Endpoint detection for thinning of silicon of a flip chip bonded integrated circuit

摘要

A system for determining the endpoint associated with removing silicon from the backside of a flip chip type die includes a tool for removing silicon and a light source for directing light to the backside of the die. An electrical measuring apparatus, such as a voltmeter, ammeter or oscilloscope, is attached across the output pins of a package to which the die is attached. The light or ions directed toward the backside of the die induce a current in the devices formed in the semiconductor. The value of the current or voltage output depends on the thickness of material between the endpoint on the backside of the die and the devices in the epitaxial layer of the die. The induced signal can be monitored to determine the thickness. Silicon can be removed globally until the thickness is reasonable such that a local thinning tool can be used to remove silicon to get to the area of interest in a reasonable amount of time. The induced current can be monitored during local thinning. A viewing mechanism such as infrared microscopy can be used to locate the specific device or devices of interest in the epitaxial layer of the die. The viewing mechanism is also used to determine where localized thinning will occur.