U.S. patent application number 10/076467 was filed with the patent office on 2003-08-21 for laser micromachining and methods and systems of same.
Invention is credited to Huth, Mark C., Pollard, Jeffrey R., Scott, Graeme.
Application Number | 20030155328 10/076467 |
Document ID | / |
Family ID | 27732503 |
Filed Date | 2003-08-21 |
United States Patent
Application |
20030155328 |
Kind Code |
A1 |
Huth, Mark C. ; et
al. |
August 21, 2003 |
Laser micromachining and methods and systems of same
Abstract
The described embodiments relate to methods and systems for
laser micromachining a substrate. One exemplary embodiment
positions a substrate in an open air environment. The substrate has
a thickness defined by opposing first and second surfaces. The
substrate can be cut by directing a laser beam at the first surface
of the substrate and introducing an assist gas proximate to a
region of the substrate contacted by the laser beam.
Inventors: |
Huth, Mark C.; (Corvallis,
OR) ; Pollard, Jeffrey R.; (Corvallis, OR) ;
Scott, Graeme; (Maynooth, IE) |
Correspondence
Address: |
HEWLETT-PACKARD COMPANY
Intellectual Property Administration
P.O. Box 272400
Fort Collins
CO
90527-2400
US
|
Family ID: |
27732503 |
Appl. No.: |
10/076467 |
Filed: |
February 15, 2002 |
Current U.S.
Class: |
216/65 ;
219/121.69; 219/121.7; 219/121.71; 219/121.84; 264/400 |
Current CPC
Class: |
B23K 26/125 20130101;
B23K 26/123 20130101; B41J 2/1632 20130101; B41J 2/1603 20130101;
B41J 2/1634 20130101; B41J 2/1628 20130101; B41J 2/1629 20130101;
B23K 26/1462 20151001; B23K 26/142 20151001 |
Class at
Publication: |
216/65 ; 264/400;
219/121.84; 219/121.69; 219/121.7; 219/121.71 |
International
Class: |
C23F 001/00; B23K
026/14; B23K 026/38 |
Claims
What is claimed is:
1. An apparatus for micromachining a substrate comprising: an open
air region within which substrates can be processed; a laser source
operably positioned relative to the open air region to generate a
laser beam configured to energize substrate material of a substrate
positioned within the open air region; a gas supply that supplies a
halogen containing assist gas into the open air region wherein at
least some substrate material can be energized by the laser beam
and wherein at least some of the energized substrate material can
chemically react with the assist gas to form one or more compounds
that can dissipate into the open air region.
2. The apparatus of claim 1, further comprising a fixture for
positioning the substrate in the open air environment and upon
which the substrate can be contacted by the laser beam and wherein
the fixture can move the substrate in relation to the laser
beam.
3. The apparatus of claim 1, further comprising a mechanism for
moving the laser source relative to the substrate.
4. The apparatus of claim 1, further comprising a fixture that
positions the substrate in the open air environment and upon which
the substrate can be contacted by the laser beams and a mechanism
that moves the laser source relative to the substrate, wherein the
fixture and the mechanism can be used in combination to move the
substrate in relation to the laser beam.
5. The apparatus of claim 1, wherein the laser beam is capable of
energizing substrate material equal to or above a material removal
threshold of the substrate.
6. The apparatus of claim 1, wherein the gas supply comprises at
least one gas supply nozzle positioned to supply the assist gas in
proximity to the substrate.
7. The apparatus of claim 6, wherein said at least one gas supply
nozzle has a circular exit aperture.
8. The apparatus of claim 7, wherein said circular exit aperture
has a diameter of about 1.0 mm.
9. The apparatus of claim 1, wherein the halogen containing assist
gas comprises a halosulfide.
10. The apparatus of claim 1, wherein the halogen containing assist
gas comprises a halocarbon.
11. The apparatus of claim 10, wherein the halocarbon comprises a
fluorocarbon.
12. The apparatus of claim 11, wherein the fluorocarbon comprises
1,1,1,2 tetrafluoroethane.
13. The apparatus of claim 1, wherein the laser beam has a peak
power density of at least about 1 GW/cm.sup.2.
14. The apparatus of claim 1, wherein less than or equal to about
0.5 percent of the energized substrate material redeposits on the
substrate.
15. The apparatus of claim 1, wherein the substrate comprises a
semiconductor substrate for use in a fluid ejecting device.
16. The apparatus of claim 1, wherein the substrate comprises a
wafer.
17. An apparatus for micromachining a substrate comprising: a laser
source operably positioned to generate a laser beam configured to
make a cut by removing material from a substrate, wherein the laser
beam is configurable to make a cut having an aspect ratio ranging
from about 4.5 to about 11.25 and at said range of aspect ratios
the laser beam removes greater than or equal to about 9,800,000
cubic microns of substrate material per joule of laser energy.
18. The apparatus of claim 17, wherein said substrate comprises
crystalline silicon.
19. The apparatus of claim 17, wherein the laser beam has a
wavelength between about 300 nm and about 1100 nm.
20. The apparatus of claim 17, wherein the laser beam has a
wavelength of about 355 nm.
21. A method of processing a semiconductor substrate comprising:
positioning a substrate in an open air region; energizing a portion
of the substrate to promote removal of at least some substrate
material; and, introducing a halogen containing assist gas
proximate to an energized portion of the substrate so that the
assist gas chemically reacts with energized substrate material to
form, at least in part, one or more volatile compounds.
22. The method of claim 21, wherein said act of energizing and said
act of introducing form a slot in the substrate.
23. The method of claim 21, wherein said act of energizing and said
act of introducing form a fluid feed slot in the substrate.
24. The method of claim 21, wherein said act of energizing and said
act of introducing cuts the substrate into multiple pieces.
25. A method of laser micromachining a substrate comprising:
positioning a substrate in an open air environment, wherein the
substrate has a thickness defined by opposing first and second
surfaces; and, cutting the substrate by directing a laser beam at
the first surface of the substrate and introducing an assist gas
proximate to a region of the substrate contacted by the laser
beam.
26. The method of claim 25, wherein said introducing comprises
introducing multiple assist gases.
27. The method of claim 25, wherein said cutting forms a slot
generally free of redeposited substrate material.
28. The method of claim 25, wherein said cutting forms a slot
generally free of redeposited substrate material during said act of
cutting.
29. The method of claim 25, wherein said cutting forms a via having
an aspect ratio of at least about 10.
30. The method of claim 25, wherein said cutting forms a via having
an aspect ratio ranging from about 10 to about 20.
31. The method of claim 25, wherein said cutting forms a via having
an aspect ratio of at least about 20.
32. The method of claim 25, wherein said cutting forms a slot at
least a portion of which is contoured.
33. The method of claim 25 further comprising removing additional
material from the substrate that, in combination with said cutting,
forms a desired feature in the substrate.
34. The method of claim 33, wherein the removing is accomplished
from the second surface of the substrate.
35. The method of claim 33, wherein the removing comprises one or
more of: sand drilling, dry etching, wet etching, and mechanical
machining.
36. The method of claim 33, wherein the removing comprises laser
machining.
37. The method of claim 36, wherein said laser machining comprises
laser machining with a laser beam having a wavelength different
from the wavelength of the laser beam utilized in said cutting.
38. A method of processing a substrate comprising: positioning a
substrate in an open air environment; projecting a laser beam at
the substrate; and, directing a halogen containing assist gas
toward an area of the substrate contacted by the laser through one
or more gas supply nozzles oriented at an angle between about 45
and about 90 degrees relative to a first surface of the
substrate.
39. The method of claim 38, wherein said directing supplies
sufficient concentrations of the assist gas to maintain the assist
gas as an excess reagent.
40. The method of claim 38, wherein said directing supplies the
assist gas at a rate of between about 0.08 gm/sec to about 0.5
gm/sec where the assist gas is 1,1,1,2 tetrafluorethane.
41. The method of claim 38, wherein said directing supplies the
assist gas at a rate of about 0.33 gm/sec where the assist gas is
1,1,1,2 tetrafluorethane.
42. A method of processing a semiconductor substrate comprising:
directing a laser beam at a print head substrate positioned in an
open air environment; introducing a halogen containing assist gas
proximate a region of the substrate at which the laser is directed;
and, wherein the laser beam in the presence of the assist gas forms
a cut in the substrate having an aspect ratio of at least about
10.
43. The method of claim 42, wherein said introducing allows the
laser beam to maintain a kerf in the substrate of essentially
uniform dimensions during the cut.
44. A method of processing a semiconductor substrate comprising:
positioning a substrate in an open air region for processing; and,
removing material from the substrate by directing a laser beam and
a halogen containing assist gas at a portion of the substrate,
wherein less than about 1.0 percent of removed substrate material
redeposits on the substrate.
45. A method of laser micromachining a substrate comprising:
positioning a substrate to be contacted by a laser beam; and,
directing a laser beam at the substrate to form a cut having an
aspect ratio in a range from about 4.5 to about 11.25, and wherein
said directing removes at least about 9,800,000 cubic microns of
substrate material per joule of laser energy for said range of
aspect ratios.
46. The method of claim 45, wherein said directing comprises
directing a laser beam having a wavelength between about 300 nm and
about 1100 nm.
47. The method of claim 45, wherein said directing comprises
directing a laser beam having a wavelength of about 355 nm.
48. The method of claim 45, wherein said directing removes
substrate material at a generally constant removal rate through the
depth of the cut.
49. A method of processing a substrate comprising: positioning a
substrate in an open air environment; cutting substrate material by
directing a laser beam at the substrate and providing an assist gas
to an area of the substrate contacted by the laser beam; and,
wherein said cutting occurs in the open air environment, and
wherein said cutting process maintains a generally constant cutting
rate for the depth of the cut.
50. The method of claim 49, wherein said cutting dices the
substrate into multiple pieces.
51. A method of cutting features on a semiconductor substrate
comprising: positioning a substrate in an open air environment;
supplying an assist gas to an area of the substrate to be cut; and,
cutting a feature into the substrate by directing a laser beam at
the substrate in the presence of the assist gas to form a feature
having an aspect ratio of greater than or equal to 10.
52. The method of claim 51, wherein said cutting a feature
comprises making multiple laser beam passes over the substrate to
achieve said feature.
53. One or more computer-readable media having computer readable
instructions thereon which, when executed by a computer, cause the
computer to: cause a laser beam to be directed at a substrate
positioned in an open air environment; and, cause an assist gas to
be introduced to a region where the laser beam contacts the
substrate.
54. A method of processing a semiconductor substrate comprising:
means for positioning a substrate in an open air region; means for
energizing a portion of the substrate to promote removal of at
least some substrate material; and, means for introducing an assist
gas proximate an energized portion of the substrate so that the
assist gas chemically reacts with energized substrate material to
form at least in part one or more volatile compounds.
Description
BACKGROUND
[0001] The market for electronic devices continually demands
increased performance at decreased costs. In order to meet these
requirements, the components which comprise various electronic
devices must be made ever more efficiently and to closer
tolerances.
[0002] Laser micromachining is a common production method for
controlled, selective removal of material. However, existing laser
micromachining technologies are hindered by several deficiencies,
such as a lack of uniformity in the cut they produce, as well as
variations in removal speed as the laser cuts deeper into a
substrate. Other laser micromachining technologies have attempted
to address these problems, but are impractical for production
techniques.
[0003] Accordingly, the present invention arose out of a desire to
provide fast, economical methods of laser micromachining various
substrates.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] The same components are used throughout the drawings to
reference like features and components.
[0005] FIG. 1 shows a perspective view of a print cartridge in
accordance with one exemplary embodiment.
[0006] FIG. 2 shows a cross-sectional view of a portion of a print
cartridge in accordance with one exemplary embodiment.
[0007] FIG. 3 shows a top view of a print head in accordance with
one exemplary embodiment.
[0008] FIG. 4 shows a front elevational view of a laser machining
apparatus in accordance with one exemplary embodiment.
[0009] FIGS. 5a-5c show a cross-sectional view of a substrate in
accordance with one exemplary embodiment.
[0010] FIGS. 6a-6b show a cross-sectional view of a substrate in
accordance with one exemplary embodiment.
[0011] FIGS. 7a-7b show a cross-sectional view of a substrate in
accordance with one exemplary embodiment.
[0012] FIG. 8 shows a flow chart showing steps in accordance with
one exemplary embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OVERVIEW
[0013] The embodiments described below pertain to methods and
systems for laser micromachining a substrate. Laser micromachining
is a common production method for controlled, selective removal of
material. In embodiments of the present invention, laser
micromachining includes processes such as cutting, slotting,
dicing, singulating, via drilling and 3-dimensional machining in a
variety of substrate materials. This can include the machining of
features either partially or completely through the substrate's
thickness.
[0014] In one exemplary embodiment, the laser micromachining
process utilizes a laser machine that can generate a laser beam for
energizing and otherwise removing substrate material in an open,
ambient environment. Energizing can comprise melting, vaporizing,
exfoliating, phase explosion, and/or ablating among other
processes. In some embodiments, the energizing can occur within an
interface region surrounding the laser beam and the substrate
material which the laser beam contacts. In further embodiments, the
efficiency of the energizing process can be improved by supplying a
halogen containing assist gas to the interface area. The assist gas
can be provided by a gas supply nozzle that directs the assist gas
to the interface area. In some embodiments, the assist gas can
react with energized substrate material to form compounds that are
more readily removed and/or dissipated than could otherwise be
achieved. By supplying the assist gas to the interface region, the
speed and efficiency of the laser machining process can be improved
without the need to operate in controlled conditions. The exemplary
laser machining apparatus works in an open air environment without
the need for chambers or other containment vessels, and is
therefore well suited for production techniques.
[0015] One exemplary embodiment of the laser machining process will
be described in the context of forming slots in a substrate. Such
slots can be used for, among other things, fluid feed slots. In one
exemplary embodiment, a substrate containing fluid feed slots can
be incorporated into a print head or other fluid ejecting device.
As commonly used in print head dice, the substrate can comprise a
semiconductor substrate that has microelectronics incorporated
within and supported by the substrate. In one exemplary embodiment,
the fluid feed slot(s) allow a fluid such as ink to be supplied to
fluid ejecting elements contained in ejection chambers within the
print head. The fluid ejection elements commonly comprise firing
resistors that heat ink causing increased pressure in the ejection
chamber. A portion of that ink can be ejected through a firing
nozzle with the ink being replaced by ink from the ink feed
slot.
[0016] Although exemplary embodiments included herein are described
in the context of providing dice for use in ink jet printers, it is
recognized and understood that the techniques described herein can
be applicable to other applications where micromachining a
substrate is desired. For example, the described embodiments can be
used for quickly and efficiently dicing or singulating
semiconductor wafers.
[0017] The various components described below may not be
illustrated accurately as far as their size is concerned. Rather,
the included figures are intended as diagrammatic representations
to illustrate to the reader various inventive principles that are
described herein.
[0018] Exemplary Products
[0019] FIG. 1 shows an exemplary print cartridge 142. The print
cartridge is comprised of the print head 144 and the cartridge body
146. Other exemplary configurations will be recognized by those of
skill in the art.
[0020] FIG. 2 shows a cross-sectional representation of a portion
of the exemplary print cartridge 142 taken along line a-a in FIG.
1. It shows the cartridge body 146 containing ink 202 for supply to
the print head 144. In this embodiment, the print cartridge is
configured to supply one color of ink to the print head, though
other exemplary configuration can supply multiple colors and/or
black ink. A number of different ink feed slots are provided, with
three exemplary slots being shown at 204a, 204b, and 204c. Other
exemplary embodiments can utilize more or less ink feed slots. Some
exemplary embodiments can divide the ink supply so that each of the
three ink feed slots 204a-204c receives a separate ink supply.
[0021] The various ink feed slots pass through portions of a
substrate 206. In some embodiments, silicon can be a suitable
substrate. In some of these embodiments, the substrate 206
comprises a crystalline substrate such as single crystalline
silicon or polycrystalline silicon. Examples of other suitable
substrates include, among others, gallium arsenide, glass, silica,
ceramics or a semi conducting material. The substrate can comprise
various configurations as will be recognized by one of skill in the
art. In this exemplary embodiment, the substrate comprises a base
layer, shown here as silicon substrate 208.
[0022] The silicon substrate has a first surface 210 and a second
surface 212. Positioned above the silicon substrate are the
independently controllable ink energizing elements or firing
elements that, in this embodiment, comprise firing resistors 214.
In this exemplary embodiment, the resistors are part of a stack of
thin film layers on top of the silicon substrate 208. The thin film
layers can further comprise a barrier layer 216. In some
embodiments, the barrier layer can comprise, among other things, a
photo-resist polymer substrate. Above the barrier layer can be an
orifice plate 218 that can comprise, but is not limited to a nickel
substrate. In an additional embodiment, the barrier layer 216 and
the orifice plate 218 are integral, formed of the same
material.
[0023] In some embodiments, the orifice plate has a plurality of
nozzles 219 through which ink heated by the various resistors can
be ejected for printing on a print media (not shown). The various
layers can be formed or deposited upon the preceding layers. The
configuration given here is but one possible configuration.
[0024] The exemplary print cartridge shown in FIGS. 1 and 2 is
upside down from the common orientation during usage. When
positioned for use, ink can flow from the cartridge body 146 into
one or more of the slots 204a-204c. From the slots, the ink can
travel through an ink feed passageway 220 that leads to a firing
chamber 222. In some embodiments, the firing chamber can be
comprised of a firing resistor, a nozzle, and a given volume of
space adjacent thereto. Other configurations are also possible.
When an electrical current is passed through the resistor in a
given firing chamber, the ink is heated and expands to eject a
portion of the ink from the nozzle 219. The ejected ink can then be
replaced by additional ink from the ink feed passageway 220.
[0025] FIG. 3 shows an embodiment of a view from above the
thin-film surface of a substrate incorporated into a print head.
The substrate is covered by the orifice plate 218 with underlying
structures of the print head indicated in dashed lines. The orifice
plate is shown with numerous nozzles 219. Below each nozzle lies a
firing chamber 222 that is connected to an ink feed passageway 220
and then to slot 204a-c. The slots are illustrated in this
embodiment as an elliptical configuration when viewed from above
the first surface of the substrate. Other exemplary geometries
include rectangular among others.
[0026] Exemplary Systems
[0027] FIG. 4 shows an exemplary apparatus or laser machine 402
capable of micromachining a substrate 206a in accordance with one
exemplary embodiment. The laser machine can be configured for use
in an open air environment or region 403. The laser machine can
have a laser source 404 capable of emitting a laser beam 406. The
laser beam can contact, or otherwise be directed at, the substrate
206a. In some exemplary embodiments, the substrate can be
positioned on a fixture 407 in the open air environment.
[0028] Exemplary laser machines are commercially available. One
such exemplary laser machine is the Xise 200 laser Machining Tool,
manufactured by Xsil ltd. of Dublin, Ireland.
[0029] Exemplary laser machines can utilize various laser sources.
A laser source has a crystal or other structure that when energized
can emit the laser beam. An exemplary laser source is the Coherent
AVIA 355-4500 which contains Crystalline Nd. YVO4 (also known as
Vanadate). Other exemplary crystals include among others, Nd:YAG
and Nd:YLF.
[0030] Each of these materials can produce a laser beam with a
fundamental wavelength of about 1064 nanometers (nm) in one
embodiment. Laser beams of various wavelengths can provide
satisfactory embodiments. For example, some embodiments can have a
wavelength in the range of less than about 550 nm.
[0031] In some exemplary embodiments, the wavelength of the laser
beam can be modified within the laser source 404. For example, one
embodiment can utilize the AVIA 355, where the frequency is tripled
to yield a laser beam wavelength of 355 nm. Another exemplary
embodiment can utilize a laser source with a wavelength of 532 nm.
For example, the Lambda Physik PG532-15 can be utilized as a laser
source that can provide a laser beam that has such a wavelength.
Other exemplary embodiments can utilize laser beams having
wavelengths ranging from less than 100 nm to more than 1500 nm.
Other satisfactory embodiments can be achieved with laser beams
having various properties as will be discussed in more detail
below.
[0032] Various exemplary embodiments can utilize one or more lens
(es) 408 to focus or expand the laser beam. In some of these
exemplary embodiments, the laser beam can be focused in order to
increase its energy density to more effectively machine the
substrate. In these exemplary embodiments, the laser beam can be
focused with one or more lenses 408 to achieve a desired diameter
where the laser beam contacts the substrate 206a. In some of these
embodiments, this diameter can range from about 1 micron to more
than 100 microns. In one embodiment, the diameter is about 20
microns. Also, the laser beam can be pointed directly from the
laser source 404 to the substrate 206a, or indirectly through the
use of one or more mirror(s) 410.
[0033] Exemplary laser beams can provide sufficient energy to
energize substrate material that the laser beam is directed at.
Energizing can comprise melting, vaporizing, exfoliating, phase
explosion, and/or ablating among others processes. Some exemplary
embodiments can energize substrate material equal to or above its
material removal threshold. The material removal threshold is the
energy density level necessary to remove substrate material by
melting, vaporizing, exfoliating, and/or phase explosion. Energy
density will be discussed in more detail below. The substrate that
the laser beam is directed at and the surrounding region containing
energized substrate material is referred to in this document as an
interface region 411.
[0034] In some exemplary embodiments, the laser machine 402 can
also have a gas supply 412 for supplying an assist gas 414 to the
interface region 411. In some exemplary embodiments, the assist gas
can be supplied via one or more gas supply nozzles 416.
[0035] Some exemplary embodiments can also utilize a debris
extraction system 418 that can remove vaporized substrate materials
and/or molecules formed from substrate material and a component of
the assist gas, as well as various other molecules. In some
embodiments, the debris extraction system can comprise a vacuum
system and filtration system positioned to evacuate material in
proximity to the laser beam and substrate. Exemplary debris
extraction systems will be discussed in more detail below.
[0036] In some embodiments, the assist gas can increase the speed
and/or efficiency at which the laser beam cuts or removes substrate
material. Various mechanisms can contribute to the increased
removal rate. For example, in some embodiments, molecules of the
assist gas can be ionized by the laser beam energy. At least some
of the resultant ions can react with energized substrate material.
Such reactions can form resultant compounds that can be volatile
and relatively non-reactive. These properties can allow the
resultant compounds to diffuse or otherwise dissipate from the
interface region and thus can decrease the incidence of
redeposition of substrate material.
[0037] This is an advantage over other embodiments of laser
machining techniques where a significant amount of the substrate
material removed by the laser redeposits back on the substrate.
Redeposited material adjacent to the interface region can result in
undesired debris or component damage. Redeposited material in the
interface region hinders the laser/substrate interaction and
reduces the material removal rate.
[0038] Further, some embodiments of laser machining processes also
lead to the formation of particulate debris typically having
dimensions or diameters of 1 micron or less. In these embodiments,
this debris can be formed from molten material directly released
from the substrate's surface as well as from condensation of the
vaporized substrate material. This particulate material or debris
can cause scattering and absorption of laser light towards the end
of the laser pulse, especially in laser pulses with a duration of
longer than 5-10 nanoseconds (nsec), decreasing the amount of
useful laser light reaching the target material surface, in this
embodiment. Such particulate material can subsequently deposit on
the area within or adjacent to the interface region.
[0039] Accordingly, these techniques result in redeposition which,
in turn, decreases the speed of cutting or machining, as well as
the quality of the finished machined substrate. Conversely, some
embodiments of the invention described herein can greatly reduce or
eliminate redeposition and can produce much cleaner, more uniform,
cuts or machining as a result. In some exemplary embodiments, less
than about 1.0 percent of removed material is redeposited. In a
particular embodiment, less than about 0.5 percent of the removed
material is redeposited.
[0040] Various mechanisms can contribute to this increased
performance, including but not limited to, the following
mechanisms. In some embodiments, the assist gas and/or
disassociated components of the assist gas can interact with
particulate debris generated by the action of the laser beam. This
interaction can reduce the dimensions of the debris and allow the
debris to be more easily removed by the extraction system. Another
of the various mechanisms can increase performance by reacting the
assist gas or its components with condensing material in a vapor
plume of substrate material in the interface region to reduce the
dimensions of any condensed material allowing it to be more easily
removed by an extraction system.
[0041] FIGS. 5a-5c show an exemplary embodiment of cross sections
through a substrate 206b. Here, a feature is being micromachined
into the substrate. In this embodiment, the feature is a trench
into the substrate that eventually is formed all the way through
the substrate to form a via. Other exemplary features can also be
formed as will be discussed below.
[0042] In the embodiments shown in FIGS. 5a-5c, the substrate can
have a thickness t defined by a first surface 210 and an opposite
second surface 212. In further embodiments, the substrate's
thickness can range from less than 100 microns to more than 2000
microns. In these exemplary embodiments, the thickness is about 675
microns.
[0043] Referring now to FIG. 5a, the laser beam 406a is shown
directed at the substrate 206b. As shown here, the laser beam is
orthogonal to the first surface 210 of the substrate, though other
configurations can provide satisfactory embodiments. The laser beam
has formed a shallow cut 500a in the substrate through the first
surface 210. In this embodiment, two gas assist nozzles (416a and
416b) are shown positioned on opposite sides of the laser beam to
supply the assist gas (not shown) to the interface area 411a.
Though two gas assist nozzles are utilized here, other satisfactory
embodiments can use more or less nozzles. The term `nozzle` is used
to describe the hardware that is used to deliver the assist gas to
the interface region of the substrate. In various embodiments, this
can include an exit aperture (502a and 502b). In some embodiments
the exit aperture can be generally circular in transverse
cross-section to plane c as shown in FIG. 5b.
[0044] In other exemplary embodiments, the exit aperture can
comprise other configurations. For example, the exit aperture can
be in a manifold configuration, an air knife configuration, and a
ring shaped annulus configuration, among others.
[0045] In one exemplary embodiment, the exit aperture (502a and
502b) of the gas assist nozzles can be about 12 mm vertically above
the first surface 210 and about 3.2 mm horizontally from the laser
beam 406, though other satisfactory embodiments position the
nozzles at different combinations of distances and angles. The
nozzles can be positioned to eject the assist gas from the exit
aperture at an angle .delta. of about 45 to about 90 degrees
relative to the first surface of the substrate. In the exemplary
embodiment shown in FIGS. 5a-5b, the angle .delta. is about 70
degrees.
[0046] The assist gas can be supplied at various delivery pressures
and velocities. For example, in one embodiment, the gas supply
nozzle's exit aperture can be a relatively small diameter to
produce higher velocities for a given flow rate or the diameter can
be relatively large to provide a lower velocity for a given flow
rate. In one exemplary embodiment, the diameter is about 1.0
mm.
[0047] Exemplary embodiments can utilize various assist gases. In
some embodiments, the assist gas can comprise a halide or a halogen
containing gas. Exemplary assist gases can comprise, but are not
limited to halocarbons and sulfur hexafluoride.
[0048] Many exemplary assist gases, including many of the
halocarbon gases can have deleterious environmental consequences.
Some exemplary embodiments can utilize a filtration system alone,
or the filtration system can be used as a component of a debris
extraction system 418 to remove or minimize any gases of
environmental concern that could otherwise diffuse into the ambient
environment from the interface area. This filtration system can
include mechanisms for converting the assist gas and various
by-product gases from the interface area into more inert
compounds.
[0049] Other exemplary embodiments can utilize assist gases such as
1,1,1,2 tetrafluoroethane that can be effective assist gases and
are understood to be relatively benign to the environment and thus
can be advantageous. Other exemplary assist gases can also combine
effectiveness in increasing laser machining performance and reduced
environmental consequences. Although embodiments utilizing a single
assist gas have been described in the exemplary embodiments, other
embodiments can utilize multiple assist gases, the combination of
which can provide beneficial characteristics.
[0050] In one exemplary embodiment the assist gas can comprise a
halogen precursor, at least some of the molecules of which can be
ionized or disassociated by laser energy in the interface area. In
a further exemplary embodiment, the assist gas can dissociate or
ionize in an extremely hot environment around the laser energized
region and can react with energized substrate material to form, at
least in part, one or more volatile compounds. This process can
decrease the incidence of redeposition and/or are more easily
removed by an extraction system.
[0051] In some embodiments, the assist gas can be supplied at a
flow rate sufficient to be an excess reagent in the interface
region. In one exemplary embodiment, where the assist gas comprises
1,1,1,2 tetrafluoroethane, the gas assist nozzles deliver the
assist gas at a flow rate in a range of about 0.08 grams/second
(gm/sec) to about 0.5 gm/sec. A further embodiment supplies about
0.33 gm/sec of 1,1,1,2 tetrafluoroethane. Other exemplary flow
rates for various exemplary assist gases will be recognized by one
of skill in the art.
[0052] FIG. 5b is an exemplary embodiment showing another cross
section of the substrate where the laser has cut a trench 500b most
of the way through the thickness of the substrate 206b. The depth
of the trench is indicated as y and can be compared to the
substrate's thickness t. In this exemplary embodiment, the assist
gas can still be supplied to the interface region 411b to maintain
efficient cutting despite the interface region being at least in
part, at the bottom of the trench 500b. This can allow the laser to
cut at generally the rate and efficiency as it did when the trench
was shallower, for example as shown in FIG. 5a. This embodiment can
also allow the laser to cut a trench of generally uniform diameter
d for the entire depth of the trench.
[0053] FIG. 5c shows the trench 500c having been completed through
the entire thickness t of the substrate. Thus, the depth y of the
trench 500c equals the thickness t of the substrate 206b. Such a
through hole, also known as a via, can be useful for many aspects
of incorporating microelectronics onto a substrate among others. As
shown here, the via has a generally consistent diameter d
throughout. In these embodiments, the diameter can be less than
about 60 microns, though larger diameters can be achieved.
[0054] Some embodiments can produce trenches and/or vias that have
diameters less than or equal to about 30 microns. The efficiencies
of these embodiments can allow these trenches or vias to have an
aspect ratio (feature depth divided by the feature width) of at
least about 10 with further embodiments having aspect ratios
greater than 20. Thus, in the trench shown in FIG. 5b, the feature
depth equals y and the feature width equals the diameter d.
Referring again to FIG. 5c the depth of the via y equals the
substrate's thickness t. So in this embodiment, the aspect ratio
equals the substrate's thickness t divided by the diameter d.
Although a via is shown here, these embodiments can also form other
features, such as trenches, slots and/or cuts, as will be discussed
in more detail in relation to FIGS. 6a-6b and 7a-7b.
[0055] The laser machining apparatus in some embodiments can cut
into a specific point on the substrate and can form a trench of
less than or about 30 microns through the same substrate without
moving the laser or substrate. This not only allows smaller
trenches to be made in the substrate, but the trench forming
process can be made correspondingly faster and of better quality,
while affecting less of the surrounding substrate material than can
be achieved with other typical technologies.
[0056] Some embodiments of the present invention allow for the
formation of trenches and vias having small diameters that are
generally consistent for their entire depth. This is achieved, by
among other things, maintaining the rate and efficiency of the
removal process by reducing redeposition and particle build-up.
[0057] In other embodiments, where technologies attempt to use
various gases to promote laser function, however, these systems
typically require a controlled environment usually achieved through
the use of a chamber into which the substrate is placed. In this
embodiment, the conditions and constituent gases of the chamber are
then altered before commencing laser machining. The constraints
imposed by having to open and close and reseal the chamber and then
reestablish the controlled environment whenever components are
added or removed has prevented such processes from becoming
commercially practicable. In contrast, some embodiments described
herein, by virtue of the fact that they are configured for use in
open air environments, are inherently well adapted to mass
production applications such as assembly lines.
[0058] FIGS. 6a-6b show a laser beam cutting or removing substrate
material to form a trench 602. FIG. 6a is a view taken in cross
section along the long axis of the trench, while FIG. 6b is a cross
section taken transverse the long axis.
[0059] FIG. 6a shows a cross section along the length of a trench
602 formed from the laser beam contacting the substrate while the
substrate was moved in the x direction relative to the laser beam.
In another exemplary embodiment, the laser beam can be moved
relative to the substrate in several ways. For example, the laser
beam can be moved, in either or both the x and y directions, while
the substrate remains stationary. The gas assist nozzles can be
moved in conjunction with the laser beam or left stationary.
Alternatively, the substrate can be moved and the laser beam kept
stationary. For example, in one embodiment, the substrate 206c can
be placed on a fixture 407 that in some embodiments has the
capability to move the substrate relative to the laser beam. Other
exemplary embodiments can utilize a combination of these
techniques, among others, to move the substrate and the laser beam
relative to one another.
[0060] FIG. 6a further shows two gas assist nozzles 416c and 416d
adjacent and parallel to the laser beam 406b so that each of them
is orthogonal to the substrate's first surface 210. This is one
exemplary configuration that can supply assist gas to the interface
area.
[0061] FIG. 6b shows an embodiment where the laser beam forms a
kerf k in the substrate. The kerf is the width of the cut formed by
the laser beam as it is moved relative to the substrate. The kerf
width can be affected by several factors including the amount of
redeposition of substrate material as well as the laser's
parameters and speed at which the laser beam is moved in relation
to the substrate.
[0062] In some exemplary embodiments, the laser parameters can
establish a laser beam with a peak power density of greater than 1
GW/cm.sup.2, with one exemplary embodiment having a peak power
density of about 4.78 GW/cm.sup.2. The laser machine, in various
embodiments, can generate the laser in pulses in any suitable range
of values. In some embodiments, pulse values range from about 1
kilohertz (kHz) to about 200 kHz. In one embodiment the pulse rate
is about 20 kHz. Other satisfactory embodiments can use rates below
and above the range given here. The laser beam pulse width can be
about 1 to 100 nanoseconds, with one exemplary embodiment using
about 15 nanoseconds.
[0063] The movement of the laser beam relative to the substrate per
unit of time is referred to in this document as the laser scan
rate. Exemplary embodiments can utilize a laser scan rate of about
1 to about 1000 millimeters/second (mm/sec). Some exemplary
embodiments can utilize a laser scan rate of about 10 to about 300
mm/sec with other exemplary embodiments utilizing about 100 mm/sec.
In one embodiment, these parameters can allow a laser to quickly
make a cut having a consistent kerf width so that the resultant
trench has a surface roughness less than existing technologies.
[0064] Maintaining a uniform kerf can result in a better quality
trench, slot or other feature that is more uniform along its length
and depth and closer to the desired dimensions. The described
embodiments improve kerf uniformity, as well as allow for increased
cutting speed.
[0065] The described embodiments can efficiently form high aspect
ratio features while maintaining high cutting efficiency. In one
embodiment, aspect ratios in the range of about 4.5 to about 11.25
can be achieved with the laser removing at least about 9,800,000
cubic microns of substrate material per joule of laser energy. In
some embodiments, the features can be made with even higher aspect
ratios with very little reduction in efficiency. This is in
contrast to other embodiments of laser machining technology where
efficiency deceases dramatically with increasing feature aspect
ratio.
[0066] FIGS. 7a-7b show an embodiment where the laser has been used
in combination with another removal technique to form a slot in the
substrate. The slot can comprise a fluid feed slot, and in some
embodiments can comprise a fluid feed slot in a substrate that can
be incorporated into a fluid ejecting device.
[0067] Referring now to FIG. 7a, a laser cut has formed a trench
702 in the substrate 206d. In this embodiment, the trench has a
depth x and a length 1.sub.1. In this example, the trench depth
passes through less than the entire thickness t of the substrate.
Other examples can be shallower or deeper than shown, or can pass
all the way through the thickness of the substrate for at least a
portion of its length to form a slot through the substrate.
[0068] In this embodiment, the trench can be formed from one or
more passes of the laser beam over the substrate. As can be seen
from this view along the long axis of the trench, the trench has a
contoured configuration. Other configurations can include tapered
and stepped configurations, among others.
[0069] FIG. 7b shows an embodiment of a cross section taken along
the long axis of the substrate and showing a second trench 704
having a length 1.sub.2 where 1.sub.2 is less than 1.sub.1, formed
through the second surface 212 to intercept at least portions of
the first trench to form a through-slot 204h. The second trench can
be formed utilizing various substrate removal techniques, including
but not limited to: sand drilling, dry etching, wet etching, laser
micromachining, and mechanical machining. If laser machining is
used as the second removal technique, the laser beam can have the
same properties as the laser beam used to make the first trench or
feature, or the second laser beam can have different properties.
For example, in one embodiment a first laser beam having a
wavelength of about 1100 nm can be used to cut a first trench
followed by a second laser beam having a wavelength of about 355 nm
to remove additional material. Such an exemplary embodiment can
take advantage of the various cutting properties of different
wavelength lasers.
[0070] In the example given in FIGS. 7a and 7b, the first trench or
feature is formed first using the laser machining process followed
by a subsequent removal process forming the second trench. Such
need not be the case, for example in some embodiments, substrate
material can be removed from a first side using sand drilling,
among others. This process can then be followed by laser machining
to remove additional substrate material. In these embodiments, the
laser machining process can be conducted from the same side or
surface as the sands drilling process or from an opposite second
side.
[0071] Other exemplary embodiments can employ additional
intermediary steps to achieve a desired feature. Some intermediary
steps can apply or deposit material that is further configured by
subsequent removal steps.
[0072] The various exemplary embodiments have so far been described
in the context of cutting or forming trenches, vias and slots in a
substrate. However, the exemplary embodiments can also be used
wherever controlled, selective, removal of material is desired.
This can include other processes such as cutting, dicing,
singulating, and 3 dimensional machining in a variety of substrate
materials. This can further include the micromachining of features
either partially or completely through the substrate's
thickness.
[0073] For example, in the semiconductor industry in recent years
there has been a drive toward smaller and smaller devices for both
size constraints of the product and for cost considerations. The
more devices per semiconductor substrate or wafer, the lower the
device cost. It is common for a semiconductor substrate to contain
a plurality of devices, which require dicing or singulation before
being packaged for assembly into an electronic device, such as a
fluid ejecting device, ink-jet print head or some other device.
[0074] Traditionally in the industry, mechanical dicing saws have
been used to singulate or dice these components. The existing
technologies are restricted to straight line cuts in the substrate
material, whereas the described laser micromachining embodiments
can form features or cuts having complex shapes, straight, curved,
non-continuous cuts, or any combination thereof.
[0075] The described embodiments can also accomplish this with kerf
widths of 10 to 15 microns and lower. Conversely, mechanical dicing
saws produce minimum kerf widths of 50 to 100 microns, depending on
the substrate material and thickness. Smaller kerfs can result in
more devices per wafer and therefore can lower device cost.
[0076] Further, mechanical dicing is a wet process that typically
uses a cooling fluid for the cutting process. The described
embodiments eliminate exposing the devices to potential damage from
the cooling fluid, and also are very efficient with little or no
redeposition of removed debris material. These and other features
allow the described embodiments to better perform many
micromachining tasks than existing technologies.
[0077] Exemplary Methods
[0078] FIG. 8 is a flow chart that helps to illustrate the various
exemplary methods described herein.
[0079] Step 802 positions a substrate in an open air environment.
Various examples of exemplary substrates have been described above.
In this embodiment, the substrate can be positioned on a fixture
407 or other suitable structure. Step 804 directs or projects a
laser beam at the substrate to energize a portion of the substrate
material. Such energizing can cut or remove substrate material in
some embodiments. Various exemplary laser machines and laser beams
have been described above.
[0080] Step 806 introduces or directs an assist gas to a region of
the substrate contacted by the laser beam. In some exemplary
embodiments the assist gas can be directed to the interface region.
Some exemplary embodiments supply the assist gas via one or more
gas assist nozzles of various configurations, exemplary embodiments
of which are described above. Various assist gases can be directed
to the interface area and can increase the performance of the laser
beam in cutting substrate material.
[0081] Conclusion
[0082] The described embodiments can utilize a laser beam to cut or
micromachine substrates in an open air environment. In several
embodiments, the laser beam cuts with greater efficiency and speed
by supplying an assist gas to the interface area where the laser
beam energizes substrate material. In particular, the laser beam,
when supplied with assist gas, can form cuts with higher aspect
ratios than existing technologies. Additionally, the cuts can be
maintained closer to desired parameters and can have less variation
in their dimensions, in some embodiments. Some of the described
embodiments can form narrower cuts than present and past technology
and the speed and efficiency of those cuts can be maintained
through the depth of the cut, while forming a higher quality
product than existing technologies. All of this can be achieved
utilizing systems and methods that are conducive to production
techniques.
[0083] Although the invention has been described in language
specific to structural features and methodological steps, it is to
be understood that the invention defined in the appended claims is
not necessarily limited to the specific features or steps
described. Rather, the specific features and steps are disclosed as
preferred forms of implementing the claimed invention.
* * * * *