JP3005043B2 - Liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to a liquid crystal display device, particularly to an active matrix type liquid crystal display device using thin film transistors and the like.

[Prior art]

An active matrix type liquid crystal display device has a nonlinear element (switching element) provided for each of a plurality of pixel electrodes arranged in a matrix. Since the liquid crystal in each pixel is theoretically always driven (duty ratio 1.0), the active system has a better contrast than the so-called simple matrix system that employs the time-division driving system. Then it is becoming an indispensable technology. A typical example of a switching element is a thin film transistor (TFT)
There is. FIG. 14 is a sectional view showing a part of a conventional active matrix type liquid crystal display device. In this liquid crystal display device, a gate electrode GT is provided on a transparent glass substrate SUB1, an insulating film GI used as a gate insulating film is provided on the gate electrode GT, and an i-type semiconductor layer AS is provided on the insulating film GI. Is provided, a video signal line DL is provided on the insulating film GI, a source electrode SD11 and a drain electrode SD21 are provided on both sides of the i-type semiconductor layer AS, and the transparent pixel electrode ITO11 is connected to the source electrode SD11.
Is provided. FIG. 15 shows another conventional active matrix type liquid crystal display device (Proceedings of the SID) Vol. 31/1, 1990 13-1.
FIG. 7 is a cross-sectional view showing a part of FIG. In this liquid crystal display device, a gate electrode GT is provided on a transparent glass substrate SUB1, and an insulating film made of a silicon nitride film is provided on the gate electrode GT.
GI1, a transparent pixel electrode ITO12 is provided on the insulating film GI1, an insulating film GI2 made of a silicon nitride film is provided on the transparent pixel electrode ITO12, and an i-type semiconductor layer A is provided on the insulating film GI12.
S is provided, a video signal line DL is provided on the insulating film GI12, a source electrode SD11 and a drain electrode SD21 are provided on both sides of the i-type semiconductor layer AS, and a source is provided through a through hole provided in the insulating film GI2. The electrode SD11 and the transparent pixel electrode ITO12 are connected. Known examples of providing an anodized film of the metal constituting the gate electrode on the gate electrode of the thin film transistor are disclosed in JP-A-61-133662 and JP-A-2-106723. However, none of the known examples takes into account the specific configuration of the storage capacitor.

[Problems to be solved by the invention]

In the liquid crystal display device shown in FIG.
Since the DL and the transparent pixel electrode ITO11 are formed on the same plane, the adjacent video signal line DL and the transparent pixel electrode ITO11 are short-circuited, causing a point defect and deteriorating display characteristics. Further, in the liquid crystal display device shown in FIG. 15, since the video signal line DL and the transparent pixel electrode ITO12 are not formed on the same plane, it is possible that the video signal line DL and the transparent pixel electrode ITO12 are short-circuited. rare. However, two layers of insulating film
GI1 and GI2 are provided, and insulating films GI1 and GI2 are plasma CVD
When formed by the plasma method, dust generated by the plasma reaction in the plasma CVD apparatus is extremely large, and the insulating films GI1, GI2
Since defects are likely to occur in the gate electrode, the occurrence of defects such as a short circuit between the gate electrode GT and the source electrode SD11 or the drain electrode SD21 increases, point defects occur, and display characteristics deteriorate. The present invention has been made to solve the above-described problem, and has as its object to provide a liquid crystal display device having good display characteristics.

[Means for Solving the Problems]

In order to achieve this object, according to the present invention, there is provided an active matrix system including a thin film transistor, a pixel electrode, and a storage capacitor as components of a pixel, and applying a voltage of a video signal line to the pixel electrode via the thin film transistor. In the liquid crystal display device, the gate electrode of the thin film transistor is made of aluminum, and the top and side surfaces thereof are provided with a first insulating film made of an oxide of aluminum, and the first electrode constituting the storage capacitor is made of aluminum. And a first insulating film made of an oxide of aluminum is provided on the upper surface and side surfaces thereof, and the first insulating film formed on each of the gate electrodes does not contact the surface on which the gate electrode is formed The pixel electrode is provided on the surface on which the gate electrode is formed. Formed on a region interposed between a first insulating film covering the side and top surfaces of the first electrode and a first insulating film covering the side surfaces and the top surface of the first electrode. A second insulating film made of silicon nitride is formed so as to cover the first insulating film and each of the first insulating film and the pixel electrode, and is in contact with the pixel electrode; A second electrode constituting the storage capacitor element is formed on the insulating film so as to face the first electrode, and the video signal line is formed on the second insulating film and the thin film transistor of the thin film transistor. It is characterized in that it is formed on the side opposite to the pixel electrode. In this case, the second electrode is made of the same material as the video signal line. Further, the first electrode is formed integrally with the gate electrode of another pixel adjacent to the pixel.

[Action]

In the liquid crystal display device according to the present invention, since the second insulating film is formed between the pixel electrode and the video signal line, there is no short circuit between the pixel electrode and the video signal line. Further, since the dielectric film of the storage capacitor is formed of the first insulating film and the second insulating film, no short circuit occurs in the storage capacitor.

【Example】

 In the following, the active matrix
Application of the present invention to a color liquid crystal display
This will be described together with the examples. In all the drawings for explaining the embodiments, the same device
Those having functions are given the same reference numerals, and the description of the repetition is given.
Is omitted. FIG. 1 shows an active matrix to which the present invention is applied.
Pixel showing one pixel and its surroundings
2A is a sectional view taken along the line IIA-IIA in FIG.
FIG. 2B is a diagram showing a cross section near the seal portion of the display panel, and FIG.
FIG. 2 is a sectional view taken along section line IIB-IIB in FIG. 1. Ma
FIG. 3 (plan view of a main part) shows a plurality of pixels shown in FIG.
The top view at the time of arrangement | positioning is shown. (Pixel Arrangement) As shown in FIG. 1, each pixel has two adjacent scanning signals.
Line (gate signal line or horizontal signal line) GL and adjacent
Two video signal lines (drain signal lines or vertical signal lines)
In the intersection area with DL (in the area surrounded by four signal lines)
Are located. Each pixel is thin film transistor TFT, transparent
It includes a pixel electrode ITO1 and a storage capacitor Cadd. Scan signal
The lines GL extend in the column direction, and a plurality of lines GL are arranged in the row direction.
You. The video signal lines DL extend in the row direction and are arranged in a plurality in the column direction.
Is placed. (Overall structure of display section) As shown in Fig. 2A, the lower transparent glass
Substrate SUB1 has thin film transistor TFT and transparent pixel
The pole ITO1 is formed and the upper transparent glass substrate SUB2 side has
-Filter FIL, black matrix pattern for light shielding
The light shielding film BM to be formed is formed. Lower transparent glass base
The plate SUB1 has a thickness of, for example, about 1.1 [mm].
You. Dip is placed on both sides of the transparent glass substrates SUB1 and SUB2.
Silicon oxide film SIO formed by
Have been. Therefore, the transparent glass substrates SUB1 and SUB2
Even if there are sharp scratches on the surface,
Since it can be covered with SIO, scanning signal lines GL and color
Can effectively prevent the filter FIL from being damaged.
You. 2A shows a cross section of one pixel portion,
The left side is the outside edge of the transparent glass substrates SUB1 and SUB2 at the left edge.
The cross section of the part where the output wiring exists is shown, and the right side is transparent.
Existence of external wiring at the right edge of the glass substrates SUB1 and SUB2
The cross section of a portion that does not exist is shown. The sealing material SL shown on each of the left and right sides of FIG.
Liquid crystal sealing port (Fig.
(Not shown) Except for transparent glass substrates SUB1 and SUB2
It is formed along the entire enclosure. For example, the sealing material SL
It is made of epoxy resin. Common transparent pixel electrode ITO2 on the upper transparent glass substrate SUB2 side
At least in one place, the silver paste material SIL
External drawer formed on the lower transparent glass substrate SUB1 side
Connected to the wire. This external wiring is gate electrode G
Same as T, source electrode SD1, drain electrode SD2
It is formed in the manufacturing process. ORI1, ORI2, transparent pixel electrode ITO1, common transparent pixel
Each layer of electrode ITO2, protective film PSV1, PSV2, insulating film GI
Is formed inside the sealing material SL. Polarizer POL1, POL2
Are the lower transparent glass substrate SUB1 and the upper transparent glass substrate, respectively.
It is formed on the outer surface of the plate SUB2. The liquid crystal LC has a lower alignment film ORI1 that sets the orientation of the liquid crystal molecules.
Sealed between the upper alignment film ORI2 and the sealing part SL
Sealed. The lower alignment film ORI1 is a protective film on the lower transparent glass substrate SUB1 side
Formed on top of PSV1. On the surface inside (liquid crystal LC side) of the upper transparent glass substrate SUB2
Is common for light shielding film BM, color filter FIL, protective film PSV2
Transparent pixel electrode ITO2 (COM) and upper alignment film ORI2
They are provided in layers. This liquid crystal display device has a lower transparent glass substrate SUB1 side and an upper
Form each layer on the transparent glass substrate SUB2 side separately,
Then, the upper and lower transparent glass substrates SUB1 and SUB2 are overlaid,
It is assembled by enclosing liquid crystal LC between people. (Thin film transistor TFT) The thin film transistor TFT has a positive via
The source-drain channel resistance
When the bias decreases to zero, the channel resistance increases.
It works to be easy. The thin film transistor TFT of each pixel has 2 pixels in the pixel.
(Multiple) thin film transistors
Transistor) It is composed of TFT1 and TFT2. Thin film
Transistors TFT1 and TFT2 are virtually the same size
(The channel length and the channel width are the same).
Each of the divided thin film transistors TFT1 and TFT2
Mainly consist of gate electrode GT, gate insulating film GI, i-type (intrinsic,
intrinsic, not doped with conductivity determining impurities)
I-type semiconductor layer AS made of amorphous silicon (Si), a pair of
It comprises a source electrode SD1 and a drain electrode SD2. What
Note that the source / drain originally depends on the bias polarity between them.
In the circuit of this liquid crystal display device, the polarity is dynamic.
Since the source and drain are reversed during operation, the source and drain are switched during operation.
I want to be understood. However, for the sake of convenience,
One is fixed as a source and the other is fixed as a drain. (Gate Electrode GT) FIG. 4 (the second conductive film g2 and the second conductive film g2 in FIG. 1)
(a plan view depicting only the i-type semiconductor layer AS).
In the vertical direction from the scanning signal line GL (FIGS. 1 and 4)
(T-shaped)
Branched into shapes). Gate electrode GT is a thin film transistor
So that it protrudes to the respective TFT1 and TFT2 formation areas.
Is configured. Thin film transistor TFT1, TFT2
Each gate electrode GT is integrated (common gate electrode
) And is formed continuously with the scanning signal line GL.
ing. The gate electrode GT is composed of a single-layer second conductive film g2.
You. The second conductive film g2 is, for example, an aluminum film formed by sputtering.
Formed with a thickness of about 1000 to 5500 [Å] using a minium film
I do. Aluminum anodic acid is placed on the gate electrode GT.
An oxide film AOF is provided. This gate electrode GT is shown in FIG. 1, FIG. 2A and FIG.
To completely cover the i-type semiconductor layer AS.
It is formed larger (as viewed from below). But
Therefore, a bag such as a fluorescent lamp is placed below the lower transparent glass substrate SUB1.
If you install Klite BL, this opaque aluminum
The gate electrode GT, which is made of
Is not exposed to the backlight and the conductive phenomenon caused by light irradiation
That is, deterioration of the off-characteristics of the thin film transistor TFT occurs.
It becomes hard. The original size of the gate electrode GT is
Minimum between the electrode SD1 and the drain electrode SD2.
Required (gate electrode GT, source electrode SD1, drain electrode S
Width (including allowance for alignment with D2) and channel
The depth length that determines the width W depends on the source electrode SD1 and the drain.
Ratio to the distance (channel length) L between the
That is, the factor W / L that determines the transconductance gm is
It depends on whether you wear shoes. The size of the gate electrode GT in this liquid crystal display device is
Of course, it is made larger than the above-mentioned original size. (Scanning Signal Line GL) The scanning signal line GL is formed of the second conductive film g2. this
The second conductive film g2 of the scanning signal line GL is the second conductive film g2 of the gate electrode GT.
Formed in the same manufacturing process as the film g2, and integrally configured
I have. (Anodic oxide film AOF) Anodized film (Al_TwoO_ThreeAOF anodizes the second conductive film g2
It is formed by doing. This anodic oxide film AOF
Intersection of scanning signal line GL with video signal line DL, gate electrode GT
And the electrode PL1. For this reason, thin film
Short circuit between electrodes in transistor TFT section, signal at wiring intersection
A short circuit between lines can be prevented, and the scanning signal line GL
Since the anodic oxide film AOF is provided only on a part of the
The wiring resistance of the line GL can be kept low. Also, Al
_TwoO_ThreeHas a relative dielectric constant of 9.2, and the relative dielectric constant of silicon nitride is
6.7, so Al_TwoO_ThreeDielectric constant of silicon nitride
30% higher than the electrical
The conductance gm can be improved about 1.5 times, and
The area of the storage capacitor Cadd can be reduced.
Therefore, the aperture ratio can be improved. In addition,
Two insulating films GI1 and GI2 made of silicon nitride
In contrast to the case where
Not necessary, so the production cost will not be expensive.
No. (Insulating film GI) The insulating film GI is the thin film transistor TFT1, TFT2.
Used as a gate insulating film. Insulating film GI is the gate electrode
GT, scanning signal line GL, transparent pixel electrode ITO1
ing. The insulating film GI is formed by, for example, plasma CVD.
A silicon nitride film is used. Next, the thickness of the insulating film GI and the thickness of the anodic oxide film AOF will be described.
Will be described. Figure 10 shows the gate insulating film as an anodic oxide film AOF
And the thickness of the insulating film GI,
The thickness of the anodic oxide film AOF and the general insulating film GI (thickness of 0.3 [μ
m]) with mutual conductance gm of 1
9 is a graph showing the relationship between the conductance gm and the increase ratio.
The insulating film GI is formed so as to be in a region indicated by hatching in this graph.
If the film thickness and the thickness of the anodic oxide film AOF are determined, mutual conductivity
Close gm can be improved. Meanwhile, the actual operating state
In the state, the gate electrode GT, the source electrode SD1, and the drain electrode SD2
Voltage of up to 25V is applied between the
Cleaning is performed. And the part without insulating film GI
It must be considered that there is a part without the anodic oxide film AOF
The thickness of the insulating film GI and the thickness of the anodic oxide film AOF
Each must be thick enough to withstand a voltage of 75V.
is there. The thickness of the insulating film GI that can withstand a voltage of 75 V is 1
Anodized film that is 200 [Å] and can withstand a voltage of 75 V
The thickness of the AOF is 1100 [Å], which is an anodic oxidation voltage of 80V.
Corresponding to Fig. 11 shows the leakage of the anodic oxide film AOF.
4 is a graph showing current characteristics. By the way, the thin film transistor
The off-current of the star TFT is about 10^-8A / cm^TwoTherefore,
Flow is 10^-8A / cm^TwoMust be: And Lee
Current is 10^-8A / cm^TwoThe following is when the anodic oxidation voltage is 80V
That is the time. From this point of view, the thickness of the anodic oxide film AOF
Must be 1100 [Å] or more. On the other hand, anodic oxidation
If the pressure exceeds the resisting pressure of the resist during anodic oxidation, the resist
Is destroyed, and the second conductive film g2 under the resist is
It is not appropriate to increase the anodic oxidation voltage
No anodic oxidation voltage of 150 V (at this time, the anodic oxide film AOF
It is desirable that the film thickness is about 2100 [Å] or less. that's all
Therefore, the thickness of the insulating film GI is set to 1200 to 2200 [Å],
The thickness of the anodic oxide film AOF is set to 1100 to 2100 [Å],
That is, the thickness of the insulating film GI and the thickness of the anodic oxide film AOF are
It is desirable to set the value within the area indicated by the lattice network in the figure. An opening HOP is provided in the insulating film GI,
Transparent pixel electrode ITO1 and source electrode SD1 through the end of section HOP
And are connected. And to provide the opening HOP
Effectively removes the insulating film GI on the transparent pixel electrode ITO1
Insulating film formed on the transparent pixel electrode ITO1
The voltage acting on the liquid crystal LC increases
can do. Moreover, the transparent pixel electrode ITO1 and the video signal
Because the insulation film GI is formed between the
There is no short circuit between the raw electrode ITO1 and the video signal line DL
Since no point defects occur, the display characteristics are good.
is there. (I-type semiconductor layer AS) The i-type semiconductor layer AS is divided into a plurality as shown in FIG.
Of each of the thin film transistors TFT1 and TFT2
Used as a tool forming area. i-type semiconductor layer AS is amorphous
Made of silicon film or polycrystalline silicon film, 200 ~ 100
It is formed with a thickness of about 0 [Å]. This i-type semiconductor layer AS is made of Si_ThreeN
_FourOf insulating film GI used as gate insulating film composed of
The same plasma CVD equipment is used for
Formed without exposure to the outside from plasma CVD equipment
You. Also, P-doped N for ohmic contact⁺
Similarly, the semiconductor layer d0 (FIG. 2A) is continuously 200 to 500.
It is formed to a thickness of [Å]. After that, the lower transparent glass
Substrate SUB1 is taken out of the CVD equipment and photo processing technology
By N⁺The semiconductor layer d0 and the i-type semiconductor layer AS are shown in FIG.
As shown in Fig. 2A and Fig. 4,
Be tuned. The i-type semiconductor layer AS is shown in detail in FIGS. 1 and 4.
As shown in the figure, the intersection (scan) between the scanning signal line GL and the video signal line DL
(Over section). This intersection
Of the i-type semiconductor layer AS and the scanning signal line GL at the intersection
It is configured to reduce a short circuit with the signal line DL. (Source electrode SD1, Drain electrode SD2) That of thin-film transistor TFT1, TFT2 divided into multiple
The source electrode SD1 and the drain electrode SD2 are shown in FIG.
2A and 5 (first to third conductive films d1 to d3 in FIG. 1)
I-type semiconductor as shown in detail in
The layers are separately provided on the layer AS. Each of the source electrode SD1 and the drain electrode SD2 is N⁺Type
From the lower side in contact with the semiconductor layer d0, the second conductive film d2, the third conductive film d2,
The conductive films d3 are sequentially superposed. Source power
The second conductive film d2 and the third conductive film d3 of the pole SD1 are connected to the drain
Same manufacturing as the second conductive film d2 and the third conductive film d3 of the electrode SD2
It is formed in a process. The second conductive film d2 uses a chromium film formed by sputtering,
500-1000 [Å] film thickness (in this liquid crystal display, 600
[膜厚]. Chromium film is thicker
When formed, the stress increases, so about 2000 [Å]
Is formed so as not to exceed the thickness of the film. Chromium film is N⁺Mold semiconductive
Good contact with body layer d0. The chromium film is the third
Aluminum in conductive film d3 is N⁺Type semiconductor layer d0
And a so-called barrier layer for preventing the above. Second conductive film
As d2, in addition to the chromium film, high melting point metals (Mo, Ti, Ta,
W) film, refractory metal silicide (MoSi_Two, TiSi_Two, TaS
i_Two, WSi_Two) It may be formed of a film. After patterning the second conductive film d2 by photo processing, the same
Using a photomask or masking the second conductive film d2
N⁺The type semiconductor layer d0 is removed. That is, i
N remaining on the type semiconductor layer AS⁺Type semiconductor layer d0 is the second conductive layer
Portions other than the film d2 are removed by self-alignment. This and
N⁺The type semiconductor layer d0 is completely removed by its thickness.
Because it is etched, the i-type semiconductor layer AS also slightly
But the degree is controlled by the etch time
Good. Thereafter, the third conductive film d3 is heated by resistance heating of aluminum.
Film thickness of 3000 to 8000 [で]
In a liquid crystal display device of this type, the film thickness is about 3500 [Å]).
It is. Aluminum film has less stress than chromium film
It can be formed to a large thickness, and the source electrode SD
1.Reduced resistance of drain electrode SD2 and video signal line DL
It is configured to be. The second conductive film d2 of the source electrode SD1 and the second conductive film d2 of the drain electrode SD2
Each of the two conductive films d2 is compared with the upper third conductive film d3.
It penetrates greatly inside (into the channel region). One
That is, the second conductive film d2 in these portions is the third conductive film.
Regardless of d3, the channel length L of the thin film transistor TFT is
It is configured so that it can be specified. Source electrode SD1 is connected to transparent pixel electrode ITO1.
You. The source electrode SD1 is formed in a step shape (the first shape) of the i-type semiconductor layer AS.
2 Film thickness of conductive film g2, N⁺Film thickness of i-type semiconductor layer d0 and i-type half
Along the step corresponding to the thickness of the conductor layer AS)
It is configured. Specifically, the source electrode SD1 is i
Conductive film formed along the step shape of the semiconductor layer AS
d2 and a third conductive film d3 formed on the second conductive film d2.
It is composed of The third conductive film d3 of the source electrode SD1 is
The chromium film of the second conductive film d2 is formed thicker due to increased stress.
Inability to overcome the stepped shape of i-type semiconductor layer AS
So it is configured to get over this i-type semiconductor layer AS
ing. That is, by forming the third conductive film d3 to be thick, the third conductive film d3 is formed.
Tep coverage has been improved. The third conductive film d3 is thick
The resistance value of the source electrode SD1 (drain voltage
The same for pole SD2 and video signal line DL)
Has contributed. (Transparent pixel electrode ITO1) The transparent pixel electrode ITO1 forms one of the pixel electrodes of the liquid crystal display.
To achieve. The transparent pixel electrode ITO1 has an opening provided in the insulating film GI.
It is connected to the source electrode SD1 via the section HOP. The transparent pixel electrode ITO1 is constituted by the first conductive film d1.
I have. This first conductive film d1 was formed by sputtering.
A transparent conductive film (Indium-Tin-Oxide ITO: Nesa film)
And a film thickness of 1000 to 2000 [Å] (in this liquid crystal display device,
The film thickness is about 1200 [Å]. The transparent pixel electrode ITO1 is the source electrode of the thin film transistor TFT1.
Pole SD1 and the source electrode SD1 of the thin film transistor TFT2.
Has been continued. Therefore, the thin film transistors TFT1, TFT2
One of the TFTs, for example, TFT1 is defective.
When it is produced, it may be
To separate the thin film transistor TFT1 from the video signal line DL.
Together with the thin film transistor TFT1 and the transparent pixel electrode ITO1
Is not a point defect or a line defect,
Defects occur simultaneously in thin film transistors TFT1 and TFT2
The probability of a point defect occurring
Can be made smaller. The transparent pixel electrode ITO1 is composed of the gate electrode GT and the anodic oxide film.
It is separated by AOF, and the insulating film G is separated from the video signal line DL.
Since they are separated by I, there are very few point defects,
Good display characteristics. Furthermore, the transparent pixel electrode ITO1 is flush with the gate electrode GT.
The number of insulating films can be reduced because
As a result, the manufacturing cost is low. (Protective film PSV1) On the thin film transistor TFT and the transparent pixel electrode ITO1
A protective film PSV1 is provided. The protective film PSV1 is mainly
Formed to protect the transistor TFT from moisture etc.
Use a material with high transparency and good moisture resistance.
You. The protective film PSV1 was formed by, for example, a plasma CVD device.
It is formed of a silicon oxide film or a silicon nitride film.
It is formed with a thickness of about [μm]. (Gate Terminal GTM) As shown in FIG. 2D, the gate terminal GTM is the first conductive film g1.
And the first conductive film d1. The first conductive film g1 is made of, for example, chromium formed by sputtering.
A (Cr) film is formed with a thickness of about 1000 [Å]. (Light shielding film BM) External light (Fig. 2A
I) used as a channel formation region
A light shielding film BM is provided so as not to be incident on the type semiconductor layer AS.
The light-shielding film BM has a pattern as shown by hatching in FIG.
It is said that. FIG. 6 shows the ITO film in FIG.
First conductive film d1, color filter FIL and light shielding
FIG. 4 is a plan view depicting only a film BM. The light shielding film BM is
High shielding properties, such as aluminum or chrome film
In this liquid crystal display, a chrome film is
The film is formed to a film thickness of about 1300 [Å] by the taring. Therefore, the i-type semiconductor of the thin film transistors TFT1 and TFT2
The body layer AS consists of upper and lower light shielding films BM and a large gate electrode
Sandwiched by GT, part of which is outside natural
No light or backlight light hits. BM 6
As shown by the hatched area in the figure,
In other words, the light shielding film BM is formed in a lattice shape (black mat
Rix), this grid partitions the effective display area of one pixel
ing. Therefore, the outline of each pixel is
Clarity and contrast are improved. In other words, shading
The film BM is a light shielding and black matrix for the i-type semiconductor layer AS.
And has two functions. In addition, the root edge of the transparent pixel electrode ITO1 in the rubbing direction is formed.
The part (lower right part in Fig. 1) facing the edge part is the light shielding film BM.
Therefore, the domain is generated in the above part because it is shielded from light
Even so, the display characteristics are poor because the domain is not visible.
It does not change. The backlight is placed on the upper transparent glass substrate SUB2 side.
And attach the lower transparent glass substrate SUB1 to the observation side (external
Side). (Common transparent pixel electrode ITO2) The common transparent pixel electrode ITO2 is on the lower transparent glass substrate SUB1 side.
And a transparent pixel electrode ITO1 provided for each pixel.
The optical state of the crystal LC depends on the pixel electrode ITO1 and the common transparent pixel electrode.
It changes in response to the potential difference (electric field) between the pole ITO2. This
A common voltage Vcom is applied to the common transparent pixel electrode ITO2 of
It is configured to: Common voltage Vcom is a video signal line
Low-level drive voltage Vdmin applied to DL and high-level
This is an intermediate potential with respect to the drive voltage Vdmax. (Color filter FIL) The color filter FIL is made of resin material such as acrylic resin.
The dyed base material to be formed is colored with a dye. Mosquito
Color filter FIL is striped at the position facing the pixel
(Fig. 7) and dyed separately (Fig. 7
First conductive film d1, light-shielding film BM and color filter in FIG.
Only FIL is drawn, each color filter of B, R, G
Tar FILs are 45 ゜, 135 ゜ and cross hatched, respectively.
Has been done). The color filter FIL is as shown in FIG.
It is large enough to cover all of the transparent pixel electrode ITO1.
The light shielding film BM is composed of the color filter FIL and the transparent pixel electrode I.
Perimeter of transparent pixel electrode ITO1 so that it overlaps the edge of TO1
It is formed inside the part. The color filter FIL can be formed as follows
You. First, a dyed substrate is placed on the surface of the upper transparent glass substrate SUB2.
Formed and the red filter formation area by photolithography technology
The dyed substrate other than the area is removed. After this, the dyed substrate is red
Dye with dye, fixation process, form red filter R
You. Next, by performing a similar process, the green color
A filter G and a blue filter B are sequentially formed. (Protective film PSV2) The protective film PSV2 dyes the color filter FIL in different colors.
Provided to prevent the dye from leaking into the liquid crystal LC.
Have been. The protective film PSV2 is made of, for example, acrylic resin or epoxy resin.
It is formed of a transparent resin material such as silicone resin. (Equivalent circuit of the entire display device) Connection diagram of the equivalent circuit of the display matrix and its peripheral circuits
Is shown in FIG. Although this figure is a circuit diagram,
It is drawn according to the geometric arrangement. AR uses multiple pixels
It is a matrix array arranged in a dimension. In the figure, X means a video signal line DL, and suffixes G, B and
R is added corresponding to green, blue and red pixels respectively
I have. Y means the scanning signal line GL, and the suffixes 1, 2, 3, ..., end
They are added according to the order of the scanning timing. The video signal lines X (subscripts omitted) alternately
Number) video signal drive circuit He, lower (or even) video signal
It is connected to the drive circuit Ho. SUP is stabilized by dividing multiple voltage from one voltage source
A power supply circuit and a host (higher
Information for CRT (Cathode Ray Tube) from TFT LCD
This is a circuit that includes a circuit that exchanges information for use. (Structure of the storage capacitor Cadd) Connected to the thin film transistor TFT of the transparent pixel electrode ITO1
The second and third conductive films d2 and d3 are connected to the end opposite to the end that is
The second and third conductive films d2 and d3 are adjacent scans.
It is formed so as to overlap with the signal line GL. This superposition
As is clear from FIG. 2B, the second and third conductive films
d2 and d3 are one electrode PL2, and the adjacent scanning signal line GL is
Capacitance element (capacitance element) Cadd as one electrode PL1
Is configured. The dielectric film of the storage capacitance element Cadd has an anode
It is composed of an oxide film AOF and an insulating film GI. others
Since the electrode PL1 and the electrode PL2 are not short-circuited,
Since no defect occurs, the display characteristics are good. As is clear from FIG. 4, the storage capacitance element Cadd is
The scanning signal line GL is formed at a portion where the width of the second conductive film g2 is increased.
Have been. It should be noted that the second portion of the intersection with the video signal line DL
The electrolytic membrane g2 reduces the probability of short circuit with the video signal line DL
It is thin. (Equivalent Circuit of Holding Capacitor Cadd and Its Operation) FIG. 9 shows an equivalent circuit of the pixel shown in FIG. No.
In FIG. 9, Cgs is the gate electrode of the thin film transistor TFT
This is the parasitic capacitance formed between GT and the source electrode SD1.
You. The dielectric film of the parasitic capacitance Cgs is an anodic oxide film AFO and insulating
Membrane GI. Cpix is transparent with the transparent pixel electrode ITO1 (PIX).
The liquid crystal capacitance formed between the bright pixel electrode ITO2 (COM)
is there. The dielectric film of the liquid crystal capacitor Cpix is composed of liquid crystal LC, insulating film GI,
The protective film PSV1 and the alignment films ORI1 and ORI2. Vlc is midpoint
Rank. The storage capacitor Cadd is formed by a thin film transistor TFT.
When performing the pitching, the midpoint potential (pixel electrode potential) Vlc
It works to reduce the effect of the gate potential change ΔVg. This
Is expressed by the following equation. ΔVlc = {Cgs / (Cgs + Cadd + Cpix)} × ΔVg Here, ΔVlc represents a change in the midpoint potential due to ΔVg.
You. This change ΔVlc is the cause of the DC component applied to the liquid crystal LC.
However, the larger the storage capacity Cadd, the larger the value
Can be reduced. Also, the storage capacitance element Cadd is
It also has the effect of prolonging the discharge time, making it a thin film transistor TFT
The video information after turning off is accumulated for a long time. Apply to liquid crystal LC
The reduction of the direct current component that is
The so-called burn-in that the previous image remains when switching the display screen
Can be reduced. As described above, the gate electrode GT completes the i-type semiconductor layer AS.
The source electrode SD1
The overlap area with the rain electrode SD2 increases, and accordingly
As a result, the parasitic capacitance Cgs increases, and the midpoint potential Vlc
Inspection) The opposite effect of becoming susceptible to the signal Vg occurs
You. However, by providing the storage capacitance element Cadd,
Disadvantages can be eliminated. Whether the storage capacitance of the storage capacitor Cadd is the writing characteristic of the pixel
4 to 8 times the liquid crystal capacitance Cpix (4 · Cpix <Cadd <
8 Cpix), 8 to 32 times the parasitic capacitance Cgs (8 Cgs <
Set to a value of about Cadd <32 · Cgs). (Connection method of storage capacitor element Cadd electrode line) First stage scanning signal used only as storage capacitor electrode line
Line GL (Y₀) Is a common transparent pixel electrode as shown in FIG.
Connect to ITO2 (Vcom). The common transparent pixel electrode ITO2 is
As shown in Fig. 2A, a silver pen
It is connected to the external lead-out wiring by the paste material SL. I
Kamo, a part of the conductive film (g1 and g2) of this external wiring
Consists of the same manufacturing process as gate terminal GTM and scanning signal line GL
Have been. As a result, the last stage storage capacitor electrode line GL is
It can be easily connected to the common transparent pixel electrode ITO2. First stage storage capacitor electrode line Y₀To the scanning signal line Yend of the last stage
And connect to a DC potential point (AC ground point) other than Vcom.
Or one extra scan pulse Y from vertical runway circuit V₀
May be connected to receive the same. Next, the method of manufacturing the liquid crystal display device shown in FIG.
explain about. First, it consists of 7059 glass (product name)
Silicon oxide film SIO on both sides of lower transparent glass substrate SUB1
After setting by dip treatment, bake at 500 ° C for 60 minutes.
Perform Next, a film thickness is formed on the lower transparent glass substrate SUB1.
Sputtered the first conductive film g1 made of chromium with 1100 [1]
Provided by a ring. Next, nitric acid as an etchant
Photolithography using ceric ammonium solution
By selectively etching the first conductive film g1.
As shown in FIG. 12, the gate terminal GTM and the drain
Terminal DTM and connect the gate terminal GTM.
Anodized power supply line ASL, connected to anodized power supply line ASL
A pad PAD is formed. Next, the resist is stripped off by using S502.
(Product name), then O_TwoRun Usher for 1 minute
U. Next, it is made of aluminum with a thickness of 2600 [Å]
The second conductive film g2 is provided by sputtering. Next,
Use mixed acid of phosphoric acid, nitric acid and acetic acid as etching solution
Etching of the second conductive film g2 by photo etching technology
The scanning signal line GL, the gate electrode GT, and the
The electrode PL1 of the capacitive element Cadd is formed. In this case, the second
The overlapping portion of the conductive film g2 and the first conductive film g1 is comb-shaped.
And a line width of 10 [μ]
[m]. Next, dry etch
To SF₆Introduce gas to remove residues such as silicon.
After removal, the resist is removed. Next, the thickness 3 [μ
m], and by photo-etching process
Intersection of the scanning signal line GL with the video signal line DL, the gate electrode
The resist of the GT part and the electrode PL1 part is removed. Next, 3%
Neutralize the tartaric acid solution with ammonia and add ethylene glycol
Or diluted 1: 9 with propylene glycol, Ph7 ± 0.
Immerse in the anodizing solution adjusted to 5 and apply anodizing power to the pad PAD.
By applying pressure, the second conductive film g2 is anodized.
Then, an anodic oxide film AOF is provided. In this case, the current
0.5 ~ 10mA / cm^TwoThe voltage is gradually increased from 0 to +1 so that
Boost to 20V (constant current oxidation), and when + 120V
The voltage is maintained as it is (constant voltage oxidation). Then about 30
Approximately 1100 [Å] of the second conductive film g2 is oxidized by
An anodized film AOF of [Å] is obtained. Next, resist
After removal, and in air or vacuum at 200-400 ° C for 60
Heat for a minute. Next, from an ITO film with a thickness of 1000 [Å]
A first conductive film d1 is provided by sputtering. Next
Used a mixed acid of hydrochloric acid and nitric acid as an etching solution
The first conductive film d1 is selectively etched by photolithography.
By doing so, the transparent pixel electrode ITO1 and the gate terminal GTM,
The uppermost layer of the drain terminal DTM is formed. Next, Plas
Ammonia gas, silane gas, nitrogen gas
Introduce a silicon nitride layer with a thickness of 1200 to 2000 [Å]
(GI) is installed, and silane gas and hydrogen gas are
And introduce an i-type amorphous silicon with a film thickness of 200 to 1000 [Å].
After the recon layer (AS) is provided, hydrogen is added to the plasma CVD equipment.
Gas, phosphine gas introduced, the film thickness is 200-500
[Å] N doped with 0.6 to 2.5% of P⁺Type silicon layer (d
0) Provide a film. Next, S as a dry etching gas
F₆, CCl_FourWith photo etching technology using N⁺Type silicon layer (d
0), selectively etch i-type amorphous silicon layer (AS)
This forms an i-type semiconductor layer AS. Next
After removing the resist, dry etching gas
And SF₆Photolithography technology using a silicon nitride layer (G
By selectively etching I), the insulation film GI
And an opening HOP is provided. Next,
After removing the dist, a 500-1000 [膜厚]
A second conductive film d2 made of a film is provided by sputtering.
You. Next, the second conductive film d2 is selectively etched by a photolithography technique.
Switching, the video signal line DL and the source electrode SD
1. To form the first layer of drain electrode SD2 and electrode PL2
First, a drain electrode DTM is connected and the anode shown in FIG.
Electrostatic discharge prevention wire (not shown) connected to oxidation feed line ASL
) Are formed. Next, before removing the resist,
CCl for light etching equipment_Four,SCIENCE FICTION₆And introduce N⁺Type
By selectively etching the concrete layer (d0), N⁺
The type semiconductor layer d0 is formed. Next, the resist was removed.
Later, O_TwoAssert for 1 minute. Next, when the film thickness is 30
A third conductive film d3 made of aluminum of 00 to 8000 [Å]
It is provided by resistance heating evaporation or sputtering. Next
Next, the third conductive film d3 is selectively etched by a photolithography technique.
The video signal line DL, the source electrode SD1, and the drain.
The second layer of the in-electrode SD2 and the electrode PL2 is formed. Next,
After removing the dist_TwoAssert for 1 minute.
Next, after removing the resist, the plasma CVD device
Ammonia gas, silane gas and nitrogen gas are introduced to
A silicon nitride layer (PSV1) having a thickness of 1 [μm] is provided. One
, SF as dry etching gas₆Photos using
Selectively etch silicon nitride layer (PSV1) by etching technology
This forms the protective film PSV1. In this method of manufacturing a liquid crystal display device, the second conductive film
To make the overlapped part of g2 with the first conductive film g1 comb-shaped
In addition, the line width in the vicinity of the overlapping portion is 10 [μm] or less.
Whiskers are prevented from forming.
Can be stopped. In other words, according to experiments conducted by the inventors,
For example, when the line width of the aluminum film is 70 [μm],
Power density is 4.9 × 10^-6Pieces / cm^TwoAnd the line of the aluminum film
The whisker density when the width is 25 [μm] is 3.6 × 10^-6Pieces / cm
^TwoWhen the line width of the aluminum film is 10 [μm].
Whisker density is 0 / cm^TwoMet. Also, the anodic oxide film AO
After providing F, heat at 200-400 ° C for 60 minutes.
As is clear from Fig. 3, the leakage current of the anodic oxide film AOF
Can be reduced by one or more digits. In addition, heat treatment temperature
If the temperature is higher than 400 ° C., the second conductive film g2 may peel off.
Therefore, it is desirable to set the heat treatment temperature to 400 ° C or less.
No. As described above, the invention made by the present inventor is described in the embodiment.
Although the present invention has been specifically described based on
It is not limited to the scope and does not deviate from the gist
It goes without saying that various changes can be made in. For example, in the above embodiment, the transparent pixel electrode ITO1
Is composed of the first conductive film d1 made of an ITO film.
In the case of the projection type, the pixel electrode may be formed of a metal film. Ma
In the above embodiment, the third conductive film d3 is made of aluminum.
Using a silicon film but containing silicon or palladium
Alternatively, an aluminum film may be used. Further, the above embodiment
, The storage capacitor element between the adjacent scanning signal line GL
A child Cadd is formed, but it is held between itself and the scanning signal line GL.
A capacitor may be formed. In the above embodiment,
Has an opening HOP in the insulating film GI,
A transparent pixel electrode through the through hole.
The electrode ITO1 may be connected to the source electrode SD1 and the electrode PL2.
Further, an opening HOP is formed in the insulating film GI made of a silicon nitride film.
When forming an i-type amorphous silicon around the opening HOP
Recon layer (AS), N⁺Isolated layer consisting of a silicon mold layer (d0)
If a turn is formed, the end face of the opening HOP becomes an inclined surface
Therefore, the transparent pixel electrode ITO1 and the source electrode SD1
Can be reliably connected via the.

【The invention's effect】

As described above, in the liquid crystal display device according to the present invention, since the second insulating film is formed between the pixel electrode and the video signal line, there is no short circuit between the pixel electrode and the video signal line. Since no point defects occur, the display characteristics are good. Further, the dielectric film of the storage capacitor element is the first.
And the second insulating film, no short circuit occurs in the storage capacitor element portion, and no point defects occur, so that the display characteristics are good. Thus, the effect of the present invention is remarkable.

[Brief description of the drawings]

FIG. 1 is a plan view of a principal part showing one pixel of a liquid crystal display portion of an active matrix type color liquid crystal display device to which the present invention is applied, and FIG. 2A is a section line IIA-IIA of FIG. FIG. 2B is a cross-sectional view of
FIG. 2C is a cross-sectional view taken along the line IIB-IIB, FIG. 2C is a cross-sectional view showing the gate terminal portion of the liquid crystal display device shown in FIG. 1, and FIG. 4 to 6 are plan views depicting only predetermined layers of the pixel shown in FIG. 1, and FIG. 7 is only a pixel electrode layer, a light shielding film, and a color filter layer shown in FIG. The main part plan drawing,
FIG. 8 is an equivalent circuit diagram showing a liquid crystal display portion of an active matrix type color liquid crystal display device, FIG. 9 is an equivalent circuit diagram of the pixel shown in FIG. 1, FIG. FIG. 11 is a graph showing the relationship between the thickness of the film and the increase ratio of the mutual conductance gm. FIG. 11 is a graph showing the leak current characteristic of the anodic oxide film. FIG. 12 is a method for manufacturing the liquid crystal display device shown in FIG. FIG. 13 is a graph showing a relationship between a heat treatment temperature and a leak current, and FIGS. 14 and 15 are cross-sectional views each showing a part of a conventional liquid crystal display device. SUB: Transparent glass substrate GL: Scan signal line DL: Video signal line GI: Insulating film GT: Gate electrode AS: i-type semiconductor layer SD: Source or drain electrode PSV: Protective film BM: … Light-shielding film LC Liquid crystal TFT Thin film transistor ITO Transparent pixel electrode g, d Conductive film Cadd… Holding capacitance element Cgs… Parasitic capacitance Cpix… Liquid crystal capacitance AOF… Anodized film HOP… Opening Department

Continuing on the front page (72) Inventor Hideaki Taniguchi 3300 Hayano Mobara-shi, Chiba Pref. Mochi Plant, Hitachi Co., Ltd. 72) Inventor Haruo Matsumaru 1-280 Higashi Koigakubo, Kokubunji-shi, Tokyo Inside Central Research Laboratory, Hitachi, Ltd. (56) References JP-A 1-267618 (JP, A) JP-A 1-274116 (JP, A) Kaihei 2-85826 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G02F 1/136

Claims (3)

(57) [Claims] An active matrix type liquid crystal display device comprising a thin film transistor, a pixel electrode, and a storage capacitor as components of a pixel and applying a voltage of a video signal line to the pixel electrode via the thin film transistor. The gate electrode of the thin film transistor is made of aluminum, and the top and side surfaces thereof are provided with a first insulating film made of aluminum oxide. The first electrode constituting the storage capacitor is made of aluminum and the top and side surfaces thereof are made of aluminum. A first insulating film made of an oxide of aluminum is provided, and a first insulating film formed on the surface on which the gate electrode is formed is separated from the gate electrode so that the first insulating film is not in contact with the gate electrode. A first electrode covering a side surface and a top surface of the gate electrode on a surface on which the gate electrode is formed; Border membrane and the first
The first insulating film is formed on a region between the first insulating film and the first insulating film covering the side surface and the upper surface of the first electrode, and is separated from each of the first insulating films. A second insulating film made of silicon nitride is formed so as to cover between each and the pixel electrode, and the first insulating film is in contact with the pixel electrode and on the second insulating film.
A second electrode forming the storage capacitance element extending so as to be opposed to the first electrode; and the video signal line being on the second insulating film and on the opposite side of the thin film transistor from the pixel electrode. A liquid crystal display device characterized by being formed. 2. The liquid crystal display device according to claim 1, wherein said second electrode is made of the same material as said video signal line. 3. The liquid crystal display device according to claim 1, wherein said first electrode is formed integrally with said gate electrode of another pixel adjacent to said pixel.