Spatial averaging technique for ellipsometry and reflectometry
US6281027A · kind A · utility
Inventors
Key dates
| Filing date | Sep 11, 2000 |
| Grant date | Aug 28, 2001 |
| Priority date | — |
| Expiry date | Sep 11, 2020 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01L22/12
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
This invention relates to ellipsometry and reflectometry optical metrology tools that are used to evaluate semiconductor wafers and is directed to reducing errors associated with material surrounding a desired measurement area or pad, either by minimizing the uncertainties in positioning the measurement beam or by taking into account the effects of the surrounding material in analyzing the measured data. One aspect the present invention utilizes a technique where initially one purposefully aims to place the optical spot of the measurement beam a few microns away from the center of the target pad. Then a series of measurements are made with each measurement separated by a small stage jog as the optical spot is scanned over the measurement pad. Provided the surrounding material is the same on both sides of the pad, one finds that the data invariably has either a cup or inverted "U" shape or an inverted cup or "U" shape when viewed as a function of position. The minimum or maximum of the curve is then used to identify the center of the pad. Another aspect the present invention makes use of a novel method of data analysis that allows for the correction of the effects of the surrounding…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.