This paper reports on a macroporous silicon arrays with high aspect ratio, the pores of which are of 162, 205, 252, 276μm depths with 6, 10, 15 and 20 μm diameters respectively, prepared by Multiplex Inductively Coupled Plasma (ICP) etching. It was shown that there are very differences in process of high aspect ratio microstructures between the deep pores, a closed structure, and deep trenches, a open structure. The morphology and the aspect ratio dependent etching were analyzed and discussed. The macroporous silicon etched by ICP process yield an uneven, re-entrant, notched and ripples surface within the pores. The main factors effecting on the RIE lag of HARP etching are the passivation cycle time, the pressure of reactive chamber, and the platen power of ICP system.
Based on wet etching theory, the silicon microchannel structure after electrochemical etching was released in TMAH solution to obtain the through-hole microchannel. The silicon wafer with the different resistivity was selected as the substrate of microchannel plate, the TMAH solution was selected in mass concentration of 28.5wt%, and the SiO2 passivation layer with the thickness of 200nm was prepared by thermal oxidation for protection of side-wall of microchannel. Contrary to the problem encountered in wet etching, Firstly, the corrosion characteristics of silicon and SiO2 thin film in TMAH solution were investigated, respectively. In addition, the effects of the pH values of TMAH solution on corrosion characteristics in microstructure releasing of silicon microchannel were studied and analyzed. The experiments show that the silicon wafer with high resistivity can be easily etched, the etching rate of SiO2 film in TMAH is uniform, and adjusting the pH value of etching solution to make it constant during etching can effectively increase the corrosion rate and decrease the surface roughness of samples.
Silicon Microchannel Plate(MCP)is a new image multiplier devices based semiconductor process technology. Compared with the traditional glass MCP, Silicon MCP has an advantage in technology that the dynode materials and the substrate materials are separate. At the same time, the dynode preparation process and the microchannel arrays are also separate. Two different dynode conductive layer films are prepared: polysilicon conductive films prepared by low pressure chemical vapor deposition (LPCVD) and AZO thin films coated by atomic layer deposition (ALD). The conductive films coated by ALD are superior to dynode conductive films prepared by LPCVD. By comparing the resistivity of conductive polysilicon thin film and AZO thin film of different Al concentrations doped, AZO thin film of different Al concentrations doped is a more suitable conductive layer dynode material to satisfy the MCP conductive layer resistivity requirements.
Silicon microchannel plates (Si-MCP) is widely used in the photomultiplier, night vision, X- ray intensifier and other areas. In order to meet the requirements of high voltage electron multiplier, Si-MCP need to prepare a layer of silicon dioxide in the microchannel to improve the insulating properties. There are many methods for preparing SiO2 layer, such as thermal growth, magnetron sputtering method and chemical vapor deposition etc. The thermal oxidation method is often used for preparation of insulating layer that it grows film thickness uniformity, compact structure, simple process and so on. There will be bending deformation phenomenon of silicon microchannel arrays in high temperature oxidation process. The warpage of Si-MCP has brought great for difficulties of subsequent processing. Silicon crystals has the properties of plastic deformation at high temperature, this article take full advantage of this properties by which the already bending deformation of silicon microchannel arrays can be restored to flat.
Anisotropic etching of monocrystalline silicon plays an important role in Microsystems technology in the recent
years. TMAH, as one of the anisotropic etchants, is used to fabricate pores with square cross-section. Careful choice of
concentration, isopropyl alcohol additives and temperature of alkaline solution allows for certain crystallographic
directions to be preferentially etched. In this way, pores with square, eight-sided (octagonal) or rotated square shapes can
be attained and convert to each other. We show the etch selectivity on (100) and (110) planes in TMAH solution with
low concentration. The etch rates on (100) and (110) planes at different temperature and concentration has been
measured. The results indicated that the perfect orthogonal array of pores with sharp edges and corners can be obtained
at more than 40℃ in 1wt% TMAH solution. There is good etch selectivity on (110) surface and the etch rate on (110)
surface is slower than (100) surface under the condition.
Microchannel plate is widely used in the field of low light level night vision, photomultiplier, tubes, X-ray enhancer
and so on. In order to meet the requirement of microchannel plate electron multiplier, we used the method of thermal
oxidation to produce a thin film of silicon dioxide which could play a role in electric insulation. Silicon dioxide film
has a high breakdown voltage, it can satisfy the high breakdown voltage requirements of electron multiplier. We
should find the reasonable parameter values and preparation process in the oxidation so that the thickness and
uniformity of the silicon dioxide layer would meet requirement. This article has been focused on researching and
analyzing of the problem of oxide insulation and thermal stress in the process of production of silicon dioxide film.
In this experiment, dry oxygen and wet oxygen were carried out respectively for 8 hours. The thickness of dry
oxygen silicon dioxide films was 458 nm and wet oxygen silicon dioxide films was 1.4 μm. Under these conditions,
the silicon microchannel is uniformity and neat, meanwhile the insulating layer's breakdown voltage was measured
at 450 V after the wet oxygen oxidation. By using ANSYS finite element software, we analyze the thermal stress,
which came from the microchannel oxygen processes, under the conditions of which ambient temperature was 27 ℃
and porosity was 64%, we simulated the thermal stress in the temperature of 1200 ℃ and 1000 ℃, finally we got the
maximum equivalent thermal stress of 472 MPa and 403 MPa respectively. The higher thermal stress area was
spread over Si-SiO2 interface, by simulate conditions 50% porosity silicon microchannel sample was selected for
simulation analysis at 1100 ℃, we got the maximum equivalent thermal stress of 472 MPa, Thermal stress is the
minimum value of 410 MPa.
The influence of several surfactants in electrolyte during silicon electrochemical etching was reported in this paper. The
morphologies of macroporous silicon arrays in n-type silicon are strongly influenced by the chemical nature of these
additives. Conventional solvents (HF-Ethanol) with cationic (hexadecyl trimethyl ammonium chloride), non-ionic
(Triton-X100) and anionic (sodium alpha-olefin sulfonate) surfactants were experimented respectively. Prominent
differences in microchannel morphologies and apertures were observed depending on the nature of the additive. The
different behaviors of the additives during the electrochemical etching process were linked to the physical properties of
the additives. We found the electric double layer model of the reaction interface partially to explain these results.
However, not only the morphology of the microchannel but also the degree of electrochemical reaction is affected by
surfactant. The anionic surfactant is more suitable for the preparation of silicon microchannel plate with high aspect ratio
and pore size uniform. The depth of microchannels etched by photoelectrochemical etching silicon with anionic
surfactant is 264 μm, and the pore size is 2 μm.
The application fields of high aspect ratio Si microchannel arrays have increased considerably, for example, Si
microchannel plates, MEMS devices and so on. By the method of photo-electrochemical etching (PEC), Si microchannel
arrays are prepared using n-Si wafer covered by anti-corrosion layers and initiation array pits. The dark current intensity
curve of an n-type silicon wafer was presented in aqueous HF. The relationship among temperature, etching voltage and
carrier transportation was presented. The influences of temperature and etching voltage on the surface morphology of
silicon microchannel arrays were researched. The perfect Si microchannel arrays structure with the pore depth of 297 μm,
the pore size of 3 μm and the aspect ratio of 99 was obtained by the method of reducing etching voltage gradually.
Spirooxazines (SOs) and spiropyrans (SPs) are typical organic compounds exhibiting photochromism. Compared to SPs, SOs show better fatigue resistance and photostability, which provides a possibility of practical applications in lenses of variable optical density, displays, filters and optical-memory devices. The maximum values of photo-induced birefringence of spirooxazine in poly(methyl methacrylate) (PMMA) films pre-irradiated by ultraviolet light was investigated as a function of He-Ne laser (632.8nm) pumping-beam intensity. A dynamics of photo-induced birefringence was recorded by a linearly polarized double-frequency Nd:YAG laser (532 nm) of 0.1 mW as a probe beam. This material exhibited a competing process between photo-orientation and photo-isomerization. The photo-orientation is predominant when the power density of He-Ne beam is lower; while the photo-isomerization is dominant at relatively high power density of He-Ne beam. An improved phenomenological model, elucidating a competition between photo-orientation and photo-isomerization, was precisely presented. Dynamic holographic recording under linear polarized writing beams at 632.8 nm was performed on spirooxazine doped PMMA matrices assisted by UV light. It was found that dynamics of the optical storage signal intensity in the polymer films were dependent on the thermal stability and aggregation of spirooxazine molecules in PMMA matrices. A theoretical description the formation and eraser of the transient orientation grating, competing with isomerization gratings, agrees well with experimental results. The interaction between the chromophores and matrices was also discussed. It was indicated that spirooxazine-doped polymer films are candidates for reversible optical storage medium.
KEYWORDS: Ions, Ion beam finishing, Aluminum, Microchannel plates, Chemical species, Monte Carlo methods, Image transmission, Transmittance, Oxygen, Particles
The stopping power of ion barrier films (IBFs) of Microchannel Plate (MCP) in Generation III image tubes for incident
positive ions was described in this paper. Nuclear Stopping Power, Electronic Stopping Power and Mean Range were
introduced. These concepts were analyzed and discussed, combined with Tomas-Fermi shielding potential. The results
of a Monte Carlo simulation on Nuclear Stopping Power, Electronic Stopping Power and Mean Range were also
presented when the ions with different energies were perpendicularly incident to Al2O3 and SiO2 films. The results
indicate that the stopping power of Al2O3 film is stronger than that of SiO2, and the selection of Al2O3 is reasonable and
feasible.
In this paper, the noise and optical aberration which were two controllable factors that affect the image quality in the
single-proximity-focusing x-ray image-intensifier were studied. By decreasing the electron gain of microchannel plate
(MCP), the noise of the x-ray image-intensifier can be decreased. The optimal operating condition for the image
intensifier and the CCD were also investigated. Based on this investigation, the flash-noise of the x-ray image-intensifier
can be decreased and the brightness of the image can be improved. At the end of the paper, some results on the
image-capturing of the cool CCD with low noise were presented.
Microsphere plate (MSP) is a new type of electron multiplier device. It is similar to the traditional microchannel plate
(MCP) in dimensions and model of operation. Compared with the MCP electron multiplier, the MSP has some unique
characteristics such as a high electron gain, without ion feedback and easy to be fabricated, thus it is widely used in the
fields of imaging and detecting. However, there are some key technologies to fabricate a satisfied MSP. In this paper, the
whole fabrication process of MSP was introduced and some of major processes such as the formation of glass beads, the
sintering of MSP body, and the formation of dynode and electrodes were specially discussed. At the end of the paper, the
optimal processed for the fabrication of MSP was given.
The fabrication of ion barrier film on microchannel plate (MCP) was introduced. The experimental system for
high-temperature vacuum baking on MCP and technological condition were given. The measurement on the electrical
properties, the dead-voltage and other parameters of MCP with an ion barrier film were shown. The changes before and
after high-temperature vacuum baking were also investigated for the MCP with ion barrier film. By analysis and
discussion, it was concluded that high-temperature vacuum baking caused the film's thickness changed, the dead-voltage
decreased, and the electron gain decreased with the increase of the film's thickness for the MCP with an ion barrier film.
The MEMS silicon-micro-machining is the main MEMS technology, which includes the
surface-silicon-micro-machining and the bulk-silicon-micro-machining technology; however the bulk-silicon
micro-machining technology has a wide application. In this paper, the formation procession of electron multiplier
on n-type Silicon substrate by bulk-silicon-micro-machining technology was investigated. A series of
electrochemical etching experiments and tests were carried out in three poles electrobath system using HF
electrolyte with different concentration. The rate of photoelectrochemical etching on the macropore depends on a
few technological parameters, such as doping concentration, operating bias, illumination intensity of the light, HF
concentration, and so on. It was found that the formation possibility of the macropore array is directly correlated
with crystal orientation of n-type Silicon substrate.
In this text the photoelectric emission principle of X-ray cathode was introduced at first. Then we provided the manufacture method of CsI/MCP X-ray cathode, analyzed the quantum efficiency and noise characteristic of reflection type and transmission type X-ray cathode, proposed the improved process, provided the output characteristic and front and sectional stereoscan photograph of CsI/MCP and pointed out the development of Lixiscope and application prospect in biomedicine.
The photomultiplier tube (PMT) that can work in different wavelength is an important detector device in remote sense technology. Microsphere plate using glass beads 50to 70μm in diameter sintered together is the core component of the microsphere plate photomultiplier tube It is a novel two-dimension electron multiplier. The electrons gain for a single plate is about 1017 and do not have the phenomenon of ion-feedback. Furthermore the fabrication process is very easy.
In this paper, much interest was put on the microsphere plate photomultiplier tube. Based on the analyses from the theory and the experiment result, we point out the key technology for fabricating PMT is how to obtain glass beads with narrow range in diameter and how to sinter the glass beads with a sufficient pylome. Factors affect the gradating technology and sintering process along with the solution to them is presented. In the last, the structure scheme and technological characteristic for fabricating microsphere plate photomultiplier tube were given. The pulse rising-time of MSP-PMT is below 400ps suitable to the detection of high-speed pulse. As easy to be fabricated and has great advantage over MCP multiplier in the ratio of performance to price, the microsphere plate photomultiplier tube is a promising dim-light detector.
New structure low intensity x-ray image system is mainly made of plane plate mode x-ray intensifier of single proximity focus and CCD data acquisition and processing system. The paper explains the noise source and characteristic of the low intensity x-ray image system. By the system composition, the image noise source of low x-ray imaging system is constituted with quantum noise, particulate noise and dark noise of CCD. Then the compound methods of the "multi-frame mean + morphological transform filter" is submitted which deals with the imaging noise. Firstly, some frame images is superimposed, then mean image is calculated from those images, which is under the principle of noise non-correlation. Secondly, distinguishing with the conventional ways of morphological transformation filtering algorithm, the differential image information is referred to de-noising. Under the multi-scale morphological thought, the differential image which is obtained from the source image includes noise and some image details. After the noise of the differential image is cut off by the wavelet translation, the differential image is added to the last filtered image by the multi-scale morphological filter, then the clean image is achieved which has no noise but keeps the image details.
In this paper, numerical analysis was investigated for the double-clad fiber lasers and experimental study on the Yb3+-doped double-clad fiber lasers was performed. The results shown that the output power increased monotonically with absorbed power, and in lossy cavity the output power is less than in the lossless cavity. The output power decreases for the lossy fiber with the reflectivity of output coupler. There was an optimum fiber length to reach a maximum output and the optimum length was mainly dependent on the loss coefficient. In experiment we obtained an output power of 21.6W, slope efficiency of 54% by using Yb3+-doped double-clad fiber and 40W LD pump source.
Theoretical foundation and principle programmer will be studied in this paper that special photosensitive Si-PSD (Si-Position Sensitive Detector) is rebuilt into electron bombardment mode device, which is based on minimal weak light detecting technical demands and exciting principle of high-energy electronic beam acting on silicon semiconductor. At the same time we will bring forward new concept device of electron bombardment mode PSD. According to the theoretical foundation and principle programmer, we present the practical measurement result that semiconductor gain of electron bombardment mode device is obtained. When incident electron energy is more than 4KeV, then obtained more than 103 gain. We have produced high-sensitivity photon-counting imaging detector (MCP-PSD tube) with 108~109 gain, which combined the research of microchannel plate (MCP) cascade applications with electron bombardment mode device. This paper also will present the substantial photograph of electron bombardment mode PSD device and MCP-PSD tube. Finally we will bring forward prospect realizing detection of minimal weak light photon-counting imaging.
The MCP ion barrier film in low-light-level imaging tube and its process techniques were introduced in this paper. The electron transmittance of this film was studied. The results of half field-of-view testing comparisons and the concept of dead voltage were presented. The dead voltage curve and the relation between dead voltage and thickness of film were tested. The composition of film was analyzed by XPS.
In this paper, proximity focus x-ray intensifier and corresponding Lixiscope system at home and abroad are introduced. The technical parameters and characteristics are given. The technical ways to improve Lixiscope and the application prospect are offered.
The formation of deep macropore array of p-type Silicon in HF electrolyte has been investigated. Then a series of electrochemical etching experiments and tests were carried out in three poles electrobath using different concentration HF electrolyte. HF concentration is a very important factor that determined whether electrochemical reaction was accomplished or not. By means of theoretical analysis and investigation, it is generally assumed that etching proceeds through sequential reaction of Si-H groups with F- to form Si-X, which determined whether electrochemical etching reaction was carried out or not. The electrochemical etching of p-type Silicon macropore array in aqueous fluoride solutions is satisfied with economic requirements for costs of fabricating deep macropores. The consequences are benefit to Silicon electrochemical deep macropore array etching technology.
This paper reports on a silicon micro-hole arrays (Si-MHA) prepared by Inductively Coupled Plasma (ICP) etching, a dry etching method. By ICP etcher, we carried out several experimental researches and process exploration for micromachining Si-MHA. The mechanism of lateral etching, sidewall passivation, gas micro-transport and some process parameters in Si-MHA micromachining, such as gas switching time, flow rate, etching rate, were analyzed. The footing effect, lag effect, longitudinal strips and RIE grass effect occurred in the ICP etching process were also studied. These process problems had reappeared in the micro-hole arrays process though these problems had be solved in the field of integrated circuits process and microelectromechanical system (MEMS). The study results reported here had demonstrated a Si-MHA that the diameter was 15 μm, the center distance 30 μm, and the depth 240 μm prepared by ICP, and had led the author to believe that the deep pore structure and the deep trench with high aspect ratio were very different in etching process. The former is a closed structure for the gas transport, and the latter is an open structure, so the process of deep hole structure is a puzzle in micromachining and MEMS technology.
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