Frequency measuring device, polishing device using the same and eddy current sensor
US7046001B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Oct 19, 2001 |
| Grant date | May 16, 2006 |
| Priority date | — |
| Expiry date | Mar 9, 2023 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01R23/10
- WIPO fieldMachine tools
- WIPO sectorMechanical engineering
Abstract
A frequency measuring device capable of accurately detecting an end point of polishing a semiconductor wafer by obtaining a frequency measurement result highly accurately in a short period of time. A device FC, which measures the frequency of a measured signal comprises a counting section including a plurality of n-nary counters, a time reference circuit which outputs a time reference signal for every predetermined time interval, and a plurality of gate circuits whose outputs are connected to the inputs of the n-nary counters. The gate circuits receive the measured signal at a first input and receive the time reference signal at the predetermined time intervals at a second input. With this structure, the counting section supplies the frequency measured result of the measured signal every predetermined time interval.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.