Mechanical wet air generator

Details Mechanical wet air generator Mechanical wet air generator

1999-08-03

2001-03-06

Smith, Duane S. (Department: 1724)

Gas and liquid contact apparatus

Contact devices

Porous mass

C096S158000, C096S181000, C096S219000

Reexamination Certificate

active

06196526

ABSTRACT:

FIELD OF THE INVENTION
The present invention generally relates to a mechanical wet air generator and more particularly, relates to a mechanical wet air generator that is equipped with an inner container and an outer container with a fluid level controller situated in the outer container and a multiplicity of Rashing rings situated in the inner container for breaking up bubbles and for maximizing wet surface areas for contact with an input air flow to produce a wet air output. The present invention mechanical wet air generator may optionally contain a demister connected in series with and downstream of the wet air generator for separating over-saturated water from the wet air.
BACKGROUND OF THE INVENTION
Mechanical wet air generators, or wet N
2
generators have been used in the chemical processing industry for providing wet air or wet N
2
. Normally, a clean dry air (CDA) or a N
2
gas contains between about 20% and about 30% RH (relative humidity) which is not suitable for many chemical processes wherein a wet air blanket or a wet N
2
blanket is necessary.
For instance, in a slurry supply tank used for an oxide slurry supply system for chemical mechanical polishing, a wet N
2
blanket must be used to shield the slurry solution from dry air and to dispense the slurry without drying the slurry particles. When the N
2
gas used has a low water content, i.e., at 20~30% RH, some of the slurry particles tend to dry up and adhere to other particles and forms particles in forming particles of significantly larger size. This presents a serious scratching problem when the slurry solution is subsequently dispensed on a wafer surface for polishing. In a normal slurry solution, the composition ratio between solids and water is approximately 1:1. When the nitrogen blanket or the clean dry air blanket covering the slurry solution contains less than 30% RH, the water content in the slurry may further vaporize and thus causing the formation of larger particles. The use of a wet N
2
, or a wet CDA blanket over a slurry solution is therefore an important processing step that must be carried out in order to assure the reliability of the CMA process.
Conventionally, wet air or wet N
2
is provided by a wet air generator or a wet N
2
generator such as that shown in
FIGS. 1 and 2
.
FIG. 1
shows a wet N
2
generator
10
constructed of three wet N
2
generation chambers
12
. In each of the generation chamber, a gas/water inlet
14
is provided at the bottom of the chamber. A mixture of N
2
gas and water is pumped into inlet
14
through a flow control apparatus
20
. Each of the wet N
2
generator
12
, also shown in
FIG. 2
, is filled with a filter-type material for retaining water and for maximizing the contact area with nitrogen gas that is fed therethrough. The wet N
2
generator chambers
12
are further equipped with heating means (not shown) such that water may be heated inside the chamber to further increase the humidity content of N
2
gas purged therethrough. The water level in each of the generator chamber
12
is controlled by level sensors “H” for high level detection and “L” for low level detection. These are shown in
FIG. 1
as
22
for the high level sensor and
24
for the low level sensor. The nitrogen gas which carries moisture then exits the wet N
2
outlet
28
mounted at the top of each of the wet N
2
generator chamber
12
.
The conventional wet N
2
generator shown in
FIGS. 1 and 2
, even though widely used, presents many processing disadvantages. First, large bubble formation in the wet N
2
generator chambers frequently causes the malfunction of the water level sensors. The malfunction causes the level sensors to be turned on and off constantly and furthermore, causes water to overflow into a slurry piping. The constant turn on and off of the level sensors further necessities frequent adjustments and maintenance procedures to be performed. Moreover, the conventional wet N
2
generator chambers are not equipped with protection devices for preventing overflow of water into the slurry piping which dilutes the slurry solution, decreases its concentration and thus makes the process control of the CMP process very difficult. The conventional wet N
2
generator chambers are not equipped with means for removing over-saturated water contained in wet N
2
. The large bubbles produced further reduces the wetting effect of water such that a higher heating temperature of water is equipped leading to a more difficult to control process.
It is therefore an object of the present invention to provide a mechanical wet air generator does not have the drawbacks or shortcomings of the conventional generators.
It is another object of the present invention to provide a mechanical wet air generator that is equipped with an inner container formed of perforated panels situated inside an outer container of fluid-tight construction for establishing fluid communication with an inner cavity of the inner container.
It is a further object of the present invention to provide a mechanical wet air generator that is capable of producing either wet air or wet N
2
.
It is another further object of the present invention to provide a mechanical wet air generator that is equipped with a reliable fluid level controller for controlling the fluid level in the generator such that an overflow of fluid into a slurry pipe is prevented.
It is still another object of the present invention to provide a mechanical wet air generator that is equipped with an inner container filled with a multiplicity of bubble-breaking solid shapes for preventing the formation of large bubbles.
It is yet another object of the present invention to provide a mechanical wet air generator which is capable of producing wet air or wet N
2
that contains at least 90% relative humidity.
It is still another further object of the present invention to provide a mechanical wet air generator that is further equipped with a demister in series connected and downstream to the wet air generator for separating over-saturated water from the wet air.
It is yet another further object of the present invention to provide a mechanical wet air generator that is equipped with an inner container further includes a heater and a thermocouple for controlling a temperature of the fluid contained in the cavity of the inner container.
SUMMARY OF THE INVENTION
In accordance with the present invention, a mechanical wet air generator that is equipped with an inner container, an outer container, a fluid level controller and a multiplicity of bubble-breaking solid shapes in the inner container that is effective in producing wet air substantially without bubbles is provided.
In a preferred embodiment, a mechanical wet air generator is provided which includes an inner container formed of perforated panels defining an inner cavity therein, the inner cavity is filled with a multiplicity of bubble-breaking solid shapes and a fluid, an outer container of fluid-tight construction for holding the inner container therein and for establishing fluid communication with the inner cavity in the inner container, a fluid level controller situated in the outer container for controlling a fluid level in the inner and outer containers by opening/closing a fluid inlet, an air inlet and an air outlet in the outer container, the air inlet is adapted for directing an air flow towards a bottom of the inner container and the air outlet is adapted for outputting wet air from a top portion of the cavity of the outer container.
In the mechanical wet air generator, the air flow may be a nitrogen gas flow or a clean dry air flow. The inner container may be formed of honeycombed panels for penetrating a fluid therethrough and for breaking large bubbles. The wet air generator may be a wet N
2
generator. The air flow through the air inlet may be a clean dry air or N
2
.
In the mechanical wet air generator, the multiplicity of bubble-breaking solid shapes is Rashing ring for preventing formation of large bubbles. The fluid level controller may include a floater, a floating valve and a linkage connecting

Affiliated with

Also associated with

Rating

Mechanical wet air generator does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Mechanical wet air generator, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Mechanical wet air generator will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2534943