Semiconductor Bump Structure with Minimized UBM Undercuts
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Solution Overview
Problem
The reduction in size of semiconductor device bumps increases the likelihood of failure due to undercuts in the under bump metallization (UBM) layer during the etching process, leading to potential collapse of the bumps.
Innovation Solution
A method is developed to form bump structures with minimized undercuts in the UBM layer by using a specific sequence of photoresist layer formation and etching, where the conductive connection patterns are formed to connect island patterns and bus bar patterns, and the photoresist layer is strategically designed to control the undercut formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the size of semiconductor device bumps is reduced to meet consumer demand for smaller devices, then the miniaturization of consumer devices is achieved, but the likelihood of bump failure due to undercuts in the UBM layer increases
Solution Approach 1:
The patent segments the UBM layer into multiple distinct layers (e.g., first UBM layer, second UBM layer) with different materials and properties. This segmentation allows each layer to perform specific functions - the first layer provides strong adhesion to the substrate while the second layer provides good adhesion to the bump, thereby preventing undercut formation and bump failure even as bump size is reduced
Solution Approach 2:
The patent employs composite material structures for the UBM layer, combining different materials (such as tungsten, copper, nickel, cobalt, or their alloys) in a multi-layer configuration. This composite structure optimizes both adhesion properties and mechanical strength, preventing undercut formation during etching and ensuring bump reliability at reduced sizes
2Ease of manufacture
If conventional etching processes are used to form bump structures, then the manufacturing process is simple, but undercuts form in the UBM layer leading to potential bump collapse
Solution Approach 1:
The patent applies preliminary protective actions by forming the multi-layer UBM structure before the bump etching process. The specific material composition and thickness of each UBM layer are predetermined to provide resistance against undercut formation during subsequent etching, allowing conventional etching processes to be used while achieving precise undercut control
Solution Approach 2:
The patent provides beforehand cushioning by designing the UBM layer structure with enhanced adhesion properties and appropriate thickness ratios. This cushioning effect protects the bump structure from undercut-induced collapse during etching, maintaining manufacturing precision without requiring complex process modifications
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
This approach limits the formation of undercuts, preventing bump collapse and ensuring reliable interconnects between stacked chips in three-dimensional integrated circuits, thereby enhancing the processing and reliability of semiconductor devices.
Implementation Method 1
A method is developed to form bump structures with minimized undercuts in the UBM layer by using a specific sequence of photoresist layer formation and etching
Data Source
AI summary
In a method of manufacturing a semiconductor device first conductive layers are formed over a substrate. A first photoresist layer is formed over the first conductive layers. The first conductive layers are etched by using the first photoresist layer as an etching mask, to form an island pattern of the first conductive layers separated from a bus bar pattern of the first conductive layers by a ring shape groove. A connection pattern is formed to connect the island pattern and the bus bar pattern. A second photoresist layer is formed over the first conductive layers and the connection pattern. The second photoresist layer includes an opening over the island pattern. Second conductive layers are formed on the island pattern in the opening. The second photoresist layer is removed, and the connection pattern is removed, thereby forming a bump structure.