The fabrication of high quality silicon junction detectors by low energy ion implantation

High quality silicon junction detectors have been made by implantation of boron and phosphorus ions into silicon wafers. Resolutions of 20 keV for Po α-particles were obtained.     

The effect of boron ion implantation and annealing on the microstructure and electrical characteristics of the diamond films

Diamond films were doped by boron ion-implantation with the energy of 120 keV. The implantation dose ranged from 10¹⁴ to 10¹⁷ cm⁻². After the implantation, the diamond films were annealed at different temperatures (600–750°C) for different times (2–15 min). Scanning Electronic Microscope, Raman and Secondary Ion Mass-spectrum were used to investigate the effect of boron ion implantation and annealing on the microstructure of the diamond films. The electrical resistivities of the diamond films were also measured. It was found that the best dose of boron ion-implantation into the diamond film was around 10¹⁶ cm⁻². The appropriate annealing temperature and time was 700°C and 2–5 min, respectively. After implantation, the resistivities were reduced to 0.1 Ω cm (almost nine orders lower than the unimplanted diamond films). These results show that boron ion implantation can be an effective way to fabricate P-type diamond films.     

Planar waveguides in neodymium-doped calcium niobium gallium garnet crystals produced by proton implantation

In this work, the fabrication and optical properties of a planar waveguide in a neodymium-doped calcium niobium gallium garnet(Nd:CNGG) crystal are reported. The waveguide is produced by proton(H~+) implantation at 480 ke V and a fluence of 1.0×10~(17) ions/cm~2. The prism-coupling measurement is performed to obtain the dark mode of the waveguide at a wavelength of 632.8nm. The reflectivity calculation method(RCM) is used to reconstruct the refractive index profile. The finite-difference beam propagation method(FD-BPM) is employed to calculate the guided mode profile of the waveguide.The stopping and range of ions in matter 2010(SRIM 2010) code is used to simulate the damage profile induced by the ion implantation. The experimental and theoretical results indicate that the waveguide can confine the light propagation.     

Stopping cross sections of 50- to 230-keV nitrogen ions in silicon measured by ion backscattering spectroscopy

The energy dependence of the total stopping cross section of 50- to 230-keV nitrogen ions in silicon (σ _S (E)) is measured in order to develop the diagnostics of heavy impurities in films of a nanometer thickness by heavy ion backscattering (HIBS) spectroscopy. At ion energies lower than 150 keV, this σ _S (E) dependence occupies an intermediate position between the dependences given in the SRIM and MSTAR data-bases; at higher energies, our dependence is closer to the former dependence. The estimation of the effect of inelastic processes on the stopping cross section demonstrates that the effect of these processes for nitrogen ions can be neglected when heavy impurities in such films are studied by HIBS.     

Defect removal after low temperature annealing of boron implantations by emitter etch‐back for silicon solar cells

Ion implantation offers new possibilities for silicon solar cell production, e.g. single side doping that can be structured in‐situ with shadow masks. While phosphorus implantations can easily be annealed at low temperature, the annealing of boron implantations is challenging. In this study, we use low energy implantations of boron (1 keV and 5 keV) with a projected range of 5.6 nm and 21.2 nm that form defects causing charge carrier recombination after a low temperature anneal (950 °C, 30 min). An ozone‐based wet chemical etching step is applied to remove this near surface damage. With increasing chemical etch‐back the electrical quality (i.e. emitter saturation current density, J_0e) improves continuously. The calculated limit for J_0e was reached with an abrasion of 35 nm for 1 keV and 85 nm for 5 keV implantations, showing that the relevant defects causing charge carrier recombination are located very close to the surface, corresponding to the as‐implanted profile depth. This emitter etch‐back allows for the fabrication of defect free boron doping profiles with good sheet resistance uniformity (standard deviation <2%). With the resulting characteristics (sheet resistance <100 Ω/sq, surface doping concentration >5 × 10¹⁹ cm^–3, J_0e < 30 fA/cm²), these boron profiles are well suited for silicon solar cells. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

铒离子注入6H-SiC的横向离散研究

利用离子注入掺杂技术设计、制作半导体集成器件时,了解离子注入半导体材料的射程分布、射程离散和横向离散规律等是很重要的.用400 keV能量的铒(Er)离子分别与样品表面法线方向成0°,45°和 60°倾角注入碳化硅(6H-SiC)晶体中,利用卢瑟福背散射技术研究了剂量为5×10¹⁵ cm^-2 的400 keV Er离子注入6H-SiC晶体的横向离散.测出的实验值与TRIM98和SRIM 2006得到的理论模拟值进行了比较,发现实验值跟TRIM98和SRIM 关键词： 离子注入 6H-SiC 卢瑟福背散射技术 横向离散     

On the fluence dependence of the sputtering yield for low-energy noble gas ions

The fluence dependence of the sputtering yield has been studied on amorphous silicon under uhv conditions with 0.5 to 5keV Ar⁺ using the KARMA technique (Kombinierte Auger/Röntgen Mikro-Analyse). It allows to measure simultaneously the surface composition, the differential sputtering yield, and the total amount of implanted gas. For all energies, the yield increases initially and reaches saturation after the removal of a layer the thickness of which is closely correlated to the ion range. Gas implantation as a cause for these fluence effects can be ruled out by quantitative analysis. The relative yield increase is found to be larger for low energies than for higher ones. Both these findings can be qualitatively explained by a simple damage collection model.     

Low energy boron implantation profiles in silicon from junction depth measurements

Some methods have been recently developed to investigate the distribution of implanted ions in semiconductors, especially into silicon. Generally, these techniques are not valid for boron due to the absence of convenient radioactive isotopes, or to a too small sensitivity when the lower part of the distribution is of interest. This corresponds to our problem, since boron implanted nuclear particle detectors prepared with high resistivity material (up to 50,000 ω.cm) are needed. The properties of these P-N junctions depend in a certain amount on the impurity distribution existing several orders of magnitude below the top of the distribution. Therefore, only the junction location method can be employed. In this method a series of N-type silicon samples, differing each from the other by an increase in resistivity are implanted with boron. The depth of the P-N junction corresponds to the point of the profile where the concentration N_A is equal to that of the substrate N_D (i.e. this latter being well known from the resistivity of the starting material). If the location of the junction can be measured, the profile can then be constructed point by point. The junction location is visualized generally by copper staining. Roosild,⁽¹⁾ Kleinfelder,⁽²⁾ Fairfield⁽³⁾ and D. E. Davies⁽⁴⁾ have used this procedure for boron implantations at energies higher than 50 keV. There is a problem due to the small penetration of the boron ion, and, for high resistivity materials, it is difficult to know the true limits of the zones stained with copper.

In our problem, when heavy particle detectors are desired, it is necessary to implant at lower energies than those indicated previously (< 20 keV). We have developed a new technique derived from the junction depth method, which is useful even at very low implant energy (≈ 10 keV). It consists in measuring the energy loss by 100 keV protons when crossing the entrance window of the P-N junctions used as detectors.

In the first part of this paper the method is described and the possible errors are analyzed and evaluated. In the second part, the distribution of 15 keV boron ions implanted under several experimental conditions is studied. Emphasis is given to the defects resulting from the silicon bombardment.     

Device fabrication by ion implantation

Ion implantation of boron and phosphorus into silicon yields material that has electrical characteristics that are similar to silicon doped by conventional techniques. These results, and the ability to control and reproduce both the number of dopant atoms and their depth distribution, have been used to considerable advantage to fabricate both discrete devices and integrated circuits by ion implantation. We have made resistors, junction diodes, hyperabrupt diodes, IMPATTS, and field effect transistors. The narrow spread in the operating characteristics and the excellent performance of these devices, illustrate the advantages gained by using ion implantation as a step in the fabrication of devices.     

低能质子在半导体材料Si 和GaAs中的非电离能损研究

非电离能损(NIEL)引起的位移损伤是导致空间辐射环境中新型光电器件失效的主要因素.由于低能时库仑相互作用占主导地位，一般采用Mott-Rutherford微分散射截面，但它没考虑核外电子库仑屏蔽的影响.为此，本文采用解析法和基于Monte-Carlo方法的SRIM程序计算了考虑库仑屏蔽效应后低能质子在半导体材料Si,GaAs中的NIEL，SRIM程序在计算过程中采用薄靶近似法, 并与其他作者的计算数据和实验数据进行了比较.结果表明：用SRIM程序计算NIEL时采用薄靶近似法处理是比较合理的，同时考虑库仑     

Carrier and mobility profile measurements in n-type ion-implanted GaAs by the differential sheet resistivity and Hall effect technique

Multiple energy ion implantation facilities have been used to prepare essentially box-shaped dopant profiles in GaAs with plateau concentrations between 2 x 10¹⁶ and 8 x 10¹⁷ cm^-3. The implanted species was ²⁸Si⁺. The ion energies ranged between 40 and 400 keV. The depletion depth correction applied to the carrier and mobility profiles in the plateaux did not affect the data values but only their depth scale. Thus, in these regions the measured data (without any feed-back correction) were used to study the electrical properties of the implanted layers. Doping efficiencies between 65% and 81% and carrier mobilities in the range 3000 to 6000 cm² V^-1s^-1 were measured. Activation thresholds in the range 10¹⁵ to 10¹⁶ cm^-3 were estimated.     

低能质子在半导体材料Si 和GaAs中的非电离能损研究

非电离能损(NIEL)引起的位移损伤是导致空间辐射环境中新型光电器件失效的主要因素.由于低能时库仑相互作用占主导地位,一般采用Mott-Rutherford微分散射截面,但它没考虑核外电子库仑屏蔽的影响.为此,本文采用解析法和基于Monte-Carlo方法的SRIM程序计算了考虑库仑屏蔽效应后低能质子在半导体材料Si,GaAs中的NIEL,SRIM程序在计算过程中采用薄靶近似法, 并与其他作者的计算数据和实验数据进行了比较.结果表明：用SRIM程序计算NIEL时采用薄靶近似法处理是比较合理的,同时考虑库仑 关键词： 低能质子 非电离能损 硅 砷化镓     

The influence of implanted xenon on the sputtering yield of silicon

Following implantation labeling with either 200 or 270 keV Xe⁺ the sputtering yield of silicon bombarded with 20 keV Xe⁺ has been determined in situ by means of the backscattering technique (Y = 3.0 ± 0.3 (atoms/ion)). Yield enhancement by up to 60% was observed in cases where the implantation-induced xenon concentrations exceeded the saturation concentration during sputtering. The effect is attributed to (i) an increase in energy deposition at the surface introduced by pronounced xenon loading of the target and (ii) lowering of the surface binding energy. As a consequence the energy dependence of the xenon sputtering yield of silicon is expected to be strongly affected by the energy dependence of the xenon saturation concentration in silicon. Available experimental data support this idea.     

Effects of Additional Vacancy-Like Defects Produced by Ion Impealations on Boron Thermal Diffusion in Silicon

The effects of additional vacancy-like defects on thermal diffusion of B atoms in silicon were investigated by using secondary ion mass spectroscopy. B atoms were introduced into silicon by 30keV B ion implantation at a dose of 2×10¹⁴cm^－2, while the additional vacancy-like defects were produced by two different ways. One was via 40 or 160keV He ion implantation at a dose of 5×10¹⁶cm－2 and followed by an annealing at 800°C for 1h, which produced a well-defined cavity band near the projected range of He ions. The other was via 0.5MeV F or O ion implantation at a dose of 5×10¹⁵cm^－2,which creates excess vacancy-like defects around the 1/2 projected range of F or O ions. Our results clearly show that the additional vacancy-like defects could suppress the boron diffusion during subsequent thermal annealing at 800°C for 30 min. The suppressing effects were found to depend on both the ion type and ion energy. The results were qualitatively discussed in combination with the results obtained by using transmission electron microscopy and Rutherford backscattering spectroscopy.     

Investigation of the lateral spread of erbium ions implanted in silicon crystal

The erbium ions at energy of 400 keV and dose of 5×10 15 ions/cm 2 were implanted into silicon single crystals at room temperature at the angles of 0,45 and 60.The lateral spread of 400 keV erbium ions implanted in silicon sample was measured by the Rutherford backscattering technique.The results show that the measured values were in good agreement with those obtained from the prediction of TRIM’98 (Transport of Ions in Matter) and SRIM2006 (Stopping and Range of Ions in Matter) codes.     

Possibilities of the formation of carbides and borides by ion implantation

In the system of boron and carbon, the formation of boron carbide was investigated after ion implantation of 25 keV B ions into carbon or of 25 keV C ions into boron and subsequent annealing. TEM and electron diffraction studies showed that the crystallization of boron carbide begins only at temperatures above 1050°C. By implantation of 20 keV C ions into iron (ion dose 10¹⁷ C ions/cm²) only the metastable ε-Fe₂O will be generated, which at above 220°C transforms into the stable cementite Fe₃C. After implantation of 20 keV B ions into iron, no formation of iron boride could be found. These experimental facts can be understood qualitatively with the help of the thermal-spike model. The energy density or the temperature in the thermal spikes is not sufficient for the generation of cementite iron boride or boron carbide.     

Lattice disorder in germanium by boron ion bombardment

Abstract

The lattice disorder produced in germanium by 56keV boron-ion bombardment has been measured using the channeling-effect technique. The dependence on dose (10¹⁴-10¹⁶ ions/cm²) and implantation temperature (?90 °C to +130°C) has been studied. It is found that at room-temperature, each incident boron ion creates ?10 times more disorder in germanium than in silicon. It is remarked that, contrary to the present results, previously established anneal stages generally occur at significantly lower temperatures in germanium than in silicon.     

Effect of boron ion implantation on the structural, optical and electrical properties of ZnSe thin films

Zinc Selenide (ZnSe) thin films were deposited onto well cleaned glass substrates using vacuum evaporation technique under a vacuum of 3×10⁻⁵ mbar. The prepared ZnSe samples were implanted with mass analyzed 75 keV B⁺ ions at different doses ranging from 10¹² to 10¹⁶ ions cm⁻². The composition, thickness, microstructures, surface roughness and optical band gap of the as-deposited and boron-implanted films were studied by Rutherford backscattering (RBS), grazing incidence X-ray diffraction, Atomic force microscopy, Raman scattering and transmittance measurements. The RBS analysis indicates that the composition of the as-deposited and boron-implanted films is nearly stoichiometric. The thickness of the as-deposited film is calculated as 230 nm. The structure of the as-deposited and boron-implanted thin films is cubic. It is found that the surface roughness increases on increasing the dose of boron ions. In the optical studies, the optical band gap value decreases with an increase of boron concentration. In the electrical studies, the prepared device gave a very good response in the blue wavelength region.     

FORMATION OF A BURIED LAYER OF ALUMINIUM NITRIDE BY HIGH DOSE N2+ IMPLANTATION INTO ALUMINIUM

Aluminium films with various thickness between 700 nm and 1μm were deposited on Si (100) substrates, and 400 keV N₂⁺ ions with doses ranging from 4.3×10¹⁷ to 1.8×10¹⁸ N/cm² were implanted into the alu-minium films on silicon, Rutherford Backscattering (RBS) and channeling, secondary ion mass spectroscopy (SIMS), Fourier transform infrared spectra (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and spreading resistance probes (SRP) were used to characterize the synthesized aluminium nitride. The experiments showed that when the implantation dose was higher than a critical dose N_c, a buried stoichiometric AlN layer with high resistance was formed, while no apparent AlN XRD peaks in the as-implanted samples were observed; however, there was a strong AlN(100) diffraction peak appearing after annealing at 500 ℃ for 1h. The computer program, Implantation of Reactive Ions into Silicon (IRIS), has been modified and used to simulate the formation of the buried AlN layer as N₂⁺ is implanted into aluminium. We find a good agreement between experimental measurements and IRIS simulation.     

Flux and fluence dependence of disorder produced during implantation of 11B in silicon

The flux and fluence dependence of disorder produced in silicon during the implantation of ¹¹B has been investigated at room temperature, -50°C. and -120°C. Implantations were carried out with 200 keV ¹¹B ions using current densities in the range from 0.06μA/cm² to 15μA/cm², and the disorder monitored by measuring the energy spectra of backscattered protons which were incident on the sample at 450 keV parallel to a (110) axis. Significant differences in the dependence of the disorder on ¹¹B flux and fluence were observed between the implantations performed at room temperature and those carried out at the two lower temperatures.