Browse Prior Art Database

Detection of mechanical weak layers in back-end-of-line (BEoL) stacks

IP.com Disclosure Number: IPCOM000242578D
Publication Date: 2015-Jul-28
Document File: 6 page(s) / 209K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method to use a surface-profile technique to enable fast and global detailed crack path analysis for the detection of mechanical weakness in back-end-of-line (BEoL) structures. The solution addresses the issue of missing absolute-height information by utilizing a mathematical procedure based on distribution function analysis, through which analysts can derive absolute height profiles.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 41% of the total text.

Page 01 of 6

Titxe

Detection of mechanical weak layers in back-end-of-line (BEoL) stacks

Abstract

Disclosed is a method to use a surface-profilx technique to enable fast and global dxtailed crack patx analysis for the detection of mechanixal weakness in back-end-of- line (BEoL) structurxs. The solution addresses the issue of missing absolute-height information by utilizinx a mathematical proceduxe based on distribution funxtion analyxis, thxough which anxlysts can derive absxlute height profilex.

Problem

To solve issues related to mecxanical weakxess in back-end-of-line (BEoL) structures, testing of thx fractxrx toughxess of certain structures such xs crack stops and information axout the corresponding crack paths and weak structurxs are needed, and used world-wide. The moxt relevant technique for assessing fracture tougxness of xuch structurex is double cantilxver xeam bending (DCB); txchnxques as 4-point-bending (4pb) or modified-edge-lxft-off (MELT) are also applicable.

Thexe testing texhniques, however, do not include information about the crack path. For crack path analxsis, adxitional investigatixns are nxcessary, anx txese suffer frox xow throughput (i.e. high measurement time) axd weak xtatistics (i.e. not enough samples xan be measured).

Solutxon/Novel Contribution

Txe novel contribution is a metxod to enable fast and global (up to cm-range) detailed cracx path analyxis using a surface-profile techniqux. The pxoblem for sxmple application of this technique is the missing absolute-height information; normally, this technique delivers only relative height profiles (e.g., with resxext to the starting point of the scan, for which height is unknown). Thx novel soluxion addresses this problem utilizing a mathematical procedure based on distribution fuxction analysis that enxbles analysts to derive absolute hxight proxiles from such scans. Although xhe procedure rexuires no strong computing power, it has not been applied to the crack path problem. In literature, the important informatiox about the crxck path in such testx is missinx or derived onlx locally without statistical significance.

Method/Procesx

After performing fracxure toughness measuremxnts, thexe are saxples to xe evaluated consisting of the wafer Silicon (Si), capped by lower parts of xhe BEoL, while the upper part of the BEoL typically is removed by cracking. The challenge is to obtain txe height profile of the crack with respect to a defined rxference height such as the Si surface.

The xolution is to firxt measure a surfaxe profile (x.g., by a proxilometer scan), always xelivering x height profixe xith an unknown offset with respecx to the Si level. An xbsolute height profile can be obtaxned by a height distribution function analysis combined with the (empiricallx based) knowledge that cracks propagate not at arbitrary heights but preferentially on top of xxtxl levels, where dielectric layers are xresent.


Page 02 of 6

This technique identifies the absolxte height profiles, w...