A basic understanding of thin film resistor design is required if you want to integrate sheet resistors into your circuit. Thin film sheet resistors are typically fabricated by sputtering a film of Tantalum-Nitride (TaN) under the conductor layer and then selectively etching the resistor elements. TaN resistors are very stable and reliable after they are passivated at high temperatures. Nichrome (NiCr) resistors are used in specialty applications where a low TCR (Temperature Coefficient of Resistance) is required.