In a method of pattern formation information including a pattern size on a reticle is received. A width of an EUV radiation beam is adjusted in accordance with the information. The EUV radiation beam is scanned on the reticle. A photo resist layer is exposed with a reflected EUV radiation beam from the reticle. An increase of intensity per unit area of the EUV radiation beam on the reticle after the adjusting the width is greater when the width before adjustment is W1 compared to an increase of intensity per unit area of the EUV radiation beam on the reticle after the adjusting the width when the width before adjustment is W2 when W1>W2.