JP4035019B2 - Manufacturing method of semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device and a method for manufacturing the same, and in particular, a pixel region having a plurality of thin film transistors (TFTs, hereinafter referred to as TFTs) on an amorphous substrate such as non-alkali glass. And a semiconductor device provided with a driver region, that is, a so-called driver pixel integrated type (System On Panel: SOP; hereinafter referred to as SOP).
[0002]
[Prior art]
Since the TFT is formed on an extremely thin and fine operating semiconductor film, it is considered to be mounted on a large-screen liquid crystal panel in consideration of the recent demand for a large area. Etc. are expected to be applied.
[0003]
In SOP, a plurality of polycrystalline semiconductor TFTs (particularly polycrystalline silicon (hereinafter referred to as p-Si) TFTs) are formed on an amorphous substrate such as alkali-free glass. In this case, after an amorphous silicon (hereinafter referred to as a-Si) film is formed as a semiconductor film, an excimer laser having an ultraviolet wavelength and a short pulse is irradiated, so that only the a-Si film is not affected by the glass substrate. The mainstream method is to obtain a p-Si film that functions as an operating semiconductor film by melting and crystallizing.
[0004]
A specific form of the conventional example will be described below with reference to the drawings.
[0005]
FIGS. 14 and 15 show a state in which the pulsed excimer laser beam is processed into a linear shape and, for example, an a-Si film is irradiated while scanning the linear laser beam.
[0006]
FIG. 14 is a diagram schematically showing the configuration of an SOP liquid crystal display device according to a conventional embodiment. In the drawing, the substrate is 1, the pixel area is 101, the data driver area is 102, and the scan driver area is 103. 104 is a semiconductor thin film (a-Si film) patterned in a linear (ribbon) form (hereinafter referred to as a semiconductor thin film ribbon). For example, the linear laser beam irradiation scans the semiconductor thin film ribbon 104 in the pixel region 101, the data driver region 102, and the scan driver region 103 in the direction of the arrow as shown in FIG.
[0007]
FIG. 15 is a diagram showing a state in which the semiconductor thin film ribbon 104 is irradiated and scanned with the linear laser beam. The width of the semiconductor thin film ribbon 104 is 70 μm, and the gap between the semiconductor thin film ribbon 104 regions is 80 μm.
[0008]
FIG. 16 is a diagram showing a state where TFT islands are formed on the semiconductor thin film ribbon 104 of FIG. 15. In the drawing, the channel region in the semiconductor thin film ribbon 104 is 105, the source / drain 106 is sandwiched between them, and these regions are included. The island region of the TFT is 107.
[0009]
As shown in FIG. 16, the a-Si film formed in the pixel region 101, the data driver region 102, and the scan driver region 103 is patterned into a semiconductor thin film ribbon 104, and the surface of the patterned a-Si film 104 or The linear laser beam is irradiated and scanned on the back surface of the substrate 1 in the direction of the arrow. Since the width dimension of the laser beam to be used is 100 μm, the semiconductor thin film ribbon 104 on the entire area of the substrate 1 is irradiated while shifting the scanning position by 150 μm. Thereafter, the ribbon-like semiconductor thin film 104 is patterned and etched to form an island region 107 of a TFT having a region to be the source / drain 106 with the channel region 105 sandwiched in the semiconductor thin film ribbon 104. At this time, when viewed from one place on the surface of the semiconductor thin film ribbon 104, the laser beam is one irradiation scan.
[0010]
The semiconductor thin film ribbon 104 in the periphery of the island region 107 is formed with an operating semiconductor film (p-Si film) that is a microcrystal because the cooling rate is high due to thermal diffusion to the periphery. Crystal grains having a width of several μm and a length of several tens of μm can be formed sufficiently late. Thereby, the crystal grain size of the channel part can be increased.
[0011]
[Problems to be solved by the invention]
An excimer laser that emits a high-power and linear beam corresponding to the increase in the area of SOP has been developed, and the p-Si film obtained by laser crystallization has a large crystal grain size and is formed uniformly in a large area. Has become possible.
[0012]
Thus, for example, in the SOP liquid crystal display device, when a TFT is manufactured using a p-Si film obtained by crystallization using the pulsed excimer laser, the pixel region and each driver region are configured. In the channel region of the TFT, the TFT having a high level of transistor characteristics with a high mobility can be manufactured because the crystal grain size is large and there are few grain boundaries present in the channel. The mobility of TFT obtained by this technique is about 150 cm 2 / Vs.
[0013]
As described above, the pulsed excimer laser is subjected to one irradiation scan on the a-Si film formed in the pixel region and the driver region, so that high mobility TFTs are uniformly formed in the entire region. However, in the pixel region, in the TFT for switching each pixel, the p-Si film serving as the operation semiconductor film obtained by this method is thick, so that the off-current There has been a problem that (leakage current) becomes large.
[0014]
Therefore, the present invention has been made in view of the above problems, and when applying the SOP to a liquid crystal display device or the like, the transistor characteristics of the TFT are set to a high level, and each TFT is optimal for pixel switching and driver high-speed driving. It is an object of the present invention to provide a semiconductor device and a manufacturing method thereof.
[0015]
Furthermore, in the present invention, when the transistor characteristics of the TFT are set to a high level and the optimum TFT is realized for each of pixel switching and driver high-speed driving, the number of irradiation times of the CW laser energy beam is made different between the pixel region and the driver region. An object of the present invention is to provide a semiconductor device capable of realizing the TFT by controlling the film thickness of a p-Si film that is an optimum operating semiconductor film, and a method for manufacturing the same.
[0016]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention includes the following aspects.
[0017]
An aspect of the present invention is a method of manufacturing a semiconductor device in which a pixel region and a driver region each having a plurality of TFTs are provided on a substrate, and the semiconductor thin film formed in the pixel region and the driver region is subjected to time. When the semiconductor thin film is irradiated with an energy beam that continuously outputs energy to crystallize each semiconductor thin film to form an active semiconductor thin film for each TFT, the number of times of irradiation of the semiconductor thin film formed in the pixel region with the energy beam Is more than the number of times of irradiation of the semiconductor thin film formed in the driver region.
[0018]
In this case, the thickness of the operating semiconductor thin film of each TFT constituting the pixel region is smaller than the thickness of the operating semiconductor thin film of each TFT constituting the driver region.
[0019]
As described above, the leakage current (off current) can be reduced by reducing the film thickness of the operating semiconductor thin film of each TFT constituting the pixel region.
[0020]
In this case, as a specific example of the energy beam, a CW laser beam, and further a semiconductor-excited solid-state laser beam (DPSS laser beam) are preferable.
[0021]
Thus, by crystallizing the semiconductor thin film with an energy beam that is continuously output with respect to time, such as a CW laser, the crystal grain size is increased to a larger grain size, specifically in the energy beam scanning direction. The crystal state of the semiconductor thin film is formed along a streamlined flow pattern with long crystal grains. The crystal grain size in this case is, for example, 10 to 100 times larger than that when crystallized by an excimer laser beam currently used.
[0022]
A laser beam such as a CW laser having a high output is processed by an optical system so as to form a square spot of several centimeters square or a linear shape having a length of 10 cm or more on the irradiated surface, and the laser beam is scanned ( A method of performing laser annealing by moving the irradiation position of the laser beam relative to the irradiated surface is preferable because it is excellent in mass productivity and industrially excellent.
[0023]
In particular, when a linear laser beam is used, the laser beam is scanned over the entire irradiated surface by scanning only in the direction perpendicular to the linear direction of the linear laser, unlike the case of using a spot laser beam that requires scanning in front, rear, left, and right. Since irradiation can be performed, high mass productivity is obtained. The reason for scanning in the direction perpendicular to the line direction is that it is the most efficient scanning direction.
[0024]
In the above aspect, it is preferable that the semiconductor thin films are patterned on the substrate in a linear or island shape.
[0025]
Crystallization technology using a CW laser has been studied for a long time in the field of SOI (Silicon On Insulator), but it has been considered that a glass substrate cannot be thermally endured. Certainly, when laser irradiation is performed in a state where the a-Si film is formed on the entire surface as a semiconductor thin film, the temperature of the glass substrate increases as the temperature of the a-Si film increases, and damage such as cracks is observed. In the present invention, by previously patterning the semiconductor thin film into a linear or island shape, the temperature of the glass substrate does not rise, and the occurrence of cracks, diffusion of impurities into the film, and the like are prevented. As a result, when forming an operating semiconductor thin film of TFT on a substrate such as glass, it is possible to use an energy beam that outputs energy continuously with respect to time typified by a CW laser.
[0026]
In the above aspect, the number of irradiation times of the energy beam that outputs energy continuously and linearly with respect to time is different between the pixel region and the driver region (specifically, in the driver region). Crystallizing by irradiating the semiconductor thin film formed in the pixel region and the driver region once to the formed semiconductor thin film, and at least twice to the semiconductor thin film formed in the pixel region; It is preferable to use an operating semiconductor thin film.
[0027]
The TFTs provided in the pixel region and the driver region have different required accuracy and need to be optimized when manufacturing them. Accordingly, it is possible to reliably form an operating semiconductor thin film having a large grain size, to make the operating characteristics of each TFT high, and to apply an energy beam that continuously outputs energy over time to the pixel region and Applying to the driver region, the number of times of irradiation of the energy beam is different between the pixel region and the driver region, and applying a linear energy beam, etc., the operating semiconductor of the TFT that respectively constitutes the pixel region and the driver region A difference is made in the thickness of the thin film. This makes it possible to achieve a desired SOP that meets the accuracy requirements of each location extremely efficiently.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings.
[0029]
─Crystalling with energy beam output continuously over time─
First, a main configuration of this embodiment, that is, an energy beam that continuously outputs energy with respect to time is a CW laser, and here, crystallization of a semiconductor thin film using the CW laser will be disclosed.
[0030]
By irradiating and scanning a semiconductor thin film such as an a-Si film with a continuous energy beam with respect to time, it is possible to form a polysilicon crystal having a large particle size. The crystal grain size at this time is about several μm, and a very large crystal can be formed. This crystal grain size is, for example, 10 to 100 times larger than the excimer laser currently used. Therefore, it is very advantageous for a TFT of a driver portion that requires high speed operation.
[0031]
FIGS. 1 to 5 show crystallization of a semiconductor thin film using a CW laser.
[0032]
FIG. 1 is a diagram schematically showing the configuration of an SOP liquid crystal display device, and the configuration is the same as that of FIG. 14 and has already been described. It shows with the same code | symbol (refer FIG. 14). For example, as shown in FIG. 1, the CW laser irradiation scans the pixel region 101, the data driver 102, and the semiconductor thin film ribbon 104 in the scan driver region 103 in the direction of the arrow.
[0033]
FIG. 2 is a diagram showing a state in which an energy beam continuously output with respect to time from the CW laser 3 to the semiconductor thin film ribbon 104 is irradiated and scanned in the direction of the arrow, which is the same as that in FIG. Are denoted by the same reference numerals. As shown in FIG. 2, the width of the semiconductor thin film ribbon 104 is 70 μm, and the gap between the semiconductor thin film ribbon 104 regions is 80 μm. A circular diagram in FIG. 2 is a schematic diagram of a plurality of TFTs formed within the width of the ribbon 104.
[0034]
FIG. 3 is a diagram showing a state where TFT islands are formed in the data driver region 102 and the scan driver region 103, and the same components as those in FIG. 16 are denoted by the same reference numerals. In the figure, a channel region in the semiconductor thin film ribbon 104 is 105, a source / drain 106 sandwiching the channel region, and an island region 107 of the TFT having these regions is 107.
[0035]
FIG. 4 is a diagram showing a state in which the semiconductor thin film ribbon 104 formed in the pixel region 101 is irradiated and scanned for the second time in the direction of the arrow with the energy beam continuously output from the CW laser 3 with respect to time. The same thing as 2 thing is shown with the same code | symbol. 4 is a schematic view of a plurality of TFTs formed in the width of the ribbon 104. In FIG.
[0036]
FIG. 5 is a diagram showing a state where TFT islands are formed in the pixel region 101. In the figure, the channel region in the semiconductor thin film ribbon 104 is 105, the source / drain 106 sandwiching it, and the island region of the TFT having these regions Is 107.
[0037]
1-3, buffer SiO ₂ The a-Si film 2 (film thickness: 100 nm) is patterned into a linear shape (ribbon shape) on the glass substrate 1 formed with the CW laser 3 on the surface of the a-Si film 2 or the back surface of the glass substrate 1. The first irradiation scan is performed in the direction of the arrow with the energy beam output continuously with respect to time. As shown in FIG. 2, since the width of the laser beam used is 100 μm, the semiconductor thin film ribbon 104 on the entire area of the substrate 1 is irradiated while shifting the scanning position by 150 μm.
[0038]
After that, as shown in FIG. 3, only the ribbon-like semiconductor thin film 104 in the data driver region 102 and the scan driver region 103 is patterned and etched to sandwich the channel region 4 in each semiconductor thin film 104 to form the source / drain 5. An island region 6 of the TFT having the region is formed. As a result, the semiconductor thin film ribbon 104 in the data driver region 102 and the scan driver region 103 is crystallized to form an operating semiconductor thin film (film thickness: about 100 nm) of each TFT film.
[0039]
Next, as shown in FIG. 4, an energy beam continuously output with respect to time from the CW laser 3 is applied to only the front surface of the ribbon-like semiconductor thin film 104 in the pixel region 101 or the back surface of the glass substrate 1 as indicated by the arrows. Second irradiation scan in the direction. As shown in FIG. 4, the width of the laser beam used is 100 μm, the second scanning is started by shifting 30 μm from the position of the first scanning region of the first laser, and the scanning position is shifted by 150 μm. However, only the semiconductor thin film ribbon 104 in the entire pixel region 101 is irradiated and scanned.
[0040]
Thereafter, as shown in FIG. 5, only the ribbon-like semiconductor thin film 104 in the pixel region 101 is patterned and etched, and the TFT having a region that becomes the source / drain 5 with the channel region 4 sandwiched in each semiconductor thin film 104. An island region 6 is formed. Thereby, the semiconductor thin film ribbon 104 of the pixel 101 is crystallized, and an operating semiconductor thin film (film thickness: about 50 nm) of the TFT film constituting the region is formed.
[0041]
Microcrystals are formed in the periphery of each island region 6 due to the high cooling rate due to thermal diffusion to the periphery, but the irradiation conditions (energy and scanning speed) of the CW laser 3 are appropriately selected inside. Thus, the cooling rate can be sufficiently slowed down, and crystal grains with a width of several μm and a length of several tens of μm are formed. Thereby, the crystal grain size of the channel part can be increased.
[0042]
In this way, the operation of the TFT that constitutes the pixel region and each driver region, such as applying a linear energy beam by changing the number of times of irradiation of the CW laser beam between the pixel region and each driver region. A difference can be provided in the film thickness of the semiconductor thin film.
[0043]
In addition, although the crystallization technique by the energy beam continuous with respect to time has been studied for a long time in the field of SOI (Silicon On Insulator), it was considered that the glass substrate cannot be thermally endured. Certainly, when laser irradiation is performed with the a-Si film formed on the entire surface, the temperature of the glass substrate increases with the temperature of the a-Si film, and damage such as cracks is observed. By processing the film into a linear shape (or an island shape) in advance, the temperature of the glass substrate does not increase, and cracks and impurities do not diffuse into the film.
[0044]
Hereinafter, specific examples of crystallization using a CW laser will be shown.
[0045]
The wavelength of the CW laser is 532 nm. Note that the wavelength may be a wavelength at which the semiconductor thin film can be crystallized. The output is 100 W, and the substrate is NA35 glass which is an amorphous substrate. The material of the amorphous substrate is not limited to this, and other non-alkali glass, quartz glass, silicon single crystal, ceramics, plastic, etc. may be used.
[0046]
Between the glass substrate and the semiconductor thin film, SiO ₂ The buffer layer is formed with a film thickness of about 400 nm. The buffer layer is not limited to this, and SiO ₂ A laminated structure of a film and a SiN film may be used. The semiconductor thin film is a silicon thin film formed by plasma CVD. Before the energy irradiation, heat treatment for removing hydrogen is performed by heat treatment at 450 ° C. for 2 hours. Here, hydrogen extraction is not limited to heat treatment. In this example, the light is transmitted from the back surface through the glass. However, the present invention is not limited to this, and the light may be irradiated from the semiconductor thin film side.
[0047]
The energy beam is formed into a long linear beam (or elliptical beam) having a size of 150 μm × 20 μm. Here, the size and shape of the energy beam are not limited to this, and may be adjusted to an optimum size necessary for crystallization. For example, the beam shape is preferably a rectangular beam (or elliptical beam), a linear beam (or elliptical beam), or the like. Note that the long linear beam (or elliptical beam), rectangular beam (or elliptical beam), and linear beam (or elliptical beam) preferably have uniform energy intensity within the beam, but they need to be uniform. Rather, an energy profile having the highest intensity at the center position of the beam may be used.
[0048]
In this example, the a-Si film 104 is patterned in a ribbon shape in the silicon region where the TFT is formed as shown in FIGS. 2 and 3, and the adjacent ribbon-shaped a-Si films 104 are separated by a predetermined distance. In other words, there is a region where the a-Si film 104 does not exist. By configuring the arrangement of the a-Si film 2 in this manner, thermal damage to the NA35 glass substrate 1 can be greatly reduced. Note that the a-Si film is not limited to a ribbon shape (linear shape), and may be an island shape.
[0049]
In this example, between the NA 35 glass substrate 1 and the a-Si film 2 which is a semiconductor thin film, a SiOCVD film having a film thickness of about 400 nm formed by PECVD. ₂ A membrane exists as a buffer layer. The buffer layer is not limited to this, and SiO ₂ 200nm or more if used alone or SiO ₂ A laminated structure of a film and a SiN film may be used.
[0050]
In this example, crystallization was performed using one CW laser having an output of 100 W and a wavelength of 532 nm. However, when the arrangement of the semiconductor thin film pattern is already known as shown in FIG. May be irradiated at the same time in alignment with the semiconductor thin film region. At this time, a plurality of energy beam generators may be used, or a plurality of energy beams may be separated from one unit.
[0051]
--TFT fabrication--
Hereinafter, an example of manufacturing an n-channel TFT using the above-described CW laser beam will be described. 6 to 9 are schematic cross-sectional views showing the manufacturing method of this TFT in the order of steps.
[0052]
As the substrate, the glass substrate 21 of NA35 which is an amorphous substrate is used as described above. First, as shown in FIG. 6A, an SiO film having a thickness of about 400 nm is formed on a glass substrate 21. ₂ A patterned Si thin film in which an amorphous silicon thin film (a-Si film) having a thickness of about 100 nm and a buffer layer 22 is formed is formed, and heat treatment is performed at 450 ° C. for 2 hours for hydrogen extraction. Note that hydrogen extraction is not limited to heat treatment.
[0053]
Subsequently, the a-Si film is crystallized by using an energy beam that is continuously output with respect to the above-described time, and the operating semiconductor thin film 11 is formed. Specifically, for example, as shown in FIG. 1 and the like, a semiconductor thin film, in this case, the a-Si film is formed in a ribbon shape, and the CW laser is used to form a linear beam having a wavelength of 532 nm and an energy beam size of 150 μm × 20 μm. The a-Si film is crystallized by irradiation scanning (see FIG. 6A). The film thickness of the operative semiconductor thin film 11 after crystallization is about 100 nm.
[0054]
Subsequently, using the energy beam, the operation semiconductor thin film 11 shown in FIG. 6A is crystallized by a second irradiation scan, and the operation semiconductor thin film 11 ′ having a thickness smaller than the film thickness of the operation semiconductor thin film 11 is obtained. (Not shown). The film thickness of the operating semiconductor thin film 11 ′ is about 50 nm. Hereinafter, only the fabrication of the TFT using the operating semiconductor thin film 11 will be described, but the same applies to the case where the operating semiconductor thin film 11 ′ is used.
[0055]
Subsequently, for example, as shown in FIG. 4, a TFT island region 6 is formed in a crystallized ribbon-like semiconductor thin film (reference numeral 104 in FIG. 4). At this time, processing is performed so that the channel region 4 of the TFT is positioned on the central axis of the ribbon-like semiconductor thin film. That is, the current flowing in the completed TFT matches the scanning direction of the laser beam. In this case, as shown in the circular diagrams of FIGS. 2 and 4, a plurality of (six in the illustrated example) TFTs may be formed within the ribbon width.
[0056]
Subsequently, as shown in FIG. 6B, a silicon oxide film 23 to be a gate oxide film is formed on the operating semiconductor thin film 11 to a thickness of about 100 nm by PECVD. At this time, other methods such as an LPCVD method or a sputtering method may be used.
[0057]
Subsequently, as shown in FIG. 6C, an aluminum film (or aluminum alloy film) 24 is formed by sputtering to have a film thickness of about 300 nm.
[0058]
Subsequently, as shown in FIG. 7A, for example, the aluminum film 24 is patterned into an electrode shape by photolithography and subsequent dry etching to form the gate electrode 24.
[0059]
Subsequently, as shown in FIG. 7B, the silicon oxide film 23 is patterned using the patterned gate electrode 24 as a mask to form a gate oxide film 23 following the shape of the gate electrode.
[0060]
Subsequently, as shown in FIG. 7C, both sides of the gate electrode 24 of the operating semiconductor thin film 11 are ion-doped using the gate electrode 24 as a mask. Specifically, an n-type impurity, here phosphorus (P), is ion-doped under conditions of an acceleration energy of 20 keV and a dose of 4 × 10 15 / cm 2 to form source / drain regions.
[0061]
Subsequently, as shown in FIG. 8A, after excimer laser irradiation is performed to activate phosphorus in the source / drain regions, the film thickness is formed so as to cover the entire surface as shown in FIG. 8B. SiN is deposited to a thickness of about 300 nm, and an interlayer insulating film 25 is formed.
[0062]
Subsequently, as shown in FIG. 9A, contact holes 26 that expose the gate electrode 24 and the source / drain regions of the operating semiconductor thin film 11 are formed in the interlayer insulating film 25.
[0063]
Subsequently, as shown in FIG. 9B, after forming a metal film 27 such as aluminum so as to bury each contact hole 26, the metal film 27 is patterned as shown in FIG. A wiring 27 is formed to be electrically connected to the gate electrode 24 and the source / drain region of the operating semiconductor thin film 11 through the contact hole 26.
[0064]
Thereafter, through formation of a protective film covering the entire surface, etc., n-channel TFTs having different film thicknesses of the operating semiconductor films 11 and 11 ′ as described above are completed.
[0065]
10 to 13 show the relationship between the film thickness of the operating semiconductor film of the n-channel TFT and the TFT characteristics according to the embodiment of the present invention.
[0066]
FIG. 10 is a graph showing the Id-Vg characteristics of the n-channel TFT according to the embodiment of the present invention, in the case where the gate voltage Vg (V) is changed with the drain voltage Vd (V) being 1V. The drain current Id (A) is shown. In the figure, the vertical axis represents the drain current Id (A) and the horizontal axis represents the gate voltage Vg (V), which is indicated by the solid line, which is an operation semiconductor film 11 ′ (film) crystallized by irradiating the CW laser beam twice. The characteristic indicated by the dotted line of the TFT having a thickness of about 50 nm (not shown) is an operation semiconductor film 11 crystallized by irradiating the CW laser beam once (film thickness: about 100 nm, see FIG. 6A). It is a TFT having
[0067]
FIG. 11 is a graph showing the S-Value characteristics of the n-channel TFT according to the embodiment of the present invention, which is indicated by the solid lines 6 to 6 within the ribbon width (1 to 6 in the circular diagrams of FIGS. 2 and 4). The increase in the gate voltage Vg (V) for increasing the drain current Id (A) by a factor of 10 (assuming the on-state current is constant) at the TFT position is shown. In the figure, the vertical axis represents the reciprocal of the slope of the Id-Vg characteristic of the TFT (V / dec), and the horizontal axis represents the position of the TFTs 1 to 6 indicated by the solid line within the ribbon width. Is a TFT having an operation semiconductor film 11 (see FIG. 6A) crystallized by irradiating once with the CW laser beam, which is indicated by ●, which is crystallized by irradiating the CW laser beam twice. This is for a TFT having an operating semiconductor film 11 ′ (not shown) (hereinafter, the same applies to the marks ● and ▲ in FIGS. 12 and 13).
[0068]
FIG. 12 is a graph showing the mobility of the n-channel TFT according to the embodiment of the present invention, which is indicated by six points within the ribbon width (shown by solid lines 1 to 6 in the circular diagrams of FIGS. 2 and 4). The mobility of the TFT at the TFT position is shown. In the figure, the vertical axis represents TFT mobility (cm). ² / Vs), the horizontal axis is the position of the TFTs 1 to 6 indicated by solid lines within the ribbon width.
[0069]
FIG. 13 is a graph showing the Vth characteristics of the n-channel TFT according to the embodiment of the present invention, and is shown in the ribbon width at six locations (shown by solid lines 1 to 6 in the circular diagrams of FIGS. 2 and 4). The gate voltage value (Vth) for turning on the TFT at the TFT position is shown. In the drawing, the vertical axis represents the Vth (V) of the TFT, and the horizontal axis represents the position of 1 to 6 TFTs indicated by the solid line within the ribbon width.
[0070]
As a result, the n-channel TFT having the operating semiconductor film 11 crystallized by irradiating once with the CW laser beam and the n-channel TFT having the operating semiconductor film 11 ′ crystallized by irradiating the CW laser beam twice. The channel TFT has the same transistor characteristics, that is, the mobility of the TFT at a high level of about 350 cm 2 / Vs, and has an operation semiconductor film 11 ′ that is crystallized by irradiating the CW laser beam twice. In the channel TFT, the thickness of each operating semiconductor film is reduced, and as a result, the off / on ratio, that is, the difference between the on-current (= constant) and the off-current is small, and therefore the gate voltage Vg is negative. It can be seen that the drain current Id, that is, the off-current is reduced.
[0071]
According to the present embodiment, when the SOP is applied to a liquid crystal display device or the like as described above, the TFT transistor characteristics, that is, the mobility of the TFT, is obtained as an optimum TFT for each of pixel switching and driver high-speed driving. Homogenizing at a high level of about 350 cm 2 / Vs, and controlling the film thickness of the p-Si film that is the optimum operating semiconductor film for each TFT (specifically, in the driver high-speed driving TFT, the CW laser beam In the pixel switching TFT, the operating semiconductor film 11 ′ having a thin film thickness that is crystallized by irradiating the CW laser beam twice. It is possible to realize each of the TFTs by applying '). As a result, a high-performance SOP liquid crystal display device including a large number of TFTs can be realized.
[0072]
【The invention's effect】
According to the present invention, the transistor characteristics of the TFT can be set to a high level, and an optimum TFT can be provided for each of pixel switching and driver high-speed driving. In particular, the on-current (leakage current) of the pixel switching TFT can be reduced. It becomes possible.
[0073]
Further, according to the present invention, when the SOP is applied to a liquid crystal display device or the like, the transistor characteristics of the TFT are set to a high level, and the energy beam that continuously outputs energy that can increase the operating characteristics of the TFT is set to the driver region and The operation of the TFT that configures the driver region and the pixel region by applying to the pixel region, changing the number of times of irradiation of the energy beam between the driver region and the pixel region, and applying a linear energy beam, etc. By providing a difference in the thickness of the semiconductor thin film, it is possible to realize a liquid crystal display device of a desired SOP that meets the accuracy requirements of each place extremely efficiently.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing a configuration of an SOP liquid crystal display device according to an embodiment of the present invention.
FIG. 2 is a view showing a state in which an energy beam continuously output from a CW laser 3 to a semiconductor thin film ribbon 104 with respect to time is irradiated and scanned in the direction of an arrow for the first time.
FIG. 3 is a diagram illustrating a state where TFT islands are formed in a scan driver region and a gate driver region.
FIG. 4 is a diagram illustrating a state in which an energy beam continuously output from the CW laser 3 with respect to time is irradiated and scanned in the direction of an arrow on the semiconductor thin film ribbon 104 formed in the pixel region 101 for the second time.
FIG. 5 is a diagram showing a state where a TFT island is formed in the pixel region 101;
FIG. 6 is a schematic cross-sectional view showing a method of manufacturing a TFT according to an embodiment of the invention in the order of steps.
FIG. 7 is a schematic cross-sectional view subsequent to FIG. 6, illustrating a method for manufacturing a TFT according to an embodiment of the present invention in the order of steps.
FIG. 8 is a schematic cross-sectional view subsequent to FIG. 7, showing a method for manufacturing a TFT according to an embodiment of the present invention in the order of steps.
FIG. 9 is a schematic cross-sectional view subsequent to FIG. 8, illustrating a method for manufacturing a TFT according to an embodiment of the present invention in the order of steps.
FIG. 10 is a graph showing Id-Vg characteristics of an n-channel TFT according to an embodiment of the present invention.
FIG. 11 is a graph showing S-Value characteristics of an n-channel TFT according to an embodiment of the present invention.
FIG. 12 is a graph showing mobility of an n-channel TFT according to an embodiment of the present invention.
FIG. 13 is a graph showing Vth characteristics of an n-channel TFT according to an embodiment of the present invention.
FIG. 14 is a diagram schematically showing a configuration of an SOP liquid crystal display device according to a conventional embodiment.
FIG. 15 is a view showing a state in which a semiconductor thin film ribbon is irradiated and scanned with the linear laser beam.
16 is a view showing a state where TFT islands are formed on the semiconductor thin film ribbon 104 of FIG.
[Explanation of symbols]
1 Substrate
3 CW laser beam
11, 11 'operation semiconductor film (p-Si film)
101 pixel area
102 Scan driver area
103 Gate driver area
104 Semiconductor thin film ribbon (a-Si film)
105 channel region
106 Source / Drain

Claims (4)

A method of manufacturing a semiconductor device in which a pixel region and a driver region each having a plurality of thin film transistors are provided on a substrate,
When the semiconductor thin film formed in each of the pixel region and the driver region is irradiated with an energy beam that continuously outputs energy with respect to time to crystallize each of the semiconductor thin films,
The semiconductor thin film formed in the pixel region is formed by increasing the number of times of irradiation of the semiconductor thin film formed in the pixel region of the energy beam to the number of times of irradiation of the semiconductor thin film formed in the driver region. A method of manufacturing a semiconductor device, characterized in that the thickness is made thinner than the thickness of a semiconductor thin film formed in the driver region. After crystallizing the semiconductor thin film formed in the driver region,
2. The method of manufacturing a semiconductor device according to claim 1, wherein the semiconductor thin film formed in the pixel region is crystallized.   3. The method of manufacturing a semiconductor device according to claim 1, wherein the energy beam that continuously outputs energy with respect to time is a CW laser beam.   4. The method of manufacturing a semiconductor device according to claim 3, wherein a beam shape of the CW laser light is any one of a round beam, a long linear beam, an elliptical beam, a rectangular beam, and a linear beam.

Images