Challenges of large Fan out multi-chip module and fine Cu line space

The growth of artificial intelligence, internet of things and 5G technology demands for much higher data rate. Though Moore's law has come to end. But, the need of high functions devices are not stopping. Thus chiplet package is evolved. Chiplet package basically contains of single chip module to connect multi-chips into one as to deliver high bandwidth transmission. The inputs/outputs counts are high and densely packed with large number of Cu line within confined package size. To fulfill these requirements, multiple chiplets packages have been designed. Fan-Out Multi Chip Module (FOMCM) is one of chiplets that designed for lower cost and high data rate transmission package.In this study, we have developed a very large chiplet package using FOMCM technology. This package has the size of 77.5 * 77.5 mm2 and contained one chip module with 2 integrated dies. Each of the die size is 26 * 16 mm2. The 2 chips are attached on the three prefabricated redistribution layers (RDLs).In TV (Test Vehicle) sample, two TVs are tested as samples. The difference between these two TVs is only in the dimension design of Cu line in RDL. Firstly, in TV1, the size of Cu line is 2/2/2.3 (line space/width/thickness, μm) in 2
^nd
and 3
^rd
layers of RDL. Then, in TV2, the size of Cu line is 1/1/2.5 in 2
^nd
layer of RDL and 1/1/1 in 3
^rd
layer of RDL.In results, firstly, in TV1, the maximum and the minimum of shifting values are 3.09 μm and 1.86 μm in chip module. Secondly, for TV1, the width of Cu line in RDL is from 1.71 μm to 2.03 μm in ISO (Isolation) zone of Cu line and is from 1.72 μm to 2.06 μm in dense zone of Cu line. For TV2, the width of Cu line in RDL is from 0.73 μm to 1.02 μm in ISO zone of Cu line and is from 0.72 μm to 1.06 μm in dense zone of Cu line. Thirdly, based on package level reliability, TV1 passes the tests of TCT B 1000x, μHAST 96 hr, and HTSL 1000 hr, while TV2 passes the tests of TCT B 1000 x, μHAST 192 hr, and HTSL 1000 hr. Fourthly, for TV1, the outcomes of TIM (Thermal Interface Material) coverage in TCT B 700 x, μHAST 96 hr, and HTSL 500 hr are separately 91%, 89%, and 83% while for TV2, the outcomes of TIM coverage in TCT B 1000 x, μHAST 192 hr, and HTSL 1000 hr are separately 91.3%, 92.3%, and 78.6%.In conclusion, the samples of fan out chip module with two chips and RDL Cu line 1/1/1 are fabricated successfully.