Gate Electrode Work Function Tuning for Lower Threshold Voltage
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Solution Overview
Problem
The semiconductor industry faces challenges in achieving optimal work function values for gate electrodes in semiconductor devices, which affects the integration density and performance of electronic components.
Innovation Solution
The work function values of gate electrodes are tuned by implanting dopants, such as lanthanum, aluminum, or magnesium, into p-type work function metal layers, and by exposing n-type work function metal layers to tuning gases like transition metal chlorides, resulting in the formation of suitable work function layers for p-type transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dopants are implanted into work function metal layers to tune work function values, then threshold voltage is reduced and device performance is improved, but manufacturing process complexity increases
Solution Approach 1:
Dopants are implanted into the work function metal layers during the gate electrode formation process, before final device operation. This preliminary doping action establishes the required work function values and threshold voltages in advance, eliminating the need for subsequent complex tuning operations and simplifying the overall manufacturing process.
Solution Approach 2:
The work function of the gate electrode is controlled by changing the dopant concentration and type in the work function metal layer. By adjusting dopant parameters (species, concentration, depth profile), the work function is precisely tuned to achieve desired threshold voltages, improving device performance through controlled parameter modification rather than complex process steps.
2Manufacturing precision
If work function metal layers are exposed to tuning gases to form work function layers, then suitable work function values are achieved for p-type transistors, but manufacturing process time increases
Solution Approach 1:
The formation of the work function layer through gas exposure is combined with the gate electrode fabrication process sequence. The tuning gas exposure step is integrated into the existing manufacturing flow, allowing the work function layer to be formed in-situ without requiring separate processing equipment or additional material deposition steps, thereby reducing overall process time while maintaining precision.
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 allows for the manufacture of semiconductor devices with lower threshold voltages, higher speed, and improved performance by optimizing the work function values of gate electrodes.
Implementation Method 1
The work function values may be tuned by implanting a dopant in a p-type work function metal layer
Implementation Method 2
exposing an n-type work function metal layer to a tuning gas. The tuning gas may be a transition metal chloride, such as tungsten chloride, tantalum chloride, hafnium chloride, titanium chloride or the like. Exposing the n-type work function metal layer to the tuning gas may deposit a tuning layer over the n-type work function metal layer
Data Source
AI summary
Methods for tuning effective work functions of gate electrodes in semiconductor devices and semiconductor devices formed by the same are disclosed. In an embodiment, a semiconductor device includes a channel region over a semiconductor substrate; a gate dielectric layer over the channel region; and a gate electrode over the gate dielectric layer, the gate electrode including a first work function metal layer over the gate dielectric layer, the first work function metal layer including aluminum (Al); a first work function tuning layer over the first work function metal layer, the first work function tuning layer including aluminum tungsten (AIW); and a fill material over the first work function tuning layer.