JPH05190853A - Display device - Google Patents

Abstract

PURPOSE:To provide a display device being high in the mobility of a carrier in the channel layer of a driver circuit for driving and little in the variation of TFT characteristics of a display part. CONSTITUTION:The channel layer 2c of the thin-film transistor of a display part is smaller in crystal grain size than the channel layers 2a, 2b of the thin- film transistor to be used for a driver circuit for driving. Because the channel layers 2a, 2b are polycrystalline silicon layers obtained by the heat treatment of amorphous silicon at a low temperature and for a long period of time, they are larger in crystal grain size than the channel layer 2c obtained by the deposition of polycrystalline silicon. Because the crystal grain size of the channel layers of the thin-film transistor to be used for the driver circuit for driving is large, the mobility of a carrier becomes higher so that a highspeed display is made possible. Also, because the crystal grain size of the channel layer of the transistor of the display part is small as compared with the size of the channel layer, a satisfactory picture quality can be obtained without any variation in transistor characteristics.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a thin film transistor (T
The present invention relates to a driver monolithic display device in which a display unit having an FT) and a driver circuit for driving the display unit are built in on the same substrate.

[0002]

2. Description of the Related Art Conventionally, a driver monolithic type TFT substrate has been used for a display device. An example of the driver monolithic type TFT substrate is shown in FIG. On the driver monolithic TFT substrate 20, the pixel electrode 2
1 and a display section 23 having the TFT 22 and the like, and a driver circuit 24a for driving the display section 23,
24b are formed. Driving driver circuit 24
Each of a and 24b has a TFT (not shown) for driving the display unit 23. Normally, driver circuit 2 for driving
The TFTs 4a and 24b include the TFT 22 of the display unit 23.
The same configuration is used.

The TFT of the display section 23 and the TFTs of the driver circuits 24a and 24b for driving have the structure shown in FIG. 7, for example. Semiconductor layers 32a, 32b, 3 such as a polycrystalline silicon layer formed on the insulating substrate 31
The channel layers 39a, 39b, 39c and the high impurity concentration regions (N ⁺ regions or P ⁺ regions) 40a, 40 in a part of 2c.
b and 40c are formed. Channel layers 39a, 3
Gate electrodes 35a, 35b and 35c are provided above 9b and 39c with the gate insulating film 34 interposed therebetween. Gate electrodes 35a, 35b, 35c and gate insulating film 34
An interlayer insulating film 36 is formed on the top. Contact hole 3 penetrating through gate insulating film 34 and interlayer insulating film 36
7a, 37b, and 37c are high-concentration impurity regions 40, respectively.
It is formed on a, 40b, and 40c. High concentration impurity regions 40a, 40b, 40c and electrodes 38a, 38b, 3
8c are contact holes 37a, 37b and 3 respectively.
It is electrically connected via 7c.

The TFTs in the driving driver circuits 24a and 24b are required to have high carrier mobility in the channel layers 39a and 39b in order to cope with high-speed display. Channel layer 3 with high carrier mobility
To obtain 9a, 39b, the channel layers 39a, 39
It is necessary to increase the crystal grain size of b and reduce the electric resistance due to the grain boundaries. For example, the semiconductor layers 32a, 32
When b is a polycrystalline silicon layer, a crystal grain size of more than 1 μm is required.

Further, the driver circuits for driving 24a, 24
Since the TFT in b is required to have a current driving capability, a TFT having a relatively large size is used.
The above TFT is required to have a smaller size in order to improve the aperture ratio.

[0006]

A driver circuit for driving 2
When the crystal grain size of the TFT channel layers 39a and 39b in the TFTs 4a and 24b is about 1 μm, the crystal grain size of the TFT channel layer 39c of the display unit 23 is also about 1 μm, which is about the same as the size of the channel layer 39c. Therefore, the characteristics of the small-sized TFT vary. Therefore, a TFT whose crystal grain size is about the same as the crystal grain size of the channel layer is unsuitable for use as a TFT in the display section.

The present invention is intended to solve the above problems, and an object of the present invention is to provide a display device in which the mobility of carriers in the channel layer of the driver circuit for driving is high and the variation in TFT characteristics of the display portion is small. To provide.

[0008]

In a display device of the present invention, a display driver having a first thin film transistor and a driving driver circuit having a second thin film transistor for driving the display device are formed on the same substrate. The display device is characterized in that the crystal grain size of the channel layer of the first thin film transistor is smaller than the crystal grain size of the channel layer of the second thin film transistor, whereby the above object can be achieved.

Next, the present invention will be described based on examples.
The case where the semiconductor layer is made of polycrystalline silicon will be described as an example, and will be described with reference to FIGS.

First, 100 n of silicon is deposited on the insulating substrate 1 made of quartz or glass by the low pressure CVD method.
m deposited. The deposition conditions are Si ₂ H as the deposition gas.
₆ (flow rate 100 sccm) and N ₂ (flow rate 400 sccm)
Of the mixed gas, the pressure is 50 Pa, and the deposition temperature is 4
The temperature was 70 ° C. In this example, since the deposition temperature was 470 ° C., the deposited silicon layer was an amorphous silicon layer.

Next, with respect to this amorphous silicon layer, N
_The amorphous silicon layer was polycrystallized by performing heat treatment at 600 ° C. for 24 hours in ₂ atmospheres to obtain a polycrystalline silicon layer.

Of the above-mentioned polycrystalline silicon layer, only the portions (2a, 2b) which will be a part of the TFT of the driver circuit for driving are left, and the other portions of the polycrystalline silicon layer are removed by etching by a usual method ( (Fig. 1).

[0013] Next, the entire substrate surface by CVD after forming the insulating layer 3 to 100nm deposited S _i O _2, by low pressure CVD method, on the entire substrate surface, 100nm deposited polycrystalline silicon (Fig. 2). The deposition conditions were SiH ₄ (flow rate 100 sccm) and N as the deposition gas.
A mixed gas of ₂ (flow rate 400 sccm) was used, the pressure was 50 Pa, and the deposition temperature was 620 ° C. (FIG. 2).

Next, a portion 2c which is a part of the TFT of the display section.
The polycrystalline silicon layer was removed by etching by a usual method, leaving only the above (FIG. 3). At this time, the polycrystalline silicon layer 2a, 2b of the drive driver circuit section, because it is protected by the insulating layer 3 of S _i O _2, not etched.

The crystal grain size of the polycrystalline silicon layers 2a and 2b of the TFT of the driving driver circuit section exceeds 1 μm, whereas the crystal grain size of the polycrystalline silicon layer 2c of the TFT of the display section is 100 nm. It is small enough as follows. This is a low temperature long-time heat treatment of an amorphous silicon layer formed by depositing polycrystalline silicon 2c using SiH ₄ as a source gas at a relatively high temperature, while depositing polycrystalline silicon 2a and 2b using Si ₂ H ₆ as a source gas. It is because it was obtained by.

Next, the insulating layer 3 on the polycrystalline silicon layers 2a and 2b of the driver circuit for driving was removed (FIG. 4).
Hereinafter, a display device was manufactured according to a usual method. That is,
First, S _i O ₂ is deposited by after forming a gate insulating film 4, a polycrystalline silicon layer 2a, 2b, the gate electrode 5 by sputtering on the gate insulating film 4 on 2c across the substrate
a, 5b, 5c were formed. Then, an interlayer insulating film 6 is deposited a S _i O ₂ to the substrate across the. Contact holes 7a, 7b, at predetermined positions of the interlayer insulating film 6,
After forming 7c, the contact holes 7a, 7b,
Higher concentration (10 to 10 atom / cm ² ) impurities (BF ₃ , PH ₃ etc.) in the polycrystalline silicon layers 2a, 2b and 2c than 7c.
Was ion-implanted to form N ⁺ type or P ⁺ type high concentration impurity regions 10a, 10b, 10c. Finally, electrodes 8a, 8b and 8c are formed on the contact holes 7a, 7b and 7c by sputtering. The display device as shown in FIG. 5 can be manufactured by the above method.

In the above manufacturing process, the amorphous silicon layer is formed to a thickness of 100 nm by the low pressure CVD method under the same conditions as the deposition conditions of the polycrystalline silicon layer 2c of the TFT of the display section.
Of polycrystalline silicon on the insulating substrate 1 and then S _i
Ion acceleration energy 60 keV, dose 1 × 1
It can also be formed by implanting into the polycrystalline silicon layer under the condition of 0 ¹⁵ cm ^-2 and making the polycrystalline silicon layer amorphous.

Further, after the polycrystalline silicon layer 2c of the TFT of the display portion is formed first, the TF of the driver circuit for driving is formed.
The T polycrystalline silicon layers 2a and 2b may be formed.

[0019]

As is clear from the above description, according to the display device of the present invention, since the crystal grain size of the channel layer of the thin film transistor for the driver circuit for driving is large, the mobility of carriers becomes high and the high speed is achieved. Can be displayed. In addition, since the crystal grain size of the channel layer of the transistor in the display portion is smaller than the size of this channel layer, there is no variation in transistor characteristics and good image quality can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a manufacturing process of a display device of the present invention.

FIG. 2 is a cross-sectional view showing the manufacturing process of the display device of the present invention.

FIG. 3 is a cross-sectional view showing the manufacturing process of the display device of the present invention.

FIG. 4 is a cross-sectional view showing the manufacturing process of the display device of the present invention.

FIG. 5 is a cross-sectional view showing an example of a display device of the present invention.

FIG. 6 is a configuration diagram showing an example of a driver monolithic TFT substrate.

FIG. 7 is a cross-sectional view showing an example of a conventional display device.

[Explanation of symbols]

 1 Insulating Substrate 2a, 2b, 2c Polycrystalline Silicon Layer 3 Insulating Layer 4 Gate Insulating Film 5a, 5b, 5c Gate Electrode 6 Interlayer Insulating Film 7a, 7b, 7c Contact Holes 8a, 8b, 8c Electrodes 9a, 9b, 9c Channel Layers 10a, 10b, 10c High concentration impurity region 20 Driver monolithic TFT substrate 21 Picture element electrode 22 TFT 23 Display section 24 Driving driver circuit 31 Insulating substrate 32a, 32b, 32c Semiconductor layer 34 Gate insulating film 35a, 35b, 35c Gate electrode 36 Interlayer insulating film 37a, 37b, 37c Contact hole 38a, 38b, 38c Electrode 39a, 39b, 39c Channel layer 40a, 40b, 40c High concentration impurity region

Claims (1)

[Claims] 1. A display device in which a display unit having a first thin film transistor and a driver circuit having a second thin film transistor for driving the display unit are formed on the same substrate, and a channel layer of the first thin film transistor. Is smaller than the crystal grain size of the channel layer of the second thin film transistor.