Abrasive tool making process – material – or composition – With inorganic material – Clay – silica – or silicate
Reexamination Certificate
1998-06-26
2003-03-18
Marcheschi, Michael (Department: 1755)
Abrasive tool making process, material, or composition
With inorganic material
Clay, silica, or silicate
C051S309000, C106S003000, C438S692000, C438S693000
Reexamination Certificate
active
06533832
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a chemical mechanical polishing slurry for semiconductor integrated circuit manufacturing and, more particularly, to improved chemical mechanical polishing slurries that are useful for polishing polycrystalline silicon (Poly-Si) and various interconnect layers, metals, and thin-films used in semiconductor integrated circuit manufacturing with especially high selectivity to interlayer dielectric materials.
2. Background of the Related Art
A semiconductor wafer typically includes a substrate, such as a silicon or gallium arsenide wafer, on which a plurality of transistors have been formed. Transistors are chemically and physically connected to the substrate by patterning regions in the substrate and layers on the substrate. The transistors and layers are separated by interlevel dielectrics (ILDs), comprised primarily of some form of silicon oxide (SiO
2
). The transistors are interconnected through the use of well known multilevel interconnects to form functional circuits. Typical multilevel interconnects are comprised of stacked thin-films consisting of one or more of the following materials: titanium (Ti), titanium nitride (TiN), tantalum (Ta), aluminum-copper (Al—Cu), aluminum-silicon (Al—Si), copper (Cu), tungsten (W), doped poly-silicon (Poly-Si), and various combinations thereof. In addition, transistors or groups of transistors are isolated from one another, often through the use of trenches filled with an insulating material such as SiO
2
, SiN
4
, or Poly-Si.
The traditional technique for forming interconnects has been improved by the method disclosed in U.S. Pat. No. 4,789,648 to Chow et al. which relates to a method for producing coplanar multilevel metal/insulator films on a substrate. The new technique, which has gained wide interest and produces multilevel interconnects, uses chemical mechanical polishing (CMP) to planarize the surface of the metal layers or thin-films during the various stages of device fabrication.
In general CMP involves the concurrent chemical and mechanical polishing of an overlying first layer to expose the surface of a non-planar second layer on which the first layer is formed. One such process is described in U.S. Pat. No. 4,789,648 to Beyer et al., the specification of which is incorporated herein by reference. Briefly, Beyer et al, discloses a CMP process using a polishing pad and a slurry to remove a first layer at a faster rate than a second layer until the surface of the overlying first layer of material becomes coplanar with the upper surface of the covered second layer. A more detailed explanation of chemical mechanical polishing is found in U.S. Pat. Nos. 4,671,851, 4,910,155 and 4,944,836, the specifications of which are incorporated herein by reference.
The composition of CMP slurries is an important factor in providing an optimal chemical mechanical polishing process. Typical polishing slurries available for CMP processes contain an abrasive such as silica or alumina in an acidic or basic solution. For example, U.S. Pat. No. 4,789,648 to Beyer et al. discloses a slurry formulation including alumina abrasives, an acid such as sulfuric, nitric and acetic acid and deionized water. Similarly, U.S. Pat. No. 5,209,816 to Yu et al. discloses an aqueous slurry including abrasive particles and an anion which controls the rate of removal of silica.
Other CMP polishing slurries are described in U.S. Pat. No. 5,354,490 to Yu et al., U.S. Pat. No. 5,340,370 to Cadien et al., U.S. Pat. No. 5,209,816 to Yu et al., U.S. Pat. Nos. 5,157,876 and 5,137,544 to Medellin, and U.S. Pat. No. 4,956,313 to Cote et al., the specifications of each which are incorporated herein by reference.
Although many of the slurry compositions are suitable for limited purposes, the slurries described above tend to exhibit unacceptable polishing rates and corresponding selectivity levels to insulator materials used in wafer manufacture. In addition, known polishing slurries tend to produce poor film removal traits for the underlying films or produce deleterious film-corrosion which leads to poor manufacturing yields.
Accordingly, a need remains for new and improved polishing slurries and processes having high selectivity to the insulator media surrounding the trenches or interconnects, e.g., silica, spin-on-glass, and low k dielectric material which are not hazardous or corrosive. A further need remains for a single slurry which is capable of providing both high and uniform removal rates of the first layer and high selectivities to the insulator films.
SUMMARY OF THE INVENTION
This invention is a chemical mechanical polishing slurry that is especially useful for polishing semi-conductive layers of a semiconductor integrated circuit at high rates.
This invention is also a chemical mechanical polishing slurry that exhibits a high selectivity towards polishing a dielectric layer in comparison to an interlevel dielectric layer (ILD) layer of an IC circuit.
Furthermore, this invention is a chemical mechanical polishing slurry that has good storage stability.
This invention is also a method for using a chemical mechanical polishing slurry to polish at least one layer of a substrate such as an integrated circuit.
In one embodiment, this invention is an aqueous chemical mechanical polishing composition for polishing a substrate containing a metal or silicon layer or thin film. The aqueous chemical mechanical polishing slurry includes at least one abrasive and at least one alcoholamine wherein the alcoholamine is preferably a tertiary alcoholamine.
In another embodiment, this invention is an aqueous chemical mechanical polishing slurry. The aqueous chemical mechanical polishing slurry comprises from about 0.5 to about 15 weight percent fumed silica, from about 50ppm to about 2.0 weight percent 2-dimethylamino-2-methyl-1-propanol, and from about 0.01 to about 1.0 weight percent ammonium bicarbonate buffering agent. The aqueous chemical polishing slurry preferably has a pH of from about 9.0 to about 10.5 and exhibits a polysilicon to PETEOS polishing selectivity of at least 500.
DESCRIPTION OF THE CURRENT EMBODIMENT
The present invention is directed to chemical mechanical polishing slurries for polishing conductive and semi-conductive layers and thin-films with high selectivity to ILD materials. The polishing slurry is an aqueous medium including at least one abrasive and at least one alcoholamine. The slurry may also include optional additives such as a buffering agent.
The first component of the slurry of this invention is at least one abrasive. The abrasive is typically a metal oxide abrasive. The metal oxide abrasive may be selected from the group including alumina, titania, zirconia, germania, silica, ceria and mixtures thereof. The CMP slurry of this invention may include from about 0.1 to about 55 weight percent or more of an abrasive. It is more preferred, however, that the CMP slurry of this invention includes from about 0.5 to about 15 weight percent abrasive and most preferably, 0.5 to about 3.0 wt % of an abrasive.
The metal oxide abrasive may be produced by any techniques known to those skilled in the art. Metal oxide abrasives can be produced using any high temperature process such as sol-gel, hydrothermal or, plasma process, or by processes for manufacturing fumed or precipitated metal oxides. Preferably, the metal oxide is a fumed or precipitated abrasive and, more preferably it is a fumed abrasive such as fumed silica or fumed alumina. For example, the production of fumed metal oxides is a well-known process which involves the hydrolysis of suitable feedstock vapor (such as aluminum chloride for an alumina abrasive) in a flame of hydrogen and oxygen. Molten particles of roughly spherical shapes are formed in the combustion process, the diameters of which are varied through process parameters. These molten spheres of alumina or similar oxide, typically referred to as primary particles, fuse with one another by undergoing collisions at their contact points to form branched, three
Mueller Brian L.
Steckenrider J. Scott
Cabot Microelectronics Corporation
Marcheschi Michael
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