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Scatterometry Outline Target for Copper Layers in the Semiconductor Process.

IP.com Disclosure Number: IPCOM000006696D
Original Publication Date: 2002-Jan-23
Included in the Prior Art Database: 2002-Jan-23
Document File: 3 page(s) / 39K

Publishing Venue

Motorola

Related People

David C. Benoit: AUTHOR [+2]

Abstract

Scatterometry is a method of measuring critical dimensions in the semiconductor manufacturing process. A spectroscopic ellipsometer is used to capture the spectra from a grating of lines and spaces. A modeling and matching process converts the spectra to a measurement. Typical tiling or slotting features that improve chemical mechanical polish (CMP) uniformity, cannot be used beneath the scatterometry grating targets without affecting the measurements. An alternative, outline mark has been developed. It assists with CMP planarization while still allowing accurate scatterometry measurements. CMP is typically used in the copper backend process for manufacturing semiconductors.

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Title:  Scatterometry Outline Target for Copper Layers in the Semiconductor Process.

Authors:  David C. Benoit and Bradley P. Smith                                                                    Date:  November 26, 2001

Abstract: Scatterometry is a method of measuring critical dimensions in the semiconductor manufacturing process.   A spectroscopic ellipsometer is used to capture the spectra from a grating of lines and spaces.   A modeling and matching process converts the spectra to a measurement.  Typical ‘tiling’ or ‘slotting’ features that improve chemical mechanical polish (CMP) uniformity, cannot be used beneath the scatterometry grating targets without affecting the measurements.   An alternative, outline mark has been developed.  It assists with CMP planarization while still allowing accurate scatterometry measurements.    CMP is typically used in the copper backend process for manufacturing semiconductors.

Problem statement: 

Typical methods of tiling or slotting to improve CMP uniformity cannot be used directly below a scatterometry target without affecting the measurements.   This was not a problem for critical dimension (CD) targets as the SEM doesn’t see through layers with an electron beam.  This is a problem for scatterometry, which uses a spectral ellipsometer that can “see” the tiles at the previous  layers.   To accommodate, an outline trench or “moat” can be placed in underlying metal levels, around the perimeter of the grating to be measured.   See figure 1 for a top view and figure 2 for a side view.    This outline trench provides the following advantages:

1)  The outline trench improves...