Browse Prior Art Database

Laser EC Sites With Transparent Substrates

IP.com Disclosure Number: IPCOM000048475D
Original Publication Date: 1982-Feb-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Moskowitz, PA: AUTHOR

Abstract

The use of an optically transparent sapphire substrate in Josephson technology will allow laser modification techniques to be used for Josephson chip engineering changes without the necessity of chip removal. Sapphire has an expansion coefficient that matches that of lead wiring more closely than that of silicon and is less susceptible to hillock formation than silicon. Also, sapphire is a close match to other super-conductors, such as niobium, and has a high coefficient of heat conductivity.

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Laser EC Sites With Transparent Substrates

The use of an optically transparent sapphire substrate in Josephson technology will allow laser modification techniques to be used for Josephson chip engineering changes without the necessity of chip removal. Sapphire has an expansion coefficient that matches that of lead wiring more closely than that of silicon and is less susceptible to hillock formation than silicon. Also, sapphire is a close match to other super-conductors, such as niobium, and has a high coefficient of heat conductivity.

Fig. 1 shows a carrier 10 having a groundplane thereon. A chip 12 is mounted on the carrier 10, where the substrates for the carrier and the chip are sapphire. Windows 14 are placed in the groundplane of the carrier so as to coincide with the engineering change (EC) laser modification sites 16 on the chip
12. In this manner, electrical contacts may be made or broken by a focused laser beam 18 without removing chip 12 from carrier 10.

In Fig. 2 a variation is shown in which the laser EC sites 16 are placed over windows 20 in the chip groundplane. This allows the EC sites 16 to be accessed with the laser beam 18 through the chip substrate.

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