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Патент USA US3096219

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July 2, 1963
H. s. lNGHAM, JR
Filed May 18, 1960
BY y@ ß l/f/ ,ff
Patented July 2, 1963
of apparatus for forming semiconductor bodies in accord
ance with the invention.
Herbert S. Ingham, Jr., Hillside Lake, Wappingers Falls,
In the ensuing discussion of a preferred embodiment
of the invention, the operation will be -described with ref
NX., assignor to international Business Machines Cor
poration, New York, NX., a corporation of New York
Filed May 18, 1960, Ser. No. 29,836
1 Claim. (Cl. 117-201)
erence ,to the use of germanium as both the source mate
rial and the substrate, and to the use of iodine as a trans
port element. It will be appreciated, however, that other
semiconductors, `such `as silicon, may serve both as the
source and as the substrate and that other transport ele
This invention relates to the formation of semiconduc
ments may be employed. It will also be understood that
tor bodies by vapor deposition and more particularly to 'an 10 in the fabrication of junction devices the conductivity type
apparatus and a method for producing the deposition
`of the source and substrate will preferably dilfer. Like
epitaxially at a higher rate and with a greater uniformity
wise, the semiconductor source material may diifer from
than has been previously attainable.
the substrate material as long as the lattice ‘constants of
In the art of vapor deposition, -a deposit on a »substrate
the source and substrate materials are reasonably similar
is said to be epitaxial if its crystal structure is of the same
in value.
orientation ‘and periodicity as the substrate.
Referring now to the FIGURE, there is shown a sche
A cyclical reaction technique for achieving epitaXiall
deposition has been previously developed. In essence, »this
matic diagram of the reaction apparatus in which utiliza
tion is made of the reversible chemical reaction:
technique involves the use of 'a lclosed straight tube con
2GeI2 (vapoUSGeL, (vapor) +Ge (solid) for which
taining a transport element, such as a halogen, a source of 20 at a given temperature and initial concentration of iodine,
semiconductor material and a substrate of the same, or of
there exists an equilibrium proportion of Gelz to Gel.,
a different, »semiconductor material, upon which the semi
vapors `over an excess of Ge. Deposition of the germa
conductor body is to be formed. ln operation, a temper
n-íum requires transportation of the vapors from la hotter
ature gradient is established along the tube with a differ
region (the source Zone A) to a cooler region (the sub
ence in temperature maintained between the source mate 25
strate zone C).
rial zone and the substrate zone. A gaseous compound of
In the cooler region the above reaction proceeds -to the
the source material and the transport element forms in the
right, resulting in cpitaxial deposition of Ge on to a sub
source zone and diffuses to the substrate zone Where it de
strate crystal of Ge. The vapor becomes richer in Gel.;
composes with the result that epitaxial deposits are formed
and is then transported back to the source zone. There
on the substrate material. The rate at which the crystals 30 a source of Ge iallows the reaction to go to the left. The
can be grown in this closed tube apparatus is limited by
process is thus cyclical and transports Ge -from one Zone
the rate at which the vapors in the cyclical reaction can be
the other.
transported from the source zone to the substrate zone
rIhe quartz tube 1 containing the vapors 2 is in the
land from the substrate zone to the source zone.
The present invention represents a significant improve
ment over the closed tube technique described above by
reason of the approach taken to increasing the rate of
transport of the vapors. The reaction container or fur
form of a flattened torofid held in a vertical plane. The
thickened portion 3, in zone A ion the right `side of the
tube contains ‘chunks 4 lof source Ge. The elbow 5 on
the left side of the tube contains a ilat shelf 6 upon which
rests a substrate Ge crystal 7. The existence of the elbow
nace is designed in the form of a closed loop so that a
»is not essential to the invention but is used to aid in con
continuous, undirectional ilow path is established for the 40 trolling the temperature of the substrate. The tube is
cyclical reaction. The source material land the substrate
are positioned on opposite sides of the container so that
when a controllable difference of temperature is estab
-evacuaed and 12 and, if desired, a carrier gas is introduced.
The electric furnace windings 8a, 8b, 8c, and 8d are on
lished between the opposite sides, rapid circulation of the
«around the toroid so that zones A, B, C and D may be
vapors is promoted due to convection. With this arrange
ment, the rate of ñow Áof the vapors can be precisely
controlled and can be varied within wide limits.
As a
result, the maximum rate of epitaxial deposition that may
sections of split quartz tubing 9 and tit concentrically
maintained at various temperatures.
In a simple version of the apparatus the entire right
hand side of the toroid is maintained at a desired source
zone temperature, typically about 650° C., by connecting
be achieved is no longer limited by the rate ‘at which the
the windings 8a and Sb in series to a source of power,
vapors can be transported but only by the restrictions in 50
not shown. The other `side of the toroid is maintained at
herent iu the physical mechanism of the crystal growth
a typical substrate zone temperature of 400‘J C. by con
process itself.
necting windings 8c and 8d to a similar source of power.
It is, therefore, an object of the present invention to
Because of the temperature difference between the two
provide an improved vapor deposition technique »for form
sides, there «is a large convection current. Vapor rich
ing semiconductor bodies.
Geiz is transported around the top of the toroid to
Another object is to provide a method of forming semi
the substrate crystal '7. Ge is deposited in the substrate
conductor bodies by which a high rate of epitaX-ial crystal
zone and the vapor proceeds around the bottom back to
growth may be obtained.
source Ge 4 which replenishes the vapor with Geiz.
A further object is to provide an improved reaction
apparatus for producing a high rate of epitaxial crystal 60 The convective flow is enhanced signiñcantly, ie. by about
30% for the temperatures quoted above 'and a pressure
about 0.3 atmosphere, by the fact that Gel, has a higher
Another object is to control the convection currents in
dens-ity than `Gelz and exists in larger concentrations on
the vapor deposition process.
the cooler side of the toroid.
A related object is to yobtain an epitaxially deposited
In a modiiied version of the apparatus the windings 8a
in zone A and windings 8b in zone B are separately cou
rl`=he foregoing and other objects, features and advan
nected to a source of power so that these individual zones
tages of the invention will be apparent from the follow
may be maintained at dilîerent temperatures.
ing more particular description of a preferred embodi
Thus, the modiñed version provides control of the con
ment of the invention, as illustrated in the accompanying 70
vective flow rate independently of the difference in tem
perature between the source `and substrate. Such ‘control
The FIGURE is an elevational View, partly in section
junction device.
3,0 seacs
is useful for studies of `the deposition process and for pro-' ducing optimum ygrow-th rates and crystal quality.
In order to aid in understanding and practicing »the
invention and to provide ’afstarting' place >for one skilled
in the art, the following set fof specifications is set ,forth
,- 1
sition involving the use of a 'closed-loop reaction appa
ratus whereby high rates of uniform epitaxia'l? crystal
growth may be obtained and whereby the rates'fof such
growth may be easily »regulatedV by reason of the4 precise
control iañorded over the convective -Ílow of the vapors in
below. It should be understood' that no limitation should
the reaction.
be construed hereby since in the light of the preceding
`- `
While the invention has been particularly shown and
Y description many sets of specifications may be devised.
. described with reference 'to a preferred embodiment there
, For example, other semiconductor materials and other
of, it will be understood by »those skilled in the-art that
K transport elements may be utilized. In ycertain situations 10
various changes in form and details may be made-therein
. involving 'these other semiconductor materials and trans
without departing from the spirit and scope ofthe in->
port elements, it will be necessary to establish a reverse
A temperature proñle, ie. the substrate will be maintained
at a higher temperature `than the source. In such situa
What is claimed is:
tions, of course, ‘the flow of vapors will then be clockwise
, or opposite to the direction shown in the FIGURE.
Container 1 :(Quartz). __'. 1l inches long, 4 inches wide.
ì i
iirst -zone on 'one side of said continuous closed-loopl reac
Heating windings 8a, Sb, 8c,V
tion container a sounce of ysemiconductor material,v posi
tioning in a second zone on another side of said container
and .8d ____________ _. Niohrome wire.
Source 4 ________ __'-___. Germanium-undoped.
'Substrate 7 ___'.__.__'___'___ Germanium-‘undoped
‘Transport element ..... _. Iodine.Temperatures: f
. .K
The method of forming semiconductor bodies compris
ing the steps ofproviding a continuous closed loop reac
.tion container in a vertical orientation, positioning in a
tive with saidV source said substrate to produce'vapors,
Zones A land B> ____ _., 650,9 C.
Zones C and-D _____. 400° C.
vat least'lone substrate of semiconductor material,V Vpvnovid
ing `in said container a transport element*cyclicallyfreac
`maintaining between said ñrst and second zonesl afiiiiîer
ence in 'temperature to eüect the cyclical.rea'cti'oná` and
25 establishing between said second zone and a Athird Zone,
y . The apparatus,y in, accordance with the above set of
speciíications, has beenV given tests, and a uniform epitax
Aial deposit `approximately 0.35 mm. thick was obtained in
23v hours. This deposit rate of 15 [.t/hr. is about 3 times 30
_greater than the normal rate observed in conventional
l closed tubes. ' Furthermore, the deposit was more uniform
_ adjacent said ñrst zone, another difference in temperature,
whereby rapid circulation of the vapors lis obtained inde
y pendently of the temperature difference between the source
and the substrate.
vReferences Cited Ain the ñle of this patent
than found in straight tubes. By increasing the cooling of
‘ the substrate by ydirecting a jet of air on the elbow 5, depo
sition rates of 130 n/ hr. were observed.
What has been described is a technique fof vapor depo
Drummond __________ __ Mar. 14,1944 '
Pedersen et al.' ________ __ Dec. 9, '1.952
Christensen et a1. _______ oct. 26, i954'
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