Interference removal
AssigneeXinix, Inc.
InventorsHerbert E. Litvak, Steven C. Leach, Edward G. Rodgers
Life of this patent
Estimating the term…
Abstract
An improved method for minimizing interferences from random noise and correlated fluctuations which obscure electrical signals converted from optical emissions. In particular, an improved method for the removal of interferences from optical emission signals during endpoint determination in dry etching processes for the fabrication of microelectronic devices which derives information in the presence of random noise, correlated fluctuations and periodic modulations of the plasma by maximizing the signal to random noise ratio and minimizing the obscuring effects of correlated fluctuation.
Claims28
In an optical emission detection method which converts a light emission intensity to a measurable electrical signal for monitoring a dry etch process for microfabrication, an improved method for minimizing interferences comprising the steps of:
- (a) measuring said electrical signal in separate channels at two or more wavelengths, thereby generating a plurality of separate electrical signals;
- (b) normalizing the separate electrical signals from said separate channels;
- (c) analyzing said Separate electrical signals for random noise, correlated fluctuations, and a dry process monitoring signal;
- (d) maximizing the signal to random noise ratio of the dry process monitoring signal;
- (e) minimizing the obscuring effects of correlated fluctuations from the separate channels by algorithms;
- thereby providing a resultant signal which is no longer obscured by random noise or correlated fluctuations.
In an optical emission detection method which converts a light emission intensity to a measurable electrical signal for monitoring a dry etch process for microfabrication, an improved method for minimizing interferences comprising the steps of:
- (a) measuring said electrical signal in separate channels at two or more wavelengths;
- (b) reducing levels of random noise in the electrical signal so that correlated fluctuations within the electrical signal become detectable and thereby become removable;
- and
- (c) combining signals from said separate channels in a manner to minimize obscuring effects of correlated fluctuations within said separate channels;
- thereby producing a resultant signal which is no longer obscured by random noise or correlated fluctuations.
In an optical emission detection method which converts a light emission intensity to a measurable electrical signal for monitoring a dry etch process for microfabrication, an improved method for minimizing interferences comprising the steps of:
- (a) measuring said electrical signal in a first separate channel including at least one first wavelength;
- (b) measuring said electrical signal in a second separate channel including at least one second wavelength, wherein said first wavelength is different from said second wavelength;
- (b) reducing levels of random noise in the electrical signal so that correlated fluctuations within the electrical signal become detectable and thereby become removable;
- and
- (c) combining signals from said separate channels in a manner to minimize obscuring effects of correlated fluctuations within said separate channels;
- thereby producing a resultant signal which is no longer obscured by random noise or correlated fluctuations.
Dependencies are inferred from the claim text.