Abrasive tool making process – material – or composition – With inorganic material
Reexamination Certificate
1999-12-01
2001-11-13
Koslow, C. Melissa (Department: 1755)
Abrasive tool making process, material, or composition
With inorganic material
C051S308000, C051S309000, C106S003000, C216S087000, C252S079100, C438S692000, C438S693000
Reexamination Certificate
active
06315803
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polishing composition to be used for polishing for planarization of the surface of semiconductors. More particularly, it relates to a polishing composition useful for forming an excellent polished surface having an excellent planarization characteristic in polishing for planarization of the surface containing copper and tantalum or a tantalum-containing compound, and a polishing process employing this composition.
2. Prior Art
Progress of so-called high technology products including computers has been remarkable in recent years, and parts to be used for such products, such as ULSI, have been developed for high integration and high speed, year after year. Along with such progress, the design rule for semiconductor devices has been progressively refined year after year, the depth of focus in a process for producing devices tends to be shallow, and planarization required for the pattern-forming surface tends to be increasingly severe.
Further, to cope with an increase in resistance of the wiring due to refinement of the wiring, it has been studied to employ copper wiring instead of tungsten wiring and aluminum wiring, as the wiring material.
By its nature, copper is hardly processable by etching, and accordingly, it requires the following process. Namely, after forming wiring grooves and perforations on an insulating layer, copper wirings are formed by sputtering or plating, and then an unnecessary copper layer deposited on the insulating layer is removed by chemical mechanical polishing (hereinafter referred to as CMP) which is a combination of mechanical polishing and chemical polishing.
However, in such a process, it may happen that copper atoms will diffuse into the insulating layer to deteriorate the device properties. Therefore, for the purpose of preventing diffusion of copper atoms, it has been studied to provide a barrier layer on the insulating layer having wiring grooves or perforations formed. As a material for such a barrier layer, metal tantalum or a tantalum-containing compound (hereinafter will generally be referred to as a tantalum-containing compound) is most suitable also from the viewpoint of the reliability of the device and is expected to be employed mostly in the future.
Accordingly, in such a CMP process for a semiconductor device containing such a copper layer and a tantalum-containing compound, firstly the copper layer as the outermost layer and then the tantalum-containing compound layer as the barrier layer, are polished, respectively, and polishing will be completed when it has reached the insulating layer of e.g. silicon dioxide or silicon trifluoride.
PROBLEM TO BE SOLVED BY THE INVENTION
In such a CMP process for forming copper wirings, the following problems exist. Namely, the most serious problems may be such that the copper wirings after polishing are recessed as compared with the insulating layer (so-called dishing), and a portion where wirings are densely formed, is recessed as compared with other portions (so-called erosion). As an ideal process, it is desired that by using only one type of a polishing composition, the copper layer and the tantalum-containing compound layer are uniformly removed by polishing in a single polishing step, and polishing will be completed certainly when it has reached the insulating layer.
However, copper and a tantalum-containing compound are different in their hardness, chemical stability and other mechanical properties and accordingly in the processability, and thus, it is difficult to adopt such an ideal polishing process. Accordingly, the following two or three step polishing process (hereinafter referred to as two step polishing or three step polishing) is being studied.
Such two step polishing or three step polishing will bring about a cumbersomeness such that CMP processing conditions have to be set for the respective steps, and an increase of costs due to the cumbersomeness. Accordingly, it has been desired to employ as small a number of types of the polishing compositions as possible which are suitable for CMP processing of both copper and the tantalum-containing compound and to selectively control the CMP processing conditions by a means not to accompany an increase of costs.
Conventional two step polishing or three step polishing is generally classified into the following two types depending upon the first polishing step (hereinafter referred to as first polishing) and the second polishing step (hereinafter referred to as second polishing).
Firstly, the first type is such that in the first polishing, using a polishing composition capable of polishing a copper layer at a high efficiency, the copper layer is polished using e.g. a tantalum-containing compound layer as a stopper until such a tantalum-containing compound layer is reached. Then, in the second polishing, using a polishing composition capable of polishing mainly the tantalum-containing compound at a high efficiency, the tantalum-containing compound layer is polished until the insulating layer is reached. (Hereinafter, this method will be referred to as an overpolishing method.) Further, if necessary, in a third polishing step (hereinafter referred to as third polishing), polishing defects (hereinafter referred to as scratches) may be mainly mended, and the insulating layer may be polished to reduce the dishing.
On the other hand, the second type is such that in the first polishing, for the purpose of not forming various surface damages such as erosion, dishing, etc., on the copper layer surface, polishing is terminated immediately before reaching the tantalum-containing compound layer i.e. while a copper layer still slightly remains, and then, in the second polishing, the remaining thin copper layer and the tantalum-containing compound layer are continuously polished, and polishing is completed when it has reached the insulating layer. (Hereinafter, this method will be referred to as an underpolishing method.) Further, as mentioned above, if necessary, in a third polishing, scratches may be mainly mended, and the insulating layer may be polished to reduce the dishing.
Further, the polishing composition to be used in the first polishing is required to have a property such that it is capable of polishing the copper layer at a high stock removal rate. With respect to such a polishing composition for a copper layer, for example, JP-A-07-233485 discloses a polishing liquid for a copper type metal layer, which comprises at least one organic acid selected from the group consisting of aminoacetic acid and amidesulfuric acid, an oxidizing agent and water, and a method for producing a semiconductor device using such a polishing liquid.
If this polishing liquid is used for polishing a copper layer, a relatively high stock removal rate is obtainable. It is believed that copper atoms on the copper layer surface become copper ions, and such copper ions are taken into a chelate compound, whereby a high stock removal rate can be obtained. Such a polishing composition is considered to be useful for the first polishing.
However, an ideal polishing composition which is useful for polishing a tantalum-containing compound layer i.e. for the second polishing, has not heretofore been proposed for the CMP process based on the above concept. Under these circumstances, the present inventors have previously proposed a polishing composition comprising an abrasive, an oxidizing agent capable of oxidizing tantalum, a reducing agent capable of reducing tantalum oxide and water, and a polishing method employing it in JP10-342106. By this invention, a tantalum-containing compound can be polished certainly at a high stock removal rate, and this polishing composition can be used for the second polishing.
However, when polishing is carried out by means of a polishing composition composed solely of the above-mentioned components, a new problem has been brought about that the copper surface after polishing is likely to be corroded. Further, when this composition for the second polishing was u
Ina Katsuyoshi
Kitamura Tadahiro
Fujimi Incorporated
Koslow C. Melissa
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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