US 7,096,085 B2 · Process control by distinguishing a white noise component of a process variance

Abstract

A method, system and medium is provided for enabling improved control systems. An error, or deviation from a target result, is observed for example during manufacture of semiconductor chips. The error within standard deviation is caused by two components: a white noise component and a signal component (such as systematic errors). The white noise component is, e.g., random noise and therefore is relatively non-controllable. The systematic error component, in contrast, may be controlled by changing the control parameters. A ratio between the two components is calculated autoregressively. Based on the ratio and using the observed or measured error, the actual value of the error caused by the systematic component is calculated utilizing an autoregressive stochastic sequence. The actual value of the error is then used in determining when and how to change the control parameters. The autoregressive stochastic sequence addresses the issue of the effects of run-to-run deviations, and provides a mechanism that can extract the white noise component from the statistical process variance in real time. This results in an ability to provide tighter control, for example in feedback and feedforward variations of process control.

Claims34

Dependent claims

A system, implemented on at least one computer, for compensating for a variance between a measured characteristic of at least one product produced by a process and a target result of the characteristic, the system comprising:

(a) means for receiving an observed value for at least one product, and receiving a target value for the at least one product;
(b) means for determining a variance between the observed value of at least one product and the target value of the at least one product;
(c) means for determining a first portion of the variance caused by white noise;
(d) means for determining a second portion of the variance caused by a systematic component;
and
(e) means, in the at least one computer, for using the determined first and/or second portions to adjust the process.

3 more elements

A computer program product for use in compensating for a variance between a measured characteristic of at least one product produced by a process and a target result of the characteristic by differentiating a white noise component of the variance from a systematic component of the variance, the computer program product comprising:

(a) at least one computer readable medium, readable by the manufacturing process;
(b) instructions, provided on the at least one computer readable medium, for receiving an observed value for at least one product, and receiving a target value for the at least one product;
(c) instructions, provided on the at least one computer readable medium, for determining a variance between the observed value of at least one product and the target value of the at least one product;
(d) instructions, provided on the at least one computer readable medium, for determining a first portion of the variance caused by white noise;
and
(e) instructions, provided on the at least one computer readable medium, for determining a second portion of the variance caused by a systematic component;
and
(f) instructions, provided on the at least one computer readable medium, for using the determined first and/or second portions to adjust the process.

5 more elements

Dependencies are inferred from the claim text.

Process control by distinguishing a white noise component of a process variance

Life of this patent

Process control by distinguishing a white noise component of a process variance

Life of this patent

Abstract

Claims34