Method of improving adhesion of dielectric cap to copper

In a method of promoting adhesion between a copper body and a dielectric layer in contact therewith, the copper body and dielectric layer are placed in a vacuum chamber, in a chamber, the copper body and dielectric layer within the chamber are heated, and SiH4 is provided in the chamber.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to electronic devices, and more particularly, to improvement of adhesion of layers therein.

2. Discussion of the Related Art

FIG. 1illustrates a damascene structure10as part of a wafer12, enlarged for clarity. The structure10includes a copper line14, a silicon nitride layer16thereon, and a dielectric layer18on the silicon nitride layer16. The silicon nitride layer16and dielectric layer10include an opening in which is provided a tantalum liner20in contact with the copper line14. Within the tantalum liner20and in contact therewith is another copper line22, which is in electrical communication with the copper line14through the tantalum liner20.

The resulting structure is then to be capped by depositing a silicon nitride cap layer24. (FIG. 2) However, it has been found that the interface condition between the copper22and silicon nitride cap24is such that adhesion between these two parts is poor. In addition, it has been found that silicon from the silicon nitride layer24diffuses into the copper line24, degrading performance thereof.

In an attempt to improve the situation, and again with reference toFIG. 1, a plasma etch is undertaken on the exposed surface of the structure10in order to remove native CuO from the surface of the copper22, with the silicon nitride layer24then being deposited thereon. While such a process has been found to improve adhesion between the copper22and the silicon nitride24, further improvement is desired so that a strong bond between the silicon nitride cap24and the copper22can be achieved.

SUMMARY OF THE INVENTION

Broadly stated, the present method of promoting adhesion between a copper body and a dielectric layer in contact therewith comprises placing the copper body and dielectric layer in a chamber, and providing SiH4in the chamber.

The present invention is better understood upon consideration of the detailed description below, in conjunction with the accompanying drawings. As will become readily apparent to those skilled in the art from the following description, there is shown and described an embodiment of this invention simply by way of the illustration of the best mode to carry out the invention. As will be realized, the invention is capable of other embodiments and its several details are capable of modifications and various obvious aspects, all without departing from the scope of the invention. Accordingly, the drawings and detailed description will be regarded as illustrative in nature and not as restrictive.

DETAILED DESCRIPTION

Reference is now made in detail to a specific embodiment of the present invention which illustrates the best mode presently contemplated by the inventors for practicing the invention.

Similar toFIG. 1,FIG. 3illustrates a damascene structure40as part of a wafer42, enlarged for clarity. The structure includes a copper line44, a silicon nitride (SiOn) layer46thereon. A dielectric layer48on the silicon nitride layer. The silicon nitride layer46and dielectric layer48include an opening in which is provided a tantalum liner50in contact with the copper line44. Within the tantalum liner50and in contact therewith is another copper line52, which is in electrical communication with the copper line44through the tantalum liner50.

However, in the present embodiment (FIG. 4), a silicon nitride layer54is deposited directly on the resulting structure, in contact with the copper line52. Then, the wafer42is placed in a vacuum chamber56(FIG. 5) and exposed to SiH4, along with N2, He, Ar, and NH3(58). The flow rate of SiH4is 1-3000 sccm, while the flow rate of the other gases is from 1-30000 sccm. This mixture of gases is provided at a pressure of 0.1 mTorr to 1 Atm, maintained by pump60of the chamber56. A heater62in the chamber56, on which the wafer42is placed, maintains a wafer temperature of from 200° to 600° C. for a time period of from 0.1 seconds to 100 seconds.

It has been found that this process greatly promotes and improves adhesion between the copper line52and the silicon nitride64thereon and in contact therewith. This is because the process causes copper atoms64to diffuse into the silicon nitride cap54to create a strong interface between the copper52and the silicon nitride layer54and eliminate silicon diffusion into the copper line52. The converted interface also reduces boundary diffusion which is believed to be a major factor in electro migration. The copper64entering the silicon nitride layer54, it is expected, forms CuxSiyin the silicon nitride layer54, greatly improving the adhesion between the copper52and silicon nitride layer54, providing a strong and stable resulting structure as desired.

It will be readily understood that the process is applicable to both single damascene and duel-damascene structures. Furthermore, the layer46may be any form of dielectric cap, such as SiON, SiCN, or SiO2.

The foregoing description of the embodiment of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Other modifications or variations are possible in light of the above teachings.

The embodiment was chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill of the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally and equitably entitled.