Browse Prior Art Database

Process Detection System

IP.com Disclosure Number: IPCOM000084478D
Original Publication Date: 1975-Nov-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 3 page(s) / 109K

Publishing Venue

IBM

Related People

Jurczyk, DH: AUTHOR [+3]

Abstract

Fig. 1 is an electronic schematic of a solid-state process end-point detection system, which is used for develop, etch, and lift-off process control.

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Process Detection System

Fig. 1 is an electronic schematic of a solid-state process end-point detection system, which is used for develop, etch, and lift-off process control.

The process end-point detecting system consists of a pluggable solid-state light-emitter diode (LED) or injection laser diode used as a light source, and a detector (phototransistor) mounted against a transparent window in a process tank (i.e., see Fig. 1, tank T1 4 and tank T2 6), an appropriate power supply 8, filters 10, and amplifier 12. A multiplexer 14 which permits monitoring two or more process tanks is connected to a computer (i.e., IBM System 7 (16)) through an analog-to-digital (A-D) converter 18 and distribution interface 20.

The computer makes the necessary calculations, in order to determine the process end point and transmits a signal to the equipment to end the process.

Fig. 2 shows the LED 22, phototransistor 24, wafer 26, and a region through the process tank 28. Both angles of the phototransistor 24 and LED 30 are equal because of optical law.

The solid-state infrared-emitting diode wavelength of peak radiant intensity is 940nm with a 2.4 to 3mW power output at 50mA and 1.4 V.

The infrared light of the solid-state emitting diode shines through a transparent tank wall onto the wafer surface with the light reflected off the wafer surface films. As an etch or photoresist develop process performs, the reflectivity changes, indicating the process progress. For instance, when th...