U.S. patent application number 15/362402 was filed with the patent office on 2018-05-31 for through-semiconductor and through-dielectric isolation structure.
The applicant listed for this patent is OMNIVISION TECHNOLOGIES, INC.. Invention is credited to Gang Chen, Chih-Wei Hsiung, Duli Mao, Dyson H. Tai, Vincent Venezia.
Application Number | 20180151609 15/362402 |
Document ID | / |
Family ID | 62165938 |
Filed Date | 2018-05-31 |
United States Patent
Application |
20180151609 |
Kind Code |
A1 |
Tai; Dyson H. ; et
al. |
May 31, 2018 |
THROUGH-SEMICONDUCTOR AND THROUGH-DIELECTRIC ISOLATION
STRUCTURE
Abstract
An image sensor includes a semiconductor material including a
photodiode disposed in the semiconductor material and an insulating
material. A surface of the semiconductor material is disposed
between the insulating material and the photodiode. The image
sensor also includes isolation structures disposed in the
semiconductor material and in the insulating material, and the
isolation structures extend from within the semiconductor material
through the surface and into the insulating material. The isolation
structures include a core material and a liner material. The liner
material is disposed between the core material and the
semiconductor material, and is also disposed between the insulating
material and the core material.
Inventors: |
Tai; Dyson H.; (San Jose,
CA) ; Mao; Duli; (Sunnyvale, CA) ; Venezia;
Vincent; (Los Gatos, CA) ; Chen; Gang; (San
Jose, CA) ; Hsiung; Chih-Wei; (San Jose, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
OMNIVISION TECHNOLOGIES, INC. |
Santa Clara |
CA |
US |
|
|
Family ID: |
62165938 |
Appl. No.: |
15/362402 |
Filed: |
November 28, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 27/1464 20130101;
H04N 5/378 20130101; H01L 27/14636 20130101; H01L 27/1463 20130101;
H01L 27/14643 20130101 |
International
Class: |
H01L 27/146 20060101
H01L027/146; H04N 5/378 20060101 H04N005/378 |
Claims
1. An image sensor, comprising: a semiconductor material including
a photodiode disposed in the semiconductor material; an insulating
material, wherein a surface of the semiconductor material is
disposed between the insulating material and the photodiode; and
isolation structures disposed in the semiconductor material and in
the insulating material, wherein the isolation structures extend
from within the semiconductor material through the surface and into
the insulating material, and wherein the isolation structures
include: a core material; and a liner material disposed between the
core material and the semiconductor material, and disposed between
the insulating material and the core material.
2. The image sensor of claim 1, wherein individual isolation
structures are disposed on opposite sides of the photodiode, and
wherein the liner material includes a dielectric material, and the
core material includes a conductive material.
3. The image sensor of claim 2, wherein the liner material includes
a high-k oxide and the core material includes at least one of a
semiconductor or a metal.
4. The image sensor of claim 1, wherein the surface is a frontside
of the semiconductor material, and wherein image light enters the
frontside of the semiconductor material and is absorbed by the
photodiode.
5. The image sensor of claim 4, wherein the isolation structures
are at least in part vertically coextensive with the photodiode to
reflect the image light that is oblique to the frontside into the
photodiode.
6. The image sensor of claim 1, wherein the surface is a backside
of the semiconductor material opposite a frontside, and wherein
image light enters the backside of the semiconductor material and
is absorbed by the photodiode.
7. The image sensor of claim 6, further comprising metal caps,
wherein the isolation structures are vertically disposed between
the metal caps and the semiconductor material.
8. The image sensor of claim 6, further comprising: a second
insulating material disposed proximate to the frontside of the
semiconductor material, wherein the semiconductor material is
disposed between the insulating material and the second insulating
material; and second isolation structures disposed in the
semiconductor material and the second insulating material, wherein
the second isolation structures extend from within the
semiconductor material into the second insulating material.
9. The image sensor of claim 8, wherein the second isolation
structures are vertically coextensive with a portion of the
photodiode, wherein the portion of the photodiode has a smaller
lateral cross sectional area than a bulk of the photodiode.
10. The image sensor of claim 8, wherein metal interconnects are
disposed in the second insulating material, and wherein the metal
interconnects are coupled to a transfer gate disposed proximate to
the semiconductor material to extract image charge from the
photodiode.
11. The image sensor of claim 8, wherein a first lateral distance
between the second isolation structures is smaller than a second
lateral distance between the isolation structures.
12. The image sensor of claim 1, wherein the isolation structures
are entirely contained within the semiconductor material and the
insulating material.
13. An imaging system comprising: a plurality of photodiodes
disposed in a semiconductor material, wherein individual
photodiodes in the plurality of photodiodes are separated by
isolation structures, and wherein individual isolation structures
are disposed between individual photodiodes; an insulating material
disposed proximate to the semiconductor material, wherein a surface
of the semiconductor material is disposed between the insulating
material and the plurality of photodiodes, and wherein the
isolation structures extend from within the semiconductor material
into the insulating material through the surface of the
semiconductor material, and wherein the isolation structures
include a core material and a liner material disposed between the
core material and the semiconductor material, and disposed between
the insulating material and the core material; control circuitry
electrically coupled to control operation of the plurality of
photodiodes; and readout circuitry to extract image charge from the
plurality of photodiodes.
14. The imaging system of claim 13, wherein the surface is a
frontside of the semiconductor material, and wherein image light
enters the plurality of photodiodes from the frontside of the
semiconductor material, and wherein metal interconnects included in
the control circuitry and readout circuitry are disposed proximate
to the frontside.
15. An imaging system comprising: a plurality of photodiodes
disposed in a semiconductor material, wherein individual
photodiodes in the plurality of photodiodes are separated by
isolation structures, and wherein individual isolation structures
are disposed between individual photodiodes; an insulating material
disposed proximate to the semiconductor material, wherein a surface
of the semiconductor material is disposed between the insulating
material and the plurality of photodiodes, and wherein the
isolation structures extend from within the semiconductor material
into the insulating material through the surface of the
semiconductor material; metal caps disposed in the insulating
material and optically aligned with the isolation structures;
control circuitry electrically coupled to control operation of the
plurality of photodiodes; and readout circuitry to extract image
charge from the plurality of photodiodes, wherein the surface is a
backside of the semiconductor material, and wherein image light
enters the plurality of photodiodes from the backside of the
semiconductor material, and wherein metal interconnects included in
the control circuitry and readout circuitry are disposed proximate
to a frontside opposite the backside.
16. (canceled)
17. The imaging system of claim 15, further comprising second
isolation structures disposed in the semiconductor material and in
a second insulating material disposed proximate to the frontside,
wherein the second isolation structures extend from within the
second insulating material into the semiconductor material.
18. The imaging system of claim 17, wherein both the isolation
structures and the second isolation structures are at least in part
vertically coextensive with the individual photodiodes in the
semiconductor material.
19. The imaging system of claim 17, wherein the second isolation
structures are separated from each other in the semiconductor
material by a smaller lateral distance than the isolation
structures.
20. (canceled)
Description
TECHNICAL FIELD
[0001] This disclosure relates generally to semiconductor
fabrication, and in particular but not exclusively, relates to
isolation trench fabrication.
BACKGROUND INFORMATION
[0002] Image sensors have become ubiquitous. They are widely used
in digital still cameras, cellular phones, security cameras, as
well as, medical, automobile, and other applications. The
technology used to manufacture image sensors has continued to
advance at a great pace. For example, the demands of higher
resolution and lower power consumption have encouraged the further
miniaturization and integration of these devices.
[0003] The typical image sensor operates as follows. Image light
from an external scene is incident on the image sensor. The image
sensor includes a plurality of photosensitive elements such that
each photosensitive element absorbs a portion of incident image
light. Photosensitive elements included in the image sensor, such
as photodiodes, each generate image charge upon absorption of the
image light. The amount of image charge generated is proportional
to the intensity of the image light. The generated image charge may
be used to produce an image representing the external scene.
[0004] The miniaturization of image sensors may result in a
decreased distance between neighboring photosensitive elements. As
the distance between photosensitive elements decreases, the
likelihood and magnitude of both electrical and optical crosstalk
between photosensitive elements may increase.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] Non-limiting and non-exhaustive examples of the invention
are described with reference to the following figures, wherein like
reference numerals refer to like parts throughout the various views
unless otherwise specified.
[0006] FIG. 1A is a cross sectional illustration of an example
frontside illuminated image sensor with isolation structures, in
accordance with the teachings of the present invention.
[0007] FIG. 1B is a cross sectional illustration of an example
backside illuminated image sensor with isolation structures, in
accordance with the teachings of the present invention.
[0008] FIG. 1C is a cross sectional illustration of an example
backside illuminated image sensor with isolation structures, in
accordance with the teachings of the present invention.
[0009] FIG. 2 is a block diagram illustrating one example of an
imaging system which may include the image sensor of FIGS. 1A-1C,
in accordance with the teachings of the present invention.
[0010] FIG. 3 illustrates an example method of image sensor
fabrication, in accordance with the teachings of the present
invention.
[0011] Corresponding reference characters indicate corresponding
components throughout the several views of the drawings. Skilled
artisans will appreciate that elements in the figures are
illustrated for simplicity and clarity and have not necessarily
been drawn to scale. For example, the dimensions of some of the
elements in the figures may be exaggerated relative to other
elements to help to improve understanding of various embodiments of
the present invention. Also, common but well-understood elements
that are useful or necessary in a commercially feasible embodiment
are often not depicted in order to facilitate a less obstructed
view of these various embodiments of the present invention.
DETAILED DESCRIPTION
[0012] Examples of an apparatus and method for
through-semiconductor and through-dielectric isolation structures
are described herein. In the following description, numerous
specific details are set forth to provide a thorough understanding
of the examples. One skilled in the relevant art will recognize,
however, that the techniques described herein can be practiced
without one or more of the specific details, or with other methods,
components, materials, etc. In other instances, well-known
structures, materials, or operations are not shown or described in
detail to avoid obscuring certain aspects.
[0013] Reference throughout this specification to "one example" or
"one embodiment" means that a particular feature, structure, or
characteristic described in connection with the example is included
in at least one example of the present invention. Thus, the
appearances of the phrases "in one example" or "in one embodiment"
in various places throughout this specification are not necessarily
all referring to the same example. Furthermore, the particular
features, structures, or characteristics may be combined in any
suitable manner in one or more examples.
[0014] Throughout this specification, several terms of art are
used. These terms are to take on their ordinary meaning in the art
from which they come, unless specifically defined herein or the
context of their use would clearly suggest otherwise. It should be
noted that element names and symbols may be used interchangeably
through this document (e.g., Si vs. silicon); however, both have
identical meaning.
[0015] FIG. 1A is a cross sectional illustration of an example
frontside illuminated image sensor 100A with isolation structures.
Image sensor 100A includes semiconductor material 101, photodiode
103, insulating material 111, isolation structures (including core
material 105 and liner material 107), transfer gate 121, contact
113, electrical interconnects 115, frontside 151, and backside
153.
[0016] Photodiode 103 is disposed in semiconductor material 101.
Insulating material 111 is disposed proximate to semiconductor
material 101 such that a surface of semiconductor material 101 is
disposed between insulating material 111 and photodiode 103.
Isolation structures are disposed in semiconductor material 101 and
in insulating material 111. Isolation structures extend from within
semiconductor material 101 into insulating material 111 and, as
stated, isolation structures include core material 105 and liner
material 107. Liner material 107 is disposed between core material
105 and semiconductor material 101, and is also disposed between
insulating material 111 and core material 105. In the depicted
example, individual isolation structures are disposed on opposite
sides of photodiode 103, and liner material 107 includes a
dielectric material (e.g., high-k oxide or the like), and core
material 105 includes a conductive material (e.g., a semiconductor,
metal, or the like). As illustrated, insulating material 111 is
disposed on the frontside 151 of semiconductor material 101, and
image light enters the frontside 151 of semiconductor material 101
and is absorbed by photodiode 103.
[0017] In the depicted example, isolation structures are at least
in part vertically coextensive with photodiode 103 to reflect the
image light that is oblique to the frontside 151 surface of image
sensor 100A into photodiode 103. The isolation structures may
extend from a surface of the semiconductor material 101 to be
coextensive with part of photodiode 103, but may not extend all the
way through semiconductor material 101. The location of the
isolation structures may help to prevent optical cross talk.
Moreover, since liner material 107 includes a dielectric, and the
isolation structures extend through the interface of semiconductor
material 101 and insulating material 111, the isolation structures
may be used to prevent electrical crosstalk. In examples where
liner material 107 includes a negatively charged material such as a
high-k oxide, liner material 107 may pin surface charges by
accumulating positive charge in semiconductor material 101,
preventing the charges from flowing between neighboring photodiodes
103, in accordance with the teachings of the present disclosure. In
one example, microlenses/color filters may be placed on top of
insulating material 111 and between the incident light and
photodiodes 103.
[0018] FIG. 1B is a cross sectional illustration of an example
backside illuminated image sensor 100B with isolation structures.
Image sensor 100B is similar to image sensor 100A in many respects.
However, as shown in the illustrated example, insulating material
141 is disposed on the backside 153 (opposite frontside 151) of
semiconductor material 101, and image light enters the backside 153
of semiconductor material 101 and is absorbed by photodiode 103.
One skilled in the art will appreciate that a frontside of an image
sensor is defined by the side of the sensor including circuitry
(e.g., metal interconnects), and the backside is the side without
the circuitry--or at least the side with less circuitry.
[0019] Another difference is that image sensor 100B further
includes metal caps 133, such that isolation structures are
vertically disposed between metal caps 133 and the semiconductor
material 101. In other words, in a vertical direction (relative to
the figure orientation) core material 105 is disposed between metal
caps 133 and semiconductor material 101. However, in some examples,
metal caps 133 may not be included in image sensor 100B and may
simply be replaced with insulating material 141. In the depicted
example, insulating materials 111 and 141 may be the same or
different materials (e.g., oxides, nitrides, or the like).
[0020] As illustrated, electrical interconnects 115 may be
electrically coupled to transfer gate 121 which may be disposed
proximate to shallow trench isolation structure 131 in the
semiconductor material 101. Shallow trench isolation structures 131
may be used to reduce electrical crosstalk between photodiodes 103
or other pieces of circuitry disposed on the frontside 151 of the
device.
[0021] FIG. 1C is a cross sectional illustration of an example
backside illuminated image sensor 100C with isolation structures.
Image sensor 100C is similar in many respects to image sensor 100B
of FIG. 1B; however, second isolation structures are disposed in
semiconductor material 101 and in second insulating material 111,
and the second isolation structures extend from within
semiconductor material 101, through the frontside 151 of
semiconductor material 101, and into second insulating material
111. The second isolation structures may be used to electrically
isolate photodiode 103 on the frontside 151 of image sensor 100C by
pinning surface charges proximate to the frontside 151. In some
examples, insulating materials 111 and 141 may have the same or
different chemical compositions.
[0022] In the depicted example, the second isolation structures are
vertically coextensive with a portion of photodiode 103, and the
portion of photodiode 103 proximate to the second isolation
structures has a smaller lateral cross sectional area than the bulk
of photodiode 103. In other words, photodiode 103 has a large
portion and a small portion, and the second isolation structures
are disposed proximate to recesses which define the small portion.
In the illustrated example, the isolation structures are disposed
at least in part in the recessed regions in photodiode 103.
Moreover, in the illustrated example, the lateral distance between
the second isolation structures is smaller than the lateral
distance between the isolation structures. Thus the two sets of
isolation structures may not be vertically aligned. However, one
skilled in the art will appreciate that in other examples, the
lateral distance between the second isolation structures may be
greater than, or the same as, the lateral distance between the
isolation structures. Also shown is that second isolation
structures are entirely contained within semiconductor material 101
and insulating material 111. In other words, second isolation
structures are entirely encapsulated between the two
materials/layers.
[0023] As in FIGS. 1A & 1B metal interconnects are disposed in
insulating material 111, and electrical interconnects 115 are
coupled (with contact 113, possibly including tungsten) to a
transfer gate 121 disposed proximate to semiconductor material 101
to extract image charge from photodiode 103. Transfer gate 121 may
be directly or indirectly coupled to a floating diffusion to output
the image charge to readout circuitry.
[0024] FIG. 2 is a block diagram illustrating one example of an
imaging system which may include the image sensor of FIGS. 1A-1C.
Imaging system 200 includes pixel array 205, control circuitry 221,
readout circuitry 211, and function logic 215. In one example,
pixel array 205 is a two-dimensional (2D) array of photodiodes, or
image sensor pixels (e.g., pixels P1, P2 . . . , Pn). As
illustrated, photodiodes are arranged into rows (e.g., rows R1 to
Ry) and columns (e.g., column C1 to Cx) to acquire image data of a
person, place, object, etc., which can then be used to render a 2D
image of the person, place, object, etc. However, photodiodes do
not have to be arranged into rows and columns and may take other
configurations.
[0025] In one example, after each image sensor photodiode/pixel in
pixel array 205 has acquired its image data or image charge, the
image data is readout by readout circuitry 211 and then transferred
to function logic 215. In various examples, readout circuitry 211
may include amplification circuitry, analog-to-digital (ADC)
conversion circuitry, or otherwise. Function logic 215 may simply
store the image data or even manipulate the image data by applying
post image effects (e.g., crop, rotate, remove red eye, adjust
brightness, adjust contrast, or otherwise). In one example, readout
circuitry 211 may readout a row of image data at a time along
readout column lines (illustrated) or may readout the image data
using a variety of other techniques (not illustrated), such as a
serial readout or a full parallel readout of all pixels
simultaneously.
[0026] In one example, control circuitry 221 is coupled to pixel
array 205 to control operation of the plurality of photodiodes in
pixel array 205. For example, control circuitry 221 may generate a
shutter signal for controlling image acquisition. In the depicted
example, the shutter signal is a global shutter signal for
simultaneously enabling all pixels within pixel array 205 to
simultaneously capture their respective image data during a single
acquisition window. In another example, image acquisition is
synchronized with lighting effects such as a flash.
[0027] In one example, imaging system 200 may be included in a
digital camera, cell phone, laptop computer, automobile or the
like. Additionally, imaging system 200 may be coupled to other
pieces of hardware such as a processor (general purpose or
otherwise), memory elements, output (USB port, wireless
transmitter, HDMI port, etc.), lighting/flash, electrical input
(keyboard, touch display, track pad, mouse, microphone, etc.),
and/or display. Other pieces of hardware may deliver instructions
to imaging system 200, extract image data from imaging system 200,
or manipulate image data supplied by imaging system 200.
[0028] FIG. 3 illustrates an example method 300 of image sensor
fabrication. The order in which some or all process blocks appear
in method 300 should not be deemed limiting. Rather, one of
ordinary skill in the art having the benefit of the present
disclosure will understand that some of method 300 may be executed
in a variety of orders not illustrated, or even in parallel.
Furthermore, method 300 may omit certain process blocks in order to
avoid obscuring certain aspects. Alternatively, method 300 may
include additional process blocks that may not be necessary in some
embodiments/examples of the disclosure.
[0029] Process block 301 describes providing a semiconductor
material with photodiodes. In some examples the semiconductor
material may include a silicon wafer with photodiodes disposed in
an array within the wafer.
[0030] Process block 303 shows depositing an insulating material on
the surface of the semiconductor material. In some examples there
may be intervening layers between the insulating material and the
surface of the semiconductor material (such as transfer gates, to
extract charge from the plurality of photodiodes in the
semiconductor material). As depicted in FIGS. 1A-1C, the surface
that the insulating material is deposited on may be the frontside
surface and/or the backside surface of the semiconductor material
depending on if the image sensor is a frontside or backside
illuminated image sensor.
[0031] Process block 305 illustrates etching trenches in the
insulating layer and semiconductor layer; as illustrated in FIGS.
1A-1C trenches may continuously extend from within the
semiconductor material to within the insulating material. Etching
may include using either a wet or dry etch depending on the
processing conditions needed to fabricate the isolation
structures.
[0032] Process block 307 describes depositing the liner material in
the trenches. In some examples, the liner material may be a
negatively charged high-k oxide which may induce a positive charge
in the surrounding semiconductor material. This may pin charged
surface states and mitigate migration of charge between neighboring
photodiodes. For example, the liner material (and the dielectric
material) may include oxides/nitrides such as silicon oxide
(SiO.sub.2), hafnium oxide (HfO.sub.2), silicon nitride
(Si.sub.3N.sub.4), silicon oxynitirde (SiO.sub.xN.sub.y), tantalum
oxide (Ta.sub.2O.sub.5), titanium oxide (TiO.sub.2), zirconium
oxide (ZrO.sub.2), aluminum oxide (Al.sub.2O.sub.3), lanthanum
oxide (La.sub.2O.sub.3), praseodymium oxide (Pr.sub.2O.sub.3),
cerium oxide (CeO.sub.2), neodymium oxide (Nd.sub.2O.sub.3),
promethium oxide (Pm.sub.2O.sub.3), samarium oxide
(Sm.sub.2O.sub.3), europium oxide (Eu.sub.2O.sub.3), gadolinium
oxide (Gd.sub.2O.sub.3), terbium oxide (Tb.sub.2O.sub.3),
dysprosium oxide (Dy.sub.2O.sub.3), holmium oxide
(Ho.sub.2O.sub.3), erbium oxide (Er.sub.2O.sub.3), thulium oxide
(Tm.sub.2O.sub.3), ytterbium oxide (Yb.sub.2O.sub.3), lutetium
oxide (Lu.sub.2O.sub.3), yttrium oxide (Y.sub.2O.sub.3), or the
like. Additionally, one skilled in the relevant art, will recognize
that any stoichiometric combination of the above
metals/semiconductors and their oxides/nitrides/oxynitrides may be
used, in accordance with the teachings of the present
disclosure.
[0033] Process block 309 shows depositing the core material. In
some examples, the core material is conductive such as a
semiconductor material (which may or may not be doped) or a metal
such as tungsten, aluminum, copper or the like. In examples where
the core is reflective, the core material may reflect light
incident on the image sensor and oblique to the illuminated
surface, so that the light reflects into the proper photodiode.
Thus the isolation structures may drastically reduce both optical
and electrical crosstalk with a single piece of device
architecture.
[0034] Although not depicted, after the core material is deposited,
the trenches may be backfilled with insulating material or may be
capped with metal caps depending on the specific geometry desired.
Thus in some examples, the isolation structures are entirely
encapsulated within the insulating material and semiconductor
material with either the insulating material or the metal cap
entirely enclosing the structures within the dielectric material
and the semiconductor material.
[0035] The above description of illustrated examples of the
invention, including what is described in the Abstract, is not
intended to be exhaustive or to limit the invention to the precise
forms disclosed. While specific examples of the invention are
described herein for illustrative purposes, various modifications
are possible within the scope of the invention, as those skilled in
the relevant art will recognize.
[0036] These modifications can be made to the invention in light of
the above detailed description. The terms used in the following
claims should not be construed to limit the invention to the
specific examples disclosed in the specification. Rather, the scope
of the invention is to be determined entirely by the following
claims, which are to be construed in accordance with established
doctrines of claim interpretation.
* * * * *