In the early 1960s, when ICs were first being developed, the largest single crystal of silicon that could be grown was about 1 inch in diameter. The technology has come a long way. Now, highly perfect single crystals of silicon can be grown 12 inches in diameter and 40 inches long The second step in IC fabrication is to slice the single-crystal rod into wafers about 25 thousandths of an inch thick and to grind and polish these wafers to an incredible degree of flatness and smoothness(note the mirror finish of the wafer in Figure 6-4). This shaping is necessary because the devices that will be formed later at and on the surface of the wafer are only 20 millionths of an inch(500 nanometers) across. Even the tiniest scratch or pore will disrupt the formation of these devices. All the precision slicing, grinding, and polishing are done with ceramics.