Abrasive tool making process – material – or composition – With inorganic material – Clay – silica – or silicate
Reexamination Certificate
2000-08-08
2002-10-29
Marcheschi, Michael (Department: 1755)
Abrasive tool making process, material, or composition
With inorganic material
Clay, silica, or silicate
C051S307000, C051S309000, C106S003000, C252S079300, C252S079400, C438S692000, C438S693000, C451S036000
Reexamination Certificate
active
06471735
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention pertains to novel compositions suitable for use in a chemical-mechanical planarization process, and methods for making same. The present invention also pertains to novel methods for planarizing a substrate using chemical-mechanical planarization. The compositions and methods of the present invention are preferably used in the formation of a shallow trench isolation structure upon a semiconductor substrate. The invention has particular applicability to the semiconductor manufacturing industry.
2. Description of the Related Art
Shallow-trench isolation (STI) structures are used to electronically isolate the components in an integrated circuit. Conventional processes for fabricating STI structures include depositing an oxide layer and a silicon nitride layer in sequence over a semiconductor substrate. Selected areas of these layers are then etched using known techniques, thereby forming trenches upon the substrate surface. The silicon nitride layer and oxide layer are sequentially etched until a desired depth in the substrate is reached. An oxide layer is subsequently deposited upon the substrate, thereby filling the trenches. Chemical-mechanical planarization (CMP) is then used to planarize the oxide layer, wherein the silicon nitride layer is used as a polishing stop. The silicon nitride layer is subsequently removed using an etchant such as, for example, phosphoric acid. Hydrofluoric acid can also be used as the etchant, for example, for etching materials other than silicon nitride. The remaining portions of oxide (formerly in the trenches) function as isolation structures.
A typical problem associated with CMP processes used in the formation of STI structures is that portions of the silicon nitride layer are unintentionally removed during the planarization of the oxide layer. Undesirable effects caused by this removal of the silicon nitride layer include, for example, the unintentional removal of the field oxide from the trench region of the device. This can result in the degradation of the electrical characteristics of the device. Thus, providing a high oxide-to-silicon nitride polish rate during the planarization of the oxide layer is desirable. However, current CMP slurries typically achieve oxide-to-silicon nitride polish rate selectivities of less than about 5:1.
Another problem in CMP processes relates to the uneven polishing of the field oxide layer of the substrate. Typically, trenches are unevenly distributed on a semiconductor substrate. As a result, typical semiconductor substrates include regions which have a relatively high density of trenches, and regions which have a relatively low density of trenches. Typically, the rate at which the field oxide present in the low-trench density regions is polished is higher than the rate at which the field oxide present in the high-trench density regions is polished. Uneven polishing of the substrate can result in the degradation of the electrical characteristics of the device.
Various alternatives have been proposed to ameliorate the aforementioned problems with CMP processes. For example, the controlled deposition of an extra film of silicon nitride on top of the silicon oxide has been proposed. See, e.g., Boyd, John M., “A One-Step Shallow Trench Global Planarization Process Using Chemical Mechanical Polishing,” Journal of the Electrochemical Society, Vol. 144, No. 5, p. 1838, May 1997. See also U.S. Pat. No. 5,923,993. However, use of an additional deposition step can increase manufacturing costs, and substrates produced thereby are typically prone to manufacturing defects due to the dependence of planarization efficiency upon the thickness of the deposited sacrificial film.
Another proposed solution relates to inserting dummy active areas between the active areas in the substrate. See, e.g., U.S. Pat. No. 5,909,628. The dummy active areas are generally formed in the same manner as the active areas of the substrate, except that the dummy active areas are not later developed into active or passive devices. The dummy active areas are inserted in the portion of the substrate which would normally be occupied by a field oxide to reduce dishing in these areas. Dishing occurs when portions of the substrate are overpolished, resulting in a non-planarized surface. While the insertion of dummy active areas may reduce the occurrence of dishing, this method typically requires a patterning (lithography) step to create the dummy active areas, which thereby increases manufacturing costs.
The use of slurries that contain abrasive particles which are made of material other than silicon oxide has also been proposed. For example, CMP slurry manufacturers have experimented with using abrasive particles made of cerium oxide. The drawbacks of using cerium oxide include the formation of microscratches on the wafer surface. In addition, the treatment and disposal of used slurries containing cerium oxide abrasive particles are not well understood.
The related art discloses various slurries for use in chemical-mechanical planarization processes, for example, in U.S. Pat. Nos. 5,728,308; 5,860,848; 5,938,505; and 6,019,806. However, the related art does not disclose the compositions of the present invention.
To meet the requirements of the semiconductor manufacturing industry and to overcome the disadvantages of the related art, it is an object of the present invention to provide a method for making a slurry composition, suitable for use in a chemical-mechanical planarization process, which can provide an increased oxide-to-silicon nitride polish rate selectivity.
Other objects and aspects of the present invention will become apparent to one of ordinary skill in the art upon review of the specification and claims appended hereto.
SUMMARY OF THE INVENTION
The foregoing objectives are met by the methods and compositions of the present invention. According to a first aspect of the invention, a method for making a slurry composition is provided, suitable for use in a chemical-mechanical planarization process. The method comprises combining:
(a) abrasive particles;
(b) a suspension medium;
(c) a peroxygen compound;
(d) an etching agent; and
(e) an alkyl ammonium hydroxide.
According to another aspect of the invention, a method for making a composition is provided, suitable for use in a chemical-mechanical planarization process wherein an abrasive planarizing surface is used. The method comprises combining:
(a) a peroxygen compound;
(b) an etching agent; and
(c) an alkyl ammonium hydroxide.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
According to one aspect of the present invention, a slurry composition is formed by combining abrasive particles, a suspension medium, a peroxygen compound, an etching agent and an alkyl ammonium hydroxide. The slurry compositions of the present invention are suitable for use in a chemical-mechanical planarization (CMP) process, preferably in the formation of a shallow trench isolation (STI) structure upon a semiconductor substrate. The slurry compositions are preferably used in a single-step CMP process and can be used with any CMP machine platform, including disk and endless belt-type platforms.
The present slurry compositions can provide an increased polish rate selectivity with respect to the oxide material in comparison with the polish stop material. For example, the slurry compositions can provide an increased oxide-to-silicon nitride polish rate selectivity during the polishing of a semiconductor substrate.
The abrasive particles of the slurry composition contribute to the mechanical planarization of a substrate surface, such as a semiconductor substrate surface, when the slurry composition is introduced between the substrate surface and a planarizing device such as, for example, a polishing pad. The specific type or types of abrasive particles employed typically depends at least on the material to be planarized. The abrasive particles can include silicon oxide, aluminum oxide, cerium oxide or combinations thereof, preferab
Hoffman Joe G.
Misra Ashutosh
Schleisman Anthony J.
Air Liquide America Corporation
Marcheschi Michael
Russell Linda K.
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