Self-Aligned Source and Drain Regions via Tape Exfoliation

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Solution Overview

Problem

The formation of source and drain regions in semiconductor devices, particularly in III-V FETs, is time-consuming and expensive due to the need for selective epitaxial growth and additional chemical-mechanical polishing steps, which can cause junction damage and process flow limitations.

Innovation Solution

The method involves patterning a gate conductor and forming a two-dimensional material on a substrate, creating recesses adjacent to the gate conductor, depositing a doped layer in these recesses, and using tape to exfoliate the doped layer from the two-dimensional material, thereby eliminating the need for selective epitaxial growth and additional CMP steps.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If selective epitaxial growth is used to form source and drain regions, then doping can be achieved without ion-implantation, but the process becomes more complex and time-consuming with additional steps

Engineering Contradiction:

Improveavoidance of junction damageVSAvoidprocess flow complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The process is segmented into distinct stages: forming recesses in the substrate, depositing doped material only in those recesses, and then selectively removing excess material. This segmentation allows doping without ion-implantation while avoiding the complexity of full selective epitaxial growth by limiting material deposition to specific locations where source/drain regions are needed.

Inventive Principle:

Principle #1Segmentation

2Manufacturing precision

If selective epitaxial growth with doped layers is used, then source and drain regions can be formed, but additional CMP steps are required which add time and risk of damage

Engineering Contradiction:

Improvesource and drain region formationVSAvoidprocess time

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The substrate surface is preliminarily prepared by forming recesses at the precise locations where source and drain regions will be formed. By pre-defining these recesses before material deposition, the doped material naturally self-limits to the correct regions, eliminating the need for subsequent CMP steps to remove excess material and reducing overall process time.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The recesses act as an intermediary structure that guides the deposition process. By creating physical cavities in the substrate, the recesses serve as a template that directs doped material deposition into the correct locations, automatically achieving spatial selectivity without requiring complex epitaxial growth conditions or subsequent removal steps.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Quantity of substance

If patterned implantation is used to form source and drain regions, then doping can be achieved, but it adds time and expense and may result in junction damage

Engineering Contradiction:

Improvedopant introductionVSAvoidprocess time and cost

Core Design Contradiction:

Quantity of substanceVSLoss of time

Solution Approach 1:

The mechanical process of ion implantation is replaced with a deposition-based approach. Instead of physically bombarding the substrate with dopant ions, the method uses vapor or liquid phase deposition to introduce dopants into pre-formed recesses. This substitution eliminates the time-consuming and expensive ion-implantation process while avoiding junction damage from high-energy ion bombardment.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 simplifies the process flow, reduces costs, and avoids potential damage to the device components by directly forming self-aligned source and drain regions without ion-implantation, while maintaining the integrity of the semiconductor device.

Implementation Method 1

The tape is removed to exfoliate the doped layer from the top of the two-dimensional material to form source and drain regions in the recesses

Methodology Applied

Scientific EffectExfoliation:

Implementation Method 2

a doped layer is deposited in the recesses and over a top of the two-dimensional material

Methodology Applied

Scientific EffectDeposition: Deposition (physical)

Data Source

PatentUS9786756B2Self-aligned source and drain regions for semiconductor devices

Publication Date: 2017.10.10 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

A method for forming a semiconductor device includes patterning a gate conductor, formed on a substrate, and a two-dimensional material formed on the gate conductor. Recesses are formed adjacent to the gate conductor in the substrate, and a doped layer is deposited in the recesses and over a top of the two-dimensional material. Tape is adhered to the doped layer on top of the two-dimensional material. The tape is removed to exfoliate the doped layer from the top of the two-dimensional material to form source and drain regions in the recesses.