LaN Buried Word Line Liner for Lower-Resistance DRAM
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Solution Overview
Problem
Current DRAM buried word line processes using titanium nitride as a liner result in high resistivity, high effective work function, and poor equivalent oxide thickness/interface trap densities, limiting the performance and density of DRAM devices.
Innovation Solution
The use of lanthanum nitride as a liner for molybdenum stacks in DRAM buried word lines, deposited via atomic layer deposition, reduces resistance and improves device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If titanium nitride is used as a liner in DRAM buried word lines, then the process is well-established and compatible with existing manufacturing, but the resistivity is high and device performance is limited
Solution Approach 1:
The patent changes the material parameter from titanium nitride to lanthanum nitride, which fundamentally alters the electrical properties (resistivity and work function) of the liner layer. This material substitution resolves the technical contradiction by achieving lower resistivity and improved device performance while maintaining compatibility with existing ALD manufacturing processes
Solution Approach 2:
The patent employs a composite structure consisting of multiple layers including lanthanum nitride liner, molybdenum layers, and titanium nitride layers. This composite material approach allows optimization of each layer's specific function - lanthanum nitride provides low resistivity and appropriate work function, while other layers provide structural support and process compatibility
2Quantity of substance
If the vertical dimensions of DRAM devices are increased to increase storage per unit space, then memory density improves, but the formation of low resistance contact becomes more difficult
Solution Approach 1:
The patent changes the electrical parameters of the liner material from titanium nitride (high resistivity, high work function) to lanthanum nitride (low resistivity, appropriate work function). This parameter change enables the formation of low resistance contacts even as vertical dimensions increase and memory density improves
Solution Approach 2:
The patent applies local quality optimization by using lanthanum nitride specifically at the interface where low resistance contact is critical, while other parts of the structure can use different materials optimized for their specific functions. This localized material optimization resolves the contradiction between high density and low contact resistance
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 implementation of lanthanum nitride liners in DRAM buried word lines achieves lower resistance and enhanced performance by reducing the resistivity of the buried word line, thereby improving memory cell density and efficiency.
Implementation Method 1
depositing a molybdenum conductor layer by an atomic layer deposition (ALD) process on the metal nitride layer
Data Source
AI summary
Methods for DRAM device with a buried word line are described. The method includes forming a metal nitride layer comprising lanthanum nitride (LaN) and a molybdenum conductor layer in a feature on a substrate. The method includes depositing the molybdenum conductor layer by atomic layer deposition (ALD) on the metal nitride layer.