Plasma etching apparatus and method and apparatus for verifying a wafer

Wafer verifying apparatus for receiving a wafer thereagainst and for verifying the wafer, wafer verifying apparatus comprising a fixture including a stage for receiving thereagainst a surface of the wafer, a vacuum assembly for effecting a vacuum coupling of the surface of the wafer to the stage, and sensor apparatus for accepting the wafer in the presence of a vacuum couple of the surface of the wafer against the stage and for rejecting the wafer absent a vacuum couple of the surface of the wafer against the stage.

FIELD OF THE INVENTION 
This invention relates generally to the field of plasma etching apparatus 
and, more particularly, to improved plasma etching apparatus and methods 
and apparatus for verifying wafers for plasma etching processes. 
BACKGROUND OF THE INVENTION 
Plasma etching apparatus are well known for etching wafers such as, for 
instance, semiconductor wafers. Typical plasma etching apparatus generally 
comprise a plasma chamber for containing a plasma field, an electrode 
mounted in the plasma chamber, a wafer feed assembly for feeding wafers to 
the electrode for plasma etching and a wafer retrieval assembly for 
retrieving etched wafers from the plasma chamber. For exemplary etching, 
it is important for the wafer to rest normal and flush against the 
electrode. However, because manufacturing flaws can result in wafers 
having surface irregularities, flawed wafers subject to plasma etching can 
become irreparably damaged. Because the prior art provides little to solve 
this long-felt problem in the art, the occasion for certain new and useful 
improvements proves necessary. 
Accordingly, it would be highly desirable to provide improved plasma 
etching apparatus and methods and apparatus for verifying wafers for 
plasma etching processes. 
It is a purpose of the present invention to provide new and improved 
apparatus for verifying wafers that is easy to implement with existing 
plasma etching technology. 
It is another purpose of the present invention to provide new and improved 
apparatus for verifying wafers that is easy to construct. 
It is still another purpose of the present invention to provide new and 
improved apparatus for verifying wafers that is easy to use. 
It is a further purpose of the present invention to provide new and 
improved apparatus for verifying wafers that is inexpensive. 
It is still a further provision of the present invention to maximize yield 
in plasma etching processes. 
It is yet still a further purpose of the present invention to provide a new 
and improved method of verifying wafers that is highly efficient and easy 
to implement. 
It is another provision of the present invention to enhance the functional 
utility of plasma etching apparatus. 
It is still another provision of the present invention to limit waste of 
flawed wafers in plasma etching processes. 
It is yet still another provision of the present invention to substantially 
eliminated unproductive operation time during plasma etching processes. 
SUMMARY OF THE INVENTION 
The above problems and others are at least partially solved and the above 
purposes and others are realized in improved plasma etching apparatus and 
methods and apparatus for verifying wafers for plasma etching processes. 
In a particular embodiment, the present invention includes wafer verifying 
apparatus for receiving a wafer thereagainst and for verifying the wafer, 
wafer verifying apparatus comprising a fixture including a stage for 
receiving thereagainst a surface of the wafer, means for effecting a 
vacuum coupling of the surface of the wafer to the stage, and sensor 
apparatus for accepting the wafer in the presence of a vacuum couple of 
the surface of the wafer against the stage and for rejecting the wafer 
absent a vacuum couple of the surface of the wafer against the stage. The 
means for effecting a vacuum coupling of the surface of the wafer to the 
stage may comprises a channel leading to an opening formed through the 
stage in substantial opposition to the surface of the wafer received 
against the stage, and means for introducing a vacuum into the channel for 
effecting vacuum coupling of the surface of the wafer to the stage. 
In accordance with a preferred embodiment, the means for introducing a 
vacuum into the channel may comprise a vacuum coupled with the channel in 
vacuum communication. Furthermore, the sensor apparatus may comprise a 
pressure sensor sensorially coupled to monitor pressure within the 
channel, and a controller coupled in communication with the pressure 
sensor for accepting the wafer in the presence of a sub-atmospheric 
condition in the channel as sensed by the pressure sensor, and for 
rejecting the wafer absent the presence of the sub-atmospheric condition 
in the channel as sensed by the pressure sensor. 
In accordance with a preferred method of verifying a wafer for processing 
such as for plasma etching processes, included are the steps of providing 
a fixture having a stage, placing a surface of a wafer against the stage, 
effecting a vacuum coupling of the surface of the wafer to the stage, 
verifying a vacuum couple of the surface of the wafer to the stage, and 
one of the steps of accepting the wafer in the presence of a vacuum couple 
of the surface of the wafer against the stage, and rejecting the wafer 
absent a vacuum couple of the surface of the wafer against the stage. 
In a specific example, the step of effecting a vacuum coupling of the 
surface of the wafer to the stage may further include the steps of 
providing a channel leading to an opening formed through the stage in 
substantial opposition to the surface of the wafer received against the 
stage, and introducing a vacuum into the channel for effecting vacuum 
coupling of the surface of the wafer to the stage. To introduce a vacuum 
into the channel may include the steps of providing a vacuum, coupling the 
vacuum to the channel in vacuum communication, and actuating the vacuum. 
To determine a vacuum couple of the surface of the wafer to the stage may 
include the steps of establishing a baseline pressure for the channel, 
observing a subject pressure within the channel, and comparing the subject 
pressure with the baseline pressure. Observing the subject pressure may 
include providing a pressure sensor and coupling the pressure sensor to 
monitor and display the pressure within the channel. With the subject 
pressure being less than or equal to the baseline pressure, the step of 
accepting the wafer may further include the step of leaving the wafer on 
the stage for processing, wherein with the subject pressure being greater 
than the baseline pressure, the step of rejecting the wafer may further 
include the step of removing the wafer from the stage.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
The present invention provides, among other things, improved plasma etching 
apparatus and methods and apparatus for verifying wafers for plasma 
etching processes. Preferred embodiments of the present invention are easy 
to implement with existing plasma etching technology and prove exemplary 
not only for decreasing unproductive operation time during plasma etching 
processes, but also for increasing the functional utility of conventional 
plasma etching apparatus. 
Turning now to the drawings, in which like reference characters indicate 
corresponding elements throughout the several views, attention is first 
directed to FIG. 1 illustrating a perspective view of plasma etching 
apparatus 10, in accordance with the present invention. As best shown in 
FIG. 2, plasma etching apparatus 10 comprises a housing 11 having a hinged 
lid 12 shown as it would appear in an open position and containing a wafer 
feed assembly 13, a wafer retrieval assembly 14 and a chamber 15 for 
containing a plasma field. 
In operation, wafers, such as semiconductor wafers, may be fed by wafer 
feed assembly 13 individually into chamber 15. Upon receipt into chamber 
15, chamber 15 may be enclosed and filled with a gas or gases. From the 
gas or gases, a plasma field may be produced by, for instance, exposing 
the gas or gases to an electric field. The plasma field operates to etch 
the wafer in a predetermined and pre-specified pattern normally consistent 
with a pattern formed on the wafer prior to exposure to the plasma field. 
After this etching process is complete, the plasma field may be evacuated 
from chamber 15, such as with a vacuum, chamber 15 opened and the etched 
wafer removed from chamber 15 by wafer retrieval assembly 14. This process 
may be repeated as necessary, either automatically or manually, for 
etching consecutive wafers. It will be generally understood that plasma 
etching apparatus 10 includes conventional electrical and processing 
circuitry and necessary and conventional operational controls generally 
designated at 16 for effecting the actuation and operation of plasma 
etching apparatus 10 and various components thereof for normal operation, 
details of which will not be herein discussed as they will readily occur 
to the skilled artisan. 
Wafers fed individually into chamber 15 for etching are received against 
and supported by a chuck assembly 20. With attention directed to FIG. 3 
illustrating an exploded perspective view of chuck assembly 20, chuck 
assembly 20 generally comprises a bell housing 21 mounted to a cylinder 
assembly 22 for effecting movement of bell housing 21 in reciprocal 
directions as generally indicated by the double arrowed line A, a base 
plate 23 carried in bell housing 21 and a fixture 24 carried in bell 
housing 21 atop base plate 23. 
In accordance with the present invention, and with continuing reference to 
FIG. 3 and additional reference to FIG. 5 illustrating a side elevational 
view of fixture 24, fixture 24 comprises an electrode including an 
electrode body 30 and a stage support 31 carried by electrode body 30, 
stage support 31 having a stage 32 for receiving thereagainst a surface of 
a wafer for plasma etching processes in chamber 15 (not shown in FIGS. 3 
and 5). Although stage support 31 is shown as a separate element, it may 
be formed integral with electrode body 30 if desired. Formed in stage 
support 31 is a channel 33 leading from an opening 34 formed, for 
instance, through stage support 31 to an opening 35 formed through stage 
32. 
With attention directed to FIG. 4 illustrating a perspective view of plasma 
etching apparatus 10 with portions thereof broken away for the purposes of 
illustration, shown is stage support 31 in addition to a vacuum 40 and 
sensor apparatus 42 together generally comprising wafer verification 
apparatus 43 of the present invention. With continuing reference to FIG. 4 
and additional reference to FIG. 6 illustrating a schematic representation 
of wafer verification apparatus 43, vacuum 40 is carried by housing 11 and 
is coupled with opening 34 (not shown in FIG. 4) via vacuum conduit 41 in 
vacuum communication. In accordance with a preferred embodiment, sensor 
apparatus 42 is interfaced with vacuum conduit 41 and sensorially coupled 
to monitor the pressure within channel 33. As shown in FIGS. 3 and 6, 
vacuum conduit 41 is coupled in vacuum communication with opening 34 via 
fitting 44. 
In operation, stage 32 is operative for receiving thereagainst a surface 50 
of a wafer 51, of which may comprise a semiconductor wafer or the like 
desired to be exposed to a plasma field in chamber 15 for etching. To 
insure wafer 51 does not become damaged when exposed to a plasma field in 
chamber 15, it is important for surface 50 to rest flush against stage 32. 
Thus, it is important not only to verify whether surface 50 is flush 
against stage 32, but also to accept wafer 51 for etching if surface 50 is 
flush with stage 32 and to reject wafer 51 for etching if surface 50 is 
not flush with stage 32. If surface 50 of wafer 51 is flush with stage 32, 
accepting wafer 51 generally includes leaving wafer 51 on stage 32 for 
plasma etching. However, if surface 50 of wafer 51 is not flush with stage 
32, rejecting wafer 51 generally includes removing wafer 51 from stage 32 
for disposal by, for instance, wafer retrieval assembly 14 shown in FIG. 
1. 
To verify whether surface 50 of wafer 51 is flush against stage 32 prior to 
etching and to one of accept and reject wafer 51 accordingly, vacuum 40 
may be actuated for introducing a vacuum into vacuum conduit 41 and for 
introducing a vacuum into channel 33 for effecting a vacuum coupling of 
surface 50 of wafer to or otherwise against stage 32. If vacuum coupling 
occurs and opening 35 is occluded or otherwise obstructed by surface 50 of 
wafer opposing opening 35, the pressure in channel 33 will drop and reside 
at a point somewhere below atmospheric pressure indicating generally that 
surface 50 is flush with stage 32 as shown in FIG. 7. If vacuum coupling 
fails to occur indicating that surface 50 of wafer 51 is not flush with 
stage 32 as shown substantially in FIG. 8, the pressure in channel 33 will 
remain substantially at atmospheric pressure. 
To monitor the pressure within channel 33, sensor apparatus 42 may comprise 
a pressure sensor 52 sensorially coupled for actuation to monitor pressure 
within channel 33, pressure sensor 52 having conventional operational 
controls 53 and a display 54 for displaying pressure readings taken from 
channel 33 as shown in FIG. 6. Pressure sensor 52 is of a conventional 
variety well known throughout the art. Therefore, further details of 
pressure sensor 52 will not be addressed as they will readily occur to the 
skilled artisan. In the presence of a sub-atmospheric pressure condition 
in channel 33 as sensed and displayed by pressure sensor 52, plasma 
etching apparatus 10 may be actuated for enclosing chamber 15, producing a 
plasma field in chamber 15 to effecting etching of wafer 51, for 
evacuating the plasma field from chamber 15, for opening chamber and for 
removing wafer 51 from stage 32 after etching by, for instance, wafer 
retrieval assembly 14 shown in FIG. 1. 
It will be generally understood that although any pressure in channel 33 
below atmospheric pressure may indicate that surface 50 is generally flush 
with stage 32, a desired sub-atmospheric pressure condition or baseline 
pressure may be chosen at a predetermined value above which the wafer will 
be rejected and at or below which the wafer will be accepted. 
Actuation of plasma etching apparatus 10 including the operation of wafer 
feed assembly 13, wafer retrieval assembly 14, vacuum 40 and pressure 
sensor 52 may, if desired, be carried out manually. As an alternative, the 
present invention may be committed to automatic operation and control. 
Regarding automatic operation, the present invention may further include a 
controller 55 of sensor apparatus 42 and coupled or otherwise interfaced 
with pressure sensor 52 via interface interconnection 56 for communicating 
with and automatically and selectively actuating wafer feed assembly 13, 
wafer retrieval assembly 14, vacuum 40, pressure sensor 52 and for 
actuating plasma etching apparatus 10 for plasma etching processes. 
Controller 55 may be of a conventional variety and provided with necessary 
processing and data or signal communication algorithms for receiving 
pressure data from pressure sensor 52 and for communicating with and 
selectively actuating wafer feed assembly 13, wafer retrieval assembly 14, 
vacuum 40, pressure sensor 52 and for actuating plasma etching apparatus 
10 for plasma etching processes. Consistent with the foregoing, a 
predetermined baseline pressure may be entered into controller 55 if 
desired for controlling the operation of plasma etching apparatus 10 
consistent with preceding discussions. During operation in this regard, 
controller 55 may operate to compare a subject pressure reading in channel 
33 as sensed by pressure sensor 52 with the baseline pressure to either 
accept the wafer if the subject pressure is equal to or less than the 
baseline pressure, or reject the wafer if the subject pressure is greater 
than the baseline pressure. 
Regarding FIG. 4, it will be generally understood that cylinder assembly 22 
is conventional, hydraulically operated and may be actuated, either 
manually or by controller 55 of which may be coupled for selectively 
actuating cylinder assembly 22 via interface interconnection 57, for 
moving bell housing 21, base plate 23 and fixture 24 in reciprocal 
directions between a first position for allowing wafers to be placed 
individually against stage 32 by wafer feed assembly 13 and a second 
position for enclosing chamber 15 by bell housing 21 and a surface of, for 
instance, hinged lid 12 shown in FIG. 1. Once enclosed, chamber 15 may be 
filled with one or more gases and transformed into plasma by exposing the 
one or more gases to an electric field by, for instance, energizing 
fixture 24 and, more particular, electrode body 30 of fixture 24. After 
the etching process is complete, plasma in the chamber may be evacuated 
and cylinder assembly 22 subsequently actuated, either manually or by 
controller 55, for moving bell housing 21 from the second position to the 
first position to open chamber 15 to permit removal of the etch wafer by, 
for instance, wafer retrieval assembly 14. Although plasma etching 
apparatus 10 may be equipped with a vacuum especially adapted for 
evacuating chamber 15 after each etching operation, vacuum 40 may be 
adapted for carrying out the evacuation operation if so desired. 
In summary, the present invention provides exemplary plasma etching 
apparatus and associated methods and apparatus for verifying wafers for 
plasma etching processes. The implementation of effecting a vacuum couple 
of a wafer to stage 32 and of monitoring the pressure within channel 33 to 
determine the existence of a vacuum couple is highly efficient, extremely 
cost effective and suitable for allowing not only the easy and inexpensive 
manufacture of new plasma etching apparatus, but also the retrofitting of 
existing plasma etching apparatus. 
The present invention has been described above with reference to a 
preferred embodiment. However, those skilled in the art will recognize 
that changes and modifications may be made in the described embodiments 
without departing from the nature and scope of the present invention. For 
instance, although only one channel has been shown for communicating a 
vacuum to stage for effecting vacuum coupling of a wafer against stage 32, 
a plurality of such channels may be implemented if so desired. 
Furthermore, and as shown in FIG. 3, base plate 23 may be fitted with pogo 
pins 60 (only one shown) receivable into and through apertures 61 formed 
through stage support 31 and movable for pushing wafers away from stage 32 
after etching for easy removal. To cool fixture 24 during plasma etching 
processes, and with attention directed to FIG. 5, stage support 31 may be 
provided with a network of interconnected canals 62 formed therein in 
opposition to stage 32 and coupled in fluid communication to a cooling 
fluid source via conduit 63 shown in FIG. 3. During operation, fluid, such 
as water or a selected coolant, may be communicated to the network of 
interconnected canals 62 for cooling stage support 31 during operation of 
plasma etching apparatus 10 as desired. As shown in FIG. 3, conduit 63 may 
be coupled in fluid communication with the network of interconnected 
canals 62 via fitting 64. 
Various changes and modifications to the embodiment herein chosen for 
purposes of illustration will readily occur to those skilled in the art. 
To the extent that such modifications and variations do not depart from 
the spirit of the invention, they are intended to be included within the 
scope thereof which is assessed only by a fair interpretation of the 
following claims. 
Having fully described the invention in such clear and concise terms as to 
enable those skilled in the art to understand and practice the same, the 
invention claimed is: