Optics: measuring and testing – Position or displacement – Triangulation
Reexamination Certificate
2002-06-26
2004-04-27
Font, Frank G. (Department: 2877)
Optics: measuring and testing
Position or displacement
Triangulation
C356S602000, C356S003100, C250S559080
Reexamination Certificate
active
06727994
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to integrated cluster tools used in the processing of semiconductors. More particularly, the present invention relates to a z-axis monitoring apparatus for monitoring the Z-axis position of a wafer support blade on a transfer robot which transfers wafers among multiple chambers in an integrated cluster tool.
BACKGROUND OF THE INVENTION
In the semiconductor production industry, various processing steps are used to fabricate integrated circuits on a semiconductor wafer. These steps include the deposition of layers of different materials including metallization layers, passivation layers and insulation layers on the wafer substrate, as well as photoresist stripping and sidewall passivation polymer layer removal. In modern memory devices, for example, multiple layers of metal conductors are required for providing a multi-layer metal interconnection structure in defining a circuit on the wafer. Chemical vapor deposition (CVD) processes are widely used to form layers of materials on a semiconductor wafer. Other processing steps in the fabrication of the circuits include formation of a photoresist or other mask such as titanium oxide or silicon oxide, in the form of the desired metal interconnection pattern, using standard lithographic techniques; subjecting the wafer substrate to a dry etching process to remove the conducting layer from the areas not covered by the mask, thereby leaving the metal layer in the form of the masked pattern; removing the mask layer using reactive plasma and chlorine gas, thereby exposing the top surface of the metal interconnect layer; cooling and drying the wafer substrate by applying water and nitrogen gas to the wafer substrate; and removing or stripping polymer residues from the wafer substrate.
CVD processes include thermal deposition processes, in which a gas is reacted with the heated surface of a semiconductor wafer substrate, as well as plasma-enhanced CVD processes, in which a gas is subjected to electromagnetic energy in order to transform the gas into a more reactive plasma. Forming a plasma can lower the temperature required to deposit a layer on the wafer substrate, to increase the rate of layer deposition, or both. However, in plasma process chambers used to carry out these various CVD processes, materials such as polymers are coated onto the chamber walls and other interior chamber components and surfaces during the processes. These polymer coatings frequently generate particles which inadvertently become dislodged from the surfaces and contaminate the wafers.
The chemical vapor deposition, etching and other processes used in the formation of integrated circuits on the wafer substrate are carried out in multiple process chambers. The process chambers are typically arranged in the form of an integrated cluster tool, in which multiple process chambers are disposed around a central transfer chamber equipped with a wafer transport system for transporting the wafers among the multiple process chambers. By eliminating the need to transport the wafers large distances from one chamber to another, cluster tools facilitate integration of the multiple process steps and improve wafer manufacturing throughput.
A typical conventional integrated cluster tool is generally indicated by reference numeral
10
in FIG.
1
. An integrated cluster tool
10
such as a Centura HP 5200 tool sold by the Applied Materials Corp. of Santa Clara, Calif., includes one or a pair of adjacent loadlock chambers
12
, each of which receives a wafer cassette or holder
13
holding multiple semiconductor wafers
28
. The loadlock chambers
12
are flanked by an orientation chamber
14
and a cooldown chamber
16
. Multiple process chambers
18
for carrying out various processes in the fabrication of integrated circuits on the wafers
28
are positioned with the orientation chamber
14
, the cooldown chamber
16
and the loadlock chambers
12
around a central transfer chamber
20
. A transfer robot
22
in the transfer chamber
20
is fitted with a transfer blade
24
which receives and supports the individual wafers
28
from the wafer cassette or holder
13
in the loadlock chamber
12
. The transfer robot
22
is capable of rotating the transfer blade
24
in the clockwise or counterclockwise direction in the transfer chamber
20
, and the transfer blade
24
can extend or retract to facilitate placement and removal of the wafers
28
in and from the load lock chambers
12
, the orientation chamber
14
, the cooldown chamber
16
and the process chambers
18
.
In operation, the transfer blade
24
initially removes a wafer
28
from the wafer cassette
13
and then inserts the wafer
28
in the orientation chamber
14
. The transfer robot
22
then transfers the wafer
28
from the orientation chamber
14
to one or more of the process chambers
18
, where the wafer
28
is subjected to a chemical vapor deposition or other process. From the process chamber
18
, the transfer robot
22
transfers the wafer
28
to the cooldown chamber
16
, and ultimately, back to the wafer cassette or holder
13
in the loadlock chamber
12
.
As illustrated in
FIG. 2
, a standard optical wafer sensor
30
is typically provided on the transfer chamber lid
26
of the transfer chamber
20
and emits a light beam
32
which passes first through a view port (not shown) in the transfer chamber lid
26
and then through an opening
25
in the transfer blade
24
when no wafer is supported on the transfer blade
24
, as illustrated. The light is reflected back through the opening
25
to the sensor
30
, which transmits a DI signal to the system controller (not shown) to indicate that a wafer is not supported on the transfer blade
24
. When a wafer is supported on the transfer blade
24
, the light from the sensor
30
is absorbed by the wafer, which covers the opening
25
. Consequently, the sensor
30
transmits an appropriate signal to the system controller to indicate the presence of the wafer on the transfer blade
24
. The optical wafer sensor
30
typically operates on 24V DC current.
One of the problems associated with the conventional wafer sensor
30
is that the sensor
30
is incapable of detecting the Z-axis position of the transfer blade
24
for accurate insertion and retrieval of the wafers
28
into and out of the wafer cassette
13
in the loadlock chamber
12
. The tolerance space between the transfer blade
24
and the wafer cassette
13
in the wafer insertion and retrieval operations is typically about 3 mm. Consequently, distortions in the configuration of the transfer blade
24
due to, for example, heat from the process chambers
18
may cause the transfer blade
24
to exceed the permissible Z-axis tolerance of the transfer blade
24
. Consequently, the tilted transfer blade
24
may scratch the wafers upon removal or replacement thereof in the wafer cassette
13
, significantly reducing the wafer yield.
Accordingly, an apparatus is needed for monitoring the Z-axis position of a wafer transfer blade on a transfer robot.
An object of the present invention is to provide an apparatus for reducing loss in wafer yield in the processing of wafers in an integrated cluster tool.
Another object of the present invention is to provide an apparatus for preventing scraping of wafers in the removal and insertion of semiconductor wafers from and into a loadlock chamber of an integrated cluster tool due to a distorted transfer blade on a transfer robot.
Still another object of the present invention is to provide an apparatus for monitoring the Z-axis position of a transfer blade on a wafer transfer robot.
Another object of the present invention is to provide an apparatus for detecting and indicating the presence or absence of a wafer on a transfer blade of a wafer transfer robot.
Yet another object of the present invention is to provide an apparatus for facilitating corrective Z-axis positioning of a transfer blade on a wafer transfer robot in order to prevent inadvertent scraping of wafers in the insertion and removal of the wafe
Hsieh Chung-Ju
Liao Hsi-Wen
Lin Yi-Ming
Nguyen Sang H.
Taiwan Semiconductor Manufacturing Co. Ltd
Tung & Associates
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