US4349394A
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Method of making a zener diode utilizing gas-phase epitaxial deposition
Assignee: Siemens Corp
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Filing: 1980-11-13
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Granted: 1982-09-14
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Expires: 2000-11-13
Abstract
Abstract A method of making a Zener diode having a Zener voltage in the range of 2.4-3.3 volts. The PN junction is preferably formed by selective epitaxial deposition of P-type silicon on a previously oxidized N-type silicon wafer in an opened region where the oxide has been etched away. The N-type wafer may be a uniform silicon wafer with resistivity in the range of 0.004 to 0.006 OMEGA -cm or a low resistivity N-type wafer having a 5-20 mu m thick N-type silicon epitaxial layer with a resistivity in a range of 0.004-0.006 OMEGA -cm. The selectively deposited P-type layer may have a resistivity of 0.001-0.003 OMEGA -cm and a thickness of 1.5-3.0 mu m. The P-type layer is grown in a gas phase epitaxial reactor by etching the N-type wafer at a first temperature and then depositing heavily-doped silicon at a second, lower temperature.
Inventors
- 👤 Lawrence S. Wei
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 08:59
CPC Classifications
H; H10; H10P; H10P14/00; H10P14/20; H10P14/29; H10P14/2901; H10P14/2902; H10P14/2905; H10D; H10D8/00; H10D8/20; H10D8/25; H10P14/24; H10P14/27; H10P14/271; H10P14/2926; H10P14/34; H10P14/3402; H10P14/3404; H10P14/3411; H10W; H10W20/00; H10W20/40; H10W74/00; H10W74/10; H10W74/131; H10W74/137; Y; Y10; Y10S; Y10S438/00; Y10S438/983
Claims Analysis
Total Claims: 41
Claim 1
Independent Claim
167 words
A method of making a Zener diode having a Zener voltage in a range of 2.4 to 3.3 volts, said method comprising the steps of: (a) providing a silicon wafer of one conductivity type having an exposed surface, said wafer having a resistivity at its surface in the range of 0.003 to 0.006 Ω-cm; and (b) growing a heavily-doped silicon layer of opposite conductivity type on said exposed surface by epitaxial deposition, said growing step comprising the steps of: (1) etching said exposed surface at a first temperature above 1100° C. to clean said surface; and (2) depositing heavily doped silicon on said exposed surface by epitaxial growth in a gas phase epitaxial reactor using silane (SiH 4 ) as a silicon source in the presence of a gaseous dopant, said epitaxial growth being effected at a second temperature in the range of 975°-1025° C. depending upon the Zener voltage desired, the heavily doped silicon layer so formed having a resistivity in the range of 0.001-0.003 Ω-cm.
Claim 2
Independent Claim
167 words
A method of making a Zener diode having a Zener voltage in a range of 2.4 to 3.3 volts, said method comprising the steps of: (a) providing a silicon wafer of one conductivity type having an exposed surface, said wafer having a resistivity at its surface in the range of 0.003 to 0.006 Ω-cm; and (b) growing a heavily-doped silicon layer of opposite conductivity type on said exposed surface by epitaxial deposition, said growing step comprising the steps of: (1) etching said exposed surface at a first temperature above 1100° C. to clean said surface; and (2) depositing heavily doped silicon on said exposed surface by epitaxial growth in a gas phase epitaxial reactor using silane (SiH 4 ) as a silicon source in the presence of a gaseous dopant, said epitaxial growth being effected at a second temperature in the range of 975°-1025° C. depending upon the Zener voltage desired, the heavily doped silicon layer so formed having a resistivity in the range of 0.001-0.003 Ω-cm.
Claim 3
Dependent Claim
14 words
The method defined in claim 1, wherein said wafer has a uniform resistivity throughout.
Claim 4
Dependent Claim
38 words
The method defined in claim 1, wherein said wafer comprises a silicon epitaxial layer of said one conductivity type having a resistivity in the range of 0.003-0.006 Ω-cm on a low resistivity substrate of the same conductivity type.
Claim 5
Independent Claim
23 words
The method defined in any one of claims 1-3, wherein said one conductivity type is N-type and said opposite conductivity type is P-type.
Claim 6
Dependent Claim
20 words
The method defined in claim 3, wherein said silicon epitaxial layer has a thickness in the range of 5-20 μm.
Claim 7
Dependent Claim
49 words
The method defined in claim 1, further comprising the step, prior to deposition, of forming an insulating layer on the surface of said wafer having a window therein exposing said surface; wherein said heavily-doped silicon layer is grown on said exposed surface by selective epitaxial deposition through said window.
Claim 8
Dependent Claim
13 words
The method defined in claim 6, wherein said insulating layer is an oxide.
Claim 9
Dependent Claim
19 words
The method defined in claim 6, wherein said insulating layer has a thickness in the range of 0.5-1.5 μm.
Claim 10
Dependent Claim
27 words
The method defined in claim 6, wherein said insulating layer forms a ring with a width of 1-2 mils and an inner window diameter of 1-13 mils.
Claim 11
Dependent Claim
44 words
The method defined in claim 1, wherein said heavily-doped layer has such a thickness that the PN junction formed at the base of said heavily-doped layer is neither physically nor electrically affected by a conductor electrode which is subsequently deposited on said heavily-doped layer.
Claim 12
Dependent Claim
19 words
The method defined in claim 10, wherein said heavily-doped layer has a thickness in the range of 1.5-3.0 μm.
Claim 13
Dependent Claim
17 words
The method defined in claim 1, wherein said first temperature is in the range of 1100°-1150° C.
Claim 14
Dependent Claim
14 words
The method defined in claim 12, wherein said first temperature is approximately 1125° C.
Claim 15
Dependent Claim
18 words
The method defined in claim 12, wherein said first temperature is maintained for a period of 0.5-2.0 minutes.
Claim 16
Dependent Claim
16 words
The method defined in claim 14, wherein said first temperature is maintained for approximately 1.0 minute.
Claim 17
Dependent Claim
24 words
The method defined in claim 12, wherein step (b) (1) includes etching said exposed surface with 0.1-1% of hydrogen chloride in a carrier gas.
Claim 18
Dependent Claim
24 words
The method defined in claim 16, wherein step (b) (1) includes etching said exposed surface with approximately 0.5% hydrogen chloride in a carrier gas.
Claim 19
Dependent Claim
12 words
The method defined in claim 16, wherein said carrier gas is hydrogen.
Claim 20
Dependent Claim
27 words
The method defined in claim 1, wherein said second temperature is in the range of 980°-1000° C., thereby to provide a Zener voltage of approximately 2.4 volts.
Claim 21
Dependent Claim
14 words
The method defined in claim 19, wherein said second temperature is approximately 990° C.
Claim 22
Dependent Claim
18 words
The method defined in claim 19, wherein said second temperature is maintained for a period of 9-12 minutes.
Claim 23
Dependent Claim
19 words
The method defined in claim 21, wherein said second temperature is maintained for a period of approximately 11 minutes.
Claim 24
Dependent Claim
17 words
The method defined in claim 1, wherein said silane has a concentration in the range of 0.04-0.06%.
Claim 25
Dependent Claim
15 words
The method defined in claim 23, wherein said silane has a concentration of approximately 0.05%.
Claim 26
Dependent Claim
19 words
The method defined in claim 1, wherein said dopant is selected from the group consisting of borane and arsene.
Claim 27
Dependent Claim
17 words
The method defined in claim 25, wherein said dopant has a concentration in the range of 0.00005-0.0002%.
Claim 28
Dependent Claim
15 words
The method defined in claim 26, wherein said dopant has a concentration of approximately 0.0001%.
Claim 29
Dependent Claim
30 words
The method defined in claim 1, wherein hydrogen chloride is also introduced into said epitaxial reactor during step (b) (2) to control the growth of silicon on said insulating layer.
Claim 30
Dependent Claim
18 words
The method defined in claim 28, wherein said hydrogen chloride has a concentration in the range of 0.1-0.3%.
Claim 31
Dependent Claim
16 words
The method defined in claim 29, wherein said hydrogen chloride has a concentration of approximately 0.125%.
Claim 32
Dependent Claim
19 words
The method defined in claim 1, wherein hydrogen gas is also present in said epitaxial reactor as a carrier.
Claim 33
Dependent Claim
26 words
The method defined in claim 6, further comprising the step of gettering said wafer with said insulating layer prior to formation of a PN junction thereon.
Claim 34
Dependent Claim
16 words
The method defined in claim 32, wherein said gettering step inclues doping said wafer with phosphorus.
Claim 35
Dependent Claim
33 words
The method defined in claim 6, further comprising the step of depositing a layer of passivation material on said insulating and said heavily-doped layer at a temperature not in excess of 900° C.
Claim 36
Dependent Claim
14 words
The method defined in claim 22, wherein said passivation material is a frit glass.
Claim 37
Dependent Claim
14 words
The method defined in claim 34, wherein said passivation material is a silicon nitride.
Claim 38
Dependent Claim
37 words
The method defined in claim 34, further comprising the step of opening a window through said passivation material to said heavily-doped layer and depositing metallization onto said heavily-doped layer through said window to provide an electrical contact.
Claim 39
Dependent Claim
15 words
The method defined in claim 37, wherein said metallization is palladium silicide followed by silver.
Claim 40
Dependent Claim
22 words
The method defined in claim 37 further comprising the step of depositing a second metallization on the back side of said wafer.
Claim 41
Dependent Claim
15 words
The method defined in claim 37, wherein said second metallization is chromium followed by silver.
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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) | 1985-09-13 | 1986-03-15 | 1986-09-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1989-09-13 | 1990-03-15 | 1990-09-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1993-09-13 | 1994-03-15 | 1994-09-14 | $7700.00 | Window Closed / Lapsed |