High-dielectric constant capacitor and memory

Details High-dielectric constant capacitor and memory High-dielectric constant capacitor and memory

1997-10-23

2002-10-08

Dinkins, Anthony (Department: 2831)

Electricity: electrical systems and devices

Electrostatic capacitors

Fixed capacitor

C361S311000, C257S295000, C257S303000, C257S306000

Reexamination Certificate

active

06462931

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to electronic devices, and, more particularly, to semiconductor capacitors and methods of fabrication.
Increasing demand for semiconductor memory and competitive pressures require higher density integrated circuit dynamic random access memories (DRAMs) based on one-transistor plus one-capcitor memory cells. But down scaling capacitors with the standard silicon oxide and nitride dielectric presents problems including decreasing quantity of charge stored in a cell. Consequently, alternative dielectrics with dielectric constants greater than those of silicon oxide and nitride are being investigated. Various dielectric materials are available; such as tantalum pentoxide (dielectric constant about 25 versus silicon nitride's dielectric constant of about 7) as described in Ohji et al, Ta
2
O
5
capacitors' dielectric material for Giga-bit DRAMs, IEEE IEDM Tech. Dig. 5.1.1 (1995); lead zirconate titanate (PZT) which is a ferroelectric and supports nonvolatile charge storage (dielectric constant ~1000) described in Nakamura et al, Preparation of Pb(Zr,Ti)O
3
thin films on electrodes including IrO
2
, 65 Appl.Phys.Lett. 1522 (1994); strontium bismuth tantalate (also a ferroelectric) described in Jiang et al, A New Electrode Technology for High-Density Nonvolatile Ferroelectric (SrBi
2
Ta
2
O
9
) Memories, VLSI Tech. Symp. 26 (1996); and barium strontium titanate (dielectric constant about 500) described in Yamamichi et al, An ECR MOCVD (Ba,Sr)TiO
3
based stacked capacitor technology with RuO
2
/Ru/TiN/TiSi
x
storage nodes for Gbit-scale DRAMs, IEEE IEDM Tech. Dig. 5.3.1 (1995), Yuuki et al, Novel Stacked Capacitor Technology for 1 Gbit DRAMs with CVD-(Ba,Sr)TiO
3
Thin Films on a Thick Storage Node of Ru, IEEE IEDM Tech.Dig. 5.2.1 (1995), Oh et al, A Stack Capacitor Technology with (Ba,Sr)TiO
3
Dielectrics and Pt Electrodes for 1 Giga-Bit density DRAM, VLSI Tech. Symp. 24 (1996). Also see Dietz et al, Electrode influence on the charge transport through SrTiO
3
thin films, 78 J.Appl.Phys. 6113 (1995) describes electrodes of Pt, Pd, Au, . . . on strontium titanate); US Patent No. 5,003,428 (PZT and barium titanate), U.S. Pat. No. 5,418,388 (BST, SrTiO
3
, PZT, PLZT, . . . ), and U.S. Pat. No. 5,566,045 (thin Pton BST).
However, each of these dielectric or ferroelectric materials and capacitor structures has problems such as adhesion to commonly used silicon integrated circuit materials (e.g., silicon dioxide), oxygen diffusion, and leakage currents.
SUMMARY OF THE INVENTION
The present invention provides contact materials for barium strontium titanate which give a Schottky barrier height greater than that of comparable (epitaxial or polycrystalline) platinum contacts and also provides oxygen compensating adhesion materials for very thin contacts.
The invention has advantages including low leakage currents and limited dielectric degradation.


REFERENCES:
patent: 5053917 (1991-10-01), Miyasaka et al.
patent: 5262920 (1993-11-01), Sakuma et al.
patent: 5554866 (1996-09-01), Nishioka et al.
patent: 5555486 (1996-09-01), Kingon et al.
patent: 5566045 (1996-10-01), Summerfelt et al.
patent: 5751540 (1998-05-01), Lee et al.

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