Chemistry: electrical and wave energy – Processes and products – Coating – forming or etching by sputtering
Reexamination Certificate
1999-03-18
2001-06-19
Bowers, Charles (Department: 2813)
Chemistry: electrical and wave energy
Processes and products
Coating, forming or etching by sputtering
C204S192170, C204S198000, C251S193000
Reexamination Certificate
active
06248220
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a physical vapor deposition, and more particularly, to an RF (radio frequency) sputtering sputtering apparatus and a film formation method using the same, capable of appropriately improving quality of a film being deposited on a wafer.
2. Description of the Background Art
The forming method of a film on a wafer may vary to a chemical method in which a gaseous material is synthesized via a chemical reaction into a solid material in form of a film or particles, and a physical method in which target particles are deposited on a wafer using a variety of physical technologies.
The chemical method includes a chemical vapor deposition (CVD) and a plating, and the physical method includes a sputtering, evaporation and spin coating.
FIG. 1
is a schematic construction view illustrating a conventional sputtering apparatus. As shown therein, the sputtering apparatus includes a substrate
16
mounted thereon by a wafer W, a chamber
14
including a target
18
(cathode) serving as a deposition material and separated from an exterior thereof, a gas supply unit
24
providing gas into the chamber
14
, a power supply unit
22
providing an RF power to respective sections, and a vacuum unit
30
vaccumizing the chamber
14
.
The target
18
is formed of one selected from a ceramic material, metal compound and insulation material. Argon gas (ArO
2
) is used for the gas.
The RF power supplied from the RF power supply unit
22
is provided to the target
18
via the cable
26
and a matching network
28
.
Reference numeral
32
denotes an ion sheath, and
34
denotes a base plate, respectively.
According to the conventional film forming method using the apparatus in
FIG. 1
, gas is supplied between the target
18
and the substrate
16
under a vacuum state. When the RF power is applied to the target
18
, the gas becomes ionized by a glow discharge so that a plasma discharge occurs between the target
18
and the substrate
16
. The positive-charged ions which exist in the discharge region become striking the surface of the target
18
by an electrical power, whereas atoms or molecules sputtered from the target
18
become deposited on the wafer W facing thereagainst.
FIGS. 2A and 2B
are graphs illustrating the substrate, the target and plasma potentials during a film forming process using the apparatus in FIG.
1
. With reference to the drawings, their inter-electrical relation and bombarding phenomenon will now be described.
As shown in
FIG. 2A
, when using argon+oxygen gas (Ar+O
2
) as a process gas, the positive-charged ions (Ar
+
) within the plasma continues its acceleration toward the target in accordance with an electrical force caused by a potential difference (Vp>Vt) of a target potential Vt and a plasma potential V
p
, thereby striking the target surface. The atoms sputtered from the target by the strike of the positive-charged ions are deposited on the wafer. However, some of the positive ions within the plasma become accelerated toward the substrate during the deposition by an electrical force caused by a potential difference (Vp>Vs) of the plasma potential Vp and the substrate potential Vs, thereby eventually bombarding the film on the wafer.
Referring to
FIG. 2B
, when argon gas is used as a process gas, a negative dc self-bias voltage Vdc is induced to the target, so that a plasma potential is decreased, thereby decreasing the bombarding of the positive ions within the plasma onto the substrate surface. In the meantime, the negative ions (O
−
) sputtered from the target become accelerated by the voltage Vdc induced to the target, thereby bombarding the film deposited on the wafer.
The conventional film formation method as described above has a disadvantage in that the film deposited by a sputtering method becomes bombarded by both the positive ions within the plasma and the negative ions sputtered from the target for thereby incurring a resputtering phenomenon in the film itself.
Further, when the film is formed on the substrate using a ceramic material as a target, the composition of the ceramic film deposited on the substrate becomes different from that of the source target due to the different sputtering yield among the respective components incorporating the ceramic material, thereby making it difficult to control the composition of the film being deposited on the substrate.
Still further, an electrical crystalline film characteristic of the film deposited on the substrate may be significantly deteriorated by the bombarding which results from both the positive ions within the plasma and the negative ions sputtered from the target.
SUMMARY OF THE INVENTION
The present invention is directed to overcoming the conventional disadvantages.
Accordingly, it is an object of the present invention to provide a sputtering apparatus and film formation method using the same which is capable of decreasing the bombarding of both positive ions within a plasma region and negative ions from a target onto a film deposited on a wafer, by applying an identical RF power to the substrate and the target, thereby improving quality of the film.
To achieve the above-described object, there is provided an RF sputtering apparatus according to the present invention which includes a chamber for proceeding a sputtering process therein to form a film, a substrate disposed in a lower portion of the chamber and mounted thereon by a wafer, a target disposed in an upper portion of the chamber and facing against the substrate, upper and lower shields disposed adjacent to the substrate and the target, a gas supply unit for supplying a reaction gas into the chamber, a power supply unit for applying the RF power to the upper and lower shields, the substrate and the target, and a vacuum unit for vaccumizing an interior of the chamber.
Further, to achieve the above-described object, there is provided an RF sputtering apparatus according to the present invention provided with a vacuum chamber, a target mounted within the chamber and serving as a deposition object, a substrate facing against the target and mounted thereon by a wafer, a gas supply unit providing a process gas into the chamber, and a power supply unit providing an RF power, which includes the steps of floating a shield adjacent to the substrate, applying an RF power to the substrate as well as the target to induce a self-bias voltage to the target and the substrate, and restricting a plasma discharge region in accordance with the ionization of a process gas to an adjacency to the target.
The object and advantages of the present invention will become more readily apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific example, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
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C.S. Ma et al. “The Role of Ambient Gas Scattering Effect and Lead Oxide Formation In Pulsed Laser Deposition of Lead-Zirconate-Titanate Thin Films” Appl. Phys. Lett. 69, Sep. 30, 1996, pp. 2030-2032.
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Bowers Charles
Fleshner & Kim LLP
Hyundai Electronics Industries Co,. Ltd.
Schilly Laura M
LandOfFree
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