JP2009111179A - Method of manufacturing semiconductor thin film, method of manufacturing thin-film transistor, semiconductor thin film, thin-film transistor, and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a semiconductor thin film which has electric characteristics enhanced and also has variation in electric characteristic suppressed, a method of manufacturing a thin-film transistor, a semiconductor thin film, the thin-film transistor, and a display device. <P>SOLUTION: Disclosed is the method of manufacturing the semiconductor thin film on a substrate, the manufacturing method including a crystallization step of forming a polycrystalline silicon film consisting of first crystal grains such that a ä101} plane is parallel to a film surface of an amorphous silicon film formed on the substrate and a <100> direction is parallel to a direction wherein crystallization energy is applied and second crystal grains such that a ä114} plane is parallel to the film surface and a <122> direction is parallel to the direction wherein the crystallization energy is applied by applying the crystallization energy to the amorphous silicon film in one direction in the film surface of the amorphous silicon film, and a crystal growing step of causing the first crystal grains to disappear and making the second crystal grains larger by applying crystallization energy to the polycrystalline silicon film. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a method for manufacturing a semiconductor thin film, a method for manufacturing a thin film transistor, a semiconductor thin film, a thin film transistor, and a display device. More specifically, the present invention relates to a method for manufacturing a semiconductor thin film suitable for a semiconductor device including a thin film transistor over an insulating substrate, a method for manufacturing the thin film transistor, a semiconductor thin film, a thin film transistor, and a display device.

In recent years, a technique for crystallizing an amorphous silicon film formed on an insulating substrate such as glass to form a semiconductor silicon film having a crystal structure (hereinafter referred to as a crystalline silicon film) has been widely studied. As the crystallization method, a thermal annealing method using a furnace annealing furnace, a rapid thermal annealing (RTA) method, a laser annealing method, and the like have been studied.

A crystalline silicon film has higher mobility than an amorphous silicon film. Therefore, a thin film transistor (TFT) is formed using this crystalline silicon film. For example, a TFT for switching a pixel, a TFT for a driving circuit for driving the pixel, etc. on one glass substrate Is used in an active matrix type liquid crystal display device and the like.

Conventionally, in order to crystallize an amorphous silicon film in a furnace annealing furnace, a heat treatment at 600 ° C. or more for 10 hours or more has been required. In this case, the substrate material applicable to crystallization is quartz, but the quartz substrate is expensive and difficult to process into a large area.

Therefore, as a method for crystallizing the amorphous silicon film, a method of obtaining a polycrystalline silicon film by irradiating the amorphous silicon film with ultraviolet rays, a short pulse excimer laser, or the like has become the mainstream. The laser annealing method is a technique that can be used not only for a glass substrate having a low strain point but also for a plastic substrate. Substrates such as glass and plastic are inexpensive and relatively easy to process in a large area. In recent years, glass substrates having a size exceeding 1 m on a side have been used.

As a technique for forming a high mobility semiconductor thin film using a laser annealing method, an amorphous silicon film is irradiated with a pulse laser, and a polycrystalline semiconductor preferentially oriented in the {100} plane parallel to the film surface. A technique is disclosed in which, after forming a thin film, crystal grains preferentially oriented in the {100} plane are enlarged by irradiating continuous oscillation laser light (see, for example, Patent Document 1).
JP 2003-151904 A

However, in Patent Document 1, the crystal orientation cannot be controlled in the in-plane orientation of the polycrystalline semiconductor thin film. When a plurality of thin film transistors are manufactured using this polycrystalline semiconductor thin film, the electrical characteristics of each thin film transistor are not controlled. There was a risk that the variation would increase.

The present invention has been made in view of the above-described situation, and provides a method for manufacturing a semiconductor thin film, a method for manufacturing a TFT, a semiconductor thin film, a TFT, and a display device that enhance electrical characteristics and suppress variations in electrical characteristics. It is intended.

The present inventor has made various studies on a method of manufacturing a semiconductor thin film that enhances electrical characteristics such as carrier mobility and suppresses variations in the electrical characteristics, and focuses on controlling the crystal orientation in the in-plane direction of the semiconductor thin film. did. Then, by applying crystallization energy to the amorphous silicon film formed on the substrate in one direction within the film surface of the amorphous silicon film, the {101} plane is parallel to the film surface. And the <100> orientation is parallel to the orientation giving crystallization energy, and the {114} plane is parallel to the film surface and the <122> orientation gives crystallization energy. A crystallizing step for forming a polycrystalline silicon film composed of second crystal grains parallel to the orientation to be applied, and applying crystal growth energy to the polycrystalline silicon film, thereby eliminating the first crystal grains. And a crystal growth step for enlarging the second crystal grains, so that crystals with an orientation outside the film surface (an orientation perpendicular to the film surface) and an orientation within the film surface (an orientation parallel to the film surface) are obtained. The orientation can be aligned, improving the electrical properties of the semiconductor thin film, One found that variation in electrical characteristics can be suppressed, conceive that can be admirably solved the above problems, it is the present invention has been completed.

That is, the present invention is a method of manufacturing a semiconductor thin film on a substrate, and the above manufacturing method is applied to an amorphous silicon film formed on a substrate in a single plane within the surface of the amorphous silicon film. By giving crystallization energy to the orientation, the first crystal grains in which the {101} plane is parallel to the film surface and the <100> orientation is parallel to the orientation giving crystallization energy, and A crystallization step of forming a polycrystalline silicon film composed of second crystal grains in which the {114} plane is parallel to the film surface and the <122> orientation is parallel to the orientation giving crystallization energy; A method of manufacturing a semiconductor thin film including a crystal growth step in which crystal growth energy is applied to the polycrystalline silicon film to eliminate first crystal grains and enlarge second crystal grains.
The present invention is described in detail below.

The present invention is a method of manufacturing a semiconductor thin film on a substrate. As the substrate, a glass substrate, a quartz substrate, a plastic substrate, or a stainless steel substrate can be used, but it is not particularly limited. When used in a display device, a transparent substrate such as a glass substrate or a transparent plastic substrate is more preferable from the viewpoint of transmitting light. By manufacturing a semiconductor thin film on a substrate, for example, a semiconductor element such as a thin film transistor can be formed at a desired location even on a large-area substrate, and productivity can be improved. The semiconductor thin film is made of silicon (silicon) and is made of a crystal having a diamond structure crystal structure, and is usually a polycrystalline silicon film, but may be a single crystal. The semiconductor thin film may contain, for example, an impurity element that generates carriers such as holes and electrons.

In the method for producing a semiconductor thin film, by applying crystallization energy to an amorphous silicon film formed on a substrate in one direction within the film surface of the amorphous silicon film, {101} A first crystal grain whose surface is parallel to the film surface and whose <100> orientation is parallel to the orientation that imparts crystallization energy, and whose {114} plane is parallel to the film surface and <122> orientation Includes a crystallization step of forming a polycrystalline silicon film composed of second crystal grains parallel to the orientation to which crystallization energy is applied. According to this, the crystal orientations of the crystal grains formed in the polycrystalline silicon film can be aligned to two. Since the first crystal grains and the second crystal grains are twinned with each other, the second crystal grains are changed from the first crystal grains to the second crystal during the crystallization process for forming the polycrystalline silicon film. The first crystal grains can be easily grown from the grains, and a polycrystalline silicon film having only the first crystal grains and the second crystal grains can be obtained by controlling the conditions for imparting crystallization energy. .
First, since it becomes possible to form a polycrystalline silicon film having only these two kinds of crystal grains, the crystal orientation in the semiconductor thin film can be controlled in the crystal growth step described later.
A crystal grain is a particle having a crystal structure composed of an ordered atomic arrangement, and each crystal grain is composed of a single crystal.

In the crystallization step, crystallization energy is applied in one direction within the film surface of the amorphous silicon film. Usually, the position where crystallization energy is applied to the amorphous silicon film is positioned at the one position. It is done while shifting along For example, in the case of applying crystallization energy by irradiating laser light, laser irradiation is performed while scanning a portion irradiated with the laser light in one position parallel to the film surface. In such a case, the crystallization energy may be applied while moving the irradiation source of the laser beam, or the portion irradiated with the laser beam while moving the substrate on which the amorphous silicon film is disposed. May be moved. Note that one direction in this case includes a reverse direction parallel to any one direction in the film plane.

In the crystallization step, the second crystal grain can be formed as a lateral crystal extending in an orientation that imparts crystallization energy. By forming crystals extending in one direction in the film plane, the crystal plane orientation of the crystals in the polycrystalline silicon film can be controlled in the crystal growth step described later.

The polycrystalline silicon film is composed of the first crystal grains and the second crystal grains, but may contain a few other crystal grains having different crystal orientations. In addition, the crystal orientation of the crystal grains that may be included other than the first crystal grains and the second crystal grains is preferably not in the range of <100> to 25 °. This is because in the case of crystal grains having an out-of-film orientation in the range of <100> to 25 °, crystal grains whose orientation is not controlled are also grown in the crystal growth step described later. In order to obtain only a second crystal grain and to obtain a semiconductor thin film having only the second crystal grain in the crystal growth process, which will be described later, at this time (after the crystallization process and before the crystal growth process) The ratio of the second crystal grains is preferably 10% or more, and the ratio of the crystal grains other than the second crystal grains is preferably less than 90% including the first crystal grains. The ratio of the second crystal grains in the polycrystalline silicon film can be easily measured by a backscattered electron diffraction image (EBSP) method using an electron beam diffractometer manufactured by TSL.

The method for manufacturing a semiconductor thin film includes a crystal growth step in which crystal growth energy is imparted to the polycrystalline silicon film to eliminate the first crystal grains and enlarge the second crystal grains. According to this, since it is possible to obtain a semiconductor thin film including the second crystal grains preferentially, the electrical characteristics such as the carrier mobility of the semiconductor thin film are improved, and the electrical characteristics in the in-plane direction are not uniform. Can be suppressed. In this case, the polycrystalline silicon film melts and is immediately solidified (crystallized) by the application of crystal growth energy. However, the crystallizing rate is higher for crystal grains having an out-of-plane orientation in the range of <100> to 25 °. The crystal grains having the second crystal grain orientation are preferentially grown.

The method for producing a semiconductor thin film of the present invention is not particularly limited as long as it includes the above-described crystallization process and crystal growth process as constituent elements, and may not include other processes as constituent elements. For example, before the amorphous silicon film is formed, a step of forming a base coat film for suppressing diffusion of impurities from the substrate side may be included on the substrate. A step of forming a film for preventing the amorphous silicon film or a film crystallized from the amorphous silicon film from being scattered on the crystalline silicon film may be included, and is not particularly limited.
In addition, {101}, {114}, {100} or {122} described above represents an equivalent surface group displayed by the Miller index. For example, in the case of the {101} plane, the (101) plane alone And includes equivalent surfaces such as the (110) plane and the (011) plane. <101>, <100>, <114>, or <122> indicates an equivalent orientation group of normal orientations corresponding to the surface displayed by the Miller index. For example, in the case of the <101> orientation Includes not only the [101] direction but also equivalent surfaces such as the [110] direction and the [011] direction.
The polycrystalline silicon film and the semiconductor thin film in this specification are both films made of silicon. However, a film made of polycrystalline silicon obtained by crystallizing an amorphous silicon film in a crystallization step is referred to as “polycrystalline. A film made of polycrystalline silicon after the crystal growth process is performed on the polycrystalline silicon film is distinguished as a “semiconductor thin film”.
The preferable form in the manufacturing method of the semiconductor thin film of this invention is demonstrated in detail below.

In the crystallization step, it is preferable to apply crystallization energy by irradiating a continuous wave laser beam. According to this, by using a continuous wave laser beam, energy can be applied constant, so that crystallization can be further stabilized. For example, in the case where crystallization energy is applied by irradiating pulsed laser light, there is a possibility that irregularities occur on the surface of the polycrystalline silicon film.

The continuous wave laser beam is preferably a solid-state laser beam, and the solid-state laser beam is more preferably a second harmonic of an yttrium aluminum garnet (YAG) laser. Since the second harmonic (λ = 532 nm) of the YAG laser is easily absorbed by the silicon film, crystallization from the amorphous silicon film to the polycrystalline silicon film can be further promoted. In addition, solid laser light such as a YAG laser has a simple oscillating structure and does not require maintenance for a long period of time. Therefore, the operation time is long, the running cost is low, and it is very advantageous as a manufacturing apparatus.

The continuous wave laser beam preferably has an intensity of 10.0 to 25.0 W. If it is less than 10 W, the silicon film may not crystallize, and if it exceeds 25 W, the crystal orientation cannot be controlled or the silicon film may evaporate.
In the crystallization step, the rate at which crystallization energy is applied is preferably 1.0 to 3.0 m / s. If it is less than 1.0 m / s, the crystal orientation cannot be controlled, or the silicon film may evaporate. If it exceeds 3.0 m / s, the silicon film may not be crystallized.
By setting the laser light irradiation conditions to such conditions, the crystal orientation in the polycrystalline silicon film can be controlled, and the electrical characteristics of the semiconductor film after the crystal growth process are further improved. In addition, it is possible to suppress variation in electrical characteristics.

The semiconductor thin film is used for a semiconductor layer of a thin film transistor, and in the crystallization process, the orientation in which crystallization energy is applied is a linear orientation connecting the source region, the channel region, and the drain region of the semiconductor layer in this order. Are preferably parallel to each other. Since the second crystal grains in the polycrystalline silicon film tend to be lateral crystals that are long in the direction in which the crystallization energy is applied, the second crystal grains become longer from the source region toward the drain region, and thus more thin film transistors. The conductivity, carrier mobility, and the like from the source region to the drain region of the semiconductor layer can be improved, and a higher performance thin film transistor can be obtained.

The crystal growth step preferably imparts crystal growth energy by irradiation with continuous wave laser light. According to this, since crystallization energy can be applied constant as compared with the case where crystallization energy is applied by irradiating pulsed laser light, crystallization can be further stabilized.

The continuous wave laser beam used in the crystal growth step is preferably a solid-state laser beam, and the solid-state laser beam is more preferably a second harmonic of a YAG laser. Since the second harmonic (λ = 532 nm) of the YAG laser is easily absorbed by the silicon film, crystallization from the polycrystalline silicon film to the semiconductor thin film can be further promoted.

The continuous wave laser beam used for the crystal growth step preferably has an intensity of 3.0 to 9.5 W. If it is less than 3.0 W, the polycrystalline silicon film may not melt and crystal growth may not occur, and if it exceeds 9.5 W, the crystal orientation may not be controlled. In the crystal growth step, it is preferable that crystal growth energy is applied to the polycrystalline silicon film formed on the substrate in one direction in the plane of the polycrystalline silicon film. In the step, the rate of applying crystal growth energy is preferably 0.5 to 2.0 m / s. If it is less than 0.5 m / s, the silicon film may evaporate, and if it exceeds 2.0 m / s, the crystal orientation may not be controlled.
By setting the irradiation condition of the laser light to such a condition, the crystal orientation in the semiconductor thin film can be further controlled, and electrical characteristics can be improved, variation in electrical characteristics can be suppressed.

In the method for producing a semiconductor thin film, it is preferable that the orientation in which crystallization energy is applied and the orientation in which crystal growth energy is applied are parallel. According to this, the 2nd crystal grain extended to the direction which provides crystallization energy in a crystallization process can be grown more efficiently.

The amorphous silicon film preferably has a thickness of 30 to 100 nm. If the film thickness of the amorphous silicon film is 30 to 100 nm, the crystallization energy and the crystal growth energy can be sufficiently transmitted to the entire film. Can be controlled. If the thickness is less than 30 nm, the crystal growth selectivity in the crystal growth step is not sufficient, and the crystal orientation may not be controlled. If the thickness exceeds 100 nm, the entire film may not be sufficiently crystallized.

The present invention is also a method for manufacturing a thin film transistor using the method for manufacturing a semiconductor thin film. According to this, since the semiconductor layer of the thin film transistor can be obtained by controlling the crystal orientation in both the in-plane direction and the out-of-plane direction of the semiconductor thin film, the electrical characteristics such as carrier mobility are improved. Thus, a thin film transistor in which variation in electrical characteristics is suppressed can be manufactured. The thin film transistor of the present invention may be a thin film transistor formed on a substrate. For example, a thin film transistor formed on a substrate may be transferred (transferred) to another substrate. There is no particular limitation.

The present invention is also a semiconductor thin film manufactured using the method for manufacturing a semiconductor thin film. The semiconductor thin film is one in which the crystal orientation is controlled in both the out-of-plane orientation and the in-plane orientation of the semiconductor thin film, so that the improvement in carrier mobility and variation in electrical characteristics are suppressed. it can.

The present invention is also a thin film transistor including the semiconductor thin film as a semiconductor layer. In the thin film transistor, the {101} plane is preferentially oriented parallel to the film surface of the semiconductor thin film, and the {114} plane is preferentially oriented in a linear direction connecting the source region, channel region and drain region of the thin film transistor in this order. Thus, a thin film transistor in which electrical characteristics such as carrier mobility are improved and variation in electrical characteristics is suppressed can be obtained. Note that a thin film transistor is usually a top-gate thin film transistor including a semiconductor layer having a source region, a channel region, and a drain region, a gate insulating film, and a gate electrode in this order from the substrate side, and a gate electrode and a gate insulating film from the substrate side. And a bottom-gate thin film transistor provided with semiconductor layers in this order.

The present invention is also a display device including the thin film transistor. Since the thin film transistor has high carrier mobility and suppressed variation in electrical characteristics, for example, a switching element of a pixel serving as a basic unit for displaying an image in a display device, or a circuit such as a driver circuit When the thin film transistor is provided, a more stable display can be performed. For example, a display device includes a thin film transistor substrate including the above-described thin film transistor and a color filter substrate that are opposed to each other, and a liquid crystal display panel in which a liquid crystal layer is disposed between a pair of opposed substrates. Examples thereof include a liquid crystal display device including a driver circuit for driving light and pixels, an organic EL display device including a driver circuit on an organic electroluminescence display panel using the thin film transistor as a switching element, and the like.

The present invention further relates to a semiconductor thin film disposed on a substrate, wherein the semiconductor thin film is a crystal grain having a {114} plane parallel to the film surface and a <122> orientation oriented in one direction in the film surface. It is also a configured semiconductor thin film. Since the crystal orientations are aligned with respect to the out-of-plane orientation and the in-plane orientation of the semiconductor thin film, the electrical characteristics such as carrier mobility of the semiconductor thin film are improved and variations in the electrical characteristics are suppressed. In the semiconductor thin film, almost all the crystal grains have {114} plane parallel to the film plane and the <122> orientation faces one direction in the film plane, but has a slightly different crystal orientation. A crystal grain may exist, and a crystal grain having a {114} plane parallel to the substrate surface and having a <122> orientation in one direction in the film surface is a ratio of 10% or more in the semiconductor thin film. It is preferable that it is contained at a ratio of 40% or more.

According to the method for producing a semiconductor thin film of the present invention, electrical characteristics such as carrier mobility can be enhanced and variations in electrical characteristics can be suppressed.

Embodiments will be described below, and the present invention will be described in more detail with reference to the drawings. However, the present invention is not limited only to these embodiments.

(Embodiment 1)
Hereinafter, a method for manufacturing a semiconductor thin film, a polycrystalline semiconductor thin film, a semiconductor device, and a display device according to Embodiment 1 will be described with reference to FIGS. 1 to 12. However, the present invention is not limited to the following embodiment. Absent.

In Embodiment 1, a case will be described in which a thin film transistor having a channel region size of 4 μm in length and 4 μm in width is manufactured. FIG. 1 is a schematic cross-sectional view in the process of manufacturing a semiconductor thin film on a substrate. FIG. 1 (a) shows a configuration before the crystallization process, and FIG. The structure before a process is shown, (c) shows the structure after a crystal growth process.
First, as shown in FIG. 1A, an RF plasma chemical vapor deposition (hereinafter, also referred to as “plasma CVD”) method using tetraethyl orthosilicate (TEOS) as a source gas is used on a glass substrate 11. A silicon oxide (SiO ₂ ) film having a thickness of 100 nm is deposited on the silicon oxide film 12, followed by a plasma CVD method using a mixed gas of silane (SiH ₄ ) gas and argon (Ar) gas. An amorphous silicon film 13 having a thickness of 75 nm is formed. A 20 nm-thickness silicon oxide protective film 16 is formed on the amorphous silicon film 13 by plasma CVD using TEOS as a source gas. The silicon oxide protective film 16 is for preventing the silicon film from scattering during the laser beam irradiation described later.

FIG. 2 is a schematic plan view showing a step of irradiating a laser, and a white arrow in FIG. 2 indicates a laser scanning direction. As shown in FIG. 2, a continuous oscillation YAG laser beam having a wavelength of 532 nm and an energy of 17.5 W is formed into a rectangular irradiation shape 29 of 300 μm in length and 20 μm in width when the silicon oxide film is irradiated. Irradiation is performed while scanning in the minor axis direction (lateral direction) at a speed of 2 m / s. As a result, a polycrystalline silicon film 14 shown in FIG. 1B is formed (crystallization process).

Here, FIG. 3A shows a crystal grain boundary of the polycrystalline silicon film after the crystallization step by a backscattered electron diffraction image (EBSP) method. In the EBSP method, measurement was performed using a field emission scanning electron microscope (trade name: S-4200 Special SE, manufactured by Hitachi) equipped with an electron beam diffraction apparatus manufactured by TSL. FIG. 3B is a diagram in which FIG. 3A is color-coded according to crystal orientation. The crystal grains included in the gray region A in FIG. 3B have {101} planes parallel to the film surface of the polycrystalline silicon film, and the crystal grains included in the white region B are polycrystalline silicon. It has {114} plane parallel to the film surface of the film. As shown in FIG. 3A, the polycrystalline silicon film 14 formed by the crystallization process includes a long and narrow lateral crystal extending about 10 μm in the scanning direction of the laser beam. Here, FIG. 4A is a pole figure of <101> orientation of silicon in the crystal grains included in the gray region A in FIG. 3B, and FIG. 4B is <100> of silicon. It is a pole figure of the azimuth. FIG. 5A is a pole figure of the <101> orientation of silicon in the crystal grains included in the white region B in FIG. 3B, and FIG. 5B is the <100> orientation of silicon. It is a pole figure. The center of the pole figure represents the direction perpendicular to the film surface, and the intersection of the straight line drawn through the center of the pole figure and the circle in the figure represents the laser scanning direction in the film surface, and the center of the pole figure The intersection of the straight line drawn on the right and left and the circle in the drawing represents a direction perpendicular to the laser scanning direction in the film surface. When these pole figures were analyzed, in the gray region A, the film surface orientation (an orientation perpendicular to the film surface) of the polycrystalline silicon film was the <101> orientation, and the laser beam scanning orientation was the <100> orientation. That is, the gray region A has a {101} plane parallel to the film surface of the polycrystalline silicon film, and is composed of crystal grains (first crystal grains) having a {100} plane perpendicular to the laser beam scanning orientation. Has been. In the white region B, the film surface orientation of the polycrystalline silicon film was <114> orientation, and the laser beam scanning orientation was <122> orientation. That is, the white region B has a {114} plane parallel to the film surface of the polycrystalline silicon film, and a crystal grain (second crystal grain) having a {122} plane so as to be perpendicular to the laser beam scanning orientation. ).

From these facts, as shown in FIG. 3B, the polycrystalline silicon film 14 is mostly occupied by the first crystal grains that form the gray region A, and the remainder forms the white region B. It can be seen that it is occupied by two crystal grains. Thus, all the crystal grains are occupied by the first crystal grains and the second crystal grains. The crystal grains constituting the polycrystalline silicon film are formed in this way because, for example, the film surface orientation is <101> and the laser beam scanning orientation under certain energy irradiation conditions such as those described above. Tends to be preferentially oriented to <100>, but in lateral crystal growth (in-plane crystal growth), the internal stress of the crystal increases as the crystal grains grow, so the internal stress exceeds the critical point. Sometimes due to the formation of twins to relieve stress.

After the polycrystalline silicon film 14 is formed, laser irradiation is performed from above the silicon oxide protective film 16 in the same manner as in the crystallization process except that the YAG laser beam having an energy of 9 W is scanned at a speed of 1 m / s. The semiconductor thin film 15 shown in (c) is formed (crystal growth step).

FIG. 6 shows a crystal grain boundary of the semiconductor thin film 15 by the EBSP method. FIG. 7A is a pole figure of the <101> orientation of silicon measured for crystal grains in the entire region in FIG. 6, and FIG. 7B is a pole figure of the <100> orientation of silicon. is there. As a result of analyzing these pole figures, the crystal grains (third crystal grains) included in the semiconductor thin film 15 have the <114> orientation as the film surface orientation (direction perpendicular to the film surface) of the semiconductor thin film 15, and laser beam scanning. The direction was the <122> direction. That is, in the third crystal grain, the film plane orientation of the semiconductor thin film 15 was the <114> orientation, and the laser beam scanning orientation was the <122> orientation. That is, the semiconductor thin film 15 has a {114} plane parallel to the film surface of the semiconductor thin film 15, and is composed of crystal grains having a {122} plane so as to be perpendicular to the laser beam scanning orientation. I understand. As described above, the polycrystalline silicon film 14 preferentially oriented in two directions is selected only from crystal grains having a {114} plane parallel to the film plane orientation and a {122} plane perpendicular to the laser beam scanning orientation. Can be grown. The silicon oxide protective film 16 is removed by immersion in hydrofluoric acid after the semiconductor thin film 15 is formed (after the crystal growth step).

It was found that under the laser irradiation conditions in the crystal growth process, only crystal grains whose film plane orientation and <100> orientation are within 25 ° can be selectively grown, and other crystal grains can be eliminated. . At this time, the crystal grain is not a lateral crystal but a granular polycrystal. That is, in the second crystallization process, only the crystal grains having the <114> orientation are grown out of the crystal grains having the <101> and <114> orientations obtained from the first crystallization process. To do. Since the crystal grains with the <114> out-of-plane orientation are aligned with the <122> laser scanning orientation, the semiconductor whose crystal orientation is controlled not only in the out-of-film orientation but also in the in-film orientation. A thin film is obtained.

By using the semiconductor thin film 15 manufactured according to the above method for an active layer (a layer forming a channel region) of a field effect thin film transistor (TFT), carrier mobility is increased and variation in electrical characteristics is reduced. It can be a TFT. In the present embodiment, the film thickness of the amorphous silicon film is 75 nm. However, when the thickness is 30 to 100 nm, the effects of the present invention can be obtained sufficiently. In the crystallization process, a YAG laser beam having a wavelength of 532 nm and an energy of 17.5 W was scanned at a speed of 2.0 m / s. However, with another continuous wave laser beam, the energy was set to 10 to 25 W and the scanning speed was changed. The effect of this invention can fully be acquired by setting it as 1.0-3.0 m / s. Furthermore, in the crystal growth process, a YAG laser beam having a wavelength of 532 nm and an energy of 9 W was scanned at a speed of 1.0 m / s, but with another continuous wave laser beam, the energy was set to 3.0 to 9.5 W. The effect of the present invention can be sufficiently obtained by setting the scanning speed to 0.5 to 2.0 m / s.

Next, a method for manufacturing an n-channel field effect thin film transistor (hereinafter referred to as “n-channel TFT”) 100 using the semiconductor thin film 15 as an active layer will be described.
FIG. 8 is a schematic plan view showing the semiconductor layer 20 on the substrate 11 after patterning the semiconductor thin film 15. As shown in FIG. 8, first, the semiconductor thin film 15 formed on the silicon oxide film 12 disposed on the glass substrate 11 corresponds to a 4 μm × 4 μm channel region 21, source region 22, and drain region 23. A semiconductor layer 23 patterned into a shape is formed. At this time, patterning is performed so that a predetermined line segment AB set so as to connect the source region 22 and the drain region 23 is parallel to the laser beam scanning direction. Thereafter, as shown in FIG. 9, a gate insulating film 24 made of silicon oxide having a thickness of 100 nm is formed by an atmospheric pressure chemical vapor deposition (APCVD) method so as to cover the patterned semiconductor layer 20. Form.

Next, as shown in FIG. 10A, an aluminum film 15a having a thickness of about 300 nm is formed on the gate insulating film 24, and the aluminum film 25a is patterned into a predetermined shape as shown in FIG. 10B. Thus, the gate electrode 25 is formed. Using the gate electrode 25 as a mask, phosphorus ions are implanted into the source region 22 and the drain region 23 at 6 × 10 ¹⁵ ions / cm ² , and the source region 22 and the drain region 23 are formed on both sides of the channel region 21 immediately below the gate electrode 25. Form.

Thereafter, as shown in FIG. 11, a silicon oxide film having a thickness of 500 nm is deposited on the entire surface of the glass substrate 11 by the APCVD method to form an interlayer insulating film 26. Next, as shown in FIG. 11, a contact hole portion is formed in the gate insulating film 24 and the interlayer insulating film 26 on the source region 22 and the drain region 23, and the electrode material is contact hole portion by sputtering. Then, an ohmic contact is realized between the electrode material and the source region 22 and the drain region 23 through the contact hole portion. The lead electrode 28 is formed by patterning this electrode material into a predetermined shape.
As described above, the n-channel TFT 100 is completed.

By using the n-channel TFT 100 thus manufactured as a switching element, a semiconductor device and a display device using the semiconductor device can be manufactured. In the above description, the n-channel TFT 100 has been described as an example of the TFT, but the present invention is not limited to this. For example, a p-channel TFT may be manufactured using the semiconductor thin film 15. Further, a semiconductor device using a p-channel TFT as a switching element and a display device including the semiconductor device may be manufactured.

When an n-channel TFT was manufactured by the above-described manufacturing method and the carrier mobility was measured, it showed high carrier mobility (270 cm ² / V · s). Further, when 100 n-channel TFTs were manufactured on the same substrate by the above-described manufacturing method and the carrier mobility was measured, the carrier mobility variation was within ± 3% and was small. It was.

A semiconductor using a polycrystalline silicon film (polycrystalline semiconductor thin film) controlled so that the {114} plane and the {122} plane in the laser beam scanning direction are preferentially oriented as described above. If a device is manufactured, the device characteristics can be improved. For example, when a transistor is manufactured as a semiconductor device, carrier mobility can be increased and the threshold voltage can be decreased. Further, when a plurality of transistors are manufactured on the same substrate, it is possible to reduce variation in characteristics between the transistors.

(Comparative Example 1)
A 200 nm-thickness SiO ₂ film was formed on a glass substrate by plasma CVD, and an amorphous silicon film having a thickness of 50 nm was formed thereon. After that, using a Xe-Cl excimer laser (wavelength 308 nm), a 150 mm × 1 mm linear beam is scanned at an energy density of 300 mJ / cm ² and a step pitch of 10 μm one shot at one position. Thereby, the amorphous silicon film is crystallized to form a polycrystalline silicon film. In this case, the polycrystalline silicon film is preferentially formed with crystals having {100} planes parallel to the film surface of the polycrystalline silicon film. Thereafter, scanning is performed in one direction on the substrate surface with an energy of 5 W beam diameter of 400 μm × 20 μm and a scanning speed of 20 cm / second by a continuous wave laser of Nd: YVO 4 (2ω, wavelength 532 nm). The semiconductor thin film thus prepared was processed in the same manner as in the first embodiment to form an n-channel TFT and the carrier mobility was measured. The maximum value was 200 cm ² / V · s, The variation in carrier mobility was ± 15%.

Based on the above results, the TFT including the polycrystalline semiconductor thin film manufactured by the manufacturing method according to the present invention exhibits higher mobility than that manufactured by the conventional manufacturing method, and the carrier mobility is high. It can be seen that the variation is also smaller.

In the manufacturing process of the semiconductor thin film according to the first embodiment, (a) is a schematic cross-sectional view showing the structure before the crystallization process, and (b) is a schematic cross-sectional view showing the structure after the crystallization process and before the crystal growth process. (C) is a schematic cross-sectional view showing the structure after the crystal growth step. FIG. 5 is a schematic plan view showing a step of irradiating laser light in the manufacturing process of the semiconductor thin film according to Embodiment 1. In the manufacturing process of the semiconductor thin film which concerns on Embodiment 1, (a) is a figure which shows the crystal grain boundary of the polycrystalline silicon film after the crystallization process measured by EBSP method. (B) is the figure which color-coded the polycrystalline silicon film after the crystallization process measured by EBSP method by the difference in crystal orientation. (A) is a pole figure of <101> in the crystal grain contained in the gray area | region A in FIG.3 (b) in the manufacturing process of the semiconductor thin film which concerns on Embodiment 1. FIG. FIG. 3B is a pole figure of <100> in the crystal grains included in the gray region A in FIG. (A) is a pole figure of <101> in the crystal grain contained in the white area | region B in FIG.3 (b) in the manufacturing process of the semiconductor thin film which concerns on Embodiment 1. FIG. (B) is a pole figure of <100> in the crystal grains included in the white region B in FIG. 3 (b). In the manufacturing process of the semiconductor thin film which concerns on Embodiment 1, it is a figure which shows the crystal grain boundary of the semiconductor thin film after the crystal growth process measured by EBSP method. (A) is a pole figure of <101> in the crystal grain contained in a semiconductor thin film in the manufacturing process of the semiconductor thin film which concerns on Embodiment 1. FIG. (B) is a pole figure of <100> in the crystal grains contained in the semiconductor thin film. FIG. 4 is a schematic plan view showing a relationship between a scanning direction of laser light and a source region, a channel region, and a drain region that constitute a TFT in a manufacturing process of an n-channel TFT according to Embodiment 1. FIG. 4 is a schematic cross-sectional view showing the structure after forming a gate insulating film in the manufacturing process of the n-channel TFT according to the first embodiment. FIG. 5A is a schematic cross-sectional view showing a structure before forming a contact hole in an interlayer insulating film before patterning an aluminum film constituting a gate electrode in the manufacturing process of the n-channel TFT according to the first embodiment. . (B) is a cross-sectional schematic diagram which shows the structure after forming a gate electrode. 6 is a schematic cross-sectional view showing a structure before forming a contact hole in an interlayer insulating film in the manufacturing process of the n-channel TFT according to Embodiment 1. FIG. 2 is a schematic cross-sectional view illustrating a configuration of an n-channel TFT according to Embodiment 1. FIG.

Explanation of symbols

11: Glass substrate 12: Silicon oxide film 13: Amorphous silicon film 14: Polycrystalline silicon film 15 after crystallization process 15: Polycrystalline silicon film 16 after crystal growth process 16: Silicon oxide protective film 20: n-channel TFT Semiconductor layer 21: n-channel TFT channel region 22: n-channel TFT source region 23: n-channel TFT drain region 24: gate insulating film 25: gate electrode 25a: aluminum film 26: interlayer insulating film 28: extraction electrode 29: Laser irradiation shape 100: Thin film transistor A: A region in the polycrystalline silicon film after the crystallization step where crystal grains having an out-of-plane crystal orientation of <101> and a laser beam scanning orientation of <100> exist.
B: A region in the polycrystalline silicon film after the crystallization step where crystal grains having an out-of-plane crystal orientation of <114> and a laser beam scanning orientation of <122> are present.

Claims (19)

A method of manufacturing a semiconductor thin film on a substrate,
The manufacturing method applies a crystallization energy to an amorphous silicon film formed on a substrate in one direction within the film surface of the amorphous silicon film, so that the {101} plane is a film. A first crystal grain that is parallel to the plane and parallel to the orientation in which the <100> orientation imparts crystallization energy, and the {114} plane is parallel to the film plane and the <122> orientation is crystallized A crystallization step of forming a polycrystalline silicon film composed of second crystal grains parallel to the orientation to which energy is applied;
A method for producing a semiconductor thin film, comprising: a crystal growth step in which crystal growth energy is applied to the polycrystalline silicon film so that the first crystal grains disappear and the second crystal grains are enlarged. 2. The method of manufacturing a semiconductor thin film according to claim 1, wherein in the crystallization step, crystallization energy is applied by irradiating a continuous wave laser beam. 3. The method of manufacturing a semiconductor thin film according to claim 2, wherein the continuous wave laser beam is a solid-state laser beam. 4. The method of manufacturing a semiconductor thin film according to claim 3, wherein the solid-state laser light is a second harmonic of an yttrium, aluminum, and garnet laser. The method of manufacturing a semiconductor thin film according to any one of claims 2 to 4, wherein the continuous wave laser beam has an intensity of 10.0 to 25.0 W. The method for producing a semiconductor thin film according to claim 1, wherein the crystallization step has a rate of applying crystallization energy of 1.0 to 3.0 m / s. The semiconductor thin film is used for a semiconductor layer of a thin film transistor,
7. The crystallizing step is characterized in that the orientation in which crystallization energy is applied is parallel to a linear orientation connecting the source region, the channel region, and the drain region of the semiconductor layer in this order. The manufacturing method of the semiconductor thin film in any one of. The method for producing a semiconductor thin film according to claim 1, wherein the crystal growth step imparts crystal growth energy by irradiating a continuous wave laser beam. 9. The method for producing a semiconductor thin film according to claim 8, wherein the continuous wave laser beam used in the crystal growth step is a solid-state laser beam. 10. The method for producing a semiconductor thin film according to claim 9, wherein the solid-state laser light used in the crystal growth step is a second harmonic of an yttrium aluminum garnet laser. The method of manufacturing a semiconductor thin film according to any one of claims 8 to 10, wherein the continuous wave laser beam used in the crystal growth step has an intensity of 3.0 to 9.5 W. The crystal growth step is characterized in that crystal growth energy is applied to a polycrystalline silicon film formed on a substrate in one direction in a plane of the polycrystalline silicon film. The manufacturing method of the semiconductor thin film in any one of 1-11. 13. The method for producing a semiconductor thin film according to claim 12, wherein the crystal growth step has a rate of applying crystal growth energy of 0.5 to 2.0 m / s. The method of manufacturing a semiconductor thin film according to claim 1, wherein the amorphous silicon film has a thickness of 30 to 100 nm. A method for producing a thin film transistor, wherein the method for producing a semiconductor thin film according to claim 1 is used. A semiconductor thin film manufactured using the method for manufacturing a semiconductor thin film according to claim 1. A thin film transistor comprising the semiconductor thin film according to claim 16 as a semiconductor layer. A display device comprising the thin film transistor according to claim 17. A semiconductor thin film disposed on a substrate,
The semiconductor thin film is composed of crystal grains whose {114} plane is parallel to the film plane and whose <122> orientation is oriented in one direction in the film plane.

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