Apparatuses and methods for etching process

A method for an etching process comprising:

• dispensing a first liquid electrolyte droplet over a layer-to-be-etched disposed over a substrate;
• coupling a first electrode to the first liquid electrolyte droplet;
• dispensing a second liquid electrolyte droplet over the layer-to-be-etched, wherein the second liquid electrolyte droplet remains isolated from the first liquid electrolyte droplet;
• coupling a second electrode to the second liquid electrolyte droplet;
• applying an alternating voltage at different frequencies between the first and the second electrodes;
• collecting impedance data between the first and the second electrodes in response to the alternating voltage;
• and
• etching the layer-to-be-etched with an etching parameter selected based on the impedance data.

An etching apparatus comprising:

• an etch chamber;
• a dispensing arm disposed within the etch chamber, the dispensing arm configured to dispense a first liquid electrolyte layer over a layer-to-be-etched of a substrate;
• a first electrode configured to be coupled to the substrate;
• a second electrode configured to be coupled to the first liquid electrolyte layer;
• and
• an impedance spectroscope coupled to the first and the second electrodes, the impedance spectroscope being configured to apply an alternating voltage at different frequencies between the first and the second electrodes to collect impedance data.