JP2000330139A - Production of electro-optic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make settable clear gradation levels by displaying with digital gradation instead of conventional analogue gradation making the data transfer frequency independent of the frequency for gradation display and displaying the digital gradation in a state where the frame frequency is not changed. SOLUTION: Pixel electrodes are formed on a first resin film on a first substrate. After a resin mixed with a black pigment is formed into a film on a second substrate 900 facing the first substrate, black stripes 901 are formed from the resin mixed with the black pigment by using a first photomask 11. Then a red filter 902, a green filter 903 and a blue filter 904 are formed on the second substrate 900 where the black stripes 901 are formed. Then a second resin film 905 is formed on the second substrate 900 where the black stripes 901, red filter 902, green filter 903 and blue filter 904 are formed, and then a common electrode 906 is formed on the second resin film 905.

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.
It is possible to set a clear gradation level.

[0002]

2. Description of the Related Art Liquid crystal compositions have different dielectric constants in a horizontal direction and a vertical direction with respect to a molecular axis due to their material properties. Therefore, liquid crystal compositions may be horizontally or vertically aligned with an external electric field. Can be easily done. 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, the gray scale display is performed by changing the voltage applied to the gate of the TFT or the voltage applied between the source and drain to adjust the voltage in an analog manner. I was

[0005]

A more detailed description will be given of a gradation display method for a liquid crystal electro-optical device using a TFT. An n-channel thin film transistor conventionally used in 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.
There is also a method of connecting the gate electrode to the scanning-side signal line and changing the source-drain voltage to control the electric field applied to the liquid crystal arbitrarily.

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 requires extremely difficulties with the present technology. That is the current situation. As can be seen from the electro-optical characteristics of the nematic liquid crystal shown in FIG. 2, 0.32 from around 2.08 V which is the boundary value in the dark state to around 2.40 V which is the boundary value in the bright state.
All gradation display must be performed between Vs. When 16 gradations are processed, 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 above, the voltage difference can be set to 0.5 V or more, so that the in-plane characteristic variation of the TFT is sufficiently reduced. Using a plurality of write frames, for example, 1
By turning on (2.5 V) 6 frames out of 0 frames and turning off (2.0 V) the remaining 4 frames,
The writing average voltage is 2.3 V, and a halftone display is possible.

However, in this case, since a plurality of frames are used, 30H which can be visually confirmed by humans is used.
There is a risk that the display becomes z or less, and this may cause display failure such as flicker depending on conditions. As a method for preventing this, increasing the driving frequency has been proposed, but the data transfer speed of the driver IC is also reduced to 20M.
There was a limit of about Hz, which required difficulty.

[0010]

Therefore, the present invention proposes means for supplying a clear gradation display level to a liquid crystal by performing digital gradation display instead of the conventional analog gradation display. At that time, the method does not simply increase the drive frequency to perform gradation display as conventionally proposed, but makes the data transfer frequency and the gradation display frequency independent to change the frame frequency. It is characterized in that the digital gradation display is performed in a state where the image is not displayed.

According to the present invention, there is provided an active matrix type liquid crystal display device, which performs gradation display of a display device using a display driving method having a display timing related to a unit time t for writing to an arbitrary pixel and a time F for writing one screen. Without changing the time F, the signal during the writing time at the time t is time-divided, whereby the average value of the electric field applied to the liquid crystal of the pixel at the time t is changed in accordance with the division ratio. The key 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 into an arbitrary pixel is time-divided, and gradations corresponding to the number of divisions can be displayed. I have to. At that 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.degree.
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 250 ° C to 350 ° C
In this example, the temperature was set to 320 ° C., and monosilane (SiH ₄ ) was used. Monosilane is not limited to (SiH _4), disilane (Si ₂ H ₆₎
Alternatively, trisilane (Si ₃ H ₈ ) may be used. These are PC
Introduced at a pressure of 3 Pa in the VD device, 13.56 MHz
The film was formed by applying high frequency power of At this time, an appropriate high frequency power is 0.02 to 0.10 W / cm ² , and in this example, 0.055 W / cm ² was used. Also, monosilane
The flow rate of (SiH ₄ ) was 20 SCCM, and the film formation 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, not only the plasma CVD but also a sputtering method and a low pressure CVD method may be used for forming the silicon layer to be a channel region of the TFT, and 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 formation temperature was 150 ° C., the frequency was 13.56 MHz, the sputter output was 400 to 800 W, and the pressure was 0.5 Pa.

In the case of forming by a reduced pressure gas phase method, 450 to 550 ° C. lower than the crystallization temperature by 100 to 200 ° C., for example, 5 to 5 ° C.
Disilane (Si ₂ H ₆ ) or trisilane (Si ₃ H ₈ ) was supplied to the CVD apparatus at 30 ° C. to form a film. The reactor pressure is 30 ~
It was set to 300 Pa. The deposition rate was 50-250 ° / 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 × 10 ²²
When compared with cm ^-3 , it was 1 atomic%.

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-mentioned method, the amorphous silicon film 52 is formed at a temperature of 500 to 5000.degree.
The film was formed to a thickness of Å.

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 was formed at a temperature of 250 ° C. to 350 ° C. In this embodiment, the temperature was set to 320 ° C., and monosilane (SiH ₄ ) and monosilane-based phosphine (PH ₃ ) having a concentration of 3% were used. These were introduced at a pressure of 5 Pa in the PCVD apparatus, and 13.56 M
The film was formed by applying a high frequency power of Hz. At this time, the high-frequency power is suitably 0.05~0.20W / cm ^2, in this embodiment using 0.120W / cm ^2. The specific conductivity of the n-type silicon layer formed by this method is 2 × 10
^-1 [Ωcm ^-1 ]. The film thickness was 50 °.

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 formation temperature was from 250 ° C. to 350 ° C. In this embodiment, the temperature was 320 ° C., and monosilane (SiH ₄ ) and monosilane-based diborane (B ₂ H ₆ ) having a concentration of 2% were used. These are PC
Introduced at a pressure of 4 Pa in the VD device, 13.56 MHz
The film was formed by applying high frequency power of At this time, the high-frequency power is suitably 0.05~0.20W / cm ^2, in this embodiment using 0.080W / cm ^2. The specific conductivity of the p-type silicon layer obtained by this method is 1 × 10
^-1 [Ωcm ^-1 ]. The film thickness was 50 °.

Thereafter, source / drain regions 55 and 56 and 57 and 58 were formed by a lift-off method. 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))

After that, using a XeCl excimer laser, the source / drain / channel regions were laser-annealed, 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.
mJ / cm ² is required. However, 220m from the beginning
When energy of J / cm ² or more is irradiated, hydrogen contained in the film is rapidly released, and the film is destroyed. For this purpose, it is necessary to first displace hydrogen and then melt it with low energy. In this embodiment, first 150 m
After purging hydrogen at J / cm ² , 230mJ
The crystallization was carried out at / cm ² .

Due to 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 to be in a crystalline state. However, since the silicon existing between these regions is bonded to each other, silicon mutually pulls each other. When measured by laser Raman spectroscopy, a single crystal silicon peak 522 is obtained.
A peak shifted to a lower frequency side than cm ⁻¹ is observed. Its apparent particle size is 50 to 5 when calculated from the half width.
Although the area is 00 °, there are actually a large number of regions having high crystallinity and a cluster structure, and a film having a structure in which each cluster is bonded to each other by silicon (anchoring) can 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 higher carrier mobility than so-called GB polycrystalline silicon. That is, electron mobility (μe) = 15 to 300 cm ² / V
Sec and hole mobility (μe) = 5-100 cm ² /
VSec was obtained.

On top of this, a silicon oxide film was formed as a gate insulating film to a thickness of 500 to 2000 {for example, 1000}. 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, 0.2-0.
6 μm thick and then a fifth photomask 7
Using 0, a window 79 for an electrode was formed. Thereafter, aluminum is further 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 method was performed to form a silicon oxide film by the method. This silicon oxide film is formed by LPCVD
Method, a photo CVD method, or a normal pressure CVD method may be used. After that, patterning was performed using the seventh photomask 81. After that, aluminum was further added to the entirety of the aluminum.
A lead 83 and a contact 84 were formed with a thickness of 3 μm by sputtering and using an eighth photomask 82. (FIG. 6 (G))

An organic resin 85 for flattening the surface, for example, a translucent polyimide resin is applied and formed.
Of the photomask 86 of FIG. 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 between room temperature and 15
Films were formed at 0 ° C. and achieved with oxygen at 200-400 ° C. or 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, the third photomask 1
3 and a blue filter 904 using the fourth photomask 14.
During these preparations, each filter was treated at 350 ° C. in nitrogen for 6 hours.
Baking for 0 minutes was performed. After that, the leveling layer 905 was formed using a transparent polyimide, also by using the spin coating method.

Thereafter, an ITO (indium tin oxide) was formed on the whole to a thickness of 0.1 μm by sputtering, and a common electrode 906 was formed using the fifth photomask 15. This ITO is deposited at room temperature to 150 ° C.
Fulfilled by oxygen at ~ 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 common signals and potential wiring were connected to leads on the substrate, and a polarizing plate was adhered 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 in a drive frequency system. One is a data latch circuit system 353 similar to the conventional driving method,
The main configuration is a basic clock φH355 for sequentially transferring 56, and 1-bit to 12-bit parallel processing is performed. The other one is a component part according to the present invention, and a clock CLK 357 according to a division ratio necessary for gradation display.
And 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 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, 50K to 1 (B)
Hz, 500 KHz, and 1 MHz. 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 the digital gradation display according to the present invention is performed, since it is hard to be affected by the variation in the characteristics of the TFT elements, it is possible to display up to 42 gradations, and in the color display, it is possible to display 7 gradations.
A variety of 4,088 colors can be displayed in subtle colors.

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 is used in which gold bumps provided on an IC chip are connected with an epoxy-based silver-palladium resin, and the IC chip and the substrate are filled and fixed with an epoxy-modified acrylic resin for the purpose of fixing and sealing. Was. 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, when a normal analog gray scale display is performed on a liquid crystal electro-optical device in which 49,152 sets of 384 × 128 dot TFTs are formed in a 50 mm square (36 sheets from a 300 mm square substrate), an amorphous TFT is used.
Since there is about ± 10% characteristic variation, 16 gradation display is the limit. However, 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 it is possible to display 256 gradations or more, and the color display is versatile with 16,777,216 colors. The display of various 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 13 are used.
00 is used to assemble the projection unit for the projection type image display device. Each one is 640 x 480
It has a dot configuration, and 307,20 in 4 inch diagonal
0 pixels were produced. The size per pixel was 127 μm square.

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 glass 601 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. ~ 3000Å
To a thickness of The process conditions are a 100% oxygen atmosphere, a film forming temperature of 15 ° C., an output of 400 to 800 W, and a pressure of 0.
5 Pa was set. 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
CVD of disilane (Si ₂ H ₆ ) or trisilane (Si ₃ H ₈ )
The film was supplied to the apparatus to form a film. Reactor pressure is 30 ~ 300
Pa. The deposition rate was 50-250 ° / min.
Threshold voltage (Vt) between PTFT and NTFT
In order to control substantially the same as in h), boron may be added at a concentration of 1 × 10 ¹⁵ to 1 × 10 ¹⁸ cm ⁻³ during film formation 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 formation temperature was 150 ° C., the frequency was 13.56 MHz, the sputter output was 400 to 800 W, and the pressure was 0.5 Pa.

When a silicon film is formed by the plasma CVD method, the temperature is, for example, 300 ° C., and monosilane (SiH ₄ ) or disilane (Si ₂ H ₆ ) is 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:
Oxygen is 5 × 10^{twenty one}cm^-3The following is preferred. This acid
If the element concentration is high, it is difficult to crystallize and the thermal annealing temperature
High or long thermal annealing times must be used.
If the amount is too small, the lamp is turned off by the backlight.
Current increases. Therefore 4 × 10¹⁹~ 4 × 10 ^{twenty one}
cm^-3Range. Hydrogen is 4 × 10²⁰cm^-3And silicon 4
× 10^{twenty two}cm^-3Was 1 atomic%.

According to the above method, a silicon film in an amorphous state is formed to a thickness of 500 to 5000 °, for example, 1500 °, and then subjected to a heat treatment 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. under 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, it has an amorphous structure at the time of film formation, and hydrogen is simply mixed therein.

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 to be in a crystalline state. However, since the silicon existing between these regions is bonded to each other, silicon mutually pulls each other. When measured by laser Raman spectroscopy, a single crystal silicon peak 522 is obtained.
A peak shifted to a lower frequency side than cm ⁻¹ is observed. Its apparent particle size is 50 to 5 when calculated from the half width.
Although it is a microcrystal with a size of 00Å, there are actually a large number of regions with high crystallinity and a cluster structure, and a semi-amorphous structure film in which each cluster is bonded to each other by silicon (anchoring). 603 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 higher carrier mobility than so-called GB polycrystalline silicon. That is, hole mobility (μh) = 10 to ²⁰⁰ cm ² /
VSec, electron mobility (μe) = 15 to 300 cm ² / V
Sec 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 a high mobility in the crystal. However, a barrier is formed in the GB to hinder the movement of carriers there. As a result, a mobility of 10 cm ² / Vsec or more cannot be easily obtained. That is, in this 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 {for example, 1000}. This was made under the same conditions as those for forming the silicon oxide film as the blocking layer. During this film formation, a small amount of fluorine is added,
Sodium ions may be immobilized.

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. Therefore, 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 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 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, optical CVD
Or a normal pressure CVD method. For example, 0.2-0.
The electrode was formed to have a thickness of 6 μm, and then a window 621 for an electrode was formed using a photomask. Further, FIG.
As shown in (1), aluminum is formed on the entire surface by sputtering, leads 622 and contacts 623 are formed using a photomask, and the surface is coated with a flattening organic resin 624, for example, a light-transmitting polyimide resin. ,
The electrode drilling was performed again using a photomask.

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 627
And a transparent conductive film electrode 625 were formed over the same glass substrate 601. The mobility of the electrical properties of the obtained NTFT is 120 (cm ² / Vs), Vth is 5.0 (V), the mobility of the electrical properties of the PTFT is 50 (cm ² / Vs), and Vth is 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 in a nitrogen atmosphere at 120 ° C. for 180 minutes 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. Thereafter, using a printing method, a translucent silicone resin was applied to a thickness of 30 μm, 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. 3 of 640 x 480 dots
When a normal analog gray scale display is performed on a liquid crystal electro-optical device in which 07,200 sets of TFTs are formed in a 300 mm square, 16 gray scale displays are performed because there is about ± 10% variation in TFT characteristics. It was the limit. T according to the present embodiment
Since the driving frequency of the FT could be increased to 2.5 MHz, the number of gray scales displayed could be up to 86 gray scales of 2.5 MHz divided by 480 scanning lines and 60 frames. Therefore, when the digital gradation display according to the present embodiment is performed, since it is hard to be affected by the variation in the characteristics of the TFT elements, it is possible to display up to 64 gradations. Color display has been realized.

In the case of displaying software such as a television image, for example, "rocks" of the same color have slightly different colors due to the amount of light corresponding to the minute depressions. When an attempt is made to display a color close to the natural colors, it is difficult to perform the display with 16 gradations, and it is 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-optic 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, a flat display, which has been difficult with a dispersion type liquid crystal display due to the use of a black dye, shows a black color when light is scattered (no electric field) and a white color when transmitted (when an electric field is applied). It can be displayed and can be displayed like characters written on paper.

As the reverse structure, it is possible to express white when scattering and black when transmitting without mixing a black dye. However, in this case, the back side shown below needs to be black. This is also possible to display like characters 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. Then, using a printing method, a white silicone resin is applied in a thickness of 55 μm,
It was 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. In reality, considering the mass productivity and the yield, 16 gradation display is considered to be the limit. In order to clarify the level, the reference voltage value is input as a signal from the controller side instead of an analog value, and the timing of connecting the reference signal to the TFT is controlled by a digital value, so that the voltage applied to the TFT is reduced. The present invention is characterized in that the present invention employs a method of controlling the characteristic variation of the TFT by controlling, so that 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 illustrates a TFT process according to the present embodiment.

FIG. 7 shows a process of a counter electrode 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 illustrates a TFT process 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.

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[Procedure amendment]

[Submission date] May 9, 2000 (200.5.9)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

Claims (17)

[Claims] 1. A thin film transistor is formed on a first substrate, a first resin film is formed to cover the thin film transistor, and a pixel electrode is formed on the first resin film. After forming a resin mixed with a black pigment on a second substrate facing the film, a black stripe was formed from the resin mixed with the black pigment using a first photomask, and the black stripe was formed. Forming a red filter, a green filter, and a blue filter on the second substrate; forming a second filter on the second substrate on which the black stripe, the red filter, the green filter, and the blue filter are formed; Forming a second resin film;
Forming a common electrode on the resin film of (1). 2. The method according to claim 1, wherein the thin film transistor includes a crystalline silicon film. 3. The resin according to claim 1, wherein the red filter is formed by depositing a resin mixed with a red pigment using a spin coating method, and then mixing the red pigment using a second photomask. The green filter is formed from a resin mixed with the green pigment using a third photomask after forming a resin mixed with a green pigment using a spin coating method, and the blue filter is formed using a third photomask. Forming a film of a resin mixed with a blue pigment by using a spin coating method, and then forming the film from the resin mixed with the blue pigment by using a fourth photomask. 4. The method for manufacturing an electro-optical device according to claim 1, wherein the common electrode is formed using a fifth photomask. 5. The method of manufacturing an electro-optical device according to claim 1, wherein the pixel electrode and the common electrode are mainly composed of ITO. 6. The electro-optical device according to claim 1, wherein the resin in which the black pigment is mixed and the second resin film are formed by using a spin coating method. Production method. 7. A TAB-shaped drive IC and a PCB having a common signal and a potential wiring are connected to leads formed on the first substrate or the second substrate according to any one of claims 1 to 6. A method for manufacturing an electro-optical device, comprising: 8. A thin film transistor is formed on a first substrate, a first resin film is formed to cover the thin film transistor, and a pixel electrode is formed on the first resin film. After forming a resin mixed with a black pigment on a second substrate facing the film, a black stripe was formed from the resin mixed with the black pigment using a first photomask, and the black stripe was formed. Forming a red filter, a green filter, and a blue filter on the second substrate; forming a second filter on the second substrate on which the black stripe, the red filter, the green filter, and the blue filter are formed; A common electrode is formed on the second resin film, and a liquid crystal material is sandwiched between the first substrate and the second substrate. A method for manufacturing an electro-optical device incorporating a liquid crystal display device. 9. The method according to claim 8, wherein the thin film transistor includes a crystalline silicon film. 10. The resin according to claim 8, wherein the red filter is formed by forming a resin mixed with a red pigment using a spin coating method, and then mixing the red pigment using a second photomask. The green filter is formed from a resin mixed with the green pigment using a third photomask after forming a resin mixed with a green pigment using a spin coating method, and the blue filter is formed using a third photomask. A film in which a resin mixed with a blue pigment is formed by using a spin coating method, and then formed from the resin mixed with the blue pigment using a fourth photomask. Method for manufacturing optical device. 11. The method for manufacturing an electro-optical device according to claim 8, wherein the common electrode is formed using a fifth photomask. 12. A method for manufacturing an electro-optical device incorporating a liquid crystal display device according to claim 8, wherein said pixel electrode and said common electrode are mainly composed of ITO. 13. The method according to claim 8, wherein the resin mixed with the black pigment and the second resin film are formed by using a spin coating method.
A method for manufacturing an electro-optical device incorporating a liquid crystal display device. 14. A TAB-shaped drive IC and a PCB having a common signal and a potential wiring are connected to leads formed on the first substrate or the second substrate according to any one of claims 8 to 13. A method for manufacturing an electro-optical device incorporating a liquid crystal display device. 15. The method for manufacturing an electro-optical device incorporating a liquid crystal display device according to claim 8, wherein the electro-optical device incorporating the liquid crystal display device is a television. 16. An electro-optical device incorporating a liquid crystal display device according to claim 8, wherein the electro-optical device incorporating the liquid crystal display device is a viewfinder for a video camera. Method of manufacturing. 17. An electro-optical device incorporating a liquid crystal display device according to claim 8, wherein the electro-optical device incorporating the liquid crystal display device is a portable computer. Method.