Gate Electrode Stack With Anti-Reaction Layer for Threshold and Resistance
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Solution Overview
Problem
The semiconductor industry faces challenges in improving the integration density of electronic components and reducing gate resistance in semiconductor devices, particularly in forming effective gate electrodes for nano-FETs, where existing methods struggle to achieve optimal threshold voltage and resistance simultaneously.
Innovation Solution
A method involving the formation of gate electrodes with an anti-reaction layer and a metal cap layer, where the anti-reaction layer provides a threshold voltage boost and the metal cap layer reduces gate resistance, by selectively depositing the metal cap layer over the p-type work function layer, which is deposited over the anti-reaction layer, allowing for improved device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional gate electrode structure is used, then the manufacturing process is simple, but the gate resistance is high and threshold voltage control is insufficient
Solution Approach 1:
The gate electrode is divided into multiple functional layers: a base gate electrode layer, a first conductive layer (n-type work function layer), a second conductive layer (p-type work function layer), and an optional metal cap layer. Each layer serves a specific function in threshold voltage control and resistance reduction, allowing optimization of device performance through layered segmentation.
Solution Approach 2:
The gate electrode structure employs composite material construction with different conductive materials having distinct work functions. The n-type work function layer (e.g., TiN, TaN) and p-type work function layer (e.g., WN, MoN) are combined to achieve both threshold voltage adjustment and low resistance, creating a composite structure that overcomes the limitations of single-material electrodes.
2Productivity
If the integration density is increased by reducing feature size, then more components fit in a given area, but the gate resistance increases and threshold voltage control becomes more difficult
Solution Approach 1:
Different regions of the gate electrode structure are assigned different material properties and functions. The n-type work function layer provides electron injection and threshold voltage control, while the p-type work function layer provides hole injection and additional threshold voltage adjustment. This local differentiation of material quality allows each region to optimize its function despite reduced overall feature dimensions.
Solution Approach 2:
The invention adjusts critical parameters including the thickness of each conductive layer, the work function values of selected materials, and the doping concentrations to maintain optimal gate electrode performance at reduced feature sizes. By carefully controlling these parameters, the structure achieves low resistance and proper threshold voltage control even as overall device dimensions are scaled down for higher integration density.
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 enhances device performance by providing a threshold voltage boost and reducing gate resistance, thereby improving the integration density and efficiency of semiconductor devices.
Implementation Method 1
the anti-reaction layer provides a threshold voltage boost
Implementation Method 2
the metal cap layer reduces gate resistance
Implementation Method 3
selectively depositing the metal cap layer over the p-type work function layer
Data Source
AI summary
Semiconductor devices having improved gate electrode structures and methods of forming the same are disclosed. In an embodiment, a semiconductor device includes a gate structure over a semiconductor substrate, the gate structure including a high-k dielectric layer; an n-type work function layer over the high-k dielectric layer; an anti-reaction layer over the n-type work function layer, the anti-reaction layer including a dielectric material; a p-type work function layer over the anti-reaction layer, the p-type work function layer covering top surfaces of the anti-reaction layer; and a conductive cap layer over the p-type work function layer.