Abrading – Abrading process – Utilizing shield
Reexamination Certificate
2002-01-18
2004-05-11
Hail, III, Joseph J. (Department: 3723)
Abrading
Abrading process
Utilizing shield
C451S028000, C451S041000, C451S060000, C451S285000, C451S286000, C451S287000, C451S289000, C451S490000
Reexamination Certificate
active
06733367
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to workpiece templates and, more specifically, to workpiece templates used in lapping and polishing silicon wafers in either single or double sided polishing machines. The present invention is a template having a plurality of cavities within the body of the surface for inserting objects such as silicon wafers intended for lapping and polishing to a thickness equal to the depth of the template cavity.
In addition, the thickness of the intended object can be varied by inserting one or more shims into the workpiece cavity.
2. Description of the Prior Art
There are templates for lapping and polishing wafers to a desirable thickness determined by the depth of the template cavity. It has been found by the inventor that they contain one or more undesirable characteristics that render them unsuitable for repeated use.
The process of lapping and polishing wafers on a single side involves placing the workpiece or workpieces into a template and placing the template upside down between a rotating pneumatic head and a table having a controlled flow of abrasive slurry flowing onto the table surface during the pneumatic head rotation whereby the wafer blanks will be honed and polished to the thickness of the template.
There are a number of undesirable side effects that can occur in the prior art. As the wafers approach the thickness of the template cavity, the amount of fluid between the template and the lapping/polishing surface decreases causing spotted changes in the surface temperature of the template burnishing the template.
Another undesirable effect of this method relates to the cross sectional thickness of the, finished wafer. The wafers can rotate within the cavity causing the wafers to continuously butt up against the wall of the cavity and rise from the cavity base whereby the edge thickness can vary from the center thickness. This is especially undesirable in applications where tolerances are measure in microns.
An object of the present invention is to overcome these shortcomings within the prior art. The present invention also addresses another shortcoming within the prior art relating to the inordinate number of templates used because of the varied thicknesses required within the end product. The present invention addresses this need through the use of shims which can have a thickness imprinted on the shim or can be classified using a color code to indicate thickness. These shims can be permanently fixed to the workpiece cavity base having indicia indicating the thickness of the end product or a color code scheme can be used to indicate the thickness of the end product. In addition one or more shims could be removably inserted into one or more cavities to vary the thickness of the finished end product.
In addition the present invention addresses another shortcoming within the prior art related to lapping and polishing of non-standard shapes such as triangles, squares, rectangles, etc. The present invention overcomes the need for creating full sized templates for the aforementioned non-standard shapes by having smaller templates having cavities conforming to the desired non-standard shapes that are of substantially equal diameter to the cavities of the larger templates, thereby enabling lapping and/or polishing of silicon wafers of a non-standard size which also provides for the lapping and polishing of mixed wafer shapes by the selection and placements of smaller templates having the preselected shape or shapes placed within one or more cavities of the larger workpiece template.
Another additional element is provided for by the present invention in the form of channels etched into the top surface of the workpiece template for the purpose of channeling the abrasive and/or polishing fluid across the surface of the workpiece template during a lapping and/or polishing operation. Again returning to the problem of workpiece template burnishing due in some part to the lack of fluid between the workpiece template and the lapping/polishing surface, the present invention channels the lapping/polishing fluid across the entire surface of the workpiece template. Furthermore, the channels also serve to reduce hydrodynamic forces between the template and lapping/polishing operational surface caused by the rotational speed of the head, the lapping/polishing surface and the fluid therebetween by limiting the planar surface area between points of fluid transition which is currently the peripheral edge of the template.
Basically, the channels provide an abundance of fluid across the non-channeled planar surface by providing channels where fluid can be transferred from or to depending on the dynamic fluid forces at any point on the non-channeled planar surface.
Therefore, because of the aforementioned problems and shortcomings of the prior art it is felt that a need exists for the present invention and while the prior art may be suitable for the purposes for which they were designed, they would not be as suitable for the purposes of the present invention, as hereinafter described.
SUMMARY OF THE PRESENT INVENTION
A primary object of the present invention is to provide a workpiece template for lapping and/or polishing silicon wafers.
Another object of the present invention is to provide a lapping/polishing workpiece template that can be repeatedly reused.
Yet another object of the present invention is to provide a lapping and polishing workpiece template having a main plate with at least one cavity therethrough for the placement of a workpiece, such as a silicon wafer, to be lapped and/or polished.
Still yet another object of the present invention is to provide a lapping/polishing workpiece template comprised of a main plate having a substantially smoothed edged circular configuration.
A further object of the present invention is to provide a lapping/polishing workpiece template having a main plate having an additional element in the form of a circumferentially notched gear-like periphery.
A yet further object of the present invention is to provide a lapping/polishing workpiece template having a main plate having a top surface and a bottom surface having a further additional element in the form of channels having a channel base and opposing channel walls placed within the top surface extending from a substantially central position to the periphery of said workpiece template.
A still yet further object of the present invention is to provide a lapping/polishing workpiece template substantially comprised of fiberglass-epoxy laminates.
Another object of the present invention is to provide a lapping/polishing workpiece template having a main plate comprising a fiberglass-epoxy laminate and having a frictionless material fixedly positioned to the bottom surface of the main plate.
Yet another object of the present invention is to provide a lapping and polishing workpiece template having a main plate comprising a fiberglass-epoxy laminate and having a Mylar backing adhesively affixed thereto.
Still yet another object of the present invention is to provide a lapping/polishing workpiece template having a main plate comprising a fiberglass-epoxy laminate and having a frictionless material fixedly positioned to the bottom surface of the main plate forming a frictionless work holder cavity base.
A further object of the present invention is to provide a lapping/polishing workpiece template having a main plate and a further additional element in the form of a backing plate being of substantially equal diameter affixed thereto.
A yet further object of the present invention is to provide a lapping/polishing workpiece template having a main plate, a backing plate with a top side and a bottom side with said top side fixedly positioned to said main plate and said bottom side having an adhesive layer.
A still yet further object of the present invention is to provide a lapping/polishing workpiece template having a main plate, a backing plate with a top side and a bottom side with said top side fixedly positioned to said main p
Hail III Joseph J.
Kroll Michael I
McDonald Shantese
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