Understanding integration damage to low-k films: mechanisms and dielectric behaviour at 100kHz and 4GHz F. Iacopi 1 , O.Richard 1 , J.Van Aelst 1 , G.Mannaert 1 , V.V.Talanov 2 2 , A.Scherz , A.R.Schwartz 2 , 1 H.Bender 1 , Y.Travaly , S.H.Brongersma ,G.A.Antonelli 1 1 3 , M.Moinpour 4 , and G.Beyer 1 IMEC, Kapeldreef 75 B-3001 Leuven, Belgium; 2 Neocera Inc., Beltsville, MD; 3 Intel Corp., Portland Tech.Dev., Hillsboro, OR; 4 Intel Corp., Sta.Clara, CA. Corresponding author: Francesca Iacopi e-mail: iacopi@imec.be Phone: 32 16 28 18 46 Fax: 32 16 28 15 76 Abstract Novel in-line characterization techniques such as SAWs and a near-field microwave probe are combined to more widely studied physical and electrical off-line methodologies for the evaluation of dielectric damage. Physical characterization of the damage with EFTEM and SAWs and capacitance evaluation at 100kHz and 4GHz point out the presence of different types of low-k damage depending on the chosen patterning processes. Besides damage location (top or sidewall), the distinction between damage with and without densification is extremely important in terms of recovery and dielectric esponse at low and high frequency. r Introduction Dielectric processing damage leads to degraded electric performance and to an increase of the k value of the integrated material. This issue has been extensively investigated since it could be a showstopper for the use of ultra-low-k materials in advanced technology nodes. Nevertheless, at the moment an accurate comprehension of the mechanisms behind dielectric damage and the consequences for RC delay at user conditions are still missing. Scope of this work is to highlight the occurrence of different types of damage with distinct dielectric responses. Experimental Single damascene structures were fabricated by patterning a CVD OSG (Aurora® ULK) film 190nm thick with 16% porosity and k value around 2.6 in a medium density plasma chamber with different combinations of the etch and in-situ ash processes reported in Table 1. Etch B was specifically developed as a highly polymerizing O layer (13nm) was deposited on top of the low-k dielectric. Meander-fork structures with 50% pattern density and varying pitch were chosen as test vehicle for damage characterization. In-line measurements with Surface Acoustic Waves (SAWs) were performed prior to metallization to retrieve indications about top and sidewall densification of the patterned dielectric [1]. The acoustic waves propagated orthogonally to the dielectric lines [2], as this measurement condition leads to superior sensitivity. Coarse grain Molecular Dynamics (MD) simulations were used to support the understanding of the acoustic dispersion behaviour. Microwave (MW) capacitance measurements at high frequency (4GHz) were also performed in-line on the meander-forks prior to metallization with a near-field microwave probe system with about 10μm 2 sampling spot size [3]. This is a non-contact measurement, as indicated schematically in Fig.1, where a lumped- element scheme of the capacitance probed by the system is also shown. After metallization and CMP the capacitance of the meander-forks was measured at 100kHz with an LCR meter. The structures were imaged by TEM, to retrieve the structure dimensions used as input for k extraction from both MW and low frequency capacitance measurements. Energy Filtering TEM maps were also retrieved to highlight differences in the relative amount of Si, O and C in the patterned low-k material. 2 -free etch process. A thin SiO 2 Bottom/Top power (W) Chemistry Etch A 600/200 O 2 / Ar/CF 4 Etch B 600/200 Ar/CF 4 /N 2 /CH 2 F 2 Ash A 600/0 O 2 / CF 4 Ash B 800/0 N 2 / H 2 Table 1 Characteristics of the used etch and ash processes SiC AlCu Si probe SiC low-k HM SiC AlCu Si probe SiC AlCu Si SiC AlCu Si probe SiC low-k HM Fig.1 Schematic of the in-line measurements with the near- field microwave probe and equivalent measured capacitance.