JP2659039B2 - Electric circuit board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an electric circuit board having a thin film transistor (TFT) array.

[0002]

2. Description of the Related Art Conventionally, electric circuit boards have been widely used in display devices and the like. An example of such a display device is a liquid crystal display device. A liquid crystal display device generally has a structure in which liquid crystal is sandwiched between two substrates. Electrodes and other elements are formed on the liquid crystal side of the substrate, and display is performed by controlling the state of the liquid crystal by the elements. On one of the two substrates, electrodes are formed uniformly on the surface, and on the other, a plurality of small block pattern (pixel) electrodes having an appropriate shape are formed on the surface. In recent years, a TFT array for switching each pixel has been attached to a substrate surface on a pixel electrode side. FIG. 2 is a schematic sectional view of a liquid crystal display device having such a TFT array, where S and S ′ are transparent substrates such as glass, 1 and 1 ′ are gate electrodes, and 2 and 2 ′ are An insulating layer, 3 and 3 ′ are semiconductor layers, 4 and 4 ′ are source electrodes, 5 and 5 ′ are drain electrodes,
6 is an insulating and orientation layer, 7 is a liquid crystal, and 8 is a transparent electrode.

In the case where a semiconductor having photoconductivity is used, it is preferable to stabilize the switching characteristics by exposing the light to as little light as possible. For this reason, a liquid crystal display device as shown in a schematic sectional view in FIG. 3 is used. That is, here, on the insulating and alignment layer 6 covering the TFT array in the device shown in FIG.
Further, light shielding layers 9 and 9 'are formed at positions corresponding to the semiconductor layers. Generally, a metal is used for the light-shielding layer.

In the above-mentioned liquid crystal display device, as the insulating layer, inorganic materials such as metal oxides such as alumina and titanium oxide, and silicon compounds such as silicon nitride and silicon dioxide have conventionally been used. However, in order to cover the TFT, it is necessary to have a certain thickness or more, and the thin film of these inorganic materials has a drawback that when the film thickness is large, the film distortion becomes large and cracks or the like are easily formed. When such a crack occurs, the TFT is also destroyed at the same time, so that the protection of the TFT is not performed and the characteristics are deteriorated. Therefore, it has been proposed to use an organic material that does not cause cracks, such as a silicon resin, an acrylic resin, or a cyclized polyisoprene, as the insulating layer instead of the inorganic material. However, the insulating layer made of a thin film of these organic materials has a drawback that the performance as a protective layer is not sufficient and the TFT characteristics become unstable.

Further, in a liquid crystal display device, as is generally well known, it is necessary to align the surface of the substrate in contact with the liquid crystal to arrange the liquid crystal molecules regularly. This alignment treatment is performed by rubbing (rubbing) the substrate surface with a cloth, velvet, or other material in a clean room under low humidity. I do. In particular, in a liquid crystal display device in which a TFT array is formed on a substrate, there is an increased risk that a strong electric field based on static electricity generated by the rubbing causes dielectric breakdown in a gate insulating film of the TFT,
Manufacturing yields were very low.

Therefore, in order to weaken the electric field applied to the gate insulating film based on the static electricity generated by the rubbing, it is conceivable to provide a protective film having a sufficient thickness so that the gate insulating film does not cause dielectric breakdown. Was. According to experiments by the inventors of the present invention, when a coating having a sufficient film thickness made of an inorganic insulating material is provided, cracks occur in the coating, and the area of the liquid crystal device is particularly large for large-screen display. It has been found that as the value of increases, the tendency of crack generation increases, and on the contrary, the characteristics of the TFT deteriorate.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned prior art,
An object of the present invention is to provide an improved electric circuit board in which an insulating layer of a TFT can exhibit satisfactory performance over a long period of time.

[0008]

According to the present invention, there is provided an electric circuit board having a thin film transistor provided with a semiconductor layer, wherein the thin film transistor is formed of an inorganic insulating material on the thin film transistor. Providing a first protective layer for protection, providing a second protective layer for protecting the thin film transistor formed of an organic insulating material on the first protective layer on the thin film transistor, On the second protective layer on the first protective layer, corresponding to the semiconductor layer
An electric circuit board provided with a light-shielding layer disposed at a position is provided.

[0009]

FIG. 1 is a schematic sectional view showing a preferred embodiment of an electric circuit board according to the present invention. In the figure, an electric circuit board is used as a component of a liquid crystal display device.

As the semiconductor layers 3 and 3 'constituting the TFT, for example, Si, CdS, CdSe, Te or the like is used, and in particular, amorphous or polycrystalline Si is suitably used.
Amorphous Si can include H atoms or halogen atoms (particularly, F atoms). The H atom or the halogen atom may be contained alone or both. The content is preferably 0.01 to 40 atomic% in total, and more preferably 0.01 to 30 atomic%.

In this embodiment, the insulating layer covering the TFT array consists of two layers (ie, 6a and 6b).

Reference numeral 6a denotes an inorganic insulating layer, which is formed by an evaporation method, a sputtering method, a CVD method, or the like using an inorganic material such as a metal oxide such as titanium oxide and alumina, or a silicon compound such as silicon dioxide and silicon nitride. Can be. The thickness of the inorganic insulating layer is preferably such that at least the channel portion of the TFT is protected, and is preferably about 500 to 3000 °.

Reference numeral 6b denotes an organic insulating layer. As a material for forming the organic insulating layer, a thermosetting resin, a thermoplastic resin, or a synthetic rubber-based resin is preferably used. Any material may be used as long as it is a material that is transparent to and can be oriented. Examples of the thermosetting resin include a phenol resin, a polyester resin, a silicone resin, an acrylic resin, and a urethane resin. A crosslinking agent, a polymerizing agent, a sensitizer and the like may be added to these thermosetting resins as needed. Examples of the thermoplastic resin include polycarbonate, polyethylene, and polystyrene. Also in this case, a stabilizer or the like may be added as necessary. Examples of the synthetic rubber-based resin include cyclized polybutadiene. Also in this case, a crosslinking agent, a sensitizer and the like may be added as necessary.

The organic insulating layer 6b is formed, for example, by dissolving a thermosetting resin or a synthetic rubber-based resin in a solvent, and then applying it on the inorganic insulating layer 6a. Alternatively, it is formed by crosslinking, polymerizing, and curing a resin in combination. In the case of using a thermoplastic resin, for example, the organic insulating layer 6b is formed by applying heat to the resin, melting the resin, applying the resin on the inorganic insulating layer 6a, and then cooling and curing the resin. The thickness of the organic insulating layer is related to the thickness of the inorganic insulating layer.
00 to 3000 °. The sum of the thicknesses of the inorganic insulating layer and the organic insulating layer is determined to be an appropriate value because an excessively large value may adversely affect the display. The heating temperature is preferably 300 ° C. or less when amorphous Si is used for the semiconductor layer forming the TFT.
This is because if the temperature is higher than 300 ° C., the characteristics of the TFT may be changed or deteriorated due to the thermal influence of the amorphous Si layer.

The light-shielding layers 9 and 9 'are formed by forming a metal such as Al on the organic insulating layer by vapor deposition or the like, and then leaving the metal layer in a desired shape and size by photolithographic etching or the like. .

In the above description, an example in which the electric circuit board of the present invention is used as a component of a liquid crystal display device has been described. It can be used as a component of the device.

An embodiment of the present invention will be described below.

Example 1 A silicon nitride layer (2000 mm thick) was further formed on the surface of a substrate on which a TFT array was formed by plasma CVD. Next, a cyclized polyisoprene-based resist (ODUR-110WR: 18 cp, manufactured by Tokyo Ohka Co., Ltd.) dissolved in xylene is spin-coated on the silicon nitride layer at 3000 rpm, cured with a high-pressure mercury lamp for 2 seconds, and further cured at 150 ° C. for 20 seconds. Baking for minutes. As a result, a colorless and transparent organic insulating layer having a thickness of about 1 μm was formed. Furthermore, metal aluminum is deposited on it,
A portion other than the required portion was removed by etching to form a light-shielding layer. Subsequently, after performing an alignment treatment from above, a liquid crystal display device was manufactured through a normal process.

When the thus obtained liquid crystal display was continuously operated in a high-temperature and high-humidity atmosphere (90 ° C., 90% RH) for 1,000 hours, good display characteristics were exhibited during the operation.

Example 2 A silicon dioxide layer (3000) was formed on the surface of a substrate on which a TFT array was formed by sputtering.
(Thickness). Next, this substrate was immersed in a 10% by weight toluene solution of urethane resin (Delpo MAX, manufactured by Toa Paint Co.), pulled up at 100 mm / min, and then dried in a 50 ° C. temperature atmosphere for 20 minutes. Subsequently, a high-pressure mercury lamp was irradiated for 40 minutes to cure the urethane resin. As a result, a colorless and transparent organic insulating layer having a thickness of about 1.5 μm was formed. Further, metal aluminum was vapor-deposited thereon, and portions other than required portions were removed by etching to form a light-shielding layer. After performing an alignment treatment from above, a liquid crystal display device was manufactured through a normal process.

With respect to the liquid crystal display device thus obtained,
When the same characteristic evaluation as in Example 1 was performed, good display characteristics were shown as in Example 1.

[0022]

According to the present invention as described above, the protection of the TFT and the stabilization of the characteristics are realized by further forming the organic insulating layer on the inorganic insulating layer. Further, an electric circuit board having stable performance has been provided for a long time. In addition, since the light shielding layer is provided, the switching characteristics are stabilized.

[Brief description of the drawings]

FIG. 1 is a sectional view of a liquid crystal display device using an electric circuit board according to the present invention.

FIG. 2 is a sectional view of a conventional liquid crystal display device.

FIG. 3 is a cross-sectional view of a conventional liquid crystal display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gate electrode 2 Insulating layer 3 Semiconductor layer 4 Source electrode 5 Drain electrode 6 Insulating layer 6a Inorganic insulating layer 6b Organic insulating layer 7 Liquid crystal 8 Transparent electrode 9 Light shielding layer S substrate

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tetsuya Kaneko 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Masao Suga 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (56) References JP-A-56-107287 (JP, A) JP-A-53-126954 (JP, A)

Claims (1)

(57) [Claims] 1. An electric circuit substrate having a thin film transistor provided with a semiconductor layer, wherein a first protective layer formed of an inorganic insulating material for protecting the thin film transistor is provided on the thin film transistor. A second protection layer formed of an organic insulating material for protecting the thin film transistor is provided on the first protection layer, and the second protection layer on the first protection layer on the thin film transistor is provided. On the surface corresponding to the semiconductor layer
An electric circuit board, comprising: a light-shielding layer disposed in a position .