Interconnect Substrate Via Structure for Dense Wiring Isolation
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Solution Overview
Problem
Existing interconnect substrates with a small volume ratio of inorganic material to the upper insulating layer tend to have via holes with large opening diameters, leading to narrow intervals between adjacent via holes and a risk of short-circuiting between adjacent interconnects.
Innovation Solution
The interconnect substrate includes a first interconnect layer, an insulating layer with a filler, a via hole penetrating the insulating layer, and a second interconnect layer filling the via hole. The insulating layer consists of a first insulating layer with a higher filler content and a thinner second insulating layer with less filler, where the inner surface of the via hole is inclined, with a larger angle in the first insulating layer than in the second insulating layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the volume ratio of inorganic material to the upper insulating layer is small, then the manufacturing is easier and the insulating layer is thinner, but the opening diameter of via holes becomes large, leading to narrow intervals between adjacent via holes and risk of short-circuiting
Solution Approach 1:
The insulating layer is segmented into a lower insulating layer and an upper insulating layer with different filler volume ratios. The lower insulating layer has a larger filler volume ratio (50-90 vol%) providing mechanical strength and structural support, while the upper insulating layer has a smaller filler volume ratio (10-50 vol%) enabling precise via hole formation and preventing short-circuiting between adjacent interconnects.
Solution Approach 2:
Different regions of the insulating layer are assigned different filler concentrations tailored to local requirements. The lower insulating layer near the first interconnect layer uses high filler content for structural integrity, while the upper insulating layer near the via hole opening uses low filler content for manufacturing precision and electrical isolation, optimizing both mechanical and electrical properties locally.
2Length of stationary object
If the volume ratio of inorganic material to the upper insulating layer is small, then the via hole opening diameter becomes large, but the interval between adjacent via holes becomes narrow
Solution Approach 1:
The insulating layer is divided into two layers with different filler ratios to decouple the requirements of via hole formation and interconnect spacing. This segmentation allows the upper layer to accommodate larger via hole openings while maintaining sufficient interval between adjacent via holes, preventing short-circuiting between neighboring interconnects.
Solution Approach 2:
The filler volume ratio parameter is changed between the lower and upper insulating layers. By reducing the filler volume ratio in the upper insulating layer compared to the lower layer, the material becomes more suitable for forming via holes with controlled opening diameters and maintaining appropriate spacing, thus resolving the conflict between via hole size and interval.
3Strength
If the inner surface of the via hole is inclined with larger angle in the first insulating layer, then the adhesion between insulating layers and interconnect layers is improved, but the via hole geometry becomes more complex
Solution Approach 1:
The via hole structure is segmented into two zones corresponding to the two insulating layers, with different inclination angles in each zone. The lower portion in the first insulating layer has a larger inclination angle for enhanced adhesion, while the upper portion in the second insulating layer has a smaller inclination angle for simplified geometry and easier manufacturing.
Solution Approach 2:
Different inclination angles are applied locally to different portions of the via hole inner surface based on functional requirements. The lower insulating layer region receives a larger inclination angle to maximize adhesion strength where mechanical bonding is critical, while the upper region uses a smaller angle to maintain geometric simplicity and facilitate via hole formation and filling processes.
Data Source
AI summary
An interconnect substrate includes a first interconnect layer, an insulating layer formed on the interconnect layer and containing a filler, a via hole penetrating the insulating layer and reaching an upper surface of the first interconnect layer, and a second interconnect layer filling the via hole and electrically connected to the first interconnect layer, wherein the insulating layer includes a first layer covering the first interconnect layer and a second layer laminated on, and thinner than, the first layer, an amount of the filler in the second layer being smaller than in the first layer, an inner surface of the via hole being inclined relative to a direction perpendicular to the upper surface, an angle of the inner surface of the via hole in the first layer with respect to the upper surface being larger than an angle of the inner surface of the via hole in the second layer.