EUV Patterning Stack with Electron Reflector for Lower Dose

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Solution Overview

Problem

In extreme ultraviolet (EUV) lithography, the low photon count due to high energy photons being difficult to absorb by most materials leads to poor quality lithography structures, especially at small sizes, due to the photon shot noise effect, necessitating methods to enhance the absorption and conversion of each photon into multiple secondary electrons.

Innovation Solution

The introduction of an electron reflector layer overlying the substrate, which reflects secondary electrons generated by the EUV resist back towards the resist, improving absorption and reducing electron loss to the substrate, using materials like aluminum and magnesium in the electron reflection layer, and optionally incorporating a glue layer and secondary electron generation layer to enhance electron transfer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If high energy EUV photons are used to improve resolution, then wavelength is decreased, but photon absorption becomes difficult and photon count is reduced

Engineering Contradiction:

ImproveresolutionVSAvoidphoton count

Core Design Contradiction:

Measurement precisionVSQuantity of substance

Solution Approach 1:

An electron reflector layer is introduced as an intermediary component between the substrate and the resist. This layer reflects secondary electrons generated in the resist back toward the resist, preventing electron loss to the substrate and thereby improving the effective utilization of absorbed photons without changing the photon wavelength or energy.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Use of energy by moving object

If EUV absorbing materials are inserted to improve photon absorption, then absorption is improved, but electron loss to substrate occurs and shot noise remains high

Engineering Contradiction:

Improvephoton absorptionVSAvoidelectron loss

Core Design Contradiction:

Use of energy by moving objectVSLoss of energy

Solution Approach 1:

The electron reflector layer converts the potentially harmful loss of secondary electrons to the substrate into a beneficial effect by reflecting these electrons back into the resist. This transforms electron loss into additional useful ionization events that enhance the lithographic process efficiency.

Inventive Principle:

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

3Use of energy by stationary object

If photon flux or exposure time is decreased to reduce dose, then dose is reduced, but total number of photons hitting resist becomes very low

Engineering Contradiction:

ImprovedoseVSAvoidtotal photon amount

Core Design Contradiction:

Use of energy by stationary objectVSQuantity of substance

Solution Approach 1:

The invention changes the effective utilization parameter of absorbed photons by introducing the electron reflector layer. Instead of changing photon flux or exposure time, the system modifies how efficiently each absorbed photon produces useful secondary electrons in the resist, thereby reducing dose while maintaining adequate photon statistics.

Inventive Principle:

Principle #35Parameter changes

4Use of energy by moving object

If resist absorption is increased to improve photon capture, then absorption improves, but photons are blocked from traveling to resist bottom and electron path becomes too long

Engineering Contradiction:

Improvephoton absorptionVSAvoidresolution and roughness

Core Design Contradiction:

Use of energy by moving objectVSManufacturing precision

Solution Approach 1:

The system segments the electron generation and reflection functions into separate components: the resist generates secondary electrons upon photon absorption, while the electron reflector layer positioned beneath the resist reflects these electrons back. This segmentation allows optimal absorption in the resist without excessive thickness, maintaining resolution while preventing electron loss.

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 approach reduces the EUV dose required for resist exposure, minimizes electron loss to the substrate, and allows for thinner, lower-cost patterning stacks with improved resolution and reduced roughness, effectively addressing the challenges of low photon absorption and shot noise.

Implementation Method 1

the EUV resist is constructed and arranged for absorbing EUV radiation and generating secondary electrons

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Implementation Method 2

the electron reflector layer is constructed and arranged for reflecting secondary electrons generated by the EUV resist back towards the EUV resist

Methodology Applied

Scientific EffectElectron reflection: Reflection

Data Source

PatentUS20240274313A1Structures for patterning substrates and methods and systems for their manufacture

Publication Date: 2024.08.15 ASM IP HLDG BV

AI summary

Structures, related methods, and related systems for reducing EUV dose. A structure as described herein can comprise a substrate; an electron reflector layer overlying the substrate; and, an extreme ultraviolet (EUV) resist overlying an electron generation layer. The EUV resist is constructed and arranged for absorbing EUV radiation and generating secondary electrons. The electron reflector layer is constructed and arranged for reflecting secondary electrons generated by the EUV resist back towards the EUV resist.