JP3571197B2 - Semiconductor device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
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. In addition, the present invention relates to an active matrix liquid crystal display device including the thin film transistor.
[0002]
[Prior art]
Thin film transistors formed on a glass substrate or a quartz substrate are known. The thin film transistor formed on this glass substrate is mainly used for an active matrix type liquid crystal display device. An active matrix liquid crystal display device can perform high-speed moving images and fine display, and is expected to replace a simple matrix liquid crystal display device.
[0003]
An active matrix type liquid crystal display device is one in which one or more thin film transistors are arranged as switching elements in each pixel, and electric charges that enter and exit pixel electrodes are controlled by the thin film transistors. A glass substrate or a quartz substrate is used as the substrate because visible light needs to be transmitted through the liquid crystal display device.
[0004]
On the other hand, liquid crystal display devices are expected as display means having a very wide range of applications. For example, it is expected to be used as a display unit used in card-type computers, portable computers, and portable electronic devices such as various communication devices. In the display means used in these portable electronic devices, more advanced information is required to be displayed in accordance with the sophistication of information to be handled. For example, there is a demand for a function of displaying not only numbers and symbols but also finer image information and moving images.
[0005]
When a function of displaying fine image information or a moving image is required by a liquid crystal display device, it is necessary to use an active matrix type liquid crystal display device. However, when a glass substrate or a 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 the weight, the substrate will crack.
-The substrate is not flexible.
There is a problem.
[0006]
In particular, card-type electronic devices are required to have the flexibility not to be damaged even when a small amount of stress is applied in handling them. Therefore, the liquid crystal display device incorporated in the electronic devices has the same flexibility (flexibility). Required.
[0007]
[Problems to be solved by the invention]
An object of the invention disclosed in this specification is to provide an active matrix liquid crystal display device having flexibility.
[0008]
[Means for Solving the Problems]
As a method for giving flexibility to a liquid crystal display device, there is a method using a plastic substrate or a resin substrate having a light-transmitting property 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 due to its heat resistance.
[0009]
Therefore, the invention disclosed in this specification is characterized by solving the above-mentioned difficulties by employing the following configuration. One of the semiconductor devices according to the invention disclosed in this specification includes a flexible substrate, a resin layer provided over the flexible substrate, and a thin film transistor provided over the resin layer. And the flexible substrate is a resin substrate .
[0010]
FIG. 1 shows a specific example of the above configuration. 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-shaped resin substrate, and an inverted staged thin film transistor is formed thereon.
[0011]
As the film-shaped resin substrate, a material 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. In addition, it is 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 higher, oligomers (polymer having a diameter of about 1 μm) precipitate on the surface or generate gas, and a semiconductor layer is formed thereon. It becomes extremely difficult to form. Therefore, it is necessary that the heat-resistant temperature be as high as possible.
[0012]
In the above structure, the resin layer has a function of flattening the surface of the resin substrate. The meaning of the flattening includes a function of preventing oligomers from being generated on the surface of the resin substrate in a step involving heating such as formation of a semiconductor layer.
[0013]
For this resin layer, an acrylic resin selected from methyl acrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate 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.
[0014]
Hereinafter, a method for manufacturing the semiconductor device of the present invention having the above structure will be described. One of the manufacturing methods includes a step of forming a resin layer on a film-like resin substrate, a step of forming a semiconductor layer on the resin layer by a plasma CVD method, and a step of forming a thin film transistor using the semiconductor layer and, that have a.
[0015]
One of the other manufacturing methods is a step of heating the film-shaped resin substrate at a predetermined temperature to measure degassing from the resin substrate, a step of forming a resin layer on the film-shaped resin substrate, forming a semiconductor layer by plasma CVD method on the resin layer, that having a, forming a thin film transistor using the semiconductor layer.
[0016]
In the above manufacturing method , the reason why the heat treatment is performed and the degassing from the resin substrate is measured is to prevent the degassing phenomenon from occurring from the resin substrate in a process following the heating. For example, if degassing from the resin substrate occurs during the formation of the semiconductor thin film on the resin substrate, large pinholes will be formed in the semiconductor thin film, and the electrical characteristics will be greatly impaired. Will be. Therefore, by performing the heat treatment at a temperature higher than the heating temperature applied in the subsequent process in advance and degassing from the resin substrate, the degassing phenomenon from the resin substrate in the later process is suppressed. can do.
[0017]
One of the other manufacturing methods is a step of heating a film-shaped resin substrate at a predetermined temperature, a step of forming a resin layer on the film-shaped resin substrate, and a step of forming a semiconductor layer on the resin layer by plasma CVD. forming by law, has a step of forming a thin film transistor, the using the semiconductor layer, the formation of the semiconductor layer in the plasma CVD method, intends row heated at the predetermined temperature or lower.
[0018]
One of the other manufacturing methods is a step of heating a film-shaped resin substrate at a predetermined temperature, a step of forming a resin layer on the film-shaped resin substrate, and a step of forming a semiconductor layer on the resin layer by plasma CVD. forming by law, and a step of forming a thin film transistor using the semiconductor layer, wherein the predetermined temperature, Ru higher temperatures der than the heating temperature in the other steps.
[0019]
Further, a semiconductor device according to another invention includes a flexible substrate, a resin layer provided over the flexible substrate, a thin film transistor provided over the resin layer, The substrate having an interlayer insulating layer provided above and a pixel electrode provided above the interlayer insulating layer and electrically connected to the thin film transistor, wherein the flexible substrate is a resin substrate. And
[0020]
FIG. 1 shows a specific example of the above configuration. The configuration shown in FIG. 1 includes a resin substrate 101 , a pixel electrode 111 , a thin film transistor connected to the pixel electrode 111 , an interlayer insulating layer 110 provided above the thin film transistor, and a resin layer for planarizing the surface of the resin substrate 101. 102 is shown.
[0021]
【Example】
[Example 1]
This embodiment shows an example in which an inverted staged thin film transistor is formed on a PET (polyethylene terephthalate) substrate which is an organic resin substrate.
[0022]
First, as shown in FIG. 1A, a PET film 101 having a thickness of 100 μm is prepared and subjected to a heat treatment for degassing. 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. at the time of forming the amorphous silicon film by the plasma CVD method is the maximum heating temperature. Therefore, the heat treatment for degassing from the PET film is 180 °. Perform at ° C.
[0023]
An acrylic resin layer 102 is formed on the PET film. For example, methyl acrylate can be used as the acrylic resin. The acrylic resin layer 102 is for preventing oligomers from being generated on the surface of the PET film in a later process in which heat is applied. In addition, the acrylic resin layer 102 has a function of flattening irregularities on the surface of the PET film. Generally, the surface of a PET film usually has irregularities on the order of several hundreds of .mu.m to 1 .mu.m. Such irregularities have a large electrical effect on the semiconductor layer having a thickness of several hundreds of square meters. Therefore, it is extremely important to flatten the base on which the semiconductor layer is formed.
[0024]
Next, a gate electrode 103 made of aluminum is formed. The formation of the gate electrode is performed by forming an aluminum film to a thickness of 2000 to 5000 (here, 3000) by a sputtering method and performing a known patterning by a photolithography process. Etching is performed so that the side surface of the pattern is tapered. (Fig. 1 (A))
[0025]
Next, a silicon oxide film 104 functioning as a gate insulating film is formed to a thickness of 1000 ° by a sputtering method. Instead of a silicon oxide film, a silicon nitride film may be used as the gate insulating film.
[0026]
Next, a substantially intrinsic (I-type) amorphous silicon film 105 is formed to a thickness of 500 ° by plasma CVD. The film forming conditions are shown below.
[0027]
Film formation 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 a substrate stage on which the resin substrate is placed. Thus, the state shown in FIG. 1B is obtained.
[0028]
In a later step, a silicon oxide film functioning as an etching stopper is formed by a sputtering method, and the etching stopper 106 is formed by patterning.
[0029]
Next, an N-type amorphous silicon film 107 is formed to a thickness of 300 ° by a parallel plate type plasma CVD method. The film forming conditions are shown below.
Film formation 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
[0030]
Thus, the state shown in FIG. 1C is obtained. Thereafter, patterning is performed by Dora Lee etching on the amorphous silicon film 105 of an amorphous silicon film 107 and the substantially intrinsic N-type (I type). Then, an aluminum film is formed to a thickness of 3000 ° by the sputtering method. Further, by etching this aluminum film and the N-type amorphous silicon film thereunder, a source electrode 108 and a drain electrode 109 are formed. In this etching step, the source / drain is reliably separated by the action of the etching stopper 106. (Fig. 1 (D))
[0031]
Then, an interlayer insulating layer 110 is formed to a thickness of 6000 ° 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, a contact hole is formed, and the pixel electrode 111 is formed using ITO. As described above, a thin film transistor arranged on each pixel electrode of an active matrix liquid crystal display device can be obtained using a light-transmitting resin substrate. (FIG. 1 (E))
[0032]
[Example 2]
In this embodiment, an example in which an active matrix liquid crystal display device is formed using the thin film transistor described in Embodiment 1 will be described. FIG. 3 shows a cross section of the liquid crystal electro-optical device shown in this embodiment.
[0033]
In FIG. 3, reference numerals 301 and 302 denote PET films each having a thickness of 100 μm and constituting a pair of substrates. An acrylic resin layer 303 functions as a flattening layer. 306 is a pixel electrode. FIG. 3 shows a configuration for two pixels.
[0034]
304 is a counter electrode. 307 and 308 are 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. Generally, a TN liquid crystal is used. Further, as the thickness of the liquid crystal layer, about several μm to 10 μm is used.
[0035]
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 shown as a representative, but similar configurations are formed in other required numbers.
[0036]
In the configuration shown in FIG. 3, since the substrates 301 and 302 have flexibility, the entire liquid crystal panel can be made flexible.
[0037]
[Example 3]
This embodiment shows an example in which a Coplanar thin film transistor used for an active matrix liquid crystal display device is manufactured. FIG. 2 illustrates 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-shaped organic resin substrate. Then, 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, ethyl acrylate is used as the acrylic resin.
[0038]
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.
Film formation 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.
[0039]
Further, an N-type amorphous silicon film is formed to a thickness of 300 ° by a parallel plate type plasma CVD method. The film forming conditions are shown below.
Film formation 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
[0040]
Then, the source region 205 and the drain region 204 are formed by patterning the N-type amorphous silicon film. (Fig. 2 (A))
[0041]
Then, a gate insulating film 206 is formed by forming a silicon oxide film or a silicon nitride film serving as a gate insulating film by a sputtering method and performing patterning. Further, a gate electrode 207 is formed of aluminum. (FIG. 2 (B))
[0042]
Next, a polyimide layer 208 is formed to a thickness of 5000 ° as an interlayer insulating film. Further, a contact hole is formed, and an ITO electrode 209 serving as a pixel electrode is formed by a sputtering method, thereby completing a thin film transistor. (Fig. 2 (C))
[0043]
[Example 4]
In this embodiment, an example in which a semiconductor layer is formed using a microcrystalline semiconductor film in the structure described in Embodiment 1 or Embodiment 2 will be described. First, film forming conditions when a substantially intrinsic semiconductor layer is a microcrystalline semiconductor layer will be described.
Film formation 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.
[0044]
Next, conditions for forming an N-type microcrystalline silicon film will be described. This is also an example in which a film is formed using a parallel plate type plasma CVD apparatus.
Film formation 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
[0045]
Generally, by setting the input power to 100 to 200 mW / cm ² , a microcrystalline silicon film can be obtained. In the case of an I-type semiconductor layer, in addition to increasing the power, it is effective to dilute silane about 10 to 50 times with hydrogen. However, when hydrogen is diluted, the film formation rate is reduced.
[0046]
[Example 5]
This embodiment relates to a configuration in which a silicon film formed by a plasma CVD method as shown in another embodiment is irradiated with laser light at a power that does not heat a film-like base (substrate).
[0047]
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 transform the amorphous silicon film into a crystalline silicon film. The semiconductor film is irradiated with laser light after implanting impurity ions imparting one conductivity type to the silicon film, so that the silicon film is crystallized (the silicon film becomes amorphous by ion implantation) and the impurity ions are activated. Techniques for performing are known.
[0048]
The configuration shown in this embodiment utilizes the above-described laser beam irradiation process, and is extremely different from the amorphous silicon film 105 in FIG. 1 and the amorphous silicon films 203 and 204 in FIG. It is characterized by irradiating a weak laser beam to crystallize an amorphous silicon film. In the case where the film formed in advance is a microcrystalline silicon film, its crystallinity can be improved.
[0049]
As a laser beam, 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} that the resin substrate 101 or 201 is not thermally damaged.
[0050]
【The invention's effect】
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.
・ The weight can be reduced.
-A substrate that does not break the substrate due to external force can be obtained.
-A product having flexibility can be obtained.
Such a liquid crystal display device can be used for a wide range of applications and is extremely useful.
[Brief description of the drawings]
FIG. 1 is a diagram showing a manufacturing process of a thin film transistor of an example.
FIG. 2 is a diagram showing a manufacturing process of a thin film transistor of an example.
FIG. 3 is a diagram schematically illustrating a 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 electrodes 104, 206 Gate insulating films 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 films 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 (17)

A substrate having flexibility, a resin layer provided over the substrate having flexibility, and a thin film transistor provided over the resin layer;
The semiconductor device, wherein the flexible substrate is a resin substrate. A substrate having flexibility, a resin layer provided over the substrate having flexibility, and a thin film transistor provided over the resin layer;
The semiconductor device, wherein the flexible substrate is a plastic substrate. A substrate having flexibility, a resin layer provided over the substrate having flexibility, and a thin film transistor provided over the resin layer;
A semiconductor device, wherein the flexible substrate is a polyethylene terephthalate substrate, a polyethylene naphthalate substrate, a polyethylene sulphite substrate or a polyimide substrate. A flexible substrate, a resin layer provided above the flexible substrate, and an inverted staggered thin film transistor provided above the resin layer,
The semiconductor device, wherein the flexible substrate is a resin substrate. A flexible substrate, a resin layer provided above the flexible substrate, and an inverted staggered thin film transistor provided above the resin layer,
The semiconductor device, wherein the flexible substrate is a plastic substrate. A flexible substrate, a resin layer provided above the flexible substrate, and an inverted staggered thin film transistor provided above the resin layer,
A semiconductor device, wherein the flexible substrate is a polyethylene terephthalate substrate, a polyethylene naphthalate substrate, a polyethylene sulphite substrate or a polyimide substrate. A flexible substrate, a resin layer provided over a substrate having the flexible, thin film transistor provided above the resin layer, an interlayer insulating layer disposed above the thin film transistor and the interlayer insulating layer Having a pixel electrode provided above and electrically connected to the thin film transistor,
The semiconductor device, wherein the flexible substrate is a resin substrate. A flexible substrate, a resin layer provided over a substrate having the flexible, thin film transistor provided above the resin layer, an interlayer insulating layer disposed above the thin film transistor and the interlayer insulating layer Having a pixel electrode provided above and electrically connected to the thin film transistor,
The semiconductor device, wherein the flexible substrate is a plastic substrate. A flexible substrate, a resin layer provided over a substrate having the flexible, thin film transistor provided above the resin layer, an interlayer insulating layer disposed above the thin film transistor and the interlayer insulating layer Having a pixel electrode provided above and electrically connected to the thin film transistor,
A semiconductor device, wherein the flexible substrate is a polyethylene terephthalate substrate, a polyethylene naphthalate substrate, a polyethylene sulphite substrate or a polyimide substrate. A flexible substrate, a resin layer provided above the flexible substrate, an inverted staggered thin film transistor provided above the resin layer, an interlayer insulating layer provided above the thin film transistor, and have electrically connected to the pixel electrode on the TFT with provided above the interlayer insulating layer,
The semiconductor device, wherein the flexible substrate is a resin substrate. A flexible substrate, a resin layer provided above the flexible substrate, an inverted staggered thin film transistor provided above the resin layer, an interlayer insulating layer provided above the thin film transistor, and have electrically connected to the pixel electrode on the TFT with provided above the interlayer insulating layer,
The semiconductor device, wherein the flexible substrate is a plastic substrate. A flexible substrate, a resin layer provided above the flexible substrate, an inverted staggered thin film transistor provided above the resin layer, an interlayer insulating layer provided above the thin film transistor, and have electrically connected to the pixel electrode on the TFT with provided above the interlayer insulating layer,
A semiconductor device, wherein the flexible substrate is a polyethylene terephthalate substrate, a polyethylene naphthalate substrate, a polyethylene sulphite substrate or a polyimide substrate. 13. The semiconductor device according to claim 1, wherein the flexible substrate has irregularities. 14. The semiconductor device according to claim 1, wherein the gate insulating film of the thin film transistor includes a silicon nitride film. 15. The semiconductor device according to claim 1, wherein the resin layer is an acrylic resin layer. 15. The resin layer according to claim 1, wherein the resin layer is a methyl acrylate resin layer, an ethyl acrylate resin layer, a butyl acrylate resin layer, or a 2-ethylhexyl acrylate resin layer. A semiconductor device characterized by the above-mentioned. 17. The semiconductor device according to claim 1, wherein a surface of the resin layer is flat.

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