Fluxless bonding of microelectronic chips
AssigneeAT&T Bell Laboratories
InventorsGerard E. Henein, Ralph T. Hepplewhite, Bertram Schwartz
Life of this patent
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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.sub.2. Low strain bonds are achieved at bonding temperatures of approximately 180.degree.-240.degree. C. in CO and 220.degree.-230.degree. C. in H.sub.2. Void-free bonds are achieved in CO at temperatures as low as about 205.degree. C. The technique is applicable to other microelectronic chips such as LEDs, for example.
Claims34
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.
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.sub.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.
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.sup.-5 Torr in order to reduce the partial pressure of CO.sub.2,
- (c) introducing into the chamber a reducing gas comprising CO at a pressure of at least 0.5 .mu.m 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.degree.-230.degree. C. so as to effect a bond between the chip and stud which exhibits a stress less than about 10.sup.8 dyn/cm.sup.2 and which is essentially void-free.
Dependencies are inferred from the claim text.