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The application of a 600 keV heavy ion implanter
Nuclear Instruments and Methods in Physics Research B55 (1991) 778-781 North-Holland
The application of a 600 keV heavy ion implanter Jiang Xinyuan, Zhao Qihua I, Guan Anmin, Shao Tianhao and Lin Chenglu Shanghai Institute of Metallurgy, Academia Sinica, 865 Chang Ning Road, Shanghai 200050, People’s Republic of China
The application of a 600 keV heavy ion implanter is described. High energy Bf and high energy doubly charged P*+ were implanted in silicon for p- and n-wells isolation in CMOS ICs. 600 keV Ar+ was implanted in silicon to form a damage layer, the perfect layer near the surface of the Si-wafer was made by defect gettering. Si+, Mg+ and Ot were implanted in GaAs, and the uniformity of the threshold voltage (I$,) of GaAs MESFETs buried with Mg or 0 layers was improved. High activation efficiencies of Mg+ and Si+ implanted GaAs after RTA were obtained by using a specially designed graphite heater. and the activation efficiencies were 100% and 92%, respectively. The isolation of GaAs and InGaAsP/InP and other compound semiconductors, the characteristics of LiNbO, and other insulators after high energy ion implantation and molecular ion implantation have also been investigated using this implanter.
2. Applications
1. Introduction Ion implantation technology has been developed since 1952. At first Bell Laboratory used H+ implantation to form p-n junctions and fabricate solar batteries. At first, application of ion implantation in silicon devices was by low energy implantation (< 10 keV). With the development of ion implantation technology, high energy ion implantation and applications in other materials became more and more attractive. The new implantation technologies stimulated applications in SO1 structures, Si, GaAs and other compound semiconductor devices, materials and insulator materials. A 600 keV heavy ion implanter (pre-accelerating and post-analyzing implanter) has been built at the Shanghai Institute of Metallurgy, Academia Sinica [l]. The implanter has the following characteristics: energy above 600 keV and stable (long-time drift less than 1 x 10p4), mass range of l-210 and mass resolving power over 210, beam stability better than 100 uA f 2.5% per hour. This ion implanter has been put into use in ion implantation applications. The applications of ion implantation using the 600 keV heavy ion implanter are now in silicon materials and devices, GaAs and other compound semiconductor materials and devices, and LiNbO, optical wave-guides, and other insulator materials.
’ Present address: Institute of Information Display and Transducer, Shanghai Jiao Tong University, Shanghai 200030, People’s Republic of China. 0168-583X/91/$03.50
2.1. Application
in silicon materials and devices
High energy doubly charged phosphorus (P”) was implanted in a (100) p-type silicon wafer to form an isolation well in CMOS technology [2]. This technique results in a significant reduction of thermal treatment time for n- and p-wells. Also, the better control over the well dopant profiles in implantation can be used to decrease latch-up susceptibility, while simultaneously increasing packing density. However, accompanying the production of P2+ during the discharge of red phosphorus in the ion source, PC is also produced. P: could turn into P+ and P with half energy each in the silicon. Contamination is introduced, which results in another peak in the carrier concentration profile of the annealed samples. The contamination of low energy P+ ions has been effectively avoided by using PF, gas as discharge material in the ion source. As shown in fig. 1, where the low peak refers to the implanted P+ of 300 keV (the half energy of the PC ion) and the P2+ energy is 1.2 MeV. The samples were annealed both by RTA (1200 o C, 10 s). Fig. 2 shows carrier concentration profiles of the samples (RTA, 1200 o C, 10 s) obtained by spreading resistance probe measurements. The implantation energy is from 0.8 to 1.2 MeV, at the same dose of 4 X 1013 cm-‘. The results of 1.0 MeV implantation meet the requirements for the retrograde well in CMOS technology: the peak concentration is 10” cmm3 located 1.0 pm from the surface, the junction is about 1.7 pm, and the carrier concentration at the surface is less than
0 1991 - Elsevier Science Publishers B.V. (North-Holland)
119
Jiang Xinyuan et al. / The application of a heavy ion implanter
1.0
0.5 Depth
1.5
(pm)
Fig. 1. The carrier concentration profiles of silicon implanted with 1.2 MeV P2+ and annealed (RTA, 1200 o C, 10 s); (0) ion source material is red phosphorus; (0) ion source material PF,-gas.
2 X 1016 cmp3. From the performances of CMOS inverter specimen, the holding current (1, = co) and holding voltage (V, = co) for latch-up of the CMOS specimen by P 2+ implantation are much higher than those (1, = 11 mA, I’, = 2.9 V) by conventional CMOS technology. Furthermore, P-/P’ epitaxy to form isolation wells is latch-up free. The radiation damage introduced in the Ar+ implanted silicon and the damage layer cannot be annealed by both RTA and FA. The high energy 600 keV Arf implantation will create a buried damage layer, which could trap the defects 131. Fig. 3 is the RBS-channelling spectrum of 600 keV Ar+ implantation. After the high energy 600 keV Art, to a dose of 4 X 101’ cmp2 and low energy 30 keV B’, to a dose of 1 X 1015 cmP2 double implantation, and annealing at llOO”C, 15 s, the perfect layer has been obtained by defectgettering near the surface. Silicon photo-diode (SPD) devices can be fabricated in this layer with low leakage current. 2.2. The application in GaAs and other compound semiconductor materials and devices
Depth(pm) Fig. 2. The carrier concentration profiles of annealed samples which are implanted with different ion energies (P2+ --f P (lOO)Si, 4 X lOI cme2, RTA 1200 o C, 10 s).
Lnnor
I
I
Samples used in the investigation are semi-insulated (S.I.) GaAs. Sit and Mgf were implanted into GaAs and RTA was performed with improved graphite heater. After using this technique, a high activation efficiency has been obtained, the activation efficiencies of Si-implanted GaAs and Mg-implanted GaAs are 92 and 100% respectively [4]. Carrier concentration profiles of Mg-implanted GaAs wafer annealed by RTA and FA are shown in fig. 4. It can be seen that higher peak concentrations with negligible redistribution can be achieved after RTA at 1120°C for 20 s. Also the high energy Mgf implantation creating a p-type buried layer I
I
I1
2MeJ4 He+ (100)Aligned
0
50
IdO
CHANNEL Fig. 3. RBS-channelling
spectrum
ls0 NUMBER
2io
25il
of a 600 keV Ar+ implanted Si-wafer. -: Ar+ 600 keV, 4 X 1Ol5 cme2 cmm2 1100 o C, 15 s; -. .-: BC 30 keV, 1 X 1Ol5 cmm2, 1100 o C, 50 s.
and Bf
30 keV, 1 x 10”
VI. MATERIALS
SCIENCE
780
Jiang Xinyuan et nL / The application of a heavy ion implanter
Dosekm-*I Fig. 6. Relations of resistance and implantation dose after 180 keV H+ In, _xGa,As,P, _,/InP (0: P-InP doped Zn, 1 X 1018 3 , P 0 : cm InGaAsP doped Zn, 1 x 10” cmm3; a: P-InGaAsP doped Zn, 1X10’“cm~‘).
Depth
(pm)
Fig. 4. The ear&r concentration profiles of Mg-impl~ted GaAS.
and high energy O+ plantation creating a compensation layer in S.I. GaAs have been used to improve the low concentration tails in Si-implanted GaAs [5]. Using Si+ and Mg+ double implantation, the carrier profiles and the p-n junction are determined as shown in fig. 5. The Si-implanted carrier concentration profile is nearly unaffected by the p-buried layer when the Mg-implanted dose is lower than 2 X 1O1' cm-‘, but apparently this changes and the p-n junction moves to-
IOfa
wards the surface when the Mg-implanted dose is higher than 5 X 1Or3 cm-‘. The GaAs MESFETs with La = 1 pm, L,, = 4 pm and different widths were fabricated on a Si and Mg double-implanted wafer, and the uniformity of the threshold voltage (Yti) of the GaAs MESFET was improved 27% compared to that of Si single-implanted GaAs MESFETs. GaAs MESFETs with a buried oxygen layer also have been fabricated and the uniformity of the threshold voltage (I’& of the GaAs MESFET was improved 31% compared to that of Si single-implanted GaAs MESFETs. The production of high-resistivity regions in GaAs and other related compounds by high energy (600 keV) proton bombardment has been well investigated. The isolation depth was very deep and the isolation resistances were very high. GaAs devices were fabricated by using HC implantation to produce isolation and planar technology and achieved high performances of the characteristics. Fig. 6 shows the resistance after H+ implantation into In,_,Ga,As,P,_,/InP. The isolation resistances changes from 10” to lo7 Q cm to meet the needs of In,_,Ga,As,P,_,/InP devices. 2.3. The application materials
_1O’i
‘E u nlo'" i
lOiS
w
0
Depth
Fig. 5. Carrier concentration distribution plotted with respect to depth.
in LiNbO,
and
other
insulator
LiNbO, is the optical material widely used in integrated optical circuits. The optical devices also can be made by ion implantation. We have investigated the damage distribution, the changes of chemical composition near the surface and after annealing, after II’, N+, Ar+ and Xe’ implantation in LiNbO,. The experiments shows that damage distribution and nuclear energy deposition will change the refraction of the LiNbOa material and an optical wave-guide can be made because of these refraction changes. The more successful LiNbO, planar wave-guides have been fabricated by
Jiang Xinyuan et al. / The application of a heavy ion implanter
Table 1 Parameters of LiNbO, planar waveguide after high-energy H+ implantation
PeVl
Implant dose [X10’6cmp2]
;$eor.) [pm]
180 180 500
3 5 3
0.64 0.64 2.85
600
3
3.66
600 650
3 3
3.66
Implant energy
Excited mode (TE)
bk-l
TEo TEo TEo TE, TEo TE, TEo TE, TE,
2.1892 2.1881 2.1881 2.1736 2.1892 2.1703 2.1858 2.1725 2.1680
781
3. Conclusion
This paper has attempted to review recent work in ion implantation by using a 600 keV heavy ion implanter. The research has been performed for silicon, GaAs and other compound semiconductors, LiNbO, and other insulator materials. The research will be developed to meet the necessity for Si and GaAs integrated circuits, optical wave-guides and devices and other new materials and new device fabrication.
References H+ implantation [6]. The H+ implantation in LiNbO, formed a buried radiation-damage layer because the damage by nuclear stopping is at the end of the range. The refraction will decrease because of lattice expansion by the stress in the buried layer, and a wave-guide layer is formed between the surface and the buried layer. The proton implantation will introduce light damage in the wave-guide layer because of electron stopping and there are no impurities as scattering centers in the waveguide layer: Also the damage can be annealed out by annealing at 3.50 o C, 30 min in an oxygen atmosphere. Table 1 shows the parameters of a LiNbO, planar wave-guide, where t, is the thickness of the planar waveguide, TE is the excited waveguide mode, and #k-l) is the constant of wave propagation.
[l] Jiang Xinyuan, Lu Shi Wan and Shi Zhi Zu, Nucl. In&. and Meth. B21 (1987) 310. [2] Guan Anmin, Geng Haiyang, Yu Bo, Cheng Jinyi, Lin Chenglu and Zhang Ming, Proc. Shanghai Workshop on Ion Implantation, Hangzhou, China, 1988, P. 164. [3] J.C. Zhou, X.Y. Jiang and J.L. Zhu, ibid., p. 63. [4] Wei Dong Fan, Xin Yuan .Tiang, Guan Qun Xia and Wei Yuan Wang, Inst. Phys. Conf. Ser. (1987) 277. [5] Ou Haijiang, Wang Weiyuan, Zhao Qihua and Jiang Xinyuan, Chin. J. Semicond. 10 (1989) 309. [6] Shao Tianhao, Proc. 7th Int. Conf. on Ion Beam Modification of Materials, Knoxville, TN, 1990, Nucl. Instr. and Meth. B, to be published.
VI. MATERIALS SCIENCE
The application of a 600 keV heavy ion implanter Jiang Xinyuan, Zhao Qihua I, Guan Anmin, Shao Tianhao and Lin Chenglu Shanghai Institute of Metallurgy, Academia Sinica, 865 Chang Ning Road, Shanghai 200050, People’s Republic of China
The application of a 600 keV heavy ion implanter is described. High energy Bf and high energy doubly charged P*+ were implanted in silicon for p- and n-wells isolation in CMOS ICs. 600 keV Ar+ was implanted in silicon to form a damage layer, the perfect layer near the surface of the Si-wafer was made by defect gettering. Si+, Mg+ and Ot were implanted in GaAs, and the uniformity of the threshold voltage (I$,) of GaAs MESFETs buried with Mg or 0 layers was improved. High activation efficiencies of Mg+ and Si+ implanted GaAs after RTA were obtained by using a specially designed graphite heater. and the activation efficiencies were 100% and 92%, respectively. The isolation of GaAs and InGaAsP/InP and other compound semiconductors, the characteristics of LiNbO, and other insulators after high energy ion implantation and molecular ion implantation have also been investigated using this implanter.
2. Applications
1. Introduction Ion implantation technology has been developed since 1952. At first Bell Laboratory used H+ implantation to form p-n junctions and fabricate solar batteries. At first, application of ion implantation in silicon devices was by low energy implantation (< 10 keV). With the development of ion implantation technology, high energy ion implantation and applications in other materials became more and more attractive. The new implantation technologies stimulated applications in SO1 structures, Si, GaAs and other compound semiconductor devices, materials and insulator materials. A 600 keV heavy ion implanter (pre-accelerating and post-analyzing implanter) has been built at the Shanghai Institute of Metallurgy, Academia Sinica [l]. The implanter has the following characteristics: energy above 600 keV and stable (long-time drift less than 1 x 10p4), mass range of l-210 and mass resolving power over 210, beam stability better than 100 uA f 2.5% per hour. This ion implanter has been put into use in ion implantation applications. The applications of ion implantation using the 600 keV heavy ion implanter are now in silicon materials and devices, GaAs and other compound semiconductor materials and devices, and LiNbO, optical wave-guides, and other insulator materials.
’ Present address: Institute of Information Display and Transducer, Shanghai Jiao Tong University, Shanghai 200030, People’s Republic of China. 0168-583X/91/$03.50
2.1. Application
in silicon materials and devices
High energy doubly charged phosphorus (P”) was implanted in a (100) p-type silicon wafer to form an isolation well in CMOS technology [2]. This technique results in a significant reduction of thermal treatment time for n- and p-wells. Also, the better control over the well dopant profiles in implantation can be used to decrease latch-up susceptibility, while simultaneously increasing packing density. However, accompanying the production of P2+ during the discharge of red phosphorus in the ion source, PC is also produced. P: could turn into P+ and P with half energy each in the silicon. Contamination is introduced, which results in another peak in the carrier concentration profile of the annealed samples. The contamination of low energy P+ ions has been effectively avoided by using PF, gas as discharge material in the ion source. As shown in fig. 1, where the low peak refers to the implanted P+ of 300 keV (the half energy of the PC ion) and the P2+ energy is 1.2 MeV. The samples were annealed both by RTA (1200 o C, 10 s). Fig. 2 shows carrier concentration profiles of the samples (RTA, 1200 o C, 10 s) obtained by spreading resistance probe measurements. The implantation energy is from 0.8 to 1.2 MeV, at the same dose of 4 X 1013 cm-‘. The results of 1.0 MeV implantation meet the requirements for the retrograde well in CMOS technology: the peak concentration is 10” cmm3 located 1.0 pm from the surface, the junction is about 1.7 pm, and the carrier concentration at the surface is less than
0 1991 - Elsevier Science Publishers B.V. (North-Holland)
119
Jiang Xinyuan et al. / The application of a heavy ion implanter
1.0
0.5 Depth
1.5
(pm)
Fig. 1. The carrier concentration profiles of silicon implanted with 1.2 MeV P2+ and annealed (RTA, 1200 o C, 10 s); (0) ion source material is red phosphorus; (0) ion source material PF,-gas.
2 X 1016 cmp3. From the performances of CMOS inverter specimen, the holding current (1, = co) and holding voltage (V, = co) for latch-up of the CMOS specimen by P 2+ implantation are much higher than those (1, = 11 mA, I’, = 2.9 V) by conventional CMOS technology. Furthermore, P-/P’ epitaxy to form isolation wells is latch-up free. The radiation damage introduced in the Ar+ implanted silicon and the damage layer cannot be annealed by both RTA and FA. The high energy 600 keV Arf implantation will create a buried damage layer, which could trap the defects 131. Fig. 3 is the RBS-channelling spectrum of 600 keV Ar+ implantation. After the high energy 600 keV Art, to a dose of 4 X 101’ cmp2 and low energy 30 keV B’, to a dose of 1 X 1015 cmP2 double implantation, and annealing at llOO”C, 15 s, the perfect layer has been obtained by defectgettering near the surface. Silicon photo-diode (SPD) devices can be fabricated in this layer with low leakage current. 2.2. The application in GaAs and other compound semiconductor materials and devices
Depth(pm) Fig. 2. The carrier concentration profiles of annealed samples which are implanted with different ion energies (P2+ --f P (lOO)Si, 4 X lOI cme2, RTA 1200 o C, 10 s).
Lnnor
I
I
Samples used in the investigation are semi-insulated (S.I.) GaAs. Sit and Mgf were implanted into GaAs and RTA was performed with improved graphite heater. After using this technique, a high activation efficiency has been obtained, the activation efficiencies of Si-implanted GaAs and Mg-implanted GaAs are 92 and 100% respectively [4]. Carrier concentration profiles of Mg-implanted GaAs wafer annealed by RTA and FA are shown in fig. 4. It can be seen that higher peak concentrations with negligible redistribution can be achieved after RTA at 1120°C for 20 s. Also the high energy Mgf implantation creating a p-type buried layer I
I
I1
2MeJ4 He+ (100)Aligned
0
50
IdO
CHANNEL Fig. 3. RBS-channelling
spectrum
ls0 NUMBER
2io
25il
of a 600 keV Ar+ implanted Si-wafer. -: Ar+ 600 keV, 4 X 1Ol5 cme2 cmm2 1100 o C, 15 s; -. .-: BC 30 keV, 1 X 1Ol5 cmm2, 1100 o C, 50 s.
and Bf
30 keV, 1 x 10”
VI. MATERIALS
SCIENCE
780
Jiang Xinyuan et nL / The application of a heavy ion implanter
Dosekm-*I Fig. 6. Relations of resistance and implantation dose after 180 keV H+ In, _xGa,As,P, _,/InP (0: P-InP doped Zn, 1 X 1018 3 , P 0 : cm InGaAsP doped Zn, 1 x 10” cmm3; a: P-InGaAsP doped Zn, 1X10’“cm~‘).
Depth
(pm)
Fig. 4. The ear&r concentration profiles of Mg-impl~ted GaAS.
and high energy O+ plantation creating a compensation layer in S.I. GaAs have been used to improve the low concentration tails in Si-implanted GaAs [5]. Using Si+ and Mg+ double implantation, the carrier profiles and the p-n junction are determined as shown in fig. 5. The Si-implanted carrier concentration profile is nearly unaffected by the p-buried layer when the Mg-implanted dose is lower than 2 X 1O1' cm-‘, but apparently this changes and the p-n junction moves to-
IOfa
wards the surface when the Mg-implanted dose is higher than 5 X 1Or3 cm-‘. The GaAs MESFETs with La = 1 pm, L,, = 4 pm and different widths were fabricated on a Si and Mg double-implanted wafer, and the uniformity of the threshold voltage (Yti) of the GaAs MESFET was improved 27% compared to that of Si single-implanted GaAs MESFETs. GaAs MESFETs with a buried oxygen layer also have been fabricated and the uniformity of the threshold voltage (I’& of the GaAs MESFET was improved 31% compared to that of Si single-implanted GaAs MESFETs. The production of high-resistivity regions in GaAs and other related compounds by high energy (600 keV) proton bombardment has been well investigated. The isolation depth was very deep and the isolation resistances were very high. GaAs devices were fabricated by using HC implantation to produce isolation and planar technology and achieved high performances of the characteristics. Fig. 6 shows the resistance after H+ implantation into In,_,Ga,As,P,_,/InP. The isolation resistances changes from 10” to lo7 Q cm to meet the needs of In,_,Ga,As,P,_,/InP devices. 2.3. The application materials
_1O’i
‘E u nlo'" i
lOiS
w
0
Depth
Fig. 5. Carrier concentration distribution plotted with respect to depth.
in LiNbO,
and
other
insulator
LiNbO, is the optical material widely used in integrated optical circuits. The optical devices also can be made by ion implantation. We have investigated the damage distribution, the changes of chemical composition near the surface and after annealing, after II’, N+, Ar+ and Xe’ implantation in LiNbO,. The experiments shows that damage distribution and nuclear energy deposition will change the refraction of the LiNbOa material and an optical wave-guide can be made because of these refraction changes. The more successful LiNbO, planar wave-guides have been fabricated by
Jiang Xinyuan et al. / The application of a heavy ion implanter
Table 1 Parameters of LiNbO, planar waveguide after high-energy H+ implantation
PeVl
Implant dose [X10’6cmp2]
;$eor.) [pm]
180 180 500
3 5 3
0.64 0.64 2.85
600
3
3.66
600 650
3 3
3.66
Implant energy
Excited mode (TE)
bk-l
TEo TEo TEo TE, TEo TE, TEo TE, TE,
2.1892 2.1881 2.1881 2.1736 2.1892 2.1703 2.1858 2.1725 2.1680
781
3. Conclusion
This paper has attempted to review recent work in ion implantation by using a 600 keV heavy ion implanter. The research has been performed for silicon, GaAs and other compound semiconductors, LiNbO, and other insulator materials. The research will be developed to meet the necessity for Si and GaAs integrated circuits, optical wave-guides and devices and other new materials and new device fabrication.
References H+ implantation [6]. The H+ implantation in LiNbO, formed a buried radiation-damage layer because the damage by nuclear stopping is at the end of the range. The refraction will decrease because of lattice expansion by the stress in the buried layer, and a wave-guide layer is formed between the surface and the buried layer. The proton implantation will introduce light damage in the wave-guide layer because of electron stopping and there are no impurities as scattering centers in the waveguide layer: Also the damage can be annealed out by annealing at 3.50 o C, 30 min in an oxygen atmosphere. Table 1 shows the parameters of a LiNbO, planar wave-guide, where t, is the thickness of the planar waveguide, TE is the excited waveguide mode, and #k-l) is the constant of wave propagation.
[l] Jiang Xinyuan, Lu Shi Wan and Shi Zhi Zu, Nucl. In&. and Meth. B21 (1987) 310. [2] Guan Anmin, Geng Haiyang, Yu Bo, Cheng Jinyi, Lin Chenglu and Zhang Ming, Proc. Shanghai Workshop on Ion Implantation, Hangzhou, China, 1988, P. 164. [3] J.C. Zhou, X.Y. Jiang and J.L. Zhu, ibid., p. 63. [4] Wei Dong Fan, Xin Yuan .Tiang, Guan Qun Xia and Wei Yuan Wang, Inst. Phys. Conf. Ser. (1987) 277. [5] Ou Haijiang, Wang Weiyuan, Zhao Qihua and Jiang Xinyuan, Chin. J. Semicond. 10 (1989) 309. [6] Shao Tianhao, Proc. 7th Int. Conf. on Ion Beam Modification of Materials, Knoxville, TN, 1990, Nucl. Instr. and Meth. B, to be published.
VI. MATERIALS SCIENCE