Semiconductor Radiation Detector Modified Internal Gate Structure

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Solution Overview

Problem

Semiconductor radiation detectors face issues such as poor blue response, red response, blooming, smear, and high leakage current due to surface defects and interface-related leakage currents, which affect measurement accuracy and flexibility.

Innovation Solution

A modified internal gate (MIG) structure is introduced to isolate signal charge from depleted interfaces, using a layered structure with alternating semiconductor regions of different conductivity types to reduce leakage current and enhance measurement accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If the substrate is thinned to improve blue response, then blue response is improved, but manufacturing yield deteriorates due to difficulty in thinning process

Engineering Contradiction:

Improveblue responseVSAvoidmanufacturing yield

Core Design Contradiction:

Illumination intensityVSEase of manufacture

Solution Approach 1:

Instead of thinning the substrate from the front side, the patent inverts the approach by using back illumination with a thick substrate. The radiation enters through the back surface, allowing the substrate to remain thick for good red response while still achieving excellent blue response through the back illumination geometry.

Inventive Principle:

Principle #13The other way round (Inversion)

2Illumination intensity

If a thick fully depleted substrate is used to improve red response, then red response is improved, but leakage current increases due to depleted interfaces

Engineering Contradiction:

Improvered responseVSAvoidleakage current

Core Design Contradiction:

Illumination intensityVSObject-generated harmful factors

Solution Approach 1:

The patent extracts or removes the depleted interface regions from the signal collection path by creating a buried channel structure. The signal charge is collected in a channel that is isolated from the depleted pn-junction interfaces, thereby eliminating the source of interface-related leakage current while maintaining thick substrate for good red response.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces a buried channel as an intermediary structure between the incident radiation and the readout electronics. This buried channel collects signal charge away from the depleted interfaces, acting as a mediator that prevents leakage current generation at the interfaces while still allowing charge collection from the thick substrate.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Loss of information

If charge is transported long distances in a CCD to read the entire image frame, then complete image reading is achieved, but operation speed deteriorates and flexibility is reduced

Engineering Contradiction:

Improvecomplete image readingVSAvoidoperation speed

Core Design Contradiction:

Loss of informationVSSpeed

Solution Approach 1:

The patent segments the image sensor into independently readable pixel regions, allowing selective reading of only the regions of interest. This segmentation enables random access to different parts of the image without requiring transport of the entire image frame, thereby improving operation speed and flexibility.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces dynamic control over charge collection and reading operations, allowing the system to adaptively select which regions to read and when. This dynamic operation enables flexible imaging modes where only relevant portions of the image are processed, significantly improving speed and efficiency compared to static frame-by-frame reading.

Inventive Principle:

Principle #15Dynamics

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 MIG structure significantly reduces leakage current, improves measurement accuracy, and allows for non-destructive signal charge reading, enabling higher operation temperatures and increased quantum efficiency for near-infrared photons, while also addressing issues like blooming and smear.

Implementation Method 1

An incident photon (or a particle, such as alfa or beta particle or proton) causes a photoelectric effect, locally creating electron/hole pairs.

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Implementation Method 2

The electric field of the depleted region segregates the charge carriers, one type of which is used as the signal charge.

Methodology Applied

Scientific EffectElectric field segregation: Electric Field

Implementation Method 3

Methodology Applied

Scientific EffectLeakage current reduction through layered structure:

Data Source

PatentUS7816653B2Semiconductor radiation detector with a modified internal gate structure

Publication Date: 2010.10.19 AUROLA ARTTO

AI summary

A semiconductor radiation detector device comprises a conductive backside layer (102) of first conductivity type and a bulk layer (103). Opposite to the conductive backside layer (102) there are a modified internal gate layer (104) of second conductivity type, a barrier layer (105) of the first conductivity type and pixel dopings (110, 112, 506, 510, 512) of the second conductivity type. The pixel dopings are adapted to be coupled to a pixel voltage, which is defined as a potential difference to a potential of the conductive backside layer (102), and which creates potential minima inside the detector material for trapping the signal charges.