Methods for improving oxygen precipitation uniformity using the concept of the precipitation S-curve/S-band (the relationship between the amount of precipitation, DELTA[Oi], and the initial interstitial oxygen content, [Oi]o) are described. Slugs from four crystals with different axial [Oi]o profiles were annealed under a complementary metal oxide semiconductor thermal cycle to illustrate this technique. A conventional axial [Oi]o profile crystal with a seed end had the highest [Oi]o and the tang end had the lowest [Oi]o resulted in a highest DELTA[Oi] variation. The crystal with the best axial [Oi]o profile for obtaining a uniform DELTA[Oi] profile was a low [Oi]o in the seed end and a higher relatively constant [Oi]o in the middle portion, and highest [Oi]o in the tang end. To design an axial [Oi]o profile for a target uniform value of DELTA[Oi] fora crystal, the S-band of the device process must be obtained first.