US20050189331A1 - Laser ablation nozzle assembly - Google Patents

Abstract

A laser ablation system includes a first embodiment of a nozzle assembly where a laser beam is emitted through the nozzle assembly to remove materials on a target. The nozzle assembly includes a nozzle having a top end, and a window placed on the top end of the nozzle. The window includes one or more apertures and the laser beam is emitted through one of those apertures. Another laser ablation system includes a second embodiment of a nozzle assembly where a laser beam is emitted through the nozzle assembly to remove materials on a target. The nozzle assembly includes a nozzle having one or more channels at a top end of the nozzle. The nozzle assembly also includes a window that is placed on the one or more channels. A gas flows through the one or more channels and that gas flow reduces debris deposition on the window. Yet another laser ablation system includes a third embodiment of a nozzle assembly that includes a nozzle that has a central channel aligned longitudinally through which said laser beam travels from a top end of said nozzle to a bottom end of said nozzle. In this embodiment, the central channel of the nozzle is threaded.

Description

BACKGROUND OF THE INVENTION
• 1. Field of the Invention
• This invention relates generally to a laser ablation system and in particular to a laser ablation nozzle assembly.
• 2. Description of the Related Art
• Laser ablation and in particular ultraviolet (“UV”) laser ablation is widely used, for example, to remove materials from substrates. Such materials may be inorganic or organic (e.g., photo-resists and polymers) and often these to-be removed materials are in thin-film form coated on a substrate. For example, materials are removed using laser ablation to produce a via hole so that there is electrical contact between a top conductive layer and a bottom conductive layer through the via hole. In another example, materials are removed from areas of a thin-film electronic device using laser ablation so that those areas can be used to encapsulate the electronic device. In this case, an inorganic substrate (e.g., a glass substrate) is coated with organic layers (e.g., photo-resist layers or polymer layers) and the resulting electronic device is encapsulated by mating a cover/encapsulating sheet (e.g., metal cans and glass sheets) with the substrate by gluing the two together with, for example, a UV-cure material. Often, however, the bonding of the glue to the substrate when certain organic layers are present on the substrate is not good and hence laser ablation is used to remove the organic layers from the substrate to allow for better bonding between the cover/encapsulating sheet and the substrate.
• In yet another example, laser ablation is used where an inorganic substrate (e.g. a glass substrate) is coated with organic layers (e.g.; photo-resist layers or polymer layers) and the resulting electronic device is encapsulated with a sputtered or evaporated organic and/or inorganic material. Bonding between the encapsulating material and the substrate when the organic layers are present on the substrate is not good and hence laser ablation is used to remove the organic layers from the substrate to allow for better bonding between the encapsulating material and the substrate. Materials may also be removed from areas on the electronic device which when exposed to humidity and oxygen cause corrosion.
• Laser ablation systems that perform the above functions are commercially available from, for example, Resonetics Corporation of Nashua, N.H., or Exitech Limited of Oxford, England.
• FIG. 1 shows a prior artlaser ablation system103. Thelaser ablation system103 includes anozzle assembly134 that includes anozzle113 and awindow122. Thenozzle113 has a top end and a bottom end. Thewindow122 is on the top end of thenozzle113 and the bottom end of the nozzle is in close proximity to a target110 (e.g., a substrate) on which the materials (e.g., polymers, photo-resists, and thin films) that are to be laser ablated reside. Alaser beam125 enters thenozzle113 by passing through awindow122 that is transparent. Thewindow122 may be comprised of transparent materials such as, for example, quartz or glass. Thelaser beam125 is generated by alaser assembly131 located above thenozzle113. Thelaser assembly131 includes the laser, laser optics, and other components used to generate and position thelaser beam125. Thewindow122 protects the laser optics and other components within thelaser assembly131 fromdebris116. Thelaser beam125 travels from a top end of thenozzle113 to the bottom end of thenozzle113.
• Thedebris116 is generated by thelaser beam125 ablating the materials resulting in ejection of thedebris116 from the ablation point. Suction pumps can be used to create a vacuum or a gas flow within avacuum channel119 to remove thedebris116 by sucking thedebris116 away from thetarget110. However, even with the vacuum or gas flow, thedebris116 may be re-deposited on thetarget110 around the ablation point, and/or thedebris116 may be re-deposited on thewindow122 thus obstructing the laser beam path. When thedebris116 is re-deposited on thetarget110, the re-deposited debris can cause, for example, weaker bonding between thetarget110 and the glue, or contaminate thetarget110 thus adversely affecting the electrical/optical performance of the resulting electronic device fabricated on thetarget110. When thedebris116 is re-deposited on thewindow122, thedebris116 can cause a reduction in the laser beam intensity at the ablation point, fluctuation in beam intensity at the ablation point resulting in poor uniformity in processing the materials, rapid degradation of the window, permanent window damage, and high costs associated with frequent replacing or cleaning of the window.
• Therefore, there is a need to reduce the debris deposition on the window and also to reduce the amount of debris being re-deposited onto the target.
SUMMARY
• An embodiment of a nozzle assembly within a laser ablation system is described that, for example, reduces debris deposition on a window. The embodiment of the nozzle assembly includes a nozzle that has a top end and the window is located on the top end of the nozzle. The window has at least one aperture and a laser beam is emitted through a particular one of the at least one aperture.
• An embodiment of a method is described that, for example, reduces debris deposition at one or more points on a window of a laser ablation system. The embodiment of this method includes generating a laser beam, and emitting the laser beam through an aperture at one of the points on the window.
• Another embodiment of a nozzle assembly within a laser ablation system is described that, for example, reduces debris deposition on the window. This embodiment of the nozzle assembly includes a nozzle having at least one channel at a top end of the nozzle, a window located on the at least one channel, and a gas that flows through the at least one channel. The gas flow through the at least one channel reduces debris deposition on the window.
• Another embodiment of a method is described that, for example, reduces debris deposition on a window of a laser ablation system. This embodiment of the method includes moving a gas through at least one channel that contacts the window to reduce the accumulation of debris on the window.
• Yet another embodiment of a nozzle assembly within a laser ablation system is described that, for example, reduces the debris being re-deposited onto a target. This embodiment of the nozzle assembly includes a nozzle that has a central channel aligned longitudinally and through which a laser beam travels from a top end of the nozzle to a bottom end of the nozzle. The nozzle assembly also includes a window located on the top end of the nozzle. In this embodiment, the central channel is threaded.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 shows a prior art laser ablation system.
• FIG. 2 shows a first embodiment of a nozzle assembly within a laser ablation system.
• FIG. 3 shows a second embodiment of a nozzle assembly within a laser ablation system.
• FIG. 4 shows a third embodiment of a nozzle assembly within a laser ablation system.
• FIG. 5 shows an embodiment of a threaded central channel according to the present invention.
• FIG. 6 shows a fourth embodiment of a nozzle assembly within a laser ablation system.
DETAILED DESCRIPTION
• A laser ablation system includes a first embodiment of a nozzle assembly where a laser beam is emitted through the nozzle assembly to remove materials on a target. The nozzle assembly includes a nozzle having a top end, and a window placed on the top end of the nozzle. The window includes one or more apertures and the laser beam is emitted through one of those apertures.
• Another laser ablation system includes a second embodiment of a nozzle assembly where a laser beam is emitted through the nozzle assembly to remove materials on a target. The nozzle assembly includes a nozzle having one or more channels at a top end of the nozzle. The nozzle assembly also includes a window that is placed on the one or more channels. A gas flows through the one or more channels and that gas flow reduces debris deposition on the window.
• Yet another laser ablation system includes a third embodiment of a nozzle assembly where a laser beam is emitted through the nozzle assembly to remove materials on a target. The nozzle assembly includes a nozzle that has a central channel aligned longitudinally through which said laser beam travels from a top end of said nozzle to a bottom end of said nozzle. A window is placed on the top end of the nozzle. In this embodiment, the central channel of the nozzle is threaded.
• FIG. 2 shows a first embodiment of anozzle assembly231 within alaser ablation system203. Alaser beam125 travels through thenozzle assembly231 to remove materials on atarget110. The target100 can be coated with electrically and/or optically active organic materials such as, for example, conductive polymers and/or conjugated polymers, molecules, dentrimers, oligomers, fluorescents, or phosphorescents. The resulting electronic device can be, for example, an organic thin-film transistor, a light detector, a solar cell, or an organic light emitting device (“OLED”) (the OLEDs can be used in, for example, signs, displays or as the light source elements of a light source).
• Thenozzle assembly231 includes anozzle213 and awindow222. Thenozzle213 has a top end and a bottom end. Thewindow222 is on the top end of thenozzle213 and the bottom end of the nozzle is in close proximity to atarget110 on which the materials (e.g., polymers, photo-resists, and thin films) that are to be laser ablated reside. Thenozzle213 may have any shape such as, for example, a cone (as shown inFIG. 2), an inverted cone, a triangle, or a cylinder. Thelaser beam125 enters thenozzle213 through thewindow222. Thelaser beam125 is generated by a laser assembly located above thenozzle assembly231. Thewindow222 protects the laser optics and other components within the laser assembly fromdebris116. Thewindow222 can be comprised of transparent materials such as quartz or glass. Alternatively, thewindow222 can be comprised of opaque materials such as an opaque metal or plastic or a coated material such as quartz or glass with a coating.
• Thewindow222 includes anaperture234 and thelaser beam125 is emitted through theaperture234. Theaperture234 can be of any size. For example, the diameter of theaperture234 can be greater than or equal to the diameter of thelaser beam125 to minimize the loss of the laser beam's225 intensity by allowing thelaser beam125 to pass through unimpeded. Alternatively, the diameter of theaperture234 can be less than the diameter of thelaser beam125 so that theaperture234 acts as a beam mask to further limit or define the laser beam dimensions. Theaperture234 can of any shape. For example, the aperture can have a circular shape (as shown inFIG. 2), a square shape, or a rectangular shape. Theaperture234 can be mechanically operated to change its size or shape depending on the process to be performed. Thewindow222 may include more than one aperture. The additional apertures can be covered with a transparent material. The additional apertures can be used, for example, to provide illumination or optical viewing. In addition, with an adjustable window (e.g., a sliding or rotatable window) and multiple apertures, the window can be adjusted such that the laser beam passes through one of the other apertures when the previous aperture becomes too dirty and/or damaged.
• Thelaser beam125 travels from a top end of thenozzle213 to the bottom end of thenozzle213 through acentral channel228. Thedebris116 is generated by thelaser beam125 ablating the materials resulting in ejection of thedebris116 from the ablation point. Suction pumps can be used to create a vacuum or gas flow within avacuum channel219 to remove thedebris116 by sucking thedebris116 away from thetarget110. Gas entering from the bottom end of thenozzle213 and/or from theaperture234 on thewindow222 are pumped out through thevacuum channel219 creating a gas flow that removes thedebris116. In one configuration of this embodiment, only one vacuum channel is used, however, in other configurations, multiple vacuum channels can be used to remove thedebris116 and these vacuum channels can be placed anywhere on thenozzle213. As used within the specification and the claims, the term “channel” includes, for example, a slit, a slot, an opening, a hole, a gap, or a chamber. The channel can have various geometrical shapes such as, for example, a rectangular shape (as shown inFIG. 2), a circular shape, or an oval shape.
• FIG. 3 shows a second embodiment of anozzle assembly340 within alaser ablation system303. Thelaser beam125 is emitted through thenozzle assembly340 to remove materials on thetarget110. Thenozzle assembly340 includes anozzle313 and awindow322. Thenozzle313 has a top end and a bottom end. Achannel337 is at the top end of thenozzle313. In this configuration of this embodiment, only one channel is used, however, in other embodiments, multiple channels can be used to pass agas346 across thewindow322. Thewindow322 is placed on thechannel337 such that thewindow322 is in contact with thechannel337. The bottom end of the nozzle is in close proximity to atarget110 on which the materials that are to be laser ablated reside. Thenozzle313 may have any shape such as, for example, a cone (as shown inFIG. 3), an inverted cone, a triangle, or a cylinder. Thelaser beam125 enters thenozzle313 through thewindow322. Thewindow322 can have no aperture, or one or more apertures. If thewindow422 includes one or more apertures, then those apertures can be any shape or size.
• Agas346 moves through thechannel337 and the flow of thegas346 across or through thewindow322 reduces debris accumulation on thewindow322. By reducing the debris accumulation on thewindow322, there may be less debris on the laser beam path resulting in a greater beam intensity at the ablation point, greater uniformity in processing the materials on thetarget110, decreased degradation of thewindow322, and reduced costs resulting from not having to frequently replace or clean thewindow322. Thegas346 includes a gas or a mixture of gasses that can carry debris away, that is used in the ablation process to prevent contamination of the resulting electronic device, or that assist in the ablation of material from the substrate. Thegas346 includes, for example, air, dry air, nitrogen, argon or a mixture of these gasses. Thegas346 is evacuated (e.g., pumped out) from thenozzle313 through anexit channel343. In this configuration of this embodiment, only one exit channel is used, however, in other configurations multiple exit channels can be used to evacuate thegas346 from thenozzle313. These exit channels can be placed anywhere on the side of thenozzle313.
• In another configuration, the channels guide thegas346 directly to the point where the laser beam passes through thewindow322 in order to reduce the amount of debris deposition at this point. In yet another configuration, thewindow322 has an aperture and thegas346 may or may not flow through the aperture (the gas flow through the aperture is in addition to the gas flow across the window322).
• Thelaser beam125 travels from a top end of thenozzle313 to the bottom end of thenozzle313 through acentral channel328. Thedebris116 is generated by thelaser beam125 ablating the materials resulting in ejection of thedebris116 from the ablation point. Suction pumps can be used to create a vacuum within avacuum channel319 to remove thedebris116 by sucking thedebris116 away from thetarget110. In one configuration of this embodiment, only one vacuum channel is used, however, in other configurations, multiple vacuum channels can be used and these vacuum channels can be placed anywhere on thenozzle313. In another configuration, thedebris116 and the debris deposition at thewindow322 can be removed through the same channel or same channels if multiple channels are used.
• FIG. 4 shows a third embodiment of anozzle assembly431 within alaser ablation system403. Alaser beam125 travels through thenozzle assembly431 to remove materials on thetarget110. Thenozzle assembly431 includes anozzle413 and awindow422. Thenozzle413 has a top end and a bottom end. Thewindow422 is on the top end of thenozzle413 and the bottom end of thenozzle413 is in close proximity to thetarget110 on which the materials that are to be laser ablated reside. Thenozzle413 may have any shape such as, for example, a cone (as shown inFIG. 4), an inverted cone, a triangle, or a cylinder. Thelaser beam125 enters thenozzle413 through thewindow422.
• Thelaser beam125 travels from the top end of thenozzle413 to the bottom end of thenozzle413 through a central channel that is threaded (i.e., a threaded central channel428). The threadedcentral channel428 is formed by machining threads to the central channel. By threading the central channel, a less turbulent flow is created that captures more of thedebris116 resulting in better removal of thedebris116 and a reduction of the amount ofdebris116 re-deposited on the materials on thetarget110 or re-deposited on thewindow422. The gas entering from the bottom end of thenozzle413, and/or if thewindow422 has an aperture, the gas entering from an aperture on thewindow422, are pumped out through thevacuum channel419 and because of the threads, the gas being pumped out creates a cork-screw type flow that is less turbulent allowing better removal of the debris from the ablated materials on thetarget110 and reducing the amount ofdebris116 re-deposited on thewindow422.
• FIG. 5 shows an embodiment of the threadedcentral channel428 according to the present invention. Athread pitch440 is the distance between two adjacent threads of the threadedcentral channel428. Athread depth452 is the depth of one of the threads of the threadedcentral channel428. Aflank angle443 is the angle between two adjacent threads of the threadedcentral channel428. Achannel length449 is the length of the threadedcentral channel428. A channel diameter446 (or major diameter) is the outside diameter of the male threads of the threadedcentral channel428. All of the above parameters of the threadedcentral channel428 can be modified to change the flow created within the threadedcentral channel428. In another configuration of this embodiment, the threads are rounded (e.g., each of the threads has a semicircular shape rather than a triangular shape).
• In this configuration of this embodiment, thevacuum channel419 is angled such that there is a smooth transition from the threads of the central channel to the vacuum channel419 (i.e., anangle455 between a thread of the central channel and thevacuum channel419 is equal to the flank angle443). Specifically, thevacuum channel419 is a smooth continuation of the threadedcentral channel428 so as to reduce any points or areas that create turbulence. In another configuration, the transition from the threads of the central channel to thevacuum channel419 is not smooth (i.e., theangle455 between the thread of the central channel and thevacuum channel419 is not equal to the flank angle443).
• In one configuration of this embodiment, a diameter of thevacuum channel419 is greater than the thread pitch440 (as shown inFIG. 5); alternatively, the diameter of thevacuum channel419 can be the same or close to thethread pitch440.
• Referring back toFIG. 4, thewindow422 can be transparent or opaque. Thewindow422 can have no aperture, or one or more apertures. If thewindow422 includes apertures, then those one or more apertures can be any shape or size. In this configuration of this embodiment, only one vacuum channel is used, however, in other configurations, multiple vacuum channels can be used and these vacuum channels can be placed anywhere on the side of thenozzle413.
• FIG. 6 shows a fourth embodiment of anozzle assembly540 within alaser ablation system503. Thenozzle assembly540 includes anozzle513 and awindow422. Thenozzle513 has a top end and a bottom end. A threadedchannel537 is at the top end of thenozzle513. In this configuration of this embodiment, only one channel is used, however, in other configurations, multiple channels can be used to pass agas546 across thewindow422. Thewindow422 is placed on the threadedchannel537 such that thewindow422 is in contact with the threadedchannel537. The bottom end of the nozzle is in close proximity to atarget110 on which the materials that are to be laser ablated reside. Thenozzle513 may have any shape such as, for example, a cone (as shown inFIG. 6), an inverted cone, a triangle, or a cylinder.
• Agas546 moves through the threadedchannel537 and the flow of thegas546 across thewindow422 reduces debris accumulation on thewindow422. The threadedchannel537 is formed by machining threads to that channel. By using the threadedchannel537, a flow is created that better captures more of thedebris116 across thewindow422 resulting in better removal of that debris from thewindow422. Thegas546 entering the threadedchannel537 is pumped out through anexit channel543 and because of the threads, the gas being pumped out creates a cork-screw type flow that better removes the debris across thewindow422. Thegas546 includes a gas or a mixture of gasses that can carry debris away, that is used in the ablation process to prevent contamination of the resulting electronic device, or that assist in the ablation of material from the substrate. Thegas546 includes, for example, air, dry air, nitrogen, argon or a mixture of these gasses. In this configuration of this embodiment, only one exit channel is used, however, in other configurations multiple exit channels can be used to evacuate thegas546 from thenozzle513. These exit channels can be placed anywhere on the side of thenozzle513.
• In one configuration of this embodiment, a threadedcentral channel528 is used in thenozzle513. The threads of the central channel provide the benefits described earlier. In another configuration, a non-threaded central channel is used within thenozzle513. In one configuration of this embodiment, only one vacuum channel is used, however, in other configurations, multiple vacuum channels can be used and these vacuum channels can be placed anywhere on the side of thenozzle513.
• The thread parameters (e.g., thethread pitch440 and the thread depth452) of the channel used to reduce debris accumulation at the window422 (e.g., the threaded channel537) can be the same or differ from the thread parameters of the channel that removes the debris116 (e.g., the threaded central channel528). The thread parameters of these channels are adjusted to optimize the gas flow, reduce the turbulence, and optimize debris removal.
• As any person of ordinary skill in the art of laser ablation will recognize from the description, figures, and examples that modifications and changes can be made to the preferred embodiments of the invention without departing from the scope of the invention defined by the following claims.

Claims (11)

1-6. (canceled)

7. Within a laser ablation system, a method to reduce debris deposition at one or more points on a window, comprising:

generating a laser beam; and

emitting said laser beam through an aperture at a particular one of said one or more points on said window.

8. The method ofclaim 7 wherein a diameter of said aperture is greater than or equal to a diameter of said laser beam.

9. The method ofclaim 7 wherein a diameter of said aperture is less than a diameter of said laser beam.

10-20. (canceled)

21. A method to produce a nozzle assembly of a laser ablation system, comprising:

inserting an aperture in a window;

depositing said window on a top end of a nozzle,

wherein a laser beam is emitted through said aperture of said window.

22. The method ofclaim 21 wherein a diameter of said aperture is greater than or equal to a diameter of said laser beam.

23. The method ofclaim 21 wherein a diameter of said aperture is less than a diameter of said laser beam.

24. The method ofclaim 21 wherein said window is transparent.

25. The method ofclaim 21 wherein said window is opaque.

26. The method ofclaim 21 wherein a shape of said aperture is any one of a circle, a square, or a rectangle.

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