CA2044402A1 - Thermal ink jet printhead and method of manufacture - Google Patents
Thermal ink jet printhead and method of manufactureInfo
- Publication number
- CA2044402A1 CA2044402A1 CA 2044402 CA2044402A CA2044402A1 CA 2044402 A1 CA2044402 A1 CA 2044402A1 CA 2044402 CA2044402 CA 2044402 CA 2044402 A CA2044402 A CA 2044402A CA 2044402 A1 CA2044402 A1 CA 2044402A1
- Authority
- CA
- Canada
- Prior art keywords
- layer
- silicon dioxide
- heating
- heating element
- heating resistor
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 238000000034 method Methods 0.000 title claims description 11
- 238000004519 manufacturing process Methods 0.000 title description 5
- 238000010438 heat treatment Methods 0.000 claims abstract description 144
- 238000002161 passivation Methods 0.000 claims abstract description 44
- BHEPBYXIRTUNPN-UHFFFAOYSA-N hydridophosphorus(.) (triplet) Chemical compound [PH] BHEPBYXIRTUNPN-UHFFFAOYSA-N 0.000 claims abstract description 15
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims abstract description 11
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 11
- 239000011574 phosphorus Substances 0.000 claims abstract description 11
- 230000001681 protective effect Effects 0.000 claims abstract 8
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 109
- 235000012239 silicon dioxide Nutrition 0.000 claims description 54
- 239000000377 silicon dioxide Substances 0.000 claims description 54
- 239000000758 substrate Substances 0.000 claims description 29
- 229910021420 polycrystalline silicon Inorganic materials 0.000 claims description 16
- 229920005591 polysilicon Polymers 0.000 claims description 16
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 14
- 229910052710 silicon Inorganic materials 0.000 claims description 14
- 239000010703 silicon Substances 0.000 claims description 14
- 229960001866 silicon dioxide Drugs 0.000 claims 35
- 239000000463 material Substances 0.000 claims 2
- 239000011521 glass Substances 0.000 abstract description 5
- 229910052715 tantalum Inorganic materials 0.000 description 20
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 19
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 18
- 229910052782 aluminium Inorganic materials 0.000 description 18
- 229910052581 Si3N4 Chemical group 0.000 description 10
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical group N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 10
- 238000009413 insulation Methods 0.000 description 6
- 238000000151 deposition Methods 0.000 description 5
- 238000005530 etching Methods 0.000 description 4
- 239000011253 protective coating Substances 0.000 description 4
- 238000000059 patterning Methods 0.000 description 3
- 230000004888 barrier function Effects 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 239000013589 supplement Substances 0.000 description 2
- 239000000356 contaminant Substances 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 239000007943 implant Substances 0.000 description 1
- 238000007641 inkjet printing Methods 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000007639 printing Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 229910052814 silicon oxide Inorganic materials 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/135—Nozzles
- B41J2/14—Structure thereof only for on-demand ink jet heads
- B41J2/14016—Structure of bubble jet print heads
- B41J2/14088—Structure of heating means
- B41J2/14112—Resistive element
- B41J2/14129—Layer structure
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/135—Nozzles
- B41J2/16—Production of nozzles
- B41J2/1601—Production of bubble jet print heads
- B41J2/1604—Production of bubble jet print heads of the edge shooter type
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/135—Nozzles
- B41J2/16—Production of nozzles
- B41J2/1621—Manufacturing processes
- B41J2/1626—Manufacturing processes etching
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/135—Nozzles
- B41J2/16—Production of nozzles
- B41J2/1621—Manufacturing processes
- B41J2/164—Manufacturing processes thin film formation
- B41J2/1642—Manufacturing processes thin film formation thin film formation by CVD [chemical vapor deposition]
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/135—Nozzles
- B41J2/16—Production of nozzles
- B41J2/1621—Manufacturing processes
- B41J2/164—Manufacturing processes thin film formation
- B41J2/1643—Manufacturing processes thin film formation thin film formation by plating
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2202/00—Embodiments of or processes related to ink-jet or thermal heads
- B41J2202/01—Embodiments of or processes related to ink-jet heads
- B41J2202/13—Heads having an integrated circuit
Landscapes
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Particle Formation And Scattering Control In Inkjet Printers (AREA)
Abstract
ABSTRACT
A thermal inkjet printhead is disclosed having improved reliability and thermal efficiency. The printhead includes heating resistors and thin protective regionspositioned above the heating resistors for protecting the heating resistors fromcorrosion and cavitation damage from the ink. The heating resistors are positioned substantially within the geometric confines of the portion of the protective regions exposed to the ink. Positioned between the heating resistors and the underlying printhead structure are field oxide regions that thermally insulate the heating resistors from the underlying printhead structure. Positioned between the heating resistors and the underlying printhead structure is a passivation layer consisting of a middle layer of phosphorous glass, an underglaze between the middle layer and the underlying printhead structure, and glass mesas between the middle layer and theheating resistors. The underglaze helps prevent phosphorus from the middle layerfrom contaminating the underlying printhead structure. Similarly, the glass mesas prevent phosphorus from the middle layer from contaminating the heating resistors.
A thermal inkjet printhead is disclosed having improved reliability and thermal efficiency. The printhead includes heating resistors and thin protective regionspositioned above the heating resistors for protecting the heating resistors fromcorrosion and cavitation damage from the ink. The heating resistors are positioned substantially within the geometric confines of the portion of the protective regions exposed to the ink. Positioned between the heating resistors and the underlying printhead structure are field oxide regions that thermally insulate the heating resistors from the underlying printhead structure. Positioned between the heating resistors and the underlying printhead structure is a passivation layer consisting of a middle layer of phosphorous glass, an underglaze between the middle layer and the underlying printhead structure, and glass mesas between the middle layer and theheating resistors. The underglaze helps prevent phosphorus from the middle layerfrom contaminating the underlying printhead structure. Similarly, the glass mesas prevent phosphorus from the middle layer from contaminating the heating resistors.
Description
-THERMAL INK JET PRINTHEAD AND METHOD OF MANUFACTUR
Field of the Invention This invention relates generally to thermal ink jet printing, and more particularly to a thermal ink jet printhead, and a process for fabricating it.
Background of the Inven~ion In thermal ink jet (TIJ) printing, the printhead comprises one or rnore ink filled channels which communicated with an ink supply chamber at one end and an orificeat the opposite end, such as disclosed in U.S. Patent No. Re. 32,572 to Hawkins, et al.
A heating element, such as a resistor, is located in each channel near the orifice. The heating resistors are individually addressed with a current pulse to momentarilyvaporize the ink and form a bubble which expels an ink droplet from the orifice. The current pulses originate in drive circuitry, which can be constructed in the printhead, and the current pulses aré conveyed to the heating resistors by interconnects, typically made of aluminum. The heating resistors typically consist of resistivematerial of substantially uniform resistance to help ensure uniform ink droplet size and velocity.
So that most of the heat from the heating resistors heats the ink, some existingprintheads separate the heating resistors from the underlying printhead structure with thermal insulation. For example, as disciosed in U.S. Patent No. 4,532,530 issues to Hawkins, existing printheads constructed from silicon substrates~ use a passivation layer to thermally isolate the heating ~resistors from the underlying semiconductor substrate. The heating resistors are fabricated on top of the passivation layer. A
typical passivation layer consists of silicon dioxide containing trace amounts of phosphorus to facilitate reflow at temperatures below the melting point of the aluminum interconnects. Reflowing the passivation layer ensures a smooth surfaceupon which the interconnects can be formed, thereby increasing the reliability of the interconnects.
Other existing printheads do not separate the heating resistors from the;
underlying printhead ;structure with a passivation layer. Instead, these existing printheads save steps in fabricating the heating resistors by fabricating the heating resistors from the same layer of polysilicon used in conventional MOS processes to construct the gate electrode of FETs, and for this reason such printheads are known as nsingie poly heating resistor" printheads. Concequently, the heating resistors in :
,-.. -. ~.
~:
'. `
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the single poly heating resistor printheads are separated from the underlying printhead structure only by the thin layer of gate silicon dioxide.
Generaily, the existing printheads perform adequately. The existing printheads, however, transfer heat to the ink at a lower e-fficiency than is desirable. In addition, the reliability of the junctions between heating resistors and aluminum interconnects is lessened by excess temperatures at these junctions. In addition, heating resistors of nonuniform resistance result from phosphorous diffusing into the heating resistors from the underlying passivation layer.
Finally, in the course of fabricating the single poly heating resistor printheads, since the heating resistors are fabricated from the same polysilicon layer used to fabricate the gate electrodes, the heating resistors are covered by the passivation layer used to passivate the gate electrodes. This passivation layer is removed before a protective coating, such as tantalum, is applied into the resulting cavity above the heating resistors to protect the heating resistors from corrosion and cavitationdamage from the ink. The are reliability problems, however, in depositing tantalum or other protective coatings into the cavi~y above the heating resistors, due toinadequate step coverage.
There is therefore a need for a thermal ink jet printhead with a higher heat transfer efficiency, more reliable junctions between heating resistors an~ aluminum interconnections, heating resistors with reduced phosphorus contamination, and an improved protective coating for heating resistors.
Summary of the Invention A thermal ink jet printhead is provided which includes ink channels and a heating resistor positioned within each ink channel. The heating resistors are fabricated on a major surface of a silicon substrate, atong with drive circuitry that powers theheating resistors, channel stops that isolate drive circuitry, and aluminum interconnects that connect drive circuitry to respective heating resistors. Moreparticularly, drive circuitry and channel stops are fabricated within the silicon substrate. The heating resistors and aluminum interconnects are fabricated on a passivation layer which covers the major surface of the substrate and electrically isolates the substrate from the heating resistors and aluminum interconnects, and thermally isolates the substrate from the heating resistors. Each heating resistor is covered by successive regions of silicon dioxide and silicon nitride, and a tantalum region which contacts the ink. These regions help prevent the ink from contaminating and cavitating the heating resistors. A second passivation layer ..
i .
~ 0 ~ 2 , covers most of the first passivation layer, including the aluminum interconnects, and overlaps the outer perimeter regions of the top surface of tantalum regions, leaving most of the top surface of the tantalum regions exposed so that the second passivation layer is not a thermal barrier between the heating resistors and the ink.
In accordance with one aspect of the invention, a double layer of polysilicon isemployed, with the bottom layer of polysilicon being used to form gate electrodes of FETs, the top layer of polysilicon being used to form heating resistors, so that reliability problems associate with step coverage of the tantalum protective coating are minimized by placing the heating resistors above the passivation layer that covers the gate electrodes of the FETs.
In accordance with another aspect of the invention, there is a contact region atopposite ends of each heating resistor. The contact regions have a much lower sheet resistance than the heating resistors. Therefore, the heating resistors wiil tend to be hotter than the contact regions during the flow of electricity therethrough. Efficient transfer of heat to the ink is aided by positioning respective heating resistors either substantially coextensive with the exposed portions of respective tantalum regions or substantially within the geometric confines of the exposed portions of respective tantalum regions. In addition, the contact regions space the junctions between contact regions and the aluminum interconnec~s from the hotter heating resistors, thereby contributing to lower junction temperatures, and thus greater junction reliability.
In accordance with another aspect of the invention, the printhead includes thickfield oxide regions constructed in the silicon substrate between the first passivation layer and the major surface directly beneath each heating resistors. The field oxide regions supplement the thermal insulation provided by the first passivation layer to thermally isolate the heating resistors from the silicon substrate. One advantage of using the field oxide regions rather than simply increasing the thickness of the first passivation layer is that contact holes are etched thru the first passivation layer to allow the interconnects to contact the drive circuitry, and a thicker passivation layer decreases the reliability of such contact. However, contact holes need not be etched through the field oxide regions since the field oxide regions are positioned beneath the heating resistors and not above the drive circuitry.
In accordance with another aspect of the invention, the field oxide regions are constructed without additional fabrication steps by constructing them in the same steps used to construct the channel stops.
Field of the Invention This invention relates generally to thermal ink jet printing, and more particularly to a thermal ink jet printhead, and a process for fabricating it.
Background of the Inven~ion In thermal ink jet (TIJ) printing, the printhead comprises one or rnore ink filled channels which communicated with an ink supply chamber at one end and an orificeat the opposite end, such as disclosed in U.S. Patent No. Re. 32,572 to Hawkins, et al.
A heating element, such as a resistor, is located in each channel near the orifice. The heating resistors are individually addressed with a current pulse to momentarilyvaporize the ink and form a bubble which expels an ink droplet from the orifice. The current pulses originate in drive circuitry, which can be constructed in the printhead, and the current pulses aré conveyed to the heating resistors by interconnects, typically made of aluminum. The heating resistors typically consist of resistivematerial of substantially uniform resistance to help ensure uniform ink droplet size and velocity.
So that most of the heat from the heating resistors heats the ink, some existingprintheads separate the heating resistors from the underlying printhead structure with thermal insulation. For example, as disciosed in U.S. Patent No. 4,532,530 issues to Hawkins, existing printheads constructed from silicon substrates~ use a passivation layer to thermally isolate the heating ~resistors from the underlying semiconductor substrate. The heating resistors are fabricated on top of the passivation layer. A
typical passivation layer consists of silicon dioxide containing trace amounts of phosphorus to facilitate reflow at temperatures below the melting point of the aluminum interconnects. Reflowing the passivation layer ensures a smooth surfaceupon which the interconnects can be formed, thereby increasing the reliability of the interconnects.
Other existing printheads do not separate the heating resistors from the;
underlying printhead ;structure with a passivation layer. Instead, these existing printheads save steps in fabricating the heating resistors by fabricating the heating resistors from the same layer of polysilicon used in conventional MOS processes to construct the gate electrode of FETs, and for this reason such printheads are known as nsingie poly heating resistor" printheads. Concequently, the heating resistors in :
,-.. -. ~.
~:
'. `
` ~ 2 1~
the single poly heating resistor printheads are separated from the underlying printhead structure only by the thin layer of gate silicon dioxide.
Generaily, the existing printheads perform adequately. The existing printheads, however, transfer heat to the ink at a lower e-fficiency than is desirable. In addition, the reliability of the junctions between heating resistors and aluminum interconnects is lessened by excess temperatures at these junctions. In addition, heating resistors of nonuniform resistance result from phosphorous diffusing into the heating resistors from the underlying passivation layer.
Finally, in the course of fabricating the single poly heating resistor printheads, since the heating resistors are fabricated from the same polysilicon layer used to fabricate the gate electrodes, the heating resistors are covered by the passivation layer used to passivate the gate electrodes. This passivation layer is removed before a protective coating, such as tantalum, is applied into the resulting cavity above the heating resistors to protect the heating resistors from corrosion and cavitationdamage from the ink. The are reliability problems, however, in depositing tantalum or other protective coatings into the cavi~y above the heating resistors, due toinadequate step coverage.
There is therefore a need for a thermal ink jet printhead with a higher heat transfer efficiency, more reliable junctions between heating resistors an~ aluminum interconnections, heating resistors with reduced phosphorus contamination, and an improved protective coating for heating resistors.
Summary of the Invention A thermal ink jet printhead is provided which includes ink channels and a heating resistor positioned within each ink channel. The heating resistors are fabricated on a major surface of a silicon substrate, atong with drive circuitry that powers theheating resistors, channel stops that isolate drive circuitry, and aluminum interconnects that connect drive circuitry to respective heating resistors. Moreparticularly, drive circuitry and channel stops are fabricated within the silicon substrate. The heating resistors and aluminum interconnects are fabricated on a passivation layer which covers the major surface of the substrate and electrically isolates the substrate from the heating resistors and aluminum interconnects, and thermally isolates the substrate from the heating resistors. Each heating resistor is covered by successive regions of silicon dioxide and silicon nitride, and a tantalum region which contacts the ink. These regions help prevent the ink from contaminating and cavitating the heating resistors. A second passivation layer ..
i .
~ 0 ~ 2 , covers most of the first passivation layer, including the aluminum interconnects, and overlaps the outer perimeter regions of the top surface of tantalum regions, leaving most of the top surface of the tantalum regions exposed so that the second passivation layer is not a thermal barrier between the heating resistors and the ink.
In accordance with one aspect of the invention, a double layer of polysilicon isemployed, with the bottom layer of polysilicon being used to form gate electrodes of FETs, the top layer of polysilicon being used to form heating resistors, so that reliability problems associate with step coverage of the tantalum protective coating are minimized by placing the heating resistors above the passivation layer that covers the gate electrodes of the FETs.
In accordance with another aspect of the invention, there is a contact region atopposite ends of each heating resistor. The contact regions have a much lower sheet resistance than the heating resistors. Therefore, the heating resistors wiil tend to be hotter than the contact regions during the flow of electricity therethrough. Efficient transfer of heat to the ink is aided by positioning respective heating resistors either substantially coextensive with the exposed portions of respective tantalum regions or substantially within the geometric confines of the exposed portions of respective tantalum regions. In addition, the contact regions space the junctions between contact regions and the aluminum interconnec~s from the hotter heating resistors, thereby contributing to lower junction temperatures, and thus greater junction reliability.
In accordance with another aspect of the invention, the printhead includes thickfield oxide regions constructed in the silicon substrate between the first passivation layer and the major surface directly beneath each heating resistors. The field oxide regions supplement the thermal insulation provided by the first passivation layer to thermally isolate the heating resistors from the silicon substrate. One advantage of using the field oxide regions rather than simply increasing the thickness of the first passivation layer is that contact holes are etched thru the first passivation layer to allow the interconnects to contact the drive circuitry, and a thicker passivation layer decreases the reliability of such contact. However, contact holes need not be etched through the field oxide regions since the field oxide regions are positioned beneath the heating resistors and not above the drive circuitry.
In accordance with another aspect of the invention, the field oxide regions are constructed without additional fabrication steps by constructing them in the same steps used to construct the channel stops.
2~4~02 , ~
In accordance with a final aspect of the invention, the passivation layer between the heating resistors and the drive circuitry includes three separate layers of silicon dioxide, a middle layer doped with phosphorous, a non-doped underglaze, and non-doped overglaze mesas. The middle layer is doped with phosphorous to facilitate reflow of the middle layer. The underglaze is positioned below and contiguous with the middle layer, and above the drive circuitry and the ~ield oxide regions. Theunderglaze prevents phosphorous from the middle doped layer from diWusing to the drive circuitry and altering its electrical characteristics, particularly the electrical characteristics in the drift regions. A respective one of overglaze mesas is positioned above the middle layer and directly beneath a respective one of the heating resistors. The overglaze mesas prevent phosphorous from the middle layer from diffusing to the heating resistors and altering their electrical characteristics. In this matter, the heating resistors can more readily be made of uniform resistance.
Other aspects of the invention will become apparent from the following description with reference to the drawings, wherein:
Brief Description of the Drawings Figure 1 is an enlarged isometric view of a ~irst embodiment oF a side shooter thermal ink jet printhead embodying the invention, showing the linear array of nozzles and ink channels;
Figure 2 is a partial sectional view of the heater board of the first preferred embodiment of the thermal ink jet printhead of Figure 1;
Figure 3 is a partial sectional view of a heater board of a second preferred embodiment of a thermal ink jet printhead;
Figures 5a - 5d show process steps for making the third preferred embodiment of a thermal ink jet printhead.
Description of the Preferred Embodiments Referring now to Figures 1 and 2, there is shown a first preferred embodiment ofa thermal ink jet (TIJ) printhead 10 embodying the present invention. Housed in the printhead 10 are a linear array of ink jets. Each ink jet includes an ink channel 12, and a heating resistor 14 positioned in ink channel 12. A droplet is expelled from the nozzle of ink channel 12 in response to a current pulse sent to the heating resistor 14 associated with that ink channel 12. The current pulse originates in drive circuitry 16 that is selectively addressed by a control signal along an addressing electrode 18 associated with its particular heating resistor 14.
2~'102 ;
Referring to Figure 1, printhead 10 comprises an electrically insulated substrate heater board 20 permanently attached to a structure board 22. Structure board 22includes parallel triangular cross-sectional grooves 24 which ex~end in one direction and penetrate through front edge 26 of printhead 10. Heater board 20 is aligned and bonded to the surface of structure board 22 with grooves 24 so that ink channels 12 are formed by grooves 24 and the surface of the heater board 20, and so that a respective one of the plurality of ink channels 12 has positioned in it a respective one of the plurality of heating resistors 14.
Referring to Figures 1 and 2, heater board 20 includes an electrically insulatedsilicon substrate 26 with a major surface 28 on which there is patterned CMOS drive circuitry 16 and channel stops 30. Of course, drive circuitry 16 could be fabricated using other fabrication techniques as well. Major surface 28, drive circuitry 16, and channel stops 30 are covered by a passivation layer 32, which consists of a 1 micron thick layer of silicon dioxide. On the top surface of passivation layer 32 there are patterned heating resistors 14, addressing electrodes 18, a power bus 34 for supplying power to heating resistors 14, and terminals 36 connected to addressing electrodes 18 and power bus 34, and aluminum interconnects 38. Aluminum interconnects 38 connect heating resistors 14 to power bus 34, and connect drivecircuitry 16 to respective addressing electrodes 18 and respective heating resistors 14.
Each heating resistor 14 is covered by successive regions of silicon dioxide 42,silicon nitride 44, and~tantalum 46, respectively, that separate heating resistor 14 from the ink (not shown) to protect the ink from contaminating or cavitating heating resistor 14. Moreover, each silicon dioxide region 42 and silicon nitride region 44 electrically insulate their respective heating resistor 14 ~rom respective tantalum region 46, which is conductive. At and near junctions 40, respective tantalum regions 46 are spaced from respective aluminum interconnects 38 to prevent short circuits.
A passivation layer 48 covers aluminum interconnects 38, power bus 34, and addressing electrodes 18. Passivation layer 48 consists of a 1 micron thick layer of silicon dioxide. Alternatively, passivation layer 48 consists of a 0.5 micron thick layer of silicon dioxide covered by a 1.0 micron thick layer of silicon nitride, with the silicon nitride layer providing increased protection against contaminants, while being separated from the tantalum region ~6. Terminals 36 are no~ covered by passivation layer 48 to allow access to terminals 36. Passivation layer 48 also overlaps ends 50 of the top surface of tantalum regions 46, leaving exposed most of the top surface of 2~4~2 -tantalum regions 46 so that passivation layer 44 is not a thermal barrier between heating resistors 14 and the ink (not shown3.
Referring now to Figure 2, in accordance with one aspect of the inverltion, eachheater board 20 includes two contact regions 54 associated with each heating resistor 14. Heating resistors 14 have a substantially greater sheet resistance than contact regions 54. Contact regions 54 are positioned adjacent to and on opposite sides of respective heating resistors 14, Contact regions 54 include junctions 40 between respective contact regions 54 and respective aluminum interconnects 38, and connect aluminum interconnects 38 to their respective heating resistors 14.
Contact regions 54 help produce a lower temperature at junctions 40 by spacing junctions 40 ~rom the hotter heating resistors 14.
The efficient transfer of heat from heatin~ resistors 14 to the ink (not shown) is aided by positioning heating resistors 14 so that they lie aligned with and either substantially coextensive with the exposed portion of tantalum regions 46, or substantially within the geometric confines of the exposed portion of respectivetantalum regions 46. More particularly, each heating resistor 14 has ends 56 that abut its respective contact regions 54, and ends 56 lie beneath and approximately coincident with edges 58 of the portion of the top surface of respective tantalum regions 46 not covered by passivation layer 48. In this manner, heating resistors 14 are separated from the ink only by silicon oxide regions 42, silicon nitride regions 44 and tantalum regions 46, respectively.
To fabricate heating resistors 14, a 0.4 micron thick layer of polysilicon is deposited on passivation layer 32, patternecl and etched, then patterned and implanted with impuritiesto form contact regions 54, then patterned and implanted with impurities to form heating resistors 14. Subsequently, passivation layer 32 is reflowed to provide a smooth surface on which aluminum interconnects 38 can be deposited. Reflow of passivation layer 32 also drives impurities into heating resistors 14 and contact regions 54, and grows silicon dioxide region 42, which is 0.04 microns thick. Silicon dioxide region 42 could be removed, since protection of heating resistors 14 is mainly performed by tantalurn regions 46, which are 0.5 microns thick, and silicon nitride regions 44, which are 0.5 microns thick, but preferably silicon dioxide regions 42 are not removed to save the steps recluired for their removal.
Referring now to Figure 3, there is shown a second preferred embodiment of a printhead 10 embodying the present invention. in accordance with another aspect of the invention, heater board 20 includes 1 micron thick field oxide regions 60 that are constructed in silicon substrate 26 directly beneath heating resistors 14.
~, , .
2 ~
Although passivation layer 32 provides some thermal insulation, a 1 micron thickness of silicon dioxide, between heating resistors 14 and substrate 26, field oxide regions 60 increase the thickness of the thermal insulation in the vicinity of the heating resistors 14, where thermal insulation is most needed. One advantage in using field oxide regions 60 to supplement the thermal insulation of passivation layer 32, rather than simply increasing the thickness of passivation layer 32, is that increasing the thickness of passivation layer 32 increases the difficulty of etching contact hole 76 in passivation layer 32 that allow interconnects 38 to reach drive circuitry 16.
In accordance with another aspect of the invention, field oxide regions 60 are constructed in the same steps used to fabricate channel stops 30. In this manner, field oxide regions 60 are constructed without adding any steps to the conventional CMOS fabrication process, or other conventional fabrication process used to fabricate drive circuitry 16.
Although the second preferred embodiment shows the use o~ field oxide regions 60 in conjunction with heating resistors 14 and contact regions 54 to provide a most thermally efficient printhead 10, it should be understood that field oxide regions 60 could be used by themselves to provide a thermally efficient printhead 10.
Referring now to Figure 4, there is shown a third preferred embodiment of a printhead 10 embodying the present invention. In accordance with another aspect of the invention, passivation layer 32 includes three separate layers, a middle layer 62 doped with phosphorous, a non-doped underglaze 64, and non-doped overglaze mesas 66. Middle layer 62 is doped with phosphorous to facilitate reflow of middle layer 62. Underglaze 64 is positioned below and in contact with and coextensive with middle layer 62, and above drive circuitry 16 and ~ield oxide regions 60.
Underglaze 64 prevents phosphorous from middle doped layer 62 frorn diffusing todrive circuitry 16 and altering the electrical characteristics, particularly the electrical characteristics in the drift regions ~not shown). A respective one of overglaze mesas 66 is positioned between middle layer 62 and a respective one of heating resistors 14. Overglaze mesas 66 prevent phosphorous from middle layer 62 from diffusing to heating resistors 14 and altering the electrical characteristics.
Referring now to Figures 4 and 5a, in fabricating printhead 10, underglaze 64 isdeposited after drive circuitry 16, channel stops 30 and field oxide regions 60 have been constructed on major surface 28. Underglaze 64 is fabricated by depositing a 0.3 micron thick layer of CVD silicon dioxide on top of drive circuitry 16 and other portions of major surface 28. Next, middle layer 62 is formed by depositing on top of 2 ~
underglaze 64 a û.7 micron thick layer of CVD silicon dioxide doped with 4% to 6%
by weight of phosphorous.
Referring now to Figures 4 and 5b, glass mesas 66 are formed on top of middle layer 62 by depositing a 0.3 micron thick overglaze 68 of CV~ silicon dioxide, then patterning and etching overglaze 6~. Prior to the patterning and etching of overglaze 68, however, heating resistors 14 are formed on top of overglaze 68. On top of overglaze 68 there is deposited a 4500 angstrom thick layer 70 of CVD
polysilicon. Referring now to Figures 4, 5b and 5c, polysilicon layer 70 is patterned and etched to form polysilicon regions 74 directly above field oxide regions 60. Next, referring to Figures 4, 5c and 5d, to facilitate reflow of middle layer 62 overglaze 68 is patterned and etched to remove it from the surface of middle layer 62, exceptwhere overglaze 66 is covered by polysilicon regions 74. The remaining portions of overglaze 68 form glass mesas 66. Polysilicon regions 74 are implanted with impuritiesto form heating resistors 14 and contact regions 54.
Next, referring to Figures 1 and 4, a reflow process is performed that reflows middle layer 62. As previously mentioned, the reflow proces also grows silicon dioxide regions 42 on top of polysilicon regions 74, and implants the impuritieswithin polysilicon regions 74 to provide heating resistors 14 a sheet resistance from between 40 to 50 ohms per square. After the reflow process, silicon nitride and tantalum regions 44 and 46 are formed by depositing a 0.5 micron thick film of high-temperature silicon nitride and a 0.5 micron thick film of tantalum, respectively, then patterning and etching the films. Contact holes 76 are opened in passivation layer 32, and a layer of aluminum is deposited, patterned and etched to form aluminum interconnects 38, terminals 36, power bus 34 and addressing electrodes 18. Passivation layer 48, a 1 micron thick layer of silicon dioxide, is deposited, and patterned and etched to expose terminals 36 and tantalum regions 46 above hea~ing resistors 14. Alternatively, passivation layer 48 consists of a 0.5 rr~icron thick layer of silicon dioxide covered by a 1.~ micron thick layer of silicon nitride.
Although the third preferred embodiment shows the use of a rniddle layer 62 doped with phosphorous, a non-doped underglaze 64, and non-doped overglaze mesas 66 in conjunction with field oxide regions 60, heating resistors 14 and contact regions 54 to provide a most reliable and thermally efficient printhead 10, it should be understood that middle layer 62, underglaze 64 and mesas 66 could be used by themselvesto provide a reliable printhead 10.
. .
. ' ' ` ' .
.
In accordance with a final aspect of the invention, the passivation layer between the heating resistors and the drive circuitry includes three separate layers of silicon dioxide, a middle layer doped with phosphorous, a non-doped underglaze, and non-doped overglaze mesas. The middle layer is doped with phosphorous to facilitate reflow of the middle layer. The underglaze is positioned below and contiguous with the middle layer, and above the drive circuitry and the ~ield oxide regions. Theunderglaze prevents phosphorous from the middle doped layer from diWusing to the drive circuitry and altering its electrical characteristics, particularly the electrical characteristics in the drift regions. A respective one of overglaze mesas is positioned above the middle layer and directly beneath a respective one of the heating resistors. The overglaze mesas prevent phosphorous from the middle layer from diffusing to the heating resistors and altering their electrical characteristics. In this matter, the heating resistors can more readily be made of uniform resistance.
Other aspects of the invention will become apparent from the following description with reference to the drawings, wherein:
Brief Description of the Drawings Figure 1 is an enlarged isometric view of a ~irst embodiment oF a side shooter thermal ink jet printhead embodying the invention, showing the linear array of nozzles and ink channels;
Figure 2 is a partial sectional view of the heater board of the first preferred embodiment of the thermal ink jet printhead of Figure 1;
Figure 3 is a partial sectional view of a heater board of a second preferred embodiment of a thermal ink jet printhead;
Figures 5a - 5d show process steps for making the third preferred embodiment of a thermal ink jet printhead.
Description of the Preferred Embodiments Referring now to Figures 1 and 2, there is shown a first preferred embodiment ofa thermal ink jet (TIJ) printhead 10 embodying the present invention. Housed in the printhead 10 are a linear array of ink jets. Each ink jet includes an ink channel 12, and a heating resistor 14 positioned in ink channel 12. A droplet is expelled from the nozzle of ink channel 12 in response to a current pulse sent to the heating resistor 14 associated with that ink channel 12. The current pulse originates in drive circuitry 16 that is selectively addressed by a control signal along an addressing electrode 18 associated with its particular heating resistor 14.
2~'102 ;
Referring to Figure 1, printhead 10 comprises an electrically insulated substrate heater board 20 permanently attached to a structure board 22. Structure board 22includes parallel triangular cross-sectional grooves 24 which ex~end in one direction and penetrate through front edge 26 of printhead 10. Heater board 20 is aligned and bonded to the surface of structure board 22 with grooves 24 so that ink channels 12 are formed by grooves 24 and the surface of the heater board 20, and so that a respective one of the plurality of ink channels 12 has positioned in it a respective one of the plurality of heating resistors 14.
Referring to Figures 1 and 2, heater board 20 includes an electrically insulatedsilicon substrate 26 with a major surface 28 on which there is patterned CMOS drive circuitry 16 and channel stops 30. Of course, drive circuitry 16 could be fabricated using other fabrication techniques as well. Major surface 28, drive circuitry 16, and channel stops 30 are covered by a passivation layer 32, which consists of a 1 micron thick layer of silicon dioxide. On the top surface of passivation layer 32 there are patterned heating resistors 14, addressing electrodes 18, a power bus 34 for supplying power to heating resistors 14, and terminals 36 connected to addressing electrodes 18 and power bus 34, and aluminum interconnects 38. Aluminum interconnects 38 connect heating resistors 14 to power bus 34, and connect drivecircuitry 16 to respective addressing electrodes 18 and respective heating resistors 14.
Each heating resistor 14 is covered by successive regions of silicon dioxide 42,silicon nitride 44, and~tantalum 46, respectively, that separate heating resistor 14 from the ink (not shown) to protect the ink from contaminating or cavitating heating resistor 14. Moreover, each silicon dioxide region 42 and silicon nitride region 44 electrically insulate their respective heating resistor 14 ~rom respective tantalum region 46, which is conductive. At and near junctions 40, respective tantalum regions 46 are spaced from respective aluminum interconnects 38 to prevent short circuits.
A passivation layer 48 covers aluminum interconnects 38, power bus 34, and addressing electrodes 18. Passivation layer 48 consists of a 1 micron thick layer of silicon dioxide. Alternatively, passivation layer 48 consists of a 0.5 micron thick layer of silicon dioxide covered by a 1.0 micron thick layer of silicon nitride, with the silicon nitride layer providing increased protection against contaminants, while being separated from the tantalum region ~6. Terminals 36 are no~ covered by passivation layer 48 to allow access to terminals 36. Passivation layer 48 also overlaps ends 50 of the top surface of tantalum regions 46, leaving exposed most of the top surface of 2~4~2 -tantalum regions 46 so that passivation layer 44 is not a thermal barrier between heating resistors 14 and the ink (not shown3.
Referring now to Figure 2, in accordance with one aspect of the inverltion, eachheater board 20 includes two contact regions 54 associated with each heating resistor 14. Heating resistors 14 have a substantially greater sheet resistance than contact regions 54. Contact regions 54 are positioned adjacent to and on opposite sides of respective heating resistors 14, Contact regions 54 include junctions 40 between respective contact regions 54 and respective aluminum interconnects 38, and connect aluminum interconnects 38 to their respective heating resistors 14.
Contact regions 54 help produce a lower temperature at junctions 40 by spacing junctions 40 ~rom the hotter heating resistors 14.
The efficient transfer of heat from heatin~ resistors 14 to the ink (not shown) is aided by positioning heating resistors 14 so that they lie aligned with and either substantially coextensive with the exposed portion of tantalum regions 46, or substantially within the geometric confines of the exposed portion of respectivetantalum regions 46. More particularly, each heating resistor 14 has ends 56 that abut its respective contact regions 54, and ends 56 lie beneath and approximately coincident with edges 58 of the portion of the top surface of respective tantalum regions 46 not covered by passivation layer 48. In this manner, heating resistors 14 are separated from the ink only by silicon oxide regions 42, silicon nitride regions 44 and tantalum regions 46, respectively.
To fabricate heating resistors 14, a 0.4 micron thick layer of polysilicon is deposited on passivation layer 32, patternecl and etched, then patterned and implanted with impuritiesto form contact regions 54, then patterned and implanted with impurities to form heating resistors 14. Subsequently, passivation layer 32 is reflowed to provide a smooth surface on which aluminum interconnects 38 can be deposited. Reflow of passivation layer 32 also drives impurities into heating resistors 14 and contact regions 54, and grows silicon dioxide region 42, which is 0.04 microns thick. Silicon dioxide region 42 could be removed, since protection of heating resistors 14 is mainly performed by tantalurn regions 46, which are 0.5 microns thick, and silicon nitride regions 44, which are 0.5 microns thick, but preferably silicon dioxide regions 42 are not removed to save the steps recluired for their removal.
Referring now to Figure 3, there is shown a second preferred embodiment of a printhead 10 embodying the present invention. in accordance with another aspect of the invention, heater board 20 includes 1 micron thick field oxide regions 60 that are constructed in silicon substrate 26 directly beneath heating resistors 14.
~, , .
2 ~
Although passivation layer 32 provides some thermal insulation, a 1 micron thickness of silicon dioxide, between heating resistors 14 and substrate 26, field oxide regions 60 increase the thickness of the thermal insulation in the vicinity of the heating resistors 14, where thermal insulation is most needed. One advantage in using field oxide regions 60 to supplement the thermal insulation of passivation layer 32, rather than simply increasing the thickness of passivation layer 32, is that increasing the thickness of passivation layer 32 increases the difficulty of etching contact hole 76 in passivation layer 32 that allow interconnects 38 to reach drive circuitry 16.
In accordance with another aspect of the invention, field oxide regions 60 are constructed in the same steps used to fabricate channel stops 30. In this manner, field oxide regions 60 are constructed without adding any steps to the conventional CMOS fabrication process, or other conventional fabrication process used to fabricate drive circuitry 16.
Although the second preferred embodiment shows the use o~ field oxide regions 60 in conjunction with heating resistors 14 and contact regions 54 to provide a most thermally efficient printhead 10, it should be understood that field oxide regions 60 could be used by themselves to provide a thermally efficient printhead 10.
Referring now to Figure 4, there is shown a third preferred embodiment of a printhead 10 embodying the present invention. In accordance with another aspect of the invention, passivation layer 32 includes three separate layers, a middle layer 62 doped with phosphorous, a non-doped underglaze 64, and non-doped overglaze mesas 66. Middle layer 62 is doped with phosphorous to facilitate reflow of middle layer 62. Underglaze 64 is positioned below and in contact with and coextensive with middle layer 62, and above drive circuitry 16 and ~ield oxide regions 60.
Underglaze 64 prevents phosphorous from middle doped layer 62 frorn diffusing todrive circuitry 16 and altering the electrical characteristics, particularly the electrical characteristics in the drift regions ~not shown). A respective one of overglaze mesas 66 is positioned between middle layer 62 and a respective one of heating resistors 14. Overglaze mesas 66 prevent phosphorous from middle layer 62 from diffusing to heating resistors 14 and altering the electrical characteristics.
Referring now to Figures 4 and 5a, in fabricating printhead 10, underglaze 64 isdeposited after drive circuitry 16, channel stops 30 and field oxide regions 60 have been constructed on major surface 28. Underglaze 64 is fabricated by depositing a 0.3 micron thick layer of CVD silicon dioxide on top of drive circuitry 16 and other portions of major surface 28. Next, middle layer 62 is formed by depositing on top of 2 ~
underglaze 64 a û.7 micron thick layer of CVD silicon dioxide doped with 4% to 6%
by weight of phosphorous.
Referring now to Figures 4 and 5b, glass mesas 66 are formed on top of middle layer 62 by depositing a 0.3 micron thick overglaze 68 of CV~ silicon dioxide, then patterning and etching overglaze 6~. Prior to the patterning and etching of overglaze 68, however, heating resistors 14 are formed on top of overglaze 68. On top of overglaze 68 there is deposited a 4500 angstrom thick layer 70 of CVD
polysilicon. Referring now to Figures 4, 5b and 5c, polysilicon layer 70 is patterned and etched to form polysilicon regions 74 directly above field oxide regions 60. Next, referring to Figures 4, 5c and 5d, to facilitate reflow of middle layer 62 overglaze 68 is patterned and etched to remove it from the surface of middle layer 62, exceptwhere overglaze 66 is covered by polysilicon regions 74. The remaining portions of overglaze 68 form glass mesas 66. Polysilicon regions 74 are implanted with impuritiesto form heating resistors 14 and contact regions 54.
Next, referring to Figures 1 and 4, a reflow process is performed that reflows middle layer 62. As previously mentioned, the reflow proces also grows silicon dioxide regions 42 on top of polysilicon regions 74, and implants the impuritieswithin polysilicon regions 74 to provide heating resistors 14 a sheet resistance from between 40 to 50 ohms per square. After the reflow process, silicon nitride and tantalum regions 44 and 46 are formed by depositing a 0.5 micron thick film of high-temperature silicon nitride and a 0.5 micron thick film of tantalum, respectively, then patterning and etching the films. Contact holes 76 are opened in passivation layer 32, and a layer of aluminum is deposited, patterned and etched to form aluminum interconnects 38, terminals 36, power bus 34 and addressing electrodes 18. Passivation layer 48, a 1 micron thick layer of silicon dioxide, is deposited, and patterned and etched to expose terminals 36 and tantalum regions 46 above hea~ing resistors 14. Alternatively, passivation layer 48 consists of a 0.5 rr~icron thick layer of silicon dioxide covered by a 1.~ micron thick layer of silicon nitride.
Although the third preferred embodiment shows the use of a rniddle layer 62 doped with phosphorous, a non-doped underglaze 64, and non-doped overglaze mesas 66 in conjunction with field oxide regions 60, heating resistors 14 and contact regions 54 to provide a most reliable and thermally efficient printhead 10, it should be understood that middle layer 62, underglaze 64 and mesas 66 could be used by themselvesto provide a reliable printhead 10.
. .
. ' ' ` ' .
.
Claims (12)
1. In an ink jet printhead having at least one ink channel, a heating element, and an interconnect, said ink channel having an open end that serves as a nozzle, said heating element being positioned in said channel for ejecting ink droplets from said nozzle by selective application of current pulses along said interconnect to said heating element, said heating element comprising:
a heating resistor;
a protective region positioned on said heating resistor and having a portion thereof exposed to said ink channel for protecting said heating resistor from ink, said heating resistor being aligned with and substantially within the geometric confines of said exposed portion of said protective region; and at least one contact region electrically connecting said heating resistor and said interconnect, saidcontact region being interposed between said heating resistor and said interconnect, said contact region having lower resistance than said heating resistor.
a heating resistor;
a protective region positioned on said heating resistor and having a portion thereof exposed to said ink channel for protecting said heating resistor from ink, said heating resistor being aligned with and substantially within the geometric confines of said exposed portion of said protective region; and at least one contact region electrically connecting said heating resistor and said interconnect, saidcontact region being interposed between said heating resistor and said interconnect, said contact region having lower resistance than said heating resistor.
2. The ink jet printhead of claim 1, wherein said printhead further includes:
a silicon substrate having a major surface, said heating element and said interconnect being located on said major surface;
a first layer of silicon dioxide positioned on said major surface of said substrate for passivation;
a second layer of silicon dioxide with phosphorous positioned on the surface of said first silicon dioxide layer, said first silicon dioxide layer preventing phosphorus from said second layer of silicon dioxide from contaminating said substrate; anda silicon dioxide mesa being positioned between and in contact with said second silicon dioxide layer, and said heating resistor and said contact region, said silicon dioxide mesa preventing phosphorus from said second layer of silicon dioxide from contaminating said heating resistor and said contact region.
a silicon substrate having a major surface, said heating element and said interconnect being located on said major surface;
a first layer of silicon dioxide positioned on said major surface of said substrate for passivation;
a second layer of silicon dioxide with phosphorous positioned on the surface of said first silicon dioxide layer, said first silicon dioxide layer preventing phosphorus from said second layer of silicon dioxide from contaminating said substrate; anda silicon dioxide mesa being positioned between and in contact with said second silicon dioxide layer, and said heating resistor and said contact region, said silicon dioxide mesa preventing phosphorus from said second layer of silicon dioxide from contaminating said heating resistor and said contact region.
3. The ink jet printhead of claim 1, wherein said printhead further includes:
a silicon substrate having a major surface, said heating element and said interconnect being located on said major surface; and a field oxide region aligned with said heating element and located between said heating element and said major surface for thermally isolating said heating element from said silicon substrate.
a silicon substrate having a major surface, said heating element and said interconnect being located on said major surface; and a field oxide region aligned with said heating element and located between said heating element and said major surface for thermally isolating said heating element from said silicon substrate.
4. In an ink jet printhead having at least one ink channel, a heating element, and an interconnect, said ink channel having an open end that serves as a nozzle, said heating element being positioned in said channel for ejecting ink droplets from said nozzle by selective application of current pulses along said interconnect to said heating element, said heating element comprising:
a heating resistor;
a protective region positioned on said heating resistor and having a portion thereof exposed to said ink channel for protecting said heating resistor from ink, said heating resistor being aligned with and substantially coextensive with saidexposed portion of said protective region; and at least one contact region electrically connecting said heating resistor and said interconnect, said contact region being interposed between said heating resistor and said interconnect, said contact region having lower resistance than said heating resistor.
a heating resistor;
a protective region positioned on said heating resistor and having a portion thereof exposed to said ink channel for protecting said heating resistor from ink, said heating resistor being aligned with and substantially coextensive with saidexposed portion of said protective region; and at least one contact region electrically connecting said heating resistor and said interconnect, said contact region being interposed between said heating resistor and said interconnect, said contact region having lower resistance than said heating resistor.
5. In an ink jet printhead having at least one ink channel, a heating element, and an interconnect, said ink channel having an open end that serves as a nozzle, said heating element being positioned in said channel for ejecting ink droplets from said nozzle by selective application of current pulses along said interconnect to said heating element, said printhead further including:
a silicon substrate having a major surface, said heating element and said interconnect being located on said major surface;
a first layer of silicon dioxide positioned on said major surface of said substrate for passivation;
a second layer of silicon dioxide with phosphorous positioned on the surface of said first silicon dioxide layer, said first silicon dioxide layer preventing phosphorus from said second layer of silicon dioxide from contaminating said substrate; anda silicon dioxide mesa being positioned between and in contact with said second silicon dioxide layer, and said heating element, said silicon dioxide mesa preventing phosphorus from said second layer of silicon dioxide from contaminating said heating element.
a silicon substrate having a major surface, said heating element and said interconnect being located on said major surface;
a first layer of silicon dioxide positioned on said major surface of said substrate for passivation;
a second layer of silicon dioxide with phosphorous positioned on the surface of said first silicon dioxide layer, said first silicon dioxide layer preventing phosphorus from said second layer of silicon dioxide from contaminating said substrate; anda silicon dioxide mesa being positioned between and in contact with said second silicon dioxide layer, and said heating element, said silicon dioxide mesa preventing phosphorus from said second layer of silicon dioxide from contaminating said heating element.
6. A thermal ink jet printhead having an ink channel structure with a plurality of nozzles at one end, said structure fixedly adjoined to an integrated circuit which contains driver logic and heating elements formed on the major surface of a common silicon substrate, said heating elements being positioned in said channels for ejecting ink droplets from said nozzles, said integrated circuit comprising:a gate oxide layer formed above said major surface of said silicon substrate;
at least one transistor switch having a source and drain region formed on said major surface of said silicon substrate and having a polysilicon gate formed upon said gate oxide layer and in close physical proximity to said source and drain regions;
conductive vias contacting said source and drain regions, said vias providing electrical connection between said transistor switch and said heating elements;
a first layer of silicon dioxide positioned on said major surface of said substrate for passivation;
a second layer of silicon dioxide with phosphorus positioned on the surface of said first silicon dioxide layer, said first silicon dioxide layer preventing phosphorus from said second layer of silicon dioxide from contaminating said substrate; andsilicon dioxide mesas positioned between and in contact with said second silicondioxide layer and said heating elements, said silicon dioxide mesas preventing phosphorus from said second layer of silicon dioxide from contaminating said heating elements.
at least one transistor switch having a source and drain region formed on said major surface of said silicon substrate and having a polysilicon gate formed upon said gate oxide layer and in close physical proximity to said source and drain regions;
conductive vias contacting said source and drain regions, said vias providing electrical connection between said transistor switch and said heating elements;
a first layer of silicon dioxide positioned on said major surface of said substrate for passivation;
a second layer of silicon dioxide with phosphorus positioned on the surface of said first silicon dioxide layer, said first silicon dioxide layer preventing phosphorus from said second layer of silicon dioxide from contaminating said substrate; andsilicon dioxide mesas positioned between and in contact with said second silicondioxide layer and said heating elements, said silicon dioxide mesas preventing phosphorus from said second layer of silicon dioxide from contaminating said heating elements.
7. The printhead of claim 6, wherein said integrated circuit further includes a first layer of polysilicon deposited to form said gate layer and a second layer of polysilicon deposited to form said heating elements.
8. The printhead of claim 6, wherein said integrated circuit further includes:
field oxide regions; and oxide regions aligned with said heating element and located between said heating element and said major surface for thermally isolating said heating element from said silicon substrate, wherein said field oxide regions and said oxide regions are formed by a single oxide growth.
field oxide regions; and oxide regions aligned with said heating element and located between said heating element and said major surface for thermally isolating said heating element from said silicon substrate, wherein said field oxide regions and said oxide regions are formed by a single oxide growth.
9. The printhead of claim 6, wherein said heating element comprises:
a heating resistor;
a protective region positioned on said heating resistor and having a portion thereof exposed to said ink channel for protecting said heating resistor from ink, said heating resistor being aligned with and substantially within the geometric confines of said exposed portion of said protective region; and at least one contact region electrically connecting said heating resistor and said interconnect, said contact region being interposed between said heating resistorand said interconnect, said contact region having lower resistance than said heating resistor.
a heating resistor;
a protective region positioned on said heating resistor and having a portion thereof exposed to said ink channel for protecting said heating resistor from ink, said heating resistor being aligned with and substantially within the geometric confines of said exposed portion of said protective region; and at least one contact region electrically connecting said heating resistor and said interconnect, said contact region being interposed between said heating resistorand said interconnect, said contact region having lower resistance than said heating resistor.
10. A process for fabricating a thermal ink jet printhead which includes the steps of:
a. Providing a substrate;
b. forming a first layer of silicon dioxide on said major surface of said substrate;
a. Providing a substrate;
b. forming a first layer of silicon dioxide on said major surface of said substrate;
11 c. forming a second layer of silicon dioxide on the surface of said first silicon dioxide layer, said second silicon dioxide layer being doped with phosphorous tofacilitate reflow;
d. forming a third layer of silicon dioxide on the surface of said second silicon dioxide layer;
e. forming a region of resistive material on the surface of said third silicon dioxide layer;
f. removing portions of said third layer of silicon dioxide not covered by said region of resistive material; and g. reflowing said second silicon dioxide layer.
d. forming a third layer of silicon dioxide on the surface of said second silicon dioxide layer;
e. forming a region of resistive material on the surface of said third silicon dioxide layer;
f. removing portions of said third layer of silicon dioxide not covered by said region of resistive material; and g. reflowing said second silicon dioxide layer.
12
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US54756790A | 1990-07-02 | 1990-07-02 | |
| US547,567 | 1990-07-02 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2044402A1 true CA2044402A1 (en) | 1992-01-03 |
Family
ID=24185172
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2044402 Abandoned CA2044402A1 (en) | 1990-07-02 | 1991-06-12 | Thermal ink jet printhead and method of manufacture |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0465212A3 (en) |
| JP (1) | JPH04232751A (en) |
| CA (1) | CA2044402A1 (en) |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4532530A (en) * | 1984-03-09 | 1985-07-30 | Xerox Corporation | Bubble jet printing device |
| US4719477A (en) * | 1986-01-17 | 1988-01-12 | Hewlett-Packard Company | Integrated thermal ink jet printhead and method of manufacture |
| US4935752A (en) * | 1989-03-30 | 1990-06-19 | Xerox Corporation | Thermal ink jet device with improved heating elements |
| US4947193A (en) * | 1989-05-01 | 1990-08-07 | Xerox Corporation | Thermal ink jet printhead with improved heating elements |
-
1991
- 1991-06-12 CA CA 2044402 patent/CA2044402A1/en not_active Abandoned
- 1991-07-02 JP JP16122591A patent/JPH04232751A/en not_active Withdrawn
- 1991-07-02 EP EP19910305984 patent/EP0465212A3/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| EP0465212A3 (en) | 1992-11-25 |
| EP0465212A2 (en) | 1992-01-08 |
| JPH04232751A (en) | 1992-08-21 |
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