positions 48a 48b 48c and 48d of fig5 a are next removed 34 ono fence removal step 34 a suitable technique is to expose the structure 62 of fig5 a to a 100 1 hydrogen fluoride hf solution at room temperature for a maximum duration of 60 seconds an alternative technique is to expose the structure 62 of fig5 a to a 40 1 hydrogen fluoride hf solution at room temperature for a maximum duration of 35 seconds a second alternative technique is to perform a conventional buffer oxide etch for 25 seconds the device is then cleaned using a conventional rca clean process a suitable technique involves dipping the device in a 5 1 1 water hydrogen peroxide and ammonia h 2 o h 2 o 2 nh 4 oh solution with a temperature of 60 degrees celsius for 5 minutes and then rinsing conventionally alternatively the structure may be dipped in a 6 1 1 water hydrogen peroxide and hydrogen chloride h 2 o h 2 o 2 hcl solution with a temperature of 60 degrees celsius for 5 minutes and then rinsed conventionally absent an ono fence removal step above or in addition to the ono fence removal step polystringers such as at positions 48a 48b 48c and 48d of fig5 a are next removed hereinafter 34 oxidation step 34 a suitable technique involves heating the wafer to approximately 900 degrees celsius o 2 gas is then directed towards the wafer with a flow rate of 14 l min for 45 minutes almost all polystringers are thereby removed by oxidation for example on an 8 inch wafer including nand type memory device core cells very few polystringers may remain on the outside edges an additional benefit of.