Tetragonal Hafnium Oxide Capacitor Stack With Lattice-Matched Seed Layer
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Solution Overview
Problem
As semiconductor devices become highly integrated, there is a need for capacitors with high capacitance in a limited area, which existing technologies struggle to achieve effectively due to challenges in crystallizing hafnium oxide into a tetragonal crystal structure with high dielectric constant and preventing leakage current.
Innovation Solution
A semiconductor device is designed with a dielectric layer comprising a hafnium oxide layer having a tetragonal crystal structure and an oxidation seed layer with specific lattice mismatch and band gap energy conditions, along with a conductive seed layer, to enhance capacitance and reliability by crystallizing the hafnium oxide at a lower temperature and preventing electrode material diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hafnium oxide is crystallized into tetragonal structure at high temperature, then dielectric constant is improved, but manufacturing complexity and energy consumption increase
Solution Approach 1:
An oxidation seed layer comprising zirconium oxide, niobium oxide, germanium oxide, tin oxide, molybdenum oxide, or titanium oxide is introduced as an intermediary between the bottom electrode and the hafnium oxide layer. This seed layer facilitates the crystallization of hafnium oxide into the desired tetragonal phase at reduced temperatures by providing a lattice-matched template, thereby achieving high dielectric constant without requiring excessive thermal processing complexity
2Reliability
If hafnium oxide layer thickness is increased to achieve high capacitance, then capacitance is improved, but leakage current increases
Solution Approach 1:
The oxidation state of the hafnium oxide layer is precisely controlled by adjusting the oxidation atmosphere conditions (oxygen partial pressure, temperature, and time) during the formation process. This parameter optimization enables thehafnium oxide to achieve a balanced state with sufficient thickness for high capacitance while maintaining low leakage current through optimized oxidation degree
3Ease of manufacture
If conventional oxidation seed materials are used, then crystallization is achieved, but lattice mismatch causes defects
Solution Approach 1:
Different oxide materials are selected for the oxidation seed layer based on their specific lattice constants to match with the hafnium oxide layer. By locally optimizing the seed layer material composition (zirconium oxide, niobium oxide, germanium oxide, tin oxide, molybdenum oxide, or titanium oxide), the lattice mismatch is minimized, reducing crystalline defects while maintaining ease of crystallization
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 solution results in a semiconductor device with high capacitance and reduced defect density, ensuring reliable operation by maintaining the tetragonal crystal structure of hafnium oxide and preventing leakage current.
Implementation Method 1
The dielectric layer includes a hafnium oxide layer including hafnium oxide having a tetragonal crystal structure... and an oxidation seed layer including an oxidation seed material. The oxidation seed material includes a lattice constant having a lattice mismatch of 6% or less with one of the horizontal lattice constant and the vertical lattice constant of the hafnium oxide.
Implementation Method 2
The dielectric layer includes an oxidation seed layer and a hafnium oxide layer between the oxidation seed layer and the conductive seed layer... The oxidation seed layer includes an oxidation seed material including a lattice constant having a lattice mismatch of 6% or less with one of the horizontal lattice constant and the vertical lattice constant of the hafnium oxide.
Data Source
AI summary
Disclosed is a semiconductor device including a bottom electrode, a dielectric layer, and a top electrode that are sequentially disposed on a substrate. The dielectric layer includes a hafnium oxide layer including hafnium oxide having a tetragonal crystal structure, and an oxidation seed layer including an oxidation seed material. The oxidation seed material has a lattice constant having a lattice mismatch of 6% or less with one of a horizontal lattice constant and a vertical lattice constant of the hafnium oxide having the tetragonal crystal structure.