TMAH Etching of Silicon - 1
• Tetra Methyl Ammonium Hydroxide
• MOS/CMOS compatible:
– No alkali metals {Li, Na, K, … }.
– Used in positive photoresist developers which do not use choline.
– Does not significantly etch SiO2 or Al! (Bond wire safe!)
• Anisotropy: (111):(100) ~ 1:10 to 1:35
• Typical recipe:
– 250 mL TMAH (25% from Aldrich)
– 375 mL H2O
– 22 g Si dust dissolved into solution
– Use at 90°C
– Gives about 1 mm/min etch rate