Oxygen Treatment of CMOS Metal Gate Work Function
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Solution Overview
Problem
Conventional poly-silicon gates in semiconductor devices face performance issues due to boron penetration and depletion effects, leading to inferior gate capacitance and work function, prompting the need for improved manufacturing methods for dual metal gates with precise thickness and composition control.
Innovation Solution
A metal gate with a multi-layered stack structure that includes oxygen, where an O2 ambience treatment is applied to at least one layer, enhancing the work function performance by varying oxygen concentration across the layer, thereby improving the gate's electrical characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional poly-silicon gate is used, then manufacturing process is simple, but performance deteriorates due to boron penetration and depletion effect
Solution Approach 1:
The patent employs a composite metal gate structure consisting of multiple metal layers (e.g., TiN, TaN, WN) with different work functions. This composite structure enables precise control of the effective work function while maintaining good electrical performance, replacing the conventional single-material poly-silicon gate and eliminating boron penetration issues.
Solution Approach 2:
The patent introduces oxygen at specific locations within the metal gate structure, particularly at the interface between the metal gate and gate dielectric layer. This localized oxygen incorporation modifies the work function in specific regions to achieve desired electrical characteristics without affecting the entire gate structure uniformly.
2Reliability
If dual metal gate method is used, then work function performance is improved, but process complexity increases
Solution Approach 1:
The patent performs oxygen treatment on the metal gate structure before subsequent processing steps. This preliminary oxygen incorporation prepares the gate structure with optimized work function characteristics in advance, simplifying later process steps and reducing overall process complexity despite using multiple metal layers.
Solution Approach 2:
The patent controls the oxygen concentration and distribution within the metal gate structure as a key parameter to adjust the effective work function. By varying oxygen content and location, the patent achieves different work function values without changing the fundamental multi-layer structure, thereby simplifying process control.
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
The O2 ambience treatment improves the work function of the metal gate, resulting in better performance and simplifying the manufacturing process by reducing the complexity of dual metal gate methods.
Implementation Method 1
An O2 ambience treatment is performed to at least one layer of the multi-layered stack structure. The concentration of oxygen in the side of one layer of the multi-layered stack structure closer to the gate dielectric layer is less than that in the side of one layer of the multi-layered stack structure opposite to the gate dielectric layer
Data Source
AI summary
A method of manufacturing a metal gate is provided. The method includes providing a substrate. Then, a gate dielectric layer is formed on the substrate. A multi-layered stack structure having a work function metal layer is formed on the gate dielectric layer. An O2 ambience treatment is performed on at least one layer of the multi-layered stack structure. A conductive layer is formed on the multi-layered stack structure.