JP3000200B2 - Electro-optical device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a configuration of an electro-optical device using a thin film transistor (hereinafter referred to as a TFT) as a driving switching element.

[0002]

2. Description of the Related Art A liquid crystal composition has different dielectric constants in a horizontal direction and a vertical direction with respect to a molecular axis due to its 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, that is, displays light and dark by controlling the amount of transmitted light or the amount of scattering of light using the anisotropy of the dielectric constant. As a liquid crystal material, TN
Materials known as (twinstead nematic) liquid crystal, STN (super twinstead nematic) liquid crystal, ferroelectric liquid crystal, polymer liquid crystal, or dispersion type liquid crystal are known. It is known that a liquid crystal does not respond to an external voltage in an infinitely short time, but takes a certain time to respond. The value is specific to each liquid crystal material.
c, It takes several hundred msec for STN liquid crystal, several tens μsec for ferroelectric liquid crystal, and several tens msec for dispersion or polymer liquid crystal.

[0003] Among electro-optical devices using liquid crystals, the one that can obtain the best image quality is the one using the active matrix system. In a conventional active matrix type liquid crystal electro-optical device, a thin film transistor (TFT) is used as an active element, an amorphous or polycrystalline semiconductor is used for the TFT, and P
In this case, a TFT of only one of the N-type and the N-type was used. That is, in general, an N-channel TFT
(Referred to as NTFT) is connected in series to the pixel. Then, a signal voltage is applied to the signal lines of the matrix, and when signals are applied from both sides to the TFTs provided at the orthogonal portions of the respective signal lines, the ON / OFF state of the liquid crystal pixels is utilized by utilizing the fact that the TFTs are turned ON. OFF was individually controlled. By controlling the pixels by such a method, a liquid crystal electro-optical device having a high contrast can be realized.

As such a driving switching element,
In an electro-optical device using a thin film transistor, the liquid
Behind the electrode for applying an electric field to the electro-optic modulation layer such as a crystal
Good optical modulation with no devising on the surface side
There was a case that could not be done.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a driving switch.
Electro-optics using thin film transistors as switching elements
An electro-optical device that performs good optical modulation
The purpose is to provide.

[0006]

Means for Solving the Problems One of the main constitutions disclosed in this specification is a first and a second substrate facing each other, a plurality of pixel electrodes formed on the first substrate, A switching element provided on each of the pixel electrodes, a counter electrode formed on the second substrate, and an electro-optic modulation layer disposed between the first and second substrates; An electro-optical device, wherein a leveling layer made of a light-emitting organic resin is disposed between the second substrate and the counter electrode.

[0007] One of the other structures is that a first and a second substrate facing each other, a plurality of pixel electrodes formed on the first substrate, and a switching element provided on each of the pixel electrodes are provided. A color filter formed on the second substrate; a counter electrode formed on the color filter; and an electro-optic modulation layer disposed between the first and second substrates. An electro-optical device, wherein a leveling layer made of a light-emitting organic resin is disposed between the color filter and the counter electrode.

In the electro-optical device, the color filter may be a polyimide containing a pigment.

The counter electrode may be indium tin oxide.

One of the other structures is a first and a second substrate facing each other, a plurality of thin film transistors provided on the first substrate, an organic resin provided over the thin film transistor, and A plurality of pixel electrodes provided on an organic resin and connected to the thin film transistor; a counter electrode provided on the second substrate; and an electro-optic modulation layer provided between the first and second substrates Wherein a leveling layer made of a translucent organic resin is provided between the second substrate and the counter electrode.

In the above electro-optical device, the organic resin may be polyimide.

[0012] Another major feature disclosed herein is a substrate having an insulating surface and a substrate provided on the insulating surface.
At least one thin film transistor, provided on the thin film transistor, an interlayer insulating film made of silicon oxide,
A wiring formed of a conductive film provided on the interlayer insulating film and electrically connected to the thin film transistor through a contact hole formed in the interlayer insulating film; and covering the thin film transistor, the interlayer insulating film, and the wiring. A flattening film made of a light-transmitting organic resin, and a pixel electrode provided on the flattening film and connected to the thin film transistor through a hole formed in the organic resin. An end portion of the organic resin in a peripheral portion is rounded, and is an electro-optical device.

In the above electro-optical device, the pixel electrode may be formed of a light-transmitting conductive film. The light-transmitting conductive film may be made of indium tin oxide.

Further, in the above electro-optical device, the organic resin film is made of a light-transmitting polyimide.

One of the other structures is a substrate having an insulating surface, at least one thin film transistor provided on the insulating surface, an interlayer insulating film made of silicon oxide provided on the thin film transistor, A wiring made of a conductive film provided on the interlayer insulating film and connected to the thin film transistor through a contact hole formed in the interlayer insulating film; and a light transmitting material provided over the thin film transistor, the interlayer insulating film, and the wiring. A flattening film made of a conductive organic resin, and a pixel electrode provided on the flattening film and connected to the thin film transistor through a hole provided in the organic resin film. The electro-optical device is characterized in that the uppermost layer is larger than the lowermost layer of the organic resin.

In another configuration, a substrate having an insulating surface, at least one thin film transistor formed on the insulating surface, and a flat surface made of a translucent organic resin provided on the entire surface of the substrate so as to cover the thin film transistor. And a pixel electrode provided on the flattening film, connected to the thin film transistor through a hole provided in the flattening film, and the organic resin in a peripheral portion of the opening. The electro-optical device is characterized in that the end of the film is rounded.

[0017]

[Embodiment 1] Conventionally, in an active matrix system, light and darkness and color tone are not considered.
However, it was extremely difficult to perform gradation display. Obedience
In the gray scale display, the light transmittance of the liquid crystal has been
A method that uses the fact that it changes depending on the size is being considered.
Was. This is, for example, the source of the TFT in the matrix.
Supply an appropriate voltage from the peripheral circuit between the drains,
By applying a signal voltage to the gate electrode in the state,
It is intended to apply a voltage of that magnitude to the liquid crystal pixels.
Was.

However, in such a method, for example,
For example, TFT heterogeneity and matrix wiring
Therefore, the voltage actually applied to the liquid crystal pixels depends on each pixel.
At least a few percent different. In contrast, the example
For example, the voltage dependence of the light transmittance of liquid crystal is extremely nonlinear.
Light transmittance changes suddenly at a certain voltage
Therefore, even if the difference is a few percent, the light transmittance is significantly different.
There was sometimes. Therefore, it actually reaches 16 gradations
Was the limit. For example, TN liquid crystal materials
In other words, the so-called transition region where the light transmittance changes,
When the width is only 1.2V and 16 gradations are to be achieved
Needs to be able to control voltages as small as 75 mV.
As a result, the production yield was significantly reduced.

As described above, it is difficult to perform gradation display.
A liquid crystal display device is a conventional general display device
Is extremely difficult to compete with the CRT (Cathode Ray Tube)
Was profitable. In this embodiment, gradation display, which has been difficult
The aim is to propose a whole new way to make it happen
It is assumed that.

The voltage applied to the liquid crystal is controlled in an analog manner.
Can control its light transmission.
As mentioned earlier, the present inventors have stated that
By controlling the time during which pressure is applied,
It was found that a gradation can be obtained.

For example, a typical liquid crystal material, TN (Tsu)
In the case of using isted nematic) liquid crystal,
For example, in FIG. 1, various pulse waveforms are shown.
However, it is necessary to apply such a waveform voltage to the liquid crystal pixels.
That it is possible to change the brightness
I found it. That is, “1”, “2”,.
It can be brightened step by step in the order of “15”
You. That is, in the example of FIG. 1, display of 16 gradations is possible.
You. At this time, a pulse of one unit length is printed at “1”.
Be added. In the case of “2”, a pulse having a length of 2 units
Applied. In “3”, one unit of pulse and two units of pulse
And a pulse of 3 units in length is printed.
Be added. At “4”, a pulse with a length of 4 units is applied.
It is. In “5”, one unit of pulse and four units of pulse
At “6”, 2 units of pulse and 4 units of pulse
Is applied. In addition, a pulse with a length of 8 units is prepared
The result is a pulse 15 units long.
Can be obtained.

That is, 1 unit, 2 units, 4 units, 8 units
By properly combining the four types of pulses
Thus, display of 2 ⁴ = 16 gradations is possible. In addition, 1
6 units, 32 units, 64 units, 128 units, etc.
In addition, by preparing many pulses,
32 gradations, 64 gradations, 128 gradations, 256 gradations
A gray scale display is possible. For example, to obtain 256 gradation display
For this purpose, eight types of pulses may be prepared.

In the example shown in FIG. 1, the voltage applied to the pixel is
The duration of the pressure is first T ₁ , then 2T ₁ , then 4T
Example of an arrangement in which the numbers increase in a geometric progression, such as _1.
This is, for example, as shown in FIG.
_1, then 8T _1, the following 2T _1, finally as 4T ₁
Is also good. By allowed to SEQ Thus, the display equipment
In this case, the load on the device for transmitting data to the user can be reduced.

If this configuration is not implemented, the liquid crystal material and
For example, TN liquid crystal, STN liquid crystal, ferroelectric liquid crystal, dispersion type
(Polymer) liquid crystal is suitable. Also, one unit of pulse width
Varies slightly depending on which liquid crystal material you choose
However, in the case of a TN liquid crystal material, 10 nsec or more is suitable.
It became clear that.

To implement this configuration, for example, FIG.
As shown, a matrix circuit using thin film transistors
All you have to do is make a road. The circuit shown in FIG. 4 uses a conventional TFT.
Used in active matrix display devices
Same as road.

In the figure, artificially in parallel with the pixel capacitor
A capacitor has been inserted. The inserted cap at this time
The pixel voltage drops due to the natural discharge of the pixel.
It has the effect of suppressing that Pixel voltage drop
The fluctuation depends on the variation of the pixels. In particular, in this embodiment,
As the voltage applied to the pixel is constant,
In the invention in which the display is performed, the image quality is reduced.
It is a spider. However, in this way the pixels
By inserting a capacitor,
Voltage drop can be suppressed significantly, and high image quality can be obtained.
Can be.

In addition, for example, tetra
Yes, such as fluoroethylene and polyvinylidene fluoride
By incorporating a ferroelectric material, the electrostatic
Increase the capacitance and thus the time constant of the pixel discharge.
By tightening, such an artificial capacitor
Stable and reproducible operation without making money
You can also.

Of course, if the pixel discharge is small enough
If you don't need such an artificial capacitor,
No. In particular, the presence of excessive capacitance can cause charging or discharging.
Takes a long time to perform the operation of the present embodiment.
Not good. Example to reduce pixel discharge
For example, make the OFF resistance of the thin film transistor sufficiently large,
And reducing the rie leakage current, between the pixel itself, such as a liquid crystal electrode
It is necessary to increase the resistance sufficiently. Especially the latter eye
In order to achieve this, the pixel electrode should be made of silicon nitride or silicon oxide.
Insulation materials such as elemental, tantalum oxide and aluminum oxide
It is effective to cover.

In such a circuit, each thin film transistor
Control the gate voltage and the source-drain voltage of the
The ON / OFF of the voltage applied to the pixel
It is possible to control OFF. In this example,
Rix is 480 x 640 dots, but to avoid complexity
Therefore, only the vicinity of n rows and m columns is shown. Same as this
You can get a complete one by expanding it up, down, left and right. this
FIG. 2 shows an operation example using a circuit.

The signal line _{X 1, X 2,.} . X _n ,
X _{n +} 1,. . X ₄₈₀ (hereinafter collectively referred to as the X-ray) is,
It is connected to the gate electrode of each TFT. And FIG.
As shown in the figure, rectangular pulse signals are applied in order.
Good. On the other hand, the signal lines _{Y 1, Y} 2,. . Y _m, Y
_{m + 1,. .} Y ₆₄₀ (hereinafter collectively referred to as Y line)
Connected to the source (or drain electrode) of the TFT
However, this is still a signal consisting of multiple pulses.
Is applied. This pulse train has a unit time T
₁ includes 640 pieces of information.

In the following, four pixels Zn _{, m} , Z
_n + _{1, m,} be noted _Z n, the _{m + 1, Z n + 1} , m + 1
The signal is not coming to both the gate electrode and the source electrode.
As the voltage of the pixel does not change, the four pixels
Is regarding the signal line _{X n, X} n _{+ 1} and _{Y m, Y} m _{+ 1}
Attention should be paid to.

As shown in the figure, the applied rectangular pulse to _{X n}
Consider the case. Now, four pixels Zn _{, m} , Z
_{n, m + 1, Z n} + 1, m, focused on the _{Z n + 1, m + 1}
, Then the current state of Y _m and Y _{m + 1}
Attention should be paid to. At this time, there is a signal _{Y m,} Y
Since there is no signal at _{m + 1} , the pixel Zn _{. m} is voltage
State, _{Z n. m + 1} goes into a non-voltage state. And the Y line
By cutting off the X-ray pulse earlier than the voltage applied to
The pixel voltage state is maintained by the pixel capacitor
Therefore, the pixel Zn _{, m} maintains the voltage state. Less than
After until the next signal is applied to X _n, basically it
The state of each pixel is maintained.

Next, a pulse is applied to _{Xn + 1} .
As shown in the figure, at which time Y _m are non-voltage-shaped
State, Y _{m + 1} is a voltage state, so that pixel Zn _{+ 1, m}
Is in a non-voltage state, and pixels Zn _{+ 1 and m + 1} are in a voltage state.
And maintain each state as described above.
You.

Next, whether a pulse was applied to _Xn first
Et al., The second pulse is applied is the signal line X _n after a time T ₁
Is the time was, _{Y m} and _{Y m + 1,} respectively, the non-conductive
The pixel Zn _{, m} is in a non-voltage state
Pixel Zn _{, m + 1} is in a voltage state,
Changes. Further, a pulse is applied to _{Xn + 1} .
As shown in the figure, at that time Y _m be Y _{m + 1}
Is also in the voltage state, so that the pixels Zn _{+ 1 and m} are also in the Z state.
_{n + 1 and m + 1} are in a voltage state. At this time, the pixel Z
_{n + 1 and m + 1} will continue the voltage state.

[0035] Then, after a time 2T _1, the third signal
It is applied to the X _n. At that time, _{Y m} be conductive even _{Y m + 1}
Pixel, the pixel Zn _{, m} is switched from the non-voltage state to the voltage
State, and the pixel Zn _{, m + 1} continues the voltage state
It will be. Further , a pulse is applied to _{Xn + 1} . So
Y for _m even Y _{m + 1} also is a non-voltage state, the field at the time of
Containing _{Z n + 1, m} be _{Z n + 1, m + 1} sounds a non-voltage state
In each case, the voltage state ends.

[0036] Then, after a time 4T _1, the fourth signal
It is applied to the X _n. At that time, _{Y m} be _{Y m + 1} also non
Because of the voltage state, the pixel Zn _{, m} is also the pixel Zn _{, m + 1}
Also changes from the voltage state to the non-voltage state. Furthermore, X
Although pulse _{n + 1} is applied, also _{Y m} be _{Y m + 1}
Is also in a non-voltage state, the pixel Zn _{+ 1, m} is also
_{n + 1 and m + 1} remain in the non-voltage state.

Thus, one cycle is completed. this
During this time, four pulses are applied to each X-ray and each Y-ray is
An information signal of 3 × 480 = 1440 is applied. Ma
And, the time of one cycle is 8T _1, as _{T 1} is
For example, 10 nsec to 10 msec is appropriate. So
Then, focusing on each pixel, the pixel Zn _{, m} has the time
Pulses of the pulse and 4T ₁ T ₁ is applied, visually the
The same effect can be obtained as the pulse of the 5T ₁ is applied
You. That is, a brightness of “5” is obtained. Similarly,
Element Zn _{, m + 1} , pixel Zn _{+ 1, m} , Zn _{+ 1, m + 1}
In the end, the brightness of "2", "6", "3" is obtained
You.

In the above example, eight gradations can be displayed.
However, by adding more pulse signals,
Higher gradations are possible. For example, during one cycle,
Five pulses were applied to the X-ray, and 3840 information was added to each Y-ray.
High gradation display of 256 gradations by applying signals
Can be achieved.

Further, if a high gradation display is to be performed,
For example, as is clear from FIG.
Is needed. For example, to realize 256 gradations
Means that at least 30 videos need to be delivered per second
_In, 256T 1 <30msec _{o Therefore, T} 1 <1
00 μsec. Therefore, for example, X-rays (gay
480 columns in the case of 480 columns)
A pulse of 200 nsec or less needs to be applied.
In the example of FIG. 3, only the NMOS TFT is used.
In order to increase the speed, a circuit having a CMOS circuit
May be connected. For example, a CMOS inverter circuit,
CMOS modified inverter circuit, CMOS modified buffer
Circuit or CMOS modified transfer circuit etc.
It does not matter.

In the above description, the description will be easy to understand.
In order to make signals clear, such as non-voltage state and voltage state
However, this is lower than the threshold voltage of the liquid crystal or TFT.
The question of whether it is below or above
So it does not have to be absolutely zero.

Also, an appropriate bias voltage is applied to the counter electrode of the pixel.
By applying pressure, the substantial
It is possible to change the voltage. For example, pixel pairs
By applying an appropriate voltage to the counter electrode, the pixel material
The direction of the voltage applied to the
You can also. Such operations are, for example, ferroelectric
Necessary for liquid crystals.

In this embodiment, a wall-mounted television is manufactured using a liquid crystal display device having a circuit configuration as shown in FIG. The TFT at that time was made of polycrystalline silicon using laser annealing.

FIG. 5 shows the actual arrangement of electrodes and the like corresponding to this circuit configuration for one pixel. First, a method for manufacturing a liquid crystal panel used in this embodiment will be described with reference to FIGS. In FIG. 6A, a magnetron RF (high frequency) is placed on a glass 50, such as quartz glass, which can withstand heat treatment at an inexpensive temperature of 700 ° C. or less, for example, about 600 ° C.
A silicon oxide film as the blocking layer 51 is formed to a thickness of 1000 to 3000 ° by using a sputtering method. The process conditions are 100% oxygen atmosphere, film formation temperature 15 ° C, output 4
The pressure was set to 00 to 800 W and the pressure to 0.5 Pa. The deposition rate using quartz or single crystal silicon as the target is 30 to 1
00 ° / min.

A silicon film 52 was formed thereon by a plasma CVD method. The film formation temperature is from 250 ° C to 35
The test was performed at 0 ° 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 ) and trisilane (Si ₃
H ₈ ) may be used. These are placed in a PCVD system in 3P
The film was introduced at a pressure of a and a high frequency power of 13.56 MHz was applied to form a film. At this time, the high frequency power is 0.02 to 0.1
0 / cm ² is appropriate, and in this embodiment, 0.055 W / cm ²
cm ² was used. The flow rate of monosilane (SiH ₄ ) was set to 20 SCCM, and the deposition rate at that time was about 120 ° /
Minutes. Even if the silicon film is a pure intrinsic semiconductor, it is also possible to use boron as a diborane to form boron at 1 × 10 ¹⁵ to 1 × 10 ^15.
It may be added during the film formation as a concentration of × 10 ¹⁸ cm ⁻³ . 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.

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 hydrogen was mixed with 20 to 80% of argon. For example, argon was 20% and hydrogen was 80%. The deposition temperature is 150 ° C., the frequency is 13.56 MHz,
The sputter output was 400-800 W and the pressure was 0.5 Pa.

When the film is formed by the reduced pressure gas phase method, 450 to 550 C lower by 100 to 200 ° C. than the crystallization temperature, for example, 5 to 5 ° C.
At 30 ° C., disilane (Si ₂ H ₆ ) or trisilane (S
i ₃ H ₈ ) was supplied to a CVD apparatus to form a film. The pressure in the reactor was 30 to 300 Pa. Film formation rate is 50-25
0 ° / 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
It is desirable to be ¹⁹ cm ⁻³ or less, preferably 1 × 10 ¹⁹ cm ⁻³ or less. However, if the amount is too small, the off-state leakage current increases due to the backlight.
This concentration was chosen. If the oxygen concentration is high, crystallization is difficult, and the laser annealing temperature must be increased or the laser annealing time must be lengthened. Hydrogen is 4 × 1
It was 0 ²⁰ cm ⁻³ , which was 1 atomic% as compared with silicon 4 × 10 ²² cm ⁻³ .

In order to 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 and then, 5 × by ion implantation of oxygen only the channel formation region of the TFT constituting the pixel ^{10 2 0 ~5 × 10 21 cm} -3
You may add so that it may become.

By the above method, a silicon film in an amorphous state was formed to a thickness of 500 to 5000 Å, and in this embodiment, 1000 Å.

Thereafter, the photoresist 53 is masked with a mask P1.
Was used to form a pattern in which only the source / drain regions were opened. A silicon film 54 serving as an n-type active layer was formed thereon by a plasma CVD method. Film formation temperature is 250 ° C
In this example, 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 are PCV
The film was introduced at a pressure of 5 Pa in the D apparatus, and high-frequency power of 13.56 MHz was applied to form a film. 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 completed by this method was about 2 × 10 ^-1 [Ωcm ^-1 ]. The film thickness was 50 °. Thus, FIG.
(A) was obtained. Thereafter, the resist 53 was removed by a lift-off method, and source / drain regions 55 and 56 were formed. Thus, FIG. 6B was obtained.

Thereafter, as shown in FIG.
Using an excimer laser, laser doping was performed on the active layer at the same time as laser annealing of the source, drain, and channel regions. At this time, the threshold energy of the laser energy is 130 mJ / cm ² , and 220 mJ / cm ² is required to melt the entire film thickness. However, when an energy of 220 mJ / cm ² or more is irradiated from the beginning, 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. After performing the flush hydrogen in the first 150 mJ / cm ² in the present embodiment was subjected to crystallization at 230 mJ / cm ^2.

Thereafter, the silicon film 52 was etched away using the mask P3 to form an N-channel type thin film transistor island region 63. Further, a silicon oxide film 64 was formed thereon as a gate insulating film to a thickness of 500 to 2000 Å, for example, 100 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, phosphorus is l-5 × 10
A silicon film having a concentration of ²¹ cm ⁻³ or a multilayer film of the silicon film and molybdenum (Mo), tungsten (W), MoSi ₂ or WSi ₂ was formed thereon. This was patterned using a fourth photomask P4 to obtain a gate electrode 66 for NTFT. (FIG. 6 (D))
As the size of the gate electrode, for example, a channel length of 7 μm
The structure of the gate electrode was phosphorus-doped silicon having a thickness of 0.2 μm and molybdenum thereon having a thickness of 0.3 μm.

At the same time, as shown in FIG. 7A, the gate wiring 65 and the wiring 68 arranged in parallel with the gate wiring 65 were also patterned.

As the gate electrode material, for example, aluminum (Al) can also be used in addition to the above materials. When aluminum is used, after patterning it with a fourth photomask P4 and then anodizing the surface, the self-alignment method can be applied.
Since the source / drain contact hole can be formed at a position closer to the gate, the characteristics of the TFT can be further improved in terms of reduction in mobility and 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 extremely suitable for a large- screen liquid crystal display device.

Further, a silicon oxide film was formed on the interlayer insulator 69 by the above-mentioned sputtering method. This silicon oxide film may be formed by an LPCVD method, a photo CVD method, or a normal pressure CVD method. For example, it was formed to a thickness of 0.2 to 0.6 μm, and then a window 79 for an electrode was formed using the fifth photomask P5. Thereafter, aluminum was further formed on the entire surface to a thickness of 0.3 μm by sputtering, and leads 74 and contacts 73 were formed using a sixth photomask P6. 6 (E) and FIG.
(B) was obtained.

After that, the surface was coated with a flattening organic resin 77, for example, a light-transmitting polyimide resin, and the electrode was drilled again with the seventh photomask P7. Further, an ITO (indium tin oxide) is formed to a thickness of 0.1 μm on all of them by sputtering to form an eighth photomask P8.
Was used to form the pixel electrode 71. This ITO is at room temperature
The film was formed at 150 ° C. and achieved by annealing at 200 to 400 ° C. in oxygen or air. Thus, FIGS. 6F and 7C are obtained.

FIG. 7D is a sectional view taken along the line AA ′ of FIG.
Shown in Actually, a counter electrode is provided with a liquid crystal material interposed therebetween, and a capacitance is generated between the counter electrode and the electrode 71 as shown in the figure. At the same time, the wiring 68 and the electrode 7
The capacitance also occurs between 1. Then, by keeping the wiring 68 at the same potential as the counter electrode, a circuit in which a capacitor is inserted in parallel with the liquid crystal pixel can be formed as shown in FIG. In particular, by arranging as in the present embodiment, the wiring 68 is parallel to the gate wiring 65,
The parasitic capacitance between the wirings is small, and therefore, there is an effect of reducing attenuation and delay of a signal transmitted through the gate wiring.

The wiring 68 thus formed is
Can be used as a ground line of a protection circuit provided at the end of each matrix when used with ground. The protection circuit is provided between a peripheral driving circuit and a pixel as shown in FIG. 10 and refers to a circuit as shown in FIG. 11 and FIG. In any case, when an excessive voltage is applied to the wiring of the pixel, it is turned on, and has a function of removing the voltage. These protection circuits include doped or undoped semiconductor materials such as silicon,
It is configured using a transparent conductive material such as TO or a normal wiring material. Therefore, it can be formed at the same time when the circuit of the pixel is formed.

This means that, for example, each of the protection circuits in FIG.
/ TFT. Further, the protection circuit of FIG. 12 does not use a TFT,
The diode is constituted by, for example, a PIN junction.
It is obvious that it has a structure such as PIP, PNP, or NPN and can be manufactured by using the manufacturing method described in this embodiment without need to explain each time.

The electrical characteristics of the TFT obtained as described above have a mobility of 80 (cm ² / Vs) and a Vth of 5.
0 (V). One substrate for a liquid crystal electro-optical device manufactured according to the above method was obtained.
FIG. 5 shows the arrangement of the electrodes and the like of the liquid crystal display device. By repeating such a structure left and right, up and down,
A liquid crystal display device having a large pixel size of 640 × 480 or 1280 × 960 can be obtained. In the present embodiment, 1920
× 400. Thus, a first substrate was obtained.

FIG. 8 shows a method for manufacturing the other substrate. A polyimide resin obtained by mixing a black pigment with polyimide is formed on a glass substrate to a thickness of 1 μm using a spin coating method,
Black stripe 8 using ninth photomask P9
1 was produced. After that, a film of a polyimide resin mixed with a red pigment was formed to a thickness of 1 μm using a spin coating method,
Red filter 8 using tenth photomask P10
3 was produced. Similarly, a green filter 85 and a blue filter 86 were manufactured using the masks P11 and P12. During the production, each filter was fired at 350 ° C. in nitrogen for 60 minutes. After that, the leveling layer 89 was manufactured using transparent polyimide also by using the spin coating.

Thereafter, ITO (indium tin oxide) was formed on the entire surface to a thickness of 0.1 μm by sputtering, and a common electrode 90 was formed using a thirteenth photomask P13. This ITO is deposited at room temperature to 150 ° C.
This was achieved by annealing in oxygen or atmosphere at 0 to 300 ° C. 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, 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. This was connected to a rear lighting device in which three cold cathode tubes were arranged, and a tuner for receiving TV radio waves to complete a wall-mounted TV. Compared to a conventional CRT system television, the device has a flat shape, so that it can be installed on a wall or the like. The operation of this LCD TV is shown in FIG.
It has been confirmed that by applying a signal substantially equivalent to that shown in FIG. 7 to the liquid crystal pixels, 8-gradation display is possible. At this time, T ₁ = 4 msec, and the pulse widths (or minimum pulse widths) of the X-rays and the Y-rays are each 5 μs.
ec and 8 μsec.

Example 2 In this example, a wall-mounted television was manufactured using a liquid crystal display device having a circuit configuration as shown in FIG. 4, and a description thereof will be given. Also T at that time
FT was polycrystalline silicon using laser annealing.

Hereinafter, a method of manufacturing the TFT portion will be described with reference to FIG. In FIG. 9A, an inexpensive material such as quartz glass is 700 ° C. or less, for example, approximately 600 ° C.
Magnetron RF on glass 100 that can withstand heat treatment
A silicon oxide film as the blocking layer 101 is formed to a thickness of 1000 to 3000 ° by using (high frequency) sputtering. Process conditions are 100% oxygen atmosphere, film formation temperature 1
5 ° C.) Output 400 to 800 W) Pressure 0.5 Pa.
The deposition rate using quartz or single crystal silicon as the target was 30 to 10 ° / min.

The silicon film 1 was formed thereon by plasma CVD.
02 was produced. The film formation is performed at a temperature of 250 ° C. to 350 ° C. In this embodiment, the temperature is set to 320 ° C.
H ₄₎ was used. Not only the monosilane (SiH _4), may be used disilane _(Si 2 _{H 6)} The trisilane _(Si 3 _{H 8).} These were introduced into a PCVD apparatus at a pressure of 3 Pa, and high-frequency power of 13.56 MHz was applied to form a film. At this time, the high frequency power is 0.02 to 0.10 W / c.
m ² is appropriate, and in this embodiment, 0.055 W / cm ²
Was used. The flow rate of monosilane (SiH ₄ ) is 20
SCCM was used, and the deposition rate at that time was about 120 ° / min. This silicon film may be an intrinsic semiconductor, or boron may be added during film formation at a concentration of 1 × 10 ¹⁵ to 1 × 10 ¹⁸ cm ⁻³ using diborane. The plasma CV is used for forming a silicon layer to be a TFT channel region.
In addition to D, a sputtering method or a low pressure CVD method may be used, and the method will be briefly described below.

In the case of performing the sputtering method, the back pressure before the sputtering was set to 1 × 10 ⁻⁵ Pa or less, and a single crystal silicon was used as a target in an atmosphere in which hydrogen was mixed with 20 to 80% of argon. For example, argon was 20% and hydrogen was 80%. The deposition temperature is 150 ° C., the frequency is 13.56 MHz,
The sputter output was 400-800 W and the pressure was 0.5 Pa.

When the film is formed by the reduced pressure gas phase method, the temperature is 450 to 550 ° C. lower than the crystallization temperature by 100 to 200 ° C., for example, 5 to 50 ° C.
At 30 ° C., disilane (Si ₂ H ₆ ) or trisilane (S
i ₃ H ₈ ) was supplied to a CVD apparatus to form a film. The pressure in the reactor was 30 to 300 Pa. Film formation rate is 50-25
0 ° / 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, since preferably it is desirable to ^1X10 19 ^{cm -3} or less, too little, the leakage current in the OFF state is increased by the backlight,
This concentration was chosen. If the oxygen concentration is high, crystallization is difficult, and the laser annealing temperature must be increased or the laser annealing time must be lengthened. Hydrogen is 4 × 1
It was 0 ²⁰ cm ⁻³ , which was 1 atomic% as compared with silicon 4 × 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.
Hereafter, preferably, it is set to 1 × 10 ¹⁹ cm ⁻³ or less, and oxygen is ion-implanted only in a channel formation region of a TFT forming a pixel to 5 × 10 ^{20 to} 5 × 10 ²¹ cm ^−3.
You may add so that it may become. By the above method, a silicon film in an amorphous state was formed to a thickness of 500 to 5000 °, in this example, 1000 °.

After that, the photoresist 103 is
Using No. 1, a pattern was formed in which only the region to be the source / drain region of the NTFT was opened. Using the resist 103 as a mask, phosphorus ions are implanted by ion implantation at a dose of 2 × 10 ^{14 to} 5 × 10 ¹⁶ cm ⁻² , preferably 2 × 10 ¹⁶ cm ⁻² to form the n-type impurity region 104. . After that, the resist 103 was removed.

Thereafter, as shown in FIG. 9B, a thickness of 50 to 300 nm, for example, 100 nm is formed on the silicon film 102.
m silicon oxide film 107 was formed by the RF sputtering method described above. Then, using a XeCl excimer laser, the source, drain and channel regions were crystallized and activated by laser annealing. At this time, the laser energy has a threshold energy of 130 mJ / cm.
² , 220 mJ / cm ² is required to melt the entire film thickness. However, when an energy of 220 mJ / cm ² or more is irradiated from the beginning, 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. After performing the flush hydrogen in the first 150 mJ / cm ² in the present embodiment was subjected to crystallization at 230 mJ / cm ^2. Further, after the end of the laser annealing, the silicon oxide film 107 was removed.

This crystallization can also be performed by a thermal annealing method. In that case, 45
0-700 ° C, preferably 550-600 ° C
The heat treatment may be performed at a temperature of 12 to 70 hours, for example, 24 hours in a non-oxidizing atmosphere, for example, a hydrogen or nitrogen atmosphere.

Thereafter, an island-shaped NTFT region 111 was formed using the photomask P3. On this, a silicon oxide film 108 is used as a gate insulating film,
It was formed to a thickness of {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.

Thereafter, 1 to 5 × 10
A silicon film having a concentration of ²¹ cm ⁻³ or a multilayer film of the silicon film and molybdenum (Mo), tungsten (W), MoSi ₂ or WSi ₂ was formed thereon. This was patterned using a fourth photomask P4 to form a gate electrode 109 for NTFT as shown in FIG. 9D. For example, a channel length was 7 μm, and a gate electrode was formed of 0.2 μm of lindobe silicon and 0.3 μm of molybdenum thereon. Although not shown in the figure, a gate wiring and a wiring parallel to the gate wiring were also formed as in the case of the first embodiment.

As a material for the wiring, for example, aluminum (Al) can be used in addition to the above-mentioned materials. When aluminum is used, the surface is anodically oxidized after patterning with a fourth photomask P4, so that the self-alignment method can be applied. Therefore, the source / drain contact holes are located closer to the gate. Since it can be formed, the characteristics of the TFT can be further improved by reducing the mobility and the threshold voltage.

Further, in FIG. 9E, a silicon oxide film was formed on the interlayer insulator 113 by the above-described sputtering method. This silicon oxide film may be formed by an LPCVD method, a photo CVD method, or a normal pressure CVD method. For example, 0.2
After that, a window 117 for an electrode was formed using the fifth photomask P5. Thereafter, further, aluminum is formed on the entire surface to a thickness of 0.3 μm by sputtering to form a sixth photomask P6.
After the lead 116 and the contact 114 were formed by using the method described above, the surface was coated with an organic resin 119 for flattening, for example, a translucent polyimide resin, and the electrode hole was formed again using the seventh photomask P7. In addition, these
TO (indium tin oxide) was formed to a thickness of 0.1 μm by a sputtering method, and a pixel electrode 118 was formed using an eighth photomask P8. This ITO is between room temperature and 150 ℃
And achieved by annealing at 200 to 400 ° C. in oxygen or air.

The electrical characteristics of the TFT obtained as described above have a mobility of 90 (cm ² / Vs) and a Vth of 4.
8 (V).

One substrate for a liquid crystal electro-optical device manufactured according to the above method was obtained. The method for fabricating the other substrate is the same as that in the first embodiment, and will not be described.
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. This was connected to a rear lighting device in which three cold cathode tubes were arranged, and a tuner for receiving TV radio waves to complete a wall-mounted TV. Compared to a conventional CRT system television, the device has a flat shape, so that it can be installed on a wall or the like. The operation of this LCD TV is shown in FIG.
By applying a substantially equivalent signal to the liquid crystal pixels,
It was confirmed that display of 128 gradations was possible.

The embodiment shown in this specification is characterized in that digital gray scale display is performed in contrast to conventional analog gray scale display. The effect is, for example, 6
Assuming a liquid crystal electro-optical device having a pixel number of 40 × 400 dots, it is very difficult to manufacture all the characteristics of all 256,000 TFTs without variation, and in reality, mass production is difficult. , considering the yield, whereas 16 gradation display is believed to limit, in example
As described above, by performing gray scale display by purely digital control without adding any analog signal, 256
A gradation display higher than the gradation display has become possible. Since it is a complete digital display, there is no ambiguity of gradation due to variation in TFT characteristics. Therefore, even if there is little variation in TFT, extremely uniform gradation display was possible. Therefore, while the yield was extremely poor in order to obtain a TFT with little variation in the past , the
With this configuration, the yield of TFTs is not so much a problem, so that the yield of TFTs is improved and the manufacturing cost can be significantly reduced.

For example, 256,0 of 640 × 400 dots
When a normal analog gradation display is performed on a liquid crystal electro-optical device in which 00 sets of TFTs are formed in a 300 mm square,
Since there is about ± 10% variation in TFT characteristics,
Six gradation display was the limit. However, as shown in the examples
When digital gradation display is performed, it is hardly affected by variation in the characteristics of the TFT elements, so that it is possible to display up to 256 gradations.
A variety of 216 colors can be displayed in subtle colors. In the case of displaying software such as television images, for example, even a “rock” made of the same color has a slightly different color due to its minute dents and the like. If you try to display something close to the colors of nature,
Difficulty is required for 16 gradations. With the gradation display according to the present invention, it is possible to impart these minute color changes.

In the embodiments disclosed in this specification , description has been made mainly on TFTs using silicon, but TFTs using germanium can be used similarly. In particular, the electron mobility of the single crystal germanium 3600 cm ² / Vs, the Hall mobility and 1800 cm ² / Vs, the single crystal silicon value of (1350 cm ² / Vs in electron mobility, 480 cm ² / Vs in hole mobility) Higher than characteristic
It is a very excellent material for high- speed operation . In addition, germanium has a lower transition temperature from an amorphous state to a crystalline state than silicon, and is suitable for a low-temperature process. In addition, the nucleation rate during crystal growth is low, and therefore, generally, large crystals are obtained when polycrystals are grown. Thus, germanium has characteristics comparable to those of silicon.

[0087]

According to the present invention, a driving switching element is provided.
In electro-optical devices using thin film transistors
To provide an electro-optical device that performs good optical modulation
Was completed.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a driving waveform according to an embodiment.

FIG. 2 shows an example of a driving waveform according to an embodiment.

FIG. 3 shows an example of a driving waveform according to an embodiment.

4 is a diagram showing an example of a matrix structure according to the embodiment.

FIG. 5 is a diagram showing a planar structure of an element according to an example.

FIG. 6 is a diagram showing a TFT process according to the embodiment.

FIG. 7 is a diagram showing a TFT process according to the embodiment.

FIG. 8 is a view showing a process of a color filter according to an example.

FIG. 9 is a diagram showing a TFT process according to the embodiment.

FIG. 10 illustrates a connection example of a protection circuit.

FIG. 11 illustrates an example of a protection circuit.

FIG. 12 illustrates an example of a protection circuit.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-2-294622 (JP, A) JP-A-1-156725 (JP, A) JP-A-2-278749 (JP, A) JP-A-1- 229 229 (JP, A) Fully open 1-114278 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/136 G02F 1/1343 G02F 1/1333 G09F 9/30 H01L 29/78

Claims (9)

(57) [Claims] A substrate having an insulating surface; at least one thin film transistor formed on the insulating surface; and a thin film transistor formed on the insulating surface so as to cover the thin film transistor.
And made a silicon oxide film, a wiring which said thin film transistor is connected, the organic resin film formed on the thin film transistor above, formed on the organic resin film and the silicon oxide film Conta
To connect to the thin film transistor through the Kutohoru
Sea urchin, wherein an electro-optical device for chromatic and the organic resin film pixel electrode formed on the end portion of Oite the organic resin film in the contact hole
And tinged with round Mi, in the silicon oxide film, the diameter of the contact hole
An electro-optical device characterized by being uniform . Wherein a substrate having an insulating surface, said at least one thin film transistor formed on an insulating surface, the shape on the insulating surface to cover the thin film transistor
And made a silicon oxide film, a wiring which said thin film transistor is connected, the organic resin film formed on the thin film transistor above, formed on the organic resin film and the silicon oxide film Conta
To connect to the thin film transistor through the Kutohoru
Sea urchin, wherein an electro-optical device for chromatic and the organic resin film pixel electrode formed on the, in the organic resin film, the diameter of the contact hole
Write from the lowermost layer of the top layer is rather large, in the silicon oxide film, the diameter of the contact hole
An electro-optical device characterized by being uniform . 3. A substrate having an insulating surface, at least one thin film transistor formed on the insulating surface, and a thin film transistor formed on the insulating surface to cover the thin film transistor.
And it made a silicon oxide film, and the organic resin film formed on the thin film transistor above, formed on the organic resin film and the silicon oxide film Conta
To connect to the thin film transistor through the Kutohoru
Sea urchin, wherein an electro-optical device for chromatic and the organic resin film pixel electrode formed on the, in the organic resin film, the diameter of the contact hole
The uppermost layer is larger than the lowermost layer, and in the silicon oxide film, the diameter of the contact hole is
An electro-optical device characterized by being uniform . 4. A substrate having an insulating surface, a semiconductor film , an insulating film, and a gate formed on the insulating surface.
A plurality of thin film transistors having a gate electrode , and the insulating surface so as to cover the plurality of thin film transistors.
A silicon oxide film formed above the the organic resin film formed to the thin film transistor above, corresponding to said plurality of thin film transistors, a plurality of con formed in the silicon oxide film and the organic resin film
And contact holes, the plurality of corresponding through said plurality of contact holes
Respectively directly connected to the thin film transistor of the semiconductor film
As described above, an electro-optical device which have a, a plurality of pixel electrodes formed on the organic resin film, in the organic resin film, the diameter of the contact hole
The uppermost layer is larger than the lowermost layer, and in the silicon oxide film, the diameter of the contact hole is
An electro-optical device characterized by being uniform . 5. A substrate having an insulating surface, and a semiconductor film , an insulating film, and a gate formed on the insulating surface.
A plurality of thin film transistors having a gate electrode , and the insulating surface so as to cover the plurality of thin film transistors.
A silicon oxide film formed thereon; and a plurality of first contact holes formed on the silicon oxide film.
Lumpur and such that each of the corresponding pre <br/> SL plurality of thin film transistors directly connected through said plurality of first contact holes
To the plurality of wirings formed on a silicon oxide film, and the organic resin film formed on the thin film transistor above, corresponding to said plurality of thin film transistors, formed on the silicon oxide film and the organic resin film Multiple second
And the contact hole, so as to respectively connect directly to the semiconductor film of said plurality of thin film transistors corresponding through said plurality of second contact holes, an electro-optic having a plurality of pixel electrodes formed on the organic resin film The device , wherein the second contact hole is formed in the organic resin film.
Is larger in the uppermost layer than in the lowermost layer, and in the silicon oxide film, the diameter of the contact hole is
An electro-optical device characterized by being uniform . 6. The method according to claim 4, wherein
The semiconductor film is a polycrystalline silicon film.
Optical device. 7. The electro-optical device according to claim 1 , wherein the pixel electrode is made of a light-transmitting conductive film. 8. The electro-optical device according to claim 7 , wherein the light-transmitting conductive film contains indium tin oxide. 9. The organic resin film according to claim 1 , wherein the organic resin film contains a light- transmitting polyimide .
Electro-optical device, characterized in that that.