Image Sensor Substrate Thinning with Edge Protective Film

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Solution Overview

Problem

In three-dimensional LSI semiconductor devices, the grinding process for thinning substrates often results in damage to lower-layer substrates due to stress-induced cracking or peeling of upper-layer substrates, leading to reliability and yield issues.

Innovation Solution

A method involving the formation of protective films on the edges of substrates to mitigate damage during thinning, either by applying a protective film to the lower-layer substrate before reducing the upper-layer substrate's thickness or by forming a thinned portion on the upper-layer substrate and using a laser to remove it, thereby preventing damage to the lower-layer substrate.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the upper-layer substrate is thinned using a grinding process, then the thickness of the upper-layer substrate is reduced, but the lower-layer substrate is damaged due to stress-induced cracking or peeling of the upper-layer substrate

Engineering Contradiction:

Improvethickness of upper-layer substrateVSAvoidintegrity of lower-layer substrate

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

A protective film is formed on the lower-layer substrate before the thinning process. This preliminary protective action prevents direct contact between the grinding surface and the lower-layer substrate, thereby preventing stress-induced cracking or peeling during the thinning of the upper-layer substrate

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

A protective film is introduced as an intermediary layer between the upper-layer substrate and the lower-layer substrate. This intermediate layer absorbs and distributes the stress during grinding, preventing it from reaching the lower-layer substrate and causing damage

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of manufacture

If the edge of the upper-layer substrate is processed in an acute-angled shape, then the thinning process is facilitated, but broken pieces from cracking or peeling strike and damage the lower-layer substrate

Engineering Contradiction:

Improveease of thinning processVSAvoidbroken pieces damaging lower-layer substrate

Core Design Contradiction:

Ease of manufactureVSObject-generated harmful factors

Solution Approach 1:

A protective film is applied to the lower-layer substrate before the thinning process. This cushioning layer absorbs the impact of broken pieces generated during acute-angled edge processing, preventing them from striking and damaging the lower-layer substrate

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The protective film converts the harmful effect of broken pieces into a beneficial outcome by absorbing their impact energy. The broken pieces that would otherwise damage the lower-layer substrate are now contained and their harmful effect is neutralized by the protective film

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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

The proposed methods effectively reduce substrate damage during thinning, enhancing the reliability and manufacturing yield of semiconductor devices by preventing contamination and dust generation from broken edges.

Implementation Method 1

an edge of an upper-layer substrate that is processed by the grinding in an acute-angled shape and that is called a knife edge as we say is unendurable against a stress to be exerted thereon

Methodology Applied

Scientific EffectStress absorption:

Implementation Method 2

selectively removing the thinned portion of the first substrate using a laser

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Data Source

PatentUS9941326B2Method of manufacturing an image sensor by joining a pixel circuit substrate and a logic circuit substrate and thereafter thinning the pixel circuit substrate

Publication Date: 2018.04.10 SONY GROUP CORP

AI summary

The present technology includes: bonding a device formation side of a first substrate having a first device and a device formation side of a second substrate having a second device in opposition to each other; forming a protective film on at least an edge of the second substrate having the second device; and reducing a thickness of the first substrate.