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Reducing Radioactive Species in Evaporated Aluminum Films by Shutting off the Initial Vapor Stream

IP.com Disclosure Number: IPCOM000052153D
Original Publication Date: 1981-May-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Sugerman, A: AUTHOR

Abstract

Aluminum has been found to have alpha particle radioactivity. This can cause "soft errors" in integrated circuitry. As the density of integrated semiconductor circuits is increased, the device size decreases, and the charge level that distinguishes a "1" bit from a "0" bit is reduced. This makes the circuits more vulnerable to extraneous charge introduction that might convert a "1" bit into a "0", or vice versa, such as that generated by electron-hole production from absorption of alpha particle radiation. Alpha particle radiation from the uranium and thorium radioactive decay chains produces this undesirable effect. Uranium and thorium are found in aluminum, and aluminum is used extensively in the interconnection metallurgy in semiconductor integrated circuit manufacture.

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Reducing Radioactive Species in Evaporated Aluminum Films by Shutting off the Initial Vapor Stream

Aluminum has been found to have alpha particle radioactivity. This can cause "soft errors" in integrated circuitry.

As the density of integrated semiconductor circuits is increased, the device size decreases, and the charge level that distinguishes a "1" bit from a "0" bit is reduced. This makes the circuits more vulnerable to extraneous charge introduction that might convert a "1" bit into a "0", or vice versa, such as that generated by electron-hole production from absorption of alpha particle radiation.

Alpha particle radiation from the uranium and thorium radioactive decay chains produces this undesirable effect. Uranium and thorium are found in aluminum, and aluminum is used extensively in the interconnection metallurgy in semiconductor integrated circuit manufacture. It has been found that the dominant radioactive species transferred to the evaporated aluminum films from the source material is radium, and that it comes off very early in the aluminum evaporation process.

To substantially reduce the deposited radium in the aluminum layer on integrated circuit substrates, the early aluminum vapor stream is intercepted by a shutter. This action lowers the soft error rate produced in the integrated circuits by alpha particles generated from these radioactive species.

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