Chemical mix and delivery systems and methods thereof
View Patent ↗The present invention relates to chemical delivery systems and methods for delivery of liquid chemicals. In one embodiment, the present invention relates to systems having multi-reservoir load cell assemblies for delivering chemicals used in the semiconductor industry. In one embodiment, the present invention provides a multi-reservoir load cell assembly, including a controller, a buffer reservoir, a main reservoir, one or more load cells, coupled to the assembly and to the controller, operable to weigh the liquid in the reservoir(s), a plurality of supply lines, each supply line having a valve and connecting one of the supply containers to the main reservoir, and a gas and vacuum sources for withdrawing the liquid from the assembly when demanded by the controller and for refilling the assembly from the supply containers.
1. A chemical delivery system, comprising:
a main reservoir in fluid communication with one or more inlet fill valves, an inlet pressure valve, and a main reservoir outlet valve;
a buffer reservoir in fluid communication with a buffer reservoir inlet valve and a buffer outlet valve;
a line connecting the main reservoir outlet valve to the buffer reservoir inlet valve;
a load cell for monitoring the weight of a chemical in the buffer reservoir and generating analog signals that are converted to digital signals indicative of the weight of the chemical in the buffer reservoir;
a proportional valve block including a buffer control inlet valve and a buffer control outlet valve that adjusts the pressure to the buffer reservoir;
a programmable logic controller receiving the digital signals and generating control signals to the proportional valve block to achieve a desired chemical flow rate.
2. The system of claim 1 , further comprising a load cell for monitoring the weight of the chemical in the main reservoir and generating analog signals that are converted to digital signals indicative of the weight of the chemical in the main reservoir.
3. The system of claim 2 , wherein the one or more inlet fill valves includes a gross fill valve and a fine fill valve, and wherein the programmable logic controller sends a signal to open the gross fill valve until the main reservoir has almost sufficient chemical, and another signal to the chatter the fine fill valve until the main reservoir has the precise amount of chemical required.
4. The system of claim 2 , wherein the programmable logic controller sends control signals to each of the one or more inlet fill valves sequentially so as to admit chemicals sequentially into the main reservoir so that the load cell of the main reservoir can weigh each chemical accurately.
5. The system of claim 4 , further comprising a mixer assembly including a motor, and a shaft and an impeller associated with the main reservoir, wherein the programmable logic controller sends control signals to engage the motor, rotate the shaft and impeller which stirs the chemicals admitted into the main reservoir.
6. The system of claim 4 , further comprising a mixer assembly including a motor, and a shaft and an impeller associated with the buffer reservoir, wherein the programmable logic controller sends control signals to engage the motor, rotate the shaft and impeller which continues to stir the mixture from the main reservoir that is admitted into the buffer reservoir.
7. The system of claim 1 , further comprising a pinch valve in fluid communication and downstream of the buffer outlet valve, wherein the programmable logic controller sends control signals to the fully open the pinch valve to allow full flow during a flush sequence and then return to a more closed determined set point.
8. The system of claim 1 , further comprising an inert gas supply that is in communication with the main reservoir and the buffer reservoir.
9. The system of claim 8 , wherein the inert gas supply is passed through an inert gas humidifier so that the gas is humidified with the liquid in the inert gas humidifier.
10. The system of claim 8 or 9 , wherein the chemical being delivered from the system is a chemical mechanical polishing formulation whose primary component is de-ionized water and the inert gas is nitrogen.
11. A method of liquid chemical delivery at low flow rates in a system comprising a multi-reservoir load cell assembly, including a main reservoir, a buffer reservoir, each reservoir having at least one load cell and a mixer, and a logic device, comprising:
isolating the main reservoir from the buffer reservoir;
reducing pressure in the main reservoir;
adding liquid chemical components sequentially into the main reservoir;
weighing each liquid chemical component by the multi-reservoir load cell assembly;
mixing the chemical components into a mixture;
supplying the main reservoir with an inert gas;
transporting mixture from the main reservoir to the buffer reservoir; and
transporting the mixture from the buffer reservoir through a pinch valve.