Thinned Substrate Detector Architecture with Optical Support

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Solution Overview

Problem

Backside illuminated photodetector arrays with thinned substrates face fragility issues due to reduced structural integrity, which can lead to damage during processing, and result in reduced detected quantum efficiency (DQE) if the substrate is too thin, causing significant attenuation of incident illumination.

Innovation Solution

The use of an optical substrate with sufficient structural support, attached to the thinned substrate, provides stability and allows for higher optical transmittance while maintaining the thinness required for reduced substrate absorption, thereby increasing the amount of incident illumination reaching the photodetectors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If the substrate is thinned to reduce substrate absorption, then optical transmittance is improved, but structural integrity deteriorates

Engineering Contradiction:

Improveoptical transmittanceVSAvoidstructural integrity

Core Design Contradiction:

Illumination intensityVSStrength

Solution Approach 1:

The substrate system is segmented into two functional parts: a thinned substrate layer (10-30 μm) optimized for optical transmittance and a separate carrier substrate optimized for structural support. This segmentation allows each layer to be optimized for its specific function without compromise.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The thinned substrate acts as an intermediary layer between the carrier substrate and the photodetector array. It provides the necessary optical transparency while the carrier substrate provides mechanical support, mediating between optical and mechanical requirements.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the substrate is thinned to increase detected quantum efficiency, then detection efficiency is improved, but fragility increases

Engineering Contradiction:

Improvedetected quantum efficiencyVSAvoidfragility

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The system segments the structural support function from the optical detection function. The carrier substrate provides mechanical strength while the thinned substrate enables high detection efficiency, allowing each to be optimized independently.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The detector assembly forms a composite structure combining the carrier substrate (for strength) and the thinned substrate (for optical performance). This composite approach combines the advantages of both thick and thin substrates.

Inventive Principle:

Principle #40Composite materials

3Illumination intensity

If the substrate is thinned to reduce attenuation, then optical transmittance is improved, but manufacturing complexity increases

Engineering Contradiction:

Improveoptical transmittanceVSAvoidprocessing complexity

Core Design Contradiction:

Illumination intensityVSDevice complexity

Solution Approach 1:

The carrier substrate is prepared in advance with attachment surfaces and structures before the thinned substrate is bonded to it. This preliminary preparation simplifies the overall manufacturing process by breaking down complex steps into manageable sequences.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The thinned substrate maintains its structural stability through the bonding process by relying on the carrier substrate's support structure. The design allows the substrate to be processed to thin dimensions while the carrier substrate automatically provides the necessary support during subsequent steps.

Inventive Principle:

Principle #25Self-service

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 enhances detected quantum efficiency (DQE) by ensuring the thinned substrate remains structurally intact during processing and maintains high optical transmittance, reducing variations in light absorption and improving detection efficiency.

Implementation Method 1

The thinned substrate reduces an effect of the substrate on illumination that passes through the substrate to the photodetectors

Methodology Applied

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

Implementation Method 2

back side illuminated photodetector arrays use thinned substrates

Methodology Applied

Scientific EffectPhotoelectric Effect: Photoelectric Effect

Data Source

PatentUS10971541B2Detector architecture using photodetector arrays on thinned substrates

Publication Date: 2021.04.06 VAREX IMAGING CORP

AI summary

Some embodiments include a method, comprising: attaching a carrier substrate to a side of at least one semiconductor substrate, the at least one semiconductor substrate including photodetectors on the side; thinning the at least one semiconductor substrate while the at least one semiconductor substrate is attached to the carrier substrate; attaching an optical substrate to the at least one semiconductor substrate while the at least one semiconductor substrate is attached to the carrier substrate; and removing the carrier substrate from the at least one semiconductor substrate.