Mikroişlenmiş ivme ölçer üretimi ve optimizasyonu
Fabrication and optimization of micro machined accelerometers
- Tez No: 39479
- Danışmanlar: Y.DOÇ.DR. HAKAN ÖZDEMİR
- Tez Türü: Yüksek Lisans
- Konular: Elektrik ve Elektronik Mühendisliği, Electrical and Electronics Engineering
- Anahtar Kelimeler: Elektronik sistemler, İvme, Electronic systems, Acceleration
- Yıl: 1994
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: Belirtilmemiş.
Özet
Process flow: - Thermal oxide growth - Patterning alignment marks - Etching silicon from the back side of the wafer through these windows - Thermal oxide growth - Patterning membrane window - Etching silicon - Patterning windows for boron diffusion from the front side of the wafer - Boron diffusion - Patterning membrane release windows - Etching through membrane release windows - Thermal oxide growth - Patterning contact windows - Metallization This process flow can be used to produce different bulk micromachined transducers such as piezoresistive silicon pressure sensors. XI
Özet (Çeviri)
Acceleration sensors can be classified in two categories: - Capacitive - Piezoresistive Capacitive accelerometers transduce acceleration in the change of capacity which can be sensed by circuitry (e.g. by using ac bridge). This capacity change can also alter the frequency of an oscillator. Complex fabrication techniques are often needed. Piezoresistive, cantilever beam microaccelerometer fabrication follows typical micromechanical processing techniques. A resistor is diflused into the surface and the cantilever beam is separated from both sides of the wafer using an anisotropic etchant. A silicon (or gold) seismic mass can be attached to the free end. Change of the resistivity because of the stress on the resistor can be detected by a Wheatstone bridge. The sensitivity of the accelerometers depends essentially on thickness, length and resonance frequency of the beam and the mass at the free end. For low frequencies the beam can follow the excitation without appreciated delay, so the response of the accelerometer can be regarded as (quasi)static. At higer frequencies, however, the dynamic characteristics of the system produce phase delays and amplitude variations, depending on the natural frequencies of the device. A high-Q resonance corresponding to the first mode of lateral vibration of the beam dominates the behavior of the accelerometer. So, the resonance frequency limits the bandwidth. Capacitive and piezoresistive accelerometers detecting down to lug over 10 Hz bandwidth [22] and up to 103 g with a bandwidth 104 Hz [23] can be produced. Nonlinearity of piezoresistive accelerometers is small [24] but the temperature dependence is one of the disadvantages. Also sensitivity of the capacitive accelerometers are high. For both types of accelerometers, special top and bottom motion Hmiting plates must be included to prevent beam damage during possible acceleration overshoots. In this work, a piezoresistive cantilever beam accelerometer with a Wheatstone bridge circuitry has been produced. It is formed by anisotropically etching the silicon using KOH. Dimensions and etch rate is determined by controlling temperature and concentration of KOH and time. Si02 are used as etch mask. PTFE sample holder has also protected the backside of the wafer during the etch process. 4 holes etched through the wafer have been used as front to backside alignment marks. The whole micromachining process has been carried out in the Microelectronics Lab. of İTÜ. Several test photo masks have been made in the same lab and the final photo masks have been produced in TÜBİTAK - YİTAL.Process flow: - Thermal oxide growth - Patterning alignment marks - Etching silicon from the back side of the wafer through these windows - Thermal oxide growth - Patterning membrane window - Etching silicon - Patterning windows for boron diffusion from the front side of the wafer - Boron diffusion - Patterning membrane release windows - Etching through membrane release windows - Thermal oxide growth - Patterning contact windows - Metallization This process flow can be used to produce different bulk micromachined transducers such as piezoresistive silicon pressure sensors. XIAcceleration sensors can be classified in two categories: - Capacitive - Piezoresistive Capacitive accelerometers transduce acceleration in the change of capacity which can be sensed by circuitry (e.g. by using ac bridge). This capacity change can also alter the frequency of an oscillator. Complex fabrication techniques are often needed. Piezoresistive, cantilever beam microaccelerometer fabrication follows typical micromechanical processing techniques. A resistor is diflused into the surface and the cantilever beam is separated from both sides of the wafer using an anisotropic etchant. A silicon (or gold) seismic mass can be attached to the free end. Change of the resistivity because of the stress on the resistor can be detected by a Wheatstone bridge. The sensitivity of the accelerometers depends essentially on thickness, length and resonance frequency of the beam and the mass at the free end. For low frequencies the beam can follow the excitation without appreciated delay, so the response of the accelerometer can be regarded as (quasi)static. At higer frequencies, however, the dynamic characteristics of the system produce phase delays and amplitude variations, depending on the natural frequencies of the device. A high-Q resonance corresponding to the first mode of lateral vibration of the beam dominates the behavior of the accelerometer. So, the resonance frequency limits the bandwidth. Capacitive and piezoresistive accelerometers detecting down to lug over 10 Hz bandwidth [22] and up to 103 g with a bandwidth 104 Hz [23] can be produced. Nonlinearity of piezoresistive accelerometers is small [24] but the temperature dependence is one of the disadvantages. Also sensitivity of the capacitive accelerometers are high. For both types of accelerometers, special top and bottom motion Hmiting plates must be included to prevent beam damage during possible acceleration overshoots. In this work, a piezoresistive cantilever beam accelerometer with a Wheatstone bridge circuitry has been produced. It is formed by anisotropically etching the silicon using KOH. Dimensions and etch rate is determined by controlling temperature and concentration of KOH and time. Si02 are used as etch mask. PTFE sample holder has also protected the backside of the wafer during the etch process. 4 holes etched through the wafer have been used as front to backside alignment marks. The whole micromachining process has been carried out in the Microelectronics Lab. of İTÜ. Several test photo masks have been made in the same lab and the final photo masks have been produced in TÜBİTAK - YİTAL.Process flow: - Thermal oxide growth - Patterning alignment marks - Etching silicon from the back side of the wafer through these windows - Thermal oxide growth - Patterning membrane window - Etching silicon - Patterning windows for boron diffusion from the front side of the wafer - Boron diffusion - Patterning membrane release windows - Etching through membrane release windows - Thermal oxide growth - Patterning contact windows - Metallization This process flow can be used to produce different bulk micromachined transducers such as piezoresistive silicon pressure sensors. XIAcceleration sensors can be classified in two categories: - Capacitive - Piezoresistive Capacitive accelerometers transduce acceleration in the change of capacity which can be sensed by circuitry (e.g. by using ac bridge). This capacity change can also alter the frequency of an oscillator. Complex fabrication techniques are often needed. Piezoresistive, cantilever beam microaccelerometer fabrication follows typical micromechanical processing techniques. A resistor is diflused into the surface and the cantilever beam is separated from both sides of the wafer using an anisotropic etchant. A silicon (or gold) seismic mass can be attached to the free end. Change of the resistivity because of the stress on the resistor can be detected by a Wheatstone bridge. The sensitivity of the accelerometers depends essentially on thickness, length and resonance frequency of the beam and the mass at the free end. For low frequencies the beam can follow the excitation without appreciated delay, so the response of the accelerometer can be regarded as (quasi)static. At higer frequencies, however, the dynamic characteristics of the system produce phase delays and amplitude variations, depending on the natural frequencies of the device. A high-Q resonance corresponding to the first mode of lateral vibration of the beam dominates the behavior of the accelerometer. So, the resonance frequency limits the bandwidth. Capacitive and piezoresistive accelerometers detecting down to lug over 10 Hz bandwidth [22] and up to 103 g with a bandwidth 104 Hz [23] can be produced. Nonlinearity of piezoresistive accelerometers is small [24] but the temperature dependence is one of the disadvantages. Also sensitivity of the capacitive accelerometers are high. For both types of accelerometers, special top and bottom motion Hmiting plates must be included to prevent beam damage during possible acceleration overshoots. In this work, a piezoresistive cantilever beam accelerometer with a Wheatstone bridge circuitry has been produced. It is formed by anisotropically etching the silicon using KOH. Dimensions and etch rate is determined by controlling temperature and concentration of KOH and time. Si02 are used as etch mask. PTFE sample holder has also protected the backside of the wafer during the etch process. 4 holes etched through the wafer have been used as front to backside alignment marks. The whole micromachining process has been carried out in the Microelectronics Lab. of İTÜ. Several test photo masks have been made in the same lab and the final photo masks have been produced in TÜBİTAK - YİTAL.Process flow: - Thermal oxide growth - Patterning alignment marks - Etching silicon from the back side of the wafer through these windows - Thermal oxide growth - Patterning membrane window - Etching silicon - Patterning windows for boron diffusion from the front side of the wafer - Boron diffusion - Patterning membrane release windows - Etching through membrane release windows - Thermal oxide growth - Patterning contact windows - Metallization This process flow can be used to produce different bulk micromachined transducers such as piezoresistive silicon pressure sensors. XI
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