Imaging Element Pad Segmentation for Bonding Damage Prevention

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Solution Overview

Problem

Conventional imaging elements are damaged during the bonding process due to the inspection probe's needle causing undulations on the semiconductor chip's surface, leading to potential damage and reduced yield.

Innovation Solution

The imaging element incorporates a second pad with a protrusion on one semiconductor chip and an insulating film between the pads to prevent damage during bonding, with the second pad having a different size than the first pad, and optionally including a protective metal film and a third pad for external connection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If electrical inspection is performed by bringing the inspection probe needle into contact with the inspection pad at high needle pressure, then electrical resistance is reduced and reliable electrical connection is achieved, but undulations are formed on the inspection pad surface causing damage to the imaging element during bonding

Engineering Contradiction:

Improveelectrical connection reliabilityVSAvoidsurface undulation damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The pad structure is segmented into two distinct types: first pads for bonding purposes and second pads for inspection purposes. This segmentation allows each pad type to be optimized for its specific function, preventing the inspection probe from damaging the bonding surface while maintaining reliable electrical connection during inspection.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the semiconductor chip are given different local qualities: the first pad region is designed for bonding with flat surfaces, while the second pad region is designed to withstand probe contact with形成的 protrusions. This local differentiation ensures that the harmful effect of probe contact is confined to the inspection pad area and does not affect the bonding quality of other regions.

Inventive Principle:

Principle #3Local quality

2Productivity

If semiconductor chips are bonded together in wafer state using WoW method, then productivity is improved, but yield is lowered due to defective chips being included in the bonded wafers

Engineering Contradiction:

Improvemanufacturing efficiencyVSAvoidproduct yield

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

Electrical inspection is performed on semiconductor chips before the bonding process. This preliminary action identifies and isolates defective chips, ensuring that only non-defective chips are bonded together. By performing inspection beforehand, the method prevents defective chips from contaminating the entire bonded wafer, thus maintaining high yield while preserving the productivity benefits of wafer-level bonding.

Inventive Principle:

Principle #10Preliminary action

3Manufacturing precision

If the inspection probe needle contacts the inspection pad at high pressure to reduce electrical resistance, then good electrical contact is achieved, but the needle creates undulations that may damage opposing semiconductor chips during bonding

Engineering Contradiction:

Improveelectrical contact qualityVSAvoidchip surface integrity

Core Design Contradiction:

Manufacturing precisionVSStrength

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The second pad acts as an intermediary structure that absorbs the mechanical impact of the inspection probe. The protrusion formed on the second pad serves as a dedicated contact point that protects the underlying chip structure and the opposing chip from damage while still enabling reliable electrical connection for inspection purposes.

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 configuration protects the imaging element from damage during bonding, improving yield by preventing contact between the inspection probe's protrusion and the opposing chip, ensuring reliable bonding and functionality.

Implementation Method 1

one of the plurality of semiconductor chips is provided with a photoelectric conversion unit for performing photoelectric conversion of incident light

Methodology Applied

Scientific EffectPhotoelectric conversion: Photoelectric Effect

Data Source

PatentUS20230139201A1Imaging element and method for manufacturing imaging element

Publication Date: 2023.05.04 SONY SEMICON SOLUTIONS CORP

AI summary

To prevent damage to an imaging element configured by bonding a plurality of semiconductor chips together. The imaging element includes a plurality of semiconductor chips each having a semiconductor substrate and a wiring region. One of the plurality of semiconductor chips is provided with a photoelectric conversion unit for performing photoelectric conversion of incident light. Two of the plurality of semiconductor chips are provided with first pads in which surfaces of wiring regions of the two semiconductor chips are bonded to each other and which are arranged on the surfaces of the wiring regions and bonded to each other. At least one of the two semiconductor chips is provided with a second pad arranged in the wiring region and having a protrusion formed thereon so as to face toward the bonded surface. The second pad is configured to have a size different from that of the first pad.