Compositionally Modulated TFT Active Region for Low-Temperature Integration

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Solution Overview

Problem

Existing thin film transistors (TFTs) made of oxide semiconductors face challenges in integration with previously fabricated devices due to high processing temperatures, which can damage front-end-of-line (FEOL) and middle end-of-line (MEOL) devices.

Innovation Solution

The formation of thin film transistors with a compositionally-modulated active region, including a continuous bottom gate dielectric layer with vertical compositional modulation and a semiconducting metal oxide layer, minimizes surface leakage and allows for direct contact between source and drain electrodes, enabling low-temperature processing without damaging underlying structures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If high processing temperatures are used to fabricate thin film transistors, then the transistor performance is improved, but previously fabricated FEOL and MEOL devices are damaged

Engineering Contradiction:

Improvetransistor performanceVSAvoiddamage to previously fabricated devices

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the temperature parameter from high to low processing conditions, enabling TFT fabrication that does not damage previously fabricated FEOL and MEOL devices while maintaining acceptable transistor performance through compositional modulation of the active region

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies compositional modulation to the active region, creating local variations in material composition that optimize transistor performance at specific locations without requiring high temperatures across the entire structure

Inventive Principle:

Principle #3Local quality

2Object-affected harmful factors

If low-temperature processing is used to preserve previously fabricated devices, then integration with existing devices is enabled, but surface leakage increases

Engineering Contradiction:

Improveintegrity of previously fabricated componentsVSAvoidsurface leakage

Core Design Contradiction:

Object-affected harmful factorsVSObject-generated harmful factors

Solution Approach 1:

The patent implements compositional modulation within the active region to create local variations in material properties, specifically designing regions with different compositions to suppress surface leakage while maintaining low-temperature processing compatibility

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses composite material structures with varying compositions within the active region, combining different material phases or stoichiometries to simultaneously achieve low surface leakage and low-temperature processing capability

Inventive Principle:

Principle #40Composite materials

Data Source

PatentUS12575137B2Thin film transistor including a compositionally-modulated active region and methods for forming the same

Publication Date: 2026.03.10 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A thin film transistor includes an active layer and at least one gate stack. The active layer may be formed using multiple iterations of a unit layer stack deposition process, which includes an acceptor-type oxide deposition process and a post-transition metal oxide deposition process. A surface of each gate dielectric within the at least one gate stack contacts a surface of a respective layer of the oxide of the acceptor-type element so that leakage current of the active layer may be minimized. A source electrode and a drain electrode may contact an oxide layer providing lower contact resistance such as a layer of the post-transition metal oxide or a zinc oxide layer within the active layer.