TPV Openings for Reliable PoP Bonding

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Solution Overview

Problem

The semiconductor industry faces challenges in forming reliable bonding structures between die packages due to issues such as copper oxide formation on through-package-vias (TPVs), which affects yield and reliability, and stress caused by varying coefficients of thermal expansion leading to warpage and cracking in package-on-package (PoP) structures.

Innovation Solution

The formation of openings surrounding the end-portions of TPVs using laser drilling to expose the top portions, allowing for a three-dimensional intermetallic compound (IMC) layer that is stronger and less prone to cracking, and the use of polymers to fill these openings or the space between die packages for stress relief.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If through-package-vias (TPVs) are used to bond die packages, then integration levels are increased, but copper oxide formation on TPVs occurs which reduces yield and reliability

Engineering Contradiction:

Improveintegration levelVSAvoidbonding structure reliability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent applies preliminary action by forming a protective conformal dielectric coating on the TPV surfaces before bonding occurs. This coating prevents copper oxide formation in advance, ensuring reliable bonding interfaces when the die packages are subsequently bonded together.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces a conformal dielectric layer as an intermediary substance between the copper TPVs and the bonding interface. This intermediate layer prevents direct oxidation of copper while maintaining electrical and mechanical connectivity, resolving the reliability issue without sacrificing integration benefits.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If die packages are bonded together in package-on-package structures, then integration density is improved, but stress from varying coefficients of thermal expansion causes warpage and cracking

Engineering Contradiction:

Improveintegration densityVSAvoidpackage structure integrity

Core Design Contradiction:

ProductivityVSStrength

Solution Approach 1:

The patent modifies the physical parameters of the bonding interface by introducing a compliant conformal dielectric coating with different mechanical properties than the rigid copper TPVs and ceramic substrates. This parameter change allows stress accommodation during thermal cycling, preventing warpage and cracking while maintaining high integration density.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite structure at the bonding interface by combining copper TPVs, conformal dielectric coating, and ceramic substrates. This composite material approach leverages the advantages of each material while mitigating their individual weaknesses, particularly the thermal expansion mismatch that causes stress in PoP structures.

Inventive Principle:

Principle #40Composite materials

3Ease of manufacture

If conventional bonding processes are used without openings around TPVs, then manufacturing is simpler, but IMC layers are prone to cracking under stress

Engineering Contradiction:

Improvebonding process simplicityVSAvoidIMC layer reliability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent applies segmentation by creating openings in the conformal dielectric coating that expose portions of the TPVs. This segmentation allows the IMC layer to form in a distributed manner around exposed TPV regions, reducing stress concentration and preventing cracking while maintaining manufacturing feasibility.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent transitions from a planar bonding interface to a three-dimensional structure with openings and exposed TPV portions. This dimensional change allows the IMC layer to form in multiple zones (both within and around the openings), creating a more robust bonding structure that resists cracking under thermal stress.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 enhances the yield and reliability of bonding structures by preventing copper oxide formation and reducing stress-induced cracking, resulting in more robust connections between die packages.

Implementation Method 1

The formation of openings surrounding the end-portions of TPVs using laser drilling to expose the top portions

Methodology Applied

Scientific EffectLaser drilling: Laser Ablation

Data Source

PatentUS10079159B2Die package with openings surrounding end-portions of through package vias (TPVs) and package on package (PoP) using the die package

Publication Date: 2018.09.18 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

Various embodiments of mechanisms for forming through package vias (TPVs) with openings surrounding end-portions of the TPVs and a package on package (PoP) device with bonding structures utilizing the TPVs are provided. The openings are formed by removing materials, such as by laser drill, surrounding the end-portions of the TPVs. The openings surrounding the end-portions of the TPVs of the die package enable solders of the bonding structures formed between another die package to remain in the openings without sliding and consequently increases yield and reliability of the bonding structures. Polymers may also be added to fill the openings surrounding the TPVs or even the space between the die packages to reduce cracking of the bonding structures under stress.