Coating apparatus – Gas or vapor deposition
Reexamination Certificate
1999-03-04
2001-01-23
Mills, Gregory (Department: 1763)
Coating apparatus
Gas or vapor deposition
C118S726000, C427S248100, C427S255120
Reexamination Certificate
active
06176930
ABSTRACT:
BACKGROUND OF THE DISCLOSURE
1. Field of the Invention
The present invention is directed toward the field of manufacturing integrated circuits. The invention is more particularly directed toward an improved apparatus and method for controlling the flow of process material into a thin film deposition system.
2. Description of the Related Art
Presently, aluminum is widely employed in integrated circuits as an interconnect, such as plugs and vias. However, higher device densities, faster operating frequencies, and larger die sizes have created a need for a metal with lower resistivity than aluminum to be used in interconnect structures. The lower resistivity of copper makes it an attractive candidate for replacing aluminum.
A well established technique for depositing copper is through the use of chemical vapor deposition (“CVD”) processing. For example, chemical vapor deposition of copper is achieved by using a precursor known as Cupraselect®, which has the formula Cu(hfac)L. Cupraselect® is a registered trademark of Schumacher of Carlsbad, Calif. The Cupraselect® consists of copper (Cu) bonded to a deposition controlling compound such as (hfac) and a thermal stabilizing compound (L). The (hfac) represents hexafluoroacetylacetonato, and (L) represents a ligand base compound, such as trimethylvinylsilane (“TMVS”).
During the CVD of copper using Cu(hfac)L, the precursor is vaporized and flowed into a deposition chamber containing a wafer. In the chamber, the precursor is infused with thermal energy at the wafer's surface. At the desired temperature the following reaction results:
2Cu(hfac)L→Cu+Cu(hfac)
2
+2L (Eqn. 1)
resulting copper (Cu) deposits on the upper surface of the wafer. The byproducts of the reaction (i.e., Cu(hfac)
2
and (2L)) are purged from the chamber which is maintained at a vacuum during wafer processing.
FIG. 1
illustrates a copper CVD system of the prior art. Specifically, a copper deposition system
90
, comprises a deposition chamber
100
, pressure control unit
120
, a precursor delivery system
130
, and a gas delivery system
140
. The chamber
100
is defined by sidewalls
102
, floor
104
and lid
106
. Process gases A and B are introduced to the chamber
100
through a showerhead
108
incorporated into the lid
106
. The pressure control unit
120
, (e.g., a vacuum pump), is coupled to the process chamber
100
via a valve
122
(e.g., a throttle valve) to control the chamber pressure.
In the precursor delivery system
130
, liquid precursor such as Cupraselect® flows from ampoule
132
through a liquid mass flow controller (LMFC)
134
, a valve
136
to a tee
138
via conduction lines
133
and
135
. In the gas delivery system, a gas “A” is delivered to the tee
138
from a gas “A” source
142
via a mass flow controller (MFC)
144
and valve
146
. The Gas “A”, an inert gas such as argon or helium, facilitates the flow of liquid precursor from the tee
138
to the showerhead
108
. The gas delivery system
140
also delivers a Gas “B”, e.g., Argon, directly to the showerhead
108
via a gas “B” source
141
, mass flow controller
143
and valves
145
and
147
. In the showerhead
108
, the liquid precursor expands into a mist and mixes with gas “B”. The showerhead
108
contains a hot plate
115
that is heated by, for example a resistive coil. The precursor mist evaporates upon striking the hot plate
115
and forms a vapor.
The deposition chamber
100
further contains a heated susceptor
112
(workpiece support) for retaining a substrate
116
such as a semiconductor wafer onto which copper is to be deposited. The susceptor
112
is fabricated from a durable metallic material such as aluminum or a ceramic material such as aluminum nitride or boron nitride. The susceptor
112
also contains additional components such as resistive heater coils
113
to generate heat within the substrate support
112
which is conducted to the wafer
116
. Copper is deposited onto the substrate
116
by CVD when the vaporized precursor contacts the heated wafer.
One problem associated with using Cupraselect® for CVD is the complicated delivery process used to couple the material from the liquid storage ampoule to the process chamber
100
. In the prior art, the liquid Cupraselect® is mixed with a gas “A” such as Argon, Helium or any other inert gas between the ampoule
132
and the process chamber
100
. To precisely deposit a thin layer of copper on the wafer surface, the flow of Cupraselect® to the vaporizer must be carefully controlled. In the prior art, a gate valve or isolation valve is needed to create a low pressure space to ensure Cupraselect® evaporation and fast pump-down through a separate diverter path. Such valves provide for high throughput but, unfortunately, have moving parts and O-ring seals that present a potential risk of mechanical particle generation. The gate valve and gas “A” delivery system also complicate the design and construction of the CVD system
90
and add to its cost. Therefore, the components used to deliver the precursor should be minimized so as to reduce cost and facilitate complete purging of the system when so needed.
Furthermore, in prior art systems, liquid precursor shut-off is problematic due to residual liquid precursor in the line between the tee
138
and the showerhead
108
. This residual liquid precursor is continuously being drawn into the chamber
100
resulting in an over-flood of precursor. Consequently, the interior of the chamber
100
and other parts of the apparatus become undesirably coated. The coating subsequently flakes off into large particles which can contaminate the wafer
116
and other parts of the apparatus.
Accordingly, it is desirable to provide an apparatus and method for improved control of a precursor material in a substrate process system to reduce the likelihood of plating or particle formation within the system as well as increase deposition rate.
SUMMARY OF THE INVENTION
The disadvantages associated with the prior art are overcome with the present invention of an apparatus and method for controlling a flow of process material from a process material source to a chemical vapor deposition chamber. The apparatus comprises an injector valve, disposed proximate the deposition chamber. An injector driver controls the opening and closing of the injector valve. The injector valve controls the flow of precursor material by repeatedly opening and closing the injector valve with a predetermined duty cycle. Liquid precursor exiting the injector valve expands and atomizes into a fine mist. The apparatus further comprises an evaporator coupled to the injector valve for evaporating the atomized precursor. In a first embodiment of the present invention, the evaporator includes a heater in the shape of a spiral channel. In this embodiment, the injector valve and evaporator are combined as an injector-vaporizer mounted directly to the deposition chamber. In a second embodiment of the present invention, the evaporator is a hot plate disposed within deposition chamber.
The present invention is also operable in a deposition system comprising a deposition chamber and an injector-vaporizer that communicates with said chamber. The injector-vaporizer has a pressure regulator that maintains a constant pressure differential between an inlet and an outlet of the injector valve.
The apparatus and system of the present invention are operable by an inventive method in which the injector valve opens for a first predetermined period of time to permit a flow of process material and closes for a second predetermined period of time to prevent a flow of said process material. The opening and closing of the injector valve is cycled for a third predetermined amount of time. Such a method is, for example, operable as program code embodied in a computer readable storage medium.
All of these aspects of the present invention lead to improved control over the delivery and vaporization of precursor material to the deposition chamber. The invention therefore allows better control of the deposition r
Chen James J.
Johnson Mark S.
Koai Keith K.
Li Sean
Schmitt John
Applied Materials Inc.
Hassanzadeh P.
Mills Gregory
Thomason Moser & Patterson
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