TiWN Conductive Film High Work Function Low EOT
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Solution Overview
Problem
The challenge is to form a metal film with a high work function while minimizing the increase in equivalent oxide thickness (EOT) in semiconductor devices, as existing metal films like titanium nitride (TiN) suffer from oxygen release during heat treatment, affecting electrical characteristics.
Innovation Solution
A method involving multiple cycles of depositing a titanium nitride (TiN) layer followed by a tungsten nitride (WN) layer, where the binding energy of tungsten with oxygen is higher than that of titanium, is used to form a conductive TiWN film with a higher work function and improved oxygen binding characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tungsten nitride film (WN film) is used to achieve a higher work function, then the work function requirement is met, but oxygen is released during heat treatment which adversely affects electrical characteristics
Solution Approach 1:
The patent applies composite materials by forming a multi-layer structure consisting of TiN layer and WN layer. The TiN layer serves as a barrier to prevent oxygen release, while the WN layer provides the required high work function. This composite structure combines the advantages of both materials: TiN's oxygen binding capability and WN's high work function, thereby resolving the contradiction between achieving high work function and preventing oxygen release during heat treatment.
Solution Approach 2:
The TiN layer acts as an intermediary between the substrate and the WN layer. It binds oxygen that would otherwise be released from the WN layer during heat treatment, mediating the harmful effect of oxygen release. The TiN layer absorbs and stabilizes oxygen, preventing it from affecting the electrical characteristics of the device while allowing the WN layer to maintain its high work function property.
2Reliability
If a metal film with higher work function is formed to meet PMOS/ NMOS requirements, then the electrical characteristics are improved, but the equivalent oxide thickness (EOT) increases
Solution Approach 1:
The patent applies local quality by creating a multi-layer structure where each layer has a specific function optimized for its role. The TiN layer is optimized for oxygen binding and interface quality, while the WN layer is optimized for providing high work function. This localized optimization allows the overall structure to achieve the required electrical characteristics without excessive EOT increase, as each layer contributes specifically to different performance requirements.
Solution Approach 2:
The patent utilizes parameter changes by controlling the thickness of each layer (TiN and WN) to optimize the balance between work function and EOT. By adjusting the thickness parameters of individual layers, the composite film achieves the required work function while minimizing the overall EOT. This parameter optimization allows tuning of the electrical characteristics to meet specific device requirements.
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 formation of a TiWN film with a high work function and low EOT, reducing leakage current and threshold voltage in MOSFETs, while minimizing oxygen release and damage to gate insulating films.
Implementation Method 1
supplying a first metal-containing gas containing the first metal element to a substrate accommodated in a process chamber
Implementation Method 2
supplying a reactive gas to the substrate
Data Source
AI summary
A technique for forming a metal film having a high work function while suppressing an increase in EOT is provided. According to the technique, there is provided a method of manufacturing a semiconductor device, including: (a) performing a first cycle a first number of times to form a first metal layer containing a first metal element; and (b) performing a second cycle to form a second metal layer containing a second metal element directly on the first metal layer, wherein a binding energy of second metal element with oxygen is higher than that of the first metal element with oxygen, wherein a cycle including (a) and (b) is performed a second number of times to form a conductive film containing the first metal element and the second metal element on a substrate, the conductive film having: a work function higher than the first metal layer; and a binding energy with oxygen higher than that of the first metal element with oxygen.