| With the evolution of advanced technology nodes of chip manufacturing,the critical dimensions are shrinking while the patterning processes are becoming more and more complex and demanding with regard to alignment accuracy.The edge placement errors(EPE)in photolithography-based "top-down" patterning process can easily lead to sharp increase in device failure probability and thus sharp decrease in yield.The development of area-selective deposition(ASD)for low dielectric thin films for fully self-aligned vias(FSAV)is expected to solve this problem.With the control of film thickness while maintaining low roughness of Cu surface,ASD possess advantage over the recess etch approach.Therefore,ASD is promising for advanced processing of next-generation interconnect structures.Cyclosiloxane polymers possess ultra-low dielectric constant,high breakdown field strength,and excellent mechanical properties,which can be synthesized via initiating chemical vapor deposition(iCVD).However,previously reported strategies to achieve area-selective atomic layer deposition(AS-ALD)are difficult to apply to iCVD processes due to the presence of free radicals.The main problem is the lack of surface control methods for free radical polymerization kinetics in iCVD.The main strategies that have been reported for ASD include;the differences in intrinsic properties of different materials,the directional activation of targeted growth areas and the directional passivation of non-targeted growth areas.However,the above surface modification strategies are only applicable to inorganic thin films deposited by atomic layer deposition.Therefore,it is of scientific significance to develop surface control strategies that can achieve ASD in iCVD systems.In this thesis,we developed an area-selective iCVD(AS-iCVD)method for selfaligned growth of cyclosiloxane polymer films.After surface modification with HBr/Ar and O2 plasma,Cu(0)was converted to Cu(II)on the surface.The inhibition of free radical polymerization by Cu(II)led to nucleation delay of poly(1,3,5-trimethyl-1,3,5trivinyl cyclotrisiloxane)(pV3D3)growth on Cu surface,resulting in a deposition selectivity of about 90%on SiO2 surface.We further investigated the effect of O2 plasma treatment time on the area selectivity of pV3D3 films.We found that the change of surface components affects the area selectivity of pV3D3,and that 2 minutes of O2 plasma treatment is the optimal condition with area selectivity up to ca.90%.The pV3D3 thin film deposited by AS-iCVD possesses dielectric constants in the range of 2.69-2.79,and breakdown field strengths exceeding 5 MV/cm.This thesis also studied the differences in the adsorption and surface reactions during the flow of di-tert-butyl peroxide(TBPO)and V3D3 on Cu and SiO2 surfaces.We used water contact angle and ellipsometry to investigate the deposition of pV3D3 films during the co-flow of TBPO and V3D3 without hot filaments,and confirmed the selective deposition of pV3D3 films on Cu surface.We studied the effect of substrate temperature and oxide removal on the deposition rates on Cu surface,and found that oxide removal by acetic acid followed by deposition at 80℃ led to the highest film growth rate.We further used in situ QCM to analyze the adsorption and surface reactions involving initiators and monomers on Cu and SiO2 surfaces.Combining XPS results,we confirmed that TBPO can react with Cu surfaces to generate free radicals.In addition,we also compare the co-flow and sequential flow of initiators and monomers,and found that sequential flow enabled high selectivity for a period longer than 1850 s.This study provides fundamental understanding for the development of AS-iCVD methods driven by intrinsic surface differences. |
