Multivariate endpoint detection of plasma etching processes

In plasma etching process it is critical to know when the film being etched has cleared to the underlying film, i.e. to detect endpoint, in order to achieve the desired device performance in the resulting integrated circuit. The most highly utilized sensor technology for determining endpoint has historically been optical emission spectroscopy (OES), because it is both non-invasive and highly sensitive to chemical changes in the reactor. Historically, the intensity of one emission peak corresponding to a reactant or product in the etch process was tracked over time, leading to a single-wavelength endpoint trace. At endpoint, the concentrations of reactant and product species undergo a step change that is detectable in the optical emission endpoint trace for many plasma etching processes. Unfortunately, for several critical etching steps (contact and via), the exposed area of the film being etched is very low (<1%, with the rest being masked with photoresist),. and this traditional method of endpoint detection has failed because of the low signal-to-noise ratio at endpoint. Our work has provided a way to improve the endpoint detection sensitivity by a factor of approximately 5-6, so that endpoint can be adequately detected for these low open area etching steps. By utilizing CCD array detection for OES sensors, it is possible to rapidly collect (2-10 Hz) full spectral data (200-900 nm in wavelength), consisting of over 1000 discrete wavelength channels from a plasma etching process. By appropriately utilizing this multi-wavelength data, we have been able to achieve significant improvements in sensitivity. Our work has focused on characterizing, analyzing, and developing new multivariate (multi-wavelength) strategies to optimize the sensitivity of the endpoint detector.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Chemical Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2002

Author dc:creator

• Goodlin, Brian E., 1974-

Advisor dc:contributor.advisor

• Herbert H. Swain and Duane S. Boning.

• Chemical Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/8498

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/8498