BD Etchant
FOR PSG-SiO2 SYSTEMS
An improved buffered etch formulation for delineation of phosphosilica glass - SiO2 (PSG), and borosilica glass - SiO2 (BSG) systems, in the passivation of transistor surfaces. BD Etchant has a low PSG/SiO2 ratio, minimizing the undercutting of the PSG passivating film.
ETCH CHARACTERISTICS OF BD ETCHANT
| 20¡É | 25¡É | 30¡É |
Dielectric Material | ¡Ê/sec | ¡Ê/sec | ¡Ê/sec |
Thermally grown SiO2 | 0.87 | 1.22 | 1.72 |
PSG (6 mole % P2O5) | 1.85 | 2.47 | 3.35 |
Etch Ratio (PSG/SiO2) | 2.12 | 2.02 | 1.95 |
Note: etch rate is dependent upon composition of PSG and BSG.
APPLICATION :
Employed as a dip etch to remove SiO2 films from contacts without the disturbance of the PSG film. BD Etchant is used prior to metallization of the contact holes of the silicon transistor wafers followed by water and alcohol rinses.