Ramp rate limiter to control stress during ramping
AssigneeTokyo Electron Limited
InventorsMark Erickson, Thorkell Gudmundsson, Sunil C. Shah
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Abstract
The present invention includes a method and system for limiting the ramp rate of a variable under control in order to control stress in a process or plant under control. The present invention takes a limit curve provided by the user and combines that limit curve with a scale factor curve obtained from a model of the system to produce an allowable limit curve. A ramp rate limiter then uses the allowable limit curve to control the ramp rate of the variable under control such that the ramp rate of the variable under control is able to achieve the maximum allowable limit but no more.
Claims22
A system for controlling stress during ramping of a variable under control comprising:
- a limiter;
- at least one controller, wherein the limiter provides a limiter value to the at least one controller that adjusts a semiconductor wafer's edge-center temperature difference to limit physical stress on the semiconductor wafer;
- and
- a plant, wherein the at least one controller is coupled between the limiter and the plant.
A system to adjust a variable-dependent ramp rate of a variable under control in a system under control, the system comprising:
- a limiter;
- at least one controller;
- and
- a plant, wherein the at least one controller is coupled between the limiter and the plant;
- wherein the limiter
- a) determines an allowable limit of the variable under control by evaluating a maximum allowable ramp rate limit curve at a previous output of a limiter;
- b) compares the allowable limit of the variable under control to a difference between a user requested value of the variable under control and the previous output of the limiter;
- and
- c) sets a new output of the limiter based upon a result of the comparison in step b).
A system to adjust a variable-dependent ramp rate of a variable under control in a system under control, the system comprising:
- a limiter;
- at least one controller;
- and
- a plant, wherein the at least one controller is coupled between the limiter and the plant;
- wherein the limiter
- a) receives a user-provided limit curve of the variable under control;
- b) obtains a scale factor curve from a model of the system under control′ and
- c) produces a maximum allowable ramp rate limit curve,
- d) determines an allowable limit of the variable under control by evaluating the maximum allowable ramp rate limit curve at a previous output of a limiter;
- e) compares the allowable limit of the variable under control to a difference between a user requested value of the variable under control and the previous output of the limiter;
- and
- f) sets a new output of the limiter based upon a result of the comparison in step e).
Dependencies are inferred from the claim text.