High Resolution Long Array Thermal Ink Jet Printhead with On-Chip LSI Heater Plate and Micromachined Si Channel Plate

Michiaki MURATA  Masaki KATAOKA  Regan NAYVE  Atsushi FUKUGAWA  Yoshihisa UEDA  Tohru MIHARA  Masahiko FUJII  Toshimichi IWAMORI  

IEICE TRANSACTIONS on Electronics   Vol.E84-C   No.12   pp.1792-1800
Publication Date: 2001/12/01
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Integrated Systems with New Concepts)
thermal ink jet,  micromachining,  drop ejector,  reactive ion etching,  electrostatic bonding,  

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This paper presents a high resolution long array thermal ink jet (TIJ) printhead which has been developed and demonstrated to operate successfully by combining two functional Si wafers, a bubble generating heater plate fabricated using LSI process and a channel plate fabricated using Si bulk micromachining technology. The heater plate consists of logic LSIs, high voltage MOS transistor, polycrystalline Si (Poly Si) heating resistor and polyimide protective layer. The polymide layer is patterned by O2 plasma reactive ion etching (RIE) and is applicable to high resolution heater array. The Si channel plate consists of an ink chamber and an ink inlet formed by KOH etching, and a nozzle formed by inductively coupled plasma RIE (ICP RIE). The nozzle formed by RIE has squeezed structures which contribute to high energy efficiency of drop ejector and therefore successful ejection of small ink drop. These two wafers are directly bonded by using a novel electrostatic bonding of full-cured polyimide to Si. The adhesive-less bonding provided an ideal shaped small nozzle orifice. And also, the bonding method enabled to use an on-chip LSI wafer because of the contamination free material and the suitable processing conditions (low temperature). The bonded wafer is diced to form printhead chip. No delamination or displacement of the chip was observed even though the chip was subjected to thermal stress during assembly process. This is because of no difference in thermal expansion coefficient between both chips (Si and Si). And therefore it is suitable for long chip concept. With the above technologies, we have fabricated a 1.3" long printhead with 1024 nozzles having a 800 dots per inch (dpi) resolution, a 2.7 pl. ink drop volume, 14 m/sec. ink drop velocity and 18 kHz jetting frequency. And we have confirmed high speed printing and high quality printing.