Static pressure stabilizer for local exhaust

Abstract

An exhaust system is provided for a plurality of machines, each machine having an exhaust stream connected to a local branch of the system. The system includes a stabilizer connected to an exhaust line in parallel to the exhaust stream of a machine. The stabilizer controls an exhaust pressure in the exhaust stream by opening and closing in response to variations in the exhaust pressure; the stabilizer opens to admit gas flow into the exhaust line when the exhaust pressure is less than a predetermined value, and closes when the exhaust pressure is greater than that predetermined value. The stabilizer unit thus provides a constant static exhaust pressure. The stabilizer provides relief flow in the exhaust stream, causing the gas flow into the exhaust line to increase when an exhaust flow in the exhaust stream decreases.

Description

FIELD OF THE INVENTION [0001] This invention relates to building exhaust systems in integrated circuit manufacturing facilities (“IC fabs”). More particularly, this invention relates to control of local static pressure in such systems. BACKGROUND OF THE INVENTION [0002] A modern IC fab has numerous sophisticated machines for performing manufacturing processes on semiconductor materials. These machines are referred to in the industry as “production tools” or simply “tools.” In general, each production tool is connected to a building-wide exhaust system for removing air or spent process gases from the interior of the tool. A typical building exhaust system is shown schematically in FIG. 1. Multiple fans and / or scrubbers 1 are connected in a manifold 2 to provide controlled, stable exhaust at header point 3. From this point a distribution system branches out in different directions throughout the building, with branches 4, sub-branches 5, and local branches 6 connecting to each of the ...

AI Technical Summary

Benefits of technology

[0007] According to a first aspect of the invention, an exhaust system is provided for a plurality of machines, each machine having an exhaust stream connected to a local branch of the system. The system includes a stabilizer connected to an exhaust line in parallel to the exhaust stream of a machine. The stabilizer controls an exhaust pressure in the exhaust stream by opening and closing in response to variations in the exhaust pressure; the stabilizer opens to admit gas flow into the exhaust line when the exhaust pressure is less than a predetermined value, and closes when the exhaust pressure is greater than that predetermined value. The stabilizer unit thus provides a constant static exhaust pressure. The stabilizer provides relief flow in the exhaust stream, causing the gas flow into the exhaust line to increase when an exhaust flow in the exhaust stream decreases.

Problems solved by technology

Even though a stable exhaust is provided at the fan manifold / header level (so that the overall system is stable), there are often fluctuations in the exhaust where a local branch connects to a set of tools (so that a particular zone of the system is not stable).

This has a negative effect on the performance of those tools.

Besides the loss of tool uptime, any degradation in performance of the production tools may be detrimental to the product yield.

However, a barometric damper does not hold a constant static pressure as the flow varies.

This can reduce the overall variation in local static pressure, but increases the load on the system and therefore makes the system more expensive to operate.

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