空气隙Cu互连结构热应力史研究

Study on Thermal Stress History in Air-Gap/Cu Interconnect

将空气引入Cu导线间形成空气隙,可有效降低等效介电常数K_(eff),但同时也使互连结构的机械稳定性面临着挑战。利用ANSYS进行了有限元热分析,研究了制备空气隙Cu互连结构的两种主流工艺过程,即CVD沉积法和热分解牺牲层法,模拟了Cu导线上的热应力变化趋势,并比较了两者的优劣,最终发现互连结构经过一系列热应力的循环作用后,各种材料在不同程度上都有较大的形变,这将影响结构的机械稳定性,甚至引起破坏。所以,需要进一步改善结构设计和使用理想电介质。

The introduction of air-gaps between copper wires can effectively reduce the equivalent dielectric constant Keff, but the mechanical stability of interconnect structure is also facing challenges. ANSYS finite element thermal analysis is used, through studying two kinds of mainstream processes for manufacturing the air-gap/Cu interconnect structure, CVD deposition method and thermal decomposition of the sacrificial layer method, to simulate the thermal stress history on the copper wire, and the pros and cons are compared. It is found that after a series of thermal stress circularly acted on the interconnect structure, many materials have large deformation in various degree, which will largely affect the structure mechanical stability and even cause damage. Therefore, further improvement is required for optimized structure design and use of proper dielectric.