Redistribution Wiring Adhesion in Semiconductor Packaging
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Solution Overview
Problem
In semiconductor device manufacturing, existing wafer level packaging techniques face challenges in reducing wiring pitch and preventing delamination between redistribution wirings and insulating layers, especially during the reflow process of solder bumps, which affects the reliability and adhesion of the semiconductor device.
Innovation Solution
The semiconductor device incorporates a redistribution layer with copper wirings, under-bump metal films, and a second insulating layer with a specific surface roughness to enhance adhesion and reduce delamination, along with a solder bump structure that overhangs redistribution wirings, allowing for a reduced wiring pitch and improved mechanical anchoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the wiring pitch is reduced to increase terminal density, then the productivity and integration density are improved, but the adhesion between redistribution wirings and insulating layers deteriorates, causing delamination during reflow process
Solution Approach 1:
The patent applies preliminary action by forming a roughened surface layer on the insulating layer before forming the redistribution wirings. This roughened surface is created in advance through plasma treatment or etching processes, which increases the surface area and provides mechanical interlocking features. When the metal wiring is deposited on this pre-roughened surface, the adhesion is significantly enhanced, preventing delamination during subsequent reflow processes even when wiring pitch is reduced.
Solution Approach 2:
The patent changes the surface parameters of the insulating layer by modifying its roughness characteristics. Through plasma treatment, chemical etching, or physical abrasion, the surface roughness parameter is increased from a smooth state to a controlled rough state with specific Ra values. This parameter change transforms the surface properties to provide better mechanical anchoring and chemical bonding sites, thereby improving adhesion without affecting the wiring pitch design.
2Ease of manufacture
If conventional wafer level packaging techniques are used, then the manufacturing process is simple, but delamination occurs between redistribution wirings and insulating layers during solder bump reflow
Solution Approach 1:
The roughened surface layer is formed as a preliminary step in the manufacturing process, before wiring deposition and solder bump formation. This preliminary surface treatment ensures that when standard manufacturing processes are subsequently applied, the adhesion is already optimized, preventing delamination during reflow without requiring complex process modifications.
Solution Approach 2:
The roughened surface layer acts as an intermediary between the insulating layer and the redistribution wirings. This intermediate structure provides a transition zone that enhances bonding between the two layers, similar to how a primer or adhesive layer works. The roughened surface creates mechanical interlocking and increases the effective bonding area, serving as a mediator that prevents direct delamination between the wiring and the smooth insulating layer.
3Reliability
If solder bumps are positioned directly over redistribution wirings, then electrical connection is achieved, but mechanical stress during mounting causes delamination
Solution Approach 1:
The roughened surface layer is prepared in advance to provide mechanical anchoring features before the solder bump mounting process. This pre-formed rough surface structure is designed to withstand the mechanical stresses of subsequent mounting operations, preventing delamination even when solder bumps are positioned over redistribution wirings and transmit mounting stresses to the wiring layer.
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 configuration enhances the mechanical anchoring between redistribution wirings and the insulating layer, reducing delamination and ensuring reliable electrical connections, even after mounting on a wiring board, while maintaining a compact wiring layout.
Implementation Method 1
a roughened surface layer formed on the insulating layer
Implementation Method 2
a solder bump overhanging at least one of the plurality of wirings not electrically coupled to the metal film
Data Source
AI summary
A semiconductor device includes: an integrated circuit having an electrode pad; a first insulating layer disposed on the integrated circuit; a redistribution layer including a plurality of wirings and disposed on the first insulating layer, at least one of the plurality of wirings being electrically coupled to the electrode pad; a second insulating layer having a opening on at least a portion of the plurality of wirings; a metal film disposed on the opening and on the second insulating layer, and electrically coupled to at least one of the plurality of wirings; and a solder bump the solder bump overhanging at least one of the plurality of wirings not electrically coupled to the metal film.