US4645116A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Fluxless bonding of microelectronic chips
Assignee: Nokia Bell Labs
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Filing: 1984-09-05
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Granted: 1987-02-24
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Expires: 2004-09-05
Abstract
Abstract Indium is used to bond semiconductor lasers to their heat-sinks without the presence of a corrosive liquid flux. Fluxless bonding is achieved in a vacuum chamber in reducing ambients of CO or H 2 . Low strain bonds are achieved at bonding temperatures of approximately 180°-240° C. in CO and 220°-230° C. in H 2 . Void-free bonds are achieved in CO at temperatures as low as about 205° C. The technique is applicable to other microelectronic chips such as LEDs, for example.
Inventors
- 👤 Gerard E. Henein
- 👤 Ralph T. Hepplewhite
- 👤 Bertram Schwartz
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 00:12
CPC Classifications
H; H10; H10W; H10W72/00; H10W72/071; H10W72/073; H10W72/0711; H10W72/30; H10W72/07118; H10W72/07331; H10W72/07334; H10W72/07336; H10W72/07341; H10W72/07351; H10W72/07352; H10W72/321; H10W72/351; H10W72/352; H10W72/90; H10W72/951; H10W72/952; H10W90/00; H10W90/701; H10W90/731; H10W90/736
Claims Analysis
Total Claims: 37
Claim 1
Independent Claim
188 words
A method of manufacturing a device, which includes bonding a metal layer on a microelectronic chip to a metalized support member, comprising the steps of: (a) providing a bonding layer of soft, ductile bonding material on at least one of the metal layer and the support member, the bonding layer having a tendency to form an oxide thereon, said oxide being reducible with the consequent generation of a gaseous reduction product, (b) placing the assembly of the bonding layer, chip and support member in an evacuable chamber, (c) reducing the pressure in the chamber to a subatmospheric pressure in order to decrease the partial pressure of said gaseous reduction product, (d) introducing a reducing gas into the chamber, (e) at a time between steps (a) and (f), bringing the bonding layer into contact with the other of the metal layer and the support member in the absence of any liquid flux, and (f) heating the bonding layer to a temperature which is above its melting point, said temperature of step (f) and said pressure of step (c) being effective for said reducing gas to reduce said oxide thereon.
Claim 2
Independent Claim
188 words
A method of manufacturing a device, which includes bonding a metal layer on a microelectronic chip to a metalized support member, comprising the steps of: (a) providing a bonding layer of soft, ductile bonding material on at least one of the metal layer and the support member, the bonding layer having a tendency to form an oxide thereon, said oxide being reducible with the consequent generation of a gaseous reduction product, (b) placing the assembly of the bonding layer, chip and support member in an evacuable chamber, (c) reducing the pressure in the chamber to a subatmospheric pressure in order to decrease the partial pressure of said gaseous reduction product, (d) introducing a reducing gas into the chamber, (e) at a time between steps (a) and (f), bringing the bonding layer into contact with the other of the metal layer and the support member in the absence of any liquid flux, and (f) heating the bonding layer to a temperature which is above its melting point, said temperature of step (f) and said pressure of step (c) being effective for said reducing gas to reduce said oxide thereon.
Claim 3
Dependent Claim
13 words
The method of claim 1 wherein said bonding material comprises a tin alloy.
Claim 4
Dependent Claim
14 words
The method of claim 2 wherein said gas comprises essentially pure H 2 .
Claim 5
Dependent Claim
41 words
The method of claim 3 wherein in step (d) the partial pressure of water vapor P H .sbsb.2 O and the partial pressure of hydrogen P H .sbsb.2 are related as P H .sbsb.2 O /P H .sbsb.2 ≲1×10 -2 .
Claim 6
Dependent Claim
10 words
The method of claim 2 wherein said gas comprises CO.
Claim 7
Dependent Claim
36 words
The method of claim 5 wherein in step (d) the partial pressure of carbon dioxide P CO .sbsb.2 and the partial pressure of carbon monoxide P CO are related as P CO .sbsb.2 /P CO ≲1.08.
Claim 8
Dependent Claim
11 words
The method of claim 1 wherein said bonding material comprises indium.
Claim 9
Dependent Claim
14 words
The method of claim 7 wherein said gas comprises essentially pure H 2 .
Claim 10
Dependent Claim
41 words
The method of claim 8 wherein in step (d) the partial pressure of water vapor P H .sbsb.2 O and the partial pressure of hydrogen P H .sbsb.2 are related as P H .sbsb.2 O /P H .sbsb.2 ≲9×10 -5 .
Claim 11
Dependent Claim
34 words
The method of claim 9 wherein in step (c) the pressure of the chamber is reduced to at least about 10 -5 Torr and P H .sbsb.2 is at least about 100 μm Hg.
Claim 12
Dependent Claim
28 words
The method of claim 10 for making a low strain bond wherein in step (f) the indium bonding layer is heated to a temperature of about 220°-230° C.
Claim 13
Dependent Claim
21 words
The method of claim 11 wherein the metal layer on the chip and metalization on the support member both comprise gold.
Claim 14
Dependent Claim
21 words
The method of claim 12 wherein the chip comprises a semiconductor laser and the support member comprises a copper heat sink.
Claim 15
Dependent Claim
10 words
The method of claim 7 wherein said gas comprises CO.
Claim 16
Dependent Claim
38 words
The method of claim 14 wherein in step (d) the partial pressure of carbon dioxide P CO .sbsb.2 and the partial pressure of carbon monoxide P CO are related as P CO .sbsb.2 /P CO ≲2×10 -2 .
Claim 17
Dependent Claim
33 words
The method of claim 15 wherein in step (c) the pressure in the chamber is reduced to at least about 10 -5 Torr and P CO is at least about 0.5 μm Hg.
Claim 18
Dependent Claim
28 words
The method of claim 16 for making a low strain bond wherein in step (f) the indium bonding layer is heated to a temperature of about 180°-240° C.
Claim 19
Dependent Claim
28 words
The method of claim 17 for making a bond which also exhibits essentially complete wetting wherein the bonding layer is heated to a temperature of about 205°-230° C.
Claim 20
Dependent Claim
22 words
The method of claim 18 wherein the metal layer on the chip and the metalization on the support member both comprise gold.
Claim 21
Dependent Claim
21 words
The method of claim 19 wherein the chip comprises a semiconductor laser and the support member comprises a copper heat sink.
Claim 22
Independent Claim
195 words
A method of manufacturing a device, which includes bonding a semiconductor laser chip to a heat sink, comprising the steps of: (a) forming a gold bonding pad on the chip, (b) forming a gold coating on the heat sink, (c) forming an indium bonding layer on the gold coating, the indium layer having a tendency to form an oxide thereon, said oxide being reducible with the consequent generation of a gaseous reduction product, (d) placing the chip and heat sink in an evacuable chamber, (e) reducing the pressure in the chamber to a subatmospheric pressure in order to reduce the partial pressure of said gaseous reduction product, (f) introducing into the chamber a reducing gas selected from the group consisting of CO and essentially pure H 2 , (g) at a time between steps (c) and (h), bringing the indium bonding layer into contact with the cold bonding pad in the absence of any liquid flux, and (h) heating the bonding layer to a temperature which is above the melting point of indium, said temperature of step (h) and said pressure of step (e) being effective for said reducing gas to reduce said oxide thereon.
Claim 23
Independent Claim
195 words
A method of manufacturing a device, which includes bonding a semiconductor laser chip to a heat sink, comprising the steps of: (a) forming a gold bonding pad on the chip, (b) forming a gold coating on the heat sink, (c) forming an indium bonding layer on the gold coating, the indium layer having a tendency to form an oxide thereon, said oxide being reducible with the consequent generation of a gaseous reduction product, (d) placing the chip and heat sink in an evacuable chamber, (e) reducing the pressure in the chamber to a subatmospheric pressure in order to reduce the partial pressure of said gaseous reduction product, (f) introducing into the chamber a reducing gas selected from the group consisting of CO and essentially pure H 2 , (g) at a time between steps (c) and (h), bringing the indium bonding layer into contact with the cold bonding pad in the absence of any liquid flux, and (h) heating the bonding layer to a temperature which is above the melting point of indium, said temperature of step (h) and said pressure of step (e) being effective for said reducing gas to reduce said oxide thereon.
Claim 24
Dependent Claim
35 words
The method of claim 21 wherein the chamber pressure is reduced to at least about 10 -5 Torr and the gas comprises essentially pure H 2 at a pressure in excess of 100 μm Hg.
Claim 25
Dependent Claim
23 words
The method of claim 22 wherein the bonding layer is heated to about 220°-230° C. so as to effect a low strain bond.
Claim 26
Dependent Claim
32 words
The method of claim 21 wherein the chamber presure is reduced to at least about 10 -5 Torr and the gas comprises CO at a pressure in excess of 0.5 μm Hg.
Claim 27
Dependent Claim
21 words
The method of claim 24 wherein the bonding layer is heated to about 180°-240° C. to effect a low strain bond.
Claim 28
Dependent Claim
33 words
The method of claim 25 wherein the bonding layer is heated to about 205°-230° C. to effect a bond which also exhibits essentially complete wetting of the indium on the gold bonding pad.
Claim 29
Independent Claim
22 words
The method of claims 22, 24, or 26 wherein the bonding layer is heated by applying electrical current to the heat sink.
Claim 30
Independent Claim
28 words
The method of claims 21, 24, or 26 wherein the chip is a double heterostructure comprising layers of material selected from the GaAs-AlGaAs and the InP-InGaAsP materials systems.
Claim 31
Independent Claim
157 words
A method of manufacturing a device, which includes bonding a gold bonding pad on a semiconductor laser chip to a gold-plated copper stud via an indium layer evaporated on the stud, comprisng the steps of: (a) placing the chip and heat sink in an evacuable chamber, (b) reducing the chamber pressure to at least about 10 -5 Torr in order to reduce the partial pressure of CO 2 , (c) introducing into the chamber a reducing gas comprising CO at a pressure of at least 0.5 μm Hg, (d) at a time prior to step (e), bringing the indium layer into contact with the gold bonding pad in the absence of any liquid flux, and (e) heating the bonding layer to a temperature in the range of about 205°-230° C. so as to effect a bond between the chip and stud which exhibits a stress less than about 10 8 dyn/cm 2 and which is essentially void-free.
Claim 32
Independent Claim
157 words
A method of manufacturing a device, which includes bonding a gold bonding pad on a semiconductor laser chip to a gold-plated copper stud via an indium layer evaporated on the stud, comprisng the steps of: (a) placing the chip and heat sink in an evacuable chamber, (b) reducing the chamber pressure to at least about 10 -5 Torr in order to reduce the partial pressure of CO 2 , (c) introducing into the chamber a reducing gas comprising CO at a pressure of at least 0.5 μm Hg, (d) at a time prior to step (e), bringing the indium layer into contact with the gold bonding pad in the absence of any liquid flux, and (e) heating the bonding layer to a temperature in the range of about 205°-230° C. so as to effect a bond between the chip and stud which exhibits a stress less than about 10 8 dyn/cm 2 and which is essentially void-free.
Claim 33
Dependent Claim
20 words
The method of claim 21, 22, 24 or 26 wherein the bonding layer is heated by an RF induction coil.
Claim 34
Dependent Claim
93 words
The method of claim 30 for bonding a plurality of laser chips to a plurality of heat sinks wherein, in step (d), the chamber includes therein a circular susceptor having a plurality of mounts around the periphery thereof for receiving the heat sinks, the coil surrounding the susceptor in the proximity of the heat sinks, in step (d), the chips are positioned on the heat sinks, and in step (h) the bonding layers are heated by applying RF power to the coil to raise the temperature of the layers to the bonding temperature.
Claim 35
Dependent Claim
31 words
The method of claim 31 further including, after step (h), the additional step (i) of cooling the bonded-chip and heat-sink-assemblies by introducing into the chamber a flow of N 2 gas.
Claim 36
Dependent Claim
88 words
The method of claim 30 for bonding a plurality of laser chips to a plurality of heat sinks wherein, in step (d), the chamber includes an elongated tube and a susceptor therein having a plurality of mounts for positioning the heat sinks along the tube, the coil being movably mounted around the tube, and in step (h), the bonding layers are heated by applying RF power to the coil to raise the temperature of the layers to the bonding temperature and by moving the coil along the tube.
Claim 37
Dependent Claim
31 words
The method of claim 29 further including, after step (e), the additional step (f) of cooling the bonded-chip and heat-sink-assemblies by introducing into the chamber a flow of N 2 gas.
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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) | 1990-02-23 | 1990-08-25 | 1991-02-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-02-23 | 1994-08-25 | 1995-02-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-02-23 | 1998-08-25 | 1999-02-24 | $7700.00 | Window Closed / Lapsed |