scispace - formally typeset
Journal ArticleDOI

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
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.
Topics: Anodic bonding (72%), Silicon (58%), Wafer (57%), Microelectromechanical systems (56%), Substrate (electronics) (55%)
Citations
More filters

Journal ArticleDOI
Abstract: Liquid-liquid mass transfer mechanism with slug flow in microreactor is investigated by means of experiments in square microchannels of 0.2 and 0.3 mm width. An experimental bench has been designed and an analytical protocol developed in order to follow the transfer of a solute from the dispersed phase to the continuous phase. The methodology used allows the identification of droplet side mass transfer coefficients. Total flow rate ranges from 5 to 50 mL.h-1, resulting in droplets velocities of 0.02 to 0.35 m.s-1. Volumetric mass transfer coefficient kda values obtained in the present work ranges from 0.89 to 9.45 s-1. The results reasonably fit with a model suggested by a previous study based on 2D direct numerical simulations. A comparison with other models available in literature shows that in the operating conditions considered in this work, the flow pattern inside the confined droplets at microscale leads to an enhancement of mass transfer compared to droplets that are not confined.

78 citations


11


Cites methods from "A single-mask substrate transfer te..."

  • ...High-aspect-ratio microchannels are fabricated in a silicon wafer by plasma etching using the deep reactive ion etching (DRIE) technique and the Bosch process (Tang et al., 2007; Laermer and Schilp, 1996)....

    [...]


Book
09 Aug 2010-
Abstract: Radio frequency (RF) microelectromechanical systems (MEMS) have been pursued for more than a decade as a solution of high-performance on-chip fixed, tunable and reconfigurable circuits. This paper reviews our research work on RF MEMS switches and switching circuits in the past five years. The research work first concentrates on the development of lateral DC-contact switches and capacitive shunt switches. Low insertion loss, high isolation and wide frequency band have been achieved for the two types of switches; then the switches have been integrated with transmission lines to achieve different switching circuits, such as single-pole-multi-throw (SPMT) switching circuits, tunable band-pass filter, tunable band-stop filter and reconfigurable filter circuits. Substrate transfer process and surface planarization process are used to fabricate the above mentioned devices and circuits. The advantages of these two fabrication processes provide great flexibility in developing different types of RF MEMS switches and circuits. The ultimate target is to produce more powerful and sophisticated wireless appliances operating in handsets, base stations, and satellites with low power consumption and cost.

49 citations


Cites background from "A single-mask substrate transfer te..."

  • ...Fig. 1 shows a wafer transfer fabrication process that specially developed for lateral DC-contact switches and switching circuits [ 6-8 ]....

    [...]


Journal ArticleDOI
10 Apr 2013-Physical Review E
TL;DR: Numerically the process of quasistatic invasion of a fluid in thin porous layers from multiple inlet injection sources focusing on the effect of trapping or mixed wettability, that is, when hydrophobic and hydrophilic pores coexist in the system is studied.
Abstract: We study numerically the process of quasistatic invasion of a fluid in thin porous layers from multiple inlet injection sources focusing on the effect of trapping or mixed wettability, that is, when hydrophobic and hydrophilic pores coexist in the system. Two flow scenarios are considered. In the first one, referred to as the sequential scenario, the injection bonds at the inlet are activated one after the other. In the second one, referred to as the kinetic scenario, the injection bonds at the inlet are activated simultaneously. In contrast with the case of purely hydrophobic systems with no trapping, studied in a previous work, it is shown that the invasion pattern and the breakthrough point statistics at the end of the displacement depend on the flow scenario when trapping or mixed wettability effects are taken into account. The transport properties of the defending phase are also studied and it is shown that a one-to-one relationship between the overall diffusive conductance and the mean saturation cannot be expected in a thin system. In contrast with thick systems, the diffusive conductance also depends on the thickness when the system is thin. After consideration of various generic aspects characterizing thin porous systems, the main results are briefly discussed in relation with the water management problem in proton exchange membrane fuel cells.

17 citations


18


Cites methods from "A single-mask substrate transfer te..."

  • ...High-aspect-ratio microchannels are fabricated in a silicon wafer by plasma etching using the deep reactive ion etching (DRIE) technique and the Bosch process (Tang et al., 2007; Laermer and Schilp, 1996)....

    [...]


01 Jan 2005-
Abstract: MEMS devices such as a vibratory gyroscope often suffer from a lower yield rate due to fabrication errors and the external stress. In the decoupled vibratory gyroscope, the main factor that determines the yield rate is the frequency difference between the sensing and driving modes. The gyroscope, fabricated with SOI (Silicon-On-Insulator) wafer and packaged using the anodic bonding, has a large wafer bowing caused by thermal expansion mismatch as well as non-uniform surfaces of the structures caused by the notching effect. These effects result in large distribution in the frequency difference, and thereby a lower yield rate. To improve the yield rate we propose a packaged SiOG (Silicon On Glass) technology. It uses a silicon wafer and two glass wafers to minimize the wafer bowing and a metallic membrane to avoid the notching. In the packaged SiOG gyroscope, the notching effect is eliminated and the warpage of the wafer is greatly reduced. Consequently the frequency difference is more uniformly distributed and its variation is greatly improved. Therefore we can achieve a more robust vibratory MEMS gyroscope with a higher yield rate.

15 citations


Journal ArticleDOI
Abstract: This paper presents a novel low-loss single-pole-double-throw (SPDT) switching circuit which integrates a silicon-core metal-coated coplanar waveguide (CPW) and two laterally moving switches in parallel. The circuit structure consists of single-crystal silicon as the core material and a thin layer of metal coated on the core surface to propagate the RF signal. The influences of the material property and the process variation on the RF performance of the silicon-core metal-coated CPW is analyzed in detail, including the silicon-core resistivity, the spreading metal on the substrate and the recess etching depth. Based on this analysis, the low-loss SPDT switching circuit is designed and fabricated using high-resistivity silicon (HRSi) as the core material and Pyrex 7740 glass as the substrate. The pull-in voltage of the laterally moving switch is 12.35 V. The insertion loss of the laterally moving switch is less than 1 dB up to 40 GHz. Both the return loss and the isolation are higher than 22 dB up to 40 GHz. The SPDT switching circuit has an insertion loss of less than 1 dB up to 22 GHz. The return loss is 17 dB and the isolation is 25 dB at 25 GHz. A silicon-on-glass (SOG)-based substrate-transfer micromachining process is developed for the SPDT switching circuit fabrication, which has the advantages of single mask, high design flexibility and low signal propagation losses.

6 citations


Cites methods from "A single-mask substrate transfer te..."

  • ...A substrate transfer process is developed for the fabrication of the SPDT switching circuit on a 500 μm thick 8′′ glass (Pyrex 7740) substrate [25]....

    [...]


References
More filters

Journal ArticleDOI
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

291 citations


Journal ArticleDOI
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.

184 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]....

    [...]


Journal ArticleDOI
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]....

    [...]


Journal ArticleDOI
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.

110 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]....

    [...]


Journal ArticleDOI
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


Performance
Metrics
No. of citations received by the Paper in previous years
YearCitations
20141
20131
20102
20081
20051