A single-mask substrate transfer technique for the fabrication of high-aspect-ratio micromachined structures
01 Aug 2007-Journal of Micromechanics and Microengineering (IOP Publishing)-Vol. 17, Iss: 8, pp 1575-1582
TL;DR: In this paper, a single-mask substrate transfer process for the fabrication of high-aspect-ratio (HAR) suspended structures is presented, where the HAR silicon structures are fabricated using a deep reactive ion etching (DRIE) technique and then transferred to a glass wafer using silicon/thin film/glass anodic bonding and silicon thinning techniques.
Abstract: In this paper, a single-mask substrate transfer process for the fabrication of high-aspect-ratio (HAR) suspended structures is presented. The HAR silicon structures are fabricated using a deep reactive ion etching (DRIE) technique and then transferred to a glass wafer using silicon/thin film/glass anodic bonding and silicon thinning techniques. The HAR structures are released using self-aligned wet etching of the glass. Two key processes are discussed. One is the silicon/thin film/glass anodic bonding, with special emphasis on the effect of the bonding material on the bonding shear strength. The other is the silicon backside thinning via aqueous solution of potassium hydroxide (KOH). A lateral RF MEMS switch has been fabricated and demonstrates low loss up to 25 GHz. This substrate transfer process has the advantages of high-aspect ratio, low loss and high flexibility.
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01 Jan 2010
TL;DR: In this article, a single-mask substrate transfer process for fabrication of high-aspect-ratio (HAR) suspended structures is presented, where the HAR silicon structures are fabricated using deep reactive ion etching (DRIE) technique and then transferred to a glass wafer though silicon/thin film/glass anodic bonding and silicon thinning techniques.
Abstract: In this chapter, a single-mask substrate transfer process for fabrication of high-aspect-ratio (HAR) suspended structures is presented [1–3]. The HAR silicon structures are fabricated using deep reactive ion etching (DRIE) technique and then transferred to a glass wafer though silicon/thin film/glass anodic bonding and silicon thinning techniques.
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TL;DR: In this paper, a single-crystal slhcon, high aspect ratlo, low-temperature process sequence for the fabelfcatlon of suspended movable smgle-crystals s&on (SCS) beam structures is presented.
Abstract: A single-crystal slhcon, high aspect ratlo, low-temperature process sequence for the fabrlcatlon of suspended rmcroelectromechamcal structures (MEMS) usmg a smgle hthography step and reactwe Ion etching (RIE) IS presented The process IS called SCRJZAM I (single-crystal reactwe etchmg and metalhzatmn) SCREAM I IS a bulk mlcromachmmg process that uses RIE of a s~hcon substrate to fabricate suspended movable smgle-crystal s&on (SCS) beam structures Beam elements wth aspect ratios of 10 to 1 and widths rangmg from 0 5 to 4 0 Frn have been fabricated All process steps are low temperature (<3OO “C), and only conventronal sd~con fabrlcation tools are used photohthography, RIE, MIE, plasma-enhanced chemxal-vapor deposrtlon (PECVD) and sputter deposlhon SCREAM I IS a self-ahgned process and uses a smgle lithography step to define beams and structures srmultaneously as well as all necessary contact pads, electrIcal mterconnects and lateral capaators SCREAM I has been specifically deslgned for integration with standard Integrated cmxnt (IC) processes, so MEM deuces can be fabricated adjacent to prefabricated analog and dIgItal carcuitry In this paper we present process parameters for the fabncatlon of discrete SCREAM I devices We also discuss mask design rules and show micrographs of fabncated deuces
295 citations
TL;DR: In this paper, the authors developed a technique to address the problem of feature size control at the interface of the ICP etch tool, which is an industry wide problem in microelectro-mechanical applications.
Abstract: Dry etching of Si is critical in satisfying the demands of the micromachining industry. The micro-electro-mechanical systems (MEMS) community requires etches capable of high aspect ratios, vertical profiles, good feature size control and etch uniformity along with high throughput to satisfy production requirements. Surface technology systems' (STS's) high-density inductively coupled plasma (ICP) etch tool enables a wide range of applications to be realized whilst optimizing the above parameters. Components manufactured from Si using an STS ICP include accelerometers and gyroscopes for military, automotive and domestic applications. STS's advanced silicon etch (ASETM) has also allowed the first generation of MEMS-based optical switches and attenuators to reach the marketplace. In addition, a specialized application for fabricating the next generation photolithography exposure masks has been optimized for 200 mm diameter wafers, to depths of ~750 µm. Where the profile is not critical, etch rates of greater than 8 µm min-1 have been realized to replace previous methods such as wet etching. This is also the case for printer applications. Specialized applications that require etching down to pyrex or oxide often result in the loss of feature size control at the interface; this is an industry wide problem. STS have developed a technique to address this. The rapid progression of the industry has led to development of the STS ICP etch tool, as well as the process.
186 citations
"A single-mask substrate transfer te..." refers methods in this paper
...Then, the movable structures are released using wet etching of the buried oxide or DRIE over etching [3, 4]....
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TL;DR: In this article, a single-sided bulk silicon dissolved wafer process is described, which has been used to fabricate several different micromechanical structures, including overhanging features.
Abstract: A single-sided bulk silicon dissolved wafer process that has been used to fabricate several different micromechanical structures is described. It involves the simultaneous processing of a glass wafer and a silicon wafer, which are eventually bonded together electrostatically. The silicon wafer is then dissolved to leave heavily boron doped devices attached to the glass substrate. Overhanging features can be fabricated without additional masking steps. It is also possible to fabricate elements with thickness-to-width aspect ratios in excess of 10:1. Measurements of various kinds of laterally driven comb structures processed in this manner, some of which are intended for application in a scanning thermal profilometer, are described. They comprise shuttle masses supported by beams that are 160-360 mu m long, 1-3 mu m wide, and 3-10 mu m thick. Some of the shuttles are mounted with probes that overhang the edge of the die by 250 mu m. Resonant frequencies from 18 to 100 kHz and peak-to-peak displacements up to 18 mu m have been measured. >
154 citations
"A single-mask substrate transfer te..." refers methods in this paper
...A bulk silicon dissolved wafer process is developed in such a way to fabricate 1–25 μm thick movable devices on a glass substrate, in which device structures are etched on a silicon wafer and are heavily boron doped, then the silicon wafer is anodically bonded to a glass followed by the silicon dissolving to leave heavily boron doped devices attached to the glass substrate [8]....
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TL;DR: In this article, anodic bonding between Si-based and glass substrates has been characterized in detail, and the effects of magnitude of applied voltage, surface properties (coating of Si substrate), and surface cleanliness (pre-bonding cleaning procedure) on the time required for complete bonding were thoroughly studied.
Abstract: Anodic bonding between Si-based and glass substrates has been characterized in detail. The effects of magnitude of the applied voltage, surface properties (coating of Si substrate), and surface cleanliness (pre-bonding cleaning procedure) on the time required for complete bonding were thoroughly studied. First, the generic bonding time versus applied voltage plot was found to be concave in shape (viewed from the origin). For bonding between p-type Si substrate and Corning 7740 glass pre-cleaned with acetone, the time required was cut down from 38 to 4 min if the applied voltage was increased from 200 to 500 V. Second, the bonding time required for five Si-based substrates in ascending order was determined to be Si (p-type), polysilicon, silicon nitride, silicon oxide and then Si (n-type). Third, the bonding between p-type Si substrate, pre-cleaned with H2SO4–H2O2 and HF, and Corning 7740 glass was completed within 1 min, which was much faster than that pre-cleaned with acetone (4 min). Finally, from bonding point of view, Corning 7740 glass was superior to Corning 7059 glass and Fisher slide due to its thermal coefficient of expansion matching with the underlying Si substrate and the presence of significant amount of sodium ions in the glass.
113 citations
"A single-mask substrate transfer te..." refers background in this paper
...To quantitatively evaluate the bonding quality, the tensile strength measurement is conducted commonly [12, 13]....
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TL;DR: In this paper, a reactive ion etching (RIE) process is used for the fabrication of submicron, movable single-crystal silicon (SCS) mechanical structures and capacitor actuators.
Abstract: A reactive ion etching (RIE) process is used for the fabrication of submicron, movable single-crystal silicon (SCS) mechanical structures and capacitor actuators. The process is called SCREAM for single crystal reactive etching and metallization process. The RIE process gives excellent control of lateral dimensions (0.2 mu m approximately 2 mu m) while maintaining a large vertical depth (1 mu m approximately 4 mu m) for the formation of high aspect ratio, freely suspended SCS structures. The silicon etch processes are independent of crystal orientation and produce controllable vertical profiles. The process also incorporates process steps to form vertical, 4 mu m deep, aluminum, capacitor actuators. Using SCREAM, the authors have designed, fabricated and tested two-dimensional x-y microstages and circular SCS structures. For the x-y stage they measured a maximum displacement of +or-6 mu m in x and y with 40 V DC applied to either x or y, or both x and y actuators. The process technology offers the capability to use a structural stiffness as low as 10-2 N m-1.
105 citations