Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Emitter Masking Technique

IP.com Disclosure Number: IPCOM000074916D
Original Publication Date: 1971-Jun-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Alexopoulos, VT: AUTHOR

Abstract

It has been a custom to use two different maskings to make openings for the emitter and reach-through diffusions. Due to the difference of oxide thicknesses in the reach-through and emitter areas, it was necessary to first open the emitter and partially the reach-through area. Then when the emitter opening is fully etched, it was necessary to strip the resist off and recoat the wafer. A second critical aligning step was then required using a separate reach-through mask. The reach-through was then etched to completion.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 96% of the total text.

Page 1 of 2

Emitter Masking Technique

It has been a custom to use two different maskings to make openings for the emitter and reach-through diffusions. Due to the difference of oxide thicknesses in the reach-through and emitter areas, it was necessary to first open the emitter and partially the reach-through area. Then when the emitter opening is fully etched, it was necessary to strip the resist off and recoat the wafer. A second critical aligning step was then required using a separate reach-through mask. The reach-through was then etched to completion.

The emitter and reach-through mask is used to open the emitter fully and the reach-through contact partially, as shown in Fig. A. Then, without stripping the Eastman Kodak KTFR negative photoresist, a layer of Shipley AZ-1350 positive photoresist is applied on top. The existing mask of base and isolation is used to cover the emitter area. There is no need for critical aligning because the mask is only used for blackout purposes. After the AZ-1350 is exposed and developed, the reach-through area is etched to completion with no chance of over-etching the emitter which is now shielded, as shown in Fig. B. Both coats of KTPR and AZ-1350 are stripped off at the same time using any one of several standard methods. The need for an additional reach-through mask and an additional stripping operation is eliminated. The same procedure is useful when there is a resistor contact to be opened along side and with the reach-through.

1

Page...