JPH0752329B2 - Driver IC for active matrix display - Google Patents

Description

The present invention relates to a drive IC for driving a display device such as LC, EL, VF, etc. by an active matrix method.

[Prior Art] In recent years, as the area of display devices such as LC and EL has become larger, a method of driving a drive circuit by an active matrix TFT to realize high-quality display has begun to be studied.
In this method, a thin film transistor (hereinafter referred to as a TFT) is provided corresponding to each cell of the display device.
A driver for driving each of the X and Y electrode lines is required to select the matrix. Recently, there has been a movement to integrate this driver with a TFT on a substrate such as glass or quartz.

[Problems to be solved by the invention]

However, an IC that has been conventionally studied is configured by sharing a polycrystalline _Si film provided on a substrate such as glass as an active layer of a transistor that configures a TFT and a driver (a circuit that drives the TFT). On the other hand, when the capacity of the panel becomes large, high-speed performance (high mobility) is required for the data driver, so the quality of the polycrystalline _Si film is improved to a level close to that of single crystal by a method such as laser annealing. The need arises. However, under the present circumstances, it is almost difficult to form such a high-quality film over a large area while suppressing variations in crystallinity. Even Obtained created tentatively, are formed in different sizes of the grains is wide plane (the number of grain boundaries differ polycrystalline S _i film by location is formed), the carrier mobility of the dispersion and leakage current TFTs with large variations are formed. In particular, the large variation in the leakage current as a characteristic of the TFT that forms the switching transistor causes the variation in the effective voltage applied to the display element (LC, etc.), and the contrast may vary greatly depending on the location. Alternatively, variations in offset voltage may cause variations in pixel deterioration characteristics. Therefore, the yield of the driving IC is significantly reduced, and it becomes almost impossible to obtain a practical IC.

It is an object of the present invention to eliminate such drawbacks of the prior art and provide a drive IC for an active matrix display device capable of driving a high-performance and large-capacity display element.

[Means for solving problems]

The present invention relates to a driving IC of an active matrix display device integrally formed on a glass substrate and arranged in an XY matrix, in which a thin film transistor and a scanning side driver for driving the thin film transistor are provided corresponding to each display cell. A data side driver and a sample hold circuit for driving the thin film transistor are formed on the amorphous S _i active layer, and the data side driver and the sample hold circuit are formed on the polycrystalline S _i active layer.

[Principle / Action]

In the present invention, firstly, the data side driver and the sample hold circuit, which are required to have a high switching speed, are formed on the polycrystalline _Si active layer. Secondly, a switching TFT and a scanning side driver which are required to operate at a low speed of 100 kHz or less are formed on the amorphous _Si active layer. With such a configuration, the polycrystalline S _i having a high mobility may be formed in a linear elongated shape, so that the occupied area thereof becomes small. Therefore, it is possible to relatively good uniformity (less variation in grain size) formed over the entire example A _r laser annealing or an excimer laser annealing or the like Recrystallization linear high-quality crystalline film by performing region. This is because the film formation region is small, and the incidence of defects and voids entering the polycrystalline S _i or amorphous S _i film before recrystallization is small. If a uniform high-quality film is obtained in this manner, variations in transistor characteristics (mobility and leak current) are small, and high-speed data dry can be obtained with good yield. Also, one of
Amorphous S suitable for large area TFT and scanning driver
_Since it is composed of _i , it is possible to maintain the characteristics of low leakage current and high yield. That is, an IC with high yield can be realized as the entire drive IC. Further, a laser annealing or the like, it is possible to use a polycrystalline S _i film of better film quality than the conventional data driver, large-capacity display device, it is possible to a large area.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a circuit configuration diagram of a drive IC of an active matrix display device for explaining an embodiment of the present invention. FIG. 2 is a sectional view of the drive IC in FIG. Here, a drive IC for driving a liquid crystal (LC) is described as an example, but it goes without saying that the present invention is also applied to a drive IC for driving another display device (ELD, VFD, etc.).

As shown in FIG. 1, in this embodiment, a data side driver 13 and a sample hold circuit 14 are formed in a high speed driver arrangement area 11, and a scanning side driver 15 and a thin film transistor forming each cell are formed in a low speed driver arrangement area 12. 16 are formed. Next, as shown in FIG. 2, a thin film transistor (TFT) 16 formed for each cell and a scanning side driver for line-sequentially selecting the TFT 16 and supplying a video signal to one side electrode of the LC cell. amorphous S _i to 15, are formed through the insulating film 22 on the glass substrate 21 was Shoshi hydrotreating
(AS _i ) formed on the active layer 24. That is, all the transistor active layers in the low-speed driver arrangement area 12 on the glass substrate 21 are
Composed of aS _i . However, since the TFT 16 and the scanning side driver 15 may normally perform switching within a pulse period of a dozen μsec, the mobility of aS _i (0.1 to ¹ cm ² / V · sec)
But it is possible enough. Therefore, with the above-mentioned configuration, there is little possibility that the operation speed will have a problem.

The data side driver 13 and the sample and hold circuit 14 in FIG. 1 are formed on the polycrystalline _Si active layer 23 shown in FIG. That is, the high-speed driver placement area on the glass substrate 21
The transistor active layers in 11 are all composed of polycrystalline S _i . In this manner, polycrystalline S _i active layer 23, Ho since better if elongated formed Isuzu linear, the area occupied in the entire IC requires only be significantly smaller than conventionally. In addition, since a horizontally long strip-shaped pattern is formed, a recrystallization technique such as laser annealing (Arcw laser annealing or excimer laser annealing) can be used, and a high-quality film with good crystallinity can be obtained. In this case, the number of scans required for recrystallization is only about several times, so the time required for recrystallization, that is, the throughput is shortened. Further, since the area where the film is formed is small, the occurrence rate of defects, voids, cracks, etc. existing in the film (polycrystal S _i or aS _i ) before recrystallization is much smaller than that of the entire chip. For this reason, it is possible to obtain a high quality film having good crystallinity and a film having relatively small variation in grain size and excellent uniformity throughout. Since a uniform and high-quality film is obtained in this way, a high-mobility transistor with small characteristic variations such as mobility and leakage current can be realized. Therefore, the data driver 13 that requires high-speed operation
The sample and hold circuit 14 can be easily realized, and the display device can have a large capacity and a large area, which has been considered impossible in the related art.

The other TFT section 16 and the scanning side driver section 15 have aS _i
Since the leakage current can be reduced, an IC suitable for driving a large-capacity and large-area LC display device can be configured. In this configuration the TFT16 in aS _i, variation in the leak current can be suppressed small LC
The variation of the effective voltage applied to the pixel can be reduced, and the variation of the pixel deterioration due to the variation of the contrast and the offset voltage can be suppressed. That is, the yield of the whole drive IC for a large-capacity display device is significantly improved as compared with the conventional configuration.

Next, manufacturing of the above-mentioned driving IC will be described.

As shown in FIG. 2, insulating on the glass substrate 21 layer 22 (S _i O ₂
Etc.), the polycrystalline _Si film 23 is formed by the low pressure CVD method or the like. Also, the S _i such insulating film 22 O ₂ consuming a low pressure CVD
Method or atmospheric pressure CVD method. Then, the polycrystalline S _i layer 23 is annealed using A _r laser or excimer laser. Then, the polycrystalline S _i film 23, for example P using an ion implantation technique, an impurity source and drain regions 23, such as A _s ', introduced into 23 ", the source 23 by performing an appropriate annealing treatment' Form drain 23 ″. Then, on this, after forming a gate insulating film 25 such as S _i O ₂ by the CVD method or the like, for example, providing the gate electrode 26 made of polycrystalline S _i subjected to P-doped.

The above-described process undergoes a relatively high temperature heat treatment (about 400 to 650 ° C.) but, aS _i region is formed at a low temperature (to 300 ° C. or less).

Madzu, on the insulating film 22, aS _i layer 24 using a glow discharge method, or the like
Forming a source by ion implantation or the like from above, the drain region 24 ', introducing an impurity of the P or A _s to 24 ".
Thereon by vapor deposition or sputtering, to deposit the S _i O ₂ or S _i N gates of _x such insulating film 25 '. Furthermore, the metal _{(A l, A u, C} r, M o, W , etc.) conductive layer 27 (gate electrode) and of 2
8 (wiring) is formed using a vapor deposition method or the like. In this case, the conductive layers 27 and 28 are the source of the polycrystalline S _i, the drain region 23 ', 2
3 "and aS _i source, drain regions 24 ', 24" are taken electrical contact with.

In this way, it is possible to manufacture drive ICs using almost ordinary techniques for forming polycrystalline S _i and aS _i , and no special process is required except for the annealing step of polycrystalline S _i. It can be easily manufactured. If the conditions for annealing the polycrystalline S _i are determined, the throughput is short and the process is hardly lengthened.

〔The invention's effect〕

As described above, according to the present invention, a high-performance data driver, a TFT having a low leakage current, and a scanning side driver can be obtained with a high yield, so that it is easy to realize a display device having a large area and a large capacity. Become. In particular, since variations in characteristics such as mobility and leakage current can be suppressed to a small level, not only the image quality of the display element is improved, but also a drive IC for an active matrix display device with less variation in deterioration of pixels is obtained. is there.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a drive IC of an active matrix display device for explaining an embodiment of the present invention, and FIG. 2 is a sectional view of the drive IC in FIG. 11 …… High-speed driver placement area, 12 …… Slow-speed driver placement area, 13 …… Data driver, 14 …… Sample hold circuit, 15 …… Scan driver, 16 …… TFT, 21…
… Glass substrate, 22,25,25 ′ …… Insulating film, 23,23 ′, 23 ″…
… Polycrystalline S _i layer, 24,24 ′, 24 ″ …… Amorphous S _i layer, 2
6,27 …… Gate electrode, 28 …… Metal conductive layer.

Claims (1)

[Claims] 1. A driving IC of an active matrix display device integrally formed on a glass substrate and arranged in an XY matrix, wherein a thin film transistor corresponding to each display cell and a scanning side for driving the thin film transistor. A driver IC for an active matrix display device characterized in that a driver is formed on an amorphous S _i active layer, and a data side driver and a sample hold circuit for driving the thin film transistor are formed on a polycrystalline S _i active layer. .