The physics and technology of a relatively new, short‐time, thermal processing technique, namely rapid isothermal processing (RIP), based on incoherent sources of light for the fabrication of semiconductor devices and circuits, are reviewed in this paper. Low‐cost, minimum overall thermal budget, low‐power consumption, and high throughput are some of the attractive features of RIP. The discussion of RIP, in the context of other thermal processes, history, operating principles, different types of RIP systems, various applications of RIP using single processing steps, and novel applications of RIP, including in situ processing and multistep processing, is described in detail. Current trends are in the direction of RIP‐dominated silicon integrated circuit fabrication technology that can lead to the development of the most advanced three‐dimensional integrated circuits suitable for applications such as parallel processing and radiation hardening. RIP is not only a superior alternative to furnace processing, but it is also the only way to perform certain crucial steps in the processing of compound semiconductor devices such as high‐mobility transistors, resonant tunneling devices, and high‐efficiency solar cells. Development of more accurate temperature measurement techniques and theoretical studies of heat transfer and other fundamental processes are needed. Dedicated equipment designed for a specific task coupled with in situ processing capabilities will dominate the future direction of RIP.

Rapid isothermal processing

Shallow p/sup +/-n and n/sup +/-p junctions were formed in germanium preamorphized Si substrates. Germanium implantation was carried out over the energy range of 50-125 keV and at doses from 3*10/sup 14/ to 1*10/sup 15/ cm/sup -2/. p/sup +/-n junctions were formed by 10-keV boron implantation at a dose of 1*10/sup 15/ cm/sup -2/. Arsenic was implanted at 50 keV at a dose of 5*10/sup 15/ cm/sup -2/ to form the n/sup +/-p junctions. Rapid thermal annealing was used for dopant activation and damage removal. Ge, B, and As distribution profiles were measured by secondary ion mass spectroscopy. Rutherford backscattering spectrometry was used to study the dependence of the amorphous layer formation on the energy and dose of germanium ion implantation. Cross-sectional transmission electron microscopy was used to study the residual defects formed due to preamorphization. Complete elimination of the residual end-of-range damage was achieved in samples preamorphized by 50-keV/1*10/sup 15/ cm/sup -2/ germanium implantation. Areal and peripheral leakage current densities of the junctions were studied as a function of germanium implantation parameters. The results show that high-quality p/sup +/-n and n/sup +/-p junctions can be formed in germanium preamorphized substrates if the preamorphization conditions are optimized. >

Optimization of the germanium preamorphization conditions for shallow-junction formation

RTA studies of B, BF 2 and As implantations in silicon are reviewed. The optical coupling properties of the wafer are considered as a motive for obtaining accurate temperature assessment. Optical pyrometer techniques with feedback control are now commonly used. Enhanced diffusion of boron is widely reported for the channel tail in the several second time frame at ∼1050°C. Boron diffusion in preamorphized and crystalline silicon are compared, and dopant interactions (gettering) with residual disorder located just beyond the amorphous/crystalline (α/c) interface are discussed. The removal of residual α/c disorder from a 5 × 10 15 As/cm 2, 100 keV implant is shown to occur with ∼5.0 eV energy, while a “normal” concentration enhanced diffusion with ∼4.0 eV activation energy is obtained including data in the several second (RTA) time frames. Shallower defect free arsenic junctions are made using high temperature-short time cycles, rather than longer times at lower temperatures. The arsenic diffusion issues are discussed.

A review of rapid thermal annealing (RTA) of B, BF 2 and As ions implanted into silicon

Pre-amorphization damage in ion-implanted silicon

Annealing of ion implantation damage (in the form of amorphous layers and/or the layers containing only dislocation loops) in silicon and gallium arsenide has been studied by electron microscopy techniques and the effects on dopant distribution have been investigated by Rutherford backscattering and secondary ion mass spectrometry techniques. The annealing of amorphous layers occurs by solid‐phase‐epitaxial growth and that of dislocation loops involves primarily loop coalescence as a result of conservative climb and glide processes. The annealing of isolated loops occurs primarily by a bulk diffusion process. Almost a ‘‘complete’’ annealing of displacement damage is possible for shallow implants provided loop coalescence does not lead to the formation of a crossgrid of dislocations. For deep implants, the free surface cannot provide an effective sink for defects as in the case of shallow implants. Dopant profiles can be controlled to less than 500 A in layers having good electrical properties. The enhanced diffusion of dopants which is observed is probably due to entrapment of point defects in the annealing regions.

Rapid thermal annealing of ion‐implanted semiconductors

Annealing of ion implantation damage and concomitant electrical activation of dopants, depth profiles, and lattice location of dopants have been studied in arsenic and boron‐implanted specimens after rapid thermal annealing. A ‘‘complete’’ annealing of displacement damage with full electrical activation of dopants and profile broadening less than 100 A can be attained for shallow implants whereas some extended defects are retained for deep implants. Mechanisms of rapid thermal annealing and its implications in solid state device fabrication are discussed.

Rapid thermal annealing of arsenic and boron-implanted silicon

Characteristics of rapid thermal and pulsed laser annealing have been investigated in boron fluoride‐ (BF+2 and BF+3) ‐implanted silicon using cross‐section and plan‐view electron microscopy. The amorphous layers recrystallize by the solid‐phase‐epitaxial growth process, while the dislocation loops below the amorphous layers coarsen and evolve into a network of dislocations. The dislocations in this band getter fluorine and fluorine bubbles associated with dislocations are frequently observed. The secondary‐ion mass spectrometry techniques were used to study concomitant boron and fluorine redistributions. The as‐implanted Gaussian boron profile broadens as a function of time and temperature of annealing. However, the fluorine concentration peak is observed to be associated with dislocation band, and the peak grows with increasing time and temperature of annealing. The electrical properties were investigated using van der Pauw measurements. The electrical activation of better than 90% and good Hall mobilit...

J. J. Wortman

Papers

Rapid thermal annealing of arsenic and boron-implanted silicon

Rapid thermal and pulsed laser annealing of boron fluoride‐implanted silicon