Gate Work Function Stack With Modifying Layer for Multi-Vt Control
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Solution Overview
Problem
Existing semiconductor devices face challenges in achieving multiple threshold voltage designs due to limitations in controlling the work function values of gate structures, which affects the performance and efficiency of transistors.
Innovation Solution
The semiconductor device incorporates a gate structure with a work function stack that includes a work function setting layer, an ultra-thin modifying layer, and a work function tuning layer. The modifying layer, made of an insulation material, is strategically positioned between the work function setting and tuning layers, and the interface surface between the modifying and tuning layers is treated with halogen material to alter the deposition process and achieve different work function values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional gate structure with single work function layer is used, then the manufacturing process is simple, but the ability to achieve multiple threshold voltage designs is limited
Solution Approach 1:
The gate structure is segmented into multiple work function layers (first work function setting layer, second work function setting layer, and work function tuning layer) with distinct functions. The first and second setting layers provide baseline work function control, while the tuning layer enables continuous adjustment, achieving multiple threshold voltage designs through layered segmentation of the gate structure.
Solution Approach 2:
The work function tuning layer introduces dynamic adjustability to the gate structure by enabling continuous modification of the work function value through controlled deposition or removal of material. This dynamic characteristic allows the threshold voltage to be tuned across a range of values rather than being fixed to discrete levels.
2Manufacturing precision
If the work function tuning layer is deposited directly on the work function setting layer, then the process is simpler, but the control precision over work function value is insufficient
Solution Approach 1:
An ultra-thin modifying layer (2-5 nm) is introduced as an intermediary between the work function setting layer and the work function tuning layer. This intermediate layer, composed of materials such as aluminum oxide, hafnium oxide, or titanium oxide, mediates the interaction between the setting and tuning layers, enabling precise control of the work function value by adjusting the thickness and composition of the modifying layer without requiring complex direct interface structures.
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 configuration allows for the achievement of multiple threshold voltage designs, enhancing the performance and efficiency of transistors by modifying the electric properties of the gate structure.
Implementation Method 1
a first work function tuning layer on the first work function setting layer and a second work function tuning layer on the second work function setting layer are formed by using a same deposition process
Data Source
AI summary
A semiconductor device including a gate structure disposed on a substrate is provided. The gate structure includes a work function setting layer and a work function tuning layer sequentially disposed on substrate. The work function tuning layer is in contact with an interface surface positioned between the work function setting layer and the work function tuning layer, and a material of the interface surface is different from the work function setting layer.