Claims:CLAIMS(10)
I Claim
1. A Compact, Multipurpose Thin Film Deposition systemcomprising of :
a water cooled, double walled plasma chamber 4 where plasma of an injected gas is produced which helps in depositing a uniform, high quality thin film on a substrate 14 kept at low temperature by Atomic Layer Deposition/Chemical Vapour Deposition/Ion Sputtering technique depending on the raw material being used;
a system for generating an iso-Gauss Electron Cyclotron Resonance curved surface inside the plasma generating chamber 4 where electrons gyrate and efficiently pick up energy from microwave power under cyclotron resonance condition and collide with the injected plasma gas to produce reactive radicals, positive ions and electrons;
a system to feed microwave directly and efficiently into the plasma chamber 4;
a gas injection system to introduce different gases into the plasma and reactor chambers 4,22 depending on the technique being implemented;
a system 13 to load the sputtering material during the operation of the apparatus as an Ion-Sputtering unit;
a system to supply plenty cold electrons to maintain a stable ECR plasma discharge;
a heating system 25 to maintain precise temperature of the substrate 14 to produce better quality films;
a system of DC and/or RF power supplies 23, 24 to bias the substrate14 to control the uniform film thickness and deposition rate;
a system consisting of demountable flanges16, 17, 18 for viewing the ECR plasma and providing access to the system; and
a vacuum system to maintain high vacuum in the plasma and reactor chamber 4,22 that results in high purity of the developed film.
2. The system for creating an iso-Gauss ECR curved surface, as claimed in claim 1, comprises of a single permanent magnet 1 along with a soft iron structure consisting of a shaped iron disc 3 and a return yoke 2.The assembly produces the resonance surface in the falling magnetic field region inside the plasma chamber 4. This structure also produces a field free region in the reactor chamber 22. This helps in developing ionic erosion free films.
3. The magnetic structures for the iso-Gauss ECR surface creation, as claimed in claim 2, comprising of permanent magnet 1, shaped iron disc 3 and a return yoke 2 are so oriented that it results in a compact system. In the apparatus, the permanent magnet 1 is placed on top of the plasma chamber 4. The return yoke 2 provides the top cap of the magnet 1 besides encompassing the sides of the chamber 4,whereas the shaped iron disc 3 sits at the boundary between the plasma chamber 4 and reactor chamber 22.
4. The system for supplying microwave power to the plasma chamber 4, as claimed in claim 1, consists of a rectangular waveguide 5 whose major dimension is oriented parallel to the chamber 4 axis.This ensures an orthogonal relation between the microwave field 200 and longitudinal component of the developed magnetic field 251. This allows efficient power absorption for high density plasma preparation. A quartz microwave window 6 is fitted to the choke flange attached to the waveguide 5 for efficient microwave injection and vacuum isolation.
5. The gas injection system, as claimed in claim 1, comprises of a port 8 to inject gas into the plasma chamber 4 for ECR plasma generation. Two ports 9, 10 are also provided at the entry of the reactor chamber 22 to introduce gas into the chamber 22 through a perforated metallic ring 11 sitting around the conical horn 12. These ports 8,9,10 are used to inject the precursor, reactive gas, inert gas depending upon the deposition technique being implemented.
6. The system to load the sputtering material, as claimed in claim 1, consists of an retractable tantalum circular ring 13 driven by a shaft. The cover flange of the plasma chamber port 16 containing the viewing window has the vacuum seal of the driving shaft. The sputtering material is placed in suitable orientationson the tantalum ring 13 which is then introduced into the active plasma region when the apparatus works as a sputtering unit. This arrangement facilitates efficient sputtering and results in high purity film development over the substrate 14. When the apparatus operates in other deposition modes, this arrangement is retracted out of the active zone.
7. The system to maintain a stable ECR plasma discharge, as claimed in claim 1, consists of an alumina plate 7 fitted in front of the quartz window 6 facing towards the plasma. It stabilizes the plasma due to emission of sufficient cold secondary electrons. Besides, it also protects the quartz window 6 from plasma impact.
8. The substrate 14, as claimed in claim 1, is placed on a rotating platform15 inside the reactor chamber 22 in a region devoid of magnetic field. This leads to ionic erosion free film development. Besides, the rotating platform 15 provides uniformity to the developed film. A conical horn 12 is also provided in the reactor chamber 22 which leads to deposition over a large substrate area. The substrate 14 is kept at stable low temperature.
9. The system of demountable flanges, as claimed in claim 1, consists of three flanges, one of them connected to a port in the plasma chamber 4, while the others are connected to the reactor chamber 22 ports. The demountable flange that is attached to the port 16 of the plasma chamber 4 is used for plasma viewing and diagnostics. Besides, it also holds the vacuum seal of the driving shaft of the retractable tantalum circular ring 13. The flanges of the ports 17,18 in the reactor chamber 22 are used for sample 14 loading and in-situ film property measurement.
10. The vacuum system, as claimed in claim 1, consists of a turbo molecular 20 and rotary pump 21 combinations that maintains high vacuum in the apparatus through a pneumatically operated gate valve19.
, Description:COMPLETE SPECIFICATION: The following specification particularly describes the nature of this invention and the manner in which it is to be performed.

FIELD OF THE INVENTION

This invention relates to a multipurpose method and system for nano-metric thin film deposition. The deposition is brought about by either of the methods, namely atomic layer deposition, chemical vapour deposition and sputtering deposition, in the apparatus. This film deposition system enhances the deposition rate and the quality of the film utilizing Electron Cyclotron Resonance (ECR) Plasma. The invention finds application in developing nanometer thin films of several high-k gate dielectric insulators for state of the art MOS devices, using either of CVD, ALD or Sputtering, depending upon the choice of the material.

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 miniaturization of Metal Oxide Semiconductor (MOS) transistor is essentially needed for the state of the art VLSI devices.In this continuous size reduction process, reducing the thickness of the SiO2 gate insulator is limited by the leakage current due to electron tunneling. To reduce the electron tunneling current, high-k dielectric materials e.g., HfO2, La2O3, ZrO2, TiO2, Ta2O5 and Al2O3 are the better replacement of SiO2, as thicker layers of high-k gate oxides offer lower equivalent oxide thickness (EOT) by virtue of their high-k values. Besides the gate oxide film preparation, films of metals and other materials are also needed for producing VLSI devices. Chemical Vapor Deposition (CVD), Atomic Layer Deposition (ALD) and ion-Sputtering are the commonly used methods for developing the thin films of various materials.
Of the various types of these deposition techniques, the plasma assisted processes yield better film properties and higher deposition rate. Electron Cyclotron Resonance plasma enhanced deposition systems offer the best quality film properties and growth rate due to the production of high density plasma.
The prior art, US patent US6163006 shows a Permanent Magnet ECR Plasma Source with Magnetic Field Optimization. In the plasma-producing device, an optimized magnetic field for Electron Cyclotron Resonance plasma generation is provided by a shaped pole piece. The shaped pole piece adjusts spacing between the magnet and the resonance zone, creates a convex or concave resonance zone and decreases stray fields between the resonance zone and the work-piece. For acylindrical permanent magnet, the pole piece includes a disk adjacent to the magnet together with an annular cylindrical sidewall structure axially aligned with the magnet and extending from the base around the permanent magnet. The pole piece directs magnetic field lines into the resonance zone, moving the resonance zone further from the face of the magnet. Additional permanent magnets or magnet arrays may be utilized to control field contours on a local scale. Rather than a permeable material, the sidewall structure maybe composed of an annular cylindrical magnetic material having a polarity opposite that of the permanent magnet, creating convex regions in the resonance zone. An annular disk-shaped recurve section at the end of the sidewall structure forms magnetic mirrors keeping the plasma off the pole piece. A recurve section composed of magnetic material having a radial polarity forms convex regions and/or magnetic mirrors within the resonance zone. This plasma enhanced apparatus is used for producing thin films.
A major drawback with the apparatus for film deposition in presence of ECR plasma known in the art is that highly powerful permanent magnets are needed for creating the resonance zone in the desired location.
Yet another drawback in the art is the possibility of microwave window failure due to plasma impact, as the window is directly viewing the ECR plasma.

OBJECTS OF THE INVENTION

The principal object of this invention is to provide a versatile film Deposition system for developing high quality nano dimensional films of different materials using Atomic Layer Deposition/Chemical Vapour Deposition/Sputtering Deposition technique.
Another object of the invention is to enhance the system efficiency by utilizing the energy stored in Electron Cyclotron Resonance Plasma.
Yet another object of this invention is to develop a uniform film over a large substrate area, kept at low temperature.
Another object of the present invention is to use more than one precursor for a specific composite film development.
Still another object of the invention is to make the system compact and user friendly.

SUMMARY OF THE INVENTION

The present invention provides a Compact, Multipurpose Thin Film Deposition system that develops good quality thin films at a high deposition rate on a substrate kept at low temperature. The invention is devoid of the limitations in the relevant art.
A major aspect of the present invention is its versatility in developing thin films of a large variety of materials using either of the three deposition techniques- Atomic Layer Deposition, Chemical Vapour Deposition and Ion-Sputtering Deposition, depending upon the available raw materials.
Another aspect of the present invention is the use of the huge stored energy in ECR plasma for the development of high quality thin films on substrates at low temperature.
Still another aspect of the invention is the use of a single permanent magnet and a soft iron structure consisting of a shaped iron disc and a return yoke. This configuration produces the desired curved ECR iso-gauss surface in the plasma chamber and field free region in the reactor chamber.
Another major aspect of the invention is that the apparatus is compact due to the compact nature of the magnetic structure and the shaped iron disc is mounted in between the plasma and reactor chamber.
Yet another aspect of the invention is the injection of 2.45 GHz microwave through a rectangular waveguide mounted on the side of the plasma chamber such that its major dimension is parallel to the axis of the chamber. The orthogonality between the EM field and static magnetic field lines results in efficient power absorption.
Still another aspect of the invention is the use of a quartz microwave window fitted to the choke flange attached to the waveguide for efficient microwave injection.
Yet another aspect of the invention is that an alumina plate is fitted in front of the quartz window facing towards the plasma. Secondary electrons emitted from the plate stabilize the plasma.
Another major aspect of the present invention is the use of three gas injection ports provided with gas dosing valves. An injection port is used to introduce the gas into the plasma chamber. Two ports spray gas and/or precursor uniformly at the entry of the reactor chamber through a perforated ring sitting around a conical horn attached to the shaped iron disc, depending on the deposition technique being implemented.
Still another aspect of the invention is the use of a retractable tantalum circular ring to load the sputtering material when the apparatus operates as an Ion-Sputtering unit. This arrangement facilitates efficient sputtering and results in high purity film development over the substrate. When the apparatus operates in other modes, this arrangement is retracted out of the active zone.
Still according to an aspect of the invention, the substrate sits on a rotating platform in the reactor chamber. The deposited film is devoid of ionic erosion as the substrate is kept in a field free region in the reactor chamber.
Further according to an aspect of the invention, the substrate is raised to a suitable temperature for better quality film deposition with the help of a heating system, as and whenever needed. The rotating platform is biased at a DC and/or RF voltage in some cases to control the uniform thickness and deposition rate.
Yet another aspect is the use of three demountable ports: one in the plasma chamber for plasma viewing, diagnostics and mounting sputtering materials; and two large ports in the reactor chamber to facilitate mounting of sample and monitoring environmental condition inside the reactor chamber. These also enable us an in-situ measurement of the film property.
Still another aspect of the present invention is the use of a turbo molecular and rotary pump combination provided with a pneumatically operated gate valve to provide ultra-high vacuum in the apparatus.

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 shows the sectional view of the Compact, Multipurpose Thin Film Deposition system according to the preferred embodiment of the invention.
Fig. 2 is a diagram showing the distribution of magnetic flux lines in the Thin Film Deposition system.
Fig. 3 is a diagram showing the axial (BY) 251 and radial (BX) 252 field plots along the axis of cylindrical symmetry for the Compact, Multipurpose Thin Film Deposition system
Fig. 4 shows the detailed view of the rectangular waveguide 5 according to the preferred embodiment of the invention
Fig. 5 shows the top view of the retractable tantalum circular ring 13 according to the preferred embodiment of the invention
Fig. 6 is a diagram showing the reactive gas, precursor, purge gas flow sequence and the growth rate of the film

DETAILED DESCRIPTION OF THE INVENTION

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 nanometric films are very much 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 properties and growth rate due to its efficient high density plasma production.
This invention provides an Electron Cyclotron Resonance-Plasma Enhanced- Compact, Multi-purpose 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 embodiment 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 Compact, Multipurpose Thin Film Deposition system in accordance with the preferred embodiment of the present invention. A single permanent magnet 1 along with a soft iron structure consisting of a shaped iron disc 3 and a return yoke 2 produces a curved ECR iso-gauss surface in the water cooled plasma chamber 4. Electrons absorb energy from 2.45 GHz microwave under resonance condition over the 875 Gauss surface. These energetic electrons collide with the neutral molecules of the gas injected into the plasma chamber via gas injection port 8 to produce ECR plasma.
The microwave power is fed directly into the plasma chamber 4 by a rectangular waveguide 5 whose major dimension is oriented parallel to the chamber 4 axis as shown in Fig. 1. This ensures an orthogonal relation between the microwave field 200, as seen in Fig. 4, and longitudinal (axial) component of the developed magnetic field 251, as seen in Fig. 3, needed for efficient power absorption. A quartz microwave window 6 is fitted to the choke flange attached to the waveguide 5 for efficient microwave injection as seen in Fig. 1. Besides, an alumina plate 7 is fitted in front of the quartz window 6 facing towards the plasma to stabilize the plasma by the emission of cold secondary electrons. A demountable flange is attached to a port 16 of the plasma chamber 4 for plasma viewing and diagnostics.
The enormous energy present in ECR plasma is utilized for developing thin films of a large variety of materials using either of the three deposition techniques in this versatile apparatus, namely Atomic Layer Deposition, Chemical Vapour Deposition and Ion-Sputtering Deposition, depending upon the available suitable raw materials.
Reactive gas is injected by port 8 following a sequence 51 as shown in Fig. 1 and 6, when the system is used as an ECR-Plasma Enhanced-ALD (ECR-PE-ALD) setup. Plasma of the reactive gas sequentially flows towards the substrate14 through a conical horn 12 attached to the shaped iron disc 3. Two ports 9, 10 are also provided at the entry of the reactor chamber 22. They are used to inject the precursor and inert gas, following the sequence 50 and 52 respectively, through a perforated metallic ring 11 sitting around the conical horn 12. This sequence results in atomic layer deposition on the substrate 14 following a staircase growth 53. The horn 12 also allows film deposition over a large substrate area.
During the operation of this versatile apparatus as an ECR-PE-CVD unit, the precursor is directly fed into the plasma chamber 4 via the port 8 as seen in Fig. 1. The huge plasma energy cracks the precursor resulting in film development over the substrate 14 kept at low temperature.
For its application as a sputtering unit, an retractable tantalum circular ring 13 driven by a shaft is introduced into the active plasma region as seen in Fig. 1 and 5. The cover flange of the plasma chamber port 16 containing the viewing window has the vacuum seal of the driving shaft. The sputtering material is placed on the tantalum ring 13 in suitable orientations. This arrangement facilitates efficient sputtering and results in high purity film development over the substrate 14. When the apparatus operates in other deposition modes, this arrangement is retracted out of the active zone.
In the apparatus, the shaped iron disc 3 sits at the boundary between the plasma chamber 4 and reactor chamber 22 as seen in Fig. 1. This configuration of the magnetic structures comprising of permanent magnet 1, shaped iron disc 3 and a return yoke 2 results in a compact system, besides providing a magnetic field lines 250 free region in the reactor chamber 22 as seen in Fig. 2. The substrate14 sits on rotating platform 15 directly on the plasma axis in the reactor chamber 22. This direct plasma visibility results in enhanced deposition rate. The deposited film is also devoid of ionic erosion as the substrate 14 is kept in a magnetic field 251,252 free region in the chamber 4 as seen in Fig. 3. The axial magnetic field 251developed in the system as seen in Fig. 3 also shows that the resonance magnetic field of 875 Gauss, the necessary condition for ECR plasma generation, is achieved in the system. The apparatus is however completely devoid of any radial field 252 in the plasma axis.Two large demountable flanges are also provided in the ports 17, 18 of the reactor chamber 22 to facilitate mounting of sample 14 as seen in Fig.1. These also enable in-situ measurement of the film property.
A heating system 25 is used to raise the substrate 14 to a suitable small temperature for better quality film deposition of specific materials.Additionally, in some cases, the substrate 14 is biased at a DC and/or RF 23, 24 voltages to control the uniform film thickness and deposition rate.
A turbo molecular 20 and rotary pump 21 combinations along with a pneumatically operated gate valve 19 is used to provide ultra-high vacuum in the apparatus. This ensures purity of the developed film.
The apparatus hence develops high quality, uniform films of various materials at a high deposition rate over a substrate kept at low temperature.