Recessed Access Gate Insulator Structure for Lower GIDL
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Solution Overview
Problem
Recessed access devices in semiconductor materials face challenges in achieving high on-current and low off-current, particularly due to gate-induced-drain-leakage (GIDL) issues, which affect the conductivity and efficiency of the devices.
Innovation Solution
The use of a gate insulator comprising both low-k and high-k materials, where the low-k material extends completely along the sidewalls and under the conductive gate, and the high-k material is laterally inward, reducing GIDL and enabling an all-metal gate construction, thereby enhancing conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional gate insulator structure is used, then the device structure is simple, but gate-induced-drain-leakage increases and on-current decreases
Solution Approach 1:
The gate insulator is segmented into two distinct materials: a low-k material forming the first portion and a high-k material forming the second portion. This segmentation allows each material to perform its specialized function - the low-k material provides mechanical support and stress control while the high-k material provides superior gate control and reduces GIDL, thereby increasing on-current without excessive complexity
Solution Approach 2:
The gate insulator employs a composite structure combining low-k and high-k materials. The low-k material (such as silicon dioxide) provides a stable base layer with appropriate dielectric properties, while the high-k material (such as hafnium oxide) adds enhanced gate control capability and reduces drain leakage, achieving superior overall performance
2Reliability
If the low-k material extends completely along sidewalls and under the gate, then GIDL is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The low-k material is deposited first to form the first portion of the gate insulator, completely lining the trench sidewalls and extending under the gate before the high-k material is added. This preliminary action ensures proper stress distribution and GIDL reduction, while the subsequent high-k material deposition is controlled to form only the second portion, managing the precision requirements through sequential processing
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 configuration reduces gate-induced-drain-leakage, allowing for higher on-current and lower off-current in recessed access devices, improving their overall performance and efficiency.
Implementation Method 1
a low-k gate-insulator material that is characterized by a dielectric constant, k, of no greater than 4.0
Implementation Method 2
a high-k gate-insulator material that is characterized by a dielectric constant, k, of greater than 4.0
Data Source
AI summary
A method of forming a recessed access device comprises forming a trench in semiconductor material. Sidewalls and a bottom of the trench are lined with low-k gate-insulator material. The low-k gate-insulator material is characterized by its dielectric constant k being no greater than 4.0. Sacrificial material is formed in a bottom portion of the trench over the low-k gate-insulator material and over the trench bottom. A high-k gate-insulator material is formed in an upper portion of the trench above the sacrificial material and laterally-inward of the low-k gate-insulator material that is in the upper portion of the trench. The high-k gate-insulator material is characterized by its dielectric constant k being greater than 4.0. The sacrificial material is replaced with a conductive gate that has its top above a bottom of the high-k gate-insulator material. A pair of source/drain regions is formed in upper portions of the semiconductor material on opposing lateral sides of the trench. A channel region is in the semiconductor material below the pair of source/drain regions and extends along the trench sidewalls and around the trench bottom. Other embodiments, including structure independent of method, are disclosed.