WO2009039551A1 - Method of removing photoresist - Google Patents
Method of removing photoresist Download PDFInfo
- Publication number
- WO2009039551A1 WO2009039551A1 PCT/AU2007/001424 AU2007001424W WO2009039551A1 WO 2009039551 A1 WO2009039551 A1 WO 2009039551A1 AU 2007001424 W AU2007001424 W AU 2007001424W WO 2009039551 A1 WO2009039551 A1 WO 2009039551A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- photoresist
- nozzle
- ashing
- ink
- gas chemistry
- Prior art date
Links
- 229920002120 photoresistant polymer Polymers 0.000 title claims abstract description 68
- 238000000034 method Methods 0.000 title claims abstract description 62
- 238000004519 manufacturing process Methods 0.000 claims abstract description 32
- 230000008569 process Effects 0.000 claims abstract description 19
- 238000000429 assembly Methods 0.000 claims description 9
- 230000000712 assembly Effects 0.000 claims description 9
- 239000000758 substrate Substances 0.000 claims description 6
- 239000011253 protective coating Substances 0.000 claims description 2
- 238000004380 ashing Methods 0.000 description 45
- 239000007789 gas Substances 0.000 description 18
- 238000007641 inkjet printing Methods 0.000 description 10
- 239000000463 material Substances 0.000 description 10
- 230000008021 deposition Effects 0.000 description 7
- 238000000151 deposition Methods 0.000 description 7
- 238000007639 printing Methods 0.000 description 7
- 230000008901 benefit Effects 0.000 description 4
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 3
- 238000010276 construction Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 238000005530 etching Methods 0.000 description 3
- 230000002035 prolonged effect Effects 0.000 description 3
- 229910052710 silicon Inorganic materials 0.000 description 3
- 239000010703 silicon Substances 0.000 description 3
- 229910052581 Si3N4 Inorganic materials 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 229910010293 ceramic material Inorganic materials 0.000 description 2
- 235000009508 confectionery Nutrition 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 2
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000001010 compromised effect Effects 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000000708 deep reactive-ion etching Methods 0.000 description 1
- 230000005686 electrostatic field Effects 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000007648 laser printing Methods 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 150000002739 metals Chemical group 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000007645 offset printing Methods 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 238000000623 plasma-assisted chemical vapour deposition Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 238000000859 sublimation Methods 0.000 description 1
- 230000008022 sublimation Effects 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
- B41J2/16—Production of nozzles
- B41J2/1601—Production of bubble jet print heads
-
- 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
- B41J2/1628—Manufacturing processes etching dry 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
- B41J2/1637—Manufacturing processes molding
- B41J2/1639—Manufacturing processes molding sacrificial molding
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/26—Processing photosensitive materials; Apparatus therefor
- G03F7/42—Stripping or agents therefor
- G03F7/427—Stripping or agents therefor using plasma means only
Definitions
- the present invention relates to the field of printers and particularly MEMS inkjet printheads. It has been developed primarily to improve fabrication of MEMS inkjet printheads, although the invention is equally applicable to any MEMS fabrication process.
- Ink Jet printers themselves come in many different types.
- the utilization of a continuous stream of ink in inkjet printing appears to date back to at least 1929 wherein US Patent No. 1941001 by Hansell discloses a simple form of continuous stream electro-static inkjet printing.
- Piezoelectric inkjet printers are also one form of commonly utilized inkjet printing device. Piezoelectric systems are disclosed by Kyser et. al. in US Patent No. 3946398 (1970) which utilizes a diaphragm mode of operation, by Zolten in US Patent 3683212 (1970) which discloses a squeeze mode of operation of a piezoelectric crystal, Stemme in US Patent No. 3747120 (1972) discloses a bend mode of piezoelectric operation, Howkins in US Patent No. 4459601 discloses a piezoelectric push mode actuation of the inkjet stream and Fischbeck in US 4584590 which discloses a shear mode type of piezoelectric transducer element.
- the present Applicant has employed photoresist as a sacrificial scaffold onto which other materials (e.g. heater material, roof structures) may be deposited.
- This technique enables relatively complex nozzle assemblies to be constructed.
- it requires deposition of relatively thick layers of viscous, heat-resistant photoresist.
- photoresist layers or plugs of up to 30 microns may be required.
- this photoresist must be thoroughly hardbaked and UV cured so that it does not reflow during subsequent high-temperature deposition steps e.g. deposition of metals or ceramic material onto the photoresist.
- a final ashing step removes all remaining photoresist in the nozzle assemblies, including photoresist scaffolds and photoresist plugs employed during the fabrication process. Hitherto, traditional O 2 plasma ashing techniques have been employed for final or late-stage removal of photoresist.
- a method of photoresist removal employing a plasma formed from a gas chemistry comprising NH 3 .
- gas chemistries comprising NH 3 are particularly efficacious in removing photoresist and provide higher ashing rates than conventional O 2 ashing.
- ashing rates are improved by at least 20%, at least 50% or at least 100%, compared with ashing rates using a conventional O 2 plasma.
- the gas chemistry consists of NH3 only.
- the gas chemistry further comprises O 2 .
- the O 2 may be a major or a minor component of the gas chemistry.
- a ratio of O 2 :NH 3 is in the range of 15:1 to 5:1, or optionally about 10:1.
- the gas chemistry consists of O 2 and NH3.
- the gas chemistry further comprises N 2 .
- a ratio of N 2 :NH 3 is in the range of 5 : 1 to 1 :5, or optionally about 1 :1.
- the gas chemistry consists of O 2 , NH3 and N 2 , and optionally in a ratio of about 10:1 :1.
- the photoresist is hardbaked photoresist.
- the photoresist is UV- cured photoresist.
- the photoresist has a thickness of at least 2 microns or at least 5 microns. Traditionally, photoresist of this nature was considered relatively difficult to remove and required prolonged ashing times. However, the present invention removes such photoresist in acceptable times with no damage to other MEMS structures.
- the method is a step of a MEMS fabrication process.
- the method is a step of a printhead fabrication process.
- the photoresist is contained in at least one of: inkjet nozzle chambers and ink supply channels.
- This photoresist may be used as a sacrificial scaffold during nozzle fabrication, but requires removal in late-stage MEMS processing.
- the photoresist is a protective coating for MEMS structures, such as inkjet nozzle assemblies.
- MEMS structures are protected with a hardbaked photoresist layer during MEMS fabrication, especially if backside processing steps are required.
- the present invention is suitable for removing such photoresist.
- a method of fabricating an inkjet printhead comprising the steps of: forming inkjet nozzle chambers on a substrate, each nozzle chamber containing at least some photoresist; and removing said photoresist using a plasma formed from a gas chemistry comprising NH 3 .
- Figure 1 is a partial perspective view of an array of nozzle assemblies of a thermal inkjet printhead
- Figure 2 is a side view of a nozzle assembly unit cell shown in Figure 1 ;
- Figure 3 is a perspective of the nozzle assembly shown in Figure 2;
- Figure 4 shows a partially- formed nozzle assembly after deposition of side walls and roof material onto a sacrificial photoresist layer
- Figure 5 is a perspective of the nozzle assembly shown in Figure 4.
- Figure 6 is the mask associated with the nozzle rim etch shown in Figure 7;
- Figure 7 shows the etch of the roof layer to form the nozzle opening rim
- Figure 8 is a perspective of the nozzle assembly shown in Figure 7;
- Figure 9 is the mask associated with the nozzle opening etch shown in Figure 10;
- Figure 10 shows the etch of the roof material to form the elliptical nozzle openings
- Figure 11 is a perspective of the nozzle assembly shown in Figure 10;
- Figure 12 shows the nozzle assembly after plasma ashing of the sacrificial photoresist
- Figure 13 is a perspective of the nozzle assembly shown in Figure 12;
- Figure 14 shows the whole thickness of the wafer after plasma ashing
- Figure 15 is a perspective of the nozzle assembly shown in Figure 14;
- Figure 16 is the mask associated with the backside etch shown in Figure 17;
- Figure 17 shows the backside etch of the ink supply channel into the wafer.
- Figure 18 is a perspective of the nozzle assembly shown in Figure 17.
- the present invention may be used in connection with any process requiring removal of photoresist.
- it will now be exemplified using the example of MEMS inkjet printhead fabrication.
- the present Applicant has previously described a fabrication of a plethora of inkjet printheads for which the present invention is suitable. It is not necessary to describe all such printheads here for an understanding of the present invention.
- the present invention will now be described in connection with a thermal bubble-forming inkjet printhead and a mechanical thermal bend actuated inkjet printhead. Advantages of the present invention will be readily apparent from the discussion that follows.
- Figure 1 there is shown a part of printhead comprising a plurality of nozzle assemblies.
- Figures 2 and 3 show one of these nozzle assemblies in side-section and cutaway perspective views.
- Each nozzle assembly comprises a nozzle chamber 24 formed by MEMS fabrication techniques on a silicon wafer substrate 2.
- the nozzle chamber 24 is defined by a roof 21 and sidewalls 22 which extend from the roof 21 to the silicon substrate 2.
- each roof is defined by part of a nozzle plate 56, which spans across an ejection face of the printhead.
- the nozzle plate 56 and sidewalls 22 are formed of the same material, which is deposited by PECVD over a sacrificial scaffold of photoresist during MEMS fabrication.
- the nozzle plate 56 and sidewalls 21 are formed of a ceramic material, such as silicon dioxide or silicon nitride. These hard materials have excellent properties for printhead robustness, and their inherently hydrophilic nature is advantageous for supplying ink to the nozzle chambers 24 by capillary action.
- a nozzle opening 26 is defined in a roof of each nozzle chamber 24.
- Each nozzle opening 26 is generally elliptical and has an associated nozzle rim 25.
- the nozzle rim 25 assists with drop directionality during printing as well as reducing, at least to some extent, ink flooding from the nozzle opening 26.
- the actuator for ejecting ink from the nozzle chamber 24 is a heater element 29 positioned beneath the nozzle opening 26 and suspended across a pit 8. Current is supplied to the heater element 29 via electrodes 9 connected to drive circuitry in underlying CMOS layers of the substrate 2.
- the nozzles are arranged in rows and an ink supply channel 27 extending longitudinally along the row supplies ink to each nozzle in the row.
- the ink supply channel 27 delivers ink to an ink inlet passage 15 for each nozzle, which supplies ink from the side of the nozzle opening 26 via an ink conduit 23 in the nozzle chamber 24.
- Figures 4 and 5 show a partially- fabricated printhead comprising a nozzle chamber 24 encapsulating sacrificial photoresist 16.
- the photoresist 16 was used firstly to plug the ink inlet 15 (shown in Figure 2), secondly as a scaffold for deposition of heater material to form the suspended heater element 29, and thirdly as a scaffold for deposition of the sidewalls 22 and roof 21 (which defines part of the nozzle plate 56).
- the photoresist plugging the ink inlet 15 has a depth of about 20 microns, while the photoresist used as a scaffold in the nozzle chambers has a thickness of at least 5 microns.
- all the photoresist 16 was hardbaked and UV cured and must be removed later on in the fabrication process.
- the next stage of MEMS fabrication defines the elliptical nozzle rim 25 in the roof 21 by etching away 2 microns of roof material 20. This etch is defined using a layer of photoresist (not shown) exposed by the dark tone rim mask shown in Figure 6.
- the elliptical rim 25 comprises two coaxial rim lips 25a and 25b, positioned over their respective thermal actuator 29.
- the next stage defines an elliptical nozzle aperture 26 in the roof 21 by etching all the way through the remaining roof material 20, which is bounded by the rim 25. This etch is defined using a layer of photoresist (not shown) exposed by the dark tone roof mask shown in Figure 9.
- the elliptical nozzle aperture 26 is positioned over the thermal actuator 29, as shown in Figure 11.
- the next stage removes the photoresist 16 by frontside plasma ashing ( Figures 12 and 13).
- Figures 14 and 15 show the entire thickness (150 microns) of the silicon wafer 2 after ashing away all the photoresist 16.
- an O 2 plasma is employed for ashing the photoresist 16.
- the ashing plasma is formed using a gas chemistry comprising NH 3 .
- the plasma is formed from a gas chemistry comprising NH 3 , superior ashing is achieved in terms of increased ashing rate and reduced damage to nozzle structures. Experimental details of ashing conditions are described in more detail in the Example section below.
- ink supply channels 27 are etched from the backside of the wafer to meet with the ink inlets 15 using a standard anisotropic DRIE. This backside etch is defined using a layer of photoresist (not shown) exposed by the dark tone mask shown in Figure 16.
- the ink supply channel 27 makes a fluidic connection between the backside of the wafer and the ink inlets 15.
- Figure 1 shows three adjacent rows of nozzles in a cutaway perspective view of a completed printhead integrated circuit.
- Each row of nozzles has a respective ink supply channel 27 extending along its length and supplying ink to a plurality of ink inlets 15 in each row.
- the ink inlets supply ink to the ink conduit 23 for each row, with each nozzle chamber receiving ink from a common ink conduit for that row.
- late-stage MEMS fabrication steps may be varied.
- backside ashing may be performed after the ink supply channels 27 have been etched.
- both frontside and backside ashing may be employed so as to completely remove the photoresist, whilst minimizing risk of damage to nozzle stuctures.
- the wafer must be subjected to ashing, either frontside ashing and/or backside ashing, in order to remove the photoresist 16 and furnish the printhead.
- gas chemistries comprising NH 3 provide superior ashing rates compared to conventional ashing conditions. Moreover, the structural integrity of the MEMS nozzle assemblies is not compromised using these improved ashing conditions.
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- Engineering & Computer Science (AREA)
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- Physics & Mathematics (AREA)
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- General Physics & Mathematics (AREA)
- Particle Formation And Scattering Control In Inkjet Printers (AREA)
Abstract
A method of photoresist removal is provided. The method employs a plasma formed from a gas chemistry comprising NH3. The method is particularly suitable for use in MEMS fabrication processes, such as inkjet printhead fabrication.
Description
METHOD OF REMOVING PHOTORESIST
Field of the Invention
The present invention relates to the field of printers and particularly MEMS inkjet printheads. It has been developed primarily to improve fabrication of MEMS inkjet printheads, although the invention is equally applicable to any MEMS fabrication process.
Background of the Invention
Many different types of printing have been invented, a large number of which are presently in use. The known forms of print have a variety of methods for marking the print media with a relevant marking media. Commonly used forms of printing include offset printing, laser printing and copying devices, dot matrix type impact printers, thermal paper printers, film recorders, thermal wax printers, dye sublimation printers and inkjet printers both of the drop on demand and continuous flow type. Each type of printer has its own advantages and problems when considering cost, speed, quality, reliability, simplicity of construction and operation etc.
In recent years, the field of ink jet printing, wherein each individual pixel of ink is derived from one or more ink nozzles has become increasingly popular primarily due to its inexpensive and versatile nature.
Many different techniques on inkjet printing have been invented. For a survey of the field, reference is made to an article by J Moore, "Non-Impact Printing: Introduction and Historical Perspective", Output Hard Copy Devices, Editors R Dubeck and S Sherr, pages 207 - 220 (1988).
Ink Jet printers themselves come in many different types. The utilization of a continuous stream of ink in inkjet printing appears to date back to at least 1929 wherein US Patent No. 1941001 by Hansell discloses a simple form of continuous stream electro-static inkjet printing.
US Patent 3596275 by Sweet also discloses a process of a continuous inkjet printing including the step wherein the inkjet stream is modulated by a high frequency electro-static field so as to cause drop separation. This technique is still utilized by several manufacturers including Elmjet and Scitex (see also US Patent No. 3373437 by Sweet et al)
Piezoelectric inkjet printers are also one form of commonly utilized inkjet printing device. Piezoelectric systems are disclosed by Kyser et. al. in US Patent No. 3946398 (1970) which utilizes a diaphragm mode of operation, by Zolten in US Patent 3683212 (1970) which discloses a squeeze mode of operation of a piezoelectric crystal, Stemme in US Patent No. 3747120 (1972) discloses a bend mode of piezoelectric operation, Howkins in US Patent No. 4459601 discloses a piezoelectric push mode actuation of the inkjet stream and Fischbeck in US 4584590 which discloses a shear
mode type of piezoelectric transducer element.
Recently, thermal ink jet printing has become an extremely popular form of ink jet printing. The ink jet printing techniques include those disclosed by Endo et al in GB 2007162 (1979) and Vaught et al in US Patent 4490728. Both the aforementioned references disclosed ink jet printing techniques that rely upon the activation of an electrothermal actuator which results in the creation of a bubble in a constricted space, such as a nozzle, which thereby causes the ejection of ink from an aperture connected to the confined space onto a relevant print media. Printing devices utilizing the electro-thermal actuator are manufactured by manufacturers such as Canon and Hewlett Packard.
As can be seen from the foregoing, many different types of printing technologies are available. Ideally, a printing technology should have a number of desirable attributes. These include inexpensive construction and operation, high speed operation, safe and continuous long term operation etc. Each technology may have its own advantages and disadvantages in the areas of cost, speed, quality, reliability, power usage, simplicity of construction operation, durability and consumables.
The present Applicant has developed a plethora of inkjet printheads fabricated by MEMS techniques. Typically, MEMS fabrication employs a plurality of photoresist deposition and removal steps. Removal of relatively thin layers of photoresist (c.a. 1 micron or less), used as photolithographic masks, is usually facile. Standard conditions employ an oxygen plasma, which oxidatively removes any photoresist in a process colloquially known in the art as "ashing".
In the fabrication of inkjet nozzle assemblies, the present Applicant has employed photoresist as a sacrificial scaffold onto which other materials (e.g. heater material, roof structures) may be deposited. This technique enables relatively complex nozzle assemblies to be constructed. However, it requires deposition of relatively thick layers of viscous, heat-resistant photoresist. As will be explained in more detail below, photoresist layers or plugs of up to 30 microns may be required. Furthermore, this photoresist must be thoroughly hardbaked and UV cured so that it does not reflow during subsequent high-temperature deposition steps e.g. deposition of metals or ceramic material onto the photoresist.
In a typical MEMS printhead fabrication process, a final ashing step removes all remaining photoresist in the nozzle assemblies, including photoresist scaffolds and photoresist plugs employed during the fabrication process. Hitherto, traditional O2 plasma ashing techniques have been employed for final or late-stage removal of photoresist.
However, thick layers of photoresist, which have been hardbaked and UV cured have increased resistance to ashing and are removed relatively slowly by traditional O2 ashing techniques. This means that prolonged ashing times are required and/or higher ashing temperatures. Prolonged ashing times and/or higher ashing temperatures are undesirable, because
there is an increased risk of damage to other MEMS structures (e.g. nozzle chambers, actuators) during the ashing process. Moreover, there is, in general, a need to increase the efficiency of each MEMS processing step so as to reduce processing time and, ultimately, reduce the cost of each printhead.
The addition of small amounts of fluorine-containing gases (e.g. CF4, C4Fg) is known to increase the rate of O2 ashing. However, fluorinated gas chemistries attack materials such as silicon nitride, which typically forms the nozzle plate in the Applicant's MEMS printheads. Accordingly, these ashing conditions are not considered suitable for use in the Applicant's fabrication process.
The use of O2/N2 has also been used to improve ashing rates, although the addition of N2 shows only moderate improvement over pure O2.
Accordingly, from the foregoing, it will be appreciated that there is a need to improve the efficiency of photoresist removal in MEMS fabrication techniques. Whilst this need has been presented in the context of printhead fabrication, it will be appreciated that any MEMS fabrication process would benefit from improved techniques for photoresist removal, especially those MEMS fabrication processes which use a relatively thick layer of sacrificial photoresist, which has been hardbaked and/or UV cured.
Summary of the Invention
In a first embodiment, there is provided a method of photoresist removal, the method employing a plasma formed from a gas chemistry comprising NH3. The present inventors have found that gas chemistries comprising NH3 are particularly efficacious in removing photoresist and provide higher ashing rates than conventional O2 ashing. Typically ashing rates are improved by at least 20%, at least 50% or at least 100%, compared with ashing rates using a conventional O2 plasma.
In some embodiments, the gas chemistry consists of NH3 only.
In other embodiments, the gas chemistry further comprises O2. The O2 may be a major or a minor component of the gas chemistry.
Optionally a ratio of O2:NH3 is in the range of 15:1 to 5:1, or optionally about 10:1.
Optionally, the gas chemistry consists of O2 and NH3.
Optionally, the gas chemistry further comprises N2.
Optionally a ratio of N2:NH3 is in the range of 5 : 1 to 1 :5, or optionally about 1 :1.
Optionally, the gas chemistry consists of O2, NH3 and N2, and optionally in a ratio of about 10:1 :1.
Optionally, the photoresist is hardbaked photoresist. Optionally, the photoresist is UV- cured photoresist. Optionally, the photoresist has a thickness of at least 2 microns or at least 5 microns. Traditionally, photoresist of this nature was considered relatively difficult to remove and required prolonged ashing times. However, the present invention removes such photoresist in acceptable times with no damage to other MEMS structures.
Optionally, the method is a step of a MEMS fabrication process.
Optionally, the method is a step of a printhead fabrication process.
Optionally, the photoresist is contained in at least one of: inkjet nozzle chambers and ink supply channels. This photoresist may be used as a sacrificial scaffold during nozzle fabrication, but requires removal in late-stage MEMS processing.
Optionally, the photoresist is a protective coating for MEMS structures, such as inkjet nozzle assemblies. Typically, MEMS structures are protected with a hardbaked photoresist layer during MEMS fabrication, especially if backside processing steps are required. The present invention is suitable for removing such photoresist.
In a second aspect, there is provided a method of fabricating an inkjet printhead, the method comprising the steps of: forming inkjet nozzle chambers on a substrate, each nozzle chamber containing at least some photoresist; and removing said photoresist using a plasma formed from a gas chemistry comprising NH3.
Brief Description of the Drawings
Optional embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings, in which:
Figure 1 is a partial perspective view of an array of nozzle assemblies of a thermal inkjet printhead;
Figure 2 is a side view of a nozzle assembly unit cell shown in Figure 1 ;
Figure 3 is a perspective of the nozzle assembly shown in Figure 2;
Figure 4 shows a partially- formed nozzle assembly after deposition of side walls and roof material onto a sacrificial photoresist layer;
Figure 5 is a perspective of the nozzle assembly shown in Figure 4;
Figure 6 is the mask associated with the nozzle rim etch shown in Figure 7;
Figure 7 shows the etch of the roof layer to form the nozzle opening rim;
Figure 8 is a perspective of the nozzle assembly shown in Figure 7;
Figure 9 is the mask associated with the nozzle opening etch shown in Figure 10;
Figure 10 shows the etch of the roof material to form the elliptical nozzle openings;
Figure 11 is a perspective of the nozzle assembly shown in Figure 10;
Figure 12 shows the nozzle assembly after plasma ashing of the sacrificial photoresist;
Figure 13 is a perspective of the nozzle assembly shown in Figure 12;
Figure 14 shows the whole thickness of the wafer after plasma ashing;
Figure 15 is a perspective of the nozzle assembly shown in Figure 14;
Figure 16 is the mask associated with the backside etch shown in Figure 17;
Figure 17 shows the backside etch of the ink supply channel into the wafer; and
Figure 18 is a perspective of the nozzle assembly shown in Figure 17.
Description of Optional Embodiments
As foreshadowed above, the present invention may be used in connection with any process requiring removal of photoresist. However, it will now be exemplified using the example of MEMS inkjet printhead fabrication. The present Applicant has previously described a fabrication of a plethora of inkjet printheads for which the present invention is suitable. It is not necessary to describe all such printheads here for an understanding of the present invention. However, the present invention will now be described in connection with a thermal bubble-forming inkjet printhead and a mechanical thermal bend actuated inkjet printhead. Advantages of the present invention will be readily apparent from the discussion that follows.
Referring to Figure 1, there is shown a part of printhead comprising a plurality of nozzle assemblies. Figures 2 and 3 show one of these nozzle assemblies in side-section and cutaway perspective views.
Each nozzle assembly comprises a nozzle chamber 24 formed by MEMS fabrication techniques on a silicon wafer substrate 2. The nozzle chamber 24 is defined by a roof 21 and sidewalls 22 which extend from the roof 21 to the silicon substrate 2. As shown in Figure 1, each roof is defined by part of a nozzle plate 56, which spans across an ejection face of the printhead. The nozzle plate 56 and sidewalls 22 are formed of the same material, which is deposited by PECVD over a sacrificial scaffold of photoresist during MEMS fabrication. Typically, the nozzle plate 56 and sidewalls 21 are formed of a ceramic material, such as silicon dioxide or silicon nitride. These hard materials have excellent properties for printhead robustness, and their inherently hydrophilic nature is advantageous for supplying ink to the nozzle chambers 24 by capillary action.
Returning to the details of the nozzle chamber 24, it will be seen that a nozzle opening 26 is defined in a roof of each nozzle chamber 24. Each nozzle opening 26 is generally elliptical and has an associated nozzle rim 25. The nozzle rim 25 assists with drop directionality during printing as well as reducing, at least to some extent, ink flooding from the nozzle opening 26. The actuator
for ejecting ink from the nozzle chamber 24 is a heater element 29 positioned beneath the nozzle opening 26 and suspended across a pit 8. Current is supplied to the heater element 29 via electrodes 9 connected to drive circuitry in underlying CMOS layers of the substrate 2. When a current is passed through the heater element 29, it rapidly superheats surrounding ink to form a gas bubble, which forces ink through the nozzle opening. By suspending the heater element 29, it is completely immersed in ink when the nozzle chamber 24 is primed. This improves printhead efficiency, because less heat dissipates into the underlying substrate 2 and more input energy is used to generate a bubble.
As seen most clearly in Figure 1, the nozzles are arranged in rows and an ink supply channel 27 extending longitudinally along the row supplies ink to each nozzle in the row. The ink supply channel 27 delivers ink to an ink inlet passage 15 for each nozzle, which supplies ink from the side of the nozzle opening 26 via an ink conduit 23 in the nozzle chamber 24.
The complete MEMS fabrication process for manufacturing such printheads was described in detail in our previously filed US Application No. 11/246,684 filed on October 11, 2005, the contents of which is herein incorporated by reference. The latter stages of this fabrication process are briefly revisited here so as to illustrate one example of the present invention.
Figures 4 and 5 show a partially- fabricated printhead comprising a nozzle chamber 24 encapsulating sacrificial photoresist 16. During nozzle fabrication, the photoresist 16 was used firstly to plug the ink inlet 15 (shown in Figure 2), secondly as a scaffold for deposition of heater material to form the suspended heater element 29, and thirdly as a scaffold for deposition of the sidewalls 22 and roof 21 (which defines part of the nozzle plate 56). The photoresist plugging the ink inlet 15 has a depth of about 20 microns, while the photoresist used as a scaffold in the nozzle chambers has a thickness of at least 5 microns. Furthermore, all the photoresist 16 was hardbaked and UV cured and must be removed later on in the fabrication process.
Referring to Figures 6 to 8, the next stage of MEMS fabrication defines the elliptical nozzle rim 25 in the roof 21 by etching away 2 microns of roof material 20. This etch is defined using a layer of photoresist (not shown) exposed by the dark tone rim mask shown in Figure 6. The elliptical rim 25 comprises two coaxial rim lips 25a and 25b, positioned over their respective thermal actuator 29.
Referring to Figures 9 to 11, the next stage defines an elliptical nozzle aperture 26 in the roof 21 by etching all the way through the remaining roof material 20, which is bounded by the rim 25. This etch is defined using a layer of photoresist (not shown) exposed by the dark tone roof mask shown in Figure 9. The elliptical nozzle aperture 26 is positioned over the thermal actuator 29, as shown in Figure 11.
With all the MEMS nozzle features now fully formed, the next stage removes the photoresist 16 by frontside plasma ashing (Figures 12 and 13). Figures 14 and 15 show the entire thickness (150 microns) of the silicon wafer 2 after ashing away all the photoresist 16.
In a traditional ashing processes, an O2 plasma is employed for ashing the photoresist 16. However, in accordance with the present invention, the ashing plasma is formed using a gas chemistry comprising NH3. When the plasma is formed from a gas chemistry comprising NH3, superior ashing is achieved in terms of increased ashing rate and reduced damage to nozzle structures. Experimental details of ashing conditions are described in more detail in the Example section below.
Referring to Figures 16 to 18, once frontside MEMS processing of the wafer is completed, ink supply channels 27 are etched from the backside of the wafer to meet with the ink inlets 15 using a standard anisotropic DRIE. This backside etch is defined using a layer of photoresist (not shown) exposed by the dark tone mask shown in Figure 16. The ink supply channel 27 makes a fluidic connection between the backside of the wafer and the ink inlets 15.
Finally, and referring to Figures 2 and 3, the wafer is thinned to about 135 microns by backside etching. Figure 1 shows three adjacent rows of nozzles in a cutaway perspective view of a completed printhead integrated circuit. Each row of nozzles has a respective ink supply channel 27 extending along its length and supplying ink to a plurality of ink inlets 15 in each row. The ink inlets, in turn, supply ink to the ink conduit 23 for each row, with each nozzle chamber receiving ink from a common ink conduit for that row.
It will be appreciated by the person skilled in the art that the exact ordering of late-stage MEMS fabrication steps may be varied. For example, backside ashing may be performed after the ink supply channels 27 have been etched. Alternatively, both frontside and backside ashing may be employed so as to completely remove the photoresist, whilst minimizing risk of damage to nozzle stuctures. Regardless, it will be appreciated that the wafer must be subjected to ashing, either frontside ashing and/or backside ashing, in order to remove the photoresist 16 and furnish the printhead.
Examples
Frontside ashing of the nozzle assembly shown in Figures 10 and 11 was performed in an ashing oven, using Recipes 1 to 3 shown in Table 1. The temperature in Table 1 refers to the chuck temperature, which is cooled using helium.
Table 1
Under all the conditions shown in Table 1, an excellent rate of photoresist removal was observed with no observable damage to either the nozzle roof 21 or the heater element 29. In particular, all the photoresist contained in the nozzle chamber was removed after about 15-30 minutes using the conditions shown in Recipes 2 and 3. By way of comparison, conventional O2 ashing or O2ZN2 ashing requires about 70-90 minutes of frontside ashing time to remove the same photoresist.
As expected, the improved ashing rates were also observed in similar backside ashing experiments. Again, the O2/NH3 and the O2/NH3/N2 gas chemistries gave the highest ashing rates, although NH3 only was still superior to O2 only or O2ZN2 gas chemistries.
From these experiments, it can be concluded that gas chemistries comprising NH3 provide superior ashing rates compared to conventional ashing conditions. Moreover, the structural integrity of the MEMS nozzle assemblies is not compromised using these improved ashing conditions.
The best results were obtained using O2/NH3 and O2/N2/NH3 gas chemistries. However, NH3 only is still superior to conventional O2 ashing conditions.
It will be appreciated by ordinary workers in this field that numerous variations and/or modifications may be made to the present invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects to be illustrative and not restrictive.
Claims
1. A method of photoresist removal, said method employing a plasma formed from a gas chemistry comprising NH3.
2. The method of claim 1, wherein said gas chemistry consists OfNH3 only.
3. The method of claim 1, wherein said gas chemistry further comprises O2.
4. The method of claim 3 , wherein a ratio of O2 :NH3 is in the range of 15 : 1 to 5 : 1.
5. The method of claim 1 , wherein the gas chemistry consists of O2 and NH3.
6. The method of claim 1 , wherein said gas chemistry further comprises N2.
7. The method of claim 6, wherein a ratio of N2:NH3 is in the range of 5 : 1 to 1 :5.
8. The method of claim 1 , wherein the gas chemistry consists of O2, NH3 and N2.
9. The method of claim 1 , wherein a rate of photoresist removal is at least 20% greater than a rate of photoresist removal using an O2 plasma.
10. The method of claim 1 , wherein said photoresist is hardbaked photoresist.
11. The method of claim 1 , wherein said photoresist is UV-cured photoresist.
12. The method of claim 1 , wherein said photoresist has a thickness of at least 2 microns.
13. The method of claim 1 , wherein said photoresist has a thickness of at least 5 microns.
14. The method of claim 1 , wherein said method is a step of a MEMS fabrication process.
15. The method of claim 1 , wherein said method is a step of a printhead fabrication process.
16. The method of claim 15, wherein said photoresist is contained in at least one of: inkjet nozzle chambers and ink supply channels.
17. The method of claim 15, wherein said photoresist is a protective coating for inkjet nozzle assemblies.
18. A method of fabricating an inkjet printhead, said method comprising the steps of: forming inkjet nozzle chambers on a substrate, each nozzle chamber containing at least some photoresist; and removing said photoresist using a plasma formed from a gas chemistry comprising NH3.
Priority Applications (2)
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PCT/AU2007/001424 WO2009039551A1 (en) | 2007-09-26 | 2007-09-26 | Method of removing photoresist |
TW097105897A TW200915023A (en) | 2007-09-26 | 2008-02-20 | Method of removing photoresist |
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PCT/AU2007/001424 WO2009039551A1 (en) | 2007-09-26 | 2007-09-26 | Method of removing photoresist |
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Citations (20)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20010024769A1 (en) * | 2000-02-08 | 2001-09-27 | Kevin Donoghue | Method for removing photoresist and residues from semiconductor device surfaces |
US20020090833A1 (en) * | 2001-01-05 | 2002-07-11 | Mitsubishi Denki Kabushiki Kaisha | Method of forming dielectric film and dielectric film |
US20020111041A1 (en) * | 2001-02-12 | 2002-08-15 | Lam Research Corporation | Post-etch photoresist strip with O2 and NH3 for organosilicate glass low-K dielectric etch applications |
US20040157462A1 (en) * | 1998-08-28 | 2004-08-12 | Larry Hillyer | Method of removing etch residues |
US20050009356A1 (en) * | 2003-05-13 | 2005-01-13 | Akihiro Kojima | Method of manufacturing semiconductor device and method of cleaning plasma etching apparatus used therefor |
US20050006346A1 (en) * | 2002-12-13 | 2005-01-13 | Annapragada Rao V. | Method for providing uniform removal of organic material |
US20050022839A1 (en) * | 1999-10-20 | 2005-02-03 | Savas Stephen E. | Systems and methods for photoresist strip and residue treatment in integrated circuit manufacturing |
US20050101135A1 (en) * | 2003-11-12 | 2005-05-12 | Lam Research Corporation | Minimizing the loss of barrier materials during photoresist stripping |
US20050130435A1 (en) * | 2003-12-16 | 2005-06-16 | Rao Annapragada | Method of preventing damage to porous low-k materials during resist stripping |
US20050136644A1 (en) * | 2003-12-22 | 2005-06-23 | Semiconductor Leading Edge Technologies, Inc. | Method of fabricating a semiconductor device having metal wiring |
US20060040474A1 (en) * | 2004-08-17 | 2006-02-23 | Jyu-Horng Shieh | Low oxygen content photoresist stripping process for low dielectric constant materials |
US20060105576A1 (en) * | 2004-11-18 | 2006-05-18 | International Business Machines Corporation | High ion energy and reative species partial pressure plasma ash process |
US20060234511A1 (en) * | 2005-04-19 | 2006-10-19 | Elpida Memory, Inc | Method for forming a semiconductor device including a plasma ashing treatment for removal of photoresist |
US20060258148A1 (en) * | 2005-05-10 | 2006-11-16 | Lam Research Corporation | Method for resist strip in presence of regular low k and/or porous low k dielectric materials |
US7183220B1 (en) * | 1998-08-27 | 2007-02-27 | Micron Technology, Inc. | Plasma etching methods |
US20070072403A1 (en) * | 2005-09-27 | 2007-03-29 | Oki Electric Industry Co., Ltd. | Semiconductor device and method for fabricating the same |
US20070090090A1 (en) * | 2005-10-26 | 2007-04-26 | Koichi Nakaune | Dry etching method |
US20070105392A1 (en) * | 2005-11-08 | 2007-05-10 | Raymond Joe | Batch photoresist dry strip and ash system and process |
US20070117341A1 (en) * | 2000-11-15 | 2007-05-24 | Texas Instruments Incorporated | Hydrogen plasma photoresist strip and polymeric residue cleanup process for low dielectric constant materials |
US20070178637A1 (en) * | 2006-01-31 | 2007-08-02 | Samsung Electronics Co., Ltd. | Method of fabricating gate of semiconductor device using oxygen-free ashing process |
-
2007
- 2007-09-26 WO PCT/AU2007/001424 patent/WO2009039551A1/en active Application Filing
-
2008
- 2008-02-20 TW TW097105897A patent/TW200915023A/en unknown
Patent Citations (22)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7183220B1 (en) * | 1998-08-27 | 2007-02-27 | Micron Technology, Inc. | Plasma etching methods |
US20040157462A1 (en) * | 1998-08-28 | 2004-08-12 | Larry Hillyer | Method of removing etch residues |
US20060128159A1 (en) * | 1998-08-28 | 2006-06-15 | Larry Hillyer | Method of removing etch residues |
US20050022839A1 (en) * | 1999-10-20 | 2005-02-03 | Savas Stephen E. | Systems and methods for photoresist strip and residue treatment in integrated circuit manufacturing |
US20010024769A1 (en) * | 2000-02-08 | 2001-09-27 | Kevin Donoghue | Method for removing photoresist and residues from semiconductor device surfaces |
US20070117341A1 (en) * | 2000-11-15 | 2007-05-24 | Texas Instruments Incorporated | Hydrogen plasma photoresist strip and polymeric residue cleanup process for low dielectric constant materials |
US20020090833A1 (en) * | 2001-01-05 | 2002-07-11 | Mitsubishi Denki Kabushiki Kaisha | Method of forming dielectric film and dielectric film |
US20020182891A1 (en) * | 2001-01-05 | 2002-12-05 | Mitsubishi Denki Kabushiki Kaisha | Method of forming dielectric film and dielectric film |
US20020111041A1 (en) * | 2001-02-12 | 2002-08-15 | Lam Research Corporation | Post-etch photoresist strip with O2 and NH3 for organosilicate glass low-K dielectric etch applications |
US20050006346A1 (en) * | 2002-12-13 | 2005-01-13 | Annapragada Rao V. | Method for providing uniform removal of organic material |
US20050009356A1 (en) * | 2003-05-13 | 2005-01-13 | Akihiro Kojima | Method of manufacturing semiconductor device and method of cleaning plasma etching apparatus used therefor |
US20050101135A1 (en) * | 2003-11-12 | 2005-05-12 | Lam Research Corporation | Minimizing the loss of barrier materials during photoresist stripping |
US20050130435A1 (en) * | 2003-12-16 | 2005-06-16 | Rao Annapragada | Method of preventing damage to porous low-k materials during resist stripping |
US20050136644A1 (en) * | 2003-12-22 | 2005-06-23 | Semiconductor Leading Edge Technologies, Inc. | Method of fabricating a semiconductor device having metal wiring |
US20060040474A1 (en) * | 2004-08-17 | 2006-02-23 | Jyu-Horng Shieh | Low oxygen content photoresist stripping process for low dielectric constant materials |
US20060105576A1 (en) * | 2004-11-18 | 2006-05-18 | International Business Machines Corporation | High ion energy and reative species partial pressure plasma ash process |
US20060234511A1 (en) * | 2005-04-19 | 2006-10-19 | Elpida Memory, Inc | Method for forming a semiconductor device including a plasma ashing treatment for removal of photoresist |
US20060258148A1 (en) * | 2005-05-10 | 2006-11-16 | Lam Research Corporation | Method for resist strip in presence of regular low k and/or porous low k dielectric materials |
US20070072403A1 (en) * | 2005-09-27 | 2007-03-29 | Oki Electric Industry Co., Ltd. | Semiconductor device and method for fabricating the same |
US20070090090A1 (en) * | 2005-10-26 | 2007-04-26 | Koichi Nakaune | Dry etching method |
US20070105392A1 (en) * | 2005-11-08 | 2007-05-10 | Raymond Joe | Batch photoresist dry strip and ash system and process |
US20070178637A1 (en) * | 2006-01-31 | 2007-08-02 | Samsung Electronics Co., Ltd. | Method of fabricating gate of semiconductor device using oxygen-free ashing process |
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