Patent Application
20160276215
The present invention generally relates to a method for manufacturing a semiconductor device and, more particularly, to a method for selectively depositing a pure cobalt (Co) cap layer on a copper (Cu) film inlaid in a low-k dielectric layer on a semiconductor device.
Damascene Cu has become a preferred material for creating conductive lines in high performance integrated circuits because of its relative low cost, processing properties and lower resistivity and higher resistance to electromigration (EM) compared to aluminum (Al).
However, Cu can readily diffuse into surrounding dielectric materials when subjected to high temperatures of subsequent fabrication processes. Diffusion of Cu into the surrounding insulating dielectric will lead to line-to-line leakages and eventual device failure. Therefore, it is necessary to fully enclose Cu lines with diffusion barriers.
Barrier and capping layers may be deposited to contain the copper. For example, tantalum, tantalum nitride, or Cu alloy with tin, aluminum, or magnesium has been used to provide a barrier layer or an adhesion promoter between Cu and other materials.
Moreover, to avoid time dependent dielectric breakdown (TDDB) phenomenon in low-k dielectrics in damascene copper interconnects, U.S. Pat. No. 8,278,216, for example, discloses a method for selectively depositing a metal nitride film on Cu lines.
In the present invention, a method for selectively depositing a pure Co cap layer on a Cu film inlaid in a low-k dielectric layer on a semiconductor device is provided to avoid time dependent dielectric breakdown (TDDB), to enhance the stability and adhesion of the Cu film and to improve the electromigration (EM) reliability of the Cu film.
It is one object of the present invention to provide a method for selectively depositing a pure cobalt (Co) cap layer on a copper (Cu) film inlaid in a low-k dielectric layer on a semiconductor device.
In order to achieve the foregoing object, in one embodiment, the present invention provides a method for manufacturing a semiconductor device. The method includes the following steps. A method for manufacturing a semiconductor device is provided. The method comprises steps as follows. At least one trench is provided in a low-k dielectric layer on a substrate. The trench is filled with a Cu film. Pure Co is deposited on a surface of the Cu film by introducing a flow of a carrier gas carrying a Co-containing precursor and a reducing agent onto the surface of the Cu film. The flowrate of the flow is within a range from 5 to 19 sccm.
The present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which:
The present invention will now be described more specifically with reference to the following embodiments. It is to be noted that the following descriptions of the embodiments of this invention are presented herein for purpose of illustration and description only. It is not intended to be exhaustive or to be limited to the precise form disclosed.
Please refer to
The trench 25 is then filled with a Cu film 30 as shown in
In
In one embodiment, as a flow of Ar carrying, for example, Co(C5H5)(CO)2 and H2 is introduced onto the surface of the Cu film 30, the Co(C5H5)(CO)2 reacts with H2 to produce Co(C5H5) 41, Co particles 42 and byproducts (not shown), as shown in
It is preferable that the CVD process is followed by a plasma treatment performed on the surface of the Cu film to further deposit pure Co on the surface of the Cu film. In one embodiment, the plasma treatment is performed using plasma of hydrogen, nitrogen, ammonia (NH3) or combinations thereof. The present invention is, however, not limited to the previous example of how the plasma treatment is implemented.
In one embodiment, the plasma treatment enables the Co(C5H5) 41 in
In the present invention, the CVD process and the plasma treatment can be repeated as multiple cycles. For example, the method for selectively depositing pure Co on a Cu film inlaid in a low-k dielectric layer on a semiconductor device may start with the CVD process as shown in
It should be noted that the method of the present invention results in formation of a pure Co cap layer on the Cu film without significant formation on the surrounding dielectric material, which is attributed to the low carrier gas flow that leads to difficulty in depositing Co on the surrounding dielectric material. In other words, lower carrier gas flow results in higher selectivity when the selectivity is defined as (Co thickness on Cu)/(Co thickness on dielectric). More particularly, with the flow rate of the carrier gas within a range from 5 to 19 sccm, the selectivity reaches 75. Preferably, the selectivity reaches 150 with the flow rate within a range from 8 to 15 sccm. Preferably, the selectivity reaches 180 when the flow rate is 10 sccm.
The main feature of the present invention is that, by employing a deposition recipe of Co with a high selectivity between the interfaces with Cu and the interface with low-k dielectric, the method results in formation of a pure Co cap layer on the Cu film without significant formation on the surrounding dielectric material. With the realization of the present invention, a method for selectively depositing a pure Co cap layer on a Cu film inlaid in a low-k dielectric layer on a semiconductor device is provided to avoid time dependent dielectric breakdown (TDDB), to enhance the stability and adhesion of the Cu film and to improve the electromigration (EM) reliability of the Cu film.
While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiment. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.
