Cleaning and liquid contact with solids – Processes – Including application of electrical radiant or wave energy...
Reexamination Certificate
2001-11-09
2004-10-05
Jolley, Kirsten C. (Department: 1762)
Cleaning and liquid contact with solids
Processes
Including application of electrical radiant or wave energy...
C134S001000, C134S021000, C134S031000, C134S034000, C134S037000, C134S902000, C427S212000, C427S240000, C427S350000, C427S422000
Reexamination Certificate
active
06799584
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to processing of semiconductor devices, and specifically to methods and apparatus for removal of foreign particles and contaminants from solid-state surfaces.
BACKGROUND OF THE INVENTION
Removal of particles and contaminants from solid state surfaces is a major problem in integrated circuit manufacture. Integrated circuit manufacture includes, but is not limited to, production of semiconductor wafers, printed circuit boards, component packaging, and the like. As the trend to miniaturize electronic devices and components continues, and critical dimensions of circuit features become ever smaller, the presence of even a minute foreign particle on a substrate wafer during processing can cause a fatal defect in the circuit. Similar concerns affect other elements used in the manufacturing process, such as masks and reticules.
Various methods are known in the art for stripping and cleaning foreign matter from the surfaces of wafers and masks, while avoiding damage to the surfaces themselves. For example, U.S. Pat. No. 4,980,536 to Asch et. al. which is incorporated herein by reference, describes a method and apparatus for removal of particles from solid-state surfaces by laser bombardment. U.S. Pat. Nos. 5,099,557 and 5,024,968 to Engelsberg, which are also incorporated herein by reference, describe methods and apparatus for removing surface contaminants from a substrate by high-energy irradiation. The substrate is irradiated by a laser with sufficient energy to release the particles, while an inert gas flows across the wafer surface to carry away the released particles.
U.S. Pat. No. 4,987,286 to Allen, which is likewise incorporated herein by reference, describes a method and apparatus for removing minute particles (even sub-micron particles) from a surface to which they are adhered. An energy transfer medium, typically a fluid, is interposed between each particle to be removed and the surface. The medium is irradiated with laser energy, and absorbs sufficient energy to cause explosive evaporation, thereby dislodging the particles.
U.S. Pat. No. 5,023,424 to Vaught, which is incorporated herein by reference, describes a method and apparatus for using laser-induced shock waves to dislodge particles from a wafer surface. A particle detector is used to locate the positions of particles on the wafer surface. A laser beam is then focused at a point above the wafer surface near the position of each of the particles, in order to produce gas-borne shock waves with peak pressure gradients sufficient to dislodge and remove the particles. U.S. Pat. No. 5,023,424 further notes that immersion of the surface in a liquid (as in the above-mentioned U.S. Pat. No. 4,987,286, for example) is unsuitable for use in removing small numbers of microscopic particles.
Removal of small particles can also potentially damage the substrate. Generally, it has been found that sub-micron particles are the most difficult to detect and remove. Shock waves may cause these particles to explode by either splitting in a few pieces or to “splash” into a large number of fragments. There is a need to find a process which can be used to clean integrated circuits, without adding contaminants, without damaging the substrate surface upon explosion of a particle, and yet with removing particles, or fragments thereof, of different contaminants and of a large range of sizes.
SUMMARY OF THE INVENTION
It is an object of some aspects of the present invention to provide improved methods and apparatus for efficient removal of contaminants from solid-state surfaces.
It is a further object of some aspects of the present invention to provide improved methods and apparatus for removal of microscopic particles on semiconductor wafers and on other elements used in semiconductor device production.
In preferred embodiments of the present invention, a system for removing a particle from a solid-state surface, such as a semiconductor wafer, comprises a fluid delivery unit and a suction module. The fluid delivery unit deposits a fluid, preferably a vapor or a spray, onto the surface. Generally, the fluid condenses on particles on the surface, so that the overall size and mass of the particles with the liquid around them are much larger than they were before. When the suction module is actuated, a turbulent mass-transfer regime surrounding the particle induced by the suction force introduces a mechanical shock to the particle. The mechanical shock, coupled with the dissolution forces of the particle into the liquid phase, tends to release the particle from the surface. The suction force enables the particle and the liquid to be removed from the surface.
Thus, the inventors have found that wetting the surface prior to applying suction provides more effective removal of microscopic particles than does suction alone. This result contrasts with suction-based particle removal systems known in the art, in which suction is applied to a dry surface. While moisture may make it more difficult to remove large particles from the surface, it increases the effectiveness of the suction in mobilizing very small particles, particularly particles below approximately 1 micron, whose small size and mass makes it otherwise difficult to remove them.
In some preferred embodiments of the present invention the system is constructed such that the fluid is delivered in a channel and the suction forces remove the particle and fluid in another channel. The channels are typically constructed to be perpendicular to the solid-state surface. Preferably, the fluid is delivered in an inner channel, and the suction force is applied in an outer annular channel. Further preferably, the outer channel has a narrow gap (radius of outer channel less radius of inner channel) of less than 1 mm, and most preferably of around 0.3 mm. The nozzle edge of both of the channels is placed approximately 0.1-0.5 mm above the solid-state surface, and most preferably about 0.2 mm above the solid-state surface.
In further preferred embodiments of the present invention the system is constructed with a vaporizer which vaporizes the fluid phase. Typically, the vaporizer comprises at least one heating element, which is configured to heat both the fluid delivery channel and suction channel concomitantly.
In preferred embodiments of the present invention, improved methods and apparatus are provided for particle removal from a surface in which the fluid phase comprises water, or water vapor. The fluid phase is typically heated to 30-80° C. When the heated fluid impacts on the solid-state surface, some or all of the fluid molecules condense on the surface.
In some aspects of preferred embodiments of the present invention, a method and system are provided for delivering the fluid phase to the solid-state surface, wherein the delivery of the fluid phase is stopped and a suction force for particle removal is applied after waiting for a time period. This has been shown experimentally to be the most effective regime for particle removal.
In further preferred embodiments of the present invention, a turbulent flow regime is introduced by means of a combination of the fluid flow and the suction forces. The flow regime at solid-state surface is such that the horizontal fluid velocity immediately above the surface and parallel thereto is at least 100 m/s and is preferably around the speed of sound (around 330 m/s). The flow regime above the surface substantially reduces or eliminates boundary layer phenomena, stagnation and laminar flow phenomena.
In some other aspects of preferred embodiments of the present invention, the system is integrated with a laser cleaning tool. The tool is typically configured to apply laser energy to the surface so as to aid in the release of the particles from the surface. The inventors have also found that condensation-based suction is effective in removing most of the particles that tend to explode during the laser cleaning process, and thus, it is useful to integrate these two methods (suction cleaning and laser cleaning).
In
Frisman Lev
Uzeil Yoram
Wachs Amir
Yogev David
Applied Materials Inc.
Blakely , Sokoloff, Taylor & Zafman LLP
Jolley Kirsten C.
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