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Apparatus for chemical vapor deposition of silicon dioxide from silanc gas. (USA)
Classified
abstracts
2391-2399
74/77468DC. This document is in rull technical accord with DIS 3563. It specifies a method for calibrating a vacuum gauge by direct comparison with a reference gauge, and though the method is not limited to a particular prcssurc range, the apparatus to be described has been designed lo cover the vacuum spectrum from 760 torr (atmospheric to IO-(’ torr. Since as stated previously this is judged to be the pressure range over which by far the largest majority of industrial calibrations are required to be made. J D Buckingham, I’acrrwn, 26 (4/5). 1976. 143-147. 32
(Bulgaria) Using a special broadband phase-scnsitivc amplifier, the output signal is investigated of a high-frequency mass-spectromctcr type farvitron having a quasi-parabolic potential well. It is shown that the information on the phase of the output signal allows the determination of the mass of the oscillating ions with a greater accuracy than by a conventional farvitron. M Mikhalev and Kh Tenchov, Rep of Ekcrron Ius/ oJ Bu/g Acad of Scierlc, No 7, 1974, 77-81 (itr B&wriatr). ‘2 2391.
2392.
Some
phase
Calibration
measurements
of a partial
on a sensitive
pressure
analyzer
farvitron.
by an absolute
method.
(USSR) Calibration of a farvitron partial pressure analyzer has been performed with the aid of a pressure reduction calibration equipment. Calibration characteristics for nitrogen are presented. The analyzer is linear up 10 pressures of IOmJ N/m’ to 10e3 N/m’. The relative coefficients of sensitivity for OL, He, Ne and CO, with respect lo N1 are 0.58. 0.14. 0.36-0.38 and 1.16-1.22. respectively. The minimum reliably meas&ablc partial pressure is 6 .. iOm6 N&i’. V V Kuzmin and E K Frolov, Probl o/Atom Scicn aud Trch~ro/, Ser Phys a& T&II of High I’acu~rfn, CON, No I, Kharkov, 1973, 4045 (in Rrrssiun). 23. PLUMBING,
VACUUM
VALVES,
BAFFLES
AND
TRAPS 23
2393.
Ultrahigh
vacuum
lock.
(USA)
An UHV lock is described that makes it possible to change samples, keeping the pressure in the UHV system at 1O-9-1O-1o Torr. The samples are mounted on a sample holder that can be heated up to about 1000°C. (Germany) G Tauber and H Viefhaus, Reel Sci butrrrm, 47 (6), 1976,772-773. 23
(GB) A new type of variable leak was developed to control the flow of gas into the ion source of an electromagnetic isotope separator. It consists essentially of a rotating member which introduces well-defined doses of gas at a predetermined rate into the evacuated enclosure. The inflow rate depends on the geometry of the valve and is linearly proportional to the rotation speed. Thus, the inflow rate may be easily and continuously controlled by adjusting the speed of the motor. The main advantages of the new valve are that it is reliable and convenient to operate-even by remote control, and its response is proportional to an electric signal. The valve is particularly suitable for applications where the inflow rate must be automatically controlled by some feed-back system. Its main drawback is the pulsed shape of its output. This can be corrected by the insertion of a simple filter which, however, results in a reduction in the speed of response. Also the ratio of the limits of the Rowrate range, for a given valve geometry is approximately 1: IO, but the range can be modified by replacing a single component of the valve. Units of various ranges covering rates from 1 mm3 s-l to 1 cm3 s-’ have been built and mounted on the ion sources of the Meira isotope separator with very satisfactory results. (Israel) 2394.
I Cbavet,
Rotating
Vucuurn,
variable
26,
leak
(4/5),
valve.
1976,
203-209.
23 2395. Large diameter cryogenic seals. (GB) Cryogenic vacuum seals are discussed with emphasis on large diameter reusable connections. Both theoretical considerations and experimental results are presented. The main subject is large diameter cryogenic vacuum seals in a horizontal vessel, where thermal distortions are encountered in particular during the cool down stage. We show a large diameter stainless steel flange designs that can take large repeatable thermal shocks and maintain a good vacuum seal at liquid helium temperatures. (Israel). N Pundak et al, Vacuum, 26 (4/5), 1976, 197-201. 42
III.
Vacuum
applications
30. EVAPORATION
AND
DEPOSITION
IN
VACUO
30 2396. Simple electron beam evaporator for aluminum. (USA) Aluminum surl’acc cvaporatcd from Ta or W baskets arc partially osidized. The contamination of the aluminum surfaces could bc rcduccd by clcctron beam evaporation. The assembly used by us is described in this paper. (Germany) C Bcnndorf c( al, Rev Sci /rr.r/rrm~. 47 (6). 1976. 778-779. 30 2397. Apparatus for chemical vapor deposition of silicon dioxide from silanc
gas.
(USA)
A description is given of an apparatus for the rormation of osidc films of uniform thickness by a low tcmperaturc (300 -500 C) chemical vapor deposition process. The reaction gases enter at the top of a rotationally symmclric reaction chamber. By means of locating two fritted-glass disks in the path of the gas. good gas mixing and turbulent conditions are maintained inside the chamber. During the process the nsis of this chamber is moved along a circle, the center of which coincides with that of a stationary substrate holder of circular form. This relative movement results in an averaging of conditions. giving a unirormity of the dielectric layer deposited. Constructing this apparatus is simple because no rotating joints are necessary for feeding in the gases. nor sliding contacts for the heater supply and temperature measuring equipment. (Netherlands) N K Mitra and C J H Hegnen, Rw Sci Iurnxm, 47 (6). 1976. 757-761. 30 2398.
The
influence layers.
of inappropriate
processes
on the
growth
of silicon
(GB) The influences of inappropriate growth processes on epitaxial layers are reviewed and summarized. They cause formation of defects in the grown layer even if the substrate, the various gaseous and other materials and the growth system are or high quality. The influence of a too-high overall deposition rate causes the appearance of ‘pyramids’ on the surface of the grown layer. The mechanism of ‘pyramid’ formation is based on the fact that the growth rate is dependent upon the crystallographic orientation. Small irregular zones on the substrate surface each have several crystallographic orientations, and as a result, ‘pyramids’ can grow there under certain conditions. The influence ol’ too-low growth temperatures causes the appearance of ‘ledges’ and ‘terraces’, i.e.. uneven, rough and sometimes irregular surfaces of the grown layer. The mechanism of formation of such a surface is associated with mobility, migration length and nucleation rates, which are decreased when the temperature is lowered. In addition, a rough surface can be formed as a result of a growth process which takes place in the gaseous phase above and not at the surface. The heterogeneous and homogeneous reaction processes are summarized, and the possibility of explaining through them the appearance of ‘pyramids’ and rough surfaces is reviewed. Experimental results are presented. (Israel) erpitaxial
H
Aharoni,
Vucrcw~~,
96,
(4/5),
1976,
149-157.
30 2399. Stacking faults in silicon epitaxial layers. (GB) A summary is given of a few specific causes responsible for the formation of stacking faults in silicon epitaxial layers grown on silicon substrates. From the technical point of view, these causes are associated with the treatment of the substrate before the growth process and with the prevention of penetration of foreign materials into the layer before and while it is growing. The location of the causes are: in the substrate (various defects and foreign materials which exist there before the growth process); in the epitaxial layer (mainly foreign materials which penetrate during the growth process); and in the interface region at and near the metallurgic junction of the substrate/layer. A brief review of the formation of stacking faults created during the layer growth process is given. In this connection, the subject of crystallographic planes and orientation of the stacking faults which determine its boundaries in respect to the rest of the epitaxial layer is touched upon. Also given is a practical summary of revealing the traces of the stacking faults on the layer surface by chemical etching. The major part of the paper is devoted to two subjects: the various causes responsible for the nucleation and formation of stacking faults and detailed examples of geometrical forms of the traces of the stacking faults on the layer surface. This is done by
abstracts
2391-2399
74/77468DC. This document is in rull technical accord with DIS 3563. It specifies a method for calibrating a vacuum gauge by direct comparison with a reference gauge, and though the method is not limited to a particular prcssurc range, the apparatus to be described has been designed lo cover the vacuum spectrum from 760 torr (atmospheric to IO-(’ torr. Since as stated previously this is judged to be the pressure range over which by far the largest majority of industrial calibrations are required to be made. J D Buckingham, I’acrrwn, 26 (4/5). 1976. 143-147. 32
(Bulgaria) Using a special broadband phase-scnsitivc amplifier, the output signal is investigated of a high-frequency mass-spectromctcr type farvitron having a quasi-parabolic potential well. It is shown that the information on the phase of the output signal allows the determination of the mass of the oscillating ions with a greater accuracy than by a conventional farvitron. M Mikhalev and Kh Tenchov, Rep of Ekcrron Ius/ oJ Bu/g Acad of Scierlc, No 7, 1974, 77-81 (itr B&wriatr). ‘2 2391.
2392.
Some
phase
Calibration
measurements
of a partial
on a sensitive
pressure
analyzer
farvitron.
by an absolute
method.
(USSR) Calibration of a farvitron partial pressure analyzer has been performed with the aid of a pressure reduction calibration equipment. Calibration characteristics for nitrogen are presented. The analyzer is linear up 10 pressures of IOmJ N/m’ to 10e3 N/m’. The relative coefficients of sensitivity for OL, He, Ne and CO, with respect lo N1 are 0.58. 0.14. 0.36-0.38 and 1.16-1.22. respectively. The minimum reliably meas&ablc partial pressure is 6 .. iOm6 N&i’. V V Kuzmin and E K Frolov, Probl o/Atom Scicn aud Trch~ro/, Ser Phys a& T&II of High I’acu~rfn, CON, No I, Kharkov, 1973, 4045 (in Rrrssiun). 23. PLUMBING,
VACUUM
VALVES,
BAFFLES
AND
TRAPS 23
2393.
Ultrahigh
vacuum
lock.
(USA)
An UHV lock is described that makes it possible to change samples, keeping the pressure in the UHV system at 1O-9-1O-1o Torr. The samples are mounted on a sample holder that can be heated up to about 1000°C. (Germany) G Tauber and H Viefhaus, Reel Sci butrrrm, 47 (6), 1976,772-773. 23
(GB) A new type of variable leak was developed to control the flow of gas into the ion source of an electromagnetic isotope separator. It consists essentially of a rotating member which introduces well-defined doses of gas at a predetermined rate into the evacuated enclosure. The inflow rate depends on the geometry of the valve and is linearly proportional to the rotation speed. Thus, the inflow rate may be easily and continuously controlled by adjusting the speed of the motor. The main advantages of the new valve are that it is reliable and convenient to operate-even by remote control, and its response is proportional to an electric signal. The valve is particularly suitable for applications where the inflow rate must be automatically controlled by some feed-back system. Its main drawback is the pulsed shape of its output. This can be corrected by the insertion of a simple filter which, however, results in a reduction in the speed of response. Also the ratio of the limits of the Rowrate range, for a given valve geometry is approximately 1: IO, but the range can be modified by replacing a single component of the valve. Units of various ranges covering rates from 1 mm3 s-l to 1 cm3 s-’ have been built and mounted on the ion sources of the Meira isotope separator with very satisfactory results. (Israel) 2394.
I Cbavet,
Rotating
Vucuurn,
variable
26,
leak
(4/5),
valve.
1976,
203-209.
23 2395. Large diameter cryogenic seals. (GB) Cryogenic vacuum seals are discussed with emphasis on large diameter reusable connections. Both theoretical considerations and experimental results are presented. The main subject is large diameter cryogenic vacuum seals in a horizontal vessel, where thermal distortions are encountered in particular during the cool down stage. We show a large diameter stainless steel flange designs that can take large repeatable thermal shocks and maintain a good vacuum seal at liquid helium temperatures. (Israel). N Pundak et al, Vacuum, 26 (4/5), 1976, 197-201. 42
III.
Vacuum
applications
30. EVAPORATION
AND
DEPOSITION
IN
VACUO
30 2396. Simple electron beam evaporator for aluminum. (USA) Aluminum surl’acc cvaporatcd from Ta or W baskets arc partially osidized. The contamination of the aluminum surfaces could bc rcduccd by clcctron beam evaporation. The assembly used by us is described in this paper. (Germany) C Bcnndorf c( al, Rev Sci /rr.r/rrm~. 47 (6). 1976. 778-779. 30 2397. Apparatus for chemical vapor deposition of silicon dioxide from silanc
gas.
(USA)
A description is given of an apparatus for the rormation of osidc films of uniform thickness by a low tcmperaturc (300 -500 C) chemical vapor deposition process. The reaction gases enter at the top of a rotationally symmclric reaction chamber. By means of locating two fritted-glass disks in the path of the gas. good gas mixing and turbulent conditions are maintained inside the chamber. During the process the nsis of this chamber is moved along a circle, the center of which coincides with that of a stationary substrate holder of circular form. This relative movement results in an averaging of conditions. giving a unirormity of the dielectric layer deposited. Constructing this apparatus is simple because no rotating joints are necessary for feeding in the gases. nor sliding contacts for the heater supply and temperature measuring equipment. (Netherlands) N K Mitra and C J H Hegnen, Rw Sci Iurnxm, 47 (6). 1976. 757-761. 30 2398.
The
influence layers.
of inappropriate
processes
on the
growth
of silicon
(GB) The influences of inappropriate growth processes on epitaxial layers are reviewed and summarized. They cause formation of defects in the grown layer even if the substrate, the various gaseous and other materials and the growth system are or high quality. The influence of a too-high overall deposition rate causes the appearance of ‘pyramids’ on the surface of the grown layer. The mechanism of ‘pyramid’ formation is based on the fact that the growth rate is dependent upon the crystallographic orientation. Small irregular zones on the substrate surface each have several crystallographic orientations, and as a result, ‘pyramids’ can grow there under certain conditions. The influence ol’ too-low growth temperatures causes the appearance of ‘ledges’ and ‘terraces’, i.e.. uneven, rough and sometimes irregular surfaces of the grown layer. The mechanism of formation of such a surface is associated with mobility, migration length and nucleation rates, which are decreased when the temperature is lowered. In addition, a rough surface can be formed as a result of a growth process which takes place in the gaseous phase above and not at the surface. The heterogeneous and homogeneous reaction processes are summarized, and the possibility of explaining through them the appearance of ‘pyramids’ and rough surfaces is reviewed. Experimental results are presented. (Israel) erpitaxial
H
Aharoni,
Vucrcw~~,
96,
(4/5),
1976,
149-157.
30 2399. Stacking faults in silicon epitaxial layers. (GB) A summary is given of a few specific causes responsible for the formation of stacking faults in silicon epitaxial layers grown on silicon substrates. From the technical point of view, these causes are associated with the treatment of the substrate before the growth process and with the prevention of penetration of foreign materials into the layer before and while it is growing. The location of the causes are: in the substrate (various defects and foreign materials which exist there before the growth process); in the epitaxial layer (mainly foreign materials which penetrate during the growth process); and in the interface region at and near the metallurgic junction of the substrate/layer. A brief review of the formation of stacking faults created during the layer growth process is given. In this connection, the subject of crystallographic planes and orientation of the stacking faults which determine its boundaries in respect to the rest of the epitaxial layer is touched upon. Also given is a practical summary of revealing the traces of the stacking faults on the layer surface by chemical etching. The major part of the paper is devoted to two subjects: the various causes responsible for the nucleation and formation of stacking faults and detailed examples of geometrical forms of the traces of the stacking faults on the layer surface. This is done by