Self-Aligned Schottky Diode in SOI Substrates
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Solution Overview
Problem
The formation of vertical p-n junction and Schottky barrier diodes in semiconductor-on-insulator (SOI) substrates is challenging due to insufficient thickness of the top semiconductor layer, and conventional methods fail to provide an adequate doped guard ring to prevent leakage current.
Innovation Solution
A self-aligned Schottky diode with a doped guard ring is manufactured in an SOI substrate, where a second-conductivity-type-doped semiconductor region is formed around a dummy gate electrode and shallow trench isolation structure, creating a metal semiconductor alloy portion that abuts the first-conductivity-type-doped semiconductor material to form a Schottky barrier, with the guard ring surrounding the Schottky barrier region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional vertical Schottky barrier diode formation is used in SOI substrate, then rectifying characteristics are achieved, but the top semiconductor layer thickness becomes insufficient to form vertical junctions
Solution Approach 1:
The patent transitions from vertical Schottky barrier formation to lateral Schottky barrier formation. Instead of forming vertical metal-semiconductor junctions through the thin top layer, the invention creates lateral junctions where the Schottky barrier forms horizontally at the interface between the doped semiconductor region and the intrinsic semiconductor, enabling diode functionality in ultra-thin SOI structures where vertical junctions cannot be formed.
2Reliability
If standard source/drain ion implantation is used to form doped guard ring, then doping is achieved, but dopants reach the buried insulator layer causing excessive leakage current
Solution Approach 1:
The patent applies localized doping through selective masking to create a doped guard ring with precise spatial control. By using a mask layer that covers the buried insulator layer during ion implantation, the doping is confined to regions above the mask, preventing dopant contamination of the buried insulator while still providing the necessary guard ring functionality to reduce leakage current at the Schottky barrier edges.
3Ease of manufacture
If thicker top semiconductor layer is used to allow vertical junction formation, then vertical Schottky barrier can be formed, but SOI substrate benefits are lost
Solution Approach 1:
The patent fundamentally changes the geometric parameters of the Schottky barrier structure from vertical to lateral orientation. This parameter change enables the diode to function in ultra-thin SOI structures (where vertical junctions cannot be formed) while maintaining manufacturing compatibility with standard SOI processing techniques, thus achieving both ease of manufacture and SOI substrate compatibility.
4Reliability
If shallow trench isolation contacts buried insulator layer, then isolation is achieved, but contact to lower terminal of vertical diode becomes difficult
Solution Approach 1:
The patent resolves the contact formation difficulty by transitioning to lateral diode structures. Instead of requiring contact to the lower terminal through the shallow trench isolation (which blocks access to the buried insulator), the lateral configuration allows contact to be made at the side of the structure, eliminating the need to penetrate through the isolation layer and simplifying the contact formation process.
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 the effective formation of a Schottky diode in an SOI substrate with reduced reverse leakage current, enhancing the rectification characteristics and practicality of diode implementation despite limited top semiconductor layer thickness.
Implementation Method 1
a metal semiconductor alloy portion that abuts the first-conductivity-type-doped semiconductor material to form a Schottky barrier
Implementation Method 2
a doped guard ring having a doping of a second conductivity type in a semiconductor-on-insulator (SOI) substrate
Data Source
AI summary
A Schottky barrier diode comprises a doped guard ring having a doping of a second conductivity type in a semiconductor-on-insulator (SOI) substrate. The Schottky barrier diode further comprises a first-conductivity-type-doped semiconductor region having a doping of a first conductivity type, which is the opposite of the second conductivity type, on one side of a dummy gate electrode and a Schottky barrier structure surrounded by the doped guard ring on the other side. A Schottky barrier region may be laterally surrounded by the dummy gate electrode and the doped guard ring. The doped guard ring includes an unmetallized portion of a gate-side second-conductivity-type-doped semiconductor region having a doping of a second conductivity type. A Schottky barrier region may be laterally surrounded by a doped guard ring including a gate-side doped semiconductor region and a STI-side doped semiconductor region. Design structures for the inventive Schottky barrier diode are also provided.