Two-Step Post Nitridation Annealing for SiOxNy Gate Dielectrics
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Solution Overview
Problem
The challenge in semiconductor manufacturing is to form a silicon oxynitride gate dielectric with a thinner equivalent oxide thickness (EOT) that reduces current leakage and maintains high gate capacitance, while preventing boron penetration and hot carrier damage, which existing thin SiO2 dielectrics fail to achieve effectively.
Innovation Solution
A method involving plasma nitridation to incorporate nitrogen into the dielectric film, followed by a two-step post plasma nitridation annealing process with varying oxygen partial pressures to densify and modify the nitrogen concentration profile, resulting in a SiOxNy gate dielectric with improved mobility and reduced EOT.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the thickness of SiO2 gate dielectric is reduced below 20 Å to increase gate capacitance and drive current, then the gate capacitance increases, but gate leakage increases, boron penetration occurs, and hot carrier damage susceptibility increases
Solution Approach 1:
The patent changes the chemical composition parameters of the gate dielectric by incorporating nitrogen into SiO2 to form SiOxNy. This compositional change allows the dielectric to maintain high capacitance while providing superior leakage resistance and boron blocking capability, resolving the contradiction between achieving high gate capacitance and preventing gate leakage
Solution Approach 2:
The patent creates a composite gate dielectric structure by combining silicon oxide with nitrogen to form silicon oxynitride. This composite material exhibits properties superior to pure SiO2, achieving both high capacitance and low leakage simultaneously, thus resolving the technical contradiction
2Reliability
If nitrogen is incorporated into SiO2 layer to form SiOxNy gate dielectric to block boron penetration and raise dielectric constant, then boron penetration is prevented, but the process complexity increases
Solution Approach 1:
The patent performs preliminary nitrogen incorporation into the gate dielectric layer before subsequent processing steps. By pre-doping the dielectric with nitrogen, the gate structure is prepared in advance to resist boron penetration, eliminating the need for additional protective layers or complex post-processing steps
Solution Approach 2:
The patent combines multiple functions into a single gate dielectric layer: nitrogen incorporation provides both high-k dielectric properties for increased capacitance and boron blocking capability. This merging of functions into one layer simplifies the overall device structure and reduces process complexity compared to using multiple separate layers
3Reliability
If plasma nitridation is used to nitride the gate oxide to achieve high nitrogen concentration at poly gate/oxide interface, then boron penetration is prevented, but the equivalent oxide thickness (EOT) increases
Solution Approach 1:
The patent applies local quality by creating a nitrogen concentration gradient within the gate dielectric, with higher nitrogen concentration at the poly gate/oxide interface to maximize boron blocking, and lower nitrogen concentration deeper in the dielectric to maintain low EOT. This spatially varying composition optimizes both protection and capacitance
4Reliability
If a two-step post plasma nitridation annealing process with varying oxygen partial pressures is used to densify and modify nitrogen concentration profile, then gate leakage is reduced and channel mobility is enhanced, but the process complexity increases
Solution Approach 1:
The patent segments the annealing process into two distinct steps with different oxygen partial pressures: a first anneal at lower oxygen pressure to densify the dielectric and reduce leakage, and a second anneal at higher oxygen pressure to adjust the nitrogen concentration profile and enhance mobility. This segmentation allows independent optimization of different dielectric properties
Solution Approach 2:
The patent employs periodic action by alternating between two annealing conditions with different oxygen partial pressures. This periodic variation in processing conditions enables sequential achievement of different objectives: first reducing leakage through densification, then enhancing mobility through nitrogen profile modification
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 effectively reduces gate leakage and enhances channel mobility by controlling the nitrogen concentration profile, preventing boron penetration and maintaining high drive current, thus addressing the limitations of thin SiO2 dielectrics.
Implementation Method 1
plasma nitridation (PN) has been used to nitride (to incorporate nitrogen into) the gate oxide
Implementation Method 2
Incorporating nitrogen into the SiO2 layer to form a SiOxNy gate dielectric
Implementation Method 3
Post Nitridation Annealing (PNA) of the silicon oxynitride at high temperature
Implementation Method 4
the nitrogen is incorporated by growing SiON at the Si-substrate/Oxide interface
Implementation Method 5
annealing the silicon oxynitride film in a second ambient comprising a second partial pressure of oxygen at a second temperature
Data Source
AI summary
A method of forming a silicon oxynitride gate dielectric. The method includes incorporating nitrogen into a dielectric film using a plasma nitridation process to form a silicon oxynitride film. The silicon oxynitride film is annealed in a first ambient. The first ambient comprises an inert ambient with a first partial pressure of oxygen at a first temperature. The silicon oxynitride film is then annealed in a second ambient comprising a second partial pressure of oxygen at a second temperature. The second partial pressure of oxygen is greater than the first partial pressure of oxygen.