Conformal Deposition of Dielectric Nanolaminates

Harvard University, Cambridge MA

Investigators

Abstract

Research: In previous work supported by NSF, the PI discovered a process for the rapid deposition of highly conformal coatings consisting mostly of silicon dioxide (silica). The method uses alternating layer deposition (ADL) from two different vapors supplied alternately to a surface to make a coating that is laminated on the nanometer scale. Each layer is formed with a highly precise atomic level of control over thickness, smoothness, conformality and composition. The PI proposes theories that should permit him to extend the capability of this deposition method in five different ways: 1. Lower dielectric constant. Carbon-doping of the silica films will be used to lower the dielectric constant (k). Carbon will be introduced into the coating by chemical modification of the precursors. 2. Selective sealing of pores. By use of the catalytic character of the ALD process, the PI plans to deposit the carbon-doped low-k material to seal the pores near the surface of the ultra-low-k dielectrics, without placing any material inside interior pores. This process will prevent the electrical leakage that occurs after deposition of electrically conductive materials onto ultra-low-k dielectric materials. 3. Selective trench filling. By another use of the catalytic character of the ALD process, the PI plans to fill the insides of narrow trenches with low-k material, while keeping adjacent flat surfaces free of any deposit. 4. Higher growth rate. Using his theoretical mechanism for the ALD process, he plans to further increase growth rate by the synthesis and testing of a new chemical precursor. 5. ALD of optical multiplayer filters. The ALD process has the right characteristics to make superior low-index layers for optical multi-layer filters, even on non-planar surfaces such as those found on lenses or focusing mirrors. A method is also being considered for ALD of layers of the other material needed for these filters. Broad Impact: Each of the five planned activities could have important impact on critical needs in the microelectronics and optical communications industries: 1. This process would extend the unique capabilities of ALD to make highly conformal low-k insulators needed in microelectronics. 2. Selective sealing of surface pores on ultra-low-k dielectrics is needed to provide the smooth surfaces needed for making interconnections in microeletronics. 3. Selective trench filling would allow the filling of isolated trenches between microelectronic transistors without the use of the expensive chemical/mechanical polishing step normally needed to remove excess silica from the top surface. 4. Achievement of still higher deposition rates will make the ALD process more cost-effective for all practical applications. 5. Wavelength-selective filters with higher quality are needed in fields such as integrated optics and electronics, and optical communications.