Single-Poly Floating Gate Sensor Array for Radiation Dosage Measurement

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Solution Overview

Problem

Existing radiation sensor technologies are unable to accurately measure low radiation doses and fail to distinguish between different radiation energies, while also being unable to compensate for non-radiation based leakage factors such as temperature and natural retention loss of charge from floating gates.

Innovation Solution

A radiation sensor array utilizing single-poly floating gate cells logically grouped into pairs, with differential read operations to identify threshold voltage differences, and a multi-layer interconnect structure with radiation filters to distinguish between radiation energies, while minimizing capacitance to enhance sensitivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If double polysilicon floating gate transistors are used for radiation sensing, then radiation detection capability is achieved, but charge loss from thermal excitation and ion presence cannot be compensated

Engineering Contradiction:

Improveradiation detection capabilityVSAvoidcharge retention stability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The sensor array is divided into sensor cells and reference cells that are physically separated. Reference cells lack the floating gate extension over field dielectric, making them insensitive to radiation. This segmentation allows differential measurement that compensates for charge loss while maintaining radiation detection capability in sensor cells

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Reference cells serve as an intermediary element that experiences the same environmental conditions (temperature, charge retention loss) as sensor cells but is insensitive to radiation. By comparing sensor cell responses with reference cell responses, the system compensates for non-radiation-related charge loss

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If single polysilicon floating gate cells are used, then device complexity is reduced, but ability to distinguish radiation energies is lost

Engineering Contradiction:

Improvepolysilicon layer structureVSAvoidradiation energy discrimination

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent introduces a temporal dimension to the measurement process by performing multiple measurements at different times. The first measurement captures total threshold voltage change, while the second measurement taken after a delay captures remaining charge. This temporal separation allows energy discrimination without adding structural complexity

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Measurement precision

If floating gate capacitance is reduced to enhance sensitivity, then low dose radiation detection is improved, but natural retention loss and temperature effects increase

Engineering Contradiction:

Improvelow dose radiation detection sensitivityVSAvoidcharge retention stability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

Reference cells with matching capacitance values serve as mediators that experience the same charge retention loss and temperature effects as low-capacitance sensor cells. By differential comparison, the system compensates for these effects while maintaining enhanced sensitivity to low dose radiation

Inventive Principle:

Principle #24Intermediary (Mediator)

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

Enables accurate measurement of both low and high radiation doses, compensates for temperature and charge retention losses, and effectively differentiates between radiation energies, improving the sensitivity and accuracy of radiation detection.

Implementation Method 1

exposing a plurality of single-poly floating gate sensor cells to radiation

Methodology Applied

Scientific EffectIonizing radiation: Radiation

Implementation Method 2

identifying a threshold voltage difference between the logical pair of the exposed sensor cells

Methodology Applied

Scientific EffectThreshold voltage change: Electric Field

Data Source

PatentUS11644580B2High resolution radiation sensor based on single polysilicon floating gate array

Publication Date: 2023.05.09 TOWER SEMICONDUCTOR LTD

AI summary

A method for radiation dosage measurement includes: (1) exposing a plurality of single-poly floating gate sensor cells to radiation; (2) measuring threshold voltage differences between logical pairs of the exposed sensor cells using differential read operations, wherein the sensor cells of each logical pair are separated by a distance large enough that radiation impinging on one of the sensor cells does not influence the other sensor cell; (3) determining whether each logical pair of exposed sensor cells is influenced by exposure to the radiation in response to the corresponding measured threshold voltage difference; and (4) determining a dosage of the radiation in response to the number of logical pairs of the exposed sensor cells determined to be influenced by exposure to the radiation. A non-radiation influenced threshold voltage shift may be measured and used in determining whether each logical pair of exposed sensor cells is influenced by radiation exposure.