Page 155 - PCMI Journal December 2020

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BP.
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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Breakpoint Control
• Typically controlled by developer conveyor speed. If Contrained – e.g. by etching or reel-to-reel operation
• Alternative control measures:
• Developer Concentration: Higher Concentration = More aggressive = Lower %
• Developer Temperature: Higher Temperature = More aggressive = Lower % BP.
Developer Concentration Control
• Theoretical pH of new developer at 1% KCO3: 11.6.
• May be slightly lower due to presence of dissolved CO2 in the developer,
• Suggested control mechanism is to dose fresh developer with HCL or alternative acid to bring the developer to the replenish point prior to introducing resist.
which can form a neutralizing acid.
• Maintains more stable development conditions for SU bath.
• Replenish pH: 10.8 or adjusted to optimize development and
developer loading as necessary.
• Limit developer loading to minimize dragout, redeposit which can inhibit etching.
• Recommended to minimize loading to 1 – 3 mils-SF/Liter • Minimize Antifoam
Issue 136 December 2020 PCMI Journal 155
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