Conventional Rapid Thermal Processing Research Articles

Rapid chemical vapor deposition of graphitic carbon nitride films

Rapid chemical vapor deposition of continuous thin films of graphitic carbon nitride (g-CN) material with stoichiometry close to its ideal g-C3N4 form on silicon and glass substrates is demonstrated. It allows fabrication of 200–1200 nm g-CN films within 3–5 min at 500–620 °C instead of earlier reported few hours. SEM, XRD and EDX analysis of the films revealed their grain-layered structure and high crystallinity. The film thickness and crystallinity were found to have maximum at synthesis temperature of 575–600 °C. Energy band gap of the material changes with the deposition temperature too and reaches its maximum of 2.98 eV at 600 °C. Dependence of the film properties on the deposition temperature evidences competition between the rates of synthesis and evaporation of the synthesized material. The developed approach is energy budget saving and could be scaled up using conventional rapid thermal processing equipment opening a way to practical g-CN based electronics and optoelectronics.

A novel strategy for the fabrication of high-performance nanostructured Ce-Fe-B magnetic materials via electron-beam exposure

Ce2Fe14B compound has a great potential to serve as a novel permanent magnet alternative thanks to the abundant and inexpensive rare-earth element (cerium), while its low magnetocrystalline anisotropy and energy product severely restrict its applications. In this work, a novel strategy combining melt-spinning and electron-beam exposure (EBE) aiming for fabricating high-performance Ce-Fe-B magnetic materials is reported to solve the above-mentioned problem. Remarkably, this strategy facilitates developing a suitable grain boundary configuration without using any additional heavy rare-earth element. Under the optimal EBE condition, the maximum energy product ((BH)max) of pure Ce-Fe-B alloy is 6.5 MGOe, about four times higher than that obtained after conventional rapid thermal processing method for the same precursor. The enhanced intergranular magnetostatic coupling effect in the EBE sample is validated by mapping the first-order-reversal-curve (FORC) diagrams. The in-situ observation of magnetic domain wall motion for Ce-Fe-B alloy using Lorentz transmission electron microscopy reveals that the boundary layers are very effective in pinning the motion of domain walls, leading to the increased coercivity under EBE, and this pinning effect is further verified by micromagnetic simulations. Our results suggest that CeFeB materials using EBE could be a promising candidate after further processing, which could fill the performance “gap” between hexaferrite and Nd-Fe-B-based magnets.

A Novel Strategy for the Fabrication of High-Performance Nanostructured Ce-Fe-B Magnetic Materials via Electron-Beam Exposure

Low magnetocrystalline anisotropy and energy product of the Ce 2 Fe 14 B compound severely restrict its application in permanent magnet applications, in spite of its potential as a novel permanent magnet alternative based on a widely abundant and inexpensive rare-earth (Cerium). A novel strategy combining melt-spinning and electron-beam exposure (EBE) aiming for fabricating high-performance Ce-Fe-B magnet is reported in this work. Remarkably, this strategy facilitates developing a suitable grain boundary configuration without using any additional heavy rare-earth element. Under the optimal EBE condition, the maximum energy product ( (BH) max ) of pure Ce-Fe-B alloy is 6.5 MGOe, about four times higher than that obtained after conventional rapid thermal process (RTP) method for the same precursor . This suggest that CeFeB materials using EBE could be a promising candidate after further processing, such as hot deforming or sintereing, to fill the performance “gap” between hexaferrite and Nd-Fe-B-based magnets. The enhanced intergranular magnetostatic coupling effect in EBE sample is further validated by mapping FORC diagrams. The in-situ observation of magnetic domain wall motion for Ce-Fe-B alloy using Lorentz transmission electron microscopy reveals that the boundary layers are very effective in pinning the motion of domain walls, leading to the increased coercivity under EBE. Micromagnetic simulations are also performed to verify the pinning effect of grain boundary configuration in the Ce-Fe-B system.

Observer-based temperature control of an LED heated silicon wafer

The key issue in semiconductor rapid thermal processing (RTP), where silicon wafers are heated to desired temperatures, is to ensure uniform wafer temperature profiles. This in turn guarantees that the manufactured integrated circuits (IC), which are spread over the entire wafer, can be processed in an equal measure. In this study, a mathematical model capturing the physical behavior of the heating-up process is presented. It relies mainly on the well-known partial differential heat equation, governing the temperature distribution in a given region of a given material. Based on this, an observer as also a control law is proposed, which in combination turned out to be superior to conventional RTP strategies. The approach is validated in practice at a real world heating system with different wafer types.

Density improvement of Si quantum dots embedded in Si-rich silicon nitride films by light-filtering rapid thermal processing

Si-rich silicon nitride (SRSN) (SiNx, x ≈ 0.49) films were deposited on Si (100) and quartz substrates by magnetron co-sputtering. For comparison, two sets of identical samples were then treated in a nitrogen atmosphere by conventional rapid thermal processing (CRTP) and light-filtering rapid thermal processing (LRTP) at temperature in a range of 950–1,100 °C, respectively. Raman spectroscopy, grazing incident X-ray diffraction, transmission electron microscope, photoluminescence (PL) and Hall measurements were used to analyze the structure, luminescence, and conductivity of the films. Experimental results show that the samples treated with LRTP posses higher dot number density, crystalline volume fraction, PL intensity and conductivity than the CRTP samples. The quantum effects in rapid thermal processing have a negative influence on the formation and density of Si quantum dots (QDs) in SRSN films. The present work opens new strategy for the formation of high density Si QDs embedded in SRSN films.

Ultrathin Ni(Pt)Si Film Formation Induced by Laser Annealing

A highly sensitive dependence of laser annealing process on the as-deposited Ni(Pt) film thickness is observed and investigated for the first time. It is revealed that a much larger thermal budget is required for the thinner as-deposited Ni(Pt) film to form a high quality Ni(Pt)Si film, which is very different from the conventional rapid thermal process. Micro-Raman spectroscopy and X-ray photoelectron spectroscopy both demonstrate that the same thermal budget can only induce a lower silicidation temperature for the thinner Ni(Pt) film. The lower silicidation temperature is attributed to the lower optical absorptivity of the thinner Ni(Pt) film.

Thin Film Polycrystalline β-FeSi2/Si Heterojunction Solar Cells via Al Incorporation and Rapid Thermal Processing

Thin film solar cells of β-FeSi2(Al)/Si heterojunctions were fabricated via Al incorporation and rapid thermal processing (RTP). The Al-incorporated FeSi2 films were polycrystalline, orthorhombic and semi-conducting. Photo-voltaic characterisation showed that device prepared with Al interlayer added between Al-doped FeSi2 film and Si exhibited short-circuit current and open-circuit voltage improvement over device without interlayer. These can be correlated to surface passivation of Si by interfacial structure and reduced dark current with Al interlayer. This alternative fabrication method via Al incorporation to β-FeSi2 films using conventional magnetron sputtering and RTP enhances the viability of β-FeSi2 for photovoltaic application.

Growth of CVD graphene on copper by rapid thermal processing

ABSTRACTWe have investigated the fabrication of graphene by chemical vapor deposition using a conventional rapid thermal processing system with infrared heating. Graphene films were grown on the pretreated copper foil in RTP at 935-960°C at pressure of 6~7 mbar. The grown films were characterized by scanning electron microscope and Raman spectroscopy to investigate morphology of graphene. The growth of graphene was initiated by small flakes that spread rapidly covering the whole copper surface as a single-layer film in ~20 seconds. Room temperature mobility and sheet resistance extracted by transfer-length method (TLM) for the graphene film transferred onto the SiO2/Si substrate were around 1,800 cm2/Vs and 260 Ω/ð with the gate voltage, respectively.

Laser annealed HfxZr1−xO2 high-k dielectric: Impact on morphology, microstructure, and electrical properties

The impact of microsecond laser annealing at 1325°C on physical and electrical characteristics of HfxZr1−xO2 is compared to films annealed at 1000°C for 5s by a conventional rapid thermal process (RTP). Atomic force microscopy analysis shows that laser annealed HfxZr1−xO2 is smoother and void free, while RTP annealed HfxZr1−xO2 exhibits void formation and is rough. The x-ray diffraction analysis revealed higher degree of tetragonality on laser annealed film, particularly for Hf0.5Zr0.5O2 and ZrO2. Furthermore, laser annealed HfxZr1−xO2 devices have good electrical properties (well behaved CV, low gate leakage, and good mobility) whereas RTP annealed devices are not functional.

Formation of germanium shallow junction by flash annealing

We have investigated flash-lamp annealing (FLA) of germanium wafers doped with phosphorous and boron introduced in the crystal by ion implantation. Annealing was performed by using pre-heating at 400–450°C in a conventional rapid thermal processing (RTP) unit and a fast (3–20ms) FLA annealing at 800°C or 900°C. Diffusion of P is suppressed during the 800°C–20ms FLA annealing, while concentration-enhanced diffusion occurs upon 900°C FLA anneals. Importantly, in both cases P activation seems to be enhanced by the FLA process. However, junction stability following the FLA process and possible deactivation are a concern.In contrast, the FLA process applied to B-doped pre-amorphized Ge layers does not show advantages as compared to a RTP conventional annealing combined with a solid phase epitaxial regrowth, in terms of B activation level.

The effect of preamorphization energy on ultrashallow junction formation following ultrahigh-temperature annealing of ion-implanted silicon

High-power arc lamp design has enabled ultrahigh-temperature (UHT) annealing as an alternative to conventional rapid thermal processing (RTP) for ultrashallow junction formation. The time duration of the UHT annealing technique is significantly reduced from those obtained through conventional RTP. This difference in time may offer the ability to maintain a highly activated ultrashallow junction without being subjected to transient enhanced diffusion (TED), which is typically observed during postimplant thermal processing. In this study, two 200-mm (100) n-type Czochralski-grown Si wafers were preamorphized with either a 48- or a 5-keV Ge+ implant to 5×1014cm2, and subsequently implanted with 3-keV BF2+ molecular ions to 6×1014cm2. The wafers were sectioned and annealed under various conditions in order to investigate the effects of the UHT annealing technique on the resulting junction characteristics. The main point of the paper is to show that the UHT annealing technique is capable of producing a highly activated p-type source∕drain extension without being subjected to TED only when the preamorphization implant is sufficiently deep.

Low temperature preparation of piezoelectric thin films by ultraviolet-assisted rapid thermal processing

Ca- and La-modified lead titanate ferroelectric thin films were prepared by a sol–gel method from photosensitive solutions and with an ultraviolet (UV)-assisted rapid thermal processor, including an arrangement of excimer lamps. The diol-based route was used in the preparation of the precursor solutions, whose UV absorption and thermal decomposition were determined. Multiple deposition and crystallization steps of the deposited solution were used to promote preferential orientation. A comparative ferro and piezoelectric study of films prepared by conventional rapid thermal processing at 650°C and films prepared at 550°C with an intermediate step of UV irradiation at 250°C will be presented to assess the value of these films for their use in integrated piezoelectric sensors and microelectromechanical systems. Piezoelectric d 33 and e 31 coefficients were determined by double-beam laser interferometry and by the direct piezoelectric effect on cantilevers, respectively. The effect of the substrate and processing method on the preferential crystalline orientation of the films and the corresponding piezoelectric properties will be reported. The role of the composition will also be discussed.

Development of RTP for industrial solar cell processing

Rapid Thermal Processing (RTP), originally developed for processing microelectronic devices has been investigated in the recent decade for its potential in the production of Si solar cells. This paper will discuss the use of RTP for industrial Si solar cells with screen-printed contacts. Printed metal contacts require adapted emitters when good fill factors should be achieved. Multi-crystalline Si substrates require to adapt the temperature ramps of RTP to avoid minority carrier lifetime degradation from activated defect centres. Finally, industrial processing requires high throughput that cannot be achieved with conventional RTP equipment. This paper will present an advanced selective emitter process and a recently developed continuous RTP system that meet for the first time the requirements to make RTP compatible with industrial solar cell processing. The limits of industrial RTP solar cell processing will be discussed.

Oxidation and roughening of silicon during annealing in a rapid thermal processing chamber

Silicon wafers were annealed at 1100 °C in nitrogen flowing ambient, using a conventional rapid thermal processing system operating at atmospheric pressure. Subsequently, silicon oxidation and the resulting surface morphology following chemical etching of the oxide film were studied. According to atomic force microscopy analysis, a significant amount of roughening occurs on the silicon surface after the high temperature anneal in nitrogen. However, by adding 10% oxygen to the nitrogen ambient, the average surface roughness was reduced by a factor of ∼3. Ellipsometry measurements were performed to study silicon oxidation following annealing. It was shown that the ellipsometric characteristics of the surface after removal of the oxide layers can be correlated to generation of surface roughness. A close agreement between the experimental results and theoretical calculations was obtained with respect to the oxidation induced surface roughening.

Low temperature shallow junction formation using vacuum ultraviolet photons during rapid thermal processing

In this letter, we have demonstrated phosphorus diffusion into silicon at a temperature of 700 °C using dual spectral source rapid thermal processing (RTP). The optical energy of vacuum ultraviolet irradiation in conjunction with tungsten halogen lamps (light source used in conventional RTP) is responsible for diffusion at low temperatures. Shallow junctions with high surface concentration were formed and no significant degradation in the bulk minority carrier lifetimes was observed. A qualitative explanation for the observed results is offered based on the role of photoeffects in RTP.

Rapid thermal processing uniformity using multivariable control of a circularly symmetric 3 zone lamp

Defect introduction and process variations commonly observed in conventional rapid thermal processing (RTP) systems have impeded its widespread acceptance in manufacturing. The main problem lies in the conventional approach of using scalar control, where optimal steady-state temperature uniformity at one set of processing conditions is used to fix the hardware geometry, leaving only one input variable-the lamp power-for control. It is demonstrated that this control is inadequate, since the radiative and convective heat exchange at the wafer are functions of the processing conditions, and that the resultant nonuniformity can be corrected by dynamic control of the spatial optical flux profile. Such control is demonstrated through two key innovations: a lamp system in which tungsten-halogen point sources are configured in three concentric rings to provide a circularly symmetric flux profile, and multivariable control whereby each of the three rings is independently and dynamically controlled to provide for control over the spatial flux profile. This approach offers good temperature uniformity over transients, thus improving reliability of individual processes.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>