Design of Transducer and Package at the Same Time

Abstract

The early effort of MEMS sensor development was focused mainly on the transducer: designing and manufacturing a mechanical device that could convert a physical input into an electrical signal using traditional semiconductor processes. With the rapid advancement in MEMS technologies, MEMS packaging is becoming increasingly critical and plays a major role in the successful commercialization of a MEMS product. Freescale has adopted the philosophy [1–2] of concurrent transducer and package designs to facilitate the rapid introduction of sensor products into the market. This paper presents a sub-modeling procedure that allows the modeling and simulation of a transducer and a package seamless at the same time.

A high aspect ratio MEMS process with surface micromachined polysilicon for high accuracy inertial sensing

“…Package stress simulations were used to determine substrate deformations which were applied to a finite element model of the transducer [10]. This technique was used to optimize the arrangement of fixed finger and proof mass anchors within the central region in what is effectively a combination of stress canceling and isolation.…”

Fixed-wing MAV attitude stability in atmospheric turbulence, part 1: Suitability of conventional sensors

“…The limitations unique to MAVs limit the choice of accelerometers to MEMS type, which has struggled to reach tactical grade (Dong et al, 2011) and more recently navigation grade (Keller, 2013). MEMS accelerometer's vulnerability to vibration and temperature variation has led to lower performance and reliability issues (Li et al, 2005, Sarihan et al, 2008. Packaging stresses due to temperature variation, humidity, and vibration can affect performance and increase the potential for sensor failures (Jian et al, 2011).…”

Stress Sensitive Capacitive Transducers to Verify Package Models

“…FEA models are required for both package thermalmechanical performance and MEMS electrostatic-mechanical performance. Often the package models and MEMS models can be run separately and then numerically linked [3,4]. Figure 1 shows a cross-section of a typical accelerometer.…”

“…A further challenge is that the stress sensing die should be the same physical dimension as the MEMS die, this is because the MEMS die design has the significant effect on the package thermal-mechanical response. It is difficult to achieve the same form factor because not only must the die size be the same, but most MEMS capacitive acceleration die have wafer-level "caps" attached that form a two-die stack as shown in figure 1 [3]. A final problem is that the piezo-resistive effect relies on resistors with fairly large temperature coefficients, and this can complicate multi-temperature testing of packaged devices.…”