WO2009057988A2 - Commutateur mems à radiofréquence - Google Patents

Commutateur mems à radiofréquence Download PDF

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Publication number
WO2009057988A2
WO2009057988A2 PCT/MY2008/000122 MY2008000122W WO2009057988A2 WO 2009057988 A2 WO2009057988 A2 WO 2009057988A2 MY 2008000122 W MY2008000122 W MY 2008000122W WO 2009057988 A2 WO2009057988 A2 WO 2009057988A2
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WO
WIPO (PCT)
Prior art keywords
aluminum
layer
thickness
photolithography process
ground
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/MY2008/000122
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English (en)
Other versions
WO2009057988A3 (fr
Inventor
Suraya Sulaiman
Mohd Ismahadi Syono
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Mimos Bhd
Original Assignee
Mimos Bhd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Mimos Bhd filed Critical Mimos Bhd
Publication of WO2009057988A2 publication Critical patent/WO2009057988A2/fr
Publication of WO2009057988A3 publication Critical patent/WO2009057988A3/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H1/00—Contacts
    • H01H1/0036—Switches making use of microelectromechanical systems [MEMS]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G5/00—Capacitors in which the capacitance is varied by mechanical means, e.g. by turning a shaft; Processes of their manufacture
    • H01G5/16—Capacitors in which the capacitance is varied by mechanical means, e.g. by turning a shaft; Processes of their manufacture using variation of distance between electrodes
    • H01G5/18—Capacitors in which the capacitance is varied by mechanical means, e.g. by turning a shaft; Processes of their manufacture using variation of distance between electrodes due to change in inclination, e.g. by flexing, by spiral wrapping
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H59/00—Electrostatic relays; Electro-adhesion relays
    • H01H59/0009—Electrostatic relays; Electro-adhesion relays making use of micromechanics

Definitions

  • the present invention relates generally to microelectroraechanical switches and more particularly, to a method of fabricating radio frequency microelectromechanical switch of the capacitive type and a radio frequency microelectromechanical switch fabricated from the same.
  • MEMS microelectromechanical
  • Capacitive micromachined devices could be used in many applications, for example radar systems and wireless communication.
  • Wireless applications such as the transmit/receive switches in cellular telephones are- the likely candidate to be replaced by capacitive ..micromachined switches.
  • capacitive switches when compared to its solid state counterparts have lower insertion loss, have higher isolation,, better nonlinearlity and have zero static power consumption.
  • capacitive micromachined RF switches have such desired characteristics, the method of fabricating them is not without their inherent problems. For example, good surface planarization is difficult to achieve resulting in lower mechanical performance. In addition, deterioration of RF performance of a typical low-resistivity silicon is prevalent .
  • RM MEMS switch is a device that uses mechanical movement to achieve a short circuit or open circuit in RF transmission line.
  • the switch generally consists of a lower electrode fabricated on the surface of silicon wafer and a thin aluminum membrane suspended over the electrode. The membrane is connected directly to grounds on either side of the electrode while a thin dielectric layer covers the lower electrode . The air gap between the two conductors determines the switch on/off capacitance.
  • a RM MEMS switch that comprises of a movable aluminum bridge actuated by a bottom electrode that is coated with a silicone nitride film.
  • the RF MEMS switch is further having the aluminum layer as the transmission line and the movable bridge, the silicone nitride as the dielectric layer and silicone dioxide as the sacrificial layer.
  • Coplanar waveguide (CPW) line is defined on the metallization layer on the substrate.
  • the RF MEMS switch further having aluminum layer as the transmission line and also for the movable bridge, silicone nitride as the dielectric layer and silicone dioxide as the sacrificial layer.
  • a method of fabricating a radio frequency (RF) microelectromechanical (MEMS) switch said RF MEMS switch comprises of a lower electrode (30) fabricated on the surface of a silicon substrate (31) , an aluminum membrane (32) suspended over said electrode, a dielectric layer (33) covering said lower electrode, characterized in that said method comprises the steps of:-
  • a dielectric layer by depositing a Silicon Nitride of 0.5 ⁇ m in thickness (9) ;
  • TEOS Tetraethooxysihme
  • the plasma etching is performed using XeF 2 vapor etching solution.
  • an air gap of 1.0 ⁇ m is formed above of the Aluminum membrane.
  • the Aluminum membrane having a Young modulus of 70 GPa, a Poisson' s ratio of 0.34 and density of 2700 kg/m 3 .
  • a radio frequency (RF) irdcroelectromechanical (MEMS) switch said RF MEMS switch comprises of a lower electrode (30) fabricated on the surface of a silicon substrate (31), an aluminum . membrane (32) suspended over said electrode, a dielectric layer (33) covering said lower electrode, characterized in that said RF MEMS switch is fabricated through the steps of:-
  • ground/signal/ground layers (7)
  • a dielectric layer by depositing a Silicon Nitride of 0.5 ⁇ m in thickness (9) ;
  • Figure 1 shows an illustration of a RF MEMS switch configure according to the embodiment of the present invention
  • Figure 2 shows the fabricating steps of RM MEMS switch according to the present invention.
  • Figure 3 shows material property table of the various switch layers.
  • the switch comprises of an aluminum bridge (32) suspended over a dielectric layer (33) deposited on the central part of the transmission line with a coplanar waveguide (CPW) configuration.
  • CPW coplanar waveguide
  • the electrical isolation of the switch will depend on the capacitive coupling between the signal line and ground lines.
  • the dielectric layer (33) functioned to act as an electrical isolation.
  • the bridge (32) is pulled-down, the bias voltage is directly applied across the dielectric layer. Since the layer is very thin, the electric field within the dielectric layer is very high.
  • the thickness of the dielectric layer should be chosen such that the electric field will never exceed the breakdown electric field. Silicone nitride film that has high breakdown electric field of about several mega-volt per centimeter could be utilized as dc block dielectric layer.
  • the thickness of the Silicone Nitride is chosen to be 0.15 pr ⁇ to provide such dc blocking and RF coupling .
  • the RF MEMS switch comprises of a movable aluminum bridge actuated by the bottom electrode and such bottom electrode is coated with a Silicon Nitride film using surface micromachining technology.
  • Four layers of masks are applied where each of the masks is created through photolithography process performed at separate stages.
  • the aluminum layer is also use as transmission line, Silicon Nitride as the dielectric layer and Silicone Dioxide as the sacrificial layer.
  • Coplanar waveguide (CPW) line is defined on the metallization layer on the substrate.
  • the critical feature for producing an improved mechanical performance of an RF MEMS switch is to get good planarization thickness of the Silicone Dioxide.
  • Silicon on glass liquid is used to fill small holes that appear on the Silicon Dioxide.
  • Back etching process is also utilized together with having thick Silicon Dioxide deposited and etch back to the desired thickness.
  • pad etchant solution is used to etch the Silicon Dioxide away.
  • high resistivity silicon wafer (with resistance of more than 10 Kohm) is preferred because low-resistivity silicon will deteriorate the RF performance.
  • the material properties and are generally shown in Figure 3 and the aluminum metal for the bridge has the following characters:
  • the preferred method to fabricate RF MEMS switch is illustrated in Figure 2.
  • the steps includes : - selecting a substrate is made of P-type dummy wafer and having resistivity of more than 10 Kilo ohm-cm (1) , removing any contamination and particle that appears on selected substrate and this is to be done after the wafer coding process (2) , applying wet oxidation (3) and setting 1 ⁇ m as a buffer oxide, performing LPCVD silicone nitride deposition to set a 0.2 ⁇ m for barrier, performing aluminum deposition to set 0.4 ⁇ m of ground/signal/ground definition, configuring a first mask using lithography process to set the ground/signal/ground definition.
  • Dry etching is applied on the deposited aluminum to form the ground/signal/ground layers.
  • the structure- is then subjected to removal of photoresist (8) used in the lithography process using plasma etcher and passivate the metal layer to prevent corrosion.
  • a dielectric layer is then formed (9) by depositing a silicon nitride having 0.5 ⁇ m in thickness.
  • the next mask is then set where hardening of the photoresist (11) used in the lithography process is perform to prevent resist reticulation and then followed by dry etch the Silicon Nitride layer to form 0.15 ⁇ m of the layer and followed by hard bake (12) .
  • Plasma etcher is then used to remove photoresist used in the process (13) .
  • the next step is performing silicon dioxide IMD deposition to obtain about 0.85 ⁇ m thickness (14), depositing 0.1 ⁇ m of silicon on a glass coating to fill up uneven deposition of the Silicon Dioxide surface for purpose of planarization of the dielectric layer (15) , followed by performing Tetraethooxysihme (TEOS) oxide deposition to obtain 0.3 um in thickness (16), and creating 1.0 ⁇ m thickness of air gap above the Silicon Nitride layer by setting thickness of 1.15 ⁇ m of the oxide layer as the sacrificial layer and isolation for CPW ground plane (17) .
  • TEOS Tetraethooxysihme
  • the next step is configuring a third mask using the same lithography process to form aluminum posts for the aluminum membrane (18) , removing the photoresist used in the process using plasma etcher (19), hardening the photoresist to prevent resist reticulation (20), dry etching the Silicon Dioxide to form 1 ⁇ m thickness layer (21) and removing photoresist used in process using plasma etcher (22) .
  • the next step is depositing aluminum layer of 1.0 ⁇ m thickness to form post and bridge of the membrane (23) .
  • the fourth mask is configure for bridge definition and photoresist development (24) , followed by hardening of the photoresist to prevent resist reticulation (25) and dry etching the aluminum layer to form the aluminum bridge for the membrane (26) and removing the Silicon Dioxide sacrificial layer using wet etching process using chemical solution called Pad Etch.
  • good planarization is crucial to obtain mechanically robust RF MEMS switch.
  • the proposed invention fulfill such requirement by employing Silicon on glass liquid deposition to fill small holes that appear on the Silicon Dioxide layer and together with the application of multiple masks, a better mechanical performance of RF MEMS switch is generally obtain.
  • modeling through the application of EMSDS* 111 software from Coventorware is performed.
  • the RF MEMS switch is modeled as capacitive shunt switch device for high frequencies applications. Considerations such as the location conductor and gap of the CPW play important role in waveguide properties especially with respect to loss and bandwidth.
  • the CPW transmission line is designed to have 50 ⁇ 50 ohm input impedance.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Micromachines (AREA)

Abstract

L'invention concerne un procédé de fabrication d'un commutateur microélectromécanique (MEMS) à radiofréquence. Ce procédé fait intervenir quatre masques, chaque masque étant conçu à différentes étapes d'un processus de photolithographie qui permet d'obtenir une surface de dioxyde de silicium sensiblement plane, la planarité étant un facteur critique permettant d'améliorer la performance mécanique du commutateur MEMS RF. Le procédé de l'invention consiste, entre autres, à : déposer du silicium sur un liquide vitreux pour remplir de petits trous afin d'obtenir une surface d'oxyde de silicium lisse; effectuer une morsure de descente d'intensité et un gravage humide à l'aide d'une solution chimique appelée Pad Etch. L'invention concerne également un commutateur RF MEMS comprenant une électrode inférieure (30) formée sur la surface d'un substrat en silicium (31), une membrane en aluminium (32) suspendue au-dessus de l'électrode et une couche diélectrique (33) couvrant l'électrode inférieure et fabriquée par le processus susmentionné.
PCT/MY2008/000122 2007-10-31 2008-10-22 Commutateur mems à radiofréquence Ceased WO2009057988A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
MYPI20071873 2007-10-31
MYPI20071873A MY146154A (en) 2007-10-31 2007-10-31 Radio frequency mems switch

Publications (2)

Publication Number Publication Date
WO2009057988A2 true WO2009057988A2 (fr) 2009-05-07
WO2009057988A3 WO2009057988A3 (fr) 2009-07-16

Family

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Application Number Title Priority Date Filing Date
PCT/MY2008/000122 Ceased WO2009057988A2 (fr) 2007-10-31 2008-10-22 Commutateur mems à radiofréquence

Country Status (2)

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MY (1) MY146154A (fr)
WO (1) WO2009057988A2 (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102205942A (zh) * 2011-05-13 2011-10-05 上海集成电路研发中心有限公司 Mems牺牲层结构制造方法
CN103345057A (zh) * 2013-05-31 2013-10-09 华中科技大学 一种微型的桥式结构及其制备方法
EP2725595A1 (fr) * 2012-10-25 2014-04-30 Delfmems Condensateur fixe MEMS comprenant un espace contenant un gaz et procédé de fabrication dudit condensateur
CN113670994A (zh) * 2021-08-26 2021-11-19 南京高华科技股份有限公司 基于相位检测原理的mems湿度传感器及制备方法
CN117097361A (zh) * 2023-07-20 2023-11-21 湖北九峰山实验室 一种集成多频段天线和射频开关的器件及其制备方法

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6621387B1 (en) * 2001-02-23 2003-09-16 Analatom Incorporated Micro-electro-mechanical systems switch
KR100893893B1 (ko) * 2002-12-02 2009-04-20 삼성전자주식회사 점착현상을 방지할 수 있는 ｒｆ ｍｅｍｓ 스위치
KR20050068584A (ko) * 2003-12-30 2005-07-05 매그나칩 반도체 유한회사 고주파 소자의 스위치 형성방법
US7265647B2 (en) * 2004-03-12 2007-09-04 The Regents Of The University Of California High isolation tunable MEMS capacitive switch

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102205942A (zh) * 2011-05-13 2011-10-05 上海集成电路研发中心有限公司 Mems牺牲层结构制造方法
EP2725595A1 (fr) * 2012-10-25 2014-04-30 Delfmems Condensateur fixe MEMS comprenant un espace contenant un gaz et procédé de fabrication dudit condensateur
WO2014064185A1 (fr) 2012-10-25 2014-05-01 Delfmems Condensateur fixe de microsystème électromécanique comprenant un écartement contenant du gaz et processus de fabrication dudit condensateur
CN104756212A (zh) * 2012-10-25 2015-07-01 德尔福芒斯公司 包括含气体的间隙的mems固定电容和用于制造所述电容器的方法
CN103345057A (zh) * 2013-05-31 2013-10-09 华中科技大学 一种微型的桥式结构及其制备方法
CN103345057B (zh) * 2013-05-31 2016-06-01 华中科技大学 一种微型的桥式结构及其制备方法
CN113670994A (zh) * 2021-08-26 2021-11-19 南京高华科技股份有限公司 基于相位检测原理的mems湿度传感器及制备方法
CN117097361A (zh) * 2023-07-20 2023-11-21 湖北九峰山实验室 一种集成多频段天线和射频开关的器件及其制备方法
CN117097361B (zh) * 2023-07-20 2024-04-30 湖北九峰山实验室 一种集成多频段天线和射频开关的器件及其制备方法

Also Published As

Publication number Publication date
WO2009057988A3 (fr) 2009-07-16
MY146154A (en) 2012-06-29

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