Apparatus for processing semiconductor wafers

Apparatus for processing semiconductor wafers is described as having a rotor mounted on a horizontal axis with support bearings at each end of the rotor. Wafers are arranged in a carrier which can be loaded and unloaded into the rotor of the apparatus through an access opening which is directed in a generally upward position when the rotor is stopped. Control means provide for automatic stopping of the rotor in a correct position for unloading and reloading at the end of each processing cycle.

BACKGROUND OF INVENTION 
1. Field of Invention 
This invention relates to apparatus especially designed for processing 
semiconductor wafers or similar disc-shaped objects. More specifically, 
the invention is concerned with providing an improved apparatus which 
permits easier or automated loading and unloading of carriers into and out 
of such apparatus for increasing productivity and quality of the 
processing carried on within the apparatus. 
2. Description of Prior Art 
It is known in the art of processing semiconductor wafers to provide for 
various forms of apparatus which allow the wafers to be coated, etched, 
cleaned, or dried, prior to eventual use of the wafers in the production 
of integrated circuits. Early efforts for treating wafers in these various 
ways involved the treatment of only a single wafer at a time, as shown for 
example in U.S. Pat. No. 4,027,686 or the treatment of a number of wafers 
in a stationary tub as shown, for example, in U.S. Pat. No. 4,092,176. 
Other developments included arrangements for spinning a plurality of 
wafers within a controlled environment so that multiple processing steps 
(such as washing with deionized water and drying with nitrogen gas) could 
be carried out during a single cycle of operations in a single apparatus. 
Representative patents showing this approach include U.S. Pat. Nos. 
3,970,471; 4,132,567; and 4,300,581. 
At the present time there appears to be a preference for processing a 
plurality of wafers in standard-sized plastic carriers which are used for 
holding and protecting wafers while they are being transported and 
processed. U.S. Pat. No. 4,300,581 discloses a type of apparatus designed 
to receive such standard carriers through an end opening of a rotor 
mounted within a stationary tub. The arrangement shown in U.S. Pat. No. 
4,300,581 provides for a tilted axis of rotation which is described as 
solving a problem of liquid being retained between wafers because of 
surface tension. However, it is also stated in the same patent that 
horizontal loading of apparatus of this type is more desirable than 
loading on a vertical axis. 
SUMMARY OF THE INVENTION 
The present invention provides for an improvement in the type of 
semiconductor wafer processing apparatus which is designed to receive 
standard wafer carriers and to spin those carriers with their retained 
wafers on a horizontal axis while carrying out coating, etching, washing, 
or drying operations within the apparatus. The present invention also 
recognizes the advantages in being able to place loaded carriers into an 
apparatus without having to orient the carriers in a way which might 
result in damage or spilling of wafers while the loading is taking place. 
However, unlike prior art arrangements, the present invention provides for 
the loading of a carrier into a rotor through an access opening which does 
not interrupt or interfere with the use of bearing supports at each end of 
the rotor. 
In accordance with the present invention, a rotor is securely and precisely 
mounted for rotation on a generally horizontal axis and is provided with 
supporting bearings at each of its ends so that no unbalanced conditions 
will be created within the rotor while it is being rotated. With this 
arrangement a longer rotor can be constructed for holding more than one 
carrier while also permitting the processing only a single carrier without 
creating an unbalanced condition in the rotor as the wafers are being 
processed. 
In order to provide for loading and unloading of a rotor which is fully 
supported at each of its ends, an access opening is provided through a 
wall of the rotor, and the access opening is directed in a generally 
upward position when the rotor is stopped at the end of a cycle. Control 
means are provided for stopping the rotor in a correct position for 
loading and unloading. The control means include a control plate mounted 
for rotation with the rotor, and the control plate has an opening formed 
in it for receiving a locking pin when the control plate and the rotor are 
in positions for directing the access opening of the rotor in a generally 
upward position. In addition, control circuitry and a program are provided 
for dictating a processing cycle which includes (a) a very slow rotation 
of the rotor at the end of each cycle and (b) an actuation of the locking 
pin during the period of very slow rotation so that the locking pin can 
enter the opening in the control plate and effectively stop all rotation 
of the rotor at the end of the cycle. In this manner, there is provided a 
positive mechanism and control for assuring the correct orientation of the 
access opening of the rotor for loading and unloading purposes. 
In an actual embodiment of the invention, the rotor is positioned and 
driven within a housing which is also provided with an access opening for 
providing entry to the rotor within the housing. The first access opening 
of the rotor and the second access opening of the housing are each 
provided with respective closure means for closing the rotor and sealing 
the housing during operations. The closure means for the rotor includes a 
mechanism for automatically opening the closure at the end of each 
operating cycle. This permits rapid and automated unloading and reloading 
of the apparatus. 
By providing for an upwardly directed access opening into the rotor, the 
apparatus of this invention lends itself very well to completely automated 
facilities which utilize robots or transfer equipment for loading, 
unloading and transporting carriers of wafers between processing stations. 
Access through the tops of housings of apparatus associated with the 
various stations provide for very suitable access which maintains each 
carrier in a preferred orientation and eliminates risk of damage or 
spillage to wafers while they are being handled and processed. 
Although this invention will be described with reference to a specific 
application in the processing of semiconductor wafers, it can be 
appreciated that the apparatus of the invention can be used for other 
similar purposes for any disc-shaped objects which are placed within a 
carrier for processing.

DETAILED DESCRIPTION OF THE INVENTION AND OF A PREFERRED EMBODIMENT 
Referring to FIGS. 1 and 2, a preferred embodiment of the invention is 
illustrated with reference to an actual working apparatus which has been 
built by the owners of the rights in this application. In this embodiment, 
a stationary housing 10 constitutes the most visible portion of the 
apparatus. The housing 10 is generally in the shape of a cylindrical drum 
having flat ends, as seen also in FIGS. 3 and 4, and the housing is 
mounted on a base 12 which is fabricated to support the housing and to 
contain many of the working components associated with the operation of 
the apparatus. In the illustrated embodiment, the housing 10 is affixed to 
an upper support plate 14 of the base 12 with a series of brackets 16 
secured between the housing 10 and the support plate 14. As shown in FIG. 
1, the upper support plate 14 is pivoted at 18 to a lower portion of the 
base 12 so that the entire upper plate 14 and its contained housing 10 can 
be lifted (as shown by the partial dashed line position to the left of 
FIG. 1) for ease of servicing of component parts contained within the base 
of the unit. When the apparatus is not being serviced, the support plate 
14 is secured to the lower portion of the base with manually operated 
fasteners 20. 
The housing 10 functions as a treatment chamber in which a rotor assembly 
can be carried together with a load of semiconductor wafers which are to 
be treated within a special atmosphere or with a particular gases or 
liquids. Various treatments, such as washing, deionizing, drying, and 
etching can be carried out with apparatus of this type. Suitable 
connections are provided to supplies of gases or liquids for supplying 
appropriate treatment materials to the chamber defined within the housing 
10, and a series of such connections are indicated generally at the 
positions 22 for receiving a liquid or gas and disbursing such liquid or 
gas to the interior of the housing through manifolds 24 associated 
therewith. The manifolds 24 and the way in which they are connected into 
the housing are well known in this art and do not form a separate part of 
this invention. In addition, a deionizing conduit 26 may be provided with 
a series of ports contained within manifolds 28 for communicating with the 
chamber defined within the housing 10. 
One of the features of the present invention is to provide for a loading of 
a housing, of the type illustrated, through a top wall portion thereof so 
that loading may be carried out with automatic transfer line equipment if 
desired. To accomplish this, an access opening 30 is defined at the top of 
the housing 10, as seen in FIGS. 1 and 2. This access opening can be 
closed and sealed with a closure means 32 comprising a curved plate which 
matches the general outside contour of the housing 10 and which can be 
swung between positions which provide for a closing and sealing of the 
opening 30 to one which provides for a complete opening of the access 
opening 30. The closure means 32 includes mounting brackets 34 for 
supporting the closure means 32 and for securing the closure means to an 
actuating mechanism illustrated in FIG. 4. The actuating mechanism 
includes a plate 36 which can be swung about a horizontal axis 38 of the 
apparatus to, in turn, swing the support structures 34 and the closure 
means 32 to the dotted line position shown in FIG. 4. This is accomplished 
with a fluid pressure device 40 which is controlled in a known manner to 
provide for swinging motions of the closure means 32. The closure means 32 
is mounted so as to clear the housing 10 without making actual contact 
with the housing while it is being moved between opened and closed 
positions. Once the closure 32 is in a closed position, an inflatable seal 
42, arranged on the underside of the closure means 32 in a position which 
surrounds the opening 30, is inflated to effect a tight seal between the 
closure means 32 and the outer surface of the housing 10. Thus, there is 
provided a means for opening and closing a major access opening through 
the top of the stationary housing 10. 
Within the housing 10 is mounted a rotor assembly 48 of the type 
illustrated in FIGS. 5 through 7. As shown in FIG. 5, this rotor assembly 
is made up of framing members 50 which are shaped and dimensioned to 
define a rectangular container for receiving one or more standard sized 
carriers designed for holding silicon wafers during various handling and 
processing steps. The illustrated embodiment of FIG. 5 is designed to 
receive two separate carriers of silicon wafers, in an end to end 
relationship, within the generally rectangular frame of the rotor assembly 
48. Axle stubs 52 are secured at each end of the rotor assembly for 
defining an axis of rotation 38 for the apparatus. Bearings and seals are 
provided around the axle stubs 52, as at 54, so that the rotor assembly is 
fully supported at each end and is mounted for rotation within the housing 
10. Rotation is achieved with known driving means which includes a drive 
belt 56 (see FIGS. 1 and 3) for receiving driving moments from a drive 
motor 58, contained within the base of the apparatus and directly 
connected to a pulley 60 mounted on its output shaft. The driving moments 
are imparted to a pulley 62 mounted on an axle stub 52 associated with one 
end of the rotor assembly. Control means, with suitable circuits and 
programming arrangements, can be provided for turning the rotor assembly 
within the housing while the rotor assembly contains a load of wafers and 
while treatment gases or liquids are admitted to the chamber. The unit 
which is illustrated is capable of rotating at very high speeds, for 
example, up to 4000 revolutions per minute for certain treating and drying 
processes which are required for semiconductor wafers. 
It can be appreciated that when the carriers of wafers are deposited into 
the frame of the rotor assembly 48, some means is required to retain the 
carriers and their contained wafers within the rotor while rapid rotation 
takes place. This is accomplished with a closure means 60 for the rotor 
itself. This closure means can be best seen in FIGS. 5 through 7 in which 
it is shown as a relatively open structure which permits an easy flow of 
gases or liquids into and out of the rotor for processing wafers contained 
therein. This relatively open structure can be formed from wire stock as 
illustrated in FIGS. 5 through 7, if desired. 
A special means is provided for opening and closing the closure means 60 
for the rotor assembly. Referring to FIG. 6, it can be seen that the 
closure means 60 generally covers the entire top of the rotor assembly and 
is mounted to pivot on an axis defined by a shaft 62. Referring to FIG. 7, 
the closure means is shown in a closed position in solid lines while shown 
in an open position with dashed lines. An actuating device consisting of a 
lever arm 64 actuated by a fluid cylinder 68 is connected to the shaft 62 
for effecting pivotal movements of the closure means 60. When the closure 
means 60 is pivoted to a closed position, as shown in FIG. 7, a further 
feature of the invention provides for an automatic locking of the closure 
means into locking slots formed in a pair of parallel flanges 68 mounted 
on each side of the rotor assembly. As shown in FIG. 5, a spring device 70 
normally urges the shaft 62 towards a locking position (towards the right 
in the FIG. 5 view) so that cross members 71 of the closure means 60 
become engaged under portions 72 of the flanges 68. Unlocking of the 
closure means is accomplished with a fluid cylinder 74 which can be 
actuated to drive the shaft 62 into engagement with a slot formed in the 
end of the shaft 62 so as to overcome the spring 70 and to urge the 
closure 60 towards the left in the FIG. 5 view. This effects an automatic 
unlocking of the closure means 60, after which it can be rotated to an 
open position as described with reference to FIG. 7. 
After a cycle of operations is completed, it is important to provide for a 
control means which guarantees the stopping of the rotor assembly 48 in a 
correct position for aligning its access opening with the access opening 
30 of the housing 10. This is accomplished by mounting a control plate 80 
on one of the axle stubs 52 of the rotor assembly for rotation therewith. 
The control plate 80 has a slot 82 formed into its surface for receiving a 
locking pin 84 when the locking pin 84 is advanced toward the control 
plate by a fluid operated device 86. With this arrangement, a processing 
cycle for the apparatus can be provided with a final rotation of the rotor 
which is very slow so that actuation of the locking pin 84 can take place 
and cause a stopping of the rotor in a position which correctly orients 
its load of wafers in an upwardly directed position for being unloaded 
from the housing 10. 
Although the invention has been described with reference to basic 
structural components, it should be understood that additional features 
and controls can be included to provide for greater automation or control, 
or whatever. For example an optical counter 90 can be mounted for rotation 
with one of the axle stubs 52 so as to count revolutions of the rotor 
assembly. Also, circuitry can be provided for fully automatic opening and 
closing of the unit, rotation of the rotor at preferred speeds, and 
controlled admission of treating fluids. These and other variations are 
intended to be included within the scope of this invention as further 
defined in the claims below.