. FIELD OF THE INVENTION
This invention relates to a field of method and system for the development of nano-dimensional thin films and nano-structures of various metallic and non-metallic materials. There are several available methods or techniques out of which Physical Vapour Deposition (PVD) exhibits utmost purity because this technique incorporates relatively high vacuum conditions inside the deposition chamber. Sputtering method is one of the most known PVD techniques. In this invention, an unbalanced type DC/RF biased magnetron sputtering apparatus has been designed for the deposition of metallic and non-metallic thin films at the higher deposition rate. The DC discharge in accordance with unbalanced magnetic field distribution and inert atmosphere inside the reactor, produces a stable magnetron discharge plasma. This plasma provides sufficient energy to deposit various target materials to achieve a thin nano-metric film on suitable substrate by sputtering phenomena. The novelty of this invention is the use of a unique sputter-head cooling mechanism, utilizing an adjacent top mating flange as heat sink. The main application of this invention is to develop thin nano-metric films of various materials which may further be used in sensor and photocatalytic application.
BACKGROUND OF THE INVENTION
Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
The present invention is related to a magnetron sputtering apparatus, more particularly, to a magnetron sputtering apparatus that is capable of uniform deposition at substantially higher rate. Several methods have been employed for the development of nano film on the surface of various substrates e.g., vacuum coating, plating, cvaporation, sputtering etc. Sputtering has considered to be the most appropriate PVD technique for the development of metallic and non-metallic thin films. Among the various sputtering techniques, the magnetron sputtering is widely utilized and preferred for its low wattage consumption and better thin film

deposition at relatively higher deposition rate maintaining purity. The unbalanced magnetic field distribution restricts the charged particles between the target and substrate which produces confined magnetron plasma improving the deposition rate. This type of deposition system is very much effective for the synthesis of various metals e.g., Cu, Al, Ni, Ti etc. and metal-oxides e.g., Cu2O, CuO, TiO2, ZnO, SiO2, HfO2, ZrO2 etc. in the application of VLSI IC design and other sensor and photocatalytic applications.
The prior art, US patent US5334302 [1] shows a magnetron sputtering apparatus. It comprises a vacuum chamber, substrate table and a sputtering gun. A vacuum of milli Torr order and an inert atmosphere of Argon gas is maintained during the sputtering process. The vacuum chamber accommodates the substrate table and the sputtering gun. The sputtering gun contains a target, an anode, a target cooling block and a magnetic circuit. The target is mounted to the sputtering gun using a holding clamp facing the substrate. The target is biased with a negative voltage through an electrode using a DC power supply and the anode is kept at a few millimeters distance from the target and maintained electrically grounded along with the chamber. The magnet assembly behind the target includes a soft iron return yoke structure that completes the magnetic circuit between target and magnet and between anode and magnet. It produces a magnetic force line parallel to the target towards anode. The cylindrical shaped target cooling block inside the sputtering gun has a refrigerant passage and it resists the target and the magnet assembly from getting heated.
There are several advantages present in this apparatus although the main disadvantage is only using ground potential to the substrate. It's inability to remove the accumulated charge shield created over the deposited non-metallic layer, reduces the deposition rate. Another disadvantage of their invention is the use of water-cooling mechanism which makes this design more complex and costlier. The prior art, US patent US4441974 [2] describes a magnetron sputtering apparatus consisting of both permanent and solenoid electromagnet as magnetic structure. They have preferably used a combination of permanent magnets with a soft iron yoke and solenoid coil for producing magnetic fields. The magnetic field produced

in such arrangements can control the incidence of charged particles on the surface of substrate and can develop a crack free metal coating layer which they have claimed.
The main disadvantage of this invention is the complexity of the design and also the use of electromagnets, consumes huge electrical power which makes this invention costly. Another disadvantage is that such design requires a rapid cooling mechanism to minimize the heating effect caused due to the consumption of high currents in solenoid magnets. Their invention didn't mention cooling mechanisms.
Patent References
[1] Publication No: US005334302A, Kofu Kenichi Kubo, Nirasaki Yasuo
Kobayashi, Yamanashi Koji Koizumi, Aug. 2, 1994. [2] Publication No: US004441974A, Reiji Nishikawa, Shozo Satoyama,
Chigasaki Yoshinori Ito, Sagamihara Hidetaka Jyo, Apr. 10, 1984.
OBJECTS OF THE INVENTION
The principal object of this invention is to provide a permanent magnet based unbalanced type DC/RF biased magnetron sputter deposition system for developing thin films and nanostructures of metallic and non-metallic materials.
Another object of the invention is to create a stable DC discharge magnetron plasma under a high vacuum condition by using unbalanced type permanent magnet assembly for efficient, high rate deposition.
One more object of the invention is to develop a nano-metric thin film deposition setup at a low electrical power consumption.
One more object of the invention is to make the development of good quality photocatalytic and other sensor-based materials under high vacuum conditions reproducible.

Still another object of the invention is to make the system economical, compact and easily serviceable.
SUMMARY OF THE INVENTION
The present invention provides a compact, economical nano-structure and nano-dimensional thin film deposition system that develops good quality nano-structures and nano-metric films. The invention is devoid of the limitations in the relevant art.
A major aspect of the invention is the gas feeding facility extensively used in the sputtering chamber during deposition process. The gas injection line, attached with the magnetron sputter-head, allows the gas to travel through the line and ejects into the sputter-head.
Another major aspect of the present invention is the cooling mechanism of the magnets in magnetron sputter-head. The sputter-head has a relatively faster cooling rate in conjunction with immediate heat dissipation through the top mating flange of the chamber and also constant flow of sputter gas into the sputter-head.
One more major aspect of the invention is the use of permanent magnets in unbalanced magnetron assembly inside the sputter-head to provide distributed magnetic field between the target and substrate for uniform sputter deposition.
Another aspect of the invention is the use of soft iron return yoke structure for holding the target material adjacent to the magnet assembly by thread coupling that reduces the complexity of the design.
Still another aspect of the invention is the use of electrically isolated hollow stainless-steel cylindrical structure of the sputter-head that works as an anode in this design. The cylindrical structure is attached with the sputter-head by thread coupling which also minimizes the design complexity of this invention. The target biasing potential can be changed upon adjusting the distance between target and this anode.

One more aspect of the invention is the use of hermetically sealed non-magnetic stainless steel (SS 304/SS 316) sputtering chamber in this design which holds high vacuum for maintaining purity.
Another aspect of the invention is the use of in-house built DC regulated power supply circuit driven by a variac for target biasing, making this invention more economical.
Still another major aspect in this invention is the use of negative DC bias to the target for efficient metal deposition and RF bias potential to the substrate for removing charge cloud generated during the deposition of insulating or non-metal nanofilm.
Another aspect of the invention is the use of a turbo-molecular pump backed by a rotary vane vacuum pump to obtain high vacuum inside the to achieve a stable magnetron discharge.
One more aspect in this invention is the use of motorized drive system to manipulate the position of the substrate support assembly to change distance between target and substrate.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The invention will now be illustrated with accompanying drawings which are intended to illustrate the embodiments of the present invention. The drawings are not intended to be taken restrictively to imply any limitation on the scope of the invention. It is to be understood that the concepts and features of the present invention can be embodied in numerous variant embodiments by those skilled in the art. Such variant embodiments are intended to be within the scope of the present invention. In the accompanying drawings:
Fig. 1 is a diagram showing the sectional view of an unbalanced type DC/RF biased magnetron sputtered nano-metric thin film deposition system 1 according to the first and preferred embodiment of the invention.

Fig. 2 is a diagram showing the sectional view of magnetron sputter-head 2 along with gas injection line 26 according to the second embodiment of the invention.
Fig. 3 is a diagram showing the front view of the magnetron sputter-head consisting unbalanced type permanent magnet assembly 3 according to the third embodiment of the invention.
Fig. 4 is a diagram showing the distribution of magnetic flux lines 301 in according to the fourth embodiment of the invention.
Fig. 5 is a diagram showing the detailed target biasing arrangement according to the fifth embodiment of the invention.
Fig. 6 is a diagram showing the substrate assembly 6 and its motorized driving system 7 along with RF biasing arrangement.
DETAILED DESCRIPTION OF THE INVENTION
The present invention aims to develop uniform, high quality films of various materials for VLSI device fabrication and other sensor-based applications. The nano-dimensional film of various materials can be developed by utilizing several methods e.g., vacuum coating, plating, sputtering, evaporation etc. Among these methods sputtering has proved to be the most useful PVD technique for the development of various nano-structures of metals and non-metals. The magnetron sputtering technique is broadly utilized for its low power consumption and the use of high vacuum condition during sputtering produces good quality thin films at higher deposition rate. The present invention used unbalanced type permanent magnet assembly to control charged particles more precisely for uniform deposition at a high deposition rate.
There will be described below the preferred embodiment of the present invention into details with reference to the accompanying drawings. Like members or elements will be designated by like reference characters. This system comprises of a sputtering chamber, magnetron sputter-head along with

combination of a turbo-molecular pump backed by a rotary vane pump for maintaining high vacuum conditions. Fig. 1 shows the sectional view of the non-magnetic SS-304/SS-316 stainless steel made cylindrical Tee shaped, compact, hermetically sealed magnetron sputter-based nano-metric thin film deposition chamber 1 in accordance with the first and preferred embodiment of the present invention. This embodiment shows a magnetron sputter-head 2 connected with a non-magnetic SS-304/SS-316 hollow Tee line inside the chamber 1. This Tee connector moves through a Wilson type vacuum seal placed at the center of top mating flange 10. A permanent magnet assembly 3 has been solely utilized for producing magnetic field lines in this magnetron sputter-head 2. The circular target material 4 has been mounted on the sputter-head 2. A high vacuum system 5 consisting of a turbo-molecular pump 52 backed by a double stage anti-suck back rotary vane pump 53 along with a pneumatically operated gate valve 51, as seen in Fig. 1, is used to provide high vacuum in the apparatus that ensures purity of the developed nanofilm. The gas injection line consists of a SS Tee connector 16 and needle valves 17 for controlling the gas injection. Inert heavier gas has been injected through SS Tee connector 16, connected with port 11 as shown according to the first and preferred embodiment of the present invention. A circular perspex flange 12 has been utilized at the right-angled port for viewing and substrate handling purpose. The substrate holding assembly 6 along with substrate 64 is illustrated in Fig. 1. The substrate table can be moved vertically very precisely with the help of a motorized drive system 7 as shown according to the first and preferred embodiment of the present invention. The substrate manipulator shaft moves through a Wilson type vacuum seal placed at the center of bottom mating flange 13 for the bottom port of the deposition apparatus. The substrate is biased through port 14 with RF power supply 41 as shown in Fig. 1.
Fig. 2 shows the sectional view of the magnetron sputter-head 2 consists of one permanent magnet assembly 3, circular target material 4, gas feeding line 26 and SS cylindrical shaped anode 21 according to the second embodiment of the present invention. The SS Tee line which is attached to the base of the sputter-head 2 by

thread coupling 81. It can be moved vertically through the Wilson type seal 42. The cylindrical sputter-head base 23 of the sputter-head assembly 2 is intentionally matched with the top mating flange 10 of the system 1 as heat sink. In the sputter-head base 23, four port apertures are made with 90° apart in contact with the gas injection line 26 that allows the inert gas to propagate through the gas outlet port 27 in the sputter-head 2 as shown in Fig. 2. There is a circular insulating disc 22 between the sputter-head base 23 and the magnet assembly 3 to make the target along with magnet assembly electrically isolated from the rest of the sputter-head 2 and deposition chamber 1. A non-magnetic stainless steel made hollow cylindrical structure covering the whole sputter-head assembly 2 and acts as anode 21 is attached with the sputter-head base 23 by thread coupling 81 according to the second embodiment of the present invention. The sputter discharge parameters can be varied by changing the distance between surface of circular target 4 and anode 21.
Fig. 3 shows the front view of the magnet assembly 3 according to the third embodiment of the present invention. A set of an annular ring-shaped ferrite permanent magnet 32 and a circular coin shaped ferrite permanent magnet 33 with different remanent magnetism (Br) value concentrically placed on a cylindrical soft iron base 31 according to the third embodiment of the present invention. The magnets are arranged in such a way that north pole of the coin shaped magnet 33 and the south pole of the annular ring-shaped magnet 32 remain at outer surface over the target 4 as shown in Fig. 3. The target 4 is held on the outer surface of the concentric magnets by a soft iron hollow cylindrical shaped return yoke 34. The return yoke is attached with the magnet assembly base 31 by a thread coupling 82 to reduce the design complexity according to the third embodiment of the present invention.
Fig. 4 shows the distribution of the magnetic field lines 301 according to the fourth embodiment of the present invention. The magnetic field configuration of the magnetic trap made by the concentric coin shaped magnet 33 and the annular ring-shaped magnet 32 favor to establish a stabilized plasma, enabling heavier energetic

particles to produce metallic deposits from the target. It is clearly seen from the field line plot that the ionized metallic particles travel along the axis towards the substrate according to the fourth embodiment of the present invention.
Fig. 5 shows the schematic view of target biasing arrangement according to the fifth embodiment of the present invention. An electrical connecting rod 36 has been inserted through a non-magnetic SS Tee line port 15 and is connected with the cylindrical soft iron base 31 of magnet assembly according to the fifth embodiment of the present invention. The target material is attached with the soft iron base 31 of magnet assembly with a soft iron hollow cylindrical return yoke 34 as shown in Fig. 5. A vacuum feed-through 37 has been coupled at port 15 for connecting the electrical connecting rod 36 with indigenously built DC regulated power supply 38 and to make the system 1 vacuum tight. The entire deposition system 1 is electrically isolated from the magnet assembly 3 and target material 4. The deposition system 1 is kept at ground potential, also keeping the anode 21 grounded.
Fig. 6 shows the schematic view of the substrate mounting assembly 6 and its motorized drive system 7 along with its RF biasing arrangement according to the sixth embodiment of the present invention. The substrate assembly 6 consists of a non-magnetic SS table 61 welded to a manipulating shaft 8, an insulator disk 62 and a non-magnetic stainless-steel substrate mounting plate 63 on which the substrate 64 is placed according to the sixth embodiment of the present invention. The insulator disk 62 makes the substrate mounting plate 63 electrically isolated from the SS table 61. The motorized drive system 7 of the substrate consists of a drive motor 72 and a gear assembly 71. The substrate assembly along with the substrate manipulating shaft 8 precisely moves vertically through the Wilson type seal 43 with the help of this motorized driving system 7 as illustrated in Fig. 6. A teflon sealed high voltage multi-strand wire 39 is inserted through the port 14 and connected with a screw 65 that is attached with the substrate mounting plate 63. A vacuum feed through 40 is coupled with the port 14 to connect the high voltage wire 39 with the RF power supply 41 and maintaining the vacuum inside the chamber 1 according to the sixth embodiment of the present embodiment.

I/We Claim
1. A compact, specially configured, economical unbalanced type DC/RF biased naturally cool magnetron sputtered nano-metric metallic and non-metallic thin film deposition system comprising of:
a non-magnetic SS-304/SS-316 cylindrical Tee shaped reactor chamber 1 where the thin film deposition is carried out on a substrate 64 placed on a substrate mounting assembly 6, by a relatively low power DC discharge magnetron sputtering under high vacuum condition;
a system for generating a stable DC magnetron discharge plasma at the mouth of the magnetron head, placed inside the sputtering vacuum chamber 1 by producing a radial magnetic field distribution, where the energetic electrons are guided by the magnetic field to collide with the gas molecules to produce ions;
a special system to bias the target with a negative DC regulated voltage supplied from an external power supply 38 for depositing metallic thin film;
a gas injection system, to introduce controlled amount of inert heavier gas into the chamber 1, through a specially designed four port aperture to produce ions for sputtering atoms from the metallic target;
a system attached with the substrate assembly 6 which helps to precisely adjust the distance between target 4 and substrate 64;
a system for feeding RF power from a RF power supply 41 to bias the substrate for maintaining constant deposition rate of dielectric materials by reducing the charge accumulation occurred during the synthesis;

a vacuum pumping system 5 to obtain a high vacuum condition inside the sputtering chamber 1 to maintain purity during thin film/structure synthesis.
A vacuum Tee connector 16 contains two precision needle valves 17 to finely control two gases simultaneously.
2. The system for creating a stable DC discharge magnetron plasma, as claimed in claim 1, comprises of an electrically isolated unbalanced type permanent magnet assembly 3 along with a soft iron return yoke 34 which acts as a target mounting facility for holding target material 4. The complete assembly produces a stable DC discharge magnetron plasma inside sputtering chamber 1 that helps to sputter out the target material 4 and deposit material on the substrate 64.
3. The magnet assembly for creating the favourable magnetic field distribution 301, as claimed in claim 2, comprises of a set of two permanent magnets with different remanent magnetism, concentrically placed on a cylindrical soft iron base 31. The hollow cylindrical soft iron return yoke 34 which also acts as a target mounting facility, attached with the base 31 by adjustable thread coupling 82 which reduces the design complexity. The whole magnet assembly is electrically isolated from the body of the magnetron head with the help of an elastomeric insulator.
4. The target biasing system, as claimed in claim 1, comprises of a vacuum isolated electrical connecting rod 36 connected to the electrically isolated magnet assembly. DC regulated voltage is supplied to the connecting rod from an external DC power supply 38 through a vacuum feed-through 37. The special design enables one to obtain stable DC discharge magnetron plasma by consuming substantially less electrical energy.
5. The gas injection system, as claimed in claim 1, comprises of a SS Tee connector 16, gas controlling needle valves 17, a gas inlet port 11, an injection line 26 and gas outlet ports 27. This injection system allows the inert gas to uniformly enter into the target region through the sputter-head with the help of a specially designed quadrant aperture to produce uniform

plasma. This arrangement also creates an inert environment at the vicinity of sputter zone which helps to maintain purity of the deposits. The specially configured gas injection process will enable to produce good purity deposition at much less consumption of gases.
6. The substrate manipulating system 7, as claimed in claim 1, comprises of a motor drive 72 and a gear assembly 71, can move the substrate assembly 6 vertically towards the target 4 to maintain the distance between target 4 and substrate 64 very precisely.
7. The high vacuum pumping system 5, as claimed in claim 1, comprises of a turbo-molecular pump 52 backed by a double-stage anti-suck back rotary vane vacuum pump 53 maintains high vacuum in the apparatus through a pneumatically operated gate valve 51.
8. The vacuum Tee connector 16 as mentioned in claim 1, contains two precision needle valves 17, with a view to finely control two gases simultaneously. The lighter gas creates plasma and the heavier gas does sputtering. This arrangement provides better plasma stability with a precise control over the deposition rate.