Secondary Electron Absorbing Tray for Semiconductor Wafer Irradiation

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Solution Overview

Problem

Wafer-to-wafer variations in electrical characteristics of semiconductor devices occur due to secondary electrons emitted during charged particle irradiation, leading to lower production yields and higher device failure rates.

Innovation Solution

A substrate carrier structure with a secondary electron absorbing material interposed between the tray and the semiconductor substrate to absorb secondary electrons emitted during irradiation, reducing variations in electrical characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If wafers are placed in trays and irradiated with charged particle beams under identical conditions, then the irradiation process can be standardized and productivity improved, but wafer-to-wafer variations occur in electrical characteristics such as gate threshold voltage

Engineering Contradiction:

Improveirradiation process standardizationVSAvoidelectrical characteristic consistency

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

A protective sheet made of secondary electron absorbing material is introduced as an intermediary between the tray and the wafer. This sheet absorbs secondary electrons emitted from the tray during irradiation, preventing them from reentering the wafer and causing variations in electrical characteristics. The protective sheet thus mediates the interaction between the tray and wafer, eliminating the harmful effect while maintaining the standardized tray structure.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention converts the harmful secondary electrons emitted from the tray into a beneficial effect by using them to activate the protective sheet's electron-absorbing function. The secondary electrons that would otherwise cause wafer variations are now absorbed by the protective sheet, transforming a harmful byproduct of the irradiation process into a functional mechanism for improving manufacturing precision.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Productivity

If secondary electrons are emitted from the tray during irradiation, then the irradiation process can proceed efficiently, but variations in electrical characteristics occur due to secondary electrons reentering the wafers

Engineering Contradiction:

Improveirradiation efficiencyVSAvoiddevice failure rate

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The protective sheet serves as an intermediary that selectively absorbs secondary electrons while allowing the irradiation process to continue efficiently. It positioned between the tray and wafer, it intercepts secondary electrons before they can reenter the wafer and cause device failures, thus improving reliability without compromising irradiation efficiency.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Device complexity

If no protective material is used between tray and wafer, then device complexity is reduced and manufacturing is simpler, but wafer-to-wafer variations increase leading to lower production yields

Engineering Contradiction:

Improvecarrier structure simplicityVSAvoidproduction yield

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The protective sheet is a simple, inexpensive, and easily replaceable component made of secondary electron absorbing material. Although it adds a minor element to the carrier structure, its low cost and simple implementation (as a thin sheet) mean it does not significantly increase device complexity, while its effect on improving production yield by eliminating wafer variations is substantial.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

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 secondary electron absorbing material effectively reduces variations in electrical characteristics of semiconductor devices by preventing secondary electrons from reentering the wafers, resulting in more consistent device performance.

Implementation Method 1

secondary electrons emitted from the tray during the irradiation step

Methodology Applied

Scientific EffectSecondary electron emission: Photoelectric Effect

Implementation Method 2

the secondary electron absorbing material reduces variations in electrical characteristics by absorbing secondary electrons

Methodology Applied

Scientific EffectElectron absorption: Absorption (physical)

Data Source

PatentUS8216919B2Method of manufacturing a semiconductor device and substrate carrier structure

Publication Date: 2012.07.10 LAPIS SEMICON CO LTD

AI summary

A substrate carrier structure includes a tray and a secondary electron absorbing material. The tray holds a semiconductor substrate having a first surface on which semiconductor device elements are formed. The secondary electron absorbing material is interposed between the tray and this first surface of the semiconductor substrate. When the semiconductor substrate is irradiated with charged particles to form lattice defects, the secondary electron absorbing material prevents unwanted trapping of secondary electrons emitted from the tray, and thereby reduces the variability of electrical characteristics of semiconductor device elements formed on the semiconductor substrate.