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A Meliorated Multi-Frequency Band Pyroelectric Sensor.

Hsiao CC, Liu SY, Siao AS - Sensors (Basel) (2015)

Bottom Line: The proposed sensor is built on a silicon substrate with a thermal isolation layer of a silicon nitride film, consisting of four pyroelectric layers with various thicknesses deposited by a sputtering or aerosol deposition (AD) method and top and bottom electrodes.The fabricated device is effective in the range of 1 KHz~10 KHz with a rapid response and high voltage responsivity, while the ZnO layers with thicknesses of about 0.8 μm, 6 μm, 10 μm and 16 μm are used for fabricating the meliorated multi-frequency band pyroelectric sensor.The proposed sensor is successfully designed, analyzed, and fabricated in the present study, and can indeed extend the sensing range of the multi-frequency band.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Design Engineering, National Formosa University, No. 64, Wunhua Rd., Huwei Township, Yunlin County 632, Taiwan. cchsiao@nfu.edu.tw.

ABSTRACT
This article proposes a meliorated multi-frequency band pyroelectric sensor for detecting subjects with various velocities, namely extending the sensing frequency under good performance from electrical signals. A tactic, gradually increasing thickness of the ZnO layers, is used for redeeming drawbacks of a thicker pyroelectric layer with a tardy response at a high-frequency band and a thinner pyroelectric layer with low voltage responsivity at a low-frequency band. The proposed sensor is built on a silicon substrate with a thermal isolation layer of a silicon nitride film, consisting of four pyroelectric layers with various thicknesses deposited by a sputtering or aerosol deposition (AD) method and top and bottom electrodes. The thinnest ZnO layer is deposited by sputtering, with a low thermal capacity and a rapid response shoulders a high-frequency sensing task, while the thicker ZnO layers are deposited by AD with a large thermal capacity and a tardy response shoulders a low-frequency sensing task. The fabricated device is effective in the range of 1 KHz~10 KHz with a rapid response and high voltage responsivity, while the ZnO layers with thicknesses of about 0.8 μm, 6 μm, 10 μm and 16 μm are used for fabricating the meliorated multi-frequency band pyroelectric sensor. The proposed sensor is successfully designed, analyzed, and fabricated in the present study, and can indeed extend the sensing range of the multi-frequency band.

No MeSH data available.


Fabricated multi-frequency band pyroelectric sensor with an improved design.
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sensors-15-16248-f004: Fabricated multi-frequency band pyroelectric sensor with an improved design.

Mentions: The fabrication flow of the meliorated multi-frequency band ZnO-film pyroelectric sensor was divided into ten steps, as follows. A silicon wafer with specifications of (100) p-type, double-side polished and resistivity of 1–10 Ω-cm, was used as a substrate to build the multi-frequency band pyroelectric sensor, as shown in Figure 3a. A 1 μm thicker low-stress silicon nitride layer was deposited on both sides of the substrate by LPCVD, which was mainly for reducing or blocking heat or electric loss through the silicon substrate, as shown in Figure 3b. Then, the bottom electrode consisting of a 100 nm-thick gold layer and a 10 nm-thick chromium layer, was deposited on the substrate by electron beam (E-beam) evaporation and patterned by the shadow mask method, as shown in Figure 3c. The shadow mask method can simplify process steps and shorten processing time. Chromium was an adhesion layer to promote the adhesion between the gold and the substrate. The next step was to deposit the aerosol ZnO films with three thicknesses of about 3, 1 and 0.6 μm by AD with three shadow masks, as shown in Figure 3d,f, and then, those were promoted by furnace annealing, as shown in Figure 3g. Subsequently, a ZnO target with 99.99% purity was adopted to deposit a 0.3 μm thick ZnO layer (the sputtered ZnO layer) onto the bottom electrode by RF magnetron sputtering (as shown in Figure 3h), which was pre-sputtered for 15 minutes to remove any surface impurities before the film was deposited. The chamber was pumped with a base pressure of up to 8 × 10−7 Torr before sputtering. The chamber was then filled with a mixture of argon and oxygen with a gas-mixing ratio of 5:3. The RF power was kept at 120 W, and the chamber pressure was 2 mTorr during the film deposition. The substrate was heated up to 200 °C while deposited, which could enhance the ZnO film quality. The top electrode was deposited on the ZnO films by an E-beam and patterned by the shadow mask method, as shown in Figure 3i. The composition of the top electrode was the same as that of the bottom electrode. Finally, a wet etchant of CH3COOH:H3PO4:H2O = 1:1:10 was adopted to pattern the ZnO layers to open the bonding pads of the bottom electrodes, as shown in Figure 3j. The meliorated multi-frequency band pyroelectric sensor was fabricated as shown in Figure 4.


A Meliorated Multi-Frequency Band Pyroelectric Sensor.

Hsiao CC, Liu SY, Siao AS - Sensors (Basel) (2015)

Fabricated multi-frequency band pyroelectric sensor with an improved design.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4541877&req=5

sensors-15-16248-f004: Fabricated multi-frequency band pyroelectric sensor with an improved design.
Mentions: The fabrication flow of the meliorated multi-frequency band ZnO-film pyroelectric sensor was divided into ten steps, as follows. A silicon wafer with specifications of (100) p-type, double-side polished and resistivity of 1–10 Ω-cm, was used as a substrate to build the multi-frequency band pyroelectric sensor, as shown in Figure 3a. A 1 μm thicker low-stress silicon nitride layer was deposited on both sides of the substrate by LPCVD, which was mainly for reducing or blocking heat or electric loss through the silicon substrate, as shown in Figure 3b. Then, the bottom electrode consisting of a 100 nm-thick gold layer and a 10 nm-thick chromium layer, was deposited on the substrate by electron beam (E-beam) evaporation and patterned by the shadow mask method, as shown in Figure 3c. The shadow mask method can simplify process steps and shorten processing time. Chromium was an adhesion layer to promote the adhesion between the gold and the substrate. The next step was to deposit the aerosol ZnO films with three thicknesses of about 3, 1 and 0.6 μm by AD with three shadow masks, as shown in Figure 3d,f, and then, those were promoted by furnace annealing, as shown in Figure 3g. Subsequently, a ZnO target with 99.99% purity was adopted to deposit a 0.3 μm thick ZnO layer (the sputtered ZnO layer) onto the bottom electrode by RF magnetron sputtering (as shown in Figure 3h), which was pre-sputtered for 15 minutes to remove any surface impurities before the film was deposited. The chamber was pumped with a base pressure of up to 8 × 10−7 Torr before sputtering. The chamber was then filled with a mixture of argon and oxygen with a gas-mixing ratio of 5:3. The RF power was kept at 120 W, and the chamber pressure was 2 mTorr during the film deposition. The substrate was heated up to 200 °C while deposited, which could enhance the ZnO film quality. The top electrode was deposited on the ZnO films by an E-beam and patterned by the shadow mask method, as shown in Figure 3i. The composition of the top electrode was the same as that of the bottom electrode. Finally, a wet etchant of CH3COOH:H3PO4:H2O = 1:1:10 was adopted to pattern the ZnO layers to open the bonding pads of the bottom electrodes, as shown in Figure 3j. The meliorated multi-frequency band pyroelectric sensor was fabricated as shown in Figure 4.

Bottom Line: The proposed sensor is built on a silicon substrate with a thermal isolation layer of a silicon nitride film, consisting of four pyroelectric layers with various thicknesses deposited by a sputtering or aerosol deposition (AD) method and top and bottom electrodes.The fabricated device is effective in the range of 1 KHz~10 KHz with a rapid response and high voltage responsivity, while the ZnO layers with thicknesses of about 0.8 μm, 6 μm, 10 μm and 16 μm are used for fabricating the meliorated multi-frequency band pyroelectric sensor.The proposed sensor is successfully designed, analyzed, and fabricated in the present study, and can indeed extend the sensing range of the multi-frequency band.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Design Engineering, National Formosa University, No. 64, Wunhua Rd., Huwei Township, Yunlin County 632, Taiwan. cchsiao@nfu.edu.tw.

ABSTRACT
This article proposes a meliorated multi-frequency band pyroelectric sensor for detecting subjects with various velocities, namely extending the sensing frequency under good performance from electrical signals. A tactic, gradually increasing thickness of the ZnO layers, is used for redeeming drawbacks of a thicker pyroelectric layer with a tardy response at a high-frequency band and a thinner pyroelectric layer with low voltage responsivity at a low-frequency band. The proposed sensor is built on a silicon substrate with a thermal isolation layer of a silicon nitride film, consisting of four pyroelectric layers with various thicknesses deposited by a sputtering or aerosol deposition (AD) method and top and bottom electrodes. The thinnest ZnO layer is deposited by sputtering, with a low thermal capacity and a rapid response shoulders a high-frequency sensing task, while the thicker ZnO layers are deposited by AD with a large thermal capacity and a tardy response shoulders a low-frequency sensing task. The fabricated device is effective in the range of 1 KHz~10 KHz with a rapid response and high voltage responsivity, while the ZnO layers with thicknesses of about 0.8 μm, 6 μm, 10 μm and 16 μm are used for fabricating the meliorated multi-frequency band pyroelectric sensor. The proposed sensor is successfully designed, analyzed, and fabricated in the present study, and can indeed extend the sensing range of the multi-frequency band.

No MeSH data available.