Title: Method of measuring implant profiles using scatterometric techniques
Abstract: The present invention is directed to several inventive methods for characterizing implant profiles. In one embodiment, the method comprises forming a first plurality of implant regions in a substrate, and illuminating the implant regions with a light source in a scatterometry tool, the scatterometry tool generating a trace profile corresponding to an implant profile of the illuminated implant regions. In another embodiment, the method comprises measuring profiles of implant regions by forming a plurality of implant regions in a substrate, illuminating the implant regions, measuring light reflected off the substrate to generate a profile trace for the implant regions, comparing the generated profile trace to a target profile trace from a library, and modifying, based upon a deviation between the generated profile trace and the target profile trace, at least one parameter of an ion implant process used to form implant regions on subsequently processed substrates. In yet another embodiment, the generated profile trace is compared or correlated to at least one of a plurality of calculated profile traces stored in a library, each of which has an associated implant region profile, and modifying, based upon the comparison of the generated profile trace and the calculated profile trace, at least one parameter of an ion implant process used to form implant regions on subsequently processed substrates.
Patent Number: 6,989,900 Issued on 01/24/2006 to Stirton
| Inventors:
|
Stirton; James Broc (Austin, TX)
|
| Assignee:
|
Advanced Micro Devices, Inc. (Austin, TX)
|
| Appl. No.:
|
824156 |
| Filed:
|
April 2, 2001 |
| Current U.S. Class: |
356/445; 356/448 |
| Current Intern'l Class: |
G01N 21/47 (20060101) |
| Field of Search: |
356/445,446,447,448
438/14,15,16
|
References Cited [Referenced By]
U.S. Patent Documents
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| 6051348 | Apr., 2000 | Marinaro et al.
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| 6078681 | Jun., 2000 | Silver.
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| 6081334 | Jun., 2000 | Grimbergen et al.
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| 6101971 | Aug., 2000 | Denholm et al.
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| 6141103 | Oct., 2000 | Pinaton et al.
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| 6151119 | Nov., 2000 | Campion et al.
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| 6245584 | Jun., 2001 | Marinaro et al.
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| 6259521 | Jul., 2001 | Miller et al.
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| 6271545 | Aug., 2001 | Schulze.
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| 6271921 | Aug., 2001 | Maris et al.
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| 6274449 | Aug., 2001 | Vasanth et al.
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| 6433878 | Aug., 2002 | Niu et al.
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| 2002/0135781 | Sep., 2002 | Singh et al.
| |
Primary Examiner: Lauchman; Layla G.
Assistant Examiner: Valentin, II; Juan D.
Attorney, Agent or Firm: Williams, Morgan & Amerson, P.C.
Claims
What is claimed is:
1. A method, comprising:
providing a semiconducting substrate;
forming a first plurality of implant regions in said substrate;
illuminating said first plurality of implant regions with a light source in a
scatterometry tool, said scatterometry tool generating a trace profile corresponding
to an implant profile of said illuminated implant regions; and
creating a library comprised of a plurality of calculated trace profiles of implant
regions having varying implant profiles.
2. The method of claim 1, further comprising generating an additional trace profile
for an additional plurality of implant regions formed in said substrate or additional
substrates, said additional plurality of implant regions having an implant profile
different from said first plurality of implant regions.
3. The method of claim 1, wherein forming a first plurality of implant regions
in said substrate comprises forming a first plurality of implant regions to thereby
define a grating structure in said substrate.
4. The method of claim 1, wherein said first plurality of implant regions are
comprised of N-type dopant material or P-type dopant material.
5. The method of claim 1, wherein said first plurality of implant regions are
illuminated using at least one of a multiple wavelength light source and a single
wavelength light source.
6. The method of claim 1, wherein said implant profile is comprised of at least
one of a width, a depth, a dopant concentration level, and a dopant concentration
profile of said implant regions.
7. A method of measuring profiles of implant regions formed in a semiconducting
substrate, comprising:
forming a plurality of implant regions in a semiconducting substrate;
illuminating said plurality of implant regions;
measuring light reflected off the substrate to generate a profile trace for said
implant regions;
comparing the generated profile trace to a target profile trace; and
modifying, based upon a deviation between the generated profile trace and the
target profile trace, at least one parameter of an ion implant process used to
form implant regions on subsequently processed substrates.
8. The method of claim 7, further comprising correlating the generated profile
trace to a profile trace from a library, the profile trace from the library having
an associated implant region profile.
9. The method of claim 8, further comprising modifying, based upon a deviation
between the generated profile trace and a profile trace from the library, at least
one parameter of an ion implant process used to form implant regions on subsequently
processed substrates.
10. The method of claim 7, wherein measuring the reflected light comprises measuring
the intensity of the reflected light.
11. The method of claim 7, further comprising providing a library of calculated
profile traces, each of which correspond to a unique profile of an implanted region.
12. The method of claim 7, wherein measuring light reflected off the substrate
to generate a profile trace for said implant regions is performed prior to the
implanted regions being subjected to an anneal process or a diffusion process.
13. The method of claim 7, wherein measuring light reflected off the substrate
to generate a profile trace for said implant regions is performed after the implanted
regions have been subjected to an anneal process or a diffusion process.
14. The method of claim 7, wherein modifying at least one parameter of an ion
implant process comprises modifying at least one of an implant energy, an implant
angle, a dopant material, and a dopant material concentration.
15. A method of measuring profiles of implant regions formed in a semiconducting
substrate, comprising:
forming a plurality of implant regions in a semiconducting substrate;
illuminating said plurality of implant regions;
measuring light reflected off the substrate to generate a profile trace for said
implant regions;
comparing the generated profile trace to a calculated profile trace in a library,
the calculated profile trace having an associated implant region profile; and
modifying, based upon said comparison of the generated profile trace and the
calculated profile trace, at least one parameter of an ion implant process used
to form implant regions on subsequently processed substrates.
16. The method of claim 15, further comprising comparing the generated profile
trace to a target profile trace from said library.
17. The method of claim 16, further comprising modifying, based upon a comparison
of the generated profile trace and the target profile trace, at least one parameter
of an ion implant process used to form implant regions on subsequently processed substrates.
18. The method of claim 15, wherein measuring the reflected light comprises measuring
the intensity of the reflected light.
19. The method of claim 15, further comprising providing a library of calculated
profile traces in a library, each of which correspond to a unique profile of an
implanted region.
20. The method of claim 15, wherein measuring light reflected off the substrate
to generate a profile trace for said implant regions is performed prior to the
implanted regions being subjected to an anneal process or a diffusion process.
21. The method of claim 15, wherein measuring light reflected off the substrate
to generate a profile trace for said implant regions is performed after the implanted
regions have been subjected to an anneal process or a diffusion process.
22. The method of claim 15, wherein modifying at least one parameter of an ion
implant process comprises modifying at least one of an implant energy, an implant
angle, a dopant material, and a dopant material concentration.
23. A method of measuring profiles of implant regions formed in a semiconducting
substrate, comprising:
forming a plurality of implant regions in a semiconducting substrate;
illuminating said plurality of implant regions;
measuring light reflected off the substrate to generate a profile trace for said
implant regions;
providing a library comprised of a plurality of calculated profile traces, each
of which correspond to a unique profile of an implanted region;
comparing the generated profile trace to at least one of said calculated profile
traces from said library; and
modifying, based upon said comparison of the generated profile trace and the
calculated profile trace, at least one parameter of an ion implant process used
to form implant regions on subsequently processed substrates.
24. The method of claim 23, further comprising comparing the generated profile
trace to a target profile trace.
25. The method of claim 24, further comprising modifying, based upon a deviation
between the generated profile trace and the target profile trace, at least one
parameter of an ion implant process used to form implant regions on subsequently
processed substrates.
26. The method of claim 23, wherein measuring the reflected light comprises measuring
the intensity of the reflected light.
27. The method of claim 23, wherein measuring light reflected off the substrate
to generate a profile trace for said implant regions is performed prior to the
implanted regions being subjected to an anneal process or a diffusion process.
28. The method of claim 23, wherein measuring light reflected off the substrate
to generate a profile trace for said implant regions is performed after the implanted
regions have been subjected to an anneal process or a diffusion process.
29. The method of claim 23, wherein modifying at least one parameter of an ion
implant process comprises modifying at least one of an implant energy, an implant
angle, a dopant material and a dopant material concentration.
30. A method of measuring profiles of implant regions formed in a semiconducting
substrate, comprising;
forming a plurality of implant regions in a semiconducting substrate;
illuminating said plurality of implant regions;
measuring light reflected off the substrate to generate a profile trace for said
implant regions;
comparing the generated profile trace to a target profile trace; and
modifying, based upon a deviation between the generated profile trace and the
target profile trace, at least one parameter of an ion implant process used to
form implant regions on subsequently processed substrates, said at least one parameter
comprised of at least one of an implant energy, an implant angle, a dopant material,
and a dopant material concentration.
31. The method of claim 30, further comprising comparing the generated profile
trace to a calculated profile trace in a library, the calculated profile trace
having an associated implant region profile.
32. The method of claim 31, further comprising modifying, based upon said comparison
of the generated profile trace and the calculated profile trace, at least one parameter
of an ion implant process used to form implant regions on subsequently processed substrates.
33. The method of claim 30, wherein measuring the reflected light comprises measuring
the intensity of the reflected light.
34. The method of claim 30, further comprising providing a library of historical
profile traces, each of which correspond to a unique profile of an implanted region.
35. The method of claim 30, wherein measuring light reflected off the substrate
to generate a profile trace for said implant regions is performed prior to the
implanted regions being subjected to an anneal process or a diffusion process.
36. The method of claim 30, wherein measuring light reflected off the substrate
to generate a profile trace for said implant regions is performed after the implanted
regions have been subjected to an anneal process or a diffusion process.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention is generally directed to the field of semiconductor processing,
and, more particularly, to a method of measuring dopant implant profiles using
scatterometric techniques.
2. Description of the Related Art
There is a constant drive within the semiconductor industry to increase the
operating speed of integrated circuit devices, e.g., microprocessors, memory devices,
and the like. This drive is fueled by consumer demands for computers and electronic
devices that operate at increasingly greater speeds. This demand for increased
speed has resulted in a continual reduction in the size of semiconductor devices,
e.g., transistors. That is, many components of a typical field effect transistor
(FET), e.g., channel length, junction depths, gate insulation thickness, and the
like, are reduced. For example, all other things being equal, the smaller the channel
length of the transistor, the faster the transistor will operate. Thus, there is
a constant drive to reduce the size, or scale, of the components of a typical transistor
to increase the overall speed of the transistor, as well as integrated circuit
devices incorporating such transistors.
During the course of manufacturing integrated circuit devices, a variety of
doped regions may be formed in a semiconducting substrate. Typically, these doped
regions are formed by performing an ion implant process wherein a dopant material,
e.g., arsenic, phosphorous, boron, boron difluoride, etc., is implanted into localized
areas of the substrate. For example, for CMOS technology, various doped regions,
sometimes referred to as wells, are formed in the substrate. The wells may be formed
using either N-type or P-type dopant atoms. After the wells are formed, semiconductor
devices, e.g., transistors, may be formed in the region defined by the well. Of
course, other types of doped regions may also be formed in modern semiconductor
manufacturing operations.
As modern device dimensions continue to shrink, the implant profiles of the various
doped regions become very important. That is, as device dimensions shrink, parameters
of the doped region, such as depth, width, dopant concentration profile, etc.,
become more important. Small variations in one or more of these parameters may
adversely affect device performance. For example, if well implants in a given device
are formed too shallow or not formed deep enough, the devices formed in the wells
may exhibit excessive leakage currents.
Various parameters reflecting the profile of implanted regions, e.g., depth,
have heretofore been determined by performing a number of calculations. These calculations
are typically based upon the implant energy, the type of dopant material, the implant
dose and/or the angle of the implant process. Ultimately, the accuracy of these
various calculations could be determined by performing destructive testing on the
device after it was completed. For example, a completed device could be cross-sectioned,
and the profile of the implant region of interest could be determined by observation
using a tunneling electron microscope (TEM).
The aforementioned technique for determining profiles of implanted regions was
problematic in that, in order to confirm any calculations of the profile, time-consuming
destructive testing of at least some devices, either production or test devices,
was required. Moreover, such destructive testing was performed at a point so far
removed in time from the implantation process that the results were not readily
available to enable, if desired, timely adjustment of the implant process performed
on subsequently processed wafers and later processing (e.g., RTA, diffusion) of
measured wafers. Thus, there is a need for a non-destructive testing methodology
for determining at least some profile parameters of an implanted region formed
in a semiconducting substrate.
The present invention is directed to a method that may solve, or reduce, at least
some of the problems described above.
SUMMARY OF THE INVENTION
The present invention is directed to several inventive methods. In one illustrative
embodiment, the method comprises providing a semiconducting substrate, forming
a first plurality of implant regions in the substrate, and illuminating the first
plurality of implant regions with a light source in a scatterometry tool, the scatterometry
tool generating a trace profile corresponding to an implant profile of the illuminated
implant regions. In another embodiment, the method comprises measuring profiles
of implant regions formed in a semiconducting substrate by forming a plurality
of implant regions in a semiconducting substrate, illuminating the plurality of
implant regions, measuring light reflected off the substrate to generate a profile
trace for the implant regions, comparing the generated profile trace to a target
profile trace, and modifying, based upon a deviation between the generated profile
trace and the target profile trace, at least one parameter of an ion implant process
used to form implant regions on subsequently processed substrates. In yet another
illustrative embodiment, the method comprises measuring profiles of implant regions
formed in a semiconducting substrate by forming a plurality of implant regions
in a semiconducting substrate, illuminating the plurality of implant regions, measuring
light reflected off the substrate to generate a profile trace for the implant regions,
correlating the generated profile trace to at least one of a plurality of calculated
profile traces, each of which have an associated implant region profile, and modifying,
based upon the comparison of the generated profile trace and the calculated profile
trace, at least one parameter of an ion implant process used to form implant regions
on subsequently processed substrates.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention may be understood by reference to the following description taken
in conjunction with the accompanying drawings, in which like reference numerals
identify like elements, and in which:
FIG. 1 is a cross-sectional view of a portion of a substrate having a plurality
of implant regions formed therein, and a patterned layer of photoresist positioned
above the substrate;
FIG. 2 is a cross-sectional view of the device shown in FIG. 1 after the patterned
layer of photoresist has been removed;
FIG. 3 is an isometric view of the structure depicted in FIG. 2; and
FIG. 4 is a schematic representation of an illustrative system in which the
present invention may be employed.
While the invention is susceptible to various modifications and alternative
forms, specific embodiments thereof have been shown by way of example in the drawings
and are herein described in detail. It should be understood, however, that the
description herein of specific embodiments is not intended to limit the invention
to the particular forms disclosed, but on the contrary, the intention is to cover
all modifications, equivalents, and alternatives falling within the spirit and
scope of the invention as defined by the appended claims.
DETAILED DESCRIPTION OF THE INVENTION
Illustrative embodiments of the invention are described below. In the
interest of clarity, not all features of an actual implementation are described
in this specification. It will of course be appreciated that in the development
of any such actual embodiment, numerous implementation-specific decisions must
be made to achieve the developers' specific goals, such as compliance with system-related
and business-related constraints, which will vary from one implementation to another.
Moreover, it will be appreciated that such a development effort might be complex
and time-consuming, but would nevertheless be a routine undertaking for those of
ordinary skill in the art having the benefit of this disclosure.
The present invention will now be described with reference to the attached figures.
Although the various regions and structures of a semiconductor device are depicted
in the drawings as having very precise, sharp configurations and profiles, those
skilled in the art recognize that, in reality, these regions and structures are
not as precise as indicated in the drawings. Additionally, the relative sizes of
the various features and doped regions depicted in the drawings may be exaggerated
or reduced as compared to the size of those features or regions on fabricated devices.
Nevertheless, the attached drawings are included to describe and explain illustrative
examples of the present invention.
In general, the present invention is directed to a method of measuring implant
profiles using scatterometric techniques. In some embodiments, the measured implant
profiles are used to control one or more parameters of an ion implant process to
be performed on subsequently processed wafers. As will be readily apparent to those
skilled in the art upon a complete reading of the present application, the present
method is applicable to a variety of technologies, e.g., NMOS, PMOS, CMOS, etc.,
and is readily applicable to a variety of devices, including, but not limited to,
logic devices, memory devices, etc.
FIG. 1 depicts an illustrative structure 11 that may be used in accordance
with the present invention. The structure 11 is formed on part of a wafer
comprised of, for example, silicon. As will become clear upon a complete reading
of the present application, the structure 11 may be a test structure, or
it may be part of an actual production integrated circuit device. As shown in FIG.
1, a patterned layer of photoresist 12 is formed above a semiconducting
substrate 10. The patterned layer of photoresist 12 has a plurality
of photoresist features 14 defined therein. An ion implantation process,
as indicated by arrows 16, is used to form a plurality of implant regions
18 in the areas of the substrate 10 not covered by the patterned
layer of photoresist 12.
The patterned layer of photoresist 12 may be formed by a variety of known
photolithography techniques. For example, the patterned layer of photoresist 12
may be comprised of a negative or a positive photoresist. The thickness 13
of the patterned layer of photoresist 12 may be varied as a matter of design
choice. In one illustrative embodiment, the patterned layer of photoresist 12
has a thickness 13 that ranges from approximately 1.2-2.5 μm (12,000-25,000
Å). Moreover, the features 14 in the patterned layer of photoresist
12 may have a width 15 that may be varied as a matter of design choice.
The ion implantation process may be performed by a variety of tools used in modern
semiconductor fabrication facilities for performing such operations. Moreover,
the implant energy, the dopant material implanted, the concentration of dopant
material, as well as the implant angle, may be varied in forming the implant regions
18 in the substrate 10.
Next, as shown in FIG. 2, the patterned layer of photoresist 12 is removed,
or stripped, using a variety of known techniques. More particularly, as shown in
FIG. 2, each of the implant regions 18 has a width 17 and a depth
19 beneath the surface 21 of the substrate 10. FIG. 3 is an
isometric view of the substrate 10, and the implant regions 18, shown
in FIG. 2. As will be recognized by those skilled in the art after a complete reading
of the present application, the implant regions 18 constitute a grating
pattern that may be measured using scatterometric techniques. Typically, such a
grating pattern will be formed in the scribe lines of a semiconducting substrate.
The number of these implant regions 18 that may be formed on an actual device
may vary. For example, the grating pattern may be formed in a 100 nm×120 nm
region in which approximately 300-400 implant regions 18 are formed (the
length of which are parallel to the short side of the region). The implant regions
18 depicted in FIGS. 1-3 reflect the as-implanted location of those regions.
However, as will be described further below, the present invention may also be
used in cases where the implant regions 18 have been subjected to one or
more diffusion and anneal processes.
As stated previously, scatterometric techniques will be used to measure the implant
profiles of the implant regions 18. As used herein, measuring the implant
profile of the implant region 18 means measuring one or more characteristics
of the implant region 18, e.g., depth, width, dopant concentration, etc.
For example, the implant profiles may reflect dopant concentration levels at various
depths into a substrate. A variety of scatterometry type tools may be used with
the present invention, e.g., so-called 2θ-type systems and lens-type scatterometry
tools. An illustrative scatterometry tool 24 comprised of a light source
20 and a detector 22 is schematically depicted in FIG. 2. In general,
the light source 20 is used to illuminate the structure 11, and the
detector 22 takes optical measurements, such as intensity, of the reflected
light. The scatterometry tool 24 may use white light, or some other wavelength
or combination of wavelengths, depending on the specific implementation. Typically,
the light source 20 will generate an incident beam that has a wide spectral
composition and wherein the intensity of the reflected light changes slowly in
comparison to changes in wavelength. The angle of incidence of the light may also
vary, depending on the specific implementation. For example, a spectroscopic ellipsometer
(single angle, many wavelengths), or a laser (single wavelength, many angles) may
be used with the present invention. Additionally, the light source 20 and
the detector 22 may be arranged in a concentric circle configuration, with
the light source 20 illuminating the structure 11 from a perpendicular
orientation, e.g., a reflectometer. The intensity of the reflected light may be
measured as s- and p-polarization over either multiple angles or at multiple wavelengths.
In general, the scatterometry tool 24 (see FIG. 4) includes optical hardware,
such as an ellipsometer or reflectometer, and a data processing unit loaded with
a scatterometry software application for processing data collected by the optical
hardware. For example, the optical hardware may include a Model OP5230 or OP5240
with a spectroscopic ellipsometer offered by Thermawave, Inc. of Fremont, Calif.
The data processing unit may comprise a profile application server manufactured
by Timbre Technologies, a fully owned subsidiary of Tokyo Electron America, Inc.
of Austin, Tex. and distributed by Thermawave, Inc.
Through use of scatterometry, a characteristic signature or profile trace,
associated with a particular implant profile or characteristic of an implant profile,
may be calculated (using Maxwell's equations and rigorous coupled wave analysis
(RCWA)) for a vast variety, if not all, possible combinations of implant profiles
readily anticipated by the design process. The correlation between the scatterometry
profile trace and the actual implant region profile may be based on a variety of
characteristics or factors, including, but not limited to, the width 17
and the depth 19 of the implant regions 18, the concentration of
the dopant material, and the dopant concentration profile. Variations in one or
more of the characteristics will cause a significant change in the diffraction
characteristics of the incident light from the light source 20. Thus, using
scatterometric techniques, a unique profile trace may be established for each unique
combination of implant profile characteristics, e.g., depth and width. A library
of profile traces corresponding to each unique combination of implant profile characteristics
may be generated and stored in a library. Scatterometry libraries are commercially
available from Timbre Technologies, Inc. Although not necessary, if desired, the
library of calculated profile traces may be confirmed by various destructive metrology
tests, where a scatterometry profile trace is measured and the actual profile of
the features is subsequently measured using a cross sectional tunneling electron
microscope metrology technique. Obviously, the number of combinations used to create
the library may vary as a matter of design choice. Moreover, the greater the number
of combinations, the greater will be the library containing the appropriate signature
profiles of the implant regions.
For example, in one embodiment, the width 17 of the implant regions 18
may vary between 0.25 and 1.25 μm, at an incremental value of, for example,
0.1 μm. The depth of the implant regions 18 may also vary between
0.1-0.5 μm, at an incremental value of 0.02 μm. Thus, considering only
these two parameters, 200 possible combinations of implant region profiles are
readily anticipated by the design process.
FIG. 4 depicts an illustrative system 50 that may be employed with the
present invention. As shown therein, the system 50 is comprised of a scatterometry
tool 24, a controller 40, and an ion implant tool 35. The
scatterometry tool 24 generates a profile trace of the implanted regions
18 formed on wafers 37 that have been processed through the implant
tool 35. Thereafter, in one embodiment of the present invention, the generated
profile trace is compared to a preselected target profile trace. The preselected
profile trace corresponds to a desired characteristic of the implant regions 18,
e.g., implant profiles of a certain desired depth. A determination is then made,
by either the controller 40 or the scatterometry tool 35, if there
is a deviation between the generated (or measured) profile trace and the target
profile trace. If so, the controller 40 may then change one or more parameters
of the operating recipe of the implant tool 35, such that implanted regions
18 formed in the subsequently processed wafers 39 are closer to the
target profile. For example, one or more parameters of the implant process, e.g.,
implant angle, implant energy, dopant material, and/or dopant concentration, to
be performed on the subsequently processed wafers 39 may be adjusted to
achieve the desired implant profile.
In another embodiment, the present invention may be employed to compare a measurement
or generated trace profile to a library of such profiles, each of which corresponds
to a particular implant profile. That is, in this embodiment, the method comprises
generating additional profile traces for implant regions having different implant
profiles, and establishing a library comprised of a plurality of the profile traces,
wherein each of the plurality of traces is correlated to a particular implant profile.
The scatterometry tool 24 is used to generate a profile trace for a given
structure 11 with implant regions 18 formed thereon. The scatterometry
tool 24 may sample one or more structures 11 in a given wafer in
a lot or even generate a profile trace for each structure 11 in the lot,
depending on the specific implementation. Moreover, the profile traces from a sample
of the structures 11 may be averaged or otherwise statistically analyzed.
A controller, either in the scatterometry tool 24 or elsewhere in the manufacturing
plant, e.g., controller 40, then compares the profile trace (i.e., individual
or averaged) generated by the scatterometry tool 24 to a library of calculated
profile traces with known implant region profiles to correlate or match the generated
or measured profile trace to a trace from the library having a known implant region
profile. Based upon these comparisons, the controller 40, if needed, may
adjust one or more parameters of an ion implant process to be performed on subsequently
processed wafers 39 in the implant tool 35.
As discussed previously, the implant regions 18 depicted in FIGS. 1-3 are
depicted in their as-implanted positions, i.e., prior to any anneal operations
being performed on the structure 11. As will be understood by those skilled
in the art, during such anneal processes, the implanted dopant atoms will migrate
from their original implanted position, typically in an isotropic fashion, such
that the regions 18 will spread out, both laterally and vertically downward,
to some degree. As will be clear to those skilled in the art upon a complete reading
of the present application, the present invention may be used to measure implant
profiles either before or after such anneal processes are performed. Moreover,
if desired, pre-anneal scatterometry measurements of the profiles of the implant
regions 18 may be correlated to post-anneal profiles of the implant regions 18.
Based on the determined implant region profile, control equations may be employed
to adjust the operating recipe of the ion implant tool 35 to account for
deviations between the measured implant profile and the target implant profile.
The control equations may be developed empirically using commonly known linear
or non-linear techniques. The controller 40 may automatically control the
operating recipes of the implant tool 35 used to form implant regions 18
on subsequently processed wafers 37. Through use of the present invention,
the deviations between the profiles of implant regions formed on subsequently processed
wafers and a target implant profile may be reduced.
In the illustrated embodiment, the controller 40 is a computer programmed
with software to implement the functions described herein. Moreover, the functions
described for the controller 40 may be performed by one or more controllers
spread through the system. For example, the controller 40 may be a fab level
controller that is used to control processing operations throughout all or a portion
of a semiconductor manufacturing facility. Alternatively, the controller 40
may be a lower level computer that controls only portions or cells of the manufacturing
facility. Moreover, the controller 40 may be a stand-alone device, or it
may reside on the implant tool 35. However, as will be appreciated by those
of ordinary skill in the art, a hardware controller (not shown) designed to implement
the particular functions may also be used.
Portions of the invention and corresponding detailed description are presented
in terms of software, or algorithms and symbolic representations of operations
on data bits within a computer memory. These descriptions and representations are
the ones by which those of ordinary skill in the art effectively convey the substance
of their work to others of ordinary skill in the art. An algorithm, as the term
is used here, and as it is used generally, is conceived to be a self-consistent
sequence of steps leading to a desired result. The steps are those requiring physical
manipulations of physical quantities. Usually, though not necessarily, these quantities
take the form of optical, electrical, or magnetic signals capable of being stored,
transferred, combined, compared, and otherwise manipulated. It has proven convenient
at times, principally for reasons of common usage, to refer to these signals as
bits, values, elements, symbols, characters, terms, numbers, or the like.
It should be borne in mind, however, that all of these and similar terms are
to
be associated with the appropriate physical quantities and are merely convenient
labels applied to these quantities. Unless specifically stated otherwise, or as
is apparent from the discussion, terms such as "processing" or "computing" or "calculating"
or "determining" or "displaying" or the like, refer to the actions and processes
of a computer system, or similar electronic computing device, that manipulates
and transforms data represented as physical, electronic quantities within the computer
system's registers and memories into other data similarly represented as physical
quantities within the computer system memories or registers or other such information
storage, transmission or display devices.
An exemplary software system capable of being adapted to perform the functions
of the controller 40, as described, is the Catalyst system offered by KLA
Tencor, Inc. The Catalyst system uses Semiconductor Equipment and Materials International
(SEMI) Computer Integrated Manufacturing (CIM) Framework compliant system technologies,
and is based on the Advanced Process Control (APC) Framework. CIM (SEMI E81-0699—Provisional
Specification for CIM Framework Domain Architecture) and APC (SEMI E93-0999—Provisional
Specification for CIM Framework Advanced Process Control Component) specifications
are publicly available from SEMI.
The present invention is directed to several inventive methods. In one embodiment,
the method comprises providing a semiconducting substrate, forming a first plurality
of implant regions in the substrate, and illuminating the first plurality of implant
regions with a light source in a scatterometry tool, the scatterometry tool generating
a trace profile corresponding to an implant profile of the illuminated implant
regions. In another embodiment, the method comprises measuring profiles of implant
regions formed in a semiconducting substrate, comprising forming a plurality of
implant regions in a semiconducting substrate, illuminating the plurality of implant
regions, measuring light reflected off the substrate to generate a profile trace
for the implant regions, comparing the generated profile trace to a target profile
trace, and modifying, based upon a deviation between the generated profile trace
and the target profile trace, at least one parameter of an ion implant process
used to form implant regions on subsequently processed substrates. In yet another
embodiment, the method comprises measuring profiles of implant regions formed in
a semiconducting substrate by forming a plurality of implant regions in a semiconducting
substrate, illuminating the plurality of implant regions, measuring light reflected
off the substrate to generate a profile trace for the implant regions, comparing
or correlating the generated profile trace to a calculated profile trace in a library,
wherein each of the profile traces in the library have an associated implant region
profile, and modifying, based upon the comparison between the generated profile
trace and the calculated profile trace from the library, at least one parameter
of an ion implant process used to form implant regions on subsequently processed substrates.
By adjusting one or more parameters of the implant tool 35 used to form
the implant regions 18 on the wafer, as described above, the resultant implant
profiles can be adjusted to reduce the overall profile variations for wafers manufactured
in a given manufacturing line. Reduced variation equates directly to reduced process
cost, increased device performance, and increased profitability.
The particular embodiments disclosed above are illustrative only, as the invention
may be modified and practiced in different but equivalent manners apparent to those
skilled in the art having the benefit of the teachings herein. For example, the
process steps set forth above may be performed in a different order. Furthermore,
no limitations are intended to the details of construction or design herein shown,
other than as described in the claims below. It is therefore evident that the particular
embodiments disclosed above may be altered or modified and all such variations
are considered within the scope and spirit of the invention. Accordingly, the protection
sought herein is as set forth in the claims below.
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