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Self Aligned Ion Implanted Guard Ring for High Junction Breakdown Voltage

IP.com Disclosure Number: IPCOM000082659D
Original Publication Date: 1975-Jan-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 3 page(s) / 62K

Publishing Venue

IBM

Related People

Putney, ZC: AUTHOR

Abstract

Described is a method for making a guard ring for high-breakdown voltage, ohmic contact and improved device performance, with a minimum of process steps and a maximum circuit density.

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Self Aligned Ion Implanted Guard Ring for High Junction Breakdown Voltage

Described is a method for making a guard ring for high-breakdown voltage, ohmic contact and improved device performance, with a minimum of process steps and a maximum circuit density.

The method employs ion implantation to form a conductivity region in a semiconductor body having a conductivity of the opposite type. In the example shown, the P-type base region of NPN transistor is formed in a background N- type collector region. The main feature is to use differential oxide thicknesses on the surface of the silicon wafer, to differentially attenuate the dopant ions incident on the surface thereof.

The process commences by coating the semiconductor surface 1 in Fig. 1 with a thick implantation mask 2 and a thin implantation mask 3, using conventional semiconductor process techniques which employ silicon dioxide, silicon nitride, photoresist, or metalization as the masking composition. The thickness of coating 2 should be sufficiently greater than the thickness of coating 3, so that significant differential ion attenuation can be obtained in the respective regions.

The condition for the thin implantation mask 3 is that it stop ions of a low- energy implantation, but pass ions of a quantity of at least equal to the 2 sigma portion of the Gaussian profile for the high-energy implantation. For example, the thin implantation mask 3 should have a thickness less than the high-energy range minus twice the 1 sigma straggle distance.

The next step in the process is a two-stage ion implantation, one stage at a high-acceleration voltage for example 100 to 300 KeV, and the other implantation at a low-acceleration vo...