微機電系統(tǒng)的未來（ MEMS） Minhang Bao a, Weiyuan Wang b Fudan University, Shanghai. 200433 Chinab Shanghai Institute of Metallurgy. Shanghai. 200050 China 摘要 基于微加工和微電子技術微機電系統(tǒng)（ MEMS）的發(fā)展已經近十年顯著。然而，這是不切實際的考慮微加工技術為傳統(tǒng)加工的微型版本技術。由于事實上，微機械加工技術，硅的平面技術梗和基本上是一個二維加工技術。另一方面，很明顯，一 個微機械不可以與常規(guī)的機械強度比較。對于 MEMS 在未來的成功發(fā)展，一個簡單的規(guī)則，建議由獲得了在過去數年的經驗：盡量為了避免盡可能多的機械耦合與外部世界的同時努力提高 MEMS 技術提升該裝置的機械功率。除此之外，被證明是正確的固態(tài)傳感器的發(fā)展戰(zhàn)略也適用： MEMS 器件應主要用于具有廣闊的市場新開發(fā)的應用程序。其取代傳統(tǒng)的應用程序不應該被視為發(fā)展的主要策略。根據這些參數， MEMS器件和技術的未來發(fā)展在本文中進一步討論 . 1。 MEMS 的發(fā)展 在本期刊的早期問題的前蓋 （傳感器和執(zhí)行器）有剛下的字幕 其內容主標題： “國際期刊致力于固態(tài)傳感器的研究和發(fā)展”。這些平實的話語對我們意味著該雜志的創(chuàng)始人， 西蒙教授預見的出現固態(tài)驅動器，并且，因此，micivelecisome chaaical 系統(tǒng)（即， MEMS），從最后的一開始十年。 微機電系統(tǒng)是集成的系統(tǒng)，包括微電子 （ IC），微致動器，并且在大多數情況下，微傳感器。 微電子技術得到了迅速發(fā)展自 1960 年以來，并已自 1970年代已經相當成熟。微技術，該技術為機械傳感器和微執(zhí)行器，一直在開發(fā)幾乎處于隨著微電子技術的平行，但前者已成熟遠遠落后。 在較早的階段，微機械加工的發(fā) 展主要集中在體微機械加工主要是與相關固態(tài)壓力傳感器。人在當時都沒有預計從微機械一體化太多結構和微電子因為批量 MEMS 技術以及固態(tài)壓力傳感器相對難以與微電子集成 . 在 1987，第一可動微機械部件是通過表面微機械加工技術制造的和典型的微致動器，靜電微電機，是成功在明年操作。由于高表面微加工和之間的兼容性微電子技術之間的融合微機械和微電子導致的誕生 MEMS 在隨后的歲月。 由于出現了微機電系統(tǒng)沒有明確的定義，在此文章中，我們考慮一個典型的 MEMS 器件為： （ 1）一種設備，包括一個微機械和微電子，其中微型機械是由控 制微電子。很多時候，微傳感器參與控制系統(tǒng)通過對微電子提供的信號。 （ 2）正在使用微加工的設備技術與 IC 工藝，即。技術批制造。 （ 3）設備有一個完整出生的，沒有個人裝配步驟的設備的主要部分以外的包裝所需的步驟 . 這些點表示的壓力傳感器不被認為是作為一個典型的 MEMS 裝置，但作為一個機械傳感器，因為沒有 MEMS 控制微機械結構。另一方面，微型電機不是典型 MEMS 器件，但一個典型的一部分微致動器。由于 MEMS 是微機械加工技術的集成和微電子（集成電路）技術，它們出現后不久，微機械在 1987 年問世。發(fā)展 MEMS 的幾 乎一個十年已經顯著： 各種新技術已經發(fā)展，許多新的器件的設計，并與其中的一些制備被商業(yè)化，并在微機電系統(tǒng)的研究已進行幾乎所有主要的大學和研究機構 ,從行業(yè)及政府享有廣泛的支持機構。該字段已被描述為“生長成 從不確定的公信力，動態(tài)和流行的青春期在不到十年的孩子 . 但每一線希望有云，這種情況下是沒有例外。在快速發(fā)展而發(fā)展的幾個問題。新的微型機器的外觀迅速激起了很高的期望從科學界甚至公眾的新聞媒體。有的傾向于認為，最復雜的機電系統(tǒng)，就像一個機器人，可以被復制到一個微版和微機械罐還是做了類似的工作，以宏觀的同行。有 一直離譜的預測，像微型機器人收集了放射性粒子在有毒場所，和 MEMS 跟蹤和攻擊病毒和癌細胞，而通過游泳。上實發(fā)展很難匹配從新聞這樣的發(fā)展模式媒體。雖然微電機的設計和制造一個接一個，他們遇到的小的通病扭矩和相對較大的摩擦在微米尺度。人通常由微型馬達的運轉激發(fā)簡單地說，不能夠期望過高的條款， F 的扭矩 /功率輸出。這似乎不切實際的把它們投入使用像傳統(tǒng)的機器。到目前為止，還沒有微機械可代替在任何實際應用傳統(tǒng)的機器。這情況已經引起了懷疑過云的未來微機電系統(tǒng) . 然而，應用程序始終是最終的驅動力任何新興技術。起始于今年年初 十年中，微致動器的實用應用已經談到越來越多的時候通過換能器社區(qū)并已使越來越多的努力，把微執(zhí)行到實際應用中。 已經有兩種方法，到目前為止，推動應用微致動器。方法之一是讓它更強大。例如，通過雙金屬結構所產生的力是夠大對于許多應用，例如打開和關閉微型閥。這項計劃相當成功，使得微型閥已經商業(yè)化。形狀記憶合金（ SMA）也能產生很大的力，并已考慮用于類似的目的。對于微型馬達，電磁電機的設計與制造。該扭矩可以是若干個數量級比靜電微電機的高一些，但仍然有相當多的有關的設計和加工問題 . 另一種方法是尋找一些新的應用其中一點力 輸出是必需的。要做到這一點，直接微型機械與機械之間的耦合應避免宏觀世界。之間的界面 MEMS 與外界將通過電學，光學和磁信號。這種方法導致了相當很多 MEMS 與實際應用的設備他們中的一些已經商業(yè)化。這次成功的經驗告訴我們， MEMS 的未來是光明的，如果微機械加工技術的本質是尊重。 2。微加工技術的性質 微機電系統(tǒng)是兩個現代技術的后代中，微電子和微機械加工技術。從的技術觀點來看，也有一些親和性這兩種技術之間。它是眾所周知，微電子從平面技術（集成電路）技術的梗硅。作為事實上的，平面的應用硅的機械結構的形成過程催生了微 加工技術。平面技術的固態(tài)成功應用壓力傳感器促進微細加工的發(fā)展在早期階段 . 基本上，有微細加工的兩個主要類別技巧：批量微加工和表面微加工。該技術被稱為體微機械加工當基片的散裝材料（一般的硅）參與的過程，就好像表面微加工的表面上只沉積（或鍍）膜基板都參與了加工過程。這兩種類型的的微加工技術具有相同的美德微電子技術，也就是說，精度高，批量制造，但它們都具有相同的限制，從而產生平面加工技術 . 首先，結構由微機械技術可以是在外觀，但它們是兩個維本質，因為它們是按照一定的演變規(guī)則從平面蝕刻掩模。該結構可以是變得更加復雜 ，重復成膜和掩蔽刻蝕不止一次，但柔韌性仍限制重復的數目和處理順序從襯底的表面開始。因此，它是不切實際的考慮微加工技術作為微版本的常規(guī)加工技術，因為它有平面工藝的局限性：一個基本上二維加工技術不適合于裝配步驟來構造一臺機器從逐張 ； 。雙重加工零件。我們不能指望微機械加工技術是一樣靈活和通用的如在傳統(tǒng)的常規(guī)機械加工世界。一些選擇性沉積和蝕刻技術聲稱有真實的三維功能正在開發(fā)中，但它仍然是太早雷斯。他們在實踐中可能的應用 . 因此，一個簡單的規(guī)則必須是九，我在心里由傳統(tǒng)的機械制造所有的機械結構在微機械技術的版本無法復 制他，和大型數組，結構簡單，比較適合用于微機械加工技術比一臺機器復雜的結構。 另一方面，很明顯，一個微型機械能很難用常規(guī)的機械強度比較和電源。較小的結構，較小的強度和功率輸出，它可以提供。在許多情況下，微型機器甚至在剛剛常規(guī)運行困難 環(huán)境由于在微觀尺度超大摩擦和灰塵，濕度等的干擾，更不用說上的功率輸出以驅動 macromachine. 對于 MEMS，多了一個簡單的開發(fā)成功規(guī)則建議：盡量避免盡可能多的機械 動力輸出的同時努力提高 MEMS 技術以提高機械強度和功率設備。 重要的是要尊重的一種新技術的本質是很重要的 使其潛能得以充分發(fā)揮。由于事實上，有在短期內已經有許多成功的經驗微機電系統(tǒng)的充分利用的優(yōu)勢和歷史避免了微機械加工技術的缺點。 3。 MEMS 器件的未來 正如上面提到的，對于 MEMS 的未來發(fā)展技術，應使兩方面的努力：一種是不斷提高微細加工技術和二是制定實際應用適當的設備據中的 MEMS 技術的本質化。該后者是當前的一項緊迫任務，第一件事我們要解決的是：什么是適當的 MEMS 器件？ 作為微加工技術具有的優(yōu)點高精度低成本的批量生產，但局限性二維掩蔽，低強度，低功率輸出和高敏感性的許多環(huán)境的干擾因素，例如灰塵，濕度等，未 來的 MEMS 設備應主要是打包獨立的子系統(tǒng)由微型機械 microelectrouics，并且在許多的情況下，微傳感器。 MEMS 結構之間的耦合設備與外界將主要是通過電，電源光，磁等非接觸式信號供應，濃度 XOL 信息，輸入和輸出信號。一大陣相對簡單的機械結構是優(yōu)選復雜的機械結構 此外，未來的 MEMS 器件應著眼于新的應用具有廣闊的市場，使該設備可批量生產，充分發(fā)掘平面工藝的優(yōu)勢在低成本的大規(guī)模生產。這里所提出的論點西蒙Middelhoek 教授硅智能傳感器適用于 MEMS 太：在替代舊的應用程序沒有創(chuàng)建一個足夠大的市場潛 力。因此， 它不能被認為是未來的一個主要策略微機電系統(tǒng)的發(fā)展。 由于事實上，在上述提到方法有被證明是成功開發(fā)的 MEMS 器件過去和將被改編為將來發(fā)育。各種滿足上述標準的 MEMS 器件將在將來開發(fā)的，并在下面描述的弧，對于慣性傳感 MF.MS 設備 。 在硅加速度計發(fā)展迅速過去十年中，且被視為下一 massproduced 硅后微機械傳感器。最吸引人型微加速度時，加速度計，實際上是在一個 MEMS 器件組成光束質量的機械結構，一個電容性傳感器用于質量塊的位置，所述信號處理電子設備為傳感器和靜電致動器施加一個反饋強制地震質量。 各種力量平衡microaccelerometers 已經發(fā)展到現在，但至今其中最成功的是完全集成的微加速度， ADXLSO，這是發(fā)布了關于生葉芝前。 該裝置的機械結構是通過制作裝置的多晶硅表面微加工，以及電子通過的BiCMOS IC 技術手段制作。針對安全氣囊釋放控制，操作應用程序該設備的范圍 50 克與 5 V 單電源供電。 整個微系統(tǒng)是制作在硅芯片上測量的 3 mm 3mm，且采用 TO-I00 可以。雖然過程被認為是相當復雜和困難的 9，開發(fā)者聲稱，他們可以在成本銷售根據 15 美元每人。此外，改進的版本操作范圍低至 5 克或 LG已經公布?；?SIMOX SOI 材料類似的設備厚外延多晶硅也被開發(fā)。 力平衡 microaccelerometers 可以被視為其中最成功的 MEMS 目前的。一個原因他們的成功是由地震感知加速度質譜是通過非接觸式的慣性力和輸出是一個電信號，使整個系統(tǒng)可以是氣密在一個包，保證了密封的性能的微機械結構不會受到任何阻礙環(huán)境干擾。第二個原因是，加速度計可以找到大量的應用在各種motioncontrol 的系統(tǒng)。一個明顯的例子是大規(guī)模應用 在汽車安全氣囊控制。這種應用從產業(yè)帶動顯著的興趣和投資 另一個慣性檢測裝置，陀螺儀 ，也有類似的操作模式的加速度，也可以找到廣泛應用在運動控制，包括汽車應用，如牽引力控制系統(tǒng)和行駛穩(wěn)系統(tǒng)，消費電子應用，如攝像機穩(wěn)定和航模穩(wěn)定計算機應用，例如慣性鼠標，機器人應用，當然，軍事應用。因此，微機械陀螺儀已接收旺盛在近幾年的發(fā)展努力 作為高速旋轉的零件，軸承在一個傳統(tǒng)的陀螺儀是很難小型化和批量制造 ,通過微機械技術生產低成本器件，微機械陀螺儀是專門振動類型，包括雙萬向支架結構，懸臂梁結構，音叉結構和振動環(huán)結構。其中的振環(huán)裝置是最先進的，這是開發(fā)由 LIGA-iike后電路工藝結合比電鑄金屬的微觀結構與 CMOS電路用于控制和讀出電子。 雖然沒有這些微機械陀螺儀的有已經商業(yè)化的是，這是很可能的是某種形式的 MEMS 陀螺儀將被大規(guī)模生產，在不久的將來。 參考文獻 1 S. 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Tat 和 D.K.妙，硅微致動器用于計算機磁盤驅動器，在日本學者 Appl 。物理學報， 35 （ 1996） 50-356 。 27四妙和 Y.C.大，縮放技術： 10 GB / 2 。研討會上微機電系統(tǒng)。 Taipai 。 Tmwan 。 3月 21 日至 24 日。 1994 頁。 36 。 Future of microelectromechanical systems (MEMS) Minhang Bao a, Weiyuan Wang b Fudan University, Shanghai. 200433 China b Shanghai Institute of Metallurgy. Shanghai. 200050 China Abstract The development of microelectromechanical systems (MEMS) based on micromachining and microelectronics technologies has been significant for almost a decade. However, it is unrealistic to consider micromachining technology as a micro version of conventional machining technology. As a matter of fact, micromachining technology stemmed from the planar technology of silicon and is basically a two.dimensional processing technology. On the other hand, it is obvious that a micromachine cannot compare with a conventional machine in strength and power. For the successful development of MEMS in the future, a simple rule is suggested by the experience gained in the past few years: try to avoid as much as possible mechanical coupling with the outside world while trying hard to improve the MEMS technology to enhance the mechanical power of the devices. In addition to that, the strategy proven to be correct for the development of solid-state sensors also applies: MEMS devices should mainly be developed for new applications with a vast market. Their substitution for traditional applications should not be considered as a main strategy of development. Based on these arguments, the future development of MEMS devices and technologies is further discussed in the paper. 1. The development of MEMS On the front cover of the earlier issues of this journal (Sensors and Actuators) there was a subtitle just under the main title which read: international journal devoted to the research and development of solid-state transducers 1. These plain words mean to us that the founder of the journal, Professor Simon Middelhoek, foresaw the emergence of solid-state actuators, and, therefore, micivelecisome, chaaical systems (i.e., MEMS), from the very beginning of the last decade. MEMS are integrated systems consisting of microelectronics (IC), microactuators and, in most cases, microsensors. Microelectronics technology has been developing rapidly since 1960 and has been quite mature since the 1970s. Micromachining technology, the technology for mechanical sensors and microactuators, has been developing almost in parallel with microelectronics technology, though the former has lagged far behind in sophistication. At an earlier stage, the development of micromachining was focused on bulk micromachining mainly associated with solid-state pressure transducers. People at the time did not expect too much from the integration of micromechanical structures and microelectronics because bulk-micromachin-ing technology as well as solid-state pressure transducers were relatively difficult to integrate with microelectronics. In 1987, the first movable micromechanical parts were fabricated by surface-micromachining technology 2 and a typical microactuator, the electrostatic micromotor, was successfully operating in the next year 3. Due to the high compatibility between the surface micromachining and microelectronics technologies, the integration between micromachines and microelectronics led to the birth of MEMS in the following years. As there has been no clear definition of MEMS, in this article we consider a typical MEMS device as: (1) A device that consists of a micromachine and microelectronics, where the micromachines are controlled by microelectronics. Quite often, microsensors are involved in the control system by providing signals to the microelectronics. (2) A device that is fabricated using micromachining technology and an IC process, i.e. technologies of batch fabrication. (3) A device that is integratedly born, without individual assembly steps for the main parts of the device except for the steps required for packaging. These points mean that a pressure transducer is not considered as a typical MEMS device but as a mechanical sensor as there is no microclectronics control over micromechanical structures. On the other hand, a micromotor is not a typical MEMS device but a typical part ofMEMS D a microactuator. As MEMS are an integration of micromachining technology and microelectronics (IC) technology, they emerged soon after the advent of the micromachine in 1987. The development of MEMS for almost one decade has been significant: various new techniques have been developed, numerous new devices have been designed and fabricated with some of them being commercialized, and research on MEMS has been conducted by almost all major universities and research institutions, enjoying wide support from industries and government agencies. The field has been described as growing into a credible, dynamic and popular adolescence from an uncertain child in less than a decade 4. But every silver lining has a cloud, and this case was no exception. Some problems developed during the rapid development too. The rapid appearance of new micromachines stirred up high expectations from the scientific communities and even public news media. Some tended to believe that the most sophisticated electromechanical system, like a robot, can be copied into a micro version and the micromachine can still do a similar job to its macro counterparts. There have aoo been outrageous predictions, like microrobots gathering up radioactive particles at toxic sites, and microsubmarines stalking and attacking viruses and cancerous cells while swimming through the bloodsueam. The real development can hardly match such a development pattern from the news media. Though micromotors have been designed and fabricated one by one, they run into the common problem of small torque and relatively large friction on the micron scale. People are usually excited simply by the functioning of a micromotor, not being able to expect too much in terms ,:f torque/ power output. It seems impractical to put them into use like a conventional machine. So far no micromachine can replace a conventional machine in any practical application. This situation has given rise to a sceptical cloud over the future of MEMS. However, application is always the final driving force for any emerging technology. Starting at the beginning of this decade, the practicai application of a microactuator has been talked about more and more often by the transducer community and more and more efforts have been made to put microactuators into real application. There have been two approaches so far to push forward the application of microactuators. One of the approaches is to make laicroactuators more powerful and stronger. For example, the force produced by a bimetal structure is large enough for many applications, such as to open and close microvalves. This scheme has been quite successful so that the electrocontrolled microvalve has been commercialized. Shape memory alloy (SMA) can also produce a large force and has been considered for similar purposes. For micromotors, electromagnetic motors have been designed and fabricated. The torque can be several orders of magnitude higher than that of an electrostatic micromotor, but there are still quite a lot of problems related to the design and processing. Another approach is to look for some new applications where little force output is required. To do this, direct mechanical coupling between the micromachine and the macro world should be avoided. The interface between the MEMS and the outside world will be through electrical, optical and magnetic signals. This approach has resulted in quite a lot MEMS devices with practical applications； some of them has been commercialized. This successful experience tell us that the future of MEMS is bright if the nature of micromachining technology is respected. 2. The nature of micromachining technology MEMS are the offspring of two modern technologies, the microelectronics and the micromachining technologies. From a technological point of view, there are some affinities between these two technologies. It is well known that microelectronics (IC) technology stemmed from the planar technology of silicon. As a matter of fact, the application of planar processes of silicon to the formation of mechanical structures gave birth to micromachining technology in the 19/0s. The successful application of planar technology in solid-state pressure transducers promoted the development of micromachining at the early stage. Basically, there are two main categories of micromachining techniques: bulk micromachining and surface micromachining. The techniques are called bulk micromachining when the bulk material of the substrate (in general silicon) is involved in the process and as surface micromachining if only the deposited (or plated) films on the surface of the substrate are involved in the machining process. Both types of micromachining technologies have the same virtues as microelectronics technology, i.e., high precision and batch fabrication, but they have the same limitations stemming from planar processing technology. First, the structures made by micromechanical technology can be three dinensional in appearance, but they are two dimensional in essence as they are evolved according to certain rules from planar etching masks. The structures can be made more complicated by repeating the film deposition and masked etching more than once, but the flexibility is still limited by the number of repititions and the processing order starting from the surface of the substrate. Therefore, it is unrealistic to consider micromachining technology as a micro version of conventional machining technology as it has the limitation of the planar process: a basically two-dimensional processing technology not suitable for assembly steps to construct a machine from indiv；.dually processed parts. We cannot expect micromachining technology to be as flexible and versatile as conventional machining in the conventional world. Some selective deposition and etching techniques claimed to have real three-dimensional capability are under. development 5,6, but it is still too early to fores.e their possible application in practice. Therefore, one simple rule that has to be Ix)me in mind is that all mechanical structures made by conventional mechanical technology cannot he copied in micromechanical versions, and large arrays with simple structure are more suitable for micromachining technology than a single machine with complicated structure. On the other hand, it is obvious that a micromachine can hardly compare with a conventional machine in strength and power. The smaller the structure, the smaller the strength and the power output it can provide. In many cases, micromachines even have difficulties in just running in a conventional environment due to the extra-large friction on the micro scale and the interference of dust, humidity, etc., not to mention on the power output to drive a macromachine. For successful development of MEMS, one more simple rule is suggested: try to avoid as much as possible mechanical power output while trying hard to improve the MEMS technology to enhance the mechanical strength and power of the devices. It is important to respect the nature of a new technology so that its potential can be fully explored. As a matter of fact, there have been many successful experiences in the short history of MEMS by making full use of the advantages and avoiding the disadvantages of micromachining technology. 3. The future of MEMS devices As mentioned above, for the future development of MEMS technology, two-fold efforts should be made: one is to improve micromachining technologies continuously and the other is to develop appropriate devices for practical applition according to the nature of the MEMS technologies. The latter is an urgent task at present, lherefore, the first thing we have to address is: what are the appropriate MEMS devices.? As micromachining technologies have the advantage of high-precision low-cost batch production but the limitations of two-dimensional masking, low strength, low power output and high susceptibility to the interference of many environment factors, such as dust, humidity, etc., the future MEMS devices should be mainly packaged independent subsystems consisting of micromachines microelectrouics and, in many cases, microsensors. The coupling between the MEMS devices and the outside world would mainly be via electrical, optical, magnetic and other non-contact signals for power supplies, conxol information, input and output signals. A large array of relatively simple mechanical structures is preferable to complicated mechanical structures. Also, the future MEMS devices should be aimed at new applications with a vast market so that the device can be mass produced to explore fully the advantage of a planar process in low-cost mass production. Here the argument made by Professor Simon Middelhoek 7 for silicon smart sensors applies to MEMS too: substitution in an old application does not have the potential to create a large enough market. Therefore, it cannot be considered as a main strategy for future MEMS development. As a matter of fact, the above-mentionod approaches have been proven successful in developing MEMS devices in the past and will be adapted for future devel)pment. A variety of MEMS devices meeting the above-mentioned criteria will be developed in the future, and arc described below. 3. MF.MS devices for inertial sensing Silicon accelerometers have been developing rapidly during the last decade and are considered as the next massproduced micromechanical sensor after silicon pressmsensors. The most attractive type of microaccelerometer, the fort.ebalanced accelemmeter, is in fact a MEMS device consisting of a beam-mass mechanical structure, a capacitive sensor for the position of the mass, the signal-processing electronics for the sensor and an electrostatic actuator to apply a feedback force to the seismic mass. A variety of force-balanced microaccelerometers have been developed by now, but so far the most successful one is the fully integrated microaccelerometer, ADXLSO, which was released for production about two yeats ago 8. The mechanical structure of the devices is fabricated by means of polysilicon surface micromachining, and the electronics are fabricated by means of BiCMOS IC technology. Aiming at applications for airbag release control, the operation range of the device is 50g with a single 5 V power supply. The entire microsystem is fabricated on a silicon chip measuring 3 mm 3 mm and housed in a TO- I00 can. Though the process is considered quite sophisticated and difficult 9, the developer claimed that they can be marketed at a cost under US$15 apiece. Furthermore, an improved version with an operation range as low as 5g or lg has been announced 10. Similar devices based on SIMOX SOI material 11 and thick epi-polysilicon have also been developed 12. Force-balanced microaccelerometers can be considered as one of the most successful MEMS at present. One reason for their success is that the sensing of acceleration by the seismic mass is through non-contact inertial force and the output is an electrical signal so that the whole system can be hermetically sealed in a package to ensure that the performance of the micromechanical structures would not be hindered by any environmental interferences. The second reason is that accelerometers can find mass application in a variety of motioncontrol systems. A notable example is for mass applications in airbag control in automobiles. This kind of application spurred significant interest and investment from industry. Another inertial sensing device, the gyroscope, has a similar operation pattern to the accelerometer and can also find wide applications in motion control, including automotive applications such as traction control systems and ride-stabilization systems, consumer electronics applications such as video camera stabilization and model aircraft stabilization, computer applications such as an inertial mouse, robotics applications and, of course, military applications. Therefore, the micromechanical gyroscope has been receiving vigorous development efforts in recent years. As the high-speed rotation parts and bearings in a traditional gyroscope are difficult to miniaturize and batch fabricate by micromechanical technologies to produce low-cost devices, micromechanical gyroscopes are exclusively of vibrating types, including double-gimbals structure 13, cantilever beam structure 141, tuning-fork structure 15 and vibrating ring structure 16. Among them the vibrating ring device is the most sophisticated one, which is developed by a LIGA-iike post-circuit process for incorporating highaspect- ratio electroformed metal microstructures with a CMOS circuit for control and readout electronics. Though none of these micromechanical gyroscopes has been commercialized yet, it is quite likely that some form of MEMS gyroscope will be mass produced in the near future. References 1 S. Middelhoek, Sensors and Actuators. ! ( 1981 ) front cover. 2 L.S. Fan, Y.C. Tai and R.S. Muller, Integrated movable micromechanical structure for sensors and actuators, IEEE Trans. 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Solid-State Sensors and Actuators/Eurosensors IX, Stockholm, Sweden, 25-29 June, 1995, Vol. 1, pp. 589-592. 13 P. Greiff, B. Boxenhom, T. King and L. Nilus, Silicon monolithic micromechanical gyroscope, Tech. Digest. 6th Int. Conf. Solid-State Sensors and Actuators (Transducers 91)