Apparatus and method for mixing fluids with degradational properties

#The present invention in general relates to an apparatus and method for preparing fluids for industrial processes. More specifically, the invention provides the capability to accurately and safely heat and dilute a process chemistry, while eliminating several issues inherent to the physical properties of the fluid and adding control feedback of multiple process variables as an option to the sequence.

#Historically hydrogen dioxide (30%) has been used to etch titanium tungsten (TiW). The etchant has been employed because of its selectivity to other materials and its less corrosive nature than alternative etchants. The etch rate is slow, so the fluid is typically heated to 40° C. to increase the etch rate. Although the process results can be excellent, the heated hydrogen dioxide presents a number of process and safety hurdles to overcome.

#Hydrogen dioxide degrades naturally and this degradation is accelerated with an increase in temperature. The degradation is the molecule splitting into water and oxygen gas. When this occurs inside vessels or other plumbing, vapor pockets form within the liquid. Liquid dispenses will then be partially liquid and partially vapor and this can greatly affect process results. It takes some time to heat and stabilize the etchant loop so during standby condition a process tool needs to maintain the fluid in circulation and at temperature. This rapidly degrades the chemistry in the standby mode, even with no production occurring. The slow etch rate (even if heated) means the processes are fairly long in duration. Accordingly the chemistry needs to be recycled to make the process economical. The material to be etched normally coincides with a range of materials. Some of these could be transitional metals or other material that will greatly increase the degradation rate of hydrogen dioxide. This can lead to safety issues where the liquid will rapidly decompose and over pressurize plumbing components to an unsafe condition.

#FIG. 1 is a schematic of an exemplary degradation mixing system including a heated deionized water (DI) loop; and

#FIG. 2 is a cross-sectional view of a mixing arm that is part of the degradation mixing system of FIG. 1.

#The present invention in general relates to an apparatus and method for preparing fluids for industrial processes. More specifically the present invention provides the capability to accurately and safely heat and dilute a process chemistry, while eliminating several issues inherent to the physical properties of the fluid and adding control feedback of multiple process variables as an option to the sequence.

#As shown in FIG. 1, the present invention is implemented in an alternately laid out plumbing path that includes a mixing arm 100 yields a number of economic, safety and process control enhancements to the process.

#As shown in FIG. 1, one exemplary degradation mixing system 10 includes a heated deionized water (DI) loop generally indicated at 12. The loop 12 includes a source of deionized water (DI) or other similar fluid 13 and is fluid connected to a recirculation vessel (tank) 14 by a first conduit 16. A pump 19 is provided along a second conduit 18 that extends between the recirculation vessel 14 and the mixing arm 100. The pump 19 is configured to pump the DI water along the second conduit 18. In addition, the second conduit 18 defines a heated fluid circuit in that the second conduit 18 a heater 20 and a heat exchanger 22. As shown, the heat exchanger 22 is downstream of the heater 20. A flow controller 30 is located along the second conduit 18 downstream of the heat exchanger 22. The flow controller 30 can be any number of different types of flow control devices that serve to control the flow (flow rate) of the DI water in the second conduit 18.