Chemistry: electrical and wave energy – Apparatus – Coating – forming or etching by sputtering
Reexamination Certificate
2000-09-26
2001-11-13
Nguyen, Nam (Department: 1753)
Chemistry: electrical and wave energy
Apparatus
Coating, forming or etching by sputtering
C118S500000, C156S345420, C269S053000, C269S054100
Reexamination Certificate
active
06315878
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to semiconductor substrate processing equipment. More particularly, the present invention relates to a method and apparatus for reducing undesirable deposition of material on the backside of the substrate during processing. Still further, the invention relates to method and apparatus for supporting a substrate in a processing chamber.
2. Background of the Related Art
The fabrication of semiconductor devices on substrates, including semiconductor substrates, typically requires the deposition of multiple metal, dielectric and semiconductor films on the surface of the substrate. The films are typically deposited on the substrates in vacuum chambers. One deposition technique is physical vapor deposition (PVD) typically referred to as sputtering, wherein a target comprised of the deposition material is exposed to a plasma and atoms or larger particles of target material are sputtered from the target and are deposited on the substrate.
To form the deposition layer on the substrate, a deposition environment must be created within the chamber adjacent to the deposition receiving surface of the substrate. In a physical vapor deposition system, the deposition environment includes a plasma maintained between the target and the substrate and a flux of sputtered target particles passes between the target and the deposition receiving surface of the substrate so that a portion of the sputtered target particles deposit on the substrate to create the deposition layer.
FIG. 1
is a simplified sectional view of a conventional PVD chamber
10
which generally includes a chamber enclosure wall
14
having at least one gas inlet (not shown) and an exhaust outlet
16
connected to an exhaust pump (not shown). A substrate support member
20
having a positioning member
47
on an edge thereof is disposed at the lower end of the chamber
10
and a target
18
is received at the upper end of the chamber
10
. In addition to providing a resting and lifting mechanism, the support member is also used to dissipate the heat generated during deposition. The target
18
is electrically isolated from the enclosure wall
14
and the enclosure wall
14
is preferably grounded so that a negative voltage may be maintained on the target
18
with respect to the grounded enclosure wall
14
. A shield
22
is suspended from the chamber cover and includes an annular, upturned, wall
24
which isolates the lower portion of the chamber when the substrate support member is in a raised position for processing.
A conventional robot arm carries a substrate
26
into the chamber
10
and positions the substrate
26
above the upper tips of the pins
30
a.
A lift mechanism
32
elevates platform
28
which lifts the pins
30
a
upwardly to lift the substrate
26
off the robot blade. The robot blade then retracts from the chamber
10
, and a substrate support lift mechanism
60
raises the support member
20
and the lift pins are lowered to place the substrate
26
on a resting mechanism coupled to the support member.
The resting mechanisms generally provided in conventional processing chambers are prone to producing contaminants by scratching the backside of the substrate. During the deposition process, the substrate is disposed on one or more rest pins
88
. The rest pin
88
is rigidly fastened to the support member
20
. Thus, vibrations in the support member are communicated to the support pins which results in friction between the support pins and the backside of the substrate. Friction between the support pins and the substrate may lead to deep scratches in the backside of the substrate, thus releasing substrate material which contaminates the environment within the chamber.
In physical vapor deposition systems, the deposition material will, if left unconfined, deposit on all of the interior surfaces of the chamber. Typically, material is sputtered in a cosine pattern. In particular, material which does not deposit on the material receiving surface of a substrate may deposit on the edge or backside of the substrate. Edge and/or backside deposition may lead to damage of the substrate and adhesion or sticking of the substrate to components of the processing chamber. In particular, backside deposition may lead to the formation of bridging layers between the backside and the support member in the chamber leading to adhesion of the substrate to the support member. Adhesion of the substrate to the support member is generally referred to as sticking.
In conventional chambers used for full coverage deposition on substrates, a large gap must be maintained between the support member and the substrate to delay the formation of a bridging layer between the substrate and the support member due to the accumulation of material in the space between the backside of the substrate and the support member. However, maintaining a large gap between the support member and the substrate may drastically reduce the efficiency of heat dissipation by the support member.
In spite of the space maintained between the support member and the substrate, deposition in the area of contact between the resting and lifting mechanism and the substrate generally results in accumulation of material capable of adhering to the substrate and the support member, thus necessitating operator intervention to separate the substrate from the resting mechanism which leads to substantial down time of the chamber.
One avenue for reducing edge and backside deposition and the related adhesion and contamination problems is provided by forming a rectangular channel in the periphery of the support member. Material which deposits at the perimeter of the substrate is collected in the channel and prevented from accumulating at the edge of the substrate and ultimately forming a bridging layer between the support member and the backside of the substrate.
FIG. 2
is a partial sectional view of a substrate support member having a rectangular collection channel
96
for material collection and a substrate support pin
88
disposed in the support member to support the substrate
82
. The upper surface
84
of the substrate
82
is exposed to a target (not shown) and the backside
86
of the substrate contacts support pin
88
. The support member
90
has a substrate receiving region
92
and a peripheral region
94
comprising a collection channel
96
disposed therein. The collection channel
96
is formed by sidewalls
102
,
104
and a base
106
. The edge
108
of the substrate
82
extends beyond the substrate receiving region
92
and over hangs the collection channel
96
when supported in the chamber. During processing, material deposits on the entire surface of the material receiving face and in the collection channel
96
. As the deposition material impacts the walls of the collection channel
96
, the material may lose kinetic energy during the impact and accumulate in the collection channel
96
. The top end of each wall
102
,
104
may be machined to include chamfers
112
,
114
that may contact particles from the depositing material and divert their trajectories to avoid contact between the material and the backside
86
of the substrate
82
.
Although the design of
FIG. 2
may allow material deposition over the full surface of the material receiving face
84
while accumulating in the collection channel
96
, the design may only marginally decrease backside deposition. After impacting the walls
102
,
104
and/or the base
106
, only particles with low kinetic energy will likely remain within the collection channel
96
while other particles contacting the walls and the base of the channel will have enough kinetic energy to continue their trajectory, have a number of impacts with the walls and the base of the channel, and possibly continue on a trajectory
101
which guides them to the backside
86
of the substrate. While the chamfers
112
,
114
may deflect some of the particles away from the backside of the substrate, other particles may impact the chamfers at angles that would
Carlson Charles
Patadia Nalin
Applied Materials Inc.
Moser, Patterson & Sheridan L.L.P.
Nguyen Nam
VerSteeg Steven H
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