Method of manufacturing nitride substrate for semiconductors
In an independent GaN film manufactured by creating a GaN layer on a base heterosubstrate using vapor-phase deposition and then removing the base substrate, owing to layer-base discrepancy in thermal expansion coefficient and lattice constant, warp will be a large ±40 μm to ±100 μm. Since with that warp device fabrication by photolithography is challenging, reducing the warp to +30 μm to −20 μm is the goal. The surface deflected concavely is ground to impart to it a damaged layer that has a stretching effect, making the surface become convex. The damaged layer on the surface having become convex is removed by etching, which curtails the warp. Alternatively, the convex surface on the side opposite the surface having become convex is ground to generate a damaged layer. With the concave surface having become convex due to the damaged layer, suitably etching off the damaged layer curtails the warp.
1. For a gallium nitride semiconductor substrate having a 0001 gallium face terminated with gallium atoms, a method of dry-etching the gallium face for reducing wrapage of the substrate, comprising:
(a) deploying the gallium nitride semiconductor substrate in a reactive-ion etching chamber to dispose the gallium face for being dry etched in the chamber;
(b) introducing a chlorine gas into the chamber; and
(c) applying an antenna power and a bias power to the substrate, the antenna power and the bias power operative to form a chlorine plasma and thereby dry etch the gallium face.
2. The gallium nitride substrate dry-etching method of claim 1 , wherein the chlorine gas is introduced into the chamber at a flow rate in the range from 5 to 100 sccm, and to a pressure in the range from 0.1 to 10 Pa.
3. The gallium nitride substrate dry-etching method of claim 1 , wherein:
the antenna power is in the range from 100 to 500 W; and
the bias power is in the range from 5 to 20 W.
4. The gallium nitride substrate dry-etching method of claim 1 , achieving an etching depth of at least 5 μm.
5. For a gallium nitride semiconductor substrate having a 0001 gallium face terminated with gallium atoms, a method of dry-etching the gallium face for reducing wrapage of the substrate, comprising:
(a) mechanically abrading the gallium face of the gallium nitride semiconductor substrate to produce a damage layer;
(b) deploying the gallium nitride semiconductor substrate in a reactive-ion etching chamber to dispose damage layer for being dry etched in the chamber;
(c) introducing a chlorine gas into the chamber; and
(d) applying an antenna power and a bias power to the substrate, the antenna power and the bias power operative to form a chlorine plasma and thereby dry etch the damage layer.
6. The gallium nitride substrate dry-etching method of claim 5 , wherein the chlorine gas is introduced into the chamber at a flow rate in the range from 5 to 100 sccm, and to a pressure in the range from 0.1 to 10 Pa.
7. The gallium nitride substrate dry-etching method of claim 5 , wherein:
the antenna power is in the range from 100 to 500 W; and
the bias power is in the range from 5 to 20 W.
8. The gallium nitride substrate dry-etching method of claim 5 , achieving an etching depth of at least 5 μm.