Segmented Through Vias for Reliable Metallization in Thick Substrates

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Solution Overview

Problem

High aspect ratio through vias in substrates for integrated circuits pose challenges in reliable metallization without voids or breaks, leading to increased package size due to the need for both narrow vias and a thick substrate, which complicates via formation and filling.

Innovation Solution

The formation of through vias with different segments of varying widths, where each segment is etched from one side of the substrate, reducing the aspect ratio subjected to processing, and metal is deposited only in the narrower segments to facilitate reliable metallization and reduce voids.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If the substrate is made thick to withstand mechanical and electrical stresses, then the mechanical strength and electrical integrity are improved, but the via aspect ratio increases making metallization difficult

Engineering Contradiction:

Improvemechanical strengthVSAvoidmetallization reliability

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The via is divided into multiple segments with different widths along its length. The via includes a first segment with a first width and a second segment with a second width, where the width ratio between segments differs from the depth ratio. This segmentation allows the via to maintain structural integrity through the thick substrate while providing narrower sections that facilitate reliable metallization without voids or breaks.

Inventive Principle:

Principle #1Segmentation

2Area of stationary object

If the via is made narrow to reduce package size, then the package area is reduced, but the via aspect ratio increases complicating via formation and filling

Engineering Contradiction:

Improvepackage areaVSAvoidvia formation ease

Core Design Contradiction:

Area of stationary objectVSEase of manufacture

Solution Approach 1:

Different segments of the via have different width characteristics optimized for different functions. The first segment has a wider width to facilitate etching and formation, while the second segment has a narrower width to reduce package area. This local variation in geometry allows the via to be both manufacturable and space-efficient.

Inventive Principle:

Principle #3Local quality

3Area of stationary object

If the via aspect ratio is increased to maintain narrow via width in thick substrate, then the package size is reduced, but the metallization reliability decreases due to voids or breaks

Engineering Contradiction:

Improvepackage areaVSAvoidmetallization reliability

Core Design Contradiction:

Area of stationary objectVSReliability

Solution Approach 1:

The via is segmented into portions with different width-to-depth ratios. By creating segments where the width ratio differs from the depth ratio, the patent ensures that no single segment has an excessively high aspect ratio that would prevent reliable metallization, while the overall via maintains a narrow profile suitable for thick substrates.

Inventive Principle:

Principle #1Segmentation

4Device complexity

If the via width is uniform throughout, then the manufacturing process is simpler, but the metallization of high aspect ratio vias is unreliable

Engineering Contradiction:

Improvevia structure complexityVSAvoidmetallization precision

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The via structure incorporates local variations in width to optimize different regions for different purposes. The first segment has one width characteristic optimized for etching access, while the second segment has a different width optimized for metallization fill. This localized optimization improves metallization reliability without requiring excessively complex manufacturing processes.

Inventive Principle:

Principle #3Local quality

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 allows for efficient metallization of high-aspect-ratio vias, reducing the package size while maintaining mechanical and electrical integrity, by effectively doubling the via aspect ratio without changing the etch and deposition processes, and enabling more precise control over via depth and alignment.

Implementation Method 1

metal can be deposited into the vias part way through the top and part way through the bottom

Methodology Applied

Scientific EffectElectroplating: Electroplating

Implementation Method 2

metal (or another conductive material) can be deposited into the vias

Methodology Applied

Scientific EffectElectroless plating:

Data Source

PatentUS9589879B2Substrates with through vias with conductive features for connection to integrated circuit elements, and methods for forming through vias in substrates

Publication Date: 2017.03.07 ADEIA SEMICON TECH LLC

AI summary

A through via (144) contains a conductor (244, 276) passing through a substrate (140) for connection to an integrated circuit element. The through via consists of two segments (144.1, 144.2) formed from respective different sides (140.1, 140.2) of the substrate and meeting inside the substrate. Each segment is shorter than the entire via, so via formation is facilitated. The second segment is etched after deposition of an etch stop layer (214) into the first segment. Due to the etch stop layer, the first segment's depth does not have to be rigidly controlled. The conductor is formed by separate depositions of conductive material into the via from each side of the substrate. From each side, the conductor is deposited to a shallower depth than the via depth, so the deposition is facilitated. Other embodiments are also provided.