Patent Publication Number: US-2019168178-A1

Title: Apparatus and Method for Mixing Fluids with Degradational Properties

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional of U.S. Non-Provisional Application No. 15/081,105, filed Mar. 25, 2016, which is based on and claims priority to U.S. Provisional Patent Application 62/141,632, filed Apr. 1, 2015, all of which are incorporated by reference, as if expressly set forth in their respective entireties herein. 
    
    
     TECHNICAL FIELD 
     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. 
     BACKGROUND 
     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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
         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 . 
     
    
    
     DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS 
     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 . 
     The DI circuit also includes a recirculation loop defined by a third conduit  40 . The third conduit  40  extends from a point along the second conduit  18  downstream of the flow controller  30  to the recirculation vessel  14 . 
     In addition, the system  10  also includes a source of degradation fluid  50 . A fourth conduit  60  extends between the degradation fluid  50  to the mixing arm  100 . Along the fourth conduit  60 , a degradation fluid pressurized vessel (tank)  70  is provided. Downstream of the vessel  70 , a degradation fluid flow controller  80  is provided to control flow (flow rate) of the degradation fluid in the fourth conduit  60  in the direction of the mixing arm  100 . 
     The heated plumbing path consists of a heated deionized water (DI) loop with a set point of 85° C. and temperature control to 0.1° C. With only the DI heated in a standby state, the hydrogen dioxide degradation is greatly reduced. The degradation rate is reduced to what it would be in storage, instead of the chemical batch needing to be replaced after a few hours at elevated temperature. 
     The heated DI is passed through a flow controller to deliver a precise volume of heated water. During standby this is recycled back to the heater loop and during processing is delivered to the mixing arm  100 . 
     The mixing arm  100  is a multi-conduit structure as shown in  FIG. 2 . More specifically, the mixing arm  100  is a hollow arm structure with a number of side ports/conduits. The mixing arm  100  has an open first end  104  and an open second end  106 . The mixing arm  100  can be in the form of a tubular structure formed of a suitable material. The mixing arm  100  includes a main conduit  101  that extends from the first end  104  to the second end  106 . This main conduit  101  defines a main fluid flow path. As described herein, the first end  104  can be thought of as being an inlet (entrance) and the second end  106  can be thought of as being an outlet (exit). As shown, the mixing arm  100  and main conduit  101  can have a non-linear construction. As shown, the mixing arm  100  can have a first bent section  102 , a linear center portion  103 , and a second bent section  105 . The first bent section  102  defines and terminates at the first end  104  and the second bent section  105  defines and terminates at the second end  106 . The first bent section  102  can be bent in a first direction and the second bent section  105  can be bent in a second direction which can be opposite to the first direction. A central axis passing through each of the first and second bent sections  102 ,  105  can be perpendicular to a longitudinal axis of the linear center portion  103 . 
     The entrance at the first end  102  defines a first station/first position in the mixing arm  100  which receives the heated DI water from the second conduit  18  of the DI loop  12  (circuit) or from some other location in alternative embodiments. Since there is a flow control device  30  (e.g., valve device) along the flow path  18  of the heated DI water, the flow of heated DI water can be controlled to regulate the flow of heated DI water into the mixing arm  100  (at the inlet). 
     The mixing arm  100  has a first side port  130  that is in fluid communication with the main conduit  101 . The first side port  130  can be in the form of tubular structure that extends outwardly from the linear center portion  103 . In one exemplary operating mode, the first side port is fluidly connected to the source  50  of ambient temperature hydrogen dioxide (degradation fluid). More specifically, the conduit  60  can be connected to the first side port  130  to deliver the degradation fluid (hydrogen dioxide) to the mixing arm  100 . Flow control device  80  (e.g., a valve device) is also provided along the flow path of the ambient temperature hydrogen dioxide to allow the flow thereof to be regulated. This allows a selected flow of ambient temperature hydrogen dioxide through the first side port  130  into the main conduit  101 . The flow of ambient temperature hydrogen dioxide into the main conduit  101  along with the heated DI thus forms a mixture in the main conduit  101 . 
     Since the flow of heated DI water is regulated by one flow control device  30  and the flow of ambient temperature hydrogen dioxide is regulated by another flow control device  80 , an accurate concentration of diluted chemistry can be provided. Because the hot DI is held at a very stable temperature and the mix ratio is stable at 1:6 (chemistry:hot DI), the resulting mixture is at a known, stable temperature. This mixture flows toward the open second end (outlet)  104  of the mixing arm  100 . 
     The mixing arm  100  is constructed to include a second side port  140  that is in fluid communication with the main conduit  101 . The second side port  140  can be in the form of tubular structure that extends outwardly from the linear center portion  103 . This second side port  140  contains a mechanism  142  to remove any excess vapors that may have formed in the mixture. Any number of different mechanisms  142 , including vent mechanisms  142 , can be used to allow discharge of vapors from the mixture as it flows within the main conduit  101  toward the outlet  104 . The second side port  140  is thus downstream of the first side port  130  and the inlet  104 . 
     The mixing arm  100  is constructed to include a third side port  150  that is in fluid communication with the main conduit  101 . The third side port  150  can be in the form of tubular structure that extends outwardly from the linear center portion  103  and is located downstream of the second side port  140 . The third side port  150  contains a thermocouple  152  (temperature sensor). This thermocouple  152  accurately monitors the temperature of the mixture just prior to it is dispensed through the outlet  106 . This monitoring (measuring) is valuable in documenting process conditions as etch rate varies by ten percent per degree C. 
     As shown in  FIG. 2 , the thermocouple  152  is disposed within the hollow interior of the third side port  150  with at least a portion (the sampling portion) of the thermocouple  152  being disposed at least partially within the main conduit  101  so as to be in contact with the fluid flowing within the main conduit  101 . However, the thermocouple  152  does not interfere with the flow of the fluid within the main conduit  101 . 
     While the first, second and third side ports  120 ,  130 ,  140  are shown as having identical or similar outer diameters, this is merely for illustrated and it will be appreciated that the sizes of the first, second and third side ports  120 ,  130 ,  140  can be different and as shown in  FIG. 2 , the inner constructions (flow paths) of each differ from one another based on their different intended operations (functions). 
     The mixing arm  100  also includes a sample port  160  that is in the form of a conduit that extends outwardly from the linear center portion  103 . The sample port  160  can be in the form of an elongated leg that extends outwardly from the linear center portion  103  downstream of the third side port  150  but prior to the outlet  106 . The sample port  160  can have a shape different than the side ports and/or the location of the sample port  160  can be different than the side ports. For example, in the illustrated embodiment, the sample port  160  is formed on the linear center portion  103  opposite the side ports. Also, the sample port  160  can have a smaller diameter compared to the side ports and has a longer length. As illustrated, the sample port  160  can have a main section  162  that has a longitudinal axis that is parallel to the longitudinal axis of the main conduit  101 . The sample port  160  terminates in an open end  165  which serves as an outlet through which a sample can pass. It will be appreciated that the sample port  160  can be fluidly connected to another structure, such as a fluid conduit that delivers the sample to another location (sampling location). A flow controller  210  can be disposed along the flow path of the sample to allow for selective sampling thereof. For example, a valve member  210  can be provided and a prescribed amount of fluid can be sampled by opening up the valve member. 
     In one embodiment the sample port  160  is used to divert a small volume of the heated process fluid to a concentration monitor  200  that is at the sampling location. The concentration of the mixture to be dispensed through the outlet  106  can be measured for purposes of process control. Although the chemistry is single pass, the fluid mixture can be dispensed at 75° C. and at ⅙ the original concentration. The higher temperature more than offsets the lower concentration in terms of etch rate. In practice, an etch rate of more than 3× is observed with the diluted chemistry. In this manner, the fluid is single pass but due to higher etch rate and no chemistry losses during standby mode, the chemistry used can be less than when full concentration chemistry is used and recycled. Finally since the chemistry is not recycled, contaminants do not build up in the recycle loop. This eliminates the potential for contaminant related accelerated degradation and greatly improves the overall safety of the operation. 
     The present invention can thus include one or more of the following features: 
     1—Immediately prior to dispense the mixing arm will remove excessive vapor that would degrade process results. 
     2—Immediately prior to dispense the mixing arm provides the capability to monitor the chemistry temperature for accurate process monitoring. 
     3—Immediately prior to dispense the mixing arm provides the capability to withdraw a fluid sample for purposes of concentration measurement. 
     4—The mixing arm is unique in having undesired vapor elimination, temperature monitoring and concentration monitoring capability for a heated, diluted degradation fluid mixing and delivery system. 
     5—point 4 highlights the process controls required to eliminate heating of hydrogen dioxide. 
     6—point 4 highlights the process controls required to eliminate the recirculation of hydrogen dioxide. 
     7—points 4, 5 and 6 combine the process controls and conditions to eliminate accelerated degradation safety issues associated with heated and recycled hydrogen dioxide.