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Method to monitor RIE damage on wafer electrically

IP.com Disclosure Number: IPCOM000235800D
Publication Date: 2014-Mar-25
Document File: 4 page(s) / 64K

Publishing Venue

The IP.com Prior Art Database

Abstract

A method of using a gated-diode structure to monitor physical damage from Reactive Ion Etching (RIE) on semiconductor wafer surfaces is set forth.

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Method to monitor RIE damage on wafer electrically

Reactive Ion Etching (RIE) is commonly used to remove layers during semiconductor chip manufacturing. To account for normal variations in thickness of the material layer to be etched, it is necessary to provide an overetch to guarantee removal of the material layer. As an example, if 100nm of material is to be removed by RIE, the thickness of the material may vary during normal manufacturing between 90nm to 110nm in thickness. Additionally, the RIE process and tool itself has variations, so additional margin must be included to account for this. So in order to guarantee that the nominally 100nm material layer is removed, a 120nm RIE may, for example, be used to account for both the material thickness and etching rate variation. The fact that the target RIE is for 120nm versus a 100nm average thickness, means this RIE process has an overetch of 20nm (120nm minus 100nm, for this particular example).

An undesired consequence of this RIE overetch is that the surface lying below the material to be etched is exposed to the RIE process that can be a harsh bombardment of etching ions, during the overetch time. This exposure to the RIE overetch often results in physical damage that degrades the electrical characteristics of the transistors and devices which are exposed during the RIE overetch. The damage can result in a variety of degration mechanisms, including resistance increase, carrier mobility reduction, or a reduction of device lifetime (reliability). T...