TiN Work Function Film Continuity Through a Sacrificial Isolation Layer
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Solution Overview
Problem
The continuity of titanium nitride (TiN) work function thin films deteriorates after heat treatment, leading to electric leakage in semiconductor devices due to oxidation and thickening, which is not effectively addressed by existing methods.
Innovation Solution
A method involving the formation of an isolation layer, such as amorphous silicon, between a tunnel oxide layer and TiN, forming a dense barrier layer (TiSiN) and a new tunnel oxide layer (SiO2) during heat treatment to prevent oxygen diffusion and maintain TiN continuity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heat treatment is performed on the tunnel oxide layer and TiN, then oxygen diffusion occurs causing TiN oxidation and thickening, but this leads to TiN discontinuity and electric leakage
Solution Approach 1:
An isolation layer comprising amorphous silicon is introduced as an intermediary between the TiN work function thin film and the silicon oxide tunneling oxide layer. During heat treatment, this isolation layer reacts with oxygen in the tunnel oxide to form a dense barrier layer (TiSiN) that prevents oxygen diffusion into the TiN film, while also forming a new tunneling oxide layer (SiO2). This mediator approach resolves the contradiction by protecting TiN continuity during necessary heat treatment processes.
Solution Approach 2:
The isolation layer is formed in advance before heat treatment to preemptively prevent oxygen diffusion. By placing the amorphous silicon layer beforehand, the system prepares a protective mechanism that activates during subsequent heat treatment, preventing the harmful oxidation and discontinuity that would otherwise occur in the TiN film.
2Stability of the object's composition
If the isolation layer is formed to prevent oxygen diffusion, then TiN continuity is maintained, but the device structure becomes more complex
Solution Approach 1:
The isolation layer is designed with specific material properties (amorphous silicon) and thickness parameters that enable it to be temporarily present during manufacturing. The layer undergoes chemical transformation during heat treatment (reacting to form TiSiN and SiO2), and is subsequently removed in wet etching processes. This parameter-based approach allows the layer to serve its protective function transiently without permanently increasing device complexity.
Solution Approach 2:
The isolation layer is intentionally designed as a temporary sacrificial layer that is fully consumed during the process. After serving its protective function during heat treatment by forming the dense barrier layer, the remaining amorphous silicon is completely removed in subsequent wet etching steps, leaving no trace in the final device structure. This eliminates permanent complexity while achieving the protective effect.
3Stability of the object's composition
If the isolation layer reacts with oxygen to form new tunneling oxide, then oxygen diffusion into TiN is prevented, but the heat treatment duration must be extended until full consumption
Solution Approach 1:
The thickness and material composition of the isolation layer are precisely controlled to match the oxygen consumption requirements of the process. By optimizing these parameters, the heat treatment duration is minimized while ensuring complete reaction of the amorphous silicon to form the protective barrier layer and new tunneling oxide, preventing excessive processing time while achieving full protection.
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 method ensures the continuity of TiN by forming a dense barrier layer that prevents oxygen diffusion and allows for the isolation layer's removal without affecting the device structure or electrical performance, thereby preventing electric leakage.
Implementation Method 1
the O element in the tunnel oxide layer enters the TIN lattice to replace the N element
Implementation Method 2
performing a heat treatment on the tunneling oxide layer, the isolation layer, and the work function layer
Implementation Method 3
the isolation layer reacts with a surface of the tunneling oxide layer to form a dense barrier layer
Implementation Method 4
the work function thin film serves as a floating gate in a semi-floating gate device to store charges and conduction electrons
Data Source
AI summary
The present application provides a method for improving continuity of a work function thin film, forming a tunneling oxide layer on a substrate; forming an isolation layer on the tunneling oxide layer; forming a work function thin film on the isolation layer, the work function thin film serves as a floating gate in a semi-floating gate device to store charges and conduction electrons, performing a heat treatment on the tunneling oxide layer, the isolation layer and the work function layer, the isolation layer reacts with a surface of the tunneling oxide layer to form a dense barrier layer, the isolation layer reacts with O in the tunneling oxide layer to form a new tunneling oxide layer, the heat treatment lasts until the isolation layer is fully consumed, and the work function thin film remaining after the reaction uniformly covers an upper surface of the dense barrier layer.