Thin-film resistor requirements

We present here an effective way to manufacture a reproducible thin film resistor, using accepted statistical techniques. The process requirements, experimental techniques, process development and characterization, examples of control charts, their Interpretation for rapid appraisal and the Impact of statistical techniques on the production yields and future developments will be described. 

In monolithic Integrated circuit technology, all circuit elements are fabricated on, or within, a single crystal piece of semiconductor material by means of a sequential series of diffusion, photolithography and thin film processes. As a production method, generally where thin film resistors are required, the following process sequence Is defined ... 

The required specifications for our thin film resistor parameters are listed in Table I. Any product that deviates from the limits has to be reworked or scrapped. 

Several such interface modifiers were found to have the potential of meeting the requirements of hermeticity and repairability. One, however, was outstanding in both categor ies. A plasma-polymer ized hexamethyldisilazane (HMDS) coating provided effective protection for nichrome thin film resistors in high temperature and humidity, power-on conditions for 1,000 hours. HMDS was a very thin coating (approximately 1000 A) which was easily removed for repair purposes. 

When the seed or adhesion layer is a thin-film material, then the completed substrate can have integral resistors. The definition of the resistors requires the use of an additional mask step. 

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