Plasma Hydrogenation Nitridization Metal Gate Effective Oxide Thickness
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Solution Overview
Problem
The reduction of dielectric thickness in MOSFETs to achieve smaller transistors leads to an exponential increase in gate leakage, posing reliability concerns and increasing power consumption, necessitating a method to reduce effective oxide thickness without exacerbating gate leakage.
Innovation Solution
A sequential hydrogenation and nitridization process is applied to semiconductor devices, involving the deposition of high-k dielectric and metal nitride layers, followed by exposure to plasma-excited hydrogen and nitrogen species, and a thermal anneal process, to reduce interfacial and bulk oxygen atoms, thereby decreasing effective oxide thickness without increasing gate leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the thickness of the dielectric layer is reduced to scale down MOSFET size, then transistor size and chip area are reduced, but gate leakage increases exponentially
Solution Approach 1:
The patent changes the physical and chemical parameters of the dielectric layer through plasma hydrogenation and nitridization processes. Hydrogenation reduces bulk oxygen content while nitridization modifies the dielectric composition, thereby reducing effective oxide thickness without proportionally reducing physical thickness. This allows scaling down transistor size while maintaining lower gate leakage compared to conventional thinning approaches.
Solution Approach 2:
The patent creates a composite dielectric structure by combining high-k dielectric material with modified regions containing hydrogen and nitrogen. This composite approach allows the dielectric layer to maintain adequate thickness for mechanical integrity while achieving lower effective oxide thickness through the modified regions, thus reducing gate leakage without requiring proportional reduction in overall dielectric thickness.
2Speed
If the thickness of the dielectric layer is reduced to improve transistor switching speed, then RC delay decreases, but reliability concerns increase
Solution Approach 1:
The patent modifies the dielectric layer parameters through plasma treatment processes that reduce bulk oxygen and change compositional ratios. These parameter changes improve transistor switching speed by reducing RC delay while simultaneously enhancing reliability by preventing dielectric breakdown that would occur with excessive thinning. The controlled modification maintains structural integrity while achieving performance improvements.
3Length of stationary object
If conventional oxide thickness is reduced linearly to scale MOSFET, then transistor dimensions are reduced, but gate leakage increases exponentially
Solution Approach 1:
The patent applies plasma hydrogenation to change the physical and chemical parameters of the oxide layer, reducing bulk oxygen content and modifying the dielectric properties. This parameter change allows the oxide thickness to be reduced linearly while the effective oxide thickness is reduced more significantly, thereby scaling MOSFET dimensions without causing exponential increase in gate leakage.
Solution Approach 2:
The patent uses plasma hydrogenation and nitridization as intermediary processes between oxide deposition and device operation. These intermediary treatments modify the oxide layer properties, creating a transition state where the oxide has reduced effective thickness but maintained structural integrity, thus enabling linear scaling without exponential gate leakage increase.
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 process effectively reduces the effective oxide thickness while minimizing gate leakage and maintaining device reliability, allowing for smaller, faster transistors with improved power efficiency.
Implementation Method 1
exposing the exposed surface to a plasma-excited hydrogen species
Implementation Method 2
exposing the exposed surface to a plasma-excited nitrogen species
Implementation Method 3
performing a thermal anneal process on the high-k dielectric layer and the metal nitride layer for a particular time and at a particular temperature
Implementation Method 4
exposing the exposed surface to a plasma-excited hydrogen species and a plasma-excited nitrogen species
Data Source
AI summary
Embodiments described herein generally relate to enable the formation of a metal gate structure with a reduced effective oxide thickness over a similar structure formed via conventional methods. A plasma hydrogenation process followed by a plasma nitridization process, or a single-step plasma hydrogenation and nitridization process, is performed on a metal nitride layer in a film stack, thereby, according to some embodiments, removing oxygen atoms disposed within layers of the film stack and, in some embodiments, adding nitrogen atoms to the layers of the film stack. As a result, an effective oxide thickness of the metal gate structure is reduced with little or no accompanying flatband voltage shift.