Abrading – Abrading process – Glass or stone abrading
Reexamination Certificate
2001-06-19
2004-08-31
Hail, III, Joseph J. (Department: 3723)
Abrading
Abrading process
Glass or stone abrading
C451S288000, C051S309000, C438S692000
Reexamination Certificate
active
06783434
ABSTRACT:
TECHNICAL FIELD
The invention relates to a CMP abrasive usable in the production of semiconductor elements, a liquid additive for CMP abrasive and a method for polishing substrates. Particularly, it relates to a CMP abrasive usable in the step of planarizing the surface of a substrate, typically the steps of Th planarizing an interlayer insulating film and forming shallow-trench separation, to a liquid additive for the CMP abrasive and to a method for polishing substrates by using the CMP abrasive.
BACKGROUND ART
In present ultra large scale integrated circuits, packaging density is increasing, and various fine processing techniques have been studied and developed. Design rules have already reached the order of sub half micron. CMP (Chemical Mechanical Polishing) is one of the techniques developed to satisfy such a strict requirement for fineness. This technique is essential for the production of semiconductor devices, typically for planarizing interlayer insulating films and for shallow-trench separation, because it can completely planarize layers to be exposed, reducing the burden on exposure techniques and stabilizing the production yield.
Colloidal silica abrasives have been investigated as common CMP abrasives to be used in the production of semiconductor devices to planarize inorganic insulating films, such as silicon oxide insulating film, formed by plasma-CVD (Chemical Vapor Deposition), low pressure-CVD or the like. Colloidal silica abrasives may be produced by using silica particles, which are typically formed from tetrachlorosilane through thermal decomposition, and adjusting pH. Such abrasives, however, cannot polish inorganic insulating films fast enough, and need higher polishing rate for their practical use.
In integrated circuits with design rules of 0.5 &mgr;m or more, devices were separated by LOCOS (Localized Oxidation of Silicon). As the processing measurements have become finer, shallow-trench separation has become used in response to the requirement for a technique giving narrower separation gap between devices. For shallow-trench separation, the surplus parts of a silicon oxide film formed on a substrate are removed by CMP, and a stopper film reducing the polishing rate is provided under the silicon oxide film to stop polishing. The stopper film is typically made of silicon nitride, and the rates of polishing the silicon oxide film and the stopper film are preferably in a large ratio. Where conventional colloidal silica abrasives are used, the ratio between the rate of polishing the silicon oxide film and the rate of polishing the stopper film is as small as the order of 3, and such abrasives cannot satisfy the requirements of practical shallow-trench separation.
On the other hand, cerium oxide abrasives have been used for polishing photo masks or the surface of glass, such as lenses. Having lower hardness as compared to silica particles and alumina particles, cerium oxide particles hardly make flaws on the polished surface and are suitable for finish mirror polishing. However, the cerium oxide abrasives for polishing glass surfaces cannot be used as abrasives for polishing semiconductors, because they contain a dispersant containing sodium salts.
DISCLOSURE OF INVENTION
An object of the invention is to provide a CMP abrasive, which can speedily polish a surface to be polished, such as a silicon oxide insulating film, without making flaws.
Another object of the invention is to provide a CMP abrasive, which can speedily polish a surface to be polished, such as a silicon oxide insulating film, without contaminating the surface to be polished with alkali metals, such as sodium ions, nor making flaws.
Another object of the invention is to provide a CMP abrasive, which is more advantageous in that it can increase the ratio of the rate of polishing a silicon oxide insulating film to the rate of polishing a silicon nitride insulating film.
Another object of the invention is to provide a CMP abrasive, which can speedily polish a surface to be polished, such as a silicon oxide insulating film, without contaminating the surface to be polished with alkali metals, such as sodium ions nor making flaws and contains a cerium oxide slurry improved in storage stability.
Another object of the invention is to provide a CMP abrasive, which can speedily polish a surface to be polished, such as a silicon oxide insulating film, without contaminating the surface to be polished with alkali metals, such as sodium ions, nor making flaws, and can increase the ratio of the rate of polishing a silicon oxide insulating film to the rate of polishing a silicon nitride insulating film to 50 or more.
Another object of the invention is to provide a liquid additive, which is to be used to give a CMP abrasive improved in storage stability.
Another object of the invention is to provide a liquid additive for CMP abrasive to be used to improve the flatness of the polished surface of a substrate.
Another object of the invention is to provide a method for polishing a substrate, which can polish a surface of the substrate without making flaws on its polished surface. Another object of the invention is to provide a method for polishing a substrate, which can speedily polish a surface to be polished, such as a silicon oxide insulating film, without making flaws, and can increase the ratio of the rate of polishing a silicon oxide insulating film to the rate of polishing a silicon nitride insulating film to 50 or more.
Accordingly, the invention relates to:
(1) a CMP abrasive comprising
a cerium oxide slurry containing cerium oxide particles, a dispersant and water; and
a liquid additive containing a dispersant and water;
(2) the CMP abrasive of (1), wherein each of the dispersants contained in the cerium oxide slurry and the liquid additive respectively is a polymer dispersant, which is a polymer containing ammonium acrylate as a copolymerized ingredient;
(3) the CMP abrasive of (1), wherein each of the dispersants contained in the cerium oxide slurry and the liquid additive respectively is a polymer dispersant, which is a polyammonium-acrylate or a polyamine-acrylate;
(4) the CMP abrasive of (2) or (3), wherein the polymer dispersants have a weight average molecular weight of 100 to 50,000;
(5) the CMP abrasive of (1), wherein the cerium oxide slurry contains 0.01 to 2.0 parts by weight of the dispersant relative to 100 parts by weight of the cerium oxide particles and contains 0.3 to 40% by weight of the cerium oxide particles based on the cerium oxide slurry;
(6) the CMP abrasive of any one of (1) to (5), wherein the cerium oxide slurry is pH 6 to 10;
(7) the CMP abrasive of any one of (1) to (6), which is 50 or more in ratio of rate of polishing a silicon oxide film to rate of polishing a silicon nitride film;
(8) a liquid additive for CMP abrasive comprising a dispersant and water;
(9) the liquid additive for CMP abrasive of (8), which contains 1 to 10% by weight of the dispersant;
(10) the liquid additive for CMP abrasive of (9), wherein the dispersant is a polyammonium-acrylate or a polyamine-acrylate;
(11) the liquid additive for CMP abrasive of (10), wherein the polyammonium-acrylate or the polyamine-acrylate has a weight average molecular weight of 1,000 to 100,000;
(12) the liquid additive for CMP abrasive of (11), wherein the polyammonium-acrylate or the polyamine-acrylate has a molecular weight distribution (weight average molecular weight
umber average molecular weight) of 1.005 to 1.300;
(13) the liquid additive for CMP abrasive of (10), wherein the polyammonium-acrylate or the polyamine-acrylate contains 10 mol % or less of free ammonia or a free amine, which does not form a salt;
(14) the liquid additive for CMP abrasive of (10), which is pH 4 to 8;
(15) the liquid additive for CMP abrasive of (10), which has a viscosity of 1.20 to 2.50 mPa·s;
(16) a method for polishing a substrate, comprising holding a substrate having, formed thereon, a film to be polished against a polishing pad of a polishing platen, followed by pressing, and moving the substrate and the polishing platen while
Akahori Toshihiko
Ashizawa Toranosuke
Hirai Keizo
Kurata Yasushi
Kurihara Miho
Hail III Joseph J.
Hitachi Chemical Company Ltd.
Ojini Anthony
Westerman Hattori Daniels & Adrian LLP
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