Contamination control on lithography components

Details Contamination control on lithography components Contamination control on lithography components

2002-12-23

2003-11-04

Lee, John R. (Department: 2881)

Radiant energy

Irradiation of objects or material

Irradiation of semiconductor devices

C250S492300, C250S372000, C430S005000, C430S270100, C422S024000

Reexamination Certificate

active

06642531

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to extreme ultraviolet (EUV) lithography, and more particularly, to contamination control and mitigation on EUV components.
BACKGROUND OF INVENTION
Extreme ultraviolet lithography, which uses a source at 13.5 nm wavelength, is a promising technology for 0.1 micron integrated circuit (IC) fabrication. Since the absorption at that wavelength is very strong in all materials, EUV lithography employs Si/Mo multilayer mirrors and reflective masks as reflective optics, rather than refractive optics and through-the-mask reticles used in longer wavelength (optical) lithography. The strong absorption requires the use of reflective mask reticles, rather than through-the-mask reticles used in longer wavelength lithography. The EUV absorption also precludes the use of a pellicle to protect the reticle from particulate contamination.
There are many issues to be resolved in order to realize EUV lithography, such as, developing a powerful EUV source, robust components that direct the radiation (mirrors), and robust components that define the integrated circuit features (reticles). An EUV source with a collectable radiation power of 50 W to 150 W at over 5 kHz in the spectral range of 13-14 nm is required to achieve requirements for high volume manufacturing of 300 mm wafers. Laser-induced and electrical discharge gas plasma devices (EUV lamps) are under investigation as promising EUV sources. These sources generate EUV radiation by heating certain materials into a plasma to such a level, in the many 100,000's C, that the material emits EUV radiation. Potential source materials which emit EUV radiation at excited energy levels include xenon, oxygen, and lithium.
FIG. 1
is a side view of an EUV reflective mask
10
. The reflective mask and, similarly EUV mirror (not shown), comprises a quartz substrate
12
upon which is deposited a multilayer coating
14
of silicon (Si) and molybdenum (Mo). In addition, the reflective mask
10
has a highly detailed absorber pattern
16
deposited on top of the Si/Mo multilayer coating
14
. A common absorber material is chrome. The reflective mask
10
is held to an electrostatic chuck
18
controlled by a chuck voltage
36
. The EUV incoming radiation
32
impinges the reflective mask
10
at an angle and is reflected as outgoing radiation
33
.
The EUV sources are emitters of high velocity particles
20
. The high velocity particles
20
are a source of harmful contamination to the reflective surfaces
17
upon which they impinge and deposit. The Si/Mo multilayer mirrors and reflective masks
10
, herein after referred to as reflective components
11
, are highly sensitive to particle
20
contamination. Assuming the particles
20
are large enough, the contamination will result in the printing of a defect in every exposure field.
Several methods are used in an attempt to address particle
20
control on EUV reflective components
11
. One method uses debris shields (not shown) through which the incoming EUV radiation
32
is passed to catch or filter the particles
20
. But in the effort to maximize photon illumination, the “mesh” size has to be a compromise between particle
20
pass-through rate and reduction in EUV power.
Another method uses electrostatic fields for particle
20
control, which relies on the induced polarization created on the particle
20
by the presence of a strong electrostatic field. This leads to poor particle
20
removal of electrically neutral particles with low polarizability. Another method uses thermophoresis, which relies on the presence of a thermal gradient between the reflective surface
17
and the area above it. Thermophoresis is only marginally successful in the removal of larger particles
20
from a reflective surface
17
.
None of these methods address the needs for preventing particulate contamination nor removing the particles
20
that do land on the reflective surfaces
17
. Therefore, even with these processes, periodic manual cleaning is still required. But the delicate multilayer coatings
14
used in EUV reflective components
11
cannot withstand harsh or frequent cleaning.
In order for EUV lithography to meet commercial requirements and demands, including reliability, productivity, and maintenance, configurations and methods are needed for providing contamination control for the EUV mirrors and reflective masks without interference with the transmission of the radiation.


REFERENCES:
patent: 5311098 (1994-05-01), Seely et al.
patent: 5512759 (1996-04-01), Sweatt
patent: 5989776 (1999-11-01), Felter et al.
patent: 6042995 (2000-03-01), White
patent: 6316150 (2001-11-01), Gianoulakis et al.

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