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Browse Prior Art Database

Low Step Height Offset Contact Design

IP.com Disclosure Number: IPCOM000108010D
Original Publication Date: 1992-Apr-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 5 page(s) / 178K

Publishing Venue

IBM

Related People

Moksvold, TW: AUTHOR

Abstract

The offset contact design is a design solution to the reliability exposure of metal opens due to metal notching over thick oxide steps. It ensures metal continuity by providing a controlled low step height contact. It reduces the step height of an NPN collector contact to that of a base contact.

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This is the abbreviated version, containing approximately 76% of the total text.

Low Step Height Offset Contact Design

       The offset contact design is a design solution to the
reliability exposure of metal opens due to metal notching over thick
oxide steps.  It ensures metal continuity by providing a controlled
low step height contact.  It reduces the step height of an NPN
collector contact to that of a base contact.

      The problem to be solved is shown in Fig. 1.  This conventional
contact design shows the metal notching and the metal open exposure
due to the high step height.

      The solution to the open collector exposure problem is shown in
Fig. 2.  This low step height offset contact design eliminates the
metal notching and metal open exposure by addressing each of the two
factors that contribute to the high step height in the conventional
contact design shown in Fig. 1: the thick field oxide and the epi
step.  The thick field oxide of uncontrolled thickness is stripped in
the contact region and replaced by a thin oxide of controlled
thickness and the contact is offset with respect to the reach-through
diffusion.  The offset is important for two reasons: to avoid the epi
step and the highly doped reach-through area where the oxide will
grow thicker than over the low-doped epi.  The low step height offset
contact is formed as shown in Fig. 3A-3H.

      If the base oxidation is used for the thin oxide, the NPN
collector contact step height is reduced to that of the base contact.
The basic principles of the low step...