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Photodiode Having Ion Implant for Improved Light Sensitivity

IP.com Disclosure Number: IPCOM000077813D
Original Publication Date: 1972-Sep-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Forbes, L: AUTHOR

Abstract

This photodiode has high efficiency due to an antireflective oxide coating, a shallow junction formed by ion implantation and the absence of metal over the sensitive area of the photodiode.

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Photodiode Having Ion Implant for Improved Light Sensitivity

This photodiode has high efficiency due to an antireflective oxide coating, a shallow junction formed by ion implantation and the absence of metal over the sensitive area of the photodiode.

A P-type substrate 10 of 2 ohm centimeters resistivity has formed in it N+ regions 12' and 12" by conventional diffusion processes. An insulating coating 14, typically an oxide of the substrate is formed by conventional processes. Openings 16' and 16" are formed in the oxide for contact members 18' and 18" deposited by standard evaporation processes. An opening 20 is formed in the oxide for regrowth of a gate oxide 22. The gate oxide thickness is grown to 1/4 of a wavelength for a visible light source having a lambda of 0.4 to 0.6 micron. The gate oxide serves as an antireflective coating for the visible light.

A shallow N- region 24 is formed between the regions 12' and 12" by a phosphorous ion implantation. An ion dose of approximately 30x10 ions per centimeters is formed through the gate oxide. The region 24 reduces absorption of the light in the N- region of the junction and gives a quantum efficiency near 100%. The ion implantation permits a diffusion to be formed in the range of 0.6 to 1.0 micron in depth, which is difficult to achieve in standard diffusion processes. The parasitic resistance of the photodiode is also reduced by the region 24. A large substrate bias, approximately 12 volts is suggested to minim...