JP2001188257A - Electrooptical device, television and wall-hung television - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrooptical device having a novel constitution, television(TV) and a wall-hung TV. SOLUTION: The display performance of the electrooptical device, the TV and the wall-hung TV can be enhanced since a fixed electric field can be applied to a liquid crystal by providing a flattened film covering a transistor and consisting of organic resin or a flattened film covering a color filter or a black strip and by fixing the distance between substrates interposing the liquid crystal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active display device, and more particularly, to an active electro-optical device, a television, and a wall-mounted television, in which a clear gradation level can be set.

[0002]

2. Description of the Related Art Liquid crystal compositions have different dielectric constants in the horizontal and vertical directions with respect to the molecular axis due to their material properties.
It can be easily arranged horizontally or vertically with respect to an external electric field. The liquid crystal electro-optical device displays ON / OFF by controlling the amount of transmitted light or the amount of dispersion by utilizing the anisotropy of the dielectric constant.

FIG. 2 shows the electro-optical characteristics of a nematic liquid crystal. When the applied voltage is small Va (point A 101),
When the transmitted light amount is almost 0% and Vb (point B 102), 3
About 0%, about 80% in the case of Vc (C point 103),
In the case of Vd (D point 104), it is about 100%. In other words, if only the points A and D are used, black and white two-gradation display is possible, and if the rising portion of the electro-optical characteristic is used like points B and C, intermediate gradation display is possible. As specific voltages confirmed by the present inventors, Va = 2.0 V, Vb =
2.18 V, Vc = 2.3 V, and Vd = 2.5 V.

Conventionally, in the case of a gray scale display of a liquid crystal electro-optical device using a TFT, a gray scale display is performed by changing a gate applied voltage of the TFT or a voltage applied between a source and a drain to adjust the voltage in an analog manner. I was

[0005]

A more detailed description will be given of a gradation display method of a liquid crystal electro-optical device using a TFT. Conventionally, an n-channel thin film transistor used for a liquid crystal electro-optical device has a voltage-current characteristic as shown in FIG. The voltage-current characteristics shown in FIG. 3 are a characteristic 201 of an n-channel thin film transistor using amorphous silicon and a characteristic 202 of an n-channel thin film transistor using polysilicon.

By controlling the voltage applied to the gate electrode in an analog manner, the drain current can be controlled, and the resistance between the source and drain can be changed. As a result, the magnitude of the electric field applied to the liquid crystals connected in series can be arbitrarily changed by the resistance division. Thereby, gradation display is possible.
Conversely, the gate electrode is connected to the scanning signal line,
There is also a method of arbitrarily controlling the electric field value itself applied to the liquid crystal by changing the source-drain voltage.

In either case, there is no difference that the analog gray scale display system largely depends on the characteristics of the TFT. However, it is difficult to make a large number of TFT elements in a matrix configuration so as to have uniform characteristics. In particular, fine adjustment of an intermediate voltage required for gradation display is very difficult with the current technology. What is needed is the current situation. As can be seen from the electro-optical characteristics of the nematic liquid crystal shown in FIG. 2, 0.3 from the vicinity of the boundary value in the dark state of about 2.08 V to the vicinity of the boundary value in the light state of about 2.40 V.
All gradation display must be performed between 2V. Assuming 16 gradations, control at an average 0.02 V interval is required.

If the points A 101 and D 104 shown in FIG.
When the voltage is controlled in a portion where the liquid crystal is completely turned on / off as described in (1), the voltage difference can be set to 0.5 V or more, which is enough to sufficiently reduce the in-plane characteristic variation of the TFT. By using a plurality of writing frames, for example, by turning on (2.5 V) 6 frames out of 10 frames and turning off (2.0 V) the remaining 4 frames, the writing average voltage becomes 2.3 V. , Half-tone display is possible.

However, in this case, since a plurality of frames are used, it can be confirmed by human eyes.
There is a danger that the display will be displayed at a frequency of less than or equal to Hz, and depending on the conditions, this may cause display defects such as flicker. As a method for preventing this, increasing the driving frequency has been proposed.
There was a limit of about 0 MHz, and it was difficult.

[0010]

Therefore, the present invention proposes a means for supplying a clear gradation display level to the liquid crystal by performing digital gradation display instead of the conventional analog gradation display. In that case, the frame frequency is not changed by simply increasing the driving frequency and performing the gradation display as conventionally proposed, but by making the data transfer frequency and the gradation display frequency independent. It is characterized in that digital gradation display is performed in a state where no change is made.

According to the present invention, in an active matrix type liquid crystal display device, unit times t and 1 to be written to an arbitrary pixel are set.
A gray scale display of a display device using a display drive method having a display timing related to a screen writing time F, a signal during the writing time of the time t is changed to time division without changing the time F, This is characterized in that the average value of the electric field applied to the liquid crystal of the pixel at time t is changed according to the division ratio, and the gray scale can be displayed.

In the case of the conventional display device, the electric field applied to the pixel electrode is determined by the strength of the electric field of the signal line in the data direction, and thereby the transmittance of the liquid crystal is determined.

According to the present invention, instead of performing such analog gradation control, a signal during a writing time of a unit time t to be written to an arbitrary pixel is time-division-divided, and gradations corresponding to the number of divisions can be displayed. I have to. At this time, the electric field change during the writing time becomes the average value during the non-writing time, and a clear gradation display is possible.

As for the data transfer speed on the information signal side, for example, in the case of a 1920 × 400 dot liquid crystal electro-optical device, a clock frequency of 5.76 MHz is required for 8-bit parallel transfer. On the other hand, when the conventional multiple frame method is used, if 10 frames are used, a clock frequency of 57.6 MHz is simply required. However, in the case of the present invention, since the clock frequency for gray scale display is independently set, it is possible to display up to about 166 gray scales when using an IC having a drive capability of a maximum of 8 MHz. If a 12.3 MHz drive IC is adopted, the value becomes sufficiently possible up to 256 gray scale display required for visual use, and is significantly superior to the conventional analog gray scale and multi-frame digital gray scale display. Nature occurs. A more detailed description will be given below with reference to examples.

[0015]

【Example】

Embodiment 1 (Image Display Apparatus / TV) In this embodiment, a wall-mounted television is manufactured using a liquid crystal display apparatus having a circuit configuration as shown in FIG. The TFT at that time was a staggered type made of polycrystalline silicon using laser annealing.

FIG. 5 shows an actual arrangement of electrodes and the like corresponding to this circuit configuration. For simplicity, only portions corresponding to 2 × 2 (or less) are described. FIG. 1 shows an actual drive signal waveform. For the sake of simplicity, the description will be made using signal waveforms in the case of a 2 × 2 matrix configuration.

First, a method for manufacturing a liquid crystal panel used in this embodiment will be described with reference to FIG. In FIG. 6A, a blocking layer 5 is formed on a glass 50 such as quartz glass which can withstand a heat treatment at an inexpensive temperature of 700 ° C. or less, for example, about 600 ° C. by using a magnetron RF (high frequency) sputtering method.
A silicon oxide film as No. 1 is formed to a thickness of 1000 to 3000 °. The process conditions were a 100% oxygen atmosphere, a film formation temperature of 15 ° C., an output of 400 to 800 W, and a pressure of 0.5 Pa. The film formation rate using quartz or single crystal silicon as a target was 30 to 100 ° / min.

A silicon film was formed thereon by a plasma CVD method. The film formation temperature is from 250 ° C. to 350 ° C.
C., and in this example, the temperature was set to 320 ° C., and monosilane (SiH
₄ ) was used. Not only monosilane (SiH ₄ ) but also disilane (Si ₂
H ₆ ) or trisilane (Si ₃ H ₈ ) may be used. These were introduced at a pressure of 3 Pa in the PCVD apparatus, and 13.56 M
The film was formed by applying a high frequency power of Hz. At this time, an appropriate high frequency power is 0.02 to 0.10 W / cm ² , and in this embodiment, 0.055 W / cm ² is used. The flow rate of monosilane (SiH ₄ ) was set to 20 SCCM, and the deposition rate at that time was about 120 ° / min. In order to control the threshold voltage (Vth) of the NTFT, boron may be added at a concentration of 1 × 10 ¹⁵ to 1 × 10 ¹⁸ cm ⁻³ during the film formation using diborane. In addition, the silicon layer serving as the channel region of the TFT may be formed not only by the plasma CVD method but also by a sputtering method or a low pressure CVD method. The method will be briefly described below.

When the sputtering method is used, the back pressure before the sputtering is set to 1 × 10 ⁻⁵ Pa or less, and single crystal silicon is used as a target in an atmosphere in which hydrogen is mixed with 20 to 80% of argon. For example, argon was 20% and hydrogen was 80%. The film forming temperature is 150 ° C. and the frequency is 13.56 MH.
z, the sputter output is 400-800 W, and the pressure is 0.
It was 5 Pa.

When formed by the reduced pressure gas phase method, 450 to 550 ° C., which is 100 to 200 ° C. lower than the crystallization temperature, for example,
At 530 ° C., disilane (Si ₂ H ₆ ) or trisilane (Si
₃ H ₈ ) was supplied to a CVD apparatus to form a film. The pressure in the reactor was 30 to 300 Pa. The deposition rate is 50-25
It was 0Å / min.

The coatings formed by these methods are:
It is preferable that oxygen is 5 × 10 ²¹ cm ⁻³ or less. In order to promote crystallization, the oxygen concentration should be 7 × 10 ¹⁹ cm ⁻³ or less,
Preferably, it is desirable to be 1 × 10 ¹⁹ cm ⁻³ or less,
If the amount is too small, the leakage current in the off state increases due to the backlight, so this concentration was selected. If the oxygen concentration is high, crystallization is difficult, and the laser annealing temperature must be increased or the laser annealing time must be increased. Hydrogen is 4 × 10 ²⁰ cm ⁻³ and silicon 4 ×
It was 1 atomic% when compared with 10 ²² cm ^-3 .

In order to further promote crystallization of the source and the drain, the oxygen concentration is set to 7 × 10 ¹⁹ cm ⁻³ or less, preferably 1 × 10 ¹⁹ cm ⁻³ or less,
Oxygen may be added only to the T channel formation region by ion implantation so as to have a concentration of 5 × 10 ^{20 to} 5 × 10 ²¹ cm ⁻³ .

According to the above-described method, the amorphous silicon film 52 is formed at a temperature of 500 to 5000.degree.
The film was formed to a thickness of 0 °.

After that, as shown in FIG. 6B, a pattern was formed by opening only the source / drain regions of the photoresist 53 by using the mask P1. A silicon film to be an n-type active layer was formed thereon by a plasma CVD method. The film is formed at a temperature of 250 ° C. to 350 ° C. In this embodiment, the temperature is set to 320 ° C., and monosilane (SiH ₄ ) and monosilane-based phosphine (PH ₃ ) having a concentration of 3% are used. 12. These are introduced into the PCVD apparatus at a pressure of 5 Pa;
A film was formed by applying a high frequency power of 56 MHz. At this time, high frequency power, 0.05~0.20W / cm ² are suitable, in the present embodiment, a 0.120W / cm ^2. The specific conductivity of the n-type silicon layer completed by this method was about 2 × 10 ⁻¹ [Ωcm ⁻¹ ]. The film thickness is 5
0 °.

On the other hand, as shown in FIG. 6 (C), a pattern was formed by opening only the source / drain regions of the photoresist 54 using the mask P2. A silicon film to be a p-type active layer was formed thereon by a plasma CVD method. The film is formed at a temperature of 250 ° C. to 350 ° C. In this embodiment, the temperature is set to 320 ° C., and monosilane (SiH ₄ ) and monosilane-based diborane (B ₂ H ₆ ) having a concentration of 2% are used. These were introduced at a pressure of 4 Pa in the PCVD apparatus, and 13.56
The film was formed by applying a high frequency power of MHz. At this time, the high frequency power is suitably 0.05 to 0.20 W / cm ² ,
In this embodiment, 0.080 W / cm ² is used. The specific conductivity of the p-type silicon layer produced by this method is
It was about 1 × 10 ⁻¹ [Ωcm ⁻¹ ]. The film thickness was 50 °.

After that, using the lift-off method,
Drain regions 55 and 56 and 57 and 58 were formed.
Thereafter, an N-channel thin film transistor island region 63 and a P-channel thin film transistor island region 64 were formed using the mask P62. (FIG. 6
(D))

Thereafter, the source, drain, and channel regions were laser-annealed using a XeCl excimer laser, and at the same time, the active layer was laser-doped. At this time, the laser energy has a threshold energy of 130 mJ / cm ² , and the melting of the entire film thickness requires 22 mJ / cm ^2.
0 mJ / cm ² is required. However, from the beginning 220
When energy of mJ / cm ² or more is irradiated, hydrogen contained in the film is rapidly released, so that the film is destroyed. For this purpose, it is necessary to first displace hydrogen with low energy and then melt it. In this embodiment, the first 15
After purging hydrogen at 0 mJ / cm ² , 230
Crystallization was performed at mJ / cm ² .

By the annealing, the silicon film shifts from an amorphous structure to a highly ordered state, and a part of the silicon film exhibits a crystalline state. In particular, a region having a relatively high order in a state after the formation of silicon is particularly likely to be crystallized into a crystalline state. However, since the silicon existing between these regions is bonded to each other, the silicon mutually pulls each other. When measured by laser Raman spectroscopy, a peak shifted from the single crystal silicon peak 522 cm ^-1 to a lower frequency side is observed. The apparent grain size is 50 to 500 ° when calculated from the half-value width. However, in practice, there are many such high crystallinity regions having a cluster structure. A coating having a bonded (anchored) structure could be formed.

As a result, the coating exhibits a state substantially free of grain boundaries (hereinafter referred to as GB). Carriers can easily move from one cluster to another through anchored locations, resulting in a higher carrier mobility than so-called polycrystalline silicon having a distinct GB. That is, electron mobility (μe) = 15 to 300
cm ² / VSec and Hall mobility (μe) = 5-10
0 cm ² / VSec was obtained.

On this, a silicon oxide film was formed as a gate insulating film to a thickness of 500 to 2000 Å, for example, 1000 Å. This was made under the same conditions as those for forming the silicon oxide film as the blocking layer. During the film formation, a small amount of fluorine may be added to fix the sodium ions.

After this, 1-5 × 10 ²¹ cm of phosphorus is placed on the upper side.
^-3 silicon film or molybdenum (Mo), tungsten (W), MoSi ₂ or
A multilayer film with WSi ₂ was formed. This was patterned using a fourth photomask 69 to obtain FIG. 6 (E). Gate electrodes 66 and 67 were formed, for example, a channel length of 7 .mu.m, a gate electrode of 0.2 .mu.m of phosphorus silicon and a thickness of 0.3 .mu.m of molybdenum thereon.

When aluminum (Al) is used as a gate electrode material, the surface is anodically oxidized after patterning with a fourth photomask 69, so that the self-alignment method can be applied. In addition, since the source / drain contact holes can be formed at positions closer to the gate, the characteristics of the TFT can be further improved by reducing the mobility and the threshold voltage.

Thus, a C / TFT can be manufactured without applying a temperature to 400 ° C. or more in all steps. Therefore, it is not necessary to use an expensive substrate such as quartz as a substrate material, and it can be said that the process is very suitable for the large-screen liquid crystal display device of the present invention.

In FIG. 6F, a silicon oxide film was formed on the interlayer insulator 68 by the above-described sputtering method. This silicon oxide film is formed by LPCVD, optical CVD
Or a normal pressure CVD method. For example, 0.2-
A thickness of 0.6 μm was formed, and then a window 79 for an electrode was formed using a fifth photomask 70. Thereafter, further, aluminum is formed on the whole by sputtering to a thickness of 0.3 μm, and a lead 74 and a contact 73 are formed using a sixth photomask 76. The silicon oxide film was formed by the sputtering method described above. This silicon oxide film is formed by L
A PCVD method, a photo CVD method, or a normal pressure CVD method may be used. After that, patterning was performed using the seventh photomask 81. Thereafter, aluminum is further formed on the entire surface to a thickness of 0.3 μm by a sputtering method.
A lead 83 and a contact 84 were formed using the photomask 82 of FIG. (FIG. 6 (G))

An organic resin 85 for flattening, for example, a translucent polyimide resin was applied to the surface, and a hole was formed again with a ninth photomask 86. Further, ITO (indium oxide / tin) was formed on the entire surface by sputtering to a thickness of 0.1 μm, and a pixel electrode 88 was formed using a tenth photomask 87. This ITO is at room temperature
Films were formed at 150 ° C. and achieved with oxygen at 200-400 ° C. or annealing in air. (FIG. 6 (H))

The electrical characteristics of the obtained TFT, NT,
FT mobility is 80 (cm ² / Vs), Vth is 5.0 (V),
The mobility of PTFT is 30 (cm ² / Vs) and Vth is 5.5
(V). One substrate for a liquid crystal electro-optical device manufactured according to such a method was obtained.

FIG. 7 shows a method for manufacturing the other substrate. A polyimide resin in which a black pigment was mixed with polyimide was formed on a glass substrate 900 to a thickness of 1 μm by a spin coating method, and a black stripe 901 was formed using the first photomask 11. Thereafter, a polyimide resin mixed with a red pigment was formed into a film having a thickness of 1 μm by spin coating, and a red filter 902 was manufactured using the second photomask 12. Similarly, a green filter 903 was manufactured using the third photomask 13 and a blue filter 904 was manufactured using the fourth photomask 14. During the production, each filter was fired at 350 ° C. in nitrogen for 60 minutes. After that, the leveling layer 905 was formed using a transparent polyimide, also by using the spin coating method.

Thereafter, ITO (indium tin oxide) was formed on the entire surface by sputtering to a thickness of 0.1 μm, and a common electrode 906 was formed using the fifth photomask 15. This ITO is formed at room temperature to 150 ° C.
Fulfilled by oxygen at 00-300 ° C. or in air, a second substrate was obtained.

A polyimide precursor was printed on the substrate by using an offset method, and baked at 350 ° C. for 1 hour in a non-oxidizing atmosphere such as nitrogen. Thereafter, a known rubbing method was used to modify the surface of the polyimide, and at least initially, a means for aligning liquid crystal molecules in a certain direction was provided.

Thereafter, the nematic liquid crystal composition was sandwiched between the first substrate and the second substrate, and the periphery was fixed with an epoxy adhesive. A drive IC having a TAB shape and a PCB having a common signal and potential wiring were connected to leads on the substrate, and a polarizing plate was attached on the outside to obtain a transmissive liquid crystal electro-optical device.

FIG. 8 is a schematic structural view of the electro-optical device according to the present embodiment. The liquid crystal panel 1000 obtained in the above process
Was installed in combination with a rear lighting device 1001 in which three cold cathode tubes were arranged. Thereafter, a tuner 1002 for receiving television waves was connected to complete the electro-optical device. Compared to a conventional CRT-type electro-optical device, the device has a planar shape, so that it can be installed on a wall or the like.

Next, the peripheral circuit of the liquid crystal electro-optical device for completing the present invention will be described with reference to FIG. The configuration is such that a drive circuit 352 is connected to the information signal side wirings 350 and 351 connected to the matrix circuit of the liquid crystal electro-optical device. The drive circuit 352 has two parts when divided by a drive frequency system. One is a data latch circuit system 353 similar to the conventional driving method, which is a basic clock φH355 for sequentially transferring data 356.
The main configuration is 1-bit to 12-bit parallel processing. The other is a component according to the present invention, in which a clock CLK35 corresponding to a division ratio necessary for gradation display is used.
7, a magnitude comparator circuit 358, and a panel driving buffer 360. The counter 359 generates a pulse corresponding to the gradation display data sent from the data latch circuit system 353.

The features of the present invention are exactly these parts. By using two driving frequencies, the number of frames for screen rewriting can be changed without changing the number of frames.
This is to enable clear digital gradation display. It is possible to avoid the occurrence of flicker and the like due to the decrease in the number of frames.

FIGS. 10 and 11 show operation waveforms of the C / TFT according to this embodiment. FIG. 10 is an oscilloscope photograph showing the input signal waveform to the C / TFT and the output signal waveform from the C / TFT. From FIG. 10 (A) to FIG.
Drive frequency of input signal is 5KHz, 50KH to (B)
z, 500 KHz, and 1 MHz are shown. As is clear from FIG.
Even at 1 MHz, the output signal waveform did not so much, and a sufficiently practical output signal could be obtained. Therefore, the number of gray scales can be calculated by dividing the driving frequency by the duty number and the number of frames. In this case, 1 MHz is divided by 400 and 60.
The number of gradation display of 2 is obtained, and it is possible to display up to 42 gradations.

When analog gradation display is performed, TF
The 16-gradation display was the limit due to the T characteristic variation. However, when performing digital gradation display according to the present invention, since it is hard to be affected by variation in the characteristics of the TFT elements, it is possible to display up to 42 gradations.
It is a variety of 4,088 colors, and a subtle color display can be realized.

Embodiment 2 (View Finder) In this embodiment, a view finder for a video camera using a liquid crystal electro-optical device having a diagonal of 1 inch was manufactured.
Since the present invention has been implemented, an explanation will be added.

In this embodiment, the number of pixels is 387 × 128, and the first substrate is provided by using the same process as in the first embodiment. Further, a color filter and a transparent conductive film ITO were formed to a thickness of 1000 ° on the insulating substrate by using the same method as in “Example 1” to obtain a second substrate.

A polyimide precursor was printed on the substrate by an offset method, and baked at 350 ° C. for 1 hour in a non-oxidizing atmosphere, for example, nitrogen. Thereafter, the surface of the polyimide was modified using a known rubbing method, and at least initially, means for aligning the liquid crystal molecules in a certain direction was provided to obtain first and second substrates.

Thereafter, the nematic liquid crystal composition was sandwiched between the first substrate and the second substrate, and the periphery was fixed with an epoxy adhesive. Since the pitch of the leads on the substrate was as fine as 46 μm, they were connected using the COG method. In this embodiment, a method of connecting gold bumps provided on an IC chip with an epoxy silver palladium resin and filling and fixing the IC chip and the substrate with an epoxy modified acrylic resin for the purpose of fixing and sealing is used. Using. Thereafter, a polarizing plate was attached on the outside to obtain a transmission type liquid crystal display device.

The TFT according to this embodiment has a channel length of 5
Because of μm, the driving frequency could be increased to about 2 MHz. Therefore, it is possible to display 260 gradations obtained by dividing 2 MHz by 128 and 60, that is, up to approximately 256 gradation display. For example, 49,152 of 384 × 128 dots
When a normal analog gradation display is performed on a liquid crystal electro-optical device in which a set of TFTs is formed into a 50 mm square (36 sheets from a 300 mm square substrate), an amorphous T
Since FT characteristic variation is about ± 10%, 16
The gradation display was the limit. However, when the digital gradation display according to the present invention is performed, it is hard to be affected by the variation in the characteristics of the TFT elements, so that it is possible to display 256 gradations or more, and the color display has a variety of 16,777,216 colors. The display of subtle colors has been realized.

[Embodiment 3] (Projection-type image display device) In this embodiment, a projection-type image display device as shown in FIG.

In this embodiment, three liquid crystal electro-optical devices 1
The projection unit for the projection type image display device is assembled by using 300. Each one is 640x48
It has a configuration of 0 dots and 307,2 in 4 inch diagonal.
00 pixels were produced. The size per pixel is 127 μm
Corners.

As a configuration of the projection type image display device, the liquid crystal electro-optical device 1300 is divided and installed for the three primary colors of light, red, green and blue, and a red filter 1301, a green filter 1302, and a blue filter 1 are provided.
303, a reflector 1304, a 150W metal halide light source 1307, and a focusing optical system 1308.

The substrate of the liquid crystal electro-optical device used in the electro-optical device of this embodiment was a substrate having a C / TFT configuration matrix circuit. High mobility TFT by low temperature process
Were formed to form a projection-type liquid crystal electro-optical device. A method for manufacturing a liquid crystal display device used in this embodiment is described with reference to FIGS. In FIG. 13A, a silicon oxide film as a blocking layer 602 is formed on a non-expensive glass 601 such as quartz glass which can withstand a heat treatment at 700 ° C. or less, for example, about 600 ° C. by using a magnetron RF (high frequency) sputtering method. 1000-3000
Make it to the thickness of Å. The process conditions were a 100% oxygen atmosphere, a film formation temperature of 15 ° C., an output of 400 to 800 W, and a pressure of 0.5 Pa. The film formation rate using quartz or single crystal silicon as a target was 30 to 100 ° / min.

A silicon film was formed thereon by LPCVD (low pressure gas phase), sputtering or plasma CVD. When formed by the reduced pressure gas phase method, the temperature is 1
450-550 ° C lower by 00-200 ° C, for example 530 ° C
With disilane (Si ₂ H ₆ ) or trisilane (Si ₃ H ₈ )
The film was supplied to the D apparatus to form a film. The pressure inside the reactor is 30 ~ 3
00 Pa. The deposition rate was 50-250 ° / min. In order to control the threshold voltage (Vth) of the PTFT and NTFT substantially the same, boron may be added during the film formation at a concentration of 1 × 10 ¹⁵ to 1 × 10 ¹⁸ cm ⁻³ using diborane. .

In the case of performing the sputtering method, the back pressure before the sputtering was set to 1 × 10 ⁻⁵ Pa or less, and single crystal silicon was used as a target in an atmosphere in which 20 to 80% of hydrogen was mixed with argon. For example, argon was 20% and hydrogen was 80%. The film forming temperature is 150 ° C. and the frequency is 13.56 MH.
z, the sputter output is 400-800 W, and the pressure is 0.
It was 5 Pa.

When a silicon film is formed by the plasma CVD method, the temperature is set to, for example, 300 ° C., and monosilane (SiH ₄ ) is used.
Alternatively, disilane (Si ₂ H ₆ ) was used. These were introduced into a PCVD apparatus, and a high-frequency power of 13.56 MHz was applied to form a film.

The coatings formed by these methods are:
It is preferable that oxygen is 5 × 10 ²¹ cm ⁻³ or less. If the oxygen concentration is high, it is difficult to crystallize, and the thermal annealing temperature must be increased, or the thermal annealing time must be increased.
If the amount is too small, the leakage current in the off state increases due to the backlight. Therefore, 4 × 10 ¹⁹ to 4 ×
The range was 10 ²¹ cm ^-3 . Hydrogen is 4 × 10 ²⁰ cm ⁻³ ,
When compared with silicon 4 × 10 ²² cm ⁻³ , it was 1 atomic%.

After forming an amorphous silicon film to a thickness of 500 to 5000 °, for example, 1500 ° by the above-mentioned method, heat treatment is performed at a temperature of 450 to 700 ° C. for 12 to 70 hours in a non-oxide atmosphere at a medium temperature. For example, it was kept at a temperature of 600 ° C. in a hydrogen atmosphere. Since a silicon oxide film having an amorphous structure is formed on the surface of the substrate under the silicon film, no specific nucleus is present in this heat treatment, and the whole is annealed uniformly. That is, at the time of film formation, it has an amorphous structure, and hydrogen is simply mixed.

By the annealing, the silicon film shifts from an amorphous structure to a highly ordered state, and a part of the silicon film exhibits a crystalline state. In particular, a region having a relatively high order in a state after the silicon film is formed tends to be crystallized to be in a crystalline state. However, since the silicon existing between these regions is bonded to each other, the silicon mutually pulls each other. When measured by laser Raman spectroscopy, a peak shifted from the single crystal silicon peak 522 cm ^-1 to a lower frequency side is observed. Its apparent particle size is calculated from the half width,
Although it is like a microcrystal having a size of 50 to 500 °, there are actually a large number of regions having high crystallinity and a cluster structure, and a semi-amorphous structure in which each cluster is bonded to each other by silicon (anchoring). The coating 603 of the structure was able to be formed.

As a result, the coating exhibits a state substantially free of grain boundaries (hereinafter referred to as GB). Carriers can easily move from each other through the anchored portions between the clusters, so that the carrier mobility is higher than that of polycrystalline silicon in which GB is clearly present. That is, the hole mobility (μh) = 10
200 cm ² / VSec, electron mobility (μe) = 15-3
00 cm ² / VSec is obtained.

On the other hand, when the film is polycrystallized by high-temperature annealing at 900 to 1200 ° C. instead of annealing at the medium temperature as described above, segregation of impurities in the film occurs due to solid phase growth from nuclei. , GB contain many impurities such as oxygen, carbon, and nitrogen, and have high mobility in the crystal. However, a barrier is formed in the GB and the movement of carriers there is hindered. As a result, a mobility of 10 cm ² / Vsec or more cannot be easily obtained. That is, in the present embodiment, a silicon semiconductor having a semi-amorphous or semi-crystalline structure is used for such a reason.

On this, a silicon oxide film 604 was formed as a gate insulating film to a thickness of 500 to 2000 Å, for example, 1000 Å. This was made under the same conditions as those for forming the silicon oxide film as the blocking layer. During the film formation, a small amount of fluorine may be added to fix the sodium ions.

Thereafter, 1-5 × 10 ²¹ cm of phosphorus is placed on the upper side.
^-3 silicon film or molybdenum (Mo), tungsten (W), MoSi ₂ or
A multilayer film 605 with WSi ₂ was formed. This was patterned using a first photomask to obtain FIG. 13 (B). In this embodiment, the channel length is 10 μm, and molybdenum is formed as a gate electrode to a thickness of 0.3 μm. At this time, the metal of the gate electrode was over-etched 600 by about 3 μm. Thereafter, a positive photoresist 607 was applied to the entire substrate.

The resist 608 can be obtained by performing exposure and development from the back surface of the substrate using a photomask. Thereafter, an n-layer was deposited by a sputtering method. After that, by lifting off the resist 608, FIG. 13D is obtained.

Similarly, after a positive photoresist 610 is applied to the entire substrate, the resist 610 is exposed and developed from the back surface of the substrate using a photomask.
Can be obtained. Thereafter, a p-layer was deposited by a sputtering method. After that, the resist 610 is lifted off to obtain FIG.

Next, annealing was performed again at 600 ° C. for 10 to 50 hours. Impurities of the sources 612 and 614 and the drains 613 and 615 were activated to produce N ⁺ or P ⁺ . Channel formation regions 618 and 619 are formed below the gate electrodes 616 and 617 as semi-amorphous semiconductors.

In this way, a C / TFT can be manufactured without applying a temperature to 700 ° C. or more in all steps, even though it is a self-aligned system. for that reason,
It is not necessary to use an expensive substrate such as quartz as a substrate material, and this is a process very suitable for the large pixel liquid crystal display device of the present invention. In this embodiment, the thermal annealing is performed as shown in FIG.
(A) and (E) were performed twice. However, the annealing in FIG. 13A is omitted depending on the required characteristics, and both are omitted in FIG.
The annealing time of (E) may also be used to shorten the manufacturing time.

In FIG. 13F, an interlayer insulator 620 is formed.
Was performed to form a silicon oxide film by the above-described sputtering method. This silicon oxide film is formed by LPCVD, light CV
The D method or the normal pressure CVD method may be used. For example, 0.2 ~
A thickness of 0.6 μm was formed, and then a window 621 for an electrode was formed using a photomask. Further, FIG.
As shown in (F), aluminum is formed on the entire surface by sputtering, and leads 622 and contacts 62 are formed.
13 is manufactured using a photomask, the surface is coated with an organic resin 624 for flattening, for example, a translucent polyimide resin, and the electrode hole is formed again using the photomask in FIG.
(G).

In order to connect the output terminal to the electrode of one pixel of the liquid crystal device as a transparent electrode, the output terminal is formed by sputtering.
A TO (indium tin oxide film) was formed. It was etched using a photomask to form an electrode 625. This ITO is deposited at room temperature to 150 ° C.
Fulfilled by oxygen at ４００400 ° C. or in air. Thus, NTFT 626 and PTFT 6
27 and the transparent conductive film electrode 625 are made of the same glass substrate 60.
1. The mobility of the electrical characteristics of the obtained NTFT 626 is 120 (cm ² / Vs), Vth is 5.0 (V),
The mobility of the electrical characteristics of the PTFT 627 is 50 (cm ² / V
s) and Vth was 5.3 (V). (FIG. 13 (G))

FIG. 14 shows an outline of the structure. 15 on the substrate
00, a fumaric acid polymer resin and nematic liquid crystal
A mixture dissolved in xylene as a common solvent at a ratio of 5:35 was formed to a thickness of 10 μm by die casting. Thereafter, the solvent was removed at 120 ° C. for 180 minutes in a nitrogen atmosphere to form a liquid crystal dispersion layer 1501. In this case, it was found that when the pressure was slightly reduced from the atmospheric pressure, the tact time could be reduced.

Thereafter, ITO (indium tin oxide film) was formed by a sputtering method to obtain a counter electrode 1502. This ITO was formed at a temperature from room temperature to 150 ° C. After that, using a printing method, the light-transmitting silicone resin is
And baked at 100 ° C. for 30 minutes to obtain a liquid crystal electro-optical device.

The functional configuration of the driving IC used in this embodiment is the same as that of the first embodiment. When a normal analog gray scale display is performed on a liquid crystal electro-optical device in which 307,200 sets of 640 × 480 dots of 307,200 TFTs are formed in a 300 mm square, variation in TFT characteristics is about ± 10%. 16 gradation display was the limit. Since the TFT according to the present embodiment could increase the driving frequency to 2.5 MHz, the number of gray scales displayed could be up to 86 gray scales where 2.5 MHz is divided by 480 scanning lines and 60 frames. Therefore, when performing digital gradation display according to the present embodiment, it is possible to display up to 64 gradations because it is hardly affected by the variation in the characteristics of the TFT elements. The display of various colors has been realized.

In the case of displaying software such as a television image, for example, even a “rock” of the same color has a slightly different color due to the degree of light corresponding to the minute depressions. When trying to display images that are close to natural colors, difficulties are required at 16 gradations.
Not suitable for expressing these subtle depressions. With the gradation display according to the present invention, it is possible to impart these minute color changes.

This liquid crystal electro-optical device can be used not only for the front type projection television shown in FIG. 12, but also for the rear type projection television.

Embodiment 4 (Portable Computer) In this embodiment, an electro-optical device for a portable computer using a reflective liquid crystal dispersion type display device as shown in FIG. 15 will be described.

The first substrate used in this example was manufactured in the same process as in Example 1. On the substrate,
A mixture obtained by dissolving a nematic liquid crystal in which a fumaric acid-based polymer resin and a black pigment are mixed at a ratio of 15% in xylene, which is a common solvent, in a ratio of 65:35 is subjected to a die casting method to obtain a mixture.
μm and then at 120 ° C in a nitrogen atmosphere for 1
The solvent was removed for 80 minutes to form a liquid crystal dispersion layer.

Here, since a black dye was used, a flat display, which was difficult in the dispersion type liquid crystal display, appears black when light is scattered (when no electric field is applied) and is transmitted when light is applied (when an electric field is applied).
Can display white, and can be displayed like characters written on paper.

As the reverse structure, it is also possible to express white when scattering and black when transmitting without mixing a black pigment. However, in this case, the back surface shown below needs to be black. This is also possible to display like a character written on paper.

Thereafter, ITO (indium tin oxide film) was formed by sputtering to obtain a counter electrode. This ITO was formed at a temperature from room temperature to 150 ° C. Thereafter, using a printing method, a white silicone resin was applied to a thickness of 55 μm and baked at 100 ° C. for 90 minutes to obtain a liquid crystal electro-optical device.

[0082]

According to the present invention, in contrast to the conventional analog gray scale display, digital gray scale display is performed using two independent driving frequencies. As an effect, for example, when assuming a liquid crystal electro-optical device having a pixel number of 640 × 400 dots, a total of 256,0
It is very difficult to fabricate the characteristics of all the 00 TFTs without variation, and in reality, when considering mass productivity and yield, 16 gradation display is considered to be the limit. In order to clarify the voltage level, the reference voltage value is input from the controller as a signal instead of an analog value, and the timing at which the reference signal is connected to the TFT is controlled by a digital value. The present invention is characterized in that the present invention employs a method of covering the variation in the characteristics of the TFTs by controlling the characteristics of the TFTs, so that a clear digital gradation display is possible.

Another advantage is that by using two driving frequencies, clear digital gradation display is possible without changing the number of frames for screen rewriting.
It is possible to avoid the occurrence of flicker and the like due to the decrease in the number of frames.

When the digital gradation display according to the present invention is performed, it is hardly affected by the variation in the characteristics of the TFT elements, so that up to about 64 gradations can be achieved. Color display has been realized. When projecting software like TV images,
For example, even a “rock” made of the same color has a slightly different color due to its fine dents and the like. If an attempt is made to perform a display close to natural colors, it is difficult to achieve 1696 gradations of 4096 colors. With the gradation display according to the present invention, it is possible to impart these minute color changes.

[Brief description of the drawings]

FIG. 1 shows a driving waveform according to the present invention.

FIG. 2 shows electro-optical characteristics of a nematic liquid crystal.

FIG. 3 shows T by polysilicon and amorphous silicon.
4 shows the electrical characteristics of FT.

FIG. 4 shows a matrix circuit according to the present embodiment.

FIG. 5 shows a planar structure of an element according to the present embodiment.

FIG. 6 shows a manufacturing process of the TFT according to the present embodiment.

FIG. 7 shows a process for manufacturing a counter substrate according to the present embodiment.

FIG. 8 shows a configuration of a liquid crystal display device (television) according to the present embodiment.

FIG. 9 shows a system configuration of a drive circuit according to the present embodiment.

FIG. 10 is a photograph showing an oscilloscope waveform of TFT characteristics according to the present embodiment.

FIG. 11 is a photograph showing an oscilloscope waveform of TFT characteristics according to the present embodiment.

FIG. 12 shows the structure of a projection-type liquid crystal electro-optical device according to the present embodiment.

FIG. 13 shows a manufacturing process of the TFT according to the present embodiment.

FIG. 14 is a sectional view of the liquid crystal electro-optical device according to the present embodiment.

FIG. 15 shows a configuration of a portable computer according to the present embodiment.

[Explanation of symbols]

 50: Glass substrate 51: Blocking layer 66: NTFT gate electrode 67: PTFT gate electrode 88: Pixel electrode.

Claims (15)

[Claims] A first substrate having an insulating surface; a channel forming region, a source region, a drain region, a gate insulating film provided in contact with the channel forming region, and a gate provided in contact with the gate insulating film. An electrode, at least one thin film transistor provided on the insulating surface, a planarization film made of an organic resin covering the thin film transistor, and one of the source region and the drain region formed on the planarization film and electrically connected to one of the source region and the drain region. A pixel electrode, a black stripe formed on a second substrate, and a counter electrode formed on the black stripe, wherein the pixel electrode and the counter electrode are spaced apart from each other. An electro-optical device, wherein the first substrate and the second substrate are disposed so as to face each other. 2. A first substrate having an insulating surface, a channel forming region, a source region, a drain region, a gate insulating film provided in contact with the channel forming region, and a gate provided in contact with the gate insulating film. An electrode, at least one thin film transistor provided on the insulating surface, a planarization film made of an organic resin covering the thin film transistor, and one of the source region and the drain region formed on the planarization film, Pixel electrodes, a black stripe formed on a second substrate, and a color filter formed on the black stripe, wherein the first substrate and the second substrate are An electro-optical device, which is opposed to the electro-optical device. 3. The electro-optical device according to claim 2, further comprising a counter electrode formed on the color filter, wherein the pixel electrode and the counter electrode face each other with a gap. 4. A first substrate having an insulating surface, a channel forming region, a source region, a drain region, a gate insulating film provided in contact with the channel forming region, and a gate provided in contact with the gate insulating film. An electrode, and at least one thin film transistor provided on the insulating surface; an interlayer insulating film covering the thin film transistor; formed on the interlayer insulating film and electrically connected to one of the source region and the drain region. A pixel electrode, a second substrate facing the first substrate, a black stripe formed on the second substrate, a flattening film made of an organic resin formed on the black stripe, An electro-optical device comprising: 5. The electro-optical device according to claim 4, further comprising a counter electrode formed on the black stripe. 6. A first substrate having an insulating surface, a channel forming region, a source region, a drain region, a gate insulating film provided in contact with the channel forming region, and a gate provided in contact with the gate insulating film. An electrode, and at least one thin film transistor provided on the insulating surface; an interlayer insulating film covering the thin film transistor; formed on the interlayer insulating film and electrically connected to one of the source region and the drain region. A pixel electrode, a second substrate facing the first substrate, a black stripe formed on the second substrate, a flattening film made of an organic resin formed on the black stripe, A counter electrode formed in contact with the flattening film; and a color filter formed on the black stripe. An electro-optical device counter electrode, characterized in that the faces with a gap. 7. The electro-optical device according to claim 6, further comprising a counter electrode formed on the flattening film. 8. The electro-optical device according to claim 1, wherein the channel forming region of the thin film transistor is made of crystalline silicon. 9. The electro-optical device according to claim 1, wherein the pixel electrode is a transparent electrode. 10. The electro-optical device according to claim 1, wherein the counter electrode is a transparent electrode. 11. The method of claim 1, 2, 4, 5, or 6.
9. The electro-optical device according to claim 1, wherein the black stripe is made of polyimide. 12. The method according to claim 1, wherein
An electro-optical device comprising a liquid crystal between the first substrate and the second substrate. 13. The electro-optical device according to claim 1, wherein the flattening film is made of polyimide. 14. A television using the electro-optical device according to claim 1. 15. A wall-mounted television using the electro-optical device according to any one of claims 1 to 14.