Impact of low-k structure and porosity on etch processes

Abstract

International audienc

Probing the microporosity of low-k organosilica films: MP and t-plot methods applied to ellipsometric porosimetry data

“…The Lorentz-Lorenz optical model [12] gives the total porosity probed by the gas molecules while the Kelvin equation can be used to relate the condensation pressure to the mesopore size (2e50 nm). EP is now routinely used for the characterization of mesoporous low-k materials [13]. A limitation of this technique based on capillary condensation is its inability to deal with micropores (<2 nm) which are often present in thin films such as in new generations of PECVD-deposited low-k materials.…”

Toward Successful Integration of Porous Low-k Materials: Strategies Addressing Plasma Damage

“…In case of the latter, the huge increase in accessible surface area leads to integration related damage, such as material modification occurring during exposure to plasma and wet chemical processes. 5,[24][25][26][27][28] Chemically, such damage typically corresponds to a loss of carbon groups and the formation of Si-OH units, see Figure 1. As a result, the insulator electrical properties, such as dielectric constant, leakage current and breakdown voltage are significantly compromised.…”

The efficacy of post porosity plasma protection against vacuum-ultraviolet damage in porous low-k materials

“…Prior to each experiment, a chamber cleaning step (O 2 plasma) and a seasoning process on a bare SiO 2 wafer were performed to ensure process reproducibility. The etch process was performed at 200 mT with 200 sccm Ar, 45 sccm CF 4 , 5 sccm CH 2 F 2 , 600 W of plasma power, and 20 G of magnetic field for 20 s. The oxygen based process is performed at 75 mT with 250 sccm O 2 and 200 W of plasma power without magnetic field for 30 s. Both plasma processes have already been investigated for porous low-k etching 11,18,19 and for resist stripping, 10,20 respectively.…”

“…[2][3][4][5][6][7][8][9] Second, highly porous low-k materials are a lot more prone to plasma damage due to a huge increase in accessible surface area. [10][11][12][13] Over the past 15 years, a lot of efforts have been devised to either prevent or mitigate plasma damage. 14 Among them, post-porosity plasma protection (P4) is the only strategy that takes advantage of the increasing porosity with decreasing dielectric constant in low-k materials.…”