U.S. patent application number 12/426061 was filed with the patent office on 2009-08-13 for ohmic contact film in semiconductor device.
This patent application is currently assigned to HUGA OPTOTECH INC.. Invention is credited to Yu-Chu Li, Chiung-Chi TSAI, Tzong-Liang Tsai.
Application Number | 20090200667 12/426061 |
Document ID | / |
Family ID | 38859552 |
Filed Date | 2009-08-13 |
United States Patent
Application |
20090200667 |
Kind Code |
A1 |
TSAI; Chiung-Chi ; et
al. |
August 13, 2009 |
OHMIC CONTACT FILM IN SEMICONDUCTOR DEVICE
Abstract
The invention provides an ohmic contact film formed between a
doped semiconductor material layer and a conductive material layer
of a semiconductor device. The composition of the ohmic contact
film according to a preferred embodiment of the invention is
represented by the general formula M.sub.xQ.sub.zN.sub.y, where M
represents the II group chemical element, Q represents the IV group
chemical element, N represents the V group chemical element,
1.ltoreq.x.ltoreq.3, 1.ltoreq.y.ltoreq.3, 1.ltoreq.z.ltoreq.3, and
x and y and z are molar numbers.
Inventors: |
TSAI; Chiung-Chi; (Tanzih
Township, TW) ; Tsai; Tzong-Liang; (Hsinchu, TW)
; Li; Yu-Chu; (Taichung, TW) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Assignee: |
HUGA OPTOTECH INC.
|
Family ID: |
38859552 |
Appl. No.: |
12/426061 |
Filed: |
April 17, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11797851 |
May 8, 2007 |
|
|
|
12426061 |
|
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|
Current U.S.
Class: |
257/750 ;
257/E23.155 |
Current CPC
Class: |
H01L 33/26 20130101;
H01L 33/40 20130101 |
Class at
Publication: |
257/750 ;
257/E23.155 |
International
Class: |
H01L 23/532 20060101
H01L023/532 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 28, 2006 |
TW |
095127869 |
Claims
1. An ohmic contact film formed between a doped semiconductor
material layer and a conductive material layer of a semiconductor
device, the composition of said ohmic contact film being
represented by the general formula: M.sub.xQ.sub.zN.sub.y, and
wherein M represents the II group chemical element, Q represents
the IV group chemical element, N represents the V group chemical
element, 1.ltoreq.x.ltoreq.3, 1.ltoreq.y.ltoreq.3,
1.ltoreq.z.ltoreq.3, and x and y and z are molar numbers.
2. The ohmic contact film of claim 1, wherein the II group chemical
element in said ohmic contact film is one selected from the group
consisting of Zn, Be, Mg, Ca, Sr, Ba, and Ra, the IV group chemical
element is one selected from the group consisting of C, Si, Ge, Si,
and Pb, and the V group chemical element in said ohmic contact film
is one selected from the group consisting of N, P, As, Sb, and
Bi.
3. The ohmic contact layer of claim 1, wherein said ohmic contact
film is formed at a temperature ranging from 400.degree. C. to
1100.degree. C.
4. The ohmic contact film of claim 1, wherein the thickness of said
ohmic contact film is in a range of from 0.5 Angstroms to 500
Angstroms.
5. The ohmic contact film of claim 1, wherein the dopant type of
the doped semiconductor material layer is N-type or P-type.
6. The ohmic contact film of claim 1, wherein the conductive
material layer is formed of a material selected from the group
consisting of Ni/Au, ITO, CTO, TiWN, In.sub.2O.sub.3, SnO.sub.2,
CdO, ZnO, CuGaO.sub.2, and SrCu.sub.2O.sub.2.
Description
[0001] This application is a Division of currently pending
application U.S. Ser. No. 11/797,851, entitled "OHMIC CONTACT FILM
IN SEMICONDUCTOR DEVICE" and filed on May 8, 2007
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates to an ohmic contact film, and more
particularly, to one formed between a doped semiconductor material
layer and a conductive material layer of a semiconductor
device.
[0004] 2. Description of the Prior Art
[0005] Light-emitting diodes can be applied to various kinds of
equipment, such as optical display equipment, regulatory signs,
telecommunication equipment, and illuminating equipment.
Light-emitting diodes, distinct from conventional light sources,
are applicable to different industries.
[0006] The radiating principle of the light-emitting diodes is that
the bonding of electrons and holes in the light-emitting layer of
P-type and N-type semiconductors forms photons to generate light on
forward bias. Because the P-type GaN semiconductor is hard to be
doped, the contact of P-type GaN semiconductor and conductive layer
produces higher resistance and consequently decreases the
efficiency of P-type GaN semiconductor.
[0007] Taiwanese Patent No. 459,407 provides a proposal to reduce
the contact resistance between a P-type GaN semiconductor layer and
a conductive layer. Referring to FIG. 1, FIG. 1 illustrates a
light-emitting diode structure having an n+ type reverse tunneling
layer. The light-emitting diode structure includes an insulated
sapphire substrate 11, a GaN buffer layer 12, an N-type GaN contact
layer 13, an N-type AlGaN constraint layer 14, an InGaN
light-emitting layer 15, a P-type AlGaN constraint layer 16, a
P-type GaN contact layer 17, an n+ type reverse tunneling layer 18,
a transparent conductive layer 19, a first electrode 21, and a
second electrode 22. The GaN buffer layer 12 is formed on the
insulated sapphire substrate 11. An N-type GaN contact layer 13 is
formed on the GaN buffer layer 12 such that a partial area of the
N-type GaN contact layer 13 is exposed. The first electrode 21 is
formed on the exposed partial area of the N-type GaN contact layer
13. The N-type AlGaN constraint layer 14 is formed on the N-type
GaN contact layer 13. The InGaN light-emitting layer 15 is formed
on the N-type AlGaN constraint layer 14. The P-type AlGaN
constraint layer 16 is formed on the InGaN light-emitting layer 15.
The P-type GaN contact layer 17 is formed on the P-type AlGaN
constraint layer 16. The n+ type reverse tunneling layer 18 is
formed on the P-type GaN contact layer 17. The transparent
conductive layer 19 is formed on the n+ type reverse tunneling
layer 18 such that a partial area of the n+ type reverse tunneling
layer 18 is exposed. The second electrode 22 is formed on the
exposed partial area of the n+ type reverse tunneling layer 18 and
contacts the transparent conductive layer 19.
[0008] The light-emitting diode improves the ohmic contact between
the P-type GaN contact layer 17 and the transparent conductive
layer 19 by adding an n+ type reverse tunneling layer 18 between
them.
[0009] However, due to a complex manufacturing process and
difficult control of the n+ type reverse tunneling layer 18, the
finished products of light-emitting diodes are not stable and have
a higher production cost as well.
[0010] Accordingly, a scope of the invention is to provide an ohmic
contact film capable of improving the ohmic contact between the
doped semiconductor material layer and the conductive material
layer. Compared to the prior art, a semiconductor light-emitting
device with the ohmic contact film has an easier manufacturing
process; it also increases the stability for production and
consequently has lower cost for production.
SUMMARY OF THE INVENTION
[0011] A scope of the invention is to provide an ohmic contact film
formed between a doped semiconductor material layer and a
conductive material layer of a semiconductor device. The
composition of the ohmic contact film according to a preferred
embodiment of the invention is represented by the general formula
M.sub.xN.sub.y, where M represents the II group chemical element, N
represents the V group chemical element, 1.ltoreq.x.ltoreq.3,
1.ltoreq.y.ltoreq.3, and x and y are molar numbers. According to
another preferred embodiment of the invention, an ohmic contact
film is provided. The composition of the ohmic contact film is
represented by the general formula M.sub.xQ.sub.zN.sub.y, where M
represents the II group chemical element, Q represents the IV group
chemical element, N represents the V group chemical element,
1.ltoreq.x.ltoreq.3, 1.ltoreq.y.ltoreq.3, 1.ltoreq.z.ltoreq.3, and
x, y and z are molar numbers.
[0012] The advantage and spirit of the invention may be understood
by the following recitations together with the appended
drawings.
BRIEF DESCRIPTION OF THE APPENDED DRAWINGS
[0013] FIG. 1 illustrates a light-emitting diode structure having
an n+ type reverse tunneling layer.
[0014] FIG. 2 is the schematic sectional view of the ohmic contact
film according to a preferred embodiment of the invention.
[0015] FIG. 3 is the drawing of the I-V test conducted for
semiconductor light-emitting devices with and without the ohmic
contact film.
DETAILED DESCRIPTION OF THE INVENTION
[0016] Referring to FIG. 2, FIG. 2 is the schematic sectional view
of the ohmic contact film 32 according to a preferred embodiment of
the invention. The ohmic contact film 32 is formed between a doped
semiconductor material layer 30 and a conductive material layer 34
of a semiconductor device. In practical application, the
semiconductor device can be a semiconductor light-emitting device.
The dopant type of the doped semiconductor material layer 30 can be
N-type or P-type. The conductive material layer 34 can be Ni/Au,
ITO, CTO, TiWN, In.sub.2O.sub.3, SnO.sub.2, CdO, ZnO, CuGaO.sub.2,
or SrCu.sub.2O.sub.2.
[0017] The composition of the ohmic contact film 32 is represented
by the general formula M.sub.xN.sub.y, where M represents the II
group chemical element, N represents the V group chemical element,
1.ltoreq.x.ltoreq.3, 1.ltoreq.y.ltoreq.3, and x and y are molar
numbers. In practical application, the II group chemical element in
the ohmic contact film 32 can be Zn, Be, Mg, Ca, Sr, Ba, or Ra. The
V group chemical element in the ohmic contact film 32 can be N, P,
As, Sb, or Bi.
[0018] In this embodiment, the ohmic contact film 32 is formed at a
temperature ranging from 400.degree. C. to 1100.degree. C. The
thickness of the ohmic contact film 32 is in a range of from 0.5
Angstroms to 500 Angstroms.
[0019] Refer to Table 1. Table 1 shows the results of a contact
resistance test of a combination structure with and without the
ohmic contact film 32. The combination structure includes a doped
semiconductor material layer 30 of P-type GaN and a conductive
material layer 34 of ITO. The ohmic contact film 32, formed between
the P-type GaN and the ITO, has the composition of MgN, where Mg is
selected from the II group chemical element, and N is selected from
the V group chemical element. As shown in Table 1, the combination
structure with MgN as the ohmic contact film 32 has a contact
resistance lower than that without MgN by about an order.
Therefore, the ohmic contact film 32 of MgN indeed improves the
ohmic contact between the P-type GaN and the ITO.
TABLE-US-00001 TABLE 1 combination structure of P-type GaN and ITO
contact resistance with MgN ohmic contact film 1.56 .times.
10.sup.-3 ohm-cm.sup.2 without MgN ohmic contact film 2.5 .times.
10.sup.-2 ohm-cm.sup.2
[0020] The calculation result in "Ferromagnetism in tetrahedrally
coordinated compounds of I/II-V elements: Ab initiocalculations" of
PHYSICAL REVIEW B 73 (2006) reveals that possible combinations of
the II group chemical element and the V group chemical element have
similar magnetic and electronic properties. It is found that all
II-V compounds have a tendency toward a ferromagnetic ground state.
On aspect of technology, it is believed that the ohmic contact film
32 according to the invention can be composed of other possible
II-V compounds not mentioned in the specification of the
invention.
[0021] Refer to FIG. 3. FIG. 3 is the drawing of an I-V test
conducted for semiconductor light-emitting devices with and without
the ohmic contact film 32. The ohmic contact film 32, included in
the semiconductor light-emitting device, is prepared by the
reaction between ammonia and Mg, and the composition of the ohmic
contact film 32 is Mg.sub.3N.sub.2. As shown in FIG. 3, the
semiconductor light-emitting device with Mg.sub.3N.sub.2 as the
ohmic contact film 32 has a lower resistance value than that
without Mg.sub.3N.sub.2.
[0022] According to another preferred embodiment of the invention,
the composition of the ohmic contact film 32 in FIG. 2 is
represented by the general formula M.sub.xQ.sub.zN.sub.y, where M
represents the II group chemical element, Q represents the IV group
chemical element, N represents the V group chemical element,
1.ltoreq.x.ltoreq.3, 1.ltoreq.y.ltoreq.3, 1.ltoreq.z.ltoreq.3, and
x, y and z are molar numbers.
[0023] In practical application, the II group chemical element in
the ohmic contact film 32 can be Zn, Be, Mg, Ca, Sr, Ba, or Ra. The
IV group chemical element in the ohmic contact film 32 can be C,
Si, Ge, Si, or Pb. The V group chemical element in the ohmic
contact film 32 can be N, P, As, Sb, or Bi.
[0024] The experimental result, according to "Ab initio band
structure calculations of Mg.sub.3N.sub.2 and MgSiN.sub.2" of
Condens. Matter 11, J. Phys (1999), proves that the energy gap of
Mg.sub.3N.sub.2 is about 2.8 eV, while that of MgSiN.sub.2 is about
4.8 eV. Because the energy gap width of Mg.sub.3N.sub.2 and
MgSiN.sub.2 is similar to that of InGaN, it is helpful to decrease
the resistance value between the P-type GaN semiconductor material
layer and the conductive material layer. Therefore, in the
embodiment, the composition of the ohmic contact film 32 can be
MgSiN.sub.2.
[0025] The ohmic contact film according to the invention is capable
of improving the ohmic contact between the doped semiconductor
material layer and the conductive material layer. Compared to the
prior art, the semiconductor light-emitting device with the ohmic
contact film has an easier manufacturing process; it also increases
the stability for production and consequently has lower cost for
production. Moreover, from the technical viewpoint, the ohmic
contact film provided by the invention is certainly applicable to
other type of semiconductor devices not described in the
specification.
[0026] With the example and explanations above, the features and
spirits of the invention will be hopefully well described. Those
skilled in the art will readily observe that numerous modifications
and alterations of the device may be made while retaining the
teaching of the invention. Accordingly, the above disclosure should
be construed as limited only by the metes and bounds of the
appended claims.
* * * * *