U.S. patent application number 09/769571 was filed with the patent office on 2001-11-15 for method for doping spherical semiconductors.
Invention is credited to Hanabe, Murali, Patel, Nainesh J., Vekris, Evangellos.
Application Number | 20010041433 09/769571 |
Document ID | / |
Family ID | 26874099 |
Filed Date | 2001-11-15 |
United States Patent
Application |
20010041433 |
Kind Code |
A1 |
Vekris, Evangellos ; et
al. |
November 15, 2001 |
Method for doping spherical semiconductors
Abstract
A method for doping crystals is disclosed. The method includes a
receiver for receiving semiconductor spheres and doping powder. The
semiconductor spheres and dopant powder are then directed to a
chamber defined within an enclosure. The chamber maintains a
heated, inert atmosphere with which to diffuse the dopant to the
semiconductor spheres.
Inventors: |
Vekris, Evangellos; (Plano,
TX) ; Patel, Nainesh J.; (Plano, TX) ; Hanabe,
Murali; (Dallas, TX) |
Correspondence
Address: |
David M. O'Dell
Haynes and Boone, LLP
Suite 3100
901 Main Street
Dallas
TX
75202-3789
US
|
Family ID: |
26874099 |
Appl. No.: |
09/769571 |
Filed: |
January 25, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60178213 |
Jan 26, 2000 |
|
|
|
Current U.S.
Class: |
438/567 ;
257/E21.14; 257/E21.141; 257/E31.038; 438/565; 438/568 |
Current CPC
Class: |
H01L 21/67109 20130101;
Y02P 70/521 20151101; Y02P 70/50 20151101; Y02E 10/547 20130101;
H01L 31/1804 20130101; H01L 21/223 20130101; H01L 31/035281
20130101; H01L 21/2225 20130101 |
Class at
Publication: |
438/567 ;
438/565; 438/568 |
International
Class: |
H01L 021/22 |
Claims
What is claimed is:
1. A method of doping a plurality of three dimensional substrates,
the method comprising the steps of: embedding the plurality of
three dimensional substrates in a dopant mixture to produce a
powder mixture; heating the powder mixture to produce a plurality
of doped three dimensional substrates; cooling the doped three
dimensional substrates; removing the doped three dimensional
substrates from the powder mixture; and etching the doped spherical
shaped semiconductors.
2. The method of claim 1, wherein the plurality of three
dimensional substrates are spherical shaped semiconductors.
3. The method of claim 1, wherein the plurality of three
dimensional substrates are polycrystalline semiconductor
substrates.
4. The method of claim 2, wherein the plurality of spherical shaped
semiconductors are p-type spherical single crystal substrates.
5. The method of claim 2, wherein the plurality of spherical shaped
semiconductors are n-type spherical single crystal substrates.
6. The method of claim 2, wherein the plurality of spherical shaped
semiconductors are oxidized spherical shaped semiconductors.
7. The method of claim 2, wherein the dopant mixture is a mixture
of a dopant oxide and silicon dioxide.
8. The method of claim 2, wherein the dopant mixture is a dopant
nitride.
9. The method of claim 2, wherein the dopant mixture is a mixture
of antimony oxide/silicon dioxide (Sb.sub.2O.sub.3/SiO.sub.2).
10. The method of claim 2, wherein the dopant mixture is a mixture
of boric oxide/silicon dioxide (B.sub.2O.sub.3/SiO.sub.2).
11. The method of claim 2, wherein heating the powder mixture
comprises diffusion and viscous flow along the surface of the
spherical shaped semiconductors.
12. The method of claim 2, wherein heating the powder mixture
comprises viscous flow along the surface of the spherical shaped
semiconductors.
13. The method of claim 2, wherein the dopant mixture is boron
nitride (BN).
14. The method of claim 2, further comprising: providing a
non-oxidizing environment during the heating step.
15. The method of claim 2, further comprising: melting the doped
spherical shaped semiconductors to produce uniformly doped
spherical shaped semiconductors; and cooling the uniformly doped
spherical shaped semiconductors.
16. An apparatus for doping a plurality of three dimensional
substrates, the apparatus comprising: a chamber having a diffusion
zone and a vaporization zone; a first carrier located in the
diffusion zone for containing the plurality of three dimensional
substrates; a second carrier located in the vaporization zone for
containing a dopant; a heater associated with the vaporization zone
for vaporizing the dopant; and an inlet for a carrier gas; whereby
the carrier gas may move through the vaporization zone to combine
with the vaporized dopant, and then to the diffusion zone to
provide the vaporized dopant to the plurality of three dimensional
substrates.
17. An apparatus for doping a plurality of spherical substrates,
the apparatus comprising: a chamber for containing the plurality of
spherical substrates; a rotator for rotating the chamber about an
axis; an inlet to the chamber; and a source for a vaporized dopant,
the source being connected to the inlet; whereby a carrier gas,
combine with the vaporized dopant, may move through the inlet to
provide the vaporized dopant to the plurality of spherical
substrates; and wherein the plurality of spherical substrates are
rotated by the rotation of the chamber about the axis to promote
uniform diffusion.
18. An apparatus for doping a plurality of three dimensional
substrates, the apparatus comprising: a chamber for containing the
plurality of three dimensional substrates; a carrier located in the
chamber for containing the plurality of three dimensional
substrates; a dopant sleeve located outside of the chamber; an
inlet connecting the chamber to the dopant sleeve; and a heater for
vaporizing the dopant sleeve to produce a vaporized dopant; whereby
a carrier gas, combine with the vaporized dopant, may move through
the inlet to provide the vaporized dopant to the plurality of three
dimensional substrates.
Description
CROSS-REFERENCE
[0001] This invention claims the benefit of U.S. Provisional patent
application Ser. No. 60/178,213 filed on Jan. 26, 2000.
BACKGROUND OF THE INVENTION
[0002] The invention relates generally to semiconductor devices,
and more particularly, to a method for doping spherical-shaped
semiconductors.
[0003] The doping process involves the controlled introduction of
an impurity to a substrate, which produces subtle changes in the
electrical resistivity of the material. Such characteristics are
necessary for solid-state electronic semiconductor devices, such as
the transistor.
[0004] In the conventional semiconductor industry, a doped silicon
substrate is created by adding the doping impurity directly into
the melt during the crystal-pulling process. The final crystal is a
uniformly doped one, from which wafers may be cut to serve as doped
substrates.
[0005] In the case of spherical semiconductors, the single crystal
substrates are not produced from a melt, but rather are made by
remelting polycrystalline silicon granules which are grown by
gas-phase reaction in a fluidized bed reactor. The random and
turbulent nature of the fluidized bed process makes the attainment
of sample-to-sample doping uniformity difficult. Therefore, the
granules cannot be doped during growth in the fluidized bed, and
must be doped by external means.
[0006] In U.S. Pat. Nos. 5,278,097, 5,995,776, and 5,223,452,
methods and apparatuses for doping spherical-shaped semiconductors
are disclosed. However, an improved method of doping the spherical
shaped semiconductors, which is simpler and more economical, is
desired.
SUMMARY OF THE INVENTION
[0007] The present invention, accordingly, provides a method for
doping spherical semiconductors. To this end, one embodiment
provides a receiver for receiving semiconductor spheres and a
dopant powder. The semiconductor spheres and dopant powder are then
directed to a chamber defined within an enclosure. The chamber
maintains a heated, inert atmosphere with which to diffuse the
dopant properties of the dopant powder into the semiconductor
spheres.
[0008] In one embodiment, the method of doping a plurality of
spherical shaped semiconductors includes: embedding the plurality
of spherical shaped semiconductors in a dopant mixture to produce a
powder mixture; heating the powder mixture to produce a plurality
of doped spherical shaped semiconductors; cooling the doped
spherical shaped semiconductors; removing the doped spherical
shaped semiconductors from the powder mixture; and chemically
etching the doped spherical shaped semiconductors.
[0009] In one embodiment, the plurality of spherical shaped
semiconductors are made from a commercially available semiconductor
material.
[0010] In one embodiment, the plurality of spherical shaped
semiconductors are p-type spherical single crystal substrates.
[0011] In one embodiment, the plurality of spherical shaped
semiconductors are n-type spherical single crystal substrates.
[0012] In one embodiment, the plurality of spherical shaped
semiconductors are oxidized spherical shaped semiconductors.
[0013] In one embodiment, the dopant mixture is a mixture of a
dopant oxide and silicon dioxide.
[0014] In one embodiment, the dopant mixture is a dopant
nitride.
[0015] In one embodiment, the dopant mixture is a mixture of
antimony oxide/silicon dioxide (Sb.sub.2O.sub.3/SiO.sub.2).
[0016] In one embodiment, the dopant mixture is a mixture of boric
oxide/silicon dioxide (B.sub.2O.sub.3/SiO.sub.2).
[0017] In one embodiment, heating the powder mixture comprises
diffusion and/or viscous flow along the surface of the spherical
shaped semiconductors.
[0018] In one embodiment, the dopant mixture is boron nitride
(BN).
[0019] In one embodiment, the method is done in a non-oxidizing
environment.
[0020] In one embodiment, the method further includes melting the
doped spherical shaped semiconductors to produce uniformly doped
spherical shaped semiconductors and cooling the uniformly doped
spherical shaped semiconductors.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a cross-sectional view of an apparatus for use in
doping spherical semiconductors according to one embodiment of the
present invention.
[0022] FIG. 2 is a flow chart of a method for doping a spherical
shaped semiconductor using the apparatus of FIG. 1.
[0023] FIG. 3 is a cross-sectional view of the apparatus of FIG. 1
in use during the method of FIG. 2.
[0024] FIGS. 4-6 are cross-sectional views of apparatuses for use
in doping spherical semiconductors according to other embodiments
of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0025] The present invention provides a method for doping
substrates. The following description provides many different
embodiments, or examples, for implementing different features of
the invention. Certain techniques and components described in these
different embodiments may be combined to form more embodiments.
Also, specific examples of components, chemicals, and processes are
described to help clarify the invention. These are, of course,
merely examples and are not intended to limit the invention from
that described in the claims.
[0026] Referring to FIG. 1, the reference numeral 10 designates, in
general, one embodiment of an apparatus used for the doping of
spherical semiconductors. The apparatus 10 includes a chamber 12
having a furnace 14 surrounding the chamber. The chamber 12 has an
inlet port 16 at one end for connecting to an inlet line 18.
[0027] The inlet line 18 is used for allowing a gas source 20 to
enter the chamber 12. The chamber 12 includes a boat 22 which can
be held in place by a base 24 which is connected to one or more
legs 26. The boat 22 may be, for example, quartz or alumina. In a
preferred embodiment, the boat 22 is quartz. The chamber 12 also
includes an outlet line 28 for exhausting the gas source 20.
[0028] Referring to FIGS. 2 and 3, a method 100 may be used in
conjunction with the apparatus 10. The method 100 is preferably
performed in an inert atmosphere. At step 102, a plurality of
spherical semiconductors 30 is placed in the boat 22. The spherical
semiconductors 30 may be, for example, any commercially available
spherical semiconductor material, any oxidized spherical
semiconductor material, an n-type spherical single crystal
substrate, or a p-type spherical single crystal substrate. In a
preferred embodiment, the spherical semiconductors 30 are
silicon.
[0029] At step 104, a dopant mixture 32 is placed in the boat 22
containing the spherical semiconductors 30. The spherical
semiconductors 30 are embedded within the dopant mixture 32. The
dopant mixture 32 preferably has particles that are approximately
less than 1 .mu.m in size. The dopant mixture 32 may be, for
example, any dopant oxide mixed with silicon dioxide (SiO.sub.2) or
any dopant nitride. In a preferred embodiment, the dopant mixture
32 is an antimony oxide/silicon dioxide (Sb.sub.2O.sub.3/SiO.sub.2)
mixture. The ratio of the dopant oxide/silicon dioxide mixture is
chosen to maximize the viscosity of the dopant mixture 32 and to
maximize the amount of the dopant oxide in the dopant mixture
32.
[0030] At step 106, the boat 22 is placed within the chamber 12 and
the chamber 12 is subjected to a predetermined thermal cycle. In a
preferred embodiment, at the process temperature, antimony oxide is
transferred from the dopant mixture 32 to the surface of the
spherical semiconductors 30. This is accomplished by diffusion
and/or viscous flow along the surface of the powder particles of
the dopant mixture 32 which are in intimate contact with the
spherical semiconductors 30. In a preferred embodiment, elemental
antimony is further diffused to a shallow depth into the spherical
semiconductors 30.
[0031] At step 108, the boat 22 is cooled and removed from the
chamber 12. The spherical semiconductors 30 are doped with antimony
and are removed from the dopant mixture 32.
[0032] At step 110, the spherical semiconductors 30 doped with
antimony, are chemically etched to remove any oxide/powder layer.
The spherical semiconductors 30 doped with antimony may be
chemically etched by any commercially available chemical etching
process.
[0033] In an alternate embodiment, the method 100 further includes
melting the spherical semiconductors 30 doped with antimony to
produce spherical semiconductors 30 uniformly doped with antimony
upon cooling.
[0034] In an alternate embodiment of the method 100, the dopant
mixture 32 is a boric oxide/silicon dioxide
(B.sub.2O.sub.3/SiO.sub.2) mixture. In this embodiment, the
semiconductors 30 would first be oxidized (in a prior, separate
step), and then mixed with and submersed in a bed of BN powder.
During the process, the BN powder would react and bond with the
oxide on the surface of the spherical semiconductors and the
transfer of Boron would take place. After the process, the
semiconductors 30 would be chemically etched to remove the layer of
oxide/powder. The process would be done under a non-oxidizing
atmosphere to prevent oxidation of the BN powder, thus allowing it
to be reused fro subsequent treatments.
[0035] In an alternate embodiment of the method 100, the spherical
semiconductors 30 are a p-type spherical single crystal substrate
and the dopant mixture 32 is an antimony oxide/silicon dioxide
(Sb.sub.2O.sub.3/SiO.sub.2) mixture. The spherical semiconductors
30 are doped to produce a p-n junction near the surface of the
spherical semiconductors 30.
[0036] In an alternate embodiment of the method 100, the spherical
semiconductors 30 are an n-type spherical single crystal substrate
and the dopant mixture 32 is a boron oxide/silicon dioxide
(B.sub.2O.sub.3/SiO.sub.2) mixture. The spherical semiconductors 30
are doped to produce a p-n junction near the surface of the
spherical semiconductors 30.
[0037] In an alternate embodiment of the method 100, the spherical
semiconductors 30 are oxidized spherical semiconductors and the
dopant mixture 32 is boron nitride (BN).
[0038] Referring now to FIG. 4, the reference numeral 150
designates, in general, another embodiment of an apparatus used for
the doping of spherical semiconductors. The apparatus 150 includes
a chamber 152 having two furnaces 154, 156 associated with the
chamber. The chamber 152 has an inlet port 158 at one end and an
opposing outlet port 160. The apparatus 150 can be used with the
method 100, as described above.
[0039] The inlet port 158 is used for allowing a carrier gas 162 to
enter the chamber 152, similar to the carrier gas from the gas
source 20 of FIG. 1. The chamber 152 includes a first boat 164 and
a second boat 166, both similar to the boat 22 of FIG. 1.
[0040] The first boat 164 and the first heater 154 are positioned
in a first area of the chamber 152, herein designated as the
diffusion zone 168. The second boat 166 and the second heater 156
are positioned in a second area of the chamber 152, herein
designated as the vaporization zone 170. Although the diffusion
zone 168 and the vaporization zone 170 are illustrated as being in
a single, common chamber 152, in other embodiments, they may be in
separate chambers.
[0041] In the present embodiment, the first boat 164 includes a
plurality of spherical semiconductors 30 and the second boat 166
has the dopant mixture 32. The dopant mixture 32 may be as
described in FIG. 3. However, in the present embodiment, the dopant
mixture 32 and the spherical semiconductors 30 are kept separate
from each other. In this way, different processing environments can
be maintained in the different zones 168, 170. For example, the
temperature of the vaporization zone 170 may be higher than that of
the diffusion zone 168.
[0042] In operation, the dopant material 32 is heated by the heater
156 and vaporizes in the vaporization zone 170. The carrier 160
moves through the vaporization zone 170 and carries the vaporized
dopant into the diffusion zone 168. At this time, the vaporized
dopant comes in uniform contact with the spherical semiconductors
30. Diffusion may then occur on the semiconductors. Exhaust 172
from the process may be expelled through the outlet 160.
[0043] Referring now to FIG. 5, the reference numeral 200
designates, in general, yet another embodiment of an apparatus used
for the doping of spherical semiconductors. The apparatus 200
includes a first chamber 202 having a furnace 204. The chamber 202
has an inlet port 206 at one end connected by a coupling 208 to a
second chamber 210. Opposing the inlet 206 is an outlet port 212.
The apparatus 200 can be used with the method 100, as described
above.
[0044] The first chamber 202 is connected to a rotating device 214
for rotating the chamber, as illustrated by the arrows 216. The
rotator 214 may be any mechanical means, such as a small motor
assembly. The rotation 216 allows a plurality of spherical
semiconductors 30 to move inside the first chamber 202.
[0045] The second chamber 210 does not have to rotate. Instead, the
coupling 208 allows the first and second chambers 202, 210 to
remain connected while only one rotates. In other embodiments, the
second chamber 210 may also rotate. The second chamber 210 also
includes a heater 220 and the dopant mixture 32, such as is
described in FIG. 3. However, like the embodiment of FIG. 4, the
dopant mixture 32 and the spherical semiconductors 30 are kept
separate from each other. In this way, different processing
environments can be maintained in the different chambers 202, 210
For example, the temperature of the second chamber 210 may be
higher than that of the first chamber 202.
[0046] In operation, the dopant material 32 is heated by the heater
220 and vaporizes in the second chamber 210. A carrier gas 160
moves through the second chamber 210 and associates with the
vaporized dopant. The carrier gas and vaporized dopant then move
into the first chamber 202. At this time, the vaporized dopant
comes in contact with the spherical semiconductors 30. Diffusion
may then occur on the semiconductors. The rotation 216 of the first
chamber 202 helps to encourage uniform contact between the
vaporized dopant and the spherical semiconductors 30. Exhaust 172
from the process may be expelled through the outlet 212.
[0047] Referring now to FIG. 6, the reference numeral 250
designates, in general, still another embodiment of an apparatus
used for the doping of spherical semiconductors. The apparatus 250
includes a chamber 252 having a furnace 204. The furnace 204 of
FIG. 6 is illustrated as a conductive coil, although many types of
heaters can be used. The chamber 252 has an inlet port 256 and an
opposing outlet port 258. The chamber 152 also includes a boat 164,
similar to that shown in FIG. 4, for containing a plurality of
spherical semiconductors 30. The apparatus 250 can be used with the
method 100, as described above.
[0048] The inlet port 256 of the chamber 252 is connected to a
dopant sleeve 260 associated with a heater 262. The dopant sleeve
260 includes a solid dopant material such as
Sb.sub.2O.sub.3/P.sub.2O.sub.5, B.sub.2O.sub.3, BN, P, Sb, or
SiP.sub.2O.sub.7. The solid dopant material may be similar to the
dopant material 32 of FIG. 3. Like the embodiment of FIG. 4, the
dopant material from the sleeve 269 and the spherical
semiconductors 30 are kept separate from each other. In this way,
different processing environments can be maintained in the
different chambers 252, 210
[0049] In operation, the dopant material in the sleeve 260 is
heated by the heater 262 and vaporizes. A carrier gas 160 moves
through the dopant sleeve 260 and associates with the vaporized
dopant. The carrier gas and vaporized dopant then move into the
chamber 252. At this time, the vaporized dopant comes in contact
with the spherical semiconductors 30. Diffusion may then occur on
the semiconductors. Exhaust 172 from the process may be expelled
through the outlet 258.
[0050] Several advantages result from the above-described
embodiments. For one, the spherical semiconductors seldom, if ever,
come in physical contact with any other device or any part of the
apparatus 10.
[0051] It is understood that several variations may be made in the
foregoing. For example, different heating mechanisms may be used
with the apparatus. Other modifications, changes and substitutions
are also intended in the foregoing disclosure and in some instances
some features of the invention will be employed without a
corresponding use of other features. Accordingly, it is appropriate
that the appended claims be construed broadly and in a manner
consistent with the scope of the invention.
* * * * *