硅KOH腐蚀<100>晶向凸角补偿技术及应用

在(100)硅上制作边沿<100>晶向的长方形掩模,用KOH各向异性腐蚀液腐蚀可制得竖直微镜,这种微镜存在凸角削角问题.研究了边沿<100>晶向掩模的凸角补偿技术,提出了2种凸角补偿图形,并应用于竖直微镜制作.实验表明:"工" 形补偿可获得方正的反射面;"Y"形补偿的微镜,反射面呈底角为75.96°的梯形.经补偿后的微镜,可提高光开关切换光束效率.讨论了(100)硅的<100>晶向掩模凸角补偿技术应用于微机械加速度计质量块制作的可能性.     

Silicon anisotropic etching in alkaline solutions II on the influence of anisotropy on the smoothness of etched surfaces

Experiments were carried out with anisotropic etching of Si(100) in alkaline solutions from the point of view of surface quality. The circumstances needed to obtain surfaces of various level of smoothness were established. The problem why etched surface is of mirror-like quality, texturized, i.e., covered on the whole with random inequality (sometime of pyramids shape) as well ones covered with single separated hillocks is discussed in the term of anisotropy. Some analogies between random texturizing, obtaining the hillocks and etching through a patterned SiO₂ mask were stated.     

Bulk micromachining fabrication platform using the integration of DRIE and wet anisotropic etching

This study presents a bulk micromachining fabrication platform on the (100) single crystal silicon substrate. The fabrication platform has employed the concept of vertical corner compensation structure and protecting structure to integrate the wet anisotropic etching and DRIE processes. Based on the characteristics of wet anisotropic etching and DRIE, various MEMS components are demonstrated using the bulk micromachining platform. For instance, the free suspended thin film structures and inclined structures formed by the {111} crystal planes are fabricated by the wet etching. On the other hand, the mesas and cavities with arbitrary shapes and the structures with different leve l heights (or depths) are realized by the characteristics of DRIE. Since the aforementioned structures can be fabricated and integrated using the presented fabrication platform, the applications of the bulk micromachining processes will significantly increase.This research is based on the work supported by WALSIN LIHWA Corporation and the National Science Council of Taiwan under grant of NSC-91–2218-E-007–034. The authors would like to thank the Central Regional MEMS Research Center of National Science Council, Semiconductor Research Center of National Chiao Tung University and National Nano Device Laboratory for providing the fabrication facilities.     

Silicon anisotropic etching in alkaline solutions I. The geometric description of figures developed under etching Si(100) in various solutions

The influence of alkaline solution concentration, type of cation (K⁺ or Na⁺) and IPA additive on etching rate of various crystallographic planes and shape of etched figures were examined. The simulation of the etching course for concave and convex figures was proposed. The results of the simulation were compared with SEM images.     

碳化硅薄膜的ICP浅刻蚀工艺研究

选用SF6/O2 混合气体对等离子体增强化学气相淀积( PECVD)法制备的碳化硅( SiC)薄膜进行了浅槽刻蚀,并通过正交试验设计方法,研究了感应耦合等离子体( ICP)刻蚀技术中反应室压强、偏压射频( BRF)功率、O2 比例三个工艺参数对碳化硅薄膜刻蚀速率的影响及其显著性.实验结果表明:BRF功率对于刻蚀速率的影响具有高度显著性,各因素对刻蚀速率的影响程度依次为BRF功率>反应室压强>O2 比例,并讨论了所选因素对碳化硅薄膜刻蚀速率的影响机理.     

4H-SiC ICP深刻蚀工艺研究

SiC是一种新型的半导体材料,由于化学性质十分稳定,目前还未发现有哪种酸或碱能在室温下对其起腐蚀作用,因此,在SiC的加工工艺中常采用干法刻蚀。采用GSE 200plus刻蚀机对SiC进行刻蚀,研究了刻蚀气体、源功率RF1、射频功率RF2及腔室压强对刻蚀结果的影响,并对产生的结果进行了相关分析。提出了一种SiC ICP深刻蚀方法,对SiC深刻蚀技术具有重要的指导意义。     

ICP工艺参数对刻蚀Pyrex玻璃影响的实验研究

影响ICP刻蚀的工艺参数包括反应室压力,偏置射频功率,氩气流量比率。通过正交试验的方法,以CHF3和Ar的混合物作为反应气体,利用电感耦合等离子体技术刻蚀Pyrex玻璃。并采用回归分析方法建立了二次回归方程模型描述腐蚀速率和三个因素之间的关系。实验结果表明,氩气的流量比率（总气体流量（CHF3+Ar）是恒定的）对刻蚀速率的影响最大,影响程度的主次顺序为氩气的流量比率,反应室压力,偏置射频功率。腐蚀速率和三个因素之间的数学表达式为：腐蚀速率=532.6800+2.0556×Ar+0.0127×（偏置射频功率）-0.9641×压力-0.0655×Ar2-0.0067×Ar×（偏置射频功率）+0.0217×（偏置射频功率）×压力-0.0504×（压力）2,实验结果证明数学拟合结果良好。     

改进的硅各向异性腐蚀GPU并行模拟

硅各向异性腐蚀过程复杂,采用元胞自动机模拟硅各向异性腐蚀非常耗时。为了加速腐蚀模拟过程,研究了基于图形处理器(GPU)进行硅的各向异性腐蚀模拟。针对串行算法直接并行化方法存在加速效率低等问题,提出了一个改进的并行模拟方法。该方法增加了并行部分的负载,减少了内存管理的开销,从而提高了加速性能。实验证明该方法能够获得较理想的加速比。     

ICP深硅刻蚀工艺掩模的研究

通过使用深硅等离子刻蚀机,以C4 F8和SF6为刻蚀气体,对以光刻胶与金属铝两种材料作为掩模的深硅刻蚀结果进行对比,研究了深硅刻蚀过程中掩模材料对刻蚀结果的影响。实验结果表明：以光刻胶做掩模,深硅刻蚀后硅侧壁和硅底部表面形貌平整,垂直度较之铝掩模相当;以金属铝做掩模,深硅刻蚀后深槽底部表面不平整,出现长草现象,但是刻蚀选择比大于光刻胶,两种掩模的硅刻蚀速率相当。     

TMAH溶液中的(110)硅各向异性湿法腐蚀及其在不同添加剂下的腐蚀特性研究

研究了TMAH溶液中(110)硅片在不同几何形状掩膜窗口下的各向异性湿法腐蚀行为,探讨了(110)硅在TMAH与不同添加剂(过硫酸铵、异丙醇等)构成的腐蚀系统下的腐蚀特性.利用场发射扫描电子显微镜(SEM)观测(110)硅的腐蚀坑腔结构,利用扫描探针显微镜(SPM)测量(110)硅腐蚀的表面粗糙度.结果表明:(110)...     

肼对硅片的各向异性腐蚀技术研究

采用肼水溶液在各种条件下对硅片进行腐蚀 ,通过分析与腐蚀速率有关的因素 ,即改变腐蚀溶液温度和肼的质量分数 ,来提高腐蚀速率。整个实验过程实质就是寻求最佳腐蚀工艺条件 ,从而提高硅片的表面质量。     

Etching behaviour of sputter-deposited aluminium nitride thin films in H3PO4 and KOH solutions

Aluminium nitride (AlN) reactively sputter deposited from an aluminium target is an interesting compound material due to its CMOS compatible fabrication process and its piezoelectric properties. For the implementation in micromachined sensors and actuators an appropriate patterning technique is needed to form elements made of AlN. Therefore, the influence of different sputtering conditions on the vertical etch rate of AlN thin films with a typical thickness of 600 nm is investigated in an etch mixture based on phosphoric acid. Under comparable conditions, such as temperature and concentration of the etchant, thin films with a high c-axis orientation are etched substantially slower compared to films with a low degree of (002) orientation. When a high c-axis orientation is present detailed analyses of the etched topographies reveal surface characteristics with a low porosity and hence, low roughness values. From temperature dependant etching experiments an activation energy of 800(± 30) meV is determined showing a reaction-controlled etching regime independent of sputter deposition conditions. For comparison, AlN films synthesized under the same conditions were etched in potassium hydroxide (KOH) at room temperature revealing comparable etching characteristics as a function of deposition parameters. Depending on the degree of (002) orientation the topography of the etched samples show a strong increase in surface roughness with time due to a selective etching behaviour between (002) and residual crystallographic planes.     

Impact of alcohol additives concentration on etch rate and surface morphology of (100) and (110) Si substrates etched in KOH solutions

The influence of alcohol concentration on etch rate and surface morphology of (100) and (110) Si planes was investigated in this paper. The etching processes were carried out in KOH solutions with different concentrations of isopropanol and butanols. The etch rate minima versus alcohol concentration were observed for all the alcohols used in the experiments. Furthermore, close to the concentrations of etch rate minima, the smooth (110) planes were obtained. However, the (100) surfaces were covered with hillocks at these concentrations. Based on the surface tension measurements and literature reports, the explanation of appearance of the etch rate minimum was suggested. In the proposed model, the adsorption maximum corresponds to the complete formation of an alcohol monolayer on Si surface and, consequently, to the etch rate minimum. At higher concentrations of alcohol, the monolayer disappears and the etch rate increases.     

The effect of the crystallization of indium tin oxide on indium tin oxide wet etching based on gate line with the structure of copper/indium tin oxide

In thin film transistor-liquid crystal display (TFT-LCD), the copper/indium tin oxide (Cu/ITO) layer was often used to be gate line. In this event, the patterning of ITO is necessary and important. However, the high temperature generated during Cu deposition will cause ITO to crystallize, which is not conducive to ITO etching. In this paper, the ITO films prepared by radio frequency (RF) magnetron sputtering were annealed according to the monitoring results of production line to simulate and study the effect of crystallization on the etching properties of ITO film. When the annealing temperature was less than 200°C, no large size grains were detected in ITO films, and the ITO films could be easily etched by etchant. However, the ITO films transformed from amorphous structure to polycrystalline structure after being annealed more than 200°C. After wet etching experiments, the polycrystalline ITO films could be hardly removed by etchant. The X-ray photoelectron spectroscopy (XPS) results showed that high temperature annealing induced a large amount of Sn⁴⁺ on ITO films surface. The Sn⁴⁺ was difficult to be dissolved by acid under normal conditions, which might be the most important factors that led to the greatly decreased etching rate for polycrystalline ITO films.     

Investigations of the capillary effect for gripping silicon chips

Capillary forces in microsystems are very powerful. During wet etching they can cause sticking or even destruction of moving or underetched parts of the microstructure. But capillary forces can also be used in a controlled way for gripping and handling of micro objects. This paper shows that forces exerted on a silicon chip with dimensions of 4 × 4 mm² and a thickness of 600 m are approximately 200-times higher than the inertial force of the chip. The force exerted is dependent on the gap height and can be estimated for different drop sizes with simple estimation formulas or with solutions from differential equations. A numerical solution gives a better understanding of the non-linear behavior of a capillary liquid in a gap. The result of the investigation shows the behavior of the capillary effect in small gaps. For small gap widths and liquid volumes the force developed is overestimated by conventional formulas and calculations. Additionally the general behavior of liquids in microgaps are shown, which also can help to design other liquid based microsystems e.g. micro biological sensor systems.The author is thankful for the support given for this work by Prof. Dr.-Ing. L. Kiesewetter from the Technical University of Brandenburg/Germany.     

Laser-induced etching parameters impact on optical properties of the silicon nanostructures

Porous silicon (PS) was fabricated by laser-induced etching (LIE) process. The objective of this study is to investigate the selected LIE parameters to control size and shape of nanostructures,which are considered important factors in semiconductor device applications. Photoluminescence output intensity becomes stronger due to the increase in the number of emitted photons on the porous surface. There is a dramatic increase in photoluminescence intensity due to the increase of porosity as a function of laser...     

On the anodic passivation of silicon in aqueous KOH solutions

This paper proposes a new explanation to account for the anodic passivation of single-crystalline silicon in aqueous KOH. The effects of experimental results.     

Residual stresses evaluation in precision milling of hardened steel based on the deflection-electrochemical etching technique

Machining operations generate residual stresses in both the surface and subsurface of the workpieces. These residual stresses have a big influence on the functionality of the machined parts, thus their evaluation is of great importance. In terms of the fatigue strength and stress-corrosion cracking resistance, the compressive residual stresses are preferred to the tensile ones. In the present study, the generation of residual stresses in the precision milling of steels is evaluated by using the deflection-electrochemical etching technique. Two different materials were used to compare the obtained results: DIN X210Cr12 and DIN 17210-86. For the first one, two different states were tested: hardened and unhardened. The results showed different trends for the materials tested. Thus, the higher residual stresses were found at the surface for the DIN X210Cr12 while the maximum values were obtained in the subsurface for the DIN 17210-86. Finally, when comparing to the X-ray diffraction method, it is stated that both the deflection-electrochemical etching and X-Ray diffraction methods can be used to evaluate the state of the surfaces, though the destructive one can give more detailed information about the residual stresses distribution.     

The spreading of a viscous microdrop on a solid surface

The spreading of a liquid microdrop across a solid surface is examined using the interface formation model. This model allows for variable surface tension at constant temperature and a flow induced Maragoni effect, by incorporating irreversible thermodynamics into the continuum model. The model is solved for small Capillary number and small Reynolds number. This problem has been considered before for much larger drops in Shikhmurzaev (Phys Fluids 9:266, 1997a), which examined the spreading of a drop for ε = τ U _CL/R ≪ 1, where U _CL is the speed of the moving contact line across the solid surface, τ is the surface tension relaxation time of the viscous liquid, and R is a typical length scale for the size of the drop. This paper extends that work by examining ε = O(1), which will be shown to be the appropriate scaling for very small liquid drops, on the scale of micrometres or less.     

ITO dry‐etching mechanism and its application in the fabrication of LCDs

Abstract— Based on HI gas‐plasma etching (high‐density plasma‐assisted RIE), the activation energy for an ITO dry‐etching reaction was obtained. The value was calculated 35–40 kJ/mol for 20 sec from the reaction starting time. The reaction dead time is characteristic of the ITO dry‐etching process, but the reaction is relatively simple. Therefore, ITO dry‐etching technology, based on HI gas plasma, is useful in the the fabrication of LCDs, and was used in a recently developed Multi‐Coaxial‐Plasma‐Source (MCPS) dry etcher.