Self-Aligned Via Structure for Fine-Pitch Redistribution Lines

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Solution Overview

Problem

Existing redistribution structures in integrated circuits face challenges in achieving high density and reduced pitch due to misalignment issues in via formation, necessitating larger metal pads for via landing, which limits the minimum pitch of redistribution lines.

Innovation Solution

A self-aligned via structure is formed by recessing metal lines to create trenches, filling them with a photo-sensitive material, and patterning to form via openings that are vertically aligned to the edges of the underlying metal lines, allowing for reduced pitch and increased density without the need for larger pads.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional via formation methods are used with metal pads, then via alignment is achieved, but the minimum pitch of redistribution lines is increased due to the need for larger pads

Engineering Contradiction:

Improvevia alignment precisionVSAvoidminimum pitch of redistribution lines

Core Design Contradiction:

Manufacturing precisionVSLength of moving object

Solution Approach 1:

The via structure uses self-aligned formation where the via opening is automatically positioned relative to the metal line through the recessing process. The photo-sensitive material is filled into the recessed region and patterned to form a via opening that is self-aligned to the metal line, eliminating the need for separate alignment processes and larger metal pads.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The invention transitions from a planar via formation approach to a three-dimensional recessing approach. By recessing the metal line to form a trench and filling it with photo-sensitive material, the via opening can be precisely positioned in the vertical dimension while maintaining minimal horizontal pitch between redistribution lines.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Manufacturing precision

If larger metal pads are used for via landing, then via alignment is improved, but the density of redistribution structures is reduced

Engineering Contradiction:

Improvevia landing alignmentVSAvoiddensity of redistribution structures

Core Design Contradiction:

Manufacturing precisionVSQuantity of substance

Solution Approach 1:

The via opening is self-aligned to the metal line through the recessing and filling process, eliminating the need for larger metal pads. The photo-sensitive material is patterned to form a via opening that automatically aligns with the recessed metal line, achieving precise via landing while maintaining high structure density.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The metal line is recessed only in the specific region where the via needs to land, creating a localized trench. This localized modification allows precise via positioning without increasing the overall size of the metal pad, thereby maintaining high redistribution structure density.

Inventive Principle:

Principle #3Local quality

3Ease of manufacture

If conventional via formation is used without recessing, then manufacturing process is simpler, but alignment precision between via and metal line deteriorates

Engineering Contradiction:

Improvevia formation process simplicityVSAvoidvia to metal line alignment

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The recessing process creates a physical structure that guides the via opening formation. The photo-sensitive material is filled into the recessed region and patterned to form a via opening that is inherently aligned with the metal line, making the alignment process self-service rather than requiring complex external alignment procedures.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The metal line is recessed in advance before via opening formation. This preliminary action creates a prepared structure that facilitates subsequent via opening formation with automatic alignment, improving precision while maintaining process simplicity through sequential rather than simultaneous operations.

Inventive Principle:

Principle #10Preliminary action

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 method enables precise alignment of vias to metal lines, reducing the minimum pitch of redistribution lines and enhancing the density of redistribution structures, thereby improving the efficiency and performance of integrated circuits.

Implementation Method 1

filling them with a photo-sensitive material, and patterning to form via openings

Methodology Applied

Scientific EffectPhotolithography: Photopolymerisation

Data Source

PatentUS20260033313A1Self-aligned via structure and the methods of forming the same

Publication Date: 2026.01.29 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A method includes forming a first metal line, forming a dielectric layer, with the first metal line being in the dielectric layer, and etching back the first metal line to form a trench in the dielectric layer. A lower part of the first metal line remains under the trench. The method further includes filling a photo sensitive material in the trench, and performing a photolithography process to pattern the photo sensitive material. A via opening is formed in the dielectric layer and the photo sensitive material. A second metal line and a via are formed, wherein the via is formed in the via opening, and the second metal line is over and joined to the via.