Resist-Defined Tapered Bumps for Narrow-Pitch Flip-Chip Reliability
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Solution Overview
Problem
The challenge of bridge failures due to surface tension during flip-chip mounting, particularly as pitch between electrode terminals narrows, and the stress-induced reliability issues with existing metal bump methods.
Innovation Solution
A method involving the use of an imprint mold to form a resist with controlled openings, followed by metal filling to create a tapered bump structure that absorbs pressure, reducing stress on the mounting substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pitch between electrode terminals is narrowed to achieve densification, then the number of pins and element density increase, but bridge failures occur due to surface tension and stress during flip-chip mounting
Solution Approach 1:
The protrusion electrode is segmented into multiple portions: a base portion, an inclined portion, and a reverse inclined portion. This segmentation creates a complex three-dimensional structure that distributes stress during mounting, preventing bridge failures while maintaining narrow pitch between electrodes.
Solution Approach 2:
The invention transitions from a simple two-dimensional bump structure to a three-dimensional protrusion electrode with multiple inclined portions. The reverse inclined portion extending in the depth direction adds a vertical dimension to stress distribution, effectively preventing bridge failures during flip-chip mounting.
2Ease of manufacture
If a simple bump structure is used for the protrusion electrode, then the manufacturing process is simple, but stress during mounting causes bridge failures
Solution Approach 1:
The invention combines multiple functional portions (base portion, inclined portion, reverse inclined portion) into a single integrated protrusion electrode structure. This merging achieves complex stress distribution functionality while maintaining manufacturing simplicity through a unified formation process using imprint molds and electrochemical deposition.
3Reliability
If a tapered fine metal bump is used instead of solder bump, then bridge failures are prevented, but the manufacturing precision requirement increases
Solution Approach 1:
The invention introduces an imprint mold as an intermediary tool that transfers a pre-formed pattern to the resist layer. This mediator enables precise formation of the complex protrusion electrode structure with multiple inclined portions, achieving high manufacturing precision without requiring direct manual or complex automated fabrication.
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
Prevents bridge failures and alleviates stress on the mounting substrate, enhancing the reliability of semiconductor devices by using a tapered bump design.
Implementation Method 1
curing the resist by applying light to the resist
Implementation Method 2
forming a bump by filling the opening with metal
Data Source
AI summary
A method for manufacturing a semiconductor device includes providing a semiconductor element having electrode terminals; forming a resist on the semiconductor element, the resist having a first surface facing the electrode terminals and a second surface opposite to the first surface; forming an opening in the resist, which covers the electrode terminals by inserting protrusions of a mold into the resist above the electrode terminals; curing the resist by applying energy to the resist; and widening the opening in a radial direction of the opening. The resist is cured in a state where the second surface of the resist faces an inner surface of the mold with a gap between the second surface of the resist and the inner surface of the mold.