Semiconductor device manufacturing: process – Making passive device – Stacked capacitor
Reexamination Certificate
2001-01-08
2001-10-09
Nelms, David (Department: 2818)
Semiconductor device manufacturing: process
Making passive device
Stacked capacitor
C438S003000
Reexamination Certificate
active
06300216
ABSTRACT:
BACKGROUND OF INVENTION
1) Field of the Invention
This invention relates generally to fabrication of a semiconductor device and more particularly to a structure and method for forming a capacitor on a semiconductor structure by depositing a yttrium barium copper oxide layer over a first plate electrode layer at room temperature using a sputtering process.
2) Description of the Prior Art
Currently, oxide
itride/oxide (ONO) or oxide
itride (ON) stacks are primarily used as capacitor dielectric layers in DRAM fabrication. However, as device dimensions continue to shrink, capacitors formed using ONO or ON as the capacitor dielectric material are not able to provide the necessary capacitance with the reduced surface area.
New high dielectric constant materials have been developed to provide increased capacitance for a given surface area. Among these newly developed materials are Ta2O5, BST, and PZT. Each of these materials suffer drawbacks for use as a capacitor dielectric material for mass production of silicon-based intergrated circuits.
For example, Ta
2
O
5
, BST, and PZT all have high leakage currents. While these leakage currents can be reduced using a high temperature anneal, high temperature anneals are detrimental to DRAM devices. Also, BST and PZT are difficult to deposit as thin films.
The importance of overcoming the various deficiencies noted above is evidenced by the extensive technological development directed to the subject, as documented by the relevant patent and technical literature. The closest and apparently more relevant technical developments in the patent literature can be gleaned by considering the following patents.
U.S. Pat. No. 5,075,281 (Testardi) shows a yttrium barium copper oxide (YBa
2
Cu
3
O
6
) high dielectric constant layer for capacitors fabricated by heating a pre-formed sample of YBa
2
Cu
3
O
6
material to a temperature of at least 850° C. and rapidly quenching it.
U.S. Pat. No. 5,348,894 (Gnade et al.) discloses various high K dielectric layers.
U.S. Pat. No. 5,605,858 (Nishoka et al.) shows a yttrium oxide capacitor dielectric.
U.S. Pat. No. 5,821,598 (Butler et al.) discloses a yttrium barium copper oxide infrared detector.
U.S. Pat. No. 5,851,896 (Summerfelt et al.) shows various oxide layers for high dielectric materials.
U.S. Pat. No. 5,555,486 (Kingon et al.) shows a “YBCO” (yttrium barium copper oxide) as a conductive metal oxide for a capacitor rather than as a capacitor dielectric.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a structure and method for forming a capacitor on a semiconductor substrate using yttrium barium copper oxide as a capacitor dielectric material.
It is another object of the present invention to provide a structure and method for forming a capacitor over a semiconductor substrate using a sputter deposited thin film of YBa
2
CU
3
O
6+X
(0.2<x <0.5), Y
2
BaCuO
5
, and/or amorphous yttrium barium copper oxide as a capacitor dielector layer.
It is another object of the present invention to provide a method for forming a yttrium barium copper oxide film at low temperature having a high dielectric constant which can be easily patterned and provides good end point detection during etching.
It is yet another object of the present invention to provide an economical and manufacturable method for forming a high dielctric constant film for use as a capacitor dielectric layer.
To accomplish the above objectives, the present invention provides a method for forming a high-K film at low temperature by sputter depositing a yttrium barium copper oxide layer from a YBa
2
Cu
3
O
7
target and vacuum annealing the yttrium barium copper oxide layer at low temperature to control the oxygen content and therefore the dielectric constant. In a preferred embodiment, the present invention provides a method and structure for forming a capacitor in a semiconductor device using a high dielectric constant, yttrium barium copper oxide layer as the capacitor dielectric layer. The process begins by providing a semiconductor structure having a conductive plug therein and having an opening, with sidewalls, over the conductive plug. The opening is shaped to accomodate a capacitor structure as is known in the art. A first conductive layer is formed on the conductive plug and on the sidewalls of the opening. A yttrium barium copper oxide layer comprising: YBa
2
Cu
3
O
6+X
(0.2<x <0.5), Y
2
BaCuO
5
, and/or amorphous YBaCuO is deposited on the first conductive layer using a sputtering process with a YBa
2
Cu
3
O
7
target. The YBa
2
Cu
3
O
6+X
layer can be annealed to control the oxygen content of the yttrium barium copper oxide. For example, YBa
2
Cu
3
O
6+X
can be controlled at between X=0.2 and X=0.5. A second conductive layer is formed on the yttrium barium copper oxide layer, thereby forming a capacitor comprising the first conductive layer, the yttrium barium copper oxide layer, and the second conductive layer.
The present invention provides considerable improvement over the prior art. A sputter deposited and annealed yttrium barium copper oxide layer with the oxygen content controlled at at the desired level can provide a dielectric constant of between about 70 and 100, which is about 10 times higher than ONO. A capacitor dielectric layer using this high dielectric constant material allows higher packing density because comparable capacitance can be acheived with less surface area.
By using a sputter process to deposit the high dielectric constant yttrium barium copper oxide layer, it can be deposited at lower temperatures than other capacitor dielectric materials known in the art. It can also be formed at lower temperatures than other “YBCO” processes described in the prior art. This lower processing temperature is particularly advantagous in DRAM fabrication. The sputter deposition and anneal steps of the present invention provide good control of thickness and oxygen content, thereby providing good control of the dielectric constant. Also, yttrium barium copper oxide is easy to pattern and its black color makes end point detection easy.
REFERENCES:
patent: 4882312 (1989-11-01), Mogro-Campero et al.
patent: 5430009 (1995-07-01), Wang
patent: 5555486 (1996-09-01), Kingon et al.
patent: 5879957 (1999-03-01), Joo
patent: 6174802 (2001-01-01), Huang et al.
patent: 6612686 (2000-12-01), Huang et al.
Ackerman Stephen B.
Dang Phuc T.
Nelms David
Saile George O.
Stoffel Willaim J.
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