Method to make wafer laser marks visable after bumping process

Details Method to make wafer laser marks visable after bumping process Method to make wafer laser marks visable after bumping process

2002-06-21

2004-08-31

Smith, Matthew (Department: 2825)

Semiconductor device manufacturing: process

With measuring or testing

C438S005000, C438S022000, C438S007000, C438S129000, C438S040000, C438S505000, C438S975000

Reexamination Certificate

active

06784002

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to semiconductor fabrication and more specifically to maintaining wafer ID characters/laser marks on semiconductor wafers.
BACKGROUND OF THE INVENTION
Semiconductor wafers are identified through the use of laser marks. However, after the wafer bumping process, the laser marks are obscured and are rendered not visible due to overlying bumps obscuring part of or all of one or more identifying letter
umbers. Thus the wafer laser marks can't be subsequently read by optical character recognition (OCR) and causes scrapping of some of the wafers due to wrong wafer ink. That is if the solder bump wafer is defective, the wafer may be incorrectly recognized causing the wafer to be incorrectly inked with an identification number.
For example, as shown in
FIG. 1
, a wafer
10
may be identified with a wafer ID number with characters
12
such as “G60539-2D8” laser marked on the wafer
10
proximate a notch
14
used to determine the orientation of the wafer
10
.
FIG. 2
is an enlarged portion of field
18
of
FIG. 1
designated “FIG.
2
” after a conventional bump process forming bumps
20
. As shown in
FIG. 2
, the bumps
20
so formed, obscure the wafer ID characters
12
since the bumps
20
are indiscriminately formed over the wafer ID characters
12
.
U.S. Pat. No. 6,121,111 to Jang et al. describes a process for removing metal from over the laser mark area.
U.S. Pat. No. 6,043,133 to Jang et al. describes a method of removing a shallow trench isolation (STI) oxide layer from over alignment marks.
U.S. Pat. No. 5,956,596 to Jang et al. describes a process to clean laser marks.
U.S. Pat. No. 5,401,691 to Caldwell describes an open frame for laser marks.
U.S. Pat. No. 6,277,658 B1 to Jeng et al. describes a method that uses a monitor wafer to monitor the shielding of metal over laser marks.
SUMMARY OF THE INVENTION
Accordingly, it is an object of one or more embodiments of the present invention to provide an improved method of making semiconductor wafer laser marks visible after bumping process.
Other objects will appear hereinafter.
It has now been discovered that the above and other objects of the present invention may be accomplished in the following manner. Specifically, a wafer having fields is provided. The wafer having at least one wafer identification character formed thereon within one or more of the fields. A dry film resist is formed over the wafer. Portions of the dry film resist are selectively exposed field by field using a mask whereby the mask is shifted over the one or more fields containing the at least one wafer identification character so that the one or more fields containing the at least one wafer identification character is double exposed after the mask shift so that all of the one or more fields containing the at least one wafer identification character is completely exposed. The selectively exposed dry film resist is developed to remove the non-exposed portions of the dry film resist. Solder is plated over the wafer exposed by the removed portions of the dry film resist to form solder bumps within the fields not containing at least one wafer identification character so that the at least one wafer identification character is readable by optical character recognition.


REFERENCES:
patent: 5401691 (1995-03-01), Caldwell
patent: 5705320 (1998-01-01), Hsu et al.
patent: 5956596 (1999-09-01), Jang et al.
patent: 6043133 (2000-03-01), Jang et al.
patent: 6121111 (2000-09-01), Jang et al.
patent: 6277658 (2001-08-01), Jeng et al.

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