JPH1197692A - Polycrystal and liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polycrystal composed of grains, having substantially uniform large diameter by heating a first substance deposited on a base material to produce a plurality of crystals, depositing a second substance in amorphous state thereon and growing a grain of the second substance using the plurality of crystals as nuclei. SOLUTION: A silicon oxide 124 is deposited on a substrate 123, which is then introduced into a super high vacuum CVD system where an amorphous silicon layer 125 is formed on the substrate 123. The amorphous silicon layer 125 is then kept in vacuum and heated. The amorphous silicon layer 125 formed on the silicon oxide 124 produces a plurality of independent crystallites 127 of silicon. Subsequently, an amorphous silicon layer 128 is formed on the substrate 123 on which the crystallites 127 of silicon are formed. Thereafter, the amorphous silicon layer 128 is fused to produce a polycrystalline silicon layer composed of crystal grains 129. According to the method, a polycrystal composed of substantially uniform grains can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polycrystal and a liquid crystal display device provided with the polycrystal.

[0002]

2. Description of the Related Art In the manufacture of semiconductor devices, the step of heat-treating a material in an amorphous state to polycrystallize greatly affects the quality of the manufactured semiconductor device. For example, the mobility of electrons in a thin film transistor (TFT) manufactured using Si can only be about 10 cm ² / V · sec at most when amorphous silicon is used as Si. Therefore, when polycrystalline silicon is used, a mobility higher than 100 cm ² / V · sec, which is higher by one digit or more, can be realized. Therefore, if polycrystalline silicon can be formed on a substrate instead of amorphous silicon, higher performance of a semiconductor element can be expected. Generally, amorphous silicon is, for example, plasma-enhanced CVD.
(Chemical vaper deposition) method. This method is suitable for forming a thin film layer of amorphous silicon at a low temperature. For example, since it can be deposited on a glass substrate, it is widely used as a channel layer of a TFT or the like mounted on a liquid crystal display device. Has been used. However, the properties of the material in the amorphous state are:
As described above, it is not always sufficient to configure a semiconductor element such as a transistor. For example, when a TFT is mounted on a liquid crystal display device, it is not suitable for high-speed operation of each pixel because of a low operation speed. In addition, a display with high image quality cannot be obtained. Therefore, polycrystalline silicon is attracting attention as a material replacing amorphous silicon.

For example, in the case of a liquid crystal display device in which polycrystalline silicon is applied to a TFT and the TFT is mounted, polycrystalline silicon is formed by heating amorphous silicon previously deposited on a substrate. In particular, ELA (excimer laser annealing) has been used as a method for producing polycrystalline silicon at high speed on a substrate having a large area exceeding 10 inches.
aling) The method is being vigorously studied. The ELA method is different from the solid-phase growth method in which a substrate is introduced into a huge furnace for several hours and is processed.
By scanning a laser beam at a high speed of 2 mm / sec, polycrystalline silicon can be generated on a large-area substrate in a few minutes, and the polycrystalline silicon can be manufactured with high throughput.

[0004] However, the size of polycrystalline grains produced by the ELA method is usually about 0.1 to 0.5 µm,
Even if the conditions are limited, there is a problem that it is at most about 1 μm and uniform crystal grains cannot be obtained.

Further, in a semiconductor device such as a TFT provided with polycrystalline silicon manufactured by the ELA method, in order to make the electron mobility exceed 100 cm ² / V · sec, it is necessary to use narrow conditions in the ELA method. It is necessary to grow polycrystals, and even if ELA is performed under these conditions, the grain size of the crystal grains will vary, resulting in non-uniform electrical characteristics. Therefore, when a screen is displayed by a liquid crystal display device equipped with the polycrystalline silicon-TFT,
Since the brightness of the display screen changes, a high-quality image cannot be displayed, and the durability of the liquid crystal display device is also reduced.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and provides a polycrystal which is composed of substantially uniform crystal grains having a large grain size and is excellent in economical efficiency. The purpose is to: Still another object of the present invention is to provide a liquid crystal display device which can display a high-quality image and has excellent durability.

[0007]

The polycrystal according to the present invention comprises:
Laminating a first substance on a substrate, generating a plurality of crystals by heating from the first substance, and forming a plurality of crystals in the amorphous state on the substrate on which the plurality of crystals have been generated. The method is characterized by being manufactured by a step of laminating two substances and a step of growing crystal grains including the second substance by using the plurality of crystals as nuclei.

According to the polycrystal of the present invention, a plurality of crystals are generated by heating from a first substance laminated on a base material, and a crystal provided with a second substance using the plurality of generated crystals as nuclei. By growing the grains, the morphology such as the size of the crystal grains can be controlled, so that a polycrystal composed of substantially uniform crystal grains can be obtained.

Therefore, the polycrystal according to the present invention is
And the like, it is possible to obtain a semiconductor element having substantially uniform electric characteristics.

Further, in the liquid crystal display device according to the present invention, there is provided a polycrystalline channel region provided on a base material, a source region and a drain region which are continuous from the channel region, and the drain region and the source through the channel region. A gate electrode that controls the movement of carriers between the region, a source electrode connected to the source region, and a drain electrode connected to the drain region; the polycrystal is formed on the base material; A step of stacking a first substance, a step of generating a plurality of crystals from the first substance by heating, and forming a second substance in an amorphous state on a substrate on which the plurality of crystals are generated. It is characterized by being manufactured by a stacking step and a step of growing crystal grains including the second substance with the plurality of crystals as nuclei.

According to the liquid crystal display device of the present invention, a plurality of crystals are generated by heating from the first substance laminated on the base material, and the second substance is provided with the generated plural crystals as nuclei. By growing the crystal grains, a channel region made of polycrystal composed of substantially uniform crystal grains is provided, so that carriers such as electrons can be rapidly and uniformly transferred between the source region and the drain region through the channel region. Since the liquid crystal display device can be moved, a change in luminance of a display screen is suppressed, a high-quality image can be displayed, and a liquid crystal display device with excellent durability can be provided.

In the present invention, a plurality of fine crystals are formed by utilizing the property that a thin film layer made of a first substance thinly deposited on a substrate is agglomerated when the surface is heated under a condition where the surface is not oxidized. After that, the second substance is deposited on the plurality of fine crystals and subjected to a heat treatment to form a polycrystal. Here, the above mechanism will be described in comparison with the conventional polycrystallization by the ELA method.

For example, in polycrystallizing amorphous silicon using the conventional ELA method, after forming only amorphous silicon on an oxide film, the amorphous silicon is heated and melted by the ELA method to recrystallize the silicon. It is a way to make it. According to the conventional method, non-uniform initial crystal nuclei are formed at random positions on the oxide film surface, and polycrystallization according to the ELA method is based on the temperature gradient based on the initial crystal nuclei. Because of the growth, crystal grains of a non-uniform form are naturally formed. At this time, the molten silicon has a direction perpendicular to the temperature gradient from the crystal nucleus, that is,
Growth starts toward the surface opposite to the oxide film, but also grows in a direction parallel to the surface of the oxide film. However, crystal grains grown from crystal nuclei adjacent to each other stop crystal growth in the parallel direction when the grain boundaries of the crystal grains come into contact with each other, so that the grain size of the crystal grains is naturally limited by the density of the initial crystal nuclei. Is done. Therefore, the conventional E
When a polycrystal is formed on the oxide film by the LA method, a crystal grain having a non-uniform shape such as a grain size of the crystal grain is formed. Therefore, when a semiconductor element, for example, a TFT is manufactured using the polycrystal, the electrical characteristics of the TFT become non-uniform,
In a liquid crystal display device equipped with a TFT, the variation in the electrical characteristics of the TFT directly affects the variation in the display in each pixel, so that it is difficult to display a high-quality image.

On the other hand, it is expected that the control of the morphology of the crystal grains can be realized by controlling the density of the initial crystal nuclei in the process of recrystallization after the amorphous silicon is melted.

By the way, for example, when a silicon thin film layer is deposited on a silicon oxide film and subjected to a heat treatment, silicon atoms move (migrate) on the surface of the oxide film to change the form of the surface, and the granular silicon There is a tendency to form crystals (agglomeration). Therefore, utilizing this property,
By controlling the thickness of the silicon thin film layer deposited on the oxide film, the annealing temperature and the time required for annealing, silicon microcrystals can be formed on the order of nm (Japanese Patent Application No. Hei 9-131016). reference). Therefore,
After silicon microcrystals are formed in advance on an oxide film, amorphous silicon is stacked on the oxide film on which the silicon microcrystals are formed, and heat treatment is performed. Recrystallization (polycrystallization)
Can be achieved.

That is, conventionally, in recrystallization of a melted amorphous layer, crystallization (polycrystallization) proceeds with a crystal nucleus randomly generated on a substrate as an initial nucleus. According to the present invention, a crystal nucleus controlled in the order of nm is naturally disposed on an oxide film at a desired density, whereas crystal grains having a small particle size can be realized because of the dependence on the nucleus density. After that, the ELA method can be applied to the amorphous layer.
It is possible to realize crystal grains that are uniform and have a large particle size as compared with polycrystals manufactured by the LA method. In addition, since recrystallization of the melted amorphous layer starts with microcrystals already existing as nuclei (seeds), in principle, only the energy necessary for melting the amorphous layer needs to be supplied by the ELA method. Therefore, it is possible to suppress the input energy when performing the ELA method more than before, and it is also possible to contribute to the expansion of the ELA process margin.

In this way, it is possible to achieve high performance such as electric characteristics of a semiconductor device in which the above-mentioned polycrystal is applied to a channel layer (channel region). In a liquid crystal display device equipped with the semiconductor device, the characteristics of each pixel are improved. Uniform display with high image quality, in which display unevenness and the like are eliminated, is achieved. Note that the first substance may be any substance that moves (migrate) on the surface of the substrate, and examples thereof include an alloy of a semiconductor and a metal such as a semiconductor, a metal, and a metal silicide. , SiGe, Ge, C and SiC and other Group IV elements and their compounds, In, As, InA
s, Ga, GaAsAl, AlAs, InAlGaAs
III such as s, InAlAs, InAlP and InP
Group V and its compounds can be applied in crystalline or amorphous state. Further, as the second substance, for example, amorphous silicon, amorphous SiGe, amorphous germanium, or the like can be used. As the base material, for example, a thin film made of various oxides such as a silicon oxide film and a substrate having an oxide film on the surface can be used.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings.

FIGS. 1 and 2 are views showing one pixel of a liquid crystal display device according to one embodiment of the present invention.

1 and 2, a liquid crystal display device has a gate insulating film formed on an active layer (including a channel region, a source region, and a drain region) 101 of a p-Si TFT and an in-plane electrode 102. And a gate electrode line 103 and a pixel electrode 104 via the contact hole 1.
07 and connected to the in-plane electrode 102. The active layer 101 and the pixel electrode 104 are connected to the electrode pattern 110 via the contact holes 108 and 109.
Are electrically connected to each other. Further, the active layer 101
And the signal line 105 are connected by a contact hole 111. In this embodiment mode, the TFT which is a semiconductor element is a coplanar TFT.

Here, the manufacturing process of the liquid crystal display device shown in FIG. 1 will be described.

First, as shown in FIG. 3A, a silicon oxide film 124 is formed on a glass substrate 123 by plasma CVD.
Was formed to have a thickness of 100 nm. Next, the substrate 123 is placed in an ultra high vacuum (UHV).
-Introduced into a CVD apparatus, and deposited a very flat amorphous silicon layer 125 having a thickness of 1 nm without heating the substrate 123. Here, a gas 126 made of Si ₂ H ₆ was used for depositing the amorphous silicon layer 125. The molecules of the gas 126 are transferred to the substrate 1 in the CVD apparatus.
23 is supplied to the substrate 123 after being thermally decomposed by an auxiliary heater installed at a position where the surface of the
A silicon thin film can be formed even at room temperature where the decomposition of the gas 126 on the surface of 23 does not occur. When forming an amorphous silicon thin film, the above UH
Apparatus using a V-CVD method (for example,
No. 263) can be preferably used,
Not limited to the apparatus, for example, a molecular beam crystal growth (MBE) method in which solid silicon is heated with an electron beam and supplied to a substrate, a plasma CVD method in which a gaseous raw material is decomposed by plasma discharge and supplied to a substrate, ECR plasma method and CV with directionality by extracting gas as raw material by electric field etc.
It can be formed by an apparatus using the D method or the like, and when a thin film manufactured by any of the apparatuses is applied, microcrystals described later can be obtained. Further, instead of the amorphous silicon, a thin film partially or wholly composed of polycrystalline silicon may be used. Here, the most important point is to prevent impurities such as oxygen from being mixed into the thin film layer of the amorphous silicon layer 125.
When a large amount of oxygen is contained in the amorphous silicon layer 125, migration of silicon atoms is hindered, so that generation (agglomeration) of microcrystals may not be controlled in some cases. Therefore, the amorphous silicon layer 125 was kept at a vacuum without being exposed to the air and heated at 830 ° C.
That is, after the amorphous silicon layer 125 is formed by the UHV-CVD apparatus, the auxiliary heater for decomposing molecules constituting the gas 126 is stopped, and the substrate 123
The substrate 123 was heated in an ultra-high vacuum for 3 minutes by heating the heater for heating the substrate 123.

As a result, as shown in FIG. 3B, the amorphous silicon layer 125 formed flat on the silicon oxide film 124 has a maximum diameter of about 40 nm and a height of about 10 nm due to the agglomeration phenomenon. And a plurality of independent silicon microcrystals 127. Here, by changing the thickness and the heating temperature of the amorphous silicon layer 125, the form such as the size of the microcrystal 127 can be controlled. For example, when the thickness of the amorphous silicon layer 125 is 0.5 nm and the heating temperature is 730 ° C., microcrystals having a maximum diameter of 25 nm and a height of about 2 nm can be obtained. Note that the reason that the amorphous silicon layer 125 before being agglomerated is not exposed to the air is to prevent the amorphous silicon layer 125 from being oxidized in the air as described above. It is not particularly necessary to hold in a vacuum if measures are taken to prevent oxidation by holding in an atmosphere of an inert gas such as nitrogen, high-purity argon and high-purity helium. During the heating, the amorphous silicon layer 1
25 that does not cause mixing or the like with silicon 25 instead of the glass substrate 123 cited in this embodiment.
Even when a substrate made of alkali glass, quartz, SiC, sapphire, various plastics, a plastic film, a vinyl film, or the like is used, the above-mentioned microcrystals can be formed (agglomerated). Further, in the present embodiment,
Although an example in which a silicon oxide film is used as a base material has been described, the base material forms microcrystals (agglomerates) by heat treatment.
The material is not particularly limited as long as the material moves (migrate) on the surface of the substrate and changes the form of the surface to generate granular crystals (microcrystals). For example, SiNx
A film, an Al film, various oxide films to which F is added, various oxide films to which nitrogen is added, a W (tungsten) film, or the like can be used. Further, if the type or composition of the gas 126 is changed and the heating conditions such as the temperature and the processing time are changed, a hydrogenated Si gas such as SiH ₄ , Si ₃ H ₈ or Ge can be obtained.
Various gases such as H ₄ and Ge ₂ H ₆ can also be applied.

Next, as shown in FIG. 3C, on a glass substrate 123 on which silicon microcrystals 127 are formed,
An amorphous silicon layer 128 having a thickness of 50 nm was formed by a plasma CVD method. Therefore, the silicon oxide film 1
A structure was obtained in which silicon microcrystals 127 were present at the interface between 24 and the amorphous silicon layer 128. Preferably, before the amorphous silicon layer 128 is formed, the silicon substrate 123 is made of 0.01% dilute H in order to remove an oxide film formed on the silicon microcrystal 127.
It is good to soak in F for about 1 second. Also, for example,
If plasma CVD can be performed using a device that can be transported in an atmosphere of nitrogen, argon, helium, hydrogen, or the like so as not to oxidize the surface of the silicon microcrystal 127, the glass substrate 123 needs to be immersed in dilute HF. However, even when the glass substrate 123 is exposed to the atmosphere, the oxide film formed on the silicon microcrystal 127 can be at most as long as the transfer of the glass substrate 123 is completed within several hours. Polycrystallization using the amorphous silicon layer 128 within several angstroms is not hindered.

Next, as shown in FIG. 3D, the amorphous silicon layer 128 formed on the silicon substrate 123 was melted by an ELA method to obtain a polycrystalline silicon layer composed of crystal grains 129. When polycrystals are formed by the ELA method, the irradiation energy density of a XeCl laser per unit area in the atmosphere is 340 mJ.
/ Cm ² , and the temperature of the glass substrate 123 at the time of irradiation was room temperature. As a result, the amorphous silicon layer 128 on the silicon oxide film 124 is melted and has a particle size of 0.1 μm.
A polycrystal composed of crystal grains 129 having a uniform degree was formed. In addition, even when the irradiation energy density per unit area of the XeCl laser was 330 mJ / cm ² , there was no change in the particle size distribution of the crystal grains constituting the polycrystal. Accordingly, since a process with a lower irradiation energy density is realized as compared with the conventional ELA method, the process margin in the ELA method using an excimer laser having a laser output fluctuation can be expanded, and the yield of polycrystalline silicon can be improved. Achieved. And FIG.
As shown in (a), the polycrystalline silicon was patterned to form an active layer 101 and an in-plane electrode 102 of the TFT.

Next, the gate insulating film is formed by an APCVD method, a PECVD method or an ECR-PECVD method.
and a metal film such as Mo, Al, Ta, W, Cu, an alloy thereof, or a doped silicon film having a thickness of 20 nm on the gate insulating film.
4 is formed so as to have a thickness of about 0 nm to 400 nm.
As shown in (b), the gate electrode lines 103 and the pixel electrodes 104 were patterned. Next, the gate electrode line 1
Using 03 as a mask, a region serving as a source / drain of the TFT and an impurity in the in-plane electrode 102, for example,
In the case of an n-ch TFT, about 1 × 10 ²² cm ⁻³ of phosphorus was introduced by ion implantation or ion doping. That is, impurities were implanted into the shaded regions shown in FIG. Next, a silicon oxide film, a silicon nitride film, or an interlayer insulating film having a structure in which these are laminated is formed by an APCVD method.
Impurities formed over the entire surface by ECVD or ECR-PECVD, etc., and activated previously were activated and reduced in resistance by excimer laser annealing or thermal annealing at about 450 ° C. to 550 ° C.

Next, as shown in FIG. 4C, contact holes 107, 108, 109 and 111 are opened, and Mo, Al, Ta, W, Cu and their alloys or doped silicon films are formed on the entire surface. Metal film of thickness 300
4 (d).
The signal line 105, the in-plane electrode line 106, and the electrode pattern 110 were formed by patterning as shown in FIG. Note that the thickness of the metal film is desirably thicker than the interlayer insulating film in view of coverage. As described above, the in-plane electrode line 106 and the in-plane electrode 102 are connected via the contact hole 107,
The pixel electrode 104 and the active layer 101 are in contact hole 1
The electrodes are electrically connected to each other through the electrode patterns 110 via 08 and 109. Also, the signal line 105 and the active layer 101
Are connected by a contact hole 111.
Next, a protective film was formed on the entire surface as necessary and patterned to form an array substrate, and a liquid crystal was filled between the array substrate and a counter substrate to obtain a liquid crystal display device.

FIGS. 5A to 5C show AA 'section, BB' section and CC 'section of the array substrate in the liquid crystal display device having the structure shown in FIG. Show. 1 and 2 have the same basic configuration. Although a protective film is not shown here, it is desirable to form the protective film as needed.
When the liquid crystal display device having the structure shown in FIGS. 1 and 2 was subjected to an alignment process to be modularized and a television screen was displayed using an interface substrate, the characteristics of each pixel were made uniform. A good moving image could be displayed at a voltage of ± 6 V, and high-quality display with no display unevenness was achieved over a long period of time.

In the present embodiment, the active element is a coplanar TFT, but a semiconductor element such as a TFT can be modified without departing from the gist of the present invention. In addition to being able to sufficiently cope with a fine pixel pitch, the area required for the drive circuit can be significantly reduced as compared with the area required for the external driver and its mounting part, and a narrow frame of the liquid crystal display device can be achieved. Since the liquid crystal display device has certain advantages, a peripheral drive circuit for controlling the liquid crystal display device can be built in the liquid crystal display device as shown in FIG. In FIG. 6, the liquid crystal display device has a P-channel TFT 120 having the above-mentioned polycrystal and an N-channel TF.
And a CMOS drive circuit 122 comprising T121.
As an example of the pixel, the pixel includes the pixel shown in FIG. 1 or FIG.

Next, another embodiment for forming a TFT active layer 101 and an in-plane electrode 102 in a liquid crystal display device having the structure shown in FIGS. 1 and 2 will be described. That is, after the silicon oxide film 124 was formed on the glass substrate 123 in advance, the prepared slit 130 was provided near the glass substrate 123, and then the amorphous silicon layer 125 was formed (FIG. 7A). Note that the gas 126 is supplied with directivity to the glass substrate 123.
The slit 130 was set at a distance of 1 mm from the substrate 123 because the slit 130 reached the glass substrate 123 from a direction substantially perpendicular to the substrate 123. Then, as described above, the glass substrate 1
By subjecting 23 to heat treatment, clustered silicon microcrystals 127 were formed at desired positions. Gas 1
Even when the supply of 26 was directly deposited at an arbitrary position on the glass substrate 123 by using a nozzle or the like, a clustered silicon microcrystal 127 could be formed at a desired position (FIG. 7B). . If patterning is performed in advance using slits having different openings, the arrangement of microcrystals can be arbitrarily controlled according to the pattern.

Next, the slit 130 used for forming the silicon microcrystal 127 on the glass substrate 123 was placed again at the above position, and the amorphous silicon layer 128 was formed through the slit 130 (FIG. 7C )). In addition,
7A, it is impossible to form the amorphous silicon layer 128 having directivity as shown in FIG. 7A. Therefore, as the distance between the slit 130 and the glass substrate 123 is reduced, only a desired position is formed. The amorphous silicon layer 128 can be formed first. And
The amorphous silicon layer 6 is formed into microcrystals 12 by the ELA method.
By performing polycrystallization with 7 as a nucleus, at a desired position,
A polycrystal composed of crystal grains 129 having a substantially uniform particle size could be formed. A liquid crystal display device having the polycrystal obtained in this manner and having the structure shown in FIGS. 1 and 2 was subjected to an alignment process to be modularized, and a television screen was displayed using an interface substrate. Were uniformized, a good moving image could be displayed at a driving voltage of ± 6 V, and high-quality display with no display unevenness was achieved for a long period of time. Note that, if the method of manufacturing a polycrystal shown in FIG. 7 is used, the grain size of a crystal grain is set only at an arbitrary position, for example, in a liquid crystal display device, at a position where a TFT of a pixel portion or a peripheral driver circuit is formed. And a polycrystal in which the form of each crystal grain is substantially uniform can be produced. On the other hand, for comparison, the conventional E
TFT having polysilicon polycrystallized by LA method
A liquid crystal display device similar to that of the above embodiment was obtained except that the device was mounted. That is, this is a liquid crystal display device equipped with a TFT provided with polysilicon which is formed by forming only amorphous silicon on a silicon oxide film and then heating and melting the amorphous silicon by an ELA method and recrystallizing the silicon.

Here, the polysilicon was manufactured as follows. First, a silicon oxide film 12 having a thickness of 100 nm is formed on a glass substrate 123 by plasma CVD.
After forming 4, an amorphous silicon layer 6 having a thickness of 50 nm was formed on the silicon oxide film 124, and polycrystal was manufactured by the ELA method. FIG. 8A shows a state immediately after laser irradiation in the ELA method. Immediately after solidification of the molten amorphous silicon layer 131 starts,
Non-uniform initial crystal nuclei 132 having a form such as a size are formed at random positions on the surface of the silicon oxide film 124. Since the crystal grains grow on the basis of the temperature gradient based on the initial crystal nuclei 132, the crystal grains are naturally 0.1 μm.
m, having a particle size of 0.2 μm or 0.1 μm or less,
Non-uniform crystal grains 133 having a shape such as a size were formed.

The liquid crystal display device thus obtained was subjected to an orientation treatment to make it a module, and a television screen was displayed using an interface substrate. Since the characteristics of each pixel were non-uniform, the driving voltage was ± 6 V. However, it was not possible to display a good moving image, display unevenness and the like were confirmed in the displayed image, and the durability was slightly inferior.

Further, as another embodiment of the present invention, as shown in FIG.
Array substrate 20 on which TFT 202 and the like connected to 1 are formed
3 and a counter substrate 205 on which a color filter and a black matrix are formed and a counter electrode 204 is formed on the surface.
Between the pixel electrode 201 and the counter electrode 204 to apply the electric field E1
The liquid crystal display device was of a type in which display was performed by orienting No. 06 and changing light transmittance. Note that the TFT 20
9B is shown in detail in FIG.
For the channel region 207, source region 208, and drain region 209, polycrystalline silicon manufactured in the same manner as in the above embodiment is used.

Comprising the polycrystalline silicon thus obtained,
When a liquid crystal display device having the structure shown in FIG. 9 was subjected to an alignment process to be modularized and a television screen was displayed using an interface substrate, the characteristics of each pixel were uniformized. Thus, a high-quality image can be displayed over a long period of time by eliminating a display unevenness and the like.

Here, in order to confirm the factors that brought about excellent display characteristics with respect to the liquid crystal display device according to the present embodiment, the polycrystalline silicon layer according to the present invention formed using the above-described manufacturing process and the above-described polycrystalline silicon layer according to the present invention are described. An n-ch TFT was formed on a polycrystalline silicon layer formed using a conventional polycrystalline growth method, and the electron mobility was measured. Here, the grain size of both polycrystals is about 0.2 μm.

As a result of the measurement of the electron mobility, as shown in FIG. 10, when the Vds was about 0.1 V, the electron mobility was about 50 cm ² / V · s. In the case where an n-ch TFT is formed in the polycrystalline silicon layer according to the above, the variation in the electron mobility is within a range of about 35 cm ² / V · s, whereas the polycrystalline layer formed using the polycrystalline growth method is used. When an n-ch TFT is formed in a silicon layer, the variation in electron mobility is 40 cm ² / V ·
s range. Therefore, when the n-ch TFT is formed on the polycrystalline silicon layer according to the present invention, the electron transfer is smaller than when the n-ch TFT is formed on the polycrystalline silicon layer formed by using the polycrystalline growth method. The degree variation was reduced by about 10%. XeCl gas laser was used to form the polycrystal, but the output (fluence) of the laser required for polycrystal generation was 325 mJ / cm when an n-ch TFT was formed in the polycrystalline silicon layer according to the present invention. cm ² , the polycrystalline silicon layer formed using the polycrystalline growth method has an n-ch TFT
Was 335 mJ / cm ² . Therefore, the n-chT
When the FT was formed, the fluence of 10 mJ / cm ² could be reduced as compared with the case where the n-ch TFT was formed on the polycrystalline silicon layer formed by using the polycrystalline growth method.

[0038]

As described above, according to the polycrystal of the present invention, a plurality of crystals are generated from the first substance laminated on the substrate by heating, and the generated plurality of crystals are used as nuclei. By growing the crystal grains including the second substance, the form such as the size of the crystal grains is controlled, so that a polycrystal composed of substantially uniform crystal grains can be provided. Therefore, when the polycrystal according to the present invention is applied to a semiconductor device such as a TFT, the electrical characteristics of the semiconductor device can be improved, and the production yield of the semiconductor device can be improved. Can be provided. In addition, a reduction in the heat treatment temperature required for forming polycrystalline silicon can be achieved, and a process margin resulting from variations in heat treatment conditions can be increased.

Further, according to the liquid crystal display device of the present invention, a plurality of crystals are generated from the first substance laminated on the base material by heating, and the second crystals are formed by using the generated crystals as nuclei.
By growing a crystal grain with a material of the type described above and providing a channel region made of polycrystal composed of substantially uniform crystal grains, carriers such as electrons can be transported at high speed between the source region and the drain region through the channel region. In addition, since the liquid crystal display device can be moved uniformly, a change in luminance of a display screen is suppressed, a high-quality image can be displayed, and a liquid crystal display device with excellent durability can be provided. That is, since the brightness of each pixel is uniform and a display in which color unevenness is suppressed is enabled, the visibility of the screen is excellent, so that eyestrain and the like can be reduced. In addition, the above-mentioned polycrystal is, in addition to pixels,
Since the liquid crystal display device can be mounted on a peripheral driving circuit, a liquid crystal display device that can respond at higher speed can be provided.

[Brief description of the drawings]

FIG. 1 illustrates a liquid crystal display device according to an embodiment of the present invention.
FIG.

FIG. 2 illustrates a liquid crystal display device according to an embodiment of the present invention.
FIG.

FIG. 3 is a diagram illustrating a manufacturing process of the liquid crystal display device shown in FIGS. 1 and 2.

FIG. 4 is a diagram illustrating a manufacturing process of the liquid crystal display device shown in FIG.

FIG. 5 is a diagram showing a cross section of an array substrate in a liquid crystal display device having the structure shown in FIG. 2;

FIG. 6 is a diagram showing a cross section of a liquid crystal display device including a driving circuit portion.

FIG. 7 is a diagram showing another embodiment in forming a TFT active layer 101 and an in-plane electrode 102 in the liquid crystal display device having the configuration shown in FIGS. 1 and 2.

FIG. 8 is a view for explaining another manufacturing process of the liquid crystal display device shown in FIGS. 1 and 2.

FIG. 9 is a diagram showing a liquid crystal display device according to another embodiment of the present invention.

FIG. 10 is a view showing the results of measurement of electron mobility.

[Explanation of symbols]

101, 118, 119 ... Active layer 102 ... In-plane electrode 103 ... Gate electrode line 104 ... Pixel electrode 1
05 ... signal line 106 ... in-plane electrode line 107, 108, 109, 111 ... contact hole 110 ... electrode pattern 113 ... gate insulating film 114 ... interlayer insulating film 116a to 116c ... metal wiring 117a, 117
b: Gate electrode line 120: P-channel TFT 121: N-channel TFT 122: CMOS drive circuit 123: Glass substrate 124: Silicon oxide film 125: Amorphous silicon layer 126: Gas 127 Silicon microcrystals 128 Amorphous silicon layer 129 Crystal grains 130 Slit 131 Amorphous silicon layer 132 Initial crystal nucleus 201 Pixel electrode 202 TFT 203
… Array substrate 204… counter electrode 205… counter substrate 206
...... Liquid crystal molecules 207 Channel region 208 Source region 209 Drain region 210 Source electrode 211 Interlayer insulating film 212 Gate electrode 213 Gate insulating film 214 Drain electrode

Claims (2)

[Claims] 1. a step of laminating a first substance on a substrate, a step of generating a plurality of crystals from the first substance by heating, and a step of: A polycrystal manufactured by laminating a second substance in a crystalline state, and growing a crystal grain including the second substance by using the plurality of crystals as nuclei. 2. A polycrystalline channel region provided on a base material, a source region and a drain region continuous from the channel region, and movement of carriers between the drain region and the source region through the channel region. A gate electrode to be controlled, a source electrode connected to the source region, and a drain electrode connected to the drain region, wherein the polycrystal has a first material laminated on the base material; Generating a plurality of crystals from the first substance by heating, laminating a second substance in an amorphous state on a substrate on which the plurality of crystals have been generated, Growing a crystal grain comprising a substance with the plurality of crystals as nuclei.