Method and apparatus for increased recirculation and filtration in a photoresist dispense system using a liquid empty reservoir

1. An apparatus for dispensing a liquid onto a substrate, comprising:

a reservoir for storing the liquid to be dispensed;

a filter comprising an inlet and an outlet, the filter inlet in fluidic communication with the reservoir;

a liquid empty (LE) reservoir comprising an inlet, a first outlet, a second outlet, and a vent port, the LE reservoir inlet in fluidic communication with the filter outlet via a first valve, the vent port comprising a second valve for selectively opening the LE reservoir to a pressure, and the second outlet in fluidic communication with the reservoir via a third valve;

a dosing pump comprising an inlet, a first pump outlet, and a second pump outlet, the pump inlet in fluidic communication with the LE reservoir first outlet, and the second pump outlet in fluidic connection with the filter inlet via a fourth valve, the dosing pump configured to dose an amount of the liquid and pump the liquid; and

a dispense nozzle in fluidic communication with the first pump outlet, the dispense nozzle configured to dispense the liquid onto the substrate;

wherein the reservoir, the filter, the LE reservoir, the dosing pump, and the dispense nozzle are arranged so that:

all the liquid that enters the dosing pump through the pump inlet is filtered by the filter before entering the pump inlet;

the liquid that is pumped through the first pump outlet is fed to the dispense nozzle without passing through the filter after leaving the first pump outlet; and

the liquid that is returned to the LE reservoir through the second pump outlet passes through the filter before returning to the LE reservoir.

2. The apparatus of claim 1 , wherein the pressure is substantially equal to atmospheric pressure.

3. The apparatus of claim 1 , further comprising a mixing system disposed between the dosing pump and the dispense nozzle, the mixing system comprising:

a solvent supply inlet in fluidic communication with a solvent supply;

a process liquid supply inlet in fluidic communication with the dosing pump outlet;

a mixing chamber in fluidic communication with the solvent supply inlet and process liquid supply inlet and configured to mix solvent and process liquid; and

an outlet in fluidic communication with the mixing chamber and the dispense nozzle and configured to supply the mixed solvent and process liquid to the dispense nozzle.

4. The apparatus of claim 3 , further comprising:

a flow valve for the solvent supply inlet; and

a flow valve for the process liquid supply inlet;

wherein the flow valves are configured to adjust the ratio of the solvent and the process liquid entering the mixing chamber.

5. The apparatus of claim 3 , wherein the mixing chamber comprises a static mixer or a holding tank and a stirrer.

6. The apparatus of claim 1 , wherein selectively opening the LE reservoir to the pressure causes liquid from the LE reservoir to flow to the dosing pump and reload the dosing pump.