Smooth diamond surfaces and CMP method for forming
A method of chemical mechanical polishing (CMP) a diamond containing surface includes providing a slurry including a plurality of particles, at least one oxidizer, and at least one acid, wherein the slurry has a pH≦3 or pH greater than 11. At least an outer surface of the plurality of particles is softer than the diamond surface or the particles are diamond particles averaging less than (<)2 μm in size. The diamond surface is pressed with respect to a polishing pad providing a Shore D Hardness less than 99 having the slurry in between while rotating the polishing pad relative to the diamond surface to form a smooth diamond surface having a root mean square (rms) surface roughness less than 15 nm.
1. A diamond article, comprising:
a substrate, and
a diamond layer on said substrate having a smooth polished diamond surface, wherein said diamond layer has a thickness from 10 nm to 200 μm:
(i) a root mean square (rms) surface roughness less than (<) 15 nm for an average grain size greater than (>) 0.5 μm, an rms surface roughness less than (<) 10 nm for an average grain size between 50 nm and 0.5 μm, and an rms surface roughness less than (<) 5 nm for an average grain size less than (<) 50 nm, and
(ii) a polishing damage index (PDI) less than (<) 10 9 /cm 2 wherein said PDI is defined by:
PDI= A−B (in units of #/cm 2 ),
wherein A=an average projected surface density of polishing induced defects including dislocations, scratches, pits, and stacking faults in the top “y” microns of said thickness down from said polished diamond surface, and B is the average projected surface defect density at a distance of said “y” microns from said polished diamond surface, and
wherein said “y” is 2 microns when said thickness is 3 microns or more, and is one half said thickness when said thickness is less than 3 microns.
2. The article of claim 1 , wherein said substrate comprises a single crystal diamond substrate that includes said diamond layer.
3. The article of claim 1 , wherein said substrate comprises silicon, diamond, GaN, AlGaN, SiC or SiN.
4. The article of claim 1 , further comprising a capping semiconductor layer or a capping diamond layer on said smooth polished diamond surface, wherein at least one electronic device is formed on said capping semiconductor layer or said capping diamond layer.
5. The article of claim 4 , wherein said capping semiconductor layer comprises GaN, GaN, AlGaN or SiC.
6. The article of claim 1 , wherein said PDI is less than (<) 10 6 /cm 2 .
7. The article of claim 1 , wherein said average grain size is greater than (>) 100 nm, said PDI is less than (<) 10 6 /cm 2 , and said rms surface roughness is less than (<) 1 nm.
8. The article of claim 1 , wherein said thickness of said diamond layer is between 5 μm and 200 μm.