Radiant energy – Irradiation of objects or material – Irradiation of semiconductor devices
Reexamination Certificate
2002-11-21
2004-08-03
Lee, John (Department: 2881)
Radiant energy
Irradiation of objects or material
Irradiation of semiconductor devices
C250S50400H, C250S491100, C250S493100
Reexamination Certificate
active
06770895
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to lithography systems. More particularly, the present invention relates to recycling light source gas in a lithography tool.
2. Background Art
Lithography is a process used to create features (e.g., devices) on a surface of one or more substrates (e.g., semiconductor wafers, or the like). Substrates can include those used in the manufacture of flat panel displays, circuit boards, various integrated circuits, and the like. During lithography, the substrate is positioned on a substrate stage and is exposed to an image projected onto the surface of the substrate. The image is formed by an exposure system. The exposure system includes a light source, optics, and a reticle (e.g., a mask) having a pattern used to form the image. The reticle is generally located between the light source and the substrate. In extreme ultraviolet (EUV) or electron beam systems, the light source is housed in a light source vacuum chamber and the exposure system and substrate are housed in an optics vacuum chamber. The light source chamber and the optical chamber can be coupled via a gaslock.
In a lithography, feature (e.g., device) size is based on a wavelength of the light source. To produce integrated circuits with a relatively high density of devices, which allows for higher operating speeds, it is desirable to image relatively small features. To produce these small features, a light source is needed that emits short wavelengths of light (e.g., around 13 nm). This radiation is called EUV light, which is produced by plasma sources, discharge sources, sycnchrotron radiation from electron storage rings, or the like.
In some systems, EUV light is created by utilizing a discharge plasma light source. This type of light source uses a gas or target material which is ionized to create the plasma. For example, the plasma-based light source can use a gas such as xenon. Then, the plasma is formed by an electrical discharge. Typically, the EUV radiation can be in the range of 13-14 nm. In other systems, EUV radiation is produced from laser produced plasma sources. In the laser produced plasma source, a jet of material (e.g., xenon, clustered xenon, water droplets, ice particles, lithium, tin vapor, etc.) can be ejected from a nozzle. A laser is spaced from the nozzle and emits a pulse that irradiates the jet to create the plasma. This plasma subsequently emits EUV radiation.
In order to produce a relatively large amount EUV light, a concentration of xenon must be relatively high where the plasma is being created (e.g., in the light source chamber). This produces a pressure that is too high for efficient transmission of the EUV light through the remainder of the system (e.g., the optics chamber). As a result, the path in which the EUV light travels must be evacuated. Usually, large vacuum pumps are used to remove the source gas as quickly as possible after it has performed its function of creating the EUV light. Unfortunately, at high machine throughput, a relatively large amount of source gas is pumped away. The cost of source gas such as xenon is substantial, and will result in a higher per wafer cost unless the source gas is recycled. Recycling the source gas is complicated by the inclusion of other gases being emitted from the remainder of the EUV lithography tool that mix with the source gas.
Accordingly, in some lithography tools the source gas is kept separate from gases in the remainder of the lithography tool by a very thin membrane. The membrane also removes unwanted radiation by functioning as a spectral filter. However, lithography tools having high throughput and high light intensity may not be able to have the membrane due to high thermal loading, which destroys the membrane. Thermal calculations show that the membrane would have to have a very large surface area to avoid vaporizing when the light source is turned on. A large surface, extremely thin membrane cannot be used in practice, even if they could be manufactured, due to their fragile nature. If the membrane is removed, a barrier between the source chamber and the rest of the tool is gone and gas mixing occurs, making the source gas recycling task extremely challenging, and in some cases completely impractical.
Therefore, what is needed is a method and apparatus of isolating gas in a light source chamber from gases being emitted from the remainder of a lithography tool to allow the gas in the source chamber to be efficiently recycled.
BRIEF SUMMARY OF THE INVENTION
An embodiment of the present invention provides a system including a first chamber including an element that emits light based on a first gas and a second chamber that uses the emitted light to perform a process and that includes a second gas. The system also includes a gaslock that couples the first chamber to the second chamber. The system further includes a gas source that supplies a third gas between the first and the second gas in the gaslock, such that the first gas is isolated from the second gas by the gaslock.
Another embodiment of the present invention provides a system, including a light source chamber having a first gas, an optics chamber having a second gas, a first means for coupling the light source chamber to the optics chamber, and a second means for passing a third gas through the first means to isolate the first gas from the second gas.
A further embodiment of the present invention provides a method including (a) producing light with a first gas, (b) processing optics with a second gas, and (c) separating the first gas from the second gas with a third gas that flows between them.
In one aspect of the embodiment, the first and third gas are pumped from the first chamber, the first gas is separated from the third gas, such that the first gas can be recycled for reuse.
Further embodiments, features, and advantages of the present inventions, as well as the structure and operation of the various embodiments of the present invention, are described in detail below with reference to the accompanying drawings.
REFERENCES:
patent: 6341006 (2002-01-01), Murayama et al.
patent: 6493423 (2002-12-01), Bisschops
patent: 6566667 (2003-05-01), Partlo et al.
patent: 2001/0004104 (2001-06-01), Bijkerk et al.
patent: 2002/0014598 (2002-02-01), Melnychuk et al.
patent: 2002/0084428 (2002-07-01), Visser et al.
ASML Holding N.V.
Hughes James P.
Lee John
Sterne Kessler Goldstein & Fox PLLC
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