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A Structure For Measuring Mass Transport Effects in VLSI

IP.com Disclosure Number: IPCOM000004360D
Publication Date: 2000-Oct-13
Document File: 2 page(s) / 31K

Publishing Venue

The IP.com Prior Art Database

Abstract

A contact holes in Very Large Scale Integration (VLSI) of semiconductors become smaller and smaller, processing effects based upon geometries impact process control. One such effect is gas mass transport, where gas molecules transport differently in very narrow holes versus larger holes. This has the effect of different etch rates on different contact hole sizes. It is difficult in VLSI processing to understand this effect. The proposed structure allows for understanding the mass transport effects by varying the hole size. The varying hole sizes create sub-lithographic images by varying the overlap between two images. Scanning Electron Microscope (SEM) cross sections of the following structure allow quantitative and qualitative analysis.

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A Structure For Measuring Mass Transport Effects in VLSI

A contact holes in Very Large Scale Integration (VLSI) of semiconductors become smaller and smaller, processing effects based upon geometries impact process control. One such effect is gas mass transport, where gas molecules transport differently in very narrow holes versus larger holes. This has the effect of different etch rates on different contact hole sizes. It is difficult in VLSI processing to understand this effect. The proposed structure allows for understanding the mass transport effects by varying the hole size. The varying hole sizes create sub-lithographic images by varying the overlap between two images. Scanning Electron Microscope (SEM) cross sections of the following structure allow quantitative and qualitative analysis.

In Figure #1, cross section 100 is shown. Contact holes 130 (filled with metal) are defined in planarized oxide layer 170. Oxide layer 170 is formed over Polysilicon Gates (Polygates) 140, with oxide spacers 115, diffusions 110 and oxide filled Shallow Trench Isolation (STI) regions 105. Polygates are defined over STI to allow a continuum of oxide above and below the Polygates to study mass transport.

By varying the contact hole 130 overlap to the Polygates 140, the over etching of oxide 170 etches into the oxide spacers 115, and STI oxide regions 105. Over etch depths A , B and C are used to provide quantitative and qualitative analysis when cross-sectioned for SEM analysis. Although not shown in Figure #1, the overlap can be varied by many more Poly Gates and contact holes, and can be done to measure two dimensional overlaps to get even more two dimensional effects of mass transport.