Method of fabricating a readable alignment mark structure using enhanced chemical mechanical polishing
 A structure of a readable alignment mark and method of manufacturing the readable alignment mark in an alignment mark area on a semiconductor substrate. A semiconductor substrate 10 comprising a product area 12 and an alignment mark area 30 is provided. The alignment mark area 30 has an outer area 40 and an inner area 50. The outer area surrounds 40 the inner area 50. A plurality of alignment mark trenches 24 is formed in the substrate 10 within the inner area 50. A pad oxide layer 20 and a silicon nitride layer 44 are formed sequentially in at least the alignment mark area 12. An isolation trench 43 is formed in the substrate 10 in at least the outer area 40. An insulating layer 46 is formed at least over the alignment mark area 30. The insulating layer 46 is chemical-mechanical polished thereby removing a first thickness of the insulating layer from the inner alignment mark area 50 and leaving a residual insulating layer 46A in the alignment mark trenches 48. Etches are used to remove the residual insulating layer 46A, silicon nitride layer 44, and pad oxide layer 42 in the alignment mark area 30 thereby exposing the alignment marks 48 and making the alignment marks readable. 
Taiwan Semiconductor Manufacturing Company, Ltd.
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Syun-Ming Ying-Ho Chen-Hua Chung-Long
Jang Chen Yu Chang