Measurement technique for ultra-thin oxides

Details Measurement technique for ultra-thin oxides Measurement technique for ultra-thin oxides

2001-01-04

2004-05-04

Rosenberger, Richard A. (Department: 2877)

Optics: measuring and testing

By polarized light examination

Of surface reflection

C356S630000

Reexamination Certificate

active

06731386

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a measurement technique for ultra-thin oxides and, more particularly, to a technique that utilizes a monitor sample in conjunction with a device-to-be measured to provide for an accurate measurement of a deposited oxide film.
BACKGROUND OF THE INVENTION
In the prior art, there has been considerable interest in developing methods and apparatus for measuring the thickness of thin films on substrates. This need is particularly acute in the semiconductor manufacturing industry where extremely thin films are deposited on silicon substrates.
One technique for measuring such films is defined broadly as “ellipsometry”. In an ellipsometer, a probe beam, having a known polarization, is directed to reflect off the surface of the film being measured at an oblique angle. The thickness of the film layer on the substrate will affect the polarization state of the reflected beam. That is, there will be a change in relative phase shift between the “P” wave, which is a vibration component parallel to the plane of incidence, and the “S” wave, which is a vibration component perpendicular to the plane of incidence, as well as the change in amplitude ratio between the two waves. Therefore, by measuring the polarization state of the reflected beam, information about the thickness of the film layer can be derived.
Ellipsometers are quite useful for providing a relatively quick and non-invasive method of measuring film thickness. However, in most practical measurement systems, an error in the range of ±30% can be expected. As film thicknesses become increasingly shallower (i.e., less than 200 Å), other techniques must be developed that exhibit a smaller range of error.
SUMMARY OF THE INVENTION
The need remaining in the art is addressed by the present invention, which relates to a measurement technique for ultra-thin oxides and, more particularly, to a technique that utilizes a monitor sample in conjunction with a device-to-be measured to provide for an accurate measurement of a deposited ultra-thin oxide film.
In accordance with the present invention, a reference sample (such as a silicon substrate) is processed to include (either by growth or deposition, for example) an oxide layer with a thickness (“t”) that is relatively easy for a conventional ellipsometer to measure. The reference sample and the actual production wafer(s) are then subjected to the same process for growing an ultra-thin oxide film, where in the case of the reference sample, the ultra-thin oxide will grow over the previously-formed oxide. A conventional ellipsometer can then be used again to measure the total thickness (“T”) on the reference sample, where the difference between these two values (T−t) is then defined as the thickness (“&dgr;”) of the ultra-thin film oxide.
It is an aspect of the present invention that any suitable type of measurement tool can be used to determine the thickness of the oxide layers formed on the reference sample, as long as the measurement tool exhibits sufficient resolution to be able to distinguish between the thickness prior to and after growth of the thin-film oxide.
Other and further aspects of the present invention will become apparent during the course of the following discussion and by reference to the accompanying drawings.


REFERENCES:
patent: 4582431 (1986-04-01), Cole
patent: 4828391 (1989-05-01), Zultzke et al.
patent: 4878755 (1989-11-01), Siegmund et al.
patent: 4999014 (1991-03-01), Gold et al.
patent: 5101111 (1992-03-01), Kondo
patent: 5120966 (1992-06-01), Kondo
patent: 5438415 (1995-08-01), Kazama et al.
patent: 5485091 (1996-01-01), Verkuil
patent: 5486701 (1996-01-01), Norton et al.
patent: 5740226 (1998-04-01), Komiya et al.
patent: 5798837 (1998-08-01), Aspnes et al.
patent: 5835221 (1998-11-01), Lee et al.
patent: 5900939 (1999-05-01), Aspnes et al.
patent: 5962079 (1999-10-01), Koberstein et al.
patent: 5963326 (1999-10-01), Masao
patent: 5973787 (1999-10-01), Aspnes
patent: 6104486 (2000-08-01), Arimoto
patent: 6222199 (2001-04-01), Freeouf

Affiliated with

Also associated with

Rating

Measurement technique for ultra-thin oxides does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Measurement technique for ultra-thin oxides, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Measurement technique for ultra-thin oxides will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3237965