Rapid and Quantitate Determination of Organic Surface Contaminations Using TOC and Contact Angle Measurement

© Fraunhofer CSP

The semi-automatic contact angle mapping provides information on the amount and distribution of the organic carbon on the wafer surface.

Irrespective of the semiconductor type and technology, organic contaminations on wafer surfaces have a detrimental impact on subsequent manufacturing steps and/or the device function. Therefore, it is of great interest to have a quick and reliable tool to detect those contaminations with sufficient sensitivity. Two such methods were developed recently at Fraunhofer CSP. In combination they enable the detection of absolute amount and distribution of organic impurities. By extraction the wafer surface and analysing the total organic carbon (TOC) of the extraction solution an integral quantification of surface organics as low as 0,5 ng per cm2 is possible. This may be complemented by a laterally dissolved determination of the surface energy which is realised by semi-automatic contact angel mapping of the surface. Usually two test solutions like water and diiodomethane are applied displaying different surface tensions. To scan the whole surface, the contact angle of 30 or more single droplets in a defined array are measured using an automated video based optical contact angle instrument. Both methods are rapid and sensitive and can be realised at comparably low costs. Thus, they are useful tools for process and quality control.