Semiconductor Chip Polymer Layer Crack Stop Design
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Solution Overview
Problem
Conventional semiconductor chips are prone to cracks due to stresses during the dicing process and thermal expansion differences between the chip and the substrate, which can lead to crack propagation and damage to the delicate circuit structures, and existing crack stop methods are insufficient in controlling crack growth.
Innovation Solution
A semiconductor chip with a polymer layer featuring a central portion and spatially separated frame portions to define channels, where an underfill material is placed to create a mechanical joint and prevent crack propagation, enhancing the interface strength and crack resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional picture frame crack stop is used, then crack propagation is partially controlled, but the crack stop does not extend to the edges allowing cracks to achieve critical length before being stopped
Solution Approach 1:
The crack stop structure is divided into multiple segments: a first crack stop segment extending from the first edge toward the center, and a second crack stop segment extending from the second edge toward the center. These segments are spatially separated and do not meet at the center, creating a segmented configuration that allows each segment to independently intercept cracks from its respective edge while maintaining structural integrity.
Solution Approach 2:
The crack stop structure is configured to extend substantially to the edges of the semiconductor die in the lateral dimension, rather than stopping short as in conventional designs. This dimensional extension ensures that cracks originating at any point along the edges are intercepted before achieving critical length, effectively addressing the limitation of conventional crack stops that do not reach the edges.
2Productivity
If the dicing operation is performed to cut individual dice from the wafer, then individual chips are obtained, but significant stresses and impact loads cause microscopic fractures particularly at die corners
Solution Approach 1:
The crack stop structure is formed during the semiconductor fabrication process before the dicing operation. This preliminary formation of the crack stop provides pre-existing fracture barriers that intercept cracks during the subsequent dicing operation, preventing microscopic fractures from propagating into larger failures that would compromise the individual chips.
Solution Approach 2:
The crack stop structure acts as a protective barrier positioned before the active circuit regions of the semiconductor die. During dicing and subsequent handling, this structure cushions against crack propagation by providing a physical barrier that stops cracks before they can reach and damage the delicate circuit structures.
3Area of stationary object
If a continuous polyimide layer blankets the front side of the chip, then coverage is provided, but the interface between polyimide and underfill becomes a weakness where cracks initiate and propagate
Solution Approach 1:
The polyimide layer is configured with a first polyimide portion and a second polyimide portion that are spatially separated and do not overlap, creating a segmented structure. This segmentation discontinues the continuous polyimide blanket, thereby eliminating the continuous polyimide-to-underfill interface that serves as a crack initiation path while maintaining adequate coverage of the chip surface.
Solution Approach 2:
The continuous polyimide layer is extracted or removed from the interface region between the chip and substrate. By discontinuing the polyimide layer in this critical interface zone, the source of crack initiation is eliminated, while the polyimide portions remaining on the chip surface continue to provide protective coverage.
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 described method effectively prevents crack propagation into the interior of the semiconductor chip by forming mechanical joints between the polymer layer and the underfill, thereby protecting the chip's circuit structures from damage caused by thermal and mechanical stresses.
Implementation Method 1
A substrate usually has CTE that is six to seven times larger than the CTE of the chip. To address issues of differential CTE, an underfill material is deposited between the polyimide layer of the semiconductor chip and the package substrate
Implementation Method 2
an underfill material is deposited between the polyimide layer of the semiconductor chip and the package substrate and hardened by a curing process
Data Source
AI summary
Various semiconductor chip reinforcement structures and methods of making the same are disclosed. In one aspect, a method of manufacturing is provided that includes providing a semiconductor chip that has a side and forming a polymer layer on the side. The polymer layer has a central portion and a first frame portion spatially separated from the central portion to define a first channel. An underfill material may be provided to invade the channel and establish a mechanical joint between the polymer layer and the underfill material.