U.S. patent application number 13/250766 was filed with the patent office on 2012-04-05 for gallium arsenide based materials used in thin film transistor applications.
This patent application is currently assigned to APPLIED MATERIALS, INC.. Invention is credited to Bhaskar Kumar, Kaushal K. Singh, Robert Jan Visser.
Application Number | 20120080753 13/250766 |
Document ID | / |
Family ID | 45888752 |
Filed Date | 2012-04-05 |
United States Patent
Application |
20120080753 |
Kind Code |
A1 |
Singh; Kaushal K. ; et
al. |
April 5, 2012 |
GALLIUM ARSENIDE BASED MATERIALS USED IN THIN FILM TRANSISTOR
APPLICATIONS
Abstract
Embodiments of the invention provide a method of forming a group
III-V material utilized in thin film transistor devices. In one
embodiment, a gallium arsenide based (GaAs) layer with or without
dopants formed from a solution based precursor may be utilized in
thin film transistor devices. The gallium arsenide based (GaAs)
layer formed from the solution based precursor may be incorporated
in thin film transistor devices to improve device performance and
device speed. In one embodiment, a thin film transistor structure
includes a gate insulator layer disposed on a substrate, a GaAs
based layer disposed over the gate insulator layer, and a
source-drain metal electrode layer disposed adjacent to the GaAs
based layer.
Inventors: |
Singh; Kaushal K.; (Santa
Clara, CA) ; Visser; Robert Jan; (Menlo Park, CA)
; Kumar; Bhaskar; (Santa Clara, CA) |
Assignee: |
APPLIED MATERIALS, INC.
Santa Clara
CA
|
Family ID: |
45888752 |
Appl. No.: |
13/250766 |
Filed: |
September 30, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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61388943 |
Oct 1, 2010 |
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61452801 |
Mar 15, 2011 |
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61468918 |
Mar 29, 2011 |
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Current U.S.
Class: |
257/347 ;
257/E21.09; 257/E21.409; 257/E29.273; 438/151; 438/478 |
Current CPC
Class: |
H01L 51/0048 20130101;
H01L 27/127 20130101; H01L 31/075 20130101; B82Y 10/00 20130101;
H01L 21/0262 20130101; Y02P 70/50 20151101; H01L 21/02631 20130101;
H01L 29/66742 20130101; H01L 31/035227 20130101; H01L 21/02579
20130101; H01L 29/78681 20130101; H01L 31/022425 20130101; H01L
31/184 20130101; Y02E 10/548 20130101; H01L 21/0237 20130101; H01L
21/02576 20130101; C23C 16/56 20130101; H01L 29/454 20130101; H01L
27/1225 20130101; H01L 29/78696 20130101; Y02E 10/544 20130101;
H01L 21/02491 20130101; H01L 21/02628 20130101; H01L 51/424
20130101; Y02E 10/549 20130101; C23C 16/301 20130101; H01L 21/02601
20130101; H01L 29/78618 20130101; H01L 31/072 20130101; H01L
31/1864 20130101; B82Y 30/00 20130101; H01L 21/02546 20130101; H01L
21/3245 20130101; H01L 29/207 20130101 |
Class at
Publication: |
257/347 ;
438/151; 438/478; 257/E29.273; 257/E21.409; 257/E21.09 |
International
Class: |
H01L 29/786 20060101
H01L029/786; H01L 21/20 20060101 H01L021/20; H01L 21/336 20060101
H01L021/336 |
Claims
1. A thin film transistor structure comprising: a gate insulator
layer disposed on a substrate; a GaAs based layer disposed over the
gate insulator layer; and a source-drain metal electrode layer
disposed adjacent to the GaAs based layer.
2. The structure of claim 1, further comprising: a doped GaAs layer
disposed between the GaAs based layer and the source-drain metal
electrode layer.
3. The structure of claim 2, wherein the doped GaAs layer includes
a p-type dopant or a n-type dopant formed therein.
4. The structure of claim 3, wherein the p-type dopant is selected
from a group consisting of metallic zinc dopants, dimethyl zinc
(DMZ), diethyl zinc (DEZ), metallic magnesium dopants,
cyclopentadienyl magnesium, carbon chlorine (CCl.sub.4) or carbon
bromide (CBr.sub.4), and the n-type dopant is selected from a group
consisting of H.sub.2S, sulfur, silane (SiH.sub.4), disilane
(Si.sub.2H.sub.6), H.sub.2Se and Se.
5. The structure of claim 1, wherein the GaAs based layer is
fabricated from a solution based GaAs containing precursor.
6. The structure of claim 5, wherein the solution based GaAs
containing precursor includes a GaAs containing precursor selected
from a group consisting of (NMe.sub.2).sub.2GaAs.sup.tBuH,
Me.sub.2GaAs(NMe.sub.2).sub.2, Me.sub.2GaAs(SiMePh.sub.2).sub.2,
Me.sub.2GaAs(SiPh.sub.3).sub.2, Et.sub.2GaAs(SiMe.sub.2Cy).sub.2,
and Me.sub.2GaAs(SiMe.sub.2Cy).sub.2.
7. The structure of claim 1, further comprising: a passivation
layer disposed over the source-drain metal electrode layer.
8. The structure of claim 1, wherein the gate insulator layer is
fabricated from a dielectric layer selected from a group consisting
of silicon oxide (SiO.sub.2), silicon oxynitride (SiON), or silicon
nitride (SiN), high-k materials or HfO.sub.2.
9. A method of forming a thin film transistor structure,
comprising: providing a substrate having a dielectric layer
disposed thereon into a processing chamber, supplying a GaAs
containing precursor disposed in a solvent to the processing
chamber; evaporating the GaAs containing precursor solvent in the
processing chamber to form a GaAs based layer on the substrate; and
forming a source-drain metal electrode layer adjacent to the GaAs
based layer to form a thin film transistor structure.
10. The method of claim 9, wherein the GaAs containing precursor is
selected from a group consisting of (NMe.sub.2).sub.2GaAs.sup.tBuH,
Me.sub.2GaAs(NMe.sub.2).sub.2, Me.sub.2GaAs(SiMePh.sub.2).sub.2,
Me.sub.2GaAs(SiPh.sub.3).sub.2, Et.sub.2GaAs(SiMe.sub.2Cy).sub.2,
and Me.sub.2GaAs(SiMe.sub.2C.sub.Y).sub.2.
11. The method of claim 9, wherein evaporating the GaAs containing
precursor solvent further comprises: annealing the GaAs based layer
formed on the substrate.
12. The method of claim 9, further comprising: forming a doped GaAs
layer on the GaAs based layer prior to forming the source-drain
metal electrode layer.
13. The method of claim 12, wherein the doped GaAs layer includes a
p-type dopant or a n-type dopant formed therein.
14. The method of claim 13, wherein the p-type dopant is selected
from a group consisting of metallic zinc dopants, dimethyl zinc
(DMZ), diethyl zinc (DEZ), metallic magnesium dopants,
cyclopentadienyl magnesium, carbon chlorine (CCl.sub.4) or carbon
bromide (CBr.sub.4), and the n-type dopant is selected from a group
consisting of H.sub.2S, sulfur, silane (SiH.sub.4), disilane
(Si.sub.2H.sub.6), H.sub.2Se and Se.
15. The method of claim 9, wherein the source-drain metal electrode
layer is fabricated by a metallic material selected from a group
consisting of copper (Cu), gold (Au), silver (Ag), aluminum(Al),
tungsten (W), molybdenum (Mo), chromium (Cr), tantalum (Ta), cobalt
(Co), germanium (Ge), tantalum (Ta), titanium (Ti), gold (Au),
alloy of titanium (Ti) and gold (Au), alloy of tantalum (Ta) and
gold (Au), alloy of germanium (Ge) and gold (Au), alloy of
aluminum(Al) and cobalt (Co), composite layers including a film
stack having aluminum layer (Al) sandwiched between molybdenum
(Mo), alloys thereof and combination thereof.
16. A method for forming a GaAs based material in a thin film
transistor structure further comprising: providing a substrate
having a dielectric layer formed thereon; forming a semiconductor
layer disposed on the dielectric layer, wherein the semiconductor
layer is fabricated from a solution based GaAs based layer; and
forming a source-drain metal electrode layer adjacent to the
semiconductor layer.
17. The method of claim 16, further comprising: forming a doped
semiconductor layer between the semiconductor layer and the
source-drain metal electrode layer.
18. The method of claim 16, wherein the solution based GaAs based
layer is fabricated from a GaAs containing precursor is selected
from a group consisting of (NMe.sub.2).sub.2GaAs.sup.tBuH,
Me.sub.2GaAs(NMe.sub.2).sub.2, Me.sub.2GaAs(SiMePh.sub.2).sub.2,
Me.sub.2GaAs(SiPh.sub.3).sub.2, Et.sub.2GaAs(SiMe.sub.2Cy).sub.2,
and Me.sub.2GaAs(SiMe.sub.2Cy).sub.2.
19. The method of claim 17, wherein doped GaAs layer includes a
p-type dopant or a n-type dopant formed therein.
20. The method of claim 19, wherein the p-type dopant is selected
from a group consisting of metallic zinc dopants, dimethyl zinc
(DMZ), diethyl zinc (DEZ), metallic magnesium dopants,
cyclopentadienyl magnesium, carbon chlorine (CCl.sub.4) or carbon
bromide (CBr.sub.4), and the n-type dopant is selected from a group
consisting of H.sub.2S, sulfur, silane (SiH.sub.4), disilane
(Si.sub.2H.sub.6), H.sub.2Se and Se.
21. A method for forming a GaAs based material on a substrate,
comprising: providing a substrate into a electrohydrodynamic jet
system; and printing a plurality of GaAs droplets onto the
substrate, wherein the GaAs droplets are supplied from a solution
based GaAs precursor disposed in the system.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims benefit of U.S. Provisional
Application Ser. No. 61/388,943 filed Oct. 1, 2010 (Attorney Docket
No. APPM/15444L), U.S. Provisional Application Ser. No. 61/452,801
filed Mar. 15, 2011 (Attorney Docket No. APPM/15444L02) and U.S.
Provisional Application Ser. No. 61/468,918, filed Mar. 29, 2011
(Attorney Docket No. APPM/15444L03), all of which are incorporated
by reference in their entirety.
[0002] This application is also related to U.S. patent application
Ser. No. ______, entitled "High Efficiency Solar Cell Device With
Gallium Arsenide Absorber Layer", filed ______, (Attorney Docket
No. APPM/15444) which is herein incorporated by reference.
BACKGROUND OF THE INVENTION
[0003] 1. Field of the Invention
[0004] Embodiments of the present invention generally relate to
methods of manufacturing thin film transistor devices. More
particularly, embodiments of the present invention relate to a
group III-V based material utilized in thin film transistor
devices.
[0005] 2. Description of the Related Art
[0006] Plasma display panels and liquid crystal displays are
frequently used for flat panel displays. Liquid crystal displays
(LCD) generally contain two glass substrates joined together with a
layer of a liquid crystal material sandwiched there between. The
glass substrate may be a semiconductor substrate, or may be a
transparent substrate such as a glass, quartz, sapphire, or a clear
plastic film. The LCD may also contain light emitting diodes for
back lighting.
[0007] As the resolution requirements for liquid crystal displays
increase, it has become desirable to control a large number of
separate areas of the liquid crystal cell, called pixels. In a
modern display panel, more than 1,000,000 pixels may be present. At
least the same number of transistors is formed on the glass
substrate so that each pixel can be switched between an energized
and de-energized state relative to the other pixels disposed on the
substrate.
[0008] In recent years, low temperature polysilicon (LIPS) TFT and
micro-crystalline silicon TFT have been developed to offer an
operation speed with a fast speed. TFT devices typically include
MOS devices built with a source region, semiconductor (e.g., or
called a channel region), and drain region formed on an optically
transparent substrate with or without an optional dielectric layer
disposed thereon. Subsequently, a gate dielectric layer is then
deposited on top of the source region, semiconductor region (e.g.,
or called a channel region) and drain region isolate a gate
electrode from the semiconductor (e.g., or called a channel
region), source and drain regions. The gate electrode is formed on
top of the gate dielectric layer. The performance of a TFT device
dependent on the quality of the films that are deposited to form
the MOS structure. The key performance elements of a MOS device are
the qualities of the semiconductor layer (e.g., or called a channel
layer), the gate dielectric layer, and the semiconductor layer
(e.g., or called a channel layer) and gate dielectric layer
interface. The quality of the semiconductor layer (e.g., or called
a channel region) has received a lot of attention in recent
years.
[0009] Therefore, there is a need for forming a semiconductor layer
with improved film qualities to provide a stable and reliable
device performance.
SUMMARY OF THE INVENTION
[0010] Embodiments of the invention provide a method of forming a
group III-V based material utilized in thin film transistor
devices. In one embodiment, a gallium arsenide based (GaAs) layer
with or without dopants formed from a solution based precursor may
be utilized in thin film transistor devices. The gallium arsenide
based (GaAs) layer formed from the solution based precursor may be
incorporated in thin film transistor devices to improve device
performance and device speed. In one embodiment, a thin film
transistor structure includes a gate insulator layer disposed on a
substrate, a GaAs based layer disposed over the gate insulator
layer, and a source-drain metal electrode layer disposed adjacent
to the GaAs based layer.
[0011] In another embodiment, a method of forming a thin film
transistor structure includes providing a substrate having a
dielectric layer disposed thereon into a processing chamber,
supplying a GaAs containing precursor disposed in a solvent to the
processing chamber, evaporating the GaAs containing precursor
solvent in the processing chamber to form a GaAs based layer on the
substrate, and forming a source-drain metal electrode layer
adjacent to the GaAs based layer to form a thin film transistor
structure.
[0012] In yet another embodiment, a thin film transistor device
includes a method for forming a GaAs based material in a thin film
transistor structure further includes providing a substrate having
a dielectric layer formed thereon, forming a semiconductor layer
disposed on the dielectric layer, wherein the semiconductor layer
is fabricated from a solution based GaAs based layer, and forming a
source-drain metal electrode layer adjacent to the semiconductor
layer.
[0013] In still another embodiment, a method for forming a GaAs
based material on a substrate includes providing a substrate into a
electrohydrodynamic jet system, and printing a plurality of GaAs
droplets onto the substrate, wherein the GaAs droplets are supplied
from a solution based GaAs precursor disposed in the system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] So that the manner in which the above recited features of
the present invention are attained and can be understood in detail,
a more particular description of the invention, briefly summarized
above, may be had by reference to the embodiments thereof which are
illustrated in the appended drawings.
[0015] FIG. 1-6 are cross sectional views of various embodiments of
thin film transistor device structure;
[0016] FIG. 7 is a flow chart of methods to manufacture a GaAs
based solar cell according to embodiments of the invention;
[0017] FIG. 8 depicts a simplified sectional perspective view of
one embodiment of an aerosol assisted chemical vapor deposition
(AACVD);
[0018] FIG. 9 depicts a simplified sectional perspective view of
one embodiment of a rapid thermal processing chamber; and
[0019] FIG. 10 depicts a simplified sectional perspective view of
one embodiment of an electrohydrodynamic jet (E-jet) printing
system.
[0020] To facilitate understanding, identical reference numerals
have been used, where possible, to designate identical elements
that are common to the figures. It is contemplated that elements
and features of one embodiment may be beneficially incorporated in
other embodiments without further recitation.
[0021] It is to be noted, however, that the appended drawings
illustrate only exemplary embodiments of this invention and are
therefore not to be considered limiting of its scope, for the
invention may admit to other equally effective embodiments.
DETAILED DESCRIPTION
[0022] Embodiments of the disclosure provide methods of forming
group III-V based materials that may be utilized in thin film
transistor devices. In one embodiment, the group III-V materials
that may be utilized to form the thin film transistor devices
includes a gallium arsenide (GaAs) based material. The gallium
arsenide (GaAs) based material may be fabricated from a GaAs
pre-engineering solution. The gallium arsenide (GaAs) based
material may also be used in photodiodes, semiconductor diode,
light-emitting diode (LED), or organic light-emitting diode (OLED),
or other suitable display applications. The gallium arsenide (GaAs)
based material provides high film mobility and stability and low
film leakage, thereby efficiently enhancing the electrical
performance of transistor devices. It is noted that the gallium
arsenide (GaAs) based material may be used in other suitable
devices beyond the application noted above.
[0023] FIG. 1 depicts a bottom gate structure thin film transistor
(TFT) device 100 according to one embodiment of the present
disclosure. The device 100 includes a gate electrode layer 106
disposed on a substrate 102 covered with a gate insulator layer
104. A semiconductor layer 108 (e.g., or called a semiconductor
active layer, an active layer or a channel layer), conventionally
often made from an amorphous silicon layer or a low temperature
polysilicon (LTPS) layer, is disposed over the gate insulator layer
104. A thin doped semiconductor layer of n-type or p-type layer
110a, 110b is disposed over the semiconductor layer 108. After
formation of the doped semiconductor layer 110a, 110b, a
source-drain metal electrode layer 112a, 112b is then disposed
thereon and a passivation layer 114 is then subsequently formed
thereon to form the thin film transistor device 100. Instead of
using conventional silicon containing layers for manufacturing the
semiconductor layer 108, a group III-V material may be used to form
as may be used to form as the semiconductor layer 108 and the thin
doped semiconductor layer 110a, 110b in the thin film transistor
100. In example of the group III-V material is a gallium arsenide
(GaAs) based material. It is believed that gallium arsenide (GaAs)
based material can provide a high electron mobility and wide band
gap so as to improve the transistor device performance and speed.
Accordingly, using gallium arsenide (GaAs) based material as the
semiconductor layer 108 and the thin doped semiconductor layer
110a, 110b is believed to provide the thin film transistor 100 a
good device performance. Details regarding the manufacture of the
gallium arsenide (GaAs) based material or doped gallium arsenide
(GaAs) based material will be discussed below with referenced to
FIGS. 7-9.
[0024] In one embodiment, the substrate 102 may be any one of glass
substrate, plastic substrate, polymer substrate, metal substrate,
singled substrate, roll-to-roll substrate, or other suitable
transparent substrate suitable for forming a thin film transistor
thereon. The gate electrode layer 106 may be fabricated from any
suitable metallic materials, such as indium tin oxide (ITO), tin
oxide (SnO), indium zinc oxide (IZO), indium tin zinc oxide (ITZO),
aluminum (Al), tungsten (W), chromium (Cr), germanium (Ge),
tantalum (Ta), titanium (Ti), gold (Au), alloy of titanium (Ti) and
gold (Au), alloy of tantalum (Ta) and gold (Au), alloy of germanium
(Ge) and gold (Au), molybdenum (Mo), InGaZnO, InGaZnON, ZnO, ZnON,
ZnSnO, CdSnO, GaSnO, TiSnO, CuAlO, SrCuO, LaCuOS, GaN, InGaN, AlGaN
or InGaAlN or combination thereof. Suitable materials for the gate
insulator layer 104 may be silicon oxide (SiO.sub.2), silicon
oxynitride (SiON), or silicon nitride (SiN), high-k materials, such
as HfO.sub.2, or other suitable materials, or the like. The
source-drain metal electrode layer 112a, 112b may be fabricated by
a metallic material selected from a group consisting of copper
(Cu), gold (Au), silver (Ag), aluminum(Al), tungsten (W),
molybdenum (Mo), chromium (Cr), tantalum (Ta), cobalt (Co),
germanium (Ge), tantalum (Ta), titanium (Ti), gold (Au), alloy of
titanium (Ti) and gold (Au), alloy of tantalum (Ta) and gold (Au),
alloy of germanium (Ge) and gold (Au), alloy of aluminum(Al) and
cobalt (Co), composite layers including a film stack having
aluminum layer (Al) sandwiched between molybdenum (Mo), alloys
thereof and combination thereof. The passivation layer 114 may be
fabricated by dielectric materials including silicon oxide
(SiO.sub.2), silicon oxynitride (SiON), or silicon nitride (SiN),
suitable polymer materials, such as polymethylmethacrylate (PMMA)
and the like.
[0025] FIG. 2 depicts a top metal gate structure thin film
transistor (TFT) device 200 according to one embodiment of the
present disclosure. The device 200 includes a metal gate electrode
204 disposed over a backside of a substrate 202. An insulator layer
203 may be formed from an opposite side (e.g., front side) of the
substrate 202 from wherein the metal gate electrode 204 is formed.
A semiconductor layer 206 (e.g., or called a semiconductor active
layer, an active layer or a channel layer), conventionally often
made from an amorphous silicon layer or a low temperature
polysilicon (LTPS) layer, is disposed over the insulator layer 203.
Subsequently, a source-drain metal electrode layer 208a, 208b is
then disposed over the semiconductor layer 206 to form the thin
film transistor device 200. Instead of using conventional silicon
containing layers for manufacturing the semiconductor layer 206, a
group III-V material may be used to form as may be used to form as
the semiconductor layer 206 in the thin film transistor 200. In
example of the group III-V material is a gallium arsenide (GaAs)
based material. It is believed that gallium arsenide (GaAs) based
material can provide a high electron mobility and wide band gap so
as to improve the transistor device performance and speed.
Accordingly, using gallium arsenide (GaAs) based material as the
semiconductor layer 206 is believed to provide the thin film
transistor 200 a good device performance may be obtained. Details
regarding the manufacture of the gallium arsenide (GaAs) based
material or doped gallium arsenide (GaAs) based material will be
discussed below with referenced to FIGS. 7-9.
[0026] The materials that may be used to form the metal gate
electrode 204, the insulator layer 203, and the source-drain metal
electrode layer 208a, 208b may be similar to the materials utilized
to form the metal gate electrode 106, the gate insulator layer 104,
and the source-drain metal electrode layer 112a, 112b described
above with referenced to FIG. 1.
[0027] FIG. 3 depicts a thin film transistor (TFT) device 300
according to one embodiment of the present disclosure. The device
300 includes a semiconductor layer 304 (or called a semiconductor
active layer, an active layer or a channel layer) disposed over a
substrate 302. An insulator layer 308 may be formed over the
semiconductor layer 304 in between a patterned source-drain metal
electrode layer 306a, 306b. A gate electrode layer 310 is then
disposed over the insulator layer 308 to form the thin film
transistor device 300. Instead of using conventional silicon
containing layers for manufacturing the semiconductor layer 304, a
group III-V material may be used to form as may be used to form as
the semiconductor layer 304 in the thin film transistor 300. In
example of the group III-V material is a gallium arsenide (GaAs)
based material. It is believed that gallium arsenide (GaAs) based
material can provide a high electron mobility and wide band gap so
as to improve the transistor device performance and speed.
Accordingly, using gallium arsenide (GaAs) based material as the
semiconductor layer 304 is believed to provide the thin film
transistor 300 a good device performance. Details regarding the
manufacture of the gallium arsenide (GaAs) based material or doped
gallium arsenide (GaAs) based material will be discussed below with
referenced to FIGS. 7-9.
[0028] The materials that may be used to form the metal gate
electrode layer 310, the insulator layer 308, and the source-drain
metal electrode layer 306a, 306b may be similar to the materials
utilized to form the metal gate electrode 106, the gate insulator
layer 104, and the source-drain metal electrode layer 112a, 112b
described above with referenced to FIG. 1.
[0029] FIG. 4 depicts a thin film transistor (TFT) device 400
according to one embodiment of the present disclosure. The device
400 includes a buffer oxide layer 404 disposed on a substrate 402.
A semiconductor layer 412 (e.g., or called a semiconductor active
layer, an active layer or a channel layer) is disposed between a
patterned source-drain metal electrode layer 406a, 406b. A gate
insulator layer 408 is then disposed over the semiconductor layer
412 followed by a metal gate electrode layer 410. Instead of using
conventional silicon containing layers for manufacturing the
semiconductor layer 412, a group III-V material may be used to form
as may be used to form as the semiconductor layer 412 in the thin
film transistor 400. In example of the group III-V material is a
gallium arsenide (GaAs) based material. It is believed that gallium
arsenide (GaAs) based material can provide a high electron mobility
and wide band gap so as to improve the transistor device
performance and speed. Accordingly, using gallium arsenide (GaAs)
based material as the semiconductor layer 412 is believed to
provide the thin film transistor device 400 a good device
performance. Details regarding the manufacture of the gallium
arsenide (GaAs) based material or doped gallium arsenide (GaAs)
based material will be discussed below with referenced to FIGS.
7-9.
[0030] The materials that may be used to form the metal gate
electrode 410, the gate insulator layer 408, and the source-drain
metal electrode layer 406a, 406b may be similar to the materials
utilized to form the metal gate electrode 106, the gate insulator
layer 104, and the source-drain metal electrode layer 112a, 112b
described above with referenced to FIG. 1.
[0031] FIG. 5 depicts a thin film transistor (TFT) device 500
according to one embodiment of the present disclosure. The device
500 includes a metal gate electrode layer 504 is disposed over a
substrate 502. A gate insulator layer 506 is disposed over the
metal gate electrode 504. A semiconductor layer 508 (e.g., or
called a semiconductor active layer, an active layer or a channel
layer) is disposed over the gate insulator layer 506. Subsequently,
a passivation layer 512 is disposed over the semiconductor layer
508 between a patterned source-drain metal electrode layer 510a,
510b. Instead of using conventional silicon containing layers for
manufacturing the semiconductor layer 508, a group III-V material
may be used to form as may be used to form as the semiconductor
layer 508 in the thin film transistor 500. In example of the group
III-V material is a gallium arsenide (GaAs) based material. It is
believed that gallium arsenide (GaAs) based material can provide a
high electron mobility and wide band gap so as to improve the
transistor device performance and speed. Accordingly, using gallium
arsenide (GaAs) based material as the semiconductor layer 508 is
believed to provide the thin film transistor device 500 a good
device performance. Details regarding the manufacture of the
gallium arsenide (GaAs) based material or doped gallium arsenide
(GaAs) based material will be discussed below with referenced to
FIGS. 7-9.
[0032] The materials that may be used to form the passivation layer
512, the metal gate electrode layer 504, the gate insulator layer
506, and the source-drain metal electrode layer 510a, 510b may be
similar to the materials utilized to form the passivation layer
114, the metal gate electrode layer 106, the gate insulator layer
104, and the source-drain metal electrode layer 112a, 112b
described above with referenced to FIG. 1.
[0033] FIG. 6 depicts a thin film transistor (TFT) device 600
according to one embodiment of the present disclosure. The device
600 includes a gate insulator layer 604 disposed over the substrate
602. A semiconductor layer 606 (e.g., or called a semiconductor
active layer, an active layer or a channel layer) is disposed on
the gate insulator layer 604. A patterned source-drain electrode
layer 608a, 608b is then disposed on the semiconductor layer 606.
Subsequently, a passivation layer 610 is then disposed on the
patterned source-drain electrode layer 608a, 608b. Instead of using
conventional silicon containing layers for manufacturing the
semiconductor layer 606, a group III-V material may be used to form
as may be used to form as the semiconductor layer 606 in the thin
film transistor 600. In example of the group III-V material is a
gallium arsenide (GaAs) based material. It is believed that gallium
arsenide (GaAs) based material can provide a high electron mobility
and wide band gap so as to improve the transistor device
performance and speed. Accordingly, using gallium arsenide (GaAs)
based material as the semiconductor layer 606 is believed to
provide the thin film transistor device 600 a greater mobility of
electrons and good device performance may be obtained. Details
regarding the manufacture of the gallium arsenide (GaAs) based
material or doped gallium arsenide (GaAs) based material will be
discussed below with referenced to FIGS. 7-9.
[0034] The materials that may be used to form the passivation layer
610, the gate insulator layer 604, and the source-drain metal
electrode layer 608a, 608b may be similar to the materials utilized
to form the passivation layer 114, the metal gate electrode layer
106, the gate insulator layer 104, and the source-drain metal
electrode layer 112a, 112b described above with referenced to FIG.
1.
[0035] It is noted that FIGS. 1-6 only depict exemplary embodiments
of thin film transistors having semiconductor layers that may be
formed from a group III-V material, such as a gallium arsenide
(GaAs) based material or a doped gallium arsenide (GaAs) based
material. Other thin film devices not illustrated here having
semiconductor layers, doped semiconductor layers, or other suitable
active or non-active layers formed therein may also suitable to be
formed as group III-V material according to the methods as
described below with referenced to FIGS. 7-9.
[0036] FIG. 7 depicts a flow diagram of one embodiment of a
processing sequence 700 for forming a solution based group III-V
material, such as a solution based GaAs layer utilized in a thin
film transistor device, such as the semiconductor layer 108, 206,
304, 412, 508, 606, or a doped semiconductor layer 110a, 110b,
formed in the thin film transistor devices 100, 200, 300, 400, 500,
600 depicted in FIGS. 1-6. In the embodiment wherein the
semiconductor layer 108, 206, 304, 412, 508, 606, or a doped
semiconductor layer 110a, 110b, are configured as GaAs based
materials, these layers may also be manufactured by the processing
sequence 700 as depicted in FIG. 7. It is noted that FIG. 7 only
depicts the process of manufacturing GaAs based layer for
illustration purpose, and is not intended to limiting the invention
scope or certain types of the layers that may be manufactured. It
should be noted that the number and sequence of steps illustrated
in FIG. 7 are not intended to limiting as to the scope of the
invention described herein, since one or more steps can be added,
deleted and/or reordered were appropriate without deviating from
the basic scope of the invention described herein.
[0037] The processing sequence 700 begins at step 702 by providing
a substrate, such as the substrate 102, 202, 302, 402, 502, 602, as
shown in FIGS. 1-6, configured to form thin film transistor devices
thereon. In one embodiment, the substrate 102 may be any one of
glass substrate, plastic substrate, polymer substrate, metal
substrate, singled substrate, roll-to-roll substrate, transparent
substrate, silicon containing substrate, such as a single crystal
silicon substrate, a multicrystalline silicon substrate, glass
substrate, quartz substrate, or other suitable materials or other
suitable transparent substrate suitable for forming a thin film
transistor thereon. The substrate may have layers previously formed
thereon to readily form a semiconductor layer 108, 206, 304, 412,
508, 606, or a doped semiconductor layer 110a, 110b, as the GaAs
based layer.
[0038] At step 704, a GaAs deposition process is performed to
deposit a GaAs layer on the substrate. The GaAs deposition process
is performed by providing a pre-engineered solution based GaAs
precursor to a processing chamber as a source precursor to
facilitate depositing the GaAs layer as the semiconductor layer
108, 206, 304, 412, 508, 606, or a doped semiconductor layer 110a,
110b on the substrate 102.
[0039] The pre-engineered solution based GaAs precursor comprises a
mixture of gallium complex and arsenic complex in solution, forming
a gallium-arsenic complex in the solution. In one embodiment, the
gallium-arsenic complex formed in the pre-engineered solution based
GaAs precursor generally has a GaAs dimer (--GaAs--), a GaAs
tetramer (--Ga.sub.2As.sub.2--), or a GaAs hexamer
(--Ga.sub.3As.sub.3--) structure, as shown below.
##STR00001##
[0040] It is believed that GaAs dimer (--GaAs--), a GaAs tetramer
(--Ga.sub.2As.sub.2--), or a GaAs hexamer (--Ga.sub.3As.sub.3--)
structures are relatively stable complexes so make them as good
candidates to be placed or stored in liquid solution under a
relatively stable status. By utilizing this relatively stable
solution based GaAs precursor, the GaAs solution may be delivered,
injected, sprayed and coated onto the substrate with high
uniformity and good film quality, thereby providing a reliable and
repeatable GaAs layer with desired film properties and high film
properties.
[0041] The GaAs dimer, GaAs tetramer, or GaAs hexamer may have
different functional groups attached thereto to form the GaAs
source precursor as a stable complex in the pre-engineered
solution. The GaAs complex may have a formula
R.sub.x(GaAs).sub.yR'.sub.z, wherein x, y, and z are integers
having a range between 1 and 15, which R and R' may or may not be
the same function groups or the like. The functional groups that
may be attached to the Ga and As elements in the GaAs dimer, GaAs
tetramer, or GaAs hexamer may include alkyl group, such as methyl
(CH.sub.3--), ethyl (C.sub.2H.sub.5--), propyl (C.sub.3H.sub.7--),
butyl (C.sub.4H.sub.9--), pentyl (C.sub.5H.sub.11--), and so on,
isopropyl and other similar isomers, aromatic groups, such as
benzal, styrene, toluene, xylene, pyridine, ethylbenzene,
acetophenone, methyl benzoate, phenyl acetate, phenol, cresol,
furan, and the like, alicyclic group, such as cyclopropane,
cyclobutane, cyclopentane, cyclopentadiene, toluene and the like,
amino group, such as NR.sub.2 (R as alkyl group), --SiR.sub.3,
--O--R, --S--R, --PR.sub.3, --POR.sub.3, halogens,
2,3,5,6-tetramethyl-1,4-benzoquinone or tetramethyl-p-benzoquinone,
bidentate ligands, expedious ligands, amines pyranine, steric
hindrance ligands and the like. In one exemplary embodiment, amino
group, such as NR.sub.2 (R as alkyl group) and steric hindrance
ligands are selected as the functional groups attached to the GaAs
dimer, GaAs tetramer, or GaAs hexamer.
[0042] The GaAs complex requires having a high solubility and
stability in solution. Accordingly, the functional groups selected
to form in the GaAs complex are desired to have 1:1 stoichiometry
preactive or formed in clusters. Additionally, the functional
groups are also desired to be able to be low temperature decomposed
into GaAs. Furthermore, the bonding energy between the functional
groups and Ga element and/or between the functional groups and As
element is configured to be weaker than the bonding energy
comprising the Ga--As bond. By this configuration, during a
depositing reaction, the bonds between the functional groups and
the Ga and/or As elements can be easily broken from the GaAs
solution precursor, thereby assisting the formation of the GaAs
layer on the substrate surface, and leaving GaAs bonding in the
complex. As the functional groups as attached are selected to be
easily removed, evaporated, or pyrolyzing during deposition or at
the subsequent baking or curing process, a GaAs layer with minimum
impurities or contamination may be thus obtained and formed on the
substrate surface.
[0043] Suitable examples of the GaAs precursors that follows the
requirements as stated above includes
(NMe.sub.2).sub.2Ga.sub.2As.sub.2(.sup.tBuH).sub.2,
Me.sub.2GaAs(NMe.sub.2).sub.2, Me.sub.2GaAs(SiMePh.sub.2).sub.2,
Me.sub.2GaAs(SiPh.sub.3).sub.2, Et.sub.2GaAs(SiMe.sub.2Cy).sub.2,
Me.sub.2GaAs(SiMe.sub.2Cy).sub.2, (Me).sub.3GaAs(NMe.sub.2).sub.3,
(Et).sub.3GaAs(NMe.sub.2).sub.3,
(Me).sub.4Ga.sub.2As.sub.2(.sup.tBuH).sub.2,
(Et).sub.4Ga.sub.2As.sub.2(.sup.tBuH).sub.2, 1:3 stoichiometry of
Ga:As, such as GaAs.sub.3.sup.tBu.sub.6, or the like. The
structures of the GaAs precursors include the followings:
##STR00002##
[0044] In one embodiment, the GaAs precursor used to form the GaAs
layer on the substrate is (NMe.sub.2).sub.2GaAs.sup.tBuH.
(NMe.sub.2).sub.2GaAs.sup.tBuH precursor may be synthesized by
mixing gallium amide (Ga(NMe.sub.2)).sub.3 with excess tert-butyl
arsine (.sup.tBuAsH.sub.2) in hexane or toluene solvent or other
suitable organic or inorganic solvent and stirring overnight, such
as stirring over 16 hours. The process temperature may be
controlled between about -40 degrees Celsius and about -90 degrees
Celsius. After the mixing process, (NMe.sub.2).sub.2GaAs.sup.tBuH
is obtained and may be stored in CH.sub.2Cl.sub.2 solvent or
toluene solvent.
[0045] In another embodiment, the GaAs layer may be formed by using
tris(dimethylamino)arsine (Me.sub.6N.sub.3As) and trimethylgallium
(GaMe.sub.3) as source precursors to synthesize and pre-engineer
the GaAs source precursor. The tris(dimethylamino)arsine
(Me.sub.6N.sub.3As) and trimethylgallium (GaMe.sub.3) are reacted
in toluene or hexane solvent to form the desired solution based
GaAs containing precursor. The process temperature may be
controlled between about -40 degrees Celsius and about -90 degrees
Celsius.
[0046] In yet another embodiment, the GaAs layer may be formed by
using [{L}HGaAsR].sub.n or [{L}.sub.2GaAs.sup.tBuH] as a precursor,
in which L is nitrogen-based donor ligand, NMe.sub.2, or hydrazines
functional groups. The precursors of [{L}HGaAsR].sub.n or
[{L}.sub.2GaAs.sup.tBuH] may be synthesized by a reaction of
As(SiR.sub.3).sub.3, R.sub.3SiAsH.sub.3, or H.sub.2As.sup.tBu with
GaH.sub.3{L} or Ga{L}.sub.3 in a hexane solution while stirring at
room temperature for over 24 hours. After the reaction is
completed, the [{L}HGaAsR].sub.n or [{L}.sub.2GaAs.sup.tBuH]
precursor may be obtained and can be used as a source of GaAs to
form the GaAs layer on the substrate when decomposed.
[0047] The GaAs containing precursor, such as
(NMe.sub.2).sub.2GaAs.sup.tBuH, [{L}HGaAsR].sub.n or
[{L}.sub.2GaAs.sup.tBuH], or other suitable precursor as described
above, is then supplied to a CVD chamber to deposit the GaAs layer
on the substrate. In one embodiment, the solution based GaAs
containing precursor is supplied in a CVD chamber to perform an
aerosol assisted chemical vapor deposition (AACVD) process. An
example of the AACVD chamber that may be used to practice the
present invention will be further discussed below with referenced
to FIG. 8. The precursor solution is atomized by using an aerosol
generator. A carrier gas is used to promote aerosol formation.
Subsequently, aerosol carrying the GaAs containing solvent
precursor is transported into CVD chamber by the carrier gas and
evaporated in the chamber. After entering into the CVD chamber, the
precursor enters into the gas phase from the liquid phase to enable
the CVD process. Subsequently, the gas phase GaAs containing
precursor is then decomposed and absorbed on the substrate to form
the desired GaAs layer on the substrate. If the precursor does not
get full vaporization, spray pyrolysis process will take place to
have the precursor become as aerosol droplets to be absorbed on the
substrate and form the GaAs layer on the substrate surface. In one
embodiment, during the AACVD deposition process, the substrate
temperature is controlled at about 550 degrees Celsius so as to
efficiently evaporate the precursor entering into the chamber.
[0048] In another embodiment, the GaAs layer may also be formed on
the substrate by using aerojet, flash evaporation, laser assisted
CVD, UV assisted CVD, laser reactive deposition, nanoparticles
spray from solution, spray CVD, metalorganic vapour phase epitaxy
(MOVPE), hydride vapor phase epitaxy (HVPE), or by other suitable
techniques as needed. Some other wet deposition process, such as
ink-jet, spin coating, meniscus coating, dip coating,
electroplating, spray coating, electrospraying, screen printing or
other suitable techniques may also employed to form the GaAs layer
on the substrate surface. Furthermore, some vacuum techniques, such
as molecular beam epitaxy (MBE), metalorganic vapour phase epitaxy
(MOVPE), pulsed laser deposition (PLD), plasma enhanced chemical
vapor deposition (PECVD), sputter, evaporate, magnetron sputter,
chemical beam deposition, atomic layer deposition (ALD), hardware
chemical vapor deposition (HWCVD), microwave plasma and some other
techniques, may also used as needed.
[0049] After deposition, the GaAs layer is formed as a
semiconductor layer in a thin film transistor device disposed on
the substrate. The GaAs layer as formed on the substrate may have a
ratio of Ga element to As element substantially between about 1:0.8
and about 1:1.2. XRD analysis indicates that the GaAs layer as
formed has a strong (111) plane peak. The XRD peak positions, at
<111>, <220> and <311> planes, match with the
standard peak positions for cubic GaAs. In one embodiment, the GaAs
layer may have a thickness between about 0.2 .mu.m and about 3
.mu.m.
[0050] In one embodiment, different dopants may be doped into the
GaAs layer. Dopants may be in form of particles, powders, gel,
liquid, solution or any other suitable forms, blending and mixing
into the solution based GaAs pre-engineered precursor. Different
dopants formed in the GaAs layer may provide different film
conductivity and mobility, thereby increasing the electrical
performance of the devices. In one embodiment, the dopants that may
be doped into the GaAs layer include Al, Zn, Mg, In, P, Si, Se, S,
C, N and the like. Suitable examples of p-type and n-type dopants
may be mixed or blended into the GaAs precursor to form a doped
GaAs solution based precursor, such as the p-type or n-type doped
GaAs layers. Suitable examples of p-type dopants may be added into
the GaAs precursor include metallic zinc dopants, dimethyl zinc
(DMZ), diethyl zinc (DEZ), metallic magnesium dopants,
cyclopentadienyl magnesium, carbon chlorine (CCl.sub.4), carbon
bromide (CBr.sub.4) or the like. Suitable examples of n-type
dopants include H.sub.2S, sulfur, silane (SiH.sub.4), disilane
(Si.sub.2H.sub.6), H.sub.2Se, Se or the like.
[0051] In one embodiment, the dopant concentration in the doped
GaAs layer may be controlled at between about 1.times.10.sup.16
atom/cm.sup.3 and about 1.times.10.sup.2.degree. atom/cm.sup.3. For
example, in a p-type doped GaAs layer, the p-type dopants may be
doped in the GaAs layer with a dopant concentration between about
1.times.10.sup.17 atom/cm.sup.3 and about 1.times.10.sup.19
atom/cm.sup.3. In another example, in a n-type doped GaAs layer,
the n-type dopants may be doped in the GaAs layer with a dopant
concentration between about 1.times.10.sup.18 atom/cm.sup.3 and
about 1.times.10.sup.20 atom/cm.sup.3.
[0052] At step 706, after the GaAs layer is formed on the
substrate, an anneal process is performed to thermally process the
GaAs layer. It is noted that different types of post treatment
processes, such as quenching, baking, laser treatment, or the like,
may also be performed on the GaAs layer as needed. As the precursor
utilized to form the GaAs layer contains elements other than Ga and
As, such as carbon, nitrogen, oxide, or other elements contained in
the precursor. The thermal annealing process and/or the post
treatment process performed on the deposited layer may assist in
the driving out of the impurities contained in the as-deposited
GaAs layer. The thermal process may also assist in the repair of
defects that may be formed in the as-deposited film during the
deposition process.
[0053] In one embodiment, the annealing process may be performed by
any suitable annealing tool, such as furnace, rapid thermal
processing (RTP) chamber, spike anneal, or laser annealing chamber,
and the like. The annealing process may be performed at a
temperature between about 400 degrees Celsius and about 600 degree
Celsius to assist in the densification and/or crystallization of
the GaAs layer formed on the substrate.
[0054] FIG. 8 depicts a simplified sectional perspective view of
one embodiment of an aerosol assisted chemical vapor deposition
(AACVD) chamber 800 that may be utilized to deposit a solution
based GaAs layer on a substrate 801, such as the substrate 102,
202, 302, 402, 502, 602, described above with referenced to FIGS.
1-6. The AACVD chamber 800 may be used to perform a AACVD
deposition process, such as the deposition process described above
with referenced to FIG. 3. It is noted that other types of
deposition process, such as MOCVD, aerojet, flash evaporation,
laser assisted CVD, UV assisted CVD, laser reactive deposition,
nanoparticles spray from solution, spray CVD, MOVPE, HVPE, or by
other suitable techniques may be used to form the GaAs layer as
needed. Some other wet deposition process, such as ink-jet, spin
coating, meniscus coating, dip coating, electroplating, spray
coating, electrospraying, screen printing or other suitable
techniques may also employed to form the GaAs based layer on the
substrate surface. Furthermore, some vacuum techniques, such as
MBE, MOVPE, PLD, PECVD, sputter, evaporate, magnetron sputter,
chemical beam deposition, ALD, HWCVD, microwave plasma and some
other techniques, may also used as needed.
[0055] The chamber 800 includes a reaction tube 822 having a first
wall 826, a second wall 828, and a reactor body 824 connecting
between the first wall 826 and the second wall 828. The first wall
826, the second wall 828, and the reactor body 824 formed in the
reaction tube 822 defines an interior processing region 818. A
graphite heating block 820 is disposed in the reaction tube 822 to
receive the substrate disposed thereon for processing. The
temperature of the substrate may be monitored by a temperature
sensor (not shown) disposed in the reaction tube 822 as needed.
[0056] An exhaust 832 is formed in the second wall 828 to
facilitate transferring the substrate into and out of the reaction
tube 822. A gas inlet port 830 is formed in the first wall 826 to
facilitate delivering reaction gases and precursors into the
interior processing region 818 during process from a mixing chamber
816. A liquid ampoule container 834 is attached to the mixing
chamber 816 through a gas delivery passageway 836. The liquid
ampoule container 834 may store precursors 808 to provide source
materials into the interior processing region 818 to deposit a GaAs
based layer based on the substrate. The mixing chamber 816 provides
a tortuous path which may extend the flow path for the GaAs
precursor 808 supplied from the liquid ampoule container 834 to
ensure thorough mixing. Examples of GaAs precursor may be stored in
the liquid ampoule container 834 include
(NMe.sub.2).sub.2GaAs.sup.tBuH, Me.sub.2GaAs(NMe.sub.2).sub.2,
Me.sub.2GaAs(SiMePh.sub.2).sub.2, Me.sub.2GaAs(SiPh.sub.3).sub.2,
Et.sub.2GaAs(SiMe.sub.2Cy).sub.2, Me.sub.2GaAs(SiMe.sub.2Cy).sub.2,
(Me).sub.3GaAs(NMe.sub.2).sub.3, (Et).sub.3GaAs(NMe.sub.2).sub.3,
(Me).sub.4Ga.sub.2As.sub.2(.sup.tBuH).sub.2,
(Et).sub.4Ga.sub.2As.sub.2(.sup.tBuH).sub.2, or the like.
[0057] In the embodiment wherein a doped GaAs based layer is
desired to be formed on the substrate 102, such as a p-type doped
GaAs based layer or a n-type doped GaAs based layer to form a doped
semiconductor layer, such as the doped semiconductor layer 110a,
110b depicted in FIG. 1, dopant containing materials may be
blended, added or mixed with the GaAs precursor in the liquid
ampoule container 834, forming a dopant containing GaAs precursor
which can be readily supplied to the interior processing region 818
for processing. As discussed above, suitable p-type dopant
materials that may be added into the GaAs precursor include zinc
containing materials, such as metallic zinc dopants, dimethyl zinc
(DMZ), diethyl zinc (DEZ), or the like, magnesium containing
material, such as metallic magnesium dopants, cyclopentadienyl
magnesium, or the like, and carbon containing materials, such as
carbon chlorine (CCl.sub.4), carbon bromide (CBr.sub.4) or the
like. Suitable n-type dopant materials that may be added into the
GaAs precursor include sulfur containing materials, such as
H.sub.2S, sulfur, silicon containing materials such as silane
(SiH.sub.4), disilane (Si.sub.2H.sub.6), and selenium containing
material, such as H.sub.2Se, Se or the like. In one embodiment, the
p-type dopant materials utilized to be added to the GaAs precursor
is DMZ or DEZ and n-type dopant materials utilized to be added to
the GaAs precursor is disilane (Si.sub.2H.sub.6).
[0058] A gas panel 810 is coupled to the liquid ampoule container
834 to supply a carrier gas to the liquid ampoule container 834
through a delivery passageway 812. The gas panel 810 introduces
carrier gases to the liquid ampoule container 834 to inject and
push the GaAs precursor 802 disposed in the liquid ampoule
container 834 to the mixing chamber 816 and ultimately into the
interior processing region 818 through the gas delivery passageway
836. Examples of gases that may be supplied from the gas panel 810
include nitrogen containing gas, such as nitrogen (N.sub.2),
N.sub.2O, and NO, among others, or oxygen containing gas, such as,
oxygen (O.sub.2) or (O.sub.3). Inert gas, such as Ar or He, may
also be used to carry the GaAs precursor 802 into the interior
processing region 818. In one exemplary embodiment described
herein, the carrier gas used to inject and push the GaAs precursor
808 to the interior processing region 818 is nitrogen (N.sub.2)
gas.
[0059] The solution based GaAs precursor 802 with/without the
desired dopants disposed in the liquid ampoule container 834 is
heated and vaporized by a humidifier 804. The humidifier 804 may
have a piezoelectric device 806 which may provide ultrasonic energy
and/or heat energy to the solution based GaAs precursor 802
disposed therein, thereby assisting heating and evaporating GaAs
precursor 802 into gas phase or in form of tiny droplets for
injection into the interior processing region 818 by the carrier
gas, as shown by the arrow 814. Some liquid 808, such as water or
other suitable liquid, may be disposed between the liquid ampoule
container 834 and the humidifier to maintain the solution based
GaAs precursor 802 within a desired temperature range. In one
embodiment, the humidifier 804 may vaporize the GaAs precursor at a
temperature between about 100 degrees Celsius and about 250 degrees
Celsius.
[0060] FIG. 9 depicts a simplified sectional perspective view of
one embodiment of a rapid thermal processing chamber 900 that may
be utilized to anneal a substrate 901, such as the substrate 102,
202, 302, 402, 502, 602 described above with referenced to FIGS.
1-6. The processing chamber 900 includes a chamber body 950 having
chamber walls 930, a bottom 932, and a top 934 defining an interior
volume 928. The walls 930 typically include at least one substrate
access port (not shown) to facilitate entry and egress of the
substrate 102, 202, 302, 402, 502, 602.
[0061] A radiant heat assembly 924 is mounted to the top 934 of the
chamber body 950. The radiant heat assembly 924 is utilized to heat
the substrate suspended by an edge ring 910 disposed around the
periphery of the substrate. The radiant heat assembly 924 includes
a plurality of lamp tubes 902 in a water jacket assembly 904. Each
tube 902 contains a reflector and a tungsten halogen lamp assembly.
The lamp tubes 902 are nested in a tight honeycomb pipe
arrangement. This close-packed hexagonal arrangement of lamp tubes
902 provides radiant energy, such as an IR radiation and/or longer
wavelength of UV radiation having a wavelength between about 400 nm
and about 4000 nm with high-power density. In one embodiment, the
radiant heat assembly 924 provides radiant energy to thermally
process the substrate, such as annealing a silicon layer disposed
on the substrate. One radiant heat assembly 924 that may be adapted
to benefit from the invention is described in U.S. Pat. No.
5,487,127, issued Jan. 23, 1996 to Gronet, et al., and is hereby
incorporated by reference in its entirety.
[0062] The edge ring 910 that supports substrate is spaced above a
stainless steel base 918 by a rotatable quartz cylinder 912 mounted
on the stainless steel base 918. The edge ring 910 may be
fabricated from a hard material with a small coefficient of thermal
expansion, such as silicon carbide, to prevent excessive expansion
and contraction during thermal processing. The quartz cylinder 912
is rotated between about 50 rpm and about 300 rpm during substrate
processing to maximize substrate temperature uniformity by
minimizing the effect of thermal asymmetries in the chamber 900 and
on the substrate. In one embodiment, the cylinder 912 may be coated
with silicon to render the cylinder opaque to a desired wavelength.
The stainless steel base 918 has a circulation circuit 946 allowing
coolant, such as water, to circulate therethrough. The coolant
circulation efficiently cools down the chamber temperature after
processing.
[0063] A reflector plate 914 is disposed below the substrate and
mounted above the stainless steel base 918. An array of temperature
probes 944 is embedded in the reflector plate 914 through openings
942 defined therein. The temperature probes 944 are connected to
pyrometers 916 through a conduit 936 that extends from the bottom
side of the stainless steel base 918 to the openings 942 in the
reflector plate 914. The temperature probes 944 and pyrometers 916
are used to obtain a metric indicative of temperatures of regions
of the substrate proximate each probe 944 such that a temperature
gradient of the substrate may be determined.
[0064] The bottom side 920 of the substrate and the upper side 938
of the reflector plate 914 bound a reflecting cavity 940
therebetween. The reflecting cavity 940 enhances the effective
emissivity of the substrate, thereby improving the accuracy of the
temperature measurement. A controller 917 may receive measurements
from the pyrometers 916 and output control signals to radiant heat
assembly 924 for real-time modify the radiation generated in the
processing chamber 900, thereby maintaining the substrate
temperature within a desired processing range.
[0065] The upper side 938 of the reflector plate 914 is highly
reflective, and reflects thermal radiation in a target wavelength
range and absorbs thermal radiation other then the target
wavelength range. One or more coating or layers may be utilized to
coat the reflector plate 914 on the stainless steel base 918 to
provide the selective reflectivity. For example, different
combination of coatings with different reflectivity and
absorbability may be utilized to enable the reflector plate 914 to
reflect thermal radiation at a desired wavelength back to the
substrate and absorb (or less reflect) thermal radiation other than
the desired wavelength. In one embodiment, the reflector plate 914
reflects the thermal wavelength between about 700 nm and about 1000
nm, and absorbs thermal wavelength below 700 nm and above 1000 nm.
One reflector plate 914 that may be adapted to benefit from the
invention is described in U.S. Pat. No. 6,839,507, issued Jan. 4,
2005 to Adams, et al., and is hereby incorporated by reference in
its entirety.
[0066] The thermal energy not reflected to back to the substrate is
absorbed by the reflector plate 914. The absorbed thermal energy is
efficiently and rapidly removed by the coolant circulating through
the stainless steel base 918 disposed below the reflector plate
914. Additionally, gas provided through holes (not shown) in the
reflector plate 914 may be utilized to promote the cooling rate of
the reflector plate 914 and the substrate positioned thereabove.
The rapid cool down rate provided by the reflector plate 914
promotes the temperature control of the substrate, thereby
efficiently providing a desired temperature processing profile. In
one embodiment, the reflector plate 914 may provide a substrate
cool date rate greater than about 200 degrees Celsius per second.
In another embodiment, the reflector plate 914 may provide a
substrate cool down rate of about 220 degrees Celsius per
second.
[0067] FIG. 10 depicts a simplified sectional perspective view of
one embodiment of an electrohydrodynamic jet (E-jet) printing
system 1000. Electrohydrodynamic jet (E-jet) printing is a
technique that uses electric fields to create fluid flow necessary
to deliver ink and/or droplet to a substrate for high resolution
(<30 .mu.m). In one embodiment, the electrohydrodynamic jet
(E-jet) printing is used herein to print a group III-V material,
such as GaAs based droplets, on the backplanes for high performance
thin film transistor (TFT) displays. The electrohydrodynamic jet
(E-jet) printing utilized to print GaAs based droplets may also be
used to create backplanes for OLED displays and high resolution,
high frequency (3D) LCD TVs. The GaAs based droplets may use GaAs
solution based precursor, as discussed above with referenced to
FIG. 7, as the source material at relatively a low temperature. The
high resolution of the electrohydrodynamic jet (E-jet) printing of
the GaAs based droplets may be obtained due to a combination of
nozzle sizes and droplet placement. The nozzle sizes may be varied
to control the size of the droplets printed onto the substrate.
[0068] In one embodiment, the electrohydrodynamic jet (E-jet)
printing system 1000 includes an ink chamber 1002 and an ink
chamber holder 1004 utilized to hold and control the ink chamber
1002 at desired positions above a substrate 1016 disposed on a
translation and tilting stage 1018. A stage heater 1020 may be
attached to the translation and tilting stage 1018 to control the
substrate 1016 at a desired temperature range. A micropipette 1010
is coupled to an end of the ink chamber 1002 to deliver the ink
from the ink chamber 1002 to an nozzle 1022 attached to an end of a
heater 1012 coupled between the micropipette 1010 and the nozzle
1022. The heater 1012 may be a NiCr heater configured to maintain
the ink delivered therethrough at a desired temperature range not
to clog the delivery path. The stage 1018 may be moved relative to
the tip of the nozzle 1022. The stage 1018 may be controlled to
have a scan speed at a desired range. In addition, the stage 1018
may be controlled to move relative to the nozzle 1022 along a
periphery region or center region of the substrate 1016 to inject
ink to desired locations defined on the substrate surface. In one
embodiment, the stage 1018 may be moved at a constant speed, an
accelerated speed or moved other paths as desired. Any suitable
translation mechanism may be used, such as a conveyor system, rack
and pinion system, or an x/y actuator, a robot, or other suitable
mechanism, to accurate movement of the stage 1018.
[0069] A back pressure source 1006 is coupled to a conduit 1008
attached to the ink chamber 1002 configured to apply a back
pressure to the nozzle 1022. Different pressure as applied may have
different amount of ink injected onto the substrate surface as
needed. Furthermore, change in back pressure and voltage as applied
to the nozzle 1022 may also affect the size and frequency of the
ink droplets. In one embodiment, the GaAs solution based precursor,
as discussed above with referenced to FIG. 7, may be stored in the
ink chamber 1002 configured to be printed or injected onto the
substrate as needed. In operation, a voltage power may be applied
between the nozzle 1022 and the substrate to create an electric
field so as to maintain and control consistent jetting conditions.
In one embodiment, the printed GaAs droplets may have an average
measured diameter between about 1 .mu.m and about 10 .mu.m.
[0070] While the foregoing is directed to embodiments of the
present invention, other and further embodiments of the invention
may be devised without departing from the basic scope thereof, and
the scope thereof is determined by the claims that follow.
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