PVD buffer layers for LED fabrication
Fabrication of gallium nitride-based light devices with physical vapor deposition (PVD)-formed aluminum nitride buffer layers is described. Process conditions for a PVD AlN buffer layer are also described. Substrate pretreatments for a PVD aluminum nitride buffer layer are also described. In an example, a method of fabricating a buffer layer above a substrate involves pre-treating a surface of a substrate. The method also involves, subsequently, reactive sputtering an aluminum nitride (AlN) layer on the surface of the substrate from an aluminum-containing target housed in a physical vapor deposition (PVD) chamber with a nitrogen-based gas or plasma.
1. A method of fabricating a buffer layer above a substrate, the method comprising:
forming a pre-seeding layer on a surface of a substrate; and
reactive sputtering an aluminum nitride (AlN) layer on the pre-seeding layer from an aluminum-containing target housed in a physical vapor deposition (PVD) chamber with a nitrogen-based gas or plasma, wherein the aluminum-containing target is one selected from the group consisting of an Al-containing metal target, an Al-containing alloy target, or an Al-containing compound target, and wherein the aluminum-containing target is doped with atoms selected from the group consisting of group II atoms and group VI atoms.
2. The method of claim 1 , wherein forming the pre-seeding layer comprises forming a layer selected from the group consisting of Al, AlO x , SiN x , ZnO, ZnS, ZrN and TiN.
3. The method of claim 1 , wherein forming the pre-seeding layer comprises nitrogen-free sputtering of a poisoned Al-containing target.
4. The method of claim 1 , wherein forming the pre-seeding layer provides protection for the surface of the substrate during the reactive sputtering of the AlN layer.
5. The method of claim 1 , the method further comprising:
prior to reactive sputtering the AlN layer, pre-treating the substrate with a technique selected from the group consisting of thermal pre-treatment, chemical pre-treatment and physical pre-treatment.
6. The method of claim 1 , wherein the substrate is one selected from the group consisting of a sapphire substrate, a SiC substrate, a Si substrate, a diamond substrate, a LiAlO 2 substrate, a ZnO substrate, a W substrate, a Cu substrate, a GaN substrate, an AlGaN substrate, an AlN substrate and a soda lime/high silica glass substrate.
7. The method of claim 1 , wherein the nitrogen-based gas or plasma comprises a gas, or is based on a gas, selected from the group consisting of N 2 , NH 3 , NO 2 and NO.