Wafer transfer robot having wafer blades equipped with sensors

Details Wafer transfer robot having wafer blades equipped with sensors Wafer transfer robot having wafer blades equipped with sensors

2002-06-14

2004-10-26

Mills, Gregory (Department: 1763)

Adhesive bonding and miscellaneous chemical manufacture

Differential fluid etching apparatus

For liquid etchant

C156S345510, C118S730000, C134S113000

Reexamination Certificate

active

06808589

ABSTRACT:

FIELD OF THE INVENTION
The present invention generally relates to an apparatus for transfer wafer from a wafer storage pod to a wafer process machine and more particularly, relates to a wafer transfer robot having a plurality of wafer blades each equipped with a sensing device for sensing the type of wafer it carries.
BACKGROUND OF THE INVENTION
A wet bench process is frequently carried out after a chemical process has been conducted on a semiconductor wafer. When residual chemical must be removed, deionized water rinse is used in a wet bench process for semiconductor wafer processing to perform two major functions of a quick dump rinse (QDR) and a cascade overflow rinse. Conventionally, the two functions are carried out in separate tanks in order to produce the desirable result. One of the major processing issues presented by the conventional dual-tank process is the particle re-deposition problem during a withdrawal step when cassettes are transported from a quick dump rinse tank to a cascade overflow tank. A second major issue is the large floor space required for accommodating the two tanks.
A conventional wet bench wafer cleaning process is shown in FIG.
1
. The wet bench wafer cleaning process
10
for cleaning wafer
12
is carried out in six separate cleaning and rinsing tanks sequentially of a HF cleaning tank
14
, a first quick dump rinse (QDR) tank
16
, a SC-1 cleaning tank
18
, a second quick dump rinse tank
20
, a SC-2 cleaning tank
22
and a third quick dump rinse tank
24
. The first HF cleaning tank is used to hold a diluted HF solution, for instance, at a concentration of 0.5% HF in H
2
O for removing a thin native oxide layer from the wafer surface. After the diluted HF cleaning process, the wafer
12
is rinsed in a first quick dump rinse tank
16
with deionized water. Wafer
12
is then cleaned in a second cleaning tank filled with SC-1 cleaning solution, i.e. a mixture of NH
4
OH, H
2
O
2
and DI water at a ratio of 1:1:5. The SC-1 cleaning solution is used at a temperature between 70-80° C. for a suitable time period. The wafer
12
is then rinsed again in a second quick dump rinse tank
20
that is filled with DI water. In the final stage of cleaning, the wafer
12
is cleaned in tank
22
filled with a cleaning solution of SC-2 which is a mixture of HCl, H
2
O
2
and DI water at a ratio of 1:1:6. The wafer
12
is then rinsed in a third quick dump rinse tank
24
with DI water.
The wet bench wafer cleaning process
10
shown in
FIG. 1
is conventionally used for pre-diffusion clean, pre-gate oxidation clean, pre-CVD clean, etc. For instance, in the ULSI fabrication of integrated devices, the conventional wet bench wafer cleaning process
10
can be advantageously used for wafer surface cleaning before a coating process in a CVD chamber or an oxidation process in a furnace. The wet bench process shown in
FIG. 1
is therefore generally used for front-end processing of a semiconductor wafer.
FIG. 2
is an exploded, perspective view of the conventional wet bench system
10
of
FIG. 1
complete with a wafer transfer robot
30
. The wafer transfer robot
30
is constructed of a robot arm
32
and a plurality of wafer blades
34
for picking-up wafers stored in a cassette pod
36
(partially shown in FIG.
2
). After picking-up wafers from the cassette pod
36
, the plurality of wafer blades
34
are turned 90° by the robot arm
32
for delivering the wafers into a wafer storage station
38
for the wet bench system
10
. A second robot (not shown) then delivers the wafers into the plurality of liquid tanks
40
shown in
FIG. 2
for chemical processing of the wafers. Lifters
42
are used for lowering the wafers into and out of the liquid stored in tanks
40
.
FIG. 3
shows a close-up view of the wafer transfer robot
30
, the plurality of wafer blades
34
and the robot arm
32
. The wafer storage station
38
for the wet bench system
10
is also shown in FIG.
3
.
In a semiconductor processing facility, wet bench cleaning or etching is also required for the back-end of processing of wafers. For instance, after the deposition of metal layers in forming various via plugs and interconnects. In the wet bench system used in cleaning the back-end wafers, there are always metal particles or metal ions present in the chemical tanks which are absent in the chemical tanks used in cleaning front-end wafers. Since the wet bench cleaning stations are normally grouped together in a semiconductor fabrication facility, i.e for ease of control of chemical dispensing and disposal of used chemicals, the wet bench process lines used for the front-end processing and for the back-end processing must be clearly distinguished. When a batch of wafers intended for front-end wet bench process is mistakenly loaded into a wet bench station used for back-end process, serious contamination of the wafers by metal ions or particles can result in the scrap of the entire lot of wafers. The cost of such mistake is extremely high and can be detrimental to the throughput of an IC device.
Conversely, when a batch of wafers intended for back-end wet bench process is mistakenly placed in a wet bench station for front-end process, the metal layers present on the wafers contaminates the chemical tanks which is very costly and time consuming to clean and replace such that they can be used for processing front-end wafers.
It is therefore an object of the present invention to provide an apparatus for transferring wafers into a wet bench station that does not have the drawbacks or shortcomings of the conventional transfer apparatus.
It is another object of the present invention to provide a wafer transfer robot for a wafer processing system capable of identifying the type of wafer it carries.
It is a further object of the present invention to provide a wafer transfer robot for a wafer processing system that is equipped with wafer blades capable of identifying the type of wafer carried on the blade.
It is another further object of the present invention to provide a wafer transfer robot equipped with a plurality of wafer blades wherein each of the blades is equipped with a sensing device.
It is still another object of the present invention to provide a wafer transfer robot equipped with a plurality of wafer blades each adapted for picking-up a wafer and identifying the wafer as a front-end processed wafer or a back-end processed wafer.
It is yet another object of the present invention to provide a wafer transfer robot equipped with a plurality of wafer blades each equipped with a sensing means capable of sensing whether a wafer it carries has metal layers on top.
SUMMARY OF THE INVENTION
In accordance with the present invention, a wafer transfer robot equipped with a plurality of wafer blades each equipped with a sensing device and a method for using the wafer transfer robot are disclosed.
In a preferred embodiment, a wafer transfer robot for a wafer processing system is provided which includes a robot arm equipped with a plurality of wafer blades each adapted for picking-up and carrying one of a plurality of wafers; the plurality of wafer blades each having a predetermined thickness, a top surface, a bottom surface and a predetermined spacing from adjacent robot blades; and a plurality of sensors with at least one mounted on the bottom surface of one of the plurality of wafer blades for sensing the presence of metal on a wafer carried on an adjacent wafer blade immediately below the one of the plurality of wafer blades.
In the wafer transfer robot for a wafer processing system, the wafer processing system may be a wet bench station. The plurality of wafer blades are formed of a metal that does not generate contaminating particles, or formed of aluminum. The predetermined spacing from adjacent wafer blades is between about 3 mm and about 15 mm, and preferably between about 7 mm and about 12 mm. The plurality of sensors are optical sensors for sensing a reflectance of light from a top surface of a wafer that is positioned immediately below the one of the wafer blades. The plurality of sensors m

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