U.S. patent application number 12/011105 was filed with the patent office on 2008-05-29 for semiconductor substrate, semiconductor device, method for manufacturing semiconductor substrate and method for manufacturing semiconductor device.
This patent application is currently assigned to Seiko Epson Corporation. Invention is credited to Juri Kato.
Application Number | 20080122024 12/011105 |
Document ID | / |
Family ID | 35905981 |
Filed Date | 2008-05-29 |
United States Patent
Application |
20080122024 |
Kind Code |
A1 |
Kato; Juri |
May 29, 2008 |
SEMICONDUCTOR SUBSTRATE, SEMICONDUCTOR DEVICE, METHOD FOR
MANUFACTURING SEMICONDUCTOR SUBSTRATE AND METHOD FOR MANUFACTURING
SEMICONDUCTOR DEVICE
Abstract
A semiconductor substrate comprising a semiconductor base, a
dielectric layer formed in at least a part of an area on the
semiconductor base, and a single crystal semiconductor layers
having mutually different film thicknesses, disposed on the
dielectric layer and formed by epitaxial growth.
Inventors: |
Kato; Juri; (Chino-shi,
JP) |
Correspondence
Address: |
Edwards Angell Palmer & Dodge LLP
P.O. Box 55874
Boston
MA
02205
US
|
Assignee: |
Seiko Epson Corporation
Tokyo
JP
|
Family ID: |
35905981 |
Appl. No.: |
12/011105 |
Filed: |
January 24, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11192898 |
Jul 28, 2005 |
7344997 |
|
|
12011105 |
|
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Current U.S.
Class: |
257/499 ;
257/E21.703; 257/E27.081; 257/E27.112 |
Current CPC
Class: |
H01L 21/76283 20130101;
H01L 27/1203 20130101; H01L 21/84 20130101; H01L 27/105
20130101 |
Class at
Publication: |
257/499 ;
257/E27.112 |
International
Class: |
H01L 27/12 20060101
H01L027/12 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 29, 2004 |
JP |
2004-221413 |
Claims
1. A semiconductor substrate characterized in comprising: a
semiconductor base; a dielectric layer formed in at least a part of
an area on the semiconductor base; and single crystal semiconductor
layers having mutually different film thicknesses, disposed on the
dielectric layer and formed by epitaxial growth.
2. A semiconductor substrate characterized in comprising: a
semiconductor base; a first dielectric layer formed in a first area
on the semiconductor base; a first single crystal semiconductor
layer formed on the first dielectric layer; a laminated layered
structure of alternately laminated layers of different selection
ratios at etching, formed in a second area on the semiconductor
base; a second dielectric layer formed on the laminated layered
structure; and a second single crystal semiconductor layer formed
on the second dielectric layer.
3. A semiconductor device characterized in comprising: a
semiconductor substrate; a dielectric layer formed in a part of an
area on the semiconductor substrate; a single crystal semiconductor
layer disposed on the dielectric layer and formed by epitaxial
growth; and semiconductor elements of mutually different usages
formed in the semiconductor substrate and the single crystal
semiconductor layer.
4. A semiconductor device characterized in comprising: a
semiconductor substrate; a dielectric layer formed in a part of an
area on the semiconductor substrate; single crystal semiconductor
layers of mutually different film thicknesses, disposed on the
dielectric layer and formed by epitaxial growth; and semiconductor
elements of mutually different usages formed in the single crystal
semiconductor layers.
5. A semiconductor device characterized in comprising: a
semiconductor substrate; a dielectric layer formed in a part of an
area on the semiconductor substrate; single crystal semiconductor
layers of mutually different film thicknesses, disposed on the
dielectric layer and formed by epitaxial growth; and semiconductor
elements of mutually different usages formed in the semiconductor
substrate and the single crystal semiconductor layers of mutually
different film thicknesses.
6. A semiconductor device according to claim 4 or 5, characterized
in further comprising element isolation regions for isolating the
single crystal semiconductor layers in a horizontal direction,
wherein the single crystal semiconductor layers of mutually
different film thicknesses are disposed in a self-alignment manner
between the element isolation regions.
7. A semiconductor device according to claim 5 or 6, characterized
in that a protection circuit or a trench memory cell is disposed in
the semiconductor substrate, and among the single crystal
semiconductor layers of mutually different film thicknesses, a
completely depleted type field effect transistor is disposed in a
single crystal semiconductor layer of a smaller film thickness, and
a partially depleted type field effect transistor or bipolar
transistor is disposed in a single crystal semiconductor layer of a
greater film thickness.
8. (canceled)
9. (canceled)
10. (canceled)
Description
BACKGROUND OF THE INVENTION
[0001] 1. Technical Field
[0002] The present invention relates to semiconductor substrates,
semiconductor devices, methods for manufacturing semiconductor
substrates, and methods for manufacturing semiconductor devices,
and it is particularly suitable for application to field effect
transistors formed on a SOI (Silicon On Insulator) substrate.
[0003] 2. Description of Related Art
[0004] The utilities of field effect transistors formed on a SOI
substrate are attracting attention because of their readiness of
element isolation, latch-up free characteristics, small
source/drain junction capacitances and the like.
[0005] Also, for example, Japanese Laid-open Patent Application HEI
7-225410 (JP '410) describes a method of forming high breakdown
voltage field effect transistors on a SOI substrate. Also, Japanese
Laid-open Patent Application 2003-158091 (JP '091) describes a
method of forming field effect transistors that are miniaturized on
the other of submicron on a SOI substrate.
[0006] It is noted here that optimum film thicknesses of SOI layers
differ for semiconductor elements of different usages. In other
words, for a high breakdown voltage field effect transistor
subjected to application of a high voltage load, its SOI layer
needs to have a larger film thickness in order to secure the PN
junction breakdown voltage, and the film thickness of the SOI layer
amounts to the order of .mu.m. For example, in the case of a high
breakdown voltage field effect transistor having a drain breakdown
voltage of about 100V, the film thickness of the SOI layer needs to
be about several .mu.m.
[0007] On the other hand, for a field effect transistor that is
miniaturized on the order of submicron, its BOX layer needs to have
a smaller film thickness in order to suppress punchthrough leakage
and reduction of threshold values by short-channel effects, and
thus the film thickness of the BOX layer becomes to be on the order
of several hundred angstrom. For example, when the effective
channel length becomes 0.1 .mu.m or less, the film thickness of the
SOI layer needs to be set to 50 nm or less.
[0008] In the meantime, accompanied by the advent of ubiquitous
societies, the SOC (System On Chip) technology that enables
mix-mounting of devices of various breakdown voltages and digital
and analog devices on a single chip is attracting attention, for
further promotion of miniaturization of information portable
devices, reduction of power consumption, greater multiple
functions, and greater capacities.
[0009] Also, Japanese Laid-open Patent Application 2002-299591 (JP
'591) describes a method of forming semiconductor elements for
different usages in active layers having thicknesses suitable for
the respective usages by embedding dielectric films at different
depths from a main surface of a semiconductor substrate, in order
to realize the SOC on a SOI substrate.
[0010] However, according to the methods described in JP '410 and
JP '091, the film thickness of the BOX layer is maintained at
constant by the SOI substrate. For this reason, for forming
semiconductor elements for different usages on a SOI substrate, the
semiconductor elements need to be independently formed on different
SOI substrates for the respective usages, which causes a problem
that presents an obstruction to realization of the SOC.
[0011] Also, according to the method described in JP '591, in order
to embed dielectric films at different depths from the main surface
of the semiconductor substrate, oxygen ions are injected in a
silicon substrate with different energies. For this reason,
physical damages are generated in the silicon substrate, and the
crystallinity and purity of the SOI layer deteriorate, thereby
causing a problem in that, when semiconductor elements are formed
in the SOI layer, their characteristics deteriorate due to PN
junction leakages or the like.
[0012] Furthermore, according to the method described in JP '591,
when mask deviations occur between the BOX layer and the element
isolation layer, lacks or duplicates may occur in the BOX layer.
For this reason, the element isolating separations among
semiconductor elements become greater, and characteristics of
elements near the element isolation regions deteriorate, which
causes problems in that the degree of integration of semiconductor
elements becomes lower, and the reliability of the semiconductor
elements becomes deteriorated.
SUMMARY OF THE INVENTION
[0013] It is thus an object of at least one embodiment of the
present invention to provide semiconductor substrates,
semiconductor devices, a method for manufacturing semiconductor
substrates, and a method for manufacturing semiconductor devices,
which can maintain the crystal quality of semiconductor layers, and
are capable of forming semiconductor layers of mutually different
film thicknesses on dielectric layers.
[0014] To solve the problems described above, a semiconductor
substrate in accordance with an embodiment of the present invention
comprises: a semiconductor base; a dielectric layer formed in at
least a part of an area on the semiconductor base; and single
crystal semiconductor layers having mutually different film
thicknesses, disposed on the dielectric layer and formed by
epitaxial growth.
[0015] By this, physical damages that may be inflicted on the
single crystal semiconductor layers can be suppressed, and film
thicknesses of the single crystal semiconductor layers can be set
to match with the respective usages of semiconductor elements. For
this reason, semiconductor elements for different usages can be
formed on the single crystal semiconductor layers that have optimum
film thicknesses, respectively, deterioration of the crystallinity
and purity of the single crystal semiconductor layers can be
suppressed, and junction leakages can be reduced while securing
high level of mobility.
[0016] As a result, while short-channel effects can be suppressed,
higher speed and further miniaturization of field effect
transistors can be achieved, and while PN junction breakdown
strength can be secured, high breakdown voltage field effect
transistors can be formed on a common SOI substrate. For this
reason, a System-On-Chip can be realized on a common SOI substrate,
and miniaturization, lower power consumption, greater multiple
functions and greater capacities of semiconductor devices can be
promoted.
[0017] Also, a semiconductor substrate in accordance with an
embodiment of the present invention comprises: a semiconductor
base; a first dielectric layer formed in a first area on the
semiconductor base; a first single crystal semiconductor layer
formed on the first dielectric layer; a laminated layered structure
of alternately laminated layers of different selection ratios at
etching, formed in a second area on the semiconductor base; a
second dielectric layer formed on the laminated layered structure;
and a second single crystal semiconductor layer formed on the
second dielectric layer.
[0018] By this, the second single crystal semiconductor layer can
be disposed on the second dielectric layer that is formed on the
laminated layered structure of alternately laminated semiconductor
layers, and the first single crystal semiconductor layer can be
disposed on the first dielectric layer that is directly formed on
the semiconductor base. For this reason, heights of the first
dielectric layer and the second dielectric layer disposed on the
semiconductor base can be made different from each other,
planarization can be achieved between the first single crystal
semiconductor layer and the second single crystal semiconductor
layer, and the first single crystal semiconductor layer and the
second single crystal semiconductor layer can be made to have
mutually different film thicknesses.
[0019] Also, a semiconductor device in accordance with an
embodiment of the present invention comprises: a semiconductor
substrate; a dielectric layer formed in a part of an area on the
semiconductor substrate; a single crystal semiconductor layer
disposed on the dielectric layer and formed by epitaxial growth;
and semiconductor elements of mutually different usages formed in
the semiconductor substrate and the single crystal semiconductor
layer.
[0020] Also, a semiconductor device in accordance with an
embodiment of the present invention comprises: a semiconductor
substrate; a dielectric layer formed in a part of an area on the
semiconductor substrate; single crystal semiconductor layers of
mutually different film thicknesses, disposed on the dielectric
layer and formed by epitaxial growth; and semiconductor elements of
mutually different usages formed in the single crystal
semiconductor layers.
[0021] By this, semiconductor elements do not need to be formed
separately on independent SOI substrates for different usages, and
semiconductor elements for different usages can be formed on single
crystal semiconductor layers having optimum film thicknesses,
respectively, such that greater performance of a system-on-chip can
be achieved.
[0022] Also, a semiconductor device in accordance with an
embodiment of the present invention comprises: a semiconductor
substrate; a dielectric layer formed in a part of an area on the
semiconductor substrate; single crystal semiconductor layers of
mutually different film thicknesses, disposed on the dielectric
layer and formed by epitaxial growth; and semiconductor elements of
mutually different usages formed in the semiconductor substrate and
the single crystal semiconductor layers of mutually different film
thicknesses.
[0023] Also, the semiconductor device in accordance with an
embodiment of the present invention further comprises element
isolation regions for isolating the single crystal semiconductor
layers in a horizontal direction, wherein the single crystal
semiconductor layers of mutually different film thicknesses are
disposed in a self-alignment manner between the element isolation
regions.
[0024] By this, lacks or duplicates of single crystal semiconductor
layers can be prevented, while film thicknesses of the single
crystal semiconductor layers can be made mutually different for the
respective usages of the semiconductor elements. For this reason,
semiconductor elements for mutually different usages can be formed
on a common SOI substrate, and higher integration and higher
reliability of semiconductor elements can be achieved.
[0025] Also, the semiconductor device in accordance with an
embodiment of the present invention is characterized in that a
protection circuit or a trench memory cell is disposed in the
semiconductor substrate, and among the single crystal semiconductor
layers of mutually different film thicknesses, a completely
depleted type field effect transistor is disposed in a single
crystal semiconductor layer of a smaller film thickness, and a
partially depleted type field effect transistor or bipolar
transistor is disposed in a single crystal semiconductor layer of a
greater film thickness.
[0026] By this, in a high-speed and low-power semiconductor
element, when the effective channel length is 0.1 .mu.m or less,
the film thickness of the single crystal semiconductor layer can be
made to be 50 nm or less, such that there can be provided a
miniaturized transistor with higher performance and higher
reliability whose short-channel effect can be suppressed. Also, in
a transistor that is subjected to application of a high voltage
load, the film thickness of the single crystal semiconductor layer
can be made greater, such that a higher junction breakdown voltage
and a greater current capacity can be secured, and a transistor of
high breakdown voltage and large current with higher performance
and higher reliability can be provided.
[0027] Also, a method for manufacturing a semiconductor substrate
in accordance with an embodiment of the present invention
comprises: a step of forming, on a semiconductor base, a first
laminated layered structure composed of a second semiconductor
layer having a smaller selection ratio at etching than a first
semiconductor layer, laminated on the first semiconductor layer; a
step of forming, in a part of an area on the first laminated
layered structure, a second laminated layered structure composed of
a fourth semiconductor layer having a smaller selection ratio at
etching than a third semiconductor layer, laminated on the third
semiconductor layer; a step of forming a first groove that
penetrates the first semiconductor layer through the fourth
semiconductor layer and exposes the semiconductor base; a step of
forming a supporting body for supporting the second and fourth
semiconductor layers on the semiconductor base on side walls of the
first semiconductor layer through the fourth semiconductor layer in
the first groove; a step of forming, in a first area divided by the
first groove, a second groove that exposes at least a part of the
first semiconductor layer through the second semiconductor layer; a
step of forming, in a second area divided by the first groove, a
third groove that exposes at least a part of the third
semiconductor layer through the fourth semiconductor layer; a step
of forming void sections under the second and fourth semiconductor
layers by selectively etching the first and third semiconductor
layers through the second groove and the third groove; and a step
of forming dielectric layers disposed below the second and fourth
semiconductor layers by thermally oxidizing the second and fourth
semiconductor layers through the void sections.
[0028] By this, the second and fourth semiconductor layers can be
supported on the semiconductor base through the supporting body
formed in the first groove, the heights of the first and third
semiconductor layers that are exposed through the second and fourth
semiconductor layers, respectively, can be made different from each
other in the first area and the second area, and etching gas or
etching liquid can be brought in contact with the first and third
semiconductor layers through the second groove and the third
groove. For this reason, the second and fourth semiconductor layers
can be stably supported on the semiconductor base, the first and
third semiconductor layers disposed below the second and fourth
semiconductor layers, respectively, can be removed, and the heights
of the first and third semiconductor layers that are removed from
below the second and fourth semiconductor layers, respectively, can
be made different from each other in the first area and the second
area. As a result, the heights of dielectric layers to be formed by
thermal oxidation after the first and third semiconductor layers
are removed can be made different in the first area and the second
area, and the film thicknesses of the semiconductor layers in the
first area and the second area can be made mutually different.
[0029] Also, a method for manufacturing a semiconductor substrate
in accordance with an embodiment of the present invention is
characterized in that the second semiconductor layer, the fourth
semiconductor layer and the supporting body consist of single
crystal Si, and the first semiconductor layer and the third
semiconductor layer consist of single crystal SiGe.
[0030] By this, lattice matching of the first through fourth
semiconductor layers and the supporting body can be made, and the
selection ratio at the time of etching the first semiconductor
layer and the third semiconductor layer can be made greater than
that of the second semiconductor layer, the fourth semiconductor
layer and the supporting body. For this reason, the second and
fourth semiconductor layers of good crystal quality can be formed
on the first and third semiconductor layers, respectively, the
supporting body can be stably formed in the first groove, and
single crystal semiconductor layers of mutually different film
thicknesses can be formed in a common semiconductor substrate
without damaging the quality of the second and fourth semiconductor
layers.
[0031] Also, a method for manufacturing a semiconductor device in
accordance with an embodiment of the present invention comprises: a
step of forming, on a semiconductor substrate, a first laminated
layered structure composed of a second semiconductor layer having a
smaller selection ratio at etching than a first semiconductor
layer, laminated on the first semiconductor layer; a step of
forming, in a part of an area on the first laminated layered
structure, a second laminated layered structure composed of a
fourth semiconductor layer having a smaller selection ratio at
etching than a third semiconductor layer, laminated on the third
semiconductor layer; a step of forming a first groove that
penetrates the first semiconductor layer through the fourth
semiconductor layer and exposes the semiconductor substrate; a step
of forming a supporting body for supporting the second and fourth
semiconductor layers on the semiconductor substrate on side walls
of the first semiconductor layer through the fourth semiconductor
layer in the first groove; a step of forming, in a first area
divided by the first groove, a second groove that exposes at least
a part of the first semiconductor layer through the second
semiconductor layer; a step of forming, in a second area divided by
the first groove, a third groove that exposes at least a part of
the third semiconductor layer through the fourth semiconductor
layer; a step of forming void sections under the second and fourth
semiconductor layers by selectively etching the first and third
semiconductor layers through the second groove and the third
groove; a step of forming dielectric layers disposed below the
second and fourth semiconductor layers by thermally oxidizing the
second and fourth semiconductor layers through the void sections;
and a step of forming semiconductor elements of different usages
under the second and fourth semiconductor layers, respectively.
[0032] By this, the heights of the dielectric layers disposed below
the second and fourth semiconductor layers can be made different
from each other without damaging the quality of the second and
fourth semiconductor layers, and the second and fourth
semiconductor layers of mutually different film thicknesses can be
disposed in a self-alignment manner between element isolation
regions. For this reason, while lacks or duplicates of the second
and fourth semiconductor layers can be prevented, the film
thicknesses of the second and fourth semiconductor layers can be
made different from each other for individual usages of
semiconductor elements, and semiconductor elements for mutually
different usages can be formed on the second and fourth
semiconductor layers, respectively, such that miniaturization,
lower power consumption, greater multiple functions, greater
capacities and higher level of reliability of system-on-chips can
be achieved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] FIGS. 1(a)-1(b) are a plan view and a cross-sectional view
showing a method for manufacturing a semiconductor device in
accordance with an embodiment.
[0034] FIGS. 2(a)-2(c) are cross-sectional views showing the method
for manufacturing the semiconductor device in accordance with an
embodiment;
[0035] FIG. 3 is a plan view and a cross-sectional view showing the
method for manufacturing the semiconductor device in accordance
with an embodiment.
[0036] FIGS. 4(a)-4(c) are cross-sectional views showing the method
for manufacturing the semiconductor device in accordance with an
embodiment.
[0037] FIGS. 5(a)-5(b) are a plan view and a cross-sectional view
showing the method for manufacturing the semiconductor device in
accordance with an embodiment.
[0038] FIGS. 6(a)-6(c) are cross-sectional views showing the method
for manufacturing the semiconductor device in accordance with an
embodiment.
[0039] FIGS. 7(a)-7(b) are a plan view and a cross-sectional view
showing the method for manufacturing the semiconductor device in
accordance with an embodiment.
[0040] FIGS. 8(a)-8(c) are cross-sectional views showing the method
for manufacturing the semiconductor device in accordance with an
embodiment.
[0041] FIGS. 9(a)-9(b) are a plan view and a cross-sectional view
showing the method for manufacturing the semiconductor device in
accordance with an embodiment.
[0042] FIGS. 10(a)-10(c) are cross-sectional views showing the
method for manufacturing the semiconductor device in accordance
with an embodiment.
[0043] FIGS. 11(a)-11(b) are a plan view and a cross-sectional view
showing the method for manufacturing the semiconductor device in
accordance with an embodiment.
[0044] FIGS. 12(a)-12(c) are cross-sectional views showing the
method for manufacturing the semiconductor device in accordance
with an embodiment.
[0045] FIGS. 13(a)-13(b) are a plan view and a cross-sectional view
showing the method for manufacturing the semiconductor device in
accordance with an embodiment.
[0046] FIGS. 14(a)-14(c) are cross-sectional views showing the
method for manufacturing the semiconductor device in accordance
with an embodiment.
[0047] FIGS. 15(a)-15(b) are a plan view and a cross-sectional view
showing the method for manufacturing the semiconductor device in
accordance with an embodiment.
[0048] FIGS. 16(a)-16(c) are cross-sectional views showing the
method for manufacturing the semiconductor device in accordance
with an embodiment.
[0049] FIGS. 17(a)-17(b) are a plan view and a cross-sectional view
showing the method for manufacturing the semiconductor device in
accordance with an embodiment.
[0050] FIGS. 18(a)-18(c) are cross-sectional views showing the
method for manufacturing the semiconductor device in accordance
with an embodiment.
[0051] FIGS. 19(a)-19(b) are a plan view and a cross-sectional view
showing the method for manufacturing the semiconductor device in
accordance with an embodiment.
[0052] FIGS. 20(a)-20(c) are cross-sectional views showing the
method for manufacturing the semiconductor device in accordance
with an embodiment.
[0053] FIGS. 21(a)-21(b) are a plan view and a cross-sectional view
showing the method for manufacturing the semiconductor device in
accordance with an embodiment.
[0054] FIGS. 22(a)-22(c) are cross-sectional views showing the
method for manufacturing the semiconductor device in accordance
with an embodiment.
[0055] FIGS. 23(a)-23(b) are a plan view and a cross-sectional view
showing the method for manufacturing the semiconductor device in
accordance with an embodiment.
[0056] FIGS. 24(a)-24(c) are cross-sectional views showing the
method for manufacturing the semiconductor device in accordance
with an embodiment.
[0057] FIGS. 25(a)-25(b) are a plan view and a cross-sectional view
showing the method for manufacturing the semiconductor device in
accordance with an embodiment.
[0058] FIGS. 26(a)-26(c) are cross-sectional views showing the
method for manufacturing the semiconductor device in accordance
with an embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0059] A semiconductor device and a method for manufacturing the
same in accordance with embodiments of the present invention are
described below with reference to the accompanying drawings.
[0060] FIG. 1-FIG. 26 are plan views and cross-sectional views
showing a method for manufacturing a semiconductor device in
accordance with an embodiment of the present invention.
[0061] Referring to FIGS. 1(a)-1(b) and FIGS. 2(a)-2(c), first
single crystal semiconductor layers 12a and 12b and second single
crystal semiconductor layers 13a and 13b are alternately laminated
on a semiconductor substrate 11 by epitaxial growth. It is noted
that, for example, Si, Ge, SiGe, GaAs, InP, GaP, GaN, SiC and the
like can be used as materials for the semiconductor substrate 11,
the first single crystal semiconductor layers 12a and 12b, and the
second single crystal semiconductor layers 13a and 13b.
[0062] It is noted here that the first single crystal semiconductor
layers 12a and 12b can use materials having a selection ratio at
etching greater than that of the semiconductor substrate 11 and the
second single crystal semiconductor layers 13a and 13b. In
particular, when the semiconductor substrate 11 consists of Si,
SiGe may preferably be used as the first single crystal
semiconductor layers 12a and 12b, and Si for the second single
crystal semiconductor layers 12a and 13b. By this, lattice matching
can be achieved among the first single crystal semiconductor layers
12a and 12b and the second single crystal semiconductor layers 13a
and 13b, and selection ratios can be secured among the first single
crystal semiconductor layers 12a and 12b and the second single
crystal semiconductor layers 13a and 13b.
[0063] It is noted that a non-BOX layer region R1, a thick film
semiconductor region R2 and a thin film semiconductor region R3 can
be provided in the semiconductor substrate 11. Then, a protection
diode or a bipolar transistor may be formed in the non-BOX layer
region R1, a partially depleted type field effect transistor may be
formed in the thick film semiconductor region R2, and a completely
depleted type field effect transistor can be formed in the thin
film semiconductor region R3.
[0064] Then, an oxide film 10 is deposited on the entire surface of
the second single crystal semiconductor layer 13b. Then, by using a
photolithography technique and an etching technique, the oxide film
10 is patterned to thereby remove the oxide film 10 in the thin
film semiconductor region R3, and expose the second single crystal
semiconductor layer 13b in the thin film semiconductor region
R3.
[0065] Then, by conducting epitaxial growth by using the oxide film
10 as a mask, a first single crystal semiconductor layer 12c, a
second single crystal semiconductor layer 13c and a first single
crystal semiconductor layer 12d are selectively formed on the
second single crystal semiconductor layer 13b in the thin film
semiconductor region R3.
[0066] Next, as shown in FIG. 3 and FIGS. 4(a)-4(c), the oxide film
10 on the second single crystal semiconductor layer 13b is removed,
and then epitaxial growth is conducted on the second single crystal
semiconductor layer 13b and the first single crystal semiconductor
layer 12d, thereby forming a second single crystal semiconductor
layer 13d and a second single crystal semiconductor layer 13b on
the first single crystal semiconductor layer 12d.
[0067] It is noted that, for example, Si, Ge, SiGe, GaAs, InP, GaP,
GaN, SiC and the like can be used as materials for the first single
crystal semiconductor layers 12c and 12d, and the second single
crystal semiconductor layers 13c and 13d. It is noted here that the
first single crystal semiconductor layers 12c and 12d can use
materials having a selection ratio at the time of etching greater
than that of the second single crystal semiconductor layers 13c and
13d. In particular, when the second single crystal semiconductor
layers 13c and 13d consists of Si, SiGe may preferably be used as
the first single crystal semiconductor layers 12c and 12d.
[0068] Also, in the embodiment described above, a method that uses
epitaxial growth using the oxide film 10 as a mask is described for
forming the first single crystal semiconductor layer 12c, the
second single crystal semiconductor layer 13c and the first single
crystal semiconductor layer 12d on the second single crystal
semiconductor layer 13b in the thin film semiconductor region R3.
However, the first single crystal semiconductor layer 12c, the
second single crystal semiconductor layer 13c and the first single
crystal semiconductor layer 12d may be formed on the entire surface
of the second single crystal semiconductor layer 13b, and then the
first single crystal semiconductor layer 12c, the second single
crystal semiconductor layer 13c and the first single crystal
semiconductor layer 12d in the non-BOX layer region R1 and the
thick film semiconductor region R2 may be selectively removed.
[0069] Next, as shown in FIGS. 5(a)-5(b) and FIGS. 6(a)-6(c), the
second single crystal semiconductor layer 13d is thermally oxidized
to thereby form a sacrificial oxide film 14 on a surface of the
second single crystal semiconductor layer 13d. Then, an oxidation
prevention film 15 is formed on the entire surface of the
sacrificial oxide film 14 by a CVD method or the like. It is noted
that, for example, a silicon nitride film can be used as the
oxidation prevention film 15. Then, by using a photolithography
technique and an etching technique, the oxidation prevention film
15, the sacrificial oxide film 14, the first single crystal
semiconductor layers 12a-12d and the second single crystal
semiconductor layers 13a-13d are patterned, to thereby form grooves
M1 in a predetermined direction that expose the semiconductor
substrate 11.
[0070] It is noted that, when the semiconductor substrate 11 is
exposed, etching may be stopped at the surface of the semiconductor
substrate 11, or recessed portions may be formed in the
semiconductor substrate 11 by over-etching the semiconductor
substrate 11. Also, arrangement positions of the grooves M1 may be
made to correspond to a part of element isolation regions that
isolate the non-BOX layer region R1, the thick film semiconductor
region R2 and the thin film semiconductor region R3 from one
another. Also, the grooves M1 may be arranged such that the non-BOX
layer region R1, the thick film semiconductor region R2 and the
thin film semiconductor region R3 are mutually isolated, and the
non-BOX layer region R1 may be further divided into smaller
areas.
[0071] Next, as shown in FIGS. 7(a)-7(b) and FIGS. 8(a)-8(c),
supporting bodies 16, each being formed on side walls of the first
single crystal semiconductor layers 12a-12d and the second single
crystal semiconductor layers 13a-13d, and supports the second
single crystal semiconductor layers 13a-13d on the semiconductor
substrate 11, are formed in the grooves M1. It is noted that, when
forming the supporting body 16 in a film on the side walls of the
first single crystal semiconductor layers 12a-12d and the second
single crystal semiconductor layers 13a-13d, epitaxial growth of
semiconductor can be used. It is noted here that, by using the
epitaxial growth of semiconductor, the supporting body 16 can be
selectively formed on the side surfaces of the first single crystal
semiconductor layers 12a-12d and the second single crystal
semiconductor layers 13a-13d and the surface of the semiconductor
substrate 11. It is noted that, for example, Si, Ge, SiGe, SiC,
SiSn, PbS, GaAs, InP, GaP, GaN, ZnSe or the like can be used as a
material for the supporting body 16. In particular, when the
semiconductor substrate 11 and the second single crystal
semiconductor layers 13a-13d consist of Si, and the first single
crystal semiconductor layers 12a-12d consist of SiGe, Si may
preferably be used as a material of the supporting body 16.
[0072] By this, lattice matching can be achieved among the
supporting body 16 and the first single crystal semiconductor
layers 12a-12d, and selection ratios can be secured among the
supporting body 16 and the first single crystal semiconductor
layers 12a-12d. Also, by using semiconductor such as Si as a
material of the supporting body 16, the three-dimensional cubic
structure by the semiconductor can be maintained, even when the
first single crystal semiconductor layers 12a-12d are removed. For
this reason, the chemical resistance property and mechanical stress
resistance property can be improved, such that a stable element
isolation process with good reproducibility can be realized. It is
noted that, besides semiconductors, a dielectric such as a silicon
oxide film may be used as the material of the supporting body
16.
[0073] Next, as shown in FIGS. 9(a)-9(b) and FIGS. 10(a)-10(c), the
oxidation prevention film 15, the sacrificial oxide film 14, the
first single crystal semiconductor layers 12a and 12b and the
second single crystal semiconductor layers 13a, 13b and 13d are
patterned by using a photolithography technique and an etching
technique, whereby grooves M2 that expose the semiconductor
substrate 11 are formed along a direction orthogonal to the grooves
M1 in the thick film semiconductor region R2. It is noted that,
when the semiconductor substrate 11 is exposed, etching may be
stopped at the surface of the semiconductor substrate 11, or
recessed sections may be formed in the semiconductor substrate 11
by over-etching the semiconductor substrate 11. Also, arrangement
positions of the grooves M2 may be made to correspond to the
element isolation regions of the single crystal semiconductor layer
13d.
[0074] Next, as shown in FIGS. 11(a)-11(b) and FIGS. 12(a)-12(c),
the oxidation prevention film 15, the sacrificial oxide film 14,
the first single crystal semiconductor layers 12c and 12d and the
second single crystal semiconductor layers 13c and 13d are
patterned by using a photolithography technique and an etching
technique, whereby grooves M3 that expose the second single crystal
semiconductor layer 13b are formed along a direction orthogonal to
the grooves M1 are formed in the thin film semiconductor region R3.
It is noted that, when the second single crystal semiconductor
layer 13b is exposed, etching may be stopped at the surface of the
second single crystal semiconductor layer 13b, or recessed sections
may be formed in the second single crystal semiconductor layer 13b
by over-etching the second single crystal semiconductor layer 13b.
Also, arrangement positions of the grooves M3 may be made to
correspond to the element isolation regions of the single crystal
semiconductor layer 13d.
[0075] Also, instead of exposing the surface of the second single
crystal semiconductor layer 13b, etching may be stopped at the
surface of the first single crystal semiconductor layer 12c, or the
first single crystal semiconductor layer 12c may be over-etched,
thereby etching halfway through the first single crystal
semiconductor layer 12c. It is noted that, by stopping the etching
halfway through the first single crystal semiconductor layer 12c,
the surface of the second single crystal semiconductor layer 13b
within the grooves M3 is prevented from being exposed. For this
reason, when the first single crystal semiconductor layers 12c and
12d are etched and removed, the time during which the second single
crystal semiconductor layer 13b within the grooves M3 is exposed to
etching liquid or etching gas can be reduced, such that
over-etching of the second single crystal semiconductor layer 13b
within the grooves M3 can be suppressed.
[0076] Next, as shown in FIGS. 13(a)-13(c) and FIGS. 14(a)-14(c),
etching gas or etching liquid is brought in contact with the first
single crystal semiconductor layers 12a and 12b through the grooves
M2, and etching gas or etching liquid is brought in contact with
the first single crystal semiconductor layers 12c and 12d through
the grooves M3, whereby the first single crystal semiconductor
layers 12a and 12b in the thick film semiconductor region R2 are
removed by etching, and the first single crystal semiconductor
layers 12c and 12d in the thin film semiconductor region R3 are
removed by etching. Further, in the thick film semiconductor region
R2, void sections 17 are formed between the semiconductor substrate
11 and the second single crystal semiconductor layer 13a, and
between the second single crystal semiconductor layers 13a and 13b;
and in the thin film semiconductor region R3, void sections 17 are
formed between the second single crystal semiconductor layers 13b
and 13c, and 13c and 13d.
[0077] It is noted here that, by providing the supporting bodies 16
in the grooves M1, the second single crystal semiconductor layers
13a-13d can be supported on the semiconductor substrate 11 even
when the first single crystal semiconductor layers 12a-12d are
removed; and by providing the grooves M2 and M3 independently of
the grooves M1, etching gas or etching liquid can be brought in
contact with the first single crystal semiconductor layers 12a-12d
disposed under the second single crystal semiconductor layers
13a-13d, respectively. For this reason, the void sections 17 can be
formed between the semiconductor substrate 11 and the second single
crystal semiconductor layer 13a, and among the second single
crystal semiconductor layers 13a through 13d, without damaging the
crystal quality of the second single crystal semiconductor layers
13a-13d.
[0078] Also, in the thin film semiconductor region R3, the depth of
the grooves M3 may be set such that the second single crystal
semiconductor layer 13b remains on the first single crystal
semiconductor layer 12b, whereby the first single crystal
semiconductor layers 12a and 12b in the thick film semiconductor
region R2 can be removed while leaving the first single crystal
semiconductor layers 12a and 12b remained in the thin film
semiconductor region R3. For this reason, in the thick
semiconductor region R2, the second single crystal semiconductor
layer 13a between the first single crystal semiconductor layers 12a
and 12b can be thermally oxidized; and in the thin film
semiconductor region R3, the second single crystal semiconductor
layer 13a between the first single crystal semiconductor layers 12a
and 12b can be prevented from being thermally oxidized, and the
second single crystal semiconductor layer 13c disposed in a layer
above the second single crystal semiconductor layer 13a can be
thermally oxidized. As a result, the height of a dielectric layer
18 that is formed by thermal oxidation of the second single crystal
semiconductor layers 13a-13d can be made different in the thick
film semiconductor region R2 and the thin film semiconductor region
R3, and the film thickness of the second single crystal
semiconductor layers can be made different in the thick film
semiconductor region R2 and the thin film semiconductor region
R3.
[0079] It is noted that, when the semiconductor substrate 11, the
second single crystal semiconductor layers 13a-13d and the
supporting body 16 consist of Si, and the first single crystal
semiconductor layers 12a-12d consist of SiGe, it is desirable to
use nitric-hydrofluoric acid as an etching liquid for the first
single crystal semiconductor layers 12a-12b. By this, a selection
ratio between Si and SiGe that ranges from about 1:1000 to 1:10000
can be obtained, such that the first single crystal semiconductor
layers 12a-12d can be removed while suppressing over-etching of the
semiconductor substrate 11, the second single crystal semiconductor
layers 13a-13d and the supporting body 16.
[0080] Next, as shown in FIGS. 15(a)-15(b) and 16(a)-16(c), the
semiconductor substrate 11, the second single crystal semiconductor
layers 13a-13d and the supporting body 16 are thermally oxidized
until the second single crystal semiconductor layer 13a in the
thick film semiconductor region R2 and the second single crystal
semiconductor layer 13c in the thin film semiconductor region R3
disappear, thereby forming dielectric layers 18 under the second
single crystal semiconductor layer 13b in the thick film
semiconductor region R2 and under the second single crystal
semiconductor layer 13d in the thin film semiconductor region R3.
It is noted here that, by having the second single crystal
semiconductor layer 13a in the thick film semiconductor region R2
disappear, gaps between the second single crystal semiconductor
layer 13b and the semiconductor substrate 11 can be completely
embedded with the dielectric layers 18 in the thick film
semiconductor region R2. Also, by having the second single crystal
semiconductor layer 13c in the thin film semiconductor region R3
disappear, gaps between the second single crystal semiconductor
layers 13b and 13d can be completely embedded with the dielectric
layers 18 in the thin film semiconductor region R3.
[0081] For this reason, while maintaining the crystal quality of
the second single crystal semiconductor layers 13b and 13d, the
heights of the dielectric layers 18 to be disposed can be made
different from one another in the thick film semiconductor region
R2 and the thin film semiconductor region R3; in the thick film
semiconductor region R2, the second single crystal semiconductor
layers 13b and 13d can be disposed on the dielectric layers 18; and
in the thin film semiconductor region R3, the second single crystal
semiconductor layer 13d can be disposed on the dielectric layer 18.
As a result, the film thickness of the second single crystal
semiconductor layers can be set to match with different usages of
semiconductor elements, respectively, and semiconductor elements
for mutually different usages can be formed on a common
semiconductor substrate 11.
[0082] Also, the film thicknesses of the second single crystal
semiconductor layers 13b and 13d after element isolation can be
defined by the film thicknesses of the second single crystal
semiconductor layers 13a-13d at the time of epitaxial growth and
the film thickness of the dielectric layer 18 formed at the time of
thermal oxidation of the second single crystal semiconductor layers
13a-13d. For this reason, the film thicknesses of the second single
crystal semiconductor layers 13b and 13d can be accurately
controlled, differences in the film thicknesses of the second
single crystal semiconductor layers 13b and 13d can be reduced, and
the heights of the dielectric layers 18 to be disposed can be made
different from one another in the thick film semiconductor region
R2 and the thin film semiconductor region R3. Also, by providing
the oxidation prevention film 15 on the second single crystal
semiconductor layer 13d, the surface of the second single crystal
semiconductor layer 13d can be prevented from being oxidized, and
the dielectric layer 18 can be formed below the second single
crystal semiconductor layer 13b or the second single crystal
semiconductor layer 13d.
[0083] Further, by forming the dielectric layers 18 in a manner to
embed the void sections 17, the second single crystal semiconductor
layers 13b and 13d can be disposed in a self-alignment manner
between the element isolation regions. For this reason, in the
thick film semiconductor region R2 and the thin film semiconductor
region R3, while lacks or duplicates of the second single crystal
semiconductor layers 13b and 13d can be prevented, the film
thicknesses of the second single crystal semiconductor layers can
be made different from one another for individual usages of
semiconductor elements, such that higher integration and higher
reliability of semiconductor elements can be achieved.
[0084] It is noted here that the first single crystal semiconductor
layers 12a-12b may be formed in the same film thickness, and the
film thickness of the second single crystal semiconductor layer 13a
may be set to about 70% of the film thickness of the first single
crystal semiconductor layers 12a-12b, whereby the film thickness of
the dielectric layer 18 under the second single crystal
semiconductor layer 13b in the thick film semiconductor region R2
can be made generally equal to the total film thickness of the
first single crystal semiconductor layer 12a, the second single
crystal semiconductor layer 13a and the first single crystal
semiconductor layer 12b. For this reason, while stress on the
dielectric layers 18 can be suppressed, the void sections 17 in the
thick film semiconductor region R2 can be completely closed with
the dielectric layers 18, an increase in the thermal resistance can
be suppressed, and deterioration of the crystallinity of the second
single crystal semiconductor layer 13c on the dielectric layer 18
can be suppressed. Further, by setting the film thickness of the
second single crystal semiconductor layer 13a to less than 70% of
the film thickness of the first single crystal semiconductor layers
12a-12b, areas below the second single crystal silicon layer 13b in
the thick film semiconductor region R2 are formed with the
dielectric layer 18 and the voids, whereby deterioration of the
crystallinity of the second single crystal semiconductor layer 13c
on the dielectric layer 18 can be suppressed, though resistance to
the thermal conductivity may become greater.
[0085] On the other hand, if the film thickness of the second
single crystal semiconductor layer 13a is set to a value that
greatly exceeds 70% of the film thickness of the first single
crystal semiconductor layer 12c, the film thickness of the
dielectric layer 18 under the second single crystal semiconductor
layer 13b in the thick film semiconductor region R2 can be made
greater than the total film thickness of the first single crystal
semiconductor layer 12a, the second single crystal semiconductor
layer 13a and the first single crystal semiconductor layer 12b. For
this reason, the second single crystal semiconductor layers 13b and
13d in the thick film semiconductor region R2 can be lifted up, and
the flatness between the thick film semiconductor region R2 and the
thin film semiconductor region R3 can be improved.
[0086] After the dielectric layer 18 is formed, high-temperature
annealing is conducted. By this, the dielectric layer 18 can be
re-flowed, stresses on the dielectric layer 18 can be alleviated,
and the interface state can be reduced.
[0087] Next, as shown in FIGS. 17(a)-17(b) and FIGS. 18(a)-18(c),
by using a CVD method or the like, a dielectric layer 19 is
deposited on the oxidation prevention film 15 in a manner that the
grooves M1-M3 with the dielectric layer 18 formed on their side
walls are embedded. It is noted that, for example, SiO.sub.2 or
Si.sub.3N4 may be used as the dielectric layer 10.
[0088] Next, as shown in FIGS. 19(a)-19(b) and FIGS. 20(a)-20(c),
the dielectric layer 19 is planarized by using a CMP (chemical
mechanical polishing) method or the like, to thereby expose a
surface of the oxidation prevention film 15 and embed the
dielectric layer 19 in the grooves M1-M3.
[0089] Next, as shown in FIG. 21-FIG. 24, the oxidation prevention
film 15 and the sacrificial oxidation film 14 on the second single
crystal semiconductor layer 13d are removed, to thereby expose a
surface of the second single crystal semiconductor layer 13d, which
has been keep clean and damage free.
[0090] Next, as shown in FIGS. 25(a)-25(b) and FIGS. 26(a)-26(c),
ions are selectively injected in the second single crystal
semiconductor layer 13d in the non-BOX layer region R1 to form
impurity diffusion layers 22c, thereby forming protection diodes in
the non-BOX layer region R1.
[0091] Also, in the thick film semiconductor region R2 and the thin
film semiconductor region R3, the surface of the second single
crystal semiconductor layer 13d is thermally oxidized; and in the
thin film semiconductor region R3, the thermally oxidized film of
the second single crystal semiconductor layer 13d is selectively
removed; and then again, in the thick film semiconductor region R2
and the thin film semiconductor region R3, the surface of the
second single crystal semiconductor layer 13d is thermally
oxidized, whereby thick gate dielectric films 20a and thin gate
dielectric films 20b are formed on the second single crystal
semiconductor layer 13d, respectively. Then, by using a
photolithography technique and an etching technique, the
polycrystalline silicon film is patterned to form gate electrodes
21a and 21b over the second single crystal semiconductor layer 13d.
Then, by using the gate electrodes 21a and 21b as a mask, impurity
ions are injected in the second single crystal semiconductor layer
13d, to thereby form source/drain layers 22a and 22b disposed at
sides of the gate electrodes 21a and 21b, respectively, in the
second single crystal semiconductor layer 13d. When the
acceleration energy is set such that the injected impurity ions
enter a position deeper than the semiconductor film thickness in
the thin semiconductor region R3, the source/drain 22a with a
greater amount of impurity and in a deeper junction depth and the
source/drain 22b in a shallower junction depth can be
simultaneously formed by a single step of injection.
[0092] By this, in the thin film semiconductor region R3, when the
effective channel length of a high-speed/lower power semiconductor
element is 0.1 .mu.m or less, the film thickness of the second
single crystal semiconductor layer 13d can be made to 50 nm or
less, whereby a completely depleted type SOI transistor in which
the short-channel effect is suppressed can be formed.
[0093] Also, in the thick film semiconductor region R2, the second
single crystal semiconductor layer 13b can be provided between the
second single crystal semiconductor layer 13d and the dielectric
layer 18, such that the film thickness of the second single crystal
semiconductor layer can be increased. For this reason, a partially
depleted type SOI transistor can be formed, while securing a high
junction breakdown voltage and a large current capacity.
[0094] Furthermore, in the non-BOX layer region R1, the BOX layer
can be omitted, such that semiconductor elements in which a large
current circulates can be formed while maintaining the performance
and reliability of the semiconductor elements. It is noted that,
besides protection diodes, bipolar transistors, trench memory cells
or the like may preferably be formed in the non-BOX layer region
R1.
* * * * *