Characterization of the impact of plasma treatments and wet cleaning on a porous low k material W. Puyrenier a, * , V. Rouessac b , L. Broussous a , D. Re ´biscoul c , A. Ayral b a STMicroelectronics, 850 rue Jean Monnet, 38926 Crolles Cedex, France b Institut Europe ´en des Membranes-UMR 5635 CNRS-ENSCM-UMII, CC047, Universite ´ Montpellier II, 2 place Euge `ne Bataillon, 34095 Montpellier Cedex 5, France c CEA Grenoble-LETI, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France Available online 19 October 2006 Abstract In the back end of line (BEOL) interconnections for 65 nm and beyond technology nodes, the integration of porous low dielectric constant (low k) materials is now needed to improve signal propagation. Porosity in low k films drives new challenges concerning the different steps of the integration. Thus, the characterization of porosity is needed to develop and optimize low k dielectric films, but also to characterize process steps that may impact the porosity: etch and cleaning processes. In this paper, the impact of several plasma treat- ments and wet cleaning process on the dielectric material were characterized. All the plasma treatments tested lead to the formation of a thin and dense layer at the material surface with different porosities (pore sealing or open porosity). The cleaning compatibility depends on this thin zone: pore sealing limits water-uptake but can lead to increase the dielectric constant. Ó 2006 Published by Elsevier B.V. Keywords: Low k; Porosity; Plasma treatments; Wet cleaning; Compatibility; Characterization 1. Introduction In 65 nm and 45 nm BEOL, porous dielectric materials are used between copper interconnections for their insula- tor properties. The porosity in low k films drives new chal- lenges at the different steps of the integration, among them, plasma treatments and cleaning process have to be compat- ible with porous low k material [1]. The main purpose of this paper is to study the impact of several plasma treat- ments [2,3] and of an aqueous cleaning [4] on a porous low k material deposited by plasma enhanced chemical vapour deposition (PECVD). In order to study those impacts, the morphology and the structural modifications of the low k material, induced by the plasma treatments and the aqueous cleaning, were characterized on blanket wafers. Two plasma treatments were used in order to simulate the interface between the low k and the next layer: surface preparation for hard mask and oxide deposition. Two other plasma treatments were performed to simulate the actual surface of pattern trench wall. A post-etch cleaning was also performed on plasma treated samples. The evolution of the thickness, the porosity and the structure of the treated low k material were studied. Finally, the impact on dielectric constant was also discussed. 2. Experimental The as-deposited porous low k material is a SiOCH film of 160 nm deposited by PECVD on a 300 mm silicon sub- strate. The plasma treatments tested on the low k material (blanket wafer) are presented in Table 1. Their potential uses in the integration scheme are also indicated. The impact of an aqueous cleaning process [6,7] (diluted HF 0.1%, labeled dHF) is tested on plasma treated mate- rial. The cleaning process (clean, rinse and dry) was per- 0167-9317/$ - see front matter Ó 2006 Published by Elsevier B.V. doi:10.1016/j.mee.2006.10.024 * Corresponding author. Tel.: +33 4 38 92 29 46. E-mail address: wilfried.puyrenier@st.com (W. Puyrenier). www.elsevier.com/locate/mee Microelectronic Engineering 83 (2006) 2314–2318