Coating processes – Direct application of electrical – magnetic – wave – or... – Pretreatment of substrate or post-treatment of coated substrate
Reexamination Certificate
1998-03-27
2001-08-07
Meeks, Timothy (Department: 1762)
Coating processes
Direct application of electrical, magnetic, wave, or...
Pretreatment of substrate or post-treatment of coated substrate
C427S255391, C427S255394
Reexamination Certificate
active
06270859
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to semiconductor fabrication equipment. In particular, the invention relates to components used in a plasma reactor for chemical vapor deposition (CVD) pertaining to gas flow through and out of the reactor chamber.
BACKGROUND OF THE INVENTION
Semiconductor integrated circuits are fabricated with multiple layers, some of them patterned, of semiconductive, insulating, and conductive materials, as well as additional layers providing functions such as bonding, a migration barrier, and an ohmic contact. Thin films of these various materials are deposited or formed in a number of ways, the most important of which in modem processing are physical vapor deposition (PVD), also known as sputtering, and chemical vapor deposition (CVD).
In CVD, a substrate, for example, a silicon wafer, which may already have patterned layers of silicon or other materials formed thereon, is exposed to a precursor gas which reacts at the surface of the substrate and deposits a product of the reaction on the substrate to thereby grow a film thereon. A simple example includes the use of silane (SiH
4
) to deposit silicon with the hydrogen forming a gaseous byproduct which is evacuated from the chamber. However, the present application is directed more to CVD of a conductive material such as TiN.
This surface reaction can be activated in at least two different ways. In a thermal process, the substrate is heated to a sufficiently high temperature to provide the activation energy for molecules of the precursor gas adjacent to the substrate to react there and deposit a layer upon the substrate. In a plasma-enhanced CVD process (PECVD), the precursor gas is subjected to a sufficiently high field that it forms a plasma. As a result the precursor gas is excited into higher energetic states, such as ions or radicals, which readily react on the substrate surface to form the desired layered material.
Zhao et al. describe an example of a CVD deposition chamber in U.S. patent application Ser. No. 08/348,273 filed on Nov. 30, 1994, now issued as U.S. Pat. No. 5,558,717, expressly incorporated herein by reference, and which is assigned to a common assignee. This type of CVD chamber is available from Applied Materials, Inc. of Santa Clara, Calif. as the CVD DxZ chamber.
As described in this patent and as illustrated in the cross sectional side view of
FIG. 1
, a CVD reactor chamber
30
includes a pedestal
32
supporting on a supporting surface
34
a wafer
36
to be deposited by CVD with a layer of material. Lift pins
38
are slidable within the pedestal
32
but are kept from falling out by conical heads on their upper ends. The lower ends of the lift pins
38
are engageable with a vertically movable lifting ring
39
and thus can be lifted above the pedestal's surface
34
. The pedestal
32
is also vertically movable, and in cooperation with the lift pins
38
and the lifting ring
39
, an unillustrated robot blade transfers a wafer into chamber
30
, the lift pins
38
raise the wafer
36
off the robot blade, and then the pedestal rises to raise the wafer
36
off the lift pins
38
onto its supporting surface
34
.
The pedestal
32
then further raises the wafer
36
into close opposition to a gas distribution faceplate
40
, often referred to as a showerhead, which includes a large number of passageways
42
for jetting the process gas to the opposed wafer
36
. That is, the passageways
42
guide the process gas into a processing space
56
towards the wafer
36
. The process gas is injected into the reactor
30
through a central gas inlet
44
in a gas-feed cover plate
46
to a first disk-shaped manifold
48
and from thence through passageways
50
in a baffle plate
52
to a second disk-shaped manifold
54
in back of the showerhead
40
.
As indicated by the arrows, the process gas jets from the holes
42
in the showerhead
40
into the processing space
56
between the showerhead
40
and pedestal
32
so as to react at the surface of the closely spaced wafer
36
. Unreacted process gas and reaction byproducts flow radially outwardly to an annular pumping channel
60
surrounding the upper periphery of the pedestal
32
. The pumping channel
60
is generally closed but on the receiving end includes an annular choke aperture
62
between the pumping channel
60
and the processing space
56
over the wafer
36
. The choke aperture
62
is formed between an isolator
64
, to be described later, set in a lid rim
66
and an insulating annular chamber insert
68
resting on a ledge
70
on the inside of the main chamber body
72
. The choke aperture
62
is formed between the main chamber and a removable lid attached to the chamber so that a fully annular choke aperture
62
can be achieved. The choke aperture
62
has a substantially smaller width than the depth of the processing space
56
between the showerhead
40
and the wafer
36
and is substantially smaller than the minimum lateral dimensions of the circumferential pumping channel
60
, for example by at least a factor of five. The width of the choke aperture
62
is made small enough and its length long enough so as to create sufficient aerodynamic resistance at the operating pressure and gas flow so that the pressure drop across the choke aperture
62
is substantially larger than any pressure drops across the radius of the wafer
36
or around the circumference of the annular pumping channel
60
. In practice, it is not untypical that the choke aperture
62
introduces enough aerodynamic impedance that the pressure drop from the middle of the wafer
36
to within the pumping channel
60
is no more than 10% of the circumferential pressure drop within the pumping channel
60
.
The pumping channel
60
is connected through a constricted exhaust aperture
74
to a pumping plenum
76
, and a valve
78
gates the exhaust through an exhaust vent
80
to a vacuum pump
82
. The constricted exhaust aperture
74
performs a function similar to that of the choke aperture
62
in introducing an aerodynamic impedance such that the pressure within the pump channel
60
is substantially constant.
The restricted choke and exhaust apertures
62
,
74
create a nearly uniform pressure around the circumferential pumping channel
60
. The resultant gas distribution flow pattern across the wafer
36
is shown in arrowed lines
84
in FIG.
2
. The process gas and its reaction byproducts flow from the center of the showerhead
40
across the wafer
36
and the periphery of the pedestal
32
along radial paths
84
and then through the choke aperture
62
to the pumping channel
60
. The gas then flows circumferentially along paths
86
in the pumping channel
60
to the exhaust aperture
74
and then through the exhaust plenum
76
and the exhaust vent
80
to the vacuum pump
82
. Because of the restrictions
62
,
74
, the radial flow
84
across the wafer
36
is nearly uniform in the azimuthal direction.
As shown in
FIGS. 1 and 3
(
FIG. 3
being a closeup view of the upper right corner of FIG.
1
), the ledge
70
in the chamber body
72
supports the chamber shield liner
68
, which forms the bottom of the pumping channel
60
. The chamber lid rim
66
forms the top and part of the outside wall of the pumping channel
60
along with part of the chamber body
72
. The inside upper edge of the pumping channel
60
is formed by the isolator ring
64
, which is made of a ceramic or other electrically insulating material which insulates the metallic showerhead
40
from the chamber body
72
.
The CVD reactor
30
of
FIG. 1
can be operated in two modes, thermal and plasma-enhanced. In the thermal mode, an electrical power source
90
supplies power to a resistive heater
92
at the top of the pedestal
32
to thereby heat the pedestal
32
and thus the wafer
36
to an elevated temperature sufficient to thermally activate the CVD deposition reaction. In the plasma-enhanced mode, an RF electrical source
94
is passed by a switch
96
to the metallic showerhead
40
, which thus acts as an electrode. The showerhe
Chang Mei
Danek Michal
Dornfest Charles
Luo Lee
Sajoto Talex
Applied Materials Inc.
Guenzer, Esq. Charles S.
Meeks Timothy
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