Pixel Sensor Layer Stack for UV Shielding During Plasma Etching

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Solution Overview

Problem

Plasma and etching processes in semiconductor manufacturing can damage photodiodes in image sensors by forming electron-hole pairs, leading to decreased dark current and white pixel performance in pixel arrays.

Innovation Solution

A layer stack comprising a first oxide layer with a band gap less than 8.8 eV and a second oxide layer with a lower band gap is used to absorb and block ultraviolet photons, preventing electron-hole pairs from migrating to the photodiodes and reducing the effects of plasma processing and etching.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If plasma and etching processes are used in semiconductor manufacturing, then manufacturing precision and productivity are improved, but photodiodes are damaged by formation of electron-hole pairs leading to decreased dark current and white pixel performance

Engineering Contradiction:

Improvepixel array fabrication precisionVSAvoidphotodiode performance

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

An intermediary layer stack comprising a first oxide layer and a second oxide layer with different band gaps is introduced between the plasma/etching environment and the photodiodes. This layer stack absorbs ultraviolet photons and prevents electron-hole pair formation in the photodiodes, thereby protecting photodiode performance while allowing plasma and etching processes to proceed for manufacturing pixel arrays

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

A composite layer structure is formed using materials with different band gap properties. The first oxide layer has a band gap less than 8.8 eV and the second oxide layer has a lower band gap, creating a composite material system that selectively absorbs ultraviolet radiation across different energy ranges, providing comprehensive protection to the photodiodes during plasma processing

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If conventional single-layer oxide protection is used, then manufacturing is simpler, but ultraviolet photons penetrate and form electron-hole pairs in photodiodes

Engineering Contradiction:

Improveprocess simplicityVSAvoidultraviolet photon penetration

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The protection function is segmented into two distinct oxide layers, each with specific band gap characteristics. The first oxide layer (band gap < 8.8 eV) and the second oxide layer (lower band gap) work in sequence to absorb ultraviolet photons of different energies, providing comprehensive protection that a single layer cannot achieve

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Inventive Principle:

Principle #40Composite materials

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 layer stack maintains dark current, white pixel, and quantum efficiency performance while protecting photodiodes from radiation damage, thereby enhancing the overall performance of pixel sensors and arrays.

Implementation Method 1

A layer stack comprising a first oxide layer with a band gap less than 8.8 eV and a second oxide layer with a lower band gap is used to absorb and block ultraviolet photons

Methodology Applied

Scientific EffectAbsorption (EM radiation): Absorption (EM radiation)

Data Source

PatentUS20230387153A1Pixel sensor including a layer stack

Publication Date: 2023.11.30 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A pixel sensor may include a layer stack to reduce and/or block the effects of plasma and etching on a photodiode and/or other lower-level layers. The layer stack may include a first oxide layer, a layer having a band gap that is approximately less than 8.8 electron-Volts (eV), and a second oxide layer. The layer stack may reduce and/or prevent the penetration and absorption of ultraviolet photons resulting from the plasma and etching processes, which may otherwise cause the formation of electron-hole pairs in the substrate in which the photodiode is included.