The present invention relates in general to flexible electronics and, more particularly, to a flexible display or electronic device using ion implantation to bond a flexible substrate to single crystal silicon substrate.
Flat panel displays are used in many applications to visually present data and images. Flat panel displays have a thin profile and provide high resolution for uses such as computer monitors and television screens. The liquid crystal display (LCD) is one type of flat panel display. The LCD uses a silicon on glass substrate. The active semiconductor-based pixels are formed on the silicon substrate. The glass substrate is conducive to high temperatures which are commonly used in many semiconductor manufacturing processes.
While LCDs have been around for some time and are generally preferred over CRT-type displays, such glass-based flat panel displays have disadvantages as well. The glass component is known to be heavy and brittle. LCDs are known to crack and are susceptible to damage. Moreover, glass displays are generally not useable in applications requiring flexibility for the display.
As new applications arise, the need for flexible flat panel displays continues to grow. Prior art flexible flat panel displays use thin film transistors (TFT) formed on amorphous silicon layers or polycrystalline silicon layers. Unfortunately, amorphous silicon and polycrystalline silicon TFTs exhibit low carrier mobility and high off-state current leakage, which reduces performance and increases power consumption. The resolution decreases and flickering may be observed in flat panel displays using TFTs formed on low carrier mobility polycrystalline silicon.
A similar problem is found in electronic devices using polycrystalline silicon. The-lower carrier mobility associated with polycrystalline type substrates reduces the performance of the electronic device.
On the other hand, single crystalline silicon is known to have greater carrier mobility. The higher carrier mobility in the presence of an electrostatic field, as found in single crystalline silicon, provides better performance for flat panel displays and electronic devices. However, single crystalline silicon typically involves higher temperature semiconductor processes. These high temperatures are incompatible with polymer and other flexible amorphous substrates.
A need exists for a flat panel display or electronic device using single crystalline silicon on a flexible substrate.
In one embodiment, the present invention is a flat panel display, comprising a flexible substrate. A single crystalline silicon substrate is disposed adjacent to the flexible substrate. The flexible substrate is bonded to the single crystalline substrate using an ion implantation process. A plurality of semiconductor devices are formed on the single crystalline silicon substrate.
In another embodiment, the present invention is an electronic device comprising a flexible substrate. A single, crystalline silicon substrate is disposed adjacent to the flexible substrate. The flexible substrate is bonded to the single crystalline substrate using an ion implantation process. A plurality of active semiconductor devices are formed on the single crystalline silicon substrate.
In another embodiment, the present invention is an electronic apparatus comprising a flexible substrate. A single crystalline silicon substrate is disposed adjacent to the flexible substrate. The flexible substrate is bonded to the single-crystalline substrate using an ion implantation process. A plurality of semiconductor devices are formed on the single crystalline silicon substrate.
In another embodiment, the present invention is a method of forming an electronic apparatus comprising providing a flexible substrate, providing a single crystalline silicon substrate disposed adjacent to the flexible substrate, wherein the flexible substrate is bonded to the single crystalline substrate using an ion implantation process, and providing a plurality of semiconductor devices formed on the single crystalline silicon substrate.
The present invention is described in one or more embodiments in the following description with reference to the Figures, in which like numerals represent the same or similar elements. While the invention is described in terms of the best mode for achieving the invention's objectives, it will be appreciated by those skilled in the art that it is intended to cover alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims and their equivalents as supported by the following disclosure and drawings.
A flexible flat panel display 10, such as shown in
In another embodiment, element 10 may be a flexible electronic device. The flexible electronic device may be an integrated circuit, or a flexible print circuit board with integrated circuits mounted thereon. The flexible electronic device can be used in diagnostic equipment, small and odd-shaped enclosures, and any application requiring a flexible form factor. The flexible electronic device also has uses in military applications similar to flat panel display 10.
In the fabrication of flat panel displays and electronic devices, it is desirable to use a single crystalline silicon substrate because of its higher carrier mobility properties in the presence of an electrostatic field. A flat panel display or electronic device made with single crystalline silicon substrate provides improved performance and response time by way of higher carrier mobility and uniform threshold voltages.
In
To be useful in flexible displays or electronic devices, single crystalline silicon substrate 20 must be strongly bonded to flexible substrate 22. An ion implantation process is used to form the strong adhesive interface or bond between silicon substrate 20 and flexible substrate 22. The ion implantation induces a mixing process at the interface to change the composition and chemical bonding state between the substrates. The mixing process makes for a strong adhesion between silicon substrate 20 and flexible substrate 22.
Turning to
In one embodiment, the ion implantation penetrates deep into silicon substrate 20 to induce an-ion cut. The ion cut involves formation of H2 gas bubbles in high internal pressure which causes a cleavage within the silicon. The ion cut facilitates separation of a thin slice of the silicon substrate.
The penetration depth of the ion beam is a function of beam particle energy. By adjusting the ion beam energy level, the ion implantation process can induce an energy loss at the interface between silicon substrate 20 and flexible substrate 22. The energy loss cause ions to be deposited at the substrate interface by ion mixing to induce adhesion between the materials. The single crystalline silicon substrate 20 bonds to the flexible substrate 22 in response to the ion beam having the appropriate energy level to induce the ion mixing at the interface between silicon substrate 20 and flexible substrate 22.
In one embodiment, the ion cut process deposits ions deeper in the silicon substrate, while the ion mixing process at the silicon and flexible substrate interface is performed in different ion implantation steps. One ion beam energy level performs the ion cut, and a second ion beam energy level causes the ion mixing at the substrate interface. Alternatively, the ion implantation deeper in the silicon substrate for the ion cut operation and the ion mixing at the silicon and flexible substrate interface is performed in the same ion implantation step.
While one or more embodiments of the present invention have been illustrated in detail, the skilled artisan will appreciate that modifications and adaptations to those embodiments may be made without departing from the scope of the present invention as set forth in the following claims.
The present non-provisional patent application claims priority to provisional application Ser. No. 60/523,022 entitled “Enhanced Adhesion of Organic Layer/Film/Substrate Surfaces to Inorganic Layer/Film/Substrate Surfaces”, filed on Nov. 17, 2003. The present non-provisional patent application further claims priority to provisional application Ser. No. 60/524,009 entitled “Adhesion between Silicon and Polymer by Implanting Hydrogen Ions through Polymer into Silicon”, filed on Nov. 21, 2003. The present non-provisional patent application further claims priority to provisional application Ser. No. 60/524,010 entitled “Adhesion between Silicon and Polymer by Implanting Hydrogen Ions through Polymer into Silicon”, filed on Nov. 21, 2003.
The U.S. Government has a paid-up license in the present invention and the right in limited circumstances to require the patent owner to license others on fair and reasonable terms as provided by the terms of Department of Defense Contract No. DMR-0308127.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/US04/38702 | 11/17/2004 | WO | 5/9/2006 |
Number | Date | Country | |
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60523022 | Nov 2003 | US | |
60524009 | Nov 2003 | US | |
60524010 | Nov 2003 | US |