JP2008243843A - Crystallization method, method for manufacturing thin-film transistor, substrate for laser crystalization, thin-film transistor, and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crystallization method for manufacturing a large crystal particle array semiconductor thin-film with proper yield, a method for manufacturing a thin-film transistor, a substrate for laser crystallization, a thin-film transistor, and a display device. <P>SOLUTION: The crystallizing method includes the steps of forming a non-single crystal semiconductor film on the substrate, forming a light absorbing film to absorb a part of laser beam for crystallization on the non-single crystal semiconductor film, and irradiating the front surface of the light absorbing film with the laser beam for crystallization to form a continuous and periodical light intensity distribution. In this crystallization method, a light absorption ratio r is selected for the light absorbing film, as a value for obtaining the desired crystal particle length, when an absorption rate of the laser beam for crystallization of the light absorbing film is defined as Acap; an absorption rate of the laser beam for crystallization of the non-single crystal semiconductor film is defined as Asi; and light absorption rate r, defined by the absorption rate Acap and the absorption rate Asi, is given by r=Acap/(Acap+Asi). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a crystallization method, a thin film transistor manufacturing method, a laser crystallization substrate, a thin film transistor, and a display device that are suitable for use in display devices such as liquid crystal and organic EL.

  A driving circuit of a display device such as a liquid crystal display device using a thin film transistor is externally attached on a substrate. Since information handled by the expansion of the IT market is digitized and speeded up, display devices are also required to have high image quality. As means for satisfying this requirement, for example, there is means for forming a switching transistor for switching each pixel in a semiconductor layer on a substrate to increase the switching speed and to improve the image quality.

For example, as a means for crystallizing an amorphous silicon layer formed on a glass substrate, an excimer laser annealing (ELA) method is known. However, the grain size of crystals obtained by this ELA method is about 0.1 μm, and when a thin film transistor (TFT) is formed in this crystallized region, a large number of crystal grains are formed in the channel region of one thin film transistor. The world is included. As a result, the field effect mobility of the thin film transistor is about 100 cm ² / Vs, which is significantly inferior to the field effect mobility of the MOS transistor formed in single crystal Si.

  The present inventors have developed an industrialization technique for forming crystal grains large enough to form a channel portion of at least one thin film transistor by irradiating the amorphous silicon layer with laser light. Unlike a conventional transistor in which a crystal grain boundary is formed in a channel region, forming a TFT in a single crystal grain has no adverse effect of the crystal grain boundary, and TFT characteristics are greatly improved. A functional element such as a sensor can be formed. As such a crystallization method, the present inventors have proposed a crystallization method described in Non-Patent Document 1, Patent Document 1, and the like.

In the former Non-Patent Document 1, an amorphous silicon film is irradiated with a phase-modulated laser beam having a fluence of 0.8 J / cm ² through a SiON / SiO ₂ cap film or a SiO ₂ (silicon dioxide) cap film. Describes a method of crystallizing an amorphous silicon film by laterally growing crystal grains in a direction parallel to the film.

Further, Patent Document 1 discloses that non-stoichiometric silicon oxide having a light absorption characteristic, a SiOx film (x is less than 2) is used as a cap film, and is irradiated with a phase-modulated laser beam. A method for crystal growth of a porous silicon film in the lateral direction is described.
W. Yeh and M. Matsumura Jpn. Appl. Phys. Vol. 41 (2002) 1909. JP 2005-076190 A

However, when a light-transmitting SiO ₂ cap film is used in the method of Non-Patent Document 1, the cap film itself does not generate heat and is insufficient, although it has an effect of suppressing cooling of the silicon layer. As a result, the crystal growth time cannot be extended without maintaining a temperature suitable for crystal growth. The grain size of the obtained crystal structure does not increase.

  Further, the light-absorbing SiON or SiOx cap film in the method of Non-Patent Document 1 and Patent Document 1 can be obtained by changing the ratio of oxygen atoms and nitrogen atoms or the ratio of silicon atoms and oxygen atoms in the film. The absorption spectrum of light changes. That is, the absorption characteristics change greatly due to slight differences in film forming conditions. When these films are used as a cap film for laser crystallization, if the absorption characteristics are suitable, the change over time in the temperature of the cap film and semiconductor layer immediately after pulse laser irradiation is suitable for crystal growth of the semiconductor layer. Thus, the grain size of the obtained crystal structure becomes large. On the other hand, if it deviates from the optimum condition, crystal growth is insufficient and the grain size does not increase.

  That is, if the film quality of the cap film corresponding to the conditions of the semiconductor layer cannot be controlled, the crystal structure formed in the semiconductor layer may be a cause. In the mass production process, the yield deteriorates. Further, in the display device, display unevenness and color unevenness occur, resulting in display failure.

  An object of the present invention is to provide a crystallization method, a thin film transistor manufacturing method, a laser crystallization substrate, a thin film transistor, and a display device capable of manufacturing a large crystal grain array semiconductor thin film stably with a high yield.

  The crystallization method of the present invention includes a step of forming a non-single-crystal semiconductor film on a substrate, a step of forming a light-absorbing film on the non-single-crystal semiconductor film to absorb part of the crystallization laser beam, Irradiating the crystallization laser light to form a continuous periodic light intensity distribution on the surface of the light-absorbing film, the crystallization method comprising: The absorption rate r of the laser light for the laser is defined as Acap, the absorption rate of the laser light for crystallization of the non-single crystal semiconductor film is Asi, and the light absorption ratio r defined by the absorption rate Acap and the absorption rate Asi is r. In the case of = Acap / (Acap + Asi), the light absorption film is characterized in that the light absorption ratio r is selected to obtain a desired crystal grain length.

  The laser crystallization substrate of the present invention is a laser crystallization substrate having a non-single-crystal semiconductor film and a light-absorbing film covering the non-single-crystal semiconductor film, wherein the light-absorbing film includes the light-absorbing film. The absorption rate r defined by the absorption rate Acap and the absorption rate Asi is defined as the absorption rate of the laser light for crystallization as Acap, the absorption rate of the laser beam for crystallization of the non-single crystal semiconductor film as Asi. The light absorption film is characterized in that the light absorption ratio r is selected to obtain a desired crystal grain length when r = Acap / (Acap + Asi).

  In the above case, the crystallization method of the present invention is characterized in that the value of the light absorption ratio r is in the range of 0.10 ≦ r ≦ 0.65. The laser crystallization substrate of the present invention is characterized in that the value of the absorption ratio r is in the range of 0.10 ≦ r ≦ 0.65.

In the above case, in the crystallization method of the present invention, the film thickness d _S and the light absorption ratio r are linear r = 0.3−0.002d _S and linear r = 0.6− in the d _S -r plane. characterized in that in the region sandwiched between the 0.002d _S. In the laser crystallization substrate of the present invention, the film thickness d _S and the absorption ratio r are linear r = 0.3−0.002d _S and linear r = 0.6−0.002d in the d _S -r plane. _It is in a region sandwiched between _S.

The crystallization method of the present invention includes a step of forming a non-single-crystal semiconductor film on a substrate, a step of forming a light-absorbing film on the non-single-crystal semiconductor film to absorb part of the crystallization laser beam, Irradiating the crystallization laser light to form a continuous periodic light intensity distribution on the surface of the light-absorbing film, the crystallization method comprising: Extinction coefficient when the complex refractive index N _cap at the wavelength of the laser beam is N _cap = n _cap −ik _cap (where n _cap is the refractive index, i is the imaginary unit, and k _cap is the extinction coefficient) The k _cap is in the range of 0.003 ≦ k _cap ≦ 0.025. The laser crystallization substrate of the present invention is a laser crystallization substrate having a non-single crystal semiconductor film and a light-absorbing film covering the non-single-crystal semiconductor film, wherein the light-absorbing film is crystallized. the extinction coefficient at the wavelength of use the laser beam is taken as k _cap, the extinction coefficient k _cap is characterized in that in the range of 0.003 ≦ k _cap ≦ 0.025.

The crystallization method of the present invention includes a step of forming a non-single-crystal semiconductor film on a substrate, a step of forming a light-absorbing film on the non-single-crystal semiconductor film to absorb part of the crystallization laser beam, Irradiating the surface of the light-absorbing film with the crystallization laser light that forms a continuous periodic light intensity distribution, wherein the film thickness of the non-single-crystal semiconductor film Is d _S (nm), and the complex refractive index of the light-absorbing film at the wavelength of the laser light for crystallization is N _cap = n _cap −ik _cap (where n _cap is the refractive index, i is the imaginary unit, k _cap is when the extinction coefficient), the thickness d line _S and the extinction coefficient k _cap is in d _S -k _cap surface k _cap = 0.010-0.0001d _S and the straight line k _cap = 0. It is in a region sandwiched between 025-0.0001 d _S. The laser crystallization substrate of the present invention is a laser crystallization substrate having a non-single crystal semiconductor film and a light-absorbing film covering the non-single crystal semiconductor film, the film being a non-single crystal semiconductor film the extinction coefficient at the wavelength of the thickness d _S crystallization laser beam is taken as k _cap, the extinction coefficient k _cap and a straight line k _cap = 0.010-0.0001d _S in d _S -k _cap surface characterized in that in the region sandwiched between the straight line k _cap = 0.025-0.0001d _S.

In the above case, in the crystallization method of the present invention, the wavelength of the crystallization laser light is λ, the film thickness of the light absorbing film is d _cap (nm), and the wavelength of the light absorbing film is λ. The complex refractive index is N _cap = n _cap −ik _cap (where n _cap is the refractive index, i is the imaginary unit, and k _cap is the extinction coefficient), and the film thickness of the non-single crystal semiconductor film is d _s (nm) The complex refractive index at the wavelength λ of the non-single-crystal semiconductor film is N _s = n _s −ik _s (where n _s is the refractive index, i is the imaginary unit, and k _s is the extinction coefficient) for crystallization. The light-absorbing film is formed so that the film thickness d _cap is such that the reflectance R is a maximum value or a minimum value, where R is the reflectance of the laser light-absorbing film surface. To do. In the laser crystallization substrate of the present invention, the wavelength of the crystallization laser light is λ, the film thickness of the light absorbing film is d _cap (nm), and the wavelength of the light absorbing film is complex at the wavelength λ. The refractive index is N _cap = n _cap −ik _cap (where n _cap is the refractive index, i is the imaginary unit, k _cap is the extinction coefficient), and the film thickness of the non-single crystal semiconductor film is d _s (nm). The complex refractive index at wavelength λ of the non-single-crystal semiconductor film is N _s = n _s −ik _s (where n _s is the refractive index, i is the imaginary unit, and k _s is the extinction coefficient) When the reflectance of the light absorbing film surface of the laser beam is R, the light absorbing film has a film thickness d _{cap at} which the reflectance R becomes a maximum value or a minimum value.

  The thin film transistor manufacturing method of the present invention includes a step of forming a crystallized region in the non-single-crystal semiconductor film using any one of the above crystallization methods, and a thin film transistor aligned with the crystallized region. And a process.

  In the above case, the thin film transistor manufacturing method of the present invention is characterized in that the crystal structure in the crystallization region is a crystal grain array including crystal grains grown in the in-plane direction by 2 μm or more.

  The thin film transistor of the present invention is formed in a partial region or the entire region of the non-single-crystal semiconductor film by using any one of the substrate, the non-single-crystal semiconductor thin film formed on the substrate, and the crystallization method described above. Crystallization region, a channel region formed in the crystallization region, a part or all of the source region, a part or all of the drain region, and a gate insulation formed in a part on the channel region And a gate electrode formed on the gate insulating film.

  In the above case, the thin film transistor of the present invention is characterized in that it has a crystal grain array including crystal grains in which the crystal structure in the crystallization region has grown in the in-plane direction by 2 μm or more.

  The display device of the present invention includes a substrate, a non-single-crystal semiconductor thin film formed on the substrate, and a partial region or the entire region of the non-single-crystal semiconductor film using any one of the above crystallization methods. The formed crystallization region, the channel region formed in the crystallization region, part or all of the source region, and part or all of the drain region, and the gate formed in part on the channel region It comprises a thin film transistor having an insulating film and a gate electrode formed on the gate insulating film, and a pixel switching circuit having the thin film transistor.

  Terms in this specification are defined as follows.

  The “non-single-crystal semiconductor film” refers to a thin film to be crystallized such as an amorphous semiconductor (for example, an amorphous silicon film), a polycrystalline semiconductor (for example, a polysilicon film), and a mixed structure thereof.

  In the present invention, “crystallization” means that the amorphous semiconductor film becomes a crystalline semiconductor film in the process of heating and cooling. There are cases where crystallization is performed from the solid phase through the liquid phase, and cases where crystallization is performed directly from the solid phase without passing through the liquid phase.

  “Lateral growth (lateral growth)” means that crystal grains grow 1 μm or more in the horizontal direction along the film surface from the solid-liquid interface, starting from the crystal nucleus through a molten state.

  “Fluence” is a scale representing the energy density of laser light for crystallization, and refers to the amount of energy of one pulse per unit area. Specifically, it is measured in an irradiation region (irradiation field). The average light intensity of laser light.

  “Light intensity distribution” refers to a two-dimensional intensity distribution of light incident on a non-single-crystal semiconductor film for crystallization. In other words, it means the light intensity (brightness) distribution on the detection surface of the irradiation light (illumination light).

  “Attenuator” refers to an optical element that attenuates the intensity of laser light. The attenuator has a function of adjusting the light intensity level of the laser light so that the substrate to be processed is not seized.

  A “phase shifter” is an element in an optical system, which is a spatial intensity modulation optical element for modulating the phase of laser light, and is distinguished from a phase shift mask used in the exposure process of a photolithography process. It is what is done. In the phase shifter, for example, a desired step is formed at a desired location on a quartz base material that does not absorb the wavelength of the laser light to be used. The step of the phase shifter is formed by a process such as etching.

  A “projection lens” is a component of an optical system for projecting an image created by a phase shifter onto a substrate surface. When the irradiation size is small, a telecentric lens is generally used. By using a telecentric lens, it is possible to prevent the size of the projected image from changing even if the distance between the substrate and the lens changes somewhat. For this reason, a single telecentric lens system in which only the substrate side is parallel or a bi-telecentric lens system in which both the substrate side and the light source side are parallel is used. In mass-production equipment, so-called “long” beams are often used as irradiation beams. For example, only a short side has a telecentric structure, and a “semi-cylinder” type projection lens (cylindrical lens) is used. It is done.

  “Homogenizer” refers to an optical element that divides incident light into a plurality of light beams, converges the divided light beams, and equalizes the light intensity on a specific surface.

  “Light absorption ratio r” means light absorption when the light absorption rate of the light absorption film (cap film) is Acap and the light absorption rate of the non-single-crystal semiconductor film (crystallization target film) is Asi. R = Acap / (Acap + Asi) where r is the light absorption ratio of the cap layer 18.

  According to the present invention, a large crystal grain array semiconductor thin film can be manufactured stably with high yield. By using the crystallization method of the present invention, a high-performance thin film transistor and a display device can be manufactured.

  Hereinafter, various preferred embodiments of the substrate for laser crystallization of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a schematic cross-sectional view showing a sample structure (substrate to be processed) for explaining the absorption ratio r and effective light intensity Ieff of the light absorbing cap layer film 18 defined in the laser crystallization substrate of the present invention. is there. The sample has a semiconductor layer 17 such as an amorphous layer, a silicon layer, and a light-absorbing cap layer 18 such as a SiOx layer, which are laminated directly or indirectly on a substrate 15 such as a plastic substrate, a semiconductor wafer substrate or a glass substrate. An example is shown in which laser light is perpendicularly incident on the surface of the SiOx layer. When the laser beam 12 is irradiated with the fluence I (J / cm 2) from the light absorbing cap layer 18 side, a part of the light is reflected on the surface of the light absorbing cap layer 18 and the other part of the light is The light-absorbing cap layer absorbs and the other part of the light is absorbed by the semiconductor layer. Here, when the reflectance at the surface of the light absorbing cap layer 18 is R, the light absorption rate of the light absorbing cap layer film 18 is Acap, and the light absorption rate of the semiconductor layer is Asi, the semiconductor layer is sufficiently thick (for example, 50 nm), when using laser light having a wavelength that is easily absorbed by the semiconductor layer (for example, when wavelength λ = 308 nm), R + Acap + Asi = 1. Assuming that the light absorption ratio defined by the absorption rate Acap and the absorption rate Asi is r, r = Acap / (Acap + Asi) is an amount that the light absorption cap layer 18 and the semiconductor layer 17 effectively absorb ( It represents the ratio of the amount (Acap) absorbed by the light-absorbing cap layer 18 to Acap + Asi).

  Further, the fluence Ieff corresponding to the amount of heat that is absorbed by the laser light that is effectively incident on the light-absorbing cap layer 18 and the semiconductor layer 17 can be expressed as Ieff × (1−R).

  These values are the laser light wavelength λ, the thickness of the light-absorbing cap layer 18, the refractive index and extinction coefficient for the wavelength λ, and the refractive index of the semiconductor layer 17 for the wavelength λ when laser crystallization is performed in the atmosphere. And is determined by the extinction coefficient.

  FIG. 2A shows a case where the substrate 8 having the sample structure shown in FIG. 1 having a different light absorption ratio r of the light absorbing cap layer 18 is effectively irradiated with laser light having the same light intensity distribution. It is a temperature distribution figure which shows a mode that light intensity is distributed to each layer by contrast. FIG. 2B is a diagram showing that the irradiation laser light incident on the target substrate 8 at that time has the same effective light intensity distribution. FIG. 2A shows a case where the light absorption ratio r in the light-absorbing cap layer 18 is small ((i) in FIG. 2 (a)) and a case where the light absorption ratio r is large ((ii) in FIG. 2 (a)). Is shown in comparison. According to the light intensity absorbed by the light-absorbing cap layer 18 and the semiconductor layer 17, a temperature distribution is formed in each layer immediately after laser irradiation. When r is small as shown in (i) of FIG. 2A, the temperature of the light-absorbing cap layer 18 does not rise as compared with the case where r is large as shown in (ii) of FIG. The temperature gradient formed in the light absorbing cap layer 18 is gentle. In addition, the temperature in the semiconductor layer 17 increases accordingly, and the temperature gradient formed in the semiconductor layer 17 becomes steep. The melting region is determined according to a temperature gradient formed in the semiconductor layer 17. As shown in FIG. 2A, the melting region becomes wider as the light absorption ratio r is smaller. This is because the high temperature region in the semiconductor layer becomes wide. The temperature gradient in the semiconductor layer having a relatively high thermal conductivity tends to collapse with time due to longitudinal thermal diffusion to the substrate 15 and lateral thermal diffusion in the semiconductor layer 17. On the other hand, since the insulating cap layer 18 has a lower thermal conductivity than the semiconductor layer 17, the temperature gradient in the cap layer 18 is maintained in the cap layer 18 for a long time. Further, the thermal diffusion to the semiconductor layer 17 suppresses the collapse of the temperature gradient in the semiconductor layer 17. This effect is more remarkable when the light absorption ratio r is larger.

  Next, with reference to FIG. 3, a method for obtaining the light intensity distribution of the incident light to the semiconductor layer 17 and the light intensity necessary for the semiconductor layer 17 to melt in the laser crystallization process in the present invention will be described. . FIG. 3A is a schematic diagram for explaining an inverted V-shaped light intensity distribution characteristic of incident light incident on the semiconductor layer 17. FIG. 3B is an SEM photograph showing the crystal structure of the semiconductor layer corresponding to each light intensity position of the inverted V-shaped light intensity distribution. In order to enlarge and lengthen the crystal grains formed in the semiconductor layer, it is necessary to grow in the lateral direction. For this purpose, it is indispensable to widen the melting region. In the region a where the light intensity is low in FIG. 3, the temperature of the semiconductor layer 17 does not rise to the temperature necessary for crystallization, and thus remains amorphous (amorphous region 105 in FIG. 18). In the region b where the light intensity is higher than that in the region a, the temperature of the semiconductor layer 17 is higher than the temperature necessary for crystallization and becomes a fine crystal, but it does not reach the melting temperature and therefore does not grow laterally. (Microcrystalline region 104 in FIG. 18). Further, in the region c where the light intensity is high, the temperature of the semiconductor layer 17 is equal to or higher than the temperature necessary for melting, and the light intensity distribution shown in FIG. In response to this, the solid-liquid interface sequentially moves, and crystal grains grow laterally (crystal grains 103 in FIG. 18). The line that starts the first-stage lateral growth, which is the boundary between the region b and the region c, is a solid-liquid interface immediately after laser light irradiation, and the light intensity corresponding to this line melts the semiconductor layer 17. This is the minimum light intensity necessary for this.

  4A shows a sample having a film structure of cap film 18 / semiconductor layer (a-Si, 100 nm) 17 / substrate 15 shown in FIG. 4B using a laser annealing apparatus (see FIG. 16). FIG. 19 is a characteristic diagram showing the relationship between the light absorption ratio r = Acap / (Acap + Asi) and the grain length l in the crystal structure (see FIG. 18) formed in the semiconductor layer 17 when the layer 17 is crystallized. In the laser annealing apparatus, a phase shifter 6 that forms a light intensity distribution of a V-shaped pattern having a bottom relative intensity of 0.2, a top relative intensity of 1, and a period T of 32 μm on the sample surface (FIG. 17A). (See (b)) was used.

  As apparent from FIG. 4A, when the thickness of the semiconductor layer 17 such as an amorphous silicon layer (a-Si) is 100 nm, the light absorption ratio r is in the range of r = 0.22 to 0.26. The length became 8 μm or more and became the longest. Further, the light absorption ratio r was 5 μm or more in the range of r = 0.1 to 0.5.

  (A), (b), and (c) in FIG. 5 show the crystal structure of each point in the relationship between the light absorption ratio r = Acap / (Acap + Asi) and the grain length l (FIGS. 4 and 5 (d)). It is a SEM photograph which shows. The light absorption ratio r at which the grain length l becomes the maximum is that the crystal structure at r = 0.22 (FIG. 5A) has an amorphous region, a fine crystal region, and a lateral growth region in order from both ends of the SEM photograph. To do. The molten region and the lateral growth region coincide with each other, and the laterally grown grains that have grown from both sides in the central line collide head-on. The length of the laterally grown grains is 8 μm, and the width of the molten region is twice that of 16 μm.

  As shown in FIG. 5 (b), when the light absorption ratio r = 0.06 is small, the width of the amorphous region and the fine crystal region is narrower than that of the crystal structure at r = 0.22, and the melted region The width of becomes wide. However, the melting region and the lateral growth region do not match. That is, the lateral growth at the first stage started from the interface between the fine crystal region and the melted region stops halfway. The longest crystal grains are laterally grown in the third stage and reach only 3.5 μm. As described with reference to FIG. 2A, when the light absorption ratio r decreases, the melting region of the semiconductor layer 17 expands, but heat escapes not only to the substrate 15 side but also to the cap layer 18 side. Since the semiconductor layer 17 is easily cooled and the return of heat from the light-absorbing cap layer 18 after a lapse of time is reduced, the temperature gradient in the semiconductor layer 17 serving as a driving force for lateral growth is reduced. Because it collapses quickly.

  On the other hand, as shown in FIG. 5C, when the light absorption ratio r = 0.48 is large, the widths of the amorphous region and the fine crystal region are larger than the crystal structure at r = 0.22. It becomes wider and the lateral growth region becomes narrower. The melting region and the lateral growth region coincide with the crystal structure at r = 0.22. The length of the laterally grown grains is 5.5 μm, and the width of the molten region is twice that of 11 μm. The grain length is shortened as the width of the melting region is narrowed.

  FIG. 6A is a characteristic diagram showing the relationship between the light absorption ratio r = Acap / (Acap + Asi) and the grain length l when the thickness of the a-Si layer as the semiconductor layer 17 is 50 nm. The crystallization conditions are the same as those in FIGS. 4 and 5 (a-Si layer thickness 100 nm) except for the thickness of the a-Si layer. As apparent from FIG. 6A, when the film thickness of the a-Si layer is 50 nm, the grain length is 8 μm or more in the range of the light absorption ratio r = 0.28 to 0.36, which is the longest. In addition, the grain length was 5 μm or more in the range of the absorption ratio r = 0.10 to 0.65.

  (A), (b), and (c) in FIG. 7 show the crystal structure of each point in the relationship between the light absorption ratio r = Acap / (Acap + Asi) and the grain length l (FIGS. 6 and 7 (d)). It is a SEM photograph which shows. From the results of FIGS. 7A, 7B and 7C, when the film thickness of the a-Si layer is 50 nm, the grain length is 8 μm or more in the range of the light absorption ratio r = 0.32 to 0.35, which is the longest. became. Further, the grain length was 5 μm or more in the range of the light absorption ratio r = 0.10 to 0.65. In the crystal structure (FIG. 7A) at the light absorption ratio r = 0.35 that maximizes the grain length, there are an amorphous region, a fine crystal region, and a lateral growth region in order from both ends of the SEM photograph. The molten region and the lateral growth region coincide with each other, and the laterally grown grains that have grown from both sides in the central line collide head-on. The length of the laterally grown grains is 8.0 μm, and the width of the molten region is twice that of 16 μm.

  As shown in FIG. 7B, when the light absorption ratio r is as small as 0.18, the width of the amorphous region is narrower and the width of the molten region is wider than the crystal structure at r = 0.35. Become. However, the melting region and the lateral growth region do not match. That is, the lateral growth at the first stage started from the interface between the fine crystal region and the melted region stops halfway. The longest crystal grains are grown in the third stage and have a grain length of 6.0 μm. As described with reference to FIG. 2, when the light absorption ratio r decreases, the melting region of the semiconductor layer 17 expands, but heat escapes not only to the substrate 15 side but also to the cap layer 18 side. The temperature gradient in the semiconductor layer 17 that becomes a driving force for lateral growth quickly collapses because the heat is easily cooled and the return of heat from the light-absorbing cap layer 18 after a lapse of time becomes small. It will end up. However, since the a-Si layer is thinner than the 100-nm thickness of the a-Si layer, the thermal diffusion in the film surface direction is limited, so that the lateral growth is easy. Collides head-on at the center line.

  On the other hand, as shown in FIG. 7C, when the light absorption ratio r = 0.46 is large, the width of the amorphous region becomes wider than the crystal structure at r = 0.35, and the laterally grown region Becomes narrower. The melting region and the lateral growth region coincide with each other in the same manner as the crystal structure at the light absorption ratio r = 0.35. The length of the laterally grown grains is 7.0 μm, and the width of the molten region is 14 μm, which is twice as long. As the width of the melting region becomes narrower, the grain length also becomes shorter.

  As is clear from the above results, in order to grow the crystal grains long, it is necessary to optimize the film structure of the substrate 8 to be processed, and in particular, the absorption ratio r of the laser light between the cap layer 18 and the semiconductor layer 17. It is indispensable to control. This applies not only to the case where the crystal is grown one-dimensionally in one direction but also to the case where a two-dimensional crystal growth is aimed at a large-area crystal grain array. Further, the crystal is not limited to a crystallization method in which a light intensity distribution is formed on the surface of the substrate 15 using a phase shifter and laser irradiation is performed, and a crystal that is laterally grown by forming a temperature distribution in the semiconductor layer 17 in the crystallization process. It is the same in all the conversion methods.

As described above, it has been found from FIGS. 4 to 7 that when the film thickness of the semiconductor layer 17 is changed, the value of the light absorption ratio r that is optimal for increasing the grain length is changed. FIG. 8A shows the range of the film thickness d _s of the a-Si layer and the light absorption ratio r in which the grain length is 7 μm or more. In the region E sandwiched between the straight line r = 0.3−0.002d _S and the straight line r = 0.6−0.002d _{S in} FIG. 8A, the grain length is 7 μm or more. Become. Desirably, the film thickness d _s and the light absorption ratio r of the semiconductor layer 17 are set in a region sandwiched between the straight line r = 0.4−0.002 d _S and the straight line r = 0.5−0.002 d _S. Good to do.

The light absorption ratio r = Acap / (Acap + Asi) is mainly determined by the extinction coefficient k _cap and the film thickness d _cap of the cap layer 18 with respect to the wavelength of the laser beam to be used. In other words, assuming that the cap layer (single layer) 18 is on the semiconductor layer (substrate) 17, it is determined by the theory of multiple reflection when laser light is incident from the surface of the cap layer 18. As the extinction coefficient k _cap of the cap layer 18 increases, the value of the absorption rate Acap of the cap layer 18 increases and the value of the light absorption ratio r increases.

  Next, a mechanism for achieving the maximum grain length when the light absorption ratio r = Acap / (Acap + Asi) is an appropriate value will be described with reference to FIG. FIG. 9 is a characteristic diagram showing the relationship between the light absorption ratio r, the effective light intensity Ieff that can be incident without ablation, and the effective light intensity Ieff that the a-Si layer that is the semiconductor layer 17 melts. FIG. 9 shows the case where the film thickness of the a-Si layer is 100 nm and 50 nm. Each effective light intensity Ieff was obtained by the method shown in FIG. In FIG. 9, the absorption ratio r which achieves the maximum grain length in the film thickness of each a-Si layer is indicated by a one-dot chain line. If the effective light intensity Ieff that can be incident is high, the temperature of the light-absorbing cap layer 18 and the semiconductor layer 17 can be raised by that amount, which is considered effective for increasing the particle size. Further, if the effective light intensity Ieff at which the a-Si layer is melted is low, the width of the melted region necessary for lateral growth can be widened, which is considered effective for increasing the particle size.

  Regardless of the film thickness of the a-Si layer, the maximum grain length is obtained in that the tendency changes in the relationship between the light absorption ratio r and the incident effective light intensity Ieff. That is, the effective light intensity Ieff that can be incident is a substantially constant value up to the light absorption ratio r value that is the maximum grain length condition with respect to the increase in the absorption ratio r, but decreases when the light absorption ratio r value becomes larger.

  On the other hand, the effective light intensity Ieff at which the a-Si layer melts is a substantially constant value up to a certain light absorption ratio r value with respect to the increase in the light absorption ratio r, but increases when the light absorption ratio r value becomes larger. To do. The maximum grain length is reached at a light absorption ratio r slightly larger than the point at which the effective light intensity Ieff at which the a-Si layer melts begins to increase.

  5 and 7, when the light absorption ratio r is larger than the maximum grain length condition, the melting region, that is, the lateral growth region is narrowed, because the effective light intensity Ieff that can be incident is lowered as shown in FIG. In addition, the effective light intensity Ieff at which the a-Si layer melts increases.

10 shows a sample of a film structure of cap layer 18 (optical constant 1.50-0.01i) / semiconductor layer 17 (optical constant 1.69-2.76i) / substrate 15 with a laser beam having a wavelength λ = 308 nm. 2 shows the relationship between the film thickness d _cap of the cap layer 18 and the reflectance R of the laser beam on the surface of the cap layer 18 in the case of incident light. The reflectance R periodically varies while taking a maximum value and a minimum value with respect to the film thickness d _cap of the cap layer 18 and attenuates according to the value of the extinction coefficient k _cap . If the fluence of the incident laser beam is constant, the fluence that is effectively absorbed by the cap layer 18 and the semiconductor layer 17 changes depending on the value of the reflectance R. That is, if the reflectance R is large, the effective absorption fluence is small, and if the reflectance R is small, the effective absorption fluence is large.

The film thickness d _{cap of the} cap film is preferably set so that the value of the reflectance R becomes a maximum value or a minimum value. When the substrate 15 for laser crystallization is formed by film formation, in-plane unevenness of the film thickness of the semiconductor layer 17 and the cap layer 18, particularly the cap layer 18 is unavoidable. In the relationship between the film thickness d _cap of the cap layer 18 determined by the optical constants of the semiconductor layer 17 and the cap layer 18 and the reflectance R, the target film thickness d _cap of the cap layer 18 is the maximum value of the reflectance R. Alternatively, if the film is formed so as to have a minimum value, the unevenness of the reflectance corresponding to the unevenness of the film thickness can be suppressed, that is, the in-plane unevenness of the effective absorption fluence can be suppressed. And a large crystal grain array can be formed stably.

If the film thickness d _cap of the target cap layer 18 is set so that the reflectance R becomes a minimum value, the incident fluence at the time of laser crystallization can be reduced, and from the viewpoint of energy saving. It is valid.

Further, if the film thickness d _cap of the target cap layer 18 is set so that the reflectance R becomes a maximum value, the incident fluence at the time of laser crystallization increases. The margin can be widened. That is, since the fluctuation of the effective absorption fluence with respect to the fluctuation of the incident fluence (in-plane fluctuation of the irradiation region and fluctuation for each shot) becomes small, it is effective from the viewpoint of yield of uniformly crystallizing a large area.

FIG. 11 shows the relationship between the film thickness d _cap of the cap layer 18 and the light absorption ratio r (= Acap / (Acap + Asi)). Calculation is performed for the same sample structure as in FIG. As the film thickness d _cap of the cap layer 18 increases, the value of the light absorption ratio r increases monotonously.

That is, in order to control the value of the light absorption ratio r, the extinction coefficient k _cap and the film thickness d _cap of the cap layer 18 are controlled, but the film thickness d _cap of the cap layer 18 as shown in FIG. Is a cause of a large change in the reflectance R of the laser beam on the surface of the cap layer 18 (see FIG. 19), it is desirable to control the absorption ratio r by controlling the extinction coefficient k _cap .

FIG. 12 shows a sample having a film structure of cap layer 18 / semiconductor layer 17 (a-Si, 100 nm) / substrate 15 on the sample surface with a bottom relative strength of 0.2, a top relative strength of 1, and a period. When a semiconductor layer is crystallized using a phase shifter (see FIGS. 17A and 17B) that forms a V-shaped light intensity distribution of 32 μm (see FIGS. 17A and 17B), The relationship between the extinction coefficient k _cap of the cap layer 18 and the grain length l is shown. When k _cap = 0.005 to 0.008, the grain length is 8 μm or more, which is the longest. Further, when k _cap = 0.003 to 0.020, the grain length becomes 5 μm or more.

FIG. 13 shows the relationship between the extinction coefficient k _cap of the cap layer 18 and the grain length l when the film thickness of the a-Si layer is 50 nm. The crystallization conditions are the same as in the case of the film thickness of the a-Si layer of 100 nm in FIG. 12 except for the film thickness of the a-Si layer. When k _cap = 0.010 to 0.011, the grain length is 8 μm or more, which is the longest. Further, when k _cap = 0.003 to 0.025, the grain length becomes 5 μm or more.

Similarly, the optimum extinction coefficient k _cap of the cap layer 18 is changed from FIG. 12 to FIG. 13 so that the value of the optimum absorption ratio r changes in order to lengthen the crystal grains when the film thickness d _s of the semiconductor layer 17 changes. It can be seen that the value of also changes.

FIG. 14 shows a range of the film thickness d _s of the a-Si layer and the extinction coefficient k _cap of the cap layer 18 in which the grain length is 7 μm or more. As shown in FIG. 14, when in the region F sandwiched between the straight line k _cap = 0.010-0.0001d _S and the straight line k _cap = 0.025-0.0001d _S, particle length 7μm That's it. Desirably the region sandwiched between the straight line k _cap = 0.015-0.0001d _S and the straight line k _cap = 0.020-0.0001d _S, the film thickness d _s and the cap layer 18 of the semiconductor layer 17 It is preferable to set an extinction coefficient k _cap .

  FIG. 15 is a diagram in which the light absorption ratio r on the horizontal axis in FIG. 9 is replaced with the extinction coefficient kcap of the cap layer 18. If the film thickness of the light-absorbing cap layer 18 is unified to substantially the same value, the same characteristic diagram is obtained even if the horizontal axis changes to the extinction coefficient kcap.

  Next, the reason for limiting the numerical values of each parameter will be described. The absorption rate of the crystallization laser light of the light absorbing film (cap layer) 18 is Acap, the absorption rate of the crystallization laser light of the non-single crystal semiconductor film (semiconductor layer) 17 is Asi, and the absorption rate Acap and absorption. When the light absorption ratio r defined by the rate Asi is r = Acap / (Acap + Asi), the value of the light absorption ratio r is desirably controlled in the range of 0.10 to 0.65. When the light absorption ratio r is smaller than 0.10, the temperature of the cap layer 18 does not rise, and the temperature gradient in the cap layer 18 formed according to the light intensity distribution of the irradiated laser light also becomes gentle. Therefore, in the crystallization process, the temperature range of the semiconductor layer 17 cannot be maintained for a long time in a range suitable for crystal growth, and the temperature gradient formed in the semiconductor layer 17 can also be maintained for a long time. The crystal grains do not stretch.

  If the light absorption ratio r is greater than 0.65, the temperature of the cap layer 18 will increase too much. Accordingly, thermal diffusion from the semiconductor layer 17 to the cap layer film 18 hardly occurs, and the semiconductor layer 17 is likely to be ablated (film evaporation) during laser irradiation. For this reason, the laser fluence that can be incident is lowered, and as a result, the crystal grains are not elongated.

As described above, the optimum value of the absorption ratio r = Acap / (Acap + Asi) varies depending on the film thickness d _s of the semiconductor layer 17.

As shown in FIG. 8, the relationship between the film thickness d _s of the semiconductor layer 17 and the absorption ratio r is such that the straight line r = 0.3−0.002 d _S and the straight line r = 0.6−0 in the d _S -r plane. It is desirable to exist in a region E sandwiched between .002d _S. If the region E deviates from the lower side, the temperature of the cap layer 18 does not rise, and the temperature gradient in the cap layer 18 formed according to the light intensity distribution of the irradiated laser light also becomes gentle. Therefore, in the crystallization process, the temperature range of the semiconductor layer 17 cannot be maintained for a long time in a range suitable for crystal growth, and the temperature gradient formed in the semiconductor layer 17 can also be maintained for a long time. The crystal grains do not stretch.

  If it deviates from this area E, the temperature of the cap layer 18 will rise too much. Accordingly, thermal diffusion from the semiconductor layer 17 to the cap layer film 18 hardly occurs, and the semiconductor layer 17 is likely to be ablated (film evaporation) during laser irradiation. Accordingly, the laser fluence that can be incident is lowered, and as a result, the crystal grains are not elongated.

Relationship between the film thickness d _s and the absorption ratio r of the semiconductor layer 17, more preferably, d _S -r straight line in the plane r = 0.4-0.002d _S and the straight line r = 0.5-0.002d _S It is good to exist in the area | region pinched | interposed between.

The extinction coefficient k _cap of the cap layer 18 is one of the factors that determine the light absorption ratio r, and is preferably in the range of 0.003 to 0.025. When the extinction coefficient k _cap is less than 0.003, the temperature of the cap layer 18 does not rise, and the temperature gradient in the cap layer 18 formed according to the light intensity distribution of the laser beam to be irradiated becomes gentle. Therefore, in the crystallization process, the temperature range of the semiconductor layer 17 cannot be maintained in a range suitable for crystal growth for a long time, and the temperature gradient formed in the semiconductor layer 17 is also maintained for a long time. The crystal grains do not stretch.

On the other hand, when the extinction coefficient k _cap exceeds 0.025, the temperature of the cap layer 18 is excessively increased. As a result, thermal diffusion from the semiconductor layer 17 to the cap layer film 18 hardly occurs, and the semiconductor layer 17 is likely to be ablated (film jump) during laser irradiation. Accordingly, the laser fluence that can be incident is lowered, and as a result, the crystal grains are not elongated.

As described above, the optimum value of the extinction coefficient k _cap of the cap layer 18 varies depending on the film thickness d _s of the semiconductor layer 17. Further, since the light absorption ratio r is mainly determined by the extinction coefficient k _cap of the cap layer 18 and the film thickness d _cap of the cap layer 18, the light absorption ratio r also varies depending on the film thickness d _cap of the cap layer 18. To do.

Relationship between the extinction coefficient k _cap of thickness d _s and the cap layer 18 of the semiconductor layer 17, as shown in FIG. 14, the straight line k _cap = 0.010-0.0001d _S in d _S -k _cap plane It is desirable to exist in a region F sandwiched between the straight line k _cap = 0.025−0.0001 d _S. If the region F deviates from the region F, the temperature of the cap layer 18 does not rise, and the temperature gradient in the cap layer 18 formed according to the light intensity distribution of the irradiated laser light also becomes gentle. Therefore, in the crystallization process, the temperature range of the semiconductor layer 17 cannot be maintained for a long time in a range suitable for crystal growth, and the temperature gradient formed in the semiconductor layer 17 can also be maintained for a long time. The crystal grains do not stretch.

  If the region F deviates from the upper side, the temperature of the cap layer 18 will increase too much. Accordingly, thermal diffusion from the semiconductor layer 17 to the cap layer film 18 hardly occurs, and the semiconductor layer 17 is likely to be ablated (evaporation of the film) during laser irradiation. Accordingly, the laser fluence that can be incident is lowered, and as a result, the crystal grains are not elongated.

Relationship between the extinction coefficient k _cap of thickness d _s and the cap layer 18 of the semiconductor layer 17, more preferably, d _S -r straight line in the plane k _cap = 0.015-0.0001d _S and the straight line k _cap = 0.020-0.0001D _S may be present in the range of the region surrounded by the.

The range of the film thickness d _cap of the cap layer 18 is not particularly mentioned as the scope of the present invention, but is preferably in the range of 100 nm to 500 nm.

As described above, the film thickness d _cap of the cap layer 18 is such that the wavelength of the laser light is λ, and the complex refractive index (optical constant) at the wavelength λ of the cap layer 18 is N _cap = n _cap −ik _cap (where n _cap is refracted). Ratio, i is an imaginary unit, k _cap is an extinction coefficient), the film thickness of the semiconductor layer 17 is d _s (nm), and the complex refractive index (optical constant) at the wavelength λ of the semiconductor layer 17 is N _s = n _s −ik _s (n _s is a refractive index, i is an imaginary unit, k _s is an extinction coefficient), and is a diagram of the film thickness d _cap of the cap layer 18 and the reflectance R of the laser beam on the surface of the cap film 17 In the relationship as shown in FIG. 10, it is desirable to set the reflectance R to a maximum value or a minimum value. When the film thickness d _cap of the cap layer 18 is in the range of 100 nm or more and 500 nm or less after satisfying this condition, 0.003 or more and 0.025 or less which is an appropriate range of the extinction coefficient k _cap of the cap layer 18 described above. The value of the light absorption ratio r can be controlled to 0.10 or more and 0.65 or less under the condition of the range.

  As a physical property of the cap layer 18, it is desirable that the material has a low thermal conductivity. This is because it becomes easy to maintain the semiconductor layer 17 at a temperature suitable for crystal growth. In addition, since the temperature gradient in the cap layer 18 formed based on the light intensity distribution at the time of laser irradiation is difficult to collapse, the temperature in the semiconductor layer 17 that tends to collapse when the semiconductor layer 17 is thick or melts. This is because it is easy to maintain the gradient.

  The crystal grain length or crystal grain size in the crystal structure of the semiconductor layer 17 is preferably long, but is 2 μm or more. If it is shorter than 2 μm, it becomes difficult to produce a high-performance thin film transistor or semiconductor device.

  Next, a process for crystallizing the non-single crystal semiconductor layer 17 and a process for manufacturing a thin film transistor and a liquid crystal display device will be specifically described with reference to the following examples.

  Next, an embodiment of a crystallization apparatus for crystallizing the semiconductor layer 17 of the substrate 8 to be processed will be described with reference to FIG. The same parts as those in FIGS. 1 to 15 are denoted by the same reference numerals, and detailed description thereof will be omitted because it is duplicated.

FIG. 16 is a configuration diagram of a projection type crystallization apparatus (laser annealing apparatus) used in this example. The crystallization apparatus 1 includes an excimer laser oscillator 2, an illumination optical system including a concave lens 3 sequentially provided on the optical axis of the apparatus 2, a convex lens 4, and a homogenizer 5, a phase shifter 6, and a projection lens 7. An imaging optical system, a mounting table 9 on which the substrate 8 to be processed is mounted, an XYZθ stage 10, and a controller 11. That is, the crystallization apparatus 1 uses the imaging optical system including the illumination optical system including the concave lens 3, the convex lens 4, and the homogenizer 5, the phase shifter 6, and the projection lens 7 to place the pulse laser beam 12 on the mounting table 9. The substrate 8 to be processed is irradiated.
For example, an XeCl excimer laser oscillator that emits excimer laser light having a wavelength of 308 nm can be used as the excimer laser oscillator 2. Other laser oscillators such as a KrF excimer pulse laser oscillator and a YAG laser oscillator can also be used.

  The homogenizer 5 converts the incident pulse laser beam into a laser beam having a uniform light intensity within the plane. The uniformized laser light is incident on the phase shifter 6. The phase shifter 6 modulates the phase of incident light and emits pulsed laser light 12 having a V-shaped light intensity distribution as shown in FIG. The pulsed laser beam 12 having a V-shaped light intensity distribution enters the imaging optical system. The imaging optical system forms an image of the pulse laser beam 12 having a V-shaped light intensity distribution on the substrate 8 to be processed. A part of the laser light incident on the substrate 8 to be processed is reflected, and the other part is absorbed by the light-absorbing cap layer 18 so as to correspond to the light intensity distribution of the incident light as shown in FIG. Due to the distribution, the cap layer 18 generates heat, and the other part is absorbed by the semiconductor layer 17 and the semiconductor layer 17 generates heat. A part of the irradiation region in the semiconductor layer 17 is melted, and a crystallization region is formed in the cooling process after the pulse laser beam is blocked.

  The exit optical path of the excimer laser oscillator 2 is provided with an attenuator for adjusting a laser light amount (not shown) to a desired light amount. A homogenizer 5 is provided on the outgoing optical path of the attenuator via a concave lens 3 and a convex lens 4. The homogenizer 5 has a function of making the in-plane light intensity distribution of the pulse laser beam 12 uniform in the irradiation region. That is, the homogenizer 5 is an optical system for homogenizing (homogenizing) the incident angle and light intensity of the passing pulse laser beam 12 to the phase shifter 6.

  Further, the homogenized pulse laser beam 12 is subjected to light intensity modulation by the phase shifter 6 shown in FIGS. The phase shifter 6 is used to phase-modulate incident laser light having a uniform light intensity by forming an uneven surface on a material transparent to the wavelength of the laser light to be used, such as quartz glass, and to crystallize it laterally. This is an optical system for emitting light intensity distribution light. As a result, for example, a light intensity distribution having a repeating pattern that repeats monotonous increase and monotonous decrease is formed on the surface of the substrate 8 to be processed. In this embodiment, as the phase shifter 6, as shown in FIG. 17C, the phase shifter 6 as shown in FIG. 17A has a bottom relative strength of 0.2, a top relative strength of 1, and a period of 32 μm. The V-shaped light intensity distribution is formed on the surface of the substrate 8 to be processed.

The pulsed laser light 12 that has undergone phase modulation (light intensity modulation) by the phase shifter 6 enters the projection lens 7. The projection lens 7 is provided so as to form an image of the phase shifter 6 on the upper surface of the substrate 8 to be processed. The projection lens 7 is an optical system in which the reduction ratio of a reduced image, for example, a reduced image is 1/5. For example, if the area of the irradiation surface of the phase shifter 6 is 100 mm ² , the corresponding projection image is 4 mm ² .

  The mounting table 9 is mounted on an XYZθ stage 10, is movable in the X-axis and Y-axis directions in the horizontal plane, is movable in the Z-axis direction orthogonal to the horizontal plane, and is rotatable about the Z-axis. is there. The power supply circuit of the XYZθ stage 10 is connected to the output unit of the controller 11 so that the X-axis drive mechanism, the Y-axis drive mechanism, the Z-axis drive mechanism, and the θ-rotation drive mechanism are controlled. By moving these in each direction, the substrate 8 to be processed can be aligned with high accuracy with respect to the crystallization optical system. The power supply circuit of the excimer laser oscillator 2 is connected to the output section of the controller 11 so that the oscillation timing, pulse interval, output magnitude, etc. of the pulse laser beam 12 are controlled.

  The controller 11 controls the conveyance of the substrate to be processed 8 to a predetermined position on the mounting table 9 by a program stored in advance, and controls the substrate 8 to be temporarily fixed, for example, an electrostatic chuck or a vacuum chuck. The controller 11 aligns the temporarily fixed substrate 8 to be processed according to a predetermined procedure. The controller 11 controls the movement of the substrate to be processed 8 based on the crystallization position information of the substrate to be processed 8 stored in advance.

  Further, the controller 11 performs control for causing the excimer laser oscillator 2 to oscillate. The emitted pulse laser 12 has a pulse width of, for example, 30 nsec.

  Various embodiments of the present invention will be described below.

Example 1
As shown in FIG. 17 (d), the substrate 8 to be processed of the present embodiment has a base protective film 16, a non-single crystal semiconductor layer film 17 such as an amorphous silicon film, and a cap layer 18 such as light on a substrate 15 such as a glass substrate. Absorbable SiOx films are stacked in this order. The cap layer film 18 has a light absorptivity with respect to the crystallization laser beam, and makes it possible to obtain a long lateral growth distance with a low fluence. Such a substrate 8 to be processed is manufactured as follows.

  First, an insulating layer to be the base protective film 16 is formed on the substrate 15. As the substrate 15, in addition to an insulating substrate such as a glass substrate, a quartz substrate, or a plastic substrate, a metal substrate, a silicon substrate, a ceramic substrate, or the like having an insulating film formed on the surface can be applied. As the base protective film 16, a silicon dioxide film having a film thickness of 50 to 2000 nm, for example, 100 nm is formed by plasma chemical vapor deposition.

Next, an amorphous silicon film is formed as the non-single-crystal semiconductor layer 17 on the base protective film 16. As a method for forming an amorphous silicon film, an amorphous Si film having a thickness of 100 nm is formed by plasma chemical vapor deposition using, for example, SiH ₄ gas and H ₂ gas.

Next, a cap layer 18, for example, a light-absorbing SiOx film (x is less than 2) is formed as a light-absorbing cap layer. This SiOx film is formed by, for example, a plasma chemical vapor deposition method using SiH ₄ gas and N ₂ O gas. The optical constant N _cap (complex refractive index N _cap ) of the SiOx film can be selectively controlled by changing the flow rate ratio of, for example, SiH ₄ gas and N ₂ O gas during film formation. The film thickness d _cap is controlled by the film formation time. As a result of measurement and analysis by ellipsometry after the dehydrogenation step described later, in this example, N _cap = 1.481−0.0054i (refractive index n = 1.481, i is an imaginary unit, extinction coefficient k _cap = 0 .0054). Further, the film thickness d _cap was in a range of 454 ± 10 nm including in-plane unevenness. At this time, the reflectance R of the laser beam on the surface of the substrate 15 is almost a minimum value in the cap film thickness d _{cap -reflectance} curve under this condition, and the value of the absorption ratio r is 0.21. These values are in an appropriate range in FIGS. 4, 8, 12, and 14.

The base protective film 16 is a material that prevents the penetration of impurities from the substrate 15 to the non-single-crystal semiconductor layer 17 and protects the substrate 15 from heat generated during the crystallization process of the amorphous semiconductor film 17. The base protective film 16 is not limited to one layer but may be two or more layers. In particular, in order to prevent the permeation of impurities from the substrate 15, for example, a configuration in which a SiNx layer is formed on the substrate 15 and a SiO ₂ layer is further formed is effective. The non-single-crystal semiconductor layer film 17 is a film to be crystallized, and is made of, for example, amorphous silicon having a film thickness of 30 nm to 200 nm.

  Next, a dehydrogenation process is performed on the thin films 16 to 18 formed on the substrate 15. This dehydrogenation treatment is, for example, a heat treatment at 570 ° C. × 2 hours in a nitrogen atmosphere. In this way, the substrate 8 to be processed is formed.

  In this example, the crystallization apparatus shown in FIG. 16 was used. As the phase shifter, the area ratio (duty) modulation type phase shifter 6 shown in FIGS. 17A and 17B, which forms the light intensity distribution shown in FIG. 17C on the substrate surface, was used.

In this example, the controller 11 controlled the incident laser fluence on the surface of the substrate 15 to 0.51 J / cm ² and emitted the pulsed laser light 12.

  After irradiating one shot of pulsed laser light, the controller 11 automatically translates the mounting table 9 on which the substrate 8 to be processed 8 is moved in parallel by a predetermined pitch distance according to a program stored in advance, and controls the excimer laser oscillator 2. The substrate 8 to be processed was irradiated with a pulse laser beam 12 of the next shot. In this manner, the step and repeat were continuously performed, and the amorphous silicon film was crystallized one after another in a predetermined element formation region.

  When the end point on the substrate 8 to be processed is detected, the laser irradiation is stopped, the substrate 8 together with the mounting table 9 is returned to the home position, and the crystallization process is completed. From the next time, when the main switch of the crystallization apparatus is turned on, the controller 11 automatically reads out apparatus parameter data, and various apparatus parameters are displayed as a list on the screen of the display apparatus. The apparatus parameters read here include at least the beam profile, the thickness of the semiconductor layer, the optical constant of the semiconductor layer, the thickness of the cap film, and the optical constant of the cap film. Further, the read apparatus parameters may include a part or all of the conditions used for the previous crystallization.

  In such a crystallization process, the excimer laser oscillator 2 and the substrate to be processed 8 are moved relative to each other. For example, the controller 11 moves the XYZθ stage 10 to continuously move a predetermined region of the amorphous semiconductor layer 17. Or intermittently over the entire surface.

  The crystallized region has a structure as shown in FIG. The crystal grains 103 in the laterally grown region were sufficiently long with a grain length of 8.7 μm, and the intended large crystal grain array was uniformly formed on the entire irradiated region.

(Example 2)
In Example 2 as well, the crystallization apparatus 1 shown in FIG. Further, the area ratio (duty) modulation type phase shifter 6 shown in FIGS. 17A and 17B was used as the phase shifter as in the first embodiment.

The substrate 8 to be processed was produced as follows. A SiNx layer having a thickness of 200 nm and a SiO ₂ layer having a thickness of 200 nm were formed as a base protective film 16 on the glass substrate 15 by a plasma chemical vapor deposition method.

An amorphous silicon film having a thickness of 50 nm was formed as a non-single crystal semiconductor layer 17 on the base protective film 16 by a plasma chemical vapor deposition method using SiH ₄ gas and H ₂ gas.

Then as the light-absorbing cap layer 18 was formed SiOx film by plasma-enhanced chemical vapor deposition in the above process using SiH ₄ gas and N _{2 O} gas. The optical constant N _cap (complex refractive index N _cap ) of the SiOx film was controlled by changing the flow rate ratio of SiH ₄ gas and N ₂ O gas during film formation. The film thickness d _cap was controlled by the film formation time. As a result of measurement and analysis by ellipsometry after the dehydrogenation step, N _cap = 1.527-0.0106i (refractive index n = 1.527, i is an imaginary unit, extinction coefficient k _cap = 0.0106 in this example. ) The film thickness d _cap was in the range of 442 ± 10 nm including in-plane unevenness. At this time, the reflectance R of the laser light on the substrate surface is almost a minimum value in the cap film thickness d _{cap -reflectance} R curve under this condition, and the value of the light absorption ratio r is 0.34. . These values are in an appropriate range in FIGS. 6, 8, 13, and 14.

  Subsequently, the thin film 16-18 formed on the board | substrate 15 was dehydrogenated by heat-processing for 570 degreeC * 2 hours in nitrogen atmosphere. In this way, the substrate 8 to be processed was formed.

During crystallization, the controller 11 controlled the incident laser fluence on the surface of the substrate 8 to be processed to 0.44 J / cm ² and emitted the pulse laser beam 12.

  After irradiation with one shot of pulsed laser light, the controller 11 automatically translates the mounting table 9 on which the substrate 8 to be processed is placed by a predetermined pitch distance according to a program stored in advance, and controls the excimer laser oscillator 2. The substrate 8 to be processed was irradiated with a pulse laser beam 12 of the next shot. In this way, the semiconductor layer 17, for example, an amorphous silicon film was crystallized one after another in a step-and-repeat manner.

  The crystallized region has a structure as shown in FIG. The crystal grains 103 in the laterally grown region were sufficiently long with a grain length of 8.1 μm, and the intended large crystal grain array was uniformly formed on the entire irradiated region.

(Example 3)
In Example 3 as well, the crystallization apparatus 1 shown in FIG. Further, the area ratio (duty) modulation type phase shifter 6 shown in FIGS. 17A and 17B was used as the phase shifter as in the first embodiment.

The substrate 8 to be processed was produced as follows. A SiNx layer having a thickness of 200 nm and a SiO ₂ layer having a thickness of 200 nm were formed as a base protective film 16 on a glass substrate 15 by a plasma chemical vapor deposition method.

An amorphous silicon film having a thickness of 40 nm was formed as a non-single crystal semiconductor layer 17 on the base protective film 16 by a plasma chemical vapor deposition method using SiH ₄ gas and H ₂ gas.

Then as the light-absorbing cap layer 18 was formed SiOx film by plasma-enhanced chemical vapor deposition using SiH ₄ gas and N _{2 O} gas. The optical constant N _cap (complex refractive index N _cap ) of the SiOx film was controlled by changing the flow rate ratio of SiH ₄ gas and N ₂ O gas during film formation. The film thickness d _cap was controlled by the film formation time. As a result of measurement and analysis by ellipsometry after the dehydrogenation step, N _cap = 1.540−0.0110i (refractive index n = 1.540, i is an imaginary unit, extinction coefficient k _cap = 0.110 in this example. ) Further, the film thickness d _cap was in a range of 438 ± 10 nm including in-plane unevenness. At this time, the reflectance of the laser beam on the substrate surface is almost a minimum value in the cap film thickness d _{cap -reflectance} R curve under this condition, and the value of the light absorption ratio r is 0.34. These values are in the appropriate ranges in FIGS.

  Subsequently, the thin film 16-18 formed on the board | substrate 15 was dehydrogenated by heat-processing for 570 degreeC * 2 hours in nitrogen atmosphere. In this way, the substrate 8 to be processed was formed.

During crystallization, the controller 11 controlled the incident laser fluence on the surface of the substrate 8 to be processed to 0.43 J / cm ² and emitted the pulsed laser beam 12.

  After irradiation with one shot of pulsed laser light, the controller 11 automatically translates the mounting table 9 on which the substrate 8 to be processed is placed by a predetermined pitch distance according to a program stored in advance, and controls the excimer laser oscillator 2. The substrate 8 to be processed was irradiated with a pulse laser beam 12 of the next shot. In this manner, the step and repeat were continuously performed, and the amorphous silicon film was crystallized one after another in a predetermined element formation region.

  The crystallized region has a structure as shown in FIG. The crystal grains 103 in the lateral growth region were sufficiently long with a grain length of 8.5 μm, and the intended large crystal grain array was uniformly formed on the entire irradiated region.

Example 4
In Example 4 as well, the crystallization apparatus 1 shown in FIG. Further, the area ratio (duty) modulation type phase shifter 6 shown in FIGS. 17A and 17B was used as the phase shifter as in the first embodiment.

The substrate 8 to be processed was produced as follows. A SiNx layer having a thickness of 200 nm and a SiO ₂ layer having a thickness of 200 nm were formed as a base protective film 16 on the glass substrate 15 by a plasma chemical vapor deposition method.

An amorphous silicon film having a thickness of 30 nm was formed as a non-single-crystal semiconductor layer 17 on the base protective film 16 by a plasma chemical vapor deposition method using SiH ₄ gas and H ₂ gas.

Then as a light absorbing layer (cap layer) 18 was formed SiOx film by plasma-enhanced chemical vapor deposition using SiH ₄ gas and _{N 2} O gas. The optical constant N _cap (complex refractive index N _cap ) of the SiOx film was controlled by changing the flow ratio of SiH ₄ gas and N ₂ O gas during film formation. The film thickness d _cap was controlled by the film formation time. As a result of measurement and analysis by ellipsometry after the dehydrogenation step, N _cap = 1.530−0.0110i (refractive index n = 1.530, i is an imaginary unit, extinction coefficient k _cap = 0.0110 in this example. ) The film thickness d _cap was in the range of 395 ± 15 nm including in-plane unevenness. At this time, the reflectance of the laser beam on the surface of the substrate 8 to be processed is almost a maximum value in the cap film thickness d _{cap -reflectance} R curve under this condition, and the value of the absorption ratio r is 0.32. is there. These values are in the appropriate ranges in FIGS.

  Subsequently, the thin film 16-18 formed on the board | substrate 15 was dehydrogenated by heat-processing for 570 degreeC * 2 hours in nitrogen atmosphere. In this way, the substrate 8 to be processed was formed.

During crystallization, the controller 11 controlled the incident laser fluence on the substrate surface to 0.54 J / cm ² to emit pulsed laser light 12.

  After irradiation with one shot of pulsed laser light, the controller 11 automatically translates the mounting table 9 on which the substrate 8 to be processed is placed by a predetermined pitch distance according to a program stored in advance, and controls the excimer laser oscillator 2. The substrate 8 to be processed was irradiated with a pulse laser beam 12 of the next shot. In this manner, the step and repeat were continuously performed, and the amorphous silicon film was crystallized one after another in a predetermined element formation region.

  The crystallized region has a structure as shown in FIG. The crystal grains in the lateral growth region were sufficiently long with a grain length of 8.0 μm, and the intended large crystal grain array was uniformly formed on the entire irradiated region.

(Example 5)
In Example 5, a SiNx film was used for the light absorbing cap layer 18. FIG. 19 shows a sample structure in which an amorphous Si film is provided as a semiconductor layer 17 on a substrate 15 directly or via a base protective film 16, and a SiNx film is provided as a light absorbing cap layer 18 on the semiconductor layer 17. The film thickness of the SiNx film that is the cap layer 18 and the reflectance on the surface of the SiNx film when the substrate 8 is irradiated with laser light having a wavelength λ = 308 nm from the light-absorbing cap layer 18 side in the atmosphere. Shows the relationship. FIG. 20 shows the relationship between the thickness of the SiNx film of the cap layer 18 and the light absorption ratio r of the cap film under the same conditions. In this embodiment, the optical constant of the SiNx film of the cap layer 18 is Ncap = 2.000-0.0200i (refractive index n = 2.000, i is an imaginary unit, extinction coefficient kcap = 0.0200), amorphous Si The optical constant of the film is Ncap = 3.600-3.5400i (refractive index n = 3.600, i is an imaginary unit, extinction coefficient kcap = 3.5400). Both of these values are shown in FIGS. Calculated from

  Unlike the case where the SiOx film of FIG. 10 is used for the light-absorbing cap layer 18, the SiNx film of FIG. 19 has a high refractive index of 2.000, so that the period of the reflectance R is shortened, and the maximum value and the minimum value are reduced. The difference from the value becomes larger. That is, when the SiNx film is employed, the margin of the film thickness unevenness is narrowed. In this embodiment, the SiNx film thickness is 150 nm. From FIG. 19, the reflectance R becomes a maximum value at this film thickness, and from FIG. 20, the absorption ratio r is 0.21. As shown in FIGS. 4 and 5, r = 0.21 is close to the maximum grain length condition when the film thickness of the a-Si layer is 100 nm.

  Also in this example, the crystallization apparatus shown in FIG. Similarly, in the phase shifter, a V-shaped light intensity distribution having a bottom relative intensity of 0.2, a top relative intensity of 1, and a period of 32 μm is formed on the surface of the substrate 8 to be processed. The one shown in b) was used.

The substrate 8 to be processed was produced as follows. A SiNx layer having a thickness of 200 nm, for example, and a SiO ₂ layer having a thickness of 200 nm, for example, were formed as a base protective film 16 on a glass substrate 15 by plasma enhanced chemical vapor deposition. An amorphous silicon film (a-Si film) having a thickness of, for example, 100 nm is formed as a non-single crystalline semiconductor layer film 17 on the base protective film 16 by plasma chemical vapor deposition using SiH ₄ gas and H ₂ gas. A film was formed.

Then, as the light-absorbing cap layer 18 was formed SiNx film by plasma chemical vapor deposition using SiH ₄ gas and NH ₃ gas and N ₂ gas. The optical constant N _cap (complex refractive index N _cap ) of the SiNx film was controlled by changing the flow ratio of SiH ₄ gas, NH ₃ gas, and N ₂ gas during film formation. The film thickness d _cap was controlled by the film formation time.

  Next, the book thin films 16 to 18 formed on the substrate 15 were dehydrogenated by heat treatment at 570 ° C. for 2 hours in a nitrogen atmosphere. In this way, the substrate 8 to be processed was formed.

As a result of measurement and analysis by ellipsometry after the dehydrogenation step, Ncap = 2.000-0.0200i (refractive index n = 2.000, i is an imaginary unit, extinction coefficient kcap = 0.0200) in this example. It became. The film thickness dcap was in the range of 150 ± 10 nm including in-plane unevenness. At this time, the reflectance R of the laser beam on the surface of the substrate to be processed 8 is almost a maximum value in the cap film thickness dcap-reflectance R curve under this condition, and the value of the light absorption ratio r is 0.21. is there. These values are in the appropriate range in FIG. During crystallization, the controller 11 controlled the incident laser fluence on the surface of the substrate to be processed 8 to 0.65 J / cm ² to emit pulsed laser light 12.

  After irradiating one shot of pulsed laser light, the controller 11 automatically moves the mounting table 9 on which the substrate 8 to be processed is placed in parallel by a predetermined pitch distance according to a previously stored program, and controls the excimer laser device 2. The substrate 8 to be processed was irradiated with a pulse laser beam 12 of the next shot. In this way, by stepping and repeating continuously, a predetermined element formation region of the amorphous silicon film was successively irradiated with one shot of pulsed laser light to be crystallized.

  The crystallized region has a structure as shown in FIG. The crystal grains 103 laterally grown from the crystal nuclei 101 in the lateral crystal growth region were sufficiently long with a grain length of 8.0 μm, and the intended large crystal grain array was uniformly formed on the entire irradiated region.

(Example 6)
In the sixth embodiment, a light intensity distribution designing method based on the present invention will be described. FIGS. 21A and 21B show the design of the light intensity distribution in the case of an a-Si film (film thickness 100 nm). For example, when the light absorption ratio r value of the light-absorbing cap layer 18 is set to around 0.22, the condition that facilitates the largest particle diameter is obtained from FIG. The effective light intensity Ieff that can be incident under this condition is 0.45 J / cm ² , and the effective light intensity Ieff at which the a-Si layer melts, that is, the lateral light growth starts, is 0.27 J / cm ² . As shown in FIGS. 21A and 21B, the top position T of the light intensity distribution is 0.45 J / cm ² and the bottom position B is slightly lower than 0.27 J / cm ² , for example, 0.22 J / cm 2. ^When it is set to about ² , it is possible to produce a long and narrow one-dimensionally grown crystal grain array with a high filling rate or a two-dimensionally grown large grain crystal grain array.

(Example 7)
Next, a manufacturing method for forming a thin film transistor (TFT) in the crystallized region will be described with reference to FIG. A thin film transistor was manufactured by using the substrate 8 to be processed having a semiconductor film which was crystallized by the above crystallization method.

A base protective film 16 is formed on a substrate 15 made of an insulator or a semiconductor, for example, a low alkali glass substrate. The base protective film 16 is an insulating film containing silicon dioxide (SiO ₂ ) or silicon nitride as a main component, for example, a silicon dioxide film having a thickness of 300 nm. The base protective film 16 is preferably formed in close contact with the glass substrate. The base protective film 16 is a film that functions to prevent impurities from diffusing from the substrate 15, for example, a glass substrate, into the amorphous semiconductor film.

  For example, an amorphous silicon film is formed on the base protective film 16 as the amorphous semiconductor film or the non-single-crystal semiconductor amorphous semiconductor film. The amorphous silicon film is an amorphous Si film having a thickness of 100 nm, for example, formed by plasma chemical vapor deposition.

  A substrate (processed substrate 8) is formed by forming a cap (insulating) layer film 18 having light absorption characteristics on the amorphous silicon film. The substrate 8 is irradiated with a pulse laser beam having a light intensity distribution having a plurality of cross-sectional inverted triangular peak patterns shown in FIGS. 3B and 17C, for example, and the crystallization process is completed.

  Next, the cap (insulating) layer 18 on the crystallized amorphous semiconductor film is removed by etching. Next, a semiconductor circuit, for example, a thin film transistor 35 shown in FIG. 22 is manufactured as follows in alignment with the crystallized region of the exposed amorphous semiconductor film. First, in order to define the shape of the active region, patterning is performed using photolithography, and a predetermined predetermined pattern of Si islands 39 substantially corresponding to the channel region 36, the source region 37, and the drain region 38 are formed in a planar field of view. Formed. At this time, the channel region 36 is formed in the crystallized region.

  Next, a gate insulating film 40 is formed on the channel region 36, the source region 37 and the drain region 38. The gate insulating film 40 is a material mainly composed of silicon dioxide or silicon oxynitride (SiON), and is a silicon dioxide film having a thickness of 10 to 200 nm or a silicon oxynitride film having a thickness of 30 to 500 nm. In this embodiment, a silicon dioxide film 41 having a thickness of 3 nm is formed on the side in contact with silicon, and a silicon oxynitride film 42 (SiON film) using silane gas, ammonia gas, and laughing gas as raw materials is formed on the upper side by plasma CVD. The gate insulating film 40 was formed with a thickness. The reason for the two layers is that the silicon dioxide film 41 having a low interface state density is used on the silicon interface side, and the SiON film 42 having a high dielectric constant is used on the upper side in order to reduce the leakage current. The present invention is not limited, and only one layer does not depart from the spirit of the present invention. Although not shown in this embodiment, a film obtained by oxidizing the surface of the island-shaped Si island 39 with oxygen plasma or the like can be used as the silicon dioxide film 41 below the gate insulating film 40.

  Next, a conductive layer was formed on the gate insulating film 40 in order to form the gate electrode 43. The conductive layer was formed using a material mainly composed of elements such as Ta, Ti, W, Mo, and Al by a known film formation method such as a sputtering method or a vacuum evaporation method. For example, a Mo-W alloy was used. The gate electrode metal layer was patterned using photolithography to form a gate electrode 43 having a predetermined pattern.

Next, the source region 37 and the drain region 38 were formed by implanting impurities using the gate electrode 43 as a mask. For example, when forming a p-channel TFT, a p-type impurity such as boron ion is implanted using an ion implantation method. The boron concentration in this region was, for example, 1.5 × 10 ^{20 to} 3 × 10 ²¹ cm ⁻³ . In this way, high-concentration p-type impurity regions constituting the source region 37 and the drain region 38 of the p-channel TFT are formed. At this time, it goes without saying that an n-channel TFT is formed if n-type impurities are implanted.

  Next, a heat treatment step is performed to activate the impurity element implanted by the ion implantation method. This step can be performed by methods such as furnace annealing, laser annealing, and rapid thermal annealing. In the present embodiment, the activation process is performed by furnace annealing. The heat treatment is desirably performed in a temperature range of 300 to 650 ° C. in a nitrogen atmosphere. In this example, heat treatment was performed at 500 ° C. for 4 hours.

  Next, an interlayer insulating film 44 was formed on the gate electrode 43 and the gate insulating film 40. The interlayer insulating film 44 may be formed of a silicon nitride film, a silicon dioxide film, a silicon nitride oxide film, or a laminated film combining them. Further, the film thickness of the interlayer insulating film 44 may be 200 to 600 nm, and is 400 nm in this embodiment.

  Next, a contact hole is opened at a predetermined position in the interlayer insulating film 44. Then, the contact holes are filled with a conductive material such as Ti or Al to form source / drain electrodes 45 and 46, respectively. Further, a conductive layer is formed on the surface of the interlayer insulating layer 44, and this conductive layer is patterned into a predetermined shape. In this embodiment, the source / drain regions 37 and 38 are set to 100 nm, and the source / drain electrodes 45 and 46 are successively formed by sputtering using a Ti film of 100 nm, a Ti-containing aluminum film of 300 nm, and a Ti film of 150 nm. A laminated film having a layer structure was obtained. Thus, the thin film transistor 35 shown in FIG. 22 was formed.

(Example 8)
Next, an eighth embodiment in which a thin film transistor is formed on the crystallized semiconductor film manufactured according to the first to fifth embodiments will be described with reference to FIGS. In this embodiment, an embodiment applied to a thin film transistor such as an N-channel TFT will be described. The present invention is not limited to the N channel type TFT, and the P channel type can be formed in substantially the same manner by changing the impurity species (dopant species). In this embodiment, a method for manufacturing a TFT having a bottom gate structure will be described.

  As shown in FIG. 23A, a gate electrode material such as Al, Ta, Mo, W, Cr, Cu or an alloy film thereof is formed on an insulating substrate 60 such as a glass plate with a film thickness of 100. The metal film is patterned to be processed into a bottom-type gate electrode 61.

Next, as shown in FIG. 23B, gate insulating films 62 and 63 are formed on the gate electrode 61 and the exposed insulating substrate 60. The gate insulating films 62 and 63 have, for example, a two-layer structure of a nitride film (SiN _x ) and an oxide film (SiO ₂ ). The gate nitride film of the gate insulating film 62 can be formed by a plasma CVD method (PE-CVD method) using, for example, a mixture of SiH ₄ gas and NH ₃ gas as a source gas. The nitride film can also be formed by using atmospheric pressure CVD or low pressure CVD instead of plasma CVD.

The film thickness of the nitride film is, for example, 50 nm. On the nitride film, an oxide film is formed as a gate insulating film 63 to a thickness of, for example, 200 nm. On this oxide film, a non-single crystal semiconductor film such as an amorphous silicon film 53 is formed in a thickness of 30 nm to 200 nm, for example, 100 nm. Further, a cap film 57 made of, for example, SiO ₂ / SiO _x or SiOx is formed on the amorphous silicon film 53 in this order in the case of a laminated film, for example, in a thickness of 30 nm, 420 nm, and in the case of SiOx, for example, 450 nm. To do. The SiOx cap film had an optical constant with a light absorption ratio r of 0.22 and an extinction coefficient k _cap of 0.0054. The two-layered gate insulating films 62 and 63, the amorphous silicon film 53, and the cap film 57 are continuously formed without breaking the vacuum system of the film forming chamber (without being exposed to the atmosphere).

  When the plasma CVD method is used in the above film formation process, dehydrogenation annealing is performed by a heat treatment in a nitrogen atmosphere at a temperature of 550 ° C. for about 2 hours, and the hydrogen contained in the amorphous silicon film 53 is converted into an amorphous state. It can be released from the silicon film 53. Thus, the to-be-processed substrate 52 for crystallization is manufactured.

  Next, a crystallization process of the amorphous silicon film 53 of the substrate 52 for crystallization is performed. The crystallization process can be performed using, for example, the laser annealing apparatus 1 shown in FIG. For example, the substrate to be processed is irradiated with the laser beam 12 according to the method of the method shown in the first to fifth embodiments, and the irradiated region of the amorphous silicon film 53 is crystallized.

  An excimer laser beam can be used as the laser light 12. After adjusting the irradiation area of the laser beam 12, the laser beam 12 is focused and irradiated so that the periodic pattern of the phase shifter 6 can be transferred to the irradiation area, and the irradiation area is shifted and repeated so as not to overlap. Irradiation is performed one shot at a time to crystallize a predetermined area within the irradiation region. In this way, a polycrystalline silicon film 65 in which a predetermined region of the amorphous silicon film 53 is crystallized is formed.

  Next, the cap insulating film 57 on the surface is peeled off by a method such as etching to expose the surface of the polycrystalline silicon film 65 in which the crystallized region is formed. On the surface of the crystallized region of the polycrystalline silicon film 65, as described above, for example, a crystallized grain array 100 composed of long crystal grains 103 as shown in FIG. 18 is formed. In this crystallized grain array 100, a plurality of TFT channel regions C are provided across a plurality of crystal grains 103, for example, as shown in FIG. In the TFT of FIG. 18, a source region S and a drain region D are provided so that electrons or holes move in a direction parallel to the crystal growth direction in order to obtain high mobility characteristics.

As shown in FIG. 23C, ion implantation for obtaining a desired threshold voltage Vth is performed as necessary for the purpose of controlling the threshold voltage Vth of the TFT. In this example, boron B + was ion-implanted so that the dose amount was about 5 × 10 ¹¹ to 4 × 10 ¹² / cm ² . In this threshold voltage Vth ion implantation, an ion beam accelerated at 10 KeV was used.

Subsequently, on the polycrystalline silicon film 65 crystallized in the previous step, SiO _{2 is formed} to a film thickness of, for example, about 100 nm to 300 nm, for example, by plasma CVD. In this example, silane gas SH ₄ and oxygen gas were plasma decomposed to deposit SiO ₂ . The SiO ₂ thus formed is patterned into a predetermined shape and processed into a stopper film 66.

  In this case, the stopper film 66 is patterned so as to be aligned with the gate electrode 61 using a backside exposure technique. The portion of the polycrystalline silicon film 65 located immediately below the stopper film 66 is protected as a channel region Ch. As described above, B + ions are implanted into the channel region Ch at a relatively low dose by ion implantation for obtaining a high threshold voltage Vth in advance.

Subsequently, an impurity (for example, P + ions) is implanted into the silicon film 65 by ion doping using the stopper film 66 as a mask to form an LDD region. The dose at this time is, for example, 5 × 10 ¹² to 1 × 10 ¹³ / cm ² , and the acceleration voltage is, for example, 10 KeV.

Further, after patterning a photoresist so as to cover the stopper film 66 and the LDD regions on both sides thereof, impurities (for example, P + ions) are implanted at a high concentration using the photoresist as a mask to form the source region S and the drain region D. . For example, ion doping (ion shower) can be used for the impurity implantation. In this example, impurities are implanted by electric field acceleration without applying mass separation. In this embodiment, impurities are implanted at a dose of about 1 × 10 ¹⁵ / cm ² to form a source region S and a drain region D. . The acceleration voltage for ion implantation is, for example, 10 KeV.

Although not shown, in the case of forming a P-channel TFT, after covering the region of the N-channel TFT with a photoresist, the impurity is switched from P + ions to B + ions, and the dose amount is about 1 × 10 ¹⁵ / cm ^2. Ion doping may be used. Here, impurities may be implanted using a mass separation type ion implantation apparatus.

  Thereafter, the impurities implanted into the polycrystalline silicon film 65 are activated by RTA (rapid thermal annealing) 49. In some cases, laser activation annealing (ELA) using an excimer laser may be performed. Thereafter, unnecessary portions of the silicon film 65 and the stopper film 66 are simultaneously patterned to separate the TFTs for each element region.

Finally, as shown in FIG. 23D, SiO ₂ is formed to a thickness of about 100 to 200 nm, and this is used as an interlayer insulating film 67. After the formation of the interlayer insulating film 67, SiNx is formed to a thickness of about 200 to 400 nm by the plasma CVD method to form a passivation film 68. At this stage, heat treatment is performed at about 350 to 400 ° C. for 1 hour in an atmosphere of nitrogen gas, forming gas, or vacuum to diffuse hydrogen atoms contained in the interlayer insulating film 67 into the silicon film 65.

  Thereafter, a contact hole for forming the source S electrode is opened, and an electrode material layer such as Mo or Al is sputtered to a thickness of 100 to 200 nm. Next, the electrode material layer is patterned into a predetermined shape and processed into the wiring electrode 69. Further, after applying a planarizing layer 70 made of acrylic resin or the like with a thickness of about 1 μm, a contact hole for the drain electrode D is opened. After a transparent conductive film made of ITO or the like is sputtered on the planarizing layer 70, it is patterned into a predetermined shape and processed into a pixel electrode 71. In this way, the TFT 112 is manufactured.

Example 9
Next, with reference to FIGS. 24A to 24C, a ninth embodiment in which the crystallized silicon film manufactured according to the above-described embodiment is applied to manufacture a TFT having a top gate structure will be described. First, as shown in FIG. 24A, two layers of base films 81 and 82 to be buffer layers are continuously formed on an insulating substrate 80 by a plasma CVD method.

The first base film 81 is made of a SiN film and has a thickness of 100 to 1000 nm. In addition, the second base film 82 is made of a SiO ₂ film, and the film thickness is also 100 nm to 1000 nm. A non-single crystal silicon film 53 made of amorphous silicon having a film thickness of 30 to 200 nm, for example, 50 nm is formed on the base film 82 made of this SiO ₂ film by plasma CVD or LPCVD.

Further, a cap film 57 made of SiO ₂ / SiOx or SiOx is formed on the non-single crystal silicon film 53 in this order in the case of a laminated film, for example, in the order of 30 nm and 420 nm, and in the case of SiOx, for example, 450 nm. The SiOx cap film 57 has an optical constant with a light absorption ratio r of 0.35 and an extinction coefficient k _cap of 0.0100. When the plasma CVD method is used to form the non-single-crystal silicon film 53 made of amorphous silicon, in order to desorb hydrogen in the film, it is 2 in a nitrogen atmosphere at 400 to 450 ° C., for example. Annealing for about an hour.

  Next, the amorphous silicon film 53 is crystallized by, for example, the crystallization method of the first to fifth embodiments. After adjusting the irradiation area of the laser light 12, the laser light 12 is focused and irradiated so that the periodic pattern arrangement of the phase shifter 6 can be transferred to the irradiation area. The irradiation area is shifted and repeatedly irradiated to crystallize a predetermined area of the amorphous semiconductor thin film 53.

Subsequently, the cap film 57 is peeled off by a method such as etching. If necessary, ion implantation is performed in advance to obtain a high threshold voltage Vth in the same manner as in the above embodiment, and the semiconductor thin film 4 is doped with B + ions at a dose of about 5 × 10 ¹¹ to 4 × 10 ¹² / cm ^2, for example. Inject. The acceleration voltage in this case is about 10 KeV.

Subsequently, as shown in FIG. 24B, the crystallized silicon film 85 is patterned into an island shape. On this, SiO ₂ is grown to 30 to 400 nm by the plasma CVD method, the atmospheric pressure CVD method, the low pressure CVD method, the ECR-CVD method, the sputtering method or the like to form the gate insulating film 83. In this embodiment, the thickness of the gate insulating film 83 is set to 100 nm.

  Next, Al, Ti, Mo, W, Ta, doped polycrystalline silicon, or the like, or an alloy thereof is formed on the gate insulating film 83 to a thickness of 200 to 800 nm, and patterned into a predetermined shape to form the gate electrode 88. To process.

Next, as shown in FIG. 24B, P + ions are implanted into the crystallized silicon film 85 by ion implantation using mass separation to provide an LDD region. This ion implantation is performed on the entire surface of the insulating film 83 using the gate electrode 88 as a mask. The dose is 6 × 10 ^{12 to} 5 × 10 ¹³ / cm ² . The acceleration voltage is 90 KeV, for example. Note that the channel region Ch located immediately below the gate electrode 88 is protected, and B + ions previously implanted by Vth ion implantation are held as they are.

After ion implantation into the LDD region, a resist pattern is formed so as to cover the gate electrode 88 and its periphery, and P + ions are implanted at a high concentration by a mass non-separation type ion shower doping method. Form. The dose amount in this case is, for example, about 1 × 10 ¹⁵ / cm ² . The acceleration voltage is 90 KeV, for example. As the doping gas, hydrogen diluted 20% PH ₃ gas was used.

In the case of forming a CMOS circuit, after forming a resist pattern for a P-channel TFT, the doping gas is switched to a 5 to 20% B ₂ H ₆ / H ₂ gas system, and the dose is set to 1 × 10 ^{15 to} 3 ×. Ion implantation may be performed at about 10 ¹⁵ / cm ² and an acceleration voltage of 90 KeV, for example. Note that the source region S and the drain region D may be formed using a mass separation type ion implantation apparatus.

  Thereafter, the activation treatment of the dopant implanted into the crystallized silicon film 85 is performed. In this activation process, RTA 49 using an ultraviolet lamp can be used as in the eighth embodiment.

  Finally, as shown in FIG. 24C, an interlayer insulating film 90 made of PSG or the like is formed so as to cover the gate electrode 88. After the formation of the interlayer insulating film 90, SiN is deposited by a plasma CVD method to a thickness of about 200 to 400 nm to form a passivation film 91.

  At this stage, annealing is performed in a nitrogen gas at a temperature of 350 ° C. for about 1 hour, and hydrogen contained in the interlayer insulating film 91 is diffused into the silicon film 85. Thereafter, a contact hole is opened. Further, Al—Si or the like is formed on the passivation film 91 by sputtering, and then patterned into a predetermined shape to be processed into the wiring electrode 92.

  Further, a flattening layer 93 made of acrylic resin or the like is applied with a thickness of about 1 μm, and then a contact hole is opened therein. A transparent conductive film made of ITO or the like is sputtered on the planarizing layer 93 and patterned into a predetermined shape to be processed into the pixel electrode 94.

  In the thin film transistor 113 illustrated in FIG. 24C, the non-single-crystal silicon film is crystallized in the same manner as the method described for the thin film transistor 112 illustrated in FIG. However, since the thin film transistor or semiconductor device of this embodiment having a top gate structure is different from the thin film transistor or semiconductor device of the embodiment having a bottom gate structure, crystallization is performed at a stage before the pattern of the gate electrode 88 is formed. The shrinkage of the insulating substrate made of glass or the like has a higher tolerance than the semiconductor device having the bottom gate structure. Therefore, the crystallization process can be performed using a laser irradiation apparatus with a higher output. In this way, the TFT 113 is manufactured.

(Example 10)
Hereinafter, an example in which the thin film transistor obtained in the above-described embodiment is actually applied to an active matrix liquid crystal display device will be described. FIG. 25 shows an example of an active matrix display device using thin film transistors. The display device 170 has a panel structure including a pair of insulating substrates 171 and 172 and an electro-optical material 173 held between the substrates. As the electro-optic material 173, a liquid crystal material is widely used. A pixel array portion 174 and a drive circuit portion are integrated on the lower insulating substrate 171. The drive circuit section is divided into a vertical drive circuit 175 and a horizontal drive circuit 176.

  A terminal portion 177 for external connection is formed at the upper end of the peripheral portion of the insulating substrate 171. The terminal portion 177 is connected to the vertical drive circuit 175 and the horizontal drive circuit 176 via the wiring 178. In the pixel array portion 174, row-shaped gate wirings 179 and column-shaped signal wirings 180 are formed. A pixel electrode 181 and a thin film transistor 112 (or 113) for driving the pixel electrode 181 are formed at the intersection of both wirings. The gate electrode of the thin film transistor 112 (or 113) is connected to the corresponding gate wiring 179, the drain region is connected to the corresponding pixel electrode 181 and the source region is connected to the corresponding signal wiring 180. The gate wiring 179 is connected to the vertical driving circuit 175, while the signal wiring 180 is connected to the horizontal driving circuit 176.

  The thin film transistor 112 (or 113) for switching and driving the pixel electrode 181 and the thin film transistor included in the vertical driving circuit 175 and the horizontal driving circuit 176 are manufactured according to the present invention and have higher mobility than the conventional one. Yes. Therefore, not only the drive circuit but also a higher-performance processing circuit can be integrated.

The cross-sectional schematic diagram of the to-be-processed substrate for demonstrating the light absorption ratio r and effective light intensity Ieff of a light absorptive cap film | membrane in embodiment of the laser crystallization board | substrate which concerns on this invention. FIG. 2 is a diagram for explaining the light intensity distribution of laser light incident on the substrate to be processed in FIG. 1 and the temperature distribution generated in the main layer in the substrate to be processed as a result, in which (a) shows the light absorption of the light absorbing cap film. A temperature distribution diagram showing, in contrast, how light is distributed to each layer when a laser beam having the same light intensity distribution is effectively irradiated to a substrate to be processed having sample structures with different ratios r. The light intensity distribution figure of a laser beam. FIGS. 3A and 3B are diagrams for explaining the relationship between the light intensity distribution of FIG. 2 and a melting region in a semiconductor film, where FIG. 2A is a light intensity distribution diagram of irradiated laser light, and FIG. . FIG. 2 is a diagram showing the relationship between the absorption ratio of a laser beam incident on the substrate to be processed of FIG. 1 and a semiconductor film, and the crystal grain length, in which (a) shows that the film thickness of Si as a crystallization target film is 100 nm. The characteristic line figure which shows the relationship between the light absorption ratio r of the cap film | membrane in this case, and the grain length l, (b) is a cross-sectional schematic diagram of a to-be-processed substrate. It is a figure which shows the relationship between the absorption ratio in the cap film | membrane and semiconductor film of the laser beam which injected into the to-be-processed substrate of FIG. 1, and a crystal grain length, (a) shows the crystallization structure | tissue when the absorption ratio r is appropriate. SEM photograph, (b) SEM photograph showing the crystallized structure when the light absorption ratio r is too small, (c) SEM photograph showing the crystallized structure when the absorption ratio r is too large, (d) is the crystallization The characteristic diagram which shows the relationship between the absorption ratio r and the grain length l in case the film thickness of an object film | membrane is 100 nm. FIG. 2 is a diagram showing a relationship between an absorption ratio of a laser beam incident on a substrate to be processed of FIG. 1 and a semiconductor film and a crystal grain length, where (a) shows a film thickness of Si as a crystallization target film of 50 nm. The characteristic line figure which shows the relationship between the light absorption ratio r of the cap film | membrane in this case, and the grain length l, (b) is a cross-sectional schematic diagram of a to-be-processed substrate. It is a figure which shows the relationship between the absorption ratio and crystal grain length in the cap film and semiconductor film of the laser beam which injected into the to-be-processed substrate of FIG. The SEM photograph shown, (b) is the SEM photograph showing the crystallized structure when the light absorption ratio r is too small, (c) is the SEM photograph showing the crystallized structure when the light absorption ratio r is too large, (d) is The characteristic diagram which shows the relationship between the light absorption ratio r and the grain length l in case the film thickness of the crystallization target film | membrane is 50 nm. A diagram showing a relationship between the thickness of the absorption ratio and the semiconductor film on the cap layer and the semiconductor film of the laser beam incident on the target substrate in FIG. 1 (a) the thickness d _S of Si is crystallized target film And (b) is a cross-sectional schematic view of a substrate to be processed. The relationship between the light absorption ratio r in the cap film and the semiconductor film of the laser light incident on the substrate to be processed in FIG. 1 and the effective light intensity that can be incident and the effective light intensity Ieff that the Si layer melts is shown in FIG. The characteristic diagram shown for every 50 nm). FIG. 2A is a reflection characteristic diagram of a laser beam incident on a substrate to be processed in FIG. 1, and (a) shows a relationship between a film thickness of a light-absorbing cap film (SiOx film) and a reflectance of the laser beam on the surface of the cap film. (B) is a cross-sectional view of the substrate to be processed showing the optical constants of the cap film and the crystallization target film used in the calculation of the characteristic diagram of (a). FIG. 2 is an absorption characteristic diagram of a laser beam incident on a substrate to be processed of FIG. 1 and shows a relationship between a film thickness of a light absorbing cap film (SiOx film) and a light absorption ratio r of the cap film. FIG. 3 is a characteristic diagram regarding an extinction coefficient of a cap film of laser light incident on the substrate to be processed of FIG. 1, wherein (a) is a light-absorbing cap film when the film thickness d _{S of} Si that is a crystallization target film is 100 nm. characteristic diagram showing the relationship between the extinction coefficient k _cap and Tsubucho l of, (b) is schematic cross-sectional view of the substrate. FIG. 3 is a characteristic diagram regarding an extinction coefficient of a cap film of laser light incident on a substrate to be processed in FIG. 1, wherein (a) is a light-absorbing cap film when the film thickness d _{S of} Si as a crystallization target film is 50 nm. characteristic diagram showing the relationship between the extinction coefficient k _cap and Tsubucho l of, (b) is schematic cross-sectional view of the substrate. A diagram showing a relationship between the thickness of the extinction coefficient and the semiconductor film with a cap layer of the laser beam incident on the target substrate in FIG. 1 (a) the thickness d _S and grain Si is crystallized target film characteristic diagram showing the relationship between the extinction coefficient k _cap of the light-absorbing cap layer equal to or greater than a length 7 [mu] m, (b) is schematic cross-sectional view of the substrate. FIG. 2 is a characteristic diagram showing the relationship between the extinction coefficient k of the laser beam incident on the substrate to be processed of FIG. 1 in the cap film and the effective light intensity Ieff in the semiconductor film for each Si film thickness (100 nm, 50 nm). The block diagram for demonstrating an example of the laser crystallization apparatus used for the crystallization method of this invention. 16 is a diagram for explaining the relationship between the configuration of the phase shifter of the apparatus and the light intensity distribution formed on the substrate to be processed, where (a) is a plan view of the phase shifter, (b) is a side view of the phase shifter, (c) is a light intensity distribution diagram of laser light phase-modulated by a phase shifter, and (d) is a schematic sectional view of a substrate to be processed. FIG. 17 is a schematic plan view showing a crystallized grain array and a source / channel / drain region of a thin film transistor formed by the crystallization method of the present invention using the crystallization apparatus of FIG. FIG. 17A is a diagram for selecting an effective cap film thickness in the crystallization process using the crystallization apparatus of FIG. 16, and FIG. The characteristic diagram which shows the relationship with a rate, (b) is sectional drawing of the to-be-processed substrate which respectively shows the optical constant of the cap film | membrane used for calculation of the characteristic diagram of (a), and a crystallization object film | membrane. 1 is a characteristic diagram showing the relationship between the film thickness of the light-absorbing cap film (SiNx film) of the substrate to be processed and the light absorption ratio r. FIG. 17A is a diagram showing a relationship between light intensity distribution and crystal growth grains in a crystallization process using the crystallization apparatus of FIG. 16, and FIG. 17A shows a design example of light intensity distribution when a one-dimensional growth crystal grain array is manufactured. Schematic diagram, (b) is a schematic diagram showing a design example of a light intensity distribution when a two-dimensionally grown crystal grain array is produced. Sectional drawing which shows typically TFT formed in the crystallization grain row | line | column formed by the crystallization method of this invention. (A)-(d) is process sectional drawing of the bottom gate type TFT manufactured using the method of this invention. (A)-(c) is process sectional drawing of the top gate type TFT manufactured using the method of this invention. The perspective view which shows the outline | summary of the liquid crystal display device of this invention.

Explanation of symbols

1: Crystallizer, 2: Excimer laser oscillator (laser light source), 3, 4: Illumination optical system, 5: Homogenizer, 6: Phase shifter, 7: Projection lens,
8: Substrate to be processed, 9: Mounting table, 10: XYZθ stage,
11: Controller, 12: Pulsed laser beam,
15: Substrate, 16: Base protective film,
17: Amorphous semiconductor film (crystallization target film, semiconductor layer, Si film),
18: Cap layer (light absorbing film, light absorbing layer, SiOx film, SiNx film),
35: thin film transistor (TFT), 36: channel region, 37: source region,
38: drain region, 39: Si island, 40: gate insulating film,
41: silicon dioxide film, 42: SiON film (cap film),
43: Gate electrode 44: Interlayer insulating film 45, 46: Wiring electrode
49: RTA (rapid thermal annealing),
53: Amorphous silicon film (non-single crystal semiconductor film), 57: Cap film,
60: Insulating substrate, 61: Gate electrode, 62, 63: Gate insulating film,
65: polycrystalline silicon film (polycrystalline semiconductor thin film), 66: stopper film, 67: interlayer insulating film,
68: Passivation film, 69: Wiring electrode, 70: Planarization layer, 71: Pixel electrode,
80: Insulating substrate, 81, 82: Base film, 83: Gate insulating film,
85: Crystallized semiconductor thin film, 88: Gate electrode, 90, 91: Interlayer insulating film,
91: Passivation film, 92: Wiring electrode, 93: Planarization layer, 94: Pixel electrode,
100: Crystallized grain array, 101: Crystal nucleus, 102: Crystal grain boundary, 103: Crystal grain,
104: Microcrystalline region, 105: Amorphous region,
112, 113: Thin film transistor (TFT),
170: display device, 171, 172: insulating substrate, 173: electro-optic material,
174: Pixel array unit, 175: Vertical drive circuit, 176, Horizontal drive circuit,
177: terminal portion, 178: wiring, 179: gate wiring, 180: signal wiring,
181: Pixel electrode.

Claims (17)

Forming a non-single-crystal semiconductor film on a substrate;
Forming a light-absorbing film that absorbs part of the crystallization laser light on the non-single-crystal semiconductor film;
Irradiating the surface of the light-absorbing film with the laser light for crystallization that forms a continuous periodic light intensity distribution,
The absorption rate of the laser beam for crystallization of the light absorbing film is Acap, the absorption rate of the laser beam for crystallization of the non-single crystal semiconductor film is Asi, and the absorption rate Acap and the absorption rate Asi are A crystal characterized in that when the defined light absorption ratio r is r = Acap / (Acap + Asi), the light absorption film is selected so as to obtain a desired crystal grain length. Method. 2. The crystallization method according to claim 1, wherein the value of the light absorption ratio r is in the range of 0.10 ≦ r ≦ 0.65. When the film thickness of the non-single crystal semiconductor film is d _S (nm), the film thickness d _S and the light absorption ratio r are linear r = 0.3−0.002d _{S on the} d _S -r plane. The crystallization method according to claim 1, wherein the crystallization method is in a region sandwiched between the straight line r = 0.6−0.002 d _S. Forming a non-single-crystal semiconductor film on a substrate;
Forming a light-absorbing film that absorbs part of the crystallization laser light on the non-single-crystal semiconductor film;
Irradiating the surface of the light-absorbing film with the laser light for crystallization that forms a continuous periodic light intensity distribution,
The complex refractive index N _cap of the light absorbing film at the wavelength of the laser beam for crystallization is N _cap = n _cap −ik _cap (where n _cap is the refractive index, i is the imaginary unit, and k _cap is the extinction coefficient). The extinction coefficient k _cap is in the range of 0.003 ≦ k _cap ≦ 0.025. Forming a non-single-crystal semiconductor film on a substrate;
Forming a light-absorbing film that absorbs part of the crystallization laser light on the non-single-crystal semiconductor film;
Irradiating the surface of the light-absorbing film with the laser light for crystallization that forms a continuous periodic light intensity distribution,
The film thickness of the non-single crystal semiconductor film is d _S (nm), and the complex refractive index of the light-absorbing film at the wavelength of the crystallization laser light is N _cap = n _cap −ik _cap (where n _cap is a refractive index) rate, i is an imaginary unit, k _cap is when the extinction coefficient), the thickness d _S and the straight line k _cap and the extinction coefficient k _cap is in d _S -k _cap surface = 0.010-0. 0001D _S and the straight line k _cap = crystallization method characterized by the region sandwiched between the 0.025-0.0001d _S. The wavelength of the laser beam for crystallization is λ, the film thickness of the light absorbing film is d _cap (nm),
The complex refractive index at the wavelength λ of the light absorbing film is N _cap = n _cap −ik _cap (where n _cap is the refractive index, i is the imaginary unit, and k _cap is the extinction coefficient), and the non-single crystal semiconductor film The film thickness is d _s (nm), and the complex refractive index at the wavelength λ of the non-single crystal semiconductor film is N _s = n _s −ik _s (where n _s is the refractive index, i is the imaginary unit, and k _s is the extinction unit) Coefficient), and R is the reflectance of the light-absorbing film surface of the laser light for crystallization, the light-absorbing film so that the reflectance R becomes a maximum or minimum film thickness _dcap. The crystallization method according to claim 1, wherein the crystallization method is formed. A laser crystallization substrate having a non-single crystal semiconductor film and a light absorbing film covering the non-single crystal semiconductor film,
The absorption rate of the laser beam for crystallization of the light absorbing film is Acap, the absorption rate of the laser beam for crystallization of the non-single crystal semiconductor film is Asi, and the absorption rate Acap and the absorption rate Asi are When the defined light absorption ratio r is r = Acap / (Acap + Asi), the laser is characterized in that the light absorption film is selected so as to obtain the desired crystal grain length. Crystallization substrate. 8. The laser crystallization substrate according to claim 7, wherein a value of the light absorption ratio r is in a range of 0.10 ≦ r ≦ 0.65. When the film thickness of the non-single-crystal semiconductor film is d _S , the film thickness d _S and the light absorption ratio r are a straight line r = 0.3−0.002 d _S and a straight line r in the d _S -r plane. The laser crystallization substrate according to claim 7, wherein the substrate is in a region sandwiched between 0.6 and 0.002 d _S. A laser crystallization substrate having a non-single crystal semiconductor film and a light absorbing film covering the non-single crystal semiconductor film,
And characterized in that the extinction coefficient at the wavelength of the crystallizing laser light of the light absorbing layer when the k _cap, the extinction coefficient k _cap is in the range of 0.003 ≦ k _cap ≦ 0.025 Laser crystallization substrate. A laser crystallization substrate having a non-single crystal semiconductor film and a light absorbing film covering the non-single crystal semiconductor film,
When the film thickness of the non-single crystal semiconductor film is d _S and the extinction coefficient at the wavelength of the laser beam for crystallization of the light absorbing film is k _cap , the extinction coefficient k _cap is d _S − laser crystallization substrate, characterized in that in the region sandwiched between the straight line k _cap = 0.010-0.0001d _S and the straight line k _cap = 0.025-0.0001d _S in k _cap surface. The wavelength of the laser beam for crystallization is λ, the film thickness of the light absorbing film is d _cap (nm), and the complex refractive index at the wavelength λ of the light absorbing film is N _cap = n _cap −ik _cap ( Where n _cap is the refractive index, i is the imaginary unit, and k _cap is the extinction coefficient), the film thickness of the non-single crystal semiconductor film is d _s (nm), and the complex refraction at the wavelength λ of the non-single crystal semiconductor film. The rate is N _s = n _s −ik _s (where n _s is the refractive index, i is the imaginary unit, and k _s is the extinction coefficient), and the reflectance of the crystallizing laser light on the light absorbing film surface is R 12. The laser crystallization method according to claim 7, wherein the light absorbing film has a film thickness d _{cap at} which the reflectance R becomes a maximum value or a minimum value. substrate. Forming a crystallized region in the non-single-crystal semiconductor film using the crystallization method according to any one of claims 1 to 6;
Forming a thin film transistor in alignment with the crystallized region;
A method for producing a thin film transistor, comprising: 14. The method of manufacturing a thin film transistor according to claim 13, wherein the crystal structure in the crystallization region is a crystal grain array including crystal grains grown in the in-plane direction by 2 [mu] m or more. A substrate, a non-single-crystal semiconductor thin film formed on the substrate, and a crystallization method according to any one of claims 1 to 6, wherein the non-single-crystal semiconductor film is partially or entirely formed in the region. The formed crystallization region, the channel region formed in the crystallization region, part or all of the source region, and part or all of the drain region, and the gate formed in part on the channel region A thin film transistor comprising an insulating film and a gate electrode formed on the gate insulating film. 16. The thin film transistor according to claim 15, wherein the thin film transistor has a crystal grain array including crystal grains in which the crystal structure in the crystallization region has grown by 2 μm or more in the in-plane direction. A substrate and a non-single-crystal semiconductor thin film formed on the substrate;
A crystallization region formed in a partial region or the entire region of the non-single-crystal semiconductor film by using the crystallization method according to claim 1, and formed in the crystallization region, respectively. A channel region, a part or all of a source region, a part or all of a drain region, a gate insulating film formed on a part of the channel region, and a gate electrode formed on the gate insulating film; A thin film transistor having
A pixel switching circuit having the thin film transistor;
A display device comprising:

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