Dummy Die Placement With Molding Overlap to Prevent Backside Chipping

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Solution Overview

Problem

The semiconductor industry faces challenges in bonding integrated circuit chips directly onto substrates due to increased integration density and warpage issues in three-dimensional package structures, leading to potential cold joints and chipping during singulation.

Innovation Solution

The use of dummy dies placed adjacent to active dies and along the periphery of the package structure, with a layer of molding compound overlapping them to prevent chipping, helps reduce warpage and enhance the reliability of the package by providing support and matching the coefficient of thermal expansion, thereby minimizing stress during singulation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If integration density is increased through repeated reductions in minimum feature size, then more components can be integrated into a given area, but the area occupied by the integrated circuit decreases making direct bonding difficult

Engineering Contradiction:

Improveintegration densityVSAvoidchip area

Core Design Contradiction:

Quantity of substanceVSArea of stationary object

Solution Approach 1:

The patent transitions from 2D planar integration to 3D vertical packaging by introducing interposers and stacking multiple chips vertically. This dimensional change allows continued increase in integration density without further reducing the physical chip area, solving the contradiction between high integration density and sufficient bonding area.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Quantity of substance

If three-dimensional package structures are used to incorporate multiple chips, then integration density is improved, but warpage issues occur leading to cold joints and chipping during singulation

Engineering Contradiction:

Improveintegration densityVSAvoidpackage reliability

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent introduces dummy dies with specific material properties (matching coefficient of thermal expansion) placed at specific locations (periphery and corners) of the package structure. This local modification of mass distribution and material composition compensates for warpage stresses without affecting the functional active dies, thereby maintaining package reliability in 3D structures.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The dummy dies act as counterweights that balance the asymmetric stress distribution caused by the 3D package structure. By placing inert mass at strategic locations, the structure compensates for warpage tendencies, preventing cold joints and chipping during singulation.

Inventive Principle:

Principle #8Anti-weight (Counterweight)

3Reliability

If dummy dies are placed along the periphery to reduce warpage, then package reliability is improved, but chipping of dummy dies occurs during singulation

Engineering Contradiction:

Improvepackage reliabilityVSAvoiddummy die integrity

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent applies a layer of molding compound over the dummy dies before the singulation process. This protective layer acts as a cushion that prevents direct mechanical contact and stress concentration on the dummy dies during cutting, thereby preventing chipping while maintaining the warpage reduction benefit.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

4Quantity of substance

If the area of the integrated circuit is reduced to increase density, then more components fit in a given area, but direct bonding onto substrate becomes difficult

Engineering Contradiction:

Improvecomponent densityVSAvoidbonding ease

Core Design Contradiction:

Quantity of substanceVSEase of manufacture

Solution Approach 1:

The patent introduces an interposer as an intermediary substrate with a larger area than the small integrated circuit chip. The interposer serves as a mediator that redistributes the bonding interface area, allowing the small high-density chip to be bonded to a larger area that is easier to handle and bond to the final substrate, thus resolving the contradiction between small chip area and bonding ease.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 significantly reduces warpage by up to 60% and prevents chipping of dummy dies during the singulation process, resulting in a more reliable and stable package structure.

Implementation Method 1

matching the coefficient of thermal expansion, thereby minimizing stress during singulation

Methodology Applied

Scientific EffectCoefficient of thermal expansion matching: Thermal Expansion

Data Source

PatentUS11990429B2Dummy die placement without backside chipping

Publication Date: 2024.05.21 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A method includes bonding a second package component to a first package component, bonding a third package component to the first package component, attaching a dummy die to the first package component, encapsulating the second package component, the third package component, and the dummy die in an encapsulant, and performing a planarization process to level a top surface of the second package component with a top surface of the encapsulant. After the planarization process, an upper portion of the encapsulant overlaps the dummy die. The dummy die is sawed-through to separate the dummy die into a first dummy die portion and a second dummy die portion. The upper portion of the encapsulant is also sawed through.