JPH06140405A - Structure of flip chip bump - Google Patents

Abstract

PURPOSE:To obtain structure of a flip chip wherein solder can be prevented from reaching an electrode via a bump, a substrate on which the electrode is formed can be excellently connected with a substrate on which a Pb-Sn based electrode is formed, the operation of solder bonding time has a margin, and the work is facilitated. CONSTITUTION:A bump 13 is formed on an electrode 12 of a substrate 11. A coating film 14 is formed on the substrate surface containing the bump 13. A specified thickness of the coating film 14 is eliminated by an anisotropic etching process E. A solder blocking belt 15 is formed by using the left coating film 14, so as to cover the non-connection part of the bump 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the structure of flip chip bumps, and more particularly to improvement of the structure of Au bumps formed on Al electrodes of a substrate.

[0002]

2. Description of the Related Art Conventionally, a substrate on which an Al electrode is formed and a P
The connection with the substrate on which the b-Sn-based electrode was formed was as shown in FIG.

As shown in the figure, an Al electrode 2 is formed on a substrate 1 located above. This board 1
As shown in FIG. 9, on the Al electrode 2 of Au,
The flip chip bumps (hereinafter, referred to as “Au bumps”) 3 formed in Step 3 are formed by, for example, a wire bonding method. Further, a Pb—Sn system electrode 5 is formed on the substrate 4 located below.

Then, as shown in FIG. 10, the connection between these substrates 1 and 4 is performed by using a Pb-Sn system solder 6 as a joining material, and the Pb-Sn system electrode 5 of the substrate 4 is connected. To the surface of the Au bumps 3 of the substrate 1 so that the solder of the solder 6 is drawn out. If the amount of protrusion of the solder 6 is proper, as shown in the drawing, the boards 1, 4
Although the connection of the is good, its joining work relies on manipulating the instantaneous joining time.

[0005]

By the way, when the boards 1 and 4 are connected to each other as described above, the amount of the solder 6 protruding is determined by the operation of the instantaneous connection time. Therefore,
If the joining time is short, as shown in FIG. 11, the amount of the solder 6 that creeps out is small, and a good connection state can be obtained. However, if the bonding time is long, as shown in FIG. 12, the amount of protrusion of the solder 6 becomes large, and the solder solder covers the entire surface of the Au bump 3 and reaches the Al electrode 2 of the substrate 1. Will be reached.

As described above, the solder solder is the Al of the substrate 1.
When reaching the electrode 2, alloying of Al and Pb—Sn occurs, and there is a problem that cracks occur in this alloy portion due to aging.

Further, there is a problem that the operation of joining time of the solder 6 is not sufficient and the work is difficult.

In view of the above problems, an object of the present invention is to prevent the solder solder from reaching the electrodes via the bumps, and to provide a substrate on which electrodes are formed and a substrate on which Pb-Sn based electrodes are formed. It is an object of the present invention to provide a structure of a flip chip bump which can be satisfactorily connected, has a margin for operation of solder joining time, and can facilitate the work.

[0009]

According to the structure of a flip chip bump of the present invention, the above object is to form a bump on an electrode of a substrate and to form a coating film on the substrate surface including the bump, A predetermined thickness is removed by anisotropic etching treatment such as reactive etching method or ion beam etching method, and a solder cutoff band is formed with the remaining coating film so as to conceal the non-connecting portion of the bump. Is achieved by

[0010]

According to the above structure, the flip-chip bump coated with the solder cut-off zone so as to cover the non-connected portion of the bump is formed on the electrode, and the substrate on which the Pb-Sn system electrode is formed. , When soldering is performed between the Pb-Sn system electrode and the connection portion of the bump which is not covered with the solder cutoff band and these substrates are connected, a solder solder that tends to flow to the surface of the Au bump is provided. Since the solder cut-off zone cuts off, even if the bonding time becomes long and the amount of solder creeping out increases, the surface of the bump is not covered with the solder solder.

This prevents the solder solder from reaching the electrode, and as a result, the substrate on which the electrode is formed and the substrate on which the Pb-Sn system electrode is formed are well connected. . Further, since the solder joining time can be manipulated, the work can be facilitated.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the structure of a flip chip bump according to the present invention will be described in detail below with reference to the accompanying drawings. First, a first embodiment of the structure of the flip chip bump according to the present invention will be described.

As shown in FIG. 1, an Al electrode 12 is formed on the substrate 11. First, this substrate 11
The Au bump 13 is mounted on the Al electrode 12 of.

Next, as shown in FIG. 2, on the substrate 11 having the Au bumps 13 formed on the Al electrodes 12,
For example, SiO _{2 in} which an inorganic compound such as a Si compound (RnSi (OH) _4-n ) is mixed with an organic binder or an organic solvent.
A system coating material is applied and deposited to form an inorganic coating 14 having a predetermined thickness. At this time, the SiO ₂ based coating material is applied so as to penetrate into the gap between the Al electrode 12 and the Au bump 13.

Then, as shown in FIG. 3, the substrate 11 having the inorganic coating 14 applied thereto is subjected to anisotropic etching treatment E from the surface side thereof by a reactive etching method (RIE) or the like.

When the inorganic coating 14 is removed by the anisotropic etching treatment E, only the vertical direction (thickness direction) of the inorganic coating 14 is etched. Therefore, when the inorganic coating 14 is removed to an arbitrary thickness, as shown in FIG. 4, only the connecting portions of the Au bumps 13 are exposed from the inorganic coating 14. That is, the inorganic coating 14 remains between the Au bumps 13,
The unconnected portion of the u bump 13 is hidden by the remaining inorganic coating 14. The remaining inorganic coating 14 forms the solder barrier zone 15.

Next, the operation of the structure of the flip chip bump of the first embodiment will be described. The above-mentioned solder cutoff band
Is formed on the surface half of the Au bump 13 on the side of the Al electrode 12, that is, the solder cutoff band 15 is covered so as to conceal the non-connection portion of the Au bump 13. In particular, as shown in FIG. 5, when the solder blocking band 15 is formed between the Au bumps 13 as well, the Au bump 13 is extremely strong on the Al electrode 12 by the solder blocking band 15. Will be held in.

The inorganic film 1 made of Si oxide or the like
Since the solder blocking zone 15 is formed on the Au bumps 13 by a dry process by applying the reactive etching method using No. 4, there is no secondary contamination due to the process.

Further, since the anisotropic etching process E by the reactive etching method is performed, the solder cut-off zone 1
Since the thickness of 5 and the processing direction can be arbitrarily manipulated, and mask alignment is not required, the placement accuracy of the Au bumps on the substrate is reduced.

Then, S forming the inorganic coating 14
Because iO ₂ based film material is a liquid coating material, in which it is possible to flatly applied and accumulated irrespective of the unevenness of the underlying substrate 11.

When connecting the substrates 11 and 4 by the structure of the flip chip bumps covered with the solder cutoff band 15 so as to conceal the non-connection portions of the Au bumps 13 as described above, FIGS. As shown in FIG. 1, the Au bump 13 is formed on the Al electrode 12 and the substrate 1 is formed.
1 is turned upside down and the substrate 4 on which the Pb-Sn system electrode 5 is formed
Of the Au bump 1 on the Pb-Sn electrode 5
It is provided so that the joint portion of 3 abuts.

After that, the Pb-Sn system electrode 5 of the substrate 4 is
The Pb-Sn solder 6 is used as a bonding material between the solder blocking zone 15 and the unbonded portion of the Au bump 13 to connect the substrates 11 and 4. Then, only the half of the Au bump 13 on the side of the substrate 4 is soldered, and the substrates 11 and 4 are well connected.

When the substrates 11 and 4 are connected in this way,
Since the solder solder that is about to flow on the surface of the Au bump 13 is blocked by the solder blocking band 15 that covers the non-connecting portion of the Au bump 13,
For example, even if the bonding time of the solder 6 is long and the amount of protrusion thereof is large, the surface of the Au bump 13 is not covered with the solder solder.

This prevents the solder solder from reaching the Al electrode 12 of the substrate 11,
Since the alloying of Pb and Sn does not occur, it is possible to avoid the occurrence of cracks at the solder joint. As a result, the substrate 11 on which the Al electrode 12 is formed and the Pb
The substrate 4 on which the -Sn electrode 5 is formed is satisfactorily connected. Further, since it is possible to give a margin to the operation of the joining time of the solder 6, the work can be easily performed.

Further, since the solder barrier zone 15 is formed of the inorganic coating film 14, there is no deterioration of material or gas release due to a high temperature atmosphere during joining, excellent solvent resistance, and permanent moisture resistance (dewetting). Can be obtained with high reliability.

Next, a second embodiment of the structure of the flip chip bump according to the present invention will be described. In the second embodiment, on the substrate 11 in which the Au bumps 13 are formed on the Al electrodes 12, for example, an inorganic derivative electric conductor such as Si oxide, Si nitride, Al oxide, or Al nitride. To P-
The inorganic coating 14 is formed by isotropic deposition by chemical vapor deposition such as CVD to a predetermined thickness.

Then, as shown in FIG. 3, the substrate 11 on which the inorganic coating 14 has been deposited is subjected to anisotropic etching treatment E from the surface side thereof by an ion beam etching method or the like.

When the inorganic film 14 is subjected to anisotropic etching treatment E by an ion beam etching method to remove an arbitrary thickness, as shown in FIG. 5, the Au bumps 13 are not connected depending on the degree of etching. The inorganic coating 14 remains so as to conceal the portion, and the remaining inorganic coating 14 forms the solder blocking zone 15.

The second embodiment has the same operation and effect as the first embodiment.

[0030]

As described above, according to the structure of the flip-chip bump according to the present invention, the solder solder is prevented from reaching the electrodes through the bumps, and the substrate on which the electrodes are formed and the Pb-Sn. It is possible to satisfactorily connect to the substrate on which the system electrode is formed, and to give a margin to the operation of soldering time so that the work can be facilitated.

[Brief description of drawings]

FIG. 1 is a schematic view showing a state in which an Au bump is placed on an Al electrode of a substrate in the present invention.

FIG. 2 is a schematic view showing a state in which an inorganic film is deposited on a substrate on which Au bumps are mounted in the present invention.

FIG. 3 is a schematic view showing a state where an inorganic film is subjected to anisotropic etching treatment in the present invention.

FIG. 4 is a schematic view showing a structure of a flip chip bump in which Au bumps are exposed from a solder shielding band by anisotropic etching treatment in the present invention.

FIG. 5 is a schematic view showing a structure of a flip chip bump in which a solder shielding band is formed only on a non-connecting portion of an Au bump in the present invention.

6 is a schematic view showing a state in which substrates are solder-bonded using the structure of the flip chip bump of FIG.

FIG. 7 is a schematic view showing a state in which substrates are solder-bonded using the structure of the flip chip bump of FIG.

FIG. 8 is a schematic view showing a bonded state of a substrate on which an Al electrode is formed and a substrate on which a Pb—Sn based electrode is formed.

FIG. 9 is a schematic view showing a state in which an Au bump is formed on an Al electrode of a substrate in the related art.

FIG. 10 is a schematic diagram showing a state in which the solder is properly joined for a conventional time.

FIG. 11 is a schematic view showing a conventional bonded state in which the solder bonding time is short.

FIG. 12 is a schematic diagram showing a conventional bonding state in which the solder bonding time is long.

[Explanation of symbols]

 6 Solder 11 Substrate 12 Al Electrode 13 Au Bump 14 Inorganic Film 15 Solder Shielding Band E Anisotropic Etching Treatment

Claims (3)

[Claims] 1. A bump is formed on an electrode of a substrate, a film is formed on a surface of the substrate including the bump, and the film is anisotropically etched to remove a predetermined thickness. A flip-chip bump structure, characterized in that a solder barrier zone is formed with the above-mentioned coating film that remains so as to conceal the above. 2. The coating film is formed by coating an inorganic material with an organic material on the surface of a substrate including the bumps, and the anisotropic etching process is performed by a reactive etching method. The structure of the flip chip bump according to claim 1. 3. The film is formed by isotropically depositing an inorganic dielectric material on a substrate surface including the bumps by a chemical vapor deposition method, and the anisotropic etching treatment is performed by an ion beam.
The structure of the flip chip bump according to claim 1, wherein the structure is performed by an etching method.