Capless Rapid Thermal Annealing Research Articles

High-temperature stable Ir-Al/n-GaAs Schottky diodes

We report on the excellent thermal stability of Ir-Al/GaAs Schottky contact based on sequentially evaporated Ir-Al bimetallic system with an aluminum concentration of approximately 25 at. %. The contact system is stable up to 950 °C for 10 s (capless rapid thermal annealing) and exhibits an enhancement of the barrier height with the temperature of annealing.

Carbon implanted into gallium arsenide

The annealing behavior of carbon implanted into GaAs at high doses has been studied. Implantations were done at room temperature and 200 °C. The implanted dopant atoms were activated by capless rapid thermal annealing. The effect of dual implantation with gallium atoms was also investigated. The activation efficiency of implanted carbon is typically low, but can be improved by implanting into a heated substrate or by coimplantation of gallium. The combination of dual implantation and implantation into a heated substrate does not lead to any improvement over the effect of a single, hot implant. It is also shown that the arsenic vacancy concentration determines the activation of the implanted carbon. The results lead to the conclusion that carbon is an amphoteric p-type dopant in GaAs.

Properties of WN x /GaAs Schottky contacts prepared by ion implantation of nitrogen

The formation of WN x /GaAs Schottky contacts using selective ion implantation of nitrogen into the sputtered tungsten film has been demonstrated. The contacts were characterized by Auger electron spectroscopy and current-voltage measurements. The composition of WN x films and the thermal stability of WN x /GaAs contacts were investigated. Good thermal stability of WN x /GaAs contacts compared with a W/GaAs contact was observed after capless rapid thermal annealing at 450, 800 and 950°C for 10 s.

Capless rapid thermal annealing of GaAs using a graphite susceptor

The results of experiments performed to evaluate the use of a commercially available rapid thermal annealer (RTA) with a graphite susceptor for capless rapid thermal annealing to activate implants in GaAs are reported. The interior of the susceptor was easily charged with As by annealing a sacrificial GaAs wafer. Wafers annealed face up in the charged susceptor showed no evidence of surface degradation (due to preferential loss of As) and no decrease in implant activation (peak doping) when compared to dielectric (SiO/sub 2/) capped anneals. Over 50 wafers have been annealed without recharging the susceptor. In addition, slip on 3-in wafers was almost completely eliminated due to the reduction of radial temperature gradients. It is concluded that capless RTA in a commercially available graphite susceptor appears to be a viable annealing technique for activating implants in GaAs and related III-V materials and is suitable for a production environment.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Elimination of slip lines in capless rapid thermal annealing of GaAs

A new rapid thermal annealing (RTA) procedure has been developed that eliminates the problem of crystallographic slip in 2 in, ion-implanted GaAs wafers. This annealing arrangement is easy to implement and is reliable. A precision machined graphite support structure and guard ring are used to insure uniform cooling across the entire wafer, thus eliminating slip line production. Characteristics of silicon ion implants have been determined using van der Pauw Hall, Polaron C–V profiling, and eddy current resistivity measurements. Characterization showed excellent dopant activation and uniformity can be achieved using this new technique. Low-temperature photoluminescence measurements were performed on samples annealed with and without graphite in the system, and no detectable difference in surface carbon contamination was found.

Capless Rapid Thermal Annealing of GaAs Implanted with Si+ Using an Enhanced Overpressure Proximity Method

A new approach for capless rapid thermal annealing of ion implanted III–V semiconductors, the enhanced overpressure proximity (EOP) technique, has been developed and applied to implanted with Si+. The EOP method relies on the use of an Sn‐coated wafer to provide a greater localized arsenic overpressure than can be achieved by the conventional proximity method which utilizes a wafer. Implant doses of have been investigated, yielding activations as high as 60 and 35%, respectively. Under the appropriate annealing conditions photoluminescence data confirm that EOP‐RTA reduces the concentration of Si on As sites when compared with the conventional proximity approach. In addition, this technique permits an increased latitude in annealing times and temperatures that can be used without degradation of the wafer surface. The EOP approach can be easily extended for capless rapid thermal annealing of other implanted dopants in as well as other III–V compounds such as and .

Rapid thermal annealing of Be+-implanted In0.52Al0.48As

A capless rapid thermal annealing method has been used to activate Be atoms implanted into n-In0.52Al0.48As. The dependence of electrical activation upon various annealing conditions has been investigated. Annealing at 800–850 °C for 2–3 s yields high electrical activation. Activation efficiencies of 76% and 49% are achieved on InAlAs layers with implant doses of 2×1013 and 2×1014 cm−2, respectively. The lowest sheet resistivity obtained was 2.2 kΩ/⧠ at an implant dose of 1.5×1014 cm−2. Electrical characteristics of Be-implanted p+-n InAlAs diodes are also presented. The forward diode currents were dominated by recombination current components at room temperature. The reverse leakage currents increase with increasing implant doses. Diodes annealed at 800 °C for 2–3 s have the lowest reverse leakage currents.

Improved activation of Mg+ and As+ dual implants in GaAs by capless rapid thermal annealing

The activation of high dose Mg+ implants (1×1015 cm−2, 100 keV) in GaAs using capless rapid thermal annealing has been improved by the co-implantation of As+. This technique reduces the outdiffusion of the implanted Mg, which can adversely affect the activation of shallow, high dose implants. Compared with an activation of 18% for an implant of Mg+ only, the co-implantation of As+ has increased the activation to as much as 61% with concomitant sheet resistance of 136 Ω/⧠. The placement of the As+ implant with respect to the position of the Mg+ profile has been determined to play a role in the activation efficiency. This technique has been applied to the formation of thick p+ regions with high surface carrier concentrations, which has important applications in device fabrication for reduction of contact resistances.

Formation of Device Quality p-Type Layers in GaAs using Co-Implantation of Mg+ and As+ and Capless Rapid Thermal Annealing

ABSTRACTLow (1 × 1014 cm-2) and high (1 × 1015 cm-2) dose implants of Mg+ in undoped GaAs have been activated using the enhanced overpressure proximity (EOP) rapid thermal annealing (RTA) technique. Hall measurements have yielded electrical activation efficiencies as high as 86% and 38% for low and high dose implants, respectively. For high dose implants, the outdiffusion of Mg+ from the wafer surface reduces the activation efficiency. A dramatic improvement in the activation for high dose Mg+ (1×1015 cm−-2, 100 keV) implants has been obtained by the co-implantation of As+. Compared with an activation of 18% for an implant of Mg+ only, the co-implantation of As has increased the activation to as much as 61% with a concomitant sheet resistance of 136 Ω/□. The placement of the As+ implant with respect to the position of the Mg+ profile has been found to play a significant role in the activation efficiency. This co-implantation technique in conjunction with the EOP-RTA method has been applied to the formation of thick p+ regions with high surface carrier concentrations, which has important applications in device fabrication for reducing contact resistance.

Formation of p-type GaAs layers using Mg+ implantation and capless rapid thermal annealing

The enhanced overpressure proximity technique has been applied to the formation of p-GaAs layers using capless rapid thermal annealing of GaAs implanted with Mg+. Carrier concentrations in excess of 1×1019 cm−3 and excellent hole mobilities have been achieved without a dielectric encapsulant using this annealing method. Implants were performed at 200 or 320 keV with doses of 1×1014 cm−2 or 1×1015 cm−2. Hall measurements have yielded electrical activations as high as 86% and 38% for the low and high dose samples, respectively. Capacitance-voltage measurements on implanted samples indicate that this annealing technique can be used to control the doping profile for use in the fabrication of devices requiring p-n junctions.

Capless rapid thermal annealing of GaAs using an enhanced overpressure proximity technique

A new approach for capless rapid thermal annealing of ion implanted III-V semiconductors, the enhanced overpressure proximity (EOP) technique, has been developed and applied to GaAs implanted with Si+. The EOP method relies on the use of a Sn-coated GaAs wafer to provide a localized arsenic overpressure around the ion implanted wafer during the annealing cycle. The arsenic overpressure resulting from this arrangement is greater than the overpressure obtained with the conventional proximity method, which utilizes an untreated GaAs wafer as an arsenic source. This new annealing technique has yielded higher electrical activation and electron mobilities in GaAs than the conventional proximity method as well as an increased latitude in annealing times and temperatures. The EOP approach can be easily extended for capless rapid thermal annealing of other III-V compounds such as InP and InGaAs.