Browsing by Author "Cho, AT"

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Alkylation of nanoporous silica thin films by high density plasma chemical vapor deposition of a-SIC : H
(2004-05-01)
Pan, FM
;
Wu, BW
;
Cho, AT
;
Tsai, KC
;
Tsai, TG
Film stacks of a-SiC:H and molecularly templated nanoporous silica thin films have been prepared, and alkylation of pore surfaces of the nanoporous silica layer by the a-SiC:H layer was studied. The a-SiC:H thin films were deposited by high-density plasma chemical vapor deposition (HDP-CVD) using trimethylsilane (3MS) as the precursor. Carbon is found to uniformly distribute in the thin nanoporous silica film, and the carbon content in the nanoporous film decreases with increasing the a-SiC:H deposition temperature. We used the modified Sanderson formalism to estimate the corresponding Si(2p) and C(1s) electron energies in x-ray photoelectron spectra (XPS) for possible terminal species on pore surfaces in the nanoporous silica layer. According to the XPS analysis and thermal desorption mass spectroscopy, the terminal species are probably in the chemical form of alkoxyl structures. The alkoxyl terminal groups introduced into the nanoporous silica thin film are believed to stem from hydrocarbons trapped in microvoids in the a-SiC:H film, which are formed during the HDP-CVD deposition. The terminal alkoxyl groups in the nanoporous silica layer can greatly enhance the hydrophobicity of the nanoporous silica dielectric, and hence improve the dielectric property of the film stack of a-SiC:H/nanoporous silica. An effective dielectric constant smaller than 1.7 can be obtained for the film stacks. (C) 2004 American Vacuum Society.
Effect of trimethylsilylation on the film stress of mesoporous silica ultralow-k film stacks
(2006)
Chen, JY
;
Pan, FM
;
Lin, DX
;
Cho, AT
;
Chao, KJ
The film stress of the ultralow-k mesoporous silica thin film and the alpha-SiC:H/ mesoporous silica film stack was studied. The as-calcined mesoporous silica exhibits a tensile film stress due to its volume contraction during bake and calcination. Trimethylsilylation of the mesoporous film results in a spring-back effect and thereby improves the mechanical properties of the porous film. Deposition of a plasma-assisted alpha-SiC:H layer on the mesoporous silica thin film can also relieve the tensile stress, and even made the film stack become compressively stressed. This is ascribed to the stress compensation and alkoxylation occurring during the alpha-SiC:H deposition.
Emission of bright blue light from mesoporous silica with dense Si (Ge) nanocrystals
(2005)
Cho, AT
;
Shieh, JM
;
Shieh, J
;
Lai, YF
;
Dai, BT
Three-dimensional Si (Ge) nanocrystals (NCs) were dispersed within the nanopores of mesoporous silica films by high-density plasma (HDP), low-density plasma, or implantation. Surface states of the resulting Si (Ge) NCs/silica arrays initiate blue-white photoluminescence (PL). HDP makes reactive species highly mobile and enables deposited NCs bonded with pore-wall well, therefore, efficiently constructing photoemission arrays. The mean density of HDP-synthesized semiconducting NCs is as high as 1 x 10(18)/cm(3). Accordingly, blue PL of arrays obtained with HDP, which is 4- 7 times stronger than those obtained with other methods, exhibits quantum-efficiency of 1%, near the reported value for green-to-red light emission from quantum-confined Si NCs. © 2005 The Electrochemical Society. All rights reserved.
Microstructure and mechanical properties of surfactant templated nanoporous silica thin films: Effect of methylsilylation
(2003-06-01)
Chen, JY
;
Pan, FM
;
Cho, AT
;
Chao, KJ
;
Tsai, TG
Microstructural and mechanical properties of organic surfactant templated nanoporous thin silica films have been studied by X-ray diffraction, Fourier transform infrared spectroscopy, and nanoindentation. Compared with many other porous low-k dielectrics, the self-assembled molecularly templated nanoporous silica films demonstrate better mechanical properties. This is ascribed to the presence of a well-ordered pore channel structure in the nanoporous silica thin films. Hardness and elastic modulus are strongly dependent on film preparation and modification methods. Trimethylsilylation by hexamethylsilazane vapor treatment effectively enhances the mechanical strength of the nanoporous silica films. When the sol precursor solution is mixed with trimethylchlorosilane (TMCS), the resulting nanoporous films have a weaker mechanical strength. The pore channel structure of the nanoporous silica film becomes less ordered for the TMCS derivatized nanoporous films. In addition, the chemical structure in the silica solid matrix of the TMCS derivatized films is more disordered than those without TMCS modification. The nanoindentation measurement results are discussed in terms of the pore microstructure of the nanoporous silica network and the springback effect due to the presence of trimethylsilyl groups in the nanopores. (C) 2003 The Electrochemical Society.
Stable blue luminescence from mesoporous silica films
(2004)
Shieh, JM
;
Cho, AT
;
Lai, YF
;
Dai, BT
;
Pan, FM
This study investigates how blue (similar to 460 nm) photoluminescence (PL) from mesoporous silica (MS) films depends on the nanostructure and chemistry of the pores. Reducing pore-size and pore-wall can increase the total area of the pore-surfaces, and therefore the number of radiative recombination centers, within the MS matrix, enhancing PL efficiency. Moreover, the number of silianol groups on pore-surfaces, which absorb moisture and degrade the PL of the MS films, is greatly reduced by silylating MS with hydrophobicity, yielding long-term stable luminescence. The quantum-efficiency of PL and the electroluminescence of the MS films are measured about 5.0 x 10(-4) and 1.0 x 10(-6), respectively. (C) 2004 The Electrochemical Society.
The preparation of mesoporous silica ultra-low-k film using ozone ashing treatment
(2005-07-01)
Cho, AT
;
Pan, FM
;
Chao, KJ
;
Liu, PH
;
Chen, JY
The ozone ash treatment has been demonstrated to effectively remove the organic template at 200-300 degrees C as well as to enhance the mechanical strength of mesoporous silica films. The resulting films are of ordered pore structure, strong mechanical strength, and smooth surface. After reacting with hexamethyidisilazane, the silica film has been modified to hydrophobic from hydrophilic and exhibits an ultra-low dielectric constant (k <= 2) and a low leakage current density (10(-7) A/cm(2)) with good electrical reliability. (c) 2005 Elsevier B.V. All rights reserved.
Thermal stability of trimethylsilylated mesoporous silica thin films as the ultralow-k dielectric for copper interconnects
(2005-09-01)
Chen, JY
;
Pan, FM
;
Chang, L
;
Cho, AT
;
Chao, KJ
Surfactant templated mesoporous silica thin films were prepared as the intermetal dielectric for ultralarge scaled integrated circuit application, and the thermal and chemical stability of the Cu/nitrided Ta/mesoporous silica film stack on the Si wafer was studied. Trimethylsilylation of the mesoporous silica thin film by hexamethyldisilazane vapor treatment significantly improves hydrophobicity of the mesoporous dielectric, and a dielectric constant (k) smaller than 2 can be obtained for the thin film. According to Fourier transform infrared spectroscopy and thermal desorption spectroscopy, decomposition of trimethylsilyl groups on the pore surface becomes significant at temperatures larger than 400 degrees C. However, when the metallized film stack was annealed at temperatures higher than 400 degrees C, the film stack shows little delamination between layers and still retains smooth interfaces according to Auger electron spectroscopy and transmission electron microscopy analyses. Ta2C nanoparticles were found to exist at the Ta(N)/mesoporous silica interface of the film stack annealed at 600 degrees C. Bias-temperature stress test of the metallized film stack shows little Cu diffusion into the mesoporous dielectric layer. (c) 2005 American Vacuum Society.