Plasma etching method
The present invention relates to a plasma etching method with which a wide-gap semiconductor substrate can be etched with high accuracy. An inert gas is supplied into a processing chamber and plasma is generated from the inert gas, a bias potential is applied to a platen on which a wide-gap semiconductor substrate is placed, thereby making ions generated by the generation of plasma from the inert gas incident on the semiconductor substrate on the platen to thereby heat the semiconductor substrate. After the temperature of the semiconductor substrate reaches an etching temperature between 200° C. and 400° C., an etching gas is supplied into the processing chamber and plasma is generated from the etching gas and a bias potential is applied to the platen, thereby etching the semiconductor substrate while maintaining the temperature of the semiconductor substrate at the etching temperature.
1. A plasma etching method for, by means of an etching apparatus having a processing chamber with a closed space, a platen on which a wide-gap silicon carbide semiconductor substrate is placed, an exhaust device for reducing the pressure in the processing chamber, a gas supply device for supplying a gas into the processing chamber, a plasma generating device having an annular coil and generating plasma from the gas supplied into the processing chamber by supplying RF power to the coil, and an RF power supply unit for supplying RF power to the platen, plasma etching the wide-gap silicon carbide semiconductor substrate on the platen, the method comprising,
after the wide-gap silicon carbide semiconductor substrate is placed on the platen, an etching gas is supplied by the gas supply device into the processing chamber the pressure in which has been reduced by the exhaust device and plasma is generated from the supplied etching gas by the plasma generating device, and a bias potential is applied to the platen by the RF power supply unit, thereby etching the wide-gap silicon carbide semiconductor substrate, and
the wide-gap silicon carbide semiconductor substrate is etched in a state of having been heated to a temperature between 200° C. and 400° C.
2. The plasma etching method according to claim 1 , in which after the wide-gap silicon carbide semiconductor substrate is heated in advance to a temperature between 200° C. and 400° C., the wide-gap silicon carbide semiconductor substrate is etched while maintaining the temperature.
3. The plasma etching method according to claim 2 , in which
when the wide gap, silicon carbide semiconductor substrate is heated in advance,
an inert gas is supplied into the processing chamber by the gas supply device and plasma is generated from the supplied inert gas by the plasma generating device, and
a bias potential is applied to the platen by the RF power supply unit,
thereby making ions which are generated by the generation of plasma from the inert gas incident on the wide-gap, silicon carbide semiconductor substrate to thereby heat the wide-gap, silicon carbide semiconductor substrate.
4. The plasma etching method according to claim 3 , in which the inert gas comprises He gas.
5. The plasma etching method according to claim 2 , in which the wide-gap, silicon carbide semiconductor substrate is heated in advance by a heater embedded in the platen.
6. The plasma etching method according to claim 2 , in which, when the wide-gap, silicon carbide semiconductor substrate is heated in advance:
an inert gas is supplied into the processing chamber by the gas supply device and plasma is generated from the supplied inert gas by the plasma generating device, and a bias potential is applied to the platen by the RF power supply unit, thereby making ions which are generated by the generation of plasma from the inert gas incident on the wide-gap, silicon carbide semiconductor substrate to thereby heat the wide-gap, silicon carbide semiconductor substrate; and
the wide-gap, silicon carbide semiconductor substrate is heated by a heater embedded in the platen.
7. The plasma etching method according to claim 6 , in which the inert gas comprises He gas.
8. The plasma etching method according to claim 1 , in which the temperature to which the wide-gap, silicon carbide semiconductor substrate is heated is set in the range of 300° C. to 400° C.
9. The plasma etching method according to claim 1 , in which the etching gas comprises SF 6 gas.
10. The plasma etching method according to claim 1 , in which the etching gas comprises a mixture of SF 6 gas and O 2 gas.
11. The plasma etching method according to claim 1 , in which the wide-gap, silicon carbide semiconductor substrate is etched using a silicon dioxide film as an etching mask.
12. The plasma etching method according to claim 1 , in which the wide-gap, silicon carbide semiconductor substrate is etched using a nickel film as an etching mask.
13. The plasma etching method according to claim 1 , in which the wide-gap, silicon carbide semiconductor substrate comprises a 4H—SiC substrate.
14. The plasma etching method according to claim 1 , in which a hole or trench is formed in the wide-gap, silicon carbide semiconductor substrate by the etching.
15. The plasma etching method according to claim 14 , in which a sub-trench is not formed in a bottom of the hole or trench and a side wall of the hole or trench is etched slightly.
16. The plasma etching method according to claim 1 , in which:
the wide-gap, silicon carbide semiconductor substrate is heated in advance to a balanced temperature between 200° C. and 400° C.; and
after the wide-gap, silicon carbide semiconductor substrate reaches the balanced temperature, the wide-gap, silicon carbide semiconductor substrate is etched while maintaining the balanced temperature.