U.S. patent application number 11/345594 was filed with the patent office on 2006-06-15 for layer with discontinuity over fluid slot.
Invention is credited to Manish Giri, Philip H. Harding, Jeffery S. Hess, Mark Sanders Taylor.
Application Number | 20060125885 11/345594 |
Document ID | / |
Family ID | 22466827 |
Filed Date | 2006-06-15 |
United States Patent
Application |
20060125885 |
Kind Code |
A1 |
Giri; Manish ; et
al. |
June 15, 2006 |
Layer with discontinuity over fluid slot
Abstract
In one embodiment, a fluid ejection device comprises a substrate
having a first surface, and a fluid slot in the first surface. The
device further comprises a fluid ejector formed over the first
surface of the substrate, and a chamber layer formed over the first
surface of the substrate. The chamber layer defines a chamber about
the fluid ejector, wherein fluid flows from the fluid slot towards
the to be ejected therefrom. The chamber layer has a discontinuity,
wherein the discontinuity is positioned over the fluid slot.
Inventors: |
Giri; Manish; (Corvallis,
OR) ; Harding; Philip H.; (Albany, OR) ;
Taylor; Mark Sanders; (Monmouth, OR) ; Hess; Jeffery
S.; (Corvallis, OR) |
Correspondence
Address: |
HEWLETT-PACKARD COMPANY;Intellectual Property Administration
P.O. Box 272400
Ft. Collins
CO
80527-2400
US
|
Family ID: |
22466827 |
Appl. No.: |
11/345594 |
Filed: |
February 1, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10327289 |
Dec 21, 2002 |
7024768 |
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11345594 |
Feb 1, 2006 |
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10135162 |
Apr 30, 2002 |
6527368 |
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10327289 |
Dec 21, 2002 |
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Current U.S.
Class: |
347/65 |
Current CPC
Class: |
Y10T 29/49155 20150115;
B41J 2/14129 20130101; B41J 2/1646 20130101; Y10T 29/49197
20150115; Y10T 29/49401 20150115; B41J 2/14145 20130101; B41J
2/1603 20130101; Y10T 29/49126 20150115; B41J 2/1404 20130101; B41J
2/1626 20130101; B41J 2/1631 20130101; Y10T 29/49128 20150115 |
Class at
Publication: |
347/065 |
International
Class: |
B41J 2/05 20060101
B41J002/05 |
Claims
1.-13. (canceled)
14. A method of forming a fluid ejection device comprising: forming
a slot through a substrate; forming an ejection element upon the
substrate along a side of the slot; defining a firing chamber that
surrounds the ejection element, wherein the firing chamber is
defined by a chamber layer; defining an orifice with the chamber
layer, wherein the orifice corresponds to the ejection element and
the firing chamber; and defining one or more slits through the
chamber layer, wherein the one or more slits are positioned over
the slot from one end to an opposite end of the slot, and where at
least one slit of the one or more slits is a closed slit.
15. A method of forming a fluid ejection device comprising: forming
stress relieving slots through a chamber layer of a fluid ejection
device, wherein the stress relieving slots are formed directly over
a fluid slot in a substrate, wherein capillary and meniscus
properties of the fluid mitigate fluid drool through the stress
relieving slots.
16. A method of forming a fluid ejection device comprising: forming
a slot through a substrate; forming an ejection element upon the
substrate along a side of the slot; forming a chamber layer over
the substrate and ejection element; and exposing the chamber layer
to define a firing chamber that surrounds the ejection element, an
orifice corresponding to the ejection element, and a discontinuity
therein over the slot.
17. The method of claim 16 wherein the discontinuity is positioned
over the slot from one end to an opposite end of the slot.
18. The method of claim 16 wherein the discontinuity has two
longitudinal sides that correspond to a length of longitudinal
sides of the slot, wherein at least in some areas along the
discontinuity the two longitudinal sides of the discontinuity are
in contact with each other.
19. The method of claim 16 wherein the discontinuity extends from a
first surface of the chamber layer to a second opposing surface of
the chamber layer.
20.-23. (canceled)
24. The method of claim 16 further including masking the chamber
layer prior to the exposing.
25. The method of claim 16 where the discontinuity is defined as a
closed slit.
26. The method of claim 16 where the discontinuity is defined to
mitigate fluid drooling through the discontinuity.
27. The method of claim 14 where the closed slit is defined with
longitudinal sides that are substantially in contact with each
other along a length of the closed slit.
28. The method of claim 14 where the one or more slits are defined
to form an expansion grate.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to fluid ejection devices, and
more particularly to a layer with a discontinuity over a fluid slot
of a fluid ejection device.
BACKGROUND OF THE INVENTION
[0002] Various inkjet printing arrangements are known in the art
and include both thermally actuated printheads and mechanically
actuated printheads. Thermal actuated printheads tend to use
resistive elements or the like to achieve ink expulsion, while
mechanically actuated printheads tend to use piezoelectric
transducers or the like.
[0003] A representative thermal inkjet printhead has a plurality of
thin film resistors provided on a semiconductor substrate. A nozzle
layer is deposited over thin film layers on the substrate. The
nozzle chamber layer defines firing chambers about each of the
resistors, an orifice corresponding to each resistor, and an
entrance to each firing chamber. Often, ink is provided through a
slot in the substrate and flows through an ink channel defined by
the nozzle layer to the firing chamber. Actuation of a heater
resistor by a "fire signal" causes ink in the corresponding firing
chamber to be heated and expelled through the corresponding
orifice.
[0004] Continued adhesion between the nozzle layer and the thin
film layers is desired. With printhead substrate dies, especially
those that are larger-sized or that have high aspect ratios,
unwanted warpage, and thus nozzle layer delamination, may occur due
to mechanical or thermal stresses. For example, often, the nozzle
layer has a different coefficient of thermal expansion than that of
the semiconductor substrate. The thermal stresses may lead to
delamination of the nozzle layer, or other thin film layers,
ultimately leading to ink leakage and/or electrical shorts. In an
additional example, when the dies on the assembled wafer are
separated, delamination may occur. In additional and/or alternative
examples, the nozzle layer can undergo stresses due to nozzle layer
shrinkage after curing of the layer, structural adhesive shrinkage
during assembly of the nozzle layer, handling of the device, and
thermal cycling of the fluid ejection device.
SUMMARY
[0005] In one embodiment, a fluid ejection device comprises a
substrate having a first surface, and a fluid slot in the first
surface. The device further comprises a fluid ejector formed over
the first surface of the substrate, and a chamber layer formed over
the first surface of the substrate. The chamber layer defines a
chamber about the fluid ejector, wherein fluid flows from the fluid
slot towards the chamber to be ejected therefrom. The chamber layer
has a discontinuity, wherein the discontinuity is positioned over
the fluid slot.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 illustrates a perspective view of an embodiment of a
fluid ejection cartridge of the present invention;
[0007] FIG. 2 illustrates a cross-sectional view of an embodiment
of a fluid ejection device taken through section 2-2 of FIG. 1;
[0008] FIG. 3 illustrates a plan view of an embodiment of a fluid
ejection device taken through section 3-3 of FIG. 2;
[0009] FIG. 4 illustrates a plan view of an alternative embodiment
of a fluid ejection device;
[0010] FIGS. 5-7 illustrate cross-sectional views showing a method
of forming the fluid ejection device embodiment illustrated in FIG.
4; and
[0011] FIG. 8 illustrates a plan view of an additional embodiment
of a fluid ejection device.
DETAILED DESCRIPTION
[0012] FIG. 1 is a perspective view of an embodiment of a cartridge
10 having a fluid drop generator or fluid ejection device 14, such
as a printhead. The embodiment of FIG. 2 illustrates a
cross-sectional view of the printhead 14 of FIG. 1 where a slot 122
is formed through a substrate 28. Some of the embodiments used in
forming the slot through a slot region (or slot area) in the
substrate include abrasive sand blasting, wet etching, dry etching,
DRIE, and UV laser machining.
[0013] In one embodiment, the substrate 28 is silicon. In various
embodiments, the substrate is one of the following: single
crystalline silicon, polycrystalline silicon, gallium arsenide,
glass, silica, ceramics, or a semiconducting material. The various
materials listed as possible substrate materials are not
necessarily interchangeable and are selected depending upon the
application for which they are to be used.
[0014] In the embodiment of FIG. 2, a thin film stack (such as an
active layer, an electrically conductive layer, or a layer with
micro-electronics) is formed or deposited on a front or first side
(or surface) of the substrate 102. In one embodiment, a capping
layer 32 is formed over a first surface of the substrate. Capping
layer 32 may be formed of a variety of different materials such as
field oxide, silicon dioxide, aluminum oxide, silicon carbide,
silicon nitride, and glass (PSG). In this embodiment, a layer 30 is
deposited or grown over the capping layer 32. In a particular
embodiment, the layer 30 is one of titanium nitride, titanium
tungsten, titanium, a titanium alloy, a metal nitride, tantalum
aluminum, and aluminum silicone.
[0015] In this embodiment, a conductive layer 114 is formed by
depositing conductive material over the layer 30. The conductive
material is formed of at least one of a variety of different
materials including aluminum, aluminum with about 1/2% copper,
copper, gold, and aluminum with 1/2% silicon, and may be deposited
by any method, such as sputtering and evaporation. The conductive
layer 114 is patterned and etched to form conductive traces. After
forming the conductor traces, a resistive material 115 is deposited
over the etched conductive material 114. The resistive material is
etched to form an ejection element 134, such as a resistor, a
heating element, or a bubble generator. A variety of suitable
resistive materials are known to those of skill in the art
including tantalum aluminum, nickel chromium, and titanium nitride,
which may optionally be doped with suitable impurities such as
oxygen, nitrogen, and carbon, to adjust the resistivity of the
material.
[0016] As shown in the embodiment of FIG. 2, an insulating
passivation layer 117 is formed over the resistive material.
Passivation layer 117 may be formed of any suitable material such
as silicon dioxide, aluminum oxide, silicon carbide, silicon
nitride, and glass. In this embodiment, a cavitation layer 119 is
added over the passivation layer 117. In a particular embodiment,
the cavitation layer is tantalum.
[0017] In one embodiment, a top layer 124 is deposited over the
cavitation layer 119. In one embodiment, the top layer 124 is a
chamber layer comprised of a fast cross-linking polymer such as
photoimagable epoxy (such as SU8 developed by IBM), photoimagable
polymer or photosensitive silicone dielectrics, such as SINR-3010
manufactured by ShinEtsu.TM.. In another embodiment, the top layer
124 is made of a blend of organic polymers which is substantially
inert to the corrosive action of ink. Polymers suitable for this
purpose include products sold under the trademarks VACREL and
RISTON by E. I. DuPont de Nemours and Co. of Wilmington, Del.
[0018] In a particular embodiment, the chamber layer 124 defines a
firing chamber 132 where fluid is heated by the corresponding
ejection element 134 and defines a nozzle orifice 126 through which
the heated fluid is ejected. Fluid flows through the slot 122 and
into the firing chamber 132 via channels formed in the chamber
layer 124. Propagation of a current or a "fire signal" through the
resistor causes fluid in the corresponding firing chamber to be
heated and expelled through the corresponding nozzle 126. In
another embodiment, an orifice layer having the orifices 126 is
applied over the chamber layer 124.
[0019] An example of the physical arrangement of the chamber layer,
and thin film substructure is illustrated at page 44 of the
Hewlett-Packard Journal of February 1994. Further examples of ink
jet printheads are set forth in commonly assigned U.S. Pat. No.
4,719,477, U.S. Pat. No. 5,317,346, and U.S. Pat. No. 6,162,589.
Embodiments of the present invention include having any number and
type of layers formed or deposited over the substrate, depending
upon the application.
[0020] As shown more clearly in the printhead 14 of FIG. 3, the
nozzle orifices 126 are arranged in rows located on both sides of
the slot 122. In one embodiment, the nozzle orifices, and
corresponding firing chambers are staggered from each other across
the slot. In FIG. 2, a firing chamber in the printhead that is
staggered across the slot from the firing chamber 132 is shown in
dashed lines.
[0021] As shown in the embodiment of FIG. 2, a discontinuity 130 is
in the layer 124, such as a gap, a stress relieving slot, or an
aperture. In one embodiment, the discontinuity 130 provides a means
for alleviating stress and strain in the layer 124. In a particular
embodiment, a force in a z-direction (or vertical direction) on the
substrate 28 and the layer 124 may move longitudinal sides of slot
122 vertically with respect to each other. Consequently, in this
embodiment, the top layer 124 may move and may tend to peel or
delaminate from the underneath layers. In this embodiment, the
discontinuity 130 tends to enable the top layer to more easily move
with the respective longitudinal sides of the slotted
substrate.
[0022] In one embodiment, the discontinuity 130 is a gap that can
have a width of up to about 16 microns. In another embodiment, the
discontinuity has a width that is minimized. In yet another
embodiment, the discontinuity has a width of about 0-2 microns,
wherein longitudinal sides of the discontinuity 130 are touching at
least in some areas along the gap (not shown in this embodiment).
In other embodiments, the width is about 6, 8, 10, or 12 microns,
depending upon the application.
[0023] In an additional embodiment, the discontinuity has a width
such that fluid drool or back pressure from the discontinuity is
minimized or mitigated. In another additional embodiment, the
discontinuity has a width such that a fluid meniscus (capillary
resistance) holds the fluid within the top layer, and keeps the
fluid from drooling out of the top layer. In yet another
embodiment, the dimensions are specific to the surface tension of
the fluid and the surface properties of the polymer film used in
the fluid ejection device. In this embodiment, the layer 124 has a
first surface 124a, and a second opposite surface 124b. In this
embodiment shown, the discontinuity 130 extends from the first
surface to the second surface.
[0024] As shown in the embodiment of FIG. 3, ends 131 of
discontinuity 130 are rounded similar to the rounded ends 123 of
the slot 122. In this embodiment shown, a length of the
discontinuity 130 is about the same as a length of the fluid slot.
Ends 123 of the fluid slot are shown in FIG. 3. In this embodiment,
a length of the longitudinal side of the slot is substantially the
same as the distance from slot end to slot end 123. In another
embodiment, the discontinuity 130 has a length such that the layer
124 substantially maintains adhesiveness to the thin film layers
underneath, and fluid drool is minimized. In yet another
embodiment, the discontinuity is as long as the trench such that
the discontinuity is effective in mitigating mechanical stresses in
the chamber layer. In alternative embodiments, the discontinuity
130 extends longer than the length of the slot 122 and shorter than
the length of the slot, depending upon the application (embodiments
not shown).
[0025] In this embodiment, the discontinuity 130 is located in
between longitudinal sides of the slot 122. In a particular
embodiment, the discontinuity 130 in the layer 124 is substantially
centered over the slot.
[0026] As shown in the alternative embodiment of FIG. 4, there is a
discontinuity or slit 130a in the layer 124. In a particular
embodiment, the slit is a closed slit. In another embodiment,
longitudinal sides of the slit are substantially in contact with
each other along a length of the slit.
[0027] FIGS. 5-7 illustrate an embodiment of forming the fluid
ejection device having the discontinuity 130 or the slit 130a in
the layer 124, in accordance with the present invention. As shown
in the embodiment of FIG. 5, a material 124a for forming the top
layer 124 is formed or deposited over the thin film stack.
[0028] As shown in the embodiment of FIG. 6, the material 124a is
masked with at least one mask 210 and then exposed to varying
levels of radiation to define the chamber layer 124. The masks
allow for controlling the entrance diameter to the firing chamber,
the exit diameter of the orifice, the firing chamber volume based
on the orifice layer height, as well as the volume of the
discontinuity. For example, for the discontinuity 130 in the
embodiment of FIG. 3, at least one of the mask shapes in a plan
view is similar to the plan view shown in FIG. 3. In this
embodiment, the lines forming the discontinuity 130, the slot 122,
the chambers 132, and the nozzles 126 in FIG. 3 can also be
interpreted as at least one of the masks used in defining the
chamber layer 124. Similarly, for the discontinuity 130a in the
embodiment of FIG. 4, at least one of the mask shapes in a plan
view is similar to the plan view shown in FIG. 4. In particular,
the lines forming the slit 130a, the slot 122, and the nozzles 126
in FIG. 4 can also be interpreted as at least one of the masks used
in defining the chamber layer 124. Accordingly, the at least one
mask 210 may have different widths for forming the discontinuity
130/130a, depending upon the width of the discontinuity desired. In
one embodiment, the slit is formed using the negative photoresist
qualities of the chamber layer material.
[0029] In this embodiment shown in FIG. 6, the material 124a is
exposed to differing intensity levels of radiation 235, 236 along
its outer surface, depending upon the shape of the chamber layer
124 desired. In one embodiment, electromagnetic radiation is used
to cross-link a photoimagable material layer using the at least one
mask 210. A more detailed example of exposing a material to
differing intensity levels of radiation to form a desired layer
shape is set forth in commonly assigned U.S. Pat. No.
6,162,589.
[0030] In one embodiment, after the material 124a is exposed to the
irradation, there is about a 6% shrinkage by volume in the layer
124 compared with the original mask. In this embodiment, the
discontinuity grows wider than the mask design.
[0031] As shown in the embodiment of FIG. 7, the slit 130a is
formed in the layer 124, and the material 124a for forming the
layer 124 is removed through a developing method. After removing
this material, the fluid path through the slot, and chamber layer
chamber and orifice is formed. In another embodiment, the
discontinuity 130 is formed in a similar manner, however, the at
least one mask is/are slightly different, accordingly.
[0032] An additional embodiment is shown in FIG. 8, wherein there
are multiple discontinuities 130, such as an expansion grate, in
the chamber layer 124. In this embodiment, the multiple
discontinuities are substantially parallel to each other along the
length of the slot. In the embodiment shown, there are two
discontinuities near the trench shelf. However, the location and
number of discontinuities are not so limited. For example, there
may be three or more discontinuities spread out over the suspended
portion of the chamber layer. In further embodiments, the
discontinuities of FIG. 8 may be similar to the discontinuities
130a, as discussed herein. It is therefore to be understood that
this invention may be practiced otherwise than as specifically
described. For example, the present invention is not limited to
thermally actuated printheads, but may also include, for example,
piezoelectric activated printheads, and other mechanically actuated
printheads, as well as other applications having a thin suspended
polymer film. Methods of alleviating stress in a thin suspended
polymer film may also be applied to micro-electromechanical systems
(MEMS devices). Thus, the present embodiments of the invention
should be considered in all respects as illustrative and not
restrictive, the scope of the invention to be indicated by the
appended claims rather than the foregoing description. Where the
claims recite "a" or "a first" element of the equivalent thereof,
such claims should be understood to include incorporation of one or
more such elements, neither requiring nor excluding two or more
such elements.
* * * * *