Abrading – Abrading process – Glass or stone abrading
Reexamination Certificate
1999-09-30
2002-02-12
Hail, III, Joseph J. (Department: 3723)
Abrading
Abrading process
Glass or stone abrading
C451S285000, C451S287000
Reexamination Certificate
active
06346032
ABSTRACT:
FIELD OF THE INVENTION
The field of the present invention pertains to semiconductor fabrication processing. More particularly, the present invention relates to a device for more efficiently polishing and planarizing a semiconductor wafer.
BACKGROUND OF THE INVENTION
Electronic systems and circuits have made a significant contribution towards the advancement of modem society and are utilized in a number of applications to achieve advantageous results. Numerous electronic technologies such as digital computers, calculators, audio devices, video equipment, and telephone systems include processors that have facilitated increased productivity and reduced costs in analyzing and communicating data, ideas and trends in most areas of business, science, education and entertainment. Frequently, electronic systems designed to provide these results include integrated circuits (ICs) on chip wafers. Usually, the wafers are produced by processes that include a polishing step to create a smooth wafer surface. Performing the polishing step in an effective and efficient manner is critical to IC wafer manufacturing.
The starting material for typical ICs is very high purity silicon. The pure silicon material is grown as a single crystal that takes the shape of a solid cylinder. This crystal is then sawed (like a loaf of bread) to produce wafers upon which electronic components are then constructed by adding multiple layers to the wafer through a process of lithography (e.g., photolithography, X-ray lithography, etc.). Typically, lithography is utilized to form electronic components comprising regions of different electrical characteristics added to the wafer layers. Complex ICs can often have many different built up layers, with each layer being stacked on top of the previous layer and comprising multiple components with a variety of interconnections. The resulting surface topography of these complex IC's are bumpy (e.g., they often resemble rough terrestrial “mountain ranges” with many rises or “hills” and dips or “valleys”) after the IC components are built up in layers.
Lithographic techniques are usually able to reproduce very fine surface geometries and greater advantages and usefulness are realized in applications in which more components (e.g., resistors, diodes, transistors, etc.) are integrated into an underlying chip or IC. The primary manner of incorporating more components in a chip is to make each component smaller. In a photolithographic process, limitations on the depth of focus impact the projection of increasingly finer images onto the surface of the photosensitive layer. Depth of focus problems are exacerbated by rough topographies (e.g., the bumpy rises and dips causes by layers produced during lithographic processes). The “bumpy” topography of complex ICs exaggerate the effects of narrowing limits on the depth of focus which in turn limits the number of components that are incorporated on a chip. Thus, in order to focus desirable mask images defining sub-micron geometries onto each of the intermediate photosensitive layers in a manner that achieves the greatest number of components on a single wafer, a precisely flat surface is desired. The precisely flat or fully planarized surface facilitates extremely small depths of focus operations, and in turn, facilitates the definition and subsequent fabrication of extremely small components.
Polishing is the preferred method of obtaining full planarization of a wafer layer. It usually involves removing a sacrificial portion of material by rubbing a polishing pad on the surface of the wafer. Polishing flattens out height differences on the surface of the wafer, since high areas of topography (hills) are removed faster than areas of low topography (valleys). Most polishing techniques have the rare capability of smoothing out topography over millimeter scale planarization distances leading to maximum angles of much less than one degree after polishing.
One of the most common polishing techniques includes chemical mechanical polishing (CMP) processes that utilize an abrasive slurry dispensed on a polishing pad to aid in the smooth and predictable planarization of a wafer. The planarizing attributes of the slurry are typically comprised of an abrasive frictional component and a chemical reaction component. The abrasive frictional component is due to abrasive particles suspended in the slurry. The abrasive particles add to the abrasive characteristics of the polishing pad as it exerts frictional contact with the surface of the wafer. The chemical reaction component is attributable to polishing agents which chemically interact with the material of the wafer layer. The polishing agents soften or dissolve the surface of the wafer layer to be polished by chemically reacting with it. Together the abrasive frictional component and a chemical reaction component assist a polishing pad to remove material from the surface of the wafer.
The manner in which the slurry is distributed to the polishing pad significantly impacts the effectiveness of the abrasive and chemical characteristics of the slurry in aiding the polishing, which in turn impacts the removal rates. The traditional slurry distribution method is to dispense the slurry onto the top of a polishing pad, and the polishing pad transports it to the wafer surface. A polishing pad material usually has a roughened surface comprising a number of very small pits and gouges manufactured into the surface of the polishing pad. The pits and grooves of the roughened surface act as pockets that collect slurry for transportation to and from the wafer surface being polished. While abrasive slurries utilized in typical chemical mechanical polishing processes offer certain benefits, they can also result in detrimental side affects.
The free floating abrasive particles in typical abrasive slurries often pose certain problems. One problem with typical abrasive CMP slurries is uneven polishing as a result of insufficient dispersion stability in most slurries. It is important to evenly distribute the slurry over the surface of the pad and wafer so that the removal of the wafer layer is even. Solid abrasion particles in most slurries tend to settle down and/or aggregate in the slurry solution. If a portion of the wafer is exposed to contact with an excessive amount of slurry it usually is removed at a faster rate and portions that are not exposed to enough slurry are usually removed at a slower rate, creating a rough topography instead of a planarized one. Thus, it is preferable to avoid detrimental uneven layer removal due to agglomeration of the slurry particles and/or non-uniform distribution.
Traditional slurry distribution systems typically do not provide a uniform distribution of slurry across a wafer surface. For example, most slurry distribution systems apply fresh slurry to the edge of a wafer and then transport it to the center of the wafer. However, by the time the slurry reaches the center of the wafer some of the abrasive characteristics of the slurry are spent. Thus fresh slurry applies more abrasive friction to the edge of the wafer removing material relatively fast and spent slurry applies less abrasive force to the center of the wafer removing material relatively slower resulting in an unevenly polished wafer surface.
As abrasive slurry is consumed during the polishing process waste particles comprising spent abrasive particles and waste “shaved” from the wafer are produced. Particulate contamination associated with spent abrasive particles can have very detrimental impacts and is a great concern with respect to the surface cleanliness after CMP. Spent abrasive particles usually cannot be readily dissolved by chemical interaction. Free spent abrasive particles in the slurry tend to increase the probability that the “waste” particles will deposit on the wafer surface. In addition, the residue of spent abrasive particles tends to lodge in the grooves and pits of the polishing pad that are otherwise intended to assist in carrying fresh slurry to the surface of the wafer. In order to maintain th
Black Andrew
Vines Landon
Zhang Liming
Hail III Joseph J.
VLSI Technology Inc.
Wagner , Murabito & Hao LLP
Wilson Lee
LandOfFree
Fluid dispensing fixed abrasive polishing pad does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Fluid dispensing fixed abrasive polishing pad, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fluid dispensing fixed abrasive polishing pad will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2980142