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Staining Solution Disclosure Number: IPCOM000073461D
Original Publication Date: 1970-Dec-01
Included in the Prior Art Database: 2005-Feb-22
Document File: 1 page(s) / 12K

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Carballo, RA: AUTHOR


This is a phosphoric sodium nitrate solution for staining beveled semiconductor surfaces.

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Staining Solution

This is a phosphoric sodium nitrate solution for staining beveled semiconductor surfaces.

The bevel and stain method of measuring junction depth is well known. A semiconductor crystal having P and N type impurities diffused therein is beveled at a very shallow angle in order to expose a cross-section of the various regions. The present stain, applied to this beveled surface sharply delineates boundaries between the various regions and shows them in technicolor. There is a sharp delineation not only between the regions of opposite impurity type, but also between regions of varying impurity concentration. Thus, a distinct difference in color is observed between an N-type collector region and an N+ type subcollector region. This is particularly advantageous in measuring the base to subcollector distance which, in turn, is important for determining breakdown voltages. With this measurement, the breakdown voltages of devices fabricated in accordance with a particular defined process can be determined early in the processing cycle, providing an opportunity to reject the wafer without the need to proceed with additional processing steps. The distance between the base and subcollector could not be measured with stains which do not show a distinct delineation between an N and N+ type region. Moreover, the sharpness of the delineation provided by the present stain permits the measurement of very shallow junction depths in both axes, vertical and horizonta...