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Process Development
Published in Michael G. Pecht, Riko Radojcic, Gopal Rao, Guidebook for Managing Silicon Chip Reliability, 2017
Michael G. Pecht, Riko Radojcic, Gopal Rao
A dielectric layer is needed between polysilicon and the first metal for insulating polysilicon interconnects from metal interconnects. Current technologies use a metal silicide to lower contact resistance and these films are susceptible to degradation under high temperature conditions. Therefore, borophosphosilicate glass (BPSG) processing and its reflow must not degrade the silicide layers or alter the junction depths of the transistors. [Penning de Vries and Osinski 1989, Burmester et al. 1989]. In order to satisfy this requirement, BPSG has replaced phophosilicate glass (PSG) as an interlevel-dielectric material. PSG films require high temperatures of around 1000°C for reflow and also require a high concentration of phosphorus to improve the flow. The high phosphorous concentrations cause a whole new set of problems, for example, metal corrosion. To decrease the reflow temperature of the PSG films, the oxide is doped with a boron compound. Lowering of the temperature is achieved by addition of boron which makes BPSG quite compatible with the current submicron technologies. The primary function of the phosphorous in BPSG is to protect transistors from mobile ion contamination such as sodium. It has been shown [Kern and Smeltzer 1985] that BPG films getter (or trap) NA+and other mobile ion contaminants similar to PSG films.
Near-infrared luminescent colloidal silicon nanocrystals
Published in Klaus D. Sattler, Silicon Nanomaterials Sourcebook, 2017
Hiroshi Sugimoto, Minoru Fujii
In the conventional synthesis approach discussed so far, a stable colloidal solution is produced only by properly functionalizing the surface of nanocrystals with organic ligands. Recently, a new type of colloidal Si nanocrystals that do not have organic ligands on the surface have been developed. The preparation procedure is summarized in Figure 17.4. Si-rich borophosphosilicate glasses (BPSG) are first prepared by cosputtering of Si, SiO2, B2O3, and P2O5 (Sugimoto et al. 2012), or HSQ with dopant acids (H3BO3 and H3PO4) (Sugimoto et al. 2014). By annealing the Si-rich BPSG, boron (B) and phosphorus (P) codoped Si nanocrystals are grown in BPSG, and they are liberated in solution by the HF etching. The B and P codoped Si nanocrystals are dispersible in alcohol or water, which is particularly important for the bio-applications, without organic ligands (Sugimoto et al. 2012). The high solution dispersibility arises from the negative surface potential induced by codoping. The size of codoped colloidal Si nanocrystals can be controlled in a wide range by the growth temperature (Sugimoto et al. 2013).
Film Deposition: Dielectric, Polysilicon and Metallization
Published in Kumar Shubham, Ankaj Gupta, Integrated Circuit Fabrication, 2021
Fabricating IC requires different kinds of thin films which can be classified into five groups: a) epitaxy layers, b) thermal oxides c) dielectric layers d) polycrystalline silicon e) metal films. The growth of epitaxial layer and thermal oxides were discussed in chapter 2 and chapter 3 respectively. Dielectric layers such as Silicon dioxide (SiO2) and silicon nitride (Si3N4) are used for insulation between conducting layers as masks for diffusion and ion implantation, for covering doped films to prevent the loss of dopants as well as for passivation to protect devices from impurities, moisture, and scratches. Phosphorus-doped silicon dioxide, commonly referred to as P-glass or phosphosilicate glass (PSG), is especially useful as a passivation layer because it inhibits the diffusion of impurities (such as Na), and it softens and flows at 950°C to 1100°C to create a smooth topography that is beneficial for depositing metals. Borophosphosilicate glass (BPSG), formed by incorporating both boron and phosphorus into the glass, flows at even lower temperatures between 850°C and 950°C. The smaller phosphorus content in BPSG reduces the severity of aluminum corrosion in the presence of moisture. Si3N4 is a barrier to Na diffusion, is nearly impervious to moisture, and has a low oxidation rate. The local oxidation of silicon (LOCOS) process also uses Si3N4 as a mask. The patterned Si3N4 will prevent the underlying silicon from oxidation but leave the exposed silicon to be oxidized. Si3N4 is also used as the dielectric for DRAM MOS capacitors when it combines with SiO2.
Mechanical adhesion of SiO2 thin films onto polymeric substrates
Published in Surface Engineering, 2018
C. Ho, J. Alexis, O. Dalverny, Y. Balcaen, A. Dehoux, S. Châtel, B. Faure
The total number of buckles measured on three different samples per configuration is, respectively, 9, 31 and 23 for sample type A, B and C. Width and height of buckles are measured at a strain before degradation of buckles, that is a strain of 4.5% for sample A, 3.3% for sample B and 4.9% for sample C. Calculated energy release rates using Hutchinson and Suo model range from 0.1 to 1 J m−2 for SiO2 Type A, 1.5 to 3.5 J m−2 for SiO2 Type B and from 1.7 to 3 J m−2 for SiO2 Type C , which is in the same order of magnitude as adhesion energies found in the literature; for example, 1.9 to 2.7 J m−2 for Tungsten-Titanium (WTi) film on borophosphosilicate glass (BPSG) substrates or 4.3 to 6.3 J m−2 for ITO layers on Hard coat on Acrylite substrate [21,22].