Cassettes for holding thin
semiconductor wafers for
safe handling are provided, along with an improved methodology for reducing the thickness of
semiconductor wafers. Embodiments include a cassette for holding thin
semiconductor wafers, having a plurality of sets of center and edge supports, the sets being spaced from each other a distance greater than a sag amount of the wafers. The thin wafers are supported in a predetermined
reference plane, so that tools such as robots or automatic handlers can be programmed to pick them up without damaging them. In another embodiment, a double into single
pitch wafer cassette is provided having a
wafer entrance section with spacing twice as large between sets of edge supports as a conventional cassette, to accommodate the sag / warp of the thin wafers, and a “flattening section” which guides and flattens the wafers between opposing edge supports as they are pushed into the cassette, such that the wafers are held substantially planar. Because the wafers are held substantially planar, they can be safely removed from the cassette by automatic tools. A methodology is also provided for reducing the thickness of a semiconductor
wafer, comprising
grinding the back side of the wafer to reduce its initial thickness to an intermediate thickness, and
plasma etching the back side of the wafer to reduce the intermediate thickness to a final thickness. The two-step
grinding /
etching process is faster and less expensive than conventional multi-step
grinding /
polishing processes, because it requires less steps, each step is accomplished relatively quickly, and it employs standard grinding and
etching equipment, rather than expensive dedicated equipment.