Parallel divided flow-type fluid supply apparatus, and fluid-switchable pressure-type flow control method and fluid-switchable pressure-type flow control system for the same fluid supply apparatus

Abstract

A fluid supply apparatus with a plurality of flow lines branching out from one regulator for adjustment of pressure, the flow lines being arranged in parallel, wherein a measure is taken that the operation, that is, opening or closing of one flow passage will have no transient effect on the steady flow of the other flow passages. For this purpose, each flow passage is provided with a time delay-type mass flow controller MFC so that when one closed fluid passage is opened, the mass flow controller on that flow passage reaches a set flow rate Qs in a specific delay time DELTAt from the starting point. Also provided are a method and an apparatus for the above in which a plurality of gas types can be controlled in flow rate with high precision by one pressure-type flow control system. To that end, a formula for calculating the flow rate of a gas is theoretically derived that flows with a pressure ratio not higher than the critical pressure ratio. From that formula, the flow factor is defined, so that the formula may be applied to a number of gas types using flow factors. The method includes calculating the flow rate Qc of a gas passing through an orifice according to formula Qc=KP1 (K=constant) with a pressure P1 on an upstream side of the orifice set at twice or more higher than pressure P2 on a downstream side, wherein the flow factor FF for each kind of gas is calculated as follows: <paragraph lvl="0"><in-line-formula>FF=(k / gammas){2 / (kappa+1)}1 / (kappa-1)[kappa / {(kappa+1)R}]½< / in-line-formula>and wherein, if the calculated flow rate of gas type A is QA, and, when gas type B is allowed to flow through the same orifice under the same pressure on the upstream side and at the same temperature on the upstream side, the flow rate QB is calculated as follows: <paragraph lvl="0"><in-line-formula>QB=(FFB / FFA)QA < / in-line-formula>where gammas=concentration of gas in standard state; kappa=ratio of specific heat of gas; R=constant of gas; K=proportional constant not depending on the type of gas; FFA=flow factor of gas type A; and FFB=flow factor of gas type B.

Description

[0001] 1. Field of the Invention[0002] The present invention relates to an apparatus for supplying gases or the like for use in the production of semiconductors, chemicals, precision machine parts, etc. More specifically, this invention relates to a parallel divided flow type fluid supply apparatus so configured that when any one of a plurality of flow passages arranged in parallel is opened for fluid to flow, the effect of that operation on the flow rates in other flow passages is minimized.[0003] The present invention also relates to a method of controlling the flow rates of various gases used in an apparatus for supplying gases or the like for use in the production of semiconductors, chemicals, precision machine parts, etc. More specifically, this invention relates to a fluid switchable pressure-type flow control method and a fluid switchable pressure-type flow control system (FCS) in which the flow of various gases can be regulated with high precision by one pressure-type flow c...

AI Technical Summary

Problems solved by technology

But a problem is encountered with an arrangement in which material gas G is supplied through one regulator and branched off into two or more flow passages. FIG. 15 shows an arrangement in which the flow of the material gas G from one regulator RG branches off to two flow passages S.sub.1 and S.sub.2.

In the process of manufacturing semiconductors, this problem could cause lattice defects in the semiconductor.

This change could lead to unpredictable problems through "chaos phenomena."

However, little transient effect is wrought on upstream pressure Po.

However, the pressure changing device is itself expensive.

That would make the whole of the fluid supply arrangement complicated and large, sending up the costs.

The problem is that each mass flow controller has its linearity corrected for a specific kind of gas and a specific low rate range.

That is, the mass flow controller cannot be used for other than the kind of gas for which the controller is adjusted.

The mass flow controller is expensive and so are replacement parts.

That increases the costs of gas supply facilities and the running costs.

Furthermore, if the mass flow controller is not replaced for a new kind of gas and, instead, the linearity is corrected every time a new gas is used, it takes long and it could happen that the operation of the manufacturing plant has to be temporarily suspended.

This transient change in turn has an affect on the process in the reaction chamber off the branch line, causing a number of problems.

If each branch line is provided with one regulator to avoid such transient changes, meanwhile, that will make the fluid supply arrangement complicated and bulky, boosting the costs.

Furthermore, a large number of expensive standby mass flow controllers have to be stocked.

That increases the costs of gas supply facilities and the running costs.

As a result, the inventors concluded that the mass flow controller cannot absorb the transient effect very well because the controller measures the flow rate on the basis of the amount of heat transfer or heat carried by the fluid, and if the change in flow rate is higher than the flow velocity, the control of the flow rate cannot follow the change in flow rate well.

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