Why are SOI wafers used for MEMS?

Silicon-on-Insulator (SOI) wafers provide a built-in buried oxide layer that acts as an etch stop and electrical insulator. This structure is ideal for creating precise resonators, comb-drives, and suspended structures with controlled thickness.

When should I use Glass instead of Silicon for MEMS?

Glass substrates (like Borofloat or Fused Silica) are preferred when optical transparency, low electrical loss (for RF applications), or thermal isolation is required. They are often used for microfluidics and RF MEMS.

What substrates are best for harsh environment MEMS?

For high-temperature or harsh environments, Silicon Carbide (SiC) and Sapphire are superior due to their high thermal stability, chemical inertness, and wide bandgap properties.

Innovative Substrate Solutions for MEMS: Silicon, SOI, Glass & More

Quick Select Guide

Silicon: Mechanical strength, CMOS compatibility.
SOI: Precise etch stops, electrical isolation.
Glass & Quartz: Transparency, low RF loss.
Sapphire: High temp & chemical stability.
SiC & GaN: Harsh environments, power MEMS.

Performance Insight:
Capacitive MEMS sensors using engineered substrates have demonstrated operation up to 500°C with extremely low temperature drift.

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Why Substrate Choice Defines MEMS Performance

In MEMS design, the substrate provides the mechanical support, thermal stability, and electrical isolation necessary for the device. As MEMS move into high-temperature and RF domains, bulk silicon is often supplemented by advanced materials.

Silicon Wafers: The Foundation

Bulk silicon remains the dominant MEMS substrate due to its excellent mechanical properties and well-understood micromachining behavior.

Applications: Pressure sensors, accelerometers, micro-mirrors.
Key Feature: Compatible with standard CMOS processing.

SOI and SIMOX: Superior Isolation

Silicon-on-Insulator (SOI) wafers introduce a thin device layer separated from the handle wafer by a buried oxide (BOX). This structure is crucial for defining precise device thickness and preventing leakage currents.

This structure is ideal for resonators and comb-drive actuators where precise etch stops are required.

Glass and Quartz: Optics & RF

When transparency or low dielectric loss is required, Glass substrates (like Borofloat 33) and Quartz are the materials of choice.

Micro-fluidics: Transparent windows allow for optical inspection.
RF MEMS: Low dielectric loss improves signal integrity in switches and antennas.

Compound and Wide-Bandgap Substrates

For harsh environments, Silicon Carbide (SiC) and Sapphire offer extreme durability.

SiC: Supports high-temperature and high-voltage MEMS.
GaAs/InP: Used for RF MEMS switches and photonic devices utilizing Gallium Arsenide or Indium Phosphide.

Substrate Services

UniversityWafer, Inc. also provides downstream services to enable MEMS fabrication, including:

Wafer Bonding: Anodic and fusion bonding for capping.
Thin Films: Deposition of Thermal Oxides and Nitrides.
Dicing: Precision cutting of complex MEMS die.