Profiled Metal Gate Electrode for Threshold Voltage Uniformity
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Solution Overview
Problem
Complementary metal-oxide-semiconductor (CMOS) technology faces challenges in achieving optimal performance with doped polysilicon gate electrodes, particularly in terms of threshold voltage uniformity and interdiffusion energy barriers, which affect the efficiency and reliability of NMOS and PMOS transistors.
Innovation Solution
The implementation of a semiconductor device with a metal gate electrode structure comprising a high-k gate dielectric layer, an intermediate work-function metal layer, a barrier layer, and a work-function adjustment layer, where the intermediate work-function metal layer is crystallized and interacts with the work-function adjustment layer during a post thermal anneal to form a crystalline work-function metal layer with ordered grain orientation, enhancing the interdiffusion energy barrier and threshold voltage uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If doped polysilicon gate electrodes are used in CMOS transistors, then the device structure is simple and manufacturing is easier, but threshold voltage uniformity deteriorates and interdiffusion energy barriers are insufficient
Solution Approach 1:
The patent employs a composite gate electrode structure consisting of multiple metal layers (e.g., TiN, WN, TaN) with different properties. These layers work together to achieve both good threshold voltage uniformity and high interdiffusion energy barriers, resolving the contradiction between manufacturing simplicity and precision by creating a multi-material system that delivers enhanced performance.
Solution Approach 2:
The patent changes the material parameters of the gate electrode by transitioning from doped polysilicon to metal materials with controlled composition, crystalline structure, and work function. This parameter change enables superior threshold voltage uniformity and interdiffusion resistance while maintaining compatibility with CMOS manufacturing processes.
2Ease of manufacture
If doped polysilicon gate electrodes are used, then the manufacturing process is simpler, but interdiffusion energy barriers are insufficient affecting reliability
Solution Approach 1:
The multi-layer metal gate structure creates composite material barriers against interdiffusion. Each metal layer (TiN, WN, TaN) provides specific barrier properties, and their combination creates a robust system that prevents unwanted diffusion while remaining manufacturable with standard semiconductor processing techniques.
Solution Approach 2:
The metal gate electrode layers act as intermediary barrier layers between the gate dielectric and the channel region. These intermediate metal layers prevent direct interaction and interdiffusion between adjacent materials, thereby protecting device reliability without complicating the overall manufacturing process.
3Manufacturing precision
If a metal gate structure with multiple layers is formed, then threshold voltage uniformity and interdiffusion barriers are improved, but device complexity increases
Solution Approach 1:
The gate electrode is segmented into multiple functional layers (TiN, WN, TaN), where each layer serves a specific purpose in achieving threshold voltage uniformity and interdiffusion barriers. This segmentation allows optimization of each layer's properties while maintaining overall device performance, managing complexity through functional division.
Solution Approach 2:
By controlling material parameters such as layer thickness, composition, and crystalline orientation during fabrication, the patent achieves precise threshold voltage uniformity. The parameter control is integrated into existing manufacturing processes, thereby improving precision without proportionally increasing device complexity.
4Reliability
If intermediate work-function metal layer and work-function adjustment layer are used, then interdiffusion energy barrier is enhanced, but manufacturing process becomes more complex
Solution Approach 1:
The intermediate work-function metal layer and work-function adjustment layer serve as intermediary structures that enhance interdiffusion barriers. These intermediate layers are strategically positioned to provide protection against diffusion while their formation is integrated into the existing manufacturing sequence, thereby improving reliability with controlled increases in process complexity.
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 improved threshold voltage uniformity and reduced interdiffusion energy barriers, leading to enhanced performance and reliability of NMOS and PMOS transistors by forming a metal gate structure with a crystalline work-function metal layer that provides a concave or convex profile, lowering resistance between source and drain extensions.
Implementation Method 1
the intermediate work-function metal layer is crystallized and interacts with the work-function adjustment layer during a post thermal anneal to form a crystalline work-function metal layer with ordered grain orientation
Implementation Method 2
interacts with the work-function adjustment layer during a post thermal anneal to form a crystalline work-function metal layer
Implementation Method 3
enhancing the interdiffusion energy barrier and threshold voltage uniformity
Data Source
AI summary
The present disclosure provides a semiconductor device with a profiled work-function metal gate electrode. The semiconductor structure includes a metal gate structure formed in an opening of an insulating layer. The metal gate structure includes a gate dielectric layer, a barrier layer, a work-function metal layer between the gate dielectric layer and the barrier layer and a work-function adjustment layer over the barrier layer, wherein the work-function metal has an ordered grain orientation. The present disclosure also provides a method of making a semiconductor device with a profiled work-function metal gate electrode.