Fluid handling – Systems – With flow control means for branched passages
Reexamination Certificate
1999-06-23
2001-02-13
Fox, John (Department: 3753)
Fluid handling
Systems
With flow control means for branched passages
C137S613000
Reexamination Certificate
active
06186177
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to gas delivery systems for ultra-high purity gases, such as systems used to provide process gases for semiconductor manufacturing. As used herein, the term “gas” includes gases and vapors.
BACKGROUND OF THE INVENTION
High purity gas delivery systems, such as those used in semiconductor manufacturing or other thin film coating processes, typically include a source of high purity gas coupled through a series of gas distribution and control components such as a mass flow controller, one or more pressure sensors and/or regulators, a heater, one or more filters or purifiers, and shutoff valves. In semiconductor processing, a series-connected set of such components is usually referred to as a “gas stick”. The components used and their particular arrangement in a gas stick can vary depending upon their design and application, with many component arrangements being known in the art. In a typical semiconductor processing arrangement, multiple gas sources are connected to the chamber through multiple gas sticks, which are typically mounted to a frame, forming a complete system known as “gas box”. See, for example, U.S. Pat. Nos. 5,662,143; 5,819,782 and 5,863,023.
As the dimensions of semiconductor devices decrease and their densities increase, semiconductor manufacturing processes have become increasingly intolerant of particulate contamination. One important source of such contamination is the gases used during the process, and particularly particulates carried by the wetted surfaces in the passageways through the components and those connecting the components of the gas stick which delivers gas from the source to the chamber. Moisture or dust which accumulates within a gas stick or component will be carried with the source gas and deposit onto the semiconductor devices being processed, creating defects. Moisture also may corrode the wetted surfaces, leading to flaking of particles from these surfaces.
To reduce contamination of this sort, gas sticks and other gas processing components used in manufacturing semiconductor devices are usually made in low-dust, low-moisture environments, and purged for lengthy periods of time at elevated pressures after manufacture. The components are then typically packaged and sealed in pressurized nitrogen for shipment. As a result, the interior of the component or stick is exposed only to the clean room environment in which the semiconductor processing equipment is located, and only for the brief period of time between removal of the packaging and sealing of the stick or component into the processing equipment.
In addition, the gas processing components in a gas stick, and other components and connections in the gas distribution system, will wear and need replacement at various times throughout the life of the assembly of equipment. Typically, a component is replaced by closing the valves most nearly adjacent to the component, uncoupling and replacing the component, and reopening the adjacent valves. To simplify this operation and minimize the extent of the gas stick exposed to room air during this procedure, each component is typically connected to its neighboring components or tubing with removable couplers, and valves are placed between components at several locations along the stick. This tubing and the removable couplers can often be the source of leaks, and require careful attachment and detachment when repairing and/or replacing component parts. Further, the act of uncoupling a component or portion of the stick and removing it from the stick exposes that component and the replacement component to ambient conditions, and also exposes substantial wetted surface between the component and the nearest valves (including the inside of any connecting tubing, and potentially other components), to ambient conditions. Thus, the gas stick must be extensively purged when the components are reassembled.
One approach to eliminating connection parts, such as tubing and couplers, and facilitating maintenance of the components of the gas stick is to “down mount” the components on multiple fixing blocks, as shown, for example, in U.S. Pat. No. 5,819,782 (Itafuji). However, each component of a gas stick typically comprises highly machined parts and expensive electrical circuitry, making each component relatively expensive to manufacture and replace. When a component fails, the entire component is replaced even though in most instances the failure is mechanical (and in the case of a mass flow sensor, it is the sensor that usually fails). Each component is typically constructed with a mounting block, which in turn is made with multiple machine operations, making the component expensive. Thus, while down mounting the component parts on multiple fixing blocks solves one problem, it still is relatively expensive to replace defective parts.
SUMMARY OF THE INVENTION
In accordance with the present invention, an improved gas delivery system designed and constructed so as to reduce the overall size and cost of the system, and yet increase the reliability of the system and allow inexpensive and easy repairs to and replacement of component parts. One design criterion is to make the total path length, or footprint, of the flow of gas as short as possible so as to minimize the wetted surface area to which the gas is exposed.
In accordance with one aspect of the invention, a gas delivery system comprises: a plurality of components including mechanical parts; and a common mounting block that supports the components in a predetermined arrangement and defines passageways between the components so that a gas can flow through the passageways and components along a predetermined flow path. The mounting block is formed so that at least a portion of at least one mechanical part of at least one component is provided in the block, the passageways connect the components together, and the portion of each component not formed in the block is removably attached to the block.
In one embodiment, the electrical control and processing circuitry used to operate each of the components are separately provided so that replacement of a component replaces those mechanical parts of the components not provided in the block, without requiring the replacement of the circuitry.
In another embodiment, at least one of the components is a valve; and the portion of at least one mechanical part is a valve seat machined into said block.
In another embodiment, at least one of the components is a mass flow sensor of a mass flow meter. The mass flow meter can be any type including temperature-based and pressure based flow meters.
In another embodiment, the block includes at least two substantially parallel passageways formed in a surface of the block, and a cover is secured over each of the passageways and sealed thereto so as to form a sealed fluid flow path through the passageway.
In accordance with another aspect of the invention, a gas delivery system comprises: a plurality of components including mechanical parts arranged so as to control the flow of gas from a source to a process chamber; and electrical control and processing circuits that are used to operate the components; wherein the electrical control and processing circuits are separately provided remote from the components so that replacement of a component replaces those mechanical parts of the components, without requiring the replacement of the electrical circuitry.
In accordance with one embodiment of the present invention, at least one of the components is a mass flow meter of a mass flow controller that provides a mass flow signal as a function of the gas flowing through the meter. In one embodiment, at least one of the components is a control valve responsive to a control signal provided by the electrical control and processing circuitry.
In accordance with another aspect of the invention, a gas box delivery system comprises: a plurality of gas sticks, each comprising a plurality of components including mechanical parts arranged so as to control the flow of gas from a source to a process cham
Fox John
McDermott & Will & Emery
MKS Instruments Inc.
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