Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – For cleaning a specific substrate or removing a specific...
Reexamination Certificate
2000-11-16
2003-03-18
Webb, Gregory E. (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
For cleaning a specific substrate or removing a specific...
C510S176000, C510S177000
Reexamination Certificate
active
06534458
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a cleaning agent for a semi-conductor substrate and a method for cleaning the same.
Structures of LSI have recently been developed into fine-processed ones in accordance with the recent trend toward high integration and thus the LSI has been molded into multi-layered structures wherein multi-level wirings are formed on a surface of a semi-conductor, and use of copper wirings having lower electric resistance has been proposed in place of so far used aluminum wirings.
In a process for preparation of a semi-conductor having a multi-layered structure wherein multi-level wirings are piled on a surface of a semi-conductor, use has been made of so-called Cu-chemical-mechanical polishing technology (Cu-CMP) wherein a semi-conductor substrate is mechanically polished during metallic Cu being oxidized so as to realize planarization on a semi-conductor substrate surface.
On the other hand, after the Cu-CMP treatment, Cu wirings and dielectric silicone oxide film which are intended to separate the Cu wirings with one another are naked on the surface of the semi-conductor substrate surface and further a surface of a wafer is contaminated with a large amount of metal impurities and particles.
Metal contamination is caused by adsorption of copper oxides on the silicone oxide which are produced from ground metallic Cu by the CMP process, and particle contamination is caused by slurry used for polishing in the CMP process.
Copper oxides existing on the silicone oxide are dispersed in the films after treatment under heating, whereby insulation is decreased to make quality of devices degraded and in the worst case the wirings previously separated are connected with one another to cause shortening, which results in breakdown of the devices. For this reason, the copper oxides have to be removed before conducting the next step of processes. Further, particle contamination has to be eliminated, because the staining gives bad influence upon the next step of processes.
Therefore, a cleaning process step in order to remove the impurities and particles is indispensable after the Cu-CMP process.
Acidic cleaning solutions such as those containing hydrochloric acid and hydrofluoric acid which have generally been used after the Cu-CMP process are accompanied with such a drawback that they dissolve not only the copper oxides deposited on the silicone oxidebut also metallic Cu in wirings so as to cause corrosion and breakdown of wirings. Use of the acidic solutions has also such a problem that a surface of a semi-conductor substrate and particles are electrostatistically pull against each other, whereby particles cannot be removed and adversely they are adsorbed on the surface.
It has been said, on the other hand, that use of alkaline cleaning solutions whereupon particles and a surface of semi-conductor substrate are repelling with each other is generally advantageous in order to remove particles. However, when a cleaning agent containing a metal ion as an alkaline source such as a cleaning agent containing sodium hydroxide or potassium hydroxide is used, those metals are adsorbed on a surface of the silicone oxide, etc. so as to reduce the insulating effect. Further, among cleaning agents containing no metal ion, an agent containing inorganic alkaline substance such as an aqueous ammonium solution cannot be used because they strongly dissolve copper.
On the other hand, a cleaning agent containing a quaternary ammonium compound has such merit as not corroding copper wirings and having high effect of removing particles, while it has such a drawback that it has high etching effect to the silicone oxide so as to cause roughness on a surface, though the surface is once made into smooth by the CMP process, because a quaternary ammonium compound is strongly alkaline.
It has also been known that hydrogen peroxide is added to the agent containing a quaternary ammonium compound whereby etching speed can be reduced. However, also in this case, such a problem is found that a surface of copper wirings is oxidized by the oxidizing effect of hydrogen peroxide whereby electric conductivity is reduced.
As explained above, there has been contrived no cleaning agent which can remove impurities on a surface of semi-conductor substrate having copper wirings on its surface without causing corrosion and oxidation of copper wirings nor causing roughness on the surface.
SUMMARY OF THE INVENTION
The present invention has been accomplished taking the above situation into consideration and the object of the invention is to provide a cleaning agent and a cleaning method for a surface of a semi-conductor substrate, particularly one having copper wirings on its surface which can effectively remove impurities on a surface without causing corrosion or oxidation of copper wirings nor causing roughness on the surface.
The present invention, thus, relates to;
(1) a cleaning agent for a semi-conductor substrate having copper wirings on its surface, comprising a nonionic surfactant,
(2) a method for cleaning a surface of a semi-conductor substrate having copper wiring on its surface, comprising treating a surface of a semi-conductor substrate having copper wirings on its surface with a cleaning agent containing a nonionic surfactant, and
(3) a semi-conductor substrate having copper wirings on its surface, which is obtained by treating a surface of a semi-conductor substrate having copper wirings on its surface with a cleaning agent containing a nonionic surfactant.
PREFERRED EMBODIMENTS OF THE INVENTION
The present inventors have made extensive study in order to realize the object mentioned above to arrive at the finding that treating a surface of a semi-conductor substrate having copper wirings on its surface with a cleaning agent containing a nonionic surfactant has made it possible to control a speed of etching on silicone oxide so as to remove impurities adsorbed on copper wirings and silicone oxide on a surface of a semi-conductor substrate having copper wirings on its surface, such as copper oxides and particles, without causing corrosion or oxidation of copper wirings nor causing roughness on the surface, further that this effect can more advantageously be attained when a nonionic surfactant having an acetylene group
—C≡C—
in its molecule is used, and stiff further that particularly when this cleaning agent is adjusted to alkaline by incorporating therein an N-containing alkaline substance such as ammonia, a primary to tertiary amine and a quaternary ammonium compound, among which a quaternary ammonium compound is most effective, this effect can be more remarkable, and on the basis of those findings the present invention has been accomplished.
As the nonionic surfactant, any one so far been known can be used, and among them, one having an acetylene group
—C≡C—
in its molecule is preferable, and one having an acetylene group
—C≡C—
and a polyoxyalkylene group is more preferable.
The polyoxyalkylene group includes one shown by the following general formula [1]
HO&Parenopenst;X—O&Parenclosest;
y
[1]
(wherein X is an alkylene group and y is a positive integer).
The alkylene group shown by X in the general formula [1] preferably includes straight chained, branched and cyclic lower alkylene group having 1 to 6 carbon atoms, which is specifically exemplified by a methylene group, an ethylene group, a propylene group, a butylene group, a methylmethylene group, an ethylethylene group, a methylethylene group, a methylpropylene group, an ethylpropylene group, a pentylene group, a hexylene group, a cyclopentylene group, a cyclohexylene group, etc., among which an ethylene and a propylene group are preferable.
The symbol y is a positive integer, generally of 1 to 10, preferably 1 to 8, and among the groups, one wherein y is 2 to 8 is most preferable because it shows low foaming ability and consequently foaming can effectively be prevented even when it is co-used with a mechanical cleaning process so as to prevent troubles by foamin
Hayashida Ichiro
Kakizawa Masahiko
Umekita Ken-ichi
Armstrong Westerman & Hattori, LLP
Wako Pure Chemical Industries Ltd.
Webb Gregory E.
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