Study of moisture penetration in chip passivation layer by deuterium oxide (D2O) isotope tracing technique

Passivation layers normally serve as protection layers to protect the active semiconductor surface from the peripheral environment. They are expected to have good adhesion, corrosion resistance, and moisture resistance. The typical passivation layers are Al
2
O
3
, SiO
2
, Si
3
N
4
and AlN. Moisture resistance is one of the important properties of the passivation layers, as the chips usually work under environment with humidity. Moisture penetration into the chip may cause failures like corrosion, ion migration and electricity short, etc. It is critical to know about how fast is the moisture penetration into the chip via the passivation layer. However, so far there is no good method to study the moisture penetration speed in passivation layer.This work applied a new deuterium oxide (D
2
O) isotope tracing method to study the moisture penetration status of the passivation layer of a chip. The chip was loaded into the temperature-humidity chamber with D
2
O (40°C, 90%RH). D
2
O gradually penetrated into the passivation layer under the 40°C, 90%RH environment. Deuterium signal of the sample was subsequently analyzed by Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS). The relationship between D
2
O moisture penetration distance and D
2
O treatment time was plotted. In the current study, the results showed that D
2
O moisture reached the organic layer under the passivation layer after 21 hours.