A Study of Atomic Layer Deposition and Reactive Plasma Compatibilitywith Mesoporous Organosilicate Glass Films
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A STUDY OF ATOMIC LAYER DEPOSITION AND REACTIVE PLASMA COMPATIBILITY WITH MESOPOROUS ORGANOSILICATE GLASS FILMS E. Todd Ryan*, Melissa Freeman†, Lynne Svedberg†, J.J. Lee†, Todd Guenther†, Jim Connor†, Katie Yu†, Jianing Sun‡, David W. Gidley‡ * Advanced Micro Devices, 1 AMD Place, Sunnyvale, CA 94088 † Motorola, APRDL, 3501 Ed Bluestein Blvd., Austin, TX 78721 ‡ University of Michigan, Department of Physics, Ann Arbor, MI, 48109 ABSTRACT The compatibility of ALD and CVD metal deposition with mesoporous and microporous carbon-doped organosilicate glass (OSG) films was examined. Blanket film studies using TEM, TOF-SIMS, and positron lifetime spectroscopy demonstrate that ALD W and TaN penetrate deep into the mesoporous film via the film’s connected pore structure. In contrast, metal penetration into microporous OSG films was not observed. He and NH3 plasma pretreatments to the mesoporous OSG film surface did not seal the mesopores to ALD metal penetration, but the plasmas did damage the bulk of the mesoporous OSG film with varying severity. The results indicate that porosity, pore size, and/or pore structure regulate ALD/CVD precursor diffusion and that ALD metal deposition is a good probe of pore sealing strategies. INTRODUCTION Low dielectric constant (low-κ) films and barrier metal deposition by atomic layer deposition (ALD) and chemical vapor deposition (CVD) are rapidly developing technologies for sub-90nm integrated circuit (IC) generations1. However, if the low-κ film is mesoporous (2-50nm diameter pores), difficulties in integrating these technologies will be encountered because the highly conformal CVD and ALD monolayer deposition processes can coat the pore walls or leave metal precursors inside the mesopores. This is especially true if the mesopores are interconnected throughout the film. Barrier materials around copper lines are necessary for good interconnect reliability. The barrier metals commonly used have a resistivity higher than that of copper. As copper lines scale smaller with each IC technology generation, the thickness of barrier layers must scale thinner. Otherwise, the total line resistance increases to unacceptable levels. The semiconductor industry is reaching the limits of physical vapor deposition (PVD) for barrier metals because it is difficult for PVD to deposit sufficiently conformal metal liners in high aspect ratio features. Thus CVD and ALD are attractive alternatives because they enable the deposition of very thin conformal metal layers. Films as thin as one monolayer can be deposited by ALD2. However, it is this feature of ALD that makes it problematic on mesoporous films. If the pores are large enough to allow easy diffusion of the CVD or ALD precursors, then metal can deposit inside the pores throughout the mesoporous film, or the precursors can get trapped inside the pores. Some reactive precursors may also damage the dielectric film. Thus, barrier metal deposition onto porous films must be better understood. EXPERIMENTAL
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