Interconnect Pad Density Variation for Crack Resistance

Solution Overview

Problem

Conventional multi-level interconnect structures in semiconductor ICs are susceptible to cracking during the die saw process due to high mechanical stress, particularly when using low-k dielectric materials, leading to increased failure rates and reduced production yield.

Innovation Solution

The implementation of interconnect structures with varying pad densities across different layers, where at least one layer has a pad density sufficient for probe testing and others have lower densities, thereby reducing the average pad density to below 50%, minimizing cracking failures during singulation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If bond pads are included in all interconnect layers with high density for probe testing, then testing capability is improved, but mechanical stress during die saw increases causing cracking

Engineering Contradiction:

Improveprobe testing capabilityVSAvoidresistance to cracking during die saw

Core Design Contradiction:

Ease of operationVSStrength

Solution Approach 1:

The pad structure is segmented across different interconnect layers with varying densities. The first through third interconnect layers have a first pad density (10-50%) optimized for mechanical strength, while the fourth and fifth layers have a second pad density (50-85%) optimized for probe testing. This segmentation allows each layer to serve different functional requirements, resolving the contradiction between testing capability and crack resistance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the interconnect structure have different pad densities tailored to their specific functions. Lower pad densities are applied in layers where mechanical strength is critical, while higher pad densities are applied in top layers where probe testing is performed. This local differentiation of quality allows the structure to simultaneously achieve both crack resistance and testing capability.

Inventive Principle:

Principle #3Local quality

2Ease of operation

If uniform high pad density is used across all interconnect layers, then probe testing capability is improved, but production yield decreases due to cracking

Engineering Contradiction:

Improveprobe testing capabilityVSAvoidproduction yield

Core Design Contradiction:

Ease of operationVSProductivity

Solution Approach 1:

The pad structure is segmented across different interconnect layers with varying densities. The first through third interconnect layers have a first pad density (10-50%) optimized for mechanical strength, while the fourth and fifth layers have a second pad density (50-85%) optimized for probe testing. This segmentation allows each layer to serve different functional requirements, resolving the contradiction between testing capability and crack resistance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the interconnect structure have different pad densities tailored to their specific functions. Lower pad densities are applied in layers where mechanical strength is critical, while higher pad densities are applied in top layers where probe testing is performed. This local differentiation of quality allows the structure to simultaneously achieve both crack resistance and testing capability.

Inventive Principle:

Principle #3Local quality

3Speed

If low-k dielectric material is used in interconnect structure, then RC delay is reduced, but brittleness increases making the structure more susceptible to cracking

Engineering Contradiction:

Improvesignal transmission speedVSAvoidresistance to cracking

Core Design Contradiction:

SpeedVSStrength

Solution Approach 1:

The pad density parameter is changed across different interconnect layers to compensate for the brittleness of low-k dielectric material. By reducing pad density in lower layers (first through third layers to 10-50%), the mechanical stress on the brittle low-k dielectric is reduced, preventing cracking while maintaining the speed benefits of low-k material in the interconnect structure.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS7714443B2Pad structure design with reduced density

Publication Date: 2010.05.11 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

An interconnect structure includes at least a first interconnect layer and a second interconnect layer. Each of the first and second interconnect layers has a pad structure and each pad structure has a respective pad density. The pad density of the pad structure of the second interconnect layer is different from the pad density of the pad structure of the first interconnect layer. The pad structures of the first and second interconnect layers are connected to each other.