Low-k Semiconductor Chip Stress Decoupling via Protection Layer
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Solution Overview
Problem
Flip-Chip packaging technologies face challenges with stress-induced defects in brittle low-k layers due to thermal mismatch and mechanical forces, particularly in future technology nodes where porous low-k layers with air gaps are introduced, leading to sensitivity to mechanical forces and potential cracking.
Innovation Solution
The semiconductor device incorporates a protection layer composed of materials like silicone, polyurethane, or epoxy over the low-k subarea, along with a redistribution layer and a lid to decouple mechanical stress from the low-k layers, and uses through-silicon vias to redirect interconnects, ensuring mechanical stability and protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If porous low-k layers are introduced for higher speed and density, then signal transmission performance is improved, but mechanical strength and resistance to cracking deteriorate
Solution Approach 1:
A protection layer is applied over the low-k subarea before packaging to cushion and absorb mechanical stresses that would otherwise crack the porous low-k layers. This protective layer acts as a stress buffer during thermal cycling and mechanical deformation, preventing damage to the brittle low-k structure while allowing the porous material to maintain its low-k properties for high-speed signaling.
Solution Approach 2:
The protection layer serves as an intermediary between the porous low-k layers and the external mechanical environment. It mediates the stress transmission, allowing the low-k layers to function electrically while being mechanically protected from cracking during packaging and operation.
2Adaptability or versatility
If first-level interconnects are placed directly on low-k subarea, then routing flexibility is improved, but risk of mechanical damage to low-k layers increases
Solution Approach 1:
The chip surface is segmented into a low-k subarea and a non-low-k subarea. Contact areas are positioned within the low-k subarea for electrical connection, while first-level interconnects are positioned outside the low-k subarea on the non-low-k subarea. This spatial segmentation allows routing flexibility to be maintained through the redistribution layer while protecting the low-k layers from direct mechanical stress.
Solution Approach 2:
The interconnect structure is extended into the vertical dimension using through-silicon vias to connect contact areas on the top surface to first-level interconnects on the bottom surface or on the non-low-k subarea. This dimensional transition allows interconnects to be routed away from the vulnerable low-k region while maintaining electrical connectivity.
3Productivity
If chip is packaged with traditional Flip-Chip technology, then manufacturing efficiency is improved, but thermal mismatch stress causes cracking in low-k layers
Solution Approach 1:
Different regions of the chip are given different properties: the low-k subarea maintains its low dielectric constant for high-speed signaling, while the non-low-k subarea provides mechanical strength and stress resistance. The protection layer is applied locally over the low-k subarea to provide targeted stress protection without compromising the overall packaging efficiency or requiring complete redesign of the Flip-Chip process.
Data Source
AI summary
A semiconductor device is described having at least one semiconductor chip, the chip having an active area on a top side thereof, the active area formed at least in part of low-k material, said low-k material defining a low-k subarea of said active area; an embedding material, in which said at least one semiconductor chip is embedded, at least part of the embedding material forming a coplanar area with said active area; at least one contact area within the low-k subarea; a redistribution layer on the coplanar area, the redistribution layer connected to said contact areas; at least one first-level interconnect, located outside said low-k subarea, the first-level interconnect electrically connected to at least one of said contact areas via the redistribution layer.