Page 141 - PCMI Journal December 2020

3
Dry Film Resist Control Topics in Photo Chemical Milling Processes Presented by: Sean Hill, Project Manager | Eternal Technology Corporation, US
12/18/20
Pretreatment
• Primary CM pretreat consists of basic PCMI chem clean • Alkaline cleaner (degreaser).
• Water Rinse.
• Acid Rinse (primarily for neutralization).
• Water Rinse.
• Typically do not include micro-etch or other resist adhesion
enhancements – need to maintain surface.
• May include brush Scrub.
• Combination of minimal treatment and smooth surface can challenge resist feature adhesion.
Surface Roughness
• Tradition RTF or Double Treat Foil: Ra = 0.7-0.8um; Rz = 8 – 10um • Present good surface for adhesion
• Standard foil: Ra 0.3 – 0.4um; Rz = 3 – 4um • Can require adhesion enhancing pretreatment.
• Very Low Profile (VLP) or Hyper VLP Surface: Rz = 2 – 3um • Challenging surface for adhesion.
• Generally benefits from adhesion enhancement pretreatment.
• Recommend a high conformance resist with higher fine feature adhesion potential.
4
Issue 136 December 2020 PCMI Journal 141
2