Fluent material handling – with receiver or receiver coacting mea – Processes – Plural materials
Reexamination Certificate
2001-07-06
2003-07-08
Walczak, David J. (Department: 3751)
Fluent material handling, with receiver or receiver coacting mea
Processes
Plural materials
C141S100000, C141S094000, C141S095000, C141S083000
Reexamination Certificate
active
06588458
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to an apparatus, system, and method for measuring and transferring the contents of a vessel. In particular, the system relates to a system where an inner vessel containing a fluid is suspended in an outer vessel containing a fluid. The amount of fluid contained in the inner vessel is determined based upon the weight or buoyancy of the inner vessel within the outer vessel. The apparatus utilizes a sensing mechanism to determine the weight of the vessel.
BACKGROUND OF THE INVENTION
Industries such as the semiconductor, fiber optics and pharmaceutical industries, among others, utilize processes which rely on highly accurate dispensation of materials, such as liquid or vapor chemicals. For instance, in the semiconductor industry, circuit manufacture involves numerous processing steps. Many of the processing steps involve the deposition of a material layer onto a semiconductor topography. These layers may be applied utilizing the deposition of a chemical vapor onto the surface of the semiconductor. Other film deposition techniques involve applying films by evaporation or sputtering. Chemical vapor deposition involves exposing the surface to gases, known as precursors, which undergo a chemical reaction to form a desired material on the surface.
Vapor deposition generally includes a liquid delivery or injection system for vaporizing a liquid chemical and carrying the vaporized liquid into the deposition process or reaction chamber for semiconductor processing. A typical liquid delivery process manages the flow of a liquid precursor or reagent, a carrier gas, and possibly one or more other gases. The liquid precursor is provided in a vaporization device and the carrier gas is delivered to the vaporization device for mixing with the vaporized liquid precursor.
The vapors or precursors are often produced in sealed containers, which have an input and output. The input carries gas into and near the bottom of the sealed container. The gas then bubbles up through the liquid. The gas combines with the liquid to form a vapor such that the upper portion of the sealed container is filled with the vapor. The output carries the vapor out of the sealed container for use in applying the material to a surface, such as a semiconductor surface.
Historically, volume measurement and flow control have been employed to achieve a desired dispensation volume or flow rate. Ever increasing demands driven by tighter delivery tolerances, material costs and waste management place greater demands on volume measurement methodologies. The volume of a given substance of otherwise constant mass can be influenced by temperature, pressure and dissolved gases. Dispensation device manufacturer's must employ highly advanced and costly measures to compensate for and/or minimize induced errors by such influences. For instance, the effect of dissolved gases is readily evident when viewed through the clear acrylic of conventional liquid micro-balances, where large bubbles accumulate on the inner wall of the float vessel. Manufacturers of precision metering systems must include a pre-dispense degassing operation, as well as tightly controlled fluid temperature and pressure.
There are numerous techniques for measuring the level of liquid in a vessel. Some common techniques for sensing liquid level include: 1) weighing the container, 2) determining a differential pressure, 3) utilizing a float, optical, or acoustic sensor, and 4) utilizing a capacitive proximity switch. These sensor technologies provide either switched or variable outputs, where switching sensors provide a single dry contact switch output, and variable sensors provide a voltage output, corresponding to the operating range of the sensor.
There are enumerable fluid handling and control applications that utilize a variety of sensor technologies to detect the presence, availability, and/or amount of a liquid. Most liquid delivery systems rely on a source, or buffer supply, of liquid. In many applications liquid level and flow control technologies are connected to the source vessel(s) to detect the availability, amount, and rate of liquid to be delivered from the vessel.
A common method of liquid measurement and control is to position a plurality of switching sensors at various elevations on a source vessel. Each sensor performs a switching function to control the operating state of the fluid handling system. For example, if a low liquid level sensor on the source vessel is switched, a valve may be actuated to refill the source vessel until the liquid level reaches a high liquid level sensor, which would, in turn, switch the refill valve to the closed position. In some cases, a pair of sensors may be utilized to supply a specific amount of liquid to a point of use, where the distance between the sensors corresponds to a volume of liquid. Although sensors can be repositioned to change the amount of liquid to be dispensed, the configuration does not lend itself well to applications that require variable amounts or rates of liquid delivery.
Another common method of liquid measurement and control is to place the vessel onto a load cell, appropriately sized to measure the weight of the vessel and its liquid contents. This method features variable signal output based on the weight of the liquid in the vessel at any liquid level. The signal output can be monitored by a controller, which in turn, can perform fluid control functions based on programmed signal set points. This measurement technique can provide real time measurement and control of the liquid contained in the vessel, and is widely used for automated liquid delivery. However, the range and sensitivity of the scale can affect its size, accuracy, and cost.
Another common measurement technique employs load cells (scales) to monitor mass transfer operations. In applications demanding repeatable accuracy, costly measures must be taken to control external influences, such as isolation from air currents, subtle vibrations, and interconnecting system transients.
Some types of sensors must be in direct contact with the liquid. Other types are positioned above the surface of the liquid. Still other sensors are positioned outside the vessel along the vertical axis of the fluid column height. Load cells are positioned underneath the liquid vessel. For most high purity liquid delivery applications, it is preferred that the sensors not be in contact with, or in the contained environment of the liquid being delivered.
Due to the various chemical characteristics or fluid dynamic conditions, some sensors may not be suitable for use. For example, optical sensors may be compromised by reflectivity of the liquid or deposits on the sensor tip. Acoustic sensors may be compromised by sound wave interference or distortion during the signal transmission. In fact, some liquid applications operate in a vacuum environment where sound waves will not travel. Capacitive sensors can “drift” from their calibrated electrical potential, and give false readings. Float sensors can fail mechanically and provide only fixed liquid level signals. Although these measurement and control techniques are very mature, they lack the ability to dynamically, and in real time, indicate liquid level and weight with a high degree of accuracy and repeatability.
Hall-effect sensors have been used to measure liquid levels. An example of such sensors is disclosed in U.S. Pat. No. 5,636,548. Buoyant vessel position monitoring has been used, as described in U.S. Pat. No. 5,606,109, for liquid volume deviation determinations. Prior devices teach volume measurement and compensation based on changes in temperature.
It is desirable to provide a system that provides improvements over prior art measurement techniques that are both efficient and cost effective.
SUMMARY OF THE INVENTION
The present invention relates to a fluid handling apparatus, a dispensing system, and a method for measuring and controlling the amount of fluid within a fluid handling apparatus. The fluid handling apparatus includes a containm
Huynh Khoa D.
Icon Dynamics LLC
Pennie & Edmonds LLP
Walczak David J.
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