The patent's assignee for patent number 8629970 is
News editors obtained the following quote from the background information supplied by the inventors: "A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In that instance, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g., comprising part of, one, or several dies) on a substrate (e.g., a silicon wafer). Transfer of the pattern is typically via imaging the pattern using an ultraviolet (UV) radiation beam onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Known lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at one time, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the 'scanning'-direction) while synchronously scanning the substrate parallel or anti-parallel to this direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.
"It has been proposed to immerse the substrate in the lithographic projection apparatus in a fluid having a relatively high refractive index, e.g., water or a hydrocarbon liquid, so as to fill a space between the final element of the projection system and the substrate. The fluid may be distilled water, although another fluid could be used. The description herein references a liquid. However, another fluid may be suitable, for example, a wetting fluid, an incompressible fluid, and/or a fluid with a higher refractive index than air and desirably a higher refractive index than water. Immersing the substrate into such a liquid enables imaging of smaller features, since the exposure radiation will have a shorter wavelength in the liquid (the effect of the liquid may be regarded as increasing the effective numerical aperture (NA) of the system and increasing the depth of focus). Organic fluids are one of the liquids being considered for use in immersion lithography. These organic fluids have a higher refractive index than water and can include hydrocarbons, such as decahydronaphthalene (also known as decalin), a fluorohydrocarbon, and a cubane dispersed in an organic solvent. Other proposed immersion liquids include, but are not limited to, water with solid particles (e.g., quartz) suspended therein.
"Submersing the substrate or substrate and substrate table in a bath of liquid means that there is a large body of liquid that must be accelerated during a scanning exposure. This requires additional or more powerful motors, and the resulting turbulence in the liquid may lead to undesirable and unpredictable effects.
"One of the solutions proposed is for a liquid supply system to provide liquid on only a localized area of the substrate and in between the final element of the projection system and the substrate using a liquid confinement system (the substrate generally has a larger surface area than the final element of the projection system)."
As a supplement to the background information on this patent, VerticalNews correspondents also obtained the inventors' summary information for this patent: "In existing immersion lithographic systems, water is used as the immersion fluid. After the high purity water passes through an immersion liquid system and has been in contact with the substrate being printed, the water is disposed of as waste. New high refractive index fluids are being investigated as a future replacement for water as the immersion fluid. These new high refractive index fluids will allow the numerical aperture of the optics to be increased beyond 1.35. However, the new fluids, which may replace water, are expensive and are potentially environmental hazards.
"It is desirable, for example, to recondition an immersion fluid that fails to meet a certain quality threshold, and then re-circulate the reconditioned immersion fluid. Further, it is desirable to provide a fluid handling and re-circulating system whose components do not contribute to the degradation of the immersion fluid.
"In an embodiment, a lithographic apparatus for immersion lithography includes a projection system configured to project a patterned radiation beam onto a target portion of a substrate, the substrate being supported on a substrate table. The lithographic apparatus includes a liquid handling system having a liquid handling structure configured to provide an immersion liquid to a space between the projection system and the substrate and/or the substrate table. A metrology device of the lithographic apparatus is configured to monitor a parameter of the immersion liquid, and a recycling control device, coupled to the metrology device, is configured to regulate a routing of the immersion liquid either to be reused or to be reconditioned. In one example, components of the liquid handling structure are manufactured and operated in a way that does not degrade the quality of the immersion liquid.
"In an embodiment, a liquid handling system for use in a lithographic apparatus includes a metrology device configured to monitor a parameter of an immersion liquid, wherein a quality of the immersion liquid is determined before directing the immersion liquid to a liquid handling structure of the lithographic apparatus. A recycling control device, coupled to the metrology device, is configured to regulate a routing of immersion liquid from the liquid handling structure after use to a regular or an intense liquid reconditioning unit, based on the determined quality of the immersion liquid.
"In an embodiment, a control system for maintaining a desired quality of an immersion liquid in a lithographic apparatus includes a sensor. The sensor includes an absorption sensor configured to measure an index of absorption of radiation at a desired wavelength of the immersion liquid; and/or a refractive index sensor configured measure a refractive index of immersion liquid; and/or a surface tension sensor configured to measure a surface tension of immersion liquid; and/or a rheology sensor configured to measure a viscosity of immersion liquid; and/or a temperature sensor. A controller is configured to receive data from the sensor(s) and to determine, based on the received data, whether the immersion liquid should be directed to a liquid handling structure of the lithographic apparatus or to a liquid reconditioning system.
"In an embodiment, a device manufacturing method provides an immersion liquid via a liquid handling structure to an area between a projection system and a substrate and/or a substrate table, allowing the projection system to have a high numerical aperture. A parameter of the immersion liquid is monitored. A routing of the immersion liquid is regulated either to be used by the liquid handling structure or to be reconditioned based on the monitoring of the parameter of the immersion liquid.
"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."
For additional information on this patent, see: Sewell, Harry; Loopstra,
Keywords for this news article include:
Our reports deliver fact-based news of research and discoveries from around the world. Copyright 2014, NewsRx LLC
Most Popular Stories
- Obama Administration Releases Proposal to Regulate For-Profit Colleges
- Apple, HP, Intel May Take a Hit from Slowdown in Smartphone Sales Growth
- Elizabeth Vargas' Husband Marc Cohn Addresses Rumors
- Keurig Adds Peet's coffee, Alters Starbucks deal
- U.S. to Relinquish Gov't Control Over Internet
- Motley Crue's Nikki Sixx Marries Model Courtney Bingham
- FDIC Files Lawsuit on Behalf of Banks Allegedly Hurt by Libor Scandal
- Chinese e-Commerce Giant Alibaba Gears for IPO in U.S.
- Some California Cities Seeking Water Independence
- Quiznos Files for Chapter 11