U.S. patent application number 12/353576 was filed with the patent office on 2009-05-07 for apparatus and method for modifying an object.
This patent application is currently assigned to RAVE LLC. Invention is credited to Barry F. HOPKINS, Jeffrey E. LeClaire, David J. Ray, Roy White.
Application Number | 20090114850 12/353576 |
Document ID | / |
Family ID | 36755533 |
Filed Date | 2009-05-07 |
United States Patent
Application |
20090114850 |
Kind Code |
A1 |
HOPKINS; Barry F. ; et
al. |
May 7, 2009 |
APPARATUS AND METHOD FOR MODIFYING AN OBJECT
Abstract
A method and apparatus includes positioning a reactant on a
surface in specific location and then directing an energy source
from a device at the reactant such that it modifies the surface to
either remove material or add material.
Inventors: |
HOPKINS; Barry F.; (Hobe
Sound, FL) ; Ray; David J.; (Agoura Hills, FL)
; LeClaire; Jeffrey E.; (Boca Raton, FL) ; White;
Roy; (Wellington, FL) |
Correspondence
Address: |
BAKER & HOSTETLER LLP
WASHINGTON SQUARE, SUITE 1100, 1050 CONNECTICUT AVE. N.W.
WASHINGTON
DC
20036-5304
US
|
Assignee: |
RAVE LLC
Delray Beach
FL
|
Family ID: |
36755533 |
Appl. No.: |
12/353576 |
Filed: |
January 14, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11415203 |
May 2, 2006 |
7495240 |
|
|
12353576 |
|
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|
11047877 |
Feb 2, 2005 |
7323699 |
|
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11415203 |
|
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Current U.S.
Class: |
250/492.2 |
Current CPC
Class: |
H01L 21/30608 20130101;
H01L 21/76892 20130101; H01L 21/31111 20130101; H01L 21/32134
20130101; H01L 21/316 20130101; H01L 21/3185 20130101 |
Class at
Publication: |
250/492.2 |
International
Class: |
G01N 13/16 20060101
G01N013/16 |
Claims
1. An apparatus for modifying an object, comprising: a reactant
that is positioned on the object; and an energy device configured
to direct its output at the reactant in order to modify the
object.
2. The apparatus as in claim 1, further comprising an assembly that
is configured to position the reactant on the object.
3. The apparatus as in claim 2, wherein the assembly is a scanning
probe microscope.
4. The apparatus as in claim 3, wherein the reactant is positioned
with a probe tip of the scanning probe microscope.
5. The apparatus as in claim 4, wherein the reactant is placed on
the probe tip through a hydrophilic process.
6. The apparatus as in claim 1, wherein the energy device is an
electromagnetic device.
7. The apparatus as in claim 1, wherein the energy device is a
laser.
8. The apparatus as in claim 1, wherein the energy device is
configured to directed radio waves at the sample.
9. The apparatus as in claim 1, wherein in the object is a single
layered device.
10. The apparatus as in claim 1, wherein the object is comprised of
at least two layers.
11. The apparatus as in claim 1, wherein the object is a
semiconductor device.
12. The apparatus as in claim 1, wherein the reactant is configured
to remove material from the object.
13. The apparatus as in claim 1, wherein the reactant is configured
to add material to the object.
14. The apparatus as in claim 13, wherein the added material is a
conductor.
15. The apparatus as in claim 13, wherein the added material is an
insulator.
16. The apparatus as in claim 11, wherein the reactant is selected
based upon the object.
17. The apparatus as in claim 10, wherein one of the at least two
layers is configured to act as a stop layer.
18. The apparatus as in claim 10, wherein the reactant is
configured to removed material from one of the at least two layers
and not react with the second of the at least two layers.
19. The apparatus as in claim 11, wherein the energy device is
configured to increase a reaction time of the reactant on the
object.
20. The apparatus as in claim 14, wherein the reactant is placed on
the probe tip through an electrostatic process.
21. The apparatus as in claim 17, wherein the added material is
linked to another portion of the object.
22. The apparatus as in claim 11, further comprising a probe
assembly and fluid delivery channel.
23. The apparatus as in claim 11, further comprising a debris
removal means.
24. The apparatus of claim 11, further comprising placing the
reactant in multiple locations to create specific shaped features.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to and is a continuation
application of U.S. patent application Ser. No. 11/415,203, filed
May 2, 2006, which is a continuation of U.S. patent application
Ser. No. 11/047,877, filed Feb. 2, 2005, now U.S. Pat. No.
7,323,699, issued Jan. 29, 2008, the disclosure of which is hereby
incorporated by reference in its entirety.
FIELD OF THE INVENTION
[0002] The present invention relates generally to the alteration of
material with a relative high degree of volumetric and positional
accuracy. More specifically, the present invention relates to the
removal and addition of material from substrates and items used in
the semiconductor industry such as in the modification of
semiconductor wafers and photomasks, which are used in
photolithography process, the creation of semiconductors and micro
and nano structures. The invention can make substrate alterations
with dimensions in the nanometer and larger range and relative to
surfaces and surface features with nanometer positional accuracy
(X, Y and Z).
BACKGROUND OF THE INVENTION
[0003] In modifying and fabricating wafers, semiconductor die,
photomasks and flat panel display/microdisplay devices for the
semiconductor industry and other industries as well as correcting
defects in masks used for processing of semiconductors, it is
sometimes necessary to create small holes and other shapes that are
relatively deep compared to their diameter or surface area. It is
also sometimes necessary to create small holes and shapes relative
to other device features with a high positional accuracy. With
regard to holes, high aspect ratio holes are difficult to create.
Note that, the ratio of the depth to width is referred to as the
aspect ratio.
[0004] Attempts to overcome the difficulty associated with high
aspect ratio structures have been relatively unsuccessful.
Generally, these solutions either bore material out of the sample
using particle beams such as ion beams, electron beams or laser
beams. For example, U.S. Pat. No. 6,403,388 to Birdsley et al.
discloses a method of using ion beams for this purpose. Such beam
devices are also used to deposit material on the sample surfaces by
introducing gasses into the beam. However, there are distinct
disadvantages with these solutions.
[0005] U.S. Pat. No. 6,827,979, U.S. Pat. No. 6,635,311 as well as
U.S. patent application Ser. No. 10/449,685, U.S. patent
application Ser. No. 10/442,188, U.S. patent application Ser. No.
10/465,794, U.S. patent application Ser. No. 10/301,843, U.S.
patent application Ser. No. 10/261,663 to Mirkin et al. teach
methods of using scanning probe microscopes to add material to
objects in small dimensions. These teachings show chemical
techniques as the mechanisms for the additive process. These
teaching do not include the activation of the additive materials by
the use of electromagnetic, particle beam or gaseous materials. The
use and apparatus of activation means described by the applicants
herein results in substantially more versatility in applicant's
invention.
[0006] U.S. Pat. Nos. 6,737,646 and 6,674,074 to Schwartz disclose
adding material to an object by coating a tip and applying that
coating to an object with an atomic force microscope. The invention
further teaches a chamber for containing gasses. However, the
invention has a distinct disadvantage in that at no point is the
coating or material activated with an energy device. By including
an energy device, the time to add the material to an object is
significantly reduced.
[0007] When using ion beams to attempt material removal, the ions
may imbed themselves in the sample or device to varying depths. As
a result, the device becomes unusable because the device properties
may be changed by the presence of the imbedded ions. The
introduction of gasses into an ion beam also poses additional
challenges in containment in and the selection of suitable gasses
in the ion beam chamber.
[0008] With electron beams, controlling the position of the beam
becomes difficult if the sample begins to develop charge. This
phenomenon occurs when the electron beam strikes a non-conductive
or poorly conductive substrate surface. As a result, the accuracy
of this method becomes a serious concern for the end user. The use
of such beams can cause uncontrolled damage, which could render the
target device unusable. The introduction of gasses into an electron
beam also poses challenges in the containment in and the selection
of suitable gasses in the electron beam chamber.
[0009] With laser light, the size of the hole may be limited by the
size of the achievable focus spot. In cases where material
modifications smaller than the nominal focus spot are achieved, the
depth of removal, and therefore the aspect ratio, is limited Laser
light then only becomes a partial solution with limited
applications due to the limitations of the focused light beam
wavelength.
[0010] Additionally, in semiconductor processing and evaluation,
physical access to subsurface features may also be needed. A small
diameter hole or small area for holes that are not round, is
desirable to prevent destruction or damage to features in the
device that are adjacent to the hole. None of the prior art
solutions are able to achieve this task with a relative degree of
accuracy and precision.
[0011] Accordingly, a technique that is able to modify a sample
such as a semiconductor with high positional accuracy and
volumetric control is needed. There is also a need to be able to
modify the semiconductor or target device to add material as
required by the end user. There is also a need to be able to remove
varying levels of materials without greatly affecting adjacent
areas. The combination of high aspect ratio features with high
positional accuracy, limits the affect to adjacent areas.
SUMMARY OF THE INVENTION
[0012] The foregoing needs are met, to a great extent, by the
present invention, wherein in one aspect an apparatus is provided
that in some embodiments permits an object such as semiconductor
device to be modified such that material is removed or added. The
present invention accomplishes this task by placing a reactant on
the device to be modified and subjecting the reactant to a form of
energy such that the reactant is able to modify the surface as
desired. The reactant is uniquely selected for the desired task
based upon the composition of the device. The energy form the
mentioned source in the various embodiments of the present
invention may be light energy, acoustic energy, or energy in the
form of heat. Alternately the energy may be particle beam energy
such as electrons, ions or other atomic particles. The reactant may
be activated by introducing a gas into the area around the
reactant.
[0013] The reactant chosen depends on whether the need is to remove
material from the sample or whether material is to be added to the
sample. The accurate placement of the reactant is typically
accomplished with a scanning probe microscope. Scanning probe
microscopes are a class of microscopes that use a probe assembly
comprising a very fine tip on a probe. The probe assembly is guided
in the X, Y, and Z directions using a very accurate positioning
mechanism. These microscopes typically make use of some particular
interaction between the probe and the surface of a sample. For
example, a scanning tunneling microscope places a small bias
voltage between the probe tip and the sample. This microscope then
detects the currents that flow to or from the tip to the sample.
Another type of scanning probe microscope is a scanning force
microscope. This microscope utilizes a very sharp tip on the probe
assembly. The tip is mounted on a cantilever. Deflections of the
cantilever caused by the attractive or repulsive interatomic forces
acting on the tip are monitored. Other types of scanning probe
microscopes use capacitive or magnetic detection mechanisms. The
invention described here typically shows a scanning force
microscope, but other types of scanning probe microscopes can
function equally well in many of the embodiments described.
[0014] In accordance with one embodiment of the present invention,
a method for modifying an object includes positioning a reactant on
the sample or an object and directing energy towards the reactant,
wherein the energy is configured to activate the reactant such that
it modifies the sample or object. The reactant is chosen or
selected based upon the composition of the sample. The sample can
be modified either by removing material or adding material.
[0015] In accordance with another embodiment of the present
invention, an apparatus for modifying an object includes a reactant
that is positioned on the object and an energy device configured to
direct its output at the reactant in order to modify the object.
This embodiment can further include an assembly that is configured
to position the reactant on the object.
[0016] In accordance with yet another embodiment of the present
invention, a product produced by the process of modifying a sample
includes positioning a reactant on the sample and directing and
energy source towards the reactant, wherein the energy along with
the reactant is configured to modify the sample. The sample is
modified by removing material or adding material.
[0017] In yet another embodiment of the invention, the reactant,
when in fluid state, may be delivered to the surface of a sample by
directing or forcing the fluid reactant through a channel formed in
the cantilever and tip assembly. U.S. Pat. Nos. 6,337,479 and
6,353,219 to Kley, which are hereby incorporated by reference,
describes a fluid delivery system using a channel in the cantilever
and tip of a scanning force microscope.
[0018] There has thus been outlined, rather broadly, certain
embodiments of the invention in order that the detailed description
thereof may be better understood, and in order that the present
contribution to the art may be better appreciated. There are, of
course, additional embodiments of the invention that will be
described below and which will form the subject matter of the
claims appended hereto.
[0019] In this respect, before explaining; at least one embodiment
of the invention in detail, it is to be understood that the
invention is not limited in its application to the details of
construction and to the arrangements of the components set forth in
the following description or illustrated in the drawings. The
invention is capable of embodiments in addition to those described
and of being practiced and carried out in various ways. Also, it is
to be understood that the phraseology and terminology employed
herein, as well as the abstract, are for the purpose of description
and should not be regarded as limiting.
[0020] As such, those skilled in the art will appreciate that the
concept upon which this disclosure is based may readily be utilized
as a basis for the designing of other structures, methods and
systems for carrying out the several purposes of the present
invention. It is important, therefore, that the claims be regarded
as including such equivalent constructions insofar as they do not
depart from the spirit and scope of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1A illustrates a scanning probe microscope probe
assembly with an amount of subtractive reactant on the probe tip
positioned above the surface of a target device.
[0022] FIG. 1B illustrates a scanning probe microscope probe
assembly with an amount of subtractive reactant on the probe tip in
proximity of the target device with the reactant wetting to the
surface of the target device surface.
[0023] FIG. 1C illustrates the target device surface with an amount
of subtractive reactant on the surface with a light beam directed
towards the reactant.
[0024] FIG. 1D illustrates the target device surface with a dimple
that is the result of activation of the subtractive reactant on the
surface. This activation is caused by the light beam.
[0025] FIG. 2A illustrates a scanning probe microscope probe
assembly with an amount of additive reactant on the probe tip above
the surface of a target device.
[0026] FIG. 2B illustrates a scanning probe microscope probe
assembly with an amount of additive reactant on the probe tip in
proximity of the target device with the reactant wetting to the
surface of the target device surface.
[0027] FIG. 2C illustrates the target device surface with an amount
of additive reactant on the surface with a light beam directed
toward the reactant.
[0028] FIG. 2D illustrates the target device surface with a bump
that is the result of activation of the additive reactant on the
surface. The activation is caused by the light beam.
[0029] FIG. 3A illustrates a scanning probe microscope probe
assembly drawing an amount of reactant from a pool of reactant.
[0030] FIG. 3B illustrates the probe tip transporting an amount of
reactant.
[0031] FIG. 4A illustrates a scanning probe microscope depositing
reactant onto a surface dimple resulting from a previous
application of subtractive reactant.
[0032] FIG. 4B illustrates an electromagnetic source directing a
beam of energy toward the reactant.
[0033] FIG. 4C illustrates the resulting void created by a second
or subsequent deposition of reactant and a stop layer of material
that is not reactive to the etchant.
[0034] FIG. 5A illustrates a scanning probe microscope depositing
additive reactant on to a surface dimple resulting from a previous
application of subtractive reactant.
[0035] FIG. 5B illustrates an electromagnetic source directing a
beam of energy toward the additive reactant.
[0036] FIG. 5C illustrates the resulting partially filled void
created by application of additive reactant on top of a stop layer
of material.
[0037] FIG. 5D illustrates the resulting filled void created by
application of additive reactant.
[0038] FIG. 6A illustrates a multi-layer device.
[0039] FIG. 6B illustrates the result of etching a hole in a sample
with the hole filled with a nonconductive residue.
[0040] FIG. 6C illustrates the result of etching a hole in the
nonconductive residue.
[0041] FIG. 6D illustrates the filled hole in the nonconductive
reside. The fill residue in this illustration is conductive.
[0042] FIG. 7 illustrates an electrostatic charge on the tip and
reactant as well as an opposite electrostatic charge on the target
device.
[0043] FIG. 8A illustrates a probe tip coated with reactant.
[0044] FIG. 8B illustrates a cantilever of a probe assembly
lowering the probe tip to a surface of the sample.
[0045] FIG. 8C illustrates reactant deposited on the surface of the
sample after the probe is moved away from the surface.
[0046] FIG. 9A illustrates a probe tip coated with reactant that
has been dipped into a solvent liquid.
[0047] FIG. 9B illustrates a second droplet of reactant that occurs
when a coated probe tip reacts with a first droplet of the
reactant.
[0048] FIG. 10A illustrates a laser chemical machining system with
a probe assembly that includes channels in the probe assembly for
delivery of fluid to the surface of the sample.
[0049] FIG. 10B illustrates the delivery of the fluid from the
channel to the surface of the sample.
[0050] FIG. IOC illustrates an energy source activating the fluid
after it has been deposited on the surface of the sample.
[0051] FIG. 11A illustrates placing multiple droplets of reactant
on a sample surface.
[0052] FIG. 11B illustrates activation of multiple droplets of
reactant on the sample.
[0053] FIG. 11C illustrates a shape resulting from the placement
and activation of droplets on a sample surface.
DETAILED DESCRIPTION
[0054] The invention will now be described with reference to the
drawing figures, in which like reference numerals refer to like
parts throughout. An embodiment in accordance with the present
invention utilizes a small amount of a liquid such as a chemical or
a particle of solid material, which is referred to as a reactant to
modify a surface of an object. This droplet or particle is
typically placed on the sample by a probe with a small point.
[0055] An embodiment of the present inventive apparatus and method
is illustrated in FIG. IA, which shows a scanning probe microscope
probe assembly with an amount of subtractive reactant on the probe
tip above the surface of a target device. In this figure, a
scanning probe microscope probe assembly 10 includes a probe lever
12 and a probe tip 14. The scanning probe microscope probe assembly
10 is used, in the preferred embodiment, to precisely and
accurately place a reactant 16 on a target device surface 18. To do
this, the reactant 16, in this instance a subtractive or removal
reactant, is placed or located on the probe tip 14. Once it is
placed on the probe tip 14, the probe tip 14, with attached
reactant 16, is then moved into the desired location over and then
onto the device surface 18.
[0056] The probe tip 10 can be of the type used in a probe
microscope. The accurate positioning of such probes over and on the
sample can be achieved by use of a probe microscope device. In this
manner, the reactant 16 is placed on the target device surface 18
of the sample with a high degree of precision, such as to the
nanometer range, relative to the surface or surface features. The
reactant 16, in the preferred embodiment, can be in the size range
of from 1 square nanometer to 60 square nanometers or larger.
[0057] FIG. 1B shows a scanning probe microscope probe assembly 10
with an amount of reactant 16, subtractive, on the probe tip 14 in
proximity of the target device with the reactant wetting to the
surface of the target device surface 18. In the preferred
embodiment of the present invention, the reactant 16 is generally
in liquid form. Surface forces (i.e. surface tension and adhesion)
are relied upon to cause the reactant 16 to adhere to the probe tip
10 of a scanning force microscope while the reactant 16 is
transported to the target device surface 18 or substrate. When
reactant 16 is brought sufficiently close to surface 18 the
reactant 16 will transfer to the surface 18 via capillary action.
In this case, the tip material and the reactant 16 are selected
from a group of materials and reactants where the tip material is
at least partially hydrophilic to the reactant 16. In addition, in
this case, the substrate material may be hydrophilic to facilitate
transfer of the reactant 16 from the tip 14 to the substrate. The
selection of tip material and reactant 16 in this embodiment is
such that the tip 14 would resist chemical reaction with the
reactant 16. In subsequent embodiments the tip material and
reactant would be selected such that a mild or possibly strong
reaction between the tip 14 and reactant 16 occurs.
[0058] In an alternative embodiment of the present invention shown
in FIGS. 8 and 9, the probe tip 14 may contain the reactant or a
component of the reactant. This is accomplished by coating the tip
60 prior to use. In this case, the tip, most likely, becomes a
consumable in the process. Transfer of the reactant from the tip 60
is accomplished by touching the coated tip to the surface, see FIG.
8B, which positions the reactant 62 (part of the coating), see FIG.
8C. Transfer could also be accomplished by dipping the coated tip
into another component of the reactant or into a solvent to
dissolve part of the coating. This process would facilitate
transfer of the coated tip reactant 74 to the substrate surface.
Again, in these embodiments, electromagnetic (EM) energy is
directed at the material transferred to the substrate to change the
transferred material to its final desired form. For this
embodiment, it is possible that the tip itself could be fabricated
from the reactant material instead of applying a coating. Note that
FIGS. 8 and 9 are described in additional detail herein.
[0059] In an alternate embodiment of the present invention, the
transfer of reactant 16 to and from the tip may also be facilitated
by creating an electric charge on the probe tip 14 and/or the
substrate. In this embodiment, the reactant 16 is attracted by
electrostatic force to the substrate and a dissolved portion of the
sacrificial tip is transferred to the substrate along with the
reactant. In a subsequent step the EM energy is directed at the
transferred material and the transferred material changes to its
final state.
[0060] FIG. 1C shows the target device surface 18 with an amount of
subtractive reactant on the surface 18 with a light beam directed
toward the reactant. In the preferred embodiment, this light beam
includes an electromagnetic source 20 with an electromagnetic beam
22 emanating therefrom.
[0061] In order to remove debris that may be generated as the
result of activating reactant 16, a gaseous transport medium 23 may
be directed over sample surface 18. Alternately gaseous medium 23
may be used to activate reactant 16 with or without the use of
source 20.
[0062] According to the preferred embodiment of the present
invention, after placement of the reactant 16 on the device surface
18, electromagnetic energy (typically derived from a laser) is
directed towards the sample surface on which the reactant 16
resides. The electromagnetic energy level is set such that the
energy is sufficient to activate chemicals in the reactant 16
causing the chemical to etch the surface of the sample leaving a
dimple approximately the size of the droplet or particle. By
repeated applications of reactant 16 and electromagnetic energy,
the dimple can be deepened until a predetermined depth or a
detected depth is reached without significant enlargement of the
diameter or surface area of the dimple and thus create a high
aspect ratio hole. During an iterative process, it can be necessary
to re-register the tip relative to surface or surface features. For
example, it may be necessary to verify the depth of the removal
spot to reach a specific final depth. In this case, the tip may be
cleaned prior to verifying the position so that residual reactant
is not placed or located onto the surface. One method to clean
residual reactant from the tip is to dip the tip into a reactant
solvent that does not substantially affect the tip material.
[0063] FIG. 1D shows the target device surface 18 with a dimple 24
that is the result of activation of the subtractive reactant 16 on
the surface caused by the light beam 22. In this instance, the user
desired to remove material that inadvertently appeared or was
created during the manufacturing process. If the material was a
semiconductor device, this material could be an improper connection
that could render the device inoperable. In many instances, the
semiconductor device would have to be reconstructed. However, with
the present invention, very small or minute features on the
semiconductor device are able to be fixed. In many instances, the
features are so small that there is no other suitable way to remove
or reconstruct them. With the present invention, these features may
be corrected in a substantially more accurate way and in a fraction
of the time.
[0064] FIG. 2A shows a scanning probe microscope probe assembly 10
with an amount of additive reactant 26 on the probe tip 14 above
the surface of a target device surface 18. The process in creating
additional material on a target device material is similar to that
of removing material.
[0065] After the additive reactant 26 is on the probe tip 14, the
scanning probe microscope probe assembly 10 places or positions the
additive reactant 26 in proximity of the target device surface 18
with the reactant wetting to the surface of the target device
surface as in shown in FIG. 2B. The location to where the material
is added, in the preferred embodiment, is known previously to the
user. The user, upon desiring to add material to a surface, selects
the additive reactant in conjunction with the problem that they are
trying to solve. Upon selecting the additive reactant 26, the
scanning probe microscope assembly 10 removes it from one location
such as from a container to the target device surface 18 via the
probe tip 14. If the tip material partially reacts to the reactant
16, then the tip may also partially dissolve into the reactant
before the transfer of the reactant to the substrate occurs. A
portion of the tip, the sacrificial tip, may dissolve in the liquid
reactant such that the dissolved portion contributes to the build
up of residue 28.
[0066] FIG. 2C shows the target device surface 18 with an amount of
additive reactant 26 on the surface with the light beam directed
toward the reactant 26. Once the probe tip 14 places or positions
the additive reactant 26 on the target device surface 18, the
additive reactant 26 is subjected to the EM beam 18 from which it
begins to react and begin the formation of additive material on the
surface of the target device 18.
[0067] FIG. 2D shows the target device surface 18 with a protrusion
formed thereon. A bump of residue 28 is created from the activation
of the additive reactant 26 on the surface caused by the EM beam
22. Once the residue 28 is created, the technician can create or
add additional residue matter if needed or remove all or portions
of the residue 28 through the method described in FIGS. 1A-1D.
[0068] The droplet or particle leaves a residue 28 on the device
after being activated by the electromagnetic energy. This residue
28 may act as a conductor or as an insulator. If the device is a
photo-mask, the residue may act as an absorber of light.
[0069] The source EM beam 22 is typically a laser, a noncoherent
light source, or in an alternate embodiment high frequency radio
waves. A laser or electromagnetic source that is tunable over a
range of wavelengths is desirable in certain applications. With
such a laser, the wavelength is tuned to excite the reactant to a
state whereby it would etch or remove material of small areas on
the sample or excites the reactant to a state that would accelerate
the rate of material removal.
[0070] Two mechanisms are used to remove from or deposit material
on the device. The first, which is the preferred embodiment, is a
photo-thermal effect. In this mechanism, the reactant is excited by
EM energy to cause a thermal increase in the reactant. This thermal
increase can cause the reactant to etch more quickly. Alternately,
employing the photo-thermal effect, the reactant may change to a
solid residue that acts as a conductor, insulator, or as an opaque
layer. The level of the EM energy is selected to excite the
reactant to a level that increases the speed of the reactance
without melting the device material.
[0071] The composition of the reactant 16 may be chosen such that
it would enter a state of excitation sufficient to cause removal of
material from the device in a chosen location and would not affect
material surrounding that location.
[0072] Alternately, the composition of the reactant 26 would be
chosen to deposit a residue that exhibited the desired properties,
and again the excitation is selected to reduce the reactant 26 to
residue without causing a change in the device material.
[0073] In an alternative embodiment, the second mechanism to remove
or deposit material is accomplished through a photochemical effect.
In this mechanism, the reactant is excited in a manner that causes
it to change in chemical property or composition. In one example,
the reactant 16 may be changed by the energy source to an
alternative material that chemically reacts with the device
material. In another example, the reactant 26 can change forms, for
example, from liquid to solid, by activating a catalyst in the
reactant mixture that causes a chemical change of the reactant
material. In this manner, a conducting or insulating material may
be added to the device material. This compositional change may also
be accompanied by a change in optical transmission of the reactant
(e.g., from transparent to partially or completely opaque). Again,
the level of the EM energy and or the wavelength is selected to
excite the reactant to a level that induces chemical reaction
without directly affecting the device material. In the case where
the EM energy is light, a tunable laser or other source can be
employed. The wavelength of the tunable source can then be adjusted
to a wavelength that causes the reaction to proceed at an
acceptable rate.
[0074] By selecting different reactants, sample materials could be
removed without disturbing surrounding or underlying sample
materials of a different type. Additionally, the selection of
materials may be made such that certain types of layered samples
may have a layer that can be used to stop the etching process.
Thus, a so-called "etch stop" layer in the target device may be
part of the process. This layer is composed of a material that does
not react significantly to the etch solution or solid and therefore
allows a process whereby the etch material along with the
excitation energy reacts with the first layers encountered but the
etch process will cease or be substantially slowed when the etch
stop layer is reached.
[0075] Typical materials that may be used with the present
invention are as follows:
TABLE-US-00001 TIP SUBSTRATE MATERIALS MATERIALS REACTANTS Silicon
Silicon Potassium Hydroxide Silicon Dioxide Quartz Sodium Hydroxide
Silicon Nitride Silicon Dioxide Sulfuric Acid Carbon Aluminum
Hydrofluoric Acid Tantalum Nitride Aluminum Oxide Ferric Chloride
Silicon Carbide Zirconium Oxide Phosphoric Acid Tungsten Carbide
Molybdenum Silicide Sodium Nitrate Chromium Nitric Acid Tantalum
Nitride Perchloric Acid Silicon doped with group II or III elements
Silicon doped with group IV, V or VI elements Titanium Ceric
Amonium Nitrate Copper Sodium Chloride Iron, Steel Germanium
Potassium Sulfate Carbon Buffered Hydrofluoric Acid Combinations of
Hydrofloric Nitric, and Sulfuric Acids
[0076] These lists are not all-inclusive but are representative of
types of elements, oxides and metals for tips and substrates and
hydroxides, acids, and compounds for reactants.
[0077] One example of the present invention would be to remove
material from a surface of a device such as silicon. Reactants that
have been found to produce removal of silicon are potassium
hydroxide and sodium hydroxide. In the present invention, an amount
of the reactant, potassium hydroxide, is taken from a source by the
probe tip 14 of a scanning probe microscope assembly 10 and then
placed in the desired position. Once into position, the amount of
potassium hydroxide that is located on the surface is then
subjected to the EM energy, which in this example is a focused
argon ion laser with laser power of approximately 1.5 Watts. Once
subject to the EM laser, removal of the materials is substantially
constrained to the location of the potassium hydroxide by the probe
tip 14.
[0078] It has been found that sodium nitrate serves generally as an
effective removal reactant for metals. Phosphoric acid, sulfuric
acid and potassium hydroxide serve as an effective removal reactant
for stainless steel and titanium.
[0079] FIG. 3A shows a scanning probe microscope probe assembly 10
drawing an amount of reactant from a reactant pool 30, which is
held in a reactant container 32. FIG. 3B shows the probe tip 14
carrying an amount of reactant. Surface forces are used, in the
preferred embodiment, to cause reactant from the reactant container
32 to adhere to the probe tip 10 of a scanning force microscope
assembly 10 while the reactant 16 is transported to the target
device surface 18 or substrate. The tip material and the reactant
16 are selected from a group of materials and reactants where the
tip material is at least partially hydrophilic to the reactant.
Additionally, the substrate material may be hydrophilic to
facilitate transfer of the reactant from the tip to the
substrate.
[0080] Tip 14 can be coated with a hydrophobic insulator 33 and
still able to attract reactant 30. In this method, the tip 14 may
be charged opposite to a charge placed on reactant 30. When the
charge difference is sufficiently great, reactant 30 will be
attracted to tip 14 with sufficient force that cohesion and
gravitational forces are overcome. Reactant 30 may then be
transported to the sample 18. The insulator 33 prevents charge
dissipation between reactant 30 and tip 14. As the tip 14 is
brought close to sample 18, the charge difference between reactant
30 and sample 18 neutralizes and the hydrophobic nature of
insulator 33 drives reactant 30 towards the sample 18. The reactant
30, in this embodiment, may be either a solid or a liquid.
[0081] In an alternative embodiment, the tip 14 is coated with the
reactant or a component of the reactant 34 or is fabricated out of
reactant material. The reactant 34 can then be transferred to the
surface 35 by direct contact of the tip 14 to the device surface,
as shown in FIG. 8C. The tip 14 could also be placed into a liquid,
in a similar manner as described for transfer of a liquid reactant,
to complete the reactant mixture or aid in transfer of the
reactant. In this embodiment, a portion of the tip coating is
dissolved in the liquid, as shown in FIG. 9A and the resulting
reactant transferred to the substrate with the reactant 34. In this
embodiment, the tip would need to be replaced more frequently in
order to effectively transfer the reactant 34.
[0082] In an alternate embodiment of the present invention, the
transfer of reactant 16 to and from the tip may also be facilitated
by creating electric charge on the tip and/or the substrate. Also,
in this embodiment a portion of the sacrificial tip is transferred
to the substrate. Subsequently, the EM energy is directed at the
transferred material and the transferred material changes to its
final state.
[0083] FIG. 4A shows a scanning probe microscope assembly 10 with
the probe tip 14 depositing the subtractive reactant 36 onto a
surface. In this figure, the reactant 36 is being deposited into a
dimple 37 that was previously created with a previous application
of the reactant 34. FIG. 4A includes a targeted device 38 that
includes multiple layers of differing materials. These multiple
layers are first device layer 40 and second device layer 42.
[0084] The dimple in the material 37, shown in FIG. 4A could also
have been created by an alternative method, prior to using the
reactant process for additional material removal. For example, the
dimple 37 could have been created during the processes used to
create the device. The dimple 37 could also have been created with
the scanning probe tip 14 by direct tip to surface contact. Other
means of creating the dimple 37 or pit include the use of an ion
beam or laser beam. The predefined dimple could be used to help
guide the reactant to the ideal location during placement. The
location could also help constrain the reactant to the desired
location during the removal or additive process. In addition,
dimples predefined during fabrication of the device could have high
positional accuracy relative to other non-accessible structure in
the device.
[0085] The repeated application of the subtractive reactant 36 in
FIG. 4A is done to achieve a clear connection to device layer two
42. Due to the thickness of the first device layer 40, multiple
applications of the subtractive reactant 36 are needed to
accomplish this goal.
[0086] In similarity to the FIG. 1A-1D, once the subtractive
reactant 36 is positioned on the surface, which in this figure is
the dimple creation, the EM energy and the resulting beam 22 is
focused, as shown in FIG. 4B, at the subtractive reactant 36 in
order to remove additional material of the first device layer
40.
[0087] FIG. 4C shows the resulting void 44 created by the repeated
application of the subtractive reactant. Additionally, it is noted
that because of the differing materials in the device layers, the
second device layer 42 is a stop layer of material that is not
reactive to the etchant. In other words, the reactant chosen for
the first device layer 40 does not have the same effect of etching
or removing material on the second device layer 42.
[0088] FIG. 5A shows a scanning probe microscope assembly 10
positioning reactant into a surface dimple 48. In this embodiment,
the technician is attempting to create additional matter on a
surface that resulted from a previous application of subtractive
reactant 16.
[0089] FIG. 5A is the targeted device 38 as detailed in the FIGS.
4A-4C. As previously detailed, the target includes a first device
layer 40 and a second device layer 42. Having removed the material
as detailed in FIGS. 4A-4C, the technician now needs to complete
the connection.
[0090] FIG. 5B shows an electromagnetic source directing a beam 22
of energy towards the additive reactant 50. By subjecting the
additive reactant 50 to the beam 22, a more rapid chemical reaction
of the additive reactant 50 to the targeted surface is created.
[0091] FIG. 5C details the results of the beam on the additive
reactant 50. The beam has caused the reactant to create a residue
52 that partially fills the void 54. A layer of material is now
created by application of additive reactant 50 on top of a stop
layer 55 of material.
[0092] FIG. 5D shows the resulting filled void 54 created by
application of additive reactant 50. In this specific example, the
additive reactant 50 can create a connection to another objection
on the targeted device. For example, if the target device is a
semiconductor, the filling of the void 54 with the additive
reactant 50 could be the connection of one transistor to another
transistor.
[0093] As can be seen from the present invention, there are endless
amounts of repair or corrections that can be made to a device. To
create such a connection as that detailed in FIG. 5D, generally
would require the complete creation of a new device. With the
present invention, a company can reuse or edit the device by simply
modifying the surface with the techniques disclosed therein.
[0094] FIG. 6A illustrates a multi-layer device. In this figure,
there are four layers, a first device layer 40, a second device
layer 42, a third device layer 56 and a fourth device layer 58. The
four layers, 40, 42, 56, 58 are respectively silicon dioxide
(SiO.sub.2), silicon (Si), silicon dioxide (SiO.sub.2) and silicon
(Si).
[0095] FIG. 6B illustrates a hole 59 that has been created through
each of the first three layers 40, 42, 56. The hole 59, in this
figure, is shown filled with a nonconducting plug 60. To create a
path way through the first device layer 40, a reactant such as
buffered hydrofluoric acid is placed on the layer by the scanning
probe microscope assembly 10. Once positioned, a beam 22 is focused
at the reactant in order to create etching or removal of the
silicon dioxide material.
[0096] The buffered hydrofluoric acid reactant is not necessarily
effective on the second device layer 42, silicon. Therefore, this
layer acts as a stop layer and prevents the reactant from burrowing
or etching into the second device layer 42.
[0097] If the second device layer 42 acts as a stop layer, then
another reactant is chosen to continue the etching process through
the device. For the second device layer 42, which is Si, a reactant
that is effective at removing the materials is sodium hydroxide.
Like the first device layer 40, the reactant is subjected to a beam
22 to remove the material. This process is continued until the
necessary material is removed to reach the third device layer 56,
which is silicon dioxide. To remove the material of the third
device layer 56, the process, as in the first device layer 40, is
repeated with buffered hydrofluoric acid as the removal reactant
for the silicon dioxide.
[0098] Once the necessary material is removed through all the
layers, a reactant is added in order to create a nonconductive
residue 60. The nonconducting plug 60 in FIG. 6B is created in
order to make an insulator for a subsequently created conducting
plug.
[0099] FIG. 6C shows the next step in which the nonconducting plug
60 further has a hole opened creating a path to the fourth device
layer 58. As is seen in this figure, layer 42 is now insulated from
layer 58.
[0100] FIG. 6D shows that the hole created in the insulator 60 in
filled with a conductive residue 61. The device to create residue
is similar to that detailed in relation to FIGS. 5A-5D. The
connection, in this figure, makes a direct connection from the
fourth device layer 58, silicon, up through the third device layer
52, second device layer two 42 and device layer one 40. The residue
61 is then located across the upper surface of the first device
layer one 40 and onto their intended connections.
[0101] FIG. 7 shows that an opposite charge may be placed on the
tip 14 and reactant 26 and substrate 18. This causes reactant 26 to
be attracted to substrate 18. After placement of charge on tip 14
and sample 18, probe 10 with reactant 26 is moved toward sample 18.
When the distance between reactant 26 and sample 18 is sufficiently
small coulomb forces will become greater than the surface forces
holding reactant 26 to tip 14. At this distance reactant 26 will
separate from tip 14 and move to sample 18.
[0102] FIG. 8A illustrates a reactive coating 62 on the probe tip
14, which is part of probe assembly 10. This figure depicts the
probe assembly 10 before it is brought to sample surface 18.
[0103] FIG. 8B illustrates the probe tip 14 with reactive coating
62. Additionally, this figure depicts the cantilever 10 lowering
the tip 14 to the sample surface 18.
[0104] FIG. 8C illustrates the instance when the probe tip 14 is
raised from sample surface 18. As the figure depicts, once the
probe tip 15 is removed an amount coating 63 remains on surface 18.
This remnant of coating 63 becomes the reactant that is
subsequently activated.
[0105] FIG. 9A illustrates the coated tip 14 that further includes
a small amount or droplet of reactant 16. In this embodiment, the
reactant 16 has reacted with the coating 62 to form a second
reactant 64 as shown in FIG. 9B This mixture occurs as the droplet
is transported from the source of reactant to the surface.
[0106] During the transportation of the reactant, this second
reactant, in most instances, contains dissolved parts of coating
62. Once transported to the desired area, the second reactant 64 is
placed or located on the sample surface 18.
[0107] FIG. 10A shows a probe assembly 65 including a cantilever 66
and a tip 68 in which the cantilever 66 and tip 68 have an interior
channel 70. The interior channel 66 is depicted in this figure as
dashed lines.
[0108] The channel 70 delivers a fluid reactant 72 as indicated in
FIG. 10B through the channel 70 to tip 68 in preparation for
delivery of fluid reactant 72 to sample surface 18. As shown in
FIG. 10C, the laser 20 activates the drop of fluid reactant 72
after the reactant 72 is placed on sample surface 18. Depending on
the type of reactant 72 selected, a portion of sample 18 is removed
or a residue on sample 18 will remain as depicted and described in
FIGS. IA-1D and 2A-2D.
[0109] FIG. 11A is a top view of a substrate. This figure
illustrates how specific shapes are created in accordance with an
embodiment of the present invention. More specifically, this figure
shows the creation of an approximate square void in the surface of
sample 18. A number of droplets of reactant 16 are placed on the
sample 18 by means of a tip (not shown). Electromagnetic source 20,
as detailed in FIG. 11B, may activate the droplets one at a time or
all together if the diameter of beam 22 is large enough to
encompass all the droplets. If reactant droplets 16 have the
sufficient viscosity then surface forces will be insufficient to
pull them together and they may all be placed on sample 18.
Reactant droplets 16 may then be activated all at once by laser
beam 22. Again, if reactant 16 has viscosity, then instead of
placing reactant 16 in the form of droplets reactant 18 may be
drawn into lines of various shapes. Such repeated applications of
reactant 16 as described here along with repeated applications of
beam 22 will create a void shape 74, as detailed in FIG. 11C, with
high aspect ratio walls of arbitrary depth in sample 18.
[0110] As can be seen, a wide variety of simple approximate shapes,
such as rectangles can be created. The creation of more complex
shapes may also be created using combinations of large and small
rectangles, squares, circles and lines. Complex shapes may also be
created in the depth as well as in the lateral dimensions. By
extension, complex additive shapes may be created in elevation as
well as laterally by the use of the additive reactants previous
described. Also, by extension an array of approximately circular
holes or shapes located with precision relative to each other or
with precision relative to other features on sample 18 may be
created. Again, the reactant creating the array may be activated at
single locations sequentially or if the focused light spot is made
large enough, the reactant may be activated in multiple locations
simultaneously.
[0111] The many features and advantages of the invention are
apparent from the detailed specification, and thus, it is intended
by the appended claims to cover all such features and advantages of
the invention, which fall within the true spirit, and scope of the
invention. Further, since numerous modifications and variations
will readily occur to those skilled in the art, it is not desired
to limit the invention to the exact construction and operation
illustrated and described, and accordingly, all suitable
modifications and equivalents may be resorted to, falling within
the scope of the invention.
* * * * *