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. 2020 May 8;11(5):484. doi: 10.3390/mi11050484

Table 1.

Summary of the published works on MEMS capacitive microphone. CMOS = complementary metal-oxide-semiconductor.

Diaphragm Backplate Performances
Authors [Ref] Year Niche Application Fabrication Method(s) Material Geometry and Topology Size Thickness (µm) Air Gap (µm) Electrode Material Backplate Materials Air Damping Mechanism Bias Voltage (V) Stray Capacitance (pF) Input SPL * (dB) Open Circuit Sensitivity (mV/Pa) Resonant Frequency (kHz)
Hohm et al. [36] (1989) none bulk, back etching, bonding Si3N4 Square flat 0.8 × 0.8 mm2 0.15 2.0 Al SiO2 none 28 6.0 88 9 N/A
Bergqvist et al. [37] (1990) none bulk, back etching, bonding Si Square flat 2.0 × 2.0 mm2 5.0 4.0 Al Glass/ Si 103 acoustic holes on back chamber 16 3.5 94 13 24
Kuhnel et al. [38] (1992) none bulk, back etching, bonding Si3N4 Square flat 0.8 × 0.8 mm2 0.15 2.0 Al SiO2/ Si perforated backplate 28 3.0 94 1.8 30
Scheeper et al. [39] (1992) hearing aid surface, Plasma-enhanced chemical vapor deposition (PECVD) Si3N4 Square flat 0.6 × 0.6 mm2 1.0 2.2 Ti/Au SiO2 acoustic holes (120–525 holes/mm2) 16 7 N/A 2 14
Bourouina et al. [40] (1992) none bulk, anodic bonding p+ silicon. Square flat 1.0 × 1.0 mm2 1.0 N/A Al Si/Al 500 acoustic holes on backplate 20 N/A N/A 3.5 120
Bergqvist et al. [41] (1994) hearing aid bonding, back-etching, surface micromachine SiO2/Si Square flat 2.0 × 2.0 mm2 5.0 2.9 Al SiO2/ Si 400 holes/mm2 on backplate, hole diameter is 30 µm 10 4.3 94 15 17
Bergqvist et al. [42] (1994) none surface micromachine Si Square flat 1.8 × 1.8 mm2 4.0 3.0 Copper Ti-Au/Copper 400 holes/mm2., where holes diameter is 30 µm 28 2.9 43 1.4 47
Scheeper et al. [43] (1994) hearing aid surface micromachining, no bonding Si3N4 Square flat 2.0 × 2.0 mm2 1.0 1,2,3 N/A Si3N4 120–525 acoustic holes per mm2 5 6.6 30 10 14
Schellin et al. [44] (1994) none bulk micromachining Si Square flat 1.0 × 1.0 mm2 1.0 N/A Al Si N/A N/A N/A N/A N/A N/A
Donk et al. [45] (1994) none N/A Si3N4 Square flat 6.0 × 6.0 mm2 2.0 40 N/A Si3N4 N/A N/A 5 N/A N/A N/A
Bay et al. [46] (1996) hearing aid bulk, back etching, anodic bonding Si3N4 Square flat 2.0 × 2.0 mm2 0.2 0.4 N/A Si pillars at the center area of backplate electrode N/A N/A N/A N/A N/A
Ning et al. [47] (1996) none bulk, surface, plasma dry etching Si3N4 Square flat 20 × 20 µm2 0.5 - 1.0 3.1 Al Si3N4 square perforated holes on backplate 6 9.5 N/A 7 10
Zou et al. [48] (1997) none bulk, back etching Si3N4 Square corrugated 1.0 × 1.0 mm2 1.2 2.6 Al Si3N4 hole volume is 3 mm3 10 N/A N/A 14.2 16
Thielemann et al. [49] (1997) none bulk, back etching SiO2/Si3N4 Square flat 1.2 × 1.2 mm2 0.4 3.0 Al/Au Si 324 perforated holes on backplate 40 N/A N/A N/A N/A
Hsu et al. [50] (1998) none N/A Si Square flat 2.0 × 2.0 mm2 N/A N/A N/A Si 60 × 60 µm 2 acoustic holes on backplate 13 16.2 N/A 20 25
Pedersen et al. [51] (1998) none CMOS, surface (dry etching) Polyimide Square flat 2.2 × 2.2 mm2 1.1 3.6 Cr/Au/Cr Polyimide 30 × 30 µm2 acoustic holes on backplate 2 N/A 120 10 15
Pedersen et al. [52] (1998) none CMOS, surface (dry etching) Polyimide Square flat 2.2 × 2.2 mm2 1.1 3.6 Cr/Au/Cr Polyimide 30 × 30 µm 2 acoustic holes on backplate 4 10.1 120 10 15
Bay et al. [53] (1999) hearing aid surface, bulk micromachining Si3N4 Square flat 2.2 × 2.2 mm2 0.2 0.4 N/A Si perforated backplate N/A N/A N/A 27 N/A
Kabir et al. [54] (1999) none bulk and surface micromachining, electroplating technique p+ silicon Square flat 850 × 850 µm2 3.0 2.2 Au Au perforated backplate 9 2.4 N/A 9.77 N/A
Buhrdorf et al. [55] (2000) ultrasonic bulk, electroplating poly-Si Square flat 0.8 × 0.8 mm2 1.0 2.0 N/A Nickel perforated backplate 8 N/A N/A N/A 110
Torkkeli et al. [56] (2000) none bulk, surface micromachining poly-Si Square flat 1.0 × 1.0 mm2 0.8 1.3 Al Si acoustic hole size = 2 × 2 µm 2, perforated hole pitch = 10 µm 3 11 N/A 4 12
Brauer et al. [57] (2001) none bulk, surface micromachining, bonding poly-Si Circular flat d = 800 − 1200 µm 0.4 N/A N/A Si N/A 4.5 N/A 120 3.2 100 Hz
Hansen et al. [58] (2000) ultrasound in air and water N/A Si3N4 Rectangular flat 0.1 × 0.8 mm2 1.3 1.0 N/A N/A N/A N/A N/A N/A N/A 300
Li et al. [59] (2001) none bulk, surface micromachining, bonding Si Square corrugated 1.0 × 1.0 mm2 1.2 2.6 Al Si 40 × 40 holes on backplate, the dimension of each hole is 10 × 10 µm 5 1.64 N/A 10 20
Mullenborn et al. [60] (2001) hearing aid N/A Si Square flat 2.0 × 2.0 mm2 0.4 1.0 N/A Si N/A 1.5 N/A 24 5 N/A
Noble et al. [61] (2001) ultrasound surface micromachining Si3N4 Square flat 5.0 × 5.0 mm2 0.5 2.0 AlSi AlSi N/A 20 N/A N/A 1.4 N/A
Kronast et al. [62] (2001) none bulk, surface micromachining, bonding Si3N4 Square flat 2.0 × 2.0 mm2 0.3 1.3 Al Si acoustic hole density = 123 holes/mm2, holes size = 60 × 60 µm2 6 N/A 37.7 11 25
Rombach et al. [63] (2002) hearing aid bulk, surface micromachining SiN & B++ poly Si Square flat 2 × 2 mm2, 1 × 1 mm2 0.5 0.9 Cr/Pt Si perforated double backplate 1.5 N/A 100 13 20Hz
Kressmann et al. [64] (2002) none bulk, back etching, bonding SiO2/Si3N4 Square corrugated 1.0 × 1.0 mm2 0.6 2.0 Al Si 144 holes, each has area of 35 × 35 µm2, 80 µm distance between each hole N/A 25 39 2.9 10
Sim et al. [65] (2002) none patterning parylene-C Circular corrugated d = 4.3 mm 3.0 N/A N/A N/A N/A N/A N/A N/A NA N/A
Jing et al. [66] (2002) none N/A Si / Si3N4 Circular corrugated N/A N/A N/A Al Si N/A 14 N/A N/A 40 15
Miao et al. [67] (2002) none bulk micromachining poly-Si Square flat 1.0 × 1.0 mm2 3.0 N/A Al slotted Al/nitride acoustic holes on backplate N/A N/A N/A 10 15
Chen et al. [68] (2003) none bulk micromachining, deep reactive ion etching (DRIE) Si / Si3N4 Circular corrugated d = 1.0 mm 0.6 2.5 Al Si N/A 14 N/A N/A 40 N/A
Scheeper et al. [69] (2003) none bulk micromachining, bonding SiN Square flat 2.0 × 2.0 mm2 0.5 20 Cr/Au Si 4 acoustic holes on backplate N/A N/A N/A 22 N/A
Tajima et al. [70] (2003) none bulk, bonding single crystalline Si Square flat 2.0 × 2.0 mm2 5.0 15 N/A Si acoustic holes on backplate 48 N/A N/A 4.4 24
Wang et al. [71] (2003) none bulk, surface micromachining poly-Si Square corrugated 1.0 × 1.0 mm2 1.3 2.6 Al Si 80 × 80 µm 2 acoustic holes on backplate 6 N/A N/A 20.8 N/A
Hansen et al. [72] (2004) wide-band operation bulk, surface micromachining Si3N4 Rectangular flat 70 × 190 µm 2 0.4 N/A Al Si N/A 5.8 N/A 63.6 N/A 100
Ning et al. [73] (2004) none bulk, surface micromachining Si3N4 Square flat 1.5 × 1.5 mm2 0.5 1.5 Al Si 40 × 40 µm 2 acoustic holes 8.3 N/A N/A 5.6 20
Wang et al. [74] (2004) none bulk, surface micromachining poly-Si Square corrugated 1.0 × 1.0 mm2 1.3 2.6 Al Si N/A 6 N/A N/A 9.8 N/A
Wang et al. [75] (2004) none bulk, surface micromachining poly-Si Square corrugated 1.0 × 1.0 mm2 1.2 2.6 Al Si N/A 5 N/A 50 16.4 20
Sezen et al. [76] (2005) bio-medical N/A Si3N4 Circular flat d = 400 µm 1.5 0.8 Al Si N/A N/A N/A N/A N/A N/A
Ko et al. [77] (2006) none bulk, surface micromachining doped-polySi Square flat 1.5 × 1.5 mm2 0.7 2.4 Au/Ti and Pt/Ti Si acoustic holes on backplate with stopper 5 N/A N/A 5.17 15
Kim et al. [78] (2006) none N/A Al Square hinge 1.5 × 1.5 mm2 N/A N/A Al SiN/Al/SOI N/A 25 N/A N/A N/A 20
Weigold et al. [79] (2006) none bulk Si Circular flat N/A N/A 3.0 N/A Si N/A N/A N/A N/A 4.4 N/A
Dehe et al. [80] (2007) hand free & hearing aid bulk, surface micromachining Si Circular corrugation edge d = 1 mm 0.4 2.0 N/A Si perforated backplate 2 N/A N/A 11.2 4
Kim et al. [81] (2007) portable terminals N/A Au Square hinge 1.5 × 1.5 mm2 0.6 1.0 N/A Si N/A 1 N/A N/A 0.01 13
Goto et al. [82] (2007) none bulk micromachining, bonding Si Square flat 2.0 × 2.0 mm2 8.0 varied up to 100 µm Al Si N/A 48 N/A 122 6.6 20
Iguchi et al. [83] (2007) none bulk micromachining, bonding Si Square flat 2.1 × 2.1 mm2 8.0 10 Al Si 10 × 10 µm2 acoustic holes on backplate 39 N/A 134 2.5 20
Kwon et al. [84] (2007) none bulk micromachining and Si DRIE Si3N4 Square flat 2.5 × 2.5 mm2 0.5 9.0 Au/Ni/Cr Si 50–60 µm radius circular acoustic holes on backplate 28 N/A 120 0.0089 5
Martin et al. [27] (2007) aeroacoustic measurement bulk, surface micromachining Si Circular flat d = 0.46 mm 2.25 2.0 N/A Si hole radius: 5 µm 9.3 N/A 164 0.39 20
Kasai et al. [85] (2007) none 4 corner supported diaphragm poly Si Square flat 1.2 × 1.2 mm2 N/A N/A N/A Si N/A 12 N/A N/A 8.8 10
Chen et al. [86] (2008) none modeling and simulation Si Circular flat d =560 µm N/A 4.0 N/A N/A acoustic holes with diameter of 4 µm 11 N/A 100 17.7 20
Ganji et al. [87] (2008) none surface micromachining Al Square perforated 0.5 × 0.5 mm2 3.0 1.0 n+ backplate electrode Si 20 × 20 µm2 acoustic holes 105 N/A N/A 0.2 20
Her et al. [88] (2008) none bulk, surface micromachining Si Circular flat d = 670 µm 1.0 3.0 Cr/Au Si perforated backplate 6 N/A 94 7.9 10
Hall et al. [89] (2008) none N/A Si Circular flat d = 1.5 mm 2.3 3.0 N/A Si perforated backplate N/A N/A N/A N/A 20
Kaur et al. [90] (2009) none SOI Si Square flat 0.5 × 0.5 mm2 10 - 20 nm 0.1 to 1.95 N/A N/A N/A 0.04 N/A N/A N/A 20
Ganji et al. [91] (2009) none surface micromachining Al Square perforated 0.5 × 0.5 mm2 3 1.0 n+ backplate electrode Si holes size of 20 × 20 µm 2, distance between holes is 80 µm 105 2.12 N/A 0.2 20
Ganji et al. [92] (2009) none simulation Al Square slotted 2.43 × 2.43 mm2 3.0 1.0 n+ backplate electrode Si N/A 105 N/A N/A N/A 528
Lee et al. [93] (2009) none surface micromachining Au Circular flat d = 300 µm N/A 2.0 Ti/Al/TiN Si N/A 5 1.87 N/A 0.57 N/A
Leinenbach et al. [94] (2010) none bulk Si Circular flat d = 0.6 mm N/A N/A N/A Si perforated backplate N/A N/A N/A N/A 12
Ganji et al. [95] (2010) none surface micromachining Al Square slotted N/A 3.0 1.3 Al Si perforated diaphragm N/A 17.5 N/A N/A N/A
Yang et al. [96] (2010) none N/A Si3N4 Circular flat d = 450 µm 1.5 2.75 Al/ Au Si3N4 N/A 12 N/A N/A 14 N/A
Mohamad et al. [97] (2010) none Poly Multi-Users MEMS Process (MUMPS) Poly-Si Square flat spring 4.0 × 4.0 mm2 4 4 Au Poly-Si 50 holes on backplate 3 N/A N/A 4.67 10.2
Chan et al. [98] (2011) none surface micromachining poly Si Circular spring d = 1 mm 3.0 2.0 N/A Si perforated rigid backplate N/A 1.81 94 12.63 24.9
Chiang et al. [99] (2011) mobile phones, laptops, hearing aids N/A Si Rectangular flat 1444 × 1383 µm 2 N/A N/A N/A N/A N/A N/A N/A 94 N/A 20
Huang et al. [100] (2011) none bulk, surface micromachining Corrugated Al Circular corrugated d = 800 µm 1.1 4.2 N/A Si air holes diameter: 20 µm 6 0.7 N/A 7.9 10
Jawed et al. [101] (2011) none bulk, surface micromachining Si Square flat N/A N/A N/A N/A Au N/A N/A 1.64 55 10 9
Je et al. [102] (2011) none surface micromachining Al Circular flat center-hole d = 500 µm 1.0 2.0 Ti/Al SiO2/Al/SiN 5 holes at the center of diaphragm, where diameter of each hole is 12 µm 6 N/A N/A N/A 20
Kasai et al. [103] (2011) none bulk, surface micromachining Si Square flat dual channel N/A N/A N/A N/A Si3N4 / Si N/A N/A N/A N/A 5.6 20
Lee et al. [104] (2012) none bulk, surface micromachining Si3N4 Circular flat d = 600 µm 0.9 2.45 Al SiO2 / Si3N4 1668 acoustic holes on backplate, where hole radius = 4 µm. 10.4 1.02 N/A 3.75 18
Ahmadnejad et al. [105] (2013) none simulation Al Square perforated 2.43 × 2.43 mm2 1.0 1.0 n+ backplate electrode Si 16 holes on diaphragm, side length = 20 µm 2.3 N/A N/A 6.916 N/A
Chao et al. [106] (2013) mobile device bulk, surface poly Si Square flat 2.0 × 2.0 mm2 1.1 3.75 N/A Si perforated backplate 4.5 2.4 N/A 1.7 10
Je et al. [107] (2013) none surface micromachining, CMOS Al/Si3N4/Al Circular flat d = 500 µm 1.0 2.5 Al Al/Si3N4/Al perforated backplate 6 N/A N/A 10.37 20
Kuntzman et al. [108] (2014) none surface micromachining poly Si Circular flat d = 630 µm 2.25 11 N/A Si air volume in the cavity with radius of 315–504 µm 100 0.25 N/A 0.167 230
Lee et al. [109] (2014) none simulation Si Square flat 900 × 900 µm 2 1.0 3 Ti/Au Si Acoustic holes with diameter of 24 µm. 12 N/A N/A 9 79.4
Lee et al. [110] (2014) none bulk, eutectic bonding Si3N4 Circular flat d = 2 mm 1.0 3.0 Ti/Au Si acoustic holes cover 18% of backplate 12 N/A N/A 13 10
Grixti et al. [111] (2015) none N/A Si Square flat 675 × 675 µm2 0.5 2.0 Au Si holes-to-backplate ratio = 0.33 6 1.53 139 8.4 1
Kuntzman et al. [112] (2015) ultrasonic N/A Si Circular flat d = 630 µm 2.3 0.3 N/A Si square holes on backplate 50 N/A N/A 10 18.8
Lo et al. [113] (2015) none bulk, surface micromachining Si Circular flat d = 600 µm 1.6 1.6 N/A No backplate N/A N/A N/A N/A N/A 1
Shin et al. [114] (2015) none electret substrate: bulk, surface Si Circular flat d = 1.2 mm 5.0 5.0 Cr/Au Si 110 µm diameter acoustic holes N/A N/A 107 N/A 20
Todorovic et al. [115] (2015) none bulk, surface micromachining Multilayer graphene Circular flat d = 12 mm 0.025 18.6 N/A N/A N/A 200 N/A 90 50 6.5
Gharaei et al. [26] (2016) aerospace application simulation Si Circular flat d = 660 µm 230 2.0 N/A Si 367 acoustic holes on backplate 11 1.15 N/A 0.478 100
Lee et al. [116] (2016) none bulk, surface micromachining TiN/Si3N4/TiN Circular flat d= 0.65 mm 0.6 1.6 Al Si3N4 acoustic holes on backplate, radius: 4 µm 11.1 0.23 N/A 5.3 10
Manz et al. [117] (2017) none N/A Si Rectangular flat 500 × 800 µm 2 N/A 0.5 N/A N/A N/A N/A N/A 73 12.5 35
Mao et al. [118] (2017) none CMOS Pure dielectric-film Circular flat d = 300 µm N/A N/A N/A No backplate N/A 13.5 N/A N/A 0.6 22
Woo et al. [119] (2017) hearing aid Bulk micromachining Graphene / Polymethylmethacrylate (Acrylic) or PMMA Circular flat d = 4.0 mm N/A 10 Au Ti N/A N/A N/A 90 100 7.0
Zawawi et al. [120] (2017) detect poisonous gas Finite element analysis (FEA) simulation 3C-SiC Square flat 1.0 × 1.0 mm2 1.0 3.0 N/A N/A perforated backplate N/A N/A N/A N/A 36
Sedaghat et al. [121] (2018) none FEA (simulation) Al Square perforated 0.5 × 0.5 mm2 3.0 1.0 N/A Si perforated diaphragm area is 0.0144 mm2 1.35 N/A N/A 6.677 21.504
Nicollini et al. [122] (2018) none CMOS Poly-Si Rectangular flat 0.5 × 1.0 mm N/A 5.6 N/A N/A acoustic holes on the backplate N/A N/A 120 12.58 20
Ganji et al. [123] (2018) none bulk micromachining using SOI wafer Si Square perforated 0.3 × 0.3 mm2 5.0 1.0 N/A Si 5 × 5 µm holes size on perforated diaphragm 5 N/A N/A 2.46 60
Jantawong et al. [124] (2019) none bulk micromachining Poly-Si Circular flat d = 930 µm 0.8 3.5 Al Si perforated backplate N/A N/A 123 N/A N/A
Wittmann et al. [125] (2019) none CMOS Graphene Circular flat d = 40 µm N/A N/A Au Si N/A 1.5 N/A N/A 1.051 100
Mustapha et al. [126] (2019) none bulk micromachining Graphene Circular flat d = 40 µm 0.5 0.2 Cr/Au Si N/A 3.0 N/A N/A 0.035 20
Auliya et al. [127] (2019) none FEA simulation Si/SiC/tungsten Circular corrugated d = 2.0 mm 18 18 N/A N/A N/A 41 N/A N/A 0.15 70
Malik et al. [3] (2019) hearing aid N/A Si3N4 Circular flat area = 7850 µm 2 2.0 N/A N/A Si perforated backplate 4.0 N/A N/A 0.086 10
Wood et al. [128] (2019) none bulk micromachining Graphene/PMMA Circular flat d = 3.5 mm 0.2 8.0 Al SiO2/Si N/A 1.0 N/A 80 10 20

* Input SPL (dB) refers to maximum sound pressure level. Some papers put 94 dB. This is the standard value that is used to test the sensitivity of their prototypes. The detailed explanation can be found in Section 5.3 of this paper. Note: N/A refers to data about specific parameter that is not provided by the authors. For example, many articles only present the diaphragm, so information on backplate are labeled as N/A. Similarly, not all papers provide complete information on the performance parameters.