Semiconductor Physics Laboratory Rt

Tamas S Horanyi

Gyorgy Ferenczi

Minority carrier bulk lifetime maps are accomplished using in-situ .mu.-PCD measurement techniques on a non-oxidized Si specimen of either polarity. Surface passivation of the specimen is accomplished chemically, preferably using a solution of iodine in ethanol with a concentration in the range of about 0.02 mol.multidot.dm.sup.-3 to about 0.2 mol.multidot.dm.sup.-3. For n-type specimens, a solution of concentrated alkaline such as ammonia, sodium- and potassium-hydroxide is especially effective. For either type specimens, a solution of HF at about 40% m/m is also effective. Surface passivation according to the present invention reduces surface recombination velocities to 10 cm/second or less. The specimen to be measured is placed in a container of passivation solution such that the specimen surfaces are covered with a solution film of about 1 mm or less. The container preferably is transparent to microwave and laser optical energy, and passivation and measurement can occur simultaneously. A method and apparatus are disclosed.

Method for chemical surface passivation for in-situ bulk lifetime

The accuracy of electrochemical profiling measurements that provide depth dependent characteristics for a semiconductor is enhanced by stabilizing the semiconductor's effective dissolution valence. According to the present invention, the semiconductor dissolution valence is stabilized by anodically dissolving the semiconductor surface using a potential associated with the electropolishing region of the semiconductor. This potential, typically 1V to 5V relative to the profiler saturated calomel reference electrode, favors quadrivalent dissolution over divalent dissolution. Dissolution valence is further stabilized by using an electrolyte having a relatively low fluoride content, a characteristic associated with a low dissolution rate (relative to a rate of electrochemical oxidation) of the oxide at the semiconductor surface. Preferably the electrolyte has a fluoride content in the approximate range 0.01 mol-dm.sup.-3 to about 1.0 mol-dm.sup.-3, and is buffered with a pH ranging from about 3 to 5. According to the present invention, the effective dissolution valence of silicon is stabilized to about 3.70, and craters etched in a silicon specimen will have a deviation from a mean profile depth within about .+-.1%.

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Budapest, Hungary

Tamas S Horanyi