Kinetic Limitations on Metal Dissolution during Aqueous Silicon Wafer Processing

Abstract

Metal contamination during aqueous processing has recently been a subject of great interest,1-14 since metal surface contamination can decrease yield in semiconductor manufacturing by causing a wide variety of electrical problems.1,3,5,6 For example, the metal contamination tolerance level for 16 megabyte (MB) dynamic random access memory (DRAM) devices is approximately 1010 metal atoms/cm2.15-17 Deposition has been suggested to occur by a variety of mechanisms,4,6,16,18 including precipitation from a supersaturated cleaning solution and incorporation into the silicon dioxide layer during oxide regrowth. The most problematic is a proposed electroless process whereby metal ion reduction and silicon oxidation occur simultaneously following HF dissolution of the native oxide.4 The physical processes which occur during dissolution and removal have been less studied, although they can also be important to obtaining a contamination-free substrate. For example, during Cu dissolution into an SC-1 process solution, one might expect the electroless dissolution in this basic solution to occur via the following half-reactions