Semiconductor device manufacturing: process – Chemical etching – Combined with the removal of material by nonchemical means
Reexamination Certificate
2001-09-17
2003-04-22
Powell, William A. (Department: 1765)
Semiconductor device manufacturing: process
Chemical etching
Combined with the removal of material by nonchemical means
C156S345130, C156S345120, C216S038000, C216S083000, C216S088000, C438S008000, C438S692000, C438S691000, C438S693000
Reexamination Certificate
active
06551933
ABSTRACT:
Provisional Applications and Regular Patent Applications which this patent claims benefit of are included herein by reference in their entirety.
BACKGROUND OF INVENTION
Chemical mechanical polishing (CMP) is generally known in the art. For example U.S. Pat. No. 5,177,908 issued to Tuttle in 1993 describes a finishing element for semiconductor wafers, having a face shaped to provide a constant, or nearly constant, surface contact rate to a workpiece such as a semiconductor wafer in order to effect improved planarity of the workpiece. U.S. Pat. No. 5,234,867 issued to Schultz et. al. in 1993 describes an apparatus for planarizing semiconductor wafers which in a preferred form includes a rotatable platen for polishing a surface of the semiconductor wafer and a motor for rotating the platen where a non-circular pad is mounted atop the platen to engage and polish the surface of the semiconductor wafer. Fixed abrasive finishing elements are known for polishing semiconductor layers. An example is WO 98/18159 PCT application by Minnesota Mining and Manufacturing.
Semiconductor wafer fabrication generally requires the formation of layers of material having particularly small thickness. A typical conductor layer, such as a metal layer, is generally 2,000 to 6,000 angstroms thick and a typical insulating layer, for example an oxide layer, is generally 3,000 to 5,000 angstroms thick. The actual thickness is at least partially dependent on the function of the layer along with the function and design of the semiconductor wafer. A gate oxide layer can be less than 100 angstroms while a field oxide is in the thousands of angstroms in thickness. In higher density and higher value semiconductor wafers the layers can be below 500 angstroms in thickness. Generally during semiconductor fabrication, layers thicker than necessary are formed and then thinned down to the targeted tolerances with techniques needed such as Chemical Mechanical Polishing. Because of the strict tolerances, extreme care is given to attaining the targeted thinned down tolerances. As such, it is particularly preferred to accurately determine just when enough of the layer has been removed to reach the targeted tolerances, this is the end point for the thinning or polishing operation. One method to remove selected amounts of material is to remove the semiconductor wafer periodically from polishing for measurements such as thickness layer measurements. Although this can be done it is time consuming and adds extra expense to the operation. Further the expensive wafers can be damaged during transfer to or from the measurement process further decreasing process yields and increasing costs.
BRIEF SUMMARY OF INVENTION
An objective of polishing of semiconductor layers is to make the semiconductor layers as nearly perfect as possible. Fixed abrasive finishing pad finishing surfaces can suffer from being overly harsh on a workpiece, causing unwanted scratching or other unwanted surface damage, thus reducing the perfection of the surface. Further, a fixed abrasive finishing pad finishing surface can suffer from having a higher than necessary coefficient of friction when finishing a workpiece. This higher than necessary coefficient of friction can lead to other unwanted surface damage. Further, fixed abrasive finishing pads can have abrasive particles unexpectedly break away from their surface during finishing and these broken away abrasive particles can scratch or damage the workpiece surface. Still further, during finishing a particle can break away from the workpiece surface forming a workpiece abrasive particle which can scratch or damage the workpiece surface. These unwanted effects are particularly preferred and deleterious to yield when manufacturing electronic wafers which require extremely close tolerances in required planarity and feature sizes.
It is an advantage of this invention to reduce the harshness of abrasive finishing pads such as fixed abrasive finishing pads on the workpiece surface being finished. It is an advantage of this invention to reduce unwanted scratching or other unwanted surface damage on the workpiece surface during finishing. It is further an advantage of this invention to reduce the coefficient of friction during finishing a workpiece to help reduce unwanted surface damage. It is an object of this invention to reduce unwanted damage to the workpiece surface when during finishing with a abrasive finishing element if an abrasive particle unexpectedly breaks away from their surface. It is an advantage of the invention to reduce unwanted damage to the workpiece surface when an abrasive workpiece particle breaks away workpiece surface during finishing. It is further an advantage of this invention to help improve yield for workpieces having extremely close tolerances such as semiconductor wafers. It is further an advantage of this invention to develop a method with improved optimization of finishing rates and boundary lubrication.
Addition of lubricants to the interface between the workpiece surface being finished and the finishing pad finishing surface can improve finishing but also changes the friction at this interface. In situ process control where lubricants are added or changed during the finishing process can change finishing performance. Friction can change due to real time changes to the workpiece surface, the finishing element finishing surface, lubricant changes, and changes to process control parameter set points. A method which use a plurality of process sensors to gain information about finishing progress and uses this information for improved finishing control is preferred. Further, the preferred real time tangential force of friction and/or coefficient of friction control can change due to the specific structure and/or topography to the workpiece being finished. By tracking the workpiece during manufacture, improved information for in real time (in situ) control of lubricant changes, tangential force of friction, and/or coefficient of friction can be effected. A method to further improve control in situ process changes due to lubricant additions and/or changes is needed in the industry. A method to track a workpiece during manufacture and to use tracking information during finishing is needed. A method which can also help improve the cost of manufacture of the semiconductor wafers during a finishing cycle time having real time friction changes would be generally desirable.
A preferred embodiment of this invention is directed to a method of finishing a semiconductor wafer surface having a uniform region and a finishing cycle time comprising a step 1) of providing a tracked semiconductor having tracked information; a step 2) providing an abrasive finishing element finishing surface; a step 3) of providing an organic lubricant to the operative finishing interface comprising the interface formed between the abrasive finishing element finishing surface and the semiconductor wafer surface being finished; a step 4) of providing a finishing control subsystem having at least three operative process sensors which include a plurality of operative friction sensors for sensing in situ process information, access to the tracked information, and a processor to evaluate the in situ process information and tracked information; a step 5) of applying an operative finishing motion in the operative finishing interface forming in the operative finishing interface a uniform region having the organic lubrication and wherein the uniform region has a coefficient of friction; and a step 6) of changing a plurality of control parameters in response to an evaluation of both the in situ process information and the tracked information and wherein changing the control parameters changes the coefficient of friction in the uniform region having organic lubrication during at least a portion of the finishing cycle time.
A preferred embodiment of this invention is directed to a method of finishing a semiconductor wafer surface having a uniform region and a finishing cycle time comprising a step 1) of providing a tracked semiconduc
Beaver Creek Concepts Inc
Powell William A.
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