Multifunctional Platform with CMOS-Compatible Tungsten Microhotplate for Pirani, Temperature, and Gas Sensor

Abstract

Abstract:A multifunctional platform based on the microhotplate was developed for applications including a Pirani vacuum gauge, temperature, and gas sensor. It consisted of a tungsten microhotplate and an on-chip operational amplifier. The platform was fabricated in a standard complementary metal oxide semiconductor (CMOS) process. A tungsten plug in standard CMOS process was specially designed as the serpentine resistor for the microhotplate, acting as both heater and thermister. With the sacrificial layer technology, the microhotplate was suspended over the silicon substrate with a 340 nm gap. The on-chip operational amplifier provided a bias current for the microhotplate. This platform has been used to develop different kinds of sensors. The first one was a Pirani vacuum gauge ranging from 10´1 to 10 5 Pa. The second one was a temperature sensor ranging from´20 to 70˝C. The third one was a thermal-conductivity gas sensor, which could distinguish gases with different thermal conductivities in constant gas pressure and environment temperature. In the fourth application, with extra fabrication processes including the deposition of gas-sensitive film, the platform was used as a metal-oxide gas sensor for the detection of gas concentration.

Excel Methods to Design and Validate in Microelectronics (Complementary Metal–Oxide–Semiconductor, CMOS) for Biomedical Instrumentation Application

“…(5) Comparing a designed device with others published in the technical literature and used in biomedical instrumentation systems, particularly how far students are from major fundamental specifications and requirements such as gain, swing, frequency response, noise, and low power characteristics. (6) Applying the designed amplifiers to CMOS-MEMS experimental devices in linear signal conditioning of multiplatform such as compound structures including Pirani, temperature, and gas sensors [42].…”

“…Another application of the low power operational amplifier is to perform signal conditioning in signals coming from CMOS-MEMS sensors [39][40][41][42] where the CMOS amplifiers are used as the standard electronic system maneuvering platform. For instance, in [42] the low power operational amplifier is used as a high input impedance instrumentation amplifier to condition signals coming from a micro-hotplate in either Pirani, Temperature, or Gas CMOS-compatible MEMS sensors. Three operational amplifiers, designed in this paper, are set up as instrumentation amplifiers like the one shown in Figure 29.…”

“…This configuration is ideal for this multifunctional sensor platform application, particularly for the results obtained by the temperature sensor as shown in Figure 32. Figure 33 shows the new instrumentation amplifier configuration used to condition the signal coming from the multiplatform temperature sensor [42] to obtain the results shown in Table 14. Figure 34 illustrates the linear conditioning performed by the instrumentation amplifier designed using the low power OTA developed by the students.…”

Overview of the MEMS Pirani Sensors

“…In Pirani sensors with a vertical configuration for heat transfer, the heater and heat sink are vertically distributed [66][67][68][69][70][71]. In these devices, the heater is usually made of NiCr [66], tungsten [67], platinum [70], polysilicon [60], etc.…”

Microhotplates for Metal Oxide Semiconductor Gas Sensor Applications—Towards the CMOS-MEMS Monolithic Approach

“…For microhotplates operating above the stability point of platinum and polysilicon, molybdenum [ 47 , 71 ] and tungsten [ 50 , 83 , 84 ] heaters were studied for applications in harsh conditions. Other than these two metals, Creemer et al investigated microhotplates based on CMOS compatible titanium nitride (TiN) heater and operating temperature can reach up to 700 °C but the high stress of TiN decrease the yield of the device [ 48 ].…”