High surface quality GaN wafer and method of fabricating same
AssigneeAdvanced Technology Materials, Inc.
InventorsXueping Xu, Robert P. Vaudo
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Abstract
A high quality wafer comprising AlxGayInzN, wherein 0<y≦1 and x+y+z=1, characterized by a root mean square surface roughness of less than 1 nm in a 10×10 μm2 area at its Ga-side. Such wafer is chemically mechanically polished (CMP) at its Ga-side, using a CMP slurry comprising abrasive particles, such as silica or alumina, and an acid or a base. The process of fabricating such high quality AlxGayInzN wafer may include steps of lapping, mechanical polishing, and reducing internal stress of said wafer by thermal annealing or chemical etching for further enhancement of its surface quality. The CMP process is usefully employed to highlight crystal defects on the Ga-side of the AlxGayInzN wafer.
Claims79
A wafer comprising AlxGayInzN, wherein 0<y≦1 and x+y+z=1, characterized by a root mean square (RMS) surface roughness of less than 1 nm in a 10×10 μm2 area at the Ga-side of the wafer.
An epitaxial AlxGayInzN crystal structure, comprising an epitaxial Alx′Gay′Inz′N thin film grown on a wafer comprising AlxGayInzN wherein 0<y′≦1, x′+y′+z′=1, 0<y≦1, and x+y+z=1, said wafer being characterized by a root mean square (RMS) surface roughness of less than 1 nm in a 10×10 μm area at the Ga-side of the wafer.
An epitaxial Alx′Gay′Inz′N crystal boule grown on a wafer comprising AlxGayInzN, wherein 0<y≦1 and x+y+z=1, said wafer being characterized by a root mean square (RMS) surface roughness of at least less than 1 nm in a 10×10 μm2 area at a Ga-side of the wafer.
An optoelectronic device comprising at least one epitaxial Alx′Gay′Inz′N crystal structure grown on a wafer comprising AlxGayInzN wherein 0<y≦1 and x+y+z=1, said wafer being characterized by a root mean square (RMS) surface roughness of at least less than 1 nm in a 10×10 μm2 area at a Ga-side of the wafer.
A microelectronic device comprising at least one epitaxial Alx′Gay′Inz′N crystal structure grown on a wafer comprising AlxGayInzN wherein 0<y≦1 and x+y+z=1, said wafer being characterized by a root mean square (RMS) surface roughness of at least less than 1 nm in a 10×10 μm2 area at a Ga-side of the wafer.
A method of chemically mechanically polishing (CMP) an AlxGayInzN wafer at a Ga-side thereof, wherein 0<y≦1 and x+y+z=1, using a CMP slurry comprising:
- abrasive amorphous silica particles having particle sizes of less than 200 nm;
- at least one acid;
- and
- optionally, at least one oxidation agent;
- wherein the pH value of the CMP slurry is in a range of from about 0.5 to about 4.
The method claim of 26, wherein the CMP slurry is filtered to remove particles larger than 100 nm in diameter before delivering to the polishing pad.
A method of chemically mechanically polishing (CMP) an AlxGayInzN wafer at a Ga-side thereof, wherein 0<y≦1 and x+y+z=1, using a CMP slurry comprising:
- Abrasive colloidal alumina particles having particle sizes of less than 200 nm;
- at least one acid;
- and
- optionally, at least one oxidation agent;
- wherein the pH value of the CMP slurry is in a range of from about 3 to about 5.
A method of chemically mechanically polishing (CMP) an AlxGayInzN wafer at a Ga-side thereof, wherein 0<y≦1 and x+y+z=1, using a CMP slurry comprising:
- amorphous silica particles having particle sizes of less than 200 nm;
- at least one base;
- and
- optionally, at least one oxidization agent,
- wherein the pH value of the CMP slurry is in a range of from about 8 to about 13.5.
The method claim of 42, wherein the CMP slurry is filtered to remove particles larger than 100 nm in diameter before delivering to the polishing pad.
A method of determining crystal defect density in an AlxGayInzN wafer at a Ga-side thereof, wherein 0<y≦1 and x+y+z=1, comprising the steps of:
- providing an AlxGayInzN wafer;
- chemically mechanically polishing said wafer at a Ga-side thereof, using a CMP slurry comprising abrasive amorphous silica articles having particle sizes of less than 200 nm, at least one acid, and optionally at least one oxidization agent, wherein the pH value of said CMP slurry is in a range of from about 0.5 to about 4;
- cleaning and drying the polished AlxGayInzN wafer;
- and
- scanning the wafer with an atomic force microscope or a scanning electron microscope to determine defect density in said wafer.
A method of fabricating wafers comprising AlxGayInzN, wherein 0<y≦1 and x+y+z=1, comprising the steps of:
- providing an AlxGayInzN wafer blank having thickness in the range from about 100 μm to about 1000 μm;
- optionally, reducing the internal stress of the AlxGayInzN wafer blank;
- optionally, lapping the AlxGayInzN wafer blank at the N-side thereof, using a lapping slurry comprising abrasives having an average particle size in a range of from about 5 μm to about 15 μm;
- optionally, mechanically polishing the AlxGayInzN wafer blank at its N-side, using a mechanical polishing slurry comprises abrasives having average particle size in a range of from about 0.1 μm to about 6 μm;
- optionally, lapping the AlxGayInzN wafer blank at a Ga-side thereof, using a lapping slurry comprising abrasives having an average particle size in a range of from about 5 μm to about 15 μm;
- mechanically polishing the AlxGayInzN wafer blank at its Ga-side, using a mechanical polishing slurry comprises abrasives having average particle size in a range of from about 0.1 μm to about 6 μm;
- chemically mechanically polishing the AlxGayInzN wafer at its Ga-side, using a CMP slurry comprising at least one chemical reactant and abrasive particles having average particle size of less than 200 nm;
- and
- optionally, etching the AlxGayInzN wafer in a mild etching condition to further reduce internal stresses of the AlxGayInzN wafer, to improve surface quality, and to produce a mat finish at the N-side,
- wherein the AlxGayInzN wafer so fabricated has a surface roughness characterized by a root mean square (RMS) surface roughness of less than 1 nm in a 10×10 μm2 area at its Ga-side.
The method claim of 58, where the AlxGayInzN boule is sliced so that the wafer blank surface is perpendicular to the c-axis.
The method claim of 58, where the AlxGayInzN boule is sliced so that the wafer blank surface is intentionally not perpendicular to the c-axis.
The method claim of 56, wherein the mild etching condition is selected from group consists of etching in aqueous acid solution and etching in aqueous base solution at a temperature below 100° C.
The method claim of 78, wherein the acid is selected from group consists of aqueous hydrofluoric acid, nitric acid, sulfuric acid, phosphoric acid, and combinations thereof.
The method claim of 78, wherein the base is selected from group consists of aqueous LiOH, NaOH, KOH, RbOH, CsOH, and combinations thereof.
Dependencies are inferred from the claim text.