JP2663941B2 - Active matrix panel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] The present invention relates to an active matrix.
It relates to the structure of the panel. [0002] 2. Description of the Related Art Conventional active matrix panel structure
Is "Nikkei Electronics September 10, 1984 issue N
o351P221 to 240 ".
Was. FIG. 2 shows the pixel portion of the active matrix panel.
It is an example of a top view. 22 is polysilicon or amorphous
TFT channel part and source
A drain electrode is formed. Reference numeral 24 denotes a thin film made of polysilicon or metal.
The gate electrode and the scanning line of the TFT are formed. 26 is
The pixel electrode 27 is a data line. [0004] However, the above-mentioned prior arts
Then, the following problems arise. First of all,
The voltage applied to the liquid crystal depends on the time constant of the liquid crystal itself.
When the temperature changes, the time constant of the liquid crystal changes and the display state changes.
Is also a problem. Especially at high temperatures
Contrast because the crystal resistance decreases and the time constant also decreases
G ratio decreases. The second problem is that the liquid crystal is driven by AC.
Normally, the video signal is inverted and used because it is necessary
However, due to the difference in polarity of this signal, writing and
Since the holding state is also different, the voltage applied to the liquid crystal is
It has a common component and produces flicker.
You. The present invention solves these problems.
The goal is to achieve a high contrast ratio even at high temperatures.
Without flickering and less flicker
This is where the structure of the Bumricks panel is given. [0006] SUMMARY OF THE INVENTION The present invention provides a method for forming a matrix on a substrate.
A pixel electrode arranged in a lithographic pattern and a contact with the pixel electrode.
Having a continuous thin film transistor and a storage capacitor,
The data signal supplied to the data line is transmitted to the thin film transistor.
Active to supply to the pixel electrode and the storage capacitor via
In a matrix panel, the thin film transistor
The source / drain region is made of silicon thin film
The capacity of the silicon thin film is different from the silicon thin film in conductivity type.
A first electrode composed of a film and the first electrode via an insulating film;
And a gate electrode of the thin film transistor,
And a second electrode formed of the same material.
I do. [0007] According to the above structure of the present invention, the capacity of the liquid crystal is almost equal to that of the liquid crystal.
The capacity of the gate insulating film is added to the column,
Since the time constant becomes longer, the contrast ratio becomes larger. Ma
Also, even if the time constant of the liquid crystal becomes
Since the capacitance of the gate insulating film does not change, the contrast ratio decreases.
It can be reduced. In addition, the video signal polarity
In the writing and holding of TFT caused by
Less flickering
You. [0008] DESCRIPTION OF THE PREFERRED EMBODIMENTS [referenceExample 1) FIG. 1A shows one embodiment of the present invention.referenceActive matrices showing examples
(B) and (c) are plan views of the panel panel.
FIG. 3A is a cross-sectional view taken along a line AB and a line CD in FIG.
is there. The manufacturing process will be described with reference to FIG. First
Polysilicon or amorphous silicon on the edge substrate 1
Is deposited and patterned as shown.
This thin film is used for the TFT channel and source / drain
It becomes an electrode for building a pole and a capacitor. Next,
Scan that forms a gate insulating film 3 and also serves as a gate electrode
A line 4 is formed. The material is polysilicon TFT
In this case, polysilicon or high melting point metal
In the case of a silicon TFT, a normal metal or a transparent conductive film is used.
Used. An interlayer insulating film 5 is deposited thereon.
Then, a contact hole is opened, and the pixel electrode 6 and the data
The substrate on which the line 7 is formed is an active matrix substrate.
You. Having a common electrode through this substrate and a space of several μm
With another substrate facing it, fill the space with liquid crystal
Are active matrix panels. FIG. 3 shows the gate of an N-type MOS capacitor.
This shows the voltage dependency. Gate voltage VG is threshold
When the voltage exceeds the threshold voltage Vth, the capacitance increases to C0.
When the voltage is lower than the minimum value, the overlap capacitance Cgso is obtained. Therefore VG
 It is desirable to use MOS capacitors in the region of> Vth,
BookreferenceIn the example, below the scanning line 4 in the previous stage of FIG.
The built-in MOS capacitor has the same conductivity type as the TFT.
For example, in the case of N type, the normal state where the TFT is OFF
In this case, since VG <Vth, the capacity becomes only Cgso.
You. However, the thickness of the gate film is limited to the space where the liquid crystal is sealed.
Is thin enough to increase the capacity per unit area.
Cg of the overlapping capacitance of the pattern as shown in FIG.
The capacitance of the liquid crystal driven by the pixel electrode 6 is included only in so.
The capacity is about 30 to 50% of the volume. This MOS capacitance is
Because it is added in parallel with the capacity of the liquid crystal,
The constant is increased, and the display performance is greatly improved. This is shown in FIG.
This will be described with reference to FIG. This figure shows the active matrix panel.
FIG. 4 is a diagram showing the potential of each part of the device, with the horizontal axis representing time and the vertical axis representing potential.
It has taken a place. As is well known, NTSC video signals
Is two interlaced fields, an odd
One frame is composed of several fields and even fields.
And one screen is completed. LCD does not drive AC
The signal on the data line is
Use the inverted one. 41 is a scanning line signal,
When driving with an N-channel TFT, such a pulse
Required. 44 and 45 are conventional and original
ClearreferenceThe potential of the pixel electrode in the example, 43 is common
This is the potential of the electrode. The potential between the common electrode and the pixel electrode
The difference or the voltage applied to the liquid crystal. From time t0 to time t
Three Up to odd field, time t3 From t6 Up to even
First, the time in the odd field
t1 The TFT turns on and the data line signal is
Is written at time t2 TFT turns off at
With a certain time constant, the pixel electrode potential moves toward the common electrode potential.
Discharge. Similarly, in the even field, the time t4
The TFT is turned on and the data line signal is applied to the pixel electrode.
Written at time t5 When the TFT is turned off at
The elementary electrode potential discharges toward the common electrode potential. Slant
The portion indicated by the line is the voltage applied to the liquid crystal in this embodiment.
This is due to the longer time constant compared to the conventional example.
It can be seen that a higher voltage can be applied
You. This increases the contrast ratio. Also, MOS
The wiring between the capacitor and the drain electrode of the TFT is shown in FIG.
Arranged between data line and pixel electrode as in (a)
Also works to block the light leaking from this gap
Therefore, while increasing the contrast ratio,
This will be better. In addition, the liquid crystal
Even if the number slightly fluctuates, the added MOS capacitance does not change
Therefore, the area of the hatched portion in FIG. 3 does not change much. Sand
In other words, it is possible to obtain a display screen with good reproducibility over a wide temperature range.
it can. In addition, flicker is 3 to 5 d compared to the conventional example.
It was confirmed by the applicant's experiment that B decreased. This is strange
TFT writing and writing in several fields and even fields
Less susceptible to asymmetrical movement in holding and holding
It is. [0010]referenceExample 2) FIG. 5 (a) shows the present invention.referenceActive mat in example 2
It is a top view of a Rix panel, and the figure (b) and (c) are
Sectional views at AB and CD of FIG.
It is. This active matrix panel is the firstreferenceAn example
It can be manufactured using exactly the same process. 61-
67 respectively correspond to 1 to 7 in FIG.
Edge substrate, 62 is polysilicon or amorphous silicon
63, a gate insulating film, 64, a scanning line, and 65,
An interlayer insulating film, 66 is a pixel electrode, and 67 is a data line.
In the case of the transmission type, a transparent conductive film is used for 66 pixel electrodes.
The 67 data lines have the same transparent conductive film as the pixel electrodes or
Uses a metal thin film. BookreferenceExample is the same as the first reference example
In addition, an MO of the same conductivity type as the TFT is provided below the scanning line 64 in the preceding stage.
TFT is turned off because S capacitance is built in
Under normal conditions, only the overlap capacity is valid. But,
BookreferenceIn the example, the scanning line 64 is as shown in FIG.
It has a shape protruding parallel to the data line.
Since the MOS capacitance can be built into thethree
ConsiderationAbout twice the capacity of the example can be added. Accordingly
Higher contrast ratio and wider temperature range
High quality display screen with little licker can be obtained
You. In addition, as shown in FIG.
By making MOS capacitance to cover the gap,
Light leaking from this gap can be blocked,
This contributes to an increase in the last ratio. [Example] FIG. 6A shows an active matrix according to the embodiment of the present invention.
(B) and (C) are plan views of the panel panel.
FIG. 3A is a cross-sectional view taken along a line AB and a line CD in FIG.
is there. This reference example is the same as the first reference example and the embodiment of the present invention.
Creates a different conductivity type MOS capacitor than TFT
No. For example, an actuator with a built-in CMOS driver
This is effective for an Eve matrix panel or the like. Referring to FIG.ImplementationExample active matrices
The structure of the panel will be described. First, place a
Silicon or amorphous silicon thin films 82 and 8
8 is deposited and patterned as shown. 82 is
It becomes the channel part of the TFT and the source / drain electrode.
Reference numeral 8 is an electrode for forming a MOS capacitor. Next,
A gate insulating film 83 is formed, and a gate electrode
A check line 84 is formed. Thereafter, ion implantation is performed selectively.
82 is an N-channel TFT, and 88 is a P-channel TFT.
MOS capacitor. Subsequent steps are the same as in Example 1.
Where 85 is an interlayer insulating film, 86 is a pixel electrode, and 87 is data
Line. In this embodiment, the conduction of the TFT and the MOS capacitor is
Electric type is different. P-channel MOS capacitor
The dependence on the gate voltage is symmetric to that of the N-channel in FIG.
G It becomes Cgso when <Vth is C0, VG> Vth. Therefore
In a normal state where the TFT is turned off, VG <Vth
Therefore, the overlapping area of the electrode 88 and the scanning line 84 is all
Works as an electrode forSCapacity C0 is added
Will be. The size of this capacitance depends on the pixel electrode 86.
Is about 100% to 20% of the capacity of the liquid crystal driven.
First and secondreferenceMuch larger than the example. Follow
The effect is also increased. Also, the previous scanning line is selected.
During this period, the MOS capacitance is turned off and the overlap capacitance Cgs
In addition to only o, there is no need to blunt the scan line waveform.
The drive state does not change due to the addition of capacitance.
No. [0014] As described above, the activator according to the present invention is used.
With a passive matrix panel, pixels can be
Can build capacity. By adding capacity
Contrast ratio increases, flicker decreases,
It is possible to obtain a screen with good reproducibility in a low temperature range. Ma
In addition, crosstalk due to capacitive coupling between data lines and pixel electrodes
Also, it has the effect of reducing the variation of picture elements on the screen,
Overall image quality is improved.Also, the electrodes 88 and the scanning lines 84
All the overlapping areas work as electrodes for the capacitance,
The MOS capacitance C0 is added. This capacity is large
The magnitude is the capacitance of the liquid crystal driven by the pixel electrode 86.
About 100% to 20%, compared to the first and second reference examples
And much larger.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A is a plan view showing a structure of an active matrix panel according to a first reference example, and FIGS. 1B and 1C are cross-sectional views thereof. FIG. 2 is a plan view showing the structure of a conventional active matrix panel. FIG. 3 is a diagram showing the gate voltage dependence of the MOS capacitance of an N-channel. FIG. 4 is a diagram showing potentials at various parts of an active matrix panel. 5 (a) is a plan view showing the structure of Akuteibu matrix panel of the second reference example of the present invention, (b), (C) is a sectional view thereof. FIG. 6A is a plan view showing the structure of an active matrix panel according to an embodiment of the present invention, and FIGS. 6B and 6C are cross-sectional views thereof. [Description of Signs] 2, 62, 82: polysilicon or amorphous silicon thin film 3, 63, 83: gate insulating film 4, 64, 84: scanning line

Claims (1)

(57) [Claims] A pixel electrode arranged in a matrix on the substrate; a thin film transistor connected to the pixel electrode; and a storage capacitor, and a data signal supplied to a data line is transmitted to the pixel electrode and the pixel electrode through the thin film transistor. In an active matrix panel for supplying a storage capacitor, a source / drain region of the thin film transistor is formed of a silicon thin film, and the storage capacitor is formed through a first electrode formed of a silicon thin film having a conductivity type different from that of the silicon thin film, and an insulating film. An active matrix panel, comprising: a gate electrode of the thin film transistor; and a second electrode formed of the same material, which is disposed to face the first electrode.