Wafer etching, cleaning and stripping apparatus

A wafer stripping, cleaning and etching apparatus includes a bowl, a table in the bowl carrying cassette of wafers, and a spray post with multiple fluid passages and ports directing fluid spray against the wafers.

BACKGROUND OF THE INVENTION 
In the processing of wafers used in the manufacture of integrated circuits, 
it is necessary in various processing steps to accomplish etching of 
certain areas of the wafer, to remove photoresist coating which may be 
applied to the wafer, and to otherwise clean the wafer. The use of an acid 
is required in all of these processing steps. 
An example of apparatus which is directed toward these process steps is 
disclosed in U.S. Pat. No. 3,990 462, to Elftmann et al. As disclosed 
therein, wafers are disposed in cassettes in turn mounted on a rotary 
turntable. A central post defines a plurality of pairs of ports, each port 
positioned to direct fluid therefrom onto an adjacent wafer as that wafer 
passes due to the rotary motion of the turntable. As disclosed in that 
patent, one port of each pair carries acid or water, while the other port 
carries gas, such as gaseous nitrogen, or air. Each pair of ports is 
positioned so that, with continuous fluid flow from that pair, an atomized 
fog-type spray is provided to the wafer. 
It will readily be understood that processing of such wafers must be done 
in an extremely even manner, so that all parts of the wafer are processed 
properly and uniformly. This has been a problem in the type of apparatus 
disclosed in the above-cited patent. Futhermore, the processing of a wafer 
in such a system is relatively slow. 
In U.S. Pat. No. 3,970,249 to Singer, secondary streams of gas are 
alternatively applied to a stream of atomized particles by applying those 
particles to a substrate. The system thereof, however, is not applicable 
to processing semiconductor wafers, in particular the removal of material 
from a semiconductor wafer through etching, stripping or cleaning. 
Of more general interest in this are U.S. Pat. No. 3,769,992 to Wallestad 
and U.S. Pat. No. 3,727,620 to Orr. 
SUMMARY OF THE INVENTION 
It is accordingly an object of this invention to provide apparatus for 
efficiently stripping, etching and cleaning wafers. 
Broadly stated, the invention comprises a semiconductor wafer processing 
apparatus comprising a body defining first and second adjacent ports 
through which fluid may flow from the body, the ports being positioned so 
that fluid flow from the first port influences fluid flow from the second 
port, means for varying fluid flow from the first port, and means for 
supporting a wafer such that at least a portion of the fluid flow moves 
generally across a major surface of a so-supported wafer.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Shown in FIG. 1 is an overall embodiment 10 of the wafer cleaning, etching 
and stripping apparatus. The apparatus 10 includes a bowl 12 having an 
outlet 14 through which fluid may exit. The bowl 12 is bolted to a fixed 
base 16. The bowl 12 has a suitable top 18 and cover 20, the cover 20 
having a hinge 22 to allow opening and closing thereof. A suitable latch 
or clamp is provided for holding the cover 20 in its closed position. 
Bearings 24 on the base 16 mount a rotary drive shaft 26 which extends 
upwardly through an opening in the bowl 12 and through a suitable seal or 
bushing 28 mounted on the base 16. 
A table 30 is mounted to the shaft 26 within the bowl 12. The table 30 has 
fixed thereto a plurality of spaced carriers 32 each configured to hold a 
cassette 34 in turn holding wafers 36. The tops of the carriers 32 are 
fixed to a continuous ring 38. 
The shaft 26 is connected through a drive belt 40 to a motor 42. Operation 
of the motor 42 rotates the table 30, carriers 32, cassettes 34, and 
wafers 36. However, as will be described further on, the table 30 may with 
advantage also be held in fixed position relative to the bowl 12. 
A spray post 44 is fixed to and suspended from the cover 20. The spray post 
44 defines passages 46, 48, and 50 which in turn are connected 
respectively to numerous sets of first, second and third ports 52, 54, and 
56. The passage 48, connected to port 54, is in turn connected to a source 
of process material 58 such as, for example, acid. The passages 46 and 50, 
in turn connected to respective of ports 52 and 56, each are connected to 
an oscillator mechanisms 60 and 62, which are fed material from a source 
64 in the form of a gas such as N.sub.2. The positioning and configuration 
of one set of three ports is shown in detail in FIG. 2. 
As shown therein, the ports 52, 54, and 56 are positioned in an elongated 
channel 66 defined by the post 44, with the ports 52, 54, and 56 in 
substantially the same plane, perpendicular to the longitudinal axis of 
the post 44. That plane is substantially coplanar with the plane of the 
particular wafer 68 held by a cassette and which is to be processed (FIG. 
2) The port 54 is positioned generally between the ports 52 and 56. The 
oscillator mechanism 60 associated with the port 52 provides a varying, in 
fact on-and-off, flow of gas from the port 52. Likewise, the oscillator 
mechanism 62 associated with the port 56 provides a varying, in fact 
on-and-off, flow of gas from the port 56. Process material flows from the 
port 54, as set forth above, and the content and flow thereof can be 
varied as chosen. In the preferred embodiment, process material flows 
continuously from the port 54, and flow from each of the ports 52 and 56 
is made to alternate in an on-and-off manner. The timing of this flow is 
such that during a period of time flow from port 52 is on while flow from 
port 56 is off, and during a period of time flow from port 56 is on while 
flow from port 52 is off. This, along with positioning of the ports 52, 
54, and 56, results in flow of ports 52 and 54 combining to flow on one 
side of wafer center line 70, and in flow of ports 54 and 56 combining to 
flow on the other side of such center line 70, during such time periods. 
It will be seen that the ports 52, 54 and 56 are positioned so that flow 
of fluid from the port 52 influences the flow of fluid from the port 54, 
and also flow of fluid from the port 56 influences flow of the fluid from 
the port 54. Because of the positioning of the wafer in relation to the 
ports as described above, fluid flow of ports 52 and 54 combines to flow 
generally across a portion of one or both major surfaces about the center 
line 70 (top surface shown at 68) of the wafer. This is also the case of 
fluid flow combined from ports 54 and 56. It is seen that the wafer is 
supported so that the plane thereof lies generally in the same plane in 
which fluid flows thereacross when fluid is not being influenced by ports 
52 and/or 56. 
Depending upon the operation to be undertaken, flow of fluid from port 52 
can overlap with flow of fluid from port 56, or there can be an interval 
during which there is no flow of fluid from either of these ports 52 and 
56. 
A significant advantage is to be gained in the embodiment where the table 
30 does not rotate. In such a situation, the post 44 defines as many 
channels 66 with sets of ports associated therewith as there are carriers 
32. Prior to use of the device, the table 30 is positioned such that each 
carrier 32 is lined up with a channel 66. Efficient cleaning, etching 
and/or stripping is achieved through the oscillating action of the 
multiple ports described above. 
This system has numerous advantages. For example, in the prior art, it was 
necessary to balance the rotary table with wafers and cassettes so that 
the table would rotate smoothly. This is not necessary in this embodiment, 
since table rotation does not take place. It has further been found that a 
spin-dry of the wafers is not necessary because of the oscillating nature 
described above. Furthermore, such a system avoids excessive acid waste. 
This is a problem in the prior art system because acid flows between the 
carriers as the turntable rotates, and is wasted. Balancing of the wafer 
load also requires additional wafer handling by the operator, with the 
possible attendant damage and expense related thereto. 
It has been found that the present form of port system, whether used with a 
rotating or fixed table, provides a great increase in efficiency in 
cleaning, etching and stripping wafers. It will be seen that the system is 
extremely simple and trouble-free, minimizing use of labor to operate it.