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Browse Prior Art Database

Wet Etch End-Point Prediction

IP.com Disclosure Number: IPCOM000038068D
Original Publication Date: 1989-Oct-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Eisenhuth, GC: AUTHOR [+4]

Abstract

Disclosed is a process which is being used to predict the total etch time required to etch Metal Masks. The concept works on the principle of predicting the total time required to etch the mask based on an etch break-thru.

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Wet Etch End-Point Prediction

Disclosed is a process which is being used to predict the total etch time required to etch Metal Masks. The concept works on the principle of predicting the total time required to etch the mask based on an etch break-thru.

The uniqueness of this technique is that it provides a means of predicting final etch dimension regardless of pattern size and dimension in a harsh wet etching process system and allows for total computer automation and control.

The system works by the transmittance of an infra-red light source which detects openings in the mask of 0.8 mils or greater. By gating off the center shaft (see Figure) the system indicates whether the break-thru signal is valid or not. If the transmitted light source is detected on the other side of the mask in the active area (circuit pattern portion of the mask), break-thru is detected and a flag signal fed back to the main control system. The main control system will record the time of break- thru of each part along with other known factors such as: mask metal thickness, ratio of Fe+2/Fe+3 concentration in the etch solution, and pH of the solution.

All of this information fed into an algorithm will be used to predict a final etch time as given by:

Predicted End-point Etch time - [Break-Thru Time] K, where K is a constant which is a function of solution concentration, metal thickness and metal pattern type.

All of these variables are input into the end-point algorithm prior to the etch ...