2008.2
About Instruments Today No. 162
Si and Ge Nanocrystal Based Photonic Devices
Progress and Status of Silicon Nanocrystal Based MOS Light Emitting Diodes [ 下載 PDF ]
Gong-Ru Lin, Cheng-Tao Lin, Chun-Jung Lin
We demonstrate the dehydrogenation/ablation and optical refinement properties of a localized CO2-laser rapid-thermal-annealed or ablated Si-rich SiOx film with buried Si nanocrystals. The synthesis of Si nanopyramids at SiOx/Si interface for enhancing electroluminescence of Si-rich SiOx is reported, which assists enhancing Fowler-Nordheim tunneling effect and internal/external quantum efficiencies in such adevice with interfacial Si nano-pyramids or nano-pillar array is premier. We demonstrate a rapid self-assembly of Ni nanodots on Si substrate covered by a less-adhesive and heat-accumulated SiO2 layers to be an etching mask for the formation of Si nano-pillars on Si substrate. Anomalous micro-photoluminescence and low refractive index of the high-aspect-ratio Si nano-pillars are determined. Up to now, the carrier injection is still a problem to further improve the light emission, however, we characterize the memory effect of Si nanocrystals by capacitance-voltage analysis to realize its charging effect and carrier escaping rate.
Germanium Quantum Dot Optoelectronic Devices —Photodetectors [ 下載 PDF ]
Pei-Wen Li, Waiting Lai, Sheng-Shung Tseng
Using thermal oxidation of SiGe-on-insulator structures for forming Ge quantum dots (QDs) embedded in a SiO2 matrix, we have systematically investigated possible structure factors that would affect the properties of Ge QDs such as size, density, and even the position. Cathodeluminescence spectra reveal significant light emission at 400–600 nm from the Ge-QDs/SiO2 system as the QD size is scaled from 9 nm to 3 nm. This finding strongly motivates the exploration of Ge-QDs/SiO2 metal-oxide-semiconductor (MOS) photodiodes (PDs) for visible to near ultraviolet photodetection. MOS PDs with Ge QDs have high rectifying ratio (~105) in darkness and a high photocurrent/dark-current ratio (~103). Increasing the number of Ge-QD layers from zero, through one to three improves the photoresponsivity from 4.64, through 482 to 812 mA/W corresponding to quantum efficiencies of 1.42, 148, and 245%, respectively.
Silicon Nanostructure Light-Emitting Devices [ 下載 PDF ]
Ching-Ting Lee, Tai-Cheng Tsai
Recently, many efforts have been undertaken to study the optical emission mechanisms of low-dimensional Si nanostructures. Many techniques and methods have been developed to grow silicon nanoclusters embedded in silicon nitride matrices. However, the formation of silicon nanoclusters must be grown or post-annealed at a high temperature to precipitate the silicon nanoclusters. The high temperature process degrades the optical and electronic performance of the resultant devices. A laser-assisted plasma enhanced chemical vapor deposition (LAPECVD) method has been used to deposit silicon nanoclusters embedded in silicon nitride matrices at a low temperature and without a post thermal annealing process. The feasibility of electroluminescence emission from these lightemitting devices was demonstrated.
SiGe MOS Photodetector [ 下載 PDF ]
Chu-Hsuan Lin, CheeWee Liu
Using Si metal-oxide-semiconductor structure, the light with photon energy larger than 1.1 eV can be detected at inversion bias. Due to Si bandgap, the near infrared at 1.3 µm and 1.55 µm can not be detected. With Ge incorporation, 1.3 µm and 1.55 µm infrared can be detected. Thin film Ge can be transferred on insulator, glass, and polyimide for different applications by wafer bonding and smart-cut, and the cost can be reduced. The broadband absorption of SiGe/Si quantum dot infrared photodetectors are demonstrated using boron δ doping in the Si spacer. The large valence band offset between Si and SiGe forms discrete quantum states in SiGe QDs. The δ doping in Si spacers provides the QDs with a sufficient hole concentration and forms a δ-doping well in Si. Under infrared exposure, the confined holes in QDs and δ-doping wells can be excited and contribute to the photocurrent.
Fabrication of Silicon Micro/Nano Photonics Devices Using Surface Atom Migration [ 下載 PDF ]
Ming-Chang M. Lee, Wei-Chao Chiu, Tse-Ming Yang, Chin-Hung Chen
Submicron silicon optical waveguides are key elements for micro/nano silicon photonics. However, surface roughness generated during microfabrication usually induces high propagation loss. Additionally, the coupling between the external light source and the waveguide is generally inefficient since the core dimension of the waveguide is relatively small. This research proposes using surface atom migration to make submicron silicon photonic wires, three-dimensional tapered couplers and microtoroid resonators. The experimental result showed the propagation loss can be as low as 1.26 dB/cm and the coupler loss can be less than 2.5 dB.
Enhanced Photoresponse of a Metal-Oxide-Semiconductor Photodetector with Silicon Nanocrystals Embedded in the Oxide Layer [ 下載 PDF ]
Jia-Min Shieh, Shia-Chia Liu
The work reported a two-terminal metal-oxide-semiconductor photodetector for which light is absorbed in a capping layer of silicon nanocrystals embedded in a mesoporous silica matrix on p-type silicon substrates. Operated at reverse bias, enhanced photoresponse from 320 to 1800 nm was observed. The highest optoelectronic conversion efficiency is as high as 160%. The enhancements were explained by a transistorlike mechanism, in which the inversion layer acts as the emitter and trapped positive charges in the mesoporous dielectric layer assist carrier injection from the inversion layer to the contact, such that the primary photocurrent could be amplified.
Development of an Auto-Focus Microscope System by Using Astigmatism Method [ 下載 PDF ]
Po-Jui Chen, Chien-Shing Lee, Wei-Yao Hsu, Lian-Tzue Chen
A real-time automatic focus module, integrated with astigmatism algorithm, is introduced in this article. With transition mechanism, engineers can joint the module to existing industrial microscopes to improve product inspection performance. The module is designed with a focus-error function to analyze the defocus distance per the shape variations of laser spot detected by quadrant photodiode. Experiments show that the module has been successfully applied to PCB boards, color filters, and IC chips, etc. and it takes less than 0.3 seconds to focus the objects with ±200 µm defocus distance.
Measurement of Thermal Conductivity and Thermal Boundary Resistance on SiO2 Thin Films [ 下載 PDF ]
Da-Jeng Yao, Wei-Chih Lai, Heng-Chieh Chien, Cheng-Ting Hsu
Heat transport inside the thin dielectric films (30 nm – 300 nm) plays an important role in many IC and MEMS devices. The application of 3ω method is investigated to achieve the measurement of thermal conductivities for two different kinds of SiO2 film. Based on 3ω method, the apparent thermal conductivity, intrinsic thermal conductivity, and interface resistance have been analyzed. Besides, temperature is an effect factor to thermal conductivity, which will be discussed latter. This simple method can be broadly applied upon the measurement of other dielectric film.
Development and Application of Functionalized Nanoparticles on Mass Spectrometry for the Analysis of Target Biomolecules [ 下載 PDF ]
Po-Chiao Lin, Huan-Ting Wu, Kai-Yi Wang, Yu-Ju Chen, Chun-Cheng Lin
In recent studies, nanomaterials show the excellent performance in diverse fields. Due to the high surface area to volume ratio, nanomaterials obviously improve the sensitivity and efficiency compared with conventional micro-scaled materials. Combined with matrix-assisted laser desorption/ionization mass spectrometry (MALDI), functionalized nanoparticles established a rapid and reliable platform for various biomolecules extraction and analysis, from cell to protein and small molecule. In this article, we will introduce several important works done by Taiwan research groups and the new developed technique 'nanoprobe-based affinity mass spectrometry' (NBAMS) by our group.
Goniometric Polarized Light-Scattering Instrument for Nanoparticles on Wafer Inspection [ 下載 PDF ]
Chen-Yang Liu, Tze-An Liu, Wei-En Fu
The diameter and distribution measurements of nanoparticles on wafers are critical parameters in the semiconductor industry for ensuring the quality of the transistors and increasing the production rate. A goniometric optical scatter instrument has been developed at CMS/ITRI to readily perform polarized light scattering measurements for the diameter and distribution measurements of nanoparticles on wafer. The designed scatter instrument is capable of distinguishing various types of optical scattering characteristics, which are corresponding to the diameters of the nanoparticles, near surfaces by using the Mueller matrix calculation. The measurement range of nanoparticle diameters is 100 nm to 1 µm on 4 inches to 8 inches wafers.
Designing a Non-Destructive Experimental Uniaxial Tensile Testing for the Mechanical Behavior of Thin Films [ 下載 PDF ]
Chi-Jia Tong, Kai-Shiang Shiu, Ming-Tzer Lin
As the feature of materials in the scale of sub-micrometer to nanometers, the mechanical properties of nanostructure materials are different from their bulk structures. The understanding of relationship between nanostructure and mechanical properties is a common challenge to semiconductor, MEMS and nanotechnologies. This article presents one of the direct non- destructive and less ambiguous experimental uniaxial stress testing techniques for the mechanical characterization of freestanding thin films using specimens with dimensions as few hundred nanometers. This testing approach was proved to yield the direct experimental mechanical property values. These data can then be used to construct an accurate stress models for the mechanical behavior of thin film materials use for semiconductor, MEMS and nanotechnologies.
Estimating Measurement Uncertainty in a Wide-Range Pressure Calibration System [ 下載 PDF ]
Yu-Wei Lin, Chien-Bao Lin, Chien-Nan Hsiao
The goal of the present research is to construct a wide-range pressure calibration system, and also to analyze the degree of uncertainty associated with the system. The design of the system took into consideration of influencing factors that include uniformity of gas distribution and the geometric location of the gauge to be calibrated. The system operates following the procedure stipulated in the comparison vacuum gauge calibration method. The calibration may range from 103‐10−6 Torr. The system makes use of capacitor vacuum gauge, SRG and hot cathode thermion vacuum gauge to estimate the degree of uncertainty associated with the system.
