Post-Passivation Interconnect Slots for Adhesion

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Solution Overview

Problem

Wafer level chip scale packaging (WLCSP) processes face polymer film peeling issues, leading to weak interfaces in post-passivation interconnect (PPI) structures and device failures due to weak interfaces and potential failures in the PPI structure.

Innovation Solution

The method involves forming slots in the passivation layer to enhance adhesion between the passivation layer and subsequent deposited material layers, followed by the formation of a PPI structure with a barrier layer and solder bump, which improves the strength of the PPI structure and reduces peeling and cracking of the polymer layer, thereby increasing joint reliability and reducing bump fatigue.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If polymer films are formed over passivation layers in conventional WLCSP processes, then the PPI structure can be formed, but polymer film peeling occurs leading to weak interfaces and device failures

Engineering Contradiction:

Improveinterface strengthVSAvoidPPI structure strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent applies preliminary action by forming slots in the passivation layer before depositing the polymer film. This pre-prepared structure creates anchoring points that prevent peeling during subsequent processing, resolving the interface strength issue without compromising PPI structure integrity

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The slots created in the passivation layer function as porous structures that allow the polymer film to penetrate and anchor into the passivation layer. This porous configuration significantly enhances adhesion between the polymer film and passivation layer, preventing peeling and strengthening the overall PPI structure

Inventive Principle:

Principle #31Porous materials

2Ease of manufacture

If conventional PPI formation processes are used, then the basic structure can be created, but peeling and cracking of the polymer layer occur reducing joint reliability

Engineering Contradiction:

ImprovePPI formation process simplicityVSAvoidjoint reliability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The slots are formed in advance during the passivation layer processing stage, before polymer deposition. This preliminary action integrates seamlessly into the existing manufacturing flow without adding complex steps, while dramatically improving joint reliability by preventing peeling and cracking

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Rather than modifying the entire passivation layer or polymer film uniformly, the invention applies local quality enhancement by creating slots only in specific regions where adhesion is critical. This localized modification maintains manufacturing simplicity while targeting the specific reliability issues

Inventive Principle:

Principle #3Local quality

3Strength

If standard passivation layer structures are used, then the basic protection is provided, but adhesion to subsequent material layers is insufficient causing interface weakness

Engineering Contradiction:

Improveadhesion strengthVSAvoidpassivation layer structure complexity

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

The passivation layer is transformed from a solid, non-porous structure to one with controlled porosity through the formation of slots. These porous features dramatically increase adhesion to subsequent material layers without requiring complex multi-layer passivation structures, maintaining relative simplicity while enhancing strength

Inventive Principle:

Principle #31Porous materials

Solution Approach 2:

The passivation layer is segmented by creating slots that divide the continuous layer into sections. This segmentation increases the surface area and creates mechanical interlocking points for subsequent layers, improving adhesion strength without significantly increasing overall device complexity

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS9006891B2Method of making a semiconductor device having a post-passivation interconnect structure

Publication Date: 2015.04.14 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A method of making a semiconductor device includes forming a passivation layer overlying a semiconductor substrate, the semiconductor substrate having a first region and a second region, wherein the first region is a conductive pad and the second region is adjacent to the first region. The method further includes forming a first protective layer overlying the passivation layer and forming an interconnect layer overlying the first protective layer. The method further includes forming a plurality of slots in the second region and forming a second protective layer overlying the interconnect layer, wherein the second protective layer fills each slot of the plurality of slots. The method further includes exposing a portion of the interconnect layer through the second protective layer; forming a barrier layer on the exposed portion of the interconnect layer; and forming a solder bump on the barrier layer.