U.S. patent number 3,870,460 [Application Number 05/457,432] was granted by the patent office on 1975-03-11 for single or multi-track fluid bearing heating apparatus and method.
This patent grant is currently assigned to GCA Corporation. Invention is credited to Alan G. Flint.
United States Patent |
3,870,460 |
Flint |
March 11, 1975 |
SINGLE OR MULTI-TRACK FLUID BEARING HEATING APPARATUS AND
METHOD
Abstract
Apparatus and method for transporting articles, such as silicon
and like wafers employed in the manufacture of semiconductor
devices, on a track between two predetermined stations and past a
heating station. The transport means utilized for the track
comprises a positive drive belt and a pair of fluid bearing track
structures for supporting the articles and moving the same in
conjunction with the belt, preferably while the articles are
rotated during movement past the heat source to insure uniform
article heating. In the preferred embodiment, the apparatus
comprises a plurality of parallel tracks each defined by a belt and
fluid bearing track structure synchronously actuated for moving a
plurality of parallel streams of wafers simultaneously past the
heating station.
Inventors: |
Flint; Alan G. (San Jose,
CA) |
Assignee: |
GCA Corporation (Bedford,
MA)
|
Family
ID: |
23816708 |
Appl.
No.: |
05/457,432 |
Filed: |
April 3, 1974 |
Current U.S.
Class: |
432/11; 432/235;
432/124 |
Current CPC
Class: |
C21D
9/63 (20130101); H01L 21/6779 (20130101) |
Current International
Class: |
C21D
9/63 (20060101); H01L 21/677 (20060101); H01L
21/67 (20060101); F27b 009/14 () |
Field of
Search: |
;432/11,124,235
;302/2R,30,31 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Camby; John J.
Attorney, Agent or Firm: Flehr, Hohbach, Test, Albritton
& Herbert
Claims
I claim:
1. Apparatus for transporting articles, such as semiconductor
wafers, past a treating station, comprising
A. infeed means at an infeed station for introducing articles in
sequence into said apparatus,
B. means at a station adjacent said infeed station for treating
articles presented thereto,
C. conveyor track means for receiving articles in sequence from
said infeed means and presenting the same in spaced sequence to
said treating station, comprising
1. directional fluid bearing structure on which articles are
supported and by which the articles are positively moved from said
infeed station to and past said treating station,
2. an endless pacer belt having article spacers carried thereon for
maintaining articles spaced during transport past said treating
station and for pacing movement of such articles by restricting
movement thereof under controlled conditions as the articles are
supported and moved by said fluid bearing structure, and
3. mechanism for positively driving said belt in accordance with a
predetermined rate schedule, and
D. means at a discharge station for receiving articles in sequence
after the same have passed from said treating station.
2. The apparatus of claim 1 in which said treating means at said
treating station comprises a heating unit positioned above said
conveyor track means for heating articles transported therebeneath
on said conveyor track means.
3. The apparatus of claim 1 in which said fluid bearing structure
includes a bi-directional section at said heating station which
introduces bearing fluid in opposite directions against said
articles supported thereby to effect rotation of such articles as
the same pass said treating station.
4. The apparatus of claim 1 in which said infeed means and said
discharge means each comprises an indexable magazine for feeding
and receiving, respectively, articles in sequence to and from said
conveyor track means.
5. The apparatus of claim 1 in which said drive mechanism for said
belt includes means for intermittently moving said belt so that
said articles are discontinuously moved past said treating station
on said conveyor track means.
6. The apparatus of claim 1 in which said conveyor track means
includes plural fluid bearing structures and belts extending in
parallel relationship past said treating station, and plural infeed
means and discharge means for feeding and receiving articles to and
from respective tracks of said plural conveyor track means.
7. The apparatus of claim 6 in which said drive mechanism of said
conveyor track structure includes means for moving each of said
belts in synchronism so that parallel aligned streams of spaced
articles may be transported past said treating station.
8. The apparatus of claim 7 in which said treating means at said
treating station comprises a heating unit positioned above said
plural fluid bearing structures and belts for heating articles
transported thereon.
9. The apparatus of claim 8 in which each of said fluid bearing
structures includes a bi-directional section at said heating
station which introduces bearing fluid in opposite directions
against said articles supported thereby to effect rotation of such
articles as the same pass said treating station.
10. The apparatus of claim 1 in which said fluid bearing structure
includes a slot extending logitudinally thereof within which said
belt moves, said belt being positioned below the upper surface of
said fluid bearing structure with only said spacers projecting
thereabove so that said articles are free of contact with said belt
during transport past said treating station.
11. Apparatus for uniformly heating semiconductor wafers and like
articles during manufacturing procedures for semiconductor devices,
comprising
A. infeed means at an infeed station for introducing wafers in
spaced sequence to a heating station,
B. a heating unit at said heating station for heat treating wafers
presented thereto,
C. conveyor track means for receiving wafers in sequence from said
infeed means and transporting the same in spaced sequence beneath
said heating unit at said heating station, comprising
1. an elongated directional fluid bearing structure on which said
wafers are supported and by which said wafers are positively moved
from said infeed station to and past said heating unit,
2. an endless pacer belt extending longitudinally of said fluid
bearing structure having wafer spacers carried thereby, against
which individual wafers come in contact, for maintaining said
wafers spaced in predetermined positions and for pacing movement of
said wafers by restricting movement thereof under controlled
conditions during such movement past said heating unit, and
3. mechanism for positively driving said belt relative to said
heating unit at a predetermined rate, and
D. means at a discharge station adjacent said heating station for
receiving heat treated wafers in sequence after the same have
passed said heating unit.
12. The apparatus of claim 11 in which said heating unit comprises
a radiant heat source which transmits a field of radiant energy
directly onto the wafers moving therebeneath.
13. The apparatus of claim 11 in which said fluid bearing structure
includes a bi-directional section beneath said heating unit which
introduces bearing fluid in opposite directions against said wafers
supported thereby to effect rotation of said wafers, as the wafers
move past said heating unit, to insure uniform heating thereof.
14. The apparatus of claim 11 in which said belt driving mechanism
includes means for intermittently moving said belt so that wafers
paced thereby are discontinuously moved beneath said heating
unit.
15. The apparatus of claim 11 in which said conveyor track means
includes plural fluid bearing structures and plural belts
associated therewith which extend in parallel relationship beneath
said heating unit, and plural infeed means and plural discharge
means for feeding and receiving wafers to and from respective
tracks of said plural conveyor track means.
16. The apparatus of claim 15 in which said drive mechanism of said
conveyor track structure includes means for moving all of said
belts in synchronism so that parallel aligned streams of spaced
wafers may be transported past said heating station.
17. The apparatus of claim 15 in which each of said fluid bearing
structures includes a bi-directional section at said heating
station which introduces bearing fluid in opposite directions
against said wafers supported thereby to effect rotation of such
wafers as the same pass said heating station.
18. A method of transporting articles to and past a treating
station, comprising
A. introducing articles in spaced sequence onto a fluid bearing
structure,
B. introducing directional article supporting fluid through said
fluid bearing structure and supporting said articles thereon while
the same are moved by said article supporting fluid past said
treating station,
C. while said articles are supported by and moved on said
supporting fluid positively restricting their movement to pace the
rate of travel thereof past said treating station, and
D. discharging treated articles in spaced sequence from said
treating station.
19. The method of claim 18 which further includes
E. rotating each of said articles at said treating station by
introducing oppositely directed streams of supporting fluid
thereagainst.
20. The method of claim 18 which includes temporarily halting
movement of said articles as the same pass said treating station by
moving the same in predetermined interrupted increments
therepast.
21. The method of claim 18 which includes heat treating said
articles at said treating station.
22. The method of claim 21 in which said articles are radiantly
heated from above at said treating station.
23. The method of claim 22 in which said articles are
simultaneously heated from below while being radiantly heated from
above.
24. A method of heat treating semiconductor wafers and like
articles during manufacturing procedures for semiconductor devices,
comprising
A. introducing a stream of spaced wafers in sequence onto a fluid
bearing structure,
B. introducing directional supporting fluid through said fluid
bearing structure and supporting said wafers thereon while moving
the same past a heat source,
C. subjecting said wafers in sequence and for predetermined times
to said heat source by moving the same on said supporting fluid
therepast,
D. while said wafers are supported on said supporting fluid
positively restricting their movement to pace their rate of travel
past said heat source, and
E. discharging heat treated wafers in spaced sequence from said
heat source.
25. The method of claim 24 which includes
F. insuring uniform heating of said wafers by said heat source by
rotating said wafers relative to said heat source during travel
thereof.
26. The method of claim 25 in which said wafers are rotated by
directing opposed streams of supporting fluid against opposite
portions of said wafers while the same are levitated thereby.
27. The method of claim 24 which includes
G. heating said supporting fluid in conjunction with introducing
the same against said wafers to assist in heat treating said
wafers.
28. The method of claim 27 which includes radiantly heated said
wafers from above by said heat source while simultaneously heating
said wafers from below by said heated supporting fluid.
29. Apparatus for transporting articles, such as semiconductor
wafers, past a treating station, comprising
A. plural infeed means at an infeed station for introducing rows of
articles in sequence into said apparatus,
B. means at a station adjacent said infeed station for treating
articles presented thereto,
C. plural conveyor track means for receiving said rows of articles
in sequence from said infeed means and presenting the same in
spaced sequence to said treating station, comprising
1. plural fluid bearing structure on which said rows of articles
are supported and moved from said infeed station to and past said
treating station,
2. plural endless belts, extending in parallel relationship
relative to each other and to said plural fluid bearing structures,
extending past said treating station in alignment with said plural
infeed means, said belts pacing movement of said rows of articles
as the articles are supported and moved by the respective fluid
bearing structures associated with each said belt, and
3. mechanism for driving each said belt in accordance with a
predetermined rate schedule, and
D. plural means at a discharge station for receiving said rows of
articles in sequence from the respective tracks of said plural
conveyor track means after such articles have passed said treating
station.
30. The apparatus of claim 29 in which said drive mechanism of said
conveyor track means includes means for moving each of said belts
in synchronism so that parallel aligned rows of spaced articles may
be transported to and past said treating station.
31. The apparatus of claim 30 in which said treating means at said
treating station comprises a heating unit positioned above said
plural fluid bearing structures and said belts for heating said
rows of articles transported thereon.
32. The apparatus of claim 31 in which each of said fluid bearing
structures includes a bi-directional section at said heating
station which introduces bearing fluid in opposite directions
against said articles supported thereby to effect rotation of such
articles as the same pass said treating station.
33. Apparatus for transporting articles, such as semiconductor
wafers, past a treating station, comprising
A. infeed means at an infeed station for introducing articles in
sequence into said apparatus,
B. means at a station adjacent said infeed station for treating
articles presented thereto,
C. conveyor track means for receiving articles in sequence from
said infeed means and presenting the same in spaced sequence to
said treating station, comprising
1. fluid bearing structure on which articles are supported and
moved from said infeed station to and past said treating
station,
2. a slot extending in said fluid bearing structure extending
longitudinally thereof,
3. an endless belt having article spacers carried thereon for
maintaining articles spaced during transport past said treating
station and for pacing movement of such articles as the articles
are supported and moved by said fluid bearing structure,
4. said belt being positioned in said slot below the upper surface
of said fluid bearing track structure with only said spacers
projecting thereabove so that said articles are free of contact
with said belt during transport past said treating station, and
5. mechanism for positively driving said belt in accordance with a
predetermined rate schedule, and
D. means at a discharge station for receiving articles in sequence
after the same have passed from said treating station.
34. Apparatus for uniformly heating semiconductor wafers and like
articles during manufacturing procedures for semiconductor devices,
comprising
A. infeed means at an infeed station for introducing wafers in
spaced sequence to a heating station,
B. a heating unit at a heating station for heat treating wafers
presented thereto,
C. conveyor track means for receiving wafers in sequence from said
infeed means and transporting the same in spaced sequence beneath
said heating unit at said heating station, comprising
1. an elongated directional fluid bearing structure on which said
wafers are supported and by which said wafers are moved from said
infeed station to and past said heating unit,
2. said fluid bearing structure including a bi-directional section
beneath said heating unit which introduces bearing fluid in
opposite directions against said wafers supported thereby to effect
rotation of said wafers, as the wafers move past said heating unit,
to insure uniform heating thereof,
3. an endless belt extending longitudinally of said fluid bearing
structure having wafer spacers carried thereby, against which
individual wafers come in contact, for maintaining said wafers
spaced in predetermined positions during movement past said heating
unit, and
4. mechanism for positively driving said belt relative to said
heating unit at a predetermined rate, and
D. means at a discharge station adjacent said heating station for
receiving heat treated wafers in sequence after the same have
passed said heating unit.
35. The apparatus of claim 34 in which said belt driving mechanism
includes means for intermittently moving said belt so that wafers
paced thereby are discontinuously moved beneath said heating
unit.
36. The apparatus of claim 34 in which said conveyor track means
includes plural fluid bearing structures and plural belts
associated therewith which extend in parallel relationship beneath
said heating unit, and plural infeed means and plural discharge
means for feeding and receiving wafers to and from the respective
tracks of said plural conveyor track means.
37. The apparatus of claim 36 in which said drive mechanism of said
conveyor track structure includes means for moving all of said
belts in synchronism so that parallel aligned rows of spaced wafers
may be transported past said heating station.
Description
CROSS REFERENCE TO RELATED APPLICATION
In Cecil A. Lasch, Jr. copending application Ser. No. 203,086,
filed Nov. 25, 1971 entitled "Fluid Bearing Transfer and Heat
Treating Apparatus and Method," an apparatus and method are
disclosed for transporting articles at varying rates through a heat
zone utilizing a fluid bearing. Such application does not, however,
utilize the positive drive and article rotation procedures and
related features disclosed herein. The apparatus and method of said
Lasch, Jr. application are designed to produce improved results and
solve handling problems in a heated atmosphere which are different
from those confronting applicant herein.
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to the field of transporting articles. More
particularly, this invention relates to the field of moving
articles between predetermined stations and past a heating station
at which the temperature of the articles being transported is
uniformly elevated for previously known treating purposes.
Still more particularly, this invention relates to the field of
handling and transporting fragile articles, such as silicon and
like wafers commonly utilized in the electronics industry in the
manufacture of semiconductor devices, and for uniformly heating
such wafers during manufacturing procedures thereon utilized to
convert such wafers into semiconductor devices.
Still more particularly, this invention relates to the field of
wafer transportation means which utilizes a track defined by a
combined fluid bearing - positive drive pacing belt structure, and
the method for transporting wafers between predetermined stations
during the manufacture of semiconductor devices from such
wafers.
While the specific aspects of the transportation apparatus
disclosed herein relate to the improved and combined fluid bearing
and positive drive handling and transporting of wafers utilized in
the manufacture of semiconductor devices, and is so disclosed
hereinafter, its applicability to other fields in which articles
are required to be transported under controlled non-manual positive
drive conditions also should be recognized.
Description of the Prior Art
Fluid bearing track structures of various types have been generally
known heretofore and the following patents disclose devices and
structures which are exemplary thereof: Hazel U.S. Pat. No.
2,778,691 dated Jan. 22, 1957; Cole U.S. Pat. No. 3,103,388 dated
Sept. 10, 1963; Coville U.S. Pat. No. 3,318,640 dated May 9, 1967;
Lasch, Jr. et al. U.S. Pat. No. 3,645,581 dated Feb. 29, 1972; and
Lasch, Jr. U.S. Pat. No. 3,718,371 dated Feb. 27, 1973.
Additionally, the aforementioned Lasch, Jr. application Ser. No.
203,086 illustrates and describes a fluid bearing utilized in
conjunction with a heating mechanism, and other prior art cited
thereagainst relates generally to fluid bearings for transporting
articles, both in ambient and heated atmospheres.
While fluid bearing track structures have been disclosed in the
noted patents and application, none of such patents or application
discloses or describes the improved combination of a fluid bearing
track structure and cooperating positive drive pacing belt
incorporating therein the improved structural and wafer handling
features of the present invention. So far as is known, the
apparatus and method of this invention have been unknown
heretofore, particularly in conjunction with the transportation of
fragile wafers between predetermined stations past a heating
station.
SUMMARY OF THE INVENTION
The present invention relates to an improved single or multi-track
heating apparatus and method. More particularly, this invention
relates to an improved apparatus and method for supporting a single
stream or plural streams or articles on a fluid base, and spacing
individual articles from each other while the same are paced by a
positive drive pacing belt engaged with successive articles in each
of such single or plural streams. In the preferred embodiment
disclosed herein, a multi-stream apparatus is disclosed in which a
plurality of parallel streams of articles are transported in
synchronization to and past a treating station between in-feed and
out-feed stations of the apparatus.
Still more particularly, this invention relates to a combined fluid
bearing track structure - positive drive belt structure by means of
which flat fragile wafers are transported to and past a heating
station in a generally straight line path without requiring manual
contact.
Still more particularly, this invention relates to an improved
heating apparatus and method by means of which streams of wafers
utilized in the manufacture of semiconductor devices are carried at
predetermined paced rates to and past a heating unit; in
conjunction with such movement, each of the wafers preferably is
continuously rotated as the same is exposed to the elevated
temperature of the heating element so that uniform heating of each
wafer is insured.
From the foregoing it should be understood that objects of this
invention include: the provision of an improved apparatus and
method for transporting articles, such as fragile semiconductor
wafers, between predetermined stations; the provision of a combined
handling track defined by an improved fluid bearing track structure
- positive drive pacing belt structure in combination for moving
articles between predetermined stations; the provision of an
improved apparatus and method for heating articles while positively
transporting the same relative to a heating source; the provision
in an improved heating apparatus and method of means for
continuously rotating the articles being subjected to heat during
movement past the heating element to insure uniform heating of each
article; the provision in a fluid bearing apparatus of fluid
bearing track structures having supporting fluid emanating in
opposite directions from adjacent track structures to effect
rotation of articles supported thereby; and the provision of
improved procedures for handling and transporting articles relative
to a heating station utilizing combined fluid bearing and positive
drive techniques.
These and other objects of this invention and various aspects
thereof will become apparent from a study of the following detailed
description in which reference is directed to the attached
drawings.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a plan view of a multi-track apparatus of this
invention.
FIG. 2 is a vertical sectional view through the apparatus taken in
the plane of line 2--2 of FIG. 1.
FIG. 3 is a vertical sectional view, on an enlarged scale, taken in
the plane of line 3--3 of FIG. 2.
FIGS. 4A and 4B are horizontal sectional views (comprising
continuations of each other) taken in the plane of line 4--4 of
FIG. 3.
FIG. 5 is a vertical sectional view taken in the plane of line 5--5
of FIG. 3 illustrating details of construction of the positive
drive belt utilized in the subject apparatus.
FIG. 6 is a vertical sectional view through one track of the
apparatus taken in the plane of line 6--6 of FIG. 4A.
FIGS. 7 and 8 are vertical sectional views through a track taken in
the planes of lines 7--7 and 8--8, respectively, of FIG. 6.
FIG. 9 is a diagrammatic view of the pneumatic system utilized in
conjunction with the illustrated embodiment of the multi-track
apparatus disclosed herein.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The drawings and description contained herein detail features of a
multi-track article transporting and heating apparatus. It should
be understood, however, that the unique features of this invention
are applicable to and may be utilized in conjunction with a single
track apparatus, or an apparatus having more or less than the four
tracks illustrated without departing from the spirit or scope of
this invention. Therefore, it should be understood that
constructional details presented herein are applicable to single or
plural track units fabricated to meet the wafer handling and
treating requirements of a particular customer.
Preliminarily, it should be understood that the subject apparatus
utilizes conveyor track means which combines a linear fluid bearing
with a positive drive pacing conveyor belt which controls the speed
and movement of articles being supported by and transported on the
fluid bearing to and past a station, such as the heating station of
the illustrated apparatus. As a result, the total heat treating
time of the articles may be precisely controlled. Additionally, as
detailed hereinafter, preferably the articles being transported are
continuously rotated during exposure to the heat source to insure
uniform heating thereof in a procedure heretofore unknown.
Reference herein to wafer handling and heating is exemplary of a
preferred utilization of this invention but other articles also may
be handled by the subject apparatus as needs dictate.
The fluid utilized to support wafers during movement through
subject apparatus may vary, depending upon the nature of the water
treatment effected therein. In conjunction with the heat treating
effected by the subject apparatus, nitrogen preferably is utilized
as the article levitating and transporting fluid.
The preferred embodiment of the illustrated apparatus is generally
designated 1 as seen in FIG. 1 and comprises three principal
sections or stations, namely, an infeed end or station 2, a central
or heat treating station 3, and an outfeed end or discharge station
4. It is between the infeed station 2 and the outfeed station 4
that wafers W are transported past the heating station 3 at a
predetermined rate as will be described.
It should be understood that the illustrated apparatus may be self
contained, as illustrated in the attached drawings, in which a
plurality wafers are inserted in carriers at the infeed station 2
and are removed in groups in carriers at the outfeed station 4 upon
completion of the heat treating step thereon. However, the subject
apparatus also is adaptable to be interfaced directly with other
apparatus utilized in the manufacture of semiconductor devices so
that wafers may be fed sequentially directly to the infeed station
from another apparatus and/or directly from the outfeed station 4
into another apparatus without intermediate storage or handling in
groups in wafer carriers. However, for simplicity of illustration
herein, the subject apparatus is illustrated as being self
contained as described.
As noted from FIGS. 1 and 2, the illustrated apparatus is
multi-track in construction and is defined by a plurality of
discrete parallel tracks, four in number in the illustrated
embodiment, designated 6, 7, 8 and 9 respectively. Hereinafter
details of each track construction will be set out with respect to
an individual track but it should be understood that such details
are applicable to all tracks utilized in the apparatus. The plural
tracks are operated synchronously to move parallel streams of
aligned correspondingly spaced wafers W to and past the heating
station 3 between the infeed and outfeed stations 2 and 4.
As noted from FIG. 1, the infeed station 2 is defined by a
plurality of wafer feeding mechanisms, designated 11, 12, 13 and 14
respectively, from which individual wafers W are discharged in
sequence onto associated tracks commencing at such feed mechanisms.
In that regard, as mentioned previously, the feed mechanisms to be
described could be eliminated and wafers could be sequentially
positioned on the respective tracks directly from other
semiconductor manufacturing apparatus. In the illustrated
embodiment, however, the respective feed mechanisms are utilized
which include carriers or feed magazines 16, 17, 18 and 19
respectively. Each magazine is supported for downward sequential
indexing so that the lowermost wafer in each magazine may be
sequentially removed therefrom and placed on an associated track as
required in the treating procedure.
At the outfeed station 4, four wafer receiving mechanisms,
designated 21, 22, 23 and 24 respectively, are provided for
receiving wafers W discharged thereto from the associated tracks.
In that regard, wafer receiving carriers or magazines 26, 27, 28
and 29 are supported by the respective receiving mechanisms for
indexing sequentially upwardly upon receipt of individual wafers
sequentially therein.
It should be understood that the four tracks of the illustrated
apparatus are intended for synchronous operation pursuant to which
full magazines each containing a predetermined number of wafers
therein, such as twenty-five, are positioned on the respective feed
mechanisms. The feed magazines are sequentially emptied by placing
wafers onto the associated tracks; the wafers are then moved past
the heating station synchronously, and are sequentially inserted
into the receiving magazines at the discharge station. When the
feed magazines are emptied, full magazines are substituted
therefor; when the receiving magazines are filled, empty magazines
are substituted therefor.
With respect to the illustrative track 6 shown in FIGS. 3 and 4, it
will be noted that feed mechanism 11 and its associated feed
magazine 16, and discharge mechanism 21 and its associated
receiving magazine 26, are supported for opposite indexing
downwardlly and upwardly respectively in conjunction with feeding
and receiving of wafers in sequence onto and from track 6 during
transportation thereof between the predetermined stations 2 and 4
mentioned previously. In that regard, details of construction of
the indexing means utilized for sequentially and automatically
indexing magazines 16 and 26 downwardly and upwardly have not been
disclosed herein in detail because such indexing means have been
known in the art heretofore, as illustrated, for example, in Lasch,
Jr. et al. U.S. Pat. No. 3,645,581 and in Lasch, Jr. et al.
application Ser. No. 404,287 filed Oct. 9, 1973.
For the present purposes, it should be understood that various
known mechanisms (mechanical, pneumatic or hydraulic in operation,
for example) may be utilized to sequentially index the feed
magazine and receiving magazine utilized in conjunction with each
track, so long as the indexing means chosen is capable of
automatically responding to control signals indicating when a wafer
should be fed from the feed magazine and when a wafer has been fed
into the receiving magazine, so that each magazine may be suitably
indexed following such outfeeding and infeeding.
As noted from FIG. 2, the respective tracks, feed mechanisms,
discharge mechanisms, and associated wafer heating structure, as
well as the belt actuating mechanism to be described, are all
supported, preferably at table height, by a lower supporting
framework, generally designated 31, which includes a plurality of
depending legs 32 of desired length. Framework 31 includes a
plurality of frame members 33 joined by welding or the like with
each other and with the supporting legs 32 to provide a horizontal
generally rectangular base for the operative components of the
apparatus, collectively designated 34.
The respective tracks 6, 7, 8 and 9 extend longitudinally of base
34 and are supported thereby. In that regard, as seen from FIGS. 2
and 3, secured to each other and to the base 34 by welding or the
like are a plurality of horizontal frame members 36 upon which the
tracks are directly supported and between which the actuating
mechanism for the belts are positioned.
Additional frame members extend upwardly from base 34 and are
secured thereto by welding or the like, as also seen in FIGS. 2 and
3. Such upright frame members are designated 37 and are joined by
welding or the like to additional horizontal frame members 38
positioned at vertically spaced locations as seen in FIG. 2 above
the base 34. Thus, the upright frame members and horizontal frame
members 37 and 38 provide mounting means for the wafer heating unit
41 to be described. Such horizontal and upright frame members also
provide means for supporting an insulating enclosure for the
heating unit, which surrounds the same substantially completely on
all sides, and is designated 42 generally. Opposite longitudinal
sides of the enclosures are designated 43, the top thereof is
designated 44, and opposite ends are designated 46.
As best seen from FIGS. 2 and 3, the insulating enclosure 42 is
supported by the upright and vertical frame members 37 and 38 so
that limited clearance is provided above the respective tracks to
permit wafers to pass over the tracks through narrow slots provided
in the opposite end walls 46 thereof. Any suitable form of
insulation may be utilized so long as the same is capable of
withstanding and effectively retaining heat within enclosure 42 at
the level generated by heater 41.
In that regard, as seen in the FIGS. 2 and 3, the heating unit 41
preferably is vertically adjustably supported by a plurality of
supporting rods 47 depending from and supported by the upper
framework described previously. A series of apertured plates 48 are
secured to outer margins of the heating unit 41 with the supporting
rods 47 passing therethrough. The supporting rods are threaded so
that adjusting nuts 49 may be threaded to predetermined positions
to locate the heating unit a predetermined distance above the
tracks passing therebeneath to satisfy predetermined temperature
requirements.
In that connection, any commercially available form of heating unit
41 may be utilized in the subject apparatus, depending upon the
nature of the heat treating operation to be effected on the wafers
passing therebeneath. Preferably, however, an infra-red radiation
heater is utilized for applying a uniform area of radiant heat to
wafers carried therebeneath. One such infra-red heater well suited
for the stated purpose is identified as "Triple Power Infra-Red
Solar Heater" distributed by CassoSolor Corporation of Kew Gardens,
New York. Such a heating unit comprises a quartz block in which
heating elements are inlaid so their full heating power can be
utilized to heat the quartz body in which the heating elements are
embedded so that the quartz body transmits virtually all the energy
created downwardly against the wafers to be heated thereby.
Although the infra-red heater of the type described is preferred,
the specific type of heating unit utilized may vary, depending upon
heating requirements and manufacturing needs.
It should be understood, however, that the heating unit employed is
positioned to overlie the major portion of the tracks between the
feed magazines and discharge magazines. In that regard, one
elongated heating unit, or a plurality of two or more discrete
heating unit sections combined to define a substantially continuous
heating unit, may be utilized.
As mentioned previously, each of the plural tracks of the
illustrated apparatus is defined by a combined fluid bearing
structure - positive drive pacing belt over which and by which a
stream of spaced wafers is transported synchronously and
sequentially beneath the heating unit 41.
Referring to FIGS. 2 and 3, the synchronous drive mechanism for the
respective belts 56 of the apparatus is designated generally 57.
Such synchronous drive mechanism 57 includes a pair of transversely
extending parallel shafts 58 and 59 positioned adjacent the
opposite infeed and outfeed ends of the apparatus. Each such shaft
has mounted thereon a plurality of laterally spaced pulley wheels
61 and 62 around which the belts 56 pass, as will be described in
greater detail hereinafter. Shaft 58 comprises the drive shaft of
the belt drive mechanism and is positively actuated through a
chain-motor drive. Such drive includes a chain 63 which passes
around a toothed sprocket 64 secured to shaft 58 and a second
toothed sprocket 66 driven by an electrical stepping motor of known
design. Sprocket 66, chain 63 and sprocket 64 are rotated by the
motor in predetermined stepped increments to correspondingly rotate
drive shaft 58 and each of the plurality of belts 56 driven thereby
in corresponding increments. That is, upon rotation of sprocket 66
by stepping motor 67, the belts 56 of the respective tracks are
moved synchronously and for uniform distances at uniform rates so
that wafers positioned on the respective tracks are synchronously
and simultaneously moved through the apparatus beneath the heating
unit in step fashion.
Each of the shafts 58 and 59 is mounted for rotation at its
opposite ends in a pair of opposed bearing blocks 68 and 69 for the
stated purpose. Note FIG. 2 in that regard with respect to shaft
58.
As seen in FIG. 3, the stepping motor is operatively mounted in
known fashion to a supporting plate 71 bolted or otherwise secured
to a second supporting plate 72 depending from the aforementioned
frame members 36 supported by base 34 of the apparatus.
To provide each belt 56 with its wafer pacing and spacing
capability, means are provided at spaced locations thereon with
which the respective wafers are engaged during movement through the
apparatus. Such means regulate the speed of movement of individual
wafers through the apparatus as the same are supported upon and
moved longitudinally of the tracks by the fluid bearing structure
of the tracks in the manner to be described. Such wafer spacing
means, as best seen in FIGS. 3 and 5, comprises a series of spacer
buttons each of which is designated 76 and each of which is defined
by a metal (such as stainless steel) or temperature resistant
plastic (such as Teflon or Kapton) pin 77 having a head 78 at one
end thereof and a shank 79 which extends through an aperture
provided in the belt 56. Each pin 77 is held in place by a metal or
plastic sleeve 81 which surrounds shank 79 and is held in
engagement with the shank by a spring washer 82, preferably of high
temperature resistant metal or plastic, which passes over the end
of pin shank 79 to hold the sleeve in place in engagement with the
surface of the belt which is opposite from the surface with which
pin head 78 is engaged.
The spacer buttons 76 constructed as described are positioned
through spaced apertures provided in belt 56 at predetermined
uniform locations along the belt.
Belt 56 preferably is formed from a high temperature material with
a flexible plastic being preferred, although a high temperature
metal, such as stainless steel could be employed. In that regard,
it has been found that a non-metallic belt formed of Kapton
polyamide plastic (produced and marketed by E. I. DuPont de Nemours
Co.) is particularly well suited for the stated purpose because of
its high temperature resistance and wide range of temperature
utilization, ranging from -200.degree.C or lower to +400.degree.C
or higher. In the present circumstances, wafer temperatures
desirably reach +200.degree.C or more in conjunction with their
heat treatment by the subject apparatus so that the Kapton material
described is particularly well suited for the stated purpose.
In addition to providing means for spacing wafers at predetermined
distances during their passage through the apparatus, the spacer
buttons 76 also provide means for pacing the rate of movement of
the wafers via the belt drive mechanism described previously. In
that regard, each drive pulley 61 adjacent the discharge end of the
apparatus is provided with a series of recesses 86 at spaced
peripheral locations around its outer edge (as best seen in FIG. 3)
contoured to receive therein the head 78 of each spacer button as a
belt passes around such pulley 61. Thus, upon positive intermittent
rotation of pulley 61 by shaft 58 as described previously, positive
intermittent drive of an associated belt 56 is effected in
accordance with the mode and rate of movement of shaft 58 by the
stepping motor 67.
Therefore, as best seen from FIGS. 3 and 4, the respective spacer
buttons 76 limit movement of the respective wafers passing through
the apparatus in accordance with the speed of movement of the
pacing belt. That is, each belt is actuated to impede or pace each
wafer in accordance with the predetermined speed desired for wafer
movement as transmitted by the belt drive mechanism to the belt. It
should be understood that during such pacing by the belt, the
wafers are supported upon and moved longitudinally of the track by
the levitating and transporting effect of the fluid emanating from
the fluid bearing structure which combines with the positive drive
belt in defining each operating track.
In that connection, as seen in FIGS. 2 and 3, each wafer W moving
along a track is supported slightly above the upper surface of the
track during movement to prevent wafer damage and to permit, when
desired, rotation of the individual wafers by the fluid bearing
track structure in the manner to be described.
Details of the fluid bearing track structure are shown in
conjunction with exemplary track 6 seen in FIGS. 3 and 4. Fluid
bearing track structure 6 is of elongated configuration and, as
seen in FIG. 1, extends the full longitudinal distance of the
apparatus between the infeed and outfeed stations 2 and 4. To
facilitate manufacture of the fluid bearing structure and to permit
selective operation thereof in different sections of the track
structure, the fluid bearing is produced, in the illustrated
embodiment, in four structurally discrete but functionally
cooperable sections 91, 92, 93 and 94. Such four sections are
arranged as end to end continuations of each other as seen in FIGS.
4A and 4B. The opposite end sections 91 and 94 preferably
constitute uni-directional sections and the central sections 92 and
93 preferably constitute bi-directional sections for the purpose to
be described.
In that regard, as noted from FIGS. 4 and 6, fluid bearing track
structure 6 comprises an elongated supporting plate 97 which
extends the length of the apparatus and provides a mounting base
for the fluid bearing track structure. Plate 97 may be formed as
one elongated member or in cooperable segments, depending upon
manufacturing limitations. In either event, plate 97 is operatively
mounted between opposed longitudinally extending bracket members 98
and 99 which in turn are secured in a suitable fashion, such as by
welding, to the frame members 36 described previously. Screw type
fasteners 101 may be utilized for securing plate 97 between
brackets 98 and 99 as seen in FIG. 6. The plate 97 may be formed of
metal or temperature resistance plastic, with metal, such as
stainless steel or high temperature aluminum or aluminum alloy,
being preferred.
Plate 97 is formed with two parallel spaced elongated longitudinal
slots 102 and 103 therein as seen in FIG. 6 for its full extent.
Such slots preferably are symmetrically arranged on opposite sides
of the longitudinal axis of the plate.
Extending longitudinally along its axis between the axes of shafts
58 and 59 mentioned previously, as best seen in FIGS. 3 and 6,
plate 97 is also provided with a stepped slot 104 having a central
depressed area 106, the latter being adapted to receive therein the
heads 78 of the pins of the spacer buttons 76. The shallower upper
portion of slot 104 is adapted to receive therein the pacing belt
56 in such fashion that the upper surface of the belt 56 is
depressed slightly relative to the upper surface 107 of the plate
97. Thus wafers W moving along the track are not in contact with a
belt but have edge contact only with the spacer buttons carried by
the belt. Plate 97, as seen in FIGS. 3 and 4, also is provided with
a pair of slots 108 and 109 in line with the pulleys 61 and 62
about which the belt 56 passes. Such slots accommodate the upper
portions of the pulleys as the same rotate relative to the
plate.
As noted from FIGS. 3 and 4, the opposite end sections 91 and 94 of
the fluid bearing track structure extend into and substantially
entirely through the associated feed magazine 16 and discharge
magazine 26. Each such magazine straddles the fluid bearing track
structure to permit the upward and downward indexing of such
magazines as mentioned previously. Such end sections of the fluid
bearing track structure include electrical or pneumatic sensing
means 110 and 110' for transmitting control signals to the
magazines for effecting magazine indexing as required. Such
magazine sensing control has been known heretofore as described in
the previously identified Lasch, Jr. patent and application.
It should be understood that positioning of section 91 of the fluid
bearing track structure within magazine 16 permits the directional
fluid bearing to sequentially withdraw the lowermost wafer from the
magazine when the magazine is properly indexed and to automatically
transfer each such wafer sequentially over track section 91 onto
track section 92. Similarly, at the opposite end of the apparatus
the positioning of track section 94 into magazine 26 permits such
section 94 to receive wafers in sequence from track section 93 and
to sequentially insert the same directly into magazine 26 as the
magazine is sequentially indexed into position.
The intermediate track sections 92 and 93 carry wafers generally
beneath the heating unit 41 and, because of the bidirectional
capability preferably imparted to such intermediate sections,
effect rotation of such wafers as the same are passing beneath the
heating unit to effect uniform heating thereof and to preclude the
formation of hot spots on the wafers.
Except for the uni-directional and bi-directional distinctions of
the track sections noted, each section is identically constructed
as best seen in FIGS. 4 and 6. Guide rails 111 and 112 are provided
along lateral margins of the fluid bearing track structure and in
the embodiment illustrated preferably are defined by elongated
strips of Kapton plastic of the type noted previously. Such guide
rails are held in place between the plate 97 and the brackets 98
and 99 between which plate 97 is mounted. For wafers of smaller
diameter such guide rails may be moved inwardly and clamped in
place in the respective slots 102 and 103 as shown in dotted lines
in FIG. 6.
The slots 102 and 103 are dimensioned to receive therein generally
L-shaped track members designated 113 and 114 respectively. Such
track members are formed in separate sections but as longitudinal
continuations of each other, as seen from FIG. 4. Each such track
member is provided with a longitudinal plenum recess 116 and 117
respectively for its full length. The respective track members are
held in place in slots 102 and 103 by screw fasteners extending
vertically therethrough into plate 97 at predetermined locations
(not shown).
The plenums of the respective tracks are operatively connected with
a source of fluid bearing material, such as the nitrogen gas
mentioned previously, via recesses 118 and 119 (FIG. 6) provided at
spaced locations through plate 97. Pneumatic fittings 121 and 122,
having hoses 123 and 124 connected with a suitable source of
nitrogen or other fluid bearing gas are engaged with the plate 97
in communication with the recesses 118 and 119. Thus, a wafer
supporting fluid medium may be introduced into the plenums defined
by track members 113 and 114 and therethrough into contact with
wafers positioned on the tracks.
To impart directional flow to the suporting fluid introduced into
the plenums of each track as described, flexible insert strips,
designated 123 and 124, are interposed between the respective track
members 113 and 114 and an adjacent wall of slots 102 and 103, as
best seen in FIG. 6. Such insert strips preferably are formed in
accordance with the teachings of Lasch, Jr. U.S. Pat. No.
3,718,371, and each is provided with a series of equidistant
similarly contoured directional fluid passages 126 and 127, as best
seen in FIGS. 7 and 8. Each such strip is formed with recesses 128
and 129 extending therethrough which adapt such strips to receive
bearing fluid from the plenum provided by track members 113 and 114
and to introduce such bearing fluid into the directional fluid
passages 126 and 127 to emanate therefrom as a layer of supporting
fluid in the manner and for the purpose described in said Lasch,
Jr. U.S. Pat. No. 3,718,371.
In that regard, as noted previously, the end sections 91 and 94 of
the fluid bearing track structure are uni-directional as shown by
the directional arrows in FIG. 4. Such uni-directional effect is
produced by inserting each of the jet strips 123 and 124 with their
directional fluid passages facing in the same direction. The
central bi-directional track sections 92 and 93 are provided with
their bi-directional capability by reversely orienting the jet
strips 123 and 124 relative to each other so that the directional
fluid passages therein face in opposite directions, as shown by the
directional arrows in FIG. 4.
Thus, wafers moving along end track sections 91 and 94 move
generally in a straight non-rotational fashion because streams of
fluid emanating from the two jet strips 123 and 124 are directed in
the same direction. However, wafers moving along the central track
sections 92 and 93 move rotationally and longitudinally over the
bi-directional track sections 92 and 93 because streams of fluid
emanate in opposite directions from the jet strips. Thus, fluid
striking the underside of a wafer positioned effects rotational
movement of such wafer as seen in FIG. 4 by the directional arrows
shown therein.
As noted, such rotation of the wafers as the same are being
supported by and moved along the fluid bearing track structure is
effected to insure uniform heating of wafers passing through the
apparatus beneath heating unit 41. However, under selected
circumstances, such wafer rotation may be eliminated if uneven
heating of articles being treated is not a problem merely by
positioning each of the jet strips 123 and 124 in central track
sections 92 and 93 to extend in the same direction.
By regulating the speed of movement of each belt 56 the rate of
movement of each wafer through the heating apparatus, and therefore
its total heat treating or bake time, may be closely controlled.
Different bake times may be achieved by varying the dwell time
after each incremental feed movement of the belt is effected. In
the illustrated embodiment, the stepping motor 67 utilized effects
120 degree rotational incremental movement of the belt before the
motor halts for a predetermined time. Thus wafers entering beneath
the heating unit at spaced intervals progress therethrough at a
predetermined rate determined by the rate of belt movement. In a
illustrative embodiment, approximately two seconds is utilized to
move each wafer a 31/2 inches increment, with an intermediate dwell
time being chosen as desired to meet particular needs. A control
switch (not shown) of conventional construction may be selectively
set to determine the aggregate time of bake for each wafer, within
wide range limits of 40 seconds to 15 minutes, for example.
Additionally, because the fluid supporting nitrogen gas passes
through the plenum defined by the fluid bearing track structure,
(which is subjected to heat from heating unit 41 such gas becomes
heated by the track structure. As a result the wafers are levitated
and moved on hot nitrogen gas which further enhances temperature
stabilization of the wafers being treated.
Also, if preferred, the nitrogen supply may be cut off during each
wafer dwell period, thereby allowing individual wafers to settle
upon the upper surface of a track structure and to be heated
directly by conduction from the track structure while the same is
simultaneously being heated from above from the intra-red radiation
source 41. Prior to movement of the pacing conveyor another next
increment, gas is introduced under the wafers to levitate them
prior to movement of the belt so that damage to the wafers due to
sticking thereof to the track structure is obviated.
In the illustrated embodiment, the heating unit 41 preferably is 36
inches long and spans ten wafer dwell positions between the infeed
and outfeed ends of the apparatus.
To prevent wafers from entering beneath the heating unit during the
time the pacing belt is moving, a known vacuum brake structure 131
is incorporated at the infeed end of the apparatus and is timed to
release a wafer only during a dwell period of the pacing belt.
Thus, wafers are allowed to sequentially enter the heating station
and contact the first protruding spacer button prior to movement of
the belt. When the belt moves, the fluid bearing track structure
urges the wafer to follow the belt, thus allowing another spacer
button to emerge from below the upper surface of the track to
constrain a subsequent wafer entering from behind. Vacuum brake 131
is provided in conjunction with the aforemention sensor 110' as
seen in FIGS. 3 and 4 and as will be described hereinafter with
respect to FIG. 9.
A similar vacuum brake structure 132 is provided in conjunction
with sensor 110 provided at the outfeed end of the apparatus as
seen in FIGS. 3 and 4. Such vacuum brake halts wafers fed into the
discharge magazine sequentially prior to indexing of the
magazine.
Conventional control switches and timers may be utilized to permit
selective variation of the dwell period of the pacing belt. Thus,
due to the synchronization effected by the belt drive mechanism
described previously, each of the multiple tracks of the subject
apparaus are actuated simultaneously and sequentially to move a
plurality of streams of wafers in equally spaced relationship to
and past the heating station as described.
Reference is now directed to FIG. 9 for diagrammatic illustration
of the pneumatic system utilized with the illustrated four track
apparatus.
Supporting fluid is introduced through a central supply line 136
from any suitable gas source and passes through a pressure
regulator 137 into supply line 138 and therefrom into a series of
branch supply lines 139, 140 and 141. Solenoid valves 142, 143 and
144, which are regulated by associated needle control valves 146,
147 and 148, control fluid pressure in branch supply lines 149, 150
and 151 which are continuations of lines 139, 140 and 141.
Supporting fluid may thus be introduced into the various track
sections of each fluid bearing track structure.
A manifold 152 receives bearing fluid from supply line 151 and
distributes the same through a series of conduits 154 to each of
the plenums provided in the uni-directional fluid bearings in each
of the end track sections 91 of the respective tracks 6, 7, 8 and
9.
Supply line 150 is connected through a T-joint 155 with a pair of
manifolds 156 and 157 with a series of conduits 158 and 159
connected with the plenums provided in the bidirectional track
sections 92 and 93 of tracks 6, 7, 8 and 9.
Finally, supply line 149 is connected through manifold 161 with
each of the plenums in the other uni-directional end track sections
94 provided adjacent the discharge end of the apparatus.
As mentioned previously, at the infeed end of the apparatus each
track is provided with a vacuum stop 131 to preclude introduction
of a wafer prematurely into the heating zone. Each such vacuum stop
is connected through a manifold 161 and cooperating conduit 162
through a control gate 163 with a suitable source of vacuum 164.
Similarly, at the discharge end of the apparatus each of the
aforementioned vacuum stops 132 is connected via manifold 166 and
associated conduit 167 through a control gate 168 with the vacuum
source 164.
Having thus made a full disclosure of the subject apparatus and
method which incorporate and utilize a fluid bearing and positive
drive conveyor system in conjunction with a heat source, reference
is directed to the appended claims for the scope of protection to
be afforded thereto.
* * * * *