Commonly Used Conductor/Resistor Films
WTi/Au
Typical Applications  Devices processed at high temperatures, such as Au/Ge eutectic bonding temps
Advantages  Film withstands excursions to 450°C
Disadvantages  WTi is a good barrier layer, in some cases a barrier layer recommended for eutectics
Temperature Guidelines  450°C for 30 minutes
Pb/Sn, Au/Sn Solderability  Possible diffusion/enrichment
Allowable Die Attach Methods
  •  Epoxies
  •  Au/Ge eutectic
  •  Au/Si eutectic
  •  Au/Sn solder
  • Pb/In eutectic
Typical TCR  n/a
Front Side Metal
  •  Sputtered WTi 300-500Å
  •  Sputtered Au 20µ”
  •  Plated Au 100 – 300µ”
Back Side Metal  Same as front side
Ti/Pt/Au
Typical Applications Laser Diode Sub-mounts
Advantages
  •  Film withstands excursions to 500°C
  • Pt is an Excellent Barrier Metal
  • No diffusion into Au
Disadvantages Pt etch requires Ion Milling
Temperature Guidelines 500°C for 30 minutes
Pb/Sn, Au/Sn SolderabilityExcellent
Allowable Die Attach Methods
  •  Epoxies
  •  Au/Ge eutectic
  •  Au/Si eutectic
  •  Au/Sn solder
  • Pb/In eutectic
Typical TCR  n/a
Front Side Metal
  •  Sputtered WTi 300-500Å
  •  Sputtered Au 20µ”
  •  Plated Au 100 – 300µ”
Back Side Metal Same as front side
WTi/Ni/Au
Typical ApplicationsDevices processed at higher temperatures requiring a solderable film
Advantages  Film withstands brief excursions to 325°C
Disadvantages Wire bonding problems may be possible due to Ni-Au diffusion when devices processed > 300°C
Temperature Guidelines 300°C for 120 minutes
Pb/Sn, Au/Sn SolderabilityGood
Allowable Die Attach Methods
  •  Pb/Sn solder
  •  Au/Sn solder
  •  Epoxies
  •  Pb/In eutectic
Typical TCR  n/a
Front Side Metal
  •  Sputtered WTi 300-500Å
  •  Sputtered Ni 2,000-5,000Å
  •  Sputtered Au 20µ”
  •  Plated Au 100 – 300µ”
Back Side Metal Same as front side
WTi/Au/Cu/Ni/Au
Typical ApplicationsHigh conductivity film allowing for wire bonding and/or soldering after high temp. processing
Advantages
  • High conductivity film
  • Pb/Sn & Au/Sn solderable
Disadvantages Wire bonding problems may be possible due to Ni-Au diffusion when devices processed > 300°C
Temperature Guidelines 300°C for 120 minutes
Pb/Sn, Au/Sn SolderabilityGood
Allowable Die Attach Methods
  •  Pb/Sn solder
  •  Au/Sn eutectic
  •  Epoxies
  •  Pb/In eutectic
Typical TCR  n/a
Front Side Metal
  •  Sputtered WTi 300-500Å
  • Sputtered Cu 40µ”
  • Electroplated Cu 40-2000µ”
  • Electroplated Ni 50-150µ”
  • Electroplated Au 50-250µ”
Back Side Metal Same as front side
TaN/WTi/Au
Typical ApplicationsHigh conductivity film allowing for wire bonding and/or soldering after high temp. processing
Advantages
  • Film withstands excursions to 450°C
  • Passivated TaN films offer good humidity resistance
Disadvantages Not Pb/Sn or Au/Sn Solderable
Temperature Guidelines Stabilize resistors at 425°C for 30.120 minutes
Pb/Sn, Au/Sn SolderabilityPoor
Allowable Die Attach Methods
  • Epoxies
  • Au/Ge eutectic
  • Au/Si eutectic
  • Au/Sn eutectic
  • Pb/In eutectic
Typical TCR  -100 ± 50 ppm/°C
Front Side Metal
  • Sputter 10-200 Ω/sq. TaN
  • Sputtered WTi 300-500Å
  • Sputtered Au 20µ”
  • Plated Au 100 – 300µ”
Back Side Metal Same as front side without the TaN layer
TaN/WTi/Ni/Au
Typical ApplicationsDevices processed at higher temperatures requiring a solderable film
Advantages
  • Pb/Sn & Au/Sn solderable
  • Passivated TaN films offer good humidity resistance
Disadvantages Wire bonding problems may be possible due to Ni-Au diffusion when devices processed > 300°C
Temperature Guidelines Stabilize resistors at 325°C for 60 minutes
Pb/Sn, Au/Sn SolderabilityGood
Allowable Die Attach Methods
  • Pb/Sn solder
  • Au/Sn solder
  • Epoxies
  • Pb/In eutectic
Typical TCR  -100 ± 50 ppm/°C
Front Side Metal
  • Sputter 10-200 Ω/sq. TaN
  • Sputtered WTi 300-500Å
  • Sputtered Ni 2,000-5,000Å
  • Sputtered Au 20µ”
  • Plated Au 100 – 300µ”
Back Side Metal Same as front side without the TaN layer