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Low energy ion implanter for negative and positive ions
Nuclear Instruments and Methods in Physics Research B24/25 (1987) 791-792 North-Holland, Amsterdam
791
LOW ENERGY ION IMPLANTER FOR NEGATIVE AND POSITIVE IONS Y A N G F e n g a n d L I U Jiarui hlstitute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beifing. PR China
A low energy ion implanter for the energy range 100 eV-60 keV has been designed, manufacturcd and tested in the ion beam laboratory of the Institute of Physics. The system consists of a 30 kV extraction system, an anal)zing magnet, a deceleration or acceleration system of changeable voltage from 0 up to 30 kV, and electrostatic scanning system and a UHV target chamber. Three different ion sources can be used at the ion implanter: a Penning ion source, a hollow cathode ion source and a negative sputtering ion source. The system has been designed for ion beam materials modification, surface analysis and atomic-molecular physics research.
1. Introduction
2. Configuration of the intplanter
A low energy ion implanter for the energy range of three orders of magnitude from 100 eV up to 60 keV is necessary for VLS IC research and other materials modification by ion bombardment, for the first wall problems in fusion research, atomic-molecular physics and many new technologies with ion beams, such as ion beam epitaxial growth of thin films. Because there is no such commercial implanter available, we have designed this implanter for the multidiscipline research projects of a number of institutes for the Chinese Academy of Sciences.
The three orders of magnitude of the energy has been achieved by an acceleration-deceleration system in an acceleration or deceleration regime. The configuration of the setup is shown in fig. 1 and here we shall describe it briefly. 2.1. Ion sources
Three different ion sources have been tested at the ion implanter. They are a cold cathode Penning ion source, a hollow cathode ion source and a Middleton type negative sputtering ion source.
X-Scanning Pla
s
"f Valve iarget
Cha.mber
I Fig. 1. Configuration of the low energy ion implanter. 0168-583X/87/$03.50 © Elsevier Science Publishers B.V. (North-Holland Physics Publishing Division)
VII. ACCELERATOR TECHNOLOGY
792
Ymlg Feng. LiuJiarui / Low energy ion implanter
(a) CoM cathode Pennhlg ion source: this is a Pennlng ion source with a permanent magnet for the plasma confinement, a small piece of LaB6 as an electron emission cathode and a thin Ta disc with a small extraction hole as an anticathode. The small discharge chamber is surrounded by a graphite anode. The main characteristics of the ion source are as follows: 300-1000 V for different gases Arc voltage 30-100 mA Arc current Discharge gas pressure 1-5 × 10 -2 Torr Total extracted current 1-5 mA 300-400 # A (He +) Typical beam current 40-80 # A (B +) > 1000 H (He + beam). Life-time (b) tIollow cathode ion source: A model 911A hollow cathode ion source from High Voltage Engineering (The Netherlands) with some modifications has been installed. All materials having a vapour pressure of 10 -2 Torr at a temperature of 1700 ° C or lower can, in principle, be used in elementary form. The beam current of most metals varies from 60 to 100 #A, while the beam emittance is less than 7 mrad cm/MeV. (c) Middleton type negative sp,atering ion source: A home-made negative sputtering ion source of the Middleton type was installed at the accelerator with reversed polarity of the power supplies. The characteristics of the ion source are better than a positive sputtering ion source and its universality overcomes many difficulties of gas discharge type ion sources. The main advantages are the stability, very long lifetime and good beam current for some solid dements, such as very pure Si beam without N 2 ion contamination.
2.4. Beam scanning system An electrostatic scanning system with a triangular voltage waveform were applied to the X- and Y-direction deflection plates to sweep the beam uniformly across the target. The sweep frequency in the X-direction is 800 Hz and in the Y-direction is 11 Hz. The maximum swept area is 50 X 50 mm:.
2.5. Target chanlber The target chamber is a stainless steel chamber of 500 mm in diameter and 600 mm in height. There are 4 ports for feedthroughs and optical measurement windows, one port for the beam line and a pumping port on the chamber. A deceleration system with a high voltage terminal for 0-30 kV (and reversible polarity) and the deceletation lenses have been installed in the chamber. There is a sample holder for 6 samples behind the deceleration lenses. The maximum area of the sampie is 50 X 50 mm 2. The sample holder is rotatable and can be viewed through a window.
2.6. Vacuum pumping system The accelerator is pumped down with two oil diffusion pumps of 1500 1/s each. The base pressure of the accelerator was 2 × 10 -6 Torr and the working pressure was less than 3 X 10 -5 Torr with the gas feeding of the ion source on. There is a turbomolecular pump of 450 l / s for the target chamber, where the base pressure was 2 x 10 -6 Torr without baking and UHV can be obtained with a bake-out.
2.2. Extraction 2.7. Accelerator characteristics A Pierce type extraction system with the maximum extraction voltage of 30 kV has been constructed. A reversible high voltage power supply has been used for negative and positive ion beams.
2.3. Analysing magnet A 90 ° analysing magnet with 380 mm radius and a maximum magnetic field > 10 kG has been used for mass-separation of the ion species. The mass-resolution is better than 250 so it is good for the mass-numbers from 1 to 240.
The main characteristics of the accelerates are as follows: Ion energy 100 eV-60 keV Energy stability 0.02% Mass number of the ion species 1-240 Typical beam currents (/~A); H+ 100-200 B+ 40-80 Si400-500 Au200 Scanning area at the target 50 × 50 mm2 Scanning uniformity < 3%
791
LOW ENERGY ION IMPLANTER FOR NEGATIVE AND POSITIVE IONS Y A N G F e n g a n d L I U Jiarui hlstitute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beifing. PR China
A low energy ion implanter for the energy range 100 eV-60 keV has been designed, manufacturcd and tested in the ion beam laboratory of the Institute of Physics. The system consists of a 30 kV extraction system, an anal)zing magnet, a deceleration or acceleration system of changeable voltage from 0 up to 30 kV, and electrostatic scanning system and a UHV target chamber. Three different ion sources can be used at the ion implanter: a Penning ion source, a hollow cathode ion source and a negative sputtering ion source. The system has been designed for ion beam materials modification, surface analysis and atomic-molecular physics research.
1. Introduction
2. Configuration of the intplanter
A low energy ion implanter for the energy range of three orders of magnitude from 100 eV up to 60 keV is necessary for VLS IC research and other materials modification by ion bombardment, for the first wall problems in fusion research, atomic-molecular physics and many new technologies with ion beams, such as ion beam epitaxial growth of thin films. Because there is no such commercial implanter available, we have designed this implanter for the multidiscipline research projects of a number of institutes for the Chinese Academy of Sciences.
The three orders of magnitude of the energy has been achieved by an acceleration-deceleration system in an acceleration or deceleration regime. The configuration of the setup is shown in fig. 1 and here we shall describe it briefly. 2.1. Ion sources
Three different ion sources have been tested at the ion implanter. They are a cold cathode Penning ion source, a hollow cathode ion source and a Middleton type negative sputtering ion source.
X-Scanning Pla
s
"f Valve iarget
Cha.mber
I Fig. 1. Configuration of the low energy ion implanter. 0168-583X/87/$03.50 © Elsevier Science Publishers B.V. (North-Holland Physics Publishing Division)
VII. ACCELERATOR TECHNOLOGY
792
Ymlg Feng. LiuJiarui / Low energy ion implanter
(a) CoM cathode Pennhlg ion source: this is a Pennlng ion source with a permanent magnet for the plasma confinement, a small piece of LaB6 as an electron emission cathode and a thin Ta disc with a small extraction hole as an anticathode. The small discharge chamber is surrounded by a graphite anode. The main characteristics of the ion source are as follows: 300-1000 V for different gases Arc voltage 30-100 mA Arc current Discharge gas pressure 1-5 × 10 -2 Torr Total extracted current 1-5 mA 300-400 # A (He +) Typical beam current 40-80 # A (B +) > 1000 H (He + beam). Life-time (b) tIollow cathode ion source: A model 911A hollow cathode ion source from High Voltage Engineering (The Netherlands) with some modifications has been installed. All materials having a vapour pressure of 10 -2 Torr at a temperature of 1700 ° C or lower can, in principle, be used in elementary form. The beam current of most metals varies from 60 to 100 #A, while the beam emittance is less than 7 mrad cm/MeV. (c) Middleton type negative sp,atering ion source: A home-made negative sputtering ion source of the Middleton type was installed at the accelerator with reversed polarity of the power supplies. The characteristics of the ion source are better than a positive sputtering ion source and its universality overcomes many difficulties of gas discharge type ion sources. The main advantages are the stability, very long lifetime and good beam current for some solid dements, such as very pure Si beam without N 2 ion contamination.
2.4. Beam scanning system An electrostatic scanning system with a triangular voltage waveform were applied to the X- and Y-direction deflection plates to sweep the beam uniformly across the target. The sweep frequency in the X-direction is 800 Hz and in the Y-direction is 11 Hz. The maximum swept area is 50 X 50 mm:.
2.5. Target chanlber The target chamber is a stainless steel chamber of 500 mm in diameter and 600 mm in height. There are 4 ports for feedthroughs and optical measurement windows, one port for the beam line and a pumping port on the chamber. A deceleration system with a high voltage terminal for 0-30 kV (and reversible polarity) and the deceletation lenses have been installed in the chamber. There is a sample holder for 6 samples behind the deceleration lenses. The maximum area of the sampie is 50 X 50 mm 2. The sample holder is rotatable and can be viewed through a window.
2.6. Vacuum pumping system The accelerator is pumped down with two oil diffusion pumps of 1500 1/s each. The base pressure of the accelerator was 2 × 10 -6 Torr and the working pressure was less than 3 X 10 -5 Torr with the gas feeding of the ion source on. There is a turbomolecular pump of 450 l / s for the target chamber, where the base pressure was 2 x 10 -6 Torr without baking and UHV can be obtained with a bake-out.
2.2. Extraction 2.7. Accelerator characteristics A Pierce type extraction system with the maximum extraction voltage of 30 kV has been constructed. A reversible high voltage power supply has been used for negative and positive ion beams.
2.3. Analysing magnet A 90 ° analysing magnet with 380 mm radius and a maximum magnetic field > 10 kG has been used for mass-separation of the ion species. The mass-resolution is better than 250 so it is good for the mass-numbers from 1 to 240.
The main characteristics of the accelerates are as follows: Ion energy 100 eV-60 keV Energy stability 0.02% Mass number of the ion species 1-240 Typical beam currents (/~A); H+ 100-200 B+ 40-80 Si400-500 Au200 Scanning area at the target 50 × 50 mm2 Scanning uniformity < 3%