Tegal O2 Plasma Asher
About
Process: This is an oxygen plasma asher designed for gentle, downstream or direct O₂ plasma treatment. It is primarily used for stripping photoresist, descumming (removing thin resist residues), surface cleaning, and activating surfaces (e.g., improving wettability or adhesion) without significant ion damage.
Hardware: Parallel-plate or downstream plasma configuration with RF excitation (likely 13.56 MHz). O₂ gas delivery with controlled flow and pressure. Substrate electrode or holder for up to 200 mm wafers/pieces. Temperature control (typically near room temp or mildly heated). Simple, reliable design for cleanroom photoresist processing.
Gases:
- O₂ (oxygen – primary plasma gas for ashing and oxidation)
Process Properties:
- High-rate photoresist ashing (organic removal via atomic oxygen)
- Gentle descum (removal of ~10–100 nm resist scum after development)
- Surface activation (increases hydrophilicity for better adhesion of subsequent layers)
- Low damage to underlying substrates (especially graphene/CNT due to no heavy ions)
- Isotropic process (good for uniform cleaning/ashing)
Applications:
- Photoresist strip after lithography or etch
- Post-develop descum to improve pattern fidelity
- Cleaning of graphene, carbon nanotubes (CNT), or organic residues
- Surface activation before deposition, bonding, or coating
- Gentle organic removal in sensitive devices
Usage: Load sample (up to 200 mm wafer/piece), pump down, set O₂ flow/power/time, ignite plasma, run process. Monitor visually or timed. Cool down before venting. Use short runs for descum to avoid over-etching.
Detailed Specifications
- Model: Tegal CU90?? (confirm exact model on tool label; legacy Tegal asher)
- Location: Advanced Photo Bay
- Substrate size: Up to 200 mm wafers or pieces
- Gas: O₂ only
- Plasma: RF-powered O₂ discharge (power level confirm on tool; typically 100–500 W range)
- Features: Simple operation, high ashing rate for organics, low-damage to sensitive materials like graphene/CNT
- Restrictions: O₂ plasma only – no fluorine or chlorine gases; avoid metals or materials reactive to oxygen radicals
- Other: Reliable for photoresist and organic cleaning in lithography workflows
Documentation
- SOP – Standard Operating Procedure
- Training required – contact lab staff (Joey)
Recipes & Data
- Standard Processes: Typical O₂ plasma runs include:
* Photoresist descum: 50–150 W, 30–120 s (low power/short time) * Full resist strip: 200–400 W, 5–20 min (depending on thickness/residue) * Graphene/CNT cleaning: Low power/short exposure to avoid damage
- Process Control: Check ash completeness visually or via microscope. Monitor for residue or over-etching. Perform particle scans post-process if needed.
- Notes: Use lowest effective power/time for sensitive materials (e.g., graphene). O₂ plasma can functionalize surfaces – good for adhesion but may oxidize some materials.
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