Thermo-molecular study of high temperature superconductor integrated circuit(IC)

高温超导体在约瑟夫森结等电子集成电路器件中有着广阔的应用前景。这些超导器件的性能在很大程度上受到温度场的影响，而温度场的预测需要原子或分子水平的微观热传导知识，即分子工程研究。本文从热分子理论以及高温超导材料集成电路中热场与电磁场的相互作用出发，研究了超导材料的热传导及相关的热特性，以阐明高温超导材料高密度集成的热问题。高温超导材料的热传导和热性质：通过求解超导材料…中原子振动和对/非对电子运动的分子动力学和玻尔兹曼方程结果表明，热能传递具有金属导热和半导体导热两个方向性，分别受电子运动和原子振动控制。当温度低于临界温度时，热主要通过原子振动传导。当材料颗粒或薄膜的尺寸为原子振动相关长度的数量级时，温度在这些边界上表现出很大的跳跃，就像辐射换热一样。这些尺寸效应在较低的温度下更容易发生，即使对于大型电路也是如此。高温超导元件的热相互作用：为了制造具有很强导热方向性的混合系统中超导和/或半导体材料的高密度集成电路，需要详细了解电路元件之间的热相互作用。在薄膜元素的边界上，原子振动和电子运动被分散、反射和传输，薄膜厚度方向和沿薄膜的热传导都受边界的影响很大。对于超导材料，这些特性分别由低于临界温度的原子振动和高于临界温度的电子运动的边界效应控制。控制这些效应的颗粒尺寸或薄膜厚度约为100 nm，分别与金属类和半导体类热传导的温度的三次方和四次方成反比。这些特性决定了集成电路的热极限在尺寸和密度上。电路元件之间的热和电磁相互作用：临界电流是温度和相关磁场的函数，决定了超导的稳定性。临界电流由局部临界电流密度在垂直于电流的横截面上的面积积分确定。同时考虑定向热传导的热特性和边界效应，可以预测温度场。对于一个简单的集成系统，计算结果表明，尺寸和构型效应控制着集成系统的热极限。较少

High temperature superconductors possess great promise for application in electronic integrated circuit devices such as Josephson junctions. The performance of these superconducting devices is greatly affected by the temperature field of which prediction requires the knowledge of heat conduction in microscale of atomic or molecular levels, that is, molecular engineering studies. In the present study, the heat conduction and the related thermal characteristics of superconducting materials are studied from the standpoint of thermo-molecular theory as well as the interaction between thermal and electromagnetic fields in the integrated circuits of high-temperature superconducting materials to make clear the thermal problems of high-density integration of these devices.1. Heat conduction and thermal properties of high-temperature superconducting materials : By solving the molecular dynamics and Boltzmann equations of atomic vibration and pair/nonpair electron motion in superconducting mater … More ials, it is shown that the transfer of thermal energy has two directional features of metallic and semiconductor heat conductions which are controlled by electron motion and atomic vibration, respectively. At temperatures lower than the critical temperature, heat is conducted mainly through the atomic vibration. When the size of material grains or thin films is of the order of the correlation length of atomic vibration, the temperature shows great jumps at these boundaries as in the radiation heat transfer. These size effects occur more easily at lower temperatures even for large scale circuits.2. Thermal interactions of high-temperature superconducting elements : In order to make high-density integrated circuits of superconducting and/or semiconducting materials in hybrid systems, which have strong directionality of heat conduction, detailed knowledge is required of the thermal interaction between the circuit elements. At the boundaries of film elements, the atomic vibration and electron motion are to be dispersed, reflected and transmitted, and the heat conduction both in the film thickness direction and along the film is greatly affected by the boundaries. For superconducting materials, these features are controlled by the boundary effects of atomic vibration and electron motion at lower and higher temperatures than the critical temperature, respectively. The size of grains or film thickness at which these effects are dominated is of the order of 100nm, being increased inversely proportional to the third and fourth power of temperature for metal-like and semiconductor-like heat conduction, respectively. The features decide the thermal limit of integration circuit in size and density.3. Thermal and electromagnetic interaction between circuit elements : The critical electric current dominates the stability of superconduction, being a function of the temperature and the associated magnetic field. The critical current is determined by the area integration of the local critical current density in the cross section normal to the current. The temperature field can be predicted by considering both the thermal features of directional heat conduction and the boundary effects. For a simple system of integrated system, the computation result shows that the size and configuration effects control the thermal limit of the integration. Less