Corner Compensation Structures Research Articles

Design of a Ka-Band Five-Bit MEMS Delay with a Coplanar Waveguide Loaded U-Shaped Slit.

This paper designs a five-bit microelectromechanical system (MEMS) time delay consisting of a single-pole six-throw (SP6T) RF switch and a coplanar waveguide (CPW) microstrip line. The focus is on the switch upper electrode design, power divider design, transmission line corner compensation structure design, CPW loading U-shaped slit structure design, and system simulation. The switch adopts a triangular upper electrode structure to reduce the cantilever beam equivalent elastic coefficient and the closed contact area to achieve low drive voltage and high isolation. The SP6T RF MEMS switch uses a disc-type power divider to achieve consistent RF performance across the output ports. When designed by loading U-shaped slit on transmission lines and step-compensated tangents at corners, the system loss is reduced, and the delay amount is improved. In addition, the overall size of the device is 2.1 mm × 2.4 mm × 0.5 mm, simulation results show that the device has a delay amount of 0-60 ps in the frequency range of 26.5-40 GHz, the delay accuracy at the center frequency is better than 0.63 ps, the delay error in the whole frequency band is less than 22.2%, the maximum insertion loss is 3.69 dB, and the input-output return rejection is better than 21.54 dB.

Pattern induced convex corner undercutting of oriented silicon microridges in potassium hydroxide

Modelling and fabrication of corner compensation structures is an active area of research involving KOH based wet etching. A useful data set has been generated to enable fabrication of efficient compensation structures used to prevent undercutting of convex corners during KOH etching. In this work, the effect of the mask pattern on the extent of undercutting the convex corners of microridges that occur during KOH etching was investigated. Microridges on silicon substrates oriented at varying angles with respect to the crystal orientation were etched in KOH solution. The ensuing undercut in the convex corners during the etching process was ascribed to the crystallographic orientation of the substrate, i.e. some crystal planes etch faster than others, contributing to a deformation of a desired structure. It was observed that the damage of the convex corners and the front face of the microridges increased with increasing angle of microridge orientation with respect to the direction. {311} planes arising from the corners making acute angles with the wafer orientation take longer to acquire a saddle point in the etching diagram. This is postulated to cause the observed complete wash out of the microridge faces for extremely acute angles.

Silicon (100) undercutting modelling and corner compensation structures design in wet anisotropic etching process

Sharp right-angled corners are indispensable parts of many microstructures, such as microsensors and actuators, which are fabricated using well-known micromachining techniques in the microelectronics industry. The convex corner undercutting phenomenon prevents the production of sharp right-angled corners and leads to deformed round shaped right-angled corners which influence the functionality of the microstructure. This undesired phenomenon will be alleviated by the use of corner compensation structures. Knowing the undercutting rate is the first necessary step in the design process of these compensation structures. In this research, the undercutting rate of right-angled corners is simulated and the design of corner compensation structures based on the obtained undercutting rate is accomplished. In the presented model, the etch rate of basic and major planes such as (100), (110), (111), and (311), as well as the etch depth, are selected as the input variables. In addition, the undercutting rate diagram, dimensions of compensation structures and the required time in order to produce sharp right-angled corners constitute the output results. The results of the presented model and the experimental results are in good agreement.

Experimental study and analysis of corner compensation structures for CMOS compatible bulk micromachining using 25 wt% TMAH

In the present work, most common compensation structures (〈110〉 squares and 〈100〉 bars) have been used for convex corner compensation with 25wt% TMAH–water solution at 90±1°C temperature. Etch flow morphology and self-align properties of the compensating structures have been investigated. For 25wt% TMAH water solution {311} plane is found to be responsible for corner undercutting, which is the fast etch plane. Etch-front-attack angle is measured to be 24°. Generalized empirical formulas are also discussed for these compensation structures for TMAH–water solution. 〈110〉 square structure protects mesa and convex corner and is the most space efficient compared to other compensation structures, but unable to produce perfect convex corner as 〈100〉 bar type structures. Both the 〈100〉 bar structures provide perfect convex corners, but 〈100〉 wide bar structure is more space efficient than the 〈100〉 thin bar structure. Implications of these compensation structures with realization of accelerometer structure have also been discussed. A modified quad beam accelerometer structure has been realized with these compensation structures using 25wt% TMAH.

A novel method for generating a rectangular convex corner compensation structure in an anisotropic etching process

Detailed characteristics of three classical rectangular convex corner compensation structures on (100) silicon substrates have been investigated, and their common design steps are summarized. By combining the basic method of a silicon wet anisotropic etching process, a general method of generating compensation structures for a rectangular convex corner is put forward. This calls for the following two steps: define the topological field and fit some borderlines together into practical compensation patterns. The rules, which must be obeyed during this process, are summarized. By introducing this method, some novel compensation patterns for rectangular convex corner structures are created on both (100) and (110) substrates, and finally simulation results are given to prove this new method's validity and applicability.

Study of corner compensating structures and fabrication of various shapes of MEMS structures in pure and surfactant added TMAH

In this research, we have studied the various shapes of corner compensation structures such as triangles, squares as well as 〈1 1 0〉 and <1 0 0> oriented beams for use with pure and surfactant added tetramethyl ammonium hydroxide (TMAH) solutions. The etchant concentrations of 10%, 20% and 25% were used with and without a small amount of surfactant NC-200 (0.1% of the total volume of the etchant). This surfactant contains 100% polyoxyethylene-alkyl-phenyl-ether with a hydrophobic head ‘CH 3(CH 2) 8–C 6H 4’ and a hydrophilic tail ‘O(CH 2CH 2O) 20H’. As the etching characteristics (such as etch rate, convex corner undercutting and etching anisotropy) of pure TMAH change dramatically when a small amount of surfactant is added, all the designs proposed for pure TMAH (or KOH) cannot be adopted for surfactant added TMAH. Among all the compensating designs, the triangular shaped geometry is found to be the optimal choice for the surfactant added 25% TMAH solution. The optimized design is successfully used for demonstrating the fabrication of grooves for chip isolation and mesa structures surrounded by bent V-grooves where limited space is available for the compensating pattern. Furthermore, the NC-200 added 25% TMAH was also used to fabricate microfluidic channels, microstructures with rounded concave and sharp convex corners, and a 45° mirror with smooth sidewalls.

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.

A NEW PROCESS FOR FABRICATING CONVEX CORNERS IN SILICON

International Journal of Computational Engineering ScienceVol. 04, No. 02, pp. 307-310 (2003) Silicon MicromachiningNo AccessA NEW PROCESS FOR FABRICATING CONVEX CORNERS IN SILICONXIAO LIN ZHANG, JANAK SINGH, AJAY AGARWAL and Q. X. ZHANGXIAO LIN ZHANGInstitute of Microelectronics, Singapore 117684, Singapore Search for more papers by this author , JANAK SINGHInstitute of Microelectronics, Singapore 117684, Singapore Search for more papers by this author , AJAY AGARWALInstitute of Microelectronics, Singapore 117684, Singapore Search for more papers by this author and Q. X. ZHANGInstitute of Microelectronics, Singapore 117684, Singapore Search for more papers by this author https://doi.org/10.1142/S1465876303001149Cited by:0 PreviousNext AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsRecommend to Library ShareShare onFacebookTwitterLinked InRedditEmail AbstractThis paper presents an innovative process scheme to fabricate convex corner in silicon for bulk micro-machined micro-mirror. This method combines deep reactive ion etching (DRIE) with anisotropy wet KOH etching process, with corner compensation structures. Using this method, proper mechanical structure, including about 650μm deep silicon recess with flat, silicon — residue free bottom, V-grooves, and U-grooves are realised simultaneously in single wafer. References Chad B. O'Neal et al., "Challenge in Packaging of MEMS" IEEE 1999 Proceedings International Symposium on Advanced Packaging Materials. Processes, Properties and Interfaces . Google Scholar Kato Y., Mori K., Mase T., Takahashi A., Imaki O., Kaku R., "Development of 4 × 4 MEMS optical switch" Optical MEMS, 2000 IEEE/LEOS International Conference Page(s): 95-96 . Google Scholar L. S. Huang, et al., "MEMS packaging for micro mirror switch", in Proc. 48th IEEE Electron. Components Technol. Conf., Seattle WA, 25-28, 1998 . Google Scholar P. Helin, M. Mita, H. Fujita, "Self-aligned vertical mirror and V-grooves: Appilied to a self-latching matrix switch for optical networks", Proceedings IEEE Thirteenth Annual International Conference on Micro Electro Mechanical Systems 2000 . Google Scholar Ki-Chang Song et al., "Micromachined Silicon Optical Bench for the Low Cost Optical Module", Technical Report, LG Electronics Institute of Technology . Google ScholarBen Kloecket al., IEEE Transactions on Electron Devices 36(4), (1989). Google Scholar FiguresReferencesRelatedDetails Recommended Vol. 04, No. 02 Metrics History PDF download

Effects of (110)-oriented corner compensation structures on membrane quality and convex corner integrity in (100)-silicon using aqueous KOH

To preserve the shape of convex corners when etching in aqueous KOH, corner compensation structures have to be used. The etching of convex corners is due to the fact that some planes etch faster than others, resulting in a loss of the desired structure. By adding extra structures at these convex corners, these structures will be removed during etching resulting in the desired convex corners. The basic corner compensation structures reported in the literature are oriented along the (100) direction or the (110) direction. This paper shows a step-by-step analysis of the etching of these structures. The results show that the (411) planes are responsible for the undercutting, which implies that a perfect compensation of a convex corner using structures oriented along the (100) direction is not possible. Moreover, it is shown that each compensation structure leaves an imprint on the membrane, which cannot be removed by further etching, as the convex corner would otherwise be etched.