Browse Prior Art Database

Automatic Process End Point Detection System

IP.com Disclosure Number: IPCOM000082120D
Original Publication Date: 1974-Oct-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 55K

Publishing Venue

IBM

Related People

Collins, JC: AUTHOR [+2]

Abstract

Process end-point is automatically detected during the delineation of metal or oxide previously deposited or grown on semiconductor surfaces.

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Automatic Process End Point Detection System

Process end-point is automatically detected during the delineation of metal or oxide previously deposited or grown on semiconductor surfaces.

The photocell circuit 1 voltage output has a direct correspondence to the reduction of the metal or oxide on the surface of the semiconductor material. This output is compared to an adjustable threshold reference 2 at the detector 3, and determines when end-point scanning begins by turning on an oscillator 4. The oscillator output is fed through a gate 8 into a binary counter 7 i.e., register
A.

The binary counter 7 feeds a weighted resistor network 6 which converts the binary count to a voltage level. This level is compared to the photocell 1 output at the end of etch level comparator 5. A compare at the level comparator will inhibit the oscillator 4 output to the binary counter 7 through gate 8. The count will hold until a reset A occurs (t4), at which time the counter (register A) will be reset to zero.

Oscillator 4 output is also fed to the variable-timer decoder 10 through gate 9. The variable-timer decoder has five outputs which occur in sequence. The first t1, is zero slope compare, it enables the compare of binary counter 7 to register B in comparator 13. The second decode t2, resets register B to zero. The third decode t3, enters A register into B register, via gate 11. The fourth event, t4, resets binary counter 7 to zero. The fifth event t5, resets the timer, which res...