U.S. patent application number 12/145922 was filed with the patent office on 2008-11-20 for mask having implant stopping layer.
Invention is credited to Katherina Babich, Todd C. Bailey, Richard A. Conti, Ryan P. Deschner.
Application Number | 20080286545 12/145922 |
Document ID | / |
Family ID | 38750063 |
Filed Date | 2008-11-20 |
United States Patent
Application |
20080286545 |
Kind Code |
A1 |
Babich; Katherina ; et
al. |
November 20, 2008 |
MASK HAVING IMPLANT STOPPING LAYER
Abstract
Methods of forming a mask for implanting a substrate and
implanting using an implant stopping layer with a photoresist
provide lower aspect ratio masks that cause minimal damage to
trench isolations in the substrate during removal of the mask. In
one embodiment, a method of forming a mask includes: depositing an
implant stopping layer over the substrate; depositing a photoresist
over the implant stopping layer, the implant stopping layer having
a density greater than the photoresist; forming a pattern in the
photoresist by removing a portion of the photoresist to expose the
implant stopping layer; and transferring the pattern into the
implant stopping layer by etching to form the mask. The implant
stopping layer may include: hydrogenated germanium carbide,
nitrogenated germanium carbide, fluorinated germanium carbide,
and/or amorphous germanium carbon hydride (GeHX), where X includes
carbon. The methods/mask reduce scattering during implanting
because the mask has higher density than conventional masks.
Inventors: |
Babich; Katherina;
(Chappaqua, NY) ; Bailey; Todd C.; (Poughkeepsie,
NY) ; Conti; Richard A.; (Katonach, NY) ;
Deschner; Ryan P.; (Poughkeepsie, NY) |
Correspondence
Address: |
HOFFMAN WARNICK LLC
75 STATE ST, 14TH FL
ALBANY
NY
12207
US
|
Family ID: |
38750063 |
Appl. No.: |
12/145922 |
Filed: |
June 25, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11420321 |
May 25, 2006 |
|
|
|
12145922 |
|
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Current U.S.
Class: |
428/218 ;
257/E21.336; 257/E21.346; 428/698 |
Current CPC
Class: |
H01L 21/266 20130101;
Y10T 428/24992 20150115; H01L 21/26513 20130101 |
Class at
Publication: |
428/218 ;
428/698 |
International
Class: |
B32B 7/02 20060101
B32B007/02 |
Claims
1. A mask comprising: an implant stopping layer over a substrate,
wherein the implant stopping layer includes at least one of
hydrogenated germanium carbide, nitrogenated germanium carbide,
fluorinated germanium carbide and amorphous germanium carbon
hydride (GeHX), where X includes carbon; and a photoresist over the
implant stopping layer.
2. The mask of claim 1, wherein the implant stopping layer has a
density greater than the photoresist.
3. The mask of claim 1, wherein the implant stopping layer prevents
doping of the substrate during a halo, extension, deep source/drain
ion implantation process.
Description
[0001] This application is related to U.S. Ser. No. 11/420,321,
filed May 25, 2006, Docket No. FIS920060038US1, currently
pending.
BACKGROUND OF THE INVENTION
[0002] 1. Technical Field
[0003] The invention relates generally to semiconductor device
fabrication, and more particularly, to a method for forming a mask
for implanting a substrate, where the mask includes an implant
stopping layer, and a mask so formed.
[0004] 2. Background Art
[0005] In the semiconductor fabrication industry continual
miniaturization of structures presents challenges relative to
modifying current techniques. One challenge is addressing problems
related to photolithography. Photolithography is a process used in
the semiconductor fabrication industry in which a photo-sensitive
material, i.e., a photoresist, is laid upon a substrate, imaged and
then etched to leave a pattern that can be used to generate other
structures within the substrate. As miniaturization continues, the
dimensions of patterned photoresists are also being minimized. Some
processing, for example, deep well ion implants, require very thick
layers of photoresist to block ion implantation into areas under
the photoresist in which the implantation is not desired. These
patterned single layer photoresists have a relatively high aspect
ratio, i.e., patterned photoresist height to patterned line width,
and, as a result, are subject to collapse. For example, FIG. 1
shows a conventional patterned photoresist 10 over a substrate 12
having trench isolations 14 therein. Patterned photoresist 10 has a
relatively high aspect ratio. As shown in FIG. 2, patterned
photoresist 10 is subject to capillary-induced line collapses in
which capillary action within patterned openings 16 (FIG. 1) draws
the photoresist inwardly and causes a collapse.
[0006] One approach to address this situation has been to employ
hard masks having two layers, one layer including silicon oxide
and/or silicon nitride to block the ion implantation. While bilayer
photoresist masks have lower aspect ratios compared to single layer
masks, during removal of these bilayer masks, trench isolations 14
(FIG. 2) within substrate 12, which typically include silicon oxide
and/or silicon nitride based materials, can be degraded because the
etching chemistry used to remove the hard mask is also effective on
the trench isolation. In addition, these conventional bilayer
photoresist masks must be inorganic, which prevents use of a wide
variety of organic photoresists. In addition, the total density of
the photoresist mask leads to ion scattering, which causes
proximity effects in neighboring devices.
[0007] In view of the foregoing, there is a need in the art for a
solution to the problems of the related art.
SUMMARY OF THE INVENTION
[0008] Methods of forming a mask for implanting a substrate and
implanting using an implant stopping layer with a photoresist
provide lower aspect ratio masks that cause minimal damage to
trench isolations in the substrate during removal of the mask. In
one embodiment, a method of forming a mask includes: depositing an
implant stopping layer over the substrate; depositing a photoresist
over the implant stopping layer, the implant stopping layer having
a density greater than the photoresist; forming a pattern in the
photoresist by removing a portion of the photoresist to expose the
implant stopping layer; and transferring the pattern into the
implant stopping layer by etching to form the mask. The implant
stopping layer may include: hydrogenated germanium carbide,
nitrogenated germanium carbide, fluorinated germanium carbide,
and/or amorphous germanium carbon hydride (GeHX), where X includes
carbon. The methods/mask reduce scattering during implanting
because the mask has higher density than conventional masks.
[0009] A first aspect of the invention provides a method of forming
a mask for implanting a substrate, the method comprising the steps
of: depositing an implant stopping layer over the substrate;
depositing a photoresist over the implant stopping layer, the
implant stopping layer having a density greater than the
photoresist; forming a pattern in the photoresist by removing a
portion of the photoresist to expose the implant stopping layer;
and transferring the pattern into the implant stopping layer by
etching to form the mask.
[0010] A second aspect of the invention provides a mask comprising:
an implant stopping layer over a substrate, wherein the implant
stopping layer includes at least one of hydrogenated germanium
carbide, nitrogenated germanium carbide, fluorinated germanium
carbide and amorphous germanium carbon hydride (GeHX), where X
includes carbon; and a photoresist over the implant stopping
layer.
[0011] A third aspect of the invention provides a method of
implanting a substrate, the method comprising the steps of:
depositing an implant stopping layer over the substrate, wherein
the implant stopping layer includes at least one of: hydrogenated
germanium carbide, nitrogenated germanium carbide, fluorinated
germanium carbide, and amorphous germanium carbon hydride (GeHX),
where X includes carbon; depositing a photoresist over the implant
stopping layer, the implant stopping layer having a density greater
than the photoresist; forming a pattern in the photoresist by
removing a portion of the photoresist to expose the implant
stopping layer; transferring the pattern into the implant stopping
layer by etching to form the mask; and implanting the
substrate.
[0012] The illustrative aspects of the present invention are
designed to solve the problems herein described and/or other
problems not discussed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] These and other features of this invention will be more
readily understood from the following detailed description of the
various aspects of the invention taken in conjunction with the
accompanying drawings that depict various embodiments of the
invention, in which:
[0014] FIGS. 1 and 2 show a conventional photoresist mask.
[0015] FIGS. 3-5 show steps of a method of forming a mask according
to one embodiment of the invention.
[0016] FIG. 6 shows use of the mask of FIG. 5 for implanting a
substrate according to another embodiment of the invention.
[0017] FIG. 7 shows the implanted substrate.
[0018] It is noted that the drawings of the invention are not to
scale. The drawings are intended to depict only typical aspects of
the invention, and therefore should not be considered as limiting
the scope of the invention. In the drawings, like numbering
represents like elements between the drawings.
DETAILED DESCRIPTION
[0019] Turning to FIGS. 3-5, one embodiment of a method of forming
a mask 100 (FIG. 5) for implanting a substrate 112 is illustrated.
As shown in FIG. 3, a first step includes depositing an implant
stopping layer 120 over substrate 112, followed by deposition of a
photoresist 122 over implant stopping layer 120. Each layer may be
deposited using any now known or later developed process. In one
embodiment, however, ion implant stopping layer 120 is deposited by
at least one of: chemical vapor deposition (CVD), low-pressure CVD
(LPCVD), plasma-enhanced CVD (PECVD), semi-atmosphere CVD (SACVD)
and high density plasma CVD (HDPCVD), rapid thermal CVD (RTCVD),
ultra-high vacuum CVD (UHVCVD), sputtering deposition, ion beam
deposition, electron beam deposition, and laser assisted
deposition. Implant stopping layer 120 may have a depth that is
greater than a depth of photoresist 122. Substrate 112 may include
any now known or later developed substrate material such as one or
more of the following: a semiconductor (e.g., silicon, silicon
germanium (SiGe), a dielectric, a glass, a metal, nonmetallic
conductor, magnetic material and a polymer. In addition, substrate
112 may include trench isolations 124 of, for example, silicon
oxide, for electrically separating devices to be generated on
substrate 112.
[0020] Implant stopping layer 120 has a density sufficient to stop
ion implanting from reaching substrate 112, as will be described in
greater detail below. That is, implant stopping layer 120 has a
density greater than photoresist 122. Hence, implant stopping layer
120 is not used as a conventional bilayer masking process because
its higher density allows for thinning of the stack compared to
conventional bilayer or single resist schemes. In one embodiment,
implant stopping layer 120 includes at least one of the following:
hydrogenated germanium carbide, nitrogenated germanium carbide,
fluorinated germanium carbide, and amorphous germanium carbon
hydride (GeHX), where X includes carbon. Implant stopping layer 120
may be deposited from a precursor including, for example, at least
one of: germane, alkyl germane, alkoxy germane, acyloxy germane,
aryl germane, cyclicgermanes, nitrogen, carbon, and fluorine. In
one embodiment, implant stopping layer 120 may be deposited from
tetramethylgermane in a reactor at a pressure of approximately 0.1
Torr to approximately 50 Torr, and substrate 112 at a temperature
of approximately 200.degree. C. to approximately 500.degree. C. In
an alternative embodiment, implant stopping layer 120 may be
deposited from germane in the presence of ethylene and/or acetylene
in a reactor at a pressure of approximately 0.1 Torr to
approximately 50 Torr, and substrate 112 at a temperature of
approximately 200.degree. C. to approximately 500.degree. C. Other
techniques may also be employed.
[0021] Photoresist 122 may include inorganic photoresist material
or organic photoresist material, i.e., including carbon (C). In any
event, photoresist 122 is photosensitive to, for example, i-line,
g-line, 248 nm, 193 nm, 157 nm, 126 nm, extreme ultraviolet
radiation, electron beam, x-ray irradiation and combinations
thereof.
[0022] Next, as shown in FIG. 4, a pattern 130 (e.g., openings) may
be formed by removing a portion(s) of photoresist 122 to expose
implant stopping layer 120 in any now known or later developed
fashion, e.g., patterning photoresist 122, exposing it to
radiation, and etching to create pattern 130. The etching may
include, for example, a wet etching. Pattern 130 may be aligned
with openings 132 between trench isolations 124, i.e., with the
appropriate well definition pattern, such that ion implantation may
occur between trench isolations 124. However, this is not
necessary.
[0023] In FIG. 5, pattern 130 is transferred into implant stopping
layer 120 by etching using patterned photoresist 122 to complete
mask 100. In one embodiment, the etching may include RIE. For
example, the transferring may include removing a portion of implant
stopping layer 120 by reactive ion etching in a plasma containing
one or more reactive species selected from the group consisting of
fluorine (Fl), fluorocarbon, chlorine (Cl), bromine (Br), oxygen
(O.sub.2), carbon monoxide (CO) and carbon dioxide (CO.sub.2).
Other techniques, however, are also possible. Patterned photoresist
122 and patterned implant stopping layer 120 collectively have an
aspect ratio of, for example, less than approximately 4.0. However,
the invention is not limited to that aspect ratio. That is, they
are collectively thinner than conventional bilayer photoresists
structures.
[0024] In FIG. 6, an ion implant 140 is conducted using mask 100.
At this stage, mask 100 includes implant stopping layer 120 over
substrate 112, and photoresist 122 over implant stopping layer 120.
Implant stopping layer 120 includes at least one of hydrogenated
germanium carbide, nitrogenated germanium carbide, fluorinated
germanium carbide and amorphous germanium carbon hydride (GeHX),
where X includes carbon. As indicated, ion implantation reaches
substrate 112, in regions 134 between trench isolations 124, via
pattern 130 through photoresist 122 and implant stopping layer 120.
However, ion implantation is stopped at a location 142 within
implant stopping layer 120 above substrate 112. Implantation into
mask 100 exhibits less scattering than conventional processes,
which allows for reduction of a threshold voltage shift of devices
subsequently generated. Implant 140 may include, for example, a
well, halo, extension, deep source/drain ion implantation process.
It is understood that implant stopping layer 120 and trench
isolations 124 may not have identical widths. For example, the far
right trench isolations 124 in FIGS. 3-7 show how trench isolations
124 may be wider. Additionally, it is understood that implant
stopping layer 120 may be designed to cover some portion of
substrate 112 that is not intended to be receive ion implant
140.
[0025] FIG. 7 shows a next step of removing photoresist 122 and
implant stopping layer 120 after implanting using mask 100. The
removing step may use any conventional processes. One advantage,
however, of implant stopping layer 120 removal is that the
particular chemistries used cause minimal damage to trench
isolations 124. Substrate 112, as shown, may be used to generate
semiconductor devices thereon in any now known or later developed
fashion.
[0026] The foregoing description of various aspects of the
invention has been presented for purposes of illustration and
description. It is not intended to be exhaustive or to limit the
invention to the precise form disclosed, and obviously, many
modifications and variations are possible. Such modifications and
variations that may be apparent to a person skilled in the art are
intended to be included within the scope of the invention as
defined by the accompanying claims.
* * * * *