Fabrication and Characterization of Epitaxial Heavily Phosphorus‐Doped Silicon

Low temperature silicon epitaxy processes capable of producing ultrathin in situ doped layers have been considered able to overcome some of the challenges in realizing advanced metal oxide semiconductor field effect transistor (MOSFET) devices. As previously demonstrated for complementary metal oxide semiconductor (CMOS), 1 for buried p-channel MOSFET (PMOSFET), 2 and for double-layer epitaxial-channel p-channel MOSFETs, 3 epitaxial deposition in forming channels is a potentially promising technique since it allows independent control of doping and thickness. This is clearly an important advantage over other doping techniques provided that ultrathin layers (Յ300 Å) with abrupt doping transitions can be obtained.Early studies on n-type doping which were performed mostly in atmospheric pressure reactors at temperatures in excess of 1000ЊC revealed several common features unique to doping using PH 3 and arsine (AsH 3 ). Namely, doping incorporation decreased as the deposition temperature increased, 4-7 and the silicon growth rate was dramatically reduced when PH 3 or AsH 3 were added as the dopant source in both polycrystalline deposition and epitaxial silicon growth. 8-11 It was confirmed through surface studies that PH 3 with its very high sticking coefficient adsorbed readily on the silicon surface and hindered SiH 4 adsorption. 12 The pyrolysis of PH 3 at low partial pressures additionally resulted in PH and PH 2 species at high temperatures. At high partial pressures, however, the existence of P 2 and P 4 species made heavy phosphorus doping difficult. 7 Another challenge in phosphorus doping is the formation of retrograde profiles with abrupt transitions desired for novel device applications. 13-15 It has been commonly reported that undoped layers grown following an in situ phosphorus doped layer using PH 3 contain high levels of phosphorus, which was attributed to the high residence time of phosphorus species. 13,16 In this report, we present experimental results on phosphorus incorporation using PH 3 , Si 2 H 6 , and Cl 2 chemistry in a temperature range of 650 to 800ЊC. Effects of phosphine partial pressure and temperature on growth rate as well as phosphorus concentration are determined. Difficulties associated with n-type doping using PH 3 , which do not exist with in situ boron doping using B 2 H 6 , are also addressed in the context of forming epitaxial layers needed for advanced devices.Ultrahigh vacuum rapid thermal chemical vapor deposition (UHV-RTCVD) has been previously introduced by this laboratory to produce ultrathin device quality epitaxial layers for ultralarge scale integration (ULSI) device applications, 17,18 UHV-RTCVD is a singlewafer, cold wall, rapid thermal processing technique that can be incorporated in a cluster tool. In UHV-RTCVD, disilane (Si 2 H 6 ) is used to achieve growth rates compatible with single-wafer manufacturing at low pressures. Epitaxial growth is achieved at 800ЊC with growth rates in excess of 200 nm/min. Selectivity to insulators is maintained with the help of Cl 2...

Section: Resultssupporting

confidence: 81%

In Situ Phosphorus Doping during Silicon Epitaxy in an Ultrahigh Vacuum Rapid Thermal Chemical Vapor Deposition Reactor

Ban

Öztürk

1999

“…Growth rate in n-type doping.-Alamo and Swanson 44 studied the growth and electrical characteristics of P-doped epitaxial Si films in atmospheric pressure CVD at 1050°C using PH 3 and SiH 4 as the precursors and H 2 as the carrier gas. The PH 3 partial pressure was between 1 ϫ 10 −8 Torr and 3.04 Torr, while the SiH 4 partial pressure was kept constant at 0.76 Torr.…”

Section: ͓21͔mentioning

confidence: 99%

“…Figure 8 shows the best fit of Eq. 27 to the experimental data, 44 with f = 0.618 and ␤ = 60. The agreement is reasonable.…”

Section: ͓21͔mentioning

confidence: 99%

See 1 more Smart Citation

A Kinetic Model for Boron and Phosphorus Doping in Silicon Epitaxy by CVD

Mehta

Tao

2005

A kinetic model based on ͑i͒ the collision theory of heterogeneous unimolecular elementary reactions, ͑ii͒ statistical physics, and ͑iii͒ the concept of competitive adsorption is proposed for both p-type and n-type doping in silicon epitaxy by chemical vapor deposition ͑CVD͒. It takes into account both homogeneous and heterogeneous reactions, which involve the precursors ͑silane and dopant precursor͒ and their homogeneous decomposition products, and four types of surface sites, hydrogen-terminated silicon and dopant sites and hydrogen-free silicon and dopant sites. The model provides analytical equations to describe dopant concentration and silicon growth rate as a function of deposition conditions, including temperature and partial pressure of dopant precursor. At low temperatures, the enhancement in growth rate with diborane is attributed to enhanced hydrogen desorption from boron sites, which act as catalytic sites for silicon growth. The relationship between boron concentration and diborane partial pressure is more complicated than a simple linear one. The suppression in growth rate with phosphine is modeled by a blocking factor that represents the extent of the "poisoning" effect of phosphorous on the surface. Homogeneous decomposition of phosphine accounts for phosphorous doping behavior at high phosphine partial pressures. The model agrees well with the experimental data.Chemical vapor deposition ͑CVD͒ and its derivatives such as ultrahigh vacuum CVD, metallorganic CVD, and atomic layer deposition are widely used in the semiconductor industry for forming epitaxial films of doped semiconductors, p-type or n-type. The critical importance of CVD prompts efforts to understand its kinetics, thermodynamics, and reaction mechanism. The basic process in CVD involves gaseous precursors that undergo decomposition reactions over a substrate and deposit a film of a material contained in the precursors. In Si epitaxy by thermal CVD, several precursors have been used as the Si source, silane ͑SiH 4 ͒, dichlorosilane ͑SiH 2 Cl 2 ͒, trichlorosilane ͑SiHCl 3 ͒, tetrachlorosilane ͑SiCl 4 ͒, and disilane ͑Si 2 H 6 ͒. The most commonly used precursor for p-type doping is diborane ͑B 2 H 6 ͒, whereas n-type dopant precursors include phosphine ͑PH 3 ͒ and arsine ͑AsH 3 ͒. Several groups have investigated the incorporation of B in Si epitaxy from various precursors. 1-5 At low temperatures, an increase in Si growth rate with B 2 H 6 partial pressure has been reported. 2,4 Glass et al. 6 attributed the growth rate enhancement at low temperatures to increased H 2 desorption due to B incorporation. Eversteyn and Put 7 observed an increase in polycrystalline Si growth rate by a factor of 2 at 680°C and a decrease in activation energy of SiH 4 decomposition in the presence of B 2 H 6 . Farrow 8 observed growth rate enhancement at temperatures from 700 to 1100°C, but with very high B 2 H 6 /SiH 4 ratios. The experiments conducted by Shiozawa et al. 9 indicated that the growth rate and B concentration varied as the square root of B 2 ...

“…The silicon growth rate is reduced at high phosphine flow rate by 60% for both 700 and 800ЊC growth, which is qualitatively similar to that using silane or disilane sources in both CVD and gas source molecular beam epitaxy systems. 3,[5][6][7][9][10][11][22][23][24][25][26][27][28][29][30] There are fewer works using dichlorosilane source, but similar phenomena have been observed with both arsenic 14 and phosphorus 15 doping using dichlorosilane in siliconselective epitaxy at 775-1050ЊC. In the case of silane, the explanation given 4,22,31 is that at temperatures higher than 400ЊC (the desorption temperature of hydrogen), a high level of phosphorus accu-S0013-4651(99)11-104-2 CCC: $7.00 © The Electrochemical Society, Inc. mulates at the silicon surface during the CVD process and blocks free active sites on the surface, thus reducing the surface reaction.…”

Section: Growth Rate and Phosphorus Levelsmentioning

confidence: 99%

Phosphorus Doping and Sharp Profiles in Silicon and Silicon-Germanium Epitaxy by Rapid Thermal Chemical Vapor Deposition

Yang

Carroll

Sturm

et al. 2000

Background-We conducted a prospective, multicenter, randomized comparison of implantable cardioverter-defibrillator (ICD) versus antiarrhythmic drug therapy in survivors of cardiac arrest secondary to documented ventricular arrhythmias. Methods and Results-From 1987, eligible patients were randomized to an ICD, amiodarone, propafenone, or metoprolol (ICD versus antiarrhythmic agents randomization ratio 1:3). Assignment to propafenone was discontinued in March 1992, after an interim analysis conducted in 58 patients showed a 61% higher all-cause mortality rate than in 61 ICD patients during a follow-up of 11.3 months. The study continued to recruit 288 patients in the remaining 3 study groups; of these, 99 were assigned to ICDs, 92 to amiodarone, and 97 to metoprolol. The primary end point was all-cause mortality. The study was terminated in March 1998, when all patients had concluded a minimum 2-year follow-up. Over a mean follow-up of 57Ϯ34 months, the crude death rates were 36.4% (95% CI 26.9% to 46.6%) in the ICD and 44.4% (95% CI 37.2% to 51.8%) in the amiodarone/metoprolol arm. Overall survival was higher, though not significantly, in patients assigned to ICD than in those assigned to drug therapy (1-sided Pϭ0.081, hazard ratio 0.766, [97.5% CI upper bound 1.112]). In ICD patients, the percent reductions in all-cause mortality were 41.9%, 39.3%, 28.4%, 27.7%, 22.8%, 11.4%, 9.1%, 10.6%, and 24.7% at years 1 to 9 of follow-up. Conclusions-During long-term follow-up of cardiac arrest survivors, therapy with an ICD is associated with a 23%(nonsignificant) reduction of all-cause mortality rates when compared with treatment with amiodarone/metoprolol. The benefit of ICD therapy is more evident during the first 5 years after the index event. (Circulation. 2000;102:748-754.)