Ashers (Technics PEII)

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