U.S. patent application number 16/174978 was filed with the patent office on 2020-04-30 for electronic device.
The applicant listed for this patent is InnoLux Corporation. Invention is credited to Toshiya INADA, Junya SHIBATA.
Application Number | 20200135959 16/174978 |
Document ID | / |
Family ID | 70327421 |
Filed Date | 2020-04-30 |
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United States Patent
Application |
20200135959 |
Kind Code |
A1 |
SHIBATA; Junya ; et
al. |
April 30, 2020 |
ELECTRONIC DEVICE
Abstract
An electronic device includes a plurality of double gate thin
film transistors (DGTFT). The plurality of DGTFTs includes a first
DGTFT, the first DGTFT includes a substrate, a first transparent
conductive layer disposed above the substrate, and a first metal
layer. The first metal layer is disposed corresponding to the first
transparent conductive layer. The first metal layer is electrically
connected to the first transparent conductive layer.
Inventors: |
SHIBATA; Junya; (Miao-Li
County, TW) ; INADA; Toshiya; (Miao-Li County,
TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
InnoLux Corporation |
Miao-Li County |
|
TW |
|
|
Family ID: |
70327421 |
Appl. No.: |
16/174978 |
Filed: |
October 30, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02F 1/1368 20130101;
G02F 1/136286 20130101; H01L 31/02164 20130101; G06K 9/0004
20130101; H01L 31/02019 20130101; H01L 31/03682 20130101; H01L
31/032 20130101; G02F 1/13624 20130101; G02F 2202/104 20130101;
H01L 31/1136 20130101; G02F 2202/103 20130101; H01L 27/14678
20130101; H01L 31/03762 20130101; G02F 2001/13685 20130101 |
International
Class: |
H01L 31/113 20060101
H01L031/113; H01L 27/146 20060101 H01L027/146; H01L 31/02 20060101
H01L031/02; H01L 31/0216 20060101 H01L031/0216; H01L 31/0368
20060101 H01L031/0368; H01L 31/0376 20060101 H01L031/0376; H01L
31/032 20060101 H01L031/032 |
Claims
1. An electronic device, comprising a plurality of double gate thin
film transistors (DGTFT), wherein the plurality of DGTFTs comprises
a first DGTFT, the first DGTFT comprising: a substrate; a first
transparent conductive layer, disposed above the substrate; a first
metal layer, disposed corresponding to the first transparent
conductive layer, wherein the first metal layer is electrically
connected to the first transparent conductive layer; and a channel
layer, disposed corresponding to the first transparent conductive
layer, wherein the first metal layer extends beyond at least one of
the boundaries of the channel layer, and wherein the channel layer
comprises a poly-silicon material layer.
2. (canceled)
3. The electronic device as claimed in claim 1, wherein the first
DGTFT further comprises: an insulating layer having an opening, in
which a part of the first transparent conductive layer is
exposed.
4. The electronic device as claimed in claim 3, wherein the first
metal layer further extends in the opening to form an opening
region.
5. The electronic device as claimed in claim 4, wherein further
comprises: an opaque material layer, disposed above the first
transparent conductive layer, wherein the opaque material layer
does not overlap the opening region in the top view of the
electronic device.
6. The electronic device as claimed in claim 5, wherein further
comprises: a passivation layer, disposed between the opaque
material layer and the first metal layer.
7. The electronic device as claimed in claim 4, wherein an angle of
an extending direction of the first metal layer extending in the
opening is greater than or equal to 85 degrees, and is less than or
equal to 95 degrees, with respect to the first transparent
conductive layer.
8. The electronic device as claimed in claim 7, wherein the angle
is greater than or equal to 85 degrees, and is less than or equal
to 90 degrees.
9. The electronic device as claimed in claim 4, further comprising:
a second DGTFT of the plurality of DGTFTs, adjacent to the first
DGTFT, wherein the second DGTFT comprises: a second transparent
conductive layer, disposed above the substrate; and the first metal
layer, disposed corresponding to the second transparent conductive
layer and at least partially overlapped the second transparent
conductive layer in the top view of the electronic device.
10. The electronic device as claimed in claim 9, further comprises:
a second metal layer, disposed in the insulating layer and
positioned between the first DGTFT and the second DGTFT.
11. The electronic device as claimed in claim 9, further
comprising: a differential subtractor circuit, wherein a terminal
of the second DGTFT and a terminal of the first DGTFT adjacent to
the second DGTFT are electrically connected to the differential
subtractor circuit.
12. The electronic device as claimed in claim 4, wherein the
plurality of DGTFTs further comprises an another first DGTFT
adjacent to the first DGTFT, wherein a length in a direction of the
opening region of the first DGTFT and the length in the direction
of the opening region of the another first DGTFT are different.
13. The electronic device as claimed in claim 12, further
comprising: a comparator circuit, wherein a terminal of the first
DGTFT and a terminal of the another first DGTFT are electrically
connected to the comparator circuit.
14. (canceled)
15. (canceled)
16. The electronic device as claimed in claim 1, wherein the first
metal layer has a reflectivity lower than 60% to visible light.
17. The electronic device as claimed in claim 1, wherein the first
metal layer comprises a chromium material.
18. The electronic device as claimed in claim 1, further
comprising: at least one thin film transistor (TFT), adjacent to
the first DGTFT.
19. The electronic device as claimed in claim 18, wherein a
terminal of the at least one TFT connects to a terminal of the
first DGTFT adjacent to the TFT.
20. The electronic device as claimed in claim 19, wherein a gate of
the at least one TFT connects to the first metal layer of the first
DGTFT adjacent to the TFT.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
[0001] The present disclosure relates to an electronic device, and
in particular to an electronic device having at least one first
double gate thin film transistors (DGTFTs) with a metal layer
electrically connected to a transparent conductive layer.
Description of the Related Art
[0002] In an electronic device, such as a photo sensor device, a
plurality of double gate type transistors (e.g., double gate
thin-film transistor, DGTFT) are arranged in an array to sense
light or images (e.g., a fingerprint pattern). In the conventional
structure of a double gate type transistor, a transparent electrode
material is applied as a top gate electrode to radiate light to the
semiconductor layer.
[0003] However, recently, photo sensor devices require high voltage
level resolution and more accurate identification. Such top gate
electrodes could have high voltage level resistance and may cause a
circuit operation delay and variations in photo data in each photo
sensing area of the photo sensor device. In addition, the photo
sensing area may be exposed not just by light reflected from an
object, but also by stray light coming from other directions.
Furthermore, when there are respective variations in the
characteristics of the double gate type transistor of each pixel in
the photo sensing area, it could also cause data variations.
Conventional photo sensor devices using a double gate type
transistor output analog data, so it's easy to be influenced by
those variations.
BRIEF SUMMARY
[0004] The present disclosure provides an electronic device that
comprises a plurality of double gate thin film transistors (DGTFT).
The plurality of the DGTFTs comprises a first DGTFT, the first
DGTFT includes a substrate, a first transparent conductive layer
disposed above the substrate, and a first metal layer. The first
metal layer is disposed corresponding to the first transparent
conductive layer. The first metal layer is electrically connected
to the first transparent conductive layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] In order to describe the manner in which the above-recited
and other advantages and features of the disclosure can be
obtained, a more particular description of the principles briefly
described above will be rendered by reference to specific examples
thereof which are illustrated in the appended drawings. It should
be understood that these drawings depict only exemplary aspects of
the disclosure and are therefore not to be considered to be
limiting of its scope. The principles herein are described and
explained with additional specificity and detail through the use of
the accompanying drawings, in which:
[0006] FIG. 1A illustrates a top view (layout) of a double gate
thin-film transistor (DGTFT) in an electronic device, in according
to some embodiments of the present disclosure.
[0007] FIG. 1B illustrates a cross-sectional view of the double
gate type transistor taken along line A-A' shown in FIG. 1A.
[0008] FIGS. 2A and 2B illustrate a cross-sectional view of an
example of DGTFT in accordance with some embodiments of the present
disclosure.
[0009] FIGS. 2C and 2D illustrate an embodiment of DGTFT sensing an
object, in accordance with some embodiments of the present
disclosure.
[0010] FIG. 3 illustrates a cross-sectional view of an embodiment
of two adjacent DGTFTs in accordance with some embodiments of the
present disclosure.
[0011] FIG. 4A illustrates a cross-sectional view of an embodiment
of DGTFT in accordance with some embodiments of the present
disclosure.
[0012] FIG. 4B illustrates a cross-sectional view of an embodiment
of two adjacent DGTFTs with a metal layer between them, in
accordance with some embodiments of the present disclosure.
[0013] FIGS. 4C and 4D illustrate a cross-sectional view of an
embodiment of DGTFT in accordance with some embodiments of the
present disclosure.
[0014] FIG. 5 illustrates a cross-sectional view of an embodiment
of DGTFT with reversed structure, in accordance with some
embodiments of the present disclosure.
[0015] FIG. 6 illustrates an embodiment of a photo sensor device,
in accordance with some embodiments of the present disclosure.
[0016] FIG. 7 illustrates an embodiment of a photo sensor device,
in accordance with some embodiments of the present disclosure.
[0017] FIGS. 8A and 8B illustrate a display device combined with
photo sensor devices in accordance with some embodiments of the
present disclosure.
[0018] FIG. 9 illustrates a DGTFT array integrated into the TFT
array of the display area in the LCD, in accordance with some
embodiments of the present disclosure.
[0019] FIG. 10A illustrates a portion of the array in FIG. 9, in
accordance with some embodiments of the present disclosure.
[0020] FIG. 10B is a timing diagram of the photo sensing of the
array in FIG. 10A, in accordance with some embodiments of the
present disclosure.
[0021] FIG. 11 illustrates a DGTFT array integrated into the TFT
array of the display area in the LCD, in accordance with some
embodiments of the present disclosure.
[0022] FIG. 12A illustrates a portion of the array in FIG. 11, in
accordance with some embodiments of the present disclosure.
[0023] FIG. 12B is a timing diagram of the photo sensing of the
array in FIG. 11A, in accordance with some embodiments of the
present disclosure.
[0024] FIG. 13 illustrates a DGTFT array integrated into the array
of the display area in the OLED, in accordance with some
embodiments of the present disclosure.
[0025] FIG. 14A illustrates the array in FIG. 13, in accordance
with some embodiments of the present disclosure.
[0026] FIG. 14B is a timing diagram of the photo sensing of the
array in FIG. 14A, in accordance with some embodiments of the
present disclosure.
[0027] FIG. 15 illustrates a DGTFT array integrated into the TFT
array of the display area in the OLED, in accordance with some
embodiments of the present disclosure.
[0028] FIG. 16A illustrates a portion of the full array of the
OLED, in accordance with some embodiments of the present
disclosure.
[0029] FIG. 16B is a timing diagram of the photo sensing of the
array in FIG. 16A, in accordance with some embodiments of the
present disclosure.
DETAILED DESCRIPTION
[0030] The following disclosure provides many different
embodiments, or examples, for implementing different features of
the invention. Specific examples of components and arrangements are
described below to simplify the present disclosure. These are, of
course, merely examples and are not intended to be limiting. For
example, the formation of a first feature over or on a second
feature in the description that follows may include embodiments in
which the first and second features are formed in direct contact,
and may also include embodiments in which additional features may
be formed between the first and second features, such that the
first and second features may not be in direct contact. In
addition, the present disclosure may repeat reference numerals
and/or letters in the various examples. This repetition is for the
purpose of simplicity and clarity and does not in itself dictate a
relationship between the various embodiments and/or configurations
discussed.
[0031] For purposes of the present detailed description, unless
specifically disclaimed, the singular includes the plural and vice
versa; and the word "including" means "including without
limitation." Moreover, words of approximation, such as "about,"
"almost," "substantially," "approximately," and the like, can be
used herein to mean "at, near, or nearly at," or "within 3-5% of,"
or "within acceptable manufacturing tolerances," or any logical
combination thereof, for example.
[0032] Furthermore, spatially relative terms, such as "beneath,"
"below," "lower," "above," "upper" and the like, may be used herein
for ease of description to describe one element or feature's
relationship to another element(s) or feature(s) as illustrated in
the figures. The spatially relative terms are intended to encompass
different orientations of the device in use or operation in
addition to the orientation depicted in the figures. For example,
if the device in the figures is turned over, elements described as
being "below" or "beneath" other elements or features would then be
oriented "above" the other elements or features. Thus, the
exemplary term "below" can encompass both an orientation of above
and below. The apparatus may be otherwise oriented (rotated 90
degrees or at other orientations) and the spatially relative
descriptors used herein may likewise be interpreted
accordingly.
[0033] For convenience, the "corresponding to" represents one
element could be disposed above/under the other element, or the two
elements could be at least partially overlapped in a top view.
[0034] FIG. 1A illustrates a top view (layout) of a double gate
thin-film transistor (DGTFT) in an electronic device (e.g., photo
sensor device), according to some embodiments of the present
disclosure. FIG. 1B illustrates a cross-sectional view of the DGTFT
taken along line A-A' shown in FIG. 1A.
[0035] Referring to FIGS. 1A and 1B, the DGTFT 100 includes a
substrate 102, an insulating layer 104 disposed above the substrate
102, a gate electrode 106 disposed in the insulating layer 104 and
above the substrate 102, a semiconductor layer 108 disposed in the
insulating layer 104 and above the gate electrode 106, a
transparent conductive layer 110 disposed corresponding to the
semiconductor layer 108 and the substrate 102, a metal layer 112
disposed corresponding to the transparent conductive layer 110, an
insulating layer 114 and an insulating layer 116 at least partially
overlapped the transparent conductive layer 110 in the top view,
and two source/drain 118 electrically connected to the
semiconductor layer 108. The source/drain 118 can also be called
the source/drain terminal (or terminal) of the DGTFT 100. In an
embodiment, the transparent conductive layer 110 is at least
partially overlapped the semiconductor layer 108 and the substrate
102 in the top view; the metal layer 112 is at least partially
overlapped the transparent conductive layer 110.
[0036] The insulating layer 104 may comprises plural sub-layers
(not shown). At least part of the plural sub-layers are disposed
between the gate electrode 106 and the semiconductor layer 108. At
least another part of the plural sub-layers are disposed between
the gate electrode 106 and the substrate 102. At least another part
of the plural sub-layers are disposed between the semiconductor
layer 108 and the transparent conductive layer 110. In another
embodiment, a first part of the plural sub-layers, the gate
electrode 106, a second part of the plural sub-layers, the
semiconductor layer 108, and a third part of the plural sub-layers
may be sequentially disposed, but the disclosure is not limited
thereto.
[0037] In one embodiment, the substrate 102 could be a rigid plate
or a flexible plate and be transparent or opaque. For example, the
rigid plate is a glass, and the flexible plate is a flexible
substrate made of, for example but it is not limited thereto,
polyimide PI or polyethylene terephthalate (PET). In another
embodiment, the substrate 102 includes a suitable elemental
semiconductor, such as germanium or diamond; a suitable compound
semiconductor, such as silicon carbide, gallium nitride, gallium
arsenide, or indium phosphide; or a suitable alloy semiconductor,
such as silicon germanium, silicon tin, aluminum gallium arsenide,
or gallium arsenide phosphide.
[0038] As shown in FIGS. 1A and 1B, in this embodiment, the gate
electrode 106 is used as the bottom gate of the DGTFT 100. The gate
electrode 106 comprises some kinds of metal materials, such as
copper, aluminum, gold, silver, another suitable metal material or
combination thereof. In this embodiment, the source/drain 118 may
also comprise metal material. The semiconductor layer 108 is used
as a channel layer of the DGTFT 100. In this embodiment, the
semiconductor layer 108 comprises polycrystalline silicon (also
called poly-Si). In some embodiments, the semiconductor layer 108
may comprise amorphous silicon (also called a-Si), Indium Gallium
Zinc Oxide (also called IGZO), another suitable semiconductor
material or combination thereof.
[0039] In the present disclosure, the transparent conductive layer
110 and the metal layer 112 are collectively called the top gate of
the DGTFT 100. The transparent conductive layer 110 may comprise
indium tin oxide (ITO), zinc oxide (ZnO), indium gallium zinc oxide
(IGZO), another transparent conductive material or combination
thereof. The metal layer 112 comprises metal material (e.g.,
copper, aluminum, gold, silver, another suitable metal material or
combination thereof).
[0040] In the present disclosure, the metal layer 112 is
respectively disposed corresponding to the transparent conductive
layer 110 and at least partially overlapping with the transparent
conductive layer 110 or the semiconductor layer 108 in the top view
of the DGTFT 100, as shown in FIGS. 1A and 1B. There is an opening
(or aperture) region disposed between the metal layer 112_1 and the
metal layer 112_2. It should be understood that the opening region
120 can be designed in any size (area) and shape. A part of the
transparent conductive layer 110 is exposed in the opening region
120. The transparent conductive layer 110 is transparent or
semi-transparent, but it is not limited thereto, so that the light
can pass through the transparent conductive layer 110 to affect the
semiconductor layer 108, thereby the DGTFT 100 can sense the
light.
[0041] The insulating layers 104, 114, and 116 comprise insulating
or dielectric material, such as silicon oxide (SiO.sub.x), silicon
nitride (SiN.sub.x), or another suitable insulating or dielectric
material. As shown in FIG. 1B, the insulating layers 104 separates
the transparent conductive layer 110, the semiconductor layer 108,
and the gate electrode 106 from each other, so that the transparent
conductive layer 110 and the gate electrode 106 can be the gate of
the DGTFT 100 (the top gate or bottom gate) to control the
threshold voltage of the semiconductor layer 108 (the channel of
the DGTFT 100).
[0042] In the present disclosure, as shown in FIG. 1B, the metal
layer 112 is disposed corresponding to and electrically connected
to the transparent conductive layer 110. The metal layer 112 and
the transparent conductive layer 110 collectively called the gate
electrode (e.g., the top gate of the DGTFT 100). It causes lower
resistance than that of the gate electrode made only by transparent
conductive material (e.g., ITO). It may cause a lower circuit
operation delay time (time constant). For example, in a DGTFT, the
gate line capacitor is about 11 pF, the gate line resistor made by
ITO is about 826 k ohm, and the gate line resistor made by metal is
about 9.4 k ohm. Therefore, the circuit operation delay time for
ITO is 9.1 us and the circuit operation delay time for metal is
103.4 ns. The circuit operation delay time improved for metal is
around 100 times less than the circuit operation delay time for
ITO.
[0043] FIGS. 2A and 2B illustrate a cross-sectional view of an
embodiment of DGTFT in accordance with some embodiments of the
present disclosure. The DGTFT 200 shares many similarities with the
DGTFT 100, but with some minor differences. The DGTFT 200 includes
a substrate 202, an insulating layer 204 disposed above the
substrate 202, a gate electrode 206 disposed in the insulating
layer 204 and above the substrate 202, a semiconductor layer 208
disposed in the insulating layer 204 and above the gate electrode
206, a transparent conductive layer 210 disposed above the
semiconductor layer 208 and the substrate 202, a metal layer 212
disposed corresponding to the transparent conductive layer 210,
insulating layer 216 disposed between the metal layer 212 and the
transparent conductive layer 210, and the source/drain 218
electrically connected to the semiconductor layer 208. The
structure of the insulating layer 204 may be similar to the
insulating layer 104. A passivation layer 220 covering a gate
electrode 206, a semiconductor layer 208, a transparent conductive
layer 210, and a metal layer 212 of the DGTFT 200. In this
embodiment, the passivation layer 220 comprises insulating or
dielectric material, as the material of the insulating layer
discussed above.
[0044] As shown in FIG. 2A, the metal layer 212 covers the at least
one of boundaries 230 of the transparent conductive layer 210 via
the insulating layer 216 having an opening to form an opening
region 224. In one embodiment, the boundary represents the most
protruding point of the transparent conductive layer 210 in a
direction Y. Similarly, the metal layer 212 is disposed
corresponding to the transparent conductive layer 210. A part of
the transparent conductive layer 210 is exposed in the opening
region 224. Furthermore, the metal layer 212 extends in the opening
and is electrically connected to the first transparent conductive
layer 210. Specifically, the metal layer 212 extends along the
sidewall of the insulating layer 216 to electrically connect to the
transparent conductive layer 210.
[0045] As shown in FIG. 2A, the metal layer 212 extends in the
opening, at an angle 222 with respect to the first transparent
conductive layer 210. In one embodiment, the angle 222 is greater
than or equal to 85 degrees, and is less than or equal to 90
degrees. In other embodiments, the angle 222 is greater than or
equal to 45 degrees, and is less than or equal to 90 degrees, but
it is not limited thereto. In another embodiment, the angle 222
also could be less than or equal to 45 degrees.
[0046] With the structure and the angle 222 of this embodiment, the
incident light can be blocked except that around on-axis direction
which is perpendicular to the top surface of the transparent
conductive layer 210. Therefore, the DGTFT 200 may sense a clear
object image (or object data). For example, a angle range of the
incident light between +10 degrees and -10 degrees may be sensed
and collected by the DGTFT 200, as shown in FIG. 2A. The incident
light with 45 degrees or more may be blocked by the metal layer 212
of the DGTFT 200, as shown in FIG. 2B. The stray light from other
direction (off-axis direction) may not be sensed and collected by
the DGTFT 200.
[0047] FIGS. 2C and 2D illustrate an embodiment of DGTFT sensing an
object, in accordance with some embodiments of the present
disclosure. In order to detect more accurate object data or images,
the aspect ratio of the metal layer hole
2 t ( W 2 H + W 3 H ) + W 1 .ltoreq. d ##EQU00001##
of the DGTFT 200 should follow the formula below:
( W 2 H and W 3 H ) ##EQU00002##
In the above formula, d is the minimum width of the range that the
DGTFT 200 can sense along a direction Y, t is the thickness of the
passivation layer 220 along a direction Z, W1 is the maximum
opening width between the metal layer 212_1 and the metal layer
212_2 along the direction Y, W2 is the minimum opening width
between the metal layer 212_1 and the metal layer 212_2 along the
direction Y, W3 is (W1-W2)/2, and H along the direction Z is the
height from a top surface of the transparent conductive layer 210
to a top surface of the metal layer 212 along the direction Z, as
shown in FIG. 2C. Using the above formula, the aspect ratio of the
metal layer hole can be designed to sense the object 226.
[0048] For example, as shown in FIG. 2D, in cases where the DGTFT
200 senses the fingerprint pattern 228, the pitch p of the
fingerprint pattern 228 is around 400 um in average. In order to
sense a clear object image, it is better to focus on a quarter of
the pitch p (100 um) to be recognized. Assume that d is 100 um, W1
is 10 um, W2 is 5 um, and t is 10 um: It can be calculated that the
height H should be no less than 1.67 um. The size of the DGTFT 200
structure can be designed using the above formula. Furthermore, it
should be understood that, according to the above formula, if the
thickness t of the passivation layer 220 increases, more layer
stacks are necessary for the metal layer 212 to increase height
H.
[0049] FIG. 3 illustrates a cross-sectional view of an embodiment
of two adjacent DGTFTs in accordance with some embodiments of the
present disclosure. The DGTFT 300 is similar to the DGTFT 200. The
DGTFT 300 includes a substrate 302, an insulating layer 304, a gate
electrode 306, a semiconductor layer 308, a transparent conductive
layer 310, an insulating layer 316 with an opening, the first metal
layer 312, two source/drain 318. The first metal layer 312 extends
in the opening to form an opening region 324. A passivation layer
320 is disposed above the DGTFT 300, an opaque material layer 322
is disposed above the passivation layer 320 and does not cover the
opening region 324 in the top view of the DGTFT 300. Specifically,
the opaque material layer 322 also has an opening region at least
partially overlap the opening region 324. It should be noted that
the metal layer 312 is enlarged to extend beyond at least one of
the boundaries 330 of the semiconductor layer 308 along a direction
Y. In one embodiment, the structure of the insulating layer 304 may
be similar to the insulating layer 104.
[0050] The opaque material layer 322 is also called a black matrix
(BM). The opaque material layer 322 can comprise opaque material,
such as chromium (Cr), polyimide, or another suitable opaque
material. The opaque material layer 322 is separated from the metal
layer 312 by the passivation layer 320 to control (or restrict)
incident light angle. Specifically, the opaque material layer 322
is disposed not to cover the opening region 324 and the passivation
layer 320 is disposed between the opaque material layer 322 and the
metal layer 312 along a direction Z, so that the angle of the
incident light can be controlled.
[0051] Similarly, with the opening region of the opaque material
layer 322 and the opening regions 324, the incident light can be
blocked except that incomes around on-axis direction which is
perpendicular to the top surface of the transparent conductive
layer 310. The DGTFT 300 may sense a clear object image (or object
data). For example, an angle range of the incident light between
+10 degrees and -10 degrees may be sensed and collected by the
DGTFT 300, as shown in FIG. 3A.
[0052] As described above, in order to detect more accurate object
data or images, the aspect ratio of the metal layer hole of the
DGTFT should follow the formula. In this embodiment, the parameter
of passivation layer thickness (e.g., thickness t of the
passivation layer 320 in FIG. 3A) in the formula may be assumed to
be 0. Therefore, the DGTFT 300 should follow the formula below:
W4.ltoreq.d
Here, d is the minimum width of the range that the DGTFT 300 can
sense, and W4 is the maximum opening width of the opaque material
layer 322 along a direction Y. It should be understood that the
opening region of the opaque material layer 322 can control the
sensing width of the DGTFT 300 using the above formula.
[0053] In this embodiment, the metal layer 312 is enlarged, as
described above. This enlarged metal layer 312 may block incident
light coming from the neighboring opening region of the opaque
material layer 322. As shown in FIG. 3, the structure of the DGTFT
300' is the same as the structure of DGTFT 300, which is not
described in detail herein. The incident light comes from opening
region of the opaque material layer 322 of DGTFT 300' can be
blocked by the metal layer 312 and may not affect the DGTFT 300.
The smaller the gap 328 between the metal layer of DGTFT 300 and
300', the more effective the blocking is. Therefore, the DGTFT 300
may sense a clear object image (or object data) not affected by
unexpected light.
[0054] In some embodiments, a metal layer 326 is disposed
corresponding to the transparent conductive layer 310 and in the
insulating layer 316 and between the two adjacent DGTFTs 300 and
300', as shown in FIG. 3. In one embodiment, the DFTFT 300' is
adjacent to the DFTFT 300, which represents the DGTFT 300' is most
close to DGTFT 300 in a direction Y. The metal layer 326 is under
the gap 328 and between the metal layer 312_1 and the metal layer
312_2 of DGTFTs 300 and 300', so that the incident light passing
through the gap 328 can be blocked. Therefore, the DGTFT 300 may
sense a clear object image (or object data) not affected by
unexpected light. In some embodiments, the metal layer 326 and the
source/drain 318 have the same fabrication. In other words the
metal layer 326 and the source/drain 318 can be formed at the same
time.
[0055] FIG. 4A illustrates a cross-sectional view of an embodiment
of DGTFT in accordance with some embodiments of the present
disclosure. The DGTFT 400 is similar to the DGTFT 200. The DGTFT
400 includes a substrate 402, an insulating layer 404, a gate
electrode 406, a semiconductor layer 408, a transparent conductive
layer 410, a metal layer 412, an insulating layer 416, two
source/drain 418, and a passivation layer 420. In one embodiment,
the structure of the insulating layer 404 may be similar to the
insulating layer 104.
[0056] In this embodiment, like the DGTFT 200 in FIGS. 2A to 2D,
the first metal layer 412 extends in the opening of the insulating
layer 416, at an angle 422 with respect to the first transparent
conductive layer 410, as shown in FIG. 4A. However, the angle 422
is substantially equal to 90.degree.. In other words, there is a
precipitous taper angle between the metal layer 412 and the
transparent conductive layer 410. In such cases, the metal layer
412 can restrict unexpected light (e.g., stray light or off-axis
light) of the incident light entering the opening region 414, as
shown in FIG. 4A. Specifically, with the structure and the angle
422 (i.e., substantially 90.degree.) of this embodiment, the
incident light can be blocked except that incomes around on-axis
direction which is perpendicular to the top surface of the
transparent conductive layer 410. Therefore, the DGTFT 400 may
sense a clear object image (or object data). It should be noted
that the metal layer 412 in this embodiment controls the sensing
width of the DGTFT 400, so that an opaque material layer with an
opening region may be unnecessary. In some embodiments, a metal
layer 426 may also be disposed in the insulating layer 416 and
between the DGTFT 400 and the neighboring DGTFT, as shown in FIG.
4B. The incident light (unexpected light) passing through the gap
424 between the DGTFT 400 and the neighboring DGTFT can be
blocked.
[0057] In some embodiments, the thickness of the insulating layer
416 is large, so that the opening region 414 is deep. The deep
opening region 414 forms a deep contact hole (deep CH), as shown in
FIG. 4C. Thanks to this deep contact hole, the DGTFT 400 may be
able to sense a clear object image (or object data).
[0058] In other embodiments, the metal layer 412 comprises a low
reflectivity material having a reflectivity lower than 60% to
visible light. The low reflectivity material includes chromium
(Cr), gold (Au), nickel (Ni), or another suitable material with low
reflectivity. The unexpected light (e.g., stray light or off-axis
light) that irradiates the metal layer 412 may not seriously affect
the sensing of the DGTFT 400, as shown in FIG. 4D. The DGTFT 400
may sense a clear object image (or object data).
[0059] Similarly, in order to detect more accurate object data or
images, the aspect ratio of the metal layer hole
( W H ) ##EQU00003##
of the DGTFT 400 should follow the formula below:
2 t ( W H ) + W .ltoreq. d ##EQU00004##
In the above formula, d is the minimum width of the range that the
DGTFT 400 can sense, t is the thickness of the passivation layer
420 along a direction Z, W is the maximum opening width between the
metal layer 412_1 and the metal layer 412_2 along a direction Y,
and H is the height from a top surface of the transparent
conductive layer 410 to a top surface of the metal layer 412 along
the direction Z, as shown in FIG. 4A. The aspect ratio of the metal
layer hole can be designed using the above formula.
[0060] As shown in FIGS. 1A-4D, the transparent conductive layer
and the metal layer collectively form the top gate of the DGTFT.
However, in some embodiments, the transparent conductive layer and
the metal layer may be collectively formed as the bottom gate of
the DGTFT. Specifically, the gate electrode (i.e., original bottom
gate shown in FIGS. 1A-4D) can be disposed as the top gate of the
DGTFT and the transparent conductive layer and the metal layer
(i.e., original top gate shown in FIGS. 1A-4D) can be collectively
disposed as the bottom gate of the DGTFT.
[0061] FIG. 5 illustrates a cross-sectional view of an embodiment
of DGTFT with reversed structure relative to the embodiments in
FIGS. 1A to 4D, in accordance with some embodiments of the present
disclosure. The DGTFT 500 includes a substrate 502, an insulating
layer 504 disposed on an upper surface of the substrate 502, a
transparent conductive layer 510 disposed in the insulating layer
504 and above the substrate 502, a metal layer 512 disposed
corresponding to the transparent conductive layer 510, a
semiconductor layer 508 disposed in the insulating layer 504 and
above the transparent conductive layer 510, a gate electrode 506
disposed above the semiconductor layer 508, an insulating layer 516
disposed above the gate electrode 506, and two source/drain 518
electrically connected to the semiconductor layer 508. In one
embodiment, the structure of the insulating layer 504 may be
similar to the insulating layer 104.
[0062] As discussed above, in this embodiment, the transparent
conductive layer 510 and the metal layer 512 are collectively used
as a bottom gate of the DGTFT 500 and the gate electrode 506 is
used as the top gate of the DGTFT 500. Similarly, the metal layer
512 at least partially overlaps the transparent conductive layer
510 or the semiconductor layer 508 in top view of the substrate
502.
[0063] In this embodiment, the DGTFT 500 senses an object 520 by
the reflected light from the object 520. Specifically, the back
light may irradiate the object 520 and then be reflected back as
reflected light to the DGTFT 500. The metal layer 512 may also
protect the DGTFT 500 from stray light from another direction, as
per the embodiments discussed above. Furthermore, in such cases,
the substrate 502 should be thinner and comprised transparent and
insulating material for light to pass through, thereby avoiding
image blur. For example, the substrate 502 may comprises silicon
oxide (SiO.sub.x), silicon nitride (SiN.sub.x), glass or another
suitable material.
[0064] In one embodiment, a photo sensor device comprises two
DGTFTs in one pixel. One of the DGTFTs is a DGTFT having an opening
region in the above embodiments, and the other is a DGTFT
(reference transistor) without an opening region in the above
embodiments.
[0065] FIG. 6 illustrates an embodiment of a photo sensor device,
in accordance with some embodiments of the present disclosure. The
photo sensor device 600 includes a DGTFT 602, a DGTFT 604, and a
differential subtractor circuit 606. The DGTFT 602 includes a metal
layer 602-1, an opening region 602-2 and a transparent conductive
layer 602-3, as per the embodiments discussed above. The DGTFT 604
is adjacent to the DGTFT 602 and includes a metal layer 604-1 and a
transparent conductive layer 604-3. However, the DGTFT 602 is
different than the DGTFT 604, as there is not an opening region. In
other words, the metal layer 604-1 covers the transparent
conductive layer 604-3 (the metal layer 604-1 is above the
transparent conductive layer 604-3). As shown in FIG. 6, a
source/drain terminal of the DGTFT 602 and a source/drain terminal
of the DGTFT 604 are respectively electrically connected to two
input terminals of the differential subtractor circuit 606 through
or not through the voltage detector and buffer circuit. When the
photo sensor device 600 is irradiated by the light, the DGTFTs 602
and 604 each generates an output data via the source/drain
terminals to the voltage detector and buffer circuit. The voltage
detector and buffer circuit receives the output data and converts
it into another output data representing the voltage difference
(also called as drop amount of the voltage, which will be discussed
in below) between the output data and a reference voltage (VREF).
The voltage detector and buffer circuit also has another buffer
circuit for reducing the influence of the small input impedance on
later circuit or long output wiring.
[0066] The differential subtractor circuit 606 compares two output
data from the source/drain terminals of DGTFTs 602 and 604 (or from
the voltage detector and buffer circuit), and then outputs the
difference value of DGTFTs 602 and 604. The DGTFTs 602 and 604 are
fabricated using substantially the same process. Since the DGTFT
604 has no opening region, the light cannot be sensed by the DGTFT
604. Therefore, in this embodiment, the photo sensor device 600 can
remove a variation in the characteristics of DGTFT caused by
process fabrication and exogenous noise by comparing two output
data from their two DGTFT when the photo sensor device 600 senses
the light. Furthermore, it should be noted that the differential
subtractor circuit 606 can be any suitable differential subtractor
circuit. The differential subtractor circuit 606 shown in FIG. 6 is
exemplary, and is not intended to limit the disclosure. In some
embodiments, one of the reference transistors (DGTFT with no
opening region, such as DGTFT 604) is placed per the number of
normal transistors (DGTFT with an opening region, such as DGTFT
602) to increase the available area. It should be understood that
the area or shape of the opening region is exemplary, and is not
intended to limit the disclosure.
[0067] In one embodiment, a photo sensor device 700 comprises
multiple DGTFTs in one pixel. Those DGTFTs have opening regions, as
discussed above, however, the area of the opening region of those
DGTFTs are different. FIG. 7 illustrates an embodiment of a photo
sensor device, in accordance with some embodiments of the present
disclosure. The photo sensor device 700 includes a DGTFT 702, a
DGTFT 704, a DGTFT 706, and a comparator circuit 708. The DGTFTs
702, 704, and 706 have opening regions 702-2, 704-2, and 706-2,
respectively, as the embodiments of DGTFT discussed above.
Furthermore, the DGTFT 702, the DGTFT 704, and the DGTFT 706 are
adjacent to each other.
[0068] As shown in FIG. 7, the area of opening regions 702-2,
704-2, and 706-2 are different. The length L3 of opening region
706-2 is longer than the length L1 and L2 of the opening regions
702-1 and 704-1. The length L2 of opening region 704-2 is longer
than the length L1 of opening region 702-2. Specifically, in this
embodiment, the area of opening region 706-2 is the largest and the
area of opening region 702-2 is the smallest. The opening regions
of DGTFTs 702, 704, and 706 have different areas, DGTFTs 702, 704,
and 706 may be affected differently by the light, and therefore
output different data. It should be understood that the area or
shape of the opening region is exemplary, and is not intended to
limit the disclosure.
[0069] A source/drain terminal of the DGTFT 702, a source/drain
terminal of the DGTFT 704, and a source/drain terminal of the DGTFT
706 are respectively electrically connected to the input terminal
of the comparator circuit 708 through or not through the voltage
detector and buffer circuit. In this embodiment, the photo sensor
device 700 is irradiated by the light. Then, the comparator circuit
708 respectively compares each output data from DGTFTs 702, 704,
and 706 with predetermined amount of light and outputs binary data.
It is possible to receive the intensity of the photo sensor as
digital data by picking up which DGTFT outputs "1" (source/drain
outputs "high voltage level"). Therefore, the output combinations
of DGTFTs 702, 704, and 706 can be coded as 2-bit data
corresponding to the light sensed by the photo sensor device 700.
It should be noted that the comparator circuit 708 can be any
suitable comparator circuit.
[0070] For example, the following table shows output data of the
DGTFTs 702, 704, 706, and the corresponding 2-bit data when the
photo sensor device 700 senses four different intensities of light
(corresponding to different gray scale levels).
TABLE-US-00001 data coding for light (for example of 4 level
gray-scale) gray scale Output of Output of Output of 2-bit level of
light DGTFT 702 DGTFT 704 DGTFT 706 data 0 0 0 0 00 1 0 0 1 01 2 0
1 1 10 3 1 1 1 11
[0071] As shown in the table, there are four different output
combinations of DGTFTs 702, 704, and 706 corresponding to four gray
scale level of light. These output combinations can be coded as
2-bit data "00", "01", "10", and "11". Therefore, the gray scale
level of light, or the intensity of light, can be transferred as
digital data. In another embodiment, because the opening regions of
DGTFTs 702, 704, and 706 have different areas, therefore, when an
intensity of light is enlarged, and the four gray scale level of
light or the transferred digital data is increased. In some
embodiments, as illustrated in FIG. 7, each output data from DGTFT
with an opening region is coded by each A/D convertor to receive
finer bits of data than using only one DGTFT with an opening
region. The photo sensor device 700 comprises three DGTFTs 702,
704, and 706, however, it should be understood that, in some
embodiments, the photo sensor device can comprise multiple DGTFTs,
such as four DGTFTs or more.
[0072] The DGTFTs discussed above are used as the photo sensor
device. In some embodiments, the DGTFTs discussed above can be
combined with display devices, such as an organic light emitting
diode display device, a quantum light emitting diode display
device, a mini light emitting diode display device, a micro light
emitting diode display device, or a liquid crystal display device,
but it is not limited thereto. A plurality of DGTFTs are used as
photo sensor area in the display device to sense light or an object
(e.g., a fingerprint pattern). For example, the photo sensor area
can be used to sense fingerprint patterns. The structure and
fabrication process of the DGTFTs are the same as or similar to the
fabrication process of the TFTs in the display devices. Therefore,
the DGTFTs used for photo sensor area and the TFTs used for pixel
of the display can be formed at the same time.
[0073] FIGS. 8A and 8B illustrate a display device combined with
photo sensor devices, in accordance with some embodiments of the
present disclosure. The electronic device 800 includes an area 802,
an area 804, a gate driving circuit 806, a gate driving circuit
808, and an IC 810. The area 802 is used for display image and the
area 804 is used for sensing light or object (e.g., a fingerprint
pattern) or display image and sensing light or object at the same
time, but it is not limited thereto. A plurality of DGTFTs are
disposed in the area 804. The area 802 is separated from the area
804. In some embodiments, the gate driving circuit 806 is use to
control the area 802 and the gate driving circuit 808 is use to
control the area 804, as shown in FIG. 8A. In other embodiments,
the gate driving circuit 806 is used to not only control area 802,
but also to control one part of the area 804, and the gate driving
circuit 808 is used for to control the other part of the area 804
as shown in FIG. 8B.
[0074] As shown in FIGS. 8A and 8B, area 802 is separated from the
area 804. Specifically, the DGTFTs used for sensing are not
integrated into the display area. In some embodiments, the DGTFTs
are integrated into the display area. Therefore, the display area
can be used for display image or sensing light or object. The
DGTFTs used as photo sensors integrated into the TFTs of the
display device are discussed below.
[0075] FIG. 9 illustrates a DGTFT array integrated into the TFT
array of the display area in the LCD, in accordance with some
embodiments of the present disclosure. For convenience, FIG. 9
merely shows a portion of the full array. The array 900 includes
four TFTs 902, four capacitors 904, and four DGTFTs 906, arranged
in column n, n+1 and row n, n+1 of the full array. Each of the
DGTFTs 906 is adjacent to one of the TFTs 902 (or one TFT 902 is
adjacent to one of the DGTFTs 906). The top gate (e.g., the metal
layer 212) of the DGTFT 906 is electrically connected to line 908
(also called a top gate line), the bottom gate of the DGTFT 906 is
electrically connected to line 910 (also called a bottom gate
line), one source/drain terminal of the DGTFT 906 is electrically
connected to line 912 (also called a readout line), and another
source/drain terminal of the DGTFT 906 is electrically connected to
line 914 (also called a ground line). The DGTFTs 906 in the same
row are electrically connected to the same line 908, line 910, line
914, and the DGTFTs 906 in the same column are electrically
connected to the same line 912, as shown in FIG. 9. The gate of the
TFT 902 is electrically connected to line 916 (also called a gate
line), one source/drain terminal of the TFT 902 is electrically
connected to line 918 (also called a data line), and another
source/drain terminal of the TFT 902 is electrically connected to
line 920 (also called a common line) through one of the capacitors
904. The TFTs 902 in the same row are electrically connected to the
same line 916, line 920, and the TFTs 902 in the same column are
electrically connected to the same line 918, as shown in FIG. 9.
Using the arrangement in this embodiment, the array 900 can be used
as a display device and can sense light and objects (e.g., a
fingerprint pattern).
[0076] FIG. 10A illustrates a portion of the array in FIG. 9, in
accordance with some embodiments of the present disclosure. For
convenience, two TFTs 902, two capacitors 904, and two DGTFTs 906
arranged in column n and rows n, n+1. As shown in FIG. 10A, one
source/drain terminal of the DGTFT 906 is electrically connected to
a reference voltage VREF by the line 912 and the switch SW. The TFT
902 for LCD can be turned off by applying a gate OFF voltage (e.g.,
-10V) to the line 916. The line 912 is electrically connected to
the line 914 when an ON voltage (e.g., +5V) is applied to the top
gate of the DGTFT 906. The line 912 becomes floating when an OFF
voltage (e.g., -10V) is applied to the top gate of the DGTFT 906.
The line 912 is also electrically connected to the voltage detector
(or the voltage detector and a buffer circuit) via the voltage
measurement line. In this embodiment, an ON voltage (e.g., +15V) is
applied to the bottom gate of the DGTFT 906 when the DGTFT 906
senses the object (e.g., a fingerprint pattern).
[0077] FIG. 10B is a timing diagram of the photo sensing of the
array 900 in FIG. 10A. In order to prevent sensing errors by
scattering or retardation caused by various liquid-crystal (LC)
arrangements in the LCD, the display image could be changed to
white or black before the DGTFTs 906 sense the light or object. As
shown in FIG. 10B, in the period 1 (i.e., before the DGTFTs 906
start to sense the light or object), the line 916 in the row n is
switched to "high voltage level" and the line 918 is switched to
biased voltage level, so that the pixel in the row n is changed to
white (or black). The line 916 in the row n+1 is then switched to
"high voltage level" and the line 918 is switched to biased voltage
level, so that the pixel in the row n+1 is changed to white (or
black). Although only two rows (n, n+1) of array are shown in FIG.
10A, it should be understood that this operation can be repeatedly
applied to all rows of the full array in the LCD, so that all
pixels in the LCD are changed to white (or black).
[0078] In the period 2 (i.e., the DGTFTs 906 start to sense the
light or object), the line 908 in the row n is switched to "high
voltage level", so that the remaining charge in the DGTFT 906 in
the row n can be removed. The switch SW is then switched to "high
voltage level", so that the line 912 can be electrically connected
to the reference voltage VREF (i.e., the line 912 is switched to
"high voltage level"). Next, the line 910 in the row n is switched
to "high voltage level", thereby the DGTFT 906 in the row n can
sense the light or object. If the DGTFT 906 is irradiated by the
light (e.g., the reflected light) reflected from the object, the
threshold voltage (Vth) of the DGTFT 906 will be different. This
Vth difference causes a leakage from line 912 to the line 914 via
DGTFT 906 in the row n so that the voltage of line 912 drops due to
the leakage. For example, as shown in FIG. 10B, the voltage of the
line 912 may drop due to leakage of the DGTFT 906 in the row n.
Since the Vth difference is affected by the different bright levels
of the light, the leakage from the DGTFT 906 in the row n will also
be different. This causes different drop amount of the voltage of
line 912, as shown in FIG. 10B (solid line and dash line). The
bright level of the light from the object can be detected by the
DGTFT 906 in the row n. After the DGTFT 906 detection in the row n,
DGTFT 906 detection in the row n+1 starts, and repeating the
detection by each row in the same way. Therefore, the array 900 can
sense the light and the object.
[0079] FIG. 11 illustrates a DGTFT array integrated into the TFT
array of the display area in the LCD, in accordance with some
embodiments of the present disclosure. For convenience, FIG. 11
merely shows a portion of the full array. The array 1100 includes
four TFTs 1102, four capacitors 1104, and four DGTFTs 1106,
arranged in column n, n+1 and row n, n+1 of the full array. Each of
the DGTFTs 1106 is adjacent to one of the TFTs 1102. The top gate
(metal layer) of the DGTFT 1106 is electrically connected to line
1108 (also called a top gate line), the bottom gate of the DGTFT
1106 is electrically connected to line 1110 (also called a bottom
gate line), one source/drain terminal of the DGTFT 1106 is
electrically connected to line 1112, and another source/drain
terminal of the DGTFT 1106 is electrically connected to line 1114
(also called a common line). The DGTFTs 1106 in the same row are
electrically connected to the same line 1108, line 1110, line 1114,
and the DGTFTs 1106 in the same column are electrically connected
to the same line 1112, as shown in FIG. 11. The gate of the TFT
1102 is electrically connected to line 1108, one source/drain
terminal of the TFT 1102 is electrically connected to line 1112,
and another source/drain terminal of the TFT 1102 is electrically
connected to line 1114 by passing through one of the capacitors
1104. The TFTs 1102 in the same row are electrically connected to
the same line 1108, line 1114, and the TFTs 1102 in the same column
are electrically connected to the same line 1112, as shown in FIG.
11.
[0080] As shown in FIG. 11, the gate of the TFT 1102 and the top
gate of the DGTFT 1106 adjacent to the TFT 1102 in the same row are
electrically connected to the same line 1108. In other words, the
gate of the TFT 1102 connects to the top gate (e.g., the metal
layer 212) of the DGTFT 1106 adjacent to the TFT 1102. One
source/drain terminal of the TFT 1102 and one source/drain terminal
of the DGTFT 1106 adjacent to the TFT 1102 are electrically
connected to the same line 1112. In other words, one source/drain
terminal of the TFT 1102 is electrically connected to one
source/drain terminal of the DGTFT 1106 adjacent to the TFT 1102.
The line 1108 can be called a gate line (for TFT) or a top gate
line (for DGTFT). The line 1112 can be called a data line (for TFT)
or a readout line (for DGTFT). Using this arrangement, the array
1100 can be used as a display device and can sense light or objects
(e.g., a fingerprint pattern).
[0081] FIG. 12A illustrates a portion of the array in FIG. 11, in
accordance with some embodiments of the present disclosure. For
convenience, two TFTs 1102, two capacitors 1104, and two DGTFTs
1106 arranged in column n and rows n, n+1. As shown in FIG. 12A,
one source/drain terminal of the TFT 1102 and the DGTFT 1106 are
electrically connected to a reference voltage VREF or data voltage
of LCD by the line 1112 and the switch SW in the same row. The
voltage of the line 1114 is the same as the ground (GND). The DGTFT
1106 should be turned off (e.g., the voltage of the bottom gate of
the DGTFT 1106 is -10V) in the operating period of the TFT 1102, so
the line 1114 and the line 1112 are not electrically connected.
[0082] FIG. 12B is a timing diagram of the photo sensing of the
array 1100 in FIG. 12A. As shown in FIG. 12B, in the period 1
(i.e., before the DGTFTs 1106 start to sense the light or object),
the line 1108 in the row n is switched to "high voltage level" and
the line 1112 is switched to "biased voltage level", so that the
pixel in the row n is changed to white (or black). The line 1108 in
the row n+1 is then switched to "high voltage level" and the line
1112 is switched to "biased voltage level", so that the pixel in
the row n+1 is changed to white (or black). The line 1114 is
maintained in "low" (e.g., in GND). The line 1110 is maintained in
"low" to turn off the DGTFT 1106, such that the line 1114 does not
electrically connect to the line 1112 through the DGTFT 1106, as
discussed above. Although only two rows (n, n+1) of array are shown
in FIG. 12A, it should be understood that this operation can be
repeatedly applied to all rows of the full array in the LCD, so
that all pixels in the LCD are changed to white (or black).
[0083] In the period 2 (i.e., the DGTFTs 1106 start to sense the
light or object), the line 1108 in the row n is switched to "high
voltage level", so that the remaining charge in the DGTFT 1106 in
the row n can be removed. The switch SW is then switched to "high
voltage level", so that the line 1112 can be electrically connected
to the reference voltage VREF. Next, the line 1110 in the row n is
switched to "high voltage level", and thereby the DGTFT 1106 in the
row n can sense the light or object. If the DGTFT 1106 is
irradiated by the light (e.g., the reflected light) from the
object, the threshold voltage (Vth) of the DGTFT 1106 in the row n
will be different. This Vth difference causes a leakage from line
1112 to the line 1114 via DGTFT 1106 in the row n, so that the
voltage of line 1112 drops due to the leakage. For example, as
shown in FIG. 12B, the voltage of line 1112 may drop because of the
leakage from the DGTFT 1106 in the row n. Since the Vth difference
is affected by the different bright levels of the light, the
leakage of the DGTFT 1106 in the row n will also be different.
Then, this causes different drop amount of the voltage of line
1112, as shown in FIG. 12B (solid line and dash line). The bright
level of the light from the object can be detected by the DGTFT
1106 in the row n. After the DGTFT 1106 detection in the row n,
DGTFT 1106 detection in the row n+1 starts, and repeating the
detection by each row in the same way. Therefore, the array 1100
can sense the light and the object.
[0084] FIG. 13 illustrates a DGTFT array integrated into the array
of the display area in the LED, in accordance with some embodiments
of the present disclosure. For convenience, FIG. 13 merely shows a
portion of the full array. The array 1300 includes two display
cells 1302 and two DGTFTs 1306, arranged in column n and rows n,
n+1 of the full array. The display cell 1302 includes a TFT 1304.
Each of the DGTFTs 1306 is adjacent to one of the display cells
1302 (or one of the TFTs 1304). The top gate of the DGTFT 1306 is
electrically connected to line 1308 (also called a top gate line),
the bottom gate of the DGTFT 1306 is electrically connected to line
1310 (also called a bottom gate line), one source/drain terminal of
the DGTFT 1306 is electrically connected to line 1312 (also called
a readout line), and another source/drain terminal of the DGTFT
1306 is electrically connected to node 1314. The node 1314 is
electrically connected to ground (GND). The DGTFTs 1306 in the same
row are electrically connected to the same line 1308 and line 1310
(not shown), and the DGTFTs 1306 in the same column are
electrically connected to the same line 1312, as shown in FIG. 13.
The gate of the TFT 1304 is electrically connected to line 1316
(also called a gate line), one source/drain terminal of the TFT
1304 is electrically connected to line 1318 (also called a data
line), and another source/drain terminal of the TFT 1304 is coupled
to node 1320. The display cell 1302 in the same row are
electrically connected to the same line 1316 (not shown), and the
display cell 1302 in the same column is electrically connected to
the same line 1318, as shown in FIG. 13. Using the arrangement in
this embodiment, the array 1300 can be used as a display device and
can sense light and objects (e.g., a fingerprint pattern).
[0085] FIG. 14A illustrates the array in FIG. 13, in accordance
with some embodiments of the present disclosure. As shown in FIG.
14A, one source/drain terminal of the DGTFT 1306 is electrically
connected to a reference voltage VREF by the line 1312 and the
switch SW. The TFT 1304 for LED can be turned off by applying a
gate OFF voltage (e.g., -10V) to the line 1316. The line 1312 is
electrically connected to the node 1314 when an ON voltage (e.g.,
+5V) is applied to the top gate of the DGTFT 1306. The line 1312
becomes floating when an OFF voltage (e.g., -10V) is applied to the
top gate of the DGTFT 906. The line 1312 is also electrically
connected to the voltage detector (or the voltage detector and a
buffer circuit) via the voltage measurement line. In this
embodiment, an ON voltage (e.g., +15V) is applied to the bottom
gate of the DGTFT 1306 when the DGTFT 1306 senses the object (e.g.,
a fingerprint pattern).
[0086] FIG. 14B is a timing diagram of the photo sensing of the
array 1300 in FIG. 14A. In this embodiment, as shown in FIG. 14B,
in the period 1 (i.e., before the DGTFTs 1306 start to sense the
light or object), the line 1316 in the row n is switched to "high
voltage level" and the line 1318 is switched to "biased voltage
level", so that the pixel in the row n is changed to white. The
line 1316 in the row n+1 is then switched to "high voltage level"
and the line 1318 is switched to "biased voltage level", so that
the pixel in the row n+1 is changed to white. Although only two
rows (n, n+1) of array are shown in FIG. 14A, it should be
understood that this operation can be repeatedly applied to all
rows of the full array in the LED, so that all pixels in the LED
are changed to white.
[0087] In the period 2 (i.e., the DGTFTs 1306 start to sense the
light or object), the line 1308 in the row n is switched to "high
voltage level", so that the remaining charge in the DGTFT 1306 in
the row n can be removed. The switch SW is then switched to "high
voltage level", so that the line 1312 can be electrically connected
to the reference voltage VREF. Next, the line 1310 in the row n is
switched to "high voltage level", thereby the DGTFT 1306 in the row
n can sense the light or object. If the DGTFT 1306 is irradiated by
the light (e.g., the reflected light) from the object, the
threshold voltage (Vth) of the DGTFT 1306 will be different. This
Vth difference causes a leakage from line 1312 to the node 1314
(electrically connected to ground (GND)) via DGTFT 1306 in the row
n, so that the voltage of line 1312 drops due to the leakage. For
example, as shown in FIG. 14B, the voltage of the line 1312 may
drop due to leakage of the DGTFT 1306 in the row n. Since the Vth
difference is affected by the different bright levels of the light,
the leakage of the DGTFT 1306 in the row n will also be different.
Then, this causes different drop amount of the voltage of line
1312, as shown in FIG. 14B (solid line and dash line). The bright
level of the light from the object can be detected by the DGTFT
1306 in the row n. After the DGTFT 1306 detection in the row n,
DGTFT 1306 detection in the row n+1 starts, and repeating the
detection by each row in the same way. Therefore, the array 1300
can sense the light and the object.
[0088] FIG. 15 illustrates a DGTFT array integrated into the TFT
array of the display area in the LED, in accordance with some
embodiments of the present disclosure. For convenience, FIG. 15
merely shows a portion of the full array. The array 1500 includes a
display cell 1502 and a DGTFT 1506, arranged in column n and row n
of the full array. The display cell 1502 includes a TFT 1504. The
DGTFT 1506 is adjacent to one of the display cells 1502 (or one of
the TFTs 1504). The top gate of the DGTFT 1506 is electrically
connected to line 1508 (also called a top gate line), the bottom
gate of the DGTFT 1506 is electrically connected to line 1510 (also
called a bottom gate line), one source/drain terminal of the DGTFT
1506 is electrically connected to line 1512, and another
source/drain terminal of the DGTFT 1506 is electrically connected
to node 1514. The node 1514 is electrically connected to ground
(GND). The gate of the TFT 1504 is electrically connected to the
line 1508, one source/drain terminal of the TFT 1504 is
electrically connected to line 1512, and another source/drain
terminal of the TFT 1504 is coupled to node 1514 through the LED
device.
[0089] As shown in FIG. 15, the gate of the TFT 1504 and the top
gate of the DGTFT 1506 adjacent to the TFT 1504 are electrically
connected to the same line 1508. In other words, the gate of the
TFT 1504 connects to the top gate of the DGTFT 1506 adjacent to the
TFT 1504. One source/drain terminal of the TFT 1504 and one
source/drain terminal of the DGTFT 1506 adjacent to the TFT 1504
are electrically connected to the same line 1512. In other words,
one source/drain terminal of the TFT 1504 electrically connects to
one source/drain terminal of the DGTFT 1506 adjacent to the TFT
1504. The line 1508 can be called a gate line (for TFT) or a top
gate line (for DGTFT). The line 1512 can be called a data line (for
TFT) or a readout line (for DGTFT). Using this arrangement, the
array 1500 can be used as a display device and can sense light and
objects (e.g., a fingerprint pattern).
[0090] FIG. 16A illustrates a portion of the full array of the LED,
in accordance with some embodiments of the present disclosure. For
convenience, two display cells 1502, two TFT 1504, and two DGTFTs
1506 arranged in column n and row n, n+1. As shown in FIG. 16A, one
source/drain terminal of the TFT 1504 and the DGTFT 1506 are
electrically connected to a reference voltage VREF or data voltage
of LED by the line 1512 and the switch SW. The node 1514 is
electrically connected to ground (GND), as discussed above. The
DGTFT 1506 should be turned off (e.g., the voltage of the bottom
gate of the DGTFT 1506 is -10V) in the operating period of the TFT
1504, so the node 1514 and the line 1512 are not electrically
connected.
[0091] FIG. 16B is a timing diagram of the photo sensing of the
array 1500 in FIG. 16A. As shown in FIG. 16B, in the period 1
(i.e., before the DGTFTs 1506 start to sense the light or object),
the line 1508 in the row n is switched to "high voltage level" and
the line 1512 is switched to "biased voltage level", so that the
pixel in the row n is changed to white. The line 1508 in the row
n+1 is then switched to "high voltage level" and the line 1512 is
switched to "biased voltage level", so that the pixel in the row
n+1 is changed to white. The node 1514 is maintained in "low"
(e.g., in GND). The line 1510 is maintained in "low" to turn off
the DGTFT 1506, such that the line 1514 does not electrically
connect to the line 1512 through the DGTFT 1506, as discussed
above. Although only two rows (n, n+1) of array are shown in FIG.
16A, it should be understood that this operation can be repeatedly
applied to all rows of the full array in the LED, so that all
pixels in the LED are changed to white.
[0092] In the period 2 (i.e., the DGTFTs 1506 start to sense the
light or object), the line 1508 in the row n is switched to "high
voltage level", so that the remaining charge in the DGTFT 1506 in
the row n can be removed. The switch SW is then switched to "high
voltage level", so that the line 1512 can be electrically connected
to the reference voltage VREF. Next, the line 1510 in the row n is
switched to "high voltage level", thereby the DGTFT 1506 in the row
n can sense the light or object. If the DGTFT 1506 is irradiated by
the light (e.g., the reflected light) from the object, the
threshold voltage (Vth) of the DGTFT 1506 will be different. This
Vth difference causes a leakage from line 1512 to the node 1514
(electrically connected to ground (GND)) via DGTFT 1506 in the row
n, so that the voltage of line 1512 drops due to the leakage. For
example, as shown in FIG. 16B, the voltage of line 1512 may drop
due to leakage from the DGTFT 1506 in the row n. Since the Vth
difference is affected by the different bright levels of the light,
the leakage of the DGTFT 1506 in the row n will also be different.
Then, this causes different drop amount of the voltage of line
1512, as shown in FIG. 16B (solid line and dash line). The bright
level of the light from the object can be detected by the DGTFT
1506 in the row n. After the DGTFT 1506 detection in the row n,
DGTFT 1506 detection in the row n+1 starts, and repeating the
detection by each row in the same way. Therefore, the array 1500
can sense the light and the object.
[0093] It should be noted that the operation of the top gate and
bottom gate of the DGTFT (i.e. the voltage applied to the top gate
and bottom gate of the DGTFT) for sensing can be exchanged. In
other words, the bottom gate of the DGTFT can be switched to "high
voltage level" for removing the remaining charge in the DGTFT and
the top gate of the DGTFT can be switched to "high voltage level"
for the DGTFT to sense light or an object. Furthermore, the TFTs
and the DGTFTs in the embodiments of FIGS. 9-16 as discussed are
n-channel type. However, in other embodiments, it should be
understood that p-channel type TFTs and DGTFTs can be applied.
[0094] The terminology used herein is for the purpose of describing
particular embodiments only, and is not intended to be limiting of
the invention. As used herein, the singular forms "a", "an" and
"the" are intended to include the plural forms as well, unless the
context clearly indicates otherwise. Furthermore, to the extent
that the terms "including," "includes," "having," "has," "with," or
variants thereof, are used in either the detailed description
and/or the claims, such terms are intended to be inclusive in a
manner similar to the term "comprising."
[0095] Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art. Furthermore terms,
such as those defined in commonly used dictionaries, should be
interpreted as having a meaning that is consistent with their
meaning in the context of the relevant art, and will not be
interpreted in an idealized or overly formal sense unless expressly
so defined herein.
[0096] The foregoing outlines features of several embodiments so
that those skilled in the art may better understand the aspects of
the present disclosure. Those skilled in the art should appreciate
that they may readily use the present disclosure as a basis for
designing or modifying other processes and structures for carrying
out the same purposes and/or achieving the same advantages of the
embodiments introduced herein. Those skilled in the art should also
realize that such equivalent constructions do not depart from the
spirit and scope of the present disclosure, and that they may make
various changes, substitutions, and alterations herein without
departing from the spirit and scope of the present disclosure.
* * * * *