Precise nanofabrication with multiple ion beams for advanced circuit edit

Gallium focused ion beam (Ga-FIB) systems have been used historically in the semiconductor industry for circuit edit. Significant efforts have been invested to improve the performance of Ga-FIB. However, as the dimensions of integrated circuits continue to shrink, Ga-FIB induced processes are being driven to their physical limits. A helium ion beam offers high spatial resolution imaging as well as precise ion machining and sub-10 nm nanofabrication capabilities because the probe size can be brought to as small as 0.25 nm. However, it is limited by its relatively low material removal rate. Recently, the new Zeiss Orion-NanoFab microscope provides multiple ion beams (He, Ne and Ga as an option) into one platform and promotes the further studies of He and Ne induced deposition and etching processes to compare with a Ga ion beam. Because of the mass difference between He, Ne and Ga ions, the interactions of ions with sample surface and precursor molecules result in different sputtering rates, implantation and deposition yields. This presentation gives an overview of our current studies using this new platform to deposit or mill nanostructures for circuit edit.     

The structure and magnetic properties of β-(Ga0.96Mn0.04)2O3 thin film

High quality epitaxial single phase (Ga0.96Mn0.04)2O3 and Ga2O3 thin films have been prepared on sapphire substrates by using laser molecular beam epitaxy (L-MBE).X-ray diffraction results indicate that the thin films have the monoclinic structure with a (-201) preferable orientation.Room temperature (RT) ferromagnetism appears and the magnetic properties of β-(Ga0.96Mn0.04)2O3 thin film are enhanced compared with our previous works.Experiments as well as the first principle method are used to explain the role of Mn dopant on the structure and magnetic properties of the thin films.The ferromagnetic properties are explained based on the concentration of transition element and the defects in the thin films.     

Giant modulation of magnetism in(Ga,Mn)As ultrathin films via electric field

Taking the advantages of semiconducting properties and carrier-mediated ferromagnetism in(Ga,Mn)As,a giant modulation of magnetism via electric field in(Ga,Mn)As ultrathin film has been demonstrated.Specifically,huge interfacial electric field is obtained by using ionic liquid as the gate dielectric.Both magnetization and transport measurements are employed to characterize the samples,while the transport data are used to analyze the electric filed effect on magnetism.Complete demagnetization of(Ga,Mn)As film is then realized by thinning its thickness down to ~2 nm,during which the degradation of ferromagnetism of(Ga,Mn)As ultrathin film induced by quantum confinement effect is suppressed by inserting a heavily-doped p-type GaAs buffer layer.The variation of the Curie temperature is more than 100 K,which is nearly 5-times larger than previous results.Our results provide a new pathway on the efficient electrical control of magnetism.     

Triple implant (In,Ga)As/InP n-p-n heterojunction bipolar transistors for integrated circuit applications

For the first time (In,Ga)As/InP n-p-n heterojunction bipolar transistors (HJBT's) applicable to integrated circuits have been fabricated by triple ion implantation. The base has been formed by beryllium ion implantation and the collector by silicon ion implantation. The implants were made into an LPE-grown n-n (In,Ga)As/InP heterostructure on an n+-InP substrate. This inverted mode emitter-down heterojunction transistor structure demonstrates to a maximum current gain of 7 with no hysteresis in the characteristics. The ideality factors of the IBversus VBE, and ICversus VBEcharacterisitics with VCB= 0, are 1.25 and 1.08, respectively, indicating that the defect level in the herterojunction is low and that minority-carrier injection and diffusion is the dominant current flow mechanism.     

(Ga,Mn)As on patterned GaAs(0 0 1) substrates: Growth and magnetotransport

A new type of (Ga,Mn)As microstructures with laterally confined electronic and magnetic properties has been realized by growing (Ga,Mn)As films on -oriented ridge structures with (1 1 3)A sidewalls and (0 0 1) top layers prepared on GaAs(0 0 1) substrates. The temperature- and field-dependent magnetotransport data of the overgrown structures are compared with those obtained from planar reference samples revealing the coexistence of electronic and magnetic properties specific for (0 0 1) and (1 1 3)A (Ga,Mn)As on a single sample.     

Implanation de sélénium dans le Ga1?xAlxAs (Implanation of selenium into Ga1?xAlxAs

Par implantation d'ions de sélénium, de fines couches de type n sont obtenues dans le Ga0.71 Al0.29As. Pour les faibles doses, I'activité électrique est proche de 100%, et I'effet de l'implantation est comparable pour le GaAs et le Ga1?x Alx As. Les mêmes resultats sont obtenus en utilisant du Si3N4 ou de l'AIN comme film de protection. By implantation of selenium ions, thin n-type layers are obtained in Ga0.71Al0.29As. For small doses, the electrical activity is close to 100%. and the effect of the implantation is comparable for GaAs and Ga1?x AlxAs. The same results are obtained when using Si3N4 or AlN as a protective film.     

Fe/(Ga,Mn)As异质结的界面结构和磁性质

Fe/（Ga,Mn）As heterostructures were fabricated by all molecular-beam epitaxy.Double-crystal X-ray diffraction and high-resolution cross-sectional transmission electron micrographs show that the Fe layer has a well ordered crystal orientation and an abrupt interface.The different magnetic behavior between the Fe layer and（Ga, Mn）As layer is observed by superconducting quantum interference device magnetometry.X-ray photoelectron spectroscopy measurements indicate no Fe₂As and Fe-Ga-As compounds,i.e.,no dead magnetic layer at the interface, which strongly affects the magnetic proximity and the polarization of the Mn ion in a thin（Ga,Mn）As region near the interface of the Fe/（Ga,Mn）As heterostructure.     

Realization of n-channel and p-channel high-mobility (Al,GA)As/GaAs heterostructure insulating gate FET's on a planar wafer surface

Self-aligned gate by ion implantation n-channel and p-channel high-mobility (Al,Ga)As/GaAs heterostructure insulated-gate field-effect transistors (HIGFET's) have been fabricated on the same planar wafer surface for the first time. Enhancement-mode n-channel (Al,Ga)As/GaAs HIGFET's have demonstrated extrinsic transconductances of 218 mS/mm at room temperature and 385 mS/mm at 77 K. Enhancement-mode p-channel (Al,Ga)As/GaAs HIGFET's have demonstrated extrinsic transconductances of 28 mS/mm at room temperature and 59 mS/mm at 77 K. There are the highest transconductance values ever reported on a p-channel FET device.     

Tunneling Anisotropic Magnetoresistance-Based Devices

The paper demonstrates the operation of several devices based on tunneling anisotropic magnetoresistance. This effect, which originates from the interplay between the magnetic and transport properties in magnetic materials with strong spin-orbit coupling such as the ferromagnetic semiconductor (Ga,Mn)As, leads to a dependence of the tunneling resistance of devices with respect to the direction of the magnetization in the (Ga,Mn)As layer. We show that such devices can be operated as either information storage elements or sensors. It was also demonstrated that they can be used in either volatile or nonvolatile mode and that they provide either two-state or multiple state devices in either of these modes. Lastly, we present experimental evidence that they can be coupled to traditional ferromagnetic materials to still further enhance the variety of possible device functionalities     

(In,Ga)As/InP n-p-n heterojunction bipolar transistors grown by liquid phase epitaxy with high DC current gain

Experimental results on heterojunction bipolar transistors made in liquid phase epitaxial (In,Ga)As and InP layers on InP substrates are described. The (In,Ga)As base layer was doped with manganese during growth and contacts were made to it by beryllium ion implantation. The maximum measured dc current gain β of these devices was in excess of 500. These devices also demonstrate for the first time in an InP-based system, the inverted emitter-down heterojunction transistor structure with a base contact, which yields a minimized collector-base junction area and should significantly improve high-frequency performance.     

Ferromagnetic Properties of Five-Period InGaMnAs/GaAs Quantum Well Structure

The effect of Mn was investigated in a synthesized multilayer system made up of five layers of InMnGaAs/GaAs quantum well (QW) grown on semi-insulating (100)-oriented substrates prepared by low-temperature molecular beam epitaxy. Magnetic moment measurements on a superconducting quantum interference device magnetometer revealed the presence of ferromagnetism with a Curie temperature above room temperature in a five-layer InGaMnAs/GaAs QW structure in a GaAs matrix. X-ray diffraction and secondary ion mass spectroscopy measurements powerfully confirmed the second phase founding of ferromagnetic GaMn and MnAs clusters. The ferromagnetism existing in five layers of InMnGaAs/GaAs QW is not intrinsic, but extrinsic due to the presence of Mn dopant clusters such as GaMn and MnAs clusters.     

Formation of heavily doped n-type layers in GaAs by multiple ion implantation

N-type layers in GaAs with high free electron concentrations have been produced by multiple implantation of Ga, As, or P with dopant species such as Se, Si, or Ge. The implants that have been investigated include Si, Si + P, Ge, Ge + As, Se, and Se + Ga. The multiple implants Si + P, Ge + As, and Se + Ga gave higher peak carrier concentrations, especially at lower anneal temperatures, than did the respective single implants Si, Ge, and Se. In fact, Ge when implanted alone produced a p-type layer while the Ge + As multiple implant produced an n-type layer. Multiple implants with Si and Ge as dopants showed significant thermal diffusion during the anneal. Multiple implants of Ga with Se, on the other hand, resulted in reduced thermal diffusion in comparison with single Se implants.     

Ion-implanted In0.53Ga0.47As/In0.52Al0.48As lateral PNP transistors

Lateral PNP transistors have been realized for the first time in the (In,Ga)As/(In,Al)As heterostructure material system. Be ion implantation has been used to form the emitter and collector junctions. A current gain of 3.8 is obtained up to 200 µA of collector current for devices with a 1.5 µm electrical base width. A hole diffusion length of 2 µm in the (In,Ga)As is estimated.     

Ion-Implanted Impurity Profiles in Ge Substrates and Amorphous Layer Thickness Formed by Ion Implantation

We evaluated profiles of B, P, As, and Si implanted in Ge substrates by secondary ion mass spectrometry, analyzed the profile data using a quasi-crystal Lindhard–Scharff–Schiott (QCLSS) theory, tuned its parameters, and established a corresponding database based on a tail function. We also predicted Ge, Sb, Ga, In, and Xe profiles in Ge substrates by using the QCLSS theory and also established a corresponding database. We further evaluated the thickness of the amorphous layers formed by ion implantation by transmission electron microscopy and reproduced it in a model by tuning a corresponding parameter of the through dose. Using a profile parameter database and this through dose, we can predict ion implantation profiles and related amorphous layer thicknesses in Ge substrates over a wide range of ion implantation conditions.      

Ion implantation damage in GaAs: A TEM study of the variation with ion species and stoichiometry

GaAs samples have been implanted with a dose of 2 × 10¹⁴ cm^?2 of each ion in the following combinations: Ga, As, Ga + As, Se, Ga + Se and As + Se. Implantation was at 200°C, and post implantation annealing at 700°C. Subsequent examination by transmission electron microscopy (TEM) showed clear and reproducible differences in the dislocation loop size and density, depending on the ion species implanted. The simplest results were obtained with the single implants, particularly Ga and As. These observed variations could be explained in terms of point defect populations, and hence rates of annealing at a given anneal temperature, being affected significantly by the stoichiometric effect of the implant. These simpler aspects were also seen to be incorporated in the more complex “dual” implants.     

基于GaAs的新型稀磁半导体材料(Ga,Mn)As

介绍了一种基于 Ga As的新型稀磁半导体材料 ( Ga,Mn) As,包括 ( Ga,Mn) As的制备方法、结构特性、磁性质及磁输运性质。最后 ,展望了 ( Ga,Mn) As的应用前景     

Ferromagnetism and anomalous transport in GaAs doped by implantation of Mn and Mg ions

GaAs layers doped by implantation of Mn and Mg ions to increase the hole concentration were synthesized and studied. Measurements using a SQUID magnetometer showed that there is ferromagnetism at temperatures as high as 400 K, which is related to the formation of the MnAs and Mn _y Ga_{1 ? y} clusters as a result of high-temperature annealing, in addition to the formation of the Ga_{1 ? x} Mn _x As alloy. The anomalous Hall effect was observed at temperatures in the range from 4.2 to 200 K. As temperature was increased starting with 4.2 K, the negative magnetoresistance with extremely large magnitude transformed into a giant positive magnetoresistance at T ≈ 35 K.     

Proton-implanted shallow-ridge quantum-cascade laser

We demonstrate a shallow-ridge quantum-cascade laser (QCL) with performance comparable or better than that of deep-ridge QCLs fabricated from the same wafer. The shallow-ridge QCL emits at /spl ap/4 /spl mu/m with a 4.6-4.8 kA/cm/sup 2/ threshold current density at room temperature which is similar to the deep-ridge QCL. At the same time the shallow-ridge QCL shows a better temperature stability, T/sub 0/=160 K, than the deep-ridge QCL, with T/sub 0/=120 K. The increase in the characteristic temperature of the shallow-ridge laser compared to the deep-ridge laser results from the improved heat dissipation out of the laser ridge through the lateral heat flow. Lateral spreading of the injection current-usually a drawback of shallow-ridge lasers-is suppressed by proton implantation into the strain-compensated InGaAs-AlAs active region layers on either side of the ridge. In contrast to the case of In/sub 0.53/Ga/sub 0.47/As layers and of In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As heterostructures lattice matched to InP, the proton implantation of strain-compensated In/sub 0.73/Ga/sub 0.27/As-AlAs heterostructure on InP creates deep (180 meV) carrier traps, resulting in this material being electrically insulating even at room temperature.     

Properties of self-organized SiGe nanostructures formed by ion implantation

Properties of self-organized SiGe quantum dots formed for the first time by ion implantation of Ge ions into Si are studied using Auger electron spectroscopy, atomic-force microscopy, and scanning electron microscopy. It is found that a spatially correlated distribution of Ge atoms is observed in Si layers implanted with Ge ions after subsequent annealing of these layers. As a result, nanometer-sized regions enriched with germanium are formed; germanium concentration in these regions is 10–12% higher than that in the surrounding matrix of the SiGe solid solution. Optical properties of the layers with SiGe quantum dots were studied using Raman scattering and photoluminescence. An intense photoluminescence peak is observed in the wavelength region of 1.54–1.58 μm at room temperature. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 38, No. 5, 2004, pp. 593–597. Original Russian Text Copyright ? 2004 by Parkhomenko, Belogorokhov, Gerasimenko, Irzhak, Lisachenko.     

Silicon LEDs with room-temperature dislocation-related luminescence, fabricated by erbium ion implantation and chemical-vapor deposition of polycrystalline silicon layers heavily doped with boron and phosphorus

Light-emitting diodes (LEDs) have been fabricated in which optically active centers are formed by implantation of erbium ions into silicon and subsequent high-temperature annealing in an oxidizing atmosphere and the p-n junction and the ohmic contact are formed by chemical vapor deposition of polycrystalline silicon layers doped with boron and phosphorus, respectively. The luminescent properties of the LEDs have been studied. Use of polycrystalline layers makes it possible to eliminate the losses in the bulk of the light-emitting Si:Er layer. These losses are inevitable if the conventional ion implantation and diffusion methods are employed. At 80 K, the variation of electroluminescence spectra in the spectral range of the dislocation-related luminescence with the drive current is well described if the spectrum is decomposed into three Gaussian components whose peak positions and widths are current-independent and amplitudes linearly increase with the current. At 300 K, a single peak is observed in the spectral range of the dislocation-related luminescence at ～1.6 μm.