TW201336057A - Array substrate and fabricating method of polysilicon layer - Google Patents

Abstract

A fabricating method of a polysilicon layer is provided. A first buffer layer is formed on a flexible substrate. A first barrier layer is formed on the first buffer layer. A second buffer layer is formed on the first barrier layer. A second barrier layer is formed on the second buffer layer. An amorphous silicon layer is formed on the second barrier layer. The amorphous silicon layer is transformed into a polysilicon layer through a laser beam.

Description

Array substrate and polycrystalline germanium layer manufacturing method

The present invention relates to a method for fabricating a substrate and a film layer, and more particularly to a method for fabricating an array substrate and a polysilicon layer.

In recent years, with the maturity of optoelectronic technology and semiconductor manufacturing technology, flat panel displays have flourished. Among them, liquid crystal displays have gradually replaced traditional cathodes based on their low voltage operation, no radiation scattering, light weight and small size. The tube display has become the mainstream of display products in recent years. In general, liquid crystal displays can be classified into two types: an amorphous silicon thin film transistor liquid crystal display and a low temperature poly-silicon thin film transistor liquid crystal display.

Since low-temperature polycrystalline germanium thin film transistors have better component characteristics such as high carrier mobility and high output current, they are widely used in product design and are often used in high-resolution displays. The formation of the low-temperature polycrystalline germanium layer is usually formed by chemical vapor deposition on a soft substrate to form an amorphous germanium layer, and then irradiating the amorphous germanium layer with a pseudo-molecular laser to pass the amorphous germanium layer through melting, nucleation, grain growth, and the like. The step is converted into a polycrystalline layer. However, since the amorphous germanium layer is generally penetrating for the wavelength of the excimer laser, light and thermal energy generated by the excimer laser irradiation may be transmitted to the flexible substrate to damage the flexible substrate. Furthermore, although a glass sheet or a metal foil can be used as a flexible substrate to withstand a relatively high temperature, since the sheets must be adhered to the carrier by an adhesive layer, light and heat may also damage the adhesive layer. In other words, the current low-temperature polysilicon process may damage the characteristics of components such as flexible substrates and adhesive layers, which may cause deterioration of the components, thereby affecting the device characteristics of the display.

The present invention provides an array substrate in which a thin film transistor including a polycrystalline germanium layer has good element characteristics.

The invention further provides a method for fabricating a polycrystalline germanium layer, which can avoid the absorption of laser light by the flexible substrate.

The present invention provides an array substrate comprising a flexible substrate, a first buffer layer, a first barrier layer, a second buffer layer, a second barrier layer, and a thin film transistor. The first buffer layer is disposed on the flexible substrate. The first barrier layer is disposed on the first buffer layer. The second buffer layer is disposed on the first barrier layer. The second barrier layer is disposed on the second buffer layer. The thin film transistor is disposed on the second barrier layer, wherein the thin film transistor comprises a polysilicon layer.

The invention further provides a method for fabricating a polycrystalline germanium layer. A first buffer layer is formed on the flexible substrate. A first barrier layer is formed on the first buffer layer. A second buffer layer is formed on the first barrier layer. A second barrier layer is formed on the second buffer layer. An amorphous germanium layer is formed on the second barrier layer. The amorphous germanium layer is converted into a polycrystalline germanium layer by laser light.

Based on the above, in the method for fabricating the polysilicon layer of the present invention, the buffer substrate and the polysilicon layer have a plurality of buffer layers and a barrier layer, and the buffer layer and the barrier layer can absorb the laser energy penetrating the polysilicon layer to Minimize the laser energy delivered to the flexible substrate. In this way, deterioration of the flexible substrate can be avoided. Therefore, when the thin film transistor has the polysilicon layer configured in the above manner, the array substrate including the thin film transistor has good element characteristics.

The above described features and advantages of the present invention will be more apparent from the following description.

1A to 1E are schematic cross-sectional views showing a process of fabricating a polysilicon layer according to an embodiment of the present invention. Referring to FIG. 1A , first, a first buffer layer 120 is formed on the flexible substrate 110 . In the present embodiment, the flexible substrate 110 is, for example, a polyimide substrate, a glass substrate, a metal substrate, or another substrate. The thickness of the flexible substrate 110 is, for example, greater than 0.01 mm. In an embodiment, the glass transition temperature of the flexible substrate 110 is, for example, less than 400 °C. The material of the first buffer layer 120 is, for example, a dielectric material including tantalum nitride, hafnium oxide or tantalum oxynitride, and its thickness is, for example, 50 nm. The method of forming the first buffer layer 120 is, for example, a plasma-assisted chemical vapor deposition method.

Referring to FIG. 1B, a first barrier layer 130 is formed on the first buffer layer 120. In the present embodiment, the material of the first barrier layer 130 is, for example, yttrium oxide, and its thickness is, for example, 150 nm. The formation method of the first barrier layer 130 is, for example, a plasma-assisted chemical vapor deposition method.

A second buffer layer 140 is formed on the first barrier layer 130. In the present embodiment, the material of the second buffer layer 140 is, for example, an amorphous germanium having a thickness of, for example, 50 nm. The method of forming the second buffer layer 140 is, for example, a plasma-assisted chemical vapor deposition method.

Referring to FIG. 1C, a second barrier layer 150 is then formed on the second buffer layer 140. In the present embodiment, the thermal conductivity of the material of the second barrier layer 150 is, for example, less than 10 W/mk. The material of the second barrier layer 150 is, for example, ruthenium oxide, and has a thickness of, for example, 1000 angstroms to 4000 angstroms. The formation method of the second barrier layer 150 is, for example, a plasma-assisted chemical vapor deposition method.

Referring to FIG. 1D, an amorphous germanium layer 160 is formed on the second barrier layer 150. In the present embodiment, the method of forming the amorphous germanium layer 160 is, for example, a plasma-assisted chemical vapor deposition method.

Referring to FIG. 1D and FIG. 1E simultaneously, the amorphous germanium layer 160 is converted into the polysilicon layer 170 by the laser light LB. In the present embodiment, the wavelength of the laser light LB is, for example, 300 nm to 310 nm, and is, for example, 308 nm. The material of the flexible substrate 110 is, for example, a strong absorption capability for the laser light LB having the above-described wavelength. The polysilicon layer 170 is, for example, a low temperature polysilicon. In the present example, a portion of the laser light LB, for example, would penetrate the polysilicon layer 170 into the second barrier layer 150. However, since the present embodiment is based on the wavelength of the laser light LB, the materials and thicknesses of the first and second barrier layers 130, 150 and the first and second buffer layers 120, 140, particularly the second barrier layer 150, are appropriately selected. And the material and thickness of the second buffer layer 140, and thus the first and second barrier layers 130, 150 and the first and second buffer layers 120, 140 can absorb the laser light LB penetrating the polysilicon layer 170.

For example, in one embodiment, the wavelength of the laser light LB is, for example, 308 nm, and the material of the second barrier layer 150 is, for example, yttrium oxide having a low thermal conductivity and the thickness thereof is, for example, 1000 angstroms to 4000 angstroms. The second barrier layer 150 can greatly absorb the heat generated by the laser light LB and reduce the probability that the laser light LB continues to be transferred to the film layer under the second barrier layer 150, such as the flexible substrate 110. Furthermore, the second barrier layer 150 is designed to have a suitable thickness, and the laser light LB can pass through the interface of the polysilicon layer 170 and the second barrier layer 150 or the second barrier layer 150 and the second buffer layer 140 by optical interference principle. The interface is reflected to reduce the likelihood that the laser light LB will penetrate the second barrier layer 150 to reach the flexible substrate 110. In addition, since the second buffer layer 140 is further disposed under the second barrier layer 150, the second buffer layer 140 may further absorb the remaining laser light LB penetrating the polysilicon layer 170 and the second barrier layer 150 to further prevent the laser light LB. The flexible substrate 110 is reached. In particular, in one embodiment, amorphous germanium is used as the material of the second buffer layer 140. In other words, the second buffer layer 140 and the amorphous germanium layer 160 have similar or identical characteristics to the laser light LB having a specific wavelength. Therefore, the remaining laser light LB is almost completely absorbed by the second buffer layer 140.

In general, the glass transition temperature of the flexible substrate 110 is much smaller than the melting temperature of the amorphous germanium layer 160. For example, the flexible substrate 110 of the polyimide substrate has a glass transition temperature of about 410 ° C, and the amorphous germanium layer. The melting temperature of 160 is typically greater than 1410 °C. Therefore, the laser light LB used to convert the amorphous germanium layer 160 into the polysilicon layer 170 generates a large amount of thermal energy which may be transferred to the flexible substrate 110 to cause it to soften, deform or decompose. In this embodiment, a first buffer layer 120, a first barrier layer 130, a second barrier layer 150, and a second buffer layer 140 having appropriate materials and thicknesses are disposed between the flexible substrate 110 and the polysilicon layer 170 for absorption. The laser light LB penetrating the polysilicon layer 170 and the energy generated thereof, or the interface between the laser light LB and the film layer is reflected to greatly reduce the penetration and transmission of the laser light LB and the energy generated thereby The possibility of flexing the substrate 110. In this way, deterioration or deformation of the flexible substrate 110 can be avoided, so that the flexible substrate 110 can retain its good characteristics.

2A-2D are schematic cross-sectional views showing a process of fabricating a polysilicon layer according to an embodiment of the invention. The method for fabricating the polysilicon layer of the present embodiment is substantially the same as the method for fabricating the polysilicon layer described in the previous embodiment. The following description is directed to the differences, and the rest may be referred to in the previous embodiment. Referring to FIG. 2A, first, an adhesive layer 104 is formed on the carrier 102. In the present embodiment, the carrier 102 is, for example, a glass carrier. The material of the adhesive layer 104 is, for example, a double-sided tape, a single-sided tape or an adhesive, which is formed, for example, by attachment, coating or the like. The heat resistant temperature of the adhesive layer 104 is, for example, lower than 350 °C.

Next, a flexible substrate 110 is formed on the adhesive layer 104. In the present embodiment, the thickness of the flexible substrate 110 is, for example, less than 0.1 mm. For example, in one embodiment, the material of the flexible substrate 110 is, for example, a polyimide, and its thickness is, for example, less than 0.025 mm. In an embodiment, the material of the flexible substrate 110 is, for example, glass, and its thickness is, for example, less than 0.1 mm. In an embodiment, the material of the flexible substrate 110 is, for example, a metal having a thickness of, for example, less than 0.08 mm.

Referring to FIG. 2B , a first buffer layer 120 is then formed on the flexible substrate 110 . In the present embodiment, the material of the first buffer layer 120 is, for example, a dielectric material including tantalum nitride, hafnium oxide or hafnium oxynitride, and the thickness thereof is, for example, 50 nm. The method of forming the first buffer layer 120 is, for example, a plasma-assisted chemical vapor deposition method.

Next, a first barrier layer 130 is formed on the first buffer layer 120. In the present embodiment, the material of the first barrier layer 130 is, for example, yttrium oxide, and its thickness is, for example, 150 nm. The formation method of the first barrier layer 130 is, for example, a plasma-assisted chemical vapor deposition method.

Then, a second buffer layer 140 is formed on the first barrier layer 130. In the present embodiment, the material of the second buffer layer 140 is, for example, an amorphous germanium having a thickness of, for example, 50 nm. The method of forming the second buffer layer 140 is, for example, a plasma-assisted chemical vapor deposition method.

Referring to FIG. 2C, a second barrier layer 150 is formed on the second buffer layer 140. In the present embodiment, the thermal conductivity of the material of the second barrier layer 150 is, for example, less than 10 W/mk. The material of the second barrier layer 150 is, for example, ruthenium oxide, and has a thickness of, for example, 1000 angstroms to 4000 angstroms. The formation method of the second barrier layer 150 is, for example, a plasma-assisted chemical vapor deposition method.

Then, an amorphous germanium layer 160 is formed on the second barrier layer 150. In the present embodiment, the method of forming the amorphous germanium layer 160 is, for example, a plasma-assisted chemical vapor deposition method.

Referring to FIG. 2C and FIG. 2D simultaneously, the amorphous germanium layer 160 is converted into the polysilicon layer 170 by the laser light LB. In the present embodiment, the wavelength of the laser light LB is, for example, 300 nm to 310 nm, and is, for example, 308 nm. The material of the flexible substrate 110 and the material of the adhesive layer 104 are, for example, strong absorption ability to the laser light LB having the above-described wavelength, and the heat resistance temperature of the material of the flexible substrate 110 and the material of the adhesive layer 104 is, for example, lower than 350 °C. The polysilicon layer 170 is, for example, a low temperature polysilicon.

In the present example, a portion of the laser light LB, for example, would penetrate the polysilicon layer 170 into the second barrier layer 150. However, since the present embodiment is based on the wavelength of the laser light LB, the materials and thicknesses of the first and second barrier layers 130, 150 and the first and second buffer layers 120, 140, particularly the second barrier layer 150, are appropriately selected. And the material and thickness of the second buffer layer 140, so the first and second barrier layers 130, 150 and the first and second buffer layers 120, 140 can greatly absorb and block the laser light LB to avoid the laser light LB and its The generated thermal energy penetrates or is transmitted to the flexible substrate 110 and the adhesive layer 104. The mechanism for absorbing and blocking the laser light LB and the heat energy generated by the first and second barrier layers 130 and 150 and the first and second buffer layers 120 and 140 can be referred to in the previous embodiment, and details are not described herein. .

In particular, in the method for fabricating the polysilicon layer of the present embodiment, the flexible substrate 110 is attached to the carrier 102 by the adhesive layer 104, but in another embodiment, as shown in FIG. The flexible substrate 110 can also be directly attached to and in contact with the carrier 102. The flexible substrate 110 can be a plastic substrate. Since the other film layers are produced in the same manner as the foregoing embodiments, they are not described herein.

In this embodiment, a first buffer layer 120, a first barrier layer 130, a second barrier layer 150, and a second buffer layer 140 having appropriate materials and thicknesses are disposed between the flexible substrate 110 and the polysilicon layer 170 for absorption. The laser light LB penetrating the polysilicon layer 170 and the energy generated thereby, or the interface of the laser light LB between the film layers is reflected. As a result, the possibility that the laser light LB and the energy generated thereby penetrate and transmit to the flexible substrate 110 and the adhesive layer 104 can be greatly reduced. Therefore, deterioration, deformation or deterioration of the flexible substrate 110 and the adhesive layer 104 can be avoided, so that the flexible substrate 110 and the adhesive layer 104 can retain their good characteristics.

4 is a cross-sectional view of an array substrate in accordance with an embodiment of the present invention. Referring to FIG. 4 , the array substrate 100 includes a flexible substrate 110 , a first buffer layer 120 , a first barrier layer 130 , a second buffer layer 140 , a second barrier layer 150 , and a thin film transistor 200 . In the present embodiment, the flexible substrate 110 is, for example, a polyimide substrate, a glass substrate, or a metal substrate. The first buffer layer 120 is disposed on the flexible substrate 110. The material of the first buffer layer 120 is, for example, tantalum nitride. The first barrier layer 130 is disposed on the first buffer layer 120. The material of the first barrier layer 130 is, for example, yttrium oxide. The second buffer layer 140 is disposed on the first barrier layer 130. The material of the second buffer layer 140 is, for example, an amorphous germanium having a thickness of, for example, 400 to 1000 Å. The second barrier layer 150 is disposed on the second buffer layer 140. The thermal conductivity of the second barrier layer 150 is, for example, less than 10 W/mk. The material of the second barrier layer 150 is, for example, yttrium oxide, and has a thickness of, for example, 1000 angstroms to 4000 angstroms. The material, the thickness, and the manufacturing method of the flexible substrate 110, the first buffer layer 120, the first barrier layer 130, the second buffer layer 140, and the second barrier layer 150 can be referred to the foregoing embodiments.

The thin film transistor 200 is disposed on the second barrier layer 150, wherein the thin film transistor 200 includes a polysilicon layer 170. In the present embodiment, the polysilicon layer 170 is fabricated, for example, by the manner described in the previous embodiments, and then passed through a patterning and doping process to serve as a channel layer in the thin film transistor. For example, in the present embodiment, the polysilicon layer 170 includes, for example, a channel region, a heavily doped region, a lightly doped region, a source region, and a drain region. The material of the polysilicon layer 170 is, for example, a low temperature polysilicon. The thin film transistor 200 is, for example, a low temperature polycrystalline thin film transistor.

In the present embodiment, the thin film transistor 200 further includes a gate 180, a source 182a and a drain 182b, a pixel electrode 186, a gate dielectric layer 188, an interlayer dielectric layer 190, and protective layers 192, 194. The gate dielectric layer 188 covers the polysilicon layer 170, for example. The gate 180 is disposed, for example, on the gate dielectric layer 188. The interlayer dielectric layer 190 is, for example, a gate electrode 180 and a gate dielectric layer 188. The source 182a and the drain 182b are disposed, for example, on the interlayer dielectric layer 190, and are electrically connected to the polysilicon layer 170, for example, via the gate dielectric layer 188 and the contact holes 188a, 190a in the interlayer dielectric layer 190. The protective layer 192 is, for example, an interlayer dielectric layer 190 and a source 182a and a drain 182b. The pixel electrode 186 is disposed, for example, on the protective layer 192, and is electrically connected to the drain 182b via a contact hole 192a in the protective layer 192, for example. The protective layer 194 is, for example, a capping electrode 186 and a protective layer 192. In the present embodiment, the thin film transistor 200 includes, for example, a pad 184 that is connected to an external circuit via contact plugs 196, 198 disposed in the contact holes 190a, 192a of the interlayer dielectric layer 190 and the protective layer 192. In particular, although the array substrate 100 has the structure of the thin film transistor 200 shown in FIG. 4 as an example, the present invention is not limited thereto. In other words, the thin film transistor 200 may have other configurations.

Furthermore, in an embodiment (not shown), the array substrate 100 further includes a carrier 102, wherein the flexible substrate 110 is disposed between the carrier 102 and the first buffer layer 120. In an embodiment (not shown), the array substrate 100 further includes a carrier 102 and an adhesive layer 104, wherein the adhesive layer 104 is disposed between the carrier 102 and the flexible substrate 110. The materials and thicknesses of the carrier 102, the adhesive layer 104, and the flexible substrate 110 can be referred to the embodiment shown in FIG. 2D and FIG. 3, and details are not described herein.

In the present embodiment, the buffer layers 120, 140 and the barrier layers 130, 150 having appropriate materials and thicknesses are disposed between the flexible substrate 110 and the polysilicon layer 170, and thus the amorphous germanium is irradiated with an energy beam such as laser light LB. When the layer is converted into the polysilicon layer 170 as the channel layer, the buffer layers 120, 140 and the barrier layers 130, 150 can absorb the laser light LB penetrating the polysilicon layer 170 and the energy generated thereof, or cause the laser light LB to be in the films. The interface between the layers is reflected. As a result, the possibility that the laser light LB and the energy generated thereby penetrate and transmit to the flexible substrate 110 and the adhesive layer 104 can be greatly reduced. Therefore, deterioration, deformation or deterioration of the flexible substrate 110 and the adhesive layer 104 can be avoided, so that the flexible substrate 110 and the adhesive layer 104 can retain their good characteristics. In addition, the buffer layers 120, 140 and the barrier layers 130, 150 also provide a buffering and blocking function when fabricating other components of the thin film transistor to further prevent the flexible substrate 110 and the adhesive layer 104 from being damaged. Therefore, the array substrate of the present embodiment has good element characteristics. In addition, the method for fabricating the array substrate of the present embodiment can be easily combined with the process of the existing array substrate, so that the manufacturing cost is not greatly increased, but the yield of the array substrate can be greatly improved.

FIG. 5 is a schematic cross-sectional view of an organic light emitting device according to an embodiment of the invention. In the present embodiment, the organic light-emitting device 300 includes an array substrate 100, a first electrode 310, an organic light-emitting layer 340, and a second electrode 370. The first electrode 310, the organic light-emitting layer 340, and the second electrode 370 are disposed on the array substrate 100, and the organic light-emitting layer 340 is located between the first electrode 310 and the second electrode 370. In the present embodiment, the array substrate 100 is the array substrate shown in FIG. 4, and includes a flexible substrate 110, a first buffer layer 120, a first barrier layer 130, a second buffer layer 140, a second barrier layer 150, and a film. The detailed structure of the transistor 200 can be referred to as shown in FIG. 4 and the previous embodiment, and the description and description are omitted here. In the present embodiment, the first electrode 310 is, for example, an anode and the second electrode 370 is, for example, a cathode. The organic light-emitting device 300 further includes, for example, a hole injection layer 320, a hole transport layer 330, an electron transport layer 350, and an electron injection layer 360. The hole injection layer 320 and the hole transport layer 330 are disposed between the first electrode 310 and the organic light-emitting layer 340, for example, and the hole injection layer 320 is disposed between the first electrode 310 and the hole transport layer 330, for example. The electron injection layer 360 and the electron transport layer 350 are disposed between the second electrode 370 and the organic light emitting layer 340, for example, and the electron injection layer 360 is disposed between the second electrode 370 and the electron transport layer 350, for example. Of course, in other embodiments, the configuration of the hole injection layer 320, the hole transport layer 330, the electron transport layer 350, and the electron injection layer 360 may also be omitted.

Furthermore, in an embodiment (not shown), the flexible substrate 110 in the array substrate 100 may be directly disposed on the carrier 102 or disposed on the carrier 102 via the adhesive layer 104. The arrangement, material, and thickness of the carrier 102, the adhesive layer 104, and the flexible substrate 110 can be referred to the embodiment shown in FIG. 2D and FIG. 3, and details are not described herein.

In the embodiment, the organic light-emitting device 300 has the array substrate 100. The buffer layers 120 and 140 and the barrier layers 130 and 150 in the array substrate 100 can prevent the flexible substrate 110 from being converted into the polysilicon layer 170. The effect of the laser light LB makes the flexible substrate 110 retain its good characteristics. As such, the organic light-emitting device 300 has better component characteristics and yield.

In particular, although in the above embodiments, the method for fabricating polycrystalline silicon is applied to a thin film transistor and an organic light-emitting device in a flexible substrate, the present invention is not limited thereto. That is to say, the method for fabricating polysilicon can be applied to various elements that need to convert amorphous germanium into polycrystalline germanium by laser light, so as to avoid damage or influence of the flexible substrate in the device.

In summary, in the method for fabricating the polysilicon layer of the present invention, the buffer substrate and the polysilicon layer have a plurality of buffer layers and barrier layers, and the buffer layer and the barrier layer can absorb the laser energy penetrating the polysilicon layer. Minimize the laser energy delivered to the flexible substrate. In this way, the deterioration of the flexible substrate and the adhesive layer can be avoided, so that the flexible substrate and the adhesive layer can retain their original good characteristics. Furthermore, when the thin film transistor has the polysilicon layer disposed in the above manner, the array substrate including the thin film transistor or the organic light-emitting device or other device including the above array substrate also has preferable element characteristics. On the other hand, since the method for fabricating the polysilicon layer of the present invention can be easily combined with the processes of existing thin film transistors, array substrates or organic light-emitting devices, without additional equipment or greatly changing the production process, This results in a substantial increase in the manufacturing cost of the above components and enables the above components to have better yield.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the invention, and any one of ordinary skill in the art can make some modifications and refinements without departing from the spirit and scope of the invention. The scope of the invention is defined by the scope of the appended claims.

100. . . Array substrate

102. . . vehicle

104. . . Adhesive layer

110. . . Flexible substrate

120, 140. . . The buffer layer

130, 150. . . Barrier layer

160. . . Amorphous layer

170. . . Polycrystalline layer

180. . . Gate

182a. . . Source

182b. . . Bungee

184. . . Solder pad

186. . . Pixel electrode

188. . . Gate dielectric layer

188a, 190a, 192a. . . Contact hole

190. . . Interlayer dielectric layer

192, 194. . . The protective layer

196, 198. . . Contact plug

200. . . Thin film transistor

300. . . Organic light emitting device

LB. . . laser

1A to 1E are schematic cross-sectional views showing a process of fabricating a polysilicon layer according to an embodiment of the present invention.

2A-2D are schematic cross-sectional views showing a process of fabricating a polysilicon layer according to an embodiment of the invention.

3 is a schematic cross-sectional view of a polysilicon layer in accordance with an embodiment of the present invention.

4 is a cross-sectional view of an array substrate in accordance with an embodiment of the present invention.

FIG. 5 is a schematic cross-sectional view of an organic light emitting device according to an embodiment of the invention.

110. . . Flexible substrate

120, 140. . . The buffer layer

130, 150. . . Barrier layer

160. . . Amorphous layer

LB. . . laser

Claims (33)

An array substrate includes: a flexible substrate; a first buffer layer disposed on the flexible substrate; a first barrier layer disposed on the first buffer layer; and a second buffer layer disposed on the first a barrier layer; a second barrier layer disposed on the second buffer layer; and a thin film transistor disposed on the second barrier layer, wherein the thin film transistor comprises a polysilicon layer. The array substrate of claim 1, wherein the flexible substrate comprises a polyimide substrate, a glass substrate or a metal substrate. The array substrate of claim 1, wherein the material of the polysilicon layer comprises a low temperature polysilicon. The array substrate of claim 1, wherein the material of the second barrier layer has a thermal conductivity of less than 10 W/mk. The array substrate of claim 1, wherein the second barrier layer has a thickness of from 1000 angstroms to 4000 angstroms. The array substrate of claim 1, wherein the material of the second barrier layer comprises ruthenium oxide. The array substrate of claim 1, wherein the material of the second buffer layer comprises amorphous germanium. The array substrate of claim 1, wherein the second buffer layer has a thickness of 400 to 1000 angstroms. The array substrate of claim 1, wherein the material of the first barrier layer comprises ruthenium oxide. The array substrate of claim 1, wherein the material of the first buffer layer comprises tantalum nitride. The array substrate of claim 1, further comprising a carrier, wherein the flexible substrate is disposed between the carrier and the first buffer layer. The array substrate of claim 11, further comprising an adhesive layer disposed between the carrier and the flexible substrate. The array substrate according to claim 12, wherein the flexible substrate is made of polyimide and has a thickness of less than 0.025 mm. The array substrate according to claim 12, wherein the flexible substrate is made of glass and has a thickness of less than 0.1 mm. The array substrate of claim 12, wherein the flexible substrate is made of a metal having a thickness of less than 0.08 mm. The array substrate of claim 1, further comprising: a pixel electrode disposed on the thin film transistor and electrically connected to the thin film transistor; an organic light emitting layer disposed on the pixel electrode And an electrode layer disposed on the organic light emitting layer, wherein the organic light emitting layer is located between the pixel electrode and the electrode layer. A method for fabricating a polysilicon layer, comprising: forming a first buffer layer on a flexible substrate; forming a first barrier layer on the first buffer layer; forming a second buffer layer on the first barrier layer; Forming a second barrier layer on the second buffer layer; forming an amorphous germanium layer on the second barrier layer; and converting the amorphous germanium layer into a poly germanium layer by using a laser light. The method for fabricating a polysilicon layer according to claim 17, wherein the laser light has a wavelength of 300 nm to 310 nm. The method for fabricating a polysilicon layer according to claim 17, wherein the second barrier layer absorbs the laser light that penetrates the polysilicon layer. The method for fabricating a polysilicon layer according to claim 17, wherein the second buffer layer absorbs the laser light that penetrates the second barrier layer. The method for fabricating a polysilicon layer according to claim 17, wherein the flexible substrate comprises a polyimide substrate, a glass substrate and a metal substrate. The method for fabricating a polysilicon layer according to claim 17, wherein the material of the polysilicon layer comprises a low temperature polysilicon. The method for fabricating a polysilicon layer according to claim 17, wherein the material of the second barrier layer has a thermal conductivity of less than 10 W/mk. The method for fabricating a polysilicon layer according to claim 17, wherein the second barrier layer has a thickness of from 1000 angstroms to 4000 angstroms. The method for fabricating a polysilicon layer according to claim 17, wherein the material of the second barrier layer comprises ruthenium oxide. The method for fabricating a polysilicon layer according to claim 17, wherein the material of the second buffer layer comprises amorphous germanium. The method for fabricating a polysilicon layer according to claim 17, wherein the material of the first barrier layer comprises cerium oxide. The method for fabricating a polysilicon layer according to claim 17, wherein the material of the first buffer layer comprises tantalum nitride. The method for fabricating a polysilicon layer according to claim 17, further comprising a carrier, wherein the flexible substrate is disposed between the carrier and the first buffer layer. The method for fabricating a polysilicon layer according to claim 29, further comprising an adhesive layer disposed between the carrier and the flexible substrate. The method for fabricating a polysilicon layer according to claim 30, wherein the flexible substrate is made of polyimide and has a thickness of less than 0.025 mm. The method for fabricating a polysilicon layer according to claim 30, wherein the flexible substrate is made of glass and has a thickness of less than 0.1 mm. The method for fabricating a polysilicon layer according to claim 30, wherein the flexible substrate is made of metal and has a thickness of less than 0.08 mm.