| AVS 61st International Symposium & Exhibition | |
| Selective Deposition as an Enabler of Self-Alignment Focus Topic | Wednesday Sessions |
| Session SD-WeA |
| Session: | Process Development for Selective Deposition and Self-Aligned Patterning |
| Presenter: | Philippe Bézard, LTM, France |
| Authors: | P. Bézard, LTM, France G. Cunge, LTM, France E. Latu-Romain, LTM, France A. Tavernier, LTM, France R. Tiron, CEA-LETI, France X. Chevalier, Arkema, France O. Joubert, LTM - CEA/LETI, France |
| Correspondent: | Click to Email |
Vertically aligned cylinder block copolymers are often considered to be used as etching masks for hole patterning with very aggressive critical dimensions (CD) – typically sub-15nm. PS-b-PMMA, as a di-block copolymers configuration, has been thoroughly studied in the past decade [1]. The transfer strategy with PS-b-PMMA features [2] is to remove PMMA by wet or dry processes and to use PS as a mask for etching. A combination of UV and acetic acid bath has shown good results [3] but requires several specific steps as PMMA residues removal in addition to brush layer [4] and hard mask opening. An all-dry strategy would consist of trading three steps (UV, wet, PMMA residues plasma etching) with a single PMMA cylinder etching one without additional CD dispersion, providing a substantial process flow simplification for industrial purpose.
A deep understanding of both PMMA and PS etching mechanisms under various plasma conditions in terms of chemistry and ion energy is then required to overcome this challenge. Rigorous material- and plasma characterisations lead to the use of H2-based plasma chemistry rather than O2-based plasmas. Conventional oxygen-based plasmas result indeed in a poor selectivity (around 2) due to similar material composition, leading to CD degradation. Selectivity in H2-based plasma benefits from PMMA-exclusive C-O and C=O bonds which are easily broken (weakening the material) when PMMA is exposed to H2 (as evidenced by XPS and MIR results).
We will present results obtained both in synchronously-pulsed [5] and continuous wave low pressure Inductively Coupled Plasmas (ICP) in H2-based chemistry. While synchronously-pulsed ICP plasmas allow efficient brush layer opening [3], best selectivity is achieved in continuous wave ICP plasmas.
As a result, transfer of sub-15nm 60nm-deep nanoholes into silicon with about 2nm CD dispersion has been achieved without using any hard mask strategy.
[1] K.W. Guarini &al., J. Vac. Sci. Technol. B 19, 2784 (2001)
[2] R.Tiron &al., Proc. SPIE 8680, Alternative Lithographic Technologies V, 868012 (2013)
[3] P.Bezard &al., Plasma etching of sub-14nm holes in silicon using PS-b-PMMA block-copolymer masks, PESM (2014)
[4] X.Chevalier &al., Proc. SPIE 8680, Alternative Lithographic Technologies V, 868006 (2013)
[5] S.Banna &al., Journal of Vacuum Science & Technology A 30, 040801 (2012)