Chemistry: electrical and wave energy – Processes and products – Coating – forming or etching by sputtering
Reexamination Certificate
1996-10-02
2001-01-30
Nguyen, Nam (Department: 1753)
Chemistry: electrical and wave energy
Processes and products
Coating, forming or etching by sputtering
Reexamination Certificate
active
06179975
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to sputtering, and more particularly, to a method wherein sputtering target usage is monitored.
BACKGROUND OF THE INVENTION
In a typical sputtering operation (FIG.
1
), a target
4
of for example titanium is provided on an aluminum support within a sputtering chamber
6
, and power is supplied to the target to cause it to sputter onto an object
8
such as a semiconductor wafer within the chamber. In such a situation, if it is desired that a pure titanium film be provided on the object, the sputtering is undertaken in the presence of pure argon. If a titanium nitride film is desired, the sputtering is undertaken in the presence of argon and nitrogen.
Typically, a sputtering machine of this sort has a kilowatt-hour counter which indicates the work undertaken in removal of target material. In a typical machine, for example, sputtering of an entire target of titanium to exclusively produce titanium film completely consumes the titanium target in 1400 kilowatt-hours. Meanwhile, the complete titanium target is consumed in 2800 kilowatt-hours for exclusive production of titanium nitride film.
If a sputtering process requires both such films to be deposited on an object, the target will be exhausted somewhere in between these two kilowatt-hour values. Furthermore, if two processes are being run, one depositing only titanium film and the other providing a titanium/titanium nitride sandwich layer, the end of target life will depend on the product volume through each process.
Typically, a sputtering machine has only a kilowatt-hour counter to sum up the amount of work undertaken, and thus there is no differentiation between one process and another to aid one in understanding how much target life is left. This understanding is important because the complete burning through of the target can lead to the ruining of product and also damage to the machine.
SUMMARY OF THE INVENTION
The present invention is a method of monitoring the consumption of a target of, for example, titanium used in providing titanium and/or titanium nitride on such object. Initially, the process work in kilowatt-hours (Y
1
) is determined for complete consumption of the target when providing only titanium, and the process work in kilowatt-hours (Y
2
) is also determined for complete consumption of the target in providing only titanium nitride. The target life is then determined in accordance with the formula;
Target
Life
=
Y
2
-
Y
1
X
2
-
X
1
(
ARCTAN
(
W
2
W
1
)
)
+
Y
1
where:
Y
2
and Y
1
are defined as above;
W
2
=actual second material process work;
W
1
=actual first material process work;
X
2
=
ARCTAN
[
lim
W
1
→
0
(
W
2
W
1
)
]
=
1.57
radians
;
X
1
=
ARCTAN
[
lim
W
2
→
0
(
W
2
W
1
)
]
=
0
radians
.
While the ARCTAN function is indicated in the above formula, any function which substantially mimics the ARCTAN function is suitable.
REFERENCES:
patent: 4166783 (1979-09-01), Turner
patent: 5427666 (1995-06-01), Mueller et al.
patent: 5487823 (1996-01-01), Sawada et al.
Kwok Edward C.
National Semiconductor Corporation
Nguyen Nam
Skjerven Morrill & MacPherson
Ver Steeg Steven H.
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