Chemical Treatment of Low-k Dielectric Surfaces for Patterning of Thin Solid Films in Microelectronic Applications

Abstract

A protocol has been developed to selectively process low-k SiCOH dielectric substrates in order to activate or deactivate them toward the deposition of thin solid films by chemical (CVD or ALD) means. The original SiCOH surfaces are hydrophobic, an indication that they are alkyl- rather than silanol-terminated and that, consequently, they are fairly unreactive. However, the chemical-mechanical polishing (CMP) sometimes done during microelectronics fabrication renders them hydrophilic and reactive. It was shown here that silylation of the CMP-treated surfaces with any of a number of well-known silylation agents such as HMDS, ODTS, or OTS caps the reactive silanol surface groups and turns them back to being hydrophilic and unreactive. Further exposure of any of the passivated surfaces to a combination of ozone and UV radiation reinstates their hydrophilicity and chemical activity. Importantly, it was also demonstrated that all these changes could be induced without altering the original mechanical, optical, or electrical properties of the samples: atomic force microscopy (AFM) images show no increase in roughness, ellipsometry measurements yield the same values for the index of refraction and dielectric constant, and infrared absorption spectroscopy attests to the preservation of the organic fragments present in the original SiCOH samples. The chemical selectivity of the resulting surfaces was tested for the atomic layer deposition (ALD) of HfO2 films, which could be grown only on the UV/O3 treated substrates.

Review—Investigation and Review of the Thermal, Mechanical, Electrical, Optical, and Structural Properties of Atomic Layer Deposited High-kDielectrics: Beryllium Oxide, Aluminum Oxide, Hafnium Oxide, and Aluminum Nitride

“…Electrical and optical properties.- Table II 18,190,191 AlN (RI = 1.8-2.2, k = 5.7-9.5), 84,86,88,[97][98][99][100][101] and BeO films (RI = 1.67-1.72, k = 6.5-6.8). 184,192 Relative to SiO 2 , all the investigated dielectrics have substantially higher values of RI and k. Relative to SiN:H, however, only HfO 2 has a significantly higher RI and k.…”

Sequential Regeneration of Self‐Assembled Monolayers for Highly Selective Atomic Layer Deposition

“…Previous studies have achieved area selective deposition of thin films using methods such as relying on inherent selectivity differences between different surface materials, choosing precursors that enhance or delay the growth on one surface versus another, using an unreactive polymer film as a blocking layer in the regions where ALD is not desired or precursor infiltration in polymers . However, more commonly, the surface of the substrate is chemically modified with self‐assembled monolayers (SAMs) . These organic monolayer films form spontaneously on solid surfaces and are important in the fabrication of micro‐ and nanostructures.…”

Nanoscale selective area atomic layer deposition of TiO2using e-beam patterned polymers

“…7, So far, majority of the AS-ALD studies have been performed using area-deactivated approach where mostly selfassembled monolayers (SAMs) are utilized as the growthblocking layers by covering the chemically reactive sites on the substrate and exposing non-reactive groups. 7,9,23,27,[29][30][31][32][33][34][35][36][37][38][39][40] Alkyl silanes e.g., alkyl trichlorosilanes, alkyl triethoxysilanes, etc. have been exploited as mono-layered surface modiers to block ALD nucleation of various metal oxide thin lms and metallic nanoparticles/thin lms.…”