JPH0566413A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To obtain a liquid crystal display device in which a protective layer for a transistor is easily formed and which has stab transistor characteristic without using the SiN based protective layer. CONSTITUTION:This device is provided with an active matrix substrate 1 where a liquid crystal display part consisting of a matrix-state picture element electrode and a thin film transistor part for driving the picture element electrode, a horizontal(scanning line) driving circuit 4 which is connected to the liquid crystal display part, and a vertical(signal line) driving circuit 5 which is connected to the liquid crystal display part are formed; an upper substrate 2 which is overall opposed to the active matrix substrate; and a liquid crystal layer interposed and held between the active matrix substrate 1 and the upper substrate 2. Then, the liquid crystal display part is protected by a silicon oxide based insulating film and the liquid crystal layer.

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,
In particular, the present invention relates to a liquid crystal display device in which a drive circuit composed of thin film transistors is built in a liquid crystal cell.

[0002]

2. Description of the Related Art A conventional liquid crystal display device, as shown in FIG. 21, has a thin film transistor (TFT) outside the liquid crystal cell portion.
Horizontal (scan line) drive circuit (horizontal-dr
iver) 4 and vertical (signal line) drive circuit (Vertical-
Each driver circuit of the driver 5 was provided. That is, only the liquid crystal cell portion is sandwiched between the upper substrate 14, the lower substrate 15 and the upper and lower substrates thereof, and the liquid crystal layers (not shown) enclosed by the spacers 16 are entirely opposed to each other. ..

As described above, in the state where the driving circuit having the TFT is provided outside the liquid crystal cell, a protective layer made of SiN is provided to prevent the entry of mobile ions such as water and sodium into the driving circuit. TF used in the drive circuit
It was necessary to use it for the T part.

On the other hand, in the liquid crystal cell, since a polyimide (PI) type is used as an aligning agent, a silicon dioxide (SiO ₂ ) type TFT transistor protective insulating film has to be used in the pixel portion.

[0005]

In the liquid crystal cell, the above-mentioned Si is used.
If a SiN-based insulating film is used as a protective layer for a transistor instead of an O ₂ -based one, the adhesion of polyimide and the uniformity of an alignment film are impaired. As a result, the alignment of the liquid crystal is impaired. Moreover, when a SiN-based protective layer is used above the transistor, the film stress remaining in the SiN shifts the transistor characteristics, such as VTH.

Further, Japanese Patent Publication No. 2-61032 discloses a liquid crystal display device in which each drive circuit is incorporated in a liquid crystal cell. However, in this liquid crystal display device, the passivation film material for transistor protection is not specified. Nonetheless, it still left the above problems.

An object of the present invention is to provide a liquid crystal display device in which a transistor protective layer can be easily formed and which has stable transistor characteristics without using a SiN-based protective layer.

[0008]

According to the present invention, the above-mentioned problem is solved by connecting a liquid crystal display section comprising pixel electrodes arranged in a matrix and thin film transistors for driving the pixel electrodes, and a liquid crystal display section. Scanning line driving circuit and a signal line driving circuit connected to the liquid crystal display device, an active matrix substrate, an upper substrate entirely facing the active matrix substrate, the active matrix substrate and an upper portion. A liquid crystal display device including a liquid crystal layer sandwiched between a substrate and the liquid crystal display unit is protected by a silicon oxide insulating film and the liquid crystal layer.

[0009]

According to the present invention, the liquid crystal display portion including the pixel electrode 13 and the thin film transistor, the scanning line driving circuit 4 and the signal line driving circuit 5 are formed on the active matrix substrate, and the active matrix substrate is entirely opposed to the active matrix substrate. Thus, since the upper substrate 2 is formed and the liquid crystal display section is protected by the silicon oxide insulating film and the liquid crystal layer, the process of forming the protective layer of the transistor is simplified. Moreover, since the SiN-based protective layer is not used, transistor characteristics due to film stress remaining in the SiN film, such as V
Does not cause deterioration such as TH.

In the present invention, PSG (phosphosilicate glass), BSG (borosilicate glass) is used as the silicon oxide insulating film.
Etc. are preferably used. Of course, SiO ₂ (silicon dioxide) may be used.

[0011]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a schematic perspective view showing an embodiment of a liquid crystal display device according to the present invention. As shown in FIG. 1, a liquid crystal display device according to the present invention includes an active matrix substrate 1 as a lower substrate in which thin film transistors are formed as active switching elements, an upper substrate 2 facing the active matrix substrate 1, and those substrates. A mode in which a liquid crystal layer sandwiched between 1 and 2 and enclosed by a spacer 3 is provided, and a horizontal (scanning line) drive circuit 4 and a vertical (signal line) drive circuit 5 are respectively incorporated in a liquid crystal cell on an active matrix substrate 1. It is provided in. Furthermore, this liquid crystal display device
As shown in more detail in FIG. 2 below, PSG is used as an insulating film (passivation film) for transistor protection.
A silicon oxide based insulating film such as is used. The liquid crystal layer itself also contributes to protection of the transistor.

FIGS. 2A and 2B are a partial sectional view of a drive circuit section and a partial sectional view of a pixel switch, respectively, of the liquid crystal display device of the present invention shown in FIG.

First, as shown in FIG. 2A, a CMOS portion is particularly shown in the drive circuit portion, and a gate insulating film 7, a polycrystalline silicon (poly-Si) gate 8, an aluminum (Al) electrode 9 are provided. , PSG protective layers 10a, 10
b, PSG interlayer insulating film 10c and polyimide alignment film 11
It is composed of.

Next, the pixel switch shown in FIG. 2B is composed of a pixel portion, a thin film transistor (TFT) portion, and a storage capacitor (Cs) portion. Figure 2
In FIG. 2B, the same symbols as those shown in FIG. 2A indicate the same elements.

Reference numeral 13 in FIG. 2B is a pixel electrode made of ITO (indium tin oxide), which is connected to the drain region. As shown in FIGS. 2A and 2B, the upper part of the transistor of the drive circuit of the liquid crystal display device of the present invention is protected by a silicon oxide-based PSG film, and the liquid crystal layer itself contains moisture and mobile ions. Has a deterrent function of
Acts as a protective layer.

FIG. 3 shows the evaluation results of the reliability of the conventional drive circuit in which the drive circuit is disposed outside the liquid crystal cell and the protective layer is SiN, and the drive circuit of the embodiment of the present invention.

The reliability of the drive circuit was judged by a high temperature operation test. High temperature operation test is 10% of rated at 85 ℃
It was evaluated by the increased driving voltage. As is clear from the figure,
It can be seen that it has almost the same reliability as the conventional example.

The process flow of the liquid crystal display device according to the present invention will be described below with reference to FIGS.

First, as shown in FIG.
A first polysilicon layer having a film thickness of 80 nm by low pressure CVD
A (poly-Si) layer 21 is formed, and silicon ions are formed.
(Si ⁺) After implantation, solid phase growth annealing at a temperature of 620 ° C.
I went. Si above⁺The conditions for the implantation of 30 KeV are
1 x 10¹⁵/ Cm²After, 50 KeV, 1 × 10¹⁵/ C
m²I went there twice.

Next, as shown in FIG. 5, the first poly-Si layer region 2 is etched by a lithography technique.
1a and 21b were formed.

Next, as shown in FIG. 6, a SiO ₂ gate insulating film 22 having a film thickness of 50 nm was formed by a thermal oxidation method.

Next, as shown in FIG. 7, the first p of the Cs (storage capacitor) portion is formed using the resist 23 as a mask.
Arsenic ions (As ⁺ ) are added to the oli-Si layer region 21a.
Ion implantation was performed under the conditions of 0 KeV and 5 × 10 ¹⁴ / cm ² .

Next, as shown in FIG. 8, a SiN film having a thickness of 30 nm was formed by a low pressure CVD method, and after partial etching, a SiN gate insulating film 24 was formed on the SiO ₂ gate insulating film 22.

Next, as shown in FIG. 9, a second polysilicon (poly-Si) layer 25 is formed to a thickness of 350 nm by a low pressure CVD method, and then a second pol is formed by PSG.
The resistance of the y-Si layer 25 was reduced.

Next, as shown in FIG. 10, patterning is performed by plasma etching to form second poly-Si layer regions 25a and 25b on the SiN gate insulating film 24.
Using CF ₄ and O ₂ as etching gas, CF ₄ / O ₂ =
It was set to 95/5.

Next, as shown in FIG. 11, the Si of the TFT is
Part of the N gate insulating film 24 is removed by etching, As ⁺ is ion-implanted into the entire surface under the conditions of 100 KeV and 1 × 10 ¹³ / cm ² , and further As ⁺ is 140 KeV on the transistor side to form an N channel, 2 × 10 Ion implantation was performed under the condition of ¹⁵ / cm ² .

Next, as shown in FIG.
After applying, boron ion (B ⁺ ) to make P channel
Was ion-implanted under the conditions of 30 KeV and 2 × 10 ¹⁵ / cm ² .

Next, as shown in FIG. 13, after removing the resist 27, a P film having a film thickness of 500 nm is formed by a low pressure CVD method.
The SG and the SiO ₂ interlayer insulating film 28 having a film thickness of 100 nm were formed.

Next, as shown in FIG. 14, the SiO ₂ interlayer insulating film 28 and the SiO ₂ gate insulating film 22 are wet-etched using HF / NH ₄ F as an etchant to form a first contact for a source or drain extraction electrode. Hole 29 was formed.

Next, an Al / Si film is formed on the entire surface by a sputtering method to have a film thickness of 600 nm, and then wet etching is performed using an etchant of H ₃ PO ₄ / H ₂ O = 2/10 as shown in FIG. Then, the Al / Si film was patterned to form the Al / Si electrode 30.

Next, as shown in FIG. 16, a PSG passivation film 31 having a thickness of 400 nm is formed by a low pressure CVD method.
And then made of SiN by PCVD method.
The N passivation film 32 was formed. After that, in a reducing atmosphere of hydrogen (H ₂ ) diluted with Ar at about 400 ° C. for 3
Hydrogen annealing treatment was performed for 0 minutes.

Next, as shown in FIG. 17, the entire SiN passivation film 32 is plasma-etched with an etching gas of CF ₄ / O ₂ = 95/5, and then HF / N.
First by wet etching with H ₄ F as etchant
A second contact hole 33 for a source or drain lead electrode reaching the polysilicon layer region 21a was formed.

Next, as shown in FIG. 18, ITO (indium tin oxide) is formed at a temperature of 400 ° C. by a sputtering method.
The film 34 was deposited on the entire surface.

Next, as shown in FIG. 19, HCl: H ₂
The ITO film 34 was patterned with an etchant of O: NO ₃ = 300: 300: 50 to form an ITO pixel electrode 34.
a was formed.

Next, as shown in FIG. 20, a polyimide (PI) film 3 for liquid crystal alignment is formed on the exposed surface, that is, on the surface of the PSG passivation film 31 and the ITO pixel electrode 34a.
5 was formed to obtain an active matrix substrate. Figure 20
After that, a liquid crystal layer was sandwiched between the upper substrate and the active matrix substrate formed by this manufacturing process to obtain a liquid crystal display device.

[0037]

As described above, according to the present invention, the process of forming the protective layer of the transistor can be simplified and it is not necessary to use the SiN-based protective layer.
The transistor characteristic does not deteriorate due to the film stress of the N film. Further, by using a SiO ₂ -based (PSG or the like) insulating film, the organic adhesive can be used with sufficient adhesive strength when forming the liquid crystal cell.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing an embodiment of a liquid crystal display device according to the present invention.

2 is a partial cross-sectional view of a drive circuit unit and a pixel switch of the liquid crystal display device of the present invention shown in FIG.

FIG. 3 is a diagram showing reliability evaluation results of a conventional device and a drive circuit according to an embodiment of the present invention.

FIG. 4 is a manufacturing process flow chart of an example.

FIG. 5 is a manufacturing process flow chart of the example.

FIG. 6 is a manufacturing process flow chart of an example.

FIG. 7 is a manufacturing process flow chart of an example.

FIG. 8 is a manufacturing process flow chart of the example.

FIG. 9 is a manufacturing process flow chart of the example.

FIG. 10 is a manufacturing process flow chart of the example.

FIG. 11 is a manufacturing process flow chart of the example.

FIG. 12 is a manufacturing process flow chart of the example.

FIG. 13 is a manufacturing process flow chart of the example.

FIG. 14 is a manufacturing process flow chart of the example.

FIG. 15 is a manufacturing process flow chart of the example.

FIG. 16 is a manufacturing process flow chart of the example.

FIG. 17 is a manufacturing process flow chart of the example.

FIG. 18 is a manufacturing process flow chart of the example.

FIG. 19 is a manufacturing process flow chart of the example.

FIG. 20 is a manufacturing process flow chart of the example.

FIG. 21 is a schematic perspective view showing an example of a conventional liquid crystal display device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Active matrix substrate 2 Upper substrate 3 Spacer 4 Horizontal (scanning line) drive circuit 5 Vertical (signal line) drive circuit 7 Gate insulating film 8 Polycrystalline silicon (poly-Si) gate 9 Al electrode 10a, 10b PSG protective film 10c PSG Interlayer insulating film 11 Polyimide alignment film 13 ITO pixel electrode 14 Upper substrate 15 Lower substrate 16 Spacer 20 Quartz substrate 21 First polysilicon (poly-Si) layer 22 SiO ₂ Gate insulating film 23 Resist 24 SiN Gate insulating film 25 Second poly- Si layer 27 Resist 28 SiO ₂ interlayer insulating film 29 First contact hole 30 Al / Si electrode 31 PSG passivation film 32 SiN passivation film 33 Second contact hole 34 ITO film 34a ITO pixel electrode 35 Polyimide (PI) film

Claims (1)

[Claims] 1. Pixel electrodes arranged in a matrix,
An active matrix substrate on which a liquid crystal display section including a thin film transistor for driving the pixel electrode, a scanning line drive circuit connected to the liquid crystal display section, and a signal line drive circuit connected to the liquid crystal display device are formed. An upper substrate that entirely faces the active matrix substrate, and a liquid crystal layer sandwiched between the active matrix substrate and the upper substrate, wherein the liquid crystal display section includes a silicon oxide insulating film and the liquid crystal layer. A liquid crystal display device characterized by being protected by.