Browsing by Author "JUANG, MH"

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A SILICIDATION-INDUCED PROCESS CONSIDERATION FOR FORMING SCALE-DOWN SILICIDED JUNCTION
(1994-09-01)
CHENG, HC
;
JUANG, MH
;
LIN, CT
;
HUANG, LM
;
電子工程學系及電子研究所
A process consideration for forming silicided shallow junctions, arising from silicidation process, has been discussed. The CoSi2 shallow p+n junctions formed by various schemes are characterized. The scheme that implants BF2+ ions into thin Co films on Si substrates and subsequent silicidation yields good junctions, but the problems about the dopant drive-in and knock-on of metal deeply degrade this scheme. In the regime that implants the dopant into Si and then Co deposition, however, a large perimeter leakage of 0.1 nA/cm is caused. Generation current, associated with a defect-enhanced diffusion of Co in Si during silicidation, dominates the leakage. A high-temperature pre-activation prior to Co deposition reduces the perimeter leakage to 0.038 nA/cm, but which deepens the junctions.
ACTIVATION MECHANISM OF IMPLANTED BORON IN A SI SUBSTRATE
(1992-12-01)
JUANG, MH
;
CHENG, HC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The recrystallization and dopant activation in the BF2+ implanted samples with a 110 keV/5 X 10(15) cm-2 condition into a Si substrate and annealed with different heating rates to various preset temperatures for zero holding time have been studied. A higher heating rate yielded a higher carrier mobility and a better crystallinity. A statistical model was proposed to characterize the dopant activation. The activated dopant concentration n was expressed as gamma exp(-E(a)/kT). The pre-exponential term gamma is a function of critical temperature T(c) due to a finite melting point of Si, and heating rate. Both the effective activation energy E(a) and T(c) values decreased with increasing heating rate. With increasing heating rate, the gamma term rapidly decreased at low rates due to the shortened effective annealing time, but showed slight increase at high rates due to the decreased T(c) value. Low heating rates facilitated the dopant activation via the gamma term, while high heating rates enhanced the activation efficiency via the E(a) term.
CHARACTERIZATION OF SILICIDED SHALLOW N+P JUNCTIONS FORMED BY P+ IMPLANTATION INTO THIN TI FILMS ON SI SUBSTRATES
(1992-10-01)
JUANG, MH
;
CHENG, HC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
High-quality silicided shallow n+p junctions have been fabricated by P+ implantation into thin Ti films on Si substrates and by moderate implant conditions as well as subsequent high-temperature rapid thermal annealing (RTA) followed by low-temperature conventional furnace annealing (CFA). RTA minimizes the diffusion of knock-on Ti but greatly reduces the drive-in efficiency because of its short annealing time. Driving the dopants out of silicides via long-time annealing was associated with the crystallinity of silicides. The junctions formed by this scheme with respect to various implant and anneal conditions have been characterized. In addition, the distribution profile of Ti penetration was correlated with the effective generation life time obtained from the reverse I-V curves.
CONVENTIONAL FURNACE AND RAPID THERMAL ANNEALING OF COBALT FILMS ON SI(111)
(1992-09-15)
JUANG, MH
;
CHENG, HC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The effects of conventional furnace annealing (CFA) and rapid thermal annealing (RTA) on the interfacial reactions of thin cobalt films on Si(111) have been investigated. The low heating rates (about 10-degrees-C s-1) associated with CFA lead to impurity segregation at the silicide-Si interface during the initial stage of interfacial reactions, while segregation is absent for high heating rates (about 100-degrees-C s-1) associated with RTA. From examination by transmission electron microscopy (TEM), RTA promotes uniform formation of silicides and epitaxial growth of twin-structure CoSi2, causing an average grain size of about 50 nm and a surface coverage area of about 70% at 500-600-degrees-C for 100-600 s. In contrast. silicidation is retarded for CFA, and grain growth is preferred to formation of epitaxial CoSi2. The electrical characterization of low doping level silicided shallow junctions correlates well with the TEM examinations of the interfacial reactions by the respective annealing schemes.
EFFECTS OF COBALT SILICIDATION ON THE ELECTRICAL CHARACTERISTICS OF SHALLOW P(+)N JUNCTIONS FORMED BY BF2+ IMPLANTATION INTO THIN POLYCRYSTALLINE SI FILMS
(1995-03-01)
LIN, CT
;
CHAO, CH
;
JUANG, MH
;
JAN, ST
;
CHOU, PF
Excellent shallow p(+)n junctions have been formed by implanting BF2+ ions into thin polycrystalline Si films and subsequent annealing. The samples implanted at 50 keV to a dose 5 x 10(15) cm(-2) show a leakage of 1 nA/cm(2) and a junction depth of about 0.05 mu m after a 800 degrees C annealing. To reduce the series resistances of the junctions, silicidation with different col;alt thickness was used to drive the as-implanted dopants in the polysilicon films into the resultant junctions of the silicon substrates. For the low energy implantation at 50 keV at all dosages, silicidation can result in poor electrical characteristics due to the confinement of the dopants by the silicidation process. On the other hand, the electrical characteristics can be retained when a higher implantation energy of 100 keV with a dosage higher than 5 x 10(15) cm 2 was used. In addition, the samples implanted at 125 keV show poor electrical characteristics for the nonsilicided junctions but good characteristics after the silicidation. It is attributed to the enhanced defect annihilation by the formed silicide. Furthermore, silicided implanted through poly-Si junctions with excellent characteristics can be fabricated after a low temperature (600 degrees C) annealing if the samples are implanted at 100 keV with a dosage higher than 5 X 10(15) cm(-2).
EFFECTS OF RAPID THERMAL ANNEALING ON THE FORMATION OF SHALLOW P+N JUNCTION BY IMPLANTING BF2+ IONS INTO THIN METAL-FILMS ON SI SUBSTRATE .1. THIN TITANIUM FILMS
(1992-02-01)
JUANG, MH
;
CHENG, HC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
High-quality Ti-silicided shallow p+ n junctions have been fabricated by implanting BF2+ ions into thin Ti films on Si substrate and subsequent silicidation/drive-in by rapid thermal annealing (RTA) or conventional furnace annealing (CFA) under proper implant and anneal conditions. For both the RTA and CFA techniques, annealing temperatures higher than 800-degrees-C degrade the junction formation because of more severe dopant confinement within the silicides and more serious diffusion of knock-on Ti into junction regions. The high-dose implant greatly enhanced the dopant activation and thus improved the junctions. The high heating rate for RTA caused an immediate formation of Ti-B compounds at high temperatures, while CFA considerably promoted the drive-in efficiency because of its low heating rates and long annealing times. Hence, CFA yielded better low-bias rectifying characteristics than RTA due to larger dopant activation. However, CFA caused much worse high reverse-bias characteristics. A rapid increase of reverse currents with bias voltage was observed for the CFA-treated samples, indicating a severe Ti penetration due to long annealing times.
EFFECTS OF RAPID THERMAL ANNEALING ON THE FORMATION OF SHALLOW P+N JUNCTION BY IMPLANTING BF2+ IONS INTO THIN METAL-FILMS ON SI SUBSTRATE .2. THIN COBALT FILMS
(1992-02-01)
JUANG, MH
;
CHENG, HC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The effects of rapid thermal annealing (RTA) on the formation of shallow p+ n junctions by the implantation of BF2+ ions into thin Co films and subsequent silicidation/drive-in have been studied. The junction formation by various implant conditions has been characterized to correlate with the dopant drive-in efficiency, defects in junctions, and junction depth under different anneal conditions. Optimum junctions were achieved by the 700-degrees-C anneal in all the present implant conditions. Annealing at 800-degrees-C degraded the junction formation due to the considerable formation of Co-B compounds caused by the high heating rate and high-temperature processings. Higher implant energy greatly lessened the dopant confinement due to deeper as-implanted dopant profile. Conventional furnace annealing (CFA) considerably enhanced the drive-in efficiency, while RTA is superior to CFA in annihilating damage, activating dopant, and forming shallow junctions. The benefits of RTA are particularly obvious for the implants of low-energy, low-dosage and high-energy, high-dosage. Consequently, low-temperature RTA processings can achieve silicided shallow p+ n junctions with good rectifying characteristics.
FILM THICKNESS EFFECT ON THE EPITAXIAL-GROWTH OF COSI2 ON SI(111)
(1992-07-30)
JUANG, MH
;
CHENG, HC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Effects of deposited cobalt film thickness on the epitaxial growth of CoSi2 on Si(111) by the solid phase epitaxy regime have been studied using transmission electron microscopy. Thinner films (30 angstrom) facilitate the growth of epitaxial CoSi2, the formation of smooth silicide-Si interfaces and even the growth of single-crystal CoSi2 at low annealing temperatures, but degrade in thermal stability. Thicker films (300 angstrom) retard the grain realignment, and yield faceted epitaxial structure after high temperature annealing. Hence, film thicknesses sufficient to benefit from easy epitaxial growth and forming flat silicide-Si interfaces and yet are thermally stable should be used. Accordingly, a facet-free, thermally stable, single-crystal CoSi2 structure has been achieved using 100 angstrom thick films.
FORMATION OF EXCELLENT SHALLOW N+P JUNCTIONS BY AS+ IMPLANTATION INTO THIN COSI FILMS ON SI SUBSTRATE
(1993-04-01)
LIN, CT
;
JUANG, MH
;
CHU, CH
;
CHENG, HC
;
電子工程學系及電子研究所
Excellent shallow n + p junctions with a leakage current density of about 0.6 nA/cm2 have been fabricated by As+ implantation into thin CoSi films on Si substrates and subsequent drive-in/silicidation. The resultant junction characteristics are strongly affected by the implant conditions. A deeper as-implanted dopant profile is more helpful to drive the dopant within the silicides into the junction regions. Because the silicidation facilitates damage annihilation, the implant conditions forming excellent junctions in this scheme own large process window and thus yield low thermal budgets. Rapid thermal annealing was not favorable to forming junctions in this scheme because of its short annealing times for the arsenic drive-in.
FORMATION OF P(+)N JUNCTIONS BY SI(+)+B(+) IMPLANTATION AND LASER ANNEALING
(1992-04-27)
JUANG, MH
;
CHENG, HC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The effects of rapid thermal annealing (RTA) and laser annealing (LA) on the activation and diffusion of ion-implanted boron in Si substrate have been investigated. The implant and anneal regimes, forming good shallow junctions, were presented. The Si+ -preamorphized samples boron implanted with a high dosage showed largely enhanced diffusion in RTA processing. The LA process serves as an excellent scheme to effectively activate the dopant and suppress the anomalous diffusion because of its very high heating rate. A high-quality p+/n junction with a leakage current density lower than 2 nA/cm2 and a forward ideality factor of about 1.01 was formed by laser processing.
FORMATION OF SELF-ALIGNED TISI2 P+-N JUNCTIONS BY IMPLANTING BF2+ IONS THROUGH THIN TI OR SIO2 FILM ON SI SUBSTRATE RAPID THERMAL ANNEALING
(1992-10-01)
JUANG, MH
;
CHENG, HC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
High-quality Ti silicided p+-n junctions have been fabricated by implanting BF2+ ions through alpha-Si/Ti films on an Si substrate (ITM), with subsequent rapid thermal processing. A leakage current density of about 4 nA cm-2, a forward ideality factor greater than 1.02 and a reverse breakdown voltage above 80 V were achieved for the specimens annealed at 800-degrees-C for 30 s. For comparison, junctions were also formed by directly implanting BF2+ ions into Si substrates, with the following depositions of alpha-Si/Ti films and silicidation/activation (ISA). Various implant and anneal conditions were studied to clarify their effects on fabricating junctions by the ISA and ITM schemes. Adequate anneal conditions must be used to vary the dopant activation, damage annihilation and Ti penetration into the junction regions so as to optimize the junctions formed by the respective schemes. In particular, ITM yielded a much higher breakdown voltage than ISA, due to a smoother TiSi2/Si interface. It is shown, for the first time, that the silicide/Si interface is mainly responsible for the diode characteristics at high reverse bias.
FORMATION OF SHALLOW P(+)N JUNCTIONS BY BF2+ IMPLANTATION INTO THIN POLYCRYSTALLINE SI FILMS
(1994-09-15)
LIN, CT
;
JUANG, MH
;
JAN, ST
;
CHOU, PF
;
CHENG, HC
Excellent shallow p(+)n junctions have been formed by implanting BF2+ ions into thin polycrystalline Si films and subsequent annealing. The samples implanted with 5X10(15) cm(-2) at 50 keV show a leakage of 1 nA/cm(2) and a junction depth of about 0.05 mu m after a 800 degrees C annealing. Various implant and annealing cases were examined to determine and characterize their effects on the resultant junctions. High energy implantations (125 and 150 keV) exhibit poor characteristics at all annealing temperatures because the Si substrates are severely damaged. However, the specimens implanted below 100 keV result in excellent diode characteristics for all implantation doses after an 800 degrees C annealing since the implantation defects are confined in the poly-Si layer. The major factors affecting the junction depth were found to be the implantation energy and annealing temperature, while a minor for the implantation dosage. Furthermore, the effects of the subsequent silicidation on the resultant junction characteristics were also investigated.
FORMATION OF SHALLOW P+N JUNCTIONS BY IMPLANTING BF2+ IONS INTO THIN COBALT FILMS ON SILICON SUBSTRATES
(1992-04-01)
JUANG, MH
;
CHENG, HC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Silicided shallow p + n junctions have been formed by implanting BF2+ ions into a-Si/Co bilayer films on Si substrates and subsequent drive-in/silicidation. The effects of implantation dose and energy on the electrical characteristics were studied. The modulation ranges of implantation energy and dose employed to form good junctions are large for the present fabrication scheme. However, high-performance silicided shallow junctions must be optimized by using moderate implant energy and dosage. The junction depth, drive-in efficiency, dopant concentration and electrical characteristics must be compromised to achieve the goal of good shallow junctions. A silicided shallow junction formed by the implantation of 70 keV at a dose of 5 x 10(15) cm-2 and subsequently annealed at 700-degrees-C exhibited characteristics with a leakage current density lower than 0.5 nA cm-2, a forward ideality factor better than 1.01 and a junction depth of about 0.13-mu-m
GROWTH OF SINGLE-CRYSTALLINE COSI2 ON (111)SI AT LOW ANNEALING TEMPERATURES BY A NONULTRAHIGH VACUUM METHOD
(1991-12-01)
CHENG, HC
;
JUANG, MH
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
By reducing the thickness of the deposited cobalt film, high-quality single-crystalline CoSi2 phase with a sheet resistivity as low as 15-mu-OMEGA cm has been achieved. A deposition of 3 nm thick cobalt film on (111)Si substrate and a subsequent rapid thermal annealing (RTA) at 500-degrees-C were used. From the examinations of transmission electron microscopy (TEM), the single-crystalline CoSi2 structure was identified as type B orientation. As far as the authors are aware of, such an annealing temperature is the lowest for the solid phase growth of single-crystalline CoSi2 on the silicon substrate in the nonultrahigh vacuum (non-UHV) deposition and annealing systems. Hence, the deposition of thinner cobalt film on the silicon substrate would be favorable to the formation of polycrystalline CoSi2 grains and the growth of single-crystalline CoSi2 structure. It is attributed to the promoting ratio of interface energy and the smaller preliminarily-formed CoSi2 grains. No facet was observed for all samples annealed at 500-degrees-C. It indicates that a smooth single-crystalline CoSi2/Si interface is formed. Annealing at 450-degrees-C yielded coexisting polycrystalline and epitaxial CoSi2 phases. The samples annealed at 700-degrees-C would exhibit a highly strained single-ctystalline CoSi2/Si interface. Furthermore, annealing at 900-degrees-C would generate large pinholes in the CoSi2 crystal to relieve the interface free energy. Sheet resistance results and current-voltage characteristics of these specimens were measured and well correlated with the TEM observations.
INFLUENCE OF IMPLANT CONDITION ON THE TRANSIENT-ENHANCED DIFFUSION OF ION-IMPLANTED BORON IN SILICON
(1992-03-15)
JUANG, MH
;
WAN, FS
;
LIU, HW
;
CHENG, KL
;
CHENG, HC
Under high-dosage boron implant, the implant condition was found to be important for reducing the transient-enhanced diffusion of boron in Si and forming shallow p + n junction with good rectifying characteristics as well as high dopant concentration in the diffused region. The BF2+-implantation resulted in not only an excellent dopant activation but also a reduced anomalous diffusion due to the formation of amorphous layer and the scarce defects underneath the amorphous/crystalline (a/c) interface. The B+-implanted crystalline samples manifested a poor activation efficiency, and a largely anomalous diffusion at the high temperature with prolonged-time annealing ascribed to much damage induced by the high-dose implant. The B+-implanted pre-Si+-amorphized samples also displayed severely transient-enhanced diffusion in spite of the good dopant activation.
NOVEL ANNEALING SCHEME FOR FABRICATING HIGH-QUALITY TI-SILICIDED SHALLOW N+P JUNCTION BY P+ IMPLANTATION INTO THIN TI FILMS ON SI SUBSTRATE
(1992-03-30)
JUANG, MH
;
CHENG, HC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A TiSi2 silicided shallow n + p junction with a leakage current density of about 3 nA/cm2, a forward ideality factor of 1.00, and a junction depth of about 0.11-mu-m has been fabricated by implanting P+ ions into thin amorphous-Si/Ti bilayer films on silicon substrate and subsequently processed by a rapid thermal annealing (RTA) at 800-degrees-C/60 s with a post-conventional furnace annealing (CFA) at 600-degrees-C/30 m. RTA not only minimizes the diffusion of knock-on Ti into the junction region, but also facilitates the silicidation and damage annihilation. The low-temperature CFA treatment following the high-temperature RTA process greatly increases the diffusion of dopants into the junction region and thus improves the junction characteristics significantly. The increased diffusion of dopants from the silicide layer into the junction region by the post-CFA process is attributed to the crystallization of the titanium silicide.
NOVEL EFFECTS OF HEATING RATE ON THE ACTIVATION RECRYSTALLIZATION OF BORON-IMPLANTED SI SUBSTRATES
(1992-07-01)
JUANG, MH
;
CHENG, HC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The effects of heating rate on the recrystallization and dopant activation, for samples under different implant conditions, have been studied. The as-implanted samples were annealed, at various heating rates, to different preset temperatures but zero holding time. Factors associated with the dopant activation have been evaluated to develop a proper activation mechanism, thus correlating with the experimental results. In the transient annealing, a higher heating rate facilitates the dopant activation via a lower effective activation energy, while lower heating rates inherently own longer effective activating times. Implant conditions strongly determine the degree, impacting the dopant activation, of respective factors. In addition, higher heating rates led to better Si recrystallization.
NOVEL PHENOMENON OF THE AL-1 WT-PERCENT-SI CONTACTS ON THE NF3/AR POST-ETCHING-TREATED N-SI SUBSTRATES
(1993-09-15)
CHENG, HC
;
CHEN, YE
;
JUANG, MH
;
YEN, PW
;
LIN, L
Post-etching treatment (PET) using an in situ NF3/Ar low-energy plasma was reported to be efficient in removing the residual layer and defects caused by reactive ion etching (RIE) as well as producing a clean surface conventionally believed suitable for electrical contacts. However, the PET process was found to increase the contact resistance between Al-1 wt%Si and n+-Si substrate for the first time. It is attributed to the formation of p-type-like Si epitaxy on the n+-Si substrate and the lower effective surface donor concentration.
SHALLOW JUNCTIONS FORMED BY BF2+ IMPLANTATION INTO THIN COSI FILMS AND RAPID THERMAL ANNEALING
(1994-07-15)
JUANG, MH
;
LIN, CT
;
CHENG, HC
;
交大名義發表
;
電子工程學系及電子研究所
Effects of rapid thermal annealing (RTA) on the shallow p+n junctions formed by BF2+ implantation into thin CoSi films on Si substrates are discussed, with comparison to the implantation into thin Co films. Excellent junctions can be achieved via conventional furnace annealing (CFA) for both the samples prepared by implanting dopant through metal (ITM) and metal silicides (ITS) films. For the RTA process, however, the junction formation for ITS was hindered, with the diodes made by ITM being much better than those by ITS due to a deeper as-implanted profile. Although the problem of knock-on Co induced by heavy dopant implant present in making n+p junctions by ITM can be largely reduced by using ITS, ITS is inferior for forming p+n junctions by RTA.
SHALLOW N(+)P JUNCTION FORMATION BY IMPLANTING P+ IONS INTO THIN CO FILMS AND LASER PROCESSING
(1993-01-01)
CHENG, HC
;
JUANG, MH
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Effects of laser annealing (LA) on the formation of silicided shallow junctions have been studied. The junctions are made by P+ implantation into thin Co films on Si substrate and subsequent drive-in/silicidation. Various implant and annealing conditions are examined. Conventional furnace annealing (CFA) is also undertaken. Good junctions can be achieved only by using low-temperature CFA due to the severe diffusion of knock-on Co atoms at high temperatures. The junctions formed by LA processing are poor in this scheme. However, the junctions formed by CFA only show small change of the dopant redistribution and the Co penetration after a subsequent LA. In addition, the silicide crystallinity and the junction characteristics can be further improved using a proper LA power. The results indicate that the laser-recrystallization technique is a promising technique for the fabrication of three-dimensional devices.