JPH02230773A - Thin film transistor element array - Google Patents

Abstract

PURPOSE:To obtain a thin film transistor element array whose gate leak current is small by forming enbloc a gate insulating film on the whole surface of a substrate. CONSTITUTION:After a source electrode 10 and a drain electrode 11 are formed on a substrate 3, the pattern thin film of an a-Si:H film as a semiconductor layer 9 is formed by photochemically decomposing disilane gas with ArF laser 1. Then the glass substrate 3 is carried into a CVD chamber 7, and an SiN film is subjected to plasma CVD using silane and ammonia as material gas, thereby forming a gate insulating film 12. By sputtering, a chromium film is formed on the glass substrate 3, and a gate electrode 13 is formed by patterning. An element array of this structure is almost free from leak current from a gate electrode, and excellent element operation is realized for a long time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thin film transistor element array.

[Prior art and its problems 1] A thin film transistor element array used for driving pixels of a liquid crystal display, etc. requires forming a large number of thin film transistors at once on a substrate. Conventionally, such a thin film transistor element array was described by Sunada in 1985, Proceedings of International Display Research Conference (Procee
ding of Iritel'rla-tional
Display Research Conference
For example, in the case of a staggered structure, as many sources as necessary can be placed on the substrate, as reported in 66.
The method used to form the train electrode was to form an amorphous silicon layer on the substrate, followed by a gate insulating film layer, and after forming the gate electrode, divide it into each thin film transistor by photolithography and etching. .

According to this fabrication method, when dividing each thin film transistor,
In order to etch the amorphous silicon to the same width as the gate electrode, it is necessary to also etch the upper gate insulating film. Therefore, in the completed device, leakage current flowing through the sidewalls of the gate insulating film cannot be ignored. In contrast,
Even if the entire surface is covered with a protective insulating film, the sidewall portions are likely to have poor dielectric strength, so it is difficult to prevent such leakage current over long-term device operation.

SUMMARY OF THE INVENTION An object of the present invention is to provide a thin film transistor element array with reduced gate leakage current that solves the problems of the prior art.

[Means for Solving the Problems] The present invention provides a plurality of thin film transistors on the same substrate, in which a semiconductor layer is formed between a source electrode and a train electrode, and a gate insulating film and a gate electrode are sequentially formed on the semiconductor layer. This thin film transistor element array is characterized in that the gate insulating film is formed all over the entire surface of the substrate.

[Function] In a thin film transistor, in a structure in which the gate electrode and gate insulating film have the same shape and area and overlap in the film thickness direction,
Since the distance from the gate electrode to the semiconductor layer or the drain and source electrodes via the sidewalls of the gate insulating film is extremely short, leakage current flowing through this path has a large effect on the electrical characteristics of the device. However, if the area of the gate insulating film is sufficiently large compared to the area of the gate electrode, and the distance between the gate electrode and the sidewall of the gate insulating film is sufficiently large compared to the thickness of the gate insulating film, then such a path can be used. The amount of leakage current that flows is extremely small.

In the present invention, a thin film transistor element array has a structure in which a semiconductor layer is selectively formed between the drain and source electrodes of each thin film transistor, and a gate insulating film is formed all over the top of these semiconductor layers and between the semiconductor layers. . Therefore, in any thin film transistor that makes up the array, the distance between the gate electrode and the side wall of the gate insulating film is sufficiently long compared to the gate film thickness, so the leakage current flowing through the side wall of the gate insulating film is The effect becomes so small that it can be ignored.

[Examples] Examples of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a partial cross-sectional view of an example of a thin film transistor element array according to the present invention. Chromium was used as the material for each electrode, SiN was used as the gate insulating film material, and non-quality hydrogenated silicon was used as the semiconductor layer.

FIG. 2 is a schematic configuration diagram showing an example of an apparatus used for manufacturing the thin film transistor element array of the present invention. In FIG. 2, a substrate 3 is placed in a laser CVD chamber 5, and a pattern is transferred between the drain and source electrodes 8 on the substrate 3 through the light emitted from the ArF laser 1 through a mask 2 and a synthetic quartz window 4. Ru. The relative position of the substrate 3 and the mask 2 can be changed together with the laser CVD chamber 5 by an XY stage 6. Also leather C
The VD chamber 5 is connected to a plasma CVD chamber 7, and the gate insulating film can be formed all at once by moving the substrate after film formation.

Using the film forming apparatus configured as described above, the thin film transistor element array shown in FIG. 1 was manufactured in the following manner.

First, a chromium film is formed by sputtering on a glass substrate 3 shown in FIG. 1, and patterned to form a source electrode 10 and a drain electrode 41.

Next, this glass substrate 3 is fixed in a laser CVD chamber 5 shown in FIG.
Source electrode 10 and drain electrode 1 through synthetic quartz window 4
The pattern is transferred during 1. By photochemically decomposing disilane (S!2H6) scum using an ArF laser 1, a patterned thin film of a-Si:HvA was formed as a semiconductor layer 9. Next, the glass substrate 3 was moved along with the laser CVD chamber 5 by the width of the area irradiated with light by the XY stage 6, and the same film forming process was repeated to form a pattern of the semiconductor layer 9 on the entire surface of the glass substrate 3.

Subsequently, the glass substrate 3 was moved to the plasma CVD chamber 7, and the gate insulating film 12 was formed by plasma CVD of the SiN film using silane and ammonia as source gases. Subsequently, a chromium film was formed on the glass substrate 3 by sputtering and patterned to form the gate electrode 13.

In the thin film transistor element array manufactured through the above steps, no leakage current flowing from the gate electrode through the side walls of the gate insulating film was observed.

Note that it is not necessarily necessary to use SiN for the gate insulating film, and SiO2 may also be used. Furthermore, each electrode does not necessarily have to be made of chromium, but may also be made of tantalum or aluminum. In addition, the semiconductor layer does not necessarily have a-3i:l-1
It is not necessary to use polysilicon, and polysilicon may be used.

Further, it is not always necessary to use laser CVD to form the semiconductor layer, and although the number of steps is increased, a semiconductor thin film that has been formed all over the substrate by plasma CVD or the like may be patterned by photolithography and etching.

Note that in terms of liquid crystal display applications, it is clear that even if the insulating film is formed as thinly as in the present invention, it will not impede pixel drive or the translucency of the glass substrate.

[Effects of the Invention] As explained above, the thin film transistor element array of the present invention has almost no leakage current from the gate electrode.
Good device operation is possible over a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view of an embodiment of the present invention, and FIG. 2 is a schematic configuration diagram of an example of an apparatus used for manufacturing a thin film transistor element array of the present invention. 1...ArF laser 2...mask 3...
(Crow) Substrate 4... Synthetic quartz window 5... Laser CVD chamber 6... XY stage 7... Plasma CVD chamber 8... Electrode

Claims (1)

[Claims] (1) In a thin film transistor element array including a plurality of thin film transistors on the same substrate, in which a semiconductor layer is formed between a source electrode and a drain electrode, and a gate insulating film and a gate electrode are sequentially formed on the semiconductor layer, the gate insulating film is a thin film transistor element array characterized by being formed all over the entire surface of a substrate.