Variable Pitch Fin Integration via Sidewall Image Transfer

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Solution Overview

Problem

Conventional sidewall image transfer (SIT) processes face challenges in integrating dense fin structures with uniform pitch and regions of variable fin spacing, particularly below the lithographic limit, making it difficult to achieve dense fin structures with variable spacing in applications like SRAM cells.

Innovation Solution

The method involves forming first and second sidewalls around mandrels, removing the mandrels, and etching an underlying layer to create dense, uniform pitch fins and variable pitch fins simultaneously by using a protective layer to isolate the regions during SIT processes, allowing for the creation of both dense and variable fin structures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If multiple SIT iterations are performed to achieve dense fin pitch below lithographic limit, then fin pitch density is improved, but integration with variable spacing regions becomes impossible

Engineering Contradiction:

Improvefin pitch densityVSAvoidintegration with variable spacing regions

Core Design Contradiction:

Manufacturing precisionVSAdaptability or versatility

Solution Approach 1:

The substrate is divided into separate uniform pitch regions and variable pitch regions, each processed independently through the SIT process. This segmentation allows each region to achieve its desired fin pitch characteristics without interfering with the other region's requirements

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Mandrels are pre-formed at different pitch configurations in different regions before the SIT process. The uniform pitch mandrels are prepared for dense fin structures while variable pitch mandrels are prepared for SRAM cell density, allowing both to undergo the same SIT process simultaneously

Inventive Principle:

Principle #10Preliminary action

2Manufacturing precision

If single fin trimming at 40 nm is attempted, then dense fin pitch is achieved, but no integration method exists with variable fin spacing regions

Engineering Contradiction:

Improvefin pitch dimensionVSAvoidprocess integration capability

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

A single SIT process flow is designed to serve multiple functions: it can process both uniform pitch mandrels to create dense fins and variable pitch mandrels to create SRAM structures. This universal process eliminates the need for separate processing streams

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Device complexity

If conventional lithography is used, then process simplicity is maintained, but feature size is limited by lithographic resolution

Engineering Contradiction:

Improveprocess simplicityVSAvoidfeature size

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The patent transitions from two-dimensional lithographic patterning to three-dimensional sidewall spacer formation. By depositing conformal spacer layers around mandrels and using anisotropic etching, the process achieves sub-lithographic dimensions through vertical dimension exploitation

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Data Source

PatentUS9378972B2Integration of dense and variable pitch fin structures

Publication Date: 2016.06.28 GLOBALFOUNDRIES US INC

AI summary

Methods for forming semiconductor devices. Methods for forming fin structures include forming first sidewalls around a first set of mandrels. The first set of mandrels is removed and second sidewalls are formed around the first sidewalls and a second set of mandrels. The first sidewalls and the second set of mandrels are removed and an underlying layer around the second sidewalls is etched.