U.S. patent application number 10/939894 was filed with the patent office on 2006-03-16 for image sensor including multiple lenses and method of manufacture thereof.
This patent application is currently assigned to Taiwan Semiconductor Manufacturing Company, Ltd.. Invention is credited to Yean-Kuen Fang, Tzu-Hsuan Hsu, Dun-Nian Yaung.
Application Number | 20060057765 10/939894 |
Document ID | / |
Family ID | 36034570 |
Filed Date | 2006-03-16 |
United States Patent
Application |
20060057765 |
Kind Code |
A1 |
Hsu; Tzu-Hsuan ; et
al. |
March 16, 2006 |
Image sensor including multiple lenses and method of manufacture
thereof
Abstract
A device includes an image sensing element. The device also
includes a Silicon Dioxide (SiO.sub.2) layer, located over the
image sensing element, exhibiting a first index of refraction. The
device further includes a first lens, located over the SiO.sub.2
layer, exhibiting a second index of refraction greater than the
first index of refraction. The device still further includes a
color filter located over the first lens and a second lens located
over the color filter.
Inventors: |
Hsu; Tzu-Hsuan; (Kaohsiung
City, TW) ; Yaung; Dun-Nian; (Taipei City, TW)
; Fang; Yean-Kuen; (Tainan City, TW) |
Correspondence
Address: |
HAYNES AND BOONE, LLP
901 MAIN STREET, SUITE 3100
DALLAS
TX
75202
US
|
Assignee: |
Taiwan Semiconductor Manufacturing
Company, Ltd.
Hsin-Chu
TW
|
Family ID: |
36034570 |
Appl. No.: |
10/939894 |
Filed: |
September 13, 2004 |
Current U.S.
Class: |
438/70 ;
438/73 |
Current CPC
Class: |
H01L 27/14685 20130101;
H01L 27/14625 20130101; H01L 27/14621 20130101 |
Class at
Publication: |
438/070 ;
438/073 |
International
Class: |
H01L 21/00 20060101
H01L021/00 |
Claims
1. A method for manufacturing an image sensor, the method
comprising: forming an image sensing element; forming over the
image sensing element, a Silicon Dioxide (SiO.sub.2) layer
exhibiting a first index of refraction; forming over the SiO.sub.2
layer, a first lens exhibiting a second index of refraction greater
than the first index of refraction; forming a color filter over the
first lens; and forming a second lens over the color filter.
2. The method of claim 1, wherein the first lens includes Silicon
Nitride (SiN).
3. The method of claim 1, wherein the second index of refraction is
approximately 2.01.
4. The method of claim 1, wherein the first index of refraction is
approximately 1.46.
5. The method of claim 1, wherein the SiO.sub.2 layer is formed by
chemical vapor deposition ("CVD")
6. The method of claim 1, wherein the first lens is formed by
CVD.
7. The method of claim 1, wherein the SiO.sub.2 layer is
planarized.
8. The method of claim 7, wherein the SiO.sub.2 layer is planarized
by chemical-mechanical planarization ("CMP").
9. The method of claim 1, wherein the SiO.sub.2 layer is
wet-etched.
10. The method of claim 1, wherein the color filter includes a
resin.
11. The method of claim 1, wherein the color filter includes a
polymer.
12. A device comprising: an image sensing element; a Silicon
Dioxide (SiO.sub.2) layer, located over the image sensing element,
exhibiting a first index of refraction; a first lens, located over
the SiO.sub.2 layer, exhibiting a second index of refraction
greater than the first index of refraction; a color filter located
over the first lens; and a second lens located over the color
filter.
13. The device of claim 12, wherein the first lens includes Silicon
Nitride (SiN).
14. The device of claim 12, wherein the second index of refraction
is approximately 2.01.
15. The device of claim 12, wherein the first index of refraction
is approximately 1.46.
16. The device of claim 12, wherein the SiO.sub.2 layer is formed
by chemical vapor deposition ("CVD").
17. The device of claim 12, wherein the first lens is formed by
CVD.
18. The device of claim 12, wherein the SiO.sub.2 layer is
planarized.
19. The device of claim 18, wherein the SiO.sub.2 layer is
planarized by chemical-mechanical planarization ("CMP").
20. The device of claim 12, wherein the SiO.sub.2 layer is
wet-etched.
21. The device of claim 12, wherein the color filter includes a
resin.
22. The device of claim 12, and comprising: one or more
inter-metal-dielectric ("IMD") layers.
23. A device comprising: an image sensing element; a first convex
lens, located over the image sensing element; a color filter
located over the first convex lens; and a second convex lens
located over the color filter.
24. The device of claim 1 wherein the first convex lens comprises a
curved surface curving toward the image sensing element.
25. The device of claim 1 wherein the second convex lens comprises
a curved surface curving away from the first convex lens.
26. The device of claim 1 wherein the first and second convex
lenses each comprises a material selected from the group consisting
of silicon nitride and silicon oxynitride.
27. The device of claim 1 wherein the first and second convex
lenses each comprises an index of refraction greater than that of
surrounding materials.
Description
FIELD OF DISCLOSURE
[0001] The present disclosure relates generally to the field of
microelectronic devices and, more particularly, an image sensor
including multiple lenses and method of manufacture thereof.
BACKGROUND
[0002] Various digital imaging devices (e.g., digital cameras) use
image sensors, such as charge-coupled device ("CCD") imaging
sensors and complementary metal oxide semiconductor ("CMOS") image
sensors. Such image sensors include a two dimensional array of
photo-receptor devices (e.g., photodiodes), each of which is
capable of converting a portion of an image to an electronic signal
(e.g., representing a "pixel"). Some devices (e.g., a display
device) are capable of receiving one or more signals from multiple
photo-receptor devices of an image sensor and forming (e.g.,
reconstructing) a representation of the image.
[0003] A photo-receptor device stores a signal in response to
intensity or brightness of light associated with an image. Thus,
for an image sensor, sensitivity to light is important.
[0004] Accordingly, what is needed is an image sensor with improved
sensitivity to light.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] In the accompanying figures, in accordance with the standard
practice of the industry, various features are not drawn to scale.
In fact, dimensions of the various features may be shown to have
increased or reduced for clarity.
[0006] FIG. 1 is a block diagram of an image sensor according to
the illustrative embodiment.
[0007] FIGS. 2-4 are successive sectional views of a photo-receptor
device according to the illustrative embodiment.
DETAILED DESCRIPTION
[0008] The following discussion references various embodiments,
and/or examples for implementing different features of the various
embodiments. Also, specific examples of components and arrangements
are described for clarity, and are not intended to limit the scope
this disclosure. Moreover, the following discussions repeat
reference numerals and/or letters in the various examples, and such
repetitions are also for clarity and does not itself indicate a
relationship between the various embodiments and/or configurations
discussed. Still further, references indicating formation of a
first feature over or on a second feature include embodiments in
which the features are formed in direct contact, and also
embodiments in which one or more additional features are formed,
interposing the first and second features, such that the first
feature and the second feature are not in direct contact.
[0009] FIG. 1 is a block diagram of an image sensor 100 according
to the illustrative embodiment. In the illustrative embodiment, the
image sensor 100 is a charged coupled device ("CCD") image sensor.
However in other embodiments, the image sensor 100 is another type
of image sensor, such as a complementary metal oxide semiconductor
("CMOS") image sensor.
[0010] The image sensor 100 includes photo-receptor devices (e.g.,
photodiodes) 110. Each of the photo-receptor devices 110 is
substantially similar to one another. The photo-receptor devices
110 are organized according to a two dimensional array. As shown,
the array includes N columns and M rows. Accordingly, the quantity
of photo-receptor devices 110 included by the image sensor 100 is
represented by a number resulting from multiplying N by M.
Information (e.g., electronic signal) stored by each of the
photo-receptor devices 110 is capable of representing a "pixel" of
an image (e.g., an image displayed by a display device). Thus, the
number resulting from multiplying N by M is also capable of
representing a resolution (e.g., screen resolution) for such an
image.
[0011] FIG. 2 is a sectional view of a photo-receptor device (e.g.,
one of the photo-receptor devices 110), indicated generally at 200,
in an initial stage of manufacture according to the illustrative
embodiment. The photo-receptor device 200 includes a sensing
element 205 that reacts to light (e.g., a light beam). In one
embodiment, the sensing element 205 includes a pn-junction device
(e.g., a diode). The photo-receptor device 200 also includes at
least one dielectric layer 210, and one or more
inter-metal-dielectric ("IMD") layers 215. Moreover, the
photo-receptor device 200 includes a "top" (e.g., upper most) IMD
layer 220, which is one of the layers included by the IMD layers
215. Each of the IMD layers 215 includes a metal layer 225 as
shown. Also, each of the IMD layers 215 includes a dielectric
layer. For example, the IMD layer 220 includes a dielectric layer
230, which is a part of the IMD layer 220.
[0012] In the illustrative embodiment, the dielectric layer 230
includes SiO.sub.2. The dielectric layer 230 is formed by atomic
layer deposition ("ALD"), chemical vapor deposition ("CVD"), such
as plasma-enhanced CVD ("PECVD"), high density plasma CVD
("HDP-CVD"), and low pressure CVD ("LPCVD"), evaporation, or any
other suitable technique. Notably, with PECVD, tetraethoxysilane
("TEOS") is used to form the SiO.sub.2 dielectric layer 230.
[0013] After its formation, the dielectric layer 230 is planarized.
Examples of planarizing techniques include thermal flow,
sacrificial resist etch-back, spin-on glass, and
chemical-mechanical planarization ("CMP"). In particular, CMP is a
technique for planarizing various disparate types of materials,
such as dielectric and metal materials. CMP is capable of
selectively removing materials from a layer (e.g., a layer of a
wafer) by mechanical polishing that is assisted by one or more
chemical reactions.
[0014] In more detail, with conventional CMP, a wafer is mounted
with its face down on a carrier. The carrier is pressed against a
moving platen that includes a polishing surface (e.g., a polishing
pad). While the carrier is rotated about its axis, aqueous material
including abrasive elements is dripped onto the polishing pad so
that the centrifugal force formed by rotating the carrier
distributes the aqueous material on the polishing pad. Accordingly,
via a combination of mechanical polishing and chemical reaction,
CMP selectively removes a portion of a layer of the wafer.
[0015] FIG. 3 is a sectional view of the of the photo-receptor
device 200, in a subsequent stage of manufacture according to the
illustrative embodiment. At this stage, a curved recess 310 is
formed on the dielectric layer 230. The curved recess 310 is formed
by using conventional photo-lithography and etching techniques. In
one example, the curved recess is formed by patterning the
dielectric layer 230 with a sequence of processes that includes:
photo-resist patterning, wet etching, and photo-resist stripping.
Also, the photo-resist patterning includes: photo-resist coating,
"soft baking", mask alignment, pattern exposure, photo-resist
development, and "hard baking". Moreover, wet etching is isotropic
etching, and accordingly, suitable for forming the curved recess
310.
[0016] In more detail, in forming the curved recess 310, a
photo-resist layer 305 is formed over the dielectric layer 230 as
shown in FIG. 3. After forming the photo-resist layer 305, wet
etching is performed on the dielectric layer 230. Subsequently, the
photo-resist layer 305 is removed. Although in the illustrative
embodiment, the curved recess 310 is formed using
photo-lithography/wet-etching, in other embodiments, the curved
recess 310 is formed using one or more other suitable techniques
such as maskless lithography.
[0017] FIG. 4 is a sectional view of the of the photo-receptor
device 200, in a subsequent stage of manufacture according to the
illustrative embodiment. At this stage of manufacture, the
photo-receptor device 200 includes the dielectric layer 230, which
includes the curved recess 310. Over the dielectric layer 230 and
its curved recess 310, a lens 405 is formed. In the illustrative
embodiment, the lens 405 includes SiN, SiON, or any other suitable
material. Also, examples of techniques used to form the lens 405
include ion implantation of N, sputtering, ALD, and CVD such as
PECVD, LPCVD, and HDP-CVD. In one example, NH3 and HCD are used in
association with LPCVD to form the lens 405 that includes SiN. As
shown, the lens 405 is a convex lens.
[0018] The photo-receptor device 200 also includes a spacer 410,
which is formed over the lens 405. In the illustrative embodiment,
the spacer 410 includes SiO.sub.2, polymer or any other material
suitable for electrical insulation and planarization. Moreover, the
photo-receptor device 200 includes a color filter layer 415 formed
over the spacer 410. In the illustrative embodiment, the color
filter layer 415 includes a resin, such as a pigment-dispersed
resin or polymer. A spacer 420, which is substantially similar to
the spacer 410, is formed over the color filter layer 415 as shown
in FIG. 4.
[0019] In addition to the lens 405, the photo-receptor device 200
includes a lens 425. The lens 425 is substantially similar to the
lens 405. Accordingly, techniques used to form the lens 425 are
substantially similar to the techniques used for forming the lens
405 as discussed above. Materials used to form lens 425 include a
resin, such as a pigment-dispersed resin or polymer. The various
layers between the lens 425 and the sensing element 205 are
sufficiently transparent to pass light from lens 425 to the sensing
element 205.
[0020] As discussed above, the photo-receptor device 200 is capable
of forming (e.g., converting) a portion of an image as an
electronic signal. The photo-receptor device 200 forms such
electronic signal in response to light (e.g., a light beam), from
an optical image, that is received through the lenses 405 and 425,
the color filter layer 415, and the IMD layers 215.
[0021] A light beam passing from one type of medium (e.g., the lens
405) to another medium (e.g., the dielectric layer 230) is
typically affected by refraction. An example of refraction can be
observed when a light beam passes from air to water. An amount of
refraction for a specified medium is characterized by its index of
refraction. In one example, index of refraction is characterized by
the following mathematical expression. n=c/v.sub.phase
[0022] In the above expression, c is the speed of light and
v.sub.phase is the phase velocity.
[0023] As discussed above, for the photo-receptor device 200, light
sensitivity of the image sensing element 205 is important. It has
been observed that, in general, light sensitivity can be improved
by receiving light from a large pixel area and focusing the light
on a small image sensing element. For improving the light
sensitivity of the image sensing element 205, the photo-receptor
device 200 includes the lenses 405 and 425 as discussed above. Also
for improving the light sensitivity of the image sensing element
205, an index of refraction for the lens 405 is greater than an
index of refraction for the dielectric layer 230.
[0024] For example, in one version of the illustrative embodiment,
the lens 405 includes SiN and the dielectric layer 230 includes
SiO.sub.2. According to one measured value, an index of refraction
for SiN is approximately 2.01 and an index of refraction for
SiO.sub.2 is 1.46. Thus, the index of refraction for the lens 405
(2.01) is greater than the index of refraction for the dielectric
layer 230 (1.46).
[0025] Although illustrative and alternative embodiments have been
shown and described, a wide range of modification, change, and
substitution is contemplated in the foregoing disclosure and, in
some instances, some features of the embodiments may be employed
without a corresponding use of other features. Accordingly, broad
constructions of the appended claims in manners consistent with the
scope of the embodiments disclosed are appropriate.
* * * * *