Electric heating – Metal heating – By arc
Reexamination Certificate
1998-12-11
2001-10-16
Evans, Geoffrey S. (Department: 1725)
Electric heating
Metal heating
By arc
C219S121680, C438S462000
Reexamination Certificate
active
06303899
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to semiconductor wafer fabrication, and more particularly to a method and apparatus for scribing a code in an inactive outer clear out area of a semiconductor wafer.
BACKGROUND OF THE INVENTION
The manufacture of semiconductor wafers to create semiconductor integrated circuit devices typically involves a sequence of processing steps which fabricate the multi-layer structure generally associated with the integrated circuit devices. Such processing steps may include (1) the deposition of metals, dielectrics, and semiconductor films, (2) the creation of masks by lithography techniques, (3) the doping of semiconductor layers by diffusion or implantation, (4) the polishing of outer layers (e.g. chemical-mechanical polishing), and (5) the etching of layers for selective or blanket material removal. Hence, the manufacture of a first type of semiconductor wafer may include a large number of processing steps which are different relative to the processing steps required to fabricate a second type of semiconductor wafer. Since many different types of semiconductor devices (e.g. different part numbers) are often manufactured in the same facility, it is necessary to identify or otherwise mark each individual semiconductor wafer so that it may be distinguished from wafers of a different type. In particular, it is necessary to mark individual wafers with an identification code which includes, for example, the part number of the integrated circuit devices contained in the wafer, the date code of the wafer, and the lot number of the wafer.
One manner of marking semiconductor wafers is to scribe the identification code in the wafer via laser ablation. In particular, a focused laser beam from a laser device, such as an excimer laser device, is impinged on the front side of the semiconductor wafer so as to scribe the identification code in the front side of the wafer. For example, as shown in
FIG. 8
, laser scribing devices which have heretofore been designed disadvantageously scribe an identification code
100
in a semiconductor wafer
102
in a linear fashion. Hence, the identification code is not completely contained within an inactive outer clear out area
104
. The inactive outer clear out area
104
is a “clear out” area which is generally not fabricated to include a resist layer or the like so as to prevent certain types of fabrication defects. Scribing the identification code such that a portion of the code is not completely contained within the inactive outer clear out area
104
has a number of drawbacks associated therewith. Firstly, the usable surface area within an active area
106
of the semiconductor wafer is undesirably decreased since a portion
108
of the identification code
100
is scribed therein. Moreover, residual resist from a photolithography step may be deposited and thereafter expelled from the pits associated with the portion
108
of the identification code
100
located in the active area
106
of the semiconductor wafer
102
thereby undesirably generating contaminants during subsequent processing steps.
In addition, in certain manufacturing processes, semiconductor wafers are sorted via use of an optical character recognition (OCR) device which reads the identification code scribed in the wafer
102
. Use of such an OCR device is complicated by the differing background colors and/or topographies associated with the portion
108
of the identification code
100
which is located in the active area
106
and a portion
110
of the identification code
100
which is located in the inactive outer clear out area
104
.
Thus, a continuing need exists for a wafer scribing apparatus and method which overcomes one or more of the above mentioned drawbacks.
SUMMARY OF THE INVENTION
In accordance with one embodiment of the present invention, there is provided a method of fabricating a semiconductor wafer. The method includes the step of generating a laser beam with a laser device. Moreover, the method includes the step of scribing a code in an inactive outer clear out area of a first side of the wafer with the laser beam such that the code is completely contained within the inactive outer clear out area of the wafer.
Pursuant to another embodiment of the present invention, there is provided a method of fabricating a semiconductor wafer having an active area and an inactive outer clear out area. The method includes the step of fabricating a number of active dies on a first side of the wafer such that each of the number of active dies is completely contained within the active area of the wafer. The method also includes the step of generating a laser beam with a laser device. Moreover, the method includes the step of scribing a code in the inactive outer clear out area of the wafer with the laser beam such that the code is completely contained within the inactive outer clear out area of the wafer.
Pursuant to yet another embodiment of the present invention, there is provided an apparatus for scribing a code in a first side of a semiconductor wafer. The apparatus includes a movable stage device configured to engage the wafer by a second side of the wafer. The apparatus also includes a laser device positioned such that a laser beam generated by the laser device is impinged on the first side of the wafer when the wafer is positioned within the stage device. The stage device is further configured to position the wafer in a number of predetermined locations relative to the laser device such that impingement of the laser beam on the first side of the wafer causes the code to be scribed in an inactive outer clear out area of the first side of the wafer. The code is completely contained within the inactive outer clear out area of the wafer.
Pursuant to another embodiment of the present invention, there is provided a semiconductor wafer. The semiconductor wafer includes an active area having a number of active dies contained therein such that each of said number of active dies is completely contained within said active area. Moreover, the semiconductor wafer includes an inactive outer clear out area having a code disposed therein such that said code is completely contained within said inactive outer clear out area.
It is an object of the present invention to provide an improved method and apparatus for scribing a code in a semiconductor wafer.
It is an object of the present invention to provide a new and useful method and apparatus for scribing a code in a semiconductor wafer.
It is a further object of the present invention to provide a method and apparatus for scribing a code in a semiconductor wafer which does not scribe any portion of the code in an active area of the semiconductor wafer.
The above and other objects, features, and advantages of the present invention will become apparent from the following description and the attached drawings.
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Johnson Gregory A.
Taravade Kunal N.
Evans Geoffrey S.
LSI Logic Corporation
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