Patent Application
20080081400
The present invention relates to a device transfer method and a display apparatus. More particularly, the present invention relates to a device transfer method and a display apparatus by or in which devices can be transferred accurately.
The device transfer method and the display apparatus according to various embodiments of the present invention will be described in detail below, referring to the drawings Where it should be appreciated that the present invention is not limited to the following description, and modifications can be appropriately made without departure from the scope of the gist of the invention.
As shown in
The device 3 is a light-emitting diode composed of a material based on a nitride semiconductor such as gallium nitride, which has, for example, a double hetero structure in which an active layer 3b is sandwiched between a p-clad layer 3p and an n-clad layer 3n. In addition, the device 3 shown here is roughly flat plate-like in shape, and is formed by a method in which the active layer and the clad layers of the device 3 are extended in planes parallel to the principal surface of a sapphire substrate on which to grow the active layer and the clad layers, and a gallium nitride crystal layer or the like is laminated by selective growth or the like. While an example in which the p-clad layer 3p is present on the temporary adhesion layer 2 side of the device 3 is shown in the figure, the device 3 may be so disposed that the n-clad layer 3n is located on the side of the temporary adhesion layer 2. Besides, though omitted in the figure, a p-electrode for lowering the contact resistance between the electric wiring which will be described later and the device 3 is formed on the surface of the p-clad layer 3p, and, similarly, an n-electrode is formed on the surface of the n-clad layer 3n.
In addition, the device 3 may not necessarily have the double hetero structure or be a light-emitting diode, and may be an electronic circuit device processed in a minute size. The shape of the device 3 may not necessarily be the roughly flat plate-like shape, and may be any of various shapes such as a hexagonal pyramidal shape; for efficient holding of the device 3 in close contact with the temporary adhesion layer 2, however, it is desirable that the surface, for contact with the temporary adhesion layer 2, of the device 3 is flat. Besides, while the devices 3 are shown to be arranged on the temporary adhesion layer 2 at a regular internal in the figure, the devices 3 may not necessarily be arranged at a regular interval.
The devices 3 are arranged on the temporary adhesion layer 2 in a matrix, i.e., the devices 3 are arranged in plurality in both a column direction and a row direction in a plane, so that a plurality of the devices 3 are arranged at a regular interval also in the direction orthogonal to the paper surface in the figure. Since the devices 3 are light-emitting diodes which function as display devices, the devices 3 arranged in a matrix can display images when driven by simple matrix driving.
Next, as shown in
Subsequently, as shown in
Since the arrangement of the devices 3 relative to the transfer substrate 4 is held by embedding the devices 3 in the pressure sensitive adhesive layer 5, it is possible to embed the devices 3 in the pressure sensitive adhesive layer 5 and, hence, to mount the devices 3 onto the transfer substrate 4, independently of the shape of the devices 3. In addition, since the plurality of the devices 3 arranged on the temporary adhesion layer 2 can be collectively embedded into the pressure sensitive adhesive layer 5 by bringing the temporary holding substrate 1 and the transfer substrate 4 closer to each other, the plurality of the devices 3 can be simultaneously mounted onto the transfer substrate 4 while maintaining the mutual arrangement conditions of the devices 3 on the temporary adhesion layer 2.
Next, as shown in
Since the devices 3 are stripped from the temporary adhesion layer 2 before hardening (curing) the pressure sensitive adhesive layer 5, the force required for separating the temporary holding substrate 1 and the transfer substrate 4 away from each other is reduced, and the possibility that the temporary holding substrate 1 or the transfer substrate 4 may be damaged at the time of stripping the devices 3 from the temporary adhesion layer 2 is lowered. Particularly, in the case of manufacturing a display apparatus having a large screen, it is necessary to enlarge the area of the transfer substrate 4, so that the lowering in the possibility of damaging of the transfer substrate 4 or the temporary holding substrate 1 promises a reduction in the manufacturing cost.
Subsequently, as shown in
Next, as shown in
In view of this, as shown in
Subsequently, as shown in
With the transfer of the devices 3 and the formation of the electric wirings 6 and the electric wirings 10 performed by the above-described method, an arrangement of the devices 3 is obtained in which the adhesive layer 8 is formed on the support substrate 7, the hardened pressure sensitive adhesive layer 5 is laminated on the adhesive layer 8, the electric wirings 6 formed on the adhesive layer 8 and the plurality of the devices 3 embedded in the pressure sensitive adhesive layer 5 are held between the adhesive layer 8 and the pressure sensitive adhesive layer 5, the contact vias 9 formed in the pressure sensitive adhesive layer 5 are filled with the metal, and the electric wirings 10 are formed on the pressure sensitive adhesive layer 5. The devices 3 arranged in a matrix on the support substrate 7 are light-emitting diodes, the electric wirings 6 are scan lines in stripes in connection with the p-clad layers 3p of the devices 3, and the electric wirings 10 are signal lines in stripes in connection with the n-clad layers 3n of the devices 3; therefore, with the arrangement of the devices shown in
In the device transfer method according to an embodiment of the present invention, one example of the method of arranging the devices 3 on the temporary adhesion layer 2 provided on the temporary holding substrate 1 so as to obtain the condition shown in
The devices 3 are configured as light-emitting diodes which are each formed from a material based on a nitride semiconductor such as gallium nitride and which are arranged in a matrix on a sapphire substrate. The device 3 is formed by a method in which an active layer and clad layers of the device are extended in planes parallel to the principal surface of the sapphire substrate on which to grow the active layer and the clad layers, and a gallium nitride crystal layer or the like is laminated by selective growth or the like.
The devices 3 are formed on the sapphire substrate in the state of being separated one by one; the devices 3 can be separated individually, for example, by RIE (Reactive Ion Etching) or the like. While the device 3 has a roughly flat plate-like shape in this example, there may be adopted a device which has an inclined crystal layer inclined against the principal surface of the sapphire substrate. Where the device 3 is, for example, a device composed of an active layer and clad layers having crystal surfaces parallel to planes inclined against the principal surface of the sapphire substrate, the devices can also be transferred in the form of chips obtained by covering the devices with a resin.
Subsequently, in the condition where the devices 3 are adhered to the temporary adhesion layer 2, the devices 3 are separated from the sapphire substrate. In separating the devices 3 from the sapphire substrate, irradiation with beams of laser such as excimer laser and YAG laser is conducted from the back side of the sapphire layer, to cause laser ablation at the interface between the devices 3 and the sapphire substrate. The laser ablation means the phenomenon in which a fixed material absorbing the irradiation beams is photochemically or thermally excited and the bonds in the atoms or molecules at the surface or in the inside thereof are broken; the laser ablation appears primarily as a phenomenon in which a part or the whole part of the fixed material undergoes a phase change such as melting, evaporation, and gasification. The laser ablation causes decomposition of the GaN-based material into metallic Ga and nitrogen, resulting in gas generation, at the interface between the devices 3 and the sapphire substrate. This enables a comparatively easy stripping of the devices 3. As the laser beams for irradiation, excimer laser is preferably used in view of its high output in the shorter wavelength region, particularly. The use of excimer laser enables an instantaneous process and swift stripping of the devices 3.
With the devices 3 stripped from the sapphire substrate serving as the growth substrate and arranged on the temporary holding substrate 1 by use of the above-mentioned laser ablation, even the devices 3 arranged extremely close to each other on the growth substrate can be arranged on the temporary holding substrate 1 at an enlarged interval, by selectively irradiating the devices 3 with laser beams and stripping the irradiated devices from the growth substrate.
With the display apparatus obtained by use of the device transfer method in which the devices 3 are embedded in the pressure sensitive adhesive layer 5, it is possible to carry out the arrangement of the devices 3 and the formation of the electric wirings 6 and the electric wirings 10. Where display is conducted through simple matrix driving by impressing a voltage on the devices 3 through the electric wirings 6 and the electric wirings 10, it is possible to display images in the same manner as in the case of an existing simple matrix driving type display apparatus.
Next, another embodiment of the present invention will be described below referring to the drawings. This embodiment is a device transfer method different from the above-described first embodiment described above in that the step of embedding the devices into the pressure sensitive adhesive layer is changed. The other steps are the same as in the first embodiment and, therefore, description thereof is omitted.
Devices 23 are arranged on a temporary adhesion layer 22 provided on a temporary holding substrate 21, a transfer substrate 24 provided thereon with a pressure sensitive adhesive layer 25 is disposed in parallel to the temporary holding substrate 21, and then the temporary holding substrate 21 and the transfer substrate 24 are brought closer to each other. In the first embodiment, the temporary holding substrate and the transfer substrate have been brought closer to each other until the temporary adhesion layer makes contact with the pressure sensitive adhesive layer, thereby embedding the devices into the pressure sensitive adhesive layer to such a degree that the surfaces of the devices and the pressure sensitive adhesive layers become flush with each other. In this embodiment, as shown in
After the devices 23 are partly embedded in the pressure sensitive adhesive layer 25, as shown in
Since the devices 23 are stripped from the temporary adhesion layer 22 in the condition where the temporary adhesion layer 22 and the pressure sensitive adhesive layer 25 do not make contact with each other, the force required for separating the temporary holding substrate 21 and the transfer substrate 24 away from each other is reduced, and the possibility that the temporary holding substrate 21 or the transfer substrate 24 may be damaged at the time of stripping the devices 23 from the temporary adhesion layer 22 is lowered. Particularly, in the case of manufacturing a display apparatus having a large screen, it is necessary to enlarge the area of the transfer substrate 24 and, therefore, the lowering in the possibility of damaging of the transfer substrate 24 or the temporary holding substrate 21 promises a reduction in the manufacturing cost.
Next, as shown in
Thereafter, in the same manner as in the first embodiment, in the condition where the devices 23 are held embedded in the pressure sensitive adhesive layer 25, an external cause for hardening (curing) the pressure sensitive adhesive layer 25, for example, a heating treatment or the like is applied to harden (cure) the pressure sensitive adhesive layer 25, electric wirings are formed on the pressure sensitive adhesive layer 25 and the devices 23, and a support substrate provided thereon with an adhesive layer is adhered to the pressure sensitive adhesive layer 25 so that the side, provided with the electric wirings, of the pressure sensitive adhesive layer 25 makes contact with the adhesive layer. After the support substrate is thus adhered, irradiation with laser beams is conducted to thereby strip the transfer substrate 24 from the pressure sensitive adhesive 25.
Subsequently, the hardened pressure sensitive adhesive layer 25 is provided with contact vias which are openings reaching the devices 23 by dry etching or the like, then the contact vias are filled with a metal and electric wirings are formed on the pressure sensitive adhesive layer 25. With the arrangements and electrically connected structures of the devices 23 and the electric wirings, it is possible to obtain a display apparatus for displaying images by simple matrix driving, in the same manner as in the first embodiment.
Next, a further embodiment of the present invention will be described below referring to the drawings. This embodiment is a device transfer method different from the above-described first embodiment in that the step of embedding devices into a pressure sensitive adhesive layer is repeated a number of times. The other steps are the same as in the first embodiment and, therefore, description thereof is omitted.
Thereafter, as shown in
After the plurality of kinds of devices are thus embedded in the pressure sensitive adhesive layer 35, in the condition where the devices 33R, 33G, 33B are held embedded in the pressure sensitive adhesive layer 35, an external cause for hardening (curing) the pressure sensitive adhesive layer 35, for example, a heating treatment or the like is applied to harden (cure) the pressure sensitive adhesive layer 35, electric wirings are formed on the pressure sensitive adhesive layer 35 and the devices 33, and a support substrate provided thereon with an adhesive layer is adhered to the pressure sensitive adhesive layer 35 so that the surface, provided thereon with the electric wirings, of the pressure sensitive adhesive layer 35 makes contact with the adhesive layer, in the same manner as in the first embodiment. After the support substrate is thus adhered, irradiation with laser beams is conducted so as thereby to strip the transfer substrate 34 from the pressure sensitive adhesive layer 35.
Next, the hardened pressure sensitive adhesive layer 35 is provided with contact vias which are openings reaching the devices 33 by dry etching or the like, then the contact vias are filled with a metal and electric wirings are formed on the pressure sensitive adhesive layer 35. With the arrangements and electrically connected structures of the devices 33R, 33G, 33R and the electric wirings, it is possible to obtain a display apparatus in which each pixel is composed of the devices for emitting light in red, green and blue colors.
The devices having different characteristics, generally, are difficult to form on the same growth substrate; therefore, it is difficult to arrange the devices having different characteristics on the temporary holding substrate and thereafter to embed the devices 33 into the pressure sensitive adhesive layer 35. The method in which the embedding of the devices 33 arranged on the temporary holding substrate into the pressure sensitive adhesive layer 35 is repeatedly carried out before the hardening of the pressure sensitive adhesive layer 35 facilitates the arrangement of the devices 33 having different characteristics into the same plane on the transfer substrate 34. In addition, the method in which the devices 33G differing in characteristics from the devices 33R are embedded into the pressure sensitive adhesive layer 35 in the condition where the devices 33R are embedded in the pressure sensitive adhesive layer 35 ensures that, in adjusting the positional relationship between the devices 33G arranged on the temporary holding substrate and the devices 33R embedded in the pressure sensitive adhesive layer 35, the arrangements can be prevented from being disordered due to interference between the devices 33G and the devices 33R.
Not only the light-emitting diodes but also light-receiving devices, driving circuit devices and the like can be used as the devices 33; therefore, arrangement of display devices and light-receiving devices in a mixed state in the same plane and arrangement of display devices and driving circuit devices in a mixed state in the same plane can be easily carried out.
A method in which the transfer of devices and the formation of electric wirings are conducted in the condition where a display device and a driving circuit device are mixedly present in each pixel makes it possible to obtain a display device of the active matrix driving type in which electric signals are sent to the driving circuit device and light emission on an pixel basis is controlled by the driving circuit devices.
Next, yet another embodiment of the present invention will be described below referring to the drawings. This embodiment is a device transfer method different from the above-described first embodiment in that the step of embedding of devices into a pressure sensitive adhesive layer is repeated a number of times. The other steps are the same as in the first embodiment and, therefore, description thereof is omitted.
Subsequently, as shown in
Next, the hardened pressure sensitive adhesive layer 45 is provided with contact vias which are openings reaching the devices 43 by dry etching or the like, then the contact vias are filled with a metal and electric wirings are formed on the pressure sensitive adhesive layer 45. With the arrangements and electrically connected structures of the devices 43 and the electric wirings, it is possible to obtain a display apparatus capable of displaying images by simple matrix driving.
The method in which devices 43 are further additionally embedded and held in an area on the transfer substrate 44 where the devices 43 have not yet been embedded, in the condition where the devices 43 are embedded in the pressure sensitive adhesive layer 45, makes it possible, even in the case where the area permitting the arrangement of the devices 43 on the temporary holding substrate is limited, to enlarge the area of the transfer substrate 44 and, hence, to arrange the devices on a substrate having a large area. This provides a device transfer method useful in the case of manufacturing a display apparatus having a large screen, particularly.
Since devices are stripped from a temporary adhesion layer before a pressure sensitive adhesive layer is hardened (cured) according to an embodiment, the force required for separating a temporary holding substrate and a transfer substrate away from each other is small, and the possibility that the temporary holding substrate or the transfer substrate may be damaged at the time of stripping the devices from the temporary adhesion layer is lowered. Particularly, in the case of manufacturing a display apparatus having a large screen, it is necessary to enlarge the area of the transfer substrate and, therefore, the lowering of the possibility of damaging the transfer substrate or the temporary holding substrate promises a reduction in the manufacturing cost.
With the devices differing in characteristics embedded into the pressure sensitive adhesive layer before the hardening (curing) of the pressure sensitive adhesive layer, it is possible to arrange and hold on the transfer substrate those devices which cannot be formed on the same growth substrate, and it is also possible to obtain a display apparatus for multicolor display by arranging light-emitting diodes for emitting light in different colors. In addition, it is possible to use not only light-emitting diodes but also light-emitting diodes and driving circuits as the devices.
By carrying out the transfer of devices and the formation of electric wirings in the condition where a display device and a driving circuit device are mixedly present in each pixel, it is also possible to obtain a display device of the active matrix driving type in which electric signals are sent to the driving circuit devices and light emission on a pixel basis is controlled by the driving circuit devices.
By further additionally embedding and holding devices in an area on the transfer substrate where the devices have not been embedded in the condition where the devices are embedded in the pressure sensitive adhesive layer, it is possible, even in the case where the area permitting the arrangement of the devices on the temporary holding substrate is limited, to enlarge the area of the transfer substrate and, hence, to arrange the devices on a substrate having a large area. This provides a device transfer method useful in the case of manufacturing a display apparatus having a large screen, particularly.
It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present subject matter and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-059540 | Mar 2003 | JP | national |
The present application is a continuation of U.S. patent application Ser. No. 10/511,699 filed on May 27, 2005 which claims priority to Japanese Patent Document No. P2003-059540 filed on Mar. 6, 2003, the disclosure of which is herein incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10511699 | May 2005 | US |
| Child | 11467007 | US |
