Semiconductor device manufacturing: process – Chemical etching – Combined with the removal of material by nonchemical means
Reexamination Certificate
1999-10-06
2002-08-20
Utech, Benjamin L. (Department: 1765)
Semiconductor device manufacturing: process
Chemical etching
Combined with the removal of material by nonchemical means
C438S693000, C216S088000, C216S089000
Reexamination Certificate
active
06436830
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to semiconductor processing, and, more particularly, to planarizing or polishing semiconductor wafer surfaces during the manufacture of integrated circuits.
BACKGROUND OF THE INVENTION
Semiconductor devices, also called integrated circuits, are mass produced by fabricating of identical circuit patterns on a single semiconductor wafer. During the process, the wafer is cut into identical dies or chips. Although commonly referred to as semiconductor devices, the devices are fabricated from various materials, including conductors (e.g. copper, aluminum and tungsten), non-conductors (e.g. silicon dioxide) and semiconductors (e.g. silicon). Silicon is the most commonly used semiconductor, and is used in either its single crystal or polycrystalline form. Polycrystalline silicon is often referred to as polysilicon or “poly”. The conductivity of the silicon is adjusted by adding impurities in a process commonly referred to as doping.
Within an integrated circuit, thousands of devices (e.g., transistors, diodes) are formed. Typically, contacts are formed where a device interfaces to an area of doped silicon. Specifically, plugs are typically formed to connect metal layers with device active regions. Vias are typically formed to connect metal layers with other metal layers. Also interconnects are typically formed to serve as wiring lines to interconnect the many devices on the integrated circuit and the many regions within an individual device These contacts and interconnects are formed using conductive materials.
The integrated circuit devices with their various conductive layers, semiconductive layers, insulating layers, contacts and interconnects are formed by fabrication processes, including doping processes, deposition processes, photolithographic processes, etching processes and other processes. At certain steps, it is often desirable to achieve a pre-determined level of surface planarity uniformity, and/or roughness. It is also desirable to minimize surface defects such as pits and scratches. Such surface irregularities may affect the performance of the final semiconductor device and/or create problems during subsequent processing steps.
One common technique to planarize a wafer is known as chemical mechanical polishing (CMP). CMP is very widely used technique which delivers a slurry of material to the wafer surface and while a polishing pad or belt is passed over the wafer surface. The slurry typically includes a plurality of abrasive particles dispersed in a liquid. For example, U.S. Pat. No. 5,728,308 entitled “Method of polishing a semiconductor substrate during production of a semiconductor device” discloses a conventional slurry used for chemical mechanical polishing including particulates comprised of metal oxides such as silica (SiO
2
), alumina (Al
2
O
3
), titanium oxide (TiO
2
), and cerium oxide (CeO
2
) of a particle size of about 10 nm in an aqueous solution of potassium hydroxide (KOH).
A problem with current CMP slurries is that polished metal in the slurry can cause scratches on the wafer surface or contaminate layers on the wafer. Therefore, the slurry is not re-usable and increases waste.
SUMMARY OF THE INVENTION
In view of the foregoing background, it is therefore an object of the present invention to remove metal particles from a slurry during CMP to avoid damaging and/or contaminating the semiconductor wafer.
It is another object of the present invention to provide a system which can process and re-use a slurry during CMP.
These and other objects, features and advantages in accordance with the present invention are provided by a chemical mechanical polishing (CMP) system including a polishing device having a polishing article for relative movement with the semiconductor wafer and with a slurry therebetween. The system further includes a slurry processor for processing used slurry from the polishing device and for delivering processed slurry to the polishing device. The slurry processor comprising a metal separator for separating metal particles, polished from the semiconductor wafer, from the used slurry. The slurry can be continuously recirculated during a CMP process without damaging and/or contaminating the layers of the semiconductor wafer.
The slurry preferably comprises a first emulsion including a continuous aqueous phase and a second emulsion. The second emulsion capturing metal particles polished from the semiconductor wafer. The slurry processor preferably comprises a first de-emulsifier for de-emulsifying the first emulsion into the continuous aqueous phase and the second emulsion. Furthermore, the second emulsion preferably comprises an organic phase and a dispersed aqueous phase. The dispersed aqueous phase capturing the metal particles polished from the semiconductor wafer. The slurry processor preferably includes a second de-emulsifier for de-emulsifying the second emulsion into the organic phase and the dispersed aqueous phase, and for providing the dispersed aqueous phase with captured metal particles to the metal separator.
Also, the slurry processor may include an emulsifier for emulsifying the dispersed aqueous phase in the organic phase to form the second emulsion, and for emulsifying the second emulsion in the continuous aqueous phase to form the first emulsion. The metal separator provides the dispersed aqueous phase without captured metal particles to the emulsifier, and the emulsifier delivers processed slurry to the polishing device.
The objects, features and advantages in accordance with the present invention are also provided by a method of chemical mechanical polishing including delivering a slurry to an interface between a semiconductor wafer and a polishing article while providing relative movement therebetween. The slurry preferably comprises a first emulsion including a continuous aqueous phase and a second emulsion. The second emulsion captures metal particles polished from the semiconductor wafer.
The method preferably further includes collecting used slurry from the interface between the semiconductor wafer and the polishing article, processing the used slurry, and delivering the processed slurry to the interface between the semiconductor wafer and the polishing article. The second emulsion may include an organic phase and a dispersed aqueous phase, the dispersed aqueous phase capturing the metal particles polished from the semiconductor wafer. Also, the step of processing the used slurry preferably includes de-emulsifying the first emulsion into the continuous aqueous phase and the second emulsion, de-emulsifying the second emulsion into the organic phase and the dispersed aqueous phase, and removing captured metal particles from the dispersed aqueous phase. The step of processing the used slurry may also include emulsifying the dispersed aqueous phase in the organic phase to form the second emulsion, and emulsifying the second emulsion in the continuous aqueous phase to form the first emulsion.
The continuous aqueous phase may include abrasive particles and the dispersed aqueous phase may comprise a dispersed aqueous acidic phase. The organic phase may comprise an alcohol or iso-alcohol and may include at least one complexing agent for reacting with metal particles polished from the semiconductor wafer to form organometallic complexes. The complexing agent may comprise at least one of ethylene diamine tetra-acetate (edta), di-ethylene triamine penta-acidic acid (dtpa), 8-hydroxy quinoline, bi-pyridine, and ortho-phenanthroline. The organic phase transports the organometallic complexes to an interface between the organic phase and the dispersed aqueous phase by diffusion. The organometallic complexes decompose at the interface to release the complexing agent into the organic phase and release the metal particles into the dispersed aqueous phase.
REFERENCES:
patent: 5366542 (1994-11-01), Yamada et al.
patent: 5516346 (1996-05-01), Cadien et al.
patent: 5662769 (1997-09-01), Schonauer et al.
patent: 5728308 (1998-03-01), Muroyama
patent: 5733819 (1998-03-01), Kodama et
Merchant Sailesh Mansinh
Misra Sudhanshu
Roy Pradip Kumar
Agere Systems Guardian Corp.
Deo Duy-Vu
Utech Benjamin L.
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