Patent ID: 7763126

Claim:
An Ag sputtering target, made by conducting a cold forging operation one or more times, the cold forging operation comprising solid forging an Ag columnar mass so as to be extended in an axial direction thereof, and cold upsetting the solid forged Ag columnar mass in the axial direction while maintaining a columnar shape of the solid forged Ag columnar mass; and slicing a cold-worked columnar mass obtained by the cold forging operation in rounds after being heat treatment, wherein the Ag sputtering target has three-dimensional fluctuation of grain sizes not more than 18%; and wherein the three-dimensional fluctuation of the grain sizes measured by: exposing a plurality of layers having sputtering surfaces by slicing the Ag sputtering target in planes parallel to a sputtering starting surface, selecting a plurality of locations on each of the exposed sputtering surfaces of the layers, and measuring grain sizes D at all the selected locations of all the exposed sputtering surfaces of the layers by executing i) to iv) below, i) taking an optical micrograph of the selected location, ii) drawing a plurality of straight lines equal to or more than four in a grid pattern on the obtained micrograph, iii) investigating a number n of grain boundaries on each of the straight lines, and calculating a grain size d (unit: μm) for each of the straight lines on the basis of the following formula: d=L /(nm) wherein L: length of the straight line, n: number of the grain boundaries on the straight line, m: magnification of the optical micrograph, and iv) calculating the grain size D at the selected location as an average value of the grain sizes d for the plurality of straight lines; calculating values A1 and B1 using the formula below and based on the results of measurement of the grain sizes D at all the selected locations of all the exposed sputtering surfaces: A 1=( D max −D ave )/ D ave *100(%) B 1=( D ave −D min)/ D ave ·100(%) wherein D max : maximum value among the grain sizes D at all the selected locations D min : minimum value among the grain sizes D at all the selected locations D ave : average value of the grain sizes D at all the selected locations; and selecting larger one of the values A1 and B1 as the three-dimensional fluctuation of the grain sizes.