High-Performance Siloxane/Carbosilane Hybrid Benzocyclobutene Resins

In recent years,ultralarge-scale integrated circuit（ULSI）has increasingly demanded high thermal stability and low dielectric constant of dielectric materials used in interlayer encapsulation.Benzocyclobutene（BCB）resins have been widely used in the electronic field as a new generation of high-performance materials due to their excellent electrothermal properties and the unique chemical properties of the thermo-crosslinking BCB units.Silacyclobutane is a kind of monomer that can be used to synthesize polycarbosilane by anionic ring opening,thermal ring opening or transition-metal catalyzing ring opening.In this thesis,based on the special structures of BCB and silacyclobutane,three kinds of curing resins were designed and prepared,which were the resins of BCB as side chain and polycarbosilane as main chain,the hybrid resins of polycarbosilane containing BCB groups introduced with BCB modified POSS（BCB-POSS）and divinyl tetramethyl disiloxane-bis-benzocyclobutene（DVS-BCB）prepolymer,respectively.The thermal stability and dielectric properties of the three kinds of resins were investigated.The results could provide more ideas for researching low dielectric materials in the field of microelectronics.1.As a kind of all-benzocyclobutene functionalized monomer,1,1-dibenzocyclobutene-1-silacyclobutane（DBCBSCB）was synthesized.All-benzocyclobutene functionalized polycarbosilanes and the derived copolymers were successfully prepared via ring-opening polymerization（ROP）of DBCBSCB and 1,1-diphenylsiletane（DPSCB）using Karstedt’s catalyst.The results of differential scanning calorimeter（DSC）and Fourier transform infrared（FTIR）indicated that the BCB functional groups on the polycarbosilane side chain could open the rings at high temperature and form the cured resin through thermal cross-linking.With increasing the copolymerization ratios of DBCBSCB and DPSCB,the5%weight loss temperature(T_5%)of cured resins was increased from 450°C to 506°C under a nitrogen atmosphere,while the dielectric constant（k）was decreased from 2.60 to2.42 at 10 MHz.Moreover,the nano-indentation test results showed that the mechanical properties of the cured resins also improved with the increasing of the molar ratio of DBCBSCB and DPSCB.The elastic modulus was increased from 3.6 GPa to 6.3 GPa,and the average hardness was increased from 0.16 GPa to 0.69 GPa.2.The ring-opening polymerization of 1-methyl-1-（4-benzocyclobutenyl）silacyclobutane（4-MSCBBCB）and 1-methyl-1-phenylsilacyclobutane（1-MPSCB）was carried out.The copolymer P（4-MB-co-1-MP）was used as the matrix material,which was physically blended with BCB-POSS and DVS-BCB prepolymer,respectively.The hybrid materials of P（4-MB-co-1-MP）/BCB-POSS and P（4-MB-co-1-MP）/DVS-BCB were prepared by thermal cross-linking curing.The results showed that the thermal stability of the cured resins was improved and the dielectric constant of the materials could be effectively reduced compared with the matrix material,because BCB-POSS was doped into the cured resins.When the mass percent of BCB-POSS in the copolymer was improved to 30%,T_5%was up to 465℃and the dielectric constant as low as 2.36（10 MHz）.With increasing of the mass percent of BCB-POSS,the thermal stability and dielectric properties of the blending materials were improved obviously.With introducing DVS-BCB prepolymer into blending materials,the dielectric constant was slightly increased,and the thermal stability was improved.When the mass percent of DVS-BCB prepolymer in the copolymer was increased to 30%,T_5%was up to 464°C and the dielectric constant was slightly increased to 2.65 at 10 MHz.In summary,the siloxane/carbosilane hybrid organosilicone resins have excellent thermal stability and low dielectric constant,signifying that they could be potentially used in the field of microelectronics.