Metallizing MEMS Devices via Semiconductor Replacement
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Solution Overview
Problem
Doped semiconductor regions in semiconductor devices often exhibit high sheet resistance, leading to significant thermal resistance noise and limiting noise performance in semiconductor devices.
Innovation Solution
Replacing semiconductor interconnection structures with conductive metal interconnection structures, such as tungsten or molybdenum, using reacting gases like WF6 or MoF6, to achieve lower sheet resistance, with the process allowing for the formation of micromachined structures that are movable and metallized to improve electrical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If doped semiconductor regions are used for electrical interconnections, then the device structure is simple and manufacturing is easy, but the sheet resistance is high leading to significant thermal noise
Solution Approach 1:
The patent changes the material parameter from doped semiconductor to metal (tungsten, molybdenum, or copper), fundamentally altering the electrical resistance characteristic. This material substitution reduces sheet resistance from hundreds or thousands of ohms to less than 20 Ω/sq, directly improving noise performance while maintaining manufacturing compatibility through established CVD and sputtering processes
Solution Approach 2:
The patent replaces the semiconductor-based electrical interconnection system with a metal-based system. This substitution eliminates the high resistance inherent in doped semiconductor regions while utilizing proven metal deposition techniques from existing semiconductor manufacturing, thereby resolving the contradiction between performance improvement and manufacturing ease
2Reliability
If metal interconnection structures are formed by replacing semiconductor atoms, then sheet resistance is reduced to less than 20 Ω/sq, but the fabrication process becomes more complex
Solution Approach 1:
The patent applies preliminary action by forming a thin seed layer of metal (50-200 Å) on the semiconductor surface before complete metallization. This seed layer facilitates subsequent metal deposition and ensures good adhesion and electrical contact, simplifying the overall process by preparing the surface in advance for efficient metal formation
Solution Approach 2:
The patent uses a metal seed layer as an intermediary between the semiconductor substrate and the final metal interconnection structure. This intermediate layer enables controlled metal deposition, ensures proper adhesion, and facilitates the transition from semiconductor to metal interconnection, thereby managing process complexity while achieving low resistance
3Adaptability or versatility
If the micromachined structure is released and movable during metallizing, then the device functionality is maintained, but controlling the metallization process becomes more difficult
Solution Approach 1:
The patent segments the metallization process into distinct phases: forming the seed layer on the movable structure, then separately depositing additional metal layers. This segmentation allows the movable structure to remain in place during each step while achieving complete metallization, thereby maintaining device functionality without compromising manufacturing 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
The solution significantly reduces sheet resistance to less than 20 Ω/sq, improving both electrical and inertial performance of micromachined devices like MEMS structures, enhancing their noise performance and functionality.
Implementation Method 1
replacing the semiconductor interconnection structure with a conductive metal interconnection structure comprises exposing the semiconductor interconnection structure to a reacting gas
Data Source
AI summary
Various embodiments produce a semiconductor device, such a MEMS device, having metallized structures formed by replacing a semiconductor structure with a metal structure. Some embodiments expose a semiconductor structure to one or more a reacting gasses, such as gasses including tungsten or molybdenum.