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Method and apparatus for controlled transient cavitation

a transient cavitation and controlled technology, applied in the direction of cleaning processes and apparatus, cleaning using liquids, instruments, etc., can solve the problems of uniform removal of particles from substrate surfaces, difficult to achieve using current approaches, and ineffective use of megasonic energy alone for particle removal, etc., to achieve rapid pressure drop

Inactive Publication Date: 2006-03-23
INTERUNIVERSITAIR MICRO ELECTRONICS CENT (IMEC VZW) +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0020] Creating gas bubbles having a selected range of bubble sizes may accomplished in any number of fashions. For example, creating the gas bubbles may include (i) dissolving gas in a liquid by means of a gasification unit or any other means to dissolve gas in the liquid; (ii) injecting gas in a liquid by means of a bubbler system, a capillary, a nozzle, a membrane contactor or any device for injecting gas bubbles into the liquid; (iii) applying a pressure drop, preferably a rapid pressure drop or applying one or multiple compression / decompression cycles; (iv) raising the temperature of a liquid, or one or more cycles of heating / cooling the liquid; (v) subjecting a liquid to an additional acoustic field; (vi) dissolving or injecting two or more different gasses into the liquid; and / or (vii) adding a surfactant to the liquid. Using the foregoing (or other) techniques, the range of bubble sizes may be varied.
[0021] An example apparatus for generating and controlling transient cavitation includes a device for creating gas bubbles having a range of bubble sizes in a liquid. The apparatus further includes an acoustic field generator for generating an acoustic field having one or more component frequencies. The acoustic field generator is acoustically coupled with the liquid. In the apparatus, at least one of (i) the device for creating gas bubbles having a range of sizes in the liquid and (ii) the acoustic field generator is adjustable so as to tune the range of bubble sizes or the acoustic field so as to control transient cavitation in the liquid for a selected range of bubble sizes.
[0022] Depending on the particular embodiment, the device for creating gas bubbles having a range of bubble sizes may include (i) a gasification unit or other device for dissolving one or more gasses in a liquid; (ii) a valve, a nozzle, a membrane contactor or other device for injecting gas bubbles (of one or more gasses) in a liquid; (iii) a heat exchanging system or any means for heating / cooling a liquid; (iv) a pressure regulating device for generating a pressure drop or generating one or multiple compression / decompression cycles; (v) a second acoustic field generator for subjecting a liquid to an additional acoustic field; and / or (vi) a device for adding a surfactant to the liquid.
[0023] Depending on the particular embodiment, apparatus for generating and controlling transient cavitation may further include a measurement unit for measuring the range of bubble sizes; and / or a control unit for controlling the device used to create gas bubbles and / or controlling the acoustic field generator.

Problems solved by technology

A common problem in these various applications is control of transient cavitation such that it occurs in a desired fashion with respect to location and mechanics of bubble collapses.
For example, in substrate cleaning technology, a common problem is non-uniform removal of particles from substrate surfaces.
This outcome is difficult to accomplish using current approaches.
As was demonstrated by FIGS. 1 and 2, the use of megasonic energy alone is not an efficient approach for particle removal as compared to gasified liquid in combination with megasonic energy.
Therefore, application of the method disclosed in Skrovan results in a non-uniform cleaning being obtained.
Further, simply gasifying the liquid used in the method of Skrovan could result in substrate damage, e.g., due to heavy collapse.
Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.

Method used

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  • Method and apparatus for controlled transient cavitation
  • Method and apparatus for controlled transient cavitation
  • Method and apparatus for controlled transient cavitation

Examples

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example 1

[0066] By means of the Young formula, which is based on the Rayleigh-Plesset model, the resonant radius of a bubble at a particular frequency can be calculated: ωr2=(3⁢γ⁢ ⁢P0ρ⁢ ⁢R02)

[0067] If the frequency (φr)=1.8 MHz and ωr=2πφr, the adiabatic constant (γ) for oxygen=1.4, the density (ρ) for DIW=1000 kg / m3 and the hydrostatic pressure (P0) at 0.25 m depth=103800 Pascal, then the resonant radius is 1.85 μm. This means that in a 1.8 MHz acoustic field, even at very low acoustic pressure (e.g. 0.1 W / cm2), bubbles with a radius of 1.85 μm will collapse. At higher acoustic pressures (e.g. 10 W / cm2), a broader range of bubbles sizes close to the resonant radius will collapse as well.

[0068] In a particular Techsonic wafer cleaning tank, an acoustic field of 1.8 MHz and 5 W / cm2 was generated. The water and gas supply system of the tank, working at 2.5 bar overpressure and containing 18 ppm oxygen after passing a Mykrolis Phasor 2 gasification unit, operated at a flow of 8 SLM with the t...

example 2

[0070] A set of silicon substrates contaminated with 34 nm SiO2-particles was used to evaluate the cleaning performance of a single wafer megasonic cleaning tool. The formation of bubbles to achieve (generate) transient cavitation, was done using a chemical supply system prior to applying a megasonic field. A backpressure regulator was used to realize a pressure drop, which created a controlled over-saturation of a specific gas, in this case argon. This process resulted in a specific bubble distribution. To obtain this bubble distribution, ultra pure water was gasified at high pressure (Pwater=2.6 bar). The amount of argon added was chosen such that the liquid was under-saturated at the 2.6 bar level (no bubbles were present), but 20% over-saturated after the pressure drop (Pwater˜1 bar). Due to the over-saturation, the excess amount of argon created a typical bubble distribution in the supply system, which is shown in FIG. 11. The generated bubble distribution was monitored by an i...

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Abstract

The invention relates to a method for creating transient cavitation comprising the steps of creating gas bubbles having a range of bubble sizes in a liquid, creating an acoustic field and subjecting the liquid to the acoustic field, characterized in that the range of bubble sizes and / or the characteristics of the acoustic field are selected to tune them to each other, thereby controlling transient cavitation in the selected range of bubble sizes. It also relates to an apparatus suitable for performing the method according to the invention.

Description

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority benefits under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No. 60 / 612,087, filed on Sep. 21, 2004. This application also claims priority benefits under 35 U.S.C. § 119(a) to European Patent Application 04447204.1, filed on Sep. 21, 2004. U.S. Provisional Patent Application 60 / 612,087 and European Patent Application 04447204.1 are incorporated herein by reference in their entirety.BACKGROUND [0002] I. Field [0003] This disclosure relates to methods and apparatus for creating and controlling transient cavitation in a liquid. [0004] II. Description of Related Art [0005] Cavitation is generally known and defined as the activity of bubbles (e.g., gas bubbles) in a liquid. Such activity includes growth, pulsation and / or collapse of bubbles in a liquid. The pulsation of bubbles is known as stable cavitation, whereas the collapse of bubbles is known as transient cavitation. The occurrence of transi...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): B01F3/04
CPCB08B3/02B08B3/12B08B2203/0288Y10S134/902H01L21/02052H01L21/67051H01L21/67057G10K15/043
Inventor HOLSTEYNS, FRANKLEE, KUNTACK
Owner INTERUNIVERSITAIR MICRO ELECTRONICS CENT (IMEC VZW)
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