Experiments showed that increasing water concentration in the bath results in higher selectivity: more Si3N4 etched and less SiO2 etched. With the installations of a water concentration monitor and a water spiking apparatus, the bath is able to control the water concentration. The partial replacement of the chemical bath after each product lot reduces dissolved silicon concentration. The addition of H2SO4 saves initial conditioning time. With all of the efforts, the bath starts at a high selectivity and maintain this selectivity for an extended bath life.
Archive for category: Technical Article
Cost of Ownership Comparison of Single Wafer Processes for Stripping Copper Pillar Bump Photomasks
A new generation of negative tone and chemically amplified positive tone photoresists by TOK, JSR, Dow Chemical and others has gained momentum for advanced packaging applications. Resist thickness requirements are increasing to the 40-100 μm range as Cu pillars and micro-bumps are adopted, to accommodate the tighter pitches required in the newest multi-chip package designs. In order to form the pillars, the resist mask must be thicker than the height of the pillars to contain the entire bump structure.
A New Approach to Tackle Wafer Contact Mark Contamination Issues in Marangoni Drying
Contact mark contamination of Si wafers in Marangoni drying is related to water retention at the contact area between wafers and a process holder. The formation of water retention at wafer/holder contact is addressed with a conceptual model. A technical approach of capillary drainage is proposed to tackle the contact mark issue, along with experimental verification.