Deep Reactive Ion Etching (DRIE) | Silicon, SOI & Glass Wafers for MEMS

Deep Reactive Ion Etching (DRIE) Applications and Wafer Selection

Deep Reactive Ion Etching (DRIE) is a critical microfabrication technology used to create deep, high-aspect-ratio structures in silicon wafers, SOI wafers, and specialty substrates. Researchers use DRIE to fabricate MEMS devices, microfluidic chips, sensors, optical components, and advanced semiconductor structures requiring precise vertical sidewalls and excellent dimensional control.

Silicon Wafers for X-Ray Micro-Lens Fabrication

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One research group used the following silicon wafer for manufacturing X-ray micro-lenses through a DRIE process:

Item #1116
100mm P/B <100> 10-20 ohm-cm 500µm SSP Silicon Wafer

High-quality silicon wafers are often selected for X-ray optics because they provide excellent dimensional stability, smooth surfaces, and compatibility with photolithography and plasma etching processes.

Glass Wafers for Deep Reactive Ion Etching

Although silicon is the most common material for DRIE, researchers also use glass wafers when optical transparency, electrical insulation, or microfluidic functionality is required.

Research Request: "This is the first time I am going to use glass wafers for my application. I need to perform deep reactive ion etching on the wafers and would like the most economical glass material suitable for DRIE processing."

Reference #158843 for specifications and pricing.

Common glass materials used in microfabrication include Borofloat 33, D263 glass, fused silica, and specialty optical glass substrates. Material selection depends on etch chemistry, thermal requirements, and device design.

Silicon Wafers Used in DRIE Research

Researchers performing deep trench etching, MEMS fabrication, and microfluidic device manufacturing frequently use wafers such as:

Item #857
150mm P/B <100> 0-10 ohm-cm 620µm SSP Silicon Wafer

Wafer thickness, crystal orientation, resistivity, and surface finish all influence DRIE performance and final device quality. Selecting the correct substrate before process development can significantly improve yield and reduce fabrication costs.

SOI Wafers for Deep Reactive Ion Etching

Silicon-on-Insulator (SOI) wafers are widely used in MEMS fabrication because the buried oxide layer acts as a natural etch stop during DRIE processing. This enables precise control of structure depth and improves device repeatability.

Researchers have successfully used the following SOI wafer for biomedical engineering and MEMS applications:

Item #1000.673501
100mm SOI Wafer with 150µm Device Layer

SOI wafers are commonly used for pressure sensors, accelerometers, gyroscopes, microfluidic devices, optical MEMS, and high-performance semiconductor applications.

What is Reactive Ion Etching (RIE)?

Reactive Ion Etching (RIE) is a plasma-based dry etching process used to selectively remove material from a substrate surface. Chemically reactive ions are accelerated toward the wafer, where they react with and remove exposed material. DRIE is an advanced form of RIE that enables significantly deeper etch depths and higher aspect ratios.

Today, DRIE and RIE technologies are widely used throughout the semiconductor, MEMS, photonics, biomedical, and microfluidics industries because they provide precise control over feature dimensions and sidewall profiles.

Deep Reactive Ion Etching on Double-Side Polished Silicon Wafers

Deep Reactive Ion Etching (DRIE) is widely used to create deep, high-aspect-ratio features in silicon wafers for MEMS devices, microfluidic chips, sensors, X-ray optics, and semiconductor research. For many DRIE projects, the best wafer depends on diameter, thickness, polish, crystal orientation, and how much material will remain after etching.

Researcher request: A university principal investigator needed optimal silicon wafers for a microfluidic device. The process required DRIE on both sides of the wafer, so the wafer needed enough thickness to withstand fluid pressure after about 60% of the original thickness was etched away.

Choosing Silicon Wafers for DRIE Processing

When selecting wafers for DRIE, researchers should first specify the wafer diameter and thickness. Common silicon wafer sizes include 50.8mm, 76.2mm, 100mm, 125mm, and 150mm. Thicker wafers are often preferred when deep trenches, through-wafer etching, or double-sided processing are required.

For two-sided etching, double-side polished silicon wafers are usually recommended because both surfaces may need accurate lithography, bonding, masking, or alignment. DSP wafers are especially useful for MEMS, pressure sensors, microchannels, and microfluidic devices where surface quality and wafer flatness affect process results.

Best Wafer Orientation for Deep Reactive Ion Etching

The wafer’s crystallographic orientation can affect device design and downstream processing. Common orientations include <100>, <111>, and <110>. For many DRIE silicon processes, <100> silicon is commonly used because it is widely available and works well for MEMS and semiconductor fabrication. <110> wafers may be selected for certain MEMS structures, while <111> wafers may be used for specialized device or epitaxial applications.

For applications that involve MEMS devices, wafer orientation, thickness, and polish should be selected before ordering so that the wafer matches the etch depth, mask design, and mechanical strength requirements.

Recommended Silicon Wafer Specification for DRIE

For many DRIE research projects, a common starting specification is:

Material: Silicon
Diameter: 100mm
Orientation: P-type <100>
Thickness: 500µm
Polish: Double-side polished
Resistivity: 10-20 ohm-cm
Grade: SEMI Prime

This type of wafer is often a good option for DRIE, microfluidic fabrication, and MEMS research because it provides enough thickness for deep etching while keeping both sides polished for processing. For projects with larger features or tighter surface requirements, prime grade silicon wafers are usually preferred over test grade wafers, since scratches, haze, and surface defects can affect lithography and etched features.

What is Deep Reactive Ion Etching?

Deep Reactive Ion Etching is an advanced plasma etching process used to produce deep, vertical structures in silicon and other materials. DRIE is commonly used when standard dry etching cannot achieve the required depth, sidewall profile, or aspect ratio.

One of the most common DRIE methods is the Bosch process, which alternates between etching and passivation steps. The etching step removes silicon, while the passivation step protects the sidewalls. Repeating these steps allows researchers to create deep trenches, vias, cavities, channels, and MEMS structures with nearly vertical sidewalls.

DRIE Applications in MEMS, Microfluidics, and X-Ray Optics

DRIE is used in many research and manufacturing applications, including:

MEMS sensors and actuators
Microfluidic channels and lab-on-chip devices
Through-silicon vias and wafer-level packaging
X-ray micro-lenses and precision micro-optics
Silicon molds for polymer casting
High-aspect-ratio trenches and cavities

Researchers developing X-ray micro-lenses may use DRIE to create accurate silicon or diamond microstructures with controlled geometry. In microfluidics, DRIE can form deep channels and cavities that must remain mechanically stable after etching.

Silicon, SOI, and Glass Wafers for DRIE

UniversityWafer, Inc. supplies silicon wafers, silicon-on-insulator wafers, and glass wafers for DRIE, RIE, MEMS, microfluidic, and semiconductor fabrication research. Available options include single-side polished, double-side polished, prime grade, test grade, custom thickness, and multiple wafer diameters.

Deep Reactive-Ion Etching (DRIE)