JP2001042364A - Electro-optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain stable display by constituting the gate electrode of each of a first P channel (PT) type thin film transistor and a second N channel (NT) type thin film transistor from a metal film or a metal film and metal silicide film, and a silicon film into which phosphorus is introduced. SOLUTION: A silicon oxide film as a blocking layer 51 is formed into specified thickness on a glass 50 having durability against specified temperature by a magnetron high frequency sputtering method. Then a silicon film is formed by a low pressure vapor phase method, sputtering method or the like. Then after a silicon film in an amorphous state is formed into specified thickness, the film is heat-treated at a specified temperature for a specified time in a nonoxidative atmosphere. Thereby, the whole film is uniformly annealed by heating so that the film has an amorphous structure during film-forming. The silicon film changes from the amorphous structure to a highly ordered state by annealing and shows a crystal state. Thus, in the obtained film, regions having high crystallinity, namely clusters are coupled with silicon atoms.

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 liquid crystal display device.
The present invention relates to an electro-optical device in which each pixel is provided with two thin-film insulated gate field effect transistors (hereinafter referred to as TFTs) of a P-channel type and an N-channel type in a complementary manner to form a pixel.

[0002]

2. Description of the Related Art Conventionally, an effective display device has been
2. Description of the Related Art An active liquid crystal display device using an FT is known. In this case, a semiconductor having an amorphous or polycrystalline structure is used for the TFT, and a TFT using only one of the P and N conductivity types is used for one pixel. That is, generally, an N-channel TFT (referred to as NTFT) is connected in series to the pixel. FIG. 8 shows a typical example.

In general, an active matrix type liquid crystal display device has a very large number of pixels of 480 × 640 or 1260 × 960. FIG. 8 shows the same meaning as above, and is shown in a 2 × 2 matrix arrangement for simplicity of explanation. Arranged orthogonally plurality of gate lines G _1, G ₂ and a plurality of data lines D _1, and D _2, is provided with a pixel display element at the intersection of the matrix. This pixel display element includes a liquid crystal unit 102 and a TFT unit 101. Peripheral circuits 106, 10 for each pixel
7, a signal is added, and a predetermined pixel is selectively turned on or off to perform display.

However, these liquid crystal display devices were actually manufactured.
When the display is manufactured and displayed, the output of the TFT, ie, the liquid crystal
The input voltage (referred to as the liquid crystal potential) V_LC100 is
Often when "1" (High) should be "1" (High)
And if it is "0" (Low) when it should be "0" (Low)
Absent. This is a switching element that applies a signal to the pixel,
That is, it occurs because there is no symmetry in the characteristics of the TFT.
In other words, the state of charging and discharging of the pixel electrode
This is because there is a bias on the characteristics. And the liquid crystal 10
2 are inherently insulating in their operation, and
When T is off, the liquid crystal potential (V_LC) Floats. This
Liquid crystal 102 is equivalent to a capacitor,
V due to the charge stored in_LCIs determined. This charge
Means that the liquid crystal is R _LCWith relatively small resistance,
Leakage due to the presence of ionic impurities, or TFT
R due to the pinhole of the gate insulating film_GS105 has occurred
In that case, the charge leaks from it and V_LCIs in an incomplete state
turn into. For this reason, 200,000 to 500 in one panel
High yield in a liquid crystal display device with 10,000 pixels
There was a problem that Mari could not be achieved.

As the liquid crystal 102, a TN (twisted nematic) liquid crystal is generally used. A rubbed alignment film is provided on each electrode to align the liquid crystal. A weak dielectric breakdown occurs due to static electricity generated by the rubbing process, leading to leakage between adjacent pixels or adjacent conductors, or leakage due to weak gate insulating film. I will.

[0006]

In an active type liquid crystal display device, it is extremely important to keep the liquid crystal potential at the same level as the initial value during one frame to keep a predetermined level. However, in practice, there are many malfunctions of the active element, and in reality, it is not always possible to keep the liquid crystal potential at the same level as the initial value and the predetermined level during one frame. In addition, in driving a liquid crystal or the like, when a voltage applied to the liquid crystal is biased to either + or-due to a signal to be applied, electrolysis or the like occurs, and the liquid crystal material is decomposed and denatured so that display can be sufficiently performed. Nothing happens. in this case,
The applied signal is converted into an alternating current so that the voltage applied to the liquid crystal material is not biased. However, the alternating signal is very complicated.

The present invention solves the above-mentioned problems, and
To increase the current margin, that is, to increase the response speed.
You. Also, the potential of the pixel in each pixel, that is, the liquid crystal
Potential V _LCIs fixed to "1" and "0" stably enough, and 1 frame
To prevent the level from drifting during
You.

Further, gray scale display is demanded to meet the demand for color display and high quality display devices, but the driving method for gray scale display is very complicated.

[0009]

According to the present invention, an NTFT and a PTFT are provided for a pixel in a complementary configuration, and the NTFT and the PTFT are provided.
A source (drain) portion of the FT is connected to a first signal line of the pair of signal lines, a source (drain) portion of the PTFT is connected to a second signal line of the pair of signal lines,
A method for driving a display device, wherein a gate electrode of the NTFT and a PTFT is commonly connected to a third signal line, and a drain (source) portion of the NTFT and a PTFT is connected to a pixel electrode. By applying a signal waveform to the third signal line during a period when a signal waveform is applied to the pair of first and second signal lines, the complementary thin film transistor (hereinafter referred to as C / TFT) is applied. ) To drive the display of the pixel on or off. In addition, the potential difference applied to the liquid crystal is changed according to the level of the voltage of the signal applied to the third signal line, thereby enabling gray scale display.

As a configuration of a display device to which the driving method of the present invention can be applied, two or more C / Cs are provided for one pixel.
One pixel may be formed by connecting TFTs. Further, one pixel may be divided into two or more, and one or more C / TFTs may be connected to each.

A typical example of the configuration of a display device to which the driving method of the present invention can be applied is shown as a circuit diagram in FIGS.
FIGS. 5, 6, and 7 show examples of actual pattern layouts (arrangement diagrams), respectively. For the sake of simplicity, a description will be given of a 2 × 2 matrix configuration as an example. In the example of the 2 × 2 matrix in FIG.
The gates of the NTFT and PTFT are connected to each other, further connected to the third signal line 3 or 4 in the Y-axis direction, and the common output terminal of the C / TFT is connected to the liquid crystal 15. An input terminal (10 side) of the NTFT is connected to a first signal line 5 or 6 of a pair of signal lines in the X-axis direction, and a PTF
The input terminal (20 side) of T is connected to the second signal line 8 or 7 of the pair of signal lines in the X-axis direction.

In such a configuration, as shown in FIG. 1, the third signal is applied during the period in which the ON signal waveform is applied between the pair of the first signal line 5 and the second signal line 8. When an ON signal waveform is applied to line 3, the liquid crystal potential (V _LC ) 1
4 is the voltage V _GG -Vth applied to the first signal line. Further, the third signal line 3 is turned on during a period in which the off signal waveform is applied between the pair of the first signal line 5 and the second signal line 8.
When the OFF signal waveform is applied, the liquid crystal potential (V _LC ) 1
4 has no potential. Further, when the ON signal waveform is not applied to the third signal line 3 during the period when the ON signal waveform is applied between the pair of the first signal line 5 and the second signal line 8, the liquid crystal potential (V _LC ) 14 similarly has no potential. As described above, the liquid crystal potential (V _LC ) 14 is given according to the voltage applied to the third signal line, and the potential difference applied to the liquid crystal can be arbitrarily changed by changing the voltage of the signal applied to this signal line. can do.

The counter electrode 16 has an offset voltage V
_{The OFFSET} is applied, and the voltage actually applied to the liquid crystal 15 has two values of V _GG + V _OFFSET −Vth or V _OFFSET . According to the driving method of the present invention, the on / off of the liquid crystal driving can be arbitrarily changed by changing the offset voltage V _OFFSET applied to the counter electrode. Also, since the threshold value for actually driving the liquid crystal differs depending on the liquid crystal material, the offset voltage V is adjusted to match the value of the liquid crystal.
Any threshold can be adjusted simply by changing _OFFSET .

In driving a liquid crystal or the like, if a voltage applied to the liquid crystal is biased to either + or-by an applied signal, electrolysis or the like occurs to decompose the liquid crystal material.
In such a case that the display cannot be performed sufficiently due to denaturation. In this case, the applied signal is converted into an alternating current so that the voltage applied to the liquid crystal material is not biased. However, according to the driving method of the present invention, the applied voltage is applied to the counter electrode. An AC signal can be generated very easily only by inverting the polarity of the offset voltage V _OFFSET and the logic of the selection signal applied to the data signal line.

In the example shown in FIG. 3, the third signal line 3 in the Y direction shares the four gate electrodes of the NTFT 13 PTFT 22 forming the first C / TFT and the NTFT 24 and PTFT 25 forming the second C / TFT. To N
The input terminals of the TFT 13 and the NTFT 24 are made common, and the input terminals of the PTFT 22 and PTFT 25 are made common and connected to the second signal line 8 in the X direction. In addition, the outputs of the two C / TFTs are shared and connected to a pixel electrode 17 which is one electrode of one liquid crystal 15. Thus, two NTFTs or two PTFTs
Even if either one of them leaks to some extent, the pixel is driven because it is in phase.

FIG. 4 shows that in one pixel 23, two pixel electrodes 17, 26 and their corresponding C / T
In this example, two FTs are provided. The gate electrode of the two C / TFTs is made common, and the first input is performed. The input of each NTFT and each PTFT of each C / TFT is connected to a first signal line 5 and a second signal line 8. Thus, one of the two pixels in one pixel does not become inoperative due to a defect such as a leak of the TFT. Further, even if the operation is delayed, the other operates normally, so that a defect is less noticeable in the matrix configuration operation.

[0017]

[Embodiment 1] In this embodiment, description will be made using a liquid crystal display device having a circuit configuration as shown in FIG. FIG. 5 shows an actual arrangement of electrodes and the like corresponding to this circuit configuration. For simplification of description, only portions corresponding to 2 × 2 are described. FIG. 9 shows an actual drive signal waveform. For the sake of simplicity, the description will be made using signal waveforms in the case of a 4 × 4 matrix configuration.

First, a method for manufacturing a liquid crystal display device used in this embodiment will be described with reference to FIGS. In FIG. 13A, a silicon oxide film as a blocking layer 51 is formed on a glass 50, such as quartz glass, which can withstand a heat treatment at an inexpensive temperature of 700 ° C. or less, for example, about 600 ° C., using a magnetron RF (high frequency) sputtering method. It is made to a thickness of 3000 mm. The process conditions are 100% oxygen atmosphere,
Film formation temperature 15 ° C, output 400-800W, pressure 0.5P
a. 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. The pressure inside the reactor is 30-30
0 Pa was set. The deposition rate was 50-250 ° / min. In order to control the threshold voltage (Vth) of the NTFT and PTFT substantially the same, boron may be added at a concentration of 1 × 10 ¹⁵ to 1 × 10 ¹⁸ cm ⁻³ during the film formation using diborane. .

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 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 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:
It is preferable that oxygen is 5 × 10 ²¹ cm ⁻³ or less. If the oxygen concentration is high, it is difficult to crystallize, and the thermal annealing temperature must be high or the thermal annealing time must be long. If the amount is too small, the leakage current in the off state increases due to the backlight. Therefore, 4 × 10 ¹⁹ ~
The range was 4 × 10 ²¹ cm ⁻³ . Hydrogen was 4 × 10 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 or less, preferably 1 × 10 ¹⁹ cm ⁻³ or less, and a channel forming region of a TFT constituting a pixel is formed. 5 × 10 ²⁰ only by oxygen ion implantation
You may add so that it may be set to about 5 * 10 < ²¹ > cm < ^-3 >. At that time,
Since light irradiation is not performed on the TFTs constituting the peripheral circuit, it is effective to reduce the mixing of oxygen and to have a higher carrier mobility for high-frequency operation.

Next, the silicon film in an amorphous state is
After fabrication to a thickness of ~ 5000mm, for example 1500mm, 4
Medium-temperature heat treatment in a non-oxide atmosphere at a temperature of 50 to 700 ° C. for 12 to 70 hours, for example, 60 hours in a hydrogen atmosphere
It was kept at a temperature of 0 ° C. 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 into a crystalline state. However, since the silicon existing between these regions is bonded to each other, the silicon mutually pulls each other. When measured by laser Raman spectroscopy, a peak shifted from the single crystal silicon peak 522 cm ^-1 to a lower frequency side is observed. The apparent grain size of the crystal is 50 to 500 ° when calculated from the half-value width, which is like a microcrystal. However, in actuality, there are many regions having high crystallinity and a cluster structure. Was able to form a film having a semi-amorphous structure in which silicon bonds with each other (anchoring).

As a result, the coating exhibits a state substantially free of grain boundaries (hereinafter referred to as GB). Carriers can easily move between each cluster through anchored locations, so-called so-called
Higher carrier mobility than polycrystalline silicon which is clearly present in GB. That is, the hole mobility (μh) = 10 to 200
cm ² / VSec, electron mobility (μe) = 15 to 300
cm ² VSec is obtained.

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

In FIG. 13A, a silicon film is subjected to photoetching using a first photomask, and a PTFT region 22 (channel width 20 μm) is placed on the right side of the drawing at NT.
A region 13 for FT was formed on the left side.

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

Thereafter, 1 to 5 × 10 ²¹ cm of phosphorus is placed on the upper side.
A silicon film having a concentration of ^-3 or a multilayer film of molybdenum (Mo), tungsten (W), MoSi ₂ or WSi ₂ was formed thereon. This was patterned using a second photomask to obtain FIG. 13 (B). PTFT
A gate electrode 55 for NTFT and a gate electrode 56 for NTFT were formed. For example, a channel length of 10 μm, a gate electrode of 0.2 μm of silicon-doped silicon and a thickness of 0.3 μm of molybdenum thereon were formed. In FIG. 13C,
A photoresist 57 is formed using a photomask,
Boron was added to the source 59 drain 58 for the PTFT by ion implantation at a dose of 1 to 5 × 10 ¹⁵ cm ⁻² . Next, as shown in FIG.
1 was formed using a photomask. A source 64 for NTFT and phosphorus as drain 62 from 1 to 5 × 10 ¹⁵ cm
A dose of ^-2 was added by ion implantation.

These operations were performed through the gate insulating film 54. However, in FIG. 13B, the gate electrode 55,
The silicon oxide on the silicon film is removed using 56 as a mask,
Thereafter, boron or phosphorus may be directly ion-implanted into the silicon film.

Next, annealing was performed again at 600 ° C. for 10 to 50 hours. The source 59 of the PTFT and the source 64 and the drain 62 of the drain 58NTFT were formed as P ⁺ and N ⁺ by activating impurities. Channel formation regions 60 and 63 are formed below the gate electrodes 55 and 56 as semi-amorphous semiconductors.

In this way, a C / TFT can be manufactured without applying a temperature to 700 ° C. or more in all steps, even though it is a self-aligned system. for that reason,
It is not necessary to use an expensive substrate such as quartz as a substrate material, and this is a process very suitable for the large pixel liquid crystal display device of the present invention.

In this embodiment, the thermal annealing is performed as shown in FIG.
(A) and (D) were performed twice. However, the annealing in FIG. 13A is omitted due to the characteristics required, and both are omitted in FIG.
The annealing time of (D) may also be used to shorten the manufacturing time. In FIG. 13E, a silicon oxide film was formed on the interlayer insulator 65 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, 0.2-0.6μ
m, and then a window 66 for an electrode was formed using a photomask. Further, aluminum is formed on the entire surface by sputtering, and leads 71 and 72 and contacts 67 and 68 are formed using a photomask. Then, the surface is flattened with an organic resin 69 for flattening, for example, a translucent polyimide resin. It was formed and the electrode drilling was performed again using a photomask.

As shown in FIG. 13 (F), in order to connect the two TFTs to a complementary structure and connect the output terminals thereof to the electrodes of one pixel of the liquid crystal device as transparent electrodes, ITO (indium oxide) is formed by sputtering. A tin oxide film). It is etched using a photomask and the electrodes 7
0 was configured. This ITO was formed at room temperature to 150 ° C., and was achieved by oxygen at 200 to 400 ° C. or annealing in the air. Thus, PTFT 22 and NT
The FT 13 and the transparent conductive electrode 70 are made of the same glass substrate 5.
0. The electrical characteristics of the obtained TFT are PT
In FT, the mobility is 20 (cm ² / Vs) and Vth is −5.9.
In (V), the mobility of NTFT was 40 (cm ² / Vs) and Vth was 5.0 (V).

A transparent electrode is provided on the entire surface of one of the substrates for the liquid crystal device and the other glass substrate manufactured according to the method as described above, and these substrates are laminated to form a liquid crystal cell.
A TN liquid crystal material was injected therein. FIG. 6 shows the arrangement of the electrodes and the like of the liquid crystal display device. NTFT1
3 is provided at the intersection of the first scanning line 5 and the data line 3, and NTFTs for other pixels are similarly provided at the intersection of the first scanning line 5 and the data line 4. On the other hand, the PTFT is provided at the intersection of the second scanning line 8 and the data line 3. An NTFT for another pixel is provided at the intersection of the adjacent first scanning line 6 and data line 3. A matrix configuration using such a C / TFT is provided. The NTFT 13 is connected to the first scanning line 5 via a contact at the input end of the drain 10, and the gate 9 is connected to the data line 3 on which a multilayer wiring is formed.
An output terminal of the source 12 is connected to a pixel electrode 17 via a contact.

On the other hand, the PTFT 22 has an input terminal of the drain 20 connected to the second scanning line 8 via a contact,
The gate 21 is connected to the data line 3 and the output end of the source 18 is connected to the pixel electrode 17 via a contact in the same manner as the NTFT. Thus, the pixel 23 made of the transparent conductive film and the C / TFT are interposed (inside) between the pair of scanning lines 5 and 8.
And thereby constituted one pixel. By repeating such a structure left, right, up and down, a liquid crystal display device having a large pixel of 640 × 480 or 1280 × 960 obtained by enlarging a 2 × 2 matrix can be obtained.

The feature here is that one pixel has two TFs.
Since T is provided in a complementary configuration, the pixel electrode 17 is fixed at three values of the liquid crystal potential _VLC . The operation will be described with reference to FIGS. FIG. 9 shows a circuit diagram of the present invention when performing a 4 × 4 matrix liquid crystal display, and FIG. 10 shows a timing chart of drive signal waveforms.

In the case of the present embodiment, X _1a X _1b , X _2a X _2b , X
Each of _3a X _3b and X _4a X _4b functions as a pair of scanning signal lines. Y ₁ , Y ₂ , Y ₃ , and Y ₄ function as data lines. .., DD in FIG. 9 indicate the addresses of the pixels at the corresponding positions.

In such a 4 × 4 display,
Dress AA, AB, BA, BB
The signal waveform, the liquid crystal potential and the potential actually applied to the liquid crystal
The timing chart of the difference is shown in FIG. Figure 10
The horizontal axis indicates time. 1 frame is time T1
From T2 to T2, the interval is divided into four, and a pair of scanning
Scanning signals are applied by sequentially scanning four pairs of lines. In the figure
X_1a, X_2a, X_3a, X_4aBut only actually
Is X_1b, X_2b, X_3b, X_4bX_1a, X_2a, X_3a, X_4a
And the same waveforms having different polarities are applied. Also,
Y₁, Y_Two, Y_Three, Y _FourThe data signal shown in FIG.
Signal is applied, and between time T1 and T2, AA
Only the pixels are selected and turned on or off. That is, T₁
To t₁Data line Y₁Apply data signal to
During this time, a threshold is applied to the liquid crystal of the AA pixel.
Voltage is applied to drive the liquid crystal. At this time, the liquid crystal table
An offset voltage is applied to a counter electrode of the display device.
In FIG. 10, the same signal wave is also used from the next time T2 to T3.
The shape is applied and AA is displayed.

Next, from time T3 to T4 and from T4 to T5
In this example, a signal that does not select four pixels is applied. Further, from time T5 to T6, a signal for selecting the AA pixel is applied again.

Next, from time T6 to T8, a signal obtained by inverting the logic of the signal applied to the data line is applied, and the counter electrode has a polarity opposite to that of the signal applied during time T1 to T6. Different offset voltages are applied and an alternating signal is applied to the liquid crystal. With this alternating signal,
It is possible to cancel the positively biased charge between the times T1 and T6. That is, of the signal which has been applied from time T2 to _{T4, Y 1, Y 2,} Y 3, inverts the logic of Y _4-wire, i.e., interchanged selection signal and a non-selection signal, the offset voltage of the counter electrode By exchanging the positive / negative, in the first frame of the time T2 to T4, A
The pixel A is selected, and in the latter half frame, an alternating signal that does not select four pixels can be applied, and the liquid crystal can be driven. This makes it possible to easily cancel the charge remaining in the pixel.

As described above, the potential difference actually applied to the liquid crystal depends on the voltage of the signal of the third signal line, in this embodiment, the pulse voltage of the data line and the offset voltage of the counter electrode.
This is the potential obtained by subtracting th. That is, if the pulse voltage of the data line is arbitrarily changed, the potential difference actually applied to the liquid crystal can be changed accordingly. Thereby, gradation display can be performed. In particular, sufficient gradation display can be performed by a driving method particularly well suited to a liquid crystal drive whose threshold value is not clear, that is, a dispersion-type liquid crystal having a gentle threshold.

As described above, according to the driving of the present invention, liquid crystal display can be performed only by applying a very simple pulse signal to the data line and the pair of scanning lines.

As another gradation method, when one screen is displayed by applying a plurality of frames of driving signals to the liquid crystal for one display screen, a selection signal to be applied to a specific pixel is set to the number of frames for all frames. By reducing the number, gradation display can be easily performed.

In this embodiment, if TN liquid crystal is used as the liquid crystal material, it is necessary to set the distance between the substrates of the liquid crystal container to about 10 μm, provide an alignment film on both transparent conductive films, and perform rubbing treatment. .

When an FLC (ferroelectric) liquid crystal is used as the liquid crystal material, the operating voltage is set to ± 20 V, and the cell interval is set.
The thickness may be 1.5 to 3.5 μm, for example, 2.3 μm, and an alignment film may be provided only on the counter electrode 16 and subjected to rubbing treatment.

When a dispersion type liquid crystal or a polymer liquid crystal is used, an alignment film is unnecessary, and an operating voltage is ± 10 to ± 15 V and a cell interval is 1 in order to increase a switching speed.
薄 く 10 μm.

In particular, when a dispersion type liquid crystal is used, since a polarizing plate is not required, the amount of light can be increased both in a reflection type and in a transmission type. Since the liquid crystal does not have a threshold, a C / TFT type in which a clear threshold voltage is defined as in the present invention provides a large contrast and crosstalk (defect with adjacent pixels). Interference) could be eliminated.

Further, as the semiconductor of the TFT used in this embodiment, materials other than those used in this embodiment can be used.

[0050]

[Embodiment 2] In this embodiment, the present embodiment was carried out using a liquid crystal display having the structure shown in FIGS. As is apparent from this drawing, the scanning line 3 of the Y line is disposed at the center, and a portion of the pair of data lines sandwiched between the first data line 5 and the second data line 8 is defined as one pixel 23. . One pixel is one pixel of one transparent conductive film
7 and two NTFTs 13, 24 and two PTFTs
22 and 25 are connected to two C / TFTs. The gate electrodes are all connected to scan line 3 and have two N
The TFT is connected to the first data line 3 and the two PTFTs are connected to the second data line 8. These two C / T
Even if one of the FTs is defective due to a leak between the gate electrode and the channel formation region, it can be operated as a pixel.

The feature here is that one pixel has two C /
Since the TFT is provided, the pixel electrode 17 has 3 pixels.
The liquid crystal potential _VLC is fixed to two values. The operation will be described with reference to FIGS. FIG. 9 shows a circuit diagram of the present invention when a liquid crystal display of a 4 × 4 matrix configuration is performed, and FIG. 11 shows a timing chart of drive signal waveforms.

In the case of this embodiment, X _1a X _1b , X _2a X _2b , X
_3a X _3b and X _4a X _4b each function as a pair of data lines. Further, Y ₁ , Y ₂ , Y ₃ , and Y ₄ function as scanning lines. .., DD in FIG. 9 indicate the addresses of the pixels at the corresponding positions.

In such a 4 × 4 display,
Dress AA, AB, BA, BB
The signal waveform, the liquid crystal potential and the potential actually applied to the liquid crystal
FIG. 11 shows a timing chart of the difference. Figure 11
The horizontal axis indicates time. 1 frame is time T1
From T2 to T2, dividing the interval into four
Y₁, Y_Two, Y_Three, Y_FourLines are scanned sequentially and scanning signals
Is applied. Also, X₁, X_Two, X_Three, X_FourOn the line
Are applied with a data signal as shown in FIG. In the figure
Is X_1a, X_2a, X_3a, X_4aOnly listed but actually
Is X_1b, X_2b, X_3b, X _4bX_1a, X_2a, X_3a, X_4a
And the same waveform with a different polarity is applied.
Between A and T2, only AA pixels are selected and turned on or off
Is done. That is, T₁To t₁A pair of data lines between
X₁Is applied to AA within this time.
The voltage exceeding the threshold is applied to the liquid crystal of
And the liquid crystal is driven. At this time, the pair of liquid crystal display
An offset voltage is applied to the anti-electrode. In FIG.
The same signal waveform is applied from the next time T2 to T3,
AA is displayed.

Next, from time T3 to T4 and from T4 to T5
In this example, a signal that does not select four pixels is applied. Further, from time T5 to T6, a signal for selecting the AA pixel is applied again.

Next, from time T6 to T8, a signal obtained by inverting the logic of the signal applied to the pair of data lines is applied, and the signal applied to the counter electrode during the time T1 to T6 is When offset voltages with different polarities are applied,
An alternating signal is applied to the liquid crystal. With this alternating signal, the charges that have been positively biased between times T1 and T6 can be canceled. In practice, from time T2 to T
4, a pair of X ₁ , X ₂ , X
_3, inverts the logic of X _4-wire, i.e. interchanged selection signal and a non-selection signal, by replacing the positive and negative offset voltage of the counter electrode, in the first half of the frame to select the pixels of AA, 4 one in the second half of the frame An alternating signal that does not select a pixel can be applied, and the liquid crystal can be driven.

As described above, according to the driving of the present invention, a liquid crystal display can be performed only by applying a pulse signal to a data line and a pair of scanning lines, which is very simple. Further, similarly to the first embodiment, gradation display can be performed by changing the signal voltage on the scanning line side.

[0057]

Embodiment 3 In this embodiment, the present embodiment was carried out using a liquid crystal display having the structure shown in FIGS. As is apparent from this drawing, the data line 3 of the Y line
Is disposed at the center, and the first scanning line 5 and the second scanning line 5
The portion between the scanning lines 8 is defined as one pixel 23. One pixel is composed of two pixel electrodes 17 and 26 made of a transparent conductive film.
The TFT 22 is connected, and the pixel 26 has an NTFT 24,
PTFTs 25 are each connected as a C / TFT configuration. The gate electrodes are all connected to data line 3 and
One NTFT is connected to the first scan line 3 and two PTFTs
Are connected to the second scanning line 8. These two C /
Even if one of the TFTs is defective due to a leak between the gate electrode and the channel formation region, the TFT can operate as a pixel. Thus, even if one of the pixels only operates halfway, the other pixel operates normally and the degree of deterioration of the gray scale can be reduced when the pixel is colorized.

The operation will be described with reference to FIGS. 9 and 12. FIG. 9 shows a circuit diagram of the present invention when a liquid crystal display of a 4 × 4 matrix configuration is performed, and FIG. 12 shows a timing chart of drive signal waveforms.

In the case of this embodiment, X _1a X _1b , X _2a X _2b , X
Each of _3a X _3b and X _4a X _4b functions as a pair of scanning signal lines. Y ₁ , Y ₂ , Y ₃ , and Y ₄ function as data lines. .., DD in FIG. 9 indicate the addresses of the pixels at the corresponding positions.

In such a 4 × 4 display,
Dress AA, AB, BA, BB
The signal waveform, the liquid crystal potential and the potential actually applied to the liquid crystal
Fig. 12 shows the timing chart of the difference. In FIG.
Here, the horizontal axis indicates time. One frame at time T
This interval is divided into 16 as between 1 and T2, and a pair of
A scanning signal is applied by sequentially scanning four pairs of scanning lines. Figure
Then X_1a, X_2a, X_3a, X_4aOnly listed but in fact
X_1b, X_2b, X_3b, X_4bX_1a, X_2a, X _3a, X
_4aAnd the same waveforms having different polarities are applied. Also, Y
₁, Y_Two, Y_Three, Y_FourThe data signal as shown in FIG.
Is applied and the timing is
At a specific time divided into 16 in one frame
The data signal is applied to the data line at times T1 to T
During the period 2, only the AA pixel is selected and turned on or off.
ing. That is, T₁To t₁Data line Y₁Against
A data signal is applied to the AA pixel within this time.
A voltage exceeding the threshold is applied to the crystal and the liquid crystal is driven.
You. At this time, the offset voltage is applied to the opposing electrode of the liquid crystal display.
Is applied. Next, from time T2 to T3, four
A signal that does not select any pixel is applied.

Next, from time T3 to T4, a signal obtained by inverting the logic of the signal applied to the data line is applied.
An offset voltage having a polarity different from that of the signal applied between times T1 and T3 is applied to the counter electrode, and an alternating signal is applied to the liquid crystal. With this alternating signal, charges that have been positively biased between times T1 and T3 can be canceled. That is, from time T1 to T2
, Y ₁ , Y ₂ , Y ₃ , Y ₄
By inverting the logic of the line, that is, exchanging the selection signal and the non-selection signal and exchanging the offset voltage of the counter electrode, the AA pixel is selected in the first half frame, and four pixels are selected in the second half frame. It is possible to drive the liquid crystal by applying an alternating signal that does not select any.

As described above, according to the driving of the present invention, a very simple pulse signal can be applied to a data line and a pair of scanning lines to perform a liquid crystal display. In this embodiment,
Although the scanning is performed with the scanning side as the Y line, the present invention is not particularly limited to this configuration, and the scanning side may be the X-ray side. Further, it is also possible to apply a data signal to each data line at random and select pixels at random. In addition, what is not described here is the same as that described in Examples 1 and 2.

[0063]

As described above, according to the driving method of the present invention, since the liquid crystal potential is not floating, a stable display can be performed. Further, since the driving capability of the C / TFT as the active element is high, the operation margin can be expanded, and the peripheral driving circuit can be made simpler, so that the size of the display device can be reduced and the manufacturing cost can be reduced. effective. In addition, high driving capability can be exhibited with very simple signals to the three signal lines and the counter electrode.

Even if some of the defective TFTs are in-phase output, it can be compensated to some extent.

Further, in order to prevent the liquid crystal material from being electrolyzed, the driving of the liquid crystal is performed by indispensable AC / DC signal driving.
This was achieved simply by inverting the logic of the signal applied to the FT gate signal line and inverting the polarity of the offset voltage applied to the counter electrode.

When the voltage of the signal on the third signal line is arbitrarily changed, the potential difference actually applied to the liquid crystal can be changed accordingly. Thereby, gradation display can be performed. In particular, when the threshold for driving the liquid crystal is not clear,
That is, for a dispersion type liquid crystal having a gentle threshold, a sufficient gradation display can be performed by a driving method particularly well suited. As another gradation method, when one screen is displayed by applying drive signals of a plurality of frames to the liquid crystal for one display screen, the number of selection signals to be applied to a specific pixel is reduced from the total number of frames. Thereby, gradation display can be easily performed.

The display medium of the present invention can be used as a transmission type liquid crystal display device or a reflection type liquid crystal display device. Also, usable liquid crystal materials include TN of the prior art.
Liquid crystal, FLC liquid crystal, dispersion type liquid crystal, and polymer type liquid crystal can be used. In addition, an ionic dopant is added to a guest-host type or dielectric anisotropic type nematic liquid crystal, and an electric field is applied to apply the electric field to a nematic liquid crystal and a mixture of the cholesteric liquid crystal and the nematic phase. A phase change liquid crystal which causes a phase change between the phases and realizes a transparent or opaque display can also be used. It should be noted that, other than liquid crystals, for example, a so-called electrophoretic display dispersion system in which pigment particles having different colors are dispersed in an organic solvent colored with a dye may be used.

In the present invention, when a liquid crystal is used as a display medium, the output of the C / TFT is a liquid crystal potential. In addition, since a medium other than liquid crystal may be used, in that case,
What is necessary is just to replace with the output voltage of C / TFT.

[Brief description of the drawings]

FIG. 1 shows a driving waveform of the present invention.

FIG. 2 is a circuit diagram of an active display device using complementary TFTs.

FIG. 3 is a circuit diagram of an active display device using complementary TFTs.

FIG. 4 is a circuit diagram of an active display device using complementary TFTs.

FIG. 5 shows a circuit diagram of a conventional active liquid crystal device.

6 is a plan view of one substrate of the liquid crystal display device corresponding to FIG.

7 is a plan view of one substrate of the liquid crystal display device corresponding to FIG.

8 is a plan view of one substrate of the liquid crystal display device corresponding to FIG.

FIG. 9 is a circuit diagram of a 4 × 4 active liquid crystal device using complementary TFTs.

FIG. 10 shows an example of a drive signal waveform of the present invention and a timing chart thereof.

FIG. 11 shows an example of a drive signal waveform of the present invention and a timing chart thereof.

FIG. 12 shows an example of a drive signal waveform of the present invention and a timing chart thereof.

FIG. 13 shows a manufacturing process diagram of the C / TFT used in the present invention.

[Description of Signs]-Process using photomask 1, 2-Peripheral circuit 3, 4-Third signal line 5, 6, ... First signal line 7, 8, ... .. Second signal line 13... NTFT 16... Counter electrode 17... Pixel electrode 22... PTFT 23.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 29/78 617M

Claims (10)

[Claims] 1. An electro-optical device comprising: a substrate having an insulating surface; and a plurality of thin film transistors including a first P-channel thin film transistor and a second N-channel thin film transistor formed on the insulating surface. The gate electrode of the first P-channel thin film transistor and the gate electrode of the second N-channel thin film transistor are made of a metal film or a metal film and a metal silicide film, and a silicon film into which phosphorus is introduced, respectively. Electro-optical device characterized. 2. The electro-optical device according to claim 1, wherein the concentration of phosphorus in the silicon layer into which phosphorus has been introduced is 1 × 10 ^{21 to} 5 × 10 ²¹ cm ⁻³ . 3. The electro-optical device according to claim 1, wherein the metal film is a molybdenum film or a tungsten film. 4. The electro-optical device according to claim 1, wherein the metal silicide film is made of molybdenum silicide or tungsten silicide. 5. The electro-optical device according to claim 1, wherein the first thin film transistor and the second thin film transistor form a complementary thin film transistor. 6. A substrate having an insulating surface; a plurality of thin film transistors formed on the insulating surface; an interlayer insulating film formed on the plurality of thin film transistors and having a first contact formed thereon; A plurality of wirings formed on an insulating film and connected to a source or a drain of the plurality of thin film transistors; an organic resin film formed on the plurality of thin film transistors, the interlayer insulating film and the wiring; An electro-optical device comprising: a plurality of pixel electrodes formed on a film and connected to each of the plurality of thin film transistors through a second contact formed on the organic resin film. 7. The electro-optical device according to claim 6, wherein the pixel electrode is a transparent conductive film. 8. The electro-optical device according to claim 7, wherein the transparent conductive film is made of ITO. 9. The electro-optical device according to claim 6, wherein the organic resin film is a translucent polyimide resin film. 10. The electro-optical device according to claim 6, wherein the plurality of thin film transistors include an N-channel thin film transistor and a P-channel thin film transistor.