Protective Layer for Via Formation
Publication Date: 2004-Mar-25
The IP.com Prior Art Database
A method of protecting the electrical circuitry on a wafer during via formation for an ink jet printhead is proposed. A polymer protective layer is coated to protect the wafer during via formation and is then removed with solvents at the conclusion of the via formation process.
As the circuitry on ink jet printheads continues to shrink and become more complex, it can become more and more sensitive to contamination and physical or electrical damage. There is an increasing need to protect the circuitry on the wafer especially during via formation. Some wafers may contain one or more imaged polymer layers over the circuitry during via formation. However, these permanent layers are intended to be used for planarization, improved adhesion, and formation of ink channels and only offer partial protection of the circuitry due to their minimal thickness and/or the presence of openings in the films. Sensitive heaters, electrical connection pads, or other circuitry can still be exposed to damage and contamination. So, there is a need for a separate, removable polymer protective layer to protect the wafer during via formation.
The invention involves: 1) coating a protective layer, 2) forming a via through the wafer, 3) removing the protective layer.
1) The protective layer is coated (preferably by spin-coating) onto a wafer. It may be coated directly onto the electrical circuitry or on top of one or more imaged polymer layers, such as photoresists used to form ink channels or provide a planarization surface on the wafer. The protective layer can be 5 to 100 microns thick. The protective layer can be made of photoresist (such as Clariant AZ P4620, SIPR-9332BEM-10 by ShinEtsu MicroSi, SPR220-7.0 by Shipley) or non-photoimageable material (such as phenolic resins, phenoxy resins, etc.). If a phot...