Compositions – Etching or brightening compositions – Inorganic acid containing
Reexamination Certificate
2000-05-04
2002-08-06
Utech, Benjamin L. (Department: 1765)
Compositions
Etching or brightening compositions
Inorganic acid containing
C438S690000, C438S691000, C438S692000, C438S693000
Reexamination Certificate
active
06428721
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
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 provides high selectivity in the polishing of semiconductor devices to which so-called chemical and mechanical polishing (CMP) technology is applied, in the processing of device wafers, and a polishing method employing such a composition.
2. Discussion of Background
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 instead of tungsten or aluminum, 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 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, metal tantalum 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 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. 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 damages 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 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 on the copper layer surface, which can not be removed by the second polishing. with respect to such a polishing composition for a copper layer, for example, JP-A-7-233485 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 be oxidized by the action of the oxidizing agent, and the oxidized copper elements are taken into a chelate compound, whereby a high stock removal rate can be obtained.
However, as a result of the experiments conducted by the present inventors, it has been found that when the above polishing liquid is used for polishing a semiconductor device having a copper layer and a tantalum-containing compound layer, the ratio (hereinafter referred to as “the selectivity ratio”) of the stock removal rate of the copper layer to the stock removal rate of the tantalum-containing compound layer, is inadequate, and if the composition, etc. are adjusted to increase the selectivity ratio, smoothness of the copper layer surface after polishing tends to be remarkably impaired. Namely, the above-mentioned polishing liquid has had problems with respect to the selectivity ratio and smoothness of the polished surface and is still required to be further improved.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above-described problems. Namely, it is an object of the present invention to provide a polishing composition and a polishing method, whereby in a CMP process in the production of a semiconductor device having at least a copper layer and a tantalum-containing compound layer, it is possible to provide a high selectivity ratio i.e. a high stock removal rate of the copper layer and a low stock removal rate of the tantalum-containing compound layer, and provides a polished surface excellent in smoothness.
The present invention provides a polishing composition comprising the following components:
(a) an abrasive,
(b) &agr;-alanine,
(c) hydrogen peroxide, and
(d) water.
Further, the present invention provides a polishing method for polishing a semiconductor device having a layer of copper and a layer of a tantalum-containing compound formed on a substrate, by means of a polishing composition comprising the following components:
(a) an abrasive,
(b) &agr;-alanine,
(c) hydrogen peroxide, and
(d) water.
According to the present invention, in a CMP process for a semiconductor device having at least a copper layer and a tantalum-containing compound layer, it is possible to provide a high selectivity ratio i.e. a high stock removal rate of the copper layer and a low stock removal rate of the tantalum-containing compound layer, and to provide a polished surface excellent in smoothness. Further, according to the present invention, it is possible to produce a semiconductor device in good yield in the above-mentioned production of the semiconductor device.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Abrasive
In the polish
Ina Katsuyoshi
Kitamura Tadahiro
Suzumura Satoshi
Fujimi Incorporated
Perez-Ramos Vanessa
Utech Benjamin L.
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