Mixed Cu Nanoparticles and Cu Microparticles with Promising Low-temperature and Low-pressure Sintering Properties and Inoxidizability for Microelectronic Packaging Applications

Nano-copper has become an important interconnection material for third-generation semiconductor devices due to its excellent electrical and thermal properties. However, nano-copper also has the characteristics of easy oxidation, which limits its application in micron packaging. In order to solve the above problems, this paper proposes to use micro-nano multi-scale composite copper powder instead of nano-copper powder. Adding micro-copper to nano-copper can improve the oxidation resistance of copper powder, while retaining a small amount of small-size nano-copper so that the copper powder remains unchanged. Possess good sintering performance. In this paper, a multi-size composite micro-nano copper powder of 200nm~1.8 m is used to prepare a micro-nano copper paste to interconnect the chip and the substrate. The hot press sintering and pressureless sintering are performed at 220 and 260 respectively. The results show that the micro-nano copper powder can obtain better sintering performance under low pressure, low temperature or no pressure conditions. The shear strength of 42.7 MPa can be obtained under sintering conditions of 220 C and 2 MPa, and the shear strength of 27.1 MPa can be obtained under pressureless sintering conditions of 260 C. A strong connection between the chip and the substrate is achieved. Through the XRD diffraction analysis of the pressureless sintered sample, it was found that the sintered body of micro-nano copper particles did not appear to be oxidized, and had better oxidation resistance. Under the conditions of low temperature, low pressure or no pressure, the multi-size composite micro-nano copper powder can obtain higher interconnection strength, and at the same time has stronger oxidation resistance and lower cost than nano-copper powder. This method provides a new idea for improving the oxidation resistance of nano-copper.