The removal of tough Ta, Zr or Hf based polymers selectively to aluminum is a challenging concern in the fabrication of High-K capacitors or specific metals stacks with thick Tantalum layers for example (fig.1, 2 ). Most of actual commercial chemistries only barely touch some of the toughest polymers generated by plasma etch process as seen in Fig 3. HF is sometimes employed but has shown moderate efficiency (fig 4,5) associated with a serious risk of metals and oxide consumption if not well controlled for some critical structures.

HF is commonly used to pattern amorphous or damaged HfO2 highK gates, and the selectivity to thermal silicon oxide has been studied in details by V. Paraschiv [2] showing the relative importance of each species in the etching mechanism. Moreover, in early studies around the use of HF for silicon dioxide etching, the need and the role of condensed water or alcohol together with HF vapor is well documented.[1, 3], and the detailed mechanism involved in the silicon dioxide dissolution in diluted HF is widely accepted [4]. Finally the hydration of hydrogen fluoride is not as rapid and straightforward as other halides like chlorine and Bromine [5] therefore at low water content hydrogen fluoride can be seen as nearly anhydrous solution.

This paper describes the work that has been done in collaboration with STMicroelectronics to evaluate a newly released chemistry IK 73 from TECHNIC France which combines the advantages of being nearly anhydrous and avoids the HF dissociation at any dilution ratio with water (see graph 1), for the removal of Ta, Hf and Zr based polymers after dry etch and ash, selectively to Aluminum eventually exposed.

The main features of the chemistry and its behavior on blanket films at different dilutions ratios will be first exposed. Morphological results (SEM-TEM) on various kinds of structures are presented, as illustrated in fig.6,7.

From the results obtained we conclude that it is possible to efficiently dissolve Ta, Zr, Hf based polymers (or their amorphous oxides) selectively to aluminum, thanks to TechniClean IK 73.

Reference

[1] Won Ick Jang, Chang Auck Choi, Myung Lae Lee, Chi Hoon Jun and Youn Tae Kim . J. Micromech. Microeng. 12 (2002) 297–306

[2] V. Paraschiv, M. Claes, M. R. Baklanov, W. Boullart, S. De Gendt, S. Vanhaelemeersch, Solid State Phenomena Vols. 103-104 (2005) pp 97-102

[3] Ron Hanestad ; Jeffery W. Butterbaugh ; Abdselem ben-Hamida ; Ilaria Gelmi Proc. SPIE 4557, Micromachining and Microfabrication Process Technology VII, 58 (September 28, 2001); doi:10.1117/12.442986

[4] D. Martin Knotter J. Am. Chem. Soc., 2000, 122 (18), pp 4345–4351

[5] Odde S, Mhin BJ, Lee KH, Lee HM, Tarakeshwar P, Kim KS The Journal of Physical Chemistry A 110(25):7918-24 · July 2006