U.S. patent number 3,686,378 [Application Number 05/058,458] was granted by the patent office on 1972-08-22 for improved separation of the deposition mandrel from a vapor phase deposited semiconductor body.
Invention is credited to Wolfgang Dietze.
United States Patent |
3,686,378 |
Dietze |
August 22, 1972 |
IMPROVED SEPARATION OF THE DEPOSITION MANDREL FROM A VAPOR PHASE
DEPOSITED SEMICONDUCTOR BODY
Abstract
An at least unilaterally open, hollow body of semiconductor
material, such as a tubular or cup-shaped body for example, is
produced by precipitating the semiconductor material from a gaseous
phase upon a heatable carrier consisting of a different material
whose thermal coefficient of expansion is greater than that of the
semiconductor material. During the process the carrier is heated to
a temperature at which the difference in thermal expansion causes
fissures or cracks to appear in the precipitated semiconductor
material. Thereafter the precipitation of semiconductor material is
continued until the cracks are closed by the further growth of
precipitating semiconductor material. Ultimately the carrier is
removed by pulling or dropping it out of the resulting cooled
semiconductor body.
Inventors: |
Dietze; Wolfgang (8 Munich 50,
DT) |
Family
ID: |
5743825 |
Appl.
No.: |
05/058,458 |
Filed: |
July 27, 1970 |
Foreign Application Priority Data
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Aug 26, 1969 [DT] |
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P 19 43 359.1 |
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Current U.S.
Class: |
264/81;
148/DIG.73; 264/431; 264/472; 148/DIG.49; 148/DIG.122; 427/248.1;
438/478; 117/920 |
Current CPC
Class: |
C23C
16/01 (20130101); Y10S 148/122 (20130101); Y10S
148/073 (20130101); Y10S 148/049 (20130101) |
Current International
Class: |
C23C
16/00 (20060101); C23C 16/01 (20060101); B01j
017/28 (); B29c 013/04 () |
Field of
Search: |
;264/81,66
;117/16R,16A,16C,16D ;148/174,175 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Frome; Julius
Assistant Examiner: Miller; John H.
Claims
I claim:
1. The method of producing an at least unilaterally open hollow
body of silicon which comprises precipitating a layer of silicon
from a gaseous compound thereof onto a graphite carrier, the
precipitation temperature being in the range from about
1,050.degree.C to about 1,200.degree.C, heating the carrier upon
precipitation of the layer of semiconductor material to a
temperature of about 50.degree.C to about 100.degree.C above the
precipitation temperature, whereby cracks occur in the layer of
precipitated semiconductor material, then continuing the
precipitation of semiconductor material until the cracks are
eliminated by further growth of precipitated semiconductor
material, cooling the carrier and pulling the carrier from the
resulting hollow semiconductor body without destroying said hollow
semiconductor body.
2. The method according to claim 1 which comprises reducing, upon
occurrence of said cracks, the temperature of the carrier to a
value between 1,050.degree.C and 1,200.degree.C.
3. The method of claim 1 which comprises heating the carrier to the
precipitation temperature until the precipitating semiconductor
material layer has attained a wall thickness of about 1 mm, then
temporarily heating the carrier a 50.degree. to 100.degree.C higher
temperature, and thereafter maintaining the carrier at
1,050.degree. to 1,200.degree.C during said continuing
precipitation of semiconductor material.
Description
My invention relates to producing an at least unilaterally open,
hollow body of semiconductor material by precipitating the
semiconductor material from a gaseous compound or phase of the
material upon a heatable carrier structure consisting of a
different material, and removing the carrier upon precipitation of
a sufficiently thick layer of semiconductor material. The
semiconductor body thus produced may have an annular or tubular
shape open at both sides, or it may consist of a unilaterally
closed tubular or cup-shaped structure. Thus the accompanying
drawing exemplifies in FIG. 1 a tubular body 1 of silicon or other
semiconductor material shown in perspective, and FIG. 2 shows in
cross section an example of a cup-shaped body or crucible boat made
of such a material.
A method of this type proposed previously requires removing the
carrier structure from the hollow semiconductor body produced
thereupon, by burning the carrier out of the body.
It is an object of my invention to devise a different process of
manufacture which, while generally involving a precipitation method
of the above-mentioned type, affords removing the carrier structure
without endangering the soundness or quality of the semiconductor
layer produced thereupon.
Another object subsidiary to the one just mentioned is to enable
the removal of the carrier structure from the precipitated hollow
semiconductor body without destruction or damage to the carrier
structure so that it remains applicable for performing one or more
further precipitation processes.
To achieve these objects, and in accordance with my invention I
precipitate the semiconductor material from the gaseous phase upon
a carrier consisting of a different material whose thermal
coefficient of expansion is greater than that of the semiconductor
material. During the precipitation process, or at some intermediate
stage, I heat the carrier to an elevated temperature at which the
difference in expansion occurring between the carrier and the
semiconductor body causes fissures or cracks to occur in the
precipitated semiconductor material. Thereafter I continue the
precipitation of semiconductor material until the further growth of
precipitated material closes and thus eliminate the cracks.
Ultimately I remove the carrier out of the resulting hollow
semiconductor body. This is done, for example, by simply pulling
the carrier out of the body or by permitting it, when cooled, to
drop out of the body.
For the purpose of the invention the carrier preferably is made of
graphite or the like industrial carbon material.
According to another preferred feature of the invention I first
heat the carrier to the processing temperature required or
advantageous for the precipitation of the semiconductor material
from the gasous phase until the precipitated layer has reached a
given thickness at which the semiconductor body remains
sufficiently self-supporting and coherent despite the subsequent
formation of fissures or cracks. I then temporarily raise the
temperature of the carrier above that employed during the
precipitation stage with the result of causing the cracks.
Thereafter I again reduce the temperature of the carrier to the one
employed during the first precipitation stage, thus causing a
further growth of semiconductor material upon the previously
precipitated semiconductor layer to make the cracks grow
closed.
The method according to the invention is performed by mounting a
carrier, for example a rod or other structure of graphite, in a
hermetically closed reaction vessel and then heating the carrier
within the vessel while simultaneously passing a gaseous compound
of the semiconductor material into the vessel. In these respects
the process and the processing equipment need not differ from the
processes and equipment known for the production of electronic
silicon material, described for example in the U.S. Pat. No.
2,999,735 of Reuschel, U.S. Pat. No. 3,146,123 of Bischoff, and
U.S. Pat. No. 3,042,494 of Gutsche.
The accompanying drawing on which;
FIGS. 1 and 2 show a tubular body 1 and a cup-shaped body 2,
respectively, as described above, and
FIG.. 3 illustrates schematically and partly in section a tubular
body 1 of silicon precipitated upon a rod-shaped cylindrical
carrier 3 of graphite.
During the process the carrier 3 is clamped at both ends and is
heated by passing electric current longitudinally through the
carrier. The heating may also be effected by electric induction
heating which is preferably applied for heating the carrier used in
the production of a cup-shaped or other unilaterally closed
semiconductor body such as the one exemplified in FIG. 2.
When, for example, if silicon is to be precipitated upon the
carrier structure, the gaseous phase to be passed into the reaction
vessel may consist, for example, of SiHC1.sub.3 mixed with
molecular hydrogen H.sub.2. When the carrier of graphite is heated
to the precipitation temperature, for example about 1,050.degree. C
to about 1,200.degree. C, the introduction of the gaseous mixture
into the reaction vessel causes crystalline silicon to precipitate
upon the carrier. This pyrolytic precipitation and deposition
process is continued until a desired layer thickness of the
semiconductor material is attained, this thickness being dependent
upon the dimensions of the hollow semiconductor body to be
produced. For example, if a unilaterally open tube having an inner
diameter of 30 mm and a wall thickness 2 mm is to be produced, the
precipitation can be interrupted when a wall thickness of about 1
mm is attained. Then the carrier is heated to a higher temperature.
This has the consequence that the carrier structure of graphite
expands more than the precipitated layer of silicon due to the fact
that the thermal coefficient of expansion of graphite is greater
than that of silicon. The difference in expansion causes the
silicon layer to crack. The temperature increase during this stage
of the process is so chosen that the silicon layer will not
completely crack away from the carrier. It has been found
advantageous, referring to a tubular semiconductor body of the
above-mentioned dimensions, to apply a temperature increase of
about 50.degree. to about 100.degree. C. Such a temperature
increase has the effect that the inner diameter of the precipitated
layer of silicon will slightly widen but the silicon layer will
remain a coherent entity.
After the fissures or cracks have thus been formed in the silicon
layer, the temperature of the carrier structure can be reduced to a
value which may be the minimum at which a further precipitation of
crystalline silicon will just remain possible, or the temperature
may be maintained at the increased value at which the fissures or
cracks have formed in the semiconductor material. Subsequently an
additional quantity of crystalline silicon is precipitated until
the cracks grow closed.
The precipitation process need not necessarily be interrupted
during the stage of increased temperature. The process rather can
also be performed so that further silicon will precipitate during
the interval of increased temperature.
When the desired ultimate layer thickness is attained, the
precipitation process is terminated and the carrier structure
together with the precipitated layer of silicon is permitted to
cool. Thereafter the carrier structure can be removed from the
tubular or other semiconductor body simply by letting the carrier
drop out of the opening of the semiconductor body. Due to its
weight and somewhat smaller diameter, the carrier structure will
readily slide out of the tubular body and can again be used for the
production of another semiconductor body.
While the method according to the invention has been specifically
described with reference to the production of a tube of silicon,
similar structure can be produced in the same manner from
germanium, silicon carbide, III-V semiconductor compounds and II-VI
compounds. Aside from tubular structures, various other hollow
bodies that are open on at least one side are producible in the
same manner.
To those skilled in the art it will be obvious from a study of this
disclosure, that with respect to shapes, materials and other
processing data, my invention is amenable to various modifications
and hence may be given embodiments other than those particularly
illustrated and described herein, without departing from the
essential features of the invention and within the scope of the
claims annexed hereto.
* * * * *