CMOS Integrated Stress Mapping Chips with 32 N-Type or P-Type Piezoresistive Field Effect Transistors

Abstract

This paper reports a novel generation of CMOS stress mapping chips comprising 32 square field effect transistors (FET) with four source/drain contacts (piezoFETs) exploiting the shear piezoresistive effect in n-type (NMOS) or p-type (PMOS) inversion layers. The sensor chips with a total die area of 2.5 x 2 mm2 are integrated with analog circuitry and digital logic. When exposed to homogenous shear or normal stress, all 32 integrated stress sensors show a linear response in excellent agreement with theoretical predictions and exhibit identical stress sensitivities. Piezo-FETs fabricated as separate devices are characterized with respect to stress sensitivity, intrinsic offset, and noise behavior. Stress sensitivities are enhanced by incorporating a central hole into the piezo-FETs. Sensitivities of -448 iV/(V MPa) and 477 iV/(V MPa) were measured for NMOS and PMOS devices, respectively.

CMOS tactile sensor systems

“…Figure 2 shows as an example the Figure 1. Optical micrographs of (a) p-channel and (b) n-channel piezo-FET stress sensing elements to measure the in-plane stress difference (σx'x' -σy'y') and shear stress σx'y' (adapted from [26]). schematic of the CMOS-based 3D tactile force sensor with membrane hinges introduced by our group.…”

“…Compared to piezoresistors, the main advantage of piezo-FETs is that these sensing elements comprise an inherent switch, namely the gate electrode. This faciltates their miniaturization, as required for high density arrays, and their integration into microelectronic circuitry [26]. Figure 1 shows the example of p-channel and n-channel piezo-FETs [26] as implemented in the CMOS-based tactile sensor systems described in Section III.…”

“…This faciltates their miniaturization, as required for high density arrays, and their integration into microelectronic circuitry [26]. Figure 1 shows the example of p-channel and n-channel piezo-FETs [26] as implemented in the CMOS-based tactile sensor systems described in Section III. The piezo-FETs comprise four source-drain contacts and a symmetrically connected gate electrode.…”

An analysis of the measurement principle of smart brackets for 3D force and moment monitoring in orthodontics

“…4) has principally the same design as a conventional bracket, but includes a microelectronic stress sensor chip manufactured using complementary metal oxide semiconductor (CMOS) technology (Bartholomeyczik et al, 2005;Gieschke et al, 2009). In the current version, the chip is powered and read out through a flexible polyimide cable connected to the sensor chip via flipchip technology with gold stud bumps.…”

“…In F/M systems dimensioned for therapeutic tooth movement, all materials remain in the linear-elastic range, and the stress sensing elements show a linear correlation between voltage signal and exerted mechanical stress (Gieschke et al, 2008). The relationship between the applied F/M system p¼ [F x F y F z M x M y M z ] T and the measured stress values s¼ [s 1 s 2 ys 32 ] T is assumed to be linear and is given by (1985)).…”