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Film Deposition: Dielectric, Polysilicon and Metallization
Published in Kumar Shubham, Ankaj Gupta, Integrated Circuit Fabrication, 2021
Polysilicon can be doped by adding phosphine, arsine, or diborane to the reactants (in-situ doping). Adding diborane causes a large increase in the deposition rate because diborane forms borane radicals, BH3, that catalyze gas-phase reactions and increase the deposition rate. In contrast, adding phosphine or arsine causes a rapid reduction in the deposition rate, because phosphine or arsine is strongly adsorbed on the silicon substrate surface thereby inhibiting the dissociative chemisorption of SiH4. Despite the poorer thickness uniformity across a wafer when dopants are incorporated, uniformity can be maintained by controlling precisely the flow of reactant gases around the samples.
Block catiomer with flexible cationic segment enhances complexation with siRNA and the delivery performance in vitro
Published in Science and Technology of Advanced Materials, 2021
Wenqian Yang, Takuya Miyazaki, Pengwen Chen, Taehun Hong, Mitsuru Naito, Yuji Miyahara, Akira Matsumoto, Kazunori Kataoka, Kanjiro Miyata, Horacio Cabral
PEG-PGBA block copolymer was synthesized by ROP and followed by brown hydroboration-amination. Briefly, MeO-PEG-OH (Mn = 12 kDa, 0.0083 mmol, 100 mg) was dissolved in benzene and frozen dried under vacuum. The polymer was then dissolved in 9 mL toluene. Then, 1, 2-epoxy-5-hexene (0.415 mmol, 46.7 μL) was added to the solution and followed by addition of iBu3Al (11 μmol, 11 μL) under argon atmosphere. The mixture was stirred at room temperature for 24 h. The reaction was stopped by adding excess amount of ethanol (2 mL). After that, the polymer was precipitated in cold ether to obtain α-methoxy-poly(ethylene glycol)-poly(glycidyl butene) (PEG-PGB) block copolymer. Brown hydroboration-amination was performed by dissolving PEG-PGB (4.8 μmol, 76.2 mg) in 6.8 mL THF. Then, the borane tetrahydrofuran complex (BH3-THF) (2.8 mmol, 3.2 mL) was added. The mixture was stirred for 3 h. After this, HOSA (2.8 mmol, 320 mg) was added to the solution. Finally, the mixture was stirred for another 3 h, and precipitated in cold ether to obtain PEG-PGBA. The DP of PGBA segments in PEG-PGBA was determined to be 40 units from the 1H-NMR (D2O; 25°C) spectrum based on the peak intensity ratio of -O-CH3 (δ = 3.39 ppm) protons in PEG side chains to -CH2-CH2-CH2-CH2-NH2 (δ = 1.25–1.53 ppm) protons in PGBA side chain (Supplementary Figure 2). The amine in the obtained polymer was estimated from 1H-NMR spectrum based on the peak intensity ratio of -O-CH3 (δ = 3.39 ppm) protons in PEG side to -CH2-NH2 (δ = 2.69 ppm) in PGBA side chain (Supplementary Figure 2).