Correction Die Assembly for Defective Wafer Stack Recovery
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Solution Overview
Problem
The challenge in implementing stacked memory arrangements is the complexity and cost of stacking techniques, as well as the inability to completely eliminate defects in volume manufacturing processes, leading to defective stacks where good dies are discarded as waste.
Innovation Solution
The solution involves identifying defective dies during manufacturing or post-manufacturing testing and replacing them with additional correction dies or dummy dies in the wafer-to-wafer or die stacks, using surface mount technology or direct bond interconnect techniques, to maintain stack integrity and reduce waste.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If volume manufacturing processes are used to produce memory dies, then productivity is improved, but defective dies are generated as waste
Solution Approach 1:
The patent performs preliminary identification of defective dies during wafer fabrication before stacking. By testing and marking defective dies at the wafer level, the system prepares the data needed for later substitution, allowing good dies to be rescued from otherwise defective stacks without retesting entire stacks after assembly.
Solution Approach 2:
Instead of discarding entire stacks containing defective dies, the patent recovers good dies by substituting only the defective ones. The substitution process replaces individual defective dies with good dies from the same wafer or other wafers, thereby recovering the value of good dies that would otherwise be wasted along with the defective ones.
2Reliability
If defective stacks are discarded to ensure quality, then reliability is improved, but productivity decreases due to waste
Solution Approach 1:
The patent applies local quality control by identifying and replacing only the specific defective dies within stacks rather than discarding entire stacks. This localized approach maintains the quality of good dies while eliminating only the defective portions, thereby preserving manufacturing yield.
Solution Approach 2:
The system recovers good dies from stacks that would otherwise be discarded by substituting defective dies with good ones. This allows the stack to be salvaged and reused, maintaining both reliability (by ensuring all dies in the final stack are functional) and productivity (by reducing waste).
3Loss of substance
If substitution of defective dies is performed, then loss of substance is reduced, but device complexity increases
Solution Approach 1:
The substitution process is simplified by performing preliminary identification and marking of defective dies at the wafer level before stacking. This pre-characterization data is stored and used during stack assembly to automatically determine which positions require substitution, eliminating the need for complex post-assembly testing and identification procedures.
Solution Approach 2:
The patent uses an intermediary data structure (lookup tables, maps, or databases) that stores the defective die information from wafer fabrication. This intermediary allows the substitution process to efficiently retrieve and apply correction information without complex real-time analysis during stack assembly, thereby reducing process complexity.
4Reliability
If additional dies are added to stacks for substitution, then reliability is improved, but volume of material increases
Solution Approach 1:
The patent recovers good dies from the same wafer or other wafers to substitute for defective ones, rather than adding entirely new dies to increase stack height. This substitution approach maintains the original stack composition and height while replacing only the defective components, thereby improving reliability without significantly increasing material volume.
Data Source
AI summary
Representative implementations of devices and techniques provide correction for a defective die in a wafer-to-wafer stack or a die stack. A correction die is coupled to a die of the stack with the defective die. The correction die electrically replaces the defective die. Optionally, a dummy die can be coupled to other die stacks of a wafer-to-wafer stack to adjust a height of the stacks.