绝缘体上硅场效应晶体管热导率尺度效应模型

Scale Effect Model of Thermal Conductivity for Silicon-on-Insulator Field Effect Transistors

针对硅微纳米薄膜热导率存在严重尺度效应的问题,提出一种等效边界散射自由程近似的全耗尽绝缘体上硅(FD SOI)金属氧化物半导体场效应晶体管(MOSFET)硅薄膜热导率尺度效应模型。探讨硅材料内声子散射机理,量化考虑束缚态与自由态电子影响的声子弛豫时间,推导得到硅材料热导率解析模型;深入研究声子边界散射机制,近似求解衡量尺度效应的衰减因子,获取等效声子边界散射平均自由程;考虑由粗糙度引起的界面效应,利用Matthiessen规则将硅材料内声子散射与声子边界散射等过程进行耦合,建立起适用于纳米FD SOI MOSFET硅薄膜热导率解析模型,并利用Asheghi原始模型与实验测试数据对等效边界散射自由程近似热导率模型进行了验证。模型计算结果表明,硅薄膜内声子边界散射等效平均自由程约为薄膜厚度的2.5倍。声子边界散射在微尺度与纳尺度声子热传输过程中占据主导地位,决定了硅薄膜内声子超快热传输特性。采用等效边界散射自由程近似的热导率模型能够与Asheghi模型及实验测试数据较好地吻合,更加凸显衰减因子的物理意义以及有效地揭示纳米器件有限空间热导率的尺度效应。

A scale effect model of thermal conductivity for silicon film in fully depleted silicon-on-insulator(FD SOI)metal-oxide-semiconductor field effect transistor(MOSFET)based on an equivalent phonon boundary scattering free path is proposed to address the problem that thermal conductivity of micro-nano scale silicon film suffers a severe scale effect.Phonon relaxation time influenced by bound state and free state electrons was quantified by studying phonon scattering mechanism in silicon materials.The analytical thermal conductivity model of silicon material was derived.In-depth studies of phonon boundary scattering mechanism were carried out.Equivalent phonon boundary scattering mean free path was obtained by solving the attenuation factor function.Phonon boundary scattering and phonon scattering in silicon material were coupled by the Matthiessen rule.An approximate analytical thermal conductivity model for nanoscale FD SOI MOSFET silicon film was established and verified by the original model of Asheghi and experimental tests.Results show that the equivalent mean free path of phonon boundary scattering in silicon film is about 2.5 times the film thickness.Phonon boundary scattering dominates microscale and nanoscale phonon heat transfer process,determining the ultra-fast heat transfer characteristics of phonons in thin silicon films.The thermal conductivity model based on the equivalent boundary scattering free path approximation is in good agreement with original model and experimental data,highlighting the physical significance of the attenuation factor and effectively revealing the thermal conductivity of the nanodevice in a limited space.