This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2009-068960, filed Mar. 19, 2009, the entire contents of which are incorporated herein by reference.
Recently, a Cu wiring having lower electric resistance than an Al wiring is used as a wiring of LSI. On the other hand, an insulating film called a low-k film having lower dielectric constant than a silicon oxide film is used as an inter-wiring insulting film.
Cu has a diffusion coefficient larger than Al, and then it can not be used as wiring material so long as an anti-diffusion film is employed. A conductive anti-diffusion film such as a Ta film is used with respect to side and bottom surfaces of the Cu wiring.
On the other hand, an insulative anti-diffusion film such as a silicon nitride film has been conventionally used with respect to an upper surface of the Cu wiring.
However, adhesion between the Cu wiring and the insulative anti-diffusion film is weak, and then electromigration (EM) lifetime has notably lowered along with a scaling of wiring. Therefore, a metal cap is used for the purpose of improving EM lifetime (see JP 2007-157959, JP 2007-103850).
The metal cap is formed by using plating process. The reason employing the plating process is that it makes possible to form the metal cap selectively on the upper surface of the Cu wiring.
However, the conventional method for forming the metal cap employing the plating process fails in plating selectivity, and then metal material of the metal cap is also deposited on the upper surface of the insulating film between the wirings. This deposited metal material (metal residue) causes a leakage path, and then leakage current between the wirings increases when a certain voltage higher than predetermined level is applied between the wirings.
According to an aspect of the present invention, there is provided a method for manufacturing a semiconductor device comprising: forming an insulating film including silicon, oxygen, carbon and hydrogen above a semiconductor substrate; forming a wiring trench in the insulating film; forming a metal film to be a metal wiring on the insulating film such that the metal film is provided in the wiring trench; forming the metal wiring by removing the metal film outside the wiring trench; performing a hydrophobic treatment to the surface of the insulating film after the forming the metal wiring; and forming a metal cap selectively on an upper surface of the metal wiring by plating after the performing the hydrophobic treatment.
According to an aspect of the present invention, there is provided a semiconductor device comprising: a semiconductor substrate; an insulating film including silicon, oxygen, carbon and hydrogen provided above a semiconductor substrate, the insulating film being provided with a wiring trench, the insulating film comprising first and second regions, the first region including a surface of the insulating film, the second region provided beneath the first region and including an interface with the first region, a carbon concentration of the second region from the interface to a predetermined distance of depth becoming lower as the depth from the interface becoming deeper, a carbon concentration of the second region deeper than the predetermined distance becoming higher as the depth becoming deeper and reaching carbon concentration higher than that of the surface of the insulating film; a metal wiring provided in the wiring trench; and a metal cap provided on an upper surface of the metal wiring.
Various embodiments will be described below with reference to the accompanying drawings.
As shown in
The bulk insulating film 3 is a low-dielectric constant insulating film called as a low-k film. This low-dielectric constant insulating film is an insulating film having a dielectric constant k less than 2.5. If the low-k film is formed by using a coating process, it is formed as an organic insulating film in general. The cap insulating 4 is a SiOC type insulating film.
Here, a multi-layer insulating film (hybrid insulating film) structure of the bulk insulating film 3 and the cap insulating film 4 is used as an inter-wiring insulating film, but only the bulk insulating film 3 formed of a single-layer insulating film or only the cap insulating film 3 formed of a single-layer insulating film may be used.
As shown in
As shown in
As shown in
As shown in
As shown in
In the step of
If such the surface region 9 (hydrophilic region) is remained at the time of forming the Co film as a metal cap by plating process, Co in the plating solution reacts with the OH group of the surface region 9. This reaction forms Co (OH)2, and Co grows on the surface region 9, hence as shown in
Therefore, in the present embodiment, the repair treatment of the damage is performed, in which the surface region 9 is imparted with a hydrophobic surface character (Si—CH3 bond) by performing the hydrophobic treatment with respect to the surface region 9. The entire surface region 9 may be imparted with the hydrophobic surface character.
As shown in
The reason of Cu atoms transport is a current flow in the Cu wiring 8 which arises by application of voltage (electric field) to the Cu wiring 8 at the time of device operation.
As shown
A region 91 denotes a region (first region) of the surface region subjected to the hydrophobic treatment, which is actually made hydrophobic. A region 92 denotes a region (second region) of the surface region subjected to the hydrophobic treatment, which is not made hydrophobic in practical.
As seen from
The reason to be such a C concentration profile is considered as follows. The C concentration is temporarily lowered since the Si—CH3 bond is cut by the
CMP process. But the C concentration is increased by the hydrophobic treatment which generates the Si—CH3 bond.
The depth is defined as the direction from the surface region 9 toward the cap insulating film 4, and the depth 0 nm is the surface of the region 9. In
As seen from
In this way, since the C concentration of the surface region 9 (C concentration reduced region) formed by CMP process is increased by the hydrophobic treatment, the effect of utilizing the cap insulating film 4 as a low-k film (reduction of inter-wiring capacitance) is obtained in the present embodiment.
In the present embodiment, the metal cap containing Co is given as one example of the metal cap selectively formed on the Cu wiring, a metal cap containing a metal material such as ruthenium (Ru) or tungsten (W), or a metal cap containing an alloy containing two or more of Co, Ru and W may be used. For example, CoWP (cobalt-tungsten-phosphorous) alloy or CoWB (cobalt-tungsten-boron) is given as the alloy containing two or more of Co, Ru and W.
A second embodiment is different from the first embodiment in that a heat treatment for removing moisture (OH group) in the cap insulating film 4 or surface region 9 is performed before or after the wet repair treatment (hydrophobic treatment) with respect to the surface region 9. The moisture causes the generation of Si—OH group.
The heat treatment is performed, for example, in a temperature range of 150° C.-400° C. If the heat treatment is performed in the temperature range, the moisture is effectively removed without causing a problem.
According to the present embodiment, the generation of Co residue (metal residue) is more effectively suppressed. Other similar effects as those obtained in the first embodiment are obtained in the present embodiment.
In the first embodiment, Si—OH (hydrophilic group) is chemically substituted with Si—CH3 (hydrophobic group) to render the surface region 9 hydrophobic, but in the present embodiment, hydrophobic substance, for example, solution containing polyallylene is absorbed in the surface region 9 to render the surface region 9 hydrophobic. As the surface region 9 has a lower concentration than the cap insulating film 4, the hydrophobic treatment by absorption of hydrophobic substance is easily performed. The same effect as the first embodiment is obtained in the present embodiment. Another method for rendering the surface region 9 hydrophobic without chemically replacing Si—OH with Si—CH3 is coating the surface region 9 with hydrophobic substance containing C, for example, an organic insulating film. The same effect as the first embodiment is obtained in this method.
In addition, the heat treatment for removing moisture may be employed in the present embodiment as in the second embodiment with the same temperature range.
Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.
Number | Date | Country | Kind |
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2009-068960 | Mar 2009 | JP | national |