U.S. patent application number 09/113440 was filed with the patent office on 2001-12-06 for cleaning apparatus.
Invention is credited to BEXTEN, DANIEL P., BRYER, CHARLES JAMES, NORBY, JERRY R..
Application Number | 20010047812 09/113440 |
Document ID | / |
Family ID | 22349423 |
Filed Date | 2001-12-06 |
United States Patent
Application |
20010047812 |
Kind Code |
A1 |
BRYER, CHARLES JAMES ; et
al. |
December 6, 2001 |
CLEANING APPARATUS
Abstract
A machine for cleaning containers has inside and outside arrays
of nozzles arranged to spray a cleaning solution onto containers
supported on a spinning rotor. Used cleaning solution is diverted
to a reclaim tank for reuse, thereby allowing low-cost cleaning
with concentrated chemicals, and with the creation of less liquid
waste requiring disposal. In a method for removing contaminants
from flat media or silicon wafer containers or carriers, a mixture
of surfactant and de-ionized water is sprayed onto containers on a
spinning rotor. The used cleaning solution is collected, filtered
and reused.
Inventors: |
BRYER, CHARLES JAMES;
(KALISPELL, MT) ; BEXTEN, DANIEL P.; (KALISPELL,
MT) ; NORBY, JERRY R.; (KALISPELL, MT) |
Correspondence
Address: |
LYON & LYON LLP
633 WEST FIFTH STREET
SUITE 4700
LOS ANGELES
CA
90071
US
|
Family ID: |
22349423 |
Appl. No.: |
09/113440 |
Filed: |
July 10, 1998 |
Current U.S.
Class: |
134/10 ;
134/102.1; 134/153; 134/2; 134/25.1; 134/25.4; 134/26; 134/28;
134/29; 134/3; 134/33; 134/95.1; 134/95.2; 134/95.3 |
Current CPC
Class: |
Y10S 134/902 20130101;
B08B 3/02 20130101; H01L 21/6704 20130101 |
Class at
Publication: |
134/10 ;
134/25.1; 134/25.4; 134/26; 134/28; 134/29; 134/33; 134/2; 134/3;
134/95.1; 134/95.2; 134/95.3; 134/102.1; 134/153 |
International
Class: |
B08B 007/04; B08B
009/08; B08B 009/20; B08B 009/093; B08B 003/00 |
Claims
We claim:
1. A method for cleaning an object comprising the steps of: loading
the object onto a rotor within a cleaning machine; spinning the
rotor carrying the object; spraying a mixture comprising water and
a surfactant towards the rotor; recovering at least some of the
used mixture of surfactant and water; and spraying the recovered
mixture of water and surfactant towards the rotor.
2. The method of claim 1 wherein the surfactant comprises from
7-13% of the mixture.
3. The method of claim 2 wherein the surfactant comprises 100% of
the mixture.
4. The method of claim 1 further comprising the step of spraying
the object with a dry gas, to dry the object.
5. The method of claim 4 wherein the dry gas comprises nitrogen or
compressed air.
6. The method of claim 1 further comprising the step of moving
filtered heated clean room air over the object.
7. The method of claim 1 wherein the water comprises de-ionized
water.
8. The method of claim 1 further comprising the step of filtering
the recovered mixture before the recovered mixture is sprayed
toward the rotor.
9. The method of claim 1 further comprising the step of spinning
the rotor at from 1-50 rpm while spraying the mixture toward the
rotor.
10. The method of claim 1 further comprising the step of spinning
the rotor at from 100-500 rpm after spraying the mixture toward the
rotor, to dry the object.
11. A method for removing contaminants from flat media carriers,
comprising the steps of: loading the carriers onto a rotor within a
flat media carrier cleaning machine; mixing a surfactant and water
to make an unused cleaning solution; spinning the rotor in a first
direction at 1-50 rpm while spraying the carriers on the rotor with
the cleaning solution; collecting the now used cleaning solution,
near the bottom of the cleaning machine; filtering the collected
cleaning solution; spraying the filtered cleaning solution and
unused cleaning solutions onto the carriers; spinning the rotor in
a second direction opposite to the first direction, while
continuing to spray filtered cleaning solution and unused cleaning
solutions onto the carriers; rinsing the carriers by spraying the
carriers with water; and drying the carriers.
12. An apparatus for cleaning flat media carriers, comprising: a
rotor rotatably mounted within a chamber; a first inside array of
nozzles and a first outside array of nozzles arranged to spray
fluid onto a flat media carrier on the rotor; a reclaim tank linked
to the chamber; a mix tank linked to the reclaim tank and to the
nozzles; a surfactant source linked to the mix tank; and a water
source connectable to the mix tank and to the nozzles.
13. The apparatus of claim 13 further comprising a plurality of
inside arrays of nozzles and a plurality of outside arrays of
nozzles, and with the mix tank connectable only to the first inside
and the first outside arrays of nozzles, and with the water source
connectable to all of the nozzle arrays.
14. The apparatus of claim 12 further comprising a housing around
the chamber, and with the mix tank supported on at least one load
cell on the housing.
15. The apparatus of claim 12 further comprising a diverter drain
connecting to the chamber, the reclaim tank, and to a waste drain,
the diverter drain including means for directing flow coming out of
the chamber to either the reclaim tank, or to the waste drain.
16. The apparatus of claim 12 further comprising a filter between
the mix tank and the first array of inside and outside nozzles.
17. The apparatus of claim 12 further comprising a plurality of
ladders on the rotor, with each ladder having multiple positions
for holding a flat media container.
Description
[0001] The technical field of this invention is cleaning apparatus
for rinsing and drying containers and carriers used to hold and
process semiconductor wafers, substrates, flat panel displays and
other flat media requiring low contamination levels.
BACKGROUND OF THE INVENTION
[0002] Flat media, such as silicon or other semiconductor wafers,
substrates, photomasks, flat panel displays, data disks, and
similar articles require extremely low contamination levels. Even
minute contaminants can cause defects. Accordingly, it is necessary
to maintain a high level of cleanliness during all or nearly all
stages of production of these types of flat media. The flat media
described may be referred to below as "wafers", although it will be
understood that "wafers" means any form of flat media.
[0003] Wafers are typically processed in batches. For example, in
manufacturing semiconductor chips, for use in computers,
telephones, televisions, and other electronic products, silicon
wafers will undergo many batch processing steps, such as oxidation,
photolithography, diffusion, chemical vapor deposition,
metallization and etching. Batch handling may occur throughout the
entire production process, or for one or more processing steps or
related handling operations. Batch processing of this type almost
always utilizes some type of carrier or container to hold the
wafers being processed.
[0004] A wafer carrier or container holds a group of wafers. The
wafer carriers can be of various designs, and are more specifically
referred to as a wafer boat. In many applications, they are made of
a suitable polymeric material, e.g., polypropylene or TEFLON.RTM.
fluoropolymer. The sides and sometimes the bottom of the wafer boat
have receiving slots formed to receive and hold the wafers in a
spaced array with the faces of the wafers adjacent to one another.
Typically, the central axes of the wafers are aligned. The wafers
are slid into the carrier or container, such as from the side or
above, and are removed by sliding them outwardly. The receiving
slots are shallow so that the wafer is engaged only at the
peripheral edges and along a thin marginal band extending inwardly
from the periphery.
[0005] Wafer carriers can also be provided in the form of a
protective case or box in which the wafers are held and are sealed
against contamination during travel within the processing facility.
Wafer carriers of this type are frequently designed to hold a wafer
boat having a complementary design. The complementary relationship
of the protective wafer carrier box and the wafer carrier boat
allow the boat and supported wafers to be fully enclosed and
securely held in place during transport. The term "carrier"
referred to below means a carrier, a container, with or without a
lid, or a wafer boat.
[0006] At certain stages in the manufacturing process, the wafer
carriers must be cleaned. Cleaning them is difficult because they
typically have features which include slots, grooves or apertures,
and inside corners. These difficulties are made worse by the
extremely low contamination levels which are required for
processing the wafers.
[0007] Accordingly, cleaning of wafer carriers remains a difficult,
time consuming and relatively costly procedure. In addition, the
carriers will often become contaminated with photoresist, a viscous
sticky material used in manufacturing various semiconductor
products. Photoresist can be especially difficult to clean away.
Sticky-back labels, fingerprints, dust, metal particles and organic
chemicals, may also contaminate the wafer carriers.
[0008] Various machines have been made and used for cleaning wafer
carriers. In these machines, the carriers are mounted on a rotor
and spin within a chamber, while cleaning solutions are sprayed
onto the carriers. The spinning movement minimizes process time and
also helps in drying the carriers. In certain applications,
surfactant has been introduced and mixed with de-ionized water, at
a concentration of approximately 1:10,000. Used in this way, the
surfactant acts as a wetting agent which helps to remove only
loosely adhered particles. The surfactant is used only once and
then discarded as waste. While this use of surfactant has improved
cleaning performance, it has been largely ineffective in removing
contaminants such as photoresist, labels, and fingerprints.
[0009] Accordingly, it is an object of the invention to provide an
improved machine for cleaning carriers and containers for flat
media.
SUMMARY OF THE INVENTION
[0010] In a first aspect of the invention, an apparatus for
cleaning flat media carriers includes a rotor rotatably mounted
within a chamber. Nozzles within the chamber are arranged to spray
a mixture of water and a detergent or surfactant on to carriers
supported on the rotor. A reclaim tank is connected to the chamber,
to collect and recycle the water and surfactant mixture. The
mixture has a concentration of surfactant sufficiently high to
remove contaminants such as photoresist, labels, and
fingerprints.
[0011] In a second aspect of the invention, used mixture of water
and surfactant is pumped through a filter before it is reused.
Filtering the used mixture allows it to be re-used many times,
without significantly reducing the cleaning effectiveness of the
machine.
[0012] In a third aspect of the invention, the water and surfactant
mixture is prepared in a mixing tank linked to the reclaim tank and
to some of the nozzles. The mixing tank facilitates achieving the
desired concentration of surfactant in the surfactant and water
solution and provides a reservoir for the solution.
[0013] In a fourth aspect of the invention, a diverter valve
diverts the run-off from the chamber to the reclaim tank, when the
water and surfactant solution is sprayed within the chamber. The
diverter valve diverts the run-off from the chamber to a waste
drain during the parts of the cleaning cycle when no surfactant is
used.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Other objects and features will become apparent from the
following detailed description taken in connection with the
accompanying drawings. However, the drawings are provided for
purpose of illustration only, and are not intended as a definition
of the limits of the invention.
[0015] In the drawings, wherein the same reference numbers denote
the same elements throughout the several views:
[0016] FIG. 1 is a front, top and right side perspective view of
the present cleaning apparatus;
[0017] FIG. 2 is a back, top and left side perspective view
thereof;
[0018] FIG. 3 is a front, top and right side perspective view of
the apparatus shown in FIGS. 1 and 2, with the covers removed;
[0019] FIG. 4 is a back, top and left side view thereof;
[0020] FIG. 5 is a back, top and left side perspective view with
various components removed for purposes of illustration;
[0021] FIG. 6 is a front, top and right side perspective view of
certain major components of the apparatus shown in FIGS. 1-5;
[0022] FIG. 7 is a perspective view of the rotor removed from the
chamber;
[0023] FIG. 8 is a plan view thereof;
[0024] FIG. 9 is a section perspective view illustrating air
movement through the apparatus;
[0025] FIG. 10 is a schematic diagram showing fluid flow and
interconnections in the present machine; and
[0026] FIG. 11 is a schematically illustrated top view showing
orientations of spray nozzles.
DETAILED DESCRIPTION OF THE DRAWINGS
[0027] Turning now in detail to the drawings, as shown in FIGS. 1
and 2, the present carrier cleaning machine 10 has a frame 12 and
housing panels 14 forming an enclosure. A back door 16 and front
door 16A are provided on the front and back surfaces of the machine
10. The machine 10 is generally installed in a clean room, of the
type used in manufacturing semiconductors. An air filter enclosure
18 is located above the front door 16A, and contains a filter which
filters clean room. An exhaust duct 26 extends out of the top of
the machine 10, at the back right corner, and is ordinarily
connected to a facility or building exhaust duct.
[0028] Referring to FIGS. 3, 6 and 9, a cylindrical chamber 24 is
supported within the frame 12. The chamber 24 has cylindrical side
walls 25 and is closed off on the top and bottom by a top plate 36
and a bottom plate 38. The top plate 36, has a central opening 37
so that air passing through the filter box 18 can flow into and
downwardly through the chamber 24. An exhaust plenum 50 at the
lower back and right side of the chamber 24 connects to the exhaust
duct 26, for moving air out of the chamber 24. A drain opening 39
at a low point of the chamber 24, in the exhaust plenum 50 drains
fluids out of the chamber.
[0029] Referring to FIGS. 5, 9 and 11, outer rinse manifolds 28,
each having e.g., 12 spray nozzles, are positioned around the
outside circumference of the chamber 24, on the chamber cylindrical
side walls 25. The manifolds 28 may be located on the outside of
the cylindrical side walls 25, as shown in FIGS. 4-6 and 10, or may
be on the inside surface of the cylindrical side walls 25, SO long
as the rinse spray nozzles 30 on the outer rinse manifolds 28 are
appropriately positioned to spray the work pieces, i.e., the wafer
carriers.
[0030] Inner rinse manifolds 29 are positioned near the center of
the chamber 24, with each inner rinse manifold having a plurality
of rinse spray nozzles 30 oriented to spray outwardly on to the
work pieces (i.e., wafer carriers, containers or lids).
[0031] Similarly, outer dry manifolds 64, each having a plurality
of dry spray nozzles 66, are spaced apart around the circumference
of the chamber 24, on the chamber cylindrical side walls 25. Inner
dry manifolds 65, each also having a plurality of dry spray nozzles
66 are positioned near the center of the chamber 24. The preferred
orientation of the dry manifolds (D1-D8) and the rinse manifolds
(R1-R8) is shown in FIG. 11.
[0032] Referring momentarily to FIG. 10, the dry manifolds are
connected via fluid lines to a supply of pressurized gas, such as
air or nitrogen. The rinse manifolds 29 are connected via fluid
lines to a source of de-ionized (DI) water, and to a mix tank 32.
Pressurized gas lines are also connected to the spray manifolds,
for purging. A boost pump 46 increases the water pressure of the
DI-water from the external source 110 to the rinse manifolds 28 and
29.
[0033] Referring to FIGS. 3-6, and 10, the mix tank 32 is suspended
on load cells 52 supported on the frame 12. A surfactant tank or
bottle 35 is connected to the mix tank 32 via a fluid line and a
surfactant delivery pump 49. An external source of de-ionized water
110 is connected to the mix tank 32 via a fluid line. The mix tank
32 is also connected via fluid lines, and via a mix tank pump 48
and control valves 47 to a outer rinse manifold 28 (manifold R6 in
FIGS. 10 and 11) and to an inner rinse manifold 29 (manifold R3 in
FIGS. 10 and 11). A filter 34 is placed in the fluid line from the
mix tank 32, before the manifolds 28 and 29. Pump 48 pumps
surfactant from the tank or bottle 35 into the mix tank 32. Pump 49
pumps the DI-water/surfactant solution from the mix tank 32, to the
rinse manifolds 28 and 30.
[0034] The drain opening 39 at the bottom of the chamber 24 leads
to a diverter 90 which connects the drain opening 39 to either a
reclaim tank 42, or to a facility waste drain 92. Referring to FIG.
10, the reclaim tank 42 is connected to the mix tank 32 via a fluid
line having a reclaim pump 44 and a reclaim filter 45. Flow sensors
33 are provided around the filters 34 and 45, to monitor filter
flow and signal for filter replacement when needed.
[0035] Referring momentarily to FIG. 9, air heaters 58 are provided
within an air inlet plenum 56 behind the air filter box 18 and over
the center or inlet opening 37 leading into the top of the chamber
24. Blanket heaters 55 are also provided around the top of the
chamber 24. A computer/controller 112 is linked to and controls the
various pumps, valves and heaters, and is linked to and receives
input from the flow sensors and load cells, described above.
[0036] Referring to FIGS. 6-9, a rotor 70 is rotatably supported
within the chamber 24 on a base 104. The rotor has a top ring 72
and a bottom ring 74 connected by a frame work 75. Ladders 76 are
pivotally supported on upper and lower ladder supports 82 extending
radially outwardly from the top ring 72 and the bottom ring 74.
Each ladder 76 has a plurality of compartments 78 for holding
containers or carriers 85, or container lids 87, as shown in FIG.
9. The configuration of the ladders 76 and the design of the
compartments 78 on the ladders 76 are adapted for the specific
sizes and types of carriers, containers, and lids to be cleaned.
The entire rotor 70 is rotatably supported on a center column 100
and a rotor axle 106 within the center column 100. A rotor drive
motor 102 spins the rotor 70. The detailed design features of the
rotor 70, center column 100 and rotor axle 106 are well known, and
are described in U.S. Pat. No. 5,224,503, incorporated herein by
reference.
[0037] A facilities panel 40 on the machine 10, as shown in FIG. 6,
has connections to input de-ionized water and gas, e.g., nitrogen
or air into the machine 10, and a connection for the waste drain
92, as well as gauges and valves for measuring and controlling
fluid/gas flow.
[0038] In use, the machine 10 is typically installed in a silicon
wafer or other flat media manufacturing facility. As the wafers are
moved through various processing steps, the carriers 85 become
contaminated, and must be cleaned before wafers are replaced into
the carriers. The door 16 or 16A of the machine 10 is opened. The
rotor 70 is turned or indexed until a ladder 76 is aligned with the
door. The ladder 76 is then turned 180.degree. SO that the empty
compartments 78 can be accessed through the door 16. The carriers
85 are loaded into the compartments 78 and the ladder is turned
back to its original position, so that the compartments 78 are
facing to the inside of the chamber 24. The ladders 76 are
preferably provided with a latch or detent to lock the ladders into
the closed or operating position, with the compartments 78 facing
the inside of the chamber 24. The next ladder 76 is then brought
into alignment with the door, for loading, by turning the rotor 70
(by hand or via control of the rotor drive motor 102). Loading
continues until all of the ladders 76 are filled.
[0039] The surfactant tank 35 is supplied with a detergent or
surfactant, for example, Valtron DP 94001 (a high pH alkaline
detergent) a preferred surfactant for removing photoresist. The
term "surfactant" as used in this application means a surfactant or
a detergent. The controller 112, via appropriate control of valves
and pumps, delivers DI-water and surfactant into the mix tank 32,
to make a desired surfactant solution in the mix tank 32.
Preferably, the solution is 4-15% surfactant, with the balance
being DI-water, and more preferably the solution is 7-13%
surfactant, with the balance being DI-water. The load cells 52
supporting the mix tank 32 provide the weight of the load tank 32
and its contents to the controller 112. Accordingly, the controller
112 can create a surfactant solution of the desired surfactant
concentration by monitoring the output of the load cell 52, as the
tank 32 is incrementally filled step-wise with water and
surfactant. The controller 112 controls the rotor drive motor 102,
causing the rotor 70 to spin in a first direction, at a low speed,
e.g., 1-50 rpm. Via control of the mix tank pump 49 and valves 47,
the DI-water/surfactant solution is sprayed onto the carriers 85 on
the spinning rotor. The surfactant solution is preferably applied
from only two manifolds, inner rinse manifold R3, and outer rinse
manifold R6 (instead of from all 8 manifolds using conventional
techniques) in order to allow more soak time.
[0040] After a sufficient duration e.g., 3-10 minutes, the rotor 70
reverses direction while the surfactant solution spraying
continues, for improved spray coverage. The inner rinse manifolds
29, located inside of the rotor 70, spray radially outwardly from
the center of the chamber 24. The outer rinse manifolds 28, located
around the chamber cylindrical side walls 25 spray radially
inwardly toward the chamber center. This dual spray action,
combined with bi-directional rotation of the rotor 70, provides
virtually complete coverage of all surfaces of the containers
85.
[0041] As the surfactant solution runs down within the chamber 24
and out the drain opening 39, the diverter 90 is switched or
positioned to channel the surfactant solution into the reclaim tank
42. When the fluid level in the reclaim tank 42 is sufficiently
high, the reclaim pump 44 switches on, pumping the reclaimed
surfactant solution through the reclaim filter 45 and into the mix
tank 32. Consequently, the surfactant solution made in the mix tank
32 (unused surfactant and DI-water) is supplemented with the
reclaimed and filtered surfactant solution. After completion of
application of the surfactant solution, the manifolds R3 and R6 are
purged by gas or nitrogen flowing through check valves and the
control valves 47, as shown in FIG. 10.
[0042] As the machine 10 begins the rinse cycle, the diverter 90
switches position, to connect the drain opening 39 to the facility
waste drain 92. DI-water is sprayed onto the carriers 85 from all
of the rinse manifolds (R1-R8), with the rotor 70 spinning in a
first direction, and then reversing and spinning in the opposite
direction, e.g., at from 1-50 rpm, preferably about 6 rpm. The
heaters 58 are then turned on, and the rotor accelerated up to
e.g., 300 rpm, so that water droplets on the containers 85 are
centrifugally flung off of the containers, and the containers are
dried. The blanket heaters 55 are located on the outside of the top
of the chamber 24 and are on continuously, for warming the top of
the chamber. The DI rinse water goes out the waste drain 92.
[0043] While the machine 10 is useful for cleaning various
contaminants, it is especially useful for removing photoresist. Due
to its adhesive characteristics, photoresist has been difficult to
remove. While it can be removed with various solvents, use of
solvents is highly disadvantageous, due to the risk of explosion or
fire resulting from volatile solvent vapors. In addition, solvents
can also be toxic and harmful to people and the environment,
therefore requiring special containers, shipping, storage,
collection and disposal procedures, all of which can be costly and
time-consuming. The specific cleaning parameters, such as duration
of surfactant, rinse water, and air/gas spray, rotation speeds and
sequences, heater operation, etc., will, of course, be varied
somewhat to achieve optimum results, with different containers and
contaminants, as is well known in this technology.
[0044] Surfactants, on the other hand, are not flammable or
explosive, and do not have the same environmental disadvantages
associated with solvents. On the other hand, surfactants can be
very expensive, e.g., $40/gallon. Automatic cleaning of containers
(in a large machine) consumes about 16 gallons of DI-water per
minute. Using a 10% surfactant solution, a 12 minute photoresist
removal step would use about 6 gallons of surfactant, costing $240,
making automatic large-scale cleaning of containers extremely
expensive or even prohibitive. However, in the present machine 10,
the surfactant solution is reclaimed, filtered and reused over and
over again. Consequently, for the cost of e.g., 6 gallons of
surfactant, many more containers can be cleaned.
[0045] Over time, and with repeated use, the cleaning efficiency of
the surfactant degrades. Consequently, periodically, (e.g, every
month) the surfactant solution is preferably removed from the
machine 10 and replaced with new surfactant. Referring to FIG. 10,
the entire contents of the reclaim tank 42 are pumped into the mix
tank 32. The mix tank drain valve 41 is opened and the drain pump
43 turned on, so that the entire contents of the mix tank 32 are
pumped out to the waste drain 92. The machine 10 is then prepared
to make a new and entirely unused, surfactant solution, as
described above. The filters 34 and 45 may be replaced more
frequently, as needed.
[0046] The machine 10, by virtue of its recovery or reclaim system,
enables use of highly concentrated cleaning solutions, such as
surfactants, detergents, and ozonated DI-water, for cleaning
containers. Solvents, although not ordinarily preferred, could also
be used and reclaimed. The reclaim or recovery system allows
repeated processing using the same chemical over and over again,
thus eliminating the large expense of one-time use. In addition,
the reclaim system is environmentally friendly as it avoids
releasing large amounts of chemicals into the waste drain.
Moreover, as the machine 10 allows the use of chemicals in a
concentrated form, more difficult forms of contaminants, such as
photoresist, sodium, sticker residues, metals, etc., can be
effectively cleaned. Thus, the present machine 10 offers improved
cleaning at reduced costs, and in a more environmentally safe
way.
[0047] Thus, a novel cleaning machine and method has been shown and
described. Various changes can, of course, be made without
departing from the spirit and scope of the invention. The
invention, therefore, should not be restricted, except to the
following claims and their equivalents.
* * * * *