Step 24. Nitride removal

Images taken by uvscope after the nitride removal: STI LOCOS

Step	Process	Date	Operator
24.1	Oxide wet etch Sink 6 1/10 HF dip for 60 s Etch thin oxide layer off from the top of the nitride film. Include PCH.	08/16/07	Pongracz
24.2	Sink7 - fresh phosphoric acid (3 bottles) @ 160 ^oC - water dripping 1 drop/10s to keep the liquid level - monitor the etch rate (QDR, SRD) - measure oxide/nitride thickness with Nanoduv LOCOS wafers W#1-5 and 11-15 and PCH 90min etch monitor nitride thickness after 30min, 45 min, 65 min, 80 min After 80 min oxide thickness is 216 A Allow 10 min more etching STI wafers W#6-10 125 min etch monitor nitride thickness after 30min, 60 min, 90 min, 105 min After 105 min nitride is still there on some places Allow 20 min more etching Nitride remained on some spots very close to the edge because of CMP non-uniformity	08/16/07- 08/17/07
24.3	Pad oxide wet etch 1/10 HF @ Sink6 until PCH dewet ~ 60 s	08/17/07
24.4	Oxide wet etch from NCH 5:1 BHF @ Sink8 until dewet ~ 5 min	08/17/07