Separation of Functional Memory Devices from Multi-Chip Stacked Packages
Dr. Amy Moll and Dr. Chad Watson
Consumer electronics such as MP3 players, smartphones, and solid state hard drives create a demand for greater memory density. Manufacturers such as Micron, Technology, are pushing the limits of multi-chip stacked die packaging. To achieve greater memory density, more memory devices are included in a single package. The inclusion of additional devices, as many as 16, creates reliability challenges. Testing recognizes multi-chip stacked packages as a single higher density device. Device level failures in these packages cannot be isolated to a specific device. The devices must be separated and tested individually. It is currently not possible to separate each die in a stacked multi-chip package and maintain 100% electrical functionality. This paper reports on the investigation of a failure analysis procedure to isolate memory devices in a two die stack. Three steps in the process were evaluated: decapsulation, die separation, and bond-pad conditioning. Techniques considered were those currently available in Micron’s failure analysis lab including chemical etching, chemical jet etching, laser ablation, mechanical abrasion, shearing, and plasma cleaning. A successful procedure would result in more complete failure analysis leading to more reliable multi-chip memory packages for Micron’s customers.