1. Field of the Invention
The present invention relates to an ink jet print head and a method for manufacturing an ink jet print head.
2. Description of the Related Art
An ink jet print head used for an ink jet printing method (liquid ejection printing method) commonly comprises a plurality of fine ejection ports and a plurality of fine liquid channels formed in an orifice plate, and a plurality of liquid ejection pressure generating sections each provided in a part of the corresponding liquid channels. The ink jet print head often further comprises a supply port formed in a head substrate in communication with the liquid channels and serving as a through-hole.
Such an ink jet print head has heat generating sections (heaters) in the respective channels, which are in communication with the corresponding ejection ports; each corresponding heat generating section, channel, and ejection port constitute a print element. Electric energy corresponding to a print signal is selectively applied to a heating resistor in the appropriate heater. The resulting energy is utilized to rapidly heat ink on a heat acting surface. This results in film boiling to generate bubbles, so that the pressure of the bubbles causes the ink to be ejected from the corresponding ejection port.
As a print head having the heaters as described above, for example, U.S. Pat. No. 6,019,457 discloses an ink jet print head of back chute type (hereinafter called print head of back chute type) comprising a liquid ejection pressure generating section on a liquid channel surface of an orifice plate. For the print head of back chute type, a general-purpose semiconductor manufacture method can be used to continuously form an orifice plate or a part thereof, and a liquid ejection pressure generating section and a driving circuit both arranged on a substrate surface.
The substrate of the print head of back chute type is manufactured by, for example, a silicon on insulator (SOI) technique. The substrate formed of a monocrystal silicon semiconductor layer on an insulator by the SOI technique provides the substrate with various advantages compared with a bulk silicon substrate on which an ordinary silicon integrated circuit is manufactured. The print head of back chute type having this SOI substrate is disclosed in U.S. Pat. No. 6,979,076.
A method for manufacturing a print head of back chute type is as described below.
B1. Step of preparing an SOI substrate 901 having an insulating layer 903 therein,
B2. Step of forming grooves reaching the insulating layer 903, in a front surface of the substrate with respect to the insulating layer 903, in alignment with positions where a wall of the liquid channel is to be formed,
B3. Step of forming a first etching stop layer 920 on the front surface of the substrate and on a surface of the groove (FIG. 8A),
B4. Step of forming an energy generating element 906 and a driving circuit therefor on the first etching stop layer 920 on the substrate surface,
B5. Step of forming a supply port 908 extending from a back surface of the SOI substrate with respect to the insulating layer 903, to the insulating layer 903,
B6. Step of forming a second etching stop layer 921 on an inner surface of the supply port 908,
B7. Step of selectively removing a part of the etching stop layer 921 which is in contact with the insulating layer 903 (FIG. 8B),
B8. Step of removing a part of the insulating layer 903 which is exposed in the supply port 908,
B9. Step of removing a part surrounded by the insulating layer 903 and first etching stop layer 920 in the substrate, via the supply port 908 by an isotropic etching technique, and
B10. Step of etching the first etching stop layer 920 to form an ejection port 910 (FIG. 8C).
In the ink jet print head manufactured by the steps B1 to B10, the part surrounded by the first etching stop layer 920 and the insulating layer 903 is removed by the etching technique to form a channel 909.
Further, the ink jet print head manufactured by the above manufacturing method must form the first etching stop layer 920 in areas that are formed into walls of the liquid channel. This generally requires a photolithography step, an etching step based on RIE and a film formation step executed on inner walls. This in turn complicates the entire process.
Moreover, in step B4, the energy generating element and the driving circuit therefor are formed. Thus, the grooves formed must be filled with the first etching stop layer 920 and the width of the grooves must be sufficiently small, for example, about 2 μm.
On the other hand, the dimension of the liquid channel perpendicular to the substrate surface, that is, the depth of the liquid channel, is preferably at least 10 μm. The grooves formed need to have a high aspect ratio. In this case, the groove formation requires a longer time, which may not result in high productivity.