An electroplaning technique achieves superior flatness of the face of a wafer. A chuck holds the wafer so the face of the wafer is oriented downwards and lowers it to an electroplaner stage. The electroplaner includes an elongated, horizontally extending cup, an elongated horizontally extending nozzle within it. Electrolyte flows non-turbulently from an upper side of the nozzle to create a meniscus of electrolyte that contacts the wafer. The electroplaner moves transversely while the chuck is held steady so that said meniscus sweeps across the face of said wafer. A rinser of similar construction likewise has a meniscus or rinse that sweeps across the wafer. The nozzle can have a row of openings along its upper side, or may be formed at least in part of a microporous material. The wafer is electrically configured as cathode.

BACKGROUND OF THE INVENTION 
This invention relates to wet process chemistry treatment of substrates, 
e.g., semiconductor wafers and the like, and is more particularly directed 
to a technique for planing or etching the surface of a flat workpiece so 
that it is left uniformly flat across the surface. The invention also 
concerns a technique that facilitates employment of robotic handling of 
the articles to be planed e.g. between plating steps. 
Electroplating plays a significant role in the production of many rather 
sophisticated technology products, such as masters and stampers for use in 
producing digital compact discs or in the manufacturing of advanced 
semiconductor wafers. However, as these products have become more and more 
sophisticated, the tolerances of the plating process have become narrower 
and narrower. Current plans to increase the circuit density of silicon 
wafers are being thwarted by the inability of plating techniques to 
control unevenness in the plating process, and especially in the axial 
direction. 
It is the current practice to employ an electrolytic etch technique to 
remove a surface layer from a wafer, for example after a plating step. In 
this technique, the wafer is held vertically, i.e, in a vertical or nearly 
vertical plane, and is sprayed or injected with an etchant electrolytic 
solution. There can be a cathode for applying an electric current across 
the solution to the surface of the wafer. The electrolyte then runs down 
the front of the wafer and drips off from the bottom edge. This creates a 
conductivity path through the electrolyte back to the cathode. Thus in 
this arrangement, even if the electrolyte does remove the material evenly 
at the point where the electrolyte is sprayed on, metallization can be 
uneven below that point. The planing is less than optimal. Also, any 
particles that may become entrained in the electrolyte continue down the 
face of the wafer and can deposit on other parts of the wafer. While it 
would be an improvement to hold the wafer horizontally and spray the 
electrolyte onto the horizontal wafer, it has not been possible to spray 
the electrolyte onto a horizontal surface and then collect it again. Thus 
a technique to produce a truly flat electro-planed workpiece has eluded 
the industry. 
OBJECTS AND SUMMARY OF THE INVENTION 
Accordingly, it is an object of this invention to provide an electroplaner 
arrangement which reliably removes material from a wafer without 
unevenness, and which avoids the drawbacks of the prior art. 
It is another object of this invention to provide an electroplaner which 
can be adapted easily to an automated wafer handling mechanism, and which 
can be automated as to the loading or unloading of the wafer. 
According to one aspect of the present invention, a planar face of a 
substrate has been subjected to a surface treatment, e.g., plated with a 
metal layer, and the top portion of the plating is to be removed, i.e., 
planed. An electroplaner comprises an elongated horizontally extending cup 
having an open top, an elongated horizontally extending nozzle within the 
cup, and a supply conduit that supplies an electrolyte to the nozzle. The 
nozzle creates a meniscus of the electrolyte in the cup that can contact a 
substrate above it. In order to plane the surface of the substrate, the 
substrate, e.g., wafer, is placed in a chuck. The chuck is rotated to 
orient the wafer horizontal and face down. Then the chuck is lowered to a 
level at which the meniscus contacts the face of the substrate. Then the 
electroplaner is moved horizontally, thus effecting relative motion 
between the substrate and the electroplaner so that said meniscus sweeps 
across the face of said substrate. Alternatively, the cathode can be a 
conductive rod within the nozzle. The nozzle can be in the form of a 
tubular finger and can serve as the cathode, whereby an electrical current 
is applied across the meniscus between the electroplaner and the 
substrate. The tubular nozzle preferably has opening(s) arranged on an 
upward side thereof, such that the electrolyte can flow non-turbulently 
from an interior of the nozzle through the openings into the meniscus. The 
electrolyte is drained from the cup and is filtered and processed. 
Alongside the electroplaner there is preferably a rinser that includes an 
elongated horizontally extending cup having an open top, a horizontally 
extending nozzle within the cup, and means supplying a rinse liquid (e.g., 
de-ionized water) to the rinser nozzle to create a meniscus of the rinse 
liquid. The rinser is positioned so that the substrate, when oriented to 
contact the electrolyte meniscus of the electroplaner, also will contact 
the rinse liquid meniscus. The rinser moves transversely with the 
electroplaner, so that when the electroplaner is moved across the face of 
the substrate, the same motion also sweeps the meniscus of rinse liquid 
behind it across the face of the substrate. The rinse liquid can be 
conducted from the rinser cup to a drain or a discharge holding tank. 
After the electroplaning operation, the chuck is lifted and then rotated so 
that the wafer is oriented face upwards. Then with a robotic arm or other 
automated means, the wafer is transported to a subsequent station. 
The above and many other objects, features, and advantages of this 
invention will become more fully appreciated from the ensuing detailed 
description of a preferred embodiment, which is to be considered in 
conjunction with the accompanying Drawing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
A wet chemistry process arrangement 10 according to an embodiment of this 
invention is illustrated in FIGS. 1 and 2. Here the arrangement 10 can 
have a cabinet, with a clean air system and automatic wafer handling 
equipment so that the wet process steps, and possibly other process steps, 
are carried out automatically for a number of wafers or other workpieces 
in sequence. As shown in the left part of FIG. 1, a wafer stacker 12 is 
located in a load station and contains a batch of wafers 14, i.e., slices 
of semiconductor crystal, on which some processing, i.e., circuit 
integration, has already taken place. In this case, this involves 
metallization, and a planing step is required. A loader mechanism 16, here 
shown as a robotic arm, picks up a wafer 14 from the stacker 12 and 
transfers the wafer, face-up, to a process station. While this station can 
be for plating, cleaning, etching or some other step, in this example the 
station is illustrated as an electroplaning station. 
As shown in FIG. 2, the loader 16 hands the wafer off to a transfer station 
18, where the wafer 14 is taken by a rotary transfer arm 20 to an 
electroplaning station 22, shown in plan in FIG. 2. The wafer 14 is laid 
upon a vacuum plate of a chuck 24. The chuck is mounted on a carriage 26 
that permits 180-degree rotation of the chuck, to orient the wafer 14 face 
down. An elevator 28 moves the carriage 26 vertically along guide rails 
30, 30 between the elevated position (for transfer of the wafer 14) and a 
lowered position (for electroplaning of the wafer 14). 
Beneath the chuck 24 is a process stage 34, where an electroplaner 36 and a 
rinser 38 are located. The electroplaner 36 and rinser 38 are elongated 
baths that lie tangent to the face or front surface of the wafer 14 when 
the chuck 24 is in the inverted and lowered position. Also shown is a 
motor 39 for effecting transverse horizontal motion of the electroplaner 
and rinser, along guide rails, across the surface of the wafer. In this 
embodiment, the chuck is held steady during the electroplaning process. In 
other possible embodiments, the chuck could be moved laterally past a 
stationary rinser and electroplaner. FIG. 1 also shows a chemical holding 
tank 40 for holding the electrolyte used for electroplaning and for 
containing de-ionized water or other rinse liquid, and a pump 42 for 
feeding the electrolyte and rinse liquid to the electroplaner 36 and 
rinser 38. Filters 44 are provided for the process chemicals that are 
returned from the electroplaner 36 to the tank 40. 
As shown in more detail in the schematic cross-sections of FIGS. 3 and 4, 
the electroplaner 36 comprises a cup 46 in the form of an elongated tray 
or basin, formed of a durable non-reactive, non-conductive material such 
as polypropylene. The cup is elongated in the horizontal direction, and 
has an open top. A nozzle 48 is situated in the cup 46 and extends 
longitudinally the length of the cup. The nozzle 48 is in the form of a 
tubular hollow finger or wand, with a row of openings 50 at its top to 
permit a laminar, i.e., non-turbulent flow of the electrolyte out over the 
top surface of the nozzle 48 into the cup 46. The openings 50 can be holes 
or slits, or can be pores or foramina. The electrolyte forms a meniscus 
over the nozzle. The meniscus is in the form or a raised ridge of fluid 
above the nozzle and extending the length thereof. In this case, the 
nozzle and meniscus are long enough to exceed the entire diameter of the 
wafer. Also shown here is a supply conduit 52 connecting the pump 42 to 
the nozzle 48 and a return conduit 54 leading from the cup back, e.g., to 
the filters 44. 
The rinser 38 is of similar construction and is located adjacent and 
parallel to the electroplaner 36. The rinser 38 comprises a cup 56, in the 
form of an elongated, open-top tray, and can be of the same material as 
the electroplaner cup. An elongated nozzle 57 is disposed along the length 
of the cup 56 and has a rinse supply conduit 58 supplying the nozzle with 
de-ionized water or another rinse liquid. A drain conduit 60 leads from 
the cup 56 to a drain or waste reservoir (not shown). The rinse liquid 
flows non-turbulently over the upper surface of the nozzle 57 and forms a 
meniscus. 
As shown schematically, an electrical power supply has a positive lead (+) 
connected to the chuck 24 which is in turn electrically coupled to the 
front surface of the wafer 14. The supply 62 also has a negative lead (-) 
connected to a cathode 64, here shown located inside the electroplaner 
nozzle 48. In other embodiments, the electroplaner nozzle can be made of 
conductive material and can itself serve as cathode. 
Instead of a row of openings 50, the nozzle 48 can be provided with a slit 
or a series of slits, or else the nozzle can be made of a microporous 
material so that the electrolyte weeps through. Still other configurations 
are possible within the scope of this invention. 
The electroplaning process of this embodiment involves first transferring 
the wafer 14, face up, from the transfer station 18 to the chuck 24, where 
vacuum is applied to hold the wafer in place. Then the chuck is inverted 
on the carrier 26, so that the wafer 14 is disposed horizontally and face 
down. The chuck 24 is moved vertically to its lowered position adjacent 
the electroplaning stage 34, so that the meniscuses of the electroplaner 
and rinser are tangent to the face of the wafer. Then the electroplaner 36 
and rinser 38 are moved horizontally below the chuck so that the 
meniscuses sweep across the face of the wafer 14. When this happens, the 
electroplaner meniscus contacts the wafer only along a horizontal line of 
contact, and the electrolyte does not flow to other areas of the wafer 
face. Likewise, the rinser meniscus contacts the wafer only along a line 
of contact. The planing and rinse are carried out non-turbulently and only 
along well defined zones of contact, resulting in extreme evenness and a 
high level of repeatability from one wafer to the next. 
The planing operation can require one pass or more than one pass, as 
required by the materials and chemistry involved. 
After the electroplaning is complete, the chuck 24 and carriage 26 are 
raised to their elevated position, and the chuck is rotated 180 degrees to 
orient the wafer face up. Then the transfer arm 20 transports the wafer 14 
to the transfer station 18, where it is conveyed to a subsequent process 
stage. The wafers so processed are eventually transported to a wafer 
stacker in an unload station (not shown), where the processed wafers are 
removed from the wet process arrangement 10. 
In some alternative embodiments, a megasonic transducer can be incorporated 
in either the electroplaner, or the rinser, or both. 
While the invention has been described with reference to a preferred 
embodiment, it should be recognized that the invention is not limited to 
that precise embodiment, or to the variations herein described. Rather, 
many modifications and variations would present themselves to persons 
skilled in the art without departing from the scope and spirit of the 
invention, as defined in the appended claims.