JPH09244045A - Liquid crystal display device and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to increase a contrast, to decrease the variations of many pixels and to reduce a manufacturing cost by forming the same electrode layer as the pixel electrodes of an image display section on the bonding pads of peripheral circuits as well. SOLUTION: The pixel electrodes 109 are disposed not only in the pixel parts but on the bonding pads 105 as well and are electrically connected via openings 111 on the pads. ITO films are most frequently used as the pixel electrodes 109. Al-Si films are adequate, for example, for the drain electrodes 105b of TFTs and the bonding pads 105c. The improvement of the ohmic property with the ITO films is executed by depositing films of, for example, titanium nitride, titanium, etc., on the Al-Si surfaces. Hydrogenation is executable after all of the stages to induce the damage of dry etching, etc., are ended in this stage and, therefore, the recovery and removal of the damage are embodied with good reproducibility. Since through-holes and the openings 111 of the pads are executable by the same stage, the production stages are simplified.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device and a method for manufacturing the same, and particularly to a poly-Si TFT (Thin-thin-
The present invention relates to an active matrix liquid crystal display device using a FIlm Transistor) and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, active matrix type liquid crystal display devices using TFTs have rapidly become popular due to their portability and high image quality. The reason for high image quality is that TFTs are used as switching elements in the pixel section, so that more pixels can be driven than in the simple matrix type, the current ON / OFF ratio can be increased, and the contrast can be improved. In an active matrix type liquid crystal display device, a shift register for driving a normal display unit, peripheral circuits such as transfer switches, and bonding pads for connecting to the outside are integrated on the same substrate.

FIG. 6 shows a typical pixel portion (for one pixel) and PA.
It is sectional drawing (a) of D part. In the figure, 101 is a silicon or quartz substrate whose surface is insulated, or a glass substrate,
Is thin polysilicon to be a TFT channel, 103 is a polysilicon gate electrode, and 104 is, for example, BPSG (B
oron-Phospho Silicate Gla
a first interlayer insulating film such as ss), and 105a to 105c are A
In the electrode layer containing 1 as a main component, 105a is a source electrode, 1
Reference numeral 05b is a drain electrode and 105c is a PAD electrode.
106 is a second interlayer insulating film such as PSG, 107
Is a light shielding layer for shielding the TFT, 108 is a third interlayer insulating film, and 109 is, for example, ITO (Indium Tin).
-Oxide) and other pixel electrodes. Here, the thin polysilicon 102 is doped with an impurity for ohmic contact to form a source region 115a and a drain region c. In this example, the gate electrode 103 is divided into two in the channel length direction to provide redundancy in order to prevent a source / drain short circuit failure of the TFT, and the heavily doped layer 115b is formed in the polysilicon layer in the region between them. Is formed. The gate electrode controls the channel of the TFT by the electric field effect through the gate insulating film 116. Pixel electrode 1
The liquid crystal 11 is formed on the upper surface of the liquid crystal layer 09 via a thin alignment film (not shown).
2 and is sandwiched between the pixel electrode 109 and the glass substrate 114 covered with the transparent common electrode 113 of the liquid crystal 112. There is no liquid crystal on the PAD electrode 105c and there is an opening 1
11 is provided so that a bonding material with the outside can be bonded. The source electrode 105a and the drain electrode 105b are respectively provided with R through the contact holes 117 and 118.
It is connected to the source region 115a and the drain region 115b of the FT, and the pixel electrode 109 is connected to the drain electrode 105b through the through hole 110.

In the plan view of FIG. 6 (b), the parts corresponding to those of FIG. 6 (a) are designated by the same reference numerals. However, the light shielding film 107
6B covers a region that is largely hatched in FIG. 6B and shields light except for the opening 119 for display.

[0005]

However, in the conventional active matrix panel, the following problems had to be solved. Minimize manufacturing man-hours and reduce costs. TF with high performance and little variation using simple process
By creating T, it is possible to display with more pixels and multiple gradations.

In the conventional example, the following elements are one of the obstacles to solving the above problems.

A) Separate masks for through holes, PAD openings, and etching steps are required. This is I
Etching solution HI (hydroiodic acid) or FeCl ₃ (iron chloride solution) for etching transparent electrodes such as TO
However, since the PAD electrode is also etched, it is necessary to first open the through hole, deposit and etch the ITO electrode, and then form the opening 105c on the PAD with another mask.

B) Since the hydrogenation step required for improving and stabilizing the characteristics of the TFT must be performed before the deposition of ITO in order to prevent the alteration (blackening) of ITO, After that, damage during plasma etching when opening the PAD portion cannot be removed. The characteristics of the TFT are deteriorated and vary from manufacturing lot to manufacturing lot.

[0009]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have made intensive efforts and, as a result, have obtained the following invention. That is, the liquid crystal display device of the present invention includes an image display unit provided with a switching element, one substrate including a peripheral circuit for outputting a signal to the image display unit, and a transparent electrode facing the one substrate. In a liquid crystal display device having the other substrate provided and the liquid crystal sandwiched between the one substrate and the other substrate, the same electrode layer as the pixel electrode of the image display unit is also used as a bonding pad of the peripheral circuit. It is characterized by being formed. Here, it is preferable that the connection between the pixel electrode and the switching element and the connection between the bonding pad and the electrode layer are both performed through a through hole. In addition, the pixel electrode and the conductive layer are made of ITO (Indium-Tin-Oxid).
e) is good. Further, it is preferable that the bonding to the bonding pad is performed via an anisotropic conductive film.

The present invention also includes the invention of a method for manufacturing a liquid crystal display device. That is, the driving method of the liquid crystal display device of the present invention is one substrate including an image display unit provided with a switching element and a peripheral circuit for outputting a signal to the image display unit, and a transparent substrate facing the one substrate. In a method of manufacturing a liquid crystal display device having the other substrate having electrodes, and the liquid crystal sandwiched between the one substrate and the other substrate, the same electrode layer as the pixel electrode of the image display unit is provided in the peripheral circuit. The bonding pad is also formed. At this time, the connection between the pixel electrode and the switching element and the connection between the bonding pad and the electrode layer may both be performed through a through hole. In addition, after forming the through hole, a hydrogenation step may be performed, and then the pixel electrode and the electrode layer may be formed. Further, it is preferable that the through hole connecting the pixel electrode and the switching element and the through hole connecting the bonding pad and the electrode layer are formed in the same photolithography process using the same mask.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION

<First Embodiment> The configuration of the first embodiment will be described with reference to FIG. In FIG. 1, (a) is a sectional view and (b) is a plan view. In order to make a comparison with a conventional one clear, the same parts as those in FIG. Further, the parts having the same names have the same functions as those of the conventional example, and the description thereof will be omitted. The points different from the conventional example will be described below. However, polysilicon 1
02 may be a general semiconductor such as amorphous or single crystal.

In the present invention, the pixel electrode 109 is provided not only in the pixel portion but also on the bonding PAD, and is electrically connected through the opening 111 on the PAD. FIG. 2 also shows that the pixel electrode layer 109 covers the bonding pad 105c.

The most commonly used pixel electrode is I
A TO film, which has a sheet resistance of 5 to 50 Ω / □ and a film thickness of about 1500 Å, is used in this embodiment.

In this embodiment, the drain electrode 10 of the TFT
5b and the bonding PAD 105c are made of, for example, Al-Si.
A membrane is preferred. In order to improve the ohmic contact with the ITO film, a film such as titanium nitride or titanium may be deposited on the Al-Si surface. In this embodiment, the TFT
A plasma fluorinated film was used as a third interlayer film on the light-shielding film 107 for hydrogenating the. By performing a heat treatment (300 to 475 ° C.) in the step after depositing this film, T
Hydrogen molecules are supplied to the polysilicon of the FT to improve the characteristics of the TFT. Alternatively, a silicon oxide film may be used as the third interlayer insulating film, and hydrogen plasma treatment (eg, 300 ° C. for 2 hours) may be performed in the subsequent step. Also, I
The bonding PAD that TO is deposited on the surface ACF (A nisotropic C onductui
n Film anisotropic conductive film) is suitable. In FIG. 2, PAD is pressure-bonded to a wiring board with an anisotropic conductive film. A resin such as silicone rubber is used as the base material of the anisotropic conductive film, and carbon fibers or nickel particles are used as the conductive material. Regarding the anisotropic conductive film, the electronic materials 1990 and p82 are detailed.

Next, a method of manufacturing the liquid crystal display device of this embodiment will be described with reference to FIGS.

Polysilicon is formed on a silicon substrate, a quartz substrate, or a glass substrate 101 having an oxide film formed on the surface thereof by using a polysilicon layer.
~ 2000Å, deposited by CVD method. A gate insulating film 116 made of a two-layer film of a silicon oxide film by thermal oxidation or an oxide film followed by a nitride film is formed by a CVD method. Next, polysilicon is deposited in the range of 1000 to 6000Å, the entire surface is doped with n-type, and then patterned to form the gate electrode 103. At this point, the source / drain region and the intermediate region 1
Doping of 15a, b, and c is performed by ion implantation or an ion doping method, and heat treatment for activation is performed.
Next, after depositing a BPSG or PSG film which is the second interlayer film 104, contact holes 117 and 118 are opened.
Next, Al-Si to be electrodes is deposited and patterned to form drain, source and pad electrodes 105a, 105b, 1
05c is formed. In order to prevent the contact from penetrating, it is preferable to form the barrier metal in the lowermost layer. Further, as described above, by providing an adhesive layer of TiN, Ti, etc. on the uppermost layer, ohmic contact with ITO is improved. Next, as a second interlayer insulating film 106, a silicon oxide film is deposited in a range of 4000 to 15000Å. As a deposition method, for example, a plasma CVD method, a thermal CVD method, or a sputtering method can be used. Next, for example, titanium is used as a light shielding film.
After depositing 00 to 5000 Å, patterning is performed to form a light shielding layer 107. On top of that, a silicon nitride film by plasma CVD is used as a third interlayer insulating film in an amount of 500 to 500.
Deposit 0Å. This film can also be used as a capacitor film for forming a storage capacitor between the pixel electrode and the light shielding layer 107. Further, in order to improve the transmittance in the display portion, the display brightness can be improved by setting the thickness to the optical non-reflection condition. For example, with a silicon nitride film having a refractive index of 2.0, 550 / is applied to light having a wavelength of 550 (nm).
It is effective to set the film thickness to a value close to an integer multiple of (2 × 2.0) = 1375Å (FIG. 3- (a)). Next, the through hole 110 of the pixel portion and the opening 111 on the PAD are formed in the same step. Dry etching for the opening is performed by, for example, 0.1 to 10 in a mixed gas of SF ₆ , CH ₂ F ₂ and Cl _2.
It is performed under a pressure of 0 Torr (FIG. 3- (b)).

Next, heat treatment is performed at 300 to 475 ° C. in hydrogen gas or a mixed gas of hydrogen / nitrogen (15 to 150).
Minutes). By this heat treatment, the plasma silicon nitride film 10
The H ₂ atoms in 8 are diffused to terminate the unbonded polysilicon of the TFT with H (hydrogenation). It is desirable that this process is performed so that exposed portions of the electrodes 105b and 105c are not unnecessarily oxidized and that air or oxygen is not introduced. Plasma and ion damage at the time of etching through holes and openings on the PAD can be recovered or removed by this hydrogenation. After that, the sputtering method I
A TO film was deposited and an ITO pattern on the pixel electrode and PAD was formed using hydroiodic acid as an etching solution. The sputtering conditions are a substrate temperature of 150 to 300.
° C., a mixture of 0.1% to 10% of O ₂ gas to the Ar gas, and sputtering a mixed sintered target of indium oxide and tin oxide. Under this condition, ohmic contact with the electrodes 105b and 105c is good. The substrate thus prepared is coated with an alignment film, rubbed on the surface thereof, and then sandwiched by a spacer (not shown) and a counter substrate having a counter transparent electrode 113 formed on the counter glass substrate 114, to form a gap. For example, TN type liquid crystal 112 is injected (FIG. 1).

Although the steps for forming the peripheral circuit using only the TFT have been described above, for example, the TFT is used for the switching element of the pixel display section and the single crystal bulk silicon is used for the peripheral circuit. In this case, the element isolation region of the peripheral circuit may be formed before the above steps, and the polysilicon gate, the electrode, and the like may use the same layer as the pixel.
Then, after injecting the liquid crystal, the substrate Si of the display section is removed to obtain a transmissive liquid crystal display device.

The liquid crystal display device of the present invention can be applied not only to an electronic viewfinder but also to a spectacle type image display device, a panel for a projection television, a direct view type display of 2 inches or more, and the like. Is demonstrated.

According to the present embodiment, hydrogenation can be performed after completing all the processes such as dry etching which cause damage, so that damage can be recovered.
Removal can be realized with good reproducibility. Therefore, the current driving force of the TFT is improved and stabilized, and at the same time, the leak current is reduced. It is possible to obtain a liquid crystal display which is uniform and has few defects such as scratches, in which the conventional TFT characteristics and the TFT characteristics of the present embodiment, that is, the display contrast is high. Compare with FIG.

Since the through hole and the PAD opening can be formed in the same process, the manufacturing process can be simplified. The manufacturing cost can be reduced by helping to improve the yield due to the effect of.

<Second Embodiment> FIG. 5 shows a sectional view of the second embodiment. In this embodiment, the through hole of the pixel portion is TF.
It is directly connected as a region to the drain of T. in this case,
Under the ITO (not shown), for example, thin TiN
By forming the layer, the ohmic property becomes good. Although the depths of the through holes and the openings on the PAD are different, it is possible to form holes having different depths by etching the bonding PAD by selecting the gas composition.

The present embodiment can be applied to the application product of the first embodiment in exactly the same manner, and the same effects as those of the first embodiment can be obtained in terms of TFT characteristics and cost reduction. .

[0024]

According to the present invention, since the through hole for connecting the pixel electrode and the TFT and the opening on the bonding pad can be formed by the same mask and photolithography process, the manufacturing cost of the liquid crystal panel can be reduced. Contribute to reduction.

Further, if the hydrogenation step is performed at the time when the etching step of the opening is completed, damage to the TFT due to the etching (specifically, deterioration of driving force, leak current) is performed without deteriorating the ITO film. Increase)
Since it can be removed, the contrast is high,
A liquid crystal display panel having more pixels can be provided with a small variation.

[Brief description of drawings]

FIG. 1 is a sectional view (a) and a plan view (b) of a liquid crystal display device of the present invention.

FIG. 2 is a bonding sectional view of the liquid crystal display device of the present invention.

FIG. 3 is a cross-sectional view showing the manufacturing method of the second embodiment of the present invention.

FIG. 4 is a diagram showing IV characteristics of a TFT according to the present invention.

FIG. 5 is a cross-sectional view of the liquid crystal display device of the second embodiment.

FIG. 6 is a sectional view (a) and a plan view (b) of a conventional liquid crystal display device.

[Explanation of symbols]

 101 substrate 102 semiconductor region 103 gate electrode 104 first interlayer insulating film 105 electrode layer 111 peripheral circuit section

Claims (8)

[Claims] 1. A substrate having an image display unit provided with a switching element and a peripheral circuit for outputting a signal to the image display unit, and another substrate facing the one substrate and having a transparent electrode. And a liquid crystal display device having the liquid crystal sandwiched between the one substrate and the other substrate, the same electrode layer as the pixel electrode of the image display unit is also formed on a bonding pad of the peripheral circuit. Liquid crystal display device characterized by. 2. The liquid crystal display device according to claim 1, wherein the connection between the pixel electrode and the switching element and the connection between the bonding pad and the electrode layer are both performed through a through hole. 3. The pixel electrode and the conductive layer are made of ITO (I
The liquid crystal display device according to claim 1, wherein the liquid crystal display device is ndium-Tin-Oxide). 4. The bonding to the bonding pad is performed through an anisotropic conductive film.
4. The liquid crystal display device according to any one of 3 to 3. 5. A substrate provided with an image display unit provided with a switching element and a peripheral circuit for outputting a signal to the image display unit, and another substrate provided with a transparent electrode facing the one substrate. And a liquid crystal sandwiched between the one substrate and the other substrate, wherein the same electrode layer as the pixel electrode of the image display unit is also formed on the bonding pad of the peripheral circuit. A method for manufacturing a liquid crystal display device, comprising: 6. The method for manufacturing a liquid crystal display device according to claim 5, wherein the connection between the pixel electrode and the switching element and the connection between the bonding pad and the electrode layer are both performed through a through hole. 7. The method of manufacturing a liquid crystal display device according to claim 6, wherein a hydrogenation step is performed after the through hole is formed, and then the pixel electrode and the electrode layer are formed. 8. A through hole for connecting the pixel electrode and the switching element and a through hole for connecting the bonding pad and the electrode layer are formed in the same photolithography process using the same mask. Alternatively, the method of manufacturing the liquid crystal display device according to item 7.