SEMICONDUCTOR CHIP WITH SOLDER BUMP SUPPRESSING GROWTH OF INTER-METALLIC COMPOUND AND METHOD OF FABRICATING THE SAME

Description

TECHNICAL FIELD

The present invention relates to a semiconductor chip with a solder bump and a method of fabricating the same, and more particularly, to a semiconductor chip having a solder bump suppressing growth of an inter-metallic compound and a method of fabricating the same.

BACKGROUND ART

In general, a semiconductor package is fabricated by employing a wire bonding technique to electrically connect electrode terminals of a printed circuit board with pads of a semiconductor chip by means of conductive wires. However, since the technique increases a size of the semiconductor package as compared to that of the semiconductor chip and it takes much time to complete a wire bonding process, it is limited to downsizing and mass-production of semiconductor chips.

Particularly, due to high integration, high performance, and high speed of the semiconductor chip, various efforts to downsize and mass-produce the semiconductor package are tried. This recent trial results in a proposal for the semiconductor package in which the electrode terminals of a printed circuit board are directly and electrically connected with the electrode pads of a semiconductor chip through metal bumps such as solder bumps formed on the electrode pads of the semiconductor chip.

This conventional semiconductor package fabricated through solder bumps will be described below with reference to FIG. 1.

FIG. 1 is a sectional view illustrating a conventional semiconductor chip having a solder bump.

Specifically, FIG. 1 illustrates that a solder bump 30 is just formed on a conventional semiconductor chip 10 before packaging work on the semiconductor chip using solder is completed.

As shown in FIG. 1, the semiconductor chip 10 has an electrode pad 11 formed thereon. Also, the semiconductor chip 10 has a dielectric layer 21 formed thereon to allow a top surface of the electrode pad 11 to be exposed. One or more under bump metal (UBM) layers, usually, three UBM layers 22, 23 and 24 are formed on the electrode pad 11, the top surface of which is exposed by the dielectric layer 21. Here, the three UBM layers include an adhesion layer 22, a diffusion barrier layer 23, and a wettable layer 24. The solder bump 30 is finally formed on the uppermost layer 24 of the UBM layers 22, 23 and 24. Here, when being formed, the solder bump 30 reacts with the UBM layers 22, 23 and 24, so that an inter-metallic compound (IMC) is created at an interface between the solder bump 30 and the UBM layers 22, 23 and 24. The creation of IMC brings about a wetting phenomenon between the solder bump 30 and the UBM layers 22, 23 and 24, and thereby practical mechanical connection is completed.

However, when the semiconductor package connected by the solder bump 30 is actually used, heat can be generated from the solder bump. This heat causes the IMC having brittle mechanical property to unexpectedly grow at the interface between the solder bump 30 and the UBM layers 22, 23 and 24, and thus the IMC may be thicker than expected. This phenomenon may produce a result of weakening the mechanical property of the semiconductor package, and exert a great influence on reliability of the semiconductor package.

Meanwhile, there may be other interfacial phenomena influencing the reliability of the semiconductor package. Among them, one is a phenomenon in which the solder bump 30 is melted into the UBM layers 22, 23 and 24. As a result, the UBM layers 22, 23 and 24 are lost, and thus the solder bump 30 comes into direct contact with a metal pad 11 in the semiconductor chip 10, so that a failure takes place between the solder bump 30 and the metal pad 11 of the semiconductor chip 10 which has bad wettability.

DISCLOSURE OF THE INVENTION

Therefore, the present invention has been made in view of the above-mentioned problems, and it is an objective of the present invention to provide a semiconductor chip having a solder bump, in which an interlayer isolation layer, and a penetration layer whose materials can penetrate into the solder bump are formed between at least one under bump metal (UBM) layer and the solder bump, thereby allowing a composition of the solder bump to be changed, and thus suppressing growth of an inter-metallic compound (IMC) at an interface of the solder bump.

According to an aspect of the present invention, there is provided a semiconductor chip having a solder bump. The semiconductor chip includes at least one metal adhesion layer formed on an electrode pad of the semiconductor chip, an interlayer isolation layer formed on the metal adhesion layer, at least one penetration layer formed on the interlayer isolation layer and penetrating into the solder bump, and the solder bump formed on the penetration layer.

With this construction, the metal adhesion layer is separated from the solder bump through the interlayer isolation layer, and a composition of the solder bump is changed through the penetration layer, so that the growth of the IMC is suppressed.

At this time, among the metal adhesion layers, a first metal adhesion layer may be formed of at least one of titan (Ti), Ti alloy, aluminum (Al), Al alloy, nickel (Ni), Ni alloy, copper (Cu), Cu alloy, chromium (Cr), Cr alloy, gold (Au), and Au alloy,

Further, among the metal adhesion layers, a second metal adhesion layer may be formed as needed, and may be formed of at least one of Ni, Ni alloy, Cu, Cu alloy, palladium (Pd), and Pd alloy. Thereby, the first metal adhesion layer is more firmly bonded with the interlayer isolation layer.

Also, the interlayer isolation layer may be formed of one of Ni, Ni alloy, Pd, and Pd alloy.

The penetration layer may be formed of at least one of Cu, Cu alloy, antimony (Sb), Sb alloy, indium (In), In alloy, tin (Sn), Sn alloy, bismuth (Bi), Bi alloy, platinum (Pt), Pt alloy, gold (Au) and Au alloy.

Further, the solder bump may be formed of one of Au, eutectic Pb solder (Sn/37Pb), high Pb solder (Sn/95Pb), and a lead (Pb)-free solder selected from one of Sn/Ag, Sn/Cu, Sn/Zn, Sn/Zn/Bi, Sn/Ag/Cu, and Sn/Ag/Bi.

According to an aspect of the present invention, there is provided a method of fabricating a semiconductor chip having a solder bump. The method comprises the steps of forming at least one metal adhesion layer on an electrode pad of the semiconductor chip, forming an interlayer isolation layer on the metal adhesion layer, forming at least one penetration layer on the interlayer isolation layer so as to penetrate into the solder bump when the solder bump is formed, and forming the solder bump on the penetration layer.

Here, the method may further comprise the step of, after the metal adhesion layer is formed, forming photoresist patterns on opposite ends of a top surface of the metal adhesion layer. The interlayer isolation layer may be formed on the metal adhesion layer between the photoresist patterns. The step of forming the interlayer isolation layer may be performed by a sputtering or plating process. The step of forming the penetration layer may be performed by a sputtering or plating process.

Further, the method may further comprise the step of reflowing the solder bump. Thereby, the penetration layer penetrates into the solder bump through the reflow process, so that the growth of the IMC is suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which:

FIG. 1 is a sectional view illustrating a conventional semiconductor chip having a solder bump;

FIG. 2 is a sectional view illustrating a semiconductor chip having a solder bump suppressing growth of an inter-metallic compound (IMC) in accordance with the present invention;

FIG. 3 is a flow chart illustrating a process of forming a solder bump on a semiconductor chip so as to suppress growth of an IMC in accordance with the present invention; and

FIGS. 4 through 12 are sectional views illustrating the process of FIG. 3.

BEST MODE FOR CARRYING OUT THE INVENTION

Reference will now be made in detail to the exemplary embodiments of the present invention.

FIG. 2 is a sectional view illustrating a semiconductor chip having a solder bump suppressing growth of an inter-metallic compound (IMC) in accordance with the present invention. As shown in FIG. 2, the semiconductor chip 100 according to the present invention has at least one electrode pad 110 formed thereon, and the semiconductor chip 100 has a dielectric layer 210 partially formed thereon to allow a top surface of the electrode pad 110 to be exposed. One or more metal adhesion layers 220 and 230 are formed on the electrode pad 110, the top surface of which is exposed by the partially-formed dielectric layer 210. An interlayer isolation layer 240 is formed on the metal adhesion layer 230. At least one penetration layer 250 is formed on the interlayer isolation layer 240 so as to penetrate into the solder bump when the solder bump is formed. Finally, the solder bump 300 is formed on the penetration layer 250.

More specifically, the electrode pad 110 may be composed of metal, and is formed on the semiconductor chip 100. The electrode pad 110 electrically connects the semiconductor chip 100 with an external circuit board. The dielectric layer 210 is formed on the semiconductor chip 100 so as to allow the top surface of the electrode pad 110 to be exposed.

Among the metal adhesion layers 220 and 230, the first metal adhesion layer 220 may be composed of at least one of titan (Ti), Ti alloy, aluminum (Al), Al alloy, nickel (Ni), Ni alloy, copper (Cu), Cu alloy, chromium (Cr), Cr alloy, gold (Au), and Au alloy, and is formed on both the partially-formed dielectric layer 210 and the electrode pad 110 whose top surface is exposed by the dielectric layer 210. The UBM layers 220 and 230 may be preferably formed at a thickness of 200 to 20000 Å.

The second metal adhesion layer 230 may be formed on the first metal adhesion layer 220. At this time, the second metal adhesion layer 230 may be composed of a material, which is suitable to bond the first metal adhesion layer 220 and the interlayer isolation layer 240, and preferably at least one of Ni, Ni alloy, Cu, Cu alloy, palladium (Pd), and Pd alloy.

The interlayer isolation layer 240 may be composed of a material, which is suitable to bond the metal adhesion layers 220 and 230 and the penetration layer 250, and preferably at least one of Ni, Ni alloy, Pd, and Pd alloy. The interlayer isolation layer 240 is formed on the second metal adhesion layer 230, and thus structurally separates the metal adhesion layers 220 and 230 from the penetration layer 250 and the solder bump 300.

The penetration layer 250 may be composed of at least one of Cu, Cu alloy, antimony (Sb), Sb alloy, indium (In), In alloy, tin (Sn), Sn alloy, bismuth (Bi), Bi alloy, platinum (Pt), Pt alloy, gold (Au) and Au alloy, and is formed on the interlayer isolation layer 240. The penetration layer 250 may have variable thickness depending on a size of the solder bump 300, and may form 0.1 to 10% by weight in the solder bump 300. Among the materials forming the penetration layer 250, Cu can give a great change to a shape and growth of the IMC when the solder bump 300 is formed of Sn-rich lead (Pb)-free solder. More specifically, a small quantity of Cu is added to the solder bump 300 of SnAg, a property of the solder bump 300 can be improved. However, when Cu is supersaturated in the solder bump 300, a melting point of the solder bump 300 may increase. To this end, the penetration layer 250 is formed between the solder bump 300 and the interlayer isolation layer 240. Thereby, when the solder bump 300 is formed through a reflow process, the penetration layer 250 is allowed to penetrate into the solder bump 300.

The solder bump 300 may be composed of one of Au, Pb-free solder, and Pb solder. Here, the Pb-free solder may be preferably composed of at least one of Sn/Ag, Sn/Cu, Sn/Zn, Sn/Zn/Bi, Sn/Ag/Cu, and Sn/Ag/Bi. The Pb solder may be selected from either one of high Pb solder and eutectic Pb solder.

FIG. 3 is a flow chart illustrating a process of forming a solder bump on a semiconductor chip so as to suppress growth of an IMC in accordance with the present invention, and FIGS. 4 through 12 are sectional views illustrating the process of FIG. 3.

The process of forming a solder bump on a semiconductor chip will be described below with reference to FIG. 3, and FIGS. 4 through 12.

First, as in FIG. 4, a electrode pad 110 is formed on a semiconductor chip 100 (S101), and then a dielectric layer 210 is formed across the semiconductor chip 100 so as to allow the top surface of the electrode pad 110 to be exposed on the semiconductor chip 100 (S102).

Subsequently, as in FIGS. 5 and 6, one or more metal adhesion layers 220 and 230 are formed on the partially-formed dielectric layer 210 and the electrode pad 110 whose top surface is exposed by means of a sputtering or plating process (S103). The metal adhesion layers 220 and 230 may have a structure composed of a first metal adhesion layer 220 alone, or the first metal adhesion layer 220/second metal adhesion layer 230.

Next, as illustrated in FIG. 7, photoresist patterns 301 are formed on the second metal adhesion layer 230 in order to form an interlayer isolation layer 240, a penetration layer 250, and a solder bump 300 (S104).

Then, the interlayer isolation layer 240 is formed on the second metal adhesion layer 230 by a plating or sputtering process using the photoresist patterns 301 (S105). At this time, the interlayer isolation layer 240 may be composed of a metal such as nickel (Ni), as described above.

As illustrated in FIG. 8, at least one penetration layer 250 is formed on the interlayer isolation layer 240 by a plating or sputtering process using the photoresist patterns 301 (S106). At this time, the penetration layer 250 may be composed of metal such as copper (Cu) as described above. The thickness or the volume ratio of the penetration layer 250 can be adjusted to control a quantity of the component of the penetration layer 250 penetrating into the solder bump 300 during reflowing so that the penetration layer 250 may form 0.1 to 10% by weight of the solder bump 300. In case of using Pt, Pt alloy, Au, or Au alloy as the penetration layer, the wettability with the solder bump can be enhanced and any oxidation of under bump metal (such as the metal adhesion layer or the isolation layer) can be prevented. These materials undergo diffusion into the solder bump during reflow process, and thereby prevent the IMC growth.

As illustrated in FIG. 9, the solder bump 300 is formed using the photoresist patterns 301 (S107). At this time, the solder bump 300 may be formed by an electroplating process, an electroless plating process, an evaporation process, a ball attach process, a screen printing process, a solder jet process and the like. As described above, the solder bump 300 may be formed of one of Au, Pb solder, and Pb-free solder.

Next, the photoresist patterns 301 are removed as illustrated in FIG. 10, the metal adhesion layers 220 and 230 are etched as illustrated in FIG. 11, and the solder bump 300 is reflowed as illustrated in FIG. 12 (S108). At this time, the metal adhesion layers 220 and 230 are etched by wet etching using chemicals, or dry etching using a physical method. Meanwhile, on reflowing, the penetration layer 250 is melted into the solder bump 300 and thus is lost. For this reason, a composition of the solder bump 300 is changed. Therefore, the growth of the IMC which is a problem of the conventional technology can be suppressed.

As can be seen from the foregoing, according to the present invention, the interlayer isolation layer and the penetration layer are formed in that order, and then the solder bump is formed on the penetration layer. Thereby, the material composing the penetration layer penetrates into the solder bump, and thus the solder bump is changed into a multi-component solder bump. Thus, the growth of the IMC is suppressed, and the reliability of the semiconductor chip can be improved.

While this invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiment and the drawings, but, on the contrary, it is intended to cover various modifications and variations within the spirit and scope of the appended claims.