Method and apparatus for plasma etching
Plasma etching a compound semiconductor substrate includes providing a substrate that includes a compound semiconductor material on a substrate support within a chamber. An etchant gas or gas mixture is introduced into the chamber. A plasma of the etchant gas or gas mixture is sustained within the chamber to plasma etch the compound semiconductor material. A pulsed electrical bias power is applied to the substrate support whilst the plasma is being sustained. The pulsed electrical bias power has a pulse frequency of less than or equal to about 160 Hz and a duty cycle of less than or equal to about 50%.
1. A method of plasma etching a compound semiconductor substrate, the method comprising the steps of:
providing a substrate on a substrate support within a chamber, wherein the substrate comprises a compound semiconductor material that includes a IV-IV, III-V or II-VI compound semiconductor;
introducing an etchant gas or gas mixture into the chamber, wherein the etchant gas or gas mixture comprises a chlorine-containing chemical etchant gas;
sustaining a plasma of the etchant gas or gas mixture within the chamber to plasma etch the compound semiconductor material, wherein the plasma is an inductively coupled plasma; and
applying a pulsed electrical bias power to the substrate support whilst the plasma of the etchant gas or gas mixture is being sustained;
wherein the pulsed electrical bias power has a pulse frequency of less than or equal to about 160 Hz and a duty cycle of less than or equal to about 50%.
2. The method according to claim 1 , in which the duty cycle is ≤40%.
3. The method according to claim 2 , in which the duty cycle is ≤25%.
4. The method according to claim 1 , in which the duty cycle is ≥5%.
5. The method according to claim 4 , in which the duty cycle is ≥15%.
6. The method according to claim 1 , in which the pulse frequency is less than or equal to about 150 Hz.
7. The method according to claim 6 , in which the pulse frequency is less than or equal to about 1 Hz.
8. The method according to claim 1 , in which the pulse frequency is ≥0.1 Hz.
9. The method according to claim 1 , in which the pulsed electrical bias power alternates between a high power and a low power, wherein the high power is in the range of 50-250 W, and the low power is in the range of 0-25 W.
10. The method according to claim 1 , in which the pulsed electrical bias power is a pulsed RF bias power.
11. The method according to claim 1 , in which the chemical etchant gas is SiCl 4 .
12. The method according to claim 1 , in which the etchant gas or gas mixture further comprises an inert sputter gas.
13. The method according to claim 12 , in which the inert sputter gas is argon gas.
14. The method according to claim 1 , in which the etchant gas or gas mixture consists of or consists essentially of SiCl 4 and argon gas.
15. The method according to claim 1 , in which the compound semiconductor material comprises a material selected from InGaAs, InP, GaN, GaP, AlGaAs, and SiC.
16. The method according to claim 1 , in which the plasma etch forms a feature, and wherein the feature is a trench.
17. The method according to claim 1 , in which the pulsed electrical bias power is a pulsed RF bias power, wherein the pulsed electrical bias power alternates between a high power and a low power, wherein the high power is in the range of 50-250 W, and the low power is in the range of 0-25 W.