Cleaning Aspects of Novel Materials after CMP

Abstract

High mobility channel materials such as Ge and III-V compound semiconductors, are explored for the sub-22nm technology node. In order to allow process integration and full scale manufacturing of these materials, they need to be introduced by epitaxial growth in narrow trenches on silicon carrier wafers. Consequently, CMP is needed to flatten the surface before constructing the gate stack. Similarly to silicon, trace contamination is expected to have a detrimental effect on the devices and therefore, an appropriate cleaning of the wafer consisting of areas with mixed substrates is an absolute requisite. This involves the removal of particulate, metallic and organic contamination while controlling surface etching of these novel materials integrated on the silicon wafer. This will be addressed in this paper and allows the development of efficient post-CMP cleaning strategies.

Chemical Mechanical Polishing of InP

“…One possible driving force for such a bond formation between Si on the silica particles, which carry a partial positive charge when bound to the more electronegative oxygen atoms, and the In on the InP surface is the lone pair of electrons on the In atoms. Vos et al, 35 showed, using X-ray Photoelectron Spectroscopy (XPS) analysis, that the ratio of In to P atoms for InP wafer coupons, first dipped in acidic aqueous solutions and then dried, is ∼1.26. This suggests a relative loss of P atoms from the InP surface in acidic pH regions.…”

Cleaning Challenges and Solutions for Advanced Technology Nodes

“…Figure 8. Removal of 30 nm SiO2 slurry particles from Ge after 5 hours of storage in clean room air as function of substrate loss using various chemistries [7].…”

“…Etch rates of InP (nm/min) in different cleaning chemistries[7].On the InP the following oxides have been identified on the surface by XPS: InPO 4 , InPO 3 and In 2 O 3 . The removal of these residual oxides from the surface is still under investigation.…”