Work Function Layer Doping for Wider PMOS Threshold Tuning

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Solution Overview

Problem

The challenge in semiconductor manufacturing is to extend the threshold voltage tuning range of transistors without adversely affecting other aspects of the transistor, particularly as transistor sizes become smaller.

Innovation Solution

Introduce first and second type dopants into the work function layer of P-type transistors to adjust the threshold voltage, using mechanisms that include reducing aluminum diffusion and altering the work function, respectively, without changing the thickness of the work function layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the thickness of the work function layer is increased to extend the threshold voltage tuning range, then the threshold voltage tuning range is improved, but the manufacturing complexity and difficulty increase

Engineering Contradiction:

Improvethreshold voltage tuning rangeVSAvoidwork function layer structure complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The work function layer is divided into multiple distinct layers (first work function layer and second work function layer) with different compositions and functions. The first layer provides baseline work function, while the second layer extends the tuning range, allowing independent optimization of each layer's properties rather than requiring a single thick layer

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs composite work function layer structures combining different materials (e.g., titanium nitride, tungsten nitride, tantalum nitride) with distinct properties. Each material contributes specific characteristics to the overall work function, enabling extended tuning range through material composition rather than increased thickness

Inventive Principle:

Principle #40Composite materials

2Adaptability or versatility

Engineering Contradiction:

Improvethreshold voltage tuning rangeVSAvoidwork function layer thickness control precision

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

By segmenting the work function layer into multiple thinner layers, each layer can be deposited with standard thickness control precision. The cumulative effect of multiple precisely-controlled thin layers achieves the same total thickness control as a single thick layer, but with reduced process difficulty and better uniformity

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the compositional parameters of the work function layer (material composition, doping concentration) rather than relying solely on thickness parameter. This allows threshold voltage tuning through composition control, which has better manufacturing precision than thickness control for thick layers

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If dopants are introduced to adjust the work function, then the threshold voltage control precision is improved, but the device complexity increases

Engineering Contradiction:

Improvethreshold voltage control precisionVSAvoidwork function layer composition complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

Different dopants are introduced at different locations within the work function layer structure (first layer vs. second layer). Each dopant placement serves a specific local function: one dopant type adjusts baseline work function while another extends the tuning range, allowing precise local control of electrical properties

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The use of composite work function layers with different dopant compositions enables precise threshold voltage control through material science rather than geometric control. The dopant concentrations and types in each layer are optimized to provide specific work function values, achieving precise control through material properties

Inventive Principle:

Principle #40Composite materials

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 effectively widens the threshold voltage tuning range for P-type transistors, enhancing device performance by allowing for more precise control of threshold voltage without impacting other physical or electrical properties.

Implementation Method 1

the dopants in the second P-type work function layer reduces aluminum diffusion from aluminum-containing N-type work function layer into the second P-type work function layer

Methodology Applied

Scientific EffectDiffusion: Diffusion

Data Source

PatentUS20250372365A1Methods of widening threshold voltage tuning range for semiconductor devices

Publication Date: 2025.12.04 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

Semiconductor devices and methods are provided. An exemplary method according to the present disclosure includes forming a dielectric layer over a portion of a substrate, forming a first p-type work function layer over the dielectric layer, wherein the first p-type work function layer comprises titanium nitride, forming a second p-type work function layer over the first p-type work function layer, wherein the second p-type work function layer comprises titanium nitride with dopants, forming an aluminum-containing N-type work function layer over second p-type work function layer, wherein the dopants in the second p-type work function layer reduces aluminum diffusion from aluminum-containing N-type work function layer into the second p-type work function layer, and forming a metal layer over the aluminum-containing N-type work function layer.