Fluent material handling – with receiver or receiver coacting mea – Filling or refilling of dispensers – By operation of means causing or controlling dispensing
Reexamination Certificate
2001-08-02
2002-08-20
Jacyna, J. Casimer (Department: 3751)
Fluent material handling, with receiver or receiver coacting mea
Filling or refilling of dispensers
By operation of means causing or controlling dispensing
C141S005000, C141S001000, C141S067000, C141S095000, C141S198000, C137S209000
Reexamination Certificate
active
06435224
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a system for supplying ultra pure and contamination sensitive chemicals to production lines for forming semiconductors, fiber optics, or like components. More particularly, this invention relates to a system carrying pyrophoric chemicals which allows the production line to operate continuously, and without interruption.
2. Description of Related Art
The manufacture of semiconductors, fiber optics, and the like components, typically requires production lines with systems for supplying high purity processing chemicals to diffusion furnaces, either directly or in carrier gases. Processing chemicals are liquids which may be directly injected into the processing stations, or which may be carried to the processing stations in a carrier gas. Direct chemical injection may be from bulk supply tanks, or may be from smaller supply containers which will be periodically refilled by bulk supply tanks. When the chemicals are applied by means of carrier gases, the liquid chemicals will be contained in temperature-controlled ampules or work cylinders, called “bubblers”. A stream of an inert carrier gas, such as nitrogen, helium, or the like, is injected into the bubbler ampules. The inert carrier gas bubbles upwardly through the liquid chemical in the bubbler ampule and creates a chemical-saturated carrier gas atmosphere in the ampule in the space above the supply of liquid chemical contained therein. The chemically saturated carrier gas is continuously drawn out of the bubbler and transferred into the component processing station, such as a diffusion furnace, as noted above.
The processing lines depend on a continuous supply of the chemicals being delivered from the chemical source in order to operate properly and efficiently. If the supply of the processing chemicals is interrupted, the production line must be shut down, and the diffusion furnace must be placed in a “idle” mode. If the chemical ampules are depleted of processing chemicals, they must be removed from the production line and replaced with freshly filled ampules.
To avoid the necessity of removing a bubbler ampule from the production line, additional bulk chemical supply containers may be incorporated into the production line. When a single bulk supply container is used in the production line, it must be periodically refilled with processing chemicals. The line must be shut down while the bulk supply container is refilled. The line can be run for a longer time period due to the use of the bulk supply container, however, the line still must be periodically shut down when the bulk supply container is depleted. When two bulk supply containers are used, one is a fixed container and the other is a replaceable mobile container. The ampule is replenished with chemicals from the fixed bulk container, and the fixed bulk container is refilled with chemicals from the replaceable, or shuttle, bulk container. The fixed bulk container is typically positioned on a scale or connected to a load cell so that the volume of chemical in the fixed bulk container is continuously monitored. Signals are transmitted to the system microprocessor controller or “junction box” which are indicative of the volume of chemical remaining in the fixed bulk container. The microprocessor controller manages about 2 points of use. For each point of use, there are four level sensors, i.e., empty, low, high or overflow. The low or high corresponds to the “start” and “stop” sensors which trigger the signal initiation to fill the ampule or the removal of the request. The empty or overflow (“overfill”) sensors are emergency sensors if the start and stop sensors fail. The supply voltage for the sensor circuit is about +24 volts. All level sensors connect to +24 volt when dry. A pressure switch generates a junction box alarm when there is not enough clean dry air (CDA) pressure. The electrical connections include main power and interface connections. Power is configured for 110 VAC or 230 VAC. A circuit breaker located where the main power is connected can be used to shut off all power to the unit. Twin fans act to cool the electronics area of the unit. A dispense request connector is used to interface with the process equipment, in addition to supplying status and alarm signals.
Typically, when the fixed bulk container is seen to be 75% full, the controller activates a chemical transfer valve system which transfers chemical from the shuttle bulk container to the fixed bulk container, and when the fixed bulk container has been refilled, the controller deactivates the chemical transfer valve system. Thus, the fixed bulk supply container will be refilled several times before the shuttle supply container must be refilled. When the shuttle bulk supply container has been substantially emptied, the shuttle container is removed from the production line and is refilled at an off-site chemical supply repository, which is typically far removed from the processing plant.
The use of fixed and shuttle bulk chemical supply containers has proven to be functionally operative, but it would be desirable to be able to provide an alternative replenishment system for the chemical ampules; and even more desirable to provide a chemical replenishment system with a controller microprocessor which can operate the system in alternative chemical replenishment modes, one having a fixed and a replaceable bulk chemical supply containers, and the other having two replaceable bulk chemical supply containers.
Transportation of ultra high purity or ultra sensitive chemicals within the production lines require additional safeguards. For that reason, pyrophoric chemicals capable of self-ignition when it is exposed to air, are rarely in production lines. Automatic liquid replacement or refill systems for liquids have been utilized in other industries where the purity requirements of the liquid are far less stringent, and where pyrophoric reactions and extreme air (oxygen and moisture) sensitivity are not commonly encountered. Moreover, these replacement systems have been based upon measuring the weight of the liquid in the working container at comparative points in time or by using a time filling sequence to ensure the proper volumetric quantity is delivered. None of the systems were designed to work with the stringent requirements needed for ultra high purity or contamination sensitive chemicals in the compound semiconductor industry, and where the systems must accommodate pyrophoric metalorganic chemicals with their need to minimize fire, and eliminate air contamination hazards.
Additionally, automatic chemical refill systems servicing a multiple number of temperature controllers and their bubblers from one central refill control system have suffered from the problem that when one temperature controller has experienced problems or malfunctions in the system, all of the refill lines have to be shutdown until the problem is corrected. In current practice, most chemical refill systems are capable of operating up to four temperature controllers concurrently to supply vapors to a corresponding number of deposition tools. Thus, a repair required of just one temperature controller in the refill system could cause all of the temperature controllers in the system to be shutdown.
The bubblers are held in liquid, temperature-controlled baths, and must be periodically replaced based on the usage of the ultra high purity pyrophoric metalorganic (PMO) source chemical. The amount of chemical used is a function of the degree of saturation of the hydrogen carrier gas carrying the PMO chemical to the metalorganic chemical vapor deposition (MOCVD) reactor and the quantity of carrier gas used. Typical carrier gases are nitrogen, argon, or helium, but the preferred gas for PMO CVD is ultra high purity hydrogen. Some typical chemicals utilized in bubblers are trimethylgallium (TMG), triethylgallium (TEG), trimethylaluminum (TMA) and dopant chemicals, such as dimethylzinc (DMZ) and diethylzinc (DEZ). When the chemical in the bubbler is
Blatt Christopher S.
Pearce Richard H.
Wentworth, III Edward H.
Williams Graham
Arch Specialty Chemicals, Inc.
Jacyna J. Casimer
Ohlandt Greeley Ruggiero & Perle LLP
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