Below we summarised definitions of few most important terms
used when discussing specifications of our technologies:
Bow of a semiconductor wafer is the deviation of the center point of
the median surface of a free, unclamped wafer from a median-
surface reference plane established by three points equally spaced
on a circle with diameter a specified amount less than the nominal
diameter of the wafer [ASTM F1241]. In SOOLC tools we replace “a
median plane” by “the front plane” of the wafer.
Warp of a free, unclamped semiconductor wafer is the difference
between the maximum and minimum distances of the median
surface from a reference plane [ASTM F1241]. In SOOLC tools we
replace “a median plane” by “the front plane” of the wafer.
Waviness is the more widely spaced component of surface texture.
Waviness may be caused by such factors as machine or work
piece deflections, vibration, and chatter. Roughness may be
considered as superimposed on a wavy surface. [ASTM F1241]
Flatness is the deviation of the front surface, expressed in total
indicator reading (see TIR defined below) relative to a specified
reference plane when the back surface of the wafer is ideally flat,
as when pulled down by a vacuum onto an ideally clean, flat chuck.
[SEMI M1-94 and ASTM F1241] . Also see global flatness and site
flatness. For the in a ceramic package flatness is the allowable
deviation of a surface from a defined reference plane. The
tolerance zone is defined by two parallel planes within which the
surface must lie. [SEMI G61-94].
TIR ( total indicator reading)
TIR of a semiconductor wafer, is the span of readings, from
minimum to maximum, for any dimension measured. [SEMI G39-
TTV (total thickness variation)
TTV of a semiconductor wafer, is the difference between the
maximum and minimum values of the thickness of the wafer.
Please note that ASTM F1241-95(2000) Standard Terminology of
Silicon Technology was withdrawn in 2003.
ZebraOptical Optoprofiler: Definitions