This paper presents Time Dependent Dielectric Breakdown (TDDB) testing of gate oxide on 0.5µm BiCMOS Technology. The gate oxide quality for the technology has been investigated and furthermore to qualify the whole set up of the foundry from the process, equipment, cleanroom control and raw material used to produce high quality gate oxide and hence good quality of BiCMOS devices. TDDB test is the most widely used testing to check the quality of gate oxide and in this paper the TDDB test done on MOS capacitors fabricated using 0.5 µm BiCMOS Technology. Seven consecutive qualification lots have been tested and the data shown that TDDB measurement is capable to differentiate between accepted wafer and rejected wafer. The data also shown that TDDB test was capable to characterise 0.5 µm BiCMOS gate oxide with higher yield and comparable with reference lot from other foundry fab.