Radiant energy – Irradiation of objects or material – Irradiation of semiconductor devices
Reexamination Certificate
2000-08-31
2003-06-24
Nguyen, Kiet T. (Department: 2881)
Radiant energy
Irradiation of objects or material
Irradiation of semiconductor devices
C250S426000, C250S42300F
Reexamination Certificate
active
06583427
ABSTRACT:
FIELD OF THE INVENTION
The invention is generally related to the field of ion implanters for semiconductor fabrication and more specifically to ARC chambers in ion implanters.
BACKGROUND OF THE INVENTION
In semiconductor processing, various regions of a semiconductor wafer are modified by implanting dopants, such as boron, phosphorus, arsenic, antimony and the like, into the body of the wafer to produce regions having varying conductivity (e.g., source and drain regions, channel adjusts, etc.). As the density of the semiconductor devices increases, stricter control of the areas to be implanted is required. Thus, ion implanters have been developed to accurately implant dopants into small areas.
In an ion implanter, an ion beam of the desired chemical species is generated by means of a current applied to a filament within an ion source chamber. One of the more common types of source is the Freeman source. In the Freeman source, the filament, or cathode, is a straight rod that can be made of tungsten or tungsten alloy, or other known source material such as iridium, that is passed into an arc chamber whose walls are the anode. The ions are extracted through an aperture in the arc chamber by means of a potential between the source chamber, which is positive, and extraction means. The size and intensity of the generated ion beam can be tailored by system design and operating conditions; for example, the current applied to the filament can be varied to regulate the intensity of the ion beam emitted from the ion source chamber.
A top view of a prior art arc chamber
10
is shown in FIG.
1
. Arc Chamber
10
typically comprises molybdenum or tungsten and is fitted with an exit aperture
12
and with means
14
for feeding in the desired gaseous ion precursors for the desired ions. Arc chamber
10
includes a filament end
18
for inserting a filament and a repeller end
16
. When power is fed to the filament, the filament temperature increases until it emits electrons that bombard the precursor gas molecules, breaking up the gas molecules so that a plasma is formed containing the electrons and various ions. The ions are emitted from the arc chamber
10
through the exit aperture
12
and selectively passed to the target.
The inner contour of arc chamber
10
is carefully designed and must be extremely accurate for proper operation. Unfortunately, the inner surface of the arc chamber
10
is damaged over time by the plasma. The surface of the arc chamber wears away. Sputtered deposits of tungsten or molybdenum from the chamber walls create an inefficiency in the extraction of positively charged ions from the source ACR chamber. After a time of 3-6 months, the arc chamber becomes unusable and must be replaced. Replacement ARC chambers cost on the order of $3000-$6000 and up. Thus, there is a desire to minimize this cost.
SUMMARY OF THE INVENTION
The invention is an arc chamber for an ion implanter. The arc chamber comprises a liner that extends the life of the arc chamber. When the liner wears out it is replaced at a significantly reduced cost compared to replacing the entire arc chamber.
An advantage of the invention is providing an arc chamber with an extended life versus the prior art.
REFERENCES:
patent: 5554852 (1996-09-01), Bright et al.
patent: 6300636 (2001-10-01), Shih et al.
Edmonds Walter J.
Vaughn Timothy B.
Brady III W. James
Garner Jacqueline J.
Nguyen Kiet T.
Telecky , Jr. Frederick J.
Texas Instruments Incorporated
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