Insulating Buffer Layer for Semiconductor Bump Stress Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Semiconductor devices face thermal and mechanical stress issues, particularly with fine pitch bumps on low dielectric constant wafers, leading to bump cracking, delamination, and interconnect defects, which decrease production yield and increase manufacturing costs.
Innovation Solution
A method is introduced to form a semiconductor device with a conductive pillar having an interior open space over a semiconductor wafer, where an insulating buffer layer is formed over the wafer, and a bump is created within the pillar to reduce stress, specifically using a ring-shaped conductive pillar and an insulating buffer layer to alleviate thermal and mechanical stress on contact pads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fine pitch bumps are used on low dielectric constant wafers, then device density and performance are improved, but thermal and mechanical stress increases causing bump cracking and delamination
Solution Approach 1:
An insulating buffer layer is introduced as an intermediary between the semiconductor wafer and the bump structure. This buffer layer acts as a stress-absorbing mediator that decouples the thermal and mechanical stress transmitted from fine pitch bumps to the wafer, preventing bump cracking and delamination while maintaining high device density
Solution Approach 2:
The dielectric constant parameter of the buffer layer is specifically selected to be low (insulating material) to change the stress transmission characteristics. This parameter change allows the buffer layer to absorb thermal and mechanical stress differently than standard dielectric materials, thereby improving bump integrity without sacrificing device density
2Reliability
If thermal and mechanical stress are reduced using an insulating buffer layer, then bump cracking and delamination are minimized, but manufacturing process complexity increases
Solution Approach 1:
The insulating buffer layer is formed preliminarily before the bump formation process. By pre-establishing the stress-absorbing buffer structure, the subsequent bump fabrication can proceed with standard processes without requiring additional stress-management steps, thus limiting the increase in manufacturing complexity
3Ease of manufacture
If standard bump structures are used without stress relief, then manufacturing process is simpler, but production yield decreases due to bump cracking and delamination
Solution Approach 1:
The bump structure is segmented into distinct functional layers: the insulating buffer layer separated from both the wafer and the bump. This segmentation allows each layer to perform its specific function independently - the buffer absorbs stress while the bump provides electrical connection - maintaining manufacturing simplicity through modular construction
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 insulating buffer layer effectively reduces thermal and mechanical stress, minimizing bump cracking and delamination, thereby enhancing production yield and reducing manufacturing costs by improving the reliability of electrical interconnects.
Implementation Method 1
forming a buffer layer over the semiconductor wafer... insulating buffer layer to reduce stress
Implementation Method 2
forming a buffer layer over the semiconductor wafer... to reduce stress on contact pads and bumps
Data Source
AI summary
A semiconductor wafer has a plurality of semiconductor die with contact pads for electrical interconnect. An insulating layer is formed over the semiconductor wafer. A bump structure is formed over the contact pads. The bump structure has a buffer layer formed over the insulating layer and contact pad. A portion of the buffer layer is removed to expose the contact pad and an outer portion of the insulating layer. A UBM layer is formed over the buffer layer and contact pad. The UBM layer follows a contour of the buffer layer and contact pad. A ring-shaped conductive pillar is formed over the UBM layer using a patterned photoresist layer filled with electrically conductive material. A conductive barrier layer is formed over the ring-shaped conductive pillar. A bump is formed over the conductive barrier layer. The buffer layer reduces thermal and mechanical stress on the bump and contact pad.