U.S. patent application number 10/818631 was filed with the patent office on 2004-12-02 for semiconductor device isolation structure and method of forming.
Invention is credited to Chen, Zhihao, Grider, Douglas T., Mehrad, Freidoon.
Application Number | 20040238915 10/818631 |
Document ID | / |
Family ID | 26872178 |
Filed Date | 2004-12-02 |
United States Patent
Application |
20040238915 |
Kind Code |
A1 |
Chen, Zhihao ; et
al. |
December 2, 2004 |
Semiconductor device isolation structure and method of forming
Abstract
A method for isolating semiconductor devices includes forming a
first oxide layer outwardly from a semiconductor substrate, forming
a first nitride layer outwardly from the first oxide layer,
removing a portion of the first nitride layer, a portion of the
first oxide layer, and a portion of the substrate to form a trench
isolation region, forming a second oxide layer in the trench
isolation region, forming a spin-on-glass region in the trench
isolation region, annealing the spin-on-glass region, removing a
portion of the spin-on-glass region to expose a shallow trench
isolation region, and forming a third oxide layer in the shallow
trench isolation region.
Inventors: |
Chen, Zhihao; (Plano,
TX) ; Grider, Douglas T.; (McKinney, TX) ;
Mehrad, Freidoon; (Plano, TX) |
Correspondence
Address: |
TEXAS INSTRUMENTS INCORPORATED
P O BOX 655474, M/S 3999
DALLAS
TX
75265
|
Family ID: |
26872178 |
Appl. No.: |
10/818631 |
Filed: |
April 5, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10818631 |
Apr 5, 2004 |
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10176383 |
Jun 20, 2002 |
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6737333 |
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60302955 |
Jul 3, 2001 |
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Current U.S.
Class: |
257/506 ;
257/E21.546 |
Current CPC
Class: |
H01L 21/76224
20130101 |
Class at
Publication: |
257/506 |
International
Class: |
H01L 021/8242 |
Claims
1-8. (cancelled)
9. A semiconductor device isolation structure, comprising: a first
oxide layer disposed outwardly from a semiconductor substrate; a
first nitride layer disposed outwardly from the first oxide layer;
a trench isolation region formed by removing a portion of the first
nitride layer, a portion of the first oxide layer, and a portion of
the substrate; a second oxide layer lining the trench isolation
region; a spin-on-glass region disposed in the isolation region;
and a third oxide layer disposed outwardly from the spin-on-glass
region.
10. (cancelled)
11. (cancelled)
12. The structure of claim 9, wherein the spin-on-glass region is
annealed at a temperature between approximately 300.degree. C. and
400.degree. C. for a time period between approximately 15 and 30
minutes, and afterward annealed at a temperature between
approximately 900.degree. C. and 1000.degree. C. for a time period
between approximately 5 and 10 minutes.
13. The structure of claim 9, wherein the spin-on-glass region is
annealed at a temperature of approximately 400.degree. C. for a
time period of approximately 30 minutes, and afterward annealed at
a temperature of approximately 1000.degree. C. for a time period
between approximately 5 and 10 minutes.
14. The structure of claim 9, further comprising a shallow trench
isolation region formed by removing a portion of the trench
isolation region, the shallow trench isolation region having a
depth between approximately 2000 .ANG. and 2700 .ANG..
15. The structure of claim 9, further comprising a shallow trench
isolation region formed by removing a portion of the trench
isolation region, the shallow trench isolation region having a
depth of approximately 2000 .ANG..
16. The structure of claim 9, wherein the second oxide layer has a
thickness of approximately 150 .ANG..
Description
TECHNICAL FIELD OF THE INVENTION
[0001] The present invention relates generally to the field of
semiconductor devices and, more particularly, to a semiconductor
device isolation structure and method of forming.
BACKGROUND OF THE INVENTION
[0002] Semiconductor devices are used in many electronic
applications. One type of semiconductor device is a transistor.
Manufacturers of transistors are continually reducing the size of
transistors to increase their performance and to manufacture
electronic devices in smaller sizes.
[0003] When many transistors are manufactured on a single
integrated circuit die, oftentimes leakage current increases and
breakdown voltage decreases, which severely degrades transistor
performance. Manufacturers of transistors use isolation methods
between transistors and other semiconductor devices to address
these problems and others.
[0004] Shallow Trench Isolation ("STI") is one method used for
isolating transistors and other semiconductor devices. However, as
transistor geometry shrinks, STI falls short of providing adequate
isolation.
SUMMARY OF THE INVENTION
[0005] According to one embodiment of the invention, a method for
isolating semiconductor devices includes forming a first oxide
layer outwardly from a semiconductor substrate, forming a first
nitride layer outwardly from the first oxide layer, removing a
portion of the first nitride layer, a portion of the first oxide
layer, and a portion of the substrate to form a trench isolation
region, forming a second oxide layer in the trench isolation
region, forming a spin-on-glass region in the trench isolation
region, annealing the spin-on-glass region, removing a portion of
the spin-on-glass region to expose a shallow trench isolation
region, and forming a third oxide layer in the shallow trench
isolation region.
[0006] Embodiments of the invention provide a number of technical
advantages. Embodiments of the invention may include all, some, or
none of these advantages. According to one embodiment,
semiconductor device isolation is improved while eliminating a
channel stop implant. This elimination reduces junction
capacitance, resulting in faster devices. In that embodiment, such
advantages are achieved without stringent lithographic alignment
requirements.
[0007] Other technical advantages are readily apparent to one
skilled in the art from the following figures, descriptions, and
claims.
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION
[0008] Example embodiments of the present invention and their
advantages are best understood by referring now to FIGS. 1 through
2F of the drawings, in which like numerals refer to like parts.
[0009] FIG. 1 is a cross-sectional view of a partially completed
semiconductor chip 100 showing a pair of trench isolation regions
102 isolating a semiconductor device 104 from other semiconductor
devices 104 (not explicitly shown). Semiconductor device 104 is any
suitable semiconductor device, such as a bipolar junction
transistor, an NMOS transistor, a PMOS transistor, a diode, a
resistor, or a capacitor.
[0010] Semiconductor devices, especially transistors, are
continually being reduced in size to increase their performance.
Some problems arise when reducing the size of transistors and other
semiconductor devices. For example, an increase in leakage current
and a decrease in breakdown voltage may occur when many transistors
are manufactured on a single integrated circuit die, which may
severely degrade performance of integrated circuits. The present
invention addresses these problems, and others, by providing a
method for isolating semiconductor devices. One embodiment of such
a method is illustrated in FIGS. 2A-2F.
[0011] FIGS. 2A-2F are a series of cross-sectional views
illustrating various manufacturing stages of trench isolation
region 102 in accordance with the teachings of the present
invention.
[0012] FIG. 2A shows a substrate 200 having a first oxide layer 202
formed outwardly therefrom and a first nitride layer 204 formed
outwardly from first oxide layer 202. Substrate 200 may be formed
from any suitable material used in semiconductor chip fabrication,
such as silicon or germanium. First oxide layer 202 comprises any
suitable type of oxide and is formed using any suitable growth
and/or deposition technique used in semiconductor processing. In
one embodiment, first oxide layer 202 is referred to as a "pad ox"
and is approximately 100 angstroms thick; however, other suitable
thicknesses may be used. In one embodiment, first nitride layer 204
is formed from any suitable type of nitride using any suitable
growth and/or deposition technique used in semiconductor
processing; however, first nitride layer 204 may be formed from
other suitable materials that act as a dielectric. In one
embodiment, first nitride layer 204 is approximately 2000 angstroms
thick; however, other suitable thicknesses may be used.
[0013] Although FIG. 2A describes first oxide layer 202 and first
nitride layer 204 as being separate dielectric layers, in other
embodiments, only one dielectric layer is grown and/or deposited on
substrate 200. For example, a layer of oxide only or another
suitable dielectric layer only may be grown and/or deposited on
substrate 200.
[0014] FIG. 2B shows a trench isolation region 206 and a second
oxide layer 208 formed in trench isolation region 206. In one
embodiment, trench isolation region 206 is formed as follows: A
photoresist layer (not explicitly shown) is applied to the outer
surface of first nitride layer 204. The photoresist layer is then
masked and selectively stripped using suitable photolithographic
techniques to expose a portion of first nitride layer 204. The
exposed portion is then etched using any suitable etching technique
to remove the exposed portion of first nitride layer 204 and a
portion of first oxide layer 202. The photoresist layer is then
stripped and removed. After stripping and removing the photoresist
layer, an anisotropic dry etch is performed on the exposed portion
of substrate 200 to etch substrate 200 down to a predetermined
depth 209. In this anisotropic dry etch process first nitride layer
204 is used as a hard masking layer. Any suitable anisotropic dry
etch process, such as a plasma etch, may be used to define trench
isolation region 206. In one embodiment, trench isolation region
206 has depth 209 between approximately 0.7 microns and 1.3 microns
and a width 207 between approximately 0.1 microns and 0.13 microns.
In a more particular embodiment, depth 209 is approximately 1
micron and width 207 is approximately 0.12 microns.
[0015] After defining trench isolation region 206, second oxide
layer 208 is formed in trench isolation region 206. Second oxide
layer 206 comprises any suitable type of oxide and is formed using
any suitable growth and/or deposition technique used in
semiconductor processing. In one embodiment, second oxide layer 208
is approximately 150 angstroms thick; however, other suitable
thicknesses may be used.
[0016] According to the teachings of the present invention, a
spin-on-glass ("SOG") region 211 is formed in trench isolation
region 206 for isolating semiconductor devices 104. One method of
forming SOG region 211 in trench isolation region 206 is outlined
below in conjunction with FIGS. 2C and 2D.
[0017] FIG. 2C shows an SOG layer 210 formed in trench isolation
region 206 and outwardly from first nitride layer 204. SOG is well
known in the art of semiconductor fabrication. The "glass" used in
SOG is typically silicon dioxide; however, other suitable silicates
may be used. In one embodiment, the application of SOG layer 210
involves applying a liquid mixture of silicon dioxide, or other
suitable silicate, in a solvent while the associated wafer
containing semiconductor chip 100 is spun. Because of the
relatively small width 207 of trench isolation region 206,
dielectric materials other than those applied as SOG will
experience difficulties when trying to fill trench isolation region
206. Polysilicon could be used to fill trench isolation region 206;
however, polysilicon has a low dielectric strength and is
inadequate for isolating semiconductor devices 104 manufactured
close to one another. One technical advantage of the present
invention is that SOG layer 210, which has adequate dielectric
properties, is able to fill trench isolation region 206 even though
a small width 207 is utilized.
[0018] After filling trench isolation region 206 with SOG layer
210, SOG layer 210 is annealed to evaporate the solvent in the SOG
material so that SOG layer 210 may be cured. In one embodiment,
annealing SOG layer 210 includes placing semiconductor chip 100
into an oven that is heated to a temperature between approximately
300.degree. C. and 400.degree. C. for a time period between
approximately 15 and 30 minutes, and then subsequently raising the
temperature to between 900.degree. C. and 1000.degree. C. for a
time period between approximately 5 and 10 minutes. In a particular
embodiment, the oven is heated to a temperature of approximately
400.degree. C. for a time period of approximately 30 minutes,
followed by raising the temperature to approximately 1000.degree.
C. for a time period between approximately 5 and 10 minutes.
[0019] FIG. 2D shows a portion of SOG layer 210 removed to define
SOG region 211 and to expose a shallow trench isolation ("STI")
region 212. In one embodiment, STI region 212 is formed by using a
plasma dry etch process that etches SOG layer 210 down to a desired
depth 213. This plasma dry etch process is highly selective, which
reduces the thickness of SOG layer 210 with only a negligible
reduction in thickness of first nitride layer 204. Other suitable
etching processes may be used to reduce the thickness of SOG layer
210 to depth 213. In one embodiment, depth 213 is between
approximately 2000 angstroms and 2700 angstroms. In a particular
embodiment, depth 213 is approximately 2000 angstroms.
[0020] FIG. 2E shows a third oxide layer 214 formed in STI region
212. Third oxide layer 214 comprises any suitable type of oxide and
is formed using any suitable growth and/or deposition technique
used in semiconductor processing. For example, an atmospheric
pressure chemical vapor deposition ("APCVD") process may be used to
form third oxide layer 214.
[0021] FIG. 2F shows trench isolation region 102 after third oxide
layer 214 is reduced in thickness by any suitable process, such as
a chemical mechanical polish ("CMP") process. First nitride layer
204 is used as a stopping layer for the CMP process, which may
result in a reduction in thickness of first nitride layer 204.
After reducing the thickness of third oxide layer 214,
semiconductor devices 104 may then be fabricated on semiconductor
chip 100 in any suitable manner. Because of the excellent isolation
that trench isolation regions 102 provide, based in part on SOG
regions 211, semiconductor devices 104 may be fabricated closer to
one another, thereby improving speed and performance of
semiconductor devices 104 while ensuring that problems, such as an
increase in current leakage or a decrease in breakdown voltage, are
substantially reduced or eliminated.
[0022] Although embodiments of the invention and their advantages
are described in detail, a person skilled in the art could make
various alterations, additions, and omissions without departing
from the spirit and scope of the present invention as defined by
the appended claims.
* * * * *