Multilayer Wiring Via Structure with Segmented Seed Layer
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Solution Overview
Problem
Conduction failures in multilayer wiring structures occur due to the destruction of seed layers caused by thermal stress and differences in thermal expansion coefficients between conductive layers and interlayer insulating films, leading to adhesion issues and potential peeling of insulating films.
Innovation Solution
A multilayer wiring structure where the seed layer is partially removed at the bottom portion of openings, allowing direct contact between main conductive layers and enhancing adhesion with the same metal material, reducing resistance values and preventing conduction failures, while the seed layer covers the inner walls and outer edges to maintain film integrity during electrolytic plating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a seed layer is formed in the via hole to enable electrolytic plating, then power feeding is enabled and main conductive layer formation is improved, but the seed layer is destroyed due to thermal stress and stress at the boundary between seed layer and main conductive layer, resulting in conduction failure
Solution Approach 1:
The via structure is segmented into three functional zones: the seed layer remains on the inner wall surface to provide adhesion and power feeding, the center bottom portion is cleared to enable direct contact between main conductive layers, and the outer peripheral edge retains seed layer coverage to prevent peeling. This segmentation allows the system to simultaneously achieve electrolytic plating capability and conduction reliability.
Solution Approach 2:
Different regions of the via hole are assigned different qualities: the inner wall surface maintains seed layer for adhesion and power feeding, the center bottom has direct metal-to-metal contact for reliable conduction, and the outer edge has seed layer coverage for mechanical support. This local differentiation resolves the contradiction between needing seed layer for manufacturing and avoiding it for reliability.
2Quantity of substance
If the main conductive layer or interlayer insulating film is formed thick to improve wiring capacity, then conductivity is improved, but the seed layer is destroyed due to stress generated at the boundary, resulting in conduction failure
Solution Approach 1:
The thick conductive structure is segmented such that the seed layer is confined to specific regions (inner wall and outer edge) while the center bottom portion consists of direct contact between main conductive layers. This segmentation prevents stress concentration at the seed layer boundary while maintaining the benefits of thick conductive layers for wiring capacity.
3Reliability
If electroless plating is used to form the plating film in the via hole, then adhesion is ensured, but the film formation rate is lower and process cost is higher compared to electrolytic plating
Solution Approach 1:
The via hole is segmented into regions requiring adhesion (inner wall surface with seed layer) and regions requiring high-speed formation (center bottom with direct contact). This allows electrolytic plating to be used in the center region for high productivity while the seed layer on the inner wall provides the necessary adhesion.
Solution Approach 2:
The seed layer on the inner wall surface acts as an intermediary that provides both adhesion to the interlayer insulating film and power feeding capability for electrolytic plating. This intermediary enables the use of faster electrolytic plating while maintaining adhesion requirements.
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 conduction failures by ensuring direct contact between main conductive layers and reduces resistance values, while maintaining film adhesion and preventing peeling of interlayer insulating films, even under severe testing conditions.
Implementation Method 1
an adhesion layer formed of chromium (Cr) or the like is often used in order to enhance adhesion between a conductive pattern and the interlayer insulating film
Implementation Method 2
it is preferable to perform the electrolytic plating in place of the electroless plating
Implementation Method 3
The seed layer is formed of a metal material such as chromium (Cr) and having a thermal expansion coefficient different from that of copper (Cu) used as a material for a main conductive layer, so that when a severe test such as a thermal shock test, a moisture absorption reflow test, or a humidity resistance performance test is executed, the seed layer is destroyed due to stress generated at the boundary between the seed layer and the main conductive layer
Data Source
AI summary
Disclosed herein is a multilayer wiring structure that includes a first metal layer; an interlayer insulating film formed on the first metal layer, the interlayer insulating film having an opening that exposes a first area of the first metal layer; a second metal layer formed on an inner wall of the opening; and a third metal layer filling the opening via the second metal layer. The first and third metal layers are direct contact with each other at a bottom of the opening.