U.S. patent application number 11/812609 was filed with the patent office on 2008-01-03 for semiconductor device and method of manufacturing the same.
Invention is credited to Atsuhiro Kinoshita, Junji Koga.
Application Number | 20080001224 11/812609 |
Document ID | / |
Family ID | 38875713 |
Filed Date | 2008-01-03 |
United States Patent
Application |
20080001224 |
Kind Code |
A1 |
Kinoshita; Atsuhiro ; et
al. |
January 3, 2008 |
Semiconductor device and method of manufacturing the same
Abstract
A semiconductor device which can effectively suppress a short
channel effect and junction leakage is provided. A semiconductor
device includes a field effect transistor. The field effect
transistor includes a first semiconductor region of a first
conductivity type, a gate electrode formed on a gate insulating
film, and source and drain electrodes. The field effect transistor
also includes second semiconductor regions of a second conductivity
type. The field effect transistor further includes third
semiconductor regions of the second conductivity type having an
impurity concentration higher than that of the second semiconductor
region and formed between the source electrode and the first and
second semiconductor regions and between the drain electrode and
the first and second semiconductor regions, and side wall
insulating films formed on both the side surfaces of the gate
electrode. The source electrode and the drain electrode are
separated from the side wall insulating films.
Inventors: |
Kinoshita; Atsuhiro;
(Kanagawa, JP) ; Koga; Junji; (Kanagawa,
JP) |
Correspondence
Address: |
FINNEGAN, HENDERSON, FARABOW, GARRETT & DUNNER;LLP
901 NEW YORK AVENUE, NW
WASHINGTON
DC
20001-4413
US
|
Family ID: |
38875713 |
Appl. No.: |
11/812609 |
Filed: |
June 20, 2007 |
Current U.S.
Class: |
257/346 ;
257/E21.409; 257/E21.438; 257/E29.054; 257/E29.063; 257/E29.255;
438/303 |
Current CPC
Class: |
H01L 29/1083 20130101;
H01L 29/6659 20130101; H01L 29/1045 20130101; H01L 29/6653
20130101; H01L 29/665 20130101 |
Class at
Publication: |
257/346 ;
438/303; 257/E29.255; 257/E21.409 |
International
Class: |
H01L 29/78 20060101
H01L029/78; H01L 21/336 20060101 H01L021/336 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 21, 2006 |
JP |
2006-171593 |
Claims
1. A semiconductor device comprising a field effect transistor
including: a first semiconductor region of a first conductivity
type having a surface portion on which a channel region is formed;
a gate electrode formed on the channel region; a gate insulating
film in between the gate electrode and the channel region; a source
electrode and a drain electrode formed on both the sides of the
channel region; second semiconductor regions of a second
conductivity type formed between the source electrode and the
channel region and between the drain electrode and the channel
region; third semiconductor regions of the second conductivity type
formed between the source electrode and the first and second
semiconductor regions and between the drain electrode and the first
and second semiconductor regions and having an impurity
concentration higher than that of the second semiconductor region;
and sidewall insulating films formed on both the side surfaces of
the gate electrode, the side wall insulating films being separated
from the source electrode and the drain electrode.
2. The semiconductor device according to claim 1, wherein a
distance of separation between the side wall insulating film and
the source electrode and between the side wall insulating film and
the drain electrode is longer than 0 and not more than 30 nm.
3. The semiconductor device according to claim 1, wherein an
impurity concentration in interfaces between the third
semiconductor region and the source and drain electrode is not less
than 8.times.10.sup.19 and not more than 5.times.10.sup.20
atoms/cm.sup.3, an impurity concentration in the third
semiconductor region at a depth of 20 nm from the interfaces
between the third semiconductor region and the source and drain
electrode is not more than 1/10 an impurity concentration in the
interfaces between the third semiconductor region and the source
and drain electrode, the second semiconductor region has a maximum
impurity concentration in a gate insulating film interface, and the
maximum impurity concentration is not more than 1/2 the impurity
concentration in the interfaces between the third semiconductor
region and the source and drain electrode, and an impurity
concentration of the second semiconductor region at a depth of 30
nm from the gate insulating film interface is not more than 1/10
the impurity concentration in the gate insulating film interface in
the second semiconductor region.
4. The semiconductor device according to claim 1, wherein a gate
length of the gate electrode is not more than 80 nm, an equivalent
physical oxide thickness (EOT) of the gate insulating film is not
more than 4 nm, and a film thickness of the side wall insulating
film is not more than 10 nm.
5. The semiconductor device according to claim 1, wherein a fourth
semiconductor region of the first conductivity type having an
impurity concentration higher than that of the first semiconductor
region is formed between the second semiconductor region and the
first semiconductor region.
6. The semiconductor device according to claim 1, wherein a fifth
semiconductor region of the second conductivity type is formed
between a bottom of the third semiconductor region and the first
semiconductor region.
7. The semiconductor device according to claim 1, wherein the side
wall insulating film is a silicon nitride film, and an upper-layer
film of the side wall insulating film is a silicon oxide film.
8. The semiconductor device according to claim 1, wherein the first
to third semiconductor regions are made of silicon.
9. The semiconductor device according to claim 1, wherein the field
effect transistor is an n-channel MIS field effect transistor, and
impurities in the second and third semiconductor regions are
As.
10. The semiconductor device according to claim 1, wherein the
source electrode and the drain electrode are made of nickel
silicide (NiSi).
11. A method of manufacturing a semiconductor device, comprising:
forming a gate insulating film on a first semiconductor region of a
first conductivity type; forming a gate electrode on the gate
insulating film; forming side wall insulating films on both side
surfaces of the gate electrode; ion-implanting an impurity in the
first semiconductor region by using the gate electrode and the side
wall insulating film as masks to form second semiconductor regions
of a second conductivity type; forming second side wall insulating
films on both side surfaces of the side wall insulating film; and
siliciding a part of the second semiconductor region of the second
conductivity type to a region deeper than the second semiconductor
region to form a source electrode and a drain electrode, and
forming third semiconductor regions of the second conductivity type
having an impurity concentration higher than that of the second
semiconductor region in interfaces between the source electrode and
the first and second semiconductor regions and between the drain
electrode and the first and second semiconductor regions by
segregation from silicide.
12. The method according to claim 11, wherein in forming the side
wall insulating film, an amount of substrate etching is not more
than 8 nm.
13. The method according to claim 11, wherein the first to third
semiconductor regions are made of silicon.
14. The method according to claim 11, wherein the impurity is As,
and the silicide is nickel silicide (NiSi).
15. A method of manufacturing a semiconductor device, comprising:
forming a gate insulating film on a first semiconductor region of a
first conductivity type; forming a gate electrode on the gate
insulating film; forming side wall insulating films each having a
footing-bottom shape at a lower surface side thereof on both side
surfaces of the gate electrode; ion-implanting an impurity in the
first semiconductor region by using the gate electrode and the side
wall insulating film as masks to form second semiconductor regions
of a second conductivity type; and siliciding a part of the second
semiconductor region of the second conductivity type to a region
deeper than the second semiconductor region to form a source
electrode and a drain electrode, and forming third semiconductor
regions of the second conductivity type having an impurity
concentration higher than that of the second semiconductor region
in interfaces between the source electrode and the first and second
semiconductor regions and between the drain electrode and the first
and second semiconductor regions by segregation from silicide.
16. The method according to claim 15, wherein in forming the side
wall insulating film, an amount of substrate etching is not more
than 8 nm.
17. The method according to claim 15, wherein the first to third
semiconductor regions are made of silicon.
18. The method according to claim 15, wherein the impurity is As,
and the silicide is nickel silicide (NiSi).
19. A method of manufacturing a semiconductor device, comprising:
forming a gate electrode on a part of a first semiconductor region
of a first conductivity type, a gate insulating film in between the
gate electrode and the first semiconductor region; depositing an
insulating film serving as a side wall insulating film of the gate
electrode; etching the insulating film serving as the side wall
insulating film by anisotropic etching not to expose an underlying
layer; ion-implanting an impurity in the first semiconductor region
from above the insulating film serving as the side wall insulating
film to form second semiconductor regions of a second conductivity
type serving as extension regions of a source and a drain; etching
the insulating film serving as the side wall insulating film which
is etched not to expose the underlying layer to form side wall
insulating films each having a footing-bottom shape at a lower
surface side thereof on both side surfaces of the gate electrode;
and siliciding a part of the second semiconductor region of the
second conductivity type to a region deeper than the second
semiconductor region to form a source electrode and a drain
electrode, and forming third semiconductor regions of the second
conductivity type having an impurity concentration higher than that
of the second semiconductor region in interfaces between the source
electrode and the first and second semiconductor regions and
between the drain electrode and the first and second semiconductor
regions by segregation from silicide.
20. The method according to claim 19, wherein the first to third
semiconductor regions are made of silicon, the impurity is As, and
the silicide is nickel silicide (NiSi).
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is based upon and claims the benefit of
priority from the prior Japanese Patent Application No. 2006-171593
filed on Jun. 21, 2006 in Japan, the entire contents of which are
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a semiconductor device and
a method of manufacturing the same, and more particularly, to a
semiconductor device having a MIS field effect transistor the
source and drain portions of which are improved and a method of
manufacturing the same.
BACKGROUND OF THE INVENTION
[0003] To advance the performance of a semiconductor integrated
circuit, the performance of a field effect transistor serving as a
constituent device must be advanced. For advancing the device
performance, scaling down of the device is effective. For this
reason, device performance has been improved by scaling down the
device by micro patterning. However, as micro patterning advanced,
a technical barrier to be solved becomes high at the same time.
According to the international semiconductor roadmap, especially in
relation to a technique for forming source and drain portions, a
solution for realizing a junction having a depth of 10 to 20 nm in
a drain-extension portion in the 65-nm generation or later cannot
be found in the existing circumstances.
[0004] In this background, in order to improve both suppression of
short channel effect and reduction of junction leakage, a device
using Schottky source and drain to which an impurity segregation
technique is applied is proposed (JP-A 2005-101588 (KOKAI)). In
particular, in the 45-nm generation or later, a channel resistance
caused by scattering of carriers is not a prevailing factor that
degrades a drain current because of a small gate length. For this
reason, improvement of device performance relying only to micro
patterning is very difficult. Therefore, in order to realize
further improvement of performance, a device using a Schottky
source-drain maximally utilizing the characteristic feature of a
Schottky junction which can inject high-speed carriers into a
channel is desired (K. Ucida et al., Appl. Phys. Lett., 76, 3992
(2000)). However, a device structure using a conventional Schottky
source-drain has the following problem. That is, the merit of the
Schottky source-drain which can inject high-speed carriers into a
channel is not always maximally utilized.
[0005] Thus, the device using a conventional Schottky source-drain
has a merit for short channel effect and suppression of junction
leakage. However, the merit of the Schottky source-drain which can
inject high-speed carriers into a channel is not always maximally
utilized. More specifically, in order to improve the device
performance by using an increase in rate of injection by the
Schottky source-drain, a device structure must be optimized.
However, up to now, it cannot be said that the device structure is
optimized.
SUMMARY OF THE INVENTION
[0006] The present invention has been made in consideration of the
above circumstances. It is an object of the present invention to
provide a semiconductor device having a field effect transistor
with a device structure which can achieve improvement of
performance by increasing an injection rate of carriers while
effectively suppressing a short channel effect and junction
leakage, and a method of manufacturing the semiconductor
device.
[0007] A semiconductor device according to an embodiment of the
present invention comprises a field effect transistor including: a
first semiconductor region of a first conductivity type having a
surface portion on which a channel region is formed; a gate
electrode formed on the channel region, a gate insulating film in
between the gate electrode and the channel region; a source
electrode and a drain electrode formed on both the sides of the
channel region; second semiconductor regions of a second
conductivity type formed between the source electrode and the
channel region and between the drain electrode and the channel
region to serve as extension regions of a source and a drain; third
semiconductor regions of the second conductivity type formed
between the source electrode and the first and second semiconductor
regions and between the drain electrode and the first and second
semiconductor regions and having an impurity concentration higher
than that of the second semiconductor region; and side wall
insulating films formed on both the side surfaces of the gate
electrode, the side wall insulating films being separated from the
source electrode and the drain electrode.
[0008] A method for producing the field effect transistor according
to another embodiment of the present invention comprises: forming a
gate electrode on a first semiconductor region of a first
conductivity type, a gate insulating film in between, and side wall
insulating films on both side surfaces of the gate electrode;
ion-implanting an impurity in the first semiconductor region by
using the gate electrode and the side wall insulating film as masks
to form second semiconductor regions of a second conductivity type
serving as extension regions of a source and a drain; forming
second side wall insulating films on both side surfaces of the side
wall insulating film; and siliciding a part of the second
semiconductor region of the second conductivity type to a region
deeper than the second semiconductor region to form a source
electrode and a drain electrode, and forming third semiconductor
regions of the second conductivity type having an impurity
concentration higher than that of the second semiconductor region
in interfaces between the source electrode and the first and second
semiconductor regions and between the drain electrode and the first
and second semiconductor regions by segregation from silicide.
[0009] A method for producing the field effect transistor according
to still another embodiment of the present invention comprises:
forming a gate electrode on a first semiconductor region of a first
conductivity type, a gate insulating film in between; forming side
wall insulating films each having a footing-bottom shape at a lower
surface side thereof on both side surfaces of the gate electrode;
ion-implanting an impurity in the first semiconductor region by
using the gate electrode and the side wall insulating film as masks
to form second semiconductor regions of a second conductivity type
serving as extension regions of a source and a drain; and
siliciding a part of the second semiconductor region of the second
conductivity type to a region deeper than the second semiconductor
region to form a source electrode and a drain electrode, and
forming third semiconductor regions of the second conductivity type
having an impurity concentration higher than that of the second
semiconductor region in interfaces between the source electrode and
the first and second semiconductor regions and between the drain
electrode and the first and second semiconductor regions by
segregation from silicide.
[0010] A method for producing the field effect transistor according
to still another embodiment of the present invention comprises:
forming a gate electrode on a part of a first semiconductor region
of a first conductivity type, a gate insulating film in between;
depositing an insulating film serving as a side wall insulating
film of the gate electrode; maximally etching the insulating film
serving as the side wall insulating film by anisotropic etching not
to expose an underlying layer; ion-implanting an impurity in the
first semiconductor region from above the insulating film serving
as the side wall insulating film to form second semiconductor
regions of a second conductivity type serving as extension regions
of a source and a drain; etching the insulating film serving as the
side wall insulating film which is maximally etched not to expose
the underlying layer to form side wall insulating films each having
a footing-bottom shape at a lower surface side thereof on both side
surfaces of the gate electrode, siliciding a part of the second
semiconductor region of the second conductivity type to a region
deeper than the second semiconductor region to form a source
electrode and a drain electrode; and forming third semiconductor
regions of the second conductivity type having an impurity
concentration higher than that of the second semiconductor region
in interfaces between the source electrode and the first and second
semiconductor regions and between the drain electrode and the first
and second semiconductor regions by segregation from silicide.
[0011] According to the present invention, there can be provided a
semiconductor device having a field effect transistor with a device
structure which can achieve improvement of performance by
increasing an injection rate of carriers while effectively
suppressing a short channel effect and junction leakage, and a
method of manufacturing the semiconductor device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is across-sectional view showing an device structure
of a MIS field effect transistor according to a first
embodiment;
[0013] FIGS. 2A and 2B are band diagram for explaining operation
and effect of the first embodiment;
[0014] FIG. 3 is a diagram showing a dependence of a drain current
on a separation distance;
[0015] FIG. 4 is a diagram showing a dependence of an increasing
rate of the drain current in a gate length;
[0016] FIG. 5 is a diagram showing a dependence of an increasing
rate of the drain current on EOT;
[0017] FIG. 6 is a diagram showing a dependence of the drain
current on a side wall thickness;
[0018] FIGS. 7 to 13 are cross-sectional views showing a first
manufacturing step for the MIS field effect transistor according to
the first embodiment;
[0019] FIG. 14 is a diagram showing a dependence of an increasing
rate of the drain current on a substrate etching amount;
[0020] FIGS. 15 to 20 are cross-sectional views showing the second
manufacturing step for the MIS field effect transistor according to
the first embodiment;
[0021] FIGS. 21 to 23 are cross-sectional views showing a third
manufacturing step for the MIS field effect transistor according to
the first embodiment;
[0022] FIG. 24 is a cross-sectional view showing an device
structure of a MIS field effect transistor according to a second
embodiment;
[0023] FIG. 25 is a cross-sectional view showing an device
structure of a MIS field effect transistor according to a third
embodiment; and
[0024] FIGS. 26 to 34 are cross-sectional views showing an device
structure of a MIS field effect transistor according to a fourth
embodiment.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0025] Embodiments of the present invention will be described below
with reference to the drawings.
First Embodiment
[0026] FIG. 1 is a sectional view showing an device structure of a
MIS field effect transistor according to a first embodiment.
[0027] A polysilicon gate electrode 102 is formed on a p-type
silicon substrate (first semiconductor region) 100 a gate
insulating film 101 in between. A gate silicide 103 is formed on
the polysilicon gate electrode 102. In this case, the gate
electrode 102 is made of polysilicon. However, a metal gate
structure in which the polysilicon gate electrode 102 and the gate
silicide 103 are replaced by a single metal layer may be
employed.
[0028] On both the side surfaces of the gate electrodes 102 and
103, a gate side wall insulating film 104 constituted by a silicon
nitride film is formed. Source and drain regions are formed in the
silicon substrate 100 to interpose a channel region under the
polysilicon gate electrode 102. The source and drain regions are
constituted by, an n-type extension diffusion layer (second
semiconductor region) 105 using, for example, As as an impurity,
source and drain suicides (source electrode and drain electrode)
107 made of, for example, nickel silicide (NiSi), and an
n.sup.+-type high-concentration impurity layer (third semiconductor
region) 106 using, for example, As as an impurity. The n.sup.+-type
high-concentration impurity layer 106 is formed between the source
and drain electrodes 107 and the silicon substrate 100 and the
n-type extension diffusion layer 105. The n.sup.+-type
high-concentration impurity layer 106 has an impurity concentration
higher than that of the n-type extension diffusion layer 105. The
impurity of the n.sup.+-type high-concentration impurity layer 106
is formed by segregating the impurity of the n-type extension
diffusion layer 105 in manufacturing of the source and drain
electrodes 107.
[0029] A characteristic feature of the embodiment is to have a
structure in which, as shown in FIG. 1, an interface of the source
and drain suicides 107 is separated (offset) from the gate side
wall insulating film 104 (L1>0).
[0030] As described above, when the structure in which the
interface of the source and drain suicides 107 is separated from
the gate side wall insulating film 104 is employed, a conspicuous
operation and effect that suppress a decrease in injection rate of
carriers from the source are obtained.
[0031] The operation and effect of the embodiment will be described
below with reference to the band diagram in FIGS. 2A and 2B. FIG.
2A includes a sectional view and a band diagram of a field effect
transistor according to the embodiment in which a gate side wall
insulating film is separated from a source-drain silicide interface
(L1>0). FIG. 2B includes a sectional view and a band diagram of
a field effect transistor using a conventional Schottky source and
drain in which a gate side wall insulating film is overlapped on a
source-drain silicide (L1.ltoreq.0).
[0032] In the embodiment, as shown in FIG. 2A, an energy difference
(.DELTA.E) is given between a Fermi level of the source and a
potential top of the channel to increase an injection rate of
carriers. However, as shown in FIG. 2B, when a source metal or a
source silicide is excessively close to a gate electrode as in a
conventional field effect transistor, a Schottky barrier of the
source moderates a gate electric field to make it impossible to
increase the injection rate of carriers. In particular, in the
interface between the gate side wall insulating film 104 and an
upper layer film thereof, an electric flux line of the gate
electric field which goes around the gate electrode from the gate
electrode side surface is terminated. For this reason, especially
when the interface of the source-drain silicide 107 is overlapped
on the gate side wall insulating film 104 (L1.ltoreq.0), a gate
electric field moderating effect achieved by the Schottky barrier
of the source becomes conspicuous to decrease the energy
difference. Therefore, a decrease in injection rate of carriers
from the source becomes large. Therefore, the structure of the
embodiment in which the interface of the source-drain silicide 107
is separated (offset) (L1>0) from the gate side wall insulating
film 104 is employed to make it possible to obtain the operation
and effect that suppress a decrease in injection rate of carriers
from the source.
[0033] The operation and effect of the embodiment are especially
effective when the material constituting the gate side wall
insulating film has a dielectric constant higher than that of the
upper layer film of the gate side wall insulating film, for
example, when the gate side wall insulating film and the upper
layer film are a silicon nitride film and a silicon oxide film,
respectively. This is because convergence of an electric line of
force on the interface of the gate electric field which goes around
the gate electrode from the gate electrode side surface becomes
conspicuous. However, when the dielectric constants are equal to
each other, for example, even though both the gate side wall
insulating film and the upper layer film are silicon nitride films,
the electric line of force of the gate electric field is terminated
due to the influence of an interface level existing on the
interface. For this reason, the operation and effect as those
described above are obtained as well.
[0034] A simulation result of characteristics of the field effect
transistor according to the embodiment will be described below with
reference to the drawings. In the simulation, as reference values
of respective parameters, a gate length (L)=30 nm, an equivalent
oxide thickness (EOT) of a gate insulating film=1.2 nm, a side wall
thickness of the gate side wall insulating film=8 nm, and a
separation distance (L1) between the gate side wall insulating film
and the source-drain silicide interface=10 nm are set. Parameters
to which conditions are not assigned are calculated to be fixed to
the reference values. The side wall thickness and the separation
distance (L1) are calculated such that the side wall thickness and
the separation distance are symmetrically changed with respect to a
gate in both the side directions. With respect to an increasing
rata of a drain current, a field effect transistor using a
diffusion layer as a source-drain having an equivalent standby
current characteristic is used as an object to be compared.
[0035] FIG. 3 shows dependence of a drain current on a separation
distance (L1) between the gate side wall insulating film and the
source-drain silicide interface. The gate side wall thickness is
calculated from three conditions (10 nm, 12 nm, and 14 nm). As is
apparent from FIG. 3, it is observed that, regardless of the side
wall thickness, the drain current sharply increases from a region
in which the separation distance L1 exceeds 0. Furthermore, when
the separation distance increases, the drain current begins to
decrease. This is because a diffusion layer resistance increases
when the length of separation portion increases.
[0036] According to the above result, the separation distance L1 is
desirably larger than 0 and 30 nm or less. This is because in the
region a drain current becomes larger than that of a conventional
field effect transistor in which a source-drain silicide interface
and a side wall insulating film overlap. Furthermore, the
separation distance L1 is desirably 4 nm or more and 20 nm or less.
This is because a drain current has a maximal value in this
region.
[0037] FIG. 4 shows a dependence of an increasing rate of a drain
current on a gate length (L). As is apparent from FIG. 4, in the
field effect transistor according to the embodiment, as a gate
length decreases, a drain current characteristic is improved in
comparison with a conventional field effect transistor in which a
diffusion layer is used as a source-drain region. When the gate
length becomes short, i.e., when a channel length becomes short, a
channel resistance becomes relatively small to a parasitic
resistance. For this reason, the effect of the embodiment which
increases an injection rate of carriers more conspicuously
appears.
[0038] According to the above result, the gate length (L) is
desirably 80 nm or less which is equal to or more than that of a
conventional field effect transistor. Furthermore, the gate length
(L) is desirably less than 30 nm where an increasing rate of the
drain current is 10% or more (1.1 times the drain current).
[0039] FIG. 5 shows a dependence of an increasing rate of a drain
current on a gate insulating film EOT. As is apparent from FIG. 5,
in the field effect transistor according to the embodiment, as the
EOT decreases in thickness, a drain current characteristic is
improved in comparison with a conventional field effect transistor
in which a diffusion layer is used as a source-drain region. This
is because the EOT decreases in thickness to make it possible to
more effectively modulate a potential of the segregation layer 106
(FIG. 1) through the n-type extension diffusion layer 105 (FIG. 1).
Therefore, the injection rate of carriers can be improved without
increasing a parasitic resistance.
[0040] According to the above result, the gate insulating film EOT
is desirably set at 4 nm or more which is equal to or larger than
the characteristic of the conventional field effect transistor such
that an increasing rate of the drain current is 0% or more.
Furthermore, the gate insulating EOT is desirably 1.3 nm or less at
which the drain current further increases.
[0041] FIG. 6 shows a dependence of a drain current of the gate
side wall insulating film thickness. As is apparent from FIG. 6, in
the field effect transistor according to the embodiment, a drain
current characteristic is deteriorated as the side wall thickness
increases. This is because, when the side wall thickness increases,
influence of a parasitic resistance of an extension diffusion layer
under the side wall increases.
[0042] According to the above result, the side wall thickness is
desirably 10 nm or less at which deterioration of a drain current
characteristic is not conspicuous, and is more desirably 8 nm or
less at which the deterioration of the drain current characteristic
is not observed.
[0043] In the field effect transistor according to the embodiment,
an impurity concentration of the n.sup.+-type high-concentration
impurity layer 106 in interfaces between the impurity layer and the
source and the drain electrode is desirably 8.times.10.sup.19 to
5.times.10.sup.20 atoms/cm.sup.3, and an impurity concentration at
a depth of 20 nm from the interfaces between the impurity layer and
the source and drain electrode is desirably 1/10 or less the
impurity concentration in the interfaces between the impurity layer
and the source and drain electrode. More specifically, a depth of a
point at which an impurity concentration decreases to 1/10 from the
interface is desirably 20 nm or less. This is because, when the
concentration in the interface is equal to or less than the above
value, the current decreases due to an insufficient decrease of a
Schottky barrier. When the depth of the point at which the impurity
concentration decreases to 1/10 from the interface is the above
depth or more, an injection rate is decreased by the resistance of
an impurity layer in traveling of carriers from the source to the
drain.
[0044] The n-type extension diffusion layer 105 desirably has a
maximum impurity concentration in a gate insulating film interface,
the maximum impurity concentration is desirably 1/2 or less the
impurity concentration of the n.sup.+-type high-concentration
impurity layer 106 in the interfaces between the impurity layer 106
and the source and the drain electrode, and an impurity
concentration at a depth of 30 nm from the gate insulating film
interface is desirably 1/10 or less the concentration in the gate
insulating film interface. More specifically, the depth of the
point at which the impurity concentration decreases to 1/10 from
the interface is desirably 30 nm or less. This is because, when the
concentration and the depth are equal to or larger than the given
concentration and the given depth, respectively, an off current
increases due to the influence of a short channel effect.
[0045] A first manufacturing method for the field effect transistor
according to the embodiment will be described below with reference
to FIGS. 7 to 12.
[0046] As shown in FIG. 7, a device isolation region (not shown) is
formed on the p-type silicon substrate (first semiconductor region)
100 having a (100) orientation plane. Thereafter, the gate
insulating film 101 is formed to have an EOT of about 1.2 nm. A
polysilicon film serving as the gate electrode 102 is deposited by
a low-pressure chemical vapor deposition (to be also referred to as
LP-CVD hereinafter) method to have a thickness of about 100 to 150
nm. Subsequently, by a lithography technique and an etching
technique such as a reactive ion etching (to be also referred to as
RIE hereinafter), the gate insulating film 101 and the gate
electrode 102 are formed. If necessary, post oxidation is performed
in a thickness of 1 to 2 nm.
[0047] As shown in FIG. 8, a silicon nitride film is deposited by
the LP-CVD method to have a thickness of about 8 nm. Thereafter,
the silicon nitride film is etched back by the RIE method to cause
the silicon nitride film to be left on only a side surface portion
of the gate electrode 102. In this manner, the gate side wall
insulating film 104 is formed. In this case, only the single
silicon nitride film is used as the side wall. However, for
example, when a dual side wall insulating film obtained by
laminating a TEOS oxide film having a thickness of about 3 nm and a
silicon nitride film having a thickness of 5 nm is formed, carrier
trap to the lower surface of the side wall insulating film is
suppressed. This is more desirable in terms of device
reliability.
[0048] As shown in FIG. 9, As having a dose of 2.times.10.sup.15
cm.sup.-2 or more is ion-implanted as an impurity at 2 KeV or less
(more desirably, 1 KeV or less) to form the n-type extension layer
(second semiconductor region) 105. Here, spike annealing at 1030 to
1050.degree. C. is performed to activate the impurity.
[0049] As shown in FIG. 10, a TEOS oxide film is deposited by the
LP-CVD method to have a thickness of about 10 nm and etched back by
the RIE method to form a second side wall insulating film 112.
[0050] After the surface of the silicon substrate 100 is cleaned
with a diluted hydrofluoric acid or the like, Ni is sputtered in a
thickness of 7 to 11 nm (more desirably, 9 nm or less) and
heat-treated at 350.degree. C. for 30 seconds, as shown in FIG. 11.
In this manner, silicon of source, drain, and gate electrodes is
silicided. At this time, with respect to the source and drain
electrodes, silicide is performed up to a position deeper than the
n-type extension layer 105. Thereafter, unreacted Ni is removed
with a mixed solution of a sulfuric acid and a hydrogen peroxide
solution or the like. Furthermore, heat treatment is performed at
500.degree. C. for about 30 seconds to form the source-drain
silicide 107 and the silicon substrate 100 and the gate silicide
103.
[0051] At the same time, an As impurity in the n-type extension
layer 105 is segregated by siliciding. The n.sup.+-type
high-concentration impurity layer 106 having a concentration higher
than that of the n-type extension layer 105 is formed in the
interface between the source-drain silicide 107 and the n-type
extension layer 105.
[0052] Thereafter, as shown in FIG. 12, the second side wall
insulating film 112 formed by the TEOS oxide film is peeled with a
diluted hydrofluoric acid or the like to make it possible to obtain
the structure shown in FIG. 1.
[0053] According to the first manufacturing method described above,
the deposited film thickness of the TEOS oxide film forming the
second side wall insulating film 112 is changed, so that the
separation distance (L1) of the interface between the gate side
wall insulating film 104 and the source-drain silicide 107 can be
set to a desired value.
[0054] In the first manufacturing method, control of an amount of
substrate etching is important when the TEOS oxide film is etched
back by the RIE method to form the second side wall insulating film
112. As shown in FIG. 13, depending on conditions in RIE of the
TEOS oxide film, the silicon substrate 100 is etched by
overetching. In this case, the amount of substrate etching means a
thickness at which the silicon is etched from the silicon substrate
surface by overetching in a direction of depth in the etch-back
operation.
[0055] FIG. 14 shows a relationship between the amount of substrate
etching at this time and an increasing rate of a drain current. In
this case, simulation is performed such that parameters other than
the amount of substrate etching are fixed to the reference values
described above. As is apparent from FIG. 14, as the amount of
etching increases, a drain current characteristic is degraded. This
is because the separation distance L1 is substantially shortened or
the side wall insulating film and the source-drain silicide overlap
since formation of the source-drain silicide 107 extends toward the
gate insulating film by etching the substrate.
[0056] According to the above result, etching conditions and
etching time are desirably controlled such that the amount of
substrate etching is set to 8 nm or less which obtain a drain
current having an increasing rate of 0% or more, i.e., equal to or
larger than that of conventional field effect transistor
characteristics, more preferably, 6 nm or less at which the drain
current further increases.
[0057] As shown in FIG. 13, to avoid the increase of parasitic
resistance caused by removal of the n-type extension layer 105
formed in advance, the amount of substrate etching is desirably
controlled at the minimum.
[0058] A second manufacturing method for the field effect
transistor according to the embodiment will be described below with
reference to FIGS. 15 to 20.
[0059] As shown in FIG. 15, the gate insulating film 101 and the
gate electrode 102 are formed as in the first manufacturing method.
If necessary, post oxidation is performed in a thickness of 1 to 2
nm.
[0060] As shown in FIG. 16, a silicon nitride film is deposited by
the LP-CVD method to have a thickness of about 8 nm and etched back
to form the gate side wall insulating film 104. At this time, the
gate side wall insulating film 104 is processed to have a
footing-bottom shape (or tailed shape) at a lower side surface as
shown in FIG. 16. This process can be performed, for example, by
the RIE method with a footing-bottom condition selected. At this
time, the degree of footing bottom is controlled by etching
conditions to control a final separation distance L1.
[0061] As shown in FIG. 17, the n-type extension layer 105 is
formed and activated by the same method as the first manufacturing
method.
[0062] As shown in FIG. 18, the source-drain silicide 107 and the
gate silicide 103 are formed as in the same method as the first
manufacturing method. At the same time, the n.sup.+-type
high-concentration impurity layer (third semiconductor region) 106
is formed in the interface between the source-drain silicide 107
and the silicon substrate 100. At this time, the interface of the
source-drain silicide 107 is located near the foot of the gate side
wall insulating film 104.
[0063] Thereafter, as shown in FIG. 19, the foot of the gate side
wall insulating film 104 is removed to obtain the structure shown
in FIG. 1. The removal of the foot may be performed by a wet
etching process after the formation of the source-drain silicide
107 or may be performed by an RIE method having strong
isotropy.
[0064] According to the second manufacturing method described
above, the step of forming a second sidewall insulating film is
unnecessary. For this reason, the manufacturing steps of the second
manufacturing method can be simplified in comparison with the first
manufacturing method.
[0065] As shown in FIG. 20, also in the second manufacturing
method, a problem of etching in the substrate 100 by overetching
when the gate side wall insulating film 104 is formed by an
etch-back process in the RIE method, and other problems are posed
as in the first manufacturing method.
[0066] Therefore, as in the first manufacturing method, etching
conditions and etching time are desirably controlled such that the
amount of substrate etching is set to 8 nm or less at which a drain
current has an increasing rate of 0% or more, and more preferably,
6 nm or less at which the drain current further increases. However,
unlike in the first manufacturing method, the n-type extension
layer 105 is formed after the etch-back process in the RIE in the
second manufacturing method. For this reason, a problem of removal
of the n-type extension layer 105 is not occurred.
[0067] In this case, in order to avoid the silicon substrate 100
from being etched, the following third manufacturing method can
also be used. More specifically, as in the first and second
manufacturing methods, the gate insulating film 101 and the gate
electrode 102 are formed by patterning. Thereafter, as shown in
FIG. 21, a silicon nitride film is deposited by the LP-CVD method
to have a thickness of about 8 nm. The silicon nitride film is
etched back by anisotropic etching such as an RIE method. At this
time, a silicon nitride film having a thickness of about 1 nm is
left on the surface of the silicon substrate 100. More
specifically, the silicon nitride film is maximally etched not to
expose the p-type silicon substrate 100.
[0068] As shown in FIG. 22, As (Arsenic) having a dose of
2.times.10.sup.15 cm.sup.-2 or more is ion-implanted as an impurity
at 2 KeV or less, more desirably 1 KeV or less, to form the n-type
extension layer 105. Here, spike annealing at 1030 to 1050.degree.
C. is performed to activate the impurity.
[0069] As shown in FIG. 23, the silicon nitride film on the surface
of the p-type silicon substrate 100 is removed to form the gate
side wall insulating film 104. At this time, the gate side wall
insulating film 104, as shown in FIG. 23, is processed to have a
footing-bottom shape on the surface of the silicon substrate 100.
This process can be performed, for example, by isotropic wet
etching such as diluted hydrofluoric acid treatment,
high-temperature phosphoric acid treatment, or hydrofluoric
glycerol treatment.
[0070] The subsequent steps are the same as those in the second
manufacturing method. As described above, in removal of the silicon
nitride film, the amount of etching of the substrate 100 can be
minimized by using wet etching which can have selectivity to the
silicon substrate 100 higher than that in the RIE method.
[0071] The field effect transistor according to the embodiment
described above has a self-aligned silicide structure. An interface
between the silicide of the source-drain portion and the silicon
substrate is separated from the gate side wall insulating film. The
interface is covered with an impurity layer having a steep impurity
concentration profile at a desired concentration or more.
Therefore, improvement of performance by increasing an injection
rate of carriers and improvement of element reliability can be
achieved while suppressing punch through and leakage current.
Second Embodiment
[0072] FIG. 24 is a cross-sectional view showing an device
structure of a MIS field effect transistor according to a second
embodiment of the present invention. Since the MIS field effect
transistor is the same as that in the first embodiment except that
an HALO diffusion layer (fourth semiconductor region) 201 is
formed, a description thereof will be omitted.
[0073] The HALO diffusion layer 201 is a p-type region the impurity
type of which is the same as that of a silicon substrate 100, and
has an impurity concentration higher than that of the silicon
substrate 100 as a characteristic feature. The field effect
transistor according to the embodiment includes the HALO diffusion
layer 201 to obtain the operation and effect of the first
embodiment and to achieve improvement of a roll-off
characteristic.
Third Embodiment
[0074] FIG. 25 is a cross-sectional view showing an device
structure of a MIS field effect transistor according to a third
embodiment of the present invention. Since the MIS field effect
transistor according to the third embodiment is the same as that of
the first embodiment except that an n.sup.+-type deep diffusion
layer (fifth semiconductor region) 301 is formed, a description
thereof will be omitted.
[0075] The n.sup.+-type deep diffusion layer 301 is formed between
an n.sup.+-type high-concentration impurity layer 106 and the
silicon substrate 100, and has a thickness of, for example, about
50 nm.
[0076] The field effect transistor according to the embodiment
includes the n.sup.+-type deep diffusion layer 301 to obtain the
operation and effect of the first embodiment and to achieve a
considerable reduction in junction leakage from the source-drain
bottom portion.
[0077] Due to the presence of the n.sup.+-type high-concentration
impurity layer 106, the n.sup.+-type deep diffusion layer 301 can
be made shallower or can have a concentration lower than a deep
diffusion layer applied to a MOSFET using a normal diffusion layer
as a source-drain region. Therefore, it is also a characteristic
feature of the embodiment that a punch through current can be
suppressed.
Fourth Embodiment
[0078] FIG. 26 is a cross-sectional view showing an element
structure of a MIS field effect transistor according to a fourth
embodiment of the present invention. Since the MIS field effect
transistor according to the fourth embodiment is the same as that
of the first embodiment except that an HALO diffusion layer (fourth
semiconductor region) 201 and an n.sup.+-type deep diffusion layer
(fifth semiconductor region) 301 are formed, a description thereof
will be omitted.
[0079] In this manner, both the HALO diffusion layer 201 and the
n.sup.+-type deep diffusion layer 301 are formed to make it
possible to simultaneously realize improvement of the roll-off
characteristic and a considerable reduction in junction leakage as
described above.
[0080] A method of manufacturing a field effect transistor
according to the embodiment will be described below with reference
to FIGS. 27 to 34.
[0081] As shown in FIG. 27, an device isolation region (not shown)
is formed on the p-type silicon substrate (first semiconductor
region) 100 having a (100) orientation plane. Thereafter, the gate
insulating film 101 is formed to have an EOT of about 1.2 nm. A
polysilicon film serving as the gate electrode 102 is deposited by
a low-pressure chemical vapor deposition (to be also referred to as
LP-CVD hereinafter) method to have a thickness of about 100 to 150
nm. Subsequently, the gate insulating film 101 and the gate
electrode 102 are formed by patterning by a lithography technique
and an etching technique such as a reactive ion etching (to be also
referred to as RIE hereinafter). If necessary, post oxidation is
performed in a thickness of 1 to 2 nm.
[0082] As shown in FIG. 28, a silicon nitride film is deposited by
the LP-CVD method or the like to have a thickness of about 24 nm.
Thereafter, the silicon nitride film is etched back by the RIE
method to form dummy gate side wall insulating films 121 on both
the side surfaces of the gate electrode 102.
[0083] As shown in FIG. 29, As having a dose of 2.times.10.sup.15
cm.sup.-2 or more is ion-implanted as an impurity at 25 KeV or
less, more desirably, 20 KeV or less, to form the n.sup.+-type deep
diffusion layer 301. Here, spike annealing at 1050.degree. C. may
be performed to activate the impurity.
[0084] The dummy gate side wall insulating films 121 are removed by
wet etching or the like. Subsequently, as shown in FIG. 30, a
silicon nitride film is deposited by the LP-CVD method to have a
thickness of about 8 nm. Thereafter, the silicon nitride film is
etched back by the RIE method to leave the silicon nitride film on
only a side surface portion of the gate electrode 102. In this
manner, the gate side wall insulating film 104 is formed. In this
case, only the single silicon nitride film is used as the side
wall. However, a dual side wall insulating film obtained by
laminating a TEOS oxide film and a silicon nitride film is
desirably formed in terms of reliability as in the first
embodiment.
[0085] As shown in FIG. 31, As having a dose of 2.times.10.sup.15
cm.sup.-2 or more is ion-implanted as an impurity at 2 KeV or less
(more desirably, 1 KeV or less) to form the n-type extension layer
105. As an impurity, B or BF.sub.2 is ion-implanted to form an HALO
diffusion layer 201. Here, spike annealing at 1030 to 1050.degree.
C. is performed to activate the impurity.
[0086] As shown in FIG. 32, a TEOS oxide film is deposited by the
LP-CVD method to have a thickness of about 10 nm and etched back by
the RIE method to form a second side wall insulating film 112.
[0087] After the substrate surface is cleaned with a diluted
hydrofluoric acid or the like, Ni is sputtered in a thickness of 7
to 11 nm (more desirably, 9 nm or less), as shown in FIG. 33.
Thereafter, heat treatment is performed at 350.degree. C. for about
30 seconds to silicide silicon of source, drain, and gate
electrodes. At this time, with respect to the source and drain
electrodes, silicide is performed up to a position deeper than the
n-type extension layer 105. Thereafter, unreacted Ni is removed
with a mixed solution of a sulfuric acid and a hydrogen peroxide
solution or the like. Furthermore, heat treatment is performed at
500.degree. C. for about 30 seconds to form the source-drain
silicide 107 and the gate silicide 103. At the same time, an As
impurity in the n-type extension layer 105 is segregated by
siliciding. In the interface between the source-drain silicide 107
and the silicon substrate 100, the n.sup.+-type high-concentration
impurity layer 106 is formed.
[0088] Thereafter, as shown in FIG. 34, the second side wall
insulating film formed by the TEOS oxide film is removed with a
diluted hydrofluoric acid or the like to obtain the structure shown
in FIG. 26.
[0089] The present invention is not limited to the above
embodiments. In the embodiments, an n-channel MIS field effect
transistor is described. However, the present invention can be also
applied to a p-channel MIS field effect transistor. In the
embodiments, the description is made by using As as impurities in
the second and third semiconductor regions, but the impurity is not
limited to As. When an n-type semiconductor region is formed, an
impurity can also be selected from elements such as P serving as a
donor. When a p-type semiconductor region is formed, the impurity
can be selected from elements such as B serving as an acceptor.
Although silicon is used as a semiconductor substrate material, the
semiconductor substrate material is not limited to silicon. Silicon
germanium (SiGe), germanium (Ge), silicon carbide (SiC), gallium
arsenide (GaAs), aluminum nitride (AlN), or the like can be
used.
[0090] The orientation of the substrate material is not limited to
a (100) orientation plane. A (110) orientation plane, a (111)
orientation plane or the like can be properly selected. The present
invention can also be applied to any MIS field effect transistor,
including a three-dimensional structure such as an Fin structure or
a double-gate structure. Furthermore, various modifications of the
present invention can be effected without departing from the spirit
and scope of the invention.
* * * * *