Page 148 - PCMI Journal December 2020

Dry Film Resist Control Topics in Photo Chemical Milling Processes Presented by: Sean Hill, Project Manager | Eternal Technology Corporation, US
12/18/20
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Measurement Tool: Step
§ Stouffer Step Tablet
− Monitors the level of exposure through the development process
§ 21 Step Table: D = 0.15 Density units.
§ 41 Step Tablet: D = 0.05 Density units (more precise)
§ Stepwedge is always placed under photo tool on standard printers.
Stouffer Step
• Characterizes Resist Cure State after Expose and Develop
• Step Types:
• Clear Step (CSTEP): Highest exposure with no resist image.
• Resist Step (RSTEP): Lowest Exposure with ≥ 50% Resist Image. • Gloss Step (GSTEP): Lowest Exposure with glossy surface.
• Relates Resist to:
• Expose (and Develop) Process and Process variation. • Resist Performance in specific process.
• Resist manufacturer recommendations:
• Nominal Exposure Energy (mJ/cm2) • Nominal RSTEP: Typically 8.
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Issue 136 December 2020 PCMI Journal 148
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