Multilayer substrate having gallium nitride layer and method for forming the same
The present invention provides a method for forming a multilayer substrate having a gallium nitride layer, wherein a mesh layer having a plurality of openings is formed on a substrate, and a buffer layer, three aluminum gallium nitride layers with different aluminum concentrations and a gallium nitride layer are formed in sequence on the substrate in the openings. The three aluminum gallium nitride layers with different aluminum concentrations are capable of releasing stress, decreasing cracks on the surface of the gallium nitride layer and controlling interior defects, such that the present invention provides a gallium nitride layer with larger area, greater thickness, no cracks and high quality for facilitating the formation of high performance electronic components in comparison with the prior art. The present invention further provides a multilayer substrate having a gallium nitride layer.
1. A method for forming a multilayer substrate, comprising the steps of:
providing a substrate;
forming a mesh layer having a plurality of openings on the substrate;
forming a buffer layer essentially consisting of a plurality of nitride layers on the substrate in the openings;
forming in sequence a lower aluminum gallium nitride layer, an intermediate aluminum gallium nitride layer and an upper aluminum gallium nitride layer with different aluminum concentrations on the buffer layer, wherein an aluminum concentration of the lower aluminum gallium nitride layer is higher than an aluminum concentration of the intermediate aluminum gallium nitride layer, the aluminum concentration of the intermediate aluminum gallium nitride layer is higher than an aluminum concentration of the upper aluminum gallium nitride layer, and while forming the intermediate aluminum gallium nitride layer, aluminum proportion is decreased along with an increase of a thickness of the intermediate aluminum gallium nitride layer; and
forming a gallium nitride layer on the upper aluminum gallium nitride layer.
2. The method of claim 1 , wherein the substrate is made of silicon, sapphire, gallium nitride, zinc oxide or silicon carbide, and the mesh layer is made of silicon nitride.
3. The method of claim 2 , wherein the step of forming the mesh layer includes the steps of:
forming a silicon nitride layer on the substrate;
forming a mesh resist layer on the silicon nitride layer;
removing a portion of the silicon nitride layer without being covered by the mesh resist layer to form the mesh layer; and
removing the mesh resist layer.
4. The method of claim 1 , further comprising the step of forming a top aluminum gallium nitride layer on the gallium nitride layer.
5. The method of claim 1 , wherein the buffer layer is a high-temperature nitride layer/low-temperature nitride layer/high-temperature nitride layer, the high-temperature nitride layer is formed at 1000-1200° C., and the low-temperature nitride layer is formed at 700-900° C.
6. The method of claim 1 , wherein the nitride layers are selected from the group consisting of an aluminum nitride layer, a gallium nitride layer and an aluminum gallium nitride layer.