Vapor HF (Hydrogen Fluoride) Etching

Advanced Dry Release Processing for Current and Next Generation MEMS Devices.

To create a MEMS microstructure, a release etch process is required in order to remove the structural material and leave the mechanical structure with clean and free surfaces. It is essential that removal (etching) of the sacrificial material does not damage or restrict the operation of the MEMS device. To ensure full performance and reliability, the remaining mechanical structure needs to be free from residues, particles and damage, and prepared for the application of an anti-stiction coating or packaging process steps. XERIC™ vapor HF (Hydrogen Fluoride) etching—or vapor phase—sacrificial release etching from memsstar offers many benefits to companies engaged in MEMS development and manufacturing.

XERIC Vapor Phase Dry Release With HF

Using memsstar’s XERIC dry anhydrous HF etching is unique because it eliminates stiction in a single process. The patented process is compatible with the widest wide range of metals—especially Al/alloy and other metals commonly used in MEMS mirrors and electrical contacts.

Sacrificial Oxides:
Thermal oxide, TEOS, SOI bonded oxide, quartz, PECVD oxide, spin-on oxide, low-temperature spin-on glass

Protective Layers:
Aluminum, silicon carbide, Si-rich LPCVD nitride, stoichiometric PECVD nitride

Metal Layers:
Gold, copper, TiW, nickel, aluminum, Ti, TiO2

XERIC Oxide Etch Features
Key characteristics	Large process window to optimize process for any structure Excellent selectivity with silicon nitride and silicon dioxide (<5% 1σ) High selectivity to underlayer and mechanical materials Industry-leading etch rates High etch rates for undercut and blanket Si Excellent uniformity (<5% 1σ) Excellent repeatability (<5% 1σ) No corrosion No stiction In-line controls—etch rate monitor, endpoint, temperature Unique endpoint capability
Application examples	Sensors, RF MEMS, micro bolometer arrays, accelerometers, RF switches, temperature gauges

XERIC Oxide Etch Features

Key characteristics

Large process window to optimize process for any structure
Excellent selectivity with silicon nitride and silicon dioxide (<5% 1σ)
High selectivity to underlayer and mechanical materials
Industry-leading etch rates
High etch rates for undercut and blanket Si
Excellent uniformity (<5% 1σ)
Excellent repeatability (<5% 1σ)
No corrosion
No stiction
In-line controls—etch rate monitor, endpoint, temperature
Unique endpoint capability

Application examples

Sensors, RF MEMS, micro bolometer arrays, accelerometers, RF switches, temperature gauges

Vapour HF Etching FAQs

1. What is vapour HF etching and why is it used for MEMS devices?

Vapour HF (hydrogen fluoride) etching is a dry, vapour-phase sacrificial release process that removes structural material and leaves a MEMS structure with clean, free surfaces. To create a MEMS microstructure, a release etch process is required to remove the structural material, leaving the mechanical structure clean. It is essential that the removal of the sacrificial material does not damage or restrict the operation of the MEMS device. Memsstar’s XERIC™ vapour HF etching delivers residue-free dry release, leaving the remaining structure ready for an anti-stiction coating or subsequent packaging steps.

2. How does memsstar’s XERIC™ vapour HF etching prevent stiction and corrosion?

Stiction and corrosion are two of the most common failure modes in MEMS release processing, and XERIC™ is engineered to eliminate both. Using memsstar’s XERIC dry anhydrous HF etching is unique because it eliminates stiction in a single process, removing the need for separate drying or pre-treatment steps. The patented process delivers no corrosion or stiction in the finished structure and is compatible with the widest range of metals – especially aluminium and alloys – as well as other metals commonly used in MEMS mirrors and electrical contacts.

3. What materials is XERIC™ vapour HF etching compatible with?

XERIC™ is designed to work across a broad range of MEMS materials, giving process engineers flexibility in their device design. On the sacrificial side, it etches thermal oxide, TEOS, SOI-bonded oxide, quartz, PECVD oxide, spin-on oxide, and low-temperature spin-on glass. For the surrounding structure, memsstar’s process is compatible with protective layers such as aluminium, silicon carbide, silicon-rich LPCVD nitride, and stoichiometric PECVD nitride, as well as metal layers including gold, copper, titanium, nickel, aluminium, titanium tungsten (TiW), and titanium dioxide (TiO2).

4. What process performance and control does XERIC™ oxide etch deliver?

XERIC™ oxide etch combines high throughput with the precision that MEMS manufacturing requires. It offers a large process window to optimize the process for any structure, excellent selectivity to silicon nitride and silicon, high selectivity for underlayers and mechanical materials, and industry-leading etch rates for undercut and blanket oxide. Memsstar also builds in tight process control, with excellent uniformity (<5% 1σ), excellent repeatability (<5% 1σ), and in-line controls including an etch rate monitor, endpoint, and temperature with unique endpoint capability.

5. What types of MEMS devices is vapour HF etching designed for?

Memsstar’s vapour HF etching supports a wide range of current and next-generation MEMS devices for which clean, reliable release is critical to performance. Typical applications include sensors, radio frequency (RF) MEMS, microbolometer arrays, accelerometers, RF switches, and temperature gauges. As part of memsstar’s ORBIS™ platform, XERIC vapour HF etching scales from R&D through to high-yield manufacturing, making it well suited to companies advancing both established and emerging MEMS applications.

Glossary

SOI: Silicon-on-insulator (SOI) technology involves a layered structure consisting of a thin layer of silicon (the device layer) on top of an insulating layer (usually silicon dioxide), which is then placed on a silicon substrate.
TEOS: Tetraethyl orthosilicate (also called tetraethoxysilane or ethyl silicate) is widely used as a precursor gas in chemical vapour deposition (CVD) processes.
PECVD: Plasma-enhanced chemical vapour deposition, where reactive gases are introduced into a vacuum chamber and energized by a plasma (ionized gas) to break down molecules and form thin solid films on a substrate.
LPCVD: Low-pressure chemical vapour deposition, a specialized thin-film deposition technique used to grow high-quality, uniform solid layers on substrates such as silicon wafers.

memsstar: Vapor HF etching for next generation MEMS devices.