Coating processes – Direct application of electrical – magnetic – wave – or... – Ion plating or implantation
Reexamination Certificate
2000-02-15
2002-02-19
Padgett, Marianne (Department: 1762)
Coating processes
Direct application of electrical, magnetic, wave, or...
Ion plating or implantation
C427S523000, C427S569000, C427S570000, C204S192300
Reexamination Certificate
active
06348238
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Referenced-applications
This application claims the priority of Japanese Patent Application No. 11-066067, filed on Mar. 12, 1999 in Japan, the entire contents of which are hereby incorporated herein by reference.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
Not Applicable
REFERENCE TO A MICROFICHE APPENDIX
Not Applicable
BACKGROUND OF THE INVENTION
1. Description of Related Art
Thin film fabrication processes such as sputtering and CVD are widely employed in the manufacture of LSI and various other electronic devices and display devices such as liquid crystal displays, etc. Meanwhile, greater and greater advances are being made in device integration and miniaturization in the field of semiconductor devices. Device miniaturization demands new techniques in device manufacture. More specifically, aspects involved comprise the filling of very fine holes with sufficient amounts of film, measures to reduce step differences in device manufacture, and the prevention of lead breakage due to electron migration or the production of heat caused by high current density. In particular, technology by which a barrier film with sufficient thickness is formed with good coverage in the bottom of a fine hole with a high aspect ratio (the ratio of the hole depth to the diameter or width of the hole's opening) is a technology which holds the key to future semiconductor device manufacture.
A barrier film is used for the purpose of preventing mutual attack and diffusion of underlying material and wiring material (ensuring a barrier characteristic) and also for the purpose of ensuring electrical conductivity and ensuring close adhesion. Laminate films consisting of titanium films and titanium oxide films, tantalum films, tantalum oxide films and laminate films consisting of tantalum films and tantalum oxide films, etc. are used as barrier films.
There is currently interest in the plasma CVD procedure and ionizing sputtering procedure, etc. in which a film is deposited while imposing a bias on a substrate as procedures for forming a barrier film on the inner surface of a fine hole which has a high aspect ratio.
FIG. 9
will be used to describe an ionizing sputtering procedure as one example of conventional procedures.
FIG. 9
is a front view which schematically shows the structure of an ionizing sputtering apparatus constituting one example of a conventional thin film fabrication apparatus.
The apparatus shown in
FIG. 9
comprises a processing chamber
1
whose interior is pumped out by a vacuum pump system
11
, a substrate holder
2
which holds a substrate
9
in a set position in the processing chamber
1
, a gas delivery system
3
which introduces a set process gas into the processing chamber
1
, and a plasma generation means which produces a plasma in the processing chamber
1
. The plasma generation means consists principally of a cathode
4
with a target
41
installed such that the surface which is to be sputtered is exposed in the processing chamber
1
, and a sputter power supply
5
which causes a plasma to be produced by imposing a set voltage on the target
41
and causing sputtering discharge to be produced.
A source which imposes a high-frequency voltage with a frequency of about 13.56 MHz on the target
41
is used as the sputter power supply
5
. When a set process gas is introduced into the processing chamber
1
by the gas delivery system
3
and a high-frequency voltage is imposed on the target
41
by the sputter power supply
5
, high-frequency discharge occurs in the process gas, and a plasma is produced. A capacitance for which a matching unit (not shown) is used is present between the sputter power supply
5
and the target
41
surface which is to be sputtered. On imposition of the high-frequency voltage via the capacitance, electrons and ions in the plasma act in charging and discharging of the capacitance, and, because of the difference between the mobility of electrons and that of ions, a self-bias voltage is produced in the target
41
. The self-bias voltage is a negative direct-current voltage which is superimposed on the high-frequency voltage. Because of this self-bias voltage, ions are drawn out from the plasma and strike the target
41
. As a result, the target
41
is sputtered.
Particles (which are normally in an atomic state, and are referred to below as sputter particles or sputter atoms) which are ejected from the target
41
by sputtering fly through the interior of the processing chamber
1
and reach the surface of the substrate
9
. Arrival of a lot of sputter particles results in the growth of a thin film. When sputtering is effected for a set time, a thin film with a set thickness is produced on the surface of the substrate
9
.
The sputter power supply
5
also serves as an ionization means which ionizes sputter particles which are ejected from the target
41
through sputtering. When a high-frequency power supply such as noted above is used as the sputter power supply
5
, electrons in the plasma collide with the sputter particles, so increasing the efficiency of ionization of the sputter particles. Sometimes, a structure in which a high-frequency voltage is imposed on a high-frequency electrode which is provided partway along the flight path of the sputter particles is employed as an ionization means.
There is further provided a bias system
6
which biases the substrate
9
in order to cause ions in the plasma to strike the substrate
9
. What is meant by ‘bias’ is that a set potential relative to the plasma's space potential is imparted to the surface of the substrate
9
in order to cause ions in the plasma to strike the substrate
9
.
The substrate holder
2
comprises a holder main body
21
made of metal which is kept at ground potential, and a dielectric block
22
, etc., which is fixed to the holder main body
21
. A bias electrode
23
is provided inside the dielectric block
22
. The bias system
6
in a conventional apparatus consists mainly of a bias power supply
61
, etc. connected to the bias electrode
23
.
When sputtering is effected while using the bias system
6
, the action of sputter particles which have been ionized (and are referred to below as ionized sputter particles) has the effect of improving the coverage in holes. This point will now be described with reference to FIG.
10
. In
FIG. 10
, which is a drawing for the purpose of description in relation to the surface potential of the substrate
9
in a conventional method and apparatus, FIG.
10
(
1
) indicates the voltage imposed on the bias electrode
23
, and FIG.
10
(
2
) indicates the surface potential of the substrate
9
.
First, the substrate
9
is set on the dielectric block
22
constituting part of the substrate holder
2
. Therefore, the potential (referred to below as the substrate surface voltage Vs) of the substrate
9
surface which is exposed to the plasma first becomes a floating potential. The floating potential (indicated as Vf in FIG.
10
(
2
)) is a negative potential of around several volts. The strength of the sheath field produced by the floating potential Vf depends on the plasma density. Further, the plasma density depends on the output of the high-frequency power supply which is used as the sputter power supply
5
.
On the other hand, the plasma's space potential (indicated as Vp in FIG.
10
(
2
), is a positive potential of about 0V to several volts. It is thought that the plasma space potential shifts slightly to the positive side because the system attempts to establish a balance as the result of electrons migrating to the surface of the substrate holder
2
, etc. A sheath field whose potential gradually falls going toward the substrate
9
is produced between the plasma which is at a space potential Vp such as this and the substrate
9
to which the floating potential Vf is imparted. The orientation of the sheath field is normal to the substrate
9
, and ionized sputter particles are accelerated by the sheath field and are incident on the substrate
9
at approximately right ang
Mizuno Shigeru
Satou Hideki
Satou Makoto
Tagami Manabu
Anelva Corporation
Burns Doane , Swecker, Mathis LLP
Padgett Marianne
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