DRAM Capacitor Lower Electrode TiON Layering
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Solution Overview
Problem
The existing methods for manufacturing DRAM capacitors face challenges in achieving high resistance to hydrofluoric acid and minimizing stress changes caused by oxygen-based gases, particularly when using TiN films as lower electrodes, as they tend to suffer from oxygen vacancy issues and increased leakage currents.
Innovation Solution
A lower electrode structure comprising TiN-based material with alternating layers of TiON films, where the outer layers have a relatively low oxygen concentration for improved acid resistance and inner layers with higher oxygen concentration to reduce stress changes, is implemented, along with a manufacturing method involving controlled oxygen concentration through specific gas supply cycles and oxidation processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a TiN film is used as the lower electrode and oxygen is added to reduce oxygen vacancy, then leakage current is reduced, but resistance to hydrofluoric acid decreases and stress change increases
Solution Approach 1:
The lower electrode is segmented into multiple layers with different oxygen concentrations. The first TiON film has lower oxygen concentration (5-20 at%) for acid resistance, while the second TiON film has higher oxygen concentration (20-40 at%) for stress control. This segmentation allows each layer to fulfill its specific function independently.
Solution Approach 2:
Different regions of the lower electrode are given different oxygen concentrations to achieve different local properties. The first TiON film (outer layer) has lower oxygen concentration for hydrofluoric acid resistance, while the second TiON film (inner layer) has higher oxygen concentration for stress change suppression. This local quality differentiation resolves the contradiction between acid resistance and stress control.
2Stability of the object's composition
If oxygen concentration in TiN film is increased to suppress stress change, then stress change is reduced, but resistance to hydrofluoric acid decreases
Solution Approach 1:
The lower electrode is divided into two TiON films with different oxygen concentrations. The first TiON film (thickness 2-5 nm) has lower oxygen concentration for acid resistance, while the second TiON film (thickness 2-5 nm) has higher oxygen concentration for stress control. This segmentation enables simultaneous achievement of both acid resistance and stress stability.
Solution Approach 2:
The patent applies local quality by creating distinct oxygen concentration zones within the lower electrode structure. The outer first TiON film maintains low oxygen concentration for acid resistance, while the inner second TiON film has high oxygen concentration for stress suppression, allowing both requirements to be satisfied in different locations.
3Ease of manufacture
If a single-layer TiN film is used, then manufacturing is simple, but it cannot simultaneously achieve high acid resistance and stress control
Solution Approach 1:
The lower electrode is segmented into two distinct TiON film layers formed by separate deposition and oxidation cycles. The first TiON film is formed with lower oxygen concentration, followed by the second TiON film with higher oxygen concentration. This segmentation provides the functional differentiation needed to achieve both acid resistance and stress control simultaneously.
Solution Approach 2:
The patent employs a composite structure consisting of two TiON films with different oxygen concentrations. This composite material approach allows the lower electrode to exhibit both acid resistance (from the first film) and stress stability (from the second film), achieving combined performance that a single-layer film cannot provide.
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 proposed solution enhances the resistance to hydrofluoric acid and reduces stress changes in the DRAM capacitor lower electrode, improving its durability and performance by maintaining a symmetrical structure and controlled oxygen distribution.
Implementation Method 1
the first TiON films having a relatively low oxygen concentration; and a second TiON film provided between the first TiON films, the second TiON film having a relatively high oxygen concentration
Implementation Method 2
then oxidizing the unit nitride film by supplying an oxidizing agent
Data Source
AI summary
A lower electrode is made of a TiN-based material and provided at a base of a dielectric film in a DRAM capacitor. The lower electrode includes first TiON films provided at opposite outer sides, the first TiON films having a relatively low oxygen concentration, and a second TiON film provided between the first TiON films, the second TiON film having a relatively high oxygen concentration.