Hafnium Silicate Gate Dielectric Leakage Reduction
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Solution Overview
Problem
As semiconductor devices are scaled down, they experience increased leakage currents and reduced output resistance due to smaller MOSFET geometries, which are exacerbated by quantum mechanical phenomena like electron tunneling through thin gate oxides, necessitating the development of high dielectric constant materials to reduce leakage currents.
Innovation Solution
The method involves depositing ultra-high purity hafnium-containing silicate films using atomic layer deposition or chemical vapor deposition, incorporating nitrogen through post-nitridation annealing, and employing a pre-cleaning process with hydrofluoric acid to minimize metal impurities and enhance the dielectric constant of the gate dielectric.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gate oxide is made thinner to increase channel conductivity and reduce subthreshold leakage, then the transistor performance is improved, but quantum mechanical electron tunneling occurs between the gate and channel, leading to increased power consumption
Solution Approach 1:
The patent changes the dielectric constant parameter of the gate dielectric material from traditional silicon dioxide (K≈4) to high-K materials such as hafnium oxide (K≥20). This parameter change allows the dielectric layer to be made thicker while maintaining the same capacitance value, thereby preventing electron tunneling and reducing power consumption while preserving transistor performance.
Solution Approach 2:
The patent employs composite material structures, combining high-K dielectric materials with metal gate electrodes. This composite approach enables the gate stack to achieve both high capacitance and low leakage current, resolving the contradiction between thin oxide requirements and tunneling prevention.
2Object-generated harmful factors
If high dielectric constant materials are used to increase dielectric thickness and reduce quantum tunneling current, then leakage current is reduced, but the difference in conduction band energy between the semiconductor and dielectric impacts leakage current level
Solution Approach 1:
The patent modifies the energy band alignment parameters by selecting specific high-K dielectric materials with appropriate conduction band offsets relative to silicon. Hafnium oxide and its silicates provide optimal band alignment with sufficient conduction band offset to prevent hole tunneling while maintaining high dielectric constant for capacitance.
3Ease of manufacture
If standard purity hafnium-containing compounds are used in deposition, then manufacturing cost is reduced, but metal impurities increase leakage current density
Solution Approach 1:
The patent changes the purity parameter of the hafnium-containing precursor material from standard commercial purity to ultra-high purity (99.999% or higher). This parameter change eliminates metal impurities that would otherwise create defect states in the band gap, thereby reducing leakage current density while maintaining cost-effectiveness through optimized deposition processes.
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 results in a significant reduction of leakage current density by up to 50% compared to standard purity compounds, achieving leakage current densities below 10−5 A/cm2 at operating voltages, thereby improving the performance and reliability of MOSFETs.
Implementation Method 1
The method comprises the decomposition, in a processing chamber, of an ultra-high purity hafnium-containing organometallic compound
Implementation Method 2
depositing hafnium metal oxides, metal nitrides, metal oxynitrides, metal silicates and metal silicon oxynitrides using atomic layer deposition or chemical vapor deposition processes
Implementation Method 3
A post-deposition annealing process is performed on the substrate
Implementation Method 4
Nitrogen atoms are incorporated into the hafnium-containing film and a post-nitridation annealing of the substrate is performed
Implementation Method 5
employing a pre-cleaning process with hydrofluoric acid to minimize metal impurities
Data Source
AI summary
Processes for making a high K (dielectric constant) film using an ultra-high purity hafnium containing organometallic compound are disclosed. Also described are devices incorporating high K films made with high purity hafnium containing organometallic compounds.