Papers by Author: Chris Reid

Abstract: The use of integration of copper interconnects in semiconductor devices has greatly advanced the development of integrated circuits and has enabled ever higher device densities. Unfortunately the oxides of copper are poorly suited to semiconductor manufacture. As Cu (I) and Cu (II) oxides are not self-limiting they can pose serious issues from a cleaning and queue time management perspective. In both post-etch and post-CMP cleaning applications it is critical that both types of Cu oxide are removed without damage to either Cu or the dielectric. With the most advanced sub 32nm nodes simply removing the oxides is not sufficient; their re-growth must also be prevented using surface passivation.

Abstract: Iminodiacetic acid (IMDA), NH(CH2CO2H)2, whose molecular structure is shown in figure 1, is a small molecule but has a very large scope for interacting with copper due to its two carboxylic acid and imine functionalities, which have been shown to bind strongly to copper [1,2,3]. The electronegative oxygen and nitrogen atoms present also make this a good candidate for hydrogen bonding, which often leads to very stable ordered two dimensional (2D) structures being formed across surfaces.

Abstract: The time and stoichiometric ratio dependence on dissolution of Cu from Cu(I)O and Cu(II)O and metallic Cu was investigated for a series of known Cu chelators. This was monitored by ICP-OES and UV-VIS. A notable difference in the rate of reaction for Cu(I)O vs Cu(II)O was observed and the impact of a copper adduct precipitating from solution discussed as this may present a redeposition issue for Cu surface cleaning. Additionally these chelators were found to selectively favour Cu0 and typically showed higher solution levels of Cu when exposed to the oxides.

Abstract: This paper described the development of two types of Advanced Aqueous Cleaners (AAC™) for Aluminium (Al) Post Etch Residue (PER) removal. The first approach was developed to address a need for cleaning chemistries with a smaller environmental footprint that were also able to clean at significantly lower process times and temperatures than conventional wet chemical cleans. A broad screening experiment was undertaken during which it was highlighted it was possible to clean Al lines in an acidic region though this technology was not extendable to cleaning via features. However, the study emphasised the need to use a selective alkaline reducing formulation to maintain a high cleaning efficiency for the more complex residues formed during via etch. The novel Back End Of Line (BEOL) PER cleaners presented in this paper were optimised using a statistical Design Of Experiment (DOE) to perform at lower temperatures and shorter process times and were Fluoride and organic solvent free while containing a minimum of 80%wt water.