Patent US4858557A successfully refreshed from Google Patents.
US4858557A
Expired / Lapsed
US
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Epitaxial reactors
Assignee: L P E SpA
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Filing: 1987-07-15
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Granted: 1989-08-22
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Expires: 2007-07-15
Abstract
Abstract A reactor for chemical vapor deposition of epitaxial layers on crystalline substrates uses a medium frequency heating system, the power for the heating being provided by a multi-turn coil, inducing electrical currents in a susceptor of electrically conductive material, such as graphite, housed in a transparent bell jar. The internal sides of the turns of the coil are optically finished to reflect back heat to the susceptor irradiated therefrom during operation. Heating is controlled by substracting or adding reactive currents from or to different turns of the coil and through properly shaping the walls of the susceptor in order to control temperature gradients therein.
Inventors
- 👤 Vittorio Pozzetti
- 👤 Piergiovanni Poggi
- 👤 Franco Preti
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 12:36
CPC Classifications
C; C23; C23C; C23C16/00; C23C16/44; C23C16/4411; C23C16/46; C30; C30B; C30B25/00; C30B25/02; C30B25/10; C30B25/12
Claims Analysis
Total Claims: 28
Claim 1
Independent Claim
169 words
A reactor for the deposition of epitaxial layers from a vapor phase on crystalline substrates comprising a susceptor rotatable about its axis and heated by means of electrical currents induced by turns of a coil, said susceptor being housed in a bell jar of insulating and optically transparent material, such as quartz, said bell jar being surrounded by a reflector for reflecting to said susceptor the heat irradiated therefrom during operation, said reflector being formed by optically finished internal sides of the turns of the coil, said turns being hollow conductors through which a cooling liquid flows, said turns being spaced apart from each other so as to have minimal discontinuities of the reflector and being fixed in a mechanically steady configuration, and means for controlling local variations in the magnetic field inside the coil, necessitated by required local power variations in said susceptor, said means subtracting or adding reactive currents from or to turns of the coil corresponding to susceptor regions in which said power variations are required.
Claim 2
Dependent Claim
169 words
A reactor for the deposition of epitaxial layers from a vapor phase on crystalline substrates comprising a susceptor rotatable about its axis and heated by means of electrical currents induced by turns of a coil, said susceptor being housed in a bell jar of insulating and optically transparent material, such as quartz, said bell jar being surrounded by a reflector for reflecting to said susceptor the heat irradiated therefrom during operation, said reflector being formed by optically finished internal sides of the turns of the coil, said turns being hollow conductors through which a cooling liquid flows, said turns being spaced apart from each other so as to have minimal discontinuities of the reflector and being fixed in a mechanically steady configuration, and means for controlling local variations in the magnetic field inside the coil, necessitated by required local power variations in said susceptor, said means subtracting or adding reactive currents from or to turns of the coil corresponding to susceptor regions in which said power variations are required.
Claim 3
Dependent Claim
59 words
A reactor as in claim 1 wherein the turns are provided by ring-shaped conductors, lying on planes substantially perpendicular to the susceptor axis in order to induce therein electrical currents perpendicular to said axis, to avoid heating pulsations connected with a perpendicular lack of said currents with respect to said susceptor axis and with the rotation of the susceptor.
Claim 4
Dependent Claim
71 words
A reactor as in claim 1 further including means for air cooling said bell jar, said cooling means including a blower, a nozzle and swirl generator for causing the air to flow between said bell jar and said coil and then outwardly from about said bell jar, a heat exchanger for cooling the air leaving said bell jar and means to pass cooled air from the heat exchanger to said blower.
Claim 5
Dependent Claim
59 words
A reactor as in claim 3 further including a pressurizing chamber surrounding the coil, the arrangement being such that air from said blower passes first to the pressurizing chamber and then passes between the bell jar and the coil both through said nozzle and swirl generator and through supplementary taps consisting of gaps between the turns of said coil.
Claim 6
Dependent Claim
40 words
A reactor as in claim 1 wherein the means to subtract reactive current from turns of said coil include inductors connected between said turns and the means to add reactive current to said turns include capacitors connected between said turns.
Claim 7
Dependent Claim
11 words
A reactor as in claim 5 wherein said inductors are variable.
Claim 8
Dependent Claim
26 words
A reactor as in claim 6 wherein at least one of said inductors is variable by connecting its taps to a short circuit conductor or bridge.
Claim 9
Dependent Claim
23 words
A reactor as in claim 6 wherein at least one of said inductors is variable by means of a ferromagnetic core movable therein.
Claim 10
Dependent Claim
15 words
A reactor as in claim 5 wherein at least one of said capacitors is variable.
Claim 11
Dependent Claim
28 words
A reactor as in claim 9 wherein at least one of said capacitors is incrementally variable by means of a shunt connecting a selectable number of capacitors members.
Claim 12
Dependent Claim
14 words
A reactor as in claim 5 including at least one inductor and capacitor combination.
Claim 13
Dependent Claim
37 words
A reactor as in claim 11 wherein said at least one inductor and capacitor combination is a parallel combination thereof with a capacitor variable by increments and an inductor variable by means of a ferromagnetic movable core.
Claim 14
Dependent Claim
37 words
A reactor as in claim 11 wherein said at least one inductor and capacitor combination is a series combination thereof with a capacitor variable by increments and an inductor variable by means of a ferromagnetic movable core.
Claim 15
Dependent Claim
29 words
A reactor as in claim 13 further including a voltage limiting member connected across said capacitors to limit overvoltages which could be formed in said capacitors near resonance conditions.
Claim 16
Dependent Claim
24 words
A reactor as in claim 1 wherein said coil is provided with ferromagnetic blocks for guiding and limiting the magnetic field outside the coil.
Claim 17
Dependent Claim
26 words
A reactor as in claim 15 wherein said blocks have an angular shape and are provided around the top and the bottom edge of said coil.
Claim 18
Dependent Claim
14 words
A reactor as in claim 16 wherein said blocks consist of ferromagnetic lamination steps.
Claim 19
Dependent Claim
13 words
A reactor as in claim 16 wherein said blocks consist of ceramic ferrite.
Claim 20
Dependent Claim
23 words
A reactor as in claim 15 wherein said ferromagnetic blocks are connected by an external ferromagnetic shell around the outside of said coil.
Claim 21
Dependent Claim
16 words
A reactor as in claim 19 wherein said blocks and said shell consist of ceramic ferrite.
Claim 22
Dependent Claim
18 words
A reactor as in claim 18 wherein said ferrite blocks are connected by ferrite columns outside said coil.
Claim 23
Dependent Claim
68 words
A reactor as in claim 1 wherein said susceptor includes a conducting shell and has the shape of a truncated pyramid with a regular polygonal base, the base having an external and an internal surface, and wherein the internal surface of said shell is provided with depressions aligned and substantially coextensive with pockets or indentations on said external surface accomodating wafers of slices of material to be treated.
Claim 24
Dependent Claim
25 words
A reactor as in claim 22 wherein thickness variations of the susceptor compensate for induced power variations associated with the pyramidal shape of said susceptor.
Claim 25
Dependent Claim
31 words
A reactor as in claim 22 wherein said depressions are planar depressions having the shape of circular trenches, surrounding a central area substantially at the same level of said internal surface.
Claim 26
Dependent Claim
27 words
A reactor as in claim 22 wherein said depressions are circular trenches bevelled starting from a central axis substantially at the same level of said internal surface.
Claim 27
Dependent Claim
31 words
A reactor as in claim 22 wherein said depressions are generally conical surfaces on the internal face of said susceptor and have vertices substantially aligned with the centers of said pockets.
Claim 28
Dependent Claim
44 words
A reactor as in claim 22 wherein the susceptor has lateral corners which are provided with bevellings larger outside than inside in order to maintain constant, or reduce locally, the susceptor thickness and thus maintain, or increase locally, the current density in the same.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-08-21 | 1993-02-20 | 1993-08-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-08-21 | 1997-02-20 | 1997-08-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-08-21 | 2001-02-20 | 2001-08-22 | $7700.00 | Window Closed / Lapsed |