XeCl Excimer Laser Annealing Research Articles

Influence of XeCl excimer laser annealing on the ferroelectric nondoped HfO2 formation deposited on a Si(100) substrate

In this research, we have investigated the effect of excimer laser annealing (ELA) on the ferroelectric nondoped HfO2 (FeND-HfO2) formation deposited on a Si(100) substrate. The XeCl (λ: 308 nm) ELA was irradiated as post-deposition annealing (PDA) in the N2 ambient to the 10 nm thick HfO2 deposited by RF-magnetron sputtering without substrate heating. The C–V characteristics of Al/HfO2/p-Si(100) metal/ferroelectrics/Si (MFS) diodes were gradually improved with the energy density of ELS from 170 mJ cm−2 to 270 mJ cm−2 irradiated at 200 Hz for 200 shots although the charge-injection type hysteresis of 0.2–0.3 V remained. The post-metallization annealing (PMA) at 400 °C/5 min in N2/4.9%H2 ambient for Al/HfO2/p-Si(100) MFS diodes markedly improved the C–V characteristics, and negligible hysteresis with ideal flat-band voltage (V FB) was realized. The memory window (MW) of 0.42 V was achieved by the program/erase (P/E) operation with the input pulses of +3 V/100 ms and −8 V/100 ms for the MFS diode with an ELA energy density of 270 mJ cm−2 at 200 Hz for 200 shots followed by the PMA.

Effect of Glass Substrate on the Film Properties of Poly Silicon by Excimer Laser Annealing

This work studies the effect of glass substrate thermal properties on the crystallization behavior and surface topography of polycrystalline silicon (poly-Si) films formed by a XeCl excimer laser annealing of amorphous silicon. Films of 60 nm hydrogenated amorphous silicon (a-Si:H) film were deposited on different glass substrates of varying thermal properties. A 500 nm SiO2 buffer layer was in between the glass and the silicon film. The silicon was crystallized by a XeCl excimer laser. The atomic force microscopy (AFM) and in-plane X-ray diffraction (IPXRD) were used to evaluate the surface topography, the surface roughness, and crystalline in-plane orientation of poly-Si, respectively. Grazing incidence X-ray diffraction (GIXRD) was employed to quantify the residual stress in poly-Si film. The film properties of poly-Si exhibit a small relationship with the glass thermal properties. The higher thermal conductivity of glass retards the poly-Si <111> texture and reduced the residual tensile stress. The higher thermal diffusivity of the glass causes a decline in the poly-Si <111> texture, the surface asymmetry and flatness. A light shield introduced between glass and buffer layer in the low-temperature polycrystalline silicon (LTPS) thin-film transistors (TFTs) structures, further weakens the impact of the glass substrate on excimer laser annealing (ELA) poly-Si properties.

Effect of Glass Substrate on the Film Properties of Poly Silicon by Excimer Laser Annealing

This work studies the effect of glass substrate thermal properties on the crystallization behavior and surface topography of polycrystalline silicon (p-Si) films formed by a XeCl excimer laser annealing of amorphous silicon. 60 nm hydrogenated amorphous silicon (a-Si:H) film was deposited on different glass substrates of varying thermal properties. A 300 nm SiO2 buffer layer was in between the glass and the silicon film. The silicon was crystallized by a XeCl excimer laser. The film properties of p-Si exhibit a small relationship with the glass substrate thermal properties. The higher thermal conductivity of glass retards the poly-Si <111> texture and reduced the residual tensile stress. The higher thermal diffusivity of the glass substrate causes a decline in the p-Si <111> texture, the surface asymmetry, and flatness.

Effect of Excimer Laser Annealing on the Performance of Amorphous Indium Gallium Zinc Oxide Thin-Film Transistors

This article reports a method for reducing the contact resistance between amorphous-InGaZnO (a-IGZO) channel and source/drain layer via XeCl excimer laser annealing (ELA) and the device performance of a-IGZO thin-film transistors (TFTs) in terms of laser energy density. The source/drain region in the a-IGZO layer was selectively ELA-treated using a mask, and the resistivity dramatically reduced compared to that of the untreated film (from 10 4 to 10 ―3 Ω cm). Our TFTs had a field-effect mobility of 21.7 cm 2 /V s, an on/off ratio of 1.2 × 10 8 , a threshold voltage of ―0.15 V, and a subthreshold swing of 0.26 V/decade.

Aligned Polycrystalline Silicon Array Thin Film by XeCl Excimer Laser Annealing for AMOLED Displays

Low temperature polycrystalline silicon (LTPS) thin film transistors (TFTs) are demanded to fabricate high performance liquid crystal displays (LCD) and organic light-emitting diode displays (OLED). The mobility of poly-Si TFT can be two orders of magnitude higher than that of amorphous Si (a-Si) TFT. Excimer laser annealing has been studied to be the most promising technology to meet the stringent requirement in high speed operation. The process parameters were identified as a-Si thickness, laser energy density, overlap ratio, annealing atmosphere and pre-clean condition. The a-Si layer of 40-50 nm was deposited by plasma enhanced chemical vapor deposition (PECVD). The XeCl excimer laser was irradiated on the a-Si film at room temperature under N2 or N2/O2 environment. The energy density ranged 250-400 mJ/cm2, and the overlap ratio was 95-99%. The highly aligned poly-Si array thin film could be obtained. The grain size has been about 0.31x0.33 μm2, and the regular arrangement in poly-Si grains was discussed. In addition, the PMOS TFT has been fabricated from the aligned poly-Si array. The mobility was as high as 100 cm2/Vs and the sub-threshold swing was around 0.24 V/dec. The threshold voltage was -1.25 V and the on/off current ratio was about 106.

Pulsed Laser Annealing of Thin Silicon Films

The 30 ns pulsed XeCl excimer laser annealing of silicon films with an average thickness of 2.2 nm formed on quartz substrates is reported. Crystallization occurred at laser energies between 150 and 170 mJ/cm2. Raman scattering spectra revealed the mixed states of small crystalline grains, and nanocrystalline and disordered amorphous regions. The amorphization of the silicon films was observed for laser irradiation above 180 mJ/cm2. Photoluminescence was observed around at approximately 3 and 2 eV from 18 to 130 K for the films annealed at 260 °C for 3 h in 1.3 ×106 Pa H2O vapor after laser irradiation at 170 mJ/cm2.

Epitaxial growth of tin oxide films on (0 0 1) TiO 2 substrates by KrF and XeCl excimer laser annealing

Epitaxial SnO 2 thin films were prepared by excimer laser annealing of amorphous SnO 2 films on a (0 0 1) TiO 2 substrate. The amorphous SnO 2 film was prepared by a metal organic deposition (MOD) using di- n-butylbis (2,4-pentanedionate) tin at 300 °C. When using a KrF excimer laser with fluence of 50 to 150 mJ/cm 2, polycrystalline SnO 2 films were formed on (0 0 1) TiO 2 substrate at 25 °C. At fluences of 200 and 250 mJ/cm 2, (0 0 2) oriented SnO 2 films were obtained. When using a XeCl laser with fluences of 150 and 200 mJ/cm 2, the (0 0 2) oriented SnO 2 films were obtained. Using the XRD φ scanning measurement, it was found that oriented SnO 2 films were epitaxially grown on the (0 0 1) TiO 2 substrate. The formation of the epitaxial SnO 2 on the (0 0 1) TiO 2 substrate was found to depend on the pre-irradiated amorphous SnO 2 film thickness, laser fluence and laser wavelength.

UV crystallization of poly-si using a CeO2 seed layer on plastic substrate for microelectronics applications

We are reporting the crystallization of amorphous silicon (a-Si) film using XeCl excimer laser annealing. Polycarbonate (PC) plastic substrate was used to deposit poly-Si film at low temperatures. We deposited the a-Si films at a room temperature using an inductive coupled plasma chemical vapor deposition (ICPCVD). Then it was crystallized as a function of laser energy density using a XeCl excimer laser. As the laser energy density increases, crystallinity value decreases from 72.78 to 81.72%. The relationship between the film transmittance and crystallinity was analyzed as a function of process pressure. In another process, CeO2 seed layer was grown by sputtering method. a-Si film was deposited over this layer using ICPCVD and then it was crystallized using the XeCl excimer laser. It was observed that the crystallization could be accomplished at lower energy density with a seed layer than that without such layer. In this paper, we present the crystallization properties of a-Si on the plastic substrate.

Excimer Laser Crystallization of Sputter Deposited a-Si Films on Flexible Substrates

AbstractIn this report, excimer laser annealed polycrystalline silicon (poly-Si) films on flexible polymer substrates are investigated. The amorphous silicon (a-Si) films were first deposited on polycarbonate (PC) and polyethersulfone (PES) substrates by radio-frequency (RF) magnetron sputter and sequentially annealed by XeCl excimer laser annealing system (λ = 308 nm). The argon concentration of a-Si films which was estimated by Rutherford Backscattering Spectrometry (RBS) was found to be dependent on the dynamic pressure during the deposition process and the sputtering gas. Typically, the argon concentration of a-Si film was 1 ∼ 2% when the film was deposited using argon gas at 6 mTorr. After the annealing process, the average grain size of the poly-Si film annealed with laser energy density of 289 mJ/cm2was 400 nm estimated from transmission electron microscope (TEM) investigations.

46.3: High Performance Dual‐Gate and Multi Channel Poly‐Si TFTs fabricated by XeCl Excimer Laser Annealing on Selectively Floating a‐Si Thin Film

AbstractA high performance poly‐Si TFTs is fabricated by a new ELA method which employs floating a‐Si thin film structure and the effect of pre‐patterning. The proposed poly‐Si TFT exhibits high performance electrical characteristics which are high mobility of 504cm2/Vsec and low subthreshold slope of 0.337 V/dec.

6.4: Crystallization of Ultra‐low Temperature ITO by XeCl Excimer Laser Annealing

AbstractThe effect of excimer laser (XeCl, λ=308nm) annealing on ITO films deposited at 25°C using DC magnetron sputtering has been studied. With increasing laser fluence, the film crystallinity is improved while retaining the as‐deposited &lt;111&gt; texture. Electrical conductivity, optical transparency, and surface roughness are all significantly enhanced by the laser annealing.

Poly-Si TFT Fabricated by Ion Beam Sputtering and Excimer Laser Annealing at 100°C

Polycrystalline silicon (poly-Si) thin film transistors (TFT's) have been fabricated by ion beam sputtering (IBS) and XeCl excimer laser annealing (ELA) at 100°C. The amorphous silicon (a-Si) films to be crystallized into poly-Si were deposited by IBS and they had very low argon content (less than 1 at. %). No explosive gas evolution was observed during the instantaneous crystallization of the a-Si film by ELA, while the a-Si film deposited by conventional RF/DC magnetron sputtering or PECVD underwent severe silicon film ablation due to the explosive argon or hydrogen evolution during ELA. The poly-Si TFT fabricated by IBS and ELA exhibited an ON/OFF current ratio of 4 × 104. The measured sheet resistance of the n+-doped source/drain resistance was less than 700 Ω/sq. and the output ID-VDS curves showed that good ohmic contacts were formed

A New Poly-Si TFT Employing XeCl Excimer Laser Annealing with Pre-patterned Al Laser Beam Mask

AbstractWe report new lateral grain growth mechanism by XeCl excimer laser annealing on a-Si film with pre-patterned Al layer. 2000Å-thick Al pattern on 800Å-thick PECVD a-Si film successfully reflects the incident laser beam and results in temperature gradient during the recrystallization process. The TEM images show that grain growth near the boundary between the liquid and the solid region exhibits a different mechanism compared with the conventional ELA. About 1.5 m-long lateral grain has been successfully obtained by single laser irradiationA poly-Si TFT with single grain boundary in the channel has been fabricated by the proposed excimer laser annealing. An excellent device characteristics such as mobility more than 250cm2/Vsec, high On/Off current ratio of 6.3×106 and low threshold voltage less than 1 V has been obtained. The experimental results show that the mobility, threshold voltage and sub-threshold slope of proposed TFTs are superior to those of the conventional TFTs.

Infra-red reflectivity of ion-implanted and pulsed excimer laser irradiated 4H-SiC

Infrared reflection measurements at near normal incidence between 400–7800 cm−1 have been performed on ion implanted bulk and epitaxial 4H-SiC. Three samples were triple implanted with N14 at 30, 80, and 140 keV to achieve a flat dopant profile. A fourth sample was implanted at 20, 40 and 60 keV at a temperature of ∼830 K in-order to reduce lattice damage. We make use of the Reststrahlen band, situated between the Transverse Optical (TO) ωTO and the Longitudinal Optical (LO) ωLO phonon modes to investigate both the damage created by ion-implantation and the lattice recovery induced by subsequent XeCl excimer laser (308 nm) annealing. We show that an optimum incident laser fluence between 0.9 and 1.0 J/cm2 exists for lattice recovery.

Characteristics of Amorphous Si Films Fabricated by Mesh-type PECVD and Their Crystallization Behavior Using Excimer Laser

It is increasingly necessary to use poly-Si n's as high resolution and integration of Tn for LCD. Excimer Laser Crystallization (ELC) of a-Si is mainly used as a low temperature process. But the ELC method for the fabrication of poly-Si has the eruption problems associated with hydrogen in the a-Si film. So we need a dehydro-genation process additionally. Hydrogen in a-Si film can degrade the quality of poly-Si film and electrical properties of device due to the hydrogen eruption and voids which occur during the excimer laser annealing. In this study, we propose mesh-type PECVD as the a-Si film deposition method for achieving the low concentration hydrogen. Mesh-type PECVD was found to reduce the hydrogen content substantially. We could obtain a as-deposited a-Si film with hydrogen contents less than at . We also investigated the behavior by XeCl excimer laser annealing of a-Si fabricated by mesh-type PECVB. As a result, we were able to confirm the broad process window in contrast to the narrow process range typically obtained in ELC. Hydrogen eruption was not observed in poly-Si films after ELC These results suggests that mesh-type PECVD is a viable method to achieve the low hydrogen content a-Si and improve the process windows for ELC.

In-Situ Fabrication of Gate Oxide and Poly-Si Film by XeCl Excimer Laser Annealing

We have proposed a new method to form the gate oxide and recrystallize the polycrystalline silicon (poly-Si) active layer simultaneously. During the irradiation of excimer laser, the poly-Si film is recrystallized while the oxygen ion impurities, which are injected into the amorphous silicon (a-Si) film, are activated by laser energy and react with silicon atoms to form SiO2. Our experimental results show that a high quality oxide, a poly-Si film with fine grain, and a smooth and clean interface between oxide and poly-Si film have been successfully obtained by the proposed fabrication method. The maximum oxide breakdown electric field which exceeds 7 MV/cm is obtained.

Double-Level Cu Inlaid Interconnects with Simultaneously Filled Via Plugs

A double-level Cu interconnection process for lower submicron generation ULSIs was developed. Cu interconnects were successfully formed by Cu/WSiN sputtering, XeCl excimer laser annealing and Cu/WSiN chemical mechanical polishing. The composition of the WSiN barrier metal was optimized to WSi0.6N and the diffusion barrier capability was confirmed by physical analyses and electrical measurements. The electrical resistivity of the inlaid Cu was 1.9±0.1 µ Ω·cm and contact resistivity between the first-level Cu and the second-level Cu was (1.54–5.78)×10-9 Ω·cm2. The electromigration lifetime of laser-annealed Cu/WSiN wiring was found to be one order of magnitude longer than that of previously reported Cu interconnects. The activation energy for electromigration was determined to be 1.1 eV.

Enhancement of Crystallinity with Fluorinated Amorphous Silicon (a-Si:H;F) Film by XeCl Excimer Laser Annealing

ABSTRACTThe Effects of fluorine atoms on laser-induced crystallization have been studied. The defect states of hydrogenated amorphous silicon (a-Si:H) film, which are related to weak hydrogen bonds, were reduced by involving fluorine atoms, before laser annealing. In laser annealing, the crystallinity was also enhanced to 63 %, while that of a-Si:H was 45 % at the energy density of 300 mJ/cm2. It may be considered that the fluorine atoms reduce the hydrogen atoms cause to the degradation of film in laser annealing, and increase the heat capacity which results in promotion of crystallinity in melt-solid phase transition.

Polycrystalline silicon recrystallized with excimer laser irradiation and impurity doping using ion doping method

Polycrystalline silicon (poly-Si) thin films having large grain size have been obtained by XeCl excimer laser annealing of a-Si deposited by plasma enhanced chemical vapor deposition on SiNx. The grain size of poly-Si reaches to about 300 nm with excimer laser irradiation around 500 mJ/cm2. For excimer laser irradiation from 500 to 600 mJ/cm2, instead of further enlargement of grains, amorphous regions appear and increase in the grains. Most of the Si layer becomes an amorphous state at pulse energy density over 600 mJ/cm2. On the other hand, impurity implantation to a-Si layers using non-mass-separated ion doping equipment and a subsequent activation step with excimer laser irradiation enable us to obtain recrystallized poly-Si layers having low resistivity. By using ion doping and excimer laser annealing, we have obtained excellent n-channel thin film transistors, the field effect mobility in excess of 40 cm2/V s and the ON/OFF current ratio of more than 106, respectively.

Bottom-gate poly-Si thin film transistors using XeCl excimer laser annealing and ion doping techniques

High mobility bottom-gate poly-Si thin film transistors (TFTs) have been successfully fabricated on a hard glass substrate using XeCl excimer laser annealing and ion doping techniques. The authors used an a-Si:H film which is deposited by a plasma-enhanced chemical vapor deposition (PECVD) as a precursor film, and then they crystallized the a-Si film by XeCl excimer laser annealing. The maximum field effect mobility and grain size obtained were 200 cm/sup 2//V-s (n-channel), and 250 nm, respectively. The poly-Si TFTs showed excellent transfer characteristics, and an ON/OFF current ratio of over 10/sup 6/ was obtained. Successful control of the threshold voltage within 4 V using an ion doping technique is also demonstrated.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>