JP2005251789A - Method of manufacturing crystalline semiconductor film, and crystalline semiconductor film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a crystalline semiconductor film by which crystal grains having a sufficiently large size can be formed without complicating a manufacturing method. <P>SOLUTION: The method of manufacturing the crystalline semiconductor film comprises a process of forming a cap layer 3C1 having a specific region which has a refractive index distribution, wherein the refractive index varies in a prescribed direction by using an insulation film deposited on top of an amorphous semiconductor film 2; and a crystallization process wherein by irradiating a light beam on the amorphous semiconductor film 2 via the cap layer 3C1 having the specific region, an irradiation energy density distribution corresponding to the refractive index distribution of the cap layer is formed in the amorphous semiconductor film 2 below the specific region, a temperature gradient is formed in the prescribed direction, and then the amorphous semiconductor film 2 is crystallized. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a crystalline semiconductor film, a crystalline semiconductor film, and a semiconductor device manufactured using the crystalline semiconductor film.

  In recent years, thin film semiconductor devices typified by thin film transistors (TFTs) have been widely used. In a thin film semiconductor element, a semiconductor thin film of several tens to several hundreds of nanometers is formed on a substrate having an insulating surface by a CVD (Chemical Vapor Deposition) method, etc., and this semiconductor thin film is used as an active layer and an insulating gate Type field effect semiconductor device, diode and the like. As an application field of TFT, an active matrix type liquid crystal display device is known. In this method, one or more TFTs are arranged on each of several hundreds of thousands or more of pixel electrodes arranged in a matrix, and charges supplied to the pixel electrodes are controlled by the TFTs.

  Although it is easy to use an amorphous semiconductor that can be easily formed for the active layer of a TFT, there is a problem that electrical characteristics are low. In order to realize high TFT characteristics, a crystalline semiconductor film may be used.

  One of crystalline semiconductor films is a polycrystalline semiconductor film. As a method for forming a polycrystalline semiconductor film, a method in which an amorphous semiconductor film is crystal-grown by heat treatment at around 600 ° C. (solid phase growth method), or an amorphous semiconductor film is melted by irradiating an excimer laser. A (re) crystallization method (excimer laser neil method) is known. In the formation of a polycrystalline semiconductor film by the excimer laser neil method, a glass substrate can be used because high energy can be given only to the amorphous semiconductor film without greatly increasing the temperature of the substrate. Therefore, it has been put to practical use in the manufacture of low-temperature process polycrystalline silicon TFTs using a large area substrate.

  Various methods for manufacturing crystalline semiconductor films using the excimer laser neil method have been studied. For example, Patent Document 1 discloses a method of forming an antireflection film on a part of an amorphous semiconductor film and performing crystallization by laser irradiation. When the amorphous semiconductor film is irradiated with laser through the antireflection film, the irradiation energy density of light incident on the region of the semiconductor film under the antireflection film can be selectively increased.

In Patent Document 1, since laser irradiation is performed on an amorphous semiconductor film through an antireflection film, a region of the semiconductor film under the antireflection film can be selectively set to a high temperature region, and the antireflection film is a semiconductor. It also describes that since it functions also as a heat insulating layer of the film, the cooling rate of the region of the semiconductor film under the antireflection film is reduced, and larger crystal grains can be formed than before.
JP 2002-260709 A

  However, in the method of Patent Document 1, the size of crystal grains formed in the semiconductor film is 0.8 μm to 1 μm, and crystal grains exceeding 1 μm cannot be formed. Moreover, since an etching process is required to form the antireflection film, the manufacturing method is complicated. Furthermore, there is a problem that it is difficult to control the film thickness of the antireflection film and it is difficult to obtain a desired antireflection film.

  An object of the present invention is to provide a method of manufacturing a crystalline semiconductor film and the like that can form crystal grains of sufficient size without complicating the manufacturing method.

  The method for producing a crystalline semiconductor film of the present invention includes (a) a step of depositing an amorphous semiconductor film on a substrate, and (b) an insulating film having a refractive index n1 on the amorphous semiconductor film. (C) forming a cap layer having a first region having a refractive index distribution in which the refractive index changes from n1 along the first direction using the insulating film; and (d). By irradiating the amorphous semiconductor film with light through the cap layer including the first region, the amorphous semiconductor film under the first region corresponds to the refractive index distribution of the cap layer. Forming a distribution of irradiation energy density, forming a temperature gradient along the first direction, and crystallizing the amorphous semiconductor film.

  In one embodiment, the step (c) includes a step of applying an impurity element to the insulating film so that a concentration distribution that varies along the first direction is formed in the first region of the cap layer. Including.

  In one embodiment, the step (c) includes the step of forming the rectangular first region extending in a second direction orthogonal to the first direction, and the refraction of the cap layer within the first region. The rate is substantially constant in the second direction.

  In one embodiment, step (c) includes forming a second region having a refractive index n1 adjacent to the first region.

  In one embodiment, the thickness d of the insulating film formed in the step (b) is d = (λ / 4n1) × (2k + 1) (λ: incident light wavelength, k: positive integer greater than or equal to 0) The step (d) includes a step of crystal growth along the first direction in a region of the semiconductor film below the first region of the cap layer.

In one embodiment, the concentration distribution of the impurity element is formed in the first region of the cap layer so as to continuously change the concentration of the impurity element along the first direction,
In the step (d), the temperature of the semiconductor film decreases along the direction in which the concentration of the impurity element in the cap layer increases.

  In one embodiment, the thickness d of the insulating film formed in the step (b) is d = (λ / 2n1) × (k + 1) (λ: incident light wavelength, k: k = 0 or more positive In the step (d), a crystal is formed along the first direction from the semiconductor film region below the second region of the cap layer to the semiconductor film region below the first region. Including a growth step.

  In one embodiment, the concentration distribution of the impurity element is formed in the first region of the cap layer so as to continuously change the concentration of the impurity element along the first direction, and the step ( In d), the temperature of the semiconductor film increases along the direction in which the concentration of the impurity element in the cap layer increases.

  In one embodiment, the temperature gradient formed in the step (d) is a temperature gradient in which the temperature decreases toward the center of the first region.

  In one embodiment, the cap layer has a concentration distribution of the impurity element in which a difference between a maximum concentration and a minimum concentration is in a range of 10 at% to 67 at%.

  In one embodiment, the step (c) includes a step of applying the impurity element to the insulating film using an ion implantation method or an ion doping method.

  In one embodiment, the insulating film includes a silicon oxide compound, a silicon nitride compound, a silicon nitride oxide compound, an aluminum oxide compound, an aluminum nitride compound, an aluminum nitride oxide compound, a silicon fluorinated oxide compound, a fluorinated silicon oxynitride compound, and an oxide. At least any one of silicon carbide compounds is included.

  In one embodiment, the impurity element includes at least one of carbon, nitrogen, oxygen, fluorine, silicon, and aluminum.

  The thickness of the insulating film is preferably 50 nm or more.

  In one embodiment, the semiconductor film includes silicon.

  In one embodiment, the thickness of the semiconductor film is preferably in the range of 10 nm to 200 nm.

  In one embodiment, the light beam is a laser beam having a wavelength of 400 nm or less.

In some embodiments, the light beam has an energy density of 250 mJ / cm ² or more 500 mJ / cm ² or less of a pulse laser.

  The crystallization process includes a lateral growth process.

  The crystalline semiconductor film of the present invention is preferably manufactured by the above manufacturing method.

  The semiconductor device of the present invention is manufactured using the crystalline semiconductor film.

  The display device of the present invention is manufactured using the above semiconductor device.

  In the method for producing a crystalline semiconductor film of the present invention, the amorphous semiconductor film is irradiated with light through a cap layer having a predetermined region having a refractive index distribution whose refractive index changes along a predetermined direction. A distribution of irradiation energy density corresponding to the refractive index distribution of the cap layer can be formed in the amorphous semiconductor film under a predetermined region of the cap layer. For this reason, since a gentler temperature gradient can be formed in the semiconductor film than in the prior art, the crystallization time can be increased in the cooling process after light irradiation, and larger crystal grains can be formed.

  Since the crystalline semiconductor film of the present invention has a larger crystal grain size than conventional ones, if the crystalline semiconductor film of the present invention is used, a semiconductor such as a thin film transistor having excellent electrical characteristics and less characteristic variations and excellent reliability. An element, a semiconductor device, and a display device can be manufactured.

  A method for manufacturing a crystalline semiconductor film according to an embodiment of the present invention uses a dielectric film deposited on an amorphous semiconductor film, and has a predetermined region having a refractive index distribution in which the refractive index changes along a predetermined direction. And forming a cap layer on the amorphous semiconductor film under the predetermined region by irradiating the amorphous semiconductor film with light through the cap layer including the predetermined region. The method includes a crystallization step of forming an irradiation energy density distribution corresponding to the refractive index distribution, forming a temperature gradient along the predetermined direction, and crystallizing the amorphous semiconductor film.

  The cap layer has a refractive index distribution in which the refractive index changes along a predetermined direction in a predetermined region. Since the amorphous semiconductor film is irradiated with light through the cap layer, a distribution of irradiation energy density corresponding to the refractive index distribution of the cap layer is formed in the amorphous semiconductor film under a predetermined region of the cap layer. it can. Since the temperature can be increased as the irradiation energy density of the semiconductor film is increased, a temperature gradient can be formed in the semiconductor film along the predetermined direction in which the refractive index of the cap layer changes. This temperature gradient is gentler than the temperature gradient formed in the semiconductor film when light irradiation is performed through an antireflection film having substantially the same refractive index in the plane (Patent Document 1). Therefore, in the method for manufacturing a crystalline semiconductor film according to the embodiment of the present invention, the cooling time of the semiconductor film is slowed down in the cooling process after light irradiation and the melting time is lengthened (longer time, the melting region). And the crystallization time can be lengthened. For this reason, a crystal grain larger than before can be formed.

  As will be described later with reference to FIG. 4, in the manufacturing method of Patent Document 1, the temperature gradient formed in the semiconductor film is substantially constant under the central portion of the antireflection film, but the end of the antireflection film It is steep because the temperature suddenly drops below the part. In the manufacturing method of the present embodiment, since the temperature gradient formed in a predetermined region of the semiconductor film is smaller than that of Patent Document 1, the cooling rate is slowed down in the cooling process after light irradiation, and the crystallization time can be lengthened. .

  In order to form a cap layer having a predetermined refractive index distribution, for example, an impurity element may be added so that a predetermined concentration distribution is formed in the cap layer. By controlling the energy pattern of the irradiated light, it is considered possible to form the same gentle temperature gradient in the semiconductor film as in the present invention, but it is difficult to control the energy pattern of the irradiated light. The production method of the present invention using a cap layer is easier.

  Although it is considered that a temperature gradient can be formed in the semiconductor film by using a cap layer with a changed film thickness, for example, the number of manufacturing steps is controlled by using an etching method. It increases and the manufacturing method becomes complicated. In particular, the manufacturing method is extremely difficult to change the film thickness continuously, and if the film thickness is changed discontinuously, a gentle temperature gradient as in this embodiment cannot be formed in the semiconductor film.

  Further, in the method for manufacturing a crystalline semiconductor film according to the embodiment of the present invention, since a cap layer formed on the entire surface of the semiconductor film can be used, unlike the above-described Patent Document 1, an etching process is performed to pattern the cap layer. Is not required and the manufacturing method is easy.

  Furthermore, in the method for manufacturing a crystalline semiconductor film according to the embodiment of the present invention, the position where the temperature gradient is formed in the semiconductor film can be controlled by controlling the position of the predetermined region where the refractive index of the cap layer changes. Since crystal nuclei are generated in a lower temperature region during light irradiation, the crystal grain generation position can be controlled by controlling the position of the predetermined region where the refractive index of the cap layer changes.

  Hereinafter, the manufacturing method of the crystalline semiconductor film of the present embodiment will be described in more detail with reference to FIGS. The manufacturing method of the crystalline semiconductor film of this embodiment can be classified into two types depending on the properties of the insulating film 3 formed on the amorphous semiconductor film. That is, a first type of manufacturing method that forms a cap layer using an insulating film that functions as a reflective film, and a second type of manufacturing method that forms a cap layer using an insulating film that functions as an antireflection film; Can be classified.

  First, the reflection film and the antireflection film will be described.

When the refractive index of the insulating film 3 is n1, the film thickness of the insulating film 3 is d1, and the incident light wavelength is λ, the insulating film 3 that satisfies the following formula (1) is a region of the semiconductor film 2 below the insulating film 3 The maximum reflectance of incident light can be achieved, and the semiconductor film under the insulating film 3 is irradiated with a light beam having a lower irradiation energy density as compared with the case where light irradiation is performed without providing the insulating film 3 on the semiconductor film 2. it can. Here, the reflectance is equal to the ratio of the difference between the irradiation light intensity and the light intensity incident on the semiconductor film with respect to the irradiation light intensity (the intensity of the light that irradiates the insulating film). The insulating film having the above action is called a reflective film.
n1 · d1 = (k + 1) · (λ / 2) (1)
(K = 0, 1, 2,... (Positive integer greater than or equal to 0))

On the other hand, the insulating film 3 satisfying the following formula (2) can minimize the reflectance of incident light in the semiconductor film region below the insulating film 3, and the insulating film 3 is not provided on the semiconductor film. Compared with light irradiation, the semiconductor film under the insulating film 3 can be irradiated with a light beam having a higher irradiation energy density. The insulating film having the above action is called an antireflection film.
n1 · d1 = (2k + 1) λ / 4 Formula (2)
(K = 0, 1, 2,... (Positive integer greater than or equal to 0))

  In the first type crystalline semiconductor film manufacturing method, the thickness of the insulating film 3 is set so as to satisfy the above formula (1), and the cap layer 3C1 is formed using the insulating film functioning as a reflective film. In the second type crystalline semiconductor film manufacturing method, the thickness of the insulating film 3 is set so as to satisfy the above formula (2), and the cap layer 3C2 is formed using the insulating film functioning as an antireflection film. .

  A method for manufacturing the first type crystalline semiconductor film will be described below.

  FIGS. 1A and 1B are views for explaining a manufacturing method of a first type crystalline semiconductor film, showing a cross-sectional view of a substrate on which an amorphous semiconductor film 2 and the like are stacked. Yes.

  As shown in FIG. 1A, an amorphous semiconductor film 2 is deposited on a substrate 1, and an insulating film 3 is formed thereon. As described above, the film thickness d1 of the insulating film 3 is set so as to satisfy the above formula (1).

  Next, using the insulating film 3, a cap layer 3C1 having a refractive index distribution whose refractive index changes along a predetermined direction (first direction) in a predetermined region F1 (first region) is formed.

  FIG. 2A is a top view of the substrate 1 shown in FIG.

  As shown in FIGS. 1B and 2A, specifically, in the predetermined region F1 of the cap layer 3C1, insulation is performed so that a concentration distribution that varies along a predetermined direction D1 is formed. Impurity element 52 is applied to film 3. In the second direction D2 that intersects the predetermined direction D1 (first direction), the concentration of the impurity element 52 is made substantially constant.

  Since no impurity element is added to the region S1 (second region) other than the first region F1, the second region S1 of the cap layer 3C1 has a refractive index equal to the refractive index n1 of the insulating film 3.

  FIG. 2B is a graph schematically showing an example of the concentration distribution of the impurity element 52 in the first direction D1 of the cap layer 3C1 shown in FIGS. 1B and 2A. The X axis represents the position of the cap layer 3C1 in FIGS. 1B and 2A in the first direction D1.

  As shown in FIG. 2B, the concentration distribution of the impurity element 52 in the cap layer 3C1 continuously changes, for example, along the first direction D1, and from the center of the first region F1 of the cap layer 3C1 to both ends. The concentration of the impurity element 52 gradually increases along the first direction D1. In FIG. 1B and FIG. 2A, the longer the length of the arrow indicating the impurity element 52 is, the more the impurity element 52 is introduced.

  Although the thickness of the cap layer 3C1 is equal to the thickness d1 of the insulating film 3, the refractive index of the first region F1 of the cap layer 3C1 to which the impurity element 52 is added deviates from the refractive index n1 of the insulating film 3. That is, since the refractive index of the second region S1 of the cap layer 3C not including the impurity element 52 is equal to the refractive index n1 of the insulating film 3 and satisfies the above formula (1), it can function as a complete reflective layer. Since the refractive index of the first region F1 of the cap layer 3C1 including the element 52 is different from the refractive index n1 of the insulating film 3, the above formula (1) is not satisfied. As the concentration of the impurity element 52 is higher, the difference from the refractive index n1 of the insulating film 3 increases, and the reflectance decreases.

  FIG. 3 is a graph showing a change in the reflectance R corresponding to a change in the refractive index n of the cap layer 3C1, for example, when the film thickness d1 of the cap layer 3C1 (insulating film) is set to a constant value of 103 nm. The wavelength of incident light is λ = 308 nm. As shown in FIG. 3, when the refractive index n = na, it functions as a reflection film satisfying the expression (1), and when n = about 1.5 na, it functions as an antireflection film satisfying the expression (2). Therefore, for example, the impurity element may be added to the first region F1 of the cap layer 3C1 so that the refractive index distribution is formed in the range of more than na and 1.5 na or less.

  FIG. 2C is a graph schematically showing the reflectance distribution in the first direction D1 of the cap layer 3C1. The X axis represents the position of the cap layer 3C1 in FIGS. 1B and 2A in the first direction D1.

  As shown in FIG. 2C, the cap layer 3C1 forms a reflectance distribution that continuously changes along the first direction D1, corresponding to the concentration distribution shown in FIG. Note that the reflectance is substantially constant in the second direction D2.

  When the semiconductor film 2 is irradiated with light through the cap layer 3C1 having the reflectance distribution, an irradiation energy density distribution is formed in the region of the semiconductor film 2 below the first region F1 of the cap layer 3C1. This irradiation energy density distribution corresponds to the reflectance distribution (FIG. 2C) of the cap layer 3C1. In the region of the semiconductor film 2 under the first region F1 of the cap layer 3C1, the region of the semiconductor film 2 under the cap layer 3C1 has a lower irradiation energy density in the region of the semiconductor film 2 below the region. The irradiation energy density gradually increases along the predetermined direction D1.

  A temperature gradient is formed by forming an irradiation energy density distribution in the semiconductor film 2. FIG. 2D is a graph schematically showing a temperature distribution of the semiconductor film 2 in the first direction D1. The X axis represents the position of the semiconductor film 2 in FIGS. 1B and 2A in the first direction D1.

  As shown in FIG. 2D, the region of the semiconductor film 2 below the first region F1 of the cap layer 3C1 continuously changes along the first direction D1 corresponding to the irradiation energy density distribution. A temperature gradient is formed. That is, in the semiconductor film 2 region corresponding to the first region F1 of the cap layer 3C1, the temperature at the center is the lowest, and the temperature is continuously increased from the center to both sides in the predetermined direction D1. For example, in order to form a crystal grain of about 5 μm, the short side length LF1 of the first region F1 of the cap layer 3C1 may be set to about 10 μm.

  The temperature gradient formed in the semiconductor film 2 is not limited to the above. For example, contrary to the above, the temperature gradient may be formed so that the temperature decreases from the center to both ends of the first region F1, but FIG. When the temperature gradient shown in FIG. 2 is formed, the crystal grains can be grown from the center of the first region F1 toward both ends, so that there is an effect that crystal grains having a larger size can be formed.

In the above formula (1), when the insulating film 3 is formed of SiO ₂ (refractive index 1.5) and nitrogen is used as the impurity element 52, the refractive index of the cap layer 3C1 is, for example, 1.5 to 2 (SiN What is necessary is just to change in the range to (refractive index). Further, when the insulating film 3 is formed of SiN (refractive index 2) and oxygen is used as the impurity element 52, the refractive index of the cap layer 3C1 is, for example, in the range of 2 to 1.5 (refractive index of SiO ₂ ). Change it.

  On the other hand, in the manufacturing method of Patent Document 1, an antireflection film 63C is selectively formed only in a predetermined region 62F of the amorphous semiconductor film 62 formed on the substrate 61, as shown in FIG. The amorphous semiconductor film 62 is irradiated with light through the antireflection film 63C. The region 62F of the semiconductor film 62 under the antireflection film 63C has a higher irradiation energy density than the region 62S of the semiconductor film 62 where the antireflection film 63C is not formed. However, unlike the embodiment of the present invention, almost the entire region 62F of the semiconductor film 62 has substantially the same irradiation energy density. Therefore, almost all the regions 62F of the semiconductor film 62 have substantially the same temperature (high temperature), and a temperature gradient that rapidly decreases in the vicinity of the region 62S (low temperature region) in the region 62F is formed.

  In the cooling process after the light irradiation, crystallization proceeds from the end of the region 62F of the semiconductor film 62 toward the center of the region 62F, but almost all the regions 62F of the semiconductor film 62 have a substantially equal temperature ( Therefore, almost the entire region 62F of the semiconductor film 62 is rapidly cooled almost uniformly. In FIG. 4, the growth direction of crystal grains is indicated by an arrow C.

  In the embodiment of the present invention, a gentler temperature gradient than that in Patent Document 1 can be formed in a predetermined region of the semiconductor film 2 (region under the first region F1 of the cap layer). In a predetermined region of the semiconductor film 2, a melted region having a larger area can be maintained for a longer time, and the growth rate of crystal grains can be reduced. Therefore, a crystal grain larger than patent document 1 can be formed. As shown in FIG. 1B by the arrow C, the crystal grain grows in the in-plane direction (lateral direction) of the semiconductor film 2.

  In the embodiment of the present invention, since crystal nuclei can be generated in the second region S1 of the cap layer, that is, the region of the semiconductor film 2 under the cap layer that functions as a reflective film, generation of crystal grains The position can also be controlled.

  Next, a method for manufacturing the second type crystalline semiconductor film will be described.

  FIGS. 5A and 5B are views for explaining a manufacturing method of the second type crystalline semiconductor film, showing a cross-sectional view of the substrate on which the amorphous semiconductor film 2 and the like are stacked. Yes.

  As shown in FIG. 5A, an amorphous semiconductor film 2 is deposited on a substrate 1, and an insulating film 3 is formed thereon. The film thickness d1 of the insulating film 3 is set so as to satisfy the above formula (2).

  Next, using the insulating film 3, a cap layer 3C2 having a refractive index distribution whose refractive index changes along a predetermined direction (first direction) D1 in a predetermined region F2 (first region) is formed.

  As shown in FIG. 5B, specifically, in the predetermined region F2 of the cap layer 3C2, the impurity element 52 is added to the insulating film 3 so that a concentration distribution that varies along the predetermined direction D1 is formed. Give. In the second direction D2 intersecting the predetermined direction D1 (first direction), the concentration of the impurity element 52 is made substantially constant.

  Since no impurity element is added to the region S1 (second region) other than the first region F1, the second region S2 of the cap layer 3C2 has a refractive index equal to the refractive index n1 of the insulating film 3.

  FIG. 5C is a graph schematically showing an example of the concentration distribution of the impurity element 52 in the first direction D1 of the cap layer 3C2 shown in FIG. The X axis represents the position in the first direction D1 of the cap layer 3C2 in FIG.

  As shown in FIG. 5C, the concentration distribution of the impurity element 52 of the cap layer 3C2 continuously changes, for example, along the first direction D1, and from the center of the first region F2 of the cap layer 3C2 to both ends. The concentration of the impurity element 52 gradually decreases along the first direction D1.

  Note that in FIG. 5B, the longer the length of the arrow indicating the impurity element 52 is, the more the impurity element 52 is introduced.

  The film thickness of the cap layer 3C2 is equal to the film thickness d1 of the insulating film 3, but the refractive index of the first region F2 of the cap layer 3C2 to which the impurity element 52 is added deviates from the refractive index n1 of the insulating film 3. That is, since the refractive index of the second region S2 of the cap layer 3C2 that does not include the impurity element 52 is equal to the refractive index n1 of the insulating film 3 and satisfies the above formula (2), it can function as a complete antireflection layer. Since the refractive index of the first region F2 of the cap layer 3C2 including the impurity element 52 is different from the refractive index n1 of the insulating film 3, the above formula (2) is not satisfied. As the concentration of the impurity element 52 is higher, the difference from the refractive index n1 of the insulating film 3 increases, and the reflectance increases. As shown in FIG. 5D, the cap layer 3C2 forms a reflectance distribution that continuously changes along the first direction D1 corresponding to the concentration distribution shown in FIG. Note that the reflectance is substantially constant in the second direction D2.

  When the semiconductor film 2 is irradiated with light through the cap layer 3C2 having the reflectance distribution, an irradiation energy density distribution is formed in the region of the semiconductor film 2 below the first region F2 of the cap layer 3C2. This irradiation energy density distribution corresponds to the reflectance distribution (FIG. 5D) of the cap layer 3C2. Since the irradiation energy density of the region of the semiconductor film 2 below the region where the reflectance of the cap layer 3C2 is large, the region of the semiconductor film 2 below the first region F2 of the cap layer 3C2 decreases from both sides to the center. The irradiation energy density gradually decreases along the predetermined direction D1.

  A temperature gradient is formed by forming an irradiation energy density distribution in the semiconductor film 2. FIG. 5E is a graph schematically showing the temperature distribution of the semiconductor film 2 in the first direction D1. The X axis represents the position of the semiconductor film 2 in FIG. 5B in the first direction D1.

  As shown in FIG. 5E, in the region of the semiconductor film 2 below the first region F2 of the cap layer 3C2, it continuously changes along the first direction D1 corresponding to the irradiation energy density distribution. A temperature distribution is formed. That is, in the semiconductor film 2 region corresponding to the first region F2 of the cap layer 3C2, the temperature at the center is the lowest, and the temperature is continuously increased from the center to both sides in the predetermined direction D1. For example, in order to form a crystal grain of about 5 μm, the short side length LF1 of the first region F1 of the cap layer 3C1 may be set to about 10 μm.

  Note that the temperature gradient formed in the semiconductor film 2 is not limited to the above. For example, contrary to the above, the temperature gradient may be formed so that the temperature decreases from the center to both ends of the first region F1, but FIG. When the temperature gradient shown in FIG. 2 is formed, the crystal grains can be grown from the center of the first region F1 toward both ends, so that there is an effect that crystal grains having a larger size can be formed.

In the above formula (2), when the insulating film 3 is formed of SiO ₂ (refractive index 1.5) and nitrogen is used as the impurity element, the refractive index of the cap layer 3C2 is, for example, 1.5 to 2 (refractive index of SiN). ). When the insulating film 3 is formed of SiN (refractive index 2) and oxygen is used as the impurity element, the refractive index of the cap layer 3C2 is changed in a range of 2 to 1.5 (refractive index of SiO ₂ ), for example. Just do it.

  In the manufacturing method of the comparative example shown in FIG. 6, the reflective film 73C is selectively formed only in the predetermined region 72F of the amorphous semiconductor film 72 formed on the substrate 71, and the amorphous semiconductor is interposed via the reflective film 73C. The film 72 is irradiated with light. The region 72F of the semiconductor film 72 under the reflective film 73C has a lower irradiation energy density than the region 72S of the semiconductor film 72 where the reflective film 73C is not formed. However, unlike the embodiment of the present invention, almost the entire region 72F of the semiconductor film 72 has substantially the same irradiation energy density. Therefore, almost the entire region 72F of the semiconductor film 72 has substantially the same temperature (low temperature), and a temperature gradient that rapidly increases in the vicinity of the region 72S (high temperature region) in the region 72F is formed.

  In the cooling process after the light irradiation, crystal grains are formed in the region 72F of the semiconductor film 72. Since almost all the regions of the region 72F of the semiconductor film 72 were at substantially the same temperature during the light irradiation, the region 72F of the semiconductor film 72 was. Almost all of the area is cooled to a constant and rapid rate. In FIG. 6, the growth direction of crystal grains is indicated by an arrow C.

  In the embodiment of the present invention, a gentler temperature gradient than the comparative example can be formed in a predetermined region of the semiconductor film 2 (region under the first region F2 of the cap layer). In a predetermined region of the semiconductor film 2, a melted region having a larger area can be maintained for a longer time, and the growth rate of crystal grains can be reduced. Therefore, larger crystal grains than the comparative example can be formed. As shown in FIG. 5B by the arrow C, the crystal grain grows in the in-plane direction (lateral direction) of the semiconductor film 2.

  In the embodiment of the present invention, crystal nuclei can be generated near the center of the region of the semiconductor film 2 below the first region F2 of the cap layer (lowest temperature region). It can also be controlled.

  The manufacturing method of this embodiment can be suitably applied to the large substrate shown in FIG. FIG. 7 is a top view of the substrate on which the cap layer and the semiconductor film 2 are stacked. Although the case where the said 1st type manufacturing method is applied is demonstrated below, even if it applies a 2nd type manufacturing method, the same effect can be acquired.

  As shown in FIG. 7A, the cap layer 3C1 includes, for example, a plurality of first regions F1 having a refractive index distribution and second regions S1 having a refractive index equal to the refractive index n1 of the insulating film 3. The first region F1 and the second region S1, for example, have a rectangular shape having a short side extending along the first direction D1 and a long side extending in the second direction D2 substantially perpendicular to the first direction D1. They are provided alternately along the direction D1. As described above, the second region S1 of the cap layer 3C1 functions as a reflective film, and the first region F1 has a refractive index distribution that varies along the first direction D1. Within the first region F1, the refractive index of the cap layer 3C1 is substantially constant in the second direction D2.

  For the light irradiation, for example, an excimer laser having a beam profile having a flat intensity distribution (having a uniform intensity distribution) having a rectangular shape with a long side of about 300 mm and a short side of about 0.4 mm is used. Use to irradiate the entire surface of the substrate once. For example, in order to form crystal grains of about 5 μm, the length of the short side LF1 of the first region F1 of the cap layer 3C1 is set to about 10 μm.

  When the semiconductor film 2 is irradiated with light through the cap layer 3C1, as shown in FIG. 7A, in each of the regions of the semiconductor film 2 below the first region F1 of the cap layer 3C1, the first region F1 Crystal grains C can be formed along the first direction D1 from the center to both sides. Further, since the crystal grains C formed in the first region F1 grow from the crystal nucleus formed in the central portion of the first region F1, the generation position of the crystal grains C is controlled. Therefore, for example, TFTs having the first direction D1 as the channel direction can be formed in each region of the semiconductor film 2 below the first region F1 along the second direction D2 with high density. In a method of obtaining a crystal grown in a scanning direction by irradiating a semiconductor film while step-scanning a laser beam in a predetermined direction (so-called SLS method), high-definition laser light scanning is necessary. This method has an advantage that a large number of semiconductor elements can be easily produced by a single laser irradiation.

  Further, if the position of the first region F1 formed in the cap layer 3C1 and the direction in which the refractive index distribution in the first region F1 changes are appropriately controlled, a plurality of TFTs having different channel region directions can be formed on the same semiconductor film. Can be formed. Specifically, for example, as shown in FIG. 7B, if the first region F1a and the first region F1b are formed so that the directions in which the refractive index distribution changes are orthogonal to each other, the direction of the channel region is changed. A plurality of TFTs orthogonal to each other can be formed on one semiconductor film.

As the insulating film 3, a SiO ₂ (silicon oxide) film or a SiN (silicon nitride) film can be used. Alternatively, silicon oxide compounds or silicon nitride compounds other than the above, silicon nitride oxide compounds, aluminum oxide compounds, aluminum nitride compounds, aluminum nitride oxide compounds, fluorinated silicon oxide compounds, fluorinated silicon oxynitride compounds, and silicon carbide compounds The same effect can be obtained even using the above.

  As the impurity element 52 applied to the insulating film 3, for example, nitrogen, oxygen, carbon, fluorine, silicon, and aluminum can be used. These elements may be applied alone to the insulating film 3, or a plurality of elements may be mixed and applied to the insulating film 3.

  The impurity element contained in the predetermined region of the cap layer is preferably set so that the difference between the maximum concentration and the minimum concentration is in the range of 10 at% to 67 at%. Here, “concentration” refers to at% of the impurity element with respect to the total composition. If it is less than 10 at%, there is a problem that the reflectance does not change sufficiently, and if it exceeds 67 at%, it is difficult to produce a film.

  The thickness of the insulating film 3 is preferably 50 nm or more. This is because if the thickness of the insulating film 3 is less than 50 nm, the impurity element imparted to the insulating film 3 may enter the semiconductor film 2. If the film thickness of the insulating film 3 is 50 nm or more, the temperature gradient in a predetermined region of the semiconductor film can be made sufficiently gentle due to the concentration distribution of the impurity element in the cap layer.

  As a method for applying the impurity element 52 to the insulating film 3, an ion implantation method, an ion doping method, or the like can be used.

  In the above-described first type or second type manufacturing method, the case where the insulating film 3 satisfies the above formula (1) or (2) has been described. However, the impurity element concentration gradient, the wavelength or energy of irradiation light, and the like. If the desired refractive index profile is formed in the cap layer formed using the insulating film 3 by controlling the parameters of the insulating film 3, the insulating film 3 can be formed if a gradual temperature gradient can be formed in the semiconductor film. It is not necessary to satisfy the expression.

For example, ultraviolet rays can be used as the light rays applied to the semiconductor film through the cap layer. The semiconductor film is irradiated with ultraviolet rays, for example, by irradiating a laser beam. The laser beam, a wavelength 400nm or less, the energy density of 250 mJ / cm ² or more 500 mJ / cm ² or less of the laser beam is preferably used. When the energy density of the laser beam is within the above range, the semiconductor film can be sufficiently melted and scattering of part of the semiconductor film does not occur.

  A method (SLS) of obtaining a crystal grown in a scanning direction by irradiating a semiconductor film while step-scanning a laser beam in a predetermined direction may be applied to the method for manufacturing a crystalline semiconductor film of the present invention. Since the crystal growth distance by one laser irradiation can be made larger than that of Patent Document 1, if the crystal growth distance by one laser irradiation is sufficient, it is not necessary to irradiate the crystalline semiconductor film a plurality of times. A sufficiently large crystal grain can be formed at this position.

  As the semiconductor film 2, a SiGe film, a GaAs film, a GaP film, an InP film, or the like can be used in addition to a silicon (Si) film.

  The film thickness of the semiconductor film 2 is preferably in the range of 10 nm to 200 nm. This is because if the thickness of the semiconductor film 2 is less than 10 nm, the energy beam is not sufficiently absorbed, and it becomes difficult to melt the semiconductor film. On the other hand, if the thickness of the semiconductor film is greater than 200 nm, an energy beam with excessive energy is required to melt the semiconductor thin film, and the semiconductor film cannot be stably melted. This is because it becomes difficult to form a temperature gradient. When the thickness of the semiconductor film is in the range of 10 nm to 200 nm, the semiconductor film can be stably melted and a gentle temperature gradient can be formed in the crystallization region.

  As described above, when the manufacturing method of this embodiment is used, large-sized crystal grains are formed in the semiconductor film region under the predetermined region of the cap layer having a refractive index distribution while controlling the generation position. it can. Therefore, if a semiconductor device is configured using the crystalline semiconductor film of the present invention, the carrier mobility is higher and the threshold voltage is lower than that when the crystalline semiconductor film of Patent Document 1 is used. A high performance semiconductor device can be obtained. Therefore, for example, a transistor with higher performance than the conventional one can be obtained by manufacturing a transistor using the crystalline semiconductor film of the present invention. In addition, a high-performance semiconductor element in which variation in characteristics is suppressed can be manufactured with high density by using one crystalline semiconductor film. This crystalline semiconductor film is suitably used for a display device, for example. For example, this crystalline semiconductor film is suitably used for manufacturing a pixel TFT of an active matrix liquid crystal display device and a TFT of a drive circuit.

  Hereinafter, although embodiment of this invention is described concretely, this invention is not limited to these embodiment.

(Embodiment 1)
8 and 9 are diagrams for explaining the method for manufacturing the crystalline semiconductor film according to the first embodiment of the present invention.

First, as shown in FIG. 8A, a 200 nm thick SiO ₂ film 14 is formed on an 80 cm × 60 cm glass substrate 13. The SiO ₂ film 14 is formed by a plasma CVD method using TEOS (tetraethoxysilane) gas and O ₃ gas.

Next, as shown in FIG. 8B, an amorphous silicon film 15 having a thickness of 50 nm is formed on the entire surface of the SiO ₂ film 14. The amorphous silicon film 15 is formed, for example, by a low pressure CVD method using Si ₂ H ₆ gas.

Next, as shown in FIG. 8C, a SiO ₂ film 16 is formed on the amorphous silicon film 15 by plasma CVD. Note that a cap layer is formed using the SiO ₂ film 16 in a later step.

The thickness of the SiO ₂ film 16 is 155 nm (calculated assuming that the refractive index of SiO ₂ is 1.5 and the λ of the excimer laser used for crystallization is 308 nm) so as to satisfy the formula (2) that functions as an antireflection film It was.

Next, nitrogen 17 as an impurity element is introduced into a predetermined region of the SiO ₂ film 16 by ion implantation or ion doping. When the substrate is scanned and doped in a line shape, the doping concentration is controlled by changing the scanning speed of the substrate to form a desired concentration distribution.

Nitrogen 17 as an impurity element is introduced so that a concentration gradient 18 is formed in the crystallization direction of the amorphous silicon film 15 within the surface of the SiO ₂ film 16 as shown in FIG. 9B. Specifically, nitrogen 17 is introduced into a predetermined region of 10 μm × 30 cm of the SiO ₂ film 16. Nitrogen 17 is introduced into the SiO ₂ film 16 so that the difference between the maximum concentration (58 at%) and the minimum concentration (10 at%) is 48 at% and a concentration gradient of about 4.8 at% / μm is formed.

The refractive index of the SiO ₂ film 16 increases as the concentration of nitrogen 17 increases, and a refractive index distribution 19 as shown in FIG. 9C is formed. This is because the introduction of nitrogen 17 into the SiO ₂ film 16 approaches the SiN film having a refractive index higher than that of SiO ₂ . In the first embodiment, since the SiO ₂ film 16 is an antireflection film, the reflectance of the SiO ₂ film 16 at the time of film formation is minimized. In this state, the nitrogen 17 is changed to a concentration gradient 18. When this is introduced, the reflectivity of the SiO ₂ film 16 increases as the nitrogen concentration increases in this film thickness (155 nm), resulting in a reflectivity distribution 20 as shown in FIG. Therefore, when the laser is irradiated, the temperature of the amorphous silicon film 15 becomes the lowest in the region where the concentration of nitrogen 17 is the highest, and a temperature distribution 21 as shown in FIG. The nucleation occurs in the low temperature region, and the crystal grows to the high temperature region. Since the temperature gradient is gently formed, the melting region of the amorphous silicon film 15 can be expanded, and as a result, a crystalline silicon film having large crystal grains can be produced. In this embodiment, a crystalline silicon film having a crystal grain size of about 5 μm can be obtained.

  Further, since crystal nuclei are generated in a region where the introduced nitrogen 17 is at the highest concentration, it is possible to control the position of crystal grains.

  The crystalline silicon film thus formed can be used as an active layer of a semiconductor element such as a thin film transistor. The semiconductor element can be used in a semiconductor device such as a driver of a liquid crystal display device, a semiconductor memory, or a semiconductor logic circuit.

(Embodiment 2)
8 and 10 are diagrams for explaining the method for manufacturing the crystalline semiconductor film of the second embodiment.

First, as shown in FIGS. 8A to 8C, the SiO ₂ film 14 and the SiO ₂ film 16 are formed on the substrate 13 by the same method as in the first embodiment.

However, the film thickness of the SiO ₂ film 16 is 103 nm (calculated assuming that the refractive index of SiO ₂ is 1.5 and the λ of the excimer laser used for crystallization is 308 nm) that satisfies the formula (1) functioning as a reflective film. .

Next, as shown in FIG. 10A, nitrogen 21 as an impurity element is introduced into the SiO ₂ film 16 by ion implantation or ion doping. Nitrogen 22 as an impurity element is introduced so that a concentration gradient 23 is formed in the crystallization direction of the amorphous silicon film 15 in the plane of the SiO ₂ film 16 as shown in FIG. Specifically, nitrogen 17 is introduced into a predetermined region of 10 μm × 30 cm of the SiO ₂ film 16. Nitrogen 21 is introduced into the SiO ₂ film 16 so that the difference between the maximum concentration (58 at%) and the minimum concentration (10 at%) is 48 at% and a concentration gradient of about 4.8 at% / μm is formed.

The refractive index of the SiO ₂ film 16 increases as the concentration of nitrogen 22 increases, and a refractive index distribution 24 as shown in FIG. 10C is formed. This is because the introduction of nitrogen 22 into the SiO ₂ film 16 approaches the SiN film having a refractive index higher than that of SiO ₂ . In the second embodiment, since the SiO ₂ film 16 is a reflective film, the reflectance of the SiO ₂ film 16 at the time of film formation is maximized. In this state, the nitrogen 22 has a concentration gradient 23. When the film is introduced, the reflectance of the SiO ₂ film 16 becomes smaller as the nitrogen concentration is higher at this film thickness (103 nm), and the reflectance distribution 25 as shown in FIG. Therefore, when the laser is irradiated, the temperature of the amorphous silicon film 15 is lowest in the region where the concentration of nitrogen 22 is low, and a temperature distribution 26 as shown in FIG. As a result, nucleation occurs in the low temperature region, and crystals grow into the high temperature region. Since the temperature gradient is gently formed, the melting region of the amorphous silicon film 15 can be expanded, and as a result, a crystalline silicon film having large crystal grains can be produced. Further, since crystal nuclei are generated in a region where the introduced nitrogen 22 is at the lowest concentration, the position control of the crystal grains can be performed.

  The crystalline silicon film thus formed can be used as an active layer of a semiconductor element such as a thin film transistor. The semiconductor element can be used in a semiconductor device such as a driver of a liquid crystal display device, a semiconductor memory, or a semiconductor logic circuit.

(Embodiment 3)
11 and 12 are diagrams for explaining the method for manufacturing the crystalline semiconductor film of the third embodiment.

First, as shown in FIG. 11A, an SiO ₂ film 28 of, eg, a 200 nm-thickness is formed on a glass substrate 27. The SiO ₂ film 28 is formed by plasma CVD using TEOS (tetraethoxysilane) gas and O ₃ gas.

Next, as shown in FIG. 11B, an amorphous silicon film 29 is formed on the entire surface of the SiO ₂ film 28. The amorphous silicon film 29 is formed to a thickness of 50 nm by, for example, a low pressure CVD method using Si ₂ H ₆ gas.

  Next, as shown in FIG. 11C, a SiN film 30 is formed on the amorphous silicon film 29 by plasma CVD. Note that a cap layer is formed using this SiN film 30 in a later step.

  The film thickness of the SiN film 30 was 115 nm (calculated assuming that the refractive index of SiN is 2 and the λ of the excimer laser used for crystallization is 308 nm) that satisfies the formula (2) that functions as an antireflection film.

Next, as shown in FIG. 12A, oxygen 31 as an impurity element is introduced into the SiN film 30 by ion implantation or ion doping. Oxygen 31 as an impurity element is introduced so that a concentration gradient 32 is formed in the crystallization direction of the amorphous silicon film 29 in the plane of the SiN film 30 as shown in FIG. Specifically, oxygen 31 is introduced into a predetermined region of 10 μm × 30 cm of the SiN film 30. Oxygen 31 is introduced into the SiO ₂ film 16 so that the difference between the maximum concentration (67 at%) and the minimum concentration (10 at%) is 57 at% and a concentration gradient of about 5.7 at% / μm is formed.

The refractive index of the SiN film 30 decreases as the concentration of oxygen 31 increases, and a refractive index distribution 33 as shown in FIG. 12C is formed. This is because oxygen 31 is introduced into the SiN film 30 to approach the SiO ₂ film having a refractive index lower than that of SiN. In the third embodiment, since the SiN film 30 is an antireflection film, the reflectance of the SiN film 30 at the time of film formation is minimized. In this state, the oxygen 31 is given a concentration gradient 32. Then, at this film thickness (115 nm), the reflectance of the SiN film 30 increases as the oxygen concentration increases, and a reflectance distribution 34 as shown in FIG. Therefore, when the laser is irradiated, the temperature of the amorphous silicon film 29 is lowest in the region where the concentration of oxygen 31 is high, and a temperature distribution 35 as shown in FIG. As a result, nucleation occurs in the low temperature region, and crystals grow into the high temperature region. Since the temperature gradient is gently formed, the melting region of the amorphous silicon film 29 can be expanded, and as a result, a crystalline silicon film having large crystal grains can be produced. Further, since crystal nuclei are generated in the region where the introduced oxygen 31 is the highest concentration, the position control of the crystal grains can be performed.

  The crystalline silicon film thus formed can be used as an active layer of a semiconductor element such as a thin film transistor. The semiconductor element can be used in a semiconductor device such as a driver of a liquid crystal display device, a semiconductor memory, or a semiconductor logic circuit.

(Embodiment 4)
FIG. 13 is a cross-sectional view for explaining the method for manufacturing the semiconductor device of the embodiment of the present invention. The semiconductor device of Embodiment 4 includes a liquid crystal driver, a semiconductor memory, and a semiconductor logic circuit using a thin film transistor or the like formed using the crystalline silicon film manufactured in Embodiment 1 or Embodiment 2 or Embodiment 3 described above. Or the like.

First, a crystalline Si thin film 36 is prepared by the method of Embodiment 1, and after patterning by RIE using SiO _{2 in} the upper layer of the Si thin film 36, TEOS gas and O ₃ gas are used as in a normal thin film transistor. A gate SiO ₂ film 37 is formed by plasma CVD, and a WSi ₂ / polycrystalline Si gate electrode 38 is formed by sputtering, followed by patterning by RIE using CF ₄ gas and O ₂ gas.

Next, P and B are implanted into the source and drain by an ion doping method, a SiO ₂ film 39 is formed by a plasma CVD method using TEOS gas and O ₃ gas, and then CF ₄ gas and CHF ₃ gas are used. Contact hole etching is performed by the conventional RIE method. An Al wiring 40 is formed thereon by sputtering, patterned by RIE using BCl ₃ gas and Cl ₂ gas, and then a SiN protective film formed by plasma CVD using SiH ₄ gas, NH ₃ gas and N ₂ gas. 41, and finally, a portion of the SiN protective film 41 is etched by an RIE method using CF ₄ gas and CHF ₃ gas to form a liquid crystal driver or semiconductor memory comprising semiconductor elements such as thin film transistors, resistors, capacitors, etc. A semiconductor device such as a semiconductor logic circuit is manufactured.

(Embodiment 5)
FIG. 14 is a cross-sectional view for explaining a method for manufacturing a display device including the semiconductor device according to the embodiment of the present invention.

  The liquid crystal display device of Embodiment 5 is a liquid crystal display device manufactured using the semiconductor device of Embodiment 4 described above.

Specifically, as shown in FIG. 14A, an SiO ₂ film 42 is formed by plasma CVD using TEOS gas and O ₃ gas on the semiconductor device manufactured up to the Al wiring 40 in the fourth embodiment. Then, through-hole etching is performed by the RIE method using CF ₄ gas and CHF ₃ gas. Next, an ITO film 43 is formed as a pixel electrode by sputtering, patterned after using HCl and FeCl ₃ , and then a SiN protective film 44 is formed by plasma CVD using SiH ₄ gas, NH ₃ gas, and N ₂ gas. To do. A polyimide film 45 is formed thereon as an alignment film by an offset printing method, and a rubbing process is performed.

  On the other hand, as shown in FIG. 14B, a film with a photosensitive resin thin film of red, green, and blue is transferred onto an insulating substrate 46 such as another glass substrate by thermocompression, and patterned by a photolithography process. Then, a black matrix portion is similarly formed in the space between red, green, and blue, and the color filter 47 is manufactured. An ITO film 48 is formed thereon by sputtering, and a polyimide film 49 is formed as an alignment film by offset printing, followed by rubbing.

  An insulating substrate 46 such as a glass substrate on which the color filter 47 is formed and an insulating substrate 13 such as a glass substrate on which a semiconductor device such as a thin film transistor is formed are bonded together with a sealing resin. At this time, in order to make the space between the two glass substrates constant, spherical silica is sprayed. After injecting liquid crystal between both substrates, a polarizing plate is pasted, and a driver IC or the like is mounted on the periphery to manufacture a liquid crystal display device.

  The crystalline semiconductor film of the present invention can be used for a semiconductor element such as a thin film transistor. The semiconductor element can be used in a semiconductor device such as a driver of a liquid crystal display device, a semiconductor memory, or a semiconductor logic circuit.

(A) And (b) is sectional drawing for demonstrating the manufacturing method of the crystalline semiconductor film of embodiment of this invention. (A) is a top view of FIG. 1 (b), (b) is a graph showing the concentration distribution of the impurity element in the first direction D1 of the cap layer, and (c) is a graph in the first direction D1 of the cap layer. It is a graph which shows typically reflectance distribution, (d) is a graph which shows typically temperature distribution in the 1st direction D1 of a semiconductor film. It is a graph which shows the change of the reflectance R corresponding to the change of the refractive index n of a cap layer. It is a figure for demonstrating the manufacturing method of patent document 1. FIG. (A) And (b) is a figure for demonstrating the manufacturing method of a 2nd type crystalline semiconductor film, (c) is a graph which shows concentration distribution of the impurity element in the 1st direction D1 of a cap layer. (D) is a graph schematically showing the reflectance distribution in the first direction D1 of the cap layer, and (e) is a graph schematically showing the temperature distribution in the first direction D1 of the semiconductor film. It is a figure for demonstrating the manufacturing method of a comparative example. (A) And (b) is a figure for demonstrating the case where embodiment of this invention is applied to a large board | substrate. (A)-(c) is sectional drawing for demonstrating the preparation methods of the crystalline-semiconductor film of Embodiment 1 and Embodiment 2, respectively. (A)-(e) is sectional drawing for demonstrating the manufacturing method of the crystalline-semiconductor film of Embodiment 1, respectively. (A)-(e) is sectional drawing for demonstrating the manufacturing method of the crystalline-semiconductor film of Embodiment 2, respectively. (A)-(c) is sectional drawing for demonstrating the manufacturing method of the crystalline-semiconductor film of Embodiment 3, respectively. (A)-(e) is sectional drawing for demonstrating the manufacturing method of the crystalline-semiconductor film of Embodiment 3, respectively. FIG. 9 is a cross-sectional view for illustrating a method for manufacturing a semiconductor device according to a fourth embodiment. (A) And (b) is sectional drawing for demonstrating the manufacturing method of the liquid crystal display device by Embodiment 5. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Semiconductor film 3 Insulating film 3C1 Cap layer 3C2 Cap layer 13 Substrate 14 SiO ₂ film 15 Amorphous silicon film 16 SiO ₂ film 17 Nitrogen 18 Concentration gradient 19 Refractive index distribution 20 Reflectance distribution 21 Temperature distribution 22 Nitrogen 23 Concentration gradient 24 Refractive index distribution 25 Reflectance distribution 26 Temperature distribution 27 Substrate 28 SiO ₂ film 29 Amorphous silicon film 30 SiN film 31 Oxygen 32 Concentration gradient 33 Refractive index distribution 34 Reflectance distribution 35 Temperature distribution 36 Crystalline silicon Film 37 Gate SiO ₂ film 38 Gate electrode 40 Al wiring 41 SiN protective film 43 ITO film 44 SiN protective film 45 Polyimide film 46 Glass substrate 47 Color filter 48 ITO film 49 Polyimide film 61 Substrate 62 Semiconductor film 63C Antireflection film 71 Substrate 72 Semiconductor film 73C Reflective film F1 First region 2 the first region F1a first region F1b first regions S1 second region S2 second region

Claims (22)

(A) depositing an amorphous semiconductor film on the substrate;
(B) depositing an insulating film having a refractive index n1 on the amorphous semiconductor film;
(C) forming a cap layer having a first region having a refractive index distribution in which the refractive index changes from n1 along the first direction using the insulating film;
(D) A refractive index profile of the cap layer is applied to the amorphous semiconductor film under the first region by irradiating the amorphous semiconductor film with light through the cap layer including the first region. Forming a distribution of irradiation energy density corresponding to the above, forming a temperature gradient along the first direction, and crystallizing the amorphous semiconductor film. Method.   The step (c) includes a step of applying an impurity element to the insulating film so that a concentration distribution that varies along the first direction is formed in the first region of the cap layer. A method for producing a crystalline semiconductor film as described in 1. above. The step (c) includes a step of forming the rectangular first region extending in a second direction orthogonal to the first direction,
The method for manufacturing a crystalline semiconductor film according to claim 2, wherein a refractive index of the cap layer is substantially constant in the second direction in the first region.   The method for manufacturing a crystalline semiconductor film according to claim 1, wherein the step (c) includes a step of forming a second region having a refractive index n1 adjacent to the first region. The film thickness d of the insulating film formed in the step (b) is expressed by d = (λ / 4n1) × (2k + 1) (λ: incident light wavelength, k: positive integer greater than or equal to 0),
5. The crystal according to claim 1, wherein the step (d) includes a step of crystal growth along the first direction in a region of the semiconductor film under the first region of the cap layer. For producing a high-quality semiconductor film. Forming the concentration distribution of the impurity element in the first region of the cap layer so as to continuously change the concentration of the impurity element along the first direction;
The method for manufacturing a crystalline semiconductor film according to claim 5, wherein in the step (d), the temperature of the semiconductor film decreases along the direction in which the concentration of the impurity element in the cap layer increases. The film thickness d of the insulating film formed in the step (b) is expressed by d = (λ / 2n1) × (k + 1) (λ: incident light wavelength, k: k: positive integer greater than or equal to 0). ,
The step (d) includes a step of crystal growth from the region of the semiconductor film under the second region of the cap layer to the region of the semiconductor film under the first region along the first direction. The manufacturing method of the crystalline semiconductor film in any one of Claim 1 to 4. Forming the concentration distribution of the impurity element in the first region of the cap layer so as to continuously change the concentration of the impurity element along the first direction;
The method for manufacturing a crystalline semiconductor film according to claim 7, wherein in the step (d), the temperature of the semiconductor film increases along a direction in which the concentration of the impurity element in the cap layer increases.   The method for manufacturing a crystalline semiconductor film according to claim 1, wherein the temperature gradient formed in the step (d) is a temperature gradient in which the temperature decreases toward the center of the first region. .   10. The method for manufacturing a crystalline semiconductor film according to claim 2, wherein the cap layer has a concentration distribution of the impurity element in which a difference between a maximum concentration and a minimum concentration is in a range of 10 at% to 67 at%. .   The method for manufacturing a crystalline semiconductor film according to claim 2, wherein the step (c) includes a step of applying the impurity element to the insulating film using an ion implantation method or an ion doping method.   The insulating film includes a silicon oxide compound, a silicon nitride compound, a silicon nitride oxide compound, an aluminum oxide compound, an aluminum nitride compound, an aluminum nitride oxide compound, a fluorinated silicon oxide compound, a fluorinated silicon oxynitride compound, and a silicon oxycarbide compound. The method for producing a crystalline semiconductor film according to claim 1, comprising at least one of them.   The method for producing a crystalline semiconductor film according to claim 1, wherein the impurity element includes at least one of carbon, nitrogen, oxygen, fluorine, silicon, and aluminum.   The method for producing a crystalline semiconductor film according to claim 1, wherein the insulating film has a thickness of 50 nm or more.   The method for manufacturing a crystalline semiconductor film according to claim 1, wherein the semiconductor film contains silicon.   The method for manufacturing a crystalline semiconductor film according to claim 1, wherein the thickness of the semiconductor film is in a range of 10 nm to 200 nm.   The method for producing a crystalline semiconductor film according to claim 1, wherein the light beam is a laser beam having a wavelength of 400 nm or less. The light beam, the energy density of 250 mJ / cm ² or more 500 mJ / cm ² or less of a pulse laser method for producing a crystalline semiconductor film according to any of claims 1-17.   The method for manufacturing a crystalline semiconductor film according to claim 1, wherein the crystallization step includes a lateral growth step.   A crystalline semiconductor film manufactured by the manufacturing method according to claim 1.   21. A semiconductor device using the crystalline semiconductor film according to claim 20. A display device comprising the semiconductor device according to claim 21.