In-Plane Packaging Stress Measurements Through Piezoresistive Sensors

Abstract

In our previous works, the piezoresistive sensors have been demonstrated to be accurate and efficient tools for stress measurements in microelectronic packaging. In this study, we first designed test chips with piezoresistive stress sensors, temperature sensors as well as heats, and the test wafers were next manufactured through commercialized IC processes. Piezoresistive sensors on silicon strips, which were cut directly from silicon wafers at a specific angle, were then calibrated, and highly consistent piezoresistive coefficients were extracted at various wafer sites so that both normal and shear stress on the test chips can be measured. Finally, we packaged the test chips into 100-pin PQFP structures with different batches and measured internal stresses on the test chips inside the packaging. After measuring packaging induced stresses as well as thermal stresses on several batches of PQFPs, it was found that the normal stress diversities were obvious from different batches of the packaging structure, and the shearing stresses were approximately zero in all of the PQFPs at different chip site.

On the study of MOSFET micro-sensors for electronic packaging

“…Figure 5 shows stress versus the relative resistance changes R/R) for transverse and longitudinal channels on different drain voltage (V D ), and the statistical inferences are listed in Table 2. Compared with 1.5 to 2 % of variations for the piezoresistive sensors under 100MPa of stress loading [10], the 2 % of variations for the p-MOSFET sensors show similar sensitivities. We next studied the thermal effect on the MOSFET devices by putting the devices in a constant temperature environment and measure the device behaviors.…”

“…The test wafers were first sliced into strip along the longitudinal (parallel to the channel length) and transverse (horizontal to the channel length) directions of an MOSFET, respectively, as shown in Figure 1 [1,7]. Next, highly consistent piezoresistance coefficients were exacted for sensors at different wafer site through the four-point-bending (4PB) [10] fixture with probing facilities. Figure 2 shows the ideal and actual 4PB fixtures, respectively.…”

In-situ reliability monitoring on PBGA packaging through piezoresistive stress sensor

“…Each of the stress-sensing cells in Figure 1 The linear models for the piezoresistors [3][4] in Figure 2 defined the relationship between the fractional resistance variations for resistors on R 1 , R 3 with the stress and temperature as: …”

Measurement of Moisture-Induced Packaging Stress With Piezoresistive Sensors

“…Based on linear models of high concentration piezoresistors [14], [15], [20], [21], as depicted in Fig. 2, the relationship between the fractional resistance variations for resistors to and the stress and temperature can be written as…”

“…Piezoresistive sensors have been used for stress measurements within microelectronic packaging because they provide in situ, real-time, and nondestructive stress measurements with relatively low cost [14]- [21]. In this paper, piezoresistive sensors manufactured on test chip surfaces were employed as …”