Metal-Gated MOSFET Oxygen Gettering for Interfacial Oxide Regrowth
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Solution Overview
Problem
The challenge in metal-gated MOSFET devices is the limited thickness of the metal gate layer, which restricts device performance due to the regrowth of the interfacial oxide region, leading to increased effective oxide thickness and degraded scaling benefits.
Innovation Solution
Incorporating a buried oxide layer as a primary background oxygen getterer, closer to the interfacial oxide layer, allows for increased metal gate layer thickness without regrowth, enhancing device performance by using a silicon-on-insulator substrate with a thin device layer and implanting oxygen getterer species like arsenic and boron.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the metal gate layer thickness is increased to enhance device performance, then device performance is improved, but regrowth of the interfacial oxide region occurs leading to increased effective oxide thickness
Solution Approach 1:
A silicon layer is introduced as an intermediary component between the metal gate layer and the interfacial oxide region. This silicon layer acts as an oxygen getter that attracts and binds background oxygen, preventing oxygen diffusion to the interfacial oxide region and thus preventing regrowth. This intermediary layer enables the metal gate thickness to be increased without causing interfacial oxide regrowth.
Solution Approach 2:
The silicon layer is positioned in advance between the metal gate and interfacial oxide region to preemptively prevent oxygen diffusion. By having the oxygen getter in place before metal gate deposition or during subsequent processing, the system prevents interfacial oxide regrowth before it can occur, allowing thicker metal gates to be used.
2Reliability
If amorphous Si or poly-Si is placed in close proximity to the interfacial oxide region to prevent regrowth, then regrowth prevention is effective, but the metal gate layer thickness is limited to about 10 nanometers
Solution Approach 1:
The silicon layer serves as an intermediary oxygen getter positioned between the metal gate and interfacial oxide. This mediator enables effective regrowth prevention while allowing the metal gate layer to be thicker than the conventional 10 nm limit, as the silicon layer intercepts oxygen diffusion paths regardless of increased metal gate thickness.
3Object-affected harmful factors
If the metal gate layer thickness is limited to maintain proximity to the interfacial oxide region, then regrowth is prevented, but device performance enhancement is restricted
Solution Approach 1:
By introducing the silicon layer as an intermediary oxygen getter, the system decouples the relationship between metal gate thickness and regrowth prevention. The silicon layer absorbs background oxygen, enabling metal gate layers thicker than 10 nm to be used without causing interfacial oxide regrowth, thus allowing device performance enhancement while maintaining regrowth control.
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 enables thicker metal gate layers, improving direct current and alternating current performance by reducing parasitic capacitance and allowing for stressed metal gate films, thus enhancing overall MOSFET device performance.
Implementation Method 1
a substrate having a buried oxide layer at least a portion of which is configured to serve as a primary background oxygen getterer of the device
Implementation Method 2
One or more oxygen getterer species are implanted into at least a portion of the buried oxide layer
Data Source
AI summary
Metal-oxide semiconductor field effect transistor (MOSFET) devices having metal gate stacks and techniques for improving performance thereof are provided. In one aspect, a metal-oxide semiconductor device is provided comprising a substrate having a buried oxide layer at least a portion of which is configured to serve as a primary background oxygen getterer of the device; and a gate stack separated from the substrate by an interfacial oxide layer. The gate stack comprises a high-K layer over the interfacial oxide layer; and a metal gate layer over the high-K layer.