Smart Subfield Method for E-beam Lithography Overlay Error

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Solution Overview

Problem

The semiconductor industry faces challenges in reducing overlay errors caused by different electron beams used at various pattern layers during the electron beam lithography patterning process, which affects the precision and complexity of manufacturing smaller and more complex integrated circuits.

Innovation Solution

A method is introduced that involves creating a 'smart boundary' to divide subfields, ensuring that patterns are written using the same electron beam across all layers, thereby minimizing overlay errors by maintaining consistent beam exposure across subfield boundaries.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If different electron beams are used at different pattern layers to enable multi-layer lithography, then productivity is improved, but overlay precision deteriorates due to boundary errors between subfields

Engineering Contradiction:

Improvemulti-layer lithography capabilityVSAvoidoverlay error at subfield boundary

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent divides the lithography process into multiple subfields, where each subfield is processed by a dedicated electron beam. This segmentation allows simultaneous multi-layer lithography in different subfields while maintaining consistent beam parameters within each subfield, thereby resolving the overlay error problem at boundaries.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent pre-defines subfield boundaries and assigns specific electron beams to specific subfields before the lithography process begins. This preliminary assignment ensures that the same electron beam is used for all layers within each subfield, preventing overlay errors before they occur.

Inventive Principle:

Principle #10Preliminary action

2Productivity

If feature size is scaled down to increase functional density, then productivity and cost efficiency are improved, but manufacturing precision deteriorates due to light diffraction

Engineering Contradiction:

Improvefunctional densityVSAvoidfeature size accuracy

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent replaces optical lithography with electron beam lithography. Electron beams have much shorter wavelengths compared to light, eliminating diffraction limitations and enabling precise patterning at smaller feature sizes, thus maintaining manufacturing precision while scaling down.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS8945803B2Smart subfield method for E-beam lithography

Publication Date: 2015.02.03 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

The present disclosure provides a method of improving a layer to layer overlay error by an electron beam lithography system. The method includes generating a smart boundary of two subfields at the first pattern layer and obeying the smart boundary at all consecutive pattern layers. The same subfield is exposed by the same electron beam writer at all pattern layers. The overlay error caused by the different electron beam at different layer is improved.