Patent Application
20080054294
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.
Firstly, refer to
It should be noted that in one embodiment of the present invention, when the material of the substrate 300 is selected from a group consisting of silicon, silicon carbide, aluminum oxide, sapphire, zinc oxide, magnesium oxide and a combination thereof, the epitaxy layer 302 formed on the substrate 300 is, for example, a nitride epitaxy material layer. The foresaid nitride epitaxy material layer is selected from one group consisting of gallium nitride (GaN), indium nitride (InN), aluminum nitride (AlN), indium gallium nitride, aluminum gallium nitride, indium aluminum nitride, aluminum indium gallium nitride and a combination thereof. When the materials of substrate 300 and epitaxy layer 302 are as mentioned above, the oxidation process 306 is performed. In the oxidation process 306, the substrate 300 comprising epitaxy layer 302 and patterned mask layer 304 thereon is, under the room temperature of 0˜80° C., immersed in an electrolytic solution to proceed the oxidation so as to completely oxidize the exposed epitaxy layer; and in this way, the blocking structures 308 are formed. In this process, the pH value of the electrolytic solution is between 3 and 10. The way to prepare this electrolytic solution is to dissolve nitrilotriacetic acid in the potassium hydroxide solution. Besides, at the time the oxidation process 308 is performed, the process of high-energy light illuminating is proceeded. Namely, using the high-energy light, e.g. the ultraviolet light, accelerates the oxidation in the electrolytic solution. The wavelength of the foresaid high-energy light is shorter than that of the light which can penetrate the epitaxy layer 302.
In another embodiment, when the material of the substrate 300 is selected from a group consisting of gallium arsenide, gallium phosphide, gallium arsenide phosphide, gallium arsenide aluminum, other arsenide and phosphide and a combination thereof, the epitaxy layer 302 is, for example, an arsenide epitaxy material containing aluminum. The foresaid arsenide epitaxy material containing aluminum is, for example, an arsenide (AlXGa(1-X)As) epitaxy material containing aluminum and gallium. Wherein, the X is larger than 0.8. That is, in the arsenide epitaxy material containing aluminum and galliumthe, the ratio between the aluminum atoms and the total number of aluminum atoms and the gallium atoms is larger than 0.8. When the materials of substrate 300 and epitaxy layer 302 are as mentioned above, the oxidation process 306 is performed. In the oxidation process 306, the substrate 300 comprising epitaxy layer 302 and patterned mask layer 304 thereon is, under the high temperature of 200˜600° C., placed in the condition of water vapor to proceed a wet oxidation step.
In the foresaid embodiment, the oxidation process 306 is performed to completely oxidize the exposed epitaxy layer so as to form the blocking structures 308. The material of the blocking structures 308 is selected from a group consisting of aluminum oxide, gallium oxide and a combination thereof.
Referring to
In the performance of the epitaxial process, due to the oxide porous characteristic of the blocking structures 308, the nitride semiconductor layer 310, such as gallium nitride, indium nitride, aluminum nitride, indium gallium nitride, aluminum gallium nitride, indium aluminum nitride, and aluminum indium gallium nitride semiconductor layer, does not form epitaxy on the blocking structures 308, but forms epitaxy on the surface of epitaxy layer 302, which fills the space between the blocking structures 308. The nitride semiconductor layer 310 grows in a lateral direction so as to block parts of the threading dislocations in the nitride semiconductor layer. Therefore, the threading dislocation density of the grown nitride semiconductor layer is reduced.
Firstly, refer to
It sould be noted that in this embodiment, the blocking structures 408 are disposed in the epitaxy layer 402. Referring to the embodiment of 3A to 3C, the blocking structures 308 are disposed on the substrate 300, and at the same time, the epitaxy layer 302 is disposed on the substrate 300 and fills the space between blocking structures 308. Different from the blocking structures 308 illustrated in the embodiment of 3A to 3C, the blocking structures 408 in this present embodiment are disposed in the epitaxy layer 402, and the bottom of the blocking structure 408 is not directly contacted with the substrate 400.
Moreover, since the material of substrate 400 and epitaxy layer 402 in this embodiment is the same with the material of substrate 300 and epitaxy layer 302 in the previous embodiment, the detailed description of material will not be explained here. Similarly, the method to form the blocking structure 408 in the epitaxy layer 402 is the same with the method to form the blocking structure 308 in the previous embodiment; the detailed description is omitted here. Further, since the material of blocking structure 408, namely the oxide material, is the same with the material of blocking structure 308, no detailed descriptions are required here.
Then, refer to
Besides, the present invention uses the technique of oxidation process to directly oxidize the epitaxy layer on the substrate so as to form the blocking structure. Compared to the prior art of applied etching process to form blocking structure, this present invention can reduce the manufacturing cost.
Although the present invention has been disclosed above by the preferred embodiments, they are not intended to limit the present invention. Anybody skilled in the art can make some modifications and alteration without departing from the spirit and scope of the present invention. Therefore, the protecting range of the present invention falls in the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 95132698 | Sep 2006 | TW | national |
