Gas and liquid contact apparatus – Contact devices – Liquid tank
Reexamination Certificate
1999-07-16
2001-08-07
Bushey, C. Scott (Department: 1724)
Gas and liquid contact apparatus
Contact devices
Liquid tank
C261S123000
Reexamination Certificate
active
06270063
ABSTRACT:
FIELD OF THE INVENTION
The instant invention pertains to semiconductor device fabrication and processing and more specifically to an apparatus for diffusing ozone in deionized-ultrapure water.
BACKGROUND OF THE INVENTION
Deionized water (“DIW” or “DI water”) is widely used throughout the semiconductor device fabrication industry. Recently, the benefits of mixing ozone in DIW were discovered. For example, a mixture of DIW and ozone was recently used to remove photoresist from bare silicon. In a broader study, the mixture of ozonated DIW was found to effectively remove most organic impurities and all kinds of particulates which are common in semiconductor device processing from a silicon wafer. In addition, the ozone/DIW mixture has been found to effectively rinse processed wafers after an etching and stripping step. Furthermore, it has been found to effectively remove metal contaminants from silicon surfaces.
However, present techniques for ozonating DIW results in low concentrations of ozone in the DIW. One such method, which is widely used, is to bubble ozone into the DIW in a DIW bath. Using this method, the ozone bubbles around the wafer as it is immersed in the DIW. Not only does this method yield very low concentration of ozone diffused in the DIW (see curve
302
of FIG.
3
), it also may result in the contamination of the wafer by small particles carried by the bubbles resulting in low ozone concentration, low particle removal efficiency, and longer process time.
Another method involves a device created by Gore Technologies. The device is configured so that a tube comprised of a porous membrane is passed within a closed container. Ozone is introduced into the container, and DIW is flowed through the container within the membrane. Optimally, the ozone passes through the membrane and ozonates the DIW. However, the ozone must remain at a fairly constant higher pressure than the DIW. In addition, the pressure of the DIW must be low and must not change too much, and the temperature of the membrane must be held at a fairly constant value which is not to high. Otherwise, the DIW will leak through the membrane and into the container. Furthermore, this method and device only marginally ozonates the DIW. Specifically, the ozone concentration is around 10 ppm using this device for its intended use in a single pass.
One other method utilizes a device fabricated by Sorbios. This device is comprised of a tube through which both DIW and ozone flow. A quartz agitator within the tube agitates the DIW and the ozone so as to ozonate the DIW. Due to its agitating nature, bubbles are generated with this device and bubbles are known to carry particles. Hence, this device may cause the contamination of a wafer, which utilizes ozonated DIW using this device. In addition, this device only marginally ozonates DIW. Specifically, the ozone concentration is around 4 ppm using this device and because the device is made of quartz, it is extremely fragile.
SUMMARY OF THE INVENTION
The diffuser as the instant invention enhances the ability of mixing the gas (preferably ozone) into a liquid stream (preferably DIW) in higher concentrations, and minimizing the time of reaching the higher concentration possible. The concentration of gas (preferably ozone) into the liquid (preferably DIW) is determined by the relative temperature of the liquid and the gas. In the particular case of ozone and DIW, the lower the temperature of the DIW, the higher the capability of concentration of ozone.
Another aspect of the instant invention involves the ability of mixing the gas (preferably ozone) and the liquid (preferably DIW) at different pressures [from 1 to 50 psi of the gas (preferably ozone) and 0.01 liters per minute to 40 liters per minute with the pressure of the gas (preferably ozone) in higher pressure than the liquid (preferably DIW)]. Another attribute of the diffuser involves the ability to separate the gas (preferably ozone) from the liquid (preferably DIW) and dispense the mixture of the liquid (preferably DIW) and the gas (preferably ozone) dissolved into the liquid without having air pockets or bubbles.
An embodiment of the instant invention is an apparatus for diffusing a first substance into a second substance, the apparatus comprising: first region where the first substance and the second substance flow in substantially the same direction; and a second region where the first substance and the second substance flow in substantially opposite directions. Preferably, the apparatus further comprises an outer structure which encompasses the first region and the second region and which is comprised of: PP, PTFE, PFA, ECTFE, PVDF, PE, PMMA, ABS, PC, PSO, PES, PEL, PBT, PPS, PEEK, PETG, Keelf, quartz, or any combination thereof. The first substance is, preferably, comprised of a substance selected from the group consisting of: ozone, ammonia, HCl, or any combination thereof, and the second substance is comprised of a substance selected from the group consisting of: DIW, ammonia, HCl, HF, peroxide, sulfuric acid, or any combination thereof.
Another embodiment of the instant invention is an apparatus for diffusing a first substance into a second substance, the apparatus comprising: a top outer wall; a bottom outer wall; a front outer wall; a back outer wall; a first side outer wall; a second side outer wall, the outer walls defining an inner space therein; a first inner wall extending from an inner surface of the bottom outer wall almost to an inner surface of the top outer wall within the inner space, a first space is present between the first inner wall and the inner surface of the top outer wall; a second inner wall extending from the inner surface of the top outer wall almost to the inner surface of the bottom wall within he inner space, a second space is present between the second inner wall and the inner surface of the bottom wall; a passage extending from first side wall substantially to the second side wall in the inner space, the first substance introduced into the passage so as to introduce the first substance into the second substance in the inner space; a first chamber formed within the inner surface and defined by the first inner wall and the first side outer wall; a second chamber formed within the inner surface and defined by the second inner wall and the second outer wall; and wherein in either the first chamber or the second chamber the first substance and the second substance flow in same direction and the first substance and the second substance flow in the opposite direction in the other of the first or second chambers. Preferably, the first inner wall, the second inner wall, the top outer wall, the bottom outer wall, the front outer wall, the back outer wall, the first side outer wall, and the second side outer wall are comprised of the same material, which is preferably comprised of: PP, PTFE, PFA, ECTFE, PVDF, PE, PMMA, ABS, PC, PSO, PES, PEI, PBT, PPS, PEEK, PETG, Keelf, quartz, and any combination thereof. The first substance is, preferably, comprised of a substance selected from the group consisting of: ozone, ammonia, HCl, or any combination thereof, and the second substance is, preferably, comprised of a substance selected from the group consisting of: DIW, ammonia, HCl, HF, peroxide, sulfuric acid, and any combination thereof.
REFERENCES:
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patent: 4673443 (1987-06-01), Fetty
patent: 5091315 (1992-02-01), McCarty et al.
patent: 5160714 (1992-11-01), Hardison
patent: 5262051 (1993-11-01), Iwatsuka
patent: 5645797 (1997-07-01), Lo
patent: 5651939 (1997-07-01), Murrer et al.
patent: 5766519 (1998-06-01), Erickson
Brady III Wade James
Bushey C. Scott
Telecky , Jr. Frederick J.
Texas Instruments Incorporated
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