CMOS Image Sensor Silicon Germanium Infrared Sensitivity

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Solution Overview

Problem

CMOS image sensors have poor sensitivity to infrared radiation due to limitations in existing manufacturing processes, which complicates the integration of silicon germanium for improved infrared absorption without increasing manufacturing costs.

Innovation Solution

A CMOS image sensor design featuring a semiconductor stack with elemental silicon and silicon germanium layers, where the photodetector is partially buried in the silicon germanium layer for enhanced infrared sensitivity, and the transistor is arranged on the elemental silicon layer, allowing for conventional CMOS process compatibility.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If silicon germanium is used to improve infrared absorption, then sensitivity to infrared radiation is improved, but manufacturing cost increases

Engineering Contradiction:

Improvesensitivity to infrared radiationVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent applies local quality by using silicon germanium specifically in the photodetector region where infrared absorption is needed, while other parts of the device can use standard silicon. This targeted material placement improves infrared sensitivity without requiring the entire device to be manufactured with expensive silicon germanium, thus resolving the cost-sensitivity contradiction.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent employs composite materials by integrating silicon germanium layers with standard silicon structures to create a hybrid device. The silicon germanium provides enhanced infrared absorption properties in the photodetector region, while the overall device maintains compatibility with conventional silicon manufacturing processes, balancing performance improvement with cost control.

Inventive Principle:

Principle #40Composite materials

2Reliability

If silicon germanium is used for photodetector, then infrared absorption is enhanced, but device complexity increases

Engineering Contradiction:

Improveinfrared absorptionVSAvoiddevice complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent segments the device into distinct functional regions with different materials: silicon germanium is used specifically for the photodetector function requiring infrared absorption, while other circuit elements use standard silicon. This segmentation allows infrared enhancement without complicating the entire device structure, as each segment can be optimized independently for its specific function.

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

This design improves the sensitivity and absorption of long-wavelength radiation, such as infrared, while maintaining cost-effectiveness by utilizing conventional CMOS processes for transistor formation.

Implementation Method 1

silicon germanium for improved infrared absorption

Methodology Applied

Scientific EffectInfrared absorption: Absorption (EM radiation)

Data Source

PatentUS9859325B2Complementary metal-oxide-semiconductor (CMOS) image sensor with silicon and silicon germanium

Publication Date: 2018.01.02 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A complementary metal-oxide-semiconductor (CMOS) image sensor with silicon and silicon germanium is provided. A silicon germanium layer abuts a silicon layer. A photodetector is arranged in the silicon germanium layer. A transistor is arranged on the silicon layer with a source/drain region that is buried in a surface of the silicon layer and that is electrically coupled to the photodetector. A method for manufacturing the CMOS image sensor is also provided.