Abrasive tool making process – material – or composition – With inorganic material – Clay – silica – or silicate
Reexamination Certificate
2001-08-15
2002-08-27
Marcheschi, Michael (Department: 1755)
Abrasive tool making process, material, or composition
With inorganic material
Clay, silica, or silicate
C051S307000, C051S309000, C106S003000, C438S692000, C438S693000
Reexamination Certificate
active
06440186
ABSTRACT:
The present invention relates to a polishing composition to be used for polishing substrates for semiconductors, photomasks and various memory hard disks, particularly to a polishing composition useful for polishing for planarization of the surface of device wafers in e.g. semiconductor industry, and a polishing method employing such a composition.
More particularly, the present invention relates to a polishing composition which is highly efficient and useful for forming an excellent polished surface in the polishing step of semiconductor devices to which so-called chemical mechanical polishing technology is applied, in the processing of device wafers, and a polishing method employing such a composition.
Progress of so-called high technology products including computers has been remarkable in recent years, and parts to be used for such products, e.g. devices 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 instead of tungsten or aluminum, as the wiring material.
By its nature, copper is highly susceptible to etching, and accordingly, it requires the following process. Namely, after forming wiring grooves and vias 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 vias formed. As a material for such a barrier layer, tantalum metal, tantalum nitride or a tantalum 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 monofluoro silicon oxide (SiOF). 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 step polishing process, i.e. a polishing process divided into two steps, is being studied.
Firstly, in the first step polishing (hereinafter referred to as 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. Here, for the purpose of not forming various surface defects such as recesses, erosion, dishing, etc., on the copper layer surface, polishing may be terminated immediately before reaching the tantalum-containing compound layer i.e. while a copper layer still slightly remains. Then, in the second step polishing (hereinafter referred to as the second polishing), using a polishing composition capable of polishing mainly a tantalum-containing compound layer at a high efficiency, the remaining thin copper layer and the tantalum-containing compound layer are continuously polished using the insulating layer as a stopper, and polishing is completed when it has reached the insulating layer.
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 without forming the above-mentioned various surface defects (such as recesses) on the copper layer surface, which can not be removed by the second polishing.
With respect to such a polishing composition for polishing a copper layer, for example, JP-A-7-233485 (Prior Art 1) 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 (hereinafter referred to as glycine) 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 are converted to copper ions by the action of the oxidizing agent, and the copper ions are taken into a chelate compound, whereby a high stock removal rate can be obtained.
However, as a result of experiments conducted by the present inventors, it has been found that when a polishing liquid merely containing an abrasive, glycine and hydrogen peroxide, like the polishing liquid of the above-mentioned Prior Art 1, is used for polishing a copper layer having a pattern formed, many pits (dents) will form in the copper wiring. This phenomenon is frequently observed particularly at a fine wiring of 0.3 &mgr;m or less. This may be explained such that defects or impurities are present during formation of the copper layer at the fine wiring, and such weak layer portions are attacked by a chemical or mechanical action during the polishing, whereby pits will be formed. Accordingly, it is desired to further improve the uniformity of the layer formation by optimizing the layer-forming conditions in the preparation of semiconductor devices. On the other hand, it is strongly desired to develop a polishing composition which does not form pits during the polishing.
The present invention has been made to solve such a problem, and it is an object of the present invention to provide a polishing composition which is capable of preventing formation of pits in the copper wiring in a CMP process in the production of a semiconductor device comprising at least a copper layer and a tantalum-containing compound layer, and a polishing method employing it.
The present invention provides a polishing composition comprising:
(a) an abrasive,
(b) a compound to form a chelate with copper ions
(c) a compound to provide a protective layer-forming function to a copper layer,
(d) hydrogen peroxide, and
(e) water,
wherein the abrasive of component (a) has a primary particle size within a range of from 50 to 120 nm.
The present invention provides the polishing composition, wherein the abrasive of component (a) is silicon dioxide.
The present invention provides the polishing composition, wherein the abrasive of component (a) is fumed silica or colloidal silica.
The present invention provides the polishing composition, wherein the content of the abrasive of component (a) is within a range of from 5 to 50 g/l based on the composition.
The present invention provides the polishing composition, wherein the compound to form a chelate with copper ions of component (b), is at least one member selected from the group consisting of glycine, &agr;-alanine, serine, quinaldic acid, hystidine and derivati
Asano Hiroshi
Ina Katsuyoshi
Kitamura Tadahiro
Sakai Kenji
Fujimi Incorporated
Marcheschi Michael
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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