JP3866249B2 - Display device - Google Patents

Description

  The invention disclosed in this specification relates to a structure of a thin film transistor formed over a substrate having flexibility (flexible mechanical properties) such as a resin substrate (including an industrial plastic substrate) and a manufacturing method thereof. The present invention also relates to an active matrix liquid crystal display device formed using the thin film transistor.

  A thin film transistor formed on a glass substrate or a quartz substrate is known. The thin film transistor formed on the glass substrate is mainly used in an active matrix liquid crystal display device. An active matrix liquid crystal display device is expected to replace a simple matrix liquid crystal display device because it can perform high-speed moving images and fine display.

  In an active matrix liquid crystal display device, one or more thin film transistors are provided as switching elements in each pixel, and charges entering and exiting the pixel electrodes are controlled by the thin film transistors. The reason why a glass substrate or a quartz substrate is used as the substrate is that it is necessary to transmit visible light through the liquid crystal display device.

  On the other hand, a liquid crystal display device is expected as a display means having a very wide application range. For example, it is expected as a display means used in a portable electronic device such as a card-type computer, a portable computer, and various communication devices. In the display means used in these portable electronic devices, display of more advanced information is required in accordance with the advancement of information to be handled. For example, there is a demand for a function for displaying not only numbers and symbols but also finer image information and moving images.

When a function for displaying fine image information and moving images is required by a liquid crystal display device, it is necessary to use an active matrix liquid crystal display device. However, when a glass substrate or quartz substrate is used as the substrate,
-There is a limit to reducing the thickness of the liquid crystal display device itself.
・ Weight increases.
・ If the thickness of the substrate is reduced to reduce weight, the substrate will break.
・ The board is not flexible.
Have the problem.

  In particular, card-type electronic devices are required to be flexible so that they are not damaged even if a slight amount of stress is applied. Therefore, the same flexibility is also applied to the liquid crystal display device incorporated in the electronic device. Required.

  An object of the invention disclosed in this specification is to provide an active matrix liquid crystal display device having flexibility.

  As a method of giving flexibility to the liquid crystal display device, there is a method of using a light-transmitting plastic substrate or resin substrate as a substrate. However, the resin substrate has a problem that it is technically difficult to form a thin film transistor on the resin substrate because of its heat resistance problem.

Therefore, the invention disclosed in this specification is characterized by solving the above-described difficulty by adopting the following configuration.
One of the inventions disclosed in this specification is:
A film-like resin substrate;
A resin layer formed on the surface of the resin substrate;
A thin film transistor formed on the resin layer;
It is characterized by having.

  A specific example of the above configuration is shown in FIG. In the configuration shown in FIG. 1, a resin layer 102 is formed in contact with a PET film (thickness: 100 μm) which is a film-like resin substrate, and an inverted staggered thin film transistor is further formed thereon.

  As the film-like resin substrate, one selected from PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PES (polyethylene sulfite), and polyimide can be used. The conditions required here are to have flexibility and to have translucency. It is also desirable to be able to withstand as high a temperature as possible. In general, when the heating temperature of these resin substrates is increased to about 200 ° C. or more, oligomers (polymers having a diameter of about 1 μm) are deposited on the surface, gas is generated, and a semiconductor layer is formed thereon. It is extremely difficult to form. Therefore, the heat resistant temperature needs to be as high as possible.

  In the above structure, the resin layer has a function for flattening the surface of the resin substrate. The meaning of the planarization includes a function of preventing oligomers from being generated on the surface of the resin substrate in a process involving heating such as formation of a semiconductor layer.

  As this resin layer, an acrylic resin selected from an acrylic acid methyl ester resin, an acrylic acid ethyl ester resin, an acrylic acid butyl ester resin, and an acrylic acid 2-ethylhexyl ester resin can be used. By forming this resin layer, even when a resin substrate is used, inconvenience in manufacturing the above-described thin film transistor can be suppressed.

Other aspects of the invention are:
Forming a resin layer on a film-like resin substrate;
Forming a semiconductor layer on the resin layer by a plasma CVD method;
Forming a thin film transistor using the semiconductor layer;
It is characterized by having.

Other aspects of the invention are:
A step of heat-treating a film-like resin substrate at a predetermined temperature to measure degasification from the resin substrate;
Forming a resin layer on a film-like resin substrate; forming a semiconductor layer on the resin layer by a plasma CVD method;
Forming a thin film transistor using the semiconductor layer;
It is characterized by having.

  In the above configuration, the heat treatment is performed to degas from the resin substrate in order to prevent the degassing phenomenon from occurring in the resin substrate in a process that follows heating. For example, if degassing from the resin substrate occurs while the semiconductor thin film is being formed on the resin substrate, a large pinhole will be formed in the semiconductor thin film, and its electrical characteristics are greatly impaired. End up. Therefore, heat treatment is performed at a temperature higher than the heating temperature applied in the subsequent process in advance, and degassing from the resin substrate is performed, thereby suppressing the degassing phenomenon from the resin substrate in the subsequent process can do.

Other aspects of the invention are:
Heat-treating the film-like resin substrate at a predetermined temperature;
Forming a resin layer on a film-like resin substrate;
Forming a semiconductor layer on the resin layer by a plasma CVD method;
Forming a thin film transistor using the semiconductor layer;
Have
When the semiconductor layer is formed by the plasma CVD method, heating is performed at a temperature equal to or lower than the predetermined temperature.

Other aspects of the invention are:
Heat-treating the film-like resin substrate at a predetermined temperature;
Forming a resin layer on a film-like resin substrate;
Forming a semiconductor layer on the resin layer by a plasma CVD method;
Forming a thin film transistor using the semiconductor layer;
Have
The predetermined temperature is higher than the heating temperature in other steps.

Other aspects of the invention are:
A pair of film-like resin substrates;
A liquid crystal material held between the resin substrates;
A pixel electrode formed on at least one surface of the pair of resin substrates;
A thin film transistor connected to the pixel electrode;
Have
The thin film transistor is formed on a resin substrate,
A resin layer for flattening the surfaces of the pair of film-like resin substrates is formed.

  A specific example of the above configuration is shown in FIG. 3 includes a pair of resin substrates 301 and 302, a liquid crystal material 309 held between the resin substrates, a pixel electrode 306, a thin film transistor 305 connected to the pixel electrode 306, and a surface of the resin substrate 301 is flattened. A resin layer 303 for this purpose is shown.

By employing the invention disclosed in this specification, in an active matrix liquid crystal display device,
-The thickness of the device itself can be reduced.
・ Weight can be reduced.
-It is possible to obtain a substrate that does not break by external force.
-What has flexibility can be obtained.
Such a liquid crystal display device can be used in a wide range of applications and is extremely useful.

[Example 1]
In this embodiment, an inverted staggered thin film transistor is formed on a PET (polyethylene terephthalate) substrate which is an organic resin substrate.

  First, as shown in FIG. 1A, a PET film 101 having a thickness of 100 μm is prepared, and heat treatment for degassing is applied. This heat treatment needs to be performed at a temperature equal to or higher than the highest temperature applied in a later process. In the process shown in this embodiment, the temperature of 160 ° C. during the formation of the amorphous silicon film by the plasma CVD method is the maximum heating temperature. Therefore, the heat treatment for measuring degassing from the PET film is performed at 180 ° C. Perform at ℃.

  An acrylic resin layer 102 is formed on the PET film. As the acrylic resin, for example, acrylic acid methyl ester resin can be used. This acrylic resin layer 102 is for preventing oligomers from being generated on the surface of the PET film in a process in which heat is applied later. The acrylic resin layer 102 has a function of flattening irregularities on the surface of the PET film. In general, the surface of a PET film usually has irregularities on the order of several hundred to 1 μm. Such unevenness has a large electrical effect on a semiconductor layer having a thickness of several hundreds of millimeters. Accordingly, it is extremely important to flatten the base on which the semiconductor layer is formed.

  Next, a gate electrode 103 made of aluminum is formed. The gate electrode is formed by sputtering to form an aluminum film having a thickness of 2000 to 5000 mm (in this case, 3000 mm) and further performing known patterning by a photolithography process. Etching is performed so that the side surface of the pattern is tapered. (Fig. 1 (A))

  Next, a silicon oxide film 104 functioning as a gate insulating film is formed to a thickness of 1000 mm by sputtering. As the gate insulating film, a silicon nitride film may be used instead of the silicon oxide film.

  Next, a substantially intrinsic (I-type) amorphous silicon film 105 is formed to a thickness of 500 mm using a plasma CVD method. The film forming conditions are shown below.

Deposition temperature (temperature for heating the substrate) 160 ° C
Reaction pressure 0.5 Torr
RF (13.56 MHz) 20 mW / cm ²
Reaction gas SiH ₄
Here, film formation is performed using a parallel plate type plasma CVD apparatus. The heating is a heating temperature of the substrate by a heater arranged in the substrate stage on which the resin substrate is placed. In this way, the state shown in FIG.

  Further, in a later process, a silicon oxide film functioning as an etching stopper is formed by sputtering, and patterning is performed to form the etching stopper 106.

Next, an N-type amorphous silicon film 107 is formed to a thickness of 300 mm by a parallel plate type plasma CVD method. The film forming conditions are shown below.
Deposition temperature (temperature for heating the substrate) 160 ° C
Reaction pressure 0.5 Torr
RF (13.56 MHz) 20 mW / cm ²
Reaction gas B ₂ H ₆ / SiH ₄ = 1/100

  In this way, the state shown in FIG. Thereafter, the N-type amorphous silicon film 107 and the substantially intrinsic (I-type) amorphous silicon film 105 are patterned by dry etching. Then, an aluminum film is formed by sputtering to a thickness of 3000 mm. Further, the aluminum film and the underlying N-type amorphous silicon film are etched to form the source electrode 108 and the drain electrode 109. In this etching step, the source / drain is reliably separated by the action of the etching stopper 106. (Figure 1 (D))

  Then, an interlayer insulating layer 110 is formed to a thickness of 6000 mm using a resin material such as a silicon oxide film or polyimide. In the case of forming a silicon oxide film, a coating solution for forming a silicon oxide film may be used. Finally, contact holes are formed, and pixel electrodes 111 are formed using ITO. As described above, a thin film transistor disposed in each pixel electrode of an active matrix liquid crystal display device can be obtained using a light-transmitting resin substrate. (Figure 1 (E))

[Example 2]
This embodiment shows an example in which an active matrix liquid crystal display device is formed by using the thin film transistor described in Embodiment 1. FIG. 3 shows a cross section of the liquid crystal electro-optical device shown in this embodiment.

  In FIG. 3, reference numerals 301 and 302 denote a PET film having a thickness of 100 μm that constitutes a pair of substrates. Reference numeral 303 denotes an acrylic resin layer that functions as a planarizing layer. Reference numeral 306 denotes a pixel electrode. FIG. 3 shows a configuration for two pixels.

  Reference numeral 304 denotes a counter electrode. Reference numerals 307 and 308 denote alignment films for aligning the liquid crystal 309. As the liquid crystal 309, a TN liquid crystal, an STN liquid crystal, a ferroelectric liquid crystal, or the like can be used. In general, TN liquid crystal is used. The thickness of the liquid crystal layer is about several μm to 10 μm.

  A thin film transistor 305 is connected to the pixel electrode 306, and charges entering and exiting the pixel electrode 306 are controlled by the thin film transistor 305. Here, the configuration of one pixel electrode 306 is representatively shown, but the same configuration is formed in other required numbers.

  In the configuration shown in FIG. 3, since the substrates 301 and 302 have flexibility, the entire liquid crystal panel can be made flexible.

Example 3
This embodiment shows an example of manufacturing a Coplanar thin film transistor used for an active matrix liquid crystal display device. FIG. 2 shows a manufacturing process of the thin film transistor described in this embodiment. First, a PET film 201 having a thickness of 100 μm is prepared as a film-like organic resin substrate. Then, a heat treatment at 180 ° C. is added to promote degasification from the PET film. Then, a layer 202 made of an acrylic resin is formed on the surface. Here, acrylic acid ethyl ester resin is used as the acrylic resin.

Next, a substantially intrinsic (I-type) semiconductor layer 203 in which a channel formation region is formed is formed by a plasma CVD method. The film forming conditions are shown below.
Deposition temperature (temperature for heating the substrate) 160 ° C
Reaction pressure 0.5 Torr
RF (13.56 MHz) 20 mW / cm ²
Reaction gas SiH ₄
Here, film formation is performed using a parallel plate type plasma CVD apparatus.

Further, an N-type amorphous silicon film is formed to a thickness of 300 mm by a parallel plate type plasma CVD method. The film forming conditions are shown below.
Deposition temperature (temperature for heating the substrate) 160 ° C
Reaction pressure 0.5 Torr
RF (13.56 MHz) 20 mW / cm ²
Reaction gas B ₂ H ₆ / SiH ₄ = 1/100

  Then, the source region 205 and the drain region 204 are formed by patterning the N-type amorphous silicon film. (Fig. 2 (A))

  Then, a silicon oxide film or a silicon nitride film functioning as a gate insulating film is formed by sputtering and patterned to form the gate insulating film 206. Further, a gate electrode 207 is formed of aluminum. (Fig. 2 (B))

  Next, a polyimide layer 208 having a thickness of 5000 mm is formed as an interlayer insulating film. Further, a contact hole is formed, and an ITO electrode 209 to be a pixel electrode is formed by sputtering to complete a thin film transistor. (Fig. 2 (C))

Example 4
In this embodiment, an example in which the semiconductor layer is formed using a microcrystalline semiconductor film in the structure described in Embodiment 1 or 2 will be described. First, film forming conditions in the case where a substantially intrinsic semiconductor layer is a microcrystalline semiconductor layer are shown.
Deposition temperature (temperature for heating the substrate) 160 ° C
Reaction pressure 0.5 Torr
RF (13.56 MHz) 150 mW / cm ²
Reaction gas SiH ₄ / H ₂ = 1/30
Here, film formation is performed using a parallel plate type plasma CVD apparatus.

Next, film forming conditions for forming an N-type microcrystalline silicon film are shown. This is also an example in which film formation is performed using a parallel plate type plasma CVD apparatus.
Deposition temperature (temperature for heating the substrate) 160 ° C
Reaction pressure 0.5 Torr
RF (13.56 MHz) 150 mW / cm ²
Reaction gas B ₂ H ₆ / SiH ₄ = 1/100

Generally, a microcrystalline silicon film can be obtained by setting the input power to 100 to 200 mW / cm ² . In the case of an I-type semiconductor layer, in addition to increasing the power, it is effective to dilute silane with hydrogen about 10 to 50 times. However, when hydrogen dilution is performed, the film formation rate decreases.

Example 5
This embodiment relates to a structure in which laser light is irradiated to a silicon film formed by plasma CVD as shown in other embodiments with a power that does not heat a film-like substrate (substrate).

  A technique is known in which an amorphous silicon film formed on a glass substrate is irradiated with laser light (for example, KrF excimer laser light) to be transformed into a crystalline silicon film. Also, after implanting impurity ions imparting one conductivity type into the silicon film, laser irradiation is performed to crystallize (the silicon film becomes amorphous by ion implantation) and activate the impurity ions. Techniques for performing are known.

  The structure shown in this embodiment uses the laser light irradiation process as described above, and is extremely different from the amorphous silicon film 105 in FIG. 1 and the amorphous silicon films 203 and 204 in FIG. The amorphous silicon film is crystallized by irradiating weak laser light. In addition, when the film formed in advance is a microcrystalline silicon film, the crystallinity can be improved.

As the laser light, a KrF excimer laser or a XeCl excimer laser may be used. It is important that the irradiation energy is 10 to 50 mJ / cm ² so as not to cause thermal damage to the resin substrate 101 or 201.

4A and 4B illustrate a manufacturing process of a thin film transistor of an example. 4A and 4B illustrate a manufacturing process of a thin film transistor of an example. The figure which shows the outline of the cross section of a liquid crystal panel.

Explanation of symbols

101, 201 PET film substrate (polyethylene terephthalate)
301, 302
102, 202 Acrylic resin layer 303
103, 207 Gate electrode 104, 206 Gate insulating film 105, 203 Substantially intrinsic amorphous silicon film 106 Etching stopper layer 107 N-type amorphous silicon film 108 Source electrode 109 Drain electrode 110 Interlayer insulating film 111, 209 Pixel electrode 205 Source region 204 Drain region 304 Counter electrode 305 Thin film transistor 306 Pixel electrode 307, 308 Alignment film 309 Liquid crystal material

Claims (16)

A pair of opposing flexible substrates;
A plurality of thin film transistors formed between the pair of substrates and formed on one substrate;
A layer made of a resin material covering the plurality of thin film transistors;
A plurality of pixel electrodes formed on the resin material layer and connected to any one of the plurality of thin film transistors;
The semiconductor layer of the plurality of thin film transistors is divided for each of the plurality of thin film transistors,
A display device , wherein a resin layer is provided on the surface of the one substrate , and the plurality of thin film transistors are provided on the resin layer . A pair of opposing flexible substrates;
A plurality of thin film transistors formed between the pair of substrates and formed on one substrate;
A silicon oxide film formed using a coating liquid for forming a silicon oxide film covering the plurality of thin film transistors;
A plurality of pixel electrodes formed on the silicon oxide film and connected to any one of the plurality of thin film transistors;
The semiconductor layer of the plurality of thin film transistors is divided for each of the plurality of thin film transistors,
A display device , wherein a resin layer is provided on the surface of the one substrate , and the plurality of thin film transistors are provided on the resin layer . A pair of opposing flexible substrates;
A plurality of thin film transistors between the pair of substrates and formed on one substrate and having a channel formation region made of amorphous silicon;
A layer made of a resin material covering the plurality of thin film transistors;
A plurality of pixel electrodes formed on the resin material layer and connected to any one of the plurality of thin film transistors;
The semiconductor layer of the plurality of thin film transistors is divided for each of the plurality of thin film transistors,
A display device , wherein a resin layer is provided on the surface of the one substrate , and the plurality of thin film transistors are provided on the resin layer . A pair of opposing flexible substrates;
A plurality of thin film transistors between the pair of substrates and formed on one substrate and having a channel formation region made of amorphous silicon;
A silicon oxide film formed using a coating liquid for forming a silicon oxide film covering the plurality of thin film transistors;
A plurality of pixel electrodes formed on the silicon oxide film and connected to any one of the plurality of thin film transistors;
The semiconductor layer of the plurality of thin film transistors is divided for each of the plurality of thin film transistors,
A display device , wherein a resin layer is provided on the surface of the one substrate , and the plurality of thin film transistors are provided on the resin layer . A pair of opposing flexible substrates;
A plurality of thin film transistors between the pair of substrates and formed on one substrate and having a channel formation region made of microcrystalline silicon;
A layer made of a resin material covering the plurality of thin film transistors;
A plurality of pixel electrodes formed on the resin material layer and connected to any one of the plurality of thin film transistors;
The semiconductor layer of the plurality of thin film transistors is divided for each of the plurality of thin film transistors,
A display device , wherein a resin layer is provided on the surface of the one substrate , and the plurality of thin film transistors are provided on the resin layer . A pair of opposing flexible substrates;
A plurality of thin film transistors between the pair of substrates and formed on one substrate and having a channel formation region made of microcrystalline silicon;
A silicon oxide film formed using a coating liquid for forming a silicon oxide film covering the plurality of thin film transistors;
A plurality of pixel electrodes formed on the silicon oxide film and connected to any one of the plurality of thin film transistors;
The semiconductor layer of the plurality of thin film transistors is divided for each of the plurality of thin film transistors,
A display device , wherein a resin layer is provided on the surface of the one substrate , and the plurality of thin film transistors are provided on the resin layer . A pair of opposing flexible substrates;
A plurality of thin film transistors between the pair of substrates and formed on one substrate and having a channel formation region made of crystalline silicon;
A silicon oxide film formed using a coating liquid for forming a silicon oxide film covering the plurality of thin film transistors;
A plurality of pixel electrodes formed on the silicon oxide film and connected to any one of the plurality of thin film transistors;
The semiconductor layer of the plurality of thin film transistors is divided for each of the plurality of thin film transistors,
A display device , wherein a resin layer is provided on the surface of the one substrate , and the plurality of thin film transistors are provided on the resin layer . A pair of opposing flexible substrates;
A plurality of thin film transistors having a channel formation region formed of crystalline silicon which is formed between the pair of substrates and formed on one of the substrates and modified by crystalline silicon by irradiation with laser light; and the plurality of thin film transistors A layer of resin material covering
A plurality of pixel electrodes formed on the resin material layer and connected to any one of the plurality of thin film transistors;
The semiconductor layer of the plurality of thin film transistors is divided for each of the plurality of thin film transistors,
A display device , wherein a resin layer is provided on the surface of the one substrate , and the plurality of thin film transistors are provided on the resin layer . A pair of opposing flexible substrates;
A plurality of thin film transistors having a channel formation region formed of crystalline silicon that is formed between the pair of substrates and formed on one of the substrates and modified into crystalline silicon by laser light irradiation;
A silicon oxide film formed using a coating liquid for forming a silicon oxide film covering the plurality of thin film transistors;
A plurality of pixel electrodes formed on the silicon oxide film and connected to any one of the plurality of thin film transistors;
The semiconductor layer of the plurality of thin film transistors is divided for each of the plurality of thin film transistors,
A display device , wherein a resin layer is provided on the surface of the one substrate , and the plurality of thin film transistors are provided on the resin layer . Oite to claim 8 or claim 9, wherein the laser beam is a display device which is a KrF excimer laser light or XeCl excimer laser beam. In any one of claims 1 to 10, wherein the resin layer is a display device which is characterized in that an acrylic resin layer. In any one of claims 1 to 10, wherein the resin layer is methyl ester resin layer acrylic acid, ethyl ester resin layer acrylic acid, 2-ethylhexyl ester resin layer butyl acrylate resin layer or an acrylic acid A display device characterized by that. 10. The display device according to claim 1 , wherein the flexible substrate is a flexible plastic substrate. 11. 10. The flexible substrate according to claim 1 , wherein the flexible substrate is a flexible polyethylene terephthalate substrate, a flexible polyethylene naphthalate substrate, a flexible polyethylene sulfite substrate, or an acceptable substrate. A display device comprising a flexible polyimide substrate. In any one of claims 1 to 14, wherein the plurality of thin film transistors display device which is a reverse Sugata thin film transistor. In any one of claims 1 to 14, wherein the plurality of thin film transistors display device which is a planar type thin film transistor.

Images