Oxide Field-Effect Transistor Contacts With Plasma-Smoothed Doped Regions

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Solution Overview

Problem

The challenge of achieving performance parity between p-type and n-type oxide devices in field effect transistors is hindered by rough interfaces and air gaps between source/drain contacts and the channel layer, leading to increased drain current in the off-state due to ambipolar effects in p-type oxide semiconductors, which degrade CMOS device operation.

Innovation Solution

A plasma treatment is applied to the source/drain contact area of the semiconductor layer before depositing a conductive layer, smoothing the interface and reducing the ambipolar effect by forming a doped region with improved surface smoothness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If a plasma treatment is applied to the source/drain contact area to smooth the interface and form a doped region, then the interface smoothness and transistor performance are improved, but the manufacturing process complexity increases

Engineering Contradiction:

Improveinterface smoothnessVSAvoidmanufacturing process complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The plasma treatment is applied to the source/drain contact area before depositing the conductive layer, preparing the surface in advance to ensure smooth interface and proper doping. This preliminary action prevents interface roughness and ambipolar effects before they can manifest in subsequent processing steps.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The plasma treatment is selectively applied only to the source/drain contact areas of the semiconductor layer, not the entire layer. This localized treatment creates doped regions with improved surface smoothness exactly where needed for contact formation, while leaving other regions unchanged.

Inventive Principle:

Principle #3Local quality

2Ease of manufacture

If the interface between source/drain contacts and channel layer is rough, then the manufacturing process is simpler, but the drain current in off-state increases due to ambipolar effects

Engineering Contradiction:

Improveinterface formation simplicityVSAvoidoff-state drain current control

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The plasma treatment changes the physical and chemical parameters of the source/drain contact area, including surface smoothness and doping concentration. These parameter changes suppress ambipolar effects and reduce off-state drain current while maintaining manufacturing feasibility.

Inventive Principle:

Principle #35Parameter changes

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 results in reduced drain current in the off-state, enhancing the performance and efficiency of p-type MOS transistors within CMOS devices by suppressing ambipolar behavior.

Implementation Method 1

Methodology Applied

Scientific EffectPlasma treatment: Plasma

Data Source

PatentUS20260052781A1Field effect transistor and formation method thereof

Publication Date: 2026.02.19 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A method of forming a field effect transistor comprises the following steps. A gate dielectric layer and a semiconductor layer are formed over a substrate in sequence. A photoresist layer is formed over the semiconductor layer. A plasma treatment is performed to the semiconductor layer to form a doped region and an undoped region laterally adjoining the doped region of the semiconductor layer using a gas. A conductive layer is formed over the doped region of the semiconductor layer and the photoresist layer. The photoresist layer is lifted off.