Method and system for autotuning of RF match
View Patent ↗A reactive correction to chamber impedance changes without the need to change the process recipe is disclosed. The reactive correction may be done automatically and repeatedly during processing. A control of RF power application to a plasma processing chamber is performed, so as to minimize reflected power and efficiently apply the RF power to the plasma. Autotuning of the RF power application is enabled without modifying a qualified process recipe. The autotuning can be applied using frequency matching and RF matching network tuning.
1. A method for operating a processing system including a plasma chamber, a local controller, and a remote manufacturing controller, comprising:
storing a process recipe, including RF match network setting for the plasma chamber, in the remote manufacturing controller;
providing local storage for storing local values of RF match network setting;
energizing the plasma chamber using values of the process recipe and selecting initial RF match network setting according to: when local values of RF match network setting are stored in the local storage, selecting the local values, and when no local values of RF match network setting are stored in the local storage, selecting RF match network setting values included in the process recipe;
monitoring reflective power from the plasma chamber;
varying setting of RF match network of the plasma chamber to achieve minimum reflected power and, when minimum reflected power is achieved, storing new RF match network setting in the local storage; and,
subsequently operating the plasma chamber according to the process recipe, but using the new RF match network setting that is stored in the local storage; and,
wherein varying setting of RF match network comprises:
comparing current reflected power to a threshold and if the current reflected power is outside the threshold performing:
incrementing the setting of the RF match network in a first direction and performing a comparison operation comprising:
determining whether reflected power increased or decreased;
if increased, incrementing the setting of the RF match network in a second direction, opposite the first direction;
if decreased, determining whether reflected power, measured after the step of incrementing the setting, is below the threshold and, if so, storing new RF matching network values in the local storage, and again incrementing the setting of the RF match network in the first direction and repeating the comparison operation until the comparison operation indicates reflected power increase, at which point the process of incrementing the setting of the RF is stopped.
2. The method of claim 1 , wherein each increment is of a preset value.
3. The method of claim 2 , further comprising continuing to increment the setting in the direction where reflected power is decreasing, until an increment indicates that reflected power is increasing; and, at that point, storing a replacement RF match network setting in the local controller.
4. The method of claim 1 , wherein the RF match network setting comprises setting of a variable element in the RF match network.
5. The method of claim 4 , wherein the variable element comprises a variable capacitor.
6. The method of claim 4 , wherein the variable element comprises a variable inductor.