Manufacturing and Characterization of Three-Axis Magnetic Sensors Using the Standard 180 nm CMOS Technology

Abstract

A three-axis micro magnetic sensor (MS) is developed based on the standard 180 nm complementary metal oxide semiconductor (CMOS) technology. The MS designs two magnetic sensing elements (MSEs), which consists of an x/y-MSE and an z-MSE, to reduce cross-sensitivity. The x/y-MSE is constructed by an x-MSE and an y-MSE that are respectively employed to detect in the x- and y-direction magnetic field (MF). The z-MSE is used to sense in the z-direction MF. The x/y-MSE, which is constructed by two magnetotransistors, designs four additional collectors that are employed to increase the sensing current and to enhance the sensitivity of the MS. The Sentaurus TCAD software simulates the characteristic of the MS. The measured results reveal that the MS sensitivity is 534 mV/T in the x-direction MF, 525 mV/T in the y-direction MF and 119 mV/T in the z-axis MF.

Foundry Service of CMOS MEMS Processes and the Case Study of the Flow Sensor

“…Figure 4a shows the deposition of the polysilicon above the substrate; Figure 4b represents the CMOS layer with an additional pattern of contact layer; Figure 4c depicts the standard CMOS layer with amorphous SiO2, metal M1-M6, metal 7 hard mask, and a passivation layer; Figure 4d developed the thick photoresist layer to perform the patterning; lastly, Figure 4e,f shows anisotropic silicon oxide etching and XeF2 isotropic silicon etching, respectively. The powerful CMOS MEMS foundry service in Taiwan has contributed to a variety of MEMS microsensor developments such as magnetic sensors [90,[98][99][100][101][102], humidity sensors [103][104][105][106][107][108], gas sensor [54,63,[109][110][111][112], pressure sensors [16,78,[113][114][115][116][117], thermoelectric energy harvesters [118][119][120][121][122], strain sensors [37,40,53], thermal sensors [123][124][125][126][127]<...…”

“…In the earlier stage, the CMOS MEMS process had a larger CD or minimum line width in the academic labs of Europe and USA [73][74][75][76][77][78][79][80]. As the CD kept on decreasing to 0.8 µm [35] The powerful CMOS MEMS foundry service in Taiwan has contributed to a variety of MEMS microsensor developments such as magnetic sensors [90,[98][99][100][101][102], humidity sensors [103][104][105][106][107][108], gas sensor [54,63,[109][110][111][112], pressure sensors [16,78,[113][114][115][116][117], thermoelectric energy harvesters [118][119][120][121][122], strain sensors [37,40,53], thermal sensors [123][124][125][126]…”

“…Figure 5a shows the CMOS standard process, which is composed of four kinds of different thin films including silicon nitride (Si3N4), silicon dioxide (SiO2), aluminum, and polysilicon on the silicon substrate. The arrangements of thin films in the order from bottom to top are silicon substrate, silicon dioxide, multiple metal layers with their inter-layer for bulk micromachining [91,165]; (c) acid etch metals (surface micromachining) [35,37]; (d) deep trench plasma etching the oxides to release the cantilever [130]; (e) acid is used to etch metals and TMAH used to etch the Si substrate [57]; (f) electroplating Ni in the process (c) [90,137]; (g) parylene or gelatin is coated on process (e) [87,88]; (h) anisotropic and isotropic etching with STI protection [96,97,102,166].…”

“…The detailed explanation has been given in Figures 2-4. STI oxide is used to protect polysilicon during XeF 2 etching [96,97,102,122].…”

“…, 0.35 µm[94,122,[130][131][132], 0.18 µm[96,100,102,109,112,128,133], and so on, the CMOS MEMS foundry service has still been running smoothly.…”