U.S. patent application number 08/996100 was filed with the patent office on 2001-11-08 for etching apparatus for manufacturing semiconductor devices.
This patent application is currently assigned to CHOUL-GUE PARK. Invention is credited to PARK, CHOUL-GUE.
Application Number | 20010037856 08/996100 |
Document ID | / |
Family ID | 19490525 |
Filed Date | 2001-11-08 |
United States Patent
Application |
20010037856 |
Kind Code |
A1 |
PARK, CHOUL-GUE |
November 8, 2001 |
ETCHING APPARATUS FOR MANUFACTURING SEMICONDUCTOR DEVICES
Abstract
An etching apparatus for manufacturing semiconductor devices
which reduces contamination of the processing surface of a wafer by
transporting a plurality of wafers stacked in a cassette with their
processing surfaces facing down from the cassette supply chamber to
one or more process chambers where the etching operation is
performed on each wafer, one at a time. The apparatus has a load
lock chamber for transferring the wafers stacked in the cassette
from the cassette supply chamber, which is maintained under
atmospheric conditions, to the process chamber, which is maintained
under a strong vacuum. The process chamber has a cathode to which a
wafer is clamped by a wafer holder with its processing surface
facing down; the process chamber may also have a removable lower
cover for easy repair and cleaning. The apparatus may also have a
wafer aligning chamber installed between the cassette supply
chamber and the load lock chamber for simultaneously aligning all
of the wafers n the cassette before they are transported to the
load lock chamber. The wafer aligning chamber also has a cassette
transport mechanism for transferring the cassette from a cassette
supply table in the cassette supply chamber to an elevator
installed in the load lock chamber.
Inventors: |
PARK, CHOUL-GUE;
(SUWON-CITY, KR) |
Correspondence
Address: |
JONES & VOLENTINE
12200 SUNRISE VALLEY DRIVE SUITE 150
RESTON
VA
20191
|
Assignee: |
CHOUL-GUE PARK
|
Family ID: |
19490525 |
Appl. No.: |
08/996100 |
Filed: |
December 22, 1997 |
Current U.S.
Class: |
156/345.31 ;
118/719; 118/731; 118/733 |
Current CPC
Class: |
H01L 21/67775 20130101;
H01L 21/68 20130101; H01L 21/67201 20130101; H01L 21/67167
20130101; H01L 21/6719 20130101 |
Class at
Publication: |
156/345 ;
118/719; 118/731; 118/733 |
International
Class: |
C23C 016/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 24, 1996 |
KR |
96-70900 |
Claims
What is claimed is:
1. An etching apparatus for manufacturing semiconductor devices,
comprising: one or more process chambers for etching a wafer, the
wafer having its processing surface facing down; a cassette supply
chamber for supplying a plurality of wafers to the process chamber,
the cassette supplying chamber having a cassette supply table for
receiving a cassette, the cassette having two or more supporting
legs and housing a plurality of wafers stacked in the cassette with
their processing surfaces facing down; a load lock chamber for
transferring the wafers housed in the cassette from the cassette
supply chamber which is maintained under atmospheric conditions, to
the process chamber which is maintained under a strong vacuum, the
load lock chamber being installed between the process chamber and
the cassette supply chamber, the load lock chamber having an
elevator for moving the cassette up and down, and having a wafer
transporting mechanism for transferring the wafers from the
cassette to the process chamber one by one while maintaining the
orientation of each wafer with the process surface facing down; and
a cassette transport mechanism for transferring the cassette from
the cassette supply table in the cassette supply chamber to the
elevator in the load lock chamber.
2. The apparatus as claimed in claim 1, wherein the process chamber
comprises: a chamber body encompassing a sealed volume and a side
opening in communication with the load lock chamber which opening
is sealed by a door, and a removable lower cover; a cathode
installed in a top part inside the chamber body, onto which cathode
the wafer is clamped with its processing surface facing down; a
wafer loading mechanism for receiving the wafer supplied to the
process chamber from the load lock chamber, and for clamping the
wafer against the cathode; and a process gas supplying component
installed in a bottom of the chamber body for supplying the process
gas to the process chamber for etching the wafer processing
surface.
3. The apparatus as claimed in claim 2, wherein the wafer loading
mechanism comprises: a loader that moves up and down between a
plurality of positions: (a) a stand-by position which allows a
wafer to be inserted into the loader; (b) a first loading position
above the stand-by position; and (c) a second loading position
above the first loading position, for adhering the wafer to the
cathode with its processing surface facing down; a holder that
moves up and down between a plurality of positions: (a) the
stand-by position which allows the wafer to be inserted into the
holder; and (b) the second loading position which permits the
holder to clamp the wafer against the cathode with its processing
surface facing down; a driving means for moving the loader and the
holder up and down between their respective positions; and a
position controller, for stopping the loader and the holder
precisely at their respective positions.
4. The apparatus as claimed in claim 3, wherein lifters are fixed
to the bottom of the loader and the holder to support the outside
of the wafer when transporting and clamping the wafer.
5. The apparatus as claimed in claim 3, wherein the drive means
comprises: a first upper actuating cylinder housing and a second
lower actuating cylinder housing stacked on top of the chamber
body, having two concentric rods passing through sealed openings in
the housings, comprising; an inner rod passing through the center
of the first and second cylinder housings, a lower part of the
inner rod passing through the chamber body, a lower end of the
inner rod suspending the cathode and being attached to a top hub of
the loader at a central position, and an upper part of the inner
rod passing through the first cylinder housing to the outside of
the process chamber; a outer rod, an upper part of which terminates
in the second cylinder housing, a lower end of the outer rod
passing through the chamber body and being attached to a top hub of
the holder at a central position; a first piston fixed to the inner
rod and positioned in the first cylinder housing; a second piston
fixed to the second rod and positioned in the second cylinder
housing; springs installed under the first and second pistons in
the respective first and second cylinder housings to supply upward
restoring forces; and air supplying lines for supplying air
pressure to the first and second cylinder housings to pneumatically
actuate the first and second pistons up and down.
6. The apparatus as claimed in claim 5, wherein the position
controller for the loader comprises: a light emitter installed on
an arm attached to the top part of the inner rod which part extends
through the first cylinder housing to the outside; and three photo
sensors installed on a vertical member that is fixed to an outside
top part of the first cylinder housing, with the photo sensors
positioned on the vertical member so that each photo sensor is
opposite to the light emitting sensor and is positioned so that the
first photo sensor determines the stand-by position of the loader,
the second photo sensor determines the first loading position, and
the third photo sensor determines the second loading position of
the loader.
7. The apparatus as claimed in claim 5, wherein the position
controller of the holder comprises: a light emitter attached to the
outside of the outer rod between the second cylinder housing and
the chamber body; and two photo sensors attached to the inside of a
bracket installed between the second cylinder and the top of the
process chamber body through an arm, so that each photo sensor is
opposite to the light emitting sensor and is positioned so that the
first photo sensor determines the stand-by position of the holder
and the second photo sensor determines the second clamping position
of the holder.
8. The apparatus as claimed in claim 2, wherein the process gas
supply component comprises: a gas spray plate installed in the
bottom of the chamber body and above the lower cover, the plate
having a plurality of gas orifices, and the plate installed at a
predetermined interval with respect to the lower cover; seals
between the chamber body and the gas spray plate, and between the
gas spray plate and the lower cover to seal the chamber body, and a
gas supply line passing through the lower sidewall of the chamber
body with one end of the line passing through the gas spray plate
and terminating between the gas spray plate and the lower cover,
thereby supplying gas to the space between the gas spray plate and
the lower cover.
9. The apparatus as claimed in claim 2, wherein the sealing means
of the lower cover comprises: a plurality of bosses attached to the
bottom of the lower cover; and a plurality of threaded supporting
legs having inserted into the bosses.
10. The apparatus as claimed in claim 9, wherein the sealing means
further comprises a plurality of levelers threaded onto the
threaded part of the supporting legs to allow the lower cover to be
raised and lowered in order to support the bosses.
11. The apparatus as claimed in claim 9, further comprising, wheels
attached to the bottom of each supporting leg on the lower cover;
and a plurality of rails attached to a base for guiding each wheel,
the rails extending beyond the process chamber body for a distance
which is at least as long as the width of the lower cover, thereby
permitting the lower cover to roll on wheels along the rail in a
horizontal direction to a position alongside the chamber body.
12. The apparatus as claimed in claim 1, wherein the cassette
supply table comprises: a base table; multiple fixing tables
stacked at a predetermined interval from each other for receiving
the cassette, each fixing table having a supporting board on which
the cassette is laid, and having vertical bars attached to both
sides of the supporting board, the fixing tables having a support
column fixed to the bottom of the lowest fixing table and passing
through the lower base table; a fixing means for fixing the
cassette laid on the fixing table; and a vertical shifting means
for raising and lowering the fixing tables.
13. The apparatus as claimed in claim 12, wherein the fixing means
comprises: pneumatic actuating cylinders installed under the
vertical bars; and a clamping bar installed in the upper part of
the vertical bars for clamping the top of the cassette, and moved
by the pneumatic actuating cylinders, the cylinders having cylinder
rods that are attached to a free end of the clamping bar thereby
enabling the clamping bar to clamp and release the cassette.
14. The apparatus as claimed in claim 12, wherein the vertical
shifting means comprises: a latitudinal plate connected to the
lower side of the lowest fixing table; a ball screw passing through
the base table and the latitudinal plate, and extending upward
through the latitudinal plate; a ball bearing disposed within the
latitudinal plate and installed between the latitudinal plate and
supporting the ball screw, the ball bearing being guided by the
ball screw and enabling the latitudinal plate to shift up and down
according to the rotating direction of the ball screw; multiple
guide rods passing through the latitudinal plate on both sides of
the ball screw, supporting the up/down movement of the latitudinal
plate, the lower part of each guide rod being attached to the base
table; a motor for rotating the ball screw; and a pair of pulleys
and a belt for transmitting power from the motor to rotate the ball
screw.
15. The apparatus as claimed in claim 1, further comprising: a
wafer aligning chamber containing a wafer aligning mechanism
installed between the cassette supply chamber and the load lock
chamber for simultaneously aligning the multiple wafers stacked in
the transported cassette, and for transferring them to the load
lock chamber.
16. The apparatus as claimed in claim 15, wherein the wafer
aligning mechanism comprises: a base to which a vertical frame is
attached; an aligning table on which the cassette is laid, with the
table being installed in the vertical frame so as to permit the
aligning table to rotate; a wafer aligner, installed on the base,
for simultaneously aligning multiple wafers stacked in the cassette
setting their flat edges together; and a driving means for rotating
the aligning table and placing the cassette on the wafer
aligner.
17. The apparatus as claimed in claim 15, wherein the aligning
table comprises: an aligning plate to receive the cassette is laid,
the plate having a slide prevention groove into which the
supporting legs of the cassette are inserted; and a clamping means
for clamping the cassette to the aligning plate.
18. The apparatus as claimed in claim 15, wherein the cassette
transport mechanism comprises: a spindle for rotating and moving
the cassette up and down, a drive mechanism for driving the
spindle, the drive mechanism positioned under the aligning plate
and fixed to the base of the wafer aligning mechanism; a fork for
gripping and lifting the cassette; and a plurality of arms
connecting the spindle to the fork.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an etching apparatus for
manufacturing semiconductor devices, and more particularly, to an
etching apparatus which reduces contamination of the surface of
wafers during the step of transporting wafers to a process chamber
and the step of etching the wafer as well as reducing the time it
takes to transport and etch the wafers.
[0003] 2. Discussion of Related Art
[0004] The manufacture of semiconductor devices involves many
processes, including photolithography, etching, and thin film
fabrication, which are repeatedly performed during the
manufacturing process. The etching process is required to eliminate
any unnecessary film on the wafer, and can be divided into
wet-etching processes utilizing chemicals, and dry-etching
processes utilizing plasma.
[0005] FIGS. 1 and 2 schematically illustrate the structure of a
conventional dry-etching apparatus. The conventional dry-etching
apparatus has multiple process chambers 1; a load lock chamber 3
disposed between the process chamber 1 and the wafer supply
mechanism part 2 which supplies wafers W to the vacuum process
chamber 1 with the processing surface of the wafers facing up; and
an aligner 4 for aligning a flat edge of the wafer W so that the
wafers W are aligned before they are supplied to process chamber
1.
[0006] In the conventional apparatus, process chamber 1 has a
cathode 5 on which the wafer W is laid with the processing surface
of the wafer facing upward. The gas supply diffuser 11 supplies a
process gas to process chamber 1 wherein the gas immediately forms
a plasma that etches the upward-facing processing surface of the
wafer. The inside of processing chamber 1 is maintained under a
strong vacuum to assure a stable etching process.
[0007] Inside load lock chamber 3, there is an elevator 6 and a
robot 7. The arm 12 of the robot 7 loads wafers from cassette 8 of
the wafer supply mechanism 2 onto elevator 6, where the wafers W
are stacked. The arm 12 of robot 7 takes one wafer W at a time from
the elevator 6 as arm 12 moves up and down to align the wafer
through the aligner 4. Arm 12 then transports wafer W to process
chamber 1 where the etching step takes place. After etching, the
wafer W is loaded in wafer block 9 on the elevator 6 and is
returned to the wafer supply mechanism 2.
[0008] Transporting wafers W from the wafer supply mechanism 2 to
the process chamber 1 is a slow process. First, the wafers W
stacked in the cassette 8 of the wafer supply mechanism 2 are
transported one by one, and sequentially inserted into the wafer
block 9 of the load lock chamber 3. The wafer supply mechanism 2
has a table 10 on which at least one cassette 8 is laid. The table
10 moves horizontally to the left and right, and thus allows for a
continuous supply of wafers W stacked in multiple cassettes 8. The
wafers W in the wafer block 9 are then transported one by one to
the aligner 4 where their flat edges are aligned. After aligning,
the wafers W are transported one at a time with the processing
surface facing upward to the process chamber 1 where they are
etched. In the conventional apparatus, the wafers are transported
and aligned individually which is slow and inefficient, resulting
in decreased productivity.
[0009] The wafer supply mechanism 2 is maintained under atmospheric
conditions, while the process chamber 1 is maintained under a
strong vacuum to facilitate the plasma etching step. When the
wafers W are transported to the wafer block 9 inside the load lock
chamber 3 from the wafer supply mechanism 2, care must be taken to
maintain the path to the process chamber 1 from the load lock
chamber 3 in the high vacuum state. To accomplish this, load lock
chamber 3 is maintained under atmospheric conditions while the
wafer W is transported from wafer supply mechanism 2 to load lock
chamber 3. Before transporting the wafer W from the load lock
chamber 3 to the process chamber 1, the path between the load lock
chamber and the wafer supply mechanism 2 is closed. The path
between load lock chamber 3 and process chamber 1 is then opened so
that the load lock chamber 3 can be put under a high vacuum thereby
reducing the pressure difference between load lock chamber 3 and
process chamber 1.
[0010] Contamination of the surface of the wafer W causes failures
in the etching process. Therefore, it is important that the inside
of the load lock chamber 3 and the process chamber 1 be clean. It
is also necessary that the apparatus itself be placed in a clean
environment to effectively prevent contamination of the wafer and
the chambers of the apparatus.
[0011] There is a high risk of contamination of the upward-facing
processing surface of the wafers W from particles that become
attached to the surface as the wafers W are transported from the
wafer supplying part 2 through load lock chamber 9 to the process
chamber 1 where they are etched. Therefore, a need exists for an
etching apparatus for manufacturing semiconductor devices that is
faster and more efficient, and that reduces particle contamination
of the wafer surface.
SUMMARY OF THE INVENTION
[0012] An objective of the present invention is to provide an
etching apparatus for manufacturing semiconductor devices which
reduces contamination of the processing surface of the wafers
caused by environmental contaminants while the wafer is transported
back and forth between the wafer supply mechanism and the process
chamber where the wafer is etched.
[0013] It is another aspect of the present invention to reduce the
process time required to transport the wafers back and forth
between the wafer supply mechanism and the process chamber where
the wafer is etched, and the time required to align the flat edges
of the wafers, thereby enhancing operational efficiency of the
etching apparatus.
[0014] To achieve these and other advantages, the present invention
provides an etching apparatus for manufacturing semiconductor
devices, having one or more process chambers for etching a wafer
with the processing surface facing down during the etching step.
The apparatus has a cassette supply chamber for supplying a
plurality of wafers to the process chamber, and the cassette
supplying chamber has a cassette supply table for receiving a
cassette housing a plurality of wafers stacked in the cassette with
their processing surfaces facing down. A load lock chamber is
provided for transferring the wafers housed in the cassette from
the cassette supply chamber which is maintained under atmospheric
conditions, to the process chamber which is maintained under a
strong vacuum, the load lock chamber being installed between the
process chamber and the cassette supply chamber, and having an
elevator for moving the cassette up and down. The load lock chamber
also has a wafer transporting mechanism for transferring the wafers
from the cassette to the process chamber one by one while
maintaining the orientation of each wafer with the processing
surface facing down; and a cassette transport mechanism for
transferring the cassette from the cassette supply table in the
cassette supply chamber to the elevator in the load lock
chamber.
[0015] In a preferred embodiment, the process chamber encompasses a
sealed volume and has a side opening in communication with the load
lock chamber which opening is sealed by a door, and a removable
lower cover for easy cleaning and repair. The process chamber also
has a cathode installed in the top part inside the chamber body,
onto which cathode the wafer is clamped with its processing surface
facing down to minimize contamination of the surface of the wafer
during transport to and from the process chamber and during
etching. The process chamber has a wafer loading mechanism for
receiving the wafer supplied to the process chamber from the load
lock chamber, and for clamping the wafer against the cathode.
Finally, the process chamber has a process gas supplying component
installed in the bottom of the chamber body for supplying the
process gas to the chamber for etching the downward-facing wafer
processing surface.
[0016] In a preferred embodiment, the wafer loading mechanism has a
wafer loader for loading the wafer onto the cathode and a wafer
holder for clamping the wafer onto the cathode. The positions of
the wafer loader and the wafer holder are determined by sensors. In
another aspect of the present invention, the wafer loader and the
wafer holder are moved up and down inside the process chamber by a
driving means that is driven by pneumatic pressure.
[0017] In a preferred embodiment, the etching apparatus has a
process gas supply component, comprising a gas spray plate having a
plurality of gas orifices that is installed in the bottom of the
chamber body at an interval above the lower cover. Process gas is
supplied by a gas supply line that passes through the lower
sidewall of the process chamber body with one end of the line
passing through the gas spray plate and terminating at a point
between the gas spray plate and the lower cover, thereby supplying
process gas to the space between the gas spray plate and the lower
cover.
[0018] In another aspect of the invention, the cassette supply
chamber has a cassette supply table that has multiple fixing tables
stacked at a predetermined interval from each other for receiving a
cassette. The fixing tables have pneumatically driven clamping bars
to fix and hold the cassette, and they can move up and down
depending on the direction of rotation of a ball screw that is
driven by a motor.
[0019] In another preferred embodiment, the etching apparatus of
the present invention has a wafer aligning chamber containing a
wafer aligning mechanism installed between the cassette supply
chamber and the load lock chamber for simultaneously aligning the
multiple wafers stacked in the cassette, and for transferring the
cassette to the load lock chamber.
BRIEF DESCRIPTION OF THE ATTACHED DRAWINGS
[0020] The accompanying drawings illustrate embodiments of the
invention, in which:
[0021] FIG. 1 is a plan view illustrating the inner structure of a
conventional etching apparatus;
[0022] FIG. 2 is a side cross section schematically illustrating
the inner structure of the conventional etching apparatus;
[0023] FIG. 3 is a top view schematically illustrating the inner
structure of an etching apparatus of the invention;
[0024] FIG. 4 is a cross section schematically illustrating the
inner structure of the etching apparatus of the invention;
[0025] FIG. 5 is a perspective view illustrating a cassette supply
table of the etching apparatus of the invention;
[0026] FIG. 6 is a frontal view illustrating the cassette supply
table of the etching apparatus of the invention;
[0027] FIG. 7 is a detail of the "clamping bar" of FIG. 6;
[0028] FIG. 8 is a perspective view illustrating a wafer aligning
mechanism of the etching apparatus of the invention;
[0029] FIG. 9 is a cross section illustrating the wafer aligning
mechanism of the etching apparatus of the invention;
[0030] FIG. 10 is a cross section of FIG. 9 taken along line 10-10
illustrating a cassette fixing mechanism of the wafer aligning
mechanisms in the etching apparatus of the invention;
[0031] FIG. 11 is a cross section illustrating the operating state
of the aligning table of the wafer aligning mechanism of the
etching apparatus of the invention;
[0032] FIG. 12 is a cross section of the wafer aligner of the wafer
aligning mechanism for the etching apparatus of the invention;
[0033] FIGS. 13 and 14 are top views illustrating the operation of
a cassette transport mechanism in the etching apparatus of the
invention;
[0034] FIGS. 15 and 16 are cross sections illustrating the
structure of the process chamber and its operation in the etching
apparatus of the invention;
[0035] FIG. 17 is an exploded perspective illustrating a wafer
loader mechanism in the process chamber of the etching apparatus of
the invention;
[0036] FIG. 18 is a detail of part A shown in FIG. 15; and
[0037] FIGS. 19A and 19B illustrate the operation of separating the
lower cover from the process chamber in the etching apparatus of
the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
[0038] An etching apparatus for manufacturing semiconductor devices
will be hereinafter described in detail with reference to FIG. 3
through FIG. 19.
[0039] As illustrated in FIGS. 3 and 4, the etching apparatus of
the invention includes: one or more process chambers 100 for
performing the etching process, in which the surface of a wafer
faces down. A cassette supplying chamber 200 supplies the wafer W
to the process chamber 100. The cassette supplying chamber 200 has
a cassette supply table 210 on which a cassette C is loaded with
multiple wafers W stacked therein so that their processing surfaces
face down. A load lock chamber 300, installed between the process
chamber 100 and the wafer supply chamber 200, receives the wafer W
stored in cassette C from the cassette supply chamber 200, which is
maintained under atmospheric conditions, and transfers the wafer W
to the process chamber 100, which is maintained under a high
vacuum. Inside the load lock chamber 300 there is an elevator 310
for moving the cassette C up and down, and a wafer transport
mechanism 320 for transferring the wafers W with their processing
surfaces facing down, one by one from the cassette C to the process
chamber 100.
[0040] In a preferred embodiment, a wafer aligning chamber 400 is
installed between the cassette supply chamber 200 and the load lock
chamber 300. The wafer aligning chamber 400 includes a wafer
aligning mechanism 410 which simultaneously aligns the flat edges
of the wafers W that are stacked in the cassette C. A cassette
transport mechanism 500 transfers the wafers W from the cassette C
in the cassette supply chamber 200 to the wafer aligning chamber
400 and the load lock chamber 300. The cassette transport mechanism
500 may be a robot, for example.
[0041] The cassette supply chamber 200, the wafer aligning chamber
400, the load lock chamber 300, and the process chamber 100 are
sequentially arranged side by side from left to right as is shown
in FIG. 3 and FIG. 4. An opening 201 for transporting the cassette
C into cassette supply chamber 200 is formed on one side of the
cassette supplying chamber 200. The path is opened/closed by a door
202. Opening 401 is formed between the wafer supply chamber 200 and
the wafer aligning chamber 400, for transferring cassette C between
chambers 200 and 400. Opening 301 is located between wafer aligning
chamber 400 and load lock chamber 300. The openings 401 and 301 are
opened/closed by doors 402 and 302, respectively. An opening 101
exists between the load lock chamber 300 and the process chamber
100, enabling a wafer W to pass from load lock chamber 300 into
process chamber 200 where the downward-facing processing surface of
wafer W is etched. The opening 101 is also opened/closed by a door
102.
[0042] Cassette C, housing multiple wafers W, is transported from
the cassette supply table 210 in the cassette supply chamber 200 to
the wafer aligning mechanism 410 in the wafer aligning chamber 400
using the cassette transporting mechanism 500 installed in the
wafer aligning chamber 400. Opening 301 between the wafer aligning
chamber 400 and the load lock chamber 400 is closed by the door 302
at this point. All of the wafers housed in cassette C are
simultaneously aligned by wafer aligning mechanism 410 before the
cassette C is transported into load lock chamber 300.
[0043] Once cassette C has been transported into wafer aligning
chamber 400 and the wafers W have been aligned, opening 401 between
the cassette supplying chamber 200 and the wafer aligning chamber
400 is closed by the door 402. Next, the door 301 to the load lock
chamber 300 is opened, and the cassette C is transported from the
wafer aligning chamber 400 to the elevator 310 in the load lock
chamber 300 using the cassette transporting mechanism 500. Once
cassette C is inside load lock chamber 300, opening 301 is closed
by door 301.
[0044] The process chamber 100 must be maintained at a high-vacuum
throughout the process of transferring each wafer W from the
cassette C on the elevator 310 to the process chamber 100 where it
is etched. To maintain a high vacuum, the opening 301 leading from
load lock chamber 300 to the wafer aligning chamber 400 is sealed
by closing door 302. The load lock chamber 300 is then placed under
a vacuum to reduce the pressure difference between the load lock
chamber 300 and the process chamber 100. Once the proper vacuum is
achieved, the wafers are supplied, one by one with the processing
surface facing down, to the process chamber 100 through opening 101
using the wafer transport mechanism 320 where each wafer is
individually and sequentially etched.
[0045] After each wafer W has been etched in process chamber 100,
it is re-stacked in the cassette C on the elevator 310 by the wafer
transport mechanism 320. Elevator 310, on which the cassette C is
laid, moves up and down to facilitate the sequential transfer of
each wafer back and forth between the cassette C and process
chamber 100 using the wafer transporting mechanism 320.
[0046] Once all the wafers have been etched and returned to the
cassette C resting on the elevator 310, the opening 101 between the
load lock chamber 300 and the process chamber 100 is shut tightly
to maintain the vacuum state in the process chamber 100. At this
point, the openings 301 and 401 of the respective load lock chamber
300 and the wafer aligning chamber 400 can be safely opened. The
cassette transporting mechanism 500 transfers the cassette C from
the elevator 310 through the openings 301 and 401, to the cassette
supply table 210 in the cassette supply chamber 200. The wafers W
are oriented with their processing surfaces still facing down
throughout the transfer from the cassette supply chamber 200 to the
process chamber 100 and throughout the etching process. The wafers
W are transported in cassette C back to cassette supply chamber 200
facing down in order to minimize the attachment of particulate
contaminants on the etched surface of the wafer W.
[0047] The present invention permits a more rapid transfer of the
cassette C from the cassette supplying chamber 200 to the load lock
chamber 300 than the conventional etching apparatus. Further, the
present invention also permits the simultaneous alignment of
multiple wafers W stacked in the cassette C which saves time.
[0048] FIGS. 5 to 7 illustrate the cassette supply table 210
installed in the cassette supplying chamber 200 of the etching
apparatus of the present invention. The cassette supplying table
210 is composed of multiple fixing tables 211 for receiving a
cassette C, stacked at a predetermined interval from each other.
Cassette C, housing multiple wafers W stacked with their processing
surfaces facing down, is laid on the fixing tables 211. The
multiple fixing tables 211 are installed on the lower base table
212 and move vertically. A support column 213, fixed to the bottom
of the lowest fixing table 211, passes through the lower base table
212 to support the base table. The fixing table is automatically
controlled by an elevating mechanism to move up and down to
predetermined heights.
[0049] The vertical shifting means includes: a ball screw 221
passing through the base table 212 and the latitudinal plate 214,
and extending upward through the latitudinal plate; a ball bearing
222 attached to latitudinal plate 214 installed between the
latitudinal plate and supporting the ball screw 221; a motor 223
for rotating the ball screw 221; and a pair of pulleys 224a and
224b and a belt 225 for transmitting power from the motor 223 to
the ball screw 221. Guide rods 226 pass through the latitudinal
plate 214 on both sides of the ball screw 221, where the lower side
of the rod is fixed to the base table 212 to guide the latitudinal
plate 214 linearly as it moves along the ball screw 221.
[0050] Accordingly, when the ball screw 221, connected to motor 223
by a pair of pulleys 224a and 224b and belt 225, rotates under the
power of driving motor 223, the multiple fixing tables 211 move up
and down by the ball bearing 222. The fixing tables 211 move
linearly without rotating, centered on support column 213, so that
the supporting column 213 supports the linear movement of the
fixing tables 211.
[0051] The vertically shifting fixing tables 211 are positioned in
front of the opening 401 leading from cassette supply chamber 200
to the wafer aligning chamber 400 by the driving motor, as
illustrated in FIG. 4. Once the cassette support table 210 has
moved cassette C into its proper position, cassette C can be
transferred by the cassette transport mechanism 500 from cassette
supply chamber 200 into wafer aligning chamber 400 through opening
401.
[0052] Two fixing tables 211 are illustrated in the drawing, but
more can be used in the actual embodiment. Each fixing table 211 on
which the cassette C is loaded includes a support board 231,
vertical bars 232 attached to both sides of the supporting board
231, and fixing mechanism 240 for preventing the cassette C from
shifting out of position. The fixing mechanism 240 has pneumatic
actuating cylinders 233 installed under the vertical bars 232, to
move clamping bars 234, installed on both sides of the vertical
bars 232, allowing the both ends of the clamping bars 234 to
rotate. Rods 233a of each pneumatic actuating cylinder 233 are
connected to the free-end of the clamping bars 234 enabling the
clamping bars to clamp and release cassette C.
[0053] As illustrated in FIG. 7, as the clamping bar 234 rotates
according to the linear movement of the rod 233a during the
operation of the pneumatic actuating cylinder 233, it is possible
to clamp or release the cassette C by pushing down on the upper
surface of cassette C placed on the supporting board 231. When the
fixing tables 211 are raised or lowered, the pneumatic actuating
cylinders 233 are activated, enabling the clamping bars 234 to
secure the cassette C, in order to prevent the cassette C from
shifting out of place. When transporting the cassette C to the
wafer aligning chamber 400, or when returning cassette C to each
fixing table 211, the clamping action of clamping bar 234 is
released to enable the transportation of cassette C.
[0054] FIGS. 8 through 14 illustrate the wafer aligning mechanism
410 installed in the wafer aligning chamber 400 and the cassette
transport mechanism 500 in the etching apparatus of the present
invention. The wafer aligning mechanism 410, as illustrated in
FIGS. 8 through 12, includes a base 411, an aligning table 413 to
which a vertical frame 412 is attached, an aligning plate 414
installed within the vertical frame 412 of the aligning table 413
to receive the cassette C, and a wafer aligner 430 installed on the
base 411 for simultaneously aligning the flat edges of the wafers W
stacked in the cassette C.
[0055] The aligning plate 414 is made to rotate 90.degree. around
shafts 416a and 416b under the power of the gear-reduced motor 415,
thereby rotating the cassette C laid on the aligning plate 414 by
90.degree., so that the wafers W stacked in cassette C can be
transported onto the wafer aligner 430. Clamping bars 418 installed
on both sides of the aligning plate 414 rotate, powered by a small
driving motor 417, and clamp the sides of the cassette C.
[0056] A slide preventing groove 414a, into which two or more
supporting legs of the cassette C are inserted, is cut into the
floor of aligning plate 414 on which the cassette C rests, so that
the cassette C does not shift when clamped by the clamping bars
418. After the cassette C has been transported from the cassette
supplying chamber 200 by the cassette transporting mechanism 500,
it is laid on the aligning plate 414. Both of the clamping bars 418
powered by the motor 417, push on the cassette C thereby pushing
cassette C onto the wafer aligner 430 as the aligning plate 414
rotates 90.degree. under the power of gear reduced motor 415. This
operation simultaneously aligns the wafers W stacked in the
cassette C. When the alignment of the wafers W is complete, the
aligning plate 414 rotates in the reverse direction by 90.degree.
thereby returning the cassette C to its original position.
[0057] As illustrated in FIGS. 11 and 12, the wafer aligner 430 has
three rollers 431, the central roller being slightly lower than the
rollers on either side. The central roller 431 is powered by a
motor 434 connected to it by a pair of pulleys 432a and 432b and a
belt 433. When the cassette C is placed on the wafer aligner 430,
the external circumference of the wafers W contacts the three
rollers 431. When the central roller 431 is rotated by the motor
434, those wafers W whose edges make contact with the central
roller 431 are rotated. The wafers will continue rotating as long
as the wafer edge contacts the central roller 431. However, when
the flat side of the wafer faces the central roller 431, contact
with the central roller 431 is broken and the wafer stops rotating,
causing the wafers to be aligned with the flat edges of the wafers
W over the central roller 431. In this way, multiple wafers W are
simultaneously aligned.
[0058] FIGS. 9, 13 and 14 depict the cassette transport mechanism
500 which includes a fork 510 for gripping and lifting the cassette
C, three linkage arms 520 connected to the fork 510, a spindle 530
capable of moving the cassette C up and down and rotating the
cassette C, and a drive mechanism 540 for driving the spindle 530.
The drive mechanism 540 is positioned under the aligning plate 414,
and is fixed to the base 411. Accordingly, as the spindle 530 is
moved vertically by the drive mechanism 540, the fork 510 is first
lifted up and then is put down on the cassette C. All of the three
arms 520 can be either extended or folded by the forward and
reverse rotation, respectively, of the spindle 530, so that the
cassette C is transferred from the fixing table 211 of the cassette
supply table 210 to the aligning plate 414 of the wafer aligning
mechanism 410. From the aligning plate 414, cassette C is
transferred to and from the elevator 310 in the load lock chamber
300.
[0059] The elevator 310 and the wafer transport mechanism 320 in
the load lock chamber 300 are of a conventional design known to
those skilled in the art. Cassette C, placed by the cassette
transport mechanism 500 onto elevator 310, is moved vertically by
the elevator 310 in load lock chamber 300 as is illustrated in FIG.
4.
[0060] FIGS. 15 to 19 illustrate the process chamber 100 in which
the wafer W, whose surface faces down during transfer from cassette
supply chamber 200 to process chamber 100, is individually etched.
Process chamber 100 includes a sealed chamber body 110. An opening
101, through which the wafer W passes, is formed on the side wall
of the chamber body 110 next to load lock chamber 300, and is
sealed with door 102. A cathode 111 to which the wafer W is held
during etching, is installed in the top part inside the chamber
body 110. A wafer loading mechanism is formed in the chamber body
110 for clamping the wafer W securely against the cathode 11 with
the wafer processing surface facing down. The wafer loading
mechanism includes a loader 121 for lifting the wafer W and
elevating it to a first loading position P1 from which position the
wafer W is transported using the fetch arm 321 of the wafer
transporting mechanism 320; a holder 122 for lifting the wafer to a
second loading position P2 from which position the wafer is clamped
against the cathode 111 in conjunction with loader 121 after fetch
arm 321 returns to the load lock chamber 300; and a driving means
for operating loader 121 and the holder 122.
[0061] The loader 121 and the holder 122, illustrated in FIG. 17,
are installed on the external or lower side of the cathode 111, and
together they form a cylinder. A groove 111a is formed in the
cathode 111, which groove allows the loader 121 and the holder 122
to move up and down. Lifters 123 and 124 are attached to the bottom
of the loader 121 and the holder 122. Each lifter grips the edges
of the wafer W without damaging the processing surface. An opening
is cut into the sides of the loader 121 and holder 122, openings
121a and 122a, respectively, so that the fetch arm 321 of the wafer
transporting mechanism 320 can transfer the wafer W to and from
loader 121 and holder 122 through the openings 121a and 122a.
[0062] The actuating cylinders for the loader 121 and the holder
122 are formed vertically adjacent to one another as a first upper
and a second lower cylinder 130 and 140, respectively, which are
stacked on top of the chamber body 110. As is illustrated in FIGS.
15 and 16, an inner rod 131 passes through the center of the first
and second cylinder housings 136 and 146, respectively, so that the
lower part of the inner rod 131 suspends the cathode 111. The top
hub of the loader 121 is attached to the end of inner rod 131. The
opposite end of the inner rod 131 passes through the first cylinder
housing 136 and is exposed to the outside of the process chamber. A
first piston 132 is fixed to the inner rod 131, positioned in the
first cylinder housing 136. A spring 133 is installed beneath the
first piston 132 in the first cylinder housing 136 to push the
first piston 132 upward. Air supplying lines 134 and 135 are
respectively connected above and below the first piston 132 in the
first cylinder housing 136 in order to selectively supply air to
housing 136 in order to pneumatically drive the first piston 132 up
and down.
[0063] The inner rod 131 moves up and down with the movement of the
first piston 132, causing the loader 121 to move up and down so
that the wafer loading operation of the loader 121 is controlled
with the first cylinder 130. The spring 133 provides the restoring
force. The spring provides the force for the loader 121 to clamp
the wafer W in second loading position P2 securely against the
cathode 111, thereby preventing the wafer from being damaged by
excessive pressure.
[0064] A second rod 141 is installed outside of the inner rod 131,
having a lower end that passes through the cathode 111 and that is
attached to the top hub of the holder 122 at a central position.
The upper end of the second rod 141 terminates in the second
cylinder housing 146 where a second piston 142 is fixed to the
second rod 141. A spring 143 is installed beneath the second piston
142 in the second cylinder housing 146. The air supply 144 is
connected to wall of the second cylinder housing 146 above the
second piston 142 installed in housing 146, so that the second
piston 142 is pneumatically driven downward.
[0065] As the second rod 141 moves down according to the movement
of the second piston 142 under air pressure, the holder 122 also
moves downward. The spring 143 is compressed until the air pressure
is released at which time the second piston 142 returns to its
original position, due to the restoring force of the spring 143.
The upward-movement of the second rod 141 and the holder 122 fixed
to its lower end is thus enabled, and the wafer clamping operation
of the holder 122 is accomplished with the second cylinder 140. The
wafer W is fixed by the holder 122, utilizing the elasticity of the
spring 143.
[0066] The loader 121 is controlled by a position controller to
move to a stand-by position P0 before the wafer W is supplied, then
to a the first loading position P1 for receiving the supplied wafer
W from the fetch arm 321, and finally to the second loading
position P2 for clamping the wafer W to the cathode 111. The
position controlling means is made of sensors installed on the top
of the first cylinder housing 136 and on the upper part of the
inner rod 131 that extends outside of the top of the process
chamber.
[0067] In a preferred embodiment, the sensors are light emitters
and/or photo sensors known in the art. One light emitter 151 is
installed on an arm 170 attached to the top part of inner rod 131
and three photo sensors 152 are installed on a vertical member 171
that is fixed to the outside top part of the first cylinder housing
136, with the photo sensors positioned on the vertical member 171
so that each photo sensor is opposite to the light emitting sensor
151. The position of the first photo sensor determines the stand-by
position P0 of the loader 121; the second photo sensor determines
the first loading position P1, and the third photo sensor
determines the second loading position P2 of the loader 121 at
which position the wafer is clamped to the cathode 111.
[0068] The holder 122 is controlled by a position controller
incorporating sensors installed on the second rod 141 between the
second cylinder 140 and the top of the chamber body 110 within
bracket 153. As with the position control means of the loader 121,
light emitters and photo sensors are preferable. One light emitting
sensor 154 is attached to the outside of the second rod 141. Two
photo sensors 155 are attached to the inside of the bracket 153
installed between the second cylinder 140 and the top of the
process chamber body 110 through an arm 172, so that each photo
sensor 155 is opposite to the light emitting sensor 154 and is
positioned so that the first photo sensor determines the stand-by
position P0 of the holder and the second photo sensor determines
the second clamping position P2 of the holder.
[0069] An example of a loading operation of the wafer W in the
present etching apparatus is set forth below:
[0070] The wafer W, whose processing surface faces down, is
inserted through the openings 121a and 122a in the loader 121 and
the holder 122, respectively, by the fetch arm 321 of the wafer
transport mechanism 320 when the loader and the holder are
positioned in the stand-by position P0. A pneumatic controller,
(not shown) supplies air to the air supplying line 135 of the first
cylinder 130 to pneumatically drive first piston 132 up and down
and thereby lift and lower the inner rod 131.
[0071] The lifter 123 attached to the loader 121 moves up, thereby
receiving the wafer W from fetch arm 321. Simultaneously, the light
emitter sensor 151 that is attached to the inner rod 131 contacts
the central photo sensor 152. The central photo sensor 152 receives
the light signal from the light emitter 151 and supplies a signal
to the pneumatic controller. The pneumatic controller supplies air
to the air supplying lines 134 and 135 to stop the inner rod 131 so
that the loader 121 stops at the first loading position P1 for
receiving the wafer W.
[0072] As described above, the fetch arm 321 having transferred the
wafer W returns to the load lock chamber 300 when the loader 121
stops at the position P1. The inner rod 131 is again activated to
lift the loader 121 to the second loading position P2. The loader
121 stops at the second loading position P2, controlled by the
light emitter 151 installed on the inner rod 131 and the photo
sensor 152 which is located opposite to the light emitter 151,
thereby clamping the wafer W against the cathode 111 with its
processing surface facing down.
[0073] As the loader 121 shifts from first loading position P1 to
second loading position P2, the second cylinder 140 is activated to
lift the second rod 141. This causes holder 122 to move from
stand-by position P0 to second loading position P2. Holder 122 is
stopped at the second clamping position P2 by the light emitter 154
and the photo sensor 155.
[0074] The lifter 124 of the holder 122 holds the outside of the
wafer W and clamps wafer W to the cathode 111 so that the wafer W
is etched with its processing surface facing down. The clamping
force on the wafer W is imparted by springs 133 and 143, installed
in the first and second cylinders 130 and 140, respectively. The
tension on springs 133 and 143 is adjusted so that excessive force
is not applied to the wafer.
[0075] To unload a wafer W that has been etched, the loading steps
set forth above are performed in the reverse order. That is, the
inner and second rods 131 and 141 descend simultaneously, driven by
first and second cylinders 130 and 140, respectively. The loader
121 stops at P1, controlled by the light emitter and photo sensor
151 and 152, respectively, while the holder 122 descends to
position P0, controlled by sensors 154 and 155. At this point, the
fetch arm 321 is inserted through openings 121a and 122a and is
placed under the wafer W. The wafer W is transferred to the fetch
arm 321 when the lifter 123, because the first rod 131 drops
further, driven by the first cylinder 130, taking the loader 121 to
the stand-by position P0. The fetch arm 321 returns the wafer W to
the cassette C sitting on elevator 310 in the load lock chamber 300
through openings 121a and 122a in the loader 121 and the holder
122, respectively.
[0076] Each wafer W stacked in the cassette C is sequentially
loaded into the process chamber 100, etched, and unloaded. The
loading and unloading operations are repeated until each wafer has
been etched.
[0077] FIG. 18 illustrates part A of FIG. 15 in detail, showing how
the process gas is supplied to process chamber 100. With the
surface of the wafer W facing down, the process gas is supplied to
the bottom of the chamber body 110. Specifically, a lower cover 160
is installed at the bottom of the chamber body 110. A gas spray
plate 161 is installed between the chamber body 110 and the lower
cover 160 with predetermined orifice sizes. Seals 162 and 163 are
mounted between the chamber body 110 and the gas spraying plate
161, and the gas spraying plate 161 and the lower cover 160,
respectively.
[0078] The gas supply line 164 is attached to one side of the
chamber body 110. One end of the gas supplying line 164 passes
through the gas spraying plate 161 and terminates between the gas
spraying plate 161 and the lower cover 160, so that gas is supplied
in the space separating them. The process gas transmitted through
the line 164 is supplied to the bottom of the chamber body 110
through the gas orifices 161 a formed in the gas spraying plate
161. The lower cover 160 can be separated from the chamber body 110
to facilitate easy repair and cleaning. As FIGS. 19A and 19B
illustrate, multiple bosses 166 are attached the bottom of the
lower cover 160 to which multiple threaded supporting legs 165 are
inserted. Wheels 167 are attached to the bottom of each supporting
leg 165, and a means for raising and lowering lower cover 160 is
respectively screwed to the supporting legs 165. Each wheel 167 is
guided along rails 169 which extend outside of the chamber body
110. A handle 170 is attached to either side of the lower
cover.
[0079] A preferred embodiment is shown in FIG. 19A. Here, a leveler
168 is screwed onto the threaded area of the supporting leg 165 and
is rotated to lift and lower the lower cover 160. The leveler 168
can be rotated to push the lower cover 160 up so that it presses
against the bottom of the chamber body 110 thereby sealing the
inside of the chamber. When disassembling the lower cover 160 for
repair and cleaning, the leveler 168 is rotated to lower the cover
160. When lowered, the handle 170 of the lower cover 160 can be
pulled, causing the cover 160 to roll on wheels 167, guided by the
rail 169, so that the lower cover 160 is easily removed from the
chamber body 110 and shifted from side to side.
[0080] The etching apparatus for manufacturing the semiconductor
devices of the present invention transfers wafers W housed in a
cassette C between the cassette supply chamber 200 to the process
chamber 100 with the wafer processing surfaces facing down. The
etching process is performed on the downward-facing processing
surface which reduces particle contamination thereby increasing
production yield by reducing the defect ratio. In addition, when
supplying the wafer from the cassette supply chamber 200 to the
elevator 310 of the load lock chamber 300, multiple wafers are
stacked in the cassette C so that wafer transport time is reduced.
Further, the present invention permits the simultaneous alignment
of multiple wafers stacked in the cassette thereby reducing the
wafer alignment time. The etching apparatus of the present
invention therefore reduces the total process time, and increases
productivity.
[0081] The present invention is not limited to the embodiments set
forth above, and it is clearly understood that many variations may
be made within the scope of the present invention by anyone skilled
in the art.
* * * * *