Method and system of monitoring and controlling deformation of a wafer substrate
A method and system are for monitoring and controlling deformation of a wafer substrate during a plasma etching of the wafer substrate. The method includes disposing a wafer substrate on a platen assembly within a process chamber so that an entire upper surface of the wafer is exposed, passing a process gas into the process chamber, applying a radio frequency bias voltage to the platen assembly, generating a plasma within the process chamber, monitoring a voltage difference between the platen assembly and the process chamber, during the etch process, and attenuating or extinguishing the plasma to prevent further etching once a threshold monitored voltage is reached.
1. A method of monitoring and controlling deformation of an electrically insulating wafer substrate during plasma etching of the wafer substrate, the method comprising:
disposing an electrically insulating wafer substrate on a platen assembly within a process chamber so that an entire upper surface of the electrically insulating wafer substrate is exposed;
passing a process gas into the process chamber;
applying a radio frequency bias voltage to the platen assembly;
etching the exposed entire upper surface of the electrically insulating wafer substrate by generating a plasma within the process chamber;
determining, during said etching, a warping of the electrically insulating wafer substrate relative to the platen assembly by monitoring a voltage difference between the platen assembly and the process chamber;
attenuating or extinguishing the plasma to prevent further etching once a threshold monitored voltage is reached.
2. A method according to claim 1 , further comprising controlling a temperature of the platen assembly, to regulate a temperature of the wafer substrate.
3. A method according to claim 1 , wherein the insulating wafer substrate is a sapphire substrate.
4. A method according to claim 1 , wherein the insulating wafer substrate is a glass substrate.
5. A method according to claim 1 , wherein the plasma is generated by inductively or capacitively coupling radio frequency (RF) power into the process chamber.
6. A method according to claim 5 , further comprising inductively coupling RF power into the process chamber by applying an RF potential to one or more antenna disposed around the process chamber.
7. A method according to claim 1 , comprising a monitoring a peak-to-peak voltage difference (Vpp) between the platen assembly and the process chamber.
8. A method according to claim 7 , further comprising attenuating or extinguishing the plasma, once the Vpp between the platen assembly and the process chamber exceeds 10% of Vpp at the start of said etching.
9. A method according to claim 7 , further comprising attenuating or extinguishing the plasma, once the Vpp between the platen assembly and the process chamber exceeds 20% of the Vpp at the start of said etching.
10. A method according to claim 7 , further comprising attenuating or extinguishing the plasma once the Vpp reduces to a predetermined value which is characteristic of a Vpp of a representative insulating wafer substrate which extends in a substantially flat orientation upon the platen assembly.
11. A method according to claim 1 , comprising or further comprising monitoring a direct current voltage difference (Vdc) between the platen assembly and the process chamber.
12. A method according to claim 11 , further comprising attenuating or extinguishing the plasma, once the Vdc between the platen assembly and the process chamber exceeds 50% of the Vdc at the start of said etching.
13. A method according to claim 11 , further comprising attenuating or extinguishing the plasma, once the Vdc between the platen assembly and the process chamber exceeds 100% of the Vdc at the start of said etching process.
14. A method according to claim 11 , further comprising attenuating or extinguishing the plasma once the Vdc reduces to a predetermined value which is characteristic of a Vdc of a representative insulating wafer substrate which extends in a substantially flat orientation upon the platen assembly.