Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Reexamination Certificate
2002-08-13
2004-05-25
Whitehead, Jr., Carl (Department: 2827)
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
C174S261000, C361S760000, C361S771000, C257S737000, C257S738000, C257S778000
Reexamination Certificate
active
06740823
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims priority of Japanese Patent Application No. Hei 11-14554, filed, the contents being incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a solder bonding method, and an electronic device and a process for fabricating the electronic device, more specifically to a solder bonding method using a solder material containing Sn as a main component, and an electronic device and a process for fabricating the electronic device.
Recently, in view of the high-speed operation of semiconductor devices, techniques for short wiring lengths have been required. What is noted is flip chip bonding in which specifically solder bumps formed on a semiconductor chip are mounted on a circuit substrate with electrodes formed on, and are melted by heating for bonding.
The solder bonding method by the conventional flip chip bonding will be explained with reference to FIG.
4
.
First, an electrical wiring
111
is formed of an Al film on a semiconductor substrate
110
with a prescribed device. Next, an electrode
116
is formed of a Ti film
112
, an Ni film
113
and an Au film
114
on an electrical wiring
111
, and a solder bump
118
is formed on the electrode
116
.
On the other hand, an electrode
130
is formed of a Cr film
122
, a Cu film
124
, an Ni film
126
and an Au film
128
on an alumina substrate
120
with a prescribed circuit. Thus, the circuit substrate
132
with the electrode
130
formed on is formed
Then, the solder bump
118
on the semiconductor substrate
110
is aligned with the electrode
130
on the circuit substrate
120
, and is heated for the flip chip bonding. Such flip chip bonding makes the connection by means of lead wires unnecessary. The wiring length can be short.
Conventionally, Pb—Sn (Pb: lead, Sn: tin)-based solder materials have been widely used in the flip chip bonding. However, the Pb contained in Pb—Sn-based solder materials have isotopes, and the isotopes are intermediate products or terminal products of the decay series of U (uranium) and Th (thorium). Uranium (U) and thorium (Th) decay by the emission of He (helium), the solder materials emit &agr;-rays. The &agr;-rays affect the operations of semiconductor devices, often causing the so-called soft errors. In a case that Pb flows into soil, the Pb is solved by acid rain, often affecting environments. From the ecological viewpoint, solder materials containing Pb as a non-main component are required.
As a solder material which replaces the Pb—Sn-based solder materials, solder materials containing Sn as a main component is noted.
However, in a case that a solder material containing Sn as a main component is used, because the Ni and Cu in the electrodes
116
,
130
are reactive to the Sn in the solder hump
118
, heat applied by the flip chip bonding produces metal compounds, etc., such as Ni—Sn, Cu—Sn, etc. When the Ni reacts to the Sn, and the Ni film
113
is lost, it is difficult that the bonding between the solder bump
118
, and the electrodes
116
,
130
can be satisfactory because the Ti film
112
, for example, and the solder bump
118
are incompatible with each other. In reliability test, such as a heat-cycle test, etc., the bonding was defective, and conduction, etc. are unsatisfactory. The reliability is poor.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a solder bonding method, and an electronic device and a process for fabricating the electronic device, which make the bonding satisfactory even by the use of a solder material containing Sn as a main component.
The above-described object is achieved by a solder bonding method comprising the step of solder bonding a first electrode to a second electrode having a solder bump of mainly Sn on an upper surface thereof, the first electrode and/or the second electrode including a metal layer of an alloy layer containing Ni and P, an alloy layer containing Ni and B, or an alloy layer containing Ni, W and P. The metal layer of an alloy layer containing impurities, such as P, etc. can prevent the Ni of the metal layer from combining with the Sn in the solder bump. Accordingly, good bonded states can be obtained.
The above-described object is achieved by a solder bonding method comprising the step of solder bonding a first electrode to a second electrode having a solder bump of mainly Sn formed on an upper surface thereof, the first electrode and/or the second electrode including a metal layer of mainly Ni, and the solder bonding step being followed by the step of heat treating the alloy layer. The heat treatment can crystallize the metal layer, whereby the Ni of the metal layer can be prevented from combining with the Sn in the solder bump.
The above-described object is achieved by an electronic device comprising a first substrate including a first electrode, a second substrate including a second electrode having a solder bump of mainly Sn formed on an upper surface thereof, the first electrode and the second electrode being solder bonded to each other, the first electrode and/or the second electrode including a metal layer of an alloy layer containing Ni and P, an alloy layer containing Ni and B, or an alloy layer containing Ni, W and P. The metal layer of an alloy layer containing impurities, such as P, etc. can prevent the Ni of the metal layer from combining with the Sn in the solder bump. Accordingly, good bonded states can be obtained. Electronic devices having good bonded states can be provided.
The above-described object is achieved by an electronic device fabrication process comprising the step of solder bonding a first electrode formed on a first substrate to a second electrode which is formed on a second substrate and has a solder bump of mainly Sn formed on an upper surface thereof, the first electrode and/or the second electrode including a metal layer of an alloy layer containing Ni and P, an alloy layer containing Ni and B, or an alloy layer containing Ni, W and P. The metal layer of an alloy layer containing impurities, such as P, etc. can prevent the Ni of the metal layer from combining with the Sn in the solder bump. Accordingly, a process for fabricating electronic devices having good bonded states can be provided.
The above-described object is achieved by an electronic device fabrication process comprising the step of solder bonding a first electrode formed on a first substrate to a second electrode which is formed on a second substrate and has a solder bump of mainly Sn formed on an upper surface thereof, the first electrode and/or the second electrode including a metal layer of mainly Ni, and the step of heat treating the metal layer being followed by the solder bonding step. The heat treatment can crystallize the metal layer, whereby the Ni of the metal layer can be prevented from combining with the Sn in the solder bump
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Mallory et al., Electrochemical Society Fall Meeting, pp. 423-424, 1975, held on Oct. 5-10, 1975, Dallas, TX.
Jr. Carl Whitehead
Patel I B
Westerman Hattori Daniels & Adrian LLP
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