Design and Experimental Evaluation of a 3rd Generation Addressable CMOS211 Piezoresistive Stress Sensing Test Chip

摘要

Piezoresistive stress sensing chips have been used extensively for measurement of211u001eassembly related die surface stresses. Although many experiments can be performed 211u001ewith resistive structures which are directly bonded, for extensive stress mapping 211u001eit is necessary to have a large number of sensor cells which can be addressed 211u001eusing CMOS logic circuitry. Our previous test chip, the ATC04, has 100 cells, 211u001eeach approximately 0.012 in. on a side, on a chip with a side dimension of 0.45 211u001ein. When a cell resistor is addressed, it is connected to a four terminal 211u001emeasurement bus through CMOS transmission gates. In theory, the gate resistances 211u001edo not affect the measurement. In practice, there may be subtle effects which 211u001eappear when very high accuracy is required. At high temperatures, gate leakage 211u001ecan increase to a point at which the resistor measurement becomes inaccurate. For 211u001eATC04 this occurred at or above 50 C. Here, we report on the first measurements 211u001eobtained with a new prototype test chip, the ATC06. This prototype was fabricated 211u001ein a 0.5 micron feature size silicided CMOS process using the MOSIS prototyping 211u001efacility. The cell size was approximately 0.004 in. on a side. In order to 211u001eachieve piezoresistive behavior for the implanted resistors it was necessary to 211u001eemploy a non-standard silicide blocking process. The stress sensitivity of both 211u001eimplanted and polysilicon blocked resistors is discussed. Using a new design 211u001estrategy for the CMOS logic, it was possible to achieve a design in which only 5 211u001esignals had to be routed to a cell for addressing vs. 9 for ATC04. With our new 211u001edesign, the resistor under test is more effectively electrically isolated from 211u001eother resistors on the chip, thereby improving high temperature performance. We 211u001epresent data showing operation up to 140 C.