Chemistry: electrical and wave energy – Processes and products – Coating – forming or etching by sputtering
Utility Patent
1997-09-29
2001-01-02
Kalafut, Stephen (Department: 1745)
Chemistry: electrical and wave energy
Processes and products
Coating, forming or etching by sputtering
C204S298060, C204S298080, C204S298130
Utility Patent
active
06168690
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to physical vapor deposition. More particularly, the present invention relates to improved methods and apparatuses for ionized physical vapor deposition.
Generally physical vapor deposition, commonly referred to as sputtering, is a method of transferring a material from a sputtering target to an object. Sputtering is normally carried out by applying a voltage differential between the sputtering target and the object to promote the migration of the material from the sputtering target to the object.
FIG. 1
depicts a prior art physical vapor deposition (PVD) apparatus
10
. Physical vapor deposition apparatus
10
includes a sputter target
15
, a chuck
20
and a direct current bias power supply
25
. The PVD apparatus
10
has an internal chamber
12
within which the sputter target
15
and chuck
20
are placed. An object
30
is typically placed on chuck
20
. Internal chamber
12
is typically kept at a very low pressure and argon gas is introduced into internal chamber
12
at low pressure. The gas in the plasma state is suitable for sputtering material off of a target.
The D.C. bias power supply
25
negatively biases sputtering target
15
relative to ground. The electric potential created between sputtering target
15
and ground promotes the ionization of the argon gas particles. The ions are bombarded against sputter target
15
, sputtering off metal particles
40
. Metal particles
40
bombard the entire chamber
12
and some of the metal particles
40
are typically deposited on to object
30
.
In order to promote a greater rate of sputtering an externally generated magnetic field
50
is typically induced near sputter target
15
. Magnetic field
50
promotes the formation of a plasma
45
having a higher density of ions closer to sputter target
15
. The presence of a greater number of ions near sputter target
15
creates a greater number of interactions between the ions and the sputter target, thus allowing a higher rate of sputtering.
One drawback of prior art PVD apparatuses has been the large amounts of power required to sputter at acceptable rates. Sometimes power supply
25
is required to generate 20 kilowatts of power in order to obtain acceptable deposition rates.
Another disadvantage of the prior art PVD apparatus
10
is that the metal particles
40
sputtered away from sputtering target
15
are isotropically distributed. That is, sputter particles
40
travel in individually random directions. For some applications of sputtering an isotropic distribution of metal particles
40
is undesirable.
FIGS.
2
A-C depict the filling of a trench
31
in object
30
that is a semiconductor substrate
30
′. In many applications of sputtering the trench
31
in a semiconductor substrate
30
′ is required to be filled with the metal sputter material. An isotropic distribution of the metal particles
40
leads to the deposition of a layer of metal
41
, as depicted in FIG.
2
B. The metallic layer
41
forms not only at the bottom of trench
31
, but also along the walls of the trench. Eventually, as seen in
FIG. 2C
, trench
31
is filled by the metallic layer
41
, but often times a void
43
is left within the trench. Voids
43
within the trenches often times lead to failures of the finished semiconductor device.
FIGS.
3
A-B depict the filling of the trench
31
by anisotropically distributed metal particles. Anisotropically distributed metal particles travel in the same general direction. Thus, anisotropically directed metal particles
40
aimed orthogonally towards the semiconductor substrate
30
′ will deposit a more uniform metallic layer
41
′. As seen in
FIGS. 3A and 3B
, metallic layer
41
′ fills trench
31
uniformly from the bottom up, and prevents the formation of voids
43
.
Prior art methods of anisotropically depositing metal particles have several disadvantages.
FIG. 4
, for example, depicts a prior art PVD apparatus
10
′ utilizing a collimator
60
. Collimator
60
screens out metal particles
40
to only allow those metal particles orthogonally directed towards object
30
to pass through. In order to ensure that metal particles
40
do not collide with other particles between the collimator
60
and object
30
(and hence become isotropically distributed), a greater vacuum is required within chamber
12
.
Screening out a large portion of the sputtered metal population lowers the rate of deposition. Therefore, higher power must be used to obtain similar rates to PVD devices without collimators.
FIG. 5
depicts another prior art PVD apparatus
10
″ utilizing induction coils
70
shown in a cross-sectional view. Induction coils
70
are connected to a radio frequency power supply
72
. The radio frequency power supply
72
provides an alternating current through induction coils
70
inducing a plasma
45
′ within the circumference of coils
70
.
Sputter target
15
may be independently biased by power supply
25
. Bias power supply
25
regulates the rate of sputtering while radio frequency power supply
72
regulates the generation of ions. Ions diffusing to the edge of the plasma fall down the potential between the plasma and the boundaries, and obtain a velocity component normal to the boundary. This process is commonly referred to as ionized physical vapor deposition.
PVD apparatus
10
″, however, has several limitations. First, it typically still requires a large amount of power to generate the bias potential and energize induction coils
70
. Next, induction coils
70
and sputter target
15
must be made of the same type and quality of material in order to prevent contamination. Third, induction coils
70
, themselves, may also be consumed in the deposition process, requiring replacement of induction coils
70
in addition to sputter target
15
.
Finally, sputter target
15
is typically not uniformly consumed. Normally, a sputter target
15
utilized in a ionized PVD system is a circular disc. The disc is typically consumed quickest in an ring pattern within the outer diameter of the disc. The non-uniformity is generally caused by externally generated magnetic field's
50
irregular attraction of ions towards sputter target
15
. This non-uniform consumption of the sputter target requires more frequent replacement of sputter target
15
.
The need, therefore, exists for a method and an apparatus of anisotropically depositing a sputter material onto an object with a lower rate of energy consumption. Additionally, it is preferred to minimize the number of elements utilized and consumed during the deposition process. Finally, an increase in the throughput of the deposition process is desired.
SUMMARY OF THE INVENTION
The invention relates to an improved sputter target that is a combination sputter target and induction antenna. The improved sputter target reduces the amount of power necessary to successfully perform physical vapor deposition operations. Additionally, the improved sputter simplifies the design of a physical vapor deposition apparatus.
In one embodiment, the improved sputter target is comprised of a sputter material. When the sputter target is energized sputter material particles are sputtered away and a plasma is induced such that the sputter material particles are anisotropically directed.
In another embodiment, the sputter target is energized by an energy source. In another embodiment, the energy source includes a bias power supply and an induction power supply. The bias power supply applies a potential to the sputter target relative to an object or ground. The induction power supply applies a current to the sputter target. The potential and the current promote the sputtering away of the sputter material, the formation of the plasma and the anisotropic distribution of the sputtered material particles.
In alternative embodiments, the sputter target may be any suitable size, shape and composition. In another embodiment, the sputter target may be attached to a chamber surface. In yet another embodiment, th
Benjamin Neil M.
Jewett Russell F.
Perry Andrew J.
Vahedi Vahid
Beyer Weaver & Thomas LLP
Kalafut Stephen
Lam Research Corporation
Mercado Julian A.
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