Ashers (Technics PEII)

Ashers (Technics PEII) Tool Type Dry Etch Location Bay 5 Supervisor Mike Day Supervisor Phone (805) 893-3101 Supervisor E-Mail day@ece.ucsb.edu Description Plasma Etching Systems Manufacturer Technics Model PE II-A Dry Etch Recipes

About

These two parallel plate plasma etching systems are generally used to clean organic residue off of semiconductor wafers (ashing), etch organic films, or etch Si₃N₄ films. The systems are both equipped with O₂ for organic removal / surface activation.

One system also has CF₄/O₂ 88% / 12% for etching Si₃N₄. These systems are operated manually and no sign-up is required.

Mechanism

This is a low-frequency RIE etch with O2 - using plasma ion bombardment, in a semi-vertical direction (although the higher 300mT pressure does attack sidewalls somewhat). The low kHz frequency allows ion to move with the RF, providing higher ion bombardment

Low-temp (energy comes from ion acceleration, not temperature).

Applications

Use this for situation where the material to be removed is resistant to chemicals (fluorocarbon polymers - think "plastic") and/or relatively hard (chlorinated PR, after a CL2/BCl2 etch), so physical bombardment is necessary to break up the material, or if high-temp is not acceptable. Typical times: ~2min and microscope inspect and repeat.

Stripping full-thickness PR's in the PEii is slow, at something like ~100nm/1min (at standard 100W/300mT).

Surface activation, eg. making the surface hydrophilic before water-based wet-etching (15sec), or dehydration of wafer surface before HMDS application. This is very important for wet-etch processing through small, high aspect ratio photoresist holes or lines.

Increase adhesion of the next deposition (~2-4min), for example right before loading into evaporator for lift-off. Etch is a bit more aggressive and will go through any monolayers (organic or otherwise), and possibly slightly roughen the surface

Detailed Specifications

• Gases used: CF₄ / O₂ (88%/12%) and O₂
• ~ 10mT ultimate chamber pressure
• 100 kHz (low frequency) directly coupled excitation source
• Sample size: pieces to 6” wafers
• Gas flow and power control

Recipes

• Typical process conditions:
  • Ashing: O2 300mT, 100W power, 30 sec up to 5 min. Make surface hydrophilic: same as above, 15-30sec
  • Si3N4 Etching: CF₄/O₂ 300mT, 100W, ~ 100–150 nm / min. etch rate