Protective coatings for radiation source components

Details Protective coatings for radiation source components Protective coatings for radiation source components

2002-12-20

2004-10-26

Lee, John R. (Department: 2881)

Radiant energy

Radiant energy generation and sources

With radiation modifying member

C250S493100, C378S119000

Reexamination Certificate

active

06809328

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to extreme ultraviolet lithography, and more particularly, to erosion resistant coatings for components of EUV sources.
BACKGROUND OF INVENTION
Optical lithography is a key element in integrated circuit (IC) production. It involves passing radiation (light) through a mask of a circuit design and projecting it onto a substrate, commonly a silicon wafer. The light exposes special photoresist chemicals on the surface of the wafer which is used to protect unetched circuit details. Integrated circuit feature resolution is directly related to the wavelength of the radiation. The demand for ever smaller IC features is driving the development of illumination sources that produce radiation having ever smaller wavelengths. Extreme ultraviolet light (EUV) has shorter wavelengths than visible and UV light and can therefore be used to resolve smaller and more numerous features.
Extreme ultraviolet lithography is a promising technology for resolving feature size of 50 nm and below. There are many problems in order to realize EUV lithography and the most serious problem is to develop the EUV radiation source. 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 will be required to achieve requirements for high volume manufacturing of 300 mm wafers.
Electrical discharge gas plasma devices (EUV lamps) are under investigation as promising EUV sources. The principle consists of heating up certain materials into a plasma to such a level that the material emits EUV radiation. Potential source materials which emit EUV radiation at excited energy levels include xenon, oxygen, and lithium. The aim is to produce as many photons as possible in the required wavelength range. A pulsed discharge of electrically stored energy across a gap between a cathode and an anode is used in the presence of the gas for the creation of plasma with temperatures of several 100,000 C. This plasma emits thermal radiation in the spectral range of around 10 nm to 20 nm.
FIG. 1
is a cross-sectional view of one possible configuration of an electrical discharge gas plasma head
10
capable of producing an EUV-emitting plasma
20
. The plasma head
10
comprises a plurality of closely positioned electrodes, in this example represented as a cathode
12
and anode
14
, separated by an insulator base
16
or ring separator. The area between the cathode
12
and anode
14
is filled with an ionizing gas
22
. A plasma discharge
17
initiated near the base
19
travels along the cathode
12
and anode
14
through self-induced electromagnetic forces. Upon reaching the cathode tip
18
and anode tip
15
, the discharge
17
compresses upon itself densifying, heating, and emitting EUV excitations.
Other electrode/insulator geometries are possible but all share the property of producing a pinched plasma in close proximity to one of more surfaces of the plasma head.
In operation, a tremendous heat load, on the order of 5 kW/cm
2
, is experienced by the components of the plasma head
10
. The plasma-facing components (PFCs) include: an inner cathode surface
11
of the cathode
12
, an outer anode surface
13
of the anode
14
, and exposed insulator base surfaces
13
of the insulator base
16
. Regardless of the specific component configuration and arrangement, there will be at least some PFCs that are susceptible to the effects of the operation of the plasma head
10
.
The PFCs are commonly only a few millimeters from the plasma
20
and in an erosive environment that quickly damages the PFC's. This erosion severely effects performance, lifetime and reliability of the discharge head
10
. In particular, the anode
14
tends to erode more quickly than the cathode
12
, which puts severe limitations on the lifetime of the discharge head
10
as well as producing debris that can impinge upon and harm the other components of the plasma head and overall system, as well as harm the exposed target
34
being illuminated.
The cathode
12
and anode
14
are commonly made from refractory metals, such as tungsten or molybdenum which are more resistant to the effects of extreme heat. These materials are expensive, difficult to machine, and are prone to cracking when structurally loaded under sever heating conditions. These materials, none the less, erode over time in this environment.
The insulator components, namely the insulator base
16
, comprise various ceramic materials, all of which suffer to some extent, from thermal cracking and erosion in these environments.
In order for the electric discharge plasma EUV sources to meet commercial requirements and demands, including reliability and productivity, lifetime-extending improvements will have to be made for the components of the discharge heat
10
.


REFERENCES:
patent: 6387572 (2002-05-01), Tong et al.
patent: 6406981 (2002-06-01), Ravi
patent: 6479830 (2002-11-01), Fornaca et al.
patent: 6566668 (2003-05-01), Rauch et al.
patent: 6586757 (2003-07-01), Melnychuk et al.
patent: 6621022 (2003-09-01), Ma et al.

Affiliated with

Also associated with

Rating

Protective coatings for radiation source components does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Protective coatings for radiation source components, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Protective coatings for radiation source components will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3326045