irradiation with the third planarizing laser beam LB3.

  In the above description, one side of the square in the first and second unit regions 251 and 261 by the first and second planarizing laser beams LB1 and LB2 is 4 μm, but one side of the square is 4 μm or less. The same flat polycrystalline silicon film can be obtained. However, the length of one side is preferably 1.0 μm or more. This is because if the length of one side is less than 1.0 μm, the image may not be accurately resolved.

  Hereinafter, a method for manufacturing a TFT using the polycrystalline silicon film 203 obtained by the above-described method will be described with reference to FIG.

  By performing a normal photolithography process such as resist coating, exposure, and development on the polycrystalline silicon film 203 formed on the quartz substrate 201, as shown in FIG. Patterning is performed on the region 206 and the region 207. The regions 205, 206, and 207 are a TFT source region, a channel region, and a drain region, respectively.

  As shown in FIG. 14B, a gate insulating film 212 made of an oxide film and having a thickness of about 45 nm is formed so as to cover the polycrystalline silicon film 203 by the APCVD method. Next, as shown in FIG. 14C, a conductive film 214 made of aluminum having a thickness of about 300 nm is formed on the gate insulating film 212.

  As shown in FIG. 14D, in the case where a gate electrode 214 ′ is formed by patterning the conductive film 214 to produce a p-type TFT, the source / drain region 205 is formed using the gate electrode 214 ′ as a mask. , 207 are implanted with boron ions. Next, as shown in FIG. 14E, an interlayer insulating film 216 is formed by depositing an oxide film having a thickness of 500 nm on the entire surface of the quartz substrate 201 including the gate electrode 214 ′ by the APCVD method.

  As shown in FIG. 14 (f), a contact hole is formed on the interlayer insulating film 216 on the source / drain regions 205 and 207, and a conductive material is deposited on the contact hole by a sputtering method. By patterning the conductive material, an extraction electrode 218 that is in ohmic contact with the source / drain regions 205 and 207 is formed. A TFT is manufactured as described above. Further, a semiconductor device using this TFT as a switching element is further manufactured.

When a p-type TFT was fabricated as described above and its carrier mobility was measured, a value of 180 cm ² / V · s was obtained. Although the thickness of the gate insulating film 212 was 45 nm, no insulation failure occurred.

(Embodiment 3)
Hereinafter, with reference to FIGS. 15 to 21, a third embodiment of the method for manufacturing a semiconductor film according to the present invention will be described.

  The manufacturing method of the present embodiment is different from the manufacturing method of the above-described embodiment in that the second planarizing laser beam is irradiated to a region partially overlapping with the region irradiated with the first planarizing laser beam. In the following description, in order to avoid redundancy, description overlapping with the above-described embodiment is omitted.

First, as shown in FIG. 15A, an amorphous silicon film 302 having a thickness of 50 nm is formed on a quartz substrate 301 by low pressure CVD using Si ₂ H ₆ gas.

Next, as shown in FIG. 15B, the amorphous silicon film 302 is crystallized by irradiating the amorphous silicon film 302 with a crystallization laser beam LA. Here, an excimer laser beam is used as the crystallization laser beam LA. The crystallization laser beam LA is shaped to have a short side of 400 μm and a long side of 450 mm, and the crystallization laser beam LA scans by 20 μm in the same direction every time it is irradiated. The energy density of the crystallization laser beam LA is 380 mJ / cm ² . The crystallization process is performed in the laser irradiation chamber, the atmospheric pressure in the laser irradiation chamber is 1 atm, the oxygen concentration in the atmosphere in the laser irradiation chamber is 20%, and the concentration of other molecules is 80%, which is the same as the normal atmosphere. It is.

  By irradiating the crystallized laser beam LA, a polycrystalline silicon film 303 obtained by crystallizing the amorphous silicon film 302 is obtained. With this crystallization, a large number of ridges are formed on the surface of the polycrystalline silicon film 303. At the same time, an oxide layer 304 is formed on the surface of polycrystalline silicon film 303. For example, when the amorphous silicon film 302 has a thickness of 50 nm, a ridge having a height of about 60 nm is formed on the surface of the polycrystalline silicon film 303. The Ra value of the polycrystalline silicon film 303 is 8 nm.

Next, as shown in FIG. 15C, the first planarizing laser beam LB1 is irradiated onto the plurality of first unit regions of the polycrystalline silicon film 303 continuously with the crystallization process. The energy density of the first planarizing laser beam is an energy density that partially melts the polycrystalline silicon film 303, and is, for example, 360 mJ / cm ² . The first planarizing laser beam LB1 is shaped using a mask (not shown) installed in the laser irradiation apparatus. For example, the irradiation of the first planarizing laser beam LB1 is performed without removing the oxide layer 304 formed on the surface of the polycrystalline silicon film 303 after the irradiation of the crystallization laser beam LA, and without the crystallization laser beam LA. The irradiation is performed without changing the pressure and atmosphere in the laser processing chamber.

  FIG. 16 shows the surface of the polycrystalline silicon film 303 irradiated with the first planarizing laser beam LB1. As shown in FIG. 16, each of the plurality of first unit regions 351 irradiated with the first planarizing laser beam LB1 has a regular hexagonal shape with a side of 2.3 μm when viewed from the normal direction of the surface of the polycrystalline silicon film 303. The plurality of first unit regions 351 are regularly arranged in a pattern. Thereby, only the corners of the first unit region 351 overlap with the adjacent first unit region 351, and the sides of the first unit region 351 do not overlap with the adjacent first unit region 351. Since the length of one side of the regular hexagon is 2.3 μm, the distance between the center of the square and each side is 2 μm.

  In FIG. 16, the non-irradiation region 352 that has not been irradiated with the first planarizing laser beam LB1 is indicated by hatching. Each non-irradiated region 352 has an equilateral triangular shape with a side of 2.3 μm when viewed from the normal direction of the surface of the polycrystalline silicon film 303, and the plurality of non-irradiated regions 352 are regularly arranged in a pattern. ing.

  FIG. 17 shows a ridge 355 formed in the first unit region 351 by irradiation with the first planarizing laser beam LB1. As shown in FIG. 17, a ridge 355 having a height of 20 nm is formed from each corner of the regular hexagon toward the center, and a vertex 356 having a height of 30 nm is formed at the intersection.

  As shown in FIG. 17, the ridge 355 has a ridge formed from the corner of the regular hexagon toward the center. This is because the melting and solidifying speeds in the first unit region 351 irradiated with the first planarizing laser beam LB1 are different. Specifically, when the first planarizing laser beam LB1 is irradiated, the first unit region 351 absorbs the energy of the first planarizing laser beam LB1 and is partially in a molten state. Since each side of the regular hexagon of the first unit region 351 is in contact with the non-irradiated region 352, heat is transferred from each side of the regular hexagon to the non-irradiated region 352. For this reason, the temperature of the first unit region 351 decreases more rapidly on each side than on the center of the regular hexagon, solidification starts from each side of the regular hexagon, and solidification proceeds from each side of the regular hexagon to the center. In order. Accordingly, the ridge 355 is formed from the corner of the regular hexagon toward the center, and forms a vertex 356 near the center of the first unit region 351.

Next, as shown in FIG. 15 (d), a plurality of second unit regions of the polycrystalline silicon film 303 are irradiated with a laser beam LB 2. The energy density of the second planarizing laser beam LB2 is 360 mJ / cm ² .

  FIG. 18 shows the surface of the polycrystalline silicon film 303 irradiated with the second planarizing laser beam LB2. As shown in FIG. 18, each of the plurality of second unit regions 361 irradiated with the second planarizing laser beam LB2 has a regular hexagonal shape with a side of 2.3 μm as viewed from the normal direction of the surface of the polycrystalline silicon film 303. The plurality of second unit regions 361 are regularly arranged in a pattern.

  In FIG. 18, the non-irradiation region 362 that has not been irradiated with the second planarizing laser beam LB2 is indicated by hatching. Each non-irradiation region 362 has an equilateral triangle shape with a side of 2.3 μm, and the plurality of non-irradiation regions 362 are regularly arranged in a pattern.

  The second unit region 361 has the same size and the same hexagonal shape as the first unit region 351 (see FIG. 16), and each second unit region 361 has a right side to each first unit region 351. This is a region moved in the direction by the same length as one side of the regular hexagon, that is, by 2.3 μm. The second planarizing laser beam LB2 is shaped using a mask (not shown) installed in the laser irradiation apparatus. In this mask, the mask used in the first planarization step is moved relative to the polycrystalline silicon film 303 by the same length as one side in the direction of one side of the regular hexagon, that is, 2.3 μm. Is.

  A ridge is also formed in the second unit region 361 as in the first unit region 351 shown in FIG. However, since the second unit region 361 partially overlaps with the first unit region 351, the ridge 355 formed by the irradiation of the first planarizing laser beam LB1 disappears by the irradiation of the second planarizing laser beam LB2. Thus, a new ridge is formed.

  FIG. 19 shows a ridge 365 formed on the polycrystalline silicon film 303 by irradiation with the second planarizing laser beam LB2. In FIG. 19, the second unit region 361 is indicated by a broken line.

  By irradiation with the second planarizing laser beam LB2, a ridge 365 having a height of 20 nm is formed on the surface of the polycrystalline silicon film 303 to form an equilateral triangle with a side of 4.6 μm. There is a 30 nm apex 366. As understood from FIG. 19, the ridge 355 formed by the irradiation of the first planarizing laser beam LB1 disappears by the irradiation of the second planarizing laser beam LB2, and the ridge 365 is formed.

As shown in FIG. 15E, a plurality of third unit regions of the polycrystalline silicon film 303 are further irradiated with a third planarizing laser beam LB3. Thereby, the surface of polycrystalline silicon film 303 can be further planarized. The energy density of the third planarizing laser beam LB3 is, for example, 350 mJ / cm ² . The energy density of the third planarizing laser beam LB3 is lower than that of the second planarizing laser beam LB2. The third planarizing laser beam LB3 is shaped using a mask (not shown) installed in the laser irradiation apparatus.

  FIG. 20 shows the surface of the polycrystalline silicon film 303 irradiated with the third planarizing laser beam LB3. As shown in FIG. 20, each of the plurality of third unit regions 371 irradiated with the third planarizing laser beam LB3 has an equilateral triangular shape with a side of 5.0 μm as viewed from the normal direction of the surface of the polycrystalline silicon film 303. The plurality of third unit regions 371 are regularly arranged in a pattern so that corners of adjacent third unit regions 371 overlap each other. In FIG. 20, the ridge 365 before irradiation with the third planarizing laser beam LB3 described with reference to FIG. 19 is indicated by a broken line, but each third unit region 371 has a ridge 365 having a side of 4.6 μm. It is arranged so as to include an equilateral triangle surrounded by.

  In FIG. 20, the non-irradiation region 372 that has not been irradiated with the third planarizing laser beam LB3 is indicated by hatching. Each non-irradiation region 372 has a square shape with a side of 2.4 μm, which is smaller than the third unit region 371, and the plurality of non-irradiation regions 372 are patterned so as not to contact each other with the adjacent non-irradiation regions 372. Are regularly arranged. The plurality of third unit regions 371 and the plurality of non-irradiated regions 372 are regularly arranged so as to form a spotted pattern.

  FIG. 21 shows a ridge 375 formed on the polycrystalline silicon film 303 by irradiation with the third planarizing laser beam LB3. In FIG. 21, the third unit region 371 is indicated by a broken line.

  Irradiation with the third planarizing laser beam LB3 forms a ridge 375 having a height of 10 nm, and a vertex 376 having a height of 15 nm is formed at the intersection. Thus, the ridge 365 shown in FIG. 19 is eliminated by the irradiation with the third planarizing laser beam LB3, and the ridge 375 shown in FIG. 21 is formed, but formed by the irradiation with the third planarizing laser beam LB3. The ridge 375 is lower than the ridge 365 formed by the irradiation with the second planarizing laser beam LB2, and the surface of the polycrystalline silicon film 303 is planarized more than before the irradiation with the third planarizing laser beam LB3.

  Here, the reason why the surface of the polycrystalline silicon film 303 is further planarized by the irradiation with the third planarizing laser beam LB3 will be described.

  As can be understood from FIG. 20, the third unit region 371 by the third planarizing laser beam LB3 includes a ridge 365 formed by irradiation of the second planarizing laser beam LB2, and the third unit region. 371 is arranged such that the ridge 365 and the vertex 366 are positioned at positions other than the center of the equilateral triangle of the third unit region 371, for example, relatively outside the equilateral triangle of the third unit region 371. When the third planarizing laser beam LB3 is irradiated, the third unit region 371 absorbs the energy of the third planarizing laser beam LB3 and is partially melted. Since each side of the equilateral triangle of the third unit region 371 is in contact with the non-irradiation region 372, heat is transferred from each side of the equilateral triangle to the non-irradiation region 372. For this reason, the temperature of the third unit region 371 decreases more rapidly at each side than at the center of the equilateral triangle, solidification starts from each side of the equilateral triangle, and solidification proceeds from each side of the equilateral triangle toward the center. The ridge 375 is formed from the corner of the equilateral triangle of the third unit region 371 toward the center, and a vertex 376 is formed near the center of the equilateral triangle of the third unit region 371. .

  In the third planarization step, since solidification starts from the vicinity of the ridge 365 relatively outside the equilateral triangle of the third unit region 371, the ridge 365 where the silicon atoms forming the ridge 365 are newly formed is sufficient. In addition, the vertex 376 of the ridge 375 is formed by irradiation with the third planarizing laser beam LB3 in the lower portion before the irradiation with the third planarizing laser beam LB3. Therefore, the height of the ridge 375 formed by the irradiation with the third planarizing laser beam LB3 can be made lower than the ridge 365 formed before the irradiation with the third planarizing laser beam LB3.

  In the above description, the first and second unit regions 351 and 361 have a regular hexagonal shape. However, if the polygon is made more polygonal than the regular hexagon, the shape of the unit region by the laser beam can be resolved. It becomes difficult, and the ridge that can be formed at the center becomes remarkably large as in the case where the shape is a circle.

  In the above description, one side of the regular hexagon in the first and second unit regions 351 and 361 is 2.3 μm. However, even if one side of the regular hexagon is 2.3 μm or less, it is similarly flat. A polycrystalline silicon film can be obtained. However, the length of one side is preferably 1.0 μm or more. This is because if the length of one side is less than 1.0 μm, the image may not be accurately resolved.

  As described above, a planarized polycrystalline silicon film 303 can be obtained.

  Hereinafter, a method for manufacturing a TFT using the polycrystalline silicon film 303 obtained by the above-described method will be described with reference to FIG.

  By performing a normal photolithography process such as resist coating, exposure, and development on the polycrystalline silicon film 303 formed on the quartz substrate 301, the polycrystalline silicon film 303 is formed in the region 305, as shown in FIG. Patterning is performed on the region 306 and the region 307. The regions 305, 306, and 307 are a TFT source region, a channel region, and a drain region, respectively.

  As shown in FIG. 22B, a gate insulating film 312 made of an oxide film and having a thickness of about 45 nm is formed by the APCVD method so as to cover the polycrystalline silicon film. Next, as shown in FIG. 22C, a conductive film 314 made of aluminum having a thickness of about 300 nm is formed on the gate insulating film 312.

  As shown in FIG. 22D, when the gate electrode 314 ′ is formed by patterning the conductive film 314 to form a p-type TFT, the source / drain region 305 is formed using the gate electrode 314 ′ as a mask. , 307 are implanted with boron ions. Next, as shown in FIG. 22E, an interlayer insulating film 316 is formed by depositing an oxide film having a thickness of 500 nm on the entire surface of the quartz substrate 301 including the gate electrode 314 'by the APCVD method.

  As shown in FIG. 22 (f), a contact hole is formed on the interlayer insulating film 316 on the source / drain regions 305 and 307, and a conductive material is deposited on the contact hole by sputtering. By patterning the conductive material, an extraction electrode 318 that is in ohmic contact with the source / drain regions 305 and 307 is formed. A TFT is manufactured as described above. Further, a semiconductor device using this TFT as a switching element is further manufactured.

When a p-type TFT was fabricated as described above and its carrier mobility was measured, a value of 180 cm ² / V · s was obtained. Although the thickness of the gate insulating film 312 was 45 nm, no insulation failure occurred.

  According to the present invention, a planarized crystalline semiconductor film can be manufactured.

  Further, even when a thin gate insulating film is used to improve the electrical characteristics of the TFT, by using the semiconductor film according to the present invention, a semiconductor device including a plurality of TFTs having high electric mobility and uniform electrical characteristics can be obtained. Can be produced.

(A)-(d) is a schematic diagram for demonstrating the manufacturing process in Embodiment 1 of the manufacturing method of the semiconductor film by this invention. 2 is a schematic plan view of a crystalline semiconductor film irradiated with a first planarizing laser beam in Embodiment 1. FIG. FIG. 3 is a schematic plan view showing a ridge formed in a first unit region by irradiation with a first planarizing laser beam in the first embodiment. 3 is a schematic plan view of a crystalline semiconductor film irradiated with a second planarizing laser beam in Embodiment 1. FIG. 3 is a schematic plan view showing a ridge formed in a crystalline semiconductor film by irradiation with first and second planarizing laser beams in Embodiment 1. FIG. (A)-(f) is a schematic diagram for demonstrating the manufacturing process of TFT using the polycrystalline-silicon film manufactured according to Embodiment 1. FIG. (A)-(e) is a schematic diagram for demonstrating the manufacturing process in Embodiment 2 of the manufacturing method of the semiconductor film by this invention. 6 is a schematic plan view of a polycrystalline silicon film irradiated with a first planarizing laser beam in Embodiment 2. FIG. 6 is a schematic plan view showing a ridge formed in a first unit region by irradiation with a first planarizing laser beam in Embodiment 2. FIG. 6 is a schematic plan view of a polycrystalline silicon film irradiated with a second planarizing laser beam in Embodiment 2. FIG. FIG. 6 is a schematic plan view showing a ridge formed in a polycrystalline silicon film by irradiation with first and second planarizing laser beams in the second embodiment. 6 is a schematic plan view of a polycrystalline silicon film irradiated with a third planarizing laser beam in Embodiment 2. FIG. 6 is a schematic plan view showing a ridge formed in a polycrystalline silicon film by irradiation with a third planarizing laser beam in Embodiment 2. FIG. (A)-(f) is a schematic diagram for demonstrating the manufacturing process of TFT using the polycrystalline-silicon film manufactured according to Embodiment 2. FIG. (A)-(e) is a schematic diagram for demonstrating the manufacturing process in Embodiment 3 of the manufacturing method of the semiconductor film by this invention. 6 is a schematic plan view of a polycrystalline silicon film irradiated with a first planarizing laser beam in Embodiment 3. FIG. 10 is a schematic plan view showing a ridge formed in a first unit region by irradiation with a first planarizing laser beam in Embodiment 3. FIG. 6 is a schematic plan view of a polycrystalline silicon film irradiated with a second planarizing laser beam in Embodiment 3. FIG. 10 is a schematic plan view showing a ridge formed in a polycrystalline silicon film by irradiation with a second planarizing laser beam in Embodiment 3. FIG. 10 is a schematic plan view of a polycrystalline silicon film irradiated with a third planarizing laser beam in Embodiment 3. FIG. 10 is a schematic plan view showing a ridge formed in a polycrystalline silicon film by irradiation with a third planarizing laser beam in Embodiment 3. FIG. (A)-(f) is a schematic diagram for demonstrating the manufacturing process of TFT using the polycrystalline-silicon film manufactured according to Embodiment 3. FIG.

Explanation of symbols

101, 201, 301 Quartz substrate 102, 202, 302 Amorphous semiconductor film, amorphous silicon film 103, 203, 303 Crystalline semiconductor film, polycrystalline silicon film 104, 204, 304 Oxide layer 105, 205, 305 Source Region 106, 206, 306 channel region 107, 207, 307 drain region 112, 212, 312 gate insulating film 114, 214, 314 conductive film 114 ', 214', 314 'gate electrode 116, 216, 316 interlayer insulating film 118, 218, 318 Lead electrodes 251, 351 First unit regions 252, 352 by the first flattened beam Non-irradiated regions 255 355 in the first flattened beam Ridge 256, 356 formed by irradiation of the first flattened beam Vertex of ridge formed by irradiation of flattening beam 2 1, 361 Second unit region 262, 362 non-irradiation region in second planarization beam 265, 365 Ridge 266, 366 formed by irradiation of second planarization beam Irradiation of second planarization beam The top of the ridge formed by 371 The third unit region by the third flattening beam 372 The non-irradiated region by the third flattening beam 375 The ridge formed by the irradiation of the third flattening beam 376 By the irradiation of the third flattening beam The apex of the formed ridge

Claims (25)

Preparing an amorphous semiconductor film;
A crystallization step of obtaining a crystalline semiconductor film by irradiating at least a part of the amorphous semiconductor film with a crystallization laser beam;
A planarization step of planarizing the surface of the crystalline semiconductor film by irradiating the crystalline semiconductor film with a planarizing laser beam continuously with the crystallization step. There,
The planarization step includes
A first planarization step of irradiating a plurality of first unit regions of the crystalline semiconductor film with a first planarization laser beam;
A second planarization step of irradiating a plurality of second unit regions, each of which is at least partially different from the first unit region, of the crystalline semiconductor film with a second planarization laser beam. .   2. The method of manufacturing a semiconductor film according to claim 1, wherein each of the plurality of first and second unit regions has a polygonal shape as viewed from a normal direction of a surface of the crystalline semiconductor film. The plurality of first unit regions are arranged in a first pattern so that sides of the polygonal shape do not overlap each other,
3. The method of manufacturing a semiconductor film according to claim 2, wherein the plurality of second unit regions are arranged in a second pattern so that sides of the polygonal shape do not overlap each other. The first planarization step includes a step of forming the first planarization laser beam using a first mask having a light transmitting region and a light shielding region,
4. The semiconductor according to claim 1, wherein the second planarization step includes a step of forming the second planarization laser beam using a second mask having a light transmitting region and a light shielding region. A method for producing a membrane.   5. The method of manufacturing a semiconductor film according to claim 4, wherein the second planarization step includes a step of using a mask different from the first mask as the second mask.   The said 2nd planarization process includes the process of using the said 1st mask as a said 2nd mask by moving the said 1st mask relatively with respect to the said crystalline semiconductor film. A method for manufacturing a semiconductor film. The polygonal side of the first unit region is in contact with the region that was not irradiated by the first planarizing laser beam,
7. The method of manufacturing a semiconductor film according to claim 2, wherein a side of the polygonal shape of the second unit region is in contact with a region not irradiated with the second planarizing laser beam.   The method of manufacturing a semiconductor film according to claim 2, wherein the polygonal shape is a regular polygonal shape.   The method of manufacturing a semiconductor film according to claim 8, wherein a distance between the center of the regular polygon shape and each side is 2 μm or less.   10. The method of manufacturing a semiconductor film according to claim 8, wherein the length of one side of the regular polygonal shape is 1.0 μm or more and 6.9 μm or less.   The method of manufacturing a semiconductor film according to claim 8, wherein the regular polygon is any one of a regular triangle, a square, and a regular hexagon.   12. The method of manufacturing a semiconductor film according to claim 1, wherein each of the plurality of second unit regions is a region that has not been irradiated by the first planarizing laser beam.   The method of manufacturing a semiconductor film according to claim 1, wherein the second planarization step includes a step of using the same laser beam as the first planarization laser beam as the second planarization laser beam.   The planarization step further includes a third planarization step of irradiating a third planarization laser beam to a plurality of third unit regions, each of which is at least partially different from the second unit region in the crystalline semiconductor film. A method for producing a semiconductor film according to claim 1.   The method of manufacturing a semiconductor film according to claim 14, wherein the third planarization step includes a step of using a laser beam having a reduced energy density of the second planarization laser beam as the third planarization laser beam.   The method of manufacturing a semiconductor film according to claim 14, wherein the third unit region partially overlaps the first unit region and the second unit region. The first unit region has a polygonal shape as viewed from the normal direction of the surface of the crystalline semiconductor film,
The second unit region is a region that has not been irradiated by the first planarization laser beam, and has a polygonal shape when viewed from the normal direction of the surface of the crystalline semiconductor film,
The third unit region has a polygonal shape as viewed from the normal direction of the surface of the crystalline semiconductor film, and is formed in the first and second unit regions in the first and second planarization steps. The method of manufacturing a semiconductor film according to claim 14, wherein the ridge is included at a position other than the center.   The method of manufacturing a semiconductor film according to claim 14, wherein the second unit region partially overlaps the first unit region. The second unit region is a region that is partially different from the first unit region, and has a polygonal shape when viewed from the normal direction of the surface of the crystalline semiconductor film,
The third unit region has a polygonal shape as viewed from the normal direction of the surface of the crystalline semiconductor film, and other than the ridge formed in the second unit region in the second planarization step. The method of manufacturing a semiconductor film according to claim 18, which is included in the position of The crystallization step includes a step of crystallizing the amorphous semiconductor film under a predetermined element composition in a laser irradiation chamber atmosphere and a predetermined atmospheric pressure,
The flattening step includes a step of performing flattening without changing the predetermined element composition and the predetermined atmospheric pressure in the atmosphere in the laser irradiation chamber in the crystallization step. A method for producing a semiconductor film as described in 1. above. The crystallization step includes a step of forming an oxide layer in which the surface of the semiconductor film is oxidized along with the crystallization of the amorphous semiconductor film,
21. The method of manufacturing a semiconductor film according to claim 1, wherein the planarization step includes a step of performing planarization without removing the oxide layer after the crystallization step.   The method of manufacturing a semiconductor film according to claim 1, wherein the planarizing step includes a step of reducing a surface roughness of a region irradiated with the planarizing laser beam in the crystalline semiconductor film. .   23. The method of manufacturing a semiconductor film according to claim 1, wherein the planarizing laser beam has an energy density that partially melts the crystalline semiconductor film.   24. The method of manufacturing a semiconductor film according to claim 1, wherein the planarizing step includes a step of using a pulsed laser beam as the planarizing laser beam.   25. The method of manufacturing a semiconductor film according to claim 1, wherein the planarization step includes a step of using a laser beam having a reduced energy density of the crystallization laser beam as the planarization laser beam.

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