U.S. patent number 3,696,779 [Application Number 05/100,115] was granted by the patent office on 1972-10-10 for vapor growth device.
This patent grant is currently assigned to Kokusai Denki Kabuskiki Kaisha. Invention is credited to Tsuyoshi Murai, Tatsuo Toi.
United States Patent |
3,696,779 |
Murai , et al. |
October 10, 1972 |
VAPOR GROWTH DEVICE
Abstract
A vapor growth device for vapor-growing semiconductor crystal
films on a plurality of semiconductor crystal wafers arranged on a
flat susceptor by injecting a reaction gas of semiconductor
compound comprises a metal chamber, a nozzle pipe extending into
the chamber and having at the top portion thereof a plurality of
holes to inject the reaction gas along directions parallel with the
flat suscepter; and a nozzle cover having a flat part and a
cylindrical part provided at the edge of the flat part connected to
the top of the nozzel pipe at the flat part so that the nozzle
cover and the suscepter provide a reaction chamber having a gap
between the cylindrical part and the edge of the suscepter, whereby
the reaction gas injected in the reaction chamber from the nozzle
pipe flows through the gap in the form of a gas curtain and then
out an exhaust hole of the metal chamber.
Inventors: |
Murai; Tsuyoshi (Kokubunji,
JA), Toi; Tatsuo (Koganei, JA) |
Assignee: |
Kokusai Denki Kabuskiki Kaisha
(Tokyo-To, JA)
|
Family
ID: |
11505948 |
Appl.
No.: |
05/100,115 |
Filed: |
December 21, 1970 |
Foreign Application Priority Data
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|
|
|
|
Dec 29, 1969 [JA] |
|
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45/1599 |
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Current U.S.
Class: |
118/725;
118/730 |
Current CPC
Class: |
C30B
25/14 (20130101) |
Current International
Class: |
C30B
25/14 (20060101); C23c 011/08 () |
Field of
Search: |
;118/48-49.5
;117/107.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Kaplan; Morris
Claims
What we claim is:
1. A vapor growth device for vapor-growing semiconductor crystal
films on a plurality of semiconductor wafers, comprising: a main
chamber composed of metal and having means therein defining an
exhaust hole; a flat suscepter supported in the main chamber to
hold said semiconductor wafers; means for heating said flat
suscepter; a nozzle pipe receptive during use of the device of a
reaction gas and extending through the center portion of said flat
suscepter into said main chamber and having means therein above the
level of said flat suscepter defining a plurality of holes
extending perpendicular to the longitudinal axis of said nozzle
pipe; means for effecting relative rotational movement between said
nozzle pipe and said flat suscepter; a nozzle cover having a flat
part and a cylindrical part provided at the edge of said flat part,
said flat part being supported on the top of said nozzle pipe and
extending parallel to and in spaced-apart relationship from said
flat suscepter to substantially cover same, said cylindrical part
being spaced-apart from the edge of said flat suscepter to define
therebetween a gap, and wherein said flat suscepter and said nozzle
cover comprise an auxiliary reaction chamber so that the reaction
gas injected into the auxiliary reaction chamber from said nozzle
pipe flows through said gap to said exhaust hole while forming a
gas curtain around said gap.
2. A vapor growth device according to claim 1, in which said flat
suscepter has a circular configuration and said nozzle pipe extends
through the center of said flat suscepter so that the reaction gas
flows out said plurality of holes and radially outwardly with
respect to said flat suscepter.
3. A vapor growth device according to claim 1, in which the head of
the nozzle pipe is exchangeable with other heads to effect
adjustment of said distance between said flat suscepter and said
flat part of said nozzle cover and/or to effect adjustment of the
flow rate of the reaction gas.
4. A device for vapor-growing semiconductor crystal films on
semiconductor wafers comprising: means defining a main chamber; a
support member disposed within said main chamber and having a flat
surface for supporting thereon a series of semiconductor wafers; a
cover member having a concave configuration disposed in a working
position within said main chamber spaced apart from and
substantially covering said flat surface to define therewith an
auxilliary reaction chamber and spaced a predetermined distance
from a peripheral portion of said support member to define
therebetween a peripheral gap; means detachably mounting said
concave cover member in said working position for detachment and
replacement with another concave cover member having a different
interior volume than said first-mentioned cover member whereby the
volume of said auxiliary reaction chamber may be selectively varied
by interchanging concave cover members; heating means for heating
the interior of said main chamber; gas injecting means having
radially directed dispensing apertures and extending into said
auxiliary reaction chamber for injecting a reaction gas during use
of the device into said auxiliary reaction chamber above the level
of said flat surface and then through said peripheral gap in the
form of a gas curtain to effectively prevent ingress of impurities
into said auxiliary reaction chamber; and means coacting with said
gas injecting means for exhausting from said main chamber the
reaction gas flowing thereinto through said peripheral gap along
with any impurities present in said main chamber; whereby the
reaction gas reacts with the semiconductor wafers to form thereon
crystal films.
5. A device according to claim 4; including means for effecting
relative rotation between said support member and said gas
injecting means.
6. A device according to claim 5; wherein said gas injecting means
comprises a gas inlet pipe connectable to a source of reaction gas
and having means therein defining a plurality of holes opening into
said auxiliary reaction chamber above the level of said flat
surface for injecting the reaction gas into said auxiliary reaction
chamber; and wherein said means for effecting relative rotation
between said support member and said gas injecting means comprises
means mounting said support member for rotational movement, and
driving means for rotationally driving said support member.
Description
This invention relates to a vapor growth device for vapor-growing
semiconductor films, such as a single silicon crystal, from a
semiconductor compound.
In a vapor growth device, the following criteria must be satisfied
in order to have an acceptable device: (i) uniformity of specific
resistance and thickness of the semiconductor films produced by
vapor growth; and (ii) good crystal structure of the films produced
by vapor growth. Since the quantity of silicon crystal wafer is
small in a conventional vapor growth device, the above-mentioned
criteria can be satisfied by effecting adjustment of the flow rate
of a gas of the semiconductor compound and by effecting adjustment
of the position of a nozzel used for delivering the gas of the
semiconductor compound to the silicon wafer. Moreover, since the
size of the device is relatively small, quartz parts used in the
vapor growth device are easy to obtain at relatively low prices.
The size of the vapor growth device has recently grown in
proportion to the increase in the required manufacturing capacity
of semiconductor in the vapor growth device. In this case, the flow
of the gas of the semiconductor compound in vapor growth device
becomes irregular in accordance with the rise of the size of the
vapor growth. Moreover, since quartz parts of large size cannot be
readily obtained at low prices, such quartz parts of the vapor
growth device must be replaced by stainless-steel parts which are
inexpensive and readily producible in a large size. However, some
impurity is usually included in the stainless steel and therefore
the uniformity of the specific resistances and thickness of the
semiconductor films is accordingly reduced in a conventional device
of large capacity.
An object of this invention is to provide a vapor growth device
having a large manufacturing capacity and capable of producing
semiconductor crystal films having uniform specific resistance and
thickness and a good crystal structure.
The principle, construction and operation of the vapor growth
device of this invention will be clearly understood from the
following detailed discussion in conjunction with the accompanying
drawings, in which the same or equivalent parts are designated by
the same reference numerals, characters and symbols, and in
which:
FIG. 1 is an elevational view including a section illustrating an
embodiment of the vapor growth device according to this invention;
and
FIG. 2 is an elevational view including a section illustrating, in
an enlarged size, a reaction chamber provided in the embodiment
shown in FIG. 1.
With reference to FIG. 1, an embodiment of this invention comprises
a metal (e.g.; SUS 32) chamber 1 containing therein a gas injection
nozzle 2 of quartz pipe having a plurality of small holes or
dispensing apertures 2c extending perpendicular to axis of the
nozzle 2 and a nozzle cover member 2a detachably held at the top of
the nozzle 2. A plurality of wafers 3 are arranged on a support
member comprising a carbon suscepter 4 which is a flat disc
enlarged in comparison with a conventional one and heating means
comprising high frequency coils 5 are positioned beneath the
suscepter for heating the wafers. A suscepter holder 6 rotatably
supports the suscepter 4 and a gas exhaust hole 7, a gas injecting
pipe 8, and a moter 10 for driving the suscepter holder 6 are also
provided. The metal chamber 1 is supported on a supporting plate 11
by the use of a gas-sealing packing 9. The nozzle 2 is extended
into the chamber 1 through the center of the flat suscepter 4 so
that all of the holes 2c are above the suscepter.
During operation of the device for performing vapor growth of
single crystal films in accordance with the hydrogen reduction
method of silicon tetrachloride (Si Cl.sub.4), a reaction gas,
obtained by mixing silicon tetrachloride with hydrogen, is injected
through the gas injecting pipe 8 in the auxiliary reaction chamber
1 while the silicon wafers 3 are heated by the high frequency coils
5 up to a temperature of 1,100.degree.C to 1,200.degree.C, so that
films of single silicon crystal are grown on the silicon wafers 3.
In the device of this invention, the nozzel cover member 2a has a
concave configuration and completely covers the carbon suscepter 4
and therefore also covers the silicon wafers. The cover member is
disposed in a working position within the main chamber and defines
with the flat surface of the carbon suscepter the auxiliary
reaction chamber and the reaction gas injected from the holes 2c of
the nozzle 2 travels into the auxiliary reaction chamber along
radial directions of the circular suscepter 4 as shown by arrows
extending parallel to the nozzle cover member 2a and the carbon
suscepter 4 and the reaction gas passes through a gap c between
respective ends of the nozzle cover member 2a and the carbon
suscepter 4 and is exhausted from the exhaust hole 7.
To obtain sufficient performance of the vapor growth device of this
invention, a distance d.sub.1 between a parallel part 2a-1 of the
nozzle cover 2a and the carbon suscepter 4 and a gap d.sub.2
between a vertical side wall part 2a-2 of the nozzle cover 2a and
the edge 4a of the carbon suscepter 4 as shown in FIG. 2, as well
as the flow rate of the reaction gas are determined in conjunction
with the size or volume of the carbon suscepter 4 and so as to
obtain an optimum uniform thickness of the grown semiconductor
films and uniform specific resistance of the grown semiconductor
films. The distance d.sub.1 is selectively adjusted by changing the
length of the nozzle head 5b, while the gap d.sub.2 is selectively
adjusted by replacing the nozzle cover member 2a with another one
having an appropriate size. In order to enable various cover
members to be interchanged with one another, the cover member 2a is
detachably mounted in its working position so that it may be easily
detached and replaced by another cover member when it is desired to
vary the volume of the auxiliary reaction chamber. Moreover, since
the gap d.sub.2 is very narrow, a gas curtain is established around
the carbon suscepter 4 by the reaction gas exhausted through the
narrow gap d.sub.2. This gas curtain completely checks and prevents
invasion of an impurity gas in the reaction chamber between the
nozzle cover 2a and the suscepter 4. Accordingly, even if an
impurity gas absorbed in the material of the metal chamber 1 is
expelled into the metal chamber 1, this impurity gas is completely
exhausted without invasion into the auxiliary reaction chamber. The
head 2b of the nozzle pipe 2 may be replaced by another head having
holes 2c of different size to adjust the flow rate of the reaction
gas.
Examples of operations of the vapor growth device of this invention
are as follows:
EXAMPLE 1
In the conventional vapor growth device having no nozzle cover, a
nozzle is provided to inject the reaction gas from the upward
portion thereof toward the carbon suscepter along a direction
perpendicular to the carbon suscepter. In this example of
operation, a nozzle is exchanged from the conventional type to the
type of this invention. Employed wafers include arsenic (As) and
have a specific resistance of 0.008 ohms/centimeters and a
thickness of 220 microns. After etching by hydrogen chloride HCl),
a reaction gas obtained by mixing hydrogen phosphide (PH.sub.3)
with silicon tetrachloride (SiCl.sub.4) was injected during a time
interval of about 12 minutes. Temperature of the wafers at vapor
growing was 1,130.degree.C for the conventional nozzle and
1,170.degree.C for the nozzle of this invention. The specific
resistances in a batch of produced films have a deviation of 13
percent for the device of this invention and a deviation of 21
percent for the conventional device. Accordingly, the deviation of
the specific resistance is effectively reduced in accordance with
this invention. Moreover, a specific resistance of 25
ohms/centimeter is obtained in a case where an impurity gas is not
included in the reaction gas in the device of this invention.
However, a specific resistance of more than 2 ohms/centimeter
cannot be obtained in the conventional device. Accordingly,
detrimental effects caused by the impurity gas is effectively
reduced in accordance with this invention.
EXAMPLE 2
Twenty-three wafers each having a diameter of 38 millimeters were
arranged on a carbon suscepter having a diameter of 220 millimeters
coated with silicon carbide (SiC), while silicon tetrachloride
(SiCl.sub.4) was employed as the reaction gas. Hydrogen phosphide
(PH.sub.3) was mixed with the reaction gas as an impurity gas. As
measured results of grown semiconductor films, a deviation of
.+-.4.8 percent for a standard of thickness of 10 microns and a
deviation of .+-.2.5 percent for a standard of specific resistance
of 0.7 ohms/centimeter were obtained. In a conventional vapor
growth device having substantially the same manufacturing capacity
as this device, the above-mentioned deviations exceeded
respectively 10 percent and 7 percent.
As mentioned above with, the vapor growth device of this invention
it is possible to completely avoid the harmful effects of an
absorbed gas and stain on the material of the metal chamber 1 even
if a metal chamber is used. Moreover, deviations for thickness and
specific resistance of crystal films grown on a number of wafers
arranged on the suscepter can be effectively reduced, so that the
grown crystal films have good and stable characteristics. In a
conventional device, if a substrate doped by arsenic (As) is
employed, undesirable effects are not avoidable due to insufficient
exhaust caused by convection, etc. However, sufficient
characteristics of grown crystal films are obtained by the vapor
growth device of this invention in the above condition.
* * * * *