光敏聚酰亚胺:低温固化设计策略

Photosensitive Polyimide:Design Strategy of Low-temperature Curing

扇出型晶圆级封装(FOWLP)由于在成本、尺寸、输入/输出密度等方面有更优化的解决方案而备受关注。随着封装厚度的薄型化,作为其中再布线层介电材料的光敏聚酰亚胺也面临着新的要求:更低介电常数、更低热膨胀系数、更低残余应力、更低固化温度等。FOWLP面临的问题主要是晶圆翘曲,减少封装工艺热预算可有效降低封装中金属材料与介电材料之间因热力学性质差异所导致的应力集中。由此,光敏聚酰亚胺需首要解决的即是传统体系在固化温度方面的限制(>300℃)。本文从聚酰亚胺合成过程角度综述了近些年来在降低光敏聚酰亚胺固化温度方面的研究进展及发展现状,介绍了基于聚酰胺酸、聚异酰亚胺、可溶性聚酰亚胺低温固化体系的优劣势,最后展望了低温固化体系的进一步发展趋势。

Fan-out wafer level packaging(FOWLP)has attracted much attention due to the more optimized solution in cost,size,input/output density,etc.With the thinning of the package thickness,photosensitive polyimide utilized as the dielectric material in redistribution layer needs to fulfill new demanding tasks:lower dielectric constant,lower coefficient of thermal expansion,lower residual stress,lower curing temperature,etc.The main problem faced by FOWLP is wafer warpage.Reducing the thermal budget in packaging process can effectively minimize the stress concentration caused by the difference in thermodynamic properties between the metal and dielectric layers.Therefore,the primary problem to be solved for photosensitive polyimide is avoiding the restriction of curing temperature(>300℃)in the conventional system.In this review,the recent research progress and development status in reducing the curing temperature of photosensitive polyimide are summarized from the perspective of polyimide synthesis process.The advantages and disadvantages of low-temperature curing systems based on polyamic acid,polyisoimide and soluble polyimide are introduced.Finally,the further development trend of low-temperature curing system is prospected.