Solid-State Imaging Element Stress Relaxation Layer

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Solution Overview

Problem

The existing methods for forming microlenses on solid-state imaging devices using an etch back process face issues with surface defects due to significant differences in film stress between inorganic and organic material layers, leading to wrinkling and distortion, which degrade the focusing properties and sensitivity of the devices.

Innovation Solution

A stress relaxation layer is interposed between the inorganic material layer and the organic material layer to attenuate the film stress difference, suppressing surface defects and improving the focusing properties of the solid-state imaging device.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If microlenses are formed by an etch back process using silicon nitride, then the refractive index difference between microlens layer and transparent resin layer is sufficient for good focusing performance, but significant film stress difference causes surface defects such as wrinkling and distortion

Engineering Contradiction:

Improvefocusing performanceVSAvoidsurface defect suppression

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

A stress relaxation layer made of silicon oxide is introduced as an intermediary between the silicon nitride microlens layer and the organic transparent resin layer. This intermediate layer has mechanical properties that bridge the gap between the inorganic microlens layer and organic resin layer, reducing the film stress difference and preventing surface defects while maintaining the refractive index difference needed for focusing performance

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent employs a composite layered structure combining different inorganic materials (silicon nitride for microlenses, silicon oxide for stress relaxation) with organic materials (transparent resin). This composite approach allows optimization of each layer's specific function: silicon nitride provides high refractive index for focusing, silicon oxide provides stress buffering, and the organic resin provides planarization and protection

Inventive Principle:

Principle #40Composite materials

2Shape

If a planarizing layer is provided on color filters to flatten the surface, then the surface uniformity is improved, but the film stress difference between inorganic microlens layer and organic planarizing layer causes wrinkling and distortion

Engineering Contradiction:

Improvesurface flatnessVSAvoidline width uniformity

Core Design Contradiction:

ShapeVSManufacturing precision

Solution Approach 1:

The stress relaxation layer acts as a mediator between the organic planarizing layer and the inorganic microlens layer. It absorbs and distributes the film stress generated by the planarizing process, preventing the transmission of stress to the microlens layer that would cause wrinkling and distortion, thereby maintaining both surface flatness and line width uniformity

Inventive Principle:

Principle #24Intermediary (Mediator)

3Shape

If the refractive index difference between microlens layer and transparent resin layer is small, then the planarized structure is achieved, but the light-converging function of microlenses becomes insufficient

Engineering Contradiction:

Improveplanarized structureVSAvoidlight collection efficiency

Core Design Contradiction:

ShapeVSManufacturing precision

Solution Approach 1:

The patent segments the optical structure into functionally distinct layers: the silicon nitride microlens layer is dedicated to light convergence with its high refractive index, while the organic transparent resin layer is dedicated to planarization and protection with its lower refractive index. The stress relaxation layer segments the mechanical stress path, allowing the optical layers to maintain their respective refractive index properties without compromise

Inventive Principle:

Principle #1Segmentation

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 use of a stress relaxation layer effectively suppresses surface defects and enhances the focusing properties and sensitivity of the solid-state imaging device, ensuring improved in-plane uniformity and line width uniformity.

Implementation Method 1

A stress relaxation layer is interposed between the inorganic material layer and the organic material layer to attenuate the film stress difference, suppressing surface defects

Methodology Applied

Scientific EffectStress relaxation: Stress Relaxation

Implementation Method 2

a microlens layer having a convexly curved surface... the incident light is converged on the photoelectric conversion parts

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentEP2595189B1Solid-state imaging element, process for producing solid-state imaging element, and electronic device

Publication Date: 2017.06.28 SONY GROUP CORP

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AI summary

The present invention relates to a solid-state imaging device having good focusing properties, a method for manufacturing such a solid-state imaging device, and an electronic apparatus. The solid-state imaging device has a semiconductor substrate 11 and a photoelectric conversion part formed in the semiconductor substrate 11. In the solid-state imaging device, a laminate including an organic material layer and an inorganic material layer is formed on the semiconductor substrate with at least one stress relaxation layer 22 interposed between the organic and inorganic material layers. This technology is applicable to, for example, solid-state imaging devices having pixels and microlenses placed thereon.