Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2001-12-21
2004-05-04
Fahmy, Wael (Department: 2814)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S631000, C438S691000, C438S692000, C438S693000
Reexamination Certificate
active
06730592
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to methods for planarization of metal-containing (preferably, Group VIII, and more preferably, platinum-containing) surfaces, particularly in the fabrication of semiconductor devices.
BACKGROUND OF THE INVENTION
Films of metals and metal oxides, particularly the heavier elements of Group VIII, are becoming important for a variety of electronic and electrochemical applications. This is at least because many of the Group VIII metal films are generally unreactive, resistant to oxidation or retard the diffusion of oxygen, and are good conductors. Oxides of certain of these metals also possess these properties, although perhaps to a different extent.
Thus, films of Group VIII metals, their alloys, and metal oxides, particularly the second and third row metals (e.g., Ru, Os, Rh, Ir, Pd, and Pt) have suitable properties for a variety of uses in integrated circuits. For example, they can be used in integrated circuits for barrier materials, for example. They are particularly suitable for use as barrier layers between the dielectric material and the silicon substrate in memory devices. Furthermore, they are suitable as the plate (i.e., electrode) itself in capacitors.
Platinum is one of the candidates for use as an electrode for high dielectric capacitors. Capacitors are the basic charge storage devices in random access memory devices, such as dynamic random access memory (DRAM) devices, static random access memory (SRAM) devices, and now ferroelectric memory (FE RAM) devices. They consist of two conductors, such as parallel metal or polysilicon plates, which act as the electrodes (i.e., the storage node electrode and the cell plate capacitor electrode), insulated from each other by a dielectric material (a ferroelectric dielectric material for FE RAMs). Thus, there is a continuing need for methods and materials for the processing of Group VIII metal-containing films, preferably, platinum-containing films.
Many surfaces that result during the formation of Group VIII metal-containing films, particularly in the wafer fabrication of semiconductor devices, do not have uniform height, and therefore, the wafer thickness is also non-uniform. Further, surfaces may have defects such as crystal lattice damage, scratches, roughness, or embedded particles of dirt or dust. For various fabrication processes to be performed, such as lithography and etching, height non-uniformities and defects at the surface of the wafer must be reduced or eliminated. Also, excess material may need to be removed to form a structure with selectivity relative to the underlying substrate. Planar removal of a substrate's top surface is also used to isolate certain features electrically. Various planarization techniques are available to provide such reduction and/or elimination. One such planarization technique includes mechanical and/or chemical-mechanical polishing (abbreviated herein as “CMP”).
The process of planarization is used to remove material, and preferably achieve a planar surface, over the entire chip and wafer, sometimes referred to as “global planarity.” Conventionally, the process of planarization, and particularly CMP, involves the use of a wafer holder that holds a wafer, a polishing pad, and an abrasive slurry that includes a dispersion of a plurality of abrasive particles in a liquid. The abrasive slurry is applied so that it contacts the interface of the wafer and the polishing pad. A table or platen has a polishing pad thereon. The polishing pad is applied to the wafer at a certain pressure to perform the planarization. At least one of the wafer and a polishing pad are set in motion relative to the other. In some planarization processes, the wafer holder may or may not rotate, the table or platen may or may not rotate and/or the platen may be moved in a linear motion as opposed to rotating. There are numerous types of planarization units available which perform the process in different manners. Alternatively, the polishing pad and abrasive slurry may be replaced by a fixed abrasive article that includes a plurality of abrasive particles dispersed within a binder adhered to at least one surface of a backing material.
The planarization of a surface that includes platinum and other Group VIII metals typically involves mechanical polishing, as opposed to chemical-mechanical polishing, because they are relatively chemically inert and/or have relatively few volatile products. Such mechanical polishing uses alumina, silica, or other abrasive particles to remove the metal physically. Unfortunately, mechanical polishing tends to smear (e.g., deform) the metals, leaving metal over undesired portions of the wafer surface, and leaving scratches in either the metal itself or other areas on the wafer surface. Also, many commercially available abrasive slurries do not effectively planarize platinum or other Group VIII metal-containing surfaces either because no material is removed or the resultant surface has defects therein.
Thus, there is still a need for methods for planarizing an exposed surface of a substrate that includes platinum and/or other Group VIII metals, particularly in the fabrication of semiconductor devices.
SUMMARY OF THE INVENTION
The present invention provides methods that overcome many of the problems associated with the planarization of a surface, particularly one that includes platinum, another of the Group VIIIB metals, and/or a Group IB metal. Preferably, the methods of the present invention are effective for the planarization of a surface containing at least one of the second and third row metals of Group VIIIB (i.e., Groups 8, 9, and 10, which includes Rh, Ru, Ir, Pd, Os, and Pt) and Group IB (i.e., Au and Ag). More preferably, the methods of the present invention are effective for the planarization of a surface containing at least one of Rh, Ru, Ir, Pd, and Pt. Such a surface is referred to herein as a “metal-containing surface.” That is, a “metal-containing surface” refers to an exposed region having a metal present, preferably at least one metal of Group VIIIB and Group IB present. In such an exposed region, the metal is preferably present in an amount of at least about 10 atomic percent, more preferably at least about 20 atomic percent, and most preferably at least about 50 atomic percent, of the composition of the region, which may be provided as a layer, film, coating, etc., to be planarized (e.g., via chemical-mechanical or mechanical planarization or polishing) in accordance with the present invention. The surface preferably includes one or more Group VIIIB and/or Group IB metals in elemental form or an alloy thereof (with each other and/or one or more other metals of the Periodic Table), as well as oxides, nitrides, and suicides thereof. More preferably, the surface includes (and most preferably, consists essentially of) one or more Group VIIIB and/or Group IB metals in elemental form or an alloy of such metals only.
The methods of the present invention involve planarizing a surface using a planarization composition that preferably includes a halogen-containing compound and a halide salt therein (dissolved or dispersed therein). A preferred group of halogen-containing compounds include the halogens (e.g., F
2
, Cl
2
, Br
2
, and I
2
), the interhalogens (e.g., ClBr, IBr, ICl, BrF, ClF, ClF
3
, BrF
3
, ClF
5
, IF
5
, and IF
7
), and halogen-generating compounds (e.g., XeF
2
, HgF
2
, SF
4
, alkyl halides, and complexes of X
2
with organic bases). The halide salts can be inorganic salts (e.g., NaI, KCl, KBr, and NH
4
F) or organic salts (e.g., Et
4
NBr, Me
3
NHCl, and Me
4
NF).
Herein, as is conventionally understood, “planarizing” or “planarization” refers to the removal of material from a surface, whether it be a large or small amount of material, either mechanically, chemically, or both. This also includes removing material by polishing. As used herein, “chemical-mechanical polishing” and “CMP” refer to a dual mechanism having both a chemical component and a mechanical component, wherein corrosion chemistry and fracture
Fahmy Wael
Le Thao X.
Micro)n Technology, Inc.
Mueting Raasch & Gebhardt, P.A.
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