Germanium Placeholder Structure for Selective Substrate Removal

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Solution Overview

Problem

Conventional semiconductor technologies face challenges in further miniaturizing FETs, particularly due to the susceptibility of uniform germanium-containing placeholders to damage during fabrication processes, which complicates the removal of the silicon substrate without compromising the placeholder structure.

Innovation Solution

A semiconductor structure is developed with a placeholder comprising a first portion of high germanium concentration for enhanced selectivity and a second portion of lower germanium concentration for protection, along with a protective liner, to facilitate controlled substrate removal and prevent damage during source/drain formation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a uniform germanium-containing placeholder is used, then the placeholder provides sufficient structural support, but it is susceptible to damage during fabrication processes and complicates substrate removal

Engineering Contradiction:

Improveplaceholder structural supportVSAvoiddamage susceptibility during fabrication

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The placeholder is divided into two regions with different germanium concentrations: a first region with higher germanium content (e.g., 30-70%) and a second region with lower germanium content (e.g., 0-30%). This local quality differentiation allows the high germanium region to provide structural support and selectivity for substrate removal, while the low germanium region maintains compatibility with subsequent fabrication processes and reduces damage susceptibility.

Inventive Principle:

Principle #3Local quality

2Manufacturing precision

If the germanium concentration in the placeholder is increased for better selectivity during substrate removal, then the selectivity is enhanced, but the placeholder becomes more susceptible to damage during source/drain formation

Engineering Contradiction:

Improvesubstrate removal selectivityVSAvoiddamage during source/drain formation

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The placeholder employs spatially varying germanium concentrations where the first region (closer to the channel) has higher germanium content to enhance substrate removal selectivity, while the second region (closer to the source/drain) has lower germanium content to reduce damage susceptibility during subsequent fabrication steps.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The placeholder is segmented into distinct regions with different material compositions. This segmentation allows each region to be optimized for its specific function: the high germanium region for substrate removal selectivity and the low germanium region for fabrication process compatibility.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS20250386544A1Placeholder structure with dielectric liner

Publication Date: 2025.12.18 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

A semiconductor device includes a first source/drain contact disposed beneath a first source/drain region and a placeholder disposed beneath a second source/drain region. The placeholder includes a first portion including a first material having a first concentration of germanium and a second portion including a second material having a second concentration of germanium that is different than the first concentration.