Printhead for thermal ink jet devices

Details Printhead for thermal ink jet devices Printhead for thermal ink jet devices

1997-02-24

1999-08-24

Hartary, Joseph

Incremental printing of symbolic information

Ink jet

Ejector mechanism

438 21, 438698, B41J 205

Patent

active

059430761

ABSTRACT:
The nucleation efficiency of a thermal ink jet printhead is improved by forming a heater element with a planar surface. A heater resistor, polysilicon in a preferred embodiment, has an irregular surface which can trap gas or vapors in the cracks or crevices. When the heater resistor is pulsed, the nucleation temperature is reduced by these trapped vapors requiring an increase in electrical input to the resistors, thereby reducing efficiency. The invention recognizes that a heater resistor with a planar surface in contact with an ink layer results in a higher nucleation temperature and increased efficiency. In one embodiment, a phosphosilicate glass (PSG) is flowed directly onto the resistor surface forming a planarization layer. Subsequent deposition of tantalum substantially replicates the underlying topography creating a heater resistor with a smooth surface adjacent the ink.
In a second embodiment, a diffusion layer which is conformal is formed on the resistor surface with the PSG layer formed on the oxide layer. The diffusion layer can be a pyrolytic CVD deposited silicon nitride or a thermally grown oxide layer. The PSG layer has a planarized surface to which the tantalum conforms.

REFERENCES:
patent: Re32572 (1988-01-01), Hawkins et al.
patent: 4719477 (1988-01-01), Hess
patent: 4951063 (1990-08-01), Hawkins et al.
patent: 5469200 (1995-11-01), Terai
Michael O'Horo et al., "Effect of TIJ Heater Surface Topology on Vapor Bubble Nucleation," SPIE Journal, pp. 58-64; Jan. 29, 1996; vol. 2658.

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