Summary and Solutions to Common Problems in Wet Development Processes

Main Types and Characteristics of Wafer Wet Development Solutions

I. Classification by Development Mechanism1. Alkaline Development SolutionsRepresentative Components: Sodium hydroxide (NaOH), sodium carbonate (Na₂CO₃), tetramethylammonium hydroxide (TMAH).Applications: Suitable for positive-tone photoresists (e.g., AZ® series), achieving pattern transfer by dissolving unexposed regions.

The Chemical Dissolution Mechanism of Wet Photoresist Stripping Machines

The core of wet photoresist stripping lies in the specific chemical reaction between solvents and photoresist. Depending on the type of photoresist (positive/negative), three primary dissolution methods are employed:1. Alkaline Stripping SolutionSuitable for positive photoresist, this method leverages alkaline solutions (e.g., tetramethylammonium hydroxide, TMAH) to trigger hydrolysis reactions with ester and ether bonds in the photoresist. These reactions break down the polymer chains into smaller, water-soluble molecules.

Top Five Core Issues and Solutions in Etching Processes

Issue 1: Etching Defects in High Aspect Ratio StructuresPhenomenon: Sidewall scalloping, bottom bowing, and unpenetrated vias (e.g., 3D NAND 60:1 deep vias).Root Cause: Insufficient ion directionality and difficulty in byproduct removal, leading to local over-etching.Solutions:Equipment Optimization:Adopt pulsed plasma technology (e.g., Lam Research’s Flex® system), which periodically switches between etching and passivation steps to protect sidewalls.Process Adjustment:Introduce sidewall protection gases (e.g., C₄F₈) to form polymer passivation layers.Optimize pressure/power ratios to enhance ion directionality (e.g., low pressure with high bias).

Common Issues in Wafer Photoresist Stripping

I. Chemical Residues and Incomplete CleaningResidue from Photoresist Stripping Solution：Wet photoresist stripping requires organic solvents or strong oxidizers (e.g., sulfuric acid/hydrogen peroxide mixtures) to dissolve photoresist.