Contacts for conductivity-type sensors
US4646009A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Apr 22, 1985 |
| Grant date | Feb 24, 1987 |
| Priority date | — |
| Expiry date | Apr 22, 2005 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01R31/316
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A conductivity-type sensor, typically for use in a wafer sorting system, for detecting the conductivity-type of semiconductor wafers. In measuring conductivity, a two-contact probe is applied to the semiconductor wafer and any static charge which may have been accumulated on the wafer is initially discharged at an accelerated rate. The charge state is measured and an acceptable level of discharge requires repeated indications of discharge below a predetermined level. Discharging and charge measurement is repeated a predetermined number of times as necessary to accomplish discharging or the wafer identified as defective. The conductivity-type of the discharged wafer is read from the rectified polarity of an oscillating signal applied to the contacts. A valid indication of conductivity-type requires two consecutive readings of the same conductivity-type. The consecutive readings can be either the first reading of a new wafer identical with the reading of a previous wafer or two consecutive identical readings on the same wafer. Each reading, to be considered an acceptable reading of conductivity-type requires five consecutive, identical conductivity measurements over a predetermined t…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.