The creation of patterns within layers of material is in many cases an essential step for the nanofabrication of useful structures. One common method of pattern creation involves removal of material, either in bulk, from the whole substrate, or selectively, from particular regions of the substrate.
WCNT supports several types of subtractive processes. The three main methods (outlined below) involve removing or etching the material by using plasma, liquids, or vapor.
Plasma etch
Includes reactive ion eching (RIE)
This is an accordion element with a series of buttons that open and close related content panels.
What it is used to do
Small features can be etched into the surface of semiconducting substrates or other material in order to enhance certain properties for use in electronic, microelectromechanical, or microfluidic devices.
Plasma processes can also be used to clean or modify the surfaces of substrates.
How it works
Plasma etching involves a plasma formed of an appropriate mixture of gases being delivered at high speed against the surface of a sample. The component species of the plasma can be either ions, or neutral atoms and radicals. During the process, the plasma generates volatile etch products from the chemical reactions between the elements of the material etched and the reactive species in the plasma. These reaction products are pumped away by the vacuum system in which the process takes place.
In most cases, ions are accelerated toward the sample by applying a DC bias voltage to the plasma chamber. This increases the anisotropy of the etch, improving its suitability for pattern transfer.
Instrumentation Available
Strengths
- RIE processes can be highly directional, and good for pattern transfer
- Etch selectivity between the substrate and a masking material can be quite high
- Processes can be tailored by varying plasma pressure, composition, and power
Limitations
- Generally can only work with thin, flat substrates
- Penetration of plasma species into the substrate can cause unwanted damage or chemical modification
Additional Reading
Wet Chemical Etch
This is an accordion element with a series of buttons that open and close related content panels.
What it is used to do
Wet etch processes can be used to remove bulk material from the surface of a substrate, or to selectively remove material to effect pattern transfer. Wet etch processes are also used for cleaning substrates before other process steps.
How it works
The substrate to be etched is immersed in a wet chemical solution. Some parts of the sample dissolve, while others remain intact.
Instrumentation Available
- Al Etch Wet Bench
- KOH Wet Bath 1
- KOH Wet Bath 2 – relaxed materials restrictions
- Nitride Etch Wet Bench
- Piranha Etch Wet Bench
- BOE / HF Wet Bench
- III-V Corrosives Wet Bench
- Corrosives Wet Bench
- Pre-Furnace Clean Wet Bench
- Solvent / Develop Bench for Photoresist
- Solvent Bench for SU-8
- Liftoff Photoresist Solvent Wet Bench
- Develop Wet Bench for Electron Beam Lithography
Limitations
Wet etch processes are not directional, so they can be a poor choice for certain pattern transfer operations.
Applications
Additional Reading
Chemical Vapor Etch
This is an accordion element with a series of buttons that open and close related content panels.
What it is used for
Applications are similar to other dry etch (plasma) techniques, but vapor phase etches may be less suitable for pattern transfer steps that require a directional etch.
How it works
Vapor phase etch processes are similar to other dry etch (plasma) processes. However, the vapor used is not ionized and not in the plasma state. No DC bias can be applied to the etch gas, so the etch results are much more isotropic than with RIE.
Instrumentation Available
Strengths
Limitations
Applications
Additional Reading
