U.S. patent application number 13/565018 was filed with the patent office on 2012-11-22 for dislocation engineering using a scanned laser.
This patent application is currently assigned to INTERNATIONAL BUSINESS MACHINES CORPORATION. Invention is credited to Chung Woh Lai, Xiao Hu Liu, Anita Madan, Klaus W. Schwarz, J. Campbell Scott.
Application Number | 20120294322 13/565018 |
Document ID | / |
Family ID | 41134607 |
Filed Date | 2012-11-22 |
United States Patent
Application |
20120294322 |
Kind Code |
A1 |
Lai; Chung Woh ; et
al. |
November 22, 2012 |
Dislocation Engineering Using a Scanned Laser
Abstract
A system for manipulating dislocations on semiconductor devices,
includes a moveable laser configured to generate a laser beam
locally on a surface portion of the semiconductor body having a
plurality of dislocations, the moveable laser being characterized
as having a scan speed, the moveable laser manipulates the
plurality of dislocations on the surface portion of the
semiconductor body by adjusting the temperature and the scan speed
of the laser beam.
Inventors: |
Lai; Chung Woh; (Singapore,
SG) ; Liu; Xiao Hu; (Briarcliff Manor, NY) ;
Madan; Anita; (Danbury, CT) ; Schwarz; Klaus W.;
(Somers, NY) ; Scott; J. Campbell; (Los Gatos,
CA) |
Assignee: |
INTERNATIONAL BUSINESS MACHINES
CORPORATION
Armonk
NY
|
Family ID: |
41134607 |
Appl. No.: |
13/565018 |
Filed: |
August 2, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13372713 |
Feb 14, 2012 |
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13565018 |
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12242990 |
Oct 1, 2008 |
8138066 |
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13372713 |
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Current U.S.
Class: |
372/24 |
Current CPC
Class: |
H01L 21/3226 20130101;
H01L 21/3221 20130101; H01L 29/1054 20130101; H01L 29/7842
20130101; H01L 21/2686 20130101; H01L 21/268 20130101 |
Class at
Publication: |
372/24 |
International
Class: |
H01S 3/10 20060101
H01S003/10 |
Claims
1. A system for manipulating dislocations on semiconductor devices,
comprising: a moveable laser configured to generate a laser beam
locally on a surface portion of the semiconductor body having a
plurality of dislocations, the moveable laser being characterized
as having a scan speed, the moveable laser manipulates the
plurality of dislocations on the surface portion of the
semiconductor body by adjusting the temperature and the scan speed
of the laser beam.
2. The system as in claim 1, wherein the moveable laser is
operative to manipulate the plurality of dislocations by scanning
across the plurality of dislocations with the laser beam such that
the plurality of dislocations grow over the length of the scan of
the laser beam enabling the removal of threading dislocations from
a relaxed layer on the semiconductor device.
3. The system as in claim 2, wherein the system is operative to
affect plurality of dislocations that grow over the length of the
scan of the laser beam when the scan speed of the laser beam is
approximately greater than 1250 degrees Centigrade and the scan
speed of the laser beam is greater than approximately 1
millisecond.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This is a divisional application of application Ser. No.
13/372,713, filed Feb. 14, 2012, which is a divisional application
of application Ser. No. 12/242,990, filed Oct. 1, 2008.
BACKGROUND
[0002] This invention relates to a system and method for
manipulating dislocations in semiconductor devices using a scanned
laser.
[0003] Currently, 65 nanometer (nm) technology and beyond makes
extensive use of strain engineering to optimize device performance.
The appearance and uncontrolled behavior of dislocations in this
context is a frequent source of problems, since these defects
provide electrical leakage paths and also lead to undesired local
strain variations. At the same time, the deliberate relaxation of
strained layers by dislocation motion is a common technique of
preparing substrates on which strained layers can be grown.
[0004] An economic determinant of integrated circuit process
technology is the yield, that is, the percentage of the total
number of chips processed that are good. The yield of complex
integrated circuits is typically a few percent. One major factor
that affects this yield is the presence of crystal defects in
silicon, or in other semiconductor wafers on which integrated
circuits are built. Some of these crystal defects can be classified
as dislocations, which can be introduced in high temperature
processing when large strains are present.
BRIEF SUMMARY
[0005] An exemplary embodiment of a method for generating patterned
strained regions in a semiconductor device includes directing a
light-emitting beam locally onto a surface portion of a
semiconductor body; and manipulating a plurality of dislocations
located proximate to the surface portion of the semiconductor body
utilizing the light-emitting beam, the light-emitting beam being
characterized as having a scan speed, so as to produce the
patterned strained regions.
[0006] An exemplary embodiment of a method for generating patterned
strained regions in a semiconductor device includes directing a
laser beam locally onto a surface portion of a semiconductor body;
operating the laser beam in a first mode of operation or a second
mode of operation, the laser beam being characterized as having a
scan speed; and manipulating a plurality of dislocations located
proximate to the surface portion of the semiconductor body
utilizing the laser beam so as to produce the patterned strained
regions, the plurality of dislocations being manipulated during the
first mode of operation and the second mode of operation.
[0007] An exemplary embodiment of a system for manipulating
dislocations on semiconductor devices includes a semiconductor body
having a plurality of dislocations; and a moveable laser configured
to generate a laser beam locally on a surface portion of the
semiconductor body, the moveable laser being characterized as
having a scan speed, the moveable laser manipulates the plurality
of dislocations proximate to the surface portion of the
semiconductor body by adjusting the temperature and the scan speed
of the laser beam.
[0008] The subject matter which is regarded as the invention is
particularly pointed out and distinctly claimed in the claims at
the conclusion of the specification. The foregoing and other
objects, features, and advantages of the invention are apparent
from the following detailed description taken in conjunction with
the accompanying drawings in which:
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0009] FIGS. 1-3 are various schematic cross sectional views of an
exemplary semiconductor device subjected to a blow-down technique
for manipulating substrate dislocations, in accordance with one
exemplary embodiment of the present invention;
[0010] FIG. 4 illustrates an exemplary microphotograph of a portion
of a cross-sectional side view of a wafer exhibiting the blow-down
phenomena in accordance with one exemplary embodiment of the
present invention;
[0011] FIGS. 5A and 5B are cross sectional views of an exemplary
semiconductor device subjected to a surfing technique for
manipulating substrate dislocations, in accordance with another
exemplary embodiment of the present invention;
[0012] FIG. 6 is a cross-sectional view of an exemplary
semiconductor device subjected to the surfing technique for
manipulating substrate dislocations to allow the generation of
uniaxial strained regions, in accordance with one exemplary
embodiment of the present invention; and
[0013] FIG. 7 is a cross-sectional view of an exemplary
semiconductor device subjected to the surfing technique to remove
threading dislocations from a relaxed strained layer, in accordance
with one exemplary embodiment of the present invention.
[0014] The detailed description explains the preferred embodiments
of the invention, together with advantages and features, by way of
example with reference to the drawings.
DETAILED DESCRIPTION
[0015] The present invention and the various features and
advantageous details thereof are explained more fully with
reference to the non-limiting embodiments that are illustrated in
the accompanying drawings and detailed in the following
description. It should be noted that the features illustrated in
the drawings are not necessarily drawn to scale. Descriptions of
well-known or conventional components and processing techniques are
omitted so as to not unnecessarily obscure the present invention in
detail. The examples used herein are intended merely to facilitate
an understanding of ways in which the invention may be practiced
and to further enable those of skill in the art to practice the
invention. Accordingly, the examples should not be construed as
limiting the scope of the invention.
[0016] Exemplary embodiments of the present invention provide
systems and methods for manipulating dislocations in various
semiconductor technologies by a light-emitting beam (e.g., laser
beam). Dislocations subject to the beam will move where the beam is
incident, allowing both temporal and spatial control of dislocation
evolution. Such systems and methods provide modes of operation that
illustrate two phenomena referred to herein as the blow-down and
surfing phenomena. These phenomena can be utilized to perform
various dislocation manipulations.
[0017] The inventors herein have recognized that the systems and
methods described herein eliminate dislocations present in silicon
on insulator (SOI) technology devices. The systems and methods
described herein further control dislocation growth during
high-temperature laser annealing (LSA) and enable localized
(patterned) relaxation of layer strain. The systems and methods
described herein further enable the generation of uniaxially
strained regions and enable the elimination of threading
dislocations in a relaxed strained layer. Such systems and methods
further enable the generation of specific dislocation patterns and
their associated strain fields for use as templates for the
spatially controlled grow of epitaxial islands and
nanostructures.
[0018] For a better understanding of the invention and its
operation, turning now to the drawings, FIG. 1 illustrates a
portion of a semiconductor body or wafer, designated generally by
10. In accordance with one exemplary embodiment, the wafer is made
up of silicon. Of course, other suitable materials can be used to
form the wafer such as germanium, gallium phosphate, gallium
arsenide or the like. The wafer 10 sits on an insulating layer, for
example a buried oxide surface layer, which is indicated as lying
below the dashed line 12. The semiconductor body 10 is fabricated
to include active regions 14 where current flows and where
semiconductor devices, such as transistors integrated circuits or
the like, are to be formed. The wafer configuration can be varied
to achieve various goals and should not be limited to the
configurations shown herein. In other words, the configurations
described herein are intended to illustrate the methods for
manipulating dislocations on semiconductor technology and
semiconductor substrates, thereby should not limit the scope of the
exemplary embodiments of the present invention.
[0019] In accordance with one exemplary embodiment, a moving
light-emitting beam, which is indicated by arrow 16, directly scans
over a surface portion of the wafer 10, and particularly over the
active regions 14 configured on the wafer 10. More specifically,
the light-emitting beam 16 heats the wafer 10 locally allowing
dislocations present on the wafer 10 and most importantly on the
active regions 14 to move by increasing their mobility.
Dislocations move due to pre-existing strains (e.g., SiGe on Si
wafers) and because the beam producing source (e.g., laser) itself
generates a large stress field moving along with the beam. As the
dislocations are driven into the buried-oxide layer and the
shallow-trench oxide, this effectively eliminates undesirable
electrical leakage paths from forming.
[0020] The light-emitting beam can be generated through any
source-type, such as a laser, configured to vary the temperature,
the sweep speed, the absorption profile, and the spot-size of the
beam. However, other beams from other sources may be used such as,
for example, a lamp. For simplistic purposes, the methods herein
will be described in the context of using a laser beam from a
scanned laser device. Such a device is used in a scanned
laser-annealing (LSA) configuration to move the dislocations as
described herein. However, other configurations can be used in
other exemplary embodiments of the present invention and should not
be limited to the examples set forth herein.
[0021] In accordance with one exemplary embodiment, the laser beam
16 is controlled such that two distinct modes of operation for
manipulating dislocations can be implemented. The first mode of
operation is referred to herein as a "blow-down". In this mode of
operation, stress from the laser beam 16 drives dislocations into
the substrate or into absorbing sinks such as buried oxide (BOX)
layers 18 or into shallow trench isolation (STI) structures 19 as
shown in FIG. 1. This mode of operation enables the elimination of
already present dislocations in the wafer 10.
[0022] A better illustration of how the blow-down technique
manipulates dislocations on semiconductor devices is shown in FIG.
2. A pre-existing dislocation or dislocation loop, generally
designated by 20, below a wafer surface 22 is subjected to a laser
beam 24 having a scan direction indicated by arrows 26. The laser
beam 24 locally heats the region below the wafer surface 22. As a
result, the dislocation 20 grows or increases in size while in the
hot spot of the laser beam 24 as shown. The dislocation 20 moves
where the beam is incident. The dislocation motion is indicated by
arrows 28. The blow-down phenomenon occurs by itself when the
maximum velocity reached by the dislocation 20 is less than the
scan speed of the laser beam 24 as illustrated in FIG. 2. The
dislocation 20 grows to the micron scale, but stops growing once
the laser beam 24 passes the dislocation 20 as illustrated in FIGS.
3A and 3B. FIG. 3A illustrates the dislocation 20 before the laser
beam 24 passes through it while FIG. 3B illustrates the dislocation
20 after the laser beam 24 passes through it. Although the
blow-down effect is described using an LSA configuration, the
blow-down effect may also occur using a flash annealing
configuration.
[0023] FIG. 4 illustrates a portion of a cross-sectional side view
of wafer 10 in a magnified form. This exemplary figure shows the
blow-down phenomena obtained by direct transmission electron
microscopy (TEM) observations. Of course, other tools and methods
of viewing the blow-down phenomena can be used as desired. This
exemplary figure shows dislocations 20 blown down and away from the
active region 14 by a 1250-Centigrade (C) laser scan.
[0024] FIG. 5A-5B illustrates a second mode of operation in
accordance with one exemplary embodiment. The second mode of
operation is referred to herein as "surfing". Using the previous
example to describe this mode of operation, surfing occurs when the
temperature of the local hot spot of the laser beam 24 is placed
high enough and the combination of laser stress and pre-existing
layer strains is large enough to allow the dislocation 20 to grow
with a speed that matches the speed of the laser beam 24. In other
words, surfing occurs when the maximum value reached by the
dislocation velocity equals or exceeds the scan speed of the laser
beam. In this mode of operation, the laser beam 24 is controlled
such that one end of the dislocation 20 keeps up with the moving
hot spot of the laser beam 24, resulting in dislocation growth over
the length of the laser scan. FIG. 5A illustrates the dislocation
before the hot spot of the laser beam passes through the
dislocation while FIG. 5B illustrates the dislocation after the hot
spot of the laser beam passes the dislocation. As shown, one end of
the dislocation 20 moves with and in the scan direction 26 of the
laser beam 24. Surfing occurs only in an LSA configuration in
accordance with one embodiment.
[0025] In accordance with one exemplary embodiment, surfing can be
used to generate desired dislocation patterns or relax specific
regions of a strained-engineering pattern by moving dislocations
from a dislocation source into other areas. In other words, the
laser beam can be used to draw out dislocations from any point on a
layer along various paths as desired in an "etch-a-sketch"
fashion.
[0026] In accordance with one exemplary embodiment, the temperature
and dwell time (laser spot thickness/LSA scan speed) of the laser
beam play a role in manipulating dislocations of various sizes in
semiconductor technology. Dislocations become more active at higher
temperatures and depending on the desired mode of operation the
scan speed of the laser beam will determine whether dislocations
will grow over the length of the scan. In accordance with one
exemplary embodiment, surfing-type growth generally occurs when the
temperature of the laser beam is approximately above 1250 C and the
scan speed is greater than about 1 millisecond (ms). At
significantly lower temperatures or lower dwell times, surfing
should not occur. For example, surfing does not occur on a 40
nano-micron (nm) dislocation loop when scanning a laser beam with a
1498 Kelvin (K) scan, while surfing occurs with a 1624 K scan.
Thus, the temperature and scan speed can be adjusted to avoid
dragging dislocations from one part of the wafer to another. It
should be understood that different wafer materials may affect the
temperatures and dwell times needed to move dislocations from
semiconductor technology or into the same depending on the
application.
[0027] The direction of the laser scan can also play a role in
separately manipulating dislocations of various kinds in
semiconductor technology in accordance with one exemplary
embodiment. Dislocations move only on specific glide planes. Thus,
dislocations on glide planes oriented perpendicular to the scan
direction of the laser beam will not exhibit the surfing phenomena.
Only dislocations on glide planes oriented along the scan direction
are subject to the surfing phenomenon. Thus, the laser beam can be
controlled so that only dislocations on glide planes oriented in
one direction can be manipulated to obtain a desired dislocation
pattern or a desired degree of asymmetric relaxation. However, all
dislocations will exhibit the blow-up phenomena in some degree when
the laser passes the dislocations.
[0028] Dislocations on the wafer 10 can also be manipulated by
adding a strained layer to the wafer 10 in accordance with one
exemplary embodiment. Since dislocations move in response to strain
(thermal-mismatch), adding additional strain to existing
dislocations on the wafer 10 will enable the dislocations to move
more quickly. For example, surfing may occur when adding a 50 nm,
1% strained layer on a wafer subjected to a 1498 K laser scan.
[0029] Using different strain-inducing materials can also be used
to manipulate dislocations since dislocations respond differently
with different strain-inducing materials. In other words,
dislocations move better with some materials and not with others.
For example, surfing may not occur on dislocations in the 1498K
scan with the strained layer as described above when the mobility
of the dislocations is reduced by, for example, a factor of
three.
[0030] In accordance with one exemplary embodiment of the present
invention, the methods described herein can be used to manipulate
dislocations such that uniaxial layer relaxation or strain
generation is provided. FIG. 6 illustrates how to provide uniaxial
layer relaxation or strain generation. In this exemplary figure,
the wafer 10 is fabricated to include an implanted region 50 and a
non-implanted region 52. In accordance with one embodiment, a
raster scan generator raster scans from the implanted region
containing dislocations into the non-implanted region, filling the
latter with oriented dislocations. In operation, the implanted
region is subjected to the laser beam 16 such that strain in the
non-implanted region 52 is relaxed in one direction, thereby
leaving strain only in one direction. Such a configuration can be
useful for various applications.
[0031] In accordance with one exemplary embodiment, the surfing
technique can be used to also remove threading dislocations from a
relaxed strained layer as illustrated in FIG. 7. Here, any
threading dislocations (i.e. ones that extend to the surface) can
be swept out of the region of interest by rastering a laser beam
operating in the surfing mode. This removes potential sources of
leakage paths from the region of the wafer on which microelectronic
devices are to be constructed.
[0032] In the above embodiment, varying the temperature, the sweep
speed, the absorption profile, and the spot-size of the laser beam
24 effectively varies the dislocation evolution. Various modeling
techniques can be used to predict the phenomena described above and
can be validated through direct experimental observations.
[0033] While the preferred embodiment to the invention has been
described, it will be understood that those skilled in the art,
both now and in the future, may make various improvements and
enhancements which fall within the scope of the claims which
follow. These claims should be construed to maintain the proper
protection for the invention first described.
* * * * *