Physical vapor deposition apparatus with modified shutter...

Details Physical vapor deposition apparatus with modified shutter... Physical vapor deposition apparatus with modified shutter...

2001-01-05

2002-08-27

Sherry, Michael (Department: 2829)

Semiconductor device manufacturing: process

Coating of substrate containing semiconductor region or of...

Insulative material deposited upon semiconductive substrate

Reexamination Certificate

active

06440879

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to the field of fabrication of semiconductor devices and, more particularly, to a physical-vapor deposition (PVD) apparatus and method of using the apparatus.
2. Description of the Related Art
Sputtering, a type of physical vapor deposition, is widely used in semiconductor manufacturing to deposit thin metal or insulating films on semiconductor wafers.
Conventional sputtering apparatus
11
shown in
FIG. 1
includes a process chamber
10
enclosing a target
12
affixed to the top thereof and a wafer pedestal
14
where a semiconductor wafer
16
rests during deposition. The target
12
is formed of a deposition material to be deposited. A lower shield
18
and an upper shield
20
are positioned within the chamber
10
such that they are electrically insulated from the chamber
10
and able to take on a floating electrical potential associated with the potential of the plasma of a gas, e.g. argon, generated within the chamber
10
. Additionally, a cover ring
22
is engaged with the lower shield
18
to keep any deposition material from being deposited on the peripheral margin of the wafer
16
.
During sputter deposition, the target
12
is bombarded by plasma ions within the chamber
10
by applying an appropriate voltage to the target
12
, which causes particles of target material to be ejected from the target
12
toward the wafer
16
. These particles deposit on the wafer
16
to form a desired film. During the deposition, however, particles of target can also deposit on the interior surfaces of the lower and upper shields
18
and
20
. Also, a portion of the particles returns to the target
12
itself.
For these reasons, after a number of wafers are processed, the sputtering shields become coated with highly stressed, brittle barrier metal films, e.g., of TiN. Without proper treatment, these films can delaminate, flake off, and shower the substrate with particles.
Thus, it is necessary to coat the shields occasionally with metal such as titanium to prevent such particulation. This process is called “pasting.” A pasting material, such as titanium, is sputtered around the interior of the shields
18
and
20
along with the target
12
. The layer of pasting material deposited onto the interior of the shields
18
and
20
forms a barrier to cracking and flaking between the layers of the high stress material. The pasting material such as titanium acts as a glue layer to secure the already-deposited films and to provide an adherent surface for any additional material particulate. The pasting material deposited on the target
12
must be cleaned before a normal sputtering process begins.
Conventionally, a standard shutter disk
24
and a shutter arm assembly
26
are used during pasting and cleaning of the target
12
. Typically, the shutter disk
24
is housed in an enclosure
30
attached to the side of the process chamber
10
. The shutter disk
24
is positioned between the pedestal
14
and the target
12
to isolate the target
12
, and to protect other areas of the chamber
10
from subsequent cleaning of the target
12
and the pasting material. The shutter disk
24
is mounted on a rotating arm
32
, i.e., an actuator arm, which is located outside the shield
18
and within the process chamber
10
. When signaled to do so, the shutter arm assembly
26
rotates the disk
24
into the process chamber
10
, overlying the wafer pedestal
14
. The shutter disk
24
can then be raised into a pasting process position (at the same level as the wafer
16
) by a wafer lift
34
. Thus, cleaning of the target (sputtering away any contaminants present on the surface of target
12
onto the disk
24
) or pasting without contaminating the surface of wafer pedestal
14
is possible because the wafer pedestal surface is protected by the shutter disk
24
. When cleaning or pasting is completed, the shutter disk
24
returns to the storage position.
In semiconductor manufacturing, it is important to align a subsequent layer to a previous underlying layer. For this reason, alignment marks
37
(
FIG. 2B
) are typically formed on a wafer or on a reticle for alignment between various layers. The alignment marks are typically formed by etching a depth into a wafer. The alignment of one layer to the next is typically accomplished using a stepper. The stepper uses a laser beam to detect the position of the alignment marks on the wafer. It becomes difficult to maintain these alignment marks, especially in the back end of the manufacturing process, as the deposition over the marks makes the marks indistinguishable.
Recently, to protect the alignment marks from being damaged or contaminated by deposition, a two-tabbed alignment block-out scheme has been introduced. One of the process chambers incorporating the two-tabbed alignment block-out scheme is Endura Model (model number ENDURA® HP PVD™), available commercially from Applied Materials, Inc.
As illustrated in
FIG. 2A
, a cover ring
22
′ has two tabs
35
protruding therefrom so that it can cover or protect alignment marks
37
of
FIG. 2B
on a semiconductor wafer
16
′ during regular deposition steps. Alignment marks
37
positioned beneath the tabs
35
can be protected. As a result, the alignment marks
37
can be better maintained during deposition, and of course better alignment is possible with well-maintained alignment marks
37
.
As shown in
FIG. 2C
, which is a cross-sectional view of a conventional cover ring taken in line
2
C—
2
C of
FIG. 2A
, pins
38
are formed in the bottom of the cover ring
22
′ in accordance with the two-tabbed alignment block-out scheme.
As illustrated in
FIG. 2D
, the cover ring
22
′ is engaged with the lower shield
18
. The pins
38
extending down from the bottom of the cover ring
22
′ are engaged in the holes
42
in a cup
19
formed under the lower shield
18
. This keeps the cover ring
22
′ from rotating so that the cover ring
22
′ with tabs
35
can be precisely fixed in place with respect to alignment marks
37
formed on a wafer
16
.
However, conventional tabbed alignment block-out hardware with the cover ring
22
′ and the lower shield
18
cannot use a standard shutter disk and shutter arm assembly because the pins
38
of the cover ring
22
′ would interfere with the shutter disk
24
as indicated at
27
of FIG.
1
. Particularly, if an actuator arm
25
were to attempt to put the shutter disk
24
onto the wafer pedestal
14
, the shutter blade
32
would run into the pins
38
extending down from the lower shield
18
.
Thus, there would be a clearance problem underneath the lower shield
18
if the shutter disk
24
were used with the two-tabbed block-out scheme.
Further, because the shutter disk
24
has to be sufficiently thick (to withstand various processing conditions), it can be inadvertently adhered to the tabs
35
by deposition during the pasting or the cleaning steps as illustrated in FIG.
3
. Therefore, production wafers instead have been used for pasting by transferring the production wafers into the chamber and pasting on the wafers to avoid the clearance and gluing problems.
Unfortunately, using expensive production wafers each time to paste the chamber (which is required before each production lot) is costly and time consuming. Particularly, this is true because operator intervention is necessary to place an extra wafer in each production lot, leading to otherwise unnecessary exposure to mis-processing and it takes a long time to transfer the wafer to the chamber to be pasted. Also, because pasting is required quite often for the PVD chamber, a large number of production wafers can be wasted. Alternatively to using a wafer for pasting, an additional chamber having a metal disk for shuttering can be attached to the main chamber body and a robot arm can be used to pick up the disk and to transfer it to the chamber for pasting or cleaning of the target.
However, these prior art methods for cleaning targets or pasting depos

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