JPH0346374A - Thin film transistor - Google Patents

Abstract

PURPOSE:To suppress an increase in a current by the irradiation with light by forming a noncrystalline semiconductor film of a polycrystallized region and the residual region of an amorphous semiconductor film, and providing the residual amorphous region corresponding to the position of a gate electrode film. CONSTITUTION:An insulating board 1, a gate electrode 2, a gate insulating film 3, an amorphous semiconductor film 4, a polycrystalline semiconductor film 6, an impurity implanted amorphous semiconductor layer 7, drain and source electrodes 8, 8, a passivation film 9 and a shielding film 10 are provided. In this case, the film 4 is formed of a polycrystallized region irradiated with a high energy beam to amorphous semiconductor and the residual region of the amorphous semiconductor film, and the residual region is provided corresponding to the position of the film 2. Accordingly, the amorphous region sensitive to light for forming a semiconductor operation channel can shield light projected from the side of the electrode 2 by the electrode 2, and even if the light is directed to the polycrystallized region having low sensitivity to the light which is not shielded, characteristic change can be suppressed. Thus, stable switching characteristic which is not affected by the influence of the light is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to the structure of a thin film transistor including an amorphous semiconductor film. (b) Prior Art Thin film transistors (hereinafter abbreviated as TPT) using non-crystalline semiconductors such as amorphous, polycrystalline and mixed semiconductors have been developed in place of crystalline semiconductors.

Among non-crystalline semiconductors, amorphous semiconductor materials, especially amorphous silicon (hereinafter abbreviated as a-Si), have stable semiconductor characteristics as transistors, and the plasma CVD method, which can form large-area films, has been used. From the advantages that can be adopted,
Suitable for mass formation of TPT on large substrates.

Therefore: In recent years, the above-described a-5iT F T has been mounted on a switching transistor array substrate of an active matrix liquid crystal display device, and has been put into practical use.

As mentioned above, this type of TPT takes advantage of the ease of forming large-area semiconductor films using plasma reactions. It also takes advantage of the fact that silicon oxide (Sin!) films can be formed continuously by simply changing the reaction gas.

Conventional active matrix type liquid crystal display devices, especially so-called liquid crystal TVs, utilize the charge storage effect of liquid crystals to
In order to display images, the charge charged to the liquid crystal for each frame must be maintained for one frame period, so if the holding voltage of the liquid crystal decreases due to current leakage during this period, the display quality will deteriorate. This will lead to deterioration.

In addition, as a liquid crystal TV, a light transmission type liquid crystal display device equipped with a backlight is common, but the above-mentioned TPT a
Since the -5i material is sensitive to light as it is also used as a solar cell material, it has the disadvantage that the 0FFii current increases under light irradiation (Japanese Patent Application Laid-Open No. 61-1458
No. 69).

As measures against such light, it has been proposed to increase the a-5i band gap of the TPT semiconductor film, or to provide a light-shielding film that completely covers the a-5i. However, the former measure inevitably deteriorates the film quality, while the latter inevitably reduces the manufacturing yield due to the addition of an odor process.

(c) Problems to be Solved by the Invention The present invention has been made in view of the above-mentioned points, and provides a TPT that can suppress the increase in hair flow under light irradiation by applying effective light countermeasures to the semiconductor film. It is something to do.

(d) Means for Solving the Problems The TPT of the present invention is a TPT in which a gate electrode film, an insulating film, an amorphous semiconductor film, a drain electrode film, and a source electrode film are stacked on an insulating substrate. The amorphous semiconductor film is composed of a polycrystalline region obtained by irradiating the amorphous semiconductor with high-energy rays and a remaining region of the amorphous semiconductor film, and the remaining amorphous region is arranged in a manner corresponding to the position of the gate electrode film. It was established.

(E) Function According to the TPT of the present invention, the inner gate ' of the amorphous semiconductor film is
The region corresponding to the 2It pole film position is an amorphous region, and the other regions are polycrystalline regions, so that when the gate is irradiated with light from the pole side, it becomes a light-sensitive amorphous region that forms a semiconductor operating channel. The region is shielded from light by the gate pole, and almost no photocurrent is generated in the polycrystalline region, which is insensitive to other unshielded light.

(F) Embodiment FIG. 1 shows a structural sectional view of an embodiment of the TPT of the present invention, and FIG. 2 shows a process sectional view thereof.

In Figure 1, (1) is an insulating substrate, (2) is a gate electrode, (3) is a gate insulating film, (4) is an amorphous semiconductor film, (6) is a polycrystalline semiconductor film, (7) is an amorphous semiconductor film, and (7) is an amorphous semiconductor film. is an impurity-introduced amorphous semiconductor film, <8! (8) is a drain electrode and a source electrode, (9) is a passivation film, and 00 is a light shielding film.

The TPT shown in FIG. 1 is characterized by that the semiconductor film consists of a polycrystalline semiconductor film (6) region and an amorphous semiconductor film (4) region, and the amorphous semiconductor film (4) region is connected to the gate electrode ( 2
) is located at a point provided corresponding to the position.

Next, the manufacturing process will be explained based on the process diagrams shown in FIGS. 2(a) to 2(e).

First, a gate electrode (2) is formed and patterned on a transparent substrate (1) made of a glass plate (Fig. 2 (a)).
. Next, a gate insulating film (3) made of SiNx and a-5
After forming an amorphous semiconductor film (4) consisting of i, this amorphous semiconductor film (4) is patterned into an island shape (see FIG.
b)).

Next, from the transparent substrate side, high-energy rays such as laser light (
In step 5), the amorphous semiconductor film (4) is irradiated. At this time, the gate pole (2) serves as a mask, and only the portions of the amorphous semiconductor film (4) corresponding to the source and drain contacts in the subsequent process are irradiated [FIG. 4(C)].

In this manner, the amorphous semiconductor film (4) region irradiated with high-energy rays is polycrystallized by the annealing effect and becomes a polycrystalline semiconductor film (6) region.

At this time, the high energy ray (5) is 1, for example, Xe
A Cl excimer laser can be used, in this case 10
Energy conditions of 0-250 mJ/cm' are preferred. In the thus obtained polycrystalline semiconductor film (6) region, it can be confirmed that the conductivity is improved and the photosensitivity is reduced.

Thereafter, an impurity-doped amorphous semiconductor film (7) made of n''a-5i doped with phosphorus, a source electrode, and a drain electrode (8) (8) are formed (FIG. 4(d)).

Note that in this example, the impurity-introduced amorphous semiconductor film i7)
The formation was carried out after the above-mentioned high energy beam (5) irradiation, but
This is possible even before irradiation.

Thereafter, a passivation film (9) and a light shielding film 00) are laminated to complete the device (FIG. 2(e)).

In the TPT obtained in this way, the dale size of the polycrystalline semiconductor film (p-5i) (6) region by laser annealing described above is 100 to 5000, and the diameter is 100 to 5000 in the dark state and in the light irradiation state. The conductivity ratio σph/σ6 becomes two digits or less. This is an amorphous semiconductor film (a-5i
) (4) The improvement in electrical conductivity is observed compared to that in the region (4), which is more than 5 orders of magnitude, and the decrease in photosensitivity can also be understood.

According to the above embodiment, the gate electrode (2) and the light shielding film (1
Polycrystalline semiconductor film (
6), the a− of the channel that does not receive light
While realizing a TPT with a large 0N10FF ratio in the 5i region, a TPT characteristic that is not affected by light is obtained in the p-5i region outside the channel that receives light.

(Effects of the Invention) In the TPT of the present invention, the region of the amorphous semiconductor film corresponding to the gate electrode film position is an amorphous region, and the other regions are polycrystalline regions, so that light irradiation from the gate electrode side On the other hand, the light-sensitive amorphous region forming the semiconductor operating channel can be shielded from light by the gate electrode, and even if the unshielded polycrystalline region with low photosensitivity is irradiated with light, changes in characteristics can be suppressed.

Therefore, according to the present invention, it is possible to realize a TPT that has stable switching characteristics that are not affected by light irradiation.

[Brief explanation of drawings]

Figure 1 is a sectional view of one embodiment of the TPT of the present invention, and Figure 2 (a
) to (e) are cross-sectional views showing the manufacturing process of the TPT shown in FIG. 1. (1)...Insulating substrate, (2)...Gate 1 as a pole,
(3)...gate insulating film, <4)...amorphous semiconductor film, (5)...high energy rays, (6)...polycrystalline semiconductor film, (7)...impurity Introducing amorphous semiconductor film, (
8)...source, drain electrode, (9) passivation film, (lO)...light shielding film.

Claims (1)

[Claims] (1) In a thin film transistor in which a gate electrode film, an insulating film, an amorphous semiconductor film, a drain electrode film, and a source electrode film are laminated on an insulating substrate, the amorphous semiconductor film has a high 1. A thin film transistor comprising a polycrystalline region irradiated with energy rays and a remaining region of an amorphous semiconductor film, the remaining amorphous region being provided corresponding to the position of a gate electrode film.