Beam lead technology

Beam lead technology is a method of fabricating a semiconductor device. Its initial application was for high-frequency silicon switching transistors and high-speed integrated circuits. This technology eliminated the labor-intensive wire-bonding process that was commonly used for integrated circuits at the time. It also enabled the automated assembly of semiconductor chips onto larger substrates, facilitating the production of hybrid integrated circuits. [1]

Beam lead integrated circuits

History

In the early 1960s, M.P. Lepselter[2][3] developed techniques for fabricating a structure that involved electroforming an array of thick, self-supporting gold patterns on a thin film Ti-Pt-Au base, leading to the term "beams." These patterns were deposited on the surface of a silicon wafer. The excess semiconductor material beneath the beams was subsequently removed, resulting in the separation of individual devices and leaving them with self-supporting beam leads or internal chiplets cantilevered beyond the semiconductor material. These contacts not only served as electrical leads but also provided structural support for the devices.

Patents

Patented inventions included:

  1. Selective Removal of Material Using Cathodic Sputtering (Plasma Etching/RIE), US Patent #3,271,286; issued 1966
  2. PtSi Semiconductor Contacts and Schottky Diodes (PtSi Schottky Diodes), US Patent #3,274,670; issued 1966
  3. Semiconductive Device Including Beam Leads (Beam Leads, Ti-Pt-Au metal system), US Patent #3,426,252; issued 1969
  4. Method for Making Closely Spaced Conductive Layers (Air-Insulated Crossovers, air bridges, RF-Switch), US Patent #3,461,524; issued 1969
  5. Vibratory Reed Device (MEMS), US Patent #3,609,593; issued 1971

Legacy

This technology, also known as air-bridge technology, has established itself in high-frequency silicon switching transistors and ultra-high-speed integrated circuits for telecommunications and missile systems. The beam lead devices, produced by the hundreds of millions, became the first example of a commercial microelectromechanical structure (MEMS).

References
  1. Rao R. Tummala et al, Microelectronics Packaging Handbook: Semiconductor packaging, Springer, 1997 ISBN 0-412-08441-4, page 8-75
  2. M.P. Lepselter, et al., "Beam-Lead Devices and Integrated Circuits", Proceedings of the IEEE, Vol. 53 No 4 (1965), p.405.
  3. Presentation at Electron Devices Meeting, October 29, 1964, Washington, D.C.
  • Beam Lead Technology, M.P.Lepselter, Bell System Technical Journal 45. (2) (1966), pp. 233–253
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