U.S. patent application number 15/003809 was filed with the patent office on 2017-04-27 for vertical transistor and the fabrication method.
The applicant listed for this patent is Zing Semiconductor Corporation. Invention is credited to Richard Chang, Deyuan Xiao.
Application Number | 20170117407 15/003809 |
Document ID | / |
Family ID | 58562032 |
Filed Date | 2017-04-27 |
United States Patent
Application |
20170117407 |
Kind Code |
A1 |
Xiao; Deyuan ; et
al. |
April 27, 2017 |
VERTICAL TRANSISTOR AND THE FABRICATION METHOD
Abstract
A vertical transistor and the fabrication method. The transistor
comprises a first surface and a second surface that is opposite to
the first surface. A drift region of the first doping type, this
drift region is located between the first surface and the second
surface; at least one source region of the first doping type and
the source region being located between the drift region and the
first surface, with a first dielectric layer located between
adjacent source regions; at least one drain region with said first
doping type and said drain region being located between said drift
region and said second surface, a gate being provided between
adjacent drain regions. Said gate includes a gate electrode and a
gate dielectric layer disposed between said gate electrode and said
drift region, and the second dielectric layer being positioned
between said gate electrode and said second surface.
Inventors: |
Xiao; Deyuan; (Shanghai,
CN) ; Chang; Richard; (Shanghai, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Zing Semiconductor Corporation |
Shanghai |
|
CN |
|
|
Family ID: |
58562032 |
Appl. No.: |
15/003809 |
Filed: |
January 22, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 29/4236 20130101;
H01L 29/7827 20130101; H01L 29/66666 20130101; H01L 29/7828
20130101; H01L 29/7813 20130101; H01L 21/02381 20130101; H01L
21/0254 20130101; H01L 29/2003 20130101; H01L 29/0847 20130101;
H01L 29/41741 20130101; H01L 21/0243 20130101; H01L 29/66522
20130101; H01L 29/0649 20130101 |
International
Class: |
H01L 29/78 20060101
H01L029/78; H01L 29/10 20060101 H01L029/10; H01L 29/66 20060101
H01L029/66; H01L 29/423 20060101 H01L029/423; H01L 29/51 20060101
H01L029/51; H01L 29/20 20060101 H01L029/20; H01L 29/08 20060101
H01L029/08 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 26, 2015 |
CN |
201510703700.1 |
Claims
1. A vertical transistor comprising: a first surface and a second
surface positioned opposite to the first surface; a drift region
with a first doping type, the drift region being located between
the first surface and the second surface; at least one source
region with the first doping type and the source region located
between the drift region and the first surface, the first
dielectric layer being located between adjacent source regions; at
least one drain region with the first doping type and the drain
region being located between said drift region and said second
surface; and a gate being provided between adjacent drain regions;
the gate including a gate electrode and a gate dielectric layer
located between the gate electrode and the drift region, and the
second dielectric layer being positioned between the gate electrode
and the second surface.
2. The vertical transistor of claim 1 further comprising a source
electrode located on said first surface and the drain electrode on
the second surface.
3. The vertical transistor of claim 1 wherein the the first doping
type is N-type.
4. The vertical transistor of claim 3 wherein the drift region is
N-type doped GaN, with a thickness of 2-50 .mu.m.
5. The vertical transistor of claim 3 wherein the source region is
heavily doped N-type GaN and the drain region is with heavily doped
N-type GaN.
6. The vertical transistor of claim 1 wherein the gate electrode is
selected from one of Ti, TiN, Ta, TaN, W, Al, Cu, Ag, Ni, Au, Cr,
and polycrystalline silicon.
7. The vertical transistor of claim 1 wherein the gate dielectric
layer comprises silicon oxide and the thickness of the gate
dielectric layer is about 2-50 nm.
8. The vertical transistor of claim 1 wherein the dielectric layer
comprises silicon oxide, SiON, or GaN, and the thickness of the
first dielectric layer is about 20-100 nm.
9. The vertical transistor of claim 1 wherein the second dielectric
layer comprises silicon oxide, SiON, or GaN, and the thickness of
the first dielectric layer is about 20-100 nm.
10. A method for processing a vertical transistor comprising:
forming a patterned semiconductor substrate; developing a first
dielectric layer on the same portion of the patterned semiconductor
substrate, and forming a source region on a remaining portion of
the patterned semiconductor substrate and the source region having
a first doping type; forming a drift layer and a drain region film
layer, the drift layer covering the first dielectric layer and the
drain region, the drain region film layer covering the drift layer,
the drift layer and the drain region film layer comprising the
first doping type; etching the drain region film layer and the
drift layer to form a trench exposing the drift layer, the
remaining drift layer forming a drift region, the remaining portion
of the drain region film layer forming the drain region; forming a
gate dielectric layer and a gate electrode, the gate dielectric
layer covering the bottom and side walls of the trench, the gate
electrode overlaying the gate dielectric layer and partially
filling the trench; forming the second dielectric layer, the second
dielectric layer covering the gate electrode, and filling said
trench of the remaining portion.
11. The method claim 10 further comprising: forming a dielectric
film layer and an electrode film layer, the dielectric film layer
covering the bottom and side walls of the trench and the drain
region, the electrode film layer covering the dielectric film
layer; planarizing the electrode film layer, so that the electrode
film layer is flush with the dielectric film layer; etching the
dielectric film layer to develop a gate dielectric layer, the gate
dielectric layer exposing the drain region; removing partially the
electrode film layer to develop the gate electrode.
12. The method of claim 10 further comprising: forming a drain
electrode, the drain electrode overlaying the second dielectric
layer, the gate dielectric layer and the drain region; removing the
patterned semiconductor substrate; forming the source electrode and
said source electrode overlaying the first dielectric layer and the
source region.
13. The method of claim 10 wherein the surface of patterned silicon
surface is characterized by a hemispherical or polygonal pattern.
Description
[0001] The present application claims the priority to Chinese
Patent Applications No. 201510703700.1, filed with the Chinese
State Intellectual Property Office on Oct. 26, 2015, which is
incorporated herein by reference in its entirety.
BACKGROUND
[0002] As a typical representative of third-generation
semiconductor materials, wide-band gap semiconductors, including
GaN, possess a plurality of outstanding performances capabilities
which silicon (Si) materials lack. GaN is an excellent
semiconductor material for high-frequency, high-voltage,
high-temperature, and high-power applications, with great prospects
for application in civil and military fields. Due to advances in
GaN technology, especially the gradual maturity and
commercialization of large-diameter silicon-based GaN epitaxial
technology, the technology of GaN power semiconductors is expected
to be a technical solution of high-performance and low success
rate. Thus the GaN power devices have drawn the attention of famous
international semiconductor manufacturers and research
institutes.
SUMMARY
[0003] The present invention aims to provide a vertical transistor
and its fabrication method. The vertical transistor is a GaN
junction-less power transistor, reducing the power consumption of
the transistor.
[0004] To solve the above technical problem, the present invention
is a vertical transistor, comprising: a first surface and a second
surface opposite to said first surface; a drift region of the first
doping type and said drift region being located between said first
surface and the second surface; at least one source region of said
first doping type and the source region being located between said
drift region and said first surface, with a first dielectric layer
located between adjacent source regions; at least one drain region
with said first doping type and said drain region being located
between said drift region and said second surface, with a gate
provided between adjacent drain regions. Said gate includes a gate
electrode and a gate dielectric layer located between said gate
electrode and said drift region, a second dielectric layer being
positioned between said gate electrode and said second surface.
[0005] Optionally, it also includes the source electrode on said
first surface and the drain electrode on said second surface.
[0006] Optionally, said first doping type is N-type.
[0007] Optionally, the drift region is N-type doped GaN, with a
thickness of 2-50 .mu.m.
[0008] Optionally, the source region is the heavily doped N-type
GaN and said drain region is heavily doped N-type GaN.
[0009] Optionally, the gate electrode is one of Ti, TiN, Ta, TaN,
W, Al, Cu, Ag, Ni, Au, Cr and polycrystalline silicon.
[0010] Optionally, the gate dielectric layer is silicon oxide and
said silicon oxide is 2-50 nm thick.
[0011] Optionally, the first dielectric layer is one of silicon
oxide, SiON or GaN. Said first dielectric layer is 20-100 nm
thick.
[0012] Optionally, the second dielectric layer is one of silicon
oxide, SiON or GaN. Said second dielectric layer is 20-100 nm
thick.
[0013] Accordingly, the present invention also provides a method
for preparing a vertical transistor comprising: providing a
patterned semiconductor substrate; forming a first dielectric layer
on one portion of the patterned semiconductor substrate and forming
a source region on the remaining portion of patterned semiconductor
substrate, said source region having the first doping type; forming
a drift layer and the drain region film layer, the drift layer
covering the first dielectric layer and the drain region, said
drain region film layer overlaying said drift layer, said drift
layer and drain region film layer having the first doping type;
etching said drain region film layer and said drift layer to form a
trench, the trench exposing the drift layer, the remaining drift
layer forming the drift region, the remaining drain region film
layer forming a drain region; forming the gate dielectric layer and
the gate electrode, the gate dielectric layer overlaying the bottom
and side walls of the trench, said gate electrode overlaying the
gate dielectric layer and filling some portions of said trench;
forming the second dielectric layer, said second dielectric layer
overlaying said gate electrode, and filling the remaining portion
of the trench.
[0014] Optionally, the steps to form said gate dielectric layer and
gate electrode comprise: forming a dielectric layer and an
electrode film layer, the dielectric layer covering the bottom and
side walls of the trench and the drain region, said electrode film
layer overlaying said dielectric film layer; planarizing the
electrode film layer, the electrode layer is set flush with the
dielectric film layer; etching said dielectric film layer to form a
gate dielectric layer, said gate dielectric layer exposing said
drain region; removing some portions of the electrode film layer to
form the gate electrode.
[0015] Optionally, they further comprise forming a drain electrode,
the drain electrode overlaying the second dielectric layer, said
gate dielectric layer and said drain region; removing the patterned
semiconductor substrate; forming a source electrode, said source
electrode overlaying the first dielectric layer and the source
region.
[0016] Optionally, the surface of the patterned semiconductor
substrate is provided with a hemispherical or polygonal
pattern.
[0017] The present invention provides a vertical transistor
comprising a source region, a drift region, a drain region and a
gate electrode, wherein the source region, the drain region and the
drift region have the first doping type, so that the transistor is
a junction-less transistor, thereby reducing power consumption of
the transistor. Moreover, the voltage applied to the gate is used
to control the passage of carriers in the drift region into the
depletion region between gates, so as control the switch of
transistor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 illustrates a schematic diagram of cross-sectional
structural view of the vertical transistor in an embodiment of
present invention;
[0019] FIG. 2 illustrates a flowchart of the method to prepare a
vertical transistor in an embodiment of present invention;
[0020] FIG. 3 illustrates a schematic diagram of the
cross-sectional structural view of the patterned semiconductor
substrate in an embodiment of present invention;
[0021] FIG. 4 illustrates a schematic diagram of the
cross-sectional structural view of the first dielectric layer and
the source region in an embodiment of present invention;
[0022] FIG. 5 illustrates a schematic structural diagram of forming
the drift layer and the drain region film layer in an embodiment of
present invention;
[0023] FIG. 6 illustrates a schematic and structural diagram of the
trench in an embodiment of present invention;
[0024] FIG. 7 illustrates a schematic and structural diagram of
forming the film dielectric film layer and the electrode film layer
in an embodiment of present invention;
[0025] FIG. 8 illustrates a schematic and structural diagram of
planarizing the electrode film layer in an embodiment of present
invention;
[0026] FIG. 9 illustrates a schematic and structural diagram of
forming the gate dielectric layer in an embodiment of present
invention;
[0027] FIG. 10 illustrates a schematic and structural diagram of
forming the gate electrode in an embodiment of present
invention;
[0028] FIG. 11 illustrates a schematic and structural diagram of
forming the second dielectric layer in an embodiment of present
invention;
[0029] FIG. 12 illustrates a schematic and structural diagram of
forming the drain electrode in an embodiment of present
invention;
[0030] FIG. 13 illustrates a schematic and structural diagram of
turning off the vertical transistor in an embodiment of present
invention;
[0031] FIG. 14 illustrates a schematic and structural diagram of
turning on the vertical transistor in an embodiment of present
invention.
DETAILED DESCRIPTION
[0032] The vertical transistor and its fabrication method are
described in more detail in conjunction with schematic views as
follows. Wherein the preferred embodiment of the present invention
is illustrated, it should be understood that those skilled in the
art may modify the invention and may still realize the advantageous
effects of the invention. Thus, the following description should be
understood to be widely known by the skills in the art and should
not be regarded as a limitation of the present invention.
[0033] The core idea of the present invention is to provide a
vertical transistor, comprising: a first surface and a second
surface opposite to the first surface; a drift region with the
first doping type, said drift region is located between said first
surface and the second surface; at least one source region with
said first doping type and the source region is located between
said drift region and said first surface, with the first dielectric
layer located between adjacent source regions; at least one drain
region with said first doping type and said drain region is located
between said drift region and said second surface, with a gate
provided between adjacent drain regions. Said gate includes a gate
electrode and a gate dielectric layer located between said gate
electrode and said drift region, the second dielectric layer is
positioned between said gate electrode and said second surface. In
the present invention, the source region, drain region and drift
region all have the first doping type so that the transistor is the
junction-less power transistor, thereby reducing the power
consumption of the transistor.
[0034] The vertical transistor and its fabrication method in the
present invention are described with reference to the drawings
below.
[0035] Referring to FIG. 1, FIG. 1 illustrates the cross-sectional
and schematic diagram of a vertical transistor 200 which comprises:
a first surface 201 and a second surface 202, opposite to the first
surface 201; a drift region 230, located between said first surface
201 and second surface 202, the drift region 230 being first N-type
doping type. For example, the drift region 230 being N-type doped
GaN. The thickness of the drift region 230 is 2 .mu.m-50 .mu.m; at
least one source region 220 being located between the drift region
230 and the first surface 201, the source region 220 being first
doping type, and the source region 220 being heavily doped N-type
GaN. The thickness of the source region 220 is 10-50 nm. The first
dielectric layer 210 is disposed between the adjacent source
regions 220. The first dielectric layer 210 is employed to isolate
the source region 220. The first dielectric layer 210 is one of
silicon oxide, SiON, or GaN. The thickness of first dielectric
layer 210 is 20-100 nm; at least one drain region 240 is located
between the drift region 230 and the second surface 202, the drain
region 240 being said first doping type. The drain region 240 is
heavily doped N-type GaN. The thickness of the drain region 240 is
10-50 nm. A gate 300 is disposed between adjacent drain regions
240. The gate 300 includes a gate electrode 260 and a gate
dielectric layer 250 located between the gate electrode 260 and
said drift region 230, the gate dielectric layer 250 being silicon
oxide and 2-50 nm thick, said gate dielectric layer 260 is one of
Ti, TiN, Ta, TaN, W, Al, Cu, Ag, Ni, Au, Cr, or polycrystalline
silicon. In addition, a second dielectric layer 270 is disposed
between the gate electrode 260 and the second surface 202. The
second dielectric layer 270 is employed to realize the electrical
insulation between the gate electrode 260 and the drain electrode,
said second dielectric layer 270 being of silicon oxide, SiON, or
GaN. The thickness of the second dielectric layer 270 is 20-100
nm.
[0036] In addition, the vertical transistor further comprises a
source electrode 290 on the first surface 201 and a drain electrode
280 on the second surface 202. The source electrode 290 is of Ti,
Ni, Al, or Au. The thickness of the source electrode 290 is 50-200
nm. The drain electrode 280 is of Ti, Ni, Al, or Au. The thickness
of the drain electrode 280 is 50-200 nm.
[0037] Accordingly, the present invention also provides a method
for preparing a vertical transistor. FIG. 2 is a flow chart for
preparing the vertical transistor. FIG. 3 to FIG. 12 illustrate the
schematic and structural view of all steps. The fabrication process
comprises following steps:
[0038] Step S1 is implemented with reference to FIG. 3. A patterned
semiconductor substrate 100 is provided. The surface of the
patterned semiconductor substrate 100 has a hemispherical or
polygonal pattern. In the present embodiment, the pattern array is
formed on the semiconductor substrate with planar surfaces. For
example, an array of polystyrene beads is attached using a
patterned array as a mask to etch the semiconductor substrate and
form the patterned semiconductor substrate. In the present
embodiment, the semiconductor substrate 100 may be a silicon
substrate, a germanium substrate, or an SiGe substrate. A silicon
substrate is preferred. It is appreciated that, due to the lattice
mismatch between the IV materials and III-V compounds, the
formation of III-V compounds on the patterned semiconductor
substrate will lead to defects. However, the pattern formed on the
surface of semiconductor substrate may reduce the defect caused by
lattice mismatch.
[0039] Step S2 is implemented with reference to FIG. 4. A first
dielectric layer 210 is formed on some portion of the patterned
semiconductor substrate 100 and a source region 220 is formed on
the remaining portion of the patterned semiconductor substrate 100.
In the present embodiment, the source region 220 has the first
doping type, e.g., the source region 220 is heavily doped N-type
GaN. The first dielectric layer 210 is silicon oxide, SiON, or GaN.
The first dielectric layer 210 is used to isolate the source region
220.
[0040] Step S3 is implemented with reference to FIG. 5. A drift
layer 231 and a drain region film layer 241 are formed. The drift
layer 231 overlays the first dielectric layer 210 and the source
region 220. Said drain region film layer 241 overlays the drift
layer 231. In this embodiment, the drift layer 231 has the first
doping type and is heavily doped N-type GaN. The thickness of the
drift layer 231 is 2 .mu.m-50 .mu.m. The drain region film layer
241 has the first doping type and is heavily doped N-type GaN.
[0041] Step S4 is implemented with reference to FIG. 6. The drain
region film layer 241 is etched and the drift layer 231 forms a
trench 310. The trench 310 exposes the drift layer 241. The
remaining portion of the drift layer 231 forms the drift region
230. The remaining portion of the drain region film layer 241 forms
the drain region 240.
[0042] Step S5 is implemented with reference to FIG. 7 to FIG. 10.
A gate dielectric layer 250 and a gate electrode 260 are formed.
The gate dielectric layer 250 covers the bottom and side walls of
the trench 310. The gate dielectric layer 260 overlays the gate
dielectric layer 250 and fills partially the trench 310. In this
embodiment, steps to form the gate dielectric layer 250 and the
gate electrode 260 specifically comprise:
[0043] With reference to FIG. 7, a dielectric film layer 251 and an
electrode film layer 261 are formed. The dielectric film layer 251
covers the bottom and side walls of the trench 310 as well as the
drain region 240. The electrode film layer 261 covers the
dielectric film layer 251;
[0044] With reference to FIG. 8, the dielectric film layer 261 is
planarized so that it is flush with the dielectric layer 251;
[0045] With reference to FIG. 9, the dielectric film layer 251 is
etched. The remaining portion of dielectric film layer 251 forms
the gate dielectric layer 250. The gate dielectric layer 250
exposes said drain region 240;
[0046] With reference to FIG. 10, the electrode layer 261 is
etched. Some portion of the electrode film layer 261 is removed.
The remaining portion of the electrode film layer 261 forms the
gate electrode 260. Therefore the gate dielectric layer 160 and the
gate electrode 250 together form the gate 300 of the vertical
transistor.
[0047] The step S6 is implemented with reference to FIG. 11. The
second dielectric layer 270 is formed. Said dielectric layer 270
overlays the gate electrode 260. Said dielectric layer 270 is used
to isolate the gate electrode 250 from the drain electrode.
[0048] With reference to FIG. 12, the fabrication method of a
vertical transistor further comprises: forming a drain electrode
280, the drain electrode 280 overlaying the second dielectric layer
270, the gate dielectric layer 250, and the drain region 240;
removing the patterned semiconductor substrate 100; forming a
source electrode 290, the source electrode 290 covering the first
dielectric layer 210 and the source region 220, thereby forming the
vertical transistor 200 as shown in FIG. 1. Wherein the first
dielectric layer 210 and the source region 220 together form the
first surface 201 of the vertical transistor; the second dielectric
layer 270, the gate dielectric layer 260, and the drain region 240
together form the second surface of the vertical transistor; the
first surface 201 being prepared on the patterned semiconductor
substrate 100. The first surface 201 is of planar structure.
However, those skilled in the art will be able to appreciate that,
after the removal of the patterned semiconductor substrate 100,
chemical and mechanical polishing is conducted to form the planar
first surface, and thereafter form the source electrodes on the
first surface and lead out the source region.
[0049] The source region 220, the drift region 230, and drain
region 240 in the vertical transistor of the present invention all
have the first doping type and are N-type doped GaN. As a
junction-less power transistor, it can be used to reduce power
consumption. Furthermore, due to the contact of
metal-oxide-semiconductor formed between the gate electrode 260 and
the drift region 230 as well as the work function difference
between GaN and the metal, a depletion region is formed between the
gate dielectric layers 250. When the depletion region runs through
the region between the gate dielectric layers 250, carriers fail to
pass through them. However the application of a voltage on the gate
enables carriers to pass through regions between the gate
dielectric layers 250. The voltage is Vt, the threshold voltage of
the vertical transistor, so that the vertical transistor of the
present invention can control the switch of transistor through
controlling the voltage value on the gate.
[0050] When reference to FIG. 13, when the gate electrode 260 is
free of voltage Vg or is applied with a voltage Vg less than Vt,
the threshold voltage of the vertical transistor, after the
application of voltage on the source electrode 290, carriers are
developed in the source region 220. The carriers pass from the
source region 220 through the drift region 230 to the drain region
240. Carriers will be completely depleted in the region (region of
the dotted line in FIG. 13) between the gate dielectric layers 250,
so that the vertical transistor is turned off. With reference to
FIG. 14, after the application of a voltage Vg greater than Vt, the
threshold voltage to turn on the vertical transistor, the depletion
region of carriers (region of the dotted line in FIG. 14) is
reduced so that carriers may pass through regions between the gate
dielectric layers 250 and reach the drain region 240 to turn on the
vertical transistor.
[0051] In summary, the vertical transistor of the present invention
includes a drift region, a source region, a drain region, and a
gate. The drift region, the source region, and the drain region are
of the first doping type, so that the vertical transistor is a
junction-less transistor, reducing the power consumption of the
transistor.
[0052] Obviously, those skilled in the art may make various
modifications and variations of the present invention without
departing from the spirit and scope of the invention. Thus, if such
modifications and variations of the present invention fall in the
claims of the invention and within the scope of equivalents
technology, the present invention is also intended to encompass
such changes and variations.
* * * * *