The residual gas pressure (RGP) in sealed cavities was measured by residual gas analysis (RGA). The cavity sealed by fusion bonding had the lowest RGP of 16 µbar. Cavities sealed by Au-Au thermocompression bonding and plasma bonding had RGPs of 0.18 and 0.22 mbar, respectively. The cavity sealed by Al-Al thermocompression bonding had RGP of 1.3 mbar. Cavities sealed by thermocompression bonding contained 0.16 – 0.21 mbar Ar. The leak rates of the four seal types were estimated by three methods. RGA measurements revealed that the maximum leakage rates were between 10-13 and 10-15 mbar·l·s-1.