Test of SOI 555 Timer with High Temperature Packaging 2008-01-2882

The thick oxide layer of silicon-on-insulator (SOI) devices significantly reduces the junction leakage current at elevated temperatures compared to similar Si devices, resulting in an elevated maximum operating temperature. The maximum operating temperature, specified by manufacturers, of commercial SOI devices/circuits with conventional packaging is usually 225°C. It is important to understand the performance and de-ratings of these SOI circuits at temperatures above 225°C without the temperature limit imposed by commercial packaging technology. This work tested a low frequency square-wave oscillator based on an SOI 555 Timer with a special high temperature ceramic packaging technology from room temperature to 375°C. The timer die was attached to a 96% aluminum oxide substrate with high temperature durable gold (Au) thick-film metallization, and interconnected with Au wires. The timer die was soaked in a table-top box oven while all the discrete passive components were at room temperature during the testing. The square-wave parameters such as frequency, pulse duration, amplitude, and rise time of the square wave as well as the total DC current supply were measured as functions of temperature. The major oscillation parameters changed a few percent from room temperature to 375°C, while the rise time increased from 37.5 ns to 42.5 ns. The test results up to 375°C and failure phenomena are discussed.