Several types of as-received and complementary metal oxide semiconductor (CMOS) thermal simulated 100 mm wafers were used for warpage study under different annealing conditions. The results indicated that as-received wafers showed little increase in warpage up to 1000-degrees-C furnace temperature and 61.0 cm/min insertion rate. For the CMOS thermal simulation processed wafers, both the prior amount of oxygen precipitation, DELTA[O(i)], where DELTA[O(i)] is the decrease in interstitial oxygen concentration, and bulk microdefect morphology affected warpage. For DELTA[O(i)] less than ca. 26 ppma, wafers with predominantly octahedral precipitates without associated dislocations plus a low density of small plate-type and dot-like precipitates underwent much less warpage than wafers with predominantly large octahedral precipitates and precipitate-dislocation-complexes (PDCs). When the DELTA[O(i)] was higher than 26 ppma, the defects consisted of a high density of large octahedral-shaped precipitates and PDCs and thus warpage became inevitable.