Dispensing – Plural sources – compartment – containers and/or spaced jacket – Cabinet-type dispenser for single mixed drinks
Reexamination Certificate
2000-02-25
2003-09-09
Mills, Gregory (Department: 1763)
Dispensing
Plural sources, compartment, containers and/or spaced jacket
Cabinet-type dispenser for single mixed drinks
Reexamination Certificate
active
06616014
ABSTRACT:
DESCRIPTION OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus and method for precisely consistently producing liquid mixtures according to a predetermined recipe, and a particular embodiment for producing slurry mixtures at the point of use for chemical mechanical polishing or planarization (CMP) processing of semiconductor wafers.
2. Background of the Invention
Much of current production CMP processing relies on mixing rather large volumes of expensive slurry in a batch preparation process somewhat remote from the point of use at a CMP workstation. The CMP processing requires many polisher workstations and hence many wafers being processed with a consistent slurry for uniform wafer results. Some slurries, particularly those including oxidizers, degrade over time. Slurry degradation results from chemical reactions that start immediately upon blending of the chemical components of the slurry. In order to maintain consistent slurries, expensive metrological instrumentation and spiking systems monitor and automatically correct mix concentrations. Often these bulk or batch slurry mixtures drift so far out of specification that restoration becomes impossible, resulting in expensive slurry waste.
More recent development has been directed to developing point of use slurry blending, or on demand blending. In U.S. Pat. No. 6,019,250, owned by the assignee of the present invention, an apparatus and method is shown for dispensing a liquid at one or more points of use from a plurality of reservoirs with a constant flow rate of liquid. This apparatus and method include a programmable logic controller for controlling valves for filling and dispensing the various liquid components to and from the reservoirs, and for controlling provision of a constant gas pressure in the reservoirs to effect the constant flow rate for the liquids. The disclosure of this patent is incorporated by reference into this application.
In another U.S. Pat. No. 5,887,974, also owned by the assignee of the present invention, a slurry mixing apparatus is disclosed using a static mixer and/or a hopper mixer in which several streams of slurry concentrate and additive chemical components are pumped together as a single stream which is blended or mixed to produce a homogeneous slurry. The disclosure of this patent is incorporated by reference into this application as well.
Other point of use slurry mixing and delivery systems are disclosed in U.S. Pat. Nos. 5,478,435 and 5,407,526. In the system of U.S. Pat. No. 5,407,526, slurry pumps preferably use a single motor to ensure the individual slurry component pumps are operated in phase for better control of the mixing of the slurry. In U.S. Pat. No. 5,478,435, the mixing of the slurry and diluting agent occurs at the point of use on the pad used in the CMP process. Liquid monitoring and control systems are used to maintain a consistent temperature and flow rate for the slurry components.
Even with such prior art on-demand or point of use slurry blending there is a desire for improved slurry consistency and greater flexibility in changing the slurry recipe during CMP wafer processing. The term slurry has a well known meaning of a mixture of liquid and finely divided particles.
There exists a general need in industry to be able to produce consistent liquid mixtures from a plurality of selected liquid components according to a predetermined recipe. It is desired that the recipe be able to be varied for flexibility of operations as well as to adjust the amounts of each liquid component not only as the desired recipe is changed, but as the characteristics of the liquid components change over time.
SUMMARY OF THE INVENTION
In accordance with the invention, a method, apparatus and system are provided for producing consistent liquid mixture according to a predetermined recipe. The apparatus comprises a plurality of liquid component reservoirs including an inlet port for loading a selected liquid component into a respective reservoir, and an outlet port through which the liquid component can be discharged. A gas manifold is provided for providing the same gas pressure within each reservoir. A plurality of valves are individually coupled to the respective outlet ports of the reservoirs. An electronic controller controls repetitive, sequences actuation of the valves to discharge precise amounts or volumes of the liquid components from the reservoirs to provide the desired liquid components as doses which are mixed together to form the liquid mixture according to the predetermined recipe.
The apparatus and method of the present invention effectuate the production of the precise, consistent liquid mixtures from the embedded electronic controller either by varying the number of actuation cycles for the valves which all have, the same actuation period, or by repetitively sequenced actuation of the valves while varying the actuation period of the valves, i.e., for normally closed valves varying the valve open periods.
In a preferred embodiment of the invention, a method, apparatus, and system are providing for producing consistent slurry mixtures to a point of use, such as a CMP polisher for semiconductor wafers. The apparatus comprises a plurality of slurry component reservoirs which include an inlet port for loading a selected slurry component into the respective reservoir, and an outlet port. Gas supply means are included to provide the same gas pressure within each reservoir. A plurality of valves, preferably having relatively high activation rates, are individually coupled to the respective outlet ports of the reservoirs. An electronic controller controls repetitive sequenced actuation of the plurality of valves to discharge upon each valve actuation precise doses of the selected components from the reservoirs to provide the desired components which are then mixed to form the predetermined consistent slurry.
The present invention also includes a system in which the apparatus of the present invention is in communication with a central operational controller which determines the selected slurry recipe which is to be blended in the apparatus for use at the point of use. The system also includes a slurry component supplier including sources of slurry components and valves via which the components fill the plurality of component reservoirs.
In a preferred embodiment, the present invention takes on-demand liquid mixing to a higher level with greater precision of resultant liquid mixture consistency and with flexibility in dynamically mixing recipes for specific CMP processing requirements. This system preferably permits varying the liquid mixture during wafer polishing and provides for rapid turn around for processing additional wafers to differing requirements.
The present invention preferably takes a different approach; mixing liquids such as slurries immediately prior to use, in the precise quantities required (for example, in the CMP embodiment, 100 to 200 ml per wafer) and allowing dynamic control of the mix recipe during wafer polishing. By utilizing relatively high frequency, rapid opening and closing valves producing many small sequential “shots” or doses from each of several component reservoirs, one can achieve a precise, repeatable slurry mixing with a statistical averaging algorithm applying to numerous very small shots as well as it applies to very large batches in achieving the desired slurry mixture.
At least three different valving techniques provide the desired valve actuation cycles to achieve the statistical averaging algorithm particularly in small mixture volume applications: 1. Solenoid driven valves, 2. Stepper motor driven rotary valves and 3. Pezio electric effect driven valves may be used to provide the repetitive small dose addition of slurry components from the reservoirs to achieve the desired slurry mixture.
Pressurized component reservoirs preferably hold enough of each component to process one wafer. A recharge module quickly refills these reservoirs just prior to wafer polishing. Flow rate is controlled by maintaining t
Pozniak Peter Martin
Provost Charles Andre
Roberts Benjamin Rush
Singh Rakesh Kumar
Vo Sau Van
Finnegan Henderson Farabow Garrett & Dunner LLP
MacArthur Sylvia R.
Mills Gregory
The BOC Group Inc.
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