Lead silicate based capacitor structures

Details Lead silicate based capacitor structures Lead silicate based capacitor structures

2000-04-06

2001-04-03

Chaudhuri, Olik (Department: 2814)

Active solid-state devices (e.g., transistors, solid-state diode

Field effect device

Having insulated electrode

C257S301000, C361S321400

Reexamination Certificate

active

06211543

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to capacitors and more particularly to lead silicate dielectric films for capacitors in dynamic random access memories (DRAM's).
BACKGROUND OF THE INVENTION
Dynamic Random Access Memory (DRAM) integrated circuits or chips are the basis for much of the computer memory applications that are presently used worldwide. These important chips are being fabricated, studied and advanced by many manufacturers. The basic device consists of a transistor and a capacitor with associated read and write connections. Information is stored in the charge state of the capacitor which has to be periodically refreshed due to leakage. The most advanced DRAM circuit under production is the 256 MBit chip which in one version uses a trench capacitor with a silicon oxide-nitride-oxide (O-N-O) sandwich with a dielectric constant of about 4. The dielectric thickness is about 7 nm. The deep trenches are slow and relatively expensive to build and much work is devoted to alternative technologies. In addition future, denser DRAM circuits will require even thinner dielectrics and electron tunneling limits will be approached. A great deal of effort around the world is being devoted to alternate dielectric materials with high dielectric constants and alternate or modified structures. With such developments it is expected that trenches can be avoided.
Many high dielectric constant materials are known and some are being investigated for DRAM application. Even with high dielectric constant materials, dielectric thicknesses less than 100 nm may be anticipated. These materials include strontium titanate (STO) and barium titanate (BTO) and their mixtures. Dielectric constants range from a few hundred to over 800 for films of these well-known materials. Mixtures of lead zirconium titanate (PZT) and lead lanthanum titanate (PLT) are also possible high dielectric materials. When these materials are used, they are generally deposited on a base electrode of Pt.
SUMMARY OF THE INVENTION
In accordance with the present invention, a capacitor and method for making such a capacitor for dynamic randomn access memories and other applications is provided comprising a lower electrode of Si, SiGe, metal or metal silicide for example, a dielectric layer of barium or lead silicate, lead silicate glass or combinations thereof, and a top electrode of metal, silicide or semiconductor for example.
The invention further provides a capacitor having a lower electrode, a first dielectric layer of barium or lead silicate, a second dielectric layer of high dielectric constant material, greater than 50, and a top electrode.


REFERENCES:
patent: 3977887 (1976-08-01), McIntosh
patent: 4772985 (1988-09-01), Yasumoto et al.
patent: 5471364 (1995-11-01), Summerfelt et al.

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