SEDL / STP / STP572-EB / STP47410S

Evaluation of the Effective Epilayer Thickness by Spreading Resistance Measurement

Murrmann, H.
Siemens AG, Munich,

Sedlak, F.
Siemens AG, Munich,

Pages: 5    Published: Jan 1974

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Abstract

Two types of double layer structure which are dealt with in the multi layer theory have been examined: 1. a top layer is insulated against a bottom layer (i.e. pn-junction, R(∞)). 2. a top layer is shorted by a bottom layer (i.e. n⁺-buried layer, R(0)). In both arrangements the Spreading Resistance depends strongly on layer thickness d and on the radius a of contact area. Knowing the effective radius the epilayer thickness can easily be evaluated from Spreading Resistance Measurement and making use of the function R(∞)R(0)=f(da). This method is nondestructive and less rime consuming than other common methods. A simple test pattern is proposed for evaluating the thickness on wafers in process. A comparison between this method and an IR-reflexion method (Digilab FTG 12) showed that both are in very good agreement in thickness range of 2.....6μm.