autodoping – dopant, from sources other than the dopant intentionally added to the vapor phase, which is incorporated into an epitaxial layer during growth.
autodoping barrier – a film or layer which impedes transport of impurity atoms from the back surface of a substrate to the epi layer during epitaxial deposition. Also known as backseal.
conductivity type – defines the nature of the majority of the carriers in silicon: n-type material, in which electrons are the majority carrier, is formed when a donor dopant impurity is added to the silicon; p-type material, in which holes are the majority carrier, is formed when an acceptor dopant impurity is added to the silicon.
crystal orientation – the crystallographic axis, on which the silicon crystal is grown. In generally supplied in <100> or <111> orientations.
dislocation – a line imperfection in a crystal which forms the boundary between slipped and nonslipped regions of the crystal.
dislocation density – the number of dislocation etch pits per unit area on an exposed wafer surface.
dislocation etch pit – a sharply defined depression in the immediate region of a stressed or defective crystal lattice, resulting from preferential etching.
dopant – a chemical element from the third (such as boron) or fifth (such as phosphorus or antimony) column of the periodic table, intentionally incorporated into a silicon crystal in trance amounts to establish its conductivity type and resistivity.
Bor 0,001 – 50 ohmcm
Phosphorus 0,1 – 40 ohmcm
Antimony 0,005 – 0,025 ohmcm
Arsenic < 0,005 ohmcm
extrinsic gettering – controlled damage or stress to the crystal lattice structure intentionally introduced by mechanical means or by deposition of a polysilicon or other film on the back surface of a silicon wafer.
flat orientation (primary) – the crystallographic plane, which ideally coincides with the surface of the primary flat, The primary flat is usually a <110> plane.
Miller indices – the reciprocals of the intercepts of a crystallographic plane with the x-, y-, and z-axes, respectively. For example, the cube face perpendicular to the x-axis is the <100> plane. A family of planes is denoted by curly brackets; e.g., all cube faces are the <100> planes. Directions are denoted by Miller indices in square brackets; e.g., the x-axis is the <100> direction an the cube diagonal is the <111> direction. Families of directions are denoted by angular brackets; e.g., all cubic axes are the <100> directions. A negative direction is denoted by a minus sign over the index; e.g., the negative x-axis is the <¯100> direction.
polycrystalline silicon (polisilicon, poly) – silicon made up of randomly oriented crystallites and containing large-angle grain boundaries, twin boundaries, or both.
radial oxygen variation – the difference between the average oxygen concentration at one or more points symmetrically located on a silicon wafer and the oxygen concentration at the center of the wafer, expressed as a percent of the concentration at the center. Unless otherwise specified, Siltec considers the radial oxygen variation to be determined using the average of the oxygen concentrations at the two points 10 mm from the edge of the wafer. Radial oxygen variation is sometimes determined using the average of the oxygen concentrations at several symmetric points half way between the center and the edge of the wafer . Also known as oxygen gradient.
radial resistivity variation – the difference between the average resistivity at one or more points symmetrically located on a silicon wafer and the resistivity at the center of the wafer, expressed as a percent of the resistivity at the center, Unless otherwise specified, we consider the radial resistivity variation to be determined using the average resistivity of four points 6 mm from the edge of the wafer on two perpendicular diameters. Radial resistivity variation is sometimes determined using the average of the resistivity at the four point half way between the center and the edge of the wafer on the same diameters. Also known as resistivity gradient.
resistivity (ohm·cm) – the ratio of the potential gradient (electric field) parallel with the current to the current density, In silicon, the resistivity is controlled by adding dopant impurities; lower resistivity is achieved by adding more dopant.
slip – a process of plastic deformation in which one part of a crystal undergoes a shear displacement relative to another in a fashion which preserves the crystallinity of the silicon. After preferential etching, slip is evidenced by a pattern of one or more parallel straight lines of 10 or more dislocation etch pits per millimeter which do not necessarily toch each other. On <111> surfaces, groups of lines are inclined at 60º to each other; on <100> surfaces, they are inclined at 90º to each other.
stacking fault – a two-dimensional defect resulting from a deviation from the normal stacking sequence of atoms in a crystal. It may be present in the bulk crystal, grow during epitaxial deposition (usually as a result of a contaminated or structurally imperfect substrate surface); or develop during oxydation. On <111> surfaces, stacking faults are revealed by preferential etching either as closed or partial equilateral triangles. On <100> surfaces, stacking faults are revealed as closed or partial squares.
striations – helical features on the surface of a silicon wafer associated with local variations in impurity concentration. Such variations are ascribed to periodic differences in dopant incorporation occurring at the rotating solid-liquid interface during crystal growth. Striations are visible to the unaided eye after preferential etching and appear to be continuous under 100X magnification.
subsurface damage – residual crystallographic imperfections apparent only after preferential etching of the polished silicon surface. Such damage is usually considered to be caused by mechanical processing of the wafer.
twinned crystal – a crystal in which the lattice consists of two parts related to each other in orientation as mirror images across a coherent planar interface known as the twinning plane or twin boundary, In silicon, this plane is a <111> plane. Also known as twin.
wafer orientation – the crystallographic plane, described in terms of Miller indices, with which the surface of the wafer is ideally coincident. Generally, the surface of the wafer corresponds within a few degrees with the low index plane perpendicular to the growth axis. In such cases, the orientation may also be described in terms of the angular deviation a of the low-index crystallographic plane from the polished wafer surface.