Ultra-Thin Wafer Stacking for High-Density 3D Semiconductor Integration
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Solution Overview
Problem
Existing semiconductor technologies face limitations in achieving high integration and high speed due to the constraints of planar packaging, necessitating innovative methods for miniaturization and improved electrical characteristics.
Innovation Solution
A method for manufacturing a semiconductor stack structure with ultra-thin dies involves forming a stop layer structure in semiconductor wafers, flipping and bonding wafers, and performing backside grinding and thinning processes to achieve ultra-thin wafers, allowing for multiple layers to be stacked with a thickness of less than 12 microns, thereby enhancing integration and speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If planar packaging technology is used, then manufacturing simplicity is maintained, but integration density and speed are limited
Solution Approach 1:
The patent transitions from planar (2D) packaging to three-dimensional (3D) stacking architecture, where multiple semiconductor wafers are bonded vertically to form a stack structure. This dimensional change enables significantly higher integration density by utilizing the vertical space, allowing multiple functional layers to coexist within a compact footprint while maintaining manufacturing feasibility through established wafer bonding techniques.
2Productivity
If wafer thickness is reduced to increase stacking layers, then integration density improves, but mechanical strength and handling difficulty deteriorate
Solution Approach 1:
The patent combines multiple ultra-thin wafers into a unified stack structure through hybrid bonding, where the collective assembly achieves mechanical strength comparable to or exceeding that of individual thicker wafers. The bonding interfaces create a rigid integrated structure that distributes mechanical loads across all layers, enabling the stack to maintain structural integrity despite each individual wafer being thinner than 12 microns.
Solution Approach 2:
The stack structure functions as a composite material system where alternating layers of semiconductor wafers and bonding interfaces create a multi-layer composite with enhanced mechanical properties. The combination of multiple thin layers bonded together produces a structure with improved strength-to-thickness ratio compared to single-layer alternatives, enabling both high integration and mechanical robustness.
3Manufacturing precision
If stop layer structure is added to enable thinning process, then manufacturing precision improves, but process complexity increases
Solution Approach 1:
The stop layer structure serves as an intermediary reference plane during the thinning process. By providing a mechanically distinct layer with different etch or polish rates, the stop layer acts as a self-aligning reference that automatically defines the precise termination point for material removal. This intermediary structure enables consistent thickness control across all wafers in the stack without requiring complex real-time measurement and adjustment systems.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method enables high integration and high speed semiconductor stack structures with better electrical characteristics and efficiency, enabling up to 57 stacked layers within a 700-micron thickness limit.
Implementation Method 1
the silicon nitride layer is manufactured by carrying out a nitrogen ion implantation process at a first depth of the semiconductor substrate first and then carrying out a high temperature treatment process to form the silicon nitride layer in a nitrogen ion implanted region
Implementation Method 2
carrying out a high temperature treatment process to form the silicon nitride layer in a nitrogen ion implanted region
Implementation Method 3
carrying out a first backside grinding process from the backside of the second semiconductor wafer to remove a portion of the second substrate part of the second semiconductor wafer
Implementation Method 4
a step of substrate removal for removing the remaining second substrate part to expose the stop layer structure
Data Source
AI summary
A method includes manufacturing a plurality of wafers each having a substrate having an active surface and a backside, and a stop layer dividing the substrate into a first substrate part at a side of the active surface and a second substrate part at a side of the backside; on a first wafer of the plurality of wafers, removing the second substrate part and the stop layer; bonding a second wafer of the plurality of wafers on the first wafer with first substrate part of the second wafer facing a surface of the first wafer that is exposed by removing the stop layer and, on the second wafer, performing the same processes of removing the second substrate part and stop layer of the second wafer; repeating the bonding and removing the second substrate part and stop layer with one or more wafers to form a stack of wafers.