Nondestructive Detection of Damage Produced by a Sharp Indenter in Ceramics

The feasibility of an ultrasonic technique using normal-incident compressional waves and a thermal wave measurement technique was evaluated for their sensitivity to surface and subsurface damage in ceramics. Well-defined damage in the form of surface and subsurface cracks was introduced by Vickers indentation in soda-lime glass and silicon nitride. The indentation impressions were first examined by optical microscopy to identify the types of cracks and to measure the size of the indents and cracks. As expected, indentation produced median/radial cracks emanating from the indent corners and subsurface lateral cracks. The ultrasonic technique was successful in detecting the subsurface lateral cracks in both materials. The signals obtained by focusing the transducer into the material (i.e., defocusing) was used to estimate the depth of subsurface cracks. The lateral cracks and the median/radial cracks were detected by the thermal wave measurement technique using the optical beam deflection method. The lateral cracks and the median/radial cracks were identified separately by using two deflection components of the probe beam. The transverse deflection component of the probe beam was used for the detection of the median/radial cracks, whereas the normal deflection component was used for the detection of the lateral cracks. The results are discussed in terms of the applicability of these two techniques as nondestructive methods for the detection of machining-induced damage in ceramics.

Defect Analysis of Rapid Thermal Processing Round Robin Results

ABSTRACTThe Greater Silicon Valley Implant Users' Group (GSVIUG) has conducted a round robin to determine the uniformity and repeatability available in wafers processed with modern RTP equipment. High-dose ion implantation (As, 5E15, 80keV) of 150mm wafers was used to monitor temperature distribution through sheet resistance. Sheet resistance maps were then used to compare the uniformity and repeatability of each vendor. As previously reported, the actual uniformity results varied significantly with RTP vendor and implant conditions, ranging from 0.77% (one sigma/mean) to 3.55%. In addition, some contour patterns were quite representative of specific vendors.Subsequently, wafers from each participating vendor were evaluated by three techniques in order to determine what damage or defects might have resulted from the RTP process: laser flatness measurement, optical-imaging inspection, and thermal wave measurement. The flatness measurement system was used to measure the warpage of each sample. The reflective-optical inspection technique is a full-field, non-destructive technique that provides a real-time visual display, evidenced by light and dark field contrast over the entire wafer. The thermal wave measurement system uses two laser probes to measure a difference in modulated reflectance which results from damage or defects within the wafer.This paper describes each of the three techniques and summarizes the measured results of wafer defects and damage due to the processing by various RTP vendors. Comparisons between the three measurement techniques are made.