TiN Schottky Diode CMOS Silicidation Prevention
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Solution Overview
Problem
The fabrication of Schottky diodes using existing CMOS processing steps is not straightforward due to the risk of undesirable silicidation when metals come into contact with silicon, which affects the diode's forward voltage drop and limits its performance, especially in high-temperature annealing processes.
Innovation Solution
The use of TiN as the Schottky forming material, which exhibits better stability against silicidation, allowing for a tuneable barrier height and forward voltage drop, enabling improved performance and wider application range by forming Schottky diodes within a standard CMOS process with specific processing steps to prevent silicidation and adjust the TiN layer thickness for desired work function.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If metal is used to form Schottky contact with silicon, then Schottky diode can be formed with low forward voltage drop, but undesirable silicidation occurs during high-temperature annealing which affects diode performance
Solution Approach 1:
TiN is introduced as an intermediary material between the metal contact and the silicon substrate. This intermediate layer prevents direct contact between the metal and silicon, thereby avoiding undesirable silicidation reactions during high-temperature annealing while still enabling Schottky contact formation with low forward voltage drop characteristics.
Solution Approach 2:
The Schottky contact structure uses a composite material system consisting of metal/TiN/silicon layers. This composite structure combines the low work function of metal for efficient carrier injection with the high thermal stability of TiN to prevent silicidation, achieving both low forward voltage drop and high reliability.
2Reliability
If TiN layer thickness is increased, then work function increases improving Schottky barrier height, but forward voltage drop increases reducing efficiency
Solution Approach 1:
The TiN layer thickness is precisely controlled as a variable parameter to optimize the Schottky diode performance. By adjusting the thickness within a specific range (5-20 nm), the work function and barrier height are tuned to achieve the desired balance between reverse breakdown voltage and forward voltage drop, enabling optimization for different application requirements.
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 TiN-based Schottky diodes demonstrate improved stability and tunable characteristics, enhancing system efficiency and compatibility with CMOS processing, making them suitable for a broader range of applications, including RFID tags where low forward voltage drop is critical.
Implementation Method 1
the work function of the metal, the latter only in the case of the Schottky diode and MOSFETs
Implementation Method 2
both Vf and VBR can be adjusted by changing the doping of the semiconductor and the work function of the metal
Implementation Method 3
TiN as the Schottky forming material, which exhibits better stability against silicidation
Data Source
AI summary
A method of manufacturing Schottky diodes in a CMOS process includes forming wells, including first wells (16) for forming CMOS devices and second wells (18) for forming Schottky devices. Then, transistors are formed in the first wells, the second wells protected with a protection layer (20) and suicide contacts (40) formed to source and drain regions in the first wells. The protection layer is then removed, a Schottky material deposited and etched away except in a contact region in each second well to form a Schottky contact between the Schottky material (74) and each second well (18).