Claims:I Claim
1. A Compact, full permanent magnet and an economical 2.45 GHz Electron Cyclotron Resonance Plasma Enhanced Multi-facility Nano-metric Film Deposition System comprising of:
a non-magnetic stainless steelreactor chamber1where a dense plasma of an injected gas is producedover a transverse planar surface which enables the synthesis of a uniform, high quality thin film of various materials on a substrate mounting assembly14, at a desired temperatureup to 6500 C,by the Chemical Vapour Deposition/Ion Sputtering technique depending on the properties of the raw material being used;
a system for generating a 875 Gauss planar surface inside the Electron Cyclotron Resonance plasma chamber 1 where electrons gyrate and efficiently pick up energy from 2.45 GHz microwave power under cyclotron resonance condition and collide with the injected plasma gas/precursor to produce reactive radicals, positive ions and electrons;
a system to feed 2.45 GHz 750 Watt microwave power directly and efficiently into the plasma chamberavoiding the direct exposure of the plasma on the quartz vacuum window;
a gas injection system to introduce gases and precursor into the plasma and reactor chambers1,depending on the technique of deposition being implemented;
a system 7 to create multi-cusp radial field to satisfy a closed azimuthal surface field of 875 gauss, needed for ECR resonance generation at 2.45 GHz microwave frequency. This externally fitted sextupolar magnet assembly is used to enhancethe radial sputtering deposition process over a large area in presence of transverse ECR discharge.
a retractable system 55to load the sputtering target material during the operation of the apparatus as an Ion-Sputtering unit;
a system consisting of apair of cartridge heater 74 are inserted inside substrate mounting platform71to maintain the substrate temperature precisely up to 6500 C for producing better quality films;
a system of DC/RF power supplies 79, 78to bias the substrate for controlling uniform thickness and deposition rate of metal and dielectric films;
a system consisting of demountable flanges32, 33, 34, 35for viewing ECR plasma and providing access to the system; and
a vacuum system6to maintain high vacuum in thedeposition chamber1,that results in high purity of the developed film.
2. The system for creating an iso-Gauss planarECR surface, as claimed in claim 1, comprises of an assemblyof permanent magnets2along with a soft ironreturn yoke3. The complete assembly produces the planar transverse iso-gauss resonance surfaceinside the plasma chamber1. This return yoke structure also restricts magnetic field penetration and createsanalmost field free region in the reactor chamber1. This helps to avoid the ionic erosion of the films.
3. The magnetic structures for creating the iso-Gauss ECR surface, as claimed in claim 2, comprising of four rectangular permanent magnet blocks2and a soft iron return yoke 3resulting in a compact system. In the apparatus, the magnet 2is placed on top of the plasma chamber1.
4. The sextupolar magnetic external assembly 7 as claimed in claim 1, to create multi-cusp radial field to satisfy 875 Gauss azimuthal surface, needed for 2.45 GHz microwave ECR resonance. This sextupolar magnet assembly is used for powerful sputtering over a large area in presence of transverse ECR discharge. This assembly is removed during ECR CVD mode film deposition.
5. The system for supplying microwave power to the plasma chamber 1, as claimed in claim 1, consists of a rectangular waveguide WR340section 201whose major dimension is oriented parallel to the chamber axis. This ensures an orthogonal relation between the microwave fieldand longitudinal component of the developed magnetic flux lines50. This enables efficient power absorption for high density plasma preparation. A quartz microwave windowis fitted to the choke flange203 attached to the E-plane bend 202for efficient microwave injection and vacuum isolation, avoiding direct exposure of plasma on the window. A 2.45 GHz magnetron 5usually used for microwave oven delivers power to the ECR plasma with the help of its co-axial antenna fitted on the broad side of the rectangular wave guide WR340at a distance one fourth of the guided wave length from the blank end.
6. The gas injection system, as claimed in claim 1, comprises of a port37to inject gas into the plasma chamber1 for generation of ECR plasma. Another port38 is also provided near the substrate mounting assembly14to spray precursor/gas into the chamber through a perforated metallic ring 9.
7. The systemto load the sputtering material, as claimed in claim 1, consists of a retractable negatively biased 58tantalum circular ring 55 driven by a shaft56 fitted through an electrically isolated rotatable vacuum seal57 sitting on the bottom flange of the reactor chamber. The tantalum ring of the sputtering assembly containing target material is introduced into the active sextupole confined plasma region when the apparatus works as aECR plasma assisted sputtering mode. This arrangement facilitates efficient sputtering and results in high purity film development over the substrate 14. During CVD mode operation this arrangement is retracted down from the active zone as shown in bottom figure of Fig. 9 and the demountable type of externally fitted sextupole assembly may also be removed if desired.
8. The substrate 14,as claimed in claim 1, is placed on a rotating platform71 inside the depositionchamber1 in a region almost devoid of magnetic field. This leads to ionic erosion free film development. The platform 71rotation provides uniformity to the developed film.
9. The system contains demountable flanges, as claimed in claim 1, consists of four flanges, one 32of themis used to view ECR plasma and carrying out plasma diagnostics, another view window 33 is dedicated for IR spectroscopy while the other twoports 34, 35 oriented orthogonally are used for sample loading and in-situ film property measurement. The flange 39of the bottom port holds the vacuum seals forboth the driving shafts.
10. The high vacuum system6, as claimed in claim 1, consists of a turbo molecular pump 61 and rotary pump 63combination that maintains high vacuum in the apparatus through a gate valve 62. , Description:The present invention aims to develop uniform, high quality films of various materials for VLSI device fabrication. Chemical Vapor Deposition (CVD), Atomic Layer Deposition (ALD) and Ion-Sputtering are the commonly used techniques for developing such thin films. However, the development of nano-metric films are extremely process dependent. Hence, none of the techniques are capable to develop films of a wide range of materials. This demands a versatile apparatus for film growth.
Of the various variants of these deposition techniques, the plasma assisted processes yield better film properties and increased deposition rate. Electron Cyclotron Resonance plasma enhanced deposition systems offer the best quality film regarding its properties and growth rate due to its efficient high density plasma production.
This invention provides an Electron Cyclotron Resonance-Plasma Enhanced (ECR-PE) Multi-facility Nano-metric Film Deposition apparatus that can develop high quality thin films of various materials over a substrate at a high deposition rate.
There will be described below the preferred embodiments of the present invention into details with reference to the accompanying drawings. Like members or elements will be designated by like reference characters.
Fig 1 shows the sectional view of the non-magnetic SS-304 stainless steel made Compact, Multi-facility Nano-metric Film Deposition chamber in accordance with the first and preferred embodiment of the present invention. A set neodymium-iron-boron (Nd-Fe-B) permanent magnets 2 along with a soft iron return yoke structure 3 has been shown in this embodiment. A 2.45 GHz microwave launching system 4, has been employed for the suitable injection of microwave energy to reactor chamber 1. Electrons absorb energy from a 2.45 GHz microwave magnetron source5, under resonance condition over the 875 Gauss surface inside the chamber 1. These energetic electrons collide with the neutral molecules of the gas injected into the plasma chamber. A High Vacuum System 6 consisting of turbo molecular 61 and rotary pump 63 combinations along with a pneumatically operated gate valve 62, as seen in Fig. 2,is used to provide ultra-high vacuum in the apparatus that ensures purity of the developed film. Plasma Gas has been injected through port 37 as shown according to the first and preferred embodiment of the present invention. A radial view port 32 is presented as seen in Fig. 1. A sputtering setup consisting of sextupole magnet assembly 7and tantalum target holder 56& biasing arrangement 58as seen in Fig. 9& Fig. 1. Another view port 33, aligned 45° to the axis of main chamber, is meant for IR spectroscopy and for online viewing of the deposited film on the desired substrate as seen in first embodiment. Fig. 1 also shows an inbuilt motorized sample/substrate manipulator assembly 8 for the rotation and vertical movement of the sample for uniform deposition. The manipulator shaft runs through a Wilson type vacuum seal placed at the centre of 160CF mating flange 39 for the bottom port of the deposition apparatus.
Fig. 2 shows the isometric view of the Electron Cyclotron Resonance-Plasma Enhanced (ECR-PE) Multi-facility Nano-metric Film Deposition apparatus 1 consisting of several numbers of ports according to the second embodiment of the present invention. The ports are used for various purposes. The rectangular port 31 is used for microwave injection. Two 16KF ports 37, 38 are specified for plasma gas and precursor injection. A 6mm outer diameter annular tube connected to the tantalum gas spraying ring, containing a large number of small holes as seen in Fig. 8, passes through the precursor injection port38. Two orthogonally oriented 100NB ports 34, 35 are used for substrate manipulation. Another 100CF pumping port 36 is connected to the intake of the turbo molecular pump (TMP) 61 through a gate valve 62, to create high vacuum inside the deposition system. The TMP is isolated from the backing pump 63 and plumb line 64 with the help of an angle valve 65.
Fig. 3 shows a magnetic assembly consisting of permanent magnets 2 and square soft iron return yoke structure 3 to produce an almost planar transverse ECR iso-gauss surface 51 of 875 Gauss inside the plasma chamber 1 according to the third embodiment of the present invention. Each of the magnets possesses remanent magnetism (Br¬) of 1.12T. The embodiment also presents the magnetic field lines 50 exist inside the chamber.
Fig. 4 shows a sextupolar magnetic assembly 7 as seen in first and preferred embodiment consisting of equi-spaced azimuthally placed six permanent magnets 52 with alternate pole facing radially towards the centre of the assembly, according to the fourth embodiment of the present invention. The magnets are assembled on an aluminum annular structure 54 with an annular soft iron return yoke 53. This embodiment is essential to create an azimuthally varying cusp iso-gauss surface of 875 Gauss for sputtering deposition.
Fig. 5 shows the magnetic flux lines 251 inside the deposition chamber and also 252 inside the soft iron return yoke according to the fifth embodiment of the present invention.
Fig. 6 displays the radial magnetic field plot 253 produced due to the sextupole assembly 7 inside the deposition chamber according to the sixth embodiment of the present invention
Fig. 7 shows the microwave launching system 4 consists of a 2.45 GHz magnetron oscillator 5 with cooling system, a rectangular waveguide section 201 of WR340, an E-Plane metered bend 202 enabling efficient microwave power injection to the chamber according to the seventh embodiment of the present invention. A quartz vacuum window 203 placed between the E-Plane Bend and straight waveguide section acts as the vacuum-atmosphere interface
Fig. 8 shows a 6mm outer diameter annular tube 11 connected to the tantalum gas spraying ring 9, containing a large number of small holes 10 according to the eighth embodiment of the present invention.
Fig. 9 shows the cross-sectional view of in-built sputtering setup along with the substrate mounting assembly 14 and its motorized drive system consisting of drive shaft 12, Wilson type vacuum seal 15, drive motor 13 and gear assembly 8, according to the ninth embodiment of the present invention. The embodiment consists of a retractable electrically isolated biased 58tantalum circular ring 55 driven by a shaft 56 fitted through a rotatable electrically isolated vacuum seal 57 sitting on the bottom flange of the reactor chamber1.
Fig. 10 shows the detail view of RF/DC biased substrate mounting assembly according to the tenth embodiment of the present invention. The assembly contains substrate mounting plate 71 and a metal plate 72 welded to the drive shaft 12. An alumina (Al2O3) insulator 73 is placed between the plates to maintain electrical and thermal isolation. Two cartridge heaters 74 are used to raise the temperature of the substrate mounting platform up to ~650° C. The temperature of the substrate mounting platform will be measured by a thermocouple 75 placed inside substrate mounting plate 71. For developing good quality metallic films at a uniform deposition rate, DC biasing 79 is applied on connecting screw 76 with the help of a Glass Metal Vacuum Seal (GMS) 77. For dielectric thin film development RF biasing 78 is used. A scheme of simultaneous RF & DC biasing is presented in this embodiment.
The apparatus hence develops high quality, uniform nano films and nano structures of various metals and dielectric materials at a high deposition rate over a large area of the substrate kept at desired temperature. The apparatus alsoensures the development ofmono and multilayers of graphene sheets at substantially low temperature.