Materials Used in Semiconductor Manufacturing (Page 2)                          

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Other Elements Used

Boron, symbol B, atomic number 5, atomic group 13 or IIIA, atomic weight 10.81, is a hard, brittle, semi-metallic element used as a dopant in semiconductor devices.  It is classified as an 'acceptor' when used as dopant for Si devices, given that its atom has one less valence electron compared to the Si atom that it replaces (B has 3 valence electrons while Si has 4).  This results in a vacancy of electron which is known as a 'hole'.  The resulting excess 'holes' make the material 'p-type.'

Germanium, symbol Ge, atomic number 32, atomic group 14 or IVA, atomic weight 72.59, is a grayish white semi-metallic element with a melting temperature of 958 deg C. It was actually the original semiconductor material used to fabricate diodes and transistors. However, the low band gap of Ge (0.66 eV) results in relatively large leakage currents in its reverse-biased p-n junctions.

Lead, symbol Pb, atomic number 82, atomic group 14 or IVA, atomic weight 207.20, is one of the two major components of solder used in finishing the external leads of the IC package.  The other major component of solder is Tin, or Sn.

Phosphorus, symbol P, atomic number 15, atomic group 15 or VA, atomic weight 30.974, is a non-metallic element used as a dopant in semiconductor devices.  It is classified as a 'donor' when used as dopant for Si devices, given that its atom 'donates' or gives up one of its 5 valence electrons when it replaces a Si atom, which only has 4 valence electrons.  The resulting excess electrons make the material 'n-type.'

Tin, symbol Sn, atomic number 50, atomic group 14 or IVA, atomic weight 118.69, is one of the two major components of solder used in finishing the external leads of the IC package.  The other major component of solder is Lead, or Pb. 

Other Materials Used (alphabetically arranged)

Alloy 42.  An alloy used for manufacturing leadframes, usually for ceramic packages such as the CerDIP.  It is composed of about 57.7% Fe, 41% Ni, 0.8% Mn, and 0.5% Co.  Its thermal coefficient of expansion is 4.3 ppm/deg C.

Borophosposilicate Glass (BPSG). A compound used as interlayer dielectric in integrated circuits for isolating conductive lines and components from each other.

Gallium Arsenide (GaAs). A dark gray crystalline solid composed of gallium and arsenic used as substrate semiconductor material for building integrated circuits.  GaAs has an energy gap of 1.35 eV, which is higher than the 1.11 eV of Si.  Energy gap is the amount of energy needed for an electron to jump from the valence band into the conduction band.  This is the reason why GaAs devices can operate at higher temperatures than Si devices - they are less prone to exhibit thermally-induced noise and leakage.

Kovar.  A vacuum-melted, low-expansion alloy used for manufacturing leadframes, usually for ceramic packages such as the CerDIP.  It is composed of about 53.48% Fe, 29% Ni, 17% Co, 0.2% Si, 0.3% Mn, and 0.02%C.  It melts at 1450 deg C, and has a resistivity of 490 microohm-mm.  

Platinum silicide (PtSi).  PtSi found a popular use in silicon integrated circuits as a highly reliable contact metallization between the silicon substrate and the upper metal layers.  PtSi is formed using a self-aligned process, making it  very reproducible and resulting in a very clean interface with silicon. A diffusion barrier metal such as Ti/Pt is often deposited over the silicide before the final metal layer such as Al is placed on top of the barrier metal..