In-line detection and assessment of net charge in PECVD silicon dioxide (oxide) layers

摘要

The present method provides for the detection and assessment of the net charge in a PECVD oxide layer deposited on a surface of a semiconductor substrate. Electrical potential differences across PECVD oxide layers on as-produced semiconductor substrates are measured. Resultant PECVD oxide charge derivative values are plotted on an control chart and compared to calculated control parameters. All measurement techniques are non-contact and non-destructive, allowing them to be performed on as-processed semiconductor substrates at any time during or following a wafer fabrication process. In a first embodiment, a contact potential difference VCPD between a vibrating electrode and the semiconductor substrate is measured while the semiconductor substrate beneath the vibrating electrode is subjected to a constant beam of high intensity illumination. The resultant value of VCPD is equal to the electrical potential difference across the PECVD oxide layer VOX (plus a constant). In a second embodiment, the semiconductor substrate is not illuminated curing the measurement of VCPD. A conventional SPV apparatus is used to measure the surface barrier potential VSP of the semiconductor substrate. Subtracting the measured value of VSP from the measured value of VCPD yields the value of VOX (plus a constant).