Robot end-effector cleaner and dryer

Details Robot end-effector cleaner and dryer Robot end-effector cleaner and dryer

1999-08-27

2001-04-10

Stinson, Frankie L. (Department: 1746)

Cleaning and liquid contact with solids

Apparatus

With spray or jet supplying and/or applying means

C134S199000, C134S902000, C134S102300

Reexamination Certificate

active

06213136

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a device for rinsing and drying flat substrates such as semiconductor wafers.
BACKGROUND OF THE INVENTION
In recent years it has become common in the semiconductor industry to polish the wafers after successive layers of conductive traces or other structures are formed on their surfaces. This produces very smooth surfaces for repeated photolithographic processes and significantly improves the yield. The polishing process, typically chemical-mechanical polishing (CMP), leaves grit and other debris on the surface of the wafer which must be removed before fabrication process can continue. This has led to the development of wafer cleaning devices, such as the device described in co-pending application Ser. No. 08/683,654, which is incorporated herein by reference in its entirety. Following cleaning, the wafers must be thoroughly dried before they can be returned to the fabrication line.
Wafer spin dryers use a combination of centrifugal force and air flow to remove all moisture from the surface of the wafer. Two known types of spin dryers are illustrated in
FIGS. 1 and 2
. In the version shown in
FIG. 1
, a wafer
10
is held by fingers
12
above a platen
13
. Platen
13
is rotated on a shaft
14
by a spin motor
15
. Rinse water is applied from above by one or more nozzles
16
to the “good” (active) side of wafer
10
. A problem with this type of dryer is that the drying chamber
17
is open to the atmosphere, which while normally quite clean still contains particulate matter. Particles which fall onto the wafer during and immediately following the drying operation will remain when the next process step begins.
In the prior art dryer shown in
FIG. 2
, the drying chamber
20
is not open to the atmosphere from above, and the wafer
10
is held by fingers
21
below the platen
22
. The platen is spun by a motor
23
which is mounted above the platen. The good side of the wafer faces downward, and one or more nozzles
24
rinse wafer
10
from below. A problem with this type of dryer is that water droplets which are thrown from the spinning wafer can strike the surface of the drying chamber and splash against the good side of the wafer.
Thus there is a need for a wafer dryer which avoids the above problems and reliably yields a clean, dry wafer suitable for further processing.
SUMMARY OF THE INVENTION
The wafer spin dryer of this invention includes a platen and a plurality of holding members or fingers which extend downward from the platen. The wafer is held with its good or active side facing upward. One or more nozzles are positioned so as to direct a rinse liquid (typically water) against the good side of the wafer. The rinsing liquid is applied to the good side of the wafer, and the wafer is rotated to create a centrifugal force which removes the liquid from the good side of the wafer. A surface laterally adjacent the edges of the spinning wafer is contoured and angled such that the liquid which flies from the wafer is directed downward to a portion of the drying chamber below the wafer. As a result, the used rinse liquid cannot come into contact with the good side of the wafer.
The wafer is preferably placed in the spin dryer by a robot. In the preferred embodiment, the wafer is held in the spin dryer by three fingers which extend downward from the platen and which are spaced at equal (120°) angles around the axis of rotation. The fingers contain notches or other concave surfaces which grip the edge of the wafer. One of the fingers is movable to allow the robot to place the wafer in a position where it can be held by the three fingers. The wafer is positioned slightly eccentric to the axis of rotation such that it is forced against the two fixed fingers as it is rotated. The rotating mass (wafer and platen) is balanced as a whole so that undue vibrations do not occur as the wafer is rotated.
In many situations, the same robot arm places the wafer into the cleaner, transfers the wafer from the cleaner to the dryer, and transfers the wafer from the dryer to the finished wafer cassette. The end-effector of the robot arm can thus become contaminated with grit and chemicals. As another aspect of this invention, the wafer dryer contains a separate chamber which is used to clean and dry the end-effector while the wafer is being dried. Thus, when the wafer is withdrawn from the spin dryer, it does not become re-contaminated with grit and/or chemicals from the end-effector.
In the preferred embodiment the end-effector cleaning chamber contains one or more nozzles which spray a rinse liquid onto the end-effector and one or more nozzles which direct a flow of nitrogen against the end-effector and sweep the rinse liquid from the end-effector as it is being withdrawn from the end-effector cleaning chamber.


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