Low cost photoresist stripper composition for wafer level packaging technology

To meet the photoresist removal requirements in wafer level packaging (WLP) technology, low cost stripper formulation with robust performance need to be developed. Reduced de-ionized water (DIwater) content in the stripper formulation is one of the main strategies to achieve good performance for current commercial products. In strong alkaline formulation with pH₂₀>12, higher content of DIwater was considered to be detrimental to the metal passivation and photoresist removal. Reported in the paper was the progress of low cost photoresist stripper development with higher DIwater content. After careful study of passivation mechanism, through unique synergism passivation effect of inhibitors blends and careful optimization of different components, excellent metal compatibility and cleaning performance by the formulation treatment was achieved. Metal etch rate of aluminum, copper, titanium, tungsten, tin and silver was controlled below 1Å/min in the operation temperature within 3days bath life. Cleaning performance on test wafer of JSR-111N, JSR151-N, MP112, etc showed no PR residue left and no pillar bump attack. Bath life time in the operation condition was also studied.