Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
1999-06-28
2001-01-16
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S639000, C438S666000, C438S239000, C438S381000
Reexamination Certificate
active
06174802
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to fabrication of semiconductor devices and more particularly to a two step process for forming a self-aligned contact, preferably composed of polysilicon, which eliminates the key hole problem in the IPO (inter-poly oxide) layer.
2. Description of the Prior Art
The use of self aligned contact (SAC) processes has resulted in higher performing, lower cost, and increased density semiconductor devices. In a self-aligned contact process, spacers are formed on the sidewalls of conductive structures (such as gates and bit lines). An IPO layer is formed over these conductive structures. A contact opening is etched through the IPO. A conductive layer, such as for capacitor crowns, is formed over the conductive structures and in the contact opening. However, as device dimensions and die sizes continue to decrease for higher density, the space between adjacent conductive structures becomes narrower. The surface of the sidewall spacers facing the contact opening become concave which leads to voids or keyholes in the subsequently formed IPO layer. The key holes can fill with conductive material during subsequent formation of a conductive contact layer causing two separate devices (such as capacitors) which are formed over the IPO layer to short. The short can result in cell failure.
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. 5,480,814 (Wuu et al.) shows a SAC with a barrier layer formed of polysilicon and a contact layer formed of a silicide.
U.S. Pat. No. 5,763,303 (Liaw et al.) shows a SAC with a polysilicon layer, a silicide layer and a contact.
U.S. Pat. No. 5,795,827 (Liaw et al.) shows a SAC with triple polysilicon.
U.S. Pat. No. 5,843,815 (Liaw) shows a SAC with a halo implant.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method for fabricating a self aligned contact using a two-step polysilicon deposition.
It is another object of the present invention to provide a method for forming a self-aligned contact which solves the keyhole problem.
It is another object of the present invention to provide a method for forming a self aligned contact which avoids capacitor crown to crown shorting by using a two-step polysilicon deposition.
It is yet another object of the present invention to provide a method for forming a self aligned contact using a two-step polysilicon deposition which is easy to integrate with current processes.
To accomplish the above objectives, the present invention provides a method for forming a self-aligned contact without key holes using a two step contact deposition. The process begins by providing a semiconductor structure having a conductive structure (such as a bit line) thereover with sidewalls and having a contact area adjacent to the conductive structure. The conductive structure comprises at least one conductive layer with a hard mask thereover. A spacer layer is formed over the hard mask and the semiconductor structure and anisotropically etched to form sidewall spacers on the sidewalls of the conductive structure. A second dielectric (e.g. IPO) layer is formed over the sidewall spacers, the hard mask, and the semiconductor structure. A contact opening is formed in the second dielectric layer over the contact area. A first conductive contact layer having poor step coverage properties is formed in the contact openings, thereby plugging the keyhole openings without filling the keyhole. A second conductive contact layer is formed over the first conductive contact layer. The first conductive contact layer and the second conductive contact layer can be used to form conductive structures such as capacitor crowns which do not have an electrical short through the IPO layer.
The present invention provides considerable improvement over the prior art. Most significantly, the keyhole which is formed in the IPO layer is plugged by the first contact layer without being filled with a conductive material, thereby preventing an electrical short between adjacent structures.
The present invention achieves these benefits in the context of known process technology. However, a further understanding of the nature and advantages of the present invention may be realized by reference to the latter portions of the specification and attached drawings.
REFERENCES:
patent: 5114530 (1992-05-01), Rao et al.
patent: 5266525 (1993-11-01), Morozumi
patent: 5275972 (1994-01-01), Ogawa et al.
patent: 5480814 (1996-01-01), Wau et al.
patent: 5739068 (1998-04-01), Jost et al.
patent: 5763303 (1998-06-01), Liaw et al.
patent: 5795827 (1998-08-01), Liaw et al.
patent: 5824562 (1998-10-01), Park
patent: 5843815 (1998-12-01), Liaw
patent: 5953635 (1999-09-01), Andideh
patent: 6015730 (2000-01-01), Wang et al.
patent: 6025260 (2000-02-01), Lien et al.
patent: 6033981 (2000-03-01), Lee et al.
Chiang Min-Hsiung
Chiang Wen-Chuan
Huang Kuo-Ching
Ying Tse-Liang
Ackerman Stephen B.
Gurley Lynne A.
Niebling John F.
Saile George O.
Stoffel William J.
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