Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
1999-04-23
2001-06-26
Bowers, Charles (Department: 2813)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S612000, C438S617000
Reexamination Certificate
active
06251775
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to methods for increasing the adhesion of a terminal to the top copper wiring level in semiconductor devices.
2. Description of the Related Art
Conventional systems have improved the adhesion of silicon nitride to an interior copper wiring surface by the addition of an intervening copper silicide layer. For example, as described in U.S. Pat. No. 5,447,887 to Filipiak et al., hereinafter “Filipiak” (incorporated herein by reference), the connections of internal levels within a semiconductor device are improved with an intervening copper silicide layer.
The silicide layer is conventionally formed within a plasma enhanced chemical vapor deposition (PECVD) reaction chamber by introducing silane (SiH
4
) in the absence of a plasma into the chamber. The silane reacts with exposed copper surfaces to form copper silicide. After a sufficient thickness of copper silicide is formed, plasma is generated and gases are introduced into the reaction chamber for deposition of silicon nitride onto the device, including onto the copper silicide layer. The intervening copper silicide layer acts as an adhesion layer between the silicon nitride and the copper.
Filipiak teaches that a silicide layer approximately 100 angstroms (100 Å) thick is sufficient to significantly increase the adhesion between the nitride and copper. More specifically, Filipiak explains that, as a general rule, the thickness of a silicide layer should not exceed 10% percent of the total thickness of the copper. A reason for limiting the thickness of the silicide layer to less than 10% of the total copper thickness is that the silicide degrades the resistivity of the copper. While generally the silicide layer should not exceed 10% of the total thickness of the copper interconnect, Filipiak shows that a silicide layer thinner than 100 angstroms (100 Å) or less than 2% of the total copper thickness is sufficient to significantly improve the adhesion of a subsequently deposited PECVD silicon nitride film to the copper member.
However, Filipiak's method is limited specifically it does not provide sufficient coverage or uniformity and, consequently, it does not provide the required adhesion strength for the terminal layer to remain connected to the last metalization (LM) layer. The invention described below solves the above problem.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a structure and method of forming a semiconductor structure that includes supplying a structure having an exposed last metalization (LM) layer, cleaning the last metalization layer, forming a silicide in a top portion of the last metalization layer and forming a terminal over the silicide.
The last metalization layer can be copper. The cleaning is performed by applying an ammonia plasma and a hydrogen plasma to the last metalization layer. The silicide is formed in the top 10% to 20% of the thickness of the last metalization layer. The forming of the terminal includes forming a lead and tin solder terminal electrically connected to the silicide. The forming of the terminal comprises forming a silicon nitride layer physically connected to the silicide. The silicon nitride layer includes an opening allowing direct electrical contact with the silicide. The structure includes insulating layers above the silicon nitride layer.
The semiconductor device has at least two levels of interconnecting metallurgy, and includes a first level of substantially silicide free metallurgy and an uppermost layer of metallurgy including a bonding pad, wherein a top of the uppermost layer includes a silicided surface. The interconnecting metallurgy is copper. Prior to formation of the silicided surface, the uppermost layer is cleaned by applying an ammonia plasma and a hydrogen plasma. The silicided surface comprises the top 10% to 20% of the uppermost layer. The semiconductor device further includes a lead or tin solder terminal electrically connected to the silicided surface. A silicon nitride layer is connected to the silicide and includes an opening allowing direct electrical contact with the silicided surface.
The invention reduces such delamination by forming the silicide layer over the last metalization layer to generally at least 10-20% the thickness of the LM layer. This extensive silicide formation is required at the LM level to resolve the copper
itrite adhesion issues discussed above. Also, because the last metalization layer comprises very thick metallurgy, it is substantially less sensitive to to resistivity shifts and therefore, the resistivity problems noted with conventional copper silicide (CuSi) systems is avoided. The improved surface coverage provided by the invention enables less resistivity shift per percent thickness of LM layer formation.
REFERENCES:
patent: 4505029 (1985-03-01), Owyang et al.
patent: 5447887 (1995-09-01), Filipiak et al.
patent: 5503704 (1996-04-01), Bower et al.
patent: 5633047 (1997-05-01), Brady et al.
patent: 5833758 (1998-11-01), Linn et al.
patent: 5844317 (1998-12-01), Bertolet et al.
patent: 6046101 (2000-04-01), Dass et al.
IBM Technical Disclosure, Cronin et al., “Copper/Polyimide Structure with Selective Cu3Si/SiO2 Etch Stop”, vol. 37, No. 06A Jun. 1994, p. 53.
Armbrust Douglas S.
Gibson Margaret L.
Serianni Laura
White Eric J.
Bowers Charles
International Business Machines - Corporation
McGinn & Gibb PLLC
Nguyen Thanh T.
Walter, Esq. Howard J.
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