MEMS Metal-Ceramic Multilayer Stack Creep Resistance
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Solution Overview
Problem
Existing MEMS components face challenges in maintaining mechanical and electrical properties during high-temperature processes due to creep in metallic layers and stress gradients in layered structures, leading to deformation and signal drift, especially with materials like aluminum, and temperature sensitivity of plastics used as sacrificial layers.
Innovation Solution
Integration of metal-ceramic multilayer stacks, specifically TiN/AlCu layers, which offer a high creep limit and low electrical resistance, allowing for precise mechanical strain adjustment and thermal expansion control, enabling the use of temperature-sensitive materials and processes, and utilizing plastics as sacrificial layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If metallic layers (e.g., aluminum) are used in mechanical functional layers, then electrical conductivity is improved, but creep occurs under mechanical loads leading to irreversible deformations and signal drift
Solution Approach 1:
The patent applies composite materials by combining metal layers with ceramic layers to form a multilayer stack. The metal layers provide electrical conductivity while the ceramic layers provide mechanical stability and creep resistance. This composite structure resolves the contradiction by integrating the beneficial properties of both materials: the metal ensures low electrical resistance for signal acquisition, while the ceramic matrix prevents creep and deformation under thermal and mechanical stresses.
2Strength
If high-temperature deposition processes are used for mechanical functional layers, then mechanical strength is improved, but temperature-sensitive materials (e.g., plastics) decompose
Solution Approach 1:
The patent segments the manufacturing process into distinct temperature stages. The metal-ceramic multilayer stack is deposited at relatively low temperatures (below 400°C) using sputtering or CVD, preserving temperature-sensitive materials. Subsequently, high-temperature processes (above 400°C) are applied only to semiconductor layers that require thermal activation. This segmentation allows both low-temperature deposition of metal-ceramic structures and high-temperature processing of semiconductors without material decomposition.
3Reliability
If thin metal layers are used to reduce creep, then creep resistance is improved, but electrical resistance becomes too high for narrow printed conductors
Solution Approach 1:
The patent uses composite materials where thin metal layers (providing creep resistance) are combined with ceramic layers (providing structural support). The metal layers can be kept thin to prevent creep while the ceramic matrix provides additional load-bearing capacity. The composite structure maintains low electrical resistance through the conductive metal pathways while the ceramic portions contribute to mechanical stability without adding significant resistance.
Solution Approach 2:
The patent merges multiple thin metal layers separated by very thin ceramic layers into a metal-ceramic multilayer stack. This combining approach allows the cumulative electrical conductivity of multiple metal layers to achieve low overall resistance, while the distributed ceramic layers throughout the stack provide comprehensive creep resistance and structural support.
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 metal-ceramic multilayer stacks provide stable mechanical and electrical properties, preventing deformation and signal drift, enabling precise adjustment of mechanical strain and thermal expansion, and allowing for the use of temperature-sensitive materials in MEMS component manufacturing.
Implementation Method 1
Metals, such as aluminum, for example, may, in fact, be deposited at lower temperatures. However, they have a tendency to creep already under low mechanical loads, which, in the case of a multiple occurrence, can lead over the long term to irreversible deformations of mechanical functional elements
Implementation Method 2
a plurality of thin metal layers, which are separated by very thin ceramic layers, may be combined in metal-ceramic multilayer stacks. It turns out that the creep limit of such a multilayer stack is on the order of magnitude of one of the thin metal layers, while the electrical resistance is significantly lower
Implementation Method 3
the originally adjusted mechanical strain condition changes at high temperatures, as occur, for example, during the soldering process or during thermal cycling
Data Source
AI summary
An MEMS component includes at least one metal-ceramic multilayer stack as a mechanical functional layer in the layered structure of the MEMS component. The metal-ceramic multilayer stack functions as a mechanical functional layer in which at least one component of the micromechanical structure of the MEMS component is configured.