Low-loss RF MEMS metal-to-metal contact switch with CSP structure

J. Micromech. Microeng.

et al. 2005

In this paper, a packaging method utilizing an LTCC (low temperature co-fired ceramic) substrate and a BCB (benzocyclobutene) adhesive layer has been developed for RF MEMS devices, and the RF performance and characteristic parameters of the package have been evaluated. LTCC substrates have good RF characteristics in high-frequency applications, and via feedthroughs can be easily incorporated during the manufacturing process. In this paper, an LTCC substrate is used as a capping wafer to reduce the complex processes for vertical interconnections. A layer of BCB, in the form of sealing rims, is used as an adhesive to bond the MEMS substrate with the LTCC cap due to the excellent properties of BCB as a packaging material. A CPW (coplanar waveguide) line has been fabricated on a quartz substrate and packaged to demonstrate the performance of the proposed packaging method. After forming the CPW lines, a 28 µm thick BCB layer is patterned by double-coating photolithography for an adhesive bonding. On the backside of the LTCC cap, a 150 µm deep cavity is formed to improve the RF characteristics. The CPW and the contact pad are connected electrically through the silver via-post in the LTCC substrate by screen-printed silver epoxy. The RF characteristics of the CPW line have been measured before and after packaging. The insertion loss of a bare CPW is 0.047 dB at 2 GHz and 0.092 dB at 20 GHz. After packaging, the insertion loss of the packaged CPW is 0.091 dB at 2 GHz and 0.312 dB at 20 GHz. A leak test has been performed using both IPA (isopropyl alcohol) soaking and the He leak tester. Most of the samples show no leakage for the IPA test, and a measured leak rate of 10−8 atm cc s−1 for the He leak test. In addition, the shear strength of the package was measured to be 25–35 MPa. From the experimental results, we showed the feasibility of a low-loss RF MEMS package from dc to 20 GHz with acceptable package performances.

Section: Introductionmentioning

confidence: 99%

Packaging for RF MEMS devices using LTCC substrate and BCB adhesive layer

J. Micromech. Microeng.

et al. 2005

“…For these reasons, many researchers have recently been focusing on the utilization of SCS as a structural material. Because SCS has a nearly zero stress and heat characteristics superior to a metallic structure, it should be the most promising material for reliable MEMS devices with a uniform performance and better mechanical characteristics [14][15][16][17].…”

Section: Introductionmentioning

confidence: 99%

A mechanically reliable digital-type single crystalline silicon (SCS) RF MEMS variable capacitor

Lee

J. Micromech. Microeng.

et al. 2005

This paper reports the first demonstration of a single crystalline silicon(SCS)-based vertical gap-tuning MEMS variable capacitor with high mechanical reliability using the SiOG (silicon-on-glass) process. The proposed variable capacitor was fabricated by silicon-based micromachining technology, and its mechanical and electrical performances were tested. By adopting SCS, which has nearly zero stresses and superior thermal characteristics as a structural material, we can improve the manufacturability, reproducibility and mechanical reliability of the fabricated devices compared with a conventional metallic variable capacitor. The variable capacitor described in this paper is fabricated on a coplanar waveguide (CPW) transmission line and the top electrode in the driving part is incorporated with a SCS actuating membrane, resulting in a highly rigid structure without structural deformations. The designed SCS variable capacitor is actuated by an electrostatic force, and the total chip size is 1.05 mm × 0.72 mm. The measured pull-in voltage was 37 V, and the RF characteristics of the fabricated SCS variable capacitor from dc to 40 GHz were measured. With and without an applied dc bias voltage, the measured S11 and S21 were changed from −15.6 to −5.1 dB, and from −0.49 to −2.3 dB at 30 GHz, respectively. The measured capacitance at the up and the down states was 30 and 140 fF, respectively, which corresponds to the capacitance ratio of 4.67. The mechanical lifetime of the fabricated variable capacitor was also measured. RF performance degradation and stiction problems were not observed, even after 108 cycles of repeated actuations.

IEEE Trans. Microwave Theory Techn.

“…Radio frequency microelectromechanical systems (RF MEMS) switches, including contact [16]- [18] and capacitive [19]- [22] type, have been developed since their introduction in 1991 [23] to very mature RF components [24]- [26]. Potentially, RF MEMS technology could combine the advantages of an electromechanical rotary switch with the advantages of a PIN diode switch, as summarized in Table I.…”

mentioning

confidence: 99%

Parameter Analysis of Millimeter-Wave Waveguide Switch Based on a MEMS-Reconfigurable Surface

Baghchehsaraei

Oberhammer

2013

This paper presents a novel concept of a millimeter-wave waveguide switch based on a microelectromechanical (MEMS)-reconfigurable surface with insertion loss and isolation very similar to high performance but bulky rotary waveguide switches, despite its thickness of only 30 m. A set of up to 1470 micromachined cantilevers arranged in vertical columns are actuated laterally by on-chip integrated MEMS comb-drive actuators, to switch between the transmissive state and the blocking state. In the blocking state, the surface is reconfigured so that the wave propagation is blocked by the cantilever columns short-circuiting the electrical field lines of the TE mode. A design study has been carried out identifying the performance impact of different design parameters. The RF measurements (60-70 GHz) of fabricated, fully functional prototype chips show that the devices have an isolation between 30 and 40 dB in the OFF state and an insertion loss between 0.4 and 1.1 dB in the ON state, of which the waveguide-assembly setup alone contributes 0.3 dB. A device-level yield analysis was carried out, both by simulations and by creating artificial defects in the fabricated devices, revealing that a cantilever yield of 95% is sufficient for close-to-best performance. The actuation voltage of the active-opening/active-closing actuators is 40-44 V, depending on design, with high reproducibility of better than 0.0605 V . Lifetime measurements of the all-metal, monocrystalline-silicon core devices were carried out for 14 h, after which 4.3 million cycles were achieved without any indication of degradation. Furthermore, a MEMS-switchable waveguide iris based on the reconfigurable surface is presented.Index Terms-Microelectromechanical (MEMS) components and techniques, MEMS switches, microwave switch, millimeter-waves, reconfigurable surface, Radio frequency MEMS (RF MEMS), waveguide switch.